US 3678451 A
A socket type contact for a fuse holder is provided with a plurality of resilient, fuse-terminal-receiving fingers, each of which are characterized by containing an embossment or knurled portion. The respective embossments on each of the resilient contact fingers are arranged to form a substantially linear contact surface for a fuse terminal that is adapted to be inserted between the contact fingers. The contact configuration thus defined affords a high pressure, line contact between the flexible fingers and a fuse terminal while at the same time enabling the terminal to be pivoted axially about the line contact without causing the fingers to move radially with respect to the contact body.
Description (OCR text may contain errors)
United States Patent Boliver [451 July 18,1972
 SOCKET TYPE CONTACT FOR A FUSE HOLDER  inventor: Vincent J. Bollver, Pittsfield, Mass.
 Assignee: General Electric Company  Filed: Dec. 7, 1970  Appl.No.: 95,660
51 mm H01rl3/l2 ,- FieltloiSearch ......339/256,258, 259, 262
[ 56] y References Cited I UNITED STATES PATENTS 2,490,317 12/1949 .Ostrak "aw/262R FOREIGN PATENTS OR APPLICATIONS 811,272 4/1937 France ..339/258 RR PrimaryyExaminer-Joseph H. McGlynn Attorney-Francis X. Doyle, Vale P. Myles, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman  ABSTRACT A socket type contact for a fuse holder is provided with a plurality of resilient, fuse-terminal-receiving fingers, each of which are characterized by containing an embossment or knurled portion. The respective embossments on each of the resilient contact fingers are arranged to form a substantially linear contact surface for a fuse terminal that is adapted to be inserted between the contact fingers. The contact configuration thus defined afl'ords a high pressure, line contact between the flexible fingers and a fuse terminal while at the same time enabling the terminal to be pivoted axially about the-line contact without causing the fingers to move radially with respect to the contact body.
7 Claim, 6 Drawing Figures Patgntml July 18, 1972 3,678,451
2 SheetsSheet 1 Patented July 18, 1972 3,678, 51
2 Sheets-Sheet 2 SOCKET TYPE CONTACT FOR A FUSE HOLDER It is well known to provide resilient clip-type holders for mounting the electrical terminals of cartridge fuses in operating position. For example, one such prior art clip-type fuse holder arrangement is shown and described in U.S. Pat. No. 2,458,5ll Harlow, which issued Jan. 11, 1949 and is as signed to the assignee of the present application. As illustrated in that patent, such prior art terminal clips are characterized by affording a conveniently accessible means for quickly placing a fuse in series in an electrical circuit, coupled with means for establishing a good high-pressure, line contact between the terminal clip and a fuse terminal that is adapted to be inserted into the clip. A disadvantage common to such prior art terminal clip arrangements is that they limit access to the terminal clips to one side thereof. In other words, the clips are designed to require side loading rather than axial or end loading. Moreover, as is the case with the apparatus shown in the above-identified patent, the close design tolerances of such prior art fuse clips require that the fuse be introduced to the clip within a narrow range of angular approaches, i.e., in order to properly secure a cartridge fuse in operating position in a pair of terminal clips, it was necessary with such prior art apparatus to carefully align the respective terminals on the fuse with both of the terminals of such a pair of fuse clips.
