Trailer nose weight measuring device

Abstract

A trailer and vehicle hitching assembly 100 comprising a tongue portion 22 for affixing to a body of the trailer or vehicle, a hitch portion 32 for selectably securing the assembly to the other of the

Description

06 11 25 Field The present invention relates to a trailer and vehicle hitching assembly for measuring the nose weight of the trailer. It also relates to a trailer nose weight measuring system and trailer having such an assembly or system. Background When towing a trailer behind a vehicle, it is crucial that said trailer is not overloaded. By having too great a load in the trailer, the trailer and vehicle can become unsafe to operate due to the excessive weight causing an impairment in the vehicle's ability to steer and brake properly. Furthermore, it can make the vehicle and trailer unstable when going around corners and the additional weight can cause strain on the tyres and other components, potentially resulting in an earlier failure condition than would be normal. As such, many countries have put in place weight restrictions on trailers that must be adhered to, else the driver of the vehicle risk legal punishment. This weight restriction legislation often includes nose weight of the trailer (that is, the weight placed on the towing vehicle when coupled to the trailer at the point of the coupling). While some users, for example those forming part of businesses involving the use of trailers, might have separate external devices that they can attach to the front of a loaded trailer to measure the nose weight, many users (such as those with personal trailers or caravans) do not have access to such equipment. As such, incorporating a method of measuring the trailer nose weight into the trailer or vehicle would allow users to ensure they are meeting the relevant road and loading regulations easily and quickly at any location (as well as ensuring safe handling of the vehicle and trailer), rather than having to find the owner of a suitable measurement device. Figures 1 and 2 show an example of such a vehicle and trailer system 10 according to the known prior art, comprising a trailer 20 affixed to a vehicle 30. The trailer 20 is formed around a frame 21 which culminates in a tongue 22 supported by a jockey wheel 23. Mounted to the tongue 22 is a coupling 24, formed from a coupling body 25 (affixed to the tongue 22) and a coupling head 27, with a draw tube 26 (also known as a drawbar) therebetween. The coupling head 27 has a downward facing recess 28. A tow bar 32 is mounted to the rear of the vehicle 30, the tow bar 32 having a tow hitch 34 culminating in a ball 36. The shape of ball 36 corresponds to the shape of the recess 28, 06 11 25 such that the front of trailer 20 can be raised via the jockey wheel 23 to have the ball 36 sit in the recess 28, allowing the towing of the trailer 20 by the vehicle 30. One known solution is to have multiple measuring devices located around the tongue 22 of trailer 20. However, this does not produce a straightforward nose weight reading, and as such multiple calculations must be done to determine an accurate trailer nose weight. As well as being more computationally difficult, these calculations also introduce potential errors and inaccuracies into the final reading. Another known solution is to place a measuring device on an inside surface at point 29 of the recess 28 of coupling head 27. By placing the measuring device at point 29 (the uppermost part of recess 28 and where the curvature of recess 28 is at a horizontal), the trailer nose weight can be measured from the force exerted upon the device. However, the contact between this point 29 and the ball 36 of towbar 32 can cause wear or damage to the measuring device. As such, over repeated use, the wear experienced by the measuring device will cause inaccuracies in the trailer nose weight reading. The present invention seeks to overcome or at least mitigate these problems by providing a system in which the trailer nose weight can be accurately measured over an extended period of use. The present invention also seeks to provide such a system that is reliable, easy to manufacture and very cost effective. Summary A first aspect of the invention provides a trailer and vehicle hitching assembly as set out in claim 1. By affixing the strain gauge to the inner wall of the tubular connecting portion, the strain gauge is further protected from wear (for example by stone strike or road debris when in use), which increases the lifespan and long-term accuracy of the system. The tubular connecting portion may have one of a square, rectangular, ovoidal, or circular cross-sectional shape. When the tubular connecting portion is hollow, the internal space formed by the hollow tubular connecting portion may have substantially the same cross-sectional shape as the tubular connection portion. This allows for a greater accuracy of strain measurement. 