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Publication numberUS3783242 A
Publication typeGrant
Publication dateJan 1, 1974
Filing dateApr 25, 1972
Priority dateApr 25, 1972
Publication numberUS 3783242 A, US 3783242A, US-A-3783242, US3783242 A, US3783242A
InventorsD Barnard
Original AssigneeSmith Industries Ltd
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrical connections using discrete, electrically-conductive particles
US 3783242 A
Abstract
An electric heater for a rear windscreen of a motor vehicle including a heater element constituted by a thin strip of electrically resistive material and a pair of terminals clamped to respective ends of the element, has discrete electrically-conductive particles disposed between the ends of the element and the terminals to establish electrical connection therebetween. The strip is coated on one surface with a layer of adhesive to facilitate mounting of the element on the windscreen, and the particles adhere to the adhesive layer at the ends of the strip and impinge on the element through the adhesive layer.
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Description  (OCR text may contain errors)

United States Patent i191 111 83,242 Barnard Jan. 1, 1974 [54] ELECTRICAL CONNECTIONS USING 2,982,934 5/1961 Browne 338/309 X DISCRETE, ELECTRICALLY-CONDUCTIVE 6&5 PARTICLES 3,529,074 9/1970 Lewis; [75] Inventor: Dominic Paul Edmund Barnard, 3,535,494 10/1970 Armbruster 219/543 X Witney, England Primary Examiner-Darrell L. Clay [73] Assignee. grrrliggnlgdustnes Limited, London, Att0mey wmiam D. Ha Vet a1 [22] Filed: Apr. 25, 1972 [57-] I ABSTRACT [21] R 5 ,7 w An electric heater for a rear windscreen of a motor 30 Foreign Application Priority Data vehicle including a heater element constituted by a thin strip of electrically resistive material and a pair of A 1971 Great mam396/U terminals clamped to respective ends of the element, [52] us Cl 219/546, 29/621 29/628, has discrete electrically-conductive particles disposed 174/84 C 338/309 339/276 T between the ends of the element and the terminals to [51 Im. Cl. 1105b 3/02 establish electrical connection therebetween- The Strip [58] Field of 7 4 88 R, 1 17 is coated on one surface with a layer of adhesive to fa- 2 9/541 54 543 549 522 338/309 32 cilitate mounting Of the element on the windscreen, 332; 29/628 610 619 621, 629; 339/276 R and the particles adhere to the adhesive layer at the 276 T ends of the strip and impinge on the element through v the adhesive layer. [56] References Cited 11 Claims, 4 Drawing Figures UNITED STATES PATENTS I 2,961,522 11/1960 Hammer 2l9/543 X ZZZ//////// SHEET 10F 2 PATENTEDJAH 1 I974 ELECTRICAL CONNECTIONS USING DISCRETE, ELECTRICALLY-CONDUCTIVE PARTICLES This invention relates to electrical connections and, more particularly, to methods of establishing electrical connections, and also to devices that include electrical connections.

A problem has been experienced in establishing a reliable electrical connection to a very thin conducting element, for example, to flexible metallic foil. It has been proposed that this problem may be overcome by clamping the element between two substantially rigid metal plates and by providing at least one of the metal plates with a plurality of sharp projections which bite into the surface of the conducting element. The connection so established is not entirely satisfactory in practice because the projections tend to tear the conducting element. Furthermore such a connection suffers from the disadvantage that expense is involved in the necessary preforming of the metal plate to provide the sharp projections.

It is an object of the present invention to provide a solution to the problem which is satisfactory in practice and which obviates the need for the preforming operation.

According to a first aspect of the present invention there is provided a method of establishing an electrical connection between a pair of electrically-conductive members by clamping the members to one another,

- characterised by the provision of discrete, electricallyconductive particles between the members.

Preferably the method includes the steps of coating one of the members with a layer of adhesive, and'of causing the particles to adhere to the adhesive layer.

According to a second aspect of the present invention there is provided a device that includes an electrical connection, comprising first and second electrically-conductive members, and discrete, electricallyconductive particles under pressure between the members to establish electrical connection therebetween.

Preferably the first member is coated with a layer of adhesive, and the particles adhere to this layer and impinge on the first member through the adhesive layer.

The adhesive may be a thermo-setting adhesive.

The particles may be of metal.

The first member may be a relaitvely thin conducting element.

The element may be clamped between the second member and a third electrically-conductive member, and, in such a case, a pad of resilient material may be interposed between the element and the third member.

According to a third aspect of the P esent invention there is provided an electric heater comprising a heater element in the form of a strip of electrically resistive material, a pair of terminals for establishing electrical connection to respective ends of the element, and discrete, electrically-conductive particles disposed under pressure between the element and each terminal.

