US 3148707 A
Description (OCR text may contain errors)
Sept. 15, 1964 A. SMYKLO ETAL AUTOMATIC HYDRAULIC BUFFER Filed March 23, 1962 r 2 Sheets-Sheet l INVENTORS ALEXANDER SMYKLO GEORGE B. SCHIL ROTH ATTORNE S p 15, 1954 A. SMYKLO ETAL 3,148,707
AUTOMATIC HYDRAULIC BUFFER Filed March 23, 1962 2 Sheefs-Sheet 2 United States Patent 3,148,707 AUTOMATHI HYDRAULIC BUFFER Alexander Smyklo, Union City, Calif., and George B.
Schiidroth, Manchester, N.H., assignors to the United States of America as represented by the Secretary of the Air Force Filed Mar. 23, 1962, Ser. No. 182,148 2 Claims. (Cl. 138-31) This invention relates to hydraulic apparatus and, more specifically, to an accumulator or buffer used on such apparatus.
Many installations of hydralic apparatus of various types include hydraulic pumps to supply high pressure fluid for driving various hydraulic motors and actuating devices. On much apparatus of this type it is practically impossible to balance the output of the pumps to the variable demands of the motors or other fluid powered devices. A common means for absorbing surplus fluid when the pump output momentarily exceeds demand, and for supplying needed fluid when demand momentarily exceeds pump output is to place an accumulator or butter into the hydraulic conduit between the pump and the fluid using devices. Such accumulator or buffer is normally T connected to the fluid carrying conduit.
A buffer, of the type to which this invention pertains, may have a floating piston in a cylinder. That portion of the cylinder on one side of the piston is in communication with the hydraulic fluid, and that portion of the cylinder on the opposite side of the piston is charged with a gas at a pressure comparable to the normal operating pressure of the hydraulic system. It is thus noted that when pump output momentarily exceeds demand, the surplus fluid will be absorbed into the hydraulic end of the butter cylinder while moving the floating piston and further compressing the gas. During the subsequent operation of the apparatus, the gas in the buffer which became compressed to an above normal pressure will tend to purge the buffer of surplus fluid in order to pro duce a pressure balance between the gas side and the hydralic side of the floating piston within the buffer.
In like manner, when demand momentarily exceeds pump output and there is a drop in hydraulic pressure, the entrapped gas, which is now at a higher pressure than hydraulic line pressure, will move the floating piston and thereby supply needed fluid to the fluid using devices. During the subsequent operation of the apparatus, hydraulic fluid will re-enter the buffer until there is a pressure balance on the floating piston. It is necessary to provide seal rings on the piston to prevent an interchange of fluid and gas.
Little difficulty is encountered in preventing ring leakage during normal operation sincethere is little, if any, pressure differential across the rings. However, when the apparatus is shut down an the hydraulic pressure decays, the pressure differential across the rings and resultant leakage of gas into the hydraulic system becomes a severe problem.
It is, accordingly, the primary object of this invention to provide a means for preventing the escape of the gas in a gas charged buffer into the hydraulic system of a hydraulic apparatus during shut-down.
It is another object of this invention to provide a means for reducing the pressure differential across the seal rings on the floating piston of a hydraulic buffer during shutdown in order to prolong ring life.
It is a further object of this invention to provide a valve means for preventing the entire escape of the fluid Within a hydraulic buffer.
It is yet another object of this invention to provide a means for accomplishing the above objectives without interference with a normal operation of the buffer.
Additional objects, advantages and features of the invention reside in the construction, arrangement and combination of parts involved in the embodiment of the invention as will appear from the following description and accompanying drawings, wherein:
FIG. 1 is a schematic drawing of the hydraulic buffer T connected at one end to a hydraulic fluid conduit and connected at the other end to a source of high pressure FIG. 2 is a partial section of the body member and piston, and showing the valve plug against its seat to entrap hydraulic fluid during shut-down; and
FIG. 3 is a partial section similar to FIG. 2 and showing the arrangement of the elements during normal operation of the hydraulic apparatus.
