US3406703A

US3406703A - Pulsating hydraulic control

Info

Publication number: US3406703A
Application number: US393866A
Authority: US
Inventors: Richard O Gordon
Original assignee: Clark Equipment Co
Current assignee: Doosan Bobcat North America Inc
Priority date: 1964-09-02
Filing date: 1964-09-02
Publication date: 1968-10-22
Anticipated expiration: 1985-10-22

Description

Oct. 22, 1968 Filed Sept. 2, 1964 FIG. I

R. o. GORDON 3,406,763

PULSAT ING HYDRAULI C CONTROL 2 Sheets-Sheet 1 so If: 76 14 46 I6 47 83 4o 57 54 64 82 I z I L 1 7 x l C W E? (1 I2 CL )5 l2 Q9 v 38 INVENTOR RICHARD O. GORDON R. o. GORDON 3,406,703

PULSAT ING HYDRAULI C CONTROL Oct. 22, 1968 FIG. 2

INVENTOR RICHARD O. GORDON United States Patent 3,406,703 PULSATING HYDRAULIC CONTROL Richard 0. Gordon, New Buffalo, Mich., assignor to Ciarir Equipment Company, a corporation of Michigan Filed Sept. 2, 1964, Ser. No. 393,866 8 Claims. (Cl. 137-99) The present invention relates to valves variably controlling hydraulic circuits.

Fixed volume pumps, because of their simplicity of construction and operation, are appreciably cheaper than the more complicated variable volume pumps, and of course also have the advantages of simplicity over complexity. These pumps, however, lack the flexibility or adaptability of variable displacement pumps, and thus in many applications must be replaced by the more expensive variable volume pumps. Fixed volume pumps also are not adapted to supply fluid to a hydraulic circuit at different volumes or pressures without varying the speed or pressure of the pump. Both fixed and variable volume pumps, moreover, are not adapted to provide fluid at different pressures and in diflerent volumes to a plurality of separate fluid circuits, unless dual, triple, or multiple pumps are employed, which again are expensive and complicated. The present invention provides means by which adjustable variable control of the output of a pump may be supplied simultaneously to a number of circuits in respectively diiferent volumes and pressures, and by which the output of a fixed volume pump maybe adjusted to a desired rate and volume without changing the operating speed of the pump or the pressure of the fluid supplied thereby, so that the pump is in etlect made the equivalent of a variable volume pump. Essentially, the invention employs a pulsating or reciprocating valve to control the proportion of fluid from a fixed volume pump employed to operate or energize a fluid circuit, or to control the proportions of the output of a pump supplied to a plurality of fluid circuits, so that diflerent volumes and pressure may be employed at will in a circuit or circuits.

The valve of this invention provides for division of flow from a fixed volume pump into two or more circuits energizing all of the circuits simultaneously, yet at diflerent volumes or rates and pressures. Such a result is not possible with any type of flow divider or flow priority valve known at the present time.

The present valve also provides for the application of the maximum pump pressure to any of a number of circuits which may require it, while at the same time energizing other circuits at the same or lower pressures.

The valve of this invention allowsthe use of a fixed volume pump for hydrostatic drive without loss of chiciency, since it provides for operating of a fixed volume pump at the most eflicient speed or rpm. The starting torque and break-away torque of hydraulic motors and the like is reduced, and a higher usable torque is made possible, by the use of the present valve arrangement, because of elimination of break-away friction which now presents a problem in hydrostatic drives.

By reason of the pulsation or vibration of the hydraulic fluid in systems employing the present invention, hysteresis or lag in the functioning of the hydraulic elements or components is avoided, so that there is no sticking, relatively movable parts being kept free and readily movable by reason of the pulsations, even though the parts may remain in a set position for long periods.

It is an object of the invention to provide a fluid con trol structure for fixed volume pumps to allow such pumps to operate, in eflect, as variable volume pumps.

Another object is the provision of hydraulic control structure which allows a pump to energize a plurality of fluid circuits at diflerent volumes and at different pressures without variation in the pump operating speed or pressure.

It is also an objectof the invention to provide hydraulic control means by which a fixed volume pump may operate at different volumes and different pressures without change in its speed or volume.

Another object is the provision of a pulsating or reciprocating valve which operates to vary the proportion of the output of a fixed volume pump supplied to a given fluid circuit.

-A further object is the provision of a pulsating valve for variably controlling the division among a plurality of fluid circuits of the flow from a pump in desired proportion and at desired pressures.

It is another object to provide'a pulsating valve for simultaneously energizing a plurality of fluid circuits from a pump at pressures independently controllable from the maximum pump pressure to substantially zero.' 1

Still another object is the provision of hydraulic control means for achieving the foregoing objects including a pulsating valve construction which controls the rate, volume and direction of the output of a pump.

Other and further objects, advantages, and features of the invention will be apparent to those skilled in the art from the following detailed description, taken in conjunc tion with the accompanying drawings, in which:

FIGURE 1 is a diagrammatic illustration of one embodiment of my invention;

FIGURE 2 is an enlarged longitudinal sectional view of the valve shown in FIG. 1;

FIGURE 3 is a diagrammatic illustration of an alternative embodiment of the invention; and

FIGURE 4 is an elevational view of a portion of the structure shown in FIG. 3, looking at the face of the disc employed therein.

