US3285282A

US3285282A - Flow control valve for fluid motors and the like

Info

Publication number: US3285282A
Application number: US405675A
Authority: US
Inventors: George J Martin
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 1964-10-22
Filing date: 1964-10-22
Publication date: 1966-11-15
Anticipated expiration: 1983-11-15

Description

Nov. 15, 1966 G. J. MARTIN 3,285,282

FLOW CONTROL VALVE FOR FLUID MOTORS AND THE LIKE I Filed Oct. 22, 1964 TANK 28 p INVENTOR GEORGE J. MART/IV BY iwflzw f 100M ATTORNEYS United States Patent 3,285,282 FLOW CONTROL VALVE FOR FLUID MOTORS AND THE LIKE George J. Martin, Lyndhurst, Ohio, assignor to Parker- Hannifin Corporation, Cleveland, Ohio, a corporation of Ohio Filed Oct. 22, 1964, Ser. No. 405,675

11 Claims. (Cl. 137--596) The present invention relates generally as indicated to a. flow control valve for fluid motors and the like and more particularly to a flow control valve which is pressure sensitive, i.e., when the fluid pressure increases, the rate of flow of fluid through the flow control valve decreases.

In the case of a fork lift truck, for example, it is conventional practice to employ a single acting hydraulic motor which, when fluid under pressure is conducted thereto, is operative to raise the lifting fork and a load thereon and which, when the fluid therefrom is permitted to drain into a tank, the lifting fork and load thereon descends. If such lifting fork has a heavy load thereon and is allowed to descend at too rapid a rate, the lift truck will be subject to severe shock load and, in fact, may be tipped when the lifting fork and load is suddenly stopped during descent or at the end of the stroke.

Accordingly, it is a principal object of this invention to provide a flow control valve which is sensitive to fluid pressure to permit rapid descent of a piston in a cylinder under light load and to permit progressively decreased rate of descent of the piston as the load is progressively increased. Thus, in the case of a fork lift truck, for example, the lift fork when empty, or lightly loaded, will descend at a rapid rate, as desired, when the directional control valve is operated to permit such descent. On the other hand, when the lift fork has a heavy load thereon, and the directional control valve is operated to permit lowering thereof, the present flow control valve will automatically restrict the flow according to the magnitude of the load.

Other objects and advantages of the present invention will become apparent as the following description proceeds. To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a side elevation view partly in cross-section illustrating a typical fork lift truck employing a single acting fluid motor for raising and lowering the lifting fork thereof; a

FIG. 2 is a cross-section view through a flow control valve embodying the present invention, said flow control valve being shown in association with a directional control valve for a single acting cylinder, said directional control valve being here shown by way of example as a three way spool-type valve; and

FIG. 3 is a fragmentary cross-section view of a moditied form of flow control valve.

Referring now in detail to the drawing; and first to FIG. 1, the reference numeral 1 denotes a fork lift truck to the lower front portion of which a telescoping mast structure 2-3 is pivotally mounted at 4. Said mast structure 2-3 is adapted to be tilted back about pivot 4 as by a double acting fluid motor 5 pivotally connected to the ice mast structure at 6 and pivotally connected at its other end (not shown) to the truck frame.

As aforesaid, the mast structure 2-3 herein is of telescoped form including a lower section 3 in which the upper section 2 is vertically slidably guided and, in turn, the lifting fork 7 is vertically slidably guided in said upper section 2. Mounted on the pivot 4 is the single-acting cylinder 8 having its piston rod 9 linked by chains or the like, not shown, to cause vertical movement of the upper mast section 2 with respect to the lower mast section 3 and upward movement of the lifting fork 7 with respect to the upper m-a'st section 2. When the piston 10 (see FIG. 2) moves down in the cylinder 8, the upper section 2 moves down into telescoped relation within the lower section 3 of the mast structure and then the lifting fork 7 moves down with respect to both

sections

2 and 3 for placing the load W on the floor F. This is schematically shown in FIG. 2 wherein the load W is lifted by admitting fluid under pressure from pump 11 via the directional control valve 12 into the lower end of the cylinder 8, and the load W is permitted to descend when the fluid in the cylinder 8 is allowed to escape into the reservoir or tank 14, via the directional control valve 12.

