FORM 2
THE Patent Act, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
Canister gas pressure indicator
Endurance Technologies Pvt Ltd R&D, E 92, MIDC Industrial Area, Waluj, Aurangabad, Maharashtra-431136
The following specification describes the invention

Field of the invention
The present invention refates to shock absorber for vehicles in general and canister gas pressure indicator in particular for two and three wheelers.
Description of prior art
Gas shock absorbers for vehicles such as motorbikes, cars, coaches, etc. are widely used in suspension system wherein it is provided with a piston sliding in a cylindrical chamber containing oil, which produces viscous damping of the stresses applied to the suspension of the vehicle during driving and the piston is mounted on a guide rod which projects from the cylindrical chamber and is secured onto the vehicle chassis. The movement of the rod in the chamber, owing to the stresses while driving the vehicle, cause variations in the volume of the oil in the chamber. For the piston to move within the shock body, the fluid within the fluid filled cavity of the shock body must travel through the piston. Therefore passages are formed through piston to control the fluid flow between each section of the shock body. The passages are typically aligned with the longitudinal axis of the piston. The openings of some of these passages may be covered with leaf valves while the remainder of the openings may be uncovered to thus serve as by-pass passages, The only restriction in the bypass passages is the viscosity of the fluid itself and the diameter of the passages.
The shock rod/piston assembly and the shock body that includes the cylindrical wall and both the end caps move in relation to one another upon the application of forces to the shock absorber. The relative movement between the shock rod/piston assembly and the shock body results in the movement of the piston through the fluid which provides the hydraulic damping for the shock absorber. As a result, the shock forces that are applied to the vehicle component to which the shock absorber is

coupled are at least partially absorbed by the shock absorber. Accordingly the shock forces that are applied to the vehicle chassis are dissipated by the shock absorber.
The movement of the shock rod/piston assembly within the fluid-filled cavity of the shock body occurs in two stages, a compression stage followed by a rebound stage.
When the vehicle moves over an un-even terrain, shock forces are applied to the vehicle component to which the shock absorber is mounted. These shock forces cause the vehicle component to move from a steady state position to a position where the vehicle component has compressed relative to the chassis. Since the shock absorber is disposed between the vehicle component and chassis, as the components move toward one another, the shock absorber compresses, the shock rod/piston assembly moves inwardly relative to the shock body, within the fluid filled cavity of the shock body. As a result, the piston moves within the fluid filled cavity of the shock body toward the first end cap. During this compression stage, the shock absorber slows or dampens the rate at which the vehicle component compresses toward the chassis.
The rebound stage follows the compression stage. The rebound stage results from the resilient expansion of the spring associated with the shock absorber, which pushes the vehicle component away from the vehicle chassis to the original steady state position. The force exerted by the spring is usually quite low by comparison with the compressive force, because in the rebound stage, the force of the spring only needs to be high enough to overcome the combined weight of the vehicle and the rider. This spring force causes the shock absorber to extend resulting in the shock rod/piston assembly extending outwardly relative to the shock body. During the rebound stage, the piston moves within the fluid filled cavity away from the first

end cap toward the second end cap. The shock absorber, as a result, slows or dampens the rate at which the vehicle component moves relative to the chassis during the rebound stage.
As the shock rod/piston assembly moves Inwardly within the shock body during the compression stroke, the shock rod displaces a volume of fluid within the shock body that is equal to the volume of the shock rod that has extended in the shock body. To accommodate this displacement of fluid, an external or interna! gas-filled reservoir is typically used in association with the shock absorber.
In order for the shock absorber to be efficient, the Shockwave or bump encountered must be of sufficient size to compress the compressible gas within the gas chamber in a canister for the piston/shock rod assembly to move inwardly relative to the shock body. Moreover, it is also very much important to maintain the pressure of gas (usually nitrogen) at the gas chamber in the canister. In the absence of gas in the canister, the resulting threshold of the shock wave or bump size to compress the chamber would be very less resulting in rider fatigue and discomfort. The prior art doesn't has a gas pressure indicator embedded in the design of the shock absorber canister that can monitor the gas pressure in the gas chamber.
Therefore, to obviate the lacunae in the prior art, the first objective of the present invention is to provide a gas chamber pressure indicator in the canister that can monitor drop in air pressure inside it.
The second objective of the present invention is to provide a cost effective and easy design.