Referring first to FIG. 1, there is shown a hydraulic system comprising a fixed volume pump indicated at 10 arranged to pump hydraulic fluid through a conduit 11 from a sump 12 and through the line 13 to the inlet 14 of the pulsating hydraulic control valve indicated generally as 15, which has an outlet 16 connected by return line 17 to the sump 12, under the control of a valve 18. .In addition to the inlet 14 and outlet 16, the valve 15 is provided with

ports

19 and 20, to each of which there is connected a fluid circuit including hydraulically operated means of any desired type.

In the present instance, the port 19 is shown as connected by a conduit 21, from which a relief valve 22 branches, through check valve 23 and manual throttling or control valve 24 to a hydraulic motor 25, through which the pressure fluid may return to sump 12, as through line 26. The motor 25 is employed todrive, as by means of a shaft 27 or any other suitable connecting means, any appropriate device or apparatus generally indicated at 28. The port 20 is shown as connected by a conduit 30, in which is disposed a check valve 31 preventing back flow through the port 20, to a steering control valve 32 of a suitable type, which may be generally similar to the control valve 15. A relief valve 33 is connected to the line 30 between check valve 31 and valve 32. The steering control valve 32 is actuated by a manually operable steering member 34 to connect line 30 with any of

conduits

35, 36 or 37. The line 37 leads to the sump 12, and in addition to being connectible to the line 30 in neutral or idle position of the valve 32, is connected with the

line

36 or 35, respectively, when the line 30 is connected to the

line

35 or 36, respectively. The

conduits

35 and 36 are connected to opposite ends of a power steering cylinder 38, suitably connected to a vehicle steering apparatus through the rod 39 of the cylinder piston.

Referring now to FIG. 2, the valve 15 is shown as comprising a valve spool 40 axially slidable in a valve chamber 41 defined within a casing 42. Thechamber 41 has three longitudinally spaced annular grooves or recesses 4 ,544 and 45 formed in the surface thereof, the recess.

43 being shown at the left in FIG. 2, and recess 44 being located between the other two. The inlet port 14 communicates with the recess 43, and the outlet port 16 with the annular groove or recess 44. The inlet port 14 also communicates with the recess 45 through

passages

46 and 47. Port 19 communicates with the chamber 41 be-- tween the

annular grooves

44 and 45, and port 20 communicates with the chamber between the

annular grooves

43 and 44. Three longitudinally. spaced

lands

48, 49 and 50 are formed on the valve spool 40, located toleave the

recesses

43, 44 and 45, respective ly, open to the valve chamber 41 in the neutral position of the spool, as shown in FIG. 2. The central land 49 is narrower than the adjacent reces s 44,

while each ,of t he lands 48 and 50 has a width or axialex'tent somewhat greater than the width of the adjacent

annular recess

43 or 45. Each land 48. and 50 may have a portion cut away as at 51 to provide a restrictedon'fice with thesurface of the ,valve chamber 41 in movement of the valve spool in one direction or the other, to damp the movement of the spool, as disclosed in my copending application for patent filed Oct. 4, 1963, Ser. No. 315,118 for Hydraulic Valve, now United States Patent 3,176,-

721, issued Apr. 6, 1965.

The end 52 of the spool 40, the left as viewed in FIG. 2, is of reduced diameter to have a sliding piston-like fit in correspondingly reduced end portion 53 of the valve chamber 41. An aperture 54 extending through the end wall of the valve casing 42 places the chamber 53 in communication with the exterior of the valve. The opposite end 55 of the spool is similarly reduced and extends axially outwardly of the land 50, the end portions preferably having the same diameter.

A rod-like projection 56 extends axially from the end 55 into a chamber 57 defined between the adjacent end wall of the valve chamber 41 and an innercentrally apertured disc or annulus 58, through which disc the reduced portion 55 may project. The axially outer portion of the chamber 57 is of reduced diameter to define a shoulder 60. Disposed on the projection 56 in encircling relation is'a helical centering spring 61, compressed between, and at its opposite ends bearing against, a pair of washers 62 slidably engaged on projection 56. The spring urges one washer inwardly against the disc 58, and the other outwardly against the shoulder 60. The washers 62 are formed with any suitable apertures 63 allowing free passage to fluid. A spacing sleeve 64 is disposed on the projection 56-between the washers to limit their approach to each other, and thus the stroke of valve spool 40. An aperture 65 through the adjacent end wall of the casing 42 provides communication with the interior of the chamber 57. The reduced

portions

52 and 55 are suitably sealed, each as by an O-ring66 disposed thereabout and engaging the cylindrical wall of the valve chamber 41. The coil spring 61 biases the valve spool 40 to the neutral posi tion shown in FIG. 2, when the hydraulic system is in an idling or inoperative condition.

The axially outer washer 62 is held against movement off the spool end projection 56 by any suitable means, shown in this case as a washer 67 serving as an abutment for the outer washer 62, disposed on a reduced extension or stem of the projection 56. The abutment washer 67 is secured in any desired manner, as for example by a cotter pin or the like, or by the' nut 68 as shown.

