AU2009213134B2 - Towbar and method for manufacturing a towbar - Google Patents

Abstract

P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 15/9/09 A towbar comprising: a bar member for connection to a vehicle; an insert receptacle fixedly attached to the bar member for receiving a tow hitch insert; 5 a front aperture plate defining a front aperture, the front aperture plate being fixedly attached to a front end of the insert receptacle; and a rear aperture plate defining a rear aperture, the rear aperture plate being fixedly attached to a rear end of the insert receptacle; wherein the front and rear apertures and the insert receptacle are sized so that, when the tow hitch insert is received in the 10 insert receptacle, the front and rear aperture plates closely fit around the tow hitch insert and the insert receptacle loosely fits around the tow hitch insert. P.\OPER\SSB\2009/3082267i AU CAP - Figures doc - 14/9/09 P:\OPER\SSB200930S22671 AU CAP - Figures doc - 14/9/09

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT (ORIGINAL) Name of Applicant: Bartlett Transport Improvements Pty. Ltd. Actual Inventors: BARTLETT, Allan James; BARTLETT, Geoffrey Norman; and BAKER, Wayne. Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, of I Nicholson Street, Melbourne, Victoria 3000. Invention Title: "Towbar and method for manufacturing a towbar" The following statement is a full description of this invention, including the best method of performing it known to us: Q \OPER\SSB\2009\SepO9\30822671 AU CAP filingdoc - 5/9/09 P:\OPER\SSB\2009\30822671 AU CAP Spec.doc - 14/9/09 TOWBAR AND METHOD FOR MANUFACTURING A TOWBAR TECHNICAL FIELD 5 The described embodiments relate to towbars and methods of manufacturing towbars. BACKGROUND 10 Towbars are generally affixed to a chassis of a vehicle at the rear of the vehicle and may have a removable coupling such as a ball and socket coupling that can be used to connect the towbar to an object to be towed. Existing towbar designs incorporate an insert portion of substantially square cross section 15 which is received into a correspondingly shaped aperture on a towbar. A pin is then inserted through a hole in the side of the towbar and a matching hole in the insert portion to secure the two parts together. The points of support and clearances between the insert portion and the towbar can allow 20 the insert portion to move under load, thereby creating wear of these components. As this wear increases, movement can also increase and wear can accelerate. It is desired to address or ameliorate one or more problems or disadvantages associated with existing towbars and/or methods of manufacturing towbars, or to at least provide a 25 useful alternative. SUMMARY Certain embodiments relate to a towbar comprising: 30 a bar member for connection to a vehicle; an insert receptacle fixedly attached to the bar member for receiving a tow hitch P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 -2 insert; a front aperture plate defining a front aperture, the front aperture plate being fixedly attached to a front end of the insert receptacle; and a rear aperture plate defining a rear aperture, the rear aperture plate being fixedly 5 attached to a rear end of the insert receptacle; wherein the front and rear apertures and the insert receptacle are sized so that, when the tow hitch insert is received in the insert receptacle, the front and rear aperture plates closely fit around the tow hitch insert and the insert receptacle loosely fits around the tow hitch insert. 10 The insert receptacle may comprise a tube of constant cross-section for receiving the tow hitch insert. The front and rear apertures may be of different sizes. The towbar may further include front and rear support plates to fixedly attach the insert 15 receptacle to the bar member. The rear support plate may comprise the rear aperture plate and the front support plate may be configured to accept the insert receptacle within an opening of the front support plate. The front and rear support plates may further include extended portions to allow the insert receptacle to be positioned adjacent to the bar member. The extended portion may include apertures for receiving the insert receptacle. 20 The towbar may further include apertures in the bar member for receiving the insert receptacle. The towbar may include the tow hitch insert. The tow hitch insert may comprise a bar 25 portion and the bar portion may be machined from a larger bar to a tolerance of 0.2mm. The tow hitch insert and the insert receptacle may have holes configured to accept a pin used to releasably fix the insert receptacle relative to the tow hitch insert. The towbar may comprise at least one reinforcement tab provided adjacent to the insert receptacle to reinforce the insert receptacle at the position where contact occurs between the pin and the 30 insert receptacle. The reinforcement tab may be fixedly attached to at least one of the P:\OPER\SSB\2009\30822671 AU CAP Spc doc - 14/9/09 -3 front support plate and the insert receptacle, the at least one reinforcement tab having a hole through which the pin can be received. The towbar may be assembled using a welding process, such as a metal inert gas (MIG) 5 welding process. The components of the towbar may also comprise mild steel, such as 350 grade mild steel. The bar member and/or insert