Sheet metal wire connecting device

Abstract: A sheet metal wire connecting device has a wire receiving slot (42) for receiving a wire (5) and being defined by opposed beams (34). The beams (34) have fixed ends (36,38) and tapered sections between the fixed ends (36,38) and intermediate sections (40) of the beams (34). The tapered sections are angularly inclined towards each other, such that when a wire (5) is inserted into the slot (42), the intermediates sections (40) of the beams (34) are plastically deformed, the remainder of the beams (34), remaining generally below the elastic limit.

Description: This invention relates to a sheet metal electrical connecting device of the type having a wire-receiving slot for forming an electrical connection with a wire. There is described and claimed in EP-A-0 404 450 from which the present application has been divided, a connector assembly including a stamped and formed sheet metal connecting device for commonly connecting a plurality of wires, the device being of the type having wire-receiving slots for the wires, the slots having opposed edges which contact the wires upon movement of the wires laterally of their axes and into the slots, the device comprising two rows of U-shaped members, each U-shaped member comprising a bight and first and second arms extending from the bight, the U-shaped members of each row being in spaced-apart aligned relationship, the first arms in each row being coplanar and the second arms of each row being coplanar, adjacent U-shaped members in each row having opposed edges which define the wire-receiving slots, each row having first and second connecting sections which extend for the length of the row, the first and second arms of each U-shaped member having ends which are integral with the associated first and second connecting sections respectively, the first arms of corresponding U-shaped members in the two rows being opposed and proximate to each other,the second arms being remote from each other and facing outwardly in opposite directions, the two rows of U-shaped members being connected to each other by a web which extends from one of the connecting sections of one of the rows to the corresponding connecting section of the other row, and a molded insulating housing body is provided for covering the connecting device, the insulating housing body having openings which are in registry with the wire-receiving slots thereby to permit movement of the wires into the slots. The present invention is intended to provide a sheet metal electrical connecting device for forming an electrical connection with a wire, which device is of relatively small size but with which an extremely stable electrical connection can be obtained. The present invention consists in a sheet metal connecting device as defined in claim 1. Embodiments of the present invention are defined in the subordinate claims. Embodiments of the present invention will now be described, by way of example with reference to the accompanying drawings in which: Figure 1 is a perspective view, with the parts in exploded aligned relationship, of an electrical connector assembly; Figure 2 is a view similar to Figure 1 showing the parts assembled to each other; Figure 3 is a top plan view of a metallic connecting device of the assembly; Figures 4, 5 and 6 are views looking in the direction of the arrows 4-4, 5-5 and 6-6 of Figure 3; Figure 7 is a plan view of a flat stamped blank from which the connecting device is to be formed; Figure 8 is a top plan view of an insulating housing for the connecting device; Figures 9 and 10 are views looking in the direction of the arrows 9-9 and 10-10 of Figure 8; Figure 11 is a top plan view of the housing cover. Figure 12 is a side view looking in the direction of the arrows 12-12 of Figure 11; Figure 13 is a view of the underside of the cover looking in the direction of the arrows 13-13 of Figure 12; Figures 14 and 15 are sectional views looking in the direction of the arrows 14-14 and 15-15 of Figures 13 and 12, respectively; Figures 16 and 17 are computer-generated representations of portions of the connecting device which illustrate the manner in which the connecting device is flexed or deformed and which show the levels of stress in the connecting device when wires are inserted into the wire-receiving slots thereof. These views are not based on actual physical test data but are rather the result of a finite element analysis of the device, and Figure 18 is a perspective exploded view of an alternative connector assembly. As shown in Figures 1 and 2, a connector assembly comprises a stamped and formed connecting device 4, an insulating housing body 6, and a housing cover 8. The connecting device 4, Figures 3-7, comprises two rows of U-shaped members, 10,10' which are in side-by-side relationship with corresponding U-shaped members in the two rows in alignment with each other. The U-shaped members in the two rows are substantially identical and a description of one will suffice for both. The device is formed from a flat blank 11, Figure 7. Each U-shaped member has a bight 12 and first and second arms 14,16 extending from the bight. The first arms 14,14' in the two rows are