Improvements in Electric Switches.
Year: 1893

page_text: Date of Application, 20th Oct., 1893
Complete Specification Left, 20th July, 1894-Accepted, 25th Aug., 1894
Improvements in Electric Switches.
I, JOHN LESLIE DURWARD of 14, Franklin Road, New Brompton, in the County
of Kent, Company Sergeant Major, Royal Engineers, do hereby declare the nature
of this invention to be as follows:-
This invention relates to switches for electric currents (heavy or powerful as well
as small or weaker currents) the two chief objects being simplicity and the prompt
change from on to off and vice versa so as to avoid " arcing" as much as possible.
In one arrangement constructed according to this invention I prefer to adopt a
sliding movement for the contact bar and to pivot upon or in connection with this
a pair of arms whose free ends are under spring compression so that normally the
arms make an obtuse angle, and when straightened out in a straight line their points
are farther apart than the norinal, such extension, having been effected against the
spring pressure. A convenient spring may be constructed in the form of a horse-
shoe provided with recesses in the ends to receive the ends of the arms. With this
arrangement the pivot of the arms may project upon either side of a straight line
passing through the points of the arms, but would not be likely to remain in the
straight line owing to the spring pressure and certainly not in an "arcing" position
and the pivot of the arms being connected with the contact bar it will be seen that
the latter can only remain in one of its two extreme positions and not anywhere
between those positions. I prefer to form the contact bar with two contact ends
lying out of the plane of the bar so that when the bar is in one position the contact
ends engage with both contact plates of the wires or leads, and when in the other
position are entirely clear of both contact plates. An insulated push bar may also
be carried upon the pivot pin and I prefer to so arrange this bar that while the
mechanism is entirely carried in a case, conveniently circular, one end of the push
bar always projects through a suitable opening in the case. Thus, when the
circuit is completed and the contact bar is engaged with the contact plates one end
of the push bar projects from one side of the case, but when the circuit is broken
the other end of the push bar projects through the other side of the case; it is
therefore only necessary to push the projecting end of the push bar so far that the
pivot passes the central line when the spring will complete the rest of the movement
whether to make or break the contact. If desired both ends of the push bar may
project beyond the case or the push bar as above described may be dispensed with
and the pivot pin carried through the case and provided with a suitable button or
handle by which the operation may be effected. Or again the movement could be
effected by providing a projection or handle upon the end of one of the arms which
by a combined turning and sliding movement will effect the change of position.
In the many modifications of which the before described switch is susceptible
without departure from the spirit of this invention the spring-controlled arms which
constitute the essential element of said invention are always retained.
In one modification I provide two sets of fixed contact plates (four in all) the
contact bar completing the circuit through one set when at one end of its stroke
and through the second set when at the opposite end of its stroke; or I may
provide three contact plates now conveniently referred to as 1, 2 and 3 so that
in one of its extreme positions the contact bar will complete the circuit through 1
and 2 and in its opposite position through 2 and 3; or the contact bar may he
provided with more than two contact faces some of which may if desired be
insulated from the others so as to make and break the circuit through any

page_text: desired number of fixed contact plates which may be either arranged below or at
the sides of or otherwise adjacent to the contact bar.
The arms instead of being controlled by a spring of horse-shoe form as herein-
before described may be acted on by one of helical form and have their outer
ends pivotted by a slotted connection to the base block or case. The connection
between the inner ends of the arms and the contact bar may also be slotted so
that said bar may only be operated during the latter part of the movement of
the push bar, the switching operation being thereby made more abrupt.
The spring-controlled arms may be operated by means of a slotted bar or link
coupling them together, and a crank the pin of which works in the slot of the
bar or link. This device has the great advantage of being able to be switched
on and off by turning the crank in either direction and if a grooved block or
pulley be attached to the crank disc the switch may be operated from a distance
by means of a cord or equivalent passing around the pulley.
It will be readily understood that besides the foregoing various other means
may be employed for applying spring-pressure to and operating the before
mentioned arms.
