US3250073A - Cylinder - Google Patents

Description

y 0, 1966 J. T. ELLIS, JR 3,250,073

CYLINDER Filed Aug. 21, 1964 M4 I I I I I NVENTOR r m 96 $670217 J 13 M 11 0 A m .14 J06 B z; 5

United States Patent 3,250,073 CYLINDER John T. Ellis, In, Chicago, Ill., assignor to Ellis Fluid This invention relates to an improved construction for a cylinder, and more specifically, a pull cylinder, toa hydraulic circuit for use with such a cylinder.

The utilization of cylinders has achieved a substantial degree of acceptance, and as more uses are found for cylinders, especially of the pull type, it becomes readily apparent that the construction of the cylinders need be simplified, in order to make the cylinders economically available to more potential users. It is readily apparent that many cylinders, especially of the hydraulic type, are over-designed in certain aspects, in order to hold a cylinder together during operation, that is, to prevent a cylinder from tearing itself apart. It may be readily appreciated that this over-design in certain instances is a needless waste, which, if eliminated, could provide substantial economies in the manufacture of a hydraulic cylinder. It is a principal object of the herein-disclosed invention to provide an improved cylinder in which the low pressure side of the cylinder is so constructed that it is capable of carrying on a return function of the cylinders piston as well as exhaust function with minimum strength of parts, by virtue of a valving arrangement which is provided in the cylinder to eliminate the necessity of providing suflicient strength of the low pressure side to hold a piston with a full pressure load applied to the piston.

A further object of the present invention is to provide an improved hydraulic circuit for use in cooperation with a cylinder which circuit has a high pressure side and a low pressure side.

A further object of the instant invention is to provide an improved cylinder construction which utilizes a relief valve connected to a' piston to allow pressure to be relieved on the high pressure side to the low pressure side upon attainment of a preselected position of the piston.

A still further object of the present invention is toprovide an improved cylinder construction which is capable of utilizing high pressures, but which is inexpensive to manufacture.

Other objects and uses of the instant invention will become readily apparent to those skilled in the art upon a perusal of the following specification in light of the accompanying drawing in which:

FIGURE 1 is a cross-sectional view of a cylinder embodying the herein-disclosed invention;

FIGURE 2 is an enlarged cross-sectional-view of a valve which is shown in FIGURE 1, but the valve being shown in an open attitude when the piston of the cylinder reaches the end of its stroke;

FIGURE 3 is a cross-sectional view taken on line 3-'3- practical embodiment of a cylinder embodying the instant invention. In this case, the cylinder is a cylinder which is used for a pulling operation to strip a material ofl a mandrel (neither of which are shown herein).

The cylinder 10 generally includes a tube 12, a back "ice head 14 closing one end of said tube, a gland 16 welded to the other end of the tube, a flange 18 welded to the gland, a rod 20 slideably mounted in the gland, a piston 22 welded to the rod, and a limit valve 24 mounted in the rod for movement with the piston to control movement of the rod and the piston.

The tube 12 is conventional in its construction, inasmuch as it is a right circular cylindrical tube having an exhaust port 26 adjacent to one end thereof. The tube has a recess 28 on the other end for receiving the gland 16.

The back head 14 is fixed to the end of tube 12 having the exhaust port by a plurality of screws 30, and a gasket 32 is positioned between the back head and that end of the tube. A stud 34 is threadedly mounted in the back head. The stud includes a threaded portion 36 and a tapered post 38 which is cooperative with the valve 24, as will be described in detail hereinafter. The studis mounted on the axis of the tube 12 and extends along said axis, so that it may have free engagement with the valve 24.-

As was mentioned above, the gland 16 is welded to the tube 12. The gland 16, which is also cylindrical, includes an inlet port 40 which has an arm 42 connecting the port with the interior of tube 12. The'gland has a bronze rod bushing 44 positioned therein for engagement with rod 20 and guiding the rod. Conventional V-packing 46 is also positioned in the gland and retained in position by a packing ring 48. The packing provides a seal between the gland and rod 20. The gland has the flange 18 welded to one end, and the flange includes a rod aperture 50 for receiving the rod.

The rod 20 is a right circular cylindrical rod having its exterior end adapted for receiving a cooperative member, thereby having internal threads 52 contained therein.

At the other end of the rod, there is a valve aperture 54 with internal threads 56 defining a portion of the valve aperture, It should be noted that the valve aperture is circular and its axis is coincidental with the axis of the rod and the axis of tube 12. The rod has an axial bleeder 58 communicating with the valve aperture, and a radial bleeder 60 communicating with the axial bleeder and the exterior of the rod.