Preferably the element is coated on one surface with a layer of adhesive to facilitate mounting of the element on a surface to be heated, and the particles adhere to the adhesive layer and impinge on the element through the adhesive layer.

The surface of the element remote from the adhesive layer may have bonded thereto a layer of electrically insulating material.

The element may be supported by a readily removable backing layer.

One form of electric heater, for a glass rear windscreen or a window of a vehicle, including an electrical connection in accordance with the present invention will now be described, byway of example, with reference to the accompanying drawings in which:

FIG. 1 is a partly-broken-away plan view of the heater;

FIG. 2 is an enlarged perspective view of part of a terminal for the heater;

FIG. 3 is an enlarged, exploded view of the terminal on the line III-III of FIG. 1 prior to final assembly of the terminal; and

FIG. 4 is an enlarged end view of the terminal after final assembly.

The heater of FIG. 1 is manufactured as follows. A rectangular laminated sheet, approximately 23% in (60 cm) long by 10 in (25 cm) wide and approximately 0.0015 in (38 pm) thick, is produced comprising a layer of aluminium foil bonded to a layer of plastics material film, for example, a polyester such as that sold in the United Kingdom under the Trade Mark MELINEX. Preferably the metal foil layer and the plastics film layer have similar thicknesses. The exposed surface of the aluminium foil layer (that is, that surface opposite the plastics film layer) is coated with a cross-linked, acrylic-based thermosetting adhesive coating, and a fairly thick sheet of backing paper or card having similar rectangular dimensions is then applied to this adhesive-coated surface. The backing is conveniently a polythene coated, silicone release, heavy Kraft paper which has a polished or smooth surface to render it readily separable from the aluminium foil and polyester film laminated sheet.

The so formed sheet is subjected to a stamping operation from the polyester film side (that is, the side opposite the backing paper). The pattern that is stamped is one of long narrow strip form such that the strip follows a sinuous path. As shown in FIG. 1, this sinuous path comprises four generally parallel sections of substantially similar longitudinal extent, the sections having respective pairs of parallel coextensive lengths 2 and 3, 6 and 7, 8 and 9, and 11 and l2 extending longitudinally of the said so-formed sheet. The lengths 2 and 3 of the first section are joined to one another at one end by a short end piece 4 and at the opposite end by an end piece 5 that continues on and forms the end piece at one end of the lengths 6 and 7 of the second section. The opposite ends of the lengths 6 and 7 are joined to one another and to one end of the lengths 8 and 9 of the third section by an end piece 10. Similarly, the opposite ends of lengths 8 and 9 are joined to one another and to one end of the lengths 11 and 12 of the fourth section by an end piece 13. The opposite ends of lengths l1 and 12 are joined to one another by an end piece 14 that continues on towards the first section where it terminates in a wider portion 15. An adjacent .is sufficient to pass wholly through both the aluminium foil and the polyester film and slightly into, but not through, the backing paper..-

Thus as shown in FIG. 1, the sheet of backing paper 20 supports adhesively only a long, narrow sinuous strip 22 (of aluminium foil 24 bonded to polyester film 26) after the remaining larger area residue (not shown) of the aluminium foil 24 and the polyester film 26 has been peeled away from the sheet of backing paper 20.

Another paper sheet 25 (only part of which is shown), having similar. dimensions to sheet 20, is coated on one side surface with a low-tack adhesive. This adhesive-coated surface is applied to the sheet 20 supporting the strip 22 so that the strip 22 is sandwiched between the sheets 20 and 25. The thickness of the sheet 25 is not very important although the thicker it is the more rigid support it will give to the strip 22 during installation (described below). The sheets 20 and 25 are formed with an M-shaped cut-out adjacent one corner in the vicinity of the end portions 15, 16 of the strip 22. These end portions and 16 are electrically connected to respective terminals 30 in the following manner.

The backing sheet is partially peeled away from said one corner to expose the strips end portions 15 and 16. Each of the adhesive-coated exposed portions 15 and 16 is impregnated with steel filings 27 which are sharp or have an irregular surface and which adhere to the adhesive coating (referenced 28 in FIGS. 3 and 4). The portion is then placed, filings downwards, within a respective short channel-sectioned brass member 31 (FIG. 2) so that the steel filings are in contact with a base 32 of the member 31 (see FIG. 3). The base 32 is slightly curved convexly to the interior of the channel, and is formed integrally with the terminal 30. A pad 33 of sulphur-free chloroprene rubber is placed upon the sheet above the base 32 and covered by a slightly bowed metal plate 34. The side walls of the member 31 are then bent over to clamp the two side margins of plate 34 and sandwich between the plate 34 and base 32, the pad 33, the sheet 25, the end portion 15 (and 16), and the steel filings adhesively attached thereto. The clamping pressure is such as to straighten both the base 32 and the plate 34 and press the steel filings 27 through the adhesive coating 28 into the aluminium foil 24 so as thereby to make a low resistance, electrical connection between the aluminium foil 24 of the strip 22 and the base 32 of the brass member 31 through the adhesive coating 28. The terminals are in the form of blade connectors.

