Slip ring device

A slip ring device comprises a cylindrical body of an insulating material, at least one ring of an electrically conductive material fitted on the outer periphery of the cylindrical body, at least one strip member of an electrically conductive material arranged on the outer periphery of the ring, a coupling member, situated between the strip member and the outer periphery of the ring, for electrically coupling the strip member and the outer periphery of the ring, at least one lead member of an electrically conductive material, having one end portion electrically connected to the ring and the other end portion led out of the inner periphery of the cylindrical body, and a brush unit of an electrically conductive material, situated in electrical contact with the strip member.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a slip ring device for transmitting 
electric power or electric signals between a stator and a rotor of a 
rotary electric machine. 
2. Description of the Related Art 
A typical rotary electric machine is a electric power apparatus such as an 
electric motor or a generator, or a medical treatment apparatus such as an 
x-ray CT scanner. This type of rotary electric machine comprises a stator 
and a rotor. In general, the stator and rotor are provided with a slip 
ring device. The slip ring device functions to transmit electric signals 
or electric power between the stator and rotor. 
A conventional slip ring device mounted in an x-ray CT scanner will now be 
described with reference to FIGS. 1 and 2. As is shown in FIG. 1, a slip 
ring device 10 comprises a cylindrical body 20 mounted on a rotor (not 
shown), and a brush unit 30 constituted by an n-number of brushes 32 and a 
block 34 mounted on a stator (not shown). In the following description, 
the n-number of brushes 32 are represented by three brushes 32a, 32b and 
32c. 
An x-ray tube 110 is fixed to the rotor (not shown). Accordingly, the x-ray 
tube 110 and the cylindrical body 20 rotate as one body. The cylindrical 
body 20, as shown in FIG. 2, includes an insulating resin cylindrical 
member 22, and an n-number of metal rings 24 arranged in parallel on the 
outer periphery of the cylindrical member 22 and distanced from one 
another. In the following description, the n-number of metal rings 24 are 
represented by three metal rings 24a, 24b and 24c. 
The brushes 32a, 32b and 32c are always put in contact with the metal rings 
24a, 24b and 24c during rotation of the cylindrical body 20. The brushes 
32a, 32b and 32c are attached to the block 34. The block 34 is connected 
to a low voltage power supply 114 via an n-number of cables 40. In the 
following description, the n-number of cables 40 are represented by three 
cables 40a, 40b and 40c. 
An n-number of electrically conductive screws 26 are penetrated from the 
metal rings 24a, 24b and 24c through the insulating resin cylindrical 
member 22, as shown in FIG. 2. In the following description, the n-number 
of screws 26 are represented by three electrically conductive screws 26a, 
26b and 26c. First end portions of an n-number of cables 42 are connected 
to the tip end portions of the screws 26a, 26b and 26c. Second end 
portions of the cables 42 are connected to the x-ray tube 110. In the 
following description, the n-number of cables 42 are represented by three 
cables 42a, 42b and 42c. 
With the above structure, even when the cylindrical body 20 and the x-ray 
tube 110 are rotated, electric power can easily be supplied from the low 
voltage power supply 114 to the x-ray tube 110 through the cables 40a, 40b 
and 40c, block 34, brushes 32a, 32b and 32c, metal rings 24a, 24b and 24c, 
electrically conductive screws 26a, 26b and 26c, and cables 42a, 42b and 
42c. 
In order to ensure good electrical connection between the low voltage power 
supply 114 and x-ray tube 110, as stated above, it is necessary to enhance 
electrical characteristics of the cylindrical body 20. In addition since 
the cylindrical body 20 is continuously rotated, wear resistance of the 
cylindrical body 20 must be increased. 
To solve this problem, a silver plating has conventionally been applied to 
the metal rings 24a, 24b and 24c, or metal rings 24a, 24b and 24c made of 
a silver-based alloy have been employed. 
The silver plating, however, incurs pollution problems, and, if the 
diameter of the silver-plated cylindrical body 20 is increased by the 
plating layer, the manufacturing cost increases. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a slip ring device having 
good electrical connection and wear resistance, resulting in low 
manufacturing cost. 
