A Method and Means of Damping Marine and other Mirror Galvanometers, Making them Absolutely Dead Beat.
Year: 1894

page_text: Date of Application, 2nd Nov., 1891
Complete Specification Left, 2nd Aug., 1895-Accepted, 7th Sept., 1895
E
PROVISIONAL SPECIFICATION.
A Method and Means of Damping Marine and other Mirror
Galvanometers, Making them Absolutely Dead Beat.
THOMAS CLARK, Electrician 66 Jeruingham Road Hatcham, London, S.E.
THOMAS EDWIN WEATHERALL Electrician 42 Annandale Road East Greenwichi,
London S.E. do hereby declare the nature of this invention to be as follows:—
Our invention consists in cutting out a portion of the metal slide (containing
the suspension) of a marine mirror galvanometer, and in this space inserting n
metal or other dampor attached to the suspension having sufficient surface to
obtain the dead beat or damping effect required.
Dated this 31st day of October 1804.
THOMAS CLARK.
THOMAS EDWIN WEATHERALL.
A Method and Means of Damping Marine and other Mirror
Galvanometers, Making them Absolutely Dead Beat.
THOMAS CLARK of 66 Jerningham Road, Hatcham, London, S.E. Electrician,
and THOMAS EDWIN WEATHERALL of 42, Annandale Road, East Greenwich,
London, S.E. 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:-
This invention relates to damping marine or other mirror galvanometers so as to
render same dead beat and consists in cutting out a portion of the "metal slide"
or so constructing the "slide" (containing the suspension) of a marine or other
galvanometer as to provide sufficient space therein for a damper according to our
present invention and in this space we insert a metal or other suitable damper such
as of very thin sheet aluminum which carries thereon the mirror and magnet in
any suitable manner the whole (damper, mirror and magnet) being suspended as
hereinafter described or in any suitable manner-the dainper (or wings or parts
forming same) having sufficient surface to produce the dead beat or damping effect
required.
And in order that our present invention may be easily understood and readily
carried into practice we will proceed to describe same with reference to the drawings
hereunto annexed.
DESCRIPTION OF THE DRAWINGS.
Fig. 1 is a view in elevation of a galvanometer "slide" having our prosent
invention applied thereto-looking at the mirror side thereof.
Fig. 2 is a similar view of same reversed i.e. looking at the magnet side thereof.
Fig. 3 is a view of same edgewise-parts of the metal slide being bruken out to
show the damper etc.

page_text: - is the ordinary metal or other suitable slide.
d is the damper of sheet aluminium, or other suitable material for the purpose
and of a length and width necessary to obtain the degrees of damping required.
y is mirror or reflector of any suitable character which may be attached to the
damper in any suitable manner for instance as in the example illustrated where n
hollow b is formed to receive the mirror (by stamping in the centre of the damper d)
and the magnet m is rivetted or otherwise suitably mounted on the other side of
the stamped-up part b.
The mirror may be mounted in position by means of the small claws c cut out
on the edge of the hollow which are turned over so as to thus secure the mirror.
The small spaces left in the damper d by the turning over of those claws may
advantageously be utilised for balancing purposes by inserting therein suitable
weights thus dispersing with shellac which has formerly been employed for securing
the mirror inagnet and weights.
The damper d is divided down the centre of its length by a slot (for instance
about 1 wide) to a position slightly outside the rim of the hollow band two lugs
(each about long) are left which project above and below the said hollow each
pierced with a pin hole to receive the fibre (or other suspending medium) e e¹ the
other end of these suspending fibres e e' being respectivoly secured to the slide in
any suitable manner.
The magnet m is very light and of any suitable form for instance as shown of
dumb-bell form.
The total weight of the damper mirror magnet aud such weights as may be
necessary for balancing etc. according to our present invention need only be about
3 grains or much about the same weight as that of the old style suspension.
The slide with the said means for damping thus arranged therein may operate in
the usual or any suitable positiou in any galvanometer or instrument to which same
is applicable.
If desired the slide having our improvements applied thereto may be inserted
or carried in a jacket (to which latter no separate claim is made herein) such as
illustrated in side view in Fig. 4 and edgo view in Fig. 6.
This case or jacket is practically air-tight when closed so that the damper acts
very rapidly to bring the mirror to rest inside same-an aperture covered with
glass or other window to being provided through which the readings (i.e. the
deflections of the mirror) can be taken as usual or in any other desired manner.
The operation is as follows:-
The slide (either with or without the said jacket) is arranged and mounted in
any suitable manner in the instrument so that the magnet will be affected in a
greater or less degree depending on the amount of current passing through the
galvanometer coils and thereby deflect the mirror and then the damper d by reason
of its large area will rapidly stop any tendency to oscillation of the mirror and
thereby almost instantaneously bring the mirror to rest and thus allow the reading
to be taken rapidly instead of having to wait a considerable period as heretofore-
the saving of time thus effected being of very great importance in such instruments.
Another point to be noted is that instruments according to our present invention
will operate at sea or elsewhere as heretofore.
Having now particularly described and ascertained the nature of our said inven-
tion and in what mauner the same is to be performed we declare that what we
claim is :-
1. The improved method of damping marine or other mirror galvanometers by
a damper of any suitable size attached to the suspension and operating in a space
larger than said damper-provided in the slide containing said suspension to thus
rapidly produce the dead beat or required damping effect on the mirror.
2. The improved method of damping marine or other mirror galvanometers by
a damper of any suitable size attached to the suspension and operating in a space-
larger than said damper-provided in the slide containing said suspension to thus

page_text: rapidly produce the dead beat or required damping effect on the mirror substantially
in the manner and for the purposes hereinbefore described.
3. In a marine or other mirror galvanometer the combination with the slide
containing the suspension of a damper attached to said suspension said slide being
provided with a space larger than said dampor in which the latter is inserted and
operates the surface of the damper being of sufficient extent to produce the dead
beat or required damping effect on the mirror.
4. In a marine or other mirror galvanometer the combination with the slide
containing the suspension of a damper attached to said suspension said slide being
provided with a space larger than said damper in which the latter is inserted and
operates substantially in the manner and for the purposes herein before described.
Dated the 1st day of August 1895,
TONGUE & BIRKBECK,
Southampton Buildings, Chaucery Lane, London, W.C.,
Agents for the Applicants.