Field of the Invention

The invention relates to vibration damping connector systems to connect between an inlet, or suction, port of a vacuum pump and a port of a vacuum chamber.

Background to the Invention

Vacuum pumps may be used to establish vacuum conditions in chambers or spaces within, or associated with, many types of equipment. Examples of such equipment include equipment used in electron microscopy, spectrometry or the manufacture, repair or testing of integrated circuits. The vacuum pump may be directly connected with the piece of equipment by a connector system that puts the chamber in flow communication with the suction port of the vacuum pump. When the vacuum pump is running, vibrations induced by rotating or other moving parts of the pump may be transmitted to the attached equipment via the connector system. For example, the vacuum pump may be a turbomolecular pump having a rotor that rotates at high speeds setting up high frequency vibrations. The rotor of a turbomolecular vacuum pump may, for example, rotate at speeds in the region of 60,000 rpm. A turbomolecular vacuum pump may include two sources of significant vibration that establish vibrations at different frequencies. One vibration source is the pump rotor and the other is the cage of the rolling bearings that support the pump rotor. It may be necessary to eliminate, or at least substantially reduce, the vibrations transmitted from the vacuum pump to the attached equipment.

Vibration damping connector systems that use an O-ring or similar elastomer elements as both a gas seal and a vibration isolation element are known. With this approach, when the system is under vacuum the external gas load applies a compressive force to the elastomer element. This can result in compression set and an associated increase in the stiffness of the elastomer element. In addition, regardless of the load applied the elastomer element will suffer from aging which can also cause an increase in its stiffness. This increase in stiffness will result in reduced vibration isolation performance. The occurrence of compression set also has the potential to cause leakage of the seal when the compressive force is removed causing a failure to seal when the vacuum pump is stopped and then restarted. Other disadvantages associated with elastomer elements include the inherent relatively high damping and a frequency dependence of the stiffness of the material. For a vibration damping connector system, the stiffness and damping should be as low as possible for optimum performance so both of these effects can result in reduced performance of the isolator.

A known alternative solution to the use of elastomers as the sealing and vibration damping elements in a vibration damping connector system is to use a bellows to form the gas seal with an elastomer element surrounding the bellows to provide stiffness to resist the compressive gas load. This solution avoids the loss of sealing capability arising from compression set, but still suffers from the other disadvantages associated with the use of elastomers as vibration isolation elements.

US2018/0363825 discloses a vibration damping connector system that uses a piston arrangement to provide a fluid filled element to act as a vibration isolator. This addresses many of the disadvantages associated with the use of elastomer elements, in particular compression set, aging and relatively high damping. However, this kind of piston arrangement results in a connector system that has high radial stiffness. In the majority of applications, low radial stiffness is required to minimise the transmission of radial vibration from the pump to the vacuum chamber. Furthermore, the vibration damping connector system disclosed by US2018/0363825 has a relatively complex structure employing numerous components and will be both relatively expensive to produce and relatively bulky.

Summary of the Invention

The invention provides a vibration damping connector system as specified in claim 1.

The invention also includes a method of providing vibration damping in a vibration damping connector system configured to connect a vacuum pump to a vacuum chamber as specified in claim Brief Description of the Drawings

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

Figure 1 is a schematic view of a vacuum pump, a vacuum chamber and a vibration damping connector system connecting the vacuum pump with the vacuum chamber;

Figure 2 is a side elevation view of the vibration damping connector system of Figure 1;

Figure 3 is a section on line III-III in Figure 2;

Figure 4 is an enlargement of a portion of Figure 3;

Figure 5 is section view on line IV-IV in Figure 3; and

Figure 6 is an enlargement of the circled portion of Figure 5.

