Year: 1897

page_text: Date of Application, 26th Mar., 1897
7100
4007 Anoted
12th Foh 4808
EDWARD WOODROWE COWAN, of Hart Hill, Woodville Road, Bowdon, Cheshire,
Civil Engineer, and ALFRED STILL, of Bow Green Farm, Bowdon, Cheshire, Civil
Engineer, do hereby declare the nature of this invention to be as follows:-
Our improvement relates to switches adapted for breaking circuits having con-
siderable self-induction, such as fields of dynamos, motor circuits etc. whereby the
arcing and burning of contacts, the result of a rise of pressure which also tends to
break down the insulation of the circuits is greatly reduced and the rise of pressure
prevented.
The principle of the action of our improved switch consists in avoiding as far
as possible all checking of the flow of the current in the circuit, by diverting it in
that part of the circuit having self induction into a bye path of practically no
resistance.
By means of our improved switch a resistance is first inserted in series with the
circuit, this resistance we prefer to make equal if possible or nearly equal to the
total resistance of the circuit.
In the next operation the circuit is short circuited on the side of the resistance,
inserted in the first instance, remote from the source of supply. In the last operation
the source of supply is disconnected from the circuit, the latter remaining short-
circuited.
The above series of operation is carried out by one movement of the handle of our
improved switch. We prefer to make the improved switch of the "Hatchet" type.
The handle is rigidly attached to a central lever which is provided on one side of
the fulcrum with contacts which short-circuit the resistance which it is required to
insert in the first operation described above and is provided on the other side of the
fulcrum with contacts which short-circuit the main circuit. On either side of this
lever are other levers which are not rigidly attached to the handle, but which are
attached rigidly to each other and rock on their own fulcrum. These levers are
provided with contacts which make & break the circuit at a point between the
inserted resistance and that part of the circuit which is short circuited by the
central lever. These external levers are provided with a spring break, and are
knocked in and out of their contacts by the movements of the central lever.
The switch could be made of a different type provided the operations described
above were carried out in the proper sequence and substantially in the manner
set forth.
..
March 1907

page_text: EDWARD WOODROWE COWAN, Hart Hill, Woodville Road, Bowdon, Cheshire,
Civil Engineer, and ALFRED STILL, Bow Green Farm, Bowdon, Cheshire, Civil
Engineer, 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 improvement relates to switches adapted for breaking circuits having con-
siderable self-induction; such as fields of dynamos, motor circuits, etc. whereby the
arcing and burning of contacts, the result of a rise of pressure which also tends to
break down the insulation of the circuits is greatly reduced and the rise of pressure
prevented. The principle of the action of our improved switch consists in avoiding
as far as possible all checking of the flow of the current in the circuit, by diverting
it in that part of the circuit having self-induction into a bye path of practically no
resistance.
By means of our improved switch, a resistance is first inserted in series with the
circuit, this resistance we prefer to make equal if possible or nearly equal to the
total resistance of the circuit. In the next operation the circuit is short circuited
on the side of the resistance inserted in the first instance, remote from the source
of supply. In the last operation, the source of supply is disconnected from the
circuit, the latter remaining short-circuited. On the accompanying drawing Figs. 1
& 2 show a switch, of the hatchet type, designed to perform the operations
described above, and Fig. 3 shows a diagram of connections. In this diagram, L is
the circuit having self induction and which our improved switch is designed to dis-
connect from the source of supply without an are being formed, and without an
abnormal rise of pressure in the circuit. R is a resistance which we prefer to
make equal to the resistance of the circuit L. S S are the supply mains, the switch
being double pole. When the circuit is closed on the source of supply, the central
and side levers are in the position shown in Fig. 1. When it is desired to open
the circuit by means of the switch, the handle H is pulled over from left to right &
this movement, in the first place, inserts the resistance R, which has little or no
self induction, in series with the circuit L, by withdrawing the end of the lever
marked B which bridges the contacts b b and therefore cuts out the resistance R to
which they are connected. As the lever is moved further over in the same direction,
the end of the lever marked C is inserted between the contacts c c and thereby
shortcircuits the circuit L to which they are connected. As the lever is moved
further over in the same direction, it comes into contact with the cross bar D which
is fixed to the two side levers, but insulated therefrom, depressing the cross bar and
thus withdrawing the ends of the levers marked K K from the contacts marked k k,
and so disconnecting the source of supply. We prefer to make the side levers
spring break.
When it is desired to close the circuit again, the movement of the handle is
reversed; the part of the central lever on the side of the fulcrum remote from the
circuit L, coming in contact with an insulated cross bar fixed to the side levers &
marked M, inserts the ends of the levers marked K K into their contacts kk. Where
space is confined we sometimes prefer to make our improved switch with parts
moving in a plane parallel to the base upon which they are mounted, about a
common centre or pivot.
Having now particularly described and ascertained the nature of our said inven-

page_text: tion, and in what manner the same is to be performed, we declare that what we
claim is:
1) The construction of electric switches, which shall by their operation, dis-
connect electric circuits having selfinduction from the source of supply in the
following manner:-insert a resistance having little or no self-induction in series
with the circuit having self-induction, then short circuit the circuit having self-
induction and finally disconnect the source of supply as herein before described.
2) The construction of a switch substantially of the design shewn on accom-
panying drawings Figs. 1 & 2 which shall carry out the series of operations specified
in our first claim in one movement and in the manner hereinbefore described.
Dated this 18th day of December 1897.
EDW. W. COWAN.
A. STILL.