Improved Device for Magnifying Small Movements and Facilitating their Measurement.
Year: 1889

page_text: Date of Application, 23rd Jan., 1889
Complete Specification Left, 25th Nov., 1889-Accepted, 22nd Feb., 1890
PROVISIONAL SPECIFICATION.
Improved Device for Magnifying Small Movements and Facilitating
their Measurement.
I, EUSTACE THOMAS, of Albany House. Prince of Wales Road, Battersea, S.W., in
the County of Surrey, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:
My invention consists of a device for magnifying small movements, and facilitating
their measurement; and of apparatus wherein this device may be employed.
I introduce a small roller between two surfaces which have been fitted to one
another, & are usually plane. These surfaces are made to move relatively to one
another by the small motion which it is the object of any invention to magnify, &
thereby impart an angular motion to the roller between them. The small circum-
ferential motion of the roller is magnified by a pointer of convenient length attached
to it; or by means of a bean of light reflected from a small mirror, (such as is used
for reflecting galvanometers) attached to the roller. The degree of magnification is
expressed by the ratio of the length of such mechanical or optical pointer to the
diameter of the roller, if the latter have its axis at right angles to the direction of the
motion.
The roller itself, & also the surfaces between which it rolls, may be of any suitable
materials, such as steel, phosphor bronze, brass, glass, ivory, &c.; & they may be
treated in any way, such as by bronzing, oxidising, dipping &c., that may be thought
desirable. The surface or surfaces may form part of the body or bodies in motion, or
may be separate from, but attached to, them.
My invention may be applied to all instruments where it is desirable to magnify a
small motion, such as micrometers, instruments for measuring expansion by heat,
elongation by magnetisation &c. & to all instruments where it is desirable to decrease
the movement of the working parts, as in some kinds of ammeters & voltmeters &c.
Dated this 22nd day of January 1889.
EUSTACE THOMAS.
COMPLETE SPECIFICATION.
Improved Device for Magnifying Small Movements and Facilitating
their Measurement.
I EUSTACE THOMAS, of Albany House, Prince of Wales Road, Battersea Park
London, in the county of Surrey, Electrical Engineer, 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 :—
There are many experiments & instruments which require a simple, but very exact
magnifying mechanism, which must be absolutely without back lash & must introduce
the least possible friction into the instruments. Such magnifying mechanism must not
be liable to easy derangement and the instruments containing it must be as portable as
possible.
By the improved device, it is sought to carry out these desiderata. It will be best
described with reference to particular instruments containing it.
Fig. 1 represents one method of employing the improved device for the construction
of micrometers for measuring small objects, distances &c. with great accuracy.
On a suitable base 6 is a block a a having a groove or slot, in which slides, without
sideplay, the bar c. This bar terminates in an accurately finished surface d. Coaxial
with, & strictly parallel to this, is a second surface & attached to the projection ƒ on
the stand or base b. The bar c & the block a are furnished with truly plane &

page_text: parallel surfaces 9 & gl. Between those is placed a small roller r made of steel or
other metal, & of perfectly circular & uniform section, or that has been so treated as to
turn always thro' the same angle for the same relative motion of the surfaces g, g.
Thus the angle turned through by the roller will be proportional to the distance by
which the surfaces d & e-between which the object to be measured is placed-are
separated. The planes & g' are pressed together by the spring h,-shown also in
Fig. 3. & so tightly grip the roller between them. By the oblique position of h, it
tends moreover to drive the bar c forwards & close the space between d&e. The
hole o in Fig. 3 is relatively too small & is drawn too close to the lever k. The bar c
can however be forced backwards by the bent lever k, actuated by the screw
Figs. 1, 2, & 3, working in the case of the instrument.
The planes & must be perfectly true & may be separate from a &c. In such a
case they may be held in position by the method shown in Fig. 4 where G is the plane,
m the body to which it is to be attached, & sa screw, whose conical head bears on the
bevelled edge of G. Or, as in Fig. 5, the plane may be cased in a sheath of metal or
other suitable substance c, which can be attached by screws, cement, solder or other
suitable means to the bar or body desired. The planes may be prepared in any way
from any material found suitable, but I prefer flattened glass.
Z is a well cast in the base of the instrument to give clearance to the planes, but is
not strictly necessary.
The hole, by which
passes through the dial, is preferably so small as to act as a
bearing to & thus keep that part of it to which the pointer is attached in the centre
of the scale engraved on the dial.
The pointer used should always be as light as possible & be of hard springy metal,
such as fine steel wire soldered or otherwise attachel, to r.
A sudden jar may cause the instrument to alter its zero by the very sudden relative
motion of g&g that may be produced. This can always be corrected by turning the
dial to follow the pointer, the dial being so mounted on its case (all shown in position
by dotted lines in Fig. 1.) that it can turn about its centre, the point by which passes
through it. As a preventive however, I may employ a dashpot fastened to the frame
of the instrument, & having a rather loosely fitting piston, which is connected directly
to the moving bar c. The dashpot is completely filled with water, or some other liquid,
& its open end completely enclosed by a cover of corrugated, very flexible metal, or a
cover of indiarubber fastened to the top of the dashpot. In either case the piston rod
passes through the cover, watertight, to be connected to the piston. The rate at
which can move is then limited by the rate at which water can pass round the edges
of the piston from one end of the dashpot to the other. Where a dashpot is used, it
is better to use, to separate the jaws, a second spring, capable of being made, by the
movement of a milled head or other suitable means, to oppose the forward tendency
of the first & separate the jaws against the tendency of to close them.
Figure 6 shows an aneroid barometer with the magnifying roller applied.
Tho bar bis cut almost through at the points c & c (c' is hidden by the post p.).
The remainder of the bar above c & c acts as a spring, tending to make the centre of
the bar curve upwards & press against the pin or fulcrum, attached to the post p, the
ends of the bar being kept up by the struts & the link as shown in the drawing.
The struts is between two pointed pins, one attached to & one to the base plate.
The post p is attached to the top of the aneroid box a (the corrugations of which are
not shown) in the ordinary way, & is supported by the spring e as usual. Thus as
rises & falls with variations in the pressure of the atmosphere, the springy parts
above c & c¹ constrain the middle of the bar to follow the pin ƒ & therefore p. As f
rises, the arms m & will separate at the top. On the arm mare mounted the rolling
surfaces g g'. As shown more clearly in the enlarged view Fig. 7, is permanently
attached to, or forms part of, m. g is held in place by the springs h & h¹ & the
links &t. The tendency of the springs & links is to press the surfaces & gl
strongly towards one another & thus grip the roller r, & at the same time, by
the oblique position of the links, shown more clearly in Fig. 8 to urge g' in the
direction of the arrow. g is however stopped by the small strut o, between g¹ & n,
22

page_text: & its movement is therefore limited by that of n & therefore dependent upon that
of the aneroid box a. The strut o has pointed ends resting in cavities in n & g.
The device shown may obviously be modified in various ways. Links only, or
struts only, may if desired, be employed. The links themselves may be made of wire.
The device may advantageously be applied to the construction of ammeters &
voltmeters.
Fig. 12 illustrates, somewhat diagrammatically, a device applicable to the
measurement of currents or differences of potential. The outer coil is fixed by
its bobbin to the bed plate. The inner coil c is supported in such a way that it
can move parallel to itself; as illustrated, this is accomplished by the springs & s².
By means of a framework, suchfas b, the movement of the coil c¹ is communicated to
the plane g. The second planey is attached to a frame, or support a fastened to the
top of the bobbin on which c is wound. The plane g¹ is supported by b in the
manner shown in Fig. 13, by the ends or points of two screws entering notches holes,
or cavities in g. The arrangement may obviously be varied in many ways in detail.
For instance the coils may be of a conical or other shape to obtain a more uniform
calibration. Iron may be used, whether fixed or movable, in conjunction with one or
both the coils.
The instrument may further be modified as in Fig. 14, where c & c¹ are wound as
flat coils or shells. The fixed plane is not shown.
Fig. 15. represents a hot wire voltmeter, in which the lengthening of a wire is
directly measured. is the wire, & g' g the surfaces, details of which are shown in
Fig. 16. The wires bare attached to the metal casing of the planes g. The
planes may be supported in any suitable manner, one method being shown in Fig. 16.
ssss are springs attached to the case. 1&are wires joining them as shown, but on
their path linking round the connecting links t&t so as to support thein & with them
the planes.
