Abstract:
A flow regulator for a gas shock absorber is connected between the primary cylinder and the secondary cylinder. The flow regulator allows a user to adjust the rate of flow of fluid from the primary cylinder to the secondary cylinder thereby varying the damping properties of the shock absorber. The adjustment is effected by rotating one of a plurality of orifices of different sizes into the fluid flow path.

Description:
TECHNICAL FIELD 
   The present invention generally pertains to shock absorbers, and more particularly to a gas shock absorber in which a flow regulator permits selective adjustment of the damping properties of the shock absorber. 
   BACKGROUND OF THE INVENTION 
   Gas shock absorbers are well known in the art. These shock absorbers include a primary cylinder which is connected to a secondary cylinder. The primary cylinder contains a substantially incompressible fluid such as oil, and the secondary cylinder contains a compressible fluid such as a gas. In use, the gas is alternatingly compressed and expanded by the action of the primary cylinder, thereby providing a desired level of damping response. One of the factors which determines the characteristics of the damping is the size of the passageway between the primary and secondary cylinders. A large passageway allows a fast interaction between the cylinders. A small passageway only allows a slow interaction. 
   The size of the passageway may be fixed or adjustable. In many situations, a fixed size is useful. In other situations, an adjustable passageway is preferred. The size of the passageway is effectively adjusted using a valve. The most common valves are needle valves but other types of valves are sometimes used. 
   For example, U.S. Pat. No. 4,153,237 shows a hydrapneumatic suspension unit for a vehicle having first and second chambers separated by a valve assembly for controlling the flow of liquid between them. The first chamber is filled with a liquid and includes a slidably  mounted piston connected by a linkage to the road wheel. The second chamber has a first compartment containing the liquid and a second compartment containing a compressible medium separated by a floating piston. The valve assembly includes a needle damping valve 37, a low-restriction check valve for permitting one-way flow of liquid from the first to the second chamber, and a damping bypass valve for enabling quick return of liquid from the second chamber to the first chamber. 
   U.S. Pat. No. 4,311,302 illustrates a shock absorber device, having a piston rod unit that is axially displaceable through a cylinder member from one end toward the other end. The cylinder forms a variable volume working chamber containing a first fluid. A spring chamber is in communication with the working chamber so that the first fluid can flow between the two chambers. A pressurized second fluid is contained within the spring chamber separate from the first fluid and acts on the first fluid to bias the piston rod unit out of the working chamber. When the piston rod unit is moved into the working chamber and approaches an inner end position, it forms at least in part a damping chamber which decelerates the movement of the piston rod unit. The passageway between the two chambers is fixed. No external adjustment of the rate of damping is available. 
   U.S. Pat. No. 4,620,694 discloses a hydraulic suspension system for a motorcycle having an adjustable shock absorber unit located between the rear wheel and main frame. The first of four adjustments is an externally accessible filler-valve enabling the rider to adjust gas pressure in one chamber to vary spring rate. A second adjustment is a valve for varying the rate of hydraulic fluid flow from a main chamber through a main piston to a third chamber to obtain the desired rate of upper wheel travel. A third adjustment is an adjustable pressure relief valve for limiting differential pressure between fluid in the main chamber and in the third chamber under conditions of severe impact. A fourth adjustment is a valve for varying the fluid flow from a fourth chamber to the third chamber during extension. 
   U.S. Pat. No. 4,921,224 illustrates a hydro-pneumatic suspension system for a car having a main housing with a damping device and a sub housing having a metal bellows. A high-pressure compressed gas is sealed inside the bellows. A passageway connects the main housing to the subhousing. No means is provided for adjusting the size of the passageway.  
   U.S. Pat. No. 4,958,706 describes an adjustable shock absorber having a needle type adjusting screw in the flow path between two chambers for altering the characteristics of the flow path. 
   U.S. Pat. No. 5,351,790 depicts a hydraulically adjustable suspension apparatus for an automobile which has a proportional type of solenoid operated valve assembly for controlling the pressure or flow rate of a pressurized fluid introduced into a cylinder tube through a fluid passage. 
   U.S. Pat. No. 4,732,244 shows a hydraulic shock damper assembly for the rear wheel of a rally-cross motorcycle and other vehicles. The hydraulic cylinder is connected through a flow channel to a dashpot having a partition element enclosing a pressurized fluid such as nitrogen. A plurality of identical apertures 41 are provided through a disk 40 for adjusting the total aperture between the hydraulic cylinder and dashpot. A control plate 43 is rotated by a knob 45 to adjust the number of apertures in the passageway. 
   Under harsh conditions such as encountered in the operation of snowmobiles and all-terrain vehicles, needle valves have limited utility because they tend to break. The valve of U.S. Pat. No. 4,732,244 is an example of a valve for use in harsh conditions that is not a needle valve. However, the control plate used is relatively thin. A valve for adjusting a gas shock absorber that is durable would be a useful improvement.  
   SUMMARY OF THE INVENTION 
   The present invention is directed to a flow regulator for a gas shock absorber. The flow regulator is placed between a primary cylinder or housing and a secondary cylinder or housing. The flow regulator allows selective adjustment of the damping properties of the shock absorber by placing one of a plurality of different sized orifices in the fluid flow path between the two cylinders. The selected orifice determines the rate at which fluid may flow from the primary cylinder to the secondary cylinder, and therefore the damping properties of the shock absorber. The flow regulator includes a one way valve which permits the fluid to flow back from the secondary cylinder to the primary cylinder, and a safety valve which opens to provide a bypass flow when a predetermined level of high pressure is reached in the primary cylinder. 
   In accordance with a preferred embodiment of the invention, a flow regulator is connected between the output chamber of the primary cylinder and the input chamber of the secondary cylinder. The flow regulator controls the flow of incompressible fluid such as oil between the output and input chambers. The flow regulator includes a body which receives a flow control member. The flow control member has a plurality of orifices of different sizes. The flow control member may be selectively positioned to cause the incompressible fluid to flow through one of the orifices from the output chamber of the primary cylinder to the input chamber of the secondary cylinder. The size of the selected orifice determines the rate of flow of the incompressible fluid, and therefore the damping properties of the shock absorber. 
   In accordance with an aspect of the invention, the flow control regulator includes a one way valve which permits the incompressible fluid to flow back from the secondary cylinder to the primary cylinder. 
   In accordance with another aspect of the invention, the flow control regulator also includes a safety valve which allows direct fluid flow from the primary cylinder to the secondary cylinder when a high pressure conditions exists. 
   Other aspects of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.  

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross sectional view of a prior art gas shock absorber; 
       FIG. 2  is a cross sectional view of the prior art shock absorber being compressed; 
       FIG. 3  is a cross sectional view of a shock absorber in accordance with the present invention having a flow regulator; 
       FIG. 4  is a cross sectional view of the shock absorber being compressed; 
       FIG. 5  is a top plan view of the body of the flow regulator; 
       FIG. 6  is a side elevation view of the body; 
       FIG. 7  is a bottom plan view of the body; 
       FIG. 8  is a cross sectional view along the line  8 — 8  of  FIG. 7 ; 
       FIG. 9  is a top plan view of a flow control member; 
       FIG. 10  is a side elevation view of the flow control member; 
       FIG. 11  is a bottom plan view of the flow control member; 
       FIG. 12  is a cross sectional view along the line  12 — 12  of  FIG. 9 ; 
       FIG. 13  is a cross sectional view along the line  13 — 13  of  FIG. 10 ; 
       FIG. 14  is a cross sectional view along the line  14 — 14  of  FIG. 10 ; 
       FIG. 15  is a cross sectional view along the line  15 — 15  of  FIG. 9 ; 
       FIG. 16  is a top plan view of a hollow member; 
       FIG. 17  is a side elevation view of the hollow member; 
       FIG. 18  is a bottom plan view of the hollow member; 
       FIG. 19  is a side elevation view of a spherical member; 
       FIG. 20  is a top plan view of a washer; 
       FIG. 21  is a side elevation view of the washer; 
       FIG. 22  is a top plan view of a second washer; 
       FIG. 23  is a side elevation view of the second washer; 
       FIG. 24  is a top plan view of a rotatable member; 
       FIG. 25  is a side elevation view of the rotatable member; 
       FIG. 26  is a bottom plan view of the rotatable member;  
       FIG. 27  is an exploded view of the flow regulator; 
       FIG. 28  is a side elevation view of the flow regulator; 
       FIG. 29  is a cross sectional view of fluid flow within the flow regulator; 
       FIG. 30  is a cross sectional view of fluid flow within the cylinder, when the fluid is flowing back from the secondary housing to the primary housing; 
       FIG. 31  is a cross sectional view of a one way valve feature of the flow regulator; and, 
       FIG. 32  is a cross sectional view of a safety valve.  
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  illustrates a cross sectional view of a prior art gas shock absorber, generally designated as  500 . Shock absorber  500  includes a primary housing  502  having a primary internal cavity containing a fluid such as an oil, a first end  504 , and an opposite second end  506 . The fluid is incompressible under the operating conditions of shock absorber  500 . A piston assembly  508  is disposed within the primary internal cavity, the piston assembly  508  longitudinally traveling within the primary internal cavity, the piston assembly  508  partitioning the primary internal cavity into a first chamber  510  disposed adjacent first end  504  of primary housing  502 , and a second chamber  512  disposed adjacent second end  506  of primary housing  502 . It may be appreciated that as piston assembly  508  longitudinally travels within the primary internal cavity, the relative sizes of first chamber  510  and second chamber  512  inversely change (refer also to  FIG. 2 ). A shock rod  514  is connected to piston assembly  508 , shock rod  14  passing through second end  506  of primary housing  502 . 
   Piston assembly  508  includes bypass valves  517  which are necessary to allow the incompressible fluid to bypass piston assembly  508  so that piston assembly  508  can move up and down within the primary internal cavity of primary housing  502 . Bypass valves  517  comprise thin washers of various diameters which bend to allow the passage of fluid between first chamber  510  and second chamber  512 , and visa versa. The number and size of the washers may be varied to “tune” the response of gas shock absorber  500 . 
   Shock absorber  500  also includes a secondary housing  516  having a secondary internal cavity, a first end  518 , and an opposite second end  520 . A piston  522  is disposed within the secondary internal cavity, piston  522  longitudinally traveling within the secondary internal cavity, the piston  522  partitioning the secondary internal cavity into a first chamber  524  disposed adjacent first end  518  of secondary housing  516 , and a second chamber  526  disposed adjacent second end  520  of secondary housing  516 . Again it may be appreciated that as piston  522  longitudinally travels within the secondary internal cavity, the relative sizes of first chamber  524  and second chamber  526  inversely change (refer also to  FIG. 2 ). Second chamber  526  contains a compressible fluid such as a gas. In practice the compressible fluid is  pressurized to a desired level such as 200 psi. Nitrogen is the gas that is typically used in gas shock absorbers. 
   The first chamber  510  of primary housing  502  is connected by a passage  528  such as tubing to the first chamber  524  of secondary housing  516  so the incompressible fluid may flow between the two first chambers. 
     FIG. 2  is a cross sectional view of the prior art shock absorber  500  being compressed. As piston assembly  508  moves toward first end  504  of primary housing  502 , some of the incompressible fluid moves past bypass valves  517  and some is forced out of first chamber  510  and into first chamber  524  of secondary housing  516  through passage  528 . Piston  522  is thereby forced toward second end  520  of secondary housing  516  compressing the gas in second chamber  526 . The action of the pistons within the two housings combine to provide the desired damping effect. 
     FIG. 3  illustrates a cross sectional view of a shock absorber in accordance with the present invention, generally designated as  20 . Shock absorber  20  includes the elements of prior art shock absorber  500 , and additionally includes a flow regulator generally designated as  22 . Flow regulator  22  is connected between first chamber  510  of primary housing  502  and first chamber  524  of secondary housing  516 . Flow regulator  22  controls the flow of incompressible fluid between first chamber  510  of primary housing  502  and first chamber  524  of secondary housing  516 . Flow regulator  22  includes a body  24  (refer to  FIGS. 5–8 ) which receives a flow control member  26  (refer to  FIGS. 9–15 ). Flow control member has a plurality of orifices  28  of different sizes (refer to  FIG. 13 ). Flow control member  26  may be selectively positioned within body  24  to cause the incompressible fluid to flow through one of the orifices  28  from first chamber  510  of primary housing  502  to the first chamber  524  of secondary housing  516 . By selecting a particular orifice  28 , the damping properties of shock absorber  20  may be selectively changed by a user. 
     FIG. 4  is a cross sectional view of shock absorber  20  being compressed. As piston assembly  508  moves toward first end  504  of primary housing  502 , some of the incompressible fluid moves past bypass valves  517  and some is forced from first chamber  510  of primary housing  502  through passage  528  to flow regulator  22  and then to first chamber  524  of secondary housing  516 . The incoming incompressible fluid forces piston  522  toward second  end  520  of secondary housing  516 , thereby compressing the gas in second chamber  526 . Through orifice  28  selection, flow regulator  22  controls the rate at which the incompressible fluid can flow into first chamber  524  of secondary housing  516 . 
     FIGS. 5–7  are top plan, side elevation, and bottom plan views, respectively, of body  24  only of flow regulator  22 .  FIG. 8  is a cross sectional view along the line  8 — 8  of  FIG. 7 . Body  24  includes an entry port  30  and an exit port  32 . Entry port  30  is connected by passage  528  to first chamber  510  of primary housing  502  (see  FIG. 4 ). Exit port  32  directly opens into first chamber  524  of second housing  516 . Body  24  includes threads  25  for installation in secondary housing  516 . Body  24  also includes a plurality of circularly spaced dimples  27  which are part of a detent mechanism (refer to  FIG. 27 ). 
     FIGS. 9–11  are top plan, side elevation, and bottom plan views, respectively, of flow control member  26  only of flow regulator  22 . Flow control member  26  comprises a cylinder  34  having an outside surface  36  and a plurality of bores  38 . Each bore  38  is connected to outside  36  surface by one of the orifices  28  (refer also to  FIG. 13 ). As used herein, connected means that there exists a passage through which the incompressible fluid may flow. Cylinder  34  may be selectively rotated within body  24  ( FIGS. 5–7 ) so that one of the orifices  28  aligns with exit port  32 . When so aligned by selection, the incompressible fluid flows from first chamber  510  of primary housing  502  ( FIG. 4 ), through passage  528 , through entry port  30 , through the bore  38  connected to the aligned orifice  28 , through the aligned orifice  28 , through exit port  32 , and into first chamber  524  of secondary housing  516  (refer also to  FIG. 29 ). The different sized orifices  28  permit the selection of a different incompressible fluid flow rate. 
     FIG. 12  is a cross sectional view along the line  12 — 12  of  FIG. 9 . In the figure, cylinder  34  has been rotated so that the orifice  28  on the right has been selected to pass the incompressible fluid. When installed in body  24 , this orifice will align with exit port  32 . It is further noted that cylinder  34  includes a circular channel  40  which connects entry port  30  with each bore  38  (also refer to  FIG. 11 ). As will be discussed later, this feature allows the incompressible fluid to freely flow back from the secondary housing  516  to the primary housing  502 . 
     FIG. 13  is a cross sectional view along the line  13 — 13  of  FIG. 10  showing one orifice  28  connected to each bore  38 . In the shown embodiment, seven orifices  28  are  circumferentially spaced around cylinder  34 . The smallest orifice  28  provides the least damping effect of secondary housing  516 , while the largest orifice  28  provides the most damping effect of secondary housing  516 . It is noted that an additional no orifice bore  39  does not connect to an associated orifice  28 . Therefore, should cylinder  34  be rotated so that exit  32  port aligns with no orifice bore  39 , no incompressible fluid can flow through flow regulator  20 . No orifice bore  39  also plays a role in allowing the incompressible fluid to freely flow back from the secondary housing  516  to the primary housing  502 . 
     FIG. 14  is a cross sectional view along the line  14 — 14  of  FIG. 10 . No orifice bore  39  is connected to an aperture  42  which is centrally disposed in cylinder  34 . In the shown embodiment, aperture  42  is threaded. 
     FIG. 15  is a cross sectional view along the line  15 — 15  of  FIG. 9 . No orifice bore  39  is connected to aperture  42  and circular channel  40 . 
     FIGS. 16–18  are top plan, side elevation, and bottom plan views, respectively, of a hollow member or threaded screw  44 . Hollow member  44  has a first inside diameter D 1  and is accepted by aperture  42  (refer to  FIGS. 12 ,  14 ,  30 , and  31 ). Hollow member  44  has an open end  46  and an opposite head end  48 . Head end  48  has a hole  50  which has a second diameter D 2  which is less than first inside diameter D 1 . 
     FIG. 19  is a side elevation view of a spherical member  52  such as a ball bearing. Spherical member  52  is disposed within threaded aperture  42  and hollow member  44 . Spherical member  52  has a third diameter D 3  which is less than first inside diameter D 1  and greater than second diameter D 2 . 
     FIGS. 20 and 21  are top plan and side elevation views respectively of a bypass washer  54 . 
     FIGS. 22 and 23  are top plan and side elevation views respectively of a second washer  56 . 
     FIGS. 24–26  are top plan, side elevation, and bottom plan views, respectively, of a rotatable member  58  such as a knob. Rotatable member  58  includes a plurality of circularly spaced dimples  60  and two holes  62 . Rotatable member  58  is connected to cylinder  34  ( FIGS. 9–11 ) of flow control member  26 , and is used to rotate cylinder  34  within body  24  (refer also to  FIG. 27 ).  
     FIG. 27  is an exploded view of flow regulator  22 . Hollow member  44  accepts spherical member  52 , and is installed in aperture  42  using washer  56  and three bypass washers  54 . A detent mechanism is connected between rotatable member  58  and body  24 , so that, using rotatable member  58 , cylinder  34  may be selectively rotated to a flow position corresponding to one of the orifices  28 , wherein the detent mechanism urges cylinder  34  to remain in the selected flow position. The detent mechanism includes ball bearings  64  and springs  66  which fit into holes  62 . As rotatable member  44  is rotated, ball bearings  64  enter one of the dimples  60  in rotatable member  58  and one of the dimples  27  in body  24 , thereby urging cylinder  34  to remain in the selected position. A hard rotation can overcome the detent action, and rotate cylinder  34  to another position within body  24 . 
     FIG. 28  is a side elevation view of the assembled flow regulator  22 . 
     FIG. 29  is a cross sectional view of fluid flow within flow regulator  22 . Also referring to  FIG. 4 , the incompressible fluid flows from first chamber  510  of primary housing  502 , through passage  528 , through entry port  30 , through selected bore  38 , through selected orifice  28 , through exit port  32 , and into first chamber  524  of secondary housing  516 . 
     FIG. 30  is a cross sectional view of fluid flow within aperture  42  of cylinder  34 , when the fluid is flowing back from secondary housing  516  to primary housing  502 . Flow regulator  22  includes a one way valve which permits the incompressible fluid to freely flow or rapidly return from first chamber  524  of secondary housing  516  to first chamber  510  of primary housing  502 . The incompressible fluid may flow from first chamber  524  of secondary housing  516 , through hole  50  in hollow member  44 , through hollow member  44 , through no orifice bore  39 , through circular channel  40 , through entry port  30 , and into first chamber  510  of primary housing  502 . It is noted that for flow in the above described direction, the structure is such that the incompressible fluid flows around spherical member  52 . 
     FIG. 31  is a cross sectional view of the one way feature of flow regulator  22 . In the forward direction of fluid flow, i.e., primary housing  510  to secondary housing  516 , the incompressible fluid cannot flow though hole  50  in hollow member  44 . This is because for forward fluid flow, spherical member  50  lodges in hole  50  to prevent the incompressible fluid from flowing from entry port  30  to first chamber  524  of second housing  516  via hollow member  44 .  
     FIG. 32  is a cross sectional view of a safety valve. Flow regulator includes a safety valve which opens allowing the incompressible fluid to flow from entry port  30  to first chamber  524  of secondary housing  516  when first chamber  510  of primary housing  502  experiences a predetermined pressure level. That is, should the pressure in first chamber  510  of primary housing  502  become too high, the safety value will permit the incompressible fluid to flow directly into first chamber  524  of secondary housing  516  without going through one of the orifices  38 . 
   The safety valve includes at least one bypass washer  54  which covers one end of bores  28 . When a predetermined high pressure level is reached, bypass washer  54  bends to allow the incompressible fluid to travel from entry port  30  through each of bores  38  and  39 , and into first chamber  524  of secondary housing  516 . 
   The preferred embodiments of the invention described herein are exemplary and numerous modifications, variations, and rearrangements can be readily envisioned to achieve an equivalent result, all of which are intended to be embraced within the scope of the appended claims.