US2164218A - Drafting machine - Google Patents

Description

June 27, 1939.

c. H.'4 LITTLE DRAFTING MACHINE 'Filed Feb. 15, 1956 4 Sheets-Sheet l AJune 27, 1939.

C. H. LITTLE DRFTING MACHINE Filed Feb. 15, 1936 4 sheets-sheet 2 INVENTOR. @b4/w55# fw-72 m M@ am ATTORNEYS June 27, 1939. c. H. LITTLE DRAFTING MACHINE Filed Feb, 15, 195e 4 Sheets-Sheet 4 @limi-V 7 fas v4 INVENTOR. 7M/nfs Uvasm JM @am ATTORNEYS Patented June 27, 1939 DRAFTING MACHINE Charles H. Little, cleveland Heights, ohio, as-

signor of one-tenth to Charles Hubbard Little, ACleveland Heights, Ohio Application February 15, 1936, Serial No. 64,141

7 Claims.

The present invention relates to drafting machines, and more particularly to drafting machines having a parallel motion arm or mechanism of the wheel and band type, wherein the parallel motion mechanism consists of a plurality of parallelograms comprising wheels operatively connected by flexible bands.

An object of the present invention is the provision of a drafting machine of the wheel and band type having struts of novel construction which will not bend sidewise under the stresses to which they are subject in operation, and form covers for the top and outside of the bands but are open at the bottom thereby being free of any tendency to collect and retain dirt, and facilitating assembly and adjustment of the band,

etc.

Another object of the invention is the provision of a novel drafting machine of the wheel and band type wherein the struts are so constructed that they will not bend sidewise under the stresses to which they are subject in operation, and are initially stressed by the bands, especially the strut of the anchor parallelogram, in such a manner as to reduce the sag of the arm, particularly at the elbow.

Another object of the invention `is the provision of a novel drafting machine of the wheel and band type having a strut comprising end sections to which the wheels are operatively connected and side rods covering the bands, in combination with a band including a turnbuokle link for adjusting the length thereof, and an operative connection between the bands and the side rods for preventing rotation of the band when the turnbuckle link is turned.

Another object of the invention is the provision of a novel band for a drafting machine of the wheel and band type comprising a plurality of members encircling the Wheels provided with means for adjusting the length of the band and equalizing the tension between the members.

Another object of the invention is the provision of a novel anchor-for attaching a drafting machine to a drawing board or table, which can be applied to boards of different thickness, and can be readily adjusted along the upper edge of the board from the draftsrnans position at the front thereof.

Another object of the invention is the provision of a novel protractor assembly comprising a holding plate, a ruler assembly rotatably supported by said holding plate, and a protractor ring carried by said holding plate and adapted to be rotatably adjusted relative thereto, whereby the zero mark on the protractor may be set at any desired angle and the subsequent readings determined therefrom.

The present invention resides in certain novel details of construction, and combinations and arrangements of parts,'and further objects and advantages thereof will be apparent from the following description of the preferred embodiment thereof described with reference to the accompanying drawings forming a part of this specication, in which similar reference characters designate corresponding parts throughout the several views and in which:

Fig. 1 is a plan of a drafting machine embodying the present invention;

Fig. 2 is an enlarged plan of the anchor end of the drafting machine shown in Fig. 1;

Fig. 3 is a section on the line 3 3 of Fig. 2, with portions in elevation.

Fig. 4 is a section on the line 4-4 of Fig. 2.

Fig. 5 is a section on the line 5-5 of Fig. 2.

Fig. 6 isr an enlarged plan of a portion of the anchor parallelogram with parts broken away to show the construction of the band.

Fig. 7 is a side elevation, with parts broken away, of the mechanism shown in Fig. 6, looking from the right.

Fig. 8 is a section on the line 8--8 of Fig. 6.

Fig. 9 is an enlarged plan of the elbow portion of the parallel motion arm of the ldrafting machine shown in Fig. 1.

Fig. 10 is a section on the line Ill-I0 of Fig. 9, with portions in elevation.

Fig. 11 is a bottom View of one of the struts shown in Fig. 1.

Fig. 12 is an enlarged plan of the protractor end of the drafting machine shown in Fig. 1.

Fig. 13 is a section on the line |3-l3 of Fig. 12.

Fig. 14 is a section on the line l4-I4 of Fig. 12,

and

Fig. 15 is a View similar to Fig. 11 showing a strut of modified construction.

While the drafting machine herein illustrated and described is the preferred embodiment of the present invention, it is only illustrative of the invention which, it is to be understood, can be otherwise embodied, and I do not wish to be limited to the particular construction shown.

