Terminal For Flexible Circuits

Abstract

A terminal for attachment to a flexible circuit, or flexible cable, serves releasably to receive a projecting male terminal in order to establish an electrical connection between the male terminal and the flexible circuit. The novel female terminal is formed as a unitary body of conductive metal having a generally planar portion together with a plurality of pointed tangs extending from the body. The tangs are adapted to be forced through the flexible circuit and then crimped against the circuit so that the terminal is attached to the circuit with a "stapling" action. The planar portion of the body is provided with a compact, effective contact structure including a series of slots defining two spaced generally parallel arms each of which is integral at both of its ends with the body. A pair of interfacing contact segments on the two arms are spaced apart from one another a distance such that the projecting male terminal is received with an interference fit. Upon insertion of the male terminal, cantilever movement of the contact segments and torsional stress in the contact arms produce firm contact between the contact segments and the projecting male terminal.

Description

The present invention relates to an improved terminal adapted to be attached to a flexible circuit for receiving a projecting male terminal.

Flexible circuits are formed of a thin layer or sheet of flexible, conductive metal of desired configuration sandwiched between thin insulating sheets or layers of flexible plastic or other material. The term "flexible circuit" as used herein is intended to encompass all such configurations including all types of more complex circuit configurations as well as relatively simple arrangements of one or several parallel conductors normally referred to as flexible cables.

Due to their thinness and flexibility, flexible circuits have advantages over conventional round wire cables and circuits. Potentially such flexible circuits could be used in place of discrete wires and wiring harnesses in many installations to reduce assembly costs, prevent miswiring errors, reduce space requirements and attain other advantages. However, adoption of flexible circuits in many instances has been prevented by the unavailability of suitable connectors or terminals for interconnecting the flexible circuits easily and reliably with other electrical components.

One known method of providing an electrical connection to a flexible circuit is to provide an uncovered region or conductive landing on the conductive layer and to clamp, press, solder or otherwise connect a conductive member against the conductive region. This approach is not satisfactory because of the cost of providing openings or landings at selected locations in the insulation layers and the cost of the connecting operations. Moreover, this approach is not well suited to automated assembly.

In order to overcome this difficulty, there have been proposed various terminal and connector devices intended to be attached to a flexible circuit for the purpose of permitting connections to other components. Devices of this type proposed heretofore have been subject to difficulties such as large size, low contact density, and the necessity for locating the terminal only at a predetermined location such as at an edge of the flexible circuit.

Important objects of the present invention are to provide a terminal for flexible circuits capable of being readily attached to any covered or uncovered region of the circuit either automatically or manually; to provide a terminal which is low in profile and small in size thus permitting high contact density; to provide a terminal having a female contact structure capable of providing reliable low resistance electrical connection to a projecting male terminal even after many insertions; to provide a terminal which can serve to support a flexible circuit on projecting male terminals and, moreover, which can leave projecting portions of these terminals uncovered for connection to other structure; and to provide a terminal capable of economical manufacture because close production tolerances, complex shapes, and expensive materials are not required.

Briefly, the above and other objects and advantages of the present invention are attained by providing a terminal in the form of a dish-shaped body fabricated of conductive metal including a generally flat, planar portion surrounded by a rim portion. Tangs formed as integral extensions of the rim extend generally normal to the planar portion of the body. In order to attach the body to either a covered or an uncovered portion of a flexible circuit, the tangs are forced through the circuit and crimped against the circuit thereby mechanically to mount the body on the circuit and moreover to establish an electrical connection between the metallic layer of the circuit and the body of the terminal.

In accordance with an important feature of the present invention the terminal is provided with an extremely small and low profile contact structure providing a reliable, low resistance electrical contact between the novel terminal and a projecting male terminal. The planar portion of the body is provided with slots or apertures defining two spaced parallel relatively narrow arms each of which is integral at both ends with the metallic body. Contact portions shorter than the arms are formed as integral lateral projections of the arms and extend toward one another to define a contact space narrower than the corresponding dimension of the male terminal to which a connection is to be made. When the male terminal is received in the contact space, an interference fit with the contact portions results in displacement of the contact portions due to twisting in the parallel arms and due to cantilever action of the contact portions.

