US2164216A - Drafting machine - Google Patents

Description

June 27, 1939. c. H. LITTLE DRAFIING MACHINE Original Filed Feb. 15, 1936 6 Sheets-Sheet l IN VENTOR.

CHAFLES f7. [/7715 ATTORNEYS June'27, 1939. c H, n- 2,164,216

DRAFTING MACHINE Original Filed Feb. 15, 1936 6 Sheets-Sheet 2 zrlllf INVENTQR. v

fie 4 BY Q7/4045: h/A/Tngg ATTORNEYS C, H. LITTLE DRAFT] NG MACHINE Original Filed Feb. 15, 1936 6 Sheets-Sheet 4 Ma l I\ 7.5422 I JNVENTOR.

June 27, 1939, r; H, y

,DRAFTING MACHINE e Sheets-Sheei 5 Original Filed Feb. 15, 1936 INVENTOR. BY 67/4945: h! L/rnz:

ATTORNEYS.

June 27, 1939. c. H. LITTLE DRAFTING MACHINE 11: Claims. (cuss-4e) Patented June 27 I I V I UNITED STATE'S'PATENT OFFICE amen:

nun-mo moms namwennas I 0116- u a Cleveland lldhtt, Ohio Application February is, use, Serial No. 64,139 Renewed May 12, 1939,

The present invention relates to draiting mathe operating center to center distances of the chines, and more particularly to drafting mawheels for the purpose of tightening the band,

* chines having the parallel motion arm or mechaetc., which, will be light in weight, rigid in connism of the wheel and band type, wherein the struction, and inexpensive tomanufacture. and

parallel motion mechanism consists of a plurality wherein the struts of the respective parallograms 5 v of parallelograms comprising wheels operatively are for the most part one-piece membersfprefconnected by flexible bands. erably made of sheet metal or the like.

'An object of the present invention is thepro- Another object of the invention is the provision of-a noveldrafting machine of the wheel vision of a novel anchor for attaching a draftand band typehaving struts which will not bend ing machine to a drawing board or table, which 10 sidewise under the stresses to which they are canbe applied to boards of diflerent thiclmess. subject in operation, and form covers for the top readily adjusted. along the upper edge of the board and outside of the bands but are open at the from the draftsmans position at the front therebottorn, thereby being free of any tendency to of, and is not dependent upon the rear edge of i5 collect and retain dirt, and facilitating assembly the board for alignment as it is moved tberealong. and adjustment of the band, etc. Another object of the invention is the "pro- Another object of the invention is the provision of a novel protractor assembly comprising r vision of a novel drafting machine 01' the wheel a holding plate, a' ruler assembly rotatably supand band type having struts comprising, end poi-ted coaxial with said'protractor ring, a prosections to which the wheels are operatively contractor ring fixed; to said ruler assembly, and a 5M nected and side rods open at the bottom but endead line mark carried by a member adjustable closing the top andoutside of the bands. The about the periphery of. said holding plate, whereside rods are preferably formed integral with the by the dead line mark may be set at any desired end sections and have outside flanges which are angle and the subsequent readings determined u continuous with outside flanges on the'end aectherefrom. tions thereby entirely surrounding the band onits 1 Another object of the invention is the pmoutside. V on of a novel protractor assembly comprising Another object of the invention is the provision a ruler assembly adapted t rotate 0 m havof a drafting machine of the wheel and band type ing means for quick settings of the rulers at the m provided with struts of novel construction whereusual angles in each of the four quadrants of the an in the operating center to center distances of the protractor.

ivheican'be IQWQM The present invention resides in certain novel Another object of the prB3eht TinVei'itl9n-i8-$h0detai1s of construction, combinations and ar- Y prov i n r a n v drafting m n f the wh ---rangemep ts of parts, and further objects and s and i type having improveil'wmmcflon advantages thereof will beapparent from the at the elbow of the arm. n following description of the preferred embodi- Another o t 1' h Present invention 18 the ment thereof, described with reference'to the acprovision of a novel drafting machine of the wheel companying drawings forming a part or thi and band t ne i a means Justin! specification, in which similar reference charac- 0 both the length of the bands and the center to designate col-responding parts throughout the 0 "center operatingdlstance the whegls' several views and in-which: l v Another object of the invention is the provision mg 1 is i of a drafting machine v of a novel drafting machine of the wheel and band i i 1 ng the present invention.