In this neutral position of the valve'15 as illustrated in FIG. 2; the flow of oil develops no significant pressure. The entire system remains'at rest. Fluid supplied by the pump from sump 12 is conducted by the line 13 to the inlet port 14, from which it flows into the valve chamber 41 through the annular recess 43, as well as through the

passages

46 and 47 and annular recess 45. Since in the neutral position the

lands

48 and 50 do not close off the

recesses

43 and 45, the fluid flows from the recesses about the lands and spool to the annular recess 44, and

' returns to the sump 12 through the port 16 and return conduit 17. The

ports

19 and 20 are in communication with both the inlet and outlet ports, as will be evident. Upon movement of the valve spool to the right as viewed in the figure, the spring 61 is compressed and the

lands

48 and 49 close off the port 20 from the inlet port 14, while leav; 'ing it in continued communication with the port 16. The port 19 is maintained in communication with the inlet port 14 by means of the passages46 and 47..It will be evident that under these conditions, fluid pumped through the conduit 13 flows through the port 19 into the conduit 21 for supply to any desired hydraulic apparatus .or mechanism,.from which it'may be returned to the sump 12. If the

ports

19 and 20 are in communication, or are connected througha fluid mechanism, fluidmay be returned through the port 20. Upon release of the force causing shifting of the valve spool 40 to the right, the spool is returnedtothe neutral position by the action of the spring 61. The relief valve 22, of course, prevents development of excessive pressure in the circuit.

If the spool 40 is shifted to the left from theneutral position, the lands 49 and .50-cut off communication between the port 19 and the inlet port 14, but the port 19 remains in communication with the outlet port 16. The port 20 is in communication about the spool 40 and through the annular recess 43 with the inlet port 14, so that fluid supplied under pressure by the pump 10 flows to any desired fluid circuit through the line 30, from which it may return to the sump. Fluid may also be returned through the conduit 30 and port 20 to the outlet port 16, in appropriate circumstances. The relief valve 33 provides for return of fluid to the sump in the event of occurrence of pressure above a predetermined valve in the circuit.

FIG. 1 illustrates hydraulic'circuits which may be connected to the pressure side of pump 10 through the

ports

19 and 20. It will be apparent that if the power steering cylinder 38 were connected by the

lines

35 and 36 to the

ports

19 and 20, the valve 15 might be employed to control extension or retraction of the cylinder and piston, fluid flowing to one end of the cylinder 38 through the inlet port 14 and one of the

ports

19 and 20, and flowing from the other end of the cylinder to the sump 12 through the other of the

ports

19 and 20, and the outlet port 16.

The valve 15 is operated to cause pulsations or reciprocation of the valve spool at a desired frequency between a range of from almost zero to almost 80 per second, and by reason of such pulsation fluid from the pump 10 may be supplied to one or more circuits at any desired rate and volume within the capacity of the pump. One simple means for effecting the desired pulsation is a hydraulic circuit connecting the outlet port 16 selectively with either end of the valve 15.

T his pulsation circuit comprises a conduit 70 connected to the return line 17 between the outlet port 16 and the control valve 18 and extending to the aperture 54 in the left-hand end of the valve casing 42 to communicate with the chamber 53. In the line 70 are connected a shutoff valve 71 and a diversion valve 72. The valve 72 is opera ble to block the line 70 and divert fluid therefrom to a conduit 73 returning the fluid to the sump 12. In the portion of the line 70 between the chamber 53 and the valve 72, there is connected a time-delay arrangement comprising a check valve 74 which allows free flow of fluid into the chamber 53, but blocks any return flow therefrom, and a line75 bypassing the check valve 74 to allow flow out of the chambers 53, under the control of a manually operable valve 76 disposed in the line 75. The valve 76 3 may be opened in varying degrees to govern the rate of flow of fluid therethrough.

The pulsation-effecting circuit also includes a line 77 connected to the line 17 between the outlet port 16 and the return control valve 18, the line 77 connecting with the aperture 64 in the right-hand end of the casing to communicate with the chamber 57. The line 77 is a substantial duplicate of the line 7 0, and has interposed therein

valves

78 and 79 corresponding respectively to the

valves

71 and 72. A line 80 leading to the sump 12 may be connected to the line 77 by means of the valve 79. Between valve 79 and the chamber 57, the same time-delay arrangement is provided as that employed adjacent the chamber 53, and comprising the check valve 81, bypass line 82, and control valve 83, corresponding respectively to the check valve 74, bypass line 75, and valve 76 already described.

