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July 19, 1938. _ 1__ v_ CANTRELL 2,124,051 DRAFTSMAN ’ S RULE Filed Feb. 24, 1937 IN VEN TORr Lorraine l/ Cantrell BY ~ _ ‘ q’, 427% ATTORNEY 2,124,051 Patented July 19, 1938 UNITED STATES PATENT OFFI€E 2,124,051 DRAFTSMAN’S RULE Lorraine V. Cantrell, Berkeley, Calif. Application February 24, 1937, Serial No. 127,449 2 Claims. My invention relates to draftsmen’s rules, and more particularly to an architect’s and engineer’s rule which may be read in interchangeable units and fractions of units. Among the objects of my invention are: To provide a rule having interchangeable unit mark ings and interchangeable vernier movements; to provide a self-reading rule for architects and engineers wherein the vernier movements may be read upon an enlarged scale; to provide a rule in units and fractions of units which may be easily read with great accuracy; and to provide a rule having removable and interchangeable combina tions of units and fractions thereof which is 15 adaptable for use where units of different char acter are involved. Other objects of my invention will be apparent or will be speci?cally pointed out in the descrip tion forming a part of this speci?cation, but I do 20 not limit myself to the embodiment of the inven (Cl. 33-—107) end of the scale, and drives through worm gear I4 a longitudinal threaded rod I5. The end of the rod I5 is ?rmly attached to a spline block I6 mounted in a bearing II. The spline block is provided with a diametrical slot I9 into which is in U! serted a vernier screw block 20, the head of which fits the spline block recess in such a manner that the vernier block will rotate with the screw block I6 and will also be prevented from coming out of the block. Vernier screw block 20 has an axial 10 threaded bore therein into which is ?tted a vernier screw 2| terminating in a square ?anged head 22, dropping into a square slot in a vernier positioning block 24 which is ?rmly attached to 15 the vernier extension III. Thus it will be seen that when the thumb screw I2 is rotated the vernier extension will be moved outwardly or inwardly in accordance with the pitch of the screw 2|. Inasmuch as the pitch of the screw ZI must necessarily be different for 20 tion herein described, as various forms may be di?erent scales, I have provided on the upper side of the scale frame I a hinged window 26, which adopted within the scope of the claims. In the drawing illustrating a preferred embodi- ~ may be opened, and when the vernier screw block and screw are in their maximum engagement the ment of my invention, Figure 1 is a top view of entire assembly of vernier block and screw may one form of my invention. Figure 2 is a sectional view taken by the line be removed from the scale by sliding the assem bly upward out of the respective engagements 2-2 in Figure 1. Figure 3 is a sectional View taken as indicated ‘ with the terminal block, and a new block and screw inserted. The cover when closed prevents by the line 3—3 in Figure 1. Figure 4 is a sectional view taken as indicated the vernier screw and block from moving out of 30 30 by the line 4—4 in Figure 1; and Figure 5 is an enlarged view of a removable vernier movement. My invention may be more fully understood by 35 direct reference to- the preferred embodiment shown herein. A rule frame I is provided with a unit scale 2 graduated in one particular type of units, as for example, in feet, as the illustrations herein show 40 a foot scale. The foot scale 2 ?ts over the bot tom of the frame I and is held thereto by an in turned front edge 3 and an inturned back edge II. The scale, therefore, may he slid onto the frame from one end, and is pushed on until the zero end 45 abuts a scale stop 5. Once in that position it is locked to the frame by a locking screw 6. The engagement with their terminal blocks. At the same time, the vernier block 20 can be seen through the transparent cover 26, and I may pre fer to- mark upon the vernier screw block 20 the ratio of vernier extension with respect to the 35 units used. The indication of the amount of extension of the vernier portion of the scale is given by an enlarged vernier scale 21 positioned under ver nier scale window 28, and the indication of the position of the vernier extension III with respect to this scale is given by an indicator block 29, traveling on screw thread I5 and carrying an in dex pointer 30 projecting over the scale 21. Inas 50 an end stop II in the same line as that projected much, however, as several different vernier scales 45 are to be used, as determined by the vernier block, I prefer to mark the enlarged vernier scale 2‘! on the periphery of a rotatable cylinder 3| rotated by a scale wheel 32 projecting through the frame. I have found that at least three, and from the main scale 2, the entire edge of this stop thus providing a convenient locating point for initiating the measurement. The vernier extension I0 is operated by a 55 thumb screw I2, preferably located at the right riphery of this cylinder. In operation, the proper unit scale desired is slipped onto the frame and ?xed. The scale Wheel 32 is then rotated until the proper frac 55 scale is preferably provided at each unit mark with marking recesses ‘I. Telescoping into the frame I is a vernier extension II) having thereon possibly more, scales can be inscribed on the pe 2 2,124,051 tions appear beneath the vernier scale window. For example, I have shown feet on the scale 2, and therefore a 12-inch scale‘ on the vernier cyl inder. thereon and abutting a stop on said frame, a vernier extension telescoping into one end of said frame and having an index point thereon Under these circumstances, then, the lining up with said scale, an enlarged scale proper vernier block and screw 20 and 2| are inserted to move the vernier so that the index pointer 30 will move the full scale range, while the vernier extension I 0 is moving the distance representing one foot as determined by scale 2. 10 If, however, the measurements are to be taken in some other units and the vernier read in tenths, then the thumb screw 32 may be rotated to bring an enlarged tenths scale under the vernier win mounted on said frame, a rotatable screw hav ing a pointer actuated by rotation of said screw dow 28, the corresponding vernier block and 15 screw inserted, and, if desired, a new main unit scale 2 substituted for the one shown. .Under these circumstances it can be seen that this scale may be equipped With accessory vernier screws and main scales together with a proper enlarged 20 scale that will give measurements of practically all the units and fractions of units utilized in draftsmanship. Furthermore, the scale can be adapted to any reduction ratios desired. The use of the rule has been found to increase the speed of scaling for architects and engineers, it produces greater accuracy, and makes the work of scaling much easier for the operator. I claim: ' and moving along said enlarged scale, and means for extending said vernier extension by rotation of said screw by an amount reduced in distance but in proportion to the divisions of said enlarged 10 scale. 2. A draftsman’s rule comprising a frame, a removable and interchangeable scale mounted thereon and abutting a stop on said frame, a vernier extension telescoping into one end of said frame andhaving an index point thereon lining up» with said scale, an enlarged scale mounted on said frame and calibrated in fractions of the units of said removable scale, a rotatable screw having a pointer actuated by rotation of 20 said screw and moving along said-enlarged scale, a reduction screw and thread linking said ro tatable screw and said extension whereby said extension will be moved by rotation of said screw by an amount reduced in distance but propor tional to the calibrations of said enlarged scale and in fractions of the units of said removable scale. 1. A draftsman’s rule comprising a frame, a 30 removable and interchangeable scale mounted LORRAINE V. CANTRELL.