Patent ID: 12209667

DETAILED DESCRIPTION

Referring to the drawings,FIG.1shows an exemplary hydraulic cylinder10with a piston rod12attached at one axial end to a piston13that is slidably disposed within a cylinder barrel14. The piston rod12is axially movable through a cylinder head bolted to a flange at a rod end16of the cylinder barrel14by a plurality of bolts15. The rod end16of the cylinder barrel14is at an opposite axial end of the cylinder barrel14from a blind or closed cap end11of the cylinder barrel14. As shown in more detail inFIGS.2-4, the piston rod12is slidably engaged along a circumferential outer periphery of the piston rod12with an array18,318,418of annular piston rod seals and wear guides axially spaced along a radially inner circumferential surface of the cylinder head and/or flange at the rod end16,316,416of the cylinder barrel14. In various exemplary embodiments, the array of annular piston rod seals and wear guides may be disposed in axially spaced annular grooves formed around the radially inner circumferential surface of one or both of the cylinder head and the flange at the rod end16,315,416of the cylinder barrel14. Reference to a radially inner circumferential surface of a rod end of the cylinder barrel throughout this specification means a radially inner circumferential surface of a flange at the rod end of the cylinder barrel and a radially inner circumferential surface of a cylinder head bolted to the flange at the rod end of the cylinder barrel.

The annular piston rod seal closest to the pressurized rod end chamber of the hydraulic cylinder10may be a buffer seal assembly that includes an annular buffer seal22,350, and an annular backup ring24,352, as shown inFIGS.2and3. The buffer seal22,350and backup ring24,352may be installed in operative position at the rod end of the hydraulic cylinder12, in an annular groove21,351extending around a radially inner circumferential surface of the rod end16,316, for slidable engagement with the piston rod12movable axially therein. The annular groove21,351may have a width27and a depth25. The hydraulic cylinder12is exemplary of hydraulic cylinders utilized for a wide variety of purposes in association with tractors, earth moving equipment, and the like. Some exemplary applications of hydraulic cylinders that include a buffer seal assembly according to embodiments of this disclosure may include hydraulic cylinders used for performing one or more operations such as extending, retracting, lifting, tilting, rotating, and performing other movements of various components on heavy machinery, such as a boom, a stick, and a bucket of an excavator, or other components of machines such as large wheel loaders, hydraulic mining shovels, large track type tractors, and other equipment.

As shown in the exemplary embodiment ofFIG.2, the buffer seal22may be an annular, elastomeric ring, formed from an elastomeric material such as polyurethane or rubber, and configured to fit within an annular groove21formed around the radially inner circumferential surface of the cylinder head316. The annular buffer seal22may include a first axial pressure side formed with a plurality of contiguous, axially facing pressure surfaces220,221,222, and223, which face toward the pressurized rod end chamber of the hydraulic cylinder12, and a second, opposite axial seal side formed with a plurality of contiguous, axially facing seal surfaces224,225, which face toward the outside of the hydraulic cylinder and are configured to contact the backup ring24,352in mating, cooperative relationship within the annular groove21. The first axial pressure side of the annular buffer seal22includes the radially outer annular pressure surface220joined to the radially inner annular pressure surface223by two contiguous and converging tapered pressure surfaces221,222that together define an annular, concave recess23in the first axial pressure side of the buffer seal. The buffer seal also includes a radially outer circumferential surface226configured to contact the bottom of the annular groove21,351, or rest adjacent the bottom of the annular groove,21,351, and a radially inner circumferential surface227configured to contact the piston rod12that is movable axially within the rod end16,316.

