FIELD OF THE INVENTION

[001] The present invention generally relates to a starter for
cranking engine of the automotive vehicle, and particularly concerned with a drive assembly coupled with an electric motor of the starter, and more particularly relates to a shock absorbing system incorporated with the drive assembly to absorb impact load acting upon the starter as well as flywheel of the engine and other relatively moving associated parts thereof.

BACKGROUND OF THE INVENTION

[002] A typical starter for the automotive vehicle has a pinion, which is a solid mass, coupled with an output shaft of the starter. Flywheel ring gear arrangement is another solid mass connected to crankshaft of an engine of the automotive vehicle. For cranking of the engine, the pinion is engaged with the flywheel ring gear arrangement and energizes an electric motor associated with the starter; said electric motor causes the pinion to rotate at desired power to crank the flywheel and thereby to start the vehicle. There have been developed various types of starters, wherein one type of starter has the pinion always in mesh with the flywheel ring gear arrangement, hereinafter referred as permanently engaged starter, whereas another type of starter has the pinion initially made to engage with the flywheel ring gear arrangement using a solenoid switch which in turn actuates the electric motor to cause the pinion at desire power.

[003] In both the types of starters, when the electric motor gets actuated, the pinion starts rotating from zero speed to a cranking speed which is necessary to turn the flywheel of the engine. At this time, full torque of the starter motor is applied on the flywheel ring gear of the engine as an impact load in a very short period. This impact load is absorbed by the flywheel ring gear arrangement and as well as the starter components. This impact load occurs during every starting of the engine and hence the life of the flywheel ring gear and associated components of the starter is getting decreased. This impact load during starting of the engine is undesirable as it also involves drawing high current during the starting. In the case of permanently engaged starter, as the pinion is constantly meshed with the flywheel ring gear arrangement, the electric motor has to follow the path of engine speed for the efficient working of the starter as well as the smooth moving of the vehicle.

[004] Similarly when the engine back rocks, high torque due to the heavy mass of flywheel and other engine moving parts is transmitted to the starter from the engine which again creates an impact load which further damages the starter internal gears. To prevent such high torque transfer, an overrunning clutch is provided in the starter motors, but the durability of this overrunning clutch gets affected due to this impact load caused by the engine back rock.

[005] In yet another type of starter, the output power of electric motor is directly fed to the pinion for cranking the flywheel without any additional gear reduction drive assembly. As the torque level compared to the size of the electric motor and the size of the engine is less, in the case of regular type of engine, the impact load transferred during cranking with is less and failures associated with this combination is also not significant. But for the compact engines, the torque developed at the output shaft of the electric motor is phenomenally high for the size of the electric motor compared to that of the compact engine. In yet another type of gear reduced starter, the impact load during cranking is high which reduce the life of the ring gear, pinion teeth and internal gears.

[006] In order to overcome aforesaid disadvantages and solve other related problems, various shock absorbing concepts have been developed.

[007] One of such concepts is disposing rubber pad between the output shaft and the pinion. In this concept, a sleeve is rigidly connected to the output shaft and the pinion is disposed over the sleeve by adding rubber pad in between. This has the effect of smooth absorption of the impact load and noiseless engagement with the flywheel ring gear arrangement. But due to more number of parts and poor reliability of the rubber pad, this concept was not satisfactory to resolve above said problems. In one aspect of this concept, leaf spring is disposed between the the sleeve and the pinion, but it does lead to complexity in number of parts and assembly process. In another concept, a snap ring is disposed between the out put shaft and the pinion. Though the design is very simple, easy to assemble and cost effective, there was a potential issue of snap ring breakage and hence poor reliability. In yet another concept, a split sleeve design is adapted between the output shaft and the pinion, but there was also a potential issue of sleeve breakage and poor reliability.

