Resistance welding fastener, apparatus and methods
AssigneeHowmet Aerospace Inc.
InventorsDonald J. Spinella, Daniel Bergstrom
Life of this patent
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Abstract
An apparatus and method for fastening dissimilar metals like steel and aluminum utilizes a steel rivet and a spot welding machine. The rivet and metals are stacked and the heat from the welder's electric current softens the lower melting point aluminum allowing the rivet to penetrate the aluminum and weld to the steel layer. The fastener may be used to join stacks with several layers of different materials and may be used to apply a threaded socket or stud made from steel or titanium to an aluminum or magnesium alloy structure. Layers of non-conductive materials like plastic and ceramics may also be affixed to a conductive layer using the fastener made from a compatible material that extends through a pilot hole.
Claims19
A method for fastening a first electrically conductive material to a second electrically conductive material using electrical resistance welding, comprising:
- placing the first and second materials together in physical and electrical contact, the first material having a lower melting point than the second material;
- placing an electrically conductive fastener with a cap having a downwardly extending peripheral lip and a shaft that is weldable to the second material in physical and electrical contact with the first material to form an electrically conductive stack inclusive of the fastener, the first material and the second material;
- wherein the shaft has a higher melting point than the first material;
- applying an electrical potential across the stack, inducing a current to flow through the stack and causing resistive heating, the resistive heating causing a softening of the first material to form a softened first material;
- while applying the electrical potential across the stack, piercing the softened first material with the fastener shaft by urging the fastener shaft through the softened first material toward the second material;
- after the fastener shaft contacts the second material, continuing to urge the fastener and apply electrical potential across the stack, compressing the shaft, welding the fastener to the second material and softening and collapsing the shaft until the peripheral lip contacts the first material,
- wherein the fastener cap is deformed from an initial configuration to a final configuration in which the peripheral lip captures and seals the material extruded therein from the first material during the steps of applying, urging, compressing, softening, collapsing and welding,
- wherein, in the final configuration, the fastener cap is deformed to conform to a shape of the material extruded therein,
- wherein, in the final configuration, the cap does not extend below an upper surface of the first material.
A fastener for fastening a first electrically conductive material to a second electrically conductive material using electrical resistance welding, comprising:
- a cap with a curved peripheral lip, and
- a shaft extending from the cap and having an end distal to the cap,
- wherein the fastener, when placed in a stack including the first and second electrically conductive materials and subjected to an electrical potential applied across the stack, is configured to conduct an electrical current that passes through the stack to cause resistive heating and soften the first material,
- wherein the first material has a lower melting point than the second material,
- wherein the shaft is capable of piercing the first material and welding to the second material at the end, and
- wherein the cap is configured to be deformed from an initial configuration to a final configuration in which the peripheral lip captures and seals material extruded therein from the first material,
- wherein, in the final configuration, the cap is conformed to a shape of the material extruded therein.
A fastener for fastening a first electrically conductive material to a second electrically conductive material using electrical resistance welding, comprising:
- a cap having a downwardly extending peripheral lip, and
- a shaft extending from the cap and having an end distal to the cap, the shaft having a hollow portion that diverges in a direction from the end to the cap,
- wherein the fastener, when placed in a stack including the first and second electrically conductive materials and subjected to an electrical potential applied across the stack, is configured to conduct an electrical current that passes through the stack to cause resistive heating and soften the first material,
- wherein the first material has a lower melting point than the second material,
- wherein the shaft is capable of piercing the first material and welding to the second material at the end, and
- wherein the cap is configured to be deformed from an initial configuration to a final configuration in which the peripheral lip captures and seals material extruded therein from the first material,
- wherein, in the final configuration, the cap is conformed to a shape of the material extruded therein.
Dependencies are inferred from the claim text.