WO2018042150A1

WO2018042150A1 - Pump assemblies with sealing

Info

Publication number: WO2018042150A1
Application number: PCT/GB2017/052384
Authority: WO
Inventors: Paul Milner
Original assignee: Edwards Limited
Priority date: 2016-09-01
Filing date: 2017-08-14
Publication date: 2018-03-08
Also published as: US20190195234A1; GB201614816D0; GB2553323A

Abstract

A pump casing assembly has a first body part (16), a second body part (18) and a seal (14) disposed between the first and second body parts. The first body part has a first face that defines a recess to receive the seal and the second body part has a first face disposed opposite the first face of the first body part and defining a first sealing surface engaged by the seal and a projection extending beyond the first sealing surface into the recess.

Description

PUMP ASSEMBLIES WITH SEALING

Field of the Invention

The invention relates to pump assemblies with sealing and particularly, exclusively to pump casing assemblies of turbomolecular vacuum pumps.

Background to the Invention

Pumps such as vacuum pumps may comprise parts that are fitted together with an intermediate seal to prevent fluid leakage between the two parts. For example, a vacuum pump may comprise two body parts that are joined to form a casing assembly. One of the body parts may have an end face that is recessed to receive a seal that is fitted between the two body parts to prevent gas leakage between them. The seal is typically an O-ring that sits in the recess and is engaged by a sealing face provided on the other of the two body parts. The two body parts may be secured to one another by one or more clamps or by a plurality of bolts or studs passing through suitable holes provided in, for example, flanges provided on the body parts.

Summary of the Invention

The invention provides a pump casing assembly as specified in claim 1.

The invention also includes a pump casing assembly comprising:

a first body part defining a hollow interior having a first longitudinal axis and having a first end face that defines a recess to receive a seal, said recess defining a sealing surface;

a second body part defining a hollow interior having a second longitudinal axis and having a first end face facing said first end face of the first body part and defining a sealing surface; and

a seal disposed in said recess in sealing engagement with the respective sealing surfaces of said first and second body parts,

wherein said first and second longitudinal axes define a lengthways direction of the pump casing assembly, wherein said second body part defines at least one projection extending beyond said sealing surface of the second body part in said lengthways direction so as to be disposed in said recess alongside said seal, and

wherein said recess defines a register surface and said projection defines a register face engaging said register surface to align said first and second body parts.

The invention also includes a pump assembly comprising a first part, a second part and a seal disposed between said first and second parts, said first part having a first face that defines a recess to receive said seal and said second part having a first face disposed opposite said first face of said first part and defining a first sealing surface engaged by said seal and a projection extending beyond said first sealing surface into said recess.

Brief Description of the Drawings

In the following disclosure, reference will be made to the drawings, in which:

Figure 1 is a side elevation view of a turbomolecular vacuum pump;

Figure 2 is a schematic section view through a portion of the turbmolecular vacuum pump of Figure 1;

Figure 3 is an enlargement of the circled portion of Figure 2; and

Figure 4 is a schematic comparison of a modification of the casing assembly shown in Figures 2 and 3 and a conventional casing assembly.

Detailed Description

In this specification the words 'first' and 'second' are used in connection with certain parts. It is to be understood that unless otherwise stated, these words are used purely as a means of identification and do not provide any indication of a number of parts or of precedence of the parts. Referring to Figures 1 and 2, an example of a pump in the form of a turbomolecular vacuum pump 10 comprises a casing assembly 12 with sealing in the form of a seal 14. The casing assembly 12 comprises a first body part 16 and a second body part 18. The seal 14 is disposed between the first and second body parts 16, 18. In use of the turbomolecular vacuum pump 10, the seal 14 prevents gas from leaking between the body parts 16, 18. The casing assembly 12 may include a third body part 20 mounted on the second body part 18. The third body part 20 may, for example, house control electronics, a user interface and a power inlet. The casing assembly 12 may be provided with an inlet port 22, a backing port 24, a purge port 26, an interstage port 28 and a vent port 30. The inlet port 22 may be defined by a flange 32. The flange 32 may be an ISO063 flange or an ISO 100 flange via which the turbomolecular vacuum pump 10 may be clamped to a body or a piece of equipment that is to be evacuated. It is to be understood that the inlet end of the turbomolecular vacuum pump 10 does not have to the take the form of an ISO flange and different end configurations or designs may be used according to the intended use of the pump. Furthermore, it is not essential that the inlet port 22 is provided at an end of the casing assembly 12, which may be closed at both ends.

