EP4450756A1 - Gear pump and use thereof - Google Patents

Abstract

Gear pump with intermeshing gears (1) enclosed by a housing with bearing journals arranged on shaft axes (9), each projecting laterally from the gears (1), which are mounted in the housing by means of plain bearings (3), each having a plain bearing length, each having a lubrication pocket (2) with radial extension, wherein the lubrication pocket (2) is spaced from a gear-side end face (7) of the respective plain bearing (3) by a first distance (d ₁ ), so that a first web (11) with a first web width (D ₁ ) with axial extension corresponding to a plain bearing surface is present. The invention is characterized in that the lubrication pocket (2) is further spaced apart from the bearing face (8) opposite the gear-side face (7) by a second distance (d ₂ ), so that a second web (12) with a second web width (D ₂ ) with an axial extension corresponding to a plain bearing surface is present, that a bore (4) leads through the plain bearing (3) and communicates with the lubrication pocket (2) at an injection point (13), and that the bore (4) is operatively connected to a conveying device for conveying lubricating medium into the lubrication pocket (2).

Description

TECHNICAL FIELD

The present invention relates to a gear pump according to the preamble of claim 1 and a use of the gear pump according to claim 15.

STATE OF THE ART

Gear pumps essentially consist of a pair of intermeshing gears which are enclosed in a housing and from which bearing journals protrude laterally, arranged around the longitudinal axis, which are seated in plain bearings lubricated by the pumping medium.

Since gear pumps have a rigid characteristic curve, they are particularly suitable for transporting media from a suction side to a pressure side. Between the two, a pressure gradient is created due to the volume flow in the downstream units, which is particularly large for highly viscous media and leads to a power transmission to each gear.

A well-known gear pump is, for example, in EP-1 790 854 A1 described, which is a gear pump in which a bearing journal diameter almost or equal to the root diameter of the gear.

The well-known gear pumps have plain bearings that are lubricated with the pumped medium. On one side of the plain bearings, there is high pressure on the gear pump outlet side, while behind the plain bearing there is almost the suction side pressure of the gear pump, which is significantly lower than the pressure on the pump outlet side. Due to this pressure difference, the pumped medium, which is required for the lubricating film build-up in the plain bearing, flows from the pump outlet into the plain bearing. A pressure lubrication groove in the front side of the plain bearing forms a direct connection from the outlet side into the plain bearing in order to supply the lubrication groove in the plain bearing with the best possible amount of pumped medium.

If a polymer melt is used as the conveying medium, which also contains high proportions of solids or solids above a critical size (generally referred to as foreign particles), this poses a problem for adequate lubrication in the plain bearing. For the plain bearings to function well, it is important to build up a lubricating film from the conveying medium. If too many or too large foreign particles get into the narrow lubrication gap between the shaft and the plain bearing, there is a risk of damage to the plain bearing or the shaft, which can lead to failure of the gear pump. This is particularly the case with a particle size that is larger than the height of the minimum lubricating film, because This leads to an interruption of the lubricant flow due to blockage in the plain bearing and thus to a failure of the gear pump. If too little melt reaches the plain bearing, there is a risk of insufficient lubrication. An increased flow of particle-laden melt (conveying medium) can also lead to increased abrasive wear on the plain bearing surfaces.

Furthermore, when a polymer is used as the conveying medium, unmelted polymer particles (small lumps) that enter the plain bearing via the lubrication groove can block the lubricant flow and lead to failure of the gear pump.

The problem of foreign particles can be addressed to a certain extent by using a plain bearing with filling pockets, as is the case in the EP 4 083 428 A1 The filling pocket incorporated into the plain bearing is characterized by a web between the gear-side face of the plain bearing and the filling pocket, whereby the web prevents large foreign particles in the conveying medium from entering the lubricating gap between the gear shaft and the plain bearing. For many applications, this approach already offers a good solution for "filtering out" solids from the main flow before the filtered medium enters the plain bearing to build up the lubricating film.

When polymer melts are used as a conveying medium with low viscosity, which can only build up a thin lubricating film in the plain bearing, this known type of filtering is sufficient of the pumped medium. Too many foreign substances still get into the lubrication gap and the risk of damage (so-called seizure) increases.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an improved gear pump which is considerably more robust in operation than known solutions.

This object is achieved by the features specified in the characterizing part of claim 1. Further embodiments of the present invention and a use are defined in further dependent claims.

