CONTROLLING THE GAP GEOMETRY IN AN ECCENTRIC SCREW PUMP

Abstract

A progressive cavity pump for transporting a liquid containing solids comprises a helical rotor, a stator having an inlet and an outlet, within which the helical rotor is rotatably disposed about a longitudinal axis of the stator, and comprising a helical inner wall corresponding to the helical rotor. The helical rotor comprises a shape tapering down toward the outlet or inlet, and the helical rotor and stator are disposed relative to each other and implemented such that at least one chamber is formed for transporting the liquid, and the chamber is cut off by a constriction. The progressive cavity pump includes an adjusting device for adjusting a relative axial position of the helical rotor and stator, wherein the adjusting device is implemented for expanding the constriction between the helical rotor and stator.

Claims

1-27. (canceled)

28. A progressive cavity pump for transporting a liquid containing solids comprising: a helical rotor; a stator within which the helical rotor is rotatably disposed about a longitudinal axis of the stator, the stator further comprising an inlet, an outlet, and a helical inner wall corresponding to the helical rotor; and wherein the helical rotor comprises a shape tapering down toward the outlet or the inlet, and the helical rotor and the stator are disposed relative to each other such that at least one chamber is formed for transporting the liquid, and the chamber is cut off by a constriction between the helical rotor and stator; and an adjusting device for adjusting a relative axial position of the helical rotor and stator, wherein the adjusting device is adapted to adjust the constriction between the helical rotor and stator.

29. The progressive cavity pump according to claim 28, wherein the shape of the helical rotor tapering down toward the outlet or the inlet is conical.

30. The progressive cavity pump according to claim 28, wherein the shape of the helical rotor tapering down toward the outlet or the inlet is of a variable eccentricity.

31. The progressive cavity pump according to claim 28, wherein the constriction between the helical rotor and stator defines a sealing line.

32. The progressive cavity pump according to claim 28, wherein the adjusting device adjusts the constriction between the helical rotor and stator to the extent that a leakage gap is implemented between the helical rotor and stator.

33. The progressive cavity pump according to claim 32, wherein the adjusting device adjusts the constriction between the helical rotor and stator depending on one or more predetermined operating parameters.

34. The progressive cavity pump according to claim 33, wherein one of the operating parameters is the temperature of the stator and/or the helical rotor.

35. The progressive cavity pump according to claim 33, wherein one of the operating parameters is the volume of liquid transported.

36. The progressive cavity pump according to claim 33, wherein one of the operating parameters is a liquid level at the inlet of the stator.

37. The progressive cavity pump according to claim 28, wherein the stator is axially displaceably supported and the adjusting device is adapted to axially displace the stator to at least partially adjust the constriction between the helical rotor and stator.

38. The progressive cavity pump according to claim 28, wherein the helical rotor is axially displaceably supported and the adjusting device is adapted to axially displace the helical rotor to at least partially adjust the constriction between the helical rotor and stator.

39. The progressive cavity pump according to claim 38, wherein a drivetrain of the helical rotor comprises a drive motor and a drive shaft displaceable together with the helical rotor.

40. The progressive cavity pump according to claim 39, wherein the helical rotor and the drive shaft are displaceable relative to the drive motor.

41. The progressive cavity pump according to claim 40, wherein a gearbox is disposed between the drive shaft and the drive motor and the gearbox allows axial displacement of the drive shaft.

42. The progressive cavity pump according to claim 39, wherein the drive shaft comprises at least two parts and an expansion member allowing lengthening and shortening the drive shaft for axial displacement of the helical rotor.

43. The progressive cavity pump according to claim 28, wherein the longitudinal axis of the stator is oriented substantially vertically during operation and the outlet of the stator is at the top.

44. The progressive cavity pump according to claim 28, wherein the stator is formed of a pliable material at least in the region of the helical inner wall.

45. The progressive cavity pump according to claim 44, wherein the stator is formed of an elastomer at least in the region of the helical inner wall.

