Trolley rails with expansion joints between them

[57] ABSTRACT

A plurality of rigid rails are connected end to end with spaces between them for thermal expansion. The front sides of the rails are provided with parallel slots extending lengthwise thereof for receiving current pickup members movable lengthwise of the rails in engagement with electrical conductor bars mounted in the slots. These bars project from one end of each rail into the adjoining rail and are connected to the bars therein. An insulating channel member surrounds three sides of each bar where it spans the space between adjoining rails. Each channel member is secured in one rail and is slidably mounted in the adjoining one.

Claims, 8 Drawing Figures

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PATENTEDAPR 21974 3.801,751

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WNTEOAPR 21974 3,801,751

SHEET 2 OF 2

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TROLLEY RAILS WITH EXPANSION JOINTS BETWEEN THEM

In my copending patent application Ser. No. 120,821, filed Mar. 4, 1971, the rails that support the metal conductor bars are made of a plastic that has a greater coefficient of thermal expansion than the conductors. The rails are disposed end to end, and the conductor bars extend from one end of each rail into the end of the adjoining rail, where they are connected to the conductor bars therein. Although the rails in my patent application are shown engaging one another end to end, it has been found in practice that when they are subjected to temperature changes of material extent they will expand or contract more than the conductor bars and therefore may present a problem. Accordingly, where such temperature changes are to be expected the rails are installed with their ends spaced apart at the joints to allow for thermal expansion. This means that the projecting conductor bars extending across the open joints have no insulation between them, so it is possible for arcing to occur between the bars, easily touched by personnel, or for dirt to accumulate between them and conduct electricity between them.

It is therefore an object of this invention to provide means for insulating the conductor bars from one another at the joints between adjoining rails, and to do so without interfering with expansion and contraction of the rails.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which

FIG. 1 is a plan or back view;

FIG. 2 is a side view partly broken away in section;

FIG. 3 is a bottom or front view;

FIG. 4 is an enlarged cross section taken on the line IV—IV of FIG. 2;

FIG. 5 is an enlarged fragmentary longitudinal section taken on the line V—V of FIG. 2;

FIG. 6 is a fragmentary longitudinal section taken on the line VI—VI of FIG. 5;

FIG. 7 is a fragmentary cross section taken on the line VII—VII of FIG. 6; and

FIG. 8 is an enlarged perspective view of an insulating channel.

Referring to the drawings, a rigid rail 1 of any desired length, such as ten to twenty feet, is extruded from a suitable plastic. High impact polyvinyl chloride is satisfactory. The rail preferably has a generally rectangular outline in cross section and may be tubular to reduce its weight, to provide a duct for wires and liquid conduits, and for other purposes. This rail is connected end to end with other like rails as shown, to form a continuous rail of any desired length, but normally gaps are left at the joints for a purpose to be explained.

In order to fasten the rail to a support beside it or above it, the back or top of the rail may be provided with a channel 2 extending lengthwise of it. The outer edges of the side walls of the channel have flanges 3 extending toward each other a short distance. Bolts 4 are disposed along the channel for connecting the rail to its support or supports. Each bolt has a rectangular head 5 that is narrow enough to be inserted between the channel flanges, but the head may be long enough so that it then can be rotated only about 90° before its ends will strike the side walls of the channel and stop further rotation. The bolts can be moved along the channel to any desired positions. These bolts are of two types. One is shaped to permit the rail to slide lengthwise; the other holds the rail tightly against its supports. It is preferred to anchor the center of each rail firmly to its support, which the rest of the hangers will permit 5 movement of the rail caused by expansion and contraction.

The channels 2 also aid in connecting the rails end to end. For this purpose as shown in FIGS. 1, 4 and 6, a rectangular plate 7 is slid into one end of a rail channel 10 and then the adjacent end of the next rail is moved up against the end of the first rail. The plate is moved along the two channels until it straddles the joint between the adjacent ends of the rails. Another plate 8 is placed against the back of flanges 3, and screws 9 that 15 are rotatably mounted in this plate are screwed into threaded holes in the first plate. By tightening the screws, the flanges of the two rails can be clamped between the two plates. The screws are tightened in a manner suitable for sliding of the rail flanges between 20 the two plates to accommodate expansion and contraction of the rails. Preferably, the plates are provided with central longitudinal channels that nest together. If desired, the two plates can be connected together loosely and handled as a single unit before the inner ²⁵ plate 7 is inserted in the rail channels.

The opposite side of the rail, which is the bottom or front side, is provided with parallel slots 10 extending lengthwise of it. There are at least two of these slots and usually three or more. As shown in FIG. 7, the inner ³⁰ sides of the slots opposite their open sides are closed by a partition wall 11 that extends across them and forms the front or lower wall of the tubular portion of the rail. The opposite side walls of each slot 10 are provided at their inner sides beside the partition wall with a pair of ⁵ opposed grooves 12 extending lengthwise of the rail. Disposed in each of the slots there is a rigid electrical conductor bar 13, the edges of which extend into the grooves to retain the bar in place. Extending lengthwise 40 ^{of each} groove is a narrow central rib 14, tapered in ^υ cross section, that engages the edges of the bar in that groove. The bars are inserted in the grooves from one end of the rail. Although the bars cannot escape from the grooves, it is preferred to secure them in place, 45 such as by an adhesive, but only at one location for each bar. The back of partition wall 11 may be provided with rearwardly projecting longitudinal ribs 15 that strengthen the wall and provide insulating barriers between conductors at the location inside one end of 50 ^{a rail where the} conductors in two rails are spliced together.

