Eccentric screw pump

Abstract

An eccentric screw pump for pumping fluids or flowing conveying media from a suction side to a pressure side, which includes a rotor and a stator, the stator being flexible and is connected to the pump housing on one side, in particular on the suction side. The rotor is connected to the drive shaft by means of an articulation. When the eccentric screw pump is in the idle state, there is no sealing contact at least in areas between the rotor and the stator in the sealing areas. When the eccentric screw pump is in the operating state, the stator is surrounded, at least in sections and/or, essentially, on the periphery by the conveying medium. The rotor and the stator are brought into contact with each other in the operating state along the sealing area.

Claims

1. An eccentric screw pump for pumping a fluid or free-flowing conveying medium from a suction side to a pressure side, the eccentric screw pump comprising: a rotor and a stator, wherein the stator is designed to be flexible and is secured to a pump housing on a suction side, wherein the rotor is connected to a drive shaft via a joint, wherein in an idle state of the eccentric screw pump, no sealing contact is formed at least in some areas between the rotor and the stator in sealing areas, wherein in an operating state of the eccentric screw pump, the stator is surrounded at least in some areas by the conveying medium, wherein the rotor and the stator are brought into contact along the sealing areas in the operating state by the conveying medium exerting pressure from outside the stator on an outer circumferential surface of the stator.

2. The eccentric screw pump according to claim 1, wherein a play is formed at least in some areas in the sealing areas between the rotor and the stator in the idle state.

3. The eccentric screw pump according to claim 2, wherein no sealing contact or a play, respectively, is formed between the rotor and the stator in the idle state in an area of between 50%-100% of the sealing areas, and wherein an overlap between the rotor and the stator is formed in the sealing areas in the operating state.

4. The eccentric screw pump according to claim 1, wherein no sealing contact or a play, respectively, is formed between the rotor and the stator in the idle state in an area of between 50%-100% of the sealing areas, and wherein an overlap between the rotor and the stator is formed in the sealing areas in the operating state.

5. The eccentric screw pump according to claim 1, wherein a first play is formed between the rotor and the stator in a first idle state of the eccentric screw pump on the suction side, and wherein a second play is formed between the rotor and the stator on the pressure side.

6. The eccentric screw pump according to claim 5, wherein the first play is formed to be larger than the second play.

7. The eccentric screw pump according to claim 6, wherein the play decreases continuously along the sealing areas between the rotor and the stator from the suction side of the eccentric screw pump to the pressure side of the eccentric screw pump.

8. The eccentric screw pump according to claim 5, wherein the play decreases continuously along the sealing areas between the rotor and the stator from the suction side of the eccentric screw pump to the pressure side of the eccentric screw pump.

9. The eccentric screw pump according to claim 1, wherein a play is formed between the rotor and the stator in a first idle state of the eccentric screw pump on the suction side, and wherein a coverage between the rotor and the stator is formed on the pressure side.

10. The eccentric screw pump according to claim 1, wherein the conveying medium, which at least partially surrounds the stator in the operating state, has the pressure side pressure.

11. The eccentric screw pump according to claim 1, wherein the stator is secured to the pump housing on one side directly via a free end area of the stator.

12. The eccentric screw pump according to claim 11, wherein, for securing to the pump housing, the free end area of the stator has an annular widening or wherein the free end area of the stator is formed as flange for securing to the pump housing.

13. The eccentric screw pump according to claim 1, wherein the joint has a central part, which is formed so as to be at least partially movable and which is made of a reinforced elastomer or plastic material.

14. The eccentric screw pump according to claim 13, wherein the reinforcement of the elastomer or plastic material is formed by a fiber reinforcement or wire reinforcement integrated in the material.

15. The eccentric screw pump according to claim 14, wherein the central part of the joint is limited on both sides by connecting pieces for fastening to at least one of the rotor or the drive shaft.

16. The eccentric screw pump according to claim 13, wherein the central part of the joint is limited on both sides by connecting pieces for fastening to at least one of the rotor or the drive shaft.

17. The eccentric screw pump according to claim 1, wherein the stator has a screw thread-shaped inner circumferential surface and includes an inlet funnel for the conveying medium on an end area of the stator, wherein the inlet funnel includes a continuation of the screw thread-shaped inner circumferential surface of the stator and is formed so as to be sealing line-free with respect to the rotor.