The pressure surfaces221,222may be axially tapered, linear or curved surfaces that converge together to define the annular, concave recess23in the first axial pressure side of the annular buffer seal22, with the recess23separating a radially outer annular leg portion having the pressure surface221and terminating at the axially facing annular pressure surface220, and a radially inner annular leg portion having the pressure surface222and terminating at the axially facing annular pressure surface223. Pressure applied into the annular recess23may cause the radially outer annular leg portion to flex radially outward and press against the bottom surface of annular groove21, and cause the radially inner annular leg portion to flex radially inward and press against the piston rod12. The radially outer circumferential surface226of the buffer seal22may be configured with portions along its axial length that sit adjacent or in contact with the bottom of the annular groove21, with a small gap left between some of the portions of the radially outer circumferential surface226and the bottom of the annular groove21, in some instances, when the pressure applied into the annular recess23falls below a certain threshold. Similarly, in various embodiments of the annular buffer seal22according to this disclosure, the radially inner circumferential surface227of the buffer seal22may be configured with portions along its axial length, or its entire axial length coming into contact with the radially outer circumferential surface of the piston rod12. Portions of one or both of the radially outer circumferential surface226and the radially inner circumferential surface227of the buffer seal22may remain spaced from the bottom of the annular groove21and the piston rod12, respectively, as the piston rod12moves axially to extend and retract relative to the cylinder head and/or flange at the rod end316of the cylinder barrel of the hydraulic cylinder10, in some instances, depending on the amount of pressure applied into the annular recess23from the pressurized rod end chamber of the hydraulic cylinder10. Higher pressures above a certain predetermined threshold, which may be introduced into the annular recess23from the rod end chamber of the hydraulic cylinder10, may cause flexure of one or both of the radially outer annular leg portion having the pressure surface221and the radially inner annular leg portion having the pressure surface222, thus creating a tighter seal between one or more portions of the annular buffer seal22and the annular groove21and/or the piston rod12.

As shown inFIG.2, the buffer seal22may be cooperatively mated along the axially facing seal surfaces224,225with the backup ring24, and the assembly of the buffer seal22and the backup ring24is cooperatively receivable in the annular groove21formed in the radially inner circumferential surface of the rod end16,316,416of hydraulic cylinder12. The axially facing annular seal surface224of the buffer seal22may be disposed at a greater distance from the first axial pressure side of the annular buffer seal22than the axially facing annular seal surface225of the buffer seal22such that an annular step or notch is formed around the inner diameter of the annular buffer seal22on the axial seal side of the annular buffer seal22where the axially facing seal surface224joins with the axially facing seal surface225. The axially facing seal surface224may be formed with a convex radius R1at the entrance to the notch, with the convex radius R1being predetermined to avoid creating a higher stress area at the entrance to the notch.

The backup ring24may be formed with a radially extending leg portion26, configured to extend along substantially the entire radial extent of the axially facing seal surface224of the buffer seal22. The radially extending leg portion26may terminate in a chamfered outer circumferential surface247with a convex radius R3formed on the radially outer edge of the side of the backup ring facing away from the buffer seal22. The reference to “substantially the entire radial extent” means at least 50%-75% of the radial extent of the axially facing seal surface224of the buffer seal22. The increased surface area of the backup ring24in contact with the radially outermost seal surface224of the buffer seal22, as compared with conventional arrangements, reduces contact forces at any point along the interface between the backup ring24and the buffer seal22, thus reducing any wear created by abrasive elements introduced in between the two components, as well as assisting in the assembly of the backup ring with the buffer seal22in the proper orientation. The backup ring24may be formed with an axially extending leg portion28, contiguous with the radially extending leg portion26, and configured to extend axially into the annular notch formed at the intersection of the axially facing seal surfaces224,225of the buffer seal22. The axially extending leg portion28of the backup ring24may be configured to mate with the annular notch of the buffer seal22along a radially outer surface243, an axial end surface244, and a radially inner surface245, with the radially inner surface245of the axially extending leg portion28being configured to contact or sit at a small spacing from the outer circumferential surface of the piston rod12passing through the buffer seal assembly. In some exemplary embodiments of this disclosure, the radially extending leg portion26may have a portion with a thickness29, in a direction substantially parallel to the piston rod12, that falls within a range from approximately 1 mm to approximately 4 mm. The surfaces241,243at the intersection of the radially extending leg portion26and the axially extending leg portion28of the backup ring24may be formed with a concave radius R2that mates with the convex radius R1at the entrance to the annular notch formed around the inner diameter of the annular buffer seal22on the axial seal side of the annular buffer seal22. The opposite surfaces246,245at the intersection of the radially extending leg portion26and the axially extending leg portion28may be formed with a convex radius R4, which also avoids the creation of any higher stress areas that may otherwise be created if the backup ring24was formed with sharp corners or circumferential edges. In some exemplary embodiments, each of the radii R1, R2, R3, and R4may be a predetermined value based on one or more of the types of material being used for the buffer seal22and the backup ring24, the fluid pressures that will be exerted against one or both of the buffer seal22and the backup ring24, the overall dimensions of the buffer seal22and the backup ring24, and other factors that may affect the hoop stresses and other stresses experienced by the parts under different operating conditions. As one, non-limiting example, each of the radii R1, R2, R3, and R4may be predetermined to have a value that is greater than or equal to one half of the thickness of the respective part in the area where the respective radius is formed.

