* GB785814 (A)

Description: GB785814 (A) ? 1957-11-06

Improvements in or relating to the production of articles from aluminiumnitride

Description of GB785814 (A) Translate this text into Tooltip

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The EPO does not accept any responsibility for the accuracy of data and information originating from other authorities than the EPO; in particular, the EPO does not guarantee that they are complete, up-to-date or fit for specific purposes.

PATENT SPECIFICATION Inventors: RAYMOND BOLLACK and MARCEL REY 785,814 4 Date of Application and filing Complete Specification April 16, 1956. No 11559156. Complete Specification Published Nov 6, 1957. Index at Accepttance:-1 -iass 227, J(I 2: 7: 1 i 2: 16: 21: 24 33). International Classification: -uC 04 b. COMPLETE SPECIFICATION Imnprovenments in or reltammzg to the Prodluction of Articles from Alum inium Nitride We, SOCIETE D'ELECTRO-CHIMIE, D'ELECTRO-METALLURGIE ET DES ACIERIES ELECTRIQUES D'UGINE, a French body corporate, of 10, Rue du General Foy, Paris (Seine), v France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention is concerned with improvements in or relating to the production of articles from aluminium nitride. Aluminium nitride which has the general formula AIN, is a very hard industrial material having a hardness on Mohs' scale of 9; it is chemically inert at temperatures up to 20000 C unless submitted to an oxidising atmosphere and it is particularly resistant to liquid or

gaseous aluminium Its dissociation tension is nil at 20000 C and its melting point is 22300 C Furthermore aluminium nitride possesses good thermal conductivity and very poor electrical conductivity. In view of these properties, aluminium nitride could advantageously be used industrially as a refractory or abrasive material; however, attempts to produce manufactured articles of aluminium nitride hitherto have, for one reason or other, been unsuccessful or uneconomic. If a refractory material composed only of aluminium nitride is required, the nitride must be agglomerated by sintering and this necessitates heating the material to a temperature of 1800 to 20000 C, which renders the cost of the product prohibitive If, on the other hand, a refractory composed of aluminium nitride agglomerated by a ceramic bond is sufficient, the requisite bonding may he obtained at industrially economic temperatures, for example about 14000 C, but the refractory properties of the nitride are then partly impaired. lPrice 3 s 6 d l The nitriding of alumina in situ has been proposed for the fabrication of these products, but owing to the fact that the molecular volume of alumina is higher than that of aluminium nitride, the products obtained by this procedure have a porous structure which impairs their refractory properties. Other methods, employing carbon, are unsatisfactory as they give rise to products wvhich are unstable in the presence of atmosphere moisture due to the fact that they contain aluminium carbide. It is therefore an object of the present invention to provide a process for the commercially economic production of articles composed principally of aluminium nitride, which articles possess substantially the same properties as aluminium nitride. According to the present invention, there iv provided a process for the production of articles from aluminium nitride which cornprises intimately mixing powdered aluminium nitride having a particle size of not more than 1 mm, a minor proportion of one or more powdered metals of group m, IV or V of the periodic classification having a particle size of not more than 1 mm, a non-aqueous binder capable of increasing the compactness of the mixture on moulding and of being completely removed from the mixture after moulding, and a non-aqueous solvent for the binder, removing the solvent from the intimate mixture, moulding the resulting mixture into the desired shape under pressure and heating the moulded mixture at a temperature above 500 C in a nitriding atmosphere substantially free from oxidising gases and gaseous carbides, out of contact with carbon, the proportion of metal to aluminium nitride in the initial mixture being such that the article obtained after firing has a higher compactness than the mixture after moulding.

The product obtained by the process 785,814 according to the invention is composed essentially of aluminium nitride crystals assembled in a compact structure and bonded together by the nitride(s) of the metal(s) of group III, IV or V of the periodic classification. The particle size distribution of the constituents of the aluminium nitride and metal mixture should be such that its compactness, which expresses the relationship between the apparent volume and the actual volume of the powdered mixture, is as great as possible It is also necessary to eliminate aluminium nitride particles in the form of aggregates of porous and brittle crystals and this may be done, when employing industrial aluminium nitride as the starting material, by eliminating particles of a size greater than 1 mm. The particle size distribution giving the maximum compactness may be continuous or discontinuous The first is given by the general equation of Wilhelmi: Y=A+( 100 A&; ( where Y is the percentage by weight of particles whose apparent diameter is less than a, and D the largest particle of the mixture; the exponent N varies from 0 3 to 0 5 The particular forw of this general equation most used in Europe is represented by the Boloney parabola which relates to permanent structures d Y= 12 + 88 D Discontinuous particle size distribution is obtained by eliminating a part or the mole of one or more fractions of particles of a chosen size from a powdered material with continuous particle size distribution Typical particle size distributions which are suitable for the materials to be used in the process according to the invention are, for example, as follows: Particle size Particle size distribution A distribution B Components (parabolic), % (discontinuous), %. Particles from 0 5 to 1 mm 30 50 Particles from 0 1 to 0 5 mm 40 10 Particles below 0 1 mm 30 40 With either type of particle size distribution the maximum compactness which can be obtained after moulding the mixture, but before fixing is approximately 74 %. The proportion of metal to aluminium nitride in the initial mixture is a critical feature of the process according to the invention. Theoretically the quantity of metal to be included in the initial mixture should be such that the secondary nitride formed from this metal completely fills the voids between the particles of the orginal 2 Auminium nitride. This void must be at least equal to 100-74 = 26 % by volume and to fill it completely, it may be calculated that at least the following proportions of metal (based on the combined weight of metal and aluminium nitride) will be required:22 % of powdered aluminium or 23 % of powdered silicon or 45 % of powdered titanium or 48 % of powdered vanadium these meals being chosen as typical examples within the invention, as each belongs to one of the groups m, IV and V of the

