Patent Application
20150349477
1. Field of the Invention
The invention relates to an electrical sliding contact arrangement and also to a method for producing the sliding contact arrangement.
Electrical sliding contact arrangements are used for transmitting electrical signals and/or electrical energy between two components mounted such that they can be moved relatively to one another. In addition to known sliding contact arrangements with linear or curved sliding paths, the present invention relates to the an electrical rotary coupling with an integrated slip ring arrangement, which essentially has two electrically conductive parts, which are mounted such they can rotate relatively to one another, concentrically about a common rotational axis, and of which one part is connected to a rotating component of the rotary coupling and the other part is connected to the stationary rotary coupling component.
2. Description of the Prior Art
A generic, compactly structured electrical rotary coupling is described in EP 2 451 028 A2, which provides an axial stack, having a multiplicity of electrically conductive slip rings of annular or disc-shaped construction, along a rotatable shaft in which the slip rings are each axially separated from one another by electrically insulating intermediate discs. Each of the slip rings is connected to an electrical signal line along the rotating shaft and thus forms an electrical transmission channel. In accordance with the number of slip rings, securely clamped brush wires are attached on one side of the stationary housing part of the rotary coupling, which individually come into tangential sliding contact with the sliding paths, which peripherally surround the slip rings. In the same way as the slip rings, the individual stationary brush wires are each respectively connected to an electrical supply and ground.
A slip ring arrangement is described in DE 10 2011 006 820 A1, which is used for electrically connecting two parts that can be rotated with respect to each other and has at least one sliding path with V grooves. At least two wire brushes run into the sliding paths, wherein the wire brushes are electrically connected to one another and arranged on different brush blocks.
DE 10 2011 077 358 B3 discloses a similar brush block arrangement for a rotationally-symmetrically constructed sliding path of the rotary coupling, in which two brushes constructed in a pin-shaped manner are in each case securely fastened on one side on different brush supports and in each case enter into tangentially sliding engagement with the sliding path.
Known electrical sliding contact arrangements, which are integrated into rotary couplings, are for the most part based on the structural combination as illustrated in
The invention is a sliding contact arrangement with two parts that are mounted such that they can be rotated relatively to one another, preferably for integration into a rotary coupling, in such a manner that the electrical sliding contact arrangement is as compact as possible, is small in structure and also has an improved electrical transmission behavior compared to previously known sliding contact arrangements. Furthermore, the production of the sliding contact arrangement should be inexpensive and reliable while always having product quality, particularly in the case of small-scaled sliding contact arrangements.
A sliding contact arrangement according to the invention comprises two parts mounted to be rotatable relative to one another. The first part has a metallic carrier ring with radial inner and outer sides. The outer and/or inner side of the metallic carrier ring is monolithically connected by at least one spring arm, which ends freely on one side. The spring arm longitudinally extends relative to the inner or outer side at least in certain sections. That is in the case of at least one spring arm monolithically connected to the inner side, the same has a spring arm longitudinally extending to be orientated longitudinally relative to the inner side at least in certain sections, which preferably has a spring arm curvature that is adapted to the curvature of the inner side. The same applies for at least one spring arm monolithically connected on the outer side of the carrier ring.
The at least one spring arm has a head located at the free end of the spring arm end, which is monolithically connected to the spring arm and has a contact surface facing away from the carrier ring, which is in sliding contact with a contact surface of the second part of the sliding contact arrangement. The sliding contact arrangement according to the invention therefore stands out on account of the monolithic design of the first part, which in sliding contact arrangements, which are known per se, corresponds to the brush support having brush wires connected thereto and also the sliding bodies attached thereto. Due to the monolithic design, it is not only possible to scale the size of the sliding contact arrangement as desired, thus in particular to miniaturize it. As the further configurations will show, it is furthermore possible to make the production of the monolithic first part of the sliding contact arrangement in particular highly precise and cost effective.
A first preferred embodiment of the sliding contact arrangement provides a first part radially encompassing the second part, on its radial inner side. The carrier ring of the first part has at least one spring arm monolithically connected to the same. The spring arm head slides on the radially outer contact surface of the second part, which is preferably of annular or disc-shaped construction. The second part is a rotating slip ring, which is mounted rotatably about an axis of rotation, to which the carrier ring of the first part is concentrically arranged.
