US3750705A - Hydraulic control device - Google Patents

Hydraulic control device Download PDF

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Publication number
US3750705A
US3750705A US00195198A US3750705DA US3750705A US 3750705 A US3750705 A US 3750705A US 00195198 A US00195198 A US 00195198A US 3750705D A US3750705D A US 3750705DA US 3750705 A US3750705 A US 3750705A
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US
United States
Prior art keywords
pressure
valve
main control
passage
control valve
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.)
Expired - Lifetime
Application number
US00195198A
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English (en)
Inventor
A Blumer
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.)
Netstal Maschinen AG
Original Assignee
Maschinenfabrik und Giesserei Netstal AG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
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Application granted granted Critical
Publication of US3750705A publication Critical patent/US3750705A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/76—Measuring, controlling or regulating
    • B29C45/82—Hydraulic or pneumatic circuits
    • 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
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • 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
    • F15B2211/2053—Type of pump
    • 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
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • 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
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional 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
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • 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
    • F15B2211/426—Flow control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/50—Pressure control
    • F15B2211/575—Pilot pressure control
    • 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
    • F15B2211/635—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements
    • F15B2211/6355—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements having valve means
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/86493—Multi-way valve unit
    • Y10T137/86574—Supply and exhaust
    • Y10T137/86582—Pilot-actuated
    • Y10T137/86614—Electric

