Technical Field

The invention relates to apparatus and methods for clamping a first pipe having a first flange to a second pipe having a second flange in a vacuum system.

Background

Vacuum systems may comprise joints between one or more pipe elements which require secure fastening or clamping together in order to ensure an effective vacuum is maintained in the system.

Such joints typically include two portions of pipe each having a flange portion to facilitate joining of the pipes. Typically, an 0 ring and/or gasket is positioned between the two flange surfaces which are clamped together to form an effective seal. The clamping means may comprise bolts extending through both flanges to secure them together or a hinged clamp as illustrated in Figure 1 .

Figure 1a shows a prior art clamp 10 in an open position prior to mounting on flanges of a pipe joint 12. The clamp of Figure 1 a has a clamp axis 14 that aligns with the axis 16 of the pipe joint 12 during clamping. The clamp 10 comprises two clamping elements 18 attached to each other at respective first ends via a hinge or pivot 20 and releasably attached to each other at respective second ends via a securing means 22. In order to mount the clamp 10, the second ends of the clamping elements 18 are moved apart from each other and the expanded clamp 10 is moved onto the joint 12 in a generally radial direction 24 so that the clamp axis 14 goes from being radially offset from the axis 16 of the pipe joint 12 to co-axial therewith and is then secured by the securing means 22 as shown in Figure 1 b. When in a clamping position the securing means 22 is positioned generally on the diametrically opposite side of the joint 12 to the hinge 20. The clamp 10 of Figure 1 generally requires two-handed mounting as the clamp 10 needs to be held on the joint 12 while it is secured. Furthermore, problems occur where there is limited access around the pipe joint such as the arrangement of Figure 1 b in which multiple joints 12 are arranged close together. Such arrangements do not facilitate the mounting and securing of such clamps without considerable difficulty.

Summary

In accordance with the invention there is provided a clamp assembly for connecting a first pipe to a second pipe in a vacuum system. The first pipe has a first flange and the second pipe has a second flange, wherein the first flange is arranged to form a joint with the second flange when the first pipe is connected to the second pipe. The clamp assembly comprises a resilient ring configured to surround a non-flanged portion of the first pipe during use. The assembly further comprises a plurality of clamping elements coupled with the resilient ring and each operable to rotate relative to the resilient ring via respective axes of rotation during use in order to move the clamping elements from an open position in which the clamping elements are not in contact with the first flange into a clamping position in which in use when the first pipe is connected to the second pipe. In such a way, the clamping elements are arranged to clamp the first flange to the second flange to form a joint between the first pipe and the second pipe.

In such an arrangement, the resilient ring allows the clamp assembly to be coupled with the first pipe prior to clamping. This facilitates the clamping process as the assembly does not need to be held onto the joint while the elements are secured into a clamping position. The resilient ring may exert a radial force onto the clamping elements to hold them against the first pipe and prevent them from naturally sliding down the pipe prior to clamping. When it is desired to join the two pipes together the user can then slide the clamp assembly along the first pipe towards the second pipe (with the clamping elements in their open position) and then bring the clamping elements into their clamping position to clamp the first and second pipes together at their flanges. The clamp assembly of the invention facilitates the maintenance of the low pressures required in the vacuum system. For example, the clamp assembly is capable of generating sufficient clamping force for sealing the joint between the first and second pipes such that it is possible to maintain a pressure within the pipes of below 10 mbar or even below 10-2 mbar.

In some embodiments, the clamp assembly may be configured for clamping pipes in a semiconductor manufacturing system and may be made from materials suitable for use in such hostile environments. Furthermore, in pump exhaust pipes in a semiconductor system the assembly may also need to be configured to withstand larger pressures for example during a fault condition of the system. In embodiments the clamp assembly may be configured to maintain clamping when pressure within the pipes reach up to 10 bar.

In embodiments, the resilient ring is a canted spring. In other words, the resilient ring comprises a helical spring in which the two ends of the helix are joined to each other to form a loop having a helix of spring material extending around the loop. The canted spring may be a metal spring, for example formed from spring steel.

