hydraulic pressure accumulator

Abstract

Hydraulic pressure accumulator (20), which in combination includes: a cylindrical body (22) with a pair of ends, each of the ends having an external thread (28) and a shoulder (40) near the thread (28), a front cap (50) with internal thread (58) which is complementary to the external thread (28) at one of the ends, a piston (80) which is arranged to seal in the cylindrical body (22), a means (106, 108) arranged between the piston (80) and the end cap (50) to preload the piston (80) away from the end cap (50), and an inlet element (70) with internal thread (74) which is complementary to the external thread (28) at the other end and which defines a fluid passage path (12) into the cylindrical body (22), characterized by that the piston (80) comprises a pair of spaced circumferential channels (82), each accommodating a guide ring (84), and a third, deeper circumferential channel (86) in which a displacement seal (88) is arranged.

Description

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 61 / 391,305, filed October 8, 2010, which is hereby incorporated by reference in its entirety. AREA

[0002] The present disclosure relates to hydraulic accumulators and, more particularly, to hydraulic accumulators constructed from an externally threaded cylinder with adjacent shoulder stops and end closures. BACKGROUND

[0003] The information in this section merely provides background information related to the present disclosure and may, but need not, constitute prior art.

[0004] Accumulators are relatively common components in hydraulic circuits and systems. As their name suggests, they are essentially storage devices that accumulate pressurized hydraulic fluid when the supply or flow of hydraulic fluid exceeds the consumption or demand of a system or device. Conversely, when the consumption or demand exceeds the supply or flow, the previously stored fluid is expelled from the accumulator to maintain the desired or required pressure or flow.

[0005] Hydraulic accumulators take many different forms. Those used in automotive automatic transmissions, which are relatively small, are formed by a deep drawing process from a sheet metal blank or plate. Considerable finishing is then required to achieve the usable configuration. Another manufacturing process involves welding several pieces, such as a plate rolled into a cylinder and two end caps along all adjacent edges. Accumulators made from formed tubes or pipes are also known, but these configurations suffer from disadvantages such as high final cost or leaks between poorly fitted accumulator parts. It is therefore evident that improvements in the field of accumulator design and manufacture are desirable, and the present invention is directed thereto.

[0006] A hydraulic pressure accumulator according to the preamble of claim 1 is known from DD 62 959 A1.

[0007] A similar hydraulic pressure accumulator, which is operated with a combination of a permanent magnet and a magnetic coil, is described in DE 10 2007 036 854 A1.

[0008] It is an object of the present invention to provide a hydraulic pressure accumulator which can be produced cost-effectively and has improved sealing properties. SUMMARY

[0009] This object is achieved by a hydraulic pressure accumulator having the features of claim 1.

[0010] The present invention provides a hydraulic accumulator having a cylindrical body or housing with external threads at each end and shoulders acting as stops near the ends of the threads closer to the center of the cylindrical body or housing. An internally threaded end cap or closure is disposed at one end of the accumulator. The accumulator may be threaded to a manifold or control valve assembly or may have a second threaded end cap having an access, i.e., inlet / outlet, port. A piston is provided within the accumulator and is biased by a pair of compression springs toward the manifold, control valve body, or second threaded end cap.

[0011] It is another aspect of the present invention to provide a hydraulic accumulator having a cylindrical body with threads near each end.

[0012] It is yet another aspect of the present invention to provide a hydraulic accumulator comprising a cylindrical body having a circumferential shoulder proximate the thread at each end.

[0013] It is yet another aspect of the present invention to provide a hydraulic accumulator having a cylindrical body with a threaded end adapted to be received in a manifold or valve body.

[0014] It is yet another aspect of the present invention to provide a hydraulic accumulator including a cylindrical body having threaded ends adapted to receive threaded end caps.

[0015] It is yet another aspect of the present invention to provide a hydraulic accumulator including a cylindrical body with an inner piston.

[0016] It is yet another aspect of the present invention to provide a hydraulic accumulator including a cylindrical body with a spring-loaded piston.

[0017] Further aspects, advantages, and areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for illustrative purposes only and are not intended to limit the scope of the present disclosure. DRAWINGS

[0018] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Fig. 1 is a perspective view of a hydraulic accumulator according to the present invention mounted on a transmission control valve body; Fig. 2 is a full sectional view of a hydraulic accumulator according to the present invention; Fig. 3 is a full sectional view of a hydraulic accumulator according to the present invention at the pressurization limit of a piston stroke; Fig. 4 is an enlarged sectional view of a hydraulic accumulator according to the present invention, illustrating the various sealing components on the piston; and Fig. Figure 5 is a full sectional view of an alternative configuration of a hydraulic accumulator according to the present invention having two end caps and one inlet / outlet port. DETAILED DESCRIPTION

[0019] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or uses.

