US1247866A - Protractor. - Google Patents

Description

P. OLMSTED.

PROTRACTOR APPLICATION FILED AUG-2.1916.

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PERRY OLMSTED, OF LOS ANGELES, CALIFORNIA.

PRGTRACTOR.

Application :tiled August 2, 1916.

To all whom t may concern Be it known that I, PERRY OLMs'rnD, a citizen of the United States, residing at Los Angeles, in the County of Los Angeles and State of California, have invented a new and useful Protractor, of which the following is a specication.

The principal objects of this invention are to provide a protractor of exceedingly simple and convenient construction constituting' not only a protractor, but also a trisquare, bevel square, center square, angle finder, and also a simple means whereby without the use of mathematics of any kind, or even tables, the length of the side of any regular polygon to be inscribed in a circle can be determined; to provide a construction by which an angle of any size can be bisected in a very simple manner; in which the angle between the movable straight edge and the stationary straight edge of the protractor can be brought to a sharp point at all small angles; in which a micrometer arrangement is provided whereby settings down to degrees and less, if desired, can be made without the necessity of division lines so close together as to require the use of a glass; in which means can be provided whereby the movable straight edge can be set conveniently to certain specified angles, as for example, ninety and forty-five degrees without the necessity of observing the scales sothat this can be done where the light is insufhcient and yet provide a device which can be folded up into a small compass. The invention also involves other features including the provision of a scale in combination with the usual degree scale lwhich will show the number of inches rise per foot at any desired angle, and which can be made to show the various angles necessary in building constructions, as for example, theheel out, plumb cut, and side cut of rafters for a hip roof at various angles.

Reference is to be had to the accompanying drawings in which- Figure l is a front elevation of a preferred embodiment of the invention showing how an angle is bisected by it;

Fig. 2 is an end view showing certain details;

Fig. 3 is a view of the rear side of the protractor showing how it is used for finding various angles necessary in constructing roofs and the like;

Fig. t is a front view showing the use of Specification of Letters Patent.

Patented Nov.l 2*?, limit.

serial no. 112,688.

the device in finding a rise in inches per foot;

F ig. 5 is a similar view showing the setting of the two movable straight edges at ninety and fortylive degrees respectively, and showing some modifications.

Fig. G is a view similar to Fig. 1, showing a modified form, and showing the application of the instrument to the problem of inscribing a polygon in a circle, and

Fio'. 7 is a similar view showing another modification.

Referring lirst to the lirst sheet of draw ings, it will be seen that the invention is shown in a form in which the instrument comprises a plate or beam a having a pivot and provided with a straight edge c extending from said pivot in one direction. This beam is also provided with a parallel straight edge CZ offset from the straight edge c and extending a-s far as the pivot from the opposite end of the plate. It will be seen that on this beam is a protractor comprising a semi-circular angle scale e and in the form shown on this sheet this scale is divided up into divisions of ten degrees each. Also inside this outer scale e is a semi-circular scale 7, the degrees on which are not numbered, but which is divided in a similar manner except that the points of division are halfway between the points of divison on the outer semi-circular scale, and from each one of them two lines g are drawn one to each of the two adjacent points marked on the scale c. These lines g are of importance as will appear. The protractor is shown as having its diameter laid olf on a straight line of which the straight edge c is a part.

Furthermore this side of the device is shown as provided with another scale which, in the form shown, Consists of three parts, one 7i parallel with the straight edge o, and the other two perpendicular to it. These scales are divided up into equal divisions and the three scales taken together extend entirely around the semi-circle. The purpose of this will be described hereinafter.

Frictionally pivoted atl the central point o are two arms 1 and Z. One is shown as on the back and the other on the front. They are provided with semi-circular offset portions covered by the fastening nut and washer m, but their inner straight edges are exactly in alinement with tbe center of this pivot on which they are adapt-ed to swing. It will be noticed that the two straight edges c and Z are at a distance apart equal to the width of these two arms if; and Z so that when they are folded together and brought into contact with the edge c the whole instrument is of rectangular form7 and .all the parts come within the rectangle.