receptacle may further comprise square hollow sections or rectangular hollow sections. The apertures may be formed using a laser cutting process or a flame cutting process. The 10 laser cutting process may allow the apertures to be formed within a tolerance of 0.1mm. The front and rear support plates may be at least 300mm wide and less than 600mm wide. The front and rear apertures and the insert receptacle may be configured to accept tow hitch inserts that are generally square in cross-section and either 50.8mm, 62.5mm or 15 75mm wide. Other embodiments relate to a method of manufacturing a towbar, including the steps of: fixedly attaching an insert receptacle to a bar member, the insert receptacle configured to accept a tow hitch insert; 20 forming apertures in front and rear aperture plates affixed to the bar member, the apertures being aligned with a hollow defined by the insert receptacle and being smaller than the internal dimensions of the insert receptacle so that, when a tow hitch insert is at least partly received in the hollow of the insert receptacle and in the apertures, the front and rear aperture plates closely fit around the tow hitch insert and the insert receptacle 25 loosely fits around the tow hitch insert; attaching the front aperture plate to a front end of the insert receptacle; and attaching the rear aperture plate to a rear end of the insert receptacle. The method may further include the steps of attaching front and rear support plates 30 adjacent to the insert receptacle and bar member. The support plates may also have apertures formed in them through which the insert receptacle can be received. The P.\OPER\SSB\2009\30822671 AU CAP Spcm do - 14/9/09 -4 support plates may further include extended portions to allow the insert receptacle to be positioned adjacent to or offset from the bar member. The bar member may have front and rear apertures formed in it to accept the insert receptacle. 5 Other embodiments relate to a method of manufacturing a towbar including the steps of: forming a support aperture in a front support plate; forming a rear aperture in a rear support plate; attaching the front and rear support plates to a bar member; attaching an insert receptacle to the support plates, the insert receptacle being 10 received through the front support aperture, and configured to accept a tow hitch insert; forming a front aperture in a front aperture plate, the front aperture being smaller than internal dimensions of the insert receptacle; and attaching the front aperture plate to the front end of an insert receptacle. 15 Other embodiments relate to a method of manufacturing a towbar including the steps of: forming a rear aperture in a rear support plate; attaching an insert receptacle to the rear support plate, the internal dimensions of the insert receptacle being larger than the rear aperture; forming front and rear apertures in a bar member; 20 forming a support aperture in a front support plate and attaching the front support plate to the front of the bar member; attaching the insert receptacle to the bar member and the front support plate such that the insert receptacle is received through the front and rear apertures of the bar member and the support aperture of the front support plate; 25 forming a front aperture in a front aperture plate, the front aperture being substantially the same size as the rear aperture in the rear support plate; and attaching the front aperture plate to a front end of the insert receptacle. The method of manufacturing a towbar may include the attachment of a tow hitch insert. 30 The portion of the tow hitch insert which is received in the insert receptacle may be machined to within a tolerance of 0.2mm. A hole may be formed in the side of the tow P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 -5 hitch insert and the insert receptacle so that a pin may be inserted to releasably fix the tow hitch insert to the insert receptacle. At least one reinforcement tab may be attached to at least one of the insert receptacle and the front support plate to strengthen the connection. 5 The components of the towbar may be attached using a welding process, such as a metal inert gas (MIG) welding process. The apertures of the towbar may be formed to within a 0.1mm tolerance. These apertures may be formed using either a laser or flame cutting process. 10 The front and rear support plates may be at least 300mm wide and less than 600mm wide. The support plates may have an approximately trapezoidal shape. The front and rear apertures and the insert receptacle may be configured to accept tow 15 hitch inserts that are generally square in cross-section and either 50.8mm, 62.5mm or 75mm wide. BRIEF DESCRIPTION OF THE DRAWINGS 20 Embodiments will be further described by way of example only with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a towbar; Figure 2 is a top view of the towbar; Figure 3A is an exploded perspective view of the towbar of figure 1; 25 Figure 3B is a perspective view of part of the towbar of figure 1; Figure 3C is a perspective view of part of the towbar of figure 1 having a tow hitch insert received therein; Figure 4 is a perspective view of an alternative towbar; Figure 5A is an exploded view of the towbar of figure 4; 30 Figure 5B is a perspective view of part of the towbar of figure 4; P:\OPER\SSB\2009\30822671 