Vane wearing detection

A vane for use in a rotary vane pump. The vane has a length L extending between a first edge of the vane and a second edge of the vane and a width W extending perpendicular to said length, the width extending between a third edge of said vane and a fourth edge of the vane, and further comprising a channel extending through said vane and provided at a position along said length L of said vane. The channel maybe positioned away from said first and second edges such that said vane has a constant length L along its width. The width of the channel may vary in shape between first and second points along the length of the vane. The channel may have a triangular shape, a rectangular shape or a circular shape. A method for detecting the decrease in length of the vane is also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to European Patent Application No. 22461532.8 filed Mar. 31, 2022, the entire contents of which is incorporated herein by reference.

TECHNICAL FIELD

The methods and systems described herein relate to rotary vane pumps and in particular, methods and systems for assessing wear of a vane of such pumps.

BACKGROUND

Sliding rotary vane pumps may be used in a plurality of different mechanical and industrial applications (e.g. they may be used in both liquid and gas pumping applications) and can be invariable exposed to a wide range of environmental conditions. One type of rotary vane pump is a dry air pumps, which are dry vacuum pumps constructed of carbon vanes and rotors which are self-lubricating. Such dry air pumps may comprise mechanical carbon rots and vanes that operate in a hardened metal cavity. Such pumps may provide a power source in a multitude of applications such as to provide power to pneumatically operated flight instruments, for example.

Although such dry air pumps do not use a liquid lubricant, they do use other lubricating methods such as self-lubricating coatings, amongst other methods. Although such lubricating methods may work well to some extent, the nature of the vane lubrication technique is still destructive to the parts of the pump. Due to this, parts of the pump, such as the vanes, can wear down over time. This results in the lengths of the vanes eventually being too short to fit into the slot in which it is positioned in use and this can result in failure of the pump. If the pump is used in an aircraft, such failure can result in one or more of the aircraft systems becoming inoperative and, since this would most often occur during use, i.e. in flight, this can be quite dangerous. It is therefore important to ensure that any wearing, or the extent of wearing of the vane can be clearly and accurately detected so that such failures do not occur.

Some known techniques, such as those discussed in U.S. Pat. No. 6,769,886 B2 assess the length of a vane using an external tool which is inserted into the pump via a designated channel. The tool is then used to measure the height of the vane. This measurement is only possible after the pump has been disassembled from the airplane and the measurement of the length vane is not precise.

SUMMARY

A vane for use in a rotary vane pump is described herein, said vane having a length L extending between a first edge of the vane16and a second edge of the vane and a width W extending perpendicular to said length, said width extending between a third edge of said vane and a fourth edge of the vane, and further comprising a channel extending through said vane (16) and provided at a position along said length L of said vane.

In any of the examples described herein, the channel may be positioned away from said first and second edges such that said vane has a constant length L along its width.

In any of the examples described herein, said channel may extend between a first point along said length and a second point along said length and wherein a width of said channel varies in shape between said first and second points.

In any of the examples described herein, the width of said channel may taper from a first channel width to a second channel width, wherein said first channel width is smaller than said second channel width. The first point may be closer to said first edge and said second point is closer to said second edge, or vice versa.

In any of the examples described herein, said channel may have a triangular shape, a rectangular shape or a circular shape.

In any of the examples described herein, the vane may comprise a plurality of said channels.

In any of the examples described herein, a first of one of said plurality of channels may be offset from a second one of said plurality of channels along said length of said vane. That is, the first one of said plurality of channels may be provided at a first position along the length of the vane and a second of said plurality of channels may be provided at a second position along the length of said vane, and wherein said first position and said section are not the same as each other, such that said first channel is closer to said first edge than said second channel.

In any of the examples described herein, said plurality of channels may be offset from each other in along said width of said vane.

A rotary vane pump is also described that comprises the vanes described herein. The pump may comprise a rotor “R” configured to rotate about a central axis; said rotor comprising a plurality of circumferentially spaced vane slots, wherein at least one of said vane slots is configured to receive one of the vanes described herein.

The vane may be inserted into the slot of the rotor R such that the second edge of the vane is positioned closer to the central axis of the rotor R than the first edge of the vane16.

