Multiple Pump Arrangement

FIELD OF THE INVENTION

The invention relates to an eccentric screw pump.

BACKGROUND OF THE INVENTION

Eccentric screw pumps are used in various areas such as for example in agriculture, in the chemical industry, the food industry and in paper production. They belong to the group of rotating positive-displacement pumps and essentially comprise, apart from a drive device, a rotor and a stator. The screw-like rotor of the eccentric screw pump is characterised by a large lead, a large pitch depth and a small core diameter. The stator comprises one thread more than the rotor and has double the lead length of the rotor. Delivery spaces are thus formed between the stator and the rotor, which move continuously from the entrance side or the exit side and in which the delivery medium can be transported.

The rotor of an eccentric screw pump is usually made of an abrasion-resistant material such as steel for example. In contrast, the stator is usually made of an elastic material such as rubber for example. Stators are however also known from the prior art which are made of a material or a material composite of metal and/or plastic.

The individual components of the eccentric screw pump are suitably dimensioned and designed for the given delivery task. For example, the delivery rate and the achievable pressure are determined by the size and configuration of the stator and the rotor. The drive device can thus be designed and constituted identically for example in two eccentric screw pumps used in quite different ways. In particular, eccentric screw pumps can achieve different delivery capacities and pressures with an identical speed of the rotors. If the demands made on the eccentric screw pump change, for example because the delivery rate to be achieved has increased and the pump is no longer suitable for this, the only option left is to replace the eccentric screw pump, since a modification is usually too costly.

An eccentric screw pump with a plurality of cylinders is known for example from U.S. Pat. No. 2,483,370, which cylinders are integrated fixedly in a housing and in which a rotor gear is also disposed. It is regarded as advantageous that the pump requires only a single seal on account of its design. The pump comprises only one outlet (exhaust port 29), for which reason the pressure cannot be varied for all the delivery modules. The delivery modules are subject to an eccentricity which has to be compensated for by the internal linkage, the effect of which is that the delivery capacity is limited and the pump is subject to a high degree of wear. The pump has only one inlet (inlet port 28) for only one delivery medium and the modules, on account of the compact design and the special drive configuration, can only be replaced in pairs at a relatively high cost.

An eccentric screw pump is also known with at least two pump stages connected in series (U.S. Pat. No. 5,820,354). The volume flow from the second pump is smaller than the volume flow from the first pump. This embodiment enables the compensation of the delivery medium by means of the cooling thereof with the aid of a cooling unit (cooling system 55) which is disposed between the pump stages. As a result of the cooling effect on the delivery medium, the volume of the latter diminishes and a smaller pump stage can be disposed downstream. The delivery direction and therefore the inlet and outlet for the delivery medium of the pump device cannot be changed.

An eccentric screw pump with two pump sections (Pa, Pb), wherein the at least one inner pump rotor is surrounded by at least one outer pump rotor, wherein the pump sections (Pa, Pb) are driven with different speeds of the rotors, is disclosed in WO 2009/038473 A1. The pump comprises an inlet (inlet flange 21) and an outlet (outlet flange 28) for delivering a fluid.

It would however be desirable to make available a pump which can be adapted to the given delivery task in a straightforward manner and at low cost. A simultaneous delivery of different products should also be possible with the pump, without a plurality of separate pumps or pump devices being required for this purpose. The load on the components of the pump that are involved in the delivery should also not be significantly increased compared to a conventional eccentric screw pump.

The known eccentric screw pumps or systems are however only inadequately suited for this purpose.

The problem underlying the invention, therefore, is to provide an eccentric screw pump, with which an increase in the delivery rate, the pressure and/or the simultaneous delivery of more than one delivery medium is possible when required, wherein the eccentric screw pump has a comparatively low energy consumption during operation of the eccentric screw pump and its production and maintenance costs are kept low.

According to the invention, this problem is solved in that an eccentric screw pump is proposed, which is provided with a modular delivery system, comprising at least two delivery modules each comprising a rotor and a stator, wherein the delivery modules are coupled together and only one drive device is assigned to the delivery system and wherein the delivery system comprises more than one inlet and/or outlet or at least one modular through-flow housing for the delivery medium.

