US3054383A

US3054383A - Fluid motor

Info

Publication number: US3054383A
Application number: US67233A
Authority: US
Inventors: Hanna John Clark
Original assignee: HANNA ENGINEERING WORKS
Current assignee: HANNA ENGINEERING WORKS
Priority date: 1960-11-04
Filing date: 1960-11-04
Publication date: 1962-09-18
Anticipated expiration: 1979-09-18

Description

Sept. 18, 1962 J, c, NA 3,054,383

FLUID MOTOR Filed NOV. 4, 1960 2 Sheets-Sheet l INVENTOR.

Sept. 18, 1962 c, HANNA 3,054,383

FLUID MOTOR Filed Nov. 4, 1960 2 Sheets-Sheet 2 INVENTOR.

Jm/ W 7 2 22 nited States Patent Qfiice 7 3,654,383 Patented Sept. 18, 1862 3,054,383 FLUID MOTOR John Clark Hanna, Chicago, 111., assignor to Hanna Engineering Works, Chicago, ill., a corporation of Illinois Filed Nov. 4, 1960, Ser. No. 67,233 9 Claims. (Cl. 12138) This invention relates to a fluid motor and, more specifically, to an improved construction of a hydraulic cylinder in combination with cooperative fluid devices which provide for cushioning of a piston in the cylinder over an extended range and the cushioning may be selectively ad justed to accommodate difierent applications of the fluid motor.

It is generally well recognized that it is desirable to brake or to slow down a piston in a fluid motor toward the end of the pistons stroke so that it does not strike violently the cylinder head at the end of its stroke. There are various devices and constructions which provide a cushion for a piston in a hydraulic cylinder. All of these devices have certain objections which make them unsuitable for universal usage. A common failing is that the cushioning apparatus in a cylinder extends the distance between cylinder heads so that the cylinder length is outside the standard length. The prior art devices also usually require that certain portions of the cylinder be machined to a greater degree of precision than normally required so that the cylinders per se are more expensive to manufacture without the added expense of additional equipment which is required. In many instances, the braking or cushioning provided by the known devices occurs instantaneously over a short range so that extraneous and transient forces are built up in the cylinder and associated devices and true cushioning is not eiiected. Furthermore, it is recognized that hydraulic cylinders are used with different types of apparatus in many types of applications so that it it desirable to vary the effectiveness of the cushion to accommodate difierent circumstances. Therefore, it is the principal object of the present invention to provide a long cushion for a hydraulic cylinder over an extended range during which there is a gradual buildup of cushioning forces toward the end of the piston stroke, but the maximum cushioning may be selectively controlled.

It is another object of the hereindisclosed invention to provide a long cushion for a hydraulic cylinder which cushion provides a gradual buildup of the cushioning force toward the end of the stroke of the piston until the maximum cushioning force is achieved.

It is a further object of the instant invention to provide a hydraulic cylinder having a long cushion which maximum force of the long cushion may be selectively adjusted.

It is a still further object of this invention to provide a cushion construction for a hydraulic cylinder wherein the distance between cylinder heads is not increased by cushioning apparatus.

It is still another object of the present invention to provide a cushion construction for a hydraulic cylinder wherein the construction of the cylinder with the cushion requires only the same degree of precision as the construction of the cylinder without the cushion, allowing the usage of standard cylinder heads in the cylinder.

Other objects and uses of the hereindisclosed invention will become readily apparent to those skilled in the art upon a perusal of the appended specification in light of the drawings, in which:

FIGURE 1 is a side elevation of a hydraulic cylinder and appurtenant devices embodying the present invention;

FIGURE 2 is partially a cross-sectional view of the hydraulic cylinder shown in FIGURE 1 showing the details of construction of the cylinder and partially a schematic view showing the relative positions of other members; and

FIGURE 3 is a cross-sectional view of a portion of a plug valve shown in FIGURE 1 in which the valve is shown in a partially closed attitude.