• dass die Schmiertasche ferner zur gegenüber der zahnradseitigen Stirnseite liegenden Lagerstirnseite um einen zweiten Abstand beabstandet ist, so dass ein zweiter Steg mit einer zweiten Stegbreite mit axialer Ausdehnung entsprechend einer Gleitlageroberfläche vorhanden ist,
• dass eine Bohrung durch das Gleitlager führt und mit der Schmiertasche bei einer Einspritzstelle kommuniziert und
• dass die Bohrung mit einer Fördereinrichtung zur Förderung von Schmiermedium in die Schmiertasche wirkverbunden ist.

A gear pump according to the invention comprises intermeshing gears enclosed by a housing with bearing journals arranged on shaft axes, each projecting laterally from the gears, which are mounted in the housing by means of plain bearings each having a plain bearing length, each having a lubrication pocket with radial extension, wherein the lubrication pocket is spaced from a gear-side end face of the respective plain bearing by a first distance, so that a first web with a first web width with axial extension corresponding to a plain bearing surface is present. The invention is characterized in that

• that the lubrication pocket also faces the bearing face opposite the gear side face is spaced apart by a second distance so that a second web with a second web width with axial extension corresponding to a plain bearing surface is present,
• that a hole leads through the plain bearing and communicates with the lubrication pocket at an injection point and
• that the bore is operatively connected to a conveying device for conveying lubricating medium into the lubrication pocket.

The gear pump according to the invention is therefore much more robust than known gear pumps, because when a polymer is used as the pumping medium, neither unmelted polymer particles (small lumps) nor foreign particles can get into the lubrication groove in the plain bearing. The risk of the lubrication flow being blocked is thus significantly reduced. The lubrication flow is therefore blocked far less, which means that the probability of failure of the gear pump according to the invention is significantly lower.

A variant of the gear pump according to the invention consists in that the first web width is at least 5% to 20%, preferably 15%, of the plain bearing length.

Further embodiments of the gear pump according to the invention consist in that the second web width is at least 5% to 15%, preferably 10%, of the plain bearing length.

Still further embodiments of the gear pump according to the invention consist in that the lubrication pocket begins in an angular range of 210° to 315°, preferably at 270°, with respect to a plane spanned by the two shaft axes and in the direction of rotation of the gears.

Still further embodiments of the gear pump according to the invention consist in that the lubrication pocket ends in an angular range of 300° to 30°, preferably at 355°, with respect to a plane spanned by the two shaft axes and in the direction of rotation of the gears.

Still further embodiments of the gear pump according to the invention consist in that the injection point is arranged centrally in the lubricating pocket in the axial extension of the lubricating pocket.

Still further embodiments of the gear pump according to the invention consist in that the injection point is arranged in relation to a plane spanned by the two shaft axes and in the direction of rotation of the gears in an angular range of 225° to 315°, preferably in an angular range of 240° to 300°, preferably at 270°.

Still further embodiments of the gear pump according to the invention consist in that the lubrication pocket is deepest in the area of the injection point.

Still further embodiments of the gear pump according to the invention consist in that the injection point, seen in the direction of rotation of the gears, is arranged at the beginning of the lubrication pocket.

Still further embodiments of the gear pump according to the invention consist in that the lubrication pocket is wider, starting from the injection point and seen in the direction of rotation of the gears.

Still further embodiments of the gear pump according to the invention consist in that cross-sectional areas of the lubrication pocket, starting from the injection point and viewed in the direction of rotation of the gears, are of equal size over 2/3 of their unrolled length and that cross-sectional areas of the lubrication pocket are continuously decreasing over the remaining unrolled length up to the end of the lubrication pocket.

Still further embodiments of the gear pump according to the invention consist in that a cross-sectional area of the bore is equal to the cross-sectional areas of the lubrication pocket in the first 2/3 of the developed length of the lubrication pocket.

Still further embodiments of the gear pump according to the invention consist in that the bore is arranged radially to an outer diameter of the respective plain bearing.

Still further embodiments of the gear pump according to the invention consist in that at least one of the bearing journals has, at least over part of its axial extent, a bearing journal diameter which lies in the range of 90% to 100% of a root circle diameter of the toothing of the associated gear.

Finally, the present invention includes a use of the gear pump according to one or more of the above-mentioned embodiments for conveying highly viscous conveying media, such as polymer, with a mass percentage of fillers (eg titanium dioxide TiO ₂ , calcium carbonate, wood flour, stone, chalk, tallow, talc, silicates, carbons, in particular in the form of soot) of more than 60% of the total mass of the conveying medium.