It is also known in the prior art to provide electrical contact terminals that are adapted to receive a plug-in terminal in an end-loading fashion. Common examples of such plug and socket terminal arrangements are to be found in the field of watthour meters, for example, where the blade terminals of a meter are plugged into resilient, end-loaded, jaws of terminals on a meter base. A U.S. patent disclosing a terminal illustrative of this type of meter socket is U.S. Pat. No. 3,152,857 Fisher, which issued Oct. 13, 1964 and was assigned to B & C Metal Stamping Company. As was the case with the fuse clip type of terminal discussed above, such meter socket terminals usually are characterized by providing a good line-contact with the blade of a meter terminal inserted therein. However, such meter socket arrangements have inherent disadvantages that make them unsuitable for use with heavy duty cartridgetype power fuses. One major disadvantages is that they rely exclusively on the structural resilience of the socket jaws to limit the range of distortion of the jaws that may occur when a terminal is inserted between them. In the normal application for which such meter sockets are designed, this limitation is acceptable because the simultaneous insertion of four or more relatively widely spaced blade-type terminals on a watthour meter into a plurality of such sockets, serves to prevent any of the individual socket jaws from being distorted beyond its range of resilience. Thus, the limits of elasticity of the jaws are not exceeded and the jaws are not destroyed or weakened in such applications, instead they continue to provide adequately strong electrical contact to assure a good conductive circuit. In the field of end-loaded power fuses, these inherent safety limitations are not present. In fact, the relatively large size of power fuses, coupled with the fact that only one terminal is inserted into a fuse holder contact at a given time, often results in very great torques being applied to the resilient jaws of a socket type fuse contact. Moreover, the terminals of such power fuses are normally cylindrical in shape so it is necessary to provide a socket type fuse holder contact that can receive a terminal of such configuration, and receive that terminal from a wide range of approach angles.
Of course, socket-type contacts have been used for fuse holders prior to the present invention. A typical contact of this type is illustrated in U.S. Pat. No. 3,471,816 Giegerich, which issued Oct. 7, 1969 and is assigned to the assignee of the present invention. Such prior art fuse contacts do not provide means for enabling a fuse terminal to pivot about a knurled, line contact in the manner afforded by my invention. Instead, in such contacts, the sidewalls of the contacts are substantially cylindrical and are designed to provide continuous engagement with a fuse terminal over most of their length. As is explained in detail below, fuse holder contacts constructed pursuant to my invention are superior to such prior art sockettype contacts for applications where fuse terminals are normally inserted into the contacts at different angles of approach.
It is a primary object of the present invention to provide a socket-type contact for a fuse holder that will overcome the afore-mentioned disadvantages of prior art fuse clips and socket type terminals.
Another object of the present invention is to provide a generally cup-shaped electrical contact for a fuse holder that affords a strong line-contact pressure point with a fuse terminal inserted therein.
A further object of the present invention is to provide an electrical contact for a fuse holder that enables a fuse terminal to be inserted therein from a wide range of different approach angles without destroying or weakening the inherent resilience of the flexible terminal-engaging fingers of the contact.
Yet another object of the invention is to provide an electrical contact for a fuse holder that has a plurality of flexible fingers each of which include an embossed portion about which a fuse terminal may be moved pivotally without mechanically stressing the fingers of the contact.
A still further object of the invention is to provide a generally cup-shaped contact for a fuse holder which embodies a plurality of flexible fuse-terminal-engaging fingers that are encased by a relatively non-resilient support member that limits the range of movement of the fingers and thereby limits the angular movement of a fuse terminal supported between the contact fingers.
In one preferred form of the invention, a generally cupshaped electrical contact for a fuse holder is formed by mounting a plurality of resiliently flexible, arcuately shaped fingers within a cylindrical contact housing. The resilient fingers are integrally formed with a spine portion, which in turn is fastened to the cylindrically shaped contact housing to maintain it in a predetermined position therein. The resilient fingers are formed to define a generally linear contact surface for a fuse terminal that is adapted to be inserted between them. This linear contact surface is spaced away from the side walls of the cylindrically shaped contact so that the fuse terminal may pivot about the linear surface without causing the side walls of the contact housing to be distorted. Therefore, a fuse terminal mounted in the contact member is free to move angularly about its linear axis within a predetermined limited range defined by the extend of movement of the flexible fingers of the contact within the rigid cylindrical backup portion thereof.
As the invention is described in greater detail below, additional advantages of it and further objects of the invention will become apparent to those skilled in the art.
Further description of the invention will be made with reference to the attached drawings, in which:
FIG. 1 is a side elevation view, partly in cross-section, of a socket-type contact for a fuse holder, shown mounted within such a fuse holder, and oriented with respect to a fuse terminal and a second fuse holder. The contact is constructed pursuant to one preferred form of the present invention.
