Centrifugal pump unit and method for moving a valve element in a pump unit

Abstract

A centrifugal pump assembly includes an electric drive motor (6, 8), a driven impeller (14) and a pump casing (2) which surrounds the impeller (14). A movable element (24; 24′) is arranged a valve element. A section of the valve element is movable from a released position into a bearing position, fixed on a contact surface (60), by pressure which is produced by the impeller in the pump casing. A control device (64) moves the valve element from one switching position into another switching position and reduces the speed of the drive motor. Upon pressure in the pump casing dropping such that the valve element is no longer fixed on the contact surface and the valve element has been moved into the other switching position, the control device increases the speed of the drive motor again. A method for moving a valve element is provided.

Claims

1. A centrifugal pump assembly comprising: an electric drive motor; an impeller which is driven by the electric drive motor; a pump casing which surrounds the impeller; a movable valve element arranged such that the valve element is movable between a first switching position and a second switching position by way of a flow which is produced by the impeller, wherein at least one section of the valve element is movable from a released position into a bearing position, in which the at least one section of the valve element is fixed on a contact surface, by way of pressure which is produced by the impeller in the pump casing; a control device which is configured such that for moving the valve element from the first switching position into the second switching position, the control device reduces the speed of the drive motor and, when the pressure in the pump casing has dropped to such an extent that the valve element is no longer fixed on the contact surface and the valve element has been moved into the second switching position, the control device increases the speed of the drive motor again.

2. A centrifugal pump according to claim 1, wherein the valve element and the contact surface are configured such that in the bearing position, the valve element is prevented from a movement between the first switching position and the second switching position by way of the fixation on the contact surface, and in the released position the valve element is movable between the first switching position and the second switching position.

3. A centrifugal pump according to claim 1, wherein the control device is configured such that for moving the valve element from the first switching position into the second switching position, the control device switches off the drive motor and, when the pressure in the pump casing has dropped to such an extent that the valve element is no longer fixed on the contact surface and the valve element has been moved into the second switching position, the control device switches the drive motor on again.

4. A centrifugal pump according to claim 1, wherein the control device is configured such that the control device increases the speed of the drive motor again after a predefined time interval.

5. A centrifugal pump according to claim 1, further comprising a position sensor detecting the switching position of the valve element and signal-connected to the control device, wherein the control device is configured such that the control device increases the speed of the drive motor again when the position sensor signals that the second switching position has been reached.

6. A centrifugal pump according to claim 1, wherein the drive motor and the control device are configured such that on starting up the drive motor, the impeller produces an adequate pressure for moving the section of the valve element into the bearing position, more quickly than producing a flow for moving the valve element into to the second switching position.

7. A centrifugal pump according to claim 1, wherein the drive motor and the control device are configured such that on switching off the drive motor, the pressure which holds the section of the valve element in the bearing position reduces more quickly than a flow for moving the valve element into the second switching position.

8. A centrifugal pump according to claim 1, wherein the control device is configured such that for switching the valve element from the first switching position into the second switching position, the control device switches off the drive motor for a first predefined time interval and for switching from the second switching position into the first switching position the control device switches off the drive motor for a second predefined time interval which is longer than the first time interval.

9. A centrifugal pump according to claim 1, wherein the control device and the drive motor are configured such that the drive motor is only operable in a predefined rotation direction.

10. A centrifugal pump according to claim 1, wherein the control device and the drive motor are configured for operation of the drive motor without a speed adjustment.

11. A centrifugal pump according to claim 1, wherein the control device is configured to change a speed of the drive motor.

12. A centrifugal pump according to claim 1, wherein the pump casing comprises at least one connection and the valve element is configured such that in at least two switching positions of the valve element, the valve element opens at least one flow path through the at least one connection to a differently wide extent.

13. A centrifugal pump according to claim 12, wherein the valve element is configured such that in the first switching position, the valve element releases a flow path through a first connection and in the second switching position, the valve element releases a flow path through a second connection.

14. A centrifugal pump according to claim 1, wherein the valve element is rotatably mounted in the pump casing such that the valve element is rotatingly movable between the first and second switching positions.

15. A centrifugal pump according to claim 1, wherein the valve element comprises at least one flow engagement surface, upon which the flow which is produced by the impeller acts for moving the valve element.

16. A centrifugal pump according to claim 1, wherein the valve element comprises a restoring means configured such that given a standstill of the impeller when no flow acts upon the valve element, the restoring means moves the valve element into a predefined switching position.