Definitions

  • the control device is designed to control a hydraulically operated piston unit, particularly the melting and injection screw unit of an injection molding machine for plastics.
  • the control device includes a main control valve reciprocable in a cylindrical guide or bore formed in a valve body, and controlling the connections between 2 source of hydraulic fluid under pressure, a pressure consumer and a return flow collector for the fluid, each of which is connected to a respective passage communicating with the guide.
  • the main control valve is subjected to axial pressures, variable in at least one stage, to control the connections between the passages.
  • a reversing valve is mounted on the housing to form a unit therewith, and one or more anticipatory control-pressure valves are also mounted on the housing. The reversing valve is effective to reverse the position of the main control valve, while the anticipatory control-pressure valves act on the main control valve to determine the magnitude of the flow area between chambers, each connected to a respective passage in the housing.
  • This invention relates to hydraulic control devices for controlling hydraulic pressure consumers and, more particularly, to a novel and improved hydraulic control device in which all necessary adjusting elements and reversing elements act on a single control valve which performs all the necessary functions with respect to supplying pressure to the pressure consumer, terminating the supply of pressure, and return of hydraulic fluid from the consumer to a hydraulic fluid receiver.
  • the main control valve comprises a housing or valve body formed with a longitudinally extending cylindrical bore constituting a cylindrical guide. This bore is radially enlarged at axially spaced area therealong to define respective chambers, and each chamber is connected to a respective passage.
  • the passages are adapted for connection, respectively, to a source of hydraulic medium under pressure, to a pressure consumer and to a return flow collector for the hydraulic medium.
  • the control valve is a cylindrical piston slidable in the bore, and has axially spaced lands thereon cooperating with the bore to control connections between the three chambers, the piston being biased in one axial direction by a spring engaged with the stem of an auxiliary piston in a further chamber.
  • the auxiliary piston is engageable with a longitudinally adjustable tubular feeler controlling supply of pressure to one side of the auxiliary piston and further limiting the movement of the auxiliary piston, and thus of the main piston or control valve, in one axial direction.
  • a reversing valve is mounted on the valve body or housing and is in communication with the bore, and one or more anticipatory control pressure valves are also mounted on the housing in communication with the bore. The reversing valve is electromagnetically operated.
  • the anticipatory control pressure valves are adjustable to set the respective control pressures, and in a modification of the invention, only a single anticipatory control pressure valve is provided and is adjustable electromagnetically under the control of a selector switch.
  • An object of the invention is to provide an improved hydraulic control device for controlling a hydraulically operated piston unit.
  • Another object of the invention is to provide such a control device in which all necessary adjusting and reversing elements act on a single control valve.
  • a further object of the invention is to provide such a hydraulic control device in which the single control valve performs all the necessary functions, thereby reducing the mounting expenditure and the transfer losses between the pressure generating point and the pressure consuming point to a minimum.
  • FIG. 2 is a view similar to FIG. 1 but illustrating the course of the pressure medium during the injection phase
  • FIG. 3 is an axial sectional view of the main control valve of the control device shown in FIGS. 1 and 2;
  • FIG. 4 is a schematic illustration, similar to FIGS. 1 and 2, illustrating a variation of the control device shown in FIGS. 1 and 2.
  • connection A is provided for a pressure line leading to a hydraulically operated piston (not shown) of the plastic melting and injection screw of a plastic injection molding machine.
  • a second connection T is provided for a line leading to a storage tank (not shown) for receiving the return hydraulic pressure medium, and a third connection P is provided for a line leading to a source of hydraulic medium uner pressure.
  • Respective lines 1, 2 and 3 connect the connection points A, T and P to a main control valve 4.
  • two anticipatory control pressure valves 5 and 6, for adjusting the back pressure of the screw and of the injection pressure, respectively, are associated with main control valve 4, as is also an electromagnetically actuated reversing valve 7.
  • the control device 4 comprises a housing 10 formed with a longitudinally extending bore or passage 11 in which there is mounted, for reciprocation, a main control valve in the fonn of a slide valve 12 of substantially circular cross section.
  • Valve 12 has three control sections or lands 14a, 14b and 140, spaced axially from each other by two circumferentially extending grooves or recesses 13a and 13b, The lands are guided in four rings or internal annular ribs 15a, 15b, 15c and 15d which define, in passage or bore 11, chambers 16a, 16b, 16c and 16d.
  • Reversing valve 7 is mounted on housing 10 and communicates, through bores 17a and 17b, with bores 17c and 17d each communicating with a respective chamber 16b and 16a.
  • Anticipatory control pressure valves 5 and 6 communicate, through a duct 18, with chambers 16a.
  • the lines 1, 2 and 3 are connected to chambers 16c, 16b and 16d, respectively.
  • a cross bore 19 in control section or land 14b connects chamber 16c with an axial bore in valve 12, and this bore 20 is open in the range of end section or land 14c of valve 12, at the axial end of valve 12.
  • a coil spring 21 which engages the stem of an auxiliary piston 22 movable in chamber I6e.
  • Chamber 16s is in communication with an axial passage 23a of a feeler 23 mounted in coaxial relation with slide valve 12 in housing 10.
  • the parts of chamber 16c on opposite sides of auxiliary piston 22 are in communication with each other through a transverse bore 24a and an axial bore 24b in piston 22.
  • the left and right parts of chamber 16e are connected by respective lines and 26 to electromagnetic reversing valve 7, shown in FIGS. 1 and 2, and valve 7 connects these two lines with either tank connection line 2 or pressure connection line 3.
  • Feeler 23 can be adjusted mechanically so that the minimum size of the space to the right of ausixliary piston 22, when piston 22 has its right face engage feeler 23 extending into chamber 16c, is determined.
  • the pressure acting in line 1, and thus on the hydraulic piston of the screw moving backwardly during the melting phase depends on the passage, in valve 4, between chambers 16c and 16d, and thus on the position of slide valve 12 and its annular groove 13b.
  • the position of slide valve 12 can be adjusted, in the embodiment of the invention shown in FIGS. 1, 2 and 3, by adjusting anticipatory control pressure valve 5.
