US3566048A

US3566048A - Current conductor rail system

Info

Publication number: US3566048A
Application number: US728009A
Authority: US
Inventors: Gerald E Martin
Original assignee: HK Porter Co Inc
Current assignee: HK Porter Co Inc
Priority date: 1968-05-09
Filing date: 1968-05-09
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A composite steel/aluminum electrical conductor rail system utilizing the structural strength and abrasion resistance of a Tshaped carbon steel insert together with the high electrical conductivity of an inverted split T-shaped aluminum body into which the stem of the steel insert is fitted. The split T stem of the aluminum body is provided with laterally outwardly projecting longitudinally extending protrusions or keys which coact with a pair of conformingly shaped aluminum splice plates with key receiving keyways to provide electrical conductivity and mechanical strength at a rail joint at least equal to that of the same length of unbroken rail. Single and dual insulator nylon coated rail supports are provided for both overrunning and underrunning rail mounting with tapered and radiused rail grips which prevent rail seizing during longitudinal expansions and contractions of the supported rail and which supports provide for installation and removal of the conductor rail without removing the rail grips from the insulators. The splice plates are also formed to permit the use of rail supports at a splice joint.

Description

United States Patent [72] lnventor Gerald E. Martin Lynchburg, Va.

[21] Appl. No. 728,009

[22] Filed May 9, 1968 [45 Patented Feb. 23, 1971 [73] Assignee H. K. Porter Company, Inc.

Lynchburg, Va.

[54] CURRENT CONDUCTOR RAlL SYSTEM 10 Claims, 12 Drawing Figs.

[52] US. Cl 191/22,

l9l/29(DM),191/321238/145, 238/243, 238/304 [51] int. Cl 860m 1/30 [50] Field ofSearch 191/22 (DM), 32; 238/243, 149, 280,1, 2, 283, 287, 349, 308, 303, 304,139, 180l84, 169, 246, 7, 317,

3,164,323 1/1965 Steele et al. 238/349 3,206,123 9/1965 Baker 238/349 FOREIGN PATENTS 775,256 5/1957 Great Britain 238/159 Primary Examiner Arthur L. La Point Assistant ExaminerGeorge H. Libman Attorney-Edelson & Udell ABSTRACT: A composite steel/aluminum electrical conductor rail system utilizing the structural strength and abrasion resistance of a T-shaped carbon steel insert together with the high electrical conductivity of an inverted split T-shaped aluminum body into which the stem of the steel insert is fitted.

The split T stern of the aluminum body is provided with laterally outwardly projecting longitudinally extending protrusions or keys which coact with a pair of conformingly shaped aluminum splice plates with key receiving keyways to provide electrical conductivity and mechanical strength at a rail joint at least equal to that of the same length of unbroken rail. Single and dual insulator nylon coated rail supports are provided for both overrunning and underrunning rail mounting with tapered and radiused rail grips which prevent rail seizing during longitudinal expansions and contractions of the supported rail and which supports provide for installation and removal of the conductor rail without removing the rail grips from the insulators. The splice plates are also formed to permit the use of rail supports at a splice joint.

CUNT CONDUCTOR RAIL SYSTEM This invention relates generally j to conductor rail systems used with electric utilities such as overhead cranes, and more particularly relates to such systems utilizing composite conductor rails made partly of aluminum and partly of steel.

A principal object of the invention is to provide a novel composite conductor rail system using a pair of interfitted T- shaped members to form a composite l-beam structure, the contact wear surface being of steel and having a stem which interfits within the split stem or web of the aluminum body.

Another object of the invention is to provide a novel composite rail structure as aforesaid in which the electrically conductive aluminum base or body section has formed on the sides of the upstanding split web a pair of laterally projecting longitudinally extending integral keys configured to fit closely within conformingly shaped recesses or keyways in electrical splice plates or bars which align and connect adjoining conductor sections, the keyed interfit providing mechanical and electrical characteristics at least as good as those of the same length of integral rail.

A further object of the invention is to provide rail supports for the composite conductor rail which permit the rail to ride easily through the support with a minimum of frictional resistance and with no tendency to bind or seize in the rail supports.

