AUXILIARY AXLE LIFTING MECHANISM

FIELD OF THE INVENTION

The present invention relates to the fields of suspension systems for automotive vehicles. The present invention specifically relates to an auxiliary axle lifting mechanism for lifting and lowering an auxiliary axle of a multi-axle vehicle.

BACKGROUND OF THE INVENTION

In heavy duty goods vehicles, a rear drive axle (1) carries about two thirds of the total load, which leads to a high load concentration over a narrow portion of the vehicle frame (2) and the rear axle (1) and thereby large stresses are developed on the suspension (3) of the vehicle. Referring to FIG. 1, a schematic view of stress distribution on a road surface under tires of a multi-axle vehicle is illustrated. In particularly, FIG. 1(a) and 1(b) describe a four wheeled vehicle and a multi-axle vehicle riding in laden condition, respectively. The stress distribution on the road surface for a single rear axle (1) is greater than that for double rear axle, i.e. tandem axle bogie, for similar load. In order to prevent the rapid deterioration of the road and distribute the load widely along the vehicles frame (2), one or more auxiliary axles are added to a standard front axle (4) and/or the rear drive axle (1) of the vehicle, without increasing the maximum permissible load on each wheel/tire (5).

In general, the auxiliary axles can be located in front of and/or behind of the real drive axle (1) of a vehicle. If the auxiliary axle is located in front of the rear drive axle (1), the axle is called as pusher axle. If the axle is located behind of the rear drive axle (1), the axle is called as tag axle. The auxiliary axle normally has its own set of leaf springs and/or air spring, wheels and tires. Such auxiliary axles in the vehicle makes difficult for all the tires (5) to touch the road surface at the same time. In order to engage the tires (5) of the auxiliary axles to the road surface, the auxiliary axles (7) are interconnected by a suitable mechanism such as reactive suspension system or non-reactive suspension system (6) as shown in FIG. 2, which illustrates a non-reactive bell crank lever and tie rod mechanism. Moreover, FIG. 2(a) and 2(b) respectively indicates the auxiliary axles (7) in normal riding position and lifted position. Thus, if one axle rises relatively to the vehicle frame (2), then the other axle can automatically be lowered, so that the load acting on the vehicle is equally distributed to these auxiliary axles.

All these mechanisms are designed for the vehicle at loaded condition. Unfortunately, the presence of an auxiliary axle (7) affects the vehicle"s fuel efficiency, wear and maneuverability under the unloaded condition, as shown in FIG. 1(c), which describes a liftable axle vehicle riding in unladen condition. The liftable auxiliary axle (7) during the unloaded cycle can reduce fuel consumption due to decrease of rolling forward resistance of the vehicle, reduce tire wear on the auxiliary axle, reduce tire scrub on the auxiliary axle (7), i.e. tag axle, during cornering of the vehicle, and reduce maintenance of suspension, axle bearing and brakes. Further, it also minimizes the road or bridge tolls on an empty or partially loaded vehicle because the toll collection is often based on the number of axles in contact with the road surface, improves ride quality when vehicle is empty and improves maneuverability by shortening the wheel base of the vehicle.

Therefore, the lifting mechanism should be designed to lift the tires (5) of the auxiliary axle (7) to a sufficient height and maintain them at this height from the road surface, to withstand shock loads encountered in the vehicle due to irregular road surface and to withstand side thrust force encountered during cornering of the vehicle. Also, it should not affect the existing vehicle performance under the loaded condition, when both the axles are in operation.

Furthermore, the leaf spring suspension and air spring suspension are two prominently used suspension systems in multi-axle vehicles. As cost of the leaf spring suspension system is relatively less than that of the cost of air spring suspension system, the leaf spring suspension is most commonly used in heavy duty vehicles. Such suspension system distributes load widely along the vehicle frame (2). Additionally, the leaf spring provides a full support for the suspended structure in vertical direction and also in longitudinal and lateral directions.

However, the implementation of a retractable suspension system, preferably retrofittable, in a conventional leaf spring suspension vehicle is relatively difficult, because a large force is required to lift the auxiliary axle against reaction force of the leaf springs and the limited packaging space availability. Most retractable mechanism can be classified as either hydraulically or pneumatically operated based on the operating medium. A manually operated mechanical system has also been designed and reported in an Indian patent (1013/CHE/2006).

