Method and device for casting a rotor of a compressor, vacuum pump and/or expander device with a longitudinal axis

Abstract

The device according to any of the preceding claims 13 to 19, characterized in that the device is further configured to carry out a method comprising the step of positioning the green sand mold (3), wherein the device is provided with levelling means configured to hold an upper side of the green sand mold (3) during step c in a parallel position in relation to a gravitationally horizontal plane.

Claims

1. A method for casting a rotor (2) with a longitudinal axis (15) for a compressor, vacuum pump and/or expander device, wherein the method comprises the following steps: a. the formation of a green sand mold (3) with a cavity (4), wherein the cavity (4) is configured to contain a core (5) with a mold cavity (6), wherein a surface of the mold cavity (6) is configured to form the rotor (2) in such a way that a longitudinal axis of the mold cavity (6) coincides with the longitudinal axis (15) of the rotor (2) formed in the mold cavity(6); b. inserting the core (5) into the cavity (4); and c. pouring molten casting material into the mold cavity (6) through an inlet (7) of the core (5), and filling the mold cavity (6) completely or almost completely with casting material to form the rotor (2), wherein, the cavity (4) is held in a tilted position by tilting means (16) during step c, with the longitudinal axis of the mold cavity (6) tilted in relation to a gravitationally vertical direction and in relation to a gravitationally horizontal plane.

2. The method according to claim 1, wherein during step c the longitudinal axis of the mold cavity (6) is tilted in relation to a gravitationally horizontal plane over an angle of at least 5°.

3. The method according to claim 1, wherein during step c the longitudinal axis of the mold cavity (6) is tilted in relation to a gravitationally horizontal plane over an angle of at most 45°.

4. The method according to claim 1, wherein the cavity (4) is held in the tilted position during step c in such a way that in relation to the inlet (7) the mold cavity (6) extends upwards with respect to the gravitationally vertical direction.

5. The method according to claim 1, wherein during step c the angle over which the longitudinal axis of the mold cavity (6) is tilted in relation to a gravitationally vertical direction and in relation to a gravitationally horizontal plane is fixed by blocking means.

6. The method according to claim 1, wherein the cavity (4) is held in the aforementioned tilted position during step b.

7. The method according to claim 6, wherein the cavity (4) is formed during step a in the aforementioned tilted position in the green sand mold (3).

8. The method according to claim 1, wherein the green sand mold (3) with the cavity (4) is formed during step a by casting and pressing green sand on a mold plate (18), which the mold plate (18) is provided with a protruding pattern (19) configured to form the cavity (4) in the green sand mold (3).

9. The method according to claim 8, wherein the mold plate (18) comprises several flat plates tilted in relation to each other, at least one of these flat plates being provided with the protruding pattern (19) and tilted in relation to a gravitationally horizontal plane at an angle corresponding to the aforementioned tilted position.

10. The method according to claim 1, wherein the method is carried out on an automatic mold line.

11. The method according to claim 1, wherein before step c the molten casting material is filtered through a metal filter (17).

12. The method according to claim 1, wherein the method further comprises the step of positioning the green sand mold (3), whereby an upper side of the green sand mold (3) is held during step c by levelling means in a parallel position with a gravitationally horizontal plane.

13. A device for casting a rotor (2) with a longitudinal axis (15) for a compressor, vacuum pump and/or expander device, wherein the device has been configured to perform a method that comprises the following steps: a. the formation of a green sand mold (3) with a cavity (4), wherein the cavity (4) is configured to contain a core (5) with a mold cavity (6), wherein a surface of the mold cavity (6) is configured to form the rotor (2) in such a way that a longitudinal axis of the mold cavity (6) coincides with the longitudinal axis (15) of the rotor (2) formed in the mold cavity(6); b. inserting the core (5) into the cavity (4); and c. pouring molten casting material into the mold cavity (6) through an inlet (7) of the core (5), and filling the mold cavity (6) completely or almost completely with casting material to form the rotor (2), wherein the device comprises the green sand mold with the cavity and the device is provided with tilting means (16) configured to hold the cavity (4) in a tilted position during step c with the longitudinal axis of the mold cavity (6) in relation to a gravitationally vertical direction and in relation to a gravitationally horizontal plane.

