Flat flexible cable terminal and electrical connection

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DESCRIPTIVE MEMORY.

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to apply for an INVENTION PATENT in the name of AMP INCORPORATED, a North American entity with address at Eisenhov/er Boulevard, Harrisburg,

Pennsylvania, United States of America for: AN ELECTRICAL CONTACT DEVICE FOR CONNECTION BY REC/LITING TO A FLAT CONDUCTOR OF A FLAT CONDUCTOR CABLE. (International Class KOI)

26.12.74 « 1 The present invention, due to Robert John

Kincaid and John Carl Asick, is concerned with electrical contacts and the electrical connections between electrical contacts and flat conductors of flat conductor cables.

From Spanish patent number 34-6906 it is known that an electrical contact for connecting by crimping to a flat conductor of a flat conductor cable does not include a housing having a grooved cross section comprising a core and two opposite side walls. The edges of the side walls are intended to pierce the insulation of a flat conducting wire from one surface of the wire and to be bent inwardly to make contact with a conductor of the conducting wire from the opposite surface of the wire. Each side wall is in the form of a pair of spaced teeth, each of which tapers to a free tip, which teeth define a narrowed space between them.

An advantage of this known contact is that it can be upset to the cable conductor without the need to remove insulation from the conductor or prepare the cable in any other way. Another advantage is that a plurality of contacts can be upset to closely separated conductors, since when they are upset

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- 2 days, the side walls of the contacts are flanged over the side edges of the respective conductors.

A disadvantage of this known contact is 5 that, in order to obtain a reliable connection, the sleeve must be pressed tightly onto the conductor.

If the thickness of the conductor or insulation varies, the crimped ferrule may only loosely fit the conductor. In other words, the known contact depends on the relative dimensions of the conductor and the cable insulation to provide a satisfactory connection.

The electrical contact of the present invention is characterized in that the apex of each narrowed space extends to the junction between the core and the respective side wall. This seemingly small modification allows an electrical connection to be made to the conductor of a flat conductor cable with less dependence on the conductor dimensions or the cable insulation. During an upsetting operation, portions of the conductor's side edges progressively meet in the narrowed spaces between adjacent teeth, such that in the finished connection, these portions are effectively wedged into the spaces. The side edges of the teeth

- 3 tees located next to the spaces bite into the wedged parts of the conductor to provide a reliable electrical and mechanical connection to the conductor, which is not

I sensitive to the variation in dimensions of the conductor 5 or cable insulation that can be expected from normal cable manufacturing techniques.

An embodiment of the invention is described below, by way of example, with reference to the figures in the accompanying drawings, in which:

Figure 1 is a perspective view of an electrical contact socket;

Figure 2 is a cross-sectional view of the bushing of Figure 1 supported on an anvil with a portion of a flat conducting wire disposed between the bushing and a die;

- Figure 3 is a cross-sectional view of the bushing of Figure 1 attached to a conductor of a flat conductor cable;

Figure 4 is a perspective view of the 20! bushing of Figure 1 attached to a conductor of a flat conductor cable;

Figure 5 is a longitudinal cross-sectional view of the upset connection of Figure 4; and

Figure 6 is a detailed plan view of the bushing of Figure 1 attached to a flat conductor.

As shown, an electrical contact 1 includes an open ferrule 3 for connection by crimping to a flat conductor 28 of a flat conducting cable 31. The ferrule 3 has a generally flat web 2 from opposite sides of which extend side walls, each in the form of a pair of teeth 4, 6. The teeth 4, 6 extend generally normally to the web 2 in the same direction, and each tooth is tapered, having a relatively wide base joined i

to the web 2 and a relatively narrow free tip 4a, 6a. The teeth 4, 6 of each pair are spaced apart and define between them a space 12, 14 which is narrowed, the apex of the narrowing extending to the junction between the web 2 and the respective side wall, as shown in Figure 1. The teeth 4, 6 of each pair are longitudinally offset relative to one another such that one tooth 4, 6 of each pair is aligned with a space 14, 12 between the opposite pair. Each tooth tip 4a, 6a is rounded, but has a sharp edge, and the flanks of the teeth also have sharp edges.

The soul 2 is formed with a raised corrugation 8 which extends longitudinally between the

- 5'26.12.74 pairs of teeth 4, 6. Channels 16 extend feral through the web 2. Each channel 16 extends over the corrugation 8 and partially along the inner surface of a tooth 4, 6.

The channels 16 have been advantageously formed by coining the surface of the web 2 and the inner surface of the teeth 4" 6 before bending the teeth out of the plane of the web 2. The coining operation not only produces the channels with sharp edges, but also work hardens the metal from which the bushing 3 is made, thereby stiffening the bushing. Therefore, the stiffened bushing 3 is self-supporting and can be stressed to a conductor without substantial support around the bushing 3.

Referring in particular to Figure 2, the bushing 3 is shown supported on an anvil 20. A rib 37, of generally trapezoidal cross-section, integral with and extending from the anvil, engages within the lower face of the corrugation 8. Opposite the anvil 20 and relatively movable toward and away from the anvil 20 is a die 22. The surface of the die includes a pair of arcuate surface portions 26, separated by a flat portion 27 aligned with the rib 37. Between the die 22 and the contact 1 there is a

- 6 I shown a part of a flat conductor cable 31 including a flat copper conductor 28 enclosed in a sheath 30 of insulating material. The flat conductor 28 has side edges 32, 34, and the width of the conductor, i.e. the dimension between the side edges 32, 34, is greater than the space between the pairs of teeth 4, 6.

