US3924971A - Device for regulating the supply of pressurized fluid of two circuit systems having at least two pumps of constant cubic capacity - Google Patents

Device for regulating the supply of pressurized fluid of two circuit systems having at least two pumps of constant cubic capacity Download PDF

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Publication number
US3924971A
US3924971A US544200*A US54420075A US3924971A US 3924971 A US3924971 A US 3924971A US 54420075 A US54420075 A US 54420075A US 3924971 A US3924971 A US 3924971A
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United States
Prior art keywords
distributor
pumps
conduit
feed conduit
control
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Expired - Lifetime
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US544200*A
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English (en)
Inventor
Jean Noel Jacquot
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Poclain SA
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Poclain SA
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Classifications

    • 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
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/17—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors using two or more pumps
    • 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
    • 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
    • F04B49/10—Other safety measures
    • 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
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • 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
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/3059—Assemblies of multiple valves having multiple valves for multiple output members
    • F15B2211/30595—Assemblies of multiple valves having multiple valves for multiple output members with additional valves between the groups of valves for multiple output members
    • 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
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40523—Flow control characterised by the type of flow control means or valve with flow dividers
    • F15B2211/4053—Flow control characterised by the type of flow control means or valve with flow dividers using valves
    • 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
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/428—Flow control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/40—Flow control
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the return line
    • 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6054—Load sensing circuits having valve means between output member and the load sensing circuit using shuttle valves
    • 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
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7142—Multiple output members, e.g. multiple hydraulic motors or cylinders the output members being arranged in multiple groups
    • 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
    • F15B2211/78—Control of multiple output members

