Technical Field

The invention relates to a coil shaping device for shaping a coil for an electrical machine, in particular for a stator of an axial flux electrical machine. A method of shaping a coil for an axial flux electrical machine is also provided.

Background

Electrical machines, including electric motors and electric generators, are already very widely used. However, concerns over our reliance on, and the pollution caused by, the fossil fuels that power internal combustion engines is creating political and commercial pressures to extend the use of electrical machines to new applications, and to expand their use in existing ones.

Electrical machines are increasingly being used in vehicles, such as electric cars, motorbikes, and aircraft. They are also used in electricity generation applications, for example generators in wind turbines.

In order to meet the needs of these applications, it will be necessary to design electrical machines that have both suitable performance properties, such as speed and torgue, and high efficiency. The efficiency of electrical machines is critically important in almost all applications: it can, for example, both increase an electric vehicle’s range and decrease the reguired battery capacity. Decreasing the reguired battery capacity can in turn decrease the weight of the vehicle, which leads to further efficiency gains. In electricity generation applications, improved efficiency of a generator can improve the overall efficiency of electricity generation.

One known type of electrical machine is the axial flux machine. As the name suggests, the direction of the lines of magnetic flux that are cut during the operation of an axial flux machine is parallel to the axis of rotation of the machine. This is in contrast to radial flux machines, in which the direction of the lines of magnetic flux that are cut during the operation of the machine is perpendicular to the rotation axis of the machine. While radial flux machines are more common, axial flux machines have been used for some applications where their form factor (a relatively small axial extent) and performance properties (such as a high torgue to weight ratio) are appreciated.

One example of a yokeless axial flux machine which utilizes a concentrated winding arrangement is described in an International Patent Application with publication number WO 2018/015293 A1. Summary of invention

The present invention is defined by the appended independent claims. Optional features of the invention are set out in the appended dependent claims.

According to a first aspect of the present invention, there is provided a coil shaping device for shaping a coil for an axial flux electrical machine, comprising: a holder for holding a pre-made substantially planar coil, the holder being configured to restrict movement of the pre-made substantially planar coil, wherein the pre-made substantially planar coil has a plurality of windings of a conductor in a first plane; and a former configured to shape the pre-made substantially planar coil, through plastic deformation, to form a shaped non-planar coil, wherein portions of the shaped non-planar coil are outside the first plane. The coil shaping device is configured to enable one end of the pre-made substantially planar coil to slide in a direction towards a middle of the pre-made substantially planar coil as the pre-made substantially planar coil is being shaped.

The coil shaping device allows for coils for an axial flux electrical machine to be shaped in a reliable and efficient manner. As movement of a first end of the planar coil is restricted, but sliding movement of the second end towards the first end is enabled, the additional conductor material required to form the deformed portions of the shaped non-planar coil may be pulled in, or drawn in, from the second end while movement of the first end is restricted.

The shaped coils may in particular be for an axial flux electrical machine having a stator comprising a plurality of circumferentially distributed conductive coils.

Optionally, the pre-made substantially planar coil comprises a central void separating a first set of conductor portions on one side of the void from a second set of conductor portions on the other side of the void.

Preferably, the pre-made substantially planar coil is formed of a conductor wound in a plane so as to form a planar winding with a plurality of turns. The planar coil winding preferably comprises outer loop sections and inner loop sections at respective ends of the first set of conductor portions and the second set of conductor portions to form the coil.

Optionally, the former is configured to form the shaped non-planar coil by shaping the first set of conductor portions in a direction out of the first plane, and the second set of conductor portions in an opposing direction out of the first plane. Optionally, the former is configured to shape the first set and the second set so that one end of the first and second sets is further out of the first plane than the other end of the first and second portions.

Optionally, the former is configured such that the one end of the first and second sets is shaped simultaneously with the other end of the first and second sets. Advantageously, this allows for even shaping of the shaped non-planar coil, and may further prevent excessive strain on the shaped non-planar coil.

Optionally, the former is configured such that the one end of the first and second sets is shaped before the second end of the first and second sets. Advantageously, this may reduce possible damage to the conductor during the shaping.

Optionally, the former is configured to over-shape the pre-made substantially planar coil so that upon the shaped non-planar coil being released from the coil shaping device, restoration of elastic deformation results in the shaped non-planar coil having a required final shape. As the conductor material will have a certain degree of resilience, over-shaping allows for the required shape of the shaped non-planar coil to be reached after release of the coil from the former. Advantageously, this allows for an exact required shape to be achieved, while still providing a conductor material with sufficient resilience to be shaped into a coil and used in a stator of an axial flux electrical machine.

Optionally, the holder is configured to hold the middle of the pre-made substantially planar coil.

Optionally, the holder is a clamp for clamping the middle of the pre-made substantially planar coil to hold it in place.

Optionally, the coil shaping device is configured to enable both ends of the pre-made substantially planar coil to slide in a direction towards the middle of the pre-made substantially planar coil as the pre-made substantially planar coil is being shaped.

Alternatively, the holder is for holding a first end of the pre-made substantially planar coil, the holder being configured to restrict movement of the first end of the pre-made substantially planar coil, and wherein the coil shaping device is configured to enable the one, second, end of the pre-made substantially planar coil to slide.

The holder may be configured to restrict movement of the first end of the pre-made substantially planar coil towards the second end of the conductive coil portion as the pre-made substantially planar coil is shaped, such that an extent of movement is less than 5 % of the length of the pre- made substantially planar coil. Optionally, the extent of movement is less than 2 % of the length of the pre-made substantially planar coil. Advantageously, by restricting the extent of movement of the first end towards the second end, consistent shaping may be achieved as the first end will be restricted from moving relative to the former. On the other hand, not holding the first end overly tightly so that some movement of the first end is permitted, may prevent damage to the coil.

Optionally, the holder comprises at least one of: a clamping means; and a slot sized to hold the first end of the pre-made substantially planar coil by interference fit. Advantageously, clamping means and interference fit are effective and simple holding methods.

