Electrical connectors – Interrelated connectors relatively movable during use – Movement about axis
Reexamination Certificate
2000-11-22
2003-02-11
Abrams, Neil (Department: 2839)
Electrical connectors
Interrelated connectors relatively movable during use
Movement about axis
Reexamination Certificate
active
06517357
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to video tape recorders. More particularly, the present invention relates to improved slip ring and brush assemblies for transmitting electrical signals and power across a rotating interface in a video tape recorder.
Video tape recorders employ rotating record/reproduce head assemblies. In such recorders, tape which is used as the recording medium is wrapped partially around a drum having a rotating record/reproduce head assembly. In general, the head assembly is connected to a rotatable spindle inside the drum. During the data recording or reproducing process, the tape is moved (or held stationary) while the recording or reproducing is accomplished, i.e., as the recording/reproducing head(s) rotates with the spindle. By way of example, representative video tape recorders utilizing record/reproduce head assemblies may include models DVW, DNW, HDW Series manufactured by Sony Corporation.
In such video tape recorders, electrical signals, as well as electrical power signals, must be transmitted to and from the rotating head assembly. Accordingly, slip ring and brush assemblies have been introduced and employed to various degrees to carry electrical signals between the rotating heads and other equipment with which the rotating head has relative motion. Slip ring and brush assemblies are typically used in electromechanical systems that require unrestrained, continuous rotation while transmitting power and/or electrical signals from a stationary conductor to a rotating structure. In general, slip ring assemblies include a rotor, which is a rotating part, and a stator, which is a stationary part about which the rotor turns. Brush assemblies typically include a brush holder and a brush, both of which are stationary. More particularly, the rotor generally comprises a rotating conductive ring, which is contacted by a non-rotating conductive brush.
To facilitate discussion,
FIGS. 1A-1C
illustrate an exemplary prior art slip ring and brush system
10
used in video recording devices.
FIG. 1A
is a side elevation view, in cross section, of the system
10
,
FIG. 1B
is a cut away top view of the system
10
, and
FIG. 1C
is a bottom view of the system
10
. As shown, the slip ring assembly
10
includes a rotor
12
and a stator
14
. The rotor
12
includes a base
16
and a shaft
18
. The base
16
is configured for mating with a drum assembly of the video recorder (not shown) and the shaft
18
is configured for carrying a plurality of slip rings
20
. As shown in
FIG. 1A
, the bottom of the base
16
includes a protrusion
22
, which physically engages a spindle of the drum assembly. The bottom of the base
16
also includes mounting posts
24
, which couple the system
10
to the spindle (e.g., with machine screws). Still further, the bottom of the base
16
includes a bottom surface
26
having a plurality of contact pads
28
disposed thereon (shown in FIG.
1
C). The contact pads
28
are separately and electrically connected to the slip rings
20
carried by the shaft
18
. The contact pads
28
are for engaging contact pins that are electrically coupled to a head assembly disposed inside the drum assembly.
With regard to the stator
14
, the stator
14
includes a support member
30
that is rotatably mounted onto the shaft
18
with a first set of bearings
32
positioned at an upper portion of the shaft
18
, and a second set of bearings
34
positioned at a lower portion of the shaft
18
. As shown, the slip rings
20
are disposed between each of the set of bearings
32
,
34
. The stator
14
also includes a first brush assembly
36
positioned to a first side of the shaft
18
, and a second brush assembly
38
positioned to a second side of the shaft
18
. The second side is opposite the first side. Both of the brush assemblies
36
,
38
are mounted to the support member
30
and each brush assembly includes a brush holder
39
and a plurality of single filament brushes
40
for electrically contacting the slip rings
20
. Furthermore, each of the single filament brushes
40
is coupled to a transport ribbon cable
42
, which is arranged for carrying electrical signals and/or power to and from an external device such as a printed circuit board. Moreover, a rectangular cover
44
is typically disposed over the stator/rotor combination.
Unfortunately, the design and implementation of the above assembly leads to problems which may shorten part life and the proper functioning of the video recording device in which it is used. One problem associated with the above assembly is that excessive vibrations may be encountered during rotation of the rotor about the stator. Excessive vibrations may be formed by an improperly mated or misaligned connection (e.g., un-balanced) at the rotor/spindle interface. For example, if the protrusion is too small then the rotor may wobble during rotation. Excessive vibrations tend to cause increased bearing wear, and may even cause the bearings to stiffen or seize Stiffened bearings may impede the rotation of the rotor or may induce more vibration. Excessive vibrations may also reduce contact between the brushes and the slip rings. Furthermore, the type of ball bearings used and the placement of the ball bearings on the rotating shaft may exacerbate the vibration problem.
Another problem with the above assembly
10
is that each of the brushes
40
is a monolithic or mono-filament member having a rectangular or cylindrical cross-section. Although the surface of the brush
40
is in contact with the rotating slip ring
20
, irregularities in the ring surface and uneven wear properties of the brush limit contact between the brush
40
and the ring
20
to only a few discrete points. These discrete points of contact between the brush
40
and the slip ring
20
cause the brush biasing force to be concentrated on these few points. This concentration of force results in localized high pressures on these few points and this leads to unexpected wear of both the brush and ring surface. Furthermore, the resultant wear debris may increase electrical resistance to the flow path of electricity through the assembly or may contaminate portions of the video recorder, for example, the head assembly found beneath the assembly.
Other problems associated with the above slip ring and brush assembly include a double brush assembly, which increases complexity and costs, a slip ring assembly that is not fully enclosed (e.g., open space
46
) and therefore may lead to contamination of both the assembly
10
and any components found beneath the assembly
10
(e.g., video recorder), and contact pads
28
that are thinly plated and thus may easily wear. By way of example, the contact pads
28
are typically formed from gold plated copper elements.
Thus, there is a need for improved slip assemblies for transmitting electrical signals and power across a rotating interface in a video tape recorder.
SUMMARY OF THE INVENTION
The invention relates, in one embodiment, to a slip ring assembly for use in a video recording device. The slip ring assembly includes a base for coupling with a rotatable spindle located in a drum assembly of a video tape recorder. The base includes a plurality of electrically conductive contact pads for electrically engaging a plurality of electrically conductive leads disposed on the rotatable spindle and electrically coupled to a record/reproduce head assembly. The slip ring assembly further includes a shaft having a first portion coupled to the base and a second portion extending longitudinally from the first portion. The slip ring assembly additionally includes a plurality of electrically conductive slip rings positioned on the second portion of the shaft, where each slip ring is separated by an insulating medium and electrically coupled to an individual one of the plurality of contact pads. The slip ring assembly also includes a pedestal rotatably supported on the first portion of the shaft.
In some embodiments, a brush assembly for transmitting electrical energy between a plurality of sta
Athanasiou Constantine
Athanasiou George
Abrams Neil
Athan Corporation
Beyer Weaver & Thomas LLP
Dinh Phuong K T
LandOfFree
Slip ring and brush assembly for use in a video recorder does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Slip ring and brush assembly for use in a video recorder, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Slip ring and brush assembly for use in a video recorder will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3146646