[008] US patent No. 3788151 discloses such kind of shock absorbing starter clutch mechanism, wherein the power drive assembly of the starter unit comprises a motor having an armature shaft coupled with a pinion shaft via a drive gear engaged with geared teeth of the armature shaft. Interposed between the drive gear and the pinion gear is a clutch assembly, which in turn comprises a drive sleeve splined with the pinion shaft and has three ears equally spaced about the periphery of the sleeve and extending axially along the length of the sleeve. The clutch assembly further comprises a clutch housing that has three equally spaced arms extending in the axial direction. A shock absorbing member is interposed in the space between each ear of the drive sleeve and each arm of the housing. The torque from the motor is coupled from the ears of the drive sleeve through each of the shock absorber to the arms of the housing. When the torque is transferred from the arm of the housing to the ears of the drive sleeve, the shock absorbing members resiliency and compressably deform to absorb this high impact load. Though this concept may give satisfactory result for a short period of time, it can not be satisfactorily applied for long term use as the reliability of such millable urethane rubber may go down as the cycle of operation goes up.

[009] Hence there was a very much need for a shock absorbing system having no such problems associated with afore said concepts. According to the preferred embodiment of the present invention, the principal intention is to provide a shock absorbing system including a clock spring between the output shaft of the starter and the pinion, thereby power from the starter output shaft is made transmitted through the shock absorbing system to absorbs the impact load and preventing it from being transferred to the flywheel ring gear.

OBJECT OF THE INVENTION

[010] The present invention overcomes the shortcomings associated with the background art and achieves other advantages not realized by the background art.

[011] The principal object of the present invention is to provide a shock absorbing system along with drive assembly of the starter to absorb impact load acting upon the starter as well as flywheel of the engine and other relatively moving associated parts thereof.

[012] Another object of the present invention is to provide a shock absorbing system that is reliable and simple in design and assembly.

[013] Yet another object of the present invention is to provide a shock absorbing system that is adapted with all types of starter with less modification irrespective of applications.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a shock absorbing system for a starter used with automotive vehicle comprising an output shaft of a drive assembly that relatively and operatively coupled with an armature shaft of an electric motor. A cam is disposed on said output shaft and is configured in a relationship with a barrel to receive a clock spring. A pinion is configured with said barrel to engage with flywheel ring gear arrangement of an engine related to the automotive vehicle.

[014] The cam is a hollow cylindrical body that has an inner surface adapted to engage said third step diametric portion and has an outer surface with a projection radially extending outward of the outer surface and extending longitudinally of said cam. Forward end of said cam has a plurality of projections radially extended outward from outer surface of said cam.

[015] The barrel is a hollow cylindrical body having a large diametric section and a small diametric section. The large diametric section has an inner surface with a projection radially extending outward of said inner surface and extending longitudinally of the large diametric section. The inner surface of the large diametric section has a plurality of projections radially extended outward from inner surface of said large diametric section to freely engage with plurality of projections of said cam. Outer surface of said small diametric section is being adapted to receive said pinion and inner surface thereof is adapted to be freely and rotatably supported over said output shaft.

[016] The clock spring is made of a strip having a thickness and a width. The strip having an inner end adapted to abut with the projection of said cam and having an outer end adapted to abut with the projection of said large diametric section of said barrel. The outer surface of said cam along with the projection is adapted to absolutely and firmly receive inner profile formed by inner turn of said strip so as to obviate relative motion between said cam and said clock spring. The inner surface of the large diametric section of said barrel along with the projection is adapted to freely receive an outer profile formed by outer turn of said strip.

[017] According to another aspect of the present invention, the drive assembly comprises a plurality of planetary gears rotatably supported over a plurality of spindles. The plurality of spindles is rigidly fixed with backward surface of a carrier plate. The output shaft has a first end provided with said carrier plate and has a second end rotatably supported with drive assembly housing. Provided between said carrier plate and second end is a first step diametric portion adapted to be rotatably supported with a stationary ring gear case, a second step diametric portion adapted to receive a washer and a third step diametric portion adapted to be operatively coupled with said shock absorbing unit.

[018] According to yet another aspect of the present invention, the plurality of projections of said cam and the plurality of projections of said barrel is made as tooth like structure and thickness of gap between two teeth is made substantially larger than thickness of single tooth so as to maintain a predefined gap, in terms of radian, between teeth of said cam and teeth of said barrel when said cam and said barrel are assembled together.

[019] Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[020] The present invention will be better understood fully from the detailed description that is given herein below with reference to the accompanying drawings of the preferred embodiments of the present invention, which, however, should not be deemed to be a limitation to the invention to the specific embodiments, but, are for the purpose of explanation and understanding only.

In the drawings:

[021] FIG.1 is a longitudinal sectional view of a starter for an automotive vehicle that is equipped with a shock absorbing system according to preferred embodiment of the present invention.

