DESC:FIELD OF INVENTION

The present invention relates to lift axle suspension in trucks. In particular, the present invention relates to rebound control of the truck’s lift axle suspension system. More particularly, the present invention relates to control the rebound of the truck’s lift axle suspension system by controlling the displacement of the suspension arms thereof.

BACKGROUND OF THE INVENTION

The main objects of the automobiles suspension system, e.g. truck suspension system, are:

• To stabilize the truck, when travelling over any type of terrain, be it smooth highways or a rough/poorly maintained countryside road.

• To cushion the chassis from road shocks and bumps to enable the driver to steer the truck easily.

• To maintain correct axle spacing and alignment.

• To provide a smooth ride, both in loaded and unloaded condition of the truck.

In the field of suspension technology, “Bump” or “Jounce” simply means the most compressed condition of the suspension (spring) or shock-absorbing system. Often, jounce blocks are used for preventing “chassis-to-axle contact”, also referred to as “suspension slam”.

Further, “Rebound” is the reactive response of a spring after being jounced, so it kicks back.

“Unsprung weight” is the weight of the chassis components, which are not supported by the suspension system, e.g. axles, wheels and it is usually kept as light as possible. This unsprung weight directly reacts through the suspension to the chassis.
Lift axle or airlift/drop axle are used in dump trucks and trailers. The lift axle can be mechanically lowered to increase the weight capacity or for weight distribution of the cargo over more wheels, for example for crossing a weight restricted bridge.

Lift axle can also be raised or lifted off the ground to save wear on the tires and axle and to increase traction in the remaining wheels. Lifting a lift axle reduces lateral scrubbing of the additional axle in very tight turns, so as to allow the vehicle to turn more readily. In some situations, the removal of pressure from the additional axle is necessary for the vehicle to negotiate a turn completely.

There are primarily two modes of rebound motion control: the first - Bump stops fitted within lift-bellow, and the second - Additional rebound straps (belt) fitted between the chassis and the axle.

• Currently rebound travel is stopped by internal bump stopper provided inside the lift bellow.

• Due to dynamic motion during sudden rebound of axle, the internal bump stopper gets damaged.

• Damaged internal bump stopper of rubber further damages the lift-bellow membrane of rubber.

• Once this rubber lift-bellow membrane gets damaged, the lift-bellow starts leaking.

• Moreover, due to excessive deformation of the internal bump stopper, the main bellow height exceeds the permissible height.

• Overextension of the main air spring causes the failure thereof.

• To overcome this problem, in some prior arts, the rebound strap is used as an additional control to restrict the rebound motion of the lift axle.

PRIOR ART

Indian Patent application no. 397/CHE/2014 discloses a self-steer lift axle suspension system for a vehicle, having ride air springs, lift air springs, upper control arms, lower control arms, jounce bump stoppers, rebound stopper belt assembly, swinging plates, and steering stabilizers.

Indian Patent application no. 1322/MUM/2014 discloses a lift axle suspension system and more particularly, a lift axle suspension system having an air spring lift member comprising vehicle chassis, shock absorber, lift springs, lift spring bracket, pivot joint, hanger, pair of suspension beam, external bumper, U-Bolt & nut, axle, ride air bag, wheel, and pneumatic circuit for providing automated action for lowering and raising the lift axle.

Patent publication no. US 4300787 A discloses a lift axle suspension wherein the mechanism for lifting the axle includes a pivotal connection located below the longitudinal frame member of the vehicle and a pair of plates, one pivotally attached to the pivotal connection and the other rigidly attached in the suspension, an air bellows located between the pair of plates and a link member functionally attached between the axle and pivotally attached plate such that expansion or retraction of the bellows lifts the axle and the opposite operation allows the axle to be lowered.

Patent no. US 6871862 B2 discloses a lift axle suspension system. In a described embodiment, a lift axle suspension system includes: an axle assembly; an air spring connected between the axle assembly and a bracket attached to a vehicle frame; a trailing arm attached to the axle assembly; and a lift air spring. The lift air spring is connected between the bracket and the trailing arm, so that the axle assembly is lifted when the lift air spring is extended.