SUMMARY OF THE INVENTION

The rotor-stator arrangement is regarded as the delivery module with the aid of which the delivery medium is transported. By means of the eccentric screw pump according to the invention and the use of more than one delivery module, different products but also identical products from different sources can be delivered simultaneously. In addition, the achievable pressure of the pump can be increased by a series connection of a plurality of delivery modules. The delivery modules are coupled together for this purpose in such a way that only one drive device is required for their drive.

The invention is based on the consideration that an adaptation to the given delivery task can be achieved particularly easily by a delivery system constituted in a modular manner. The inlets and outlets for the delivery medium and the number of delivery modules should be able to be extended and combined in an essentially arbitrary manner. As a result of a modular system thus made available, an effective adaptation of the pump to the user's requirements can take place.

This is achieved by the fact that at least two delivery modules are coupled together. The delivery modules each comprise a stator and a rotor, wherein the rotor is driven by only one drive device. For this purpose, the rotors are connected to one another in order to transmit the forces occurring during operation of the eccentric screw pump, in particular the torque forces generated by the drive device. The delivery modules are preferably coupled together in such a way that a phase difference of 180° is obtained between the vibrations caused by the respective rotors of the delivery modules and a pressure pulsation dependent on the angle of rotation. Since the frequency of the vibrations is the same, due to the fact that only one drive system is used, the vibrations are thus reduced to a minimum.

The delivery modules are preferably coupled together by a suction housing, a pressure housing or a through-flow housing. This has the advantage that the eccentric screw pump can be mounted individually depending on the delivery task. The suction housing and pressure housing are provided with a connecting piece for the connection to the delivery lines. A suction line can thus be connected to the suction housing and a pressure line can be connected to the pressure housing.

By a suitable combination and selection of the housings, an adaptation or modification of the eccentric screw pump depending on the given delivery task can be carried out at a relatively low cost. The delivery modules can be coupled together optionally with a pressure housing, suction housing or through-flow housing, or finally with a pressure housing or suction housing. In addition, the delivery modules can be constituted differently, so that the delivery rates of the delivery modules are different with identical rotation frequency of the rotors. When different products are delivered, a specific mixing ratio can thus be fixed.

The rotors assigned to the delivery modules are preferably coupled together by means of a rigid connection inside the housing, so that a transmission of the forces acting from the drive device on the rotor can take place play-free and loss-free. The rotors can be coupled by means of a rigid or rigidly constituted connection known from the prior art that is suitable, depending on the application, for transmitting torques and axial forces. For example, reference is made here to firmly bonded connections such is weld joints, glue joints or solder joints or to friction-locked and/or form-fit connections such as screw connections, clamp connections or pin connections. However, the rotors can of course also be connected to one another by articulated joints.

In a preferred embodiment, the rotors are connected to one another detachably. The assembly and dismantling of the delivery modules is thus simplified and improved. Thus, it is possible to retrofit the eccentric screw pump according to the invention according to the changed delivery task.

In a further embodiment, it is proposed to constitute the rotor in one piece for at least two delivery modules. Since there are no connection points, this design is particularly well suited for delivering, for example, abrasive and aggressive media. In the assembly, the housings and stators are pushed over the one-piece rotor. With this special embodiment, the stator is regarded as the delivery module, even though the delivery module performs its function only after the assembly together with the respective rotor section.

The eccentric screw pump is preferably constituted in such a way that axial force F acting in the direction of the drive device approaches zero or is at least reduced. This is achieved by the fact that in each case two delivery modules deliver in opposite directions with an identical speed and an identical direction of rotation of the rotors. For this purpose, the delivery modules have opposite leads. In the case of an eccentric screw pump with for example two delivery modules, the one delivery module has a left-handed lead and the other delivery module a right-handed lead. The axial forces occurring in each case per delivery module during the operation of the eccentric screw pump act in opposite directions and almost completely cancel each other out if delivery modules of the same kind are used. Of the same kind is understood to mean, apart from the different leads, a specific embodiment and dimensioning of the delivery elements. The axial force resulting on the drive side then approaches zero, for which reason cost-intensive bearing elements of the drive device, which essentially comprise a drive component and a pump housing with connecting pieces, can for example be replaced by less costly bearing elements. As a result, the overall load of the drive device is markedly reduced.

