Year: 1898

page_text: Date of Application, 1st Mar., 1898
Complete Specification Left, 30th Nov., 1898-Accepted, 28th Jan.,
1899
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, do hereby declare the nature of this invention to be as follows:--
The invention relates to electric switches.
One object of the invention is to construct an electric switch, which shall,
although no special care is taken to adjust or fit the contacts with reference to each
other, be capable of carrying large currents and having good connection between
the fixed and movable contacts.
Another object of the invention is to construct an inexpensive quick break
switch having large current carrying capacity in proportion to its dimensions and
which is certain in its operation.
According to the invention good contact is ensured between the fixed and moving
parts of the switch by the provision of spring washers between said parts. Said
washers are somewhat concave and preferably radially slit or slotted at their edges,
and are secured to the fixed or moving parts of the switch with their convex sides
against said part. For example in one method of carrying out the invention the
fixed terminals of the switch take the form of jaws, the movable parts of the switch
consisting of a bar pivoted between the jaws forming one terminal and adapted
to engage between the jaws forming the other terminals when the circuit is to be
closed. The spring washers are secured to the movable bar with their convex sides
applied to said bar and the distance between the jaws forming the terminals is made
somewhat less than the normal distance between the peripheries of each pair of
washers. Consequently at the pivot good contact will be made between the edges
of the washers and the jaws which embrace said edges and at the terminals where
the circuit is interrupted the edges of the washers will be forced nearer together
when the bar is pressed between the jaws forming the terminal. In order to render
the switch somewhat easier to close, the jaws may be bevelled at their outer edges,
so that the bar and washers can be easily pressed into engagement therewith. The
edges of the washers may also be slightly rounded in order to preclude any possible
cutting of the engaging parts. The washer need not be circular as other forms may
be employed if desired.
In constructing a quick-break switch according to the invention a switch of the
kind hereinabove described known generally as a "knife switch" is provided with
an additional fixed terminal adjacent to the terminal where the circuit is inter-
rupted, and the blade or movable portion of the switch has a tongue pivoted thereto
adapted to engage with the additional fixed terminal. Said tongue is further con-
nected to the blade by a spring, and a stop is provided on said blade which limits
the rotation of the tongue upon its pivot. The supplementary fixed terminal is

page_text: so arranged that when the blade of the switch is operated to open the circuit the
supplementary terminal retains the tongue, which rotates on its pivot against the
resistance of the spring above mentioned; consequently the circuit although inter-
rupted at the main terminals is still closed through the tongue and supplementary
terminal. When however the further rotation of the tongue is stopped the move-
ment of the blade releases it from the supplementary terminal, and the spring
causes a quick break between said tongue and terminal thereby finally interrupt-
ing the circuit.
Means are preferably provided for ensuring good electrical connection between
the tongue and the blade of the switch irrespective of the contact between them
through the pivot of the tongue.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, 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:-
The invention relates to electric switches.
One object of the invention is to construct an electric switch, which shall,
although no special care is taken to adjust or fit the contacts with reference to each
other, be capable of carrying large currents and having good connection between
the fixed and movable contacts.
Another object of the invention is to construct an inexpensive quick break
switch having large current carrying capacity in proportion to its dimensions and
which is certain in its operation.
According to the invention good contact is ensured between the fixed and moving
parts of the switch by the interposing between said parts of spring washers some-
what concave and preferably radially slit or slotted at their edges. In some cases
these washers are secured to the fixed or moving parts of the switch. By this means
there will be secured a good spring pressure between the parts of the switch, which
will ensure good electrical connection between them, at the same time said parts
can be made roughly and without great attention being paid to the finish of the
same.
In constructing a quick break switch according to the invention, I add to a knife-
switch of suitable design a supplementary terminal with which engages a tongue,
pivoted to the main moving portion or blade of the switch. This pivoted tongue
Tags behind when the blade of the switch is rotated to interrupt the circuit until it
is caused by means of a stop to follow said blade in its movement, and when once
the tongue has left the supplementary terminal a spring ensures a quick break.
In order that the invention may be clearly understood I will now proceed to
describe the accompanying drawings in which,
Figure 1 is a side elevation of a knife switch constructed according to my inven-
tion, the switch being open.
Figure 2 is a plan of the same.
Figure 3 is a plan shewing the switch closed.
Figure 4 is an end elevation of the stationary jaw terminal with which the
movable member co-operates to open and close the circuit.