The use of a spring allows energy to be easily held in the ring for a long period of time without significant degradation or creep, particularly in the hostile environments of many vacuum systems. In alternative embodiments the resilient ring may comprise an elastomer or other resilient material which may or may not be in a helical form. In embodiments, the resilient ring may comprise resilient connections between adjacent clamping elements such that the clamping elements also form part of the resilient ring. Most generally the resilient ring is configured to the such that it can bias the clamping elements against the pipe around which it is to be mounted but still allows movement of the clamping elements towards a clamping position thereof.

The resilient ring may have a spring stiffness of between 0.005 and 0.05 N/m, e.g. between 0.008 and 0.02 N/m. Such a stiffness has been found to be particularly advantageous as it provides enough force to hold the clamping elements onto the first pipe during mounting thereon but not too much force that it is difficult to mount the clamping arrangement in the first place. In embodiments, the resilient ring may have a stiffness and length such that the ring exerts between 0.05 N and 5 N force on the clamping elements when assembled on the pipes. In particular embodiments the force may be between 0.05 N and 2 N such as 1 N.

The resilient ring may comprise a latching mechanism for mounting the clamp assembly to the first pipe and removing the clamp assembly after use. For example, the resilient ring may comprise a length of resilient material having each end attached to the other at via the latching mechanism to form a loop of resilient material for surrounding the first pipe in use. The latching mechanism may comprise a grub screw having a thread engaged with the resilient material at each end. For example, the grub screw thread may be engaged with the helical structure of a spring of the resilient material. Additionally or alternatively, the latching mechanism may comprise a hook positioned at a first end of the resilient material and a loop at the second end of the material for releasable engagement with the loop.

The axes of rotation of each of the clamping elements may be configured to be generally perpendicular to the axis of the first and second flange in use. This differs from the traditional clamping mechanisms in which the clamping elements are generally articulated about one or more axes that are generally parallel to the flange axes. The parallel axes usually result in the clamp assembly having to be mounted from the side of the joint, in a radial direction with respect to the flange such that securing of the clamp needs to be done on the other side of the joint to the operative or otherwise the clamp needs to be carefully manipulated during mounting which can cause considerable difficulty in pipe arrangements with limited access such as that shown in Figure 1 b. By having the axes generally perpendicular, the clamping elements can be mounted onto the flange from above or below such that clamp assembly is co-axial with the first pipe or flange prior to and during clamping. The clamp assembly may be expanded to fit over the pipe or flange and/or attached via a latching mechanism for a considerable time prior to clamping. The first pipe may be provided with an open clamp assembly ready for clamping at a later stage of assembly of the vacuum system.

In embodiments, the clamping elements are positioned at different circumferential positions around the resilient ring such that the axis of rotation for each clamping element is offset from the axis of rotation of each of the other clamping elements. As such each clamping element has its own axis of rotation and operates independently from each of the other clamping elements.

The resilient ring may be sized such that when the clamp assembly is connected to a first pipe and when all of the clamping elements are in their open position, the clamp assembly is able to slide axially along the first pipe

The clamp assembly may comprise two or more clamping elements. The inventor has found that using more clamping elements may provide an improved the clamping function of the assembly due to an increased number of contact points. For example, the clamp assembly may comprise 4 or more of the clamping elements or between 4 and 10 clamping elements. Having 10 or fewer elements may reduce the complexity of the assembly and make it easier to manufacture and manipulate during clamping. Embodiments comprise 3, 4, 5, 6, 7 and 8 clamping elements.

The clamping elements may be formed from a metal material, for example. Metal clamping elements may be particularly suitable for use in hostile environments such as semiconductor manufacture. In embodiments, the clamping elements may be formed from a plastics, ceramics or composite material.