Detailed Description

Referring to Figure 1, a vacuum pump 10 is shown connected with a vacuum chamber 12 by means of a vibration damping connector system 110. The vacuum pump 10 may be a turbomolecular pump having a primary pumping mechanism that comprises a plurality of rotor blades 14 mounted on a rotor shaft 16 and a plurality of stator blades 18 disposed in interleaving relationship with the rotor blades. The rotor shaft 16 may be supported by a bearing system 20 and driven by a motor 22. The bearing system 20 may comprise a lower bearing in the form of a rolling bearing and an upper bearing in the form of a magnetic bearing that may be coupled with a backup in the form of a second rolling bearing. It is to be understood that the references to upper and lower bearings are not intended to be limiting and are simply references to the vacuum pump 10 in the orientation shown in Figure 1. The vacuum pump 10 may additionally comprise a secondary pumping mechanism 24. The secondary pumping mechanism 24 may comprise a molecular drag pumping mechanism such as a Gaede mechanism, a Holweck mechanism or a Siegbahn mechanism. The pumping mechanism or mechanisms are operable to pump gases and vapours from an inlet or suction port 26 of the vacuum pump 10 to an outlet, or exhaust port 28. The vibration damping connector system 110 places the suction port 26 in flow communication with a port, or opening, 30 of the vacuum chamber 12 so that the vacuum pump 10 can be used to establish vacuum conditions in the vacuum chamber. The vacuum chamber 12 is a chamber (or space) in, or associated with, a piece of equipment 32 in which vacuum conditions are to be established. Such equipment 32 may, for example, be equipment used in electron microscopy, spectrometry or the manufacture, repair or testing of integrated circuits. The piece of equipment 32 may support the weight of the vacuum pump 10 via the vibration damping connector system 110. Thus, for example, the vacuum pump 10 may be suspended from the piece of equipment 32 via the vibration damping connector system 110.

Referring to Figures 2 to 4, the vibration damping connector system 110 comprises a first end member 112 having a through-passage 114 and a second end member 116 having a through-passage 118. The through-passage 114 of the first end member 112 is in flow communication with the through-passage 118 of the second end member 116. Although not essential, the through-passages 114, 118 may each be axially aligned with the longitudinal axis 120 of the vibration damping connector system 110. First and second inflatable sealing members 122, 124 are disposed intermediate the first and second end members 112, 116 to provide respective gas seals between the first and second end members. In use, as shown by way of example in Figure 1, the first end member 112 is connected to the piece of equipment 32 and the second end member 116 is connected to the vacuum pump 10 to provide a gas tight flow path between the vacuum pump and the vacuum chamber 12. Securing members 126 provide a releasable secured connection of the first end member 112 with the second end member 116. Resilient members 128, 130 are disposed intermediate the securing members 126 and the first and second end members 112, 116 such that when the inflatable seals 122, 124 are compressed by a pressure reduction caused in use by operation of the vacuum pump 10, the resilient members 128, 130 can expand to enable the securing members to maintain the secured connection between the first and second end members 112, 116. Accordingly, there should be no substantial change in the status of the security of the secured connection between the first and second end members 112, 116 when the vacuum pump 10 switches between its operating and non-operating states. Still referring to Figures 2 to 4, the first end member 112 may comprise a first (or inboard) end in the form of a first flange 134, a second (or outer) end in the form of a second flange 136 and a tubular body 138 extending between the two flanges. Similarly, the second end member 116 may comprise a first (or inboard) end in the form of a first flange 140, a second (outer) end in the form of a second flange 142 and a tubular body 144 extending between the two flanges. Thus, the first and second end members 112, 116 may each comprise a generally tubular body with the through-passages 114, 118 extending between the respective first and second flanges 134, 140, 136, 142. The first flanges 134, 140 may be larger in radial extent than the two second flanges 136, 142. The second flanges 136, 142 may be industry standard vacuum flanges for securing to respective fittings on the vacuum pump 10 and piece of equipment 32 using standard ISO clamps 34 (Figure 1). The first and second end members 112, 116 may be made of a metal, for example, an aluminium alloy.

Referring to Figures 2 to 6, the vibration damping connector system 10 may further comprise an isolator mass 150 disposed in series with and at least partially between the first and second end members 112, 116. The isolator mass 150 is an annular body defining a through-passage 152 that is configured to cooperate with the through-passages 114, 118 to define a continuous flow passage extending between the opposite ends of the vibration damping connector system 110, as represented by the second flanges 136, 142. The isolator mass 150 has a mass that is relatively large compared to the mass of the first and second end members 112, 116. The isolator mass 150 may be made of a metal, for example, a stainless steel.

