AU2011239230A1

AU2011239230A1 - Drawbar Support

Info

Publication number: AU2011239230A1
Application number: AU2011239230A
Authority: AU
Inventors: Guiseppe Inturrisi; Joe Inturrisi
Original assignee: TURRISI ENTPR Pty Ltd
Current assignee: Al Ko Chassis Systems Pty Ltd
Priority date: 2010-10-20
Filing date: 2011-10-20
Publication date: 2012-05-10
Anticipated expiration: 2031-10-20
Also published as: AU2011239230B2

Abstract

A reinforcing bar 90 comprising a reinforcing web 92 or strap attached by welding along a substantial length of the drawbar arm 72b from close to the flat plate 74, under the front beam 5 40 and through to a position inside the footprint of the grid 30. An optional additional upper reinforcing bar 90 can be attached to the upper surface of the drawbar arms 72 where further load capacity is required. The reinforcing bar 90 further includes a transverse flange 94 set substantially at right angles to the reinforcing web 92 whereby the reinforcing bar 90 in cross section is in the shape of an I, T or L, preferably a T. The transverse flange 94 is a more rigid 0 and stiff member than the strap or web 92, is spaced from the drawbar arm 72b and extends generally parallel thereto and in a parallel plane to the underside surface of the drawbar arm 72b. However, at each end of the reinforcing bar 90 the transverse flange 94 ramps towards the drawbar arm 72b via a ramp section 91, the reinforcing web 92 tapers and the transverse flange 94 meets with the drawbar arm 72b underside surface 78 in the form of a section of 5 flat strap 93. IZ7-

Description

Editorial Note 2011239230 There are only 9 pages of Description DRAWBAR SUPPORT Area of the Invention This invention relates to the area of trailable vehicles and the trailer structure and towing means. In particular the invention relates to an improved drawbar for connection between a 5 trailer and a towing vehicle. Background to the Invention Conventional wheeled trailers have a frame which is adapted to be coupled to a towing vehicle by means of a drawbar connected between the two. In order to maximise the stability of the towing arrangement it is commonplace for a pair of 0 triangularly arranged drawbars to be used extending from either side of a trailer and converging towards a towing point at its leading end for hitching at the rear of the towing vehicle. The drawbars, however, are subject to strong forces which can tend to cause deformation of the bars, including permanent damage and weakening. One approach could be to err towards 5 over-engineering the design and structure, using particularly strong materials to fabricate these items. However, this has adverse weight implications which can be critical with regard to the towing capacity of the towing vehicle. Another approach to counteracting this problem has been to provide a metal strap device supported by and welded to the drawbar as a means of reinforcement of the drawbar '0 apparatus. These strap devices are suspended from the drawbars by vertical struts. Whilst they do not add particularly to the overall weight of a trailer, they are a relatively labour intensive addition to a drawbar. In addition, while these strap devices do act to strengthen the drawbars they are subject to damage themselves when they bottom onto bumps on a road, such as road humps and the 25 like, or when people use the straps as tie down means for loads. It is an object of this invention to provide an improved drawbar for a trailer to be towed by a vehicle which drawbar is stronger than the conventional drawbar and strap arrangement and avoids the problems associated with these. Outline of the Invention The invention is a web and flange device for strengthening a trailer drawbar the longitudinal web extending along and below the general length of the draw bar and extending up to the drawbar at either end of the web and having at least one flange affixed between the web and drawbar. 5 The draw bar preferably comprises a pair of bars shaped in the form of V, the diverging ends thereof attached to the front lateral beam of the trailer. The trailer may include side beams extending longitudinally down either side of the trailer. The draw bar or other beams of the chassis may include a reinforcing bar extending along a substantial proportion of its length. The reinforcing bar may include a reinforcing web or 0 strap extending in a plane normal to the surface of the beam or bar to which it is attached. The reinforcing web may be in the form of a continuous length of reinforcing web or strap extending along the beam or bar. The reinforcing bar may include a transverse flange extending along the length of the reinforcing web and generally spaced from the beam or bar to give the reinforcing bar structure greater strength and rigidity by having an additional 5 substantially co-extending component in a plane normal to the reinforcing web. The reinforcing web may include a first elongate surface whereby contact with the drawbar is intermittent, with contact regions spaced from each other. The reinforcing web may include a second elongate surface whereby contact with the transverse flange is intermittent, with contact regions spaced from each other. The contact regions of the first and second elongate '0 surfaces may be off-set relative to one another. The first and second elongate surfaces may comprise radiused curves which may follow a wave pattern. The first and second elongate surfaces may be attached at their contact regions by weld spots. Each of the side beams may include reinforcing bars to strengthen critical sections of the side beams. Advantageously, the front portion of each side beam may include a reinforcing bar, 25 either above, to the side of, or below the side beam. Where the reinforcing bar is mounted to the side of the side beam or the side of the draw bar, the reinforcing web will, of course, be a horizontal reinforcing web. However, for most applications, because the majority of stress forces are generally vertically directed, advantageously the reinforcing bar will be attached to the upper or lower surface of 30 the beam or bar, so that the reinforcing web or strap will generally lie in a vertical plane. Accordingly, preferably, the reinforcing web is a planar structure lying in a vertical plane.

