ROTARY VANE PUMP VANE WEAR DETECTION

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and the benefit of, EP Patent Application No. 24195756.2, filed, Aug. 21, 2024 and titled “ROTARY VANE PUMP VANE WEAR DETECTION,” which is incorporated by reference herein in its entirety for all purposes.

FIELD

The present disclosure is concerned with an arrangement for detecting wear of vanes in a rotary vane pump.

BACKGROUND

Sliding rotary vane pumps are used in a range of applications, including applications operating in extreme environments, such as vacuum pumps used in aircraft. Typically, rotary vane pumps now in use are dry vacuum pumps (i.e. without the use of an oil lubricant). Such rotary vane pumps typically have a rotor in which radial slots are formed and within which vanes are slidably mounted to reciprocate within the slots - extending and retracting relative to the slots—as the rotor rotates. The vanes are usually made of a carbon or carbon-composite material, often with a self-lubricating coating to reduce wear of the vane. Even with such materials/coatings, the constant reciprocal movement of the vanes, together with the often harsh environmental factors such as ice and debris, causes the vanes to wear and lose length during operation of the pump. Eventually, the length of the vane is so short that the vane can fall out of the slot or not reciprocate properly and the pump will no longer operate properly. Wear of the vanes can, therefore, cause the pump to fail and/or can cause damage to the pump. In many applications, including in aviation, the consequences can be catastrophic.

Research has found the degree of wear that can lead to pump failure and steps have to be taken to avoid the vanes wearing to such an extent. Conventionally, vanes have been removed and replaced based on the amount of time they have been in use. Because wear is not always linear, though, and can accelerate, such monitoring needs to be extremely conservative and may result in vanes being replaced even if they are not worn to a problematic degree. Alternatively, vanes can be examined at periodic maintenance intervals to determine their degree of wear, but this requires the pump to be disassembled during down time of the pump and is time and labor intensive. U.S. Pat. No. 6,769,886 B2 teaches a method of monitoring for wear of vanes without needing to disassemble the pump, using a measuring stylus that is inserted into an access port in the pump housing to monitor the length of the vanes according to the length of insertion of the stylus in the access port to contact the vane. Whilst this solution allows for an individual determination of the wear of each vane and can be performed without needing to disassemble the pump, this measurement can still only be performed during down time of the pump (and when the pump is disassembled from e.g. the aircraft). Furthermore, the wear measurement is not precise and conservative criteria need to be applied when deciding whether a vane needs to be replaced due to the lack of accuracy.

There is a desire for an assembly for more precisely measuring wear of individual vanes of a rotary vane pump during operation of the pump.

SUMMARY

According to the present disclosure, there is provided an assembly for detecting wear of a rotary vane pump vane. In one aspect, there is provided an assembly for detecting wear of a vane of a rotary vane pump, the assembly comprising: a vane configured to be mounted in a radial slot of a rotor of a rotary vane pump, the vane having a vane body of non-electrically conductive material, the vane body configured to, in use, extend from the slot to contact an electrically earthed housing of the rotor; the vane being provided with a marking having at least one characteristic that varies in the radial direction; the assembly further comprising a detector fixed relative to the housing and arranged to read the marking at a predetermined radial distance from the housing.

In another aspect, there is provided a rotary vane pump incorporating such an assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the wear detection assembly according to the disclosure are described with reference to the drawings. It should be noted that these are examples only and that variations are possible within the scope of the claims.

FIG. 1a shows an example of a wear detection assembly according to the disclosure incorporated into a rotary vane pump;

FIG. 1b is a detail view of an example of the detector in the example shown in FIG. 1a;

FIG. 1c is a detail view of an example of the detector reading the marking in the example shown in FIG. 1a;

FIG. 2 is an example of a marking on a vane in an example of the assembly;

FIG. 3 shows a section of the pump of FIG. 1 where the vane is not worn to such a degree that an indication of wear is provided by the wear detection assembly or that the vane needs to be replaced;

FIG. 4 shows a section of the pump of FIG. 1 where the vane is worn to such a degree that an indication of wear is provided by the wear detection assembly; and

FIG. 5 is an example of an alternative arrangement according to the disclosure.

DETAILED DESCRIPTION

The solution provided by this disclosure to detecting wear of a vane involves providing a marking on the body of the vane that has characteristics that vary in the radial direction, and a detector for reading the marking at a given radial position for identifying the length and, therefore, degree of wear of the vane based on which characteristics the marking has at the location where it is read by the detector. As the vane wears, the vane shortens which means that the part of the marking (and, hence its characteristics) that is read by the fixed detector changes, and this provides a real-time determination of the degree of wear of the vane.