The piston 22 includes a piston body 62 which has three ring grooves 64 formed on its outer periphery. Piston rings 66 are mounted in the ring grooves and are engageable with the interior surface of tube 12 to provide a seal between the piston and .the tube. Thus, a low pressure chamber 68 is defined within the tube between the back head and the piston, and a high pressure chamber 70 is defined between the piston and the gland Within the tube. The piston has a recess 72 on the side adjacent to the gland to provide a flow path. for hydraulic fluid from the arm 42 around the piston head.

Looking now to FIGURES 2 and 3, the construction of the valve 24 may be seen therein. The valve 24 includes a copper valve 'body 74 which has a threaded portion 76 mateable with the internal threads 56 of the rod. A hexagonal head 78 is formed integral with the threaded portion, and the hexagonal head has a face 80 which sealignly engages the rod. The valve body has an axial aperture 82 formed therein, with a valve seat 84 defining a portion of the aperture. A relief port 86 is a portion of the aperture 82, which aperture communicates with the axial bleeder 58. A ball valve or check valve 88 is positioned in the enlarged portion of aperture 82 and a coil spring 90 engages the ball and the rod to urge constantly the ball toward seating engagement with the valve seat 84.

Referring now to FIGURE 4, which shows schematically the fluid power system connected to the cylinder 3 10, it may be appreciated that though specific valves and pumps are not shown herein, these items are well-known to those skilled in the art and any suitable devices may be utilized. The inlet port 40 of cylinder is connected to a first conduit 92 which conduit is connected to a. high pressure side of a pump 94. The pump has its inlet connected to a reservoir as through a fluid conduit 98. A high pressure relief valve 11H which, in this instance, is a 10,000 pound per square inch relief valve, is connected to the first fluid conduit through conduit 102. The high pressure relief valve has its exhaust side connected to the reservoir 96 by a conduit 104. The exhaust port 26 of the cylinder is connected to a second fluid conduit 106 Which is in turn connected to a low pressure relief valve 108. In this instance, the low pressure relief valve is operative at 25 pounds per square inch, and the exhaust side of the valve is connected to reservoir 96 by a conduit 110. A control valve 112 is connected to the first and second fluid conduits by a conduit 114.

In the operation of the instant device, it will be assumed that the cylinder is originally in an attitude whereby piston 22 is against gland 16 with the rod fully extended. The valve 112 is closed, and the pump is placed into operation to provide a hydraulic fluid under pressure to the cylinder from the reservoir 96. As is conventional, the fluid flows in through the first conduit 92 and into the inlet port 40, so that a high pressure is created in high pressure chamber '70. As the pressure is built up, fluid flows into the bleeders 60 and 58 to seat more positively ball 88 in valve seat 84. With the build up of pressure, the piston along with rod 20' is moved toward the back head 14. Fluid contained in the low pressure chamber 68 is expelled through the exhaust port 26 and out through the second conduit 106. It may be appreciated that the second pressure relief valve 108 is a low pressure valve, namely, 25 pounds per square inch, so that the fluid is readily returned to reservoir 96. As was mentioned above, the instant cylinder is used as a portion of a stripper, however, the cylinder may be put to any use desired.

It should be noted that inasmuch as a low pressure relief valve is connected to the low pressure chamber, there is no need for a heavy back head to withstand high pressures which may be built up in the chamber during the movement of the piston toward the back head. As the piston approaches the back head, it may be appreciated that it is desirable to stop the piston, so that the back head is not pushed off the tube by the force of the piston. When the piston comes close to the back head, tapered post 38 of the stem enters the bleeder port 86 and engages ball 88 to unseat the ball. It may be thus appreciated that the high pressure chamber 70' is connected to the low pressure chamber 68 through the bleeder apertures 58 and 60 and through the valve 24. In view of the fact that the low pressure chamber 68 is connected to the high pressure chamber, there is an effective connecting of the low pressure relief valve 108 with the high pressure chamber to relieve the pressure in the high pressure chamber. Thus, the piston is effectively stopped, and the force urging the piston to go into engagement with the back head 14 is interrupted, so that the back head construction may be light. It should be further noted that when the valve 24 is open, the effective force on the piston is to move the piston toward the gland, due to the differential area on opposite sides of the piston.

It is the differential area on opposite sides of the piston which provides the means for returning the piston. In order to return the piston, the control valve 112 is opened, and the pump is allowed to operate at a low pressure, so that the piston is moved toward the gland because of the differential area of the piston.

From the foregoing description, -it is readily apparent that the instant arrangement provides a safe system of operation. The high pressure relief valve provides a safety valve for the high pressure side of the cylinder, and the low pressure relief valve provides a means whereby the piston in the cylinder may be returned by the simple operation of a control valve, and the low pressure relief valve connected to the low pressure cylinder provides a means whereby the piston reaching the end of its stroke has an effective force applied to it to return the piston, thereby stopping the movement of the piston. However, it should be noted that the pressure is not dumped entirely.