The delivery modules are particularly preferably disposed in series in the proposed eccentric screw pump. The torque transmission from the drive device to the rotors or to the rotor can thus be kept particularly straightforward. For example, it is thus also possible, as already proposed, to constituted the rotor in one piece. With this embodiment, therefore, only one rotor is required for all the delivery elements of the eccentric screw pump.

In a further preferred configuration, two adjacent delivery modules are coupled together by a through-flow housing and are constituted for identical delivery directions. For this purpose, the leads are identical in both delivery modules, the delivery modules preferably having a left-handed lead. The product is thus delivered in one direction via the inlet connecting piece of the pump housing into a first delivery module, through a through-flow housing and a second delivery module. Since each delivery module represents a pressure stage, the resultant pressure can be increased by a plurality of delivery modules connected in series.

Furthermore, it can be advantageous to couple together two adjacent delivery modules by a suction housing or pressure housing, wherein the delivery modules are designed for mutually opposite delivery directions. For this purpose, the leads are different in the two delivery modules. The eccentric screw pump can thus comprise a first delivery module with a left-handed lead and a second delivery module with a right-handed lead, which are both coupled together by a pressure housing, so that the delivery medium is delivered through the delivery modules to the pressure housing. In a second embodiment, the eccentric screw pump can comprise a first delivery module with a right-handed lead and a second delivery module with a left-handed lead, wherein both are connected by a suction housing, so that the delivery medium is sucked through the delivery modules and delivered in opposite directions.

In an advantageous embodiment, the eccentric screw pump comprises only two delivery modules. Even though only two delivery modules are used, the eccentric screw pump can be configured for the delivery task according to the given requirement and nonetheless has a compact design.

The eccentric screw pump can for example be configured such that, compared to a conventional eccentric screw pump, it achieves, with the same speed and direction of rotation, double the delivery rate with an unchanged single pressure output. For this purpose, a first delivery module coupled with the drive device has a left-handed lead and a second delivery module connected in series has a right-handed lead. The two delivery modules are coupled together by a pressure housing. The second delivery module comprises a suction housing at its end lying opposite the pressure housing. As in the case of conventional eccentric screw pumps, the delivery medium is sucked via a suction connecting piece on the pump housing, but here also via a suction connecting piece on the suction housing. In the operational state of the pump, the delivery medium is thus delivered coming from two sides towards the pressure housing and exits via a pressure connecting piece on the pressure housing. Different delivery media can thus also be fed. The delivery medium or the delivery media are brought together, wherein a mixing ratio can be set by a suitable selection of the delivery modules.

A configuration of the eccentric screw pump is however also possible which, with a single delivery rate, as in the case of a conventional eccentric screw pump, achieves double the pressure. For this purpose, the eccentric screw pump is provided with two delivery modules having an identical lead, preferably a left-handed lead. The two delivery modules are coupled together by a through-flow housing. The second delivery module comprises a pressure housing at its end lying opposite the through-flow housing. In this variant, the delivery medium is sucked via the suction connecting piece of the pump housing and delivered via the first delivery module, the through-flow housing and the second delivery module towards the pressure housing, which is provided with a pressure connecting piece.

In a further variant, the eccentric screw pump comprises a total of four delivery modules. This thus makes it possible, depending on the configuration, in contrast with a conventional eccentric screw pump, to achieve either four times the delivery capacity with unchanged pressure or double the delivery capacity with double the pressure.

In order to achieve four times the delivery capacity, two delivery modules with a different lead are coupled together in each case by a pressure housing, the two delivery module pairs thus constituted in turn being coupled together by a suction housing. A further suction housing is disposed at the end of the eccentric screw pump lying opposite the drive device. The delivery medium can thus be delivered via a total of three suction connecting pieces and two pressure connecting pieces. The delivery modules preferably have, from the first of the fourth delivery module, the leads left-handed/right-handed/left-handed/right-handed.

