Sensor components

Abstract

A sensor assembly (12) for use in an apparatus including at least one moving part (18) and at least one stationary part (16), the assembly comprising a probe (32) and means (58) for mounting the sensor to the stationary part (16) of the apparatus. The probe (32) comprises a portion of an incomplete circuit which, when completed, produces a signal. In use, when the probe (32) is engaged by the moving part of the apparatus, the signal is produced. A vacuum pump or compressor pump including the sensor and a method for preventing apparatus failure are also provided.

Description

Technical Field

[0001] The present invention relates to a sensor assembly for use in a device having a stationary part and a moving part, such as a vacuum pump. The present invention also relates to a vacuum pump comprising such a sensor assembly, and a method for preventing failure of a device such as a vacuum pump. Background Art

[0002] Equipment including moving and stationary parts is used in various fields of technology. For example, vacuum pumps are used in many industrial applications, including the manufacture of semiconductor devices, where a good and clean environment is preferred to minimize contamination during the production of semiconductor wafers.

[0003] Dry vacuum pumps, such as Roots vacuum pumps, are commonly used to evacuate chambers in which semiconductor wafer manufacturing is performed. Roots vacuum pumps work by drawing air through a pair of intermeshing lobe-shaped rotors mounted inside a stator. Dry vacuum pumps are particularly preferred for manufacturing high-performance products, such as semiconductor devices, because they do not contain a sealing fluid between the stator and the rotor(s). This is desirable because the sealing fluid can vaporize and migrate into the processing chamber, resulting in contamination of the semiconductor being processed.

[0004] Instead, the efficiency of the pump depends on maintaining the clearance between the stator and the rotor(s) or any intermeshing rotor components within a specified tolerance. Currently, this relies on good design and manufacturing techniques to maintain the proper clearance throughout the operating cycle of the pump, including at elevated temperatures. If proper clearance is not maintained, the rotating mechanism can seize, which can cause expensive and potentially irreparable damage to the pump and may result in prolonged inoperation.

[0005] In some pumps, sensors are used to measure the gap between the stator and the rotor(s). The prior art is to use sensors to continuously measure and output data related to the gap between the stator and the rotor(s).

[0006] FR-A-2812041 discloses a dry vacuum pump of the Roots vacuum pump type, in which a proximity sensor is mounted on the stator to detect the axial thermal expansion of the rotor. The signal generated by the sensor is used to control the stator cooling unit in order to maintain the axial clearance of the rotor at a value greater than the minimum permissible value. This is achieved by determining whether the output signal of the sensor is above a predetermined threshold, whereupon an additional cooling circuit is activated.

[0007] WO-A-2017 / 025722 discloses a dry vacuum pump, wherein a sensor is mounted on a stator to detect the absolute distance between a point on the surface of a rotor and the inner surface of the stator. In use, the sensor continuously measures the gap between the rotor and the stator and outputs the data to a processing circuit.

[0008] These sensor systems, when used, each continuously collect and output data about the relative position of the stator and (multiple) rotors. Due to the high volume and complexity of the output data, their processing and analysis requires specific technical knowledge and expertise that the pump operator may not possess. In addition, due to their complexity, this type of sensor is expensive to purchase and operate. Therefore, it is common for pumps to operate without any such sensors, which risks catastrophic failure of the device.

[0009] Therefore, there is a need for a sensor suitable for use with various devices having moving parts, and in particular vacuum pumps, such as Roots vacuum pumps, having reduced complexity and data output, preferably at reduced cost.

[0010] Vacuum pumps often have to run continuously for days. Therefore, continuously monitoring the output data from the sensor is undesirable and may not be feasible. Therefore, there is also a need for a sensor that, if triggered, will stop the operation of the pump to prevent failure.

[0011] The present invention solves these and other problems of the prior art. Summary of the invention

[0012] According to the present invention, there is provided a sensor assembly for use in a device comprising at least one moving part and at least one stationary part.

