Method Of Manufacturing Electrical Terminals

Abstract

Electrical terminals are manufactured by stamping, from sheet metal stock, a blank for the terminal, forming a hole in the blank which is spaced from an edge of the blank, and driving a punch through the hole in a manner such that the surface portions of the blank which separate the hole from the edge are reoriented so that they extend transversely of the plane of the blank. These surface portions are utilized as the contact surfaces of the terminal and are substantially greater than the surface area available for contact purposes on the edge of the blank.

Parent Case Text

This application is a continuation-in-part of our co-pending application, Ser. No. 716,491, filed Mar. 27, 1968, and now U.S. Pat. No. 3,503,036.

Description

BACKGROUND OF THE INVENTION

In the art of manufacturing electrical contact terminals by stamping and forming methods, it is common practice to either bend portions of the terminal blank to provide the contact surface or to utilize a sheared edge portion of the blank as a contact surface. Where a sheared edge is used as a contact surface, the amount of surface available is limited by the thickness of the stock metal from which the blank is formed. When the contact surface is formed by bending a portion of the blank relative to the plane of the blank, an extensive contact surface area can be obtained. Both of these methods of obtaining a contact surface in a stamped and formed terminal can be used only with relatively thick metal stock; if extremely thin stock were to be used for a terminal having a bent contact surface, the terminal would lack adequate strength and rigidity and an extremely thin stock does not provide an adequate surface area to permit the use of the edge of the blank as a contact surface.

The present invention is directed to the achievement of an electrical contact terminal which has a substantial contact area, relative to the thickness of the stock from which it is formed, and which does not require the previously known bending techniques to achieve this area. While contact terminals of any desired thickness can be made in accordance with the invention, the invention is particularly advantageous where it is desired to form terminals from extremely thin metal stock.

It is accordingly an object of the invention to provide an improved method of manufacturing electrical terminals. A further object is to provide a manufacturing method which permits the use of relatively thin metal stock in a contact terminal without the sacrifice of electrical contact area. A still further object is to provide a new method of forming a contact surface on a stamped electrical terminal.

These and other objects of the invention are achieved in a preferred embodiment thereof which is briefly described in the foregoing abstract, which is described in detail below, and which is shown in the accompanying drawing in which:

FIG. 1 is a perspective view of an electrical contact terminal having contact areas formed in accordance with the invention.

FIG. 2 is a fragmentary perspective view showing the tooling used to develop the contact area of the terminal of FIG. 1 and showing a strip progression of the stages in the manufacture of the terminal as it passes through a progressive die.

FIG. 3 is a fragmentary view on an enlarged scale of the end portion of one of the arms of a terminal blank, this arm including surface portions which become the contact area in the finished terminal.

FIG. 4 is a view similar to FIG. 3 but showing the end of the arm of the terminal after the contact area has been formed.

FIG. 5 is a transverse sectional view through the tooling shown in FIG. 2 illustrating the positions of the parts at the beginning of the contact surface forming operation.

FIGS. 6 and 7 are views similar to FIG. 5 but showing the positions of the parts at an intermediate stage of the forming operation and after completion of the forming operation respectively.

FIG. 8 is a view of the twisting punch which constitutes part of the tooling of FIG. 5.

FIG. 9 is a view taken along the lines 9--9 of FIG. 5 and showing the position of the terminal blank on the die insert prior to commencement of the twisting operation.

FIGS. 10 and 11 are views similar to FIG. 9 and illustrating the manner in which the contact surface is formed as the punches move through the holes 29 in the blank.

Referring first to FIG. 1, an exemplary terminal 2 in accordance with the invention comprises a yoke or web 4 having a pair of arms 6, 8 extending from its upper edge. A mounting post 10 extends downwardly from the lower edge of the yoke 4 and a pair of supporting feet 12, 14 are provided on each side of this mounting post. The mounting post 10 has a U-shaped cross section and is formed from material on each side of the center line of the connector.

