US2925718A - Hydraulic system control - Google Patents

Description

Feb. 23, 1960 R. 1 swlrzER 2,925,718

HYDRAULIC SYSTEM CONTROL Original Filed July 2, 1956 2 Sheets-Sheet 1 rn- I Feb. 23, 1960 R, L. SWITZER HYDRAULIC SYSTEM CONTROL Grignal Filed July 2, 1956 2 Sheets-Sheet 2 United States Patent O HYDRAULIC SYSTEM CONTROL Robert L. Switzer, Long Beach, Calif., assignor to Union Oil Company of California, Los Angeles, Calif., a corporation of California Original application July 2, 1956, Serial No. 595,535. Divided and this application July 24, 1958, Serial No. 750,684

7 Claims. (Cl. 60-97) This invention relates to the automatic control of hydraulic systems for the delivery of power by means of hydraulic cylinders and particularly relates to improvements in the control of such systems whereby the mechanically actuated pilot valves normally associated with the hydraulic cylinder in such systems have been eliminated. The invention also relates to an improved hydraulic cylinder modified to permit automatic hydraulic signalling when the end of the extension and retraction strokes are reached by the piston.

Reciprocal motion of mechanical elements is widely used in mechanical devices of all kinds, some of which deliver power in appreciable quantities and others of which are merely used to actuate other elements at low force levels. Hydraulic cylinders containing a piston and piston rod are frequently used to generate such reciprocating motion, but heretofore they have required some means for detecting and signalling the time when the piston reached the end of its stroke in the cylinder. Ordinarily this detection and signalling is by means of a mechanically actuated pilot valve placed near the piston rod and tripped by means of kickers attached to it. The movement of the pilot valve alters the iiow of hydraulic fluid through the valve and ultimately permits the reversal of the fluid ow to and from the cylinder so as to either retract or extend it depending upon which extreme has caused the signal generation. j

Although such pilot valves are generally reliable, they are frequently diicult to maintain in some locations, particularly if they are submerged in a liquid medium, or located within a closed vessel, or in any other elements inaccessibly located.

One specific example of such inaccessibility lies in the feeder case enclosing the oscillating-reciprocating feeder mechanism employed in the upiiow oil shale retort. Herein the reciprocating feeder is operated by a hydraulic cylinder which is contained within the feeder case and completely submerged therein in a body of shale oil. lt is in general of advantage to eliminate the customary mechanical pilot valves in any situation since it constitutes a moving part of the mechanism which can be a source of trouble.

The present invention is therefore directed to an improved hydraulic system in which some or all such pilot valves are eliminated. The invention further relates to an improved hydraulic cylinder modified to provide self-signalling when the piston reaches either extreme of its stroke.

It is therefore a primary object of this invention to provide an improved hydraulic system for the generation of a reciprocating motion at any desired power level without the requirement of hydraulic pilot valves associated with the mechanism.

It is a more specific object of this invention to provide an improved hydraulic means for operating reciprocating pumps without the use of pilot valves.

'One specific object of this invention is to provide an improved automatic hydraulic system for operating a ice single reciprocating load, such as an oil well pump, hydraulically without the use of pilot valves.

Another object of this invention is to provide an improved hydraulic system for operating the oscillating and reciprocating solids feeder in the upow shale retorting process.

It is another `object of this invention to provide an improved hydraulic cylinder modified to provide selfsignalling when the piston reaches either extreme of the stroke.

It is also an object of this invention to provide an improved apparatus capable of effecting the foregoing objects.

Other objects and advantages of the present invention will become apparent to those skilled in the art as the description and illustration thereof proceed.

Briefly the present invention comprises an improved hydraulic system having for its essential element a modified hydraulic cylinder containing a piston and piston rod, provided with the conventional uid inlets and outlets adjacent each end of the cylinder, and modified to provide pilot fluid inlets in the cylinder wall adjacent each end of the piston stroke. These pilot uid inlets are located a distance away from the end of the cylinder which is less than the thickness of the piston contained therein, or less than the span occupied by piston -rings on the piston side, so that when the piston has moved to either extreme of the cylinder, the pilot fluid inlet at that end is sealed either by the piston or by or between the piston rings, or both, so that no pilot fluid may enter or leave the cylinder through the pilot inlet.