[0013] The sensor assembly includes a probe that includes a portion of an incomplete circuit. The probe is configured to form a complete circuit when engaged by at least one moving component.

[0014] The sensor assembly also includes means for mounting the sensor assembly to a stationary component of the device. The assembly is configured to generate a signal when the circuit is completed.

[0015] The apparatus may include a mechanical device having two or more components in relative motion. For example, the apparatus may include a vacuum pump, such as a dry vacuum pump. In an embodiment, the apparatus includes a Roots vacuum pump. In an alternative embodiment, the apparatus includes a compressor pump.

[0016] In use, if the probe is not engaged by at least one moving part of the device, the circuit remains incomplete so that there is no signal output from the circuit. In the context of the present disclosure, the term "incomplete" takes its ordinary meaning in the art, and therefore, refers to a state in which there is a break in the circuit so that no current flows in the circuit.

[0017] When the sensor assembly is in use, the circuit is adapted to output a signal only when a member of the device in which it is installed engages the probe, and it is adapted not to output a signal otherwise. Advantageously, the data output is lower than that of prior art sensors because a signal is only generated when a moving part of the device makes contact with a stationary part.

[0018] The assembly can be mounted to the stationary component such that the probe extends a predetermined distance from the stationary component to the moving component, such that the assembly can be used to monitor whether the clearance between the stationary component and the moving component has been reduced to below an acceptable clearance, which is equal to or corresponds to the predetermined distance. In other words, the distance between the two components has been reduced below an allowable clearance distance. The clearance distance is typically selected by the user and depends on the equipment in which the device is installed and associated safety factors.

[0019] In an embodiment, the sensor assembly is configured to initiate a shutdown process of the device when the signal is generated. For example, the assembly may include a cut-off switch configured such that when the signal is output, it can activate the cut-off switch, stopping the operation of the device. The cut-off switch can stop powering the device so that it is no longer powered until the switch is deactivated.

[0020] In an embodiment, the cut-off switch may initiate a gradual reduction in the power supplied to the device. For example, the shut-off process may be one of a pulsed shut-off or a ramped shut-off process. For example, this may be advantageous in causing the rotational speed (i.e., power) of the moving parts to be gradually reduced to prevent the gap between the moving parts and the stationary parts of the device from being further reduced. Additionally or alternatively, the assembly may include means for generating a "warning" to the user, such as an audio or visual alarm, when a signal is output to indicate that action is required, such as to allow the user to manually activate the cut-off switch.

[0021] Advantageously, the shutdown process ensures that the operation of the equipment in which the assembly is installed will be stopped, thereby avoiding potential damage, such as the jamming of parts that are not designed to contact. This feature enables the equipment to be operated without direct supervision and / or with fewer maintenance interruptions, reducing the risk of failure due to stuck parts. This is beneficial because some equipment, such as Roots vacuum pumps, may need to run continuously for several days with only short breaks between repeated process cycles.

[0022] The probe can have an elongated three-dimensional shape and can be, for example, substantially defined by a cylinder, although other suitable probe forms are apparent to those skilled in the art. Typically, the cross-sectional length, such as the radius of the cylinder, can be between about 1.5 mm and about 5 mm, preferably between about 2 mm and about 4 mm, such as about 2.5 mm. The length of the probe can range from about 40 mm to about 100 mm, more preferably from about 60 mm to about 80 mm, such as about 65 mm to about 70 mm, such as about 67 mm.

[0023] The first end of the probe may have a rounded shape, for example such that it generally takes the form of a hemisphere with a radius equal to that of a cylinder.The first end of the probe may be configured to be engaged by a member of the apparatus, and the second opposing end may include means for electrically coupling the probe to a circuit.

[0024] The assembly may further comprise a sleeve. The sleeve may be configured to encase the first portion of the probe such that, in use, the second portion of the probe protrudes from the sleeve. The sleeve may comprise means for mounting the sensor to a stationary component of the apparatus.