06 11 25 The strain gauge may be affixed to the inner wall of the connecting portion via one of welding or adhesives. These methods of affixing the strain gauge to the inner wall provide the necessary secure attachment required for accurate strain measurements in the hitching assembly. The strain gauge is located in a mounting component, the mounting component being affixed to the wall of the tubular connecting portion. The mounting component may have at least one surface shaped to conform with the wall of the tubular connecting portion. The use of a mounting component allows for improved manufacturing, as the strain gauge can be protected until fitted and more easily and accurately positioned on the connecting portion, whilst still providing the secure connection required for accurate measurements. The tubular connecting portion may lie on a vertical plane bisecting the trailer in a longitudinal direction, the strain gauge being substantially parallel with the vertical plane. The strain gauge may further have a longitudinal axis, said axis being substantially coincident to the vertical plane. By mounting the strain gauge in this fashion, a direct measurement can be taken that (after unit conversion) can be output to indicate trailer nose weight without the need for any major calculations that could introduce inaccuracies. The trailer and vehicle hitching assembly may further comprise a second strain gauge affixed to a wall of the tubular connecting portion. This second strain gauge may be affixed to a wall of the tubular connecting portion opposite the strain gauge. The second strain gauge adds redundancy to the system, improving reliability, whilst increasing accuracy by allowing for comparison of measurements. The strain gauge may be a thin film strain gauge. These strain gauges are cost efficient but reliable methods of strain measurement. A second aspect of the invention provides a trailer nose weight measuring system comprising the trailer and vehicle hitching assembly as described above, a processor and a display, wherein the processor is connected to the strain gauge and is programmed to receive signals from the strain gauge and output the nose weight of the trailer to the display. The strain gauge may be connected to the processor via a wired connection. Alternatively, the strain gauge may be connected to the processor via a transmitter connected to the strain gauge and a corresponding receiver connected to the processor. 06 11 25 The processor may be connected to the display via a wired connection. Alternatively, the processor may be connected to the display via a transmitter connected to the processor and a corresponding receiver connected to the display. The display may provide at least one of visual and audio feedback in dependence on the signals from the strain gauge. In this way, the measurement provided by the strain gauge can be used to display the nose weight of the trailer to the user. As such, this is an easy, cost effective and accurate method of allowing users to follow the relevant regulations and maintain their vehicle's safety. A third aspect of the invention provides a trailer comprising the trailer and vehicle hitching assembly or the trailer nose weight measuring system as described above. Brief Description of the Drawings Embodiments will now be described, by way of example only, with reference to the accompanying figures in which: FIGURE 1 is a side view of a trailer and vehicle coupled by a system according to the prior art; FIGURE 2 is a side view of the system of Figure 1; FIGURE 3 is a perspective view of a system according to a first embodiment of the present invention; FIGURE 4 is a schematic side view of the system of Figure 3; FIGURE 5 is a perspective view of a part of the system of Figure 3; FIGURE 6 is a schematic section end view of the system of Figure 3; FIGURE 7 is an exploded perspective view of a device according to a second embodiment of the present invention; FIGURE 8 is a schematic section end view of the system of Figure 7; FIGURE 9 is a top view of a strain gauge carrier according to the first and second embodiments of the invention; and FIGURE 10 is an end view of the carrier of Figure 9. 06 11 25 Detailed Description of Embodiments With reference to Figures 3 to 6, below is described a system 100 according to a first embodiment of the present invention. System 100 comprises strain gauge 110 affixed to a draw tube 120. Strain gauge 110 is a thin film strain gauge, but other types of strain gauge are also envisaged. Furthermore, other types of measuring devices could also be used, as long as they are capable of measuring strain. The strain gauge 110 is formed along a central longitudinal axis A-A. Draw tube 120 (as shown in Figure 5) has a cylindrical shape formed along a central longitudinal axis Z-Z and, as in the prior art system 10, connects the coupling body 25 and the coupling head 27. Other cross-sectional shapes of draw tube 120 are also envisaged (such as a square or rectangle), as long as the draw tube 120 is strong enough to withstand the loads placed upon it in use and to meet the relevant legal requirements. Draw tube 120 has a first end 122 and a second end 124, the first end 122 having a pair of bores 126 (the function of which is described below). The draw tube 120 further has an outer surface 127 and is hollow (for weight saving and other benefits described