Field of invention;

The present invention relates to a retractable lift axle suspension system for a multi-axle vehicle comprising of atleast a lifting means for desirably lifting the tag axle assembly of a multi-axle vehicle and lowering the tag axle assembly to its initial position.

Background of the invention;

In multi axle vehicle, it is often desirable to have an axle lifting feature that lifts the axle assembly from road surface when the vehicle is not operating under laden condition. Therefore it is advantageous to have a lift able axle in multi-axle vehicle which can be lifted above the road surface when the vehicle is operating in an unladen condition or lightly loaded condition and lowered when the vehicle is loaded sufficiently.

It is known in the art to interconnect the axles in multi-axle vehicles with leaf sprig suspension through a tie rod, bell crank and shackle, so that the load that acts on rear side of the vehicle is equally distributed to both the rear drive and tag axle. Therefore, the multi-axle vehicle is capable to carry large amount of load. However, high fuel consumption, low tire life and low maneuverability (ride quality) are the important issues associated with the multi axle vehicles. In addition, as has been discussed in US patent documents, US 3285621 and US 6883813 B2 cornering of the vehicles is also difficult.

In order to overcome the above-mentioned drawbacks associated with the multi axle vehicle, the tag axle may be lifted from the road surface during the return trip of the vehicle if the vehicle is empty. However, the axle lifting system should work in such a way that when the tag axle is lowered into road engagement, the leaf spring suspension system is able to distribute the load to both the rear and tag axle. When the tag axle is not needed, for example in unladen condition, the axle lifting system lifts the tires of tag axle from the road surface to a sufficient height and maintain them in position. Thereby, irregular road contact can be prevented on the tag axle even when the vehicle is operated on the undulated and humped roads. In this way, life of tires and brakes and its associated components can be increased. Moreover, the better fuel economy and maneuverability can also be achieved.

US6883813 B2, US3502348 and US3704896 describe implementation of a retractable system, i.e. tag axle lifting system, in an air spring suspension vehicle. In most of the air suspension systems, two ride air bellows and two lift air bellows are employed. The ride air bellows are used to lower the axle whereas the lift air bellows, i.e. retractable air spring, are used to lift the tag axle from road surface, as disclosed in US4773670, US5403031, US6158750, US6845989, US6871862, US 6880839 and US6883813. The ride air spring and the lift air spring are simply deflated and inflated respectively, to lift the auxiliary axle whereas the ride air spring and the lift air spring are inflated and deflated respectively, to lower the auxiliary axle.

Although there are numerous systems known in the art for lifting the auxiliary axle of a multi axle vehicle , only a few of them are commercially viable due to important factors such as easy manufacturability, simple function, low maintenance, high reliability, easy assembly and serviceability. However, such conventional axle lifting systems are quite expensive, very difficult and complex in arrangement.

Therefore, the inventors felt the need to develop a simpler and low cost lift axle suspension system for lifting and lowering the tag axle of a multi-axle vehicle, which would improve fuel economy, vehicle maneuverability and life of the auxiliary axle's components.

Summary of the invention;

Accordingly, the invention provides a retractable lift axle suspension system for a multi-axle vehicle comprising of atleast a lifting means attached to vehicle frame, said lifting means comprising of:

- a lever arm, disposed beneath a tag axle assembly of said multi-axle vehicle, adapted for lifting the tag axle assembly to a predetermined height, and lowering the tag axle assembly to its initial position, wherein said lever arm is provided with a wear plate at portion which underlie said tag axle assembly;

- a pair of hanger brackets, a main hanger bracket disposed on one side of said lever arm, and a support hanger bracket disposed on other side of said lever arm, to which said lever arm is pivotally attached at its rear end by means of pivot pins; wherein each said hanger bracket is provided with a stop pinfor limiting the turning movement of said lever arm;

- an air bellow, having its one end secured with an air bellow bracket and its other end secured to said lever arm, for actuating said lever arm; and

- a pneumatic actuator, operatively connected to said lever arm, for disengaging said lever arm from said tag axle assembly when the tag axle assembly is to be lowered.

