Vacuum pump with elastic spacer

Abstract

A vacuum pump includes a housing, a rotatable shaft extending in an axial direction within the housing, a first pumping arrangement including a first stator arrangement and a first rotor arrangement, and a second pumping arrangement including a second stator arrangement and a second rotor arrangement. The vacuum pump further includes a spacer arranged between the first pumping arrangement and the second pumping arrangement. The spacer is coupled between the first stator arrangement and the second stator arrangement and is configured to provide a defined elasticity in the axial direction allowing an elastic deformation of the spacer in the axial direction.

Claims

1. A vacuum pump, comprising: a housing; a rotatable shaft extending in an axial direction within the housing; a first pumping arrangement comprising a first stator arrangement and a first rotor arrangement, wherein the first stator arrangement is coupled with the housing, and the first rotor arrangement is coupled with and rotatable by the shaft to pump fluid when the first rotor arrangement is rotated with respect to the first stator arrangement; a second pumping arrangement comprising a second stator arrangement and a second rotor arrangement, wherein the second stator arrangement is coupled with the housing, and the second rotor arrangement is coupled with and rotatable by the shaft to pump fluid when the second rotor arrangement is rotated with respect to the second stator arrangement; a pump inlet through which gas can pass through the first pumping arrangement and the second pumping arrangement; and a spacer arranged between and abutting the first pumping arrangement and the second pumping arrangement, wherein: the spacer comprises a plurality of ribs and a plurality of openings, each opening separating two of the ribs, and the ribs are step-shaped; and the spacer is configured to provide a defined elasticity in the axial direction allowing an elastic deformation of the spacer in the axial direction, and the spacer is more elastic than the first stator arrangement and the second stator arrangement such that, in response to a force acting in the axial direction, the elastic deformation of the spacer in the axial direction is greater than an elastic deformation of the first stator arrangement and the second stator arrangement in the axial direction.

2. The vacuum pump of claim 1, wherein the spacer is provided as an axial spring element.

3. The vacuum pump of claim 1, wherein the spacer is configured to provide essentially the entire elasticity in the axial direction of all components in the vacuum pump coupled to the housing.

4. The vacuum pump of claim 1, wherein the spacer comprises an upper ring, a lower ring, and an elastic structure, and wherein: the upper ring is configured to abut against the first stator arrangement; the lower ring is configured to abut against the second stator arrangement; and the elastic structure is arranged in the axial direction between the upper ring and the lower ring and configured to provide the defined elasticity in the axial direction.

5. The vacuum pump of claim 4, wherein each rib comprises a first leg coupled with one end to the upper ring, a second leg coupled with one end to the lower ring, and a third leg coupled between the other ends of the first leg and the second leg.

6. The vacuum pump of claim 4, wherein the upper ring has a smaller diameter than the lower ring.

7. The vacuum pump of claim 1, comprising at least one of: the first stator arrangement and the second stator arrangement are coupled with the housing; the housing comprises an envelope and a body, wherein the first stator arrangement and the second stator arrangement are coupled with the envelope, and the body comprises a driving unit for rotating the shaft, and wherein the spacer is configured for positioning the first stator arrangement and the second stator arrangement while maintaining the envelope and the body in contact with each other.

8. The vacuum pump of claim 1, wherein the first pumping arrangement and the second pumping arrangement are arranged in series in the axial direction.

9. The vacuum pump of claim 1, wherein at least one of the first pumping arrangement and the second pumping arrangement is selected from the group consisting of: a turbomolecular pumping unit comprising one or more turbomolecular stages with each turbomolecular stage having a rotor and a stator; a molecular drag stage; a Gaede pumping mechanism; a Holweck pumping mechanism; and a Siegbahn pumping mechanism.

10. The vacuum pump of claim 1, wherein the pump inlet through which gas can pass through the first pumping arrangement and the second pumping arrangement is a first pump inlet, and further comprising a second pump inlet through which gas can pass only through the second pumping arrangement, wherein the spacer is arranged between the first pumping arrangement and the second pumping arrangement in proximity to the second pump inlet.

11. The vacuum pump of 1, wherein the spacer has a circumference orthogonal to the axial direction, the ribs have an arc length along the circumference, and the openings have an arc length along the circumference greater than the an arc length of the ribs.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following more detailed description of embodiments in connection with the accompanying drawing(s). Features that are substantially or functionally equal or similar will be referred to by the same reference sign(s). The illustration in the drawing is schematically.

(2) FIG. 1 shows a split-flow vacuum pump according to an embodiment of the present disclosure.

(3) FIG. 2A is a cross-sectional elevation view of a spacer according to an embodiment of the present disclosure.