[0025] The assembly may also include means for adjusting the position of the probe relative to the cannula. For example, in an embodiment, the probe may include an external thread adapted to operatively engage with the means for adjusting the position of the probe relative to the cannula. The means for adjusting the position of the probe relative to the cannula may include a thumb wheel, wherein the thumb wheel includes a central conduit having an internal thread therein, the internal thread adapted to engage with the external thread of the probe. Alternatively, the means for adjusting the position of the probe relative to the cannula may include a cam mechanism or a lever mechanism to adjust the position of the probe.

[0026] When the assembly includes a thumb wheel, it can be configured such that when the thumb wheel is rotated in a first direction, interaction between the internal threads of the thumb wheel and the external threads of the probe causes the probe to move relative to the cannula such that the portion of the probe extending from the cannula increases. Furthermore, when the thumb wheel is rotated relative to the sensor in a second direction opposite to the first direction, the probe moves relative to the cannula in an opposite direction such that the portion of the probe extending from the cannula decreases. Advantageously, this enables the position of the probe relative to the cannula, and therefore the position of the probe within the device, to be adjusted while the sensor is mounted to the device.

[0027] The sensor may include means for maintaining a sealed vacuum or alternatively a positive internal pressure within the device in which the sensor is mounted during use of the device. Preferably, in this case, the position of the probe can still be adjusted. Typically, the means for maintaining a sealed vacuum or a sealed positive pressure within the device include an O-ring seal located around a portion of the probe within the cannula. Other suitable means for sealing the sensor assembly will be apparent to those skilled in the art, and their form will generally depend on the shape of the probe.

[0028] The means for mounting the sensor on the device may comprise an external thread on the probe, the external thread being configured to engage with a corresponding internal thread of the device. Preferably, the longitudinal axis of the external thread is substantially the same as the longitudinal axis of the probe, so that adjustment of the position of the probe is substantially along this longitudinal axis. Preferably, the external thread may be integrated as part of the probe and is typically made of the same material as the cannula.

[0029] The sleeve preferably comprises an insulating material capable of withstanding temperatures typically encountered during operation of an apparatus such as a vacuum pump, for example from about 0°C to about 250°C, and more preferably from about 20°C to about 150°C. Preferably, the sleeve comprises a polymeric material, which is more preferably a high temperature polymer selected from the group comprising polyetheretherketone (PEEK), polyethersulfone (PES) or polytetrafluoroethylene (PTFE). Other suitable sleeve materials include laminated plastic materials such as those available from Tufnol Composites Ltd. (Birmingham, UK) under the trade name TUFNOL. Most preferably, the sleeve comprises polyetheretherketone (PEEK).

[0030] In an embodiment, the probe is formed by a single electrode. In such an embodiment, the incomplete circuit can be arranged so that in use, when the probe is engaged by a moving part of the device, the circuit is completed by the part and a signal is output, and the moving part of the device is more preferably a conductive member of the device. In this way, the circuit can be considered as a so-called "volts free" circuit, because power is applied to the circuit by the user of the device, and when the circuit is completed, a useful output can be obtained from the circuit. For example, the sensor electrodes and the device can be connected to a pair of terminals on a variable speed drive, and the variable speed drive disconnects the power supply when the circuit is formed. Therefore, the component used to complete the circuit can be considered as a "voltage free" component, that is, no current flows through it before it is contacted by the electrode.

[0031] In more detail, the current flows from the device that couples the probe to the circuit, along the electrode in the probe, through the moving member that engages the end of the probe, and back through the device to complete the circuit and thereby activate the disconnect switch to which the circuit is attached. Completion of the circuit may be only instantaneous, depending on how quickly the disconnect switch stops the device from operating after the circuit is completed.