14. The device according to claim 13, wherein the device is provided with blocking means in order to fix, during step c, the angle over which the longitudinal axis of the mold cavity (6) is tilted in relation to a gravitationally vertical direction and in relation to a gravitationally horizontal plane.

15. The device according to claim 13, wherein the device is configured to hold the cavity (4) in the aforementioned tilted position during step b and that the cavity (4) is formed during step a in the aforementioned tilted position in the green sand mold (3).

16. The device according to claim 13, wherein the device is configured in such a way that the green sand mold (3) with the cavity (4) is formed during step a by casting and pressing green sand on a mold plate (18), which the mold plate (18) is provided with a protruding pattern (19) configured to form the cavity (4) in the green sand mold (3).

17. The device according to claim 16, wherein the mold plate (18) comprises several flat plates tilted in relation to each other, at least one of these flat plates being provided with the protruding pattern (19) and tilted in relation to a gravitationally horizontal plane at an angle corresponding to the aforementioned tilted position.

18. The device according to claim 13, wherein the device is carried out as an automatic mold line.

19. The device according to claim 13, wherein the device is provided with a metal filter (17) configured to filter the molten casting material before step c.

20. The device according to claim 13, wherein the device is further configured to carry out a method comprising the step of positioning the green sand mold (3), wherein the device is provided with levelling means configured to hold an upper side of the green sand mold (3) during step c in a parallel position in relation to a gravitationally horizontal plane.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) To better demonstrate the characteristics of the invention, the following describes, by way of example without any restrictive character, a number of preferred embodiments of the method and the device according to the invention, with reference to the accompanying drawings, in which:

(2) FIG. 1a shows a conventional device for horizontal casting of a rotor for a compressor, vacuum pump and/or expander device;

(3) FIG. 1b shows a conventional device for vertical casting of a rotor for a compressor, vacuum pump and/or expander device;

(4) FIG. 2a shows a device according to the invention for casting a rotor of a compressor, vacuum pump and/or expander device with a longitudinal axis;

(5) FIG. 2b shows a variant of the device in FIG. 2a;

(6) FIG. 3 shows a variant of the device in FIGS. 2a and 2b;

(7) FIG. 4a-4c show a device according to the invention for casting a rotor of a compressor, vacuum pump and/or expander device with a longitudinal axis.

DETAILED DESCRIPTION OF THE INVENTION

(8) A conventional device 1 for horizontal casting of a rotor 2 of a compressor, vacuum pump and/or expander device in a green sand mold 3 is shown in FIG. 1a.

(9) In this green sand mold 3 a cavity 4 is formed and this cavity 4 is configured to contain a core 5 with a mold cavity.

(10) When horizontally casting the rotor 2, molten casting material is casted through an inlet 7 of the core 5 into the mold cavity 6, and the mold cavity 6 is filled completely or almost completely with casting material to form rotor 2 in the mold cavity 6.

(11) The green sand mold 3 and or core 5 can comprise several separate parts. Typically, green sand mold 3 consists of two halves 8, 9, with the cavity 4 extending along both sides of a sub plane between these two halves 8, 9.

(12) The green sand mold 3 is provided with a casting device 10 which includes a casting channel 11 with a casting funnel 12 on the outside of the green sand mold 3 and a feed chute 13 on the inlet 7 of the core 5, along which casting device 10 can direct molten casting material to and into the inlet 7 of the core 5.

(13) The green sand mold 3 is also provided with a riser 14, along which molten casting material can leave the mold cavity 6, and where a reservoir of molten casting material can form when the mold cavity 6 is completely or almost completely filled with casting material. When the rotor 2 solidifies in the mold cavity 6, the rotor 2 will shrink, as a result of which molten casting material from the reservoir of the riser 14 is sucked back to and into the mold cavity 6. In this way, the formation of holes in the cast rotor 2 which are not filled with casting material during the solidification of the rotor 2 is avoided or at least reduced.

