US2477724A - Protractor - Google Patents

Description

A. R. cREAxN PROTRACTOR 2 SheetS-Sheet l Filed July` 19' 1947 H amm Patented Aug. 2, 1949 UNITED STATES `PATENT OFFICE PROTRACTOR Alfred R. Creain, Covingtomlly. Application July' 19, 1947,' Serial No. 762,157

8 Claims. (Cl. 33-91) The present invention relates 4to a -protractor for use 4in connection Vwith a lstraight edge by draftsman and the like.

An object of the invention is to provide a protractor device affording accurate layout of angles from a straight edge.

Another object of vthe invention is to provide a device .of this character lthat is capable of rapid adjustment to simultaneously attain selected equal angles on either side of a vertical center line.

Still another object ofthe invention is to provide a protractor enabling the layout of lines that are at right angles to each other and on opposite sides'of a vertical center line.

A further object of the invention is to provide for the simultaneous layout of'selected equal angles from the vertical and the horizontal so that the complements of said angles are likewise available.

A still further object ofthe invention is to provide a device vaffording a layout of lines closer to a straight edge thanv that afforded by other available instruments of similar nature.

It is a special object of the invention to provide an instrument which is easily set to attain accurate angle measurements together with the op'- posite and the complement thereof without necessity of mathematical calculation and a new adjustment based on such mathematical calculation.

These and other objects are attained by the means described herein and disclosed in the accompanying drawings, in which:

Fig. 1 is a fragmental top p lanV view'of aprotractor of the invention.

Fig. 2 is a bottom end elevational view of the device .of Fig. l.

Fig. 3 is a cross-sectional view taken on line 3-3 of Fig. 2, and showing in'full and dotted lines the limits of adjustment of the straight edges.

Fig. 4 is a cross-sectional View taken on line 4 4 of Fig. 1.

Fig. 5 is a cross-sectional view taken on li'ne 5-5 of Fig. 1.

Fig. 6 is a crosssec.tiona1 view-taken on line E-6 of Fig. 1.

Fig. '7 is a cross-sectional view taken'on line l--l of Fig. 1.

Fig. 8 is a cross-sectional View taken von line 8--8 of Fig. 1.

The protractor of the' invention comprises'a relatively flat hollow housing 'I'I'I havinga straight edge II adapted to rest against the 'straight edge (not shown) which is used with the drawing board. Within the hollow housing I0 are contained co-operating elements (hereafter described) whereby associated straight edges I2, I3, Ill, and I5 are simultaneously moved toward univform angles of adjustment about two pivot studs 'I6 and Il which are suitably journaled in the upper and lower parts ofthe housing I0.

Referring now to Figs. 1, 3 and 8 it Vwill be seen that stud I6 has an intermediate shoulder or angular flange I8 below which is a gear segment I9 journaled on the stud between the bottom of housing I il and flange I8. Segment I9 has an integral arm 2) t0 which straight edge I3 is secured in suitable fashion as lby screws 2|. It will be noted further that another gear segment 22 is mounted for rotation on the stud Iii between the top of ange I3 and the upper half vof housing ID. Segment 22 has an integral arm 23, to the bottom of which the straight edge I2 is secured by means of screws such as 2 I. The gear segments VI9 and 22 are recessed on adjacent faces and coiled spring 24 is disposed in the space between the segments and surrounding ilange I8. As can be best seen in Figs. 3 and 4 spring 24 has its respective opposite ends turned upwardly and downwardly from the plane of the coil and anchored to the segments I 9 and 22 respectively by entering the ends 26 and 2l into perforations in said segments. In a generally similar arrangement stud I1 has an integral shoulder 28 and serves as a pivotal support for an upper gear segment 29 and a lower gear segment 30 the respective segments having arms 3l and 32 to which the straight edges I4 and I5 respectively are secured. A pinion 33 is journaled on a stud 34and meshes with the upper gear segments 29 and 22 so that arms 23 and 3l carrying straight edges I2 and I4 are moved simultaneously and in the same direction whenever movement is imparted to either of them. It will be noted that the straight edges I2 and I4 are at right angles to each other.

In a similar fashion the lower gear segments I9 and 30 are arranged to mesh with a pinion .35 which is journaled on a stud 36 having an upwardly projecting integral screw stud 3l. These Vlower gear segments I9 and 30 carryarms 29 and 32 respectively to which straight edges I3 Vand l5 are attached. Thus the movement otarm I3 or I5 will impart to the remaining arm a like motion and in the same direction. It should be now observed that pinion 35 also meshes with pinion 33; which latter pinion meshes with the segment carrying the arms to which straight edges I2 and VIII are attached.` Hence the movement .of straight edge I5, for example, from the full line position in Fig. 3 to the dotted line position thereof will impart a precisely corresponding movement of straight edge I3 from its full line position to its dotted line position. This much .of the movement is aiorded through segment 3U, pinion 35, and segment I9. This movement of pinion 35 will ailord a corresponding movement of pinion 33 in the opposite direction so that straight edges I2 and I4 will be simultaneously moved from the full line position to the dotted line position.

The initial disposition of arms 20 and 32 at right angles to each other and arms 23 and 3| at right angles to each other is maintained by the action of the springs 24 in their respective sets of superposed segments. The springs are at all times in opposition to any play in the teeth of the pinions and segments.

A generally quadrant shaped sheet metal plate 38 has a flatwise sliding movement on the top of housing I and it is fixed with the stud 34 so as to move therewith as the arms carrying the straight edges are moved. The mounting may be effected by means of a washer 39 which is slightly sunken in a suitable annular recess in the top of plate 38, said washer and plate being secured to the top of stud 34 by means of a screw 4U which is threadedly entered into a tapped hole in said stud. A pin 4I is passed eccentrically through the washer and plate and into said stud before the screw 40 is attached.

Plate 38 has an arcuate slot 42 formed on a radius having stud 34 as a center and located so as to enable the screw stud 31 on the top of stud 36 to extend through the slot and permit movement of the plate 38. A threaded cap or nut 43 on screw 31 may be tightened to bind the plate 33 against movement over the top of the housing I0 and it thus serves to hold the straight edge scales I2, I3, I4 and I5 in adjusted positions when desired.

The edge of plate 33 is grooved and it rides on a concentric tongue or rib 44 of an index plate 45.

The matching edges of the relatively moveable plates 38 and 45 are provided with graduated scales for the purpose of enabling rapid and accurate adjustments of the'straight edges to select'ed angles. A 90 arc on the edge of plate 38 is divided to provide indexing marks representative of forty-five degrees of adjustment and at both ends a few additional like graduations are provided. The graduations are marked with a double set of iigures which indicate respectively 0 to 45 and 45 to 90. Y'I'he fixed plate 45 has a zero index line at its center and is graduated on opposite sides thereof with subdivisions Yrepresenting minutes for plus or minus reading and adjustment. The effect/of the moveable angle scale and the fixed minutes scale is substantially that of a Vernier adjustment.Y v Y It will be understood that the specicstructuralY details of the device as illustrated may be subject to modication within the spirit of-the invention and the scope of the appended claims.

Ihe operation of the device will be readily apparent to those Vconversant with the graphic mechanical arts. It will be noted that the springs E4 operate to resist play in the meshingy engagement of the several segments and pinions and hence accurate adjustments4 of the straight edges to selected angles mayY be reliedupon. In use Vthe straight bottom Vedge'll lofthe housing would be. placedv against the straightedge onthe draw- 2 associated straight edges.

ing board. The ends of the straight edges I2, I3, I4 and I5 adjacent housing Ill will be noted to be at all times closer to the straight edge on the drawing board than is possible with the selectively adjustable devices of this general character now available. When an adjustment to a given angle is to be made with one side of one of the straight edges, the cap or nut 43 is loosened and the selected adjustable straight edge e. g. I5 is merely moved to the desired angle. In moving one straight edge I5 a given number of degrees away from the horizontal, the corresponding straight edge I2 moves a like number of degrees from the horizontal on the opposite side of the vertical center line. At the same time straight edges I3 and I4 move away from the vertical center line in opposite directions so that they assume angles which are the complement to that to which the associated straight edge was set. Furthermore straight edges I2 and I4 will also remain at right angles to each other throughout the full range of adjustment and straight edges I3 and I5 which are right angles als-o will remain at right angles to each other. The Vernier adjustment enables the user to avoid error of adjustment according to an incorrect mathematical calculation as Well as the mechanical error ofadjustment to a mathematical calculation Vwhich sometimes occurs, particularly where it is desired to lay out an angle in degrees and minutes at one place and to also lay out the complement of said angle, possibly as an opposite complement. For example, if the straight edge I3 is to be set at 70 20 it would be moved until the character lll on the plate 38 yregisters with the 0 on plate 45 then it vWould be shifted further until the 20 mark matches with the next succeeding mark on plate 38.Y The cap 43 may then be tightened to bind the parts against movement, whereupon it would be found that the straight edge I4 has been moved to an opposite angle of 70 20f and the straight edges I2 and I5 Will have assumed opposite angles of 19 40', which are the complement to the settings of the The layout of beveled gear'trainsv in machine drawings will be appreciated as a simple example of the Yeiectiveness of the protractor of the present invention both asto accuracy and as to time saving.

What is claimed ls: Y

1. In a protractor the combination of a at hollow housing, a pairof pivot studs in the housing in spaced parallel relation, a pair ofsuperposed gear segments on each stud, a pair of straight. edgemembers disposed at .right angles to each other and mounted respectively for movement with the lower gear segments, a pinion intermediate and meshing with said lower gear segments, a second pair of straight edge .members disposed .atrightangles to each other and mounted respectively for movement withltheupper gear segments, and a second pinion intermediateY and. meshing with the uppergearsegments and also meshing with the first. mentioned pinion. -V Y. -f Y 2. In a protractor the combination ofa flat yhollow housing, a pair of pivot studs 'in the. houstermediate and meshing-with said lower l gear .segmentaasecondpair ofstraight edge members 'disposedat right .angles ,toeach other and,

mounted respectively for movement with the upper gear segments, and a second pinion intermediate and meshing with the upper gear segments and also meshing with the first mentioned pinion, one straight edge of each of said pairs of straight edges being disposed at all times intermediate the straight edges of the other pair.

3. In a protractor the combination of a flat hollow housing, a pair of pivot studs in the housing in spaced parallel relation, a pair of superposed gear segments on each stud, a pair of straight edge members disposed at right angles to each other and mounted respectively for movement with the lower gear segments, a pinion intermediate and meshing with said lower gear segments, a second pair of straight edge members disposed at right angles to each other and mounted respectively for movement with the upper gear segments, a second pinion intermediate and meshing with the upper gear segments and also meshing with the iirst mentioned pinion, and externally disposed means for securing one of said pinions against movement for retaining all of the segments and the associated straight edges in adjusted positions.

4. In a protractor the combination of a flathollow housing, a pair of pivot studs in the housing in spaced parallel relation, a pair of superposed gear segments on each stud, a pair of straight edge members disposed at right angles to each other and mounted respectively for movement with the lower gear segments, a pinion intermediate and meshing with said lower gear segments, a second pair of straight edge members disposed at right angles to each other and mounted respectively for movement with the upper gear segments, a second pinion intermediate and meshing with the upper gear segments and also meshing with the first mentioned pinion. a quadrant shaped plate fixed for movement with one of said pinions and slidable over the exterior of the housing, said plate having graduations denoting degrees of angular adjustment of the Segn ments and associated straight edges; and a xed plate on the housing having at least one indexing line.

5. In a protractor the combination with a pair of spaced apart parallel studs, of a lower gear segment on each stud, an upper gear segment on each stud, a pair of pinions meshing with each other, one of said pinions meshing with the lower segments, the other of said pinions meshing with the upper segments, straight edges iixed to the respective lower segments and disposed at right angles to each other, straight edges xed to the respective upper segments and disposed at right angles to each other, and spring members yieldably urging the companion upper and lower segments in opposite directions.

6. A protractor comprising a pair of parallel studs, straight edge members having toothed segmental ends mounted for movement about said studs as centers, said members disposed at right angles to each other, a pinion meshing at opposite sides with the respective toothed segmental ends, and means yieldably urging the segments into toothed driving engagement with the pinion in one common direction, and yieldably resisting toothed driving engagement thereof with the pinion in the opposite direction.

'7. A protractor comprising a housing having a straight bottom edge and provided with slots extending longitudinally through the remaining edges, two spaced apart pairs of sup-erposed concentric gear segments rotatably mounted within said housing and each having a tangential arm extending through an edge slot in the casing, and a pair of mutually meshing pinions rotatably mounted intermediate said spaced pairs of gear segments and meshing respectively with the upper gear segments and the lower gear segments respectively of said spaced pairs of gear segments, the arms of the lower gear segments being disposed at ninety degrees to each other and the arms of the upper gear segments being disposed at ninety degrees to each other, the said pinions retaining said ninety degree angularity of said arms during rotary movement of the meshing pinions and segments, and serving to simultaneously move the arms of the lower gear segments in one direction and the arms of the upper gear segments in the opposite direction.

8. A protractor comprising a housing having a straight bottom edge and provided with slots extending longitudinally through the remaining edges, two spaced apart pairs of superposed concentric gear segments rotatably mounted Within said housing and each having a tangential arm extending through an edge slot in the casing, a pair of mutually meshing pinions rotatably mounted intermediate said spaced pairs of gear segments and meshing respectively with the upper gear segments and the lower gear segments respectively of said spaced pairs of gear segments, the arms of the lower gear segments being disposed at ninety degrees to each other and the arms of the upper gear segments being disposed at ninety degrees to each other, the said pinions retaining said ninety degree angularity of said arms during rotary movement of the meshing pinions and segments, and serving to simultaneously move the arms of the lower gear segments in one direction and the arms of the upper gear segments in the opposite direction, and spring means urging each pair of superposed gear segments in opposite directions and into toothed driving Aengagement with the pinion meshing therewith.

ALFRED R. CREAIN.

REFERENCES CITED UNI IE D STATES PATENTS Name Date Wall et al Feb. 13, 1917 Number

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