AU CAP Specdoc - 14/9/09 -6 Figure 5C is a perspective view of part of the towbar of figure 4 having a tow hitch insert received therein; Figure 6 is a flow chart of a manufacturing process according to some embodiments; 5 Figure 7 is a flow chart of a manufacturing process according to other embodiments; Figure 8 is a flow chart of a manufacturing process according to still further embodiments; and Figure 9 is a perspective view of a further alternative towbar having a tow hitch 10 insert received therein. DETAILED DESCRIPTION 15 The described embodiments relate to a towbar which may be fitted to a vehicle and to methods of manufacturing the towbar. Such a towbar is generally fitted to the rear of a vehicle by attaching the towbar to structural members of the vehicle, for example such as plates extending downwardly from a chassis of the vehicle. 20 A towbar of this configuration can accommodate a tow hitch insert extending rearward from the vehicle and allowing a trailer to be connected thereto. Examples of the towbar are described herein using the perspective of a person standing in a position behind a vehicle and looking at a towbar, hence a tow hitch insert extends towards the person and components that are closer to the observer are labelled as front components while those 25 further away from the observer are labelled as rear components. Referring to figures 1 to 3C, there is shown a towbar 100 according to some embodiments. Towbar 100 includes a bar member 110, a front aperture plate 120 having a generally square front aperture 125, a rear support plate 130 including a generally 30 square rear aperture plate aperture 135, a front support plate 140 including a front support P:\OPER\SSB\200900822671 AU CAP Spec doc - 14/9/09 -7 aperture 145, a reinforcement tab 150, an insert receptacle 160 and a securing pin 170. Towbar 100 may also comprise a tow hitch insert 190. The front support plate 140 and the rear support plate 130 are fixedly attached to the bar 5 member 110, using for example a welding process. Bar member 110 has a front and rear aperture for receiving the insert receptacle 160. Front support plate 140 has a front support aperture 145. Front and rear apertures in bar member 110 and front support aperture 145 are arranged to be substantially in-line when 10 towbar 100 is assembled, so that insert receptacle 160 can be received through these apertures. Insert receptacle 160 is fixedly attached to front support plate 140 and rear support plate 130. Insert receptacle 160 is generally centred in relation to bar member 110 and also generally mounted in a perpendicular manner to bar member 110 (as can be seen in figure 3B which shows insert receptacle 160 attached to rear support plate 130). 15 In this example, insert receptacle 160 is received through rear support aperture 135 and the rearward end of insert receptacle 160 may pass through rear support aperture 135, extending towards the front of the vehicle, or it may lie flush with a rear face of the rear support plate 130. 20 A front aperture plate 120 is fixedly attached to the front end of the insert receptacle 160 and a rear aperture plate (not shown) may be fixedly attached to the rear end of the insert receptacle 160. Alternatively, rear support plate 130 can comprise the rear aperture plate and the rear support aperture 135 can be configured to support tow hitch insert 190. In 25 this alternative arrangement, insert receptacle 160 may be attached to rear support plate 130 in an abutting manner, as can be seen in figure 3B which shows insert receptacle 160 attached to rear support plate 130. A tow hitch insert 190 of generally square cross-section is received within a hollow 30 defined by insert receptacle 160, and secured to the insert receptacle 160 through use of a securing pin 170 passing through a hole formed in the insert receptacle 160 and tow hitch P\OPER\SSB2009\30822671 AU CAP Spec.doc - 14/9/09 -8 insert 190, as can be seen in figure 3C which shows an assembled towbar 100 with tow hitch insert 190 inserted. Generally the hole is formed in a central region of a side face of insert receptacle 160, although it may be formed in different positions and orientations. A securing device (not shown) may be provided at the end of the pin to prevent the pin from 5 falling out. The securing device may comprise a spring loaded clip or pin, or some kind of lockable device. The aperture 125 of the front aperture plate 120 and aperture 135 of the rear aperture plate or rear support plate 130 are smaller than the internal dimensions of the insert receptacle 10 160, hence the tow hitch insert 190 is supported (when received in insert receptacle 160) by the front aperture plate 120 and either the rear aperture plate or the rear support plate 130. Front aperture 125 and rear aperture 135 may have different dimensions to accommodate a tow hitch insert having a varied cross-sectional profile. For example, the tow hitch insert may be smaller-dimensioned at the end that is first received in the 15 aperture 125 during initial insertion thereof and may be larger-dimensioned at the part of the tow hitch insert that rests within aperture 125 following full insertion. In use, tow hitch insert 190 extends from the towbar in a direction rearward of the vehicle to allow connection of a trailer, for example via a ball and socket coupling. 