Abstract
The invention relates to a method for operating a piston pump with a differential cylinder drive (1) with at least two differential cylinders (2, 3) for driving at least two conveying pistons movable in conveying cylinders, each conveying piston being driven via an associated differential cylinder (2, 3) of the differential cylinder drive (1) for operating the piston pump, with a hydraulic circuit (4) for driving the differential cylinder drive (1) by the action of hydraulic fluid. The invention also relates to a piston pump for carrying out the method.
Claims
1-22. (canceled)
23. A method for operating a piston pump with a differential cylinder drive with a first differential cylinder and a second differential cylinder for respectively driving a first conveying piston and a second conveying piston respectively movable in a first conveying cylinder and a second conveying cylinder, the first conveying cylinder being driven via the first differential cylinder of the differential cylinder drive, the second conveying cylinder being driven via the second differential cylinder of the differential cylinder drive, with a hydraulic circuit for controlling the differential cylinder drive and/or for driving the differential cylinder drive by action of hydraulic fluid, the method comprising the following cyclically performed steps: suctioning material to be conveyed via the first conveying cylinder by driving the first differential cylinder and simultaneously discharging material to be conveyed via the second conveying cylinder by driving the second differential cylinder; pre-compressing the sucked-in material via the first conveying cylinder by driving the first differential cylinder and simultaneously discharging material via the second conveying cylinder by driving the second differential cylinder; discharging material via the first conveying cylinder by driving the first differential cylinder and simultaneously suctioning material to be conveyed via the second conveying cylinder by driving the second differential cylinder; and discharging material via the first conveying cylinder by driving the first differential cylinder and simultaneously pre-compressing the sucked-in material via the second conveying cylinder by driving the second differential cylinder.
24. The method claim 23, wherein the pre-compressing steps are divided into at least two phases, wherein in a first phase the hydraulic circuit causes the pre-compression using a first conveying piston speed by controlling the hydraulic fluid at a first volume flow and a first pressure, wherein in a second phase the hydraulic circuit causes the pre-compressing using a second conveying piston speed, which is lower than the first conveying piston speed, by controlling a second volume flow and a second pressure, the second volume flow is lower than the first volume flow and the second pressure is higher than the first pressure.
25. The method of claim 23, wherein the hydraulic circuit comprises a main hydraulic source for applying hydraulic fluid to the first and second differential cylinders to pre-compress the sucked-in material and to simultaneously discharge material from the second conveying cylinder.
26. The method of claim 23, wherein after the pre-compressing of the sucked-in material, the method further comprises discharging material via the first and the second conveying cylinders simultaneously by parallel driving of the associated differential cylinders, before suctioning material to be conveyed.
27. The method of claim 23, wherein the hydraulic circuit comprises a main hydraulic source for acting on the first and second differential cylinders with the hydraulic fluid when material to be conveyed is sucked into the first and second conveying cylinders by the first and second conveying pistons and sucked material is discharged from the first and second conveying cylinders by the first and second conveying pistons, and an auxiliary hydraulic source for driving the first and second differential cylinders when material to be conveyed is pre-compressed in the first and second conveying cylinders in the time between the suction of material to be conveyed and expulsion of pre-compressed material.
28. The method of claim 27, wherein the pre-compressing steps are divided into at least two phases, wherein in a first phase the auxiliary hydraulic source and the main hydraulic source cause pre-compression of the sucked-in material, and in a second phase only the main hydraulic source causes the pre-compression of the sucked-in material.
29. The method of claim 28, wherein application of equal pressure by the main hydraulic source is established in the first and second differential cylinders at the end of the second phase of the pre-compression before the discharge of pre-compressed material from the conveying cylinder which has completed the pre-compression is started.
30. The method of claim 27, wherein the first and second differential cylinders are additionally acted upon by the auxiliary hydraulic source for driving the first and second conveying pistons via the hydraulic circuit during the suction to accelerate the suction of material to be conveyed.
31. The method of claim 30, wherein the additional acting of the first and second differential cylinders for accelerating the suction of material to be conveyed from the auxiliary hydraulic source takes place on respective rod-side working surfaces of the first and second differential pistons of the first and second differential cylinders, wherein respective rod sides of the first and second differential pistons are connected via a swing line which is connected by the hydraulic circuit to the auxiliary hydraulic source.
32. The method of claim 31, wherein the first and second differential cylinders are acted upon by the hydraulic circuit on respective piston-side working surfaces of the first and second differential pistons when material to be conveyed is discharged from the first and second conveying cylinders by the main hydraulic source.