Briey stated, the drafting machine shown comprises a parallel motion mechanism or arm provided at one end with an anchor for attachment to a drawing board or the like, and at the other end with a protractor assembly including rulers, etc. The parallel motion mechanism or arm consists of two parallelograms comprising llexible bands, designated generally by the reference characters A and B, encircling grooved wheels I0 and II, and I2 and I3, respectively, of equal diameter and held apart or in spaced relation by frame members or struts C and D. The flexible bands A and B are alike in construction and, as shown, each comprises a flat ilexible steel band I6 encircled by a flexible cable band I'I which makes two loops about the Wheels. The respective ends of the ilat steel band I6 and the cable band I1 are connected together through the medium of a single take-up or turnbuckle link for adjusting the length of theband, and equalizers for distributing the tension .equally therebetween.

The construction of the take-ups and equalizers is clearly shown in Figs. 6 and 7. Both ends of the flat steel band are reenforced by -members I 8 secured thereto in any suitable manner, and the ends of the cable band I1 are provided with terminal members 20. The ends of the flat steel band I6and the cable band I I adjacent each other are connected to opposite ends of equalizer cables 2l and 22 through the medium of members 23-and 24 detachably connected to providefor replacement, etc., to the members I8 and 20, respectively as by screws 25. The equalizer cables 2| and 22 pass over small sheaves 26 rotatably supported on pins 28 secured in the forked ends of members 29 provided with tapped apertures into which opposite ends of the turnbuckle link 30 provided with right and left hand threads are threaded. A hexagonal portion intermediate the threaded ends of the turnbuckle link 3|] Yprovides means for rotating the same, and rectangularl members 3l fixed to the-members 29 and engaging -within the channel of the side members or rods of the struts prevent rotation of the cable when the turnbuckle link '30 is rotated. Themembers 3| are cut out l at 32 as clearly shown in Fig. 9-in such a manner that they will not interfere with the free lmovement of the upper loop ofthe'cable I1. While-in the preferred embodiment illustrated 4two equalizers are employed in each band, one-ateither-end of the take-unit Ywill be understood that-in some instances one equalizer in each cable-will be suflicient. This is especially true when a cabley making onlyone loopv about the Wheelsis employed rather than twofloops, Vas illustrated. `From the foregoing, it will be apparent that the length-of the bands A and B can be adjusted by-rotating the turnbuckle link 30 therein and that the tension` in the'various parts of each band is Vat lall times equalized.

The upper wheel I0 of the anchor parallelogram, which in' some respect forms a part of the anchor mechanism, maybe formed `either integral with the anchor proper, as illustrated, or separate and secured thereto, as desired. The wheel I I at the elbow ofthe arm is held in spaced relation to the wheel I l)` by the one-piece strut C preferably stamped from a single piece of sheet metal. The strut preferably has the center thereof cut away to reduce the weight'of the same but may be continuous, as shown in Fig. l5. The preferred construction of strut is clearly shownin-Fig. 11 and consists of two disk-like end-sections 35 and'36 provided withcentral apertures defined by cylindrical flanges 31 and-38, respectively, the former of Iwhich has an inturned flange 34 formed thereabout. The disk-like end sections 35 and 36 'are connected by channel side rods or members 35|and- 4I)` of inverted U-shaped crosssectionl formed integral therewith. The inside flanges 4I and 42 of the side rods 39 and 40 continue around the inside of the disk-like end sections 35 and 36,- forming thereon flanges 43 and 44, respectively, and the outside ilanges 45 and 46 of the side rods continue around the ends of the strut forming outside flanges 41 and 48 on the end sections 35 and 35, respectively. As shown the outside flanges 45 and 45 have a plurality of lugs 49 formed integral therewith which help to retain the band within the channel of the side rods and prevents it from flying about and possibly injuring the draftsman in the event it --should break. The strut may be varied in .construction from that shown, as will be apparent to those skilled in the art, and the side rods 39 and 40 where employed may be of any desired shape.

The upper end of the strut C is pivotally connected concentric with the wheel IU toa cylindrical projection or member 52 formed integral with the wheel, through the medium of an anti-friction bearing comprising balls 53 retained between `inside and outside races 54 and 55. The inside race is secured on the member 52 in any suitable manner, as by a plate 56 secured to the member 52 by a screw, and the outside race is fixed within the flange 31 in a similar manner by a disk-like member 5l', secured to the end section/35 by screws 58 threaded into a ring member 59 located underneath the strut. The member5'I covers the bearing and in addition to excludingdirt, presents a finished appearance. The wheel I I is rotatably supported in the lower disklike end section 36 of the strut C through the medium-of an anti-friction bearing comprising balls v6I) retained between inside and outside races 6I and 62. The inside race 5I is fixed, as by a forced fit, on a cylindrical hub or projection 63 formed integral with the wheel I I, and the outside races 52 is secured in a like manner within the lflange 38. The bearing is provided with a cover plate B4 secured to the upper end of the hub 63 by a screw 65.

v"lhestrut C of the anchor parallelogram may be strengthened as desired. In the event that the entire Weight of the arm and protractor assembly is carried from the anchor, as is often the case since' this facilitates movement of the protractor: assemblyabout the drawings, it is espeoially'd-esirable to strengthen the anchor strut. In'the embodiment illustrated, the upper ends of the-Iside rods'39 and 40 are provided with short outwardly extending flanges 68 and 69 formed integral ywith the lower edge of the outside flanges 45 and 46 thereof, and with short inwardly extending flanges "I0 andII formed integral '-with the lower edge of the inside flanges 4I -and 42. The flanges 'IU and v'II continue around the-flange forming thereon a flange l2.