20 At least one reinforcement plate 150 may be provided adjacent to the insert receptacle 160 to reinforce the insert receptacle at the position where contact occurs between the pin and insert receptacle 160. Reinforcement plate 150 is shown attached to the side of insert receptacle 160, although it may also be attached to front support plate 140. Reinforcement plates 150 may be provided at either or both sides of insert receptacle 160. 25 Bar member 110 can be made from a 100mm square steel hollow section, with a wall thickness of 6mm. Any suitable steel may be used that complies with the relevant standards, but in the described embodiments case 350 grade mild steel is used for its higher strength. 30 Front support plate 140 and rear support plate 130 may be made from 350 grade mild P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 -9 steel, although other grades may be suitable. In the embodiments shown both front support plate 140 and rear support plate 130 are cut from 8mm thick plate. Either a laser cutting process or a flame cutting process can be used for manufacturing front support plate 140 and rear support plate 130. 5 Insert receptacle 160 can also be made from square steel hollow section. In the embodiment shown, insert receptacle 160 is manufactured from 350 grade mild steel and has a wall thickness of about 5mm. 10 Front aperture plate 120 may also be made from mild steel, such as 350 grade mild steel, and may be 12mm thick, for example. The front aperture plate 120 may bear a significant proportion of the load, hence it may be desirable to manufacture this part in thicker material than other parts of the towbar to ensure reasonable surface area contact with tow hitch insert 190 to distribute the load over a larger area. 15 In the embodiment depicted, front aperture 125 is 63mm, which is suitable to accept a 62.5mm tow hitch insert. It is desirable for the aperture to be 0.5mm larger than the tow hitch insert which is to be received in it. This is a great improvement over some existing designs which may have a tolerance between the tow hitch insert and aperture it is 20 received in of greater than 2mm. Example tow hitch sizes, relating to the generally square cross section, which may be accepted into a suitably sized but tightly toleranced front aperture 125 and into a larger dimensioned insert receptacle 160 include: 50.8mm (approximately 2 inches), 62.5mm (approximately 2.5 inches) and 75mm (approximately 3 inches). 25 The rear aperture plate or rear support plate 130 bears a smaller proportion of the load and therefore can be manufactured from a thinner material. The rear support plate 130 may be manufactured from 8mm plate, also of 350 grade mild steel. Either a laser cutting process or a flame cutting process can be used to manufacture the rear aperture plate or rear 30 support plate 130. Laser cutting is preferable as it generally achieves a tolerance of 0.1 mm. Other cutting or forming processes with a similarly low or lower tolerance can P:\OPER\SSB\2009\30822671 AU CAP Spec.doc - 14/9/09 - 10 alternatively be used. Front support plate 140 and rear support plates 130 are shown as a wide trapezoidal shape with bevelled sides. The bevel angle may be acute or obtuse. Front support plate 140 and 5 rear support plate 130 may alternatively be substantially square or rectangular. The width of these plates is measured along a line approximately passing through the centre of the aperture. In the embodiments shown, the width of front support plate 140 and rear support plates 130 is about 400mm. This dimension could be larger, for example up to about 600mm, although it could be as low as about 300mm. It is also possible for front 10 support plate 140 and rear support plate 130 to be of different widths. Tow hitch insert 190 is also made from mild steel. It is cut to the desired length, using any traditional cutting process such as flame or abrasion cutting, and then milled down to the required cross-sectional size. The tolerance on this milling operation is generally 15 0.2mm. The overall tolerance on the clearance between the tow hitch insert 190 and the front aperture plate aperture 125 and rear support aperture 135, through which the tow hitch insert 190 is received, is about 0.5mm. In alternative embodiments, tow hitch insert 190 may be of multiple layer construction with a core piece surrounded by a sleeve, the sleeve being fixedly attached to the core, for example by welding. The sleeve may be 20 machined to the desired tolerances before being attached to the core piece. Referring to figures 4 to 5C, an alternative towbar 200 is shown. Towbar 200 includes a bar member 210 (similar to bar member 110), a front aperture plate 220 (similar to front aperture plate 120) having a generally square front aperture 225 (similar to front aperture 25 125), a rear support plate 230 (similar to rear support plate 230) having generally square rear support aperture 235 (similar to 135), a front support plate 240 (similar to front support plate 140) having a front support aperture 245 (similar to front support aperture 145) a reinforcement tab 250 (similar to reinforcement tab 150) an insert receptacle 260 (similar to insert receptacle 160) and a securing pin 270 (similar to securing pin 170). 30 Towbar 200 may also comprise a tow hitch insert 290 (similar to tow hitch insert 190).