below), forming an inner surface 128. The outer and inner surfaces 127, 128 have the same cross-sectional shape, taken as seen in Figure 6 along a vertical axis Y-Y and a transversal axis X-X of draw tube 120. However, different surface crosssections and solid formulations are also envisaged. Draw tube 120 can be the draw tube 26 of the prior art system 10, allowing for easy modification of existing systems. As seen in Figures 4 to 6, the strain gauge 110 is affixed to the inner surface of the draw tube 120. This provides protection to the strain gauge 110 from stone strikes and other sources of potential damage. The strain gauge 110 is affixed such that the strain gauge's axis A-A is parallel to the draw tube's longitudinal axis Z-Z and further that, when the draw tube 120 is part of the coupling 24, the strain gauge 110 is at the lowermost part of the inner surface 128 (i.e., is coincident with the vertical axis Y-Y). This location allows for a more accurate and straightforward calculation of trailer nose weight, as is discussed in further detail below. However, other locations for affixing the strain gauge 110 around the draw tube 120 are envisaged, either on the outer or inner surface 127, 128, such as locations coincident with the transversal axis X-X. These 06 11 25 potential locations are shown in dashed lines in Figures 4 and 6, Figure 6 being an end section view taken on a cut through the draw tube 120. Meanwhile, for clarity, Figure 5 shows a bottom view of the draw tube 120 with the wire 112 connected to the strain gauge 110 in the anticipated position, with some of the other envisaged positions also shown. The strain gauge 110 is attached by adhesive, as this provides a strong, durable, and long-lasting attachment (to ensure the accuracy of the measurements) without damaging the strain gauge or the draw tube 120. However, other attachment methods (such as welding) are also envisaged. When being assembled (as shown in Figures 3 and 4), first end 122 of the draw tube 120 is slid through a corresponding hole 25h in coupling body 25, such that the second end 124 is proximate to the coupling body 25 and the draw tube 120 extends away from the trailer tongue 22. Coupling head 27 is then secured to the first end 122 via bolts through bores 126. Other securement methods (such as welding) are also envisaged. Strain gauge 110 is positioned before assembly such that (as seen in Figure 4) it is located in the middle of the points where the coupling body 25 and coupling head 27 extend over the draw tube 120. Strain gauge 110 is connected via a wire 112 to a processor (not shown). Wireless transmission of the signals from the strain gauge 110 to the processor is also envisaged. The processor then translates the raw data from the strain gauge 110 into a trailer nose weight reading and outputs said reading. The output may be to any (or a combination) of a visual display, an audio warning sound (for if the weight exceeds a set limit) or any other feedback device suitable for informing the user of the trailer nose weight. The location of the strain gauge 110 allows for a straightforward calculation of the trailer nose weight, meaning the computational power required is less and the opportunity for errors (from operations such as the rounding of figures) is reduced, all whilst only using a single strain gauge 110. This makes the system 100 cheaper, more accurate and less computationally intensive than previous systems. It has also been found that placing the strain gauge 110 on the lower inner surface 128 of draw tube 110 (as seen in Figures 4 to 6) can produce better results, as some of the strain gauges 110 used can be more accurate when reading tension measurements. It is also alternatively envisaged that the system 100 could utilise multiple strain gauges 110, located in various of the locations mentioned above. The use of multiple strain 06 11 25 gauges 110 does add computational complexity, but allows for the comparison / checking of measurements against each other to reduce the likelihood of total system failure. When using multiple strain gauges 110, it is useful to affix them in pairs on either of the outer or inner surfaces 127, 128 of the draw tube 120, with each strain gauge 110 opposite the other. This allows for more useful and easier comparisons of the data they produce. System 100 as described above is for an EU style of trailer and vehicle hitching arrangement; however the principles of the invention apply equally to a US style of trailer and vehicle hitching arrangement. This is exemplified in system 200 according to a second embodiment of the present invention, which is described below with reference to Figures 7 and 8. In this system 200, a subframe 210 is mounted to the rear of the vehicle 30, the subframe 210 comprising a pair of mounting points 212 (for affixing the subframe 210 to the vehicle 30) with a crossbeam 214 extending therebetween. From the centre of this crossbeam 214 there extends a receiving tube 216 with bores 218 therethrough, the receiving tube 216 being hollow and ending in an open aperture 217. The system 200 also comprises a removeable tow hitch 220 with a first end 222 and