periodic classification For the purpose of this invention silicon is to be considered as a metal. It is found in practice, however, that if the theoretical quantities of pulverulent metals are employed in the initial mixture, a part of the the molten metal exudes to the surface of the moulded article with consequent loss of metal and obstruction or blocking of the pores of the moulded mixture so that the interior of the mixture is not nitrided; the finished article thus remains porous. We have found by experience that to obtain compact articles, the most suitable proportions are about one half of the theoretical proportions calculated as above, that is to say: % 2 % of aluminium 12 % 2 % of silicon %+ 4 % of titanium 22 % 4 % of vanadium Suitable binders for use in the process according to the invention are organic compounds of high molecular weight which are soluble in organic solvents Examples of such binders are industrial waxes, such as paraffin waxes, ceresine and ozokerite, and highly viscous polyglycols Such binders have the requisite bonding and lubricating properties, the latter allowing the particles of the mixture to slide over each other so as to take up positions giving the highest compactness, under the moulding pressure. Suitable non-aqueous solvents for the binder, in particular the binders specifically mentioned above will be apparent to those skilled in the art In general all organic solvents for waxes are suitable; the least expensive of these is trichloroethylene. In order that the invention may be well understood the composition of certain suitable 785,814 initial mixtures which give good results (the parts being by weight) will now be given, by way of illustration only:MIXTURE 1 > Aluminium nitride, (particle size distribution A)Powdered aluminium for paints sized 100, and finer Ceresine TrichlorethyleneMIXTURE 2 Aluminium nitride, (particle size distribution B) Iron-silicon alloy containing 96 + 2 % Si sized 75 pand finer Ceresine Trichlorethylene MIXTURE 3 Aluminium nitride, (particle size distribution B) Sponge titanium pulverised 100 k and finer Polyglycol 400 TrichlorethyleneMIXTURE 4 Aluminium nitride, (particle size distribution A) Iron-vanadium alloy containing 78 % vanadium pulverized 150 u and finer Ozokerite Trichlorethylene 2 12 2 3 22 4 As already stated the mixtures whose compositions are set out above are given by way of example only and combinations of other metals from groups III, IV or V of the periodic classification, other binders and other solvents may be used Thus in Mixture 3 above, the 20 % of pure titanium may be replaced by 18 % of titanium-aluminium alloy (containing 72 % of titanium) pulverised to a fineness of 100 ga. The preparation of the initial mixture used in the proces according to the invention is preferably carried out in three stages Firstly the powdered metal, the binder and the solvent are intimately mixed in a

suitable mixer, the mixture obtained is then poured on to the powdered aluminium nitride which is contained in a second mixer and all the constituents of the mixture are thoroughly mixed together Finally the solvent is evaporated whereby the mixture takes on a sand-like consistency; it is then ready for moulding. Moulding is preferably carried out in steel moulds under hydrostatic pressure The most compact manufactured articles are obtained by pressing the sandy mixture slowly under a high pressure, which should not however exceed approximately 3000 kg/cm', the moulds being kept at a temperature of about 800 C. Nitriding of the moulded mixture may be carried out directly by heating the formed articles at a temperature above 5000 C pre 65 ferably at 14000 C or higher, in, for example an electric furnace, and in a nitriding atmosphere The nitriding atmosphere may consist of purified commercial nitrogen, or ammonia, or a mixture of these two gases, provided how 70 ever: that these gases or their mixtures do not contain more than 0 3 % of oxygen in any free or nascent state, arising for example from the decomposition reaction CO 2 =CO+O The articles should also be prevented from coming 75 into contact with carbon during the firing, as if they do the nitrides are decomposed and the corresponding carbides are formed in their place; the latter are undesirable as they are unstable and decompose in the presence of 80 atmospheric moisture with the result that if carbides are present to any appreciable extent in the products of the invention the latter tend to split and break up when stored in cold air. For the same reason it is also highly desirable 85 to avoid the presence of gaseous carbides in the nitriding atmosphere. After such treatment, relatively compact articles are obtained but their compactness does not exceed 78 % Although such a result 90 is in accordance with the invention, a modification of this nitriding procedure has been developed whereby articles having a compactnes of 88 % or more may be obtained. According to this modification the moulded 95 mixture is first fired at a temperature of about 4500 C in an oxidising atmosphere, for example in air; this initial firing eliminates all carbon from the article so that no carbon which may impair a part of the nitride by car 100 bonisation is present during the further firing. The article at this stage is porous and brittle and holds in its pores adsorbed oxygen which, if it were not removed prior to the succeeding nitriding treatment, would oxidise the 105 powdered metal In order to remove this adsorbed oxygen from the fired article it is maintained in an atmosphere of amomnia for about 48 hours; by this treatment ammonia replaced the adsorbed oxygen and the weight 110 of the article increases by 10 % or more.

The article is then submitted to a nitriding treatment as described above, that is to say it is heated at a temperature above 5000 C, preferably of 1400 C or more in a nitriding 115 atmosphere. The articles obtained by the process according to the invention show no irreversible variation in volume, not only after firing, but also after long storage in cold air They may be 120 employed for all refractory purposes, for example as furnace linings, muffles, crucibles, burners and diffusers, even under reducing conditions; they are also suitable for all abrasive purposes, for example as grinding wheels, 125 785,814 buffing stones, cutting stones, wire drawing dies and thread guides, and for combined abrasive and refractory purposes.

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* GB785815 (A)

Description: GB785815 (A) ? 1957-11-06

Improvements relating to methods of and apparatus for analysing gases

Description of GB785815 (A)

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FR1133575 (A) FR1133575 (A) less Translate this text into Tooltip

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The EPO does not accept any responsibility for the accuracy of data and information originating from other authorities than the EPO; in

particular, the EPO does not guarantee that they are complete, up-to-date or fit for specific purposes.

COMPETE SPECIFICATION Improvements relating to Methods of and Apparatus for Amalysang Gases I, EIEINRICH FEICHTINGER, a citizen of Liechtenstein, of Place Chevelu 6, Geneva, Switzerland, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: Methods of analysing gases are known in which the gases are reacted with various absorption or other reagents in several stages and in which the component gases are determined quantitatively from the volumes of gas absorbed from time to time in the process. In these cases, the gases are frequently tested in a single reaction chamber which, according to the course of the analysis operation, is filled in stages with the different reagents. Owing to the charging with absorbents and to the washing out of the reaction chamber necessary before and after each charge, however, gas residues or residues of other substances are left from time to time which frequently cause appreciable errors of measurement, so that precision analyses, in particular analyses of small volumes of gas, cannot be carried out therewith. It is furthermore, known, in gas microanalysis methods, to measure the gas volumes in graduated capillary tubes, similar errors of measurement however occur. Finally, it has also already been proposed to convey the gas to be analysed through different reaction chambers arranged in series. However, as the latter are separated from one another by cocks or valves, dead spaces occur in which gas residues are left behind and which again cause inaccurate measurements. The object of the present invention is to provide a method of, and apparatus for carrying out gas analyses, even of small volumes of gas, quickly and with precision. Amongst other purposes, such analyses are commonly made of the flue gases of blast furnaces for the purpose of controlling the ore refining operation. According to the invention, this is achieved essentially by forcing the mixture of gases to be analysed step by step through a series of interconnected chambers, in each of which the mixture is reacted with an absorbent or other reagent, by means of a conveying liquid, the volume of the mixture entering or leaving each chamber at a constant pressure being determined by measuring the volume of conveying liquid required to force the mixture past a measuring mark associated with the chamber.