Dated this 20th day of October 1893.
W. P. THOMPSON & BOULT,
Of London, Nottingham, Liverpool, and Manchester,
Agents for the Applicant.
I, JOHN LESLIE DURWARD of 14, Franklin Road, New Brompton, in
the County of Kent, Company Sergeant Major, Royal Engineers, 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 aud by the following
statement :-
This invention relates to switches for electric currents (heavy or powerful as
well as small or weaker currents) the two chief objects being simplicity and the
prompt change from on to off and vice versa so as to avoid "arcing" as much as
possible.
In the accompanying drawings
Figures 1 and 3 are internal views of one form of the improved switch,
Figure 2 being a cross section upon the line X X of Figure 1.
Figure is a view similar to Figure 2 and shows a modification where the contact
bar is moved directly by a sliding handle.
In the internal view Figures 5 and 6 a similar handle is employed to the arms.
Figure 7 is an internal view and
Figure 8 a cross section of an arrangement in which the arms are worked by a
crank pin.
Figures 9 and 10 are respectively a plan and a vertical cross section of a switch
in which the helical spring is placed around one of the arms, and
Figure 11 is a plan of the contact bar.
Figure 12 is a plan of a slightly modified switch.
Like letters represent like parts throughout the drawings.
In the arrangement shown in Figure 1 I prefer to adopt a sliding movement for
the contact bar A and to pivot upon this a pair of arms B whose free ends are
under spring compression so that normally the arms make an obtuse angle, and
when straightened out in a straight line their points are farther apart than the
normal, such extension having been effected against the spring pressure.
convenient spring may be constructed in the form of a horse-shoe C provided with
A

page_text: recesses at C¹ in the ends to receive the ends of the arms B.
With this arrange-
ment the pivot of the arms may project upon either side of a straight line passing
through the points of the arms, but would not be likely to remain in the straight
line owing to the spring pressure and certainly not in an "arcing "position and
the pivot of the arms being connected with the contact bar it will be seen that
the latter can only remain in one of its two extreme positions and not anywhere
between those positions. I prefer to form the contact bar with two contact
ends A¹ A lying out of the plane of the bar see Figure 2 so that when the bar is
in one position the contact ends engage with both contact plates of the wires or
leads, and when in the other position are entirely clear of both contact plates. An
insulated push bar D may also be carried upon the pivot pin D' and I prefer to so
arrange this bar that while the mechanism is entirely carried in a case E,
conveniently circular, one end of the push bar always projects through a suitable
opening E in the case. Thus, when the circuit is completed and the contact bar
is engaged with the contact plates one end of the push bar projects from one side
of the case as in Figure 1, but when the circuit is broken the other end of the push
bar projects through the other side of the case as in Figure 3; it is therefore
only necessary to push the projecting end of the push bar so far that the pivot
passes the central line when the spring will complete the rest of the movement
whether to make or break the contact. If desired both ends of the push bar may
project beyond the case or the push bar as above described may be dispensed with
and the pivot pin as shown in Figure 4 carried through the case and provided
with a suitable button or handle F by which the operation may be effected. Or
again the movement could be effected by providing a projection or handle G
Figure 5 upon the end of one of the arms B which by a combined turning and
sliding movement upon the pivot G₁ which passes through a slot G2 in the
bar & will effect the change of position. In Figure 5 the horse-shoe spring
is dispensed with and a helical spring C substituted which operates in the same
manner.
In one modification I provide two sets of fixed contact plates (four in all) the
contact bar completing the circuit through one set when at one end of its stroke and
through the second set when at the opposite end of its stroke, as illustrated in
Figures 1, 2 and 3; or I may provide three contact plates, 1, 2 and 3 Figure 6 so that
in one of its extreme positions the contact bar will complete the circuit through 1
and 2 and in its opposite position through 2 and 3. Or the contact bar may be
provided with more than two contact faces some of which may if desired be insulated
from the others so as to make and break the circuit through any desired number of
fixed contact plates which may be either arranged below or at the sides of or
otherwise adjacent to the contact bar.