The present invention also includes a use of the gear pump according to one or more of the above-mentioned embodiments for conveying conveying media with low viscosity (greater than or equal to one Pascal second), as well as polymer melts loaded with foreign particles, in which the foreign particles have a size that is equal to or larger than the minimum lubricating film in the plain bearing.

The mentioned embodiments of the present invention can be combined in any order. Only those combinations of embodiments are excluded which would lead to a contradiction as a result of the combination.

SHORT DESCRIPTION OF THE CHARACTERS

Fig. 1

ein bekanntes Zahnrad mit Lagerzapfen für eine erfindungsgemässe Zahnradpumpe in perspektivischer Darstellung,

Fig. 2

einen Schnitt durch ein erfindungsgemässes Gleitlager parallel zu einer Längsachse des Zahnrades mit Blick auf eine Bohrung mit Schmiertasche,

Fig. 3

einen teilweisen Schnitt quer durch das erfindungsgemässe Gleitlager im Bereich der Bohrung,

Fig. 4

einen Schnitt gemäss Fig. 3 durch das erfindungsgemässe Gleitlager mit Winkelangaben zur Positionsbestimmung der Bohrung und der Schmiertasche und

Fig. 5

eine graphische Darstellung des Querschnittverlaufs der erfindungsgemässen Schmiertasche in Funktion eines Rotationswinkels.

Embodiments of the present invention are explained in more detail below with reference to figures. These are for illustrative purposes only and are not to be interpreted as limiting. They show:

Fig. 1

a known gear with bearing pin for a gear pump according to the invention in perspective view,

Fig. 2

a section through a plain bearing according to the invention parallel to a longitudinal axis of the gear with a view of a bore with a lubrication pocket,

Fig. 3

a partial section through the plain bearing according to the invention in the area of the bore,

Fig. 4

a cut according to Fig. 3 by the inventive plain bearing with angle specifications for determining the position of the bore and the lubrication pocket and

Fig. 5

a graphical representation of the cross-sectional profile of the lubrication pocket according to the invention as a function of a rotation angle.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a perspective view of a gear 1 known per se with bearing journals 5 and 6 for a gear pump according to the invention. The bearing journals 5 and 6 have a bearing journal diameter D _L over part of their axial extent, which is approximately as large as a root diameter D _F of the gearing. At least the bearing journal diameter D _L is in the range of 90% to 100% of the root diameter D _F . Of course, this also applies to the Fig. 1 not shown bearing journal of the second gear. However, it is expressly pointed out that the mentioned design variant with the above-defined bearing journal diameter and root circle diameter does not necessarily have to be implemented in this way. A conventional design variant is also conceivable in which the bearing journal diameter is smaller than 90% of the root circle diameter.

In contrast to the proven principle of bearing lubrication by means of a conveying medium, which is fed into the plain bearings through grooves (see for example EP 833 068 B1 ), becomes A new clean, foreign matter-free lubricant for the lubricating film build-up is provided by a separate external conveyor and fed through a bore 4 ( Fig. 2 ) into a lubrication pocket 2 ( Fig. 2 ) into the plain bearing 3 ( Fig. 2 ). In this way, the lubricating film build-up between the plain bearing 3 and the bearing journal 5, 6 is largely independent of the lubricating film-building properties of the conveying medium, since this task is taken on by a suitable, clean and largely foreign matter-free lubricating medium. Express reference is made to the advantage that this external lubricating medium for building up the lubricating film can be different from the conveying medium to be recycled. It is expressly emphasized that the external lubricating medium can differ significantly from the conveying medium. Depending on the application data, a suitable external conveying medium (lubricating medium) with specific properties can be selected, not least due to the fact that only a negligible amount is required for lubricating the plain bearings. For example, a lubricating medium is used that has a viscosity of 1 Pas when pumpable.

Fig. 2 shows a cross section through a plain bearing 3 according to the invention with a plain bearing length L. The cutting surface runs parallel to the shaft axis 9 and is positioned such that the lubrication pocket 2 incorporated into the plain bearing 3 is visible.

As already mentioned Fig. 2 , the lubrication pocket 2 is spaced from a gear-side end face 7 (also referred to as the inner side of the bearing) of the plain bearing 3 by a first distance d ₁ , so that a first web 11 with a radial extension corresponding to the sliding surface of the plain bearing 3 is present. The first web 11 has a first web width D ₁ , which is smaller than the first distance d ₁ , because a transition from the sliding surface to the end face of the plain bearing 3 does not belong to the first web 11. It has been shown that the web width D ₁ should be 5 to 20%, preferably 15% of the plain bearing length L. It should be noted that the web width D ₁ is a minimum value, ie a gear-side edge of the lubrication pocket 2 does not have to run parallel to the gear-side end face. Furthermore, it is not absolutely necessary for the lubrication pocket 2 to have the minimum web width D ₁ at all.

Furthermore, the lubrication pocket 2 on the other side of the bearing is spaced apart by a second distance d ₂ from a second end face 8 (also referred to as the bearing outer side), which is opposite the gear-side end face 7 of the plain bearing 3, so that a second web 12 is present which has a second web width D ₂ , which is in turn smaller than the second distance d ₂ , because a transition from the sliding surface of the plain bearing 3 to the second end face 8 of the plain bearing 3 is in turn not counted as part of the second web 12. It has been shown that the web width D ₂ should be 5 to 15%, preferably 10% of the plain bearing length L. It should also be noted here that that the web width D ₂ is a minimum value, ie an edge of the lubrication pocket 2 on the outside of the bearing does not have to run parallel to the outside of the bearing. In addition, it is not absolutely necessary for the lubrication pocket 2 to have the minimum web width D ₂ at all.

Thus, a maximum axial extension (with respect to the shaft axis) of the lubrication pocket 2 is determined by the above definitions of the first and second webs 11 and 12, respectively. A maximum extension of the lubrication pocket 2 along the sliding surface of the plain bearing 3 is determined below using Fig. 3 and 4 be explained.

Fig. 3 shows a partial section across the plain bearing 3 according to the invention in the area of the bore 4 and the associated lubrication pocket 2, whereby the lubrication pocket 2 shown is only one of many possible embodiments of the present invention. The position of the lubrication pocket 2 is represented by an angle to a plane spanned by the two shaft axes 9, the so-called angle reference plane 10, and the angle is specified in the direction of rotation R of the shaft in the plain bearing 3. The angle reference plane 10 is thus perpendicular to a chord surface 14 of the plain bearing 3. The lubrication pocket 2 begins at an entry edge 16 in the lubrication pocket 2. Viewed in the direction of rotation R and in relation to the angle reference plane 10, the lubrication pocket 2 begins with the entry edge 16 after a starting angle α and ends with the exit edge 15 after an end angle β. In the embodiment of the inventive lubrication pocket 2 according to Fig. 3 the starting angle is α = 265° and the end angle β = 355°. The bore 4, through which the lubricating medium is fed into the lubricating pocket 2, has an injection point 13, which at least partially coincides with the leading edge 16. After the injection point 13, the lubricating medium is distributed both in the axial direction and in the direction of rotation R within the lubricating pocket 2 until the lubricating medium enters a lubricating gap at the exit edge 15, which is formed on the one hand by the shaft or the bearing journal 5, 6 and on the other hand by the plain bearing 3, and forms a lubricant film.

Based on Fig. 4 , which has a cut according to Fig. 3 through the entire plain bearing 3, the angle ranges according to the invention are defined within which both the starting angle α and the end angle β as well as the injection point 13 of the bore 4 in the lubrication pocket 2 are located. It has been shown that the lubrication pocket 2 has a minimum starting angle α of 210° and a maximum end angle β of 30°, thus such a lubrication pocket 2 covers the maximum angle range from 210° to 30°. The injection point 13 and thus one end of the bore 4 in the lubrication pocket 2 is in an angle range from 225° to 315°, whereby the injection point 13 must always end in the lubrication pocket 2: In other words, the injection point 13 must be arranged after the starting angle α and before the end angle β of the selected lubrication pocket 2, but at the same time also within the angular range of 225° to 315°. The injection point 13 is preferably within an angular range of 240° to 300°. It has also been shown that the injection point 13 is particularly located at an injection point angle δ of 270°. The lubrication pocket 2 in turn preferably extends over an angular range of 265° to 355°.

From the above angle specifications it follows that the injection point 13 does not necessarily have to be located immediately after the starting angle α, even if this is preferably provided. Rather, it is conceivable that the injection point 13 - taking into account the above-mentioned conditions for the angle range for the injection point 13 and the extent of the lubrication pocket 13 - can be at any location, in particular also in the area of the end angle β.

While the position of the injection point 13 is sufficiently defined, the associated bore 4 is designed, for example, as a radial bore 4 through the plain bearing 3. However, any drilling direction through the plain bearing 3 to the injection point 13 is conceivable.

This means - now again with regard to Fig. 2 - a maximum frame 20 is marked out, within which the lubrication pocket 2 is located or which the lubrication pocket 2 fills to the maximum. This maximum frame 20 is in Fig. 2 represented by a dashed line.

As already briefly mentioned in connection with explanations of the Fig. 2 As was pointed out, the lubrication pocket 2 incorporated in the plain bearing 3 is supplied with a lubricant which is pressed through the bore 4 via the injection point 13 into the lubrication pocket 2. Viewed in the direction of rotation R of the bearing journal 5, 6, the lubrication pocket 2 can begin at or in front of the injection point 13 at a minimum lubrication pocket start and end at a maximum lubrication pocket end. While the maximum width of the lubrication pocket 2 is defined by the web widths D ₁ and D ₂ as a proportion of the plain bearing length L, the maximum length of the lubrication pocket 2 - viewed in the direction of rotation R of the bearing journal 5, 6 - is defined by the lubrication pocket start 16 and the lubrication pocket end 15 by means of angle specifications which are based on Fig. 4 explained above.

As already mentioned, the injection point 13 can be located anywhere within the maximum frame 20 ( Fig. 2 ). Preferably, the injection point 13 is located in the middle of the frame 20 and becomes steadily larger with increasing angle, as is the case in Fig. 2 concrete embodiment for the lubrication pocket 2.

In contrast to the proven principle of bearing lubrication using a conveying medium, which is fed through grooves into the plain bearings according to the state of the art, a clean, low-impurity lubricating medium is now supplied to build up the lubricating film from a separate external Conveying device, which can be an extruder or a gear pump, for example, and pressed into the plain bearing 3. In this way, the lubricating film build-up is largely independent of the lubricating film-building properties of the conveying medium, since this task is taken over by a suitable, clean and, above all, low-impurity lubricating medium. The advantage is expressly referred to that this external lubricating medium for the lubricating film build-up can be different from the conveying medium. However, the lubricating medium must be selected in such a way that it is compatible with the lubricating medium, since the lubricating medium subsequently mixes with the conveying medium, ie after it leaves the plain bearing gap.

According to the invention, the geometry of the plain bearing 3 and the design of the lubrication pocket 2 in the plain bearing 3 are designed in such a way that the hydrodynamic plain bearing 3 requires as little lubricant as possible. At the same time, the design of the plain bearing 3 and the geometry of the lubrication pocket 2 must ensure that as little contaminated conveying medium as possible from the main conveying flow reaches the plain bearing 3, since otherwise the good lubricating properties of the clean externally supplied lubricant cannot be used. By selecting the appropriate geometry for the plain bearing 3 and the design of the lubrication pocket 2, it is ensured that the contaminated lubricant can be removed without additional components in the gear pump itself (such as a shaft seal, etc.). The conveying medium is largely kept away from the lubricating gap of the plain bearings 3.

In further development of the above statements, it is expressly pointed out that the present invention can also be used excellently for critical applications in which no foreign particles are contained in the conveying medium, but a very thin lubricating film is nevertheless desired in the plain bearing, i.e. when the conveying medium does not permit such a thin lubricating film.

Fig. 5 shows a course of the cross-sectional area Q as a function of an increasing angle of rotation r, starting from the starting edge 16 ( Fig. 2 ) of the lubrication pocket 2, which widens steadily as the angle of rotation r progresses. This is a variant of a lubrication pocket 2 which has a constant cross-sectional area Q over a significant extent in the direction of rotation R. Preferably, the cross-sectional area of the bore 4 - and consequently also the cross-sectional area of the injection point 13 - is constant over large areas of its extent (for example over 2/3 of the total extent of the lubrication pocket 2 in the direction of rotation R up to a boundary line 21). In the last third of the lubrication pocket 2 (again viewed in the direction of rotation R), the cross-sectional area Q decreases steadily up to the exit edge 15. Due to the lubrication pocket 2 widening steadily in the direction of rotation R (see Fig. 2 ) takes a Depth of the lubrication pocket 2 in the first 2/3 of the extension of the lubrication pocket 2 in the direction of rotation R such that the cross-sectional area Q is constant. This achieves an optimal distribution of the lubricating medium within the lubrication pocket 2 before the lubricating medium reaches or is pressed into the plain bearing gap between the shaft and the plain bearing 3.

REFERENCE SYMBOL LIST

1

gear

2

lubrication pocket

3

plain bearings

4

drilling

5.6

bearing journals

7

Bearing inside; Gear side face; Gear face

8

Bearing outer side; face opposite the gear side face; bearing face

9

shaft axis

10

angular reference plane

11

first bridge

12

second bridge

13

injection point

14

tendon surface

15

trailing edge

16

starting edge

20

maximum frame

21

border line

R

direction of rotation of the shaft

r

rotation angle

α

starting angle

β

end angle

δ

injection point angle

DL

bearing journal diameter

DF

root diameter

L

plain bearing length

Q

cross-sectional area

d1

first distance of the lubrication pocket from the gear-side face of the plain bearing

d2

second distance of the lubrication pocket from the opposite side to the gear-side face of the plain bearing

D1

first web width

D2

second web width

Claims (15)

Gear pump with intermeshing gears (1) enclosed by a housing with bearing journals (5, 6) arranged on shaft axes (9) and projecting laterally from the gears (1), which are mounted in the housing by means of plain bearings (3) each having a plain bearing length (L), each having a lubrication pocket (2) with radial extension, wherein the lubrication pocket (2) is spaced from a gear-side end face (7) of the respective plain bearing (3) by a first distance (d ₁ ), so that a first web (11) with a first web width (D ₁ ) with axial extension corresponding to a plain bearing surface is present, characterized in that - that the lubrication pocket (2) is further spaced apart from the bearing face (8) opposite the gear-side face (7) by a second distance (d ₂ ), so that a second web (12) with a second web width (D ₂ ) with axial extension corresponding to a plain bearing surface is present, - that a bore (4) leads through the plain bearing (3) and communicates with the lubrication pocket (2) at an injection point (13) and - that the bore (4) is operatively connected to a conveying device for conveying lubricating medium into the lubrication pocket (2). Gear pump according to claim 1, characterized in that the first web width (D ₁ ) is at least 5% to 20%, preferably 15%, of the plain bearing length (L). Gear pump according to claim 1 or 2, characterized in that the second web width (D ₂ ) is at least 5% to 15%, preferably 10%, of the plain bearing length (L). Gear pump according to one of the preceding claims, characterized in that the lubrication pocket (2) begins in an angular range of 210° to 315°, preferably at 270°, with respect to a plane spanned by the two shaft axes (9) and in the direction of rotation (R) of the gears. Gear pump according to one of the preceding claims, characterized in that the lubrication pocket (2) ends in an angular range of 300° to 30°, preferably at 355°, with respect to a plane spanned by the two shaft axes (9) and in the direction of rotation (R) of the gears (1). Gear pump according to one of the preceding claims, characterized in that the injection point (13) is arranged centrally in the lubricating pocket (2) in the axial extension of the lubricating pocket (2). Gear pump according to one of the preceding claims, characterized in that the injection point (13) in With respect to a plane spanned by the two shaft axes (9) and in the direction of rotation (R) of the gears (1) it is arranged in an angular range of 225° to 315°, preferably in an angular range of 240° to 300°, preferably at 270°. Gear pump according to one of the preceding claims, characterized in that the lubrication pocket (2) is deepest in the region of the injection point (13). Gear pump according to one of the preceding claims, characterized in that the injection point (13), seen in the direction of rotation (R) of the gears (1), is arranged at the beginning of the lubricating pocket (2). Gear pump according to claim 9, characterized in that the lubrication pocket (2) is wider when viewed from the injection point (13) and in the direction of rotation (R) of the gears (1). Gear pump according to claim 10, characterized in that cross-sectional areas of the lubricating pocket (2), starting from the injection point (13) and viewed in the direction of rotation (R) of the gears (1), are of equal size over 2/3 of their unwound length and that cross-sectional areas of the lubricating pocket (2) are continuously decreasing over the remaining unwound length up to the end of the lubricating pocket (2). Gear pump according to claim 11, characterized in that a cross-sectional area of the bore (4) is the same size as the cross-sectional areas of the lubrication pocket (2) in the first 2/3 of the developed length of the lubrication pocket (2). Gear pump according to one of the preceding claims, characterized in that the bore (4) is arranged radially to an outer diameter of the respective plain bearing (3). Gear pump according to one of the preceding claims, characterized in that at least one of the bearing journals (5, 6) has, at least over part of its axial extent, a bearing journal diameter (D _L ) which lies in the range of 90% to 100% of a root circle diameter (D _F ) of the toothing of the associated gear (1). Use of the gear pump according to one of the preceding claims for conveying highly viscous conveying medium, such as polymer, with a mass percentage of inorganic fillers in the total mass of conveying medium of more than 60%.

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