Method of making flat cable

United States Patent [w]

Schilson

US006026563A [ii] Patent Number: [45] Date of Patent:

6,026,563 Feb. 22, 2000

[54] METHOD OF MAKING FLAT CABLE

[75] Inventor: Tom Schilson, Hamilton, 111.

[73] Assignee: Methode Electronics, Inc., Chicago, 111.

[21] Appl. No.: 08/627,136 [22] Filed: Apr. 3, 1996

[51] Int. CI.7 H01R 43/00

[52] U.S. CI 29/825; 156/47; 156/52;

156/55

[58] Field of Search 29/825, 850, 872;

156/52, 47

[56] References Cited

U.S. PATENT DOCUMENTS

3,168,617 2/1965 Richter 156/47 X

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3,523,844 8/1970 Crimmins et al 156/52

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3,802,974 4/1974 Emmel 156/55

3,810,304 5/1974 Heibye et al 156/47

4,197,154 4/1980 Pfaff, Ir 156/47 X

4,305,988 12/1981 Kocher 428/158

4,333,978 6/1982 Kocher 428/158

4,375,379 3/1983 Luetzow 156/52

4,400,227 8/1983 Riemersma 156/73.1

4,427,485 1/1984 Kutnyak et al 156/429

4,539,442 9/1985 Puis et al 179/115.5

4,659,872 4/1987 Dery et al 174/117

4,748,293 5/1988 Kikuchi et al 174/117

4,767,492 8/1988 Fukusima et al 156/580

5,250,127 10/1993 Hara 156/52

5,268,179 12/1993 Rudella 424/449

5,387,298 2/1995 Takagi et al 156/47

5,487,667 1/1996 Bolen 439/164

FOREIGN PATENT DOCUMENTS

709373 5/1967 Canada 156/52

1-82694 3/1989 lapan 29/850

4-56 011 2/1992 lapan 156/52

4-87219 3/1992 lapan 156/52

5-5932 1/1993 lapan 156/52

OTHER PUBLICATIONS

"Ultrasonics Responds to the Unique Application Considerations of Fabric and Film," Waves—Conversations in Ultrasonics vol. 3 No. 1 pp. 1-2.

Primary Examiner—Carl J. Arbes

Attorney, Agent, or Firm—David L. Newman

[57] ABSTRACT

A flat electrical cable and a method of assembling a flat electrical cable is provided wherein the flat cable includes an upper layer having ribs protruding along its length and substantially parallel to one another, continuous substantially parallel and adjacent seams formed between and upper an lower insulator layer conductors between the upper and lower layer adjacent the seams and a pattern formed in the surface of the lower insulator layer. The present invention may have upper and lower polyester layers having copper conductors therebetween and the seams ultrasonically welded in order to provide flat electrical cable for various applications such as incorporation in an automobile clockspring.

12 Claims, 2 Drawing Sheets

1

METHOD OF MAKING FLAT CABLE

BACKGROUND OF THE INVENTION

The present invention pertains to flat cable and a method of making flat cable and, in particular, flat electrical cable with exposed conductors without adhesive residue.

Flat electrical cables are well known in the art having conductors sandwiched between two insulating layers. Flat conductor cable is known in the art having an upper insulator layer having an adhesive adhered to a first side of the upper layer and a lower layer of insulating material having an 10 adhesive adhered to a first side of the lower layer. A conductor or strands of conductors are placed between the upper and lower insulator layers and all three layers are secured together by the adhesive. However, use of adhesive to bond the layers is disadvantageous in that upon heating of 15 the adhesive, the conductors may float in the free flowing adhesive causing the spacing between the conductors to be inconsistent and non-parallel. Upon drying and attempted attachment of the flat cable to a component, the improperly placed conductor may not align with the conductive leads of 20 the component. The cable is to be attached to and the flat cable is unusable and must be discarded. Further, when the cable is stripped to expose the conductors for connection of the cable to a component, the conductors have an adhesive residue thereon which inhibits the conductive properties of 2J the conductor. Also, if any scrap material of the insulator layers is produced, the scrap may not be recycled due to the presence of the adhesive on the insulator layer.

