Cross-reference to Related Applications [0001] The present application claims the benefit of the Singapore patent application No. 10201704289V filed on 25 May 2017, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

[0002] Embodiments generally relate to a rotary vane apparatus.

Background [0003] Positive Displacement compressors are in existence for more than 100 years and are classified as reciprocating type or rotary type. Rotary compressors are generally preferred over reciprocating type because of their simple yet compact design, better volumetric capacity, and reduced noise and vibrational issues. However, all existing rotary compressors require relatively large rotor for them to work properly. That is to say that the rotor in these compressors occupies large space within the compressor, which otherwise can be utilized as the working chamber. Therefore, these compressors are bulky in design and require relatively large material for manufacturing.

[0004] US Patent no. US2373656 discloses a rotary machine which addressed the problem of compressors being bulky, consisting of large number of parts and requiring larger manufacturing cost.

[0005] However, the problem associated with the rotary machine described in said US patent is that the tips of the blade have to be in contact with the inner wall of the cylinder at all time for the product to work, otherwise, the significant internal leakage will render the compression process to fail. To address this, the blade was held and guided in a slot called shuttle. As a result, the rotary machine as described in said US patent has high load factor at the vane tips and at the guide-shuttle interface even at the low speed of operations. Hence the machine cannot be operated at high rotation speeds. [0006] PCT international publication number WO2010131103 A2 discloses a single vane pump which is similar to the rotary machine as described in the above US patent. In the single vane pump, a second rotor was introduced to overcome the high load at the vane tip, the pin-joint and the shuttle interface of the rotary machine of the above US patent. However, the key problem found in the single vane pump was that the single vane pump became bulkier than the rotary machine of the above US patent and would require more power in order to operate.

[0007] US Patent no. US 4,604,041 discloses a rotary vane pump comprising a cylindrical housing, a cylindrical rotor including a slot mounting a pair of hook- shaped overlying vanes that can slide over each other. The basic principle of the rotary vane pump is that the vanes need additional force to push the vane tips to form sealing contact with the housing wall and this force can be acquired from the pressurized oil flow flowing to the hook spaces from the oil pathways built into the rotor and housing end walls. These hook spaces are formed when the hook head of the vane enters into the rotor. The hook spaces are then bounded by the lateral surface of the hook head, the planar surface, the bottom surface of the trailing vane, the cutaway portions and the walls forming the slot in the rotor. The resulting hook space formed by the rear end of the trailing vane entering into the rotor expands when the leading vane rotates from a horizontal position to a vertical position. This volume increment creates the suction process for oil to fill in the hook space and the pressurized oil provides the pressure force to push the vanes and form sealing contact with the housing walls. Similarly, when the same leading vane rotates to assume the horizontal position, the corresponding hook spaces tend to become smaller, which will create the throttling effect on the oil to push the oil out to the oil output pathways.

[0008] However, the rotary vane pump of the above US patent has two limitations that result in the rotor size being relatively big with respect to the housing and hence reduce the working space for compressing fluid in the chambers formed by the housing, the rotor, and the vanes.

[0009] As a first limitation, the oil recess features in the form of cut-outs on the back of the vane must always be inside the rotor to pump oil into the hook-spaces. This requirement will ensure the hook-spaces are sufficiently sealed to create the pumping effect for the oil to flow in/out of these spaces. Failure, in this case, will cause the leakage of oil into the chambers which would result in the failure of the mechanism of the rotary vane pump. Similarly, these oil recess features must kinematically coincide with oil pathways within the rotor for the oil to flow in/out of hook spaces to prevent excessive pressurizing the oil into generating unbalanced forces. These conditions require the size of the rotor (relative to the cylinder chamber) to be sufficiently big to seal the hook-spaces and to adequately align the hook spaces with the oil pathways while ensuring the operation of the rotary vane pump.

[00010] As a second limitation, in order for the vane in the fully extended condition to have sufficient rigidity to prevent excessive bending and for the rotor to grip the vanes together to prevent the vanes from slipping out of the slot resulting in failure of the rotary vane pump, the ratio of the size of the rotor relative to the chamber must be sufficiently big.

Summary [00011] According to various embodiments, there is provided a rotary vane apparatus. The rotary vane apparatus may include a housing which has an inner wall enclosing a cylindrical cavity defining a central cavity axis. The rotary vane apparatus may further include a cylindrical rotor defining a central rotor axis, around which the rotor is rotatable, and which extends parallel and offset to the central cavity axis. The rotor may be sealed against the inner wall along an axial line parallel to the central cavity axis of the cylindrical cavity. The rotor may be further provided with a through slot which diametrically extends through the rotor. The rotary vane apparatus may further include a first vane and a second vane which are received within the through slot in a manner so as to be slideable therein relative to the rotor in the diametrical direction of the through slot, and so as to be slideable relative to each other in the diametrical direction of the through slot. The first vane and the second vane may define a first mating face and a second mating face, respectively, which first and second mating faces may extend parallel to the diametrical direction of the through slot and overlap each other. The rotary vane apparatus may further include a guiding mechanism arranged between the first and second mating faces of the first and the second vane, by which the sliding movement between the first and the second vane is guided. The guiding mechanism may include an engagement arrangement, via which the first and second vanes are permanently engaged with each other in such a manner that the first and second vanes are non- separable in a direction perpendicular to their mating faces.

Brief description of the drawings

[00012] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings, in which:

FIG. 1 shows a schematic illustration of a rotary vane apparatus according to various embodiments;

FIG. 2A to FIG. 2C show a rotary vane apparatus according to various embodiments;

FIG. 2D and FIG 2E show first and second vanes respectively of the rotary vane apparatus of FIG. 2A to FIG. 2C according to various embodiments;

FIG. 3 shows a schematic diagram to illustrate the forces and contact points of the first and second vanes of the rotary vane apparatus of FIG. 2A to FIG. 2C according to various embodiments;

FIG. 4A to FIG. 4G show the working principle (or one cycle of operation) of the rotary vane apparatus of FIG. 2A to FIG. 2C according to various embodiments;

FIG. 5 shows the result of the numerical analysis of the rotary vane apparatus of FIG. 2A to FIG. 2C according to various embodiments;

FIG. 6A to FIG. 6E show various diagrams of the rotary vane apparatus of

FIG. 2A to FIG. 2C when being used as a coupled vane compressor;

FIG. 7 shows a diagram of the rotary vane apparatus of FIG. 2A to FIG. 2C when being used as a coupled vane pump;

FIG. 8A shows a rotary vane apparatus according to various embodiments; FIG. 8B and FIG. 8C show a rotor of the rotary vane apparatus 800 of FIG. 8A according to various embodiments;

FIG. 8D shows various views of a first vane of the rotary vane apparatus of FIG. 8A according to various embodiments; FIG. 8E shows various views of a second vane of the rotary vane apparatus of FIG. 8A according to various embodiments;

FIG. 9 illustrates the operations of the rotary vane apparatus of FIG. 8A according to various embodiments;

FIG. 10A and FIG. 10B show the pressure forces acting on the vanes of the rotary vane apparatus of FIG. 8A according to various embodiments;

FIG. 11 shows a rotary vane apparatus according to various embodiments;

FIG. 12 shows a rotary vane apparatus according to various embodiments; and

FIG. 13 shows a configuration of a first vane, a second vane and a guiding mechanism for a rotary vane apparatus according to various embodiments.

Detailed description

[00013] Embodiments described below in the context of the apparatus are analogously valid for the respective methods, and vice versa. Furthermore, it will be understood that the embodiments described below may be combined, for example, a part of one embodiment may be combined with a part of another embodiment.

[00014] It should be understood that the terms "on", "over", "top", "bottom", "down", "side", "back", "left", "right", "front", "lateral", "side", "up", "down" etc., when used in the following description are used for convenience and to aid understanding of relative positions or directions, and not intended to limit the orientation of any device, or structure or any part of any device or structure. In addition, the singular terms "a", "an", and "the" include plural references unless context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise.

[00015] Various embodiments of a rotary vane apparatus have been provided to address at least some of the issues identified earlier.

[00016] According to various embodiments, the rotary vane apparatus may be a rotary compressor, a rotary pump, a rotary vane pump, a rotary vane compressor, an apparatus for compressing and/or conveying fluid, or any suitable apparatus with rotary vane for compressing and/or conveying fluid. According to various embodiments, fluid may include liquid or gas or incompressible fluid or compressible fluid. [00017] Various embodiments introduce a unique rotary vane apparatus with sliding vane which includes two-uniquely combined "half vanes (or coupled vanes) to address the issues identified earlier. The uniqueness of the various embodiments is that it uses the inherent operational characteristic of the rotary vane apparatus to allow the vanes to operate. According to various embodiments, the vane tip wear may no longer be a problem, which typically would reduce the vane length and cause internal leakage, throughout the whole lifespan of the rotary vane apparatus. Further, the rotary vane apparatus according to the various embodiments may also reduce the manufacturing cost because the inner shape of the compressor cylinder has been changed to be circular (or substantially circular), which would be easier to be manufactured, as compared to a cardioid shape in some conventional rotary compressor.

