EP3045736A1 - Hydraulic actuators - Google Patents
Hydraulic actuators Download PDFInfo
- Publication number
- EP3045736A1 EP3045736A1 EP15275009.7A EP15275009A EP3045736A1 EP 3045736 A1 EP3045736 A1 EP 3045736A1 EP 15275009 A EP15275009 A EP 15275009A EP 3045736 A1 EP3045736 A1 EP 3045736A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- hydraulic actuator
- assembly
- accumulator
- hydraulic
- motor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/027—Installations or systems with accumulators having accumulator charging devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B1/00—Installations or systems with accumulators; Supply reservoir or sump assemblies
- F15B1/02—Installations or systems with accumulators
- F15B1/022—Installations or systems with accumulators used as an emergency power source, e.g. in case of pump failure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B20/00—Safety arrangements for fluid actuator systems; Applications of safety devices in fluid actuator systems; Emergency measures for fluid actuator systems
- F15B20/004—Fluid pressure supply failure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
- F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
- F15B2211/7051—Linear output members
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B2211/00—Circuits for servomotor systems
- F15B2211/80—Other types of control related to particular problems or conditions
- F15B2211/875—Control measures for coping with failures
- F15B2211/8752—Emergency operation mode, e.g. fail-safe operation mode
Definitions
- the present invention relates to hydraulic actuators and hydraulic actuator systems.
- the present invention relates in particular to, but is not limited to, hydraulic actuators and hydraulic actuator systems for aircraft.
- hydraulic actuators for example in aircraft, are well established. For example, they are used for flight control applications such as moving control flaps, for landing gear extension and retraction, and so on.
- a plurality of actuators are coupled to a common hydraulic circuit that comprises a reservoir and a pump.
- An advantage of hydraulic actuators is the ability to provide a relatively high power density.
- a disadvantage of the above described arrangements is that servicing or replacement of individual actuators can be relatively complex due to the possibility of requiring to bleed, flush and replenish the whole hydraulic circuit.
- the present inventor has realised that in many applications, although a relatively high power density is required or desirable, this does not need to be continually available.
- the invention provides a hydraulic charging and driving system for extending and retracting a hydraulic actuator, comprising: a motor assembly; and an accumulator assembly, the motor assembly and the accumulator assembly being hydraulically coupled to each other; wherein the motor assembly is arranged to recharge the accumulator assembly with hydraulic fluid at a relatively slow rate that is slower than the rate at which the accumulator assembly is arranged to discharge when actuating the hydraulic actuator.
- the system may further comprise a selector valve.
- the accumulator assembly may comprise an accumulator chamber, and a compression means provided within the accumulator chamber.
- the motor assembly may comprise a motor arranged to vary a volume of a hydraulic charging chamber of the motor assembly.
- the system may further comprise a hydraulic actuator comprising a bottom chamber and a piston-side chamber; wherein the accumulator assembly may be hydraulically coupled to the bottom chamber via a first setting of the selector valve to provide extension of the hydraulic actuator.
- the accumulator assembly may be further hydraulically coupled to the piston-side chamber, in addition to being hydraulically coupled to the bottom chamber, via the first setting of the selector valve to provide extension of the hydraulic actuator.
- the piston-side chamber may be hydraulically coupled to the motor assembly via a further setting of the selector valve to provide retraction of the hydraulic actuator.
- the system may further comprise an emergency assembly arranged to provide at least emergency extension of the hydraulic actuator.
- the invention provides a method of operating a hydraulic system comprising a hydraulic actuator, a selector valve, and a motor assembly and an accumulator assembly hydraulically coupled in a hydraulic circuit; the method comprising: hydraulically extending the hydraulic actuator; thereafter, recharging the accumulator assembly with hydraulic fluid via the hydraulic circuit at a relatively slow recharge rate such that the recharge takes longer than the time taken to extend the hydraulic actuator.
- the step of recharging the accumulator assembly with hydraulic fluid may be performed by a motor of the motor assembly varying a volume of a hydraulic charging chamber of the motor assembly.
- the step of hydraulically extending the hydraulic actuator may be performed by hydraulically coupling the accumulator assembly to a bottom chamber of the hydraulic actuator by setting the selector valve to a first setting.
- the step of hydraulically extending the hydraulic actuator may be performed by, in addition to hydraulically coupling the accumulator assembly to a bottom chamber of the hydraulic actuator, also hydraulically coupling the accumulator assembly to the piston-side chamber, by setting the selector valve to the first setting.
- the method may further comprise hydraulically retracting the hydraulic actuator.
- the method may further comprise, after hydraulically retracting the hydraulic actuator, recharging the accumulator assembly with hydraulic fluid via the hydraulic circuit at a relatively slow recharge rate such that the recharge takes longer than the time taken to retract the hydraulic actuator.
- the method may further comprise performing at least an emergency extension of the hydraulic actuator.
- Figure 1 is a schematic illustration (not to scale) of a first embodiment of a hydraulic actuator system 1.
- the hydraulic actuator system 1 comprises a linear hydraulic actuator 2 that is hydraulically coupled to a hydraulic charging and driving system 4 adapted to hydraulically charge the linear hydraulic actuator 2.
- the linear hydraulic actuator 2 comprises a cylinder barrel 6, a piston (which may also be termed an actuator valve) 8, and a piston rod 10 attached to the piston 8.
- the piston is arranged to be able to move back and forth along the cylinder barrel 6.
- the cylinder barrel 6 is closed at one end by a cylinder base (which may also be termed cap) 12.
- the cylinder barrel 6 is closed at its other end by a cylinder head 14 where the piston rod 10 comes out of the cylinder barrel 6.
- the piston 8 divides the inside of the cylinder barrel 6 into two chambers, namely a bottom chamber 16 at the cylinder base 12 side of the piston 8 and a piston rod side chamber 18 at the cylinder head 14 side of the piston 8.
- the piston 8 is provided with sliding rings and seals (not shown).
- the piston rod 10 is provided with an actuator load connector 19, for connecting the moving piston rod 10 with the load that is to be moved by operation of the linear hydraulic actuator 2.
- the hydraulic charging and driving system 4 comprises an accumulator assembly 20, a motor assembly 22, a three-position selector valve 24, and an optional emergency assembly 26.
- a hydraulic circuit 28 hydraulically couples the above described elements as follows: the accumulator assembly 20 is hydraulically coupled to the motor assembly and the three-position selector valve 24.
- the motor assembly 22 is further coupled to the three-position selector valve 24.
- the three-position selector valve 24 is further coupled to the emergency assembly 26 and the linear hydraulic actuator 2.
- the emergency assembly 26 is further coupled to the linear hydraulic actuator 2.
- the accumulator assembly 20 comprises an accumulator cylinder 30 and a bellows 32.
- the bellows 32 is provided within the accumulator cylinder 30.
- the accumulator assembly 20 is further provided with a pressure switch (not shown).
- the motor assembly 22 comprises a motor assembly cylinder 34.
- a floating piston 36 is provided within the motor assembly cylinder 34.
- the floating piston 36 is arranged to be able to move back and forth along the motor assembly cylinder 34.
- the floating piston 36 divides the inside of the motor assembly cylinder 34 into two chambers, namely a charging chamber 38 and an air chamber 40.
- the piston 8 is provided with sliding rings and seals (not shown).
- the motor assembly further comprises a motor and a lead screw 44 coupled to the motor 42.
- the motor 42 drives the lead screw 44 in an inward direction inside the motor assembly cylinder 34 to push the floating piston 36 along the inside of the motor assembly cylinder 34 (thereby reducing the volume of the charging chamber 38), and at certain other stages of operation the motor 42 retracts the lead screw 44 in an outward direction inside the motor assembly cylinder 34 to thereby leave the floating piston 36 in floating mode.
- the motor assembly 22 is further provided with two pre-set retract switches, namely a first retract switch 82 at a first retract position 83, and a second retract switch 84 at a second retract position 85.
- the two retract switches with their respective differing retract positions provide for the end of the led screw 44 and consequently the position of the floating piston 36 to have two available floating positions each of which is used at different stages of operation when the charging chamber 38 is to be filled, thereby providing two different volumes of hydraulic liquid in the charging chamber 38, one of which is used when setting the hydraulic actuator system 1 in a ready-to-retract status, and the other one of which is used when setting the hydraulic actuator system 1 in a ready-to-extend status, thereby accommodating the difference in volume between the maximum volume of the bottom chamber 16 of the cylinder barrel 6 and the maximum volume of the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 provides links (or blocks the potential links) between lengths of the hydraulic circuit 28 so as to hydraulically connect (or block connection of) the accumulator cylinder 30 or the charging chamber 38 to the bottom chamber 16 of the cylinder barrel 6 or the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 is adjustable between three positions, namely a first open position 50, a closed position 52, and a second open position 54.
- the accumulator cylinder 30 is connected to the bottom chamber 16 of the cylinder barrel 6, and the charging chamber 38 is connected to the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 When, instead, the three-position selector valve 24 is in the closed position 52, there is no connection between the accumulator cylinder 30 and either of the bottom chamber 16 of the cylinder barrel 6 or the piston rod side chamber 18 of the cylinder barrel 6, and also there is no connection between the charging chamber 38 and either of the bottom chamber 16 of the cylinder barrel 6 or the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 is in the second open position 54, the accumulator cylinder 30 is connected to the piston rod side chamber 18 of the of the cylinder barrel 6, and the charging chamber 38 is connected to the bottom chamber 16 of the cylinder barrel 6. It is noted that in Figure 1 the three-position selector valve 24 is in the closed position 52.
- the optional emergency assembly 26 comprises an accumulator cylinder 60 and a bellows 64, for convenience termed herein an emergency cylinder 60 and an emergency bellows 64, respectively.
