GB2493977A

GB2493977A - Slip ring apparatus

Info

Publication number: GB2493977A
Application number: GB201114790A
Authority: GB
Inventors: David Watkins
Original assignee: Overview Ltd
Current assignee: Overview Ltd
Priority date: 2011-08-26
Filing date: 2011-08-26
Publication date: 2013-02-27
Also published as: GB201114790D0

Abstract

A slip ring apparatus 100 comprises: a first component 10 with electronic circuitry 17 that is connected to a first conductive element 14 (e.g. conductive grooved ring 15) via a first conductive link 16 of predefined constant length; and a second component 20 with a second conductive element that is in electrical communication with the first conductive element 14 during rotation of the first and second components 10, 20 relative to each other. The second component 20 may also comprise electronic circuitry connected to a second conductive link 26, also having a predefined constant length. The first and second components 10, 20 may respectively comprise a plurality of first and second conductive elements and a corresponding plurality of first and second conductive links 16, 26, wherein each of the first conductive links 16 are of equal length and each of the second conductive links 26 are of equal length. The predefined constant length of the conductive links 16, 26 enables changes in impedance as a result of changes in signal path length due to rotation of the components to be quantified and minimised, enabling high bandwidth signal to be conveyed through the slip ring apparatus with a defined signal distortion, which can also be minimised.

Description

Improved Slip Ring Apparatus

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 Al. 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.

Summary of the Invention

The slip ring apparatus of the present invention is designed to overcome this 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 electiical 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.

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 accoiding to an 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; and 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.

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 toform the slip ring apparatus 100.

The tirst 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 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.

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

<claim-text>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 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 rotation of the first and second components relative to each other.</claim-text> <claim-text>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.</claim-text> <claim-text>3. The apparatus of any one of the preceding claims, wherein the first conductive link is wholly within a body of the first component.</claim-text> <claim-text>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.</claim-text> <claim-text>5. The apparatus of claim 4, wherein the first substrate is contained wholly within the first component.</claim-text> <claim-text>6. The apparatus of claim 4 or claim 5, wherein the substrate is a circuit board on which the buffer is mounted.</claim-text> <claim-text>7. The apparatus of any one ot the preceding claims, turther 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.11. 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, wherein the second electronic circuitry comprises a second buffer which is in electrical communication with the second conductive link.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 1210 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 18, 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. An apparatus substantially as hereinbefore described with reference to and as shown in the attached drawings.</claim-text>