In operation this modied hydraulic cylinder is supplied with hydraulic liuid through the usual inlets and outlets to move the piston in either direction in the conventional way. A pilot iiuid obtained from the hydraulic pump supplying fluid to the cylinder is introduced at a rela: tively low rate into each of the pilot inlets through separate lines andv preferably each of these lines is provided with a check valve permitting flow into the cylinder only. When the piston is moving from one extreme to the other, pilot uid will not ordinarily flow into the pilot Huid inlet adjacent the high pressure end of the cylinder because the pilot uid pressure will not ordinarily exceed the pressure of the main hydraulic uid stream. The other end of the cylinder is venting displaced iiuid to the hydraulic reservoir a-t a low pressure and therefore pilot fluid will flow into the pilot inlet near the low pressure or venting end of the cylinder and flow directly out again through the main uid connection as it is displaced by the moving piston. At the end of the stroke however the pilot inlet at that end is sealed by the piston or its rings and accordingly the pilot iiuid pressure in this inlet rapidly rises signalling the end of the piston stroke. This pressure increase is the pilot signal obtained from the modified hydraulic cylinder of this invention so that no mechanically operated pilot valve is needed. The signal so obtained can be used to operate the main direction reversing hydraulic valve controlling liow of hydraulic uid to and from the cylinder through the principal or main connections so as to reverse the principal fluid ow and cause the piston to move in the reverse direction. At the end of this reverse stroke, the other pilot inlet is sealed in the same manner, and a pressure rise is generated in that pilot uid inlet. This signal indicates the other end of the stroke and causes the direction reversing hydraulic valve to be moved back into the original position completing the hydraulic cycle.

The present invention is most readily understood by reference to the accompanying drawings in which:

Figure 1 shows a schematic piping and instrumentation diagram of a hydraulic system using a single hydraulic cylinder operated in a two-step sequence, and

n Figure 2 shows a schematic piping and instrumentation dlagram of hydraulic system utilizing two .hydraulic cylinders operated in a four-step sequence to oscillate and reciprocate one of the cylinder System, Fig. 1 modification Referring now particularly to Figure 1, hydraulic cylinder provided with piston 12 and having piston rings 14 is mounted by means of supports 16 and connected to a suitable reciprocating load, not shown but which may to a load such as a bottom hole oil well pump, by means of piston rod 18. Cylinder 10 is provided with the conventional main connections 18 and 20 for hydraulic fluid. Also provided according to this invention are pilot fluid connections or inlets 22 and y24 opening through the wall of hydraulic cylinder 10 a distance from each end thereof which is less than the thickness of piston 12, or the span of piston rings 14. This distance is determined so that with piston 12 in the position shown, pilot inlet 22 is sealed against fluid introduction by the piston or its rings. Similarly pilot Huid inlet 24 is sealed when piston 12 is at the top of the stroke in Figure 1. Hydraulic fluid from oil reservoir 26 flows through outlet line 28 into oil pump 30. Oil is pumped therefrom through check valve 32 and on through rrate control valve 34 into a four-way directional control valve DCV having port, P, T, 1 and 2. The high pressure oil opens thereinto lthrough port P. Directional control valve DCV is connected from port 1 by means of line 36 to upper main hydraulic oil connection 18 and lower main Iconnection 20 communicates through line 38 to port 2 of DCV. The Vented hydraulic oil displaced `from cylinder 10, is removed from port T of DCV, ows through line 40 provided with check. valve 42, and continues back to reservoir 26 through lter and cooler 44. With directional control valve DCV in* .the position shown, high pressure oil is supplied through line 36 to the top of cylinder 10 moving piston 12 downwardly therein, While displaced oil is vented through lines v38 and 40 back to reservoir 26. With DCV moved to the left, the hydraulic oil passes through DCV between ports P and 2, is introduced to the bottom connection of cylinder 10 causing piston 12 to rise, and the displaced hydraulic oil passes through line 36 and through DCV between ports 1 and T back to reservoir 26.

Directional control valve DCV thus selects the main `hydraulic oil connection of cylinder 10 to which the high .pressure oil is supplied and thus determines the direction -of movement of piston 12. DCV is actuated and moved `from left to right between the two extereme positions Iby means of hydraulic operators 46 and 48. These -operators are in turn actuated by a pilot pressure impulse from either of control valves CV-l or CV-2. Control valve CV-l in turn is actuated by hydraulic operators 50 'and 52 while -control valve CV-Z is actuated by hydraulic operators 54 and 56. Control Valves CV-l and CV-Z are Spring loaded by means of springs 58 and 60 biasing them into the positions shown whereby DCV operators 46 and 48 are vented into reservoir 26. -Each of control valves CV-1 and CV2 controls the tlow of pilot iluid to the hydraulic operators 46 and 48 to actuate directional control valve DCV in response to the signal pressure increase in the pilot fluid connections. The signal pressure rise actuates control valves CV-1 and CV-2 through their hydraulic operators against loading springs 58 and 60. Ports 2 of each of CV-l and CV-2 are blocked so that these valves are in reality three-way control valves. Port 1 of CV-l is connected through line 70 to hydraulic operator 4S and port'l of CV-2 is connected through line 72 to hydraulic operator 46, .both of which operators actuate directional control valve DCV. A supply of pilot uid is taken from point 62 on the main high pressure hydraulic oil line, and is counected by means of pilot oil manifold 64 and line 66 to port P of CV-l and line 68 to port P of CV-Z. These ports are normally closed because of loading springs 58 and 60. Ports T of each of CV-1 and CV-2 are conneoted through pilot oil vent manifold 70 to reservoir 26.

