Two hand safety modules help prevent injury to machine operators by keeping their limbs away from dangerous machine movement. Two hand safety modules are made up of two elements, a control board and a safety control module. The control board has two control devices that force the use of two-hand activation simultaneously. A two hand safety module provides an emergency stop signal to the machine control circuitry when the two-hand safety device inputs are removed or released. The various types of two hand safety modules are: Type I, which requires provision of two control devices requiring the concurrent actuation by both hands; Type II, which requires the release of both control devices before machine operation may be reinitiated; and Type III, which requires concurrent actuation of the control devices within a certain time limit. Other two hand safety modules are commonly available.
How Two Hand Safety Modules Function
There are several ways in which two hand safety modules function. In a safety control module, the machine safety is not limited to the use of safety sensors alone, but relies on the correct design of the safety interface. The weakest part in the safety chain of two hand safety modules will determine the overall safety category. A two-hand control requires constant, concurrent pressure by the operator to activate the machine. Monitoring of two-hand controllers requires a part-revolution clutch, brake, and a brake monitor if used on a power press. With this type of device the operator’s hands are required to be on control buttons, and at a safe distance from the danger area of the machine. A two hand control station circuit uses capacitive proximity switches to imitate the function of mechanical switches. A two hand control station is comprised of an isolation transformer, an enclosure, an electrically coupled isolation transformer, and a capacitive proximity switch. An adjustable two hand safety module includes both pneumatic models and electric models. Two hand safety modules are designed and manufactured to meet most industry specifications.
Two hand safety modules are used in many applications. Some examples include preferred protection devices for use in setting-up work and single-stroke operations for feed and removal processes. A safety control module is applied in presses for metal working, powder metallurgy, printing and paper processing machines, croppers, as well as machinery in the rubber, plastic, and chemical industries. Also, two hand safety modules are used to interface safety devices such as safety light curtains, safety mats, safety laser scanners, safety switches, and Hall Effect sensors in a safe and reliable manner. Two hand safety modules should adhere to the safety standards established by the American National Standards Institute (ANSI).