GB2250964A

GB2250964A - Wheel lift mechanism for multiple axle vehicle

Info

Publication number: GB2250964A
Application number: GB9027995A
Authority: GB
Inventors: Brian Talbot
Original assignee: LUNAR CARAVANS Ltd
Current assignee: LUNAR CARAVANS Ltd
Priority date: 1990-12-22
Filing date: 1990-12-22
Publication date: 1992-06-24
Also published as: GB9027995D0

Abstract

To lift one set of wheels (42) of a twin axle vehicle, such as a caravan, to facilitate non-powered manoeuvering of the vehicle, one of the sets of wheels (44) is mounted to its axle (48) by way of pivotal wheel carrier (52) and a piston and cylinder arrangement (60, 62) acts between a fixed member (65) and said carrier (52) to pivot the latter and raise or lower the attached wheels (44). In one arrangement (as shown) the wheels (44) on the pivotal carrier (52) are lowered, thus raising the other set of wheels (42) and the vehicle undercarriage. In an alternative arrangement (not shown) the wheels on the pivotal carrier may themselves be raised, leaving the other set on the ground. <IMAGE>

Description

WHEEL LIFT MECHANISM FOR MULTIPLE AXLE VEHICLE This invention relates to a mechanism for lifting one set of wheels of a multiple axle vehicle, and is particularly but not exclusively applicable to twin-axle trailers, such as caravans.

Traditionally, caravans have had only a single, substantially centrally located axle, and many still do. However, with the increasing size of caravans in recent years, provision of twin axles, i.e. two adjacent sets of wheels, has become more common. This enhances the general stability of the van and in particular improves its load-holding ability under tow.

The latter factor is even more important now that the speed limit for caravans under tow in UK has been increased to 60 mph.

These advantages of twin-axle vehicles are to some extent offset by difficulties experienced in manoeuvering such vehicles for purposes of parking, bearing in mind that it is often desirable to park or store caravans in very restricted spaces.

The object of the present invention is to overcome this difficulty by providing a mechanism whereby the wheels of one axle can be lifted, or lowered, whenever required to permit ready manoeuvre of the vehicle on the wheels of the remaining axle.

Pursuant hereto, the invention provides, in accordance with a first aspect, a vehicle undercarriage support assembly comprising a first axle with a first wheel mounted thereon, a second axle with a second wheel mounted thereon by way of a wheel carrier which is pivotal relative to said second axle, and a fluid-actuable piston and cylinder arrangement mounted between the wheel carrier and a fixed member of the assembly, the piston being extensible and retractable to lift or lower (or vice versa) the second wheel by pivoting the carrier.

The first wheel may conveniently be mounted upon the first axle by way of a respective wheel carrier which is fixedly attached to said first axle. In some embodiments of the invention the fixed member may be mounted upon the first axle, or may be constituted by a portion of said fixed wheel carrier.

In preferred embodiments of the invention there are two wheels mounted upon each axle, each wheel has -its own wheel carrier, and a respective piston and cylinder arrangement is mounted at each side of the support assembly between the wheel carriers of the corresponding first and second wheels, so as to pivot the wheel carriers of the second wheels.

Preferably the or each piston and cylinder arrangement is double-acting so that a positively driven stroke of the piston pivots the or each second wheel carrier in each direction. In other words, the second wheels are both raised and lowered by positive actuation.

Preferably, the or each piston and cylinder arrangement is hydraulically actuable, and in cases where there are two or more such arrangements these are actuable by common hydraulic pressure means. In any event, the hydraulic pressure means advantageously comprises a single pump which is mounted upon the support assembly, or a vehicle body supported thereby and is manually operable.

There are two alternative ways in which such a support assembly may be operated, and these depend upon respective mounting arrangements of the piston and cylinder arrangement and the pivotal wheel carrier In one of the arrangements, the relative positions of these components are such that extension (or retraction) of the piston pivots the carrier so as to raise the relevant (second) wheel from its rest position, i.e. from alignment with the other (first wheel), so that only the latter remains in contact with the ground. Obviously, the wheel which has been raised can subsequently be lowered again by reversing the actuation of the cylinder, i.e. retracting (or extending) the piston.

In the other arrangement, the relative positions of these components are such that extension (or retraction) of the piston pivots the carrier so as to lower the relevant (second) wheel relative to the other (first) wheel. In effect, of course, this serves to raise the other (first) wheel from its rest position in alignment with the said (second) wheel, as well as raising the remainder of the support assembly and any vehicle supported thereby relative to the said (second) wheel. Again, the wheel and the rest of the assembly which have been raised are readily lowered again by reverse actuation of the cylinder.