[0032] In an alternative embodiment, the probe comprises at least two electrodes, one of which is a positive electrode and one of which is a negative electrode. The at least two electrodes may be separated by an electrical insulator. A portion of each electrode may be exposed from the electrical insulator. In an embodiment, a first electrode is formed by a conductive wire extending along the axis of the probe, and a second electrode is formed by a conductive tube surrounding the first electrode and substantially concentric with the first electrode. Alternatively, the electrodes may each comprise a conductive wire, the two electrodes extending parallel to each other along the length of the probe.

[0033] Suitable materials for use as the insulator are the materials described above for the bushing.

[0034] Preferably, the portion of each electrode exposed from the insulator is contained within, ie located above, the portion of the probe extending from the sleeve.

[0035] In use, when two or more electrodes are simultaneously engaged by a moving part of the device, which is preferably conductive, the circuit is completed and a signal is output. This is achieved by current flowing from the first electrode through the moving part of the device to the second electrode. As described above, with respect to embodiments where the probe is formed by a single electrode, the completion of the circuit may be only instantaneous, depending on the time that elapses between the completion of the circuit and the activation of the disconnect switch, which stops the operation of the device and, therefore, also stops the movement of the device components.

[0036] Typically, at least a portion of the portion of each electrode exposed from the insulator, and preferably all, is covered by a sacrificial coating. In use, when a moving member of the device contacts the sacrificial coating, at least a portion of the sacrificial coating on each of the electrodes is removed so that the circuit is completed. This arrangement is particularly advantageous because it prevents "false" completion of the circuit when the moving conductive member of the device does not engage the electrode. An example of such a "false" completion of the circuit is when condensation accumulation on the probe bridges the gap between two of the electrodes and completes the circuit.

[0037] Typically, the sacrificial coating comprises a layer of electrically insulating paint or lacquer, such as a high temperature paint. Preferably, the sacrificial coating is adapted to be removed when engaged by a moving member of the device without causing any damage to the moving member or the probe. It should be understood that such a coating may be applied to any of the embodiments described herein.

[0038] Typically, in this aspect of the present disclosure, the sleeve may comprise a metallic material, which may be similar to the material used to make the device components. For example, it may comprise iron or steel, and preferably comprises stainless steel.

[0039] In another aspect, the present invention provides a vacuum pump comprising the sensor as described above. More preferably, the vacuum pump is a dry vacuum pump having a Roots, screw, claw or scroll mechanism, and more preferably a vacuum Roots intensifier.

[0040] Typically, the pump comprises at least one stator and at least one rotor. Preferably, the stator comprises at least one internal chamber in which the at least one rotor is rotatably mounted.

[0041] Typically, the sensor can be mounted to the pump via a conduit located in the stator so that a portion of the probe protrudes into the aforementioned internal chamber of the device. If the sensor includes means for adjusting the position of the probe relative to the cannula, such means are located on the exterior of the stator to allow ease of adjustment.

[0042] In another aspect, the present disclosure provides a method for preventing malfunction of an apparatus having at least one moving component and at least one stationary component. The method comprises mounting a sensor as previously described on the apparatus. Thus, the sensor is typically mounted at a distance from the moving component of the apparatus, the distance typically being set by the user of the apparatus, so that if the probe is engaged by the moving component of the apparatus, a signal is generated that preferably affects a cut-off switch to stop operation of the apparatus.

[0043] Advantageously, the sensor may be fitted during manufacture of the device, or may be fitted to an existing device.The ability to retrofit the sensor to existing devices is beneficial because it reduces the costs associated with redesigning or adapting existing devices.

[0044] Preferably, the device used in the above method is a compressor pump or a vacuum pump, more preferably a dry vacuum pump including a Roots, screw, claw or scroll mechanism, and most preferably a vacuum Roots intensifier.

