US 3562694 A
Abstract available in
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Description (OCR text may contain errors)
Feb. 9,1971 P. T. HOWE I 3,562,694
ELECTRICAL GROUNDING CLAMP Filed Jan. 26, 1970 I n L: s:::::' INVENTOR 0 51 PHILIP T. HOWE ATTORN EYS States Patent 3,562,694 ELECTRICAL GROUNDING CLAMP Philip T. Howe, 4939 Warsaw Drive, Jackson, Mich. 49201 Filed Jan. 26, 1970, Ser. No. 5,530 Int. Cl. H01r 7/08 U.S. Cl. 339-14 7 Claims ABSTRACT OF THE DISCLOSURE A clamp for temporarily grounding an electrical terminal, which may be remotely operated by insulated means, if desired, utilizing an elongated head having terminal engaging portions located at its ends, and a movable clamping element associated with the head for engaging the terminal and clamping the head into a firm supporting and electrical conducting relationship with the terminal.
BACKGROUND OF THE INVENTION The invention pertains to the field of electrical conductor devices wherein a conductor is connected to an electrical terminal by means of a clamping element mounted upon a conductor associated fitting.
In the servicing of high voltage equipment, such as cables, transformers and the like, it is usually a required, and highly desirable, safety practice to ground the equipment terminals connected to conductors being serviced after the conductors have been deenergized by operation of a switch, the pulling of a fuse, or the circuit has been otherwise opened. The purpose of this practice is to prevent the possibility of harm to the service personnel as the grounding of the conductors being serviced will eliminate the danger of electrocution or shock.
In order to employ consistent safety procedures the grounding of electric terminals and conductors, prior to servicing, should be accomplished by means of an isulated hotstick wherein injury to the service operator will not occur upon application of the grounding clamp to an energized conductor. Prior devices used for grounding terminals and conductors have not been readily applicable to the item to which they are to be connected, and difi1- culty has been encountered in applying grounding clamps in compact electricalequipment using specially shaped terminals such as used in pad mounted transformers and other compact high voltage equipment which is now being used in the electrical transmission art. Present clamps used for this purpose, sometimes known as hot-tap clamps, have not been readily usable with transformers and other electrical equipment utilizing terminals including spaced plates having notches defined therein for receiving the end of fuses or other connectors.
SUMMARY OF THE INVENTION It is the basic purpose of the invention to provide a grounding clamp for grounding an electric terminal which is particularly useful for use with a terminal consisting of a pair of spaced notched plate elements, wherein the clamp may be applied to the terminal by an insulated shotgun type hotstick, and the installation and removal of the grounding clamp to the terminal may be conducted under prescribed safety techniques.
A further object of the invention is to provide a grounding clamp of novel construction wherein the grounding clamp may be easily and quickly properly oriented to the terminal with which it is to be associated, even though held in an insulated hotstick, and is capable of being firmly connected to the terminal to insure an effective electric connection therewith.
The grounding clamp of the invention includes a body 3,562,694 Patented Feb. 9, 1971 member having an elongated head defined thereon, the head being of such configuration as to be inserted between the plate elements of the terminal with which it is to be associated. Terminal engaging portions or ears are 5 defined on the ends of the head for being received within the notches in the terminal plates, and orienting shoulder surfaces are defined on the head for readily aligning the head and ears with the terminal plates that the ears may be readily dropped into the terminal notches. The head is fixed to the terminal by means of an adjustable clamping element associated with the head through a screw arrangement, and the screw is provided with a loop-type handle that it may be gripped by a conventional insulated shotgun-type hotstick. Rotation of the screw causes the clamping element to be moved toward the head for engagement with surface edges of the terminal plates in opposition to its notches, drawing the clamp ears into firm engagement with the edges of the notches to establish a positive electrical connection. The ground conductor is directly attached to the body member on which the head is defined to insure the positive electrical connection to ground.
A grounding clamp constructed in accord with the invention is economical to manufacture, relatively fool proo in operation, readily usable by service personnel using conventional saftey equipment, and capable of meeting all safety requirements.
BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects and advantages of a grounding clamp constructed in accord with the invention will be appreciated from the following description and accompanying drawings wherein:
FIG. 1 is an elevational side view of an embodiment of a grounding clamp in accord with the invention, a portion thereof being broken away for purpose of illustration,
FIG. 2 is a detail, top plan view of the grounding clamp of FIG. 1,
FIG. 3 is an elevational, sectional view taken along Section IIIIII of FIG. 1,
FIG. 4 is a side, elevational view of another embodiment of a grounding clamp in accord with the invention,
FIG. 5 is a detail, top plan view of the body member and clamping element of the embodiment of FIG. 4.
FIG. 6 is a perspective view of the type of electrical terminal with which the grounding clamp of the invention is employed, the grounding clamp embodiment of FIGS. 1 through 3 being shown in dotted lines in operative relationship to the terminal,
FIG. 7 is an elevational view of the grounding clamp embodiment of FIGS. 4 and 5 as related in operative connection to an electrical terminal as shown in FIG. 6, and
FIG. 8 is an elevational, sectional view as taken from the right of FIG. 7 along Section VIII-VIII thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENTS A grounding clamp constructed in accord with the concept of the invention may taken several forms, and in the drawings, two embodiments are shown which have proven themselves practical in all respects as a means for practicing the invention.