opposed to, and proximate to each other and the second arms 16,16' are remote from each other and face in opposite directions. The first arms have their outer ends integral with a first connecting section 18 and the second arms have their outer ends integral with a second connecting section 20. The first connecting section 18 has spaced-apart notches 22 in its lower edge for cooperation with latching means on the housing cover. The two rows of U-shaped members are connected to each other by a flat web 24 which extends between the second connecting sections 20, 20'. An ear 26 extends from the web at one end of the device and has an opening therein for securing the device to a grounding surface. A dimple may be provided, as shown at 27, adjacent to the ear to stiffen the web in the vicinity of the ear. Each of the first and second arms has an oblong, generally oval-shaped opening 28 therein excepting the arms at the end which have openings 29. Each opening 28 has an upper end 30 and a lower end 32, the openings having a major axis which extends between the ends and a minor axis which extends transversely of the major axis. The major axis extends parallel to adjacent slots 42 (described below) and the minor axis extends transversely of the slots. The openings are somewhat irregular in shape and their configuration determines the manner in which the device is stressed, as will be described below. The openings define beams 34, each beam having fixed upper and lower ends 36, 38 and an intermediate portion 40. The fixed upper and lower ends are proximate to the bight 12 and the adjacent connecting section 18 or 20, respectively, and the beams extend somewhat laterally in their central portions towards the corresponding or adjacent beam of an adjacent U-shaped section. The opposed edges of adjacent beams 34 in adjacent U-shaped members 10, 10' define the wire-receiving slots 42. Each slot has a relatively wide entrance 44 and a relatively wide enlarged inner end 46. The intermediate portion 48 of each slot is relatively narrow and it is in this intermediate portion of the slot that the wire is held after it has been inserted. The U-shaped members at the ends of each row have openings 29 which are about one-half the size of the openings 28 which are provided in the intermediate U-shaped members. The U-shaped members at the ends of the rows have only one beam and it is preferable to reduce the size of the openings in order that the end U-shaped members will have maximum strength. The wire-receiving slots 42 between adjacent first arms 14, 14' are preferably more narrow in their central portions 48 than the slots between adjacent second arms 16, 16' so that the device will be capable of accommodating a range of wire sizes. In other words, the slots in the second arms may have a width such that contact will be established with a relatively heavier gauge wire than the slots between the beams of adjacent first arms. The oversized wires may overstress the beams in the first arms 14, 14' but such overstressing would not affect the electrical connection between the inserted oversized wire and the slots between adjacent beams in the second arms 16, 16'. The device can be produced in any desired size; however, where it is intended for use as a grounding connector for automotive wiring, it is desirable that the size be kept to a minimum. A connecting device in accordance with one embodiment of the invention, for example, has an overall height of only about 13mm and an overall length, including the ear, of only about 36mm. The material preferred for a connecting device of this size should preferably have a relatively high yield strength, for example, a beryllium copper alloy having a yield strength of about 96000 psi (6750 Kg/cm 2 ). The housing body 6, Figures 8-10, is molded of a suitable polyester material and comprises a plurality of E-shaped sections 50, each of which has a central leg 52, outer legs 54, and a transverse back member 56 from which the legs extend. The ends of the central legs are integral with a central frame or rib member 58 which extends for the full length of the housing between the end sections 60, 61 thereof. Relatively thin panel sections 62 (Figure 1) extend between the end portions of the outer legs and ribs 64 extend outwardly on the sides beyond these panel sections. Integral flexible arches 66 extend between adjacent ribs 64 and provide a wire supporting surface which is flexed, or deformed, when the cover member is assembled to the housing body in order to clamp the wires as will be described below. The central legs 52 have openings 68 extending centrally therethrough from their outer ends. These openings reduce the amount of material in the central legs and in the central rib and additionally permit the molding of integral retaining ears 70 which extend laterally over the space between adjacent E-shaped members. The ears function to retain wires in the housing member prior to assembly of the cover member to the body. The central legs also have latch ears 72 thereon which cooperate with the notches 22 of the connecting device in order to secure the housing body to the metallic connecting device. Additional latch