[0020] In the Fig. 1 and Fig. 2, a valve body of an automatic transmission is shown and generally designated by the reference numeral 10. The valve body 10 includes various and numerous passageways 12 communicating between a plurality of cylindrical chambers housing a like plurality of control valve spools (both not shown). The valve body 10 also includes hydraulic fittings attached to and connecting with various hydraulic lines 16 that communicate with other components (not shown) of the automatic transmission. The valve body 10 is typically cast and machined aluminum. A hydraulic accumulator 20 according to the present invention is attached to the valve body 10 in fluid communication with one of the passageways 12.

[0021] As in the Fig. 2 and Fig. 3, the hydraulic accumulator 20 includes a central cylindrical body or housing 22 having a smooth, preferably machined, inner surface 24. At each end of the cylindrical body or housing 22, there is an external thread 28 on an outer surface 26. Preferably, although not necessary, the threads 28 have the same pitch and the same configuration. Disposed near each end of the threads 28 closer to the center of the body or housing 22, that is, opposite the ends of the body or housing 22, is a circumferential channel or groove 32. The channels or grooves 32 each receive an O-ring seal 34, preferably made of an elastomer, for retaining it.Further, a circumferential stop 40 is provided near each channel or groove 32 and the O-ring seal 34 on the side closer to the center of the body or housing 22 and away from the threads 28. The circumferential stops 40 are symmetrically arranged and each have a radially oriented, outwardly extending surface 42 and a radiused or curved surface 44 closer to the center of the body or housing 22.

[0022] At one end of the cylindrical housing or body 22 is an end cap 50. The end cap 50 includes a flat end plate 52 that merges into a depending peripheral sidewall 54 and is sized to fit over the end of the cylindrical body or housing 22. The inner surface 56 of the depending sidewall 54 has an internal thread 58 that is complementary in all respects to the external thread 28 on the body or housing 22.The sidewall 54 includes an end surface or shoulder 62, the axial inner length of the sidewall 54 being slightly longer than the distance from the outwardly facing surface 42 of the circumferential stop 40 to the body or housing 22, so that when installed and tightened on the body or housing 22, the end surface or shoulder 62 contacts or abuts the outwardly facing surface 42 on the circumferential stop 40 before the threads 28 and 58 reach the limit of their travel or before the end of the body or housing 22 contacts the inner surface of the flat end plate 52 of the end cap 50. The end cap 50 also includes a smooth and thread-free annular region 64 on its inner surface 56 proximate the end surface or shoulder 62, against which the adjacent O-ring seal 34 seats when the end cap 50 is installed and fully seated on the end of the body or housing 22.

[0023] At the opposite end of the cylindrical body or housing 22, the external threads 28 are received in the valve body 10, which includes a cylindrical opening or fitting 70 with an inner surface 72 having internal threads 74 complementary in all respects to the external threads 28 on the body or housing 22. At the outer end of the cylindrical opening or fitting 70, there is an end surface or shoulder 76. It should be appreciated that the configuration of the cylindrical opening or fitting 70, i.e., itsits axial length, and the location of the end surface or shoulder 76 are in turn such that during assembly, the adjacent outwardly facing surface 42 of the adjacent circumferential stop 40 on the body or housing 22 contacts or abuts the end surface or shoulder 76 before any other movement limiting contact is made between the threads 28 and 74 or the end of the body or housing 22 and the interior of the valve body 10. The inner surface 72 also includes a smooth or unthreaded annular portion 78 proximate the end ring or end shoulder 76 upon which the adjacent O-ring seal 34 seats when the cylindrical body or housing 22 is assembled and fully seated within the cylindrical opening or fitting 70 of the valve body 10.As mentioned above, one of the fluid passageways 12 in the valve body 10 communicates with the internal volume of the accumulator 20.

[0024] In the Fig. 2, Fig. 3 and Fig. 4, the cylindrical body or housing 22, as also mentioned above, defines a smooth, preferably machined inner surface 24 that receives a piston 80. The piston 80 includes a pair of spaced circumferential channels or grooves 82, each receiving and retaining a guide ring 84. The guide rings 84 are preferably made of PTFE and assist in the proper axial orientation of the piston 80 within the body or housing 22. Between the pair of channels or grooves 82 and the guide rings 84 is a third, deeper circumferential channel or groove 86 that receives a displacement seal 88. The displacement seal 88 includes a blade or wiper 92 and serves as the primary fluid seal between the piston 80 and the surface 24 of the piston or housing 22.The blade or wiper 92 of the displacement seal 88 is oriented so that increased pressure in the accumulator 20 forces or drives the blade or wiper 92 into closer, tighter contact with the inner surface 24 of the body or housing 22, thereby improving the seal. The displacement seal 88 is preferably made of Vamac. ® or made of a similar material. Vamac is a registered trademark of E.I. DuPont de Nemours Company for its brand of ethylene acrylic elastomers. An elastomer O-ring seal 94 is provided in a channel or groove 96 on the inner surface 24 of the body or housing 22 near its end near the valve body 10.

