ORBITAL PUMP

Abstract

A safety device for an orbital pump has first and second interleaved parts which are operable to follow an orbital path with respect to each other, the safety device comprising: a first member fixable with respect to the first interleaved part; and a second member fixable with respect to the second interleaved part, the second member defining an aperture into which the first member is receivable, the aperture being dimensioned to prevent movement of the first interleaved part with respect to the second interleaved part beyond the orbital path. In this way, the members of the safety device help to prevent the moving components of the pump contacting, thereby preventing damage.

Claims

1. A safety device for an orbital pump having first and second interleaved parts which are operable to follow an orbital path with respect to each other, the safety device comprising: a first member configured to be fixed with respect to the first interleaved part; and a second member configured to be fixed with respect to the second interleaved part, the second member defining an aperture into which the first member is is configured to be received, the aperture being dimensioned to prevent movement of the first interleaved part with respect to the second interleaved part beyond the orbital path, wherein the aperture is dimensioned to accommodate movement of the first member without contact when following the orbital path.

2. The safety device of claim 1, wherein the first member is elongate, at least an axial portion of which is configured to be received within the aperture.

3. The safety device of claim 1, wherein the first member configured to be fixed to the first interleaved part which forms part of a casing of said orbital pump.

4. The safety device of claim 1, wherein the first member comprises a rod have a circular cross-section.

5. The safety device of claim 1, wherein the second member is planar.

6. The safety device of claim 1, wherein movement of the first interleaved part with respect to the second interleaved part follows the orbital path and the aperture is dimensioned to match the orbital path.

7. (canceled)

8. The safety device of claim 1, wherein the aperture is dimensioned to accommodate movement of the first member without contact when following the orbital path plus a tolerance amount.

9. The safety device of claim 1, wherein the aperture is dimensioned to contact with the first member when exceeding the orbital path.

10. The safety device of claim 1, wherein the aperture is dimensioned to contact with the first member when exceeding the orbital path plus a tolerance amount.

11. The safety device of claim 1, wherein the aperture and the first member are dimensioned to prevent further movement of the first interleaved part with respect to the second interleaved part beyond the orbit.

12. The safety device of claim 1, wherein at least a part of the first member and the second member is conductive.

13. The safety device of claim 1, wherein contact between the first member and the second member facilitates transmission of a signal to prevent operation of the orbital pump.

14. An orbital pump, comprising: first and second interleaved parts which are operable to follow an orbital path with respect to each other; and the safety device of claim 1.

15. A method, comprising: fixing a first member fixed with respect to a first interleaved part of an orbital pump having the first interleaved part and a second interleaved part, wherein the first and second interleaved parts are operable to follow an orbital path with respect to each other; fixing a second member with respect to the second interleaved part, the second member defining an aperture into which the first member is configured to be received; dimensioning the aperture to prevent movement of the first interleaved part with respect to the second interleaved part beyond the orbital path.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0036] Examples of the present disclosure will now be described further, with reference to the accompanying drawings.

[0037] FIG. 1 illustrates an orbital pump or compressor such as scroll pump or compressor according to one example.

[0038] FIG. 2 illustrates a safety device fitted to the pump of FIG. 1 in more detail.

DETAILED DESCRIPTION

[0039] Before discussing the examples in any more detail, first an overview will be provided. Examples provide a mechanism which mechanically prevents moving components of an orbital pump or compressor from moving beyond their expected paths, which would otherwise cause the components to contact, causing damage to the pump or compressor. The mechanism has two parts, one of which attaches to one of the components and the other attaches to the other component. One part extends into an opening in the other part. When too much movement occurs, the parts contact each other and mechanically prevent further movement of the components. In addition, the contact between the parts can complete a circuit which cuts power to the pump motor causing it to stop, thereby preventing further damage.

[0040] Examples can be applied to both common orbital pump or compressor, such as scroll pump or compressor configurations: Type 1 in which one scroll is stationary and the other orbits, and Type 2 in which both scroll components rotate.

[0041] Pump

[0042] FIG. 1 illustrates an orbital pump or compressor such as scroll pump or compressor 100 according to one example. A scroll may be used as a vacuum pump for example for evacuating a process chamber in which semiconductor products are processed. The pump 100 comprises a pump housing 102 and a drive shaft 104 having an eccentric shaft portion 106. The shaft 104 is driven by a motor 108 and the eccentric shaft portion is connected to an orbiting scroll 110 so that during use rotation of the shaft 104 imparts an orbiting motion to the orbiting scroll 110 relative to a fixed scroll 112 for pumping fluid along a fluid flow path between a pump inlet 114 and pump outlet 116 of the pump 100.

