US 3830427 A
A cable clamp for bonding an electrical conductor to the rail to provide electrical interconnection therebetween which includes a clamp base portion underlying the rail having a hook on one end to engage the base of the rail and the opposite end extending above the base in a resilient spring arm. A contoured contactor block engages the juncture of the base and web of the rail and includes a channel therein in which the conductor is received. A compression block including mating configurations with the contactor block overlies the conductor and a threaded compression member interacts between the spring arm and the compression block to provide a resilient spring bias maintaining the assembly in electrical contact with the rail.
Claims available in
Description (OCR text may contain errors)
United States Patent 11 1 Polidori RAILWAY CONDUCTOR BONDING CLAMP  Inventor: Thomas P. Polidori, Pennsauken,
 Assignee: Contemporary Products Incorporated, Pennsauken, NJ.
221 Filed: Feb. 12,1973
211 App]. No.: 331,991
[451 Aug. 20, 1974 Primary ExaminerM. Henson Wood, Jr. Assistant ExaminerRichard A. Bertsch Attorney, Agent, or Firm--Char1es F. Duffield 5 7 ABSTRACT A cable clamp for bonding an electrical conductor to the rail to provide electrical interconnection therebetween which includes a clamp base portion underlying the rail having a hook on one end to engage the base of the rail and the opposite end extending above the base in a resilient spring arm. A contoured contactor block engages the juncture of the base and web of the rail and includes a channel therein in which the conductor is received. A compression block including mating configurations with the contactor block overlies the conductor and a threaded compression member interacts between the spring arm and the compression block to provide a resilient spring bias maintaining the assembly in electrical contact with the rail.
5 Claims, 4 Drawing Figures 1 RAILWAY CONDUCTOR BONDING CLAMP BACKGROUND OF INVENTION The present invention concerns cable clamps for bonding electrical conductors to railroad rails and the like and, more specifically, to a cable clamp of the type which maintains a resilient force on the conductor.
In the railroad industry today, and especially commuter trains and the like in metropolitan areas, the motive power is usually electric motors associated with the cars. The means of transferring the electric current to the electric motors is usually through what is known as a third rail which carries the hot side of the system and one of the two rails upon which the cars run which constitutes the ground rail.
Inasmuch as the rails extend over great distances, it is impractical to attempt to feed the rails with current at a remote point and expect the voltage and current levels to remain proper throughout'the length of track which may be miles in many cases. Accordingly, the practice is to feed the hot rail and ground the ground rails at multiple points along the track system.
However, even where the tracks are fed at multiple points along the system, there will be many independent sections of the rails bolted together between the various feed and ground points. Resistance due to corrosion and the like will develop at the rail joints. Accordingly, it is necessary to run a conductor the entire length between the feed points to the rails and attach the conductor to the rails at various intervals, in common practice at about 120 foot spacings apart.
Different ways have been devised to electrically attach the conductor to the rails at the various contact points. One such way is to weld or braze the conductor permanently to the rail. However, the conductor is a large stiff cable with a great inertia. The constant expansion and contraction of the rails as well as the vibrations induced therein by the cars passing over the rails often causes the weld joint to break away from the rail thus opening up the electrical connection.
Another way which has been tryed is to use a metallic clamp which will compress the conductor against the rail. These clamps are stiff bulky members which, in various ways, compress the cable against the rail. However, all of these clamps, as a class, lack any resiliency or spring action and suffer from the common problem that expansion and contraction of the rail or deformation of the conductor under the pressure will let the clamp loosen. When this occurs, arcing and poor electrical contact occurs. Additionally, clamps of this type must be constantly readjusted or tightened adding to the cost of operation of the system.
OBJECT AND SUMMARY OF INVENTION It is the object of the present invention to provide a cable clamp for securing a conductor electrically to a railroad rail of the type which will apply a resilient force against the conductor and maintain it in electrical contact with the rail in a manner to avoid the necessity of retightening and adjusting the clamp once set in place.
The foregoing object is carried out by the present invention by the utilization of a clamp member which includes a base portion which underlies the rail and a hook portion on one end which engages the edge of the base flange of the rail. The opposite end of the clamp includes a spring arm which projects upwardly beyond the opposite edge of the base flange. A first contactor block is employed which is contoured to mating configuration with the juncture of the base flange and web of the rail and which includes a channel therein into which the conductor lies. A compression block of a mating configuration with the contactor block overlies the conductor and serves to hold the conductor within the channel. A compression member consisting of a threaded member anchored at one end into the spring arm bears against the compression block and compresses the compression block against the conductor within the channel and resiliently maintains the contactor block and its included conductor in electrical contact with the rail. The spring arm is sufficiently resilient to maintain a nearly constant compressive force upon the assembly notwithstanding variations of thermal expansion, deformation and vibration occurring in the system.
