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Stabilisation System for Road Vehicles
This invention relates to stabilisation of road vehicles and is concerned particularly with a load compensation means designed to prevent or resist roll-over accidents involving commercial vehicles. Nevertheless the basic principles underlying the invention are applicable to road vehicles generally.
There has been a greater tendency in recent years to provide vehicles with softer suspension since this has the advantage of safeguarding the load better and giving a smoother ride to passengers . Softer
suspension however, carries with it the disadvantage that it tends to cause the vehicle to pivot or roll to a greater extent on corners and in extreme cases this can cause the vehicle to roll over completel3> * or, in the case of articulated vehicles, can be a contributory factor in jack-knifing accidents, even on dry surfaces. There is a further difficulty which is peculiar to articulated vehicles that, unlike rigid vehicles, the driver does not sense any instability of the trailer until it is often too late.
The present invention provides a simple system which effectively assists the suspension of the vehicle during or just before the vehicle begins to execute a turning of pivoting movement, but normally has no effect upon the vehicles normal suspension during normal
travelling motion in a straight line. Thus, by virtue of the present invention it is possible to gain the advantages of softer suspension while minimising its disadvantages.
According to one form of the present invention there is provided a road vehicle having a stabilisation system comprising at least one load compensator which is located so as to be capable of assisting the
vehicle suspension said device being connected to a source of pneumatic or hydraulic pressure fluid via valve means and normally being in an inoperative
condition, and means for actuating said valve means to cause pneumatic or hydraulic pressure to be applied to the device whereby said device assists the vehicle suspension and reduces its tendency to roll during motion,

The stabilisation system of the present
invention can be readily fitted to existing vehicles with minor constructional modification. In operation the load compensator devices do alter the rate of the
springs of the suspension but assist the suspension by taking some of the load imparted to the springs.
Normally the valve means is operated automatically by a signal received from sensing means
capable of detecting rolling or turning movement or

OMPI WIPO uneven or excessive loading of the vehicle, it is,
however, possible and sometimes desirable to provide a
manually operated valve, either in addition to or instead of an automically controlled valve to operate the load
Although it is theoretically possible to
provide a single load compensator which exerts some
stabilisation effect on the vehicle, most practical
constructions will involve at least two load compensators, each being located on opposite sides of the centre-line of the vehicle. In the case of a single compensator,
this can be mounted transversely of the vehicle and be
provided with oppositely extending levers to exert a
stabilising force on each side of the centre-line of the vehicle.
The compensator devices are conveniently
located adjacent to at least one axle of the vehicle,
normally at opposite ends of the axle, one relatively
movable element of the device being connected to the
chassis and the other to the axle. In the case of tandem axles, one device may be mounted adjacent to one end of the pair of axles and be provided with two operating arms carried by a single body part, the free ends of the arms being connected to respective axles.
In the case of the articulated vehicle the
compensator devices may be fitted only to the axles of the trailer but for optimum stability of the vehicle, the devices are preferably also

/,- W"WIJ-PfOU ,- fitted to the axles of the tractor.
It has been found to be advantageous in the case of articulated vehicles fitted with semi-trailers to fit devices which resist tilting
movement of the fifth wheel during turning of the vehicle. A compensator device may be mounted by one of its elements, preferably the body part, on the rear axle of the tractor, while the other element is
connected to or bears on the underside of the trailing portion of the fifth wheel plate. When an articulated vehicle executes a turn while on an inclined surface, there is a tendency for the fifth wheel to pivot on its trunnions. This can cause instability in the vehicle and if the trailer has a high centre of gravity and the conditions are in other respects unfavourable, the vehicle can topple over. By providing a compensator device which is operated automatically from the vehicle' steering mechanism or manually by the driver so that the fifth wheel plate is maintained in a horizontal position during turning, the above-mentioned danger is reduced.
Preferably the -compensator device
takes the form of a plurality of plates, at least some of which have friction surfaces, one or more of the plates being connected to the body part of the device and the other plate or plates being connected to the

" IP other relatively movable element. In operation, means are provided for compressing the plates together to thereby provide a resistance to relative movement of the body part and movable element and hence the relative movement of the axle and chassis . The compression of the stack of plates is conveniently achieved by means of a piston operated by pneumatic or hydraulic fluid. Since most heavy commercial vehicles utilise compressed air for operating the brakes, it would generally be most convenient to utilise air pressure for operating the stack of plates which comprise the braking means.
The compensator devices may be actuated by a turning movement of the vehicle or by means which
detects turning movement of the vehicle. The latter may consist of a device such as a mercury switch which is sensitive to turning movement and which is arranged to trigger a signal to an electromagnetic valve, the valve causing the compensator devices to be actuated. In the case where turning movement of the vehicle actuates the compensator devices , a linkage may be provided from the steering of the vehicle or the pivoting point in the case of an articulated vehicle which senses turning movement of the vehicle and causes the devices
to be actuated as soon as significant turning movement of the vehicle occurs.

