WO2013030563A1

WO2013030563A1 - Improved slip ring apparatus and method of manufacturing a slip ring

Info

Publication number: WO2013030563A1
Application number: PCT/GB2012/052106
Authority: WO
Inventors: David Watkins
Original assignee: Overview Ltd
Current assignee: Overview Ltd
Priority date: 2011-08-26
Filing date: 2012-08-28
Publication date: 2013-03-07
Anticipated expiration: 2014-02-26

Abstract

A slip ring apparatus is provided comprising a first component having a first conductive element and a second component having a second conductive element. The first component comprises first electronic circuitry which is connected to the first conductive element via a first conductive link having a predefined constant length. The first and second components are rotatable relative to each other. The first and second conductive elements are in electrical communication with each other during rotation of the first and second components relative to each other.

Description

Improved Slip Ring Apparatus and Method of Manufacturing a Slip Ring

Field of the Invention

The present invention relates to a slip ring apparatus for conveying high bandwidth signals.

Background of the Invention

It is known that slip rings provide electrical continuity through a continuously rotating mechanical joint and, in their simplest form, use a gold alloy brush wire resting in a grooved ring, with as many rings as the circuit needs i.e. one for each signal or power path.

Even when the brush and ring are very small, the impedance of the brush and ring can be significantly different from that of rest of the circuitry surrounding the slip ring assembly.

Additionally, the impedance varies as the ring rotates because the static connection to each ring is made at one point, and as the ring rotates, the path length from that point to the point where the brush wire(s) contacts the ring varies.

There is a growing need to convey high bandwidth signals greater than 1 GHz through slip rings whilst maintaining the signal quality; this is very difficult due to the interference that is introduced into the signal from the slip ring as it rotates, principally due to the variation in impedance (as explained above). Furthermore, the connection to the rings is made with wire which forms a bundle and this bundle is not defined. Hence, the wires will lie differently between slip rings from the same production batch and the performance will not be constant throughout a batch. Where performance is marginal, error correction can be used, but this involves additional complex circuitry and/or signal processing of signals within the slip ring itself.

Known slip rings are described in US 5952762 A and WO 93/06573 A1. However, whilst there have been some efforts to achieve impedance matching and amplification before transmission through a slip ring to reduce slip ring noise, none of these efforts achieves the elimination of the effect of a slip ring-brush pair on very high frequency signals.

Slip ring assemblies are mechanical arrangements of concentric rings in a stack with each ring separately connected to a wire. Often, all of the wires in the slip ring are bundled through the bore of the slip ring stack to the outside of the assembly. Individual spring wires are then arranged to bear on the outside diameter surface (normally grooved) of each slip ring in the stack, and again are connected to individual wires which are bundled to the opposite end of the assembly.

The slip ring stack and the assembly of brush wires are arranged to rotate relative to each other. As many separate signals can be passed through a rotating mechanical coupling joint as there are pairs of brush wires and slip rings. As a result, slip rings can be assembled in many ways, but all are labour intensive.

It is one purpose of an aspect of the present invention to provide a new slip ring apparatus which permits the manufacture of each complete slip ring apparatus to be automated.

Summary of the Invention

The slip ring apparatus of the present invention is designed to overcome these and other problems.

In view of the foregoing and in accordance with a first aspect of the invention, there is provided a slip ring apparatus comprising:

a first component having a first conductive element; and

a second component having a second conductive element,

wherein the first component comprises first electronic circuitry connected to the first conductive element via a first conductive link having a predefined constant length,

wherein the first and second components are rotatable relative to each other, and wherein the first and second conductive elements are in electrical communication with each other during movement (e.g. rotation) of the first and second components relative to each other.

Connecting the first electronic circuitry to the first conductive element via a first conductive link having a predefined constant length provides an advantage that changes in impedance as a result of changes in signal path length due to the rotation of the first component and the second component relative to each other can be quantified, and ultimately minimised. This means that high bandwidth signals, which would otherwise have been badly affected by changes in impedance, can be conveyed through the slip ring apparatus with a defined signal distortion, which can then be minimised. In one embodiment of the present invention, the first and second conductive elements are in continuous electrical communication with each other during movement of the first and second components relative to each other. This ensures that signals can be passed/transmitted between a fixed (e.g. non-rotating) component of the apparatus to a moving (e.g. rotating) component of the apparatus.

Preferably, the first conductive link is wholly within a body of the first component. This ensures that the signal distortion along the conductive link is reduced by keeping the link wholly within the moving component of the slip ring.

Moreover, the first component may comprise:

a first substrate on which the first electronic circuitry is mounted,

wherein the first electronic circuitry may comprise a first buffer which is in electrical communication with the first conductive element,

wherein the first buffer may be electrically connected to the first conductive element via the first conductive link.

In a preferred embodiment, the first substrate is contained wholly within (a body of) the first component, and the substrate is a circuit board on which the buffer is mounted.

The apparatus can further comprise a plurality of first conductive elements and a plurality of corresponding first conductive links. The apparatus can also then further comprise a plurality of buffers, wherein each conductive link connects a corresponding conductive element to a corresponding one of the plurality of buffers. This permits the apparatus to transmit a plurality of signals independently between the first and second components.

Preferably, each first conductive element is electrically connected to the first electronic circuitry via a corresponding first conductive link of substantially constant (and known) length.

Advantageously, the length of the conductive links in the plurality of first conductive links can be substantially equal. This minimises the signal distortion across the plurality of links and ensures that any such distortion is known, and quantified.

In a preferred embodiment of the invention, the length of each first conductive link is less than 50mm, 40mm, 30mm, 25mm, 20mm, 15mm, 10mm or 5mm. In an additional advantageous embodiment of the invention, the second component comprises second electronic circuitry connected to the second conductive element, wherein the second conductive element comprises a second conductive link having a predefined constant length.

Preferably, the second conductive element consists solely of the second conductive link having a predefined constant length.

Moreover, the second component can further comprise:

a second substrate on which the second electronic circuitry is mounted,

wherein the second electronic circuitry comprises a second buffer which is in electrical communication with the second conductive link.

Advantageously, there can be further provided a plurality of second conductive elements and a plurality of corresponding second conductive links wherein, preferably, each second conductive element is electrically connected to the second electronic circuitry and comprises a

corresponding second conductive link of substantially constant length.

Preferably, each second conductive element consists solely of a corresponding second conductive link having a predefined constant length.

Advantageously, the length of all of the conductive links in the plurality of second conductive links is substantially equal.

In a preferred embodiment, the length of each second conductive link is less than 50mm, 40mm, 30mm, 25mm, 20mm, 15mm, 10mm or 5mm. In a preferred embodiment of the invention, a total length of each electrical connection from the first buffer to the second buffer via the first and second conductive links is in the range 10mm to 20mm, 5mm to 25mm, 5mm to 30mm, or 5mm to 40mm during movement (e.g. rotation) of the first and second components relative to each other.

According to a second aspect of the present invention, there is provided a slip ring apparatus comprising:

a first substrate; and

a first conductive connector, wherein the first conductive connector is mounted on the first substrate and connected to the ground plane of the first substrate, and wherein the first substrate is configured to rotate about the first conductive connector. Preferably, the apparatus further comprises a second conductive connector connected to the ground plane of the first substrate, wherein the first and second conductive connectors are mounted on opposing ends of the first substrate.

Preferably, the first substrate is configured to rotate about an axis which passes through the first and second conductive connectors.

Preferably, the apparatus further comprises a conductive track extending between and in electrical communication with the first and second conductive connectors.

Preferably, the conductive track comprises a coaxial cable, and the first and second conductive connectors comprise end-launch coaxial connectors.

Preferably, the first and second conductive connectors are in electrical communication with a fixed component.

Preferably, at least one of the first and second conductive connectors is configured to rotate relative to the fixed component.

Preferably, the first conductive connector is configured to rotate relative to the fixed component, and the second conductive connector is configured not to rotate relative to the fixed component.

Preferably, the first conductive connector is configured to rotate about the axis which passes through the first and second conductive connectors.

Preferably, the conductive track is dimensioned to minimise variation in the impedance of the slip ring apparatus.

In view of the foregoing and in accordance with a third aspect of the invention, there is provided a slip ring apparatus comprising:

a first component having a first conductive element; and

a second component having a second conductive element,

wherein the first and second components are rotatable relative to each other, wherein the first and second conductive elements are in electrical communication with each other during rotation of the first and second components relative to each other, and wherein the first and second conductive elements are located at least partially within the first component. The provision of first and second conductive elements which are located at least partially within the first component allows the manufacture of the slip ring apparatus to be automated. The entire second component (which can comprise a brush wire assembly) can be loaded into the first component (which can comprise a stack of slip rings). The simplified method of manufacture allows easy inspection of the slip ring apparatus at all stages of manufacture, a vital requirement for automatic assembly if machine vision checking is used.

The first component may comprise a plurality of first conductive elements and the second component may comprise a plurality of second conductive elements, wherein each second conductive element may be in electrical communication with a corresponding first conductive element.

Each second conductive element may be located at least partially within an outer perimeter defined by its corresponding first conductive element. Each second conductive element may be located wholly within an outer perimeter defined by its corresponding first conductive element. The second component may be located at least partially within the first component. The second component may be located wholly within the first component.

The first and second conductive elements may be in continuous electrical communication with each other during rotation of the first and second components relative to each other.

Each first conductive element may comprise a conductive ring. Each conductive ring may comprise a groove which extends around the internal diameter of the ring.

The provision of grooved conductive rings allows each second conductive element to be easily and precisely located and retained within its corresponding conductive ring.

Each second conductive element may comprise an arc comprising conductive material. Each second conductive element may comprise two arcs of conductive material. Each arc may comprise a sprung wire element. Each arc may be deformable to permit it to be inserted into the first component.

The apparatus may further comprise means for deforming each arc so that it can be inserted into the first component. The arc of conductive material may comprise two ends, wherein the arc contacts the first conductive element at a contact point adjacent each end. Each arc of conductive material may be sized to fit within a corresponding conductive ring and each arc may be adapted to contact its corresponding conductive ring at at least one contact point. Each arc of conductive material may be adapted to contact the ring at at least two contact points. Each arc may be adapted to sit partially within the groove on its corresponding ring.

The second component may comprise a substrate. The substrate may comprise one or more electrical connections. The substrate may comprise an electrical connector in electrical communication with the one or more electrical connections. The electrical connector may comprise a high-definition video connector. The apparatus may further comprise internal electronic circuitry on the substrate electrically connected to the one or more electrical connections. The substrate may be a printed circuit board (PCB).

Each arc may be connected to the substrate. Each arc may be pre-formed prior to being connected to the substrate. Each arc may pass through the substrate and be fixed to it. Each arc may be soldered to the substrate. Each arc may be connected to an edge of the substrate. Each arc may be electrically connected to a corresponding electrical connection on the substrate.

The fact that each second conductive element may be in the form of an arc does not

necessarily mean that they are curved along their entire length. Each arc can comprise at least one straight portion (i.e. not curved). The straight portion of the arc may be the portion which passes through the substrate, which can be a PCB. It is advantageous for the straight portion of each second conductive element to be perpendicular to the substrate to facilitate subsequent forming of the second conductive elements, which can be carried out on all second conductive elements simultaneously, into their arced form. Alternatively, the second conductive elements can be preformed individually and then soldered individually to an edge of the substrate.

Each first conductive element may provide an electrical connection for connection of the slip ring apparatus to an external electrical device. Each first conductive element may be electrically connected to external electronic circuitry. The electrical connections of the substrate may be connected to the external electronic circuitry via the first and second conductive elements.

The apparatus may further comprise at least one bearing configured for permitting rotation of the first component relative to the second component. The apparatus may further comprise a plurality of location elements for permitting multiple longitudinal fixed positions of the first component relative to the second component to be set. The electrical connector may be an end-launch connector located at one end of the substrate. The end-launch connector may be a rotating connector. The end-launch connector may be a bearing configured for permitting rotation of the first component relative to the second component. The at least one bearing may be located at an end of the substrate. The substrate may further comprise a buried ball joint at an opposite end of the substrate to the end which has the end-launch connector, wherein the buried ball joint locates on an internal bearing spider.

In a fourth aspect of the invention, there is provided a method of manufacturing the slip ring apparatus of any one of the preceding claims, comprising:

providing the first component; and

inserting the second component into the first component such that each first conductive element locates against a corresponding second conductive element.

The second component may be inserted into the first component along substantially a longitudinal axis of the first component / slip ring apparatus.

Each arc of conductive material may be deformed from an undeformed form into a deformed form prior to insertion of the second component into the first component, and then each arc may be returned to its undeformed form when the second component is located within the first component. This deforming may be performed by tooling means. This method may be fully automated.

Brief Description of the Drawings

The invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a perspective view of a first component of a slip ring apparatus according to a first embodiment of the present invention;

Figure 2 shows a perspective view of the second component of the slip ring apparatus of the embodiment shown in Figure 1 ;

Figure 3 shows the slip ring apparatus according to the embodiment of Figures 1 and 2 comprising both the first and second components; Figure 4 shows a schematic view of the electric circuit formed by the slip ring apparatus according to the embodiment of Figure 3;

Figure 5 shows a perspective view of a first component of a slip ring apparatus according to a second embodiment of the present invention;

Figure 6 shows a perspective view of a connector according to the embodiment shown in Figure 5;

Figure 7 shows a perspective view of a first substrate and first and second connectors according to the embodiment shown in Figures 5 and 6;

Figure 8 is a perspective view of a first example of a slip ring according to a third embodiment of the present invention;

Figure 9 is a perspective view of a second example of a slip ring according to an embodiment of the present invention;

Figure 10 is a perspective view of an end housing of a slip ring apparatus according to an embodiment of the present invention;

Figure 1 1 is a perspective view of a plurality of exemplary slip rings according to an embodiment of the present invention arranged in a stack with an end housing and bearing at either end;

Figure 12 is a perspective view of a slip ring apparatus according to an embodiment of the present invention;

Figure 13 is a cross-sectional view of a slip ring apparatus according to an embodiment of the present invention taken at a right angle to the rotation axis;

Figure 14 is a perspective view of an exemplary second conductive element of a slip ring apparatus according to an embodiment of the present invention;

Figure 15 is a perspective view of a substrate and a plurality of second conductive elements of a slip ring apparatus according to an embodiment of the present invention; and Figure 16 is a perspective view of a substrate and a plurality of second conductive elements prior to formation into a slip ring apparatus according to an embodiment of the present invention.

Detailed Description of the Drawings

Figure 1 shows a first component 10 of a slip ring apparatus 100 according to an embodiment of the present invention. Figure 2 shows, according to the same embodiment, a corresponding second component 20 of the slip ring apparatus 100. Figure 3 shows, according to the same embodiment, the first and second components 10, 20 combined together to form the slip ring apparatus 100.

The first component 10 has first conductive elements 14 and the second component 20 has second conductive elements 24. When the first and second components 10, 20 are combined in use (as described below with reference to Figure 3), the first and second components 10, 20 can rotate relative to each other. A given first conductive element 14 is connected to a given corresponding second conductive element 24. Each first conductive element 14 is in electrical, conductive contact with its corresponding second conductive element 24 during the relative rotation of the first and second components 10, 20. The electrical connection between the conductive elements 14, 20 permits an electrical signal to pass from the first component 10 to the second component 20 via a given first conductive element 14 and its corresponding second conductive element 24.

In the exemplary embodiment of the first component 10 shown in Figure 1 , it can be seen that each first component 10 has a body formed of a grooved cylinder 13, itself made up of a plurality of conductive grooved rings 15, separated by insulating rings 15a. Each conductive grooved ring 15 forms a first conductive element 14.

The first component 10 also comprises electronic circuitry 17 which is mounted on a first circuit board 18; in particular the electronic circuitry 17 comprises a corresponding buffer/amplifier 19 for each signal path, such that each buffer/amplifier 19 is connected to a corresponding one of the first conductive elements 14 (i.e. a corresponding grooved ring 15). The electronic circuitry 17 on the first circuit board 18 is contained wholly within the grooved cylinder 13.

Each buffer/amplifier 19 is connected to its corresponding conductive element 14 (i.e. its corresponding grooved ring 15) via a first conductive link 16. Each conductive link 16 has a predefined constant length which is the same or similar for all of the first conductive links, which are also wholly contained within the grooved cylinder 13.