Yet a further object of the invention is to provide a novel conductor rail splicing structure utilizing splice plates which are so configured that rail supports may be fixed to the conductor rail at a splice joint with no mechanical interference between the splice plates and rail supports.

Yet another object of the invention is to provide a conductor rail system as aforesaid in which the rails may be quickly secured to the rail supports or disconnected therefrom without disassembling the support structure.

The foregoing and other objects of the invention will appear more fully hereinafter from a reading of the following specification in conjunction with an examination of the appended drawings, wherein:

FIG. 1 is a perspective view of a portion of the novel conductor rail taken at a splice joint, showing a splice plate securement, and a single insulator rail support shown in underlying support position;

FIG. 2 is an enlarged perspective view of the conductor rail splice plate seen in FIG. 1, but with the inside or rail contacting surface viewed;

FIG. 3 is an enlarged cross section through the splice joint of the showing of FIG. I as would be seen when viewed along the line 3-3 thereof;

FIG. 4 is an enlarged perspective view from above of the single insulator rail support also seen in FIG. 1 but with the conductor rail removed therefrom to disclose details of the structure;

FIG. 5 is a cross-sectional view through the supported rail of FIG. 1 as would be seen when viewed along the line 5-5 thereof, the showing being on an enlarged scale;

H6. 6 is a vertical jump sectional view through a portion of the conductor rail and rail support as would be seen when viewed along the line 6-6 of FIG. 5;

FIG. 7 is a horizontal sectional view through a portion of the rail and the rail support as would be seen when viewed along the line 7-7 ofFIG. 5; 1,

FIG. 8 is a perspective view of a section of the conductor rail according to the invention but showing a double insulator rail support utilized in a hanger type supporting arrangement;

PEG. 5 is a perspective view from above on an enlarged scale of the-double insulator rail support shown in FIG. 8 but inverted to disclose certain configurational details;

FiG. i0 is a vertical sectional view through the supported rail structure shown in FIG. 8, on an enlarged scale, as would be seen when viewed along the line 10-10 of FIG. 8;

FIG. 11 is a horizontal sectional view through a portion of the supported rail base and the rail supports as would be seen when viewed along the line 11-11 of FIG. 10; and

FIG. 12 is a vertical sectional view through the rail grip bolting securement of the rail support head as would be seen when viewed along the line 12-12 of FIG. 10.

in the several figures, like elements are denoted by like reference characters.

Turning now to the drawings, and considering first FIGS. 1, 3 and 5, thereis seen the composite conductor rail generally designated as 20 having a cap part 21 of T-shape in cross section and a base or body part 22 of inverted T in cross section. The depending stem part 23 of the T-shaped cap 21 tapers from a broader upper end where the stern joins the head of the cap to a somewhat narrower terminating lower end, and the upstanding stem or web of the body part 22 is vertically split or bifurcated into a pair of longitudinally extending laterally spaced arms 24 with a channel therebetween complementally shaped to close fittingly contactingly receive the stem 23 of the T-shaped cap part 21. The base arms 24 extend upward to the top of the cap stem and terminate where the cap stem 23 joins the cap head 25.

Formed integrally with and projecting laterally outward from the base arms 24 in a region thereof spaced downward from the top of and upward from the bottom of the arms 24 are continuously longitudinally extending protrusions or keys 26 illustrated in the drawings as being generally of trapezoidal shape. These keys 26 perform several functions. First, since they enlarge the cross section of the highly conductive body part, normally made of aluminum, they provide additional current carrying capability and help to reduce the current density in the conductor rail. Additionally, they provide a reinforced section of high strength through which the compression bolts 27 best seen in FIGS. 1 and 5 are projected to rigidly clamp together the cap 21 and base 22 of the conductor rail 20. The compression bolts 27 prevent any long time tendency of the cap 21 and the base 22 toward mechanical separation even though they are tightly press fitted together and bonded at their interfaces with an electrically conductive no-oxide compound.

