|Title of Invention
A MULTI SPRING VEHICLE SHOCK ABSORBER
|A shock absorber (1,201) comprising a spring combination (17,18) having first and second spring elements (17,18) having capacity to store energy from vehicle vibrations said first and second spring elements (17,18) being operatively to share load due to road induced vibrations during the motion of the vehicle (100) are within allowable limits Spring elements (17,18) may be disposed over a hydraulic cylinder (4) forming a further element of the shock absorber. Such a shock absorber (1,201) has cost, comfort and reliability advantages when applied to vehicles as motorcycles.
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
PROVISIONAL SPECIFICATION (See section 10 and rule 13)
TITLE OF THE INVENTION
A shock absorber for a motor vehicle
Name : Nationality : Address :APPLICANTS Abraham JosephIndian National ,Bajaj Auto Limited, Akurdi, Pune 411035,Maharashtra, India
Name : Nationality : Address : Bajaj Auto LimitedIndian CompanyAkurdi, Pune 411035, Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention :
FIELD OF INVENTION
This invention relates to a shock absorber for a motor vehicle.
This invention also relates to a motor vehicle comprising the shock absorber.
BACKGROUND OF INVENTION
Shock absorbers used in a motor vehicle absorb or dampen road induced vibrations due to uneven road surfaces and give comfort and safety to the rider(s). Besides, they also bear the vehicle load. A typical shock absorber comprises a damper body and a helical compression spring precompressed to a predetermined load value and disposed over the hydraulic cylinder of the damper body between the lower spring seat and upper spring seat of the damper body. The lower spring seat is adjustable on the hydraulic cylinder so as to adjust marginally the length of the precompressed spring. The spring is precompressed to a predetermined load value having regard to parameters like the vehicle weight and load on the vehicle and desired shock absorption capacity of the shock absorber. During motion of the vehicle, the spring is subjected to frequent compression and expansion due to road induced vibrations. This creates shear stresses in the spring and leads to spring fatigue and may cause premature, spring failure thereby reducing the life of the shock absorber. Spring failure during motion of the vehicle can
lead to serious accidents. The capacity of the shock absorbers to absorb or dampen road induced vibrations and bear vehicle load depends on various factors including the spring diameter and length and spring characteristics. In order to give the required comfort level to the rider(s), the spring has to have certain diameter and length and characteristics. Reduction in the length of the spring leads to reduction in the number of turns for given wire diameter and mean coil diameter of the spring and to harder suspension and reduced riding comfort. The overall length of the shock absorber depends on the precompressed length of the spring. Inspite of the marginal length adjustment of the spring being possible with the lower spring seat adjustment, still in the case of a shock absorber located close to a motor cycle body, the chain case on one side and muffler or silencer on the other side of the vehicle are generally required to be provided with depressions in order to provide sufficient clearance, for proper location of the lower spring seat of the shock absorbers. The depressions call for additional manufacturing cost as they require additional operation. Besides they create limitation in the orientation of the silencer and also spoil the aesthetics of the vehicle. During motion of the vehicle, there are also chances of the chain rubbing against the depression in the chain case creating noise which is undesirable and irritating. Alternative is to mount the shock absorbers
away from the vehicle body providing sufficient clearance with the vehicle body. In such a case the shock absorbers overhang and require additional reinforcements which add to the cost of the vehicle.
OBJECTS OF INVENTION
An object of the invention is to provide a shock absorber which has
improved reliability and life.
Another object of the invention is to provide a shock absorber which comprises precompressed spring of. reduced length without compromising riding comfort and which can be conveniently mounted on a motorcycle without depressions in the chain case and muffler thereby eliminating additional manufacturing cost, limitation in the orientation of the silencer, irritating noice and additional reinforcements and maintaining the aesthetic look of the vehicle.
DETAILED DESCRIPTION OF INVENTION
According to the invention there is provided a shock absorber comprising a damper body and a pair of helical compression springs precompressed to a predetermined load value, the springs constituting an inner spring disposed
over the hydraulic cylinder of the damper body and an outer spring disposed over the inner spring, the lower ends and the upper ends of the springs being located against the adjustable lower spring seat and the upper spring seat of the damper body, respectively.
According to an embodiment of the invention, the lower end of the outer spring is located on an outer locator which is located on the lower spring seat and the lower end of the inner spring is located against an inner locator which is located on the lower spring seat.
