PRELOAD FORCE TOOL

Abstract

The invention relates to a bearing preload force gauge for indicating the bearing preload force on a turbomolecular pump rotor bearing. The gauge comprises a housing, an indicator for indicating the bearing preload force, and actuator coupled to an impeller engagement surface by a member configured to provide a resilient bias between the actuator and the impeller engagement surface. The invention also relates to a bearing preload tool and methods for measuring the bearing preload force on a turbomolecular pump.

Claims

1. A bearing preload force gauge for indicating the bearing preload force on a turbomolecular pump rotor bearing, the gauge comprising a housing, an indicator for indicating the bearing preload force, and actuator coupled to an impeller engagement surface with a member configured to provide a resilient bias between the actuator and the impeller engagement surface.

2. The gauge according to claim 1, wherein, in use, the bearing preload force is indicated by coupling the impeller engagement surface with a pump impeller and moving the actuator relative to the engagement surface against the action of the resilient bias member to overcome the bearing preload force.

3. The gauge according to claim 1 wherein the actuator, the resilient bias member, and an impeller location member comprising the impeller engagement surface are movable in a reciprocating motion relative to the housing.

4. The gauge according to claim 1 wherein when the bearing preload force is overcome the indicator provides an indication as to whether the bearing preload force is within or outside a predetermined preferred range.

5. The gauge according to claim 4 wherein when the bearing preload force is overcome the indicator provides a first indication if the bearing preload force is within the predetermined preferred range.

6. The gauge according to claim 5 wherein when the bearing preload force is overcome the indicator provides a second indication if the bearing preload force is outside the predetermined preferred range, said second indication being different from the first indication.

7. The gauge according to claim 4 wherein when the bearing preload force is overcome if the bearing preload force is outside the predetermined preferred range the indicator indicates whether the bearing preload force is above or below the predetermined preferred range.

8. The gauge according to claim 1 wherein the indication provided by the indicator is visual.

9. The gauge according to claim 1 wherein the indicator comprises indicium coupled to the housing or actuator and an indicium identifier, wherein in use the indicium and identifier are movable relative to one another to indicate the bearing preload force.

10. The gauge according to claim 9 wherein an indicium indicates the lower limit of a predetermined preferred preload force range and an indicium indicates the upper limit of the predetermined preferred preload force range.

11. The gauge according to claim 9 comprising an indicium indicating when the bearing preload force is in a predetermined preferred range.

12. The gauge according to claim 9 wherein the indicium comprises a stepped upper surface on the housing and wherein a first step indicates a lower limit of a predetermined preferred preload force range and a second step indicates the upper limit of the predetermined preferred preload force range.

13. The gauge according to claim 12 wherein the first step and the second step each comprise a secondary indicium indicating the predetermined preferred preload force range.

14. The gauge according to claim 1 wherein the resilient member comprises a spring, preferably a compressive spring, preferably a helical compressive spring.

15. The gauge according to claim 1 wherein overcoming the bearing preload force is accompanied by an audible signal.

16. The gauge according to claim 1 further comprising a preload force adjuster for altering the bearing preload force on the rotor bearing of the turbomolecular pump.

17. A preload force tool for a turbomolecular pump comprising a rotor bearing under an adjustable preload force, the tool comprising a preload force gauge and a preload force adjuster.

18. The tool according to claim 17 wherein the gauge comprises a housing, an indicator for indicating the preload force, and actuator coupled to an impeller engagement surface with a member configured to provide a resilient bias between the actuator and the impeller engagement surface.

19. A method for measuring the bearing preload force on a turbomolecular pump rotor bearing, the method comprising the steps of: a) providing a turbomolecular pump comprising a rotor bearing having a preload force applied thereto; b) providing preload force gauge comprising a housing, an indicator for indicating the bearing preload force, and an actuator coupled to an impeller engagement surface with a member for providing a resilient bias; c) coupling the impeller engagement surface with the impeller; d) moving the actuator relative to the impeller engagement surface against the resilient bias so as to overcome the bearing preload force on the rotor bearing; and e) reading an indication of the bearing preload force from the indicator when the bearing preload force is overcome f) further comprising adjusting the bearing preload force using the gauge and optionally remeasuring the bearing preload force without removing the gauge from the turbomolecular pump.

20-22. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURES

[0053] Preferred features of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0054] FIG. 1 shows a section view of a bearing preload force gauge.

[0055] FIG. 2 shows a section view of a bearing preload force gauge in situ.

[0056] FIG. 3 shows a bearing preload force gauge.

[0057] FIG. 4 shows a schematic of a beating preload force gauge illustrating an indicator preferred range.

[0058] FIG. 5 shows a hearing preload force gauge at rest.