The present invention also contemplates the velimination ofthe sag at the elbow of the arm, or at least areduction thereof, by placing the anchor strut under stress in the reverse direction 4by'raising one or both of the bearingsl above the centerline ofthe band. As illustrated only the .bearing at the anchor is raised, and the upper side of the strut is placed under compression and the lower side thereof .under tension. The amount of stress imparted thereto can be varied either Yby increasing the tension on the band or by increasingthe height of the bearing above the centerline lof lthe band. vThe proper height of the bearing :above the band can be readily deter- .minediineachinstance VInithe drawings the bearing israised .an amountl designated Vas X.

construction to the anchor strut C` and comprises two disk-like end sections 80v and 8| provided with central apertures defined'by cylindrical l flanges 82 and B3, respectively. TheV disk-like end Sections are connected by channel side rods 84 and 85 of inverted Ll-shaped `cross-section formed integral therewith.V The insidev iianges of the channel-shaped side rods 84 and `85 continue around the inside of the disk-like end sections '83 and 8|, forming thereon flanges 83and 89, re spectively, and the outside-flanges of the side rods continue around the vends of the strut forming outside flanges 92 and 93 on the end sections thereof, 80 and 8|-, respectively. Like the strut C, the strut D may be varied in construction from that shown, as will be apparent to those skilled in the art, and the rods 84 and 85 may be of any desired shape.

The wheel I2 of the protractor parallelogram has a cylindrical hub 94 formed integral therewith secured, as by a forced t in a cylindrical aperture formed in the underside of the wheel I I. The left-hand end of theestrut D isl pivotally connected concentric with the wheel I2 to the cylindrical hub 94 thereof through the medium of an anti-friction bearing comprising balls `95 retained between inside and outside races 95 and 91. The inside race 99 is secured on the hub 94 as by a force fit, and the outside race is retained within the flange 82 in a similar manner, v `The wheel I3 is provided with a tubular hub 99 formed integral therewith and through the medium of which it is rotatably supported in the right-hand disk-like end section 8| of the strut D by an anti-friction lbearing comprising balls |09 Vretained between inside and outside races I| and |02. The inside race IIlI isfsecured on the tubular hub 99 as by a force ffit, and the Aoutside race |02 is secured within the "flange 83 in a like manner.

The protractor assembly comprises a disk-like holding plate |09 provided with a hub I I0 xed to the hub 99 of the wheel I3 above the end section 8| of the strut in any convenient manner, as by being forced thereon. A protractor ring I I I provided with the usual graduations is rotatably supported on the upper face of the disk-like holding plate |09 and is adapted to be clamped in any adjusted position thereon by a pair of clamps comprising members I I2 positioned underneath thumb screws I I3 threaded into tapped apertures in projections II4 on the sides of the holding plate |09. The members I|2 project slightly ovei4V the upper surface of the protractor ring III and clamp the same therebetween and the holding plate |09 when the thumb screws ||3 are tightened.

The ruler arms I I and I I6 carry rulers I I'I and I I8, respectively, of conventional construction detachably secured thereto in any well known manner. They are formed in. one piece and are xed to the lower end of a stub shaft projecting upwardly through a cylindrical opening in the hub 99 of the wheel I3. A second disk-like member I2 I, formed in two pieces, as shown, or in a single piece, as desired, is fixed to the shaft |20 above the disk-like holding plate |09. The periphery of the member I2| engages in a groove formed in the protractor ring III, and is provided with a dead line mark |22 for setting the rulers. A hand grasp |23 secured to the disk-like member |2| facilitates manipulation of the instrument. A dead line mark |24 formed on a member |25 fixed to the periphery of the holding plate |09 and projecting over the protractor ring III facilitates thersetting of the protractor ring at'ariy desired angle. The rulers may be clamped in any angular position by a clamp comprising a winged nutV |28 threaded onto 'a headed screw |29 provided with two washer-like members|30 and |3I,V adapted to clamp the protractor ring |`II and the peripheryvof the disk-like member I2| therebetween. e

