Introduction

1.1 Background info

A scissors platform, also known as aerial work platform (AWP), elevating work platform (EWP) or mobile elevating work platform (MEWP) is a mechanical device used to provide temporary access for people or equipment to inaccessible areas, usually at height. They can be operated with hydraulics, pneumatics or mechanically via screws or a rack-and-pinion system. They are either unpowered units, requiring an external force to move them, self-propelled with controls at the platform or mounted to a vehicle for movement.

The scissors platform invention is widely credited to John L. Grove, an American inventor and industrialist. However, even before his first model, a company named Selma Manlift introduced a model in 1966. As for John L. Grove, after selling his previous business, Grove Manufacturing, in 1967 he and his wife headed out on a road trip. During a stop at the Hoover Dam, Grove witnessed two workers electrocuted while working on scaffolding. Through this “tragic event” John Grove saw a large untapped market for a product that could put workers in the air more safely to perform construction and maintenance tasks.When Grove returned home from his trip, he formed a partnership with two friends, bought a small metal fabrication business, and began designing concepts for the aerial work platform. The company was named JLG Industries Inc., and with the aid of 20 employees it released its first aerial work platform in 1970. Scissors platforms eventually began being designed with a variety of additional features. Many are now equipped with electrical outlets, compressed air connectors, and various other adaptations for tools.

An example of a simple scissor lift

1.2 Special features/ Functions of Scissors platform

The scissors platform are generally used for temporary, flexible access purposes such as maintenance and construction work or by firefighters for emergency access, which distinguishes them from permanent access equipment such as elevators. The design of lift is usually less than a ton with high safety. They are capable of being set up and operated by a single person. Regardless of the task they are used for, scissors platforms may provide additional features beyond transport and access, including being equipped with electrical outlets or compressed air connectors for power. They may also be equipped with specialist equipment, such as carrying frames for window glass. Under bridge units are also available to lift operators down to a work area.

There are several distinct types of aerial work platforms: aerial device, scissors life and hotel lift. Let us look into more details for these platforms, Aerial devices were once exclusively operated by hydraulic pistons, powered by diesel or gasoline motors on the base unit. Lightweight electrically powered units are gaining popularity for window-cleaning or other maintenance operations, especially indoors and in isolated courtyards, where heavier hydraulic equipment cannot be used. For scissor lift, it is a type of platform that can usually only move vertically. The mechanism to achieve this is the use of linked, folding supports in a criss-cross "X" pattern, known as a pantograph (or scissor mechanism). The upward motion is achieved by the application of pressure to the outside of the lowest set of supports, elongating the crossing pattern, and propelling the work platform vertically.

The power assisted drive (if fitted) and lift functions of an AWP are controlled by an operator, who can be situated either on the work platform itself, or at a control panel at the base of the unit. Some models are fitted with a panel at both locations or with a remote control, giving operator a choice of position. Controls vary by model, but are frequently either buttons or a joystick. The type and complexity of these will depend on the functions the platform is able to perform. The controls can control features such as:

Vertical movement Lateral movement Rotational movement (cardinal direction) Platform / basket movement — normally, the system automatically levels the

platform, regardless of boom position, but some allow overrides, tilting up to 90° for work in difficult locations.

Ground movement (in self-propelled models)