The invention together with the above and other objects and advantages may be best understood from the following detailed description of an embodiment of the invention shown in the accompanying drawing, wherein:

FIG. 1 is a perspective view illustrating a group of female terminals each constructed in accordance with the principles of the present invention attached to a flexible circuit and serving to mount the flexible circuit on and to establish electrical connections to a group of male terminals associated with an electrical device;

FIG. 2 is an enlarged top plan view of a terminal constructed in accordance with the principles of the present invention;

FIG. 3 is a sectional view taken along the line 3--3 of FIG. 2;

FIG. 4 is a side elevational view of the terminal of FIG. 2; and

FIG. 5 is an end elevational view of the terminal of FIG. 2

Having reference now to the drawings, in FIGS. 2-5 there is illustrated a terminal generally designated by the reference numeral 10 embodying features of the present invention. In general, the terminal 10 is adapted to be attached to a flexible circuit 12 and to releasably provide an electrical connection between the flexible circuit 12 and a standard male electrical terminal 14. In accordance with important features of the present invention, the terminal 10 is provided with a novel female contact structure generally designated by the reference number 16 for reliably and releasably receiving the male terminal 14 even after multiple insertions and removals of the male terminal. Moreover, the terminal 10 includes a novel attaching structure generally designated as 18 with which the terminal 10 is attached to the flexible circuit. In combination the contact structure 16 and the attaching structure 18 provide a terminal 10 having many important advantages including small size, low profile, ease of attachment to the flexible circuit and ease of connection of the terminal with the male terminal 14.

Proceeding now to a description of the structure and use of the terminal 10, the terminal 10 preferably comprises a unitary metal body which may readily be formed in an automatic operation from sheet stock by means of suitable press operations. The terminal 10 includes a generally flat or planar body portion 20 surrounded by a continuous relatively narrow lip 22. The flat portion 20 and lip 22 cooperate to provide a generally dish-shaped configuration.

Referring now more specifically to the attaching structure 18, the terminal 10 is provided with a plurality of projecting tangs 24 formed integrally with the lip 22 and initially extending normal to the plane of the flat portion 20 as illustrated in FIGS. 4 and 5. The tangs 24 are generally triangular in shape and include pointed ends 26 to facilitate forcing of the tangs through the flexible circuit. In order to permit mounting or "stapling" of the terminal 10 reliably and firmly to the flexible circuit, preferably the tangs are arranged in opposed pairs. Although in the illustrated arrangement there are two opposed pairs, or a total of four tangs, it should be understood that other configurations could be used for particular terminal sizes and shapes.

As is well known to those skilled in the art, the flexible circuit 12 includes outer layers of insulating material 30 sandwiched around an internal conductive metallic layer 32. The circuit 12 is provided with an opening 33 over which the terminal 10 is located. Attachment of the terminal 10 to the flexible circuit 12 is accomplished by driving or forcing the tangs 24 through the flexible circuit 12 and by inwardly bending or crimping the tangs against the surface of the flexible conductor as shown in FIGS. 2 and 3. This attaching operation can readily be carried one either manually by means of a suitable pliers tool or automatically by means of suitable equipment. Each tang 24 penetrates the full thickness of the flexible circuit 12 and is bent inwardly against an outer layer of the circuit. Inward crimping of the tangs produces a slight flexing or bending of the flexible circuit as shown in somewhat exaggerated fashion in FIG. 3 in order firmly to hold the flexible circuit between the tangs 24 and the edge of the lip 22 as indicated by the reference numeral 28 in FIG. 3.

Electrical contact between the body of the terminal 10 and the metallic layer 32 occurs at the regions where the tangs 24 pierce the flexible circuit 12. The slight bending or flexing of the flexible circuit created by crimping of the tangs serves to provide a resilient spring contact between the metallic layer 32 and the tangs 24 sufficient to provide a large area, low resistance path for the flow of current between the terminal 10 and the metallic layer. It is not necessary for the pointed ends 26 of the tangs 24 to reenter the flexible circuit in order to provide sufficient electrical contact. However, if desired, the tangs upon attachment of the terminal 10 can be driven against an anvil of suitable configuration to produce such reentry. It also is not necessary that the terminal 10 be attached to an uncovered region of the metallic layer 32, and good contact is achieved upon both covered and uncovered regions.

Referring now more specifically to the contact structure 16 of the present invention, the flat portion 20 of the terminal 10 is provided with three slots or apertures 34, 36 and 38 serving to define two elongated narrow spaced arms 40 and 42. Each arm 40 and 42 is provided with a central contact portion 44 and 46.

As best shown in FIGS. 2 and 3, the contact portions 44 and 46 project from the arms 40 and 42 toward one another to provide a contact receiving space designated by the reference numeral 48. The distance between the contact portions 44 and 46 is selected to be smaller than the corresponding dimension of the terminal 14 with which the terminal 10 is to be used. Thus, upon insertion of the terminal 14, there exists an interference fit between the terminal 14 and the contact portions 44 and 46.

In order to facilitate both insertion and withdrawal of the terminal 14 and in order to permit insertion of the terminal 14 from either direction relative to the terminal 10, the contact portions are curved or rounded to present smooth curved surfaces 50 interfacing in the contact space 48.

