EP0042774A1 - Einrichtung zum Erzeugen von Hydraulikflussmengen hintereinander abgestufter Werte - Google Patents

Einrichtung zum Erzeugen von Hydraulikflussmengen hintereinander abgestufter Werte Download PDF

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Publication number
EP0042774A1
EP0042774A1 EP81400883A EP81400883A EP0042774A1 EP 0042774 A1 EP0042774 A1 EP 0042774A1 EP 81400883 A EP81400883 A EP 81400883A EP 81400883 A EP81400883 A EP 81400883A EP 0042774 A1 EP0042774 A1 EP 0042774A1
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EP
European Patent Office
Prior art keywords
pumps
pressure
threshold
differential
brake
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.)
Granted
Application number
EP81400883A
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English (en)
French (fr)
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EP0042774B1 (de
Inventor
Jean-Max Marie Silhouette
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Safran Aircraft Engines SAS
Original Assignee
Societe Nationale dEtude et de Construction de Moteurs dAviation SNECMA
SNECMA SAS
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Publication of EP0042774A1 publication Critical patent/EP0042774A1/de
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Publication of EP0042774B1 publication Critical patent/EP0042774B1/de
Expired legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
    • F04D15/02—Stopping of pumps, or operating valves, on occurrence of unwanted conditions
    • F04D15/029—Stopping of pumps, or operating valves, on occurrence of unwanted conditions for pumps operating in parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
    • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
    • F04B49/007—Installations or systems with two or more pumps or pump cylinders, wherein the flow-path through the stages can be changed, e.g. from series to parallel
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C15/00—Component parts, details or accessories of machines, pumps or pumping installations, not provided for in groups F04C2/00 - F04C14/00
    • F04C15/0057—Driving elements, brakes, couplings, transmission specially adapted for machines or pumps
    • F04C15/0061—Means for transmitting movement from the prime mover to driven parts of the pump, e.g. clutches, couplings, transmissions

