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US3722084A Expired / Lapsed US ⏱️ 0.0 years remaining

Method of making power resistors

Assignee: Individual

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Filing: 1971-09-23

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Granted: 1973-03-27

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Expires: 1991-09-23

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Abstract

Abstract A disc-shaped metal body or base of anodized aluminum has an upstanding central post, the body and post being centrally bored to receive a bolt for stacking or mounting of the resistor. A ceramic wafer or washer is seated on the body and around the post, and has a resistive film provided on the upper surface thereof. The configuration of the resistive film is such that the temperature generated in the central region of the resistor, relatively adjacent the post, thus setting up a highly effective thermal gradient which maximizes the dissipation of heat from the resistor. Terminal lugs or leads connect to the resistive film and extend outwardly generally in the plane of the washer, there being a connection between each lug and the washer by means of a rivet the ends of which are embedded in thermosetting synthetic resin. All of the components are maintained protected from the environment by a mass of thermosetting synthetic resin which extends upwardly from the film and surrounds the post, the upper surface of the resin being flush with the top of the post and parallel to the bottom of the metal body, in order to permit stacking of the resistors. The body and/or central post incorporate undercut means to prevent axial and rotational movement of the resin relative to the body, despite high thermal and other stresses. In accordance with the method, the pre-assembled body and ceramic washer (bearing the resistive film) are mounted as inserts in a mold cavity the depth of which is approximately equal to the distance between the upper end of the post and the bottom surface of the metal body. Thus, despite the absence of a plug in the central bore in the post, no molding material enters such bore. Molding is effected by transfer molding, and the mold gate is disposed adjacent the parting line and also generally adjacent or above the ceramic washer. The terminal lugs or leads extend outwardly from the mold cavity through corresponding grooves or recesses located at the parting line.

Inventors

👤 R Caddock

Bibliographic Details

Application Number —

Jurisdiction US

Data Source google_patents

Last Synchronized 2026-11-08 13:37

CPC Classifications

H; H01; H01C; H01C17/00; H01C17/02; H01C1/00; H01C1/08; H01C1/084; H01C1/14; H01C7/00; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49002; Y10T29/49082; Y10T29/49087; Y10T29/49101

Claims Analysis

Total Claims: 13

Claim 1

Independent Claim 45 words

The invention as claimed in claim 1, in which said method further comprises providing not over a few thousandths of an inch clearance between said upper end regions of said post and said upper wall portion of said mold cavity during said transfer molding step.

Claim 2

Dependent Claim 67 words

The invention as claimed in claim 1, in which said method further comprises causing said mold cavity to have a lower wall parallel to said upper wall portion thereof, and causing the distance between said upper wall portion and said lower cavity wall, during molding, to be substantially equal to the distance between said upper end regions of said post and said lower surface of said base.

Claim 3

Dependent Claim 136 words

The invention as claimed in claim 3, in which said method further comprises defining said mold cavity by means of an upper mold element and a lower mold element adapted when said mold cavity is empty to meet at a parting line intermediate said upper mold wall portion and said lower mold wall, and in which said method further comprises causing the distance between said upper end regions of said post and said lower surface of said base to be greater than the distance between said upper wall portion and said lower mold wall when said upper and lower mold elements are in contact with each other, the amount greater being not over a few thousandths of an inch whereby to prevent outflow of resin through said parting line between said upper and lower mold elements.

Claim 4

Dependent Claim 117 words

The invention as claimed in claim 3, in which said method comprises defining said mold cavity by means of an upper mold element and a lower mold element adapted when said mold cavity is empty to meet at a parting line intermediate said upper mold wall portion and said lower mold wall, and further comprises providing first and second terminal conductors in electrical contact with the terminals of said current-carrying component, causing said conductors to extend radially outwardly and generally parallel to said lower surface of said base, and causing the outer portions of said conductors to be disposed snugly in recesses in at least one of said upper and lower mold elements during the molding operation.

Claim 5

Dependent Claim 29 words

The invention as claimed in claim 1, in which said method further comprises employing as said thermosetting synthetic resin a thermosetting silicone resin containing very short particles of fiber.

Claim 6

Dependent Claim 61 words

The invention as claimed in claim 1, in which said method further comprises employing as said metal base and post an integral part formed of aluminum and anodized, said part being shaped to cause interlocking with said synthetic resin whereby to prevent movement of said synthetic resin relative to said base and post as the result of mechanical or thermal stresses.

Claim 7

Dependent Claim 27 words

The invention as claimed in claim 1, in which said method further comprises employing as said current-carrying component a film-type resistor adhered to an insulating ceramic wafer.

Claim 8

Independent Claim 125 words

A method of manufacturing an environmentally-protected film-type power resistor, which comprises: providing on the upper surface of an electrically-insulating and heat-transmissive planar wafer a film of resistive material, providing a metal base having planar upper and lower surfaces, disposing the lower surface of said wafer on the upper surface of said base in effective flatwise heat-transfer relationship thereto, disposing the thus-assembled wafer and base in a mold cavity, and transfer molding a thermosetting synthetic resin into said mold cavity above said base by injecting said resin through a gate disposed in a plane located at an elevation at least substantially as high as that of said wafer, whereby the hydraulic forces incident to said transfer molding step do not separate said wafer from said base.

Claim 9

Dependent Claim 63 words

The invention as claimed in claim 9, in which said method further comprises providing on the upper surface of said base an upwardly-extending tubular post which extends through a hole in said wafer, and causing the upper end of said post to substantially engage the upper wall of said cavity whereby to prevent inflow of synthetic resin into the opening in said post.

Claim 10

Dependent Claim 82 words

The invention as claimed in claim 9, in which said method further comprises causing the wall of said cavity adjacent the peripheral edge of said base to correspond substantially to the size and shape thereof, whereby to prevent flow of resin between the peripheral edge of said base and the wall of said cavity or between the lower wall of said cavity and the lower surface of said base, whereby said base may be mounted in effective heat-transfer contact with a chassis.

Claim 11

Dependent Claim 23 words

The invention as claimed in claim 11, in which said method further comprises causing said peripheral edge of said base to be circular.

Claim 12

Dependent Claim 114 words

The invention as claimed in claim 9, in which said method further comprises connecting termination conductors to said resistive film, causing said conductors to extend outwardly from said film generally in the plane thereof, defining said mold cavity by means of upper and lower mold elements having a parting line located adjacent the plane of said film, and causing at least one of said upper and lower mold elements to have, at regions adjacent said parting line, recess means adapted to snugly receive said conductors, whereby said resin does not flow in excessive amounts around said conductors during the molding operation, and whereby said conductors are readily removed from the mold after opening thereof.

Claim 13

Dependent Claim 52 words

The invention as claimed in claim 1, in which said method further comprises mounting an additional heat-transmissive metal base in said mold cavity above, and in heat-transfer relationship to, said current-carrying electrical component, said additional base having an upper surface which is substantially flush with said upper end regions of said post.

References Cited (Backward Citations)

US1531308A Cited

US2179566A Cited

US2844692A Cited

US2880296A Cited

US2960754A Cited

US3377414A Cited

US3541489A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1976-03-26	1976-09-25	1977-03-27	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1980-03-26	1980-09-25	1981-03-27	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1984-03-26	1984-09-25	1985-03-27	$7700.00	Window Closed / Lapsed

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