A CONTROL CIRCUIT UTILIZING TEMPERATURE ACTUATED SWITCHES AND SILICON CONTROLLED RECTIFIERS FOR REVERSING THE POLARITY OF DIRECT CURRENT APPLIED TO A LOAD
First Claim
1. A control circuit for maintaining the temperature of a substance, such as medicine, between specific limits by reversing the polarity of direct electrical current applied to a thermoelectric element, said circuit including:
- positive and negative input terminals, a bridge connecting said input terminals, a thermoelectric element connected across the bridge output terminals, a temperature actuated switch located in each leg of the bridge connected to the positive input terminal, said temperature actuated switches being normally open and one of said switches operating at a higher temperature range than the other of said switches with said temperature actuated switch operating in the higher range closing at an upper temperature limit and opening at a slightly lower temperature limit and said temperature actuated switch operating in the lower temperature range closing at a lower temperature limit and opening at a slightly higher temperature limit, a semiconductor device located in each leg of the bridge connected to the negative input terminal, and means to gate the semiconductor device in the opposite leg of the bridge when either temperature actuated switch is closed.
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Abstract
A control circuit for reversing the polarity of direct current applied to a load. The circuit utilizes temperature actuated switches and silicon controlled rectifiers located in a bridge connected between positive and negative direct current input terminals. In one embodiment of the invention, the load is a thermoelectric element connected between two heat conductive members, one of which is located inside an insulated container and the other of which is located on the exterior of the same container. In the preferred embodiment of the invention, the container is intended to be used for storing medicines which must be maintained between fixed temperature limits.
46 Citations
9 Claims
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1. A control circuit for maintaining the temperature of a substance, such as medicine, between specific limits by reversing the polarity of direct electrical current applied to a thermoelectric element, said circuit including:
- positive and negative input terminals, a bridge connecting said input terminals, a thermoelectric element connected across the bridge output terminals, a temperature actuated switch located in each leg of the bridge connected to the positive input terminal, said temperature actuated switches being normally open and one of said switches operating at a higher temperature range than the other of said switches with said temperature actuated switch operating in the higher range closing at an upper temperature limit and opening at a slightly lower temperature limit and said temperature actuated switch operating in the lower temperature range closing at a lower temperature limit and opening at a slightly higher temperature limit, a semiconductor device located in each leg of the bridge connected to the negative input terminal, and means to gate the semiconductor device in the opposite leg of the bridge when either temperature actuated switch is closed.
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2. The control circuit of claim 1 in which said temperature actuated switch operating in the higher temperature range closes at an upper temperature of approximately 55* F. and opens at a lower temperature of approximately 50* F. and said temperature actuated switch operating in the lower temperature range closes at a lower temperature of approximately 40* F. and opens at an upper temperature of approximately 45* F.
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3. The control circuit of claim 1 in which said thermoelectric element is connected between two heAt conductive elements, one of which is located inside an insulated container and the other of which is located on the exterior of the same insulated container.
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4. The control circuit of claim 3 in which said temperature actuated switches are mounted on said heat conductive element located inside said insulated container.
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5. The control circuit of claim 4 in which said heat conductive element located inside said insulated container is formed and adapted to support materials to be heated or cooled.
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6. An insulated container for storing medicines and the like including an insulated storage compartment adapted to receive and hold containers of medicine, a heat conductive element positioned in said storage compartment and located in heat transfer relationship to said containers of medicine, a second heat conductive element located on the exterior of said insulated container, a thermoelectric element connected between said heat conductive elements, a source of direct current connected to positive and negative input terminals, a bridge connecting said input terminals with said thermoelectric element being located across said bridge output terminals, a temperature actuated switch located in each leg of the bridge connected to the positive input terminal, a silicon controlled rectifier located in each leg of the bridge connected to the negative output terminal, and means to gate the silicon controlled rectifier in the opposite leg of the bridge when a temperature actuated switch is closed.
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7. The container of claim 6 in which said temperature actuated switches are normally open and said silicon controlled rectifiers are normally non-conductive.
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8. The insulated container of claim 6 in which one of said temperature actuated switches operates at a higher temperature range than the other of said switches.
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9. The insulated container of claim 8 in which said temperature actuated switch operating in the upper range closes at an upper temperature limit and opens at a slightly lower temperature limit and said temperature actuated switch operating in the lower temperature range closes at a lower temperature limit and opens at a slightly higher temperature limit.
Specification