US3026497A

US3026497A - Center bolt connectors

Info

Publication number: US3026497A
Application number: US679627A
Authority: US
Inventors: Robert R Myers; Jay W Atman
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1957-08-22
Filing date: 1957-08-22
Publication date: 1962-03-20
Anticipated expiration: 1979-03-20

Description

March 20, 1962 R. R. MYERS ET AL 3,026,497

CENTER BOLT CONNECTORS Filed Aug. 22, 1957 I VENTORS ROBERT/ MYERS f J/"IY W. ATMAN ATTORNEY 3326,49? Patented Mar. 20, 1962 3,026,497 CENTER BOLT CONNECTORS Robert R. Myers, McKeesport, and Jay W. Atman, Canonshurg, Pa., assignors to Aluminum Company of America, Pittsburgh, Pin, a corporation of Pennsylvania Filed Aug. 22, 1957, Ser. No. 679,627 3 Claims. (Cl. 339-246) This invention relates to cable-receiving and restraining devices, such as cable or conductor clamps and the like; more particularly, it is directed to center bolt connectors incorporating a cable-receiving and supporting member having parallel cable-receiving grooves in combination with a cable-engaging pusher member removably and adjustably associated with the first-mentioned member and securably connected thereto by one or more bolts, or the like, substantially intermediately disposed between the aforesaid cable-receiving and supporting grooves.

The center bolt or side-by-side type of connector for conductors has not achieved substantial exploitation due to a variety of limitations inherent in clamps of this type prior to the present invention. Among these has been the inadequacy of these clamps to perform satisfactorily under conditions of thermal change, especially when high loadings were applied. This limitation has substantially prevented the use of such clamps as universal connectors unless surface contact and electrical efficiency were to be sacrificed. Attempts to adapt such accessories as were known prior to this invention resulted in mechanical or electrical failure of the clamp or severe creep of the conductor, all of which are highly undesirable in a cable connector.

It is an object of this invention to provide a center bolt connector incorporating a cable-receiving member having substantially parallel spaced grooves, in association with a cable-engaging pusher member and detachable connecting means, which function to exert substantial clamping pressure and restraining force on the conductors or cables received therein and which further provides ilexural characteristics capable of accommodating variations in the crosssection of the conductors received there capable of receiving a range or series of conductor sizes,

accomplishing substantial deformation thereof, and retaining substantially uniform contact with the surface of cross-section thereof.

Other objects and advantages of the center-bolt clamps falling within the scope of the present invention will be apparent and understood on reference to the following descriptions and illustrations, in which:

FIG. 1 is a side elevational view of a center-bolt connector embodying the invention;

FIG. 2 is an end elevational view of the connector, as employed with cables of equal diameter;

FIG. 3 is an end elevational view similar to FIG. 2, with the exception that two sizes of groove and pusher combinations have been employed in a single connector;

FIG. 4 is an end elevational view similar to FIG. 2, wherein the minimum and maximum conductor diameters for the particular groove and pusher combination have been deformed under normal clamping pressure.

The success and efiiciency of the connector of the present invention lies in the discovery of certain elements of structural design which must be incorporated therein to provide a connector adapted to maintain conductors under substantially high compression and yet possessing flexural characteristics capable of accommodating variations in the cross-section of the conductors'occasioned by thermal change.

Theoretically, if all elements of the assembly,"the clampinvention may be described in detail.

ing members, the bolts and the conductors, were of material having substantially similar coefficients of expansion, there should be no increases in compression or loading of the individual elements by reason of thermal change provided that such thermal change were uniformly and instantaneously translated into all elements. However, such is not generally the case, since a condition of thermal change may often arise wherein a conductor may suddenly heat and expand by reason of increased current loading or a temporary short circuit. In such a situation, the temperature change in the conductor is extremely rapid and is translated into expansion before the connector can conduct the heat away to establish equilibrium heat conditions throughout or effect dissipation. In such circumstances, increased stress is developed which may result in cracking or deformation of a weak connector, or elongation of the bolt, or in creep or extrusion of the conductor. Upon attainment of equilibrium conditions or cooling resulting in the contraction of the conductor, the initial conditions of compression and surface contact will no longer exist and the resistance of the assembly will most generally increase.

Referring to the drawings, a center bolt connector embodying the invention is illustrated wherein a cable-receiving or grooved member 2 is comprised of two curvilinear, substantially U-shaped

outboard portions

4 and 6 integral with a common or intermediately disposed boss 8, the inner curvilinear surfaces of the U-Shaped

outboard portions

4 and 6 providing substantially

parallel grooves

10 and 12 for receiving

conductors

14 and 16 of equal size (FIG. 2) of unequal size (FIGS. 3 and 4).