In the embodiment of FIGS. 1 through 3, the body member 10 is of a somewhat inverted L-shape configuration including a horizontal portion 2, as illustrated, a vertically disposed portion 14, and an elongated head 16 located at the downwardly extending terminating end of the portion 12. The body member 10 is preferably constructed of bronze, brass or aluminum, but may be of any material which has good electrical conducting characteristics.
The head 16 is of a generally elongated cylindrical configuration having a central region 18, and is preferably designed as an integral part of the body member 10. The end regions of the head 16 include radially disposed shoulders 20 which are perpendicular .to the longitudinal length of the head, and terminal engaging portions or ears 22, of a cylndrical configuration, extend from the shoulders 20 and define the ends of the head. The diameter of the cylindrical portions 22 is significantly less than the diameter of the central region 18 wherein the radial shoulder surfaces 20 constitute effective Erienting surfaces as will be later described.
The body member portion 14 is provided with a threaded bore 24 which receives the threaded screw rod 26, and the threaded rod is provided at its outer end with a ring type handle 28 for cooperation with an insulated hotstick of conventional construction. The inner end of the threaded rod 26 is provided with a coaxial, reduced diameter, stud 30 upon which the clamping element 32 is rotatably mounted. The end of the stud is headed over wherein the clamping element is axially fixed with respect to the rod 26, by the stud head and the rod shoulder 34.
The clamping element 32 has a configuration which would be best appreciated from FIG. 3, and includes a recess in its upper portion defined by a U-shaped edge 36 partially encompassing the linear surface 38 formed on the body member portion 12. In this manner the body member portion 12, and surface 38, cooperate with the clamping element edge 36 to prevent relative rotation of the element 32 to the body member about the axis of the threaded rod 26. Thus, it will be appreciated that as the rod 26 is rotated, the element 32 is moved toward and away from the head 16, depending upon the direction of rotation of the rod. The width of the clamping element 32 is slightly greater than the length of the head 16 wherein the end regions 40 of the element will be radial alignment with the terminal engaging portions 22, as appreciated from FIG. 2.
A threaded hole 42 is provided in the body member portion 14 for receiving bolt 44, employed to attach the end fitting 46 of the grounding cable 48 to the body member in electrical conducting relationship. Thus, it will be appreciated that the grounding cable is connected to the body member in a positive electrical conducting manner.
The terminal 50 with which the grounding clamp of the invention is employed is shown in FIG. 6. This terminal is of a generally U-shaped configuration including a base member 52 from which depend leg element plates 54. The terminal 50 may be mounted in a transformer, switch box, or other electrical apparatus, and is electrically connected to other conductors, or electrical connections, not shown. The purpose of the clamp of the invention is to ground the terminal 50, and thus it will be apparent that the terminal 50, will be electrically connected to those conductors which are to be grounded during servicing.
The terminal includes a notch 56 defined in each plate 54, the notches being set into the plates from the front edges 58 and having an upwardly disposed access throat 60. The notches each include an edge 62, which is in spaced relationship to the associated edge 58, and the vertical depth of the notches is sufiicient to provide the edge 62 with a significant vertical dimension.
The grounding clamp embodiment of FIGS. 1 through 3 is associated with the terminal 50 as shown in dotted lines in FIG. 6. The threaded rod 26 is rotated to space the clamping element 32 from the head 16 a distance greater than the spacing between the terminal edges 58 and 62. Thereupon the ring handle 28 is gripped by a conventional insulated hotstick, of the type used by public utility companies for opening and closing high tension switches, and the like, and the grounding clamp may therefore be safely handled and positioned as desired by the operator. Prior to applying the ground clamp to the terminal 50 the cable 48 is attached to a known ground connection, not shown. Thereupon the clamp is oriented to the terminal 50 such that the head central region 18 may be received between the terminal leg plates 54 and the ears or terminating portions 22 are lowered into the notches 56. During this operation the shoulder surfaces 20 are helpful in that the spacing between the surfaces 20 is slightly less than the spacing between the terminal plates 54 and this permits the head to be readily centered between the plates, and the portions 22 to be properly located within their respective notches. The portions 22 are permitted to rest upon the bottom of the notches and, upon this relationship being established, the rod 26 is rotated in a clockwise direction which will cause the clamping element 32 to move into engagement with the terminal edges 58, and tightening of the rod firmly draws the portions 22 into engagement with the notch edges 62 to establish a positive electrical connection between the body member 10 and the terminal 50. Of course, as the width of the clamping element 32 is slightly greater than the spacing between the terminal plates 54 both of the terminal plates will be engaged by the clamping element and the forces imposed upon the terminal, head and clamping element will be equalized.
When it is desired to remove the clamping element from the terminal 50 the rod 26 is rotated in the opposite direction by the insulated hotstick and the assembly procedure is reversed.