Definitions

  • ABSTRACT PP N05 544,200 This invention relates to a device for supplying two circuits and 11 by means of four pumps 2, 3, 4, 5.
  • Foreign Application Priority Data The delivery pressures of the two circuits act on the Jan. 30, 1974 France 74.03096 Control jacks 38, 39, 43 and 44 of two Cutting distributors which, when they are actuated, put pump 52 US. (:1. 417/286 4 ahd/or P p 3 in communication With the reservoir 51 Im. cl. F04B 49/00 avoiding for the engine 1 an excessive load [58] Field of Search 417/286, 287, 288, 426, exceeding its maximum p 417/428 An application of the invention is the achievement of a high efficiency of a supply circuit.
  • the present invention relates to a device for regulating the supply of pressurised fluid of two circuit systems having at least two pumps of constant cubic capacity.
  • Pressurised fluid feed devices which, by means of a plurality of pumps of constant cubic capacity, driven by a single Diesel engine, feed two circuit systems.
  • One of these devices consists in making one or more of the pumps normally supplying each of the circuits, without pressure to a fluid tank. This communication with the tank, of the delivery of the pumps, is moreover effected by controlling distributors disposed in the delivery conduits, control by the delivery pressure itself of each circuit. Nevertheless, the said control does not allow optimum use of the power of the Diesel engine, particularly in the case of the delivery of all the pumps being able to be directed towards one of the circuits only.
  • the invention proposes a new type of control of the distributors, by means of a judicious combination of the effects of the pressures of the two circuit systems. In this manner, it enables the connection between the delivery of one pump and the circuit system connected thereto to be maintained, for a pressure in this circuit which may be greater than the cut-off pressure beyond which, in the known devices, said delivery is placed in communication with the tank.
  • the invention seeks to provide a device feeding two circuit systems with pressurised fluid, constituted by:
  • a first two-way distributor disposed in the first feed conduit, ensuring, in its first position, the continuity of the first feed conduit and, in its second position, the communication of that part of the feed conduit included between the first pump and the first distributor with the tank,
  • a second two-way distributor disposed in the second feed conduit, ensuring, in its first position, the continuity of the second feed conduit and, in its second position, the communication of that part of the second feed 2 -conduit, included between the second pump and the second distributor, with the tank,
  • a third two-way distributor disposed in the second feed conduit between the second distributor and the second circuit system, and
  • a connecting conduit which connects the third distributor to that part of the first feed conduit included between the first distributor and the first circuit system.
  • the third distributor in its first position, establishes communication between the second distributor and the second circuit system and, in its second position, establishes communication between the second distributor and the connecting conduit and obturates that part of the second feed conduit connected directly to the second feed circuit.
  • First and second control members, as well as a first return member, are coupled to the first distributor, each of the first and second control members having an effect opposing that of the first return member, and said latter having an effect tending to place this first distributor in its first position, whilst third and fourth control members, as well as a second return member, are coupled to the second distributor, each of the third and fourth control members having an effect opposing that of the second return member, and said latter having an effect tending to place this second distributor in its first position.
  • a first control conduit connects that part of the first feed conduit, included between the first distributor and the first circuit system, to the first control member
  • a second control conduit connects that part of the second feed conduit included between the second distributor and the third distributor to the second control member
  • an auxiliary conduit connects that part of the first feed conduit included between the first distributor and the first circuit system to that part of the second feed conduit included between the second and third distributors, a shuttle valve being disposed in said auxiliary conduit,
  • a third control conduit connects that part of the second feed conduit included between the second and third distributors to the third control member
  • a fourth control conduit connects the output of the shuttle valve to the fourth control member.
  • the pumps of the first and second groups of pumps are coupled to a single drive motor, of which the maximum power is lower than the sum of the maximum powers of the various pumps.
  • the first and second control members each consists of a hydraulic ram the ratio of the cross-section of said rams is equal to the ratio of the sum of the cubic capacities of the pumps of the first group and the sum of the cubic capacities of the pumps of the second group, less the value of the cubic capacities of the second pump of the said second group respectively.
  • the third and fourth control members each consists of a hydraulic ram the ratio of the cross-sections of said rams is equal to the ratio of the sum of the cubic capacities of the pumps of the second and first group respectively.
  • FIG. 1 is the diagram of a supply device in accordance with the invention.
  • FIG. 2 is a diagram showing the conditions of operation of the device of FIG. 1.
  • the device shown in the drawings includes:
  • the driving shafts 12, 13, 14, of the pumps 2, 3, 4, 5 are rigidly fixed in rotation with pinions 16, 17, 18, 19 respectively.
  • a pinion is rigidly fixed in rotation with the output shaft 21 of the engine 1.
  • Pinion 17 meshes with pinions 16 and while pinion 18 meshes with pinions 19 and 20.
  • a conduit 22 connects the first distributor 7 with the first circuit of utilisation 10, while a conduit 23 connects said distributor 7 with the reservoir 6 and a return conduit connects circuit 10 with reservoir 6.
  • the pump 2 is connected to the reservoir 6 by its suction conduit 25 and to conduit 22 by its discharge conduit 26.
  • the pump 3 is connected to reservoir 6 by its suction conduit 27 and to the first distributor 7 by its discharge conduit 28.
  • the pump 4 is connected to reservoir 6 by its suction conduit 29 and to the second distributor 8 by its discharge conduit 30.
  • the second distributor 8 is in turn connected to the third distributor 9 by conduit 31, while the second circuit of utilisation 11 is connected to the reservoir 6 by return conduit 32 and to the third distributor by conduit 33.
  • a conduit 50 connects the second distributor 8 to the reservoir 6.