Thus, according to a second aspect, the invention provides a vehicle having a chassis which includes two axles and respective wheels mounted thereon, characterised by a mechanism for lifting the wheel or wheels mounted on one of the axles out of contact with the underlying surface, said mechanism comprising wheel carrier means pivotally mounted on said one axle and carrying said liftable wheel or wheels, a piston and cylinder arrangement mounted between said wheel carrier means and a fixed member on the chassis, and means for supplying fluid to said arrangement to extend and/or retract said piston and thereby pivot the carrier means and lift the relevant wheel or wheels.

On the other hand, according to a third aspect, the invention provides a vehicle having a chassis which includes two axles and respective wheels mounted thereon, characterised by a mechanism for lifting the wheel or wheels mounted on one of the axles out of contact with the underlying surface, said mechanism comprising wheel carrier means pivotally mounted on the other of the axles and carrying the wheel or wheels which remain in contact with the ground, a piston and cylinder arrangement mounted between said wheel carrier means and a fixed member on the chassis, and means for supplying fluid to said arrangement to extend and/or retract said piston and thereby pivot the carrier means and lift the relevant wheel or wheels.

In either case the vehicle may be a twin axle caravan, which by virtue of the said mechanism can be temporarily converted into a single axle van for purposes of unhitched manoeuvre (which is thereby greatly facilitated). However, the invention is in no way limited thereto and could be applicable to any other form of vehicle. Indeed, it may be particularly usefully applied to towable trailers other than caravans.

The invention will be described further, by way of example, by reference to its specific application to a caravan and by reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of a twin axle caravan incorporating a first embodiment of the wheel lift mechanism of the invention; Fig. 2 is an enlarged schematic side view illustrating part of the lift mechanism at one side of the caravan chassis; Fig. 3 is an illustration of the pump, which constitutes the actuator for the mechanism; Fig. 4 is an enlarged schematic side view illustrating part of a second embodiment of wheel lift mechanism in rest position; and Fig. 5 is a similar view illustrating the mechanism in operative condition, with one wheel raised.

Referring firstly to Figs. 1 to 3, caravan 10 has front and rear pairs of wheels 12, 14, mounted on respective front and rear axles 16, 18, which are not visible in Fig. 1, but are part of the chassis supporting the vehicle body 11. As is conventional, the wheels of each pair are disposed at the opposing sides of the body 11. Only the right side wheels 12, 14 are shown in Figs. 1 and 2, but the other side corresponds. It will be noted that the front and rear wheels 12, 14 lie relatively close together, below a central region of the body 11, and that again is a conventional feature of twin axle caravans. A towing hitch 13 and hand brake 15 are provided at the front end of the van body 11.Compartments are provided in the side of the van body 11 for a battery 17 (a power source for internal electrical facilities) and for a pump 19 for operation of a wheel lift mechanism, which is now to be described. These compartments are accessed by raising a flap 21, which is closed flush to the bodywork to conceal the pump 19 and battery 17 when access is not required.

Referring to Fig. 2, the wheels 12, 14 are not mounted directly onto the front and rear axles 16, 18, but are connected thereto by respective carriers 20, 22. The rear carriers 22 (there is one at each side, for each wheel 14) are fixed to the rear axle 18. In this illustrated example each carrier 22 is in the form of a bracket 24 fixedly mounted on the axle 18 and a trailing arm 26 extending therefrom to the rear and carrying the wheel 14 at its free end. The front carriers 20 are of comparable form, each of these also consisting of a bracket 23 and a trailing arm 25, which carries the respective wheel 12. However, the crucial difference is that the brackets 23 are pivotally mounted on the front axle 16.

At each side of the van body 11, a respective hydraulic cylinder 30, with piston or ram 32 is mounted between the front and rear brackets 23, 24, the piston 32 in each case having its protruding end pivotally connected to the pivotal front bracket 23. Hydraulic fluid inlet/outlet ports 33, 34 are shown at respective ends of the cylinder 30 in Fig. 2.

The inlet/outlet ports 33, 34 of both cylinders 30 are connected, via hydraulic pipelines, which are not shown, to the pump 19, which is shown in more detail in Fig. 3. A switch over valve (not shown, but of conventional type) in the hydraulic pipeline, is actuable by a lever 39 on the pump housing 19 to allow hydraulic fluid to be pumped into port 33 of each cylinder so as to extend the pistons 32, thereby pivoting the front carriers 20 and causing the front wheels 12 to swing upwards. With the front wheels 12 thus raised, the condition of the aforesaid valve can be changed over, by said lever 39, so as to permit hydraulic fluid to be pumped into port 34 of each cylinder so as to retract the pistons 32, pivot the carriers 20 in the opposite direction and lower the front wheels 12 again.Pumping is effected manually by inserting a handle in aperture 36 of pump 19 and moving this up and down like a lever.

