Method for compacting a winding of a rotor of an electric machine and compaction tool

Abstract

The invention relates to a method for compacting windings (9) of wound salient poles (6) of a radial flux rotor (2) having a longitudinal axis (A1), the wound salient poles defining inter-pole spaces (22) therebetween, the method comprising: - a step of providing a compaction tool (1) comprising at least a first pusher (13, 13') and a second pusher (19, 19'), - a step of moving the compaction tool (1) in translation in a direction parallel to the longitudinal axis (A1) so as to engage the first pusher (13, 13') and the second pusher (19, 19') in different inter-pole spaces (22), and - a step of compacting the windings (9), comprising a movement of the first pusher (13) and the second pusher (19) so that they exert a compressive force on the windings (9).

Description

TITLE OF THE INVENTION: METHOD FOR COMPACTING MACHINE ROTOR WINDING ELECTRIC AND COMPACTION TOOL TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates generally to the field of electrical machines, and in particular to the production of the rotor of such machines.

[0002] It relates more particularly to a method for compacting the winding of an electric machine rotor and a compacting tool for the winding of an electric machine rotor. STATE OF THE ART

[0003] A radial flux rotor has a generally cylindrical structure extending about the rotor's axis of rotation. The rotor has a longitudinal body and a plurality of poles projecting radially from the body along the length of the body. Each pole includes a base (the "radial extension portion") and a pole head that projects beyond the radial extension portion.

[0004] A winding wire is wound around the radial extension portions, under the pole heads, to form windings. In order to protect the winding wire from the pole edges (at the pole ends), the poles are provided, at each of their ends, with "winding head guides" which give the pole ends radii of curvature which are not harmful to the wire (or, in other words, which provide the poles with rounded corners).

[0005] In order to improve the retention of the windings during rotation of the rotor, it is known to insert shims between the wound poles. These shims are, for example, of triangular cross-section and preferably extend over the entire length of the salient poles, in a manner adjusted between the windings.

[0006] In some cases, the winding does not fit perfectly with the winding head guide and forms a bump at the bend, reducing the inter-pole space at this point. Inserting the shim into the inter-pole space is then hindered by this reduction in the inter-pole space.

[0007] A solution exists to overcome this problem, and it consists of inserting a pressing tool into the inter-pole spaces, in a radial direction, of way of crushing the winding at the level of the bump and thus compacting the bump. However, this solution has at least two drawbacks. First, some pole structures, particularly those in which the pole heads are particularly close to each other, do not allow the press to pass through the inter-pole space and therefore access the bump. Second, the force applied to the bump creates a stress on the protruding pole which can lead to deformation or cracking of the latter. PRESENTATION OF THE INVENTION

[0008] In order to overcome the aforementioned drawbacks of the state of the art, the present invention provides a tool for compacting the bumps of the wound poles of a rotor, which preserves the integrity of the salient pole and which adapts to any salient pole structure, in particular those whose pole heads are very close.

[0009] According to one aspect of the invention, there is provided a method of compacting wound salient pole windings of a radial flux rotor having a longitudinal axis, the wound salient poles delimiting interpole spaces between them, the method comprising: - a step of providing a compacting tool comprising at least a first pusher and a second pusher, - a step of translating the compacting tool in a direction parallel to the longitudinal axis so as to engage the first pusher and the second pusher in separate inter-pole spaces, and - a step of compacting the windings, comprising a movement of the first pusher and the second pusher so that they exert a compressive force on the windings.

[0010] Thanks to the invention, the tool implemented in this method and its engagement in the inter-pole space in a direction parallel to the rotor axis allows access to the bumps regardless of the gap between the pole heads.

[0011] Preferably, in the translation step, the first pusher and the second pusher are engaged in neighboring inter-pole spaces and in the compaction step, the first pusher and the second pusher exert compression forces on either side of the same winding.

[0012] Applying a compressive force to the winding by two pushers, rather than an asymmetrical force, advantageously allows compact the winding without damaging the pole.