[0059] FIG. 6 shows a bearing preload force gauge in a fail configuration (preload force is too low).

[0060] FIG. 7 shows a hearing preload force gauge in a pass configuration.

[0061] FIG. 8 shows a hearing preload three gauge in a fail configuration (preload force is too high).

[0062] FIG. 9 shows an alternative indicator in a series of configurations.

DETAILED DESCRIPTION

[0063] The present invention provides a bearing preload force gauge for indicating the bearing preload force on a turbomolecular pump rotor bearing.

[0064] As illustrated in FIG. 1, in an example, the gauge (100) comprises a housing (1), an impeller location member (2), an actuator (4) and a resilient member (3) (in the illustrated example a helical compression spring) between the actuator (4) and the impeller location member (2).

[0065] Referring also to FIG. 2, the impeller location member (2) is configured to transmit a force applied thereto by the actuator (4) to the impeller (6) of the turbomolecular pump (7). The impeller location member (2) comprises a forward portion (8) configured to extend forward of the housing (1) to couple with the pump impeller (7) and a radially extending circumferential flange (9) that slidably engages with an inner wall (10) of the gauge housing (1). The circumferential flange (9) may be located generally centrally along the length of the impeller location member (2), dividing the forward portion (8) of the location member from a rear portion (11). The illustrated impeller location member (2) further comprises a rearward portion (11) slidably receivable within the spring (3) and actuator (4).

[0066] At its tip the impeller location member (2) comprises a impeller engagement surface (12) which, in use, couples with the impeller (6), preferably the surface (12) directly engages the impeller (6), preferably the surface directly engages the rotor shaft (13).

[0067] The illustrated housing (1) is generally cylindrical with a central channel configured to receive the actuator (4), resilient member (3) and the impeller location member (2). The wall of the central channel (formed by the inner wall of the housing (10)) may comprise ribs or channels configured to engage with corresponding protrusions or indentations on the actuator (4) and/or impeller location member (2), to aid sliding. The channel further includes shoulders (14, 15, 16) at proximal (17) and distal (18) ends thereof to retain the actuator (4) and impeller location member (2) within the housing (1).

[0068] The housing (1) further includes a series of steps (19, 20, 21) on its upper surface (22). These, along with a circumferential indentation (23) on the actuator (4), form the indicator for indicating whether the bearing preload force is within a predetermined preferred range.

[0069] As better illustrated in in FIGS. 3 and 4, in the example, the upper step (19) indicates lower limit of the predetermined preferred bearing preload force range and the second step indicates the upper limit of the predetermined preferred bearing preload three range (20). In this example, the circumferential indentation (23) on the actuator (4) is the indicium identifier, whereas the steps form the primary indicia. The steps (19, 20) further include secondary indicia Go and No Go formed in their surfaces. If, when the bearing preload force is overcome, the indicium identifier (23) is located between the upper step (19) and second step (20), as illustrated in FIG. 4, this is a pass (i.e. the bearing preload force is in the predetermined preferred range). Alternatively, if, when the bearing preload force is overcome, the indicium identifier is located above the upper first step (19), as illustrated in FIG. 4, this is a fail (the bearing preload force is too low).

[0070] As illustrated in FIG. 2, the lower end of the gauge housing (1) is configured to couple with the housing of the turbomolecular pump (24) so that the gauge housing (1) remains substantially stationary relative to the pump housing (24) whilst a bearing preload force measurement is taken. The lower (distal) end of the exemplified housing (1) further includes three adjustor drive legs (25, 26, 27) (better illustrated in FIGS. 5 to 8). The adjustor drive legs (25, 26, 27), as well as contributing to the stability of the gauge (100) during use, are configured to allow the gauge (100) to adjust the bearing preload force, typically by facilitating movement of the inner race (28) of the passive magnetic bearing (30) relative to its outer race (29). By rotating the device (100) about its longitudinal axis (A) in one direction the bearing preload force can be increased, whereas by rotating the device (100) about its longitudinal axis (A) in an opposite direction the bearing preload force can be decreased. Advantageously, the bearing preload force can be measured and adjusted by the same device (100) and without decoupling said device (100) from the turbomolecular pump (101). Typically, the hearing preload force is adjusted when the gauge (100) is in an at rest configuration.

[0071] The actuator (4) comprises rearward facing user interface (5) which in use may be pressed by an operator thumb or finger. The actuator (4) further comprises a resilient member (e.g. spring) engagement surface (31), in the example the downward (forward) facing surface (31) of a radially extending circumferential flange (32) at a distal end of the actuator (4). The actuator (4) is configured to slide in a reciprocating motion within the housing channel (10). The actuator (4) comprises an inner channel (33) configured to receive the rearward portion (11) of the impeller location member (2) in a reciprocating sliding arrangement.