  • the pump is connected to the reservoir 6 by its suction conduit 34 and to the conduit 31 by its discharge conduit 35. Finally, joining conduit 36 connects the third distributor 9 to the conduit 22.
  • Two rams 38 and 39 having respective sections S and S are coupled to distributor 7 and their effect opposes that of a first spring 40, also coupled to the said distributor. These rams are respectively connected to conduits 22 and 31 by conduits 41, 42.
  • rams 43, 44 of respective sections S S are coupled to distributor 8 and their effect opposes that of a second spring 45, also coupled to the said distributor.
  • C C C and C are the cubic capacities of pumps 2, 3, 4 and 5 respectively.
  • the first position corresponds to the predominance of the effect of spring 40 on the effects of rams 38, 39, to the placing in communication of conduits 22 and 28 and to the obturation of conduit 23 at the level of this distributor, and
  • the first position corresponds to the predominance of the effect of spring 45 on the effects of rams 43, 44, to the placing in communication of conduits 30 and 31 and to the obturation, at the level of this distributor, of conduit 50, and the second position, to the placing in communication of conduits 30 and 50 and to the obturation of conduit 31 at the level of this distributor.
  • the first position corresponds to the placing in communication of conduits 31 and 33 and to the obturation of conduit 36, at the level of this distributor, and
  • the second position corresponds to the placing in communication of conduits 31 and 36 and to the obturation of conduit 33 at the level of this distributor.
  • a member for voluntary control in the present case manual control, is furthermore coupled to the third distributor 9.
  • the graph of FIG. 2 shows the zones of variation of the pressure P prevailing in the conduit 22, at the input of circuit 10, in accordance with the values of pressure P prevailing in the conduit 33 at the input of circuit 11.
  • Pressures pA and pC in A and C are equal to 320 kgp/cm for example.
  • Two other segments of straight line cross at D, in the zone OABC, segment DE being parallel to Op, and segment DF being parallel to Op
  • Another segment of straight line GH is parallel to DF and corresponds to a pressure pI-l superior to pH but inferior to pC.
  • the jacks 39 and 44 do not exist:
  • Q supplying circuit 11 (distributor 9 in its first position); zone AEDP, Q only supplying circuit 10, (Q Q supplying circuit 11;
  • the first equation means that before placing in communication the discharge of pump 4 (conduit 30) with the reservoir 6 by means of the second distributor 8, the sum of the power of pumps 2 to 5 (product of the pressure by the outflow) is equal to the maximum power P of engine 1.
  • zone l-IGKMG (Q Q supplying circuit and Q only supplying circuit 11;
  • equations (1) and (2) may also read:
  • the second distributor 8 puts the discharge conduit of pump 4 in communication with the reservoir 6 before the first distributor 7 puts in communication with reservoir 6 the discharge conduit of pump 3, this being obtained by selecting the characteristics of the control rams of distributors 7 and 9 and springs 40 and 45.
  • the solution suggested makes it possible to obtain a gain of flow for the operations corresponding to the hatched zones of the diagram of FIG. 2. In the example shown, these gains of flow are 33 percent and 100 percent for the circuits 10 and 11 respectively. It is then obvious that adopting the solution suggested allows an important increase in the output of the supply device, while still not exceeding the value P of the maximum power of engine 1.
  • the word distributor has been taken in a broad sense and designates a distributing valve of any type which directs the fluid in a predetermined direction; in practice this valve may consist either in a slide valve or in a controlled valve.
  • a first two-way distributor disposed in the first feed conduit ensuring, in its first position, the continuity of the first feed conduit and, in its second position, the communication of that part of the feed conduit included between the first pump and the first distributor with the tank,
  • a second two-way distributor disposed in the second feed conduit ensuring, in its first position, the continuity of the second feed conduit and, in its second position, the communication of that part of the sec ond feed conduit, included between the second pump and the second distributor with the tank,
  • a third two-way distributor disposed in the second feed conduit between the second distributor and the second circuit system and a connecting conduit which connects the third distributor to that part of the first feed conduit included between the first distributor and the first circuit system, whilst the third distributor in its first position, establishes communication between the second distributor and the second circuit system and, in its second position, establishes communication between the second distributor and the connecting conduit and obturates that part of the second feed conduit connected directly to the second feed circuit, well as a first return member are coupled to the first distributor each of the first and second control members having an effect opposing that of the first return member, and said latter having an effect tending to place this first distributor in its first position, whilst third and fourth control members, as well as a second return member are coupled to the second distributor each of the third and fourth control members having an effect opposing that of the second return member, and said latter having an effect tending to place this second distributor in its first position, a first control conduit connecting that part of the first feed conduit, included between the first distributor and the first circuit system to
  • Device characterized in that power f which is lower than the sum of the maxi the third and fourth control members each consists ot a hydraulic ram the ratio of the cross-sections of said powers the vanfjus pumps jacks is equal to the ratio of the sum of the cubic capac- 2.
  • Device characterized in that ities f the pumps f the Second and fi t group reshecthe first and second control members each consists of a tively.
  • the third and fourth control members each consists of a ities of the pumps of the first group and the sum of the hydraphc ram the ratio of the crosysectlon? of sald l0 rams is equal to the ratlo of the sum of the cubic capaccubic capacities of the pumps of the Second group less ities of the pumps of the second and first group respecthe value of the cubic capacity of the second pump of i l the said second group respectively.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Details Of Reciprocating Pumps (AREA)
US544200*A 1974-01-30 1975-01-23 Device for regulating the supply of pressurized fluid of two circuit systems having at least two pumps of constant cubic capacity Expired - Lifetime US3924971A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR7403096A FR2259255B1 (zh) 1974-01-30 1974-01-30