Referring to Figure 2, the first body part 16 may comprise a generally annular wall 38 that defines a hollow interior 40 and has a longitudinal axis, or centre line, 42. The second body part 18 may comprise a generally annular wall 44 that defines a hollow interior 46 and has a longitudinal axis, or centre line 48. The first and second body parts 16, 18 may house a rotor shaft 50. The axis of rotation of the rotor shaft 50 may be coaxial with the longitudinal axes 42, 48. The second body part 18 may house a first pumping mechanism comprising a plurality of stator blades 52 and a plurality of interleaving rotor blades 54. The stator blades 50 may be fixed to the second body part 18 and the rotor blades 52 may be fixed to the rotor shaft 50. The first body part 16 may house a second pumping mechanism 56 and an electric motor 58 that is operable to drive the rotor shaft 50. The second pumping mechanism 56 may, be a Holweck drag mechanism. It will be understood that the positioning of the second pumping mechanism 56 within the first body part 16 as shown in Figure 2 is not essential and that a part of the second pumping mechanism may be housed in the second body part 18. It will also be understood that in some examples the second pumping mechanism may be omitted or different pumping mechanisms such as a Gaede mechanism, Siegbahn mechanism or an aerodynamic pumping mechanism comprising a regenerative mechanism may be included as a second pumping mechanism. As best seen in Figure 3, the first body part 16 has a first end face that defines a recess 60 that receives the seal 14. The second body part 18 has a first end face that is disposed opposite the first end face of the first body part 16 and defines a first sealing face 62 that is engaged by the seal 14 and a projection 64 that extends into the recess 60 beyond the first sealing surface 62. With respect to the longitudinal axis 48, the projection 64 may be disposed radially outwardly of the first sealing surface 62 so as to surround the first sealing surface. The first sealing surface 62 may be an annular surface and the projection 64 may extend continuously around a circumference of the annular surface. The projection 64 may have a height that is less than the height of the seal 14 and may be disposed in the recess 60 in side by side relation with the seal.

The recess 60 may define a second sealing surface 66 that is disposed opposite the first sealing surface 62 and is engaged by the seal 14. Although not essential, in the illustrated example the first and second sealing surfaces 62, 66 are planar surfaces disposed in parallel spaced apart relationship. The first and second sealing surfaces 62, 66 may be disposed perpendicular to the longitudinal axes 42, 48 of the first and second body parts 16, 18. The recess 60 may define a register surface 68 that extends transverse to the second sealing surface 62 and the projection 64 may define a register face 70 that engages the register surface 68 to locate the second body part 18 relative to the first body part 16. The register surface 68 and register face 70 may be configured to locate the second body part 18 relative to the first body part 14 such that the longitudinal axes 42, 48 are aligned. The register surface 68 may extend perpendicular to the second sealing surface 66 and parallel to the longitudinal axis 42 of the first body part 16. The register face 70 may extend perpendicular to the first sealing surface 62 and parallel to the longitudinal axis 48. At least one of the register surface 68 and register face 70 may comprise an annular surface extending continuously about the respective longitudinal axis 42, 48. The first end face of the first body part 16 may additionally define an annular surface 72 disposed perpendicular to the longitudinal axis 42 of the first body part 16. The annular surface 72 may be disposed radially outwardly of the recess 60 to form a seat for an annular surface 74 that is defined by the first end face of the second body part 18. The annular surface 74 may be disposed radially outwardly of the projection 64 so as to be disposed opposite the annular surface 72 perpendicular to the longitudinal axis 48 and parallel to the annular surface 72. In the illustrated example, the end of the annular wall 38 disposed remote from the recess 60 and annular surface 72 is closed by a plate or other suitable body so that when the first body part 16 is secured to the second body part 18, the hollow interiors 40, 46 define a sealed enclosure accessible via the ports 22-30. In addition to the rotor shaft 50, first and second pumping mechanisms 52-56 and electric motor 58, the hollow interiors 40, 46 may house associated parts (not illustrated) such as rotor shaft bearings and their associated lubrication system. The first and second body parts 16, 18 may be secured to one another by means of bolts or studs extending along through-holes provided in one of the annular walls 38, 44 to engage in threaded apertures provided in the other. In other examples, the first and second body parts 16, 18 may be secured to one another by clamps or by studs or bolts received in apertures provided in flanges or lugs provided on the outer sides of the first and second body parts. 16, 18 As best seen in Figure 3, the side face 76 of the projection 64 adjoining the first sealing surface 62 may be configured such that in cross section the projection tapers so as to have a first thickness adjacent the first sealing surface and a second thickness at its tip that is less than the first thickness. The side face 76 may have an arcuate profile. Advantageously the projection 64 may protect the first sealing surface 62 against damage during assembly and transport of the second body part 18. For example, if the second body part 18 is placed on a supporting surface such as a work bench with the first sealing surface 62 face down, the projection 64 seats on the supporting surface and supports the second body part so that the first sealing surface does not contact the supporting surface. This avoids potential damage to the first sealing surface 62 that may arise from contact with the supporting surface objects lying on the supporting surface. Figure 4 provides a comparison between a prior art casing assembly P and a casing assembly 112 that is a modification of the casing assembly 12 shown in Figures 2 and 3. In the casing assembly 12 shown in Figures 2 and 3, the register face 70 of the second body part 16 is defined solely by the projection 64. In the casing assembly 112 illustrated by Figure 4, the projection 64 is a constituent part of a register face 70. An advantage provided by the casing assembly 112 when compared with the conventional casing assembly P is that since the projection 64 defines a part of the register face 70, it is possible to obtain a register face that has the same height X as the prior art register face 70P of the conventional casing assembly while reducing the overall height, or length, of the casing assembly by a height Y corresponding to the height of the projection 64. It will be understood that the same advantage is obtainable with the casing assembly 12 shown in Figures 2 and 3. In that example, the register face 70 defined by the projection 64 is disposed within the recess 60 alongside the seal 14 and does not add to the overall height of the casing assembly 12.

