GEAR PUMP AND USE THEREOF

Abstract

Gear pump with intermeshing gear wheels enclosed by a housing with bearing journals arranged on shaft axes, each projecting laterally from the gear wheels, which are mounted in the housing by means of slide bearings, having a slide bearing length, the slide bearings being lubricated with pumped medium. The invention is characterized in that a filling pocket with radial expansion is incorporated in each of the slide bearings in the region of a pump pressure side, the filling pocket being spaced from a gear-side end face of the respective slide bearing by a distance, so that a bar with a bar width with axial expansion corresponding to a slide bearing surface is formed, and in that a lubrication groove with a tampering cross-section is provided in each of the slide bearings, the lubricating groove starting from an end on the gearwheel side towards a slide bearing end and starting at the filling pocket on the gearwheel side and communicating therewith.

Claims

1. Gear pump with intermeshing gear wheels (1) enclosed by a housing with bearing journals (5, 6) arranged on shaft axes (9), each projecting laterally from the gear wheels (1), which are mounted in the housing by means of slide bearings (3), having a slide bearing length (L), the slide bearings (3) being lubricated with pumped medium, characterized in that a filling pocket (2) with radial expansion is incorporated in each of the slide bearings (3) in the region of a pump pressure side, the filling pocket (2) being spaced apart from a gear-side end face (7) of the respective slide bearing (3) by a distance (d), so that a bar (11) with a bar width (D) with axial expansion corresponding to a slide bearing surface is formed, and in that a lubricating groove (4) with a tampering cross-section is provided in each of the slide bearings (3), the lubricating groove (4) starting from an end on the gearwheel side towards a slide bearing end and starting at the filling pocket (2) on the gearwheel side and communicating therewith.

2. Gear pump according to claim 1, characterized in that the distance (d) between the gear-side end face (7) of the slide bearings (3) and the respective filling pocket (2) is 5% to 10%, preferably 7%, of the slide bearing length (L).

3. Gear pump according to claim 1, characterized in that the bar width (D) is at least 1% to 10%, preferably 3%, of the slide bearing length (L).

4. Gear pump according to claim 1, characterized in that the filling pocket (2) has a maximum width (Br) in the axial direction with respect to the shaft axis (9) which is 5% to 20%, preferably 10%, of the slide bearing length (L).

5. Gear pump according to claim 1, characterized in that the filling pocket (2) starts at an angle of 225? to 315?, preferably at 270?, with respect to a plane spanned by the two shaft axes (9) and in the direction of rotation of the gear wheels.

6. Gear pump according to claim 1, characterized in that the filling pocket (2) ends at an angle of 315? to 360?, preferably at 330?, with respect to a plane spanned by the two shaft axes (9) and in the direction of rotation of the gear wheels (1).

7. Gear pump according to claim 1, characterized in that a cross-section in the transition region (12) from the filling pocket (2) to the lubrication groove (4) is formed continuously.

8. Gear pump according to claim 1, characterized in that the lubrication groove (4) runs at an acute angle (?) with respect to the shaft axis (9) in the direction of the slide bearing end.

9. Gear pump according to claim 1, characterized in that the lubricating groove (4) extends to the end of the slide bearing.

10. Gear pump according to claim 1, characterized in that at least one of the journals (5, 6) has, at least over part of its axial extent, a journal diameter (D.sub.L) which lies in the range from 90% to 100% of a root circle diameter (D.sub.F) of the toothing of the associated gear wheel (1).

11. Use of the gear pump according to claim 1 for conveying highly viscous conveying medium, such as polymer, with a mass percentage of inorganic fillers in total mass of conveying medium of more than 60%.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0025] Examples of embodiments of the present invention are explained in further detail below with reference to figures. These are for explanatory purposes only and are not to be construed restrictively. They show:

[0026] FIG. 1 a known gear wheel with bearing journals for a gear pump according to the invention in perspective view,

[0027] FIG. 2 a section transverse to the shaft axis according to section line B-B in FIG. 3 through a slide bearing according to the invention,

[0028] FIG. 3 a section through the shaft axis according to section line C-C in FIG. 2 through the slide bearing according to the invention shown in FIG. 2, and

[0029] FIG. 4 a top view of a filling pocket incorporated in the slide bearing according to the invention with adjoining lubrication groove.

DETAILED DESCRIPTION OF THE INVENTION

[0030] FIG. 1 shows a perspective view of a gear wheel 1 known per se with journals 5 and 6 for a gear pump according to the invention. Over part of their axial extent, the journals 5 and 6 have a journal diameter D.sub.L which is approximately as large as a root circle diameter D.sub.F of the toothing. At least the journal diameter D.sub.L is in the range of 90% to 100% of the root diameter D.sub.F. Of course, this also applies to the journals of the second gear wheel not shown in FIG. 1.

[0031] FIG. 2 shows a cross-section through a slide bearing 3 according to the present invention. The sectional area is transverse to the shaft axis 9 and centered through a filling pocket 2 according to the present invention, which is incorporated in the sliding surface of the slide bearing 3 according to the present invention. The cut surface is also shown in FIG. 3, which will be explained later, and is designated there as cut surface B-B.