46. The progressive cavity pump according to claim 28, wherein the adjusting device is adapted to expand the constriction between the helical rotor and stator prior to beginning a startup procedure or during or after a shutdown procedure of a drive motor for rotating the helical rotor, and the adjusting device is adapted to contract the constriction between the helical rotor and stator prior to beginning during the startup procedure of the drive motor.

47. The progressive cavity pump according to claim 28, wherein the adjusting device comprises an input interface for receiving a pressure signal and expands or contracts the constriction between the helical rotor and stator depending on the pressure signal.

48. The progressive cavity pump according to claim 28, wherein the adjusting device comprises an input interface for receiving a volume signal and expands the constriction between the helical rotor and stator depending on the volume signal, such that for a value of the volume signal signaling that a volume transported since the beginning of a transport procedure corresponds to a specified volume the constriction between the helical rotor and stator is expanded such that no further transporting of a volume out of the outlet of the stator occurs.

49. The progressive cavity pump according to claim 28, wherein the adjusting device adjusts the axial position of the helical rotor relative to the stator while the helical rotor rotates relative to the stator.

50. A method for operating a progressive cavity pump comprising a helical rotor, a stator within which the helical rotor is rotatably disposed about a longitudinal axis of the stator, the stator further comprising an inlet, an outlet, and a helical inner wall corresponding to the helical rotor, wherein the helical rotor comprises a shape tapering down toward the outlet or the inlet, and the helical rotor and the stator are disposed relative to each other such that at least one chamber is formed for transporting the liquid, and the chamber is cut off by a constriction between the helical rotor and stator, and an adjusting device for adjusting a relative axial position of the helical rotor and stator, wherein the adjusting device is adapted to adjust the constriction between the helical rotor and stator, wherein the method comprises the steps of: driving the helical rotor for transporting a liquid; and adjusting the constriction between the helical rotor and stator by axially displacing the helical rotor and stator relative to each other.

51. The method according to claim 50, wherein the step of adjusting the constriction between the helical rotor and stator further comprises the step of: adjusting a leakage gap between the helical rotor and stator.

52. The method according to claim 50, further comprising the steps of: measuring a temperature of the helical rotor and/or of the stator; axially relatively displacing the helical rotor and stator depending on the measured temperature.

53. The method according to claim 50, further comprising the steps of: determining a liquid level at the inlet of the stator; axially relatively displacing the helical rotor and stator depending on the liquid level determined.

54. The method according to claim 50, further comprising the steps of: determining a liquid volume transported per revolution of the helical rotor; and axially relatively displacing the helical rotor and stator depending on the liquid volume determined.

55. The method according to claim 50, wherein the constriction between the helical rotor and stator is expanded at the start of a startup of a drive motor for rotating the helical rotor, and the constriction between the helical rotor and stator is contracted after starting the startup procedure of the drive motor.

56. The method according to claim 50, wherein a pressure is measured by a pressure sensor, and the constriction between the helical rotor and stator is expanded or contracted depending on the pressure.

57. The method according to claim 50, wherein a specified volume is measured and the constriction between the helical rotor and stator is expanded or contracted depending on the specified volume.

58. The method according to claim 50, wherein the helical rotor is adjusted relative to the stator in the axial direction along the axis of rotation, while the helical rotor is driven about the axis of rotation in a rotary motion for transporting the liquid relative to the stator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention is described in more detail below, using five embodiment examples and referencing the attached figures. Shown are:

[0045] FIG. 1 is a schematic cross section through a progressive cavity pump according to a first embodiment example;

[0046] FIG. 2a is a schematic cross section of the inlet of and through a progressive cavity pump perpendicular to the longitudinal axis with a sealing line set;

[0047] FIG. 2b is a schematic cross section along the longitudinal axis of the progressive cavity pump according to FIG. 2a;

[0048] FIG. 2c is a schematic cross section of the outlet of the progressive cavity pump perpendicular to the longitudinal axis according to FIG. 2b;

[0049] FIG. 3a is a schematic cross section of the inlet of and through a progressive cavity pump perpendicular to the longitudinal axis with a leakage gap set;

