Field

This invention relates to improvements in air suspension systems for load carrying prime mover vehicles having multiple driven axles supported by a plurality of air bags on either side of each axle.

Background

Air suspension systems for load carrying prime mover vehicles can include as many as eight air suspension bags supporting the two driven axles in pairs on either side of each axle. In one well-known prime mover, the pairs of air bags are connected by a common large diameter air lines extending between correspondingly positioned air bags on adjacent axles.

The common air lines are each connected by an air line to a control valve which controls the air supply to the common air lines to adjust the inflation of the air bags to ensure that the prime mover is kept level as it is driven over variable road conditions.

'While the known air suspension systems may be adequate for slowly changing road conditions, they are not sufficiently responsive to rapidly changing conditions such as are experienced in cornering and on rough sections of road. As a result the vehicle becomes unstable, reducing driver control, increasing driver fatigue, causing increased tyre wear and potential damage to the freight.

Summary

It is an object to provide an improved air suspension system which is more responsive under changing driving conditions.

The invention provides an air suspension system for a multi-axle prime mover vehicle having a plurality of air bags supporting each side of an axle, each air bag having an air line connected between the air bag and a level controlling valve which separately controls air flow through the air lines to the air bags on either side of the vehicle, whereby the air supply to the air bags supporting each axle is independent and the air supply to the air bags on each side of the axles is independent, thereby ensuring that air is supplied rapidly and in sufficient volumes under changing driving conditions to maintain stability.

In comparison with the known air suspension system described above, a system embodying the invention will allow the air bags to rapidly respond to the changing road conditions maintaining stability and enabling the truck to be more easily controlled.

In one form, each axle has a pair of air suspension bags supporting each side of the axle and separate air lines extend from the valve controlling each side to the separate air bags.

In one arrangement, the air bags on each side are interconnected by common air lines extending between air bags in similar positions on adjacent axles, the separate air lines being connected to the common air lines adjacent the respective air bags.

To further improve responsiveness, each level controlling valve has a separate air feed line from the air supply tank of the prime mover.

The level controlling valves are actuated by control means extending to a common rigid bar fixed to the means attaching the air bags on either side to one axle.

The air bags supporting the axles of a trailer may similarly have separate air lines to each air bag supporting one side of each axle. Again separate level control valves are provided to control air supplied to the air bags on each side from an air supply tank associated with the trailer.

Brief Description of the Drawings:

In the drawings:

Figure 1 is a schematic fragmentary plan view of a prime mover chassis having an air suspension system embodying the invention;

Figure 2 is a similar plan view of a prime mover chassis having a modified air suspension embodying the invention;

Figure 3 is a schematic fragmentary plan view of a trailer chassis having a suitable air suspension system, and

Figure 4 is a schematic fragmentary plan view of a prime mover having another modified air suspension system embodying the invention

Description of Embodiments

Referring first to Figure 1, the prime mover chassis 1 has front and rear driven wheeled axles 2 and 3, which are supported in a known manner on the chassis 1 by pairs of air suspension bags 4 and 5, 6 and 7, 8 and 9 and 10 and 11, positioned as illustrated on either side of the axles 2 and 3. - A -

The air bags 4 and 8, 5 and 9, 6 and 10 and 7 and 11 are connected in a known manner by common large capacity air lines 12 to 15 respectively, which are usually about 5 cm (2 inches) in diameter. The air suspension system so far described is typical of a Kenworth Airglide 200 as found on a Kenworth T 904 prime mover.

Under normal circumstances, the common lines 12 to 15 on either side of the axles are connected by an air line (not shown) to suitable level controlling valves 16 and 17, such as Hadley valves, but in the present embodiment they are supplied with air, at the air line connector fittings of each air bag, by separate air lines 18 to 21 respectively on one side and 22 to 25 on the other side, connected to junction fittings 26 and 27 which are supplied with air by lines 28 and 29 extending from the level control valves 16 and 17. To ensure an adequate supply of air to each valve 16 and 17, separate air lines 30 and 31 are connected to an air supply tank (not shown) mounted on the prime mover in the usual manner. The lines to the front air bags 4 and 6 are connected in the usual manner, as indicated by the arrows, to the gauges and dump switch (not shown) in the cabin of the prime mover.

The provision of the separate air lines 18 to 21 and 22 to 25, and the connection of these lines to the separately supplied level control valves 16 and 17, ensure that an adequate volume of air is rapidly supplied to the air bags so that they respond more quickly to changes in road conditions relayed to the valves 16 and 17 by their control rods 32 and 33 via a rigid bar 34 mounted under the bags 9 and 11 as illustrated. The air lines 18 to 21 and 22 to 25 suitably have a bore diameter of about 1.3 cm (1/2 inch) .

In the embodiment of Figure 2, the common air lines 12 to 15 have been omitted. Otherwise the system is as described in relation to Figure 1 and the same reference numerals identify similar components. In this embodiment, the feed lines 28 and 29 from the level valves 16 and 17 are connected to branch lines which are connected to the lines 18 to 25 as illustrated. It will be appreciated that a line arrangement similar to that shown in Figure 1, absent the common lines 12 to 15, could also be used.

Figure 3 schematically illustrates a trailer chassis 40 having three wheeled axles 41, 42 and 43, supported on each side by air suspension bags 44 to 49. The bags are fed with air by separate air lines 50 to 55 respectively extending from junction fittings fed on either side by centrally located level control valves 56 and 57 supplied with air from supply tank 58. The control valves are operated similarly to the above arrangements by control rods 59 and 60 attached to the central axle 42. This arrangement operates similarly to the prime mover system and further improves the controllability of the prime mover and trailer combination.

In the embodiment of Figure 4, the pairs of air suspension bags 4,5;6,7,-8,9 and 10,11 are connected to each other by common air lines 12a to 15a, similar to common air lines 12 to 15 in Figure 1. As in the embodiment of Figure 1, air is supplied to the air line connector fittings of each air bag 4 to 11 by separate air lines 18 to 25 connected to junction fittings 27 and 28 supplied with air by air lines 28 and 29 from level control valves 16 and 17. This arrangement operates in the same way as the embodiment of Figure 1.

While the embodiments of the invention have been described in connection with an air suspension typical of Kenworth prime movers, such as the Airglide 200 on the T 904 prime mover, it will be appreciated that the invention is equally applicable to other Kenworth suspensions, such as the Airglide or AG 400, AG 460 or the AG 690, and all other air suspension systems having four or more air bags supporting each driven axle.