EP2338211A1

EP2338211A1 - Slip ring unit

Info

Publication number: EP2338211A1
Application number: EP09778446A
Authority: EP
Inventors: Ludwig Angerpointner; Norbert Friese
Original assignee: LTN Servotechnik GmbH; MD Elektronik GmbH
Current assignee: LTN Servotechnik GmbH; MD Elektronik GmbH
Priority date: 2008-10-15
Filing date: 2009-09-10
Publication date: 2011-06-29
Anticipated expiration: 2029-09-10
Also published as: DE102008051671A1; US20120129360A1; CN102217151B; CN102217151A; EP2338211B1; DE202009018554U1; WO2010043290A1; US8348677B2

Abstract

The invention relates to a slip ring unit for the electric connection of two structural elements (11, 12; 21, 22) which can be rotated relative to each other. A structural element is designed as a first cable (21) which has a core (21.1) and a shield (21.3). The slip ring unit comprises first, second and third brush elements (1.1, 1.2, 1.3) and first, second and third slip bodies (2.1, 2.2, 2.3). The first slip body (2.1) has a an axially continuous recess through which a first cable (21) is guided for transmitting the voltage applied to the core (21.1). Moreover, the second brush element (1.2) is arranged with a radial off-set (X) relative to the third brush element (1.3).

Description

Slip ring unit

The invention relates to a slip ring unit for the electrical connection of two relatively rotatable components, according to claim 1.

Among other things, slip ring units consist of a slip ring brush and grinding wheels, in particular slip rings, whereby the slip ring brush has sliding contact with rotating slip rings during operation. Such slip ring units are used in many technical fields to electrical voltages, in particular signals or electrical power z. B. to transfer from a stationary to a rotating electrical unit. It is important that there is a good and lasting contact between the slip ring brush and the slip rings, for example through springy brush elements.

For example, for the rotatable coupling of electronic cameras, it may be necessary for both high-frequency digital image signals and analog streams, such as the power supply of the camera, to be reliably transmitted. For example, there is a desire in medical technology for surgical applications to operate such rotatable cameras safely.

The patent EP 1808941 shows a slip ring unit in which bent brush wires transmit electrical voltages or currents or signals to rotatable slip rings. However, such arrangements are not suitable for transmitting high-frequency digital signals, which are usually transmitted in shielded lines, in addition to the analog currents from the brush wires to a relatively rotating slip ring.

The invention has for its object to provide a compact slip ring unit for reliable and secure transmission of electrical voltages, in particular of analog currents and digital signals, which can be produced with little effort. This object is achieved by the features of claim 1.

Accordingly, the slip ring unit according to the invention is configured so that it is suitable for the electrical connection of two relatively rotatable components. One of the components is configured as a first cable having a core and a screen. The slip ring assembly includes a first brush member which is in electrical contact with a first abrasive member. Furthermore, the slip ring unit comprises a second brush element, which is in electrical contact with a second abrasive body, for transmitting a voltage applied to the core. Finally, the slip ring unit comprises a third brush element, which is in electrical contact with a third abrasive body for transmitting a voltage applied to the screen or an applied electrical potential. The first abrasive body has an axially continuous recess through which the first cable is guided for transmitting the voltage applied to the core. The second brush element is arranged with radial offset to the third brush element.

In this case, in each case a contact pressure force can be generated by the relevant brush element on the respective grinding body on the brush elements, which has a radial direction component. In addition to the radial offset with respect to the third brush element, the second brush element can also be arranged in the axial direction to overlap with the third brush element. That is, both the second brush member and the third brush member are arranged in one (one and the same) cross section of the slip ring unit. The cross section of the slip ring unit is a section through the slip ring unit, which is aligned orthogonal to the axis of rotation.

With a transmission of electrical voltages is in principle also accompanied by a transmission of electrical currents, unless there is an infinitely high electrical resistance. Thus, in the following, a transfer of voltage generally also means a transfer of current. Furthermore, electrical signals are physi- Also on electrical voltages, so that the transmission of voltages can also mean a transmission of signals. Since electrical voltages are often also referred to as electrical potentials, shielding potentials can also be transmitted by the slip ring unit.

The first brush element, which is in electrical contact with a first grinding body, may be designed, for example, to transmit analog currents for supplying power to an electrical device.

The second brush element, which is in electrical contact with the second abrasive body, can be used to transmit a signal applied to the soul, in particular a digital high-frequency signal.

