Note: Descriptions are shown in the official language in which they were submitted.
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LATCH MECHANISM FOR A PLUG-IN CARTRIDGE OR THE LIKE
Field of the Invention
The present invention relates generally to
latching mechanisms. In particular, the present invention
relates to latching mechanisms ~or aiding the insertion into,
the removal from, and the retention in, of objects relative
to a mating piece of apparatus.
Background of the Invention
Printed circuit boards (PCBs) are generally
mounted in frame~, with a large number of PCBs mounted in
each frame, with as high a density as possible, in order to
save space. A typ~cal PCB comprises a pattern of electrical
interconnections on a flat rectangular sheet of insulating
material carrying a number of components. The four edges of
the PCB can be referred to as a front edge, a back (or rear)
edge, a top edge, and a bottom edge. The PCB slides into
guide channels in the frame, the PCBs lying normally in a
vertical plane with the top edge in a top guide channel, the
bottom edge ~n a bottom guide channel, and the rear edge
carrying a set of conn~ctions which mate with a corres~onding
set of connections mounted to the frame. The front edge of
the PCB may carry two devices (one usually near the top, and
one usually near the bottom) to aid in inserting, removing or
retaining the PCB relative to the frame.
Various prior art devices for performing this
function are depicted in the following U.S. patents and
attention is directed to them: U.S. Pat. No. 4,648,009 dated
Mar. 3 1987 to R.A. Beun et al.; U.S. Pat. No. 4,632,588
dated Dec. 3Q, 1986 to M.H. Fitzpatrick; U.S. Pat. No.
4,606,591 dated Aug. 19, 1986 to K.A. Bloch; U.S. Pat. No.
4,596,907 dated June 24, 1986 to A.S. LaGreco et al.; U.S~
Pat. No.4,445,740 dated May 1, 1984 to K.L. Wallace; U.S.
Pat. No. 4,313,150 dated Jan. 26, 1982 to Pak-Jong Chu; U.S.
Pat. No. 4,233,646 dated Nov. 11, 1980 to E.C. Leung et al.;
U.S. Pat. No. 4,064,551 dated Dec. 20, 1977 to R. Lightfoot;
U.S. Pat. No. 3,952,232 dated April 20, 1976 to R.A. Coules;
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and U.S. Pat. No. ~,798,507 dated March 19, 1974 to N.F.
Damon et al. Another prior art device is pictured on pages
78 and 79 of the Fall 1975 issue of ~elesis published by
Bell-Northern Research Ltd., ottawa, Ontario, Canada.
The Leung patent discloses a latching lever having
a latching mechanism which comprises a hooked portion
flexibly connected to the body portion of the latching lever,
an actuating member solidly connected to the hooked portion
for moving the hooked portion relative to the body portion,
lo and a stop portion, solidly connected to the body portion for
limiting the movement o~ the actuating member. A stud
carried by the PCB is engaged by the hooked portion of the
lever to enable the lever to latch. Moving the actuating
member disengages the hooked portion from the stud, thereby
unlatching the lever, and leaving the lever free to pivot
about its pivot polnt.
Pr~or art devices of the type described above have
the disadvantage of having weak areasj such as where the
actuating member and the hooked portion are attached, which
may not withstand the stresses incurred from repetitive
insertion and removal of a PCB. over time the web ~oining
th~ actuating member, or the hooked portion, to the lever may
wear out allowing either, or both, to break off. Without
these items the device will not function as intended.
Other prior art devices, such as described in the
Chu patent, have the disadvantage that the lever must be
attached by means of a rivet or screw and nut assembly.
This can add to the cost and time of manufacturing and
assembling the lever.
Summary of the Invention
The present invention is a latching mechanism
which is of simple one piece rigid construction. Assembly of
the latching mechanism to a cover plate is easily
~5 accomplished by snap fitting the latch assembly over a pair
of pivot pins. Additionally, the latching mechanism of the
present invention provides a simple yet effective means of
locking the latching mechanism in a latched position by
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providing a pair of detents which forcibly interact with a
pair of channels thereby further providing a tactile and
audible feedback. Furthermore, the flush appearance of the
latch assembly provides a minimum gap and protrusion making
the latch assembly tool-removable to comply with national
safety standards. Moreover, the present invention aids the
insertion into, the removal from, and the retention in, of a
plug-in cartridge or the like relative to a cabinet while
maintaining a flush appearance with a face plate of the plug-
in cartridge or the like.
Stated in other terms, the present invention is alatching mechanism for use with an object for aiding the
entry of the ob;ect into a mating apparatus, for securing the
object in the mating apparatus, and for aiding the removal of
the object from the mating apparatus, the latching mechanism
comprising: a body portion; a pair of walls extending from
the body portion, the walls having means for rotatably
mounting, about a pivot point, the object therebetween,
facing-portions of the walls having facing channels snap
locatable onto detents on opposite face~ of the objact to
resiliently latch the latching mechanism when the object is
fully inserted into the mating apparatus: a camming portion,
mounted to the body portion, and pro~ecting therefrom at an
end of the body portion nearest the pivot point, for engaging
a projection on the mating apparatus; and, an actuating
portion remote from the pivot point, for selectively
disengaging the latching meahanism from the mating apparatus
and for providing leverage for the camming portion; the
camming portion and the actuating portion cooperating to
function as a lever, the camming portion engageable with an
inside surface of the projection to establish a first
engagement about which the latching mechanism is levered to
overcome an insertion force, and engageable with an outside
surface of the mating apparatus to establish a second
engagement about which the latching mechanism is levered to
overcome an extraction force.
Stated in yet other terms, the present invention
is the combination of a printed circuit board (PCB), a face
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plate, and a latching mechanism for use in aiding the entry
of the PCB into a mating apparatus, for securing the PCB in
the mating apparatus, and for aiding the removal of the PCB
from the mating apparatus, the co~bination characterized by:
the latching mechanism comprising: a body portion; a pair of
walls extending from the body portion, the walls having means
for rotatably mounting, about a pivot point, the ob~ect
therebetween, facing portions of the walls having facing
channels snap locatable onto detents on opposite faces of the
object to resiliently latch the latching mechanism when the
ob;ect is fully inserted into the mating apparatus~ a camming
portion, mounted to the body portion, and projecting
therefrom at an end of the body portion nearest the pivot
point, for engaging a projection on the mating apparatus;
and, an actuating portion remote from the pivot point, for
selectively disengaging the latching mechanism from the
mating apparatus and for providing leverage for the camming
portion; the camming portion and the actuating portion
cooperating to function as a lever, the aamming portion
engageable with an inside surface of the projection to
establish a first engagement about which the latching
mechanism is levered to overcome an insertion force, and
engageable with an outside surface of the mating apparatus to
establish a second engagement about which the latching
mechanism is levered to overcome an extraction force.
Brief Description of the Drawings
The invention will ba readily understood by the
following description of a preferred embodiment, by way of
example, in con~unction with the accompanying diagrammatic
drawings, in which:
Figure 1 is a perspective view of a plug-in
cartridge utilizing the la~ching mechanism of the present
invention;
Figure 2 is an exploded view of a face plate
having attached thereto the latching mechanism of the present
invention;
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Figure 3 is an enlarged view of the partial
exploded view of FigurP 2;
Figure 4 is a perspective view of the latching
mechanism;
Figure 5 is a cross-sectional view of the latching
mechanism of the present invention in a fully open position;
Figure 6 is a cross-sectional view of the latching
meahanism of Figure 4, but showing the latching mechanism in
an intermediate position; and
Figure 7 is a cross-sectional view of the latching
mechanism of Figure 4, but showing the latching mechanism in
a latched position.
Detailed Description of the Invention
Referring to the Figures, there is illustrated a
plug-in cartridge 10 consisting of a printed circuit board 12
having a face plate 20 affixed thereto. The face plate 20 is
affixed to the printed circuit board 12 by a suitable
fastener placed through openings 26 (one of which is
illustrated in Figure 1). Pivotally affixed to th~ face
plate 20 are a pair of latahing mechanisms 40, one at each
end. The latching mechanisms 40 are designed to reside in
recesses 22 within the face plate 20 so as to be flush with
the front face 24 of the face plate 20 when the latching
mechanisms 40 are in a latched position. Figure 1 further
illustrates a pair of slots 28 formed in the face plate 20
which are provided 'o aliow an object7 such as a blade or a
screwdriver, to be slipped under the latching mechanisms 40
when in their latched positions (as shown in Figure 1) to
thereby pry the latching mechanisms 40 open. Further
depicted in Figure 1 is a camming member 42 integrally formed
with the latching mechanism 40. Camming member 42 is
provided to aid the insertion into, the removal from, and the
retention in, of the plug-in cartridge 10 relative to a
mating frame or cabinet 60 (shown in Figures 5-7).
