Push Button Switches
ALX-HB4-BS442 Mushroom Head Turn-to-Release Push Button | 22mm 1NC
22 mm mushroom head push button with turn-to-release (twist reset) latch, 30 mm and 40 mm caps, 1 NC contact, zinc alloy chrome bezel, screw terminals, 600 V AC 10 A.
The HB4-BS442 is a maintained mushroom button: press the cap and it latches down, turn the cap and it releases. That twist-release action is what distinguishes an emergency-stop style actuator from a momentary one, because the machine cannot be restarted until someone has deliberately reset the button. Two cap sizes, 30 mm and 40 mm, share the same bezel.
Technical Specifications
Item | Specification |
Mounting hole | 22 mm (22.3 mm cutout) |
Bezel / head material | Zinc alloy, chrome plated |
Contact housing | Plastic |
Contact configuration | 1 NC |
Operation | Maintained, turn to release |
Actuator | Mushroom head, 30 / 40 mm dia. |
Actuator colour | Red |
Illumination | None |
Rated voltage / current | 600 V AC, 10 A (AC-15 duty) as marked on the contact block |
Termination | Screw terminals |
Both cap sizes are normally-closed and latch when pressed. The release is a quarter turn of the cap; there is no key and no separate reset coil.
Design Features
- Press-to-latch, turn-to-release action: the contact stays open until the cap is deliberately twisted back
- Available with a 30 mm or 40 mm cap on the same 22 mm bezel, so the panel punch is unchanged
- Normally-closed contact block, so the stop state is also the de-energised state of the circuit
- Chrome-plated zinc alloy bezel and metal clamping ring hold alignment through repeated latching
- Contact block unclips from the rear for replacement without removing the bezel from the panel
Model Options
Model | Cap diameter | Contact |
HB4-BS442-30 | 30 mm | 1 NC |
HB4-BS442-40 | 40 mm | 1 NC |
For a key-released version see HB4-BS142; for a push-pull version see HB4-BT42. All three fit the same 22 mm cutout.
Applications
Emergency-stop and fault-stop circuits on machine tools, conveyors, mixers, compressors and process lines where a deliberate reset is required.