Referring now to the pivoted arm which is on the front, it will be seen that its inner straight edge is scaled in inches and twelfths and that it extends beyond its pivotal point and is provided with four division marks a at equal distances apart. These divide up the space between the two graduated circles c and j into live equal divisions. In this form the line along which these marks are located is radial, that is in exact aline-ment with the center Z). The object is to provide a micrometer arrangement whereby the protractor can be divided into a liner degree of division than that indicated by the division points thereon. This will explain why the lines g are not radial, but have a certain slant. Y

In the use of the instrument for this purpose the pivoted arm L can be brought for example tothe point indicating` seventy degrees with its straight edge on that division of the outer circle, and then its angle with the straight edge 0 will be just seventy degrees, but if it is desired to mark off seventj two degrees it is moved over further until the second of the division marks n, on its .shortarnn registers with the line g extending fromthe seventy degree point of the outer circle to the next point on the inner circle. In this way aline division can b e secured without necessitating the use of iner graduated marks on the outer circle. These divisions on the short arm ot the member /c are much farther apart than the corresponding divisions would have lto be on the circle e. In the size shown, angles involving` divisions under thirty minutes can be readily estimated, and this is liner than is usually necessary in carpenter work. To facilitate the use of this part of the device the space between the circles c and 7" is divided by ive concentric circleslspaced equally.

rl`he use of the scales 7L is also very practical for they are divided up into equal divisions to indicate rises in inches per toot. The first division on the right indicates that if the straight edge 7a is set to correspond with that division it gives a rise of one inch `per foot, and so on throughout the scale.

The divisions on the two vertical scales are exactly equal to each other. The divisions on the scale j shown in these igures constitute a continuation of the two scales 71..

In the use of this device for bisecting angles, the two arms Z2 and Z have to be employed and for the purpose of using` them .without reference to the back not' the instrument one'o'f them, as for example Zr, can be set to the vangle desired, as for example thirty degrees, and then the rear one Z brought into register with it, then the front one 7c can 4be moved to the fifteen degree angle which will bisect the angle formed by the arm Z, the short arm of the member Za being used for measuring the angles in both cases.

Where it is desired to find the facts about a polygon to be inscibed in a circle, the instrument is used as shown in Fig. 6. First, .the central angle subtended by one side of the polygon is obtained. For example, if it is an Octagon, this angle is forty-Jive degrees. The arm 7a is set at an angle of forty-live degrees from the straight edge c. N ow the length of the radius of the circle in which it is to be inscribedis laid ott on the straightfcdge c, measuring from the center Z), and also on the adjacentstraight edge of the member r from the same point. The instrument is so placed, as indicated in Fig. 5, that these two points on the straight edges c and will be located on the surface of the circle, and then these points marked in any desired way. This gives the ends of one side of the polygon and the remainder of the figure can be lound in any desired way. rllhe geometrical figure appearing on Fig. proves without any mathematical ldemonstration that this process is correct.

Another feature ot the instrument shownin Figs. l and 2 is a bar o adapted to t either on the straight edge c Vor on one of the arms u-or Z. It has a groove o adapting it to lit rictionally. Its use is to permit the completion of a' sharp angle, as indicated in Fig. 1. TWithout it the apex of the angle would be lilled by the washer. j

@n the rear of the beam are placed scales formed to provide for showing various angles, as may be desired. For example, on the irst scale p at the top are ltwo sets of lines indicating the plumb cut and `end cut respectively of the rafters ot a hip roof. For example, if the hip roof has a pitch of seventeen inches to the foot the angles at which the plumb cut Vand end cutare to be made are indicated by the lines marked 17 on this scale. Various other things can be shown at this place, as for example, the

butt cut and miter cut of chords used in constructing polygons or portions of 1polygons, as for example, in the making of a bay-window. In this case the second scale g is shown as marked in this way. The ining vemployed to assist the operator in fget- Corresponding cuts for other lll@ pas

Leanser) en ting the proper angles to mark off on his work.

Another way in which the instrument can be used is in sighting along the straight edge of a pivoted arm if: or Z to get an angle, especially an angle of elevation. For this purpose the beam is placed in horizontal position, a level being used, and the arm to be sighted along is tipped to the proper angle and the sight taken along it to the point indicated, as for example, the top of a building` or the like. Then the angle indicated without change in the position of any of the parts is read directly on the protractor.

The instrument can be used in other ways for various measuring purposes.

For the purpose of setting the arms at the most common angles, as for example, ninety and forty-five degrees, each one is provided with a projection having a straight edge, as for example, le and Z at ninety degree and forty-five degrees respectively t0 the straight edge. Then as shown in Fig. 5, the operator can readily bring this edge into registration with the straight edge c by his lingers without looking at them. Therefore the arms can be set in the dark if desired. This ligure also shows some modifications in markings. VThe lines g are replaced by lines g all slantin g in the same way instead of alternating. The scale 71. in this case is provided with divisions equal to the divisions on the scales As half of it is just equal in length to a scale y', complementary angles can be found by placing one arm to read on one scale and the other at the correspondingly numbered division on the other` This brings them just ninety degrees apart. The scales y' shown in Figs. 1 and 5 can of course be put on the same beam.