Since the first conductive links 16 have a predefined constant length, and each link is of the same, or similar, length, changes in impedance of the links 16, as a result of changes in signal path length due to the rotation of the first component 10 relative to the second component 20, can be avoided. Hence, high bandwidth signals, which would otherwise have been badly affected by changes in the impedance of the various links, can be conveyed with high precision through the slip ring apparatus 100.

It is advantageous for the buffer/amplifiers 19 to be positioned as close as possible, and/or adjacent to their corresponding first conductive element 14. This means that making each first conductive link 16 as short as possible is desirable. Such a configuration contributes towards eliminating changes in inductance along each conductive link 16, during rotation of the first component 10, thereby making it possible to convey very high frequency signals through the slip ring assembly 100.

Referring now to Figure 2, the second component 20 is shown having a second circuit board 28 (being a part of the second component 20). The second circuit board 28 has electronic circuitry 27 mounted on it. In a similar way to the circuitry 17 for the first component 10, this circuitry 27 includes a buffer/amplifier 29 for each second conductive link 26, and electrically connected thereto. Each second conductive link 26 is preferably made from a conductive metal, such as gold or copper, and is formed as a pair of splayed-apart, sprung arms 26a (each arm is known as a "brush wire") which are dimensioned to locate each side of the first component's grooved cylinder 13, such that the arms sit in the groove of a corresponding grooved ring 15, with a contact point 30 formed on opposing sides of the grooved ring (see Figure 3 described below). Each arm 26a can be formed from any conductive metal, advantageously such as gold or copper.

Figure 3 shows the combined, assembled slip ring apparatus 100 of the present invention with the first and second components 10, 20 combined together such that each second conductive link 26 of the second component 20 is electrically connected to a groove of its corresponding grooved ring 15. The first component 10 and the second component 20 are able to rotate relative to each other. The grooved cylinder 13 of the first component 10 has as many grooves as the apparatus 100 requires to provide a specific number independent signal paths. Each buffer/amplifier 19, 29 has a corresponding input/output (not shown) which connects the input/output of each buffer/amplifier (on the opposing side to its connection to the conductive links 16, 26) to additional electronic components (not shown) that process the signals passed through conductive links 16, 26 of the slip ring apparatus 100. These additional components are fixed relative to one or other of the first and second components 10, 20 of the skip ring apparatus 100.

The contact points 30 of the arms 26a of each second conductive link 26 in its corresponding grooved ring 15 of the first conductive element 14 rotates around the ring 15 as the first component 10 rotates relative to the second component 20. Since the length of each first conductive link 16 is known, and defined with a constant length, the overall length of the entire conductive signal paths between the buffer/amplifiers 19 of the first component 10 and the buffer/amplifiers 29 of the second component 20 changes within a set range which is the same for all of the signal paths. This reduces the signal distortion for each signal path (which would be due to the change in inductance as the first component 10 rotates and the signal path length changes), and the signal interference between all the signal paths (which would be due to different signal paths having different path lengths at different times in the rotation).

Furthermore, by providing the buffers 19 and 29 in very close proximity, i.e. in direct connection with the conductive elements that connect the signal pathways of the components 10, 20, signal distortion can be reduced very close to the point at which it is generated, thereby reducing additional interference that results from the distorted signals interfering with each other across the signal paths (i.e. before the signals reach the additional electronic circuitry at which additional signal processing takes place).

Figure 4 shows a schematic view of an electric circuit 200 formed by the slip ring apparatus 100 according to the embodiment of Figure 3. The circuit 200 shown is the circuit formed between corresponding buffers 19 and 29, with each buffer 19 and 29 having an input/output connecting it to external circuitry (not shown). As can be seen from Figure 4, each buffer 19 is electrically connected via a first conductive link 16 to a corresponding first conductive element 14, which is shown in Figure 4 as a variable inductor. Also shown in Figure 4 are the contact points 30 between arms 26a of the second conductive link 26 and the first conductive element 14. The arms 26a of the second conductive link 26 are connected to a buffer 29.

Figure 5 shows the first component 310 according to a second embodiment of the present invention. As shown in Figure 5, the first component 310 according to the second embodiment of the present invention includes all of the features of the first component 10 according to the first embodiment of the present invention.

Furthermore, in an exemplary embodiment (not shown), the first component 310 according to the second embodiment of the invention is connected to a second component having all the features of the second component 20 of the first embodiment in the manner described above and as shown in Figures 1 to 4.

As shown in Figures 5 and 6, the first component 310 according to the second embodiment of the present invention further comprises a conductive track 350 which extends between a first connector 354 and a second connector 356. The conductive track 350 comprises a coaxial cable which is mounted on the first substrate 352 which, as described above with reference to the first embodiment, is a pcb. In the embodiment shown in Figures 5 and 6, the conductive track 350 is mounted on an opposite surface of the first substrate 352 to the buffers/amplifiers as described hereinbefore. In an alternative embodiment (not shown), the first substrate is a multilayer pcb and the buffers/amplifiers are internal to the first substrate.

The first 354 and second 356 connectors, which are shown in more detail in Figures 6 and 7, are end-launch coaxial connectors which, as shown in Figures 5 and 6, are mounted on first 358 and second 360 edges of the first substrate 352, respectively. In the exemplary

embodiment shown in Figures 5 and 6, the first 354 and second 356 connectors are mounted on opposing edges of the first substrate 352.

The first 354 and second 356 connectors are in electrical communication with the second component, and project from the first substrate 352 at opposing edges of the first substrate 352. One of the first 354 and second 356 connectors rotates with the first component 310 relative to the second component, whereas the other of the first 354 and second 356 connectors is fixed. The one of the first 354 and second 356 connectors which rotates relative to the second 356 component is loosely connected to the second substrate of the second component and rotates about the longitudinal axis of the first component 310.

The conductive track 352 is dimensioned to minimise variation in the impedance of the slip ring apparatus. Figure 8 shows a perspective view of an example of a slip ring 1010 according to another embodiment of the present invention. The ring 1010 has an internal circumferential groove 1012 to guide contact with internal brush wires, and an external circumferential groove 1014 to locate the ring accurately on a rack. The rack has ribs spaced at regular intervals to engage with a number of slip rings for accurate positioning and alignment of the slip rings.

Figure 9 shows a second example of a slip ring 1020 according to an embodiment of the present invention. The ring 1020 is the same as that shown in Figure 8, but has a projection 1022 instead of a groove on the outer diameter for location on an external placement jig. In this case, the rack has grooves spaced at regular intervals to engage with a number of slip rings.

Figure 10 shows an end housing 1030 for a ball bearing having the same location features 1032 (e.g. ribs and/or grooves) as the slip ring to ensure overall accurate positioning. Paired ball bearings at opposite ends of a stack of rings keep a brush wire assemble accurately on the longitudinal axis of a slip ring assembly for rotation.

Slip rings such as those shown in Figures 8 and 9 are arrangable in a stack. Figure 1 1 shows such a stack 1040 of slip rings 1010 with an end housing 1030, such as that shown in Figure 3, and a bearing at each end. One or more racks 1042 are also provided to locate the rings.

Figure 12 shows a perspective view of a slip ring apparatus 1 100 according to an embodiment of the present invention The apparatus comprises a first component 1 102 comprising a stack of slip rings 1 1 10 (as described previously), each ring having a first conductive element 1 104 in the form of a conductive ring in the shape of a groove. The apparatus 1 100 also comprises a second component 1 106 comprising a substrate 1 108, such as a printed circuit board (PCB) on which internal electronic circuitry is mounted and/or an end connector connected to second conductive elements. The plurality of second conductive elements 1 1 12 (shown in Figures 13 to 15) are in the form of arcs of conductive material, for example sprung wire elements or brush wires. Ideally, each second conductive element 1 1 12 comprises two arcs of conductive material, each located on an opposite side of the substrate to the other. Each arc of conductive material has two ends 1 1 14, wherein the arc contacts the first conductive element 1 104 at a contact point adjacent each end where the wire curves round back on itself. As such, each arc of conductive material 1 1 12 is sized to fit within the conductive ring 1 104 and contact the ring 1 104 at at least one contact point. The first 1 102 and second 1 106 components are rotatable with respect to each other by virtue of bearing elements located at each end of the slip ring apparatus 1 100. Each second conductive element 1 1 12 is in electrical communication with a corresponding first conductive element 1 104. Each second conductive element 1 1 12 is located, wholly or partially, within an outer perimeter defined by its corresponding first conductive element 1 104. The second component 1 106 is located, wholly or partially, within the first component 1 102. The first 1 104 and second 1 1 12 conductive elements are in continuous electrical communication with each other during rotation of the first 1 102 and second 1 106 components relative to each other. Each arc passes through the substrate 1 108 and is electrically connected to the internal electronic circuitry.

Each first conductive element 1 104 is electrically connected to external electronic circuitry. The internal electronic circuitry is electrically connected to the external electronic circuitry via the first 1 104 and second conductive elements 1 1 12.

Figure 13 shows a cross-sectional view of the slip ring apparatus 1 100 at a right angle to the rotation axis, and shows how the brush wires 1 1 12 contact the conductive rings 1 104, and how the feature at the end 1 1 14 of the wires 1 1 12 allows the brush wires 1 1 12 to be drawn together to clear the rings 1 104 when the brush wire assembly is being loaded axially into position.

Figure 14 shows a suitable form for the second conductive elements 1 1 12 to take; alternative shapes are clearly possible. The arced form allows contact towards the end 1 1 14 of the wire 1 1 12 furthest from the PCB 1 108 with a radius at that point only very slightly smaller than the slip ring 1 1 10 internal diameter. The curved end 1 1 14 feature allows the wires 1 1 12 to be drawn inside the slip ring 1 1 10 internal diameter to allow the brush wire array to be inserted into the slip ring stack by automatic insertion means which allow the brush wires 1 1 12 to rest in their respective ring internal grooves 1 104 when the insertion means are withdrawn, and the wires spring apart. The 'free' form of the wires 1 1 12 has a slightly larger radius than the internal diameter of the slip ring 1 1 10, and the adjustment of the difference governs the contact force between the wire and the ring.

The fact that each second conductive element 1 1 12 may be in the form of an arc does not necessarily mean that they are curved along their entire length. As shown in Figure 14, each arc 1 1 12 can comprise at least one straight portion 1 122 (i.e. not curved). The straight portion 1 122 of the arc 1 1 12 may be the portion which passes through the substrate 1 108, which can be a PCB. It is advantageous for the straight portion 1 122 of each second conductive element 1 1 12 to be perpendicular to the substrate 1 108 to facilitate subsequent forming of the second conductive elements 1 1 12, which can be carried out on all second conductive elements simultaneously, into their arced form shown in Figure 14. Alternatively, the second conductive elements 1 1 12 can be preformed individually and then soldered individually to an edge of the substrate 1 108.

Figure 15 shows, in exemplary form, the central PCB 1 108 with wires 1 1 12 for use with eight slip rings, and an end-launch high-bandwidth connector 1 1 16 in place to allow HD signals to pass through, which are then routed straight along the PCB 1 108.

If the diameter of the wires 1 1 12 is relatively large, then the spring rate at the point of contact is fairly 'sharp' and requires very tight assembly tolerances; these can be reduced by 'crushing' part of the brush wire 1 1 12 along its length to form one or more flattened sections 1 1 12a, e.g. leaf spring cross sections, as shown in Figure 14 rather than a round cross section. This means that there is a lower modulus of elasticity of the leaf section for a given wire cross sectional area. For example, in an assembly with a ring internal diameter of 12mm, a wire of 0.2mm diameter has an approximate spring rate of 0.001 " per gram force at the contact point, but a wire of 0.15mm diameter has a spring rate of 0.010" per gram. Since the target contact force is 3 grams, assembly is less critical with the thinner wire although this thinner wire is more difficult to handle and carries less electrical current.

As discussed above, the apparatus shown in Figure 12 also comprises an end connector 1 1 16, such as a high definition (HD) video connector. The end connector 1 1 16 is free to rotate about the PCB 1 108 or slip ring longitudinal axis A. The end connector 1 1 16 has two features on its outer end; one which permits soldering to a flexible PCB which is then connected to a stack PCB, and the other allows a spring to give very light axial force and to constrain this connector to rotate with the stack PCB.

During manufacture, the wire brush assembly on the second component is fed inside the stack assembly and held in place longitudinally and horizontally with respect to the first component by two bearings which are connected to the second component. A first bearing is formed through insertion of a ball into a spider at a distal end of the slip ring apparatus (with respect to the proximal end of the apparatus through which the second component is inserted into the first component). The second component is thus constrained at its distal end by a universal joint ball and socket bearing which allows a small degree of compliance to make loading easier until the bearing is in place. The other second bearing is slightly pre-loaded by a nut on the end connector located at the proximal end of the PCB (second component). The end connector is threaded for this purpose and thus forms a second bearing opposite the first bearing when the nut is held at the distal end of the slip ring apparatus. Thus, the second component is free to rotate relative to the first component. The second conductive elements 1 1 12 can be formed by soldering an array of brush wires onto a PCB 1 108 and deforming them all together to give the required shape, and the entire brush wire assembly can be loaded internally into the slip ring stack 1 140. When 'free' the wires 1 1 12 rest in the ring internal grooves 1 104, but when drawn together they clear the internal ring diameters to allow the brush assembly to slide along the stack axis.

This method of manufacture allows easy inspection during all stages of manufacture, a vital requirement for automatic assembly if machine vision checking is used.

The slip rings 1 1 10 are located in 'racks' 1 1 18 shown in Figure 13 arranged in a three point star on an outer circumference of the slip ring, but any similar arrangement can also be used. The bearing end housings 1 130 are also held by the same racks 1 1 18. The racks comprise multiple location elements 1 131 which permit multiple longitudinal locations of the slip rings 1 1 10 relative to the second conductive elements 1 1 12. While the slip ring stacks 1 140 and bearing caps 1 130 are located by the racks 1 108, which is a part of the automated assembly, alternative location means (additional separate racks or even strips of glue) are introduced to effect a permanent stack assembly once the automation racks are removed.

The brush wire PCB 1 108 is shaped so that the ends 1 1 14 can pass easily through the bearings, but the central portion running between the slip rings 1 1 10 has a diameter close to the slip ring internal diameter.

The brush wires 1 1 12 are inserted into the PCB and soldered in place and connected to electrical tracks or connections on the PCB. Thus, each wire extends from both sides of the PCB straight and at right angles to the PCB. Clamping dies are the fed between the wires and closed to give each wire 1 1 12 an arc-like form, and then withdrawn.

As mentioned, each brush wire 1 1 12 has an arc-like shape, specifically in the depicted embodiment the brush wires 1 1 12 have three elements forming this arc-like shape. The ends 1 1 14 are folded back so that they can be gripped collectively, which can be done by a tooling means/feature (not shown) during automated manufacture of the slip ring. This tooling feature draws them together so that the wires clear the ring internal bores so they can be passed through the bore of the slip ring stack to a required longitudinal position; when the tooling feature is withdrawn the wires spring outwards and rest in the slip ring grooves. The form of the wire 1 1 12 where it contacts its associated slip ring 1 1 10 is very slightly smaller radius than the ring 1 1 10 it contacts, thereby ensuring good contact between each wire 1 1 12 and its associated ring. The brush wires 1 1 12 have relatively short lengths meaning that their displacement force is quite high for small movement; they may therefore also be 'crushed' to a flattened form along much of their length, which substantially reduces the brush wire force at contact, and avoids the need for very tight tolerances.

As discussed previously, each second conductive element 1 1 12 can comprise at least one straight portion 1 122 (i.e. not curved) which passes through the substrate 1 108, which can be a PCB. It is advantageous for the straight portion 1 122 of each second conductive element 1 1 12 to be perpendicular to the substrate 1 108 to facilitate subsequent forming of the second conductive elements 1 1 12, which can be carried out on all second conductive elements simultaneously, into their arced form. Alternatively, the second conductive elements 1 1 12 can be preformed individually and then soldered individually to an edge of the substrate 1 108.

