mprovements in Double Contact Switches especially adapted to Telephones.
Year: 1897

page_text: PROVISIONAL SPECIFICATION.
mprovements in Double Contact Switches especially adapted to
Telephones.
We, MAX BYNG, Electrical Engineer, and FRANCIS GEORGE BELL, Electrician,
both of No. 71 Queen Victoria Street in the City and County of London, do hereby
declare the nature of this invention to be as follows:-
Our invention relates to certain improvements in double contact switches,
especially adapted to telephones, and has for its objects, first, the attainment of
simplicity in construction, and secondly to afford a rubbing contact instead of a
mere impact, such rubbing contact preventing deterioration by oxidation, or the
accumulation of dust or dirt.
In order that our invention may be the better understood we have appended
the accompanying sheet of drawings, in which Figure 1 is a plan view of a
telephone transmitter, with the cover removed, and showing the improved switch
in place: Figure 2 is a plan view of the same showing how the switch lever pro-
jects through the cover, so that the receiver may depress it as shown, and Figure 3
is an elevation of the same, partly in section. Figure 4 is a plan view of the
switch lever and spindle, and Figure 5 is a side elevation of the same, showing
the contacts, both these figures being drawn to a larger scale to facilitate descrip-
tion. Similar letters of reference indicate corresponding parts throughout the
several views.
a
A,
we employ a switch lever
In carrying our invention into effect
which is attached to or formed upon a spindle B. Referring to Figure 5 it will
be seen that said lever A is tapered toward the contact end, which terminates with
a thin elastic strip of metal and as an additional provision we use for perfect
contact platinum or other refractory and non-oxidisable contact pins a attached
thereto, these being extended in the direction of the length of the switch lever to
a greater extent than is necessary in the case of an impact contact. The spindle B
rests upon two pin journals 6 61 and is kept in tension so that the switch lever
contact is touching one of the fixed contacts, (the lower one, C, for instance) by
spiral springs one end of which is attached to the spindle B and the other forming
a contact between any part of the circuit and the switch lever A. When said
switch lever is depressed by any kind of pressure, the contact is broken between
a and C and established between a and D, a slight bending or deflection of the
elastic strip carrying a causing it to rub the opposite contact on D, thus cleaning
it and preventing deterioration by oxidation, or the accumulation of dust or dirt
of any kind. The end c of the spring s is held either by tension or direct attach-
ment to any part of the frame, case, or other fixed portion of the switch or the
instrument to which it is adapted. It will be observed, that the tension of said
springs, when effecting the contact between a and C, produces the same rubbing
contact as herein before described by virtue of the reaction.
Referring now to Figures 1, 2, and 3, which represent the adaptation of the
switch according to our said invention to a telephone transmitter T, in which the
Và

page_text: depression of the switch lever A is effected by the introduction of the receiver R
into a slotted casing F, when said telephone is not in use. In this case the switch
lever A is always connected to the line by the contact E, and when the 'receiver R.
is in place, and the telephone is not in use, contact is maintained between
A and D), which connects the line-with the home.bell. When, however, the receiver
is removed for transmitting and receiving messages, the tension of the spring s
immediately causes the switch lever A to assume the opposite position, connecting
the line with the telephone and cutting out the bell.
We may adapt this, switch to any electrical apparatus in which a double
contact with a light spring action is required, modifying the various parts to suit
the conditions of such adaptations without departing from the essential features
of our invention as aforesaid.
Dated 1000
T
1007
FREDK. WALKER,
73 St. Stephen's Road, Upton Park, E., Agent for the Applicants.
"
COMPLETE SPECIFICATION.
Improvements in Double Contact Switches especially adapted to
Telephones.
We, MAX BYNG, Electrical Engineer, and FRANCIS GEORGE BELL Electrician,
both of No. 71 Queen Victoria Street in the City and County of London do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
Our invention relates to certain improvements in double contact switches
especially adapted to telephones, and has for its objects, first, the attainment of
simplicity in construction, and secondly to afford a rubbing contact instead of a
mere impact, such rubbing contact preventing deterioration by oxidation or the
accumulation of dust or dirt.
In order that our invention may be the better understood, we have appended
to our Provisional Specification a sheet of drawings, in which Figure 1 is a plan
view of a telephone transmitter with the cover removed, and showing the improved
switch in place.
Figure 2 is a plan view of the same showing how the switch lever
projects through the cover so that the receiver may depress it as shown, and
Figure 3 is an elevation of the same, partly in section. Figure 4 is a plan view
of the switch lever and spindle, and Figure 5 is a side elevation of the same
showing the contacts, both these figures being drawn to a larger scale to facilitate
description. Similar letters of reference indicate corresponding parts throughout
the several views.
In carrying our invention into effect we employ a switch lever A, which is
attached to, or formed upon a spindle B. Referring to Figure 5 it will be seen
that said lever A is tapered toward the contact end, which terminates in a thin
elastic strip of metal and as an additional provision to ensure perfect contact we
use contact pins a of platinum or other refractory and non-oxidisable metal, these
being attached to the lever A and extended in the direction of the length thereof
to a greater extent than is necessary in the case of a simple impact contact. The
spindle B rests upon two pin journals b b and is kept in tension so that a is
touching one of the fixed contacts, (the lower one, C for instance) by means of a
spiral springs one end of which is attached to the spindle B, and the other end
forming a contact between any part of the circuit and the switch lever A. When
A is depressed by any kind of pressure, the contact is broken between a and Ca
1 t..
and

page_text: established between a and D, a slight bending or deflection of the elastic strip
carrying a causing it to rub the opposite contact D thus cleaning both, and pre-
venting deterioration by oxidation, or the accumulation of dust or dirt of any
kind. The end c of the springs is held either by tension or direct attachment
to any part of the frame, case or other fixed portion of the switch or the instrument
to which it is adapted. It will be observed that the tension of said spring s when
effecting the contact between a and C produces the same rubbing contact as
hereinbefore described, by the reaction thereof.
Referring now to Figures 1, 2 and 3 which represent the adaptation of the
switch according to our said invention to a telephone transmitter T in which the
depression of the switch lever A is effected by the introduction of the receiver R
into a slotted casing F when said telephone is not in use. In this case the switch
lever A is always connected to the line by the contact E, and when the receiver R
is in place, and the telephone is not in use, contact is maintained between A and D
which connects the line with the home bell. When, however, the receiver is
removed for transmitting and receiving messages, the tension of the spring s
immediately causes the switch lever A to assume the opposite position, connecting
the line with the telephone and cutting out the bell.
We may adapt this switch to any electrical apparatus in which a double
contact with a light spring action is required, modifying the various parts to suit
the conditions of such adaptations without departing from the essential features
of our invention as aforesaid.
Having now particularly described and ascertained the nature of our said
invention, and in what manner the same is to be performed, we declare that what
we claim is: -
First. In an improved double contact switch, the combination of a switch
lever A, elastic rubbing contact a, and contacts C and D with a transverse
spindle B and spiral spring s substantially as herein described and shown by the
drawings.
Second. In an improved double contact switch as referred to in the preceding
claim, the method of, and means for adapting it to a telephone, substantially as
and for the purposes herein described with reference to the drawings.
Dated this 11th day of August 1897.
FREDK. WALKER,
73 St. Stephen's Road, Upton Park, London, E.,
Agent for the Applicants.