US2711717A - Self-shifting distributing valve for double-acting reciprocating motors - Google Patents

Description

June 28, 1955 J, STACEY 2,711,717

SELF-SHIFTING DISTRIBUTING VALVE FOR DOUBLE-ACTING RECIPROCATING MOTORS Filed Dec. 13, 1951 3 Sheets-Sheet 1 INVENTOR HUGH 7- sneer BY )E/CHEY, WA TTEDGEEE/VJNQVENNY ATTORNEYS June 28, 1955 H. J. STACEY 2,711,717

SELF-SHIFTING DISTRIBUTING VALVE FOR DOUBLE-ACTING RECIPROCATING MOTORS Filed Dec. 13, 1951 3 Sheets-Sheet 2 (I 320' J M M- P 4 -6 Fm? .BLOC/(Efli I .96 32 2a 34d 34 .30 3a 3/ 57 37 a q MM 38 ,2, W a

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' SELF-SHIF TING DISTRIBUTING VALVE FOR DOUBLE-ACTING RECIPRQCATING MOTORS Filed Dec. 13, 1951 3 Sheets-Sheet 3 L0 LO Q N H FH mvsmoa 1 Hugh Jfiiaceg BY Q ZI' 4.

ATTORNEYS United States atent ii SELF-SHIFTING DISUTING VALVE FOR DOUBLE-ACTING RECIPROCATING MOTORS Hugh J. Stacey, Willoughby, Ohio, assignor, by mesne assignments, to The New York Air Brake Company, New York, N. Y., a corporation of New Jersey Application December 13, 1951, Serial No. 261,546

8 Claims. (Cl. 12146.5)

This invention relates to hydraulic motors and more particularly to an improved valve mechanism for fluid motors of the reciprocating type adapted to cause automatic reciprocation of the motor.

In many hydraulic installations such as machine tools, presses, washing machines and many other machines it is desirable to have a reciprocating piston and cylinder assembly which is entirely automatic in its action under control of a valve, whereby reciprocation of the work cylinder or piston continues so long as the supply of fluid under pressure is maintained.

Various arrangements have been proposed to attain these ends, which arrangements fall into three general categories. These are:

( 1) Mechanically-tripped valve elements including levers or cams actuated by the work motor to cause reversal;

(2) Systems wherein special passages in the work cylinder are covered and uncovered by the piston to trip or actuate the reversing control valve;

(3) Systems wherein the reversing control valve is fully automatic and all hydraulic, and is merely connected to the two pipes leading to a standard doubleacting hydraulic motor without special control ports or passages.

' The principal object of the present invention is to simplify the construction of the fully automatic type of valve and to make possible fully automatic control with a valve employing but one movable'control plunger.

Another object is to insure that the control device will not stop with the single plunger on dead center.

A further object is to insure that the work cylinder will always start from rest in the same direction when fluid-pressure is applied.

Still another object is to protect the pilot plunger from damage due to over-travel which is accomplished by incorporating a damping function in the valve structure.

A further object is to reduce the size of the valve unit and to facilitate service, cleaning and repair thereof.

Still another object is to provide a simple adjustment for the maximum force exertible by the work cylinder which adjustment will be maintained during repeated operation of the system.

A further object is to provide a control valve that will continue to function, that is, cause reciprocation of the fluid motor even though the latter be prevented from making a full stroke in one or both directions. Also, it is an object of the invention to minimize throttling of the fluid as it passes through the valve which, in turn, prevents over-heating of the fluid and the associated parts.

In view of the nature of-the construction of the valve of this invention, the manner in which the aforesaid objects are accomplished will be best understood from the following description and drawings disclosing a preferred embodiment of the invention.

In the drawings:

Fig. 1 is a diagram of a typical installation;

Fig. 2 is a vertical section through the valve;

which intersects the through bore.

ice

work cylinder or motor M is of the double-acting type and,

includes a cylinder and the usual piston for reciprocation within the cylinder. A source of hydraulic fluid under pressure is supplied by a pump P which withdraws such fluid from the reservoir or tank T by means of line 10 and supplies it under pressure by means of line 11 to a manually-operable valve S. The valve S is of any suitable construction and is merely arranged so that, with the control handle at one position, fluid from the pump is by-passed by line 12 whereas, with the handle in the other position, fluid is directed by means of line 13 to the reversing pilot valve V, which forms the subject'matter of this invention.

