Patent Publication Number: US-4734063-A

Title: Radially resilient electric socket

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of our co-pending application Ser. No. 824,116, filed Jan. 30, 1986, now U.S. Pat. No. 4,657,335. 
    
    
     BACKGROUND OF THE INVENTION 
     In the above-identified parent application, there is disclosed one embodiment of a radially resilient electrical socket of the type sometimes referred to as a barrel terminal and a method for making the barrel terminal disclosed in that application. 
     In barrel terminals of the general type with which the present invention is concerned, contactor strips or wires are stretched and extend through the interior of a cylindrical sleeve from a first circumferential location at one end of the sleeve to a second circumferential location at the opposite end of the sleeve which is angularly displaced about the sleeve axis from the first circumferential location. A plurality of such strips so mounted within a cylindrical sleeve collectively lie on a surface of revolution of a generally hourglass shape whose diameter varies from a minimum diameter midway between the ends of the sleeve and a maximum diameter at the ends of the sleeve. When a cylindrical electric contact of a diameter intermediate the minimum and maximum diameters referred to above is axially inserted into such a barrel terminal, the contactor strips will collectively exert a radially resilient grip upon the contact. 
     Prior art barrel terminals have proven extremely difficult to manufacture. Generally speaking the terminals have either been designed to be formed from a single piece of material (see Bonhomme U.S. Pat. Nos. 3,396,364 and 3,641,483) or to be built up or assembled from parts which include a plurality of individual contactor strips or wires (see Bonhomme U.S. Pat. Nos. 3,557,428 and 4,203,647). Where the terminal is formed from a one piece member, several rather complex machining and forming steps are required, while the construction of a barrel terminal starting with individial contactor strips involves a painfully tedious assembly process. 
     In our aforementioned parent application, there is disclosed a barrel terminal which can be readily contructed on a mass production basis from four basic parts-namely a cylindrical sleeve, a stamped sheet metal blank and a pair of annular rings which can be readily assembled in five simple steps. 
     The present invention is directed to additional embodiments of barrel terminals employing the basic concepts disclosed in the parent case, together with improved techniques for assembling such terminals. 
     SUMMARY OF THE INVENTION 
     In common with the barrel terminal disclosed in our aforementioned parent application, the various embodiments of barrel terminals of the present application are all so designed that the contactor strips for each terminal are initially formed by stamping a flat sheet metal blank in a manner such that all of the contactor strips are integrally connected in fixed relationship to each other by one or more connecting webs. This enables all of the individual contactor strips to be manipulated as a single unit through the assembly process. 
     Various forms of contactor strip blanks are disclosed, together with assembly methods particularly adapted to the particular forms of blanks. 
     In all embodiments, the contactor strips are initially formed by a stamping operation which forms a flat metal blank with a plurality of spaced parallel elongate contactor strips connected to each other at or near one or both ends by a transversely extending connecting web integral with the strips. In one embodiment, the connecting web takes the form of a rectangular member with the contactor strips projecting perpendicularly from one edge of the member. In this particular embodiment, the rectangular member is then folded along a fold line parallel to the edge from which the contactor strips project into face-to-face engagement with the contactor strips and the folded blank is then formed into a cylindrical tube with the rectangular memeber at the outside of the cylinder to function as the cylindrical sleeve of the completed barrel terminal. 
     In another embodiment, a rectangular blank is stamped with connecting webs extending along two opposite sides of the blank and spaced parallel contactor strips extend from one connecting web to the opposite connecting web. Two versions of this particular embodiment are disclosed. In one of these versions, score lines are formed in one of the connecting webs. The blank is then formed into a hollow cylindrical tube and inserted into a close fitting cylindrical sleeve. The unscored connecting web is axially aligned with one end of the sleeve and welded to the sleeve, while the scored connecting web is projected axially from the opposite end of the sleeve. The scored web is then radially expanded to break the connecting web apart along each score line so that the projecting portions of the strip may in a subsequent step of the assembly process, be reversely bent around the end of the sleeve to lie flat against the exterior surface of the sleeve. 
     In a second version, both connecting webs are scored and so located as to project beyond both opposite ends of the sleeve. 
