Claims:

1. An improved slipper suspension system for heavy commercial vehicles comprising
at least one drive axle (15) and at least one non-drive axle (16) configured to be secured on at least one chassis fame (14);
at least one rear forward axle torque rod (3) and at least one rear rear axle torque rod (4) along with the spring eye are configured to position the axles in longitudinal direction;
at least one rear forward hanger bracket (5), at least one rear middle hanger bracket (6) and at least one rear rear hanger bracket (7) configured to be mounted on chassis frame (14) through bolting arrangement;
at least one fulcrum assembly (9) is configured to equalize the loads between two axles by tilting according to the load reaction of each axle within the chassis frame (14);
at least one drive axle spring (1) to secure axle with the chassis frame (14) and
at least one two stage stiffness spring (10a,10b) to secure the non-drive axle (16) to chassis frame (14).

2. The improved slipper suspension system as claimed in claim 1, wherein said non-drive axle (16) is configured with first stage stiffness spring (10a) with lesser stiffness to increase the deflection of the non-drive axle spring (10a) and to reduce the chassis height of non-drive axle (16) to equalize it with the chassis height of the drive axle (15) in vehicle unladen condition by activation of fulcrum (9).

3. The improved slipper suspension system as claimed in claim 1, wherein said first stage stiffness spring (10a) is configured to reduce the chassis height of non-drive axle (16) to equalize it with the chassis height of the drive axle (15) in vehicle unladen condition and to generate an additional load on drive axle (15)

4. The improved slipper suspension system as claimed in claim 1, wherein said first stage stiffness spring (10a) of the non-drive axle (16) is configured to act only in vehicle unladen condition.

5. The improved slipper suspension system as claimed in claim 1, wherein said non-drive axle spring (10a) is configured with the unladen stiffness of 50% of that of the drive axle spring (1) for increasing the load on the drive axle (15) by 20% to provide extra traction for drive axle (15).

6. The improved slipper suspension system as claimed in claim 1, wherein said non-drive axle (16) is configured with second stage stiffness spring (10b) to provide same spring stiffness as of drive axle spring (1) in laden condition.

7. The improved slipper suspension system as claimed in claim 1, wherein said non-drive axle (16) is configured with two stage stiffness spring (10a,10b) to provide higher traction at unladen condition and to equally distribute the load on both drive axle (15) and non-drive axle (16) at vehicle laden condition to prevent overloading of any components like spring, axle, tire, etc.
, Description:FORM 2

THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003

COMPLETE SPECIFICATION
(See Section 10 and Rule 13)

Title of invention:
AN IMPROVED SLIPPER SUSPENSION SYSTEM FOR HEAVY COMMERCIAL VEHICLES

Applicant:
Tata Motors Limited
A company Incorporated in India under the Companies Act, 1956
Having address:
Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400001,
Maharashtra, India

The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION

[001] The present invention generally related to the slipper suspension is tandem axle suspension for heavy commercial vehicles, and more particularly the present invention is related to an improved slipper suspension system for rear tandem axles.

BACKGROUND OF THE INVENTION

[002] Suspension is one of those components of your vehicle that you often overlook until you run into problems. When functioning correctly, suspension absorbs shock from the road, keeps your vehicle level, gives you a smooth ride, ensures necessary traction to drive wheels and reduces wear and tear on your frame and tires.
[003] Basically, slipper suspension is tandem axle suspension which is used on heavy commercial vehicles. Out of two rear axles one is drive axle and the other is non drive axle. Rear forward hanger bracket (5), rear middle hanger bracket (6) and rear hanger brackets (7) are mounted on chassis frame (14) through bolting arrangement. This suspension uses four springs to secure axle with chassis frame (14), two at drive axle (15) and two at non-drive axle (16). Combination of spring eye and torque rods (3,4) are used to position the axles in longitudinal direction.

[004] Rear forward axle spring (1) front end is supported by rear forward hanger bracket (5). Rear end of spring assembly is supported by fulcrum assembly (9). Spring ends are having sliding type contact at both or at least at rear end. This fulcrum assembly (9) helps to equalize the loads between two axles. Similar to rear forward axle spring (1), rear rearward axle spring(2) is mounted between fulcrum assembly(9) and rear hanger bracket(7), spring ends are having sliding type contact at both ends.