(4) FIG. 2B is a perspective view of the spacer illustrated in FIG. 2A.

(5) FIG. 3A is a perspective view of a spacer according to another embodiment of the present disclosure.

(6) FIG. 3B is a perspective view of a spacer according to another embodiment of the present disclosure.

(7) FIG. 3C is a perspective view of a spacer according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

(8) FIG. 1 shows a split-flow vacuum pump 10 according to an embodiment of the present invention. The vacuum pump 10 has a housing 20 which comprises an envelope 25 and a body 28. A shaft 30 is arranged and extending in an axial direction (indicated by arrow A) within the housing 20.

(9) The envelope 25 houses a first pumping arrangement 40 comprised of a first stator arrangement 42 and a first rotor arrangement 45. The first rotor arrangement 45 is mechanically attached with the shaft 30, while the first stator arrangement 42 is mechanically attached with the envelope 25 of the housing 20. The first pumping arrangement 40 in the embodiment of FIG. 1 is provided by seven turbomolecular stages 47A-47G, each stage consisting of a respective turbomolecular rotor element (being part of the first rotor arrangement 45) and a respective turbomolecular stator element (being part of the first stator arrangement 42), as readily known in the art, which in operation rotate with respect to each other to cause movement of molecules (under molecular flow conditions) through the pump 10.

(10) A first pump inlet 48 is provided on top side (with respect to the representation shown in FIG. 1) of the pump 10 and in closest proximity to the first turbomolecular stage 47A of the first pumping arrangement 40. A flange 49 can be provided to close the first pump inlet 48 e.g. for transporting.

(11) The envelope 25 further houses a second pumping arrangement 50 comprised of a second stator arrangement 52 and a second rotor arrangement 55. The second rotor arrangement 55 is mechanically attached with the shaft 30, while the second stator arrangement 52 is mechanically attached with the envelope 25 of the housing 20. The second pumping arrangement 50 in the embodiment of FIG. 1 is provided by five turbomolecular stages 57A-57E, each stage consisting of a respective turbomolecular rotor element (being part of the second rotor arrangement 55) and a respective turbomolecular stator element (being part of the second stator arrangement 52), as readily known in the art, which in operation rotate with respect to each other to cause movement of molecules (under molecular flow conditions) through the pump 10.

(12) A second pump inlet 58 is provided at a lateral side (with respect to the representation shown in FIG. 1) of the pump 10 and in closest proximity to the first turbomolecular stage 57A of the second pumping arrangement 50.

(13) A spacer 60 is provided between the first pumping arrangement 40 and the second pumping arrangement 50 and arranged in proximity to the second pump inlet 58. Exemplary embodiments of the spacer 60 will be shown in greater detail in FIGS. 2A-3C.

(14) The body 28 can be mechanically attached to the envelope 25 e.g. by one or more screws, thus fixing the body 28 and the envelope 25 closely together in the axial direction A.

(15) The body 28 in the embodiment of FIG. 1 comprises a driving unit 70 coupled to and allowing to rotate the shaft 30. A first bearing 72 and a second bearing 74 are provided for bearing rotation of the shaft 30. It is clear that the bearings 72 and 74 may also be provided at other positions (with respect to the shaft 30). For example, the (upper) second bearing 74 may be provided higher up (in the representation of FIG. 1) towards the first pump inlet 48.

(16) The pump 10 further comprises an outlet 80.

(17) For operation, the first pump inlet 48 of the pump 10 can be coupled to a first chamber to be evacuated (not shown in FIG. 1) and the second pump inlet 58 can be coupled to a second chamber to be evacuated (not shown in FIG. 1). When rotating the shaft 30, gas from the first chamber (to be evacuated) will be sucked in by the pump 10 at the first pump inlet 48, pass through the first pumping arrangement 40 as well as the second pump arrangement 50, and exit through the outlet 80. Gas from the second chamber (to be evacuated) will be sucked in by the pump 10 at the second pump inlet 58, pass (only) through second pump arrangement 50, and also exit through the outlet 80.

(18) FIGS. 2A and 2B illustrate one exemplary embodiment of the spacer 60, with FIG. 2A showing a (cut-through) cross-sectional view, and FIG. 2B showing a three-dimensional view. The spacer 60 comprises an upper ring 200, a lower ring 210, and an elastic structure 220. The upper ring 200 is configured to abut against the first stator arrangement 42, and in the embodiment of FIG. 1 against the lowest turbomolecular stage 47G (with respect to the first pump inlet 48). The lower ring 210 is configured to abut against the second stator arrangement 52, and in the embodiment of FIG. 1 against the upper turbomolecular stage 57A (with respect to the first pump inlet 48).

