Abstract:
A three-part seal to be fixed in a gland formed on the first of two mating cylindrical structures in a hydraulic apparatus. A continuous Teflon nondeformable bearing ring is provided in the gland. The bearing ring has a first cylindrical surface for contact with the second cylindrical structure, a second cylindrical surface opposite the first surface and a conical rearward facing end surface. A continuous Teflon nondeformable backup seal ring is provided in the gland for mating with the rearward facing conical end surface of the bearing ring against its forward facing conical end surface. A continuous compressible resilient ring is provided on the side of the bearing ring opposite the second cylindrical structure for contacting the bearing ring and the backup seal ring.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to seal ring systems for a hydraulic apparatus, and more particularly, to composite seal ring systems. 
     2. Discussion of the Prior Art 
     Conventional O-rings in chevron type packings of the type employed in a hydraulic apparatus have recently been replaced by multiple-element sealing arrangements having both deformable and nondeformable components. These multiple component systems work especially well in high pressure applications. In such systems, a gland typically contains a three-part seal in which a wear-resistant plastic ring makes contact with a moving shaft. A deformable resilient ring may be disposed between the contact ring and the gland walls so that pressure applied to the deformable ring results in contact of the wear-resistant rings against the moving surface. U.S. Pat. Nos. 2,513,533, 3,817,517 and 3,394,941 disclose seal assemblies in which elastomeric rings bear against wear-resistant plastic rings which make contact with reciprocating cylindrical structures. These assemblies, however, all use a single contact ring. Applicant&#39;s improvement provides an elastomeric ring and two contact rings, a bearing ring and a backup seal ring. Pressure applied to the bearing ring enhances contact by the backup seal ring to provide a high pressure dynamic seal. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to providing an improved dynamic seal between reciprocating cylindrical structures in a hydraulic apparatus. 
     In accordance with the present invention, the three-part seal is adapted to be fixed in a gland formed on the first of two mating cylindrical structures. A continuous nondeformable bearing ring having a first cylindrical surface for contact with the second cylindrical structure and a second cylindrical surface of greater length than the first cylindrical surface facing away from the second cylindrical structure and having a conical rearward facing end surface is disposed in the gland. A continuous nondeformable backup seal ring having a forward facing conical end surface mates with a rearward facing conical end surface of the bearing ring. A continuous compressible resilient ring is disposed in the gland on the side of the bearing ring opposite the second cylindrical structure to contacting the bearing ring and the backup seal ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and for further objects and advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a section view of a hydraulic assembly in which the preferred embodiment is employed in female form; 
     FIG. 2 is a detailed section view of the gland shown in FIG. 1; and 
     FIG. 3 is a section view of a hydraulic assembly in which the preferred embodiment is employed in male form. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a hydraulic piston rod 10 is shown disposed in a hydraulic cylinder or barrel 12 containing hydraulic fluid 14 under high pressure. The outside of the barrel is at atmospheric pressure. The direction of hydraulic pressure in the barrel is indicated by the arrow 16. Piston rod 10 is retained in barrel 12, free to reciprocate in an axial direction. Structure is provided to dynamically seal the rod in the barrel to retain the high hydraulic pressure. In the first embodiment in which the dynamic seal is employed on female structure, static and dynamic sealing is provided by an annular retaining plug 18 disposed concentrically between the concave cylindrical inside surface 20 of the barrel 12 and the convex outer surface of piston rod 10. Retaining plug 18 contains an annular groove 22 opening oppositely piston rod 10 towards inside surface 20 and a gland 24 opening towards piston rod 10. Groove 22 is designed to house a conventional O-ring 25 to effect a static seal between retaining plug 18 and the barrel&#39;s inner surface 20. Gland 24 receives a sealing assembly 26 which effects a dynamic seal between retaining plug 18 and piston rod 10. 
     The annular retaining plug 18, disposed concentrically between the barrel&#39;s inner surface 20 and piston rod 10, extends outside the barrel and abuts against the outer end thereof as shown in FIG. 1. Retaining plug 18 is firmly secured by a barrel cap 28 which threadedly engages the barrel&#39;s outer surface 29. An excluder retainer 30 is disposed between retaining plug 18 and barrel cap 28. A separator ring 32 and an excluder ring 34 are disposed rearward of gland 24 between retaining plug 18 and piston rod 10 and to provide a static seal between retaining plug 18 barrel 12 and the barrel cap 28. 
     As best shown in FIG. 2, seal assembly 26 contains a bearing ring 40, a backup seal ring 42 and a compression ring 44. The end surface 45 of cylindrically shaped separator ring 32 forms the rearward boundary of gland 24 and enhances the seal between piston rod 10 and retaining plug 18. Excluder ring 34 disposed between the separator ring 32 and retaining member 30 has a cylindrical inner face 36 which mates with piston rod 10 (FIG. 1). 