17. A centrifugal pump according to claim 1, further comprising a force generating means which subjects the valve element or the at least one section of the valve element to a force to move the valve element or at least one section of the valve element out of the bearing position into the released position.

18. A centrifugal pump according to claim 1, wherein the control device comprises as least one signal input or a sensor, from which the control device receives at least one switching signal, and the control device is configured such that on receiving the switching signal, the control device controls the drive motor such that the valve element is moved from the first switching position into the second switching position.

19. A centrifugal pump according to claim 18, further comprising an electronics housing, wherein the control device is arranged in the electronics housing and the sensor for producing the switching signal is arranged in the electronics housing, wherein the sensor is a magnet sensor configured to detect a displacement of a magnetic field which is produced outside the electronics housing.

20. A method for moving a valve element which is arranged in a centrifugal pump assembly, said valve element being arranged and configured such that the valve element is movable from a first switching position into a second switching position by way of a flow which is produced by the impeller of the centrifugal pump assembly and that at least one section of the valve element is movable from a released position into a bearing position, in which the at least one section of the valve element is fixed on a contact surface, by way of pressure which is produced by the impeller, the method comprising the steps of: reducing the speed or switching off a drive motor, by which means the pressure at the outlet side of the impeller is reduced to such an extent that the valve element or the at least one section of the valve element gets into the released position and the valve element is moved from a first switching position into a second switching position by way of the flow which is produced by the impeller; increasing the speed or switching on the drive motor, so that the pressure at the outlet side of the impeller is increased to such an extent that the valve element or the at least one section of the valve element is moved into the bearing position.

21. A method according to claim 20, wherein the valve element in the bearing position is prevented from a movement between the first switching position and the second switching position by way of the fixation on the contact surface.

22. A method according to claim 20, wherein for moving the valve element out of the second switching position and into the first switching position, the drive motor is switched off for so long until the flow at the outlet side of the impeller has died away, so that the valve element is moved back into the first switching position by a restoring element and the drive motor is subsequently brought into operation such that pressure which moves the valve element or the at least one section of the valve element into the holding position builds up at the outlet side of the impeller, before a flow which would move the valve element into the second switching position builds up.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a perspective view of a centrifugal pump assembly according to the invention;

(3) FIG. 2 is a perspective exploded view of the centrifugal pump assembly according to FIG. 1;

(4) FIG. 3 is a plan view upon the opened pump casing of the centrifugal pump assembly according to FIGS. 1 and 2, with a valve element in a first switching position;

(5) FIG. 4 is a view according to FIG. 3, with the valve element in a second switching position;

(6) FIG. 5 is a plan view upon the face side of the centrifugal pump assembly according to FIGS. 1 to 4;

(7) FIG. 6 is a sectioned view of the centrifugal pump assembly according to FIG. 5, along the line A-A in FIG. 5, with the valve element in a bearing position;

(8) FIG. 7 is a sectioned view according to FIG. 6 with the valve element in a released position;

(9) FIG. 8 is a lateral view of the centrifugal pump assembly according to FIGS. 1 to 7;

(10) FIG. 9 is a sectioned view of the centrifugal pump assembly according to FIG. 8 with a flow sensor in a first position;

(11) FIG. 10 is a sectioned view according to FIG. 9 with a flow sensor in a second position;

(12) FIG. 11 is a perspective view of the valve element 24 of the centrifugal pump assembly according to FIGS. 1 to 10;

(13) FIG. 12 is a schematic circuit diagram of a heating facility with a centrifugal pump assembly according to FIGS. 1 to 11; and

(14) FIG. 13 is a perspective exploded view of a centrifugal pump assembly according to a second embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

(15) Referring to the drawings, a centrifugal pump assembly which is shown in FIGS. 1 to 11 is provided for installation into a hydraulic block, i.e. into a hydraulic construction unit for a heating facility, in particular a compact heating facility as is schematically shown in FIG. 12. The centrifugal pump assembly comprises a pump casing 2 with a motor casing 4 which is attached to this. In the known manner, an electrical drive motor, consisting of a stator 6 and a rotor 8 is arranged in the motor housing 4. The shown drive motor is configured as a wet-running electrical drive motor, concerning which the rotor space, in which the rotor 8 rotates, is separated from the surrounding stator space, in which the stator 6 is situated, by way of a can pot or can 10. The rotor 8 is connected to an impeller 14 in a rotationally fixed manner via a rotor shaft 12. A terminal box 16 which contains the electric connections as well as necessary electric and electronic components for activating the drive motor is arranged on the outer side of the motor housing 4.