- the emergency assembly 26 is hydraulically coupled to the hydraulic circuit 28 via an emergency extend valve 66.
- the emergency bellows 64 is compressed, with the emergency cylinder 60 therefore at its maximum volume and full of hydraulic fluid available for insertion into the linear hydraulic actuator 2 in the event of failure of the main operation of the hydraulic actuator system 1, as will be described later below with reference to Figure 10 .
- the hydraulic circuit 28 further connects the accumulator cylinder 30 to the charging chamber 38 via a first shuttle valve 70. Also, the hydraulic circuit 28 further connects the bottom chamber 16 of the cylinder barrel 6 to the emergency extend valve 66 of the emergency assembly 26 via a second shuttle valve 72.
- Figure 2 is a process flowchart showing certain steps of a cyclic method of actuation using the hydraulic actuator system 1.
- Figure 1 and Figures 3 to 9 show the hydraulic actuator system 1 at respective stages of the method of Figure 2 .
- Figure 10 shows the hydraulic actuator system 1 when an optional emergency actuation process is carried out using the above described optional emergency assembly 26.
- the hydraulic actuator system 1 is in a retracted state ready for extension (i.e. ready to extend the piston rod 10).
- the bottom chamber 16 of the cylinder barrel 6 is in its lowest volume state, and the bellows 32 of the accumulator assembly 20 are at their minimum extension, hence the accumulator cylinder 30 is in its largest volume state.
- the three position valve 24 is in the earlier described closed position 52.
- the lead screw 44 is in one of its retracted positions, more particularly the first retract position 83, i.e. the lead screw 44 has previously been moved in an outward direction inside the motor assembly cylinder 34 until movement was stopped by the first retract switch 82 due to the end of the lead screw 44 reaching the first retract position 83, to thereby leave the floating piston 36 in floating mode.
- step s4 the three position valve 24 is moved to the earlier described first open position 50. Consequently the bellows 32 of the accumulator assembly 20 extend and hydraulic fluid flows in the hydraulic circuit 28 with a net effect of flowing from the accumulator cylinder 30 via the three position valve 24 to the bottom chamber 16 of the cylinder barrel 6, and from the piston rod side 18 of the cylinder barrel 6 via the three position valve 24 to the charging chamber 38 of the accumulator assembly 20. As a result, the piston rod 10 of the linear hydraulic actuator 2 extends, and also the floating piston 36 of the accumulator assembly 20 is repositioned at the end of the retracted lead screw 44, i.e. at the first retract position 83.
- step s4 may be summarised as the three position valve 24 being moved to an extend position (the first open position 50) thereby leading to extension of the actuator under charge pressure.
- the resulting state of the hydraulic actuator system 1 is shown in Figure 3 .
- step s6 the three position valve 24 is moved to the earlier described closed position 50.
- step s6 may be summarised as the three position valve 24 being reset to neutral position.
- the resulting state of the hydraulic actuator system 1 is shown in Figure 4 .
- the motor 42 of the accumulator assembly 20 is used to drive the lead screw 44 in an inward direction into the motor assembly cylinder 34, thereby pushing the floating piston 36 against the hydraulic fluid in the motor assembly cylinder 34 thereby transferring the hydraulic fluid in the motor assembly cylinder 34 into the accumulator cylinder 30 via the shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging the accumulator cylinder 30.
- the pressure switch (not shown) of the accumulator cylinder 30 signals the motor 42 to stop driving the lead screw in the inward direction (and instead, to thereafter commence the retreat motion described below as part of step s10).
- the motor 42 may be a relatively small motor i.e.
- step s8 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly).
- the resulting state of the hydraulic actuator system 1 is shown in Figure 5 .
- step s10 the motor 42 retracts the lead screw 44 in an outward direction inside the motor assembly cylinder 34 until the second retract switch 84 stops the retraction of the lead screw 44 when the end of the lead screw 44 reaches the second retract position 85, to thereby leave the floating piston 36 in floating mode.
- the hydraulic actuator system 1 is put in in a state that is ready for retraction of the actuator i.e. ready for retraction of the piston rod 10.
- step s10 may be summarised as resetting the lead screw 44 thereby making the hydraulic actuator system ready for retraction.
- the resulting "ready for retraction" state of the hydraulic actuator system 1 is shown in Figure 6 .
- step s12 the three position valve 24 is moved to the earlier described second open position 54. Consequently the bellows 32 of the accumulator assembly 20 extend and hydraulic fluid flows in the hydraulic circuit 28 with a net effect of flowing from the accumulator cylinder 30 via the three position valve 24 to the piston rod side 18 of the cylinder barrel 6, and from the bottom chamber 16 of the cylinder barrel 6 via the three position valve 24 to the charging chamber 38 of the accumulator assembly 20. As a result, the piston rod 10 of the linear hydraulic actuator 2 retracts, and also the floating piston 36 of the accumulator assembly 20 is repositioned at the end of the retracted lead screw 44, i.e. at the second retract position 85.
- step s12 may be summarised as the three position valve 24 being moved to a retract position (the second open position 54) thereby leading to retraction of the actuator under charge pressure.
- the resulting state of the hydraulic actuator system 1 is shown in Figure 7 .
- step s14 the three position valve 24 is moved to the earlier described closed position 50.
- step s14 may be summarised as the three position valve 24 being reset to neutral position.
- the resulting state of the hydraulic actuator system 1 is shown in Figure 8 .
- the motor 42 of the accumulator assembly 20 is used to drive the lead screw 44 in an inward direction into the motor assembly cylinder 34, thereby pushing the floating piston 36 against the hydraulic fluid in the motor assembly cylinder 34 thereby transferring the hydraulic fluid in the motor assembly cylinder 34 into the accumulator cylinder 30 via the shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging the accumulator cylinder 30.
- the motor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes.
- this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s4, which may only, for example, take less than thirty seconds, or may even take less than ten seconds and likewise compared to the time for the actuator retraction step s12 also described above).
- step s16 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, as stated above, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly).
- the resulting state of the hydraulic actuator system 1 is shown in Figure 9 .
- step s18 the motor 42 retracts the lead screw 44 in an outward direction inside the motor assembly cylinder 34 until the first retract switch 82 stops the retraction of the lead screw 44 when the end of the led screw 44 reaches first retract position 83, to thereby leave the floating piston 36 in floating mode.
- step s18 may be summarised as resetting the lead screw 44 thereby making the hydraulic actuator system ready for extension.
- the resulting "ready for extension" state of the hydraulic actuator system 1 is the same state as described at step s2 and already shown in Figure 1 , i.e. the hydraulic actuator system 1 is back at the Figure 1 state of its cyclic operational capability, and accordingly any or all of steps s4 to s18 may be repeated if desired.
- an optional emergency actuation process is provided using the above described optional emergency assembly 26, as described in the following paragraph.
- the optional emergency assembly is not included in the hydraulic actuator system 1.
- an emergency assembly is provided, however it is of a different arrangement to that described below.
- FIG 10 shows the hydraulic actuator system 1 implementing the optional emergency assembly 26 in order to carry out an emergency extension of the actuator.
- the emergency extend valve 66 is activated to allow the emergency bellows 64 to expand thereby pushing the hydraulic fluid in the emergency cylinder 60 from the emergency cylinder 60 into the bottom chamber 16 of the cylinder barrel 6.
- the piston rod 10 of the linear hydraulic actuator 2 extends.
- Figure 11 is a schematic illustration (not to scale) of a further embodiment of a hydraulic actuator system 101.
- the hydraulic actuator system 101 comprises a linear hydraulic actuator 2 that is hydraulically coupled to a hydraulic charging and driving system 4 adapted to hydraulically charge the linear hydraulic actuator 2.
- the linear hydraulic actuator 2 comprises a cylinder barrel 6, a piston (which may also be termed an actuator valve) 8, and a piston rod 10 attached to the piston 8.
- the piston is arranged to be able to move back and forth along the cylinder barrel 6.
- the cylinder barrel 6 is closed at one end by a cylinder base (which may also be termed cap) 12.
- the cylinder barrel 6 is closed at its other end by a cylinder head 14 where the piston rod 10 comes out of the cylinder barrel 6.
- the piston 8 divides the inside of the cylinder barrel 6 into two chambers, namely a bottom chamber 16 at the cylinder base 12 side of the piston 8 and a piston rod side chamber 18 at the cylinder head 14 side of the piston 8.
- the piston 8 is provided with sliding rings and seals (not shown).
- the piston rod 10 is provided with an actuator load connector 19, for connecting the moving piston rod 10 with the load that is to be moved by operation of the linear hydraulic actuator 2.
- the hydraulic charging and driving system 4 comprises an accumulator assembly 20, a motor assembly 22, a three-position selector valve 24, and an optional emergency assembly 26.
- a hydraulic circuit 28 hydraulically couples the above described elements as follows: the accumulator assembly 20 is hydraulically coupled to the motor assembly 22, the three-position selector valve 24, and the optional emergency assembly 26.
- the motor assembly 22 is further coupled to the three-position selector valve 24 and the optional emergency assembly 26.
- the three-position selector valve 24 is further coupled to the emergency assembly 26 and the linear hydraulic actuator 2.
- the emergency assembly 26 is further coupled to the linear hydraulic actuator 2.
- the accumulator assembly 20 comprises an accumulator cylinder 30 and a bellows 32.
- the bellows 32 is provided within the accumulator cylinder 30.
- the accumulator assembly 20 is further provided with a pressure switch (not shown).
- the motor assembly 22 comprises a motor assembly cylinder 34.
- a floating piston 36 is provided within the motor assembly cylinder 34.
