GB2214142A - Adjustable height air suspension - Google Patents

Abstract

A pneumatically operable height control system for adjusting the height of a vehicle. The air springs of a vehicle are controlled by use of a height control actuator (2) which comprises a pivoting arm (3) whose rotational position operates a valve in the actuator to control air to the air springs. The regulator is pivotally mounted on the vehicle frame (1) via arm (6) and an adjusting cylinder (8) is connected to the pivotting arm (6) to provide stepless adjustment of the required datum height position for various operational conditions. A pneumatic circuit including adjustable control valves (15,17,22,24) (fig 3 not shown) is used to adjust pressure to the cylinder (8) in a stepless manner. <IMAGE>

Description

Height control system for the frame height of a vehicle with air suspension.

This invention relates to a height control system for governing the height of the frame of a vehicle with air suspension by filling and emptying of the air springs, in which a height control actuator is mounted to the frame of the vehicle and cooperates with the lever which is connected to the axle of the vehicle and which rotates with changes of height between frame and axle and thus operates the moving part of a multiple passage valve in the height control actuator, cooperating with a normally stationary part thereof with ports or the like such that said valve in its zero position closes the air springs as to air supply or discharge and which at deviating position of said lever as a result of a change in height between frame and axle charges or discharges air from said air springs so that said height is maintained constant.

Such systems are known in practice. It is desirable to be able to adjust the height control system to particular situations, especially situations in which it is desired to adapt the height of the frame to the height of the loading or discharging platform, and situations in which for vehicles with more axles at least one axle is lifted, in which case often a greater height of the frame with respect to the road is desired to obtain more freedom between the lifted wheels and the road.

In this respect height control systems are known which have two zero positions of adjustment and in which relatively easily a switching from one zero position to the other is possible for on the one hand normal transport and for moving with one or more axles lifted. It is also known, for loading and discharging, to adjust the desired height of the frame by manual operation while switching off the automatic height control. Said frame height will then change during loading or discharging by a changing load of the air springs. It is known to avoid this by emptying the air springs when loading and discharging the vehicle, but this does not allow free adjustment of the height of loading and discharging.

In electronically operating height control systems a much more sophisticated adjusting and control pattern is possible. The disadvantage of electronic systems is, however, that there should be a source for electrical energy, which is not always the case, in particular with trailer vehicles but the invention is directed to obtaining a situation allowing also trailer vehicles even in the condition in which they are disengaged from a tractor or pulling vehicle to control the height by energy from a reservoir for air under pressure, which is already present for the air springs, without supply of electric energy.

In view thereof the invention aims at providing a pneumatically operating height control system as given above, which allows an easy and simple adjustment of the frame height with respect to the axles and maintaining said height equal to operate optimally for normal transport and, if desired, for transport with one or more lifted axles or in other situations as to be given below and to allow an easy adjustment of the frame for loading and discharging of the vehicle to adapt the height of the load carrying surface to a stationary loading platform or the like so that said height is maintained constant notwithstanding changing load of the vehicle.

To this end a system as given in the preamble is according to the invention characterized in that said normally stationary part of said height control actuator such as the external casing thereof is mounted for stepless pivoting to the frame for changing said zero position of said actuator, and that the control system connected to said normally stationary part to adjust said zero position for the frame height during moving and for loading and discharging in a stepless manner at a value, kept constant by the height control after adjustment, is constituted by a pneumatic system, with means to adjust the value of the gas pressure for the choice of said zero position, which gas pressure acts against a spring in the control member, coupled directly with said movable and normally stationary part of said height control actuator for movement thereof, in order to provide a determined position of equilibrium to the moving part of said control member at each adjusted gas pressure.

It is thus possible in all situations occurring in practice to keep the height of the frame constant in a reliable way after a simple adjustment of the desired height. For loading and discharging the height control actuator does not have to be switched off, which is important for simplicity and safety. As said height control actuator is mounted onto said frame supported by the air springs, the adjusted positions of the normally stationary part thereof are always positions of equilibrium between gas pressure and spring, not disturbed by vibrations in the axle(s) of the vehicle, because the concerning normally stationary part is connected to the spring supported part of the vehicle.