With the pump 19 mounted in the illustrated side compartment, the operator can watch the wheels 12 at that side as they are raised and lowered.

In a preferred practical example, the hydraulic cylinders 30 employed are capable of producing a force of 2500 psi and are tested to 4.3 tons each, making it possible to lift a maximum total of 8.6 tons with the two cylinders used. As the wheels 12 and their associated carriers 20 should not present a load approaching anything like this, there is clearly a considerable margin of safety and reliable operation is virtually assured. The cylinders 30 employed have a diameter of 57.75mm and their pistons 32 are capable of extension to 69cm, the latter also being far in excess of the extension likely to be required in any practical situation.

In use, the wheel lift mechanism just outlined should be operated only when the caravan 10 is on level ground, and the procedure to be followed by a user should be as follows: Firstly, the caravan 10 should be detached from any towing vehicle and the handbrake 17 applied. With the flap 21 raised, the handle 30 of the pump 19 can be placed in the "lift" position, which is vertical (see Fig. 3). A jack handle (not shown) can then be inserted into aperture 36 and moved up and down. As mentioned above, this leads to supply of fluid to the cylinders 30 via ports 33, and extension of the pistons 32, and as a consequence the wheels 12 are gradually raised. Once these are clear of the surface pumping should be continued until it is no longer possible owing to reaction, indicative that further extension of the pistons 32 is not possible.The handbrake 17 can then be released again and the van 10 readily manoeuvered by pushing and pulling by one or two persons. A full turn through 360C can readily be achieved as the van 10 is supported only upon the single pair of rear wheels 14. Once the desired parking or storage position for the van 10 is reached, the procedure should be reversed, the handbrake 17 again being applied, and the pump handle 39 being returned to the horizontal "lower" position so that the switch over valve allows hydraulic flow in to port 34 and out of port 33. The pump 19 is then pumped again, but this time, of course, it serves to retract the pistons 32 and lower the wheels 12 back to the ground. Once the wheels 12 are firmly on the ground pumping is no longer possible. The jack handle can then be removed and the flap 21 lowered.

The foregoing is, of course, only intended as one exemplary embodiment of the invention, and is not limitative. Many variations are possible. It should be obvious that the specific details given in respect of the hydraulic cylinders and the pump may vary in other embodiments. More importantly, the pivotal carriers for the wheels which are liftable may be arranged in a different way so that extension of the pistons lowers the wheels and retraction raises them.

Although in the illustrated embodiment it is the wheels of the front axle which are capable of being lifted, in other embodiments it could be the rear axle wheels. Indeed, there might in some situations be a requirement to raise one set of wheels in a vehicle which has more than two axles/two sets of wheels, and that could also be accomplished in accordance with the invention.

Furthermore, in other embodiments, the piston and cylinder arrangement need not be mounted between respective wheel carriers (one fixed, one pivotal), although that is quite a favourable, compact arrangement. The only requirement is for the piston and cylinder arrangement to be mounted between the pivotal wheel carrier and any fixed member on the chassis or elsewhere.

Figs. 4 and 5 illustrate an alternative lifting arrangement, also within the scope of the invention, which can be employed in place of the arrangement shown in Fig. 2.

In this embodiment, front and rear wheels 42, 44 are again mounted onto front and rear axles 46, 48 by respective carriers 50, 52. However, in this case, in contradistinction to the previous embodiment, it is the front carrier 50 which is fixed to its axle 46, while the rear carrier 52 is pivotally mounted on its axle 48 and has the distal end of a hydraulic piston or ram 62 pivotally attached thereto.

In this respect, the front carrier 50 is in the form of a bracket 53 fixed to the axle 46 and a trailing arm 55 extending therefrom and carrying the front wheel 42. The rear carrier 52, in contrast, comprises two arms 54, 56, fixed to each other for pivoting relative to the rear axle 48, the trailing arm 56 carrying the rear wheel 44 and the other arm 54 being attached to the piston 62. An additional support bracket 57 for the vehicle is fixedly mounted on the axle 48, but that is not considered part of the wheel carrier 52.

The piston 62 is the operative, extensible element of a double-acting hydraulic cylinder 60, which is connected to a fixed cross-piece 65 of the undercarriage assembly or chassis, and which has hydraulic fluid inlet/outlet ports 63, 64, as shown.

A matching arrangement is, of course, provided at each side of a vehicle.

The pumping arrangement and procedure is exactly as previously described. Stating from the rest position shown in Fig. 4, the pump lever is put to the "lift" position and upon pumping fluid is supplied to the cylinder 60 via port 64 so as to extend the piston 62. This pivots the rear carrier 52 anticlockwise as seen in Fig. 4, and urges the rear wheel 44 downwards. However, as the wheels are on the ground, the effect is to raise front wheel 42 instead, along with its carrier 50 and the entire chassis/vehicle, as illustrated in Figs. 5.

