US3027880A

US3027880A - Quick-acting reversing valve with pressure compensation

Info

Publication number: US3027880A
Application number: US36014A
Authority: US
Inventors: Hendrik K J Van Den Bussche
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1959-06-22
Filing date: 1960-06-14
Publication date: 1962-04-03
Anticipated expiration: 1979-04-03

Description

April 3, 1962 H. K. J. VAN DEN BUSSCHE 3,027,880

QUICK-ACTING REVERSING VALVE WITH PRESSURE COMPENSATION Filed June 14, 1960 2 Sheets-Sheet 1 FIG.3

INVENTOR H.K.J. VAN DEN BUSSCHE BY mam.-

IS AGENT April 3, 1962 H. K. J. VAN DEN BUSSCHE 3,027,880

QUICK-ACTING REVERSING VALVE WITH PRESSURE COMPENSATION Filed June 14, 1960 2 Sheets-Sheet 2 FlG.4

H. K.J. VAN DEN BUSSCHE';

BY IS AGENT United States The invention relates to a quick-acting valve for automatically reversing the supply and the discharge of pressure medium respectively to or from the working space of a double-acting cylinder containing a working piston, which valve comprises a stationary housing provided with ports, a free valve body contained in the housing and cooperating with the said ports, and two cylinder spaces extending along the longitudinal axis of the valve body, which spaces are each bounded at one side by the said valve body, and a control member adapted to be adjusted with respect to the valve body by the working piston for alternately connecting the cylinder spaces to the pressure medium inlet and the pressure medium outlet.

Quick-acting valves of the above type are especially suitable for operating hydraulic piston engines, since the use of such valves completely eliminates a stoppage period of the working piston at the end of the stroke thereof, which occurs when conventional valves are employed. The quick-acting valve of the present invention may be used in operating a hydraulic piston engine as described in co-pending US. patent application Serial No. 842,363,

filed September 25, 1959, now Patent No. 2,965,077

issued on December 20, 1960.

It has been found, however, that the stroke of the working piston of a hydraulic piston engine provided with a quick-acting valve of the above-mentioned type is not constant under all conditions, but increases with decreasing load of the piston engine. As a result the piston would abut against the cylinder covers when it is in its end position so that there is another stoppage period at the end of the stroke. The higher the load, the shorter will be the piston stroke, which means that in order to ensure that the total travel of the piston per unit of time is constant (which is desired, for example, when the engine drives a piston pump giving a required constant output), the frequency has to be increased which adversely affects the wear (e.g.-, of the valves of a pump which is being driven).

The object of the invention is to obviate this drawback.

To this end, according to the invention, the port alternately connecting the cylinder spaces to the pressure medium inlet is provided with a member which, when the pressure difference between the inlet and the outlet increases or decreases, reduces or enlarges respectively the passageway of the port.

This member preferably consists of a pressure-sensitive element connected at one side to the medium inlet, and at the other side to the medium outlet, and of a throttle element connected to the pressure-sensitive element and provided in the passageway of the said port.

The pressure-sensitive element may be a piston-shaped body provided in a bore in one of the collars of the valve body.

The invention will be explained with reference to the drawing, wherein:

FIGURES 1, 2 and 3 are diagrams of longitudinal sectional views of the quick-acting valve in three different positions of the valve body and the control member;

FIGURE 4 is a view in enlarged detail of the part of the valve housing containing the control member; and,

FIGURE 5 is a view taken on the line V-V in FIGURE 4.

' atent o" 3,027,888 Patented Apr. 3, 1862 FIGURE 1 shows a double-acting cylinder 1 containing working piston 2 which is connected by means of a piston rod to a work-absorbing appliance (not shown). The piston rod 3 is coupled to an abutment member 4 and is adapted to adjust, via the latter, the control member 7 of the quick-acting valve 8 by way of the two

levers

5 and 6. The

levers

5 and 6 are pivotally supported by the fixed fulcrums 9 and 10 and interconnected by a hinged coupling rod .11. The displacement of the valve may also be hydraulically derived from that of the piston as described in the U.S. patent application, Serial No. 842,363, filed September 25, 1959, now Patent No. 2,965,077 issued on December 20, 1960.

The

working spaces

12 and 13 of the cylinder 1 communicate with the housing 16 of the quick-acting valve 8 through

conduits

14 and 15, respectively. The housing 16 is provided with

ports

17, 18, 19, 20 and 21 of which the port 19 is connected to a hydraulic medium inlet, the

ports

17 and 21 to a hydraulic medium outlet. Port 18 communicates with working space 12 through conduit 14 and port 20 communicates with working space 13 of cylinder 1 through conduit 15.

A free cylindrical valve body 22 is contained in the housing 16 and is provided with shoulders of enlarged diameter or

collars

23 and 24. An annular space within the valve body 22 is divided into two

cylinder spaces

27 and 28 by a piston 26 mounted on a control rod 25 of the control member 7. Abutment members 29 are provided at both ends of the space enclosed by the housing 16 limiting the extreme positions .of the valve body 22.

The hydraulic medium is supplied to and discharged from the

cylinder spaces

27 and 28 through the inlet opening 30 provided in the valve body 22 and through

longitudinal grooves

31 and 32 which are provided in the control rod 25.

The member controlling the passageway of the inlet opening 30 in dependency of the diflference between the inlet pressure and the outlet pressure, the parts of which member being shown in FIGURES 4 and 5 on a larger scale than in the FIGURES 1, 2 and 3, comprises a plunger 34 adapted to be moved in a bore 33 and coupled to a throttle element 36 mounted for movement in a conduit 35 and provided with a profiled fluid port 37. In addition, the plunger 34 is provided with a shoulder 38, between which shoulder and the collar 23 a compression spring 39 is arranged.

The quick-acting valve 8 operates as follows. In FIG- URE 1, the working piston 2 is in its extreme right-hand position in the cylinder 1. In this case the piston 26 of the control member 7, which control member is connected to the piston rod 3 of the piston 2 by way of the lever 6, is in such a position relative to the inlet opening 30 of the valve body 22 that the cylinder space 28 communicates with the space 40 bounded by the

collars

23 and 24 of the valve body 22 and the housing 16. In this position, the said space 40 also communicates with the high-pressure inlet port 19, so that high-pressure hydraulic medium may enter the cylinder space 28. Since, moreover, in this position the cylinder space 27 communicates with the outlet port 17 through the groove 31 and the space to the left of the collar 23, there is a pressure in the space 27 which is lower than that in the space 28. Since the pressures prevailing in the spaces to the left of the collar 23 and to the right of the collar 24 are equal, as both communicate with an outlet port, the valve body 22, being mounted for free movement in the housing 16, will quickly move to the right relative to the piston 26. This movement continues until the valve body 22 abuts against the abutments 29 provided on the right-hand side of the housing 16. In this position (see FIGURE 2) the collar 23 is between the

ports

18 and 19 and the collar 24 between the

ports

20 and 21. Consequently, communication is established between the conduit 14 and the outlet port 17 through the port 18, and between the conduit and the inlet'port 19 through the port 20. As a result, the working piston 2 will be displaced to the left in the cylinder 1, during which displacement both the valve body 22 and the control member 7 remain in the position shown in FIGURE 2 since the pressures on either side of the valve body 22 are equal, and the high pressure prevailing in the space 28 is unable to move valve body 22 relative to control member 7, as the piston 26 is already pressed against the left-hand side of the space Within the valve body 22.

Before the piston 2 reaches its extreme left-hand position (position shown in dotted lines in FIGURE 1) the control member 7 begins to move tothe right by means of the lever 5, the coupling rod 11 and the lever 6, which lever system is started by the abutment means 4 of the piston rod 3 engaging the lever 6. Inst before the piston 2 reaches the extreme left-hand position, the piston 26 of the control member 7 exposes the opening (see FIGURE 3) and thus establishes communication between the cylinder space 27 and the high-pressure inlet 19. The communication between the cylinder space 27 and the outlet port 17 through the groove 31 is simultaneously broken. In this position the cylinder space 28 simultaneously communicates with'the outlet port 21 through the groove 32, so that as a result of the pressure difference prevailing between the

spaces

27 and 28 the valve body 22 will rapidly move to the left relative to the piston 26 mounted on the control device 7. This displacement is arrested by the abutments 29 mounted on the left-hand side of the housing 1 6. The latter position of the valve body 22 corresponds with the position shown in FIGURE 1 wherein the supply and discharge to and from the

working spaces

12 and 13 of the cylinder l are interchanged relative to the position shown in FIGURE 3.