As this control system now governs the control in all conditions by such a lever, the region in which the point of zero position is adjusted can easily be chosen so that the air springs and shock absorbers are never extremely loaded, as said lever always interrupts the air supply to the air valves before the maximum deflection thereof and/or of the shock absorbers in which the stroke would be limited mechanically, is reached. Safety stop valves or mechanical stroke limiting means such as catch tables reaching a tight position are thus not necessary.

The end of the lever of the height control actuator, which is connected to the axle, should be able to have a large stroke in total in order to be able not only to take up the normal spring movements of the vehicle, but also to cover a wide range of adjustment such as for normal transport, axle lift situations and loading and discharging so that said lever has to be relatively long. As the normally stationary part of the height control actuator is pivotable such a wide range can thereby easily be covered with small displacements, exactly in view of the necessary considerable length of the lever, much easier than if this should for instance have to be covered by a vertical sliding movement of the actuator for this entire range.It is thus also always easily possible to apply height control actuators normally available in the trade, even if these themselves have no or only a very limited adjustment possibility of the zero position, if desired after a slight change such as by providing pivoting trunnions or a trunnion to give rotation to the casing thereof. It is thus easily possible to give the height control actuator a change of adjustment of zero position by said pivoting in a particularly simple way such that the height control can steplessly adjust the frame height and keep it constant for different conditions as mentioned.

The system allows easily to adjust for instance a height much higher than the normal transport height, for instance for strong c-urvatures in the road surface such as when boarding or disembarking from ferries and at railroad crossings, in particular for deeploading vehicles, or much lower than the normal transport height, for instance in zones of locally limited height of thoroughfare, or for kneeling buses and the like to be lowered in stationary position or at low speed, or for keeping the vehicle in horizontal position in longitudinal or transverse direction, for instance for vehicles with a tilting or extendable part.

The system, which is remotely controllable, may thus operate by manual operation, but may also have automatically controlled functions, for instance control by a speed signal, a sensor for height or thoroughfare, horizontal levelling, etcetera.

Preferably the invention is embodied as given in the enclosed claim 2. This allows adapting of each control circuit very well to the specific requirements which have to be made thereto as to the range of adjustment and the number of positions to be adjusted, a larger or a smaller number, stepless or not.

For loading and discharging the system is preferably embodied as given in the enclosed claim 3, which will be described in more detail with reference to the enclosed drawings.

The invention will now be explained in more detail with reference to said drawings. Therein: Figure 1 is a diagrammatic side view of a height control system with pivotable connection of the actuator thereof to the frame of a vehicle; Figure 2 is the same diagrammatic view as in Figure 1 with the actuator shown in full lines in a position pivoted upwardly and in dot and dashlines in a position pivoted downwardly, with the average normal axle height shown therein; Figure 3 is a diagrammatic view of the pneumatic system for operating said pivotable mounting of the actuator.

Of the frame of the vehicle only a small part of a longitudinal frame beam 1 is shown and this has a height control actuator 2. Such height control actuators are known as such and usual. Such actuators have a lever 3, connected pivotally at its free end to a vertical link 4 which is adapted to transmit forces pivotally both upwardly and downwardly and which at its lower end is connected to an axle 5 of the vehicle. The lever 3 has a central (zero) position in which it keeps an air valve in actuator 2 in closed position. If frame 1 is in a lower position with respect to axle 5, lever 3 will for instance be in position 3', will thereby open said air valve and thus causes air to flow to the air springs of the vehicle to bring the vertical distance between frame 1 and axle 5 back to the originally adjusted value.If the frame 1 is higher with respect to axle 5, lever 3 will for instance be in position 3" and thereby said air valve will discharge air from the air springs. Thereby this system tends to keeping the height of the frame at the same level with respect to this axle of the vehicle. As usual, the actuator has the necessary pneumatic inertia by a small passage of said air valve therein to correct only deviations in height which are of somewhat longer duration and in order not to react more than negligeably on the normal spring behaviour and inclinations of the vehicle in curves, etcetera.

