DESC:TECHNICAL FIELD OF THE INVENTION

[001] The subject matter of the present invention, in general, relates to a vehicle suspension system, and more particularly, pertains to a leaf spring suspension for self-steer lift axle system that enables lifting mechanism and provide robustness.

BACKGROUND OF THE INVENTION

[002] Suspension refers to the use of front and rear springs to suspend a vehicle’s frame, body, engine and power train above the wheels. In particular, it is the system of tires, tire air, springs, shock absorbers and linkages that connects a vehicle to its wheels and allows relative motion between the two. They support both road holding/handling and ride quality that are at odds with each other. It provides vertical compliance so the wheels can follow the uneven road, isolating the chassis from roughness in the road. It also maintains the wheels in the proper steer and camber attitudes to the road surface. It also protects the vehicle itself and any cargo or luggage from damage and wear. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the road or ground forces acting on the vehicle do so through the contact patches of the tires.

[003] Axle suspension systems may be classified as having two general forms. A first form of axle suspension systems does not require auxiliary roll stabilizers because it utilizes leaf springs, coil springs and/or air springs which have a high vertical spring rate. The high vertical spring rate, however, provides for relatively uncomfortable riding conditions. A second form of axle suspension systems utilizes leaf springs, coil springs and/or air springs which have a soft vertical spring rate. Although this second form of axle suspension systems provides for relatively comfortable riding conditions, it generally lacks sufficient roll stability. The use of auxiliary roll stabilizers in such systems is often necessary, which increases the total cost and weight of these suspension systems.

[004] A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a laminated or carriage spring, and sometimes referred to as a semi-elliptical spring or cart spring, it is one of the oldest forms of springing, dating back to medieval times.

[005] The 8x2 and 10x2 rigid trucks in India conventionally uses a pneumatic or air suspension for the self-steer axle with a provision to lift the axle. The typical design comprises of a set of air bellows that act as suspension and a set of air bellows with linkages that is used to lift the axle. There are different configurations of the linkage mechanism but they all serve the same purpose of lifting the axle. The air bellows are generally mounted below the chassis and are exposed to environment. Hence these are susceptible to physical damages. Also the system requires a dedicated pneumatic circuit for air suspension and lifting. The complex pneumatic circuit is prone to frequent air leaks due to the number of joints in the system. Typical air suspensions also require a higher capacity air compressor that needs to run and continuously maintain the air pressure under all operating conditions of the suspension.

[006] Typically, self-steer axle is used at following positions of the vehicle-

8x2 10x2
Position on Vehicle Self-steer Pusher axle, 2nd axle Self-steer Pusher axle, 3rd axle
Or Self-steer last axle, 5th axle

[007] In India, all other axles of the 8x2 and 10x2 vehicles are fitted with mechanical leaf spring suspension while the self-steer axle is fitted with air suspension. Due to this mixed configuration, there is little or no benefit from air suspension with respect to ride comfort. Some of the current suppliers of self-steer lift axle systems in India use air suspension based designs susceptible to physical damages.

[008] Hence, there is a need for suspension designs and method pertaining to self-steer axle which is advantageous to be used on spaces available on 8x2 and 10x2 vehicle configurations. Further, for design of leaf springs, a number of specific features are desirable which may include but not limited to, advantages of robustness, unique design enabling lifting of the axle and suspension system that still functions in case of pneumatic system failure. Considering the basic requirements, some design of self-steer lift axle suspension systems is disclosed in the prior art, however they don’t provide advantages of robustness and ability to work independent of suspension and lifting in case of pneumatic system failure.

[009] For some existing suspension devices and methods pertaining to self-steer axles, reference is made to US 8616565 B1, which discloses a vehicle suspension system including a steering knuckle assembly with steer return device, and a biasing device comprising of an elastomeric toroid which is deformed by the steer return device. This document generally relates to vehicle suspension systems providing a self-steer lift axle suspension system having a suspension system which is liftable relative to a frame, so that the tires of the suspension system are out of contact with a road surface.

[0010] Reference is further made US 8029008 B2, which discloses a vehicle leaf spring suspension having a low spring rate wherein said suspension having an axle seat secured to a vehicle axle. The leaf spring clamped at its spring seat area to the axle seat at the clamp group mounting surface of the axle seat asymmetrically positioned with respect to the vehicle axle centerline thereby reducing the leaf spring stress for a given amount of axle travel.