[0013] Other advantageous and non-limiting characteristics of the method according to the invention, taken individually or in all technically possible combinations, are the following: - in the translation step, the first pusher and the second pusher are engaged in neighboring inter-pole spaces and in the compaction step, the first pusher and the second pusher exert compression forces on either side of the same winding; - the compacting tool comprising a first annular frame to which the first pusher is secured and from which the first pusher extends radially inwards, a second annular frame, coaxial with the first annular frame, to which the second pusher is secured and from which the second pusher extends radially inwards, the two frames having an internal diameter greater than the overall diameter of the rotor, in the translation step, the two annular frames are coaxial with the longitudinal axis and the translation of the compacting tool is carried out in such a way that the two frames are engaged around the rotor, the compacting step comprises rotating the annular frames relative to each other around the longitudinal axis so as to generate the movement of the first pusher and the second pusher; - the compacting step comprises rotating the annular frames around the longitudinal axis in a first direction so that each pusher exerts a compressive force on a first of the windings, then rotating the annular frames around the longitudinal axis in a second direction opposite to the first direction so that each pusher exerts a compressive force on the winding at the level of the bump of a second wound salient pole (6). - the rotor comprising a central body, each wound salient pole of the rotor comprising a pole extension portion which extends radially from the central body and a pole head which is located at a free end of the pole extension portion and which forms ortho-radial projections cantilevered on either side of the pole extension portion, each pusher comprising a pusher extension portion which extends radially from its annular frame and a pusher head which flares from a free end of the pusher extension portion, the gap between two adjacent pole heads being less than the maximum gap between two adjacent pole extension portions, the translation step is performed by engaging each of the pusher extension portions between two adjacent pole heads. - the compacting tool comprising a number of pushers equal to the number of inter-pole spaces of the rotor, the pushers being, in at least one relative position of the two annular frames, circumferentially distributed regularly on the tool with an alternation of pushers secured to the first annular frame and pushers secured to the second annular frame, the rotation of the annular frames in the first direction makes it possible to compress on each side half of the wound salient poles and the rotation of the annular frames in the other direction makes it possible to compress on each side another half of the wound salient poles.

[0014] According to another aspect, there is provided a winding compacting tool for a wound radial flux rotor having a plurality of wound salient poles, the tool comprising: - a first annular frame and a second annular frame centered on the same longitudinal axis and movable in rotation around said longitudinal axis, - at least one first pusher secured to the first annular frame and extending radially towards the inside thereof, - at least one second pusher secured to the second annular frame and extending radially towards the inside of the latter, - actuating means configured to set the two annular frames in relative rotation around the longitudinal axis.

[0015] Other advantageous and non-limiting characteristics of the method according to the invention, taken individually or in all technically possible combinations, are the following: - the tool is configured in such a way that the annular frames (12, 18) are adapted to be inserted, in the axial direction relative to the axis of the rotor, around the rotor coaxially with the rotor and in such a way that the first pusher and the second pusher are placed in the inter-pole spaces on either side of the same pole so as to move the first pusher and the second pusher (19, 19') so that they exert a compressive force. - each tappet has a tappet extension portion that extends radially from its annular frame and a tappet head that flares at from a free end of the pusher extension portion, the pusher head having a maximum ortho-radial dimension relative to the axis of the annular frame greater than the maximum ortho-radial dimension of the pusher extension portion (14, 20) by a ratio of 3 to 1. - the pushers are, in at least one relative position of the two annular frames, distributed circumferentially in a regular manner on the tool with an alternation of pushers secured to the first annular frame and pushers secured to the second annular frame. - the first annular frame has a surface facing a second surface of the second annular frame, the first surface comprising a bump cooperating with a hollow of the second surface so as to form a stop limiting the relative rotation of the first annular frame and the second annular frame (18).

[0016] According to another aspect, there is provided a method of manufacturing a rotor comprising: - a supply of a rotor frame comprising a central body and poles which project radially from the central body, - winding a wire around each pole to form windings, characterized in that it then comprises compacting the windings according to a compacting method in accordance with the invention.

[0017] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive. DETAILED DESCRIPTION OF THE INVENTION

[0018] The description which follows with reference to the appended drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0019] On the attached drawings:

[0020] [Fig. 1] is a perspective view of a rotor of an electric machine according to the invention,

[0021] [Fig. 2] is a schematic front view of the rotor of Figure 1 and of a compacting tool according to a first embodiment of the invention,

[0022] [Fig. 3] is a schematic perspective view of the rotor and compacting tool of Figure 2,

[0023] [Fig. 4] is a schematic view of the rotor of Fig. 1 and a compacting tool according to another embodiment of the invention.