Valve V is connected to opposed ends of the work cylinder by means of lines 14 and 15, and the valve is connected to the reservoir tank T by return line 16. As indicated by the arrows in Fig. 1, the valve V is arranged to direct pressure fluid through line 14 to cause motion of the piston to the right (in the drawing) and the valve also receives the exhaust fluid from line 15 from the other side of the motor M, and directs it to the tank T by means of the exhaust line 16. Upon completion of the stroke of motor M, fluid flow in lines 14 and 15 is reversed.

The construction of the valve unit is best seen in Figs.

2-4. The valve body is formed with a through bore for receiving the single unitary control plunger P, which bore is intersected or interrupted by various chambers formed within the body, the walls of such chambers forming lands between the chambers. Referring to the construction of the valve body, the body is formed with an inlet chamber 20 which has an inlet that connects to the inlet line 13 to receive fluid under pressure from the source. Also formed in the body are two work chambers 21 and 21a which connect to opposite ends of the fluid motor by means of threaded ports 22 and 22a respectively. At this point it should be mentioned that the valve and plunger are in many ways symmetrical, the two sides (left and right in Figs. 2 and 4) of the valve being largely alike and such sides merely exchanging functions as the plunger P shifts in the body. Thus, for clarity, where the functions of corresponding parts on the two sides are the same, the same reference characters are applied with the subscript (a) added to the parts of the valve disposed on the right side of the valve in Figs. 2 and 4.

Continuing the explanation of the valve body construction, opposed lands 23 and 23a are formed between the inlet chamber 20 and the work chambers 21 and 21a. Also formed in the valve bodyis an exhaust or reservoir chamber 24 which has a threaded outlet port 25 for connection to line 16 leading to the reservoir. The reservoir chamber has two branches 26 and 26a each of Thus, with this con struction, lands 27 and 27a are formed between the work chambers 21 and 210. andthe branches 26 and 26a of the Formed at each side of the'valve body (as seen in Figs. 2 and 4) are control chambers 23 reservoir chamber.

semblies 30 and 30a which are of identical construction. For example, the left hand relief valve assembly 30 comprises a sleeve 31 threaded into the body wall and extending into the control chamber 23. An adjusting screw 32 is threaded into the sleeve and is locked by a lock nut 33 in its adjusted position. This screw serves to back up a relief valve spring 34 at one end and the spring engages a relief valve ball 36 at its other end. A removable valve seat member 37 is mounted in the wall between the control chamber and the adjacent work chamber and has a reversing port 38 formed therein which is normally closed by the relief valve ball 36. As seen in Fig. 3, a set screw 39 retains the member 37 in place in the valve body. These parts have their counterparts at the right hand side of the valve assembly as seen in Figs. 2 and 4.

The construction of plunger P will now be described. The plunger reciprocates in the bore formed by the various lands referred to and has a central reduced section 40 which connects to end sections 41 and 41:: having the form of sleeves. These sleeves are formed by drilling or otherwise machining the plunger to form cavities 42 and 42a in the end sections thereof, which cavities serve to conduct exhaust fluid into reservoir chamber 24. The walls of the plunger sleeves are drilled as at 43 and 43:1 to form exhaust inlet ports leading into the plunger cavities, and such walls are also drilled at 44 and 44a to form dual-purpose ports. Relatively small bleed ports 45 and 45a are formed in the plunger sleeves between the exhaust inlet ports 43 and 43a and ports 44 and 44a and (as will be seen) serve a damping function for plunger motion.

The parts of the plunger just described are symmetrical and as the plunger reciprocates they exchange functions. However, in order that the plunger will never stop on dead center and to insure that the work cylinder will always start in the same direction, the right hand side (Figs. 2 and 4) of the valve is specially constructed. The plunger is elongated'somewhat as at 46 and this elongation is surrounded by a spring 47 one end of which bears against a washer 48. Extension 46 is of reduced diameter relative to the rest of the sleeve, thereby providing a shoulder 49 that may be brought into engagement with the Washer 48. The washer 48 also normally bears against a shoulder on the valve body. The other end of spring 47 engages threaded plug 50. With this arrangement, the plunger may move freely to the left in the drawings but can only move to the right of the position shown in Fig. 2 by compressing the spring 47. After the plunger P and the spring and Washer are inserted in the valve body, the caps 50 and 51 are assembled to seal the unit and maintain the 5,

plunger in place. As seen in Figs. 1 and 3, complete assembly includes insertion of caps or cover screws 52 and 52a to protect the set screw 39.