P\OPER\SSB\2009\30822671 AU CAP Spec doc - t419/09 - 11 Front support plate 240 and rear support plate 230 are fixedly attached to bar member 210, using for example a welding process. Front support plate 240 and rear support plate 230 both have extended portions 255 that are configured to extend below the bottom edge of bar member 210 when towbar 200 is attached to the chassis. Extended portions 255 5 allow insert receptacle 260 to be vertically offset from the bar member 210, and removes the necessity for apertures to be machined in bar member 210. In the embodiment shown, in use insert receptacle 260 is mounted lower than bar member 210 and is generally centred on, and perpendicular to, bar member 210 (as can be seen in figure 5C which shows insert receptacle 260 attached to towbar 200). Advantageously, the towbar 200 10 may be mounted lower in this case. Front support aperture 245, and rear support aperture 235 are arranged to be substantially in-line so that insert receptacle 260 may be received through at least the front support aperture and fixedly attached to the front support plate 240 and rear support plate 230, 15 using for example a welding process. In one example, insert receptacle 260 is received through rear support plate 235 and the rearward end of insert receptacle 260 may pass through rear support aperture 235 extending toward the front of the vehicle or it may be fixedly attached to it in an abutting 20 manner. A front aperture plate 220 is fixedly attached to the front end of the insert receptacle 260 and a rear aperture plate (not shown) may be fixedly attached to the rear end of the insert receptacle 260. Alternatively, the rear support plate can comprise the rear aperture plate 25 and the rear support aperture 235 can be configured to support tow hitch insert 290. In this alternative arrangement, insert receptacle 260 may be attached to rear support plate 230 in an abutting manner as can be seen in figure 5C which shows towbar 200 in an assembled state. 30 A tow hitch insert 290 of generally square cross-section is received within a hollow defined by insert receptacle 260, and secured to the insert receptacle 260 through use of a P.\OPER\SSB\2009U0822671 AU CAP Spec doc - 14/9/09 - 12 securing pin 270 passing through a hole formed in the insert receptacle 260 and tow hitch insert 290, as can be seen in figure 5C which shows towbar 200 in an assembled state with tow hitch insert 290 inserted. Generally the hole is formed in a central region of a side face of insert receptacle 260, although it may be formed in different positions and 5 orientations. A securing device (not shown) may be provided at the end of the pin to prevent the pin from falling out. The securing device may comprise a spring loaded clip or pin, or some kind of lockable device. The aperture 225 of the front aperture plate 220 and aperture 235 of the rear aperture plate 10 or rear support plate 230 are smaller than the internal dimensions of the insert receptacle 260, hence the tow hitch insert 290 is supported (when received in insert receptacle 260) by the front aperture plate 220 and either the rear aperture plate or the rear support plate 230. In use, tow hitch insert 290 extends from the towbar in a direction rearward of the vehicle to allow connection of a trailer, for example via a ball and socket coupling. 15 At least one reinforcement plate 250 may be provided adjacent to the insert receptacle 260 to reinforce the insert receptacle at the position where contact occurs between the pin 270 and insert receptacle 260. Reinforcement plate 250 is shown attached to the side of insert receptacle 260, although it may also be attached to front support plate 240. 20 Reinforcement plates 250 may be provided at either or both sides of insert receptacle 260. Bar member 210 is made from 100mm square hollow section, with a wall thickness of 6mm. Any suitable steel may be used that complies with the relevant standards, but in the described embodiments 350 grade mild steel is used for its higher strength. 25 Front support plate 240 and rear support plate 230 may be made from 350 grade mild steel, although other grades may be suitable. In the embodiments shown both front support plate 240 and rear support plate 230 are cut from 8mm thick plate. Either a laser cutting process or a flame cutting process can be used for manufacturing front support 30 plate 240 and rear support plate 230.