33. The method of claim 27, wherein the auxiliary hydraulic source, during a first phase of pre-compression, provides a higher volume flow of hydraulic fluid but a lower pressure compared to the main hydraulic source when driving the first and second differential cylinders.
34. The method of claim 27, wherein a check valve in the hydraulic circuit closes after a pressure of the hydraulic fluid is present during the pre-compression which is higher than pressure provided by the auxiliary hydraulic source, the closing of the check valve representing transition from a first phase of the pre-compression to a second phase of the pre-compression.
35. The method of claim 34, wherein the auxiliary hydraulic source presses the check valve open during the pressurization of the first and second differential cylinders in the first phase of the pre-compression.
36. The method of claim 34, wherein respective drive lines between the first and second differential cylinders and the main hydraulic source are controllable via proportional valves, wherein the proportional valves are opened slowly at the end of the second phase of the pre-compression after the equal pressure has been reached respectively in the first and second differential cylinders for discharging pre-compressed material from the first and second conveying cylinders and being closed slowly after the material to be conveyed has been discharged from the first and second conveying cylinders.
37. The method of claim 27, wherein the first and second differential cylinders for pre-compression of material to be conveyed in the first and second conveying cylinders by the first and second conveying pistons are acted upon with hydraulic fluid by the auxiliary hydraulic source via a check valve of the hydraulic circuit and simultaneously by the main hydraulic source via a flow control valve of the hydraulic circuit.
38. The method of claim 27, wherein during the pre-compressing of material to be conveyed in one conveying cylinder, the other conveying cylinder is driven for discharge of material to be conveyed via the associated differential cylinder, the associated differential cylinder being acted upon by the hydraulic circuit by the main hydraulic source of the hydraulic circuit for supplying the associated differential cylinder with the hydraulic fluid from the main hydraulic source via a drive line branching off upstream of a flow control valve.
39. The method of claim 38, wherein for simultaneous discharge of material to be conveyed from the first and second conveying cylinders, the associated differential cylinders are supplied with the hydraulic fluid in parallel via separate drive lines from the main hydraulic source bypassing the flow control valve from the hydraulic circuit.
40. A piston pump comprising: a differential cylinder drive with first and second differential cylinders that are configured and arranged to drive respective first and second conveying pistons that are movable in respective first and second conveying cylinders, each of the first and second conveying pistons arranged to be driven via respective first and second differential cylinders for operating the piston pump, a hydraulic circuit is configured to control the differential cylinder drive and/or to drive the differential cylinder drive by the action of hydraulic fluid.
41. The piston pump of claim 40, wherein the hydraulic circuit is arranged to effect, in a first phase, pre-compression of sucked-in material in at least one of the first and second conveying cylinders at a first conveying piston speed by acting on the associated differential cylinder with the hydraulic fluid at a first volume flow and at a first pressure, and, in a second phase, pre-compression of the sucked-in material in the at least one of the first and second conveying cylinders at a second conveying piston speed, which is lower than the first conveying piston speed, by acting on the associated differential cylinder at a second volume flow and at a second pressure, the second volume flow is lower than the first volume flow and the second pressure is higher than the first pressure.
42. The piston pump of claim 40, wherein the hydraulic circuit has at least one main hydraulic source for driving the differential cylinders to be acted upon the differential cylinders at least at times simultaneously by the main hydraulic source with hydraulic fluid under equal pressure for driving the first conveying pistons from the hydraulic circuit.
43. The piston pump of claim 40, wherein the hydraulic circuit comprises: a main hydraulic source configured to drive the first and second differential cylinders when material to be conveyed is sucked into the first and second conveying cylinders and when sucked material is discharged from the first and second conveying cylinders; and an auxiliary hydraulic source configured to drive the first and second differential cylinders during pre-compression material to be conveyed in the first and second conveying cylinders before discharge of pre-compressed material, wherein each of the first and second differential cylinders, at least at times, for pre-compression in the associated conveying cylinder, can be acted upon simultaneously by the main hydraulic source and the auxiliary hydraulic source from the hydraulic circuit with the hydraulic fluid.
Description
[0040] Further features, details and advantages of the invention will be apparent from the following description and from the drawings, which show examples of embodiments of the invention. Corresponding objects or elements are provided with the same reference signs in all figures. They show:
[0041] FIG. 1 Hydraulic circuit according to the invention,
[0042] FIGS. 2 to 7 hydraulic circuit in various switching positions and
[0043] FIG. 8 Pressure limiting circuit for auxiliary hydraulic pump.
