US3828813A - Control device for load-independent flow regulation - Google Patents

Control device for load-independent flow regulation Download PDF

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Publication number
US3828813A
US3828813A US33227473A US3828813A US 3828813 A US3828813 A US 3828813A US 33227473 A US33227473 A US 33227473A US 3828813 A US3828813 A US 3828813A
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US
United States
Prior art keywords
bore
conduit
pressure difference
slide valve
control apparatus
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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
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English (en)
Inventor
H Haussler
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.)
BERINGER HYDRAULIK BERINGER R and CO CH
BERINGER HYDRAULIK GmbH
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BERINGER HYDRAULIK GmbH
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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
    • 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
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/0416—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor with means or adapted for load sensing
    • 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
    • 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
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • F15B13/0416—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor with means or adapted for load sensing
    • F15B13/0417—Load sensing elements; Internal fluid connections therefor; Anti-saturation or pressure-compensation valves
    • 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
    • Y10T137/87169—Supply and exhaust
    • Y10T137/87177—With bypass
    • Y10T137/87185—Controlled by supply or exhaust valve

Definitions

  • the first section passes through the slide valve and, when the slide valve is moved out of the neutral position, opens into an annular groove provided in the slide valve bore.
  • the second section extends from this annular groove and has located therein an operating piston which in one position connects a chamber of the pressure difference balance containing the pressure spring to this conduit and in the other position connects this chamber to a return conduit to a tank.
  • the invention relates to a control apparatus for loadindependent flow regulation. More specifically it relates to apparatus of this type'which comprises at'least one control unit with a slide valve for connecting a pump conduit with at least one conduit to a consumer unit connected to the latter, also a pressure difference balance for maintaining a constant yet adjustable pressure difference between the pump conduit and the respectively connected consumer unit conduit, as well as a conduit whichreports the pressure in the consumer unit to the pressure difference balance before the consumer unit is connected to the pump conduit.
  • The-first section passes through the slide valve and, when the slide valve is moved out of the neutral position, opens into an annular groove provided in the slide valve bore of the housing of the control apparatus.
  • the second section extends from this annular groove in the housing and has located therein an operating piston which in one position connects the chamber of the pressure difference balance containing the pressure spring to this conduit and in the other position connects this chamber to the return conduit to a tank.
  • FIG. I shows a housing for two control slide valves and a pressure difference balance
  • FIG. 2 is a section along line II-II of FIG. 1;
  • FIG. 3 is a section along line III-III of FIG. 1, showing the slide valve in neutral position;
  • FIG. 4 is a section along line IVIV of FIG. 1, showing the other slide valve in an operating position
  • FIG. 5 is a vertical section through the pressure difference balance and the operating piston, along line V--V of FIG. 1;
  • FIG. 6 is a cross-section through the same parts, along line VIVIof FIG. 5;
  • FIG. 7' is a cross-section similar to FIG. 2, but through another embodiment of the control apparatus.
  • FIG. 8' is-.a section along the VIIIVIII of FIG. 7.
  • control apparatus is described hereafter with reference to one embodiment with a pressure difference balance-and two connected control slide valves.
  • two control slide valves 2 and a pressure difference balance 3 are located in a housing 1'.
  • the slide valves are mounted to move axially in bores 4-in the housing.
  • a channel 5 (running horizontally in FIG. 1) which extends from the left-hand side of the housing in the figure to the pressure difference balance 3'. It is connected by way of a channel Slrunning at right-angles thereto (see also FIG. 5) to a pump which is not shown.
  • Two return channels 6 areprovided parallel to this channel.
  • the lower of the two channels (FIG. I) likewise terminates in the bore of the pressure difference balance 3 and is at this point connected by means of a channel 61 running at right-angles thereto to a return tank which is not shown.
  • the upper return channel 6 is shorter, it is connected by a vertical channel 62 to the lower channel 6 and thus is likewise connected to the'return channel 61 (FIGS. 1 and 2).
  • FIG. 1 Two further channels 7' parallel to the return channels 6*may be seen in FIG. 1.