(16) The pump casing 2, in which the impeller 14 rotates, comprises two suction connections 18 and 20, as well as a delivery connection 22. A rotatable valve element 24 which in this embodiment example is configured in a drum-like manner is arranged in the inside of the pump casing 2. The valve element 24 serves for selectively creating a flow connection from one of the suction connections 18, 20 to the suction port 26 of the impeller 14.

(17) The valve element 24 is formed by a pot-like lower part 28 and a cover 30. Both are fixedly connected to one another. The cover 30 centrally comprises an opening with an annular collar, said collar forming an inlet branch or stub 32 which engages into the suction port 26 of the impeller 14. The lower part 28 is fastened on a bearing sleeve 34. This sleeve could also be configured as one piece with the lower part.

(18) The bearing sleeve 34 is supported on the base of the pump casing 2 via a spring 36 which is configured as a compression spring. The spring 36 hence presses the valve element 24 into the released position which is shown in FIG. 7. The bearing sleeve 34 is moreover rotatably mounted on a bearing bolt 46 which, departing from the base extends in the direction of the longitudinal axis X into the inside of the pump casing 2. The bearing bolt 76 engages into a hole which in the bearing sleeve 34 extends in the longitudinal direction, so that the bearing sleeve 34 is slidingly mounted on the bearing bolt 46. The bearing bolt 46 is firmly fixed in the base of the pump housing 2. Apart from the rotational movement, the bearing sleeve 34 can also slide on the bearing bolt 46 in the longitudinal direction X when the valve element 24 is displaced from the released position which is shown in FIG. 7, into the bearing position which is shown in FIG. 6. The mounting of the bearing sleeve 34 on the bearing bolt 46 in this embodiment permits a rotation movement as well as an axial movement.

(19) The valve element 24 in its lower part 28 comprises a switching opening 48 as can be seen in FIGS. 3 and 4. The cover 30 is removed in the representations in FIGS. 3 and 4. The switching opening 48 lies in the base surface of the lower part 28 which extends transversely to the longitudinal or rotation axis X. The switching opening 48 herein lies radially distanced to the rotation axis X, so that it moves into another angular position on rotation of the valve element 24 about the rotation axis X on an arcuate path. FIG. 3 shows the first switching position of the valve element 24, at which switching position the switching opening 48 overlaps an inlet opening 50 in the base of the pump casing 2. The inlet opening 50 is in flow connection with the suction connection or suction branch 20. In the second switching position of the valve element which is shown in FIG. 4, the switching opening 48 overlaps with the inlet opening 52 which is in flow connection with the suction connection 8. Furthermore, a restoring element in the form of a weight 54 is arranged or formed on the base of the lower part 28. The weight 54 is likewise arranged in a manner distanced to the rotation axis X, so that it can produce a torque about the rotation axis X. The weight 54 is placed such that in the first switching position which is shown in FIG. 3, it lies at the bottom in the represented, envisaged installation position of the pump assembly. The rotation axis X is always extends horizontally in the case of the specified installation position. If the valve element 24 is rotated into the second switching position which is shown in FIG. 4, then the weight 54 is lifted, so that a restoring torque is produced upon the valve element 24, and this seeks to move the valve element 24 back into the first switching position.

(20) The valve element 24 on its outer side comprises a stop element 56 in the form of a projection or rib, which extends away from the base 28 in a manner parallel to the longitudinal axis X. This stop element 56, in the second switching position which is shown in FIG. 4, comes into contact with a second stop element 58 in the form of a firm rib in the inside of the pump casing 2. The rotation movement of the valve element 24 is therefore limited, so that it cannot be rotated beyond the second switching position which is shown in FIG. 4.