As best seen in FIG. 2, the contact portions 44 and 46 are shorter in length than the arms 40 and 42 and are located substantially in the center of the arms 40 and 42. Thus, the arms 40 and 42 include end portions of relatively narrow width extending between the contact portions and the main body of the terminal 10. Upon insertion of the terminal 14 with an interference fit between the contact portions 44 and 46, the arms 40 and 42 twist as a torsional stress is placed upon the arms. Moreover, to some degree, the contact portions 44 and 46 serve as short cantilever beams placed in bending stress by insertion of the terminal 14. The overall effect of the torsional stress and the bending stress in the arms 40 and 42 and in the contact portions 44 and 46 is to provide a firm resilient biasing of the smooth curved surfaces 50 intimately against the terminal 14. In this manner there is provided a reliable low resistance electrical connection between the contact portions 44 and 46 and the surfaces of the terminal 14. Moreover, this reliable electrical connection is maintained even after many insertions and withdrawals of the terminal 14. It has been found that close production tolerances are not necessary since the contact design affords substantial variation in contact spacing while still providing good electrical contact. In addition, twisting and/or skewing of the terminal 14 in the terminal 10 does not interfere with the electrical connection.

The combination of the contact structure 16 and the attaching structure 18 provides a terminal 10 which is extremely small in size requiring only minimal area. As a result, high contact density is possible and the terminals 10 can be mounted quite close to one another. Moreover, the thickness or profile of the terminal 10 is small and adds only slightly to the thickness of the flexible circuit. In addition, the terminal 10 can be attached to any desired location on the flexible circuit and does not require removal of an insulating layer from the circuit.

As indicated in the somewhat diagrammatic illustration comprising FIG. 1, these several important advantages of the terminal 10 greatly facilitate the use of a flexible circuit with electrical devices or electrical equipment such as the electrical device 52 indicated in phantom in FIG. 1. It should be understood that the device 52 may comprise any electrical component such as a switching device, controlling device, appliance or the like including several projecting male terminals 14 arranged in any desired configuration. The flexible circuit illustrated in FIG. 1 and designated as 54 includes discrete conductive metallic layers 56 arranged in suitable configuration for connection to the plurality of male terminals 14.

Upon insertion of the several male terminals 14 of the device 52 into the several properly located terminals 10 supported by the circuit 12, the flexible circuit is self-supported upon the terminals 14 and no additional external supporting structure is required. The arrangement of FIG. 1 has several important advantages as compared with conventional discrete wire connections. The entire operation may be carried out automatically, and manual miswiring errors and the like are avoided. In addition, assembly costs are reduced and the space requirements for connection to the device 52 are minimized.

Another important advantage of the terminal 10 can be seen from FIG. 1. As there illustrated, each male terminal 14 projects well beyond each terminal 10 due to the minimal thickness or low profile of the terminal 10. This makes possible further connections to each male terminal 14. Thus, there is illustrated a releasable slip-on terminal 58 engaging the exposed portion of one terminal 14 which extends beyond the corresponding terminal 10.

Although the invention has been described with reference to details of the illustrated embodiment, it should be understood that the invention is not limited to the illustrated embodiment but rather is defined by the scope of the following claims.

Claims

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A terminal for releasably establishing an electrical connection between

1. a flexible circuit including a flexible conductive layer having an opening therein, and

2. a projecting male contact having a predetermined thickness;

said terminal comprising:

a dish-shaped body formed of flexible conductive metal and including a generally planar portion and a rim portion extending generally normal to said planar portion;

apertures in said planar portion forming a plurality of relatively narrow arms each integral at both ends with said body;

contact portions shorter than said arms formed as lateral projections of said arms and extending toward one another to define a contact space narrower than the predetermined thickness of the male contact;

and a plurality of tangs formed as integral extensions of said rim and extending in the same direction as said rim and generally normal to said planar portion, said tangs being adapted to be forced through the flexible circuit and crimped against the flexible circuit.

2. The terminal of claim 1, said contact portions being rounded in shape to form smooth contact receiving surfaces.

3. The terminal of claim 1, said tangs being generally pointed and triangular in shape.

4. The terminal of claim 1, said rim surrounding said planar portion.

5. A connection comprising a flexible circuit and a terminal adapted to receive a projecting male contact, said terminal comprising a dish-shaped body formed of sheet metal having a generally planar portion and a rim extending generally normal to said planar portion, a contact structure in said planar portion including apertures forming a plurality of relatively narrow arms each integral at both ends with said body, contact portions shorter than said arms formed as lateral projections of said arms and extending toward one another to define a contact space for receiving the male contact with an interference fit, and a plurality of tangs formed as integral extensions of said rim, said tangs extending through said flexible circuit and being inwardly crimped against said flexible circuit to hold said flexible circuit against said rim and to bend said flexible circuit toward said planar portion.

6. The connection of claim 5, the height of said rim exceeding the distance that said flexible circuit is bent toward said planar portion so that said flexible circuit is spaced from said contact structure.

7. The connection of claim 5, said flexible circuit including a central conductive layer sandwiched between insulating layers, said insulating layers being intact adjacent said tangs.

8. The connection of claim 7, said tangs extending through both said insulating and said conductive layers.

9. The connection of claim 5, further comprising an opening in said flexible circuit aligned with said contact structure.