Fig. 6 has been referred to for the purpose of showing one use of the instrument, but this figure shows a modification in that the arm h', instead of being provided with a straight edge on its short arm in alinement with the pivot, is provided with an edge h2 at an angle thereto and in this case the lines g2 which correspond with the lines g of the first ligure are radial. In this case the reading of the angle is done in the same way as before and the result is equivalent. Tn this form the four semi-circles between the circles e and f are omitted as they can be if desired in any of the forms.

Fig. 7 shows another modication in which the straight edge is located in an angular position in a di'erent way, but also equivalent to the other forms.

lt will be seen that all these features of utility are secured by an instrument which has only three or four elements and which is practically as simple as any form of trisquare or protractor that has any moving parts at all. This is an important advantage of the device because when not in use it can be folded up into avery compact form, both arms 7c and Z registering with each other and occupying the space j ust beyond the straight edge c. 1n this way it can be carried around in the poclreV as it has no projecting parts. lt is no more trouble than an ordinary two-foot rule.

Although T have illustrated and described only a few forms of the invention T am aware of the fact that other modifications can be made therein by any person skilled in the art without departing from the scope of the invention as expressed in the claims. Therefore l do not wish to be limited to any of the forms shown, but what l do claim is- 1. As an article of manufacture, a measuring device comprising a beam having an angle scale thereon, and an arm having a straight edge pivoted at the center of said scale, the beam having a straight edge and a plurality of scales thereon having identically marked divisions indicating the pitches of hip roofs, and showing the positions at which the arm should be set to give, between it and said straight edge on the beam, the angles of the several cuts for the rafters of the hip roof.

2. As an article of manufacture, a plate having a semi-circular pretractor scale, an arm pivoted at the center of said scale and having at each end a scale perpendicular to a diameter of the protractor scale and divided into equal divisions each indicating a rise of an inch per foot, and a third scale connecting the other two and so located that the three inclose the protractor scale, and also indicating rises in inches per foot, said third scale constituting a continuation of the end sca-les.

3. An article of the class described, having a circular angle scale thereon and a straight edge in alinement with its center provided with a scale extending from said center, and an arm having a straight edge pivoted so that the latter straight edge is in alinement with said center, said arm having a projection beyond the center also provided with an edge in alinement with the straight edge of the arm, said angle scale being provided with an inner circle divided up into divisions equal in angular length to the divisions on the outer circle and connected with them by lines, the projection from said arm having an edge thereon equal to the distance between said circles radially and having equal divisions thereon, the last named edge and the lines between said circles being located at an angle to each other in all positions of the arm, whereby said arm always intersects one or more of said lines, and whereby the point of intersection indicates the fraction of the angular distance of the arm from the adjacent division on the outer circle.

4. An article of the class described provided with a pivot, a scale arranged about said pivot as a center and having an outer curve and an inner curve, the outer curve being divided into equal divisions representing multiples of one degree, and the inner curve being divided into divisions each representing the same number of degrees as the ones on the outer curve, straight radial lines connecting the divisions on the inner curve with the adjacent divisions on the outer curve, and an arm pivoted to the main member at said center and having a non-radial edge provided with a scale thereon equal to the distance between said two curves and divided into a number of equal divisions whereby it can be read on said connecting lines to indicate jactions of the divisions on the outer curve. 4

5. An article of the class described, comprising a main member or beam and two arms pivoted thereto on the same axis, said member having a protractor on one side, and one of said arms having anextension beyond the pivot adapted to pass over said lprotractor as the arm swings to indicate the angle that arm makes with respect to the base of the protractor, said beam having a straight edge in line withsaid base, the other arm also being set by bringing it into registration with the arm having the extension.

6. Anarticle of the class described, comprising a main member or beam and two arms pivoted thereto on the same axis but on opposite sides, said member having a protractor on one side, and the arm on that side having an `extension beyond the pivot adapted to pass over said protractor as the arm swings, whereby an angle can be bisected conveniently by setting the front arm twice, iirst to the angle itself, and second to half the angle and at `the time of the irst setting bringing the rear arm into registration with it and keeping it there.

7. An article of the class described, hav ing a main member and an arm pivoted thereto,.each having a straight edge, anda member having a groove in one edge adapted to -iit on one straight edge, ;the opposite edge of said member being parallel with the groove, whereby said `member is adapted to make a complete sharp angle with'the other straight edge. a

In testimony whereof I have lhereunto affixed my signature. Y

PERRY .OLMSTED Copies of this patent may be obtained for five cents each, by addressing thevommissoner Vof Patents.

Washington, D. C.

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