Referring to Figures 4 and 5, the isolator mass 150 comprises a relatively thinner inner annular portion 154 that is disposed between the first flanges 134, 140 and a relatively thicker outer annular portion 156 disposed radially outwardly of the respective outer peripheries of the first flanges. Although not essential, the inner annular portion 154 may project radially inwardly from the radially inner side of the outer annular portion 156 from a position intermediate the oppositely facing annular major faces 157, 159 of the outer annular portion so that the isolator mass 150 has a generally T-shaped cross-section. Positioning at least a portion, or part, of the isolator mass 150 radially outwardly of the first and second end members 112, 116, or at least the respective first flanges 134, 140. provides the potential advantage of enabling the provision of a relatively large mass to obtain a desired vibration isolating function without significantly increasing the length of the vibration damping connector system 110 as consequence of the series connection of the mass with the first and second end members. In this context the length L of the vibration damping connector system 110 and thicknesses of the inner and outer annular portions 154, 156 of the isolator mass 150 are dimensions measured in the axial, or lengthways, direction of the vibration damping connector system/through-passages. It is to be understood that other forms of isolator mass may be used in the vibration damping connector system 150 and the disclosure relating to the isolator mass is not to be taken as limiting.

Referring to Figures 4 to 6, the inner annular portion 154 of the isolator mass 150 defines oppositely facing annular channels in the form of grooves 158 and the first flanges 134, 140 define respective annular channels in the form of grooves 160 disposed opposite and facing the grooves 158. The facing pairs of grooves 158, 160 cooperate to define respective annular seats, or split housings, for the first and second inflatable sealing members 122, 124. The grooves 158, 160 may be rectangular in cross-section to define a generally rectangular cross-section annular seat for receiving the inflatable sealing members 122, 124. Although not essential, the grooves 160 provided in the isolator mass 150 may be deeper than the grooves 158 provided in the first flanges 134, 140. The first and second inflatable sealing members 122, 124 provide respective gas seals between the first and second end members 112, 116 and the isolator mass 150 so that the continuous flow passage defined by the through-passages 114, 118, 152 is gas tight. It is to be understood that it is not essential that the sealing members 122, 124 and their seats have generally rectangular cross sections. For example, the grooves 158, 160 may be generally circular so as to define substantially circular section annular seats for generally circular-section inflatable sealing members 122, 124. In the illustrated examples, the channels that house the inflatable sealing members are formed by grooves that are provided in at least one of the isolator mass 150 and the first end members 112, 116. It will be understood that one or more channels may be defined by ridges provided on an isolator mass or end member. As best seen in Figure 4, in this example the securing members comprise elongate threaded members in the form of bolts or screws 126. The inner annular portion 154 of the isolator mass 150 defines respective threaded apertures 162 to receive the bolts 126. The threaded apertures 162 may comprise partially threaded through-holes or oppositely disposed blind holes. The threaded apertures 162 are disposed radially outwardly of the grooves 158. The first flanges 134, 140 are provided with respective clearance holes 164 disposed radially outwardly of the grooves 160 such that when the first and second end members 112, 116 and isolator mass 150 are assembled, they are axially aligned with the threaded apertures 162. The through-holes 164 are sized such that the bolts 126 may pass through for insertion into the threaded apertures 162. The threaded apertures 162 and through-holes 164 may be equi-spaced on a pitch circle diameter so that when the bolts 126 are tightened, an even clamping force is applied to the inflatable sealing members 122, 124 and the isolator mass 150 sandwiched between the first and second end members 112, 116.