[0044] FIG. 1, denoted by the reference sign 1, shows a differential cylinder drive 1 with a hydraulic circuit 4 for operating a piston pump according to the invention. The differential cylinder drive 1 comprises at least two differential cylinders 2, 3 for driving at least two conveying pistons of a piston pump which are movable in conveying cylinders. Each of the conveying pistons is driven via an associated differential cylinder 2, 3 of the differential cylinder drive 1 for operating the piston pump. The piston pump comprises the hydraulic circuit 4 for switching the differential cylinder drive 1. The hydraulic circuit 4 has at least one main hydraulic source 5, which is preferably designed as a main hydraulic pump 5, for driving the differential cylinders 2, 3 when material to be conveyed is sucked into the conveying cylinders by the conveying pistons. The main hydraulic source 5 may be designed as a main hydraulic pump 5, as indicated in the figures. Alternatively, the main hydraulic source 5 may also be designed as a hydraulic accumulator, which is preferably charged by a hydraulic pump. The discharge of sucked-in material from the conveying cylinders by the conveying pistons is also performed by driving the differential cylinders 2, 3 via the main hydraulic pump 5. The hydraulic circuit 4 also has an auxiliary hydraulic source 6, which is preferably designed as an auxiliary hydraulic pump 6, for driving the differential cylinders 2, 3 when material to be conveyed is pre-compressed in the conveying cylinders by the conveying pistons. The auxiliary hydraulic source 6 may be designed as an auxiliary hydraulic pump 6, as indicated in the figures. Alternatively, the auxiliary hydraulic source 6 can also be designed as a hydraulic accumulator, which is preferably charged by the main hydraulic pump 5 and/or another hydraulic pump. In a particularly preferred embodiment, a hydraulic pump charges the main hydraulic source 5 designed as a hydraulic accumulator and the auxiliary hydraulic source 6 designed as a hydraulic accumulator. Pre-compression advantageously takes place in time between suction of material to be conveyed into the conveying cylinders and discharge of pre-compressed material from the conveying cylinders and ensures continuous conveyance of material to be conveyed by the piston pump. To accelerate the suction of material to be conveyed into the conveying cylinders, the auxiliary hydraulic pump 6 can also additionally pressurize the differential cylinders 2, 3 to drive the conveying pistons. By acting on the differential cylinders 2, 3 to accelerate the suction, the auxiliary hydraulic pump 6 can shorten the suction via the hydraulic circuit 4. The hydraulic circuit 4 shown has two proportional valves 12, 13 by means of which the drive lines 15, 16 between the differential cylinders 2, 3 and the main hydraulic pump 5 can be controlled. With the use of proportional valves 12, 13, the differential cylinders 2, 3 can be slowly pressurized with hydraulic pressure for discharging pre-compressed material from the conveying cylinders. For this purpose, the proportional valves are opened slowly. Furthermore, after the material to be conveyed has been discharged from the conveying cylinders, the proportional valves 12, 13 can be closed slowly to achieve a smooth transition between discharge and suction. To accelerate the pre-compression, the auxiliary hydraulic pump 6 can apply hydraulic pressure to the differential cylinders 2, 3 via two speed mode valves 17, 18. Here, two check valves 10, 11 are each pressed open by the auxiliary hydraulic pump 6. These check valves 10, 11 of the hydraulic circuit 4 close as soon as a pressure is applied during pre-compression that is higher than the pressure provided by the auxiliary hydraulic pump 6. In addition, the hydraulic circuit 4 has two return valves 19, 20, via which the pressureless return flow of hydraulic fluid into a tank 21 can be enabled or blocked. In addition to the drive lines 15, 16 with the proportional valves 12, 13, the hydraulic circuit 4 has a branch 22 in which a flow control valve 14 is arranged. Via two creep mode valves 23, 24, the hydraulic flow of the main hydraulic pump 5 limited via the flow control valve 14 can thus be applied to the differential cylinders 2, 3 of the differential cylinder drive 1, bypassing the proportional valves 12, 13 in the drive lines 15, 16. Via a swing oil supply valve 25, the swing line 9 connecting the rod sides of the differential pistons 7, 8 in the differential cylinders 2, 3 can be supplied with hydraulic fluid by the auxiliary hydraulic pump 6. This additional swing oil may further be drained toward the tank 21 through a swing oil drain valve 26. The hydraulic circuit 4 also preferably has two pressure gauges 27, 28 which measure the pressure in the drive lines 15, 16 upstream of the differential cylinders 2, 3 of the differential cylinder drive 1. For emergency operation, the hydraulic circuit 4 also has two sensors 29, 20 or initiators at the stop of the differential pistons 7, 8 in the differential cylinders 2, 3. Furthermore, the hydraulic circuit 4 preferably has a displacement measuring system 31, 32 for each of the two differential cylinders 2, 3.
