GB2395985A - Pump idler rotor lands forming bearing faces - Google Patents

Pump idler rotor lands forming bearing faces Download PDF

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Publication number
GB2395985A
GB2395985A GB0326358A GB0326358A GB2395985A GB 2395985 A GB2395985 A GB 2395985A GB 0326358 A GB0326358 A GB 0326358A GB 0326358 A GB0326358 A GB 0326358A GB 2395985 A GB2395985 A GB 2395985A
Authority
GB
United Kingdom
Prior art keywords
screw
edge
idler
pump
land
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.)
Withdrawn
Application number
GB0326358A
Other versions
GB0326358D0 (en
Inventor
Soren Edstrom
David Thomas Black
Tim Buttery
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.)
Dana Automotive Ltd
Original Assignee
Dana Automotive Ltd
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
Priority to GB0226529A priority Critical patent/GB0226529D0/en
Application filed by Dana Automotive Ltd filed Critical Dana Automotive Ltd
Publication of GB0326358D0 publication Critical patent/GB0326358D0/en
Publication of GB2395985A publication Critical patent/GB2395985A/en
Withdrawn legal-status Critical Current

Links

Classifications

    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2/00Rotary-piston machines or pumps
    • F04C2/08Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C2/12Rotary-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
    • F04C2/14Rotary-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
    • F04C2/16Rotary-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
    • F04C2/165Rotary-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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2/00Rotary-piston machines or pumps
    • F04C2/08Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C2/082Details specially related to intermeshing engagement type machines or pumps
    • F04C2/084Toothed wheels

Abstract

A pump including a power screw 10 and an idler screw 12 which meshes with the power screw and being rotatable in housing 20. The idler screw has a screw form including a helical groove 14, 14' and helical land surface 16, 16' with first 16a, 16a' and second 16b, 16b' edges, each adjacent the groove. The distance between the land surface and a longitudinal axis A of the idler screw varying between the first and second edges. The distance between the respective first and second edges and the axis being substantially constant over the length of the screw. The distance between the surface and axis may increase continuously between the edges or may increase to an intermediate portion and thereafter be constant. The surface shape allows pumped fluid to act as a hydrodynamic bearing. The edges may be radiused.

Description

Title: Pump Description of Invention

5 The present invention relates to a pump particularly to a pump including a power screw and at least one idler screw mounted in a housing, the idler screw which meshes with the power screw such that rotation of the power screw causes rotation of the idler screw.

Such a pump is commonly known as a screw pump, and pumping of 10 fluid within the housing is effected by fluid becoming trapped and pressurised between the meshing screws.

Typically, such pumps include one or two cylindrical idler screws.

Where two idler screws are provided they are typically mounted on diametrically opposite sides of the power screw. The idler screws need not be 15 attached to the housing but may simply be retained within the housing.

Alternatively, the idler screws may be mounted at an end in a bearing provided in the housing. In both cases, the pressure from the pumped fluid exerts a force on the idler screws which tends to push the idler screws away from the power screw into the housing. As a result, frictional forces between the idler screws 20 and the housing can cause significant energy losses. This is a particular problem when the idler screws are not mounted in a bearing.

According to the invention a pump including a power screw and at least one idler screw which meshes with the power screw, the power screw and idler screw being rotatable in a housing, the idler screw having at least one screw 25 form including a generally helical groove and a generally helical land surface, the land surface having a first and a second edge portion, each of which is adjacent to the or a groove, the distance between the land surface and a longitudinal axis of the idler screw varying between the first edge portion and the second edge portion, the distance between the first edge portion and the

longitudinal axis of the idler screw being substantially constant over the length of the screw form and the distance between the second edge portion and the longitudinal axis of the idler screw being substantially constant over the length of the screw form.

5 By virtue of the shape of the idler screw, the pumped fluid acts as a hydrodynamic bearing, supporting the idler screw and reducing the frictional forces between the idler screw and the housing.

In one embodiment, the distance between the or the at least one land surface and the longitudinal axis increases continuously from the first edge 10 portion to the second edge portion. In a preferred embodiment, the distance between the or the at least one land surface and the longitudinal axis, initially increases from the first edge portion to a position intermediate the first and second edge portions, and then remains generally constant from the intermediate position to the second edge portion. The intermediate position 15 may be approximately half way between the first and second portions. Such an arrangement may be easier to manufacture and gauge than where the distance increases continuously. Also in use, the hydrodynamic pressure drop between where the second edge portion separates from the adjacent housing wall as the idler screw rotates, and where the next first edge portion engages the housing 20 wall is reduced compared within a continuously ramped arrangement.

In each case, preferably the idler screw is arranged so that the first edge portion leads the second edge portion as the idler screw rotates in use.