Recesses 16 extend downwardly, as viewed in FIG. 1, into the yoke 4 adjacent to the arms 6, 8. In the disclosed embodiment, ribs 20 are embossed on these arms to control their stiffness and to ensure application, the contact portions of the terminal will engage the conductors on an inserted printed circuit board with an adequate contact force. Additionally, and where the terminal is stamped from extremely thin stock metal, these ribs function to maintain the arms in the same plane as the body portion of the terminal and prevent their being flexed laterally of the plane of the body portion. The ends 22 of the arms are of reduced width and are pointed as shown at 24 to facilitate the insertion of the connector into a connector housing of the type shown in our co-pending application. Ser. No. 716,491, now U.S. Pat. No. 3,503,036.

The arms 6, 8 are provided with contact surfaces 26 integral with their opposed edges. The contact surfaces of these arms are generally arcuate and are connected to the inner edges of the arms by connecting straps 28, 30. The contact surfaces 26 are spaced from the body portions of the arms by generally semi-circular openings 29 which are formed in a manner described below. The connecting straps 28, 30 have compound surfaces which may be described as being generally helical, that is, the type of surface which is generated if the ends of a relatively narrow strip of metal are grasped and twisted in opposite directions. As will be explained below, the contact surfaces 26 are provided by a forming operation which includes a degree of twisting of these straps. The cold working of the metal of the straps renders them extremely hard and strong, notwithstanding the thinness of the metal from which the terminal is made so that they are able to support the contact surfaces 26 rigidly with respect to the arms 6, 8. It will be apparent from FIGS. 1 and 6 that the contact areas 26 are relatively wide and are formed from stock metal which was originally located in the plane of the body portion of the terminal. The contact areas 26 are thus of a much greater extent than they would be if only the edges of the arms were utilized for contact purposes. Furthermore, these contact areas will be plated surfaces (when the terminal is formed from pre-plated stock) rather than sheared edges of exposed base metal.

The terminal of FIG. 1 can be manufactured from relatively thin metal stock 34 by stamping and forming operations which are performed on the stock as it passes through a progressive die. The progression 32, FIG. 2, thus shows the various openings that are punched in the stock and which define the areas or zones that ultimately become the parts of the terminal described above, the same reference numerals, differentiated by prime marks, being used to denote corresponding parts of the progression and the finished terminal.

During the final stages of the forming operation, the contact areas 26 of the finished terminal are formed in one of the final stages of the progressive die by punches 62, mounted in a punch holder 36, and by a die insert 38. It will be understood that the punch holder 36 and the insert 38 will be mounted on the upper and lower plates respectively of a die set which may be of the general type described in U.S. Pat. No. 2,422,775. Such die sets are mounted on the ram and platen of a punch press so that during each operating cycle of the press, the punch holder 36 will move relatively towards and away from the insert 38. The strip stock 34 is fed during each cycle a distance equal to the pitch of the strip by a suitable strip feed mechanism.

The insert 38 comprises a center block 40 and end blocks 42, 44 which are secured to the center block by suitable screws 45. Center block 40 has a central groove 46 extending across its upper surface to permit movement of the mounting post along the feed path of the strip and to facilitate the forming of the contact surfaces 26 as will be described below. Recesses 48 are provided on the sides of the center block 40 so that these recesses and the adjacent sides of the blocks 42, 44 define openings for reception of the punches 62.

The punch holder 36 comprises a center block 50 and end blocks 52, 54 secured to the center block by fasteners 55. The undersides of the end blocks have relatively shallow grooves 57 therein for the accommodation of the ribs 20 of the stock and the center block 50 has a relatively deep groove 56 therein, the sides of which are stepped as shown at 58. The center block 50 is also provided with vertically extending grooves 60 on its sides in which the punches 62 are slidably mounted.

It should be explained at this point that the composite punch holder comprising the blocks 50, 52, 54 is resiliently mounted by suitable springs (not specifically shown) on the upper plate of the die set and that the punches have a lost motion connection to the punch holder so that when the punch holder 36 moves towards, and into engagement with, the die insert 38, the lower surfaces of the punch holder are first moved against the insert and clamp the side portions 65 of the terminal blank as shown in FIG. 5. Upon further downward movement of the upper plate of the die set, the springs interposed between the punch holder and the upper plate will be compressed and the punches 62 will be moved downwardly to the positions of FIG. 7.