According to an embodiment of the invention, the shock absorber comprises a spacer provided between the springs and located in the upper spring seat.
The following is a detailed description of the invention with reference to the accompanying drawings, in which :
Fig 1 is a cross sectional view of a shock absorber according to an embodiment of the invention; and
Fig 2 is a cross sectional view of a shock absorber according to another embodiment of the invention.
The shock absorber 1 as illustrated in Fig 1 of the accompanying drawings comprises a damper body 2 comprising a hydraulic cylinder 4 provided with an adjustable lower spring seat 5. The lower spring seat is provided with a plurality cam profiles 6 at different levels of height. The hydraulic cylinder is provided with a pair of oppositely disposed lugs, only one of which is seen and is marked 7, the other being directly behind and hidden. The height of the lower spring seat on the hydraulic cylinder can be adjusted by rotating or turning the lower spring seat on the hydraulic cylinder when the lower spring seat slides up or down on the hydraulic cylinder against the lugs and engages in an upper or lower cam profile to raise or lower the height of the lower spring seat on the hydraulic cylinder as required. 8 is a piston reciprocating in the hydraulic cylinder. 9 is the piston rod. 10 is an oil seal washer of the cylinder. 11 is an upper spring seat fitted to the piston rod 9. 12 is compression bump stop fitted to the piston rod. 13 is a dust cover located against the upper spring seat. 14 is a lock nut fitted on the piston rod. The upper and lower eyelets for mounting the shock absorber to the vehicle body (not shown) are marked 15 and 16, respectively. 17, 18
are a pair of helical compression springs precompressed to a predetermined load value having regard to parameters like vehicle weight and load on the vehicle and desired shock absorption capacity of the shock absorber. The springs constitute an inner spring namely 17 disposed over the hydraulic cylinder and an outer spring namely 18 disposed over the inner spring. The outer spring 18 is located against an outer locator 19 which is located on the lower spring seat. The inner spring 17 is located against an inner locator 20 which is located on the lower spring seat. The upper ends of the springs are located against the upper spring seat.
During running condition of a vehicle fitted with the shock absorber of the invention, both the springs bear the vehicle load and are subjected to frequent compression and expansion due to road induced vibrations. The shear stresses resulting from the compression and expansion of the springs are shared by the springs. Therefore, spring fatigue and chances of premature spring failure are reduced. Even if one of the springs fails during motion of the vehicle the shock absorber can still function with the other spring at least for some time. Chances of both springs failure are practically nil. Thus the life and reliability of the shock absorber is improved. As the shock absorber comprises two springs by proper selection of the spring
parameters like spring diameter and length and spring characteristics, shear stresses can be distributed and at the same time the effective length of the precompressed springs can be reduced without reducing the characteristics of the shock absorber and riding comfort to the rider(s). It is estimated that the precompressed spring length can be substantially reduced over and above the reduction in spring length that can be achieved by adjustment of the lower spring seat. Therefore, the lower spring seat height on the hydraulic cylinder can be correspondingly raised to mount the shock absorber conveniently on a motor cycle without forming depressions in the chain case and muffler to accommodate, the lower spring seat of the shock absorber. The additional manufacturing cost and limitations in the orientation of the silencer and irritating chain noice are thus avoided. Also the aesthetic look of the vehicle is not spoiled and cost of the additional reinforcements for mounting the shock absorber away from the vehicle is eliminated.
In the case of the shock absorber of Fig 2 of the accompanying drawings, the springs are provided with a spacer, 21 between them. The spacer is located in the upper spring seat. The shock absorber of Fig 2 is otherwise
similar to that of Fig 1. The spacer is essentially to prevent contact between the springs and can be made of materials such as nylon or polypropylene.
The spring locators are optional and there can be more than two compression springs. The spacer is also optional. Such variations of the invention are to be construed and understood to be within the scope of the invention.
(Jose M A)
of Khaitan &Co
Agent for the Applicants
Dated this 9th day of June 2005
|Indian Patent Application Number
|PG Journal Number
|Date of Filing
|Name of Patentee
|BAJAJ AUTO LTD
|Akurdi, Pune 411035.
|PCT International Classification Number
|PCT International Application Number
|PCT International Filing date