[0045] Therefore, the present invention also relates to the use of a sensor as previously described to prevent failure of an apparatus comprising at least one moving part and at least one stationary part, the apparatus being preferably a vacuum pump, more preferably a dry vacuum pump, and most preferably a vacuum roots pump. If two components of the apparatus are so close that there is a risk of collision, the sensor prevents failure of the apparatus by generating a signal. Advantageously, the signal can activate a cut-off switch, thereby stopping the operation of the apparatus. Advantageously, the use of the sensor reduces the risk of failure of the apparatus without the need to continuously measure and output data related to the relative positions of the components of the apparatus.

[0046] Thus, the present disclosure provides a simple and extremely effective sensor device for preventing failures in various devices including moving parts. The device can be used for vacuum pumps, especially dry vacuum pumps, and especially vacuum roots intensifiers. It provides an efficient and cost-effective way of monitoring such equipment to avoid catastrophic damage, which includes reduced complexity and reduced data output compared to solutions proposed in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Preferred features of the present disclosure will now be described with reference to the accompanying drawings, in which:

[0048] Figure 1 is a cross-sectional view of a vacuum pump incorporating a sensor assembly according to an embodiment of the present invention;

[0049] Figure 2 is a detailed view of a portion of a sensor assembly according to an embodiment of the present invention;

[0050] Figure 3 is a detailed view of an example probe according to an embodiment of the present invention;

[0051] Figure 4 is a detailed view of an alternative example probe according to another embodiment of the present invention; and

[0052] Figure 5 is a flow chart illustrating an example method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] Figure 1 A schematic diagram of a vacuum pump 10 incorporating a sensor assembly 12 according to an embodiment of the present invention is shown. The pump 10 in the illustrated embodiment is a Roots-type vacuum pump, also known as a Roots intensifier. It should be understood that the present invention can be applied to any other type of vacuum pump having components that move relative to each other. More generally, the present invention can be applied to other types of pumps or mobile devices, such as compressors.

[0054] The pump 10 includes at least one moving part and one stationary part. In the illustrated example, the pump includes two moving parts in the form of rotors 14 (sometimes referred to as impellers) mounted to rotate within a stationary stator 16 of the pump 10 surrounding the two rotors 14. Each rotor 14 includes a plurality of intermeshing blades 18 that, in use, are in close proximity to an arcuate inner surface 20 of the stator 16 during at least a portion of their rotational cycle. The blades 18 are designed to form an effective seal with the arcuate surface 20 of the stator 16 to drive air trapped between adjacent blades 18 from an inlet port 22 of the pump 10 to an outlet port 24.

[0055] In use, the rotors 14 rotate in opposite directions to each other and do not touch each other or the stator inner surface 20. As such, there is a gap or clearance 26 between the rotor 14 and the stator 16. In many applications, when the pump 10 is cold, the clearance 26 is ideally between 0.1 and 0.5 mm. The size of the clearance 26 between the rotor 14 and the stator 16 is important to the function of the pump 10 and must be maintained above a predetermined size to ensure safe and efficient operation of the pump 10. As described above, operational effects may cause the clearance 26 to decrease below this predetermined size.

[0056] The pump 10 also includes a sensor assembly 12 mounted on the stator 16. The sensor assembly 12 is configured so that when the gap 26 between the rotor 14 and the stator 16 is reduced to below a predetermined size, the sensor assembly 12 generates a signal. The sensor assembly 12 includes a sensor circuit 28 and a processor 30, the sensor circuit 28 is configured to generate a signal, and the processor 30 is configured to receive the signal and generate an output. In an embodiment, the processor 30 is configured to generate an output that triggers a shutdown process to stop the operation of the pump 10. In an embodiment, the shutdown process includes communicating with a controller (not shown) for controlling the operation of the pump 10 to perform a controlled shutdown process, such as a pulsed shutdown process described in WO 2004 / 038222 or a ramped shutdown process known in the art. Alternatively, the output may trigger a cut-off switch to immediately shut down the pump 10.