a second end 224. The first end 222 has a ball 226 as per the ball 36 in the prior art system 10. However, other known attachment methods are also suitable, such as a ring and pin type hitch. The second end 224 has an elongate member 228 with bores 229 arranged therethrough proximate to the second end 224. The elongate member 228 is hollow, and sized and shaped such that it can be inserted into the receiving tube 216 via aperture 217 with minimal clearance and secured via bolts through aligned bores 218, 229. In this way, a removable tow hitch 220 is provided. In this embodiment, as seen in Figures 7 and 8, the strain gauge 110 is located on the elongate member 228, on an inner surface 228a. When assembled, the strain gauge 110 is not located on a part of the elongate member 228 covered by the receiving tube 216. As with the first embodiment described above, mounting the strain gauge 110 internally increases the protection to, and accuracy of, the strain gauge 110, whilst decreasing the computational requirement for producing the trailer nose weight measurement. However, similar positions on the elongate member 228 can be used for affixing the strain gauge 110, including those as are envisaged for the draw tube 120 of the first embodiment, as can the use of multiple strain gauges 110. As with the first embodiment, other potential strain gauge locations are shown in dashed lines in Figures 06 11 25 7 and 8, including those on an outer surface 228b of elongate member 228 (of which Figure 8 is a cut though end section view). The same strain gauge 110 and attachment methods can be used in this second embodiment as are used in the first embodiment described above. This second embodiment allows for the same accurate, cheap and computationally efficient trailer nose weight measurement as in the first embodiment, but suitable for towing systems that do not include a draw bar 120 (as in the US, for example). In both the first and second embodiment, the strain gauge 110 is mounted on a carrier 300, as seen in Figures 9 and 10 and described below. The carrier 300 comprises a substantially rectangular cuboidal body 310 shaped (i.e., large enough) to fully accommodate the strain gauge 110. The body 310 has a flat first side 312 opposite a second side 314. The second side 314 has a recess 320 shaped to fit the strain gauge 110 as further described below. The recess 320 has an open end 330 to allow for easy connection of the strain gauge 110 to the wire 112. The second side 314 may also have chamfered longitudinal edges 340, the function of which is explained below. The recess 320 is formed of, from the open end 330 in order as seen in Figure 9, a connector recess 322, a channel 324, a solder recess 326 and a strain gauge recess 328. The connector recess 322 is deep enough to house the wire 112 surrounded by insulation, the insulation allowing the wire 112 to be adhered to the carrier 300. The channel 324 holds the wire 112 as is deep enough so the wire 112 does not contact the draw tube 120. The solder recess 326 is deep enough to hold a soldered connection between wire 112 and strain gauge 110 without the solder touching the draw tube 120, which would short circuit the system. Finally, strain gauge recess 328 holds the strain gauge 110 itself and is shallower than the thickness of the strain gauge 110, for reasons that will be discussed below. The carrier 300 is made of a single piece of plastic for easy manufacture and attachment to the draw tube 120 or elongate member 228 via adhesive, although other materials (such as any non-reactive metals) are envisaged. When using the carrier 300, it is arranged on / in the draw tube 120 or elongate member 228 such that the second side 314 is facing the surface to which the strain gauge 110 is attached, to ensure the strain gauge 110 is flat against said surface to maintain the 06 11 25 accuracy of the measurements. In the cases where the surface in question is curved, the chamfered edges 340 of the carrier 300 allow this secure positioning despite the curvature. The strain gauge 110 is adhered to the carrier 110 by a flexible glue, so the carrier 110 does not influence the strain gauge's 110 readings. The depth of the strain gauge recess 328 ensures the strain gauge 110 is properly located on and secured to the required surface. As such, the carrier 300 provides protection to the strain gauge 110 prior to and during the assembly process and helps to ensure a secure and accurate attachment to the necessary surface, whilst not affecting the measurements taken by the strain gauge 110. The carrier 300 also increases protection from factors such as stone strike and road debris when the strain gauge 110 is fitted to an external surface. However, systems not using the carrier 300 are also envisaged. For example, the surfaces 127, 128, 228a, 228b where the strain gauge 110 may be fitted could be etched to provide a location for the strain gauge 110 to sit. Whilst the description of these embodiments has been with reference to a trailer 20, it should be understood that the systems 100, 200 would be suitable for any towed object (such as a caravan) using similar coupling methods.

