US3161721A

US3161721A - Clamps of spacing devices for overhead electrical conductors

Info

Publication number: US3161721A
Application number: US240119A
Authority: US
Inventors: Torr Ralph Percival
Original assignee: Andre Rubber Co Ltd
Current assignee: Andre Rubber Co Ltd
Priority date: 1961-07-06
Filing date: 1962-11-26
Publication date: 1964-12-15
Anticipated expiration: 1981-12-15
Also published as: BE625725A; GB929693A; FR1339921A; NL286504A

Description

R. P. TORR Dec. 15, 1964 CLAMPS OF SPACING DEVICES FOR OVERHEAD ELECTRICAL CONDUCTORS 2 Sheets-Sheet 1 Filed Nov. 26, 1962 Inventor RALPH PERC IVHL TORR y 24"74 Attorney Dec. 15, 1964 R. P. TORR 3,161,721

CLAMPS OF SPACING DEVICES FOR OVERHEAD ELECTRICAL. CONDUCTORS Filed Nov. 26, 1962 2 Sheets-Sheet 2 Inventor RRL PH PERCIVAL TORB M ZQOZZZ:

A tlorneyS United States Patent 3 161,721 CLAMPS 0F SPAClNGi DEVICES FOR GVERHEAD ELECTRICAL @UNDUCTORS Ralph Percival Torr, New Malden, England, assignor to Andre Rubber Company Limited, Hook Rise, Toiworth, Surhiton, urrey, England, a British company Filed Nov. 26, 1962, Ser. No. 240,119 8 Claims. (Cl. 17 3-4-13} This invention relates to spacing devices for spacing the individualconductors of an electrical transmission line, usually those of one phase or pole of an electrical transmission line having a plurality of conductors per phase or pole, and has for its object to provide an improved form of clamp of the kind that is lined with a bush consisting of resilient or elastomeric material, through which bush one conductor is passed to secure the conductor to the spacing device.

The conductors of overhead lines spaced by such spacing devices, are liable to be deflected at one or both ends of the bushes of the spacing devices from alignment with the axes of the bushes, this tending to result in somewhat acute bending of the conductors where they issue from the ends of the bushes when the bushes have cylindrical bores and are housed in clamps having a cylindrical interior surface. One of the objects of the present invention is to provide a construction of clamp and bush of a spacing device that permits divergence of the associated conductor from coaxiality with the clamp and bush in any direction within a substantial cone coaxial with the bush. A further object of the invention is to utilize the resilience of the resilient bush itself for positively locking the securing means of the clamp.

According to the invention, in a clamp of the kind referred to, the interior surface of the clamp, when closed, and the exterior surface of the bush are flared outwardly from the median plane transverse to the axis of the clamp and bush towards the ends of the area over which the bush seats in the clamp, the cross-sections of the clamp in planes containing the axis being internally convex and the similar cross-sections of the bush being externally concave. The cross-sections in planes containing the axis of the end portions of the walls of the bush are preferably convex and merge into flared end-portions of the bore of the bush. Furthermore, the end-portions of the in terior surface of the clamp may be concave in the crosssections containing the axis and are normally spaced from the convex ends of the wall of the bush, when the clamp is closed, but, when the bush is strained by deflection of a conductor gripped thereby fromcoaxiality with the bush and clamp, contact locally at one side with the convex end-portions of the Wall of the bush which yield resiliently under this contact. The concave and convex endportions of the clamp and the bush respectively may be circular arcs in cross-section. Moreover the radius of curvature of the concave end-portion of the clamp is preferably greater than that of the convex end-portion of the bush.

The bore of the bush is preferably generally cylindrical at least at its mid-portion. However, the bore of the bush may be provided with helical lands and grooves to mate with the external surface of a conductor comprising a plurality of strands laid together. Alternatively, however, the bore of the bush may be serrated or knurled.

In a preferred construction, the internal diameter of the 3,161,721 Patented Dec. 15, 1964 mid-portion of the clamp, when closed, in any plane transverse to its axis is smaller than the corresponding external diameter of the bush, when uncompressed, so that closure of the clamp on the bush causes deformation of the bush. The invention thus includes the combination of a conductor with a clamp as set forth wherein the cross-sectional area of the bore of the bush is not less than the cross-sectional area of the conductor, so that, when the clamp is closed, the bush is pre-stressed or subjected to substantial resilient deformation. Alternatively, the internal diameter of the mid-portion of the clamp, when closed, in any plane transverse to its axis may be substantially equal to the corresponding external diameter of the bush. In this case, the cross-sectional area of the bore of the bush is less than the cross-sectional area of the conductor, so that, when the clamp is closed, the bush is pre-stressed or subject to substantial resilient deformation.