[0057] The sensor assembly includes a probe 32 disposed in an inner bore 34 extending radially through the sidewall of the stator 16 from an outer surface 36 of the stator 16 to its arcuate inner surface 20. A portion 38 of the probe 32 extends beyond the arcuate inner surface 20 into an interior cavity 40 of the pump 10 such that an end surface 42 of the probe 32 contacts or engages the rotor 14 when the gap 26 is below a predetermined value. In an embodiment, the predetermined value represents a gap size at which operation of the pump 10 may be compromised, e.g., beyond which the risk of sticking is unacceptable.

[0058] During normal use, when there is an acceptable size gap 26 between the rotor 14 and the stator 16, the probe 32 and the sensor circuit 28 together form part of an incomplete circuit such that the circuit does not generate a signal. However, when the gap 26 is reduced to a predetermined value, i.e., when the gap is too small, the probe 32 is engaged by the rotor 14. The engagement of the probe 32 with the rotor 14 completes the circuit formed by the probe 32 and the sensor circuit 28, and the sensor assembly 12 generates a signal.

[0059] Figure 2An enlarged version of a portion of a sensor assembly 12 is shown according to one embodiment. In the illustrated example, the sensor assembly 12 includes a probe 32 as described above. The assembly 12 also includes a sleeve 50, wherein the sleeve 50 substantially surrounds or covers at least a portion of the probe 32. At a first end 52 of the probe 32, a portion 54 of the probe 32 extends from the sleeve 50 and is configured to engage with a moving part of the device, such as the above-described Figure 1 The rotor 14 of the pump 10 is depicted engaged. At a second, opposite end 56 of the probe 32, the probe 32 is configured to connect to a sensor circuit as described above to form an incomplete circuit.

[0060] The sleeve 50 includes means 58 for mounting the sensor assembly to a device, such as the pump stator 16 described above. In the illustrated embodiment, the means 58 includes external threads on the sleeve 50 that are configured to engage internal threads of the device, such as Figure 1 The cannula 50 also includes a means 60 for adjusting the position of the probe 32 relative to the cannula 50, in this example, the means for adjusting the position of the probe 32 relative to the cannula 50 includes a thumb wheel 60. The thumb wheel 60 is configured so that manual manipulation of the thumb wheel causes the probe to move axially in one or two directions relative to the cannula 50 to allow the portion 54 of the probe 32 extending from the cannula 50 to be adjusted as needed, such as in the case where the predetermined size / value of the gap needs to be adjusted or adjusted. In an alternative embodiment, the cannula 50 and / or the probe 32 may include a means (not shown) for adjusting the cannula 50 and the probe 32 together relative to the device to which it is mounted so that the predetermined value can be adjusted or adjusted as needed.

[0061] like Figure 2 As shown, the assembly also includes an O-ring seal 60 that extends around the probe within the sleeve 50 and forms a seal between the probe 32 and the sleeve 50 to reduce or prevent gas leakage along the probe 32, such as toward the interior cavity 40 of the pump 10.

[0062] exist Figure 2 In the example shown, the probe 32 is formed from a single electrode so that in use, if engaged by a conductive moving member of a device to which the sensor assembly is mounted, the circuit to which the probe 32 is connected is completed through the sensor assembly and the device and a signal is output by the circuit.

[0063] refer to Figure 3, an alternative probe 132 is shown. In this example, the probe 132 includes two electrodes 162, 164 extending along the longitudinal length 166 of the probe 132. The first electrode 162 includes a wire extending generally centrally throughout the length of the probe 132. The second electrode 164 includes a conductive tube surrounding the first electrode 162 and substantially concentric with the first electrode 162. The probe 132 also includes an electrical insulator 168, which is located between the first electrode 162 and the second electrode 164 to electrically insulate the electrodes 162, 164 from each other along the length 166 of the probe 132. In one embodiment, the insulator 168 includes an adhesive, such as an epoxy, which can also be used to secure the two electrodes 162, 164 relative to each other.