[0045] With the hydraulic circuit 4 shown, the piston pump can be driven via the differential cylinder drive 1 in the following cyclically cycled steps: [0046] Suction of material to be conveyed by means of a first conveying cylinder by driving the associated differential cylinder 2, 3 and simultaneous discharge of material to be conveyed by means of a second conveying cylinder by driving the associated differential cylinder 2, 3, [0047] pre-compression of the sucked-in material by means of the first conveying cylinder by driving the associated differential cylinder 2, 3 and simultaneous discharge of the material by means of the second conveying cylinder by driving the associated differential cylinder 2, 3, [0048] discharge of the material by means of the first conveying cylinder by driving the associated differential cylinder 2, 3 and simultaneous suction of material to be conveyed by means of the second conveying cylinder by driving the associated differential cylinder 2, 3, [0049] discharge of the material to be conveyed by means of the first conveying cylinder by driving the associated differential cylinder 2, 3 and simultaneous pre-compression of the sucked material by means of the second conveying cylinder by driving the associated differential cylinder 2, 3,
in order to achieve a continuous conveying of conveyed material by the piston pump. After the pre-compression of the sucked-in material by means of a conveying cylinder by driving the respectively assigned differential cylinder 2, 3 via the hydraulic circuit 4, a discharge of the material by means of the first and the second conveying cylinder can also take place simultaneously by parallel driving of the assigned differential cylinders 2, 3, before a suction of material to be conveyed by means of a conveying cylinder by driving the respectively assigned differential cylinder 2, 3 via the hydraulic circuit 4 is started again. The valve positions in the hydraulic circuit 4 required to operate the piston pump for this purpose are explained with reference to FIGS. 2-7, which show the hydraulic circuit 4 according to FIG. 1 during the individual steps.
[0050] The switching positions of the valves in the hydraulic circuit 4 shown in FIG. 2 provide for suction of material to be conveyed by means of a first conveying cylinder by driving the left differential cylinder 2 and for simultaneous discharge of material to be conveyed by means of a second conveying cylinder by driving the right differential cylinder 3. In the switching positions shown here, the main hydraulic pump 5 supplies hydraulic fluid to the right differential cylinder 3 on the piston side in order to drive the associated conveying cylinder of the piston pump for the discharge of material to be conveyed from the conveying cylinder. For this purpose, the right-hand proportional valve 13 in the right-hand drive line 16 is open and the piston-side effective surfaces of the right-hand differential piston 8 are acted upon by the main hydraulic pump 5 as a result. Via the open swing oil supply valve 25, the left differential piston 7 is additionally acted upon by the auxiliary hydraulic pump 6 to accelerate the suction of material to be conveyed. This additionally accelerates the conveying piston, which is driven by the left differential cylinder 2, during the suction of material to be conveyed. By supplying the rod-side chamber in the differential cylinders 2, 3 with additional swing oil, the piston 7 of the left differential cylinder 2 retracts faster during the suction process. Via the open left return valve 19, the hydraulic fluid displaced by this from the piston side of differential cylinder 2 can simply flow off in the direction of tank 21.
