Improvements in Electric Indicators.
Year: 1888

page_text: Date of Application, 29th Oct., 1888
Complete Specification Left, 23rd Aug., 1889-Accepted, 28th Sept., 1889
PROVISIONAL SPECIFICATION.
Improvements in Electric Indicators.
I, ROBERT WILLIAM PAUL, of 10, Ravensdale Road, Stamford Hill, N. in the
county of Middlesex, Electrical Instrument Maker, do hereby declare the nature of
this invention to be as follows:-
The improvement of electric indicators with mechanical replacement by shortening
the magnetic circuit reducing friction to a minimum increasing their simplicity by
the employment of one moving part only which acts as armature and indicating disc
while certainty of action is secured by the employment of a novel locking mechanism
of which the working is independent of gravity or friction. I prefer to make the
electromagnet in the form of an iron pot with central core and a bobbin of insulated.
wire enclosed between the pot and core the pot being partly or wholly closed at
bottom but open at top and forming a framework for the mechanism. A Hat disc of
iron is pivotted to a point in the rim of the pot by a hole near its circumference so
as to be capable of turning in a plane parallel to its mouth, and capable of slight
motion at right angles to the saine, while a bent stud passing into a hole in the
opposite side of the disc holds it in a position almost covering the opening of the pot
a light spring pressing the disc upwards on to the end of the stud, except when, by
the action of the current the disc is drawn off the stud being then free to turn about
the pivot and display a signal. The armature-disc may carry a suitable projection by
which it can be replaced in the locked position.
Doted this 20th day of Dotahan 1888
COMPLETE SPECIFICATION.
Improvements in Electric Indicators.
I, ROBERT WILLIAM PAUL, Electrical Instrument Maker, formerly of 10, Ravens-
dale Road, Stanford Hill, N. in the county of Middlesex, but now of Frith Knowl,
Elstree in the county of Hertfordshire 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:-
This invention consists in the improvement of electric indicators by shortening the
nagnetic circuit so as to reduce the magnetic resistance, by reducing mechanical
friction and increasing the simplicity of the apparatus by the employment of one
moving part only which acts both as armature and indicating disc or signal whilst
certainty of action is secured by the use of a novel locking mechanism of which the
working is independent of gravity or friction, and the magnet may be of such a form
that the mechanisin may be supported by and attached to it without detriment to its
magnetic properties thereby increasing the compactness and substantiality of the
whole, and contact pieces may be attached for connecting the indicator in circuit.
The invention is particularly applicable to mechanical replacement indicators or
'drops' for use in domestic electric bell circuits on board ship or in telephone
exchanges. Such indicators usually consist of the following essential parts: an
electromagnet (1) an armature (2) which when attracted by the electromagnet
against the action of gravity or a spring lets fall either directly or through a
lever (3) or its equivalent a disc or tablet (4) and exhibits a signal (5) which may
or may not be separate from the disc or tablet. The whole may be attached to a
frame or base (6). An indicator made according to my invention may consist simply
of the electromagnet which also forms the frame or base of the instrument and an:
г.
7

page_text: armature of such form as to render a separate lever disc or signal unnecessary
together with a catch to hook the armature in the normal position ready to be dropped
by the action of the current passing through the electromagnet.
The form of electromagnet which I prefer to employ is that usually known as a
pot magnet and consists of a pot of iron which may be forged cast or malleable cast
in the centre of which is a cylindrical stem which may be cast in one piece with the
pot or screwed into its base. Outside this stem or core but inside the pot is a
bobbin of insulated wire the ends of which may be brought through holes or grooves
in the pot or one end may be connected to the pot and the other brouglit through
but insulated from it or connected to suitable terminals or contact pieces. The end
of the core forms one magnetic pole and the other pole is round the edge of the pot.
Another suitable form of magnet consists of a U shaped piece of iron with a core
between the limbs of the U upon which a bobbin of insulated wire may be placed,
or one of the limbs of the U may be omitted. The magnet may have Ings or pro-
jections formed upon or attached to it for the attachment of the mechanism or for
securing the magnet to the backboard of the case in which the indicator movements
are placed or the core may be prolonged for the same purpose. The shape of the
armature is adapted to that of the electromagnet and may have ears or projections
for convenience in pivotting replacing and being held by the catch. The armature
is pivotted at one end to the magnet so that it may move freely in a plane parallel to
the face of the electromagnet but with a slight play in the direction at right angles
to that plane. It may have painted or fastened upon it a signal such as a
number etc.
The catch or locking mechanism is so arranged that the armature is held up on a
projecting pin stud or pawl on to which it is pressed by a light spring, then on the
passage of the current through the electromagnet the armature is drawn off the
projecting pin stud or pawl against the pressure of the spring and may also be
slightly rotated about the pivot by the attraction of the magnet. The armature is
then free to drop and exhibit the signal unless held to the magnet by a too powerful
current in which case it drops only when this is switched off: in ordinary use it drops
immediately.
In cases where the indicator movement is required to be readily removable from
the board or other base to which it is attached I connect the ends of the coil of the
electromagnet to the frame of the magnet and to an insulated collar or tube
respectively and arrange corresponding contact pieces in the form of washers plates
or tubes on the base board so that the electromagnet is put in circuit by placing the
indicator movement in position.
Referring now to the accompanying drawings Fig. I represents in front elevation
an indicator movement in the normal position constructed according to my invention
together with a replacement bar of the ordinary kind, Fig. 2 represents the same in
side elevation, Fig. 3 shows the same in front elevation after the passage of a current
the armature signal now showing before an opening or window in the case to which
the whole is attached, Fig. 4 shows a cross-section of the magnet.
A represents the iron pot D the core screwed into the bottom of A and prolonged
at m to form an attachment to the backboard M as clearly seen in Fig. 2, it also
forms one terminal of the magnet coil E. Two lugs a and b are formed upon A,
to a is loosely pivotted the armature B by the car c through which passes the stud-
screw h, to b is screwed the spring g and the catch or pawl above it. The pro-
jection d engages with fand holds the armature B up, d is bevilled or rounded on its
upper edge so that it may slide under when the armature is replaced after being
dropped the replacement is effected by pushing from left to right the bar F which
slides in the cocks G G and is held back by the spiral spring H till. the pin in the
bar F acting on the projection e brings the armature again into the normal position
as shown in Fig. 1 where it will be seen that in this position the armature is not
concentric with the magnet. The action of the apparatus is as follows:
passage of a current the electromagnet A is energised and attracts. the armature B
on the
against the pressure of the spring 9 from off the pawl and slightly rotates it about h