By the construction according to the invention, a particularly advantageous arrangement is provided, so that with a compact and simple manufacturing Schleifringeinheit various types of electrical voltages, in particular currents and digital signals, can be transmitted rotatably, ensuring an effective shielding for the transmission of the signals becomes. Accordingly, the shield potential is also transmitted to shielding lines that are rotatable relative to one another.

Advantageously, the slip ring unit comprises a plurality of first brush elements and a plurality of first grinding bodies for transmitting electrical voltages, in particular analog currents, wherein the first brush elements and the first grinding bodies are each arranged with axial offset from one another.

Advantageous is a construction in which the first abrasive body has an axially continuous central bore for receiving the first cable. In this case, the abrasive body can be designed annular and thus be referred to as a slip ring. In a further embodiment of the invention, the second brush element can be arranged axially offset from the first brush element.

Advantageously, the first cable is rotatably arranged relative to the first brush element. Accordingly, then the first cable can be arranged non-rotatably relative to the first grinding body in the slip ring unit. For example, during operation of the slip ring unit, the first cable may rotate with the first abrasive wheel.

In a further embodiment of the invention, electrical voltages are transferable from the first cable to a second cable by the slip ring unit, wherein the second cable has a core and a screen, wherein the screen of the second cable is electrically connected to a sleeve and the screen of the first Cable is electrically connected to the third abrasive body, and the sleeve and the third abrasive body in the axial and in particular also in the radial direction are arranged overlapping. The first cable and the second cable may be configured as coaxial cables.

Frequently, the voltages to be transmitted, in particular digital signals, have a comparatively high frequency, not infrequently greater than 250 MHz, or greater than 1 GHz. It is therefore important that the slip ring unit does not radiate any electromagnetic interference pulses with regard to the transmission of the digital signals, but that it is also particularly protected against the effects of external electromagnetic fields. In particular, a high level of safety in this regard is required in medical technology applications.

Advantageously, by the slip ring unit electrical voltages, in particular analog currents, transferable from a third cable to a fourth cable, wherein the third cable can be guided by the axially continuous recess of the first grinding body.

In an advantageous embodiment, the slip ring unit is configured so that electrical voltages, in particular analog currents, from a third cable to a fourth cable can be transmitted by the slip ring unit and electrical voltages, in particular digital signals, from the first cable to a second cable are transferable, wherein the fourth cable is guided within a housing of the slip ring unit offset radially outward of the second cable.

In a further embodiment of the invention, either the second brush element or the third brush element or both brush elements are designed as a hollow body. In this case, one of the brush elements or both brush elements can be configured such that the relevant brush element or the brush elements have radially resilient properties. In particular, the second brush element or the third brush element or both can have radially resilient tongues. Alternatively, the second brush element or the third brush element or both brush elements can also be designed as flat spiral springs with cycloid-like geometry, to allow a comparatively soft sliding contact.

Advantageously, the core of the first cable is electrically connected to the electrically conductive second abrasive body and a potting compound is provided which surrounds the second abrasive body and the core for receiving at least a portion of the torque required for the operation of the slip ring assembly.

Furthermore, the slip ring unit for receiving at least a portion of the torque required for the operation of the slip ring unit can be designed such that electrical voltages, in particular digital signals, can be transmitted from the first cable to a second cable and the second cable has a core and a screen, wherein the core of the second cable is electrically connected to an electrically conductive element. In this case, a potting compound is provided, which surrounds the element and the soul. The element can serve as a holder for the second brush element, so that during operation of the slip ring unit, a torque resulting from tangential frictional forces is introduced via the element into the slip ring unit. Potting compound, for example, an initially flowable and then curable material, including an adhesive understood. In a further embodiment of the invention, the potting compound is surrounded by a sleeve. In addition, an improvement of the torque transmission can be achieved if a) the grinding body or b) the said element has at least one recess for non-positive connection of the casting compound with the grinding body or the element.

Advantageous embodiments of the invention will remove the dependent claims.

Further details and advantages of the slip ring unit according to the invention will become apparent from the following description of an embodiment with reference to the accompanying figures.

It show the

FIG. 1 shows a sectional view of a slip ring unit, FIG. 22 shows a detail of the sectional view of the slip ring unit, in particular the area for transmitting digital signals,

FIG. 3 shows a detail of the sectional representation of the slip ring unit, in particular the area for the transmission of analogous currents,

FIG. 4 a shows a side view of a brush element for transmitting digital signals,

FIG. 4b shows a top view of the brush element for transmitting digital signals,

Figure 5a is a side view of another brush element for transmitting the electrical potential of a screen, Fig. 55bb is a plan view of the further brush element for transmitting the electrical potential of the screen.

