EP0692073A1

EP0692073A1 - Gear pump for delivering a liquid

Info

Publication number: EP0692073A1
Application number: EP94913058A
Authority: EP
Inventors: Ulrich Pfuhler
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-03-31
Filing date: 1994-03-26
Publication date: 1996-01-17
Also published as: DE4310518C1; WO1994023209A1; US5620315A; JPH09502234A; KR960702064A

Abstract

A gear pump or motor for delivering a liquid has the following characteristics: meshing pairs of gears (1, 2) with parallel axes; a housing (3) that encloses the gears and has an envelope wall (3.1, 3.2); an inner wall surface that forms delivering gaps with the gears, said delivering gaps extending over part of the circumference of the gears; a low pressure chamber arranged in the inlet area of the feeding gap provided with an inlet and a high pressure chamber arranged in the outlet area of the feeding gap, provided with an outlet for the liquid to be delivered; one of the gears is rigidly fixed to the housing whereas the other gear is movable in the axial direction. The invention has the following characteristics: the movable gear (1) carries a face wall (7, 8) firmly secured to each of its two ends; both face walls (7, 8) sealingly lie on the inner surface of the envelope wall (3.1, 3.2) of the housing (3); the inner wall surface is made of a wall (9) which interconnects both movable face walls (7, 8) and forms together with them a carriage movable in the housing (3); the fixed gear (2) carries at its free end a front wall (6) firmly linked thereto which sealingly lies on the inner surface of the wall (9).

Description

Gear pump for pumping a flowable medium

The invention relates to a gear pump for conveying a flowable medium. Reference is made to the preamble of claim 1.

Gear pumps of this type are used for both stationary and mobile operation. The known advantages mainly consist in achieving high and very high pressures with a relatively precise volumetric dosage.

From numerous documents it is known to shift intermeshing gear wheels in the axial direction relative to one another in order to change the delivery rate during operation. This idea is contained, for example, in US Pat. No. 5,184,947. There, an axially immovable gear is mounted in a housing. A second gear, which meshes with the first, is mounted in a slide which can be moved axially parallel to the first gear.

DE 41 21 074 AI describes an external gear pump with a continuously variable flow rate. Here, too, two gear wheels which are displaceable relative to one another are provided. The driven gear is mounted in a housing, while the rotating gear is adjusted depending on the fluid pressure difference applied to the pump.

These known devices have the disadvantage of poor sealing of the work space. The seals are subject to very high pressures and therefore high wear, which limits the life of the gear pump.

The invention has for its object to design a gear pump according to the preamble of claim 1, that their main purpose of easily and quickly changing the flow rate during operation is perfectly fulfilled, but that the seal is less exposed to wear than previously known gear pumps, and that the construction effort is kept within limits.

This object is solved by the characterizing features of claim 1.

In particular, the following can be achieved in this way: Simply by moving two meshing gears in the axial direction relative to one another, and thus by changing the mutual degree of coverage, the delivery rate can be varied. The pump has only rotating parts, no impact parts. The pump can be geometrically reduced or enlarged. Basically, the same or the same components can be used when manufacturing series; to change the maximum flow rate you only need to change the overall length of the main components.

The invention is explained in more detail with reference to the drawing. The following is shown in detail:

Fig. 1 shows a pump equipped with two gears in a longitudinal section.

2 to 5 are cross sections in the planes A-A, B-B, C-C and in the offset planes D-D.

Fig. 6 shows in an enlarged, perspective

Representation of the non-displaceable of the two gears with details of a displaceable end wall plus associated sealing elements.

Fig. 7 shows the pump in three different operating states. 8 shows a further embodiment of a gear pump according to the invention with two fixed gear wheels which are coaxial with one another and with a displaceable gear wheel which is axially parallel to the first two.

The gear pump shown in Figures 1 to 6 has two gears 1 and 2. These are arranged axially parallel to each other and mesh with each other over part of their length. A housing 3 is provided

Has peripheral walls 3.1 and 3.2, also end walls 3.3 and 3.4. One of the two gears, namely gear 2, is axially immovable. It is supported at its right end in the housing end wall 3.4, and at its left end on an intermediate wall 6; this forms a single part with the housing outer wall 3.2, which in the present case is a cast part. The other of the two gearwheels, namely gearwheel 1, is displaceable in the axial direction, and thus also relative to gearwheel 2 and to housing 3. It is mounted in end walls 7, 8, which can be moved together with gear 1. The movable walls 7, 8 are also firmly connected to one another by a bridge 9, which will be discussed in more detail below. The displaceable partition walls 7, 8 and the bridge 9 thus form an axially displaceable carriage. The two

Spaces between the left-hand housing end wall 3.3 and the displaceable end wall 7 on the one hand and between the right-hand housing end wall 3.4 and the displaceable end wall 8 on the other hand are each provided with connections 10, 11 for the entry or exit of a control medium.

From Figure 2 it can be seen that the two gears 1, 2 mesh with each other. They are surrounded in a very specific way by the peripheral wall 3.2 of the housing 3 on the one hand and by the bridge 9 on the other. As can be seen from Figure 2, namely forms the inner surface of the peripheral wall 3.2 with gear 1 on a part of its circumference a conveyor gap 15. The inner wall surface of the bridge 9, however, forms a conveyor gap 16 with gear 2 on a part of its circumference Gears 1, 2 off. An inlet area 17 with an inlet 17.1 and an outlet area 18 with an outlet 18.1 are formed for the conveyed medium. From Figure 2 it can be seen that the above-mentioned areas 17, 18 with the cooperation of the inner surfaces of the housing U wall 3.2 and bridge 9 and the scope of the two gears 1 and 2 are limited. From Figure 1 it can be seen that the right surface in the drawing of the intermediate wall 6 and the left surface in the drawing of the displaceable end wall 8 are used in the axial direction for limitation. The latter two areas also limit the actual working space of the gear pump.