The clamp preferably comprises two jaws hinged to one another, each jaw having a hollow or channel that is, in any cross-section perpendicular to the hinge axis, of substantially arcuate or semi-circular shape, the areas of the cross-sections of the bore embraced or formed by the hollows or channels, when closed, being less than the sum of the corresponding cross-sectional areas of an uncompressed bush, when the latter embraces a conductor, and of the conductor, so that, when the hinged jaws are closed, the bush is subjected to resilient deformation or pie-loading. The areas of the cross-sections of the bore may be less than the areas embraced by the external periphery of the uncompressed bush in corresponding cross-sections.

A locking device may be combined with the clamp, this locking device being such that it is positively retained in a locked attitude, securing the two jaws in a closed position about the bush, by force due to pre-loading of the bush. The locking device may comprise a headed shank extending through a slot or hole in one jaw, with its head abutting against that jaw, extending through a slot in the other jaw and provided with a transverse cotter adapted to overlie that other jaw and to seat in a groove formed in the outer surface of that other jaw. The length between the head and the cotter may be such that, in order that the cotter may pass over the other jaw into the groove, the bush must be substantially compressed or strained beyond the state of compression in which it remains after engagement of the cotter in the slot.

For the better understanding of the invention one example of clamp for a spacing device will now be described with reference to the accompanying drawings in which:

FIG. 1 is an elevation of a clamp showing in cross-section a conductor to which the clamp is secured;

FIG. 2 is a section in the plane II-II of FIG. 1;

FIG. 3 is a section in the plane III-1H of FIG. 1;

FIG. 4 is a plan view of one of the components of a split bush such as is shown in FIGS. 1 to 3; and

FIG. 5 is a section on the line V-V or FIG. 4.

Referring now to the accompanying drawings, the clamp there shown by way of example comprises two jaws 1 and 2 that are hinged together by means of a hinge pin 3. The jaw 1 is mounted upon an arm 4 or other part of a spacing device for individual conductors of an electrical transmission line, which spacing device will usually hear one or more additional clamps for other conductors of the transmission line.

The clamp houses between the jaws 1 and 2 a bush 5 of elastomeric material, as shown in FIG. 3. The interior surface of each jaw 1 and 2 of the clamp is flared outwardly at 6 and 7 from the median plane transverse to the axis of the clamp. Likewise the exterior surface of the bush 5 is flared outwardly from the median plane transverse to its axis at 8 and 9 as shown most clearly in FIG. 4. Thus the cross-sections of the clamp in planes containing the axis are internally convex at 6 and 7, while the similar cross-sections of the bush 5 are externally concave at 8 and 9. The end-

portions

11 and 12 of the walls of the bush 5 are convex and merge into slightly flared end-portions of the bore of the bush 5. The endportions of the interior surfaces of the jaws 1 and 2 are concave at 10 and are normally spaced from the convex end-

portions

11 and 12 of the wall of the bush 5, when the clamp is closed, but, when the bush 5 is strained by deflection of a conductor 13 gripped thereby from coaxiality with the bush and clamp, contact locally at one side with the convex end-

portions

11 and 12 of the bush which yield resiliently under this contact. The concave portions 10 of the clamp jaws and the

convex portions

11 and 12 of the bush 5 are preferably circular arcs in cross-section. The mid-portion of the bore of the bush 5 is generally cylindrical, but may be provided with helical lands and grooves to mate with the external surface of a conductor comprising a plurality of strands or wires laid together. However, as indicated in FIGS. 3 and 4, the surface of the bore of the bush 5 is preferably serrated or knurled.

The bush 5 consists of two substantially semi-circular halves, so that it may be easily applied to a conductor without the need for passing it over an end of the conductor. It may have incorporated in it one or more layers 14 of square-mesh textile or wire or other reinforcement. Each half of the bush is preferably provided with a lug 15 projecting radially from its external periphery for engagement with a hole 16 in the jaw 1 or 2 of the clamp so as to hold the bush in the jaw and thus facilitate application of the clamp to a conductor.

In order to secure the clamp in a closed and locked attitude, a locking device is provided that is positively retained in a locked attitude, securing the jaws 1 and 2 in a closed position about the bush 5, by the force due to pre-loading of the bush in a manner that will be later described. This locking device comprises, in the example illustrated in the drawings, a shank 17 having a head 13 and extending through a slot or hole 19 in the jaw 1 with its head abutting against that jaw. The shank 17 extends through a slot 20 in the other jaw 2 and is provided with a transverse cotter 21 that is adapted to overlie the jaw 2 and to seat in a groove 22 formed in the outer surface of that jaw. The length between the head 18 and cotter 21 is such that, in order that the cotter 21 may pass over the jaw 2 into the groove 22, the bush 5 must be substantially compressed or strained beyond the state of compression in which it remains after engagement of the cotter 21 in the groove 22.