P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 - 13 Insert receptacle 260 can be formed as a tube and can be made from square steel hollow section. In the embodiment shown, insert receptacle 260 is manufactured from 350 grade mild steel and has a wall thickness of about 5mm. 5 Front aperture plate 220 may also be made from mild steel, such as 350 grade mild steel, and may be about 12mm thick, for example. The front aperture plate 220 may bear a significant proportion of the load, hence it may be desirable to manufacture this part in thicker material than other parts of the towbar to ensure reasonable surface area contact with tow hitch insert 290 to distribute the load over a larger area. 10 In the embodiment depicted, front aperture 225 is 63mm, which is suitable to accept a 62.5mm tow hitch insert. It is desirable for the aperture to be 0.5mm larger than the tow hitch insert which is to be received in it. This is a great improvement over some existing designs which may have a tolerance between the tow hitch insert and aperture it is 15 received of greater than 2mm. Example tow hitch sizes, relating to the generally square cross section, which may be accepted into a suitably sized but tightly toleranced front aperture 125 and into a larger dimensioned insert receptacle 160 include: 50.8mm (approximately 2 inches), 62.5mm (approximately 2.5 inches) and 75mm (approximately 3 inches). 20 The rear aperture plate or rear support plate 230 bears a smaller proportion of the load and therefore can be manufactured from a thinner material. The rear support plate 230 may be manufactured from 8mm plate, also of 350 grade mild steel. Either a laser cutting process or a flame cutting process can be used to manufacture the rear aperture plate or rear 25 support plate 230. Laser cutting is preferable as it generally achieves a tolerance of 0.1 mm. Other cutting or forming processes with a similarly low or lower tolerance can alternatively be used. Front support plate 240 and rear support plates 230 are shown as a wide trapezoidal shape 30 with bevelled sides. The bevel angle may be acute or obtuse. Front support plate 240 and rear support plate 230 may alternatively be substantially square or rectangular. The width P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 - 14 of these plates is measured along a line passing through the centre of the aperture. In the embodiments shown, the width of front support plate 240 and rear support plates 230 is 400mm. This dimension could be larger, for example up to 600mm, although it could be as low as 300mm. It is also possible for front support plate 240 and rear support plate 230 5 to be of different widths. Tow hitch insert 290 is also made from mild steel. It is cut to the desired length, using any traditional cutting process such as flame or abrasion cutting, and then milled down to the required cross-sectional size. The tolerance on this milling operation is generally 10 0.2mm. The overall tolerance on the clearance between the tow hitch insert 290 and the front aperture plate aperture 235 and rear support aperture 235, through which the tow hitch insert 290 is received, is about 0.5mm. In alternative embodiments, tow hitch insert 290 may be of multiple layer construction with a core piece surrounded by a sleeve, the sleeve being fixedly attached to the core, for example by welding. The sleeve may be 15 machined to the desired tolerances before being attached to the core piece. Referring to figure 6, a flow chart outlines the manufacturing process of a towbar according to some embodiments. The process starts with step 310, fixedly attaching an insert receptacle (160,260) to a bar member (110,210). Front support plates (140,240) 20 and rear support plates (130,230) may be provided to accomplish this and the attachment may be completed using for example a welding process. Whilst step 310 is being performed, step 315 can be completed. Step 315 includes forming an aperture (125,225) in a front aperture plate (120,220) and forming a rear 25 aperture (135,235) in a rear aperture plate. These apertures can be formed using either a flame or laser cutting process. Step 320 can then be performed; in which front aperture plate (120,220) is fixedly attached to a front end of insert receptacle (160,260) and the rear aperture plate can be fixedly attached to a rear end of insert receptacle (160,260), for example using a welding process. The rear support plate may comprise the rear aperture 30 plate, hence the rear aperture plate aperture will be the rear support plate aperture (135,235). A reinforcement tab (150,250) can be attached to either the insert receptacle P.\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 - 15 (160,260), front support plate (140,240), or both in step 330 using a welding process. Referring to figure 7, a flow chart illustrates an alternative towbar manufacturing process. Step 410 includes forming a support aperture (145,245) in a front support plate (140,240) 5 whilst a rear aperture (135,235) is formed at step 415 in a rear support plate (130,230). Front support plate (140,240) and rear support plate (130,230) are then attached to a bar member (110,210) in step 420 using a welding process, and then the insert receptacle (160,260) is attached to front support plate (140,240) and rear support plate (130,230) in step 430 also using a welding process. An aperture (125,225) is then formed in a front 10 aperture plate (120,220) at step 440, for example using either a flame cutting or laser cutting process. Apertures (125,225 or 135/235 or 145/245) are formed using either a flame cutting or laser cutting process. Front aperture plate (120,220) is then attached to the front end of the insert receptacle (160,260) and also, if used, a rear aperture plate attached to the rear of the insert receptacle (160,260) at step 450, for example using a 15 welding process. A reinforcement tab (150,250) can be attached to either the insert receptacle (160,260), front support plate (140,240), or both in step 460, for example using a welding process. 20 Referring to figure 8, a rear aperture is first formed in a rear support plate (130,230) at step 510, for example using either a flame cutting or laser cutting process. Next, an insert receptacle (160,260) is attached to the rear support plate (130,230) at step 520, using a welding process. Front and rear apertures are then formed in a bar member (110,220) in step 530. Then a support aperture (145,245) is formed in a front support plate (140,240) 25 at step 540, for example using either a flame cutting or laser cutting process. The insert receptacle (160,260) is then received through the front and rear apertures in bar member (110,210) and attached to the bar member (110,210) and front support plate (140,240) in step 540, for example using a welding process. Then an aperture (125,225) is formed in a front aperture plate (120,220) at step 545 using either a flame cutting or laser cutting 30 process. Finally, the front aperture plate (120,220) is attached to the front end of the insert receptacle (160,260) at step 550, using a welding process.