[0024] The invention relates to the compaction of winding bumps on rotors for electrical machines using a compaction tool. Figure 1 illustrates a wound rotor 2 to which the invention applies, here a rotor with salient poles and radial flux.

[0025] This rotor is designed to pivot relative to a stator, around an axis of rotation A1 corresponding in practice to the longitudinal axis of this rotor.

[0026] In this description, any direction parallel to the axis of rotation A1 of the rotor is considered to be a longitudinal direction. Any direction orthogonal to the axis of rotation A1 of the rotor and passing through the axis of rotation A1 of the rotor is considered here to be a radial direction. Any direction orthogonal to the axis of rotation A1 of the rotor and not passing through the axis of rotation A1 of the rotor is said to be circumferential or orthoradial (a circumferential trajectory is therefore a circular trajectory). The same applies to the directions relative to the axis of the compacting tool presented below.

[0027] The wound rotor 2 here comprises a body 3 and a shaft 4 which extends through the body 3. The body 3 of the rotor 2 comprises a central body 5 of generally cylindrical shape and a plurality of salient poles 6, here eight salient poles, which extend radially from the central body 5 away from the axis of rotation A1 of the rotor 2. The salient poles 6 extend longitudinally over the entire length of the body 3 and are regularly distributed around the axis of rotation A1.

[0028] Each salient pole 6 comprises a base called "pole extension portion 7" which extends radially from the central body 5 to an associated pole head 8, which forms ortho-radial projections cantilevered from the pole extension portion 7. Thus, as better shown in Figure 2, the cross-section of each pole 6 generally has a mushroom shape, of which the extension portion 7 forms the feet and the pole head 8 forms the cap.

[0029] The salient poles 6 define inter-pole spaces between them. The salient poles 6 being identical and distributed regularly around the circumference of the rotor 2, all the inter-pole spaces have the same geometry and the same dimensions.

[0030] Each salient pole 6 is wound. Thus, a conductive wire is here wound around each extension portion 7 so as to form turns constituting a winding 9. Each winding 9 is here made so that its turns are mutually parallel. In the remainder of this description, the expression “wound pole” will designate the assembly formed by a salient pole 6 and the winding 9 which is wound around it.

[0031] The pole extension portions 7 of the salient poles 6 generally have parallelepiped shapes.

[0032] At their ends along the axis of rotation A1, they have edges which would damage the conductive wire if it were wound directly around the salient pole 6. In order to avoid this drawback, each salient pole 6 is provided, at each of its ends, with a winding head guide 23 which gives the ends of the salient poles 6 non-zero radii of curvature.

[0033] In order to gain compactness, the radius of curvature conferred by the winding head guides is small, for example less than 4 millimeters. Given the intrinsic rigidity of the conductive wire, the winding does not perfectly match the shape of the salient pole 6 at its curvatures. In other words, at the ends of each salient pole 6 (at each corner), the winding is spaced from the pole 6. A space exists between the turns of the winding 9 and the salient pole 6. At these locations, the winding 9 therefore forms a bump. Each salient pole 6 therefore has four bumps, including two bumps at each end. At the ends of the salient poles 6, the circumferential dimension of the interpole spaces is therefore reduced by the presence of the bumps.

[0034] A compacting tool 1 according to one embodiment of the invention, as illustrated in Figures 2 and 3, is configured to compact the bumps by applying a compressive force to each salient pole 6, at the level of the bump of the winding 9. In Figures 2 to 4, the compacting tool 1 is engaged around the rotor 2. In Figure 2, a first end of the rotor 2 is visible and the axis of rotation A1 of the rotor is orthogonal to the plane of Figure 2.

[0035] The compacting tool 1 comprises two tool parts 10 and 11 which have similar structures. A first tool part 10 comprises a first annular frame 12, the inner diameter of which is greater than the overall diameter of the rotor 2, and a first pusher 13 which is integral with the first annular frame 12 and which extends radially towards the inside of the first annular frame. 12.

[0036] The first pusher 13 comprises a base called "first pusher extension portion 14", which extends from the first annular frame 12 to a first pusher head 15. The first pusher 13 has a shape substantially complementary to that of a wound inter-pole space (its section orthogonal to the axis of rotation A1 has in practice a quasi-identical shape, but smaller dimensions in order to be able to slide therein freely). Here, the minimum width of the first pusher extension portion 14 (measured in the ortho-radial direction) is less than the distance between two adjacent pole heads 8, so that the first pusher extension portion 14 can be engaged between two pole heads 8.The first pusher head 15 has a width (measured in the ortho-radial direction) which is maximum at the first pusher extension portion 14 (and greater than that of the pusher extension portion 14) and which decreases towards the center of the first annular frame 12. In particular, the maximum width (measured in the orthoradial direction) of the first pusher head 14 is greater than the minimum width of the first pole extension portion 14. The cross section of the first pusher 13 therefore has an arrowhead shape.

[0037] The first pusher 13 has bearing surfaces 16 formed by the sides of this arrowhead and which are configured to extend longitudinally in the inter-pole space and to, when the compacting tool 1 is engaged around the rotor 2, be opposite a flank of a pole extension portion 7 and parallel to it. Longitudinally, the pushers are configured to extend over only a portion of the length of the rotor 2. For this purpose, they have a length measured along the axis of rotation A1 at least three times less than that of the rotor 1.

[0038] The first tool portion 10 here comprises a second pusher 13' of identical structure to the first pusher and diametrically opposite the first pusher 13.

[0039] The second tool part 11 has a shape identical to that of the first tool part 10, with a second annular frame 18, a third pusher 19 which comprises a third pusher extension portion 20 and a fourth pusher 19'.

[0040] Here, the first pusher 13 and the third pusher 19 form a first pair of pushers, and the second pusher 13' and the fourth pusher 19' form a second pair of pushers.

[0041] The first tool part 10 and the second tool part 11 are preferably secured to each other coaxially and so as to establish a pivot connection between them around the axis of rotation A1. The first pusher 13, the second pusher 13', the third pusher 19 and the fourth pusher 19' are placed on the compacting tool 1 at different angular positions, with an alternation between the pushers 13, 13', secured to the first annular frame 12 and the pushers 19, 19' secured to the second annular frame 18. In this configuration, the relative rotation of the two tool parts 10, 11 makes it possible to move the pushers of the two tool parts 10, 11 apart or closer together depending on the direction of rotation.

[0042] The compacting tool 1 comprises actuating means 24 configured to rotate, in opposite directions, the two tool parts 10, 11 around the common axis of rotation A1. Here, the actuating means 24 comprise a first actuator 25 secured to the first annular frame 12 and which projects radially outward from the first annular frame 12, and a second actuator 26 secured to the second annular frame 18 and which projects radially outward from the second annular frame 18. The actuating means 24 are thus configured to place the first annular frame 12 and the second annular frame 18 in relative rotation, by bringing the actuators 25, 26 closer to or further apart.

[0043] In this example, as visible in Figure 3, the compacting tool 1 comprises means for restricting the amplitude of the relative rotation of the first tool part 10 and the second tool part 11. Here, the first annular frame 12 and the second annular frame 18 have for this purpose facing surfaces of particular shapes. The restriction means are here formed by pointwise deviations of these surfaces around the radial plane. The surfaces thus form bosses and recesses provided which cooperate to form a stop system. For example, in Figure 3 are visible a recess 27 provided in the first annular frame 12 and a boss 28 provided in the second annular frame 18 and engaged in this recess 27. The circumferential dimension of the recess 27 is here greater than the circumferential dimension of the boss 28. The difference between these two dimensions defines the maximum relative rotational travel of the first tool part 10 and the second tool part 11.

[0044] Each tool part 10, 11 is for example produced in a single block, in particular by molding, for example from a metallic material.

[0045] The compacting tool 1 as described above is suitable for use in a method of compacting winding bumps. Such a method is carried out after the step of winding the salient poles.

[0046] During a first step of this method (translation step), the compacting tool 1 is positioned at a distance from the rotor 2, coaxially with the rotor 2, at a distance from it, then is translated towards the rotor 2 along the axis of rotation A1 of the rotor so that the two annular frames 12, 18 are engaged around the rotor 2 and so that the pushers of each pair of pushers are engaged in an inter-pole space on either side of the same wound pole, at one end of the rotor 2 (included in the longitudinal direction). In this configuration, each pusher has a bearing surface opposite a winding bump. The dimensions of the pushers are for example chosen so that there remains only a very small clearance between the pusher heads and the wound poles.

[0047] During a second step of the method (compaction step), the first annular frame 12 and the second annular frame 18 are rotated about the axis of rotation A1, here by bringing the actuators 25 and 26 together, so as to move the pushers of each pair of pushers so that they exert a compressive force on the corresponding winding 9, at the level of the bumps of the same end of the pole. The compressive force exerted is sufficient to compact the bump. This compressive force being symmetrical on either side of the wound pole, it does not exert a torque on the salient pole and therefore does not damage the latter.

[0048] The pushers 13, 13', 19, 19' are then moved away from the corresponding winding 9 so that they return to their initial angular position. The compacting tool 1 is then - either translated to its initial position (disengaged from the rotor 2) so as to be able to restart the process for other salient poles (after rotation of the compacting tool 1 as a whole, so as to position the pairs of pushers opposite inter-pole spaces located on either side of the wound poles not yet compacted), - either kept engaged on the rotor 2 and translated longitudinally to the other end of the rotor, at the level of winding bumps located at this other end, so as to implement the compacting step previously described in order to compact the bumps of said other end.

[0049] The present invention is in no way limited to the embodiments described previously in connection with Figures 1 to 3.

[0050] In particular, a compacting tool has been previously described having four pushers forming two pairs of cooperative pushers. In variants, the compacting tool may comprise a different number of pairs of pushers, for example a single pair of pushers. The compacting tool may also comprise, as illustrated in FIG. 4, a number of pushers equal to the number of inter-pole spaces. In this latter configuration, the second compacting step comprises a first sub-step of rotating the first annular frame 12 and the second annular frame 18 in a first direction so as to compact the windings of a first part of the poles (here half of the poles, i.e. four poles), and a second sub-step of rotating the first annular frame 12 and the second annular frame 18 in a second direction opposite to the first direction so as to compact the windings of a second half of the poles.Thus, during the first sub-step and during the second sub-step, the same pusher cooperates successively with two different pushers.

[0051] Actuating means projecting from the annular frames have been described previously. The invention is compatible with any other actuating means, in particular motorized automatic means.

[0052] Previously described are pushers which extend over only a portion of the length of the pole, and which are therefore suitable for compacting the bumps of only one of the pole ends at a time. The invention is also compatible with pushers which extend over the entire length of the pole, thus making it possible to compact the winding bumps of a pole at both ends at once.

[0053] A compacting tool has previously been described comprising annular frames from which pushers extend. The invention is not limited to the presence of the annular frames, and the compacting tool may comprise pushers mounted at the end of pair-shaped actuating means. scissors.

[0054] Finally, it should be noted here that while it is preferable to engage two pushers on either side of a wound pole in order to simultaneously crush the bumps in the winding of this pole, the compacting tool could of course be used differently, by engaging these two pushers in inter-pole spaces which are not neighboring. However, this variant is not preferred since it would cause stresses on the salient poles.

Claims

CLAIMS

1. Method for compacting windings (9) of wound salient poles (6) of a radial flux rotor (2) having a longitudinal axis (A1), the wound salient poles (6) delimiting between them inter-pole spaces (22), the method comprising: - a step of providing a compacting tool (1) comprising at least a first pusher (13, 13') and a second pusher (19, 19'), - a step of translating the compacting tool (1) in a direction parallel to the longitudinal axis (A1) so as to engage the first pusher (13, 13') and the second pusher (19, 19') in separate inter-pole spaces (22), and - a step of compacting the windings (9), comprising a movement of the first pusher (13) and the second pusher (19) so that they exert a compressive force on the windings (9).

2. Method according to claim 1, in which, in the translation step, the first pusher (13, 13') and the second pusher (19, 19') are engaged in neighboring inter-pole spaces (22) and in the compaction step, the first pusher (13, 13') and the second pusher (19, 19') exert compression forces on either side of the same winding (9).

3. Method according to claim 1 or 2, in which, the compacting tool (1) comprising a first annular frame (12) to which the first pusher (13, 13') is integral and from which the first pusher (13, 13') extends radially inwards, a second annular frame (18), coaxial with the first annular frame (12), to which the second pusher (19, 19') is integral and from which the second pusher (19, 19') extends radially inwards, the two frames (12, 18) having an internal diameter greater than the overall diameter of the rotor (2), - in the translation step, the two annular frames (12, 18) are coaxial with the longitudinal axis (A1) and the translation of the compacting tool (1) is carried out in such a way that the two frames (12, 18) are engaged around the rotor, - the compacting step comprises rotating the annular frames (12, 18) relative to each other around the longitudinal axis so as to generate the movement of the first pusher (13, 13') and the second pusher (19, 19').

4. The method of claim 3, wherein the compacting step comprises: - rotating the annular frames (12, 18) around the longitudinal axis (A1) in a first direction so that each pusher exerts a compression force on a first of the windings (9), then - rotating the annular frames (12, 18) around the longitudinal axis (A1) in a second direction opposite to the first direction so that each pusher exerts a compressive force on the winding (9) at the level of the boss of a second wound salient pole (6).

5. A compacting method according to claim 3 or 4, wherein: - the rotor comprising a central body (5), - each wound salient pole (6) of the rotor (2) comprising a pole extension portion (7) which extends radially from the central body (5) and a pole head (8) which is located at a free end of the pole extension portion (7) and which forms ortho-radial projections cantilevered on either side of the pole extension portion (7), - each pusher (13, 13', 19, 19') comprising a pusher extension portion (14, 20) which extends radially from its annular frame (12, 18) and a pusher head (15, 21) which flares from a free end of the pusher extension portion (14, 20), - the gap between two adjacent pole heads (8) being less than the maximum gap between two adjacent pole extension portions (7), the translation step is carried out by engaging each of the pusher extension portions (14, 20) between two adjacent pole heads (8).

6. Method according to claim 5, in which, the compacting tool (1) comprising a number of pushers equal to the number of inter-pole spaces (22) of the rotor (2), the pushers being, in at least one relative position of the two annular frames, circumferentially distributed so as to regular on the tool (1) with an alternation of pushers secured to the first annular frame (12) and pushers secured to the second annular frame (18), - rotating the annular frames (12, 18) in the first direction makes it possible to compress on each side half of the wound salient poles (6) and - rotating the annular frames (12, 18) in the other direction makes it possible to compress another half of the wound salient poles (6) on each side,

7. A winding compacting tool (9) for a radial flux wound rotor (2) having a plurality of wound salient poles (6), the tool comprising: - a first annular frame (12) and a second annular frame (18) centered on the same longitudinal axis (A1) and movable in rotation around said longitudinal axis (A1), - at least one first pusher (13, 13') secured to the first annular frame (12) and extending radially towards the inside thereof, - at least one second pusher (19, 19') secured to the second annular frame (18) and extending radially towards the inside of the latter, - actuating means (25, 26) configured to set the two annular frames (12, 18) in relative rotation around the longitudinal axis (A1).

8. A tool according to claim 7, wherein each pusher (13, 13', 19, 19') comprises a pusher extension portion (14, 20) which extends radially from its annular frame (12, 18) and a pusher head (15, 21) which flares from a free end of the pusher extension portion (14, 20), - the pusher head (15, 21) having a maximum ortho-radial dimension relative to the axis of the annular frame (12, 18) greater than the maximum ortho-radial dimension of the pusher extension portion (14, 20) by a ratio of 3 to 1.

9. Tool according to claim 7 or 8 in which the pushers (13, 13', 19, 19') are, in at least one relative position of the two annular frames (12, 18), distributed circumferentially in a regular manner on the tool (1) with an alternation of pushers integral with the first annular frame (12) and pushers secured to the second annular frame (18).

10. A tool according to any one of claims 7 to 9, wherein the first annular frame (12) has a surface facing a second surface of the second annular frame (18), the first surface comprising a boss cooperating with a recess in the second surface so as to form a stop limiting the relative rotation of the first annular frame (12) and the second annular frame (18).

11. Method of manufacturing a rotor comprising: - a supply of a rotor frame comprising a central body (5) and poles which project radially from the central body (5), - winding a wire around each pole to form windings (9), characterized in that it then comprises compacting the windings (9) according to a compacting method according to any one of claims 1 to 4.

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