The arms B instead of being controlled by a spring C of horseshoe form
may be acted on by one of helical form and have their outer ends pivotted by a
slotted connection to the base block or case. The connection between the inner
ends of the arms B and the contact bar A may also be slotted so that the bar may
only be operated during the latter part of the movement of the push bar, the
switching operation being thereby made more abrupt.
The spring-controlled arms B may be operated by means of a slotted bar or
link I coupling them together, and a crank the pin J of which works in the
slot I of the bar or link I as illustrated in Figures 7 and 8 of the accompanying
drawings.
This device has the great advantage that it can be switched on and off by turning
the crank in either direction and if a grooved block or pulley K Figure 8 be attached
to the crank disc the switch may be operated from a distance by means of a cord or
equivalent passing around the pulley.
In a modification shown in Figures 9 and 10 the helical spring C is applied upon
one of the arms B which is pivotted at B' to the other arm B and at its free end
has a slot B passing round a pin L fixed in the base block or case H in the top of
which the other arm B is also pivotted. The apparatus is moved by the

page_text: extension G of the arm B and it will be seen that the arms remain at one end
of their stroke under the influence of the spring C which is compressed when by
moving the handle G the pivot B' is forced to the opposite side of the apparatus
as indicated in Figure 10, the turning of the arms necessitating the compression
of the spring C since the slotted arm B when moved by the other arm moves
down upon the pin L thus compressing the spring as will be well understood. The
contact bar A is shown detached in Figure 11 and the operation is the same as that
previously described. The contact bar may be made for example of vulcanite with
a brass end or ends. M are the contacts which may be insulated from the block H
or the block may in all cases be made of suitable insulating material; the wire
leads will preferably be connected to the screws N Figure 9. In Figures 9 and 10
the contact bar A is shown out of contact with the surfaces M the switch
being "off."
In Figure 12 a similar arrangement to that shown in Figure 10 is adopted but
the springs are duplicated the arms lying in a horizontal plane whereas in Figure 10
they would be in a vertical plane. The arms can be operated by any of the
previously described arrangements say as in Figure 1 or Figure 4 for example, the
arrangement shown in the drawing Figure 12 however being similar to that shown
in Figure 2, but the push bar D is passed through the centre of the contact bar A.
The operation is the same as previously described. The pins O confine the back
ends of the springs C.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed I declare that what I
claim is :-
1. An electric switch in which the making or breaking of contact is effected by
spring pressure the spring being so arranged that it is only extended during the
operation of changing the position the spring at other times being in its normal
condition of only slight tension or no tension at all.
2. An electric switch in which the contact is made or unmade by a sliding
contact har such as A operated by spring-controlled arms such as B substantially
as described and illustrated in the accompanying drawings.
3. In an electric switch the combination with a sliding contact bar such as A and
pirotted arms such as B of a horse-shoe spring such as C substantially as described
and illustrated in Figures 1 to 3 of the accompanying drawings.
4. In an electric switch the combination with a sliding contact bar such as A
and spring-controlled pivotted arms such as B of a separate push bar such as D
substantially as described and illustrated in Figures 1, 2, 3 and 12 of the accom-
panying drawings.
5. In an electric switch the combination with a sliding contact bar and
spring-controlled pivotted arms such as B B2 of a bar such as II and crank pin J
substantially as described and illustrated in Figures 7 and 8 of the accompanying
drawings.
6. In an electric switch the combination with a sliding contact bar such as A
of a pivotted arm such as B spring C slotted pivotted arm B B2 and pin L
substantially as described and illustrated in Figures 9, 10 and 11 of the accom-
panying drawings.
7. In an electric switch the combination with a sliding contact bar such as A of
two slotted pivotted arms such as B springs C and pins L substantially as described
and illustrated in Figure 12 of the accompanying drawings.
Dated this 19th day of July 1894.
JOHN L. DURWARD.
W. P. Thompson & Boult,
Agents for the Applicant.