[022] FIG.2 is an enlarged partial longitudinal sectional view illustrating arrangement of the shock absorbing system of FIG.l according to the preferred embodiment of the present invention.

[023] FIG.3 is an exploded view of the shock absorbing system of FIG.2 demonstrating various components associated with the shock absorbing system according to the preferred embodiment of the present invention.

[024] FIG.4 is a cross sectional view taken along line A-A of FIG.2 illustrating the relationship with which a clock spring is associated with a cam and barrel arrangement of the shock absorbing system according to the preferred embodiment of the present invention.

[025] FIG.5 is a view along line B-B of FIG.3 showing the relation between the cam and barrel according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[026] While this invention is susceptible of embodiments in many different forms, the detailed description of the preferred embodiments with reference to the corresponding drawings shown herein below are to be understood that the present disclosure shall be deemed as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of FIG 1- 5

[027] Referring to FIG.l, a starter for starting automotive vehicle by cranking internal combustion engine associated with the vehicle is designated with a numeral (100), wherein said starter (100) is operatively disposed in relationship with a flywheel ring gear arrangement of the engine (not shown) to crank the engine and thereby to start the motor vehicle. The starter that is embodied in the present disclosure for describing the preferred embodiment of the present invention is a permanently engaged starter, which is always in an engaged relationship with the flywheel ring gear arrangement of the engine to crank the flywheel spontaneously immediate to the actuation of ignition switch without undue delay. However, the kind of starter disclosed herein below should not be construed as a limiting factor to the scope of the present invention as it is very much obvious to a person skilled in the art to employ the present invention with other types of starter with or without modification in the present invention without departing from the scope of the present invention. The starter (100) embodied herein has an electric motor (101) for deriving output from the starter (100), a solenoid switch (102) for energizing the electric motor (101) and a drive assembly (103) for receiving the output from the electric motor (101) and convert it into a desired output power for cranking flywheel of the engine.

[028] The electric motor (101) includes an armature assembly having an armature shaft (104) that is rotatably and longitudinally disposed inside a motor housing (105) and has an forward end (106) provided with a first diametric portion (107) having splines (108) and a second diametric portion (109) adapted to be rotatably supported with an output shaft (110) of the drive assembly (103). The drive assembly (103) has a plurality of planetary gears (111) which are in continuous mesh with the splines (108) provided on the first diametric portion (107) of the armature shaft (104) and a stationary ring gear (112) that is having provided with inner teeth. Said plurality of planetary gears (Ill) are being rotatably supported on each of a plurality of spindles (113), wherein said plurality of spindles (113) are being rigidly fixed on a carrier plate (114), which forms an integral part of the output shaft (110). Shock absorbing system (115) according to the preferred embodiment of the present invention is also incorporated with the drive assembly (103) along with a pinion (116). The pinion (116) is positively coupled with the shock absorbing system (115) and is in constant mesh with the flywheel ring gear arrangement of the engine. The solenoid switch (102) comprises a coil assembly (117) for energizing the solenoid switch and a plunger assembly (118) for energizing the electric motor (101) by closing an electric current contact between battery and the electric motor (101).

[029] As the vehicle is keyed, the ignition switch becomes closed and facilitates completeness of the electrical circuit to supply electric current to the solenoid switch (102) to energize the coil assembly (117), which in turn, by virtue of magnetic induction, actuates the plunger assembly (118) to move towards a battery positive terminal (119) and an electric motor positive terminal (120). A linear actuation of the plunger assembly (118) establishes a contact between the battery positive terminal (119) and the electric motor positive terminal (120) to energize the electric motor (101) to drive the armature shaft (104) at desired RPM. The rotary power output of the armature shaft (104) is transmitted to the plurality of planetary gears (111) via splines (108). Due to the reduced gear ratio, the rotary speed of the output shaft (110) gets reduced compare to that of the armature shaft (104) and thereby the speed of the pinion (116) goes down and the torque required to crank the flywheel of the engine goes up.