  • valve 5 it is possible to adjust, through line 18, the pressure in chamber 160, and thus the position of slide valve 12 and the flow area of the passage between chambers 16c and 16d through groove 13b.
  • the desired back pressure can also be regulated in several stages, if necessary, in which case a corresponding number of anticipatory control pressure valves can be provided.
  • magnetic reversing valve 7 is energized and switched into the position shown in FIG. 2, with slide valve 12 being displaced into the solid line position shown in FIG. 3, or to the right.
  • Pressure line 3 is thus connected through groove 13a of valve 12 to pressure consumption line 1, while collar 14b seals consumption line 1 from tank or return line 2.
  • the desired injection pressure is adjusted on anticipatory control pressure valve 6, through which the pressure in chamber 160, acting on the end 14a of slide valve 12, is determined.
  • the passage between chamber 16b and 16c, as to its flow area through groove [30, is thus determined by the position of slide valve 12.
  • valve 12 If the hydraulic pressure of the load, or that acting on the screw, has risen to the value adjusted on valve 6, this valve opens and effects, in chamber 16a, a pressure drop causing valve 12 to move correspondingly to the left as viewed in FIG. 3. Due to the pressure loss between the pressure consumption point and connection A, the pressure on the right hand side of the slide valve 12 varies so that slide valve 12 moves automatically into the correct position.
  • a single-stage back pressure is provided, and is adjusted by means of valve 6.
  • the back pressure during injection can also be adjusted in two or more stages by supplying the pressure medium, for example, through a corresponding magnetic reversing valve, through different anticipatory control pressure valves. In this way, different injected pressures can be set.
  • the auxiliary piston 22 is moved similtaneously with the start of the injection phase by the magnetic reversing valve 7 into the end position in chamber 162, as shown in FIG. 3 on the right side, so that it closes the opening to feeler passage 23a.
  • the pressure medium supplied to the part of chamber 16:: to the left of piston 22 is applied, through bores 24a and 24b acting on a diaphragm, in the chamber part to the right of auxiliary piston 22, so that a back pressure is provided on slide valve 12.
  • FIG. 4 illustrated an embodiment in which the anticipatory control pressure valve 6 also can be adjusted by a selector switch 60, and the adjustment of the back pressure can be effected automatically by electric means.
  • the anticipatory control pressure valve 6 also can be adjusted by a selector switch 60, and the adjustment of the back pressure can be effected automatically by electric means.
  • the electrical contacts can be controlled through end keys in dependence on the distance, or in time dependence, through relays, or electronically, with infinite variation through preselected control cams.
  • a main advantage of the control device is its compactness. That is, all function controls, for example pressure and velocity of the piston unit to be controlled, are effected by means of a signle control valve, the associated auxiliary elements, such as electromagnetic reversing valves, anticipatory pressure control valves, etc., being assembled with the slide vale to form a unit.
  • the following functions are possible by a corresponding combination of anticipatory pressure control valves 5 and 6, magnetic reversing valve 7 and auxiliary piston 22 with a single control valve 12 and a valve body 10:
  • a hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages; a reversing valve mounted on said housing and communicating with said guide; at least one anticipatory controlpressure valve mounted on said housing and communicating with said guide; said reversing valve controlling displacement of said main control valve to open and close a first channel connecting the passage for connection of a'so'urce of hydraulic medium under pressure to the passage for connection to a pusher consumer, and controlling opening and closing of a second channel connecting the passage for connection to a pressure consumer to the passage for connection to
  • each anticipatory control valve is manually adjustable.
  • a hydraulic control device as claimed in claim 1, including electric means operable to adjust automatically each anticipatory control pressure valve.
  • a hydraulic control device for controlling a hydraulically operated piston unit, particularly the melting unit and injection screw unit of an injection molding machine for plastics, said control device comprising, in combination, a housing having a bore forming a cylindrical guide; respective passages in said housing for connection of said guide to a source of hydraulic medium under pressure, to a pressure consumer, and to a return flow collector for a hydraulic pressure medium; a main control valve reciprocable in said guide; means operable to subject said main control valve through axial pressures, variable in at least one stage, to control the connections between said passages, said passages including, considered axially of said guide, a first end passage for connection to a source of hydraulic medium under pressure, a second intermediate passage for connection to a pressure consumer, and a third end passage for connection to a return flow collector; said bore being radially enlarged at axially spaced locations therealong to form first, second and third chambers communicating, respectively, with said first end passage, said second intermediate passage and said third end passage; said main control valve being formed with a land, intermediate
  • a hydraulic control device including an electromagnetically operated reversing valve mounted on said housing; passage means in said housing connecting said reversing valve to said first and fourth chambers for supply thereto and exhaust therefrom of a pressure medium to control displacement of said main control valve; at least one anticipatory control pressure valve mounted on said housing; and further passage means connecting said anticipatory controlpressure valve to said fourth chamber to supply operating fluid under pressure thereto or to exhaust operating fluid therefrom to modulate the axial position of said main control valve as set by said reversing valve to vary the effective cross-sectional area of said channels; said main control valve being formed with an axial passage therethrough extending from said opposite end thereof and communicating, through a cross bore, with said second chamber; said auxiliary piston being formed with passage means therethrough interconnecting the portions of said fifth chamber on opposite sides of said auxiliary piston.
  • a hydraulic control device as claimed in claim 5, in which said housing comprises a single valve body acting as a slide valve housing; each anticipatory control-pressure valve, said electromagnetically operated reversing valve and said auxiliary piston acting conjointly with said-single main control valve and said single valve body to perform, selectively, the following functions:

