Note: Descriptions are shown in the official language in which they were submitted.
il ~ 3
The present invention relates to a pushbutton switch
assembly for use with telephone sets haviny a printed circuit pro-
vided with contacts and conductors and a swi-tching mat oE elastic
material placed thereover, which comprises domes associated with
pushbutton keys, and in -the cavities of which the moving contacts
are accommodated.
Such pushbutton switch assemblies with a pri.nted circuit
as the base for the fixed contacts, and a switching mat as the base
for the moving contaets are already known, for example, from the
German Published Patent Applica-tion (DE-OS) 30 33 134. The switeh-
ing mat eonsists of rubber or of a rubber-elastie plastics material
and is provided with dome-like archings which are associated with
the pushbutton keys. Inside the arehing there is positioned a
moving eontaet whieh, upon depressing a pushbutton key, comes in
touch with the corresponding fixed contact on the printed circuit.
With modern types of telephone sets, such pushbutton
switch assemblies employing switchi.ng mats, are used to an increas-
ing ex-tent as pushbutton dialling units. Moreover, in the case of
:inte:rcommunication and secretarial systems, for switching the
~0 operational states, such as for programming service features or
blocking -toll line authorisations, there is required an additional
loek-down switch. This loek-down switch is a separa-te structural
unit which eonsists of a loek cylinder with a removable key, with
a eam capable of rotating about the cylinder axis, cooperating with
contact springs, being connected to the lock cylinder. All parts
are accommodated in a cylindrical housing of plastics material
which is either screwed to the chassis of the telephone set, or can
be attaehed thereto in a form-fit eonnection (German Utili-ty Model
--.
(DE-GM) 75 28 008).
It is an object of the present invention to in-tegrate -the
lock-down switch into the pushbutton swi-tch assembly. This objec-t
is achieved by employment of a lock-down switch, whose lock
cylinder comprises a rotatable trip cam, disposed in such a way
above the switching mat that a dome becomes operable upon rotation
of the trip cam. By the configuration according -to the invention
there is attained the advantage -that a separate lock-down switch
group becomes superfluous. The space required for this and -the
wiring can be used otherwise. Both the construction ar;d the assem-
bly of the -telephone set are more simple and inexpensive than with
conventional types. Also the retrofitting can be carried out
easily because no soldering work is required. The wiring is already
provided for in a printed circuit.
The invention will now be described in grecter detail with
reference to examples of embodiments shown in Figures 1 to 4 of the
accompanying drawings, in which:
Figure 1 shows a lock-down switch according to the inven-
tion, in a neutral position be-tween two switching-mat domes, in a
cross-sectional view,
Figure 2 shows the same lock-down switch as in Figure 1,
but in the actuated pcsition above one dome of the switching mat,
Figure 3 shows a modified design of the lock-down switch
in -the non-actuated position above a dome of the switching mat, and
Figure 4 shows the lock-down switch of Figure 3 in the
actuated position.
In the pushbutton switch assembly as shown in Figures 1
and 2, a switching mat 5 having dome-shaped convexities 6 is dis--
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posed over a printed circuit 4 having the fixed con-tacts and con-
ductors 8. The printed circuit 4 is Eormed by a printed circuit
board or a conductor foil. The switching rna-t 5 consis-ts of an
elastic, rubber-like plas-tics material.
Inside the domes 6 oE the switching mat 5 there are the
moving contacts 7 which cooperate with the fixed contacts 8 on the
printed circuit 4. When the assembly is used with a pushbutton
dialling unit for telephone sets, the domes are actuated by push-
buttons placed respectively above them, but not shown in the
accompanying drawings.
Between respectively two domes 6 there is disposed one
lock-down switch 1 whose lock cylinder 2 is provided at i-ts lower
end with a rotatable trip cam 3 formed by a wing-type attachment of
the lock cylinder 2 (as seen in Figures 1 and 2). The rotation of
both the lock cylinder and its trip cam is effected, in the usual
way, with the aid of a (not shown) key. In Figure 1, the trip cam
3 is shown in its neutral center position between two domes 6 of
the switching mat 5. As is indicated by the double arrow, it can
be rotated in both directions about its axis. In Figure 2, it is
~Q shown to have been -turned to the left and to have depressed in the
course of this, the left-hand dome 6, so that the contact 7 thereof
comes in touch with the contact 8 on the printed circuit. The
domes 6 associated with the lock-down switch are provided for in
addition to the pushbutton-actuated domes on the switching mat.
It is sufficient to provide two domes, but equally well
also four domes may be disposed in such a way around the lock
cylinder as to become operable by the trip cam 3 thereof. In cases
where the lock-down switch 1 is required not at all, there is merely
.,
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omit-ted the lock cylinder, and the corresponding opening in the
control panel is closed by means of a (not shown) dummy plug.
Conversely, in retrofitting the telephone set, the dummy plug is
replaced by a lock-down switch.
In the type of embodiment as shown in Figures 3 and 4,
unlike in the previously described type of embodiment, the lock-
down switch 1 is disposed coaxially above one dome 6 of the switch-
ing mat 5. Accordingly, only one dome can be actuated.
In this case, the trip cam 3 of the lock cylinder 2 con-
sists of a bevel of the lower end of the rotatable portion of thelock-down switch. This cam 3 is opposed by the complimentarily
bevelled end of a coaxially disposed plunger 9 which is supported
capable of being moved in the axial direction only. If now, the
cam 3 is turned from the position as shown in Figure 3 into the
position as shown in Figure ~, the plunger 9, in accordance with
the inclination of the bevels on both the cam and the plunger, is
moved downwardly towards the dome 6, causing the latter to be
depressed, so that the contacts 7 and 8 come in touch with one
~nother. Upon turning back the lock-down switch 1, the plunger 9
reassumes its normal position.
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