GB2515546A

GB2515546A - Drawbar mounting

Info

Publication number: GB2515546A
Application number: GB1311535.7A
Authority: GB
Inventors: Robert Clive Browning Davis
Original assignee: Ifor Williams Trailers Ltd
Current assignee: Ifor Williams Trailers Ltd
Priority date: 2013-06-27
Filing date: 2013-06-27
Publication date: 2014-12-31
Anticipated expiration: 2033-06-27
Also published as: GB201311535D0; GB2515546B

Abstract

A central cage device 30 provides an opening 50 configured for receiving a drawbar 10 which extends there through allowing rocking motion of the drawbar. At each side of the central cage 30, a respective connector device 31, 32 is provided for connection to a trailer 20 or other equipment to be towed. Mutually opposed plates 37, 38 are provided at each side of the cage 30 and at facing ends at each associated connector device 31, 32. These plates extend at an acute angle relative to the vertical, preferably symmetrically and substantially parallel to each other at each side and the angle may be between 5Â° and 45Â° or between 7.5Â° and 20Â° relative to the vertical. At least one resilient block 35, 36, or a plurality of blocks of resilient material, with metal plates interleaved between, are arranged between mutually opposed plates 37, 38 on each cage side. The invention is aimed at allowing limited rocking of a trailer or agricultural equipment whilst addressing a prior situation where resilient material may have overheated.

Description

DRAWBAR MOUNTING

TECHNICAL FIELD

[0001] This invention relates to a drawbar mounting assembly, particularly but not exclusively for trailers.

BACKGROUND

[0002] Agricultural tractors and trailers conventionally have no suspension, other than for the wheels/axles in some cases. The connection between the tractor and a trailer or any other agricultural equipment being towed by the tractor, typically a drawbar and its mounting arrangement, similarly, conventionally have no means of suspension, so all torces and impacts are transmitted to the tractor without any damping. Given the jarring and bouncing which the driver experiences as a result of travelling over rough and uneven terrain, this is both uncomfortable and positively detrimental to the back and spine of the driver.

[0003] Mounting of drawbars for trailers by an arrangement which provides flexibility by use of springs, specifically helical springs, is known.

[0004] Resilient blocks comprising a multiplicity of metal plates interleaved with and bonded to resilient material, typically rubber, natural, synthetic or a combination of both, are known. Such blocks allow relatively high shear deflections of the respective mounting surfaces by virtue of relatively low shear stiffness. A consequence of the construction necessary to deliver this shear deflection is a relatively high compressive stiffness. It is a characteristic of such resilient blocks that, in both shear and compression, but especially compression, the stiffness characteristic is non-linear; as the compressive deflection increases the compressive stiffness increases.

[0005] Rubber or rubber-like resilient materials possess a degree of natural damping.

This can be used beneficially to inhibit the build up of cyclic oscillation, especially where the resilient block is part of a complex springing system. However, it is important that installations using such resilient blocks are structured so as to avoid overheating of the resilient material.

[0006] An object of the present invention is to provide an improved drawbar mounting assembly for trailers for agricultural use.

SUMMARY OF THE INVENTION

[0007] According to the present invention a drawbar mounting assembly comprises a central cage device providing an opening configured for receiving a drawbar which in use extends there through in a manner allowing limited movement and rocking motion of the drawbar, and, at each side of the central cage, a respective connector device, for connecting the cage device to a trailer or other equipment to be towed, characterised in that mutually opposed plates are provided at each side of the cage device and at facing ends at each associated connector device, these plates extending at an acute angle relative to vertical, and at least one resilient block is arranged between the opposing plates.

[0008] In preferred embodiments a plurality of blocks of resilient material, with metal plates interleaved between these blocks, are arranged at each side between the opposite plates on the side of the cage device and on the connector device. The respective pairs of opposing plates on the side of the cage device and on the connector device and identical resilient blocks are preferably arranged symmetrically. The plates of each pairs of opposedly facing plates are preferably arranged parallel to each other. However, other dispositions are possible in other embodiments.

[0009] The use of resilient blocks, conveniently blocks of resilient material, such as rubber or synthetic rubber, in accordance with the present invention, is preferred over use of any other forms of spring mounting! as by helical springs, as it can provide suitable damping of vibrations and jolts and movements of the trailer in addition to resilience/flexibility.

The arrangement of the resilient blocks at an acute angle to the vertical is to strike a balance between the greater strength of the blocks when in a horizontal disposition and the greater flexibility and resilience when in a vertical disposition. Preferably the opposed plates and the resilient blocks arranged there between lie at an angle in the range 5° to 45° relative to the vertical. More preferably the opposed plates and the resilient blocks arranged there between lie at an angle of between 750 and 200 relative to the vertical.

Further, as mentioned, a symmetrical arrangement of the resilient blocks and plates at each side of the cage device is desirable. This is because so long as the rear of the drawbar is pivotally mounted to the trailer chassis, which it will be, the resilient block devices will deliver a strong centring effect on the drawbar, which necessarily must be a symmetrical effect.

[0010] It is also possible to mount a drawbar 10 to the front of a trailer 20 in an unsprung manner by means of a frame member 24 of metal plate, and a pair of elongate connector elements 26 at each side thereof, as shown in figure 1. These connector elements 26 connect the frame member 24 to the trailer chassis, as shown in figure 2, with apertures 25, 27 at ends of the elements 26 and corresponding apertures (not visible) in upper corners of the frame member 24 and on flanges 22 of the trailer chassis for reception of bolts (not shown) for making the connections.

[0011] Such an unsprung mounting arrangement is then preferably designed to be interchangeable with preferred practical embodiments of the spring drawbar mounting assembly of the invention so that at point of sale (or afterwards) a purchaser of a trailer can choose between unsprung and sprung drawbar mounting. For this purpose, the size of the unsprung mounting arrangement, particularly the length of the connector elements 26 are chosen to fit into the place on the trailer chassis where configurations of the cage device and the connector devices of preferred versions of the mounting arrangement of the invention would fit. In other words, apertures in outer ends of the connector elements 26 and apertures in the connector devices of the inventive embodiments are of appropriate size and distance apart to be bolted to the same trailer chassis flanges 22 without any adaptation of the trailer being required. This is apparent from a comparison of figure 3 and figure 2.

[0012] Furthermore, the cage device, in preferred embodiments, may include a frame member 34 substantially identical to that of an unsprung drawbar mounting, but with such frame member 34 connected instead to a bridging device which co-operates with the connector devices at each side to mount the opposing plates and the resilient block or blocks there between.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a trailer drawbar and unsprung mounting arrangement therefor; Figure 2 is an enlarged fragmentary perspective view showing the drawbar mounted to a trailer by the arrangement of figure 1; Figure 3 is a view corresponding to figure 2 showing the drawbar mounted to a trailer by a preferred practical embodiment of the drawbar mounting assembly of the present invention; Figure 4 is a perspective view showing the same as figure 3 but to a smaller scale so that the entire trailer is shown; Figure 5 is an enlarged front perspective view of the mounting assembly of figures 3 and 4 shown in isolation and with frame member omitted; and Figure 6 shows the same drawbar mounting assembly as in figure 5 but viewed from above and at a different angle compared to figure 5.

DETAILED DESCRIPTION

[0014] With reference to figures 3 to 6, a preferred practical embodiment of the sprung drawbar mounting assembly of the invention comprises a central cage device 30, a respective connector device 31, 32 at each side of the central cage, and respective resilient block devices 35, 36 mounted between plates 37, 38 at mutually opposed facing ends of the cage device 30 and the respective connector devices 31, 32.

[0015] The mutually opposed plates 37, 38 are substantially parallel to each other and the respective pairs are arranged symmetrically at respective sides of the assembly. At each side of the plates 37, 38 slope downwards and outwards at an angle of between about 7.5° and 20° relative to vertical (as determined when the assembly is placed on a horizontal surface in its mounting orientation, as shown in figure 5). This has been found to be a suitable range of angle of inclination of the spring blocks to achieve optimum balance of their strength, stiffness both in sheer and compression and damping properties, while also using blocks of appropriate size (therefore cost) and resilient material formulation (also related to cost) when the assembly is for use on a trailer for agricultural purposes. In other embodiments other angles of disposition of the resilient blocks which serve as the spring part of the suspension are possible.

[0016] In this illustrated embodiment and other preferred embodiments, a plurality of resilient blocks are provided in each device 35, 36, these blocks being of a thickness of about 8.0 to 8.5 cm and interleaved by metal plates for strength and durability. Further, these blocks, with interleaved metal plates, are each mounted between a pair of inclined end plates 33, 39 as a separately sourced component.

[0017] The cage device 30 comprises a bridging device, designated generally by reference 40, and a frame member 34, substantially identical to the frame member 24 of the unsprung drawbar mounting means shown in figures 1 and 2. Upon production of the overall assembly the aforesaid resilient block components 35, 36 are mounted between the respective facing end plates 37, 38 of the bridging device 40 and of the respective connector devices 31, 32 with close metal to metal contact between the plates 33, 37, on the one hand, and 38, 39, on the other hand, at each side, as evident in figures 5 and 6.

[0018] As best shown in figure 6, the bridging device 40 comprises a substantially parallel pair of bridging plates 42 mounted onto the central tubular element 44, which in use extends substantially axially of the trailer to which the drawbar 10 is filled, as well as the respective plates 37 mounted to outer ends of the plates 42 at the predetermined angle of between about 7.5° and 20° to the vertical.

[0019] Each connector device 31, 32 similarly comprises a substantially parallel pair of connector plates 43 of curving contour mounted onto a tubular element 45 which in use extends substantially parallel to the axis of the trailer to which the drawbar 10 is fitted, as well as respective plates 38 mounted to inner ends of the plates 43 at the predetermined angle between about 7.5° and 20° to the vertical. Tapering outer and upwardly inclined ends of the connector plates 43 are provided with openings 53 for bolting onto the trailer chassis 22, as shortly to be explained further. The connector devices 31, 32 are connected to each other by respective front and rear crossbars 47, 48 of shallow channel section form. The respective tubular elements 45 engage through circular openings in the crossbars 47, 48 and edges of the plates 38 also extend through slots in the crossbars 47, 48. This results in an overall structure of the assembly being extremely strong. Its weight is reduced by additional circular apertures 49 along the crossbars 47, 48.