18. The eccentric screw pump according to claim 1, wherein at least one solar panel provides solar power to a drive for rotating the rotor.

19. The eccentric screw pump according to claim 1, wherein in the operating state of the eccentric screw pump, the stator is surrounded completely by the conveying medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention and their advantages will be described in more detail below on the basis of the enclosed figures. The size ratios of the individual elements relative to one another in the figures do not always correspond to the actual size ratios, because some shapes are illustrated in a simplified manner, and other shapes are illustrated in an enlarged manner as compared to other elements for illustrative purposes.

(2) FIG. 1 shows an eccentric screw pump according to the invention in an idle state.

(3) FIG. 2 shows an eccentric screw pump according to the invention in an operating state.

(4) FIG. 3 shows a further illustration of an eccentric screw pump according to the invention in an operating state.

(5) FIG. 4 shows the forces acting on the eccentric screw pump in the operating state.

(6) FIG. 5 shows a first embodiment of an end-side fastening of the stator of an eccentric screw pump.

(7) FIG. 6 shows a second embodiment of an end-side fastening of the stator of an eccentric screw pump.

(8) FIG. 7 shows a perspective illustration of a first embodiment of a joint.

(9) FIG. 8 shows a sectional illustration of the first embodiment of a joint according to FIG. 7.

(10) FIG. 9 shows a perspective illustration of an intermediate product during the production of the first embodiment of a joint according to FIG. 7.

(11) FIG. 10 shows a sectional illustration of the intermediate product during the production of the first embodiment of a joint according to FIG. 7.

(12) FIG. 11 shows a connecting piece of a joint according to FIG. 7.

(13) FIG. 12 shows a perspective illustration of a second embodiment of a joint.

(14) FIG. 13 shows a sectional illustration of the second embodiment of a joint according to FIG. 12.

(15) FIG. 14 shows a component of the second embodiment of a joint according to FIG. 12.

(16) FIG. 15 shows the eccentric screw pump of FIG. 1 coupled to a drive shaft of a motor, which is depicted schematically.

DETAILED DESCRIPTION

(17) Identical reference numerals are used for identical elements of the invention or for elements having identical effects. For the sake of clarity, only reference numerals, which are required for the description of the respective figure, are further illustrated in the individual figures. The illustrated embodiments only represent examples for how the device according to the invention can be designed, and do not represent a final limitation.

(18) FIG. 1 shows a schematic view of an eccentric screw pump 1, in particular of a wobble pump 2, in an idle state, and FIG. 2 shows the eccentric screw pump 1 in an operating state AZ. The eccentric screw pump 1 comprises an elastomeric stator 3 comprising a helically coiled inner side and a rotor 4. The stator 3 has one more thread pitch than the rotor 4. The rotor 4 is accommodated in the stator 3. The rotor 4 and the stator 3 form the rotor-stator system 11. The rotor-stator system 11 is arranged in the pump housing 6, wherein an annular chamber 12 is formed between the pump housing 6 and the outer jacket surface of the stator 3.

(19) The rotor 4 is coupled to the drive shaft 7 of a drive 30 (FIG. 15), for example of an electric motor, and performs a rotation around the longitudinal stator axis or around the longitudinal axis L, respectively, of the eccentric screw pump 1, and simultaneously a circular translation determined by the eccentricity e of the rotor-stator system 11. This means that the rotor 4 moves eccentrically in the stator 3.

(20) The rotor 4 is coupled to the drive shaft 7 via a cardan joint 5. The eccentric movement of eccentricity e, respectively, between rotor 4 and stator 3 is compensated by means of torque transmission by means of the cardan joint 5. On the free end 8, which is located opposite the cardan joint 5, the stator 3 is secured to the pump housing 6 of the eccentric screw pump 1 on one side, in particular flexibly clamped. This allows for a further cardanic degree of freedom. The eccentricity e can be compensated by means of the distance of these two cardanic degrees of freedom, each having angle α. The axis of the stator essentially describes a cone shape during production.

(21) For securing to the pump housing 6, the free end 8 of the stator 3 has, for example, an annular widening 9, which is held for example in a clamping manner on the pump housing 6. If applicable, the annular widening 9 can serve as flange 10, via which the stator 3 can be connected, for example screwed, to the pump housing 6.