(14) The term ‘horizontal casting’ implies that when the mold cavity 6 is completely or almost completely filled with casting material and consequently the rotor 2 is formed in the mold cavity 6, the longitudinal axis 15 of the formed rotor 2 lies in a gravitationally horizontal plane.

(15) Due to the more or less complex geometry of a rotor of a compressor, vacuum pump and/or expander device and the positioning of a single riser 14 in FIG. 1a, it can clearly be deduced that impurities and/or inhomogeneities can only to a limited extent be removed from the mold cavity 6 by flotation on the upper surface of molten casting material via riser 14. A large part of these impurities and/or inhomogeneities will end up in a gravitationally vertical direction in relation to the upper part of the mold cavity 6, where they will be trapped as contamination in the formed rotor 2 during solidification. This contamination can have a negative influence on surface quality and/or mechanical properties and/or a balanced distribution of weight around the longitudinal axis 15 of the formed rotor 2 as final product.

(16) A conventional device 1 for horizontal casting of a rotor 2 of a compressor, vacuum pump and/or expander device in a green sand mold 3′ is shown in FIG. 1b.

(17) In addition to core 5, the resin bonded sand mold 3′ in the direction of the longitudinal axis 15 of the formed rotor 2 in the mold cavity 6 should now also include riser 14 according to its longest dimension, which implies a loss of useful space for core 5 in the resin bonded sand mold 3′ and consequently a waste of sand in the resin bonded sand mold 3′.

(18) In addition, in this case a required length of the casting channel 11 in the resin bonded sand mold 3′ is greater than when casting a rotor 2 horizontally with the same dimensions as shown in FIG. 1a.

(19) FIG. 2a shows an embodiment of the device according to the invention.

(20) The green sand mold 3 is hold in a tilted position during the casting of the rotor 2 together with a core 5 in cavity 4 by tilting means 16, wherein the longitudinal axis 15 of the finally formed rotor 2 is tiled in relation to a gravitationally vertical direction and in relation to a gravitationally horizontal plane. The mold cavity 6 extends upwards with respect to the inlet 7 in a gravitationally vertical direction.

(21) Tilting means 16 is typically an elevating support on which the green sand mold 3 is placed along one of its sides, as shown in FIG. 2a, or a lifting device configured to lift the green sand mold 3 along one side. It is of course not excluded that the tilting means 16 consists of a sand mold 3 in which a ground plane of this sand mold 3 is parallel to a gravitationally horizontal plane and the sub plane between the halves 8, 9 is tilted in relation to a gravitationally horizontal plane.

(22) In this case, the sub plane between halves 8, 9 of the green sand mold 3 and the core 5 are tilted in relation to a gravitationally horizontal plane at an angle of 15°.

(23) This angle can be fixed by blocking means, which in this case coincide with the tilting means 16.

(24) The feed chute 13 can optionally be fitted with a metal filter 17. This metal filter 17 is typically made of a ceramic foam. The use of a metal filter 17 just before the inlet 7 has the following advantages: the reduction of a turbulent flow of molten casting material coming from the casting channel 11 before it is fed into the inlet 7 of the core 5, allowing a homogeneous filling of the mold cavity 6, thus reducing or even preventing the formation of inhomogeneities and/or erosion in the mold cavity 6; the removal of impurities in the molten casting material coming from the casting channel 11, which results in a better surface quality and/or mechanical properties and consequently a lower rejection rate of the formed rotors 2. simplifying the casting device 10, since a trap for metal slag or a change in the feed chute 13 is no longer required to provide the inlet to core 5 with a laminar flow of pure molten casting material.

(25) FIG. 2b shows a variant of the device in FIG. 2a.

(26) In this case, the sub plane between halves 8, 9 of the green sand mold 3 and the core 5 are tilted in relation to a gravitationally horizontal plane at an angle of 45°.

(27) Comparison of the devices in FIGS. 2a and 2b clearly shows that a required length of the casting channel 11 must be greater when, during the casting of rotor 2, the angle at which the sub plane between halves 8, 9 of the green sand mold 3 and the core 5 are tilted in relation to a gravitationally horizontal plane is greater.