[0043] The fixed scroll 112 forms part of the pump housing 102 and comprises a scroll wall 118 which extends perpendicularly to a generally circular base plate 120. The orbiting scroll 110 comprises a scroll wall 124 which extends perpendicularly to a generally circular base plate 126. The orbiting scroll wall 124 co-operates, or meshes, with the fixed scroll wall 118 during orbiting movement of the orbiting scroll. Relative orbital movement of the scrolls causes a volume of gas to be trapped between the scrolls and pumped from the inlet 114 to the outlet 116.

[0044] As mentioned above, radial clearances need to be accurately maintained since otherwise the two scrolls 110, 112 may contact, causing damage. To restrict the relative movement of the two scrolls 110, 112, a safety device 200 is fitted within the housing 102. The safety device 200 has a plate 210 fitted to the base plate 126 of the orbiting scroll 110 and a rod 220 fitted through the housing 102.

[0045] Safety Device

[0046] FIG. 2 illustrates the safety device 200 in more detail. The rod 220 has an end 230 which typically extends through the housing 102 and it attached to a fixing (not shown). This secures the rod 220 to the housing 102 and fixes its location spatially with respect to the fixed scroll 112. The rod extends from the housing 102 towards the orbiting scroll 110. The plate 210 has fixings apertures 240 through which fixings (not shown) fix the plate 210 to the base plate 126 of the orbiting scroll 110. This secures the plate 210 to the orbiting scroll 110 such that the plate 210 follows the orbital path of the orbiting scroll 110.

[0047] The rod 220 has another end 250 which extends through an orbital aperture formed in the plate 210. The orbital aperture is sized and shaped to match the orbital path followed or relative movement between the fixed scroll 112 and the orbiting scroll 110. That is to say that if a fixed point on one of the scrolls was observed from the other scroll while moving, the locus followed by that fixed point would match the orbital aperture. In this example, the orbital aperture 250 is slightly enlarged to account for manufacturing tolerances of the pump 100. Although in this example, the aperture is generally circular, it will be appreciated that this need not be the case and that the aperture is shaped to match the orbital path.

[0048] The rod 220 and the plate 210 are both conductive and connect to wires 260, 270 (one of the wires can be omitted if one of the rod 220 and the plate 210 are connected to the housing 102). The wires 260, 270 couple with a controller (not shown) which controls the operation of the motor 108.

[0049] In operation, the motor 108 drives the drive shaft 104 and the orbiting scroll 110 follows an orbital path with respect to the fixed scroll 112. In normal operation, the rod 220 fails to contact the orbital aperture 250 and instead describes a similar path a distance within the orbital aperture 250. Should a fault occur and the orbiting scroll 110 begins to move outside the orbital path by more than the tolerance amount, then the rod 220 will contact the orbital aperture, mechanically preventing further movement outside the orbital path. In addition, contact between the rod 220 and the plate 210 causes a circuit to be made which signals the controller to stop the motor 108 to prevent damage.

[0050] Accordingly, one example provides an anti-clash sensor for use on an oscillating or orbiting pump mechanism. Scroll vacuum pumps depend on the radial position of the orbiting scroll being fixed, so that it cannot clash with the adjacent fixed scroll. If there is a failure of the component(s) that fixes the scroll radial position, then a high degree of internal damage can occur with partial or total loss of function. One example performs two functions in order to protect an orbiting pump mechanism from damaging itself in the case of failure: first, it enables an electrical signal to automatically switch off the mechanism; and second, it limits the movement of the oscillating/orbiting part relative to the stationary parts, hence avoiding internal damage. In other words, one example auto protects the pump mechanism when loss of radial position occurs. In particular, one example allows the development of a new scroll pump, preventing damage if an internal failure occurred when testing was unattended (i.e. running overnight and at weekends).

[0051] In one example, a probe which is electrically conductive projects through the front cover of a scroll pump, being fixed into an insulating mount (made of PEEK or similar material). A metal sensor ring is attached to the internal orbiting scroll, which in this example uses bolt fixings. The probe is positioned within the internal diameter of the ring, such that the locus of ring relative to the fixed probe allows full orbiting motion of the scroll plus additional radial clearance between the probe and ring. If radial control of the orbiting scroll is lost (the anti-rotation device fails), then the probe will contact the inside diameter of the ring and two things will happen: first, an electrical circuit will be completed between probe and ring; second, excessive rotation of the orbiting scroll is limited, which would otherwise cause catastrophic contact between orbiting and fixed scroll. One example is able to limit the movement of the oscillating/orbiting part relative to the stationary parts, hence avoiding internal damage even when normal control of radial position has failed. This function is combined with the other function—to stop the pump when in the fault condition.

[0052] Although illustrative examples of the disclosure have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the disclosure is not limited to the precise example and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the disclosure as defined by the appended claims and their equivalents.