The steel filings 27 are of a particular size such that in a sieve analysis carried out as detailed in British Standards Specification 1796:1952, all of the filings 27 pass through a No. 60 British Standard mesh (that is, a mesh having 60 apertures per inch) but not through a No. 200 British Standard mesh, and at least 45 percent of the. filings 27 pass through a No. 100 British Standard mesh but not through a No. 150 British Standard Mesh. Nos. 60, 100, 150 and 200 British Standard meshes, according to British Standards Specification 410:1969, have nominal aperture sizes of 250 m, 150 pm, 160 pm, and 75 pm respectively (that is to say when formed of wire cloth the preferred average wire diameter is approximately 160 am, 100 um, 71 um, and 50 pm respectively). The steel filings or chips are conveniently of a rustless or stainless steel, such as a steel within the En 56 range of British Standards Specification 970:1955, and that prior to filing has a Brinell 4 Hardness No. in the range 201 to 255. Preferably the steel is that known as 8.8. 9702En 56 AM/R which has between 12.0% and 14.0% chromium and no more than 0.12% carbon, 1.00% silicon, 1.50% manganese, 1.00% nickel, 0.75% sulphur, 0.045% phosphorus, 0.60% molybdenum, 0.60% selenium, 0.60% zirconium and 0.35% lead (the total of the last four constituents being no more than 1.00%).

Each terminal 30 is completed (see FIG. 4) by snapping a semi-rigid polyvinylchloride cover 35 on to the bent-over side walls of member 31 to cover them and the exposed portion of plate 34, and by adhesively attaching to the underside of the base 32 a pad 36 having its lower exposed surface treated with a contactadhesive.

The strip 22 is installed in a vehicle in the following manner so that the element constituted by its aluminum foil part 24 can be used as a rear glass windscreen (or window) heater. The interior glass surface is first cleaned with methylated spirit and allowed to dry. The backing sheet 20 is then peeled away from the strip 22 which is thus left adhesively mounted on the sheet 25. The strip 22 supported by sheet 25 is placed to the screen so that the low tack adhesive of the sheet 25 and the thermosetting adhesive 28 covering the aluminium foil part 24 of strip 22 contact the clean interior surface of the glass. The strip 22 and the terminals 30 are pressed firmly to the glass and adhere thereto by the adhesive on the strip 22 and on the pads 36. A check for good adhesion is obtained by viewing the exterior surface of the glass (that is, from the outside of the vehicle) to see that there are no air bubbles. The supporting sheet 25 is then stripped off starting at the corner furthest from the terminals 30, and torn off at the terminals whose edges may be used as cutters. A short electrical lead or wire having a female tag connector at one end connects one blade connector terminal 30 to an earth point on the vehicle body; and another, long, electrical lead or wire similarly connects the other blade connector 30 via a dashboard-mounted electric ON/OFF switch to a battery voltage point that is only energised when the vehicle ignition is ON. If desired a warning light can be fitted by wiring it between the side of the switch towards the aluminium heater element 24 and earth. Such a warning light can be incorporated in the apparatus sold by Smiths Industries Limited under the Trade Mark WARNALITE. Furthermore, the electric ON/OFF switch may be such as that described in US. Pat. No. 3,731,021.

When the installed heater is first used, the heat cures the thermosetting adhesive 28 to provide for pennanent installation of the heater, and the heater is then usable for demisting and defrosting purposes.

I claim:

1. An electric heater comprising a heating element which is of electrically resistive material in strip form and which has two ends and a pair of opposed surfaces, a coating of adhesive on one surface only of the said element to facilitate mounting of the said element'on a surface to be heated, a pair of terminals electrically connected to respective said ends of the element, each terminal comprising an electrically-conductive member, means clamping each said member to the said element, and discrete, electrically-conductive particles adhering to the said adhesive coating at the said ends of the element and disposed under pressure between each of said members and the said element impinging onto the said element through the said adhesive coating establishing electrical connection between the said members and the respective said ends of the element.

2. An electric heater according to claim 1, wherein the said adhesive is a thermo-set adhesive.

3. An electric heater according to claim 1, wherein the surface of the said element remote from the said adhesive coating has bonded thereto a layer of electrically insulating material.