The clamp assembly may be configured to move between an open position in which all the clamping elements are in their respective open positions and a clamping position in which all the clamping elements are in their respective clamping positions. The open position being a position of the assembly in which the clamping elements are in contact with the first pipe and the clamp assembly is operable to slide (by a user providing a force) axially along the first pipe towards the second pipe. The clamping position being a position of the assembly in which the clamping elements are in contact with the first and second flanges in order to connect the first and second pipes. Moving the clamp assembly between the open and clamping positions may comprise rotating the clamping element about a pivot.

The clamp assembly may further comprise a securing ring configured to engage with an outer surface the clamping elements in order to secure the clamp assembly in the clamping position. In embodiments the securing ring may be configured to rotate the clamping element into the clamping positions. More particularly, axial movement of the securing ring over the clamping elements may exert a radial force thereon causing them to pivot into a clamping position.

The outer surface of the clamping elements in this instance refers to the radially outer surface of the elements with respect to the pipes and resilient ring, in use. In embodiments the securing ring encircles and engages the radially outer surface of all the clamping elements. The securing ring preferably has an adjustable diameter or internal dimension such that the securing ring can be tightened around the clamping elements to increase the clamping force of the clamp assembly. More specifically, reducing the diameter or internal dimension of the securing ring while it is positioned over and engaged with the clamping elements increases a radially inward pressure on the clamping elements towards the first and second flanges. In embodiments, the geometry of the clamping elements is such that the increase in radial pressure on the clamping elements is transferred, at least in part, to an increase in axial pressure on the first and second flanges. The securing ring may comprise one or more fasteners configured to reduce the inner diameter of the securing ring to clampingly engage the clamping elements with the first and second flanges.

In embodiments the clamping elements comprise an outward-facing side configured to engage with the securing ring in use and an inward-facing side configured to engage with the first and second pipes in use. The inward-facing side comprises a resting surface configured to engage with the first pipe when the clamp assembly in in the open position and clamping surfaces configured to engage with the first and second flanges when the clamp assembly is in the clamping position. The clamping surfaces may be opposing clamping surfaces sloping towards each other from an outer edge to a midportion of the inward-facing side. The inward facing side may further comprise a pivot positioned between the resting surface and the clamping surfaces. For example, the clamping surface closest to the resilient ring and the resting surface may join each other at an angled junction which forms the pivot. The pivot may have a radius that facilitate smooth movement of the element when moving between the open and clamping positions.

The clamping elements may be biased into the open position by the resilient ring. For example, the resilient ring may be positioned closer to the resting surface that to the clamping surfaces. In embodiments the resilient ring is axially offset from the pivot toward the resting surface urging the clamping elements into the open position.

In embodiments, the resilient ring may extend through an aperture or slot formed in the clamping elements. More broadly the resilient ring may comprise resilient connections between adjacent clamping elements that may be attached to or extend through the clamping elements. The resilient ring may be a continuous ring of resilient material or may comprise a number of connecting elements that, together with the clamping elements form a continuous ring.

In embodiments, the outward facing side of one or more of the clamping elements comprises a shoulder to limit axial movement of the securing ring in use. Such a shoulder may facilitate clamping by providing an end stop for the securing ring during clamping of the assembly. The shoulder may further help keep the securing ring in position during use, preventing the securing ring from moving relative to the clamping elements due to vibration of the pipes for example. The outward facing side may have a surface for engagement with the securing ring which may be angled relative to the axis of the pipe when in a clamping position such that, when the securing ring is tightened, it is urged towards the shoulder. In embodiments the surface on the outward facing side is angled from the axis of the pipe by between 2 and 6 degrees when in a clamping position.

Also in accordance with the invention, there is provided a vacuum system comprising a first pipe having a first flange, a second pipe having a second flange and a clamp assembly according to any of the embodiments described above connecting the first pipe to the second pipe at the respective flanges.

The inner diameter of the clamp assembly may be smaller than the outer diameter of the first pipe such that the resilient ring must expand to allow the clamping elements to fit over the first pipe. The tension in the resilient ring may thus exert sufficient radial force on clamping elements to hold them in position against the first pipe and prevent them from sliding down the pipe prior to clamping. In embodiments, the resilient ring may have a stiffness and length such that the resilient ring exerts between 0.05 N and 5 N force on the clamping elements when assembled on the pipes. In particular embodiments, the force may be between 0.05 N and 2 N such as 1 N.