OMPI The invention also includes a stabilisation system comprising a plurality of load compensator
devices connected by an hydraulic or pneumatic circuit to a valve, the valve being actuatable by means adapted to sense turning or pivoting movement of the vehicle.
Several embodiments constructed in accordance with the invention will now be described with reference to the accompanying drawings.
In the accompanying drawings :- Figure 1 is a schemetic representation of a stabilisation system suitable for an articulated vehicle;
Figure 2 is a sectional view of one load
compensator" device;
Figure 3 is a plan view of the device of Figure 2;
Figure 4 is a view showing one means of
connecting a pair of compensator devices between the chassi and tandem axles of a vehicle;
Figure 5 is a view showing a single compensator device fitted with two operating arms and connected to tandem axles of a vehicle;
Figure 6 is an underneath plan view of a
rigid vehicle shoλving schematically compensator devices fitted to each axle;
Figure 7 is side elevation of the embodiment

OMPI IPO shown in Figure 6.
Figure 8 is a plan view of part of the tractor of an articulated vehicle showing a fifth wheel plate fitted with compensator -devices and;
Figure 9 is a side elevation of the embodiment shown in Figure 8.
Referring to the drawings, Figure 1 shows the lay-out of the stabilisation system as fitted to the trailer of an articulated vehicle. As shown in Figure 1, a compensator device 1 is itted to each end of the axles indicated schematically by lines A and B so that when in use the devices are capable of resisting relative
movement between the axles and the chassis- of the trailer. Each compensatordevice comprises a body part 2 and a radius arm 3 which is mounted on a shaft 13 (see Figure 2) which is rotatably mounted in body part 2.
Each body part 2 contains braking means which can be operated to resist pivoting movement of the arm 3. Operation of the braking means by compressed air supplied from control valve 5 and air lines 4. The valve 5 is supplied by conduits (not shown) with an air supply from the vehicle road wheel braking system. In vehicles with a conventional 3-line braking system, the control valve 5 is conveniently connected to the emergency line to provide compressed air to the braking means within body parts 2. Control valve 5 is actuated by a linkage 6 which is capable of reciprocating as shown by the double-ended arrow 7. Reciprocation of linkage 6 occurs on turning movement of modified king pin 8. This
reciprocal movement of linkage 6 is achieved by forming the king pin 8 with a notch adapted to receive the end of the linkage 6 remote from control valve 5. If king pin 8 rotates in one direction or the other, linkage rod 6 will be moved towards the control valve 5, while return of the king pin to its equilibrium position will allow the linkage to return to its original position. Such movement causes control valve 5 to open and admit
compressed air to the compensator devices 1, which in turn assists the suspension of the vehicle until the vehicle returns to a straight and steady course.
The construction of the individual load
compensator devices 1 is shown in more detail in Figures 2 and 3. Referring to these Figures, each device
comprises a casing 10 by which the body part of the device can be mounted to the chassis of the vehicle or to the axle assembly. Welded to the casing 10 is a foundation ring 11 onto which the body 2 of the device is mounted. Rotatably received within the body 2 is a splined shaft 13 which carries a gear 14. Gear 14
rotates together with shaft 13 by virtue of inter-