Alternative embodiments of this disclosure may include a buffer seal22with a shallower notch formed around the inner diameter of the buffer seal than shown in the exemplary embodiment ofFIG.2, or another interconnecting configuration between the buffer seal and the backup ring. For example, rather than a notch with a relatively sharp corner at the bottom of the notch, as shown inFIG.2, alternative interconnecting configurations between the buffer seal and the backup ring may include axially tapering or curved surfaces on the axial seal side of the buffer seal and on the mating surfaces of the backup ring.

In some exemplary embodiments, the backup ring24may be made of a material that is both stiffer and stronger than the material used for the buffer seal22. Examples of materials suitable for use for the backup ring24may include polytetrafluoroethylene (PTFE), Acetal (POM), Nylon, and other rigid plastic materials, composites, or matrixes. The buffer seal22may be formed from materials such as polyurethane, rubber, or other elastomers.

Under no-to-low load or pressure conditions, a clearance may exist between at least a portion of the radially inner surface245of the axially extending leg portion28of backup ring24and the outer peripheral surface of the piston rod12. This clearance may provide an area or distance for some displacement of the backup ring24during higher pressure applications. This displacement area may also provide for an absorption of energy created by hoop stresses in the backup ring24, and reduce the overall contact forces and frictional forces between the backup ring24and the buffer seal22. In the exemplary embodiment shown inFIG.2, the backup ring24is configured with the axially extending leg portion28engaged in the annular notch formed at the intersection of the axially facing seal surfaces224,225of the buffer seal22, and with the radially extending leg portion26extending along substantially the entire radial extent of the axially facing seal surface224of the buffer seal22such that the backup ring24provides optimal extrusion resistance for the buffer seal22. The cooperative mating relationship between the backup ring24and the buffer seal22also maintains the optimal stress profile in the area of the backup ring24by essentially limiting deformation of the buffer seal22relative to the backup ring24. The backup ring24, which is made of a stronger material relative to the buffer seal22, enables accommodation of a greater amount of the force associated with increased pressure on the buffer seal assembly than would be possible with no backup ring, or with a backup ring that does not extend along substantially the entire radial extent of the axially facing seal surface224of the buffer seal22. As discussed above, reference to “substantially the entire radial extent” means 50%-75% or more of the radial extent of the axially facing surface224of the buffer seal22.

As shown inFIGS.1,3, and4, the buffer seal assembly according to various embodiments of this disclosure may be incorporated as part of an arrangement of piston rod seals axially spaced along an inner circumferential surface of the rod end16,316,416to form a sealing assembly between the piston rod12and the rod end16,316,416. A rod end chamber may be formed between the piston13and the rod end16,316,416within the barrel14of the hydraulic cylinder10. As shown inFIGS.3and4, the rod end16,316,416according to various embodiments of this disclosure may include, in order from the rod end chamber in the hydraulic cylinder10to the axial end surface of the rod end16,316,416through which the piston rod12extends, a cylindrical metallic wear guide360,460, seated within an annular groove361,461, formed around the inner circumferential surface of the cylinder head and/or flange at the rod end of the cylinder barrel, the buffer seal assembly with a buffer seal22,350,450and backup ring24,352,452, seated within an annular groove21,351,451, a U-cup seal340,440, seated within an annular groove341,441, a cylindrical plastic wear guide330,430, seated within an annular groove331,431, and a triple lip wiper seal320,420, including three ringed lip portions322,422:324,424; and326,426; seated within an annular groove, or plurality of adjacent annular grooves321,421.

Each of the wear guides, the buffer seal assembly, the U-cup seal, and the triple lip wiper seal may engage the outer peripheral surface of the piston rod12as it moves axially within the cylinder head and flange at the rod end of the cylinder barrel to extend and retract relative to the hydraulic cylinder. The metallic wear guide360,460and plastic wear guide330,430may assist in maintaining the piston rod in a centered position within the buffer seal assembly, U-cup seal, and wiper seal, in addition to providing an additional sealing interface between the piston rod and the cylinder head. Centering the piston rod within each of the axially spaced seals may improve the sealing capabilities of each of the annular seals by equalizing the contact forces exerted around the entire outer circumferential periphery of the piston rod by each of the annular seals. Each of the wear guides may include one or more annular rings that are disposed in one or more annular grooves formed in the inner circumferential surface of the cylinder head. The buffer seal assembly with the buffer seal22,350,450and the backup ring24,352,452is the seal positioned closest to the rod end chamber within the barrel14. The triple lip wiper seal320,420is the outermost seal. The U-cup seal340,440and plastic wear guide330,430may be disposed between the buffer seal assembly and the wiper seal.