[030] Referring to FIG.2, first end of the output shaft (110) has said carrier plate (114) for rotatably supporting said plurality of planetary gears (111) via said plurality of spindles (113). At backward face of the carrier plate (114), there is provided a bore (121) axially adapted to receive the forward end (106) of the armature shaft (104) via a bush (122). Immediate to forward face of the carrier plate (114), there is a first step diametric portion (123) adapted to be rotatably supported with a stationary ring gear case (124) via a first bearing (125). According to the preferred embodiment of the present invention, said stationary ring gear (112) is made as an integral part of said stationary ring gear case (124). However, having stationary ring gear as a separate part and disposing it with the stationary ring gear case should not be deemed to be deviating from the scope of the present invention described herein as it is very much obvious to a person skilled in the art to have a different configurations of stationary ring gear and stationary ring gear case with or without modification. According to one aspect of the present invention, a tolerance ring shall be disposed between the stationary ring gear case and stationary ring gear to avoid transferring of power from the flywheel to the starter when the flywheel rotate at a speed which is beyond acceptable speed limit of the pinion. Next to the forward of the first step diametric portion (123) is a second step diametric portion (126) adapted to receive a washer (127). Next to the forward of the second step diametric portion (126) is a third step diametric portion (128) provided with straight line splines adapted to be operatively coupled with the shock absorbing system (115) in accordance with the preferred embodiment of the present invention. Second end (130) of the output shaft (110) is rotatably supported with drive assembly housing (131) via a second bearing (132).

[031] The shock absorbing system (115) is described herein below in details with reference to FIG.2 to FIG.5. The shock absorbing system (115) comprises a cam (133) and a barrel (134), wherein the cam (133) is a hollow cylindrical body having an inner surface (135) provided with straight line splines adapted to engage with the splines provided on the third step diametric portion (128) and has an outer surface (136) having a projection (137) radially extended outward of the outer surface (136) and extended longitudinally of the cam (133). Forward end of the cam (133) has a plurality of projections (138) radially extended outward from outer surface (136) of the cam (133) adapted to be configured with the barrel (134). The barrel (134) is a hollow cylindrical body having a large diametric section (139) at backward end thereof and a small diametric section (140) at forward end thereof, wherein the small diametric section (140) is conjoined at forward surface (141) of the large diametric section (139). The large diametric section (139) has an inner surface having a projection (142) radially extended outward of the inner surface and extended longitudinally of the large diametric section (139), and the diametric profile of the inner surface is in such a way to receive the cam (133) along with the plurality of projections (138) thereof. Inner face of the large diametric section (139) has plurality of projections (143), corresponding to the plurality of projections (138) of the cam (133), radially extended outward from inner surface of the large diametric section (139) adapted to be seated and abutted with the plurality of projections (138) of the cam (133) thereby to receive and dispose a clock spring (144) between the outer surface (136) of the cam (133) and inner surface of the large diametric section (139) of the barrel (134). Axial thickness of the plurality of projections (138) of the cam (133) and that of the plurality of projection (143) of the barrel (134) is equal to one another thereby to provide a flat surface at inner face of the forward surface (141) of the large diametric section (139), and thereby to firmly abut the clock spring (144) with the flat surface. Outer surface of the small diametric section (140) is being adapted to receive the pinion (116) and inner surface thereof is adapted to be freely rotatably supported over the output shaft (110). According to preferred embodiment of the present invention, a tolerance ring (145) is disposed between the outer surface of the small diametric section (140) and the pinion (116) for avoiding transfer of power from the flywheel to the starter (100) when the speed of flywheel goes beyond the acceptable limit of the pinion (116) during back rock condition of the engine. The tolerance ring (145) has the inherent property of regaining its original form once it is relieved from the deflected position which is happened at unexpected back rock condition of the engine. However, the aforesaid configuration of the barrel and the pinion should not be deemed as a limiting factor to the scope of the present invention as different configurations of the barrel and the pinion including integration of these two parts as a single part are obvious to a person skilled in the art. According to one embodiment of the present invention, axial movement of the pinion (116) to the forward thereof over the small diametric section (140) is restricted by a stopper means (146) such as a plate, which is being inserted from the forward end of the output shaft (110) through the central hole provided therein. The stopper means (146) is further arrested via a clip (147) which is inserted from the forward end of the output shaft (110).