Definitions

  • the present invention relates to a device for successively producing hydraulic fluid flows of staggered values, intended for a circuit of use, for example a hydraulic cylinder, requiring fluid flows which vary rapidly.
  • the operating circuit can be supplied with hydraulic fluid by a centrifugal pump, capable of producing flow rates of hydraulic fluid capable of varying rapidly between staggered values.
  • a centrifugal pump capable of producing flow rates of hydraulic fluid capable of varying rapidly between staggered values.
  • the pump operates at high speed, and produces a low flow rate, a large fraction of the driving energy is dissipated by heating the pump and the hydraulic fluid; in this case, not only is the efficiency of the installation very poor, but this results in wear of the pump and its drive device.
  • French Patent No. 2,247,112 (POCLAIN) describes a device for simultaneously sending flow rates of hydraulic fluid, in two separate operating circuits, by two pumps, which are driven by a single motor, one of which has variable displacement; when the priority needs in hydraulic fluid of one of the two use circuits increase significantly, it is planned, to avoid stalling of the single engine, to reduce the displacement of the pump supplying the other use circuit; the latter therefore then receives a flow rate of hydraulic fluid which may be temporarily lower than its requirements, which is only admissible for very specific applications.
  • French Patent No. 2,271,416 (POCLAIN) describes a supply device similar to that described in the patent previously mentioned, but intended to supply a single operating circuit in parallel, by the two pumps.
  • a regulator of the variable displacement of one of the two pumps is provided, designed so that, when it exerts its regulating function, the maximum power absorbed by the two pumps is constant and equal to the maximum power. of the motor.
  • French Patent No. 1,545,432 (GENERAL ELECTRIC Cy) describes a fuel supply system for the post-combustion device of a gas turbine engine, comprising two centrifugal pumps with respective, significantly different flow capacities, which are continuously rotated by the rotors of the turbine; Valves and fluid control devices are used to supply only the lower flow pump first, and then only the higher flow pump, depending on the operating conditions of the turbine. Each of the two pumps is therefore constantly rotated, even during periods when it does not have to deliver fuel, which leads to energy losses.
  • French Patent No. 2,234,463 (TRW INC.) Describes a fuel pumping device comprising a centrifugal pump driven constantly in rotation, and a positive displacement pump, which is only driven, by means of a clutch, during the start-up period, when the discharge pressure of the centrifugal pump is insufficient.
  • the purpose of this device is therefore essentially to compensate for the insufficiency of the discharge pressure of a centrifugal pump at low speed, rather than to deliver a fuel flow rate varying rapidly between staggered values.
  • the use of a clutch, subject to relatively rapid wear, is also undesirable for the applications which are envisaged in the context of the present invention, and which have been mentioned previously.
  • French Patent No. 2,046,559 (ROBERT BOSCH) describes systems of several pumps whose rotors, with parallel axes, are provided for example with axial pistons, controlled by fixed inclined plates; gears allow the rotors of at least two pumps to be coupled to each other at will, so as to obtain actuation, from a single motor shaft, of a single pump, or of at least two pumps.
  • gears allow the rotors of at least two pumps to be coupled to each other at will, so as to obtain actuation, from a single motor shaft, of a single pump, or of at least two pumps.
  • French Patent No. 2,307,994 (CHANDLER EVANS) describes a pumping device, in particular for the supply of fuel to gas turbine engines, comprising two pumps with significantly different flow rates, which are driven by a single drive shaft, one directly and the other via a clutch.
  • This device does not make it possible to operate only the high flow pump, since the low flow pump is always in service.
  • it offers the disadvantage of using a clutch, susceptible to rapid wear.
  • the device according to the present invention for successively producing hydraulic fluid flow rates of staggered values, also comprises several rotary pumps of suitably staggered nominal flow rates, driven from a single motor, as well as means for selectively switching each of said pumps between stop and nominal speed; however, it does not have any of the drawbacks of the prior devices, previously mentioned.
  • the device according to the present invention is of the type which has just been indicated, and it is characterized in that the different pumps are coupled respectively to the output shafts of a mechanical transmission, comprising one or more epicyclic differentials, connected in cascade , the input shaft of the first differential of the cascade being coupled to the motor, that a brake is associated with each of said pumps, and that means are provided for causing each brake to be controlled by crossing a threshold determined by the pressure delivery of said pumps.
  • the device according to the present invention offers a high degree of reliability and a long service life; the brakes which it comprises in fact only work for a short time, at each stop of a pump previously in service; the following advantages are added: the power of the single motor can be chosen to be significantly lower than the power which would be necessary to drive a single pump, having to supply the maximum flow rate required under the maximum pressure required, whence substantial savings on installed power and energy consumption; it also prevents excess power from being dissipated by heating the pump and the hydraulic fluid, which also goes in the direction of increasing the reliability and the service life of the device.
