US3814557A - Fluid displacement apparatus having helical displacement elements - Google Patents

Fluid displacement apparatus having helical displacement elements Download PDF

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Publication number
US3814557A
US3814557A US00158479A US15847971A US3814557A US 3814557 A US3814557 A US 3814557A US 00158479 A US00158479 A US 00158479A US 15847971 A US15847971 A US 15847971A US 3814557 A US3814557 A US 3814557A
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pitch
elements
tooth
displacement apparatus
fluid displacement
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US00158479A
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English (en)
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H Volz
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Allweiler GmbH
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Allweiler AG
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    • 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
    • F04C2/00—Rotary-piston machines or pumps
    • F04C2/08—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C2/12—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C2/14—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons
    • F04C2/16—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type
    • F04C2/165—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with toothed rotary pistons with helical teeth, e.g. chevron-shaped, screw type having more than two rotary pistons with parallel axes

Definitions

  • PATENTEDJUH 4M4 3314551 sum 0a 0? 10 PATENTEnJlm 4l974 3.814.557
  • the invention relates generally to a fluid displacement apparatus such as a pump or motor having at least two helical displacement elements arranged with their axes parallel in intermeshing relationship and in which at least one element is driving or driven and the other acts as a seal.
  • the elements are tightly enclosed by a housing, and the apparatus is effective to provide a constant, or nearly constant, displacement over its working range.
  • the specific throughput of fluid is the product of the cross section of the displacement element for the delivery of the fluid, formed by the gaps between the teeth of the helical thread and the pitch thereof.
  • Conventional displacement apparatus of this category have a constant delivery cross section and constant pitch within their operating areas. In order to obtain the highest possible specific fluid throughput, the pitch and the delivery cross-section must therefore be large. For reasons related to wear, the delivery cross-section is dependent upon the specific dimensions of the helical thread.
  • the displacement elements a helical-thread profile in which the specific design of the width of the threads and the magnitude of the gaps between the teeth results in the displacement elements, which serve as seals, which are driven hydraulically, so that for practical purposes no torque is transferred by the flanks of the helical thread. If one were to depart from these relatively ideal dimensions, at least to any great extent, the flanks of the threads would be subjected to very heavy abrasion which would lead to rapid wear in the apparatus. Basically, therefore, if it is desired to increase the specific fluid throughput in a apparatusof this kind, it is only possible to increase the pitch. However, in the case of displacement apparatus used as pumps, the pitch cannot be increased at will, since pump suction depends upon the pitch.
  • This object is accomplished by a displacement apparatus in which the effective pitchof the helical thread of the displacement element, and the delivery surface formed by the gaps between the teeth of the helical threads, are not constant over the operating range; but in which the displacement is inversely proportional, or almost inversely proportional to pitch and delivery surface; and in which the product of the delivery surface and the effective pitch of the helical thread gives the same, or almost the same, value for any desired cross section in the operating area.
  • the displacement apparatus in accordance with the present invention accomplishes these aims because the pitch of the helical thread of the displacement element and the delivery surface do not need to be constant within the operating area in order to achieve uniform displacement. It is possible to vary the pitch within the displacement apparatus and adapt it to the particular operating conditions.
  • Another characteristic of the invention resides in that the delivery surface is altered by altering the width of the teeth of the helical thread in the displacement element. Assuming that the displacement elements are provided with helical threads which differ in their diameter ratios while maintaining their cylindrical shape, this approach ensures the changing of the delivery surface. If a change in delivery surface were to be effected, for instance by changing the diameter of the addendum circle in the operating area, the cylindrical shape of the spindles could no longer be maintained. The production of the displacement elements, and of the housing closely surrounding them would be technically extremely difficult.
  • the displacement elements according to the invention may be made of solid material.
