Method of manufacturing an electrical slip ring base

An electrical slip ring base is constructed of flexible and moldable or extrudible material so as to be capable of being formed into a variety of profiles or shapes. A rigid backing or hub stiffens or reinforces the base member. Any form of conductive rings can be used, and the base member can be formed to accommodate them.

BACKGROUND OF THE INVENTION 
This invention relates to an electrical slip ring assembly, more 
particularly, the base portion of the electrical slip ring and a method of 
manufacturing that base portion. 
Electrical slip rings are now well known devices for communicating 
electrical signals from one structural member to another where one of the 
structural members is rotatable with respect to the other. Such a slip 
ring assembly, for example, may comprise a relatively rotatable annular 
base member which has a plurality of conductive rings extending around an 
outer circumferential face thereof. A series of electrically conductive 
brushes is arranged on a relatively stationary structural member to make 
electrical contact with the aforementioned conductive rings thereby 
forming a series of electrical connections between the two structural 
members. Of course, conversely, the base member may be stationary and the 
brushes may be relatively rotatable. 
Heretofore, the base assemblies for the slip rings have been generally 
constructed in such a fashion that the conductive rings are molded therein 
as a part of the base while the base itself is being molded. 
Alternatively, the conductive rings might be plated into previously 
completed slip ring bases having grooves formed therein for that purpose. 
Where the above mentioned molding process is used, expensive tooling must 
be provided to support and maintain the rings at the proper position as 
the molding process proceeds. Using these prior art techniques where 
plating occurs after molding, it is not unusual to find that the plating 
does not adhere properly to the base member. And then, machining and 
replating must occur. Losses using this process can be significant. The 
above techniques require expensive tooling and are now proving to be 
prohibitively expensive. 
Commonly assigned U.S. Pat. No. 5,054,189 describes a method where a rigid 
annular slip ring base is molded and then grooves are machined into the 
outer circumferential surface of the slip ring. The conductive material 
which may be formed as a continuous strip is cut to a series of lengths to 
form conductive rings. These rings are then anchored at one end to the 
outer circumferential surface of the slip ring base, and a rolling 
pressure is exerted on them around the circumference of the base to cause 
the rings to be press fit into the grooves previously formed on the base. 
All of the above prior art structures and methods of manufacturing them do 
not readily lend themselves to the wide varieties of shapes, profiles and 
diameters which are now used in connection with modern electrical slip 
ring assemblies. The prior art structures and methods of manufacture do 
not lend themselves well, for example, to linear or non-circular 
applications. All of the prior art manufacturing methods are proving to be 
too expensive for the price pressures being experienced in today's market. 
It is therefore an object of this invention to provide a new form of 
construction for electrical slip ring bases which lends itself to a 
variety of shapes, profiles, lengths or diameters. 
Another object of this invention is to provide an electrical slip ring base 
assembly which is less expensive to manufacture but can maintain precise 
dimensions while being useable in connection with the manufacture of slip 
rings of a variety of shapes and sizes. 
A further object of this invention is to provide an electrical slip ring 
base structure which is of a material wherein the barriers between each of 
the plurality of conductive rings is such that should the brush assembly 
stray from its path, the brushes will not be damaged by the barrier 
material. 
Still another object of this invention is to provide an electrical slip 
ring base assembly structure wherein the base and the conductive strips 
are formed in a continuous structure and that the strip or ring can be 
assembled onto the base by simple flexure of the base and then allowing 
the base to return to its original shape. 
SUMMARY OF THE INVENTION 
The foregoing and other objects are achieved in a structure and method of 
manufacture of that structure according to the invention wherein a slip 
ring base is constructed to have a base member of a flexible, and moldable 
or extrudable material. Such a base member is capable of being formed into 
a variety of profiles or shapes allowing significant cost advantages to be 
achieved over prior art structures and manufacturing methods. A rigid 
backing or suitable hub for stiffening and reinforcing the foregoing base 
member is provided, or alternatively, the base member can be molded or 
extruded from a flexible, nonconductive material which has sufficient 
rigidity to support the conductive rings. Any form of conductive ring or 
strip may be used, i.e., flat, grooved or channeled, as well as those 
which may be plated to enhance the low noise conductivity characteristics 
of the slip ring. The base member and the conductive strip or rings are 
formed as continuous members, respectively, so that the base member is 
simply flexed out of shape to allow the conductive ring or rings to be 
placed therearound and the base member then resumes its original shape to 
frictionally engage the conductive rings. Alternatively, the base member 
or a continuous member and the rings can be wrapped or otherwise inserted 
into the base. (See, for example, U.S. Pat. No. 5,054,189).

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIGS. 1a through h are end cross sectional views illustrating a variety of 
shapes or profiles of electrical slip ring base members 10 drawn in the 
shapes shown from a flexible, elastomeric material. The shapes as shown 
can be molded or extruded depending on the specific material chosen. The 
shape or profile of the base member can readily be changed in the known 
manner by simply changing the mold or die or varying the extrusion 
process. The electrically nonconductive materials used to manufacture the 
base member may be of varying hardnesses (durometer rating). A flexible 
material is chosen to allow for flexible mounting on a suitable support or 
hub and for flexure to allow for mounting conductive rings or strips 
thereon. Each of the illustrated embodiments is in the form of an annular 
slip ring assembly wherein the base member 10 is a continuous annular 
structure as are the conductive rings to be described below. For example, 
the FIG. 1a configuration includes a web portion 12 extending between 
vertical end members 11 and 13 which extend radially outwardly of the 
circumferential surface of annular base member 10a. Barriers 14 and 16 are 
spaced between end members 11 and 13 forming spaces 15 between the 
barriers and end members to allow for mounting conductive rings or strips 
therein. The depressions 17 in each of the barriers and end members form a 
so-called "creep path" between the conductive rings so that stray voltages 
attempting to cross the barriers confront a path longer than the width of 
the barrier thereby materially reducing the possibility that such stray 
voltages will be able to cross from conductive ring to conductive ring. 
The determination of whether to use barriers having such depressions is 
generally made on the voltage conditions to be encountered and available 
spacing between conductive rings. As can be seen from the various profiles 
illustrated in FIGS. 1a through h barriers without such depressions may be 
used. 
FIG. 1c illustrates a second embodiment of a slip ring base member 10c 
having a flat linear web portion 18 and a plurality of barrier members 20 
extending radially outwardly of the annular circumferencial surface of the 
slip ring base member 10c. End members 21 and 23 extend radially inwardly 
of web 18 to form flange like members 25 and 27 thereby forming slots 26a 
and 26b. The purpose for the slots will become clear from the description 
given herein below. 
Another example of the versatility of the form of construction of the slip 
ring base member described herein is illustrated in FIG. 1f wherein it is 
shown that a stepped configuration can be formed. The remaining portions 
of FIG. 1 illustrate a variety of other shapes illustrating the variety of 
structural configurations for electrical slip ring bases which can be used 
in accordance with the invention. 
It is contemplated that electrical slip ring bases can be formed according 
to the invention wherein the conductive rings are placed around either the 
inner or the outer circumferential surfaces of, for example, continuous 
annular slip ring base assemblies. FIG. 2a illustrates a slip ring base 
member having profile 10a from FIG. 1a and arranged so that conductive 
ring members 30a-c inserted in spaces 15 are arranged about the interior 
surface of the electrical slip ring base assembly. 
Alternatively, in FIG. 2b it is shown that the conductive rings 30a-c are 
arranged about the exterior circumference of base member 10a. 
Elements 30a, 30b and 30c illustrate examples of the differing 
cross-sectional shapes of conductive ring members which may be used 
depending on the electrical and noise conditions being encountered. In 
these embodiments the conductive rings are continuous undivided annular 
members made of any desired conductive material which meets the electrical 
requirements at hand. 
FIGS. 3a and 3b are illustrative of the manner of assembly of a conductive 
ring, such as 30a, to the slip ring base member in accordance with the 
invention. FIG. 3a is a partial perspective view of a base member 10a 
wherein at least a portion of the base member is flexed in the area of 
section line A--A to allow the mounting of a continuous conducting ring 
30a in one of the spaces 15 in the base member. FIG. 3b, a cross sectional 
view taken along the line A--A, illustrates the conducting rings 30a-c 
showing their partial insertion into spaces 15 in the flexed portion of 
the base member 10a. After the conducting rings 30a-c are arranged in 
their respective spaces 15 the flexed portion of base member 10a is 
allowed to resume its original shape and the conducting rings are thereby 
frictionally engaged in the spaces 15 on base member 10a. Although not 
shown, it is possible to install the conductive rings in the form of 
flexible strips by a exerting a rolling pressure on those strips to force 
them into the respective spaces 15. 
As stated, the slip ring base members 10a-h are of an elastometer 
materials, and if the materials chosen are too flexible and not subject to 
holding a suitable shape under mechanical stress, a rigid base may be 
utilized to provide support for the elastomer slip ring base. As shown in 
FIG. 4a, the base member 10b from FIG. 1c is designed to be provided with 
such a rigid base 40. The base materials used for the rigid base 40 may be 
any material which is relatively more rigid than the elastomer materials 
used to form member 10b; examples of such base materials can be epoxy 
compounds. In the FIG. 4a embodiment the rigid base 40 is simply inserted 
into slots 26a and 26b formed in base member 10b as discussed herein above 
in connection with FIG. 1b. 
FIG. 4b illustrates a base member 10f from FIG. 1f provided with a rigid 
base 42. The rigid base 42 in this case is joined with base member 10f by 
means of a suitable adhesive or friction. 
The principles of this invention are described herein above by describing 
preferred embodiments constructed accordingly. It is to be understood that 
the described embodiments can be modified or changed while remaining 
within the scope of the invention as defined by the appended claims.