The transverse flange may form a T or L- cross section when combined with the reinforcing web. The transverse flange may lie substantially in a plane parallel to the plane of the upper surface of the beam or bar to which it is attached. The transverse flange may extend either side of the reinforcing web. The transverse flange may extend to one side only of the 5 reinforcing web. The ends of the reinforcing web may taper towards one or both ends. The ends of the Transverse flange may ramp down towards the beam or bar. The ends of the transverse flange may ramp down towards the beam or bar where the reinforcing web tapers. The transverse flange ends may continue beyond where the reinforcing web terminates to form a flat strap attached to the beam or bar. 0 The drawbar may comprise a pair of drawbars joined in a V-formation. The draw bar or draw bars may have a reinforcing bar on the underside or on the top of the drawbar. The draw bar or draw bars may have reinforcing bars on both the underside and on the top of the drawbar. A reinforcing bar extending along the underside of the draw bar may extend well under the chassis past the from lateral beam. A reinforcing bar extending along the top side of the draw 5 bar may extend to a place on the draw bar short of the chassis in front of the front lateral beam. It is preferred that the device be constructed of metal and that a single flange extend between the web and drawbar from a generally mid line along the length of the web. It is further preferred that the web and flange be spot welded together and that the resulting '0 web and flange device be spot welded to a lower face of the drawbar. It is also preferred that apertures be provided along the length of the flange and while the shape of these is not restricted in the invention these may included slots or circles or other such shapes. It may be further preferred that apertures be provided in the web to permit water to drain 25 through it and also to reduce weight however this is not an essential feature of the invention. In a second optional aspect of the invention the terminal ends of the web which are welded to the lower drawbar face are provided with relieved portions for welding to ensure that linear welds do not occur across the drawbar lower face to weaken it. In this aspect of the invention it is preferred that the extreme ends of the web are curved. 30 In order that the invention may be more readily understood we shall describe by way of non limiting example a particular embodiment of the invention.

Brief Description of the Drawings The invention may be better understood from the following non-limiting description of preferred embodiments, in which: Figure 1 is a schematic top plan view of a chassis according to one aspect of the 5 invention; Figure 2 is a schematic partial side elevation of a portion of a drawbar and front lateral beam of the embodiment shown in Figure 1; Figure 3 is a schematic section view from a front perspective of a left hand arm of the drawbar shown in Fig. 1; 0 Figure 4 is a schematic sectional view of a right hand side beam and part of a transverse joist. Figures 5a and 5c are perspective views of a reinforcing bar according to another aspect of the invention; Figure 5b is a perspective view of the flat strap portion of the reinforcing bar shown in 5 Fig. 5a; and Figure 6a - 6e are perspective views of reinforcing bars according to further aspects of the invention. Detailed description of preferred embodiments of the Invention The invention is an improved drawbar for a trailer towed by a motor vehicle. 20 As previously discussed, conventional drawbars are constructed from rectangular sectioned extrusions which are strengthened using strap members suspended from the base of the drawbar section by supports or struts and which are subject to damage in use. The invention is a web and flange device for strengthening a trailer drawbar with a longitudinal web extending along and below the general length of the draw bar and extending 25 up to the drawbar at either end of the web. The device has at least one flange affixed between the web and drawbar and it is this embodiment of the invention which will be described although it is envisaged that the invention need not be restricted to a single flange. In this embodiment of the invention the device is constructed of metal and has a single flange extend vertically between the web and drawbar from a generally mid line along the length of 30 the web.

