Method and device for venting the suction side of a synthetically commutated hydraulic pump

Abstract

The invention relates to a method of venting a synthetically commutated hydraulic pump (2). The connecting fluid conduits (8, 16), connecting said synthetically commutated hydraulic pump (2) with a fluid reservoir (7) is vented at least on start-up of the synthetically commutated hydraulic pump (2), using a fluid intake device (14, 17, 20) that connects to a fixed displacement pump (3).

Claims

1. A fluid working machine arrangement, comprising a synthetically commutated hydraulic fluid working machine, having at least one working chamber with at least one actuated valve, wherein said at least one actuated valve fluidly communicates with a connecting fluid conduit, wherein said connecting fluid conduit comprises at least one venting device that is fluidly connected to a fluid intake device, wherein a high pressure line of the synthetically commutated hydraulic fluid working machine and a high pressure line of the fluid intake device are arranged in parallel, and wherein operation of the fluid intake device on start-up causes air entrapped in a low pressure line of the synthetically commutated hydraulic fluid working machine to enter a low pressure line of the fluid intake device.

2. The fluid working machine arrangement according to claim 1, wherein said synthetically commutated hydraulic fluid working machine comprises a plurality of working chambers, wherein preferably a plurality of working chambers connect to a common connecting fluid conduit.

3. The fluid working machine arrangement according to claim 1, wherein for at least one of said at least one working chamber said at least one actuated valve connects to a common connecting fluid conduit and/or wherein at least part of said synthetically commutated hydraulic fluid working machine is designed as a synthetically commutated hydraulic fluid pump.

4. The fluid working machine arrangement according to claim 1, wherein said synthetically commutated hydraulic fluid working machine comprises at least one working chamber with at least two actuated valves, wherein said at least two actuated valves preferably connect to different connecting fluid conduits.

5. The fluid working machine arrangement according to claim 4, wherein for at least two different connecting fluid conduits each of said fluid conduit comprises a venting device, wherein preferably fluid switches are used to selectively connect to said venting devices with said fluid intake device.

6. The fluid working machine arrangement according to claim 1, wherein said at least one venting device is designed, at least in part, as a fluid orifice and/or as a check valve device and/or as a single way fluid throughput device.

7. The fluid working machine arrangement according to claim 6, wherein said at least one fluid intake device is designed as an active fluid intake device.

8. The fluid working machine arrangement according to claim 7, wherein said synthetically commutated fluid working machine is designed and arranged for use in an open fluid hydraulic circuit and/or in that at least said synthetically commutated fluid working machine fluidly connects to at least a fluid reservoir, either directly and/or indirectly.

9. The fluid working machine arrangement according to claim 7, wherein said at least one fluid intake device is designed and arranged for use in an open fluid hydraulic circuit and/or in that it connects to said at least one venting device and/or to at least one alternative fluid source, in particular to a fluid reservoir.

10. The fluid working machine arrangement according to claim 9, wherein said at least one venting device and/or the fluid connection between said at least one venting device and said fluid intake device comprises a fluid throughput restriction means and/or is designed, at least in part, as a fluid throughput restriction means, wherein said fluid throughput restriction means is preferably a fixed and/or a variable fluid throughput restriction means.

11. The fluid working machine arrangement according to claim 1, wherein said at least one venting device is arranged at least in the vicinity of the locally highest point of the respective connecting fluid conduit.

12. The fluid working machine arrangement according to claim 1, wherein said at least one venting device connects to said synthetically commutated hydraulic fluid working machine.

13. The fluid working machine arrangement according to claim 2, wherein for at least one of said plurality of working chambers said at least one actuated valve connects to a common connecting fluid conduit and/or wherein at least part of said synthetically commutated hydraulic fluid working machine is designed as a synthetically commutated hydraulic fluid pump.

14. The fluid working machine arrangement according to claim 2, wherein said synthetically commutated hydraulic fluid working machine comprises at least one working chamber with at least two actuated valves, wherein said at least two actuated valves preferably connect to different connecting fluid conduits.

15. The fluid working machine arrangement according to claim 2, wherein said at least one venting device is designed, at least in part, as a fluid orifice and/or as a check valve device and/or as a single way fluid throughput device.

16. The fluid working machine arrangement according to claim 3, wherein said at least one venting device is designed, at least in part, as a fluid orifice and/or as a check valve device and/or as a single way fluid throughput device.

