Push button mechanism for controlling a contact unit

摘要

A push button mechanism includes a housing (1) including a push button control key (2) and microswitches (4) actuated by pushing the key. There are two common modes of push button operation: either a non-locking operation in which the position of the switch contacts corresponds to the position of the key; or a locking operation in which pushing the key changes the position of the switch which then remains in the new position after the key is released. From the manufacturing point of view it is desireable to provide a single mechanism which can act in either mode depending on the position of a selection component (7). From the user's point of view it may be advantageous to be able to change the mode of a switch which is already installed and wired. The present invention provides an operating key which may be withdrawn from the mechanism through the end face of the housing. The key carries a selection finger (7) for actuating a locking mechanism (8). For non-locking operation the finger is turned into a recess in the key while for locking operation it projects forwardly of the key. When the key is withdrawn it is simple to change the position of the finger.