Figures 2 and 3 illustrate the face plate 20 with
one of the latching mechanisms 40 removed. In these Figures
a pair of plvot support~ 30 ar shown extending ernm the end
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41 of the face plate 20. Affixed to each of the pivot
supports 30 is a pivat pin 32 (only one of which is visible
in the Figures). Each of the pivot pins 32 is bevelled along
a portion 33 to facilitate attachment of the latching
mechanism 40. During assembly the latching mechanism 40 is
held in an open position (such as shown in Figure 5) and snap
fitted over the pivot pins 32. The assembly is aided by the
provision of the bevels 33 and by a pair of channelled ramps
46 on each wall 45 (as shown in Figure 4) of the latching
mechanism 40. The channelled ramps 46 help direct the pivot
pins 32 into the pivot openings 44 and help spread th~
resiliently flexible walls 45 allowing them to slip over the
pivot pins 3~.
Further illustrated in Figures 2 and 3 is one of a
pair of detents 34. Each of the detents 34 are positioned so
as to forcibly engage with one of a pair of channels 48
formed in each of the walls 45 (as shown in Figure 4). The
detents 34 provide a means of locking the latching mechanism
40 in à latched position (as shown in Figure 7).
Furthermore, the action of the dQtents 34 against the walls
of the channels 48 provide a tactile and audible feedback.
Figures 5 to 7 illustrate the latching mechanlsm
40 in operation. With the latching mechanism 40 i~ an open
position, as illu~trated in Figure 5, the plug-in cartridge
10 is inserted into a cabinet 60 and pushed in as far as
possible so as to engage connectors (not shown) on the
printed circuit board 12 with connectors in the cabinet 60.
Due to the shape of the latching mechanism 40 the latching
mechanism 40 will automatically engage a cabinet cover 62 and
rotate toward a closed position, as illustrated in Figure 6.
As the latching mechanism 40 is rotated toward the face plate
20, the camming member 42 engages a projection 64 on the
cabinet cover 62. Further rotation of the latching mechanism
40 by pressing on the actuating portion 47 causes the camming
member 42 to act against the cabinet cover 62. The latching
mechanism 40 can therefore be used to overcome the insertion
stress of the plug-in cartridge 10, thereby forcing the plug-
in cartridge 10 into the cabinet 60. The operator then
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rotates each latching mechanism 40 to a latched position, as
illustrated in Figure 7, which will push the plug-in
cartridge 10 fully into the cabinet 60 thereby fully engaging
the connectors. When each latching mechanism 40 approaches
the latched position, the walls 45 of the latching mechanism
40 ride over the detents 34 until the detents 34 align with
the channels 48 allowing the walls 45 to snap back to their
original orientation. In doing so, the detents 34 provide a
tactile feed back and a click is heard. The detents 34 and
the channels 48 cooperate to maintain the latching mechanism
40 in a latched position.
To remove the plug-in cartridge 10 a blade or
screw driver is inserted in the slot 28 to provide sufficient
leverage on actuating portion 47 to free the walls 45 from
the detents 34. Latching mechanism 40 can then be opened by
hand. In doing so a lip 49 on latching mechanism 40 pushes
against the cabinet cover 62 thus providing a means for
counteracting the removal stress of the plug-in cartridge 10,
thereby pulling the plug-in cartridge 10 from the connectors
and the cabinet 60.
In a preferred embodiment, a stop member 43
(visible in Figures 3 and 4) iB integrally formed with the
latching mQchanism 40. The stop member 43 interacts with
stop portion 36 on the face plate 20 to prevent the latching
mechanism 40 from being over rotated during opening. This
helps maintain the latching mechanism 40 in a practical
position for reinsertion into the cabinet 60.
It can be readily realized that: if the latching
mechanism 40 is in a alosed position, ie. maintained against
the face plate 20 by the detents 34; when the plug-in
cartridge 10 is not inserted in the cabinet 60, the camming
member 42 will prevent the insertion of the plug-in cartridge
10 into the cabinet 60. This can be a useful feature where
it is desired to disconnect a plug-in cartridge 10 from a
connector but still keep the plug-in cartridge 10 supported
in the cabinet 60 while preventing accidental insertion.
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Numerous modifications, variations, and adapta-
tions may be made to the particular embodiments of the
invention described above without departing from the scope of
the claims.
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