TECHNICAL FIELD

Present disclosure generally relates to automobiles. Particularly, but not exclusively, the present disclosure relates to a tandem axle leaf spring suspension unit for a vehicle. Further, embodiments of the disclosure disclose a spring assembly for the tandem axle suspension of the vehicle.

BACKGROUND OF THE DISCLOSURE

Suspension is one of the most important systems of a vehicle. It is a flexible system that connects wheels with a main frame or chassis rail of the vehicle and provides stability to the vehicle in dynamic conditions like high speed, sharp turns and braking. The suspension system is a combination of various components like knuckle or upright arms or linkages and a shock absorber which are operatively coupled together to enable the relative motion between the vehicle wheels and the mainframe. The shock absorbers along with a spring protect the main frame from shocks produced due to rough road conditions by absorbing and releasing energy and makes the ride smooth.

Suspension is mainly classified into two types i.e., dependent suspension systems and independent suspension systems. In a dependent suspension system, all the pairs of wheels are connected with a solid axle and the bump in any wheel causes the lift in all the other wheels. In independent suspension systems, all the wheels are connected independently with the frame and there is no relative motion between the left (LH) and right (RH) side wheels. The suspension systems include flexible mechanical components which are used to absorb shocks produced by the road conditions and is placed between the linkages (wishbone, solid axle, multi-links, bell cranks) and the main frame such that the road shocks are minimized before transmitting to the main frame of a vehicle. These components are mainly known as shock absorbers or springs. For heavy duty trucks, leaf springs are used in the suspension. The main advantage of leaf springs is that it acts as a structural member and can withstand higher vertical loads, lateral loads, driving and braking torques. Further, most of the heavy trucks which are equipped with tandem axles which use a leaf spring suspension unit and are referred to as tandem axle suspension systems. The tandem axle suspension system is connected to two rear axles of a truck to support weight of the truck and prevents the body from road shocks due to bounce, pitch, roll or sway.

Conventionally, there are two main types of leaf springs such as multi-leaf spring and parabolic or tapered leaf springs. In the rear suspension systems of heavy-duty trucks, the springs are required to carry higher loads. The multi-leaf springs are a stack of leaves in which each leaf has a uniform rectangular cross-section throughout its length and are tightly connected to each other without any gap between the leaves. During operation, the leaves rub against each other and provide a frictional damping in the system to damp out the vibrations without needing any additional dampers. However, with the increased load carrying capacity and in turn higher stiffness requirement, the weight of the multi- leaf spring increases significantly. This in turn increases the kerb weight of the vehicle and reduces the payload capacity. On the other hand, a parabolic spring is a leaf, or a set of leaves that are tapered along the length in a parabolic way rather than a linear way. They are thick in the middle and taper in a parabolic manner towards the ends. Further, there is a gap between parabolic leaves, which reduces the friction between the leaves. The parabolic spring contain lesser no of leaves as compared to a conventional multi-leaf spring, but can carry equal loads. For the same stiffness, the weight of the parabolic spring assembly is approximately 30% lesser as compared to multi-leaf spring assembly. This reduces the kerb weight of the vehicle thus increasing the payload capacity. Due to absence of interleaf friction in a parabolic spring (due to gap between each spring), there is no natural damping, which can make the system unstable. Hence, it is required to introduce controlled damping in the system by using dampers. Thus, for each parabolic spring used in tandem axle suspension system, a damper is necessary. This increases the overall cost of the system.

The present disclosure is directed to overcome one or more limitations stated above or other such limitations associated with the prior art.

SUMMARY OF THE DISCLOSURE

One or more shortcomings of conventional multi-leaf spring are overcome, and additional advantages are provided through a spring assembly as claimed in the present disclosure. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered as a part of the claimed disclosure. In one non-limiting embodiment of the disclosure, a suspension assembly for a vehicle is disclosed. The spring assembly comprises a first stack of leaves connectable to a chassis rail of the vehicle. Each leaf of the first stack of leaves is defined with a thickness gradually tapering towards ends from a central portion of each leaf spring of the first stack of leaves. Further, a second stack of leaves is stacked with the first stack of leaves. Each leaf of the second stack of leaves is defined with a uniform cross section. A bottom surface of the first stack of leaves is configured to overlap with an upper surface of the second stack of leaves to form a unitary leaf spring structure.

In an embodiment of the disclosure, first leaf of the first stack of leaves is defined with an attachment eye at either ends.