An example of the wear detection assembly is shown in FIG. 1a which shows a rotary vane pump having a rotor 2 rotatable within a housing 6. As is known, radial slots 3 are provided around the rotor, within which are mounted, for reciprocal radial movement, vanes 4. As the rotor rotates relative to the housing 6, the vanes 4 synchronously extend from and retract into their respective slots 3, making contact with the housing 6 when extended. The housing 6 is electrically earthed.

As mentioned above, during the life of the pump, the vanes 4 will become worn and will shorten such that eventually they may fall out of the slots when extending. It is important to detect wear of the vanes before they have become so worn that failure occurs—i.e. a predetermined degree of wear, such that when the vanes have reached that degree of wear, they can be replaced.

According to this disclosure, the wear of the vanes 4 is detected by means of a readable marking 5 provided on a surface of the vane 4 and a sensing device 8 that is mounted to the housing at a fixed location relative to the housing and configured to read or detect the marking on the vane 4.

The marking 5 has a characteristic that varies in the radial direction i.e. in the length direction of the vane (where the length direction is defined from the end of the vane in the slot 3 and the end of the vane that contacts the housing 6). This means that as the length of the vane 4 becomes shorter, due to wear, the characteristic of the part of the marking that is detected or read by the fixed sensing device 8 varies. The length of the vane 4 at any time can, therefore, be determined based on the characteristic of the marker that is detected by the sensing device 8.

In one example, the marking may be in the form of a bar code which is provided e.g. printed or otherwise formed on the vane 4 and which varies in the vane length direction. The marking may otherwise be e.g. etched or adhered onto the vane. The sensing device 8 may then be a bar code reader device. This may be e.g. a laser sensor that emits a laser beam to read the bar code. Other forms of marking and appropriate sensing or reading devices are also possible as is known in the sensing art.

In the example shown in FIGS. 1a, 1b and 1c. the marking is in the form of a series of bar codes having a first code pattern at a first radial location along the length of the vane, and further, different code patterns at different radial locations on the vane.

In the example shown, the sensing device may be a laser sensor such as shown in FIG. 1b. this may be mounted to the housing (e.g. in a holder 9 provided for the sensor). The sensor emits a laser beam 10 into the space between the rotor and the housing and directed against the marking on the surface of the vanes extending out of the slot when the vane 4 is in contact with the housing 6.

Depending on the characteristic of the marking detected by the sensing device, the current length (indicative of the depth of the vane 4 in the slot 3) of the vane can be determined. The sensing device can send signals indicative of the currently detected characteristic to e.g. a controller or processor or to avionics or to some other location where the detected characteristics can be interpreted to determine the current length (or depth in the slot) of the vane 4. This can be done in real time, without needing to dismount the pump.

FIG. 2 shows an example of a bar code marking 5 on a vane 4 that has three different characteristics or codes. The vane 4 has a first end 4a that comes into contact with the housing 6 during operation, and a second end 4b that is the opposite end, that is the end located in the slot 3 during operation. A first part 5a of the marking 5 located adjacent the first end 4a of the vane defines a first characteristic—here a first bar code, a second part 5b of the marking, radially inwards of the first part, defines a second characteristic—here a second bar code, and a third part 5c of the marking is the radially innermost part and defines a third characteristic i.e., here, a third bar code. Of course, three characteristics is only an example, and any number of different marking parts with different characteristics may be provided on the vane. The different characteristics are indicative of the length of the vane when detected by the sensing device (e.g., in this example, when read by the laser beam 10). If the laser beam 10 impinges on the first part of the marking (see FIG. 3), the code it senses indicates that the vane is ‘ok’—i.e. is not so worn that it needs to be replaced. As the outer part of the vane (the first end 4a) starts to wear, the first marking part 5a is also worn such that, when the vane comes into contact with the housing, eventually, the second marking part 5b will be at the radial position where the first marking part previously was, and so the sensor will read the second bar code instead (see FIG. 4). The signal generated by reading the second bar code 5b is indicative of a different blade length—here, it is indicative of the vane being worn to such a degree that it should be replaced within a short time. When the vane is even more worn, when it contacts the housing, both the first and second marking parts have been worn away and so the sensor now reads the third marking part 5c. The resulting signal can be indicative e.g. of the vane being so worn that it needs to be replaced immediately. Again, it must be stressed that the types, number, gradation and interpretation of the marking can vary according to use and design.

In another example, such as shown in FIG. 5, the sensing means can be replaced by e.g. a reflection sensor 12 to indicate the degree of wear of the vane based on the reflected signals from the vane surface.

Depending on the marking used, there is flexibility as to the degree of precision with which the vane wear is determined (e.g. just good/bad or multiple stages of wear).

The wear detection assembly of this disclosure allows wear of the vanes to be monitored in real time and separately for each vane and during operation of the pump without needing to disassemble the pump or dismount it from its environment (e.g. an aircraft). The assembly provides a precise indication of wear which means that the vanes are not replaced too soon, and so their life, and time between replacement, is maximized.