[0050] FIG. 3b is a schematic cross section along the longitudinal axis of the progressive cavity pump according to FIG. 3a;

[0051] FIG. 3c is a schematic cross section of the outlet of the progressive cavity pump perpendicular to the longitudinal axis according to FIG. 3b;

[0052] FIG. 4 is a schematic cross section through a progressive cavity pump according to a second embodiment example;

[0053] FIG. is a schematic cross section through a progressive cavity pump according to a third embodiment example;

[0054] FIG. 6 is a schematic cross section through a progressive cavity pump according to a fourth embodiment example;

[0055] FIG. 7 is a schematic cross section through a progressive cavity pump according to a fifth embodiment example; and

[0056] FIG. 8 is a flowchart of an embodiment example of a method for operating a progressive cavity pump.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] A progressive cavity pump 1 comprises a stator 2 and a rotor 4. The stator has a center axis L.sub.1 extending centrally through an inner cavity 6 of the stator 2. The stator 2 comprises an inner wall 8 bounding the cavity 6 and formed of an elastomer material. The inner contour of the wall 8 is formed so as to define a double helix. The rotor 4 is also helical in overall design, wherein the pitch of the helix of the stator 2 has double the pitch with respect to the rotor 4. Individual chambers 5 separated by a constriction 7 are thus formed.

[0058] The stator 2 further comprises an inlet 10 and an outlet 12. The inlet 10 is connected to an inlet housing 14 comprising an inlet flange 16 to which an inlet pipe 18 is connected. The outlet 12 further has an outlet housing 20 comprising an outlet flange 22 to which an outlet pipe 24 is connected.

[0059] A drive shaft 26 extends through the inlet housing 14 and is connected to the rotor 4 by means of a first Cardan joint, and connected to an output shaft 32 of a gearbox 34 by means of a second Cardan joint 30. In place of such a drive shaft 26 having two Cardan joints 28, 30, a thin flexible shaft is also preferable and allows eccentric driving. The input side of the gearbox 34 is connected to a drive motor 36 implemented as an electric motor according to the present embodiment example.

[0060] The progressive cavity pump 1 according to the invention comprises an adjusting device 39 for expanding the constriction 7 between the rotor 4 and stator 2 in order to set an optimal gap geometry. According to the present embodiment example (FIG. 1), the adjusting device 39 is implemented such that the stator 2 is axially displaceably supported. The stator 2 is displaceable along the longitudinal axis L1 as indicated by the arrow 38. To this end, the stator 2 is received in segments of the inlet housing 14 and the outlet housing 20 and sealed off by means of seal 40, 42. The adjusting device 39 comprises an engaging segment 44 for displacing the stator 2 and potentially connected to a drive provided for this purpose.

[0061] FIGS. 2a, 2b, and 2c, as well as FIGS. 3a, 3b, and 3c, illustrate the change in gap geometry, that is, the expanding of the constriction 7 using a schematic depiction.

[0062] While FIGS. 2a-2c show a gap geometry having a sealing gap, wherein there is contact between the rotor 4 and the stator 2, FIGS. 3a-3c illustrate expanding of the constriction 7 so that a leakage gap S is set. FIG. 2b shows a section along the longitudinal axis L1, as also shown in FIG. 1. The rotor 4 is at a maximum upper position relative to FIGS. 2a-2c, as can be seen particularly in FIGS. 2a and 2c, each showing sections perpendicular to the longitudinal axis L1. FIG. 2a shows a section near the inlet 10 and FIG. 2c. shows a section at the outlet 12. As can be seen particularly in FIGS. 2a and 2c, a segment of the circumferential surface 3 of the rotor 4 contacts an inner wall 9 of the stator 2. A sealing line D is formed in the constriction 7 by the contact. It is typically provided that the rotor 4 is positioned axially in the stator 2 such that deformation occurs in the radial direction. The stator 2 is made of a flexible material, such as particularly an elastomer. Pretension in the radial direction thus results in elastic deformation of the stator 2 in the region of the sealing line D. The friction is thereby relatively high. High friction also leads to high wear. During operation, it can occur that said radial pretension increases further, for example due to swelling of the material of the stator 2 or due to expansion of the materials due to heat input.