[00018] The rotary vane apparatus according to the various embodiments may also have the following advantages as compared to other existing conventional compressors. According to various embodiments, the rotary vane apparatus may include fewer parts. For example, the rotary vane apparatus may include only three major components, namely a rotor, a cylinder, and vanes. According to various embodiments, the rotary vane apparatus may also be compact. According to various embodiments, the rotary vane apparatus may be extremely compact as its rotor may occupy an exceedingly small space and hence allows most of the available space to be used as a productive working chamber. Further, as compared to the conventional rotary sliding vane, rolling piston or revolving vane compressor, the rotary vane apparatus according to various embodiments may consume about 50% less material to be manufactured for a given capacity. According to various embodiments, the rotary vane apparatus may also be manufactured at lower production cost. Since the rotary vane apparatus, according to various embodiments, has fewer components, it requires less material and the inner cylinder wall is circular which is easier to manufacture, it is expected that it may cost less for manufacturing. According to various embodiments, the rotary vane apparatus may include an innovative new vane configured to eliminate the need to use extra parts such as spring. This innovative vane may utilize the fluid pressure under compression to minimize the leakage gap between the vane tip and the compressor cylinder inner wall. Additionally, the new vane may allow the rotor size to be exceedingly small or smaller relative to the chamber defined by the cylinder inner wall. [00019] According to various embodiments, there is provided a rotary vane apparatus, which may be an apparatus for compressing and conveying fluid. The apparatus may include a stator having a circular inner sidewall and having a first centre axis. The apparatus may further include a rotor in surface-to-surface engagement with the inner sidewall of the stator. The rotor may include a diametric slot. The rotor may further have a second centre axis arranged eccentrically with respect to the first central axis of the stator. Furthermore, the apparatus may include a plurality of (or two or more, or a pair of, or multiple, or multiple pairs of) slideable vanes, which may slide through and rotate along the diametric slot. According to various embodiments, a working chamber may be defined jointly by the stator, the rotor, and the vanes. The volume of the working chamber may vary while the rotor is rotating. According to various embodiments, the tips of the vanes may be sealingly coupled to the inner sidewall of the stator at all time when the rotor is rotating.

[00020] According to various embodiments, the apparatus may include two vanes, wherein the first vane has a slot and the second vane has a protrusion that is coupled to the slot of the first vane, such that the two vanes are overlapping and in sliding contact.

[00021] According to various embodiments, the apparatus may include an inlet and an outlet on the sidewall of the stator.

[00022] As identified earlier in the background, existing conventional compressors with split vane systems generally require extensive oil pathway systems for the desired functioning. Further, such compressors also require larger rotor sizes (relative to the chamber defined by the inner wall of the stator) to prevent failure. This limitation reduces the overall volumetric capacity of the compressor to compress the fluid.

[00023] According to various embodiments, to maximize the chamber space, the rotor size must be made small as much as possible relative to the chamber space of the stator. Additionally, when the vanes are fully extended, the rotor must be able to hold the vanes without letting the vanes slip out of the rotor due to the rotation and the bending due to the pressure from the compressed fluid.

[00024] Currently, existing conventional rotary compressors have rotor-to-chamber ratio defined as follows: [00025] According to various embodiments, the rotary vane apparatus may have a rotor-to-chamber ratio of less than 0.65. The rotor of the rotary vane apparatus according to various embodiment may also be made small enough such that the rotary vane apparatus may have a rotor-to-chamber ratio of approximately 0.5 or less, that is,

0.5 —

^sh&mbsr (1)

[00026] FIG. 1 shows a schematic illustration of a rotary vane apparatus 100 according to various embodiments. In particular, FIG. 1 illustrates the rotary vane apparatus 100 having a rotor-to-chamber ratio of 0.5. As shown, the rotary vane apparatus 100 may include a housing 110 (or a stator) which has an inner wall 112 (or stator inner wall) enclosing a cylindrical cavity 114 (or a chamber or a working chamber) defining a central cavity axis. The rotary vane apparatus 100 may further include a cylindrical rotor 120 defining a central rotor axis, around which the rotor 120 may be rotatable and which extends parallel and offset to the central cavity axis. The rotor 120 may be sealed against the inner wall 112 along an axial line parallel to the central cavity axis of the cylindrical cavity 114. The rotor 120 may be provided with a through slot 125 which diametrically extends through the rotor 120. The rotary vane apparatus 100 may include a first vane 130 and a second vane 150 which may be received within the through slot 125 in a manner so as to be slideable therein relative to the rotor 120 in the diametrical direction of the through slot 125, and so as to be slideable relative to each other in the diametrical direction of the through slot 125.

[00027] As shown in FIG. 1, in a vertical orientation of the first vane 130 and the second vane 150, the first vane 130 may be extended from the second vane 150 such that one end (or a vane tip) of the first vane 130 may be in contact with a part of the inner wall 112 of the housing 110 while an opposite end (or a vane tip) of the second vane 150 may be in contact with an opposing part of the inner wall 112 of the housing 110. Accordingly, the extended disposition of the first vane 130 and the second vane 150 may form a continuous vane stretching from one part of the inner wall 112 of the housing 110 to an opposing part of the inner wall 112 of the housing 110.

[00028] Referring back to FIG. 1, a horizontal orientation of the first vane 130 and the second vane 150 is shown in dotted lines. As shown, in the horizontal orientation, the first vane 130 may exactly overlap the second vane 150 such that the first vane 130 may be exactly on top of the second vane 150 in a manner whereby the first vane 130 may not protrude or extend from the second vane 150. [00029] To verify that, geometrically, the rotor-to-chamber ratio of 0.5 is achievable in the various embodiments, the necessary condition is that the minimum vane length {Lmin) must be less than the maximum coupled vane length (L _max ), because the vanes must fit at both maximum (horizontal orientation) and minimum (vertical orientation) vane length positions.

[00030] In FIG. 1,

[00031] Accordingly, the rotor- to -chamber ratio of 0.5 can be verified by combining Equation (1) with Equation (2) and Equation (3) respectively, where it is obtained, Lmin = 0.75D 'chamber and, L _ma x = 0.866D _cham ber- Hence, from the results obtained, it is verified that the rotary vane apparatus with the rotor-to-chamber ratio of 0.5 according to the various embodiments is achievable.

[00032] In conventional compressors with split vane systems, it is not possible to reduce the rotor-to-chamber diameter ratio beyond 0.5. This is because, a vane may suffer significant bending during loads of compression, and this may cause the vane to slip out of the rotor slot during its operation. The bending may also increase the wear on the vane side during its entry into the slot. Eventually, after number of hours of operation, the vane wear rate may increase and the vane may become much thinner due to continuous wear.

[00033] Accordingly, various embodiments seek to provide a rotary device or rotary vane apparatus wherein the force required to maintain the sealing contact between the vanes and stator wall is achieved from the centrifugal force due to rotational motion of the vanes and the pressure forces from the compression of working fluid themselves. Hence, the vanes may need to be so configured to withhold higher loading capacity. The above would then allow the building of a rotor, of which, the diameter may be less than 65%, or even equal or less than 50%, of the size of the chamber.

[00034] Referring to the rotary vane apparatus 100 of FIG. 1, according to various embodiments, the the first vane 130 and the second vane 150 of the rotary vane apparatus 100 may define a first mating face 136 and a second mating face 156, respectively, which first and second mating faces 136, 156 may extend parallel to the diametrical direction of the through slot 125 and overlap (or in engagement with) each other. Further, the rotary vane apparatus 100 may include a guiding mechanism (not shown) arranged between the first and second mating faces 136, 156 of the first and second vanes 130, 150, by which the sliding movement between the first and second vanes 130, 150 may be guided. The guiding mechanism may include an engagement arrangement, via which the first and second vanes 130, 150 may be permanently engaged with each other in such a manner that the first and second vanes 130, 150 may be non-separable in a direction perpendicular to their mating faces.

[00035] According to various embodiments, the engagement arrangement of the guiding mechanism may include a tongue and groove sliding arrangement. A tongue and a groove of the tongue and groove sliding arrangement are configured to engage in a manner such that the tongue and the groove are slideable in the diametrical direction of the through slot and the tongue and the groove are prohibited from relative movement in the direction perpendicular to the first and second mating faces of the first and second vane.

[00036] According to various embodiments, the tongue and groove sliding arrangement may include a dovetail tongue and groove sliding arrangement, or a T- shaped tongue and groove sliding arrangement, or a J-shaped tongue and groove sliding arrangement, or an L- shaped tongue and groove sliding arrangement or a hooked-like tongue and groove sliding arrangement.

[00037] According to various embodiments, the first mating face 136 of the first vane 130 may include the tongue which extends along the first mating face 136 in the diametrical direction of the through slot 125. Further, the second mating face 156 of the second vane 150 may include the groove which extends along the second mating face 156 in the diametrical direction of the through slot 125.