A C-shaped cable-engaging or pusher member 18 provided with a pair of projecting, substantially parallel

arcuate pusher surfaces

20 and 22, joined by an integral arcuate web 24 is opposed to the cable-receiving member connector to the conductors with which it is associated.

The use of the laterally extending oversize apertures 28 and washers 30, underlying the heads of the bolts 26, and the arcuate web 24 arched outwardly away from the cable-receiving member 2' permit anmilar adjustment of the pusher member 13 to accommodate any slight or intentional dimensional diiferences in the conductors 14- and 16 within the designed conductor range.

As is readily seen from the accompanying illustrations, the cross-section thickness (A and B) of the cablereceiving member 2 underlying each of the grooves is reduced relative to that of the upstanding boss 8 (C) and is small relative to the lengths of the beams (D and E) defined by the centers of the grooves and the center or axis of the bolt, and may further taper towards the lips 32 of the outboard portions 4 and 6 (crosssections F and G). The cross-section (H) of the arcuate connecting web 24 is small relative to the lengths of the beams (I and K) defined by the centers of the pusher faces and the center of the bolt. Further, the curvilinear configuration of the

connector members

2 and 18 is to be noted since increased strength is provided, thereby permitting reductions in cross-section to permit fiexure over greater lengths of the

outboard portions

4 and 6 and of the connecting web 24.

Referring further to FIG. 4, the efficacy of the present The conductors l4 and 16 are placed within the

grooves

10 and 12 and the

pusher surfaces

20 and 22 are brought into clamping relationship by means of the bolts 25, A substantial compression is placed upon the assembly whereby the conductors 14- and 16 are deformed into maximum peripheral contact with the surfaces of the grooves and 12. In so doing, points of stress may be developed and are relieved by fiexure of the members about their reduced cross-sections. In addition it is sometimes desirable to develop some fiexure of the members in the initial compression to accommodate possible contraction of the cables.

Upon conditions of thermal shock or relatively instantaneous expansion of one or both conductors, the increased size is translated into force acting against the

clamping members

2 and 18 and the bolts 26. Because of the reduction in cross-section of the metal underlying the

grooves

10 and 12 and the reduced cross-section of the arcuate web 24, the reaction of the clamping members is in fiexure about these points. Upon reaching equilibrium temperature throughout the assembly or contraction of the cable through cooling, the stress causing the fiexure is relieved and the members follow the cable in what has been described as spring-follow actions.

The reduction in cross-section should not be excessive so as to be incapable of providing adequate structural strength but sufficient to provide the spring follow action desired. The cross-sections of the arcuate web and the metal underlying each of the grooves should generally be about 25-65 percent of the length of the beams defined by the axis of the bolt and the center of the respective groove or pusher surface. As examples of employable size relationships, dimensions found satisfactory for sections A, B, C, D, E, F, G, H, J, and K, as located in FIGS. 2 and 3, are set forth in the tables below.

TABLE 1 Dimensions for Connectors Having Equal Size Groove and Pusher Combinations (in inches) Diameter of conductors receive .162 to 325..-- .292 to .502

gag?

TABLE 2 and/ or 0.01 to 0.5 percent titanium may be added. Small amounts of oxidation inhibitors such as 0.0005 to 0.02 percent beryllium may also be included.

The wrought articles are desirably subjected to a con ventional solution heat treatment at 925-1050 F., generally for a period of 1 to 12 hours, and an artificial aging process at 275500 F. for a period of up to 24 hours, whereby high tensile properties are developed, i.e., a minimum yield strength of 30,000 p.s.i., and preferably 35,000 p.s.i., or above.

An example of a desirable metal employed in such connectors in extruded form is an alloy nominally consisting of aluminum, 1.0 percent magnesium, 0.6 percent silicon, and 0.25 percent copper, which is solution heat treated at 970 F. for /26 hours and artificially aged at 350 F. for 6-10 hours depending upon the thickness of the section. Such product has the following typical properties: tensile strength-45,000 p.s.i.; yield strength- 40,000 psi; elongation-l2% in 2 inches.

The cable receiving groove and pusher face, may be, and preferably are, of the universal type described in the copending application of Robert R. Myers, Serial No. 642,547, filed February 26, 1957, wherein details of construction and dimensioning of these elements are set forth.

