GB2040847A

GB2040847A - Towbars for trailers

Info

Publication number: GB2040847A
Application number: GB8000523A
Authority: GB
Original assignee: RUBERY OWEN WREXHAM Ltd
Current assignee: RUBERY OWEN WREXHAM Ltd
Priority date: 1979-01-12
Filing date: 1980-01-08
Publication date: 1980-09-03
Also published as: GB2040847B

Abstract

A towbar adjustable to compensate for differences in height between its pivotal connections to a towing vehicle and trailer, has locking means separate from the pivotal connections whereby the towbar is locked in adjusted positions. Preferably the towbar comprises two parallel, vertically spaced, links (5,11) pivoted at their ends to mounting means (2,4) fixed to a hitch (1) and a member (3) which connects to or is part of, a trailer chassis. The locking means preferably acts between the links and comprises a rack (18) on one link (11) engaged by a mating rack (23) carried by a bolt (19) on the other link(S). The bolt passes through a slot in the first-mentioned link and is fitted with a nut (29) which when tightened causes the racks to be clamped together. Alternatively, the locking means may comprise plates on one link which straddle the other link and have a number of aligned holes. In adjusted positions of the links pairs of the holes align with a bore at the other link and a pin is inserted in the registering holes and bore to lock the links. There may be only one link in which case the locking means acts between the ends of the link and the mounting means. <IMAGE>

Description

SPECIFICATION Towbars This invention relates to towbars for trailers, particularly, though not exclusively, mobile plant equipment such as compressors, generators and other wheeled appliances which require to be towed by a towing vehicle.

Trailers may be towed by a variety of vehicles, this is very often the case with mobile plant equipment, and in consequence it is necessary to provide a towbar which is adjustable to compensate for any difference in height between a towing connection on the towing vehicle and the connection on the trailer.

The adjustable towbars currently in use comprise a hitch for connection to the towing vehicle and a connecting member which connects the hitch to the chassis of the trailer. The joints between hitch, connecting member and chassis comprise mating member each having a central hole and radially extending teeth. The teeth of one member engage in the recesses between adjacent teeth of the other member and they are held in clamped relationship by a through bolt and a nut which has a lever secured to it. Thus the nut can be tightened by hand without the need for a spanner, so facilitating the making of rapid and simple adjustments. It will be appreciated that use of this two bar requires two adjustments to be made, that is to say an adjustment at the hitch/connecting member joint and at the connecting member/chassis joint.The bolts provide pivots at each end of the connecting member only when the nuts are released to allow separation of the mating toothed members so that they may be rotated into a different angular relationship. Varying the angle which the connecting member makes with the hitch and the chassis varies their vertical separation whilst enabling the hitch and chassis to be maintained substantially parallel to one another.

This towbar is widely used but is expensive to make and suffers from the defect that in use the nuts work loose allowing play and even slip to develop at the joints. To counteract this defect users are known to adjust the towbar to a suitable setting for a particular towing vehicle/trailer combination and then weld it in this setting so that it is no longer adjustable for use with a different vehicle/trailer combination.

The present invention consists in a towbar comprising first and second members adapted for connection to a towing vehicle and a trailer respectively, first and second mounting means fast with the first and second members respectively, at least one link pivotally connected between the said mounting means and locking means separate from the pivoted connections for securing the link or links in a desired angular relationship relative to the members.

There may be separate locking means between each end of the or each link and the mounting means to which that end of the or each link is pivoted.

There may be more than one link. Thus two links may be pivotally connected between the mounting means in parallel vertically spaced relationship and the locking means may be arranged between the two links, or between either link and one of the mounting means.

In a preferred form the locking means comprises a rack component and a mating component of which one is fast with the link, or one of the links, and the other is fast with a support relative to which the link moves during pivotal movement relative to the mounting means. Clamping means releasably clamp the rack and mating components together in any one of a plurality of adjustable relative positions in order to secure the link, or links, in a desired angular relationship relative to the first and second members. This preferred form of locking means enables an appreciable number of possible angular positions to be provided in which the link, or links, may be secured relative to the first and second members.

Where there are two links the mating component may be on the other link. The mating component may also comprise a rack which is complementary to the rack component.

The locking means may take other forms. It may comprise apertured or socketted parts between which there is relative movement as the angular relationship of the link or links relative to the first and second members is adjusted. A peg or the like can be inserted into registerng apertures or sockets of said parts when the angular adjustment has been made so as to retain the link or links in the adjusted angular position. In another form the locking means may comprise a screwjackwhich serves to adjust the angular position of the or each link and to lock it in an adjusted position.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which, Figure 1 is a side view of a first embodiment of a towbar in accordance with the present invention, Figure 2 is an enlarged section along the central longitudinal axis of the towbar, Figure 3 is a plan view of one link of the towbar, Figure 4 is a section on line 4-4 of Figure 2, Figure 5 is a fragmentary section showing a modified form of locking means, Figure 6 is a fragmentary section showing a further modified form of locking means, Figure 7 is a side view of a second embodiment of a towbar, Figure 8 is a side view of a third embodiment, and Figures 9 and 10 are diagrammatic fragmentary side and end views respectively of a fourth embodiment.

Referring to Figures 1 to 4 of the drawings, the towbar includes a hitch 1 which constitutes a first member adapted for connection to a towing vehicle.

A pair of parallel laterally spaced depending plates 2 secured to the hitch 1, as by welding, constitutes first mounting means. A tube 3 adapted for connection to, or being part of, the chassis of a trailer constitutes a second member of the towbar. Two parallel laterally spaced plates 4 secured to the tube 3, as by weldng, constitute second mounting means.

An upper link 5 formed as a metal forging generally of inverted channel section has an integral transverse tubular portion 6 at each end whereby it is pivotally secured by a bolt 7 passed through the tubular portion and a nut, not shown, between the depending plates 2 at one end and the parallel plates 4 at the other end. Within the channel at the middle of the length of the link there is an integral bearing 8 having a through bore 9 which extends perpendicularly to and opens through the web of the channel section. A key-way 10 is formed along one side of the bore.

A lower link 11 is also formed as a metal forging generally of inverted channel section and has an integral transverse tubular portion 12 at each end whereby it is pivotally secured by a bolt 13 passed through the tubular portion and a nut, now shown, between the depending plates 2 and the parallel plates 4 spaced below and parallel to the upper link 5. The upper and lower links and the plates 2, to which they are pivoted constitute a parallelogram linkage. At the central portion of the lower link there is a slot 14 in the web of the channel which extends longitudinally of the link. The thickness of the web is increased locally within the channel section around the slot 14, as indicated at 15.In the undersurface of the thickened portion 15 a groove 16 is formed which extends longitudinally of the link, symmetrically relative to the slot, and is undercut so that opposed inwardly projecting flanges 7 are defined along opposite sides of the groove.

Afirst locking rack 18 is formed on the upper surface of the web of the channel section of the lower link 11, surrounding the slot 14, Figure 3.

A locking bolt 19 has a cylindrical upper portion 20 and a smaller diameter lower portion 21 which passes through the slot 14 and has a screw threaded end 22. A second locking rack 23 has teeth 24 which are similar to the teeth on the first locking rack 18.

The locking bolt 19 passes through a central hole 25 in the second locking rack 23 so that a shoulder 26 between the upper and lower portion 20 and 21 of the bolt engages a planar upper surface 27 of the rack and the two parts are secured together, as by welding. The upper portion 20 of the bolt is a sliding fit in the bore 9 of the bearing 8 of the upper link 5. A radial key 28 fixed in the upper portion 20 engages in the key-way 10 and prevents the locking bolt from rotating in the bore. A wing nut 29 is fitted to the threaded end 22 of the bolt 19. The nut fits into the groove 16, from either end, and has an annular groove 30 which is engaged by the flanges 17, as shown in Figure 4, such that the nut can rotate but cannot move axially along the axis of rotation. Thus rotation of the nut causes the locking bolt to move axially.When the wing nut 29 is slackened the bolt 19 is lifted so that the second locking rack 23 is clear of the first locking rack 18 and the links can be adjusted and set in the desired orientation relative to one another and to the mounting means in order to accommodate a difference in height between two vehicles to which the towbar is to be connected. The slot 14 in the lower link 10 enables this to be done by allowing the bolt to move bodily along the slot longitudinally of the link. When the links are set in the desired orientation the nut is tightened, thereby lowering the bolt so that the racks are re-engaged with one another, and clamped together, and hence the links are locked in that orientation.

The fact that the nut causes the bolt to be lifted and the second locking rack is lifted with it, reduces the problem of separating the racks if they should become corroded together after a prolonged period in a set position, or stuck together by paint or other matter.

In addition to preventing rotation of the locking bolt 19 the bore 9 in the upper link 5, the engagement of the key 28 at the upper portion of the locking bolt with the key-way 10 in the bore 9 ensures correct alignment of the second locking rack 23 with the first locking rack 18 when the second locking rack is secured, or integral with, the locking bolt. This facilitates adjustment of the towbar. However, the second locking rack 23 may be made free on the locking bolt 19 and still be clamped to the first locking rack 18 by way of the shoulder 26. In this case alternative provision, which may be manual, may be made for alignment of the racks during adjustment of the towbar.

In a modified form of locking means, as shown in Figure 5, first and second locking racks 18 and 23 are again provided but the groove 16 is omitted and the wing nut is replaced by a castle nut 31 having a lever 32 secured to it. Also the upper portion of the locking bolt 19 projects above the upper link 5, has a reduced diameter externally threaded end portion 33, and is fitted with a washer 34 which seats on a shoulder 35 between the upper portion proper and the end portion 33 and is retained by a nut 36 screwed on to the end portion. A strong compression spring 37 is fitted about the upper portion above the upper link and bears at one end on the web of the link and at the other end on the washer, thereby normally urging the bolt upwardly to separate the locking racks.As before the second locking rack is fixed to the bolt and the bolt is restrained from rotation in the bearing of the upper link. The bolt is drawn downwards against the spring action to engage and clamp the racks together, and so lock the links when they have been adjusted to a required orientation relative to one another and to the mounting means. The spring action reduces the likelihood of the locking racks becoming stuck together in an adjusted position.

In the further modification shown in Figure 6 ofthe drawings in which the locking bolt 19 is substantially similar to that in the embodiment as illustrated by Figures 1 to 4, a castle nut 38 having lever 39 is applied to the threaded end 22 of the lower portion 21 of the locking bolt. The castle nut is restrained from axial movement in similar manner to the wing nut 29. When the links have been set in a desired orientation and the castle nut has been tightened to clamp the racks together, the nut is locked by a pin 40 passed through the bolt and engaged with aligned recesses 41 of the nut. The pin 40 is attached to the nut by a flexible tie 42 to avoid its being mislaid when not engaged with the bolt.

Referring now to the embodiment illustrated by Figure 7 of the drawings, the upper and lower links, 5 and 11 respectively, are both formed from square or rectangular section tube. The upper link has squaresection bars 43, 43a welded across each end, their upper faces being co-planar with the upper surface of the tube. Each bar has a through bore 44 the axis of which is normal to the longitudinal axis of the tube. A plate 45 is fixed, as by welding to each side of the upper link 5 centrally along its length, and the plates receive the lower link 11 between them. The lower link is generally similar to the upper link except that it is inverted and the plates 45 are omitted, and it has an axially bored bar 46, similar to the bars 43, 43a fixed, as by welding, to the lower surface of the tube.Lower faces of square-section bars 47, 47a welded across the ends of the tube of the lower link, are co-planar with the lower surface of the tube. The bars 47, 47a again have through bores 48 the axes of which are normal to the longitudinal axis of the tube.

One end of each link 5,11 is entered between the plates 2 secured to the hitch 1 so that the bores 44, 48 of the bars 43, 47 are in register with aligned holes in the plates. Pins 49 are entered in the bores and holes to secure the links whilst allowing pivoting movement relative to the plates 2.

The bars 43a, 47a at the other ends of the links 5, 11 are similarly received between the plates 4 fixed to the tube 3 and are secured by pins 50 in a like manner.

A number of equispaced aligned holes 51 (five are shown) are provided in the plates 45 fixed to the upper link 5 and lie on the locus of the bore of the axially bored bar 46 fixed to the lower link. In use the links are set in a desired orientation in which a pair of the holes 51 are in alignment with the bore in the bar 46. A pin 52 is then inserted through the registering holes and locked.

In the embodiment shown in Figure 8, the towbar has a single link 53 of square or rectangular section tube pivoted at its ends between pairs of parallel plates 54 and 55 respectively secured to the hitch 1 and the tube 3. The link 53 has an upwardly extending lug 56 at each end having a bore normal to the axis of the link which aligns with holes 57 in the respective pairs of plates 54, 55. Pins 58 inserted and retained in the aligned holes and bores pivotally connect the link to the pairs of plates so that the inclination of the link relative to the hitch and tube can be adjusted. A depending lug 59 is also provided at each end of the link.Aligned holes 60 are formed in the pairs of plates 54,55 along the locus of the bore in the respective depending lug 59, whereby a pin 61 can be inserted in the bore and registering holes 60 to lock the adjustment of the link in the plates at each end.

Referring now to the embodiment illustrated by Figures 9 and 10, the towbar has upper and lower links 5, 11 and mounting means, not shown, generally similar to those of the embodiment illustrated by Figure 7. Opposed racks 62 are secured to the sides of the upper link centrally along the length of the link and depending to span the lower link 11. The lower link has a through hole 63 in its sides centrally thereof and is reinforced by a tube 64 which receives a locking bolt 65 for locking adjustment of the links.

The bolt 65 carries two further racks 66, respectively engaging the depending racks 62, and a castle nut 67 with a lever 68 clamps the racks in engagement to secure the links in any adjusted orientation. Relative movement between the bolt 65, the racks 66 it carries, and the depending racks 62 for adjustment of the orientation of the links, is accommodated by aligned arcuate slots 69 in the depending racks. A pin, not shown, passed through the bolt and engaged with aligned recesses of the castle nut 67 secures the nut against turning on the bolt when the racks have been clamped together.

The above-mentioned embodiments of the towbar provide constructions which are generally less expensive than those of the previously known towbars.

Whilst the single link embodiment illustrated by Figure 8 provides a particularly simple and cheap construction, the other embodiments having the pairs of links have the advantage that a single adjustment only is required to set the links at a desired orientation, and the adjustment is locked by locking bolts and nuts, or a pin, not normally subjected to forces tending to cause unlocking as in the previously known construction described at the beginning of this specification.

It will be appreciated that a towbar in accordance with the present invention may be incorporated as an integral part of a trailer.

Claims

1. Atowbarcomprising first and second members adapted for connection to a towing vehicle and a trailer respectively, first and second mounting means fast with the first and second members respectively, at least one link pivotally connected between the said mounting means and locking means separate from the pivotal connections for securing the link or links in a desired angular relationship relative to the members.

2. Atowbar according to claim 1 wherein a single link is pivotally connected between the mounting means and separate locking means is provided between each end of the link and the mounting means to which that end of the link is pivoted.

3. Atowbar according to claim 2 wherein the locking means between each end of the link and the mounting means to which the end is pivoted comprises a plurality of holes or sockets on one of either the end or the mounting means, a hole or socket on the other one of the end or the mounting means which registers with any one of the plurality of holes or sockets according to the angular position of the link relative to the members, and a pin or the like which is inserted in the registering holes or sockets to secure the link in that angular position.

4. Atowbar according to claim 1 wherein two links are pivotally connected between the mounting means in parallel vertically spaced relationship and the locking means is arranged between one ofthe links and one of the mounting means.

5. Atowbar according to claim 1 wherein.two links are pivotally connected between the mounting means in parallel vertically spaced relationship and the locking means is arranged between the two links.

6. A towbar according to any of claims 2,4 and 5 wherein the locking means comprises a rack component and a mating component of which one is fast with the link, or one of the links, and the other is fast with a support relative to which the link, or the said one link, moves during pivotal movement relative to the mounting means, and clamping means whereby the components can be releasably clamped together in any one of a plurality of adjustable relative positions to secure the link or links in a desired angular relationship relative to the members.

7. A towbar according to claim 6 as dependent from claim 4 wherein the support is one of the mounting means.

8. Atowbar according to claim 6 as dependent from claim 5 wherein the support is the other one of the links.

9. Atowbar according to any of claims 6 to 8 wherein the mating component comprises a rack which is complementary to the rack component.

10. A towbar according to any of claims 6 to 9 wherein the ciamping means comprises a bolt which extends between the components and acts on one of the components, and a nut which is engaged with the bolt and which when tightened on the bolt acts on the other component to urge the components together.

11. A towbar according to claim 10 wherein the bolt is fixed to the mating component.

12. A towbar according to claims 8,9 and 10 or claims 8,9 and 11, wherein the bolt extends through and between the links and one of the links has a slot through which the bolt passes and permits relative longitudinal movement between the links during adjustment of the angular relationship of the links relative to the members.

13. Atowbar according to claim 12 wherein the bolt is engaged in a complementary bore in the other link and key means is provided between the bolt and the link whereby the bolt is restrained from rotation in the bore but can move axially in the bore.

14. Atowbar according to Claim 13 as dependent from Claim 11 wherein the key means serves to locate the mating component in alignment with the rack component.

15. A towbar according to Claim 13 or Claim 14 wherein the link having the slot has means for retaining the nut, which means permits rotation of the nut but restrains the nut from movement relative to that link along the axis of rotation of the nut.

16. Atowbar according to claim 15 wherein the nut has an annular groove in its external surface co-axial with the axis of rotation of the nut, and the link having the slot has a groove in which the nut is engaged and which has opposed flanges which engage in the annular groove and retain the nut to the link.

17. Atowbar according to any of Claims 12 to 14 as dependent from claim 11 wherein a spring acts between the bolt and one of the links and normally urges the bolt in a direction which causes the mating component to be separated from the rack component.

18. A towbar according to any of claims 10 to 17 wherein the nut is a castle nut and a pin is releasably passed through the bolt and engaged with aligned recesses of the nut to secure the nut to the bolt against rotation when the rack and mating components are clamped together.

19. Atowbar according to any of claims 6 to 18 wherein the rack component is made integral with the, or one, link.

20. Atowbar according to claim 5 and any of claims 6 to 19 wherein each link is a metal forging substantially of channel-section.

21. A towbar according to claim 20 wherein each link has integral tubular portions at its ends in which pivot pins are engaged which pivotally connect the link to the mounting means.

22. Atowbar according to any of claims 1 to 19 wherein the or each link is of square or rectangular section tube.

23. A towbar according to claim 22 wherein each link has a bar fixed across each end of the tube having a through bore the axis of which is normal to the longitudinal axis of the tube, and which bore is engaged by a pivot pin whereby the end of the link is pivotally connected to the respective mounting means.

24. A towbar according to claim 5 wherein the locking means comprises a plurality of holes or sockets on one of the links at an intermediate part of the length of the link, a hole or socket on the other link which registers with any one of the plurality of holes or sockets according to the angular position of the links relative to the members, and a pin or the like which is inserted in the registering holes or sockets to secure the links in that angular position.

25. A towbar substantially as described herein with reference to and as illustrated by Figures 1 to 4 of the accompanying drawings.

26. Atowbarsubstantiallyasdescribed herein with reference to and as illustrated by Figures 1 to 4 as modified by Figure 5 of the accompanying drawings.

27. Atowbarsubstaniallyas described herein with reference to and as illustrated by Figures 1 to 4 as modified by Figure 6 of the accompanying drawings.

28. A towbar substantially as described herein with reference to and as illustrated by Figure 7 of the accompanying drawings.

29. A towbar substantially as described herein with reference to and as illustrated by Figure 8 of the accompanying drawings.

30. A towbar substantially as described herein with reference to and as illustrated by Figures 9 and 10 of the accompanying drawings.

31. A trailer including a towbar as claimed in any preceding claim.