Referring now to the drawings and especially to FIG- URE l, which shows a specific embodiment of the present invention, a hydraulic cylinder generally indicated by numeral 10 has a plug valve 12 connected to one end and a second plug valve 12a identical in construction to the first mentioned plug valve connected to the other end. The cylinder 10 is connected to a ball check valve 13 and flow regulating valve 14 which are connected in parallel to each other and to plug valve 12. A second bail check valve 13a and flow regulating valve 14a, which are identical in construction to the first mentioned check valve 13 and flow regulating valve 14, respectively, are connected to the other end of cylinder 10 and are connected in parallel to each other and to plug valve 12a. The plug valve 12, ball check valve 13 and valve 14 are connected through a cross 16 to a spool valve 18 which is also conected to the

valves

12a, 13a and 14a through a cross 16a. The spool valve 18 is connected to a pump 20 and reservoir 22 through fluid conduit means. A regulating valve 24 is positioned between the pump and the reservoir tank to control the flow of fluid from the tank.

Looking now to FIGURE 2, it may be seen that the cylinder 10 has a conventional construction except for the addition of the plug valves 12 and 12a. The cylinder 10 includes a tube 26 which has one end closed by an interior face of a head 28 and the other end closed by an interior face of a head 30. A piston '32 is reciprocally mounted in the tube 26 to move between heads 28 and 30 under appropriate fluid pressure, as will be described hereinafter. The piston 32 has mounted thereon conventional piston rings 34 which mate with the interior wall of tube 26 in a conventional fashion to form a seal therebetween. A gland 36 mounted in head 30 carries a plurality of seals 38 which cooperate with a piston shaft 40 which is reciprocal through the head 30. The piston 32 is secured to the rod 40 for movement with the rod, and the rod or shaft is connected to a cooperative device which device is not shown in this instance.

The head 28 contains a recess cavity 42 which opens into the interior of tube 26. The recess cavity communicates with a port 44 which port 44 is connected to a cross 46 by means of piping 48. The cross 46 is in turn connected to valve 12a by piping 50 and to

valves

13a and 14a. It maybe seen that valve 12a is connected to cross 16a by piping 52 so that

valves

12a, 13a and 14a are in parallel and the cross 16a is connected to valve 18 by piping 54.

Head 30 has similar construction to head 28 in that it includes a recess 56 which communicates with the interior of tube 26. A port 58 connects the recess 56 with piping 60 which connects the port with a cross 62. In turn, the cross 62 is connected to

valves

13 and 14, and to valve 12 by means of piping 64. The valve 12 is in turn also connected to cross 16 by means of piping 66 and the cross 16 is conneted to

valve

18 and 14 so that

valves

13 and 14 are in parallel to valve 12. The cross 16 is in turn connected to valve 18 by means of piping 68. Thus, the piping provides a fluid conduit means between the cylinder and the various values.

Valve 12, which has an identical construction to valve 12a, generally consists of a sleeve support 70 mounted in head 3%, a housing 72 connected to support 70 in a sealing relationship, and a plug 74 which is reciprocally mounted in support '70 and movable to housing 72.

The support 70 is fixed in a plug valve aperture 76 in head 30. A pair of O-

rings

78 and 80 are mounted on the outer periphery of the support 70 to provide a seal between the support and the head. The support has a third O-ring 82 on its interior surface in engagement with plug 74 to form a seal between the plug and the support. The support has an axial cylindrical aperture 84 which extends over the greater portion of its length, and a smaller aperture 86 which is coaxial with aperture 84 and open thereon. A collecting groove 88 is defined in the interior of the support adjacent to the junction of the apertures 84 and 86. A second groove 90, which is on the outer surface of the groove between O-

rings

78 and 80, is connected to the interior groove 88 by means of apertures 92, so that fluid may flow from the interior of the support to the groove 90 in the outer surface of the support.