[032] Referring to FIG.3 & FIG.4, according to preferred embodiment of the present invention, the clock spring (144) is made of a strip (148) having a thickness (T) sufficient enough to absorb the impact load generated due to the cranking and back rock condition of the engine by deflecting at a predefined radian and having a width (W) defined between backward end and forward end of the cam (133). The strip (148) having an inner end (149) provided with a flattened face in such a way to abut with a flattened face provided in the projection (137) of the cam (133) and having an outer end (150) provided with a flattened face in such a way to abut with a flattened face provided in the projection (142) of the large diametric section (139) of the barrel (134). During the operation of cranking and back rock, the inner end (149) and the outer end (150) of the strip (148) tends to abut with the flattened surface of the projection (137) and the projection (142), respectively, and absorb the impact load by deflecting at a predefine radian. Circular profile of the outer surface (136) of the cam (133) along with the projection (137) is adapted to absolutely and firmly receive an inner profile formed by inner turn of the strip (148) so as to obviate relative motion between the cam (133) and the clock spring (144), wherein circular profile of the inner surface of the large diametric section (139) of the barrel (134) along with the projection (142) is adapted to freely receive an outer profile formed by outer turn of the strip (148).

[033] FIG.5 shows the position of cam (133) with respect to the barrel (134), wherein the plurality of projections (138) associated with the cam (133) is freely engaged with the plurality of projections (143) related to the barrel (134). According to one embodiment of the present invention, the plurality of projections (138) of the cam (133) and the plurality of projections (143) of the barrel (134) are made as tooth like structure and, thickness of gap between two teeth (Tl) is made substantially larger than thickness (T2) of a single tooth. Hence, when the cam (133) and the barrel (134) are assembled together, a predefined gap (T3), in terms of radian, is maintained between a tooth of the cam (133) and a tooth of the barrel (134). According to the preferred embodiment of the present invention, a 10° gap is maintained between teeth of cam (133) and teeth of barrel (134). Said gap (T3) is designed in consideration with the amount of impact load, in terms of torque, required to be absorbed by the clock spring (144) with a predefined deflection of the clock spring (144) within the permissible limit thereof by restricting the rotation of the cam (133) to said predefined angle so as to avoid failure of the clock spring (144). The plurality of projection (138) of the cam (133) is thus act as a stopping medium for the deflection of the clock spring. However, it should be understood by a person skilled in the art that the requirement of deflection of the clock spring (144) varies with the amount of impact load to be absorbed and the requirements; hence said angular distance of the present invention should not be construed as a limitation to the scope of the present invention.

[034] Referring to FIG.2, FIG.4 & FIG.5, during the cranking operation of the starter (100), the output shaft (110) of the drive assembly (103) receives power from the armature shaft (104) of the electric motor (101) through speed reduction mechanism, which includes plurality of planetary gears (111) constantly engaged between the splines (108) provided on first diametric portion (107) of the output shaft (110) and the stationary ring gear (112) disposed with the stationary ring gear case (124). Due to the speed reduction mechanism, the rotational speed available at the output shaft (110) becomes less than the speed available at the forward end (106) of the armature shaft (104). As the cam (133) is engaged with the output shaft (110), the the power available at the output shaft is transferred to the cam (133) which in turn transfer the power to the barrel (134) via the clock spring (144), wherein said pinion is mounted with the barrel (134) to transfer the power to the flywheel ring gear arrangement of the engine. As a result of predefined stiffness of the clock spring (144), the clock spring (144) absorb the sudden release of potential energy possessed by the flywheel by deflecting at an angular distance, in terms of radian, to give smooth cranking of the engine. The angular distance of deflection effected by the clock spring (144) is limited to a distance of 10° radian, according to the preferred embodiment of the present invention, by the plurality of projections (138) of the cam (133) by engaging with plurality of projections (143) of the barrel (134), thus to protect the clock spring (144) from failure due to deflection beyond the predefined limit. During engine back rock condition, the impact load caused due to the heavy mass of flywheel and other moving parts of the engine is transferred through the pinion (116) then through the barrel (134). The kinetic energy associated with the flywheel is absorbed by the clock spring by deflecting at a predefined distance. Thus the shock absorbing system of the present invention eliminate the disadvantages and shortcomings of the prior arts and provide a best method of shock absorbing system in accordance with the objective of the invention.

[035] It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts disclosed in the foregoing description. Accordingly, the preferred embodiments described in detail herein are illustrative only and are not limiting to the scope of the invention, which is to be given the full extent of the appended.