FIG. 2 is a side elevation view, partly in cross-section, of a generally cup-shaped electrical contact, such as the one de picted in FIG. 1 of the drawing.
FIG. 3 is a top plan view of the contact illustrated in FIG. 2.
FIG. 4 is a side elevation view of one of the component parts of the contact illustrated in FIGS. 2 and 3 of the drawing, showing a flattened form of the resilient, eventually arcuately shaped, flexible contact fingers, prior to their assembly within the contact.
FIG. 5 is a side elevation view, partly in cross-section, of a second embodiment of the invention, wherein an electrical contact member analogous in function to the contact depicted in FIG. 2 and 3, is shown.
FIG. 6 is a side elevation view, partly in cross-section, of a portion of a contact similar to that shown in FIG. 5, illustrating still another embodiment of the invention.
Referring now to FIG. 1 of the drawing, there is shown a pair of fuse holder members 1 and 2, which are, respectively, adapted to receive a third fuse holder member 3 and hold it in water-tight, sealed relationship such that an electrical circuit completed by a cartridge-type fuse mounted in the member 3 is protected from moisture and ambient contamination when the fuse holder members I, 2 and 3 are assembled in operating position. Although it is not particularly important to an understanding of the present invention, it will be appreciated by those skilled in the field of underground power distribution that the fuse holder members 1-3 are modular components of a type that is finding common use in underground distribution systems. If a more detailed description of the structure or function of these member 1-3 is desired, reference may be made to U.S. Pat. No. 3,513,425 Arndt, which issued May 19, 1970 and is assigned to the assignee of the present invention.
In order to understand the instant invention, it need only be comprehended that the operating components of fuse holders 1 and 2 are substantially identical, and both of them contain a socket-type contact that is constructed pursuant to the teaching of my invention. Accordingly, such a contact is only shown in detail with respect to one of the fuse holder members 1. As shown in cross section in FIG. 1, the fuse holder 1 has a generally cup-shaped electrical contact member 4 mounted therein substantially concentric with its central axis. As explained in the afore-mentioned Arndt patent, the body of fuse holder 1 comprises an elastomeric insulating housing 5 that may be formed of Nordel, an elastomer commercially available from E.I. du Pont de Nemours & Company of Wilmington, Delaware, or any other suitable conventional insulating material. The contact member 4 is supported in the housing 5 by being screwed into a metal block 6 that is provided with a suitable threaded bore 6a, and that is fastened onto a cable 6b which is inserted into the housing 5 from its opposite end.
Since it is normally desirable to be able to remove the contact member 4 from the fuse holder 1 after it becomes worn, the contact 4 is provided with a notch 7 that is large enough to receive a screwdriver, or other conventional linemans tool, which may be used to exert a torque on the contact member 4, thereby forcing it to rotate in the threaded bore 6a from which it can be removed with a screwing motion. Of course, the notch 7 also afiords a convenient means for screwing the contact 4 into operating position. Thus, it can be seen that the contact member 4 can be, and normally is, formed as a component part entirely separate from the fuse holder 1 in which it is normally mounted in use. Therefore, aside from describing the orientation of the contact member 4 in its normal operating environment, in order to reveal some of the unique advantages inherent in its structure, the novel features of the contact member 4 will be described with reference to FIGS. 2-4 of the drawing, which depict the contact member 4 as a separate entity.