This object can be achieved by a slip ring device comprising: 
a cylindrical body of an insulating material; 
at least one ring of an electrically conductive material fitted on the 
outer periphery of the cylindrical body; 
at least one strip member of an electrically conductive material arranged 
on the outer periphery of the ring; 
coupling means, situated between the strip member and the outer periphery 
of the ring, for electrically coupling the strip member and the outer 
periphery of the ring; 
at least one lead member of a electrically conductive material, having one 
end portion electrically connected to the ring and the other end portion 
led out of the inner periphery of the cylindrical body; and 
a brush unit of an electrically conductive material, situated in electrical 
contact with the strip member. 
In addition, the object can be achieved by a slip ring device comprising: 
a cylindrical body of an insulating material; 
at least one ring of an electrically conductive material fitted on the 
outer periphery of the cylindrical body; 
at least one strip member of an electrically conductive material arranged 
on the outer periphery of the ring; 
at least one lead member of an electrically conductive material, having one 
end portion electrically connected to the ring and the other end portion 
led out of the inner periphery of the cylindrical body; and 
a brush unit of an electrically conductive material, situated in electrical 
contact with the strip member. 
Furthermore, the object can be achieved by a slip ring device comprising: 
a cylindrical body of an insulating material; 
at least one strip member of an electrically conductive material arranged 
on the outer periphery of the cylindrical body; 
at least one lead member of an electrically conductive material, having one 
end portion electrically connected to the strip member and the other end 
portion led out of the inner periphery of the cylindrical body; and 
a brush unit of an electrically conductive material, situated in electrical 
contact with the strip member. 
Additional objects and advantages of the invention will be set forth in the 
description which follows, and in part will be obvious from the 
description, or may be learned by practice of the invention. The objects 
and advantages of the invention may be realized and obtained by means of 
the instrumentalities and combinations particularly pointed out in the 
appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A slip ring device according to the present invention, which has been 
applied to an x-ray CT scanner, will now be described. As is shown in FIG. 
3, in an x-ray CT scanner, a stator 102 is arranged within a gantry 100. 
The stator 102 and a rotor 104 constitute a closed space 106. A 
subject-insertion hole 108 is formed at a center part of the rotor 104. An 
x-ray tube 110 and an x-ray detector (not shown) are arranged so as to 
interpose the hole 108 therebetween. The x-ray tube 110 and the x-ray 
detector are rotated relative to a subject (not shown), and x-rays are 
radiated from the x-ray tube 110 on to one side of the subject; thus, the 
x-ray detector can obtain x-ray transmission information from the other 
side of the subject. The x-ray transmission information is 
signal-processed by a signal processing system (not shown), thereby 
reconstructing a tomogram. 
In general, in a third-generation x-ray CT scanner, both x-ray tube 110 and 
x-ray detector are installed in the rotor 104. The x-ray detector is an 
arcuated multichannel detector. In a forth-generation x-ray CT scanner the 
x-ray tube 110 is installed in the rotor 104, and the x-ray detector, 
which is an annular multichannel detector, is installed in the stator 102. 
The x-ray tube 110 has an anode and a cathode. A high voltage is supplied 
from a high voltage power supply 112 to the anode, and a filament current 
is supplied from a lower voltage power source to the cathode. Since the 
high voltage power supply 112 and low voltage power supply 114 are 
installed in the stator 102 or stationary part (floor), a high voltage 
from the high voltage power supply 112 or filament current from the low 
voltage power supply 114 must be supplied from the stator to the rotor 
side via transmission means. An example of the transmission means is a 
slip ring device. 
The x-ray detector has a bias electrode and a signal electrode. In a 
third-generation x-ray CT scanner, the x-ray detector is installed in the 
rotor 104. In addition to the x-ray detector, a signal collector (not 
shown) constituted mainly by an A/D converter is installed in the rotor 
104. The x-ray detector and signal collector are supplied with control 
voltage from the low voltage power supply 114. An electric signal 
proportional to the quantity of incident x-rays is obtained from the x-ray 
detector and signal collector. Since the low voltage power supply 114 is 
installed in the stator 102 or stationary part (floor), the control 
voltage from the low voltage power supply 114 must be supplied from the 
stator 102 to the rotor side via transmission means. The electric signal 
must be input to the signal processing system. Since the signal processing 
system is installed in the stator 102 or stationary part (floor), the 
electric signal from the x-ray detector and signal collector must be 
supplied from the rotor 104 to the stator side via transmission means. An 
example of this transmission means is a slip ring device. 
