US 4,392,050 AGranted

Rapid response thermal switch for isolated load control

AssigneeHarper-Wyman Company

InventorOtto J. Cousins

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Abstract

A rapid response thermal switch for isolated load control includes a bimetallic switch electrically connected to a controller and operatively connected to a switch follower which controls the operation of a second switch electrically connected to a load so that the load is electrically isolated from the controller. While energization of the bimetallic switch by the controller causes the bimetallic switch to move away from its switch follower, the switch follower is biased to follow the bimetallic switch. The initial movement of the switch follower allows the load current controlling switch to close, energizing the load. The bimetallic element, heated by the controller currents flexes to cycle itself on and off while maintaining the load controlling switch in the closed position. When the bimetallic element sufficiently cools after deenergization, it returns the bimetallic switch to its closed position. The load current control switch is quickly opened, when the controller turns off, by the reverse movement of the bimetallic element since the switch follower is always in contact with the bimetallic switch and the bimetallic switch maintains itself in a position to quickly operate the load current controlling switch.

Claims11

Dependent claims

A thermal switch for controlling the energization of a load in response to a control signal from a controller, said thermal switch comprising:

a bimetallic actuator;
an electrical heater adjacent said bimetallic actuator;
a first set of contacts movable between open and closed positions in response to movement of said bimetallic actuator;
a control circuit including said first set of contacts and said heater, adapted to be connected to said controller for energization of said heater with the control signal when said first set of contacts is in said closed position;
a second set of contacts electrically isolated from said first set of contacts and being movable between closed and open positions in response to movement of said bimetallic actuator;
means responsive to movement of said bimetallic actuator for operating said second set of contacts between said closed and open positions;
a load circuit including said second set of contacts, adapted to be connected to said load and to a power source for energization of said load once said second set of contacts is in said closed position;
said bimetallic actuator having a normal position when unheated, said first set of contacts being closed and said second set of contacts being open in said normal position;
and
said bimetallic actuator being movable in response to heat from said energized heater to a position wherein said second set of contacts closes and in response to additional heat from continued energization of said heater to a position wherein said first set of contacts opens and said second set of contacts remains closed.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 06/255,660Filed 20 Apr 1981
Granted: 5 Jul 1983
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

H01H 61/02
Electrothermal relays: wherein the thermally-sensitive member is heated indirectly, e.g. resistively, inductively
G05D 23/1921
Characterised by the type of controller: using a thermal motor
G05D 23/275
Characterised by the use of electric means: with sensing element expanding, contracting, or fusing in response to changes of temperature
H01H
Electric switches

Family

No related US applications are recorded in the indexed filing history.

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