In operation, assuming first that the line 77 is shut off from the return line 17 by means of valve 78, and that the valve 83 is open and the valve 79 connects line 77 to line 80 and thus opens the chamber 57 to exhaust, the valve 18 is closed sufficiently so that the flow from pump through the valve in its neutral position causes a buildup or increase in pressure in the outlet side of the valve, that is, in the line 17 between the valve and the control valve 18. The valve 71 is open, and the valve 72 is also open between the sections of the line 7 0, closing the sump line 73. The valve 76 is fully open. The pressure in line 17 therefore is transmitted to the chamber 53, and acts upon the end face of the end portion 52 of the valve spool 40. When the pressure is suflicient to overcome the force of spring 61, the valve spool is shifted to the right, the inner washer 62 being engaged by the shoulder formed between the valve spool portion 55 and projection 56 to move with the spool and compress the spring against the outer washer 62, which is engaged against the shoulder 60. The port 19 thus is connected with the inlet port 14 and cut off from communication with the outlet port 16, as previously described, so that fluid under pressure flows through the line 21 under control of the valve 24 to the fluid motor 25, returning to sump 12 through the conduit 26, as previously explained, for recirculation by the pump 10. The motor 25 drives any desired apparatus 28, as has been described. As soon as the valve spool 40 shuts off communication between the port 19 and the outlet port 16, it also cuts off communication between the inlet port 14 and the outlet port, with the result that the pressure in the

lines

17 and 70 drops, whereupon the spring 61 moves the inner washer 62 to the left and thus returns the spool 40 to its neutral position, with the outlet port 16 in communication with the inlet port 14. This relieves the pressure in line 21 so that the motor 25 now coasts, the low back pressure in the return line 17 as the valve returns to its neutral or open-center position to begin building up of the pressure in the return line of course being present also in conduit 21. The pressure then builds up in the

lines

17 and 70 to again shift the valve spool to the right, and thus cause the motor 25 to be driven by the pressure fluid from the pump 10. It requires only a very short time for the valve spool to be moved to the right and then back to the center, the frequency of the pulsation or reciprocation varying with the adjustment of the valve 18.

If the valve 18 is completely closed, the valve 15 allows flow of fluid directly from the pump 10 into the circuit connected to the valve by the port 19, without interruption, since the pressure acting on the end portion 52 of the spool is not relieved to allow the spring 61 to return the spool to its neutral position. The motor 25 then operates at its maximum speed. The pressure of the fluid in the hydraulic motor circuit is determined by the load applied to the motor, or in other words the resistance to the fluid flowing from the pump, as is of course the usual case. If the valve 18 is opened slightly, just enough to allow pulsation of the valve spool 40, the frequency of reciprocation of the spool is substantially at its maximum, as for example between 70 and 80 cycles per second, since with the valve almost closed the pressure in return line 17 and its branch line 70 builds up rapidly. Progressively greater opening of the valve 18 produces progressively lower frequency of the valve spool cycles, until with the valve almost fully opened the spool has a very low frequency, say some three or four cycles per second, due to the longer time required for the pressure to build up to the point at which it will overcome the spring 61.

The frequency of 70 to cycles per second which is entirely feasible with the valve 15 is faster than the common and in fact almost universal 60 cycles per second frequency of alternating electric current. Pulsations of such high frequency provide substantially the same practical effect as uninterrupted or unpulsed flow, and this is true both of alternating current and of hydraulic fluid flow. Yet the pulsating hydraulic flow allows the use of a portion of the fluid under pressure for a circuit or circuits in addition to the first circuit energized by the fluid, or to provide for adjusting or controlling a characteristic or characteristics of such first circuit. Pulsations at 60 cycles per second in hydraulic circuits coincide exactly with the 60 cycle per second frequency normally used in alternating electric current. The frequency of hydraulic pulsation may be increased considerably above 80 per second, if desired, by the use of a suitable valve similar to the valve 15 disclosed.

For half of each cycle, regardless of the frequency, the pulsing valve connects the inlet line 13 to the conduit 21,- to drive the motor 25, and for the other half cycle it connects the inlet and return

lines

13 and 17, as well as the

lines

13 and 21. In this half cycle, the pressure in line 21 is equal to the low back pressure in

lines

17 and 70 resulting from the partial closing of valve 18. Assuming that the load on the motor 25 requires a pump pressure of 2,000 psi. and that the pressure resulting from the setting of valve 18 is 50 psi, the pump pressure for half of the time of operation of the valve 15 is the high motondriving pressure 0 2,000 psi, and for the other half is the low return line pressure of S0 p.s.i. The speed of the motor 25 may readily be increased, without in creasing the speed of the pump 10, by increasing the frequency of cycling of the valve 15, the speed of the motor being variable from say 2 or 3 r.p.m. with the rotation being barely or perhaps not even detectable by the unaided eye, when the valve frequency is at its minimum; to say 3,000 r.p.m. when the valve frequency is at its maximum. It will be evident that by employing the valve 16 to control the supply of fluid from the pump 10 to a single fluid circuit in the manner which has been explained, the pump is in effect converted into a variable volume pump, a desired proportion of the pump fluid being diverted from the circuit to the sump or return, in this case half the fluid. At the same time, the speed of the motor, which depends upon the rate of flow of fluid through the conduit 21 or in other words the gallons per minute supplied to the circuit, may be varied by increas ing or decreasing the frequency of the valve spool cycle. The invention as so far described thus permits a fixed volume pump to operate as a variable displacement pump to supply fluid at different rates and pressures to selected hydraulic apparatus.