' The aforementioned plug 74, which has its axis parallel to the axis of rod 40, includes a body 94 which body has a diameter slightly less than the inside diameter of aperture 84 so that there is a sliding fit between the plug and the support 70. The body has a stem 96 formed integral therewith, which stem 96 has a diameter slightly less than the diameter of aperture 86 so that the O-ring 82 forms an effective seal between the stem and the support, The stem 96 protrudes into the interior of tube 26 for engagement with the piston 32. The body 94 has a nose 98 formed integral with the body on the end away from the tube 26. The nose 98 is tapered for reasons which will become apparent hereinafter.

, Considering now the detailed construction of housing 72, it may be seen that the housing has a cylinder port 100 which has piping 64 connected therewith. A controlled flow port 102 is adjacent to port 108 and piping 66 communicates with the port 102. The housing has an axial chamber 104 which is coaxial with the apertures 84 and 86 of support 70. Chamber 104 has one end closed by pipe plug 106 which is threadedly mounted in the housing 72. The chamber 104 has formed therein a flow passage 108rbetween the

ports

108 and 102 which flow passage has a diameter less than chamber 184 but just slightly greater than body 94. When body 94 of plug 74 is positioned in flow passage 108 the flow of fluid between the ports 100 and 102 is cut 011 for reasons which will become apparent hereinafter.

' In the event that any fluid leaks along the plug body 94, the fluid collects in the annular groove '88 and passes through apertures 92 into groove 98. The annular groove 90 communicates with a drain port 110 in head 38. The drain port is connected to the reservoir tank 22 through piping 112, T 114 and piping 116 as may be clearlyseen in FIGURE 1. 7

Plug valve 12a which is identical in construction to plug valve 12 has identical parts identically numbered with the suflix a added. The plug valve 12a, which has its axis'parallel to rod 40, generally consists of a sleeve support 70a, a housing 72a sealingly connected to support 70a, and'a plug 74a reciprocally mounted in the support and housing The support 70a is fixed in a plug valve aperture 120 in head 28 in the same manner that sleeve support 76 is mounted in head 30. A pair of O-rings 78a and 80a form a seal between'the support and head 28. A third O-ring 82a provides a seal between the support and plug 74a. The support 70a includes an axial cylindrical aperture 84a and a second aperture 86a'which communicates with the interior of the tube 26 and the aperture 84a. An interior annular groove 88a is defined in the interior of the support. An exterior annular groove 90a, which is between O-ringS 78a and 80a, is formed on the outer surface with a plurality of apertures 92a providing communication between the interior and exterior grooves 88a and The plug 74a includes a body 94a which has a diameter slightly smaller than the diameter of aperture 84a so that the plug is free to move axially in the support 70a. A stem 96a is formed integral with the body 9411 and is engageable with the piston 32. A tapered nose 98a is formed integral with the body 94a on the end opposite the stern 96a.

The housing 72a has a port 100a which is connected to piping 50 and a second port 182a which is connected to piping 52. The ports communicate with an axial chamber 104a which is coaxial with the apertures 84a and 86a. A pipe plug 106a closes one end of the housing. A flow passage 108a is positioned between the two ports 108a and 102a to divide the chamber 104a into two parts. As

may be seen in the FIGURE 2, when the plug body 98a is positioned in the flow passage 108a fluid communication between

ports

102a and 100a through the housing 721: is effectively terminated.

The head 28 includes a drain or leakage port 122 which communicates with the outer annular groove 92a. The port 122 is connected to T 114 by means of piping 124, which conducts any fluid, which leaked past the plug, to reservoir 22 by means of piping 116 as mentioned above.

The operation of the cylinder 10 is conventional in many respects; however, the present invention provides a gradual buildup of resistance to the movement of the piston at the end of its stroke over a long stroke so that there is a smooth transition from noncushioning to a maximum cushioning. Considering now the specific operation of the present invention. -When the cylinder is in the attitude as shown in FIGURE 2, the piston 32 is moved to the left by proper application of fluid under pressure. The pump 20 provides hydraulic fluid under pressure from reservoir 22 to the spool valve 18. Spool valve controls the flow of fluid sothat the fluid under pressure is directed into piping 54. The fluid flows to cross 16a where a portion of the flow flows to piping 52 and toward port 102:: of valve':12a. It may be appreciated that the flow of fluid is effectively stopped by plug 74a. However, in the event that any fluid were to flow between the support 79a and body 98a, the fluid which leaks by is returned to the reservoir through port 122 and through piping 124.

The remainder of the bulk of the fluid flows from cross 16a through ball check valve 13a. It should be noted that a-minor portion of the fluid does flow through regulating valve 14a but does rejoin the major portion of the fluid at cross 46; At the cross 46, the fluid applies a pressure to the end of the plunger 74a to urge it toward the piston 32. The fluid is conducted by the conduit means in the form of piping 48 to port 44 where the fluid passes through port 44 and into recess 42 to apply'a pressure to the right side of the piston 32, thereby moving the piston toward the left which carries with it rod 40. It is appreciated that the rod 40 is connected to a cooperative device which is not shown in this instance.

As the piston 32 moves toward the head 30 the fluid which is contained in the interior of tube 26 flows out of the tube through recess 56and into port 58 where the exhaust fluid is conducted by the conduit means to cross 62. At cross 62 the exhaust fluid divides so that a portion of the fluid passes through valve 12 and a portion through valve 14. Inasmuch as the valve 13 is a check valve in this direction there is no free flowof exhaust fluid through valve 13. A small portion of the exhaust fluid passes through the regulating valve. The remainder and the majority of the exhaust fluid flows from cross 62 into the conduit meansin the form of piping 64 into port 100, thence through the free flow passage 108 and out through port102. Then, the fluid is conducted from port 102 into cross 16 by piping 66 to rejoin the minor portion of fluid which flows through valve 14. The fluid is then conducted to spool valve 18 by fluid conduit means 68 and from the spool valve it'is returned to the reservoir tank '22. It may be appreciated that in this instance there is a substantially free flow of exhaust fluid from the cylinder to the reservoir.

As the piston 32 approaches the end of its stroke toward the head 30, it is desirable to gradually increase the resistance pressure in the exhaust fluid in order to slow down the piston in its movement toward the head 30. The piston 32 engages the stem 96 of valve 12 to move the plug 74 toward the free flow passage 198. Initially, the movement of the plug has no appreciable eifect on the flow of fluid through the flow apertures. However, the tapered nose 98, which has an exponential curve, finally enters the stream of the fluid flowing through aperture 108 to bring about a resistance to flow through the passage 108. Initially, the resistance is slight but as the piston 32 moves further toward head 30, the exponentially tapered nose 98 enters the passage 1% even further. As may be seen in FIGURE 3, the tapered nose substantially restricts the opening of aperture 108 so that there is a substantial resistance to flow of exhaust fluid from port 100 to port 102. Actually the flow of fluid through valve '14 continues as described above.

Finally, the further movement of piston 32 plugs the aperture 108 with valve body 94 so that there is no flow through the aperture. Thus, all of the flow must pass through valve 14. It may be appreciated that the change from the substantially free flow to a regulated flow through valve 14 was a gradual change which occurred toward the end of the stroke of the piston over a substantially long period and the tapered construction of the nose of the plug allowed a smooth transition from an open to a closed attitude of valve 12. In this manner, the transient and extraneous forces were held to a minimum.

As was mentioned above, the fluid pressure which is used to move the piston 32 toward head 31) also moves plug 74a out of the aperture 108a, thereby resetting the plug for use when the piston 32 moves toward the head 28. Inasmuch as the leakage port 122 provides a means for fluid which leaked along plug body 94a to escape, there is no fluid trapped in the plug Valve which prevents the plug from being reset. The piston 32 is engageable with stem 96a in the same manner that it engages stem 96 with the same result occurring. It may be appreciated that the spool valve 18 is used to control the flow of fluid under pressure to the proper sides of the cylinder and to control the flow of exhaust fluid to the return tank.

From the foregoing description it is clear that the present invention allows standard cylinders to be easily adapted for use as cushion cylinders without painstaking precision machining of the cylinder heads.

All that is required is to form the bore 76 and to tap the bleed connection 110. The plug valve assembly can then be telescoped into the bore and held therein by any desired means, with sealing being eflected by the O-

rings

78, 80. Thus, the unit is to be contrasted with conventional arrangements which require outboard attachment to a standard type of actuator.

To summarize the operation, it will be apparent that during the exhaust stroke, for example, during the time that fluid is being exhausted from the fluid connection 66, the throttling

ports

64, 66 associated with the plug valve are efiectively in series with the connection 60 to control the rate of exhaust. However, during the forward or power stroke, the check valve 13 opens, providing a direct fluid supply connection to the left hand end of the actuator, free of any throttling obstruction. Simultaneously, pressure fluid is applied to the

plug valve ports

64, 66 to cause the plug valve to move to its extended position in readiness for an ensuing cycle. Thus, during the power stroke, the regular inlet to the actuator and the plug valve are effectively connected in panallel with one another.

While a specific embodiment of the hereindisc-losed invention was shown and described in detail above, it is to be appreciated that there are many applications which may be made to the hereindisclosed invention without departing from the spirit and scope of the invention which is limited only by the appended claims.

What is claimed is:

1. In a fluid actuator the combination comprising a cylinder having heads at the ends thereof providing connections for admission and exhaust of fluid, a piston slidable in said cylinder and having a piston rod telescoped through one of said heads, a plug valve in at least one of said heads, said plug valve having a valve sleeve and a plug therein with the stem of the plug projecting into the cylinder and in the path of final movement of the piston, said valve sleeve having first and second ports connected by a fluid passage and said plug being so con structed that the effective area of the passage is progressively reduced with progressive throttling of fluid between the ports as the plug is moved by the piston, means for connecting the ports of the valve in series with the connection on the associated cylinder head so that as the fluid is exhausted from the latter it is progressively throttled to produce a smooth deceleration of the piston as it approaches the end of its stroke and means including a valve for applying pressure fluid directly to the connection on the piston head for producing reverse movement of the piston free of any obstruction provided by the plug valve.

2. In a fluid actuator the combination comprising a cylinder having heads at the ends thereof providing connections for admission and exhaust of fluid, a piston slidable in said cylinder and having a piston rod telescoped through one of said heads, a plug valve in at least one of said heads, said plug valve having a valve sleeve and a plug therein with the stem of the plug projecting into the cylinder and in the path of final movement of the piston, said valve cylinder having first and second ports and said plug being so constructed that progressive throttling of fluid occurs between the ports as the plug is moved by the piston, and means for connecting the ports of the valve in series with the connection on the associated cylinder head so that as the fluid is exhausted from the latter it is progressively throttled to produce a smooth deceleration of the piston as it approaches the end of its stroke.

3. In a fluid actuator the combination comprising a cylinder having heads at the ends thereof providing connections for admission and exhaust of fluid, a piston slidable in said cylinder and having a piston rod telescoped through one of said heads, a plug valve in at least one of said heads, said plug valve having a valve sleeve and a plug with the stem of the plug projecting into the cylinder and in the path of final movement of the piston, said valve sleeve having first and second ports and said plug being so constructed that progressive throttling of fluid occurs between the ports as the plug is moved by the piston, means for connecting the ports of the valve in series with the port on the associated cylinder head so that as the fluid is exhausted from the latter it is progressively throttled to produce a smooth deceleration of the piston as it approaches the end of its stroke, and valve means for simultaneously applying fluid pressure to the connection on the head and to the ports of said plug valve to cause immediate reversal of the piston free of throttling by said plug valve and accompanied by movement of the plug valve to its extended position.