l The present invention also contemplates an anchor that can be adjusted along the upper edge of the board from the draftsmanfsy position at the front thereof. The advantages of this construction will be apparent to those familiar with the art to which the invention relates. Referring to Figs. 2 and 3, particularly, the anchor proper, consists of a channel-shaped bracket adapted to receive the upper edge of the drawing board |36 between the upper and lower flange thereof. The bracket |35 is clamped to the board |36 by two wedge-shaped clamps |31 and |38, the upper flat faces of which are adapted to engage the underside of the board. 'I'he lower inclined surfacesI or faces of the wedges engage an inclined surface on the upper side of a member |40, supported on two screws |44 and |45 threaded into the lower flange of the bracket |35 and rotatably secured to the under surface of the member |40. the screws |44 and |45provide vertical adjustment of the member |40, thereby readily adapting the anchor for use with boards of various thickness. The wedges |31 and |38 are reciprocated to clamp and unclamp the. board by screws I 4| and |42 respectively, threaded therein and rotatably and slidably supported, but fixed against longitudinal movement in the bracket |35.

When it is desired to shift the anchor along the upper edge of the board, the draftsman grasps the screws |4I and 142, one of which is preferably provided with left hand threads, without changing his position at the front of the board. After the screws have been loosened they can be used as handles for shifting the anchor to the desired position. In shifting the anchor along the upper edge of the board the draftsman naturally pulls the screws towards the front of the board and in so doing keeps the anchor in close contact with the upper edge of the board, at all times. When the member |40 has been adjusted, by the screws |44 and |45, for any given board it will usually be unnecessary to touch the same again until the drafting machine is moved to a board of different thickness.

The modified form of strut previously referred to, having a continuous upper surface except for the apertures within which the bearing'races are secured, is shown in Fig. l5. This strut consists of a metal stamping |50 having a continuous upper surface except for the apertures defined by the downwardly projecting flanges |5| and |52 adapted to receive the bearing races, and a flange |53 extending entirely around the periphery of the strut.

From the foregoing description of thel preferred embodiment of the invention, it will be apparent that the objects of the invention have been accomplished and that a novel drafting machine which can be readily adjusted along the upper edge of the board has been provided, in which the parallel motion mechanism or arm is light, strong, capable of being readily assembled and disassemlbled, and which gives a high degree of stability to the rulers. The bands are covered, which, in addition to presenting a nished appearance, protects the operator in the event they should break in operation.` 'Since thestrutsiopen downward-V ly, there is no tendency for dirt to collect therein;

While the preferred embodiment of the invention has been illustrated and described in some detail, I do not wish to be limited to the particular construction shown which may be varied within the scope of this invention. Nu-

merous changes in Vthe construction shown will member operatively connected to said wheels for maintaining the same in spaced relation, and anti-friction bearings interposed between -said wheels and said strut.

2. A drafting machine comprising a pair of wheels, a flexible band encircling said wheels, and

a strut operatively connected to said wheels for maintaining the same in spaced relation, said strut comprising a one-piece member including disk-like end sections overlying said wheels and connected by side members of inverted U-shape enclosing said band.

3. A drafting machine comprising a parallel motion arm, said parallel motion arm comprising a pair of wheels, a strut operatively connected to said wheels, a compound flexible band operatively connected to said wheels, said band comprising two separate members encircling said wheels and means for automatically equalizing the tension therebetween.

4. A drafting machine comprising a parallel motion arm, said parallel motion arm comprising a pair of wheels, a strut operatively connected to said wheels for maintaining the same in spaced relation, a flexible band operatively connected to said wheels, said flexible band comprising a at metal band and a cable band encircling said flat band, and means for automatically equalizing the tension between said flat band and said cable band.

5. A drafting machine comprising a pair of wheels, a flexible band encircling said wheels, and a strut operatively connected to said wheels by bearings adjacent the opposite ends of the strut for maintaining the wheels in spaced relation, the mid-plane of one of said bearings being above the mid-plane of the band.

6. A drafting machine comprising a jointed arm, a protractor assembly connected to one end of said arm, an anchor for connecting the other end of said arm to a drafting table, said anchor comprising a bracket, means for detachably clamping said bracket to the upper or rear edge of a drafting board, said means comprising a screw rotatably supported against longitudinal movement in said bracket with the head thereof projecting to the rear and the shank adapted to project underneath the board, and a wedge-like member having threaded engagement with the shank of said screw.

7, An anchor for a drafting machine comprising a bracket, means for detachably clamping said bracket to the upper or rear edge of a drafting board, said means comprising a screw rotatably supported against longitudinal movement in said bracket but movable vertically in said bracket with the head thereof projecting to the rear and the shank adapted to project underneath the board, means for preventing longitudinal movement of said screw, a tapered gib having threaded engagement with the shank of said screw, a backing member for said gib, and means for adjusting said backing member to raise or lower said gib.

CHARLES H. LITTLE.

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