The slip ring unit presented in the exemplary embodiment serves for the transmission of electrical voltages, here in particular of analog currents and digital signals, so that, for example, a rotatable electronic The camera can be connected to a stationary unit. As analog currents come about currents to move servomotors, z. B. a zoom drive, into consideration and streams for the operation of the camera electronics. The camera delivers high-frequency digital signals for image transmission, which can also be transmitted without interference by the slip ring unit.

According to FIG. 1, the slip ring unit comprises a stator 1 and a rotor 2. The rotor 2 is arranged to be rotatable relative to the stator 1 by means of bearings 3. Concentric with the axis of rotation, among other things, a first cable 21, which is designed as a so-called coaxial cable, guided in the rotor 2 (see also Figure 3). The first cable 21 serves to transmit the digital signals having a frequency in the GHz range. It has a central electrically conductive core 21.1, which is surrounded by a dielectric layer 21.2. The dielectric layer 21.2 is in turn surrounded by a screen 21.3, the screen 21.3 comprises in the presented embodiment, a metal mesh. Furthermore, the first cable 21 has an outer insulation 21.4.

The screen 21.3 of the first cable 21 is shown in FIG 1 with a sleeve 2.3, which serves as (third) abrasive body, electrically connected, for. B. by a crimp connection. Furthermore, the core 21.1 of the first cable 21, here with a solder connection, electrically contacted with a pin 2.2 and mechanically fixed against rotation. The pin 2.2 has a central axial blind hole, in which the soul 21.1 is introduced. As will be explained below, pin 2.2 in the slip ring assembly acts as a (second) abrasive article. So that the solder joint can be produced in the course of assembly of the slip ring unit, a radially oriented bore 2.31 is incorporated into the sleeve 2.3 so that accessibility to the intended solder joint is ensured. To reinforce the mechanical connection between the soul 21.1 and serving as an abrasive pin 2.2 2.2 2.25 a potting compound is introduced through the bore 2.31 after soldering, which helps to accommodate the resulting during operation of the slip ring unit torque. For this purpose, a radial recess is additionally provided at pin 2.2. hen, which is not shown in the figures, but in principle as the groove 1.41 described below is configured. The potting compound 2.6 is surrounded by the sleeve 2.3, so that the radial distance between the sleeve 2.3 and the pin 2.2, or between the sleeve 2.3 and the soul 21.1 is filled in an axial section with potting compound 2.6. Thus, both the sleeve 2.3 and the pin 2.2 and the soul 21.1 surrounded by the potting compound 2.6.

The sleeve 2.3 is surrounded by a component 2.5 of the rotor 2, which is supported on one of the bearings 3.

The first cable 21 is surrounded radially by a third cable 22, which consists of several isolated individual strands. The individual strands of the third cable 22 are each guided radially outwardly through a slot in an electrically insulating support sleeve 2.4 of the rotor 2 to a respective first abrasive body, here in each case a slip ring 2.1. At the radial inner side of the slip rings 2.1, the individual strands of the third cable 22 are each contacted. The slip rings 2.1 are axially aligned with the axial offset Y on the insulating support sleeve 2.4, wherein optionally between adjacent slip rings 2.1 an electrically non-conductive insulating ring is arranged. In the exemplary embodiment shown, all the grinding rings 2.1 are arranged coaxially. Each slip ring 2.1 has a circumferential groove, which has a V-shaped geometry (see also Figure 3).

Furthermore, in the housing 1.10 of the stator 1 coaxially a second cable 1 1 is arranged, in addition to the substantially parallel axis, a fourth cable 12 extends.

The second cable 11 is used to transmit the digital signals and is also designed as a coaxial cable, so in principle as the first cable 21 constructed so that it has a soul 11.1, a dielectric 1.2, a screen 11.3 and an insulating outer layer 11.4. The screen 1 1.3 is electrically connected for example by a crimp connection with a hollow body 2.7. On the hollow body 2.7 is in axial extension a attached further sleeve, which is referred to below as a holder sleeve 1.7.

As shown in detail in FIG. 2, the core 11.1 of the second cable 11 is electrically and mechanically non-rotatably connected to a sleeve-shaped element 1.4 by a soldered connection 1.8. The sleeve-shaped element 1.4 has a recess in the form of a groove 1.41. Alternatively, a plurality of recesses can be incorporated into the element 1.4. The soldering is done by a radial bore 1.71 in the holder sleeve 1.7. After the soldering process potting compound 1.6 is pressed through the bore 1.71 in the cavity between the holder sleeve 1.7 and the element 1.4 or between the holder sleeve 1.7 and the soul 1 1.1. The potting 1.6 then hardens and serves to accommodate at least a portion of the torque required for the operation of the Schieifringeinheit. The load capacity of this connection is enhanced by the recess 1.41, through which a non-positive connection of the potting compound 1.6 is made with the sleeve-shaped element 1.4. In addition, a frictional connection of the potting compound 1.6 is achieved with the holder sleeve 1.7. Because the volume of the potting compound 1.6 is distributed so that casting compound 1.6 also remains in the bore 1.71, so that there goes radially beyond the inner diameter of the holder sleeve 1.7 out and so there is also a positive connection is generated.

Incidentally, the rotor-side connection between the potting compound 2.6 and the sleeve 2.3 is formed analogously to the described connection with the stator-side potting compound 1.6.

The fourth cable 12 serves to transmit the analog currents and also has several individual strands. Within the housing 1.10, the individual strands are brought into contact with first brush elements 1.1. In the example shown, the first brush elements 1.1 are fastened to a holder which is designed as a printed circuit board and, incidentally, is not shown in the figures. The first brush elements 1.1 are also shown here as fe running end wire bracket, which are arranged with axial offset Y to each other.

As a second brush element 1.2, which is arranged between the pin 2.2 as the second grinding body and the sleeve-shaped element 1.4, serves a resilient sheet. FIGS. 4a and 4b show the second brush element 1.2. The second brush element 1.2 is made of a thin (0.1 mm) sheet metal strip, which is bent into an open ring and are incorporated into the recesses or openings by an etching process, so that tongues 1.21 arise. These tongues 1.21 are bent radially inwards to achieve the spring action. Each tongue 1.21 also includes a radially inwardly directed protrusion, produced by a bending process, which serves to produce a sliding contact on the surface of the pin 2.2. The second brush element 1 .2 can be inserted axially into the element 1.4, wherein an axial securing of the second brush element 1.2 relative to the sleeve-shaped element 1.4 is produced by a return in the element 1.4.

Analogously, according to FIGS. 5a and 5b, the third brush element 1.3 is constructed, which likewise comprises resilient tongues 1.31. The third brush element 1.3 is fixed in the holder sleeve 1.7 according to the same principle as the second brush element 1.2 in the sleeve-shaped element 1.4. For the sake of clarity, FIG. 5b omits the representation of the contours visible through the slits in the brush element 1.3.

After the second brush element 1.2 and the third brush element 1.3 are fixed, the pin 2.2 and the sleeve 2.3 can be inserted into the brush elements 1.2 and 1.3 respectively. Thereafter, the stator-side holder sleeve 1.7 and the rotor-side sleeve 2.3 are arranged overlapping in the axial direction, which is particularly important for the shielding of electromagnetic radiation, since the holder sleeve 1.7 and the sleeve 2.3 with the umbrellas 1 1.3, 21.3 are electrically contacted. During operation of the slip ring unit, the axis of rotation of the rotor 2 is simultaneously the axis of rotation of the slip ring unit, so that the rotor 2 is rotatable about the axis of rotation relative to all the brush elements 1.1, 1.2, 1.3. The new design creates a very compact and reliable grinding ring unit. In particular, by the slip ring unit both digital signals between the relatively rotatable first and second cables 21, 11 and analogous currents between the relatively rotatable third and fourth cables 12, 22 can be transmitted. The design is characterized, inter alia, by the fact that the first cable 21 is guided in the cavity formed by the axially juxtaposed slip rings 2.1. In addition, the second brush element 1.2 is arranged with a radial offset X (see FIG. 2) to the third brush element 1.3. This design allows a very reliable electrical transmission, which allows despite the respective sliding contacts insensitive to electromagnetic interference operation.

For receiving radial compensating movements, the holder sleeve 1.7 and / or the sleeve-shaped element 1.4 can be arranged radially floating in the slip ring unit.

Incidentally, it is possible to dispense with one of the bearings 3, in particular the bearing 3 located further inside in the housing 1.10. In particular, in such a construction then a machine element, such as a snap ring, be provided for axially securing the rotor 2 relative to the stator. Furthermore, in this design modification of the slip ring unit, the second and the third brush element can be designed such that they absorb radial forces in the sense of a bearing.