[0051] FIG. 3 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the left differential cylinder 2 is driven for pre-compression of the sucked-in material by means of the first conveying cylinder, while at the same time the right differential cylinder 3 continues to be driven for discharge of the material by means of the second conveying cylinder. In the first phase of pre-compression shown here, the left differential cylinder 2 is driven, i.e. pressurized with hydraulic fluid, by the auxiliary hydraulic pump 6 and the main hydraulic pump 5. For pre-compression of material to be conveyed in the first conveying cylinder, the left differential cylinder 2 is pressurized by the hydraulic circuit 4 through the auxiliary hydraulic pump 6 via a check valve 10 of the hydraulic circuit 4 and simultaneously by the main hydraulic pump 5 via a flow control valve 14 of the hydraulic circuit 4. In this first phase of pre-compression, the auxiliary hydraulic pump 6 provides a higher volume flow of hydraulic fluid at a lower pressure compared to the main hydraulic pump 5 via the hydraulic circuit 4 to drive the left differential cylinder 2. In this case, the auxiliary hydraulic pump 6 presses open the left check valve 10 as long as a pressure is present during pre-compression that is lower than the pressure provided by the auxiliary hydraulic pump 6. Thus, during the pre-compression of material to be conveyed in the conveying cylinder, the left differential cylinder 2 is pressurized by the hydraulic circuit 4 through the auxiliary hydraulic pump 6 via the check valve 10 and at the same time is driven with hydraulic fluid by the main hydraulic pump 5 via a flow control valve 14 of the hydraulic circuit 4. For this purpose, the left creep mode valve 23 is open while the right creep mode valve 24 is closed. The oil from the auxiliary hydraulic pump 6 overcomes the check valve 10 as long as the pre-compression pressure is still low and the oil pressure of the auxiliary hydraulic pump 6 at the check valve 10 is greater than the pressure building up from the main hydraulic pump 5 in the left differential cylinder 2 during pre-compression. As a result, pre-compression is accelerated and pre-compression can be completed before the right differential cylinder 3 reaches the stop when discharging material from the associated conveying cylinder. During this phase, the flow control valve 14 ensures that only a constant minimum amount of hydraulic fluid is used by the main hydraulic pump 5 for pre-compression by the left differential cylinder 2. As a result, the hydraulic fluid pressure drop and thus the flow rate drop for the still pumping right cylinder 3 are minimal when the main hydraulic pump 5 simultaneously contributes to the pre-compression. During pre-compression, the main hydraulic pump 5 could also be readjusted via a control algorithm. The amount of hydraulic fluid withdrawn from the main hydraulic pump 5 for pre-compression may also be readjusted at the main hydraulic pump 5. The flow control valve 14 preferably includes a pressure compensator, so that the pressure difference Δp across the flow control valve 14 always remains constant. Therefore, the quantity flowing over the flow control valve 14 always remains constant, regardless of the level of the pressures upstream and downstream of the flow control valve 14. The excess swing oil in this phase is drained off to the tank 21 via the open swing oil drain valve 26. In order to be able to meter the discharge of the excess swing oil precisely, the swing oil drain valve 26 is preferably designed as a proportional valve.
[0052] FIG. 4 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the left differential cylinder 2 continues to be driven for pre-compression of the sucked-in material by means of the first conveying cylinder, while at the same time the right differential cylinder 3 is also driven for discharge of the material to be conveyed by means of the second conveying cylinder. In the second phase of pre-compression shown here, the left differential cylinder 2 is driven only by the main hydraulic pump 5. The left check valve 10 in the hydraulic circuit 4 closes because the pressure generated during pre-compression is higher than the pressure provided by the auxiliary hydraulic pump 6. The auxiliary hydraulic pump 6 no longer contributes to the pre-compression in this phase, since its hydraulic pressure would be insufficient anyway. This represents the transition from the first phase of pre-compression to the second phase of pre-compression. The main hydraulic pump 5 now continues to increase the pressure in the piston-side chamber of the left differential cylinder 2 on its own while also continuing to supply the right pumping differential cylinder 3. During the second phase of pre-compression of the sucked in material the one conveying cylinder, the left differential cylinder 2 and, for simultaneous discharge of the material from the other conveying cylinder, the right differential cylinder 3 are supplied with equal pressure by the main hydraulic pump 5 via the hydraulic circuit 4. At the end of this second phase of pre-compression, an equal pressure is thereby established in the two differential cylinders 2, 3. At the end of pre-compression, this equal pressure is determined by pressure measurement with pressure gauges 27, 28, so that the transition to the next phase can take place in the next step. At the same time, the pre-compression pressure thus also reaches the conveying line pressure of the concrete, which is why an outlet slide valve on the conveying cylinder can be switched over more easily when there is equal pressure on its inlet and outlet side. The excess swing oil in this phase is discharged to tank 21 via the open swing oil drain valve 26.
[0053] FIG. 5 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. Here, the left proportional valve 12 in the left drive line 15 is opened slowly to realize a particularly smooth transition between pre-compression and discharge of the pre-compressed material via the left differential cylinder 2. At the same time, the right proportional valve 13 in the right drive line 16 is slowly closed so that the right differential cylinder 3 can slowly end the pumping process. In this phase, discharge of the material by means of the first and second conveying cylinders takes place simultaneously by parallel drive of the right-hand 3 and left-hand differential cylinders 2. The excess swing oil in this phase is discharged to the tank 21 via the open swing oil drain valve 26.