Other bonding techniques are known in the art for bonding multiple layers such as ultrasonic welding. Generally 3Q ultrasonic welding has been used for spot welding with thermoplastic materials using a plunge mode. Ultrasonic welding using a continuous weld or a shear mode has only been known for welding metals. Therefore, the known methods of welding thermoplastic materials using ultrason- 35 ics did not provide for a continuous welded seam and the seam, therefore, does not have great pull strength. In the area of electrical cables, seams of great pull strength are required and the previously known welding techniques are not sufficient. Therefore, it is an object of the present invention to 4Q provide a flat electrical cable which is bonded without use of adhesives and provides for a continuous seam.

It is another object of the invention to provide a method of assembling a flat cable by bonding without using adhesives and to provide a continuous seam. 45

It is a further object of the present invention to provide a flat cable having exposed conductors without an adhesive residue.

It is another object of the present invention to provide a flat cable which has a pattern on one side of the cable in 50 order to reduce friction of that one side against other surfaces.

It is a further object of the present invention to provide a method of assembling a flat cable which allows for the recycling of waste materials and provides for a quick and 55 inexpensive method of manufacturing the flat cable.

It is a further object of the present invention to provide a method of manufacturing flat cable which may be tested by a vision system in order to ensure that a proper bond has been formed between the insulator layers. 60

It is another object of the present invention to provide a flat cable which allows for the exposure of the conductors without the use of grinding equipment.

SUMMARY OF THE INVENTION 65

A principal object of this invention is to provide a flat electrical cable comprising an upper insulator layer, a lower

2

insulator layer connected to the upper layer, a lower insulator layer connected to the upper layer along continuous parallel spaced-apart seams and an intermediate layer comprised of individual strands of conductors which lie adjacent and parallel to the seams and the conductors do not have an adhesive residue thereon. The upper layer may include a plurality of raised surfaces running parallel to each other along the length of the flat cable. The lower layer may be substantially planar and include a pattern formed on the majority of the surface of the lower layer. The upper and lower insulator layers may be polyester. The conductors may be copper. The seams may be ultrasonically welded. The conductors may be exposed at an end portion of the flat cable beyond the upper and lower insulator layers. The cable may include a continuous seam except for a nonbonded area where the upper and lower insulator layers are not connected. The cable may include a continuous seam except for a nonbonded area where the upper and lower insulator layers include windows that expose the conductors.

In another embodiment of the invention, a flat electrical cable is provided comprising an upper layer of polyester having a ribbed surface, a lower layer of polyester connected to the upper layer along continuous parallel spaced-apart ultrasonically bonded seams and individual strands of copper conductors lying substantially parallel and adjacent to the seams between the upper and lower layers. The lower layer may have a pattern along the majority of its exposed surface.

In another embodiment of the invention, a clockspring is provided for electrically connecting an airbag in a steering wheel of a vehicle through a steering column to crash sensors, the clockspring comprising a housing having an inner chamber and a flat electrical cable including an upper insulator layer, a lower insulator layer connected to the upper layer along continuous parallel spaced-apart seams and an intermediate layer comprised of individual strands of conductors which lie adjacent and parallel to the seams and the conductors do not have an adhesive residue thereon, the flat electrical cable being mounted in the chamber of the clockspring.

A method of assembling a flat electrical cable is provided comprising the steps of feeding an upper and lower layer of insulator material and an intermediate layer of conductors simultaneously between a rotary horn and a rotary anvil, wherein the rotary horn operates via a shear mode and ultrasonically bonding the upper and lower layers together along a seam substantially parallel and adjacent the conductors. The rotary horn may be a full horn. The rotary anvil may include a series of grooves and protrusions corresponding to the arrangement of the conductors oriented between the insulator layers wherein the insulator layers are compressed between the protruding portion and a weld surface of the rotary horn in order to form the seams. The insulator layers may be a polyester material and the conductors copper. The rotary horn may include a weld surface having a pattern. The rotary anvil may be formed in order that the insulator material is not ultrasonically welded to the conductors. The method may include the additional steps of periodically stopping the ultrasonic welding operation to provide for nonbonded portions of the flat electrical cable. The method may further include the steps of cutting the flat cable into individual lengths and stripping the ends of the cable. The stripping of the end of the cable may be accomplished by inserting the end into a rotary grinding machine to remove the upper and lower insulator layers to expose a width of the conductors and removing the excess end portion of the cable to leave the conductors protruding beyond the