Hydraulic operator S0 of CV-l is connected through line 74 and line 38 to lower main hydraulic connection 20 of cylinder 10. Hydraulic operator 54 of CV-2 is connected through line 76 and line 36 to upper main hydraulic connection 18 of cylinder 10. Thus when a high pressure exists in either of the main connections 18 or 20, as when the high pressure oil is applied therethrough to move piston 12 in one direction or the other, it is reflected through lines 36 and '76 or lines 38 and 74 so that hydraulic operators 54 and 50 respectively, in conjunction with loading springs 58 and 60, force control valves CV-l or CV-2 to the right into the positions shown. The loading springs are required to prevent the main high pressure fluid from backing up through pilot lines 78 and 80 and actuating operators 52 and 56 thereby moving CV-l and CV-2 in the reverse direction.

The supply of pilot fluid injected directly at pilot inlets 22 and 24 near the ends of cylinder 10 is obtained from the main hydraulic lines 36 and 38 referred to previously. Lower inlet 22 receives pilot fluid through line 78 provided with control valve 81 and check valve 83 and it also connects to and actuates hydraulic operator 52. Upper pilot iluid inlet 24 receives oil from main hydraulic line 38 through line S0 provided with control valve 85 and check valve 84 and is also connected with hydraulic operator 56. With this connection a high pressure at lower pilot inlet 22 signalling the arrival of piston 12 at the bottom of hydraulic cylinder 10 actuates hydraulic operator 52 moving CV-l to the left against loading spring 58 and thereby supplies pilot hydraulic fluid to hydraulic operator 48 moving DCV to the left. Similarly the arrival of piston 12 at the top of the stroke seals pilot inlet 24, causes the pressure in line to rise, actuates hydraulic operator 56 moving CV-Z to the left against loading spring 60, and thereby supplies pilot iluid pressure through line 72 to actuate hydraulic operator 46 moving DCV back to the right in the position shown. In this Way the movements of piston 12 in hydraulic Icylinder 10 signal the arrival of the piston at the extremes of piston travel and causes a reversal of the main flow of hydraulic fluid so as to return the piston toward the opposite extreme. The system continues in this reciproeating motion indefinitely at a rate controlled by valve 34 and pump 30 which regulate the rate at which high pressure hydraulic fluid is supplied tol cylinder 10 to move piston 12.

peration, Fig. 1 modification A complete descrip-tion of the movement sequence of each of the three valves DCV, CV-l, and CV-Z, and the reciprocation of piston 12 in hydraulic cylinder 10 is given immediately below to provide a concise and clear description of the operation of this modication of the apparatus of this invention. In Figure 1 piston 12 is shown arriving at the bottom of its downstroke. During the downstroke the weight of the load, if any, plus the weight of piston rod 18 and piston 12, plus the supply of high pressure tluid through line 36 to upper inlet 18 of the cylinder causes piston 12 to move downwardly through cylinder 10. During this time a small ilow of pilot uid into the lower pilot uid inlet 22 is maintained from line 36 through pilot line 78. Meanwhile displaced luid ows through lower main hydraulic connection together with the ypilot fluid -which is introduced through inlet 22 and flows through line 38 and DCV back to reservoir 26.

When lpiston 12 arrives at the lowest position, pilot inlet 2-2 is sealed and the pressure there and in line .78 rises suiciently to lactuate operator 52 and move CV-l to the `left against lspring 58, This places pilot fuid pressure through ports P and 1 of CV-1 onto operatorl 48 moving DCV to the left. This connection vents hydraulic uid from the top of cylinder while supplying high pressure fiuid through lower main connection 20 to raise piston 12. Since connection 18 is now vented, this relieves pressure at pilot inlet 24 permitting CV-Z to return to its right-hand position shown through the action of spring 60.

The piston now moves upwardly connected to the load through connecting rod 18. When the piston arrives at the top of the stroke, upper pilot inlet 24 is sealed against further pilot iiuid ow from line 38 through line 80. The pressure rises and this pressure impulse is transmitted through line 80 to operator 56 movin-g CV2 to the left against spring 60 thereby placing pilot iiuid pressure therethrough between ports P and 1 and through line 72 to operator 46 moving DCV to the right thereby reversing the main flow of hydraulic uid. The bottom of cylinder 10 is now vented through line 38 and high pressure uid is supplied through line 36 to return the piston toward the bottom position. This relieves the high pressure formerly below piston 12 and also at the lower pilot inlet 22 lowering the pressure at operator 52 and permitting CV-l to return to the right-hand position shown by means of loading spring 58.

