EP2216550A2 - Gear wheel pump with shaft seal - Google Patents

Abstract

The pump (10) has shaft journals (18B) rotatably connected with a drive gear (16A) and rotatably mounted in housing covers (14A, 14B) at both sides of the drive gear. A shaft seal (26) controls leakage of fluid to be pumped and seals an actuator pivot (18A) with respect to one of the housing covers penetrated by the actuator pivot. The shaft seal is arranged at an inner side of one of the housing covers that is penetrated from the actuator pivot, where the inner side faces the drive gear and another drive gear (16B).

Description

FIELD OF THE INVENTION

The invention relates to a gear pump with the features of the preamble of claim 1. Accordingly, a gear pump is provided with at least two externally meshing gears, which bear with their flat sides directly or indirectly on housing covers of the gear pump. At least one drive gear is provided with shaft journal and rotatably connected thereto, wherein the shaft journals are arranged on both sides of the at least one drive gear and rotatably mounted in the respective adjacent housing cover. One of the shaft journals of the drive gear is extended and guided as a drive pivot through the adjacent housing cover to the outside. To prevent the escape of fluid to be pumped, a shaft seal is provided for the drive pivot. This acts sealingly between the drive pivot and the housing cover penetrated by it and is on the pump gear wheels facing the inside of the penetrated by the drive pivot pin first Housing cover arranged in a gear-side recess of the housing cover.

TECHNOLOGICAL BACKGROUND

Gear pumps of the type described above are known in their basic principle for decades and are used, inter alia, for driving hydraulic systems in vehicle technology, where high efficiency with simple and cost-effective production and the generation of high pressures in the foreground. The construction and the principle of operation of a gear pump is particularly clear in the DE 24 11 492 C2 described. The pump is constructed of three plate-shaped housing parts, which is why such pumps are also referred to as "plate pumps". Of the sandwiched plates, the middle takes up the pump chamber with the two pump gears in this case (pump plate). On both sides of the pump plate are at her sealing housing cover, which close the pump chamber in the axial direction (first and second cover plate). In the opposite cover plates are mutually aligned bores for receiving shaft journals, which protrude axially on both sides at least the drive gear and are rotatably connected thereto. The shaft journal receiving holes in the cover plates have a slight oversize relative to the pin diameter, so that with a small gap a certain radial clearance between the pivot and the housing covers remains. To the outside of the housing, three of the bearing bores are sealed by a lid. The liquid to be pumped, which enters the bearing gap and thereby lubricates it, so can not escape to the outside of the pump. Thus, on the part of the drive pivot pin, which is guided by the housing cover to the outside of the pump housing, no liquid to be pumped can escape, the housing cover has at this point a stuffing box or the like for receiving a shaft seal. Even the drive pivot therefore remains lubricated with liquid Such a shaft seal is indeed in the DE 24 11 492 C2 as known per se, not shown as such, but only their receiving space. Such shaft seals were, eg already from the DE 81 01 898 U1 known on plate pumps. In this way, all four shaft journals of the pump gears are hydraulically supported by the liquid to be pumped and protected against wear, and due to the rotating with the pump gears shaft journal is a constantly exchanging surface film of the liquid to be pumped on the radial surfaces of the shaft journals.

Such pumps can also be used for problematic pumping liquids, such as adhesives. However, it has been found that, especially reactive adhesives such as e.g. PUR adhesives lead to rapid aging of the shaft seal.

A gear or plate pump is also used in the DE 81 01 898 U1 described. To reduce the leakage in the engagement region of the promotional gears there is proposed to pressurize piston end face against the gears in the engagement area. The pressure effect can be taken from an acting in the axial direction Federkraftbeaufschlagung the piston or from the hydrostatic pressure of the fluid to be delivered. To seal the high pressure side of the piston against the low pressure side sealing rings are provided, which are arranged in a pressure-loaded annular space. A disadvantage of such an arrangement is in addition to a high cleaning effort that the front side of the promotional gears are exposed by the action of the pistons heavy wear.

A contrast easier to clean (metering) gear pump can the US Pat. No. 6,857,860 B1 be removed. The seal of the delivery volume relative to the pump housing and with respect to the drive shaft is effected by a sealing ring arranged in a recess of a housing plate, which is pressed against the driving gear, which is non-rotatably connected to the shaft. The pressing is done by spring force. In addition, it can be provided that the recess receiving the sealing ring is subjected to a pressurized sealing liquid. Also in this metering gear pump, the front side of the driving Gear exposed by the acted upon by mechanical or hydrostatic pressure sealing ring strong mechanical loads, which are a wear reduction of the pump, but in particular of the gear, detrimental.

A structurally complex gear pump with preferably three gears can the DE 69 24 726 U be removed. There, the conveying gears are driven by a third gear, which is in engagement with the driving gear, wherein the drive takes place on the low pressure side of the delivery volume. The arrangement of the drive shaft on the low pressure side of the pump leads to lower demands on the sealing effect of the seal. In the housing cover, a recess is provided, in which a plate can be used for fixing the gears.

A suitable for promoting not self-lubricating media gear pump can the DE 19 27 514 U1 be removed. Thus, the gears do not touch within the pumped volume of the pump, therefore, the gears are driven individually and synchronously. The synchronous drive is carried out in a the volume to be delivered upstream gear housing, which is closed to the oil volume to be delivered. The seals are arranged so that they are accessible from the volume to be delivered.

A gear pump with a movably mounted on the drive shaft first gear, which is in engagement with a bearing mounted in the housing without a second gear, the DE 18 22 807 U be removed. The bearing of the drive shaft is effected by two ball bearings, which are arranged spaced apart in the axial direction in a housing chamber. The chamber is sealed from the volume to be delivered by a packing.

PRESENTATION OF THE INVENTION

On this basis, the invention is based on the problem in a generic pump to extend the life of the shaft seal for the drive pivot, so that a low maintenance is achieved even for problematic fluids to be pumped.

To solve this problem, a gear pump with the features of claim 1 is proposed. Accordingly, it is provided that the recess is provided with an arranged on the side facing the pump chamber prechamber, wherein the prechamber supplies the shaft seal with constantly exchanging fluid to be pumped.

It has surprisingly been found that shortened lifetimes of the shaft seal no longer occur even when pumping problematic pumping liquids when the shaft seal is displaced from the outside of the affected housing cover on the inside in a recess with a prechamber. For example, disturbing crystal formations, as observed in external shaft seals, no longer occur in the invention.

If the radial bearing of the drive pivot pin is insufficient because of now lack of lubrication of the fitting gap to the housing cover, a further improvement, which also affects the durability of the shaft seal can be achieved by using a bearing bush instead of the fitting gap between the rotary drive pin and the housing cover in question , which absorbs the radial bearing forces and ensures good low-friction bearing and the inner shaft seal better protects against radial loads. In the bearing bush can be different means for pivot bearing, such as plain bearings or pivot bearings act.

As an alternative to such a bearing bush, it is also possible to provide the outside of the affected housing cover part of the drive pivot pin with a countershaft in the form of a drive side rotary sealed chamber. This can be filled if necessary with a fluid for lubrication. Dry running problems in the fitting gap between the drive pivot and the associated housing cover can be completely excluded. Under certain circumstances, the storage of the drive pivot is improved.

The above-mentioned and the claimed components to be used according to the invention described in the exemplary embodiments are not subject to special conditions of size, shape, material selection and technical design, so that the selection criteria known in the field of application can be used without restriction

Further details, features and advantages of the subject matter of the invention will become apparent from the dependent claims, as well as from the following description of the accompanying drawings and table, in which - by way of example - an embodiment of a gear pump is shown. Also, individual features of the claims or of the embodiments may be combined with other features of other claims and embodiments.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1

eine Zahnradpumpe in einer ersten Ausführungsform in Seitenansicht, zum Teil aufgebrochen:

Fig. 2A

eine zweite Ausführungsform einer Zahnradpumpe in der gleichen Darstellungsart mit einem Vorgelege,

Fig. 2B

von der zweiten Ausführungsform eine andere Bauart in Axialschnitt- ansicht sowie

Fig. 3

eine dritte, mehrstufige Ausführungsform einer Zahnradpumpe in Axialschnittansicht.

In the drawing show

Fig. 1

a gear pump in a first embodiment in side view, partially broken:

Fig. 2A

a second embodiment of a gear pump in the same representation with a countershaft,

Fig. 2B

from the second embodiment of another type in axial section view and

Fig. 3

a third, multi-stage embodiment of a gear pump in axial section view.

DETAILED FIGURE DESCRIPTION

In the FIGS. 1 and 2A / B generally designated 10 gear pump is designed as a plate pump, in which both sides of a pump plate 12 first and second plate-shaped housing cover 14A, 14B are sealingly applied to the pump plate 12. Two externally meshing pump gears 16A, 16B are arranged in known and intersecting cylindrical openings of the pump plate 12. The drive-side pump gear 16 A is rotatably connected to a drive shaft 18. This has (in the drawing on the left) on the drive side a housing cover 14A outwardly projecting drive pivot pin 18A. On the drive opposite side of the pump gear 16A, the drive shaft has a shaft journal 18B rotatably supported in a mating bore 32A of the second (rear) housing cover 14B with a small radial gap. This bore can be designed as a blind bore or otherwise be sealed against the end face of the pump space.

The second pump gear 16B meshing with the first pump gear 16A may be radially and axially supported in any desired manner. The entry of the pumping fluid takes place for example via a lateral inlet opening 20 of the pump plate 2 approximately in the contact region of the two pump gears. The outlet opening is generally diametrically opposite to the inlet opening 20. The drive-side rotary mounting of the drive shaft 18 takes place in the embodiment according to FIG. 1 via a bearing bush 22, which is recessed into the first (front) housing cover 14A on the side opposite the pump plate 12. in this connection it may, for example, be a self-lubricating plain bearing or a roller bearing.

According to the embodiments located on the pump plate 12 side facing the first (front) housing cover 14A a housing cover recess 24 in which a ring seal as a shaft seal 26 for radial sealing of the drive shaft 18 relative to the pump chamber and the first (front) housing cover 14A is used. A towards the pump chamber towards, preferably conically, expanding antechamber 24A of the recess 24 provides the shaft seal 26 with constantly exchanging fluid to be pumped.

According to the embodiment FIG. 2A instead of the bearing bush 22, a radial fitting gap is provided between the drive shaft 18 and the first (front) housing cover 14A. On the drive side, the drive pivot pin 18A is surrounded by a countershaft 28 with a chamber 28A which is open toward the drive pivot pin 18A and can be acted upon by lubricant via radial bores 28B, 28C. At the drive-side end of the countershaft 28, a shaft seal 30 seals the chamber 28 A from the outer part of the drive shaft 18 fluidly.

According to the embodiment FIG. 2B it is provided that the second housing cover 14B rests on its outside tightly against a pump plate, wherein the supply and the discharge for fluid to be pumped (not shown) through the second housing cover 14B through. The second pump gear 16B is seated with the necessary radial play rotatably on a second shaft 19 which is mounted in the first housing cover 14A in a blind bore and rotatably seated in the second housing cover 14B. Also in this embodiment, the shaft journal 18B is rotatable with respect to the second housing cover 14B, wherein the pump chamber 21 located in the pump plate 12 may be sealed by a pump chamber seal 21A against the second housing cover 14B and the shaft journal 18B if necessary. Finally, the gear wheel side arranged in the first housing cover 14A shaft seal 26 in axial Direction via a support ring 26A supported on the second housing cover 14B.

In the FIG. 1 The embodiment shown can be modified in a similar manner as the embodiment of the FIG. 2B in relation to those in FIG. 2A , wherein the bearing bush 22 may also be significantly larger in circumference than in FIG. 1 so that common needle roller bearings can be used as a bearing bushing 22, wherein a housing part receiving the needle roller bearing and the needle roller bearing may be partially extended within the first housing cover 14A and partly outside thereof. Bearing bushes 22 used in accordance with the invention can, in particular in one embodiment, also be provided as pump bearings on the pump side or on both sides with additional shaft seals. The possible outlines of a bearing bush 22 in the form of a encapsulated by a housing needle roller bearings are in FIG. 1 drawn in dashed form as an alternative.

A section through a multi-stage gear pump 10, the Fig. 3 are removed, wherein the drive shaft 18 is connected in axial succession with at least 2 gears 16A, 16A 'by keyways 18D. The gears 16A, 16A 'are respectively engaged with a plurality of circumferentially distributed pump gears 16B, 16B' and 16B ", 16B"'. The pump gears are arranged on a second shaft 19 and a third shaft 19 '. The shafts 19, 19 'are arranged in cylindrical openings of the pump plates 12 and 12'. Due to the multi-stage design, the delivery volume of the pump according to Fig. 3 relative to the volume of a pump according to the FIGS. 1 . 2A or 2 B be multiplied. For example, according to Fig. 3 about a fourfold or eightfold increase in the delivery volume possible.

Of the Fig. 3 It can be seen that in the housing cover 14A gear side, a recess 24 is provided, in which a shaft seal 26 is arranged. The recess 24 is provided with an on the pump chamber facing side arranged prechamber 24A. As a result, the shaft seal 26 can be supplied with constantly exchanging fluid to be pumped.

LIST OF REFERENCE NUMBERS

10

gear pump

12, 12 '

pump plate

14A

first housing cover

14B

second housing cover

16A, 16A '

first pump gear (drive gear)

16B, 16B ', 16B ", 16B"'

second pump gear

18

drive shaft

18A

Drive trunnion

18B

shaft journal

18C

Adjusting spring

18D

Adjusting spring

19, 19 '

second wave

20

inlet opening

21

pump chamber

21A

Pump chamber seal

22

bearing bush

24

recess

24A

antechamber

26

shaft seal

26A

support ring

28

countershaft

28A

chamber

28B / C

radial bores

30

shaft seal

32A

fitting bore

32B

fitting bore

Claims (4)

gear pump - With at least two externally meshing gears (16 A, 16 B), which abut with their flat sides on first and second housing covers (14 A, 14 B) of the gear pump, - With shaft journals which are at least in rotation with the drive gear (16A) and rotatably mounted on both sides of the drive gear (16A) in the first and second housing cover (14A, 14B), - With a through the first housing cover (14 A) outwardly guided drive pivot (18 A) and - with a the drive pivot (18A) against the penetrated by him housing cover (14A) sealing and the leakage of fluid to be pumped preventing shaft seal on the pump gears (16A, 16B) facing the inside of the drive pivot (18A) penetrated by the first housing cover (14A) in a gear-side recess (24) of the housing cover (14A) is arranged, characterized in that the recess (24) with a pump chamber on the side facing the pre-chamber (24A) is provided, whereby the shaft seal (26) constantly replaceable fluid to be pumped is supplied. Gear pump according to claim 1, characterized in that the prechamber (24A) extends towards the pump chamber, preferably conically. Gear pump according to claim 1 or 2, characterized in that the first housing cover (14 A) on its outer side with a drive pivot (18A) overlapping bearing bush (22) is provided. Gear pump according to one of claims 1 to 3, characterized by an on the outside of the first housing cover (14A) provided for, the actuator pivot (18A) surrounding the lubricant chamber (28A).

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