In general, the slip ring device is classified into a low voltage slip ring 
device and a high voltage slip ring device. The x-ray CT scanner shown in 
FIG. 3 is assumed to be a forth-generation x-ray CT scanner. As is shown 
in FIG. 3, the forth-generation x-ray CT scanner according to the present 
embodiment comprises a low voltage slip ring device 116 situated in the 
outside atmosphere, and a high voltage slip ring device arranged within a 
closed space 106 in which an insulating gas such as SF.sub.6 is sealed. 
The x-ray CT scanner comprises these two types of slip ring devices 116 
and 118 because it must treat greatly different voltages. 
FIG. 4 is a perspective view showing a low voltage slip ring device 116-1 
according to a first embodiment of the present invention. As is shown in 
FIG. 4, the slip ring device 116-1 comprises a cylindrical body 60 mounted 
on a rotor (not shown) and a brush unit 30 mounted on a stator (not 
shown). An x-ray tube 110 is fixed to the rotor. Accordingly, the x-ray 
tube 110 and the cylindrical body 60 are rotated as one body. 
The cylindrical body 60, as shown in FIG. 5, comprises an insulating resin 
cylindrical member 62, an n-number of metal rings 64 arranged on the outer 
periphery of the cylindrical member 62 in parallel with intervals from one 
another, an n-number of adhesive double coated tapes or coupling means 66 
made of a material such as silver with good electrical conductivity, an 
n-number of metal tapes 68 or strip members made of a material such as 
silver with good electrical conductivity, and an n-number of electrically 
conductive screws 70. 
In the following description, the n-number of metal rings 64 are 
represented by three metal rings 64a, 64b and 64c the n-number of adhesive 
double coated tapes 66 by three adhesive double coated tapes 66a, 66b and 
66c, the n-number of metal tapes 68 by three metal tapes 68a, 68b and 
68c, and the n-number of electrically conductive screws 70 by three 
electrical conductive screws 70a, 70b and 70c. 
The cylindrical body 60 is manufactured in a manner which will now be 
described. An insulating resin such as epoxy resin is molded into an 
annular body by a mold process. An n-number of grooves or striae, which 
are parallel along the axis of the annular body, are formed in the annular 
body by a cutting process, thus obtaining the insulating resin cylindrical 
body 62 having a plurality of striae arranged in parallel along its axial 
direction. That is, the grooves are annular, extending in the 
circumferential direction of the annular body. The n-number of metal rings 
64 of an electrically conductive material such as brass are fitted on an 
n-number of ridges left between the grooves. The n-number of adhesive 
double coated tapes 66 are attached to the entire periphery of the n-metal 
rings 64. Further, the n-metal tapes 68 are attached to the entire 
periphery of the n-adhesive tapes 66. As is shown in FIG. 6, the mutually 
facing end faces of the beginning terminal portions 68S and ending 
terminal portions 68E of the metal tapes 68 are coated with epoxy 
resin-based adhesive, thereby preventing peeling. In addition, as is shown 
in FIG. 5, the n-screws 70 are inserted from the metal rings 64a, 64b and 
64c, penetrating the insulating resin cylindrical member 62. 
First end portions of an n-number of cables 42 are connected to the tip 
portions of the electrically conductive screws 70a, 70b and 70c, and 
second end portions thereof are connected to the x-ray tube 110. In the 
following description, the n-cables 42 are represented by three cables 
42a, 42b and 43c. The ending terminal portions 68E of the metal tapes 68 
are overlapped on the beginning terminal portions 68S, as shown in FIG. 7. 
The brush unit 30, as shown in FIG. 8, comprises a block 38 and an n-number 
of brushes 36 constituted by an n-number of brush shanks 32 made of 
electrically conductive spring material and an n-number of contacts 34 
made of a material such as silver with good electrical conductivity. First 
end portions of the brush shanks 32 are connected to the contacts 34, and 
second end portions thereof are fixed to the block 38. In the following 
description, the n-brushes 36 are represented by three brushes 36a, 36b 
and 36c. 