- Piston 12 is now moving downwardly toward the lower position to begin the cycle all over again. The cycle continues indefinitely at a rate determined by the rate of supply and the pressure of the main stream of hydraulic fluid. The end of each of the two steps is signalled by the pilot pressure increase, and this begins the next step. The weight of the piston 12, shaft 18, and the load is prevented from causing the piston downstroke by check valve 162, valve 164, and back pressure controller 166 which maintain during the downstroke a pressure below piston 12 which is suflicient to support the weight. A slightly greater pressure above piston 12 will cause the downward movement.

As stated briey above, the modification shown in Figure l is particularly adaptable to the hydraulic pumping of oil wells by means of a hydraulic cylinder having a diameter of from 2 to 12 inches or more and a stroke of from 2 to 40 feet located at the surface of the earth and connected through a string of sucker rods to a bottom hole pump in the well. Obviously the apparatus is adapted to any other use in which a reciprocal motion in power application is required. This reciprocal movement can be vertical as described, horizontal, or at any other angle. These other applications of course will present description.

System, Fig. 2 modification Referring now -more particularly to Figure 2, a more complex four-step modification of the present invention is shown using one mechanically actuated pilot valve employing two hydraulic cylinders and is adapted for use in operating the solids feeding mechanism of the upflow shale retorting process. In this modification, a first or main feed cylinder 100, which drives the piston in a solids feeder, is oscillated between the vertical position shown and an inclined position, not shown, around trunnion 102. This oscillation is imparted by means of a second or oscillating cylinder 104 provided with piston 106 and piston rod 1108 which is integrally connected by any means not shown to cylinder 100. Feed cylinder 100 is provided with piston 110, piston -rod 112, and the solids feeder not shown at the upper end of the piston rod. Cylinder 100 is inclined from the vertical by extending cylinder 104 at a time when piston 110 is extended. Crushed oil shale is supplied to the top of the solids feeder piston and cylinder system, piston 110 is retracted accepting a charge of shale, feeder cylinder 100 is returned from this charging position to the vertical feeding position by retractingoscillating piston 10,6, and

The end of each step in the sequence signals the start of the next step. This four-step sequence cycle is continued to force periodic charges of oil shale upwardly into the retort.

In Figure 2 the piping and instrumentation connections by means of which the foregoing sequence of operations is effected are shown schematically. The main hydraulic conduits are shown as solid lines while the pilot fluid connections are shown as broken lines. Feeder cylinder is provided with upper and lower ends with the usual main hydraulic fluid connections 114 and 1.16, hydraulic fiuid being introduced through 114 and vented through 116 to extend piston 110 and piston rod 112, and subsequently being introduced through inlet 116 and vented through 114 to retract piston 110 and piston rod 112. Also provided adjacent each end of feeder cylinder 100 are lower and upper pilot tiuid connections 118 and 120. These pilot fluid connections are disposed a distance from the end of the cylinder which is less than the thickness of piston 110. Piston is providedwith piston rings 122 which seal, as shown in the drawing, pilot uid connection 118. Pilot fluid connection is similarly sealed when piston 110 is in its upper or extended position. The function of these connections so placed has been referred to above in connection with Figure 1 to provide a pressure signal indicating the arrival of the piston at the ends of its stroke. This signal is utilized to change the flow of hydraulic fluid in the system so as to continue automatically the sequential operation of feeder cylinder 100 and oscillating cylinder 104.

The present system is provided with hydraulic fluid reservoir 124 having filling line 126. Outlet line 128 opens into iiuid pump which delivers high pressure hydraulic uid into manifold 132. This fluid is divided into two principal streams, one iiowing through line 134 at a rate controlled by valve 136 through four-way rlirection reversing valve DCV-2 to oscillating cylinder 104, and the other through line 138 at a rate controlled by valve 140 through four-way direction reversing valve DCV-1 to feeder cylinder 100. Displaced hydraulic fluid is vented from oscillating cylinder 104 through line 157, back through valve DCV-2 and through line 135 into low pressure manifold 137. Displaced low pressure hydraulic iiuid passes from feeder cylinder 100 through valve DCV-1 through line 139 through low pressure manifold 137. The returning hydraulic fiuid is passed through a cooler and a filter indicated generally at 141 and returned to reservoir 124. The rate of movement of piston 106 in oscillating cylinder 104 is ycontrolled by the setting of valve 136. Similarly the rate of movement of piston 110 in feeder cylinder 100 is controlled by the setting of valve '140.

