LIFT AXLE SUSPENSION SYSTEM

Field of Invention:

The present invention relates to a lift axle suspension system for a tandem axle of a vehicle for lifting one of the rear axles of a vehicle to a predetermined height and lowering the axle back to its initial position, when necessary.

Background of the invention:

To avoid damage to roads Commercial Motor Vehicle Regulation (CMVR) puts limit on the load that each axle of a vehicle can carry. According to CMVR requirement, the load that a tandem rear axle can carry is almost double the load carried by a single rear axle. Hence, vehicles intended for carrying heavy loads will need to have tandem axle
Tandem axles are of two categories:

a) Tandem axle having one auxiliary axle and one drive axle b)Tandem axle having both the axles as drive axle.

The choice of the tandem axle to be used for the vehicle depends on the load to be carried. For example, if the load is 25 tons then the vehicle will have tandem axle with one tag and one drive, since the tractive effort required is less and can be provided by a single drive axle. But if the load is higher, say 49 tons, then the vehicle will have to have tandem axle with both drive axle to provide higher tractive effort.

Usually, vehicles having tandem axle do not operate in full load condition all the time. It has been found that nearly half of the time a vehicle runs empty i.e. unladen condition. In the empty run condition or partially loaded condition, the service of a tandem axle is not required because the load borne on each axle is much less than the maximum permissible load of the axles. Thus, one of the axles may be lifted in unladen condition to reduce tyre wear and to improve fuel efficiency of the vehicle.

Broadly, there are two types of lift axle suspension systems known in the art, viz. air suspension system and leaf spring suspension system. Conventional lift axle suspension systems are bulky in shape and hence it has limited application. In other words, conventional lift axle suspension systems suffer from the disadvantages that they cannot be used in certain location of the vehicle or would require rearrangement of major components of the vehicle.

Moreover, most of the commercial lift axle suspension system has air springs (i.e., air bellows) to hold the axle in lifted position. Such lift axle suspension systems with air springs/air bags have been disclosed in patent documents US 6,997,464 B2, and US 6899348 B2. These air springs are accident prone in the sense that any loss of air from these springs would results in dropping of the axle onto the ground surface due to its own weight. Further, conventional lift axle suspension systems are costly and complex in design.

Yet another limitation of commercially available lift axle suspension systems is that they are configured to lift the auxiliary axle only and not the drive axle such as tandem axles.
Accordingly, the inventors felt the need to develop a compact and low cost lift axle suspension system that would safely hold the axle in its position with positive lock and would be able to lift both drive axle and auxiliary axle of a tandem axle.

Summary of the invention:

Accordingly, the present invention proposes a lift axle suspension system for a tandem axle of a vehicle comprising:
- a pair of lifting means for lifting one of the rear axles of a vehicle to a predetermined height and lowering the axle back to its initial position when necessary,
- a pair of pneumatic locking means adapted to secure the lifted axle in its position, upon the axle being raised to the predetermined height, and release said axle from its secured condition thereby enabling lowering of the axle back to its initial position, and
- an actuating means operatively connected to said lifting means and pneumatic locking means,
wherein each of said lifting means comprises a piston actuated hydraulic cylinder and a linking mechanism linked with the axle to be lifted such that the reciprocating motion of the piston of said hydraulic cylinder is transmitted to said axle, via the linking mechanism attached thereto, for lifting up and lowering down the axle.

Preferably, in the invented lift axle suspension system the hydraulic cylinder is rigidly secured to the side frame of the vehicle by means of mounting brackets and mechanical fasteners.

According to a preferred embodiment of the invention, said linking mechanism comprises of a chain and a pulley, wherein said chain is supported on said pulley and wherein one end of said chain is attached with the piston of said hydraulic cylinder and other end of the chain is linked with the axle to be lifted.

According to a particular embodiment of the invented lift axle suspension system the pulley of said linking mechanism is secured to the frame of the vehicle by means of Z brackets and fasteners. One end of the chain of said linking mechanism is linked with the axle by means of a bracket.

According to another embodiment of the invention said pneumatic locking means of the invented suspension system comprises a pneumatically actuated sliding pin, a pneumatic cylinder operatively connected to said sliding pin and a plurality of slotted brackets, such that said sliding pin is engagable into slots provided with said slotted brackets. Preferably, at least one of said slotted brackets is rigidly fixed with the vehicle axle, while the other brackets are rigidly fixed with the vehicle frame.

According to yet another embodiment of the invented lift axle suspension system said pneumatic cylinder is rigidly secured to vehicle frame by means of mounting brackets and mechanical fasteners.

Brief Description of the Drawings;

For better understanding, an illustrative embodiment of the invention will 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 shows a schematic perspective LHS view of the invented lift axle suspension system, with the axle in lowered position.

Figure 2 shows schematic perspective LHS view of the invented lift axle suspension system, with the axle in raised position.

Figure 3 shows a schematic top view of the invented lift axle suspension system attached with vehicle body.

Figure 4 shows a side elevation view of vehicle in unladen condition with rear most axle lifted.

Figure 5 shows a side elevation view of vehicle in laden condition.

Detailed Description of the Drawings

The invented lift axle suspension system for a tandem axle of a vehicle comprises a) a pair of lifting means for lifting one of the rear axles of a vehicle to a predetermined height and lowering the axle back to its initial position when necessary, b) a pair of pneumatic locking means adapted to secure the lifted axle in its position, upon the axle being raised to the predetermined height, and release said axle from its secured condition thereby enabling lowering of the axle back to its initial position, and c) an actuating means operatively connected to said lifting means and pneumatic locking means.