[00038] According to various embodiments, each of the first and second vanes 130, 140 may include a vane tip portion having a rounded cross-sectional profile, wherein the respective vane tip portions may be in contact with the inner wall 112.

[00039] According to various embodiments, the rounded cross-sectional profile of the respective vane tip portions may be symmetrical.

[00040] According to various embodiments, the rounded cross-sectional profile of the respective vane tip portions may be asymmetrical.

[00041] According to various embodiments, the rounded cross-sectional profile of the respective vane tip portions may include a first radius section and a second radius section. A radius of the first radius section may be smaller than a radius of the second radius section. Preferably, the first radius section may be towards a side of the respective vanes 130, 150 with the respective mating faces 136, 156, and the second radius section may be towards an opposite side of the respective vanes 130, 150.

[00042] According to various embodiments, a first inner surface of the through slot 125 may include a first elongate cut extending from a first slot opening towards a second slot opening for a predetermined distance and a second opposing inner surface of the through slot 125 may include a second elongate cut extending from the second slot opening to the first slot opening for the predetermined distance. The first and the second inner surface of the through slot 125 may be parallel to the first and second mating faces 136, 156 of the first and second vanes 130, 150. The first vane 130 may be in sliding contact with the first inner surface and the second vane 150 may be in sliding contact with the second inner surface. Further, the first vane 130 may project from the first slot opening to contact the inner wall 112 and the second vane 150 may project from the second slot opening to contact the inner wall 112.

[00043] According to various embodiments, the first vane 130 may include a first indent which may be at free end of a first auxiliary face of the first vane 130, the first auxiliary face may be opposite the first mating face 136 of the first vane 130 and the free end may be opposite of an end (or a vane tip) of the first vane 130 in contact with the inner wall 112. The second vane 150 may include a second indent which may be at a free end of a second auxiliary face of the second vane 150, the second auxiliary face may be opposite the second mating face 156 of the second vane 150 and the free end may be opposite of an end of the second vane 150 in contact with the inner wall 112.

[00044] According to various embodiments, the inner wall 112 of the housing 110 may include a depression extending along the axial line parallel to the central cavity axis of the cylindrical cavity 114, wherein the depression may have a cross-sectional profile corresponding to a pre-determined arc of the cylindrical rotor 120, wherein the rotor 120 may sealingly sit with the pre-determined arc in the depression.

[00045] According to various embodiments, a diameter of the cylindrical rotor 120 may be less than 65%, or may be equal or less than half, of a diameter of the cylindrical cavity 114 of the housing 110.

[00046] FIG. 2A shows a front view of a rotary vane apparatus 200 according to various embodiments. FIG. 2B shows a sectional view cut at the line represented by A-A of the rotary vane apparatus 200 of FIG. 2A. FIG. 2C shows a sectional view cut at the line represented by B-B (in FIG. 2B) of the rotary vane apparatus 200 of FIG. 2A.

[00047] In FIG. 2A, FIG. 2B and FIG. 2C, 210 is a housing (or a cylindrical stator housing or a stator). The inner wall 212 (or inner stator wall or inner cylindrical wall) geometry may be cylindrical or at least substantially cylindrical, but the outer wall 211 (or outer stator wall) may be of any shape convenient for manufacturing or assembly. 216 and 217 are the end wall covers (or upper cover and lower cover respectively) of the stator 210. 220 is a cylindrical rotor (or a rotor or a rotor-shaft). Arc X-Y (see FIG. 2C) may represent a contact surface between the rotor 220 and the housing 210. This surface may also be called a sealing arc as it may deter the leakage of compressed flow into the suction chamber from the discharge chamber. A through slot 225 (or a slot) may be cut centrally through diametrically about the axial midpoint of the cylindrical rotor 220. Through the through slot 225, first and second vanes 230 and 250 (or coupled vanes) may rotatably slide. 270 is a suction port (or an inlet port) and 280 is a discharge port (or an outlet port). 282 is a thin reed valve (or a discharge reed valve) to check the flow of pressurised fluid out of the housing 210. 284 is a valve stopper to stop the reed valve 282 from fully deflecting and thereby reducing the repeated fatigue loading on the reed valve 282. 290-294 are cylindrical channels through which oil can lubricate the moving parts such as bearing surfaces and vane end-surfaces. 290 and 291 may be axial oil holes. 292-294 may be radial oil holes. O-rings 298 may ensure that the housing 210 is sufficiently sealed to prevent leakage. 295 may be oil feed hole for supplying lubricating oil.

[00048] FIG. 2D and FIG. 2E shows the vanes 230, 250 of the rotary vane apparatus 200 according to various embodiments. Referring to FIG. 2D, the first vane 230 (also labelled as vane 230 in FIG. 2B and FIG. 2C) may be one of the couple vanes 230, 250 with the male dovetail feature 233. This vane 230 may slide into the female dovetail feature 253 of the second vane 250 shown in FIG. 2E (also 250 in FIG. 2B and FIG. 2C). 231 and 251 in FIG. 2D and FIG. 2E are semi-cylindrical vane tip portions. 232 and 252 mark the surface along which vanes 230, 250 may be cut off to form the relief on which dovetail features 233 and 253 may be machined. 234 and 254 represent the rear ends of the respective vanes 230, 250. The couple vanes 230, 250 fitted together may slide upon one another and inserted into the axial slot 225 shown in FIG. 2C. During the operation, one vane may act as a leading vane and the other may act as a trailing vane. [00049] One of the innovative part of the rotary vane apparatus 200 is that two unique sliding vanes 230, 250 may be used to slide inside the through slot 225 of the rotor 220 and the configuration of the vanes 230, 250 may make use of fluid pressure in compression to force the respective vanes 230, 250 to be in contact with the inner wall 212 at all time, throughout the whole working life of the rotary vane apparatus 200. This feature may allow the rotor 220 to be configured less than 65%, or even equal or less than 50%, of the size of a cylindrical cavity 214 (or a working chamber or a chamber) of the housing 210 (or the stator).

[00050] FIG. 3 shows a schematic diagram to illustrate the forces and contact points of the vanes 230, 250 of the rotary vane apparatus 200 according to various embodiments. According to various embodiments, the vanes 230, 250 may be configured so that they may have the following functions as described. Two unique sliding vanes mean that the vanes 230, 250 may extend or contract as necessary depending on the geometry of the chamber 214. The fluid under compression may be in contact with the leading face 235 of the first vane 230 as shown in FIG. 3. This fluid pressure force at leading face 235 together with the centrifugal force of the first vane 230 may ensure that the vane tip portion 231 may always be in contact with the inner cylinder wall 212. This novel technique may eliminate the need to use additional components such as pin joints, springs, cams, or supply of pressurized fluid to achieve vane tip-cylinder contact. This feature may also eliminate the in-chamber vane tip leakage completely. The vane tip portions 231, 251 of the vanes 230, 250 shown in FIG. 2D and FIG. 2E may be configured to ensure a smooth sliding and with low friction at the sliding contact between the respective vane tip portions 231, 251 and the inner wall 212 of the circular geometry. This configuration also minimizes the wear and tear of the vane tip portions 231 , 251.

[00051] FIG. 4A to FIG. 4G shows the working principle (or one cycle of operation) of the rotary vane apparatus 200 according to various embodiments. FIG. 4A shows stage 1 of one cycle of operation of the rotary vane apparatus 200. In stage 1, a starting position of one cycle of operation of the rotary vane apparatus 200 may be as shown. FIG. 4B shows stage 2 of one cycle of operation of the rotary vane apparatus 200. In stage 2, rotational forces of the first vane 230 and the fluid pressure at the vane tip portion 231 of the first vane 230 pushes the first vane 230 against the inner wall 212 of the housing 210. The resulted space formed may be called a suction chamber 272 (see FIG. 4C). FIG. 4C shows stage 3 of one cycle of operation of the rotary vane apparatus 200. In stage 3, the fluid flows through the suction port 270. Further rotation may allow more fluid to flow into the suction chamber 272. FIG. 4D shows stage 4 of one cycle of operation of the rotary vane apparatus 200. In stage 4, the suction ports 270 are sealed off and compression process may begin in the compression chamber 274. FIG. 4E shows stage 5 of one cycle of operation of the rotary vane apparatus 200. In stage 5, compression may be achieved because the compression chamber 274 volume decreases rapidly following the rotation of the vanes 230, 250. FIG. 4F shows stage 6 of one cycle of operation of the rotary vane apparatus 200. As the leading vane 230 approaches the discharge port 280, the pressure in the compression chamber 274 increases. When this pressure reaches the discharge pressure, the compressed fluid is discharged through the discharged port 280. FIG. 4G shows stage 7 of one cycle of operation of the rotary vane apparatus

200. When the rotation reaches 540 , the cycle ends. The same process from stage 1 to stage 7 then repeats for the next cycle of operation of the rotary vane apparatus 200.