Apart from the preferred embodiment of the eccentric screw pump provided with a total of four delivery modules, wherein the pump system comprises two suction housings and two pressure housings, the delivery modules are coupled together by a suction housing, two through-flow housings and a pressure housing in a further advantageous embodiment. Two delivery modules with the same lead are coupled together in each case by a through-flow housing, the delivery module pairs thus constituted in turn being coupled together by a pressure housing. The suction housing is disposed at the end of the eccentric screw pump lying opposite the drive device. The delivery modules preferably have the leads left-handed/left-handed/right-handed/right-handed.

In the coupling region of the delivery modules, the eccentric screw pump preferably comprises means for mixing coupled with the rotor. This makes it possible for the delivery medium or the delivery media to be mixed during transport. This is particularly advantageous when two different products are introduced into the eccentric screw pump, for example when the one product is introduced via a first suction housing and the other product is introduced via a second suction housing. For particularly effective mixing of the products, the means for mixing is disposed inside the pressure housing and coupled directly with the rotor. A separate drive is not therefore required.

According to a preferred development, the housings are constituted essentially identical. In particular, suction housings and pressure housings are identical and it is only by the nature of their use that they become defined. In contrast with this, the through-flow housing is preferably formed by a suction housing or a pressure housing, wherein the suction connecting piece or pressure connecting piece is provided with a closure means. The closure means can for example be constituted as a blank flange, which is fastened by a flange connection to the housing connecting piece.

The advantages achieved with the invention consist in particular in the fact that a delivery of different delivery media in a specific predefined mixing ratio can be achieved with only one pump system. The pump system can be adapted to the delivery task particularly easily by the number and selection of the delivery modules and the coupling means. Due to the fact that the delivery capacity and delivery rate in an eccentric screw pump are determined and influenced by various factors such as the geometry and lead of the rotor and stator, the delivery capacity can thus be adjusted particularly easily with the aid of the modular pump structure. The mixing ratio of the delivery media can be influenced by the use of delivery modules with different delivery rates. A cost saving is also possible. Energy and material costs can also be saved, since the modular structure of the eccentric screw pump according to the invention functions without coupling rods and articulated joints and the number of moving parts in the delivery medium is thus kept comparatively small. The frictional forces which adversely affect the efficiency of the pump and its service life also are thus reduced. The delivery modules can be disposed in such a way that the axial forces almost completely cancel each other out. The delivery direction can be changed by reversing the direction of rotation of the rotor or of the rotors.

A further advantage is that only one sealing system is required and has to be maintained at the suction side of the drive system.

The delivery capacity can for example be doubled by using the eccentric screw pump according to the invention as a so-called immersion pump, with the same pipe diameter, i.e. bore or bunghole.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention are described by way of example by reference to the appended drawings, in which:

FIG. 1 shows diagrammatically an eccentric screw pump with two delivery modules, which are coupled together by a through-flow housing and at the end of which a pressure housing is disposed,

FIG. 2 shows diagrammatically an eccentric screw pump with two delivery modules delivering in opposite directions, which are coupled together by a pressure housing and at the end of which a suction housing is disposed,

FIG. 3 shows diagrammatically an eccentric screw pump with two delivery modules conveying in opposite directions, which are coupled together by a pressure housing and at the end of which a suction housing is disposed, with a drive device comprising a compensating coupling,

FIG. 4 shows diagrammatically an eccentric screw pump with a total of four delivery modules, which are coupled together by a suction housing and two pressure housings and at the end of which a suction housing is disposed,

FIG. 5 shows diagrammatically an eccentric screw pump with a total of four delivery modules, which are coupled together by a pressure housing and two through-flow housings and at the end of which a suction housing is disposed,

FIG. 6 shows diagrammatically a delivery system known from the prior art, wherein a total of four eccentric screw pumps are connected in parallel.

DETAILED DESCRIPTION OF THE INVENTION

The device according to FIG. 1 shows an eccentric screw pump 2 with a first and a second delivery module 4, 6, comprising in each case a stator 8 and a rotor 10, which are coupled together by a through-flow housing 12. A pressure housing 16 with a pressure connecting piece 18 is disposed on second delivery module 6 at the end of eccentric screw pump 2 lying opposite a drive device 14. Both delivery modules 4, 6 are constituted structurally identical and have a left-handed lead L. Through-flow housing 12 is a pressure housing or a suction housing, which is provided with a closure means 20. Closure means 20 should be disposed close to the pressure housing in order to prevent dead space, which can adversely affect the course of the flow and in which delivery medium can be deposited.