One function of the buffer seal assembly, as the seal axially adjacent the metallic wear guide360,460and the closest of the three sealing rings to the rod end chamber, is to create a high-pressure seal to prevent the escape of fluid from the rod end chamber. It is expected, however, that some fluid may leak through the buffer seal assembly along the outer peripheral surface of the piston rod12.

The U-cup seal340,440provides a second barrier to prevent fluid from leaking out of the hydraulic cylinder10. Any fluid that leaks past the buffer seal assembly may be scraped from the outer peripheral surface of the piston rod12by the lip of the U-cup seal340,440. This fluid may be collected in a recess formed in the U-cup seal340,440. When the pressure of the fluid in the rod end chamber decreases to a relatively low level, the pressure of the fluid in the recess formed in the U-cup seal may act on the buffer seal350,450to move the lip of buffer seal22(a portion of the surface227at the distal end of the radially inner annular leg portion of the buffer seal having the pressure surface222inFIG.2, and terminating at the axially facing annular pressure surface223) out of engagement with the outer peripheral surface of the piston rod12. The disengagement of the buffer seal from the outer peripheral surface of the piston rod allows the trapped fluid to return to the rod end chamber of the hydraulic cylinder.

One function of the triple lip wiper seal320,420, as the outermost seal, is to prevent dirt and debris from contaminating fluid of the hydraulic cylinder. The wiper seal may be forcibly fit into the annular groove321,421. When the triple lip wiper seal320,420is in position within the annular groove321,421in the rod end316,416, of the cylinder barrel, the piston rod12may be inserted through the central opening in the wiper seal. The central opening through the wiper seal is configured to have a close tolerance with the outer peripheral surface of the piston rod so that each of the lips of the triple lip wiper seal forms a compression-type seal with the outer peripheral surface of the piston rod12. In other words, the insertion of the piston rod12through the opening in the wiper seal causes each of the lips322,324,326to exert a force on the outer peripheral surface of the piston rod12, thereby creating a seal. The cutouts adjacent each of the lips of the triple lip wiper seal provide areas into which each body portion of each of the lips may flex when the piston rod12passes through the wiper seal. This flexing action of the body portions of each of the wiper seal lips reduces the amount of compression in the individual body portions and, thus, reduces the amount of force exerted on the outer peripheral surface of the piston rod by each of the lips, without significantly reducing the contact area of the lips on the outer peripheral surface of the piston rod12. In this manner, the wiper seal creates an effective seal with the outer peripheral surface of the piston rod without unduly wearing the surface of the rod when the rod slides within the cylinder housing.

INDUSTRIAL APPLICABILITY

The present disclosure is directed to a buffer seal assembly including an annular buffer seal and mating backup ring, and an entire arrangement of axially spaced annular seals and annular wear guides disposed in annular grooves formed in an inner circumferential surface of a rod end of a cylinder barrel of a hydraulic cylinder. As discussed above, the inner circumferential surface of the rod end of the cylinder barrel may be the inner circumferential surface of the flange and/or the cylinder head at the rod end of the cylinder barrel. The arrangement of axially spaced annular seals and annular wear guides may or may not include the disclosed buffer seal assembly. In an arrangement that includes the buffer seal assembly, the buffer seal22may be cooperatively mated with the backup ring24and seated within an annular groove formed in an inner circumferential surface of the rod end of a hydraulic cylinder. As discussed above, the annular buffer seal22may include a first axial pressure side formed with a plurality of contiguous, axially facing pressure surfaces220,221,222, and223, which face toward the pressurized rod end chamber of the hydraulic cylinder10, and a second, opposite axial seal side formed with a plurality of contiguous, axially facing seal surfaces224,225, which face toward the outside of the hydraulic cylinder and are configured to contact the backup ring24in mating, cooperative relationship within the annular groove21. The buffer seal22also includes a radially outer circumferential surface226configured to contact the bottom of the annular groove21,351, along portions or the entirety of the outer circumferential surface, and a radially inner circumferential surface227configured to contact the piston rod12that is movable axially within the rod end16, along portions or the entirety of the inner circumferential surface.