[00052] To verify that the rotary vane apparatus 200 addresses the issues identified earlier, numerical analysis has been conducted on the vane dynamics of the rotary vane apparatus 200, analysing the forces acting on the respective vanes 230, 250. It was observed that for the respective vane tip portions 231, 251 to remain in contact with the inner cylinder wall 212, the contact force at the respective vane tip portions 231, 251 should be positive throughout the entire compression and discharge cycle.

[00053] FIG. 5 shows the result obtained for the numerical analysis. The pressures from fluid acting on the rotary vane apparatus 200 were obtained using the equation of state for real gas and the first law of thermodynamics. The result in FIG. 5 shows that the respective vane tip portions 231, 251 remain in contact with the cylinder wall 212. At the two positions when the vane tip portions of the vanes 230, 250 are entering the rotor slot 225, the fluid leakage across the vane tip portions may be inconsequential because it occurs after and not during the discharge process.

[00054] Referring back to FIG. 2A to FIG. 2E, the rotary vane apparatus 200 according to various embodiments may include the housing 210 which has an inner wall 212 enclosing the cylindrical cavity 214 defining a central cavity axis 213. Accordingly, the housing 210 may include the inner wall 212 configured and shaped in a cylindrical manner or at least substantially cylindrical manner to define the cylindrical cavity 214. Further, the cylindrical cavity 214 may have the central cavity axis 213 extending through a center of the cylindrical cavity 214 in the axial direction. [00055] According to various embodiments, the rotary vane apparatus 200 may include the cylindrical rotor 220 defining a central rotor axis 223, around which the rotor 220 is rotatable and which extends parallel and offset to the central cavity axis 213. Accordingly, the rotor 220 has the central rotor axis 223 extending through a center of the rotor 220 in the axial direction and the rotor 220 is rotatable about the central rotor axis 223. The rotor 220 may be disposed within the housing 210 such that the central rotor axis 223 of the rotor 220 may be parallel and set laterally apart from the central cavity axis 213. As shown in FIG. 2B, the rotor 220 may be mounted within the housing 210. The cylindrical cavity 214 of the housing 210 may be at a middle portion 215 of the housing 210. The housing 210 may further include end wall covers 216, 217 respectively on each end portions of the housing 210 such that the middle portion 215 of the housing 210 with the cylindrical cavity 214 may be directly between the end portions of the housing 210. The end wall covers 216, 217 of the housing 210 may sandwich the middle portion 215 of the housing 210 and may be configured to receive the respective ends of the rotor 220 so as to rotatably couple the rotor 220 to the housing 210.

[00056] According to various embodiments, the rotor 220 may be sealed against the inner wall 212 of the housing 210 along an axial line 219 parallel to the central cavity axis 213 of the cylindrical cavity 214. Accordingly, the rotor 220 may form a sealing contact lengthwise with the inner wall 212 of the housing 210. Hence, the rotor 220 may be in contact with the inner wall 212 of the housing 210 along a length of the rotor 220. According to various embodiments, the rotor 220 may further be provided with a through slot 225 which diametrically extends through the rotor 220. Accordingly, the through slot 225 may cut through the rotor 220 from a portion of the cylindrical surface of the rotor 220 to an opposite portion of the cylindrical surface of the rotor 220 across a diameter of the rotor 220.

[00057] According to various embodiments, the rotary vane apparatus 200 may include the first vane 230 and the second vane 250 which are received within the through slot 225 in a manner so as to be slideable therein relative to the rotor 220 in the diametrical direction of the through slot 225, and so as to be slideable relative to each other in the diametrical direction of the through slot 225. Accordingly, in the rotary vane apparatus 200, the first vane 230 and the second vane 250 may be inserted in the through slot 225 such that each of the first vane 230 and the second vane 250 may be slideable with respect to the through slot 225 of the rotor 220 in the diametrical direction, and slideable with respect to each other also in the diametrical direction. As shown in FIG. 2B and 2C, the through slot 225 may be along a portion of the rotor 220 which corresponds to the position of the cylindrical cavity 214 in the housing 210. Accordingly, the through slot 225 may be at a middle portion of the rotor 220 such that the first vane 230 and the second vane 250 may slide in and out of the through slot 225 respectively to maintain contact with the inner wall 212 of the cylindrical cavity 214 of the housing 210 during operation of the rotary vane apparatus 200 when the rotor 220 rotates.

[00058] According to various embodiments, the first vane 230 and the second vane 250 may define a first mating face 236 and a second mating face 256, respectively, which first and second mating faces 236, 256 extend parallel to the diametrical direction of the through slot 225 and overlap each other. Accordingly, the first vane 230 may have the first mating face 236 and the second vane 250 may have the second mating face 256, wherein the first mating face 236 and the second mating face 256 are configured to overlap or cover or lay directly over each other such that the first vane 230 and the second vane 250 may be in contact or couple or engage with each other via the first and second mating faces 236, 256. Further, the first and second mating faces 236, 256 may be parallel to the through slot 225 in the diametrical direction such that the first vane 230 and the second vane 250 may slide in and out of the through slot 225 in the diametrical direction and may be slideable with respect to each other in the diametrical direction along the first and second mating faces 236, 256.

[00059] According to various embodiments, the rotary vane apparatus 200 may include a guiding mechanism 202 arranged between the first and second mating faces 236, 256 of the first and second vanes 230, 250, by which the sliding movement between the first and second vanes 230, 250 is guided. The guiding mechanism 202 may include an engagement arrangement 204, via which the first and second vanes 230, 250 are permanently engaged with each other in such a manner that the first and second vanes 230, 250 are non-separable in a direction perpendicular to their mating faces 236, 256. Accordingly, the guiding mechanism 202 between the first and second mating faces 236, 256 of the first and second vanes 230, 250 may be configured to couple the first and second vanes 230, 250 either directly or indirectly to each other and may be configured to guide the relative sliding movement of the first and second vanes 230, 250 with respect to each other. Further, the engagement arrangement 204 of the guiding mechanism 202 may be configured to engage with the first and second vanes 230, 250 such that the first and the second vanes 230, 250 may not be pulled apart, or separated, or break away from each other laterally with respect to the first and second mating faces 236, 256.

[00060] According to various embodiments, the engagement arrangement 204 of the guiding mechanism 202 may include a tongue and groove sliding arrangement. According to various embodiments, a tongue and a groove of the tongue and groove sliding arrangement may be configured to engage in a manner such that the tongue and the groove may be slideable in the diametrical direction of the through slot 225 and the tongue and the groove may be prohibited from relative movement in the direction perpendicular to the first and second mating faces 236, 256 of the first and second vane 230, 250. According to various embodiments, the tongue and groove sliding arrangement may include a dovetail tongue and groove sliding arrangement, or a T-shaped tongue and groove sliding arrangement, or a J- shaped tongue and groove sliding arrangement, or an L- shaped tongue and groove sliding arrangement or a hooked-like tongue and groove sliding arrangement, or any suitable tongue and groove sliding arrangement.

[00061] Referring to FIG. 2D, the first mating face 236 of the first vane 230 may include the tongue 238 in the form of a raised portion, or a protrusion, or a projection, or an elevated portion. The tongue 238 may extend along the first mating face 236 in the diametrical direction of the through slot 225 when the first vane 230 is inserted in the through slot 225. Accordingly, the tongue 238 may extend or stretch between the vane tip portion 231 of the first vane 230 and the opposite end 234 of the first vane 230. As shown in FIG. 2D, the tongue 238 may have a top surface 237 (or a topmost surface or a roof surface or a crown surface) with a bell-shaped outline when viewed directly at the first mating face 236 (i.e. when the eyes of the viewer are aligned perpendicular to the first mating face 236). The bell-shaped outline may have a stretch of parallel sides. As shown in FIG. 2D, the tongue 238 may be oriented with a mouth of the bell-shaped outline directed towards the vane tip portion 231 of the first vane 230. According to various other embodiments, the tongue may have a rectangular outline or other suitable elongated outlines with a stretch of parallel sides. Also shown in FIG. 2D, a transverse cross-sectional profile of the tongue 238 may be a dovetail profile. According to various other embodiments, the transverse cross- sectional profile of the tongue 238 may also be a T-shaped profile, or a J-shaped (or an inverted J-shaped) profile, or a L-shaped (or an inverted L-shaped) profile, or a hook-like profile. Accordingly, an edge of the top surface 237 of the tongue 238 may form an overhanging edge such that the top surface 237 of the tongue 238 may be larger than a base or a bottom of the tongue 238.

[00062] Referring to FIG. 2E, the second mating face 256 of the second vane 250 may include the groove 258 in the form of a recessed portion, or a depression or a crater or a concavity. The groove 258 may extend along the second mating face 256 in the diametrical direction of the through slot 225 when the second vane 250 is inserted in the through slot 225. Accordingly, the groove 258 may extend or stretch between the vane tip portion 251 of the second vane 250 and the opposite end 254 of the second vane 250. As shown in FIG. 2E, the groove 258 may have a bottom surface 257 (or a bottommost surface or a bed surface or a base surface) and a groove opening 259. The bottom surface 257 and the groove opening 259 may have a bell- shaped outline when viewed directly at the second mating face 256 (i.e. when the eyes of the viewer are aligned perpendicular to the second mating face 256). The bell- shaped outline may have a stretch of parallel sides. As shown in FIG. 2E, the groove

258 may be oriented with a mouth of the bell-shaped outline directed towards the opposite end 254 of the second vane 250. According to various other embodiments, the groove 258 may have a rectangular outline or other suitable elongated outlines with a stretch of parallel sides. Also shown in FIG. 2E, a transverse cross-sectional profile of the groove 258 may be a dovetail (or an inverted profile). According to various other embodiments, the transverse cross- sectional profile of the groove 258 may also be a T-shaped (or an inverted T-shaped) profile, or a J-shaped profile, or an L-shaped profile, or a hook-like profile. Accordingly, a rim of the groove opening

259 of the groove 258 may form an overhanging edge such that the bottom surface 257 of the groove 258 may be larger than the groove opening 259 of the groove 258.

[00063] According to various embodiments, each of the first and second vanes 230, 250 may include the respective vane tip portion 231, 251 having a rounded cross- sectional profile. Accordingly, a lateral cross-section of the respective vane tip portion 231, 251 may have a rounded profile or a curved profile. Further, the respective vane tip portions 231, 251 may be in contact with the inner wall 212 of the housing 210. According to various embodiments, the respective vane tip portions 231, 251 may be configured to form a sealing contact with the inner wall 212 of the housing 210. Accordingly, fluid may not flow from one side of the respective first and second vanes 230, 250 to the other side via the contact between the respective first and second vanes 230, 250 and the inner wall 212 of the housing 210.

[00064] According to various embodiments, the rounded cross-sectional profile of the respective vane tip portions 231, 251 may be symmetrical or asymmetrical. As shown in FIG. 2C, the rounded cross-sectional profile of the vane tip portions 231, 251 may be symmetrical. Accordingly, the rounded cross-sectional profile of the vane tip portions 231, 251 may be a semi-circular profile.

[00065] According to various embodiments, the inner wall 212 of the housing 210 may include a depression 218 extending along the axial line 219 parallel to the central cavity axis 213 of the cylindrical cavity 214. The depression 218 may have a cross- sectional profile corresponding to a pre-determined arc of the cylindrical surface of the cylindrical rotor 220. Further, the rotor 220 may sealingly sit with the predetermined arc X-Y in the depression 218 of the housing 210. Accordingly, the depression 218 may be in the form of a sealing arc X-Y and may stretch lengthwise along the housing 210. The rotor 220 may be seated in tight contact with the housing 210 along the depression 218 of the housing 210 such that the pre-determined arc of the cylindrical surface of the cylindrical rotor 220 fits perfectly into the sealing arc X- Y of the inner wall 212 of the housing 210. In such a configuration, the contact between the rotor 220 and the housing 210 along the depression 218 may minimize leakage of fluid through the contact between the rotor 220 and the housing 210 along the depression 218.

[00066] According to various embodiments, the rotor 220 and/or the through slot 225 of the rotor 220 may be free of springs or biasing elements or ducts/passages/inlets supplying pressurized fluid or any other elements for generating a force to bear against the first vane 230 and/or the second vane 250 such that the first vane 230 and/or the second vane 250 may be biased or pushed so as to be in contact with the inner wall 212 of the housing 220. Rather, according to various embodiments of the rotary vane apparatus 200, sealing contact between the respective first and second vanes 230, 250 and the inner wall 212 of the housing 200 may be solely or entirely achieved from the centrifugal force due to rotation motion of the vanes 230, 250 and the pressure forces acting on the first and second vanes 230, 250 (which arises from the configuration of the rotary vane apparatus 200 as described herein and/or the configuration of the first and second vanes 230, 250 as described herein) from compressing the working fluid during operation of the rotary vane apparatus 200.

[00067] According to various embodiments, a diameter of the cylindrical rotor 220 may be less than 65%, or equal or less than half, of a diameter of the cylindrical cavity 214 of the housing 210. The above may be achieved due to the configuration of the rotary vane apparatus 200 as described herein and/or the configuration of the first and second vanes 230, 250 as described herein.

[00068] According to various embodiments, the rotary vane apparatus 200 may be further improved so as to be energy saving. Such energy saving improvements may minimize expansion and compression losses in a gap between the vanes 230, 250 inside the through slot 225 of the rotor 220 when the rotary vane apparatus 200 is used as a coupled vane compressor working with a compressible fluid. Such energy saving improvements may also improve the durability of the vanes 230, 250 significantly by minimizing the wear and tear of the vane tip portions 231, 251 when the rotary vane apparatus 200 is used as a coupled vane pump working with an incompressible fluid.

[00069] In the following, a possible scenario leading to a degraded performance of the rotary vane apparatus 200 when the rotary vane apparatus 200 is used as a coupled vane compressor with compressible working fluid, for example, gas, is described.

[00070] FIG. 6A shows a schematic diagram of the rotary vane apparatus 200 when being used as a coupled vane compressor. FIG. 6B illustrates the expansion and the compression of the gas in the gap between the vanes of the rotary vane apparatus 200 within the through slot of the rotor. Referring to FIG. 6A, during the operation of the rotary vane apparatus 200 as a coupled vane rotary compressor (CVRC), the compressed gas trapped in the gap 'G' between the coupled vanes 'D' and Έ' and the rotor slot 'C undergoes expansion and then compression (shown figuratively in FIG. 6B). During expansion, the pressure of the gas in the gap 'G' may drop below the suction chamber pressure 'P _s '. This may cause the compression chamber pressure 'P _c ' and the suction chamber Pressure 'P _s ' on the vane tip portion of the leading vane 'D' to push the vanes 'D' and Έ' into the rotor slot 'C. This may result in the formation of leakage gaps between the vane tip portion of the leading vane 'D' and the inner wall of stator Ά'. The leakage of the compressed gas from the compression chamber to the suction chamber through this leakage gap may reduce the volumetric efficiency of the compressor leading to degraded performance. [00071] To investigate the drop in the pressure during the expansion of the gas in the gap between the vanes within the through slot of the rotor, the expansion process may be assumed to be polytropic. FIG. 6C illustrates the instance when the vane tip portion is entering the rotor slot. As shown in FIG. 6C, when the gap between the vanes just formed inside the rotor, the pressure in the gap may be the same as the discharge chamber pressure 'P _d '. The cross-sectional area of the gap may be assumed to remain the same throughout the process. The length of the gap in this instance is 'Li'. As this length increases, the gap volume increases and the pressure in the gap decreases. To find out the length of the gap when the pressure in the gap becomes equal to the suction pressure, the equations (4) and (5) may be used.

P* * tL _i 'Ar = Px~ lL ₉ -Ar (4)

^ ^{" ¾ "} (¾.) (5)

[00072] The length Li for the instance shown in FIG. 6C was calculated to be 1.28 mm. Assuming ¾ = 1000 kPa and ¾ = 100 kPa, the length L ₂ at which the pressure in the gap drops to suction chamber pressure P _s was found to be 6.6 mm. Hence, this may imply, for the length of the gap greater than 6.6 mm, the expansion may cause the pressure to drop below the suction chamber pressure P _s .

[00073] FIG. 6D illustrates the gap between the vanes inside the through slot of the rotor expanded to maximum volume. For example, for the instance shown in the FIG. 6D, the length of the gap between the vanes reaches the maximum value, L _max . The pressure in the gap may be found by using equations (6) and (7).

P _x = P _d - (L L _ms (7)

[00074] Consequently, the pressure in the gap for this instance was calculated to be 65 kPa which is well below the suction chamber pressure of 100 kPa.

[00075] FIG. 6E shows the pressure forces on the various cross-sections of the vane (e.g. the vane tip, the neck and the rear end). For this instance, the normal surface area on which the pressure acts on these cross-sections may be the same. Hence, the forces pushing the vane along these cross-sections may be proportional to the pressure acting on these cross-sections. For the leading vane, the suction chamber pressure and the compression chamber pressures 'P _s ' and 'P _c ' at the leading vane tip may be pushing the vane into the rotor slot. The pressure in the gap 'Ρ _Χ ' and the compression chamber pressure 'P _c ' at the leading vane neck may be acting on the respective surface areas to push the leading vane towards the inner wall of the stator. Since, in this case, P _s acting on the vane tip is larger than P _x , the force pushing the leading vane into the rotor slot may be larger. This phenomenon may have an effect when the operating speed of the compressor is low. In this case, the total force including the centrifugal force acting to push the leading vane against the inner stator wall may be small. Accordingly, this may cause the leading vane to slide into the rotor slot.

[00076] In the following, a possible scenario leading to a degraded performance of the rotary vane apparatus 200 when the rotary vane apparatus 200 is used as a coupled vane pump working with an incompressible fluid, for example water or oil, is described.

[00077] FIG. 7 illustrates the possibility of large contact force in a coupled vane pump. In the case of using the rotary vane apparatus 200 as coupled vane pump or liquid pumping device, the wear and tear of vane tips may be severe when the gap volume between the vanes within the through slot of the rotor is compressing liquids such as water or oil, which are incompressible fluids. Hence, any attempt to compress the liquid, as in an instance shown in FIG. 7, may cause the liquid to resist compression. Therefore, a very high pressure may develop in the gap between the vanes inside the through slot of the rotor that may push the vanes strongly against the inner wall of the stator. This may result in significant frictional wear of the vane tip portions and the stator wall. In the worst-case scenario, the pressure from the liquid in the gap may be so large that the vanes cannot slide into the rotor slot which may cause the rotor to jam.

[00078] FIG. 8A shows a rotary vane apparatus 800 according to various embodiments. FIG. 8B shows an enlarged top view of a segment of the rotor 820 of the rotary vane apparatus 800. FIG. 8C shows a cross-sectional view along section A- A of the rotor 820 of FIG. 8B. FIG. 8D shows various views (including a front view, a plane view, a side view and a perspective view) of a first vane 830 of the rotary vane apparatus 200 of FIG. 8A. FIG. 8E shows various views (including a front view, a plane view, a side view and a perspective view) of a second vane 850 of the rotary vane apparatus 200 of FIG. 8A. According to various embodiments, the rotary vane apparatus 800 is similar to the rotary vane apparatus 200 of FIG. 2A to FIG. 2E, except for the following differences. According to various embodiments, a first inner surface 826 of the through slot 825 of the rotor 820 may include a first elongate cut 827 (or a first canal or a first channel or a first gutter or a first groove) extending from a first slot opening 821 towards a second slot opening 822 for a predetermined distance and a second opposing inner surface 828 of the through slot 825 of the rotor 820 may include a second elongate cut 829 (or a second canal or a second channel or a second gutter or a second groove) extending from the second slot opening 822 to the first slot opening 821 for the predetermined distance. The first and second inner surfaces 826, 828 of the through slot 825 may be parallel to the first and second mating faces 836, 856 of the first and second vanes 830, 850. Further, the first vane 830 may be in sliding contact with the first inner surface 826 and the second vane 850 may be in sliding contact with the second inner surface 828. Furthermore, the first vane 830 may project from the first slot opening 821 to contact the inner wall 212 of the housing 210 and the second vane 850 may project from the second slot opening 822 to contact the inner wall 212 of the housing 210.

[00079] According to various embodiments, the first vane 830 may include a first indent 839 (or a first short groove or a first recess or a first cutout) which may be at a free end 844 of a first auxiliary face 846 of the first vane 830. The first auxiliary face 846 may be opposite the first mating face 836 of the first vane 830 and the free end 844 may be opposite of the vane tip portion 831 (or an end) of the first vane 830 in contact with the inner wall 212 of the housing 210. According to various embodiments, the second vane 850 may include a second indent 859 (or a second short groove or a second recess or a second cutout) which may be at a free end 864 of a second auxiliary face 866 of the second vane 850. The second auxiliary face 866 may be opposite the second mating face 856 of the second vane 850 and the free end 864 may be opposite of the vane tip portion 851 (or an end) of the second vane 850 in contact with the inner wall 212 of the housing 210.

[00080] According to various embodiments, a length of the first elongate cut 827 on the first inner surface 826 and a length of the first indent 839 on the first vane 830 may be configured such that a pressure in a gap 809 between the first vane 830 and the second vane 850 inside the through slot 825 of the rotor 820 may be maintained at the suction chamber pressure. According to various embodiments, a length of the second elongate cut 829 on the second inner surface 828 and a length of the second indent 859 on the second vane 850 may be configured such that a pressure in a gap between the first vane 830 and the second vane 850 inside the through slot 825 of the rotor 820 may be maintained at the suction chamber pressure. As shown in FIG. 8D and FIG. 8E, the first and second indents 839, 859 may have a length 'L _v ' and the width 'W _v '. The first and second indents 839, 859 may have an elongated-D shape outline or other suitable outline. As shown in FIG. 8B and FIG. 8C, the first and second elongate cuts 827, 829 may have a length 'L _R ' and diameter 'D _R '. The first and second elongate cuts 827, 829 may have a semi-circular cross-sectional profile or other suitable cross-sectional profile.

[00081] According to various embodiments, the function of the first and second elongate cuts 827, 829 and the first and second indents 839, 859 is to connect the gap (formed between the first vane 830 and the second vane 850 inside the through slot 825 of the rotor 820) with the suction chamber so that the pressure in the gap may not drop below the suction chamber pressure. Accordingly, since the pressure in the gap may not drop below the suction chamber pressure, referring to FIG. 6E, P _x may always be greater than or equal to P _s . Hence, the vane tip portion of the leading vane may be able to maintain continuous contact with the inner wall 212 of the housing 210 throughout the operation of the rotary vane apparatus 800 as a rotary vane compressor working with a compressible fluid. Further, when the gap size is reduced, any fluid (gas or liquid) present in the gap may maintain the pressure equivalent to the suction chamber pressure as fluid may escape from the gap as the size is reducing. Hence, the potential issue of compressing incompressible fluid to cause excessive frictional wear on the vane tip and the inner wall, related to operating the rotary vane apparatus as a rotary vane pump working with an incompressible fluid, may be mitigated. Specifically, in case of coupled vane pump, the length of the first and second elongate cuts 827, 829 and the first and second indents 839, 859 may be configured such that the fluid in the gap may not undergo expansion or compression.

[00082] FIG. 9 illustrates the operations of the rotary vane apparatus 800 according to various embodiments. With reference to FIG. 9, the following steps describe the function and the working mechanism of the first and second elongate cuts 827, 829 and the first and second indents 839, 859.

[00083] In step 1: following the anticlockwise rotation, the trailing vane 'Tv' may be compressing the fluid to discharge pressure.

[00084] In step 2: at the instance shown, the tip of the trailing vane 'Τ _ν ' may be entering into the slot 825 forming the gap 809 between the first vane 830 and the second vane 850 within the slot 825. The gas (or liquid or fluid) trapped in the gap may be at the discharge chamber pressure. At this instance, the first and second indents 839, 859 may still be apart from the first and second elongate cuts 827, 829 respectively.

[00085] In step 3: the gas trapped in the gap 809 may undergo expansion. In case of the coupled vane compressor, the gas expansion may be allowed until the suction pressure is reached. When the gas in the gap attains the suction chamber pressure, the kinematic motion of the vane and rotor may connect the first and second indents 839, 859 with the first and second elongate cuts 827, 829 respectively. For coupled vane pump, the length of the first and second elongate cuts 827, 829 may be longer so that the gap can connect to suction chamber without forcing the liquid to undergo expansion or compression.

[00086] In step 4: the gap length may reach its maximum but the pressure in the gap 809 may stay the same as the suction chamber pressure due to the first and second elongate cuts 827, 829 and the first and second indents 839, 859.

[00087] In step 5: after step 4, the length of the gap 809 may start decreasing and the volume of the gap 809 may decrease, but the pressure may still remain at suction chamber pressure. However, at this stage the first and second indents 839, 859 on respective first and second vanes 830, 850 may disconnect from the first and second elongate cuts 827, 829 on the rotor slot 825.

[00088] In step 6: following step 5, the tip of the leading vane 'L _v ' may protrude out of the rotor slot 825 and thus, connects the gap with the suction chamber again.

[00089] Referring back to FIG. 8A to FIG. 8E, according to various embodiments, each of the first and second vanes 830, 850 may include respective vane tip portions 831, 851 each having a rounded cross-sectional profile. The respective vane tip portions 831, 851 may be in contact with the inner wall 212 of the housing 210. As shown in FIG. 8D and FIG. 8E, the rounded cross-sectional profile of the respective vane tip portions 831, 851 may be asymmetrical. Accordingly, the rounded cross- sectional profile of the respective vane tip portions 831, 851 may include a first radius section 876, 878 and a second radius section 877, 879, wherein a radius of the first radius section 876, 878 may be smaller than a radius of the second radius section 877, 879. Further, the first radius section 876, 878 may be directed towards a side of the respective vanes 830, 850 with the respective mating faces 836, 856, and the second radius section 877, 879 may be directed towards an opposite side of the respective vanes 830, 850. Accordingly, the second radius section 877, 879 of the vane tip portions 831, 851 with a larger radius 'R _v ' may always face towards the chamber with lower pressure, and the first radius section 876, 878 of the vane tip portions 831, 851 with a smaller radius 'R _f ' may always face towards the chamber with higher pressure.

[00090] FIG. 10A and FIG. 10B shows the pressure forces acting on the vanes 830,

850 according to various embodiments. As shown in FIG. 10A, the pressure forces acting on the respective vanes 830, 850 either pushes the respective vanes 830, 850 away from the inner wall 212 or pushes the respective vanes 830, 850 against the inner wall 212. If the forces pushing the respective vanes 830, 850 away from the inner wall 212 are larger, the vanes 830, 850 may have the tendency to move into the rotor slot 825. Hence, the vane tip portion 831, 851 may fail to make continuous contact with the inner wall 212 and hence a leakage gap may be formed between the vane tip portion 831, 851 and inner wall 212. According to various embodiments, the asymmetrical rounded cross-sectional profile of the respective vane tip portions 831,

851 may ensure continuous contact between the vane tip portions 831, 851 with the inner wall 212.

[00091] Referring to FIG. 10A, the first radius section 878 of the vane tip portion 851, R _f , of the second vane 850 (or the trailing vane) directed towards the discharge chamber pressure may be made smaller than the second radius section 879 of the vane tip portion 851, R _v , of the second vane 850 (or the trailing vane). The discharge chamber pressure, P _d , may always be several times larger than the compression chamber pressure P _c . Consequently, the force, 'F ₅ ', due to P _d may be several times larger than the force, 'F ₆ ', due to P _c if the normal surface area where the pressure acting is the same. The smaller radius of the first radius section 878 of the vane tip portion 851, directed towards the discharge chamber pressure may reduce the normal surface area where the discharge pressure acts. This may allow the pressure force, F5, due to the discharge pressure 'P _d ' to be exceedingly small. In this way, the total force pushing the vane tip portion 851 away from the inner wall 212 may be reduced.

[00092] The force, F ₇ , due to the discharge pressure at the vane neck 886 may be larger than the F5. Thus, the sum of pressure forces F ₇ and F ₈ may be larger than the sum of pressure force F5 and F ₆ . Hence, the forces pushing the second vane 850 (or trailing vane) against the inner wall 212 (or stator wall) may be larger, which may ensure continuous contact between the vane tip portion 851 with the stator inner wall 212.

[00093] Referring to FIG. 10B, various angular positions of the first vane 830 (or the leading vane) may be considered when analysing the forces influencing the contact between the vane tip portion 831 and the inner wall 212. The various angular positions of the first vane 830 (or the leading vane) may be considered because a working chamber on one side of the vane transitions from being a suction chamber to a compression chamber.

[00094] As shown in FIG. 10B, in position 1, when both sides of the first vane 831 are the working chambers undergoing suction process, the forces Fi, F ₂ and F ₃ depend upon the suction chamber pressure and the normal surface area on which these forces act. Of these, Fi and F ₂ push the first vane 830 away from the inner wall 212 of the housing 210 (or the stator) and F ₃ pushes the first vane 830 towards the inner wall 212. F ₄ is the product of the discharge chamber pressure and the vane rear end surface area, and this force acts to push the vane tip portion 831 of the first vane 830 against the inner wall 212 of the housing 210.

[00095] As the vane tip portion 831 of the first vane 830 protrudes out of the rotor slot 825 while in counterclockwise rotation, generally, a midpoint of the second radius section 877 of the vane tip portion 831 of the first vane 830 contacts with the inner wall 212 of the housing 210. This means the normal surface area of forces, Fi and F ₂ , may be approximately equal. Similarly, the normal force areas for the F ₃ and F ₄ may also be approximately equal. Therefore, at these positions of the first vane 830, the normal surface area for all the forces may be approximately equal. This means the magnitudes of the forces depend upon the working chamber pressure. Since, discharge pressure, P _d , may be several times larger than suction pressure, P _s , the sum of the forces F ₃ and F ₄ may then be larger than the sum of the force Fi and F ₂ . Additionally, the centrifugal force from the rotation may also aid the forces F ₃ and F ₄ in pushing the vane tip portion 831 of the first vane 830 against the inner wall 212 of the housing 210.

[00096] Following the counterclockwise rotation of the vanes 830, 850, as figuratively illustrated in position 2 in FIG. 10B, the forward side of the first vane 830 may face compression chamber pressure and the backward side of the first vane 830 may face suction chamber pressure. Also, the first indent 839 on the first vane 830 and the first elongate cut 827 of the rotor 820 may be still apart but may be about to connect.

[00097] In this case, Fi is the force due to the suction chamber pressure, P _s , F ₂ is the pressure force from the compression chamber pressure, P _c . The normal surface areas of these forces may be approximately equal. But because the compression chamber pressure may be larger than the suction chamber pressure, F ₂ may be larger than Fi. Similarly, F ₃ is the pressure force due to compression chamber pressure acting on the vane neck 885 of the first vane 830. F ₄ is the pressure force from the pressure in the gap 809 and the first indent 839 on the first vane 830. This pressure may be less than the discharge chamber pressure but may be greater than the compression chamber pressure. Again, the magnitude of all the pressure forces depends on the working chamber pressures. Thus, the sum of the forces F ₃ and F ₄ may be greater than the sum of the forces Fi and F _2.

[00098] Finally, as shown in position 3 in FIG. 10B, in angular positions where the first indent 839 of the first vane 830 and the first elongate cut 827 of the rotor 820 have connected, the pressure within the gap 809 and the first indent 839 of the first vane 830 may then be equal to the suction chamber pressure.

[00099] In these angular positions, the normal force area of Fi starts increasing which means, the normal force area of F ₂ decreases. However, since compression chamber pressure, P _c , is larger than suction chamber pressure, P _s . Moreover, following the counterclock-wise rotation of the vanes 830, 850, P _c may be increasing while P _s may remain nearly the same. F ₃ , which is also due to compression chamber pressure, may be larger than F ₂ , because the normal force area for F ₂ may be decreasing. Similarly, F ₄ may provide counterforce against Fi. Overall, the sum of the forces F ₃ and F ₄ may be greater than the sum of the force Fi and F ₂ .

[000100] Consequently, for the first vane 830, the sum of the pressure forces pushing the vane tip portion 831 against the inner wall 212 of the housing 210 may always be larger than the sum of the pressure forces acting against it. This means the vane tip portion 831 may be in continuous contact with the inner wall 212 of the housing 210.

[000101] FIG. 11 shows a rotary vane apparatus 1100 according to various embodiments. According to various embodiments, the rotary vane apparatus 1100 is similar to the rotary vane apparatus 800 of FIG. 8A to FIG. 8D, except for the following differences. According to various embodiments, each of the first and second vanes 1130, 1150 may include respective vane tip portions 1131, 1151 each having a rounded cross-sectional profile. The respective vane tip portions 1131, 1151 may be in contact with the inner wall 212 of the housing 210. As shown, the rounded cross-sectional profile of the respective vane tip portions 1131, 1151 may be symmetrical. Accordingly, the rounded cross-sectional profile may be a semi-circular cross-sectional profile.

[000102] FIG. 12 shows a rotary vane apparatus 1200 according to various embodiments. According to various embodiments, the rotary vane apparatus 1200 is similar to the rotary vane apparatus 200 of FIG. 2A to FIG. 2E, except for the following differences. According to various embodiments, each of the first and second vanes 1230, 1250 may include respective vane tip portion 1231, 1251 having a rounded cross-sectional profile. The respective vane tip portions 1231, 1251 may be in contact with the inner wall 212 of the housing 210. As shown, the rounded cross- sectional profile of the respective vane tip portions 1231, 1251 may be asymmetrical. Accordingly, the rounded cross-sectional profile of the respective vane tip portions 1231, 1251 may include a first radius section 1276, 1278 and a second radius section 1277, 1279, wherein a radius of the first radius section 1276, 1278 may be smaller than a radius of the second radius section 1277, 1279. Further, the first radius section 1276, 1278 may be directed towards a side of the respective vanes 1230, 1250 with the respective mating faces 1236, 1256, and the second radius section 1277, 1279 may be directed towards an opposite side of the respective vanes 1230, 1250. Accordingly, the second radius section 1277, 1279 of the vane tip portions 1231, 1251 with a larger radius may always face towards the chamber with lower pressure, and the first radius section 1276, 1278 of the vane tip portions 1231, 1251 with a smaller radius may always face towards the chamber with higher pressure.

[000103] According to various embodiments, the asymmetrical rounded cross- sectional profile of the respective vane tip portions 1231, 1251 may ensure continuous contact between the vane tip portion 1231, 1251 with the inner wall 212 of the housing 210.