Brief description of the invention
According to the present invention, the said canister assembly comprises a gas cap, a set of circlips, a membrane, an indication pin, an indication pin guide, a set of O rings, a spring, a non return valve, a defined gas path, et. al. The gas filled through a gas pin passes through the said assembly through a non return valve. The gas passes through the said gas path and forces the floating indication pin to compress the spring. The spring used here has stiffness less than the applied force generated due to gas pressure over the floating indication pin. When the pressure falls below a pre-determined level in the diaphragm/gas chamber, the applied force drops over the indication pin and the spring pushes the indication pin through the indication pin guide. The indication pin comes out of the canister showing the drop in the gas chamber indicating the reference to fill the gas chamber again. In the second embodiment of the present invention an arrangement can also be made wherein, when the pressure is high above the pre-determined level, the indication pin pops out and when the pressure is below the predetermined level, the indication pin falls into the canister assembly pin guide, thus indicating the time for refill of gas.
In the third embodiment of the present invention, same results are achieved by placing a pressure sensor in the vicinity of the diaphragm in the gas chamber suitably and an indicator around the vicinity of head pipe of the vehicle chassis.
Brief description of the drawing
Figure 1 illustrates an isometric view of a general suspension unit.
Figure 2 illustrates an expanded view of a general suspension unit.

Figure 3 illustrates an exploded view of canister assembly according to the present invention.
Figure 4 illustrates cross sectional view of canister assembly according to the present invention.
Figure 5 illustrates cross sectional view of canister assembly when the indicator is actuated according to the present invention.
Figure 6 illustrates another embodiment of the present invention.
Detailed description of the invention
A selected illustrative embodiment of the present invention will be now described with respect to the accompanying figures 1, 2, 3, 4, 5 and 6. An exemplary shock absorber/suspension unit constructed in accordance with an embodiment of the invention is identified generally by the reference numeral in figure 1 and figure 2. The shock absorber 1 is designed to be positioned between a vehicle chassis, and a wheel-carrying hub in a manner known in the art. The suspension unit 1 includes a cylinder assembly or housing 2 which is provided with a first end wall or cap 3. The end wall 3 carries a bracket 4 so as to provide a pivotal connection to the vehicle chassis.
The cylinder housing 2 having a longitudinal axis includes a cylinder bore that is closed at one end by the end wall and at the other end by the gland. The opposite end of the cylinder housing is enclosed by an end wall or cap 3 that carries a sealing gland. A piston rod assembly 5 extends through the sealing gland out of an aperture formed in the wall in a sealing arrangement while providing a translational guide or an inner tube 6 for the rod to allow the rod to translate within the cylinder housing 2.

The rod has an elongated portion on which is carried a yoke 7 that provides the connection to the wheel-carrying hub. A coil compression spring 8 encircles the cylinder housing and the exposed end external to the housing of the piston rod 5. One end of this spring rests against a collar 9 that is connected to the cylinder housing 2. The opposite end of the spring 8 rests against a spring retainer 10 that is carried by the piston rod assembly 5 and is adjacent to the yoke 7. In this arrangement, the spring 8 will be loaded as the piston rod moves relative to the cylinder housing 2 upon suspension movement of the wheel or hub relative to the chassis of the vehicle. A snubber 11 is carried by the spring retainer 10 and wilt engage with the end cap 3 so as to provide a cushioned, yet positive stop, providing a limit to the total compression of the shock absorber 1.
An elastic gas chamber 12 is contained within a bore of a canister 13 which is an integral part of the end wall cap 3. An inert gas such as nitrogen may be filled in gas chamber 12 or a diaphragm 12 formed in the canister 13 so as to maintain a fluid pressure on the fluid in the shock absorber chambers. The inert gas may be inserted through a non return valve 14.
According to the present invention, the said canister assembly 13 comprises a gas cap 21, a set of circlips 15, a membrane, an indication pin 16, an indication pin guide 17, an set of O rings 18, a spring 19, a non return valve 14, a defined gas path 20, et al as shown in figure 3 and figure 4. The gas filled through a gas pin passes through the said assembly through a non return valve 14. The gas passes through the said gas path 20 and forces the floating indication pin 16 to compress the spring 19 as shown in figure 4. The spring 19 used here has stiffness less than the applied force generated due to gas pressure over the floating indication pin 17. When the pressure falls below a pre-determined level in the diaphragm/gas chamber 12, the