Thus, the movement of the working piston 2 is quickly reversed, and after the control member 7 has been switched over to the position shown in FIGURE 1 at the end of the subsequent stroke, the cycle described above is repeated.

If during operation of the piston engine. the work taken up by the work-absorbing appliance (not drawn) decreases, this decrease in the load on the hydraulic piston engine will be reflected as a reduction in the supply pressure in the inlet port 19 and the spaces communicating therewith. As a result of this reduction in the supply pressure there will be a decrease in the difference over the pressure-sensitive element 34 (see FIGURES 4 and 5) and the throttle element 36 is moved to the right by the action of the compression spring 39. As the profiled port 37 of the throttle element 36 in its extreme right-hand position exposes a larger passageway of the opening 30 than in its extreme left-hand position, this displacement will result in a larger passageway of the opening 30., The liquid flowing to the cylinder space 28 through this opening 3% now meets with less resistance in this opening, so that the pressure drop in the space 28. caused by the pressure drop in the inlet port 19 iscompensated. Thus, the force which acts on the valve body 22, and is required for the reversal thereof, is practically unchanged by the pressure drop in the inlet port 19, and, since the resistance to beovercome by the, valve body 22 in the reversal is practically constant, the valve body is reversed between its extreme positions in the same period as was the case before the load o-f the piston engine 1 decreased.

v Conversely, theload on thepiston engine 1 increases, the pressure in the inlet port 19 will also increase. The effect of the resultant increase of the pressure difference prevailing over the collar 23, is that the pressure-sensitive element 34 moves to the left against the action of the compression spring 39. The throttle element 36 then also moves to the left and the profiled port 37 of the throttle element 36 reduces the passageway of the opening 30. The resistance met by the liquid stream in the opening 30 increases, whereby a pressure drop occurs in this opening which compensates the pressure rise in the space 28 which results from the increase in the load. In this case also the reversing speed of the valve body 22 remain-s unchanged.

The excess travel of the piston 2 in its extreme positions after the piston 26 has opened the inlet port in the valve body 22, depends on the reversing speed of the valve body 22. Since the invention has provided means with which the reversing speed may be kept constant or substantially constant at different loads on the piston engine, the length of the total stroke of the piston 2 in the cylinder 1 also depends on the load on the piston engine.

This prevents the piston 2 from abutting against the covers of the cylinder 1 at low loads of the piston engine, which, except for possible breakage, has the drawback that there is a period when the piston stops at the ends of the stroke, whereby the continuity in the delivery of energy is broken. The. use of the invention is also important inhydraulic piston engines adapted to drive an appliance for the proper operation of which a constant stroke is required.

The invention is not limited. to the embodiment of the valve as shown in the drawing. If desired, the valve body may be designed as a fiat valve. Nor is the invention limited to the embodiment of the pressure-sensitive element 34 and the throttle element 36 as shown in the drawing.

It is essential, however, that the. change; in the pressure in the inlet opening 19 be compensated by a change in the flow resistance in the opening 30. If in this case the supply pressure is P and the pressure drop over the opening SOAP, the pressure available for moving the valve body is P-AP. This difference in pressure PAP should remain constant at varying supply pressure P. From this it follows that the filling rate through the opening 30 (which filling rate equals the product of flow rate V in opening 30 and surface area 0 of the passageway of this opening 30) is also constant. Since, in addition, the pressure drop AP over the opening 30 is proportionate to the square of the rate V in opening 30, the requirement regarding the constant value of the difference P-AP may also be expressed by the formula P %=eonstant In the latter formula C is a constant.