In an embodiment of the disclosure, the first stack of leaves and the second stack of leaves are connectable to an axle of the vehicle about a vertical axis A-A of the unitary leaf spring structure through a saddle, u bolt and nut.

In an embodiment of the disclosure, the bottom surface of a last leaf of the first stack of leaves and the upper surface of the top leaf of the second stack of leaves are defined with a complementing profile.

In an embodiment of the disclosure first stack of leaves are parabolic spring type and the second stack of leaves are of a multi-leaf type.

In an embodiment of the disclosure, the multi-leaf spring is defined with a plurality of flat plates stacked above one above one other such that, a length of each flat plate of the plurality of flat plates gradually reduces from a top plate towards a bottom plate.

In an embodiment of the disclosure, the first stack of leaves and the second stack of leaves are defined with an aperture to receive a fastener, and wherein the first and second stack of leaves are stacked by passing the fastener through the aperture.

In another non-limiting embodiment of the disclosure, a vehicle is disclosed. The vehicle comprises a frame defined by chassis rails. A first axle and a second axle are mounted on the chassis rail through suspension. A tandem axle leaf spring suspension unit is configured to connect the first axle and the second axle to the chassis rail. The spring assembly comprises a first stack of leaves operatively coupled to the frame of the vehicle. Each leaf of the first stack spring is designed with a thickness gradually tapering towards ends from a central portion of each leaf. A second stack of leaves are operatively coupled to the first stack of spring-assembly. The second stack of spring are proximate to the first axle and the second axle. A bottom surface of the last leaf of the first stack of leaves overlaps with an upper surface of a top leaf of the second stack leaves (2) to form a unitary leaf spring structure.

In an embodiment of the disclosure, the first stack leaves are parabolic springs.

In an embodiment of the disclosure, the second stack leaves (2) are defined with the plurality of flat plates stacked one above one other such that a length of each flat plate of the plurality of flat plates gradually reduces from a top plate towards a bottom plate.

In an embodiment of the disclosure, the top leaf of the first stack of leaves (1) is defined with an attachment eye (4) at both ends to couple to the chassis rail (23).

It is to be understood that the aspects and embodiments of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiments may be combined together to form a further embodiment of the disclosure.

The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become apparent by reference to the drawings and the following detailed description.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS

The novel features and characteristic of the disclosure are set forth in the appended claims. The disclosure itself, however, as well as a mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of embodiments when read in conjunction with the accompanying drawings. One or more embodiments are now described, by way of example only, with reference to the accompanying drawings wherein like reference numerals represent like elements and in which:

Figs, la and lb illustrates a perspective view and a front view of a spring assembly, in accordance with an embodiment of the present disclosure;

Fig. 2a illustrates a perspective view of a first die for shaping a bottom surface of a last leaf of the first stack of leaves in accordance with an embodiment of the present disclosure; and Fig. 2b illustrates a perspective view of a second die for shaping an upper surface of the top leaf of the second stack of leaves in accordance with an embodiment of the present disclosure;

Fig.3 illustrates a schematic view of a tandem leaf spring suspension unit for a vehicle.

The figures depict embodiments of the disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods illustrated herein may be employed without departing from the principles of the disclosure described herein.

DETAILED DESCRIPTION

While the embodiments in the disclosure are subject to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the figure and will be described below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternative falling within the scope of the disclosure.

It is to be noted that a person skilled in the art would be motivated from the present disclosure and modify various features of the method and the system, without departing from the scope of the disclosure. Therefore, such modifications are considered to be part of the disclosure. Accordingly, the drawings show only those specific details that are pertinent to understand the embodiments of the present disclosure, so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skilled in the art having benefit of the description herein. Also, the method of the present disclosure may be employed in variety of vehicles having different specification.

The terms “comprises”, “comprising”, or any other variations thereof used in the disclosure, are intended to cover a non-exclusive inclusions, such that of an assembly and a system that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such an assembly, a system, method, or assembly, or device. In other words, one or more elements in a system or device proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or device. Embodiments of the present disclosure discloses a spring assembly for a vehicle with a first stack of leaves and a second stack of leaves. Leaf springs are used in suspension systems of commercial vehicles such as heavy trucks for withstanding loads and to provide smooth ride. The leaf spring suspension include parabolic springs and multi-leaf springs connected to a chassis rail of the vehicle and supports the axle through saddle u bolt and nut. The parabolic springs have varying thickness towards its ends and are used to withstand heavy loads due to minimal interleaf friction between each leaf spring of the parabolic springs. The multi-leaf springs are flat plates extending longitudinally and are arranged one above the other. All the flat plates are defined with a uniform cross section and are in contact with each other, thus providing natural damping to the suspension system. However, to withstand higher loads the number of leaves or flat plates must be increased which increases overall weight and cost of the suspension system which may lead to decrease the payload capacity of the vehicle.