[0011] Reference is also made to US 2004/0188971 A1, which relates to a self-steering axle assembly which can be supported to a vehicle including an axle such that the suspension and steering system is interposed between the axle and the vehicle are rotatable as a unit around a motion axis of the axle. A pivotally supported member such as a platform can tilt to rotate the suspension and steering system. A mover such as a piston and cylinder assembly is connected to determine the angular displacement of the platform with respect to the vehicle. When the actuator is in a first position, caster is positive and when the platform is in a second position, caster is negative enabling the vehicle to self-steer in the reverse mode.

[0012] Further, reference is made to US 5364113 A, which relates to a self-steering axle systems for motor coaches and similar commercial vehicles having a truss which hingedly supports an axle beam for pivotal movement between a normal positive caster angle and a negative caster angle when the vehicle is driven in reverse. The system includes a caster lock for rendering the axle non-steerable in the event of system failure or above predetermined operational speeds.

[0013] Further, reference is also made to DE 3928844 A1, which discloses a leaf spring, supporting a vehicle fixed axle having a main leaf with one end rolled upwards to form a mounting loop and a further leaf extending beneath the loop supporting the main leaf. Both the leaves are kinked at their end sections to lower the loop axis w.r.t the upper flat surface of the main leaf. This document teaches a lower leaf spring mounting point which improves the vehicle understeer.

[0014] Further, reference is made to US 6293570 B1, which relates to an improved steerable axle suspension system for vehicles, providing improved mechanism whereby the caster angle of a wheeled axle may be adjusted to allow for steerability in either forward or reverse direction of travel.

[0015] Further reference is also made to US 5018756 A, which discloses a suspension system incorporating upper and lower torque rods pivotally connected between a hanger and an axle seat wherein the upper part is preferably a hydraulic cylinder and piston assembly, the length of which is adjustable between extended and retracted conditions. In extended condition, the upper torque rod pivots the axle to a forward pitch at which it is self-steering when the vehicle is driven forward.

[0016] Further reference is also made to non-patent literature available at the link, http://de.technolab.org/en/leaf-spring-pc-with-self-steering-axle entitled “Leaf Spring with self-steering axle”. The reference suggests that when the wheel to the outside of the turn is compressed, the nature of the axle suspension means that the when moves forward and the axle swings slightly inwards.

[0017] In nearly all prior art as discussed hereinabove, and modern constructing vehicle suspension system, provide advances by means of reducing weight, manufacturing cost, inventory and maintenance requirement for the suspension system. However, none of them provides the advantages of robustness, provision to enable lifting of self-steer axle for the axle position particular to 8x2 and 10x2 configured trucks/trailers and also provides for relatively comfortable riding conditions for the vehicle.

[0018] Accordingly, there exists a dire need to provide a leaf spring design for self-steering axle suspension system with improved robustness, and that enables lifting for 8x2 and 10x2 trucks/trailers.

SUMMARY OF THE INVENTION

[0019] The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

[0020] An object of the present invention is to provide a unique leaf spring design by usage of a new design of leaf spring suspension for self-steer lift axles which enables lifting mechanisms for 8x2 and 10x2 trucks/trailers.

[0021] Another object of the present invention is to provide a suspension design that use full slipper springs or semi slipper springs for self-steer axle for a smooth and comfortable ride

[0022] Yet another object of the present invention is to provide a design comprising of leaf springs as mentioned above that provide suspension characteristics and enables independent lifting of axle wherein the axle can be lifted vertically with a lift device.

[0023] Yet another object of the present invention to provide a unique leaf spring design wherein the self-steer axle is used at the axle positions which is not susceptible to physical damages and which provides ride comfort.

[0024] Still another object of the present invention is to provide a leaf spring design for self-steering axle system where the lift mechanism works independent of suspension.

[0025] In one aspect, there is provided a vehicle suspension system comprising:
a suspension mechanism provided with a mechanical full/semi slipper leaf spring means to enable lifting mechanism of an axle and/or suspension mechanism; and/or
an independent lift device, wherein:
said lift device operatively situated on a chassis frame, adapted to enable lifting of said axle vertically;
characterized in that,
said semi-slipper leaf spring means is provided with an arrangement of pivoted end with rubber or metallic bushes at one end and a sliding contact at the other end, that enables lifting of said axle due to said sliding contact at said other end of said semi-slipper leaf spring means; and
said full slipper leaf springs provided with both ends having sliding or rolling contacts to enable lifting of said axle, and a torque rod connected with said axle beam between mounting brackets, provides longitudinal stability.

[0026] To overcome the drawbacks in the conventional systems and to achieve the desired objectives, the present invention discloses a leaf spring design for self-steering axle system where the lift mechanism works independent of suspension and also the leaf spring and the arrangement are positioned on the axle such that the self-steering of the tyres is accommodated.