Two or more spring arms are preferably monolithically connected to the carrier ring along the radial inner side of the carrier ring. The spring arms are arranged in as evenly distributed a manner as possible along the inner ring side. In this case, all of the spring arms monolithically attached on the inner side extend with a uniform orientation with the ends (the spring arm heads) of the spring arms pointing uniformly in the clockwise or anti-clockwise direction. All spring arms are identically constructed, have a uniform spring arm length and moreover each have a uniformly shaped spring arm head with a preferably rounded sliding surface. Each individual spring arm which is attached on the inner side of the carrier ring additionally has a uniform spring arm curvature at least in certain sections, which is configured to the curvature of the inner side of the carrier ring or is identical thereto. The spring arms constitute spring beams clamped on one side, which have a radially orientated spring stiffness and deflectability, which can be predetermined individually by the choice of the spring arm length, spring arm geometry and also the material from which the carrier ring, including spring arms is made.
Preferably, all the spring arms which are monolithically connected to the carrier ring are identically constructed, so that the spring arm heads of the individual spring arms are in a force-free state, such that the spring arm heads do not bear in a spring-loaded manner on the contact surface of the second part and are disposed on a virtual circle running concentrically to the carrier ring.
The second part of the sliding contact arrangement has a contact surface constructed in a circular manner with a diameter, that may be the same, but is preferably chosen to be larger than the diameter of the virtual circle, which is predetermined by the position of the spring arm heads. Resulting from the concentric mounting of the second part relative to the first part, the contact surfaces of the multiplicity of spring arm heads are spring loaded to bear by contact surfaces and to slide against the contact surface of the second part.
Advantageously, the contact surfaces of the individual spring arm heads are constructed in a rounded manner so that a bidirectional relative movement between first and second part is possible, without the contact surfaces of the spring arm heads having a tendency to catch the opposite contact surface of the second part.
In order to improve the sliding and/or contact properties, one embodiment provides for the construction of the spring arm heads to be coated with a highly electrically conductive material, for example with gold, nickel, etc., to construct the contact surface.
A further embodiment of a sliding contact arrangement according to the invention provides for an annularly constructed second part, which at least has a metallic ring inner side, corresponding to the contact surface of a rotating slip ring. The first part of the sliding contact arrangement by contrast has a metallic carrier ring with at least one spring arm attached on the ring outer side but preferably multiple spring arms arranged to be evenly distributed along the ring outer side. The spring arms are monolithically connected to the carrier ring. The spring arm heads of the individual spring arms are arranged, in the same manner as described in the previous example, along a virtual circle. The diameter of the virtual circle is dimensioned larger than the diameter of the circular contact surface of the second part, which radially encompasses the first part. In this way, the spring arm heads reach radially outwardly in a spring-loaded manner onto the contact surface of the annularly constructed second part.
Due to the completely monolithic configuration of the first part, including having the carrier ring and the spring arms attached thereon, including spring arm heads, a possibility exists for a very precise production method, which is very cost-effective in terms of process engineering. The production method relates back to the methods of electrical discharge machining, spark erosion, laser-beam cutting or water-jet cutting.
A metallic sheet or plate like surface piece is used as a starting point, for example a brass alloy, copper beryllium or high-grade steel may be used, which can have a sheet or plate thickness in the tenth-of-a-millimeter range to two- to three-figure millimetre range. On the basis of information defining the shape and size of the geometric configuration of the first part, for example in the form of CAD information, the surface piece is machined with one of the preceding separation methods, in which the complete final shape of the first part, comprising the carrier ring and also the spring arms monolithically attached along the inner and/or outer side of the carrier ring, including spring arm heads, can be obtained by separation from the machined surface piece. The second part of the sliding contact arrangement can be obtained in the same way with the separation method mentioned, from metallic sheet- or plate-like surface pieces or can be created in some other manner. Finally, the sliding contact arrangement may have both parts arranged such they can rotate relatively to one another, concentrically about a common axis, preferably in the context of an electrical rotary coupling.