- the floating piston 36 is arranged to be able to move back and forth along the motor assembly cylinder 34.
- the floating piston 36 divides the inside of the motor assembly cylinder 34 into two chambers, namely a charging chamber 38 and an air chamber 40.
- the piston 8 is provided with sliding rings and seals (not shown).
- the motor assembly further comprises a motor and a lead screw 44 coupled to the motor 42.
- the motor 42 drives the lead screw 44 in an inward direction inside the motor assembly cylinder 34 to push the floating piston 36 along the inside of the motor assembly cylinder 34 (thereby reducing the volume of the charging chamber 38), and at certain other stages of operation the motor 42 retracts the lead screw 44 in an outward direction inside the motor assembly cylinder 34 to thereby leave the floating piston 36 in floating mode.
- the motor assembly 22 is further provided with two pre-set retract switches, namely a first retract switch 82 at a first retract position 83, and a second retract switch 84 at a second retract position 85.
- the two retract switches with their respective differing retract positions provide for the end of the led screw 44 and consequently the position of the floating piston 36 to have two available floating positions each of which is used at different stages of operation when the charging chamber 38 is to be filled, thereby providing two different volumes of hydraulic liquid in the charging chamber 38, one of which is used when setting the hydraulic actuator system 101 in a ready-to-retract status, and the other one of which is used when setting the hydraulic actuator system 101 in a ready-to-extend status, thereby accommodating the difference in volume between the maximum volume of the bottom chamber 16 of the cylinder barrel 6 and the maximum volume of the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 provides links (or blocks the potential links) between lengths of the hydraulic circuit 28 so as to hydraulically connect (or block connection of) the accumulator cylinder 30 or the charging chamber 38 to the bottom chamber 16 of the cylinder barrel 6 or the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 is adjustable between three positions, namely a first open position 50, a closed position 52, and a second open position 54.
- the accumulator cylinder 30 is connected to both the bottom chamber 16 of the cylinder barrel 6 and to the piston rod side chamber 18 of the cylinder barrel 6.
- the three-position selector valve 24 is in the closed position 52, there is no connection between the bottom chamber 16 of the cylinder barrel 6 and either of the accumulator cylinder 30 and the charging chamber 38, and also there is no connection between the piston rod side chamber 18 of the cylinder barrel 6 and either of the accumulator cylinder 30 and the charging chamber 38.
- the accumulator cylinder 30 is connected to the piston rod side chamber 18 of the of the cylinder barrel 6, and the charging chamber 38 is connected to the bottom chamber 16 of the cylinder barrel 6. It is noted that in Figure 11 the three-position selector valve 24 is in the closed position 52.
- the optional emergency assembly 26 comprises an accumulator cylinder 60 and a bellows 64, for convenience termed herein an emergency cylinder 60 and an emergency bellows 64, respectively.
- the emergency bellows 64 is provided within the emergency accumulator cylinder 60.
- the optional emergency assembly 26 is further provided with a pressure switch (not shown).
- the emergency assembly 26 is hydraulically coupled to the hydraulic circuit 28 via an emergency extend valve 66 and via an emergency charge valve 80.
- the emergency bellows 64 is compressed, with the emergency accumulator cylinder 60 therefore at its maximum volume and full of hydraulic fluid available for insertion into the linear hydraulic actuator 2 in the event of failure of the main operation of the hydraulic actuator system 101, as will be described later below with reference to Figures 19 and 20 .
- the hydraulic circuit 28 further connects the accumulator cylinder 30 to the charging chamber 38 via a first shuttle valve 70. Also, the hydraulic circuit 28 further connects the bottom chamber 16 of the cylinder barrel 6 to the emergency extend valve 66 of the emergency assembly 26 via a second shuttle valve 72. Also, the hydraulic circuit 28 further connects the piston rod side chamber 18 of the cylinder barrel 6 to the emergency extend valve 66 of the emergency assembly 26 via a third shuttle valve 73.
- Figure 12 is a process flowchart showing certain steps of a cyclic method of actuation using the hydraulic actuator system 101.
- Figure 11 and Figures 13 to 18 show the hydraulic actuator system 101 at respective stages of the method of Figure 12 .
- Figures 19 and 20 show the hydraulic actuator system 101 when an optional emergency actuation process is carried out using the above described optional emergency assembly 26.
- the hydraulic actuator system 101 is in a retracted state ready for extension (i.e. ready to extend the piston rod 10).
- the bottom chamber 16 of the cylinder barrel 6 is in its lowest volume state, and the bellows 32 of the accumulator assembly 20 are at their minimum extension, hence the accumulator cylinder 30 is in its largest volume state.
- the three position valve 24 is in the earlier described closed position 52.
- the lead screw 44 is in one of its retracted positions, more particularly the first retract position 83, i.e. the lead screw 44 has previously been moved in an outward direction inside the motor assembly cylinder 34 until movement was stopped by the first retract switch 82 due to the end of the lead screw 44 reaching the first retract position 83, to thereby leave the floating piston 36 in floating mode.
- step s104 the three position valve 24 is moved to the earlier described first open position 50. Consequently the bellows 32 of the accumulator assembly 20 extend and hydraulic fluid flows in the hydraulic circuit 28 with a net effect of flowing from the accumulator cylinder 30 via the three position valve 24 to the bottom chamber 16 of the cylinder barrel 6, and, in this embodiment, additionally also from the piston rod side 18 of the cylinder barrel 6 via the three position valve 24 to the bottom chamber 16 of the cylinder barrel 6.
- the piston rod 10 of the linear hydraulic actuator 2 extends, and in this embodiment during this step position of the floating piston 36 of the accumulator assembly 20 remains at the end of the retracted lead screw 44, i.e. at the first retract position 83.
- step s104 may be summarised as the three position valve 24 being moved to an extend position (the first open position 50) thereby leading to extension of the actuator under charge pressure.
- the resulting state of the hydraulic actuator system 101 is shown in Figure 13 .
- step s106 the three position valve 24 is moved to the earlier described closed position 50.
- step s106 may be summarised as the three position valve 24 being reset to neutral position.
- the resulting state of the hydraulic actuator system 101 is shown in Figure 14 .
- the motor 42 of the accumulator assembly 20 is used to drive the lead screw 44 in an inward direction into the motor assembly cylinder 34, thereby pushing the floating piston 36 against the hydraulic fluid in the motor assembly cylinder 34 thereby transferring the hydraulic fluid in the motor assembly cylinder 34 into the accumulator cylinder 30 via the first shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging the accumulator cylinder 30.
- the pressure switch (not shown) of the accumulator cylinder 30 signals the motor 42 to stop driving the lead screw in the inward direction (and instead, to thereafter commence the retreat motion described below as part of step s110).
- the motor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes.
- this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s104, which may only, for example, take less than thirty seconds, or may even take less than ten seconds (and likewise compared to the time for the actuator retraction step s112 described later below).
- step s108 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly).
- the resulting state of the hydraulic actuator system 101 is shown in Figure 15 .
- step s110 the motor 42 retracts the lead screw 44 in an outward direction inside the motor assembly cylinder 34 until the second retract switch 84 stops the retraction of the lead screw 44 when the end of the lead screw 44 reaches the second retract position 85, to thereby leave the floating piston 36 in floating mode.
- the hydraulic actuator system 101 is put in in a state that is ready for retraction of the actuator i.e. ready for retraction of the piston rod 10.
- step s110 may be summarised as resetting the lead screw 44 thereby making the hydraulic actuator system 101 ready for retraction.
- the resulting "ready for retraction" state of the hydraulic actuator system 101 is shown in Figure 16 .
- the three position valve 24 is moved to the earlier described second open position 54. Consequently the bellows 32 of the accumulator assembly 20 extend and hydraulic fluid flows in the hydraulic circuit 28 with a net effect of flowing from the accumulator cylinder 30 via the three position valve 24 to the piston rod side 18 of the cylinder barrel 6, and from the bottom chamber 16 of the cylinder barrel 6 via the three position valve 24 to the charging chamber 38 of the accumulator assembly 20.
- the piston rod 10 of the linear hydraulic actuator 2 retracts, and also the floating piston 36 of the accumulator assembly 20 is repositioned at the end of the retracted lead screw 44, i.e. at the second retract position 85.
- step s112 may be summarised as the three position valve 24 being moved to a retract position (the second open position 54) thereby leading to retraction of the actuator under charge pressure.
- the resulting state of the hydraulic actuator system 101 is shown in Figure 17 .
- step s114 the three position valve 24 is moved to the earlier described closed position 50.
- step s114 may be summarised as the three position valve 24 being reset to neutral position.
- the resulting state of the hydraulic actuator system 101 is shown in Figure 108.
- the motor 42 of the accumulator assembly 20 is used to drive the lead screw 44 in an inward direction into the motor assembly cylinder 34, thereby pushing the floating piston 36 against the hydraulic fluid in the motor assembly cylinder 34 thereby transferring the hydraulic fluid in the motor assembly cylinder 34 into the accumulator cylinder 30 via the first shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging the accumulator cylinder 30.
- the motor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes.
- this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s104, which may only, for example, take less than thirty seconds, or may even take less than ten seconds and likewise compared to the time for the actuator retraction step s112 also described above).
- step s116 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, as stated above, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly).
- the hydraulic actuator system 101 is now in a state that is ready for extension of the actuator i.e. ready for extension of the piston rod 10.
- This "ready for extension" state of the hydraulic actuator system 101 is the same state as described at step s102 and already shown in Figure 11 , i.e. the hydraulic actuator system 101 is back at the Figure 11 state of its cyclic operational capability, and accordingly any or all of steps s104 to s116 may be repeated if desired.