A number of hydraulically liftable auxiliary axles are proposed such as US3915470, US3936072, US4102424, US4842302 and US 4134604. In a typical hydraulically liftable axle, the operating mechanism consists of a hydraulic actuator and a mechanical leverage system. The hydraulic pump is actuated to push the piston out, which activates the mechanical leveraging mechanism to lift the auxiliary axle. Similarly, deactivation of the pump lowers the auxiliary axle. Main drawback of the hydraulic liftable auxiliary axle is that the lifting mechanism is subjected to high shock force when the vehicle is operated over undulated road, i.e. irregular roads. The shock force is transmitted to all the components of the lifting mechanism and the axle assemblies, which causes damage to the components of the lifting mechanism, including hydraulic cylinders. Moreover, all the components of the lifting mechanism are also subjected to side thrust force, namely lateral force, while the vehicle is cornering. The side thrust force produces a high strain on the cylinder seals, which leads to a premature failure of the hydraulic cylinder and leakage of hydraulic oil.

US6883813 B2, US3502348 and US3704896 describe implementation of a retractable system, i.e. lifting system, in an air spring suspension vehicle, which is relatively simple and also practically viable. In most of the air suspension systems, two ride air bellows and two lift air bellows are assembled. The ride air bellows are used to lower the axle whereas the lift air bellows, i.e. retraceable air spring, are used to lift the auxiliary 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. The air bellows lifting system described in US6883313 B2 also suffers from a few problems such as low life of the air bellows.

US3771812, US 4293145 and US 5853183 disclose that two helical coil compression springs are used instead of lift air bellows, for automatically lifting the auxiliary axle. When the air is released from the air bellows, the helical coil spring pull the axle upwardly. After lifting the axle, the helical springs hold the axle at a desired height from the road surface. When the air springs are pressurized, the axle is forced downwardly to engage the tire with road surface. The helical spring withstands the shock load that exerted at the axle due to irregular road surface. Further, the manufacturing cost and operating cost are relatively reduced. In some of the prior arts US 3730549, US 3877718 and US4000913, the leaf spring has also been used to lift the axle when the air springs are deflated.

There are numerous mechanisms employed in the vehicle for lifting the auxiliary axle. Despite the many designs, only a few mechanisms are commercially viable due to important factors such as easy manufacturability, simple function, low maintenance, high reliability, easy assembly and serviceability. With respect to the conventional arts, such lifting mechanisms are quite expensive, very difficult and complex in arrangement.

Therefore, it is desirable to provide an auxiliary axle lifting mechanism for lifting and lowering an auxiliary axle of a multi-axle vehicle, which improves fuel economy, vehicle maneuverability and life of the auxiliary axle"s components.

OBJECT OF THE INVENTION

An object of the present invention is to provide an auxiliary axle lifting mechanism, which lifts an auxiliary axle of a multi-axle vehicle to a sufficient height such that it does not interfere with undulant from the road surface.

Another object of the present invention is to provide an auxiliary axle lifting mechanism, which withstands dynamic loads and shocks.

Yet another object of the present invention is to provide an auxiliary axle lifting mechanism, which improves fuel economy, vehicle maneuverability and life of the auxiliary axle"s components.

Yet another object of the present invention is to provide an auxiliary axle lifting mechanism, which is simple, highly reliable and retrofittably mountable in the vehicle without modification of existing components.

Yet another object of the present invention is to provide an auxiliary axle lifting mechanism, which is implemented in other kinds of multi-axle vehicles.

SUMMARY OF THE INVENTION

According to one aspect, the present invention, which achieves the objectives, relates to an auxiliary axle lifting mechanism comprising a set of coil springs that is clamped with a cross member and a platform. The cross member consists of a U frame that is fastened to a vehicle frame by using U brackets. A power actuating cylinder is fastened to the U frame, where an axle clamping device is mounted on the platform. The power actuating cylinder actuates the coil springs by forcing a piston to extend the coil springs and move the platform downward, such that the tension in the coil springs aids to lift the auxiliary axle above the road surface while the axle clamping device holds the auxiliary axle. Such mechanism lifts the auxiliary axle to a sufficient height such that it does not interfere with undulant from the road surface and also improves fuel economy, vehicle maneuverability and life of the auxiliary axle"s components.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be discussed in greater detail with reference to the accompanying Figures.