[0063] For shear-sensitive media, for example, it is also preferable to form a sealing line D and simultaneously also achieve relatively high radial pretension, so that medium is clearly separately at the sealing lines D between the chambers and little shearing occurs.

[0064] By axially adjusting the rotor 4 having an overall conical shape, it is possible to expand the constriction 7 and thus reduce a radial pretension or even set a leakage gap S instead of a sealing line D. It should be understood that a leakage gap S also seals off and the rotor 4 floats on a liquid film in the constriction 7 in this state. Expanding the constriction is achieved in that the rotor 4 is displaced in the direction of the conical expansion, that is, to the left with respect to FIGS. 2a-3c. The constriction 7 is thereby further expanded and a leakage gap S can form.

[0065] In the inverse case, it is also possible to make the constriction 7 smaller, that is, to contract said construction further, for example in order to eliminate a leakage gap S and to set a sealing line. This can be advantageous at high pressures, for example. High pressure can cause the stator 2 to expand radially and automatically set a leakage gap S. In order to still retain the optimal gap geometry, in such a case an axial displacement in the direction of the conical constriction, that is, to the right with respect to FIGS. 2a-3c.

[0066] The eccentricity e1, e2 in the present embodiment example (FIGS. 2a-3c) is constant, while the diameter D1, D2 of the rotor 4 becomes smaller in the direction of the outlet 12. That is, e1 and e2 are identical, while D1 is greater than D2. Embodiments are also comprised in which the diameter is constant, that is, D1 is identical to D2, and the eccentricity changes, that is, e1 is greater than e2. The effect when axially displacing varies accordingly.

[0067] FIG. 4 shows a modified embodiment example with respect to FIG. 1, wherein similar elements are labeled with the same reference numeral. In this respect, reference is made in full to the above description of the first embodiment example (FIG. 1). With respect to the geometry of the gap in the constriction 7, reference is made to FIGS. 2a through 3c.

[0068] In contrast to the first embodiment example, in the present embodiment example (FIG. 4) the adjusting device 39 is implemented so that the rotor 4 is axially displaceable, including the entire drivetrain 25, comprising the drive shaft 26, the gearbox 34, and the drive motor 36 in the present embodiment example. In this respect, the arrow 37 indicates that the drive motor 36 is also displaced. To this end, the housing 46 of the gearbox 34 is displaceably supported in a segment 48 of the inlet housing 14 opposite the inlet 10 of the stator 2, and is sealed off from the surrounding area by a seal 50.

[0069] A separate drive 52 is provided to this end for displacing the rotor 4 in the axial direction and can displace the drivetrain 25 by means of a spindle drive 54 (shown schematically only) so that the constriction 7 between the rotor 4 and the stator 2 is expanded. When necessary, the constriction 7 can be expanded far enough that a leakage gap S results in the region of the sealing line D between the rotor 4 and the stator 2. A pretension between the rotor 4 and stator 2 is typically not entirely relieved thereby, as the transported liquid exerts a counterpressure.

[0070] The drive 52 is preferably connected to a controller to this end by means of a signal line 56. The controller is preferably integrated in or connected to a controller 58, for example by means of the signal line 60. The controller preferably has an input interface, by means of which control or regulating data is input and is implemented for performing the controlling or regulating depending on said control or regulating data. For example, a specified volume or a difference between a specified volume and an actual volume can be input into the controller by means of said interface. The interface can thereby be a user interface or an interface for connecting a sensor or switch. The controller 58 serves to determine whether and to what degree the gap geometry should be changed, that is, the constriction 7 between the rotor 4 and stator 2 should be expanded. In the present embodiment example, the controller 58 is first connected to this end to a sensor 62 disposed in the stator 2. The sensor 62 is implemented as a temperature sensor and serves for capturing the temperature of the stator 2. It should be understood that the sensor 62 can also be disposed so as to capture the temperature of the rotor 4. To this end, the sensor 62 can either detect the outer surface of the rotor 4, or said sensor or an additional sensor can be disposed in the rotor 4. The controller 58 then determines, based on the temperature measured by the sensor 62, whether a threshold temperature has been reached and, based thereon, whether and to what degree the gap geometry should be modified. Said result is sent to the drive 52 in the form of an adjusting signal via the lines 60 and 56, so that the drivetrain 25 is displaced in order to expand the constriction 7 between the rotor 4 and stator 2.