The first and/or second edge portion may be slightly radiussed if desired so as to provide a lead-in to the or an adjacent groove.

25 Preferably the power screw includes at least one generally helical ridge which engages with the generally helical groove of the or each idler screw.

Preferably, each idler screw includes two generally helical grooves of substantially the same pitch and two generally helical land surfaces, each land surface having a first and a second edge portion, each of which is adjacent to a

groove, the distance between each land surface and a longitudinal axis of the idler screw varying between the first edge portion and the second edge portion over at least part of the length of the idler screw. In this case, the power screw includes two generally helical ridges of substantially the same pitch.

5 Preferably the pump includes two idler screws located at diametrically opposite sides of the power screw.

The difference in the distance between the longitudinal axis of the idler screw and the land surface at the first edge portion and the second edge portion may be up to 4% of the largest distance between the longitudinal axis of the l O idler screw and the land surface.

An end of the or each idler screw may be mounted in a bearing provided in the housing.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which, 15 FIGURE 1 is an illustration of a power screw and idler screws and a housing of a pump according to the invention, FIGURE 2 is an illustration of a transverse cross-section through the power screw and idler screws of Figure 1.

FIGURE 2a is a view similar to Figure 2 but showing a preferred idler 20 screw form; FIGURE 3 is an illustration of a longitudinal section through a pump according to the invention, in the direction shown by arrow X in Figure 2.

FIGURE 4 is an illustration of a longitudinal section through a pump according to the invention in the direction shown by arrow Y in Figure 2.

25 Referring now to the figures, there is shown a power screw 10 and idler screws 12 of a screw pump, the two idler screws 12 located at diametrically opposite sides of the power screw 10. Longitudinal axes A of the idler screws 12 are generally parallel to the longitudinal axis B of the power screw 10. Each idler screw 12 has two screw forms which include first and second generally

helical grooves 14, 14' which each extend along substantially the entire length of the screw 12. The two grooves 14, 14' are both of substantially the same pitch and sense, and the turns of the grooves 14, 14' are interposed such that when the screw 12 is viewed in transverse crosssection one groove 14 is 5 diametrically opposite the other 14'.

The grooves 14, 14' are separated by first and second generally helical land surfaces 16, 16', each land surface having a first edge portion 16a, 16a' and second edge portion 16b, 16b' adjacent to one of the grooves 14, 14'. The first edge portion 16a of the first land surface 16 is adjacent to the second 10 groove 14' and the second edge portion 16b of the first land surface 16 is adjacent to the first groove 14. The first edge portion 16a' of the second land surface 16' is adjacent to the first groove 14, and the second edge portion 16b' of the second land surface 16' is adjacent to the second groove 14'.

In the Figure 2 embodiment, the distance between each land surface 16, 15 16' and the longitudinal axis A of the idler screw 12 increases continuously from the first edge portion 16a, 16a' to the second edge portion 16b, 16b'.

In the embodiment of Figure 2a, on which all like parts to those on Figure 2 are labelled with the same references, the distance between each land surface 16, 16 and the longitudinal axis A of the idler screw 12 increases from 20 the first edge portion 16, 16a continuously to an intermediate position I, I, which intermediate position I, I is in this example, approximately half way between the respective first and second edge portions 16a, 16a; 16b, 16b.

From the intermediate positions I, I to the second edge portions 16b, 16b, the distance between the land surface 16, 16 and the longitudinal axis A of the 25 idler screw 12 is generally constant.

In each example, if desired, the first and/or second edge portions 16a, 16a', 16b, 16b may be slightly radiussed so as to provide a lead-in to the adjacent respective groove 14, 14'.

Typically, the difference in the distance between the first edge portion 16a, 16a' of each land surface 16, 16' and the longitudinal axis A and the distance between the second edge portion 16b, 16b' of each land surface 16, 16' and the longitudinal axis A is up to 4% of the largest outside diameter of 5 the idler screw 12, i.e. the distance between the second edge portion 16b, 16b' of each land surface 16, 16' and the longitudinal axis A. Thus it is apparent that this difference has been exaggerated in Figures 2 and 2a for clarity.

The power screw 10 and idler screw 12 are both generally cylindrical, however, and thus it will be appreciated that the distance between each first 10 edge portion 16a, 16a and the longitudinal axis A of the idler screw 12 is substantially constant over the length of the idler screw 12, as is the distance between each second edge portion 16b, 16b and the longitudinal axis A. The power screw 10 is provided with first 18 and second 18' generally helical ridges which each extend along substantially the entire length of the 15 screw 10. The two ridges 18, 18' are both of substantially the same pitch & sense, and the turns of the ridges 18, 18' are interposed such that when the screw 10 is viewed in transverse crosssection, one ridge 18 is diametrically pposite the other 18'.