Having thus illustrated and described our invention, we claim:

1. A low electrical resistance wrought metal connector clamp characterized by exhibiting fiexural reaction on clamped assembly on a pair of electrical conductors to provide and maintain close conformity and uniform loading and electrical contact with and between electrical conductors clamped therein under initial and subsequent varying thermally-induced electrical loading thereof, said connector clamp comprising a cable-receiving member having a pair of laterally offset outboard arms disposed on either side of an intermediate boss formed integrally therewith, each outboard arm having a similarly directed open top concave cable-receiving groove in respective parallel-spaced relationship, the cable-receiving member being of uniform cross-section transverse to the parallel axes of the grooves and having at least one outboard arm of substantially U-shaped cross-section with its exterior Dimensions for Connectors Having Unequal Size Groove and Pusher Combinations (in inches) Diameter of conductors received A B C D E F G H J K Large groove Small groove The deformation of the conductors illustrated in FIG. defining curved surface extending below a lower exterior 4 is typical for this type of connector. Therein, each of surface of the intermediate boss in the form of an exthe conductors has been deformed in such a manner as terior surface contiguous with the curved exterior surto distribute the individual strands in peripheral surface face of the outboard U-shaped arm and reversely curved contact with substantially, if not entirely, the entire adin respect thereto, the thickness of the transverse crossjacent periphery of the surfaces of the grooves in the section underlying each groove being less than the length conductor-receiving member and the arcuate pusher surof each individual beam defined by the distances between faces. This has accounted for maximum conductor conthe centers of the axes of the grooves and an axis parallel tact force and high electrical contact efliciency of the thereto substantially centrally disposed through the interconnectors of the present invention. mediate boss, the said transverse cross-section thickness The connectors may be wrought, preferably extruded, underlying each groove being also small relative to the from an aluminum base alloy providing a high degree of axial thickness of the intermediate boss and progressively corrosion resistance as well as good electrical conducreduced therefrom towards terminal edges of the lateraltivity and workability. Such an alloy is one consisting 1y offset outboard arms, a threaded aperture extending essentially of aluminum and 0.7 to 3.0 percent magnesium silicide (Mg Si); an excess of up to 1.0 percent magnesium or silicon may be present and it is generally desirable to include 0.1 to 0.5 percent of copper or chromium, or both. In addition, small amounts of grainthrough the intermediate boss coincident with its substantially centrally disposed axis, a Cshaped cable-engaging member having a pair of substantially parallel-spaced arcuately concave pusher surfaces integrally connected by an arcuate web, said pusher surfaces being disposable refining elements, such as 0.001 to 0.1 percent boron, in overlying facing relationship to the parallel grooves in the cable-receiving member with the arcuate connecting web arched outwardly away therefrom in cable-connecting assembly of the connector clamp ona pair of electrical conductors, the cross-section of the cable-engaging member transverse to the parallel axes of the pusher surfaces being uniform over the axial length thereof with the thickness of the cross-section of the arcuate connecting web intermediate the pusher surfaces being of the order of each of the reduced transverse cross-sectional thicknesses of the cable-receiving member underlying its parallel grooves and small relative to the length of each individual beam defined by the distances between the axes of the pusher surfaces and an axis parallel thereto coincident with the axis of the threaded aperture in the intermediate boss of the cable-receiving member, an aperture extending through the arcuate connecting web, and a detachable threaded load-applying, connecting and securing bolt extending through the aperture for engagement with the threaded aperture in the intermediate boss of the cable-receiving member, said aperture being oversize in respect to said bolt diameter.

2. A low electrical resistance wrought metal connector clamp characterized by exhibiting flexural reaction on clamped assembly on a pair of electrical conductors to provide and maintain close conformity and uniform loading and electrical contact with and between electrical conductors clamped therein under initial and subsequent varying thermally-induced electrical loading thereof, said connector clamp comprising a cable-receiving member having a pair of substantially U-shaped arms disposed laterally outboard of an intermediate boss formed integrally therewith, each outboard arm having a similarly directed open top concave cable-receiving groove in respective parallel-spaced relationship extending below a surface defining the upper surface extremity of the integral intermediate boss, the exterior curved surfaces of the U- shaped outboard arms being connected by a surface reversely curved in respect thereto and contiguous therewith to define a lower surface extremity of the integral intermediate boss disposed above the lowermost exterior surface of each of the U-shaped outboard arms, the crosssection of the cable-receiving member transverses to the parallel axes of the grooves therein being uniform over the axial length thereof with the thickness of the crosssection underlying each groove less than the length of each individual beam defined by the distances between the centers of the axes of the grooves and an axis parallel thereto substantially centrally disposed through the intermediate boss, the said cross-section thickness underlying each groove being also small relative to the thickness of the intermediate boss measured between its upper and lower surface-defining extremities and being progressively reduced therefrom towards terminal edges of the U- shaped arms, a threaded aperture extending through the intermediate boss coincident with its substantially centrally disposed axis, a C-shaped cable-engaging member having a pair of substantially parallel-spaced arcuately concave pusher surfaces integrally connected by an arcuate web, said pusher surfaces being disposable in overlying facing relationship to the parallel grooves in the cable-receiving member with the arcuate connecting web arched outwardly away therefrom in cable-connecting assembly of the connector clamp on a pair of electrical conductors, the cross-section of the cable-engaging member transverse to the parallel axes of the pusher surfaces being uniform over the axial length thereof with the thickness of the cross-section of the arcuate connecting web intermediate the pusher surfaces being of the order of each of the reduced cross-sectional thicknesses of the cable-receiving member underlying its parallel grooves and small relative to the length of each individual beam defined by the distances between the axes of the pusher surfaces and an axis parallel thereto coincident with the axis of the threaded aperture in the intermediate boss of the cable-receiving member, an aperture extending through 6 the arcuate connecting web, and a detachable threaded load-applying, connecting and securing bolt extending through the aperture for engagement with the threaded aperture in the intermediate boss of the cable-receiving member, said aperture being oversize in respect to said bolt diameter.

