Europaisches Patentamt European Patent Office

Office europeen des brevets (g) Publication number: 0 435 587 A2

12 EUROPEAN PATENT APPLICATION

@ Application number : 90314050.7 © Int CI.5 : B60G 5/00, B60G 11/27, B60G 17/052 (22) Date of filing : 20.12.90

(So) Priority : 23.12.89 GB 8929185 @ Inventor : Griffiths, Paul John 13 East Green, Sealand Manor, Sealand Deeside, Clwyd, CH5 2SG, Wales (GB) (43) Date of publication of application : 03.07.91 Bulletin 91/27 @ Representative : Spall, Christopher John et al BARKER, BRETTELL & DUNCAN 138 Hagley @ Designated Contracting States : Road BE DE DK ES FR IT NL Edgbaston Birmingham B16 9PW (GB)

(71) Applicant : RUBERY OWEN-ROCKWELL LIMITED P.O. Box 10, Booth Street, Darlaston Wednesbury West Midlands WS10 8JD (GB)

(3) Multi- air suspension system for a vehicle.

@ A multi-axle air suspension system for a tipping vehicle having towards its near a rear axle (7'") and at least one other axle (7", T) forward of the rear axle, provides selective over-riding of the normal load equalising system between the during tipping so as to alleviate hogging bending moments on the vehicle's chassis. A selectively operable pressure reducing (41) is in circuit with a pressure air source, air springs (7C, 8C) of the rear axle (7"') and with first and second (23, 32), selectively operated by a third valve (39), which are in circuit with the air springs (7C, 8C ; 7B, 8B ; 7A, 8A) of the rear axle (7"') and the other axle(s) (7", 7). Operation of the first and second valves (23, 32) isolates the air springs (7C, 8C) of at least the rear axles (7"') from those of the other axle or axles (7", 7') and connects the pressure reducing valve (41) to the latter air springs (7B, 8B ; 7A, 8A) so as to lower the air pressure in those air springs.

CM <

oo m

CO -a-

CL 111 Jouve, 18, rue Saint-Denis, 75001 PARIS FIG.3. 1 EP 0 435 587 A2 2

MULTI-AXLE AIR SUSPENSION SYSTEM FOR A VEHICLE

This invention relates to a multi-axle air suspen- The purpose of this invention is to provide for sion system for a vehicle. selective overriding of the normal equalisation system There has been in recent years a substantial of a multi-axle air suspension system for a vehicle so growth in the number of heavy goods vehicles which 5 that the leading axle or axles may be selectively are built with multi-axle air suspensions for the axles. loaded more lightly than the trailing axle whereby the This is because of the much improved ride character- adverse loading condition which has been described istics and equalisation of loads between axles which is alleviated. air suspension provides, as compared with mechani- The multi-axle air suspension system to which the cal suspensions. 10 present invention is applicable is for a vehicle having This change to air suspensions has brought to mounted towards the rear of the vehicle a rear axle light certain problems which had not previously been and at least one other axle forward of the rear axle, the apparent One such problem, aggravated by a trend system having for each of these axles a first air spring towards lightweight vehicle chassis construction in and a second air spring each adapted to be mounted order to increase useful payload, occurs on multi-axle 15 to act between a chassis of the vehicle and a respec- tipper lorries and trailers. In use the body rests on the tive end of the axle, first and second interconnecting vehicle chassis and its load is distributed along the means pneumatically interconnecting the first air chassis. When the body is tipped the load then springs and the second air springs respectively, and becomes supported between the lifting jack at the suspension levelling valve means pneumatically con- front and the pivot point of the body at the rear, which 20 nected between a source of pressure air and the first is behind the rear axle. What was formerly a distri- and second air springs and being adapted to be con- buted load along the length of the chassis then nected mechanically between an axle and the chassis becomes loading at each end of the chassis, giving of the vehicle for operation. Such a multi-axle air sus- rise to a hogging bending moment along the chassis. pension system is hereafter referred to as "a multi- Considering, for example, the case of a mechani- 25 axle suspension system of the type described". The cally suspended tri-axle trailer, when the body is tip- reference to an axle also includes a pair of aligned ped loading is transferred to the rear axle and reduced stub axles, for example as in an independent air sus- on the leading and centre axles. This is accentuated pension system, an example of which is described by the rearward movement of the centre of gravity of and illustrated in our British Patent No. 2 165 195. the load as the front of the body is raised. 30 According to one aspect of the present invention The equalisation system on a conventional multi- a multi-axle air suspension system of the type des- axle mechanical spring suspension is unable, due to cribed is provided which includes first and second frictional forces and geometrical limitations, to equal- valve means in pneumatic circuit with the first and ise the loading between the axles and the loading con- second air springs respectively of each of the axles, dition described during tipping can even result in the 35 pressure reducing valve means in pneumatic circuit of the leading axle lifting clear of the ground. with a source of pressure air and with the first and sec- The situation is different with an air suspension ond valve means, and third valve means to operate because the inter-connection of the air springs for the the first and second valve means, the arrangement axles on each side of the vehicle gives much more being such that operation of the first and second valve efficient equalisation of the load between the axles. 40 means causes the air springs of at least the rear axle The result of this is that the wheels of the front axle to be isolated from the air springs of the other axle or stay on the ground and, due to the load equalisation, axles forward of the rear axle and connects the press- an upward force is applied to the chassis by the air ure reducing valve means to the air springs of said springs of the suspensions of the front, middle and axle or axles forward of the rear axle whereby the air rear axles. These forces are applied to the chassis 45 pressure in the air springs of said axle or axles forward through the lever arms represented by the distances of the rear axle is controlled at a lower pressure than of the air springs of these axles forward of the pivot in the air springs of at least the rear axle. point. Thus, the combination of increased upward The multi-axle air suspension system may loading and the associated lever arms in respect of include a "dump system" to allow selective deflation the forward and middle axle air springs further so of the air springs. The dump system may comprise increases the hogging moment applied to the vehicle fourth and fifth selectively operable valve means in chassis. This hogging moment is evidenced by signifi- pneumatic circuit between the levelling valve means cant deflection of the vehicle chassis, which is unde- and the first and second air springs respectively, and sirable. One solution to this problem would be to sixth valve means to operate the third and fourth valve stiffen the chassis but this incurs a significant weight 55 means whereby the air springs are disconnected from and cost penalty. the levelling valve means and are connected to 3 3 EP 0 435 587 A2 4 atmosphere to allow deflation of the air springs. axles 7', 7", T" — are referenced 7A, 7B, 7C from When a dump system is included as described front to rear of the trailer. Second air springs at the there is preferably also provided in circuit with it inter- other side of the trailer for the axles are referenced lock means which is operable when the fourth and fifth 8A, 8B, 8C. Thus, the leading axle T has air springs valve means are operated for deflation of the air 5 7A, 8A, the middle axle 7" has air springs 7B, 8B and springs so as to disable the third valve means, and so the rear axle T" has air springs 7C, 8C. prevent operation of the first and second valve means The conventional trailer air system includes a fil- to isolate the air springs of at least the rear axle from ter 9, pressure protection valve 11, air reservoir the airsprings of the other axle or axles forward of the 12, suspension levelling valve 13 and associated con- rear axle. 10 necting pipes for connecting these components According to a second aspect of the present together and to a compressor, not shown, on the trac- invention a tipping vehicle is provided which is fitted tor vehicle. with a multi-axle air suspension system in accordance As illustrated the air suspension system includes with the first aspect of the invention herein set forth. a dump system comprising pilot operated two-position An embodiment of the invention will now be des- 15 spring return valves 14, 15 (constituting fourth and cribed by way of example with reference to the accom- fifth selectively operable valve means) and a two- panying drawings in which : position manually operated pilot return dump valve 1 6 Figure 1 is a schematic drawing showing a side (constituting sixth valve means, for operating valves elevation of a towing vehicle and a tipping trailer 14, 15), shown in the "Dump" selection in which the in transport mode, 20 pilots of valves 14, 15 are connected to atmosphere Figure 2 is similar to Figure 1 but shows the trailer and the airsprings are also connected to atmosphere in tipping mode, via the valves 14, 15. Dump valve 16 is reverted by Figure 3 is a pneumatic circuit diagram, and air pressure at its pilot from a pipe 65 which is press- Figure 4 shows a modification to the circuit diag- urised when the vehicle service brake is applied. ram of Figure 3. 25 Alternatively, it could be reverted by other means, for Referring to Figures 1 and 2 of the drawings, a example solenoid operation actuated from the brake- tractor vehicle 1 is coupled to a tipping trailer 2 light circuit. through a conventional fifth coupling, not The levelling valve 13 receives a pressure air shown. The trailer 2 has a chassis 3, a body 4 pivoted supply via the reservoir 12 and a pipe 17. Valve 13 is to the chassis at a pivot 5 and a telescopic jack 6, for 30 connected to air spring 7C via a pipe 1 8, valve 1 4 and example an hydraulic jack, pivotally connected be- pipes 19, 21, and on to airsprings 7A, 7B via pipe 22, tween the chassis 3 and the body 4. The trailer has a valve 23 and pipes 24, 25. three axles, being a leading axle 7', a middle axle 7" Levelling valve 13 is also connected to air spring and a rear axle 7"', towards its rear and an air suspen- 8C via pipes 26, 27, valve 15 and pipes 28, 29, and sion system of known construction is connected be- 35 on to air springs 8A, 8B via pipe 31, a valve 32 and tween each axle and the chassis 3 so that the axles pipes 33, 34 and 35. are carried by pivotally mounted trailing arms, not The valves 23, 32 (constituting, respectively, first shown, with an adjacent air spring acting generally and second selectively operable valve means) are between each end of each axle and the chassis. two-position pilot operated spring return valves, and As is seen in Figure 1 , the body 4 rests on the 40 their pilots are connected by pipes 36, 37, 38 to a two chassis 3 so that its load is, distributed along the position manually operated valve 39 (constituting length of the chassis. Turning now to Figure 2, the jack third valve means, for operating valves 23, 32) having 6 has been extended, lifting the front of the body 4 an override pilot operated return. away from the chassis 3. The weight of the body (and A pilot operated pressure reducing valve 41 its load) is now reacted between the ends of the chas- 45 receives a pressure air supply via the levelling valve sis 3, giving rise to a hogging bending moment on the 13, pipes 26, 27, valve 15, pipe 28 and a pipe 42. Its chassis. It will also be seen that the leading and mid- pilot is connected to pipe 42 by a pipe 43. The down- dle axles 7', 7" are located a significant distance for- stream side of valve 41 is connected to valve 23 via ward of the pivot 5 and so the air springs for these pipes 44, 45 a two-way restrictor 46 and a pipe 47. axles have a significant lever arm through which they so Similarly, valve 41 is connected to valve 32 via pipes apply a further hogging moment to the chassis 3. The 44, 48, two-way restrictor 49 and pipe 51. pressure in these air springs will be substantially the A two-position pilot operated spring return valve same as the pressure in the airsprings of the rear axle 52 (constituting interlock means) receives a pressure 7"' so that the upward loads they exert on the chassis air supply from reservoir 12 via pipe 53 and this also 3 will be substantially the same, but applied through 55 supplies valve 39 via pipe 54. A pipe 55 connects lever arms of increasing length from rear to front. valve 52 to the pilot of valve 39. Referring now to Figure 3, first air springs — that A pipe 56 connects reservoir 12 to valve 16 to is to say the air springs at one side of the trailerfor the supply pressure air through valve 16 to the pilots of 1 5 EP 0 435 587 A2 6 valves 14, 15 and 52 via pipes 57, 58 and 59. It will be seen that valve 39 cannot be operated Input to a load sensing valve (for modulating to effect load re-distribution between the axles if dump brake air pressure dependent on the vehicle