FIG. 1 shows a schematic view of stress distribution on a road surface under tires of a multi-axle vehicle;

FIG. 2 illustrates a schematic view of a non-reactive bell crank lever and tie rod mechanism;

FIG. 3 shows an assembled model of an auxiliary axle lifting mechanism, in accordance with an exemplary embodiment of the present invention;

FIG. 4 illustrates the auxiliary axle lifting mechanism with a wedge positioned between a lock block and a platform, in accordance with an exemplary embodiment of the present invention;

FIG. 5 illustrates the auxiliary axle lifting mechanism fitted in a multi-axle vehicle, in accordance with an exemplary embodiment of the present invention; and

FIG. 6 illustrates operational sequences of the auxiliary axle lifting mechanism, in accordance with an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 3, an assembled model of an auxiliary axle lifting mechanism is illustrated, in accordance with an exemplary embodiment of the present invention. The auxiliary axle lifting mechanism comprises of a lifting mechanism, an axle clamping device and a locking mechanism. The auxiliary axle lifting mechanism consists of a platform (9), a cross member (10) and a helical coil springs (8) that are placed adjacent to a hydraulic cylinder (13). For the purpose of clarity and explanation, the detailed description set forth in this specification deal with the hydraulic cylinder in order to provide a thorough understanding of the present invention. However, the present invention is not limited to this specific application, where it may be pneumatic cylinder or other power actuating cylinders. The cross member (10) is formed of a U frame (11) and two U brackets (12). The U brackets (12) aid to fasten the U frame (11) to the vehicle frame (2). The hydraulic cylinder (13) can be mechanically fastened to the U frame (11).

Moreover, one end of the coil spring (8) is securely clamped with the cross member (10) and other end of the coil spring (8) is securely clamped with the platform (9), preferably by using a flat U bolt (14) and a spring spacer block (15). The coil spring (8) can be assembled with two holes at the both ends, in which split pins (not shown) are inserted. The split pins are provided for locking the coil spring (8), which prevents slip that occurs due to vibration. The U bolt (14) can be flattened off by forging, where the flat portion in the U bolt (14) is especially provided to increase contact area, which prevents slip that occurs due to vibration.

Referring to FIG. 4, the auxiliary axle lifting mechanism with a wedge (20) positioned between a lock block (19) and the platform (9) is illustrated, in accordance with an exemplary embodiment of the present invention. The platform (9) carries an axle clamping device, where the axle clamping device consists of two shafts (16), four pillow block bearings (17), two parallel rectangular keys, two claws (18), two lock blocks (19) and wedge (20). The claw (18) can be utilized to hold the auxiliary axle (7) when the auxiliary axle (7) is being lifted. The claw (18) is formed as a bent shaped hot forged component, in which an eye head portion of the claws (18) is provided to insert the shaft (16).

Furthermore, the rectangular key way is also provided in the eye head portion of the claw (18), such that the shaft (16) is secured to the claw (18) by a key with set screw. Then, the assembled unit of the shaft (16) and claw (18) is pivoted to the pillow block bearing (17).

A copper sleeve is affixed to the hole of the pillow block bearing (17) by press fit in order to reduce wear, that generally occurs in the pillow block bearing (17). A circlip is housed in a groove provided in the outer periphery of the shaft (16) to prevent its translation thereafter. The axle clamping device is mounted on the platform (9) by means of fasteners.

In the locking mechanism, the lock block (19) and the wedge (20) are used to lock the auxiliary axle (7) with the axle clamping device, where the lock block (19) is keyed to the shaft (16). when the axle clamping device is pivoted to the pillow block bearing (17), the axle clamping device can be turned to a desired angle manually. The axle clamping device can be locked by inserting the wedge (20) between the lock block (19) and the platform (9). In this auxiliary axle lifting mechanism, the axle clamping device is operated manually to lift the auxiliary axle (7) of the multi-axle vehicle as shown in FIG. 5, which illustrates the auxiliary axle lifting mechanism fitted in the multi-axle vehicle, in accordance with an exemplary embodiment of the present invention.

Referring to FIG. 6, operational sequences of the auxiliary axle lifting mechanism are illustrated, in accordance with an exemplary embodiment of the present invention. In initial stage, the helical coil spring (8) is in neutral state whereas the claws (18) are in open position, as shown in FIG. 6(a). In order to lift the auxiliary axle (7), pressurized oil is supplied to the hydraulic cylinder (13), which forces the piston to move downward and press the platform (9). Then, it results in the extension of the helical coil spring (8) and movement of platform downward, as shown in FIG. 6(b).