,- WIFO meshing of splines on shaft 13 with corresponding
internal splines on gear 14. Gear 14 is also provided with external splines which mesh with correspondingly shaped formations on the inside of some of the annular friction discs in a stack 15. Friction discs 15 consist of two series of discs. One series of discs are steel plates which mesh with gear 14 so as to be rotatable therewith and this series of discs is interleaved with a second series of discs which have a high friction surface and which are connected in the region of their periphery with housing 12 but are not connected with the gear 14. The connection with the housing 12 may be by way of splines or some other means which prevents the second series of discs rotating* ith the shaft 13- and gear 14 but enable the discs to move to a limited extent axially of the shaft 13. A cover plate 16 is provided to complete the housing and radius arm 3 is splined onto the end of shaft 13 so that arcuate movement of arm 3 in the direction of the arrows shown in Figure 3 is translated into rotational movement of shaft 13 and gear 14. Located within the space between cover plate 16 and the stack of discs 15 is an annular piston 18 which can be
caused to compress the stack of discs 15 between the piston and the housing 12 on admission of compressed air to spa.ce 17 between the piston 18 and cover plate 16.
It will be appreciated that when this occurs the two series of discs are compressed together and this action has the effect of resisting the relative
rotational movement between the two series of discs and hence between the body part 2 of the compensator device and the radius arm 3. As soon as the compressed air in the air lines 4 is vented to atmosphere, on the return of the vehicle to a straight and steady course, the two series of discs 15 are no longer compressed and the radius arm 3 is free to move with respect to the body part 2 and, accordingly, the suspension of the vehicle ceases to be influenced by the devices 1.
The internal construction of the devices 1 may be similar to that of the anti-jack-knife device described in British patent 1,075,802 and U.S. Patent 3328051 (issued 27th June, 1966 to Hope and Lambert), the disclosure of which is incorporated herein. The construction shown in Figures 8 and 9 of the above U.S. Patent is preferrred.
Alternative methods of mounting the
compensator devices and connecting them between the chassis and axles of a vehicle are shown in Figures 4 and 5, although

/,, IPO it will be appreciated that other arrangements are possible. Figure 4 shows a part of a vehicle chassis 21 having tandem axles 22 and 23, each axle being linked to an associated compensator device 24 and 25. As can be seen, the body parts of the devices 24 and

25 are attached to the chassis 21 and each device has a radius arm 26 or 27 which is connected to the respective axles by a link rod 28 or 29. The ends of the link rods 28 and 29 are secured to U-bolts 30 and 31 which secure the axles 22 and 23 to leaf springs 32 and 33.
Compensator devices are mounted in a similar fashion on the opposite side of the chassis and are linked to the axles on that side of the vehicle. Normally all four compensator devices associated with a pair of tandem axles are connected to the same pneumatic or hydraulic operating means so that all four devices are actuated simultaneously .
An alternative arrangement for assisting the suspension of a vehicle having tandem axles is shown in Figure 5. In this arrangement, a mounting bracket 41 is located between axles 42 and 43 and is bolted to the chassis 44 so as to depend therefrom. A compensator device 45 is secured to the bracket 41 by its body part and has a radius arm 46 which extends towards axle 42. Axle 42 is connected to chassis 44 via an air spring 47 and a spring mounting bracket 48. Radius arm 46 is connected to bracket 48 by means of link rod 49. thus in operation a force which resists pivoting of radius arm 46 in the directions of the double-ended arrow 50 will apply a force to bracket 48 which resists deflection of the air spring 47. A
corresponding radius arm 51 extends towards the axle 43 and is connected to mounting bracket 52 of air spring 53 by means of link rod 54. Radius arm 51 may be carried on a shaft which is rotatably mounted in the body part of a compensator device attached to the opposite side of bracket 48, this compensator device being separate from device 45. It will usually be more convenient, however, to employ a single casing for housing the braking means which control both radius arms 46 and 51. This may be achieved by securing one radius arm to a rod and the other radius arm to a tube which is concentric with the rod, both rod and arm being housed partly or wholly within the body part 45. Annular braking discs similar
to discs 15 in Figure 2 are contained within the body part 45 so as to encircle the rod and tube. One or more discs are secured so as to be rotatable with each of the rod and tube, while at least one disc is secured against rotation with either the rod or the tube. On operation of an annular piston similar to piston 18 in Figure 2, the discs are compressed and rotation of the tube and rod are both resisted.