[0025] The piston 80 includes a shoulder 100 between the piston itself 80 and an intermediate diameter region 102, and an elongated shaft portion 104 having a diameter smaller than the intermediate diameter region 102. Two inserted compression springs are positioned and received around the intermediate diameter region 102 and extending to the end cap 50: an outer compression spring 106 and an inner compression spring 108. Typically, the outer compression spring 106 has a higher spring rate than the inner compression spring 108. Both compression springs 106 and 108 have a fully compressed length that is shorter than the distance from the end of the elongated shaft portion 104 to the shoulder 100.Therefore, before high pressure in the accumulator against the face of piston 80 can fully compress or "bottom out" compression springs 106 and 108, the end of elongated stem portion 104 contacts the inner surface of end cap 50, as shown in FIG. Fig. 3 is shown.

[0026] In Fig. 5, an alternative configuration 20' of the accumulator 20 is shown. The accumulator 20' includes the cylindrical body or housing 22, a first end cap 50, the piston 80, the springs 106 and 108, and a second end cap 50' substantially similar to the first end cap 50, with the addition of an inlet / outlet port or fitting 112. The accumulator 20' is therefore suitable for mounting on a manifold or at a location remote from, for example, an automatic transmission, to which it is connected by a hydraulic line 114.

[0027] Depending on the application, the operating pressure range of accumulators 20 and 20' can be between 275 kPa and 800 kPa, or less or more. Depending on the operating pressure range, the material from which accumulators 20 and 20' are made can be steel or aluminum. For lower pressures, they can be manufactured from reinforced plastic.

[0028] It should be appreciated that a hydraulic accumulator according to the present invention provides several benefits and advantages. First, from a manufacturing or fabrication standpoint, all components of the hydraulic accumulator 20 can be turned without additional finishing. Therefore, the hydraulic accumulator 20 is manufactured efficiently and easily on conventional equipment and machinery. Second, the volume of the hydraulic accumulator 20 can be readily varied by adjusting the length of the cylindrical body or housing 22 and by using end caps 50 of various lengths. Furthermore, the length of the piston shaft 104, the length of the compression springs 106 and 108, and the spring rate of the compression springs can all be varied to suit a particular application.Third, the removable end caps 50 facilitate quick maintenance of the piston 80, the various seals and the springs 106 and 108, if necessary.

[0029] The description of the invention is merely exemplary in nature, and modifications that do not depart from the spirit and scope of the invention are intended to be within the scope of the invention. Such modifications are not to be regarded as a departure from the spirit and scope of the invention.

Claims

[1] Hydraulic accumulator (20) comprising in combination: a cylindrical body (22) having a pair of ends, each of the ends having an external thread (28) and a shoulder (40) near the thread (28), a front cap (50) with an internal thread (58) complementary to the external thread (28) at one of the ends, a piston (80) sealingly arranged in the cylindrical body (22), a means (106, 108) disposed between the piston (80) and the end cap (50) for biasing the piston (80) away from the end cap (50), and an inlet element (70) with an internal thread (74) which is complementary to the external thread (28) at the other of the ends and which defines a fluid passageway (12) into the cylindrical body (22), characterized by , that the piston (80) comprises a pair of spaced circumferential channels (82), each receiving a guide ring (84), and a third, deeper circumferential channel (86) in which a displacement seal (88) is arranged. [2] Hydraulic pressure accumulator (20) according to claim 1, wherein the means (106, 108) for preloading comprises at least one compression spring (106, 108). [3] Hydraulic pressure accumulator (20) according to claim 1, wherein the means (106, 108) for preloading comprises two compression springs (106, 108). [4] Hydraulic accumulator (20) according to claim 1, wherein the inlet element (70) is a component of a transmission. [5] Hydraulic accumulator (20) according to claim 1, wherein the inlet element (70) is a second end cap (50'). [6] Hydraulic accumulator (20) according to claim 1, wherein the external threads (28) extend to the ends of the cylindrical body (22) and the shoulders (40) are arranged at a distance from the ends of the cylindrical body (22). [7] Hydraulic accumulator (20) according to claim 1, wherein the piston (80) has a rod (104) extending to the end cap (50).

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