The web and flange are spot welded together and the resulting web and flange device is spot welded to a lower face of the drawbar. In the preferred embodiment of the invention the terminal ends of the web taper up to the drawbar where they are welded to it, these ends being provided with relieved portions for welding to ensure that linear welds do not occur to 5 weaken the drawbar. In this aspect of the invention the extreme ends of the web are curved for this reason. In the preferred embodiment of the invention apertures are provided along the length of the flange and while the shape of these is not restricted in the invention these may included slots or circles or other such shapes. The use of these apertures in the flange is not an essential 0 feature of the invention. It may also be further preferred that apertures be provided in the web to permit water to drain through these and to reduce weight however this is also not an essential feature of the invention. In this preferred embodiment of the invention a strengthened drawbar for a trailer is provided 5 which removes the problems associated with support straps of the kind previously used. Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. '0 With reference to the drawings and particularly Fig. 1, there is shown a plan view of a chassis 10 for a trailer or caravan according to one aspect of the invention. The chassis 10 provides a onto which a flat tray or floor can be mounted. It is important that the platform 20 presents a support structure aligned in a single upper plane 22 (shown in Fig. 2), so that all upper surfaces required to support the platform 20 lie in that plane 22. The upper surfaces of the 25 front and rear lateral beams 40,42, the side beams 34,36 and the central beam 38 all lie in the upper plane 22. The chassis 10 includes a drawbar 70, and a grid frame 30 comprising side beams 34,36, the continuous central beam 38, a plurality of transverse joists 32 and front and rear lateral beams 40,42. 30 Referring now also to Figs. 2 - 4, on the drawbar 70, there is provided reinforcing bars 90 that provide strength and rigidity to the drawbar arms 72a-b. The drawbar arms 72a-b diverge rearwardly in traditional V-formation from their apices where they meet at a flat plate 74. A tow hitch 76 is attached to the flat plate 74. The draw bar arms 72a-b are welded to the underside of the front lateral beam 40 and this join is reinforced by the provision of a bifurcated bracket 50 on the outer side face of each of 5 the drawbar arms 72a-b. An additional bifurcated bracket 52 may be optionally attached to the inner side face of each of the drawbar arms 72a-b for further strengthening the draw bar 70. The bifurcated bracket 50,52 may be comprise a single fork or V-shaped slot 51 and a base extending in one direction, or a may comprise double bifurcated slots 51 extending in opposite directions as shown. 0 The bifurcation forming broad fork teeth 52 that extend away from a vertical triangular brace member 54 aligned parallel to the longitudinal axis of the front beam 40 and extend out normally from the base 56 of a single bifurcated bracket 50, or a point 58 intermediate a double bifurcated bracket 50 to provide strength in the vertical plane 53 normal to the bracket plane 57 in which the bifurcated bracket 50 lies. The brace member 54 is heavily welded to 5 the underside of the front beam 40 and the reinforcing bracket 50 by weld regions 59. The weak region of the drawbar arm 72b would normally be focussed around the welded join of the brace member 54, but the provision of the bifurcated bracket 50 surprisingly redistributes the load and the weakest region to a region 55 offset from the bracket 50 further along the drawbar arm 72b (and there is a matching arrangement on the drawbar arm 72a). '0 Testing of the drawbar arm 72b was carried out to determine the weakest point thereof using the down force of a 4 ton ram. The testing indicated that the weakest point is significantly offset from the locale of the brace member 54 to the region 55 on the drawbar arm 72b. The region was found to be about 50 - 80 % of the length of the tapered fork teeth 52 beyond the bracket 50 and the tip of the teeth 52, indicating that the drawbar arm's 72b overall strength 25 had been increased significantly by the use of the bifurcated bracket 50. The reason for the weakest point being offset to such an extent from the tip