Safety switches in stairlifts
S870 and S880 microswitches are used in safety edges on stairlifts.
The stairlift’s two guide rods are each enclosed by two powerful drive rollers that pull the lift up the stairs. Especially on a curved track, i.e. on winding staircases, this traction drive is far superior to a conventional rack-and-pinion drive. But what if the user gets off while the stairlift is moving? Or if a child comes rushing down the stairs?
What task do the Schaltbau microswitches perform?
If the user’s foot comes between the footrest and the stairs, the lift must stop immediately. For this reason, the footrest is fitted with a safety edge. Various S870 microswitches are installed here to interrupt the power circuit as soon as they are actuated. The safety edge responds to lightweight obstacles like bags or boxes, and of course if it makes contact with a person.
Why was the S870 chosen?
Because of its short actuator travel and precise switching behaviour, the S870 detects the slightest touches. Self-cleaning contacts ensure high contact reliability, and the mechanical positive opening operation opens the power circuit even if the contacts are welded, for example after a short-circuit caused by a fault in the system. The following data were decisive for choosing the switch:
- Housing dimensions: 30 × 16 × 10.5 mm (L x H x W)
- Mechanical positive opening operation in accordance with DIN EN 60947-5-1, Annex K
- Self-cleaning contacts