4. In a fluid actuator the combination comprising a cylinder having heads at the ends thereof each provided with a fluid connection, a piston and piston rod slidable in said cylinder, at least one of said heads having an axially extending bore formed therein, a plug valve subassembly, including a valve sleeve having one end dimensioned to fit in said bore and having ports at its opposite end, a plug slidable in said sleeve having a stem which projects axially from said cylinder into the path of final movement of the piston and having its other end so formed that as the plug moves under the urging of the piston flow through said ports is progressively throttled, and valve means for efiectively connecting the head connection in series with the valve ports for progressive throttling of fluid during the exhaust stroke and for eflectively connecting the head connection in parallel with said ports and to a source of pressure fluid during the pressure stroke.

5. In a fluid actuator, the combination comprising a cylinder including heads secured at each end thereof which include connections for admission and exhaust of pressure fluid, a piston and piston rod slidable therein, at least one of said heads having a bore axially formed therein, a plug valve assembly, said plug valve assembly having a sleeve dimensioned to fit snugly in said bore and having ports at its opposite end, a plug slidable in said sleeve and having a stern which projects into. the path of final movement of the piston and operatively associated with the valve so that throttling takes place between the valve ports as the plug is moved by the piston.

6. A fluid actuator comprising, in combination, a cylinder having cylinder heads each provided with fluid connections, a piston and piston rod slidable in the cylinder, at least one of said cylinder heads having an axially extending valve sleeve, a plug slidable in said valve sleeve and having a stern which projects into the path of final movement of the piston, said valve sleeve having ports spaced along the length thereof and having a flow passage therebetween, the end of the plug and the contour of the flow passage being such that the opening between the ports is progressively throttled as the plug is moved by the piston, and means for connecting said ports effectively in series with the connection on the associated head during the exhaust stroke for progressive throttling of the exhaust fluid and progressive deceleration of the piston.

7. A fluid actuator comprising, in combination, a cylinder having heads at the ends thereof with respective connections for pressure fluid, a piston and piston rod slidable in the cylinder, a plug valve in at least one of said heads having a plug and having ports for progressive throttling of pressure fluid as the plug is engaged by the piston during the terminal portion of its stroke, means for'connecting the ports of the plug valve in series with the associated connection in the head so that during the piston exhaust stroke the exhausted fluid is throttled by the plug valve during the terminal portion of the stroke, and a check valve connected between the ports of the plug 8 Valve for admitting fluid directly to the connection on the head for reverse movement of the piston free 'of throttling restriction.

8. A fluid actuator comprising, in combination, a cylinder having heads at the ends thereof each provided with a fluid connection, a piston in said cylinder having a piston rod and reciprocable therein, a plug valve in at least one of said heads adjacent said piston rod and having a sleeve and a plug slidable therein, said plug having a stem projecting through the head and into the path of movement of the approaching piston, said plug valve having ports arranged for progressively throttling by the associated plug upon movement thereof by the piston, said plug valve being vented to accommodate leakage of fluid along said stem.

9. In a fluid actuator, the combination comprising, a cylinder having heads at the ends thereof providing connections for admission and exhaust of fluid, a piston slidable in said cylinder and having a piston rod telescoped through one of said heads, a plug valve in at least one of said heads, said plug valve having a valve sleeve and a plug therein with the stem of the plug projecting into the cylinder and in the path of final movement of the piston, said valve sleeve having first and second ports and said plug being so constructed that progressive throttling of fluid occurs between the ports as the plug is moved by the piston, means for connecting the ports of the valve in series with the connection on the associated cylinder head so that as the fluid is exhausted from the latter it is progressively throttled to produce a smooth deceleration of the piston as it approaches the end of its stroke, and a manually adjustable throttling valve, connected across the ports in said plug valve for adjusting the throttling action at the terminal portion of the stroke.

References Cited in the file of this patent UNITED STATES PATENTS 899,795 Osmer Sept. 29, 1908 2,114,334 Conklin Apr. 19, 1938 2,338,845 Gunner et al Jan. 11, 1944 2,743,704 Banker May 1, 1956 2,783,742 Shafer Mar. 5, 1957