Device or Instrument for Calculating Interest.
Year: 1889

page_text: Date of Application, 11th July, 1889-Accepted, 5th Oct., 1889
COMPLETE SPECIFICATION.
Device or Instrument for Calculating Interest.
I FILIP DRHA of Trebnitz Bohemia in the Empire of Austria Manufacturer do
bereby 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 :-
The invention hereinafter described relates to a device or instrument for calculating
interest having a dial or its equivalent filled up with suitably culculated figures
arranged in circles on the dial or its equivalent and a hand rotating round the centre
and passing along or over the said circles such hand being divided and marked for
divers rates of interest and periods so that by a merely mechanical operation the
amount of interest on a given capital at any desired rate per cent. and for any period
may be found.
The accompanying drawing illustrates this invention and shews a portion or
segment of a dial Fig. 1. and the hand or index moving over the same Fig. 2.
The outer eight circles which may be termed "capital" circles contain figures
indicating the amount of capital interest on which is to be calculated at a given rate
and for a given period. As shewn on the index the "capital" circles indicate (from
the periphery inward)
The first
The second
The third
The fourth
The fifth
The sixth
The seventh
The eighth or innermost
or outermost circle the capital at 3
circle the capital at 4
circle the capital at 4
circle the capital at 5
circle the capital at 5
circle the capital at 6
circle the capital at 6
circle the capital at 7
per cent.
per cent.
per cent.
per cent.
per cent.
per cent.
per cent.
per cent.
The twentysix circles next following (proceeding towards the centre) may be termed
the "Interest" circles and shew the amount of interest at the rates above indicated
for periods of from one day to 180 days. The hand or index fixed at the centre is
marked with the rates above referred to for each of the outer circles and with the
period corresponding to each interest circle (days and months) as shown in the
drawing.
The twelve outermost interest circles are divided into 15 segments which are again
subdivided into a certain number of equal parts for example the outermost interest
circle is divided into 15 segments each segment into 12 equal parts each of these parts
being again subdivided into 5 divisions making 900 divisions round the circle.
The 14 innermost interest circles shewing interest for periods of from one day to
fourteen days are divided into 5 segments each segment being divided into one more
equal part than the segment immediately next it (nearer the centre). For example
the innermost segment has only one subdivision the next circle two subdivisions and
so on till the fourteenth circle (interest circle for 14 days) from the centre is reached
each segment of which has fourteen subdivisions.
The divisions of the capital circles is such that 8th or innermost circle corresponding
to 7% interest four divisions (in the present case for decimal monetary systems such

page_text: as marks and pfennigs) are equal to fourteen subdivisions of the outermost interest
circle or of the circumference thereof whilst
In the 7th circle (6) non cont \ 4 divisions - 13 of the outermost interest circl
as marks and pfennigs) are equal to fourteen subdivisions of the outermost interest
circle or of the circumference thereof whilst
In the 7th circle (hit non cont \ & divisions- 13 of the outermost interest circl
In the 6th
In the 5th
In the 4th
0170
"
(6
per cent.) 4
=
000
13
"
"1
"
(5
per cent.) 1
201
13
"
22
"
(5
per cent.) 4
"
,,
"
"
"
(4
per cent.) 4
"
080
"
"
"
(4
per cent.) 4
"
080
"
"3
,,
In the 1st
"
(3
per cent.) 4
"
"
"
"
In the 3rd
In the 2nd
The following example shews the application of the apparatus.
If it is desired to ascertain how much interest say 320 marks yield at 5% in
60 days the hand or index is adjusted to 320 in the 5% circle (4th capital circle) so
that the figure indicating the capital is in line with the figure shewing the percentage
rate (in this case 5 %) on the hand and the hand will in the interest circle (for 60 days
9th circle) shew the amount 267 or 2 marks 67 pfennigs as shewn by the line a b.
If the hand is between two figures in the interest circle the subdivisions shewn by
the short gradation lines must be taken into consideration which short lines in the
device illustrated by the drawings indicate pfennigs.
If for instance it is to be ascertained bow much 375 marks yield at 4 per cent. in
135 days the index will in the fourth interest column stand at 562 as indicated by
line ed which shews the interest to be 5 marks 62 pfennigs.
Instead of the index hand moving over the dial the former may be fixed and the
latter rotate.
It is obvious that this arrangement of figures may be developed upon a cylindrical
spherical or conical surface in the first case the circles would be parallel instead
radiating from a centre and the index hand would in these cases be a fixture and the
said surfaces revolve beneath it.
Having now particularly described and ascertained the nature of my said
invention and the manner in which the same is to be performed I declare that
what 1 claim is
An interest calculating device or instrument arranged and operated substantially as
set forth
Toted this Eleventh dow of Lul 1880
loted this Eleventh dow of Ll❤ 1880
BROWNE & Co.,
9 & 10, Southampton Buildings, London, W.C., Agents for Applicant.
BROWNE & Co.,
9 & 10, Southampton Buildings, London, W.C., Agents for Applicant.