(19) The elastic structure 220 is arranged in the axial direction A between the upper ring 200 and the lower ring 210 and configured to provide a defined elasticity in the axial direction A. Accordingly, when the envelope 25 and the body 28 are mechanically tightened to each other (e.g. by screwing one or more screws), the stator of the pump 10 (consisting of the first stator arrangement 42, the second stator arrangement 52, and the spacer 60 coupled in between the first stator arrangement 42 and the second stator arrangement 52) is mechanically fixed and prestressed in the axial direction A within the housing 20. While the first stator arrangement 42 and the second stator arrangement 52 are provided as mechanically rigid components substantially providing no elasticity in the axial direction A, the spacer 60 is configured “spring-like” i.e., having a defined elasticity in the axial direction A. In other words, a force acting in the axial direction A will lead to an elastic deformation of the spacer 60 in the axial direction A. On removal of the force in the axial direction A, the spacer 60 will substantially resume its initial shape (before applying the force in axial direction A).

(20) The spacer 60 thus provides an elastic spring element that allows to hold firmly in position (in particular axially) the entire package of stators of the first pumping arrangement 40 and the second pumping arrangement 50, while allowing the closure of the contact between the body 28 and the envelope 25. Without a defined elasticity of the spacer 60 (which may be considered as an elastic “yielding” element), there is a risk that the envelope 25 and the second pumping arrangement 50 do not come into contact, which may reduce a heat exchange between the parts. Moreover, without the defined elasticity of the spacer 60, the axial positioning of the stator components of the first pumping arrangement 40 and the second pumping arrangement 50 would be more variable, which may force the designer to maintain greater axial gaps between rotor and stators, thus decaying the performance of the turbomolecular pump.

(21) In the embodiment of FIGS. 2A and 2B, the elastic structure 220 is comprised of a plurality of step shaped rips (or ribs) 220, presently embodied having a Z-shape. The embodiment of FIG. 2 is shown with four rips 220A-220D, however, the number of rips can be considered as a design parameter allowing to adjust the desired degree of axial elasticity of the spacer 60. In the exemplary embodiment of FIG. 2, each rip 220 comprises a first axial bar 222 extending in the axial direction A from the lower ring 210, a second axial bar 224 extending in the axial direction A from the upper ring 200, and a horizontal (or radial) bar 226 bridging between the first axial bar 222 and the second axial bar 224. In other words, a first end of the first axial bar 222 is fixed to the lower ring 210, while a second end of the first axial bar 222 is fixed via a first bending 227 to a first end of the horizontal bar 226, and a first end of the second axial bar 224 is fixed to the upper ring 220, while a second end of the second axial bar 224 is fixed via a second bending 228 to a second end of the horizontal bar 226.

(22) The Z-shape of the elastic structure 220 allows the upper ring 200 and lower ring 210 to be elastically pressed against each other in the axial direction A, i.e. the elastic structure 220 can undergo an elastic deformation into the axial direction A.

(23) The elasticity of the elastic structure 220 can be designed to assume a defined and/or desired value of elasticity in particular by designing one or more of the parameters: material, breadth, height, and/or thickness of the first axial bar 222, the second axial bar 224, the horizontal part 226, the first bending 227, and/or the second bending 228, radius of the first bending 227 and/or the second bending 228, number of rips 220, a radius R1 of a rounding between the first axial bar 222 and the lower ring 210, a radius R2 of a rounding between the second axial bar 224 and the upper ring 200, et cetera.

(24) FIGS. 3A-3C show additional exemplary embodiments of the spacer 60. FIG. 3A shows an embodiment similar to FIGS. 2A and 2B, however with only three Z-shaped rips (or ribs) 220A-C. FIG. 3B shows an embodiment with five rips (or ribs) 220A-220E each extending straight between the upper ring 200 and the lower ring 210. FIG. 3C shows an embodiment similar to FIG. 3B, however, with only three rips (or ribs) 220A-C each embodied as double-rip (or double-rib) having a cut-out in between.

(25) While the invention has been exemplarily described with respect to an embodiment as a split-flow pump, it is clear that a respective spacer 60 according to embodiment of the present invention can also be applied in other types of vacuum pumps with only one pump inlet as well as with more than two pump inlets. In the latter, a respective spacer may be applied in close proximity to one or more of the pump inlets.

(26) While the invention has been exemplarily described with respect to an embodiment having two pumping arrangements (40 and 50), it is clear that more than two pumping arrangements can be applied, e.g. with a respective spacer 60 according to embodiments of the present invention situated axially between adjacent pumping arrangements.