  • the device according to the present invention makes it possible to send in a single circuit of use a flow rate of hydraulic fluid, which is quickly switchable between two values, minimum and maximum, respectively; for this application, the device according to the present invention is characterized in that two pumps with different nominal flow rates, coupled respectively to the two output shafts of a single epicyclic differential, flow in parallel in the input of the use circuit, and that means are provided for controlling two brakes each associated with one of the two pumps, by crossing a threshold determined by the pressure at the input of the operating circuit.
  • This particularly simple and reliable embodiment is perfectly suited for align for example a high pressure hydraulic cylinder, requiring fluid flow rates which can vary very quickly between a maximum value and a minimum value, for example for aeronautical applications previously mentioned.
  • a preferred embodiment of the device according to the present invention comprises, in the same assembly, an epicyclic differential, an input shaft, coupled to a first axis of the differential, two rotary pumps, coupled respectively to the second and third axes of the differential, and at least one brake associated with each of the two pumps.
  • 1 designates an epicyclic differential, comprising an input shaft 1a, and two output shafts 1b and 1c.
  • Na B.Nb + C.Nc, in which B and C are constant coefficients, positive or negative, depending on the characteristics of the gears constituting the differential 1.
  • To its input shaft 1a is coupled the shaft of a motor 2, of any type, the rotation speed of which we will designate.
  • To the output shafts 1b and 1c of differential 1 are coupled to the respective axes of a main pump, 3b, at high flow rate, and an auxiliary pump, at low flow rate, 3c.
  • a hydraulic fluid tank into which a supply line 8, connected in parallel to the inputs of the two pumps 3b and 3c, and a return line 9, to which the outputs of the pressure detector are connected in parallel threshold 5 (at least if it operates hydraulically), as well as the operating circuit 6; a pressure limiter 10 is inserted between the inlet 6a of the operating circuit 6 and the return line 9.
  • the brake 4c of the auxiliary pump 3c is applied, while the brake 4b of the main pump 3b is released, only the latter flows into the inlet 6a of the accumulator 6; as the main pump 3b is then rotated at the speed the fluid flow rate that said pump 3b sends to accumulator 6 increases progressively to a value corresponding, in FIG. 2, to the abscissa of point A, and proportional to the driving speed of pump 3b, N 0 / B, therefore also at the speed N 0 of the motor 2.
  • the motor 2 continuing to drive the main pump 3b at its speed N 0 , its flow rate itself ceases to increase, and the pressure of the liquid filling the accumulator 6 gradually increases above atmospheric pressure, up to a first determined threshold, S1, which corresponds, in FIG. 2, to the ordinate of point E.
  • S1 a first determined threshold
  • the hydraulic pressure detector 5 sends to the brakes 4b, 4c a signal which simultaneously controls the applying brake 4b and releasing brake 4c.
  • the main pump 3b ceases to flow into the accumulator 6, which is supplied only by the auxiliary pump 3c; as the latter is rotated by the motor 2 at its speed N 0 / C, proportional to the speed N 0 of said motor 2, the fluid flow rate that the auxiliary pump 3c delivers to the accumulator 6 has its nominal value, corresponding to the minimum flow forecast; in FIG. 2, this minimum flow corresponds to the abscissa of point F.
  • the flow of the auxiliary pump 3c in the accumulator 6 then causes an increase in the pressure in the accumulator, from the threshold 51, corresponding to the point F in FIG. 2, up to the maximum pressure ⁇ PM , which is determined by the pressure relief valve 10, and which, in FIG.
  • the pressure detector 5 is arranged to be sensitive, when it detects decreasing pressures, to this second threshold S2, lower than the first threshold, 51, to which it is sensitive when it detects increasing pressures. In other words, the pressure detector 5 is arranged so as to present a hysteresis phenomenon, and a possible embodiment will be described later.
  • the detector 5 sends a signal to the brakes 4b, 4c, which simultaneously causes the brake 4c to be applied and the brake 4b to be released.
  • the auxiliary pump 3c is consequently stopped and the main pump 3b again sends to the accumulator 6 a flow of hydraulic fluid corresponding, in FIG. 2, to the abscissa of point H, and under a pressure corresponding to the ordinate , 52, from point H.
  • FIG. 2 there have been shown in broken lines arcs of hyperbola passing respectively through points E, F and D of the diagram, as well as through point B, which corresponds to the case where the liquid filling the accumulator 6 would have been brought to its maximum pressure by the single flow of the main pump 3b.
  • These hyperbola arcs are parts of equi-power curves, corresponding respectively to the powers P E , P B , P D and P F provided by the device of FIG. 1 when its operating point is respectively at E, B, D and F.
  • the power supplied is all the greater when the corresponding arc of hyperbola is further from the origin 0 of the coordinates.
  • the time t has been plotted on the abscissa, starting from the instant in which the engine 2 of the device of FIG. 1 is started, and, on the ordinate, the power P supplied by this device. If the filling of the accumulator 6 with hydraulic fluid at the maximum pressure ⁇ PH had been obtained by constantly delivering the only main ponp 3b in the accumulator 6, the power supplied would have varied according to the curve DAEB X. In the case previously described, of the alternating operation of pumps 3b and 3c, the power supplied varied according to the curve OAEFD Y.