type having a strut comprising an end section hi 1 th wheel is adjust! com F18. 2 is an enlarged plan of the anchor end of 5 to w s y i the drafting machine shown in Fig. 1.. t v. nected, and side rods covering the bands, in com- \lbmation withapandmcmdmg a turnbuckle m Fixing. 3 is a perspective view on the line 3-4 of [for a 'ustin githe en' h thereoi', and operative w conne c tions between the bands and the side rods F1844 is a section n H for preventing rotation'or the band when the with tions in e evation. 5o turnbuckle link Mei v i Fig. 5 is an enlarged plan of the elbow portion Another objector the present invention is the of the parallel motion arm of the drafting ma provision of a drafting machine of the wheel and chine shown in Fig. 1. V bandtype provided with a parallel motion mech Fig. 6 is a 'ira mental section on the line H anlsm or arm provided with means for adjusting of Pig; 5 with portions in elevation. I u

section on the line 1-1 oi Fig. 5,

in elevation. 1

section on the line H of Fig. 5. a plan of the strut shown in Figs.

'1 a portions Fig. 13 is asectlon on the line "-18 of Fig. 10. Fig. 14 is a section on theline ll-lloi Fig. 10. Figs, 15 to 21 inclusive, are perspective views similar to Fig. 3 but showingside rodsoimodiflcd construction.

1 1g. 22 is aplansimilartol'ig. Shut showing a modifled construction. v

Fig. 231s asectionon theline 2H8 01m. 22. Fig.24isaplansimilartol'iga5and2fl'but showing a further modifled construction. and.

The drafting machines herein illustrated and described are the preferred embodiments of the invention, but it is to be understood that they are only illustrative oi the invention which can be 2 otherwise embodied, and I do not wish to be limited to the particular construction shown.

Briefly stated, the drafting machine shown comprises a parallel motion mechanism or arm provided atone end with an anchor for attach- Nmenttoadrawingboardortable, andatthe other end with a protractor assembly including etc. The parallel motion or arm consists of two paralleiograms comprising flexible bands. designated generally by the reierence characters A and B, encircling grooved wheels 12 and I3, and II and II, respectively. of equal diameter and held apart or in spaced relatlonbyframemembersorstrutscandn. The flexible bands which encircle the wheels may be of any desired construction. Preferably they are similar in construction to the bands disclosed in my oop nding application Serial No. 64,141 flied of even date herewith, and comprise flat steel bands it encircled by cable bands 11, and include take-ups in the nature of turnbuckle links II for adjusting the length thereof and equalizers II at opposite ends of the take-ups for equalizina the tension between cable band 11. Another construction or band suitable '!or the present purpose wherein the single cable band encircling each flat band twice is replaced by two separatecahle bands, is disclosed in my copending application. Serial No. 44,747, flied October 12, 1935.

The upper wheel 7 gram is formed integral with the anchor desig; nated generally, bythe reference emitter I! --adaptedto be detachably secured or clamped to the upper or rear edge of the drafting board II 00 or the like, in a manner hereinafter more iully pointed out. The strut C which holds the wheel II in spaced relation to the wheel I! is made in two parts 21 and 2! adjustable relative to each other for the purpose oi'adiusting the operating center to center distance of the wheels 41 and II. The member 2|is preferably stamped from sheet metal and comprises two disk-like end sections 25 and It connected by.channel-shaped side rods 21 and a of inverted U-shaped crosssection formed integral therewith. The inside flanges oi the rods continue around the inside oi. the disk-like end sections forming thereon flanges 20 and 3|, respectively, and the outside flanges oi! the rods continue around the ends of the strut 15 forming outside flanges Ii and 32 on the end secthe flat band I. and the I! of the anchor parallels-s tions 2' and 2, respectively. The construction of the strut C may be varied from that shown as will be apparent to those skilled in the art, and the rods 21 and 28 may be of diflerent crosssectional shape, as suggested by Figs. 15 to 21, 5 hereinafter specifically referred to.

