AUSTRALIA Patent Act 1990 COMPLETE SPECIFICATION SHOCK ABSORBER The Invention is described in the following statement Shock absorber. This invention is related to the vehicle shock absorber and its valve system. Background: There are two main shock absorber designs currently existing in the market place. They are the mono tube design and the twin tube design. The twin tube design has two separate tubes namely the pressure tube and the reserve tube, which are fitted between upper and lower mounting brackets with fluid as a working media filling the enclosed cavities. A piston assembly is fitted within the pressure tube interior enclosed cavity with the rod end connected to the vehicle chassis and the lower end of the shock absorber is connected to vehicle wheel assembly. A compressive spring arrangement is also fitted between vehicle chassis and the wheel assembly. The spring assembly is designed to convert the kinetic energy from the vehicle chassis oscillation as it rides over road irregularity to spring potential energy and the shock absorber is designed to damp this potential energy of the spring and convert it to heat energy. The o piston of the shock absorber reciprocates inside the enclosed pressure tube cavity as the vehicle rides over a bump, forcing the fluid in and out via two restrictor valving systems namely the rebound valve at the piston end and the compression valve which is fitted at the pressure tube base. Both these said valves are designed to handle maximum fluid flow and damping force in most 5 of the road conditions. Often a needle valve used as a secondary valve for varying the damping force by bleeding off the fluid flow. A needle valve consists of a small pointer piston plug that can be adjusted to vary the size of the outlet opening hence varying the fluid flow rate and damping forces. The needle valves have two inherent common problems that prevent them from being used for the main primary compression and rebound valves on vehicle shock absorbers. The problems are hydraulic locking and lessened damping force generating ability. 5 The hydraulic locking, where the fluid is momentarily locked and cannot flow due to the volume flow rate changes being too high and the fluid passage and the opening of the needle valve too small, causes excess internal pressure and hence destroys the internal components including the valve seals. The second problem is lessened damping generating ability due to limited small fluid flow D volume upon its physically relatively small outlet opening to generate the bulk of the damping force required. Summary of the Invention This invention aims to overcome the hydraulic locking problem mentioned as 5 well as to increase the damping force generating capacity of a needle valve. Hence it can be used as the main primary compression and rebound valve of the shock absorber. One of the features of this invention is the arrangement of the valve systems 20 including the plural cylindrical discs stacked on top of each other and in a single column. This single column of discs is fitted within a valve housing that has a closed hollow cylindrical shaped interior. The concentricity and the clearance of the said cylindrical discs column and the valve hollow cylindrical interior are in fine tolerance. An external compression force continues to 25 apply to the disc column to keep the discs in closed position and retain the gap and the cavities between discs as the fluid flows through and tends to force them apart, hence the majority of the damping force is produced.
If we incorporate this valve assembly into a conventional shock absorber, then two valve assemblies are needed, namely the compression valve assembly and the rebound valve assembly with their associated and unique fluid flow loops. On the compression stroke, the shock absorber piston pushes the fluid through 5 the main compression valve, firstly via the inlet opening and clearance gap between the housing and the discs column outside diameter, through the cavities between the said discs column, through the central cavity of the disc column and exits on the outlet opening of the valve and into the other side of the main piston of the shock absorber. A non return valve is included on the fluid flow loop to differentiate the compression stroke fluid flow loop from the rebound stroke fluid flow loop. On the rebound stroke, the fluid flows through the valve inlet, through the central cavities of the disc column, through the gap and cavities between the discs and exits on the outlet opening. Once again, a non return valve is incorporated on the fluid path for the same reason 5 as mentioned previously. Another feature of this invention is the cylindrical valve housing with either two or three openings. All openings are fully sealed to prevent any premature fluid leakages. If the option is using three openings arrangement, then two of 0 these openings are for the instantaneous fluid inlet and outlet openings, one at the end of the cylindrical housing and the other along the cylindrical perimeter of the valve housing. The third opening is located axially and at the other end of the cylindrical valve housing for a spring loaded piston that continues to exert force on the disc column. In the two holes arrangement, the 5 instantaneous fluid inlet and the spring loaded piston are in the same opening and the other opening is for instantaneous fluid outlet. The inlet and outlet of the said valve fluid passage can have a relatively larger predetermined cross section area so that there is no hydraulic lock occurring.