Two of the pressure surfaces on the axial pressure side of the buffer seal22may be axially tapered surfaces that converge together to define an annular, concave recess23in the axial pressure side of the annular buffer seal22, with the recess23separating a radially outer annular leg portion and a radially inner annular leg portion, and with a distal end of the radially inner annular leg portion forming a lip configured to seal against an outer circumferential surface of the piston rod12as the piston rod extends and retracts relative to the rod end of the cylinder barrel of the hydraulic cylinder. In alternative embodiments of the buffer seal, pressure surfaces on the axial pressure side of the buffer seal22may form more than one concave, annular recess along the radial extent of the buffer seal. Pressure from the rod end chamber of the hydraulic cylinder10may pass the metallic wear guides360,460and enter the annular recess23, or more than one recesses defined in the axial pressure side of the buffer seal22. This pressure may cause a radially outer annular leg portion of the buffer seal22to flex radially outward and press against the bottom surface of annular groove21, and cause a radially inner annular leg portion of the buffer seal22to flex radially inward and press against the piston rod12.

The radially outer circumferential surface226of the buffer seal22may be configured with portions along its axial length that sit adjacent or in contact with the bottom of the annular groove21, with a small gap left between some of the portions of the radially outer circumferential surface226and the bottom of the annular groove21when the pressure applied into the annular recess23falls below a certain threshold. Similarly, in various embodiments of the annular buffer seal22according to this disclosure, the radially inner circumferential surface227of the buffer seal22may be configured with portions along its axial length, or its entire axial length coming into contact with the radially outer circumferential surface of the piston rod12. Portions of one or both of the radially outer circumferential surface226and the radially inner circumferential surface227of the buffer seal22may remain spaced from the bottom of the annular groove21and the piston rod12as the piston rod12moves axially to extend and retract relative to the rod end316of the cylinder barrel of the hydraulic cylinder10, depending on the amount of pressure applied into the annular recess23from the pressurized rod end chamber of the hydraulic cylinder10. Higher pressures above a certain predetermined threshold, which may be introduced into the annular recess23from the rod end chamber of the hydraulic cylinder10, may cause flexure of one or both of the radially outer annular leg portion having the pressure surface221and the radially inner annular leg portion having the pressure surface222, thus creating a tighter seal between one or more portions of the annular buffer seal22and the annular groove21and/or the piston rod12.

As shown inFIG.2, and discussed above, the buffer seal22may be cooperatively mated along the axially facing seal surfaces224,225with the backup ring24, and the assembly of the buffer seal22and the backup ring24is cooperatively receivable in the annular groove21formed in the radially inner circumferential surface of the rod end16,316,416of hydraulic cylinder12. The axially facing annular seal surface224may be disposed at a greater distance from the first axial pressure side of the annular buffer seal22than the axially facing annular seal surface225such that an annular notch is formed around the inner diameter of the annular buffer seal22on the axial seal side of the annular buffer seal22where the axially facing seal surface224joins with the axially facing seal surface225. Alternative embodiments of the buffer seal and mating backup ring may eliminate or change the dimensions or configuration of the annular notch, with the entire radial extent of the axially facing seal side of the buffer seal being substantially coplanar, curved, stepped or notched with one or more annular steps or notches, or otherwise configured. As shown in the exemplary embodiment ofFIG.2, the axially facing seal surface224may be formed with a convex radius R1at the entrance to the notch, with the convex radius R1being predetermined to avoid creating a higher stress area at the entrance to the notch.

The above disclosed buffer seal assembly and/or entire arrangement of annular seals and wear guides may be incorporated into a sealing assembly of any hydraulic component. Thus, the seals and combinations of seals and wear guides of the present disclosure have wide applications in a variety of machines that include hydraulic actuators and/or hydraulic cylinders. Some of the advantages of the disclosed embodiments include providing a robust piston rod sealing system with multiple barrier contaminant controls, higher resistance to the potentially detrimental effects of temperature, moisture, and pressure in a hydraulic actuator, optimized side loading on the components of a hydraulic cylinder incorporating the disclosed features, fewer machine stoppages for servicing hydraulic cylinders, longer life of the hydraulic cylinder components, including increased piston rod life, and extended oil life for the hydraulic cylinders as a result of avoidance of penetration of contaminants into the hydraulic cylinders or leakage of hydraulic fluid from the hydraulic cylinders.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed individual seals, seal assemblies, and seal arrangements without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and their equivalents.