  • the latter serve for transmitting the pressure prevailing in the consumer unit to the pressure difference balance before this consumer unit is connectedto the pump.
  • the position of both channels 7 may be seen-in FIG. 3. Similar to the channels 6, the channels 7 are connected to each other at one of their ends by a channel 71 passing at right-angles thereto, to which a further channel 72 is connected,
  • all these channels 5, 6, 61, 62, 7, 71 and 72 and the slide valve bores 4 are constructed as bores, which begin at one of the outer sides of the housing, The housing may therefore be machined on a boring machine, which is less expensive and quicker than on a lathe.
  • the channels are closed by plugs 70 at the outer side of the housing 1.
  • Those bores which are relatively long and therefore during their manufacture tend to run out of center (deviation from a straight line) have a relatively large diameter so that they may be manufactured with a larger and therefore more rigid boring tool, whereas the shorter bores may have smaller diameters.
  • the bores are arranged with respect to each other so that they only intersect each other such that deviations from the position provided have no effect on the control functions and therefore greater tolerances can be permitted. For all these reasons the manufacture is substantially simplified and made less expensive.
  • channels as bores are not limited solely to the aforesaid channels; further channels to be mentioned hereafter are constructed in this manner.
  • two bores 8 and 9 open into each slide valve bore 4. These bores extend at right angles to each other and lead to a consumer unit not illustrated. Depending on the position of the slide valve one of the two bores serves for the influx of control fluid to one side of the consumer unit, the other serves for the return to the tank from the other side of the latter.
  • Each slide valve bore 4 has at its ends a widening portion 41 of considerably greater diameter than the bore diameter itself.
  • An annular groove 42 is located at a slight distance therefrom.
  • These annular grooves are connected to the associated pressure indicating channels 7 by means of a connecting channel 73 respectively.
  • the widening portions 41 are made necessary by the manufacture; as can be seen from FIG. 3 their diameter and depth are chosen such that it is possible to bore the connecting channels 73 from outside the housmg.
  • the slide valve bore 4 is intersected by channels 5 and 6.
  • the sizes of these intersections, within certain limits, is unimportant so that the channels 5 and 6 may be produced with relatively large tolerances. Certain deviations in their position with respect to the slide valve bore have no effect on the control functions.
  • each control slide valve 2 has two terminal flanges 21 and two control flanges 22, 23 respectively, which are separated by a restriction 24.
  • the control flanges 23 have leading edges 25.
  • Constrictions 26 are provided between the control flanges 22 and the terminal flanges 21 andbetween the control flanges 23.
  • Each control slide valve 2 has two bores 27 respectively extending from the end of the control slide valve co-axially to its longitudinal axis to the restriction 24. At this point it is penetrated by a transverse bore 28. A transverse bore 2.9 is also present in each terminal flange 21. The latter'transverse'bores are arranged such that in the neutral position of the slide valve they are closed by the wall of the bore 4.-The longitudinal bores 27 are closed at their ends by plugs 271.
  • the pressure difference balance 3 (FIG. 5) is of the construction known from U.S. Pat. No. 3,488,953 and Swiss Pat. No. 513,340.
  • a piston 31 with a restriction 32 between its two ends has a longitudinal bore 33 and a transverse bore 34, by which the pressure in the conduit 51 may be directed to the underside of the piston 31, so that the latter may be displaced against the action of a spring 35, which is located in a spring chamber 36.
  • the present pressure difference balance 3 differs in that the pre-tensioning of this spring 35 may be adjusted by a spring washer 38 which is axially displaceable by means of a screw 37.
  • the screw 37 extends through a cover plate so that it may be turned from outside.
  • the spring chamber 36 is connected to the aforementioned pressure indicating channel 72 by a short transverse channel 74 and a vertical bore 110.
  • An operating piston 111 is arranged to slide in bore 110.
  • Piston 111 has two flanges 112, 113.
  • the upper edge 114 of the flange 112 is spaced from the lower edge 115 of the flange 113 by a distance which is slightly greater than the diameter of the transverse bore 74.
  • a transverse bore 116 As in the piston 31 of the pressure difference balance 3, provided between the flanges 112, 113 is a transverse bore 116, which opens into a longitudinal bore 117, which terminates at the upper side of the piston 111.
  • Located above the piston 111 is an abutment 118, which may be displaced axially, as required, by a screw 119 in the cover plate 100.
  • the transverse bore 74 extends beyond the pressure difference balance 3 (FIGS. 5 and 6) and terminates in a vertical bore 120 in which an adjustable servo-excess pressure valve 121 is located.