P:\OPER\SSB\2009\30822671 AU CAP Spccdoc - 14/9/09 - 16 A reinforcement tab (150,250) can be attached to either the insert receptacle (160,260), front support plate (140,240), or both in step 560, for example using a welding process. 5 During assembly, parts may be first tack-welded in place to ensure a good fit. Once an acceptable fit has been obtained, the parts may then be welded together in a more secure manner. Referring to figure 9, an alternative towbar 300 is shown. Towbar 300 includes a bar 10 member 310 (similar to bar members 110 and 210), a rear support plate 330 (similar to rear support plates 130 and 230) having generally square rear support aperture 335 (similar to 135 and 235), a front support plate 340 (similar to front support plates 140 and 240) having a front support aperture 345 (similar to front support apertures 145 and 245) a reinforcement tab 350 (similar to reinforcement tabs 150 and 250) an insert receptacle 360 15 (similar to insert receptacles 160 and 260) and a securing pin 370 (similar to securing pins 170 and 270). Towbar 300 may also comprise a tow hitch insert 390 (similar to tow hitch inserts 190 and 290). Front support plate 340 and rear support plate 330 are fixedly attached to bar member 20 310, using for example a welding process. Front support plate 340 defines a front support aperture 345 and rear support plate 330 defines a rear support aperture 335 through which tow hitch insert 390 can be received. Separate front and rear aperture plates are not required in this embodiment, as the front and rear support plates 340, 330 have the front and rear support apertures 345, 335 formed therein and effectively perform the function of 25 providing a closely toleranced fit with the tow hitch insert 390. Front support plate 340 and rear support plate 330 both have extended portions 355 that are configured to extend below the bottom edge of bar member 310 when towbar 300 is attached to the chassis, with the front and rear support apertures 345, 335 being formed in the respective extended portions 355. Extended portions 355 allow insert receptacle 360 to be vertically offset 30 from the bar member 3 10, and removes the necessity for apertures to be machined in bar member 310. In the embodiment shown, in use insert receptacle 360 is mounted lower P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 - 17 than bar member 310 and is generally centred on, and perpendicular to, bar member 310. This configuration allows the towbar 300 to be mounted lower in this case. Front support aperture 345, and rear support aperture 335 are arranged to be substantially 5 in-line so that tow hitch insert 390 can be received through and is supported by front support aperture 345 and rear support aperture 335. Insert receptacle 360 may be placed between and fixedly attached to the front support plate 340 and rear support plate 330 in an abutting manner, using for example a welding process. 10 A tow hitch insert 390 of generally square cross-section is received within a hollow defined by insert receptacle 360, and secured to the insert receptacle 360 through use of a securing pin 370 passing through a hole formed in the insert receptacle 360 and tow hitch insert 390, as can be seen in figure 9 which shows towbar 300 in an assembled state with tow hitch insert 390 inserted. Generally the hole is formed in a central region of a side 15 face of insert receptacle 360, although it may be formed in different positions and orientations. A securing device (not shown) may be provided at the end of the pin to prevent the pin from falling out. The securing device may comprise a spring loaded clip or pin, or some kind of lockable device. 20 The front aperture 345 of the front support plate 340 and rear aperture 335 of the rear support plate 330 are smaller than the internal dimensions of the insert receptacle 360, hence the tow hitch insert 390 is supported (when received in insert receptacle 360) by the front support plate aperture 345 and rear support plate aperture 335. Front aperture 345 and rear aperture 335 may have different dimensions to accommodate a tow hitch insert 25 having a varied cross-sectional profile. In use, tow hitch insert 390 extends from the towbar in a direction rearward of the vehicle to allow connection of a trailer, for example via a ball and socket coupling. At least one reinforcement plate 350 may be provided adjacent to the insert receptacle 360 30 to reinforce the insert receptacle at the position where contact occurs between the pin 370 and insert receptacle 360. Reinforcement plate 350 is shown attached to the side of insert P:\OPER\SSB\2009\0822671 AU CAP Spec.doc - 14/9/09 - 18 receptacle 360 in a position location between front support plate 340 and rear support plate 330, although it may also be attached to front support plate 340 or rear support plate 330. By placing reinforcement plate between front support plate 340 and rear support plate 330, the length of insert receptacle 360, and therefore the overall length of towbar 5 300 can be reduced. Reinforcement plates 350 may be provided at either or both sides of insert receptacle 360. Bar member 310 is made from 100mm square hollow section, with a wall thickness of 6mm. Any suitable steel may be used that complies with the relevant standards, but in the 10 described embodiments 350 grade mild steel is used for its higher strength. Front support plate 340 and rear support plate 330 may be made from 350 grade mild steel, although other grades may be suitable. In the embodiments shown both front support plate 340 and rear support plate 330 may be about 12mm thick, for example. The 15 front support plate 320 may bear a significant proportion of the load, hence it may be desirable to manufacture this part in thicker material than other parts of the towbar to ensure reasonable surface area contact with tow hitch insert 390 to distribute the load over a larger area. Rear support plate 330 bears a smaller proportion of the load and therefore may be manufactured from either a thinner material. For example, the rear support plate 20 330 may be manufactured from 8mm plate, also of 350 grade mild steel. Either a laser cutting process or a flame cutting process can be used for manufacturing front support plate 340 and rear support plate 330. Laser cutting is preferable as it generally achieves a tolerance of 0.1 mm. Other cutting or forming processes with a 25 similarly low or lower tolerance can alternatively be used. Insert receptacle 360 can be formed as a tube and can be made from square steel hollow section. In the embodiment shown, insert receptacle 360 is manufactured from 350 grade mild steel and has a wall thickness of about 5mm. 30 In the embodiment depicted, front aperture 325 is 63mm, which is suitable to accept a P:\OPER\SSB\2009\30822671 AU CAP Spec doc - 14/9/09 - 19 62.5mm tow hitch insert. It is desirable for the aperture to be 0.5mm larger than the tow hitch insert which is to be received in it. This is a great improvement over some existing designs which may have a tolerance between the tow hitch insert and aperture it is received of greater than 2mm. Example tow hitch sizes, relating to the generally square 5 cross section, which may be accepted into a suitably sized but tightly toleranced front aperture 325 and into a larger dimensioned insert receptacle 360 include: 50.8mm (approximately 2 inches), 62.5mm (approximately 2.5 inches) and 75mm (approximately 3 inches). 10 Front support plate 340 and rear support plates 330 are shown as a wide trapezoidal shape with bevelled sides. The bevel angle may be acute or obtuse. Front support plate 340 and rear support plate 330 may alternatively be substantially square or rectangular. The width of these plates is measured along a line passing through the centre of the aperture. In the embodiments shown, the width of front support plate 340 and rear support plates 330 is 15 400mm. This dimension could be larger, for example up to 600mm, although it could be as low as 300mm. It is also possible for front support plate 340 and rear support plate 330 to be of different widths. Tow hitch insert 390 is also made from mild steel. It is cut to the desired length, using 20 any traditional cutting process such as flame or abrasion cutting, and then milled down to the required cross-sectional size. The tolerance on this milling operation is generally 0.2mm. The overall tolerance on the clearance between the tow hitch insert 390 and the front aperture plate aperture 335 and rear support aperture 335, through which the tow hitch insert 390 is received, is about 0.5mm. In alternative embodiments, tow hitch insert 25 390 may be of multiple layer construction with a core piece surrounded by a sleeve, the sleeve being fixedly attached to the core, for example by welding. The sleeve may be machined to the desired tolerances before being attached to the core piece. Throughout this specification and the claims which follow, unless the context requires 30 otherwise, the word "comprise", and variations such as "comprises" and "comprising", P:\OPER\SSB\2009\30822671 AU CAP Spec.doc - 14/9/09 - 20 will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from 5 it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. 10 While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above 15 described exemplary embodiments.