  • the production of the helical thread is relatively difficult and requires special apparatus capable of producing flanks for threads not of constant pitch.
  • the invention furthermore provides that the displacement elements consist, as known per se, of tooth-profile discs axially aligned in rows and twisted in relation to each other to correspond to the pitch.
  • These tooth-profile discs may be placed onto a shaft having the pitch and representing the core of the displacement element, and they may be aligned to the correct pitch and clamped into position.
  • the pitch applied to the shaft may be constant, but this will make it necessary for the clamping connection to change its angular position in accordance with the change in pitch from one tooth-profile disc to' another.
  • tooth-profile disc onto a shaft of non-constant pitch which doesnot correspond to the desired pitch, while the tooth-profile discs are provided with a clamping. connection, the angular position of which is staggered from disc to disc in such a manner that the effective pitch of the helical thread, resulting from the pitch on the shaft and the angular position of the disc-clamping connection, produces the pitch desired.
  • the tooth-profile discs may, however, also be provided, as is known per se, with a multi-groove profile, especially a notched-tooth profile, or a splined-shaft profile, and may be placed on an appropriately designed shaft staggered in relation to each other at angles corresponding to the pitch.
  • the displacement elements consist, as is known per se, of profile discs arranged axially in rows and staggered in relation to each other according to the pitch, the tooth-profile discs in each displacement element being placed onto a shaft provided with the pitch, and being arranged thereon and clamped in accordance with this pitch, in that the shafts provided with the pitch are made longer than the length of the rows of toothprofile discs, the discs being arranged in such a manner that they may be moved axially along the shafts.
  • tooth-profile discs can be moved axially along the shafts, they may be brought into engagement with different pitch areas. If the profile discs are in engagement with a large pitch, the specific delivery volume is large; on the other hand, if they are in engagement with a small pitch, the specific delivery volume is small.
  • the tooth-profile discs are fixed axially in relation to the surrounding housing, the tooth-profile discs, together with the surrounding housing, being displaceable on the axially stationary shafts.
  • the tooth-profile discs bring into play another pitch area and thus another specific delivery volume.
  • the apparatus according to the invention must be accurately positioned axially in relation to each other, provision is also made for mutual axial positioning bf the shafts and displacement elements to be effected, as known per se, by means of shaft collars engaging each other. In order to make certain that this axial positioning can be accurately adjusted, at least the shaft collar on one of the cooperating displacement elements is infinitely adjustable.
  • FIG. 1 is a longitudinal section of a displacement pump according to the invention having solid displacement elements
  • FIG. 2 is an enlarged cross section of the displacement elements
  • FIG. 3 is a graphic illustration of the relationship between the delivery surface, the tooth angle resulting from the width of the helical thread, and the pitch of the axial extension of the displacement elements;
  • FIG. 4 is further example of a displacement apparatus according to the invention.
  • FIGS. 5 and 6 are cross sections through the displacement apparatus according to FIG. 4, taken along the lines CC and DD, respectively;
  • FIG. 7 shows a further modification of a displacement apparatus according to the invention.
  • FIGS. 8 and 9 are transverse cross sections of the displacement apparatus according to FIG. 7;
  • FIG. is a longitudinal cross section of an infinitely adjustable displacement apparatus according to the invention.
  • FIGS. 11 and 12 are top views of the displacement elementsin the displacement apparatus shown in FIG. 10, in the maximal and minimal displacement position;
  • FIG. 13 is a graphic illustration of the relationship between the delivery surface, the pitch, the tooth angle, and the specific delivery volume when the displacement elements are shifted within the displacement apparatus shown in FIG. 10;
  • FIGS. 14 and 15 are cross sections through the infinitely adjustable pump taken along lines EE and F-F, respectively, of FIG. 10;
  • FIG. 16 is another longitudinal section of the device staggered through 90 in relation to the device shown in FIG. 10.
  • displacement elements 1,2,3 are enclosed with very little play by a housing 4 within the operating area.
  • the outside diameters of the displacement elements are shown longitudinally batched in the drawings.
  • Central displacement element 1 which has a stub-shaft 6 fitted with a key 5 so that it may drive or be driven, carries at one end twoshaft collars 7,8 which locate in the axial direction shaft collars 9,10 fitted to displacement elements 3,2 on each side, serving as seals.