Thus, in the method according to the invention, the volume of gas runs through various measuring and absorption stages in an always constant direction since the chambers are connected in series with each other and is measured indirectly on passing the measuring marks provided in the individual measuring and absorption stages. Dead spaces and gas residues which are not determinable are thereby completely obviated. The conveyance of the volume of gas to be analysed is therefore effected exclusively by means of the hydrostatic pressure of the conveying or displacement liquid or of the absorption solution. Mercury, oil or some other suitable liquid is expediently used for the former. It is, therefore, also possible for a displacement liquid to be employed which dries the gas, or effects a partial absorption which is desired to begin with, for example if potash lye is used, which dissolves the COn out of the gas but does not affect the other components. Advantageously, for carrying out the method according to the invention an apparatus is used which comprises a gas measuring chamber and two or more absorbent or reaction chambers directly connected together in series by capillary tubes, each chamber communicating with a pressure equalizing vessel, the capillary tubes each having a measuring mark, and means for forcing a measured volume of a conveying liquid through the chambers, whereby the mixture or gases to be analysed is carried into and through the chambers With the chambers connected together in series, each intermediate chamber has at least two capillary tube connections on opposite sides and the mixture of gases and the conveying liquid pass into the chamber through one connection through the chamber and out through another connection. Since the connections between the chambers are direct, that is to say there are no valves or cocks in the capillary tube, the possibility of leakage occurring during the passage of the gas between the chambers or the trapping of small quantities of gas in dead spaces caused by valves, both of which occurrences would cause inaccuracies in the analysis, is avoided. Control of the volume of gas within the measuring and reaction chambers is carried out by opening from time to time a valve which allows the pressure equalizing vessel belonging to the chamber in question to communicate with the atmosphere. In this way, the volume of gas to be analysed can be carried round on its path as desired, without passing through shutoff devices. Two examples of apparatus according to the invention are illustrated diagrammatically in the accompanying drawings in which: Figure 1 shows a first embodiment of the gas analysis apparatus; and Figure 2 shows an alternative arrangement of the measuring and reaction chamber system.

The apparatus shown in Figure 1 is suitable for analysing mixtures of gases, containing Carbon dioxide, Carbon monoxide, Hydrogen and Nitrogen. The chamber system serving for the actual analysis comprises a preliminary gas measuring chamber 1 and reaction chambers 2 and 4 which are in communication with pressure equalizing vessels 1', 2' and 4', respectively, each of which in turn is arranged to be dosed by means of a valve 6, 7, 8. Between the reaction chambers 2 and 4 there is provided a sealing chamber 3 equipped with a bell 17. The sealing chamber 3 is partly filled with a sealing liquid, for example paraffin oil or silicone oil, which prevents the mixing of the liquids provided in the chambers 2 and 4 or the migration of ions, and has a deaerating closure device 10. On the outlet side of the chamber 4 a gas outlet chamber 5 is connected, which is also arranged to be closed by means of a valve 9. All the chambers 1 to 5 are enclosed by a jacket provided with inlet and outlet connections 13 and 13', respectively, and through which a liquid is circulated for maintaining the reaction chambers and measuring positions at a uniform temperature and which also strengthens the apparatus. The gas measuring chamber 1 is connected in series through the feed pipe 18 with a gas collecting chamber 23 which is connected by way of the valve 22 to the gas feed pipe 19 and by a flexible tube to the levelling vessel 20 for receiving conveying liquid. To the gas collecting chamber 23 there can furthermore be connected, through a valve 24', a vessel 24 from which absorbents or suitable sealing solutions can be introduced into the chamber 23. In addition, a feed pipe 25' which can be closed by a valve 25 and which enables special reaction gases, for example oxygen, to be supplied, is also provided. Finally, there is also connected to the gas collecting chamber 23 a supply container 26 for the conveying liquid which is constructed as a pressure cylinder and the piston 27 of which is coupled to a precision dial gauge 32 indicating the quantity of liquid displaced by said piston. The displacement of the pressure piston 27 is effected by means of a rack and pinion gear 31 or the like. The piston 27 is advantageously provided with a plurality of packing rings 28, 23' and 30, in the intermediate spaces 29 and 29' of which there is a suitable lubricant. The main sealing action is produced by the packing ring 28, while the packing 30 prevents the lubricant 29' from flowing away to the outside. The result of this is that the main packing 28 is surrounded both in front and at the back by the same lubricant, so that it is evenly lubricated both on forward and on rearward movement, the lubricant simultaneously acting as a seal. In fact, when the piston is moved forward, a thin sealing film of lubricant travels out of the space 29 into the space 29' between the wall of the cylinder 26 and the packing

ring 28. On reverse movement of the piston, substantially the same quantity of the sealing lubricant travels back again. In this way, therefore, a measuring piston is obtained which enables very accurate volumes to be displaced on forward and rearward movement and penmits of reading said volumes off on the precision dial gauge 32. At the start of the analysis, all the chambers and connecting pipes or tubes of the apparatus are filled with displacement liquid. sealing solution or liquid reagent and all the valves and cocks are closed. By opening the cock 19' and lowering the levelling vessel 20, the gas to be analysed is sucked into the supply container 21. Thereafter, the cock 19' is closed, the valve 22 opened and the gas or a partial quantity of the gas is introduced into the gas collecting chamber 23 by means of a rearward movement of the piston 27. The valve 22 is thereupon closed, the valve 6 opened and the quantity of gas forced through into the preliminary measur ing chamber 1 by forward movement of the piston 27. By opening the valve 7 for a short time, the voluine of gas is then allowed to advance into the transfer capillary tube between the chambers 1 and 2 as far as a measuring mark 14, the piston 27 being moved forward a little. With the valve 6 open, the fluid levels in the two chambers 1 and 1' can be equalized by a suitable movement of the piston, the volume of gas contained in the chamber 1 is thus brought to outside pressure conditions. If the upper parts of the pressure equalizing vessels 1', 2', 4' are in direct communication with the atmosphere, the pressure is of course atmospheric; if as is shown in the case of the vessel 1', the upper part of the pressure equalizing vessels is closed against the external pressure by means of a cap or dome 38, pressure equalization takes place through a connection 39 and is equal to the pressure in a gas container 40. In this case, the valve 6 is lifted, for example, by an electromagnetic opening device 41. Closing the pressure equalizing vessels against the atmosphere is only necessary when absolute gas measurements which are independent of the atmospheric pressure and temperature are carried out. In most cases, when it is only a question of determining gas compositions on a percentage basis, the gas container 40 and the closure 38 against the atmospheric pressure can be omitted, so that the upper part of the equalizing vessels is in communication with the atmosphere, as, for example, as is shown for the equalizing vessel 2'. As soon as the quantity of gas in the chamber 1 which is to be analysed has been brought to the desired pressure conditions, the valve 6 is closed, the dial gauge 32 is set at zero and the valve 7 opened. Then the gas is transferred from the chamber 1 to the succeeding second stage, that is to the reaction chamber 2. Initially the gas is only displaced until the displacement liquid reaches the measuring mark 14. In this way.