- an optional emergency actuation process is provided using the above described optional emergency assembly 26, as described in the following two paragraphs.
- the optional emergency assembly is not included in the hydraulic actuator system 101.
- an emergency assembly is provided, however it is of a different arrangement to that described below.
- FIG 19 shows the hydraulic actuator system 101 implementing the optional emergency assembly 26 in order to carry out an emergency extension of the actuator.
- the emergency extend valve 66 is activated to allow the emergency bellows 64 to expand thereby pushing the hydraulic fluid in the emergency cylinder 60 from the emergency cylinder 60 into the bottom chamber 16 of the cylinder barrel 6, flow through the second shuttle valve 72 taking place due to the additional hydraulic pressure.
- the piston rod 10 of the linear hydraulic actuator 2 extends.
- An advantage of the above described hydraulic actuator system 1 is that it further optionally allows the emergency assembly 26 to be rechargeable (although this does not need to be the case in other embodiments).
- Figure 20 shows the hydraulic actuator system 101 implementing such an optional recharge of the optional emergency assembly 26 having previously performed the emergency extend process described in the preceding paragraph.
- the emergency extend valve 66 is returned to closed position, and the emergency charge valve 80 is opened.
- the motor 42 of the accumulator assembly 20 is used to drive the lead screw 44 in an inward direction into the motor assembly cylinder 34, thereby pushing the floating piston 36 against the hydraulic fluid in the motor assembly cylinder 34 thereby transferring the hydraulic fluid in the motor assembly cylinder 34 into the emergency cylinder 60 via the first shuttle valve 70 and the now open emergency charge valve 80 (this fluid compressing the emergency bellows 64) thereby recharging the emergency cylinder 60.
- the pressure switch (not shown) of the emergency cylinder 60 signals the motor 42 to stop driving the lead screw in the inward direction.
- the resulting state of the hydraulic actuator system 101 is shown in Figure 15 .
- the charge valve 80 is returned to closed position, leaving the hydraulic actuator system 101 in the same state as that at the end of step s108 as described above i.e. in the same state as that shown in Figure 15 .
- An advantage of the above described embodiments is that, whilst nevertheless only requiring relatively low powered motors (due to the approach of charging the accumulator over a time span greater than the operating time of the actuator), single modular hydraulic actuators can be provided, rather than one large overall hydraulic circuit, and thus servicing or replacement of individual actuators can be reduced in complexity due to avoiding or alleviating the need to to bleed, flush and replenish the whole hydraulic circuit. Furthermore, the aspect of charging the accumulator over a time span greater than the operating time of the actuator is acceptable for many applications, for example deployment of landing gear where an "up" request would not normally be followed by a “down request” and vice versa, aircraft door opening/closing, and so on.
- valves, and/or pressure switches and/or position switches may be omitted or modified with either resulting diminished performance or efficiency, or in other cases, no diminution of performance, for example if alternative elements and arrangements are provided.
- any cylinders may be replaced by alternative shaped chambers.
- the details of the linear hydraulic actuator may be changed, by use of other forms of hydraulic actuator that nevertheless benefit from the remaining details of the above described embodiments of hydraulic actuator systems.
- alternative switching arrangements are provided instead of the particular three position selector valve apparatus and arrangements used by way of example in the above described embodiments.
- different forms of the motor assembly 22 are provided compared to those described in the above embodiments. For example, different forms of motor and/or lead screw, or equivalent elements, may be provided. Also, other details, including for example the use of a floating piston, may be varied, by the use of other arrangements that provide the same or at least suitably equivalent effect or capability.
Abstract
A hydraulic charging and driving system (4), and corresponding method, for extending and retracting a hydraulic actuator (2), comprising: a motor assembly (22); and an accumulator assembly (20), the motor assembly (22) and the accumulator assembly (20) being hydraulically coupled to each other; wherein the motor assembly (22) is arranged to recharge the accumulator assembly (20) with hydraulic fluid at a relatively slow rate that is slower than the rate at which the accumulator assembly (20) is arranged to discharge when actuating the hydraulic actuator (2). The system may further comprise a selector valve (24). The accumulator assembly (20) may comprise an accumulator chamber (30), and a compression means (32) provided within the accumulator chamber (30). The motor assembly (22) may comprise a motor (42) arranged to vary a volume of a hydraulic charging chamber (38) of the motor assembly (22).
Description
- The present invention relates to hydraulic actuators and hydraulic actuator systems. The present invention relates in particular to, but is not limited to, hydraulic actuators and hydraulic actuator systems for aircraft.
- The use of hydraulic actuators, for example in aircraft, is well established. For example, they are used for flight control applications such as moving control flaps, for landing gear extension and retraction, and so on.
- Conventionally, a plurality of actuators are coupled to a common hydraulic circuit that comprises a reservoir and a pump. An advantage of hydraulic actuators is the ability to provide a relatively high power density.
- A disadvantage of the above described arrangements is that servicing or replacement of individual actuators can be relatively complex due to the possibility of requiring to bleed, flush and replenish the whole hydraulic circuit.
- The present inventor has realised that in many applications, although a relatively high power density is required or desirable, this does not need to be continually available.
- In a first aspect, the invention provides a hydraulic charging and driving system for extending and retracting a hydraulic actuator, comprising: a motor assembly; and an accumulator assembly, the motor assembly and the accumulator assembly being hydraulically coupled to each other; wherein the motor assembly is arranged to recharge the accumulator assembly with hydraulic fluid at a relatively slow rate that is slower than the rate at which the accumulator assembly is arranged to discharge when actuating the hydraulic actuator.
- The system may further comprise a selector valve.
- The accumulator assembly may comprise an accumulator chamber, and a compression means provided within the accumulator chamber.
- The motor assembly may comprise a motor arranged to vary a volume of a hydraulic charging chamber of the motor assembly.
- The system may further comprise a hydraulic actuator comprising a bottom chamber and a piston-side chamber; wherein the accumulator assembly may be hydraulically coupled to the bottom chamber via a first setting of the selector valve to provide extension of the hydraulic actuator.
- The accumulator assembly may be further hydraulically coupled to the piston-side chamber, in addition to being hydraulically coupled to the bottom chamber, via the first setting of the selector valve to provide extension of the hydraulic actuator.
- The piston-side chamber may be hydraulically coupled to the motor assembly via a further setting of the selector valve to provide retraction of the hydraulic actuator.
- The system may further comprise an emergency assembly arranged to provide at least emergency extension of the hydraulic actuator.
- In a further aspect, the invention provides a method of operating a hydraulic system comprising a hydraulic actuator, a selector valve, and a motor assembly and an accumulator assembly hydraulically coupled in a hydraulic circuit; the method comprising: hydraulically extending the hydraulic actuator; thereafter, recharging the accumulator assembly with hydraulic fluid via the hydraulic circuit at a relatively slow recharge rate such that the recharge takes longer than the time taken to extend the hydraulic actuator.
- The step of recharging the accumulator assembly with hydraulic fluid may be performed by a motor of the motor assembly varying a volume of a hydraulic charging chamber of the motor assembly.
- The step of hydraulically extending the hydraulic actuator may be performed by hydraulically coupling the accumulator assembly to a bottom chamber of the hydraulic actuator by setting the selector valve to a first setting.
- The step of hydraulically extending the hydraulic actuator may be performed by, in addition to hydraulically coupling the accumulator assembly to a bottom chamber of the hydraulic actuator, also hydraulically coupling the accumulator assembly to the piston-side chamber, by setting the selector valve to the first setting.
- The method may further comprise hydraulically retracting the hydraulic actuator.
- The method may further comprise, after hydraulically retracting the hydraulic actuator, recharging the accumulator assembly with hydraulic fluid via the hydraulic circuit at a relatively slow recharge rate such that the recharge takes longer than the time taken to retract the hydraulic actuator.
- The method may further comprise performing at least an emergency extension of the hydraulic actuator.