Another embodiment of a clamping element employing the concept of the invention is shown in FIGS. 4 and 5. In this embodiment the body member is represented at 64 and includes an upper head portion 65 having a central region 66, radial orienting surface shoulders 68 and terminal engaging ears 70. The dimensions and relationships of the head 65 are similar to those of the previously described embodiment. The body member also includes a threaded bore 72 which, preferably, passes through the axis of the head 65 and a threaded rod 74 is received within the bore 72. The threaded rod '74 is provided with a ring handle 76 at its outer end, and is swaged over at its other end at 78. The rod 74 is also provided with a cylindrical portion 80 of reduced diametrical dimension upon which the clamping element 82 is rotatably mounted. The clamping element 82 includes a vertically extending plate portion 84 having a hole therein for rotatably mounting the same on the rod portion 80, and a horizontally extending flat portion 86 is located at the upper region of the clamping element plate 84. The portion 86 extends over the planar upper surface 88 of the body member 64 and moves over surface 88 as the clamp is operated. This relationship between the clamping element 82 and the body member surface 88 prevents relative rotation of these elements about the axis of the rod 74. The clamping element 82 is axially fixed upon the threaded rod by means of the snap ring 90.
A threaded hole 92 is formed in the downwardly extending portion of the body member 64 for receiving the bolt 94 employed to attach the grounding cable end fitting 96 to the body member.
The embodiment of FIGS. 4 and 5 is used with the terminal 50 shown in FIG. 6, and FIGS. 7 and 8 illustrate the relationship of the embodiment of FIGS. 4 and 5 with the terminal. It will be appreciated from FIG. 7 that the head 65 is located between the terminal plates 54 in the manner described in FIG. 6, and the head portions 70 will be received within the terminal notches 56. The rod 74 is rotated until the clamping element 82 engages the terminal edges 58, which draws the head portions 70 into firm engagement with the notch edges 62. During rotation of the rod the proper orientation of the clamping element 82 to the terminal is maintained by the interrelationship between the body member surface 88 and the clamping element portion 86. The Width of the clamping element 82 is slightly greater than the spacing of the terminal plates 54, FIG. 8, and thus the forces imposed on the grounding clamp in the embodiment of FIGS. 4 and 5 will also be equalized, as in the case with the previously described embodiment. The grounding clamp installation of FIGS. 7 and 8 is disassembled by reversal of the aforedescribed process.
The embodiment of FIGS. 4 and 5 employs less material than the embodiment of FIGS. 1 and 3, and is thus less expensive to manufacture. It will be appreciated that both embodiments of the invention utilize common techniques and inventive concepts, and the grounding clamp in accord with the invention provides a most effective and safe manner for grounding terminals of the disclosed type.
It is appreciated that other embodiments of the invention may be apparent to those skilled in the art without departing from the scope of the invention.
What is claimed is:
1. An electrical terminal clamp comprising, in combination, a body member having an elongated head defined thereon, said head having a longitudinal axis and including end portions, each of said end portions including a rod-like terminal engaging portion extending in the direction of said axis, screw operator clamp element ad justment means mounted on said body member, a clamp element mounted on said adjustment means whereby upon actuation of said adjustment means said clamp element is selectively translated toward and away from said body member head, said clamp element including portions in radial alignment with said rod-like terminal engaging portions for clamping terminal portions between said terminal engaging portions and said clamp element portions, and electrical conductor attachment means defined on said body member.
2. An electrical terminal clamp as in claim 1 wherein said adjustment means includes a threaded rod received within a threaded bore defined in said body member having an axis substantially perpendicular to said head axis, and a handle defined on said rod for facilitating rotation thereof.
3. In an electrical terminal clamp as in claim- 2, a rotatable connection mounting said clamping element upon said threaded rod, and orienting means defined on said clamping element adapted to cooperate with and engage said body member preventing rotation of said clamping element with respect to said body member about said threaded rod.
'4. In an electrical terminal clamp as in claim 3 wherein said orienting means includes a linear surface defined on said body member substantially parallel to the length of said threaded rod and a guide surface defined on said clamp element disposed adjacent said linear surface and adapted to be translated therealong.
5. In an electrical terminal clamp as in claim 1, an alignment surface defined upon each end portion of said head adjacent each terminal engaging portion transversely disposed to said head axis.
6. In an electrical terminal clamp as in claim 5 wherein said head includes a central region, said head terminal engaging portions being of reduced transverse cross sectional dimension with respect to said central region, radial extending shoulders defined on said central region intersecting said terminal engaging portions, said alignment surfaces "being defined on said shoulders.
7. In an electrical terminal clamp as in claim 6 wherein said terminal engaging portions are cylindrical,
References Cited UNITED STATES PATENTS 1,720,030 7/1929 Bodendieck et a1. 339264 (L) 2,464,565 3/1949 Evans et al. 339272X 2,506,010 5/1950 Birkenmaier 339264(L) 2,507,417 5/1950 Noyes 339268X 2,523,293 9/ 1950 Hagenbook 269494X MARVIN A. CHAMPION, Primary Examiner R. A. HAFER, Assistant Examiner US. Cl. X.R. 339263, 272