Abstract:
Apparatus for assembling a multi-sectional trackway has a plurality of like track sections which can be joined together, in series. Each track section has first and second transverse edges with respect to the length of the trackway, and has a first abutment surface on one transverse edge and a complementary abutment surface on the other transverse edge. The abutment surfaces slidingly interengage directly or indirectly, in the transverse direction, in order to withstand tensile forces along the length of the trackway. The joint is completed by a bridging plate which spans the interengaged abutment surfaces and is bolted in position thereafter to restrain sliding disengagement of the track sections. A security bolt may be employed to hold the bridging plate in position.

Description:
BACKGROUND TO THE INVENTION  
       [0001]     a) Field of the Invention  
         [0002]     This invention relates to a method for interconnecting adjacent track sections of a multi-sectional trackway, and also apparatus for assembly into such a multi-sectional trackway.  
         [0003]     b) Description of the Prior Art  
         [0004]     The use of pierced steel planking (PSP) for ground-reinforcement and thus the construction of temporary roadways goes back at least 60 years, probably longer. PSP is however heavy, cumbersome and liable to suffer distortion in use which may render it incapable of re-use. Other forms of metallic ground-reinforcement have therefore been sought, and of late track sections made of extruded aluminium alloys have attracted interest. Suitably profiled, these have great strength against compressive stresses and thus are not easily distorted, while they are relatively light in weight. They are however not without fault. While each track section can itself adequately withstand the tensile stresses that arise, the relatively thin aluminium webs of an extruded profile cannot bear the shear stresses that tend to be generated where one track section is interconnected with another.  
         [0005]     A method and apparatus has now been devised for interconnecting track sections of a multi-sectional trackway that it is believed better resolves these various conflicting considerations. This method and apparatus can achieve a further objective, of making the assembled trackway pilfer-resistant, which is of significant benefit, given that such a trackway is of significant value, even as scrap metal.  
       SUMMARY OF THE INVENTION  
       [0006]     According to one aspect of the present invention, there is provided a method of detachably interconnecting two successive like track sections of a multi-sectional trackway so as to assemble a second track section to a first track section in the longitudinal direction of the trackway. Each like track section has first and second transverse edges with at least one abutment surface provided on the first transverse edge and at least one complementary abutment surface formed on the second transverse edge. The at least one abutment surface of a first track section is inter-engageable directly or indirectly through the intermediary of a joining section with the at least one complementary abutment surface of a second track section. When interengaged, the abutment and complementary abutment surfaces resist tensile stress in said longitudinal direction. Each track section has at least one aperture formed adjacent each of its transverse edges. The method of this invention comprises: 
        slidingly interengaging in said transverse direction the at least one abutment surface of the second track section directly or indirectly with the at least one complementary abutment surface of the first track section;     spanning the interengaged abutment surfaces with a bridging plate, said bridging plate having at least two bores normal to a plane containing said longitudinal and transverse directions to receive a bolts each having a respective head, each bore being configured to accommodate substantially fully the head of a received bolt;     aligning the bores of the bridging plate with the respective apertures in the interengaged adjacent track sections; and     inserting respective bolts through the aligned bores and apertures so as to prevent sliding disengagement of either of the track sections.        
 
         [0011]     According to another aspect of this invention, there is provided apparatus for assembly to form a trackway having a longitudinal direction. This apparatus comprises a plurality of like track sections each having first and second transverse edges which extend in a transverse direction at right angles to said longitudinal direction when the track sections are assembled together form a trackway. Each track section has at least one abutment surface provided on the first transverse edge and at least one complementary abutment surface formed on the second transverse edge whereby the at least one abutment surface of a first track section is inter-engageable directly with the at least one complementary abutment surface of a second like track section. Alternatively, the at least one abutment surface of a first track section is interengageable indirectly with the at least one complementary abutment surface of a second track section, through the intermediary of a joining section also having at least one abutment surface and at least one opposed complementary abutment surface. The abutment and complementary abutment surfaces of the track sections when interengaged resist tensile stress in said longitudinal direction.  
         [0012]     Each track section has at least one aperture formed adjacent each of its transverse edges and there is provided a plurality of bolts each having a stem and a head. A bridging plate has at least two bores extending normal to a plane containing said longitudinal and transverse directions, each bore being configured to receive one bolt with the head of the bolt accommodated substantially fully in the bore.  