17. The fluid working machine arrangement according to claim 4, wherein said at least one venting device is designed, at least in part, as a fluid orifice and/or as a check valve device and/or as a single way fluid throughput device.

18. The fluid working machine arrangement according to claim 5, wherein said at least one venting device is designed, at least in part, as a fluid orifice and/or as a check valve device and/or as a single way fluid throughput device.

19. The fluid working machine arrangement according to claim 7, wherein said at least one fluid intake device is designed as an active fluid intake device taken from the group comprising fluid working machines, fixed displacement fluid working machines, variable displacement fluid working machines, cogwheel fluid working machines, piston fluid working machines, passive-valve fluid working machines, non-synthetically commutated fluid working machines, scroll fluid working machines, Gerotor fluid working machines, fluid pumps, fixed displacement fluid pumps, variable displacement fluid pumps, cogwheel fluid pumps, piston fluid pumps, passive valve fluid pumps, non-synthetically commutated fluid pumps, scroll fluid pumps, and Gerotor fluid pumps.

20. The fluid working machine arrangement according to claim 12, wherein said at least one venting device connects to an interior part of said synthetically commutated hydraulic fluid working machine.

21. The fluid working machine arrangement according to claim 1, wherein the high pressure line of the synthetically commutated hydraulic fluid working machine and the high pressure line of the fluid intake device are configured to connect to different hydraulic consumers.

22. A method of venting a synthetically commutated fluid working machine, wherein at least one connecting fluid conduit, connecting said synthetically commutated fluid working machine with a different hydraulic device, is vented at least at times of a working interval of said synthetically commutated fluid working machine, using a fluid intake device, wherein a high pressure line of the synthetically commutated fluid working machine and a high pressure line of the fluid intake device are arranged in parallel, and wherein operation of the fluid intake device on start-up causes air entrapped in a low pressure line of the synthetically commutated hydraulic fluid working machine to enter a low pressure line of the fluid intake device.

23. The method according to claim 22, wherein it is employed for a fluid working machine arrangement comprising a synthetically commutated hydraulic fluid working machine, having at least one working chamber with at least one actuated valve, wherein said at least one actuated valve fluidly communicates with a connecting fluid conduit, wherein said connecting fluid conduit comprises at least one venting device that is fluidly connected to a fluid intake device.

24. The method according to claim 22, wherein the high pressure line of the synthetically commutated hydraulic fluid working machine and the high pressure line of the fluid intake device are configured to connect to different hydraulic consumers.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages, features, and objects of the invention will be apparent from the following detailed description of the invention in conjunction with the associated drawings, wherein the drawings show:

(2) FIG. 1: a first possible embodiment of a fluid pump arrangement in a schematic view;

(3) FIG. 2: a second possible embodiment of a fluid pump arrangement in a schematic view;

(4) FIG. 3: a third possible embodiment of a fluid pump arrangement in a schematic view;

(5) FIG. 4: a fourth possible embodiment of a fluid working machine arrangement in a schematic view;

(6) FIG. 5: a fifth possible embodiment of a fluid working machine arrangement in a schematic view.

DETAILED DESCRIPTION

(7) In FIG. 1, a fluid pump arrangement 1 is shown in a schematic view. The fluid pump arrangement 1 comprises a synthetically commutated fluid pump 2 (also known as DDP® or Digital Displacement Pump®) and a non-synthetically commutated fluid pump, presently a fixed displacement pump 3.

(8) The synthetically commutated fluid pump 2 comprises a pumping chamber 4 that is defined by a cylindrical cavity 5 and a piston 6 that moves up and down within the cylindrical cavity 5. Therefore, the pumping chamber 4 comprises a repetitively changing volume that is used for pumping hydraulic fluid from a fluid reservoir 7 via a low-pressure line 8 to a high-pressure line 9. The fluid reservoir 7 is essentially at ambient pressure, so the fluid pump arrangement 1 serves a so-called open loop hydraulic circuit.

(9) The synthetically commutated fluid pump 2 design is as such known in the art. An electrically actuated low-pressure valve 10 connects and disconnects the low-pressure line 8 and the pumping chamber 4 selectively. When the piston 6 goes down, the volume of the pumping chamber 4 increases and the low-pressure valve 10 opens due to the pressure differences. When the piston 6 has reached its lower dead centre, the piston 6 will start to move up again, the pumping chamber 4 decreases in volume, and fluid is pushed out of the pumping chamber 4.