The lands on the plunger at opposite ends of the re duced portion 40 have zero lap as to the motor ports 21 and 21a respectively. This fact is illustrated in Figs. 3 and 4 but there it is somewhat obscured by the shading. Fig. illustrates it clearly. Similarly, in mid-position the exhaust ports 43, 43a have zero lap as to the control edges of motor ports 21 and 21a. Thus there would be a momentary but only a momentary hydraulic lock as the valve shifts through mid-position.

The operation of the device as connected into a system such as shown in Fig. 1 will now be explained. At the beginning of operation, the plunger P will normally be in the position shown in Fig. 2, or at least it will not be to the right of that position. Under these conditions, fluid admitted to the inlet chamber 20 now passes into the work chamber 21 because the reduced portion 40 of the plunger clears the land 23. Thus, fluid is directed to the left hand side of the motor M causing motion of the work piston to the right, as viewed in Fig. 1. On the other hand, land 23a is engaged by the plunger sleeve section 41a which blocks chamber 21a and hence the other side of the motor from pressure fluid, but it should be noted that the plunger is balanced against inlet pressure. In normal operation, inlet pressure is also exerted against the relief valve ball 36 through the reversing port 38 but the adjustment of the relief valve spring 34 is such that, normally, ball 36 remains seated during the motion of the piston to the right. Exhaust fluid from the right hand side of the motor (as viewed in Fig. 1) enters chamber 21a and passes through the exhaust inlet port 43a in plunger section 41a, into the plunger cavity 42a, and out port 44a (which now serves as an exhaust outlet port) and into branch 26a of the reservoir chamber.

The relation of the ports in the plunger and the lands on the valve body is such that, initially, the dual-purpose port 44a is almost closed by land 29a, causing a throttling of the fluid exhausting from the motor M at this area. This, in turn, causes a build up of pressure in the cavity 42:: of the plunger and in control chamber 28a of the valve body and results in an unbalanced force tending to move the plunger to the left in the drawings. As the plunger moves to the left communication through the exhaust port 44:: is opened but the entry of the plunger part 41 into the left hand control chamber 28 displaces fluid from such chamber. The displaced fluid can only find its way to the reservoir chamber 24 by way of the relatively small damping port 45, the throttling action of which serves to prevent rapid motion of the plunger to the left and also provides for a gradual starting of the work piston.

Before the work piston reaches the end of its stroke, the unbalanced force on the plunger will have caused the plunger P to move to the left far enough for the damping port 45 to reach the land 29. Further motion of the plunger to the left is now considerably retarded because the damping port 45 henceforth is increasingly restricted, which tends to place a steadily increasing hydraulic block in left hand control chamber 28. As a matter of fact, in normal operation, damping port 45 becomes completely or substantially completely blocked at which time leftward motion of the plunger P is stopped entirely by hydraulic action. Because of the relative positions of the damping port 45 and land 29 this occurs before the plunger P strikes the body of the valve which prevents damage to both the valve body and the plunger.

When the piston in the hydraulic motor M reaches the end of its stroke, either as determined by the limits of the cylinder or by the load, further motion of the piston is prevented or at lea-st is abnormally retarded. However, the pump continues to supply fluid under pressure so that pressure in the motor and in chamber 21 immediately builds up to a value higher than that present in normal operation. As soon as such pressure builds up to a value corresponding to the setting of relief valve assembly 30, such pressure, acting through the reversing port 38, will unseat the ball relief valve 36. This pressure is immediately reflected into the control chamber 28 and is exerted against the left hand portion 41 of the valve plunger causing a relatively large unbalanced force (as indicated in Fig. 4) tending to move the plunger to the right. This unbalanced pressure is maintained on the plunger until it starts to move, whereupon the damping port 45 is uncovered and thence the unbalanced pressure begins to decrease. Even when so vented however, the unbalanced force is sufiicient to move the plunger rapidly to the right until inlet chamber 20 is closed by valve portion 41 and land 23, at which time inlet pressure is directed to the work chamber 21a (formerly serving as an exhaust chamber) by cooperation of the reduced portion on the plunger and the land 23a. Pressure in chamber 28 immediately drops and ball relief valve 36 is seated.

Movement of the plunger through the neutral midposition is dependent on the momentum of the valve plunger, which is considerable. The use of substantially zero lap reduces the range of the hydraulic lock efiect practically to Zero, and using commercial methods of manufacture, zero lap can be approximated closely enough to assure that the valve will coast through a midposition in which, theoretically, it could be expected to lock. After all, hydraulic liquids contain occluded air and so are not strictly incompressible and the lock period with zero lap is strictly momentary. The use of negative lap (clearance), would increase internal leakage and since its use is not necessary to permit the valve to shift, it should be avoided.

