Note: Descriptions are shown in the official language in which they were submitted.
~3~3~
This invention relates to a zero insertion force
circuit board edge electrical connector, comprising an
insulating housing having an elongate opening for
receiving a circuit board along a board insertion
path; a-t least one row of electrical terminals
positioned beside the opening and extending in the
longitudinal direction thereof, each terminal having
a resilient contact portion for engaging the circuit
board when such has been inserted into the opening
along the insertion path; a groove formed in the
bottom of the opening and extending longitudinally
:thereof; an elongate cam mounted for rotation about
its longitudinal axis in the groove and extending
longitudinally thereof; and a cam follower having
a first surface engaging the cam, the cam follower
being displaceable normally of the base of the
groove by rotation of the cam, to cause the cam
follower to move between a first position in which
it displaces the contact portions from the insertion
path and a second position in which the cam follower
is retracted to allow the contact portions to ~ .
intersect the insertion path. : -
The use of a rotary cam as opposed to a
linear action cam has the advantages that no space
is required to accommodate reciprocatiny movement of
the cam and that the cam can be of very simple
construction, being for example of oblong or of
.. j , ~b
.
,
- - . :
,: ': ' '
.
~3~'~3~
substantially eliptical, cross-section.
However, in known connectors of the above'kind
$he cam follower is returned from its first to its
second position by virtue of the resilience of the
contact portions o~ the terminals, which resilience
also serves to maintain the cam follower in its second
position. It has been found, that their exercise of
this return function tends to cause the contact portions
to loose resilience with the result that the cam
10~ follower, after an extended period of use of the
connector, can no longer be fully returned to its
second position so that the connector becomes inoperative,
or the cam follower i5 readily displaced from its ,
second position~, Especially where the connector is
subjected to vibration whilst in use or is mounted
so that the return of the cam follower is not assisted
by gravity, this latter disadvantage will result in
intermittent impairment of the integrity of the
electrical connections between the contact portions
and the conductors of the circuit board.
i~ccoxding to the present invention therefore,
in a connector as defined in the first paragraph of
this specification, the cam follower has a second
surface spaced from the first surface towards the
base of the groove and which is engageable b~ the cam,
~s the cam is rotated to cause the cam ollower to
move'from its'first to iks second position, so that
. ,~,
" , ~ .
,
: - . ~ . , , : . .
. ~, . - . . .
. - ~ , , i . . , ., , " , : ..
-: ~ , . ..
. ,
.... . .
~3f~3~
*he cam positively drives -the cam follower to its
second position, in which position the second surface
engages the side of the cam nearest to the base of
the groove so that the cam follower is secured in
its second position by the cam, against unintended
movement.
For a better understanding of the invention
an embodiment thereof will now be described by way
of example with reference to the accompanying drawings
in which:-
Figure 1 is a perspective sectional view ofa zero insertion force circuit board edge electrical
connector;
Figure 2 is a longitudinal, vertical sectional
view through an end portion of the connector;
Figure 3 is an enlarged perspective, sectional
view of a cam and a cam follower of the connector;
and
Figures 4 to 6 are cross-sectional views of the
connector illustrating the operation thereof.
-The.connector-comprises.an insulating.housing
10, a cam 12, a cam follower 14 and a plurality of
electrical terminals 16.
The housing 10 defines an elongate central
openiny 18 for receiviny an edge portion of a circuit
board 20 (Figure 1) along a board insertion path A, a
row of spacer members 22 on each ~ide o~ the opening 18
- 4 -
.
.
- . . : .
,
''
~.~ 3~
defining recesses 24 each recei~ing a terminal 16
extending through a passage 26 in the base 27 o the
housing 10, which passage communicates with the recess
24~
~he opening 18 communicates with a groove 28
formed in the base 27, which defines the bottom of the
opening 18, the groove 28 extending longitudinally
thereof. The groove 28 receives the cam 12 for free
rotation therein~
At each end thereof the housing 10 has a mounting
lug 30 (only one is shown) with a screw hole 32.
The cam follower 14 (best seen in Figure 3),
which is channel shaped, comprises a base 34 having
parallel side walls 36 and 38, extending in the same
direction from the base 34, a wall 40 extending from
.a flat, cam engagement surface 35 of the base 34, in
alignment with, and in the opposite direction to, the :
side wall 36 and terminating in an inwardly directed
flange 42 having a flat, inner abutment surface 43
parallel to, and overlapping the base 34. The base 29
of the groove 28 has therein a longitudinal recess 44
dimensioned to receive the flange 42.
.The base 34 of the cam follower 14 is disposed
ln the groove 28 so that the surface 35 o~ the base
34 is engaged by the cam 12, the wall 40 protruding
into the groove 28 beside the cam 12. ::
The c,am 12, which is elongate in the direction
.: .- .:. , . : ~ , - ,. ~. .: ,, ~...... .. .
. , . . . . .- ..
...
. ~ . , .
:
. . :: , , , :,
~13~
of the groove 28 and which can be rotated from ou-tside
the housing 10 as shown in Figure 2, is of elongate
cross-section having parallel major sides 45 and convex
minor sides 47. The surface 35 of the base 34 is
:spaced from the surface 43 of the flange 42 by a
distance slightly exceeding that between the major sides
45 of the cam 12, the flange 42 overlapping the base 34
by a distance which does not exceed that between the
sides 45.
The terminals 16 are in the form of metal
strips having looped resilient contact portions 50
wlthin the housing~ free end portions 52 of the contact
portions 50 engaging chamfered outer sides of the
free longitudinal edges of the side walls 36 and 38
of the cam follower 14. The terminals have locking
tongues 54 on post portions 56 thereof, which
portions extend through the passages 26, the tongues
54 serving to retain the terminals 16 in the housing
10.
Figure 4 shows the cam follower 14 in a first
-~position in which it has been advanced normally of
the base.29 of the groove 28, by the cam 12
so that the side walls 36 and 38 of the cam follower
have spread apart the contact portions 50, displacing
them from the insertion path A, to allow entry of the
board 20 into the openi.ng 18 along such path, with
substantially zero insertion force. So to advance
- 6 -
.
' , . ` , ' . . ,
3~ol3~
the cam follower 14, the cam 12 wa.s rotated in
an anticlockwise (as seen in Figures 4 to 6) sen~e~
to an extent limited by a stop 58 on the left hand
(as seen in Figures 4 to 6) side of the groove 28.
As the cam 12 is rotated in the opposite sense,
to retract the cam follower 14 in the groove 28,
normally of the base thereof, to a second position,
so as to allow the contact portions 50 to close so as
to intersect the path A of the board 20 (which is
not shown in Figures 4 to 6), one major side 45 ofthe cam 12 engages the flange 42, as shown in Figure
5, to ~rive the cam follower 14 positively towards
the base of the groove 28, until, as shown in
Figure 6, the flange 42 is fully received in the
recess 44 and the major sides 45 of the cam 12 are
in full surface to surface engagement with surface
35 of the cam follower 14 and with the basé 29 of
the groove 28, respectively, one convex minor
side of the cam 12 being received between the base
34 and the flange 42. In the isecond position of the
cam follower 14, the surface 43 of the flange 42
engages the side 45 of the cam 12, nearest to the base
29 of the groove 28, as shown in Figure 6, so that
the cam follower 14 is locked in its second position
by the cam 12.
Since the cam follower 14 is poisitively dr~ven
by the cam 12, in the event that the contact portions 50
, . . , .. , ,: .
.. .... ..
.,
~.~L3~3~
should lose resilience through use, they are
nevertheless returned fully to th~ir closed positions so
as to apply the required contact force against the
conductors of the board 20, even in the event that
the connector is mounted in an orientation in which
the return of the cam follower is not assisted by
~ravity.
By virtue of the engagement of the cam 12
against the surface 43 of the flange 42, in the
second position of th-- cam follower 14, the cam
follower 14 is secured in its fully retracted
position so that it cannot be unintentionally moved
under the action of vibration for example, so as
to impair the integrity of the electrical connections
between the contact portions 50 and the conductors
of the circuit board 20.
. For making connection to only one side of a
circuit board, the connector may have only one row
of terminals, one side of the cam follower being
omitted and the base thereof on that side being
: arranged to slide against a blank wall of the housing.
,
~5
- 8 -
: - .. . .
,
~, . . .
:., .: . : , ,.
.
