Abstract:
A telescoping drawbar is provided to insure a variable length connection between a pulled trailer and a tandem connected trailer supported on a portable dolly. The telescoping drawbar includes a number of telescoped tube segments which are aligned and secured with interlocking wedges, plates and mating stops located on the surfaces of overlapping telescoping sections. The wedge-shaped plates and associated stops securely interlock the telescoping sections and accurately align locking openings for insertion of locking bolts.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to over-the-road semitrailer trucks and in particular to a tandem arrangement of trucks wherein a lead truck pulls a second, tandem-connected truck which is supported by a dolly connected to the pulling truck with drawbar. This disclosure deals with a new and improved drawbar for securely interconnecting the two trailers. 
     2. Description of the Prior Art 
     Because of varying state regulations regarding spacing between axles of tandem trailers, it is necessary to provide a drawbar interconnecting the two trailers that has the capability of being adjusted to different lengths. Telescoping members are easily adjusted, however, as with any telescoping members there can be excessive vertical deflection as well as lateral swaying during transit and which must be limited to properly control movement of the second trailer and to prevent permature failure and wear of the telescoping drawbar. While telescoping drawbars have been disclosed in the art such as that shown in U.S. Pat. No. 3,717,363 (1973) to H. Berends, problems can occur when such a complicated mechanism is provided. Further, the patent referred to, while providing internal stops which limit extension of the telescoping tubes, the internal stops do not provide automatic alignment of locking openings and do not provide a feature of securely fitting together telescoping members. 
     SUMMARY OF THE INVENTION 
     This disclosure pertains to a telescoping drawbar having a number of pieces of telescoping tubing, each having connected thereto locking and alignment plates which include wedge-shaped portions which mate in such a fashion to securely connect the telescoping pieces and align locking openings for additional location of a mechanical fastener which positively and securely locks the drawbar in the desired, extended position. 
     In operation, the locking and alignment plates are located on the inside of the larger tubing and the outside of the associated smaller, telescoped piece of tubing and are positioned in such a manner that when the telescoping tubing is extended, each locking wedge will automatically mate together with a stop plate having a suitably shaped, wedge-shaped cutout welded to a smaller sized telescoping tube. Such a mated connection provides locking openings that are thereby automatically aligned. A mechanical fastener such as a high strength bolt may be positioned within the aligned openings to securely and positively secure the telescoped pieces of tubing in an extended position. 
     It is thus an object of the disclosure to show a drawbar arrangement for tandem trailers whereby the drawbar includes a number of telescoping segments to allow the drawbar to be adjusted in length to comply with various state regulations regarding space in between trailer axles. 
     Another object of the disclosure is to provide a telescoping drawbar arrangement having alignment and rigidifying members which automatically interconnect telescoping sections of tubing to prevent excessive sway and vertical deflection during transit. 
     Another object of the disclosure is to show telescoping drawbar arrangement wherein the telescoping segments include alignment plates having contoured, mating surfaces which mesh together and securely interconnect the adjacent telescoped pieces of tubing and provide for alignment of locking openings within the associated pieces of telescoping tubing. 
     These and other objects will become apparent to those having ordinary skill in the art with reference to the following drawings, description and appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view showing tandem trailers and the connecting, telescoping drawbar; 
     FIG. 2 is a top view shown in the drawbar illustrated in FIG. 1; 
     FIG. 3 is an enlarged elevational view of the drawbar shown in FIG. 2; 
     FIG. 4 is a view taken generally along lines 4--4 of FIG. 2; 
     FIG. 5 is a view taken along lines 5--5 of FIG. 4; 
     FIG. 6 is a view taken generally along lines 6--6 of FIG. 4; 
     FIG. 7 is a view taken generally along lines 7--7 of FIG. 2; and 
     FIG. 8 is an enlarged pictorial illustration showing the locking and aligning components used with the telescoping members. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a pair of trailers with a leading trailer 10 attached to a driven or trailing tandem connected trailer 12. Each trailer includes the usual king pin 13 for attachment to the fifth wheel of a tractor or for attachment to the fifth wheel of a dolly 14. The trailers may include a flat bed or the usual body 16 and a so-called landing gear 18 which allows for support of the trailer when not in transit. Each trailer includes a rear axle unit 20 which may be of a variety of conventional designs which are well known in the art. 
     Because the tandem trailer 12 is supported by a dolly, it is necessary to provide an interconnecting member to securely lock the trailer 12 to the leading trailer 10. Thus, a so-called drawbar or drawbar means 22 extends from dolly 14 to a hitch 25 of the trailer 10. As shown in FIG. 2, the drawbar 22 includes a number of individual telescoping members or sections and has a dolly-connecting frame 24 at one end to allow the drawbar to be securely attached to the trailer-supporting dolly. Connecting frame 24 includes a transverse beam 26 which is reinforced by diagonal braces 28. A reinforcing metal plate or web 30 may be used to further rigidify the connecting frame 24. 