3. A low electrical resistance extruded and thereafter solution heat treated and artificially aged aluminum alloy connector clamp, said aluminum alloy having a composition by weight comprising 0.7 to 3.0 percent magnesium silicide and at least one of the elements copper and chromium within the range 0.1 to 0.5 percent, said connector clamp characterized by exhibiting flexural reaction on clamped assembly on a pair of electrical conductors to provide and maintain close conformity and uniform loading and electrical contact with and between electrical conductors clamped therein under initial and subsequent varying thermally-induced electrical loading thereof, said connector clamp comprising a cable-receiving member having a pair of substantially similarly configurated U-shaped arms disposed laterally outboard of an intermediate boss formed integrally therewith, each outboard arm having a similarly directed open top concave cable-receiving groove in respective parallel-spaced relationship extending below a surface defining the upper surface extremity of the integral intermediate boss, the exterior curved surfaces of the U-shaped outboard arms being connected by a surface reversely curved in respect thereto and contiguous therewith to define a lower surface extremity of the integral intermediate boss disposed above the lowermost exterior curved surfaces of the U-shaped outboard arms, the cross-section of the cable-receiving member transverse to the parallel axes of the grooves therein being uniform over the axial length thereof with the thickness of the cross-section underlying each groove less than the length of each individual beam defined by the distances between the centers of the axes of the grooves and an axis parallel thereto substantially centrally disposed through the intermediate boss, the said transverse cross-section thickness underlying each groove being also small relative to the thickness of the intermediate boss measured between its upper and lower surface-defining extremities and being progressively reduced therefrom towards terminal edges of the U-shaped arms, a threaded aperture extending through the intermediate boss coincident with its substantially centrally disposed axis, a C-sh'aped cable-engaging member having a pair of substantially parallel-spaced arcuately concave pusher surfaces integrally connected by an arcuate web, said pusher surfaces being disposable in overlying facing relationship to the parallel grooves in the cable-receiving member with the arcuate connecting Web arched outwardly away therefrom in cable-connecting assembly of the connector clamp on a pair of electrical conductors, the cross-section of the cable-engaging member transverse to the parallel axes of the pusher surfaces being uniform over the axial length thereof with the thickness of the cross-section of the arcuate connecting web intermediate the pusher surfaces being of the order of each of the reduced cross-sectional thicknesses of the cablereceiving member underlying its parallel grooves and small relative to the length of each individual beam defined by the distances between the axes of the pusher surfaces and an axis parallel thereto coincident with the axis of the threaded aperture in the intermediate boss of the cable-receiving member, an aperture extending through the arcuate connecting web, and a detachable threaded loop-applying, connecting and securing bolt extending through the aperture for engagement with the threaded aperture in the intermediate boss of the cablereceiving member, said aperture being oversize in respect to said bolt diameter.

(References on following page) 7 References Cited in the file of this patent UNITED STATES PATENTS 715 977 1,635,200 Zi11iox July 12, 1927 713 332 1,699,211 Rose Jan. 15, 1929 5 828,865 2,791,623 Lock et a1. May 7, 1957 8 FOREIGN PATENTS Germany Jan. 10, 1942 Germany Mar. 21, 1942 Germany Ian. 21, 1952 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,026,497 March 20, 1962 Robert R. Myers et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6 line 69, for "loop-applying read load-applying Signed and sealed this 3rd day of July 1962.

SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents