Improvements in and Connected with Electrical Safety Cut-outs.
Year: 1888

page_text: Date of Application, 14th July, 1888
Complete Specification Left, 14th May, 1889-Accepted, 14th Oct., 1889
PROVISIONAL SPECIFICATION.
Improvements in and Connected with Electrical Safety Cut-outs.
I, ERNEST PERRETT, of 2, Neva Road, Weston-super-Mare, Electrician, do hereby.
declare the uature of this invention to be as follows:-
According to this invention I employ a piece of wire of such a section as to permit
the normal current of the installation to just pass through it without heating.
.
This piece of wire is held in tension by a spring forming part of the circuit and
made of such a form and so arranged relatively to the wire that if the latter should
become the least heated through excess of current passing through it, the said spring
shall immediately be released and break the circuit. A suitable form of spring is that
of a flat piece of steel set into a bow shape and then bent into a curve of nearly the
same flexure but in the contrary direction when inserted in the apparatus for putting
the wire in tension. In one form of this apparatus I stretch the piece of wire between
a terminal in the circuit and a lever and I insert the flat spring bent as stated into
the opposite curve between the lever and another terminal in the same line of the
circuit. The spring is of such a size as to form ample contact at each end and of
ample section to carry the current. In another form of apparatus I place the wire in
a tube attaching it to a bridge cap or bottom piece at one end and to a hinged bridge
cap or lever at the other end and insert the spring between the said hinged cap or lever
and a projection in or on the tube.
When the wire should expand by becoming heated the spring will first tend to
straighten and will thereupon while returning to its original opposite curvature be
released and fly off, thus breaking the circuit. I sometimes cause the spring to performi
an additional operation to that of breaking the circuit viz. that of completing a local
circuit for setting an alarm ringing, or lighting a coloured signal lamp or actuating
any other signalling appliance."
T1000
COMPLETE SPECIFICATION.
Improvements in and Connected with Electrical Safety Cut-outs.
I, ERNEST PERRETT, late of 2, Neva Road, Weston-super-Mare, 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:
According to this invention I employ a piece of wire of such a section as to permit
the normal current of the circuit or installation to just pass through it without heating.
This piece of wire is held in tension by a spring or its equivalent which may form part
of the circuit and is made of such a form and so arranged relatively to the wire that
if the latter should become heated through excess of current passing through it the
said spring or a part connected thereto shall immediately be released and break the
circuit.
Fig. 1 of the accompanying drawings is a plan view and fig. 2 a side view of one
arrangement of apparatus more especially suitable for small currents. A is a spring in
the form of a flat piece of steel set into a bow shape and then bent into a curve of
nearly the same flexure but in the contrary direction when inserted in the apparatus
for the purpose of putting the wire B in tension. Instead of one such wire I may in
this and in the constructions to be hereafter described use two or more wires connected
C
-

page_text: in series or in parallel are and thus greatly varying the carrying capacity. The
wire B is stretched between the terminal C in the circuit, and a lever D which has its
fulcrum at D. The flat spring A. having first, been set in one direction as stated and
then bent into opposite curve as shown is inserted between the lever D and another
terminal E in the same line of the circuit. The spring A is of such ample section as
to carry the current. One end of the spring is curled round the peg E¹ of the
terminal E and the other end is bent and bedded in the correspondingly formed end of
the lever D, all so as to form ample contact at each end. When the wire B should
expand by becoming heated the spring A will first tend to straighten and will
thereupon while returning to its original opposite curvature be released and fly off at
the lever end thus breaking the circuit.
"
Fig. 3.is plan view of another form of this apparatus, in which a contact A¹ on the
spring A forms contact with a peg or screw F on the terminal F in a local circuit
for ringing a hell or lighting a signal. In this case the spring A does not fly out, so
.far as to leave. its bed in the end of the lever D.
Where it is found advisable to use a longer length of wire than could conveniently
be contained on a small foundation plate I may wind it backwards and forwards so as
to have any desired length enclosed in a small space and for this purpose the wire B
is connected at one end to the terminal Cas before described and is carried backwards
and forwards over and round insulating pegs and d or the like to the lever D.
In fig. 4 is shown a plan view of another form in which the spring A when the
wire B expands first closes a local circuit of a signalling appliance of some sort, by
the lever D coming in contact with a spring F on a terminal F and thereupon in
flying out at the lever end breaks the contact with the lever.
Fig. 5 is a plan view and fig. 6 a vertical cross section of an apparatus combined
with a switch and if required for working a signal. The wire B is at one end fixed in
the boss C of the terminal Cand at the other end fixed above the fulcrum D of the
lever D which is cranked as shown at fig. 6 and at its outer end has a peg De which
enters a recess or hole in a flat steel disc H. This latter turns on a pivot in the slate,
ebonite, or other insulating foundation plate I. To the piece H is fixed one end of a
spring A the other end of the spring being fixed round a peg E¹. On the disc H is
mounted a rectangular contact block M provided with insulating pieces M² M² and two
other sides make contacts with the springs K and L and which has a lower projecting
peg M. The upper terminal prolongation of the block M pivots in the casing N.
The disc H has a projecting stop or nose H. The spring A tends to turn the disc II
in the direction of the arrow but is prevented from turning it by reason of the
peg D2 on the lever D being held in the aforesaid recess in the disc H. When the
wire B expands through heat by-reason of excess current the outer end of the lever D
rises being assisted by the spring A¹ so that its peg D2 leaves its recess in the disc H,
the spring A then pulling the disc round in the direction of the arrow and turns round
with it the contact block M being carried round also by the peg M catching against
the edge till the contact springs K and L rest on the insulating pieces Me. The
switch is quite independent of the cut out unless the current gets dangerous. This
form of apparatus is specially suitable for use in incandescent lamp installations.
"
Fig. 7 is plan view of a carbon contact switch. The wire B from the terminal C¹ is
stretched between the lever D which pivots round the fulcrum D₁ as in the previous
example and has a similar peg D². B¹ is another wire stretched between the lever D
and the boss Cx. The peg 12 enters a recess in the lever H M M which has its
fulcrum in the base plate and in the bracket N. Round this fulcrum piu is coiled a
spiral spring A one end of same being fixed to the said pin and the other hooked on to
peg in the underside of the bracket N. The two ends M M form contact with the
plates Land K which carry the carbon point L' and K'. O and P are levers pivoting
round the same fulcrum as the lever H M M and provided with carbon points (1
and P. Q and R are springs for holding the carbon points in contact., S and T are
stops for limiting the movement of the levers O and P which latter have corresponding
faces Ox and Px. When by excess of current the wires B B expand and the peg De
consequently by the action of the spring A¹ is forced out of its recess, the spring A

page_text: will turn the lever H in the direction of the arrow and thereby the parts M M of
same will leave the contacts K and I which carry the larger portion of the current
while the carbon points which carry the smaller portion of the current are still kept in
contact by the springs Q and R.
As soon as the contact is broken at M, L and M K the pins T and S coming in
contact with the stop faces Ox and Px will carry the levers O and P along with them
and thus break contact at the carbon points. The sparking in this form takes place
between the carbons which can be conveniently renewed thus saving the metal
contacts L M and K M. This form of instrument is specially suitable for a main cut
out or one that takes a large current.
Figure 8 is vertical longitudinal section and Figure 9 a plan view of another form of
apparatus. In this case the wire B is placed in a tube I the wire being at one end
attached to a cap P or bridge or bottom piece with terminal screw Cand with an
insulating sleeve O of vulcanite fibre or other suitable material and at the other end
attached to a lever D the spring A being inserted between the lever D or hinged cap
and a projection E' with terminal screw E on the tube I (or in it). The boss of the
projection E is insulated from the tube I by the bush K. The tension of the wire B
can be adjusted by the nut L and when a wire peg M has been screwed into one of
several holes in the nut an eye on the peg M can be tied to an eye on a peg N (which
is screwed into the body of the cap P) and sealed so as to prevent being tampered
with.
Figure 10 is a plan section and Figure 11 an end view of another form of cut-out
suitable for insertion in a wall or in a switchboard thereon. The wires B B and
levers D D are here duplicated and the said levers are of bell crank form and carry
the bow shaped spring A between them being attached to one and resting in a recess
in the other. The current entering at the terminal C and by the wire C passing to the
lower end of the wire B passes by the latter to the lever D and spring A to the lever D¹
and wire B' and thence by a wire to the other terminal E.
In all the aforesaid cases the wire or wires B may be held in tension by a weight or
weighted part instead of a spring.
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 —
First A safety cut-out consisting of a wire or wires inserted in the circuit and
held in a stretched condition by means of a spring (or weight) in such manner that
when by excess of current the wire becomes heated the spring or a part connected
therewith shall he released and break the circuit the parts operating substantially as
described and shewn.
Second A safety cut-out consisting of a wire inserted in the circuit and held in a
stretched condition by means of a spring also in the circuit in such a manner that
when by excess of current the wire becomes heated the spring shall be released and
break the circuit substantially as described and shewn.
Third: A safety cut out as firstly and secondly claimed in combination with a bell
or other signalling apparatus substantially as described and shewn.
Fourth In a safety cut out a stretched wire Ba lever D and a spring A operating
in combination substantially as set forth.
Fifth
The construction of safety cut-outs with and without signalling appliance
and switch substantially as shewn in the drawings.
Dated the 14th day of May 1889.
JENSEN & SON,
7, Chancery Lane, London, W.C., Patent Agents.