terfit with splice plates or bars designated generally at 28 which are formed with a trapezoidally shaped longitudinally extending recess or keyway 29 of the same cross-sectional size and shape as that of the rail keys 26 so that the rail keys 26 are close fittingly nestable within the splice plate keyways 29. The multiple surface engagement between the rail keys 26 and splice plate keyways29 provides a larger surface contact at a given cross section point than is possible with a single plane engagement surface of the same height, so that a shorter vertical section is possible as well as a reduced length of the splice plate in order to provide no more than a specified maximum current density through the interfaces of the splice joint. Additionally, the trapezoidal shape provides strong reinforcing resistance to bending moments about a horizontal axis perpendicular to the longitudinal axis of the conductor rails to thereby reinforce the rails. at the splice joint against vertical deflection. The vertical extent of the rail keys 21 is preferably in the range between forty percent and sixty percent of the height of the composite web of the conductor rail.

As best seen from FIGS. 1, 2 and 3, the splice plates 28 are rigidly clamped to the conductor rails by bolts 30 projected through apertures 31 and 32 in the splice plates and conductor rails respectively, and secured by lock washers 33 and nuts 34. The planar face of the splice plate through which the keyway 29 opens does not contact the outer faces of the arms 24. As

described, to supportingly engage the conductor rail base flange 38 at the splice joint without interference from the splice plate structure. The depending portions 35 of the splice plates of course add substantially to the ability of the splice plate to resist vertical deflection of the conductor rail at the joint.

Referring now also to FIGS. 4 through 7, there is shown a rail support including an insulator 39 provided at opposite ends with threaded inserts into which are affixable respectively a support 40 and a bolt 41 which latter secures to one end of the insulator 39 a rail support head 42. The rail support head, as best seen from FIGS. 4 and 5, is of generally C-shape having a main substantially horizontally extending base wall 43 from which vertically extend at opposite ends of the base wall a pair of arms each having a vertical section 44 terminating at the upper end in an inturned horizontal section 45. Spaced inward from each of the vertical sections 44 and extending upward from the base wall 43 are vertical support walls 46 each having a high point 47 lower than the low point 48 on the underside of the horizontal section 45 by an amount at least equal to or slightly greater than the height of the outer'edge 37 of the conductor rail base part flange 38, and the vertical sections 44 are separated at their near points 49 by a distance at least equal to the width of the conductor rail base part 38. The entire rail support head 42 is covered with a low friction plastic coating 50, such as nylon.

As best seen from the showing of FIG. 6, the undersurface of horizontal section 45 tapers upward in opposite directions from the low point 48 while the upper surface of the vertical support walls 46 taper downward in opposite directions from the high point 47. Similarly, the inside walls of vertical sections 44 taper outward from the near points 49, and a similar tapered effect is shown in FIG. 40;: the inside faces of the horizontal section 45. While the single insulator support shown in FIGS. 1, and 4 to 7 is illustrated as holding the conductor rail in position for overrunningoperation, it will be appreciated that underrunning operation may be readily provided by merely inverting the entire assembly so that the conductor rail is supported on the horizontal'sections 45 of the rail support head 42 instead of upon the vertical support walls 46.

As best seen from FIGS. 4, 6 and 7, the tapered faces of the rail support head 42 which are engageable by-the composite conductor rail are tapered to provideminimum contact surface with the conductor rail, and are provided with a low friction coating, so that together these aspects allow the conductor rail to slide smoothly through the rail support head during installation and also during operation upon the occurrence of normally encountered expansions and contractions of the conductor rail.

Considering now FIGS. 8 through 12,-there is seen a double I insulator rail support including a pair of spaced apart insulators 51 each having affixed to oneend thereof an insulator support 52 by means of which the rail support is fixedly secured to a main supporting structure, not shown. Secured to the opposite end of each of the insulators 51 by means of bolts 53 is a rail support head designated generally as 54.