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Figure 1 is a schematic illustration (not to scale) of a hydraulic actuator system; -
Figure 2 is a process flowchart showing certain steps of a cyclic method of actuation using the hydraulic actuator system ofFigure 1 ; -
Figures 3 to 9 (and above mentionedFigure 1 ) show the hydraulic actuator system at respective stages of the method ofFigure 2 ; -
Figure 10 shows the hydraulic actuator system when an optional emergency actuation process is carried out; -
Figure 11 is a schematic illustration (not to scale) of a further hydraulic actuator system; -
Figure 12 is a process flowchart showing certain steps of a cyclic method of actuation using the hydraulic actuator system ofFigure 11 ; -
Figures 13 to 18 (and above mentionedFigure 11 ) show the hydraulic actuator system at respective stages of the method ofFigure 12 ; and -
Figures 19 and 20 show the hydraulic actuator system when an optional emergency actuation process is carried out. -
Figure 1 is a schematic illustration (not to scale) of a first embodiment of ahydraulic actuator system 1. - In this embodiment the
hydraulic actuator system 1 comprises a linearhydraulic actuator 2 that is hydraulically coupled to a hydraulic charging anddriving system 4 adapted to hydraulically charge the linearhydraulic actuator 2. - In this embodiment the linear
hydraulic actuator 2 comprises acylinder barrel 6, a piston (which may also be termed an actuator valve) 8, and apiston rod 10 attached to thepiston 8. The piston is arranged to be able to move back and forth along thecylinder barrel 6. Thecylinder barrel 6 is closed at one end by a cylinder base (which may also be termed cap) 12. Thecylinder barrel 6 is closed at its other end by acylinder head 14 where thepiston rod 10 comes out of thecylinder barrel 6. Thepiston 8 divides the inside of thecylinder barrel 6 into two chambers, namely abottom chamber 16 at thecylinder base 12 side of thepiston 8 and a pistonrod side chamber 18 at thecylinder head 14 side of thepiston 8. In conventional fashion thepiston 8 is provided with sliding rings and seals (not shown). Thepiston rod 10 is provided with anactuator load connector 19, for connecting the movingpiston rod 10 with the load that is to be moved by operation of the linearhydraulic actuator 2. - In this embodiment the hydraulic charging and
driving system 4 comprises anaccumulator assembly 20, amotor assembly 22, a three-position selector valve 24, and anoptional emergency assembly 26. - In this embodiment a
hydraulic circuit 28 hydraulically couples the above described elements as follows: theaccumulator assembly 20 is hydraulically coupled to the motor assembly and the three-position selector valve 24. Themotor assembly 22 is further coupled to the three-position selector valve 24. The three-position selector valve 24 is further coupled to theemergency assembly 26 and the linearhydraulic actuator 2. Theemergency assembly 26 is further coupled to the linearhydraulic actuator 2. - In this embodiment the
accumulator assembly 20 comprises anaccumulator cylinder 30 and abellows 32. Thebellows 32 is provided within theaccumulator cylinder 30. Theaccumulator assembly 20 is further provided with a pressure switch (not shown). - In this embodiment the
motor assembly 22 comprises amotor assembly cylinder 34. Afloating piston 36 is provided within themotor assembly cylinder 34. Thefloating piston 36 is arranged to be able to move back and forth along themotor assembly cylinder 34. Thefloating piston 36 divides the inside of themotor assembly cylinder 34 into two chambers, namely acharging chamber 38 and anair chamber 40. In conventional fashion thepiston 8 is provided with sliding rings and seals (not shown). The motor assembly further comprises a motor and alead screw 44 coupled to themotor 42. In operation, as will be described in more detail later below, at certain stages of operation themotor 42 drives thelead screw 44 in an inward direction inside themotor assembly cylinder 34 to push thefloating piston 36 along the inside of the motor assembly cylinder 34 (thereby reducing the volume of the charging chamber 38), and at certain other stages of operation themotor 42 retracts thelead screw 44 in an outward direction inside themotor assembly cylinder 34 to thereby leave thefloating piston 36 in floating mode. Themotor assembly 22 is further provided with two pre-set retract switches, namely afirst retract switch 82 at afirst retract position 83, and asecond retract switch 84 at asecond retract position 85. As will be described in further detail later below, the two retract switches with their respective differing retract positions provide for the end of theled screw 44 and consequently the position of the floatingpiston 36 to have two available floating positions each of which is used at different stages of operation when thecharging chamber 38 is to be filled, thereby providing two different volumes of hydraulic liquid in thecharging chamber 38, one of which is used when setting thehydraulic actuator system 1 in a ready-to-retract status, and the other one of which is used when setting thehydraulic actuator system 1 in a ready-to-extend status, thereby accommodating the difference in volume between the maximum volume of thebottom chamber 16 of thecylinder barrel 6 and the maximum volume of the pistonrod side chamber 18 of thecylinder barrel 6. - In this embodiment the three-
position selector valve 24, provides links (or blocks the potential links) between lengths of thehydraulic circuit 28 so as to hydraulically connect (or block connection of) theaccumulator cylinder 30 or thecharging chamber 38 to thebottom chamber 16 of thecylinder barrel 6 or the pistonrod side chamber 18 of thecylinder barrel 6. - In more detail, in this embodiment the three-
position selector valve 24 is adjustable between three positions, namely a firstopen position 50, a closedposition 52, and a secondopen position 54. When the three-position selector valve 24 is in the firstopen position 50, theaccumulator cylinder 30 is connected to thebottom chamber 16 of thecylinder barrel 6, and thecharging chamber 38 is connected to the pistonrod side chamber 18 of thecylinder barrel 6. When, instead, the three-position selector valve 24 is in theclosed position 52, there is no connection between theaccumulator cylinder 30 and either of thebottom chamber 16 of thecylinder barrel 6 or the pistonrod side chamber 18 of thecylinder barrel 6, and also there is no connection between the chargingchamber 38 and either of thebottom chamber 16 of thecylinder barrel 6 or the pistonrod side chamber 18 of thecylinder barrel 6. When, instead, the three-position selector valve 24 is in the secondopen position 54, theaccumulator cylinder 30 is connected to the pistonrod side chamber 18 of the of thecylinder barrel 6, and the chargingchamber 38 is connected to thebottom chamber 16 of thecylinder barrel 6. It is noted that inFigure 1 the three-position selector valve 24 is in theclosed position 52. - In this embodiment the
optional emergency assembly 26 comprises anaccumulator cylinder 60 and abellows 64, for convenience termed herein anemergency cylinder 60 and an emergency bellows 64, respectively. Theemergency assembly 26 is hydraulically coupled to thehydraulic circuit 28 via an emergency extendvalve 66. When theemergency assembly 26 is in standby mode (as is the case inFigure 1 and also laterFigures 3-9 ), the emergency bellows 64 is compressed, with theemergency cylinder 60 therefore at its maximum volume and full of hydraulic fluid available for insertion into the linearhydraulic actuator 2 in the event of failure of the main operation of thehydraulic actuator system 1, as will be described later below with reference toFigure 10 . - Details of certain further connections provided by the
hydraulic circuit 28 are as follows. Thehydraulic circuit 28 further connects theaccumulator cylinder 30 to the chargingchamber 38 via afirst shuttle valve 70. Also, thehydraulic circuit 28 further connects thebottom chamber 16 of thecylinder barrel 6 to the emergency extendvalve 66 of theemergency assembly 26 via asecond shuttle valve 72. - Operation of the
hydraulic actuator system 1 of this embodiment will now be described with reference toFigures 1 to 10 .Figure 2 is a process flowchart showing certain steps of a cyclic method of actuation using thehydraulic actuator system 1.Figure 1 andFigures 3 to 9 show thehydraulic actuator system 1 at respective stages of the method ofFigure 2 .Figure 10 shows thehydraulic actuator system 1 when an optional emergency actuation process is carried out using the above describedoptional emergency assembly 26. - For convenience the process will be described by starting from the condition that is shown for the
hydraulic actuator system 1 inFigure 1 . However, it will be appreciated that the cyclic process may equally in fact be considered as starting at any of the stages to be described below, i.e. starting from any of the conditions that are shown for thehydraulic actuator system 1 in any ofFigure 1 orFigures 3 to 9 . - At step s2, and as shown in
Figure 1 , thehydraulic actuator system 1 is in a retracted state ready for extension (i.e. ready to extend the piston rod 10). In this state, thebottom chamber 16 of thecylinder barrel 6 is in its lowest volume state, and thebellows 32 of theaccumulator assembly 20 are at their minimum extension, hence theaccumulator cylinder 30 is in its largest volume state. The threeposition valve 24 is in the earlier describedclosed position 52. Thelead screw 44 is in one of its retracted positions, more particularly the first retractposition 83, i.e. thelead screw 44 has previously been moved in an outward direction inside themotor assembly cylinder 34 until movement was stopped by the first retractswitch 82 due to the end of thelead screw 44 reaching the first retractposition 83, to thereby leave the floatingpiston 36 in floating mode. - At step s4, the three
position valve 24 is moved to the earlier described firstopen position 50. Consequently thebellows 32 of theaccumulator assembly 20 extend and hydraulic fluid flows in thehydraulic circuit 28 with a net effect of flowing from theaccumulator cylinder 30 via the threeposition valve 24 to thebottom chamber 16 of thecylinder barrel 6, and from thepiston rod side 18 of thecylinder barrel 6 via the threeposition valve 24 to the chargingchamber 38 of theaccumulator assembly 20. As a result, thepiston rod 10 of the linearhydraulic actuator 2 extends, and also the floatingpiston 36 of theaccumulator assembly 20 is repositioned at the end of the retractedlead screw 44, i.e. at the first retractposition 83. In overview, step s4 may be summarised as the threeposition valve 24 being moved to an extend position (the first open position 50) thereby leading to extension of the actuator under charge pressure. The resulting state of thehydraulic actuator system 1 is shown inFigure 3 . - At step s6, the three
position valve 24 is moved to the earlier describedclosed position 50. In overview, step s6 may be summarised as the threeposition valve 24 being reset to neutral position. The resulting state of thehydraulic actuator system 1 is shown inFigure 4 . - At step s8, the