OMPI The stabilisation system of the present invention can be fitted to both rigid and articulated vehicles. Figure 6 and 7 show diagrammatically an embodiment of the system fitted to a passenger coach, rigid truck or similar high sided vehicle. As can be seem from Figures 6 and 7 compensator devices 61, 62, 63 and 64 are fitted to the end of each axle 65 and 66. The body parts of the compensator devices are attached to the longitudinal members 67 and 68 of the vehicle's chassis. The construction of the compensator devices is as described above and illustrated in Figures 2 and 3 and each device has a radius arm which is connected by a link rod 69, 70, -71 or 72 to one end of an axle 65 or 66. Braking means within each device is operated by compressed air supplied from compressed air reservoir 73 and controlled by valve 74. Valve 74 is actuated to admit air to airlines connected to the braking means by an operating lever 75, which is attached at one end to a track rod 76 of the vehicle's steering mechanism.
Figures 8 and 9 illustrate an embodiment in which compensator devices are fitted to the fifth wheel plate 89 of the tractor of an articulated semi-trailer vehicle. This arrangement assists the suspension of the vehicle when executing turns and enables the driver to sense by the behaviour of the vehicle a change in its stability. Fifth wheel plate 89 is mounted in
conventional manner on trunnion bearings 90 on the rear part 91 of the chassis of the tractor. A pair of
compensatordevices 92 and 93 are located at opposite sides of the plate 89 and mounted by their body parts 94 and 95 on brackets 96 and 97 which are clamped to the rear axle 98 by U-bolts . The construction of the compensator devices is substantially as illustrated in Figures 2 and 3 and each compensatordevice includes a radius arm 99 or 100 which is connected to one of the trailing tails 101 or 102 of the plate 89 by a link rod 103 or 104. The connection between the ends of the link rods and the fifth wheel plate "89 is by means of trunnion bearings 105 or 106. The braking means within each compensator device are supplied with compressed air or hydraulic fluid from the tractor's braking system and the supply of pressure fluid is controlled by a control valve (not shown) which is linked to the vehicle's steering
mechanism in a similar way to the control valve 74 in Figure 6. During movement of the vehicle in a straight line, the braking means within the devices 92 and 93 are not actuated so that the radius arms 99 and 100 are free to pivot and the plate 89 is also free to pivot about bearing 90 to accommodate undulations in the road surface. When the vehicle begins to turn a corner, the

OMPI W WIIFFOO braking means within the devices 92 and 93 are operated so as to resist pivoting of the fifth wheel plate 89.
This tends to stiffen the rear suspension of the tractor and transmits to the driver a feeling of solidity which is similar to that experienced when driving a rigid vehicle. The maintenance of the plate 89 in a horizontal position and the stiffening effect on the rear suspension also imparts a degree of stability to the vehicle which assists safe turning of corners, particularly on an incline and where the centre of gravity of the trailer is high. It will be appreciated that in an alternative form of this embodiment, the compensator devices may be mounted on the chassis of the tractor and a pair of radius arms extended to the fifth wheel plate and to the axle, the construction of the devices being similar to that shown in Figure 5.
In the foregoing description, the compensator devices are actuated by a valve which senses turning movement of the
Alternatively the compensator devices may be controlled by other detection means. For example, the compensator devices may be linked to a load-sensing circuit so that the devices are operated to assist the suspension when the load increases above a predetermined level. A sensing device may be provided which detects uneven loading and the compensator devices operated non-uniformly in order to compensate for the

OMPI uneven loading. As a further alternative, detection means may be provided which sense rolling movement of the vehicle and supply pressure fluid to the devices to compensate for this.
The stabilisation system may alternatively be actuated when the brakes are applied, thus preventing excessive load transfer onto the springs of the vehicle during hard braking.
Instead of modifying the king pin as shown in Figure 4 it is possible to provide an alternative sensing means for detecting pivoting movement of the trailer of an articulated vehicle fitted with a standard king pin. This may be achieved by providing sensing means on one of the mutually pivoting members comprising the fifth wheel and the trailer rubbing plate. Preferably the sensing means are located on the trailer rubbing plate and are arranged to sense the proximity of the trailing ends of the fifth wheel plate. For example, the sensing means may be located on the trailer rubbing plate in the spatial locations with respect to the fifth wheel plate 89 indicated in Figure 8 by reference numerals 110 and 111. The sensing means 110 and 111 may operate by physical contact with the portions 112 or 113 of the fifth wheel plate (for example, they may be hydraulic plungers) or they may be devices which -do not actually

OMPI require physical contact, such as electrical proximity switches.
The invention is not limited to the use of compensator devices which embody friction braking means and includes, for example, other methods of resisting transfer of load to the vehicle spring by, for example, providing an hydraulic cylinder in which a free flow of oil from one chamber to another is restricted by closing of a valve when it is desired to stiffen the suspension.
It is possible to fit the compensator devices to an articulated vehicle which is fitted with an anti-jack-knife device as described in the above-mentioned British and U.S. patents. In such a case, the king pin would be modified in a different manner from that shown in Figure 1 so that it controlled the air valve 5 and was also connected to the friction discs of the anti-jack-knife device.
While the invention has been described with particular reference to the use of positive fluid pressure to cause operation of the compensator devices, it is also possible to employ a vacuum actuation system wherein a negative fluid pressure causes actuation of the
compensator device, e.g. under influence of a spring, and the following claims should be construed accordingly.