Claims

06 11 251. A trailer and vehicle hitching assembly comprising:a coupling body for mounting to a body of one of the trailer or the vehicle;a hitch portion including a coupling head for removably hitching the trailer and vehicle hitching assembly to the other of the trailer or the vehicle,a tubular connecting portion arranged between the coupling body and the coupling head, the tubular connecting portion being hollow thereby forming an inner wall; anda strain gauge having an axis, wherein the strain gauge is affixed to the inner wall of the tubular connecting portion at a lowermost part of the inner wall when the hitching assembly is mounted to the body of the one of the trailer or the vehicle in its operational orientation, and wherein the axis of the strain gauge is parallel to a longitudinal axis of the tubular connecting portion, andwherein the strain gauge is located in a mounting component, the mounting component being affixed to the wall of the tubular connecting portion.

2. The trailer and vehicle hitching assembly according to any of the preceding claims, wherein the tubular connecting portion has one of a square, rectangular, ovoidal, or circular cross-sectional shape.

3. The trailer and vehicle hitching assembly according to claim 2, wherein the internal space formed by the hollow tubular connecting portion has substantially the same cross-sectional shape as the tubular connecting portion.

4. The trailer and vehicle hitching assembly according to any of the preceding claims, wherein the strain gauge is affixed to the inner wall of the tubular connecting portion via one of welding or adhesives.

5. The trailer and vehicle hitching assembly according to claim 1, the mounting component having at least one surface shaped to conform with the wall of the connecting portion.

6. The trailer and vehicle hitching assembly according to any of the preceding claims, wherein the tubular connecting portion lies on a vertical plane bisecting the trailer in a longitudinal direction, the strain gauge being substantially parallel with the vertical plane.06 11 257. The trailer and vehicle hitching assembly according to claim 6, wherein the strain gauge has a longitudinal axis, said axis being substantially coincident to the vertical plane.

8. The trailer and vehicle hitching assembly according to any of the preceding claims, further comprising a second strain gauge affixed to a wall of the connecting portion.

9. The trailer and vehicle hitching assembly according to claim 8, wherein the second strain gauge is affixed to a wall of the connecting portion opposite the first strain gauge.

10. The trailer and vehicle hitching assembly according to any of the preceding claims, wherein the strain gauge is a thin film strain gauge.

11. A trailer nose weight measuring system comprising the trailer and vehicle hitching assembly according to any of the preceding claims, a processor and a display, wherein the processor is connected to the strain gauge and is programmed to receive signals from the strain gauge and output a nose weight of the trailer to the display.

12. The trailer nose weight measuring system according to claim 11, wherein the strain gauge is connected to the processor via a wired connection.

13. The trailer nose weight measuring system according to claim 11, wherein the strain gauge is connected to the processor via a transmitter connected to the strain gauge and a corresponding receiver connected to the processor.

14. The trailer nose weight measuring system according to any of claims 11 to 13, wherein the processor is connected to the display via a wired connection.

15. The trailer nose weight measuring system according to any of claims 11 to 13, wherein the processor is connected to the display via a transmitter connected to the processor and a corresponding receiver connected to the display.

16. The trailer nose weight measuring system according to any of claims 11 to 15, wherein the display provides at least one of visual and audio feedback in dependence on the signals from the strain gauge.

17. A trailer comprising the trailer and vehicle hitching assembly according to any of claims 1 to 10 or the trailer nose weight measuring system of any of claims 11 to 16.06 11 25

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