Supports: racks – Special article – Platelike
Reexamination Certificate
2001-10-18
2002-11-05
Gibson, Jr., Robert W. (Department: 3634)
Supports: racks
Special article
Platelike
C361S796000, C361S752000, C312S265400
Reexamination Certificate
active
06474480
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a vibratory motion restrainer, and more specifically to a mechanism for reducing or depressing externally applied oscillations to a rack-mounted card cage by way of a rack, which cage accommodates a plurality of printed circuit boards.
2. Description of Related Art
As is known in the art, groups of printed circuit boards are interconnected by placing them in card cages (also known as shelves or sub-sacks) which include hardware for housing the printed circuit boards.
Prior to turning to the present invention, it is deemed preferable to briefly describe, with reference to
FIGS. 1 and 2
, a conventional rack and card cages, to which the present invention is applicable.
FIG. 1
is a perspective view schematically showing part of rack
10
and one card cage
12
to be housed therein. As shown, the rack
10
comprises four frames
14
a
-
14
d
vertically provided at four corners of the rack
10
, two side panels
16
a
and
16
b
secured to the frames
14
a
-
14
d
, and a back panel
16
c
fixed to the frames
14
b
and
14
c
. The rack
10
further comprises a plurality of pairs of card cage ledges (shelves), each pair of which is used to support the card cage at left and right bottoms thereof. More specifically,
FIG. 1
shows that the card cage
12
is supported by a pair of cage ledges (only one ledge
20
a
is partially shown). On the other hand, another pair of cage ledges
22
a
-
22
b
are secured to the opposite inner sides of the rack
10
so as to support another card cage (not shown) to be installed into the rack
10
above the cage
12
.
The card cage
12
comprises four frames
24
(one frame is hidden in
FIG. 1
) transversely positioned to tops and bottoms of front and rear portions thereof. The cage
12
further comprises two side panels
26
a
-
26
b
respectively secured to the right and left sides of the cage
12
, and a rear panel
26
c
fixed to the rear portion thereof. The side panels
26
a
-
26
b
respectively have front edges
27
a
-
27
b
which are respectively used to detachably fix the card cage
12
to the rack frames
14
a
-
14
b
. Further, a plurality of guide rails
28
are mounted at the tops and bottoms of the four frames
24
at regular intervals between the side panels
26
a
-
26
b.
A plurality of card units
30
are detachably inserted into the corresponding guide rails
28
, leaving a predetermined space. between the adjacent ones. The removing and extracting of the card units is for maintenance, upgrade or other purposes. Each card unit
30
is provided with a front panel
32
, a printed circuit board
34
, a unit connector
36
mating with a corresponding connector
38
(
FIG. 2
) provided on the inner wall of the rear panel
16
c
. Further, each unit
30
comprises a pair of ejectors
40
in the vicinity of top and bottom portions of the front panel
32
. It is preferable to provide the ejector
40
with a suitable unit locking mechanism so as to prevent unintentional removal of the card unit
30
from the cage
12
. It is to be noted that
FIG. 1
omits a plurality of resilient supporting members provided between the rack
10
and the card cage
12
, which will be referred to in FIG.
2
.
FIG. 2
is a sectional plan view taken along a section line A—A of FIG.
1
. In order to simplify the drawing, the front panel
32
, the guide rails
28
, etc. are omitted in that they are impertinent to the present invention.
As shown in FIG.
2
. the cage
12
, which has accommodated the multiple printed circuit boards
34
, is housed in the rack
10
(FIG.
1
), in the case of which each card unit connector
36
is electrically coupled to the corresponding cage connector
38
. The card cage
12
is detachably secured to the rack frames
14
a
and
14
d
respectively at the elongated front edges
27
a
-
27
b
using a suitable fastening member
50
such as a screw. On the other hand, resilient support members
52
are respectively fixed to the rack frames
14
b
and
14
c
using screws
54
at the rear portions thereof. The above-mentioned support members
52
, however, may be welded to the corresponding rack frames
14
b
-
14
c
in place of the screws
54
. When the card cage
12
is completely inserted into the rack
10
as illustrated, the resilient support members
52
press the rear side portions of the cage
12
, thereby rigidly supporting the same in the transverse direction, viz., a direction normal to that along which the printed circuit board
34
are inserted. The resiliently supporting technology, as just mentioned above, is disclosed in Japanese Laid-open Patent Application No. 10-93264. As an alternative, the resilient support members
52
may be fixed, using screws (for example), to the rear sides of the card cage.
12
.
When the rack
10
is transported by land, sea, or air while accommodating the card units
30
(viz., printed circuit boards
34
)within the cage(s)
12
, the rack
10
is typically subject to vibrations or oscillations with a variety of frequencies and magnitudes. Further, even after the rack
10
has been set, the rack
10
may be subject to vibrations with low frequency and large amplitude due to earthquake (for example). Therefore, if the cage
12
is secured to the rack
10
using the rigid supporting members
52
at the rear portions, and fixed to the rack frames
14
a
-
14
d
at the front edges
27
a
-
27
b
, it is not expected to effectively reducing the externally applied vibrations with high frequencies and relatively low amplitude. On the other hand, if the supporting members
52
are made of material with high elasticity so as to high frequencies and low amplitude vibrations, it is in turn unable to effectively absorb the vibrations with low frequencies and large amplitudes.
If the vibrations applied to the card cage
12
coincides with the characteristic (natural) frequency of the printed circuit board, the electronic components may be damaged due to sympathetic vibrations. Further, in such a case, the adjacent card units may collide with each other, resulting in damages of the card units and/or the printed circuit boards mounted thereon.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a mechanism for reducing vibratory motions applied to the rack-mounted card cage by changing a spring constant of a resilient member in response to the magnitude and frequencies of the vibration.
In brief, the object is achieved by the techniques wherein a mechanism for reducing vibratory motion applied to a card cage mounted in a rack is provided. The cage accommodates a plurality of printed circuit boards arranged in parallel at regular intervals. The mechanism comprises dampers provided between the rack and the card cage. Each of the dampers is responsive to external vibrations applied to the rack in a transverse direction relative to a direction along which the plurality of printed circuit boards are arranged, and changes damping characteristics thereof in two stages depending on strengths and frequencies of the external vibrations.
One aspect of the present invention resides in a mechanism for reducing vibratory motion applied to a card cage mounted in a rack, the card cage accommodating a plurality of printed circuit boards arranged in parallel at regular intervals, the mechanism comprising: damping means, provided between the rack and the card cage, for responding to external vibrations applied to the rack in a transverse direction relative to a direction along which the plurality of printed circuit boards are arranged, and changing damping characteristics thereof in two stages depending on strengths and frequencies of the external vibrations.
REFERENCES:
patent: 3863113 (1975-01-01), Ward
patent: 4713714 (1987-12-01), Gatti et al.
patent: 5253147 (1993-10-01), Kleyner
patent: 5460348 (1995-10-01), Cox
patent: 5657649 (1997-08-01), Lim
patent: 6115259 (2000-09-01), Karner
patent: 6155660 (2000-12-01), Nicolai
patent: 6202860 (2001-03-01), Ludwig
patent: 10-93264 (1998-04-01), None
Gibson , Jr. Robert W.
NEC Corporation
Sughrue & Mion, PLLC
LandOfFree
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