In embodiments, the vacuum system is configured to maintain a pressure within the first and second pipes of below 10 mbar or even below 10’ ² mbar. In such a vacuum system the first and second pipes may be made from a metal, for example stainless seal. The pipes may be generally cylindrical, and the flanges may extend radially out from an end of the first and second pipes to form a generally annular surface for abutting against the other of the first and second flange.

In embodiments, the assembly may further comprise one or more sealing elements such as an 0-ring or gasket positioned between the first and second flanges to facilitate sealing thereof. The first and/or second flanges may comprise one or more grooves for receiving such sealing elements. Also in accordance with the invention, there is provided a method of clamping a first flange of a first pipe to a second flange of a second pipe of a vacuum system using a clamp assembly. The clamp assembly comprises a resilient ring configured to surround (a non-flanged portion of) the first pipe during use and a plurality of clamping elements coupled with the resilient ring and each operable to rotate relative to the first pipe via respective axes of rotation during use in order to move the clamping elements from an open position in which the clamping elements are not in contact with the first flange into a clamping position in which in use when the first pipe is connected to the second pipe the clamping elements are arranged to clamp the first flange to the second flange to form a joint between the first pipe and the second pipe. The clamp assembly may further comprise any of the features described in the embodiments above.

The method may comprise first securing the clamp assembly to the first pipe and then moving the clamping elements from an open position in which the clamping elements are in contact with the first pipe only to a clamping position in which the clamping elements are in contact with the first and second flanges to form a vacuum tight engagement therebetween. Moving the clamping elements may comprise rotating the clamping elements about a pivot thereof.

A securing ring may be used to move the clamping elements into engagement with the first and second flanges. The securing ring may be tightened around the clamping elements to urge the clamping elements to clampingly engage with the first and second flange.

Brief Description of the Drawings

Figure 1a shows a clamp assembly of the prior art;

Figure 1 b shows the clamp assembly of Figure 1 a in a clamping position;

Figure 1c shows a sectional view of a pipe arrangement; Figure 2a shows a side view of a first and second pipe secured together with a clamp assembly according to an embodiment of the invention;

Figure 2b shows a top view of the pipes and clamp assembly of Figure 2a;

Figure 3a is a perspective view of a clamping elements according to an embodiment,

Figure 3b shows the clamping element of Figure 3a in an open position;

Figure 3c shows the clamping element of Figure 3a in a closed position;

Figure 4a shows a resilient ring for use in the clamp assembly of Figure 2a;

Figure 4b shows the resilient ring of Figure 4a in an unlatched position;

Figure 5 shows a securing ring for use in the clamp assembly of Figure 2a

Figure 6a shows a clamp assembly according to an embodiment in an open position prior to clamping; and

Figure 6b shows the clamp assembly of Figure 6a in a clamping position.

Detailed Description

The present invention provides an improves clamp assembly for connecting two pipes together in a vacuum system. The clamp assembly is configured such that it may hold itself onto one of pipes prior to clamping so does not need to be manually held in place prior to and during clamping of the pipe flanges. Figure 2a shows a pipe joint 12 in a vacuum system including a first pipe 26 having a first flange 28 and a second pipe 30 having a second flange 32. The first pipe 26 and second pipe 30 are configured to be clamped together at a joint 12 formed by the first flange 28 and second flange 32. In this embodiment a resilient sealing element 34 in the form of an elastomeric gasket or 0-ring is positioned between the first and second flanges 28, 32 to form a seal between to first and second pipes 26, 30 to prevent gas from entering the pipes via the joint 12. It will be appreciated that alternative sealing elements such as metallic sealing elements may be used or that the flanges 28, 32 may be configured such that no additional sealing element is required. Although the figures show the flanges 28, 32 having a uniform radial thickness as they extend away from the pipes 26, 28 it will be appreciated that the thickness may also taper as per standard pipe flanges known in the art of vacuum systems.

Figure 2a further shows a clamp assembly 36 according to an embodiment of the invention. The clamp assembly 36 engages with the flanges 28, 32 on each pipe 26, 30 in order to fix the pipes 26, 30 relative to each other in both an axial and radial direction and provides an axial load to the flanges 28, 32 in order to prevent twisting about the joint axis. The axial load may also create an improved seal at the joint 12 by compressing the flanges 28, 32 against the gasket 34. The term ‘axial direction’ is used herein to refer to a direction along the axis of the joint 12 which generally corresponds to the axis 38 of the flanges and pipes (where straight). The term ‘radial direction’ is used herein to refer to a direction perpendicular to the axis 38 along a radius of the joint 12.

The clamp assembly 36 comprises four clamping elements 40 arranged circumferentially around the joint 12. The clamping elements 40 are each mounted on a resilient ring 42 extending through an aperture 44 in each of the clamping elements 40 and are secured in sealing engagement with the flanges 28, 32 by a securing ring 46 which encircles each of the clamping elements 40. The securing ring 46 is shown in phantom in Figure 2a but more clearly shown in Figure 2b. Although four equally spaced clamping elements 40 are shown, it will be appreciated that the clamping elements 40 need not be arranged with equidistant spacing and any number of clamping elements 40 may be used. Preferably the clamping assembly 36 includes two or more such clamping elements 40, for example, three, four, five, six, seven, eight or more clamping elements 40 may be arranged around the joint 12.

Figures 3a-c show one of the clamping elements 40 of Figure 2 in greater detail.

The clamping element has an inward-facing side 48 configured to engage with the pipe flanges 28, 32 during use and an outward-facing side 50 configured to engage with the securing ring 46 during use.

On the inward-facing side 48, the clamping element 40 comprises a resting surface 52 configured to engage with the non-flanged outer surface of the first pipe 26 when in an open position as shown in Figure 3b. Also on the inward-facing side 48, there are opposing clamping surfaces 54 for engagement with the first and second flanges 28, 32 when in a clamping position as shown in Figure 3c.

The clamping element 34 further comprises an aperture 44 extending through it for mounting onto the resilient ring 42 and a pivot 56 about which the clamping element 40 can rotate between the open position and the clamping position as described above. The pivot 56 is positioned between the resting surface 52 and the clamping surfaces 54 and is in the form of a curved protrusion on the inward-facing side 48 of the clamping element 40.

Although the embodiments show an aperture 44 for receiving the resilient ring 42, it will be appreciated that the clamping elements 34 may alternatively comprise a slot or other such feature for receiving the resilient ring 42.

The outward-facing side 50 comprises a generally planar surface 58 for engagement with the securing ring 56 and a shoulder 60 configured to limit axial movement of the securing ring 56 when the assembly is in the clamping position. An alternative configuration in which the surface 58 is angled relative to the axis 38 of the pipe when in a clamping position is shown in phantom in Figure 3c. Such a configuration urges the securing ring 56 towards the shoulder 60 to prevent it sliding off during use. The surface 58 may be angled relative to the pipe axis 38 by an angle a of between 2 and 6 degrees. In an embodiment the angle a is 3 degrees.

The resilient ring 42 is in the form of a canted coil spring formed from spring steel as shown in Figure 4a. The resilient ring 42 comprises a helical spring in which the two ends of the helix are joined to each other to form a loop having a helix of spring material extending around the loop.

The resilient ring 42 further comprises a latching mechanism 62 by which the ends of the spring can be released from each other, as shown in Figure 4b, to allow the resilient ring 42 to be mounted to or removed from the second pipe 30. In this example, the latching mechanism 62 comprises a hook 64 positioned at a first end of the resilient material and a loop 66 at the second end of the material for releasable engagement with the hook 64.