  • Displacement elements 1,2,3 are designed in such a manner that the pitch increases from the shaftcollar end towards stub-shaft end 6. At the same time, the width of the teeth of helical thread 11 of the central displacement element decreases, whereas the width of the teeth of helical threads 12 of lateral displacement elements 2 increases.
  • the changes in delivery surface and pitch should be continuous, being in the form of a geometrical progression. If the distance between A and B is divided into a specific number of stages n, the
  • the relationships to the axial extension are shown in the diagram in FIG. 3.
  • the values relate to a displacement apparatus as shown in FIG. 1, having one central and two lateral displacement elements, based on the following dimensions:
  • the displacement apparatus illustrated in FIG. 4 is of approximately the same design as that shown in FIG. 1,
  • Displacement elements 27,28,29 consist of tooth-profile discs 30,31,32 arranged axially in rows which,'as shown in the upper half of the figure, are fitted to shafts 35,36 having helical grooves 33,34.
  • the tooth-profile discs are shown symbolically only by the outside and core diameters.
  • the pitches of helical grooves 33,34 are not constant, but behave in accordance with the formula:
  • tooth-profile discs 30,31,32 are positively aligned with helical grooves 33,34 by means of cylindrical pins 37,38. Since the angular settings of the cylindrical pins in relation to the tooth center of the tooth-profile elements does not alter, the pitch of helical threads 11,12, formed by the tooth-profile elements, and shown in thin, full lines, corresponds to the pitch of helical grooves 33,34 on shaft 35,36. According to the formula:
  • the displacement apparatus shown in FIG. 7 corresponds substantially to that shown in FIG. 4, the difference being that the tooth-profile discs 39,40,41, as may be seen very clearly in FIGS. 8 and 9, are fitted to splined shafts 42,43, 44 in staggered relationship to each other which depends upon the pitch desired.
  • three shafts 46,47,48 are arranged in a tubular housing 45, the shafts being provided with helical grooves 49,50,51.
  • the housing 45 is closed off by covers 52 and 53.
  • the central shaft 46 passes through cover 52 and is equipped with a stub-shaft 55 having a key-groove 54, so that it may drive or be driven.
  • a ball- 1 bearing 56 retains the shaft axially and radially.
  • a herringbone gearwheel 57 which meshes with herring-bone gearwheels 58,59 fitted to shafts 47,48.
  • herring-bone gearwheels 58,59 are infinitely adjustable on shafts 47,48 by means of clamping elements 60,61.
  • the shafts 47,48 are each provided with an extension 62,63 mounted in cover 52 for radial guidance, the front areas thereof communicating, through bore 64 in the cover, and through bore 65 in the central shaft, with pressure chamber 66 in the displacement apparatus.
  • Internal bore 67 in housing 45 encloses, with very little play, another axially displaceable housing 68 which, in turn encloses tooth-profile discs 69,70,71, fitted to shafts 46,47,48.
  • the toothprofile discs are located axially in housing 68 by means of discs 74,75 provided with perforations 72,73. As may be seen from FIGS. 14,15,16, discs 74,75 are held in place by means of screws 76. Housing 68, may be moved axially by means of a threaded shaft 77 fitted with a handwheel 78 and rotatably mounted in cover 53. Since the tooth-profile discs are aligned by means of cylindrical pins 79,80 according to the pitch of helical grooves 49,50,51, the said tooth-profile discs adapt themselves automatically to the pitch of the said helical grooves when housing 68v is moved axially.
  • the tooth-profile discs thus form displacement elements made in accordance with the embodiment shown in FIG. 4.
  • FIG. 14 shows a view of cover disc 75, indicating the shape of the perforations 73 through which the working medium flowing through the displacement machine can enter or leave the apparatus.
  • Cover disc 74 is of substantially the same design as disc 75.
  • turning handwheel 78 causes housing 68 to be displaced in housing 45. If, in the embodiment illustrated, the housing is moved as far as splined gears 57,58,59 then tooth-profile discs 69,70,71 assume the shape shown in FIG. 11 of the helical threads with a larger pitch. In this connection, the thin, full lines show the paths of helical threads 11,12 of the displacement elements marked 82,83,84. The tooth-profile discs therefore assume a portion corresponding to a helical thread having a smaller pitch if, as shown in FIG. 12, housing 68 assumes the position in the vicinity of cover 53 illustrated in FIG. 10.
  • the diagram in FIG. 13 shows the relationship between delivery surface, pitch and the axial length of shafts 46,47,48.
  • the diagram is based on the same tooth-profile dimensions as the diagram in FIG. 3, i.e. within 20 jumps, the delivery surface alters from 3.4 cm to 4.12 cm
  • the effective pitch becomes smaller and the specific delivery volume decreases, but remains constant within the row of toothprofile discs.
  • the specific fluid throughput may be steplessly adjusted from about 27 cm to about 21.5 cm.
  • the values given are not limit values for the range of adjustment of a pump of this kind.
  • the geometrical mean of tooth-angle amounts to as at approximately this angle no appreciable torque is transferred, by the flanks of the helical thread, to the lateral displacement elements, provided a helical profile of the type shown herein is used.
