Improvements in Switches for Electrical Circuits.
Year: 1890

page_text: Date of Application, 30th May, 1890
Complete Specification Left, 19th Sept., 1890-Accepted, 1st Nov., 1890
"
PROVISIONAL SPECIFICATION.
Improvements in Switches for Electrical Circuits.
BERNARD MERVYN DRAKE, JOHN MARSHALL GORHAM and PERCIVAL JOHN PRINGLE
all Electrical Engineers of 66 Victoria Street, London S.W., do hereby declare the
nature of this invention to be as follows:-
دو
This invention consists in a new construction of switch for making or breaking
electrical circuits. The object of the construction is to provide an instantaneous
on or off" motion and to thus effectually prevent the formation of an electrical
arc at the points of contact & yet at the same time to place the switch bar
under the direct control of the handle or thumb piece should the governing
spring fail at any time to draw the contact bar " on or off" at the desired
"
"
moment.
"
Before describing the manner in which we attain this object we wish to remark
that although switches have been made to break the circuit instantaneously and
independently of the rate of motion of the actuating thumb piece yet to the best
of our knowledge and belief it has been possible with all these switches to produce
Fan "are"-at-the-forward-motion-of-the-switch-as-the-contact-bar-in-them-can-
be pressed forward against its spring directly or solely by the thumb piece or
handle.
In our invention the thumb piece changes the shape & position of a spring
which re-acts upon the switch bar drawing it instantly home into the contact
pieces & allowing the thumb piece to follow it; in breaking the circuit the thumb
piece acts upon the spring and the springs instantly "draws off" the contact bar
in the same manner as when closing the circuit.
The contacts and working parts of the switch are mounted upon a base of some
insulating material; in the small size switch we prefer to use two contact pieces
fitted radially upon the base and in such a manner that the contact bar bridges
them across and completes or opens the circuit simultaneously at the two contact
pieces.
A fixed pin passes up through the centre of the switch and constitutes the axis
and support of the working parts of the switch.
The contact bar or bridge piece is first fitted upon this pin; above this is a
trigger piece which consists in a horizontal projection which carries towards its
point, one end of an S shaped steel wire spring the other end of this spring
being fixed to the switch base; the said horizontal projection is of such a length
that it will engage either of two vertical projections fitted upon the contact bar;
a further projection is provided at the back end of the trigger piece, this is turned
upwards to fit in a wide slot in the under side of the thumb piece which is also a
loose fit upon the supporting axis.
"direction it engages the trigger
afore mentioned S spring to the
where the two ends of the spring
When the thumb piece is turned in the ". on
piece and carries it against the pressure of the
crossing point of the spring namely, to the point
come in line with the axis of the trigger piece.
The action of the spring upon the trigger piece on crossing its dead point is reversed
thus instantly pulling over the trigger piece in the "on direction, the trigger
piece engaging the contact bar as above described and completing the circuit
between the two contact pieces. This action is quite independent of the rate of
motion of the thumb piece.
"
In switching off, the thumb piece again engages the trigger piece & on crossing the
neutral point instantly shoots to the full "off" position carrying with it the contact

page_text: bar.
It will be seen that should the spring or trigger part fail to act in the desired
manner the thumb piece follows up and turns the contact bar.
30th May 1890.
BERNARD MERVYN DRAKE.
JOHN MARSHALL GORHAM.
PERCIVAL JOHN PRINGLE.
COMPLETE SPECIFICATION.
Improvements in Switches for Electrical Circuits.
BERNARD MERVYN DRAKE, JOHN MARSHALL GORHAM, and. PERCIVAL. JOHN
PRINGLE, all Electrical Engineers of 66 Victoria Street in the City of Westminster,
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:-
.on
This invention consists in a new construction of switch for making or breaking
electrical circuits. The object of the construction is to provide an instantaneous".
and "off" motion and to thus effectually prevent the formation of an electrical "arc"
at the points of contact and yet at the same time to place the switch bar under the
direct control of the handle or thumb piece, should the governing spring fail at any
time to draw, the contact bar "on" or "off" at the desired moment. In our invention
the chief feature is the improved form of spring, which allows of a much more compact
and simple arrangement of the working parts of the switch. The particular S shape
of the spring used allows of its acting across the centre axis of the switch, but without
interfering with it in any way, as is the case with an ordinary spiral spring. This
allows the centre axis to be carried through in one piece and support all the working
parts.
When
Referring now to the accompanying drawings, we will now fully describe the manner
in which we attain our object. The contacts C. C. and working parts of the switch
are mounted upon a base of some insulating material A. A fixed pin B. passes up
through the centre of the switch and constitutes the axis and support of the working
parts of the switch. The contact bar or bridge piece D is first fitted upon the pin B.
Above this is a trigger piece E which consists of a horizontal projection which carries
towards its point one end of an S shaped steel wire spring F the other end of which is
fixed to the switch base A by the pin G. The trigger piece E is of such a length that
it will engage with one or other of the two projections, H H on the contact bar D
when turned in either direction. The trigger piece E also has two projections I. I.
upon it with which the thumb piece or handle J engages when turned in either direction.
This thumb piece. J is also supported loosely upon the centre pin or axis B.
the thumb piece J is turned in the off direction it engages the trigger piece E and
carries it against the pressure of the spring F to the crossing point of the spring,
namely to the point where the two ends of the spring and the centre axis of the trigger
piece E come in a line. The action of spring upon the trigger piece E on crossing
its "dead point" is reversed, thus instantly pulling over the trigger piece E in the
on" direction. The trigger piece E engages sharply with the projections Fl & carries
the contact bar D instantaneously between the contact pieces C. C. thus completing the
electrical circuit. This action is perfectly independent of the rate of motion of the
thumb piece J. In switching "off" the action is similar but in the reverse direction.
It will be seen that should the spring F or trigger part E fail to act in the desired
manner the thumb piece J will itself follow and carry on the contact bar D to its
proper position.
"
Having now particularly described and ascertained the nature of our said inven-
tion and the manner in which the same is to be performed, we declare that what
we claim, is:
I. In switches for electrical purposes the use of a spring for producing a anick

page_text: make and break having the peculiarities and shape, substantially as described above
and shewn in accompanying drawings.
II. The combination of the above spring with trigger piece, loose contact bar, and
thumb piece for producing a quick make and break switch, substantially as described
above, and shewn in accompanying drawings.
Dated this 19th day of September 1890.■
BERNARD MERVYN DRAKE.
JOHN MARSHALL GORHAM.
PERCIVAL JOHN PRINGLE.