[0064] At a first end 170 of the probe 132, the electrodes 162, 164 are exposed from the insulator 168 to define an annular gap 174 between each electrode 162, 164, which is configured to form a physical break in the circuit of the sensor assembly 12 described above. At a second, opposite end 172 of the probe 132, the conductive electrodes 162, 164 are configured to be coupled to the circuit as described above via a connector 175 known in the art. In use, if the gap 174 between the exposed ends of the electrodes 162, 164 is bridged by a conductive member of the device to which the sensor assembly is mounted, the circuit is complete and a signal is output.

[0065] Figure 3 The probe 132 shown in FIG. 1 can be incorporated into the Figure 2 In such an embodiment, the sleeve is preferably formed of an electrically insulating material to prevent conduction through the components and surrounding structures of the pump. The probe 132 also includes a sacrificial layer 176 located at the first end 170. The sacrificial layer 176 extends over the portion of the electrode exposed from the insulator 168 of the probe 132. The sacrificial layer 176 is configured to be at least partially removed when engaged by a moving member. For example, when used in Figure 1 14, the sacrificial layer 176 can be sheared away from the end 170 of the probe 132 when engaged by the rotating rotor 14 of the pump 10, on which the probe 132, which forms part of the sensor assembly 12, is mounted. The removal of the sacrificial layer 176 exposes the ends of the electrodes 162, 164, allowing the rotor 14 to bridge the gap 174 between the electrodes 162, 164 and thereby complete the circuit.

[0066] Figure 4 Another alternative probe 232 for use in the assembly of the present invention is shown. The probe includes two electrodes 262, 264, each electrode including a wire extending along the length 266 of the probe 232. The two electrodes 262, 264 are generally parallel to each other and parallel to but offset from the central axis of the probe 232.

[0067] The probe 232 also includes an electrical insulator 268 that surrounds the first electrode 262 and the second electrode 264 to form a conductive layer similar to the conductive layer of the first electrode 262. Figure 3 The insulator 268 of the embodiment of the present invention electrically isolates the electrodes 162, 164 from each other along the length 266 of the probe 232. The insulator 268 may be made of the same material as described above with respect to Figure 3 The insulator 168 is formed of the same material described above.

[0068] Return to reference Figure 4 At a first end 270 of the probe 232, the electrodes 262, 264 are exposed from the insulator 168 to define a gap 274 between the two electrodes 262, 264, which gap 274 is configured to form a physical break in the circuit of the sensor assembly 12 described above. At a second, opposite end 272 of the probe 232, the conductive electrodes 262, 264 are configured to be coupled to the circuit as described above via a connector 275 known in the art. In use, if the gap 274 between the exposed ends of the electrodes 262, 264 is bridged by a conductive member of the device to which the sensor assembly is mounted, the circuit is complete and a signal is output.

[0069] Figure 4 The probe 232 of the embodiment also includes a sacrificial layer 276 located at the first end 270. The sacrificial layer 276 extends over the portion of the electrode exposed from the insulator 268 of the probe 132 to contact the electrode 276 with respect to the first end 270. Figure 3 The sacrificial layer 276 is configured to be at least partially removed when engaged by the moving member. For example, when used in Figure 1 14, the sacrificial layer 276 can be sheared away from the end 270 of the probe 232 when engaged by the rotating rotor 14 of the pump 10, and the probe 232 forming part of the sensor assembly 12 is mounted on the rotating rotor 14 of the pump 10. The removal of the sacrificial layer 276 exposes the ends of the electrodes 262, 264, allowing the rotor 14 to bridge the gap 274 between the electrodes 262, 264 and thereby complete the circuit.

[0070] Figure 4 The probe 232 shown may also be incorporated into the cannula. However, the cannula may not need to be formed of an electrically insulating material because both electrodes 262, 264 are contained within the electrical insulator 168. Thus, the cannula material may be selected from a wider range of materials.