Referring to FIG. 1, the buffer referred to generally as 14) has a housing or body member 11 containing a closed end cylinder 12, which houses a free floating piston 14 adapted for dividing the cylinder into two end chambers 13 and 15. Chamber 13 is adapted for use as a high pressure air or gas chamber, and chamber 15 is adapted for use as a hydraulic fluid chamber. The piston is provided with ring sealing means for preventing the leakage of fluid or gas from one end chamber into the other, while at the same time permitting axial movement of the piston. The sealing means consists of a continuous O ring 16 and an 0 ring 18 which is served to provide a small gap 20 for a purpose to be hereinafter described. Both rings 16 and 18 are preferably neoprene or similar nonmetallic ductile material. The chamber 15, which forms the hydraulic end of buffer 10, has an orifice 23 which is T connected to hydraulic fluid conduit 22 by means of conduit 24. It is presumed that conduit 22 is carrying hydraulic fluid from a pump not shown to a hydraulic motor not shown and that the fluid flow is in the direction indicated by the arrows. The opposite, or gas chamber 13 end of cylinder 12 has a closed end containing an orifice 27 which is connected to a source of high pressure gas or air 26 by means of conduit 28. It is noted on FIG. 1 that the gas pressure is always acting against piston 14, and that the hydraulic fluid is free toenter or leave chamber 15, the direction of flow being dependent upon whether or not the hydraulic fluid pressure is greater or less than the pressure of the gas. A static flow condition exists when there is a pressure balance across the piston.
Referring more specifically to FIG. 3, the housing or body member 11 may be made of pipe or tubing having one end closed by Welded or threaded means to provide a closed end. Or, body member 11 may be made of a casting having an integrally closed end, or a closed end which is bolted in place or otherwise joined in various manners well known to the art. The hydraulic end of cylinder 12 is openably closed with an end member or plug 30 having external threads 32 which engage corresponding internal threads in cylinder 12. A valve seat 34 having an externally threaded shank 36 engages a correspondingly threaded bore in end member 30. The internal end of valve seat 34, which also provides orifice 23, has a spherical seat faced with a facing 3%. Facing 38 may be made of soft ductile metal such as copper, aluminum or gold; or of plastic, and may be joined to valve seat 34 invarious manners well known to the art. The use of a facing such as facing 38 is not absolutely necessary, but is desirable under certain conditions to assure a readily obtainable leak-proof closure upon shut-down. A plurality of bosses 46 project from the inner face of end plug 30. The bosses are of uniform height and limit the movement of the piston during shut-down in a manner and for a purpose to be hereinafter explained. If desired, other means such as an integral ring joined to end plug 34, or a plurality of pins may be substituted for bosses 40. Likewise, the piston travel limiting means may be on the piston itself, rather than on the end plug. Sealing means well known to the art may be provided to prevent the escape of hydraulic fluid. The buffer 1% may be joined to the hydraulic system by means of a tubing connection, a manifold, or any desired method, such method of joining not constituting a part of this invention.
The hydraulic end face of piston 14 contains a threaded counterbore which is coaxial with valve seat 34 and which threadably receives retainer cup 42. A ball of valve plug 44, of steel or other suitable material, has joined thereto a rod or stem 46. A suitable compression spring 4-8 is brazed or otherwise joined to a face of washer 50.
Ball 44 with attached stem 4-6, compressionspring 48 with attached washer 5t? and retainer cup 42 are assembled into a sub-assembly by placing the free end of the spring onto the ball in such manner that stem 46 passes through a bore in washer 5i Washer 56 is received within bore 52 of retainer cup 4-2 while stem 46 passes through bore 54 in the end of cup 42 where it is retained by retainer washer 56 which is riveted or otherwise joined to the free end of stem 46. After washer 56 is joined to stem 46, the ball or valve plug 44 is slidably retained for axial movement within cup 42 and biased outwardly by compression spring 48. The sub-assembly is threadably joined to the hydraulic end of piston 14 by means of a pin spanner wrench engaging holes 58 in retainer cup 42. Retainer washer 56 moves axially within counterbore 66 when ball 44 moved against spring 4%. Although the valve plug used in the embodiment of the invention shown and described was a ball, the plug could be made in other forms such as conical or elliptical.