(28) Furthermore, it is clear that from a certain value for this angle it is no longer possible to orient a connection between riser 14 and an exterior of green sand mold 3 in a gravitationally vertical direction, so that a maximum pressure height to be reached in a gravitationally vertical connection between riser 14 and the exterior of green sand mold 3 can inevitably not be reached.

(29) With regard to the devices shown in FIGS. 2a and 2b, it cannot of course be excluded that during the casting of rotor 2, the green sand mold 3 and the core 5 are tilted in relation to a gravitationally horizontal plane at an angle with a different value, as long as the green sand mold 3 does not collapse under the static pressure and/or impact of the molten material in the mold cavity 6 and as long as impurities and/or inhomogeneities accumulated by flotation on the upper surface of molten casting material in the mold cavity 6 are removed from the mold cavity 6 via the riser 14.

(30) FIG. 3 shows a variant of the device in FIGS. 2a and 2b.

(31) In this case, during the casting of rotor 2, only core 5 is held in the tilted position, while an upper side of green sand mold 3 remains horizontally oriented by levelling means in relation to a gravitationally horizontal plane.

(32) In the simplest case, the levelling means is simply a correct orientation of an underside of green sand mold 3, in other words a side on which the green sand mold 3 rests. It is not excluded that the levelling means consists of an elevating support on one side of green sand mold 3 or a lifting device configured to lift the green sand mold 3 on one side.

(33) In this device, the required length of the casting channel 11 is independent of the angle at which the core 5 is tilted in relation to a gravitationally horizontal plane.

(34) In addition, the orientation of the connection between the riser 14 and the exterior of the green sand mold 3 can always be chosen according to a gravitationally vertical direction, so that the maximum pressure height to be reached in riser 14 can now be achieved.

(35) FIGS. 4a-4c illustrate a method for casting a rotor 2 of a compressor, vacuum pump and/or expander device.

(36) In step a the cavity 4 is formed in the green sand mold 3, wherein the cavity 4 is configured to contain the core 5 with the mold cavity 6.

(37) In this case, the cavity 4 is already formed in the tilted position during step a. The cavity 4 is formed in this step by casting and pressing a green sand on a mold plate 18, with the mold plate 18 having a protruding pattern 19 configured to form the cavity 4 in the green sand mold 3.

(38) The mold plate 18 in this case has a geometry that includes several flat plates tilted relative to each other. In this case, the cavity 4 is formed in green sand mold 3 by means of a protruding pattern 19 on at least one of these flat plates, with this flat plate tilted at an angle corresponding to the aforementioned tilted position of the cavity 4. The other flat plates of the mold plate 18 are configured to form the rest of the green sand mold 3 and are preferably largely parallel to a gravitationally horizontal plane. The geometry of mold plate 18 with flat plates tilted in relation to each other means that a sub plane 20 of the formed green sand mold 3 will not be flat in one direction but broken flat.

(39) In the next step b, the core 5 with the mold cavity 6 is placed in the cavity 4.

(40) During this step b, in this case also the casting channel 11, the feed chute 13 and the riser 14 are formed in green sand mold 3. The metal filter 17 is also placed in the feed chute 13.

(41) However, it is not excluded that the forming of the casting channel 11, the feed chute 13 and the riser 14 in the green sand mold 3 and/or the installation of the metal filter 17 in the feed chute 13 already takes place during step a.

(42) After forming the cavity 4 into the green sand mold 3 in step a and placing the core 5 into the cavity 4, in a subsequent step c the rotor 2 is cast and formed from molten casting material. To this end, in this step c, through an inlet 7 of the core, 5 molten casting material is casted into the mold cavity 6, and the mold cavity 6 is completely or almost completely filled with casting material to form the rotor 2.

(43) Optionally, the core 5 can be provided with a second inlet 21 through which additional molten casting material can be guided to and into the mold cavity 6 during the solidification and shrinking of the formed rotor 2 in the mold cavity 6.

(44) This invention is by no means limited to the embodiments described by way of example and shown in the drawings, but a method and device according to the invention for casting a rotor of a compressor, vacuum pump and/or expander device with a longitudinal axis can be realized in all kinds of variants without going beyond the scope of the invention.