(10) If the electrically actuated low-pressure valve 10 is closed by an appropriate actuation signal, pressure will build up in pumping chamber 4 and fluid will be pressurised and ejected through check valve 11 to the high-pressure line 9. However, if no closing signal is applied, the low-pressure valve 10 remains open and fluid in the pumping chamber 4 will be simply pushed back into low-pressure line 8 and fluid reservoir 7 again. Since no significant pressure difference has to be overcome, only very little mechanical energy is consumed in this mode.

(11) As can be seen, the synthetically commutated fluid pump 2 can be switched between a full-stroke mode (closing of the low-pressure valve 10 at the bottom dead centre of the piston 6) and an idle mode (low pressure valve 10 remains open) on a cycle-by-cycle basis.

(12) Furthermore, it is possible to close the electrically actuated low-pressure valve 10 while the piston 6 moves upward and the volume of the pumping chamber 4 contracts. This way, a certain volume being equivalent to a certain fraction of the total volume of the pumping chamber 4 can be pumped towards the high-pressure line 9 (part-stroke mode).

(13) The described situation applies when the synthetically commutated fluid pump 2 operates positively, in particular when the low-pressure line 8 is completely filled with hydraulic oil (or any other type of hydraulic fluid).

(14) However, a different situation can occur, in particular due to the presently depicted geometrical arrangement of the various components of the fluid pump arrangement 1 in which the fluid reservoir 7 is arranged to be lower than the synthetically commutated fluid pump 2. Here, after initial manufacture of the fluid pump arrangement 1 or after an extensive servicing of the fluid pump arrangement 1, the low-pressure line 8 and/or the pumping chamber 4 will be filled with entrapped air, at least to a certain extent. A similar or even the same situation might occur after a somewhat extended shut down period of the fluid pump arrangement 1. A weekend or a one-week holiday break might be sufficient for this situation to occur (as an example). This is because small gaps might be around in the fluid arrangement 1 so that air can enter the various components and hydraulic oil will eventually flow into the fluid reservoir 7. In this context, it should be mentioned that all devices (in particular the synthetically commutated fluid pump 2 and the fixed displacement pump 3) might show a certain fluid leakage, where the leakage oil is usually returned back to the fluid reservoir 7 by means of leakage oil lines (not shown). This usually includes the various hydraulic consumers (not shown) that are served through the high-pressure line 9 of the synthetically commutated fluid pump 2 and/or the fixed displacement pump 3.

(15) When air is entrapped in the low-pressure line 8 and/or the pumping chamber 4, a synthetically commutated fluid pump 2 is normally not able to start pumping hydraulic oil on its own. As already described, this can be due to the fact that the actuated valve 10 closes late or not at all, if a too high content of air is present. Instead, air that is entrapped in the low-pressure line 8 and/or the pumping chamber 4 will simply be pressurised and depressurized. A successive filling of the low-pressure line 8 and/or the pumping chamber 4 with time is normally not (yet) effectuated, in particular if the air content is above a certain critical margin. Once this critical margin has been reached, usually a condition will be reached where the remaining residual air will be successively pumped toward the high-pressure line 9 in the course of several pumping cycles (some kind of a hydraulic oil foam will be pumped).

(16) The fixed displacement pump 3 is arranged in parallel to the synthetically commutated fluid pump 2. In particular, it is possible that both pumps 2, 3 are driven by the same energy source (for example a combustion engine, an electric motor or the like; not shown). However, different energy sources are possible as well, of course.

(17) The fixed displacement pump 3 also intakes oil from the fluid reservoir 7 through a low-pressure line 12 and ejects the pressurised fluid to its high-pressure line 13. While it is possible that the high-pressure line 9 of the synthetically commutated fluid pump 2 and the high-pressure line 13 of the fixed displacement pump 3 are combined to serve the same hydraulic consumer, this is normally not the case. Instead, usually the high-pressure line 13 of the fixed displacement pump 3 serves a different consumer. Usually, a critical hydraulic consumer is served that provides a critical safety feature. An example for this is a hydraulic steering, hydraulic brakes or similar functions of a forklift truck. This also means that the fixed displacement pump 3 may continue to pump irrespective of the fact that the start-up process for the synthetically commutated fluid pump 2 is (sufficiently) sufficiently proceeded/completed. Indeed, the decision on whether the fixed displacement pump 3 pumps, or does not pump (including the fluid flow rate of the pumped fluid) can be based on different considerations, for example on the actual fluid flow requirements by the consumer(s) that is (are) served by the fixed displacement pump 3.