(21) Apart from the movement between the two switching positions, the valve element 24, as specified, can carry out an axial movement along the longitudinal axis X, as is shown in FIGS. 6 and 7. In FIG. 6, the valve element 24 is situated in a bearing position, in which it is pressed into bearing contact with the pump casing 2 by way of the outlet-side pressure which is produced by the impeller 14. The pressure which is produced by the impeller 14 acts upon the surface of the cover 30 which faces the impeller. The suction-side pressure of the centrifugal pump assembly acts on the rear side of the cover 30, in the inside of the valve element 24. A differential force which acts against the spring 36 therefore results, and, if the pressure is adequately high, presses the valve element 24 into the bearing position which is shown in FIG. 6. Herein, the lower part 28 comes into sealing contact on an annular shoulder 60 in the inside of the pump casing. The suction side is therefore sealed with respect to the delivery side by way of the valve element 24, and the valve element 24 is moreover fixed in the pump casing 2 in a non-positive manner, so that it cannot be rotated between the switching positions. If the speed of the drive motor and thus of the impeller 14 is reduced or the impeller 14 is at a standstill, then the fluid pressure which acts upon the cover 30 reduces, so that the pressure force reduces and the spring force of the spring 36 exceeds this pressure force again. In this condition, the valve element 24 moves into the released position which is shown in FIG. 7 and in which the lower part 28 of the valve element 24 lifts from the shoulder 60, is thus no longer non-positively held on the base of the pump casing 2 and can rotate freely between the switching positions. The spring 36 and the drive motor are matched to one another such that the drive motor produces a pressure which permits the force of the spring 36 to be overcome for displacing the valve element 24. The spring is simultaneously dimensioned such that when the pressure drops below a certain limit value, the valve element 34 can move into the released position which is shown in FIG. 6.

(22) As is shown in FIGS. 9 and 10, control electronics 62 which control the switching procedure by way of rotating the valve element 44 are located in the inside of the terminal box 16. Concerning the drive motor which is shown here, it is the case of a conventional unregulated asynchronous motor which is not activated via a frequency controller. I.e., an electronic speed change is not envisaged. In contrast, the control electronics 64 are preferably merely configured such that they can switch off the drive motor for certain time intervals in a targeted manner. The switching procedure of the valve element 24 is merely effected by way of switching off the drive motor for predefined time intervals. The switching position of the valve element 24 could also be detected instead of a pure time control, in order to determine or define the end of the respectively required time interval.

(23) In the initial position, the valve element 24 is situated in the first switching position which is shown in FIG. 3, since the weight 54 automatically rotates the valve element 24 into this position. The drive motor is configured such that when it is switched on, such a high pressure directly builds up in the peripheral region of the impeller 14 that the valve element 24 is pressed into the bearing position which is shown in FIG. 6 and is non-positively held in this position. I.e. in this condition, the impeller delivers fluid into the delivery connection 22 via the suction connection 20. If the control electronics 64 now switch off the drive motor for a short time interval which is selected such that the pressure in the peripheral region of the impeller 14 reduces to such an extent that the valve element 24 is moved by the spring 36 into the closed position, then the valve element 24 can be rotated into the shown second switching position. This is effected since the flow in the peripheral region of the impeller 14 and possibly in a connected hydraulic system does not immediately disappear, but a flow still remains in the pump casing for a certain time duration on account of the inertia of the delivered fluid. This flow acts upon the valve element 24, so that this is co-rotated with the flow in the rotation direction A, until the stop element 56 comes to abut on the second stop element 58 and the switching opening 48 covers the inlet opening 52. The control electronics 64 now switches the drive motor on again, by which means such a pressure is built up in a direct manner that the valve element 24 is pressed again into the bearing position, wherein the inlet opening 50 is closed by the base of the lower part 28. In this condition, the impeller 14 delivers fluid to the delivery connection 22 via the suction connection 18.

(24) The control electronics 64 switch off the drive motor for a second longer time interval in order to move the valve element 24 out of this second switching position into the first switching position again. This time interval is selected such that not only does the pressure in the peripheral region of the impeller 14 reduce, but also the annular flow dies down to such an extent that the torque which is created by the weight 54 becomes greater and the valve element 24 can rotate back again into its first switching position. Thereafter, the drive motor can then be taken into operation again, so that the valve element 24 is held in this switching position by way of the direct pressure build-up. For this switching procedure too, the control device can select a pure time control. Here too, it is alternatively possible to actually detect the switching position of the valve element 24.