The rail support head 54 is of generally (Z-shape and includes an elongated flat bar rectangular base 55 apertured at both ends to permit passage therethrough of the securing bolts 53, and a pair of rail grips designated generally as 56. Each of the rail grips 56 has a main body portion 57 which overlies the base 55 and has depending from opposite sides thereof skirts 58 which prevent the rail grips 56 from rotating relative to the base 55 when the bolts 53 are tightened'down. As best seen from FIGS. 9 and 11, the front faces of the main body 57 between the side skirts 58 which face the conductor rail base flange 38 are radiused so that each includes a near point 59 from which the front face recedes toward the side skirts 58, the main body front face curving away fairly sharply as at 60 toward one of the side skirts and curving away much more gradually on a larger radius of curvature as at 61, toward the other side skirt 58.

Formed integrally with the rail grip main body 57 and extending horizontallyinward overlying the base 35 is a flange retainer 62 having a front edge arcuately curved as at 63, the flange retainers 62 holding the conductor rail base flange 38 captive between the support head base 55 and rail grips 56, as best seen in the showing of MG. 10'. The support head rectangular base 55 and the rail grips 56 are also covered with a low friction plastic coating 64, such as nylon, which together with the radiused front faces of the rail grip main bodies 57 and the upwardly tapered undersurfaces 65 of the flange retainers 62 prevents binding of the conductor rail in the support head and permits easy sliding movement of the rail therethrough.

Additionally, the conductor rail may be quickly installed to and removed from the rail support head 54 by loosening the bolts 53 sufficiently to allow the rail grips side skirts 58 to clear the surface of the rectangular base 55 so that the rail grips 56 may be rotated through to shift the flange retainers 62 out from its rail capturing position and thereby release the rail from the support head.

Having now described the invention in connection with a particularly illustrated embodiment thereof, it will be understood that modifications and variations thereof may now occur from time to time to those persons normally skilled in the art without departing from the essential scope or spirit of the invention, and accordingly it is intended to claim the same broadly as well as specifically as indicated by the appended claims.

I claim:

l. A pair of current conductor rails endwise aligned in closely spaced relationship and rigidly secured together by a pair of splice plates, each of said current conductor rails being of general l-beam cross section and comprising a rigid electrically conductive base flange, a rigid electrically conductive web integral with and extending upward from said base flange, a rigid electrically conductive head part integral with said web and substantially parallel to said base flange, and a pair of keys formed integrally with and projecting laterally outward respectively from opposite sides of. said web in a region thereof spaced downward from said head part and upward from said flange part, said keys extending continuously longitudinally of said conductor rail and being of a constant vertical extent in the range between forty percent and sixty percent of the height of said web and of lesser width than height, each said splice plate being of substantially greater vertical extent than that of said rail key and being'of a width substantially greater than the lateral projection of said keys from said web and having a planar face extending longitudinally from end to end of said splice plate through'which face opens a keyway recess of substantially the same cross-sectional size and shape as that of the said rail keys but of slightly shallower depth so that the said planar splice plate face does not mechanically engage the side of the rail web from which extends the said rail key and the rail keys close fittingly nest within said keyways in broad surface contact therewith, the vertical extent of said splice plates adjacent to said rail web being substantially equal to but somewhat less than the clear distance between said conductor rail head part and base flange, and the lower edge of said splice plates in the region of the base flange outer edges being spaced above said base flanges a sufficient distance to permit securement of conductor rail support heads to the said base flanges of said conductor rails throughout the longitudinal extent of said splice plates.

2. A pair of current conductor rails endwise aligned in closely spaced relationship and rigidlysecured together by a pair of splice plates, each of said current conductor rails being of general l-beam cross section and comprising a rigid electrically conductive base flange, a rigid electrically conductive web integral with and extending upward from said base flange, a rigid electrically conductive head part integral with said web and substantially parallel to said baseflange, and a pair of keys formed integrally with and projecting laterally outward from said flange part, said keys extending continuously longitudinally of said conductor rail and being of a constant vertical extent in the range between forty percent and sixty percent of the height of said web and of lesser width than height, each said splice plate being of substantially greater vertical extent that of said rail key and being of a width substantially greater than the lateral projection of said'keys from said web and having a planar face extending longitudinally from end to end of said splice plate through which face opens a keyway recess of substantially the same cross-sectional size and shape as that of the said rail keys but of slightly shallower depth so that the said planar splice plate face does not mechanically engage the side of the rail web from which extends the said rail key and the rail keys close fittingly nest within said keyways in broad surface contact therewith, each -.of said rail keys being generally of trapezoidal shape in cross section and the upper and lower surfaces of which are the sides of the trapezoid with the outer lateral surface of each key being the smaller base of the trapezoid, the said keyway recesses in said splice plates having recess walls closely surface conforming to the said sides and smaller base of said trapezoidal rail keys.