load) is valve 16 is in the "Dump" selection because the inter- provided by a pipe 61 connected to pipe 19 and by a lock valve 52 causes pressurisation of the pilot of pipe 62, also by a pipe 63 connected to pipe 26 and 5 valve 39. by a pipe 64. If a dump system is not fitted the valves 14, 15 Assuming that the vehicle service brake is and 16 are omitted and there is no need for the inter- applied, air pressure in pipe 65 causes reversion of lock valve 52. In consequence a two-position man- valve 16 (reversion will in fact be the normal mode for ually operated valve can be substituted for the this valve). Pressure from reservoir 12 passes 10 manually operated pilot override return valve 39. through pipe 56, valve 16, pipes 57, 58 and 59 to oper- It may be desirable to provide for an automatic ate valves 15, 14, 52 respectively whereby the air reversion of the air suspension system to the normal springs are connected to the levelling valve 1 3 and the transport mode following completion of load dis- pilot of valve 39 is connected to atmosphere. charge, in case the operator fails to reset valve 39 If valve 39 is now operated pressure air from 15 manually. reservoir 12 passes through pipes 53, 54, valve 39 Referring now to Figure 4 of the drawings, the and pipes 38, 36, 37 to operate the pilots of valves 23, hydraulic system for tipping the body of the vehicle to 32 causing these valves to change over. The air discharge the load is represented by a pipe 71 springs 7A, 7B and 8A, 8B at the forward and middle through which a pump 72 draws hydraulic fluid from axles 7', 7" are now respectively isolated from the air 20 a reservoir (not shown) and discharges it through a springs 7C, 8C at the rear axle 7"' and are connected pipe 73 to a selector valve 74. From selector valve 74 by pipes 47, 51 , restrictors 46, 49 and pipes 45, 48, fluid can be supplied through a pipe 75 to the hyd- 44 to the downstream side of pressure reducing valve raulic jack 6. A pipe 76 connects pipe 75 to a two-posi- 41 . The latter is operated by its pilot fed with pressure tion pilot operated spring return valve 77 (seventh air through pipe 43, and controls the pressure in the 25 valve means) inserted in pipe 38 of Figure 3. air springs 7A, 7B, 8A, 8B at a reduced level. The When the selector valve 74 is selected to cause pressure reducing valve 41 preferably has a facility for extension of the jack 6 the hydraulic pressure gener- setting the output pressure, so that it may be adjusted. ated causes valve 77 to change over. Operation of The reduced pressure output required will depend on manually operated valve 39 will cause reduction of the the configuration of the vehicle and its axles, its con- 30 air pressure in the air springs 7A, 8A and 7B, 8B as struction and loading. Preferably the lower pressure is has been described. set to be between 50% and 70% of the pressure of the On completion of load discharge the selector air springs of the rear axle. In the example of the tri- valve 74 is operated to return the body 4 so that it rests axle tipper trailer which has been described the on the chassis 3. The hydraulic pressure in pipes 75, reduced pressure output may be of the order of 60% 35 76 decays allowing valve 77 to revert whereby the of the input pressure. That is to say, the airsprings 7C, pilots of valves 23, 32 are connected to atmosphere. 8Cof the rear axle 7"' will be at 100% of the pressure Valves 23, 32 revert and the air suspension reverts to downstream of levelling valve 13 and the airsprings the normal transport mode even though the valve 39 7A, 8A ; 7B, 8B of the front and middle axles 7', 7" will has not been reset manually. be at 60% of that pressure, thus reducing the hogging 40 It will be appreciated that the valve 77, instead of moment applied to the chassis via the air suspension being pilot operated direct from the hydraulic system, as compared with the situation when all the airsprings could be solenoid operated with the signal being are at the same pressure. derived from a pressure operated switch at the jack 6 Clearly, if valves 23, 32 are located alternatively or in pipe 75. between air springs 7A, 7B and 8A, 8B then the 45 If wholly automatic operation is required so that reduced pressure will be supplied to the air springs the pressure in the air springs 7A, 8A and 7B, 8B is 7A, 8A of the front axle 7' and full pressure will be sup- automatically reduced when body tipping is selected, plied to the airsprings 7B, 7C and 8B, 8C at the middle this may be effected by omitting the valve 39 so that and rear axles 7", 7"'. valve 77 (or its solenoid operated replacement) is The restrictors 46, 49 are provided to give a deg- 50 supplied with pressure air from pipe 54. As the body ree of roll stiffness to the air suspension (that is, be- is reverted so will the air suspension revert to the nor- tween air springs 7A, 7B and 8A, 8B) when the mal transport mode as already described. reduced pressure system is in operation, serving the It will also be appreciated that the valve 77, same purpose as the restrictors shown on the down- instead of having pilot operation, could be mechani- stream side of valve 13. 