Preferably, in the invented retractable lift axle suspension system portion of the tag axle which overlies the said lever arm is provided with an axle sliding block which is in line contact with said wear plate provided on said lever arm and the axle sliding block is in the form of a truncated round block.

According to a particular embodiment of the invented retractable suspension system, the surface of the wear plate in contact with the axle is inclined so as to ensure smooth translation of the tag axle on the wear plate in lifted condition.

According to another embodiment of the invented retractable lift axle suspension system both the hanger brackets, the main hanger bracket and the support hanger-bracket, are provided with a pair of bosses, pivot boss and stop pin boss, for pivotal connection with said lever arm. In order to hold the pivot pins rigidly, holes are provided on the bosses for insertion of cotter pins.

According to yet another embodiment of the invented suspension system, the lever arm is provided with a curve shaped slotted hole in which stop pin is guided when the lever arm rotates about said pivot pin. Preferably, lever arm is provided with a boss for mounting a greased bearing bush for insertion of said pivot pin.

According to a further embodiment of the invented retractable lift axle suspension system, the air bellow is secured to said lever arm by means of a disc plate. Preferably, the air bellow bracket is fastened to both of the cross member and vehicle frame rail of multi-axle vehicle via a support air bellow bracket.

Preferably, in the invented retractable lift axle suspension system the pneumatic actuator is attached to the main-hanger bracket by means of an actuator mounting bracket.

According to the most preferred embodiment the invented lift axle suspension system is provided with a pair of lifting means to provide additional stability to the axle at its lifted condition.

Brief Description of the Drawings;

For better understanding an illustrative embodiment of the invention will now be described with reference to the accompanying drawings. It will however be appreciated that the embodiments exemplified in the drawings is merely illustrative and not limitative to the scope of the invention, because it is quite possible, indeed often desirable, to introduce a number of variations in the particular embodiment that has been shown in the drawings.

Figure 1 schematically shows the working mechanism of an lift axle suspension system according to prior art. Figure 1 a) shows a schematic side view of a vehicle when the auxiliary axle is on the ground and figure 1 b) shows a schematic side of a vehicle when the auxiliary axle is lifted above the ground with the aid of an lift axle suspension system.

Figure 2 shows schematically a preferred embodiment of system filled in a chassis frame of a multi axle vehicle.

Figure 3 shows schematically a perspective view a preferred embodiment of invented retractable suspension.

Figure 4 shows a perspective view of main hanger bracket according to a particular embodiment of the invention.

Figure 5 shows a perspective view of support hanger bracket according to a particular embodiment of the invention.

Figure 6 illustrates a perspective view of lever arm according to a particular embodiment of the invention.

Figure 7 illustrates air bellow bracket and air bellow support bracket according to a particular embodiment of the invention.

Figure 8 shows schematically an axle sliding block according to a preferred embodiment of the invention.

Figure 9 shows schematically a wear plate according to a particular embodiment of the invention.

Detailed description of the drawings:

Figure 1 of the accompanying drawings shows a multi axle vehicle provided with conventional axle lifting system (1). In normal operating condition, i.e. when the vehicle is laden, the tag axle (2) remains on the ground as shown in figure 1 (a). When the vehicle is unladen it is desirable to lift the tag axle (2) off the ground. The conventional axle lifting system (1), as has been shown in figure 1, utilizes a non-reactive bell crank lever and tie rod mechanism, and comprises of tie rod (3), bell crank (4) and shackle (5) attached to a leaf spring suspension system (6). When the tag axle (2) is desired to be lifted the bell crank lever and tie rod mechanism is activated to lift the axle above the ground, as shown in figure 1 (b). Such convention lifting mechanism is expensive and complex in arrangement.

The invented retractable lift axle suspension system is a leverage system. According to a preferred embodiment , as shown in figures 2 and 3 of the accompanying drawings , the invented retractable lift axle suspension system (7) for a multi-axle vehicle comprising of a pair of lifting means (8),. Each lifting means (8) comprises of lever arm (9), air bellows (10), main hanger bracket (11), support hanger bracket (12), air bellow bracket (13), pivot pins (14), wear plate (15), axle sliding block (16), pneumatic actuator (17), stops pin (18), lock nut (19), lock washers (not shown) and support air bellow bracket (20). Referring to figure 2, the main hanger brackets (11) and support hanger brackets (12) are attached to the vehicle frame rail (21) and cross member (22) of the vehicle respectively by means of conventional nut and bolt joint and extended downwardly therefrom. Each lever arm (9) is pivotally attached to the main hanger bracket (11) and support hanger bracket (12) by means of pivot pins (14). The main hanger bracket (11) is disposed on outer side of the lever arm (9) while the support hanger bracket is disposed on the inner side of the lever arm (9). The air bellow bracket (13) and air bellow support bracket (20) are mechanically fastened to both the cross member (22) and vehicle frame rail (21) of the vehicle. The air bellows (10) are employed to activate the lever arms (9). One end of the air bellow (10) is securely attached with the air bellows bracket (13) and other end of the air bellows (10) is securely attached with the lever arms (9). The free end of the lever arms (9) are positioned below the tag axle assembly (23) to be lifted. A pair of pneumatic actuators (17) is attached to the main hanger brackets (11). The pneumatic actuators (17) are operatively connected to the lever arms (9) and are used to disengage the lever arms (9) from tag axle (6) when the vehicle is operated in laden condition.

A unique of the present invention is positioning of the air bellows (10). The aii: bellows (10) are positioned in such a way to avoid accordion effect (i.e., angular expansion of the air bellows). More specifically, the angle should not exceed 30° due to restriction in the air bellows (10) construction. Advantageously, the air bellows (10) improve the suspension of the vehicle and provide better ride comfort.

A pair of stop pin (18) is attached to the hanger brackets (11, 12). The stop pin (18) is provided to limits the maximum turning movement of the lever arm (9). When the lever arm (9) rotates about the pivot pin (14), the stop pin (18) is guided in a slotted hole (not shown) provided in the lever arm (9). In order to hold the stop pin (18) rigidly, a cotter pin is used. The cotter pin is inserted in a hole provided in the stop pin boss (24) of the main hanger bracket (11) as has been shown in figure 4.

An important feature of the present invention is the axle sliding block (16). It is attached at the bottom of the tag axle assembly (23). It has been observed from experiments conducted on multi-axle vehicles that when the tag axle assembly (23) is lifted, the tag axle (2) revolves itself and raise upward. This imparts large twisting force on any part in connection with the tag axle (2). With a view therefore to avoid such twisting force, a truncated round block is provided in the axle sliding block (16). The axle sliding block (16) has been shown separately in figure 8. The round surface of the sliding block (16) and flat surface of the wear plate (15) is in a line contact at the interface; therefore friction at the interface is reduced. Therefore, when the tag axle assembly (23) is lifted, it rotates around its axis and translates on the wear plate (15) smoothly. Preferably, a slope is provided in the wear plate (15), as shown in figure 9 of the accompanying drawings. It assists the tag axle (2) to translate smoothly on the wear plate (16) when the tag axle assembly (23) is lifted.

Referring to figures 4 and 5 of the accompanying drawings, the main hanger bracket (11) and the support hanger bracket (12) have two bosses namely pivot boss [25] and stop pin boss (24), where the pivot pins (14) are inserted. In order to hold the pivot pins (14) rigidly, cotter pins (not shown) are inserted into holes provided in the bosses (24, 25) of the main hanger bracket (11) and support hanger bracket (12). The cotter pins prevent the rotational movement and translation movement of the pivot pins (14). Therefore, each pivot pin (14) act as a fulcrum about which the lever arm (9) rotates when the air bellows are (10) inflated or deflated. A lock nut (19) with a lock washer (not shown )is provided at the end of the each pivot pin (14), which is mainly for clamping the pivot pin (14) with the main hanger bracket (11) and provide support thereto.

Referring to figure 6 of the accompanying drawing, the lever arm (9) is provided with a disc plate (26) to which once ends of the air bellow (not shown) abuts. The lever arm is provided with a boss for mounting a greased bush bearing (27) for engaging with pivot pin (14).