page_text: Figure 5 is a detail view drawn to an enlarged scale.
Figure 6 is a side elevation partly sectional of a quick break switch constructed
according to my invention the switch being closed.
Figure 7 is a plan view of the same.
Figure 8 is a section on the line - Fig. 6.
Like letters of reference denote the same parts throughout the drawing.
Referring now to Figures 1 to 5, 1 is the base of the switch, 2 and 3 are the
fixed jaw terminals to which the ends of the circuit are attached one of said ter-
minals being shewn in elevation in Fig. 4. 4 is the blade of the switch provided
with spring washers 5, these washers are preferably provided with radial slits
extending inwards some distance from their edges, as clearly shewn in Figure 1,
and are rivetted or otherwise secured to the side of the blade 4. The washers are
normally slightly concave as shewn very clearly in Figure 5 which is a sectional
view of a portion of a switch bar with a washer secured thereto. The distance
between the jaws forming the terminals is somewhat less than the normal distance
between the peripheries of each pair of washers. Consequently at the pivot good
contact will be made between the edges of the washers and the jaws which embrace
said edges, and at the terminal where the circuit is interrupted the edges of the
washers will be forced nearer together when the bar is pressed between the jaws
forming the terminal. It will furthermore be seen that the washers being yield-
ing will adapt themselves to jaws which differ slightly in width, consequently there
is no necessity to finish up the terminals to exactly fit the blade of the switch, and
this very considerably cheapens the manufacture. The upper contact terminal
of the switch, shewn in Figure 4, at which the circuit is interrupted, is preferably
made somewhat flaring at the place where the blade enters the same or the inner
edges are rounded or bevelled so that the switch may be readily closed without
injury to the contact surfaces. The peripheries of the washers are also slightly
rounded in order to preclude any possible cutting of the engaging parts. The
washers are not necessarily circular as other shapes may be employed.
The switch thus constructed is adapted for making and breaking the circuit in
the ordinary manner. If it is desired however to ensure a quick break, I provide
additional parts shewn in Figures 6 to 8 of the drawing. The terminal 2 is con-
nected to two spring arms 14 which project substantially parallel to each other,
and somewhat beyond the outer ends of said terminals. The ends 15 of these
spring arms 14 are curved inwardly towards each other, as shewn in Figure 8, or
they may be otherwise constructed so that the space between them is less at their
outer ends than it is nearer to the base. The blade 4 has secured to it on either side
the plates 7, to which is pivoted at the back of the blade a tongue 8, said tongue is
provided with two curved strips 9 which extend outward and fit against the two
faces of the blade 4. The inner edges of said strip also fit against the correspond-
ing outer edges of the plates 7, as shewn in Figure 6, the curvature of both these
edges being that of an are of a circle having the pivot of the tongue 8 as a centre.
The plates 7 are provided with projections 10 which stop and limit the rotation of
the tongue 8 on its pivot. The tongue 8 is further connected to the blade 4 by
means of the springs 12 and has at its upper end a head 16, the ends of which are
normally in contact with the inner faces of the arms 14.
The construction of the spring tongue and of the supplemental contacts 14 may
obviously be considerably varied, for example, either or both of these devices may
be designed to yield with reference to the other in order that a quick break of the
circuit may be effected.
The operation of the switch is as follows:-
When the blade 4 is moved out by means of its handle the spring tongue S will
follow it more or less closely depending upon the friction between the head 16
and the arms 14, when however said head comes in contact with the inwardly
curved parts 15 of the said arms further movement of the tongue will cease until
the blade reaches the position shewn in dotted lines in Ficure 6, the springs 12
being extended, and further lagging of the tongue is prevented by the stops 10.

page_text: When this happens said tongue will be forced out from between the arms 14 after
which the spring 12 will draw the tongue quickly into its normal position against
the blade 4 and the circuit, which up to this time has been passing through the
tongue and supplemental terminal 14, will be quickly interrupted.
"
It will be understood that my invention is not limited to the type of switch
shewn in the drawings and it will be obvious that it may be applied to various
kinds of switches in which one moving part is required to make electrical contact
with a fixed part, the connection hitherto secured by highly finishing the surfaces
can be obtained in as efficient a manner by inserting a spring washer between said
surfaces the electric current passing through the edges of the washer. At those
places where the circuit is required to be broken by the separation of the parts
the washer may be secured to one of the parts but where the two parts are pivoted
together and current is desired to be conducted from one to the other the pivot may
pass loosely through the washer in order to maintain it in place.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondent, I declare that what I claim is :-
1. An electric switch having spring washers interposed between its fixed and
movable portions so that the electric current passes mainly or wholly through the
edges of the washers.
2. Switches constructed substantially as described with reference to Figures 1
to 5 or to Figures 6 to 8 of the accompanying drawings.
Dated the 30th day of November 1808
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.