In view of the above, embodiments of the present disclosure disclose a spring assembly for a vehicle. The spring assembly comprises a first stack of leaves connectable to a chassis rail of the vehicle. Each leaf of the first stack of leaves is designed with a thickness gradually tapering towards both either ends of the first stack of leaves. A second stack leaves are stacked with the first stack leaves, each leaf of the second stack of leaves is defined with a uniform cross section. Further, a bottom surface of a last leaf of first stack of leaves is configured to overlap with an upper surface of the top leaf of second stack of springs-to form a unitary leaf spring structure.

The following paragraphs describe the present disclosure with reference to Figs, la to 3. In the figures, the same element or elements which have similar functions are indicated by the same reference signs.

Figs, la and lb illustrates perspective view and a front view of the spring assembly (100) for a vehicle. The spring assembly (100) among other components include a first stack of leaves (1), a second stack of leaves (2), bushings provided in attachment eye. In accordance with embodiments of the present disclosure, the first stack leaves (1) are parabolic type stacked to form a pack and a second stack of leaves (2) are multi leaf type stacked to form a pack.

The first stack of leaves (1) is formed by stacking a plurality of parabolic springs, one above the other to form a stack. Each leaf spring of the first stack (1) is designed with a thickness in a central portion (3) which reduces gradually towards either ends of each leaf spring. In an embodiment, the thickness in the middle portion (3) of the first stack of leaves (1) is same for each leaf of the first stack of leaves (1) and gradually tapers towards the ends. Such a configuration cannot be considered as a limitation and the thickness may be varied for each leaf based on the requirement. Each leaf of the first stack of leaves (1) is defined with a radius of curvature and are configured to be in contact with each other at either ends of the first stack leaves (1). This contact of the leaf springs at either ends define a space between each leaf spring of the first stack of leaf springs (1). A plurality of liners (5) is provided between each leaf of the first stack of leaves (1) to separate them and contact in parabolic zone. Further, an attachment eye (4) is defined at either ends of an upper most leaf spring of the first stack of leaves (1) to couple the first stack of leaves (1) with a chassis rail (23) of the vehicle. The attachment eye (4) is defined with a loop extending radially inward from either ends of the upper most leaf (1) of the first stack of leaves (1).

Further, the second stack of leaves (2) are defined with a plurality of leaves layered above one another. Each leaf of the second stack of leaves (2) is designed with a uniform thickness and varying length. In an embodiment, the second stack leaves (1) are of multi-leaf type. The second stack leaves (2) are a plurality of flat plates stacked one above one other such that a length of each flat plate of the plurality of flat plates gradually reduces from a top plate (16) towards a bottom plate (18). In an embodiment, each leaf of the second stack of leaves (2) are configured in a semi-elliptical shape. In an embodiment, the second stack of leaf springs (2) are proximate to an axle (22, 24) of the vehicle. An upper surface (8) of a top leaf the second stack of leaves (2) is configured with a similar profile which is complementary to a bottom surface (6) of a last leaf first stack of leaves (1) to overlap with the first stack of leaves (1). A vertical axis A-A is defined at the central portion (3) of the first stack leaves (1) and the second stack leaves (2). An aperture (10) is defined at a central portion (3) of each leaf spring of the first and second stack of leaves (1, 2) along the vertical axis A-A to receive a fastener (12) for securing the first and second stack of leaves (1, 2) and to form a unitary leaf spring structure. In an embodiment, the fastener (12) may be a bolt and nut. However, this cannot be considered as a limitation and any suitable fastening means may be used for the purpose. The unitary leaf spring structure is coupled to the axle (22, 24) at the central portion (3) through a bracket a U- shaped bracket, u bolt and nut (not shown in figures) or any other type of bracket may be used to secure the unitary leaf spring structure to the axle (22, 24). In an embodiment, the first stack leaves (1) are parabolic springs and the second stack of leaves are multi-leaf spring. The parabolic leaves and the multi-leaf leaves are integrated with each other to form a unitary leaf spring.