Of course, the operation of the slip ring unit can also be reversed, so that the stator 1 is rotating during operation and the rotor 2 is stationary.

Claims

claims

1. slip ring unit, for electrically connecting two relatively rotatable components (11, 12, 21, 22), wherein a component as a first cable (21) is configured, which has a soul (21.1) and a screen (21.3), and the slip ring unit - a first brush element (1.1), which in electrical

Contact with a first abrasive body (2.1) is, and - comprises a second brush element (1.2) which is in electrical contact with a second abrasive body (2.2), for transmitting a voltage applied to the soul (21.1), - a third brush element ( 1.3), which in electrical

Contact with a third grinding body (2.3) is for transmitting a voltage applied to the screen (21.3), wherein the first grinding body (2.1) has an axially continuous recess through which the first cable (21) for transmitting to the soul (21.1) is applied voltage and the second brush element (1.2) with a radial offset (X) to the third brush element (1.3) is arranged.

2. slip ring unit according to claim 1, wherein the slip ring unit comprises a plurality of first brush elements (1.1) and a plurality of first grinding body (2.1) for transmitting stresses, which are each arranged with axial offset (Y) to each other.

3. slip ring unit according to claim 1 or 2, wherein the first grinding body (2.1) has an axially continuous central bore for receiving the first cable (21).

4. slip ring unit according to one of the preceding claims, wherein the second brush element (1.2) axially offset from the first brush element (1.1) is arranged.

5. slip ring unit according to one of the preceding claims, wherein the first cable (21) relative to the first brush element (1.1) is rotatable.

6. slip ring unit according to one of the preceding claims, wherein by the slip ring unit electrical voltages from the first cable (21) to a second cable (11) are transferable, wherein the second cable (11) has a soul (11.1) and a screen (11.3) wherein the screen (11.3) is electrically connected to a sleeve (1.7) and the screen (21.3) of the first cable (21) is electrically connected to the third abrasive member (2.3), and the sleeve (1.7) and the third abrasive member (11) 2.3) are arranged overlapping in the axial direction.

7. slip ring unit according to one of the preceding claims, wherein by the slip ring unit electrical voltages from a third cable (22) to a fourth cable (12) are transferable and the third cable (22) through the axially continuous recess of the first grinding body (2.1) out is.

8. slip ring unit according to one of the preceding claims, wherein by the slip ring unit electrical voltages from a third cable (22) to a fourth cable (12) are transferable and also electrical voltages from the first cable (21) to a second cable (1 1) transferable are, wherein the fourth cable (12) within a housing (1.10) of the slip ring unit offset radially outward of the second cable (1 1) is guided.

9. slip ring unit according to one of the preceding claims, wherein the second brush element (1.2) and / or the third brush element (1.3) each configured as a hollow body and is configured so that the brush element (1.2, 1.3) has radially resilient properties.

10. slip ring unit according to claim 9, wherein the second brush element (1.2) and / or the third brush element (1.3) radially resilient tongues (1.21, 1.31).

11. slip ring unit according to one of the preceding claims, wherein the soul (21.1) of the first cable (21.1) electrically connected to the second

Abrasive body (2.2) is connected and a potting compound (2.6) is arranged, which surrounds the second abrasive body (2.2) and the core (21.1), for receiving at least a portion of the torque required for the operation of the slip ring unit.

12. slip ring unit according to one of the preceding claims, wherein by the slip ring unit electrical voltages from the first cable (21) to a second cable (11) are transferable and the second cable (11) has a soul (11.1) and a screen (11.3), wherein the core (11.1) of the second cable (11) is electrically connected to an element (1.4), wherein a potting compound (1.6) is arranged, which surrounds the element (1.4) and the core (11.1), for receiving at least one Part of the torque required to operate the slip ring unit.

13. The slip ring unit according to claim 11 or 12, wherein the casting compound (1.6, 2.6) is surrounded by a sleeve (1.7) or by the third abrasive body (2.3).

14. slip ring unit according to claim 11 or 13, wherein the grinding body (2.3) has a recess for non-positive connection of the potting compound (2.6) with the grinding body (2.3).

15. slip ring unit according to claim 12, 13 or 14, wherein the element (1.4) has a recess (1.41) for non-positive connection of the potting compound (1.6) with the element (1.4).