applied force drops over the indication pin 16 and the spring pushes the indication pin 16 through the indication pin guide 17. The indication pin 16 comes out of the canister 13 as shown in figure 5 showing the drop in the gas chamber 12 indicating the reference to fill the gas chamber 12 again.
Figure 6 illustrates second embodiment of the present invention wherein when the pressure inside the gas chamber/ diaphragm 12 is less than the prescribed level; the indication pin 16 becomes apparently loose and falls back in to the canister assembly 13. In the normal scenario when the pressure inside the gas chamber 12 is as per the prescribed level, the spring 19 pushes the indication pin 16 through the indication pin guide 17 and as a result a visible popped-up indication pin 16 is realised. Once the pressure drops down as a result of less pressure in the gas chamber 12, the force under the spring 19 is reduced and thus the indication pin 16 becomes loose and falls back in to the canister assembly 13. In other words when the pressure is high above the pre-determined level, the indication pin 16 pops out and when the pressure is below the predetermined level, the indication pin 16 falls into the canister assembly pin guide 17, thus indicating the time for refill of gas. In both the said embodiments, an additional limiter may be provided that restricts the movement of indication pin on either side as per requirement. In the third embodiment of the present invention, similar results are also achieved by placing a pressure sensor in the vicinity of the diaphragm in the gas chamber suitably and an indicator around the vicinity of head pipe of the vehicle chassis. When the pressure inside the gas chamber reduces below a prescribed predetermined level, the sensor sends the pressure drop signal to an indicator which then prescribes the user for recharge or refill of gas in the canister assembly. A pressure sensor is used in the present case to get more accurate results.

Normally, the predetermined pressure in the gas Chamber for normal operating
condition for twin shock absorber is 7 to 9 Bar and for mono shock absorber it is 16
to19Bar.
Although the subject matter has been described in considerable detail with reference
to certain preferred embodiments thereof, other embodiments are possible. As such,
the spirit and scope of the appended claims should not be limited to the description
of the preferred embodiment contained therein.

Claims We claim:
1. A canister gas pressure indication system for a snock absorber comprising a gas chamber, an indication pin, an indication pin guide, a defined gas path and a spring arrangement with a coil spring.
2. The canister gas pressure indication system as claimed in claim 1, wherein the gas passes from said gas chamber through said gas path and compresses said spring arrangement and when the gas pressure over the spring reduces due to less pressure in said gas chamber, the spring expands and said indication pin comes out of said canister assembly.
3. The canister gas pressure indication system as claimed in claim 1, wherein said spring has stiffness less than force generated due to the pressure in said gas chamber when it is full.
4. A canister gas pressure indication system for a snock absorber comprising a gas chamber, an indication pin, an indication bin guide, a defined gas path and a spring arrangement with a spring wherein wnen the pressure inside said gas chamber is more than a pre-determined level the indication pin is visible outside and when pressure is less than said pre-determined level, said indication pin becomes slack.
5. A canister gas pressure indication system for a snack absorber for a two and a three wheeled vehicle with a head pipe comprising a gas chamber, a sensor and an indicator wherein the sensor is placed in vicinity of said gas chamber and said indicator is placed around vicinity of head pipe of said vehicle.

6. A canister gas pressure indication system for a shock absorber for a two and a three wheeled vehicle as claimed in claim 5, wherein said sensor is a pressure sensor.
7. A two and a three wheeled vehicle as claimed in claim 1 or claim 4 or claim 5.
8. A canister gas pressure indication system as herein substantially described and illustrated with reference to the accompanying drawings.