In Fig. 17 the wire is not straight but is bent several times at right angles. The
angles are supported by the links w w making an angle of 135° or hereabouts with
both of them. Any sinall lengthening, for example, in 11 is transmitted by the link
as an equal lengthening to,& in its own direction (that of 6111). The wires 6" & ¿!!
may be at any angle, & the device may be applied to stiff links at 6¹¹ & b",
insulated from the support by insulation e.
a is
Fig. 18 shows the application of the device to steam engine indicators.
Steam is admitted to a corrugated tube c whose length increases under the pressure.
The plane g is thus caused to rise, & the roller rolls between it & the fixed plane g.
g' is attached to c by the nut n and dished washer w so that it can turn round the
axis of c. The tube T turning on the inner tube t, can also turn round the axis of c, its
movement being controlled by the end of the screw s moving in a groove turned in t,
or by some equivalent device. The pencil or marking point p is attached to a sleeve m,
capable of moving on a vertical guide n. The arm attached to the roller has a
slot S at the end, in which a pin on m engages. The curve of the slot is such that
the movement of p shall be proportional to that of g'. The cylinder to carry the paper
is merely indicated by dotted lines. Both I&K are thin & springy, & a slot limits
the motion of T so that only a gentle pressure can be exerted on the paper by the
point or pencil p. By unscrewing the ring R. the tube c can be removed & replaced
by another of different strength.
The above represents only one method of applying the roller, & may be varied in
any details. In Fig. 19 showing the application to pressure guages, the opening to c
is contracted to a narrow aperture o, to prevent rapid oscillations of the pointer, due
to sudden variations in the pressure of the stean. The roller in Figs. 18 & 19 may
vary widely from the sizes represented. In all instruments suitable supplementary
springs may be used to increase the pressure between g & g' & thus prevent slipping
of the roller. The roller must be of accurately circular section, & should be perfectly
cylindrical. It may be made of quasi-circular section, (especially if fine) by twisting
one end with reference to the other, till a strong permanent set is acquired. Steel is
best so treated while hot.

page_text: Having now particularly described & ascertained the nature of my said inven-
tion, & in what manner the saine is to be performed, I declare that what 1
claim is :-
1. For the accurate measurement in a commercial manner of small movements, the
employment of a small roller, the cross-section of which has been rendered perfectly
circular or quasi-circular, capable of rolling between two planes to which relativo
movement is communicated, by the motion of one of the planes.
2. The magnification, for accurate measurement, of small movements, by means of
a roller of perfectly circular or quasi-circular section (hereinafter called an "accurate"
roller), rolling between two planes, to both of which movement is communicated.
3. The methods of securing the planes of a roller magnifying mechanism
substantially as illustrated & described with reference to Figs. 4 & 5.
4. The application of an "accurate" roller mechanism to the construction of
micrometers for measuring accurately small distances or small alterations of distances.
5. The micrometer substantially as illustrated & described with reference to
Figs. 1 to 3.
6. The application of an "accurate" roller mechanism to the construction of instru-
ments for measuring fluid pressures by aneroid methods.
7. The aneroid barometer substantially as illustrated & described with reference to
Figs. 6 to 11.
8. The method of altering the direction of a motion by means of links, substantially
as illustrated & described, Fig. 17.
9. The application of an "accurate" roller mechanism to the construction of
instruments for measuring electrical quantities where magnification is desirable.
10. The construction of ammeters & voltmeters substantially as illustrated &
described with reference to Figs. 12 to 14, applicable also to Wattimeters.
11. The construction of voltmeters substantially as illustrated & described with
reference to Figs. 15 & 16.
12. The construction of voltmeters substantially as described with reference to
Figs. 17 & 16.
13. The employment of a corrugated tube for measuring the pressure of fluids by
its alteration of length.
14. The application of an
"
"
accurate roller mechanism to the construction of
pressure gauges & steam engine indicators.
15. The combination of an "accurate" roller mechanism with a corrugated tube for
steam engine indicators & pressure gauges.
16. Rendering rollers quasi-circular in section, as described.
Dated this 23rd day of November 1889.
EUSTACE THOMAS.