(22) The stator 3 and the rotor 4 are formed so as to be dimensioned in such a way that, in a first idle state RZ according to FIG. 1 of the eccentric screw pump 1, a play 100 or distance, respectively, is formed at least in some areas along the at least two sealing contact surfaces 14 between the rotor 4 and the stator 3. The rotor 4 in particular has dimensions A(4), which are smaller than the inner dimensions I(3) of the stator 3, at least in some areas. As shown in FIG. 15, a first play 100a is formed between the rotor and the wobble stator on the suction side S in the idle state of the wobble pump, and a second play 100b is formed between the rotor and the wobble stator on the pressure side D. The first play 100a on the suction side is in particular larger than the second play 100b on the pressure side.

(23) In the operating state AZ of the eccentric screw pump 1 according to FIG. 2, the conveying medium FM reaches via an inlet 15 into the eccentric screw pump 1 and is transported through the moving conveying chambers FR, which are formed from the movement of the rotor 4 and the mutual contact of stator 3 and rotor 4 on the sealing contact surfaces 14, from the suction side S to the pressure side D of the eccentric screw pump 1 in the conveying direction TR. The conveying medium FM is discharged from the eccentric screw pump 1 via the outlet 16 and is supplied to its further use or processing, respectively. As shown in FIG. 3, the rotor-stator system 11 has an inlet-side end portion, in which a sealing line-free inlet funnel 28 is formed between the stator 3 and the rotor 4 along a funnel length, wherein the screw thread-shaped inner circumferential surface 26 of the stator 3 is formed in a central main portion of the rotor-stator system and in the inlet-side end portion.

(24) If conveying medium FM is pumped through the eccentric screw pump 1 (FIG. 2), the conveying medium FM effects a pressure, which is directed radially to the outside, onto the stator 3 in the conveying chambers FR formed between rotor 4 and stator 3, whereby the elastically deformable material of the stator 3 is pushed radially to the outside. To ensure a sufficient sealing of the conveying chambers RF, conventionally known wobble pumps have a coverage between the stator and the rotor in the idle state. This means that a prestress exists between the stator and the rotor. This prestress is attained in particular in that the outer dimensions of the rotor are larger than the inner dimensions of the elastomeric stator.

(25) In the case of the illustrated eccentric screw pump 1 in the form of a wobble pump 2, the pressure of the conveying medium FM(FR) located within the conveying chambers FR is counteracted in the operating state AZ via the conveying medium FM(D), which has already been conveyed to the pressure side D. The conveying medium FM(D), which has the pressure side pressure, in particular flushes around the stator 3, which protrudes into the pressure side area D, and thereby pushes the stator 3 against the rotor 4. Due to the play 100 formed between the stator 3 and the rotor 4 in the idle state RZ, the start-up of the eccentric screw pump 1 can take place without the disadvantageously large starting torque of wobble pumps with coverage formed between rotor and stator in the idle state. The conveying effect can then always start with a very low value, and can be increased with the increase of the conveying medium FM(D), which is conveyed through the eccentric pump 1.

(26) Due to the pressure exerted by the conveying medium FM(D) on the stator 3, the latter is in particular pressed against the rotor 4 in the area of the at least two sealing contact surfaces 14, whereby the individual conveying chambers FR are spatially separated from one another in a reliable manner. Due to the solid body contact between the rotor 4 and the stator 3 formed in the operating state AZ, a real separation of the conveying chambers FR as well as a separation between the suction side S of the eccentric screw pump 1 and the pressure side D of the eccentric screw pump 1 is attained.

(27) A significant advantage of such an eccentric screw pump 1 or wobble pump 2, respectively, is in particular that a smaller expenditure of force is necessary to overcome the breakaway torque when transferring the eccentric screw pump 1 from a standstill or from the idle state RZ, respectively, into an operating state AZ, due to the play 100 formed at least in some areas between the rotor 4 and the stator 3 during start-up of the eccentric pump 1.