Eccentric screw pump 2 is provided with support feet not represented here. The connecting pieces of through-flow housing 12 not used for the delivery can advantageously be used as a support foot or as a base for assembling of a support foot.

The delivery system essentially comprising delivery modules 4, 6 and housings 12, 16 is coupled with drive device 14, which comprises a pump housing 22 with a suction connecting piece 24 and a drive component 26. The force transmission to rotor 10 of the first delivery module 4 takes place with the aid of drive shafts 30 coupled by articulated joints 28. Furthermore, drive device 14 is provided with a seal 32 in order to prevent delivery medium from passing to the exterior.

Rotors 10 of delivery modules 4, 6 are connected to one another by a rigid coupling 34. During the operation of eccentric screw pump 2, the delivery medium passes from a suction line, not represented here, via suction connecting piece 24 into housing 22 and is delivered by means of delivery modules 4, 6 through through-flow housing 12 up to pressure housing 16, where it is then transported via pressure connecting piece 18 into a pressure line not represented here. The axial forces thereby arising act against the delivery direction and are taken up by a bearing provided for the purpose. Since delivery modules 4, 6 are connected in series in this embodiment, double the pressure is achieved compared to a conventional eccentric screw pump which is provided with only one rotor-stator arrangement.

An eccentric screw pump 2 with two delivery modules 4, 6 coupled by a pressure housing 16 is represented in FIG. 2. First delivery module 4 comprises a left-handed lead L and second delivery module 6 a right-handed lead R. Rotors 10 are connected to one another by a rigid coupling 34. A suction housing 36 provided with a suction connecting piece 24 is disposed at the end of eccentric screw pump 2 lying opposite drive device 14. As in the case of eccentric screw pump 2 represented in FIG. 1, pump housing 22 comprises a further suction connecting piece 24.

As a result of the different left-handed/right-handed leads L, R of delivery modules 4, 6, the housing disposed at the end of eccentric screw pump 2 acts as a suction housing 36. The delivery medium is thus transported via both suction connecting pieces 24 into pressure housing 16 and conveyed through pressure connecting piece 18. Despite the same direction of rotation of rotors 10, which are driven by a common drive device 14, the delivery media are transported in opposite directions. The effect of this is that the axial forces occurring during the operation of eccentric screw pump 2 and acting on rotors 10 counteract one another, as a result of which the resultant force acting on the bearings of drive device 14 approach zero or is at least reduced. Coupling 34 for rotors 10 should be designed in such a way that the latter can take up the tensile forces arising. Drive shafts 30, articulated joints 28 and bearings 32 are thus advantageously subjected to less load, which results in a lower degree of wear. The components of eccentric screw pump 2 can also be dimensioned correspondingly more cost-effectively. A means for mixing is disposed in pressure housing 16 in the region of coupling 34, which means is coupled with the rotors and is constituted as an agitator element 37. Since delivery modules 4, 6 in this embodiment are connected in parallel, double the delivery rate is achieved compared to a conventional eccentric screw pump.

As an alternative embodiment (not represented here) in the example of FIG. 2, rotor 10 can also be constituted in one piece. A coupling 34 can thus be dispensed with. For this purpose, rotor 10 comprises two sections for delivery modules 4, 6. A first section with a left-handed lead L and a second section with a right-handed lead R.

FIG. 3 shows an eccentric screw pump 2 as represented in FIG. 2, but with another drive device 14. The drive device comprises a compensating coupling 33 for transmitting the torque to the rotors. As a result of the compact design of drive device 14, the elongated design of eccentric screw pump 2, due to delivery modules 4, 6 connected in series, can be almost completely compensated for.