In an exemplary embodiment, the multi-leaf spring is defined with a plurality of flat plates layered above one another. The plurality of flat plates extends longitudinally in a semi-elliptical shape and a length of each flat plate of the plurality of flat plates reduces sequentially from a top plate towards a bottom plate.

In an embodiment, the number of leaves in the first stack of leaves (1) and the second stack leaves (2) may be selected based on the stiffness requirement of the suspension system of the vehicle.

Referring to Figs. 2a and Fig. 2b, a first die (21) and a second die (21) are disclosed. The first die (21) is used for shaping a bottom surface of the last leaf of the first stack of leaves (1) and the second die (22) is used for shaping the upper surface of the top leaf of the second stack of leaves (2). The die profiles (21, 27) are identical to a surface of the last leaf of the first stack of leaves (1) and to the upper surface of the second stack of leaves (2). The bottommost leaf of the first stack of leaves (1) and the topmost leaf (16) of the second stack of leaves (2) are heated to a recrystallization temperature and then pressed on the die to take the shape of the profile (21). In an embodiment the first stack of leaves (1) and the second stack leaves (2) are heated around 800-900 °C for hot pressing to required shape and profile. In an embodiment, shaping of the bottommost leaf of the first stack of leaves (1) and the topmost leaf (16) of the second stack of leaves (2) may be carried out through cold pressing process to obtain complementary profile on bottom surface (6) and the upper surface (8).

Referring to Fig. 3, which illustrates a tandem leaf spring suspension unit (200) of a vehicle. The vehicle comprises a frame defined by a chassis rail (23). A first axle (22) and a second axle (24) are mounted on the chassis rail (23). The first axle (22) and the second axle (23) are driven in tandem by a vehicle transmission. A tandem leaf spring suspension unit is connected to the first axle (22) and the second axle (24) to the chassis rail (23). The tandem leaf spring suspension unit maintains the relative motion between the first and second axles (22, 24) throughout the travel of the vehicle. The tandem leaf spring suspension unit includes a suspension assembly (100) comprises a first stack of leaves (1) operatively coupled to the chassis rail (23) of the vehicle. In an embodiment, a top leaf is coupled to the chassis rail (23). Each leaf of the first stack of leaves (1) is defined with a thickness gradually tapering towards ends from a central portion (3). A second stack of leaves (2) are operatively coupled to the first stack of leaves (1). The second stack leaves (2) are arranged proximate to the first axle (22) and the second axle (24). A bottom surface (6) of a last leaf-(l) is configured to overlap with an upper surface (8) of a top leaf of the second stack of leaves (2) to form a unitary leaf spring structure. A first unitary leaf spring structure (25) is operatively connected to the first axle (22) and a second unitary leaf spring structure (26) is operatively connected to the second axle (24). The first and second unitary leaf springs (25, 26) are coupled to the chassis rail (23) at a first end (32) and a second end (34) through a bracket (30). The first unitary leaf spring and the second unitary leaf spring (25, 26) are connected to each other through an equalizer arm (28). The equalizer arm (28) is pivotally mounted to the chassis rail (23) through a bracket (30) and is configured to distribute load experienced by the first and second leaf springs (25, 26). In an embodiment the first unitary leaf spring structure (25) and the second unitary leaf spring structure (26) are connected to the equalizer arm (28). The first and second leaf springs (25, 26) are configured to bear the weight of the vehicle or a truck body which is laden on the chassis of the vehicle which in turn are transmitted to the chassis rail (23). In an embodiment, the weight of the vehicle and the vibrations subjected to the first and second axles (22, 24) are supported by the unitary leaf spring-(lOO).

In an embodiment, the loads and stresses induced from the vehicle body and the payload are distributed between the first stack leaves (1) and the second stack of leaf springs (2).

The spring assembly (100) improves load bearing capacity of the vehicle with the use of first stack of leaves (1) along with required-dampening properties by using the second stack of leaves (2).

The weight of the spring assembly (100) is reduced by the integration of the first stack of leaves

(1) with the second stack of leaves (2). Further, the configuration of the second stack of leaves

(2) with uniform cross section provides the interleaf friction and eliminates the requirement of dampers. Thereby overall cost of the spring assembly (100) is reduced.

It is to be understood that a person of ordinary skill in the art may develop a suspension assembly of similar configuration without deviating from the scope of the present disclosure. Such modifications and variations may be made without departing from the scope of the present invention. Therefore, it is intended that the present disclosure covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents .

Equivalents:

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B .” While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.

Referral Numerals: