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Title:
SLIP RING ARRANGEMENT AND CONNECTION SYSTEM EMPLOYING SAME
Document Type and Number:
WIPO Patent Application WO/2020/234455
Kind Code:
A1
Abstract:
Disclosed is a slip ring comprising one or more arcuate sections connected end-to-end. Each section comprises an electrically conductive bearing surface for contacting a brush. At the ends of each section, the bearing surface edge is not orthogonal to the rotation direction of the slip ring, such that the ends of the one or more sections are connected at an intersection region in which both of the bearing surfaces at adjacently connected ends intersect a line orthogonal to the rotation direction. Also disclosed is a connection system comprising a slip ring and at least one brush in electrical contact with a bearing surface of the slip ring, The brush is configured to travel along the bearing surface of the slip ring. The slip ring sections are connected end-to-end such that, as the at least one brush travels around the bearing surface of the slip ring, the at least one brush remains in electrical contact with the bearing surface of at least one section of the slip ring at all times.

Inventors:
DAVIES JAMES (GB)
Application Number:
PCT/EP2020/064282
Publication Date:
November 26, 2020
Filing Date:
May 22, 2020
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ELEKTA LTD (GB)
International Classes:
H01R39/08; H01R43/10
Foreign References:
CN108258556A2018-07-06
EP3217487A12017-09-13
RU2591783C22016-07-20
US20020171313A12002-11-21
Attorney, Agent or Firm:
ROBERTS, Gwilym (GB)
Download PDF:
Claims:
Claims

1. A slip ring comprising one or more arcuate sections connected end-to-end, each section comprising an electrically conductive bearing surface for contacting a brush, wherein, at the ends of each section, the bearing surface edge is not orthogonal to the rotation direction of the slip ring, such that the ends of the one or more sections are connected at an intersection region in which both of the bearing surfaces at adjacently connected ends intersect a line orthogonal to the rotation direction.

2. The slip ring of claim 1 , wherein the bearing surface edge at the ends of each section is angled relative to the rotation direction of the slip ring.

3. The slip ring of claim 1 , wherein the bearing surface edge at the ends of each section comprise at least one protruding portion and at least one corresponding recessed portion, and wherein the at least one recessed portion is configured to receive the at least one corresponding protruding portion of an adjacently connected end.

4. The slip ring of claim 1 , wherein the bearing surface edge at the ends of each section comprises a stepped portion, wherein the stepped portion is configured to receive the stepped portion of an adjacently connected end.

5. The slip ring of any of claims 1 - 4, further comprising interface PCBs that join the ends of the one or more sections of the slip ring and that cause adjacently connected ends to be electrically connected.

6. A section for a slip ring as claimed in any of claims 1 - 5.

7. A connection system comprising the slip ring of any of claims 1 - 5, and further

comprising at least one brush in electrical contact with a bearing surface of the slip ring, wherein the at least one brush is configured to travel, with respect to the slip ring, along the bearing surface of the slip ring, and wherein the slip ring sections are connected end-to-end such that, as the at least one brush travels around the bearing surface of the slip ring, the at least one brush remains in electrical contact with the bearing surface of at least one section of the slip ring at all times.

8. The connection system of claim 7, wherein the connection system is configured to

transmit data signals between the at least one brush and the slip ring.

9. The connection system of claim 7, wherein the connection system is configured to transmit power between the at least one brush and the slip ring.

10. A radiotherapy device comprising the connection system of any of claims 7 to 9.

11. A connection system comprising:

a slipring configured to rotate around its central axis; and

a brush fixed relative to the slip ring and positioned to contact a bearing surface of the slipring through rotation of the slipring and to provide an electrical connection with the slip ring;

wherein:

the slip ring comprises one or more sections connected in end-to-end, wherein adjacently connected ends are connected at a connection interface;

wherein the connection interface between adjacent ends is not parallel to the brush such that, as the slipring rotates through the connection interface, the brush has

simultaneous contact with the bearing surface of both of the adjacent ends of the one or more sections.

12. The connection system of claim 11 wherein the brush is elongated and orientated such that it is not orthogonal to the rotation direction.

13. The connection system of claim 11 wherein the connection interface between adjacent sections is not orthogonal relative to the rotation direction of the slip ring.

Description:
Slip Ring arrangement and connection system employing same

The present disclosure is related to connection systems comprising a rotor and a stator, wherein the rotor and stator are in electrical contact for transmitting signals. More

specifically, the present disclose is related to slip rings. Yet more specifically, the present disclosure relates to a slip ring for use in a connection system, the slip ring comprising one or more arcuate sections connected in series.

Background

In the field of electrical connections, there exists many connection systems that include a rotating element (a rotor) and a stationary element (a stator), whereby the rotor is required to be in electrical contact with the stator. It is often the case that the rotor and stator are required to maintain electrical contact at all times as the rotor rotates. This is typically because electrical signals such as data signals, control signals or power signals need to be transmitted between the stator and rotor as the rotor rotates. It is therefore necessary to ensure that the rotor and the stator are in constant electrical contact such that electrical signal transmission can be continuous and not interrupted by a loss of connection as a result of a loss of electrical contact.

One way of achieving this that is known in the art is to employ a slip ring and brush arrangement. The rotor may comprise a circularly symmetric ring that is in constant electrical contact with electrically conductive brushes attached to the stator. Alternatively, the slip ring may remain stationary whilst brushes attached to the rotor rotate around the ring. The slip ring comprises a bearing surface that maintains contact with the brushes as the slip ring rotates/the brushes rotate around the slip ring. In order to maintain contact, the slip ring bearing surface must be smooth and devoid of irregularities.

It is essential to maintain a connection between the stator and the rotor, particularly if the connection is used for communication.

Embodiments of the present disclosure seek to address these and other disadvantages encountered in the prior art.

Summary

Some aspects of the present disclosure relate to a slip ring comprising one or more arcuate sections connected end-to-end. Each section comprises an electrically conductive bearing surface for contacting a brush and, at the ends of each section, the bearing surface edge is not orthogonal to the rotation direction of the slip ring. This means that the ends of the one or more sections are connected at an intersection region in which both of the bearing surfaces at the adjacently connected ends intersect a line orthogonal to the rotation direction.

In more detail, the‘rotation direction’ of the slip ring refers to the direction that follows the circumference of the slip ring. The rotation direction therefore follows a line around the circumference of the slip ring. This means that at any point on the bearing surface, the rotation direction is tangential to the slip ring and orthogonal to the radial direction at that point. The rotation direction is orthogonal to the axial direction of the slip ring. In some embodiments, the slip ring may be used in a connection system comprising a brush configured to travel relative to the slip ring around the circumference of the slip ring. The brush may be fixed in place and the slip ring may be configured to rotate or the slip ring may be fixed and the brush may be configured to rotate about the centre of the slip ring and thus traverse the circumference of the slip ring. In either of these systems, the rotation direction may be considered to represent to direction of the brush travel relative to the slip ring.

Because the edges of the bearing surfaces at the ends of each section are not orthogonal to the rotation direction of the slip ring, this means that when adjacently connected ends of the one or more sections are connected together at their ends, the bearing surface edges at the ends of the adjacently connected ends are not orthogonal to the rotation direction and so there exists a region in which both bearing surfaces intersect a line that is orthogonal to the rotation direction. In other words, the bearing surfaces overlap along a line orthogonal to the rotation direction.

In more detail, the intersection region defines an area of the bearing surfaces of adjacently connected ends of the one or more sections that includes a part of the bearing surface of each of the connected ends. Within the intersection region, a notional line that lies orthogonal to the rotation direction of the slip ring, and that also lies in the plane of the bearing surfaces, will pass through the bearing surfaces of both sections, because the bearing surface edges of the sections are not orthogonal to the rotation direction and are therefore not parallel to the notional line. This means that the notional line intersects both of the bearing surfaces of the adjacently connected ends of the one or more sections within the intersection region.

This intersection region provided by the bearing surface edges that are not orthogonal to the rotation direction means that a brush contacting the bearing surface and traversing the circumference of the slip ring (a brush travelling along the bearing surface in a direction parallel to the rotation direction of the slip ring) will simultaneously be in contact with both of the bearing surfaces of the adjacent sections as the brush travels through the intersection region.

In a rotor-stator connection system comprising a brush in electrical contact with the bearing surface of the slip ring, the rotation direction defines the direction of travel of the brush with respect to the slip ring. In this system the slip ring may be stationary and the brush travels around the circumference of the slip ring in the rotation direction. Alternatively the brush may be stationary and the slip ring rotates about its centre point and so the bearing surface travels in the rotation direction as the slip ring rotates.

Other aspects of the present disclosure relate to a slip ring comprising one or more arcuate sections connected end-to-end at connection interfaces of the sections. In other words, the one or more sections are joined together at ends of the one or more sections to form a ring. Each section comprises an electrically conductive bearing surface for contacting a brush. At the connection interfaces, the edges of the bearing surfaces of adjacently connected ends of the one or more sections overlap along the axial direction of the slip ring.

By having the bearing surfaces of adjacently connected ends overlapping along the axial direction of the slip ring, a brush contacting the bearing surface and traversing the circumference of the slip ring will simultaneously be in contact with both of the bearing surfaces at the adjacently connected ends as the brush passes over the connection interface. This is because the overlap of the bearing surfaces at the connection interface is along the axial direction which is orthogonal to the direction of travel of the brush. In other words, the overlap of the sections along the axial direction means that the connection interface is not parallel to the axial direction and is therefore not orthogonal to the brush travel direction.

In more detail, an overlap along the axial direction of the slip ring means that, when viewing the connection interface between adjacently connected ends from a direction that is parallel to the axial direction of the slip ring, it appears as if the adjacently connected ends are overlapping one another.

In other words, any gap at the connection interface between adjacently connected ends cannot be seen from this perspective (when viewing the interface along a line parallel to the axial direction of the slip ring). The overlap of the adjacently connected ends along this line means that when viewed from this perspective, the two separate sections appear to be overlapping and appear to be a single continuous section. In other words, no gap between the sections can be seen. This effect is caused by the overlap of the sections along a line parallel to the axial direction of the slip ring. It can therefore be said that the connection interface is not perpendicular to the direction of travel of

In more detail, the axial direction is defined as being parallel to a line that extends through the centre of the slip ring, and is orthogonal to the plane within which the ring lies. For example, if the slip ring lies in a x-y plane defined in cartesian axes, then the axial direction is defined by the positive or negative z axis.

In some embodiments of the present disclosure, at the ends of each section, the bearing surface edges are angled relative to the rotation direction of the slip ring., This means that the bearing surfaces of adjacently connected ends overlap along the axial direction. In other words, the edges of the bearing surfaces are angled relative to the rotation direction of the slip ring which means they are not orthogonal to the rotation direction. The angle that the edge of the bearing surface makes with respect to the rotation direction may be any acute angle. In other words, the angle athat the edge of the bearing surface makes with the rotation direction may be 0° < a < 90°.

In these embodiments, the overlap of the bearing surfaces is caused by the bearing surfaces being angled with respect to the axial direction. The angled ends of the sections means that the connection interface is not parallel to the axial direction and is also not orthogonal to the brush travel direction. Therefore, when viewing the connection interface along a line parallel to the axial direction, the angled ends cause the appearance of an overlap of the adjacently connected ends such that it appears to be a single, continuous section with no gaps. A brush in contact with the bearing surface and traversing the connection interface will therefore not experience an interruption due to a gap as it appears that the bearing surface is continuous across the connection interface.

In other words, in these embodiments, the bearing surfaces have angled edges at the ends of the sections, which means that at the connection between adjacently connected ends, there exists an interface region in which a line orthogonal to the rotation direction of the slip ring intersects the bearing surfaces of both of the adjacently connected surfaces.

In further embodiments of the present disclosure, at the ends of each section the bearing surface edges comprise at least one protruding portion and at least one corresponding recessed portion. The at least one recessed portion may be configured to receive the at least one corresponding protruding portion of an adjacently connected end of the one or more sections, such that the bearing surfaces of adjacently connected ends overlap along the axial direction.

In these embodiments, the overlap of the bearing surfaces is caused by the protruding portion of one section being received in the recessed portion of an adjacent section. The protruding and recessed portions means that the connection interface between adjacently connected ends is not flat and therefore is not parallel to the axial direction of the slip ring and not orthogonal to the brush travel direction. When viewing the connection interface along a line parallel to the axial direction, the protruding portion of one section received in the recessed portion of an adjacent section causes the appearance of an overlap of the adjacent sections such that is appears to be a single, continuous section with no gaps. A brush in contact with the bearing surface and traversing the connection interface will therefore not experience an interruption due to a gap as it appears that the bearing surface is continuous across the connection interface.

In other words, in these embodiments, the bearing surfaces have protruding and recessed portions at the ends of the sections, which means that the edge of the bearing surface is not straight. Instead the edge is irregular in shape and so the connection interface between adjacent sections is not straight. This means that, at the connection between two adjacent sections of the slip ring, there exists an interface region in which a line orthogonal to the rotation direction of the slip ring intersects the bearing surfaces of both of the adjacently connected sections.

In yet further embodiments of the present disclosure, at the ends of each section the bearing surface comprises a stepped portion, wherein the stepped portion is configured to receive the stepped portion of an adjacently connected end of the one or more sections, such that the bearing surfaces of adjacently connected ends overlap along the axial direction. In other words, the edges of the bearing surfaces are not straight are irregular in shape. This means that the connection interface between two adjacently connected ends is not straight, and so there exists an intersect region in which a line orthogonal to the rotation direction of the slip ring intersects the bearing surfaces of both of the adjacently connected sections.

In some embodiments, the slip ring comprises interface PCBs that join adjacent ends of the one or more sections of the slip ring and that cause adjacent ends to be electrically connected. The interface PCBs that join adjacent sections of the slip ring together allow all the sections to be electrically connected to each other such that the slip ring is a single conductor. In more detail, the interface PCB that joins two sections is electrically connected to the bearing surfaces of both sections. The interface PCBs may be positioned on a surface of the slip ring sections that is different to the bearing surface such that the interface PCBs doesn’t interfere with brushes traversing the bearing surfaces of the sections of the slip ring.

Some embodiments of the invention relate to a section of the slip ring according to the embodiments described above.

Another aspect of the present disclosure relates to a connection system comprising the slip ring according to any of the embodiments described above. The connection system further comprises at least one brush in electrical contact with the bearing surface of the slip ring.

The at least one brush is configured to travel, with respect to the slip ring, along the bearing surface of the slip ring, and the slip ring sections are connected end-to-end such that, as the at least one brush travels around the bearing surface of the slip ring, the at least one brush remains in electrical contact with at least one section of the slip ring at all times. By using the slip ring of any of the embodiments described above that provide an overlap of the bearing surface of adjacently connected ends of one or more sections along the axial direction, the brush is able to maintain contact with the bearing surface of at least one of the sections of the slip ring at any time as the brush traverses the full circumference of the slip ring (i.e. as the brush travels in the rotation direction with respect to the slip ring).

This is because, the overlap of the bearing surfaces along the axial direction at the connection interface means that a brush passing over the connection interface will be in contact with both sections at the same time even if there is a gap at the connection interface, and so connection is never lost between the brush and the slip ring. In other words, because the edges of the bearing surfaces are not orthogonal to the brush travel direction (the rotation direction), this means that there exists an intersection region in which a line orthogonal to the brush travel direction intersects both of the bearing surfaces of the adjacently connected ends. When the brush travels through this intersection region from one section to the next, the brush will be in contact with the bearing surfaces of both sections at the same time, and so the brush will always maintain electrical contact with the slip ring.

In some embodiments, the connection system is configured to transmit data signals between the at least one brush and the slip ring. In some embodiments, the connection system is configured to transmit power between the at least one brush and the slip ring. This allows data or power to be transmitted between two or more components in a system where at least one component is configured to rotate and at least one other component is stationary. This may be used, for example, in a radiotherapy device in which data and power must be transmitted between a control system and instruments mounted on a rotating gantry.

Another aspect of the present disclosure relates to a connection system comprising a slipring configured to rotate around its central axis and a brush fixed relative to the slip ring. The brush is positioned to contact a bearing surface of the slipring through rotation of the slipring and provides an electrical connection with the slip ring. The slip ring comprises one or more sections connected end-to-end and each section is connected to the next section at a connection interface. The connection interface between adjacent sections is not orthogonal relative to the rotation direction of the slip ring such that, as the slipring rotates through the connection section, the brush has simultaneous contact with both of the adjacent sections.

Brief description of the drawings

Specific embodiments are described below by way of example only and with reference to the accompanying drawings in which:

Figure 1a illustrates a radiotherapy device comprising a slip ring in accordance with embodiments of the present disclosure;

Figure 1b illustrates a side-view of a radiotherapy device of Figure 1a;

Figure 1c illustrates a further side-view of a radiotherapy device of Figure 1a;

Figure 2a illustrates a slip ring in accordance with examples known in the art;

Figure 2b illustrates a section of a slip ring in accordance with examples known in the art;

Figure 2c illustrates a plan view of the section of Figure 2b;

Figure 2d illustrates a plan view of the connection interface between sections of the slip ring of Figure 2a;

Figure 2e illustrates a view along the axial direction of the connection interface of Figure 2d.;

Figure 3a illustrates a slip ring in accordance with embodiments of the present disclosure; Figure 3b illustrates a section of the slipring of Figure 3a;

Figure 3c illustrates a plan view of the section of Figure 3b;

Figure 3d illustrates a plan view of the connection interface between sections of the slip ring of Figure 3a;

Figure 3e illustrates a view along the axial direction of the connection interface of Figure 3d;

Figure 4a illustrates sections of a slip ring according to embodiments of the present disclosure;

Figure 4b illustrates a closer view of the sections of Figure 4a;

Figure 4c illustrates sections of a slip ring according to alternative embodiments of the present disclosure;

Figure 5 illustrates an interface PCB for connecting adjacent sections of a slip ring according to embodiments of the present disclosure;

Figure 6 illustrates an arrangement according to some embodiments of the present disclosure.

Detailed description of the drawings

Application of the present invention - rotating radiotherapy gantries, wind turbines, motors and generators or any other system involving a rotor and a stator.

Figure 1a depicts a radiotherapy device 120 comprising a slip ring. The arrangement described provides one specific example of an implementation of the slip ring according to the present disclosure and it will be understood that other arrangements are possible and can be used to incorporate embodiments of the slip ring described herein. In particular, a slip ring according to the present disclosure can be incorporated into any system comprising a rotating element (a rotor) and a static element (a fixed element) wherein electrical signals are transmitted between the rotor and the stator.

The Figures and the description thereof illustrate a specific embodiment of the disclosure, which the skilled person will understand is non-limiting. The Figure shows a cross-section through a radiotherapy device 120 comprising a radiation source 100 and a detector 102 attached to a gantry 104. The radiation source 100 and the detector 102 are fixed to the gantry 104 and rotate with the gantry. The gantry 104 comprises a circular support track 106. The radiation source 100 and the detector are arranged diametrically opposed to one another. In some examples, the gantry is annular and further comprises a central bore 107. The radiation device 120 is suitable for delivering imaging or therapeutic radiation to a patient.

Figure 1a also shows a patient support surface 110. The support surface 110 may be moved longitudinally relative to the gantry 104, for example to aid positioning of a patient lying on the support surface. In other words, the support surface 110 is configured to move in an axial direction position the subject 108. During treatment, the gantry rotates on the circular support track 106 causing the radiation source 100 to rotate around a patient laying on the support surface 110 to deliver a radiation dose to a radiation isocentre in the patient from different angles. This allows the radiation does received by healthy tissue to be spread around a larger region of the healthy tissue, whilst building up a prescribed dose of radiation at a target region.

The gantry 104 further comprises a slip-ring 105 concentric with the gantry 104 and mounted to the gantry. The slip ring may be fixed to the gantry and thus may rotate with the gantry. In embodiments of the present disclosure, the slip ring comprises one or more arcuate sections connected end-to-end. In other words, the arcuate sections are connected in series to form the circular slip ring 105.

Figure 1 b depicts a further view of a radiotherapy device according to the present disclosure. While Figure 1a may depict a radiotherapy device 120 from a longitudinal end of the radiotherapy device 120, Figure 1 b may depict a radiotherapy device 120 from a lateral side of the radiotherapy device 120. In other words, Figure 1b may depict a side profile of the radiotherapy device 120. From this view, it can be seen that the radiation source 100 is disposed on a support arm 114, which may connect the radiation source 100 to the gantry 104. The detector 102 is disposed on a support arm 116, which may connect the detector 102 to the gantry 104. In the example depicted in Figure 1b, the slip ring 105 is be disposed on the opposite side of the gantry to the radiation source 100, detector 102 and support table 110. However, in other examples the slip ring may be disposed on the same side of these components (i.e. of the front of the gantry) or may disposed within the gantry itself. In alternative examples, this slip ring may be disposed in any configuration that causes it to be concentric with the gantry.

Figure 1c depicts an example radiotherapy device 120 in accordance with the configuration of Figure 1 b. The radiotherapy device comprises an outer housing 130 which houses the gantry 104 and the slip ring 105 mounted to the gantry. The housing may be considered as a ‘stator’ element of the radiotherapy device 120, since the housing does not rotate as the gantry rotates. In other words, the gantry and slip ring are configured to rotate within the housing about an axis of rotation extending through the centre of the gantry in an axial direction. The gantry may be considered as a‘rotor’ structure of the radiotherapy device 120, since the gantry rotates with fixed to the fixed stator element of the device.

Housing 130 further comprises a printed circuit boards (PCBs) 132 and 134 connected to a fixed control system module 140. The PCBs 132 and 134 comprise brushes 136 and 138 respectively which are configured to maintain contact with a bearing surface on the outer surface of the slip ring 105 as the slip ring rotates. The brushes and the bearing surface of the slip ring are electrically conductive and the brushes are positioned to be in electrical contact with the slip ring. The brushes are configured to transmit electrical signals to the slip ring through the electrical contact. Alternatively or additionally, the brushes may be configured to receive electrical signals from the slip ring. The electrical signals are communicated between the control system module 140 and one or more of the components fixed on the gantry 104, for example the radiation source 100 or the detector 102. The communication between the stator element and the rotor element of the radiotherapy device is enabled by the electrical connection between brushes 136 and 138 and the slip ring 105.

It may therefore be considered that the radiotherapy device 120 illustrated in Figure 1c comprises a communication system comprising slip ring 105 and brushes 136 and 138 for transmitting and receiving electrical signals between a stator and rotor element of the device. In this example, the radiotherapy device 120 comprises two brushes contacting the slip ring 105, however the device may instead comprise one brush or any other number of brushes in electrical contact with the slip ring and connected to the control system module 140.

The control system module may be comprised within the housing 130 or may be a separate module connected to the radiotherapy device via a wired or wireless connection. The control system module may be able to control some or all of the functions of the radiotherapy device 120. For example, the control system module may be able to control the radiation source via control signals transmitted through the brushes 136 and 138 to the slip ring 105. In some examples, the control system may be able to receive feedback signals from the rotor element of the radiotherapy device 120. For example, the control system module may be able to receive data signals from detector 102, the data signals transmitted through the slip ring 105 to brushes 136 and 138 connected to the control system.

In some examples, there may be a plurality of control system modules within the housing or connected to the radiotherapy device. In these examples, each control system module may be dedicated to a different function of the radiotherapy device.

In some examples, the rotor element of the radiotherapy device 120 may have a second slip ring that is concentric with slip ring 105 and gantry 104. Additionally, the stator element may comprise a corresponding second set of PCBs and brushes that maintain electrical contact with the second slip ring. In these examples, the second slip ring and brush arrangement may be configured to transmit power to the components fixed on the gantry 104. Thus, in these examples, the radiotherapy device comprises; a first connection system comprising the slip ring 105 and brushes 136 and 138, the first communication system configured to transmit and receive control and data signals between the rotor and stator elements of the device; and further comprises a second communication system comprising the second slip ring and second set of brushes, the second connection system configured to transmit power from the stator element to the rotor element of the radiotherapy device.

Slip ring

With respect to Figure 2a, a slip ring according to examples known in the art is illustrated.

As described above, it is essential that contact is maintained between the sip ring and the brushes to avoid a break in communication between the stator and the rotor. In order to maintain contact, the slip ring bearing surface must be smooth and devoid of irregularities.

A known way of achieving this result is to form the slip ring out of a single piece of electrically conductive material, such as copper, constructed as a single seamless ring (either platter or drum).

Whilst this method works well for slip rings used in small connection systems, it is much more difficult to manufacture a slip ring out of a single piece of material for larger slip rings, such as those used in radiotherapy systems with a radiation source mounted on a rotating gantry. In such a system, the slip ring is typically required to be large enough to receive a patient through the centre, which means the slip ring is of the order of 1 metre in diameter or more. It is impractical to build a slip ring of this diameter out of a single piece of material in terms of transportation and fitting the ring into a system in a hospital. Furthermore, a slip ring of this size would not have the required fault tolerances needed for a complex and high precision radiotherapy system, and would also be expensive and difficult to manufacture.

One solution to these issues is to build large slip rings out of individual arcuate sections that can be connected together end-to-end to form the entire ring. Multiple smaller sections can be transported far more easily than a single large ring. For example, multiple sections can be transported separately to a hospital treatment room and the slip ring can be built in situ. Furthermore, each section can be manufactured with the required mechanical tolerances.

Another solution is to build one singular long section that may be transported either flat or rolled up, so that it may be taken through narrower constraints than it could as one seamless ring. The slip ring can be formed in situ from the single section by bending the section to form a ring, such that opposite ends of the section meet and are connected at a connection interface. In this solution the slip ring will have a single connection interface between opposite ends of the section. This solution would present fewer gaps between arcuate segments than a slip ring made of several sections.

An example of a known slip ring is illustrated in Figure 2.

This slip ring is an example of a slip ring 105 used in the radiotherapy device 120 of Figures 1a - 1c. The slip ring 200 has a bearing surface on the outer surface for contacting brushes such as those described with reference to Figure 1c. The slip ring 200 comprises arc-shaped sections 210, 220, 230 and 240. An end of each section is placed adjacent to an end of another segment to form a circular ring. In other words, the slip ring 200 comprises arcuate sections 210, 220, 230 and 240 that are connected end-to-end to form the slip ring. In other words, the arcuate sections of the slip ring are connected together at the ends of the sections to form a ring. It may thus be said that the arcuate sections are connected in series. The sections are connected at connection interfaces 215, 225, 235 (not shown), and 245. As described in more detail below, the ends of each section are orthogonal to a circumferential direction around the slip ring and are parallel to the axial direction (illustrated by line X-X).

The sections are thus joined at connection interfaces that are parallel to the axial direction and orthogonal to the circumferential direction at the connection interface. The

circumferential direction can also be considered as the rotation direction of the slip ring. In a connection system, the slip ring may be configured to rotate in the rotation direction whilst a brush in electrical contact with the slip ring is fixed in place relative to the slip ring.

Alternatively, the slip ring may be fixed in place whilst the brush is configured to travel around the circumference of the slip ring in the rotation direction.

Figure 2b provides a more detailed illustration of section 210, and Figure 2c illustrates a plan view of the section, as viewed from above. Section 210 comprises a bearing surface 216 on the outer surface, a first end 212 and a second end 214 at the opposite end of the section to the first end. The bearing surface 216 extends between the ends 212 and 214 of the section. In other words, the bearing surface edges are at the ends of the sections. Arrow 222 indicates a longitudinal direction along the length of the section which follows the arcuate curvature of the section. In other words, the arrow 222 indicates a circumferential direction or rotation direction of the slip ring on the bearing surface. Arrow 224 indicates a lateral direction across the width of the section that is orthogonal to the longitudinal or

circumferential direction (arrow 222). In other words, arrow 224 represents an axial direction of the slip ring parallel to line X-X in Figure 2a. The line X-X represents the axial direction of the slip ring and lies along the centre axis of the slip ring about which the slip ring is configured to rotate.

The rotation direction 222 indicates the direction of brush travel over the bearing surface of the slip ring when the slip ring is used in a rotor and stator connection system arrangement. As the slip ring rotates about its central axis, the brushes fixed to the stator element in contact with the bearing surface effectively travel around the circumference of the slip ring in the rotation direction. This is because the brushes remain fixed whilst the slip ring rotates, and so from the reference frame of the slip ring, the brushes travel around the circumference of the slip ring. The rotation direction 222 that indicates either the actual brush travel direction (if the brushes rotate around a stationary slip ring) or the effective brush travel direction (if the brushes are stationary and the slip ring rotates) may be referred to as the brush travel direction.

Alternatively, the brushes may be fixed to the rotor and the slip ring may remain stationary, in which case the brushes in contact with the bearing surface of the slip ring actually do travel in a circumferential direction around the slip ring.

As can be seen in Figures 2b and 2c, the first and second ends (212 and 214) of the sections of the slip ring known in the art are straight edges that are orthogonal to the circumferential direction 222 and are parallel to the axial direction 224. In other words, from this plan-view perspective, the sections of the slip ring known in the art have a rectangular profile. It would therefore be appreciated that in a flattened form (i.e. the arcuate curvature of the section is straightened out), the sections have a rectangular profile and the bearing surface 216 on the outer surface equally also has a rectangular profile. This means that the edges of the bearing surfaces are orthogonal to the rotation direction of the slip ring.

Accordingly, the connection interface 215 between adjacent sections 210 and 220 in figure 2A lies along a line parallel to the axial direction (parallel to line X-X). This is illustrated in Figure 2d which shows adjacent sections 210 and 220 as viewed from the side of the slip ring and looking in an inward radial direction. The axial direction is indicated by arrow 224 and it can be seen that the connection interface 215 lies parallel with the axial direction. The brush travel direction is indicated by arrow 222. The brushes extend width-wise across the slip-ring, and are orientated along the axial direction. In other words, the brushes extend in the lateral direction across the width of each section of the slip ring. Therefore the brushes are perpendicular with the direction of travel and are parallel to the axial direction. The brushes are therefore parallel with the connection interface. As discussed above, at the connection interface between adjacent sections there may be a small gap that a brush has to travel over as it travels from one section to the next, due to mechanical tolerances in the manufacture of the sections.

Figure 2e depicts another view of the sections 210 and 220 of a known multi-section slip ring. The view illustrated in Figure 2e is looking at the connection interface along the axial direction. From this view of the connection between the adjacent sections, an interface PCB 226 can be seen which connects the two sections 210 and 220. The interface PCB 226 may perform the function of physically and electrically connecting the adjacent sections of the slip ring. The interface PCB and the physical and electrical connection between adjacent sections is discussed in more detail with respect to Figure 5. In this example the bearing surface 216 that contacts with brushes is on the outer surface of the sections 210 and 220. In other words, the bearing surface faces radially away from the centre of the slip ring. It would be appreciated that in other examples, the bearing surface may be on the inner surface (facing radially inwards).

This figure further illustrates a brush PCB 250 comprising a brush 260 in electrical contact with the bearing surface 216. The brush travel direction is indicated the dashed arrows which follow the circumferential direction around the circumference of the slip ring. A closer view of the connection interface 215 between the two sections illustrates the gap across which the brush must travel as it travels in the circumferential direction with respect to the slip ring. As explained above, the brushes are orientated along the axial direction and therefore extend across the width of the sections of the slip ring. The brushes are orientated parallel to the connection interface and so the brush is only in contact with one section of the slip ring at a time. The brush travels from one section to the next, over the interface. As discussed above, the gap may be sufficiently large enough, due to the mechanical tolerances in the manufacture of the slip ring, such that the brush loses electrical contact with the bearing surface of both sections as the brush travels across the gap at the connection interface. There may therefore be a temporary loss in transmission of signals or power between the brush and the bearing surface, which may be undesirable in many practical applications of a multi-section slip ring.

Accordingly, one issue with the known methods of building a multi-section slip ring is that at small gaps may be present between the bearing surfaces of adjacent sections when the sections are joined together. The gaps arise due to production tolerances in the slip ring sections and other elements of the rotor/stator to which the ring is attached. The gaps between the bearing surfaces can cause problems because the electrical contact between the slip ring and the brushes is interrupted as the brush passes over the connections, thus interrupting the connection between the stator and the rotor.

Embodiments of the present disclosure seek to address the problem of connection loss as the brush passes over the connection interface between slip ring sections.

Figure 3a illustrates a slip ring according to some embodiments of the present disclosure.

Slip ring 300 comprises arcuate sections 310, 320 330 and 340 which are connected in series to form the ring. The sections 310, 320, 330 and 340 are connected end-to-end, that is to say, connected in series, at connection interfaces 315, 325, 335 and 345 as illustrated. In this embodiment, the slip ring comprises four arcuate sections. However, the embodiments disclosed herein are equally applicable to a slip ring comprised of any number of sections.

For example, the slip ring may comprise of two semi-circular shaped sections. In some embodiments, the slip ring comprises six arcuate sections connected in series.

The figures and description herein generally refer to a slip ring comprising two or more sections connected end-to-end, that is to say, connected in series. However, it would be appreciated by the skilled person that embodiments of the present disclosure additionally extend to slip rings comprised of a single section. As an example, in some embodiments of the invention, the slip ring comprises a single section that is wrapped around to form a circle, and there exists a connection interface between the opposite ends of the section where the ends of the section are joined to form a ring. In these embodiments in which the slip ring comprises a single arcuate section, the term‘connected end-to-end’ would necessarily be understood to mean that the opposite ends of the single section are connected together to form a ring such that the section forms a ring. In other words, the single section is still connected end-to-end to form the slip ring. Additionally, it may be considered that in these embodiments, the term‘adjacent sections’ refers to the opposite ends of the section that are adjacent to one another when the opposite ends are joined to form the ring. In these embodiments, adjacently connected ends would necessarily be understood to refer to the opposite ends of the section that are connected together to form the slip ring.

In embodiments of the present disclosure in which the slip ring comprises a single section, the opposite ends are connected together similar to adjacent sections in a multi-section embodiment, such that the ends of the section are connected at an intersection region in which both of the bearing surfaces at the adjacently connected ends of the section intersect a line orthogonal to the rotation direction of the ring.

Embodiments of the present disclosure generally relate to a slip ring comprising one or more arcuate sections connected in end-to-end. However, it would be apparent to the skilled person that embodiments of the invention would work in other connection systems comprising a moving element electrically connected to a static element. For example, embodiments of the invention can relate to a brush electrically connected to and travelling along a flat track, wherein the flat track comprises a plurality of flat sections connected in series (connected end-to-end). The connection interfaces according to embodiments described below may be equally be applicable to any such track comprising a plurality of sections connected together, or a single section that has opposite ends connected together.

Line X-X indicates the axial direction of the slip ring and extends through the centre of the annular opening of the ring. In practical applications of the slip ring, for example if the slip ring is part of a rotor in a rotor and stator connection system, the slip ring is configured to rotate about line X-X. Alternatively, in some other practical applications, the slip ring is fixed and one or more brushes in electrical contact with a bearing surface of the slip ring are configured to rotate about line X-X and thus travel in a rotation direction around the circumference of the slip ring.

As can be seen from Figure 3a, and in contrast to the slip ring known in the art illustrated in Figure 2a, the connection interfaces are not parallel with respect to the axial direction and are not orthogonal with respect to the circumferential direction at the connection interface. In other words, the edges of the bearing surfaces of the slip ring sections are not orthogonal to the rotation direction of the slip ring. The connection interface and arcuate sections according to some embodiments of the present disclosure are discussed in more detail below.

Figure 3b provides a more detailed illustration of section 310 of Figure 3a, and Figure 3c illustrates a plan view of section 310 (viewed from above and looking radially inwards).

Section 310 comprises a bearing surface 316 on the outer surface, a first end 312 and a second end 314 at the opposite end of the section to the first end. The bearing surface extends between the ends 312 and 314 of the section, meaning that 312 and 314 indicate the edges of the bearing surface 316. Arrow 322 indicates the circumferential (longitudinal) direction along the length of the section which follows the arcuate curvature of the section. Arrow 322 therefore indicates the rotation direction of the slip ring. Arrow 324 indicates a lateral direction across the width of the section that is orthogonal to the rotation direction 322. It would be understood therefore that arrow 324 represents the axial direction of the slip ring and is therefore parallel to the line X-X illustrated in Figure 3a.

Analogous to Figures 2a - 2d, the rotation direction 322 of Figures 3a-3d indicates the direction of brush travel over the bearing surface of the slip ring when the slip ring is used in a rotor and stator connection system arrangement. As the slip ring rotates about its central axis, the brushes fixed to the stator element in contact with the bearing surface effectively travel around the circumference of the slip ring in the rotation direction. This is because the brushes remain fixed whilst the slip ring rotates, and so from the reference frame of the slip ring, the brushes travel around the circumference of the slip ring. As discussed above, the actual brush travel direction (if the brushes rotate around a stationary slip ring) or the effective brush travel direction (if the brushes are stationary and the slip ring rotates) is referred to as the brush travel direction.

In the embodiment illustrated in Figures 3a, the first and second ends (312 and 314) of the sections 310, 320 330 and 340 are angled with respect to the axial direction 324 and the circumferential direction 322. In other words, the edges of the bearing surfaces of these sections are not orthogonal to rotation direction 322. Instead, the edges of the bearing surfaces at 312 and 314 are angled at an acute angle with respect to the rotation direction 322. The embodiment illustrated in Figure 3c demonstrates that section 310 has the profile of a parallelogram in a plan-view perspective. In other words, if section 310 was flattened (i.e. the arcuate curvature was straightened), the section, and the bearing surface on the outer surface of the section, would have a parallelogram profile. In other embodiments, the ends of the sections of the slip rings are angled so as to give the section a trapezoid profile. Due to the non-rectangular profile of the sections, the connection interface 315 between adjacent sections 310 and 320 in Figure 3A lies along a line that is not parallel to the axial direction (line X-X) and is not orthogonal to the circumferential direction 322. This is illustrated in more detail in Figure 3c and 3d which show adjacent sections 310 and 320 as viewed in the plane of the slip ring and looking in an inward radial direction. In this figure, it can be seen that the connection interface 315 between sections 310 and 320 lies at an angle with respect to the axial direction. In other words, the adjacent sections, or adjacently connected ends, overlap along the axial direction at the connection interface. The overlap of sections 310 and 320 at the connection interface 315 is demonstrated by the arrow indicating the axial direction 324 at the connection interface. It can be seen that the adjacent sections are overlapping in the axial direction at the respective connecting ends of the sections. The overlapping region, i.e. the region in which the adjacent sections overlap in the axial direction, is indicated by dashed box 328.

In other words, dashed box 328 indicates an intersection region at the connection between the two adjacent sections 310 and 320. Within the overlapping region, a line that lies on the surface of either section and that lies orthogonal to the rotation direction 322 will cross over both the bearing surface of section 310 and the bearing surface of section 320. In other words, a line in that is orthogonal to the rotation direction would intersect the bearing surfaces of both sections in the intersection region 328.

A brush extending across the width of the bearing surface of the sections of the slip ring (the width of the bearing surface being the extension of the bearing surface in the axial direction 322) and travelling along the bearing surface in the travel direction 322 would therefore be in electrical contact with both sections 310 and 320 when the brush travels through the intersection region 328. In other words, the sections are configured such that at the connection interface between adjacent sections the bearing surfaces of the adjacent sections overlap along the axial direction. The sections are therefore configured such that a brush travelling in the brush travel direction (the rotation direction 322) will be in electrical contact with the bearing surfaces of both sections 310 and 320 as the brush travels across the connection interface 315 in the intersection region 328.

Furthermore, a brush travelling in the brush travel direction will also be in mechanical contact with the bearing surfaces of both sections as the brush travels across the connection interface 315. In other words, the brush will always be in mechanical contact with at least one of the sections of the slip ring at any time as the brush travels around the circumference of the slip ring. A further advantage of embodiments of the present disclosure is that the brush is not subject to any unnecessary mechanical force as the brush loses and then regains contact with the bearing surface, since the brush is always in mechanical contact with the bearing surface of the slip ring, even as it passes from one section to the next.

This contrasts examples known in the art in which the brush loses electrical and mechanical contact as it passes over the gap between adjacent sections or adjacently connected ends of the sections. In these examples, a mechanical force is applied to the brush as it resumes contact with the bearing surface, causing the brush to oscillate and therefore subsequently lose contact with the surface again. The present disclosure therefore mitigates this effect since the brush does not leave electrical or mechanical contact with the slip ring in the first place.

It would therefore be appreciated that despite the presence of a gap between the sections, a brush will maintain electrical contact with at least one of the sections of the slip ring through a 360° rotation of the slip ring (or alternatively a 360° rotation of the brush around the slip ring), thus mitigating the connection-loss issues that are caused by the gap.

Figure 3e depicts another view of the sections 310 and 320 of a slip ring according to embodiments of the present disclosure. The view illustrated in Figure 3e is looking at the connection interface of the sections along the axial direction, similar to the view depicted in Figure 2e for sections of a slip ring known in the art. From this view of the connection interface 315 between the adjacent sections 310 and 320, an interface PCB 326 can be seen which connects the two sections. The interface PCB may perform the function of physically and electrically connecting the adjacent sections of the slip ring. The interface PCB and the physical and electrical connection between adjacent sections is discussed in more detail with respect to Figure 5. In this example the bearing surface 316 that contacts with brushes is on the outer surface of the sections 310 and 320. In other words, the bearing surface faces radially away from the centre of the slip ring. It would be appreciated that in other examples, the bearing surface may be on the inner surface (facing radially inwards).

This figure further illustrates a brush PCB 350 comprising a brush 360 in electrical contact with the bearing surface 316. The brush travel direction is indicated the dashed arrows which follow the circumferential direction around the circumference of the slip ring. A closer view of the connection interface between the two sections depicts the overlap region by dashed box 328, and shows how the overlap in the axial direction of the bearing surfaces of adjacent sections 310 and 320 mitigates the issues caused by the gap between the sections. In particular, in the closer view of the connection interface, shaded area 332 represents a gap at the connection interface between sections 310 and 320 at a near side of the sections, whereas shaded area 334 represents the gap at a far side of the sections. A brush 360 in electrical contact across the width of the sections therefore will always be in contact with at least either section 310 or 320 as it travels across the connection interface. In other words, problems with loss of connectivity as the brush passes over the gap between the sections is mitigated by the bearing surfaces of the sections being configured to overlap in the axial direction, such that when the brush passes over the gap, at least one part of the brush will at least be in contact with either section 310 or 320, or both.

Figures 3a - 3e illustrate one exemplary embodiment of the present disclosure wherein the overlap of the bearing surfaces of adjacent sections is caused by the ends of the sections being angled with respect to the circumferential and axial directions as illustrated. In other words, the edges of the bearing surfaces are angled relative to the rotation direction at the ends of the sections. However, it would be appreciated that the overlap between adjacent sections can be caused by other configurations of the sections and the bearing surfaces of the sections. In other words, embodiments of the present disclosure extend to any configuration of the sections wherein the bearing surfaces of adjacent sections overlap along an axial direction.

Figures 4a - 4c illustrate sections of a slip ring 410 and 420 according to other exemplary embodiments of the present disclosure. These figures illustrate slip ring sections from a plan-view perspective, similar to Figures 2c and 3c and illustrates the bearing surface 416 on the outer surface of the sections. According to these embodiments, the slip ring section 410 comprises joining portions at the ends which provide an overlap of the bearing surfaces of adjacent sections along the axial direction, such that when a brush travels over the connection interface between the adjacent sections, the brush will always be in electrical contact with at least one of the sections. In other words, the bearing surface edges at the end of each of the sections 410 and 420 are not orthogonal to the rotation direction (indicated by arrow 430). According to the embodiment illustrated in Figure 4a, the ends of each section 410, 420 comprise at least one protruding portion 412, 422 and at least one recessed portion 414, 424 configured to receive the protruding portion of an adjacent section. Arrow 430 indicates the rotation direction (the brush travel direction) and arrow 440 indicates the axial direction of the slip ring.

In some embodiments, each section may have a plurality of recessed portions and a plurality of protruding portions at the ends of the section, wherein the recessed and protruding portions alternate side-by-side so as to form a castellated edge. The recessed portions of each section may be configured to receive the corresponding protruding portions of an adjacent section so as to form an overlap of the bearing surfaces along the axial direction.

Figure 4b illustrates a closer view of the sections 410 and 420 of Figure 4a when these sections are connected in end-to-end to form the slip ring. In this figure, it can be seen that the protruding portion 412 of section 410 is received within the recessed portion 424 of section 420. Similar to the illustration of figure 3d, dashed box 428 indicates an intersection region at the connection between the two sections. Within the intersection region, a notional line that lies orthogonal to the rotation direction 430 and lies in the plane of the bearing surface of either section will intersect and cross over the bearing surfaces of both sections, since the protruding portion 412 and recessed portions 424 are overlapping along the direction of the notional line. In other words, a line that is orthogonal to the rotation direction would intersect the bearing surfaces of both sections in the intersection region. It may be considered that arrow 440 represents the notional line that is orthogonal to the rotation direction 430. It can be seen from figure 4b that arrow 440 within the intersection region 428 intersects and crosses over both sections 410 and 420.

According to the embodiment illustrated in Figure 4c, each section comprises a stepped portion at the ends of the section configured to receive a corresponding stepped portion of an adjacent section to provide an overlap of the bearing surfaces along the axial direction. In the illustrated embodiment, it can be seen that the stepped portion comprises 3‘steps’, however it will be appreciated that the overlap along the axial direction between adjacent sections can be achieved using a stepped arrangement comprising any number of 1 or more steps.

In the embodiments illustrated in Figures 4a - 4c, the protruding portions, recessed portions and stepped portions comprise square edges. However, it will be apparent to the skilled person that the overlap along the axial direction between adjacent sections can equally be achieved using rounded-off edges to the protruding, recessed and stepped portions, or any other such edge. Accordingly, embodiments of the invention extend to any arrangement wherein the adjacently joined sections are configured to cause the respective bearing surfaces to overlap along the axial direction. In other words, embodiments of the invention extend to any arrangement wherein the edges of the bearing surfaces of adjacently joined sections are not orthogonal to the rotation direction, such that there exists an intersection region in which a line orthogonal to the rotation direction would intersect the bearing surfaces of both sections. Figure 5 illustrates an interface PCB according to some embodiments of the present disclosure. The slip ring sections 310 and 320 are joined together at the ends of the sections via an interface PCB 510. The interface PCB is joined to the sections on a surface of the sections different to the bearing surface.

Interface PCB 510 comprises a first joining portion comprising fasteners 512 and 514 that fasten section 310 to the interface PCB 510. The fasteners cause the interface PCB to be attached to the section 310, and may also be in electrical contact with the section 310. Specifically, the fasteners 512 and 514 may be in electrical contact with the bearing surface of the section 310.

Interface PCB 510 further comprises a second joining portion comprising fasteners 516 and 518 that fasten section 320 to the interface PCB 510. The fasteners cause the interface PCB to be attached to the section 320 and may also be in electrical contact with the section 320. Specifically, the fasteners 516 and 518 may be in electrical contact with the bearing surface of the section 320.

Fasteners 512, 514, 516 and 518 may be any type of fastener apparent to the skilled person that is suitable for physically and electrically connecting the slip ring sections to the interface PCB. In some embodiments, the fasteners are pogo pins.

The first joining portion and second joining portion of the interface PCB are also in electrical contact, so as to cause sections 310 and 320 to be in electrical contact via the interface PCB. In the illustrated embodiment, the interface PCB comprises an electrically conductive portion 522 connecting fasteners 512 of the first joining portion and 516 of the second joining portion, and further comprises an electrically conductive portion 524 connecting fasteners 514 of the first joining portion and 518 of the second joining portion. In some embodiments, the portions 522 and 524 may be an electrically conductive rail or wire or any other arrangement capable of connecting the fasteners of the first and second joining portions.

It will be understood that interface PCB may be used to connect any adjacent sections of the slip ring. Accordingly, adjacent sections of the slip ring are connected together and are in electrical contact via the interface PCB, and specifically via the fasteners 512, 514, 516, 518 and portions 522 and 524 of the interface PCB.

In the illustrated embodiment, first and second joining portions each comprise 2 fasteners however embodiments of the present disclosure extend to interface PCBs comprising any number of 1 or more fasteners. Furthermore, embodiments of the invention extend to any connecting arrangement that causes adjacent slip ring sections to be connected and in electrical contact with one another.

Embodiments of the present disclosure are directed to slip rings and sections of slip rings wherein the bearing surface that contacts a brush is on the outer surface of the slip ring. In other words, some embodiments are directed to slip rings comprising multiple sections with bearing surfaces that face radially away from the centre of the slip ring. In these

embodiments, the brushes travel around the outside of the slip ring.

In some other embodiments, the bearing surface of each section is on an inner surface (i.e. on a surface of the section that faces radially inwards towards the centre of the slip ring). In these embodiments, the brushes travel around the inside of the slip ring.

In yet further embodiments, the bearing surface of each section is on a side-facing surface of the section. In other words, the bearing surface is on a surface that faces along an axial direction of the slip ring. It may therefore be said that in these embodiments the bearing surface lies in the plane of rotation of the slip ring, or in the plane within which the brushes rotate around the slip ring.

Figure 6 illustrates another arrangement according to some embodiments of the present disclosure. In this embodiment, sections of the slip ring 610 and 620 have straight, squared edges that are parallel to the axial direction of the slip ring indicated by arrow 624. The sections according to these illustrated embodiments are similar to those illustrated in Figures 2a - 2e. The edges are therefore orthogonal to a circumferential direction (indicated by arrow 622) around the slip ring. The circumferential direction 622 also indicates the brush travel direction as brushes travel around the circumference of the slip ring. Since the connection interface is orthogonal to the brush travel direction 622, the connection interface 615 between the sections 610 and 620 is parallel to the axial direction 624 of the slip ring, similar to examples illustrated in figures 2a - 2e.

The embodiment illustrated in Figure 6 further comprises at least one brush 625 in electrical contact with the bearing surface of the sections of the slip ring. The brush is configured to travel along the circumferential direction (the brush travel direction 622) around the circumference of the slip ring. In this embodiment, as can be seen from the figure, the brush 625 is angled with respect to the rotation direction 622 and the axial direction 624. In other words, in contrast to the examples described with reference to figures 2a - 2e, the brush 625 is orientated in such a way that it is not parallel to the connection interface between 615 between adjacent sections 610 and 620. Therefore, the brushes are not parallel to the axial direction and are not perpendicular to the direction of travel 622. Since the brushes are not parallel with the connection interface, as the brush travels over the connection interface it is possible for the brush to simultaneously maintain electrical contact with both sections 610 and 620. Therefore the brush will not lose electrical contact with the slip ring as it passes over a gap at the connection interface between adjacent sections, since the brush will be in contact with at least one section at any time. Features of the above aspects can be combined in any suitable manner. It will be understood that the above description is of specific embodiments by way of aspect only and that many modifications and alterations will be within the skilled person’s reach and are intended to be covered by the scope of the appendant claims. For example, the skilled person would appreciate that the embodiment of the angled section edges illustrated in figures 3a - 3e or Figures 4a - 4c could be combined with the angled brush embodiment illustrated in figure 6.