The upper end of the strut C is pivotally connected, concentric with the wheel 12, to a cylindrlcal projection or member 34 formed integral with the anchor, through the medium of an anti-friction bearing comprising balls 35 retained between inside and outside races 36 and 31, respectiveiy. The inside race is forced onto the member I4 and secured thereto by a plate 38 attached to the upper end of the member by a 15 screw II. The outside race 31 is positioned within an aperture in the disk-like end section 25 of the strut and defined by a flange 40 formed integral therewith, and is retained therein between a casting ll bolted to the upper side of the strut by screws threaded into a ring "engaging the underside of the strut and an inwardly projecting flange 43 formed integral with the flange 40. For thepurpose of adjusting the tension of the band in the event that no take-ups are directly employed therein, or for supplementing the adjustment obtained by said take-ups if employed, the wheel 13 is supported'in the strut C such a manner that its axis of rotation can in be moved lengthwise thereof. For this purpose the disk-like end 28 of the strut is provided with a rectangular aperture It within which the wheel I: is rotatably supported and moved lengthwise of the strut through the medium of the member II. The hub ll of the wheel I! is formed integrai'therewith and is rotatably supported in the member I! by anti-friction bearings comprising balls it retained between inside and outside races 41 and ll, respectively. The inside race 41 is fixed to the hub II- and retained in position thereon by a disk-like member 49 secured to the end of the hub II by a bolt it accessible through an aperture II in the member 22. The outside race II is located in a counterbore in the underside of the member 22 and retained in position therein by a ring-like member 52 secured to the member 22 by screws It, The bolt extends through anaperture in the wheel 13 and is threaded into the hub 54 of the wheel 14, which hub projects into a cylindrical counterbore in 50 the lower side of the wheel l3. An upwardly pro- ,iecting annular flange 55 formed about the periphery of the member 49 and prW- an annular groove QLsin-the unde of the member'H gcludesdirt from the bearing.

'lhe'iiiember 22 is slidably supported in the. aperture 44 by inwardly projecting flanges 63, formed integral with a downwardly projecting internal flange 84 andextending longitudinally of the strut along both sides of the aperture H, 30 which flanges engage in grooves formed by undercut portions oi the member 22 and the ring-like member 52. The upper end of the member 22, as viewed in Fig. 5, projects in the direction of the anchor beyond the disk-like end section 26 and has a downwardly projecting flange 66 formed integral with its upper end. The entire assembly at the elbow of the arm including the wheels 13 and I4, and the member 22,

etc. 'is adapted to be adjusted lengthwise of the strut by a screw 1 rotatably supported in the projection 66 and threaded into a plate 68 secured to the flange ill by a plurality of screws 0! extending through an external plate 111 and the flange'll and threaded into tapped apertures is the plate es. The screw :1 is provided with a flange against which the projection 50 abuts, and a hexagonal head orthe like, to facilitate manipulation thereof. In order to help guide the member 22 and make the structure more rigid 'theext ernal plate I is providedwith projections 'II which overhang finished portions I2 of the member 22, see Fig. 8. y

In the event that the entire weight or the arm and protractor assembly is carried from the anchor it is desirable to strengthen the strut-C oi the anchor parallelogram in some suitable man ner. As shown the rods 21 and 28 are connected intermediate their ends by across member 14 which, in turn, is pivotally connected by a rod I5 to the upper end of a projection IS on a casting .4I secured to the disk-dike end section 25 of the strut above the wheel I2. A knurled nut threaded on the lower end of the rod Ii provides means for adjusting the length thereof. If desired the bearing of the anchor can be raised above the center line of the band and the strut thereby stressed in a manner to reduce the sea at the elbow, as more fully pointed out in my aforesaid application SerialNo. 64,141.

As previously stated the left hand wheel I4 of the protractor parallelogram has a cylindrical hub 54 formed integral therewith which projects into a suitable aperture in thelower side of the wheel I3 and within-which it is secured by the screw 50. The protracto'rstrut D is similar in construction to the anchor strut C and comprises amember 85 preferably formed from sheet metal consisting of two disk-like end sections 85 and 81 connected by channel-shaped side rods 88 and 88 of inverted U-shape cross-section formed integral therewith. The inside flanges of the rods pontinue around the inside of the disk-like end sections forming flanges. and 8| thereon, and

the outside flanges of the rods continue around I the ends of the strut forming outside flanges 92 and 83 on the disk-like end sections 80 and 81,

respectively. The left hand and of the strut D is provided with an aperture similar-to the aperture 44 defined by a flange 04 and is pivotally connected concentric with the wheel I4 through of a member 85, preferably made of i cast metal, slidably attached to the member 85 in a manner similar to that in which-the member 22 is slidably attached to the member 2 I. The

member 85 is rotatably supported about the huh I of the wheel I4 through the medium of an antifriction hearing comprising balls 04 retained between inside and outside races 81 and 58. respectively. The inside race 01 is positioned on the hub 54 and retained in position thereon by the wheel I3 and the outside race 88 is secured .within a counter-bore in the underside of the member 85 by a ring-like member 09 secured to the member 95 by a plurality of screws.- The member 55 can be readily adjusted or moved relai tive to the member 88 by a screw I00 rotatably supported in a downwardly extending flange IN on the member 05 and having threaded engagement in a plate I02 fixed to the flange 90. A cooperating annular tongue-ari'd groove formed on the adjacent sides of the member 05 and the wheel I3 excludes dirt, etc., from the bearing. 0

The wheel I5 is provided with an upwardly extending tubular hub I05 of relatively large diameter formed integral therewith and through the -medlum of which the wheel is rotatably support-- ed in the right hand disk-like end section 01 of the strut D by an anti-friction bearing comprising balls I00 retained between inside and outside .ner.

races I01 and I08, respectively. The inside race I01 is forced onto the tubular hub I05 of the wheel and retained thereon by a holding or wheel plate IIO threaded on the upper end of the hub- I05 and, in turn, retained in position thereon by a lock screw II I. The outside race I08 is secured within a downwardly extending flange I I2 formed is herein referred to as the wheel or holding plate fixed to the hub I05 of the wheel I5 above the strut D, and a protractor plate I located above the holding plate, fixed to the upper end of a short shaft I 2I oflarge diameter rotatably secured within the hub of the wheel I5' by the protractor plate attached to the upperend thereof and a ruler plate I22 secured to the lower end by screws I23. The protractor plate I20 is provided with the usual graduations which in the the present instance extend 360- around the.

same, and has a plate I25 secured to the underside thereof by ,screwsl". The plate I25 has apertures I21 therein at the 0, 45 and 60 reading of the protractor in each of the four quadrants to facilitate setting the rulers, in any.

quadrant, at themost common angles. The arms I25 and-I20 forming part of the ruler plate carry horizontal and vertical rulers I30 and I3I, re-

spectively, of conventional construction detach ably connected thereto in any well known man- A third arm I82 extending in a direction opposite to that of the other arms and provided with a foot member I32 provides a steady support for the protractor assembly. A hand grasp I34 secured to the upper surfaceof the protractor plate serves the usual purpose. I

. A pawl I40 adapted to engage in apertures I21 of the plate I25 is carried by a movable seg- -ment'designated generally by thereference character F, comprising upperand lower plates I and I 42,'respectively, the former of which car--' rles a dead line mark I43 with or without. a Vernier, and projects over the edge of the protractor plate I20, while the latter projects underneath the holding plate IIO which is of substantially the same diameter as the protractor plate. The plate I is undercut on its inner periphery and projects over the rim of the protractor plate, which is of reduced thickness but slightly greater in depth than the undercut in the plate I for a purpose hereinafter referred to. The construction is such that the upper surfaces or the protractor plate [20 and the plate or member I are substantially flush. The lower plate I42 is adapted to be clamped to the holding or wheel plate III! by clamp washers or members I46 positioned between the plates I and I42 adjacent opposite ends thereof. The external ends of each of the clamp members I46 have a downwardly projecting flange which'engages the upper surface of the plate I42 and about which they fulcrum, and the internal ends overlie the periphery of the wheel or holding plate. The clamp members I lv are operated to clamp the holding plate III against "the plate 1.42, or in.