  • the threshold pressure detector 5 can be of any type, suitable for the brakes 4b and 4c.
  • the pressure detector 5 must be produced so as to transmit a first electrical signal for controlling the application of the brake 4b and the release of the brake 4c, when it detects the passage of an increasing pressure by the first threshold S1, and a second electrical signal for controlling the release of the brake 4b and the application of the brake 4c, when it detects the passage of a decreasing pressure through the second threshold, S2.
  • threshold pressure detector 5
  • this detector is combined with a pressure switch, making it possible to use the hydraulic fluid discharged by one of the two pumps, 3b, 3c. to control the application of its brake and the release of the brake of the other pump by a hydraulic cylinder, an embodiment of which will be described next using FIG. 6.
  • 11 designates a cylindrical chamber, which is arranged in a sealed casing and which is preceded by an anteroom 11a, also cylindrical, and of slightly smaller diameter, so that it is connected to the chamber 11 by an annular bearing 12.
  • 11a is freely slidably mounted a drawer 13, of length less than the sum of the lengths of said chambers; on the side of the anteroom 11a, the drawer 13 firstly has a cylindrical section 13a, with a diameter slightly smaller than that of the anteroom 11a, and, beyond this section 13a, cylindrical sections 13b to 13d , at least the first of which is adjusted in the anteroom 11a so as to ensure leaktightness while allowing the slide 13 to slide freely.
  • the drawer 13 has annular rings 13e to 13g, which are adjusted so as to seal with the wall of the chamber 11, while allowing the slide 13 to slide freely.
  • known sealing means can be provided at the sections 13b, 13e, 13f and 13g of the drawer 13. The latter therefore delimits in the chamber '11 compartments 11b, 11c, and 11d, which are sealed from each other, as well as from the anteroom 11a.
  • a first conduit 13h which communicates the anteroom 11a with the compartment 11c
  • a second conduit, 13i which communicates the compartment 11d of the chamber 11 with its rear compartment 11e.
  • a helical spring 14 which bears, on one side, on the base of the annular ring 13g of the drawer 13, and, on the other side, on a cup 15, itself carried by the end of a threaded rod 16, tightly screwed into a threaded hole in the rear wall 17 of the detector casing 5.
  • a conduit 18 is also arranged which allows to bring into the anteroom 11a the pressure prevailing at all times at the inlet 6a of the use circuit 6, a conduit 19 which is connected, on one side, by branches 19a and 19b, respectively to the compartments 11b and 11d or 11c, and, on the other side, to a line 20, leading to a hydraulic brake control cylinder 4b and 4c, as well as a conduit 21, connecting the rear compartment 11e of the chamber 11 to the line of return 9 (see also Figure 1).
  • the pressure switch detector illustrated in FIGS. 4 and 5 operates as follows: as long as the pressure at the inlet 6a of the operating circuit 6 is less than the first threshold, 51, this pressure, which also prevails in l the anteroom 11a and, via the conduit 13h, in the compartment 11c, is insufficient to overcome the thrust of the compressed spring 14, so that the latter keeps the left end of the drawer 13 applied against the corresponding terminal surface of the 'anteroom 11a, as illustrated in Figure 4.
  • the rear compartment 11e, the duct 13i of the drawer 13, the compartment 11d, the conduits 19b, 19, 19a, 20 and the compartment 11b are then filled hydraulic fluid at atmospheric pressure, so that the hydraulic cylinder for controlling the brakes 4b and 4c is not actuated, which corresponds to the release of the brake 4b and the application of the brake 4c.
  • the pressure at the inlet 6a of the operating circuit 6 approaches the first threshold S1 (point E in FIG. 2), the result of the forces which the pressure prevailing in the anteroom 11a exerts on the left face and the annular crown 13i of the drawer 13 becomes sufficient to overcome the thrust of the spring 14 and consequently to move said drawer 13 to the right of FIG. 4.
  • the fluid hydraulic under the pressure S1 is transmitted by the circuit 18, 11a, 13h, 11c, 19a, 19b, 19, 20 to the hydraulic cylinder which immediately controls the application of the brake 4b and the release of the brake 4c.
  • the acceleration, previously indicated, of the displacement of the slide 13 the switching of the pressure prevailing in the line 20, from the minimum value (for example atmospheric pressure), to the control value 51, takes place so quickly that the time during which the two pumps 3b and 3c are simultaneously driven by the motor is reduced as much as possible.
  • the switch 5 thus produces a very rapid switching of the flow rate sent into the input 6a of the use circuit 6, from its minimum value, corresponding to the abscissa of point G in FIG. 2, to its maximum value, corresponding to l abscissa of the point H, and this as soon as the detector 5 has detected the reduction in the pressure at the input of the use circuit to the value of the second threshold 52, lower than that of the first threshold S1.
  • the value of the first threshold 51 can be adjusted by adjusting the minimum compression of the spring 14, by rotation of the threaded rod 16 outside the housing of the detector 5.
  • the device illustrated in Figure 6 is an assembly 22 comprising in housings 22a to 22e, a differential planetary 1, the first axis of which, 1a, is coupled to an input shaft, which can itself be coupled to any motor shaft, two rotary pumps, one, 3b, of high flow rate, which is coupled to the second axis, 1b, of differential 1 and the other, 3c, at low flow, which is coupled to the third axis, 1c, of differential 1, as well as two disc brakes, 4b and 4c, associated respectively with pumps 3b and 3c , and in particular to the axes 1b and 1c to which they are respectively coupled, finally a hydraulic cylinder 23, serving for the simultaneous control, and in phase opposition, of the two disc brakes 4b and 4c.