[0027] Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0028] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0029] Figure 1(a) & (b), illustrates vehicle suspension system for self –steer axle of 8x2 and 10x2 commercial trucks, according to one implementation of the present invention.

[0030] Figure 2 illustrates the components of mechanical leaf spring suspension for self –steer axle of 8x2 and 10x2 commercial trucks, wherein the suspension is with semi- slipper leaf springs according to one implementation of the present invention.

[0031] Figures 3 illustrates the components of mechanical leaf spring suspension for self –steer axle of 8x2 and 10x2 commercial trucks, wherein the suspension is with full slipper leaf springs according to one implementation of the present invention.

[0032] Figure 4 illustrates an arrangement for semi slipper leaf spring with rubber or metallic bushes for the pivoted end of the leaf spring, according to one implementation of the present invention.

[0033] Figure 5 illustrates an arrangement for full slipper leaf spring with both ends having sliding or rolling contact and with a torque rod or a radius rod connected with axle beam, according to one implementation of the present invention.

[0034] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0035] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0036] Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0037] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

[0038] It is to be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.

[0039] By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0040] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0041] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or component but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0042] The present invention relates to improvements in axle suspensions for trucks and trailers and in certain components of such systems. More particularly, it relates to self-steering axle suspensions wherein a uniquely designed leaf spring is included as a component of the suspension. Thus, the subject invention lies in providing a mechanical leaf spring suspension system for self-steer lift axle of a vehicle.

[0043] The present invention pertains to a mechanical leaf spring suspension for self-steer lift axle system. The self-steer lift axle suspension system comprises leaf springs that provide not only the suspension characteristics but also enables lifting of axle. The axle can be lifted vertically with a lift device which is centrally located on the chassis.

[0044] In one implementation, there is provided a new design of leaf spring suspension for self-steer axles for 8x2 and 10x2 commercial trucks which comprises of leaf springs that provide both suspension characteristics and enable lifting of axle wherein axle can be lifted vertically with a lift device which may be centrally located between the chassis.

[0045] In one implementation, reference is made to figures 1(a) & (b) there is provided a self-steer axle of an 8x2 and 10x2 commercial trucks comprising of a lift device that may be located centrally between the chassis to enable the axle to be lifted vertically. The Figures illustrates a lift device (1) that is located centrally between the chassis frame to enable the axle to be lifted vertically, a suspension with semi-slipper leaf springs (2) with an arrangement for pivoted rubber or metallic bushes at one end and a sliding contact at the other end that enables lifting of the axle, and a suspension mounting comprising two mounting brackets (3) housed on the arm ends of the leaf spring that still function in case of pneumatic system failure.

[0046] In one implementation, reference is made to figure 2 which illustrates the vehicle suspension system with semi-slipper leaf springs mechanism. In the arrangement, semi-slipper leaf spring means is provided with an arrangement of pivoted end with rubber or metallic bushes at one end (4) and a slipper end with a sliding contact (5) at the other end, that enables lifting of the axle.

[0047] In one implementation, reference is made to figure 3 with full slipper leaf springs that also enables lifting of axle; and a suspension mounting brackets that houses the leaf springs and enables lifting of axle. There includes a lift device (1) that is located centrally between the chassis frame to enable the axle to be lifted vertically, a suspension with full slipper leaf springs (2) with both ends having sliding contact (5) with an arrangement for a torque rod or a radius rod (7) connected with axle beam and the mounting that provides the longitudinal stability and also enables lifting of the axle, and a suspension mounting comprising two mounting brackets (3) housed on the arm ends of the leaf spring that still function in case of pneumatic system failure.

[0048] In one implementation, reference is made to figure 4, illustrates an enlarged view of the arrangement for semi slipper leaf spring with rubber or metallic bushes for the pivoted end of the leaf spring. This pivoted arrangement allows the suspension to take longitudinal load and still enable lifting of the axle due to the slipper end on the other side of the leaf spring. The rubber or metal bush helps to provide the compliance required during maneuvering.

[0049] In one implementation, reference is made to figure 5, illustrates an enlarged view of the arrangement for full slipper leaf spring with both ends having sliding or rolling contact and with a torque rod or a radius rod connected with axle beam. The full slipper leaf springs with both ends having sliding or rolling contact allows lifting of axle while the torque rod or radius rod connected between the mounting bracket and the axle takes care of the longitudinal load. The rubber bushes in the torque rod or radius rod provide compliance required for lifting the axle.