Publications (1)

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US3924971A true US3924971A (en) 1975-12-09

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US544200*A Expired - Lifetime US3924971A (en) 1974-01-30 1975-01-23 Device for regulating the supply of pressurized fluid of two circuit systems having at least two pumps of constant cubic capacity

Country Status (11)

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US (1) US3924971A (zh)
JP (1) JPS598683B2 (zh)
AR (1) AR204734A1 (zh)
BE (1) BE824844A (zh)
BR (1) BR7500555A (zh)
CA (1) CA1009538A (zh)
DE (1) DE2503801A1 (zh)
ES (1) ES434262A1 (zh)
FR (1) FR2259255B1 (zh)
GB (1) GB1489438A (zh)
IT (1) IT1027415B (zh)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4089166A (en) * 1974-03-20 1978-05-16 Tyrone Hydraulics, Inc. Automatic pump control system
US4256439A (en) * 1978-11-20 1981-03-17 The Japan Steel Works Ltd. Power control system for multiple pumps
US4787204A (en) * 1987-09-28 1988-11-29 J. I. Case Company Common relief valve
US5228289A (en) * 1983-06-29 1993-07-20 Peter Norton Plural hydraulic pump system with unloading valve
US5842837A (en) * 1995-08-29 1998-12-01 Aisin Seiki Kabushiki Kaisha Tandem pump apparatus
US20160102687A1 (en) * 2014-10-08 2016-04-14 Weber-Hydraulik Gmbh Hydraulic unit

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
LU76197A1 (zh) 1976-11-12 1978-07-10
DE4317397A1 (de) * 1993-05-25 1994-12-01 Linde Ag Flurförderzeug mit einem Lastaufnahmemittel und zwei parallel geschalteten Hubzylindern
JP6434462B2 (ja) 2016-08-30 2018-12-05 ファナック株式会社 溶接の状態を判定するスポット溶接装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3695783A (en) * 1969-12-03 1972-10-03 Ingebret Soyland Means for regulating power for pumps
US3716308A (en) * 1970-01-28 1973-02-13 Bosch Gmbh Robert Hydraulic system
US3723026A (en) * 1970-04-22 1973-03-27 I Soyland Effect regulator for constant and variable volume-flow pumps

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3695783A (en) * 1969-12-03 1972-10-03 Ingebret Soyland Means for regulating power for pumps
US3716308A (en) * 1970-01-28 1973-02-13 Bosch Gmbh Robert Hydraulic system
US3723026A (en) * 1970-04-22 1973-03-27 I Soyland Effect regulator for constant and variable volume-flow pumps

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4089166A (en) * 1974-03-20 1978-05-16 Tyrone Hydraulics, Inc. Automatic pump control system
US4256439A (en) * 1978-11-20 1981-03-17 The Japan Steel Works Ltd. Power control system for multiple pumps
US5228289A (en) * 1983-06-29 1993-07-20 Peter Norton Plural hydraulic pump system with unloading valve
US4787204A (en) * 1987-09-28 1988-11-29 J. I. Case Company Common relief valve
US5842837A (en) * 1995-08-29 1998-12-01 Aisin Seiki Kabushiki Kaisha Tandem pump apparatus
US20160102687A1 (en) * 2014-10-08 2016-04-14 Weber-Hydraulik Gmbh Hydraulic unit
US10041508B2 (en) * 2014-10-08 2018-08-07 Weber-Hydraulik Gmbh Hydraulic unit

Also Published As

Publication number Publication date
DE2503801A1 (de) 1975-07-31
CA1009538A (en) 1977-05-03
FR2259255B1 (zh) 1976-11-26
BR7500555A (pt) 1975-11-11
JPS50107386A (zh) 1975-08-23
JPS598683B2 (ja) 1984-02-27
AR204734A1 (es) 1976-02-27
ES434262A1 (es) 1976-12-16
IT1027415B (it) 1978-11-20
FR2259255A1 (zh) 1975-08-22
BE824844A (fr) 1975-05-15
GB1489438A (en) 1977-10-19

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