(28) FIG. 3 shows a further stylized illustration of an eccentric screw pump 1 according to the invention, and FIG. 4 shows the forces acting on the eccentric screw pump 1 in the operating state AZ. The flexible area 20 of the stator 3 on the free end area 8 is identified in FIG. 3. Due to the play 100 formed between rotor 4 and stator 3 in the idle state RZ (see FIG. 1), the rotor-stator system 11 does not have a prestress in the idle state RZ. During start-up of the eccentric screw pump 1, the starting torque is thus approximately zero and the operating torque is also small in the case of small differential pressures between the suction side S and the pressure side D. Said starting torque increases to the pressure side pressure p(D) as the conveying quantity increases. In the case of higher torque loads due to the increasing differential pressure between the suction side S and the pressure side D, the flexible area 20 of the stator 3 has a correspondingly higher prestress.

(29) Due to the fact that the stator 3 is secured to the pump housing 6 only on one side, the ability to move of the stator 3 is only limited on one side. When calculating the pressing force F as a function of differential pressure Δρ and radial stability rS, a largely even pressing of the stator 3 against the rotor 4 results between pressure side D and suction side S.

(30) Due to the play 100 formed between rotor 4 and stator 3 in the idle state RZ (see in particular FIGS. 1 and 2), only small oscillations are created, so that a wobble pump 2 comprising a correspondingly formed rotor-stator system 11 can be operated at higher speeds than conventionally known wobble pumps. Due to the play formed in the idle state RZ, in particular fewer excitations of the system, which is able to oscillate, result in the rotational direction. Wobble stators 3 according to the invention can thus be used in an advantageous manner in the case of speed-variable eccentric screw pumps 1 with predetermined power, for example solar-operated wobble pumps 2, in the case of which only lower differential pressures Δρ can usually still be overcome at higher speeds. As shown in FIG. 15, the solar-operated wobble pump 2 is driven by a drive 30 that is powered by a solar module 40, for example a solar or photovoltaic panel.

(31) FIG. 5 shows a first embodiment of an end-side fastening of the stator 3 of an eccentric screw pump 1, and FIG. 6 shows a second embodiment of an end-side fastening of a stator 3 of an eccentric screw pump 1. According to the embodiment illustrated in FIG. 5, the stator 3 has an annular widening 9 on its free end area 8, via which the stator 3 is secured to the pump housing 6. The annular widening 9 serves for example as flange 10 in order to screw the stator 3 to the pump housing 6 or the like.

(32) According to the embodiment illustrated in FIG. 6, the stator 3 has, on its free end area 8, a flange structure 17, which extends in the direction of the opposite suction-side end area 13 and which encloses the stator 3 at least in some areas, wherein an annular chamber 19 is formed between the outer jacket surface of the stator 3 and the flange structure 17, which annular chamber is in fluidic connection with the above-described annular chamber 12, which is formed between the stator 3 and the pump housing 6. The flange structure 17, which extends in the direction of the opposite suction-side end area 13, merges into a free end area 18. The free end area 18 is secured to the pump housing 6, the stator 3 is in particular fastened to the pump housing 6 via the free end area 18 of the flange structure 17 in a central area 6M of said pump housing.

(33) In the case of the two embodiments illustrated in FIGS. 5 and 6, the conveying medium FM can in each case flush largely completely around the stator 3 from the suction-side end area 8 to the pressure-side end area 13 (see in particular FIG. 2).

(34) FIG. 7 shows a perspective illustration of a first embodiment of a cardan joint 5, 5a, and FIG. 8 shows a sectional illustration. FIG. 9 shows a perspective illustration of an intermediate product 5*, 5a* during the production of the first embodiment of a cardan joint 5, 5a according to FIG. 7, and FIG. 10 shows a sectional illustration. FIG. 11 shows a connecting piece 60 of a joint 5, 5a according to FIG. 7.

(35) The joint 5, 5a comprises an internally reinforced elastomer part 50. Tests have shown that between 0.5 and 1.5-times the outer diameter dA is already sufficient as free bending length LB in order to compensate an angular offset α of between 1° and 2°, which is common in wobble pumps 2. Fewer oscillations are created due to this short length of the joint 5, 5a, which also leads to an increased efficiency of the wobble pump 2, longer service life of the components of the wobble pump 2, and higher possible maximum speeds of the wobble pump 2.

(36) For special embodiments, for example wobble pumps 2, which are subjected to particularly high stresses, the advantageous oscillation properties and the ability to transfer compressive forces of the short joint bodies 5, 5a, which are only stressed with angular deflection, can be combined with inner support bodies (not illustrated), which are known from the prior art. For example a ball, granulate, a helical spring, a cylindrical shaft piece or a flexible elastomer or plastic body, respectively, can thereby be used as inner support bodies. The combination of support body with a lubricant is recommended here. In addition, a more or less viscous supporting liquid can also be used.