Referring now in detail to FIG. 2, there is provided a housing 15 which has a bore 16 therethrough intersected by a bypass passage 17 which at one end communicates with the inlet port 18 and which at the other end communicates with tank port 19, by a pair of

pressure feed passages

20, 20 which straddle the branches 2-1, 21 of the bypass passage, by a pair of

motor passages

23, 23, and by a pair of

return passages

24, 24 which lead to the aforesaid tank port 19.

Reoiprocable in said bore 16 is a three-way valve spool 25 and it can be seen that when said spool 25 is in the neutral position N as shown in FIG. 2, the pump 11 will freely circulate fluid through the bypass passage 2117 into the tank 14. When the spool 25 is shifted to raise position R, the bypass passage 21-17 will be closed by the

lands

26 and 27, and fluid communication will be opened between the right pressure feed and

motor passages

20 and 23, whereby fluid under pressure delivered by the pump 11 into the inlet port 18 Will flow through the check valve 28 into the right pressure feed passage 20 and thence to the right motor passage 23 wherefrom the fluid under pressure flows through the

passages

29 and 3 0 and through the flow control valve 31 into the lower end of the cylinder 8 thus to act on the piston 10 to raise the same and the load W thereon.

When the spool 25 is shifted to the lower position L, the bypass passage 21-17 remains open, and fluid communication is established between the right motor passage 23 and the right return passage 24, whereby the load W on the piston 10 will displace the liquid in the cylinder 8 through the flow control valve 31 and

passages

30 and 29 into the tank 14 via the right motor and

return passages

23 and 24 and tank .port 19. When the spool is in neutral position N, the lands 27 and 32 thereof block communication of the right motor passage 23 with the adjacent pressure feed and

return passages

20 and 24, whereby fluid is trapped in the cylinder 8 so that the piston 10 and load W thereon are locked in raised position.

In FIG. 1, the operating lever 34 will be operatively connected with the spool 25 to shift it to its various positions aforesaid and it is understood that the valve housing 15 may have another spool therein for controlling the mast tilt cylinder 5. Furthermore, while not shown herein, the spool 25 may have associated therewith the usual spring centering mechanism which automatically returns the spool to the N position upon release of the control lever 34, and it is further contemplated that suitable detent mechanisms may be employed to yieldably retain the spool 25 in either or both the R and L positions, whereby the operator may manipulate the lever 34 to the desired position and use both hands for driving the truck while the load W is being raised or lowered.

The flow control valve 31 herein comprises a sleeve member 40 having passages 41 through the wall thereof which register with the annular passage 42 in the housing 15. Reciprocable in said sleeve member 40 is the flow control member 43 which has a plurality of apertures 45 of varying sizes therethrough which, as can be seen, when the flow control member 43' moves to the right as viewed in FIG. 2, the largest apertures 45 will progressively be covered by the right edges of the passages 41 of the sleeve member 40 to decrease the aggregate flow capacity through apertures 45. As the member 43 continues to move to the right the second largest, then the third largest, etc., apertures 45 will progressively be covered until only the smallest apertures 45 will remain uncovered for most restricted flow. The member 43 is capable of movement to the right even to the extent where the smallest apertures 45 are covered by the right edges of the sleeve passages 41, whereby exhaust flow from the cylinder 8 under extremely heavy load may be substantially completely blocked except for leakage around the sleeve member 40 and through the sliding fit between the flow control member 43 and sleeve 40.

The flow control member 43 is biased to its full open position, as shown in FIG. 2, by the spring 46 which bears on the member 47, and said plunger member 47, in turn, bears on flow control member 43 through spring 48 and plug member 49. Said plunger member 47 has a plunger stem 50 which is axially slidably sealed in cylinder member 51. The plug and

plunger members

49 and 47 have pressure equalizing orifices 52 and 53 therethrough so that the fluid pressures in the chambers 54 and 55 will be equal to that in the chamber 56 in the flow control member 43. The housing has a passage 57 leading from passage 30 to chamber 58 so that fluid pressure may act on the end of plunger stem 50.

When the spool 25 is in the neutral position N, the flow control member 43 will be in the position shown in FIG. 2 regardless of the load W on the piston 10, since in that condition of the spool 25, the pressures are equalized on both sides of the plunger stem 50 in the

chambers

56, 54 and 55 and in the

passages

30 and 57 and chamber 58. However. when the spool 25 is shifted to the lower position L, the communication of the motor passage 23 with the right return passage 24 results in a pressure drop in the

passages

29, 30 and 57 and in chamber 58 leading to the plunger stem 50, whereupon the higher pressure in the

chambers

56, 54, and 55 acting on the area of said plunger stem 50 will cause the flow control member 43 to move to the right compressing spring 46 thus to decrease the flow rate through the apertures 45. The greater the load W, the greater the pressure differential acting on plunger stem 50 due to decreasing flow capacity through apertures 45 and thus as the load W is increased, the rate of descent thereof is decreased.