  • This valve corresponds to the servo-excess pressure valve according to U.S. Pat. No. 3,488,953 and Swiss Pat. No. 513,340 and is connected to a separate channel 122 which leads to the return channel 62.
  • the valve 121 may be adjusted to a given opening pressure by a regulating screw 123 inserted in the cover plate 100.
  • a further channel 75 passes above the latter. It opens into a channel 76 running at right-angles thereto, which intersects the common return conduit 62.
  • a connection from the spring chamber 36 of the pressure difference balance 3 to the return channel 61 is formed.
  • these channels 74, 75, 76 are arranged such that they may be bored from outside, which simplifies the manufacture.
  • the branches of these channels which are not required are then closed by plugs 70.
  • the channels only intersect each other, for example like the channels 76 and 62, so that tolerances which are as great as possible may be allowed in the manufacture.
  • the connection between the consumer unit connector 8 and the pump channel 5 via the bore 4, past the central restriction 26, is initiated by further raising the slide valve 2. However, this only takes place after approximately one quarter of the stroke, i.e., after the control flange 23 with its leading edge has been raised sufficiently far. Since the pressure in the pump channel 5 is now already higher, any unintentional return flow from the consumer unit channel '8 to the pump channel 5 is reliably avoided. The remaining three-quarters of the slide valve stroke are now available for the sensitive and progressive opening of the connection from the pump channel 5 to the consumer unit connector 8.
  • the actuation of the slide valve may take place manually, mechanically, hydraulically, pneumatically or electro-magnetically, which will not be discussed in detail. 7
  • the consumer unit pressure in the channel 72 does not reach the spring chamber 36 of the pressure difference balance 3 directly, but is flrstly directed to the lower end face of the hydraulically operated piston 111.
  • the effective force presses the latter against its upper abutment 118 and opens the connection to the spring chamber 36 via the transverse bore 74, whereas the lower edge 115 of the flange 113 by lifting produces the connection between the channels 72and 74 (FIG. 5), while simultaneously the control flange 112' interrupts the connection between the channels 74 and 75.
  • the pressure may reach the spring chamber 36 of the pressure difference balance 3 and the latter, in known manner, regulates the flow from the channel 5a past the restriction 32 into the return channel 61 and thus the pressure of the portion of the control fluid flowing into the pump channel 5.
  • the abutment 118 may be adjusted, due to which the crosssection of the passage between the channels 72 and 74 may be adjusted.
  • the speed of the piston 31, which moves downwards as a result of the increase in pressure may be influenced and also the speed of the pressure rise may be adjusted.
  • the operating piston 111 has a further task, which consists in reducing the pressure prevailing in the spring chamber 36 as quickly as possible after the return of the slide valve 2 to the central position, in order that the pump is returned to a condition in which it works almost without pressure.
  • the circulation channels used in the prior art which had a small diameter, long lengths and thus made a one-piece construction practically impossible (several slide valves in a single housing).
  • the circulating pressure i.e., the pressure in the pump channel 5 in the central position of all the slide valves, may also be altered, so that, with an electrohydraulic anticipatory control, sufficient control pressure is available when moving from the central position.
  • the adjustable servo-excess pressure valve 121 in known manner limits the maximum possible pressure in the-spring chamber 36 of the pressure difference balance 3, and in the case of an excess pressure allows the control fluid flowing from the consumer unit to flow into the return channel 122 so that a further pressure increase in the pump channel 5 leads to an automatic opening of the pressure difference balance 3 to the return, whereby the latter also carries out the function of a servo-controlled excess pressure valve.
  • FIGS. 7 and 8 illustrate a further embodiment, offering another possibility of altering the pressure difference effective at the throttle point between the pump channel 5 and consumer unit, which throttle point may be altered by the slide valves.
  • This embodiment is used aboveall when individual consumer units, which are actuated by the same control unit, are to receive amounts of fluid flow which are substantially smaller than the flow conveyed by the pump.
  • This connection is firstly produced by a bore 52 located at 90 thereto, in which, however, an adjustable non-return valve is located.
  • the latter has a compression spring 131, which is held by an adjusting pin 132.
  • the latter is screwed into the housing 1 and has a slot 133 on the outer side, which serves for turning the pin 132.
  • the pressure drop between the pump channel 5 and the consumer unit may thus be reduced by any desired amount, so that at the throttle points which can be regulated by the slide valve 2 (leading edge 25 in FIGS. 3 and 4), a smaller pressure drop may be adjusted, due to which the rate of flow to the consumer unit is correspondingly reduced.