Direction reversing valve DCV-2 is actuated by means of hydraulic operators 142 and 144 and serves to provide high pressure hydraulic fluid to and vent low pressure hydraulic fluid from the fluid connections at the end of oscillating cylinder 104. Similarly, direction reversing valve DCV-1 is actuated by hydraulic operators 146 and 148 and provides hydraulic fluid to and vents uid from ticrnections 114 and 1,16 at the ends of feeder cylinder Operators 142 and 144 which actuate directional control valve DCV-2 are themselves actuated by pilot fluid through control valves CV-l and CV-2.

Control valve CV-l is actuated by hydraulic operators 143 and 145, and control valve CV-2 is actuated by operators 150 and 152 by means of signal pressures obtained in part from the pilot fluid lines and in part from rotary pilot valve RPF. As noted on the drawing, control valves CV1 and CV-Z are spring loaded by means of loading springs 147 and 1 49 whichtendto ,biasgthem to the assuma left into the positions :shown in which both operators 142 and 144 of DGV-2 are vented .to reservoir 124. Thus the impulse generated by operators 143 and 150 must overcome the compression force of these loading springs in order to move valves CV-l and CV-Z to the right. Once the signal pressure is removed from operators 143` and 150, the loading springs return then to the positions shown in the drawing. In the present invention where feeder cylinder 100 oscillates about trunnion 102, it is simple to bring an extension rod through the feeder case from trun-nion 102 provided with arm 154 and kicker 156 which actuates rotary pilot valve RPV at the extremes of the oscillation. The extremes of reciprocation of piston 110 are diicult to sense however because of the location of this cylinder within a sealed oil filled case. Accordingly the pilothydraulic inlets 120 and 1118 are respectively used according to the present invention to provide the signal pressures to actuate operator 150 when piston 110 reaches the top of its stroke and hydraulic operator 143 when piston 110 is in the position shown at the bottom of its stroke.

Briefly, then, rotary pilot valve RPV signals the extremes in the oscillation of feeder cylinder 100, which actually is the same yas signalling the extremes of reciprocation of oscillating cylinder 104, so as to actuate directional control valve DCV-l through hydraulic operators 14-6 and 148. Pressure increases in connections 118 and 120 signal the arrival of piston 110 at the extremes of travel in feeder cylinder 100 so as to operate control valves CV-l and CV-2 which in turn operate direction reversing valve BCV-2 for the purposes discussed above.

Direction reversing valve BCV-2 is connected at ports 1 and 2 by means of lines 155 and 157 to oscillating cylinder 104. Direction reversing valve DGV-1 is connected at ports 1 and 2 respectively with main iuid connections 116 and 114 of feeder cylinder 100 by means of lines 158 and 160. As will be noted, lthese latter two lines are provided with several check valves and back pressure controllers for the specific purposes discussed below.

Line 160 is provided with check valve 162, permitting fluid flow only therethrough into connection 114, and control valve 164 actuated by back pressure controller 166 connected in parallel therewith. The purpose of this back pressure controller is to maintain during the downstroke of piston 110 a predetermined minimum hydraulic pressure below piston 110 which prevents the Piston from moving downwardly, because of its own weight and the weight of the piston rod and the load 'attached thereto, atan undesirably high rate.

Line 158 is provided with check valve 168, permitting outflow of hydraulic fluid from connection 116 only, and control valve 170 connected in parallel therewith and actuated by pressure reducer 172. The purpose of this pressure reducer is to limit the maximum hydraulic pressure which can be placed in cylinder 100 at port 116 above piston 110 during the retraction stroke. LThis pressure need not be as great as the pressure applied to lift piston 110 since the weight of the load, the piston rod 112, and piston 110 act in a direction which aids the retraction of the piston.

Line 158 is further provided with check Ivalve 174, permitting outflow of fluid only from cylinder 100 .above piston 110, and control valve 176 connected in parallel therewith and actuated by back pressure controller 178i. The purpose of this back pressure controller is to generate a back pressure in line 158 at point 180 during the retraction stroke of piston 110 so as to generate a signal pressure through control lines 182 and 184 -at pilot fluid inlet 118 when piston 110 reaches its retracted position, which pressure signal is sufficiently high -so that it Will actuate Ithrough line 186 hydraulic operator 143 against the loading spring 149 in control valve CV-L Hydraulic pilot uid flow into connections 118 and 120 is derived from the high pressure fluid flow directed through direction reversing valve DCV-l and through lines 158 and 160 into main connections 116 and 114.