Other objects and advantages of the present invention will become apparent to those skilled in the art following the detailed description thereof taken in conjunction with the drawing.
DESCRIPTION OF DRAWING FIG. 1 is an exploded partially cut away perspective view of the cable clamp assembly of the present invention;
FIG. 2 is an assembled end view of the cable clamp of the present invention;
FIG. 3 is a detail end view of a modification of the anchoring end of the clamp; and
FIG. 4 is a detail end view of a further embodiment of clamp and anchor.
DETAILED DESCRIPTION OF INVENTION The cable clamp assembly of the present invention is shown both in exploded perspective view in FIG. 1 and in assembled end view in FIG. 2 of the drawing and the following description thereof will be taken in respect to both FIGS. 1 and 2 simultaneously.
The clamp assembly includes a clamp 10 which has a base portion 11 which underlies the base flange 12 of a typical third rail 13. The clamp 10 terminates at one end in an anchor hook 14 which engages one end of the base flange 12, as shown in FIG. 2. The opposite end of the clamp 10 terminates in an upwardly extending spring arm 15. The spring arm 15 extends above the base flange 12 a considerable distance and of length sufficient to provide a resilient arm as shown in FIGS. 1 and 2.
The clamp assembly further includes a contactor block 16. The contactor block includes a contoured bottom" portion 17 which is formed at a mating angle or complimentary configuration to the juncture of the base flange and web of the rail as shown in FIG. 2. This configuration provides for greater surface or area of electrical contact and also prevents displacement of the contactor block from the rail. It is, however, to be understood that the principles of the present invention are not limited to the contactor block engaging the juncture of the web and base of the rail but the contactor block could be applied to the flat portions of the web or rail if desired.
The contactor block 16 further includes an elongate channel 18 running through the length of the contactor block. The channel 18 is of semicircular configuration and of a diameter approximating that of the conductor 19 when the insulation has been removed from the conductor as shown in FIG. 1. The conductor is adapted to nest within the channel as shown.
The clamp assembly of the present invention further includes a compression block 20. The compression block is adapted to overlie the cable within the channel of the contactor block and to form a complimentary fit with the contactor block to compress the cable within the channel intov electrical contact with the contactor block.
The configuration of the compression block 20 is that, on its underside, there is included an arcuate groove or minor channel 23 which is adapted to conform to and engage the strands of the conductor 19. The sides of the compression block include opposed grooves 21 on either side of the block and also opposed projections 22 as best shown in FIG. 1. The grooves and projections on the compression block are adapted to mate in complimentary configuration with corresponding projections 23 and grooves 24 in the sides of the channel 18 of the contactor block 16 as best shown in FIG. 1.
The depth of the grooves and length of the projections in the conductor block are such that the compression block will firmly engage and compress against the strands of the cable 19 before bottoming out in the bottom of the grooves. In this manner, great latitude in the radial compression of the cable 19 is possible while at the same time insuring against longitudinal displacement of the compression block 20 from the conductor block 16.
The compressive force between the compression block 20 and spring arm is accomplished by means of a'screw jack arrangement as shown in FIGS. 1 and 2. The screw jack includes a threaded bolt 25 which is threaded into a threaded aperture 26 in the upper end of the spring arm 15. The lower end of the bolt includes a pin 27 of reduced diameter. The pin 27 on the end of the bolt 25 engages an aperture 28 in a spring washer 29 and, in that manner, keeps the spring washer in alignment with the bolt 25. If desired, the pin 27 could be peened over to retain the spring washer to the bolt as an assembly. The spring washer 29, in turn, fits into a corresponding recess 30 in the upper surface of the compression block and is prevented from falling into misalignment by the recess.