Figure 16 shows a substrate 1208 and a plurality of second conductive elements 1212 prior to formation of the second conductive elements 1212 into arcs, such as the arcs shown in Figures 14 and 15. The second conductive elements 1212 shown in Figure 16 are deformed using a tool (not shown) into arcs for inclusion in the slip ring apparatus of the present invention.

The present invention has been described above in exemplary form with reference to the accompanying drawings which represent a single embodiment of the invention. It will be understood that many different embodiments of the invention exist, and that these embodiments all fall within the scope of the invention as defined by the appendant claims.

Claims

1 . A slip ring apparatus comprising:

a first component having a first conductive element; and

a second component having a second conductive element,

wherein the first and second components are rotatable relative to each other, and wherein the first and second conductive elements are in electrical communication with each other during rotation of the first and second components relative to each other.

2. The apparatus of claim 1 , wherein the first and second conductive elements are in continuous electrical communication with each other during rotation of the first and second components relative to each other.

3. The apparatus of any one of the preceding claims, wherein the first conductive link is wholly within a body of the first component.

4. The apparatus of any one of the preceding claims, wherein the first component comprises: a first substrate on which the first electronic circuitry is mounted,

wherein the first electronic circuitry comprises a first buffer which is in electrical communication with the first conductive element,

wherein the first buffer is electrically connected to the first conductive element via the first conductive link.

5. The apparatus of claim 4, wherein the first substrate is contained wholly within the first component.

6. The apparatus of claim 4 or claim 5, wherein the substrate is a circuit board on which the buffer is mounted.

7. The apparatus of any one of the preceding claims, further comprising a plurality of first conductive elements and a plurality of corresponding first conductive links,

8. The apparatus of claim 7 when dependent on claim 4, further comprising a plurality of buffers, wherein each conductive link connects a corresponding conductive element to a corresponding one of the plurality of buffers.

9. The apparatus of claim 7 or claim 8, wherein each first conductive element is electrically connected to the first electronic circuitry via a corresponding first conductive link of substantially constant length.

10. The apparatus of any one of claims 7 to 9, wherein the length of the conductive links in the plurality of first conductive links is substantially equal.

1 1 . The apparatus of any one of claims 4 to 10, wherein the length of each first conductive link is not more than 20 mm.

12. The apparatus of any one of the preceding claims, wherein the second component comprises second electronic circuitry connected to the second conductive element, wherein the second conductive element comprises a second conductive link having a predefined constant length.

13. The apparatus of claim 12, wherein the second conductive element consists solely of the second conductive link having a predefined constant length.

14. The apparatus of claim 12 or claim 13, wherein the second component comprises:

a second substrate on which the second electronic circuitry is mounted,

15. The apparatus of claim 14, further comprising a plurality of second conductive elements and a plurality of corresponding second conductive links.

16. The apparatus of claim 15, wherein each second conductive element is electrically connected to the second electronic circuitry and comprises a corresponding second conductive link of substantially constant length.

17. The apparatus of claim 16, wherein each second conductive element consists solely of a corresponding second conductive link having a predefined constant length.

18. The apparatus of claim 16 or claim 17, wherein the length of the conductive links in the plurality of second conductive links is substantially equal.

19. The apparatus of any one of claims 12 to 18, wherein the length of each second conductive link is not more than 20 mm.

20. The apparatus of any one of claims 12 to 19, when dependant on claim 4, wherein a total length of each electrical path from the first buffer to the second buffer via the first and second conductive links is in a range 10 to 20mm during rotation of the first and second components relative to each other.

21 . A slip ring apparatus comprising:

a first component configured to rotate relative to a second component;

a first conductive connector,

wherein the first conductive connector is configured to rotate with the first component.

22. The apparatus of claim 21 , wherein the first conductive connector is connected to a first conductive corresponding connector and rotates relative to the first conductive corresponding connector about a rotation axis which passes through both the first conductive connector and the first conductive corresponding connector.

23. The apparatus of claim 21 or claim 22, wherein the first conductive connector is mounted on a first substrate contained, at least partially, within the first component.

24. The apparatus of claim 21 , 22 or 23, further comprising a second conductive connector configured to rotate with the first component.

25. The apparatus of claim 24, wherein the second conductive connector is connected to a second conductive corresponding connector and rotates relative to the second conductive corresponding connector about a rotation axis which passes through both the second conductive connector and the second conductive corresponding connector.

26. The apparatus of claim 24 or 25, when dependent on claim 23, wherein the first and second conductive connectors are mounted on opposing ends of the first substrate.

27. The apparatus of claim 26, wherein the first substrate is configured to rotate about an axis which passes through the first and second conductive connectors and their axis of rotation.

28. The apparatus of claim 26 or 27, further comprising a conductive track extending between, and in electrical communication with, the first and second conductive connectors.

29. The apparatus of claim 28, wherein the conductive track comprises a coaxial cable, and the first and second conductive connectors comprise coaxial connectors.

30. The apparatus of claim 28 when dependent on claims 22 and 25, wherein the first and second corresponding connectors are corresponding coaxial connectors.

31 . The apparatus of any one of claims 24 to 29, wherein the conductive track is dimensioned to minimise variation in the impedance of the slip ring apparatus.

32. A slip ring apparatus comprising:

a first component having a first conductive element; and

a second component having a second conductive element,

wherein the first and second components are rotatable relative to each other, wherein the first and second conductive elements are in electrical communication with each other during rotation of the first and second components relative to each other, and wherein the first and second conductive elements are located at least partially within the first component.