of the teeth 52 may be that the ability of the narrow, wedged shaped teeth 52 to marginally flex and absorb torsional forces has the affect of strengthening what would normally be the weakest region (around the join between the drawbar arm 72b and the front beam 40), so that the actual weakest region is 30 focussed around region 55. The weld spots 58a-b, particularly weld spot 58a, are strategically located to ensure both a good strong join to the drawbar arm 72b, but also to permit very minimal flexing of the bracket 50 at the tip of the teeth 52 thereby projecting or displacing load and stress regions further down the drawbar arm 72b to weak region 55. Also shown in Fig. 2 is a reinforcing bar 90 comprising a reinforcing web 92 or strap attached by welding along a substantial length of the drawbar arm 72b from close to the flat plate 74, 5 under the front beam 40 and through to a position inside the footprint of the grid 30. An optional additional upper reinforcing bar 90 can be attached to the upper surface of the drawbar arms 72 where further load capacity is required. The reinforcing bar 90 further includes a transverse flange 94 set substantially at right angles to the reinforcing web 92 whereby the reinforcing bar 90 in cross section is in the shape of an 0 I, T or L, preferably a T as shown in Fig. 3. The transverse flange 94 is a more rigid and stiff member than the strap or web 92, is spaced from the drawbar arm 72b and extends generally parallel thereto and in a parallel plane to the underside surface of the drawbar arm 72b. However, at each end of the reinforcing bar 90 the transverse flange 94 ramps towards the drawbar arm 72b via a ramp section 91, the reinforcing web 92 tapers and the transverse 5 flange 94 meets with the drawbar arm 72b underside surface 78 in the form of a section of flat strap 93. The reinforcing web 92 can be a planar strip of metal preferably welded at spaced points 98a along its length to the underside surface 78, and to the inside surface of the transverse flange 94 at weld points 98b. In the preferred form, the reinforcing web 92 has regular spaced cut '0 outs 95 interposed by lateral portions 97 that branch out from a continuous central strip of web material 96 and are attached to the respective points along the drawbar arm underside 78 and inner surface of the transverse flange 94 at weld points 98a,b. The cut outs 95 save weight and any loss of strength is minimal. The reinforcing web 92 is to provide tensile strength in the relationship between the drawbar arm 72b and the transverse flange 94 to 25 minimise any flexing of the drawbar arm 72b when under load. In Fig. 4, the side beam 34 section is shown. The extruded beam 34 comprises multiple hollow structures 39 including a main trapezoid hollow section 31 and an open groove 33 that serves as a conduit housing for running lines. The hollow structures 39 contribute to a significant reduction in weight of the side beams 34,36, whilst maintaining strength and 30 rigidity, important properties where the grid 30 components are made of Aluminium. Extending between the side beams 34,36 are a plurality of transverse joists 32. The transverse joists may have a variety of sectional shapes, such as I, T, U or L shapes, preferably being in the form of a channel having a joist web 60 extending between spaced and parallel upper and lower joist flanges 62,64. The joist web 60 has multiple spaced hollow structures 61 regularly spaced to reduce weight whilst trading away minimal strength of the joist web 60. The rounded edges 63 of the hollow structures 61 distribute the torsional, 5 tensile and compressive forces applied to the joist web 60 to ensure that stress regions are spread. Intersecting each joist web 60 and upper flange 62 is the continuous central beam 38. The continuous nature of the central beam 38 and side beams 34,36 create an extremely strong grid 30 structure. The continuous nature of the transverse joists 32 extending between the side beams 34,36 reduce the opportunity for undesired play and twisting of the transverse 0 joists. The welding and close fit of central beam 38 in the rectangular slot 66 defined by the cut out of the upper flange 62 and joist web 60 mean that forces applied downwards on the transverse joists 32 with consequent compressive forces on the side walls 65 of the central beam 38 are resisted by the compact rectangular sectioned hollow structure of the central beam 38. 