Figure 6 shows that the movable partition 8 not only serves to limit and seal the work space, but also has a bearing function for gear 2. 6 shows the wall 8 in detail, a radial bearing 8.1 carried by it, a seal 8.2 for sealing the tooth contour against the radial bearing 8.1, a shaft seal 8.3 and a seal 8.4 for sealing the displaceable wall 8 against the peripheral wall 3.2 of the

Housing 3. A cutout of bridge 9 and a slide cover 8.5 can also be seen.

As can also be seen, there are three chambers 20, 21, 22 in the housing 3. One of these chambers, namely chamber 21, is located within the bridge 9. It is advantageous that the two chambers 21 and 22 are under pressure. Thus the walls 6 and 8 and thus also the circumferential seals 8.2, 8.3 and 8.4 are also pressurized from the outside, which relieves all seals between the fixed and the moving parts. It is advantageous to establish a conductive connection between the chambers 21 and 22 so that one chamber can feed the other.

The mode of operation of this first embodiment of a gear pump according to the invention is shown in FIG. 7, with individual working positions resulting from FIGS. 7.1, 7.2 and 7.3.

In the embodiment according to FIG. 7.1, the mentioned slide with gear wheel 1 is brought into a middle position, the axial degree of overlap of the two gear wheels 1, 2 taking on an intermediate size. In this state, the volume delivered has an average value.

In the working position according to FIG. 7.3, the degree of coverage of the two gear wheels 1, 2 is as large as the construction of the pump allows. The slide, and thus also gear 1, have been shifted to the right as far as possible. The degree of coverage is maximum. Accordingly, the funding volume is also maximum.

In the working position according to FIG. 3, the degree of coverage tends to zero, and with it the delivery rate.

The carriage is controlled via the above-mentioned connections 10 and 11 by a corresponding pressurized control medium. This allows the carriage to be moved continuously and held in any position. It can be seen from this that a continuous adjustment of the delivery rate is possible during operation.

The pump can be adjusted by externally generated or self-generated hydrostatic pressure, in the latter case only during operation. A pressure accumulator could be provided so that adjustment pressure is always available. This only needs to have minimal dimensions and can optionally be accommodated between the outer walls 3.1, 3.2 on the one hand and the bridge 9 on the other.

The second embodiment of an inventive

Gear pump, shown in Fig. 8, differs from the first in that a total of three gears are provided, namely a lower, axially displaceable gear 1 and two upper, fixed gears 2.1, 2.2, which are arranged coaxially to one another. One can also see here again a housing 3 with U initial walls 3.1, 3.2, end walls 3.3 and 3.4 and essentially all other components of the first embodiment.

The advantage of this three-wheel embodiment is that there are two work spaces. The width of these working spaces is indicated by the reference symbols a- and a ₂ . The working spaces are delimited by the two outer, displaceable end walls 7, 8 of the slide and by a fixed intermediate wall 6.

As can best be seen from the longitudinal sections, the bottom of the tooth space is placed somewhat deeper radially inwards at the end of the individual gear on the working space side, the bottom falling off towards the end face of the gear in question. This enables perfect removal of squeeze oil into the low-pressure region 17.

It is also clear that the term "gear" cannot be understood too narrowly. For example, rolling elements of considerable axial extent are provided in the drawings, in which the ratio of axial length to diameter is quite large, for example 2: 1. Instead, the invention can also be applied to

Gears that are quite flat and therefore a very have a low ratio of the axial extension to the diameter.

Furthermore, it goes without saying that the invention can be applied not only to pumps, but also to hydrostatic motors.

Claims

Expectations

1. Gear pump or motor for pumping a flowable medium with the following features:

1.1 with gear wheels (1, 2) which are arranged axially parallel to one another and which mesh with one another in pairs;

1.2 with a housing (3) which surrounds the gears (1, 2) and has a peripheral wall (3.1, 3.2); 1.3 forms an inner wall surface with the gears (1, 2) conveyor gaps (15, 16), each of which extends over part of the circumference of the gears (1, 2);

1.4 in the inlet area (17) of the delivery gaps (15, 16) is a low-pressure chamber with an inlet (17.1) and in the outlet area (18) of the delivery gaps (15, 16) is a

High-pressure chamber provided with an outlet (18.1) for the pumped medium;

1.5 one of the gears (1, 2) is fixed to the housing (3), while the other (2) is displaceable in the axial direction; characterized by the following features:

1.6 the displaceable gear (1) carries at each of its two ends a front wall (7, 8) firmly connected to it; 1.7 the two end walls (7, 8) lie sealingly on the inner surface of the peripheral wall (3.1, 3.2) of the housing (3);

1.8 the inner wall surface is formed from a wall (9) which bridges the two movable end walls (7, 8) and together with these one in the housing

(3) forms sliding carriage;

1.9 the fixed gear (2) carries at its free end a fixed end wall (6) which bears sealingly against the inner wall surface of the wall (9).

2. Gear pump according to claim 1, characterized in that the two adjoining the work space in the axial direction (20, 22) are each connectable to a pressure medium.

3. Gear pump according to claim 1 or 2, characterized in that at the working space end of the individual gear (1, 2) the tooth space base is recessed radially inward for the removal of Quetschol in the low pressure region.