In an alternative embodiment, (not shown) the latching mechanism comprised a grub screw having a thread along its length which is engaged at each end with the resilient ring 42. In a particular example, the resilient ring 42 is formed from a helical spring having an outer diameter of 3.175mm and a wire thickness of 0.355mm. A M3 grub screw is then used to connect the two ends of the spring by rotating the thread into engagement with the helical form of the spring. This forms a joint between the ends of the spring with sufficient strength for the clamp assembly and also provides a smooth external profile or the resilient ring 42.

Figure 5 shows the securing ring 46 in more detail. The securing ring 46 is in the form of a flexible band having an inner surface 64 for engagement with the outward-facing side 50 of the clamping elements 40. The securing ring 46 has fastening means 66 for reducing the internal diameter of the securing ring 46 to tighten it around the clamping elements 40. In this example the fastening means 66 comprises opposing radial protrusions 68 having opposing apertures 70 through which a fastener 72 (shown in Figure 2b) such as a screw or bolt may pass through. Tightening of the fastener 72 brings the radial protrusions 68 closer together and thereby reduces the diameter of the securing ring 46 around the clamping elements 40.

The clamp assembly 36 may further comprise attaching means (not shown) for attaching the securing ring 46 to the clamping elements 40 and/or resilient ring 42 such that the securing ring 46 can move relative to the clamping elements 40 but does not slide too far away down the pipe work away from the joint 12. In examples, the attaching means comprises a cord extending between the securing ring 46 and one or more clamping elements 40 and/or resilient ring 42. In other examples the attaching means comprises a frangible connection that holds the securing ring 46 relative to the one or more clamping elements 40 and/or resilient ring 42 prior to clamping, the frangible connection configured to break to allow the securing ring 46 to be moved in place over the clamping elements 40.

Figures 6a and 6b show the clamp assembly in an open position and a clamping position respectively. In Figure 6a the clamping elements 40 are mounted onto the first pipe 26 and held in place via the resilient ring 42 such that the user does not have to hold the clamping elements 40 in position. The inner diameter of the clamp assembly 36 is smaller than the outer diameter of the first pipe 26 such that the resilient ring 42 must expand to allow the clamping elements 42 to fit over the first pipe 26. The tension in the resilient ring 42 exerts sufficient radial force on clamping elements 40 to hold them in position against the first pipe 26 and prevent them from sliding down the first pipe 26 away from the joint 26 prior to clamping.

The resting surface 52 of each of the clamping elements 40 is held against the first pipe 26 in the open position. The position of the resilient ring 42 relative to the pivot 56 ensures that the clamping element 40 is biased into the open position prior to clamping. More specifically the aperture 44 through which the resilient ring 42 extends is on the side of the pivot 56 closer to the resting surface 52 than to the clamping surfaces 54.

In order to move the clamp assembly 36 into the clamping position, the clamping elements 40 need to be rotated about their respective pivots 56 so that the clamping surfaces 54 come into contact with the flanges 28, 32. This requires the application of radially inward force on the clamping elements 40 on the side of the pivot 56 closer to the clamping surfaces 54. The radially inward force must be greater that the biasing force of the resilient ring 42.

The radially inward force is provided by the securing ring 46 which is axially moved over the clamping elements 40 to the required position. The shoulder 60 limits the axial movement of the securing ring 46 such that it remains in the required position for optimal clamping. The securing ring 46 is retained in the required position via the fastening means 72 as described above.

The above described embodiment relates to an assembly which is mounted from below the first and second flanges 28, 32. However, it will be appreciated that the present invention could be applied to an assembly configured for clamping from above the flange, by inverting the clamping assembly 36 for example.

10 clamp

12 joint

14 clamp axis

16 joint axis

18 clamping elements

20 pivot

22 securing means

24 radial direction

26 first pipe

28 first flange 30 second pipe

32 second flange

34 resilient sealing element

36 clamp assembly

38 joint axis

40 clamping element

42 resilient ring

44 aperture

46 securing ring

48 inward facing side

50 outward facing side

52 resting surface

54 clamping surfaces

56 pivot

58 planar surface

60 shoulder

62 latching mechanism

64 inner surface

66 fastening means

68 radial protrusions

70 apertures

72 fastener