As shown in FIG. 6(c), when the platform (9) is just above the tag axle (7), the axle clamping device is activated to hold the tag axle (7). After locking the tag axle (7), the hydraulic oil is released from the hydraulic cylinder (13). As a result, the force caused by the hydraulic cylinder (13) drops below the spring force on it, such that the coil spring (8) lifts the auxiliary axle (7) clamped to the claws (18), as shown in FIG. 6(d). Therefore, the tires (5) of the auxiliary axle (7) are disengaged from the road surface.

The entire auxiliary axle assembly is lifted above the road surface and maintained at a required distance from the road surface. Since the entire auxiliary axle assembly is held by the helical coil spring (8), the damage of components caused by shock loads can be prevented. Similarly, the coil spring (8) lowers the auxiliary axle (7) to the road surface when the claws (18) are opened. When the auxiliary axle (7) touches the ground, the clamp mechanism is deactivated and then the hydraulic actuator is de-pressurized to lift the platform (9) and the coil spring (8) upwards.

Such lifting mechanism prevents the damage of hydraulic cylinder (13) caused by shock loads, because the hydraulic cylinder (13) is operated only at the time of lifting and lowering the tag axle (7). Since the hydraulic cylinder (13) is completely disengaged from the tag axle (7) when the vehicle is in motion, and thus it is not subjected to dynamic loads. Additionally, the lifting mechanism can be retrofitted with minimal modification to the existing vehicle and also implemented in other kinds of multi-axle vehicles.

Moreover, the mechanism does not affect the performance of the suspension under loaded condition when both the tires touch the road surface. The lifting mechanism is modular in nature which can be fitted on a vehicle with both pneumatic and leaf spring base suspension. It also avoids stress on the frame when the hydraulic cylinder (13) activates to lift and lower the tag axle (7), since the force can be cancelled by the reaction force at the spring end.

Claims

1. An auxiliary axle lifting mechanism, comprising:

one or more coil springs clamped with a cross member and a platform, said cross member consists of a U frame that is fastened to a vehicle frame by using a plurality of U brackets;

at least one power actuating cylinder fastened to said U frame; and an axle clamping device mounted on said platform, wherein said power actuating cylinder actuates said one or more coil springs by forcing a piston to extend said one or more coil springs and move said platform downward, such that the tension in said one or more coil springs aids to lift the auxiliary axle above the road surface while said axle clamping device holds the auxiliary axle.

2. The mechanism as claimed in claim 1, wherein said axle clamping device
further comprising:

one or more claws adapted to hold the auxiliary axle when the auxiliary axle is lifted;

one or more shafts secured to said one or more claws by a key way provided in an eye head portion of said one or more claws, said eye head portion is provided to insert said one or more shafts; and

a lock block keyed to said one or more shafts for locking the auxiliary axle with said axle clamping device, wherein said one or more shafts and said one or more claws are pivoted to a pillow block bearing, such that said one or more claws are turned to a desired angle.

3. The mechanism as claimed in claim 2, wherein said axle clamping device is locked by inserting a wedge between said lock block and said platform.

4. The mechanism as claimed in claim 1, wherein said one or more coil springs are clamped with said cross member and said platform by using a U-shaped bolt and a spring spacer block.

5. The mechanism as claimed in claim 1, wherein said one or more coil springs and said at least one power actuating cylinder are mounted on said vehicle frame above the auxiliary axle.

6. The mechanism as claimed in claim 1, wherein said one or more coil springs are locked by inserting a split pin into holes at both ends of said one or more coil springs.

7. The mechanism as claimed in claim 2, wherein said one or more shafts are arranged with a groove with a circlip in its outer periphery.

8. The mechanism as claimed in claim 1, wherein said at least one power actuating cylinder is disengaged from the auxiliary axle when the vehicle is in motion.

9. The mechanism as claimed in claim 1, wherein said axle clamping device is deactivated to lift said platform upwards when the auxiliary axle touches the road surface.

10. The mechanism as claimed in claim 1, wherein said at least one power actuating cylinder is a hydraulic cylinder.

11. The mechanism as claimed in claim 11, wherein the pressurized oil is supplied to said hydraulic cylinder for actuating said one or more coil springs.

12. The mechanism as claimed in claim 11, wherein the pressurized oil is released from said hydraulic cylinder after locking the auxiliary axle in said axle clamping device, such that the auxiliary axle is disengaged from the road surface by the tension in said one or more coil springs.

13.   The mechanism as claimed in claim 1, wherein said at least one power actuating cylinder is a pneumatic cylinder.