     Telescoping tubular members or means comprise a first, large tube 32 which is securely attached to the connecting frame 24. Extending from the first tube 32 is a smaller, telescoping tube 34. Similarly, a smaller tube 36 fits within tube 34 and the smallest of the telescoping tubes 38 is fitted within and may extend from tube 36. As shown in FIG. 2, the end tube 38 has a hook means or an eye member 40 securely attached to the end to permit easy attachment to the trailer hitch 25. A stop bar or an locating means 41 (FIG. 3) permits easy location of the drawbar eye for connection with a pin in the hitch 25. 
     A wheel support or height adjustment means 42 is attached to one of the telescoping members of the drawbar 22 and is rendered adjustable with the rotating handle 43 which may be moved to raise and lower tire 44. Thus, the drawbar may be easily aligned with hitch 25 and easily stored above the ground when not in use. 
     Each of the telescoping tubes 32, 34, 36 and 38 has openings at each end to permit insertion of a locking pin 46. As shown in FIG. 2, when the drawbar is fully extended, three locking pins are utilized to maintain the tubing sections in a fully extended configuration. Similarly, if it is desired to shorten the length of the bar, the telescoped tubing is merely pushed within one another until associated locking openings are in alignment and a single or plurality of locking pins may be used. When the drawbar is fully collapsed, all the locking openings will be in alignment and only a single locking pin will be necessary. 
     This disclosure provides a simplified, reliable arrangement of plates attached to the end portion of the telescoping tubing which not only interlocks the pieces of tubing in a secure fashion, but also are used to align the locking openings prior to insertion of locking pins 46. The plates or grooved alignment member consist of a so-called stop plate 50 which includes a pair of tapered arms extending outwardly from a bottom to provide a generally modified, U-shaped opening. The stop or groove member 50 cooperates with a locking wedge or wedge member 48 which has a similarly shaped, modified, U-shaped end member and guide surfaces 54 which cooperate with guide surfaces 52 of the stop plate 50 to guide the telescoping members into a lock and align position. As shown in FIG. 8, the locking wedge 48 and stop plate 50 are arranged in an alternate manner around each end of the telescoping tube. Thus, tube 34 has one end with plates 48 and 50 arranged alternately around the outside. Likewise, tube 34 has stop or locking plates 48 and 50 also arranged in an alternate fashion at the opposite end but on the inside surface of the tube. The same construction is present on the other telescoping tube members. 
     Thus, it is shown that when the tubing members are extended and plates located on the outside of one telescoped tube interlock with associated tubes on the inside portion of the larger piece of associated tubing, not only do the tapered guide surfaces of wedges 48 and stops 50 guide the pieces of tubing into a secure locked relationship but such arrangement also insures that the associated locking openings are aligned for easily inserting locking pins 46. When locking pins 46 are inserted, collapse of the telescope pieces of tubing is prohibited. 
     The following description will show how the telescoping drawbar car be easily assembled and disassembled in the event it is desired to change the length of the various sections of the tubing or when it is necessary to repair or replace a damaged section of tubing. As shown in the illustration, a unique feature of this arrangement is that with each telescoping piece of tubing the locking and alignment plates 48, 50 are on the exterior of only one end. Referring to FIG. 8, for example, if it is desirable to remove tubing 34, 36, all that is necessary is that tubing 36 be slid completely through the overlapping pieces of tubing, 32, 34. The locking and alignment plates 48, 50 located on the exterior surface of the inside end of tube 36 will slide through the larger pieces of tubing 32, 34. Because there are no locking plates on the exterior of the opposite end of tubing 36, that end is free to slide through and pass locking plates 48, 50, which are located on the inside end of tubing 34. 
     Similarly, in assembling the telescoping drawbar, it is more practical and economical to preconstruct each piece of tubing as a subassembly and then assemble the fabricated tubes at the cite where final assembly takes place without the need for any welding, measuring or alignment. Thus, it is shown with the foregoing, this novel drawbar arrangement provides a positive interlocking and alignment feature between the extended pieces of tubing. The method of assembling the telescoping pieces of tubing is also unique insofar as it is economical and accomplished quickly and also provides an arrangement that may be easily disassembled for repair or replacement of any of the telescoping segments. 
     The foregoing description and drawings merely explain and illustrate the invention and the invention is not limited thereto, except insofar as the appended claims are so limited, as those who are skilled in the art and have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.