[000104] FIG. 13 shows a configuration of a first vane 1330, a second vane 1350 and a guiding mechanism 1302 for a rotary vane apparatus according to various embodiments. The configuration of the first vane 1330, the second vane 1350 and the guiding mechanism 1302 as shown in FIG. 13 may be incorporated in the rotary vane apparatus 200 of FIG. 2A to FIG. 2E, the rotary vane apparatus 800 of FIG. 8A to FIG. 8D, the rotary vane apparatus 1100 of FIG. 11, or the rotary vane apparatus 1200 of FIG. 12. According to various embodiments, the guiding mechanism 1302 may include an intermediate plate 1306 arranged between the first and second vanes 1330, 1350. The engagement arrangement 1304 of the guiding mechanism 1302 may include a first sub-engagement arrangement 1303, via which the first vane 1330 is permanently engaged with the intermediate plate 1306 in such a manner that the first vane 1330 and the intermediate plate 1306 are non-separable in a direction perpendicular to the mating faces 1336, 1356 of the first and second vanes 1330, 1350. The engagement arrangement 1304 of the guiding mechanism 1302 may further include a second sub-engagement arrangement 1305, via which the second vane 1350 is permanently engaged with the intermediate plate 1306 in such a manner that the second vane 1350 and the intermediate plate 1306 are non-separable in a direction perpendicular to the mating faces 1336, 1356 of the first and second vanes 1330, 1350.

[000105] According to various embodiments, the first and second sub-engagement arrangements 1303, 1305, each may include a tongue and groove sliding arrangement, wherein a tongue and a groove of the tongue and groove sliding arrangement may be configured to engage in a manner such that the tongue and the groove may be slideable in a direction parallel to the first and second mating faces 1336, 1356 of the first and second vanes 1330, 1350, and the tongue and the groove may be prohibited from relative movement in a direction perpendicular to the first and second mating faces 1336, 1356 of the first and second vanes 1330, 1350. According to various embodiments, the tongue and groove sliding arrangement may include a dovetail tongue and groove sliding arrangement, or a T-shaped tongue and groove sliding arrangement, or a J-shaped tongue and groove sliding arrangement, or an L-shaped tongue and groove sliding arrangement or a hooked-like tongue and groove sliding arrangement.

[000106] As shown in FIG. 13, the first and second sub-engagement arrangements 1303, 1305, each may include first and second tongues provided on first and second sides of the intermediate plate 1306, respectively, and extending in the diametrical direction of the through slot of the rotor when inserted into the through slot, and first and second grooves provided in the first and second mating faces 1336, 1356, respectively, of the respective first and second vanes 1330, 1350 and extending in the diametrical direction of the through slot of the rotor when inserted in the through slot. The first and second tongues may be engaged with the first and second grooves, respectively.

[000107] According to various embodiments, the intermediate plate 1306 may include a stopper element 1308 at each end of the intermediate plate 1306. The stopper element may be configured to prevent the respective first and second vanes 1330, 1350 from sliding out of the intermediate plate 1306.

[000108] The following examples pertain to further embodiments.

[000109] Example 1 is a rotary vane apparatus including: a housing which has an inner wall enclosing a cylindrical cavity defining a central cavity axis; a cylindrical rotor defining a central rotor axis, around which the rotor is rotatable and which extends parallel and offset to the central cavity axis, wherein the rotor is sealed against the inner wall along an axial line parallel to the central cavity axis of the cylindrical cavity, and wherein the rotor is provided with a through slot which diametrically extends through the rotor; a first vane and a second vane which are received within the through slot in a manner so as to be slideable therein relative to the rotor in the diametrical direction of the through slot, and so as to be slideable relative to each other in the diametrical direction of the through slot, wherein the first vane and the second vane define a first mating face and a second mating face, respectively, which first and second mating faces extend parallel to the diametrical direction of the through slot and overlap each other; and a guiding mechanism arranged between the first and second mating faces of the first and second vanes, by which the sliding movement between the first and second vanes is guided, wherein the guiding mechanism includes an engagement arrangement, via which the first and second vanes are permanently engaged with each other in such a manner that the first and second vanes are non-separable in a direction perpendicular to their mating faces.

[000110] In example 2, the subject matter of example 1 can optionally include that the engagement arrangement of the guiding mechanism includes a tongue and groove sliding arrangement, wherein a tongue and a groove of the tongue and groove sliding arrangement are configured to engage in a manner such that the tongue and the groove are slideable in the diametrical direction of the through slot and the tongue and the groove are prohibited from relative movement in the direction perpendicular to the first and second mating faces of the first and second vane.

[000111] In example 3, the subject matter of example 2 can optionally include that the tongue and groove sliding arrangement includes a dovetail tongue and groove sliding arrangement, or a T-shaped tongue and groove sliding arrangement, or a J- shaped tongue and groove sliding arrangement, or an L- shaped tongue and groove sliding arrangement, or a hooked-like tongue and groove sliding arrangement. [000112] In example 4, the subject matter of example 2 or example 3 can optionally include that the first mating face of the first vane includes the tongue which extends along the first mating face in the diametrical direction of the through slot, and wherein the second mating face of the second vane includes the groove which extends along the second mating face in the diametrical direction of the through slot.

[000113] In example 5, the subject matter of any one of examples 1 to 4 can optionally include that each of the first and second vanes includes a vane-tip portion having a rounded cross-sectional profile, wherein the respective vane-tip portions are in contact with the inner wall.

[000114] In example 6, the subject matter of example 5 can optionally include that the rounded cross-sectional profile of the respective vane-tip portions is symmetrical.

[000115] In example 7, the subject matter of example 5 can optionally include that the rounded cross-sectional profile of the respective vane-tip portions is asymmetrical.

[000116] In example 8, the subject matter of example 7 can optionally include that the rounded cross-sectional profile of the respective vane-tip portions includes a first radius section and a second radius section, wherein a radius of the first radius section is smaller than a radius of the second radius section.

[000117] In example 9, the subject matter of example 8 can optionally include that the first radius section is towards a side of the respective vanes with the respective mating faces, and the second radius section is towards an opposite side of the respective vanes.

[000118] In example 10, the subject matter of any one of examples 1 to 9 can optionally include that a first inner surface of the through slot includes a first elongate cut extending from a first slot opening towards a second slot opening for a predetermined distance and a second opposing inner surface of the through slot includes a second elongate cut extending from the second slot opening to the first slot opening for the predetermined distance, the first and second inner surfaces of the through slot are parallel to the first and second mating faces, the first vane is in sliding contact with the first inner surface and the second vane is in sliding contact with the second inner surface, and the first vane projects from the first slot opening to contact the inner wall and the second vane projects from the second slot opening to contact the inner wall.

[000119] In example 11, the subject matter of example 10 can optionally include that the first vane includes a first indent which is at free end of a first auxiliary face of the first vane, the first auxiliary face being opposite the first mating face of the first vane and the free end being opposite of an end of the first vane in contact with the inner wall, and the second vane includes a second indent which is at a free end of a second auxiliary face of the second vane, the second auxiliary face being opposite the second mating face of the second vane and the free end being opposite of an end of the second vane in contact with the inner wall.

[000120] In example 12, the subject matter of any one of examples 1 to 11 can optionally include that the inner wall of the housing includes a depression extending along the axial line parallel to the central cavity axis of the cylindrical cavity, wherein the depression has a cross-sectional profile corresponding to a pre-determined arc of the cylindrical rotor, wherein the rotor sealingly sits with the pre-determined arc in the depression.

[000121] In example 13, the subject matter of any one of examples 1 to 12 can optionally include that a diameter of the cylindrical rotor is less than 65% of the diameter of the cylindrical cavity of the housing.

[000122] In example 14, the subject matter of any one of examples 2 to 13 can optionally include that the guiding mechanism includes an intermediate plate arranged between the first and second vanes, wherein the engagement arrangement includes: a first sub-engagement arrangement, via which the first vane is permanently engaged with the intermediate plate in such a manner that the first vane and the intermediate plate are non-separable in a direction perpendicular to the mating faces of the first and second vanes; and a second sub-engagement arrangement, via which the second vane is permanently engaged with the intermediate plate in such a manner that the second vane and the intermediate plate are non-separable in a direction perpendicular to the mating faces of the first and second vanes.

[000123] In example 15, the subject matter of example 14 can optionally include that the first and second sub-engagement arrangements each includes: first and second tongues provided on first and second sides of the intermediate plate, respectively, and extending in the diametrical direction of the through slot; and first and second grooves provided in the first and second mating faces, respectively, of the respective first and second vanes and extending in the diametrical direction of the through slot; wherein the first and second tongues are engaged with the first and second grooves, respectively. [000124] In example 16, the subject matter of example 14 or example 15 can optionally include that the intermediate plate includes a stopper element at each end of the intermediate plate, wherein the stopper element is configured to prevent the respective first and second vanes from sliding out of the intermediate plate.

[000125] Various embodiments have provided a rotary vane apparatus with vanes configured to withstand higher loading and minimizes wear of the vanes which allows a reduction in the rotor-to-chamber ratio so as to increase the capacity of the working chamber. Various embodiments have also provided a rotary vane apparatus wherein the force required to maintain a sealing contact between the vanes and the stator wall is achieved solely from the centrifugal force from the rotation of the rotor and the pressure forces from compressing the working fluid without requiring additional biasing elements, such as spring or pressurized fluid. Various embodiments have provided a rotary vane apparatus with easy to manufacture parts such that the manufacturing costs may be reduced.

[000126] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes, modification, variation in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.