the quantity of gas transferred is determined indirectly by measuring the quantity of conveying liquid required for forcing the quantity of gas past the measuring mark 14. This quantity can be read from the precision dial gauge 32. The gas is then completely transferred to the reaction chamber 2 and the combustible component of the gas is burned by means of an ignition coil 11 disposed therein. The remaining gas is thereafter brought up to the next measuring mark 15 by raising the valve 8. If it is necessary to add oxygen to the gas for combustion, the oxygen is sucked in by way of the cock 25 through the first measuring stage 1 into the second measuring stage to the gas sample and is measured in addition to the sample. After combustion, the measurement of the volume of the gas is effected by the measuring method described for the previous stage. If the pressure equalizing vessel 2' were closed against the atmospheric pressure similarly to the vessel 1', the upper part of the pressure equalizing vessel 2' would similarly be in communication with the common gas container 40. However, this has not been shown to simplify the drawing. After the gas has been conducted completely through the sealing chamber 3 into the last reaction chamber 4, which, in the case of the present combination of gases, is filled, for example, with aqueous caustic potash, the carbon dioxide produced during the combustion is absorbed therein. Thereafter, measurement of the residual volume is effected at the measuring mark 16, while the unabsorbed remainder of the gas is finally expelled with the valve 9 open. By means of the above-described method of operation the volumes of gas are measured by the volume of liquid required to convey them and are thus measured at the same time as they are conveyed thus greatly reducing the time taken for the analysis. As there are no dead spaces along the entire path of the gases through the apparatus which would cause erroneous measurements, the method produces very accurate results, even if only small quantities of gas of about 0.1 cc and less are available for the analysis. If less accurate gas analyses are to be carried out with the apparatus, the conveyance of the gases is effected solely by the levelling vessel 20, instead of by the piston 27 coupled to the precision dial gauge 32. In this case, the procedure is as follows:- With the valves 22 and 6 open, the quantity of gas introduced through the cock 19' into the supply container 21 is conveyed into the measuring chamber 1 by raising the vessel 20. By opening the valve 7 for a short time, the gas is forced into the transfer capillary tube as far as the mark 14. Then, with the valve 6 open, equality of the levels is produced in the two chambers 1 and 1' by raising or lowering

the levelling vessel 20 and at the same time the liquid level is read off in the levelling vessel 20 which is provided with a suitable calibration. There after, the valve 6 is closed, the valve 7 opened and by raising the vessel 20 the gases are again forced out of the chamber 1 through the capillary tube into the chamber 2 until the following liquid reaches the measuring mark 14. The valve 22 is again closed and the new level is read off in the vessel 20. In this case, the quantity of gas transferred again corresponds to the quantity of conveying liquid displaced, and this can easily be determined from the difference in the two readings at the levelling vessel 20. On transfer to the further reaction stages or chambers, the same procedure is followed. The calculation of an entire analysis is obtained in the case of the present type of gas from the quantity of gas introduced, which is measured when the measuring mark 14 is passed, the contraction on combustion, which is determined from the quantity of gas passing the mark 15, and the absorption of carbon dioxide which can be read off at the measuring mark 16. If the gas in the reaction chamber 2 is not burned, the pure carbon dioxide content of the gas to be analysed can be determined when the quantity of gas travels past the mark 16. The apparatus shown in Figure 2 corresponds in principle to that shown in Figure 1, but in this case two reaction chamber systems are arranged in parallel and are directly interconnected without the interposition of cocks or valves, through a distributor element 33 arranged after the gas collecting chamber 1 and its associated measuring mark 14. The gas to be analysed is conducted through the distributor element 33 either to one chamber system shown on the left in the drawing, or the other right-hand chamber system, according to requirements. A gas sample is again received from the gas collecting chamber 21 (Fig. 1) through the chamber 23. The gas sample is transferred into the collecting chamber 1 with the valve 6 open (Fig. 2). From the collecting chamber, the gas sample can either follow the righthand absorption path by opening the valve 34 or the left-hand absorption path by opening the valve 36. Thus, two analyses are carried out in this case for determining the quantities of two gas components, reaction chambers 2 being charged with an absorption solution or solid absorbents which absorb one of the gas components to be analysed, while other reaction chambers 4, which are charged with another solid or liquid absorbent, absorb the other component. It should be noted in this case also that transfer is effected by way of the distributor element 33 without the gas having to pass through a cock or valve in the process. Of course, it is also possible, instead of using the two-part gas

analysis apparatus shown in Figure 2, to design the apparatus so that three or even more capillary tubes meet at the distributor element 33, so that the gas coming from the collecting or preliminary measuring chamber 1 can be conducted through suitable distributing pipes into an equal number of the above-described absorption chamber systems and be analysed therein. The distributor element 33 and the valves 34, 35, 36, 37 indirectly controlling the conveyance of the gas, thus render it possible to combine as many analysis sys- tems as desired into a single directly interconnected structural unit and to house them in a common enveloping jacket containing circulation water at a constant temperature. so that uniform pressure and temperature conditions prevail everywhere at the measuring and reaction positions. If solid absorbents are to be used for certain gas absorption operations, they are introduced into the individual absorption chambers. In such cases, it is necessary to provide the individual absorption chambers with additional closure devices through which the solid absorbents are introduced or exchanged. For the sake of clarity, such closures, for example ground glass stoppers, have not been shown in the drawings. What I claim is: 1. A method of quantitatively analysing a mixture of gases in which the mixture is reacted in stages with absorbents or other reagents, the change in volume of the mix- ture after each reaction being measured, wherein the mixture is forced step by step through a series of interconnected chambers by the pressure of a conveying liquid, the volume of the mixture entering or leaving each chamber at a constant pressure being determined by measuring the volume of conveying liquid required to force the mixture past a measuring mark associated with the chamber. 2. An apparatus for quantitatively analysing a mixture of gases, comprising a gas measuring chamber and two or more absorbent or reaction chambers directly connected together in series by capillary tubes each chamber communicating with a pressure equalizing vessel, the capillary tubes each having a measuring mark, and means for forcing a measured volume of a conveying liquid through the chambers, whereby the mixture of gases to be analysed is carried into and through the chambers. 3. An apparatus according to Claim 2, in which the pressure equalising vessels each have a valve for shutting off the vessel from the associated reaction chamber and the means for forcing the conveying liquid through the chambers comprises a storage vessel arranged to discharge a measured volume of liquid into the gas measuring chamber. 4. An apparatus according to Claim 3, comprising two or more systems

of reaction chambers arranged in parallel, the chambers in each system being in series, and the first chamber of each system communicating with the gas measuring chamber. 5. An apparatus according to Claim 3 or Claim 4, having a sealing chamber for containing a sealing liquid arranged between two reaction chambers, which prevents mixing together of liquids contained in the reaction chambers but allows gases to pass between the chambers. 6. An apparatus according to any one

