AU2015357838A1

AU2015357838A1 - Length compensation device

Info

Publication number: AU2015357838A1
Application number: AU2015357838A
Authority: AU
Inventors: Hisham Kamal; Christian Kneidl; Johann Kreidl; Thomas Streubel; Stephan Voit
Original assignee: Netzsch Pumpen and Systeme GmbH
Current assignee: Netzsch Pumpen and Systeme GmbH
Priority date: 2014-12-04
Filing date: 2015-12-03
Publication date: 2017-07-06
Anticipated expiration: 2035-12-03
Also published as: KR20170091687A; DE102014117932B3; JP2017536507A; WO2016086911A1; AU2015357838B2; EP3227555A1; RU2017123351A3; CN107002668B; RU2017123351A; CN107002668A

Abstract

The invention relates to a length compensation device (4), in particular for a progressive cavity pump with a rotor and an axially adjustable stator (2). The aim of the invention is to produce a length compensation device which compensates the length in a reliable and effective manner. According to the invention, the length compensation device (4) comprises at least one axially flexible support body (10, 12) in which a bellows body (16) which is associated with the support body (10, 12) and which is used to guide a conveying medium, is arranged.

Description

-1- 2015357838 13 Jun2017

P11057DE/ar NPS

Description

Length compensation device

The invention relates to a length compensation device, in particular for an eccentric screw pump having a rotor and an axially adjustable stator, the length compensation device being assigned to the stator. The invention, furthermore, relates to an eccentric screw pump having a length compensation device.

The eccentric screw pump counts among the rotating displacement pumps, the pump section of which comprises a rotating part (rotor) and a stationary part (stator). Here, the rotor is designed helically with a large pitch and turn depth as well as a relatively small core diameter. The stator has one thread turn more and has twice the pitch length of the rotor. Thus, delivery spaces are created between the rotor and the stator which continuously move from the inlet to the outlet side. Usually, the stator consists of an elastomer body and a stator jacket, which surrounds the elastomer body. The elastomer body brings about a sealing between rotor and stator, which is created in that the inner contours of the stator are smaller than the outer contours of the rotor. By way of the preload, an uninterrupted sealing line is created, which seals the delivery chambers following one another and makes possible building up a delivery pressure.

To raise the lifespan and for the purpose of adapting to different operating conditions, solutions are known from the prior art in the case of which the elastic stator can be axially adjusted or readjusted. DE 1303705 for example shows an eccentric screw pump, the inner diameter of the stator of which is constrictable by compression, wherein the housing inner wall and the outer surface of the elastic stator are designed

P11057DE/ar NPS -2- 2015357838 13 Jun2017 conically and the stator is axially adjustable in the housing. Between pump housing and stator, compensation elements are provided. This serves to achieve that after prolonged operation manifestations of wear can be compensated for by adjusting the stator in axial direction.

An eccentric screw pump, in the case of which the stator inner dimensions can be adapted to circumstances that occur during the operation, is known from DE 102005042559A1. For this purpose, the eccentric screw pump comprises a stator jacket and an elastic stator lining arranged therein, wherein at both ends of the elastic stator lining a stop for its axial delimitation is provided and means are present at least at one end in order to change the axial position of the stop. By way of the adjustment of the stator jacket, a pulling or thrust force acts on the elastic stator lining, as a result of which the thrust on the rotor and thus the preload changes. The inner cross section of the lining is thus correctable.

In order to be able to ensure an adjustment of the stator, means for its length compensation are required. In the case of the solutions known from the prior art, for example adjusting rings or compensation discs are employed for this purpose, wherein the adjusting ring can also be moveably arranged in an adjusting device in order to positively act on the stator lining even during a pump operation.

Here, the adjusting ring is in contact with the delivery medium which is why means are required in order to be able to ensure a sealing between the adjusting ring and the pump housing or stator jacket. However, a compensation device would be desirable with which the length change of the stator because of the axial adjustment can be compensated without parts of the compensation device coming into contact with the delivery medium. The

P11057DE/ar NPS -3- 2015357838 13 Jun2017 compensation device should preferentially also make possible an axial guiding of the stator. However, the solutions known from the prior art of the type mentioned above are only inadequately suited for this purpose.

The invention is therefore based on the object of stating a length compensation device for conducting a delivery medium, with which a length change, in particular of the stator of an eccentric screw pump, is effectively and safely made possible.

According to the invention, this object is solved in that the length compensation device comprises at least one axially flexible support body, in which a bellows for conducting a delivery medium assigned to the support body is arranged.

