Fusible resistor

Claim 2

A fusible resistor, the combination comprising: a cylindrical substrate made of an electrically insulating material and having ohmic contacts disposed at its ends; a pair of lead wires fastened to the ends of said cylindrical substrate and in electrical contact with said ohmic contacts; a resistive film deposited on the surface of said cylindrical substrate between said ohmic contacts, said resistive film being divided into two resistor sections by a gap which interrupts electrical continuity between said lead wires; and a fusible link deposited on said substrate and within said gap to provide electrical continuity between said resistor sections at normal operating temperatures, said fusible link including a fusing layer which melts at a preselected temperature to open circuit.

Claim 3

A fusible resistor, the combination comprising: a cylindrical substrate made of an electrically insulating material and having ohmic contacts disposed at its ends; a pair of lead wires fastened to the ends of said cylindrical substrate and in electrical contact with said ohmic contacts; a resistive film deposited on the surface of said cylindrical substrate between said ohmic contacts, said resistive film being divided into two resistor sections by a gap which interrupts electrical continuity between said lead wires; and a fusible link deposited on said substrate and within said gap to provide electrical continuity between said resistor sections at normal operating temperatures, said fusible link including a fusing layer which melts at a preselected temperature to open circuit.

Claim 4

A fusible resistor, the combination comprising: a cylindrical substrate made of an electrically insulating material and having ohmic contacts disposed at its ends; a pair of lead wires fastened to the ends of said cylindrical substrate and in electrical contact with said ohmic contacts; a resistive film deposited on the surface of said cylindrical substrate between said ohmic contacts, said resistive film being divided into two resistor sections by a gap which interrupts electrical continuity between said lead wires; and a fusible link deposited on said substrate and within said gap to provide electrical continuity between said resistor sections at normal operating temperatures, said fusible link including a fusing layer which melts at a preselected temperature to open circuit.

Claim 5

The fusible resistor as recited in claim 1 in which said fusing layer is coated with a layer of flux which inhibits oxidation of the fusing material at elevated temperatures.

Claim 6

The fusible resistor as recited in claim 2 in which a protective coating covers said resistive film and said fusible link.

Claim 7

The fusible resistor as recited in claim 1 in which said fusing layer is cadmium.

Claim 8

The fusible resistor as recited in claim 2 in which said flux includes water white rosin flux and a heat stabilizer.

Claim 9

A fusible resistor the combination comprising: a substrate made of an electrically insulating material and having a pair of spaced termination points; a resistive film deposited on the surface of said substrate between said termination points, said resistive film being divided into two resistor sections by a gap which interrupts electrical continuity between said termination points; and a fusible link deposited on said substrate and within said gap to provide electrical continuity between said resistor sections at normal operatiNg temperatures, said fusible link including a fusing layer made from a material having substantially less resistance per square than said resistive film and which is responsive to the heat generated in said resistive film to melt at a preselected temperature and said fusing layer material has a relatively high surface tension when in the liquid state and is drawn out of said gap by surface preferred wetting when said preselected temperature is exceeded to open circuit.

Claim 10

A fusible resistor the combination comprising: a substrate made of an electrically insulating material and having a pair of spaced termination points; a resistive film deposited on the surface of said substrate between said termination points, said resistive film being divided into two resistor sections by a gap which interrupts electrical continuity between said termination points; and a fusible link deposited on said substrate and within said gap to provide electrical continuity between said resistor sections at normal operatiNg temperatures, said fusible link including a fusing layer made from a material having substantially less resistance per square than said resistive film and which is responsive to the heat generated in said resistive film to melt at a preselected temperature and said fusing layer material has a relatively high surface tension when in the liquid state and is drawn out of said gap by surface preferred wetting when said preselected temperature is exceeded to open circuit.

Claim 11

The fusible resistor as recited in claim 6 in which said fusing layer material is selected from the group consisting of cadmium, silver, indium, tin, lead, and zinc.

Claim 12

The fusible resistor as recited in claim 6 in which a layer of flux is disposed on said fusing layer to inhibit the oxidation of said fusing layer material at elevated temperatures.

Claim 13

The fusible resistor as recited in claim 8 in which a protective coating is placed over said resistor film and said fusible link.

Claim 14

The fusible resistor as recited in claim 8 in which said fusing layer is formed by depositing metal ions on said substrate.

Claim 15

The fusible resistor as recited in claim 10 in which said fusing layer includes cadmium ions which are deposited by an electrolysis process.

Claim 16

A fusible resistor the combination comprising: a substrate made of an electrically insulating material and having a pair of spaced termination points; a resistive film selected from the group of carbon composition and cermet resistive materials and deposited on the surface of said substrate between said termination points; and a fusible link deposited on said substrate in series connection with said resistive film to provide electrical continuity between said termination points, said fusible link including a metallic fusing layer which has substantially less resistance per square than said resistive film material, which is supported by the substrate and which melts at a preselected temperature to open circuit by surface preferred wetting.

Claim 17

A fusible resistor the combination comprising: a substrate made of an electrically insulating material and having a pair of spaced termination points; a resistive film selected from the group of carbon composition and cermet resistive materials and deposited on the surface of said substrate between said termination points; and a fusible link deposited on said substrate in series connection with said resistive film to provide electrical continuity between said termination points, said fusible link including a metallic fusing layer which has substantially less resistance per square than said resistive film material, which is supported by the substrate and which melts at a preselected temperature to open circuit by surface preferred wetting.

Claim 18

The fusible resistor as recited in claim 12 in which said fusing layer is coated with a layer of non-acidic flux.

Claim 19

The fusible resistor as recited in claim 13 in which said fusing layer material is selected from the group consisting of cadmium, silver, indium, tin, lead, and zinc.

Claim 20

A fusible resistor, the combination comprising: a substrate made of an electrically insulating material and having a pair of spaced termination points; a resistive film deposited on the surface of said substrate between said termination points; a fusible link deposited on said substrate in series connection with said resistive film to provide electrical continuity between said termination points, said fusible link including a fusing layer which melts at a preselected temperature to open circuit by surface preferred wetting; and ohmic contacts disposed to each side of said fusing layer and when said fusing layer material melts, it flows to said ohmic contacts.

Claim 21

A fusible resistor, the combination comprising: a substrate made of an electrically insulating material and having a pair of spaced termination points; a resistive film deposited on the surface of said substrate between said termination points; a fusible link deposited on said substrate in series connection with said resistive film to provide electrical continuity between said termination points, said fusible link including a fusing layer which melts at a preselected temperature to open circuit by surface preferred wetting; and ohmic contacts disposed to each side of said fusing layer and when said fusing layer material melts, it flows to said ohmic contacts.