motor 42 of theaccumulator assembly 20 is used to drive thelead screw 44 in an inward direction into themotor assembly cylinder 34, thereby pushing the floatingpiston 36 against the hydraulic fluid in themotor assembly cylinder 34 thereby transferring the hydraulic fluid in themotor assembly cylinder 34 into theaccumulator cylinder 30 via the shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging theaccumulator cylinder 30. When the hydraulic pressure in theaccumulator cylinder 30 has reached a pre-determined level, the pressure switch (not shown) of theaccumulator cylinder 30 signals themotor 42 to stop driving the lead screw in the inward direction (and instead, to thereafter commence the retreat motion described below as part of step s10). Themotor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes. In particular, this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s4, which may only, for example, take less than thirty seconds, or may even take less than ten seconds (and likewise compared to the time for the actuator retraction step s12 described later below). In overview, step s8 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly). The resulting state of thehydraulic actuator system 1 is shown inFigure 5 . - At step s10, the
motor 42 retracts thelead screw 44 in an outward direction inside themotor assembly cylinder 34 until the second retractswitch 84 stops the retraction of thelead screw 44 when the end of thelead screw 44 reaches the second retractposition 85, to thereby leave the floatingpiston 36 in floating mode. Accordingly, thehydraulic actuator system 1 is put in in a state that is ready for retraction of the actuator i.e. ready for retraction of thepiston rod 10. In overview, step s10 may be summarised as resetting thelead screw 44 thereby making the hydraulic actuator system ready for retraction. The resulting "ready for retraction" state of thehydraulic actuator system 1 is shown inFigure 6 . - At step s12, the three
position valve 24 is moved to the earlier described secondopen position 54. Consequently thebellows 32 of theaccumulator assembly 20 extend and hydraulic fluid flows in thehydraulic circuit 28 with a net effect of flowing from theaccumulator cylinder 30 via the threeposition valve 24 to thepiston rod side 18 of thecylinder barrel 6, and from thebottom chamber 16 of thecylinder barrel 6 via the threeposition valve 24 to the chargingchamber 38 of theaccumulator assembly 20. As a result, thepiston rod 10 of the linearhydraulic actuator 2 retracts, and also the floatingpiston 36 of theaccumulator assembly 20 is repositioned at the end of the retractedlead screw 44, i.e. at the second retractposition 85. In overview, step s12 may be summarised as the threeposition valve 24 being moved to a retract position (the second open position 54) thereby leading to retraction of the actuator under charge pressure. The resulting state of thehydraulic actuator system 1 is shown inFigure 7 . - At step s14, the three
position valve 24 is moved to the earlier describedclosed position 50. In overview, step s14 may be summarised as the threeposition valve 24 being reset to neutral position. The resulting state of thehydraulic actuator system 1 is shown inFigure 8 . - At step s16, the
motor 42 of theaccumulator assembly 20 is used to drive thelead screw 44 in an inward direction into themotor assembly cylinder 34, thereby pushing the floatingpiston 36 against the hydraulic fluid in themotor assembly cylinder 34 thereby transferring the hydraulic fluid in themotor assembly cylinder 34 into theaccumulator cylinder 30 via the shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging theaccumulator cylinder 30. As stated above, themotor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes. In particular, this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s4, which may only, for example, take less than thirty seconds, or may even take less than ten seconds and likewise compared to the time for the actuator retraction step s12 also described above). In overview, step s16 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, as stated above, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly). The resulting state of thehydraulic actuator system 1 is shown inFigure 9 . - At step s18, the
motor 42 retracts thelead screw 44 in an outward direction inside themotor assembly cylinder 34 until the first retractswitch 82 stops the retraction of thelead screw 44 when the end of the ledscrew 44 reaches first retractposition 83, to thereby leave the floatingpiston 36 in floating mode. Accordingly, thehydraulic actuator system 1 is put in in a state that is ready for extension of the actuator i.e. ready for extension of thepiston rod 10. In overview, step s18 may be summarised as resetting thelead screw 44 thereby making the hydraulic actuator system ready for extension. The resulting "ready for extension" state of thehydraulic actuator system 1 is the same state as described at step s2 and already shown inFigure 1 , i.e. thehydraulic actuator system 1 is back at theFigure 1 state of its cyclic operational capability, and accordingly any or all of steps s4 to s18 may be repeated if desired. - As mentioned above, in this embodiment an optional emergency actuation process is provided using the above described
optional emergency assembly 26, as described in the following paragraph. However, this need not be the case, and in other embodiments the optional emergency assembly is not included in thehydraulic actuator system 1. In yet further embodiments, an emergency assembly is provided, however it is of a different arrangement to that described below. -
Figure 10 shows thehydraulic actuator system 1 implementing theoptional emergency assembly 26 in order to carry out an emergency extension of the actuator. The emergency extendvalve 66 is activated to allow the emergency bellows 64 to expand thereby pushing the hydraulic fluid in theemergency cylinder 60 from theemergency cylinder 60 into thebottom chamber 16 of thecylinder barrel 6. As a result, thepiston rod 10 of the linearhydraulic actuator 2 extends. -
Figure 11 is a schematic illustration (not to scale) of a further embodiment of ahydraulic actuator system 101. - In this embodiment the
hydraulic actuator system 101 comprises a linearhydraulic actuator 2 that is hydraulically coupled to a hydraulic charging and drivingsystem 4 adapted to hydraulically charge the linearhydraulic actuator 2. - In this embodiment the linear
hydraulic actuator 2 comprises acylinder barrel 6, a piston (which may also be termed an actuator valve) 8, and apiston rod 10 attached to thepiston 8. The piston is arranged to be able to move back and forth along thecylinder barrel 6. Thecylinder barrel 6 is closed at one end by a cylinder base (which may also be termed cap) 12. Thecylinder barrel 6 is closed at its other end by acylinder head 14 where thepiston rod 10 comes out of thecylinder barrel 6. Thepiston 8 divides the inside of thecylinder barrel 6 into two chambers, namely abottom chamber 16 at thecylinder base 12 side of thepiston 8 and a pistonrod side chamber 18 at thecylinder head 14 side of thepiston 8. In conventional fashion thepiston 8 is provided with sliding rings and seals (not shown). Thepiston rod 10 is provided with anactuator load connector 19, for connecting the movingpiston rod 10 with the load that is to be moved by operation of the linearhydraulic actuator 2. - In this embodiment the hydraulic charging and driving
system 4 comprises anaccumulator assembly 20, amotor assembly 22, a three-position selector valve 24, and anoptional emergency assembly 26. - In this embodiment a
hydraulic circuit 28 hydraulically couples the above described elements as follows: theaccumulator assembly 20 is hydraulically coupled to themotor assembly 22, the three-position selector valve 24, and theoptional emergency assembly 26. Themotor assembly 22 is further coupled to the three-position selector valve 24 and theoptional emergency assembly 26. The three-position selector valve 24 is further coupled to theemergency assembly 26 and the linearhydraulic actuator 2. Theemergency assembly 26 is further coupled to the linearhydraulic actuator 2. - In this embodiment the
accumulator assembly 20 comprises anaccumulator cylinder 30 and a bellows 32. The bellows 32 is provided within theaccumulator cylinder 30. Theaccumulator assembly 20 is further provided with a pressure switch (not shown). - In this embodiment the
motor assembly 22 comprises amotor assembly cylinder 34. A floatingpiston 36 is provided within themotor assembly cylinder 34. The floatingpiston 36 is arranged to be able to move back and forth along themotor assembly cylinder 34. The floatingpiston 36 divides the inside of themotor assembly cylinder 34 into two chambers, namely a chargingchamber 38 and anair chamber 40. In conventional fashion thepiston 8 is provided with sliding rings and seals (not shown). The motor assembly further comprises a motor and alead screw 44 coupled to themotor 42. In operation, as will be described in more detail later below, at certain stages of operation themotor 42 drives thelead screw 44 in an inward direction inside themotor assembly cylinder 34 to push the floatingpiston 36 along the inside of the motor assembly cylinder 34 (thereby reducing the volume of the charging chamber 38), and at certain other stages of operation themotor 42 retracts thelead screw 44 in an outward direction inside themotor assembly cylinder 34 to thereby leave the floatingpiston 36 in floating mode. Themotor assembly 22 is further provided with two pre-set retract switches, namely a first retractswitch 82 at a first retractposition 83, and a second retractswitch 84 at a second retractposition 85. As will be described in further detail later below, the two retract switches with their respective differing retract positions provide for the end of the ledscrew 44 and consequently the position of the floatingpiston 36 to have two available floating positions each of which is used at different stages of operation when the chargingchamber 38 is to be filled, thereby providing two different volumes of hydraulic liquid in the chargingchamber 38, one of which is used when setting thehydraulic actuator system 101 in a ready-to-retract status, and the other one of which is used when setting thehydraulic actuator system 101 in a ready-to-extend status, thereby accommodating the difference in volume between the maximum volume of thebottom chamber 16 of thecylinder barrel 6 and the maximum volume of the pistonrod side chamber 18 of thecylinder barrel 6. - In this embodiment the three-
position selector valve 24, provides links (or blocks the potential links) between lengths of thehydraulic circuit 28 so as to hydraulically connect (or block connection of) theaccumulator cylinder 30 or the chargingchamber 38 to thebottom chamber 16 of thecylinder barrel 6 or the pistonrod side chamber 18 of thecylinder barrel 6. - In more detail, in this embodiment the three-
position selector valve 24 is adjustable between three positions, namely a firstopen position 50, aclosed position 52, and a secondopen position 54. When the three-position selector valve 24 is in the firstopen position 50, theaccumulator cylinder 30 is connected to both thebottom chamber 16 of thecylinder barrel 6 and to the pistonrod side chamber 18 of thecylinder barrel 6. When, instead, the three-position selector valve 24 is in theclosed position 52, there is no connection between thebottom chamber 16 of thecylinder barrel 6 and either of theaccumulator cylinder 30 and the chargingchamber 38, and also there is no connection between the pistonrod side chamber 18 of thecylinder barrel 6 and either of theaccumulator cylinder 30 and the chargingchamber 38. When, instead, the three-position selector valve 24 is in the secondopen position 54, theaccumulator cylinder 30 is connected to the pistonrod side chamber 18 of the of thecylinder barrel 6, and the chargingchamber 38 is connected to thebottom chamber 16 of thecylinder barrel 6. It is noted that inFigure 11 the three-position selector valve 24 is in theclosed position 52. - In this embodiment the