[0071] In the present embodiment example (FIG. 4), the progressive cavity pump 1 further comprises a fill level sensor 64 for determining the fill level of liquid at the inlet 10 of the stator 2. Said sensor 64 is also connected to the controller 58. The controller 58 determines a displacement of the rotor 4 relative to the stator 2 on the basis of the received fill level and sends a corresponding signal to the drive 52 for adjusting the drivetrain 25.

[0072] The progressive cavity pump 1 according to the present embodiment example (FIG. 4) further comprises a flow rate sensor 66 measuring a flow rate of liquid through the stator 2. Said sensor 66 is also connected to the controller 58, and the controller 58 determines the flow rate or flow volume per revolution on the basis of the signal from the sensor 66 and the speed of the rotor 4. If said flow rate is low, this indicates that a relatively large amount of gas is being transported, whereby the friction between the rotor 4 and the stator 2 is increased and the cooling is simultaneously reduced. This typically leads to increased material expansion and in turn to increased pretension between the rotor 4 and stator 2 and consequently to increased wear. Adjusting the gap geometry is then preferable. A pressure sensor 66 can also be provided in place of the flow rate sensor 66, allowing pressure regulating by means of adjusting the constriction between the rotor and stator. By means of such a pressure sensor, the maintaining of a minimum pressure or a maximum pressure can also be regulated or controlled by means of adjusting the constriction. It should be fundamentally understood that such a pressure sensor can also be provided in addition to the flow rate sensor 66. The pressure sensor can also be disposed in the region of the stator or on the inlet side.

[0073] It should be understood that embodiments are also preferred in which only one of the three sensors 62, 64, 66 is present. It should be further understood that the controller 58 can also be integrated in the controller of the drive 52 and/or in the controller of the drive motor 36.

[0074] FIG. 5 shows a further embodiment example, fundamentally similar to the embodiment example of FIG. 4. Identical and similar elements are labeled with identical reference numerals, so that full reference is made to the description above. It should be understood that the sensors 62, 64, 66, described with respect to FIG. 4, can also be used in the embodiment examples of FIGS. 1, 5, 6, and 7, separately or in combination.

[0075] According to the present embodiment example (FIG. 5), the rotor 4 in turn is disposed displaceably to the stationary stator 2. In the present embodiment example, however, the drive motor 36 is also stationary and not displaceable. Overall, the drive shaft 26, in turn, is connected to the drive shaft 32 of the drive motor 36 by means of a Cardan joint 30. In order to allow displacing the rotor 4 and drive shaft 26, the drive shaft 32 is axially displaceably supported in the output gear 68 of the gearbox 34. The gear 68 is coupled to the output shaft 32 by means of an axially displaceably shaft-hub connection. The gearbox 34 is thus equipped with a gear 68 implemented as a hollow shaft, in which the shaft 32 can be displaced. The output shaft 32 in turn is guided through a seal 70 so that no liquid can penetrate from the drive inlet housing 14 into the gearbox 34. A drive 52 (see FIG. 4) can in turn be disposed at an outer segment 72 of the output shaft 32 for axially displacing the output shaft 32 and consequently the rotor 4.

[0076] A further embodiment modified with respect thereto is shown in FIG. 6. Identical and similar elements are again labeled with identical reference numerals, so that full reference is made to the description above.