  • the nonreturn valve 130 With simultaneous actuation of two slide valves in one control unit, a flow from a heavily loaded consumer unit via the pump channel 5 to the slightly loaded consumer unit is avoided, which would lead to an unintentional movement of the heavily loaded consumer unit.
  • control valves for load-independent flow regulation in a one-piece construction.
  • control apparatus may also be built as a so-called sandwich construction (individual control elements arranged together) or as a so-called mounting plate construction (allcontrol elements and the pressure difference balance arranged on a base plate, which contains all the connecting bores and connectors).
  • a further advantage consists in that the conduit which conveys the consumer unit pressure to the pressure difference balance, needs only to be accurately machined at certain points and in particular at points where this accuracy is readily achieved, namely in the control slide valves.
  • the conduit which conveys the consumer unit pressure to the pressure difference balance needs only to be accurately machined at certain points and in particular at points where this accuracy is readily achieved, namely in the control slide valves.
  • it is possible to provide a section point with a very small diameter in this conduit which is necessary in order to be able to keep the overall length of the slide valve and of the housing as small as possible.
  • the other sections of the conduit namely those which are located inside the housing, may have greater diameters, which are easier to bore and with which large tolerances may be allowed .without drawbacks. Solely the annular grooves 42 must be accurately positioned, which however causes few-difficulties because they are located directly below the surface of the housing.
  • a control apparatus for lead-independent flow regulation comprising at least one control unit having a housing with a bore and an annular groove communicating with said bore, and a slide valve in said bore movable to and from a neutral position, a first conduit connecting said slide valve to a pump, a second conduit connecting said slide valve to a consumer unit, a pressure difference balance for maintaining a constant, but adjustable pressure difference between said first conduit" and the respectively connected second conduit,
  • said pressure difference balance having a chamber, a pressure spring in said chamber, a third conduit for communicating the pressure in the second conduit to the pressure difference balance prior to connection of the latter to said first conduit, said third conduit having a first section which is located in said slide valve and which, when said slide valve is displaced from the neutral position, opens into said annular groove, and also having a second section which extends from said annular groove, an operating piston which is located in said second section and which in one position connects said chamber of said pressure difference balance to said third conduit and in another position connects said chamber to a reservoir.
  • said first section of said third conduit comprises a first transverse bore connected to said second conduit, a longitudinal bore connected to said first transverse bore, and a second transverse bore penetrating said longitudinal bore, said second transverse bore opening into said annular groove upon actuation of said slide valve.
  • a control apparatus comprising a bore, said operating piston being arranged to be movable in said lastmentioned bore, said last-mentioned bore having a first connecting channel leading to said pressure difference balance, and a second connecting channel leading to the reservoir.
  • a control apparatus wherein said operating piston has two control flanges, one of said flanges adapted to block the connection between said second section and said first connecting channel, and the other flange being adapted to block the connection between said first connecting channel and the reservoir.
  • a control apparatus including an abutment in said last-mentioned bore for limiting the movement of said operating piston, and an adjusting screw for axially adjusting the position of said abutment.
  • a control apparatus according to claim 4, said operating piston having edges spaced apart by a distance which is slightly greater than the diameter of said first connecting conduit between said last-mentioned bore and said pressure difference balance.
  • said second section comprises a third connecting channel extending at an angle from said annular groove and wherein said bore has a widening portion at each end, the diameter and depth of said widening portion being such that an extension of said third connecting channel lies inside said widening portion.
  • said operating piston has a transverse bore connected to said chamber, and a longitudinal bore connected to said transverse bore, said longitudinal bore terminating at that end face of said operating piston which is adjacent said abutment.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Safety Valves (AREA)
US33227473 1972-02-18 1973-02-14 Control device for load-independent flow regulation Expired - Lifetime US3828813A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH238572A CH534816A (de) 1972-02-18 1972-02-18 Steuervorrichtung für lastunabhängige Durchflussregelung