A method for detecting a decrease in the length of a vane (i.e. wear of the vane16) provided in a rotary vane pump is also described herein. The method comprises providing a rotor “R” configured to rotate about a central axis; said rotor comprising a plurality of circumferentially spaced vane slots, wherein at least one of said vane slots is configured to receive a vane, inserting said vane into said at least one vane slot, said vane having a length L extending between a first edge of the vane and a second edge of the vane and a width W extending perpendicular to said length, said width extending between a third edge of said vane and a fourth edge of the vane, and said vane further comprising a channel extending through said vane and provided at a position along said length L of said vane, said method comprising measuring a pressure in said rotary vane pump, and detecting a decrease in said pressure of said rotary vane pump, said decrease in pressure indicating that said vane has decreased to a length corresponding to said channel.

The method may be used in combination with any of the vanes described herein.

DETAILED DESCRIPTION

A rotary vane pump comprises a central annular body of stator, S, a cross-section of which is shown inFIGS.2and4. The pump comprises a rotor R that provides a bearing surface for rotary movement of rotor R about its central axis12. In the example shown inFIGS.2and4, the rotor R is provided with six circumferentially spaced vane slots15that are angled slightly from a radial direction and which extend over the entire longitudinal length of rotor R. Although each rotor R is depicted here with six slots15, the examples described herein are not limited to this and another number of slots15may also be used. Each slot15is configured to receive, and receives, a vane16that slides in and out of slot15as rotor R is rotationally driven about its center axis12.

Each vane16is made from a material that during use, wears and produces a form of dry lubrication for the pump when in use. For example, vanes16can be made from carbon material, graphite, and various organic binders. In some examples, a self-lubricating coating may be applied to the pump parts to inhibit wear between the slidable vanes16and pump rotor R.

A stator S is provided that surrounds the rotor R. The stator S has two symmetrically opposite lobes18and19, the surfaces of which act as cams that regulate the two extension and retraction cycles for the vanes16during each rotation of the rotor R. As is known in the art, the longitudinal spaces defined by the adjacent vanes16and the external surface of the rotor R, as well as the surface of a stator lobe, and end plates of the pump serve as pumping pockets which are moved from an intake zone to an exhaust zone to accomplish the pumping action of the pump R.

FIG.5depicts an end view of a vane16which may be inserted into the slots15of the rotor R as described above with reference toFIGS.1to4.FIG.6depicts a front view of the vane16ofFIG.5andFIG.7depicts a perspective view of the vane16ofFIGS.5and6.

As can be seen inFIGS.6and7, the vane16has a length L that extends between a first edge16cof the vane16and a second edge16dof the vane end the vane has a width W that extends between a third edge16aand a fourth edge16bof the vane16. In use, the vane16is inserted into the slot15of the rotor R such that the second edge16dis closer to the central axis12of the rotor R than the first edge16cof the vane16. The length L of the vane16is therefore dictated by the length of the slot15into which it is inserted and the width W of the vane16is dictated by the width of the rotor R of the pump.

In known rotary pumps, the vane is solid, and as the vane wears down, the length L of the vane gets shorter and shorter until the lengths of the vanes eventually become too short to fit into the slots of the rotor. As mentioned in the background section above, this results in failure of the pump.

In the examples described herein, however, the vane16comprises a channel17which extends through the vane16. This channel17may be any number of shapes, including circular, square, rectangular, triangular, to name a few. The channel17may also be tapered.

The channel17may be provided so as to extend through the vane16and also between a first point P1and a second point P2along a portion of the length L of the vane as shown inFIGS.6to13. In use, the first edge16cof the vane wears down, such that the length L of the vane16decreases. At some point, the vane16has worn down to such an extent that the channel17is reached, which creates a drop in pressure of the longitudinal space(s) defined by the adjacent vanes16as discussed above. If the position of the channel17on the length of the vane16is known, it is therefore possible to correlate this drop in pressure with the fact that the vane has worn down to a specific length. This provides a warning signal that the wear of the vanes is now in its early stages and should be monitored.

Whilst the channel remains in communication with the longitudinal space of the pump, this drop in pressure will remain as the vane continues to wear down. Once the vane16is worn down to such an extent that the channel17has been passed, the pressure in the longitudinal space will again increase and this provides a second warning signal that the vane16has worn down significantly to a length wherein the vane should be replaced.

