US1224748A - Device for the study of common fractions. - Google Patents

Description

E. C. JACOBS. DEVICE 'FOR THE STUDY OF COMMON FRACTIONS. APPLICATION FILED DEC. 12, mm RENEWED NOV. 22. 19l6.

1,224,748, Patented May1,1917.

M3883 fizz/9712467 5a 1295 A2 barren snares Parana enrich.

EDWIN G. JACOBS, OFNORWALK, OHIO.

DEVICE 11011 THE srnnY or COMMON rnAcrIoNs.

Application filed December 12, 1913, Serial No. 806,209. Renewed November 22, 1916. Serial No. 132,913.

To all 10. mm it may concern:

e it known that I, EDWIN O. JAcoBs, a citizen of the United States, and resident of Norwalk, in the county of Huron and State of Ohio, have invented certain new and useful Improvements in Devices for the Study of Common Fractions, of which I hereby declare the following to be a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

The objects of the invention are to provide a disk or disks graduated to fractional parts of a circle and having fractional quantities displayed thereon in a graphic manner, so as to illustrate at a glance a series of fractional parts of a circle, and the relations of the fractional parts to each other, and also includes a base provided with a center pin upon which the disks are revoluble.

A ruler is also preferably employed having radial edges extending from the center of the disk beyond the circumference by means of which radial lines can be drawn and the corresponding degrees upon the margin can be read.

The invention is designed to assist in the drawing of fractional parts of a circle, and in drawing geometric figures such as stars, the points of which are spaced equally apart, and incose equal angles.

The disks may be two or more in number and there may be displayed upon one disk the single orunitary fractions only with arcs of circles, and showing their relative values, and upon the other disk all the fractions comprising each unit can be displayed, up to the limit of needed use in ordinary school work, or only one disk maybe used if desired, illustrating either method of grouping fractions, or additional disks can be added to increase the number of fractions, since arcs illustrating all fractions can not be drawn, upon a single disk.

The invention is illustrated in the accompanying drawings, hereinafter further described with the method of its use, and is specifically pointed out inthe claims.

In th is a plan view of the device showing one method of its use; Fig. 2 is a plan view of a modified form of disk. Fig. 3 is a side elevation of the disk and a base plate upon which the disk is mounted.

In Fig. 1 a disk A is shown having the Specification of Letters Patent.

e accompanying drawings Figure 1* Patented May 1, 191?.

degrees of a circle marked upon a graduated tional part of a circle, at 45. A ruler R pivoted at the center of the disk at C has a radial edge R by means of which any radial line can be followed to its corresponding degree.

The same is true of all the fractional parts, such as the fraction 1/18 designated by the numeral 18, and indicated on the graduated margin by 20, and as the fraction 1/20 indicated upon the margin by 18 or the fraction 1/7 indicated by the numeral 7 and upon the margin by 51-3/7". In every case the fraction is more simply indicated if it is a single or unitary fraction, by marking only the denominator in the corresponding are which may be long or short provided its marginal radial lines run to the graduated margin.

For instance, the arc 8 has a radial line at each end and 45 are included between them. Also the are 10 has radial lines at each end including 36 between them. It is therefore easy for the student to see at a glance that the difference between l/S, and l/10 is 9 or 1/40 and 40 can be marked directly upon this smaller arc as shown in Fig. 1.

Also it is evident the sum of fractions included between two radii equals the arc included between the same radii since as shown in Fig. 1,

D in degrees and reduced to common fractions, or read on the dial of Fig. 1.

For instance employing the ruler QR first on radial lines L and then on radial line M, a difference of 42 is read between the arcs representing 3/10 and 5/12 and equals 7/60. The horizontal line 11 it is understood is used as a common starting point or base line. The ruler It pivotel upon the center 0 can revolve so that its radial edges register with any of the radial lines and it should extend beyond the graduated margin.

The disk or dial shown in Fig. 2 can be used in connection with a radial ruler R to measure differences between fractions having a unit for a numerator and also to indicate differences between fractions having plural numbers for numerators.

1n the arringement shown in Fi 1 a great number of arcs of different lengths can be drawn when the numerators are units, and in the arrangement shown in Fi 2 both units and plural numbers can be used for numerators. For convenience in use the disk A is mounted upon a base A which is provided with a needle A that projects through the center C of the disk. The ruler It is also pivoted in this disk and preferably extends beyond the disk A so that the graduations or any of them can be marked upon a piece of paper E, inserted between the disk and its base and from the points thus indicated the various angles of geometric figures can be drawn to produce stars or other effects.

The radial ruler is provided with regularly spaced openings 0, 0, by means of which arcs of circles of specified diameter can be drawn by a pupil by inserting the point of a pencil therein. One or more small holes P, 1 at the left of the center and on the base line are shown in Fig. 1, which pass through the disk A, and are used as centers to enable the pupil to draw a larger circle without the pivoted ruler.

Openings Q, Q are also made at spaced intervals in the disk through which arcs and circles can be drawn if desired.

When, however, the radial ruler is used circles and arcs can be drawn through spaced openings 0, 0 therein.

Having described the invention what I claim as new and desire to secure by Letters Patent is:

1. In a device to assist in the study of fractions, a foundation disk having a central upwardly extendingpoint, a disk centrally mounted and rotatable upon said point, said disk graduated in degrees of a great circle upon its edge, said disk having represented thereon radial lines, including fractional. parts of the circle between them Copies of this patent may be and arcs included between said radial lines, the fractional amount being represented upon each arc in common fractions, and a ruler revoluble upon said center pin and having a radial side extending beyond the graduated edge, whereby the sum of any plural number of the fractions represented by said arcs and differences between them can be read in degrees of the great circle, and also in divisions of said arcs.

2. In a device to assist in the study of fractions, in combination, a disk having its outer edge graduated in degrees of a great circle, and provided with a series of arcs, representing divisional parts of the circle, and with a representation of a common fraction upon each arc, the limits of each are being designated by radial lines, and a ruler rotatable upon the center of said disk, and having a radial edge, whereby the number of degrees subtended by each arc or portions of an arc can be read upon said graduated margin of said disk.

3. In a device for the graphical representation of operations in fractions, a disk having a radial base line extending thereacross, and provided with a graduated margin, arcs of circles originating in said base line and radial lines defining said ares, said arcs designating fractional parts of the circle, additional radial lines, further subdividing some of these arcs, the fractional values of said ares being represented thereon in common fractions, and a pivoted ruler having a radially extended edge, adapted to correspond in turn with said radial lines, and serving to register with the graduations on said graduated edge.

41:. In a device for the graphical representation of operations in common fractions, and also adapted for the construction of angles in geometric forms, a centrally pivoted disk, provided with a graduated edge, and a radial base line, a series of arcs, of different lengths, and limiting radial lines therefor represented upon said disk, said arcs designated by the denominators of the common fractional parts they represent, and a centrally pivoted ruler having a radial edge adapted to register with said radial lines in turn and with the graduations on said edge, and extending beyond said edge, whereby the fractional amount included between any two of said arcs or the amount of difference between them can be read upon said graduated edge.

In testimony whereof, I hereunto set my hand this 4th day of September, 1913.

ED'WIN C.'JACOBS In presence of WM. M. MONROE, Anonsrus W. BELL.

by addressing the Commissioner of Patents,

Images