[0032] As can already be seen from FIG. 2, the filling pocket 2 is spaced from a gear-side end face 7 of the slide bearing so that there is a bar 11, to be explained later, with radial extension corresponding to the sliding surface of the slide bearing 3. The position of the filling pocket 2 is defined below by angles around the shaft axis 9, i.e., the shaft axis 9 is defined as the origin in the section shown in FIG. 2. Furthermore, angles are given in relation to an angular reference plane 10, which is spanned by the two shaft axes of the gear pump. In FIG. 2, in which a section transverse to the shaft axis 9 is shown, the reference plane 10 can be seen as a line running upwards, whereby the reference direction for angle indications (0? angle) is a ray which, on the one hand, starts from the origin (shaft axis 9) and which, on the other hand, runs perpendicularly through the second shaft axis (not shown in FIG. 2). Angles specified in the direction of rotation R of the shaft are positive and angles specified against the direction of rotation are therefore negative.

[0033] Based on these definitions, a start of the filling pocket 2 with a start angle ? and the end of the filling pocket 2 with an end angle ? can be specified. It has been found that in a first embodiment, the starting angle ? is in a range of 225? to 315?, and in a specific embodiment, the starting angle ? is equal to 270?. The end angle R is in a range of 315? to 360?, wherein in a specific embodiment the end angle ? is equal to 330?.

[0034] In one embodiment of the present invention, the filling pocket 2 has a small cross-section at the beginning, i.e., in the region of the starting angle ?, which becomes larger as the angle increases and which in turn decreases towards the end angle ?. This can already be clearly seen from the section through the filling pocket 2 shown in FIG. 2.

[0035] FIG. 3 shows a section through the shaft axis 9 according to the sectional plane C-C indicated in FIG. 2 through the slide bearing 3 according to the invention. The filling pocket 2 and the lubricating groove 4 communicating with it can be clearly seen, which in the embodiment shown is worked into the sliding surface of the slide bearing 3 at an angle ? with respect to the shaft axis 9 of the slide bearing 3. The lubricating groove 4 has the task of supplying the slide bearing 3 sufficiently with lubricanti.e. pumping mediumso that a lubricating film between the shaft and the slide bearingin the so-called lubricating gapdoes not break off. For this purpose, the lubrication groove 4 is designed to taper, i.e. its cross-section, which initially corresponds to the cross-section of the filling pocket 2, decreases towards the sealing side. In the embodiment of the invention shown in FIG. 3, a so-called dirt groove 13 is incorporated in the last third of the lubrication groove 4, which has a substantially constant cross-section and is open towards the rear and ensures that foreign particles are flushed out of the slide bearing 3. The cross-section of the dirt groove is therefore dimensioned in such a way that the largest foreign particles to be expected in the pumped medium can be flushed out. This prevents clogging of the dirt groove and thus also of the lubrication groove 4.

[0036] FIG. 4 shows a top view of the filling pocket 2 incorporated in the slide bearing 3 according to the invention. Part of the lubrication groove 4 connected to the filling pocket 2 is also visible.

[0037] Of decisive importance for the present invention is the fact that the filling pocket 2 is spaced from the end face of the slide bearing 3 to such an extent that a bar 11 with an axial extent corresponding to the surface of the plain bearing 3 remains. This ensures that foreign bodies larger than the sealing gap cannot enter the filling pocket 2 and thus also the lubrication groove 4. Consequently, clogging of the lubrication groove 4 can be largely prevented, resulting in a significantly lower probability of failure of the gear pump. The gear pump according to the invention is thus considerably more robust than known gear pumps.

[0038] The gear pump according to the invention can therefore also optimally process pumped media, such as polymer melts with a high proportion of solids or with solids above a critical size (foreign particles), which was not the case until now. The bar 11 prevents too many or too large foreign particles from entering the narrow lubrication gap between the shaft and the slide bearing 3. The bar 11 thus acts as a kind of filter that only allows foreign particles up to a certain size to pass through. If the lubrication groove 4 and the dirt groove, if any, are dimensioned according to the size of the foreign particles that are just allowed to pass through, an extremely robust gear pump is obtained, because clogging of the lubrication groove 4 and thus breaking off of the lubricating film in the slide bearing 3 are prevented.

[0039] The geometry of the filling pocket 2 is such that it initially becomes deeper in the direction of rotation of the shaft, i.e. the cross-section increases in the direction of rotation of the shaft.

[0040] In further embodiments of the present invention, the filling pocket 2 has a maximum width Br in the axial direction with respect to the shaft axis 9, which is 5% to 20%, preferably 10%, of the slide bearing length L. Here, a distance d between the end face of the slide bearings 3 and the respective filling pocket 2 can be, for example, 5% to 10%, preferably 7% of the slide bearing length L. The distance d can be maintained, for example, over a substantial part of the unwound extent of the filling pocket 2, i.e. over more than 50%, in particular over more than 80%, of the unwound extent of the filling pocket 2. Furthermore, the distance d may comprise any radius in the case of a rounded transition from the end face to the sliding bearing surface. It is important in the presence of a rounded transition from the end face to the sliding bearing surface that the bar 11 has a bar width D in the axial direction at the level of the sliding bearing surface, the bar width D being at least 1% to 10%, preferably 3%, of the sliding bearing length L.

LIST OF REFERENCE SIGNS

[0041] 1 gear wheel [0042] 2 filling pocket [0043] 3 slide bearing [0044] 4 lubrication groove [0045] 5,6 bearing journal [0046] 7 gear-side end face [0047] R direction of rotation of the shaft [0048] 9 shaft axis [0049] 10 angular reference plane [0050] 11 bar [0051] 12 transition area [0052] 13 Dirt groove [0053] ? start angle [0054] ? end angle [0055] ? tilt angle [0056] D.sub.L bearing journal diameter [0057] D.sub.F root circle diameter of the toothing [0058] L slide bearing length [0059] Br width [0060] d distance of the filling pocket from the face of the slide bearing [0061] D bar width