Extending the Length of these Scales.
Year: 1886

page_text: :
c. Extending the Length of these Scales.
HENRY SAMUEL SPILLER WATKIN The Wilderness, Cantwell Road, Woolwich
Major Royal Artillery, do hereby declare the nature of this invention to be as
follows:
The hand' of the dial' as it travels round' is made to move in or out by various
contrivences so. that its indicating end may point say first to an outer circle of
figures, and when it has completed one turn, be shortened' to point to a second
inner-circle of figures, on completion of, another turn to a third circle and so on;
the reverse action taking place on the pointer moving in the reverse direction. Or
preferably the circles of figures should' consist of'n continuous spiral round and
round' the dial, in which case the end of the pointer would' be gradually drawn in
to exactly follow the spiral when going in one direction, and gradually pulled out
when going in the other.
One method of effecting this 'is as follows
The indicating needle moves freely in suitable bearings at right angles to the
spindle, a light flexible cord or chain is fastened to one end of the needle thence
round and round a raised drum fixed to the dial; free from, but concentric with the
spindle, thence to the other end of the needle. It follows that as the spindle
revolves one portion of the flexible cord or chain wraps round the drum, the other
unwraps to exactly the same extent causing one end of the needle to shorten the
other to lengthen, the reverse action taking place on reversing the motion of the
spindle.
Another method of working the invention is to have a raised or sunken spiral
on the dial, a projecting piece on the needle (which is freely moveable at right
angles to the spindle as before described) works in the spiral, the needle is thus
moved in or out according to the trace of the spiral.
This principle of a moving index can be applied to all' natures of instruments so
as to extend the length of their scales. Thus in an aneroid barometer instead of
one circle of figures we may have several circles or spirals giving thus a long range
with a very open scale.
I claim The application of an indicating needle or arm which moves in and out
in its travel round a dial' so as to point either to a continuous spiral of graduations,
or to different circles of graduations.

page_text: Length of these scales,
HENRY SAMUEL SPILLER WATKIN Major Royal Artillery The Wilderness,
Cantwell Road, Woolwich, 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:- 4
C
The invention consists in causing the finger or index of a dial when revolved
to slide in or out so that one end may advance or recede from the centre and thus
follow a spiral or other form of scale.
+
A dial may thus instead of a circular scale, have a scale consisting of several
convolutions one inside the other..
Fig. 1 shows two positions. A B, C D of the index hand when applied to a
spiral scale consisting of two complete turns: The spindle to which the index is
applied being turned in a direction reverse to that of the hands of a watch, the
point A of the index is gradually drawn towards the centre, so that the end A
continuously follows the trace of the spiral.
3.
There are various means or methods by which the movement of the index point
may be accomplished. ;
Fig. 2 shows one method, Attached to the spindle A B is a cross piece CD in
which slides the index E F. A hollow drum G fixed to the dial plate L M, has a
flexible chain (or cord made of suitable material depending on the nature of the
apparatus to which the invention is applied) wound round it; the ends being
fastened to projecting pins HK rivited to the index-It follows from this construc-
tion that if the spindle A B and the piece C B attached to it is revolved one portion
of the chain or cord unwraps off the drum, the other, being wound on to the samé
'extent, the index is thus caused to slide through the cross piece C B, the direction
of motion being controlled by the direction in which the spindle is revolved.
'
Fig. 3 shows another method. Instead of using a chain or cord the index has a
rack cut upon it so as to engage teeth cut on the drum 'fixed to the dial plate, the
finger being supported and sliding in a cross piece as before described-On the
spindle revolving the index is made to slide in one direction or the other according
to the motion of the spindle.
Fig. 4 shows a similar arrangement in which there are two slides with racks
which are impelled in opposite directions on the spindle being revolved.
By varying the size or shape of the drum a different rate of motion may be
imparted to the index.
The invention has been applied to various apparatus with a view to increasing
the length & distinctness of their scales.
The important application of the invention has been the extension of the scale
of an Aneroid Barometer, the index travelling over a spiral consisting of three
complete turns, In order to obtain the necessary delicacy of action for this
instrument the index E F Fig. 2 must be made as light as possible and the cord
must be of a most flexible material-The best results hitherto have been obtained
11

page_text: by employing human hair-The addition of light springs as shown at H, K. Fig. 2
has been found advantageous. In order to prevent any slip of the cord on the
drum it is advisable to fasten one of the turns round the drum to the drum-
It has also been found advantageous to employ a different form of spring to that
usually employed to control the movement of the spindle.
"
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is-
The sliding backwards and forwards of the index finger of a dial in order to
cause one end to advance or recede from the centre so as to follow the trace of a
spiral or other, curved scale.