         [0013]     The trackway is assembled by slidingly interengaging directly or indirectly (using the joining section) the abutment and complementary abutment surfaces of adjacent sections and the assembled sections are held against sliding movement by passing bolts into the bores of the bridging plates aligned with the apertures in the respective track sections. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     A specific embodiment of trackway construction of this invention is described hereinafter and is illustrated in the accompanying drawings. In the drawings:  
         [0015]      FIG. 1  is a side elevational view of two track sections assembled together with an intervening bridging plate to form part of the embodiment of a multi-sectional trackway in accordance with this invention;  
         [0016]      FIG. 2  is a perspective view showing one side and the upper surface of the assembly of  FIG. 1 ;  
         [0017]      FIG. 3  is a purely diagrammatic plan view of a length of trackway formed from an array of side-by-side juxtaposed individual trackway lengths interconnected by bridging plates; and  
         [0018]      FIG. 4  shows a security bolt and operating tool, for use in the embodiment of trackway. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     The method of this invention may be applied to the interconnection (and  mutatis mutandis  to the subsequent disconnection) of track sections made of any material suitable for trackway construction, but which will almost certainly be metallic or predominantly metallic. The invention has been developed particularly to suit track sections made by extrusion from aluminium alloys to have appropriate profiles.  
         [0020]     In a case where the track sections are directly interengaged, it would be possible to provide an aperture in each section which together form a single hole when the sections are assembled together, a bolt passing through the bridging plate being received in that single hole to prevent relative transfer sliding movement of the two track sections. In such a case, it may be advantageous to provide an additional backing plate, on the opposed face of the trackway and threaded to receive the bolt.  
         [0021]     In the alternative case where the track sections are indirectly interengaged, the bridging plate may be formed integrally with the joining section and in this case the bridging plate will require, at each location where the sections are to be secured against relative sliding movement, two bores, one for alignment with each track section aperture, respectively. Then, bolts may be fitted into those bores and aligned apertures, so as to secure the track sections against relative sliding movement.  
         [0022]     Though a single bolt could be used to secure directly connected track sections against relative sliding movement, it is preferred to provide at least two bolts for each direct connection, spaced apart along the length of the transverse edges of the track sections. Depending upon the width of the trackway, greater numbers of bolts may be provided to give adequate security and wear resistance.  
         [0023]     Though there could be a single bridging plate spanning the junction between each pair of adjacent track sections, any one bridging plate need not extend the full width of the adjacent track sections transverse to the length of the trackway. Two or more shorter lengths of bridging plate may be employed rather than a single full-length bridging plate.  
         [0024]     An arrangement involving shorter than full-length bridging plates has a an important advantage. The length of each track section in the transverse direction can be sufficient to provide a trackway of the required width for the intended purpose of the trackway. If however the track section width is less than that desired for the finished trackway, two or more lengths of trackway may be laid side-by-side, abutting each other.  
         [0025]     In the case of a complete trackway having two side-by-side abutted lengths of trackway, these may very conveniently be interconnected by means of a bridging plate which spans both parts of the side-by-side trackways as well as the adjacent track sections of both trackways.  
         [0026]     As a precaution against the consequences of the loss or dysfunction of any individual bolt used to prevent transverse sliding movement of the track sections, it is advantageous to use a pair of closely-adjacent bolts wherever a bolt is required to fulfil the function of preventing said sliding movement. Loss of one bolt, or of its functionality, will not prevent the remaining bolt performing the required function of holding the trackway sections together.  
         [0027]     In order to obtain a preferred feature of this invention, at least some of the bolts are keyed security bolts so constructed that to drive the bolt fully home within the bore in the bridging plate, and to remove the bolt therefrom, a complementarily-keyed tool must be employed. Advantageously, the bolt head is received wholly within a counter-bore in the bridging plate and is a snug fit therein, whereby access can be gained solely to the exposed face of the head of the bolt. That head may be provided with a plurality—and preferably three—of recesses, in an irregular distribution. Such a bolt head may be turned solely by a key having a corresponding number and arrangement of projections receivable in the recesses of the bolt.  
         [0028]     Various oppositely-directed and interengageable abutment surfaces may be provided on the individual track sections. In a preferred arrangement, one transverse edge of a track section has a rib with an enlarged head (hereinafter for convenience referred to generically as a “T-section rib”). The other transverse edge of a track section will then have a channel adapted to accommodate and slidingly receive the T-section rib. Such a channel will also have a T-shaped cross-section with a constricted throat through which the head of the rib cannot be withdrawn. Thus, the T-section rib of one track section may be interengaged with the channel of another section solely by transverse sliding movement.  
