Spring load reduction thermostat
AssigneeGeneral Electric Company
InventorsJames P. Frank, Manuel L. Gonzalez, Ronald W. Poling
Life of this patent
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Abstract
A temperature responsive switch includes a housing, electrical contacts, an actuator arm, a rotatable shaft, and a cam assembly to open and close an electrical power circuit in response to environmental conditions. The cam assembly includes a cam and a cam follower attached to the actuator arm with a bias spring and contacting a cam surface. The cam surface has a first portion for adjusting the temperature calibration of the switch, and a second portion for positioning the cam follower in an OFF position that reduces the load on the bias spring. Thus, spring losses are avoided when the cam follower is in the OFF position, and the switch may be more accurately calibrated and adjusted when the switch is returned from the OFF position.
Claims16
A condition responsive electric switch comprising:
- a housing;
- a first electrical contact and a second electrical contact within the housing, at least one of said first and second contacts moveable between an open position breaking an electrical circuit and a closed position completing an electrical circuit in response to environmental conditions outside said housing;
- an actuator arm pivotally mounted within said housing for moving at least one of said first electrical contact and said second electrical contact;
- a rotatable shaft partially extending through said housing, said shaft comprising a center axis;
- a cam within said housing and connected to said shaft, said cam comprising a cam surface comprising a first portion, a second portion, and a third portion, said cam surface first portion comprises a first end and a second end, said first end positioned a greater radial distance from said center axis than said second end, said cam surface second portion comprises a first end and a second end, said first end positioned a greater radial distance from said center axis than said second end, said cam surface third portion longitudinally displaced from said cam surface first portion and second portion relative to said shaft center axis, said cam surface third portion positioned a greater radial distance from said center axis than said first end of said second portion;
- a cam follower contacting said cam surface, said cam follower moveable in response to said cam surface as said cam and said shaft are rotated;
- and
- a spring connected to said cam follower and to said actuator arm, said spring including a preset calibration position corresponding to a preset calibration load and an adjustable calibration position corresponding to an adjustable load from rotation of said shaft and said cam when said cam follower contacts said cam surface first portion, said spring connected to said actuator arm such that said spring is returned to said preset calibration position when said cam follower contacts said second portion.
A cam assembly for a condition responsive electric switch including an actuator arm for moving an electrical contact to open and close an electrical connection in response to environmental conditions external to said switch, and a shaft for adjustment of the conditions which cause the actuator arm to open and close the electrical connection, said cam assembly comprising:
- a cam attached to the shaft, said cam comprising a cam surface comprising a convex first portion, a second portion inwardly directed toward the shaft;
- and a third portion, said cam surface third portion separated from said first portion and said second portion, said cam surface third portion longitudinally displaced from said cam surface first portion and said cam surface second portion relative to a shaft center axis;
- and
- a spring loaded cam follower attached to the actuator arm and contacting said cam surface.
Dependencies are inferred from the claim text.