Patent no. EP 0662418 B1 (US 543031 A) discloses a parallelogram lift axle suspension system with a control for axle caster adjustment. It includes a bi-directional airlift spring having opposite end plates at either end located between two parallel control arms where expansion of the air spring pivots the upper and lower control arms with respect to a frame bracket thereby lifting an axle and wheels attached to it from engagement with the road surface. The end plates of the bi-directional air spring move about equally in opposite directions and remain parallel to one another throughout expansion and contraction of the air spring so as to about equally distribute forces of expansion of the air spring between the upper and lower control arms.

Patent no. US 8522933 B2 discloses an adjustable run height lift axle suspension system includes an axle assembly, an air spring and a lift actuator. A device may be releasably attached to the axle assembly and connected to each of the air spring and the lift actuator, the device spacing the air spring away from the axle assembly. A selected one of multiple devices may be used, the suspension system having one run height when one device is releasably attached to the axle assembly and connected to each of the air spring and the lift actuator, and a different run height when another device is used. The air spring may have approximately the same operational height when the suspension system is at the different run heights.

Patent no. US 5230528 A discloses an improved, light-weight left axle wheel assembly attached to the frame of a load carrying vehicle, used to increase the capacity, performance and safety of the vehicle. The left axle wheel assembly has a pair of inflatable airbags for alternately raising or lowering an attached pair of wheels and tires. The left axle wheel assembly has a pair of resilient bushings that dampen and reduce the transfer into the vehicle frame of the torque and stress caused when the tires traverse uneven terrain such as curbs.

Patent no. US 6311993 A discloses a lift axle pivotally mounted to the frame of a vehicle for selectively providing additional flotation for the vehicle. A pair of frame brackets are secured to the frame members of the vehicle and have horizontally disposed mounting plate portions adjacent the lower ends thereof which have transversely extending bolt slots formed therein. First and second trailing arm mounting brackets are positioned below the first and second frame brackets, respectively, and have bolt openings provided in an upper mounting plate portion thereon to enable bolts to adjustably secure the trailing arm mounting brackets to the frame brackets. The lift axle suspension system is operatively connected to the mounting brackets. The connection of the first and second mounting brackets with respect to the first and second frame brackets permits the lift axle assembly to be mounted on frame members having varying distances therebetween and having varying frame thicknesses.

US 6880839 A discloses a parallelogram lift axle suspension system includes an in-line lift bellows located between and vertically aligned with a pair of upper and lower control arms so as to provide bi-directional expansion and contraction of the lift bellows for raising and lowering the suspension while increasing the space available between the longitudinal frame rails enabling use of the suspension in certain vehicles by avoiding interference with other vehicle components of the vehicle located in this space.

DISADVANTAGES WITH THE PRIOR ART

A major limiting factor in the conventional self-steer lift axle suspension system is that the conventional control arms must account for bending, buckling and torsion.

The prior art documents cited above involve lift-bellow internally fitted with rebound stopper. These also require an additional rebound travel arresting mechanism in the form of rebound strap/belt is.

Above prior arts do not disclose external rebound stopper to control rebound motion/travel of the truck’s lift axle. The main disadvantages with the conventional lift axle suspension systems discussed above, are as summarized below:

• Failure of the rubber bump stops inside the lift bellow.

• Permanent set of the rubber bump stops inside the lift bellow.

• Dislodgement of the rubber bump stops inside lift bellow.

• Above failures not identifiable from outside, since rubber membrane is opaque.

• Limited life of the rebound strap due to failures of fibers/stitches and environmental effects.

• Flexible rebound strap forms a slack/loop, while axle is in a lifted condition. Thus, interference with adjoining parts is critical from packaging aspects.

• Rebound strap length increases over time and loses control of the rebounding motion.

• Flexible rebound strap does not steadfastly control the rebounding motion.

Therefore, to overcome these problems and to enhance the performance of the self-steer lift axle suspension system, there is a need to develop an improved lift axle suspension system for rebound control therein.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a suspension system for efficiently controlling the rebound motion of lift axles in trucks.

Another object of the present invention is to provide a suspension system with the rebound motion control of lift axles, which prevents any damage to the internal rubber bump stoppers.

Still another object of the present invention is to provide a suspension system with the rebound motion control of lift axles, which prevents any damage to the rubber lift-bellow membranes.