The bore of the bush 5 may conveniently have a crosssectional area substantially equal to that of the conductor 13 that it is to embrace. In this case the internal diameter of the mid-portion 9 of the clamp, when closed, in any plane transverse to its axis is substantially smaller than the corresponding external diameter of the bush 5. However, alternatively, the cross-sectional area of the bore of the bush 5 may be substantially less than that of the conductor 13, in which case the internal diameter of the said portion 9 of the clamp, when closed, in any plane transverse to its axis is substantially equal to the corresponding external diameter of the bush. In either case, when the bush is assembled on a conductor and the clamp is closed about it, the bush is subject to substantial precompression and resilient deformation.

Without prejudice to the generality of the preceding description certain typical dimensions for a clamp and bush, the bush being made of elastomeric material such as synthetic rubber, preferably semi-conducting, so as to have a hardness of 70 British Standard, and the clamp being suitable for a standard 1% outside diameter stranded steel and aluminum conductor have a copper equivalent of 0.4 S.C.A., are given below with reference to FIGS. 3 and 4-:

Dimensions of clamp (FIG. 3)-

A 1.75" dia.

B 2.25" dia.

Gradius 0.25.

H radius 0.75.

Jradius 0.125". Dimensions of bush (FIG. 4)-

D 1.09" dia. prior to knurling.

E 1.675" dia.

F 2.14 dia.

Iradius 0.72.

(radius 0.22".

Lradius 0.25".

Since considerable force is required to close the jaw 2 over the bush and conductor and to compress the bush sufliciently to allow engagement of the cotter 21 in the groove 22, a manually operable screw clamp may be provided as an accessory, by means of which the jaws 1 and 2 may be easily forced together sufficiently for engagement of the cotter.

When the jaws 1 and 2 are closed and secured by the cotter 21, the bush 5 is subjected to substantial compression and deformation so that the bush is securely attached to the conductor. However, if the conductor is deflected from coaxiality with the bush, the latter is capable of further deformation, thus to accommodate such deflection without local injury to the conductor.

It will be appreciated that one particular form of clamp and certain detailed modifications have been described with reference to the accompanying drawings, and that certain specific dimensions have been stated, by way of example only; and that many variations may be made without departing from the scope of the invention as defined in the appended claims.

What I claim is:

1. A clamp for a spacing device for spacing the individual conductors of an electrical transmission line comprising at least two rigid jaws, a bush consisting of elastomeric material embraced and compressed by said jaws and adapted to embrace an electrical conductor, the interior surfaces of said jaws and the exterior surface of said bush being of circular symmetary about an axis and being flared outwardly from the median plane transverse to the axis of said clamp and bush towards the ends of the area over which said bush seats in said clamp, the cross-section of the interior surfaces of said jaws in planes containing the axis being the arc of a circle and convex, the similar cross-sections of the exterior surface of said bush being the arc of a circle and concave, and the radius of curvature of the said cross sections of said interior surfaces of said jaws being greater than the radius of curvature of said cross-sections of said exterior surface of the uncompressed bush.

2. A clamp for a spacing device for spacing the individual conductors of an electrical transmission line comprising at least two rigid jaws, a bush consisting of elastomeric material embraced and compressed by said jaws and adapted to embrace an electrical conductor, the interior surfaces of said jaws being in cross-section containing the axis of said jaws and said bush, of a convex and circular arc configuration along the axial length of said jaws upon which said bush seats on said jaws, the exterior surface of said bush being in cross-section containing the axis thereof, of a concave and circular are configuration, the radius of curvature of said interior surface of said jaws being greater than the radius of curvature of said exterior surface of the uncompressed bush, and said interior and exterior surfaces merging into terminal portions of said jaws and said bush that are spaced from one another and are respectively concave and convex in crosssection, the radius of curvature of said cross-section of said terminal portions of said jaws exceeding that of said cross-sections of said terminal portion of said bush.

3. A clamp according to claim 1 wherein the bore of said bush is provided with helical lands and grooves to mate with the external surface of a conductor having a plurality of strands laid together.

4. A clamp according to claim 1 wherein the bore of said bush is serrated.

5. The combination of an electrical conductor and a clamp thereof, said clamp comprising at least two rigid jaws, a bush of elastomeric material embraced and cornpressed by said jaws and embracing said conductor, the interior surfaces of said jaws and the exterior surface of said bush being flared outwardly from the median plane transverse to the axis of said clamp towards the ends of the area over which said bush seats in said clamp, the cross-section of the interior surfaces of said jaws in planes containing the axis being the arc of a circle and convex, the similar cross-sections of exterior surface of said bush being the arc of a circle and concave, and the combined cross-sectional area of the uncompressed bush and said conductor in a plane transverse to the axis of said clamp exceeding the corresponding cross-sectional areas mounted by the said interior surface of said jaws whereby said bush is placed under compression between said jaws and said conductor.