     In another embodiment, a sheet metal blank is stamped with a single connecting web extending transversely of and integrally joined to the elongate contactor strips at a location spaced inwardly from one end of the blank. 
     All of the various contactor strip blanks referred to above may, when stamped, be integrally connected to a carrying strip in uniformly spaced relationship so that the blanks may be successively advanced by the strip, in step by step movement to and through a series of work stations at which various assembly steps are performed. 
     Other objects and features of the invention will become apparent by reference to the following specification and to the drawings. 
    
    
     IN THE DRAWINGS 
     FIG. 1 is a top plan view of a sheet metal blank employed in constructing one form of barrel terminal according to the present invention; 
     FIG. 2 is a side elevational view of the blank of FIG. 1 formed into a cylinder; 
     FIG. 3 is a perspective view showing a close fitting cylindrical sleeve received upon the blank of FIG. 2; 
     FIG. 4 is a perspective view of a subsequent step in the construction of a barrel terminal from the blank of FIG. 1; 
     FIG. 5 is a perspective view showing the next subsequent step in the construction of a barrel terminal from the blank of FIG. 1; 
     FIG. 6 is a perspective view showing the next subsequent step in the construction of a barrel terminal from the blank of FIG. 1; 
     FIG. 7 is a perspective view of an assembled barrel terminal utilizing the blank of FIG. 1; 
     FIG. 8 is a cross-sectional view, with certain parts broken away or omitted, of an electrical connector employing the barrel terminal of FIG. 7; 
     FIGS. 9 and 10 are schematic diagrams illustrating the relationship of the longitudinal strips of a barrel terminal in their final assembled relationship; 
     FIG. 11 is a top plan view of a second embodiment of flat sheet metal blank employed in the construction of a first modified form of barrel terminal; 
     FIG. 12 is a top plan view showing the blank of FIG. 11 formed into a hollow cylindrical configuration; 
     FIG. 13 is a top plan view showing a cylindrical sleeve fitted onto the blank of FIG. 12; 
     FIG. 14 is a subsequent step in the manufacture of a barrel terminal from the bent blank of FIG. 11; 
     FIGS. 15, 16, 17 and 18 show further successive steps in the construction of a barrel terminal from the blank of Fig. 11; 
     FIG. 19 is a top plan view of another form of flat sheet metal blank for constructing another form of barrel termimal; 
     FIG. 20 is a top plan view showing an initial step in the assembly of the blank of FIG. 19 into a barrel terminal; 
     FIGS. 21, 22, 23, 24, and 25 show successive further steps in the construction of a barrel terminal from the blank of FIG. 19; 
     FIG. 26 is a top plan view of another embodiment of sheet metal blank for constructing a barrel terminal; 
     FIGS. 27, 28 and 29 show successive steps in the assembly of the blank of FIG. 26 into a barrel terminal; and 
     FIG. 30 is a view similar to FIG. 28 showing a variation in the method of assembling a blank of FIG. 26 into a barrel terminal. 
    
    
     FIGS. 1-8 show the successive steps in the assembly of a barrel terminal as disclosed in our aforementioned parent application Ser. No. 824,116, whose disclosure is hereby incorporated herein by reference. This disclosure is included in the present application to show the relationship between the blank and method disclosed in that application and those of the present application and the adaptation of a basic method to the assembly of barrel terminals of different structure. 
     A barrel terminal as shown in FIGS. 7 and 8 of the drawings is constructed by first forming a flat sheet metal blank, as by a stamping operation, into the configuration shown in FIG. 1. The blank, designated generally 20, is formed with a pair of transversely extending connecting webs 22 integrally joined to each other by a plurality of spaced parallel elongate contactor strips 24. A plurality of spaced parallel longitudinally extending tabs 26 extend outwardly from the outer edge of each connecting web 22. 
     In FIG. 2, the blank of FIG. 1 is shown formed into a hollow cylindrical tube which is then inserted into a close fitting hollow cylindrical sleeve 28 as in FIG. 3, with the tabs 26 projecting from the opposite ends of sleeve 28. 
     In FIG. 4, the next step in the assembly process finds the tabs 26 being bent over the respective ends of sleeve 28 to project radially outwardly from the sleeve. 