optional emergency assembly 26 comprises anaccumulator cylinder 60 and abellows 64, for convenience termed herein anemergency cylinder 60 and an emergency bellows 64, respectively. The emergency bellows 64 is provided within theemergency accumulator cylinder 60. Theoptional emergency assembly 26 is further provided with a pressure switch (not shown). - The
emergency assembly 26 is hydraulically coupled to thehydraulic circuit 28 via an emergency extendvalve 66 and via anemergency charge valve 80. When theemergency assembly 26 is in standby mode (as is the case inFigure 11 and also laterFigures 13-18 ), the emergency bellows 64 is compressed, with theemergency accumulator cylinder 60 therefore at its maximum volume and full of hydraulic fluid available for insertion into the linearhydraulic actuator 2 in the event of failure of the main operation of thehydraulic actuator system 101, as will be described later below with reference toFigures 19 and 20 . - Details of certain further connections provided by the
hydraulic circuit 28 are as follows. Thehydraulic circuit 28 further connects theaccumulator cylinder 30 to the chargingchamber 38 via afirst shuttle valve 70. Also, thehydraulic circuit 28 further connects thebottom chamber 16 of thecylinder barrel 6 to the emergency extendvalve 66 of theemergency assembly 26 via asecond shuttle valve 72. Also, thehydraulic circuit 28 further connects the pistonrod side chamber 18 of thecylinder barrel 6 to the emergency extendvalve 66 of theemergency assembly 26 via athird shuttle valve 73. - Operation of the
hydraulic actuator system 101 of this embodiment will now be described with reference toFigures 11 to 20 .Figure 12 is a process flowchart showing certain steps of a cyclic method of actuation using thehydraulic actuator system 101.Figure 11 andFigures 13 to 18 show thehydraulic actuator system 101 at respective stages of the method ofFigure 12 .Figures 19 and 20 show thehydraulic actuator system 101 when an optional emergency actuation process is carried out using the above describedoptional emergency assembly 26. - For convenience the process will be described by starting from the condition that is shown for the
hydraulic actuator system 101 inFigure 11 . However, it will be appreciated that the cyclic process may equally in fact be considered as starting at any of the stages to be described below, i.e. starting from any of the conditions that are shown for thehydraulic actuator system 101 in any ofFigure 11 orFigures 13 to 19 . - At step s102, and as shown in
Figure 11 , thehydraulic actuator system 101 is in a retracted state ready for extension (i.e. ready to extend the piston rod 10). In this state, thebottom chamber 16 of thecylinder barrel 6 is in its lowest volume state, and thebellows 32 of theaccumulator assembly 20 are at their minimum extension, hence theaccumulator cylinder 30 is in its largest volume state. The threeposition valve 24 is in the earlier describedclosed position 52. Thelead screw 44 is in one of its retracted positions, more particularly the first retractposition 83, i.e. thelead screw 44 has previously been moved in an outward direction inside themotor assembly cylinder 34 until movement was stopped by the first retractswitch 82 due to the end of thelead screw 44 reaching the first retractposition 83, to thereby leave the floatingpiston 36 in floating mode. - At step s104, the three
position valve 24 is moved to the earlier described firstopen position 50. Consequently thebellows 32 of theaccumulator assembly 20 extend and hydraulic fluid flows in thehydraulic circuit 28 with a net effect of flowing from theaccumulator cylinder 30 via the threeposition valve 24 to thebottom chamber 16 of thecylinder barrel 6, and, in this embodiment, additionally also from thepiston rod side 18 of thecylinder barrel 6 via the threeposition valve 24 to thebottom chamber 16 of thecylinder barrel 6. As a result, thepiston rod 10 of the linearhydraulic actuator 2 extends, and in this embodiment during this step position of the floatingpiston 36 of theaccumulator assembly 20 remains at the end of the retractedlead screw 44, i.e. at the first retractposition 83. In overview, step s104 may be summarised as the threeposition valve 24 being moved to an extend position (the first open position 50) thereby leading to extension of the actuator under charge pressure. The resulting state of thehydraulic actuator system 101 is shown inFigure 13 . - At step s106, the three
position valve 24 is moved to the earlier describedclosed position 50. In overview, step s106 may be summarised as the threeposition valve 24 being reset to neutral position. The resulting state of thehydraulic actuator system 101 is shown inFigure 14 . - At step s108, the
motor 42 of theaccumulator assembly 20 is used to drive thelead screw 44 in an inward direction into themotor assembly cylinder 34, thereby pushing the floatingpiston 36 against the hydraulic fluid in themotor assembly cylinder 34 thereby transferring the hydraulic fluid in themotor assembly cylinder 34 into theaccumulator cylinder 30 via the first shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging theaccumulator cylinder 30. When the hydraulic pressure in theaccumulator cylinder 30 has reached a pre-determined level, the pressure switch (not shown) of theaccumulator cylinder 30 signals themotor 42 to stop driving the lead screw in the inward direction (and instead, to thereafter commence the retreat motion described below as part of step s110). Themotor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes. In particular, this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s104, which may only, for example, take less than thirty seconds, or may even take less than ten seconds (and likewise compared to the time for the actuator retraction step s112 described later below). In overview, step s108 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly). The resulting state of thehydraulic actuator system 101 is shown inFigure 15 . - At step s110, the
motor 42 retracts thelead screw 44 in an outward direction inside themotor assembly cylinder 34 until the second retractswitch 84 stops the retraction of thelead screw 44 when the end of thelead screw 44 reaches the second retractposition 85, to thereby leave the floatingpiston 36 in floating mode. Accordingly, thehydraulic actuator system 101 is put in in a state that is ready for retraction of the actuator i.e. ready for retraction of thepiston rod 10. In overview, step s110 may be summarised as resetting thelead screw 44 thereby making thehydraulic actuator system 101 ready for retraction. The resulting "ready for retraction" state of thehydraulic actuator system 101 is shown inFigure 16 . - At step s112, the three
position valve 24 is moved to the earlier described secondopen position 54. Consequently thebellows 32 of theaccumulator assembly 20 extend and hydraulic fluid flows in thehydraulic circuit 28 with a net effect of flowing from theaccumulator cylinder 30 via the threeposition valve 24 to thepiston rod side 18 of thecylinder barrel 6, and from thebottom chamber 16 of thecylinder barrel 6 via the threeposition valve 24 to the chargingchamber 38 of theaccumulator assembly 20. As a result, thepiston rod 10 of the linearhydraulic actuator 2 retracts, and also the floatingpiston 36 of theaccumulator assembly 20 is repositioned at the end of the retractedlead screw 44, i.e. at the second retractposition 85. In overview, step s112 may be summarised as the threeposition valve 24 being moved to a retract position (the second open position 54) thereby leading to retraction of the actuator under charge pressure. The resulting state of thehydraulic actuator system 101 is shown inFigure 17 . - At step s114, the three
position valve 24 is moved to the earlier describedclosed position 50. In overview, step s114 may be summarised as the threeposition valve 24 being reset to neutral position. The resulting state of thehydraulic actuator system 101 is shown in Figure 108. - At step s116, the
motor 42 of theaccumulator assembly 20 is used to drive thelead screw 44 in an inward direction into themotor assembly cylinder 34, thereby pushing the floatingpiston 36 against the hydraulic fluid in themotor assembly cylinder 34 thereby transferring the hydraulic fluid in themotor assembly cylinder 34 into theaccumulator cylinder 30 via the first shuttle valve 70 (this fluid compressing the bellows 32) thereby recharging theaccumulator cylinder 30. As stated above, themotor 42 may be a relatively small motor i.e. of relatively low power, and this recharging process may take place relatively slowly, over a relatively large time period, for example taking longer than one minute, even for example taking longer than three minutes. In particular, this recharge time period may be significantly longer than the time taken for the actuator to extend in the course of above described step s104, which may only, for example, take less than thirty seconds, or may even take less than ten seconds and likewise compared to the time for the actuator retraction step s112 also described above). In overview, step s116 may be summarised as performing relatively slow accumulator recharge using a relatively low powered motor. (However, as stated above, in other embodiments, a larger powered motor may be used, and accumulator recharge may be performed more quickly). Furthermore, in this embodiment, as a result of implementing step 116, thehydraulic actuator system 101 is now in a state that is ready for extension of the actuator i.e. ready for extension of thepiston rod 10. This "ready for extension" state of thehydraulic actuator system 101 is the same state as described at step s102 and already shown inFigure 11 , i.e. thehydraulic actuator system 101 is back at theFigure 11 state of its cyclic operational capability, and accordingly any or all of steps s104 to s116 may be repeated if desired. - As mentioned above, in this embodiment an optional emergency actuation process is provided using the above described
optional emergency assembly 26, as described in the following two paragraphs. However, this need not be the case, and in other embodiments the optional emergency assembly is not included in thehydraulic actuator system 101. In yet further embodiments, an emergency assembly is provided, however it is of a different arrangement to that described below. -
Figure 19 shows thehydraulic actuator system 101 implementing theoptional emergency assembly 26 in order to carry out an emergency extension of the actuator. The emergency extendvalve 66 is activated to allow the emergency bellows 64 to expand thereby pushing the hydraulic fluid in theemergency cylinder 60 from theemergency cylinder 60 into thebottom chamber 16 of thecylinder barrel 6, flow through thesecond shuttle valve 72 taking place due to the additional hydraulic pressure. As a result, thepiston rod 10 of the linearhydraulic actuator 2 extends. An advantage of the above describedhydraulic actuator system 1 is that it further optionally allows theemergency assembly 26 to be rechargeable (although this does not need to be the case in other embodiments). -