By connecting the outlet of the pump 10 to the port 16 as the valve inlet, and employing the port 14 as the outlet port, fluid from the pump can be directed to the port 20 and its connected fluid circuit, and the port 19 will be an idle port instead of the port 20. This is un necessary, however, since if only one circuit is to be controlled by the valve 15, only one port need be employed for passage of pressure fluid to the circuit. Also, port 20 may be employed for flow of fluid to a fluid circuit, and port 19 be made the idle port, by causing the spool to shift between its neutral and right-hand positions, as more fully explained herebelow. Furthermoreflf a plurality of alternate circuits are to be operated selectively through the valve 15, this may be done by providing conventional valve means for selectively connecting the port 19 to the several circuits.

By means of the time-delay arrangement, the proportions of fluid supplied to the outlet port and to the port 19 may be varied from the equal or half-and-half division, without changing the speed of the pump, by closing the valve 76 to a desired extent. Fluid then flows from the return line 17 through the line 70 to shift the valve spool 40 and connect the port 19 with the inlet port 14, but when the consequent drop in pressure in line 17 occurs, the spool is not immediately returned to the neutral position because flow of fluid from the chamber 53 is restrained and slowed by reason of the restriction imposed by valve 76. The fluid in the chamber thus maintains a pressure, for a period of time corresponding to the restriction or throttling of the bypass line 75, suflicient to hold the spool in its shifted position against the force of the spring 61. Fluid flows to the port 19 and its circuit for a portion of the valve pulse cycle greater than that during which it flows to the outlet port 14. The duration of each valve cycle is increased for any given setting of the valve 18, since while the time required for the pressure in

lines

17 and 70 to rise to the point necessary to shift the valve spool from its neutral position remains the same, a longer time is required for return of the spool to its neutral position by reason of the time-delay adjustment.

The flow proportioning or dividing adjustment made possible by the time-delay arrangement may be added to or imposed upon the cycle frequency adjustment to provide for additional adjustment and control of fluid devices in the circuit connected to the port 19, for example in varying the speed of the motor 25. No change is required in the speed of the pump 10 or in the volume of fluid supplied by it, which is utilized to a greater or lesser extent, as determined by adjustment of the valve as explained, so that it operates as a variable-volume pump. The proportion of fluid passing from the pump 10 to the fluid circuit through the port 19 may be varied from the half when the time-delay arrangement is not utilized, to almost the entire flow when the valve 76 is almost completely closed. If adjustment of the flow through port 19 to less than half the volume is desired, this may be accomplished by reversing the check valve 74 to allow free flow out of the chamber 53, while restricting entry of the fluid into the chamber by means of the valve 76, so as to delay the development of pressure on the left-hand face of the spool 40 suflicient to shift the spool to the right against the force of spring 61. Thus the fluid supplied to the port 19 may be reduced almost to zero.

The valve spool 40 may be shifted or reciprocated between its neutral position and an extreme left-hand position in the same manner as described for its shifting to the right from the neutral position, by means of the circuit provided by the line 77 and its associated valve arrangement. For this purpose, the valve 71 in line 70 is closed, with the chamber 53 open to exhaust through valves76 and 72, and the

valves

78 and 79 in line 77 operated to allow the line to conduct fluid from line 17 into chamber 57 through the time-delay

device comprising valves

81 and 83 and bypass line 82. Pressure is built up in the portion of line 17 between outlet 16 and valve 18 by operation of the valve 18, causing the valve spool 40 to be shifted to the left and thus connecting port to inlet port 14 while cutting it off from outlet port 16, and shutting ofI" port 19 from port 14 while leaving it in communication with outlet 16. The circuit connected to port 20 is thus energized, pressure acting through line 30 to operate the steering control cylinder 38 under the control of the valve 34, as already explained. Pressure in line 17 then drops, allowing the spring 61 to return the spool to its open or neutral position, whereupon the port 20 and line 30 are placed in communication with the outlet port 16 to relieve the pressure in the fluid circuit momentarily. The pressure in line 17 then again increases and so on, as described in connection with the fluid circuit to the left-hand end of the valve spool, to effect repeated reciprocation of the spool 40. The operation of the valve 15 is adjusted in this case in the same manner 8 as when the spool pulses between the neutral and righthand positions, by means of the valve 18 and the timedelay arrangement. The operation of the latter is the same as that of the time-delay at the left-hand end of the valve, the

parts

81, 82, and 83, as already explained, corresponding to the check valve 74, bypass line 75, and throttle valve 76.

The flow of fluid from the pump 10 may be divided substantially equally or in any desired proportion between the two

circuit ports

19 and 20, except for the slight interval of connection between the inlet and outlet ports just suflicient to provide for the shifting of the valve spool between its extreme positions on opposite sides of the neutral position.