(18) The fixed displacement pump 3 can be essentially of any type. As an example, it could be a cogwheel pump, a Gerotor pump, a standard piston-and-cylinder pump or the like. Furthermore, the fixed displacement pump 3 can be even of a variable pump design (not shown in the present embodiment), for example a wobble plate pump or a swash plate pump.

(19) The fixed displacement pump 3 is of a design that it provides an automatic start-up, i.e. it can pump air as well. Therefore, if air is entrapped in the low-pressure line 12 and/or the fixed displacement pump 3, hydraulic oil that is contained in the fluid reservoir 7 will be successively sucked in, eventually replacing the entrapped air in low-pressure line 12 and/or fixed displacement pump 3. This can easily take several seconds or several tens of seconds (just to name an example). Even if the start-up takes a minute or more this is usually not a problem since such a start-up phase typically only occurs after a comparatively prolonged shutdown time of the arrangement 1. If, for example, such a start-up is necessary after a weekend, such a start-up will only take place once a week. So, a start-up time even in the order of minutes is negligible.

(20) According to the present suggestion, the ability of the fixed displacement pump 3 for a start-up on its own will be used for the synthetically commutated fluid working machine 2.

(21) This is effectuated by a fluid throttle 14 (where the fluid throttle 14 can be of a type with a fixed size of the orifice, but also with a variable size of the orifice, where the size of the orifice can be changed using an appropriate actuator). Usually, however, there is always a certain fluid flow connectivity through the fluid throttle 14 remaining. This reduces the amount of required components. (However, an on-off-functionality might be envisaged as well.) Furthermore, such a design can guarantee a failsafe fallback position: even if the fluid flow through the fluid throttle 14 is very limited, a start-up of the synthetically commutated fluid pump 2 is still possible (although the required time might be comparatively long). The fluid throttle 14 forms part of the venting line 20 that connects the low-pressure line 12 of the fixed displacement pump 3 with the low-pressure line 8 of the synthetically commutated fluid pump 2. The cross-sectional size of the fluid throttle 14 is significantly lower than the cross sections of the two low-pressure lines 8, 12.

(22) On start-up of the fluid pump arrangement 1, the synthetically commutated fluid pump 2 will be initially in a mode where it is “stuck” (i.e. it is not able to start-up on its own due to the air entrapped in the low-pressure lines 8, 12 and/or the pumping chamber 4). The fixed displacement pump 3, however, will successively pump air to the high-pressure line 13, so that at a certain point the low-pressure line 12 will be filled with hydraulic oil. In parallel, a slight amount of air will also pass through the fluid throttle 14. Therefore, low-pressure line 8 of the synthetically commutated fluid pump 2 will eventually fill up with hydraulic oil from the fluid reservoir 7 as well, although this usually takes longer as compared to the filling time of the fixed displacement pump's 3 low-pressure line 12. Nevertheless, at a certain point the amount of entrapped air in the synthetically commutated fluid pump 2 and/or its low-pressure line 8 will be sufficiently low, so that the synthetically commutated fluid pump 2 will start to pump actively. It is to be noted that initially the pumping ability of the synthetically commutated fluid pump 2 is possibly lower as compared to its nominal value, since initially still entrapped residual air is simply pressurised and depressurized. However, with time the content of residual air will fade (normally due to the fact that “hydraulic oil foam” will be pumped by the synthetically commutated fluid pump 2, so that after a certain time span the synthetically commutated fluid pump 2 will be fully vented and will be able to operate at nominal performance.

(23) In other words, an automatic start-up of the fluid pump arrangement, including both the synthetically commutated fluid pump 2 and the fixed displacement pump 3 is possible by virtue of the fluid throttle 14.

(24) In particular, a fluid intake into the fluid throttle 14 may continue, even when the start-up sequence of the synthetically commutated fluid pump 2 is sufficiently proceeded/completed. No on-off-fluid valve is needed for this purpose. The respective fluid passage may be present permanently.