Claims (20)

1. A towbar comprising: a bar member for connection to a vehicle; 5 an insert receptacle fixedly attached to the bar member for receiving a tow hitch insert; a front aperture plate defining a front aperture, the front aperture plate being fixedly attached to a front end of the insert receptacle; and a rear aperture plate defining a rear aperture, the rear aperture plate being fixedly 10 attached to a rear end of the insert receptacle; wherein the front and rear apertures and the insert receptacle are sized so that, when the tow hitch insert is received in the insert receptacle, the front and rear aperture plates closely fit around the tow hitch insert and the insert receptacle loosely fits around the tow hitch insert. 15

2. A towbar according to either of claim 1, wherein the front aperture and rear apertures are of different sizes to accommodate a tow hitch insert that has a varied cross-sectional profile. 20

3. A towbar according to any one of claims 1 or claim 2, further including front and rear support plates fixedly attaching the insert receptacle to the bar member.

4. A towbar according to claim 3, wherein the rear support plate comprises the rear aperture plate and the front support plate includes a front support aperture configured to 25 accept the insert receptacle.

5. A towbar according to any of claims 1 to 4, wherein the bar member comprises front and rear apertures through which the insert receptacle is received. 30

6. A towbar according to any of claims 1 to 5, further including a tow hitch insert received in the insert receptacle. H:\jll\1nterwsoven\NRPonbl\DCC\ILL\7751499_1.doc-4/05/2015 - 22

7. A towbar according to claim 6, wherein the tow hitch insert comprises a bar portion and the bar portion is machined from a larger bar to within a tolerance of 0.2mm. 5

8. A method of manufacturing a towbar, including the steps of: fixedly attaching an insert receptacle to a bar member; forming apertures in front and rear aperture plates affixed to the bar member, the apertures being aligned with a hollow defined by the insert receptacle and being smaller than the internal dimensions of the insert receptacle, so that, when a tow hitch insert is at 10 least partly received in the hollow of the insert receptacle and in the apertures, the front and rear aperture plates closely fit around the tow hitch insert and the insert receptacle loosely fits around the tow hitch insert; attaching the front aperture plate to a front end of the insert receptacle; and attaching the rear aperture plate to a rear end of the insert receptacle. 15

9. A method of manufacturing a towbar according to claim 8, further including the step of fixedly attaching front and rear support plates adjacent to the insert receptacle and the bar member. 20

10. A method of manufacturing a towbar according to claim 7, further including the step of creating front and rear apertures in the front and rear support plates and bar member to accept the insert receptacle.

11. A method of manufacturing a towbar according to either of claim 9 or 10, wherein 25 the front and rear support plates have extended portions such that the insert receptacle is positioned adjacent the bar member.

12. A method of manufacturing a towbar according to any of claims 8 to 11, further including machining an aperture in the bar member to accept the insert receptacle. 30

13. A method of manufacturing a towbar, including the steps of: H:\jii\lntenvovcn\NRPorbl\DCC\JLL\7751499_ 1.docx-4/05/2015 - 23 forming a support aperture in a front support plate; forming a rear aperture in a rear support plate; attaching the front and rear support plates to a bar member; attaching an insert receptacle to the support plates, the insert receptacle being 5 received through the front support aperture, and configured to accept a tow hitch insert; forming a front aperture in a front aperture plate, the front aperture being smaller than the internal dimensions of the insert receptacle; and attaching the front aperture plate to a front end of the insert receptacle. 10

14. A method of manufacturing a towbar, including the steps of: forming a rear aperture in a rear support plate; attaching an insert receptacle to the rear support plate, the internal dimensions of the insert receptacle being larger than the rear aperture; forming front and rear apertures in a bar member; 15 forming a support aperture in a front support plate and attaching the front support plate to the front of the bar member; attaching the insert receptacle to the bar member and the front support plate such that the insert receptacle is received through the front and rear apertures of the bar member and the support aperture of the front support plate; 20 forming a front aperture in a front aperture plate, the front aperture being smaller than internal dimensions of the insert receptacle; and attaching the front aperture plate to a front end of the insert receptacle.

15. A method of manufacturing a towbar according to any of claims 8 to 14, further 25 including attaching of a tow hitch insert to the insert receptacle.

16. A method of manufacturing a towbar according to claim 15, wherein at least a portion of the tow hitch insert to be received in the insert receptacle is machined to within a tolerance of 0.2mm. 30 H:\jll\l ntenovcn\NRPortbl\DCC\JLL\77514991 doex-4/05/2015 - 24

17. A method of manufacturing a towbar according to any of claims 8 to 16, further including creating a hole in the insert receptacle and tow hitch insert to accept a pin which releasably connects the tow hitch insert to the insert receptacle. 5

18. A method of manufacturing a towbar according to any of claims 8 to 17, wherein the apertures are formed to within a 0.1 mm tolerance.

19. A towbar substantially as hereinbefore described with reference to the drawings and/or Examples. 10

20. A method of manufacturing a towbar substantially as hereinbefore described with reference to the drawings and/or Examples.