ears 74 are provided on the end sections for cooperation with latch arms on the cover member. An integral trough-like cable retainer 76 is connected to the end section 61 by a connecting section 78 that has an opening 80 therein for a fastener. A wiring harness can be held in the retainer by a bundle tie or other means. When the device is placed in service, the metallic connecting device 4 is bolted or otherwise secured to a metallic grounding surface but it is also desirable to anchor the housing body 6 independently by means of a fastener so that if a force is applied to the harness which is received in the harness retainer, it will not be transmitted to the housing body but will be borne by the fastener in the opening 80. The housing cover 8, Figures 11-15, is generally rectangular and has an external surface 82, an internal surface 84, and sides 94. Latch arms 86 extend from the ends of the cover and have openings for cooperation with the ears 74 on the body portion. Transverse ribs 88 extend between the sides 94 on the internal major surface 84 and are contoured to provide wire stuffer sections 90 and wire clamping portions 92. When the device is placed in service, the wires are located in the entrance portions of the wire-receiving slots 42 and retained therein by the ears 70 as noted above. Thereafter, when the cover 8 is assembled to the molded body portion 6 of the housing, the stuffer portions 90 of the ribs 88 push the wires in the wire-receiving slots of the connecting device. At the same time, the clamping portions 92 of the ribs clamp the wires against the deformable arches 66 and provide a strain relief for the wires entering the wire-receiving slots. The flexible arches and the wire-clamping portions 92 of the ribs serve the added function of retaining the wires in predetermined locations in the wire-receiving slots; in other words, the wires are prevented from moving downwardly beyond a desired location in the slots which will produce optimum contact pressure as will be discussed below. Figures 16 and 17 are graphical representations which illustrate the behavior of the connecting device, and particularly the beams, when wires 5 are inserted into the wire-receiving slots. These views are not based on physical test data but are rather a result of a finite element analysis of the connecting device and the views themselves were originally produced by the computer. Figure 16 shows the manner in which the beams will be deformed, the wires 5 having been added to this view in order to indicate their positions. Figure 17 illustrates the deformation of two individual beams and indicates the actual stress level produced as a result of insertion of the wire. For the finite element analysis, it was assumed that the device was produced from a beryllium copper alloy having a yield strength of about 96000 psi (6750 Kg/cm 2 ). It can be seen from Figure 17 that the central portions of the beams are stressed at a level higher than the yield strength of the material and the metal in the central portions therefore has been plastically deformed and somewhat work hardened. However, the fixed ends of the beams are not stressed beyond the elastic limit of the material, although the stress at the upper ends of the beams in Figure 17 is somewhat higher than the stress at the lower ends and localized plastic deformation has taken place at the upper ends. The significance of Figure 17 is that it shows that, notwithstanding the relatively small size of the device, the contact force can be maintained by the elastically deformed portions of the beams as well as the plastically deformed central portions so that an extremely stable electrical connection will be obtained. The openings 28 and the beams may take a variety of forms depending upon the material thickness and its elastic limit and the dimensional limitations placed on the designer such as the maximum permissible height of the connecting device. Under many, or most, circumstances, the beams will extend arcuately from their ends to their central portions and the openings 28 will therefore be generally oval shaped but somewhat irregular as shown, for example, by the disclosed embodiment. When a particular connecting device is designed in accordance with the invention, the designer will choose the shape of the openings and fix the other variables such that the ends of the beams are stressed within the elastic limit of the material and material is highly stressed only in the central portions of the beams. Figure 18 shows an alternative connector assembly comprising a metallic connecting device 96, a housing body 98, and a housing cover 100. The connecting device 96 has a central web 102 which is integral with and extends between the first connecting sections 104, 104' of the first arms of the U-shaped devices or members. The ears 106 in this case are integral with and extend from the second connecting sections 108. The wires are clamped by means of surfaces 110 on the sides of the housing body and resilient clamping portions 112 of the cover. The cover is produced of a relatively firm hard plastic material but the clamping sections are overmolded of a softer material. Connector assemblies