As shown best in FIG. 8, the punches each have a semi-cylindrical surface 66. The lower end of each punch is tapered to a chisel point as shown at 63 and 64 and flat surfaces of decreasing depth are formed by grinding the cylindrical surface 66 as shown at 70, 72 and 74, the surfaces 70, 74 extending parallel to the axis of the punch while the surface 72 is inclined towards the axis.

As shown in FIGS. 5-7 and 9-11, the contact surfaces 26 are produced, after the side portions 65 of the blank have been clamped, by the downward movement of the punches through the openings 29'. During such downward movement, the strap portions 28', 30' are twisted about their own medial planes while the surface portions 26 of the blank are being reorientated from the horizontal positions of FIG. 5 to the vertical positions of FIG. 7. This twisting operation is carried out progressively as the punches descent as a result of the movement of the tapered lower ends of the punches and the flat surfaces 70, 72, 74 on the sides of the punches through the holes 29. After the contact surfaces 26 have been formed as shown in FIGS. 7 and 11, the edges 76, 78 on each side of the surfaces 26 will be contained between the opposed surfaces of the sides 58 of groove 56 in the punch holder and the surface of the groove 46 in the insert.

A significant advantage of the invention is that a terminal of the type shown at 2, or many other types of terminals, can be manufactured from extremely thin metal stock without sacrifice of the contact area of the terminal. For example, terminals of the general type shown in FIG. 1 having an overall height (from the end of the post portion 10 to the ends of the arms) of about 0.700 inch can be manufactured from metal stock having a thickness of 0.008 inch. Notwithstanding the extreme thinness of the stock metal, the contact areas of such terminals are rigidly connected to the arms 6, 8 by the straps 28, 30 because of the fact that the metal in these straps is rigorously cold worked and hardened.

A further salient advantage of the invention is that none of the forming tooling comes into physical contact with the contact surfaces 26 during the forming operations. These surfaces are thus free from any tool marks and the plating on these surfaces cannot become damaged in any way.

Obvious modifications and alternative embodiments of the invention will be apparent to those skilled in the art. While the invention possesses substantial advantages in the manufacture of terminals from extremely thin metal stock, the principles of the invention can also be used to advantage where the terminals are of relatively heavy stock; the simplified tool which is used to form the contact surfaces is advantageous in that the need for making complex bends in the terminal is avoided. It is also feasible to use a single punch to form two contact surfaces by driving such a punch through a central opening between two edges. The principles of the invention can, of course, be used to produce terminals of a wide variety of shapes and it was not intended that the practice of the invention should be limited to the fork type contact shown or to fork type contacts in general.

Claims

What is claimed is:

1. A method of manufacturing an electrical contact terminal from thin sheet stock metal comprising the steps of:

stamping a blank from said stock metal having a web and at least one arm extending from said web,

punching an elongated opening in said arm, said opening extending in the direction of said arm and defining an isolated contact area which is connected to said arm by strap portions,

reorienting said contact area by turning said area out of the plane of said stock metal and concomitantly twisting said strap portion whereby,

said terminal is provided with a contact area of substantial extent on said arm, said area having a width which is substantially greater than the thickness of said stock metal and being formed of metal which originally was in the surface of said stock metal.

2. A method of manufacturing an electrical contact terminal from thin sheet stock metal comprising the steps of:

stamping a blank from said stock metal having a web and a pair of parallel arms extending from said web,

punching an elongated opening in each of said arms, said openings extending in the direction of said arms and defining isolated contact areas which are connected to said arms by strap portions,

reorienting said contact areas by turning said areas out of the plane of said stock metal and concomitantly twisting said strap portions whereby,

said terminal is provided with a contact area of substantial extent on each of said arms, each of said areas having a width which is substantially greater than the thickness of said stock metal and being formed of metal which originally was in the surface of said stock metal.