In FIG. 3, there is illustrated a hydraulic circuit employing a pulsating valve according to the present invention, in which a mechanical device is provided for regulating the frequency of cycling of the valve, and also ,to adjust the valve for dividing in any desiredproportion the flow of pressure fluid between a pluralityof fluid circuits connected thereto. In this form of the invention, a pulsating control valve is provided which is substantially similar to the valve 15 previously described, with the valve spool 40 longitudinally reciprocable in the valve chamber 41 defined by the valve casing 42, which in this embodiment, however, is completely closed at the left end thereof, and at the right end is closed except for a bore 86 through which projects a stem 87 which is secured at its inner end to the right-hand end 55 of the spool 40, and is pivotally connected at its outer end, as at 88, to a lever 89 which has a free end pivoted to one end of a valve control rod 90 and the other end pivoted to a mounting link 91 pivoted on the casing42 of the valve 85. The valve casing is formed with the interior

annular recesses

43, 44 and 45, with which, in the open-center valve position, communicate respectively the inlet port 14, outlet port 16, and passage 47 which is connected to the inlet port 14 by the passage 46. ,The

ports

19 and 20 are provided substantially as in the case of the valve 15, and the valve spool 40 has the

lands

48, 49 and 50 provided thereon substantially as previously described. The

chambers

53 and 57 serve merely to provide the space required for movement of the spool and for accommodation of the spring 61. The seals 66 are provided as previously described. A vent 92 may be provided for the chamber 53, the chamber 57 venting through the bore 86.

A disc 93 is mounted in spaced relation to the lever 89 for rotation as -by means of a shaft 94, and an abutment member or striker 95 is mounted on the disc 93 for adjustment radially thereof. The striker 95 is shown as circular in this instance, and is rotatably carried by a rectangular T-section base 96 which is slidable in an undercut groove or slot 97 formed in the face of the disc 93 and extending diametrically thereof, as shown in FIGS. 3 and 4. A stud portion 98 projects perpendicularly from the base 96 out of the slot, and has the striker 95 swiveled on its outer end. A nut member 99 works on a threaded intermediate portion of the stud so that it may be tightened against the face of the disc so as to clamp the base in any desired radially adjusted position on the disc, thus locating the striker 95 at any desired position radially or diametrically of the disc 93. A cliametrical passage through the strike 95 slidably receives the control rod 90 in projecting relation therethrough. An abutment element 100 is slidably disposed on the rod 90 between the pivoted end thereofand the striker 95, and a similar abutment element -101.is disposed between the free end of the rod and the abutment member. Each of the

abutment elements

100 and 101 may be secured at any selected point on the rod 90 by any suitable means, such as the set screw 102 which may be-mauually tightened and released. The disc 93 may be rotated by any desired appropriate means, such as a variable speed, reversible electric motor 103 connected to 9 the disc through a speed reducer 104, the output shaft of which may be the disc shaft 94.

When the striker 95 is adjusted to an eccentric position on the disc 93, it provides an eccentric or crank with a throw or stroke determined by its distance from the center of the disc. In such eccentric position, striker 95 will upon rotation of the disc 93 cause oscillation of the control rod 90 about its pivotal connection to lever 89, with relative sliding movement of the rod and abutment member, but with no appreciable longitudinal movement of the rod, if the

abutment elements

100 and 101 are not located for engagement by the striker 95. By adjusting the

abutment elements

100 and 101 on the rod 90 to positions such as to be engaged by the striker 95 during opposed portions of its circular movement about the center of the disc 93, movement of the control rod 90 is effected to cause shifting of the valve spool 40 in one direction or the other, by means of the lever 89 and valve stem 87. It will be evident that if the disc 93 is rotated in a clockwise direction, the striker 95, if starting from the position shown in FIG. 4, will first engage the abutment element 101 and shift the rod 90 to the right, causing the lever 89 to swing clockwise and move the spool 40 to the right from its neutral position. As the rotation of the disc continues, the striker 95 engages the other abutment element 100, and shifts the rod 90 longitudinally to the left as viewed in the figure, swinging the lever 89 to cause the stem 87 to shift the valve spool to the left. The spool is thus shifted between two extreme positions, such as that in which fluid is directed from the inlet port 14 to the port 19, and that in which fluid will flow from the inlet port to the port 20, the spool passing through the centered or neutral position in moving between the two extremes. Thus a plurality of fluid circuits may be energized and operated simultaneously, at different speeds or rates and pressures if desired. The frequency or pulsation of the valve spool of course is determined by the rotational speed of the disc, which may be varied through a wide range from almost zero to a very high speed, so that the valve cycle frequency may vary at least through the range provided by the hydraulic pulsation-effecting arrangement previously described, that is, from a very few per second to 70 or 80 per second. The distance through which the valve spool 40 travels can be adjusted by varying the position of the striker 95 along the slot 97, and the dwell of the valve spool at either end of its movement is determined by the position of the

abutment elements

100 and 101, together with the speed of the disc rotation and the stroke of the abutment member or striker 95. The abutment elements may be set in such relation to each other and to the striker 95 as to provide for flow from the inlet port to only one of the

ports

19 or 20, with the valve spool moving only between its neutral position and the position opening one of the

ports

19 and 20 to the inlet port while cutting off the other therefrom. From what has already been said, it will be obvious that the proportion of the pressure fluid from pump directed to any of the

ports

16, 19, or from the inlet port 14, or the division of the flow of fluid as between any two or more of the parts, may readily be controlled and adjusted. The arrangement illustrated in FIGS. 3 and 4 shows one mechanical apparatus which may be employed to control the pulsations of the valve, but of course other arrangements might be employed. Particularly, the several adjustable elements of the apparatus as disclosed may be formed and arranged so that they may be shifted and adjusted as desired without interrupting the operation of the valve or the rotation of the disc 93. This may be readily accomplished by the provision of suitable conduits and passages for application of fluid pressure to the adjustable parts for shifting the same to desired positions, under the control of suitable valve means.