During operation of the hydraulic apparatus to which the buiier is joined, the floating piston assumes a position as shown on FIG. 1 and H6. 3. During shut-down, the floating piston will assume a position as shown on FIG. 2 with the ball 44 engaging valve seat 34. As shown on FIG. 3, a portion of the hydraulic fluid is entrapped in the butter. The entrapped fluid will be at the same pressure as the gas acting on the other side of the piston. Gap 2% in ring 18 permits the area between the seal rings to assume the same unit pressure as that of the chambers at each end of the piston, with a resulting zero pressure differential across the rings. pressure across the rings assures long ring life. Bosses 49 on end plug 3% are a protective means, in case of leakage during shut-down, for preventing sufficient piston travel to cause the valve plug on the seat to support the entire force of the applied gas on the other side of the piston, and thereby damage the valve mechanism.
It is noted that the bosses 40 may be eliminated by making cup 42 of greater depth, thereby permitting further movement of ball 44 into the cup, in order that the face of the piston will engage the inner face of end plug 36 before the plug reaches the inner limit of its permissible axial movement.
It is further noted that the amount of fluid entrapped on shut-down will be determined by the length of stem 46 which controls the position of the piston at the time the ball plug engages its seat.
If desired, valve seat 34 may be installed into the closed end of housing 11, in which case the open end of the cylinder would become the gas end. When such arrangement is used, piston travel limiting means such as bosses 46 may be attached to the end of the piston.
It is to be understood that the embodiment of the present invention as shown and described is to be regarded as illustrative only and that the invention is susceptible to variations, modifications and changes within the scope of the appended claims.
1. A hydraulic buffer comprising: a body member, an open end cylinder within said body member, an end member for openably closing the open end of said cylinder, a floating piston within said cylinder, said piston being axially movable within said cylinder and adapted for dividing said cylinder into opposing end chambers, sealing means on said piston, said sealing means comprising a plurality of ductile non-metallic rings adapted to prevent leakage from one of said chambers into the opposing Y chamber, an orifice communicating with each end of said The zero differential cylinder, at least one of said orifices being coaxial with said cylinder and passing through said end member, a valve seat communicating with said coaxial orifice, and a valve plug subassembly coaxial with said cylinder and said valve seat, and comprising a retainer cup having external threads engaging a threaded counterbore in the end of said piston with the bottom of the retainer cup against the bottom of the counterbore, a ball valve plug, a stem joined to said ball valve plug and slidably passing through the bottom of said retainer cup, means joined to said stem for retaining said stem in said retainer cup, and a compression spring disposed over said stem and nesting on said ball valve plug to axially bias said ball valve plug from the face of said piston.
2. A hydraulic buffer comprising: a body member, an open end cylinder within said body member, an end member for openably closing the open end of said cylinder, a floating piston within said cylinder, said piston being axially movable within said cylinder and adapted for dividing said cylinder into opposing end chambers, sealing means on said piston, said sealing means comprising two ductile nonmetallic rings adapted to prevent leak age from one of said chambers into the opposing chambers, one of said rings being severed to provide a small gap permitting the area between the rings to communicate with one of said chambers, an orifice communicating with each end of said cylinder, at least one of said orifices being coaxial with said cylinder and passing through said end member, a valve seat communicating with said coaxial orifice, and a valve plug subassembly coaxial with said cylinder and said valve seat, and comprising a retainer cup having external threads engaging a threaded counterbore in the end of said piston with the bottom of the retainer cup against the bottom of the counterbore, a ball valve plug, a stem joined to said ball valve plug and slidably passing through the bottom of said retainer cup, means joined to the end of said stem for retaining said stem in said retainer cup, a Washer axially passing over said stem and resting against the bottom of said retainer cup, and a compression spring disposed over said stem with one end joined to said washer and the other end nesting on said ball valve plug to axially bias said ball valve plug from the face of said piston.
References Cited in the file of this patent UNITED STATES PATENTS