Thus when high pressure fluid is being introduced through connection 114 during the extension stroke of piston 110, a minor portion of the uid flows through line 190 provided with control valve 192 and check val-ve 194 through the upper pilot hydraulic connection 120. The pressure rise in this line from the vent pressure Ito the supply value generated by the arrival of piston 110 at the extension end of the stroke is transmitted through line 196 to operato-r 150 which moves control valve CV-2 to the right against loading spring 149. When high pressure hydraulic fluid is being introduced through line 158 to the upper main connection 116 in feeder cylinder 100' during the retraction stroke, a minor ow is taken from line 158 at point 180, is passed through line 182 provided with .control valve 198 and check valve 200, then through line 184 into lower pilot hydraulic inlet 118. The pressure rise from the vent pressure to the supply valve signalling the `arrival of piston 110 at the retracted extreme, as shown in the drawing, is detected at point 202 and is transmitted through line 186 thereby actuating hydraulic operator 143 and moves control valve CV-l to the right against loading spring 147.

As stated above, these aforementioned movements to the right of control valves CV-l and CVeZ permit the ow of pilot hydraulic fluid from high pressure manifold 134 through pilot uid manifold 204 provided with valve 206 and, respectively, through lines 208 and 212 through control valve CV-l at ports P and 2 through line 214 to actuate operator 144 and move DGV-2 to the left, and through line 210 through control valve CV-2 at ponts P and 2 through line 216 to :actuate operator 142 to move DGV-2 to the right. The ow of hydraulic fluid to and from oscillating cylinder 104 is thus controlled.

High pressure pilot manifold 204 is also connected through line 218 to port P of rotary pilot valve RPV. As stated above, this pilot valve is mechanically actuated by the :oscillation of feeder cylinder 100. When the feeder cylinder reaches the vertical or feeding position shown in the drawing, a position in which the piston 110 is also in its lower or retracted position, rotary pilot valve RPV is internally connected between ports P and 2 thereby permitting the high pressure hydraulic pilot fluid to flow through line 220 to hydraulic operator 148 moving direction reversing DCV-l to the left. This permits the ow of high pressure hydraulic fluid through the main line 138 through DGV-1, ports P and 2, on through line 160 to the bottom connection 114 of cylinder 100 thereby raising piston 110. At the top of this stroke and as previously described, feeder cylinder is oscillated into an inclined position which again actuates rotary pilot valve RPV by means of kicker 156 so as tto connect ports P and 1. This permits high pressure pilot fluid to ow through RPV, through line 222 to hydraulic operator 146 which moves DCV-l into the position shown. This supplies `a main high pressure stream of hydraulic uid through lines 138 and 158 to open connection 116 to retract piston in feeder cylinder 100.

Ports T on each of rotary pilot valve RPV and control valves CV-l and CV-2 are connected respectively by means of lines 224, 226, and 228 to low pressure pilot fluid manifold 230 through which it is returned to fluid reservoir 124.

The foregoing discussion briefly describes the functions and the interconnections between each of the essential elements of the system described in Figure 2. The operation will be perhaps most readily understood by following the motions of each element through a complete cycle of operation. Such a cycle is described immediately below.

Operation, Fig. 2 modification Figure 2 shows the feeder cylinder 100 in its fully re. tracted position and also shows the oscillating cylinder 104 in its fully retracted position. Ihe setting of RFV shown, resultingfrom the movement ofcylinder 100 into the vertical position, supplies high pressure pilot uid through ports P and 2 to hydraulic'operator 148 While venting hydraulic operator 146 through ports T and 1 thereby shifting directional control valve DCV-l to the left. This connects ports P and 2 and connects ports 1 and T in DCV-l thereby directing high pressure uid through line 160 to the bottom of cylinder 100 causing piston 110 to rise delivering shale into the kiln. The uid lying about piston 110 is vented through connection 116 and through line 158, through ports 1 and T of DGV-1, and lines 139 and 137 to reservoir 124.

At the same time as high pressure iluid is introduced through inlet 114, a small pilot uid stream passes into upper pilot fluid inlet 120 through line 190. When piston 110 reaches the fully extended position, this pilot uid flow at inlet 120 is cut oi causing the pressure at 181 in line 190 to rise signalling the end of the feeder cylinder 100 extension stroke. This places a high signal pressure through line 196 on hydraulic operator 150 suicient to actuate it against loading spring 149 thereby moving control valve CV-2 to the right. This connects ports P and 2 and ports 1 and T of CV-2. High pressure pilot uid is thereby passed through ports P and 2 through line 216 on to hydraulic operator 142 moving direction reversing valve DGV-2 to the right. This places high pressure hydraulic fluid through line 134, connected ports P and 1 in DGV-2, through line 155 to the lower port of oscillating cylinder 104 causing piston 106 to move into the extended position thereby oscillating feeder cylinder 100 into the inclined charging position while piston rod 112 is extended.