6. The combination claimed in claim 5 wherein the cross-sectional area of the bore of said bush is less than the cross-sectional area of said conductor whereby said bush is subjected to substantial resilient deformation.

7. A clamp for a spacing device for spacing the individual conductors of an electrical transmission line comprising a bush consisting of elastomeric material, a pair of jaw hinged to one another at one end and embracing and compressing the bush, said jaws having aligned elongate slots formed in their other ends and one of said jaws having a transverse groove formed in the external surface thereof and intersecting the slot therein, fastening means comprising a shank extending through said slots having near one end thereof a transverse cotter detachably engaging said groove and having at its other end a head engaging the exterior of the other of said jaws, said shank being retained under tension and said cotter being retained in said groove by the compression of said bush between said jaws, the interior surface of said jaws and the exterior surface of said bush being of a circular symmetry about an axis and being flared outwardly from the median plane transverse to the axis of said clamp and said bush towards the ends of the area over which said bush seats in said clamp, the cross sections of the interior surfaces of said jaws in planes containing the axis being the are of a circle and convex, the similar cross-sections of the exterior surface of said bush being the arc of a circle and concave, and the radius of curvature of said cross-sections of said interior surfaces of said jaws being greater than the radius of curvature of said cross-sections of said exterior surface of the compressed bush.

8. A clamp for a spacing device for spacing the individual conductors of an electrical transmission line, compressing a bush consisting of elastomeric material, a pair of jaws hinged to one another at one end and embracing and compressing the bush, said jaws having aligned elongate slots formed in their other ends and one of said jaws having a transverse groove formed in the external surface thereof and intersecting the slot therein, fastening means comprising a shank extending through said slots having near one end thereof a traverse cotter detachably engaging said groove and having at its other end a head engaging the exterior of the other of said jaws, said shank being retained under tension and said cotter being retained in said groove by the compression of said bush between said jaws, the interior surfaces of said jaws being, in cross-section containing the axis of said jaws and said bush, each of a convex and circular arc configuration over the axial length of said jaws over which said bush seats on said jaws, the exterior surface of said bush being, in cross-section containing the axis thereof, of a concave and circular arc configuration, the radius of curvature of said interior surfaces of said jaws beings greater than the radius of curvature of said exterior surface of said bush with said interior and exterior surfaces merging into terminal portions of said jaws and said bush that are spaced from one another and are respectively concave and convex in cross-section containing the axis of said jaws and said bush and the radius of curvature of said crosssection of said terminal portion of said jaws exceeding that of said cross-section of said terminal portion of said bush.

References Cited by the Examiner UNITED STATES PATENTS 92,299 7/69 Fry 174-154 888,154 4/09 Friend 174-155 918,905 4/09 Pond 174-155 1,527,346 2/25 Brady 248-74 X 2,024,831 12/35 Meyer 174154 2,915,580 12/59 Gill et al 174-146 X FOREIGN PATENTS 722,083 1/55 Great Britain.

JOHN F. BURNS, Primary Examiner.

r JOHN P. WILDMAN, Examiner.

Claims

1. A CLAMP FOR A SPACING DEVICE FOR SPACING THE INDIVIDUAL CONDUCTORS OF AN ELECTRICAL TRANSMISSION LINE COMPRISING AT LEAST TWO RIGID JAWS, A BUSH CONSISTING OF ELASTOMERIC MATERIAL EMBRACED AND COMPRESSED BY SAID JAWS AND ADAPTED TO EMBRACE AN ELECTRICAL CONDUCTOR, THE INTERIOR SURFACES OF SAID JAWS AND THE EXTERIOR SURFACE OF SAID BUSH BEING OF CIRCULAR SYMMETARY ABOUT AN AXIS AND BEING FLARED OUTWARDLY FROM THE MEDIAN PLANE TRANSVERSE TO THE AXIS OF SAID CLAMP AND BUSH TOWARDS THE ENDS OF THE AREA OVER WHICH SAID BUSH SEATS IN SAID CLAMP, THE CROSS-SECTION OF THE INTERIOR SURFACES OF SAID JAWS IN PLANES CONTAINING THE AXIS BEING THE ARC OF A CIRCLE AND A CONVEX, THE SIMILAR CROSS-SECTIONS OF THE EXTERIOR SURFACE OF SAID BUSH BEING THE ARC OF A CIRCLE AND A CONCAVE, AND THE RADIUS OF CURVATURE OF THE SAID CROSS SECTIONS OF SAID INTERIOR SURFACES OF SAID JAWS BEING GREATER THAN THE RADIUS OF CURVATURE OF SAID CROSS-SECTIONS OF SAID EXTERIOR SURFACE OF THE UNCOMPRESSED BUSH.