Switch apparatus requiring the hand of the operator to activate the switch by breaking a light beam

Abstract

A manually operable switch apparatus for a machine having at least one mode of operation actuated by a control circuit includes a spaced pair of switches which are simultaneously manually operable without the application of exertive contact by an operator. Preferably, each switch includes an infrared emitter spaced from an infrared receiver, and a single or double pole, double throw relay actuated when the beam between the emitter and receivers are broken, so as to cause actuation of an alternative mode of machine operation. The use of switches which do not require exertive contact obviates the injury to wrist and finger tendons experienced by machine operators when conventional palm buttons are employed on machines requiring repetitive operator manipulations. The use of a spaced pair of such switches requires that the operator place both hands on the switches in order to operate the machine, so that the operator cannot inadvertently place a hand in or adjacent to the machine during operation, thus serving to prevent injury to the worker. Such a switch apparatus is substantially more reliable then conventional mechanical and pneumatic switches, subject to significantly less breakdown in use.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates to machine controls, and more particularly to a switch assembly for initiating or changing a mode of operation of a machine.2. Description of the Prior ArtIt has long been known to use a spaced pair of manually operable switches (often of the type known as palm buttons) to activate the operational modes of machines such as stamping presses, riveters, tube benders, spot welders or the like. The purpose of the spaced pair of manually operable switches is to ensure that both hands of the worker are positioned away from the machine prior to operation. For this purpose of safety, the switches of such a machine must be operated simultaneously and must be spaced sufficiently far apart or otherwise suitably obstructed to prevent simultaneous actuation of the switches with a single hand. The Federal Occupational Safety and Health Administration, of course, sets the criteria which must be met by such machine ope...

AI Technical Summary

Benefits of technology

When the infrared beams of the switches are broken by the fingers of a user, each paired emitter and receiver close a circuit containing the associated solenoid, and energize the control means and anti-tiedown circuitry so as to operate the machine in one mode or another. The simultaneous breaking of the infrared beams of the two spaced switches, when controlled by the anti-tiedown circuit and control means, thus allows actuation of alternative modes of machine operation without requiring the machine operator to apply exertive contact against any switches or other objects, thus avoiding the mechanical breakdown associated with such switches, and the attendant physical effects upon the wrist and finger tendons of the operator.

Problems solved by technology

It is undesirable to use simple single throw switches to replace the palm buttons 110 because this can obviate the protection given to the worker when the second switch is employed.

If one switch is left in an operative position while the other switch can be operated by a single hand of a worker, the worker's free hand can become entangled with operative portions of the machine, sometimes resulting in potentially fatal injury.

While the use of a spaced pair of palm buttons has been adequate for the intended purpose of safety, such buttons are subject to the drawback that the worker must apply significant exertive contact to the palm buttons, in order to achieve actuation of them.

A substantial number of machine operators are now recognized as being subject to fatigue from the repetitive application of exertive contact against conventional palm buttons.

Indeed, operators are increasingly experiencing inflammation of the tendons, due to this repetitive and forceful action of the fingers and wrists.

The ailment has increased worker fatigue and complaints, has decreased productivity and has increased the frequency of disability claims under the workmen's compensation laws and programs.

These effects are injurious to the worker and substantially increase the costs associated with operations of the machine in question.

Additionally, palm buttons and like devices are subject to unacceptably great wear and breakage, due in part to the frictional movement of the members making them up, for example, such as the shaft and bore of a conventional palm button.

Images