Upon reaching the fully inclined position, kicker 156 again actuates RPV thereby connecting ports P and 1 and connecting ports T and 2. High pressure pilot lluid ows from line 218 through connected ports P and 1 in RPV, through line 222 to actuate hydraulic operator 146 moving DCV-l to the right connecting ports 1 and P and connecting ports 2 and T thereof. This places high pressure hydraulic uid from pump 130 through line 158 into upper inlet 116 while venting displaced hydraulic fluid from cylinder 100 through lower connection 114, line 160, connected ports 2 and T in DCV-1, back to reservoir 124. While high pressure fluid thus ows through line 158 into upper connection 116, a small high pressure pilot stream flows through lines 182 and 184 into lower pilot uid inlet 118 only so long as piston 110 does not seal this inlet. When piston 110 is fully retracted, in accepting a fresh charge of oil shale, pilot uid inlet 118 is sealed causing pressure to rise at point 202. This actuates through line 186 hydraulic operator 143 moving CV-l to the right against loading spring 147 thereby connecting ports P with 2 and port l with T in CV-l. Pilot hydraulic uid ows from lines 132, 204, 208 and 212 through ports P and 1 of CV-1, through line 214 actuating hydraulic operator 144, moving direction reversing valve DCV-Z to the left thereby connecting ports P and 2 and ports T and 1 in DGV-2. High pressure hydraulic lluid then ows through DCV-Z through connected ports P and 2, through line 156 to the upper connection on oscillating cylinder 104. This causes the piston 106 to retract. Hydraulic fluid is vented from the lower connection in cylinder 104 through line 155 and connected ports 1 and T in DGV-2, through lines 135 and 137 to reservoir 124. This brings oscillating cylinder 104 back into the position shown in Figure 2 thereby oscillating feeder cylinder 100 into the vertical or feeding position also shown in the drawing. This causes kicker 156 again to trip rotary pilot valve RPV thereby interconnecting ports P and 2 and ports T and 1. This begins the cycle all over again. Pilot fluid flows through line 21S and connected ports P and 2 and RPV, then through line 220 actuating hydraulic operator 148 moving direction reversing valve DCV-l to the right thereby connecting port P with 2 and port to lower connection 114 in feeder cylinder .'100 forcing piston 110 upwardly to deliver the charge of oil shale into the kiln.

The cycle automatically repeats in the aforementioned steps causing a continuous alternate extension and retraction of each of cylinders and 104 in the sequence described.

It is obvious from the foregoing description the manner in which the pilot valves formerly used have been eliminated from the mechanism associated with piston rod 112 in cylinder 100 and have been substituted with lower and upper hydraulic fluid inlets 11S and 120. Rotary pilot valve RPV was only used because trunnion 102 was readily fitted with a sealed shaft which could be brought through a seal in the feeder case enclosing feeder cylinder 100 and oscillating cylinder 104. It should be understood that in other situations it may be inconvenient to use rotary pilot valve RPV and it may be eliminated together with its mechanical actuation means and oscillating cylinder 104 may be provided with the two hydraulic fluid inlets at each end in a manner entirely analogous to that shown in connection with feeder cylinder 100. In this situation all pilot valves are eliminated and the moving cylinders may be completely enclosed in inaccessible positions and the signals indicating the end of each piston stroke obtained by pressure increases in the hydraulic iluid inlet lines as described in connection with cylinder 100 in Figure 2.

The system shown in Figure l was employed in actuating a bottom hole pump in an oil well located in southern California. The well was 7,800 feet deep, the actuating cylinder was 30 feet long, and 8 inches in diameter. Hydraulic fluid was applied thereto at a pressure of 500 to 800 p.s.i. to move the sucker rod upwardly so as to actuate the pump. The cycle was continued at a rate of approximately 6 strokes per minute while pumping at a rate of 400 barrels per day. The system was entirely successful, operated for extended periods without maintenance, and made substantially no noise while in operation.

The system of Figure 2 was employed in actuating the so-called rock pump in the upow shale retorting process. In this modification crushed shale rock was fed to the retort at a rate of about 350 tons per day in a retort which was 17 feet in diameter and about 35 feet high. The shale feeder cylinder was 66 inches in diameter, had a stroke of 24 inches, and was operated at a rate of l0 strokes per hour by means of the hydraulic system indicated in Figure 2. The oscillating cylinder had a stroke of 4 feet and was 16 inches in diameter. The feeder cylinder, which actuated the shale piston feeder, had a stroke of 2 feet and was 32 inches in diameter. The hydraulic fluid was supplied in the system at a maximum of 2,000 p.s.i.g., the pilot hydraulic iiuid was used in the system at a maximum pressure of about 200 p.s.i.g. by means of valve 206 shown in Figure 2, the lower feeder cylinder pressure was maintained by means of back pressure controller 164 to a value of about 200 p.s.i.g. during the downstroke, the pressure in the top of feeder cylinder 100 was limited by means of pressure controller 172 during the downstroke to a maximum of about 1,000 p.s.i.-g., and back pressure controller 178 during this same downstroke maintained a pressure differential of about 200 p.s.i.g. across valve 176 so as to supply at point 180 a source of pilot hydraulic fluid of a suicient pressure during the downstroke to generate at point 202 when piston is in its fully retracted position a hydraulic pressure suiciently high to actuate hydraulic operator 143 in control valve CV-1.