The first ridge 18 meshes with the first groove 14 of each idler screw 12, 20 and the second ridge 18' meshes with the second groove 14' of each idler screw 12, and thus rotation of the power screw 10 about its longitudinal axis B in the direction indicated by the respective arrow, causes rotation of the idler screws 12 about their longitudinal axes A in the opposite rotational direction as indicated by the respective arrows.

25 The power screw 10 and idler screws 12 are mounted in a housing 20, part of which is illustrated in Figures 2 and 2a, 3 & 4, which is shaped to provide minimum clearance between the screws 10, 12 and the housing 20, whilst permitting rotation of the screws 10, 12 within the housing 20. The housing 20 thus includes an elongate cavity in which the screws 10, 12 are

housed. In cross-section, the cavity includes a central part circular portion 20a of a larger diameter adapted to house the power screw 10, and two part circular lobe portions 20b located on diametrically opposite sides of the central portion of 20a, which each have a smaller diameter and are adapted to house the idler 5 screws 12.

As illustrated in Figures 3 & 4, the housing 20 also includes an outlet port 22 and an inlet port 24, the inlet port 24 being arranged such that fluid enters the cavity adjacent to first ends of the driven and idler screws 10, 12 and the outlet port 22 being arranged such that fluid leaves the cavity adjacent to 10 second ends of the driven and idler screws 10, 12. The inlet port 24 is connected to a supply of fluid to be pumped.

The power screw 10 is connected to a motor (not shown) by means of a drive shaft 26, the drive shaft 26 being mounted in bearings 28 provided in the housing 20. Operation of the motor causes the power screw 10 to rotate about 15 its longitudinal axis B in a first sense, and which thus causes the idler screws 12 each to rotate about their longitudinal axes A in an opposite sense to the power screw 10. The screws 10, 12 are oriented such their rotation causes fluid to be drawn from the inlet port and moved along the length of the screws 10, 12 to the outlet port. Fluid trapped between the ridges 18, 18' and the grooves 14, 20 14' as the screws 10,12 mesh becomes pressurised and exerts an outward force on both the idler screws 12, which tends to push the idler screws 12 towards the housing 20.

The idler screws 12 are configured such that the first edge portions 16a, 16a' of each land surface 16, 16' lead the second edge portions 16b, 16b' as the 25 idler screws 12 rotate. The resulting change in separation between the land surfaces 16, 16' and the housing 20 compresses the fluid between the housing 20 and the land surfaces 16, 16', the resultant local fluid pressures enable the fluid to act as a hydrodynamic bearing, supporting the idler screws 12, and

reducing frictional forces between the housing and the land surfaces 16, 16' of the idler screws 12. Thus, the efficiency of the pump is improved.

Such a pump advantageously is used to pump fluid for hydraulic systems which may include actuators.

5 In the examples described, the idler screws 12 are not connected to the housing 20, but it is possible to mount the idler screws 12 on bearings connected to the housing 20.

It is not necessary to provide each idler screw 12 with two grooves 14, 14' and the power screw 10 with two ridges 18, 18'. Each idler screw 12 may 10 be provided with one or more than two grooves 14, 14', and the power screw 10 provided with a corresponding number of ridges 18, 18'.

The features disclosed in the foregoing description, or the following

claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process 15 for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (14)