otberwordabetw'eenthe rlatsillandthemem hers Ill, by knurled nuts .Ill threaded on the upperendsoiscrews Illilxedtotheplate ill and p ting upward through the clamp memgbersandtheplate Ill. Theplate Iliiscut away adjacent the screws Ill leaving suliicient clearance torthe reducedlower partotthenuts Ill to project therethrough and engage the clamp members Ill. The clearance between the 10 plate Ill and the nuts ill is a minimum, since the upper plate I is held ln'assembled relation totheothermemberainpartbythesenuts, which permit a limited movement thereof withoutatanytimeinterieringwiththetreeopera- 1 tion oi the device.

The lower plate Ill hasan arcuate projection III on the upper surface thereof which engages in an annular groove illiormed in the underside the holding plate III and holds the plate Ill and. in turn, the segment I in assembled position with reference to the wheel or holding plate-III, when the nuts I" are loosened to permit angular movement or the sector about the periphery of the protractor and holding plates.

. Upon tightening the knurled nuts Ill, the periphery oi the plate III is securely clamped between the inner end of the clamp members and the plate Ill and the movable segment F secured in the position about the periphery of the plate III to -a which it has been moved or adjusted.

With the segment 1" secured in position the rulerscanbeclampedinanydesiredangularpositionby a winged nut ill threaded on the upper endoi a screw ill ilxed in the under plate ill,

3, and projecting through the plate Ill. The winged nut Illengages the upper suriace oi the plate Ill and clamps the periphery oi the protractor plate Ill between the latter and a spacer member or washer Ill interposed between the plates ill go and- Il! surrounding the screw Ill. As previously stated. the flange on the protractor plate Ill over which'the plate I projects is thicker than the cut-out portion of the plate Ill, which gives suillcient clearance between the plate Ill 5 andthespacermember llltoeii'ect theclamp- Therulersarenormallyheldinsuchaposition withrei'erence to the-protractor plate that the zero mark on the protractor coincides with the godeadlineonthesegmentl'andcanbereadily set in the other podtions at which the apertures I21 are formed in the plate Ill by the pawl Ill. The pawl ill which projects between the holding plate ill and the protractor plate III is formed as integral with an operating lever Ill, and pivot- .gg screws ill, while the other leg engages the upper surface of the plate Ill. The pawl is continuously urged in a counter-clockwise direction, as viewed in Fig. 10, by a leaf spring I, one end o! which is attached to the outside of the operat- -ing lever ill, where it bends around the plate Ill, while the other end engages the periphery ottheplates ill and ill.

As previously stated, the struts may be of any desired shapeand this is especially true of the Pieterablytbescsiderodsareopcn at the bottom so that they will not collect and retain dirt and are of such shape that they will cover the bands and partly, if not wholly enclose the same, thereby protecting the draitsman from being cut by the sharp edges of the band, getting is caught between the band and other parts of the machine, or by the band flying, should the same break under the high tension to which it is subject. In the preferred embodiment illustrated the side rods are inverted U-shaped channel sec- 10 tions, and other forms are shown in Figs. to 21 inclusive.

Fig. 15 shows a side rod ill of inverted rectangular channel shape open at the bottom and having the edges thereof bent upwards to rein- 15 force the same. A side rod I'll having a section substantially that or an angle iron positioned so as to extend over the top and outside of the band is shown in Fig. 16. This construction is quite satisfactory from the standpoint of protecting the operator, since the band is most apt to fly outwardly upon breaking. The side rod I12 shown in Fig. 17 is similar to that shown in Fig. 16, except that the sldes thereotare both bent inwardly. Fig. 18 shows a side rod adapted to completely enclose the band, and comprising an inverted U- shaped channel I13 having a U-shaped closure ill for the bottom adapted to be pressed ,or snapped into position. between the sides of the channel Ill and retained therein by spring presso by merely closing the channel at spaced intervals as illustrated in Fig. 19, which shows a side 'rod I'll oi inverted U-shaped channel section pro- .vided with a small clip or member I'll positioned 40 across the open part of the channel. Side rods of cylindrical section are shown in Figs. 20 and 21. As shown in 1"ig.-20, the-side rod IIl is open at the bottom along its entire length which permits the band to be readily assembled or replaced. 4;

