US2412100A - Protractor - Google Patents

Description

'Del. 3,1946.^ `NQSMWH f 2,412,100.

PROTRACTOR Filed Nov. 29. 1944 Patented Dec. 3, 1946 UNITED STATE y ritoTnAoifoR V M Neil C. smith, Minneapolis, Minn.

" Appneaiion November 29,1944, serial No. 565,697

lt/ly'present invention relates vto improvements in protractors of the type having a rotatable turret andra blade slidably mounted thereon.

The object of this invention isvto provide an extremelyisirnple and highly eflicient protractor" having commonV means for simultaneously locking the'turret against rotation and the blade against sliding movement.

Other objects vof the invention will be apparent fromthe following description, reference :being had to the accompanying drawing.

3 To the above end, generally stated, the invention consists of the novel devices andcombination of devices hereinafter described and dened in the claims.

In the accompanying drawingwhich illustrates the invention, like characters indicate like parts throughout the several views.

Referring to the drawing:

Fig. 1 is a plan View of the improved protractor;

Fig. 2 is a bottom plan View of the turret and the blade removed from the body of the protractor;

Fig. 3 is a fragmentary plan view of the body with the turret and the blade removed therefrom;

Fig. 4 is a view partly in side elevation and partly in section taken on the line 4-4 of Fig. 1, on an enlarged scale;

Fig. 5 is a plan view of the Washer removed from the protractor, as shown in Fig. 4; and

Fig. 6 is a bottom plan View of the washer as shown in Fig. 5.

The numeral 'l indicates the body of the protractor which, as shown, is in the form of a blade, the longitudinal edges of which are parallel. One end portion of the body I is enlarged to afford a head 8. At the center of the head 8 is an upstanding tubular pivot 9, the lower end portion of which is reduced in diameter and mounted in a hole in said head. An annplar shoulder l is formed by reducing the lower end portion of the pivot 9 and which shoulder I0 rests directly on the head 8. The lower end of the pivot 9 is upset within the plane of the body 'l to rigidly secure the pivot 9 to the head 8 with its axis perpendicular to the plane of the body 1. This method of securing the pivot 9 to the head 8 leaves the bottom of the body 'l perfectly smooth so that said body will rest flat on a support.

A flat turret Il is mounted on the pivot 9 for rotation about the axis thereof in a plane parallel to the plane of the body Substantially 180 degrees of the turret II is on the arc r vturret I I.

ofa circle having' its center at -the axis of said turret II. This section of the Aturret is -beveled to a relatively sharp edge at its underside,v as indicated at I2.

A thin narrow blade I3 is mounted in a channel I4 in the under side of the turret `for endwise sliding movement. This channel'M is in the opposite side of the turret |I from' the intermediate portion of the bevel I2. A springY member I5 in the channel I4, between one side thereof and the adjacent longitudinal'edge "of the blade I3, yieldingly holds said blade pressed against the other side of said channel whereby the blade I3 is frictionally held where endwis'eadjusted in the channel I4. The spring'mem-` ber I5 is held in the channel I4 by a pin I6. The blade I3 rests atwise directly on the head 8- and the central portion of the turret I I also rests directly on said head. Said turret l I, lat its outer portion, has a working clearance with the body 1, see Fig. 4.

The longitudinal edge of the blade I3 that is in direct engagement with the side of the channel I4 has dove-tailed engagement with the The upper end portion of the pivot 9 extends outwardly of the turret II and is reduced in diameter and diametrically opposite sides of this reduced portion are flattened, as indicated at Il. A washer I8 is mounted on the reduced outer end portion of the pivot 9 and the hole therein has the same contour as the respective portion of the pivot 9 and is thereby held from turning on the pivot 9. The under side of the Washer I8 is dished at I9 so that only its outer marginal portion bears on the turret I I.

A screw 20 extends into the tubular pivot 9 and has threaded engagement therewith. This screw 20 has a large head 2|, the periphery of which is beveled and knurled. On the under side of the screw head 2| is a thin hub 22 that bears directly on the washer I8.

Obviously, by tightening the screw 20, the turret II will be frictionally clamped onto the lbody 'l and thereby held against rotation and at the same time the blade I3 will be frictionally clamped onto thebody 'I and thereby held against endwise sliding movement. It will be noted that the screw head 2| extends outwardly of the washer I8 so that the same can be easily gripped with the ngers. The size of the screw head 2| makes it very easy to manipulate. The turret II, the washer I8, the screw 20 and the screw head 2| all have their axis at the axis of the pivot which lends itself for accuracy and easy assembly. The washer I8, due to its dished under side, bears only on'its outer portion on the turret II. This structure gives an even pressure on the turret in a complete circle that is concentric to the pivot 9, thereby holds the turret II in a plane that is parallel to the plane of the body 1 and prevents tilting thereof on the pivot 9 and thus prevents undue wear and strain on said pivot.

By reference to Fig. 4 it will be noted that there is a working clearance between the upper end of the pivot 9 and the hub 22. The dished under side of the washer I8 affords a good working clearance between the shouldered upper end of the pivot 9 and said Washer and the surface of the turret I I underlying said dished portion of the washer I8.

The body 1 and the blade I3 each Vhas Ythereon a scale of inches as indicated at 23 and 24, respectively. A circle, outward of the curved portion of the turret II and having its center at the axis 4of the pivot 9 is divided into quarters, and each quarter vgraduated into 90 degrees, Vas indicated at 25. These degrees read from two diametrically opposite zero points. Tw'o zero marks 26 and 21 are shown on the turret II spaced 90 degrees apart for co-operation with the degree graduations 25. By means of one of these zero points 25 and 26, the turret II may be adjusted to position the blade I3 at a required angle relative tothe body 1 and the degree reading at .the other zero point will give the component angle. A Vernier scale 28 on the turret II has its zero point at the zero point 21 and reads in opposite directions therefrom. The close proximity of the beveled edge of the turret II with the degree markings 25 lends itself to easy and accurate reading of said degrees.

vWhat I claim is:

1. In a device of .the class described, a body having an upstanding pivot, a turret turnably mounted on the pivot with freedom for axial movement and resting on the body, a blade mounted on the turret for endwise sliding movement and resting on the body, a washer mounted on the pivot with freedom for axial movement, held against relative turning movement and resting on the turret, a member having threaded engagement with the pivot and bearing on the washer and operable to simultaneously frictionally clamp the turret onto the body and thereby hold the turret from turning on the pivot and frictionally clamp the blade between the body and the turret and thereby hold the blade from sliding endwise relative to the turret and the body.

2. In a device of the class described, a body 'having an upstanding tubular pivot, a turret turnably mounted on the pivot with freedom for axial movement, resting on the body, and having a channel in itsl under side, a blade mounted in said channel for endwise sliding movement and resting on the body, a Washer mounted on the pivot with freedom for axial movement, held against relative turning movement and resting on the body, a thumb-screw having threaded engagement With the tubular pivot with its head bearing on the washer and operable to simultaneously frictionally clamp the turret onto the body and thereby hold the turret from turning on the pivot and frictionally clamp the blade between the body and the turret and hold the blade from sliding endwise relative to the turret and the body.

3. The structure defined in claim 2 in which the Washer is dished on its underside and thereby engages the turret only at its perimeter.

NE1L C. SMITH.

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