Electromagnetically actuated switches exist in a variety of forms and for a variety of functions. Typically, they serve the function of opening and closing electrical circuits by controlling the bridging of a pair of contacts by a movable conductor. That conductor forms part of, or is carried by, an armature, the displacement of which is controlled by the selective energization of an electrical coil. In most such instances, the coil remains energized to maintain the contacts in one of their operative states, either open or closed. However, in many other instances, it may be necessary or at least desirable to maintain the associated switching circuitry in each of its stable states without requiring continued energization of the coil.
Exemplary of one type of the latter mentioned class of electromagnetic switches are U.S. Pat. Nos. 820,119; 1,824,973; 2,528,520; 2,851,646; 2,892,059; and 3,401,892. Each of these patents depicts an electromagnetic switch in which a linearly-moving armature or plunger is caused to rotate as a result of linear reciprocation. Such rotation is operative to move a bridging conductor between successive, angularly-displaced contacts, typically for some form of sequential control.
Exemplary of another type of electromagnetic switches of the class described earlier are U.S. Pat. Nos. 1,908,567; 2,703,348; 2,874,244; and 2,922,861. These electromagnetic switches are typically concerned with simply moving the contact-bridging element between either one of two stable states, e.g. "Contacts Closed" or "Contacts Open". Apart from the brief application of an actuating potential to the coil for moving the contact-bridging structure between its two stable states, no further energization of the coil is required. Such switches have, in some instances, been characterized as bistable relays or solenoids and will be so characterized herein. Typically, these electromagnetic switches are of a solenoid configuration in which an armature or plunger is reciprocated axially of an annular coil. Moreover, some portion of the plunger is usually axially coextensive with the coil during some portion of operation. In such bistable solenoid switches, it has been relatively common to effect the requisite bistable operation by means of a pin-and-slot arrangement. A pin, carried by the plunger, is subjected to the camming action of a stationary slot during axial displacement to provide the requisite rotational control of the plunger. U.S. Pat. Nos. 1,908,567; 2,874,244; and 2,922,861 are of that type. In another configuration represented by the aforementioned U.S. Pat. No. 2,703,348, the pin may be stationary and the slot may be formed in the plunger. The pin extends radially inward from the coil and into the slot.
The provision of such pin-and-slot arrangement to obtain a bistable solenoid switch complicates the manufacturing process and thereby increases its cost. Moreover, the integrity of the resulting system may, in some respects, be compromised. Certainly the assembly of the pin-and-slot structure in the aforementioned U.S. Pat. No. 2,703,348 patent presents a significant challenge.