We claim:

1) A shock absorbing system for a starter used with automotive vehicle comprising:

an output shaft (110) of a drive assembly (103) that relatively and operatively coupled with an armature shaft (104) of an electric motor (101);

a cam (133) disposed on said output shaft (110); said cam (133) is configured in a relationship with a barrel (134) to receive a clock spring (144);

a pinion (116) arranged with said barrel (134) to engage with flywheel ring gear arrangement of an engine of the vehicle.

2) The shock absorbing system according to claim 1 has said drive assembly (103) comprising:

a plurality of planetary gears (111) rotatably supported over a plurality of spindles (113), said plurality of spindles (113) is rigidly fixed with backward face of a carrier plate (114);

said output shaft (110) has a first end formed with said carrier plate (114) and has a second end (130) rotatably supported with drive assembly housing (131); provided between said carrier plate (114) and second end is a first step diametric portion (123) adapted to be rotatably supported with a stationary ring gear case (124), a second step diametric portion (126) adapted to receive a washer (127) and a third step diametric portion (128) adapted to be operatively coupled with said cam (133).

3) The shock absorbing system according to claim 1, wherein said cam (133) is a hollow cylindrical body that has an inner surface (135) adapted to engage said third step diametric portion (128) and has an outer surface (136) with a projection (137) radially extending outward of the outer surface (136) and extending longitudinally of said cam (133),

4) The shock absorbing system according to claim 1, wherein forward end of said cam (133) has a plurality of projections (138) radially extended outward from outer surface (136) of said cam (133).

5) The shock absorbing system according to claim 1, wherein said barrel (134) is a hollow cylindrical body having a large diametric section (139) and a small diametric section (140),

wherein said large diametric section (139) has an inner surface with a projection (142) radially extending outward of said inner surface and extending longitudinally of the large diametric section (139),

wherein outer surface of said small diametric section (140) is being adapted to receive said pinion (116) and inner surface thereof is adapted to be freely and rotatably supported over said output shaft (110).

6) The shock absorbing system according to claim 1, wherein said inner surface of the large diametric section (139) has a plurality of projections (143) radially extended outward to freely engage with plurality of projections (138) of said cam (133).

7) The shock absorbing system according to claim 1, a tolerance ring (145) is disposed between the outer surface of the small diametric section (140) and the pinion (116) for avoiding transfer of power from the flywheel to the starter (100) when speed of flywheel goes beyond acceptable limit of the pinion (116) speed during back rock condition of the engine.

8) The shock absorbing system according to claim 4, a tolerance ring (145) is disposed between the outer surface of said small diametric section (140) and said pinion (116) to avoid transfer of power from the flywheel to said starter (100) when speed of flywheel goes beyond acceptable limit of said pinion speed (116) during back rock condition of the engine.

9) The shock absorbing system according to claim 1, axial movement of said pinion (116) to forward thereof over said small diametric section (140) is restricted by a stopper means (146), which is further arrested via a clip (147).

10) The shock absorbing system according to claim 1, wherein said clock spring (144) is made of a strip (148) having a thickness (T) and a width (W),

wherein said strip (148) having an inner end (149) adapted to abut with the projection (137) of said cam (133) and having an outer end (150) adapted to abut with the projection (142) of said large diametric section (139) of said barrel (134); hence the power received from the output shaft (110) by said cam (133) is transferred to said barrel (134) via said clock spring (144) and then to said pinion (116).

11) The shock absorbing system according to claim 1, the outer surface (136) of said cam (133) along with the projection (137) is adapted to absolutely and firmly receive inner profile formed by inner turn of said strip (148) so as to obviate relative motion between said cam (133) and said clock spring (144),

wherein the inner surface of the large diametric section (139) of said barrel (134) along with the projection (142) is adapted to freely receive an outer profile formed by outer turn of said strip (148).

12) The shock absorbing system according to claim 3 and 4, the plurality of projections (138) of said cam (133) and the plurality of projections (143) of said barrel (134) is made as tooth like structure and thickness of gap between two teeth (Tl) is made substantially larger than thickness (T2) of single tooth so as to maintain a predefined gap (T3), in terms of radian, between teeth of said cam (133) and teeth of said barrel (134) when said cam (133) and said barrel (134) are assembled together.