Yet another object of the present invention is to provide a suspension system with the rebound motion control of lift axles, which prevents any leakage from the lift-bellows.
A further object of the present invention is to provide a suspension system with the rebound motion control of lift axles in trucks, which properly maintains the height of the lift-bellows within permissible limits.

A still further object of the present invention is to provide a suspension system with the rebound motion control of lift axles to prevent main air spring failure.
A yet further object of the present invention is to provide a suspension system with the rebound motion control of lift axles in trucks, which avoids uncontrolled rebound due to increased length of the rebound strap, causing interference with adjoining components.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a system for truck’s lift axle suspension configured with a rebound control mechanism, wherein said system is operated by controlling displacement of the suspension arms and by controlling rebound by means of a rebound stopper disposed external to the lift bellow/air spring assembly and an external bump stopper plate fitted on the main bellow/ air spring assembly thereof.

Typically, the rebound control mechanism comprises:

• a pair of main bellows assembly fitted under the truck chassis;

• a pair of hangers fitted under the truck chassis;

• a respective lift bellow assembly fitted on each hanger;

• a cross-channel laterally fitted between said pair of hangers;

• a respective link assembly fitted on said hangers and disposed between said hanger and respective main bellows assembly;

wherein said link assemblies are configured to control the displacement of the suspension arms by controlling the rebound of the truck’s suspension system by means of the rebound stopper disposed external to said lift bellows or lift air springs and the external bump stopper plate fitted on said main bellows assembly.

Typically, the lift bellow assembly comprises a lift bellow laterally mounted on a respective hanger and each pair of said bellows face each other.

Typically, each of said main bellow assembly is mounted between a respective lower beam assembly and top mounting bracket; a respective damper attached to said lower beam assembly.

Typically, the link assembly comprises an upper link and a lower link mounted substantially parallel to each other between said hanger and said lower beam assembly and fitted between a respective link arm bush therefor and wear pad.

Typically, a respective external rebound stopper is fitted top of said upper link, said external rebound stopper preferably made of rubber, more preferably polyurethane.

Typically, a respective external bump stopper plate is fitted on each lower beam assembly; said bump stopper plates of each pair of main bellow assembly facing each other.

Typically, the external rebound stopper fitted external to said lift bellows with a gap provided between said upper and lower links in the ride condition of said lift axle suspension.

Typically, an external rebound stopper is fitted with said gap also between said external bump plate and an extended bracket of said lower beam assembly fitted to said lower link assembly in the ride condition of said lift axle suspension.

Typically, the gap closes or becomes zero in the rebound condition of said lift axle suspension to restrict the bump travel in said suspension assembly.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings.

Figure 1a shows the conventional lift axle suspension system using a rebound strap during the ride condition.

Figure 1b shows the conventional lift axle suspension system using a rebound strap with the internal bump stopper during the lift condition.

Figure 1c shows the conventional lift axle suspension system using a rebound strap during the rebound condition re-inflated air-spring.

Figure 2a shows the side view of a typical double convoluted air spring for the lift axle suspension system.

Figure 2b shows a perspective view of a truck lift axle suspension system configured in accordance with the present invention, for controlling the rebound thereof by controlling the displacement of the suspension arms.

Figure 2c shows the side view of the lift axle suspension system of Figure 2b in a ride condition thereof.

Figure 2d shows the side view of the lift axle suspension system of Figure 2b in a rebound condition thereof.

DETALED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, the truck lift axle suspension system configured for controlling rebound in accordance with the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1a shows the conventional lift axle suspension system 50 using rebound strap 52, air-spring 54 and lift air spring 56 during the ride condition.

Figure 1b shows the conventional lift axle suspension system 50 using a rebound strap 52 with the internal bump stopper 58 during the lift condition, in which air spring 54 is deflated.

Figure 1c shows the conventional lift axle suspension system 50 using rebound strap 52 and lift air spring 56 during the rebound condition with re-inflated air-spring 54.

Figure 2a shows the side view of the arrangement of a typical double convoluted air spring for the lift axle suspension system. It includes twin air-bellows 62, 64 with a girdle hoop 66 disposed on the neck 68 formed therebetween, bumper 70, upper and lower bead plates 72, 74, a blind nut 76 and an air fitting 78.