[0020] Upon assembly, the resilient block devices 35, 36 are positioned between the respective outer ends of the bridging device 40 and the inner ends of the connector devices 31, 32, more specifically with the plates 33, 39 of the devices 35, 36 between the plates 37 and 38 and in direct metal to metal contact with them. The contacting plates 33, and 38, 39, respectively, can be bolted together by way of openings 51, the bolts not being shown in the drawings for clarity.

[0021] The frame member 34 for supporting the drawbar 10 is not shown in figures 5 and 6, but as is apparent in figures 3 and 4, it is bolted to one of the bridging plates 42 as bush reinforced openings 52 are provided in lower regions of the plates 42 for that purpose.

Again, the bolts are not shown in the drawings for clarity. The spacing between the openings 52 is chosen so that the frame member 34 used can be the same as the conventional frame member 24 shown in the prior art figures 1 and 2. Economy in manufacture results as different configurations of components do not then have to be fabricated for unsprung and sprung drawbar mounting assemblies.

[0022] In use, the assembly is mounted to the front of the trailer 20 as shown in figures 3 and 4. The distance between the openings 53 in the connector plates 43 of the respective connector devices 31, 32 is chosen to allow for mounting of this sprung drawbar mounting assembly between the same flanges 22 provided as standard on the trailer 20 for mounting of the prior art, conventional and unsprung mounting means by the elongate elements 26, as shown in figures 1 and 2. Thus, this embodiment and, indeed, other preferred embodiments of the sprung drawbar mounting assembly of the invention are interchangeable with an unsprung mounting arrangement so that a purchaser can make a choice between the two at point of sale. This also has the advantage that the retailer does not need to stock different trailers, merely the two different mounting arrangements one of which can then be fitted at point-of-sale, and the customel does not have to enduie possible long waits if the required type is not in stock. Alternatively, the sprung assembly of the invention can be later retrofitted to an existing trailer in place of the unsprung mounting.

[0023] The foregoing is illustrative and not limitative of the scope of the invention. In othei words, the invention is not restricted to the details of the foregoing embodiment, and many variations are possible in other embodiments. In particular, the shape and configuration of the various parts, namely the cage device, the connector devices and the resilient block devices may be other than as illustrated. Connection between the connected devices can be accomplished in a diffeient manner to the crossbais in the illustrated embodiment. The angle of inclination to the vertical of the various plates used for mounting the resilient blocks may vary. Also, respective plates on the resilient block device and on the connector device and bridging device are not essential and in other variants only a single plate may be provided at those locations. Further, use of a frame member identical to conventional for encircling the drawbar is advantageous, but not essential. For example, a separate U-shaped component could be bolted to the underside of the bridging device to support the drawbar in comparable manner. Many other possible variations in detail will be appalent to a person skilled in this technical field.

[0024] Yet further, it will be understood that the mounting assembly in accoidance with the invention is not exclusively for use in respect of trailers and could be used in respect of any other equipment which is to be towed.

[0025] The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims and drawings).

[0026] Throughout the description and claims of this specification, the words "comprise" and "contain" and valiations of them mean "including but not limited to", and they are not intended to (and do not) exclude other components. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otheiwise.

Claims

CLAIMS1. A drawbar mounting assembly comprising a central cage device providing an opening configured for receiving a drawbar which in use extends there through in a manner allowing limited movement and rocking motion of the drawbar, and, at each side of the central cage, a respective connector device, for connecting the cage to a trailer or other equipment to be towed, characterised in that mutually opposed plates are provided at each side of the cage and at facing ends at each associated connector device, these plates extending at an acute angle relative to vertical and at least one resilient block is arranged between the opposing plates.
2. A drawbar mounting assembly according to claim 1 wherein a plurality of blocks of resilient material, with metal plates interleaved between these blocks, are arranged at each side between the opposing plates on the side of the cage device and on the connector device.
3. A drawbar mounting assembly according to claim 1 or 2 wherein the opposed plates and the resilient blocks arranged there between lie at an angle in the range 5° to 45° relative to the vertical.
4. A drawbar mounting assembly according to claim 3 wherein the opposed plates and the resilient blocks arranged there between lie at an angle of between 7.5° and 20° relative to the vertical.
5. A drawbar mounting assembly according to any preceding claim wherein the opposed plates and the resilient blocks arranged there between are disposed symmetrically.
6. A drawbar mounting assembly according to any preceding claim wherein the cage device and the respective connector devices are fixedly attached to each other by at least one transversely extending bar.
7. A drawbar mounting assembly according to any preceding claim wherein the cage device comprises a frame member configured to receive and mount the drawbar and a bridging device, which is connected to the frame member, and which co-operates with the connector devices at each side to mount the opposing plates and the resilient block or blocks there between.
8. A drawbar mounting assembly substantially as hereinbefore described with reference to and as illustrated by figures 3 to 6 of the accompanying drawings.