As can be seen in the enlarged view of the contact member 4, which is illustrated in FIG. 2, an electrically conductive insert member 8 comprising a spine portion 8a and a plurality of fingers 8b, each of which extend from one side of the spine portion 8a, is mounted within the cylindrically shaped walls of the generally cup-shaped contact member 4. In addition, the contact member 4 is provided with an integrally formed bolt portion 4a that is adapted to be screwed into the threaded bore 6a of a fuse holder, such as the fuse holder 1 illustrated in FIG. I. The spine portion 8a of insert member 8 is shaped to generally complement the inner surface 4b of the contact member 4 adjacent the outer edge thereof. This configuration may best be seen in FIG. 3 of the drawing, which depicts a top view of the assembly shown in FIG. 2. Pursuant to the invention, means for holding the spine portion 8a of the insert member 8 in a predetermined position within the cup-shaped contact member 4 are provided so that relativeimovement is prevented between these component parts when a fuse terminal is inserted between the resilient fingers 8b thereof. In some applications, a simple press fitting of the preformed insert member 8 into the cup-shaped contact member 4 may be sufiicient to hold these members in such a predetermined position; however, in the preferred embodiment of the invention, the spine portion 8a is mechanically crimped at a predetermined portions thereof, such as are shown at 9a and 9b in FIG. 3, so that the contact member 4 and the crimped portions 9a and 9b of spine portion 8a interengage to form cooperating holding surfaces that prevent relative movement of these two components. Of course, those skilled in the art will appreciate that spot welding or other suitable means may also be used to secure the spine portion 8a in a desired predetermined position with respect to cup-shaped contact member 4.
In order to provide the sought-after objectives noted above for the present invention, the resilient fingers 8b are arcuately shaped so that their ends are supported, respectively, by the spine portion 8a and a base portion of the wall surface 4b of contact member 4. Accordingly, the central section of each finger 8b is spaced inwardly in relationship to the inner surface 4b of the contact member 4. In addition, all of the resilient fingers 8b are substantially identical in length and are formed to have arcs of substantially equal radius; therefore, a generally linear contact surface is provided by their respective central sections 8c. This linear contact surface, that is defined by the central portions 8c of the fingers 8b, serves to provide a highpressure electrical contact for a fuse terminal, such as the fuse terminal 10 (shown in FIG. 1), when it is forced between the fingers 8b. In addition, since the respective sections 8c are spaced inwardly from the surface 4b of the walls of contact member 4, it can be seen that a fuse terminal, such as terminal 10 may be pivoted about the generally linear contact defined by the sections 8c, without appreciably moving the fingers 8b radially outward. Thus, a major objective of the invention is afiorded by allowing the terminal 10 to be forced into the resilient fingers 8b within a substantial range of approach angles, measured by the angular displacement from the central longitudinal axis of the contact member 4, without unduly bending the resilient fingers 8b. It has been found that, particularly in underground distribution systems where the space available for manipulating fuse holder modules, such as the holders 1-3 shown in FIG. 1, is relatively limited, such a desirable range of angular movement is most advantageous. In addition, it will be noted that the relatively rigid walls of contact member 4 back up and reinforce the resilient fingers 8b. Therefore, the range of angular movement afforded a fuse terminal 10 by the resilience of fingers 8b is limited by the strong walls of contact member 4, without placing a destructive burden on the terminal-engaging resilient fingers 8b. Accordingly, the chance of damaging these resilient fingers 8b is appreciably reduced and the life of the contact member 4 is extended even when it is subjected to relatively heavy abuse in field applications.
Before continuing with a description of other embodiments of my invention, some additional detailed description of the insert member 8 may be useful to a complete understanding of this preferred embodiment of the invention. It will be understood that any suitable electrically conductive material may be used to form the cup-shaped contact member 4 and the insert member 8. In the preferred embodiment of the invention, contact member 4 is formed of electrical grade copper, and insert member 8 is formed of a suitable phosphor bronze. Of course, other suitable electrically conductive, wear resistant and resilient materials may be used for these components in other embodiments of the invention. More specifically, referring to FIG. 4 of the drawing, the insert member 8 is formed from a flat sheet of metal stock 8 that is stamped to define the fingers 8b therein. Of course, such a configuration might be formed by suitably cutting a piece of metal stock or using other conventional metal forming techniques. It is only important to note that the resilience and mechanical strength of the fingers 8b must satisfy the load requirements encountered in underground distribution applications. Also, it is necessary to provide sufficient space between the fingers 8b to allow them to be bent inwardly to define their arcuate configurations, as shown in FIGS. 2 and 3, while maintaining a maximum contact surface for a fuse terminal that is adapted to be inserted therebetween. In the preferred embodiment of the invention, I have found that a desirable degree of arcing of the fingers 8b maybe obtained when each of the fingers is spaced from the fingers next adjacent to it by a distance measured at either end of the fingers that is at least as great as one-fourth the width of said finger. This relationship is shown in FIG. 4 where the width of one of the central fingers is identified as 4n, and the spacing between the fingers is designated as n".
