Expansible chamber devices – With assembly or disassembly facilitating means
Reexamination Certificate
1999-10-05
2001-07-24
Ryznic, John E. (Department: 3745)
Expansible chamber devices
With assembly or disassembly facilitating means
C092S16500R
Reexamination Certificate
active
06263779
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to closures, and more particularly to blind closures for retaining end caps or rod guides in hydraulic dampers.
BACKGROUND
Shocks, struts and other dampers, generally known as hydraulic dampers or monotube dampers, typically are used in vehicle shock absorbing systems to dissipate vibrational, shock and other forces applied to the wheel assemblies of motorized vehicles. Such dampers typically operate by transmitting the forces that are sustained by the wheel assemblies to a rod/piston combination. The rod/piston is slidably mounted in a fluid-filled chamber in the damper. As the piston is urged through the chamber, the hydraulic fluid in the chamber is forced through and around the piston. The movement of fluid through and around the piston resists movement of the piston with a force directly proportioned to the force sustained by the wheel assembly. In this manner vibrational and shock forces applied to an associated wheel assembly are dampened.
Hydraulic dampers of this type typically include a cylinder that is sealed by an end cap at one end and include a rod guide assembly at the other end. The rod guide assembly guides and centers the rod and piston as they reciprocate within the cylinder. While the end cap generally can be welded to the cylinder, the rod guide must be secured in the cylinder after the hydraulic fluid and piston assembly are installed in the cylinder.
Accordingly, in order to insure that hydraulic fluid does not leak from a hydraulic damper, it is desirable for a rod guide to be secured in a fluid-tight relationship with the cylinder. Additionally, due to the above-mentioned design constraints with the damper, it is desirable for the rod guide to be secured in a “blind” configuration, meaning that access to the underside of the rod guide is not required in order to secure the rod guide into the end of the cylinder. While blind fastening devices are useful in many applications, they are particularly useful in sealed hydraulic fluid applications, such as the above described hydraulic dampers, for a variety of reasons. In particular, access to the underside of the rod guide can be difficult due to the relatively long length and narrow diameter of the cylinder. Furthermore, after the hydraulic fluid has been dispensed into the cylinder, access to the underside of the rod guide becomes extremely difficult.
Prior art closure methods and devices have used blind snap ring closures in hydraulic damper applications with some success. For example, U.S. Pat. No. 3,650,182 to Phillips discloses the use of a snap ring closure apparatus for securing a piston rod bearing into a cylindrical barrel. However, that snap ring closure apparatus uses only a single snap ring to secure the bearing into the barrel. Thus, all of the movement of the bearing inward and outward of the barrel is prevented by a single snap ring, thereby placing a large amount of stress on this single element. Furthermore, the design of that snap ring is such that the snap ring needs to be compressed and fitted into a groove in the barrel after insertion of the bearing, but before the bearing is moved into final position. This can be a difficult procedure to accomplish effectively since the assembly requires holding the bearing in place with one hand while compressing and installing the snap ring with the other hand. Additionally, a great deal of pressure (either hydraulic or mechanical) is necessary to “force” the bearing onto the snap ring. Thus, the assembly of a hydraulic damper using such snap ring devices can be difficult and time consuming.
Another type of snap ring closure is disclosed in U.S. Pat. No. 3,494,652 to Langland. That snap ring closure uses two snap rings and a retainer ring to secure the hydraulic damper head in the cylindrical sleeve. While the configuration of that snap ring closure does distribute the stress created by the movement of the head over more than one snap ring, it also requires a relatively complex assembly. In particular, the first snap ring must be forced into a groove in the sleeve after insertion of the head but prior to completion of the assembly. Then, once the head is moved into contact with the snap ring, a retainer ring must be placed adjacent to a beveled edge of the sleeve and a second snap ring must be secured in a groove in the head into an interference fit with the retainer ring.
Accordingly, three separate assembly operations are required to secure the head in the sleeve using such closure systems. Furthermore, while the second snap ring used in that retainer ring against the beveled edge of the cylindrical sleeve absorbs some of the stress from the movement of the head outward of the cylinder, it does not create a seal that is as strong as might be desired or could be achieved if the force were received by a flange that was integral with the head.
Thus, given the disadvantages of prior art blind closures, there is a need for a blind closure useful in hydraulic damper applications that is relatively easy and simple to secure, and relatively easy to fabricate.
SUMMARY OF THE INVENTION
The present invention is a snap ring closure system suitable for use in a vehicle damping system, particularly for securing a rod guide, or in some instances an end cap, in a hydraulic damper or shock absorber. The snap ring closure system consists of a cylindrical rod guide or end cap having an annular, double-lobed groove formed about its outer circumference and a flange located at an outer end thereof, and a cylinder for receiving the rod guide, having an annular groove formed in the inner circumference thereof, which is aligned with the double-lobed groove. The closure system includes two snap rings. The first snap ring is slightly oversized and is seated in the double-lobed groove in the cylindrical rod guide. The second snap ring is positioned between the flange and the top of the cylinder.
The lobes of the double-lobed groove are of varying depths, with the outer lobe (closer to the flange) having a greater depth than the inner lobe. The first snap ring initially is positioned in the outer (deeper) lobe of the double-lobed groove, so that when the rod guide is initially inserted and pressed into the cylinder, the first snap ring is moved fully into the outer lobe, thereby providing sufficient clearance with the cylinder and is prevented from outward expansion by the walls of the cylinder. Then, when the first snap ring reaches the annular groove in the cylinder wall, the first snap ring expands outwardly into the annular groove.
The rod guide is then pulled slightly outwardly until the first snap ring contacts the bottom face of the second (shallower) lobe of the double-lobed groove, thereby preventing further outward movement of the rod guide from the cylinder. Finally, the second snap ring is positioned between the top edge of the cylinder and the rod guide flange. The second snap ring is positioned on the underside of the rod guide flange and prevents inward movement of the rod guide, thereby maintaining the locking engagement between the first snap ring and the cylinder groove. In this manner, the rod guide is secured to the end of the cylinder.
Accordingly, it is an object of the present invention to provide a snap ring closure system, particularly useful in securing the rod guide or end cap to a cylinder in hydraulic damper applications; a closure system that is relatively easy and simple to secure; that is relatively easy to fabricate and is durable; a closure system that provides a strong seal and prevents fluid leakage; and a closure system that is inexpensive to assemble.
REFERENCES:
patent: 2478818 (1949-08-01), Geiger et al.
patent: 2619717 (1952-12-01), Gober
patent: 2890917 (1959-06-01), Prince
patent: 3070127 (1962-12-01), Gratzmuller
patent: 3334937 (1967-08-01), Jofeh
patent: 3494652 (1970-02-01), Langland
patent: 3650182 (1972-03-01), Phillips
patent: 4077232 (1978-03-01), Grosseau
patent: 4225263 (1980-09-01), Asberg
patent: 4321987 (1982-03-01), Dressell, Jr. et al.
patent: 4924758 (1990-05-01),
Hopkins Patrick Neil
Kruckemeyer William Charles
Lisenker Ilya
Oliver Michael Leslie
Delphi Technologies Inc.
Ryznic John E.
Sigler Robert M.
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