page_text: SO CART IT IS not possible for the armature to my bitch
shown in Fig. 3.
we position
Figs. 5 6 7 and 8 show the application of the U shaped magnet before mentioned;
Fig. 5 shows an indicator in front elevation and Fig. 6 in side elevation the arma-
ture being in the normal position, Fig. 7 shows the electromagnet in longitudinal
section and Fig. 8 shows the method of pivotting the armature B to the magnet at a
the washer being interposed. A is a U shaped forging or casting of iron D an iron
core screwed into A B the armature pivotted at an ear formed upon or attached
to A to carry the spring g and pawl e a pin screwed into B for convenience of
replacement E the bobbin c. insulated wire.
The action of this apparatus is the same as that before described.
Figs. 9 10 and 11 show the application to this indicator of a one-coil magnet with
two poles. Fig. 9 is a front elevation, Fig. 10 a side elevation of the indicator move-
ment with the armature in the normal position and Fig. 11 is a longitudinal section
of the magnet.
A is an iron forging or casting D a core screwed into A and
projecting at m B the armature pivotted to A by means of the stud-screw and
having a projection d and replacement pin e as before. The pawl and spring g are
attached to the bobbin-end t which is of brass or other suitable material secured to
the core D and the action of the whole is as before described.
Fig. 12 shows in side elevation and Fig. 13 in front elevation another form of
catch applied to the indicator with pot magnet; it consists of a bent wire stud f
screwed into or otherwise fastened to the lug b of the electromagnet A and pro-
jecting at the other end into a hole d in the armature B which is pressed outwards by
the spring 9.
This form is suitable for use when the indicator is liable to jarring or
shaking. Fig. 14 shows a modification of this form in which the lug b is formed
into, a goose-necked cock and carries a screw the pointed end of which passes into
a hole in the armature or under a suitable projection from it the screw ƒ providing
for adjustment.
Fig. 15 shows in section part of an indicator to which is applied a contact piece
for connecting the magnet coil in circuit when the indicator movement is placed in
position. A is the magnet the core D of which is prolonged at m and screwed, it
bears an insulating collar o on which is secured a metallic washer n having one end
of the magnet coil connected to it the other end being connected to the magnet
frame.
When the indicator is screwed up to the backboard M on which are placed strips or
contact plates sp one on each side contact is made between s and m and between
pand n respectively so that the indicator may be joined in circuit.
Figs. 16 17 18 19 20 and 21 represent a method of readily connecting the indicator
in circuit which is suitable for telephone exchanges or other positions where it is
required to be readily replaceable in case of injury. Fig. 16 is a side elevation of
the contact pieces on the switchboard or other support, Fig. 18 a front elevation and
Fig. 20 a cross-section of the same. To the back of the board M is secured a collet
and to the front a similar but larger collet p separated from s by a ring of insulating
material v. Fig. 17 is a side elevation Fig. 19 a back elevation and Fig. 21 a cross-
section of part of the indicator with attached contact pieces. A is the magnet of
which the core D is formed into a projecting cylinder m on which is secured a
sleeve O of insulating material carrying the metallic ferrule n to which one end of the
magnet coil is connected, the other end being connected to m. The action of the
apparatus is as follows: when placed in position the core m fits into the collets and
the ferrule n into the collet p both of which may have one or more longitudinal saw-
kerfs to enable them to spring slightly and make good contact and to hold the
indicator movement firmly in position.
Though this invention has been described as applied to indicators with mechanical
replacement certain portions thereof for example the formation of the electromagnet
and the arrangement of contact pieces are equally applicable to other forms of
indicator such as pendulum indicators.

page_text: 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. The combination into one piece of the moving parts of an electric indicator for
use with mechanical replacement.
2. In an electric indicator the use of a movable piece which acts both as armature
and signal and which may have projections formed upon it for purposes of replace-
mert and locking.
5. In an electric indicator the use of the forms of electromagnet substantially as
described.
4. In an electric indicator the formation of the electromagnet so as to act as a
support to the mechanism substantially as described.
5. In an electric indicator the use of a locking mechanism or catch which locks
the armature in position by the action of a spring which keeps it on a pin stud or
pawl or their equivalent.
6. In an electric indicator the use of the locking mechanism or catch substantially
as described.
7. The application to electric indicators of the forms of contact pieces substantially
as described with reference to the accompanying drawings.
8. The electric indicator substantially as described.
Dated this 23rd day of August 190a
ROBT. W. PAUL.