When the load W on the piston 10 is a minimum, that is, the weight of the lifting fork 7 and of the upper mast section 2, the bias of the spring 46 is preferably such that the plunger stem 50 will not move toward the right under the influence of the relatively small fluid pressure diiferential in the

chambers

56 and 58.

Assuming now that the lifting fork 7 has a maximum load W thereon for which the equipment is designed, such that, for example, there is built up a pressure of 1000 psi. on the liquid in the lower end of the cylinder 8. So long as the spool 25 is in its neutral position N such 1000 psi. pressure is prevalent throughout the system from cylinder 8 to motor passage 23, and thus all of the parts of the flow control assembly will remain as shown in FIG. 2. However, when the spool 25 is shifted to lower position L, the pressure in the chamber 58 will drop substantially whereupon the pressure in the

chambers

56, 54, and 55 acting on the area of the plunger stem 50 will compress the spring 46 to permit movement of flow control member 43 to the right to decrease the flow capacity through the apertures 45 to the desired extent so that the lifting fork 7 and its load W will descend at the desired rate so as not to shock the equipment or to tip it over when the fork 7 reaches its lowest point, or when the spool 25 is shifted back to neutral position N. Similarly, when the fork 7 has a load W thereon between minimum and maximum, the resulting pressure differential in the

chambers

56 and 58 will compress the spring 46 to less extent with the result that the flow control member 43 will move to the right to permit flow through apertures 45 at a desired rate which will be less than the maximum rate (with no load on fork 7) but greater than the minimum rate (with maximum load W on fork 7).

When the spool 25 is shifted to raise position R, the motor passage 23 is communicated with the feed passage 20 whereupon fluid under pressure flows through

passages

29 and 30, and apertures 45 to the lower end of cylinder 8 to raise the load W. In that case, the pressure in chamber 58 is greater than in

chambers

56, 54, and 55 due to pressure drop in passage 30 and apertures 45 and thus the flow control member 43 will be held in FIG. 2 position by spring 46 and by the higher fluid pressure in chamber 58 acting on the end of the plunger stem 50. The pressure drop across passage 59 also aids in maintaining flow control member 43 in its maximum flow position.

With further reference to the flow control member 43, and plunger member 47, they are, in effect, integral, but because of the provision of the equalizing orifice 52 of smaller size than the equalizing orifice 53, the chamber 54 becomes a dashpot or cushioning chamber to minimize the efiect of shock loads in the system. For example, when the spool 25 is shifted from lower position L to neutral position N the load W will be suddenly stopped and its 7 inertia will cause shock pressure in the system, but because of the orifice 52 the pressure in the chamber 54 cannot be instantly increased and thus plug member 49 may move slightly to the right compressing spring 48 to isolate the shock from plunger member 47. Moreover, if the load W is a very heavy one, only the smallest apertures 45 will be open to dissipate shock pressures in the

downstream passages

30, 29, and 57.

'When the load W is at rest with the spool 25 in the neutral position N, pressure in the system due to the load W will be equalized and the flow control elements, that is, the flow control member 43, the plug member 49, the plunger member 47 and the cylinder member 51 will be in the positions shown in FIG. 2. Now, if the spool 25 is shifted to raise position R, the pressure in the system will have to increase to a value greater than that due to the load W in order to overcome the inertia of the load W and to raise the load. As the pressure supplied by the pump 11 flows into the system through the inlet port 18, check valve 28, pressure feed passage 20, and motor passage 23, the increasing fluid pressure may tend to actuate the cylinder member 51 toward the left against the spring 46 to displace the fluid in the chamber 55 through the equalizing orifice 53 into the chamber 54 and the build-up of pressure in the chamber 54 (due to smaller orifice 52) resists the opposing pressure in chamber 56 so as to avoid pulsating or fluttering movement of the flow control member 43. Here again the chamber 54 (and also chamber 55) acts as a cushioning chamber or dashpot.