[005] The working principal of these axles is as described further. The equalizing fulcrum tilts according to the load reaction of each axle within the chassis to ground height variation limits. It constantly adjusts the relative lift or fall of each axle to suit the profile of the road. As this is a torque, reactive type suspension drive axle inherently gets closer to the chassis as compared to dummy axle during acceleration. This causes more load on drive axle. The issues associated with such suspensions are, when practically it is seen that this extra load on drive axle is not sufficient to generate enough traction on gradient with loose gravel.
[006] At present the method followed is the use of differential lock on drive axle. This feature on the drive axle when switched ON connects the wheels on either side of drive axle thus preventing slip of one side wheel and improving the overall road holding. This reduces severity of loss of traction. Although it improves traction, this is not a foolproof solution. This requires at least one side wheel to have proper road holding. This also requires additional initial cost and maintenance cost. There is possibility of unintentional engagement of differential lock which may lead to excessive tire wear.

[007] Accordingly, there is a need of cost-effective suspension system which can overcome the above-mentioned problems.

OBJECTS OF THE INVENTION

[008] One object of the present disclosure is to provide an improved slipper suspension system for heavy commercial vehicles.

[009] Another object of the present disclosure is to provide an improved slipper suspension system for heavy commercial vehicles to ensure the higher traction at unladen condition and at the same time ensure that springs will get equally loaded at vehicle laden condition.

[0010] Yet another object of present disclosure is to provide an improved slipper suspension system for heavy commercial vehicles with two stage stiffness spring on dummy axle wherein the first stage stiffness spring will act only in vehicle unladen condition.

[0011] Also, yet another object of the present disclosure is to provide an improved slipper suspension system for heavy commercial vehicles which increases deflection on the non-drive axle spring to reduce the chassis height.

[0012] Yet another object of present disclosure is to provide an improved slipper suspension system for heavy commercial vehicles wherein the fulcrum equalizes the chassis height thus resulting higher load on drive axle.
[0013] Also, yet another object of the present disclosure is to provide an improved slipper suspension system for heavy commercial vehicles which provides the stiffness of the non-drive axle spring same as drive axle spring stiffness for same load distribution between the axles in laden condition.’

SUMMARY OF THE INVENTION

[0014] The present subject matter discloses an improved slipper suspension system for heavy commercial vehicles comprising at least one drive axle and at least one non-drive axle configured to be secured on at least one chassis fame. At least one rear forward axle torque rod and at least one rear rear axle torque rod along with the spring eye are used to position the axles in longitudinal direction. At least one rear forward hanger bracket, at least one rear middle hanger bracket and at least one rear rear hanger bracket are mounted on chassis frame through bolting arrangement. At least one fulcrum assembly is provided to equalize the loads between two axles by tilting according to the load reaction of each axle within the chassis frame. At least one drive axle spring is provided to secure axle with the chassis frame and at least one two stage stiffness spring to secure the non-drive axle to chassis frame. The non-drive axle is configured with first stage stiffness spring with lesser stiffness to increase the deflection of the non-drive axle spring , to reduce the chassis height of non-drive axle to equalize it with the chassis height of the drive axle in vehicle unladen condition by activation of fulcrum . The first stage stiffness spring is configured to reduce the chassis height of non-drive axle to equalize it with the chassis height of the drive axle in vehicle unladen condition to generate an additional load on drive axle to transfer higher load on drive axle. The non-drive axle spring is configured with the unladen stiffness of 50% of that of the drive axle spring for increasing the load on the drive axle by 20% to provide extra traction for drive axle. The non-drive axle is configured with second stage stiffness spring to provide same spring stiffness as of drive axle spring in laden condition. The non-drive axle is configured with two stage stiffness spring to provide higher traction at unladen condition and to equally distribute the load on both drive axle and non-drive axle at vehicle laden condition to prevent overloading of any components like spring, axle, tire, etc.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES

[0015] The foregoing detailed description of embodiments is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present subject matter, an example of construction of the present subject matter is provided as figures.
[0016] The present subject matter is described in detail with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to refer various features of the present subject matter. One or more embodiments are now described, by way of example only, with reference to the accompanying figures wherein like reference numerals present like elements and in which:
[0017] Figure 1 illustrates a schematic diagram of a conventional slipper suspension layout.

[0018] Figure 2 illustrates a schematic diagram of an improved traction with slipper Suspension, in accordance with embodiment of the present invention.

[0019] The figures depict embodiments of the disclosure for the purpose of illustration only. One skilled in the art readily recognize from the following description that alternative embodiments of the system illustrated herein may be employed without departing from the principles of the disclosure described herein.