While the cylindrical body 60 is being rotated, the brushes 36a, 36b and 
37c are always put in contact with the metal rings 64a, 64b and 64c. The 
block 38 is connected to the low voltage power supply 114 via an n-number 
of cables 40. In the following description, the cables 40 are represented 
by three cables 40a, 40b and 40c. With the above structure, even when the 
cylindrical body 60 and the x-ray tube 110 are rotated continuously, 
electric power can easily be supplied from the low voltage power supply 
114 to the x-ray tube 110 through the cables 40a, 40b and 40c, block 34, 
brushes 36a, 36b and 36c, metal rings 64a, 64b and 64c, electrically 
conductive screws 70a, 70b and 70c, and cables 42a, 42b and 42c. 
According to this embodiment, only by attaching the electrically conductive 
metal tapes 68a, 68b and 68c to the metal rings 64a, 64b and 64c via 
electrically conductive adhesive double coated tapes 66a, 66b and 66c, the 
electrical conductivity and wear resistance are enhanced. Thereby, the 
efficiency in assembly of the cylindrical body 60 is enhanced, and the 
cost of the slip ring device 116 can be reduced. 
FIG. 9 is a perspective view of a low voltage slip ring device 116-2 
according to a second embodiment of the invention. In a cylindrical body 
60' according to the second embodiment, the electrically conductive 
adhesive double coated tapes 66 are omitted from the cylindrical body 60 
of the first embodiment. Specifically, in the second embodiment, coupling 
means such as an adhesive is interposed between the metal tapes 68 and the 
metal rings 64. In this embodiment, the metal tapes 68 can be put in 
contact with the metal rings 64 by the coupling means with low contact 
resistance, and the tapes 68 can be firmly coupled to the rings 64. 
FIG. 10 is a perspective view showing a low pressure slip ring device 116-3 
according to a third embodiment of the invention. The third embodiment 
differs from the preceding embodiments only with respect to a cylindrical 
body 160. The cylindrical body 160 of the third embodiment comprises an 
insulating resin cylindrical member 162, an n-number of barriers 164 of an 
insulating material such as rubber, which are arranged on the outer 
periphery of the cylindrical member 162 in parallel with intervals from 
one another, an n-number of metal tapes 166 of a material such as silver 
with high electrical conductivity, and an n-number of electrically 
conductive screws 168. 
In the following description, the n-number of barriers 164 are represented 
by three rubber rings 164a, 164b and 164c, the n-number of metal tapes 166 
by three metal tapes 166a, 166b and 166c, and the n-number of electrically 
conductive screws 168 by three screws 168a, 168b and 168c. 
The cylindrical body with the above structure is manufactured by the 
following process. An insulating resin material such as epoxy resin is 
molded into an annular body by a mold process. The annular body is 
provided with a groove by a cutting process, thus obtaining the insulating 
resin cylindrical member 162. The groove is annular, extending in the 
circumferential direction of the annular body. The n-number of barriers 
164 are fixed in the groove by means of an adhesive. The n-number of metal 
tapes 166 are attached around the entire groove between the barriers 164 
by coupling means 167, such as the adhesive double coated tape described 
in detail above. The screws 168a, 168b and 168c are inserted from the 
metal tapes 166a, 166b and 166c through the insulating resin cylindrical 
member 162. 
First end portions of an n-number of cables 42 are connected to the tip end 
portions of the electrically conductive screws 168a, 168b and 168c, and 
second end portions thereof are connected to the x-ray tube 110. 
According to this embodiment, the metal rings and electrically conductive 
double coated tapes in the first and second embodiments may be omitted, 
and, only by attaching the electrically conductive metal tapes 166a, 166b 
and 166c to the electrically insulating resin cylindrical member 162, the 
electrical conductivity and wear resistance are enhanced. Thereby, the 
efficiency in assembly of the cylindrical body 160 is enhanced, and the 
cost of the slip ring device 116-3 can be reduced. 