5 The overall structure of the grid 30 and drawbar 70 is extremely strong and resistant flexing, even when made from a lightweight material such as Aluminium or a lightweight alloy, despite the weaker inherent properties of such metal materials. Each of the side beams 34,36 may include reinforcing bars 90 to strengthen critical sections of the side beams 34,36. Advantageously, the front portion of each side beam 34,36 may '0 include a reinforcing bar, either above, to the side of, or below the side beam 34,36 with Fig. 1 showing the reinforcing bars on the top of the side beams 34,36. In Figures 5a to 5c, there is shown a reinforcing bar 190 according to another embodiment having a T shaped cross-section in which the bar of the T is a flange 194 extending substantially in a first plane adapted to be spaced from the drawbar 72b and to converge 25 towards the drawbar 72b at its ends, terminating in two end flat straps 193. At right angles to the flange 194 is a web or strap 192. The flat straps have several spaced recesses or cut outs 195 to facilitate an improved weld join to the drawbar 72b by providing a higher surface edge for the join. The web 192 and the flange 194 have regularly spaced holes 200 to lessen the weights of these component parts without losing any measurable or significant strength. The 30 holes 200 are located adjacent each other and spaced regularly and in correspondence with each other along the lengths of the web 192 and the flange 194. The cut outs 195 have a flat, long edge 196 and end with radiused or otherwise concave curved ends 197 leading up to the outer edge 198 of the flat strap 193. The cut outs there provide a good recess to bond the drawbar 72b using a long weld, The terminal ends of the flat straps 193 have a convex curved head 199a with concave recesses or cut outs 199b either side to permit weld spots to be placed at the recesses 199b. 5 In Figures 6a to 6e, variations of the reinforcing bar 190 are shown as reinforcing bars 290 and 390. The reinforcing bar 290 includes holes on the flange 294,394 that are staggered to spread the potential weak points uniformly along the length of the flange 294,394. The holes are either staggered at equispaced intervals as in holes 200a on either side of the web 292 or are positioned as offset pairs as show in relations to holes 200b. 0 Throughout the specification and claims the word "comprise" and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word "comprise" and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the 5 contrary is expressly stated or the context requires otherwise. Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the front lateral beam uppermost. '0 It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention. While we have described herein one particular embodiment of the invention it is to be understood that variations and modifications in the features described can still lie within the 25 scope of the invention.

Claims

1. A reinforcing bar in the form of a web and flange device for strengthening a trailer drawbar or trailer beam, the device having a longitudinal flange extending along and below the general length of the draw bar and extending up to the drawbar at either end of the flange, 5 at least one web affixed between the web and drawbar.

2. The reinforcing bar according to claim 1, wherein the device is constructed of metal and has a single web extending vertically between the flange and drawbar from a generally mid line along the length of the flange.

3. The reinforcing bar according to claim 1 or 2, wherein the web and flange are spot 0 welded together and the resulting web and flange device is spot welded to a lower face of the drawbar.

4. The reinforcing bar according to claim 1 - 3, wherein the terminal ends of the flange taper up to the drawbar where they are welded to it, these ends being provided with relieved portions for welding to ensure that linear welds do not occur to weaken the drawbar.

5 5. The reinforcing bar according to claim 1 - 4, wherein the extreme ends of the flange are curved for this reason.

6. The reinforcing bar according to claim 1 - 5, wherein apertures are provided along the length of the flange in the form of slots or circles.

7. The reinforcing bar according to claim 6, wherein apertures are provided in the flange '0 to permit water to drain through these and to reduce weight.