* GB785816 (A)

Description: GB785816 (A) ? 1957-11-06

Combination radiant and convection heating system

Description of GB785816 (A)

PATENT SPECIFICATION Date of Application and filing Complete Specification: August 29, 1955. 7859816 No 24758/55 ' Y 5 J J J Application made in United States of America on September 1, 1954 Complete Specification Published: November 6, 1957 Index at acceptance:-Classes 64 ( 2), G 1 A 5; 64 ( 3), 523 A; and 137, B 3 E. International Classification:-F 24 d, f F 25 h. COMPLETE SPECIFICATION Combination Radiant and Convection Heating System We, VAPOR HEATING CORPORATION, a corporation of Delaware, United States of America, 80, East Jackson Boulevard, Chicago, Illinois, United States of America, we pray that a patent may be granted to do hereby declare the invention,,for which us, and the method by which it is to be performed, to be particularly described in and by the following statement:- JO The improved heating system comprising the present invention has been designed for use primarily An connection with the heating of buses, house trailers, and other road vehicles The system is, however,

capable of other uses, for example, the heating of railway passenger cars and other similar vehicles. Specifically, the present invention relates to an improved system of "trench heating", so-called because the heat radiating instrumentalities proper are disposed within a trench-like depression formed in a floor structure wherein they underlie the main floor and are thus concealed from view. It is among the principal objects of the invention to provide an improved trench heating system for road or railway vehicles of the type outlined above in which the heating effect obtained within the enclosure to be heated As partly the result of heat radiation from the main floor of the vehicle and partly the result of air entering the trench and directed into contact with the heat radiating element of he system, whereby the air is heated and passes through openings into the enclosure, the heating effect produced in either instance being of a uniform nature at all regions within the enclosure to produce uniform temperature distribution and consequent maximum occupant comfort. Another object of the invention, in a heating system of this character, relates to the constructional aspects of the vehicle wherein the heat radiating devices per se are assembled and installed within a duct construction which constitutes a "package type" unit capable of being manufactured at the factory as a prefabricated transportable sub-assembly for shipment to the 5 e vehicle assembly plant for installation in the floor trench of the vehicle sub-floor during assembly of the vehicle body for subsequent connection in the heating system 55 The provision of a duct construction or sub-assembly of the type briefly outlined above which, in the main, may be constructed of sheet metal and which therefore may be manufactured at a low cost; one 6 G, which is of light weight construction, and one which may with but slight modification or variation in its constructional details be adapted for use in dfferent environments to accommodate vehicles having differently 65 compartmented enclosures, are further desirable features that have been borne in mind in the development of the present invention. In the accompanying drawings forming 7 O. a part of this specification, several embodiments of the invention have been shown. In these drawings: Fig 1 is a perspective view, somewhat schematic in its representation, of an en 75 closed vehicle, for example, a house trailer to which the heating system of the present invention has been applied; Fig 2 is an enlarged fragmentary sectional view taken on the vertical plane re 8 B presented by the line 2-2 of Fig 1; Fig 3 is a fragmentary perspective view, partly in section, of a portion of the floor construction of the

vehicle of Fig 1 showing the heating system of the present in 85 vention applied thereto; Fig 4 is a fragmentary sectional view taken substantially centrally and vertically through the rear end of the vehicle shown in Fig 1; 9 O ,' 785,816 Fig 5 is a fragmentary plan view of a portion of the sub-assembly units employed in connection with the invention with the top plate thereof removed; S Fig 6 is a fragmentary perspective view partly in section, of a modified form of sub-assembly; and Fig 7 is a fragmentary perspective view similar to Fig 6 showing another modified form of sub-assembly. Referring now to the drawings in detail and particularly to Fig 1, the heating system of the present invention has been shown as being applied to a house trailer coach 10 but it will be understood that the illustration is purely exemplary and the system may, with or without modification, be used for the heating of buses or other road vehicles or rolling stock such as railway passenger cars. The coach 10, with certain exceptions that W 1 l appear presently, is of conventional design and includes a composite floor 11, composite side walls 12 and 13 (Fig. 2) and composite front and rear walls 14 and 15, respectively The coach further includes a top wall or roof 16 which may be of a suitable insulated type and which bears no specific relation to the prosent heating system other than to complete the trailer enclosure 17 undergoing heating. The composite floor 11 is best illustrated in Figs 2 and 3 and comprises a sub-floor supported from a pair of longitudinally extending metal side sills or beams 21 The sub-floor includes upper and lower spaced sheet metal members 22 and 23 between which there is interposed a suitable insulating material 24 which is preferably either preformed or of the package type The members 22 and 23 may be unitary or these expanses may consist of overlapping widths of the sheet material The central regions of the sheet metal members 22 and 23 are deformed to provide a longitudinal trough or trench 25 which extends substantially the entire length of the coach floor 11 and in which trench there is adapted to be installed a completely assembled "packagte type" heating unit, three forms of which have been 'illustrated ini Figs 3, 6 and 7, respectively, and which, independently and in combination with the heating system as a whole, constitutes a novel feature of the present invention The details of these units Will be set forth presently. Supported at their ends on longitudinally extending wooden beams 27, which may be of the 2 " x 4 " variety are a plurality of d 60 transversely extending interlocking main floor channels 28 having side flanges 29 (see also Fig 4) and intermediate depending ribs or flanges 30 The side flanges 29 are supported on the sub-floor assembly 20 and