In the illustrated examples, the pump casing assembly comprises two body parts 16, 18 secured to one another with a seal 14 clamped between respective end faces of the body parts, an auxiliary body part 20 and a plate to close an end of the first body part. It will be understood that this is purely an example of a pump casing assembly utilising the invention and that many other configurations are possible. For example, a pump casing assembly may comprise three or more body parts comprising annular walls secured to one another in series with respective seals between them. In some examples, both ends of the pump casing assembly may be closed by respective end plates or the like. In other examples, one or both body parts may comprise an integral end wall. The skilled person will understand that the invention may be utilised in all such configurations of pump casing assembly and in many others not described herein.

In the illustrated examples the projection 64 is an annular member encircling the first sealing surface 62. It is to be understood that this is not essential and that a plurality of discrete projections may be provided. For example, three projections may be disposed about the first sealing surface at, for example, intervals of 120° to define a tripod arrangement for supporting the second body part 18. In other examples a larger number of projections may be provided to form a castellated wall surrounding the first sealing surface 62.

The illustrated examples the pump casing assembly with sealing is for a turbomolecular vacuum pump. It will be understood that the invention is not limited to this application. For example, the invention may be applied to pump casing assemblies generally. The invention may also be applied to other pump assemblies in which the ends of two parts are clamped to one another with a seal between them.

Claims

A pump casing assembly comprising a first body part, a second body part and a seal disposed between said first and second body parts, said first body part having a first face that defines a recess to receive said seal and said second body part having a first face disposed opposite said first face of said first body part and defining a first sealing surface engaged by said seal and a projection extending beyond the first sealing surface into said recess.

A pump casing assembly as claimed in claim 1, wherein said first sealing surface is a planar surface.

A pump casing assembly as claimed in claim 1 or 2, wherein said recess defines a second sealing surface disposed opposite said first sealing surface and engaged by said seal and a register surface extending transverse to said second sealing surface and said projection defines a register face that engages said register surface to locate said second body part relative to said first body part.

A pump casing assembly as claimed in claim 3, wherein said first body part defines a hollow interior having a first longitudinal axis, said second body part defines a hollow interior defining a second longitudinal axis and said register face and register surface are configured to locate said second body part relative to said first body part such that said first and second longitudinal axes are aligned.

A pump casing assembly as claimed in claim 3 or 4, wherein said register surface and said register face each extend perpendicular to said second sealing surface.

A pump casing assembly as claimed in claim 3, 4 or 5, wherein at least one of said register surface and said register face comprises an annular surface.

A pump casing assembly as claimed in any one of the preceding claims, wherein said projection has a tip and a side face adjoining said first sealing surface and extending to said tip, said side face being configured such that in cross section said projection tapers so as to have a first thickness adjacent said first sealing surface and a second thickness at said tip that is less than said first thickness.

8. A pump casing assembly as claimed in claim 7, wherein said side face comprises an arcuate profile.

9. A pump casing assembly as claimed in any one of the preceding claims, wherein: said first body part comprises an annular wall having a first end that defines said first face of said first body part, a second end disposed opposite said first end and a length defined by said first and second ends,

said second body part comprises an annular wall having a first end that defines said first face of said second body part, a second end disposed opposite said first end and a length defined by said first and second ends,

said first and second body parts have a lengthways direction from said second end of said first body part to said second end of second body part,

said seal has a height in said lengthways direction, and

said projection has a height in said lengthways direction that is less than said height of said seal, and

said seal and projection are disposed side by side.

10. A pump casing assembly as claimed in any one of the preceding claims wherein said projection surrounds said first sealing surface.

11. A pump casing assembly as claimed in any one of the preceding claims, wherein said first sealing surface is an annular surface and said projection extends around a circumference of said annular surface.

12. A pump casing assembly as claimed in any one of claims 1 to 9, comprising a plurality of said projections disposed in spaced apart relation about said first sealing surface. A turbomolecular vacuum pump comprising a pump casing assembly as claimed in any one of the preceding claims.