(37) The elastomer parts 50 of the joint 5a preferably consist of a commercially available hydraulic hose or another suitable hose comprising an inner reinforced structure. The inner reinforced structure can be formed, for example, by means of reinforcements, which are interlaced in a cross-shaped manner, in one or a plurality of layers. The reinforcement can thereby be made of metallic fibers or wires, plastic fibers and/or textile fibers or the like. A connecting piece 60 is in each case fastened to the two free ends of the hose piece 51, which forms the elastomer part 50. The two connecting pieces 60 are preferably formed with retaining grooves 62 in the axial direction and/or possibly also in the radial direction and possibly have further retaining means (not illustrated) for fastening and securing in and/or to the free end areas of the hose piece 51. The connecting pieces 60 preferably have an n-edged attachment area 63, whereby n corresponds to the number of the jaws of the subsequently used hose press (hose presses usually have six or eight jaws). The connecting piece 60 is in case assigned a sleeve 52 for retaining the respective end of the hose piece 51 (see FIGS. 9 and 10). The sleeves 52 are compressed with the help of a hose press, the sleeves 53 compressed in this sway (see FIGS. 7 and 8) in particular have, at least in some areas, an outer contour, which corresponds to the outer contour of the n-edge attachment area 63 of the respective connecting piece 60. The hose piece 51 is secured between the two connecting pieces 60 in this way. The n-edged area 63 on the connecting piece 60 is to thereby be oriented so as to be angular with the jaws of the hose press. After the pressing, a reliable connection is created between the respective connecting piece 60 and the respective sleeve 53, and thus also a reliable connection between the respective connecting piece 60 and the respective free end of the hose piece 51.

(38) At least two sleeves 52 are preferably pressed simultaneously in a suitable jaw construction. A higher torque can be allowed for the construction by means the n-edged pressing between sleeve 52 and connecting piece 60, because a relative movement between the hose piece 51 and a sleeve 52 as well as between the hose piece 51 and the connecting piece 60, which is assigned to the sleeve 52, has to take place simultaneously for a slipping of the hose piece 51. The n-edged outer contour of the n-edged attachment area 63 can additionally be used as contact surface for tools, when for example detachable threads are used as connection to the adjacent parts, in particular the rotor 4 and/or the drive shaft 7 (see FIGS. 1 and 2). In the alternative, a cylindrical area, which is formed to be thin, can also be used instead of an n-edged outer contour of the connecting piece 60. In response to the pressing process, this thin area can then also be brought into the n-edged shape.

(39) To protect the free ends of the hose piece 51, for example against environmental influences, such as penetrating fluid or the like, and/or to reinforce the bond between hose piece 51 and sleeves 52, 53 or hose piece 51 and connecting piece 60, respectively, a sealing and/or adhesive mass can additionally be used, which is introduced in particular between the free ends of the hose piece 51 and the respective sleeve 52, 53.

(40) FIG. 12 shows a perspective illustration of a second embodiment of a cardan joint 5, 5b, and FIG. 13 shows a sectional illustration. FIG. 14 shows a component 65 of the second embodiment of a cardan joint 5b according to FIG. 12. This embodiment provides to use a commercially available metallic insert for injection molded parts 66 as component 65. The n-edged connection between the connecting piece 60 and the pressed sleeve 52 can possibly be forgone here. In the illustrated exemplary embodiment, the connecting piece 60 is formed as threaded pin 64 comprising an internal thread for fastening to the rotor 4 and/or the drive shaft 7 (see FIGS. 1 and 2). In the alternative, threaded pins can be used, which provide external threads for fastening to the rotor 4 and/or the drive shaft 7.

(41) The embodiments, examples and alternatives of the preceding paragraphs, the claims or the following description and the figures, including the various views thereof or respective individual features can be used independently of one another or in any combination. Features, which are descried in connection with an embodiment, can be applied to all embodiments, unless the features are incompatible. The invention has been described with reference to preferred embodiments. It is conceivable for a person of skill in the art that modifications or changes can be made to the invention, without thereby leaving the scope of protection of the following claims. It is possible to use some of the components or features of one of the examples in combination with features or components of another example.