[0020] REFERRAL NUMERALS:

Element Description Reference Numeral
Rear Forward axle spring 1
Rear Rearward axle spring 2
Rear Forward axle torque rod 3
Rear Rear axle torque rod 4
Rear Forward Hanger bracket 5
Rear middle hanger bracket 6
Rear Rear hanger bracket 7
Guide plate 8
Fulcrum assembly 9
Two stage non-drive axle first stage spring with lesser stiffness 10(a)
Two stage non-drive axle second stage spring with normal stiffness 10(b)
Top saddle 11
Bottom saddle 12
U-bolt and nut 13
Chassis frame 14
Drive axle 15
Non drive axle 16

DETAILED DESCRIPTION

[0021] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words "comprising", “having”, and "including," and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. It must also be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Although any devices and methods similar or equivalent to those described herein can be used in the practice or testing of embodiments of the present disclosure, the exemplary devices and methods are now described. The disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms.

[0022] Various modifications to the embodiment will be readily apparent to those skilled in the art and the generic principles herein may be applied to other embodiments. However, one of ordinary skill in the art will readily recognize that the present disclosure is not intended to be limited to the embodiments illustrated but is to be accorded the widest scope consistent with the principles and features described herein.

[0023] The present invention discloses an improved slipper suspension system for heavy commercial vehicles with two stage stiffness spring on non-drive axle (16). The first stage stiffness spring (10a) is with lesser stiffness and will act only in vehicle unladen condition. This will generate an additional load on drive axle (15), by use of two stage stiffness spring (10a, 10b) on non-drive axle (16) as shown in figure 2. The non-drive axle (16) spring (10a, 10b) is made with differential stiffness where the first stage stiffness spring (10a) will act only in vehicle unladen condition. These deliberate differences in the spring stiffness of the drive and non-drive axles are provided such that, the stiffness of the non-drive axle spring (10a) is kept less than that of the spring of the drive axle, to increase the deflection of the non-drive axle spring (10a) and this will result in reduction in the chassis height of the non-drive axle (16). The fulcrum (9) will try to equalize the chassis height of the non-drive axle, resulting to transfer higher load on drive axle (15).

[0024] If the unladen stiffness of non-drive axle spring (10a) is less by 50% as compared to drive axle spring (1), there is 20% load increase on drive axle (15). This increase in load at unladen condition will provide extra traction for drive axle (15). In laden condition, the non-drive axle (16), spring stiffness will be same as drive axle stiffness because of the second stage stiffness spring (10b) and hence load distribution between the axles will be same. This will ensure the higher traction at unladen condition and at the same time ensure that springs will get equally loaded at vehicle laden condition, thus preventing overloading of any component like spring, axle, tire etc.

[0025] The present invention discloses an improved slipper suspension system for heavy commercial vehicles comprising at least one drive axle (15) and at least one non-drive axle (16) configured to be secured on at least one chassis fame (14). At least one rear forward axle torque rod (3) and at least one rear rear axle torque rod (4) along with the spring eye are used to position the axles in longitudinal direction. At least one rear forward hanger bracket (5), at least one rear middle hanger bracket (6) and at least one rear rear hanger bracket (7) are mounted on chassis frame (14) through bolting arrangement. At least one fulcrum assembly (9) is provided to equalize the loads between two axles by tilting according to the load reaction of each axle within the chassis frame (14). At least one drive axle spring (1) is provided to secure axle with the chassis frame (14) and at least one two stage stiffness spring (10a,10b) to secure the non-drive axle (16) to chassis frame (14).

[0026] The non-drive axle (16) is configured with first stage stiffness spring (10a) with lesser stiffness to increase the deflection of the non-drive axle spring (10a), to reduce the chassis height of non-drive axle (16) to equalize it with the chassis height of the drive axle (15) in vehicle unladen condition by activation of fulcrum (9). The first stage stiffness spring (10a) is configured to reduce the chassis height of non-drive axle (16) to equalize it with the chassis height of the drive axle (15) in vehicle unladen condition to generate an additional load on drive axle (15) to transfer higher load on drive axle (15). The non-drive axle spring (10a) is configured with the unladen stiffness of 50% of that of the drive axle spring (1) for increasing the load on the drive axle (15) by 20% to provide extra traction for drive axle (15).

[0027] The non-drive axle (16) is configured with second stage stiffness spring (10b) to provide same spring stiffness as of drive axle spring (1) in laden condition. The non-drive axle (16) is configured with two stage stiffness spring (10a,10b) to provide higher traction at unladen condition and to equally distribute the load on both drive axle (15) and non-drive axle (16) at vehicle laden condition to prevent overloading of any components like spring, axle, tire, etc.