In the modification illustrated in FIG. 3, the chamber 58 is vented to the atmosphere by passage 60 instead of being communicated with

passages

29 and 30 by way of passage 57 as in FIG. 2. Accordingly, static fluid pressure in

chambers

56, 54, and 55 will move plunger stem 50 to the right against spring 46 a distance proportional to the magnitude of the pressure, thus correspondingly relaxing the spring 48. When the spool 25 is shifted to lower position L with a heavy load W on piston 10 even a very small pressure drop across passage 59 will move the

members

43 and 49 against relaxed spring 48 to effect substantial restriction of flow by apertures 45. On the other hand if there is a light load W, the spring 46 will not be further compressed at all or only very slightly whereby even a substantial pressure drop across passage 59 will not move the member 43 appreciably against spring 48 to flow restricting position and thus the light load W can descend rapidly. In this FIG. 3 embodiment, the spring 46 is sufficiently strong so as not to require assistance of fluid pressure in chamber 58 as is the case in FIG. 2 wherein fluid pressure has access to chamber 58 through passage 57. Accordingly, when spool 25 is shifted to raise position R, the pressure drop across passage 59 and the force of spring 48 will urge the sleeve 43 toward the left for full flow through apertures 45 even though high pressure due to heavy load W holds the plunger 47 at its rightward actuated position.

Other modes of applying the principle of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A flow control valve'comprising a housing having a passage therethrough, a flow control sleeve means having an aperture through the wall thereof disposed in said housing for movement in one direction from a position whereat said aperture is in direct open alignment with said passage to effect a progressive closing of said aperture as said aperture is moved out of alignment with said passage, means within said housing defining a chamber having restricted fluid communication with fluid pressure upstream of said aperture, a fluid pressure actuated plunger in said housing having its respective ends exposed to fluid pressure downstream of said aperture via a branch passage leading to one end of said plunger and to fluid pressure in said chamber, and spring means biasing said plunger and sleeve means in a direction maintaining said aperture in such direct open alignment with said passage, said chamber constituting a cushioning chamber to resist sudden changes in fluid pressure therein.

2. A flow control valve comprising a housing having a passage therethrough, and a flow control member movable in said housing to vary the rate of flow of fluid through said passage, said flow control member comprising a plunger means having a portion thereof exposed to fluid pressure on the upstream side thereof for actuation thereby, sleeve means axially reciprocable in a bore in said housing and having apertures through the wall thereof, first spring means biasing said plunger means in opposition to such fluid pressure for yieldably maintaining said sleeve means in a position whereat said apertures are in full fluid communication with said passage, said sleeve means also having a portion thereof exposed to fluid pressure on the upstream side thereof for actuation thereby in one direction during actuation of said plunger means by increasing fluid pressure to cause a progressive closing of said apertures for reduced fluid communication between said apertures and passage, and a second spring means between said plunger means and sleeve means for exerting decreasing resistance to movement of said sleeve means in such one direction as said plunger means is thus actuated by increasing fluid pressure.

3. The valve of claim 2 wherein said plunger means has another portion opposite said first mentioned portion vented to the atmosphere.

4. The valve of claim 2 wherein said plunger means has another portion opposite said first mentioned portion exposed to fluid pressure downstream of said apertures via a branch passage leading to one end of said plunger means.

5. The valve assembly of claim 2 further comprising a plug member disposed in said bore between said sleeve means and plunger means, said plug member being maintained in engagement with said sleeve means by said sec- 0nd spring means and defining with said plunger means and the wall of said bore a chamber having restricted fluid communication with the fluid pressure on the upstream side thereof to minimize the effect of shock loads on said plunger means.

6. A flow control valve comprising a housing having a passage therethrough, a flow control sleeve axially slidably received in a bore in said housing and having apertures through the wall thereof, a plunger and plug member disposed in said bore with said plug member located between said sleeve and plunger, said plug member and plunger defining with the wall of said bore a first chamber having restricted fluid communication with fluid pressure upstream of said apertures, spring means engaging said plunger for biasing said plunger and thus said sleeve in a direction maintaining said apertures in substantially full fluid communication with said passage, said plunger also defining with the wall of said bore a second chamber having restricted fluid communication with said first chamber, said plunger having a stem portion projecting into said second chamber, and means for isolating the outer end of said stern portion from the fluid pressure in said second chamber so as to provide a larger area on said plunger exposed to fluid pressure in said first chamber than in said second chamber, whereby there is a progressive movement of said plunger and thus said sleeve in the opposite direction for effecting a progressive reduction in fluid communication between said passage and apertures as the fluid pressure upstream of said apertures is increased.