The balance of the action of the valve plunger is like that just described with all functions exchanged. Throttling occurs as fluid is exhausted from the left hand side of the fluid motor (by way of port 43) and such exhaust fluid passes into the reservoir chamber through port 44 now serving as an exhaust outlet port, which port is only partially uncovered due to land 29. As before, this throttling generates an unbalanced force tending to continue motion of the plunger to the right, as viewed in Fig. 4. The damping port 45a at the right hand side of the valve is the only port that precludes a hydraulic block as the plunger enters control chamber 28a and so port 451.: now functions to damp the motion of the plunger to the right. Port 45a is eventually closed by land 29a, effectively blocking further motion of the plunger before it strikes the body. The unbalanced force tending to shift the plunger to the right caused by throttling at plunger port 44 is more than great enough to overcome the spring 4'7.

When the piston in the work cylinder again reaches the end of its travel (to the left in Fig. l in this case), pressure builds up in chamber 21a unseating ball relief valve 36a causing a rapid initial shift of the plunger to the left, whereupon it is again in the position shown in Fig. 2 and the cycle is repeated.

it is seen that when source pressure is removed, the spring 47 acts so as to insure that the plunger will always be in a position to direct fluid through the same side of the hydraulic motor. In other words, work chamber 21 is always in communication with inlet chamber Zll at the time when pressure is initially supplied to the valve unit. Thus, the plunger will never be left in dead center or neutral position and when pressure is supplied the work piston will always start in a given predetermined direction unless it has reached the end of its stroke in that direction, with which the reversing action will occur. Thus, it can be seen that full automatic control is provided by a valve having only one shiftable plunger therein.

It will also be noted that various ports in the plunger, lands in the valve body, and end sections of the plunger perform multiple, alternative functions as the device operates. For example, a given end section of the plunger will alternatively serve as a piston that shifts the plunger, and as a piston that damps plunger shifting. The same multiple function action is characteristic of ports 44 and 44a, ports 45 and 45a, and their associated lands, as will be understood from the detailed description of the operation of the device.

The plunger and the check valves may be readily removed for cleaning, servicing and replacement. The device is compact and economical to manufacture. Due to the construction of the reduced portion 40 of the plunger and of the exhaust ports in the plunger as well as the sleeve-like arrangement of the plunger, very little throttling of the work fluid occurs. Also, reversal will occur automatically whenever the work piston is stopped, either because it is at the end of its normal stroke or in case of a jam or other obstruction to its motion. The device can be incorporated into a standard hydraulic system and requires no special ports or other chambers, or connections at the work cylinder or at any other of the units.

Having completed a detailed description of a preferred embodiment of the present invention so that others skilled in the art may be able to understand and practice the same, I state that what I desire to secure by Letters Patent is not limited by said preferred embodiment but rather is defined in what is claimed.

.What is claimed is:

1. A self-shifting distributing valve for interchanging supply and exhaust connections to the opposed working spaces of a double acting hydraulic motor, said valve comprising in combination, a ported housing having a bore, and a ported plunger reciprocable in said bore, the housing having in communication with said bore a supply port at mid-length of the bore, two exhaust ports spaced in opposite directions therefrom, and two motor ports each adapted for connection with a corresponding working space of said hydraulic motor and respectively interposed between said supply port and a corresponding one of said two exhaust ports, the plunger having lands which separate an inlet port substantially at mid-length of the plunger from exhaust ports in respective end portions of the plunger, which lands in the neutral position of the plunger close with substantially zero lap both of the motor ports in the housing, the housing having control chambers which enclose respective ends of the plunger and function as opposed working spaces of a secondary hydraulic motor for shifting the plunger, and the plunger having restricted bleed ports which in said neutral position connect respective control chambers with exhaust; biasing means urging said plunger away from said neutral position; and springloaded relief valves one for venting each motor port into the corresponding control chamber when over-pressure in the related motor part results from arrested motion of the controlled double acting motor, whereby the plunger is shifted by hydraulic pressure regardless of the urge of said biasing means.

2. A valve as defined in claim 1 in which at least the end portions of the plunger are tubular and communicate with respective control chambers and the'plunger exhaust ports and the bleed ports lead through said tubular walls.

3. A valve as defined in claim 1 in which at least the end portions of the plunger are tubular and communicate with respective control chambers and the plunger exhaust ports and the bleed ports lead through said tubular walls and the bleed ports are each so located relatively to an exhaust port in the housing that when the plunger has started to move in response to high pressure in a control chamber one of said bleed ports opens and partially dissipates that pressure.