(25) It is to be noted that the start-up time that is required for this embodiment (and other embodiments as well) might have a duration that makes it practically unusable for certain technical applications.

(26) In FIG. 2, a different fluid pump arrangement 15 is shown in a schematic circuitry. Significant parts of the fluid pump arrangement 15 are similar to the fluid pump arrangement 1 according to FIG. 1, so for similar parts (or even identical parts), identical reference numerals are chosen. For brevity, the synthetically commutated fluid pump 2 is not shown in detail, but only as a graphic symbol.

(27) Different from the previous embodiment, a common low-pressure line 16 is used in the present embodiment, through which hydraulic oil is sucked in from the fluid reservoir 7. At branching point 17, the common low-pressure line 16 is split up into two different low-pressure lines 8, 12, serving the synthetically commutated fluid pump 2 and the fixed displacement pump 3, respectively. The branching point 17 is arranged to be at the same level or to be higher than the position of the synthetically commutated fluid pump 2.

(28) On start-up, the fixed displacement pump 3 will start to intake oil from the fluid reservoir 7 through common low-pressure line 16 and “dedicated” low-pressure line 12, replacing the entrapped air, while the synthetically commutated fluid pump 2 will be initially in a “stuck mode”. Due to the positioning of the branching point 17 and the action of the fixed displacement pump 3, the low-pressure line 8, serving the synthetically commutated fluid pump 2, will fill up with hydraulic oil as well, as soon as the oil level reaches and eventually exceeds the height of the branching point 17. Due to this, the synthetically commutated fluid pump 2 will be able to start pumping hydraulic oil “on its own”, albeit initially with a reduced performance due to the residual entrapped air. However, with time, the fluid pump arrangement 15 according to FIG. 2 will fill up completely, resulting in a fully vented arrangement 15 that is able to run at nominal performance.

(29) In particular, a fluid intake through the common low-pressure line 16 (and/or also “dedicated” low-pressure line 12) may continue, even when the start-up sequence of the synthetically commutated fluid pump 2 is sufficiently proceeded/completed. No on-off-fluid valve is needed for this purpose. The respective fluid passage may be present permanently.

(30) In FIG. 3, a fluid pump arrangement 22 is shown that constitutes a slight variation of the fluid pump arrangement 15 according to FIG. 2. The basic difference between the two fluid pump arrangements 15 (FIG. 2) and 22 (FIG. 3) is the rearrangement of the fluid input lines 8, 12, 16, connecting the two fluid pumps 2, 3 to the fluid reservoir 7.

(31) According to the third embodiment of a fluid pump arrangement 22 as shown in FIG. 3, the low-pressure line 12 of fixed displacement pump 3 does not directly connect to the low-pressure line 8 of synthetically commutated fluid pump 2 by means of a branching point 17. Instead, the low-pressure line 12 of fixed displacement pump 3 inputs the fluid from inside the housing 23 of synthetically commutated fluid pump 2. In the presently described embodiment, the fluid intake takes place from the crankcase (not shown) of the synthetically commutated fluid pump 2. However, a different suitable part or area/volume of the synthetically commutated fluid pump 2 could be chosen for the fluid intake into low-pressure line 12 of fixed displacement pump 3 as well. Despite of the different arrangement, the functionality of this design is similar to the design as shown in FIG. 2 and reference is made to the previous description.

(32) In particular, a fluid intake through “dedicated” low-pressure line 12 may continue, even when the start-up sequence of the synthetically commutated fluid pump 2 is sufficiently proceeded/completed. No on-off-fluid valve is needed for this purpose. The respective fluid passage may be present permanently.