In like manner, in order to assure optimum electrical contact between the fingers 8b and a fuse terminal 10, I have found that each of the fingers 8b should be spaced from the the spacing between the adjacent fingers is substantially less than one-quarter the width of any of the fingers 8b, as
desighatedby the identifying numeral 11, which indicates the minimum spacing between two adjacent fingers at the center section 80 thereof. g
As shown in FIG. j4, each of the fingers 8b is generally rectangular in configuration and in order to allow them to be arcuately shaped as shown in FIGS. 2 and 3, the fingers 8b are at leastfour times as long as they are wide. This relationship affords substantial radial movement of the central sections 8c of the fingers 8b with respect to the central axis of the cupshaped member 4 while providing fuse-terminal engaging fingers that are adequately resistant to distortion by twisting when the fuse terminal 10 is inserted between them. It will be appreciated that relatively thinner flexible fingers 8b may be suitable for some fuse holder applications; however, with the relatively strenuous mechanical forces applied by large power fuses of the type utilized in underground power distribution systems, the four to one relationship has been found to be a desirable minimum to assure an adequate life span for the resilientfingets 8b.
Turning now to FIG. 5, it will be seen that there is shown another species .of asocket-type contact for a fuse holder, constructed pursuant to the teaching of my invention. This contact also comprises a generally cup-shaped electrical contact member 4' having an integral threaded bolt portion 4a at its bottom end, which provides a holding means for maintaining the contact in operating position within a suitable fuse holder, such as the holder module 1 designated in FIG. 1 of the drawing. It will be understood that the contact member 4 may be substituted in such a fuse holder 1, in place of the contact member 4 illustrated in FIG. 1.
In this embodiment of the invention, the walls 4b of contact member 4 are divided into a plurality of flexible fuse-terminal-engaging fingers by suitable means defining a plurality of slots 12 in the walls of the contact member 4. It will be understood that any given suitable number of flexible fingers may thus be formed, but in this particular embodiment of the invention the.slots 12 are disposed at predetermined spaced points aroundthe circumference of the cup-shaped contact member 4' at diametrically opposed, equally spaced-apart points on the periphery thereof so that four substantially equal-sized, flexible fingers are formed in the walls 4b of contact member 4. Each of the slots 12 is long enough to extend from points respectively adjacent the bottom of the cupshaped contact member 4' to the outer edge 40 thereof. Each of the resilient fingers 13 thus formed has an inner surface that includes a first arcuately shaped section 4d adjacent the bottom of the cupshaped contact member 4 and also includes a second arcuately shaped section that incorporates a boss portion 4e therein. The apex 4 f of the boss portion 4e is positioned between the upper end of the first arcuate section 4d and the outer edge 40 of its respective resilient finger 13.
Since each of the slots 12 is substantially parallel to the longitudinal axis of contact member 4 the respective resilient fingers 13 will tend to be pivoted about their junction with the bottom of the cup-shaped contact member 4' when a fuse terminal, such as the fuse terminal 10 shown in FIG. 1, is forced between the fingers 13. The resilient bias of fingers 13 tends to maintain them in their initial cup-shaped configuration while allowing them to be moved in this pivotal manner radially outward to receive a fuse tenninal having a larger diameter than the innermost walls of the generally linear contact defined by the apex or knurled portion 4f of the boss portions 4e of the fingers. As can be seen from the cross section view of the boss portion 4e shown in FIG. 5, each boss portion 4e on the respective fingers 13 is a generally triangular cross section culminating in a knurled apex 4f that serves as an effective pivot about which a fuse terminal 10 may be pivotally moved to allow angular motion between the cup-shaped contact member 4 and a fuse terminal 10 without causing appreciable radial movement of the fingers 13. Thus, again in this embodiment of the invention, the advantageous objectives of the invention are attained since a contact member for a fuse holder is provided which allows the afore-mentioned angular movement of a fuse terminal while maintaining a good electrical line contact between the terminal 10 and the contact member 4.