If P is increased the movement of the pressure-sensitive element should be such that by narrowing the passage- -way O by the throttle element the above requirement is spaces located at both ends of the free valve body as.

shown in U.S. patent specification 2,361,757.

I claim as my invention:

1. A quick-acting valve for automatically reversing. the 2 supply and the discharge of pressure medium respectively to and from the workingspaces of a double-acting cylinder containing a working piston, which valve comprises a stationary housing provided with pressure medium inlet and outlet ports, a free valve body contained in the housing and for selectively opening and closing said ports, and a control member adapted to be adjusted by the working piston and forming within the valve body two cylinder spaces, the control member being provided with, a piston forming a partition between the cylinder spaces which are alternately connected to the pressure medium inlet and the pressure medium outlet ports through the displacement of the valve body relative to the control member, a port in said valve body alternately connecting the cylinder spaces to the pressure medium inlet, pressure-responsive variable opening throttle valve means for controlling fluid flow through said port in said valve body in response to changes in the pressure difference between the inlet and the outlet pressure medium ports.

2. The quick-acting valve of claim 1, wherein the pressure-responsive valve means comprises a pressure-sensitive element in communication on one side to the medium inlet pressure and on the other side to the medium outlet pressure, and a throttle element connected to the pressuresensitive element and positioned in the said port.

3. A quick-acting valve as claimed in claim 2, wherein the pressure-sensitive element is constituted by a pistonshaped body provided in a bore in one of the collars of the valve body.

4. A quick-acting valve for automatically reversing the supply and the discharge of a pressure medium respectively to and from the working spaces of a double-acting cylinder containing a working piston, said valve comprising a stationary valve housing provided with a port in communication with each working space of said double-acting cylinder, inlet port means intermediate the ends of said valve housing adapted to communicate with a source of hydraulic pressure fluid, discharge port means for discharging a hydraulic pressure fluid from said valve housing, a free valve body having a chamber formed longitudinally therethrough and being mounted for sliding movement within said valve housing, a pair of spaced collars of enlarged diameter carried outwardly on said valve body and providing flow passages on the outside thereof, the spacing between the collars being such that the hydraulic pressure fluid inlet port means at any time is in communication with only one of said housing ports in communication with a working space of said doubleacting cylinder, fluid port means through the wall of said valve body intermediate the collars, a control member extending through the chamber of said valve body and out at least one end of said valve housing, said control member adapted to be operatively connected to and positioned by the working piston of said double-acting cylinder, said control member forming an annular chamber outside thereof in said valve body, a piston carried on said control member dividing said annular space into two annular spaces, said piston being slidably movable with said control member and so positioned thereon to place the annular spaces alternately in communication with the port means through the wall of said valve body, throttling flow passage means formed longitudinally in the surface of said control member on opposite sides of said piston, said throttling flow passage means having an eifective length so as to be closed when the annular space on one side of the piston is in open communication through the port in the wall of valve body, and diflerential pressure responsive valve means in communication with said hydraulic pressure fluid for controlling the flow of fluid through the port in the wall of said valve body.

5. A quick-acting valve for automatically reversing the supply and the discharge of pressure medium respectively to and from the working spaces of a double-acting cylinder containing a working piston, which valve comprises a stationary housing provided with pressure medium inlet and outlet ports, a free valve body contained in the housing and for selectively opening and closing said ports, and two cylinder spaces extending along the longitudinal axis of the valve body, which spaces are each bounded at one side by the said valve body, and a control member adapted to be adjusted with respect to the valve body by the working piston for alternately connecting the cylinder spaces to the pressure medium inlet and the pressure medium outlet ports, a port in said valve body alternately connecting the cylinder spaces to the pressure medium inlet, and pressure-responsive variable opening throttle valve means for controlling fluid flow through said port in said valve body in response to changes in the pressure difference between the inlet and the outlet pressure medium ports.

References Cited in the file of this patent UNITED STATES PATENTS 2,361,757 Fink Oct. 31, 1944 2,500,627 Chinn Mar. 14, 1950 2,748,752 Baghuis June 5, 1956