(33) A yet other modification of a fluid pump arrangement 24 is shown in FIG. 4. This embodiment is in a certain sense a combination of the embodiments of a fluid pump arrangement 1, 22, as shown in FIGS. 1 and 3, respectively. Namely, the low-pressure line 12 of fixed displacement pump 3 essentially connects to a fluid reservoir 7 (in particular with respect to the maximum achievable fluid flow and/or the tube diameters). However, similar to the embodiment of a fluid pump arrangement 1 as shown in FIG. 1, a branching point is arranged in low-pressure line 12, so that a venting line 20 branches off and connects via fluid throttle 14 (either comprising an orifice of a fixed size and/or an orifice of a variable size, similar to fluid pump arrangement 1 according to FIG. 1) to the synthetically commutated fluid pump 2 (similar to the fluid pump arrangement 22, as shown in FIG. 3). The area/volume, where the fluid intake from synthetically commutated fluid pump 2 is effectuated can be essentially a volume part inside the housing of the synthetically commutated fluid pump 2 that is (particularly) prone to an accumulation of air. In particular, the respective fluid orifice can be arranged at the more or less uppermost part of the respective volume, so that the entrapped air can be removed essentially completely. However, a “vertically lower” arrangement of the orifice can be used as well, as long as a start-up of the synthetically commutated fluid pump 2 can be realised in a sufficiently fast and reliable way.

(34) The advantage of the embodiment of a fluid pump arrangement 24 according to FIG. 4 is that, contrary to the embodiment of a fluid pump arrangement 22 according to FIG. 3, the fixed displacement pump 3 can be used as a hydraulic supply pump for hydraulic consumers (even those necessitating a significant fluid flux). This is due to the fact that a sufficiently high fluid flux can be realised through fixed displacement pump 3 without interfering too much with the interior fluid flow behaviour of synthetically commutated fluid pump 2, since the major part of the fluid flux can originate from fluid reservoir 7 (or a different fluid source).

(35) In particular, a fluid intake through venting line 20, fluid throttle 14 and/or the appropriate section of the low-pressure line 12 may continue, even when the start-up sequence of the synthetically commutated fluid pump 2 is sufficiently proceeded/completed. No on-off-fluid valve is needed for this purpose. The respective fluid passage may be present permanently.

(36) In FIG. 5, another variation of a fluid working machine arrangement 18 is shown. Again, the fluid working machine arrangement 18 shows quite some similarities to the fluid pump arrangements 1, 15 according to FIGS. 1 and 2. Presently, however, the synthetically commutated fluid pump is replaced by a synthetically commutated fluid working machine 19. In the synthetically commutated fluid working machine 19, both low-pressure and high-pressure valves are replaced by electrically actuated valves (which is as such known in the state-of-the-art). When an appropriate actuation of the low-pressure and the high-pressure valves is performed, it is possible to operate the synthetically commutated fluid machine 19 both in a pumping mode (fluid movement from the left to the right in FIG. 5), and in a motoring mode (fluid movement from the right to the left in FIG. 5).

(37) Air might be entrapped on both sides of the synthetically commutated fluid working machine 19, namely in the low-pressure line 8 and the high-pressure line 9 on start-up of the synthetically commutated fluid working machine 19, leading to a “stuck condition”. Therefore, a venting line 20a, 20b connects to low-pressure line 8 and high-pressure line 9, respectively. The venting lines 20a, 20b fluidly connects the low-pressure line 8/the high-pressure line 9 to the low-pressure line 12 of the fixed displacement pump 3 through fluid throttle 14. As previously discussed, low-pressure line 12 will be successively filled with hydraulic oil, thus replacing any air in low-pressure line 12 that is present on start-up of the fixed displacement pump 3.

(38) Depending on the operating mode 19 of the synthetically commutated fluid working machine 19, a shuttle valve 21 is switched to an appropriate position, so that the appropriate venting line 20a, 20b connects the current intake side of the synthetically commutated fluid working machine 19 with the low-pressure line 12 through fluid throttle 14. Therefore, the current fluid intake line 8, 9 can be vented, so that a start-up of the synthetically commutated fluid working machine 19 is possible.

(39) In particular, a fluid intake through (one of) the venting line(s) 20a, 20b into the fluid throttle 14 may continue, even when the start-up sequence of the synthetically commutated fluid pump 2 is sufficiently proceeded/completed. No on-off-fluid valve is needed for this purpose. The respective fluid passage may be present permanently.

(40) In the present context, it should be mentioned that the synthetically commutated fluid working machine 19 can be operated as a pump and/or as a motor in both directions. Therefore, a mode is possible as well, in which fluid is actively transported from the right side to the left side by means of synthetically fluid working machine 19, so that the pressure in the high-pressure line 9 can be even lower as compared to the pressure on the low-pressure line 8 under certain operating conditions. Therefore, a venting on both sides of the synthetically commutated fluid working machine 19 might prove to be essential.

(41) While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.