Ducts and connections of this actuator are not shown in Figures 1 and 2 but these will become clear from the description of Figure 3.

Such a height control actuator 2 known as such is according to the invention itself pivotably connected to the frame by pivoting in the plane of pivoting of lever 3. To this end the casing of actuator 2 is rigidly connected to a pivoting arm 6, which is connected at 7 pivotably about a horizontal transverse axis to the frame. An adjusting cylinder 8 is connected rigidly to the frame and the piston rod 9 thereof engages pivotably pivoting arm 6. Of course such a pivoting of the actuator can also be obtained by other means such as a rotating cylinder, connected to the casing 2 thereof, or by a pinion on said actuator cooperating with a toothed rack rotating this pinion and itself operated by a cylinder like 8 in adapted position.The cylinder 8 is an air cylinder, in which a piston or the like is charged by air under pressure against the action of a spring therein as shown in Figure 3.

In Figure 2 the result of such a pivoting of the actuator casing is shown. If axle 5 has to be in a high position with respect to the frame (position 5'), casing 2 is lifted to the position shown in full lines by cylinder 8. If the axle has to have a low position with respect to the frame (position 5") the casing 2 of the actuator is pivoted to the position shown in dot and dash lines.

Figure 3 is a diagrammatic drawing also in this sense that parts are turned into the plane of the drawing which may be perpendicular thereto in reality. This is also true for the position of the actuatcr 2 and cylinder 8 and their mutual positions, which should be as shown in Figures 1 and 2.

Cylinder 8 is steplessly adjustable under the influence of air pressure, supplied thereto by the pneumatic system shown therein, in which equilibrium is reached by said spring against the air pressure. This system has a supply 10 which may comprise a compressor, driven by the engine of the vehicle or of a tractor thereof, with an air pressure accumulator vessel as usual, which may be mounted on a trailer and may operate the system even when there is no connected tractor with compressor. Said supply is connected to height actuator 2 by duct 11 for exerting the described function of supplying the air spring bellows or the like with air or for discharging air therefrom, as usual. A duct 12 from said supply has four connections in parallel within a casing 13, indicated by dotted lines.

A connecting duct 14 leads to a pressure reducing adjusting valve 15 serving to adjust the height of the frame for transport with lifted axle(s) or other comparable situations.

A connecting duct 16 leads to a pressure reducing valve 17, adjustable for adjusting a normal height of movement of the vehicle.

A connecting duct 21 leads to the control valve 22 with fine control (stepless or in many steps) for adjusting the height of the frame during loading and unloading in order to reach the desired height of the load carrying surface of the vehicle and to maintain this during loading and discharging. Control valve 22 can be adjusted by hand at this valve itself or, if desired, at a distance, for instance from the driver's cabin.

A connecting duct 23 leads to a valve 24 suited for manual operation and present behind a door or pivotable hatch or the like 25 of casing 13.

Reducing valve 15 leads through duct 18 to a valve 19 and reducing valve 17 leads through duct 20 to this same valve, which is operated by control duct 28. In the position shown duct 20 is in connection with duct 29 behind it through valve 19, so that the adjustment of the normal moving height of the vehicle in reducing valve 17 can be transmitted to duct 32 and thus to cylinder 8 in the corresponding position of valve 31. If it is desired to drive with one or more axles lifted or in one or more other comparable situations as described, a corresponding signal, normally an air pressure signal from the axle lift system, is transmitted to duct 28, so that valve 19 moves to the position in which duct 18 becomes connected to duct 29, so that the adjustment of the driving height of the frame with lifted axle or axles in the reducing valve 15 can be transmitted to cylinder 8.