In FIG. 3, the valve 85 is illustrated as employed to control one of the tilt cylinders 105 for the mast M of a fork lift truck T. This is readily accomplished, in much the same manner as disclosed in connection with the power steering cylinder 38 of FIG. 1, by connecting line 21 to one end of cylinder 105, and line to the opposite end of the cylinder. With the valve in the neutral position, as by having the striker 95 centered on the axis of shaft 94, or by interruption of the rotation of disc 93, no pressure fluid will be supplied to either end of the cylinder 105. Upon operation of the valve 85 to connect the line 30 with the inlet line 13, fluid will flow to the forward or rod end of the cylinder, and cause retraction of the piston rod to effect rearward pivoting of the mast M to an upright or to a rearwardly tilted position. It will be noted that in this operation of the cylinder, fluid is exhausted from the head end of the cylinder to the line 21 to flow through the return line 17 to the sump 12. If the valve is operated to connect the inlet port with the port 19, fluid flows through the line 21 to the head end of the cylinder 105, causing projection of the piston rod thereof, so as to swing the mast M forwardly, fluid being exhausted from the rod end of the cylinder through the line 30 and returned to the sump through line 17. It is to be understood, of course, that in referring to operation of the valve for directing fluid to the line 21 or the line 30, the pulsing operation of the valve is meant, and the advantages pointed out hereinabove as resulting from such pulsation of the valve are obtained in this instance as in the cases heretofore described. Any suitable valve arrangement may be employed to control the flow through each

line

21 and 30 so as to provide the necessary operational control of the cylinder 105. If desired, the

conduits

21 and 30 may be provided with relief valves to guard against development of excessive pressures.

It will be apparent that the invention provides a novel apparatus for and manner of dividing fluid under pressure from a fixed volume pump into a plurality of hydraulic circuits for simultaneous energization at selective volumes and pressures, or delivering to a single fluid circuit a desired proportion of the flow to energize the circuit as desired. Great flexibility and versatility are thus provided for fixed volume pumps, so that they may be employed in many applications heretofore requiring variable pumps. The invention is not limited to use with fixed volume pumps, however, as will be obvious, since it allows variable volume pumps to energize a plurality of hydraulic circuits. The pulsation frequency may be considerably higher than the to cycles per second employed with the valve 15 disclosed, although the disclosed frequency is practical and provides efficient operation. The effect of the pulsing flow is substantially the same as that of a continuous and uninterrupted flow or stream, even at frequencies considerably lower than 70 to 80 per second.

It is not necessary, at least not in all cases, that the frequency of the valve pulsation cycles be adjustable, and the same is true as to the proportioning of the dwell of the spool at the opposite ends of its movement in each cycle. In any instance in which substantially constant conditions of volume, rate, speed or similar factors of operation obtain over a long period in a fluid circuit controlled by the pulsating valve, the valve may be constructed with such characteristics as frequency and dwell fixed, and with no provision for adjustment, resulting in a simpler and more economical yet quite satisfactory construction.

While a valve employing a shuttling spool as the reciprocating member is disclosed herein, other types of valves with oscillating or reciprocating elements capable of the desired frequencies may be employed, since the invention contemplates the use of other types of valves besides spool valves.

It will be understood that the disclosure of the invention herein is exemplary of the inventive concept, and that modifications and variations in embodiments thereof may be made without departing from the concept. Some of'the possible changes and variations of the disclosed invention have been pointed out hereinabove, and others will readily suggest themselves to those skilled in the art. Since the invention may readily be adapted for use under various conditions without deviation from the principles thereof, it is not intended that it be limited to the specific details thereof set forth herein, or otherwise than required by the spirit and scope of the appended claims.

I claim:

1. A hydraulic system comprising a fixed volume pump; a fluid circuit energizable by said pump and imposing a variable load thereon; a pulsing valve for controlling flow from the pump to said circuit, said valve having a casing defining a valve chamber, an inlet port and an outlet port each opening into said chamber, a circuit port opening from the chamber to said fluid circuit, a valve spool reciprocable in said chamber between a neutral position placing the inlet and outlet ports in communication with each other and a shifted position placing the circuit port in communication with the inlet port while shutting ofi the outlet port from the inlet and circuit ports; means biasing the spool to said neutral position; and means for effecting reciprocation of the valve spool comprising a valve for throttling flow out of the outlet port, and a conduit connecting one end of the valve chamber to a point between said throttling valve and the outlet port, whereby selected restriction of flow from the outlet port by said throttling valve develops pressure acting through said conduit on the valve spool in opposition to said biasing means.