[0054] FIG. 6 shows the switching positions of the valves in hydraulic circuit 4 at a subsequent step. Here, the right differential cylinder 3 has reached the stop, which is detected by the displacement sensor 32 and alternatively by the sensor 30. The right proportional valve 13 in the drive line 16 of the right differential cylinder 3 now closes, while the left proportional valve 12 in the drive line 15 of the left differential cylinder 2 is fully open. From now on, the left differential cylinder 2 takes over the pumping operation and the conveyance of material into the conveying line alone, and the right differential cylinder 3 goes over to driving the suction operation for the associated conveying cylinder.
[0055] FIG. 7 shows the switching positions of the valves in the hydraulic circuit 4 in a subsequent step. The switching positions of the valves in the hydraulic circuit 4 shown here provide for discharge of material to be conveyed by means of the first conveying cylinder by driving the left differential cylinder 2 and for simultaneous suction of material to be conveyed by means of the second conveying cylinder by driving the right differential cylinder 3. In the switching positions shown here, the main hydraulic pump 5 supplies hydraulic fluid to the left differential cylinder 2 on the piston side in order to drive the associated conveying cylinder of the piston pump for the discharge of material to be conveyed from the conveying cylinder. For this purpose, the left-hand proportional valve 12 in the left-hand drive line 15 is open and the piston-side effective surface of the left-hand differential piston 7 is acted upon by the main hydraulic pump 5. Via the open swing oil supply valve 25, the right differential piston 8 is additionally acted upon by the auxiliary hydraulic pump 6 to accelerate the suction of material to be conveyed. This additionally accelerates the conveying piston, which is driven by the right differential cylinder 3, during the suction of material to be conveyed. By supplying the rod-side chamber in the differential cylinders 2, 3 with additional swing oil, the piston 8 of the right-hand differential cylinder 3 retracts faster during the suction process. Via the open right return valve 20, the hydraulic fluid displaced by this from the piston side of differential cylinder 3 can simply flow off in the direction of tank 21. After the material to be conveyed has been sucked in by means of the second conveying cylinder by driving the right differential cylinder 3, pre-compression then takes place analogously in the second conveying cylinder via the hydraulic circuit 4.
[0056] FIG. 8 shows a simple pressure relief circuit 33 for auxiliary hydraulic pump 6. The pressure relief circuit 33 shown here has a pressure relief valve 34 downstream of which a pilot valve 35 for high pressure is connected. A pilot valve 37 for low pressure can be used via a changeover circuit 36 to limit the hydraulic pressure of the auxiliary hydraulic pump 6 and to discharge excess hydraulic fluid in the direction of the tank 21. The pressure limiting circuit 33 shown here also has a hydraulic accumulator 38 downstream of which a pressure limiter 39 is connected.
—Reference Sign List—LIST OF REFERENCE SIGNS
[0057] 1 Differential cylinder drive [0058] 2 Differential cylinder L [0059] 3 Differential cylinder R [0060] 4 Hydraulic circuit [0061] 5 Main hydraulic pump (A), main hydraulic source [0062] 6 Auxiliary hydraulic pump (B), auxiliary hydraulic source [0063] 7 Differential piston L [0064] 8 Differential piston R [0065] 9 Swing line [0066] 10 Check valve L (m) [0067] 11 Check valve R (n) [0068] 12 Proportional valve L (a) [0069] 13 Proportional valve R (b) [0070] 14 Flow control valve (I) [0071] 15 Drive line L [0072] 16 Drive line R [0073] 17 speed mode valve L (c) [0074] 18 speed mode valve R (d) [0075] 19 Return valve L (e) [0076] 20 Return valve R (f) [0077] 21 Tank [0078] 22 Branch [0079] 23 Creep mode valve L (g) [0080] 24 Creep mode valve R (h) [0081] 25 swing oil supply valve (i) [0082] 26 swing oil drain valve (k) [0083] 27 Pressure gauge L (o) [0084] 28 Pressure gauge R (p) [0085] 29 Sensor L (q) [0086] 30 Sensor R (r) [0087] 31 displacement measuring system L (s) [0088] 32 displacement measuring system R (t) [0089] 33 Pressure relief circuit [0090] 34 Pressure relief valve [0091] 35 Pilot valve (high pressure) [0092] 36 Changeover circuit [0093] 37 Pilot valve (low pressure) [0094] 38 Hydraulic accumulator [0095] 39 Pressure relief