The valve 22 for fine adjustment is adjusted at the desired height of the load carrying floor of the vehicle for loading and discharging. The resulting signal can as such not have an influence on the height control as valve 31 normally closes the exiting duct 30 of valve 22. If, however, the vehicle is stationary and has to be loaded or discharged, door or hatch 25 of box 13 can be opened and valve 24 can then be placed in its lowest position (as seen in the drawing) by hand, in which position air pressure from connection 23 is transmitted to duct 27 through 24, which duct 27 then operates as a control duct to bring valve 31 into its highest position as shown. It is now possible by operating valve 22 to adjust the height of the load carrying surface of the vehicle by hand very finely in a stepless manner or in small steps and the height of the frame thus adjusted is maintained as long as valve 24 is in the described position. If valve 24 is moved back to the closing position, duct 27 is relieved of pressure, so that valve 31 returns to the lowest position in which duct 30 is closed and duct 29 is in connection with duct 32, so that the height control again depends on the adjustment of either pressure reducing valve 17 or pressure reducing valve 15.

It is preferable to position the door or hatch 25 so that it can only be closed if valve 24 is in the closed position or so that it itself will close valve 24 when moving to its closed position, which will be clear from Figure 3. Moreover it is preferable to provide the door or hatch 25 in such a zone that the open position thereof is conspicuous, for instance clearly visible from the driver's seat.

In duct 27 there may be a signalling device 26 for giving a visible or audible signal at this point and/or at a distance therefrom, for instance on the dashboard in the driver's cabin. Door or hatch 25 may itself also be provided with such a signaling device.

In this way it can easily be checked whether the system is in the position for moving the vehicle or not.

It is well possible to apply the invention in such a way that there are two height control actuators on one axle, one at each side and both fed with the same adjusting signal. For height control actuators on different axles it is often possible to give them a same adjustment and to change the adjustment simultaneously for them while using a single operating system for this adjustment as shown in Figure 3.

Claims (4)

1. A height control system for governing the height of the frame of a vehicle with air suspension by filling and emptying of the air springs, in which a height control actuator is mounted to the frame of the vehicle and cooperates with the lever which is connected to the axle of the vehicle and which rotates with changes of height between frame and axle and thus operates the moving part of a multiple passage valve in the height control actuator, cooperating with a normally stationary part thereof with ports or the like such that said valve in its zero position closes the air springs as to air supply or discharge and which at deviating position of said lever as a result of a change in height between frame and axle charges or discharges air from said air springs so that said height is maintained constant, characterized in that said normally stationary part of said height control actuator such as the external casing thereof is mounted for stepless pivoting to the frame for changing said zero position of said actuator, and that the control system connected to said normally stationary part to adjust said zero posi tion for the frame height during moving and for loading and discharging in a stepless manner at a value, kept constant by the height control after adjustment, is constituted by a pneumatic system, with means to adjust the value of the gas pressure for the choice of said zero position, which gas pressure acts against a spring in the control member5 coupled directly with said movable and normally stationary part of said height control actuator for movement thereof, in order to provide a determined position of equilibrium to the moving part of said control member at each adjusted gas pressure.

2. A system according to claim 1 in which said control system includes control circuits in parallel for a number of different types of height adjustments such as for normal driving height, for driving with one or more lifted axles and for height adjustment of the load carrying surface for loading and discharging, at least one of which being adjustable in the range of heights in stepless manner or in a considerable number of small steps, there being one or more multiple passage valves connecting at will only one of said control circuits to said operating member.

3. A system according to claim 2 in which said pneumatic system is taken up in a box, a door or hatch of which is pivotable and, when opened, gives access to a hand operated valve, which in one position allows adjustment of the height of the load surface of the vehicle and the maintaining thereof at a constant value during loading and discharging by pneumatic operation of one of said multiple passage valves so that the adjustment of the height of the frame by said operating member is closed, in which said door or hatch in closed condition cooperates with said hand-operated switch in such a manner that the closed position of the door or hatch can only be taken up when said valve is in the position in which the height adjustment circuit for loading and discharging is closed with respect to said operating member.

4. A height control system for governing the height of the frame of a vehicle with air suspension substantially as hereinbefore described with reference to the accompanying drawings.