2. A hydraulic system substantially as defined in claim 1, wherein said reciprocation-effecting means include a time-delay structure for adjustably varying the proportions of a pulse cycle during which said spool remains in its neutral and shifted positions, said structure comprising check valve means in said connecting conduit preventing flow out of said one chamber end, a line by- Y passing said check valve means, and a valve in said by-pass line for adjustably restricting flow therethrough.

3. A hydraulic system comprising a fixed volume pump; a fluid circuit energizable by said pump and imposing a variable load thereon; a pulsing valve for controlling fiow from the pump to said circuit, said valve having a casing defining a valve chamber, an inlet port and an outlet port each opening into said chamber, a circuit port opening from the chamber to said fluid circuit, a valve spool reciprocable in said chamber between a neutral position placing the inlet and outlet ports in communication with each other and a shifted position placing the circuit port in communication with the inlet port while shutting ofi the outlet port from the inlet and circuit ports; and means for effecting reciprocation comprising a longitudinally reciprocable rod, means connecting the valve element to said rod for reciprocation thereby, rotatable eccentric means having connection means slidably engaged on the rod and including striker means, abutment elements on the rod alternately impinged by said striker means upon rotation of the eccentric means for effecting alternate movement of the rod in opposite longitudinal directions, and means for rotating the eccentric means.

4. A hydraulic system substantially as defined in claim 3, including means for adjusting the abutment elements along the rod.

5. A hydraulic system substantially as defined in claim 3, including means for varying the eccentricity of said eccentric means.

6. A hydraulic system substantially as defined in claim 3, including means for adjusting the speed of rotation of the eccentric means.

7. A hydraulic system comprising a pump; a fluid circuit energizable by said pump; a valve for controlling flow from the pump to said circuit, said valve having a casing defining a valve chamber, an inlet port and an outlet port each opening into said chamber, a circuit port connecting the chamber to the fluid circuit, a valve element reciprocable in said chamber between a neutral position placing the inlet and outlet ports in communication with each other and a shifted position placing the circuit port in communication with the inlet port while shutting off the outlet port from the inlet and circuit ports; means biasing said element to said neutral position; and means for efiecting reciprocation of the valve element comprising means for developing back pressure at the outlet port, and means connecting one end of the Valve chamber to the outlet port for application of said back pressure on the valve element in opposition to said biasing means.

8. A hydraulic system substantially as defined in claim 7, wherein said reciprocation-efifecting means include a time-delay structure for adjustably varying the proportions of a pulse cycle during which said element remains in its neutral and shifted positions, said structure comprising means in said connecting means preventing return flow out of said one chamber end, a line by-passing said return-preventing means, and means in said by-pass line for restricting flow therethrough.

References Cited UNITED sTATEs PATENTS 2,679,235 5/1954 Van Meter 251 5o x 2,681,116 6/1954 Treseder 91-429 x 3,191,505 6/1965 Defibaugh 6: al. 91 407 724,566 4/1903 Gooley 7440 2,782,647 2/1957 Wildhaber 74-600 2,919,681 1/1960 Schultz 251-50 2,966,890 1/1961 Panissidi 91 429 FOREIGN PATENTS 782,367 9/1957 Great Britain.

WILLIAM F. ODEA, Primary Examiner.

D. ZOBKIW, Assistant Examiner.

Claims

1. A HYDRAULIC SYSTEM COMPRISING A FIXED VOLUME PUMP; A FLUID CIRCUIT ENERGIZABLE BY SAID PUMP AND IMPOSING A VARIABLE LOAD THEREON; A PULSING VALVE FOR CONTROLLING FLOW FROM THE PUMP TO SAID CIRCUIT, SAID VALVE HAVING A CASING DEFINING A VALVE CHAMBER, AN INLET PORT AND AN OUTLET PORT EACH OPENING INTO SAID CHAMBER, A CIRCUIT PORT OPENING FROM THE CHAMBER TO SAID FLUID CIRCUIT, A VALVE SPOOL RECIPROCABLE IN SAID CHAMBER BETWEEN A NEUTRAL POSITION PLACING THE INLET AND OUTLET PORTS IN COMMUNICATION WITH EACH OTHER AND A SHIFTED POSITION PLACING THE CIRCUIT PORT IN COMMUNICATION WITH THE INLET PORT WHILE SHUTTING OFF THE OUTLET PORT FROM THE INLET AND CIRCUIT PORTS; MEANS BIASING THE SPOOL TO SAID NEUTRAL POSITION; AND MEANS FOR EFFECTING RECIPROCATION OF THE VALVE SPOOL COMPRISING A VALVE FOR THROTTLING FLOW OUT OF THE OUTLET PORT, AND A CONDUIT CONNECTING ONE END OF THE VALVE CHAMBER TO A POINT BETWEEN SAID THROTTLING VALVE AND THE OUTLET PORT, WHEREBY SELECTED RESTRICTION OF FLOW FROM THE OUTLET PORT BY SAID THROTTLING VALVE DEVELOPS PRESSURE ACTING THROUGH SAID CONDUIT ON THE VALVE SPOOL IN OPPOSITION TO SAID BIASING MEANS.