1. A pump including a power screw and at least one idler screw which meshes with the power screw, the power screw and idler screw being rotatable 5 in a housing, the idler screw having at least one screw form including a generally helical groove and a generally helical land surface, the land surface having a first and a second edge portion, each of which is adjacent to the or a groove, the distance between the land surface and a longitudinal axis of the idler screw varying between the first edge portion and the second edge portion, 10 the distance between the first edge portion and the longitudinal axis of the idler screw being substantially constant over the length of the screw form and the distance between the second edge portion and the longitudinal axis of the idler screw being substantially constant over the length of the screw form.
15
2. A pump according to claim 1 wherein the distance between the or the at least one land surface and a longitudinal axis increases continuously from the first edge portion to the second edge portion.
3. A pump according to claim 1 wherein the distance between the or at 20 least one land surface and the longitudinal axis initially increases from the first edge portion to a position intermediate the first and second edge portions, and then remains generally constant from the intermediate position to the second edge portion.
25
4. A pump according to claim 3 wherein the intermediate position is approximately half-way between the first and second edge portions.
5. A pump according to anyone of claims 1 to 4 wherein the idler screw is arranged so that the first edge portion leads the second edge portion as the idler screw rotates in use.
5
6. A pump according to any one of the preceding claims wherein the first and/or the second edge portions include a radiussed lead-in to the or an adjacent groove.
7. A pump according to any one of the preceding claims wherein the power 10 screw includes at least one generally helical ridge which engages with the generally helical groove of the or each idler screw.
8. A pump according to any one of the preceding claims wherein each idler screw includes two generally helical grooves of substantially the same pitch and 15 two generally helical land surfaces, each land surface having a first and a second edge portion, each of which is adjacent to a groove, the distance between each land surface and a longitudinal axis of the idler screw varying between the first edge portion and the second edge portion over at least part of the length of the idler screw.
9. A pump according to claim 8 wherein the power screw includes two generally helical ridges of substantially the same pitch.
l O. A pump according to any one of the preceding claims wherein the pump 25 includes two idler screws located at diametrically opposite sides of the power screw.
11. A pump according to any one of the preceding claims wherein the difference in the distance between the longitudinal axis of the idler screw and
the land surface at the first edge portion and the second edge portion is up to 4% of the largest distance between the longitudinal axis of the idler screw and the land surface.
5
12. A pump according to any one of the preceding claims wherein an end of the or each idler screw is mounted in a bearing provided in the housing.
13. A pump substantially as hereinbefore described with reference to and as shown in the accompanying drawings.
14. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.
GB0326358A 2002-11-14 2003-11-12 Pump idler rotor lands forming bearing faces Withdrawn GB2395985A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0226529A GB0226529D0 (en) 2002-11-14 2002-11-14 Pump

Publications (2)

Publication Number Publication Date
GB0326358D0 GB0326358D0 (en) 2003-12-17
GB2395985A true GB2395985A (en) 2004-06-09

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Family Applications (2)

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GB0226529A Ceased GB0226529D0 (en) 2002-11-14 2002-11-14 Pump
GB0326358A Withdrawn GB2395985A (en) 2002-11-14 2003-11-12 Pump idler rotor lands forming bearing faces

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB0226529A Ceased GB0226529D0 (en) 2002-11-14 2002-11-14 Pump

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US (1) US20040146422A1 (en)
GB (2) GB0226529D0 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2401033A (en) * 2003-04-17 2004-11-03 Hoover Co Vacuum cleaner with removable bucket having pivotable handle

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3247580A (en) * 1962-05-09 1966-04-26 Laval Turbine Method of making screw pumps
US5066205A (en) * 1989-05-19 1991-11-19 Excet Corporation Screw rotor lobe profile for simplified screw rotor machine capacity control
US5911743A (en) * 1997-02-28 1999-06-15 Shaw; David N. Expansion/separation compressor system

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2588888A (en) * 1949-02-08 1952-03-11 Laval Steam Turbine Co Pump
US3291061A (en) * 1963-07-23 1966-12-13 Kosaka Kenkyusho Ltd Screw pump or hydraulic screw motor
US3289600A (en) * 1964-03-13 1966-12-06 Joseph E Whitfield Helically threaded rotors for screw type pumps, compressors and similar devices
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
US5123821A (en) * 1990-03-08 1992-06-23 Allweiler Ag Screw spindle pump with a reduced pulsation effect
FI104440B (en) * 1995-06-22 2000-01-31 Kone Corp Screw pump and screw pump screw
KR100384925B1 (en) * 1995-12-11 2003-08-21 아뜰리에 부쉬 에스.에이. Double worm gear system
CN1093228C (en) * 1996-09-12 2002-10-23 爱特里尔斯布时股份公司 Screw rotor set
US6019586A (en) * 1998-01-20 2000-02-01 Sunny King Machinery Co., Ltd. Gradationally contracted screw compression equipment
TW463883U (en) * 2000-02-02 2001-11-11 Ind Tech Res Inst Dual-spiral rotor mechanism using pressure difference to automatically adjust gap

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3247580A (en) * 1962-05-09 1966-04-26 Laval Turbine Method of making screw pumps
US5066205A (en) * 1989-05-19 1991-11-19 Excet Corporation Screw rotor lobe profile for simplified screw rotor machine capacity control
US5911743A (en) * 1997-02-28 1999-06-15 Shaw; David N. Expansion/separation compressor system

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2401033A (en) * 2003-04-17 2004-11-03 Hoover Co Vacuum cleaner with removable bucket having pivotable handle
US7152274B2 (en) 2003-04-17 2006-12-26 The Hoover Company Handle and latch for a removable dirt separation system
GB2401033B (en) * 2003-04-17 2007-11-14 Hoover Co Vacuum cleaner and method of operation thereof

Also Published As

Publication number Publication date
GB0326358D0 (en) 2003-12-17
GB0226529D0 (en) 2002-12-18
US20040146422A1 (en) 2004-07-29

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