4. An electric heater according to claim 1, wherein the ends of the said element are of enlarged width.

5. An electric heater according to claim 1, wherein the said element follows a sinous path.

6. An electric heater according to claim 1, wherein the said element is supported by a readily removable backing layer.

7. An electric heateraccording to claim 1, wherein the said adhesive coating extends over the whole of the said one surface of the element.

8. A method of establishing an electrical connection between'an electrically-conductive member and a thin electrically-conductive element which is to be supplied with electric current and which has a pair of opposed surfaces, comprising the steps of a. applying a coating of adhesive to one surface only of the said element,

b. applying discrete, electrically-conductive particles to a part of the said adhesive coating,

0. bringing the said member into contact with the said particles, and

d. clamping the said member and the said element together causing the said particles to impinge onto the said element through the said adhesive coating providing the said electrical connection between the said member and the said element.

9. A device that includes an electrical connection comprising a thin electrically-conductive element having first and second opposed surfaces, an electricallyclamping means includes a plurality of deformed projections carried by one of said members and engaging the other said member.

11. A method of forming an electric heater comprising the steps of p a. forming, from electrically resistive material, a heating element in strip form having two ends and a pair of opposed surfaces,

b. applying a coating of adhesive to one surface only of the said element to facilitate mounting of the said element on a surface to be heated,

c. applying discrete, electrically-conductive particles to the said adhesive coating at the said ends of the I element,

d. bringing a pair of electrically-conductive terminal members into contact with the said particles at respective said ends of the element, and

e. clamping each of the said terminal members to the said element causing the said particles to impinge onto the said element through the said adhesive coating providing an electrical connection between the said terminal members and the respective said ends of the element.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2961522 *Jul 30, 1957Nov 22, 1960Mayflower Electronics CorpHeating panel
US2982934 *Aug 27, 1956May 2, 1961Libbey Owens Ford Glass CoElectrically conducting glass unit
US3205299 *Mar 3, 1961Sep 7, 1965Hi Shear CorpConductive connector
US3387248 *Apr 23, 1965Jun 4, 1968Midland Silicones LtdFlexible electrical heating devices
US3529074 *May 7, 1968Sep 15, 1970Sierracin CorpExternal busbar system
US3535494 *Oct 4, 1967Oct 20, 1970Armbruster FritzElectric heating mat
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5213828 *Mar 25, 1992May 25, 1993Ppg Industries, Inc.Heatable windshield
US6615521 *Dec 13, 2000Sep 9, 2003Daktronics, Inc.Outdoor electrical display sign with an electrical resistance heater
US6840780Jul 26, 2002Jan 11, 2005Antaya Technologies CorporationNon-solder adhesive terminal
US20150181653 *Nov 2, 2012Jun 25, 2015Saint-Gobain Glass FrancePolymeric panel having an electrically conductive structure
DE4335524A1 *Oct 19, 1993Apr 20, 1995Blaupunkt Werke GmbhArrangement for attaching a flexible film to a printed circuit board
Classifications
U.S. Classification219/546, 174/84.00C, 439/879, 338/309, 29/877, 29/621
International ClassificationH05B3/84
Cooperative ClassificationH05B2203/016, H05B3/84
European ClassificationH05B3/84
Legal Events
DateCodeEventDescription
Feb 1, 2008ASAssignment
Owner name: INTERDYNAMICS, INC., NEW YORK
Free format text: TERMINATION OF SECURITY INTEREST;ASSIGNOR:BRIDGE HEALTHCARE FINANCE, LLC;REEL/FRAME:020442/0509
Effective date: 20071120
Apr 13, 2006ASAssignment
Owner name: BRIDGE HEALTHCARE FINANCE, LLC, AS AGENT, ILLINOIS
Free format text: SECURITY AGREEMENT;ASSIGNORS:INTERDYNAMICS TEXAS LP;INTERDYNAMICS HOLDINGS, INC.;INTERDYNAMICS, INC.;AND OTHERS;REEL/FRAME:017468/0061;SIGNING DATES FROM 20060405 TO 20060406
Aug 8, 1986AS02Assignment of assignor's interest
Owner name: INTERDYNAMICS, INC., 80 39TH STREET, BROOKLYN, NEW
Effective date: 19860728
Owner name: SMITHS INDUSTRIES LIMITED
Aug 8, 1986ASAssignment
Owner name: INTERDYNAMICS, INC., 80 39TH STREET, BROOKLYN, NEW
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:SMITHS INDUSTRIES LIMITED;REEL/FRAME:004600/0575
Effective date: 19860728
Owner name: INTERDYNAMICS, INC.,NEW YORK
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SMITHS INDUSTRIES LIMITED;REEL/FRAME:4600/575
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:SMITHS INDUSTRIES LIMITED;REEL/FRAME:004600/0575