3. Apparatus as defined in claiml further including at least one conductor rail support head secured to and carried by at least one electrical insulator, said support head being generally of C-shape when viewed endwise and comprising a main substantially horizontally extending support head base and a pair of rail grip arms extending vertically from the said support head base at opposite ends thereof and turning inward toward one another as flange retainers into overlying relationship to the outer edges of the base flange of one of said rails and underlying relationship to a part of each of said splice plates, the underside of said rail base flange resting on said support head base.

4. Apparatus as defined in claim 3 wherein, the undersurfaces of the portions of said rail grip arms which overlie the outer edges of said conductor rail base flange as flange retainers have a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the sidesurfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange have substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail.

5. Apparatus as defined in claim 3 wherein, the undersurfaces of the portions of said rail grip mean arms which overlie the outer edges of said conductor rail base flange as flange retainers have a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the side surfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange have substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail, and the support head base includes a pair of upstanding support walls each having a substantially longitudinally centered high point from which the upper surface of each of said support walls tapers downward in opposite longitudinal directions.

6. Apparatus as defined in claim 3.wherein, the undersurfaces of the portions of said rail grip arms which overlie the outer edges of said conductor rail base flange as flange retainers have a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the side surfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange have substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail, said rail grips each being detachably fixedly secured by securing means to said support head base and each such rail grip comprising, a main body portion overlying said support head base and having a skirt depending from each side thereof along opposite sides of said support head base to thereby prevent rotation of said rail grips relative to said su port head base when secured by said securing means, said s irts being raisable by release or said securing means to clear the surface of said support head base so that said rail grips are movable to shift said flange retainers and thereby release said conductor rail from said support head. 7

7. Apparatus as defined in claim 3 wherein, the undersurface of the portions of said rail grip arms which overlie the outer edges of said conductor rail base flange as flange retainers have a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the side surfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange have substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail, the rate of outward taper of said side surfaces from the said near point of each being markedly different in opposite longitudinal directions.

8. A current conductor rail support head for use with a current conductor rail characterized by the inclusion of a rigid longitudinally extending base flange having outer side edges, said rail support head being generally of C-shape when viewed endwise and comprising in combination, a main substantially horizontally extending support head base, a pair of rail grip arms extending vertically from the said support head base at opposite ends thereof and turning inward toward one another as flange retainers into overlying relationship to the outer edges of the base flange of the said conductor rail, the undersurfaces of the portions of said rail grip arms which overlie the outer edges of said conductor rail base flange as flange retainers having a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the side surfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange having substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail, and a pair of upstanding support walls each having a substantially longitudinally centered high point from which the upper surface of each of said support walls tapers downward in opposite longitudinal directions.

9. A current conductor rail support head as defined in claim 8 wherein said rail grips are each detachably fixedly secured by securing means to said support head base and each such rail grip comprises, a main body portion overlying said support head base and having a skirt depending from each side thereof along opposite sides of said support head base to thereby prevent rotation of said rail grips relative to said support head base when secured by said securing means, said skirts being raisable by release of said securing means to clear the surface of said support head base so that said rail grips are movable to shift said flange retainers and thereby release said conductor rail from said support head.

10. A current conductor rail support head as defined in claim 8 wherein, the rate of outward taper of said side surfaces from the said near point of each of said rail grips is markedly different in opposite longitudinal directions.