Another feature of this invention includes the mentioned cylindrical disc with central cavity. The cylindrical disc end faces consist of either a squared face groove or angular face groove on one end on a particular pitch diameter. The 5 other end face includes a double bevel circumferential edges upon a pitch diameter which is the same as the other end face groove pitch diameter. The included angle of both end profiles of the cylindrical disc is unequal so that all the are discs stacked and arranged for the circumferential edge of the grooves of the end face contacts and rest on the adjacent disc double bevel end face. 0 The same nesting arrangement mentioned applies to the rest of the cylindrical discs on the disc column or stacker. The gap and the cavities between these cylindrical disc end faces form the restricted radial passages to the fluid flow. Another feature of this invention is that the outside diameter of the cylindrical 5 disc and its axial length are designed to maintain the required reciprocating movement without jamming against the interior of the cylindrical valve housing. The slide clearance between the outside diameter of the disc stacker and the inner diameter of the cylindrical housing is kept to a minimum. and also it serves as the fluid distributing passage from the inlet opening or to the !0 outlet opening as described above. Another feature of this invention is that the number of cylindrical discs used is in proportional relation with the damping force capacity. 5 A further feature of this invention is the induced force upon the disc stacker by the spring loaded piston. A compression spring is fitted into one end of the said piston and it can be changeable to a predetermined compression spring or a disc spring to suit the specified application. A suitable screw threaded with handle knob is incorporated on the other end of the spring loaded piston for manual adjustment. The handle knob can be replaced and coupled to either an electromagnetic drive or to a pneumatic actuator for remote control application. 5 To assist with understanding the invention a reference will be made to accompanying drawings. Figure 1 shows one form of the invention. A half section of the isometric view of the cylindrical profile disc of the invention. Figure 2 shows a another form of the invention. An enlarged view A of figure 0 3 of the invention. Figure 3 shows another form of the invention. The assembly cross sectional view of the invention. Figure 1 shows a half section of the isometric view of the profile cylindrical disc of the invention. The disc 1 consists of upper portion with angle3 formed 5 by the double bevel faces 7 and 8. It is preferred that angle 3 is not equal to angle 2. When discs are stacked the circumferential line 5 and circumferential line 6 are resting on slope face 7 and slope face 8 as shown on figure 2. Both angles 2 and 3 may vary from 15 degrees to 180 degrees in value but they are never equal. The cylindrical disc I consists of central cavity 9 and the outside 2O cylindrical face 10. A flat face 13 may be incorporated on the outside cylindrical face 10 for more fluid flow passage. The slit or hole 4 can be incorporated on either the lower portion as shown or at the top portion of the disc 1 to allow tiny fluid leakage through, hence damping force is produced during initial preloading of the shock absorber. The number and the size of the 25 holes or slits 4 may vary to suit the application. The disc 1 can be manufactured from suitable metal or non-metal and by a conventional process such as machining, press metal, forging or by elevated temperature powdery material sintering process.
Figure 2 shows an enlarged view A of figure 3 of the invention. The fluid flow 15 is shown as many arrows flowing out from compressive volume 26 of the figure 3 via the valve inlet openingl4. The pressure of fluid 15 will try to open the gap between the circumferential edge 5 ,6 and face 7,8 of the 5 adjacent disc in order for the fluid to flow through via central cavities 9 , and to the valve outlet opening 17 of figure 3.The fluid also flows via the cylindrical clearance gap 16 between the cylindrical interior of the valve housing 12 into the adjacent discs cavity. The cylindrical clearance gap 16 is between the outside 10 of the disc I and the valve cylindrical housing interior D cavity wall and it must be kept to a minimum of within a few thousandths of an inch, only allowing a sufficient guide for a slide fit without introducing any unwanted negative affects on damping force capacity. A flat face 13 may be added to outside of disc lto increase the flow volume rate capacity to the next adjacent cavity while keeping the required clearance gap 16 within the i required limit. The circular cavity 11 plays a very important role in damping force generation and where fluid flow changes direction, velocity drops. Figure 3 shows the assembly cross sectional view of the invention in compression cycle as the piston moves in the direction 29. In the rebound cycle, the piston assembly is moving in the opposite of direction 29.The piston 0 and rod subassembly 13 is fitted into body 12 with a guide rod 32 allowing subassembly 13 to reciprocate within the predetermined stroke. The central cylindrical cavity of body 12 is divided into three chambers as shown, namely the chamber 27, the chamber 26 and the gas chamber 24.The chamber 26 pressure is momentarily higher than 27 and pressure level will change over as 5 the cycle changes to rebound cycle. The one way valves 30 and 31 allow the fluid flow in one direction. In this case during the compression cycle, there is no fluid flow on the left hand side but a fluid flow on the right hand side of figure 3.The piston 13 will push the fluid flow 15 through valve passage inlet 14 from chamber 26 and then through the cavities between the discs 1, as well through 33 and 30 into chamber 27. At the rebound cycle, the fluid flow is in the reverse direction but on the left hand side passage. The gas chamber 24 can be replaced by a through shaft arrangement or gas bladder fitted into specified 5 cavities within the body12. The compressive forces from springs 19 and 21 of figure 3 are exerted on the c disc stacker which in turn puts pressure on the edges 5,6 and against faces 7,8 as well as on the disc at the end adjacent to end seal collar 17 and 18. End seal collar 17 and 18 are fitted with o-rings to prevent premature fluid leakage. 0 Once the fluid opening pressure builds up and overcomes the spring forces then the fluid starts to flow hence more damping forces are created. The compressive springs 19 and 21 forces can be adjusted externally and manually by fitting a hand knob on threaded end 22 or by coupling an electric or pneumatic motor /actuator into it for remote control application. 5 20 25