Here, the invention is based on the consideration that a length compensation device or parts thereof are sensitive to dirt and should therefore not come into contact with the delivery medium. By using lubricants, friction and wear could be kept low and a sealing effect increased. Here it should also be preferably avoided that operating materials such as oils and greases, for example as a consequence of seal wear and leakages, can enter the delivery medium.

This is achieved in that the length compensation device comprises a support body which does not come into contact with a delivery medium. Within the support body, a bellows body is arranged, which is in contact with the delivery medium and through which the delivery medium can flow. In order to achieve a supporting of the bellows body upon an axial movement, upon stretching or compression of the bellows body, the support body is designed in such a manner that the same can perform the axial movement along with the bellows body. Because of this, the entire length compensation device can be advantageously

P11057DE/ar NPS -4- 2015357838 13 Jun2017 stretched or compressed. For example, the bellows body can be in contact with the support body so that the same can directly support itself on the support body.

However, for achieving the supporting function, the bellows body can also be coupled to the support body via suitable means. To this end, the support body is preferentially coupled in a pressure-proof manner to the bellows body in such a manner that a fluid chamber between support and bellows body is formed, which supports the bellows body in a radial direction. Because of this, the bellows body is not exposed to a shape-changing pressure loading and thus substantially remains dimensionally stable .

In a preferred further development, a pressure sensor assigned to the fluid chamber is provided for measuring the pump internal pressure. Advantageously, the pressure sensor does not come into contact with the delivery medium because of this and the measurement device cannot for example clog up. The fluid in the fluid chamber thus serves as pressure transmitter for pressure detection and can also be utilised as overpressure protection.

The support body can be formed from one or more compensating elements, wherein the compensating elements in turn are coupled to one another in a pressure-proof manner.

The bellows body preferentially consists of an elastically deformable plastic which is elastically deformed during the adjusting of the stator. The support body can for example be unitarily formed from a metallic material in the form of a corrugated bellows as compensation element. Here, the corrugated bellows has an adequately high radial stiffness in order to be able to absorb the thrust forces acting on the bellows body.

P11057DE/ar NPS -5- 2015357838 13 Jun2017

Preferentially, the bellows body has a funnel-like shape which tapers towards the pump. Because of this it is achieved that the bellows body assumes a flow-optimised shape even in the compressed state. Because of the particular shape a compact design of the length compensation device is made possible, furthermore, since the bellows body during the compression can contract, which for example in the case of a simple corrugated bellows is not possible and which therefore requires comparatively more space in axial direction even in the compressed state.

Preferentially, the length compensation device is arranged on the product outlet side. Accordingly, the arrangement and design of the drive elements on the pump side can be advantageously left out of consideration during the configuration of the device according to the invention.

In a particularly preferred embodiment, the support bodies are formed as a cylinder-piston pairing in such a manner that the cylinder as a first outer compensation element is coupled in a pressure-proof manner to the pistons as a second inner compensation element, in that preferentially in the piston recesses for sealing means are introduced. Piston and cylinder are preferentially configured in such a manner that the support body simultaneously serves as guiding means. Because of this, a supporting or guiding of the stator on the product side can be omitted.

In a preferred version, the bellows body comprises predetermined folding points. With the help of the predetermined folding points, the shape of the bellows bodies upon its compression can be advantageously influenced. The predetermined folding points can be created for example in that the bellows body has a certain basic shape and/or in that the material thickness is

P11057DE/ar NPS -6- 2015357838 13 Jun2017 enlarged or reduced in size in points or regions intended for this purpose. However, attaching or introducing auxiliary elements, for example in the form of a ring, which on the fluid chamber side runs about the bellows body and forms a predetermined folding point or a circumferential predetermined fold line.

In a particularly advantageous configuration, the bellows body comprises flats adjoining in the axial direction and running about the bellows body, the transitions of which form the predetermined folding points or predetermined fold lines. The flat regions of the bellows body can have different material thicknesses for this purpose and/or be arranged angularly with respect to one another.

According to a preferred further development, the support body, for regulating fluid within the fluid chamber comprises at least one closable opening or a valve. Preferentially, fluid is filled into the fluid chamber via a valve, wherein on an opposite location of the support body air displaced by fluid can escape.

Preferably, the fluid quantity in the fluid chamber is regulatable so that the shape and the compression behaviour of the bellows body can be additionally influenced. To this end, a control device can be provided which makes it possible to increase or lower the pressure in the fluid chamber as a function of measured pump parameters.