Publications (1)

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US3828813A true US3828813A (en) 1974-08-13

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US33227473 Expired - Lifetime US3828813A (en) 1972-02-18 1973-02-14 Control device for load-independent flow regulation

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US (1) US3828813A (de)
JP (1) JPS5650152B2 (de)
AT (1) AT322933B (de)
CA (1) CA982020A (de)
CH (1) CH534816A (de)
DE (1) DE2304334C2 (de)
FR (1) FR2172398B1 (de)
GB (1) GB1412485A (de)
IT (1) IT979208B (de)
NL (1) NL7301676A (de)
SE (1) SE377488B (de)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4303091A (en) * 1979-03-01 1981-12-01 Barmag Barmer Maschinenfabrik Hydraulic control apparatus for load independent flow regulation
US4736770A (en) * 1984-04-18 1988-04-12 Andre Rousset Hydraulic distributor of the proportional type, with load sensing of the highest pressures in the operating circuits
US4794846A (en) * 1985-02-23 1989-01-03 Barmag Ag Proportional action valve with a biased spring unproportionately variable to the load pressure
US4981159A (en) * 1988-01-29 1991-01-01 Danfoss A/S Hydraulic control valve with pressure sensing means
US5244358A (en) * 1987-01-29 1993-09-14 Mollo James R Load sensed variable output gear pump
US5368061A (en) * 1987-01-29 1994-11-29 Mollo; James R. Load sensed variable discharge fixed displacement pump control with low unload features
US5487403A (en) * 1987-01-29 1996-01-30 Mollo; James R. Variable discharge pump with low unload to secondary
US5515879A (en) * 1987-01-29 1996-05-14 Mollo; James R. Load sensed multi-purpose pressure control valve

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2514624C3 (de) * 1975-04-03 1986-10-23 Danfoss A/S, Nordborg Steuereinrichtung für mindestens einen hydraulisch betriebenen doppeltwirkenden Verbraucher
DE3312511A1 (de) * 1983-04-07 1984-10-18 Mannesmann Rexroth GmbH, 8770 Lohr Wegeventil mit steuerleitungen zum melden des verbraucherdruckes
DE3428403A1 (de) * 1983-08-01 1985-04-11 Závody těžkého strojírenství Výzkumný ústav stavebních a zemních stroju, Brünn/Brno Zweistufige, druckkompensierte hydraulische steuereinrichtung fuer mindestens zwei verbraucher
DE3543231A1 (de) * 1985-12-06 1987-06-11 Sauer Getriebe Ag Proportionalwegeventil mit einzeldruckwaage
JPH07103882B2 (ja) * 1989-03-22 1995-11-08 株式会社小松製作所 圧力補償付液圧弁
DE3913838A1 (de) * 1989-04-27 1990-10-31 Schwarzwaelder Uhrwerke Fabrik Dosierventil

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1648012B1 (de) * 1967-04-27 1972-05-31 Heilmeier & Weinlein Mengengeregelte Steuerschiebervorrichtung

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4303091A (en) * 1979-03-01 1981-12-01 Barmag Barmer Maschinenfabrik Hydraulic control apparatus for load independent flow regulation
US4355655A (en) * 1979-03-01 1982-10-26 Barmag Barmer Maschinenfabrik Hydraulic control apparatus for load independent flow regulation
US4736770A (en) * 1984-04-18 1988-04-12 Andre Rousset Hydraulic distributor of the proportional type, with load sensing of the highest pressures in the operating circuits
US4794846A (en) * 1985-02-23 1989-01-03 Barmag Ag Proportional action valve with a biased spring unproportionately variable to the load pressure
US5244358A (en) * 1987-01-29 1993-09-14 Mollo James R Load sensed variable output gear pump
US5368061A (en) * 1987-01-29 1994-11-29 Mollo; James R. Load sensed variable discharge fixed displacement pump control with low unload features
US5487403A (en) * 1987-01-29 1996-01-30 Mollo; James R. Variable discharge pump with low unload to secondary
US5515879A (en) * 1987-01-29 1996-05-14 Mollo; James R. Load sensed multi-purpose pressure control valve
US4981159A (en) * 1988-01-29 1991-01-01 Danfoss A/S Hydraulic control valve with pressure sensing means

Also Published As

Publication number Publication date
JPS5650152B2 (de) 1981-11-27
IT979208B (it) 1974-09-30
CA982020A (en) 1976-01-20
NL7301676A (de) 1973-08-21
AT322933B (de) 1975-06-10
FR2172398A1 (de) 1973-09-28
JPS4890025A (de) 1973-11-24
FR2172398B1 (de) 1978-08-04
SE377488B (de) 1975-07-07
DE2304334C2 (de) 1982-09-23
CH534816A (de) 1973-03-15
GB1412485A (en) 1975-11-05
DE2304334A1 (de) 1973-08-30

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