  • a fluid displacement apparatus such as a pump or motor, comprising: a housing; at least two helical displacement elements arranged within said housing in meshing engagement and with their axes parallel to each other, at least one element thereof being adapted to drive or be driven and another being effective to act as a seal, said elements having helical threads in which the effective pitch and the delivery surface formed by the space between the teeth in the helical threads, within the operating area of the elements, are variable; the change in the pitch and the change in the delivery surface being substantially inversely proportional, and the product of said delivery surface and of the effective pitch of said helical threads providing substantially the same value at any desired cross-section of the operating area.
  • a fluid displacement apparatus such as a pump or motor, comprising: a housing; at least two helical displacement elements arranged within said housing in meshing engagement and with their axes parallel to each other, at least one element thereof being adapted to drive or be driven and another being effective to act as a seal, said elements having helical threads in which the effective pitch and the delivery surface formed by the space between the teeth in the helical threads, within the operating area of the elements are variable; the change in the pitch and the change in the delivery surface being substantially inversely proportional, and the product of said delivery surface and of the effective pitch of said helical threads providing essentially the same value at any desired cross-section of the operating area.
  • a fluid displacement apparatus wherein said elements have threads with an inside and outside diameter of different dimension and the variation in the delivery surface is effected by changing the tooth widths of the helical threads of said elements.
  • a fluid displacement apparatus according to claim 2, wherein said housing has an inlet and outlet providing a pressure and suction region with the pitch of the helical threads of said elements being larger in the pressure region than in the suction region.
  • a fluid displacement apparatus wherein the common axial location of said displacement elements is effected by means of shaft collars in engagement with each other, at least the shaft collar on one of two cooperating displacement elements being steplessly adjustable in an axial direction.
  • a fluid displacement apparatus comprising multishaped tooth-profile discs arranged axially in rows and staggered in relation to each other and to said pitch.
  • a fluid displacement apparatus wherein said shaft has a non-constant pitch, with the angular position of said discs being staggered relative to each other so that the effective pitch resulting from the pitch of the shaft and the angular position of the tooth-profile discs coincides with the desired predetermined pitch of the helical thread.
  • said elements comprise a central and two side elements with the geometrical mean value of the tooth-widths at the forward and rear ends of said central displacement element corresponding approximately to the tooth-width at which no torque is trans ferred to said side displacement elements through the flanks of the helical threads.
  • each of said elements comprises a shaft and said tooth-profile discs are mounted on said shaft, the latter having a predetermined pitch, and said discs are aligned relative to said pitch.
  • a fluid displacement apparatus wherein said shaft is grooved, and pins projecting into said grooves securing said discs to said shaft.
  • a fluid displacement apparatus wherein said shaft has a constant pitch with the angular position of said discs varying in relation to the pitch.
  • a fluid displacement apparatus wherein the common axial location of said shafts is effected by shaft collars in engagement with each other, at least the shaft collar on one of two cooperating shafts being steplessly adjustable in an axial direction.
  • a fluid displacement apparatus wherein said shafts have a common axial location effected by means of herring-bone gearwheels with at least one of two engaging gears being steplessly adjustable in an axial direction, and clamping means between said two gears.
  • tooth-profile discs are formed with a multi-groove profile.
  • a fluid displacement apparatus according to claim 14, wherein said multi-groove profile has a splined shaft configuration.
  • a fluid displacement apparatus according to claim 14, wherein said multi-groove profile has a serrated tooth configuration.
  • a fluid displacement apparatus wherein said shafts are longer than the length of the rows of tooth-profile discs, and said tooth-profile discs are arranged to be axially displaceable along said shafts.
  • tooth-profile discs are axially fixed in relation to said housing, and said tooth-profile discs and said housing are axially displaceable along and relative to said shafts.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
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US00158479A 1970-07-04 1971-06-30 Fluid displacement apparatus having helical displacement elements Expired - Lifetime US3814557A (en)