         [0029]     An embodiment of the invention will now be described with reference to the drawings. In  FIG. 1 , generally indicated at  10  there is shown apparatus comprising first and second track sections  11 , 12  and a bridging plate  13 . The track sections  11 , 12  are each provided at one end  14 , 14 ′ thereof with a T-section rib  15 , 15 ′, and at the other end  16 , 16 ′ thereof with a complementarily-shaped T-section channel  17 , 17 ′. Each rib  15 , 15 ′ and each channel  17 , 17 ′ extends transversely across the respective end  14 , 14 ′, 16 , 16 ′ of its respective track section  11 , 12 . The bridging plate  13  is also provided with a like T-section rib  15 ″ and a like complimentarily-shaped T-section channel  17 ″, both formed on or in a central web  18  extending between upper and lower plates  19 , 20 .  
         [0030]     The track sections are made by an extrusion process from an aluminium alloy of a suitable grade, the sections being cut to have a suitable length for the intended purpose of the finished trackway. Likewise, the bridging plate  13  also is an aluminium alloy extrusion cut to have an appropriate length as will be described below.  
         [0031]     Referring now to  FIG. 2 , it can be seen that the bridging plate  13  is provided with bores  22  extending through the upper plate  19  thereof. Each bore  22  is counter-bored as shown, so as to be capable of accommodating the head  52  of a security bolt  50  as shown in  FIG. 4 . Apertures  23  are provided in each end  14 , 14 ′, 16 , 16 ″ of the first and second track sections  11 , 12 , each aperture  23  being alienable with a bore  22  so as to receive a security bolt (not shown) therethrough. Each such aperture is in the form of a notch cut into the transverse edge of the track section. The central web  18  of the bridging plate  13  also has a corresponding notch at each bore  22 . When the bridging plate is fitted to adjacent track sections, each such notch in the central web is aligned with the aperture  23  of a track section thereby providing a full hole through which the bolt  50  may pass. In the lower plate  20  of the bridging plate  13 , the bores  22  are threaded, to permit a bolt  50  passed through the aligned notches to be threaded thereunto and tightened down.  
         [0032]      FIG. 4  shows a security bolt  50  and driving tool  51  therefor. The bolt  50  has a head  52  of cylindrical form, the diameter and length of the head  52  being substantially the same as the dimensions of the counter-bore of each bore  22  in the bridging plates. Let into the upper surface  53  of the bolt head  52  are three cylindrical recesses  54 , irregularly positioned with respect to the bolt axis.  
         [0033]     The driving tool  51  has a T-bar  55  carrying a boss  56  on the stem  57  of the bar. The boss  56  is of cylindrical form and has a planar lower face from which project three pegs  58 , receivable in the recesses  54  of the bolt head. The recesses  54  and pegs  58  are coded such that the tool  51  is usable only with bolts having the same arrangement of recesses. For any one trackway, all of the bolts used therewith should have the same configuration and coding, but different trackways may be provided with differently configured bolts and tools.  
         [0034]     As extruded, the track sections  11 , 12  are hollow and are profiled to comprise an upper load-bearing surface  24  and a lower ground-contacting surface  25 , which are spaced apart and interconnected by a plurality of transverse strengthening webs  26  therebetween. The upper and lower surfaces  24 , 25  may be formed with transverse ridges  27  extending thereacross to enhance grip.  
         [0035]     Referring now to  FIG. 3 , it will be seen that a sequence of track sections  30 , 31 , 32  extends in the longitudinal direction A and these are interconnected by bridging plates  33 , 34 , 35  so as to form a length of trackway having the same width in the transverse direction B as the track sections themselves. Juxtaposed in side-by-side abutting relationship therewith is a further sequence of track sections  36 , 37 , 38  again extending in the longitudinal direction A and similarly interconnected by bridging plates  39 , 40 , 41  to form a similar length of trackway.  
         [0036]     The two such trackway lengths are interconnected to form a unitary trackway by further bridging plates  42 , 43 , 44  which simultaneously span the junctions in the longitudinal direction A and also the intersection in the transverse direction B between the two side-by-side juxtaposed lengths of trackway. The central bridging plates  42 , 43 , 44  thus serve both to join together the two separate trackway lengths and also the sections of each separate trackway length. The bridging plates  33 , 34 , 35  and  39 , 40 , 41  along the outer side edges of the trackway lengths function in precisely the same manner as has been described above with reference to  FIGS. 1 and 2 .