the ribs 30 are of lesser extent than the flanges 29 so that there is a clear air space or duct 35 within each channel 28. The channels 28 are preferably formed of aluminum on account of the lightness of this metal and also on account of its ex 70 cellent heat-conductive qualties A baffle 36 (Figs 2 and 3) extends longitudinally of the vehicle through slots 37 formed:n the ribs 30 of the floor element 28 for air distribution purposes as will be described 75 subsequently A bottom shield or plate 38 is coextensive with the floor 11 and is secured at its longitudflinal edges to skirts 49 which depend from the side sills 21. The side walls 12 and 13 are of sim:lar 80 construction and each wall includes an outer panel or "skin" 41, an intermediate wall panel 42 and an inner panel 43 which in part defines the enclosure 17 The panels 41 and 42 are secured as by welding or 85 riveting to vertical sill flanges 44 and insulating material 24 is disposed between these two panels The inner wall panel 43 is supported at its lower edge by means of curved metal strips 45 from the interlock 90 ing channels 28 The space 46 exist ng between the panels 42 and 43 communicates with the various ducts 35 existing within the channels 28 Longitudinally extending resilient sealing members 47 are supported 95 on the side sills 21 between the wooden beams 27 and the inner sill flanges 44 The side walls 12 and 13 are provided with the usual window openings 50 and, as shown in Figs 2 and 4, louvered air dischar-e 100 openings 51 establish communication be. tween the space 46 and the enclosure 17 immediately below the window openings 50. The rear wall 15 (Fig 4) includes inner and outer wall panels 52 and 53, respec 105 tively, between which there is contained in. sulating material 24 A space 54 is provide-1 for intake of air from a louvered opening (see also Fig 1) and this space communicates with the trench 25 through a 110 suitable blower 56 by means of which air is circulated through the passages provided for it by the heat Ing system as will be de. scribed when the operation of the system is set forth A damper 57 on the inner wall 115 panel 54 regulates the volume of fresh air admitted to the system and also allows air within the enclosure 17 to be proportionately recirculated through the svstem, an opening 58 being formed in the wall panel 120 54 for this purpose. In Figs 3, 6 and 7 there have been shown three forms of heating and heat distributing assemblies capable of being operatively installed within the trench 25 beneath the 125 floor channels 28 for operative connection in the heating system Each of these assemblies is in the form of a "package type" unit capable of being manufactured and assembled at the factory and shipped ii 130 785,816 its entirety to

the coach assembly plant for installation purposes The unit shown in Fig 3 is designated in its entirety at 60 and includes an elongated, trough-like, US shaped member 61 of sheet metal having a flat bottom 62, and upstanding side walls 63 provided with laterally turned flanges 64 extending along their upper edges A cover plate 65 extends across the trough l O member 61 and is suitably secured to the flanges 63 by spot welding or screws, thus providing a tubuiar casing structure. Nested within the trough member 61 is an elongated duct or partition member 66 i S ot irregular V-shape design -The duct member 66 is suitably secured within the trough member 61 as by welding and is provided with generally inclined side walls 67 which serve to divide the composite tubular member 65, 66 into three longitudinally extending air passages including a central passage 68 and side passages 69 Disposed within each side passage 69 and extending completely along the length thereof is a radiator assembly each consisting of two aligned radiator units R of the type having a central pipe section 71 for flow of a heating fluid therealong and heat radiating fins 72 spaced therealong As shown, the fins 72 are of rectangular design and are diagonally disposed within the passages 69 and serve to present a relatively large heat radiating area therein, the radiators being arranged in their diagonal position in the flow path of the air streams so that the air will wipe the entire area of each fin 72. A row of spaced openings 73 extends along the lower edge of each of the side walls 67 and similar rows of spaced open. -40 ings 74 are formed along the opposite edges of the cover plate 65 The openings 73 establish communication between the central passageway 68 and the two side passageways 69 while the openings 74 establish communication between each of the side passageways 69 and the various ducts provided by the floor channels 28. Referring now to Fig 1, the radiator pipe sections 71 are adapted to be connected in and from an integral part of a closed fluid heating circuit including parallel heating loops one of which accommodates the forward regions of the enclosure 17 and the other of which accommodates the -S rear regions thereof The heating circuit extends from a suitable heating coil 80 through a pipe section 81, leading to a Pump 82, and from thence through a line 83 extending to a pair of branch fittings 84 and 85 The radiator pipe sections 71 of the various radiators are connected to the fittings 84 and 85 and return lines 86 and 81 extend from the ends of the radiator pipe sections 71 along the side wall 13 adjacent i 65 the bottom thereof and communicate with a common return pipe 88 leading to the heating coil 80 A suitable drip and discharge fitting 89 extends through the floor below the return

pipe 88 A riser 90 extends upwardly from the end of the pipt 70 section 83 to an expansion tank 91 for the heating fluid used in the system Any suitable heating fluid may be used, for example water or an anti-freeze solution such as ethylene glycol A pipe 92 may extend 75 from the tank 91 and serve as an inlet for filiing the system with the liquid. A heater 93 is positioned below the heating coil 80 and may be supplied with kerosene or other suitable fuel contained 80 within a fuel tank 94 It will be understood of course that any form of heating means may be employed whether the same be electrical or of the fuel burning type. During the operation of the system for 85 heating purposes, the system is filled, as previously described, with water or other fluid through the pipe 92 The burner 93 is then lighted for producing the desired amount of heat and the pump motor M is 90 set into operation to circulate the heating fluid throughout the closed loops provided for it If desired automatic control of the system may be effected by employing the usual "Aquastat" (Registered Trade Mark) 95 for the heater and the usual thermostat for controlling the motor. When the overall temperature of the heating fluid contained within the system has been brought to a desired degree, the 100 radiator assemblies including the pipes 71 and radiating fins 72 become hot and air entering the system through the louvered opening 55 in the rear wall 15 passes downwardly through the passage 54 and enters 105 the blower 56 (Fig 4) by means of which the air is forced into the rear end of the central passageway 68 provided in the heat distributing unit 26 A certain amount of air pressure is developed within the passage 110 68 and by virtue of the spaced row of openings 73, the air is caused to traverse the entire longitudinal extent of the passage and flow outwardly in opposite directions into the side passages 69 below the level of the 115 radiators R The air thus expelled through the openings 73 flow upwardly between the spaced radiating fins 72 and around the pipes 71 from whence it passes through the openings 74 into the various ducts 35 120 existing within the walls of the aluminum floor channels 28 The baffle 36 being positioned centrally of the vehicle insures equal distribution of the air to opposite sides of the vehicle through the various ducts 35 125 the size of the openings 74 may be pro. gressively increased so that these openings gradually become larger as they progress toward the front of the vehicle. The air within the ducts 35 applies heat 130 785,816 to the main floor so that heat is radiated into the enclosure The air issuing from the two parallel rows of openings 74 flows outwardly in opposite directions and enters the spaces 46 provided between the inner and