Figure 20 shows thehydraulic actuator system 101 implementing such an optional recharge of theoptional emergency assembly 26 having previously performed the emergency extend process described in the preceding paragraph. The emergency extendvalve 66 is returned to closed position, and theemergency charge valve 80 is opened. Then, in a process step analogous to step s108 described earlier above, themotor 42 of theaccumulator assembly 20 is used to drive thelead screw 44 in an inward direction into themotor assembly cylinder 34, thereby pushing the floatingpiston 36 against the hydraulic fluid in themotor assembly cylinder 34 thereby transferring the hydraulic fluid in themotor assembly cylinder 34 into theemergency cylinder 60 via thefirst shuttle valve 70 and the now open emergency charge valve 80 (this fluid compressing the emergency bellows 64) thereby recharging theemergency cylinder 60. When the hydraulic pressure in theaccumulator cylinder 30 has reached a pre-determined level, the pressure switch (not shown) of theemergency cylinder 60 signals themotor 42 to stop driving the lead screw in the inward direction. The resulting state of thehydraulic actuator system 101 is shown inFigure 15 . Thereafter, thecharge valve 80 is returned to closed position, leaving thehydraulic actuator system 101 in the same state as that at the end of step s108 as described above i.e. in the same state as that shown inFigure 15 . - An advantage of the above described embodiments is that, whilst nevertheless only requiring relatively low powered motors (due to the approach of charging the accumulator over a time span greater than the operating time of the actuator), single modular hydraulic actuators can be provided, rather than one large overall hydraulic circuit, and thus servicing or replacement of individual actuators can be reduced in complexity due to avoiding or alleviating the need to to bleed, flush and replenish the whole hydraulic circuit. Furthermore, the aspect of charging the accumulator over a time span greater than the operating time of the actuator is acceptable for many applications, for example deployment of landing gear where an "up" request would not normally be followed by a "down request" and vice versa, aircraft door opening/closing, and so on. As mentioned above, further particular advantages that tend to be provided by the embodiment shown in
Figure 11 include the possibility of providing a rechargeable emergency operation system. Another advantage that tends to be provided by the embodiment shown inFigure 11 is that the volume requirement of theaccumulator cylinder 30 is reduced by the way the extend command is ported having been changed (compared, as it were, to the embodiment shown inFigure 1 ). By directing pressure to both sides of the piston on extend, the resultant force is proportional to the difference in the piston's area from the piston rod side to the extend side. Consequently, the force upon extend is reduced but is more in line with the retract capability. In comparison, the embodiment ofFigure 1 uses a larger accumulator to develop maximum extend thrust and needs a larger accumulator volume to achieve this. - It will be appreciated that in other embodiments details of individual elements of the above described arrangements may be replaced by alternative elements providing equivalent effects. For example, one or more of the various bellows described in the above embodiments may be replaced by alternative compression and/or energy storing means and/or pressure exerting means and/or hydraulic fluid flow control means, for example springs. Where appropriate, additional pistons and the like may be used in association with such alternative means. Also, in other embodiments, elements such as pistons and so on may be omitted if the use of one or more alternative compression and/or energy storing means and/or pressure exerting means and/or hydraulic fluid flow control means renders one or more existing pistons and so on redundant or less desirable. Similarly, in other embodiments, one or more of the above described valves, and/or pressure switches and/or position switches may be omitted or modified with either resulting diminished performance or efficiency, or in other cases, no diminution of performance, for example if alternative elements and arrangements are provided. Also, any cylinders may be replaced by alternative shaped chambers. In yet further embodiments, the details of the linear hydraulic actuator may be changed, by use of other forms of hydraulic actuator that nevertheless benefit from the remaining details of the above described embodiments of hydraulic actuator systems. In yet further embodiments, alternative switching arrangements are provided instead of the particular three position selector valve apparatus and arrangements used by way of example in the above described embodiments. In yet further embodiments, different forms of the
motor assembly 22 are provided compared to those described in the above embodiments. For example, different forms of motor and/or lead screw, or equivalent elements, may be provided. Also, other details, including for example the use of a floating piston, may be varied, by the use of other arrangements that provide the same or at least suitably equivalent effect or capability.
Claims (15)
- A hydraulic charging and driving system (4) for extending and retracting a hydraulic actuator (2), comprising:a motor assembly (22); andan accumulator assembly (20), the motor assembly (22) and the accumulator assembly (20) being hydraulically coupled to each other;wherein the motor assembly (22) is arranged to recharge the accumulator assembly (20) with hydraulic fluid at a relatively slow rate that is slower than the rate at which the accumulator assembly (20) is arranged to discharge when actuating the hydraulic actuator (2).
- The system according to claim 1, further comprising a selector valve (24).
- The system according to claim 1 or claim 2, wherein the accumulator assembly (20) comprises an accumulator chamber (30), and a compression means (32) provided within the accumulator chamber (30).
- A system according to any of claims 1 to 3, wherein the motor assembly (22) comprises a motor (42) arranged to vary a volume of a hydraulic charging chamber (38) of the motor assembly (22).
- A system according to any of claims 2 to 4, further comprising a hydraulic actuator (2) comprising a bottom chamber (16) and a piston-side chamber (18);
wherein the accumulator assembly (20) is hydraulically coupled to the bottom chamber (16) via a first setting of the selector valve (24) to provide extension of the hydraulic actuator (2). - A system according to claim 5, wherein the accumulator assembly (20) is further hydraulically coupled to the piston-side chamber (18), in addition to being hydraulically coupled to the bottom chamber (16), via the first setting of the selector valve (24) to provide extension of the hydraulic actuator (2).
- A system according to claim 5 or claim 6, wherein the piston-side chamber (18) is hydraulically coupled to the motor assembly (22) via a further setting of the selector valve (24) to provide retraction of the hydraulic actuator (2).
- A system according to any of claims 1 to 7, further comprising an emergency assembly (26) arranged to provide at least emergency extension of the hydraulic actuator (2).
- A method of operating a hydraulic system comprising a hydraulic actuator (2), a selector valve (24), and a motor assembly (22) and an accumulator assembly (20) hydraulically coupled in a hydraulic circuit (28); the method comprising:hydraulically extending the hydraulic actuator (2);thereafter, recharging the accumulator assembly (20) with hydraulic fluid via the hydraulic circuit (28) at a relatively slow recharge rate such that the recharge takes longer than the time taken to extend the hydraulic actuator (2).
- A method according to claim 9, wherein the step of recharging the accumulator assembly (20) with hydraulic fluid is performed by a motor (42) of the motor assembly (22) varying a volume of a hydraulic charging chamber (38) of the motor assembly (22).
- A method according to claim 9 or claim 10, wherein the step of hydraulically extending the hydraulic actuator (2) is performed by hydraulically coupling the accumulator assembly (20) to a bottom chamber (16) of the hydraulic actuator (2) by setting the selector valve (24) to a first setting.
- A method according to claim 11, wherein the step of hydraulically extending the hydraulic actuator (2) is performed by, in addition to hydraulically coupling the accumulator assembly (20) to a bottom chamber (16) of the hydraulic actuator (2), also hydraulically coupling the accumulator assembly (20) to the piston-side chamber (18), by setting the selector valve (24) to the first setting.
- A method according to any of claims 9 to 12, the method further comprising hydraulically retracting the hydraulic actuator (2).
- A method according to claim 14, the method further comprising, after hydraulically retracting the hydraulic actuator (2), recharging the accumulator assembly (20) with hydraulic fluid via the hydraulic circuit (28) at a relatively slow recharge rate such that the recharge takes longer than the time taken to retract the hydraulic actuator (2).
- A method according to any of claims 9 to 14, the method further comprising performing at least an emergency extension of the hydraulic actuator (2).
Priority Applications (1)
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EP15275009.7A EP3045736A1 (en) | 2015-01-14 | 2015-01-14 | Hydraulic actuators |
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EP15275009.7A EP3045736A1 (en) | 2015-01-14 | 2015-01-14 | Hydraulic actuators |
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EP3045736A1 true EP3045736A1 (en) | 2016-07-20 |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2018094969A (en) * | 2016-12-08 | 2018-06-21 | 住友精密工業株式会社 | Eha system of aircraft landing gear |
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GB773755A (en) * | 1954-08-18 | 1957-05-01 | Electric Auto Lite Co | Improvements relating to method of producing self-regulating hydraulic power of highpressure from a variable fluid pressure of low value and apparatus for carrying out the method |
DE3133111A1 (en) * | 1981-08-21 | 1983-04-14 | Robert Bosch Gmbh, 7000 Stuttgart | Pressure-supplying arrangement |
US20030188529A1 (en) * | 2002-03-04 | 2003-10-09 | Messier-Bugatti | Hydraulic system architecture for controlling steering |
US20060070378A1 (en) * | 2004-10-01 | 2006-04-06 | David Geiger | Closed-system electrohydraulic actuator |
US20110278068A1 (en) * | 2010-04-07 | 2011-11-17 | Atlas Copco Drilling Solutions, Llc. | Regenerative drive mechanism for hydraulic feed cylinders in hydrostatic or hydraulic circuits |
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2015
- 2015-01-14 EP EP15275009.7A patent/EP3045736A1/en not_active Ceased
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GB773755A (en) * | 1954-08-18 | 1957-05-01 | Electric Auto Lite Co | Improvements relating to method of producing self-regulating hydraulic power of highpressure from a variable fluid pressure of low value and apparatus for carrying out the method |
DE3133111A1 (en) * | 1981-08-21 | 1983-04-14 | Robert Bosch Gmbh, 7000 Stuttgart | Pressure-supplying arrangement |
US20030188529A1 (en) * | 2002-03-04 | 2003-10-09 | Messier-Bugatti | Hydraulic system architecture for controlling steering |
US20060070378A1 (en) * | 2004-10-01 | 2006-04-06 | David Geiger | Closed-system electrohydraulic actuator |
US20110278068A1 (en) * | 2010-04-07 | 2011-11-17 | Atlas Copco Drilling Solutions, Llc. | Regenerative drive mechanism for hydraulic feed cylinders in hydrostatic or hydraulic circuits |
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JP2018094969A (en) * | 2016-12-08 | 2018-06-21 | 住友精密工業株式会社 | Eha system of aircraft landing gear |
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