     The seal assembly 26 is shown in greater detail in FIG. 2. Gland 24 is defined by a front wall 46, a bottom wall 48 and bounded by the forward end surface 45 of separator ring 32. The two contact rings, bearing ring 40 and backup seal ring 42, are manufactured of plastic, such as Teflon, which is highly wear-resistant, nondeformable and has a low coefficient of friction. A continuous (nonsplit) compression ring 44 is employed between the gland walls and the contact rings to contact the bearing ring and the backup seal ring. Compression ring 44 is manufactured of rubber or other suitable resilient material and is disposed in gland 24 adjacent rings 40 and 42 between front wall 46 and bottom wall 48 of the gland. Compression ring 44 is thus separated from movable piston rod 10 so as not to be subject to wear from direct contact by the rod. 
     Bearing ring 40 is a relatively thin ring having a cylindrical inner face 52 which makes contact with piston rod 10, a concentric cylindrical outer face 54, and forward and rearward conical end surfaces 56 and 58. Conical end surfaces 56 and 58 slope inwardly toward inner face 52, so that outer face 54 is wider than the inner face 52. 
     As best illustrated in FIG. 2, backup seal ring 42 is foot-shaped in cross section and includes a relatively thin toe portion 60 and an ankle portion 62, of thickness substantially the depth of gland 24. The inner face 64 of ring 42, which bears against piston rod 10, has a conical forward end surface 68 which makes an angle of about 45 degrees with inner face 64. Toe portion 60 thus tapers inwardly toward the planar forward end surface 70 of ankle portion 62. The 45 degree angle of conical forward edge 68 compliments the conical rearward edge 58 of bearing ring 40 so that end surfaces of rings 40 and 42 are maintained in edgewise abutment as hereafter described. The ring&#39;s cylindrical outer face 66, which is narrower in width than inner face 64, rests against bottom wall 48 of the gland. The planar rearward end surface 72 of ring 42 interfaces with the forward planar end surface 45 of separator ring 32, which is the rearward boundary of gland 24. 
     Compression ring 44 is retained in gland 24 with its cylindrical outer face 76 disposed against the bottom wall. The ring&#39;s rearward end surface 78 is contoured to mate with end surfaces 68 and 70 so that the ring 44 bears against the backup seal ring under compression. Compression ring 44 has sufficient thickness so that its inner face 80 mates with and bears against the outer face 54 of bearing ring 40. 
     As hydraulic pressure builds up in the gland, compression ring 44 is compressed and exerts force against the outer face 54 of bearing ring 40 and against the conical end surface 68 of the backup ring. The pressure on the bearing ring forces its end surface 58 against the abutting end surface 68 of the backup ring. The pressure exerted on backup ring 42 by bearing ring 40 and compression ring 44 enhances the contact between the backup ring and the piston rod. The slope and orientation of the end surfaces 58 and 68, of course, makes it possible to direct the force applied to backup ring 42 against the piston rod. 
     FIGS. 1 and 2 thus illustrate a unique multiple-component seal assembly employed on the female structure of a hydraulic apparatus in which both a bearing ring and backup seal ring are used to effect a dynamic seal between the piston rod and barrel. 
     Turning now to FIG. 3, a second embodiment of the invention in which a dynamic seal is provided by a seal assembly in the male structure of a hydraulic apparatus is illustrated. 
     A piston rod 100 is shown in a barrel 102, free to reciprocate along the axis thereof. Barrel 102 has a cylindrical inner surface 104. In the second embodiment shown in FIG. 3, the gland 106 is formed in the piston rod 100, rather than in a peripheral retaining plug as in the embodiment shown in FIGS. 1 and 2. An annular gland 106 is notched in the cylindrical surface of piston rod 100 to define a forward gland wall 108 and an annular bottom gland wall 110. A rearward gland wall is provided by the end surface of a retainer 112 secured to the posterior end surface 114 of the rod by a bolt 120. 
     A bearing ring 124, a backup seal ring 126 and a compression ring 128 are configured to fit in gland 106 and have the identical structural and functional relationship as bearing ring 40, backup seal ring 42 and compression ring 44 described in connection with FIGS. 1 and 2 above. This seal assembly 122 creates a dynamic seal between piston rod 100 and inner surface 104 of barrel 102. 
     Utilizing the seal assembly in male form obviates the need for a retaining plug and rings to effect a static seal between the retaining plug and barrel. 
     It will thus be seen that the present invention provides a unique dynamic seal assembly for concentric reciprocating cylindrical surfaces capable of use in a high pressure hydraulic apparatus. The invention would especially be useful in applications such as hydraulic actuaters on aircraft. 
     Although particular embodiments of the invention have been illustrated in the drawings and described herein, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of rearrangement, modification and substitution of parts and elements without departing from the spirit of the invention.