The present invention has been described above by way of illustration in connection with two processes in which it has been used. The apparatus of Figure 1 and T with 1. This supplies high pressure hydraulic fluid 75 Example l is relatively simple employing a single hy.

.draulic cylinder which has been provided at its end'with two oscillating pilot hydraulic fluid inlets for the purposes described. The system of Figure 2 and of Example 2 is more complicated because of its simultaneous reciprocating and oscillating movements. The princi- '.ples employed are the same however and from the foregoing description those skilled in the art will readily understand how the invention may be applied to other and more complex systems as well as to other uses in which .power at any level is to be delivered through reciprocating motion to a load.

A particular embodiment of the present invention has been hereinabove described in considerable detail by way of illustration. It should be understood that various other modifications and adaptations thereof may be made by those skilled in this particular art without departing from the spirit and scope of this invention as set forth in the appended claims. This application is a division of my copending application Serial No. 595,- 535, tiled July 2, 1956.

I claim:

1. An apparatus comprising a nid pressure line; a first reciprocating hydraulic motor consisting of a cylinder, a piston and an attached piston rod; means for supporting said rst hydraulic motor so as to permit the cylinder thereof to oscillate around a pivot; a first direction reversing valve and conduits connecting the same -with the opposite ends of the cylinder of said iirst hydraulic motor and with said fluid pressure line; a first hydraulic valve actuator for operating said .rst direction reversing valve; a second reciprocating hydraulic motor consisting of a cylinder, a piston, and an yattached piston rod connected to the cylinder of the said 'rst hydraulic motor, whereby operation of said second hydraulic motor causes the cylinder of said first hydraulic motor to oscillate around said pivot; a second direction reversing valve and conduits connecting the same with the opposite ends of the cylinder of said second hydraulic motor and with said uid pressure line; a second hydraulic valve actuator for operating said second direction reversing valve; a pair of spring-loaded hydrauli- `cally actuated pilot uid control valves connected between said fluid pressure line and said second hydraulic valve actuator; a mechanically activated pilot fluid control valve connected between said liuid pressure line and said rst hydraulic valve actuator, said pilot fluid control valve being actuated directly by said oscillation of the cylinder of said irst hydraulic motor; a first pilot fluid line communicating between one end of the cylinder of said rst hydraulic motor and one of said springloaded hydraulically actuated pilot duid control valves;

12 a second lpilot uid line communicating between 'the other end `of the cylinder `of-'said first hydraulic m'otor and the otherpof said v'spring-'loaded hydraulically actuated pilot fluid control valves, whereby the pistons 'of 'said 'first and second hydraulic motors each extend and retract continuously in their respective cylinders in a four-step sequence 'so 'long-as pressure exists in said uid pressure line.

2. An apparatus according to claim 1 wherein said lirst hydraulic cylinder is provided with a shaft and trunnion bearing support to permit its oscillation in a vertical plane.

3. An apparatus according to claim 2 wherein said Amechanically actuated pilot fluid control valve is a rotary valve in combination with an actuating arm therefor connected at right angles to the trunnion shaft.

4. lAn apparatus according to claim 1 in combination with a back pressure controller connected in the conduit 'between said rst direction reversing valve and the lower end of the cylinder of said rst hydraulic motor, said pressure controller connected to maintain at least a predetermined minimum pressure below the piston in said cylinder during the downstroke to prevent the weight of the piston and piston rod therein and of the load attached thereto from alone causing the downstroke of the piston.

5. An apparatus according to claim l in combination with a back pressure controller connected in the conduit between said rst direction reversing valve and the upper end of the cylinder of said rst hydraulic motor, said controller connected to maintain at least a predetermined pressure in the line between said valve and said controller during the -downstroke of the piston in said cylinder, which pressure is sullcient to actuate the spring loaded pilot uid control valves against the spring load.

6. An apparatus according to claim 1 in combination with a pressure controller connected in the conduit between the iirst direction reversing valve and the upper end of the cylinder of said iirst hydraulic motor, said controller being connected to limit the hydraulic pressure which can be applied above the piston in said cylinder during the downstroke thereof.

7. An apparatus according to claim 1 wherein each of said first and second pilot fluid lines opens into the cylinder of said rst hydraulic motor at a point which is covered and sealed by 'the piston of said motor in its extreme position.

No references cited.

Images