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DE2033201A DE2033201C3 (de) 1970-07-04 1970-07-04 Schraubenspindelmotor oder -pumpe

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4144001A (en) * 1977-03-29 1979-03-13 Fordertechnik Streicher Gmbh Eccentric worm pump with annular wearing elements
US4405286A (en) * 1982-01-21 1983-09-20 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Actively suspended counter-rotating machine
US4671749A (en) * 1984-07-04 1987-06-09 Kabushiki Kaisha Kobe Seiko Sho Screw compressor
US4797077A (en) * 1984-09-27 1989-01-10 Anderson Dean R G Rotary expansible chamber device
US4896016A (en) * 1989-04-24 1990-01-23 Century Mfg. Co. Plasma arc metal cutting apparatus with actuation spring
US5123821A (en) * 1990-03-08 1992-06-23 Allweiler Ag Screw spindle pump with a reduced pulsation effect
US5653585A (en) * 1993-01-11 1997-08-05 Fresco; Anthony N. Apparatus and methods for cooling and sealing rotary helical screw compressors
US6312242B1 (en) * 2000-05-12 2001-11-06 Industrial Technology Research Institute Asymmetric double screw rotor assembly
WO2003036046A1 (en) * 2001-10-19 2003-05-01 Imperial Research Llc Offset thread screw rotor device
EP1475537A1 (en) * 2003-05-08 2004-11-10 Automotive Motion Technology Limited Screw pump
US20050129561A1 (en) * 2001-10-19 2005-06-16 Heizer Charles K. Gapless screw rotor device
US20060216190A1 (en) * 2004-11-08 2006-09-28 Beaven Robert W Pump
US20070020112A1 (en) * 2004-09-30 2007-01-25 Rockwell David M Compressor sound suppression
US20070293962A1 (en) * 2004-02-01 2007-12-20 Thk Co., Ltd. Design Method for Industrial Product Using Clothoid Curve, Industrial Products Designed by the Design Method, and Method and Device for Numerical Control Using the Clothoid Curve
US20100021332A1 (en) * 2008-07-25 2010-01-28 Koichi Hashida Screw pump
IT202100004139A1 (it) * 2021-02-23 2022-08-23 Settima Mecc S R L Assieme di viti per pompa a tre viti e pompa a viti comprendente detto assieme

Families Citing this family (1)

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Publication number Priority date Publication date Assignee Title
DE2944714A1 (de) * 1979-11-06 1981-05-14 Helmut 1000 Berlin Karl Rotationskolbenmaschine

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US1940410A (en) * 1930-10-02 1933-12-19 Auburn Foundry Pumping apparatus
GB384355A (en) * 1931-08-05 1932-12-08 Frederick Charles Greenfield Improvements in and relating to rotary machines for the compression and propulsion of
US2095167A (en) * 1935-02-26 1937-10-05 Burghauser Franz Screw pump
US2325617A (en) * 1938-01-13 1943-08-03 Jarvis C Marble Rotor
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Cited By (30)