7. The valve of claim 6 wherein said outer end of said stem portion is exposed to the atmosphere.

8. The valve of claim 6 wherein said outer end of said stem portion is exposed to fluid pressure downstream of said apertures via a branch passage leading to said outer end of said stem portion.

9. The valve of claim 8 wherein said means for isolating the outer end of said stem portion from the fluid pressure in said second chamber comprises a cylinder member disposed in said bore for receipt of said stem portion, and there is a greater fluid restriction between said first chamber and the fluid pressure upstream of said apertures than between said first and second chambers, whereby any increase in the fluid pressure in said second chamber will be resisted by the opposing pressure in said first chamber so as to avoid fluttering of said flow control sleeve.

10. A valve assembly for actuation of a fluid motor comprising a housing having an inlet port for connection with a fluid pressure source, a motor port for connection with a fluid motor, and a return port for connection with a fluid reservoir; a directional control valve member movable in said housing from a neutral position blocking fluid communication between said motor port and said inlet and return ports to operating positions selectively communicating said motor port with said inlet port or said return port; and a flow control valve contained within said housing for varying the rate of flow of fluid from said motor port to said return port when said valve member is in that operating position, said flow control valve comprising a plunger means having a portion thereof exposed to fluid pressure on the motor port side thereof for actuation thereby, a sleeve means axially reciprocable in a bore in said housing and having apertures through the wall thereof, first spring means biasing said plunger means in opposition to such motor port fluid pressure for yieldably maintaining said sleeve means in a position whereat said apertures are in full fluid communication with said motor port, said sleeve means also having a portion thereof exposed to fluid pressure on the motor port side thereof and actuated thereby in one direction during actuation of said plunger means by increasing fluid pressure in said motor port to cause a progressive closing of said apertures for reduced fluid communication between said apertures and motor port, and a second spring means between said plunger means and sleeve means for exerting decreasing resistance to movement of said sleeve means in such one direction by flow of fluid therethrough as said plunger means is thus actuated by increasing fluid pressure.

11. The valve assembly of claim 10 further comprising a plug member disposed in said bore between said sleeve means and plunger means, said plug member being maintained in engagement with said sleeve means by said second spring means and defining with said plunger means and the wall of said bore a chamber having restricted fluid communication with fluid pressure in said 10 motor port to minimize the effect of shock loads on said plunger means.

References Cited by the Examiner UNITED STATES PATENTS M. CARY NELSON, Primary Examiner.

MARTIN P. SCHWADRON, Examiner.

R. J. MILLER, Assistant Examiner.

Claims

1. A FLOW CONTROL VALVE COMPRISING A HOUSING HAVING A PASSAGE THERETHROUGH, A FLOW CONTROL SLEEVE MEANS HAVING AN APERTURE THROUGH THE WALL THEREOF DISPOSED IN SAID HOUSING FOR MOVEMENT IN ONE DIRECTION FROM A POSITION WHEREAT SAID APERTURE IS IN DIRECT OPEN ALIGNMENT WITH SAID PASSAGE TO EFFECT A PROGRESSIVE CLOSING OF SAID APERTURE AS SAID APERTURE IS MOVED OUT OF ALIGNMENT WITH SAID PASSAGE, MEANS WITHIN SAID HOUSING DEFINING A CHAMBER HAVING RESTRICTED FLUID COMMUNICATION WITH FLUID PRESSURE UPSTREAM OF SAID APERTURE, A FLUID PRESSURE ACTUATED PLUNGER IN SAID HOUSING HAVING ITS RESPECTIVE ENDS EXPOSED TO FLUID PRESSURE DOWNSTREAM OF SAID APERTURE VIA A BRANCH PASSAGE LEADING TO ONE END OF SAID PLUNGER SAID FLUID PRESSURE IN SAID CHAMBER, AND SPRING MEANS BIASING SAID PLUNGER AND SLEEVE MEANS IN A DIRECTION MAINTAINING SAID APERTURE IN SUCH DIRECT OPEN ALIGNMENT WITH SAID PASSAGE, SAID CHAMBER CONSTITUTING A CUSHIONING CHAMBER TO RESIST SUDDEN CHANGES IN FLUID PRESSURE THEREIN.