Still referring to Figure 4, in this example, the resilient members 128, 130 take the form of respective bushes disposed between the heads of the bolts 126 and the respective oppositely facing major faces 166, 168 of the first flanges 134, 140 that face the respective second flanges 136, 142 of the first and second end members 112, 116. Accordingly, the clamping pressure applied to the first and second end members 112, 116 by the bolts 126 is applied via the resilient members 128, 130. In some examples, the resilient members 128, 130 may comprise bushes as shown in Figure 4 in combination with resilient washers, which may be made of the same material as the bushes. In some examples, metal washers 170 may be disposed between the resilient members 128, 130 and the heads of the bolts 126 so that the clamping pressure exerted by the bolts is evenly distributed across the width of the resilient members. In some examples, the resilient members 128, 130 may comprise nosepieces 172 configured to engage in the through-holes 164. The nosepieces 172 may assist in locating and retaining the resilient members 128, 130 during assembly of the vibration damping connector system 110 and in providing electrical isolation of the first and second end members 112, 116 (to be described in more detail below). Providing nosepieces 172 on the resilient members 128, 130 may also provide radial vibration isolation and prevent metal to metal contact between the bolts 126 and the first flanges 134, 140. The resilient members 128, 130 are made of a resilient material, or materials, that may be electrically insulating and may each be made of a visco-elastic material, for example an elastomer. For example, the resilient members may be made of nitrile and the resilient members may be made of supersoft urethane (SU). It is not essential that the resilient members 128, 130 are bushes as shown in the drawings. For example, one or more of the resilient members may take the form of a mechanical spring or an inflatable sealing member.

Referring to Figures 5 and 6, the inflatable sealing members 122, 124 comprise respective endless arcuate hollow bodies. The inflatable sealing members 122, 124 may have a generally rectangular cross-section to complement the annular seat formed by the grooves 158, 160. In one example, the inflatable sealing members 122, 124 may comprise three generally planar sides 174-178 and an outwardly arched side 180. The sides 174, 178 may extend perpendicularly from the opposite edges of the side 176 and parallel to one another. The arched side 180 may be disposed opposite the side 176 and connect the sides 174, 176. Each inflatable sealing member 122, 124 is provided with a filling tube 182. The filling tubes 182 may be permanently sealed once the inflatable sealing members have been inflated to a desired pressure. Alternatively, the filling tubes 182 may be closed with plugs or stoppers that can be removed for refilling or with valves. The filling tubes 182 may extend from a periphery of the arcuate hollow bodies that form the inflatable sealing members 122, 124. For example, the filling tubes 182 may extend from the respective side walls 174 of the inflatable sealing members 122, 124.

The inflatable sealing members 122, 124 may be made of any non-metallic resilient material with sufficient resilience to allow inflation and that will accommodate the varying applied gas loads. For some applications the material will also need to be able to resist degradation by corrosive vapours pumped through the vibration damping connector system 110. The inflatable sealing members 122, 124 may, for example, be made of a fluoroelastomer such as FKM. The inflatable sealing members 122, 124 may have fibre- reinforced walls for added robustness. The inflatable sealing members 122, 124 may be custom made or may be existing products. For example, the inflatable sealing members 122, 124 may be selected from the range of ISO-FLATE ™ inflatable sealing members marketed by Sealing Projex Limited, Unit C2 Walter Leigh Way, Moss Industrial Estate, Leigh, Greater Manchester, United Kingdom.

The inflatable sealing members 122, 124 are pressurised by filling with a gas. The gas used is preferably air. The currently preferred option is to inflate the inflatable sealing member or members when the vibration damping connector system is assembled in the factory or the like. However, inflation may be carried out on site. There may be some advantages to inflating the inflatable sealing member or members on site. This would make it possible to tune the vibration damping connector system to some degree by adjusting the fill to adjust the spring rate provided by the inflatable sealing member or members.