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Moulds For Moulding Plastics Or The Like (AREA)
US00195198A 1970-11-19 1971-11-03 Hydraulic control device Expired - Lifetime US3750705A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1719570A CH524075A (de) 1970-11-19 1970-11-19 Hydraulische Steuereinrichtung

Publications (1)

Publication Number Publication Date
US3750705A true US3750705A (en) 1973-08-07

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ID=4423504

Family Applications (1)

Application Number Title Priority Date Filing Date
US00195198A Expired - Lifetime US3750705A (en) 1970-11-19 1971-11-03 Hydraulic control device

Country Status (8)

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US (1) US3750705A (enExample)
JP (1) JPS5841366Y2 (enExample)
CA (1) CA932241A (enExample)
CH (1) CH524075A (enExample)
DE (1) DE2150501A1 (enExample)
FR (1) FR2115229B1 (enExample)
GB (1) GB1372593A (enExample)
IT (1) IT940596B (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4638720A (en) * 1980-12-01 1987-01-27 Deere & Company Electro-hydraulic control system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102235392A (zh) * 2011-05-20 2011-11-09 上海光塑机械制造有限公司 一种插装阀先导油控制装置

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2962002A (en) * 1956-04-10 1960-11-29 Sanders Associates Inc Two-stage hydraulic servo valve
US2983956A (en) * 1958-03-13 1961-05-16 Essex Wire Corp Injection molding machine
US3286734A (en) * 1964-11-16 1966-11-22 Goodyear Tire & Rubber Three way pressure control servo valve
US3410306A (en) * 1966-10-27 1968-11-12 Gen Signal Corp Control valve with lockout element
US3508583A (en) * 1965-08-30 1970-04-28 Ford Motor Co Servo control valve
US3520322A (en) * 1965-08-30 1970-07-14 Ford Motor Co Fluid pressure control system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2962002A (en) * 1956-04-10 1960-11-29 Sanders Associates Inc Two-stage hydraulic servo valve
US2983956A (en) * 1958-03-13 1961-05-16 Essex Wire Corp Injection molding machine
US3286734A (en) * 1964-11-16 1966-11-22 Goodyear Tire & Rubber Three way pressure control servo valve
US3508583A (en) * 1965-08-30 1970-04-28 Ford Motor Co Servo control valve
US3520322A (en) * 1965-08-30 1970-07-14 Ford Motor Co Fluid pressure control system
US3410306A (en) * 1966-10-27 1968-11-12 Gen Signal Corp Control valve with lockout element

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4638720A (en) * 1980-12-01 1987-01-27 Deere & Company Electro-hydraulic control system

Also Published As

Publication number Publication date
CA932241A (en) 1973-08-21
CH524075A (de) 1972-06-15
FR2115229B1 (enExample) 1975-07-18
DE2150501A1 (de) 1972-06-08
FR2115229A1 (enExample) 1972-07-07
GB1372593A (en) 1974-10-30
JPS5372086U (enExample) 1978-06-16
IT940596B (it) 1973-02-20
JPS5841366Y2 (ja) 1983-09-19

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