[0071] Figure 5is a flow chart illustrating an exemplary method for preventing failure of an apparatus including at least one moving component and at least one stationary component according to another embodiment of the present invention. The method includes first installing a sensor assembly to a stationary component of the apparatus at step 301. The sensor assembly used in the exemplary method may have features of any of the above-described embodiments such that it is operable to generate a signal when the sensor detects the presence of a minimum gap. The sensor may be installed so that the sensor can detect when a minimum gap exists between the moving component and the stationary component. The installation step may be performed during the initial manufacture of the apparatus, or may be performed as a "retrofit" on an existing pump after initial manufacture.

[0072] The method also includes a step 302 of shutting down the operation of the device when the sensor generates a signal. As described above, the signal represents the minimum gap between the stationary component and the moving component. When the associated control system generates the signal, the shut-down operation can be performed automatically, or the signal can alert the operator of the device to manually perform the shut-down.

Claims

1. A sensor assembly (12) for use in a device comprising at least one moving part and at least one stationary part, the sensor assembly comprising: a probe (132) comprising a portion of an incomplete circuit and configured to complete the circuit when engaged by at least one moving component; as well as a sleeve (50) configured to enclose a first portion of the probe such that, in use, a second portion (54) of the probe protrudes from the sleeve, and wherein the sleeve includes means (58) for mounting the sensor to a stationary component of the device, wherein the assembly is configured to generate a signal when the circuit is completed; and wherein the probe (132) includes at least two electrodes, wherein one electrode is a positive electrode (162) and the other electrode is a negative electrode (164), wherein the at least two electrodes are separated by an electrical insulator (168), and wherein a portion of each electrode is exposed from the electrical insulator; as well as At least a portion of the exposed portion of each of the electrodes is covered by a sacrificial coating (176) comprising an electrically insulating paint or lacquer such that in use when the sacrificial coating is contacted by a moving part of the device, at least a portion of the coating is removed from each electrode and the circuit is completed.

2. The sensor assembly (12) according to claim 1, wherein: The component is configured to initiate a shutdown process of the device when the signal is generated (302).

3. The sensor assembly (12) according to claim 2, wherein: The closing process is one of a pulse closing process or a ramp closing process.

4. The sensor assembly (12) according to any one of claims 1 to 3, wherein: The assembly also includes means for adjusting the position (60) of the probe relative to the cannula.

5. The sensor assembly (12) according to claim 4, wherein: The means for adjusting the position of the probe relative to the cannula may comprise a cam mechanism or a lever mechanism acting on the probe, or an external thread adapted to operatively engage the means for adjusting the position of the probe relative to the cannula.

6. The sensor assembly according to any one of claims 1 to 3, wherein: The portion of each electrode exposed from the insulator is contained in the portion of the probe extending from the sleeve.

7. The sensor assembly according to any one of claims 1 to 3, wherein: The device is a vacuum pump (10), and wherein the at least one moving part comprises a rotor (14) and the at least one stationary part comprises a stator (16).

8. A vacuum pump (10), comprising: A sensor assembly as defined in any one of claims 1 to 7; and At least one rotor (14) and at least one stator (16), wherein the stator includes at least one internal chamber, the at least one rotor is rotatably mounted in the internal chamber, and the sensor is mounted in the stator through a conduit located in the stator so that a portion of the probe extends into the internal chamber.

9. A method for preventing failure of an apparatus comprising at least one moving component and at least one stationary component, the method comprising: mounting a sensor assembly as defined in any one of claims 1 to 7 to a stationary part of the device; and When the sensor generates a signal, the operation of the device is shut down (302).

10. The method according to claim 9, wherein: Shutting down the device is automatically performed when the signal is generated.

11. The method according to claim 9 or claim 10, wherein: The sensor is assembled during the manufacture of the device.

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