In use, the second flange 136 of the first end member 112 is secured to the piece of equipment 32 and second flange 142 of the second end member 116 is secured to the vacuum pump 10 to securely connect the vacuum pump to the vacuum pump and the vacuum chamber. The second flanges 136, 142 may be secured to the vacuum chamber 32 and vacuum pump 10 respectively by standard ISO clamps 34. When the vacuum pump 10 is operated to establish vacuum conditions in the vacuum chamber 12, the increasing differential between the pressure in the through-passages 114, 118, 152 and the external ambient pressure causes the inflatable sealing members 122, 124 to compress. As they compress, the inflatable sealing members 122, 124 maintain a gas seal between the first and second end members 112, 116, while the resilient members 128, 130 expand to compensate for the compression of the sealing members to maintain the tightness of the secured connection between the first and second end members that is provided by the bolts 126. Accordingly, there should be no loosening of the connection between the first and second end members 112, 116. Without the compensating expansion of the resilient members 128, 130, the connection between the first and second end members 112, 116 might be loosened, a problem that may be exacerbated by the vibrations set up in operation of the vacuum pump 10. The electrically non-conducting inflatable sealing members 122, 124 and resilient members 128, 130 may provide an electrically insulating barrier so that the first end member 112 and second end member 116 are electrically isolated from one another. Thus, an electrically insulating barrier is provided between the vacuum pump 10 and piece of equipment 32 that defines the vacuum chamber 12, or with which the vacuum chamber is associated, regardless of the operational state of the vacuum pump.

In Figures 2 to 5, the securing members 126 are shown as bolts or screws screwed into respective threaded apertures 162 provided in the isolator mass 150. This is not essential as the opposed pairs of bolts could be replaced by a nut and bolt combination and the threaded apertures 162 provided in the isolator mass 150 may be replaced with clearance holes. In another example, instead of nuts and bolts, threaded studs with nuts at each end may be used. In yet another example, bolts could extend through clearance holes provided in one of the first flanges 134, 140 and the isolator mass 150 and screw into threaded apertures provided in the other of the first flanges. However, an arrangement as shown in Figures 2 to 5 in which bolts or screws 126 are screwed into threaded blind holes (or partially threaded through-holes) in the isolator mass 150 that define an end position for the bolts or screws provides the potential advantage of allowing the initial compression of the inflatable sealing members 122, 124 and resilient members 128, 130 to be controlled by the depth of the blind holes or the depth to which the threads extend in the holes. This removes the need to set a specified tightening torque for the bolts 126 and allows the vibration damping connector system 110 to be easily assembled on site using basic tools.

Although having resilient members 128, 130 between the securing members 126 and the isolator mass 150 may provide advantages, it is not essential. In other examples, the resilient members may be omitted so that the securing members 126 directly engage the first flanges 134, 140, optionally via metal washers. In that case, the advantage of permanent isolation of the vacuum pump from the piece of equipment 32 is lost and isolation will only occur when there is a vacuum present to provide the upwards thrust due to the gas load that causes separation of the securing members 126 and the first flanges 134, 140. In some examples the isolator mass 150 may be omitted, in which case there may be just one inflatable sealing member interposed between the first flanges 134, 140 to provide a gas seal and vibration isolation.

By using one or more inflatable sealing members to provide a gas seal and vibration isolation in a vibration damping connector system, it is possible to overcome one or more of the disadvantages associated with the use of elastomers in conventional vibration damping connector systems, including compression set, aging and stiffening of the elastomer material, the high damping associated with elastomers and the frequency dependence of the stiffness on the excitation frequency associated with elastomer materials. The or each inflatable sealing member functions as a gas-filled spring element to provide the spring force required to resist the gas load in a vibration damping connector system and provides the advantage of a lower radial stiffness than is found in connector systems that use conventional O-rings or other solid elastomer support elements. Thus, vibration damping connector systems comprising one or more inflatable sealing members may have a relatively low axial and radial stiffness, providing improved vibration isolation when compared with conventional vibration damping connector systems.

In the example illustrated in Figure 1, the vibration damping connector system is shown in use supporting a turbomolecular vacuum pump 10 that is suspended from a piece of equipment 32 by the vibration damping connector system 110. It is to be understood that this is just one example of the ways in which the vibration damping connector system may be used and that it is not essential the vibration damping connector system supports the weight of the vacuum pump to which it is connected.

Although the vibration damping connector system has been described above as being used to connect a turbomolecular vacuum pump with a vacuum chamber, it is to be understood this is not to be taken as limiting. In principle, the vibration damping connector system may be used to connect any form of vacuum pump with a vacuum chamber.