When the tag axle assembly (23) is required to be lifted, the air bellows (10) are inflated. This inflation of the air bellows (10) force the lever arms (9) to lift the tag axle assembly (23). The entire tag axle assembly (23) and the wheels attached thereto (not shown) is lifted above the road surface and maintained in position at a required distance from the road surface. Therefore the air bellows (10), force the lever arms (9) to lift the tag axle assembly (23). Since the entire tag axle (23) is held by the air bellows (10), the damage of components caused by shock loads can be prevented.

In order to lower the tag axle assembly (23), the air bellows (10) are deflated. During deflating the air bellows (10), the axle assembly (23) is forced downward due to the downward force of the leaf springs (not shown). At the same time, compressed air is supplied to pneumatics actuator (17), to force the lever arms (9) downwards and disengage it from the tag axle (2). Since the lever arms (9) are completely disengaged
from the tag axle (23) when the vehicle is operated in laden condition, the components of the mechanism are not subjected to dynamic loads caused by shock loads. Advantageously, the invented retractable suspension system (7) can be retrofitted with minimal modification to the existing vehicle and also implemented in other kinds of multi-axle vehicles.

Moreover, the invented retractable suspension system (7) does not affect the performance of the suspension under laden condition when both the tires touch the road surface. The retractable suspension system (7) is modular in nature which can be fitted on a vehicle with both pneumatic and leaf spring base suspension.

As already mentioned, the foregoing description is illustrative of the invention and not limitative to its scope, because it will be apparent to persons skilled in the art to device other alternatives embodiments without departing from the broad ambit of the disclosures made herein.

We claim:

1) A retractable lift axle suspension system for a multi-axle vehicle comprising of atleast a lifting means attached to vehicle frame, said lifting means comprising of:

- a lever arm, disposed beneath a tag axle assembly of said multi-axle vehicle, adapted for lifting the tag axle assembly to a predetermined height, and lowering the tag axle assembly to its initial position, wherein said lever arm is provided with a wear plate at portion which underlies said tag axle assembly;

- a pair of hanger brackets, a main hanger bracket disposed on one side of said lever arm, and a support-hanger bracket disposed on other side of said lever arm, to which said lever arm is pivotally attached at its rear end by means of pivot pin; wherein each said hanger bracket is provided with a stop pin for limiting the turning movement of said lever arm;

- an air bellow, having its one end secured with an air bellow bracket and its other end secured to said lever arm, for actuating said lever arm; and

- a pneumatic actuator, operatively connected to said lever arm, for disengaging said lever arm from said tag axle assembly when the tag axle assembly is to be lowered.

2) The retractable lift axle suspension system as claimed in claim 1, wherein portion of said tag axle assembly which overlies the said lever arm is provided with an axle sliding block which is in line contact with said wear plate provided on said lever arm.

3) The retractable lift axle suspension system as claimed in claim 2, wherein the axle sliding block is in the form of a truncated round block.

4) The retractable lift axle suspension system as claimed in claim 1, wherein said air bellow bracket is fastened to both of the cross member and vehicle frame rail of multi-axle vehicle via a support air bellow bracket.

5) The retractable lift axle suspension system as claimed in claim 1, wherein the surface of said wear plate in contact with the axle is inclined to ensure smooth translation of the tag axle on the wear plate in lifted condition.

6) The retractable lift axle suspension system as claimed in claim 1, wherein each said hanger bracket is provided with a pair of bosses, pivot boss and stop pin boss, for pivotal connection with said lever arm.

7) The retractable lift axle suspension system as claimed in claim 6, where said bosses are provided with holes for insertion of cotter pins.

8) The retractable lift axle suspension system as claimed in claim 1, wherein said lever arm is provided with a curve shaped slotted hole in which said stop pin is guided when said lever arm rotates about said pivot pin.

9) The retractable lift axle suspension system as claimed in claim 1, wherein said lever arm is provided with a boss for mounting a greased bearing bush for insertion of said pivot pin.

10) The retractable lift axle suspension system as claimed in claim 1, wherein said air bellow is secured to said lever arm by means of a disc plate.

11) The retractable lift axle suspension system as claimed in claim 1, wherein said pneumatic actuator is attached to said principal-hanger bracket by means of an actuator mounting bracket.