[0077] In the embodiment example according to FIG. 6, the rotor 4 is also displaceable, while the stator 2 is stationary and received in the inlet housing 4 and the outlet housing 20. According to the present embodiment example, the drive shaft 26 is implemented in two parts and comprises a first part 74 and a second part 76. The two parts 74, 76 are inserted in each other in a telescopic manner and an expansion member 80 is implemented in a recess 78 in the first element 74 between the two parts 74, 76. The expansion member 80 serves for allowing the axial length of the drive shaft 26 to be adjusted by displacing the second part of the shaft 76 relative to the first part of the shaft 74. By expanding the expansion member 80 or contracting the expansion member 80, displacing of the rotor 4 is made possible.

[0078] It is conceivable to implement the expansion member 80 as a passive expansion member, particularly as a hydraulic member. A hydraulic member serves for maintaining approximately constant pretension between the rotor 4 and the stator 2, so that the preload force acting on the rotor 4 is substantially constant. When the material of the stator 2 and/or of the rotor 4 expands, it is thus possible for the rotor 4 to deflect to the left with respect to FIG. 4 and is compensated for by means of the hydraulic member in the expansion member 80. Excessive wear is thereby also prevented, just as by actively adjusting the rotor 4 and/or stator 2 by means of a drive. The pressure acting in the hydraulic member can then be adapted to the pump pressure.

[0079] FIG. 7 finally shows an embodiment example of the progressive cavity pump 1 in turn allowing displacing of the rotor 4 relative to the stator 2. In the present embodiment example, the drive shaft 26 in turn is implemented as a single part, as in the first three embodiment examples of FIGS. 1, 4, and 5. The drive shaft 26 is connected to the drive shaft 32 by means of a Cardan joint 30.

[0080] In the embodiment example according to FIG. 7, the shaft stub 82 connecting the Cardan joint 28 to the rotor 4 is implemented in two parts and comprises a first part 84 rigidly connected to the rotor 4 and a second part 86 connected to the Cardan joint 28. The parts 84 and 86 are inserted into each other telescopically and an expansion member 80, corresponding to the expansion member 80 according to FIG. 4, is implemented in the part 84. Said expansion member 80 can in turn be active or passive, for example, passive in the form of a hydraulic member. Alternatively, it can also be provided that a drive acts on the end face 88 of the rotor 4 and axially displaces the rotor 4.

[0081] FIG. 8 shows an example of a sequence of a method for operating a progressive cavity pump according to one of the preferred embodiments of a progressive cavity pump described above according to one of the embodiment examples 1 through 7. In step 100, the progressive cavity pump 1 is started and the rotor 4 is induced to rotate. Step 102 indicates transporting liquid from the inlet 10 to the outlet 12 of the stator 2 by rotating the rotor 4. During the present step of transporting 102, the temperature of the stator 2 is measured in step 104 by means of a temperature sensor.

[0082] Said measured temperature is compared with one or more threshold values in step 106. In step 108, it is then determined whether the threshold value, or which of the plurality of threshold values, has been exceeded, and if no threshold value has been exceeded, or the pretension, that is, the axial position of the rotor relative to the stator and thus the gap geometry, that is, the geometry of the restriction 7, matches the threshold value determined in step 106, then in step 108 the decision is made to continue to transport liquid, and to return to step 102. Otherwise, in step 110 a corresponding pretension is set. After the gap geometry has optionally been newly adjusted in step 110, the sequence can return to step 102.

[0083] It is conceivable, for example, that the temperature measured in step 104 is determined relative to a plurality of threshold values in step 106, wherein each threshold value represents an equivalent to a relative axial position of the rotor 4 and stator 2 to each other. In step 110, the corresponding axial position provided for the threshold value determined in 106 is then set. At the same time, liquid continues to be transported in step 102.

[0084] Fundamentally, at the beginning of a transport procedure, that is, prior to starting the rotational motion of the rotor relative to the stator, the constriction between the rotor and stator is expanded far enough that no or only a low transport rate takes place due to the internal leakage. The construction is then contracted according to a time-limited startup procedure of about 1.5 seconds, until a desired transport rate or a desired transport pressure is thus achieved.