A compression nut 31 is threaded onto the lower end of the bolt 25. The compression nut is designed to be threaded upon the stud to a point to permit the pin 27 to project from the nut sufficient to enter the aperture 28 of the spring washer 29. The under surface of the compression nut 31 provides the bearing force upon the upper surface of the spring washer 29. In this manner, a much larger bearing area is obtained through the compression nut 31 while obtaining the advantages of the alignment pin 27 without placing undue bearing forces upon the shoulder of the pin itself. Lastly, a lock nut 32 is positioned on the bolt 25 on the inside of the spring arm 15 and serves to lock the bolt against further turning once the clamp assembly has been tightened.
In some installations, the thickness of the base flange of the rail will differ. Accordingly, it is preferable that some means of adjusting the radius of the anchor hook be provided. One such modification to the anchor hook, in accordance with the present invention, to accomplish this is shown in FIG. 3 of the drawing. In this modification, the anchor hook 14 is made of a greater radius than that of the embodiment shown in FIGS. 1 and 2. The end of the anchor hook includes a threaded aperture. A stud 33 is threaded into the aperture and abuts the top of the base flange of the rail until the base 11 of the clamp is drawn snugly against the bottom surface of the rail. Thereafter, a lock nut 34 is brought into engagement with the top surface of the anchor hook 14 to lock the assembly in place.
A further embodiment of anchor hook is shown in FIG. 4 of the drawing. In this embodiment, the base 1 l of the clamp is astraight member rather than a hooked one. A snubbing block 36 is provided which has an overhanging edge 39 which engages the upper surface of the base flange. The lower portion of the block has a projection 37 which fits into a mating groove cut into the end of the clamp base 11 as shown in FIG. 4.
The snubbing block 36 is held into engagement with the base flange and the clamp base by means of a bolt 38. The end of the clamp base 11 includes a nonthreaded aperture 35 through the base. The bolt 38 passes through this aperture and engages a threaded aperture within the snubbing block 36 to secure the assembly together.
In using the clamp assembly of the present invention, the clamp 10 is first passed beneath the rail and the anchor hook brought into contact with the base flange of the rail. Thereafter, the contactor block 16 is positioned and the conductor 19 placed in the channel of the conductor block after removal of the insulation. Thereafter, the compression block 20 is placed in mating engagement with the conductor block. The spring washer 29 is positioned within the recess 30 and the bolt 25 screwed inwardly in the spring arm until the compression nut 31 engages the spring washer. Thereafter, the nut is torqued down to a predetermined torque which will flex or deflect the spring arm 15 to achieve the desired compression of the assembly. The lock nut is then set and the assembly has been completed.
In one embodiment of clamp assembly, the thickness of the clamp member itself was a inch and the width of the clamp member was 1 to 1 k inches. The clamp was made of heat treated 4,340 steel and the conductor block was made of copper while the compression block was formed of brass. The compression bolt employed was a steel bolt of 5/11 diameter.
From the above description of invention, it will be appreciated that there has been provided a cable clamp assembly for use with third rails and the like wherein the resilient spring arm will flex sufficiently to accommodate for thermal expansion, deformation of the condoctor and vibration in a manner sufficient to maintain the assembly in constant compression and good electrical contact.
. The invention has been described in respect to particular embodiments thereof shown in the drawings. As a result of this description, other modifications and variations will become apparent to those skilled in the art. Accordingly, it is to be understood that no limitation of the scope of the invention was intended by the showing of specific embodiments but, instead, the invention is to be defined by the appended claims.
1. A cable clamp assembly for securing and electrically interconnecting a conductor with a rail comprismg:
a clamp having a base portion adapted to underlie the base flange of the rail perpendicular to the longitudinal axis of the rail and including 'means at one end to engage the edge of the base flange and the opposite end terminating in a spring arm projecting upwardly beyond the base flange;
a conductor block adapted to engage the side of the rail adjacent the spring arm and including a channel therein for reception of the conductor;
a compression block adapted to overlie and maintain the conductor within the channel of the conductor block; and
compression means cooperating between the clamp spring arm and the compression block to compress and resiliently maintain the compression block, conductor and conductor block in electrical contact with the side of the rail.
2. The cable clamp of claim 1 wherein the compression means is a threaded screw member.
3. The cable clamp of claim I wherein the conductor block is contoured on the side thereof contacting the rail for mating configuration with the juncture of the base flange and web of the rail.
4. The cable clamp of claim 1 wherein the conductor block and compression block are of complimentary configuration pennitting compression of the cable therebetween but restricting longitudinal movement one to another.
5. The cable clamp of claim 4 wherein the complimentary configuration of the conductor block and compression block includes mating projections and grooves.