as described above are better adapted for stranded wires than most known types of wire in slot connecting devices for the reasons that the strain relief and clamping of the wire by the clamping ribs and arches maintain the strands of the wire in a compacted bundle and prevent migration of the strands, a phenomenon which results in a lowering of the contact force and a resulting increase in electrical resistance. Also, the high contact forces which can be achieved will produce a low resistance connection whether the wire is solid or stranded. Advantageously, the slots between the inner or first arms 14, 14' are more narrow than the slots between adjacent second or outer arms 16, 16' so that the connecting device is capable of making electrical connections to a range of wire sizes. For example, the slots between the first arms can be of a width such that they will receive wires in the AWG 18-20 range and the slots between adjacent second arms can be such that they will receive wires in the AWG 14-16 range. A benefit is achieved if the slots between adjacent outer second arms are wider than the slots between adjacent inner first arms in that the wider slots are closer to the mounting ear than are the slots between adjacent inner first arms. The heavier gauge wires which would be connected to the device in the wider slots would carry a higher current than would wires connected by the inner slots and it is desirable that the higher current have the shortest path to the ground connection through the ear. A connector assembly as described above can be produced at relatively low cost by simple manufacturing operations. The connecting device 4 is produced by simple stamping and forming operations and the plastic parts can be manufactured by injection molding operations with a straight action mold; that is, a mold which has all of its core pins extending in the same direction as the directions of the movement of the mold parts when the mold is opened and closed. There is no requirement for core pins which extend transversely of the directions of movement of the mold parts. The latter molding technique requires a more complex mold and is inherently an expensive manufacturing operation. The type of wire receiving slot used in the connecting devices, having the openings 28 which are on each side of the slot, can be used under circumstances other than those of the disclosed embodiment; for example, in a single plate-like member having a single slot. The portions of the plate-like member which are between the openings and the slot function as beams having fixed ends, the fixed ends being proximate to the wire entrance portion and the inner end of the slot. The beams extend from their fixed ends to their central portions, towards each other and have a controlled width as measured between the edges of the slot and the openings such that after insertion of the wire into the slot the beams are flexed by the wire, and contact forces on the wire are maintained by the flexed beams so that the plate-like member is otherwise essentially unflexed and unstressed.

Claims: A sheet metal connecting device for forming an electrical connection with a wire (5), the device comprising a plate-like member having a wire receiving slot (42), the slot having a wire-receiving end (44), an inner end (46), and a central portion, the slot being defined by opposed beams (34) having fixed ends (36,38) proximate the wire-receiving end (44) and the inner end (46) of the slot, the beams (34) being configured with tapered sections between the fixed ends (36,38) and the intermediate sections of the beams adjacent the central portion of the slot (42), the tapered sections being angularly inclined towards each other from the fixed ends (36,38) to the intermediate sections (40), such that upon insertion of a wire (5) into the slot, the intermediate sections of the beams adjacent the central portion of the slot are plastically deformed, with the stresses in the fixed ends (36,38) of the beams (34) adjacent the wire-receiving end (44) and the inner end (46) of the slot, and in said tapered sections remaining generally below the elastic limit. The sheet metal connecting device of claim 1, characterized in that the plate-like member has a wire-receiving end, the wire-receiving slot (42) extending into the wire-receiving end, the wire-receiving end (44) of the slot (42) and the inner end (46) being relatively wider than the central portion. The sheet metal connecting device of claim 2 characterized in that the plate-like member has a pair of substantially oval shaped openings (28) therein, one opening being provided on each side of the wire-receiving slot (42), each opening having a major axis which extends parallel to the slot (42) and a minor axis which extends normally of the slot, portions of the plate-like member which are between the openings (28) and the slot (42) comprising the beams (34).

Inventors: HAYES EARL JAMES, JOHNSON DANIEL LEN, MARTIN GALEN MONROE, SUMNER JAMES ELMO, HAYES,EARL JAMES, JOHNSON, DANIEL LEN, MARTIN,GALEN MONROE, SUMNER, JAMES ELMO
Applicants: WHITAKER CORP, THE WHITAKER CORPORATION
Application year: 1990
Main classification: H01R4
IPC codes: H01R4