33. The apparatus of claim 32, wherein the first component comprises a plurality of first conductive elements and the second component comprises a plurality of second conductive elements, and wherein each second conductive element is in electrical communication with a corresponding first conductive element.

34. The apparatus of claim 32 or claim 33, wherein each second conductive element is located at least partially within an outer perimeter defined by its corresponding first conductive element.

35. The apparatus of any one of claims 32 to 34, wherein each second conductive element is located wholly within an outer perimeter defined by its corresponding first conductive element.

36. The apparatus of any one of claims 32 to 35, wherein the second component is located at least partially within the first component.

37. The apparatus of claim 36, wherein the second component is located wholly within the first component.

38. The apparatus of any one of claims 32 to 37, wherein the first and second conductive elements are in continuous electrical communication with each other during rotation of the first and second components relative to each other.

39. The apparatus of any one of claims 32 to 38, wherein each first conductive element comprises a conductive ring.

40. The apparatus of claim 39, wherein each conductive ring comprises a groove which extends around the internal diameter of the ring.

41 . The apparatus of any one of claims 32 to 40, wherein each second conductive element comprises an arc comprising conductive material.

42. The apparatus of claim 41 , wherein each second conductive element comprises two arcs of conductive material.

43. The apparatus of claim 41 or claim 42, wherein each arc comprises a sprung wire element.

44. The apparatus of any one of claims 41 to 43, wherein each arc is deformable to permit it to be inserted into the first component.

45. The apparatus of claim 44, further comprising means for deforming each arc so that it can be inserted into the first component.

46. The apparatus of any one of claims 41 to 45, wherein the arc of conductive material comprises two ends, wherein the arc contacts the first conductive element at a contact point adjacent each end.

47. The apparatus of any one of claims 41 to 46 when dependent on any one of claims 39 or 40, wherein each arc of conductive material is sized to fit within a corresponding conductive ring and each arc is adapted to contact its corresponding conductive ring at at least one contact point.

48. The apparatus of claim 47, wherein each arc of conductive material is adapted to contact the ring at at least two contact points.

49. The apparatus of claim 47 or claim 48 when dependent on claim 40, wherein each arc is adapted to sit partially within the groove on its corresponding ring.

50. The apparatus of any one of claims 32 to 49, wherein the second component comprises a substrate.

51 . The apparatus of claim 50, wherein the substrate comprises one or more one electrical connections.

52. The apparatus of claim 51 , wherein the substrate comprises an electrical connector in electrical communication with the one or more electrical connections.

53. The apparatus of claim 52, wherein the electrical connector comprises a high-definition video connector.

54. The apparatus of claim 51 , further comprising internal electronic circuitry on the substrate electrically connected to the one or more electrical connections.

55. The apparatus of claim 54, wherein the substrate is a printed circuit board (PCB).

56. The apparatus of any one of claims 50 to 55 when dependent on any one of claims 41 to 49, wherein each arc is connected to the substrate.

57. The apparatus of claim 56, wherein each arc is pre-formed prior to being connected to the substrate.

58. The apparatus of claim 56 or claim 57, wherein each arc passes through the substrate and is fixed to it.

59. The apparatus of any one of claims 56 to claim 58, wherein each arc is soldered to the substrate.

60. The apparatus of any one of claims 56 to claim 59, wherein each arc is connected to an edge of the substrate.

61 . The apparatus of any one of claims 56 to 60 when dependent on claim 51 , wherein each arc is electrically connected to a corresponding electrical connection on the substrate.

62. The apparatus of any one of claims 32 to 61 , wherein each first conductive element provides an electrical connection for connection of the slip ring apparatus to an external electrical device.

63. The apparatus of claim 62, wherein the each first conductive element is electrically connected to external electronic circuitry.

64. The apparatus of claim 63 when dependent on claim 51 , wherein the electrical connections of the substrate are connected to the external electronic circuitry via the first and second conductive elements.

65. The apparatus of any one of claims 32 to 64, further comprising at least one bearing configured for permitting rotation of the first component relative to the second component.

66. The apparatus of claim 65, further comprising a plurality of location elements for permitting multiple longitudinal fixed positions of the first component relative to the second component to be set.

67. The apparatus of any one of claims 32 to 66 when dependant on claim 52, wherein the electrical connector is an end-launch connector located at one end of the substrate.

68. The apparatus of claim 67, wherein the end-launch connector is a rotating connector.

69. The apparatus of any one of claims 32 to 68, wherein the end-launch connector is a bearing configured for permitting rotation of the first component relative to the second component.

70. The apparatus of claim 65 or claim 69, when dependent on claim 50, wherein the at least one bearing is located at an end of the substrate.

71 . The apparatus of claim 70 when dependent on claim 67, wherein the substrate further comprises a buried ball joint at an opposite end of the substrate to the end which has the end- launch connector, wherein the buried ball joint locates on an internal bearing spider.

72. A method of manufacturing the slip ring apparatus of any one of claims 32 to 71 , comprising:

providing the first component; and

73. The method of claim 72, wherein the second component is inserted into the first component along substantially a longitudinal axis of the first component.

74. The method of claim 72, when dependent on claim 41 , further comprising:

deforming each arc of conductive material from an undeformed form into a deformed form prior to insertion of the second component into the first component, and returning each arc of conductive material to its undeformed form when the second component is located within the first component.

75. The method of claim 74, wherein deforming is performed by tooling means.

76. The method of any one of claims 72 to 75, wherein the method is fully automated.

77. The slip ring apparatus of any one of claims 1 to 71 substantially as hereinbefore described with reference to the accompanying drawings.