Bi-stable relay

#This invention is in the field of electrical relays for controlling external circuits.

#It has been proposed to provide relays or circuit controlling apparatus relying on the change of shape of thermally responsive bimetallic elements. However, in general, such devices have been of such nature that the external circuit is controlled in the desired manner only as long as heat is supplied to the thermally responsive elements. In this regard, see the following patents:

#U.S. Pat. No. 2,769,938, Pauly;

#The single FIGURE of the drawing is a schematic representation of a bistable relay embodying the present invention.

#In the drawing, numerals 2 and 4 indicate a pair of electrically conductive reeds each carrying a contact. The contact 6 is mounted on reed 2 whereas the contact 8 is mounted on reed 4 and the reeds are normally in such position that the contacts 6 and 8 are spaced from each other. At least the reed 4 is flexibly resilient and can be flexed toward the reed 2 to engage the contacts 6 and 8. As shown, reed 4 extends upwardly beyond the contacts 6 and 8 and at its upper end is provided with a curved end portion 10. Between the end 10 and the contact 8, the reed 4 is provided with a transverse rod 12 fixed thereto. The rod 12 is preferably substantially rigid and extends laterally of the reeds with its ends extending toward snap acting thermally responsive discs 14 and 16, respectively. The discs 14 and 16 may be identical, each being a bimetallic member of known construction and normally assuming the curved condition shown in the figure at ambient temperature. The snap discs 14 and 16 are of such nature that they assume the position shown at ambient temperatures but when heated will snap inwardly and bow inwardly toward the reeds 2 and 4. Each is arranged to bow inwardly sufficiently far to engage the rod 12 and forcibly flex reed 4, as will be described.

#In a fixed position there is provided a spring or resilient latch element 18 having a projecting end projecting into the path of movement of the curved end 10 or reed 4. The spring latch element 18 is fixed on a suitable base upon which the discs 14 and 16 and the reeds 2 and 4 are mounted with at least the portions of the base on which the reeds are mounted being of electrical insulating material.

#Adjacent each disc 14 and 16, outwardly thereof, there is an electrical resistance heater. Heater 20 is adjacent disc 14 and heater 22 is adjacent disc 16.