  • the epicyclic differential 1 consists essentially of a plate with conical teeth, 1d, wedged on the first axis 1a, a crown 1e, of the same diameter and of the same conical teeth as the plate 1d, and integral of the second axis, 1b, itself of tubular shape, as well as two planetary gears, 1f and 1g, wedged between the plate 1d and the crown 1e, on the same radial axis, 1h, so as to mesh simultaneously with the respective teeth said plate and said crown; the third axis 1c, which is internal and coaxial with the second tubular axis, 1b, and of greater length than it, is fixed by one end to the radial axis 1h of the planetary, in the extension of the first axis 1a of the differential.
  • the pumps 3b and 3c are, for example, positive displacement pumps.
  • the driven pinion of the main pump 3b is fixed on a shaft 24, mounted freely rotating in the casing, and it is rotated by a pinion 25, keyed on the second tubular axis, 1b, of the differential 1.
  • the auxiliary pump 3c is disposed in the casing following the main pump 3b, and its driven pinion is rotated by a pinion 27 keyed on the end part of the third axis, 1c, of the differential 1, which extends beyond its second axis, tubular, 1b.
  • the disc supports, Db, De of the two brakes 4b, 4c are keyed respectively on the second and third axes, 1b and 1c of the differential 1; these discs are themselves arranged in a room cylindrical of the casing 22d, which is interposed between the two pumps 3b and 3c; the fixed linings Gb1 and Gc1 of the two brakes 4b and 4c are fixed, one opposite the other, at the level of the corresponding discs, to the end walls of the mentioned chamber; the movable linings Gb2 and Gc2 of the two brakes 4b and 4c are also mounted back to back, between the two corresponding discs, Db and Dc, on an annular piece 23a, which is itself coupled in translation to the piston 23b of the hydraulic control cylinder 23, by at least one threaded rod 23d parallel to the axis 1c.
  • the chamber 23e of the jack 23 is itself arranged in the casing 22e at the end opposite to that where the differential 1 is mounted; its piston 23b has in particular the shape of a bowl, on the bottom of which bears a return spring 26.
  • 23f designates the outlet, in the chamber 23e of the jack, of its supply pipe, which can be connected for example by a line 20 to channel 19 of the pressure switch detector 5, illustrated in FIGS. 4 and 5 and previously described.
  • FIG. 6 is susceptible of numerous variants, all of which fall within the scope of the invention.
  • the rotational speeds of the three axes 1a to 1c are linked by the linear relationship: so that when the input shaft 1a is driven at the speed, No, of the motor, or else the pump 3b rotates in the opposite direction to the motor, at the same speed N 0 , or else the pump 3c rotates in the same direction, at half speed, N O / 2.
  • Different relationships between the respective speeds of the two pumps and that of the motor could be obtained by swapping the roles of the three axes of the differential.
  • FIG. 7 represents a second embodiment of the invention comprising four epicyclic differentials, 1A to 1D, which are connected in cascade; the first axis a, or input axis, of the first differential 1A, is coupled to the shaft of a motor 2; the second axis, such as Ab, (respectively, Bb, Cb, Eb) of each of the differentials, such that 1A (respectively 1B, 1C, 1D) is coupled to the axis of a rotary pump such as 3a, (respectively 3b, 3c, 3d), while its third axis, such as Ac (respectively Bc, Cc) is coupled to the first axis, or input axis of the next differential of the cascade, for example 1B (respectively 1C, 1D) to with the exception of the third axis, Ec, of the last differential, 1D, of the cascade, which is also coupled to the shaft of a rotary pump, 3e.
  • the second axis such as Ab
  • the various pumps 3a to 3e are associated respectively with brakes 4a to 4e, for example of the electromagnetic type.
  • the aspirations of pumps 3a to 3e are supplied by appropriate pipes, from hydraulic fluid reservoirs, which can be provided in a number equal to that of the pumps, or else grouped in a common tank 7.
  • the outlets of the various pumps 3a to 3e are connected by appropriate pipes to the input 6a of the use circuit 6; a bypass of the discharge line of the five pumps leads to a control device 5, from which electrical lines leave, intended to transmit electrical control signals to the various electromagnetic brakes 4a to 4e.
  • the automatic control device 5 is capable of numerous known embodiments, adapted to the application envisaged in each case.
  • the automatic control device 5 is arranged so as to simultaneously produce the application of the brakes associated with all the pumps, except a single, the brake of which can then be applied at a programmed time, at the same time as the brake of one of the other pumps is immediately released; this latter switching is triggered by the automatic device 5 when the threshold pressure detector incorporated therein, which detects the discharge pressure of the pump currently in service, passes through a determined threshold, by increasing or decreasing values, as previously described in connection with the first embodiment.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Regulating Braking Force (AREA)
  • Valves And Accessory Devices For Braking Systems (AREA)
EP81400883A 1980-06-19 1981-06-03 Einrichtung zum Erzeugen von Hydraulikflussmengen hintereinander abgestufter Werte Expired EP0042774B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8013581A FR2485110A1 (fr) 1980-06-19 1980-06-19 Dispositif pour produire successivement des debits de fluide hydraulique de valeurs echelonnees
FR8013581 1980-06-19