Referring to figures 1, 2 and 3 of the accompanying drawings, each said lifting means is comprised of a piston actuated hydraulic cylinder (1), chain (2) and pulley (3) (not shown in figure 3) to support said chain (2). The hydraulic cylinder (1) is secured to the vehicle frame (4) rigidly by means of cylinder mounting brackets (5, 6) and mechanical fasteners, while the pulley (3) is rigidly fixed with the vehicle frame (4) by means by means of Z bracket (7). One end of the chain (2) is mechanically linked with the piston (not shown) of the hydraulic cylinder (1) and the other end of the chain (2) is secured with the axle (8) to be lifted by means of an attachment (9) (not shown in figure 3).

Each pneumatic locking means comprises of a sliding pins (10), a pair of axle holding brackets (11), a sliding bracket (12) and a pneumatic cylinder (13) as shown in figures 1 and 2. The pneumatic cylinder (13) is attached to the vehicle frame (4) by means of pneumatic-cylinder mounting brackets (14) and mechanical means. The sliding pin (10) is operatively connected with the pneumatic cylinders (13) by means of a bracket (15). The axle holding brackets (11) are attached with the frame (4) of the vehicle, while the sliding bracket (12) is welded to top of the axle (8) to be lifted. The axle holding brackets (11) and the sliding bracket (12) are provided with square slots in which the sliding pin (10) is inserted for locking the lifted axle (8).

Each of said lifting and pneumatic locking means of the invented lifted axle suspension system is disposed towards either end of the axle (8) to be lifted, as shown in figure 3 of the accompanying drawings.

The use and operation of the invented lift axle suspension system will now be explained with reference to figures 1 to 3 of the accompanying drawings. When the axle (8) is to be lifted, the actuating means (not shown) is operated to activate the pair of hydraulic cylinders (1). Upon receiving activation signal from the actuating system, the piston of each hydraulic cylinder (1) starts moving inwardly. The inward motion of the piston is transmitted to the axle (8) to be lifted, via the chains (2). As a result, the axle (8) is lifted above the road surface as shown in figure 4. This lifting of the axle (8) is continued till the square slots provided in the axle holding brackets (11) and sliding bracket (12) are aligned. This is to * ensure easy insertion of the sliding pin (10) into the square slots of the axle holding brackets (11) and sliding bracket (12). Once slots of the axle holding brackets (11) and sliding bracket (12) are aligned, the pneumatic cylinders (13) are actuated to push the sliding pins (10) into the slots; thereby the axle holding brackets (11) and sliding bracket (12) get engaged. Thus a positive lock for the lifted axle (8) is provided. The pressure in the hydraulic cylinders (1) is then released.

When the vehicle is to be operated in laden condition, the load needs to be borne by both the rear axles. Accordingly, the lifted axle (8) is required to be lowered down to the road surface. A reverse operation of the above mechanism brings the lifted axle (8) down to its initial position as shown in figure 5. This operation is done by contraction of the pneumatic cylinders (13). The inward motion of each pneumatic cylinder (13) withdraws the sliding pin (10), operatively connected thereto, from the slots of the axle holding brackets (11) and sliding bracket (12). Thereby the axle holding brackets (11) and sliding bracket (12) are disengaged. Thus, the lifted axle (8) is unlocked (i.e., released). The hydraulic cylinders (1) are then actuated by the actuating system and the pistons of the hydraulic cylinders (1) start moving outwards. This outward motion of the piston is transmitted to the axle (8) through the chains (2). As a results, the axle (8) is lowered back to engage to the road surface.

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 lift axle suspension system for a tandem axle of a vehicle comprising:

- a pair of lifting means for lifting one of the rear axles of a vehicle to a predetermined height and lowering the axle back to its initial position when necessary,
- a pair of pneumatic locking means adapted to secure the lifted axle in its position, upon the axle being raised to the predetermined height, and release said axle from its secured condition thereby enabling lowering of the axle back to its initial position, and
- an actuating means operatively connected to said lifting means and pneumatic locking means,
wherein each of said lifting means comprises a piston actuated hydraulic cylinder and a linking mechanism linked with the axle to be lifted such that the reciprocating motion of the piston of said hydraulic cylinder is transmitted to said axle, via the linking mechanism attached thereto, for lifting up and lowering down the axle.

2. The lift axle suspension system for a tandem axle of a vehicle as claimed in claim 1, wherein said hydraulic cylinder is rigidly secured to the side frame of the vehicle by means of mounting brackets and mechanical fasteners.

3. The lift axle suspension system for a tandem axle of a vehicle as claimed in any of claims 1 and 2, wherein said linking mechanism comprises of a chain and a pulley, wherein said chain is supported on said pulley and wherein one end of said chain is attached with the piston of said hydraulic cylinder and other end of the chain is linked with the axle to be lifted.

4. The lift axle suspension system for a tandem axle of a vehicle as claimed in claim 3, wherein the pulley of said linking mechanism is secured to the frame of the vehicle by means of Z brackets and fasteners.

5. The lift axle suspension system for a tandem axle of a vehicle as claimed in claims 3 8B 4, wherein one end of the chain of said liking mechanism is linked with the axle by means of a bracket.

6. The lift axle suspension system for a tandem axle of a vehicle as claimed in any of claims 1 to 5, wherein each of said pneumatic locking means comprises a pneumatically actuated sliding pin, a pneumatic cylinder operatively connected to said sliding pin and a plurality of slotted brackets, such that said sliding pin is engagable into slots provided with said slotted brackets.

7. The lift axle suspension system for a tandem axle of a vehicle as claimed in claim 6, wherein at least one of said slotted brackets is rigidly fixed with the vehicle axle, while the other brackets are rigidly fixed with the vehicle frame.

8. The lift axle suspension system for a tandem axle of a vehicle as claimed in claims 6 and 7, wherein said pneumatic cylinder is rigidly secured to vehicle frame by means of mounting brackets and mechanical fasteners.