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Publication number Priority date Publication date Assignee Title
US4144001A (en) * 1977-03-29 1979-03-13 Fordertechnik Streicher Gmbh Eccentric worm pump with annular wearing elements
US4405286A (en) * 1982-01-21 1983-09-20 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Actively suspended counter-rotating machine
US4671749A (en) * 1984-07-04 1987-06-09 Kabushiki Kaisha Kobe Seiko Sho Screw compressor
US4797077A (en) * 1984-09-27 1989-01-10 Anderson Dean R G Rotary expansible chamber device
US4896016A (en) * 1989-04-24 1990-01-23 Century Mfg. Co. Plasma arc metal cutting apparatus with actuation spring
US5123821A (en) * 1990-03-08 1992-06-23 Allweiler Ag Screw spindle pump with a reduced pulsation effect
US5653585A (en) * 1993-01-11 1997-08-05 Fresco; Anthony N. Apparatus and methods for cooling and sealing rotary helical screw compressors
US6312242B1 (en) * 2000-05-12 2001-11-06 Industrial Technology Research Institute Asymmetric double screw rotor assembly
US20050129561A1 (en) * 2001-10-19 2005-06-16 Heizer Charles K. Gapless screw rotor device
US6913452B2 (en) 2001-10-19 2005-07-05 Imperial Research Llc Offset thread screw rotor device
US6719547B2 (en) 2001-10-19 2004-04-13 Imperial Research Llc Offset thread screw rotor device
US20040151609A1 (en) * 2001-10-19 2004-08-05 Heizer Charles K. Offset thread screw rotor device
US6599112B2 (en) * 2001-10-19 2003-07-29 Imperial Research Llc Offset thread screw rotor device
US7008201B2 (en) 2001-10-19 2006-03-07 Imperial Research Llc Gapless screw rotor device
WO2003036046A1 (en) * 2001-10-19 2003-05-01 Imperial Research Llc Offset thread screw rotor device
US20070134121A1 (en) * 2003-05-08 2007-06-14 Beaven Robert W Screw pump
US7232297B2 (en) 2003-05-08 2007-06-19 Automotive Motion Technology Limited Screw pump
US7452194B2 (en) 2003-05-08 2008-11-18 Buhler Motor Gmbh Screw pump
US20040258550A1 (en) * 2003-05-08 2004-12-23 Beaven Robert William Pump
EP1475537A1 (en) * 2003-05-08 2004-11-10 Automotive Motion Technology Limited Screw pump
US20070293962A1 (en) * 2004-02-01 2007-12-20 Thk Co., Ltd. Design Method for Industrial Product Using Clothoid Curve, Industrial Products Designed by the Design Method, and Method and Device for Numerical Control Using the Clothoid Curve
US7860592B2 (en) * 2004-02-27 2010-12-28 Thk Co., Ltd. Design method for industrial product using clothoid curve, industrial products designed by the design method, and method and device for numerical control using the clothoid curve
US20070020112A1 (en) * 2004-09-30 2007-01-25 Rockwell David M Compressor sound suppression
US7234925B2 (en) 2004-11-08 2007-06-26 Automotive Motion Technology Limited Screw pump
US20060216190A1 (en) * 2004-11-08 2006-09-28 Beaven Robert W Pump
US20100021332A1 (en) * 2008-07-25 2010-01-28 Koichi Hashida Screw pump
US8282371B2 (en) * 2008-07-25 2012-10-09 Advics Co., Ltd. Screw pump
IT202100004139A1 (it) * 2021-02-23 2022-08-23 Settima Mecc S R L Assieme di viti per pompa a tre viti e pompa a viti comprendente detto assieme
WO2022179745A1 (en) 2021-02-23 2022-09-01 Settima Meccanica S.R.L. Screw assembly for a triple screw pump and screw pump comprising said assembly
KR20230155473A (ko) 2021-02-23 2023-11-10 세티마 메카니카 에스.알.엘. 삼중 나사 펌프용 나사 조립체 및 상기 조립체를 포함하는 나사 펌프 (Screw assembly for a triple screw pump and screw pump comprising said assembly)

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DE2033201C3 (de) 1979-02-01
SE375830B (xx) 1975-04-28
CH524068A (de) 1972-06-15
DE2033201A1 (de) 1972-01-20
DE2033201B2 (de) 1978-06-01

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