Publications (2)

Publication Number Publication Date
EP0042774A1 true EP0042774A1 (de) 1981-12-30
EP0042774B1 EP0042774B1 (de) 1983-09-14

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EP81400883A Expired EP0042774B1 (de) 1980-06-19 1981-06-03 Einrichtung zum Erzeugen von Hydraulikflussmengen hintereinander abgestufter Werte

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US (1) US4420289A (de)
EP (1) EP0042774B1 (de)
DE (1) DE3160874D1 (de)
FR (1) FR2485110A1 (de)

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US5842848A (en) * 1997-01-03 1998-12-01 Knowles; Frederick W. Compact high-volume gear pump
WO2007031084A1 (de) * 2005-09-13 2007-03-22 Sauer-Danfoss Aps Hydraulische maschine
CN104632739A (zh) * 2014-12-09 2015-05-20 西南石油大学 一种伺服电机换向阀

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BR0103443A (pt) * 2001-08-21 2004-03-09 Petroleo Brasileiro Sa Sistema e método de bombeio multifásico
US20050110337A1 (en) * 2003-11-25 2005-05-26 Yuhong Zheng Electronic pressure relief strategy
US9028222B2 (en) * 2011-08-26 2015-05-12 Hamilton Sundstrand Corporation Variable output pump
US10428816B2 (en) 2016-10-24 2019-10-01 Hamilton Sundstrand Corporation Variable speed multi-stage pump

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US5842848A (en) * 1997-01-03 1998-12-01 Knowles; Frederick W. Compact high-volume gear pump
WO2007031084A1 (de) * 2005-09-13 2007-03-22 Sauer-Danfoss Aps Hydraulische maschine
CN104632739A (zh) * 2014-12-09 2015-05-20 西南石油大学 一种伺服电机换向阀

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FR2485110B1 (de) 1984-11-30
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US4420289A (en) 1983-12-13
EP0042774B1 (de) 1983-09-14

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