The 803-B4 Rotating Cam Limit Switch is a circuit control switch by Allen-Bradley which are used for control of machinery with dedicated operational cycles, in industrial processes where machine motion is determined by the cam switch’s shaft rotation. It makes uses of its shaft-mounted cam which produces actuation as the shaft rotates, and it is suitable for heavy-duty operations with its long life and minimal maintenance needs. The device is a control switch in the Style “B” series, and it has 3 circuits with a snap-action contact block, and it comes with a contact-mounted spring-loaded cam-roller assembly. The 803-B4 has 3 independently-operated cam assemblies with variable heavy-duty higher and lower cam segments, and a 150 RPM rotating shaft, on which the cam is mounted. It has a keyway (shaft slot) which is used for connecting machines to the driven shaft, and like all Style “B” switches, it comes with a factory standard left shaft extension. The circuit is activated when the shaft rotates, driving the upper cam segment against the cam roller, thereby opening contact 1 and 2 of the 10A snap-action contact, and closing contacts 3 and 4, and the circuit is de-activated as the cam valley (lower cam segment) passes by the cam roller.

The 803-B4 has a timing measured in degree, which is the moment when the cam activates the circuit, and a cam dwell time, which is the amount of time for which the cam lobe activates the circuit, and it is determined by the size of the cam lobes. Both the dwell and timing can be internally adjusted when the machine is not in motion, and the timing can be set a total range of 14 to 346 degrees, and the settings of the dwell and timing determine machine’s operation. The device has a cast iron side plate, and it comes with a NEMA Type 1 rated enclosure. The 803-B4 has a working temperature range of -30 to 66 degrees Celsius (-22 to 150 degrees Fahrenheit), with a storage range of -30 to 93 degrees Celsius (-22 to 200 degrees Fahrenheit), and it is built for rugged, and heavy-duty operations like steel forming, packaging/assembling, and punch presses operations. The 803-B4 weighs approximately 10.9 kilograms (24 pounds), with total dimensions of 144.5 x 82.6 x 177.8 millimeters (5.69 x 3.25 x 7 inches), and it is CE, UL, and CSA-certified.