4. A valve as defined in claim 1 in which at least the end portions of the plunger are tubular and communicate with respective control chambers and the plunger exhaust ports and the bleed ports lead through said tubular walls and the bleed ports are each so located relatively to an exhaust port in the housing, that as the plunger approaches the end of its shift one of the bleed ports is interposed in the path of flow from the control chamber toward which the plunger is moving.

5. A valve as defined in claim 1 in which at least the end portions of the plunger are tubular and communicate with respective control chambers and the plunger exhaust ports and the bleed ports lead through said tubular walls and the bleed ports are each so located relatively to an exhaust port in the housing, that when the plunger has started to move in response to dominant pressure in one control chamber one of said bleed ports opens and partially dissipates the dominant pressure and as the plunger approaches the end of its motion the other of said bleed ports is interposed in the path of flow from the other control chamber and gradually arrests the motion of the plunger.

6. A self-shifting distributing valve for a double-acting fluid motor comprising a body having a central inlet chamber for connection to a source of fluid under pressure, a work chamber at each side of said inlet chamber for connection to the motor, an exhaust chamber having a branch at the outer side of each work chamber, and a pair of control chambers one at the outer side of each of said exhaust branches, a bore in said body communicating with all of said chambers forming lands therebetween, a plunger freely slidable in said bore, a cavity formed in each end of said plunger and open to said control chambers, the central portion of said plunger being relieved and the ends of said plunger being ported so that with said plunger shifted to one position one work chamber is connected to said inlet chamber past said relieved portion and the other work chamber is connected to the exhaust chamber by means of a plunger cavity, and with said plunger shifted to a second position said one work chamber is connected to the exhaust chamber by means of the other plunger cavity and the other work chamber is connected to said inlet chamber past said relieved portion, the ends of said plunger forming piston means movable into and out of said control chambers, whereby a pressure differential between said control chambers tends to shift said plunger, a port between each work chamber and the adjacent control chamber, and a spring-loaded relief valve for each port closed against a predetermined pressure in the associated worl;

chamber.

7. A self-shifting distributing valve for a double-acting fluid motor comprising a body having a central inlet chamber for connection to a source of fluid under pressure, a work chamber at each side of said inlet chamber for connection to the motor, an exhaust chamber having a branch at the outer side of each work chamber, and a pair of control chambers one at the outer side of each of said exhaust branches, a bore in said body communicating with all of said chambers and forming lands therebetween, a plunger freely slidable in said bore, a cavity formed in each end of said plunger to form sleeve-like pistons open to said control chambers, the central portion of said plunger being relieved and the Walls of each plunger piston each having a set of axially-spaced ports, said relieved portion and ports being arranged so that with said plunger shifted to a first position one work chamber is connected to said inlet chamber past said relieved portion and the other work chamber is connected to a plunger cavity by means of the inner port of one set of plunger ports, said cavity is connected to the exhaust chamber by means of the outer port of said one set of plunger ports, and the inner port of said other set of'plunger ports is closed by the land between said one work chamber and the adjacent exhaust branch; and with said plunger shifted to a second position said connections are reversed, a port between each Work chamber and the adjacent control chamber, and a spring-loaded relief valve for each port closed against a predetermined pressure in the associated work chamber.

8. A self-shifting distributing valve for a double-acting fiuid motor comprising a body having a central inlet chamber for connection to a source of fluid under pressure, a work chamber at each side of said inlet chamber for connection to the motor, an exhaust chamber having a branch at the outer side of each Work chamber, and a pair of control chambers one at the outer side of each of said exhaust branches, a bore in said body communicating with all of said chambers and forming lands therebetween, a plunger freely slidable in said bore, a cavity formed in each end of said plunger to form sleeve-like pistons open to said control chambers, the central portion of said plunger being relieved and the walls of each plunger piston each having a set of axially-spaced ports comprising inner and outer ports with a restricted bleed therebetween, said relieved portion and ports being arranged so that with said plunger shifted to one position one work chamber is connected to said inlet chamber past said relieved portion and the other Work chamber is connected to a plunger cavity by means of the inner port of one set of plunger ports, said counterbore is connected to the exhaust chamber by means of the outer loaded relief valve for each port closed against a predetermined pressure in the associated work chamber.

References {lifted in the file of this patent UNITED STATES PATENTS 1,952,690 Strom, Sr. Mar. 27, 1934 2,342,450 Campbell Feb. 22, 1944 2,387,549 Wineman Oct. 23, 1945 2,389,661 Fischer Nov. 27, 1945 2,617,257 Douglas Nov. 11, 1952

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