Figure 2b shows a perspective view of a truck lift axle suspension system 150 configured in accordance with the present invention with a rebound control mechanism 100 for controlling the rebound of the lift axle suspension system 150 by controlling the displacement of the suspension arms. The suspension system 150 includes a cross-channel 102, an upper link 104, a bracket/plate 105 extended from the upper link 104, a lower link 106, link arm bushes 108, lower beam assembly 110, damper 112, an external rebound stopper 114, external bump-stopper 116, a pair of main air springs (bellows) 120, a pair of air bellow acting as lift air springs (lift bellows) 122, a pair of air bellow top mounting brackets 126, wear pads 130 and hanger 132. Here, the external rebound stopper 114 is located on a bracket/plate 105 extended from the upper link 104.

Figure 2c shows the side view of the lift axle suspension system 150 of Fig. 2b in a ride condition thereof. There is a gap G provided between the rebound stopper 114 assembled on top of the upper link 104 and stopper plate or external bump plate 116 (Figure 2b) provided on the lower link 106.

Figure 2d shows the side view of the lift axle suspension system 150 of Fig. 2b in a rebound condition thereof. When axle travels in rebound direction, the rebound stopper 114 touches the extended bracket/plate 105 provided between upper link 104 and lower link 106. In axle’s rebound condition, the gap G between the rebound stopper 114 and the external bump plate 116 closes (G=0) and the external rebound stopper 114 touches the extended bracket/plate 105. When the external rebound stopper 114 comes in contact with the extended bracket 105, the rebound motion of the axle is stopped effectively. Since this rebound stopper 114 is located external to the lift-bellow, it is referred to as external rebound stopper 114. This external rebound stopper 114 is an independent component installed external to the lift bellows 122 to work more efficiently than the conventional internal rebound/bump stopper 58 present inside the lift-bellows/air spring 54 of Fig. 1b.

DESCRIPTION OF THE INVENTION

In accordance with the present invention, the upper and lower control arms are manufactured by using casting process. These upper and lower control arms act as a couple in lifting the axle assembly, while the rebound belt assemblies and jounce bump stoppers are employed in protecting the air springs and the upper control arm from failure.

The lift axle involves an air-suspension mechanism which lifts the axle, when not in use.

When the truck is unladen, the lift axle is lifted-off the ground to avoid the tyres making any contact with the ground. This lifting of the axle decreases tyre wear and tear and thus increases the service life thereof. It also enhances the truck’s fuel economy due to reduced tyre rolling resistance.
In the conventional arrangements (Fig. 1b), the axle articulations are limited by providing internal bump stoppers 58 of rubber built into the lift air springs 56. These internal bump stoppers 58 present in the main air spring 54 (main bellow) limit the upward movement of the axle. The rebound travel is also limited by the rubber bump stoppers 58 present inside the lifting air spring 56 (lift-bellow).

Therefore, an external bump stopper 116 (Fig. 2b) is devised in accordance with the present invention, which fully controls the rebound of the axle. The bump travel is also restricted by this external bump stopper 116.

WORKING OF THE INVENTION

As the external rebound stopper 114 is compressed, the rebound control is positive, because after rubber failure, the rebound is stopped, and a metal to metal contact is achieved. Whereas, in the conventional rebound strap arrangement, no positive stopping was possible after the failure of rebound strap 52, which experienced tensile loads, causing damage to it.

However, the external rebound stopper 114 configured according to the present invention experiences compressive loading, which is substantially less damaging than the tensile loading experienced in the conventional arrangement of rebound strap 52. Thus, the external rebound stopper 114 provides improved life and facilitates in a better rebound control with a longer life of the over rebound stopper mechanism/arrangement.

Moreover, the conventional rebound strap 52 is disposed between the chassis and the lower beam assembly, whereas the external rebound stopper 114 of the present invention is located between the upper and lower links.

This also enables a compacter packaging. Therefore, the clearance is easy to package even in front of a live axle. Whereas, the clearance of the conventional rebound strap 52 with the propeller shaft was very critical to package effectively.
TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The lift axle suspension system configured in accordance with the present invention to effectively control the rebound travel by controlling the displacement of the suspension arms has the following technical and economic advantages:

- Wear and tear of the rebound stopper can be easily checked as it is located externally.