FIG. 4 represents an eccentric screw pump 2 with a total of four delivery modules 4, 6, 38, 40, wherein two delivery modules coupled together by means of pressure housing 16 similar to the embodiment in FIG. 2, are coupled together by a suction housing 36, in such a way that delivery modules 4, 6, 38, 40 of the delivery system comprise, proceeding from drive device 14, the leads left-handed/right-handed/left-handed/right-handed. A suction housing 36 with a suction connecting piece 24 is disposed at the end of eccentric screw pump 2 lying opposite drive device 14. Rotors 10 are connected to one another by rigid couplings 34. The delivery medium is delivered via a total of three suction connecting pieces 24 and two pressure connecting pieces 18. Since the four delivery modules 4, 6, 38, 40 are connected in parallel in this embodiment, four times the delivery rate is achieved compared to a conventional eccentric screw pump. On account of the equal number of delivery modules 4, 6, 38, 40 with a left-handed and a right-handed lead, the resultant force acting on the bearings of drive device 14 approaches zero or is at least reduced.

A further alternative embodiment with a total of four delivery modules 4, 6, 38, 40 is represented in FIG. 5. In this embodiment, two delivery modules pairs connected in series and coupled together by a through-flow housing 12, a first delivery module pair 4, 6 and a second delivery module pair 38, 40, are in each case coupled together by a pressure housing 16. Delivery module pairs 4, 6 and 38, 40 connected in series have different leads, so that the delivery system comprises in total delivery modules 4, 6, 38, 40 with the leads left-handed/left-handed/right-handed/right-handed.

During the operation of eccentric screw pump 2, the delivery medium is sucked by means of suction connecting pieces 24 on the suction housing 36 and on pump housing 22 and transported away via only one pressure connecting piece 18. Since, in this embodiment, two delivery modules are connected in series in each case and the two delivery module pairs thus formed represent a parallel connection, double the delivery rate and double the pressure is achieved compared to a conventional eccentric screw pump. On account of the same number of delivery modules 4, 6, 38, 40 with a left-handed and a right-handed lead, the resultant force acting on the bearings of drive device 14 approaches zero or is at least reduced.

For the purpose of comparison, FIG. 6 represents an arrangement known from the prior art with a plurality of structurally identical conventional eccentric screw pumps 42. As can be seen from the flow courses of the delivery medium represented by dashed lines, the total of four eccentric screw pumps 42 are connected in parallel in order to achieve four times the delivery rate compared to a single eccentric screw pump. Compared to eccentric screw pump 2 constituted in a modular manner according to the invention, the arrangement known from the prior art involves, amongst other things, a disadvantageously high energy requirement for the operation of the pump, high production and maintenance costs and a large space requirement.

Each of the four eccentric screw pumps 42 comprises in each case a drive device 14, a rotor-stator arrangement 44 and a pressure housing 16 disposed at the end lying opposite drive device 14, said pressure housing being provided with a pressure connecting piece 18. The delivery medium is sucked via suction connecting pieces 24 on pump housing 22 and delivered in the direction of pressure housing 16, from where it is transported via pressure connecting pieces 18 into pressure lines not represented here.

The device according to the invention is directed specifically towards an eccentric screw pump 2, which can be used flexibly and with which costs and outlay can be saved. As a result of the particularly straightforward modular structure, eccentric screw pump 2 can be adapted to the given delivery task by the number and selection of suitable delivery modules 4, 6, 38, 40 and housings 16, 36. Only one drive device 14 is required for this, which in particular keeps the energy and maintenance requirement relatively low. As a result of the mutual arrangement of delivery modules with different leads L, R, the axial forces acting on the bearings of the eccentric screw pump can also be reduced.

LIST OF REFERENCE NUMBERS

• 02 eccentric screw pump
• 04 first delivery module
• 06 second delivery module
• 08 stator
• 10 rotor
• 12 through-flow housing
• 14 drive device
• 16 pressure housing
• 18 pressure connecting piece
• 20 closure means
• 22 pump housing
• 24 suction connecting piece
• 26 drive component
• 28 articulated joint
• 30 drive shafts
• 32 seal
• 33 compensating coupling
• 34 coupling
• 36 suction housing
• 37 agitator element
• 38 third delivery module
• 40 fourth delivery module
• 42 eccentric screw pump (prior art)
• 44 rotor-stator arrangement (prior art)