Improvements in Planimeters.
Year: 1895

page_text: PROVISIONAL DICITIVATION
Improvements in Planimeters.
I, PERCY ARCHIBALD HILLHOUSE, B.Sc., of Whitworth, Busby, North
Britain, Naval Architect, do hereby declare the nature of this invention to be as
follows:-
:-
==
This invention relates to improvements in planimeters and has for its object to
so construct a planimeter than it may be used for larger areas and a larger
number of multipliers are provided whereby the said multipliers may be chosen at
pleasure to suit any particular operation and the readings of the instrument will
ouly require to be multiplied by simple factors, such as 2, 3, 10 or other number
and so reduce the labour of calculations.
In carrying out my said invention as applied to an ordinary "Amslers"
planimeter or area measurer I lengthen or extend the sliding bar and engrave or
otherwise provide it with a decimal scale of multipliers, so arranged that its
reading gives the distance in quarter-inches between the two points on the top of
the instrument and also the distance between the pivot and the tracing pointer,-
which two distances will be equal. The said sliding bar is provided with an extra
balance weight so as to compensate the extra length of bar. Also in accordance
with my said invention I correspondingly lengthen the pivot bar, and dispense
with the 3, 4 or other number of fixed marks at present used.
The said instrument is used in conjunction with a card of instructions and
numerical constants so as to enable the sliding bar to be fixed according to the
purpose required.
My improvements may be applied to any planimeter having a sliding bar, and
the instrument may be used for measuring the mean pressures from indicator
diagrams, for giving areas in any required units from a drawing on any scale and
for giving the weights per unit of length of any section of material, in all cases,
by using simple multipliers only.
Dated this 4th day of June 1895.
I, PERCY ARCHIBALD HILLHOUSE, B.Sc., Naval Architect, of Whitworth,
Busby, North Britain, 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:-
My invention relates to such planimeters as have a sliding or adjustable bar, and
consists in engraving upon or otherwise providing such sliding bar with a
continuous scale of multipliers or setting points, decimally graduated in any
convenient units.
The instrument so provided will be used in conjunction with a card or book of

page_text: instructions and numerical tables showing how to set or fix the sliding bar in
order to perform any required operation and the corresponding multiplier to be
used.
The object of these improvements is to obtain the advantage of being able
readily to set the instrument to suit any particular operation so that the necessary
multiplier will be a simple number, such as 2, 3, 10, or other number easy of
application and also by such simplification of multipliers and by following the
instructions given in the tables to enable a greater number of operations of
different natures to be performed with simpler multipliers than with ordinary
planimeters. Thus my improved instrument and tables may be used to find the
area of any figure in any desired units from an outline drawn on any scale what-
ever; to find the weight per foot length of any bar or beam of uniform section ;
to find the number of lineal feet of material of a given breadth, required to cover
a given surface; to find the cost of treating any surface in any manner when the
cost per unit of area is known, or generally to find from the drawing of an area,
any other quantity which depends solely upon that area, in all cases by using
simple multipliers only.
I shall describe my invention referring to the accompanying drawings.
Figure 1 is an elevation, and
Figure I is a plan of an ordinary "Amsler's" planimeter embodying my
improvements.
Figure III is a portion of one of the numerical tables to be used in conjunction
with my improved instrument.
On the sliding bar 1 is engraved the decimal scale 2 in such a manner that its
reading at the index 3 is equal or proportional to the number of quarter-inches
between the tracing pointer 4 and the pivot 5 and also between the two points 6, 6
on the upper side of the instrument, which two distances will be equal. The
scale 2 may be of any length, the length of the sliding bar 1 being made to suit
that of the scale.
A balance weight 7 may be provided to prevent the weight of the portion 8, 9
of the sliding bar from raising the tracing-pointer 4 off the surface 10 upon which
it rests.
In accordance with my invention I dispense with the three, four, or other number
of marks at present found upon adjustable planimeters, on the sliding bar.
To find the area enclosed by any boundary line 11 by means of my improved
planimeter, the instrument must be placed somewhat as shown in Figure II with
the tracing pointer 4 upon any point of the boundary, the pivot 12 fixed into any
convenient point of the surface upon which the area is drawn and the rolling-
wheel 13 resting upon the same surface. The rolling wheel is then set to zero
upon the vernier 14, the pointer 4 passed once completely round the boundary 11
and the reading (R) of the rolling wheel taken. This reading, multiplied by
the length (L) of the sliding bar from 4 to 5, will give the area (= A)
required.
In symbols R × L
= A.
The area A will be in units depending upon the units in which the readings of
the rolling wheel and of the sliding bar are taken. Thus if both the rolling-wheel
and the sliding bar are graduated in quarter-inches, the area will be in square
quarter-inches if the drawing be full size, in square feet if the drawing be on a
scale of one quarter-inch to one foot; in square miles if the scale of the drawing
be four miles to one inch.
If the area be required in other units, it is evident that the quantity RL must
be divided by some factor F. or

page_text: the tables of setting points and corresponding multipliers show how this can be
done.
These tables will be substantially as shown by Figure III which is a portion of
the table to be used when the area is required in square feet. This table would be
used in conjunction with the instrument as follows:
Supposing it were required to find in square feet, the area of any surface from
a drawing of that surface ou a scale of "1', or th full size, the index 3 of my
planimeter would be set either at the point 25 of the sliding bar or at the
point 35.71 according to the size of the area. The rolling-wheel would be set to
zero and the pointer passed once completely round the boundary. The reading of
the rolling wheel would then be taken and multiplied by 100 or by 1000, the
multipliers found from the tables to correspond to the settings 25 and 35.71
respectively. The product would-be the required area in square feet.
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 omission of the marks at present found upon the sliding bars of
adjustable planimeters.
(2.) The provision of a continuous decimally graduated scale to be applied to
the sliding bar of adjustable planimeters substantially as and for the purposes
described.
(3.) A set of instructions and numerical tables of setting points and corre-
sponding multipliers, substantially as and for the purposes described.
(4.) An extra balance weight, substantially as and for the purposes described.
Dated this 2nd day of March 1896.
PERCY A.. HILLHOUSE, B.Sc.,
Applicant.