An Improved Electric Bell for Mines and Outdoor Use generally, with Damp-proof or Hermetically Sealed Contact-breaker.
Year: 1894

page_text: Date of Application, 25th Oct., 1894.
Complete Specification Left, 22nd July, 1895-Accepted, 7th Sept.,
1895
PROVISIONAL SPECIFICATION.
An Improved Electric Bell for Mines and Outdoor Use generally,
with Damp-proof or Hermetically Sealed Contact-breaker.
I, FREDERICK CHARLES ALLSOP of 165 Queen Victoria Street London E.C.
Electrical Engineer do hereby declare the nature of this invention to be as
follows:-
My invention relates to an improved electric bell in which the making & breaking
of the contact is effected by a seperate armature to that moving the hammer but
worked from the same magnetic poles or extensions thereof. The bell is so
arranged that although the armature moving the hammer is outside as in the
ordinary electric bell, that operating the contact breaker is enclosed or boxed off
by a box of metal, wood, or other suitable material, which box can be rendered
damp-proof or if so desired hermetically sealed. Thus the bell may be placed out
of doors or in any exposed position without the contact arrangements being in any
way affected by damp, fumes, or gases and the bell may be placed in mines and
similar places without fear of the spark at the contact breaker igniting any
inflammable or explosive gases.
In carrying out my invention I provide an electro-magnet or magnets with
armature, gong, etc., similar to the ordinary electric bell with metal or wood base
& cover.
I then affix extensions to the poles in such a manner that when I place
a second armature in front of these extensions, this armature will be attracted
I then
each time the armature working the hammer of the bell is attracted.
provide a suitable contact spring & contact screw at the back of this second
armature so that when the armature is attracted the bell circuit is broken & when
broken the armature falls back again on to the contact screw. Thus both
armatures of the bell will be attracted & released in unison, & the bell will ring
like the ordinary electric bell. I next provide a suitable metal case which may be
seperate from or cast on to the bell base & this case passing over the poles of the
magnet completely encloses the second or contact breaking armature, contacts &
magnet coils, & being fitted with a lid allows of ready access to the second armature
when desired, which can at all other times be hermetically sealed in this box. The
one side of the box passes right over the magnet poles leaving the ordinary poles
outside but the polar extensions inside.
In some forms I insulate the poles where they pass through the side of the box
by ebonite, vulcanised fibre, or other suitable material in order to insulate the
poles & cores from the base. In order to prevent the vibrations of the contact
breaking armature being too rapid for the other armature the contact breaking
armature is weighted in order to slow down its vibrations.
October 25th 1891
FREDERICK CHARLES ALLSOP.

page_text: An Improved Electric Bell for Mines and Outdoor Use generally,
1
with Damp-proof or Hermetically Sealed Contact-breaker.
I, FREDERICK CHARLES ALLSOP, Electrical Engineer of 165 Queen Victoria
Street London E.C. 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 :-
My invention relates to an improved electric bell in which the making &
breaking of the contact is effected by a seperate armature to that working the
hammer but worked from the same magnetic poles or extensions thereof. The
bell is so arranged that although the armature moving the hammer is outside as in
the ordinary electric bell that operating the contact breaker is enclosed or boxed
off by a box of metal wood or other suitable material which box can be rendered
damp-proof or if so desired hermetically sealed. Thus the bell may be placed out
of doors or in any exposed position without the contact arrangements being in any
way affected by damp, fumes or gases, and the bell may be placed in mines &
similar places without fear of the spark at the contact breaker igniting any
inflammable or explosive gases.
In carrying out my invention I provide an electro-magnet or magnets o, with
armature, b, hammer, r, & gong gas in the ordinary electric bell having a metal or
wood base & cover. I next affix polar extensions, n, to the magnet poles in such a
manner that when I place a second armature, a, in front of these extensions, this
second armature will be attracted each time the armature b, working the hammer
of the bell is attracted. These polar extensions which consist of pieces of soft iron
about of an inch thick & " wide are fixed so as to project upwards, inside the
box, at right angles to the cores & press flat against the bobbin cheeks jutting out
such distance beyond them as to allow of sufficient surface for attracting the second
armature u. The polar extension on one of the cores (the right hand one in the
accompanying illustration) is further prolonged to form a support for the spring
carrying the armature, though this is not absolutely necessary as the spring can
just as well be fixed to a portion of the metal containing box. The cores of the
bell movement are made slightly longer than is customary with the ordinary bell
movement & have a thread cut on them so that when the polar extensions are bored
& tapped they screw up on the cores to the bobbin cheeks, the ends of the exten-
sions projecting out about an inch beyond the edge of the bobbin cheeks. To the
bottom of the armature a, is fixed a hammer m, the weight of which is so adjusted
that it balances the weight of the hammer r, (taking into consideration the
difference in lengths etc. of the two hammer rods) so that the two armatures &
hammers will swing in unison. The armature, a, is carried by a metal contact
spring, t, the end of which makes contact with the contact in the contact post, c.
I next take a metal box f of iron, brass or any suitable material which is
moulded or cast to the shape shown or other convenient shape & provided with a
removable lid, a, fixed by screws & packed with rubber etc. so as to form a water-
tight joint. Inside this box is placed the movement of the bell in such a manner
that while the magnet poles of the bell project through the side of the box & are
clamped, brazed or otherwise fixed so as to make the box watertight the polar
extensions, armature a contact spring t, contact post, c, are inside as shown in the
illustration.
Connections are made to the terminals fixed on the top of the box which
are clamped right through & insulated from the metal by ebonite or washers of
similar material. Thus when the lid, r, is put on the whole of the movement of
the bell is boxed off leaving only exposed outside the ends of the magnet poles,

page_text: armature, b, hammer r,
gong, g. The screw d, carried by the metal bridge over
the armature, b, is a stopscrew only, its duty being to adjust the throw of the
hammer r.
When the containing box & base of the bell are of iron in which metal I prefer
to make them, the side through which the magnet poles project must of course be
of brass or some other non-magnetisable metal, this side either being brazed or
screwed to the other sides of the box.
In soine cases I prefer not to have a removable lid at the top of the box as
shown in the figure but to make the side through which the magnet poles pass
removable, the rest of the box being one complete casting. This side is then fixed
by screws as shown in the figure & when the side is removed the whole of the bell
movement comes out with it.
The action of the bell is as follows:-When the current is put on to the
terminals it passes from the right hand terminal (let us say) to the magnet coils,
through the magnet coils to contact post, c, contact spring, t & thence to the left-
hand terminal. This magnetises the cores of the electro-magnet causing the poles
& polar extensions to attract both the armature b & armature, a.
The spring, t
has a considerable amount of play so that when both armatures are almost attracted
up to the poles, the spring breaks contact with the contact screw & both armatures
fall back to their original positions only to repeat the movement so long as the
current is turned on to the bell. After the first or second movement the armatures
obtain considerable swing & the hammer, r, is impelled forcibly against the gong, 9,
the armature, a, making & breaking the circuit & controlling the armature, b.
The adjustment is effected by altering the screw, d, & also the screw in the
contact post, c.
Brass stops for the armatures are provided in both the poles & polar extensions.
In some cases instead of letting the magnet poles working the armature outside
the case project right through it is preferable to leave a thin layer of the brass at
the end of the poles as this does away with the necessity for stops.
Having now particularly described & ascertained the nature of my said inven-
tion & the manner in which the same is to be performed I declare that what I
claim is :-
In electric bells the employment & use of polar extensions to the magnet cores
in such a manner that the said polar extensions are inside a watertight or
hermetically sealed case & work; a contact breaker, while the usual poles project
through & work or work without quite projecting through, an ordinary electric
bell armature outside the case substantially as described with reference to the
accompanying illustration.
Dated this Twenty-second day of July 1895.
FREDERICK CHARLES ALLSOP.