Although a specific embodiment of the herein-disclosed invention has been shown and described in detail above, it is understood that those skilled in the art may make various modifications and changes without departing from the spirit and scope of the present invention. It is to be expressly understood that the instant invention is limited only by the appended claims.

What is claimed is:

1. A fluid circuit for use with a cylinder having a piston and a rod connected to said piston comprising, in combination, a first fluid conduit connected to the cylinder adjacent to the end of the cylinder having the rod, a high pressure relief valve connecting the first fluid conduit with a reservoir, a pump connected to the reservoir and the first fluid conduit to provide a fluid under pressure to the first fluid conduit and the cylinder, a second fluid conduit connected to the opposite end of the cylinder, a low pressure relief valve connected to said second fluid conduit to connect the second fluid conduit with the reservoir, and a valve connecting the first and second fluid conduits, whereby when the valve is closed and the pump operates, high pressure fluid is delivered to the first fluid conduit to move the rod inward of the cylinder and fluid is exhausted into the second conduit and out through the low pressure relief valve into the reservoir; and opening of the valve and reducing the pressure generated by the pump to a pressure below the pressure required to operate the low pressure relief valve causes the rod to be expelled from the cylinder due to the differential area of the piston.

2. A fluid power system comprising, in combination, a tube, a gland mounted on one end in said tube for closing said end, a back head mounted on the other end of said tube closing said end of the tube, a rod reciprocally mounted in said gland, a piston connected to said rod and being sealingly cooperating with an interior surface of said tube, said rod having a threaded valve aperture on the end of the rod adjacent to the back head, an axial exhaust port extending into said rod and communicating with the valve aperture, a radial exhaust port in said rod communicating with the axial exhaust port and the space between the piston and the gland, a valve body having a threaded portionmounted in the threaded valve aperture, said valve body having a flange in engagement with said rod to provide a seal therebetween, said valve body having an axial flow aperture extending therethrough, said valve body having an enlarged control aperture being a portion of the axial flow aperture, a valve seat in said valve body defining a portion of the enlarged control aperture, a ball movably mounted in the enlarged control aperture and engageable with the seat to control the flow of fluid through the valve body, a spring in engagement with the ball constantly urging the ball into engagement with the seat, an axial stud mounted on the back head and engageable with the ball to unseat the ball from its seat as the rod approaches the back head, said gland having a port providing communication be tween the space between the piston and the gland and the exterior of said gland, a second port in said tube adjacent to the back head, a first fluid conduit connected to the port in said gland, a second fluid conduit connected to the-port in said tube, a high pressure relief valve connected to the first fluid conduit, said high pres- 5. sure relief valve having its relief side connected to a reservoir, a pump having its inlet connected to said reservoir and having its outlet connected to the first fluid conduit and to the inlet to the high pressure relief valve, a low pressure relief valve having its inlet con- 5 nected to the second fluid conduit and its outlet connected to the reservoir, and a control valve connecting the first and second fluid conduits, whereby closing of the control valve and operation of the pump to provide a fluid under high pressure delivers fluid under pressure 10 to the first conduit to move the piston toward the back head, and opening of the control valve and operating the pump to provide a fluid under pressure below the pressure required to operate the low pressure relief valve causes the'pisto n to move toward the gland.

References Cited by the Examiner UNITED STATES PATENTS 6/1891 Mayo 251-333 4/1900 Pedrick 91-417 X 1/1909 Camp 6052 10/ 1925 Ferris 6052 4/ 1933 Anthony et a1 6052 3/1941 Ernst et al. 6052 X 3/ 1943 Campbell 6052 X 11/1951 Leeds 91-399 X FOREIGN PATENTS 7/1934 Germany.

15 EDGAR W. GEOGHEGAN, Primary Examiner.

Claims (1)

1. A FLUID CIRCUIT FOR USE WITH A CYLINDER HAVING A PISTON AND A ROD CONNECTED TO SAID PISTON COMPRISING, IN COMBINATION, A FIRST FLUID CONDUIT CONNECTED TO THE CYLINDER ADJACENT TO THE END OF THE CYLINDER HAVING THE ROD, A HIGH PRESSURE RELIEF VALVE CONNECTING THE FIRST FLUID CONDUIT WITH A RESERVOIR, A PUMP CONNECTED TO THE RESERVOIR AND THE FIRST FLUID CONDUIT TO PROVIDE A FLUID UNDER PRESSURE TO THE FIRST FLUID CONDUIT AND THE CYLINDER, A SECOND FLUID CONDUIT CONNECTED TO THE OPPOSITE END OF THE CYLINDER, A LOW PRESSURE RELIEF VALVE CONNECTED TO SAID SECOND FLUID CONDUIT TO CONNECT THE SECOND FLUID CONDUIT WITH THE RESERVOIR, AND A VALVE CONNECTING THE FIRST AND SECOND FLUID CONDUITS, WHEREBY WHEN THE VALVE IS CLOSED

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