Claims

1. A pair of current conductor rails endwise aligned in closely spaced relationship and rigidly secured together by a pair of splice plates, each of said current conductor rails being of general I-beam cross section and comprising a rigid electrically conductive base flange, a rigid electrically conductive web integral with and extending upward from said base flange, a rigid electrically conductive head part integral with said web and substantially parallel to said base flange, and a pair of keys formed integrally with and projecting laterally outward respectively from opposite sides of said web in a region thereof spaced downward from said head part and upward from said flange part, said keys extending continuously longitudinally of said conductor rail and being of a constant vertical extent in the range between forty percent and sixty percent of the height of said web and of lesser width than height, each said splice plate being of substantially greater vertical extent than that of said rail key and being of a width substantially greater than the lateral projection of said keys from said web and having a planar face extending longitudinally from end to end of said splice plate through which face opens a keyway recess of substantially the same cross-sectional size and shape as that of the said rail keys but of slightly shallower depth so that the said planar splice plate face does not mechanically engage the side of the rail web from which extends the said rail key and the rail keys close fittingly nest within said keyways in broad surface contact therewith, the vertical extent of said splice plates adjacent to said rail web being substantially equal to but somewhat less than the clear distance between said conductor rail head part and base flange, and the lower edge of said splice plates in the region of the base flange outer edges being spaced above said base flanges a sufficient distance to permit securement of conductor rail support heads to the said base flanges of said conductor rails throughout the longitudinal extent of said splice plates.

2. A pair of current conductor rails endwise aligned in closely spaced relationship and rigidly secured together by a pair of splice plates, each of said current conductor rails being of general I-beam cross section and comprising a rigid electrically conductive base flange, a rigid electrically conductive web integral with and extending upward from said base flange, a rigid electrically conductive head part integral with said web and substantially parallel to said base flange, and a pair of keys formed integrally with and projecting laterally outward respectively from opposite sides of said web in a region thereof spaced downward from said head part and upward from said flange part, said keys extending continuously longitudinally of said conductor rail and being of a constant vertical extent in the range between forty percent and sixty percent of the height of said web and of lesser width than height, each said splice plate being of substantially greater vertical extent that of said rail key and being of a width substantially greater than the lateral projection of said keys from said web and having a planar face extending longitudinally from end to end of said splice plate through which face opens a keyway recess of substantially the same cross-sectional size and shape as that of the said rail keys but of slightly shallower depth so that the said planar splice plate face does not mechanically engage the side of the rail web from which extends the said rail key and the rail keys close fittingly nest within said keyways in broad surface contact therewith, each of said rail keys being generally of trapezoidal shape in cross section and the upper and lower surfaces of which are the sides of the trapezoid with the outer lateral surface of each key being the smaller base of the trapezoid, the said keyway recesses in said splice plates having recess walls closely surface conforming to the said sides and smaLler base of said trapezoidal rail keys.

3. Apparatus as defined in claim 1 further including at least one conductor rail support head secured to and carried by at least one electrical insulator, said support head being generally of C-shape when viewed endwise and comprising a main substantially horizontally extending support head base and a pair of rail grip arms extending vertically from the said support head base at opposite ends thereof and turning inward toward one another as flange retainers into overlying relationship to the outer edges of the base flange of one of said rails and underlying relationship to a part of each of said splice plates, the underside of said rail base flange resting on said support head base.

4. Apparatus as defined in claim 3 wherein, the undersurfaces of the portions of said rail grip arms which overlie the outer edges of said conductor rail base flange as flange retainers have a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the side surfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange have substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail.

6. Apparatus as defined in claim 3 wherein, the undersurfaces of the portions of said rail grip arms which overlie the outer edges of said conductor rail base flange as flange retainers have a substantially longitudinally centered low point from which the undersurface tapers upward in opposite longitudinal directions, and the side surfaces of the portions of said rail grip arms which face the side edges of said conductor rail base flange have substantially longitudinally centered near points from which the side surfaces taper outward in opposite longitudinal directions away from said rail, said rail grips each being detachably fixedly secured by securing means to said support head base and each such rail grip comprising, a main body portion overlying said support head base and having a skirt depending from each side thereof along opposite sides of said support head base to thereby prevent rotation of said rail grips relative to said support head base when secured by said securing means, said skirts being raisable by release of said securing means to clear the surface of said support head base so that said rail grips are movable to shift said flange retainers and thereby release said conductor rail from said support head.