FIGS. 11 to 13 are perspective views showing a low voltage slip ring device 
116-4 according to a fourth embodiment of the invention. The fourth 
embodiment differs from the third embodiment, with respect to the manner 
of attaching metal tapes 264 to a cylindrical body 260. As is shown in 
FIG. 11, the cylindrical body 260 of the fourth embodiment comprises an 
insulating resin cylindrical member 262 having holes 262A in the 
circumferential direction, an n-number of barriers (not shown) of an 
insulating material such as rubber, which are arranged on the outer 
periphery of the cylindrical member 262 in parallel with intervals from 
one another, an n-number of metal tapes 264 of a material such as silver 
with good electrical conductivity, and an n-number of lead members 266. 
Each metal tape 264, as shown in FIG. 12, has projections 264A of an 
electrically conductive material at end portions on that side surface 
which is adhered to the insulating resin cylindrical member 262. On the 
other hand, each lead member 266, as shown in FIG. 13, comprises a block 
268 of an electrically conductive material having holes 268A, and an 
electrically conductive screw 270 having a tip end portion inserted in the 
block 268. The block 268 is fitted in the hole 262A in the insulating 
resin cylindrical member 262. The screw 270 is exposed on the inside of 
the cylindrical member 262. The metal tape 264 is attached to the outer 
periphery of the cylindrical member 262, with its projections 264A fitted 
in the holes 268A of the block 268. The beginning portion and ending 
portion of the metal tape 264 are coupled by solder 272. 
As has been described above, according to this embodiment, only by 
attaching the electrically conductive metal tapes 264 directly to the 
insulating resin cylindrical member 262, the electrical conductivity and 
wear resistance are enhanced. Thereby, the efficiency in assembly of the 
cylindrical body 260 is enhanced, and the cost of the slip ring device 
116-4 can be reduced. 
FIG. 14 is a perspective view showing a low voltage slip ring device 116-5 
according to a fifth embodiment of the invention. The fifth embodiment 
differs from the preceding embodiments only with respect to a cylindrical 
body 360. The cylindrical body 360 of the fifth embodiment, as shown in 
FIG. 14, comprises an insulating resin cylindrical member 362, an n-number 
of metal rings 364 arranged on the outer periphery of the cylindrical 
member 362 in parallel with intervals from one another, an n-number of 
metal tapes 366 of a material such as silver with good electrical 
conductivity, and an n-number of electrically conductive screws (not 
shown). The metal ring 364 has a groove 364A for grounding the metal tape 
366 and clamp portions 364B on both sides of the groove 364A. Accordingly, 
the metal ring 364 has a C-cross section. The metal tape 366 is adhered to 
the groove 364A of the metal tape 366. Pressure is applied to the clamp 
portions 364B in the direction of arrow 370 (shown in FIG. 14); thereby, 
the metal tape 366 is held by the clamp portions 364B. The arrangement of 
the electrically conductive screws (not shown) are the same as is shown in 
FIG. 10. 
As has been described above, according to this embodiment, only by 
attaching the electrically conductive metal tapes 366 directly to the 
insulating resin cylindrical member 362, the electrical conductivity and 
wear resistance are enhanced. Thereby, the efficiency in assembly of the 
cylindrical body 360 is enhanced, and the cost of the slip ring device 
116-5 can be reduced. 
The above embodiments are those of the low voltage slip ring device shown 
in FIG. 3. Of course, the structures shown in FIGS. 4 to 14 are applicable 
to the high voltage slip ring device shown in FIG. 3. 
In addition, in the above embodiments, the present invention has been 
applied to the slip ring device mounted in the x-ray CT scanner; however, 
this invention is applicable to rotary electric machines such as an 
electric motor and a generator. 
The present invention can provide the slip ring device wherein, only by 
attaching the electrically conductive metal tapes to the insulating resin 
cylindrical member, the electrical conductivity and wear resistance are 
enhanced, resulting in high efficiency in assembly of the cylindrical 
body, and low cost of the slip ring device. 
Additional advantages and modifications will readily occur to those skilled 
in the art. Therefore, the invention in its broader aspects is not limited 
to the specific details, and representative devices shown and described 
herein. Accordingly, various modifications may be made without departing 
from the spirit or scope of the general inventive concept as defined by 
the appended claims and their equivalents.