Optionally, the coil shaping device further comprising at least one of: a cover having a cut-out sized to allow the pre-made substantially planar coil to pass through the cut-out into a shaping position; and a base plate having a base plate cut-out sized to allow the shaped non-planar coil to pass through the base plate cut-out. In this way, an easy drop-in, drop-out device may be provided, in which a planar coil may be dropped into the device into a shaping position, shaped into the shaped non-planar coil, which may then drop out of the bottom of the former. Advantageously, this may speed up the shaping process and may further allow for easier automation of the shaping.

Optionally, the former comprises at least one cooperating pair comprising a male former and a female former. Advantageously, a cooperating pair of male and female formers may allow for the coil to be shaped efficiently and within small tolerances.

Preferably, the male former and female former are configured to shape involute portions, or naturally curved portions, of the shaped coil at each end of the first set of conductor portions and the second set of conductor portions.

Optionally, the coil shaping device further comprises two levers, and at least one male former is attached to one lever, and at least one cooperating female former is attached to the other lever, so as to cooperate to shape the pre-made substantially planar coil. Advantageously, levers may allow for the shaping to be carried out manually by a user moving the levers towards one another. Further, levers reduce the force required for shaping the coil.

Optionally, the coil shaping device further comprises an actuator for actuating movement of at least one of the levers. Advantageously, an actuator may be capable of providing the exact same amount of force each time a coil is shaped, and reduces the need for manual handling of the device. Optionally, the coil shaping device further comprises coupling means configured to functionally couple the levers so that the levers move simultaneously. This means that the levers, and therefore the cooperating male and female formers, move in conjunction, and as such, the shaping of the coil is better controlled, which may reduce potential damage to the coil during shaping.

Optionally the coupling means is a gear set. Advantageously, a gear set may conveniently couple movement of the levers together, allowing for force to be provided on only one of the levers.

Optionally, the actuator is configured such that the levers are moved at a first speed up to a certain point in the shaping process, and a second, slower, speed after the certain point in the shaping process. The certain point in the shaping process may be the point at which the shaped non-planar coil is in a desired final shape, so that the levers are moved at the slower speed only during over-shaping.

Optionally, the pre-made substantially planar coil has a plurality of stacked windings of the conductor in a second plane, parallel to the first plane, and wherein the former is configured to shape the pre-made substantially planar coil, through plastic deformation, so that the stacked windings in the second plane are shaped in a same direction and a same distance as the stacked windings in the first plane. Advantageously, shaping a pre-made substantially planar coil having windings in two parallel planes may allow for the former to shape a broader range of coils.

Optionally, the former comprises an outer shell having internal surfaces which are substantially shaped to form an external shape of the shaped non-planar coil. Advantageously, this may allow for the external shape of the shaped non-planar coil to be precisely shaped from the planar coil.

Optionally, the former comprises two heads, each having three fingers, wherein each head is movable, in the plane of the pre-made substantially planar coil, such that the three fingers of each head interdigitate with the windings in the first and second planes. By interdigitating the fingers with the windings in the planes, the former may shape the windings in both planes at the same time, while supporting the windings from both sides during the shaping process.

Advantageously, this may reduce the risk of damage to the winding material during shaping.

It is noted that while these optional embodiments refer to a planar coil having windings in two parallel planes, the planar coil may have windings in any suitable number of planes, and the heads may have any suitable corresponding number of fingers required to interdigitate the windings. For example, if the planar coil has windings in three parallel planes, the heads may have four fingers each; if the planar coil has windings in four parallel planes, the heads may have five fingers each.

Optionally, a first end of each central finger configured to be positioned between the first and second planes of the pre-made substantially planar coil comprises a hinged tip configured to shape involute portions, or naturally curved portions, of the windings in the first and second coil portions. Optionally, the second end of the central finger comprises a hinged tip.

Advantageously, the hinged tip may allow for the involute portions, or naturally curved portions, to be shaped more easily.

Optionally, a first end of each innermost finger comprises a fixed curved portion configured to shape an involute portion, or a naturally curved portion, of the windings in the first or second plane. Optionally a second end of each innermost finger comprises a fixed curved portion. Advantageously, having a fixed curved portion on the innermost finger allows for an involute portion, or a naturally curved portion, of the “inner coil” to be shaped more easily. Alternatively, at least one of the first and second end of each innermost finger comprises a hinged tip.

Optionally, a first end of each outermost finger comprises a fixed curved portion configured to shape an involute portion, or a naturally curved portion, of the windings in the first or second plane. Optionally a second end of each outermost finger comprises a fixed curved portion. Advantageously, having a fixed curved portion on the outermost finger allows for an involute portion, or a naturally curved portion, of the “inner coil” to be shaped more easily.

Optionally, the holder comprises receiving portions in the outer shell for receiving the first end of the pre-made substantially planar coil and at least one intermediate holder portion, configured to be positioned between first ends of stacked windings in the first plane and the second plane. Optionally the at least one intermediate holder portion is movable in conjunction with the at least one head in the first plane. Advantageously, this allows for the head to be moved towards the planar coil, and the intermediate holder portion to passively move together with the head, reducing the required steps to shape the coil.

Optionally, the number of heads and intermediate holder portions is equal. Alternatively, there may be two heads and only one intermediate holder portion having a length which is about equal to a width of the planar coil. Optionally, the holder comprises a pin configured to engage the central void of the pre-made substantially planar coil. Advantageously, this may allow for the shape of the central void to be maintained during shaping, and additionally, the pin may act to limit movement of the first end towards the second end. Optionally, instead of a pin, the holder may comprise an elongate projection configured to engage the central void of the pre-made substantially planar coil.

Optionally, the or each head is rotatable relative to the first plane and second plane so as to shape the pre-made substantially planar coil into the shaped non-planar coil.

Optionally, the coil shaping device further comprises at least one actuator configured to actuate the, or each, head.

Optionally, the coil shaping device comprises a pair of heads on opposite sides of the holder, wherein the heads are movable independently of one another. Optionally, the coil shaping device comprises one actuator per head. Individual actuators for each head may enable precise servo control for each head, thereby enabling precise and repeatable shaping of planar coils.

Optionally, the coil shaping device further comprises a second holder for holding a second end of the pre-made substantially planar coil, so as to restrict movement of the second end out of the first plane. Advantageously, providing a second holder which prevents movement of the second end out of the first plane allows for the coil to be easily shaped while maintaining the first end and the second end in the first plane.

Optionally, the second holder comprises at least one of: a pair of stops; second receiving portions in the outer shell for receiving the second end of the pre-made substantially planar coil and at least one second intermediate holder portion; and a sprung clamp.

The pair of stops may be configured to receive the second end of the pre-made substantially planar coil and allow movement out of the, or each, plane only between the stops.

The second receiving portions in the outer shell for receiving the second end of the pre-made substantially planar coil and the at least one second intermediate holder portion may be configured to be positioned between second ends of stacked windings in the first plane and the second plane. Optionally, the at least one second intermediate holder portion is movable in conjunction with the at least one head, and further optionally wherein the number of heads and second intermediate holder portions is equal. Alternatively, the at least one second intermediate holder portion is movable independently of the at least one head. The sprung clamp may be configured to clamp the second ends of stacked windings.

Advantageously, providing a pair of stops, second receiving portions and at least one second intermediate holder portion, and/or a sprung clamp allows for the shaped non-planar coil to be easily removed from the shell.

Optionally, if the pre-made substantially planar coil is formed of a plurality of stacked winding of a conductor in each of the plurality of substantially parallel planes, the sprung clamp comprises an intermediate clamp portion, configured to be received between parallel planar layers of the pre-made substantially planar coil.

It is noted that the first and/or second receiving portions in the outer shell preferably comprises recesses configured to accommodate portions of the substantially planar coil. Alternatively, the first and/or second receiving portions may merely be plane surfaces of the outer shell configured to engage portions of the substantially planar coil.

In a second aspect of the present invention, there is provided a coil shaping method for shaping a coil for an axial flux electrical machine. The method comprises: providing a pre-made substantially planar coil, wherein the pre-made substantially planar coil has windings of a conductor in a first plane; restricting movement of a first end of the pre-made substantially planar coil; and shaping, through plastic deformation, the pre-made substantially planar coil to form a shaped non-planar coil, so that the shaped non-planar coil has portions outside the first plane, wherein as the pre-made substantially planar coil is being shaped, a second end of the pre-made substantially planar coil slides in a direction towards the first end of the pre-made substantially planar coil.

Optionally, the pre-made substantially planar coil comprises a central void separating a first set of conductor portions on one side of the void from a second set of conductor portions on the other side of the void.

Optionally, shaping comprises shaping the first set of conductor portions in a first axial direction, and shaping the second set of conductor portions in the opposite axial direction.

Optionally, a first end of the first set and the second set is deformed further in a radial direction than a second end of the first set and the second set. Optionally, the first end of the sets is deformed before the second end of the active portions is deformed. Alternatively, the first end and the second end of the first set and the second set are deformed at the same time Optionally, movement of the first end of the conductive coil portion is restricted by at least one of: clamping and an interference fit.

Brief of the

Embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 A is a plan view of a conductive coil portion illustrating how the conductive coil portion may be wound in a flat plane;

Figure 1 B is a side view of the conductive coil portion illustrated in Figure 1A;

Figure 1 C is a perspective view of the conductive coil portion illustrated in Figures 1A and 1 B;

Figure 2 is a perspective view of an embodiment of a coil shaping device;

Figure 3 is a plan view of the coil shaping device of Figure 2;

Figures 4A and 4B are cross-sectional side views of the coil shaping device of Figures 2 and 3;

Figure 4C is a side view of the coil shaping device of Figures 2, 3, 4A, and 4B;

Figure 5A shows plan and underneath views of a single conductive coil element having a single pair of radially extending active sections;

Figure 5B shows two perspective views of the conductive coil element of Figure 5A;

Figure 6A is a plan view of part of a stator that includes a plurality of the conductive elements of Figures 5A-5B circumferentially distributed around the stator, showing spaces resulting from their overlap;

Figure 6B is a plan view showing the stator of Figure 6A;

Figure 7A shows plan and underneath views of a conductive coil that includes two pairs of circumferentially overlapping radially extending active sections connected in series;

Figure 7B shows two perspective views of the conductive coil of Figure 7A; Figure 7C shows a side view of a pre-made substantially planar coil having a plurality of stacked windings of the conductor in a second plane, before forming into the shaped non-planar coil of Figures 7A and 7B;

Figure 8 is a perspective view of another embodiment of the coil shaping device;

Figure 9 is a plan view of the coil shaping device of Figure 8;

Figure 10a is a perspective view of the coil shaping device of Figure 8 and 9;

Figure 10b is a perspective view and a side view of a single-wind coil after forming into a non- planar coil; and

Figures 11 a to 11 h show perspective views of another embodiment of the coil shaping device, and a process of shaping a coil.

Like reference numbers are used for like elements throughout the description and figures.

Detailed

In the following, embodiments of a coil shaping device according to the present disclosure will be described. The coil shaping devices according to the present disclosure are configured to shape a pre-made substantially planar coil 100 as shown in Figures 1A, 1 B, and 1C into a shaped non-planar coil 120 as shown in Figures 5A and 5B for use in an axial flux electrical machine.

Figures 1A, 1 B, and 1 C illustrate how a planar coil 100 is formed by winding a length of conductor. As illustrated in Figure 1 A, the conductor is wound around a pair of support elements 102A, 102B (which protrude perpendicularly out of the plane of the page) in a single plane so as to form a flat, planar winding with a number (in this case fourteen) of turns or layers. The flat, planar winding comprises straight, longitudinal portions 104 and outer loop sections 122 and inner loop sections 125 defining the turns. The planar coil has a central void 105.

It should be appreciated that the planar coil 100 can be wound in a variety of different ways, and the particular method of winding the planar coil 100 that is illustrated is not intended to limit the invention. The outermost winding of the length of conductor terminates at a first connection portion 128, which will be referred to as the outer tail 128. The outer tail 128 extends within the plane of the planar coil 100. As will be described in more detail below, this facilitates convenient connection of the shaped non-planar coils 120 to a multi-phase power supply. The innermost winding turn portion terminates at a second connection portion 129, which will be referred to as the inner tail 129.

That the winding is flat is best appreciated from Figures 1 B and 1 C. The innermost winding terminates at the inner tail 129 and the outermost winding terminates at the outer tail 128. The outer tail 128 in this example is further used to connect the shaped non-planar coil 120, to a conveyor, or to a busbar. That is, the outer tail 128 may serve as an attachment portion of the shaped non-planar coil 120.

The length of conductor that forms the planar coil 100 is wound such that there are a plurality of winding turn portions 131a, 131 b stacked parallel to the axis of rotation of the electrical machine. In the example of Figures 1A-1C, there are fourteen axially stacked winding turn portions 131a, 131 b, though this is not intended to limit the invention as other numbers of stacked winding turns are equally possible.

Although it has been described, using Figures 1 A-1C, how a planar coil 100 having windings in a single plane may be shaped, it will be readily apparent that a similar process may be used to wind a planar coil having windings in two parallel planes, made from a single length of conductor.

It will also be appreciated that the windings may be arranged differently to the specific example disclosed in Figures 1A-1 C.

Having formed the flat winding shown in Figures 1A-1 C, the three-dimensional shape of the shaped non-planar coil 120 is formed by shaping/bending/deforming the flat winding or planar coil 100 into the shape shown in Figures 5A and 5B.

The shaping of the planar coil 100 is performed using a coil shaping device 200 as shown in Figures 2, 3, and 4. The coil shaping device 200 provides a space 202 for receiving a premade substantially planar coil 100 to be shaped into a shaped non-planar coil 120.

At one end of the space 202 for receiving the planar coil 100, there is a clamp 204B. The clamp 204B is sized to receive the outer loop section 122 of the planar coil 100. The clamp is tightened so as to hold the outer loop section 122 sufficiently to allow only minimal movement of outer loop section 122 towards the inner loop section 125. At the other end of the space 202 there is a further clamp 204A for restricting movement of the inner loop section 125 out of the plane of the planar coil 100. However, upon deformation of the planar coil 100 into the shaped non-planar coil 120, the further clamp 204A allows the inner loop section 125 to slide towards the outer loop section 122.

The further clamp 204A is configured to clamp the inner loop section 125 with a clamping force that is sufficient to prevent inadvertent movement of the planar coil 100, and to provide some tensioning during deformation, but which is not so large that it prevents the inner loop section 125 from sliding towards the outer loop section 122.

The coil shaping device 200 also comprises two levers 206, having handles 207. Each of the levers 206 comprises a former 208. The formers 208 on the levers 206 are provided as a pair of a male former and a female former.

Each lever 206 is attached to a base plate 209 of the coil shaping device 200 by a pivot bolt 210 allowing for pivoting motion of the formers 208 towards one another. As shown in Figure 3, the formers 208 comprises pluralities of projections 300, 302 configured for cooperation to shape the planar coil 100 to form the shaped non-planar coil 120 shown in Figure 3.

As will be discussed in more detail in relation to Figures 5A and 5B, the formers 208 are configured such that the longitudinal portion, a first set of conductor portions, of the winding on one side of the central void is shaped in one direction out of the plane of the planar coil 100, and the other longitudinal portion, a second set of conductor portions, on the other side of the central void is shaped in an opposing direction out of the plane of the planar coil 100. This is achieved by each of the formers 208 comprising a male portion and a female portion, on different (planar) sides relative to the central void 105.

Figures 5A and 5B show a shaped non-planar coil 120 shaped from the planar coil 100 by the coil shaping device 200. As is best appreciated from the top-down views of Figure 5A in which the axis of rotation of the axial flux electrical machine is perpendicular to the plane of the page, a shaped non-planar coil 120 includes a pair of circumferentially pitched apart, radially extending active conducting sections 121a, 121 b. These radially extending active sections 121a, 121 b are referred to as “active” sections because, when the shaped non-planar coil 120 is positioned in a stator, they are disposed within a stator core and so interact with a magnetic field provided by magnets of rotors. It will be appreciated that since the active sections extend in a generally radial direction, which is approximately perpendicular to the axial flux in the core, the flux linkage is at least close to maximized. The angle y by which the two active sections 121 a, 121 b are pitched apart will be referred to as the coil span. The coil span can be the same as or different (less or more) than a pole pitch a (defined by the angle between the centres of the permanent magnets of the rotor). Turning to Figures 6A and 6B, these show a sixteen-pole, three-phase coil pack 10’ for an axial flux electrical machine. The shaped non-planar coils 120a, 120b, 120c of coil pack 10’ are circumferentially distributed around the coil pack and circumferentially adjacent conductive coils circumferentially overlap.

In use of the shaped non-planar coil 120 in an axial flux electrical machine, current will flow along the two active sections 121a, 121 b of the shaped non-planar coil 120 in opposite directions (that is, inward and outward parallel to the radially extending direction). The reversal of the current direction is provided by outer loop sections 122 of the winding turn portions 131a, 131 b and by inner loop sections 125 of the winding turn portions 131 a, 131 b. Each of the outer loop sections 122 includes a first portion 123 and a pair of second, involute, portions 124a, 124b (one for each of the pair of active sections 121a, 121 b) which connect the active sections 121a, 121 b to the first portion 123. Similarly, each of the inner loop sections 125 includes a first portion 126 and a pair of second portions 127a, 127b (one for each of the pair of active sections 121a, 121 b) which connect the active sections 121 a, 121 b to the first portion 126. The pair of second portions 127a, 127b may be involute portions, or may be naturally curved portions.

With regards to the outer second portions 124a, 124b and the inner second portions 127a, 127b, while they appear substantially straight in Figures 5A-5B, they are in fact slightly curved. Specifically, the shape of each of the outer first portions 124a, 124b is a section of a first involute, and so the first portions 124a, 124b together form outer substantially involute parts 134a, 134b of the shaped non-planar coil 120. Similarly, the shape of each of the inner second portions 127a, 127b may be a section of a second involute, and so the first portions 127a, 127b together form inner substantially involute parts 137a, 137b of the shaped non-planar coil 120. Alternatively, the inner parts 137a, 137b may be naturally curved parts rather than substantially involute parts.

As is particularly clear from Figure 6A, the circumferential overlap of the coils 120a, 120b, 120c defines circumferential spaces between active sections of the coils. These circumferential spaces, which are elongated in the radial direction, can receive flux guides (not shown), such as lamination packs.

As can be seen from Figure 5B, the two active sections 121 a, 121 b are axially offset from each other. This facilitates stacking, or overlapping, of the shaped non-planar coils 120 in the circumferential direction, and also facilitates the circumferential stacking, or overlapping of shaped non-planar coils 120 comprising windings in a plurality of parallel planes. This allows for more stator poles and more slots per pole per phase, both of which can provide for greater efficiency.

As can also be seen in Figure 5B, the length of conductor that forms the shaped non-planar coil 120 is wound such that there are a plurality of winding turn portions 131 a, 131 b stacked parallel to the axis of rotation of an electrical machine. The resulting cross-section of the shaped non- planar coil 120 that is perpendicular to the radial direction of each active section 121a, 121 b is elongate with a major dimension parallel to the axis of rotation. In the example of Figures 5A and 5B, there are fourteen axially stacked winding turn portions 131a, 131 b, though the shaped non-planar coil 120 may equally have any other number of turn portions 131a, 131 b.

As can be seen from Figure 5B, the outer first portions 123 together form an outer part 133 of the coil element 120 with a surface that is substantially parallel to the axis of rotation. In the specific example of Figures 5A and 5B, the outer first portions 123 are substantially semicircular and so the outer part 133 is a substantially flat half-disk 133, but other shapes are possible. For example, each of the outer first portions 123 may have a shape corresponding to three sides of a rectangle, such that they together form an outer part 133 which has a flat rectangular surface. As another example, the outer part 133 of the shaped non-planar coil 120 formed by the outer first portions 123 need not be flat or planar, it may have a curved profile and therefore curved surface.

In use, a planar coil 100 as shown in Figures 1A to 1C is placed within the space 202 and attached to the clamp 204B via the outer loop section 122 of the planar coil 100. The clamp 204B is tightened to hold the outer loop section 122 to prevent movement, such as sliding, of the outer loop section 122 towards the inner loop section 125. The other clamp 204A is loosely holding the inner loop section 125 to prevent movement of the inner loop section 125 out of the plane, without hindering movement, such as sliding, of the inner loop section 125 towards the outer loop section 122.

Once the planar coil 100 is securely held, the ends of the levers 206 having the handles 207 are moved towards one another, causing the formers 208 to move towards one another. The plurality of projections 300, 302 (which may be considered to be “male formers”) engage the planar coil 100, to deform the longitudinal portions 104 of the planar coil 100. The projections 300 of one former 208 engage with female former portions (e.g. slots) on the other former 208 to deform longitudinal portions 104 on one side of the central void 105 in one direction out of the plane of the planar coil 100. The projections 302 of the other former 208 engage with the female former portions (e.g. slots) on the other former 208 to deform longitudinal portions 104 on the other side of the central void 105 in an opposing direction out of the plane of the planar coil 100. The male and female formers are further shaped so as to form the involute portions of the shaped coil.

Plastic deformation of the planar coil 100 forms the shaped non-planar coil 120 shown in Figures 5A and 5B. However, the formers 208 deform the somewhat resilient planar coil 100 slightly beyond the desired shape, so that restoration of elastic deformation results in the required final shape of the shaped non-planar coil 120. Alternatively, instead of deforming the planar coil 100 “beyond” the desired shape, the shaped non-planar coil 120 may be stamped to the desired form, e.g. in two strokes.

Various modification and alternatives may be apparent to those skilled in the art. For example, the coil shaping device 200 may comprise an actuator for actuating the levers 206. The coil shaping device 200 may further comprise a gear set for coupling movement of one of the levers 206 to movement of the other lever 206.

As noted above, each planar coil 100 may comprise winding in only one plane, or may comprise windings in two or more parallel planes. If the planar coil 100 comprises windings in two or more parallel planes, the shaped non-planar coil 120 comprises two, circumferentially overlapping, conductive coil portions. An example of a shaped non-planar coil that includes two circumferentially overlapping conductive coil portions 120, 120’ will now be described with reference to Figures 7A-7B.

Figure 7A shows above and below views of a shaped non-planar coil 12 which includes two conductive coil portions 120, 120’. The features of each of the two conductive coil portions 120, 120’ are the same as those of the single shaped non-planar coil 120 described above with reference to Figures 5A and 5B, and so their features will not be described again.

To form the shaped non-planar coil 12, two identical conductive coil portions 120, 120’ are electrically connected together in series at their inner tails 129, 129’. In the examples illustrated herein, the inner tails 129, 129’ are connected using a ferrule 130. However, there are other ways of connecting the inner tails 129, 129’, such as brazing or welding or mechanical connections. To connect the two elements 120, 120’, one of the two conductive coil portions 120, 120’ is rotated 180° about a longitudinal axis of the one conductive coil portion 120, 120’, so that the outer tails 128, 128’ of the two conductive elements 120, 120’ are in opposite directions and the inner tails 129, 129’ are adjacent and therefore readily connected by a ferrule 130. Alternatively, a planar coil 100 comprising windings in two or more parallel planes may be formed as a single piece, i.e. by winding a conductor so as to create windings in two parallel planes, eliminating the need for a ferrule 130 (such a coil is shown in Figure 10b).

The planar coil 100 which was formed into the shaped non-planar coil 12 of Figures 7A and 7B consists of two planar coils 700, 700’ as shown in Figure 1 C, with their inner tails 129 connected by ferrule 130. This (two-layer) planar coil 100 is shaped into the shaped non-planar coil shown in Figure 7A and 7B by coil shaping device 800 as shown in Figures 8, 9, and 10. Such a (two-layer) planar coil 100 is shown in Figure 7C, showing planar windings 700, 700’ in two parallel planes separated by a gap 702. The windings 700, 700’ are connected via the respective inner tails 129, 129’ by ferrule 130.

However, as noted above, instead of a planar coil 100 comprising windings in two or more parallel planes comprising two planar coils 700, 700’ attached to one another by a ferrule 130, the planar coil 100 comprising windings in two or more parallel planes may be wound from a single length of conductor, with no need for a ferrule 130. In such a case, the windings in the two parallel planes may comprise a “connected” inner tail of windings in a first plane and outer tail of windings in a second plane.

As set out above, although Figure 7B shows the inner tails 129, 129’ being adjacent and therefore readily connected by a ferrule 130, the two conductive elements could be integrally formed as a single piece, i.e. wound from a single conductor. Figure 10b shows such a single piece, non-planar coil 1000, wound from a single winding and then formed into the single-wind, non-planar coil 1000 shown in Figure 10b. The non-planar coil 1000 may have the same or similar features (e.g. gap 143a, 143b, outer loop sections 122, 122’, inner loop section 125, 125’) as the coil 12 shown in Figures 7A and 7B, except for the ferrule 130.

The outer tails 128, 128’ of the two conductive elements 120, 120’ are shown in Figure 7B to be in opposite directions. Of course, it will be appreciated that the windings may be arranged differently. For example, both in a (planar and non-planar) coil wound from a single conductor, and such a coil made from two conductive elements connected at their inner tails by a ferrule, the outer tails 128, 128’ may point in the same direction.

Returning to Figure 7A and 7B, the resulting shaped non-planar coil 12 has two pairs of circumferentially overlapping, pitched apart pairs of active sections 121a, 121 b; 121a’, 121 b’. Notably, the overlap of the two pairs of active sections defines two spaces 142a, 142b. The first space 142a is defined between one (a first) active section 121a of a first of the conductive coil portions 120 of the coil 12 and between one (a first) active section 121 a’ of the second of the conductive coil portions 120’ of the coil 12. The second space 142b is defined between the other (the second) active section 121 b of the first shaped non-planar coil 120 of the coil 12 and between the other (the second) active section 121 b’ of the second shaped non-planar coil 120’ of the coil 12. That is, the two spaces 142a, 142b are circumferential spaces between adjacent active sections 121a, 121a’; 121 b, 121 b’ of two different pairs of active sections 121 a, 121 b; 121a’, 121 b’ of the same coil 12. Flux guides (not shown), such as lamination packs, are inserted into the spaces.

As may be seen from Figures 7A and 7B, the coil shaping device 800 is configured to shape the shaped non-planar coil 12 so that the shaped non-planar coil 12 has a gap 143a between the second portions 124a, 124a’ of the outer loop sections 122, 122’ which form one pair of outer naturally curved parts 134a, 134a’ of the two conductive coil portions 120, 120’. Likewise, there is a gap 143b between the second portions 124b, 124b’ of the outer loop sections 122, 122’ which form the other pair of outer naturally curved parts 134b, 134b’. There is also a gap 144a between the second portions 127a, 127a’ of the inner loop sections 125, 125’ which form one pair of inner naturally curved parts 137a, 137a’. Finally, there is also a gap 144b between the second portions 127b, 127b’ of the inner loop sections 125, 125’ which form the other pair of outer naturally curved parts 137b, 137b’.

The width of these gaps 143a, 143b, 144a, 144b remains substantially constant along the length of the naturally curved sections of the conductive coil portions 120, 120’. The naturally curved sections are formed from deformation of active sections 121a and 121 b. This advantageously reduces the resulting diameter of the motor for a given rating and losses in the coils.

The coil shaping device 800 is shown in Figure 8 after a planar coil 100 as shown in Figure 7C has been formed into the shaped non-planar coil 12 of Figures 7A and 7B. The coil shaping device 800 comprises an outer shell which comprises a lower shell 802 and an upper shell 804. The upper shell 804 is hingedly connected to the lower shell 802. Upon closing the outer shell, the internal surfaces of the outer shell are substantially shaped to form an external shape of the shaped non-planar coil 12. It is noted that the coil shaping device 800 may equally be used to form a shaped non-planar coil (such as coil 1000) from a planar coil formed from a single winding (i.e. not having a ferrule 300), as described below, instead of from the planar coil 100 as shown in Figure 7C.

The device 800 further has a pair of opposing heads 803, 803’, which each have attachment portions 805, 805’ which are rotatable, and slidable, relative to a bar 806, on opposite sides of the lower shell 802. The heads 803, 803’ each have three fingers 810, 810’ facing towards the other head 803, 803’, so that when the heads 803, 803’ are slid towards one another via the attachment portions 805, 805’ along the bar 806, the middle one of the three fingers 810, 810’ projects into the gap 702 between the windings 700, 700’.

The device 800 further comprises an intermediate holder portion 812, 812’, inwardly of each of the heads 803, 803’, which are configured to project into the gap 702 between the inner loop sections 125 as the heads 803, 803’ slide towards one another along the bar 806. The intermediate holder portions 812, 812’ each comprise an attachment having an aperture 813’ (only one visible), through which the bar 806 extends. As such, the intermediate holder portions 812, 812’ are attached directly to the bar 806, but not the heads 803, 803’; in this manner, the heads 803, 803’ are rotatable about the bar 806 without causing the intermediate holder portions 812, 812’ to also rotate.

Within each of the attachments 805, 805’, the device 800 comprises actuators (not shown) to drive linear movement of the heads 803, 803’ along the bar 806, and rotational movement of the heads 803, 803’ relative to the bar 806. The separate actuators allow for independent movement of each of the heads 803, 803’.

The device 800 also has a sprung clamp 814 rotatable about a hinge pin 815 relative to the lower clamp shell 802. The sprung clamp 814 is configured to project into the gap 702 on an opposite end of the planar coil 100 to the intermediate holder portions 812, 812’. The lower and upper shells 802, 804 are also hingedly connected by the hinge pin 815.

As shown in Figure 9, in which only one of the sets of fingers 810’ and intermediate holder portions 812’ is shown for clarity, each set of fingers 810, 810’ has an innermost finger 904, a central finger 906 and an outermost finger 908, which, in use, interdigitate the layers of windings of the shaped non-planar coil.

The upper and lower shell comprise cut-outs 900’, 900, 901’, 901 for receiving portions of the windings. The innermost finger 904 and central finger 906 comprise rounded ends 910 configured to create the required naturally curved sections of the shaped non-planar coil 12.

Figure 10a shows one of the heads 803 after removal from the formed, i.e., shaped non-planar coil 12.

In use, a planar coil 100 having windings in two parallel planes is inserted into the lower shell 802, with the sprung clamp 814 projecting into the gap 702 between the windings in the two parallel layers/planes on one end of the planar coil 100. The upper shell 804 is then rotated about the hinge pin 815 to close the shell.

Once the shell is closed, the heads 803, 803’ are simultaneously moved, using actuators (not shown) in the attachment portions 805, 805’, towards one another by sliding along the bar 806, so that the fingers 904, 906, 908 interdigitate the windings of the planar coil 100. As the heads 803, 803’ are moved towards one another, the intermediate holder portions 812, 812’ are also moved towards one another, so that in the final linear position, they project into the gap 702 between the inner loop sections 125 of the planar coil 100 at an opposite end of the planar coil 100 to the sprung clamp 814.

Once the final linear position is reached by the heads 803, 803’ and the intermediate holder portions 812, 812’, the heads 803, 803’ are rotated relative to the bar 806 in opposite directions away from the plane of the planar coil 100. This causes the planar coil 100 to deform so as to shape the shaped non-planar coil 12. The heads 803, 803’ are moved independently of one another under servo control, but simultaneously so that the portions of the planar coil 100 are deformed simultaneously.

The sprung clamp 814 allows for further winding material to be drawn into the lower and upper shells 802, 804, or drawn towards the other end of the coil, to accommodate for the deformation. In other words, the sprung clamp 814 and the portions of the lower and upper shell 802, 804 in contact with an outer loop section or inner loop section of the planar coil 100 (depending on the orientation of the planar coil 100), are configured to clamp the respective loop section with a clamping force that is sufficient to prevent inadvertent movement of the planar coil 100, and to provide some tensioning during deformation, but which is not so large that it prevents the respective loop section from sliding towards the middle/the other end of the coil. The other end of the coil 100 is clamped by the intermediate holder portions 812, 812’ and portions of the lower and upper shell 802, 804 adjacent the intermediate holder portions 812, 812’, to prevent movement of the other end of the coil 100.

In an alternative embodiment, instead of the sprung clamp 814, the intermediate holder portions 812, 812’ allow for further winding material, i.e. further material of the coil 100, to be drawn towards the other end of the coil 100, to accommodate for the deformation. In other words, the intermediate holder portions 812, 812’ and the portions of the lower and upper shell 802, 804 adjacent the intermediate holder portions 812, 812’ in contact with an outer loop section or inner loop section of the planar coil 100 (depending on the orientation of the planar coil 100), are configured to clamp the respective loop section with a clamping force that is sufficient to prevent inadvertent movement of the planar coil 100, and to provide some tensioning during deformation, but which is not so large that it prevents the respective loop section from sliding towards the middle/the other end of the coil. The other end of the coil 100 is clamped by the sprung clamp 814 and portions of the lower and upper shell 802, 804, to prevent movement of the other end of the coil 100.

In a further alternative embodiment, both the sprung clamp 814 and the intermediate holder portions 812, 812’ allow for further winding material to be drawn towards the respective other end of the coil 100, to accommodate for the deformation. In other words, the intermediate holder portions 812, 812’ and the portions of the lower and upper shell 802, 804 adjacent the intermediate holder portions 812, 812’ in contact with a first loop section of the planar coil 100 are configured to clamp the first loop section with a clamping force that is sufficient to prevent inadvertent movement of the planar coil 100, and to provide some tensioning during deformation, but which is not so large that it prevents the first loop section from sliding towards the middle/other end of the coil. Similarly, the sprung clamp 814 and the portions of the lower and upper shell 802, 804 in contact with the second loop section of the planar coil 100 are configured to clamp the second loop section with a clamping force that is sufficient to prevent inadvertent movement of the planar coil 100, and to provide some tensioning during deformation, but which is not so large that it prevents the second loop section from sliding towards the middle/the other end of the coil.

Upon the final angular position being reached by the heads 803, 803’, the lower and upper shells 802, 804 are squeezed together to overshape the shaped non-planar coil 102. Upon release of the shell, resilient restoration of the shaped non-planar coil 12 results in the final desired shape of the shaped non-planar coil 12.

Various alternatives and modifications are apparent to those skilled in the art. For example, at least the central finger 906 may have a hinged portion which upon deformation of the planar coil 100 into the shaped non-planar coil 12 rotates relative to the remaining portion of the finger so as to form the inner naturally curved section of the shaped non-planar coil 12.

The planar coil 100 may be imparted with additional strength so that the winding material maintains its shape during the shaping process. In one example, the conductor has a heat- or solvent-activated outer bond layer so that after shaping, the turns/layers can be bonded together to maintain the shape.

Figures 11 a to 11 h show perspective views of another embodiment of a coil shaping device

1100. The coil shaping device 1100 is similar to coil shaping device 800. However, as set out below, there are some constructional differences between coil shaping devices 800 and 1100. The coil shaping device 1100 is shown in Figure 11 a after a planar coil 100 having windings in two parallel planes has been introduced into the device 1100. The planar coil 100 is similar to the planar coil 100 shown in Figure 7c, but is formed from a single winding, and then formed in the process described below with reference to Figures 11a to 11 h into the non-planar coil 1100 of Figure 10b. Like coil shaping device 800, the coil shaping device 1100 comprises an outer shell comprising a lower shell 802 and an upper shell 804. The upper shell 804 is hingedly connected to the lower shell 802. Upon closing the outer shell, the internal surfaces of the outer shell are substantially shaped to form an external shape of the shaped non-planar coil 12.

The device 1100 further has a pair of opposing heads 803, 803’, each of which are attached in a rotatable and slidable manner to a bar 806, on opposite sides of the lower shell 802. The heads 803, 803’ each have three fingers 810, 810’ facing towards the respective other head 803, 803’, so that when the heads 803, 803’ slide towards one another along the bar 806, the middle one of the three fingers 810, 810’ projects into the gap 702 between the windings 700, 700’, so that the fingers interdigitate the windings 700, 700’ in the first and second plane.

The device 1100 further comprises an intermediate holder portion 812, 812’, inwardly of each of the heads 803, 803’, which are configured to project into the gap 702 between the inner loop sections 125 as the heads 803, 803’ slide towards one another along the bar 806. The intermediate holder portions 812, 812’ each comprise an attachment having an aperture through which the bar 806 extends. As such, the intermediate holder portions 812, 812’ are attached directly to the bar 806, but not the heads 803, 803’; in this manner, the heads 803, 803’ are rotatable about the bar 806 without causing the intermediate holder portions 812, 812’ to also rotate.

The device 1100 further comprises manual controls 1102 and 1102’ configured to, respectively, cause movement of the heads 803, 803’ towards the planar coil 100 by rotation of the manual controls 1102 and 1102’. The upper shell 804 comprises a handle 1104 which allows for the upper shell 804 to be manually closed by pivotal movement towards the lower shell 802.

The device 1100 also has two further intermediate portions 1106 and 1106’ which are slidably attached to a second bar 1108 so that when they slide, as indicated by arrows 1110, towards one another, e.g. using handles, they project into the gap 702 on an opposite end of the planar coil 100 to the intermediate holder portions 812, 812’.

As in device 800, each set of fingers 810, 810’ of device 1100 has an innermost finger 904, a central finger 906 and an outermost finger 908, which, in use, interdigitate the layers of windings of the planar coil 100. In use, as shown in Figure 11 a, a planar coil 100 having windings in two parallel planes, wound from a single winding (such as that shown in Figure 10b), is inserted into the lower shell 802, so that a central, longitudinal projection 1112 of device 1100 projects through the central void 105 of the planar coil 100, thus holding planar coil 100 in place. As shown in Figure 11 b, the second intermediate portions 1106 and 1106’ are then moved along the second bar 1108 so that they project into the gap 702 on the opposite side of the planar coil 100 to intermediate holder portions 812, 812’.

The heads 803, 803’ are then moved towards the planar coil 100 by rotation of the manual controls 1102 and 1102’, as indicated by arrows 1114 and 1114’ in Figure 11 c. The movement of the heads 803, 803’ causes the intermediate holder portions 812, 812’ to slide along the bar 806 as the heads 803, 803’ move towards the planar coil 100. When the heads 803, 803’ have reached their final position by sliding along bar 806, the sets of fingers 810 and 810’ interdigitate the windings of the planar coil 100.

Once the heads 803, 803’ have reached their final position along the bar 806, the shell may be closed by hingedly moving the upper shell 804 towards the lower shell 802, as shown in Figure 11 d. As indicated by arrows 1116 and 1118, the upper shell 804 and lower shell 802 may then be clamped together by actuation using a further handle 1120 attached to a clamping mechanism 1122.

Pressing the button 1124 as shown in Figure 11e actuates a rotation of the heads 803, 803’, in opposite directions, as indicated by arrows 1126 and 1126’ in Figure 11 e. Meanwhile, the intermediate holder portions 812, 812’, which are not fixedly connected to the bar 806, do not rotate along with the heads 803, 803’, so that the outer loop sections 122 (or inner loop sections 125 depending on the orientation of the planar coil 100) are retained in the same plane. Once the final rotational position is reached, the clamping mechanism 1122 is released by actuation of the further handle 1120, and the upper shell 804 may be hingedly moved away from the lower shell 802 to open the shell and reveal the shaped, non-planar coil 12, with the sets of fingers 810 and 810’ still interdigitating the windings of the non-planar coil 12, as shown in Figure 11f.

Movement of the handles 1102 and 1102’ in the opposite direction of that shown in Figure 11 c, i.e. as indicated by arrows 1128 and 1128’ in Figure 11 g, causes the heads 803, 803’ to sliding along bar 806, as shown by arrows 1130 and 1130’, so as to retract the heads 803, 803’ from the shaped coil 12. This also causes retraction of the intermediate holder portion 812, 812’.

Finally, to allow the shaped non-planar coil 12 to be removed from the device 1100, the two further intermediate portions 1106 and 1106’ are retracted, by sliding movement away from one another, as indicated by arrows 1132, 1132’, e.g. using handles, along the second bar 1108, as shown in Figure 11 h. Once the components of the device 1100 are in the positions as shown in Figure 11 h, the shaped non-planar coil 12 may simple be taken from the device 1100 and off the central, longitudinal projection 1112 of the device 1100.