[0072] When pushed in a forward (downward) direction, the actuator (4) pushes the spring against the impeller location member (2), thereby compressing the spring (3). The impeller location member (2) transmits the force to the impeller (6) of the turbomolecular pump (101). By increasing the force applied to the actuator (4), the spring (3) is compressed further and the spring's restoring (reaction) force increases: likewise, the force transmitted to the impeller (6) (and rotor bearing) increases. The force applied to the actuator (4) is increased until the force transmitted to the impeller (6) is sufficient to overcome the bearing preload force. At that point a click will be heard and the indicator is read to establish whether the bearing preload force is within its predetermined preferred range.

[0073] Releasing the actuator (4) allows the gauge (100) and turbomolecular pump (101) to return to their respective at rest positions.

[0074] If the bearing preload force was not within the predetermined preferred range for that turbomolecular pump (101), the bearing preload force can be adjusted and the bearing preload force remeasured. The process may be repeated until the bearing preload force is within the predetermined preferred range.

[0075] The exemplified device is for use on a nEXT85 available from Edwards Vacuum and is configured to have a predetermined preferred bearing force range of from about 8.3 N to about 10.3 N. The illustrated spring is a LC036G05S available from Lee Spring Ltd. with a spring rate of 1.05 N/mm The distance between the uppermost step and the next step is 2 mm. The skilled person will appreciate that the specific spring and indicator arrangement will be chosen depending on the preferred hearing preload force range for a specific turbomolecular pump.

[0076] The illustrated device may be handheld and/or manually actuated. By manually actuated it is understood that the force required to overcome the bearing preload force is applied to the actuator by the operator's hand.

[0077] The housing, actuator and impeller location member are additive manufactured from Objet Veroblue RGD840.

[0078] FIGS. 5 to 8 illustrate the device in various configurations. FIG. 5 shows the device (100) in its at rest configuration. In this configuration, no force is applied to the actuator (4), the spring (3) is not displaced or compressed, and the actuator (4) and the impeller location member (2) are in their most upward positions. in this configuration, the circumferential groove (23) of the indicator is well above the top step (19) of the gauge housing (1).

[0079] FIG. 6 illustrates the device (100) in a configuration where the bearing preload force is too low. The spring (3) is compressed and the actuator (4) has moved downward (forward) relative to the housing (1); however, the circumferential groove (23) is above the top step (19) of the gauge housing (1) indicating that bearing preload force is too low.

[0080] FIG. 7 illustrates the device (100) in a configuration where the bearing preload force is within the predetermined preferred range. The spring (3) is further compressed and the actuator (4) and impeller location member (2) have moved further downward (forward) relative to the housing (1). In this configuration, the circumferential groove (23) is below the top step (19) of the gauge housing, but above the second step (20), illustrating that bearing preload force is within the predetermined preferred range.

[0081] FIG. 8 illustrates the device in a configuration where the bearing preload force is too high. The spring (3) is compressed further still and the actuator (4) and impeller location member (2) have moved even further downward (forward) relative to the housing (1). In this configuration, the circumferential groove (23) is below the second step (20) of the gauge housing (1), indicating that bearing preload force is too high.

[0082] FIG. 9 illustrates an alternative example of an indicator suitable. for use in the present invention in a series of configurations. In this example, the indicator comprises two indicia (34, 35) in form of circumferential grooves formed in the surface of the actuator (4). in use, as the actuator (4) is pushed into the housing (1), the upper groove (34) indicates the lower limit of the predetermined preferred range for the hearing preload force, whereas the lower groove (35) indicates the upper limit of the predetermined preferred range for the bearing preload force. In this example, the indicium identifier (23) is the upper surface of the gauge housing (1) immediately adjacent the actuator (4).

[0083] Thus, in contrast to the previous example, the indicium (34, 35) are located on the actuator (4) and movable relative to a stationary indicium identifier (23) located on the housing (1).

[0084] Accordingly, as illustrated, if as the bearing preload force is overcome during testing both grooves (34, 35) are above the housing (1) then the bearing preload force is too low, whereas if neither of the grooves is above the housing (1) then the bearing preload force is too high. In contrast, if when the bearing preload force is overcome the upper groove (34) is above the housing (1) but the lower groove is not, then the bearing preload force is within the predetermined preferred range. In this example, no secondary indicia are employed. It will be appreciated that the grooves could be replaced with printed lines or other suitable indicia.

[0085] It will be appreciated that various modifications may be made to the embodiments shown without departing from the spirit and scope of the invention as defined by the accompanying claims as interpreted under patent law.

[0086] Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

[0087] Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.