A modified form of the species of my invention shown in FIG. 5 is illustrated by the drawing in FIG. 6, which is a sectional view of a cup-shaped contact member 4" that is substantially identical in all respects to the cup-shaped member 4 shown in FIG. 5, except for the novel configuration of the boss portion 4e on the fingers 13. Since it is apparent that each of the boss portions 4e need only have a sloping surface that extends inwardly from the outer edge 40 of the fingers 13' to the apex 4] of the boss portion 4e in order to afford an inclined surface for receiving a fuse tenninal between the fingers 13' which will cause these fingers to spread apart as a fuse terminal, such as terminal 10, is forced to slide along this sloped surface toward the bottom of the cup-shaped contact member 4", the boss portion 4e is truncated adjacent its apex 4f in this embodiment of the invention. Thus, rather than providing a generally triangularly shaped boss portion 4e, as depicted in FIG. 5, the boss portion 4e of the modification of the invention illustrated in FIG. 6 provides a generally open area within the cup-shaped contact member 4" below the apex 4 of the boss portion 4e, so that the amount of copper needed to form the contact member 4' is somewhat less than that required to form the contact member 4' illustrated in FIG. 5. It will be apparent to those skilled in the art that further modifications of my invention might be made without departing from the true spirit and scope of the invention which is described herein and is intended to be encompassed within the scope of the following claims.
What I claim as new and desire to secure by Letters Patent of the United States is:
l. A socket-type contact for a fuse holder comprising a generally cup-shaped electrical contact member, an electrically conductive insert member comprising a spine portion and a plurality of fingers extending from one side thereof, said spine portion being shaped to generally complement the inner surface of said contact member adjacent the outer edge thereof, each of said fingers being resilient and arcuately shaped with the ends thereof supported respectively by said spine portion and a base portion of the walls of said contact member, and the central section of each finger being positioned, in a spaced inwardly relationship from the wall of said contact member, whereby said central sections of said fingers are positioned to define a resilient, generally linear contact surface for a fuse terminal forced therebetween, said fingers being disconnected from one another at the ends thereof spaced farthest from said spine portion, and means for holding the spine portion of said insert member in a predetermined position within said cup-shaped contact member when a fuse terminal is inserted between said fingers, said disconnected ends of the fingers being spaced away from the bottom of said cup-shaped contact member, and the ends of the fingers supported by the base portion of the walls of said contact member being movable axially with respect to said walls in a direction away from said spine portion when a fuse terminal is inserted between the fingers.
2. An invention as defined in claim 1 wherein the spine portion and the fingers of said insert member are an integral part.
3. An invention as defined in claim 2 wherein said insert member is formed from a flat sheet of metal stock that is shaped to be force fitted into the cup-shaped space defined by said contact member.
4. An invention as defined in claim 1 wherein said means for holding includes mechanically crimped portions of said spine portion and said cup-shaped contact member that interengage to form cooperating holding surfaces.
5. An invention as defined in claim 2 wherein each of said fingers is spaced from the fingers next adjacent to it by a distance measured at either end thereof that is at least as great as one-sixth the width of said finger.
6. An invention as defined in claim 5 wherein each of said fingers is spaced from the fingers next adjacent to it by a distance measured at the center thereof that is less than onequarter the width of said finger.
7. An invention as defined in claim 5 wherein each of said fingers is generally rectangular in configuration and is at least four times as long as it is wide, thereby to afiord substantial radial movement of the central section of the finger with respect to the central axis of said cup-shaped contact member while providing fuse-terminal-engaging fingers that are resistant to distortion by twisting when a fuse terminal is inserted between them.