- Failure of this rebound stopper can be easily detected, unlike the conventional internal rebound stopper present inside the lift-bellow.

- Since this rebound stopper is a separate part fitted externally, there is no immediate effect on the lift air-spring due to any damage to the external rebound stopper.

- Accessibility and serviceability are improved, as there is no need to remove lift-bellow for replacing this external rebound stopper, because this can be accessed from outside the truck, thus facilitates its operation.

- External rebound stopper is located between the upper and lower links with minimum lateral offsets, thus extra bending moments are avoided on the upper and lower link pivots.

- External rebound stopper increases main air-spring and lift air-spring’s life.

- Offers reduced maintenance/ spare cost of tackling lift axle air spring failures.

- Rubber/Polyurethane is used as rebound control device, which work best under compression (compared to extension of the conventional rebound strap/belt working under tension).

- Rebound motion/travel control of the axle is under control even after failure or wear and tear of rubber, as the metal plates can still control rebound motion of the axle.

- Omission of the conventional internal bump stopper disposed inside the lift-bellow due to the use of external rebound stopper, thus the mechanism is durable and flexible and performance deterioration over time is avoided.
- Use of widely available materials like Polyurethane/Rubber (as compared to conventional proprietary rebound strap material, which is quite costly).

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. The description provided herein is purely by way of example and illustration.

The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, the skilled person will recognize that the embodiments herein can be practiced with modification within the spirit and scope of embodiments described herein.

Therefore, the skilled person can easily make innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies, assemblies and in terms of the size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention. ,CLAIMS:We claim:

1. A system for truck’s lift axle suspension (150) configured with a rebound control mechanism (100), wherein said system is operated by controlling displacement of the suspension arms and by controlling rebound by means of a rebound stopper disposed external to the lift bellow/air spring assembly and an external bump stopper plate fitted on the main bellow/ air spring assembly thereof.

2. System (150) as claimed in claim 1, wherein said rebound control mechanism (100) comprises:

• a pair of main bellows assembly fitted under the truck chassis;

• a pair of hangers (132) fitted under the truck chassis;

• a respective lift bellow assembly fitted on each hanger;

• a cross-channel (102) laterally fitted between said pair of hangers;

• a respective link assembly fitted on said hangers and disposed between said hanger and respective main bellows assembly;

wherein said link assemblies are configured to control the displacement of the suspension arms by controlling the rebound of the truck’s suspension system by means of the rebound stopper disposed external to said lift bellows or lift air springs and the external bump stopper plate fitted on said main bellows assembly.

3. System (150) as claimed in claim 2, wherein said lift bellow assembly comprises a lift bellow (122) laterally mounted on a respective hanger (132) and each pair of said bellows (122) face each other.

4. System (150) as claimed in claim 2, wherein each of said main bellow assembly is mounted between a respective lower beam assembly (110) and top mounting bracket (126); a respective damper attached to said lower beam assembly (110).

5. System (150) as claimed in claim 4, wherein said link assembly comprises an upper link (104) and a lower link (106) mounted substantially parallel to each other between said hanger and said lower beam assembly (110) and fitted between a respective link arm bush therefor and wear pad.

6. System (150) as claimed in claim 5, wherein a respective external rebound stopper (114) is fitted top of said upper link (104), said external rebound stopper (114) preferably made of rubber, more preferably polyurethane.

7. System (150) as claimed in claim 6, wherein a respective external bump stopper plate (116) is fitted on each lower beam assembly (110); said bump stopper plates (116) of each pair of main bellow assembly facing each other.

8. System (150) as claimed in claim 7, wherein said external rebound stopper (114) is fitted external to said lift bellows (122) with a gap (G) provided between said upper and lower links (104, 106).

9. System (150) as claimed in claim 8, wherein said wherein an external rebound stopper is fitted with said gap (G) also between said external bump plate (116) and an extended bracket of said lower beam assembly (110) fitted to said lower link assembly in the ride condition of said lift axle suspension (150).

10. System (150) as claimed in claim 9, wherein said gap (G) closes or becomes zero in the rebound condition of said lift axle suspension (150) to restrict the bump travel in said suspension assembly.

Digitally Signed.

Dated: this day of 31st AUGUST 2017. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT