US3828897A

US3828897A - Special piston seal

Info

Publication number: US3828897A
Application number: US00319023A
Authority: US
Inventors: S Nandyal
Original assignee: Maremont Corp
Current assignee: Maremont Corp
Priority date: 1972-12-27
Filing date: 1972-12-27
Publication date: 1974-08-13
Anticipated expiration: 1991-08-13

Abstract

A ring with a non-circular cross section which functions both as a seal between the piston and cylinder wall and also acts as a spring for a compression regulating valve in the piston of a double action hydraulic shock absorber.

Description

United States Patent 1191 Nandyal SPECIAL PISTON SEAL Inventor: Srinath Nandyal, Park Forest, 111.

Assignee: Maremont Corporation, Chicago,

Filed: Dec. 27,1972

App1.No.:3l9,023v

US. Cl 188/317, 188/320, 188/322, 277/102, 285/D1G. 11

Int. Cl F16f 9/34 [58] Field of Search 188/282, 317, 316, 320, 188/322; 267/152, 153, 140, 141; 277/102, 113; 2 85/DIG. 11

References Cited UNlTED STATES PATENTS 2/1931 Sykes 285/D1G. 19

1451 Aug. 13, 1974 2,507,267 5/1950 Patriquin 188/320 10/1966 Thomasetal. 267/153 Primary'ExaminerGeorge E. A. Halvosa Attorney, Agent, or FirmCushman, Darby & Cushman [57] ABSTRACT A ring with a non-circular cross section which functions both as a seal between the piston and cylinder wall and also acts as a spring for a compression regulating valve in the piston of a double action hydraulic shock absorber.

' 2 Claims, 7 Drawing Fignres PATENTEDMIH 31w 3.828.897

sorber.

SPECIAL PISTON SEAL BACKGROUND OF THE INVENTION This invention relates to a shock absorber, in particular to a fluid shock absorber. Although the invention is applicable to various types of fluid shock absorbers, it is illustrated and explained herein by way of example as embodied in a double action hydraulic shock ab- This invention and certain of its aspects is an improvement on the invention disclosed in the US. Pat. No. to Patriquin 2,507,267 of May 9, 1950. In the Patriquin patent a shock absorber piston is provided with a resilient annular piston ring that performs the dual function of sealing to prevent flow of fluid between the exterior of the shock absorber piston and the interior of the shock absorber cylinder and also functions to resiliently urge a valve member to its respective seat. This resilient annular piston seal is mounted on the opposite side of the valve member from its seat and between the valve member and annular seal carrier. The annular seal carrier is held in place by the force of a coil spring member which forces the annular seal carrier in a direction toward said piston seal. Thus as the fluid energy forces the valve member to move away from the seat, the piston seal is compressed between the valve member and the annular seal carrier.

To improve thedesign shown in the Patriquin patent, the clearance between the valve member and the internal cylinder wall was reduced and the durometer of the piston seal was increased, thus, eliminating extrusion of the seal between the valve member and cylinder wall during high dampingfluid pressures. This improved design resulted in acceptable sealing and resistanceto extrusion but caused a higher spring rate of the seal.

To reduce this spring rate, the present invention contemplates the use of a sealing member which is of a non-circular cross section. The seal herein described is constructed of a resilient material that will provide a good seal against the interior surface of the shock absorber cylinder and in addition, provide substantial improvement in the spring characteristic'of the seal. The improvement in the spring characteristics of the seal will permit a greater degree of control and improved operation of the compression valving arrangement that is a part of the piston assembly.

Referring to the accompanying drawings which illustrate an embodiment of the above invention:

FIG. 1 is a fragmentary sectional view of a shock absorber;

FIG. 2 is a fragmentary sectional view through the working cylinder of the shock absorber withthe piston shown partly in section and partly in elevation;

FIGS. 3, 4, 5 and 6 are perspective views of various parts of the shock absorber piston; and

FIG. 7 is a cross sectional view of the piston seal.

DESCRIPTION OF THE PREFERRED EMBODIMENT The shock absorber illustrated in FIG. 1 comprises a substantially cylindrical casing 110 which has relative telescoping movement within a cylindrical guard housing 111 that is spaced radially outwardly from the casing 110. The upper end of the housing 111 is closed by an inverted cup-shaped closure or cap member 112 provided on its outer side with an eye 113 while the piston rod 2 is operatively connected to the member 112 and eye 113. The lower end of the casing is closed by a cup-shaped closure member which has secured to its outer side, a lower eye 116. The

closure members

112 and 115 extend into the housing 111 and the casing 110, respectively, and are secured thereto by welding or by other suitable means.

In mounting the shock absorber upon a motor vehicle similar mounting pins or trunnion rods (not shown) may be connected, respectively, to the frame and axle of the vehicle in any suitable manner so as to extend outwardly therefrom in substantially parallel relationship and pass through the

eyes

113 and 116. These pins or rods may be operatively connected with the

eyes

113 and 116 by suitable means, well known in the art, wherefore relative movement between the frame and axle of the vehicle will cause relative telescoping movement between the casing 110 and the housing 111 and relative movement of the piston rod 2 and the piston 5 secured thereto in the pressure or working cylinder now to be described.

The pressure or working cylinder 1 of the shock absorber is disposed within the casing 110 in spaced concentric relationship therewith so that the space defined by the casing 110, cylinder 1, closure member 115 and a suitable closure member for the upper end of the casing and cylinder (not shown but well understood in the art) constitutes a reservoir 118 for the oil, liquid or fluid in the shock absorber.

The cylinder 1 at its lower end has secured therein a closure plate 119. This closure plate 119 is provided with an upwardly directed shoulder 120 which serves to retain the closure plate in position on the end of the cylinder 1. This closure plate is provided with a plurality of circumferentially spaced internal grooves or channels 121 which place the reservoir 118 in communication with the space between the closure plate 119 and the bottom of the cup-shaped closure member 115. The closure plate 119 may be provided with suitable valving 117 to allow the oil to pass from the working cylinder to the reservoir during the impact stroke and which allows oil to return to the working cylinder at a relative rapid flow rate during the recoil stroke.

The upper or high pressure end of the cylinder 1 is closed by plug member (not shown but well understood) which fits into the cylinder and is suitably secured in position therein and is provided with a central opening through which the piston rod slideably extends. It will be understood that suitable packing is provided at the upper end of the shock absorber to prevent the escape or leakage of oil.

Referring now to FIG. 2, a shock absorber working cylinder 1 is shown with a shock absorber piston assembly located therein. This piston assembly divides the chamber formed by the working cylinder 1 into an upper portion 23 and lower portion 24.

A piston rod 2 is located in the interior of the working cylinder 1 for transmitting motion to the shock absorber piston assembly. This piston rod 2 is provided with the exterior threaded portion 3 and with a radial shoulder 4 located just above the threaded portion 3. A piston 5 comprises a body portion which has an upper and reduced portion 7 and a lower and larger portion 6. The lower piston portion 6 has a clearance 25 between the interior wall of the working chamber. The lower and larger portion 6, is bored to form counterbore 8, which is in fluid communication with the lower portion 24 of the working chamber. Flow restricting ports 9 are provided in the sides of the wall surrounding the counterbore and provide fluid communication between the counterbore 8 and the clearance 25.

The upper portion 7 of the piston body is provided with a central bore 11 which is internally threaded so that the threaded end 3 of the piston rod can be screwed into the bore 11 to unite the piston body to the piston rod. The upper portion 7 of the piston body is also provided with a plurality of circularly spaced axial extending peripheral recesses or grooves 12 which extend from the lower piston part 6 to the upper end of the piston part 7.

A piston stop washer or spring abutment plate 13 is provided with central bore 14 which is of sufficient diameter to allow the threaded portion 3 of the piston rod to be inserted therein. This bore 14 is small enough so that the washer 13 will abut against the shoulder 4 to limit the axial movement of the washer 13 onto the rod. The washer 13 is shaped so that arcuate cut out portions 15 form a space 16 between the exterior of washer l3 and the interior surface of the working cylinder 1.

A resilient annular piston seal 17 is mounted on a rigid carrier 18 which is slidable on the upper portion 7 of the piston body. FIG. 7 illustrates the crosssectional view of the preferred embodiment of the resilient annular piston seal. This seal is provided with an outer peripheral arcuate surface 26 which seals with the interior surface of the working cylinder 1. The inner peripheral surface 27 is shown as being arcuate but because the inner surface does not perform a sealing function other shapes could be used for the inner surface. The-seal is constructed with two ridges 29, each of which is formed by the intersection of two surfaces 28 at an obtuse angle X. The obtuse angle is such that the force per unit of deflection due to axial compression is less than theforce per unit of deflection due to radial compression. Such lesser deflection rate is obtained by virtue of the fact that the rate of divergence 4 a limited amount of distortion of the seal caused by the axial movement of the carrier 18 can be obtained.

A valve member 22 in the form of a flat annular ring is mounted on the carrier 18 between the piston seal 17 and the uppermost shoulder of the lower portion 6 of the piston. The ring 22 and the carrier arms 19 and 20 form an annular groove in which the resilient annular piston seal 17 is compressed.

The carrier ring 18 has notches 21 cut in the lower extremity of the arm 19 to allow fluid to flow from one side of the lower arm 19 to the other when the ring 22 moves toward arm 18 and out of sealing engagement with the lower piston portion 6. I

A coil spring member 30 is mounted around the upper piston portion 7 and between the spring abutment plate 13 and the radially extending arm 20 on the rigid carrier 18. This spring member 30 normally maintains the carrier, piston seal, and valve member in the position shown in FIG. 2. g

. In operation, when the piston is moving in a downward direction to compress the fluid in the lower portion 24 andto expand the fluid in the upper portion 23, a pressure differential is created between the upper portion 23 and the lower portion 24 of the working chamber which causes the fluid to tend to flow from the lower portion to the upper portion. With the piston moving in the downward direction the higher energy of this fluid in the lower chamber is exerted on the valve member 22. This energy will cause the valve member 22 to move slightly on the carrier to compress the piston seal 17 in an axial direction as long as the force exerted on the valve member does not exceed the force of the spring member 30. The movement of the valve member 22 relative to the carrier 18 and the piston seal 17 will provide a limited leak of fluid from the lower portion 24 by way of the counterbore 8, through the 7 ports 9, past the valve member 22, through the notches of each pairof surfaces 28 is less than the rateof radially inward divergence of the arcuate surface 26, as is evident from the drawings. It has been found that with a seal constructed of material with a durometer of 75 i 5 that an angle X of 135 is satisfactory. These four planar surfaces 28 are joined together at their other ends by the

arcuate surfaces

26 and 27. When the seal is located in the carrier ring, these two ridges 29 are 10- catedon the seal such that an imaginary line passing through each of the ridges would be parallel to the interior surface of the working cylinder.

A rigid annular carrier ring 18 is inserted onto the upper reduced portion 7 and has a cross section having an arm 19 which extends axially toward the piston and slidably contacts the upper piston portion 7 and has a radially extending arm 20 which forms one side of the groove in which the resilient annular piston seal 17 rides. It will thus be seen that as the sealing ring 17 moves with the carrier 18, it is in sealing engagement with the interior wall of the working cylinder as it slides toward and away from the piston portion 6. The arm 19 of the carrier has its length fixed so that when the piston seal 17 is in the position shown in FIG. 2, the free end of the arm 19 contacts the lower piston portion 6. By fixing the size of the resilient annular piston seal 17,

21 of the carrier member, up along the axial extending peripheral recesses 12, and through the cut out portions 15 in the spring abutment plate 13 to the upper portion 23 of the working cylinder.

When the energy of the fluid in the lower chamber 7 reaches a sufficiently high level, the rigid carrier 18, piston seal 17, and valve member 22 will lift from the lower piston portion 6 due to the fluid energy overcoming the force of the coil spring member 30. Oil can then flow from the lower working chamber to the upper chamber without the notches 21 of the carrier 18 forminga flow path restriction.

As can be seen from the above description of the operation of the piston valve member 22, the resilient annular piston seal 17 may be compressible in the axial direction so that the valve member can move a sufficient distance to allow the notches 21 to become completely effective but without exerting a force on the carrier which would overcome the force exerted by the coil spring member 30.

In the one embodiment of this piston seal 17, the two ridges 29 contact the valve member 22 and the radially extending arm 20 of the rigid carrier 18. It is between these two points of contact that the seal is compressed to give the desired compression characteristics in the direction of valve movement, while the outer peripheral arcuate surface 26 provides a seal with the interior surface of the working cylinder 1. By elongating the seal configuration in the axial direction and retaining the outer arcuate surface the sealcan perform the two functions of (1) providing an adequate seal between the piston and the interior surface of the working cylinder 1 and (2) functioning as a spring for controlling the movement of the valve member 22. It is anticipated that the surface 28, which in the preferred embodiment is a flat planar surface, could be either a concave or convex surface and the seal could still have sufficient spring and sealing characteristics to solve the problems presented in the disclosed shock absorber configuration.

It will be understood that the principles of the present invention are applicable to any conventional type shock absorber and the utilization of the improved seal and seal assembly is not limited in its application to the specific type and construction of the remaining conventional component elements of the shock absorber shown.- For example, other types of connectors such as stud connectors or the like, can be utilized in lieu of the

eyes

113 and 116. Other structural arrangements for providing a flow path of fluid during the compression stroke from the cylinder portion 24 to the seal assembly of the present invention can be provided in lieu of the passage 9. For example, such passage may be provided by grooves in the periphery of the piston itself. Moreover, the principles of the present invention including the seal and its cooperation with the sealing assembly carried by the piston would have utility in shock absorbers of the type in which the reserve chamber is disposed in axial alignment with the damping chamber rather than annularly thereabout.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing preferred specific embodiment has been shown and described for the purpose of illustrating the functional and structural principles of this invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

What is claimed is:

1. In a shock absorber of the type including a cylindrical walled damping chamber for receiving a damping liquid and a piston dividing said chamber into a first and second portion and mounted for reciprocal movement within said chamber, means carried by said piston for controlling flow of damping liquid from said first portion of the chamber to said second portion during the movement of said piston within said chamber in one direction, said control means including: an annular valve seat on said piston; and annular valve member moved by fluid energy within said first chamber portion to and away from sealing engagement with said valve seat for controlling the flow of damping liquid during a first operational range from said first portion of said chamber to said second portion of said chamber; an annular seal carrier moved to and away from engagement with said valve seat by fluid energy during a second operational range of fluid flow from said first portion of said chamber to said second portion of said chamber, a resilient annular seal carried by said seal carrier positioned between said valve member and said seal carrier for sealing the flow of damping liquid between said valve member and said wall of said damping chamber, means defining flow passages between said valve seat and said annular seal carrier for restricting the flow of fluid from said first portion to said second portion of said chamber during said first operational range of fluid flow; a spring member for resiliently forcing said seal carrier in a direction toward said valve seat and for biasing said seal carrier against said valve seat during said first operational range of fluid flow from said first portion of said chamber to said second portion of said chamber, the improvement which comprises said annular seal being formed solely of a resilient material of a durometer sufficient to prevent extrusion thereof between said valve member and said wall of said damping chamber under maximum axial compression thereof between said valve member and said seal carrier, said annular seal having a radially outer peripheral surface portion of 'arcuate cross-sectional configuration disposed in sliding sealing relation with said wall of said damping chamber and axially opposed peripheral surface portions disposed in engagement with said valve member and said seal carrier respectively, said axially opposed peripheral surface portions having nonarcuate cross-sectional configurations which diverge axially inwardly at a rate less than the rate of radial inward divergenece of said radially outer peripheral surface portion so as to present a force per unit deflection due to compression by movement of said annular valve member during said first operational range of fluid flow which is less than the force per unit deflection due to compression of said seal in a radial direction and a total force less than the force exerted by said biasing spring member to hold said seal carrier against said valve seat.

tion is in the form of an angle from to

Claims

1. In a shock absorber of the type including a cylindrical walled damping chamber for receiving a damping liquid and a piston dividing said chamber into a first and second portion and mounted for reciprocal movement within said chamber, means carried by said piston for controlling flow of damping liquid from said first portion of the chamber to said second portion during the movement of said piston within said chamber in one direction, said control means including: an annular valve seat on said piston; and annular valve member moved by fluid energy within said first chamber portion to and away from sealing engagement with said valve seat for controlling the flow of damping liquid during a first operational range from said first portion of said chamber to said second portion of said chamber; an annular seal carrier moved to and away from engagement with said valve seat by fluid energy during a second operational range of fluid flow from said first portion of said chamber to said second portion of said chamber, a resilient annular seal carried by said seal carrier positioned between said valve member and said seal carrier for sealing the flow of damping liquid between said valve member and said wall of said damping chamber, means defining flow passages between said valve seat and said annular seal carrier for restricting the flow of fluid from said first portion to said second portion of said chamber during said first operational range of fluid flow; a spring member for resiliently forcing said seal carrier in a direction toward said valve seat and for biasing said seal carrier against said valve seat during said first operational range of fluid flow from said first portion of said chamber to said second portion of said chamber, the improvement which comprises said annular seal being formed solely of a resilient material of a durometer sufficient to prevent extrusion thereof between said valve member and said wall of said damping chamber under maximum axial compression thereof between said valve member and said seal carrier, said annular seal having a radially outer peripheral surface portion of arcuate cross-sectional configuration disposed in sliding sealing relation with said wall of said damping chamber and axially opposed peripheral surface portions disposed in engagement with said valve member and said seal carrier respectively, said axially opposed peripheral surface portions having non-arcuate cross-sectional configurations which diverge axially inwardly at a rate less than the rate of radial inward divergenece of said radially outer peripheral surface portion so as to present a force per unit deflection due to compression by movement of said annular valve member during said first operational range of fluid flow which is less than the force per unit deflection due to compression of said seal in a radial direction and a total force less than the force exerted by said biasing spring member to hold said seal carrier against said valve seat.

2. A shock absorber as described in claim 1 wherein the cross-section of each axial peripheral surface portion is in the form of an angle from 130* to 140*.