Ring electrode for a slip ring

Abstract

The invention relates to a ring electrode for a slip ring for transmitting electrical energy between machine parts, of which at least one machine part can be rotated in relation to another machine part. The ring electrode and corresponding slip ring can be economically produced and have low wear. The electrode is made of a rod material made of stainless steel, which is rolled into a ring and the free ends of the ring are brought together to form a closed ring.

Claims

1. A slip ring for the transmission of electrical energy between a stationary and a rotating machine part comprising an insulating carrier material in the form of a ring and at least one ring electrode mounted thereto, in particular embedded therein, the at least one ring electrode comprising a rod material of high-quality steel having free ends which is rolled to form a ring and the free ends of which are brought together to form a closed ring having a diameter in a range of between 40 cm to 2 m, metal-bearing carbon electrodes being provided as pick-up electrodes in rubbing contact with the at least one ring electrode of high-quality steel.

2. The slip ring as set forth in claim 1 characterised in that the metal-bearing carbon electrodes have a silver content of up to 60% or a copper content of up to 75%.

3. The slip ring as set forth in claim 1 wherein the at least one ring electrode is one of a plurality of ring electrodes and wherein a respective plurality of carbon electrodes are arranged on a common pick-up rail for each ring electrode.

4. The slip ring as set forth in claim 1 wherein the free ends of the rod material which is rolled to a ring shape are welded or brazed together.

5. The slip ring as set forth in claim 4 characterised in that the free ends of the rod material which is rolled to a ring shape are cut on a miter.

6. The slip ring as set forth in claim 1 characterised in that the rod material is of a rectangular cross-section of minimum dimensions of 55 mm.sup.2 and maximum dimensions of 3030 mm.sup.2.

7. The slip ring as set forth in claim 1 wherein the insulating carrier material is a plastic carrier material whose coefficient of thermal expansion at an operating temperature of between 40 and 80 C. is within a factor of 2 in a region around the coefficient of thermal expansion of high-quality steel.

8. The slip ring as set forth in claim 1 wherein the at least one slip ring has a plurality of ring electrodes.

9. The slip ring as set forth in claim 8 characterised in that the plurality of ring electrodes are of different diameters and are arranged concentrically in a common radial plane.

10. The slip ring as set forth in claim 8 characterised in that the plurality of ring electrodes are respectively of the same diameter and are arranged parallel in a common cylindrical surface of the insulated carrier material.

11. The slip ring as set forth in claim 1 characterised in that besides at least one ring electrode of high-quality steel there are provided further ring electrodes of another conductive material.

12. The slip ring of claim 11 wherein the other conductive material is brass.

Description

(1) Further advantages, features and possible uses of the present invention will be apparent from the description hereinafter of a preferred embodiment and the related Figures in which:

(2) FIG. 1 show a plan view of a ring electrode and FIG. 1a shows a corresponding partial enlarged view in the region of a weld seam.

(3) FIG. 2 shows a plan view of a slip ring,

(4) FIG. 3 shows a cross-section through a slip ring,

(5) FIG. 4 shows a carbon brush in rubbing slip contact with a ring electrode, and

(6) FIG. 5 shows a brush block for providing slip contacts with a plurality of ring electrodes.

(7) FIG. 1 shows a plan view of a diagrammatically illustrated ring 1 which comprises high-quality or stainless steel and the cross-section of which, for example as shown in FIG. 3, can be square of dimensions of 1010 mm.sup.2.

(8) The portion A is shown on an enlarged scale in the upper part of FIG. 1 and diagrammatically indicates by means of a broken line a weld seam 8 which extends along a miter cut.

(9) To produce such a cut a rod material with a slight over-length is used and is rolled to form a corresponding ring and the free ends which overlap somewhat because of the over-size are placed one over the other and then cut in a miter cut jointly along a line corresponding to the weld seam 8. The cut surfaces are then placed flush against each other and welded so that the weld seam 8 is of the configuration shown in FIG. 1. The surface of the ring is then smoothed by milling or grinding. The entire ring surface can possibly also be subjected to turning again when the ring electrode is gripped in a corresponding apparatus or embedded in the slip ring 20 shown in FIGS. 2 and 3.

(10) FIG. 2 shows a plan view of a slip ring comprising a carrier disk 5 of ring shape, which is made from an insulating plastic material, preferably polyurethane, with a mineral filler, wherein the filler provides that the plastic material overall has a coefficient of thermal expansion which is of the order of magnitude of the thermal expansion of high-quality steel and at any event in the temperature range of interest of between 40 and 80 C. differs by less than a factor of 2 from the coefficient of thermal expansion of high-quality steel.

(11) The carrier disk 5 has overall four embedded slip rings 1, 2, 3 and 4. The common axis 10 of the carrier disk 5 and the rings 1, 2, 3 and 4 is indicated at the center of the disk. FIG. 3 shows a cross-section through the carrier disk 5 with the four embedded ring electrodes 1, 2, 3 and 4 which project somewhat beyond the surface 6 which extends in a radial plane. The projection of the surfaces of the ring electrodes 1, 2, 3 and 4 relative to the surface 6 can for example be between 1 and 3 mm. The ring electrodes 1, 2, 3 and 4 which are of square cross-section are respectively embedded to more than half in the material of the carrier disk 5. The surfaces of the ring electrodes 1, 2, 3 and 4, that extend parallel to the radial plane 6, are in turn preferably smoothed, for example by grinding, turning or milling, and are disposed jointly in a plane 6 which is parallel to the plane 6 and which is indicated by a broken line.

(12) FIG. 4 diagrammatically shows a side view of a ring electrode 1 which is in rubbing slip contact with a carbon brush 11, the carbon brush being shown again only diagrammatically in section. The carbon brush 11 overall comprises a metal-filled or metal-impregnated graphite block 12, a guide sleeve 13, a cap 14 and a spring 15 which holds the graphite block 12 in engagement with the surface of the ring electrode 1.

(13) The carbon brush 11 is typically mounted in a rail of a brush block 21, as shown in FIG. 5. Desirably the sleeve 13, the cap 14 and the spring 15 comprise an electrically conductive material, typically metal, and optionally a flat flexible contact lug or line can also be arranged between the spring 15 and the graphite block 12, being connected with a free end thereof to the cap 14 and/or the sleeve 13 to provide good electrical contact between the graphite block 12 and the sleeve 13 or cap 14.

(14) As shown in FIG. 5 typically a plurality of carbon brushes 11 are connected to an electrically conducting contact rail 22 of a brush block 21, in specific terms each being accommodated in a suitably fitting bore in the contact rail 22. For example the sleeve 13 could be pressed or shrink-fitted into a bore in the rail, possibly also screwed or soldered, and in that way connected fixedly and electrically conductingly to the contact rail 22. A plurality of carbon brushes 11 arranged on the same contact rail 22 can come into rubbing slip contact with the same ring electrode 1 at the same time and one behind the other. The bores for receiving the carbon brushes 11 on the contact rail 12 can possibly follow the arcuate configuration of a ring electrode 1, when the ring electrode is of large diameters however that is generally not required as even carbon brushes arranged linearly on a short portion remain in contact with the ring electrode, in spite of a slight curvature of the ring electrode.

(15) The adjacent contact rails 23, 24 are shown here without carbon brushes, but obviously in turn generally also carry carbon brushes 11 which come into contact with adjacent ring electrodes, for example the ring electrodes 2 and 3 in FIG. 3. It will be appreciated that the housing 25 of the brush block 21 is electrically insulating so that the individual contact rails 22, 23, 24 fixed thereto are electrically insulated from each other.

(16) In operation the slip contacts are held in contact with the surface of the ring electrodes 1, 2, 3 and 4 under a spring bias, in which case either the carrier disk 5 with the ring electrodes 1, 2, 3 or 4 or however a machine part, to which the slip contacts are mounted, rotates about the common axis 10, in which case the slip contacts are continuously in contact with the surface of the ring electrodes 1, 2, 3 and 4 and in that way can continuously transmit electrical energy or power. By virtue of the preferred material pairing of high-quality steel for the ring electrodes 1, 2, 3 and 4 on the one hand and a silver graphite with up to 60% silver or a copper graphite with up to 75% copper, very good contact resistance, low contact noise and a high level of transmission efficiency between the stationary and the rotating machine parts is achieved by the formation of a patina, which is very good due to the materials involved.

(17) The method according to the invention of producing the ring electrodes by rolling from high-quality steel also has inter alia the advantage that rings or ring electrodes of almost any diameter can be manufactured from one and the same rod material as long as the material can just be rolled to a desired diameter. In that respect there is almost no material cutting wastage (apart from the ends which are cut for example on the miter), the surfaces have and retain high quality and the material is extremely resistant to wear and presents only slight friction in relation to metal-bearing graphite electrodes so that the total wear of the system comprising slip ring and slip contact also remains extremely slight and at the same time excellent power data are achieved in relation to current-carrying capability and signal quality. In that way the ring electrodes and slip rings according to the invention are suitable in particular for use on imaging medical equipment with rotating pick-ups or sensors or radiation emitters.

(18) For the purposes of the original disclosure it is pointed out that all features as can be seen from the present description, the drawings and the appended claims by a man skilled in the art, even if they are described in specific terms only in connection with certain other features, can be combined both individually and also in any combinations with others of the features or groups of features disclosed here insofar as that has not been expressly excluded or technical aspects make such combinations impossible or meaningless. A comprehensive explicit representation of all conceivable combinations of features and emphasis of the independence of the individual features from each other is dispensed with here only for the sake of brevity and readability of the description.