(25) In this embodiment example, the control electronics 64 comprise a magnet sensor 66 which is situated close to the outer wall of the terminal box 16. This can produce a signal which initiates the control electronics 64 into switching over the switching positions. In this embodiment example, a pipe element 68, in which a movable sensor body 70 is arranged for detecting a flow is arranged on the outer side of the terminal box 16, close to the wall, on which the magnet sensor lies 66. If no flow runs through the pipe element 68, then the sensor body 70, held for example by a spring element, is located in the idle position which is shown in FIG. 9. A magnet 72 is arranged in the sensor body 70. In the idle position which is shown in FIG. 9, the magnet 70 does not lie opposite the magnet sensor 66 which for example can be a Reed contact. If now a flow arises in the pipe element 68 in the direction of the arrow S, then the sensor body 70 is displaced into the position which is shown in FIG. 10, by which means the magnet 72 comes into a position lying opposite the magnet sensor 66. The magnet sensor 66 detects the magnetic field of the magnet 72 and outputs a switching signal which can initiate the valve element 24 into switching over.

(26) The described centrifugal pump assembly can be applied for example in a heating system as is shown in FIG. 12. The heating system comprises two circuits, a heating circuit 74 which serves for heating a building, as well as a circuit 76 through a secondary heat exchanger 78 for heating service water. The heating circuit 74 as well as the second circuit 76 branch from an outlet of a primarily heat exchanger 80, said heat exchanger for example able to be formed by a gas heater. A centrifugal pump assembly 82 which corresponds to the preceding centrifugal pump assembly is arranged at the inlet side of the primary heat exchanger 80. The heat transfer medium flows into the primary heat exchanger 80 from the delivery connection 22 of the centrifugal pump assembly 82. The return of the heat circuit 74 is connected to the suction connection 20, whereas the return from the secondary heat exchanger 78 is connected to the suction connection 18. The described pipe element 68 with the flow monitor which is formed by the sensor body 70 lies in a flow path for the service water which is to be heated. If the centrifugal pump assembly is taken into operation in the first switching position, as described above, then it delivers the heat transfer medium in the circuit through the primary heat exchanger 80 and the heating circuit 74. If now service water flows through the pipe element 68, this leads to the described displacement of the sensor body 70, by which means the control electronics 64 recognizes a demand for the service water heating. This initiates the control electronics 64 into switching off the drive motor for a first shorter time interval, so that the valve element 24 rotates into the second switching position which is shown in FIG. 4. In this switching position, the control electronics 64 bring the drive motor back into operation after the completion of the time interval, so that the centrifugal pump assembly 82 then delivers the heat transfer medium through the second circuit 76 from the primary heat exchanger 80 through the secondary heat exchanger 78. If the centrifugal pump assembly is switched off again for a longer, i.e. second possible time interval by way of the control electronics 64 when there is no longer a demand for service water heating, then the valve element 24 moves back into the first switching position on account of gravity.

(27) A safety function which can prevent an overheating of the primary heat exchanger 80 can also be realized by this arrangement. If for example, in the heating circuit 74, all radiators valves are closed and heat is no longer taken, then this can be recognized by a temperature sensor. If, in this condition, the centrifugal pump assembly 82 is now briefly switched off, then the valve element 24 moves again into the second switching position. A circulation via the secondary heat exchanger 78 can then be maintained in this second switching position.

(28) Concerning the previously described embodiment example, the switching-over is effected via the valve element at the suction side of the impeller 14. However, a switching-over at the delivery side could also be effected in a corresponding manner. Such an example is shown in FIG. 13. Concerning this embodiment example, the pump casing 2′ comprises two delivery connections 22′ and merely one suction connection 18′. The valve element 24′ is configured in a pot-like manner and surrounds the impeller 14, so that the flow which is produced by the impeller 14 and the pressure which is produced by the impeller 14 acts in the inside of the valve element 24′. The valve element 24′ in the inside comprises an inlet stub (branch) 32′ which, as described above, is engaged with the suction port of the impeller 14. Again, a weight 54′ is arranged in the valve element 24′. Moreover, the valve element 24′ can be pressed by a spring 36 into a released position and be pressed into a position bearing on the pump casing 2′ by the pressure in the inside of the valve element 24′, against the spring force. The valve element 24′ comprises a switching opening 48′ in a rear wall or outer peripheral wall which in a switching position overlaps with an outlet opening 84, so that a flow path from the inside of the valve element 24′ to a first of the delivery connections 22′ is given. In the second switching position, the switching opening 48′ is brought to overlap with a second outlet opening 84, so that a flow path is opened to the second delivery connection 22′. The switching of the valve element 24′ between the switching positions is effected in the same manner as has been described above by way of the first embodiment example.

(29) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.