     In the next step a tight fitting annular ring or collar 30 is press fitted over one end of sleeve 28 to fixedly clamp the tabs 26 at that end in face-to-face engagement with the exterior of sleeve 28. 
     In the next step a hollow tubular tool 32 having circumferentially spaced teeth 34 is engaged between the radially projecting tabs 26 and rotated about the axis of sleeve 28 through a predetermined angle while sleeve 28 is held stationary. This angularly offsets the individual contactor strips 24 into a skewed relationship to the axis of sleeve 28, schematically illustrated in FIGS. 9 and 10, to cause the strips collectively to define a slightly concave hourglass shaped envelope in the interior of sleeve 28 in a manner described in more detail in our parent application Ser. No. 824,116. 
     In FIGS. 11-18, a modified form of barrel terminal is disclosed. In the embodiment of FIGS. 11-18, a flat sheet metal blank designated generally 20a is formed in a stamping operation in which the blank as formed is connected to a carrying strip 46 by a link portion 48. Strip 46 may be of indeterminant length and have successive like blanks 20a progressively stamped at spaced intervals as an elongate strip of sheet metal stock is fed through the stamping machine and advanced to carry the blanks 20a to and through a series of work stations. It will be appreciated that the location on the blank 20a which is connected to strip 46 may be varied in accordance with the tooling employed. 
     The blank 20a is formed with a single connecting web 22a having a plurality of spaced parallel contactor strips 24a projecting from one side edge of web 22a and a plurality of relatively short &#34;tabs&#34; 26a projecting from the opposite edge of web 22a. 
     After the blank is formed flat as shown in FIG. 11, it is then formed into a hollow cylindrical tube as shown in FWIGg. 12. 
     In the next assembly step shown in FIG. 13, a close fitting cylindrical sleeve 28a is slipped onto the tubular blank, the length of sleeve 28a being such that &#34;tabs&#34; 26a project axially from one end of the sleeve while the end portions of contactor strips 24a project axially from the opposite end of the sleeve. 
     In the next step, as shown in FIG. 14, the projecting ends of contactor strips 24a are bent from the position shown in FIG. 13 radially outwardly across the adjacent edge of sleeve 28a to project radially outwardly from the axis of sleeve 28a. A close fitting collar 30a is then press fitted onto the lower end of sleeve 28a, as viewed in FIG. 15, to bend the projecting ends of the contactor strips 24a into face-to-face engagement with the exterior of the sleeve to fixedly clamp the strips 24a to the sleeve at its lower end as viewed in FIG. 15. 
     The steps illustrated in FIGS. 11-15 may all be performed while the blank 20a remains attached to strip 46, and, as stated above, strip 46 may be employed to carry the components of the terminal being assembled from one work station to the next. 
     After the collar 30a has been press fitted as shown in FIG. 15, the assembly is severed from strip 46 and the upwardly projecting &#34;tabs&#34; 26a are then flared radially outwardly across the upper edge of sleeve 28a as viewed in FIG. 16, the tool 32 (FIG. 6) is then employed as in the previously described embodiment to angularly offset one end of the contactor strips 24a from the other as previously described, and after this offsetting step is performed, a second collar 36a is press fitted in place as described above to complete the assembly. 
     The embodiment of FIGS. 11-18 differs from the embodiment of FIGS. 1-8 primarily in that only one connector web 22a is employed and the flat metal blank which constitutes the contactor strips is formed integrally with a carrying strip 46. 
     Another embodiment of barrel terminal is shown in FIGS. 19-25. In this embodiment, as shown in FIG. 19, a flat sheet metal blank 20b is formed with a solid generally rectangular portion 50 having a plurality of spaced parallel contactor strips 24b projecting perpendicularly from one edge 52 of rectangular portion 50. The remaining three edges of rectangular portion 50 are identified respectively by reference numerals 54, 56 and 58. 
     The next step in the assembly of a barrel terminal from the blank 20b is illustrated in FIG. 20 and finds the rectangular portion 50 folded about a fold line 60 extending in adjacent parallel relationship to edge 52 through 180° into flat face-to-face engagement with one side of contactor strips 24b. As best seen in FIG. 20, the strips 24b project beyond the edge 56 of the folded rectangular portion 50. 