During an upsetting operation, the die 22 moving towards the anvil 20 will engage the wire

31 and will propel the conductor 28 into the space between the pairs of teeth 4, 6. In other words, the tooth tips 4a, 6a will penetrate through the sleeve 30 adjacent to each side edge of the conductor, thereby bulging, compressing or deforming the portions 32a, 34a of the side edge 32, 34 immediately adjacent to the teeth (see Figure 7).

It has been found that when the bushing 3 is cut and press formed from a 0.0254 mm thick blank, the optimum radius for the tooth tips 4a, 6a is 0.127 mm, which allows penetration of the tips 4a, 6a through the sleeve 30 while, at the same time, preventing penetration of the tips into the conductor 28.

Thus, as shown in Figures 4 and 6, the parts 32a, 34a of the side edges are 26.12.74

- 7 formed inwards, but the parts 32b, 34b comprising cLidaa between the parts 32a, 34a and aligned with the spaces 12, 14 are not deformed inwards. In this way, the teeth 4, 6 imperatively grip the i

conductor 28, deforming conductor 28 inwardly at parts 32a, 34a.

A. As the teeth 4, 6 progressively penetrate the sheath 30 by virtue of their tapered shape, they gather or wedge a substantial length of the side edges 32, 34 of the conductor into the tapered spaces 12, 14. This gathering action causes the portions 32b, 34b to bow or buckle outwardly from the conductor 28 and enhances the inherent resiliency of the conductor material to bow outwardly into the spaces 12, 14 between the teeth.

• As shown in Figure 6, the edges of the teeth 4, 6 define relatively sharp corners that cut through the sheath 30 to establish multiple points of contact with the side edges 32, 34 of the conductor.

After the tooth points 4a, 6a have penetrated through the sleeve 30, they are applied to the arcuate surfaces 26 of the die 22, as the die 22 approaches the anvil 20. This causes the points to be beaded (see figure 3), to pe

- 8 26.12.74 penetrate through the sleeve 30 in order to engage the conductor 28 and press the conductor against the corrugation Θ The pressure of the teeth 4, 6 forces the material of the sleeve 30 into the channels 16 of the corrugation 8, causing the sharp corners of the channels to penetrate through the sleeve 30 and come into contact with the conductor 28, further establishing multiple points of contact between the bushing 3 and the conductor 28.

Since the teeth 4, 6 of each pair are longitudinally offset relative to one another, the tooth tips 4a, 6a will not engage or interfere with one another during the crimping operation. Furthermore, the staggered relationship allows at least one tooth tip 4a to be disposed opposite the space 14 which will press against the conductor 28 at a location immediately adjacent the portion 34b of the side edge 34 of the conductor. In this way, the pressure of the tooth tip 4a tends to flatten the conductor 28, wedging the joined parts 34b more closely into the narrowed space 14 and thus improving the electrical connection between the sharp corners of the teeth 6 and the lateral edge 34 of the conductor. The same occurs with the tooth 6 located opposite the space 12.

The finished connection resists separation26.12.74

- 9 tion of the conductor 28 of the imperative and tenacious grip of the teeth 4, 6 on the parts 32a, 34a of the conductor side edge, deformed inwards. The resulting electrical connection is originated by the contact of the teeth 4, 6 on the side edge 32a,

34a of the conductor. deformed inwards and over the additional portions 32b, 34b of the conductor side edges wedged into the spaces 12, 14. Likewise, the tooth tips 4a, 6a penetrate the insulating jacket to engage the conductor 28 and establish additional points of electrical contact. Sufficient upsetting pressure is obtained to establish the electrical connection without complete assurance of the extent of crushing of the teeth 4, 6. Variations in the thickness of the conductor 28 and the sheath 30 will have little effect on the variation in the upsetting pressure, because the safety in the total crushing of the bushing 3 to establish the desired electrical connection is reduced.

The projecting corrugation 8 of the web 2 provides a relatively raised surface against which the prongs 4a and 6a will press the conductor 28. In this way, the presence of the corrugation 8 further reduces the amount of crushing of the prongs necessary to create the gripping pressure.

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As shown in Figure 3, the teeth 4, 6 are flanged to project the tips 4a,

6a perpendicular to the curvature surface of the corrugation 8. In many upsetting cases, this is not always possible. However, if properly designed, the tooth tips 4a, 6a will always tend to project perpendicularly from the surface of the corrugation 8. This ensures that sufficient upsetting pressure is achieved without causing an excessive amount of tooth crushing.

The rib 37 prevents the crushing of the corrugation 8, when the dies are closed, as shown in Figure 3. The tooth tips 4a, 6a will press on the corrugation 8 and will also be compressed by the presence of the part 27 at the intersection of the arcuate parts 26 of the die surface. Although portion 27 terminates in spaced relation to the surface of corrugation 8, tooth tips 4a, 6a will nevertheless be sandwiched in compression between die surfaces 26 and corrugation 8. As shown more particularly in Figure 5, when the dies are closed, teeth 4, 6 will not only penetrate through sleeve 30, but will also forcibly press the teeth 4a, 6a against the sleeve 30.

26.12-74 parts of the conductor inside the channels 16.

The channels 16 are wide enough to receive the prong tips 4a, 6a therein, in conjunction with portions of the conductor 28. The sheath material 30 will also be extruded or otherwise accommodated in the channels 16, but the corners of the channels 16 will penetrate through the material to engage the portions of the conductor which are pressed into the channels by the prong tips.

10- The application, which corresponds to the one filed in the United States of America on January 9, 1974, under number 432,112, is entitled to the benefits of Article 51 of the current Industrial Property Statute.