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US 4,400,679 AGranted
Snap acting switch for thermostats
AssigneeTherm-O-Disc, Incorporated
InventorHarold F. Snider
Life of this patent
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AssigneeTherm-O-Disc, Incorporated
InventorHarold F. Snider
Estimating the term…
A snap acting switch structure for thermostats or the like is disclosed in which the switch's movable contact is supported on a pair of arms the first of which is placed in compression and the second of which is placed in tension by a bistable spring system. The first arm is formed of relatively thin metal providing deep flanges to cause the arm to act as a rigid beam pivoted at one end. The two arms are welded together in face-to-face adjacency and the actuating force applied to the switch is applied substantially at the joint between the arms. Therefore, there are no substantial bending forces applied to the first arm, and the switch efficiently produces good wiping between the contacts and sufficient shear forces to break welds which may occur therebetween. The operating temperature differential is established for a given contact gap value by selecting the position of a calibration screw along the length of one leg of the snap spring system so that it cooperates with the stiffness of such leg to control the position of the joint between the snap spring legs to cause proper temperature differential.
A condition-sensing switching device comprising a body, a fixed contact, a movable contact, a bistable movable contact support assembly mounted on said body and supporting said movable contact for movement into and out of engagement with said fixed contact with snap action, said contact support assembly providing a first substantially rigid, elongated arm connected at one end to said body by pivot means, a second elongated arm connected at one end to said first arm substantially adjacent to the other end of said first arm, said movable contact being mounted on the other end of said second arm, spring means placing said first arm in axial compression and said second arm in axial tension and operating to produce an unstable condition when the connection between said arms is in a predetermined location, and condition-responsive means operably connected to cause movement of said connection between said arms through said predetermined position and causing said contacts to open and close with snap action, said connection between said arms being structured to prevent bending of said first arm under normal loading thereof whereby said first arm functions as a rigid beam pivoted at one end, said arms being structured so that the planes thereof intersect with a small angle so that relatively small forces applied to said connection between said arms produce substantial shear forces between said contacts to break welds which occur therebetween.
A thermostat comprising a switch, and a thermal actuator connected to operate said switch in response to changes in temperature, said switch including a fixed contact and a movable contact, a first arm pivotally supported at one end, a second arm, a mounting securing said second arm to the other end of said first arm in face-to-face contact, said movable contact being supported on said second arm at a location spaced from said mounting, and bistable spring means operating to place one of said arms in compression and the other of said arms in tension and causing said contacts to open and close with snap action, said first arm and said second arm each lying along a plane, said planes intersecting substantially at said mounting, said thermal actuator being connected to said arms substantially at said mounting whereby said first arm is substantially free of bending moments.
A method of producing a thermostat with a desired operating temperature differential comprising producing a switch having a rigid first arm pivoted at one end and a second arm pivotally connected to said first arm at the other end thereof, providing said arms with associated integral legs connected together at a leg joint, placing said first arm in compression and said second arm along with said leg of said first arm in tension, providing thermal sensing means to move the connected ends of said arms in response to temperature changes, and providing a calibration element operable to adjustably position said joint, and establishing the position of said calibration element along the length of said leg of said first arm in relation to the stiffness of such leg to provide the desired temperature differential.
Dependencies are inferred from the claim text.