     The folded blank of FIG. 20 is then formed into a hollow tubular configuration as shown in FIG. 21 with the opposite side edges of rectangular portion 50, edges 54 and 58, located in face-to-face engagement with each other. The rectangular portion 50 of blank 20b has now been transformed into the equivalent of the hollow cylindrical sleeve 28, 28a of the two previously described embodiments. An annular collar 30b is force fitted onto the lower end of the assembly as in FIG. 22. 
     The remainder of the assembly proceeds as in the previously described embodiments, with the projecting ends of strips 24b being bent radially outwardly (FIG. 23), then rotated by tool 32 (FIG. 24) and finally clamped to the exterior of the cylindrical sleeve by force fitting an annular collar 36b as in the previous embodiments. Although not so illustrated, it will be appreciated that the blank 20b of FIGS. 19-25 could be formed integrally with a carrying strip 46 as described above in connection with the FIGS. 11-18 embodiment. 
     Still another embodiment is illustrated in FIGS. 26-29. In this embodiment, a flat generally rectangular blank 20c is formed with connecting webs 22c extending along and constituting two opposed parallel edges of the blank. A plurality of spaced parallel contactor strips 24c are integrally joined at their opposite ends to strips 22c. Score lines 62 are formed in the connecting webs 22c to extend laterally across the webs between adjacent pairs of contactor strips 24c. 
     As in previously described embodiments, after the flat blank is formed it is rolled into a hollow cylindrical tube (FIG. 27) and inserted into a close fitting hollow cylindrical sleeve 28c as shown in FIG. 28. The axial length of sleeve 28c is such that the connecting webs 22c and adjacent end portions of contactor strips 24c project axially outwardly beyond the opposite ends of the sleeve. 
     The connecting web 22c at one end of sleeve 28c is then radially expanded to break the connecting web at each of score lines 62 so that the projecting portions of the contactor strips 24c and their attached segments of the now broken connecting web 22c may be flared radially outwardly across the adjacent end edge of sleeve 28c. A collar, now shown, is then force fitted onto that end of the sleeve 28c as in the previous cases. 
     The connector web at the opposite end of sleeve 28c is then similarly radially expanded to segment the connecting web and the projecting portions bent radially outwardly across the edge of sleeve 28c. The rotating tool 32 of the previously described embodiments is then employed to angularly offset this end of the connector strips and a second collar, not shown, is force fitted to clamp the strips in face-to-face engagement with the exterior of sleeve 28c. 
     Still another embodiment is illustrated in FIG. 30. In the embodiment of FIG. 30, a blank 20c as illustrated in FIG. 26 is formed, rolled into a hollow cylindrical configuration and inserted within a close fitting hollow cylindrical sleeve 28d. In the embodiment shown in FIG. 30, the lower edge of the inserted blank 20c is lined up with the lower edge of sleeve 28d. The sleeve and blank are then welded to each other along their adjacent edges as at 64. It is not necessary in this particular embodiment that the lower connecting web 22c be scored. The connecting web 22c at the upper end of the assembly of FIG. 30 is then radially expanded, flared, rotated and clamped by a collar as in the embodiment of FIGS. 26-29. 
     The metal from which the various flat metal blanks are stamped is preferably a beryllium copper alloy which has both mechanical and electrical properties well suited to this particular application. It will be appreciated that the overall dimensions of barrel terminals made in accordance with the present invention will vary in accordance with the specific application. A typical terminal may have an axial length of about one inch with an internal diameter of the cylindrical sleeve being approximately one half inch. For terminals of these dimensions, a rotary offset, produced by the use of the tool 32, of approximately 15 to 20 degrees between the circumferential position of one end of a contactor strip to the other, will result in a reduction in the internal radius between the midpoints of the contactor strips of about 30 to 40 one thousandths of an inch. The properties of the beryllium copper alloy are such that the metal will set at the angular displacement produced by operation of the tool 32, while the contactor strips possess sufficient resilience to clamp an inserted cylindrical contact quite firmly while accommodating manual insertion or withdrawl of the contact from the barrel terminal. 
     While various embodiments of the invention have been described, it will be appreciated that the embodiments which have been described may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting, and the true scope of the invention is that defined in the following claims.