UUMERIE DERIVATION Differential Measuring Gear for Relative Motion
Year: 1895

page_text: Date of Application, 13th May, 1895-4ccepted, 27th July, 1895
UUMERIE DERIVATION
Differential Measuring Gear for Relative Motion
I, JOHN HENRY TUDSBERY TUDSBERY of Rossmore, Melrose Road, Londou,
S.W., Civil Engineer, do hereby declate the nature of this invention and in what
mauuer the same is to be performed, to be particularly described and ascertained
in and by the following statement.—
The motions of two bodies, X and Y, are transmitted by means of separate
flexible cords or wires, a and b, attached thereto, to the peripheries of two flanged
wheels, A and B, of equal diameter, around which the colds lap. The position of
the axis of the wheel, A, is fixed, and, connected with the wheel and revolving
with it upon the same axis, is a third flauged wheel C Connected with the
wheel, B, and revolving with it upon the same axis is a fourth flanged wheel, D
The common axle of the wheels B and D) 18 carried in a stirip, E, which 18
attached by a flexible cord or wiro, c, to the periphery of the wheel C, lapping
round it in the same direction as the cold, a, laps tound the wheel A.
A similar cord or wire, d, attached to the periphery of the wheel, D, and
lapping round it in a direction opposite to that in which the cord, b, laps round the
wheel B, transmits the motion of the periphery to a recording pen or pencil, F
The position of F, by means of the invention described, then indicates con-
Linuously with reference to a zero-point a fraction of the distance between two
parallel planes in which the bodies X and Y are respectively situated.
In order to effect the measurement of the fraction of the aforesaid distance, the
wheels A, B, C and D, are so formed that the diameter of the wheel D bears to
that of the wheel B the ratio represented by the required fraction of the distance
between the two planes, and that the diameter of the wheel C bears to that of the
wheel A the ratio represented by a fraction, the denominator of which exceeds by
one the first mentioned fraction
Springs or weights are applied to the wheels A and C, and to the cords a, b, e
and d, exerting sufficient force to keep the cords taut and to maintain equilibrium
the entne system Suitable guides are also applied to ensure that the motions
of the sturup, E, and of the pen, F, may be rectilinear
The action of the gear is as follows
The body being fixed and stationary, if the body Y be moved any distance
Lowards the point of contact of the cord & with the wheel B,-this wheel rotates in
a direction contrary to that of the hands of a clock, caying with it the wheel D
from which is unwound a proportional length of the cord d, and thus the pencil F
moves away from B through a corresponding distance. This distance is the same
Taction of the given distance through which Y is moved, as the diameter of the
wheel D 18 of that of the wheel B.
Agam, if Y be fixed and stationary, and if X be moved towards the point of
contact of the cord a with the wheel A though the same distance as in the
preceding case Y was noved, the wheel A, being caused to rotate (also contra-
clockwise) by the sping or weight applied to it to the extent allowed by the
motion of the cord a, tiansmits its motion to the wheel C upon which is therefore
wound a length of the cord c, and the stirrup E is drawn towards it. E being thus
moved towards the wheel A whilst Y is fixed, the wheels B and D rotate in the
same direction as the hands of a clock; and the pencil F 18 drawn towards the
wheel D by the cord d winding round the latter and by the motion of the stirrup E
towards C.

page_text: The distance through which the pencil
1
moves is found thus .-
Let be the ratio of the diameter of the wheel D to that of B, then, by the
"
construction above stated,
1
1 + 1
is the ratio of the diameter of C to that of A.
If, then, the distance through which X is moved towards the wheel A is taken
as unity, the stup E will be drawn towards the wheel (a distance represented 5
by
1
and, Y being fixed, the pencil will be caused to travel by the joint
7 + 1'
movement of the stup which carries the axis of the wheels B and D, and the
rotation of the latter, thiough a distance represented by the fraction
which action represents precisely the distance through which F travels away
from the wheel B due to a like equal movement of Y when X is stationary, as in
the case first considered.
Movements of X and of Y in the direction opposite to that above considered,
ie away from the wheels A and B, produce corresponding opposite imovements of
the pencil away from B and towards B respectively, but in either case the
movement of F 18 the same fraction of the movement of X o of Y as the diameter
of the wheel D 18 of that of B
Hence, it is apparent that any single movements whatever of X and Y in
parallel straight lines through the points of contact with A and B of the cords
respectively connecting them with those wheels, produce conesponding fractional
movements of the pencil F-oppositely directed if the motions of X and Y are in
the same duection, and uce versa. Consequently the motion of F measures a
fraction of the distance between planes through X and Y.
The gear may be applied, for example, to measure continuously a fraction of the
difference between the levels of two water-sm faces, both of which are variable; as
In certain cases of gauging by submerged orifices In such cases, the bodies X
and Y are floated upon the two water-surfaces, a definite fraction of any movement
of either water-sui face being communicated by the gear, fixed vertically above X
and Y, to the pencil F. When such movements occur simultaneously, bas
conveyed to it the same fraction of the relative motion of the two water-sun faces
The pencil F therefore indicates continuously, ou a dingrain moving under it, with
reference to a zero point on line, the given fiaction of the difference of lovel
between the two water-surfaces upon which X and Y float.
Having now particularly described and ascertamed the nature of iny said inven-
tion, and in what manner the same 18 to be performed, I declare that what 1
olaim 18:
The invention of the system of wheels and cords described, where the wheels
are formed with diameters having the particular relations one to another above set
forth.
Dated this Eleventh day of May 1895
JOHN HENRY TUDSBERY TUDSBERY.