In the example described and shown with reference toFIGS.2and3the channel17is triangular shaped, such that, in use, the tip of the triangle is further from the central axis of rotation12than the bottom of the triangle. Due to this, once the wear of the vane16has reached the point wherein the length L of the vane reaches the tip of the triangle, a small drop in pressure will indicate to the user that the length of the vane has worn down to this particular point. Since the triangle has a width that increases in the direction of the central axis12, as the length of the vane decreases further, the channel17will become wider and wider, and the pressure will decrease further and further. Once the length of the vane16has decreased to such an extent that the bottom of the triangle has been reached and the channel17is no longer present, the pressure will again increase and the user will know that the length of the vane16is sufficiently short such that the vane should be replaced.

FIG.2depicts the cross-sectional view of the pump along the line A-A ofFIG.1whereasFIG.4depicts the cross-sectional view of the pump along the line B-B ofFIG.3. As can be seen from these figures, inFIGS.1and3, the shortened length Ls of the vane16corresponds to a shorter length of the vane16in use in comparison to the shortened length inFIG.3. Although in this example, each of the vanes have been provided with a channel extending therethrough, in some examples wherein the vanes are expected to wear at the same rate, only one vane16may be provided with a channel17extending therethrough.

Although the channel17shown inFIGS.5and6relates to a triangular shape, other shapes can be used, as mentioned above, including those which do not have a width that changes over time. In such examples, the initial drop in pressure and the later increase in pressure would indicate to the user that the length of the vane16has reached a length where it has starting to be worn and a length where it may be critically short and the vane may have to be replaced.

The channel17may be positioned along the length L of the vane such that it is away from, i.e. not at, or cut into, the first or second edge. The length of the vane16therefore remains constant along the width of the vane and the channel17does not shorten the length of the vane at any point along its width. For example, the channel17may be positioned at a point approximately midway along the length L of the vane16. In other examples, the channel may be positioned closer to one of the first or second edges rather than the other. In other words, the channel may not be in contact with the first edge16cprior to use, or in contact with the second edge16dprior to use but is positioned at a point between the first and second edges16c,16d, such that the drop in pressure can be detected due to wear.

In other examples, wherein the channel17is not triangular shaped, other shapes may be used wherein the channel17has a varying and/or tapered with along its length and between the end16cwhich is being worn during use and the opposite end16dwhich is closest to the central axis of the stator S during use. Although in the examples shown inFIGS.5and6, the width of the channel17increases as the length L of the vane gets shorter, in other examples, the channel17may have a varied or tapering width, wherein the width decreases as the length of the vane gets shorter.

Another example of a new type of vane16is shown inFIGS.8to10. As can be seen inFIGS.9and10, in this example, a plurality of rectangular shaped channels17are provided in a position that initially lies approximately midway along the length of the vane. Of course, in other examples, only one, or two, or more such shaped channels could be provided in the vane16. This example functions in the same manner as described above. that is, as the vane16wears down and the length shortens, the channel17, or plurality channels17become exposed and result in a drop in pressure. The drop in pressure is maintained until the vane16becomes even shorter, wherein the channel17is no longer present, as that section of the vane has been worn away. Once the user is warned that the pressure has increased again, they are aware that the vane has shortened in length to a length that is less than the end of the channel17and the vane should be replaced. In the example depicted inFIGS.11to13, the channel has a circular shape. Again, a plurality of channels is depicted here, however, the vane may have any number of channels in order to perform the required function.

In the example shown inFIGS.8to10, the plurality of channels17are provided at different positions along the length of the vane16. For example, as shown inFIGS.9and10, the channel17ais positioned closest to the edge16cof the vane that wears during use. The second channel17bis positioned along the length of the vane16such that it is further away from the edge16cin comparison to the first channel17a. The third channel17cis positioned along the length of the vane16such that it is the furthest away from the edge16cwhich wears during use. Due to this, when the edge16cwears in use, the first channel17awill become exposed and there will be a resulting drop in pressure in the pump. The user will then be warned that the length of the vane has been shortened to this extent. As the vane wears further, the second channel17bwill then become exposed and the pressure will drop again. The same will occur when the third channel17cis reached. Due to this, the user can detect the extent to which the vane has shortened in length based on the pressure readings taken from the pump.

Another example of this is shown inFIGS.11to13. In this example, the same concept is used as inFIGS.8to10, however in this example the channels17are formed to be circular. Again, they are provided at different positions along the length of the vane such that as each channel17is reached, the change in pressure of the pump will indicate to the user the length to which the vane has shortened.