US2471099A - Microprotractor - Google Patents

Description

May 24, 1949. w. M. DETHLFs ETAL 2,471,099

MICROPROTRACTOR Filed Aug. 24, 1945 Zw" e A MZ/)mier le 9 4am( Patented May 24, 1949 MICROPROTRACTOR Walter M. Dethlefs, Santa Monica, and Fred Minder, Los Angeles, Calif.

Application August 24, 1945, Serial No. .612,472

1 Claim. 1

The present invention relates to protractors, and is particularly concerned with a micro-protractor for the use of tool and die makers.

The primary object of the invention is to provide a device of the said type which will read not only in degrees, but to one-sixtieth oi a degree, or one minute in one operation.

Another object of the invention is to provide a micro-protractor of simpler and more compact construction than is disclosed by prior devices.

With the foregoing and other objects and advantages, the invention consists of the novel arrangement and construction of parts hereinafter described and claimed.

In the accompanying drawings illustrating the invention:

Figure 1 is a top plan view of the invention with a portion of cover for gear housing broken away.

Figure 2 is a vertical transverse section thereof on line 2-2 of Figure l.

Figure 3 is a detail sectional view taken ver; tically through the bushing recess in the gear housing.

Like numerals designate the same parts of construction when referred to in the description anddrawings.

In its simplest and barest essentials, the invention consists of a protractor, a straight-edge pivoted thereto, a frame, one edge of which is aligned with the base of the protractor, rotary supplemental scales and mechanism attached to the frame and adapted to coordinate said scales and the protractor to accurately indicate the angle to minutes.

The frame Il consists of a flat rectangular ele` ment to which is suitably attached a gear housing 2 which is substantially semi-circular in contour and box-like with a removable cover 3. A rectangular compartment 4 is set off from the interior of the housing approximately at the middle of its perimeter. In the main compartment of the housing a. gear-toothed sector 5, slightly more than a quadrant, is secured in a horizontal position, at its center, on a vertical pin 6 which is revolvably mounted in said housing centrally of the arcuate housing. The lower end of pin B passes through the bottom of the housing and into a rotatable, rectangular straight-edge l, to which it is secured fast by a head set ush therein. The upper end of pin` 6 is provided with an index pointer 8 adapted to be rotated by the pin.

On the cover 3 of the housing is an arcuate scale 9, of one 90 sector with 15 graduations.

2 These graduations are numbered from right to left in 6 steps, as for example, 0-6-12-18-24, etc. The pin 6 is positioned in the center of this arcuate scale, and said scale is concentric with the gear-toothed sector 5. The base of the protractor is in alignment with an edge of the frame I.

Located in the compartment 4 is a worm gear Ill which is mounted on a short revolvable shaft II journaled in the opposite side walls of the compartment. This worm engages the toothed sector 5 and is adapted to rotate same as desired. One end of said shaft is contained in a recess I 2 in one wall of compartment Il of the housing and the shaft passes into the recess through a circular opening leading from the interior of compartment 4 to recess I2. This circular opening I3 is larger than the diameter of the shaft I I', to permit a slight lateral movement of the shaft. A bushing I4 located in the rear of said recess is adapted to receive the end of said shaft and provide a bearing therefor. This bushing is round except for flattened surfaces on opposite sides. These prevent the bushing from revolving with the shaft and also allow a slight movement of the worm toward and away from gear 5. A coiled spring I5 maintains pressure on the said bushing to maintain the Worm in engagement and is confined in the recess by the threaded plug I6.

The opposite end of the shaft I I passes through a bearing in the complemental Wall of the compartment 4 and projects through .a sleeve I8 fixedly mounted on the other side of said Wall and beyond the sleeve thereof. To this projecting end is secured a thimble I6 which is provided with a milled head I1 adapted to facilitate minute rotation of the shaft. The thimble I6 is cylindrical in form and includes a tapering portion I6c which loosely and slidably embraces the complemental end of sleeve I8, and an enlarged portion I 6b intermediate the tapering portion I6c and the milled head Il. Sleeve I8 is provided on its periphery with a graduated scale numbered from 0 to 14, both inclusive, while the periphery of the enlarged portion I 6b of the thimble I6 is provided with a graduated scale of 24 divisions, which is progressively numbered as follows, vis: 0, 15, 30, 45, 1; 15, 30, 45, 2; 15, '30, 45, 3; 15, 30, 45, 4; 15, 30, 45, 5; 15, 30, 45 back to the initial 0. These graduations are alternately three short ones, and a long one. Disposed about the periphery of the tapering portion I6c of the thimble I9 are a plurality of scale lines s'o formed thereon as to coact with the scale lines of the scale on the sleeve I8 3 and the scale on the enlarged portion I6b of the thimble I6.

In operation, the straight-edge 'I is rotated from frame I through 90 by means of the worm and gear-toothed sector. These gears have a 60 to 1 reduction, hence each revolution of the head I'I equals 6, the value of each gradation on the arcuate scale 9 of the protractor. The index pointer will, therefore, on one revolution of I1 indicate the angle to the nearest 6. Portion I6b of the thimble has 24 divisions to its peripheral scale and each division represents one-quarter degree or 15 minutes. On portion IGa are fifteen divisions in the scale, these occupying a space equal to that of fourteen divisions on portion IGb. The difference between the Width of one of the fifteen divisions on portion IBa and that of one of the fourteen divisions on portion IGZ)` is therefore one-fifteenth of a space on portion Ilia, at one time. Hence, the gradations on the portion IGa represent one-fifteenth of a quarter degree, or one minute. This is the Vernier principle used on most micrometers reading in ten-thousandths.

Having thus described our invention, What We claim as new and desire to secure by Lettersl Patent is:

A micro-protractor consisting of a frame provided With a housing and a removable cover, a protractor with suitable arcuate scale to record degrees of an angle mounted on said cover with its base aligned on a straight-edge of the frame, an index-pointer mounted concentrically with said arcuate scale, a straight-edge mounted beneath said frame concentrically with said arcuate scale 4 and adapted to rotate in conjunction with the index-pointer which is aligned therewith, a rotatable vertical shaft mounted in said housing to which is secured said straight edge and index pointer, a gear toothed sector carried by said shaft, a horizontally disposed shaft mounted for limited lateral play, a Worm on said last named shaft in meshing engagement with said gear sector, a coiled spring adapted to bear on said last named shaft laterally to maintain the Worm in mesh with said sector, a thimble attached to the end o'f the last named shaft exteriorly of said housing and having a scale disposed about its periphery divided into one-quarter degrees or fifteen minutes, a sleeve fixedly mounted on said frame in cooperative association with said thimble and having a scale disposed about its periphery, each division of which is equal to one-fifteenth of the circumference of the sleeve.

WALTER M. DETHLEFS. FRED MINDER.

REFERENCES CITED 'The following references are of record in the 25 file of this patent:

UNITED STATES PATENTS

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