The depth of rail slots 10 is such that the exposed front surfaces of the conductor bars are spaced a considerable distance inwardly from the front face of the ₅₅ rail. Consequently, there is little danger of something accidentally coming in contact with the recessed conductor bars. On the other hand, the conductor bars are engaged by current pick-up members that extend into the slots. These may be trolley wheels or sliding shoes ¢0 supported at their outer ends in any suitable manner. For example, as shown in FIG. 4, shoes 16 may be mounted on the base 17 of a trolley that has upwardly extending side flanges 18 straddling the rail and provided with wheels 19 that travel along the opposite sides of the rail in channels 20 that form tracks for the wheels. The contact shoes are electrically connected in the trolley to conductors 21, by which current is carried away from them.

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To increase the electrical leakage distance of the side walls of the slots, they are provided with a further pair of grooves 23 that leave longitudinal ribs 24 and 25. This increased surface area or leakage distance makes it extremely unlikely that carbon dust from the contact 5 shoes, which may accumulate to some extent on the slot walls, will cause trouble.

To connect the conductor bars 13 of one rail with the bars in another rail aligned with it, the partition wall 11 in one rail terminates short of the end of that rail that 1( is adjacent the other rail, so that the backs of slots 10 where the partition wall is missing are not closed, as shown in FIGS. 5 and 6. This exposes the backs of end portions of the conductor bars in the first rail. The conductor bars in the other rail have projecting end por- 15 tions 27 that extend into the first rail and are offset rearwardly far enough to overlap the exposed backs of the bars therein.

To secure the overlapping end portions of the bars tightly together, those in the first rail are provided with 2C countersunk holes in which screws 28 are rotatably mounted. The heads of the screws are flush with the outer surfaces of the bars. These screws extend through openings in the offset end portions 27 of the adjoining bars and into nut members 29 behind them. By tighten- 25 mg the screws, the overlapping end portions of the bars are clamped tightly together. Preferably, the rail is furnished with the screws in place and in the nut members. In that case, the offset ends of the bars in the adjoining rail are provided with open end slots 30 so that they can ³⁰be slid across the screws in the space between the nut members and the screw-carrying bars when the rails are moved together. The screws are then tightened to clamp the overlapping bars together. Of course, in each rail that is not to form an end rail of the system, the ³⁵conductor bars carry the screws and nut members at one end and have the projecting slotted offset end portions at the opposite end.

The plastic from which the rails are made has a high coefficient of thermal expansion; considerably higher ⁴⁰than that of the conductor bars that usually are copper. This means that a problem can arise when the rails are subjected to temperature changes of any material extent. The rails therefore should be installed with gaps between their ends to allow for expansion on hot days ⁴⁵or in plants where they may be subjected to considerable heat. As the rails expand, of course the width of the gaps becomes less. When the atmosphere around the rails becomes cooler, the gaps open up. These gaps take care of expansion and contraction of the rails, but ⁵⁰they create another problem, which is that unless something is done about it there will be nothing between the short lengths of the conductor bars that span the gaps. With nothing between them, there can be electrical leakage or arcing between them, or dirt may accumu- ⁵⁵late between the bars and become damp and form conductors between them.

It is therefore a feature of this invention that means are provided for insulating the conductor bars from one another in the locations where they bridge the gaps be- ⁶⁰tween adjacent rails. Accordingly, a rigid insulating channel member 32 (FIG. 8) surrounds three sides of each conductor bar where it extends across the gap between adjacent rails, and the ends of the channel member extend into aligned slots 10 in both rails. To pro- ⁶⁵vide space in the slots to receive the channels, the side walls of the slots are recessed. This is done by cutting away the ribs 14 so that there will be a narrow space between the edges of each bar and the adjacent side walls of the slot, and also cutting back ribs 24 to the same extent. There is enough looseness of fit of the bars in grooves 12 to permit the thin webs of the channel members to be inserted between the conductor bars and the partition wall 11 above them at the end of the rail from which the bars project. The channel members can be held rigidly in place in that rail in any suitable manner, such as by gluing them to the side walls of the slots. The side flanges of each channel are very thin, but their free longitudinal edges are thickened as shown in FIG. 4 so that the space between those edges is the same as the width of the open sides of the slots to help guide the contact shoes of the trolley across the gap between the rails so that they will not catch on the end of a rail as they enter it.

The channel members extend from the rail in which they are anchored outwardly along the projecting conductor bars to a point beyond the inclined portions of the bars that are due to their offset ends. The channels are deeper in this area to accommodate the bar offsets and nut members 29 when the rails expand lengthwise. When two aligned rails are pushed together during installation so that their conductor bars can be connected, the deep projecting portions of the channel members slide into the end of the rail with the cut-back partition wall 11. This rail, to receive the channel members, also has its ribs 14 and 24 removed between the end of the partition wall and the adjacent end of the rail to accommodate the sides of the channels. When the rails expand or contract lengthwise, the free ends of the channels slide farther into or farther out of the rail into which they project, but at all times the portions of the conductor bars bridging the gap between the rails are separated by the sides of the channel members so that electrical leakage or arcing cannot occur between the bars, especially since the sides of the channels extend forward a considerable distance beyond the contact front surfaces of the bars.

If desired, the webs of the channel members could be omitted, which would leave only their parallel sides in the form of separate insulating strips between the conductor bars. However, it is preferred to use channel members because they are easier to handle and instal, there are fewer pieces to handle, and their webs provide some additional insulating protection.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.