[0050] A leaf spring takes the form of a slender arc-shaped length of spring steel of rectangular cross-section. This arc shaped spring has a contoured central body with a pair of substantially symmetrical arms that end with cylindrical protrudes. In the most common configuration, the center of the arc provides location for the axle, while tie holes are provided at either end for attaching to the vehicle body. For very heavy vehicles, a leaf spring can be made from several leaves stacked on top of each other in several layers, often with progressively shorter leaves. Leaf springs can serve locating and to some extent damping as well as springing functions. While the interleaf friction provides a damping action, it is not well controlled and results in stiction (the friction which tends to prevent stationary surfaces from being set in motion) in the motion of the suspension.

[0051] The suspension with full/semi-slipper leaf spring for a self-steer lift axle enables lifting of the axle. The suspension brackets not only structurally transfer the loads; they also enable lifting of the axle. The leaf spring provides the requisite robustness while also enabling lifting of the axle thereby providing a robust suspension design that is independent of lift mechanism. Significantly, the suspension continues to function even in case of a pneumatic system failure. Moreover, the overall design of the leaf spring suspension is such that it is suitable for the space available for self-steer axles on 8x2 and 10x2 vehicle configurations.

[0052] The ends of the leaf spring play an important role that attaches between the leaf spring and the vehicle frame. It allows for the leaf spring to work through length changes during suspension articulation. The leaf packs, or leaf springs, position and centre the axle under the vehicle. They also support the vehicle's weight, since these are a primary component of the suspension system. As a leaf spring flexes up or down, its length changes depending on the sliding contacts provided at each or one end. The semi-slipper leaf spring has one end pivoted with a rubber or metallic bush that takes the longitudinal forces during braking or acceleration conditions along with the vertical load as the sliding end allows the leaf spring to flex.

[0053] As a full slipper leaf spring compresses (upward wheel travel), it essentially becomes longer as the spring arc flattens out. As the leaf spring relaxes (downward wheel travel), it becomes shorter as the spring arc returns into its resting state. The torque rod allows this movement to happen, and increasing or decreasing its length will greatly affect the springs total movement. The full slipper leaf spring can structurally take vertical loads as it flexes. The torque rod provides the longitudinal stability required during braking or acceleration conditions.

[0054] Some of the noteworthy features of the present invention, are as follows:

a) In the present invention, suspension with semi slipper leaf spring with rubber or metallic pivots or full slipper suspension with sliding ends and a torque rod attached between axle and bracket is used for self-steer lift axle which enables lifting of axle.
b) In the present invention, there is provided suspension brackets that not only structurally transfers the loads but also enables lifting of axle.

[0055] Some of the non-limiting advantages of the present invention are as follows:

c) The leaf spring design of the present invention provides robustness.
d) The other attractive characteristics is the leaf spring design of self-steer lift axle which enables lifting of the axle.
e) The suspension is designed to be independent of lift mechanism whilst providing suspension characteristics.
f) The suspension still functions even in case of pneumatic system failure.
g) The present inventions packages suitable for self-steering of the axles under various articulated conditions.
h) The present invention packages suitable for space available for self-steer axles on 8x2 and 10x2 vehicle configurations.

[0056] Although a simple, economic, robust, compact and capable industrial application of design of a leaf spring for a self-steering axle system where the lift mechanism works independent of suspension has been described in language specific to the process steps indicated hereinabove, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or components or devices or methods described therein. Rather, the specific features are disclosed as examples of implementations of a self-steer lift axle suspension system.
,CLAIMS:1. A vehicle suspension system comprising:
a suspension mechanism provided with a mechanical full/semi slipper leaf spring means to enable lifting mechanism of an axle and/or suspension mechanism; and/or
an independent lift device, wherein:
said lift device operatively situated on a chassis frame, adapted to enable lifting of said axle vertically;
characterized in that,
said semi-slipper leaf spring means is provided with an arrangement of pivoted end with rubber or metallic bushes at one end and a sliding contact at the other end, that enables lifting of said axle due to said sliding contact at said other end of said semi-slipper leaf spring means; and
said full slipper leaf springs provided with both ends having sliding or rolling contacts to enable lifting of said axle, and a torque rod connected with said axle beam between mounting brackets, provides longitudinal stability.
2. The vehicle suspension system as claimed in claim 1, comprises a suspension mounting with at least two suspension brackets housed on arm ends of said full/semi leaf spring means.
3. The vehicle suspension system as claimed in claim 1-2 is adapted for self –steer axle of 8x2 and 10x2 commercial vehicle configuration.