To lower the vehicle/front wheel 42 again, the procedure is similar, but the operation is reversed once the hydraulic circuit switch has been changed over by putting the pump lever to the "lower" position. Fluid is then supplied via inlet port 63 to retract the piston 62, thus swinging back the rear carrier 52 and lowering the front wheel 42.

Variants and modifications of this arrangement, along the lines already mentioned in connection with the first embodiment, will readily be apparent to those skilled in the art.

As is clear, the invention is especially applicable to twinaxle caravans. It could, however, be equally well applied to other trailers or vehicles. The relevant wheel lift mechanism could also be retro-fitted to existing trailers or caravans, in cases where it is not installed at the time of manufacture.

Claims

1. A vehicle undercarriage support assembly comprising a first axle with a first wheel mounted thereon, a second axle with a second wheel mounted thereon by way of a wheel carrier which is pivotal relative to said second axle, and a fluid-actuable piston and cylinder arrangement mounted between the wheel carrier and a fixed member of the assembly, the piston being extensible and retractable to lift or lower (or vice versa) the second wheel by pivoting the carrier.

2. An undercarriage support assembly as claimed in Claim 1 wherein the first wheel is mounted upon the first axle by way of a respective wheel carrier which is fixedly attached to said first axle, and the fixed member, to which the piston and cylinder arrangement is attached, is constituted by said fixed wheel carrier.

3. An undercarriage support assembly as claimed in Claim 2 wherein there are two wheels mounted upon each axle, each by way of its own wheel carrier, and a respective piston and cylinder arrangement is mounted at each side of the support assembly between the wheel carriers of the corresponding first and second wheels, so as to pivot the wheel carriers of the second wheels.

4. An undercarriage support assembly as claimed in Claim 1, 2 or 3 wherein the or each piston and cylinder arrangement is double-acting so that a positively driven stroke of the piston pivots the wheel carrier or the or each second wheel carrier in each direction.

5. An undercarriage support assembly as claimed in Claim 3 wherein the piston and cylinder arrangements are hydraulically actuable by common hydraulic pressure means.

6. An undercarriage support assembly as claimed in any preceding claim where the piston and cylinder arrangement or arrangements is/are actuable by a single pump which is mounted upon the support assembly, or a vehicle body supported thereby, and which is manually operable.

7. An undercarriage support assembly as claimed in Claim 1 wherein the mounting arrangement of the piston and cylinder arrangement and the pivotal wheel carrier is such that extension (or retraction) of the piston pivots the carrier so as to raise the wheel attached to that carrier from its rest position, i.e. from alignment with the other wheel, so that only the latter remains in contact with the ground.

8. An undercarriage support assembly as claimed in Claim 1 wherein the mounting arrangement of the piston and cylinder arrangement and the pivotal wheel carrier is such that extension (or retraction) of the piston pivots the carrier so as to lower the wheel attached to that carrier relative to the other wheel, thereby effectively raising said other wheel, as well as raising the remainder of the support assembly and any vehicle supported thereby, relative to the wheel attached to said carrier, so that only the latter remains in contact with the ground.

9. A vehicle having a chassis which includes two axles and respective wheels mounted thereon, characterised by a mechanism for lifting the wheel or wheels mounted on one of the axles out of contact with the underlying surface, said mechanism comprising wheel carrier means pivotally mounted on said one axle and carrying said liftable wheel or wheels, a piston and cylinder arrangement mounted between said wheel carrier means and a fixed member on the chassis, and means for supplying fluid to said arrangement to extend and/or retract said piston and thereby pivot the carrier means and lift the wheel or wheels attached thereto.

10. A vehicle having a chassis which includes two axles and respective wheels mounted thereon, characterised by a mechanism for lifting the wheel or wheels mounted on one of the axles out of contact with the underlying surface, said mechanism comprising wheel carrier means pivotally mounted on the other of the axles and carrying the wheel or wheels which remain in contact with the ground, a piston and cylinder arrangement mounted between said wheel carrier means and a fixed member on the chassis, and means for supplying fluid to said arrangement to extend and/or retract said piston and thereby pivot the carrier means and lift the other wheel or wheels.

11. A vehicle undercarriage support assembly substantially as hereinbefore described with reference to and as illustrated by Fig. 2 or Figs. 4 and 5 of the accompanying drawings.

12. A vehicle having a chassis which includes two axles, respective wheels mounted thereon, and a mechanism, as claimed in any of Claims 1 to 8, for lifting the wheel or wheels mounted on one of the axles out of contact with the ground.