Particularly preferably, the bellows body is configured in such a manner that the length compensation device can additionally act as shut-off element. To this end, the bellows body is formed from a highly elastic elastomer body. For shutting-off, the pressure is increased for example by means of a controllable pressure source in the fluid chamber so far until the bellows

P11057DE/ar NPS -7- 2015357838 13 Jun2017 body is deformed and seals the passage in the length compensation device. Because of this it is achieved that for example assembly work on the pump or the delivery system are made possible without additional shut-off elements.

The advantages achieved with the invention consist in particular in that the medium that flows through does not come into contact with the support body, in particular not into contact with the sealing elements of the same because of the shutting-off by means of the bellows body, in particular by an elastomer bellows body. A hollow space formed between the bellows body and the support body can be filled up with lubricating fluid, as a result of which sealing and conducting means are permanently lubricated to protect it from excessive wear. In addition, the use of a relatively thin-walled bellows body is also made possible because of the fact that the bellows body is not exposed to any substantially shape-changing high thrust loading, as a result of which its folding behaviour further improves. Because of a funnel-like shape of the bellows body a particularly short design is possible, since the bellows body can contract. It is also advantageous that only the bellows body as wear part or component with certain physical or chemical characteristics and requirements regarding the delivery medium can be easily replaced without replacing the entire length compensation device.

Exemplary embodiments of the invention are explained in more detail by way of drawings. Therein it shows:

Figure 1 schematically, the stator of an eccentric screw pump with a length compensation device connected on a pressure side, comprising a bellows body and a cylinder-piston pairing as support body surrounding said bellows body, -8- 2015357838 13 Jun2017

Figure 2 the length compensation device from Figure 1 in the state of maximum deflection and contracted bellows body,

Figure 3 the length compensation device from Figure 1 in the state of maximum deflection and uncontracted bellows body,

Figure 4 a length compensation device in the state of maximum deflection and contracted bellows body with predetermined folding points running in the circumference,

Figure 5

Figure 6

P11057DE/ar NPS a length compensation device with a corrugated-type bellows body and a length compensation device with a corrugated-type bellows body and a pressure sensor.

In all figures, same parts are marked with the same reference characters .

Figure 1 shows the stator 2 of an eccentric screw pump with a length compensation device 4 connected thereon at the face end. The stator 2 comprises an elastomer body 6 which is arranged within a stator jacket 8, wherein the stator 8 at its end which is not shown here is coupled to a pump housing.

At the end on the housing side, the elastomer body 6 is fixed so that during the adjusting of the stator 2 the length compensation device 4 is activated. The representation of the length compensation device 4 shown in this figure allows both a

P11057DE/ar NPS -9- 2015357838 13 Jun2017 negative and also a positive axial movement, illustrated by the shown arrows . A cylinder-piston pairing serves as two-part support body 10, 12 of the length compensation device 4, wherein the piston 10 comprises recesses 14 running in the circumference, in which sealing means which are not shown here are arranged. Upon a positive movement during an adjusting operation the distance between stator flange 18 and pump flange 20 increases, the elastomer body is thrust-loaded and thus compressed. As a consequence of this, the thrust on the rotor (not shown) increases. In contrast with this, the elastomer body upon a negative movement is stretched and the thrust on the rotor is reduced.

Within the support body 10, 12 an elastomer bellows body 16 is arranged, which is clamped-in in a in a pressure-proof manner on the stator side between a stator flange 18 and piston 10 as well as a pump flange 20 and the cylinder 12 on the thrust side. On its side facing the bellows body 16, the piston 10 is provided with a chamfer on the end side in each case in order to keep a mechanical loading of the bellows body 16 as low as possible. A fluid chamber 22 formed between the bellows body 16 and the support body 10, 12 is filled with a lubricating fluid (not shown). By way of a lower valve opening 24 in the cylinder 12, the fluid can be filled in, wherein via an opposite opening 26 in the cylinder 12, air can escape during a filling operation.

In order to prevent fluid exiting from the opening 26 and in order to achieve the desired supporting effect for the bellows body 16, the opening 26 is again closed in a pressure-proof manner after the filling operation.

Seen in axial direction, the bellows body 16 has different wall thicknesses; the wall thickness on the side of the pump flange

P11057DE/ar NPS -10- 2015357838 13 Jun2017 18 for example is smaller than on the stator side. This produces an adequately great stiffness of the bellows body 16 in a region which should not be deformed or only slightly so. An achieved change in shape upon activating the length compensation device 4 thus occurs substantially only in a region intended for this purpose . A length compensation device 4 in a state of maximum positive and maximum negative deflection is shown in the Figures 2 and 3. The bellows body 16 shown in Figure 2 assumes the shown shape in the contracted state because of its basic shape and different material thickness. Fig. 3 shows the bellows body 16 in its basic shape without elastic deformation within the length compensation device in the state of maximum positive deflection.

In the Figure 4, a length compensation device 4 analogous to Figure 2 is only shown without represented recesses for sealing elements, which comprises a contracted bellows body 16, but which because of its special configuration comprises predetermined folding points, in particular closed predetermined fold lines 28, which run in the circumference of the bellows body 16. To this end, the bellows body 16 comprises a plurality of flat sections 30 in the circumference, which during the compression of the bellows body 16 bring about the desired shape. The flat sections 13 are arranged angularly relative to one another at least in the non-deformed state of the bellows body 16, wherein the transitions from a flat to the neighbouring flat form the predetermined fold lines 28. Via fluid (shown dotted) in the fluid chamber 22, between the bellows body 16 and the support body 10, 12, the bellows body 16 is supported. A bellows body 16 which in its basic shape is formed wave-like in the longitudinal section is shown in Figure 5, which because of its shape can be compressed and stretched. In places, the 2015357838 13 Jun2017

P11057DE/ar NPS -ll- bellows body 16 lies against the piston 10 and forms the chambers subdividing the fluid chamber 22. In order to ensure or improve a flow through between the individual chambers, longitudinally extending recesses can be introduced (not shown) in the cylinder-support body 22 in the region of the contact points with the bellows body 16, which form flow ducts and connect the individual chambers with one another.

Figure 6 shows the length compensation device with a bellows body 16 of wave-like design as in Figure 5, wherein the fluid chamber 22 via the upper valve opening is coupled to a valve 34 and a pressure gauge 32 thereby connected. Here, the valve 34 serves as shut-off and damping valve. Instead or complementarily thereto, the fluid chamber 22 can be coupled to a controllable pressure source (not shown) via the upper valve opening in order to control or regulate by means of a pressure sensor the pressure in the fluid chamber 22.

The device is preferentially aligned with adjustable stators of an eccentric screw pump. By using a bellows body which in particular is stabilised via a fluid chamber by means of a support body advantageously brings about that for example guide means designed as support body, which should be lubricated for a safe operation, cannot come into contact with the delivery medium. A funnel-like shape of the bellows body has a positive effect on the flow of the delivery medium and its folding behaviour . 2015357838 13 Jun2017

P11057DE/ar NPS -12-

List of reference numbers 2 Stator of an eccentric screw pump 4 Length compensation device 6 Elastomer body 8 Stator jacket 10 Piston as support body (inner) 12 Cylinder as support body (outer) 14 Recesses for sealing elements 16 Bellows body (elastomer) 18 Stator flange 20 Pump flange 22 Fluid chamber 24 Valve opening 26 Opening 28 Predetermined fold lines 30 Flat sections 32 Pressure gauge 34 Valve

Claims

Patent Claims

1. A length compensation device (4), in particular for use in an eccentric screw pump having a rotor and an axially adjustable stator (2), comprising at least one axially flexible support body (10, 12), in which a bellows body (16) assigned to the support body is arranged for conducting a delivery medium.
2. The device according to Claim 1, wherein the support body is coupled to the bellows body in a pressure-tight manner in order to form a fluid chamber which supports the bellows body.
3. The device according to Claim 1 or 2, wherein the bellows body (16) is formed funnel-like.
4. The device according to Claim 3, wherein the bellows body (16) tapers towards the pump funnel-like.
5. The device according to Claim 1 to 4, wherein the bellows body (16) is arranged on the product outlet side.
6. The device according to Claim 1 to 5, wherein support bodies (10, 12) are formed as a cylinder-piston pairing.
7. The device according to Claim 6, wherein the support bodies (10, 12) are designed as guide elements.
8. The device according to Claim 6 or 7, wherein the support bodies (10, 12) comprise recesses (14) for means for sealing.
9. The device according to Claim 1 to 8, wherein the bellows body (16) comprises predetermined folding points (28).
10. The device according to Claim 1 to 9, wherein for regulating fluid within a fluid chamber (22) a support body (10, 12) comprises at least one closable opening (26) and/or a valve opening (24).
11. The device according to Claim 1 to 10, wherein the fluid quantity in the fluid chamber (22) is regulatable.
12. An eccentric screw pump with a length compensation element according to Claim 1.