In order to improve the economic efficiency of the production method, it therefore makes sense to provide a multiplicity of metallic sheet- or plate-like surface pieces in the form of a sheet stack, which is supplied to one of the previously mentioned separation methods for constructing at least the first part in each case.
In view of the above-described separation methods, any post-processing steps on the components separated from the surface piece are superfluous. Thus, it is possible to construct even minimally dimensioned structures, as occur in particular in the region of the spring arm head, finely and in a burr-free manner.
The invention is described by way of example in the following drawings without limiting the invention on the basis of exemplary embodiments with reference to the drawings. In the figures:
a and b illustrate the sliding contact arrangement according to the invention;
a, b, c and d show different exemplary embodiments for the carrier ring having spring arms;
a shows a sliding contact arrangement constructed according to the invention, having an annularly constructed second part II, which is arranged radially such that it can rotate coaxially about an axis of rotation 6 located radially inwardly relatively to a first part I and which integrally has a metallic carrier ring 7 and also a multiplicity of spring arms 9 monolithically connected to the carrier ring 7 on the radial inner side 8 thereof. The monolithic design of the first part I can be seen in detail on the basis of the detailed illustration given in
The first part I is preferably machined from a flat metallic material and has a thickness d, typically of a few tenths of a millimeter up to a two- to three millimeter range. A spark erosion or electrical discharge machining method, and if appropriate also laser cutting or water jet cutting methods, are particularly advantageously suitable for producing the first part. By using these methods, the first part can be produced in an integral design on the basis of a CAD data set or in the manner of a CAM operating method.
Each of the individual spring arms 9 is integrally monolithically connected to the carrier ring 7 at a longitudinal end and has a spring arm head 10 located at the free or loose end thereof, which has a contact surface 11, which is constructed to be burr-free and being bidirectionally curved, so that the contact surface 11 can enter into uniformly sliding engagement with the contact surface of the second part II constructed as a slip ring, for relative movement orientated in a clockwise or anti-clockwise direction between the first and second parts.
Each of the spring arms 9 which is monolithically connected to the carrier ring 7 on the inner side 8 has a central radial spacing r with respect to the inner side 8 of the carrier ring 7, in this manner, the spring arm 9 can be deflected radially bidirectionally and has a spring stiffness dependent on the spring arm length l and also the chosen material of the first part I. The length l of the spring arm 9 is typically chosen to be twice to 30-times as long as the central spacing r.
The number of the spring arms 9 provided along the inner side 8 of the carrier ring 7, the geometry of each individual spring arm and also curvature and relative position of the spring arm with respect to the carrier ring 7 can be suitably chosen, in order to produce a desired electrical contact between both parts I and II. The inner second part II has an electrical contact surface 12 on the external circumference thereof. Preferably, the second part II is also made completely from a metallic material, such as, for example brass or high-grade steel. The external diameter of the second part II, which in the exemplary embodiment illustrated in
The
A variant of the first part I, shown in
In all embodiments, it is advantageous to construct the shape of the spring arm heads 10 so that a bidirectional relative movement between the first and second parts is possible, without the spring arm heads 10 catching on the respectively radially opposite contact surface 12 of the second part.
With the use of an electrical discharge machining or spark erosion method, a cost-effective and also precise production of the carrier ring having the spring arms can be achieved in the stack method. The setting of the spring stiffness or the spring characteristic of the individual spring arms can be chosen individually by the choice of the geometry and also the choice of the material from which the carrier ring is manufactured. Additionally, the separation methods allow a burr-free construction of the individual spring arms, which are monolithically connected to the carrier ring. Therefore, a post-processing of the sliding surfaces provided on the spring arm heads is not necessary.
The sliding contact arrangement according to the invention enables a compact design for producing a rotary coupling, used for the transmission of electrical signals and/or electrical energy between two components arranged such that they can rotate relatively to one another. In particular, a sliding contact arrangement constructed according to the invention has a substantially smaller installation space than conventional sliding contact arrangements. Also, the simple production by method technology based on CAD data, which contain the geometric construction of the first part, allows virtually any desired scaling of the respectively first part, so that sliding contact arrangements with diameter dimensions of less than one centimeter can be achieved.