55 cally actuated by movement of the body during tip- The valve 39 is reset manually to revert the air ping. suspension system to the normal transport mode fol- Again, the valve 39 has been described as man- lowing completion of load discharge. ually operated but this could be replaced by a sol- 5 7 EP 0 435 587 A2 8 enoid valve, for example remote operated from the ve- second valve means (23 ; 32). hicle cab. The restrictors 46, 49 (and corresponding restric- 3. A multi-axle air suspension system as claimed in tors in valve 13) have been described as being two- Claim 1 or Claim 2 characterised in that the press- way restrictors, that is, flow is restricted in both 5 ure reducing valve means (41) is pilot operated. directions. It may be advantageous in certain appli- cations for these to be one-way restrictors so as only 4. A multi-axle air suspension system as claimed in to restrict flow to the air springs and not from the air any one of Claims 1 to 3 characterised in that the springs. pressure reducing valve means (41) is adjustable to facilitate setting of said lower pressure to a des- ired value. Claims 5. A multi-axle air suspension system as claimed in 1. A multi-axle air suspension for a vehicle having any preceding Claim characterised in that said mounted towards the rear of the vehicle a rear 15 lower pressure is set to be between 50% and 70% axle (7"') and at least one other axle (7", 7') for- of the pressure obtaining in the air springs (7C, ward of the rear axle (7"'), the system comprising 8C) of at least the rear axle (7"'). for each of said axles (7"', 7", 7') a first air spring (7C, 7B, 7A) and a second air spring (8C, 8B, 8A) 6. A multi-axle air suspension system as claimed in each adapted to be mounted to act between a 20 any preceding claim characterised in that it chassis of the vehicle and a respective end of the includes dump means (14, 15, 16) for releasing axle (7"', 7", 7'), first and second interconnecting pressure air from the airsprings (7C, 8C, ; 7B, 8B; means (18, 14, 19, 21, 24, 25 and 26, 27, 15, 28, 7A, 8A), and interlock valve means (52) in circuit 29, 31 , 33, 34, 35) pneumatically interconnecting with the dump means (14, 15, 16) whereby oper- the first air springs (7C, 7B, 7A) and the second 25 ation of the dump means to release pressure air airsprings (8C, 8B, 8A) respectively, and suspen- from the air springs causes the interlock valve sion levelling valve means (13) pneumatically means (52) to prevent operation of the third valve connected between a source of pressure air (12) means (39), thereby preventing operation of the and the first and second air springs and being first and second valve means (23 ; 32) to isolate adapted to be connected mechanically between so the air springs (7C, 8C) of at least the rear axle an axle (7"', 7", 7') and the chassis of the vehicle (7"') from the other airsprings (7B, 8B ; 7A, 8A). for operation, and the system being characterised in that it is provided with first and second valve 7. A multi-axle air suspension system as claimed in means (23 ; 32) in pneumatic circuit with the first Claim 6 characterised in that the dump means and second air springs (7C, 7B, 7A ; 8C, 8B, 8A) 35 comprises fourth and fifth valve means (14 ; 15) respectively of each of the said axles (7"', 7", 7'), which are pilot operated and in circuit between pressure reducing valve means (41) in pneumatic the levelling valve means (13) and the first and circuit with a source of pressure air and with the second air springs (7C, 7B, 7A ; 8C, 8B, 8A) re- first and second valve means (23 ; 32), and third spectively, and a sixth valve means (16) in circuit valve means (39) to operate the first and second 40 with a pressure air supply and operable to con- valve means, the arrangement being such that nect the air supply to the pilots of the fourth and operation of the first and second valve means fifth valve means (14 ; 15) to operate them and so (23 ; 32) causes the airsprings (7C, 8C) of at least connect the respective air springs to atmosphere. the rear axle (7"') to be isolated from the air springs (7B, 8B ; 7A, 8A) of the other axle or axles 45 8. A multi-axle air suspension system as claimed in (7", 7') forward of the rear axle (7"') and connects Claim 7 characterised in that the third valve the pressure reducing valve means (41) to the air means (39) and the interlock valve means (52) springs (7B, 8B ; 7A, 8A) of said axle or axles (7", are pilot operated and the sixth valve means (16), 7') forward of the rear axle (7"') whereby the air on operation, also connects the air supply to the pressure in the airsprings of said axle or axles for- 50 pilot of the interlock valve means (52) causing ward of the rear axle is controlled ata lower press- operation thereof, whereby a pressure air supply ure than in the air springs (7C, 8C) of at least the to the interlock valve means (52) is connected to rear axle (7"'). the pilot of the third valve means (39) rendering the third valve means inoperable to isolate at 2. A multi-axle air suspension system as claimed in 55 least the air springs (7C, 8C) of the rear axle (7"') Claim 1 characterised in that restriction means from the other air springs (7B, 8B ; 7A, 8A). (46, 49) are provided in circuit between the press- ure reducing valve means (41) and the first and 9. A multi-axle air suspension system as claimed in 6 9 EP 0 435 587 A2 10

any preceding Claim characterised in that the first and second valve means (23 ; 32) are two-posi- tion three way pilot operated spring return valves.

1 0. A multi-axle air suspension system as claimed in 5 any preceding Claim characterised in that it includes in circuit with the third valve means (39) a seventh valve means (77) having a first condi- tion in which it isolates the third valve means (39) from the first and second valve means (23 ; 32) 10 and a second condition in which it connects the third valve means (39) to the first and second valve means (23 ; 32), the seventh valve means (77) being adapted to be operable to the second condition in response to commencement of a tip- 1 5 ping operation of a tipper vehicle to which the air suspension system is fitted for use.

11. A multi-axle air suspension system as claimed in Claim 10 characterised in that the seventh valve 20 means (77) comprises a two-position pilot oper- ated spring return valve, the pilot thereof being adapted to be connected to the pressure hyd- raulic system of a tipping jack of a tipper vehicle. 25 12. A tipping vehicle characterised in that it is fitted with a multi-axle air suspension system as claimed in any preceding Claim.

7 8 EP 0 435 587 A2

FIG.3.

9 EP 0 435 587 A2

FIG. A

10