Catalogs > Safety Products Catalog > Principles, Standards and Implementation > Protective Measures and Complementary Equipment
Protective Measures and Complementary Equipment
| Introduction |  |
Preventing Access | |
Detection Devices | |
Safety Switches | |
Guard Locking Switches | |
| Non-Contact Interlock Switches | |
Hinge Switches | |
Position (Limit Switch) Interlocks | |
Trapped Key Interlocks | |
Operator Interface Devices | |
| Logic Devices | |
Integrated Safety Controllers | |
Safety Networks | |
Output Devices | |
Connection Systems | |
Cam operated actuation usually takes the form of a positive mode limit (or position) switch and a linear or rotary cam (as shown in Figure 73). It is generally used on sliding guards. When the guard is opened, the cam forces the plunger down to open the control circuit contacts. The simplicity of the system allows the switch to be both small and reliable.
|
| Figure 73: Positive Mode Limit Switch |
Position (limit) interlocks must not be used on lift-off or hinged guards.
It is extremely important that the switch plunger can only extend when the guard is fully closed. This means that it may be necessary to install additional stops to limit the guard movement in both directions.
It is necessary to fabricate a suitably profiled cam that will operate within defined tolerances. The guard-mounted cam must never become separated from the switch as this will cause the switch contacts to close. Such a system can be prone to failures due to wear, especially when badly profiled cams or the presence of abrasive materials is a factor.
It is often advisable to use two switches as shown in Figure 74. One operates in positive mode (direct action to open contact), and one operates in negative mode (spring return).
|
| Figure 74: Diverse Redundant Position Switches |