outer side wall panels 42 and 43 Finally, the heated air after heating the wall surfaces emerges from the louvered openings 51 at the level of the windowsills and enters the passenger compartment 17 from whence it may be recirculated through the system by entering the opening 58 for return to the blower 56 or it may be expelled from the passenger compartment 17 by exfiltration when the damper 57 is closed upon the opening 58. From the above description it will be observed that by the heating system just described the passenger compartment 17 is supplied with heat both by convection of the heated air issuing from the openings 51 and by radiation of heat upwardly from the floor surface afforded by the interlocking aluminum floor channels 28 Because of the relatively large heat radiating surfaces afforded by the radiators R which are confined within the relatively small enclosures 69, the air issuing from the openings 74 has been brought to a relatively high degree of heat This heat flows along the underneath surfaces of the floor channels in direct contact therewith and as:i result thereof a considerable portion (of this heat may be absorbed by the floor and wall channels and radiated into the enclosure Such heat as is not extracted in this manner from the air passes inwardly through the louvered openings 51 to the passenger compartment 17 thus serving principally to heat the upper regions of the compartment. It should be observed that the wooden beams 27 prevent any direct metal-to-metal contact between the side sills 21 or any 4 A other part of the floor sub-structure and the metal floor proper These beams 27 thus serve both as structural and insulating members so that no appreciable amount of heat will be lost by conduction through the composite floor structure. In Fig 6 a modified form of packagetype heating unit is disclosed This unit is designated in its entirety at 100 and is similar in many respects to the unit 60 shown in Fig 3 The trough member 101 and cover plate 102 remain substantially the same as in the previously described form but the radiators R 2 consist of pipe sections 103 having associated therewith circular disk-like radiating fins 104 which nest within the curved bottom regions of the trough member 101 An inverted Ushaped baffle member 105 is welded or otherwise secured to the underneath face of the cover plate 102 and has depending side flanges 106 which terminate short of the trough bottom thus providing in effect elongated slots or openings 107 through which the unheated air forced into the tubular structure by the blower 56 may 70 pass for intimate contact with the heat radiaing fins of the radiators R 2 The heated air passes outwardly through two rows of openings 108 and enters the ducts as previously described 75 In Fig 7, yet another modified form of package unit is shown In this form of the unit a

vertical partition wall 120 extendsbetween the bottom of the trough member121 and cover plate 122 and is provided 80with longitudinal side flanges 123 and 124 which may be welded to the bottom of the trough member and to the cover plate re spectively The member 120 thus divides the space within the trough member 121 85 into two passageways 125 and 126, respectively A radiator R 3 is disposed withi n the passageway 125 adjacent the partition and includes pipe sections 127 having associated therewith rectangular heat radia 90ting fins 128 which are vertically disposed. A row of openings 129 extends longitudinally along the partition 120 substantially medially thereof and a simliar row)f openings 130 are provided longitudinally in 95 j the cover plate 122 on the side of the radiator R 3 remote from the partition wall The trough member 121 is generally rectilinear design and when it is installed within the trench 25, the passageway 126 lo 00 is in communication with the blower 56. Thus it will be seen that air forced into the passageway 126 will be discharged through the openings 129 from whence it will pass across the heat radiating surfaces 105. of the radiator R 3 and flow upwardly throuigh the openings 130 into the various ducts 35.

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* GB785817 (A)

Description: GB785817 (A) ? 1957-11-06

Improvements in or relating to means for slidably mounting closure membersin a frame

Description of GB785817 (A)

PATENT SPECIFICATION 7859817 Date of Application and filing Complete Specification: September 12, 1955 No 26087/55 Complete Specification Published: November 6, 1957 Index at acceptance:-Classes 20 ( 3), Bl(B 1 Bl:C), J( 1 R:21 H:2 J), K; and 52 ( 1), C 4 B 5. International Classification:-A 47 b E 04 f. COMPLETE SPECIFICATION Improvements in or relating to Means for Slidably Mounting Closure Members in a Frame 1, RUBEN OSVALDO PERRONE, a citizen of the Republic of Argentina, of Uriburu 335Beccar-Provincia de Buenos Aires, Republic of Argentina, do hereby declare the invention for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: - This invention relates to closures for openings. The present invention provides a closure for an opening comprising a frame including a lintel and a sill and a closure member, the closure member being constrained for sliding movement within the frame by means of a plurality of freely rotatable first rollers mounted on the sill of the frame which are engagable by the side walls of a recess formed in the bottom edge of the member, a plurality of freely rotatable second rollers mounted on the top edge of the member which engage the side walls of a recess formed in the lintel of the frame, and a plurality of third rollers each freely rotatable about a horizontal axis which bear on the upper surface of the sill of the frame. One embodiment of the present invention will now be described in greater detail, by way of example only, with reference to the accompanying drawings, of which, Fig 1 is an elevation, partly in section, of the embodiment. Fig 2 is a sectional view of the embodiment on the line A-A of Fig 1. Fig 3 is a sectional view of the embodiment on the line B B of Fig 1, and Fig 4 is a fragmentary plan view of the means for locating members relative to each other when they are in their closed position. As shown in the drawings, in which the closure is for a window opening, there are provided two closure members or windows a each slidable in the same plane within a frame b formed by a lintel 5, a sill 3 and two jambs 4, the sill being stepped to provide I' three horizontal faces 2, 27 and 28 On the middle face 2 of the sill are mounted by means of screws 13 a plurality of freely rotatable first rollers 12 which are engageable by the side walls of a recess 14 formed in the 50 bottom edge of the rail 1 of each of the windows. Mounted on the top edge of upper rail 6 of each of the windows are

individual pairs of second rollers 15 each freely rotatable on 55 a shaft 16 which extends from adjacent one end of its respective supporting plates 17. The rollers 15 engage the side walls of a recess 7 in the lintel 5 A plurality of third rollers 9 each mounted on a shaft 10 within 60 a cavity 8 in lower rail 1 are also provided, the rollers 9 bearing on face 2 of the sill 3. Secured to the face 2 of the sill 3 is a locating member 18 constituted by a plate of rhomboidal shape the divergent sides of 65 which, which start from respective points 19, form male wedging surfaces which cooperate with the sides of notches 21 formed in plates 20, each of which is secured to the lower rail 1 of the respective window a so 70 that the notches extend inwardly from the front edge of the respective window When the windows are in their closed position the points 19 each lie within their respective notches 21 in order to locate the windows, 75 and thus ensuring that the windows are in a position wherein a latch 22 can be engaged by means of a handle 23, on one window, with a catch 24 on the other window. Both windows a are provided with flanges 80 each of which etxends downwardly from the lower rail 1 of its respective window to a point below the plane of face 2 of the sill 3 in front of side face 26 The uppermost face 28 of the sill is positioned above the 85 level of the bottom edge of the rail 1 of each window This arrangement reduces the ingress of foreign matter onto the face 2 which might otherwise interfere with the free operation of the windows 90 785,817 It will be seen that the above described apparatus, by virtue of the fact that there are no sliding surfaces directly in contact one with another, provides a particularly advantageous way for mounting closure members in openings in which displacement of the members is constrained to movement in the direction for opening and closing the members. Although in the above described embodiment the present invention has been described as applied to a window opening it will be appreciated that the present invention is applicable to other closures for openings of the type employing slidable closure members, for example, doors, walls or partitions of buildings or to slidable doors in articles of furniture. The above described invention provides 20) means for slidably mounting closure members which are vibration free and therefore reduce the risk of damage to any glass or crystal which may form part of the closure members Furthermore there is provided means which allow easier movement of the closure members than was hitherto possible.

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* GB785818 (A)

Description: GB785818 (A) ? 1957-11-06

Process for the production of regenerated cellulose threads and films fromviscose

Description of GB785818 (A)

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BE540586 (A) CH337609 (A) FR1139301 (A) NL87098 (C) US2974004 (A) BE540586 (A) CH337609 (A) FR1139301 (A) NL87098 (C) US2974004 (A) less Translate this text into Tooltip

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PATENT SPECIFICATION 785818 Date of Application and filing Complete Specification: Oct 3, 1955. No 28119155. Application made in Germany on Nov 25, 1954. Complete Specification Published: Nov 6, 1957. Index at acceptance:-Class 2 ( 2), B 2 V( 1 C 2 A: 7: 8: 9). International Classification:-D Olf.

COMPLETE SPECIFICATION Process for the Production of Regenerated Cellulose Threads and Films from Viscose We, VEREINIGTE GLANZSTOFF-FABRIKEN A.G, of Wuppertal-Elberfeld, Germany, a Body Corporate organised under the laws of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a process for the production of regenerated cellulose threads and films from viscose. Regenerated cellulose threads having a strong peripheral zone are acquiring ever increasing importance because they have good elastic properties and low degrees of swelling, and for the production of such threads processes have become known in which alkalisoluble monoamines are added to the viscose from which the threads are spun These monoamines must, however, be soluble in the spinning baths which are used The amounts of the additives should not amount to more than 4 millimoles per 100 g of viscose Monoamines in substantially the same amounts have also been introduced into the spinning baths The spinning baths which are used contain zinc sulphate, the latter being present in amounts of 3-25 % by weight It is well known that it is difficult to spin viscoses which contain monoamines, as the spinning conditions must be maintained within very narrow limits In addition, when using these processes, it is necessary to maintain thread or film withdrawal speeds of not more than 2025 m/min, if the desired effect is to be obtained Consequently, the use of monoamines on a large scale is not convenient and presents considerable problems in operation. It has now been found that regenerated cellulose threads and films with a strong peripheral zone and greatly improved strength and elasticity properties are produced if imidazole lPdce 3 s 6 d l H-C N 11 11 H-C C-H H or a substituted imidazole is added to a viscose, preferably with a gamma value of 42-50, from which the threads and films are obtained Included among the substituted imidazoles are those which are substituted in the 2 and/or 4-position by alkyl or alkanol groups The 2-carbon atom can carry an organic acid radical, for example a -CI 1 I CO OH radical It has been shown that the difficulties arising when viscoses containing monoamines are spun are obviated when using these imidazoles and that it is possible to use thread or film withdrawal speeds of 40-50 m/min and still attain the required result. The said compounds are added to the viscose in an amount of 0 06-0 4 % by weight, preferably 0 12-0 15;% by weight, and can if desired be added during the dissolution of the xanthate The compounds can be added to any viscose which has a conventional composition, examples of

which are those containing 7-8 % of cellulose and 5-7 % of sodium hydroxide The aqueous coagulation baths to be used must contain zinc sulphate in amounts of 30-50 g/l The sulphuric acid content of the bath may fluctuate within the limits of 40-65 g/l The sodium sulphate content of the bath is preferably within the usual limits, namely between about 160 and 260 g/l The bath temperature should preferably be between 45 and 700 C, and the thread or film withdrawal speed between 40 and 50 m/min The withdrawal speed can be further increased if known measures are taken which ensure that the bath, at least over the first section of travel after the nozzle, has imparted to it a speed which is substantially equal to the speed of the thread, so that the friction between the thread and bath is substantially reduced The bath should be at least cm long The thread is then stretched by 80-120 %, preferably 95-100 %, in a second, hot aqueous decomposition bath which contains 2-10 g/l of H 504 and which preferably has a temperature higher than 90 ' C. The thread can thereafter be laid on to a bobbin, into a centrifuge or on to a perforated band The threads spun by the process of the invention have strength values of 400-420 g/100 den, and these values can be increased to 430-460 g/100 den by after-stretching. They are characterised by a very high shrinkage (a feature of value for example in the production of very thick webs), a high rubbing resistance value and a low degree of swelling. The process of the invention is further illustrated in the following example: EXAMPLE: Alkali cellulose made from linters and wood cellulose is xanthated for 5 hours with 42 % carbon disulphide and the xanthate obtained is dissolved to form a viscose with 7 3-% of cellulose and 5 5 % of Na OH During the dissolving operation, 0 12 % by weight of imidazole is introduced into the-viscose The viscose is then filtered, de-aerated and ripened in the usual manner and spun at a viscosity of 60 poises and at a gamma value of 44 0. The viscose is extruded into an aqueous coagulation bath which contains 52 g/l of sulphuric acid, 40 g/l of zinc sulphate and g/1 of sodium sulphate, and has a temperature of 580 C to form threads The thread consists of 1000 individual threads with an individual count of 1 65 den and travels over a path of 65 cm in the bath and is withdrawn by a roller at a speed of 21 m/min The thread then travels through a second, aqueous decomposition bath which contains 8 g/l of H 2 SO 4 and has a temperature of 91 C and is withdrawn by a second roller at a speed of 42 m/min, i e, it is drawn by an amount of % From the second roller the thread runs into a centrifuge which is rotating at 4600 r.p m and is given therein a twist of about turns per metre The thread is

then washed, softened and dried after a final afterstretching of 8 % It has the following textile properties: Strength dry 4.4 g/den wet 3.0 % Elongation dry wet 14 27

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