In Fig. fllthe opening in the side rod III is shown in the lower side but facing upwardly. Other forms of side rods will suggest themselves to those skilled in the art, and the present invention is not limited to the specific constructions shown. so

It will be apparent to those skilled in the art to which the present invention relates, that the manipulation oi a take-up in the nature of a turn-buckle link located in one side of the band only will rault in an angular shifting of the rulers but that the tension in the band can be adjusted by moving the wheel lengthwise oi the strut without this etiect. I have found it desirable to have both adjustments in a single machine. On some occasions an angular adjustment so of the rulers is necessary, while on other occasions a mere tightening oi the bands is required.

In any event a take-up directly in the band is desired for initially tightening the same when first assembled with the wheels, since the movemerit of the wheel lengthwise oi the strut and in turn the amount of take-up obtained thereby is more or less limited in practical constructions where a compact, light arm is required.

A specific construction of arm comprising means for adjusting the operating center to center distance of the wheels has already been described in detail with reference to the preferred embodiment of the invention illustrated in Figs. .1 to 14 inclusive. A modification oi the preferred to mam Figs. 22 and 23, wherein the duplicate parts are designated by the same reference characters. In the present instance the castings III and ill which correspond to the castings 32 and 83 in the preferred embodiment are similar in construction to the castings 22 and 95 with the excaption that they do not extend as far towards the other end oi the strut, and are elidably supported in the disk-like end sections or the shots in a like manner. The principal diderence he tween the two constructions resides in the means i'or moving or adjustin g the cast lengthwise of the strut. As shown in Flat. wand 23, this means comprises two short screws tilt, one end or each of which is rotatably supported in a cutcutportion oi the casting, while the other ends have threaded engagement with nuts it! fixed to the flange 6,6. The screws lat arendapted to be rotated in either direction for the of adjusting the length of the strut bye. short shaft .ltt rotatably supported in the casting and provided with a gear wheel I81 on the inner end thereof continuously in mesh with two gears not formed integral with the screws m. A knurled or winged grasp I89 is provided at the outer end of the shaft I86 for manual operation thereof. The castings I80 and l8l are alike with the ex+ ception that the sides of the under one are built out to accommodate an annular tongue lot which projects into a groove in the underside of the wheel i3 and cooperates therewith to exclude dirt fromthe hearing. 7 3

Another modification or the construction heretofore referred to is shown in Figs. flinnd hfi. As shown in these figures the wheel assemblyat the elbow of the arm including the wheels-i3 and it, etc. is supported in the lower end of the anchor strut by a disk-like or cylindrical memher 2th rotatably supported in the strut 2M eccentric to the hearing or, in other words, the

Ill

" grooves therein which. hoth silo.

counterhore within which the outside race cfthe hearing is located. The strut 2M is similar to the strut (3 previously describedwith the exoeption that the rectangular aperture M in the strut me and ithil fiitiiiil carried hr the strut r in adj noted hosttion.

e nrotractor strnt iltii in construction to the strait is ported coaxial with the wheel a month it similar to theniernher tilt rotetahiw scorned within the aperture in the stint eccentric to the hearing. The inernher isprot'ided with.

handle ttt for adjusting the some and a. cotoperatine annular tona ne and eroore on the member tilt and the wheel iii excludes dirt, etc...

from the hearing. With this construction of arm it is especially desirable to employ hands including take-ups located directly therein since only. a limited amount oi. adjustment can he obtained in the strut.

The present'invention also contemplates the provision of an anchor that can be readily adjusted along the upper edge of the board withr in out the draltsman leaving his position at the trout, and one which does not take its alignment from the rear edge oi. the board. The preferred embodiment oi anchor, see Figs. 2 and 4, com

prises an l.. -'shaped bracket 2| 0 adapted to engage over the upper and rear edges or the board ill. The upper flange oi the bracket 2H! is provided intermediate its ends with a projection 2l2 with which the wheel I! may be formed integral, as she or separate and connected thereto. The rear iianaeencae'es the rear ee oi, a rectangular state i it coected to the hoard it by two screws till, one at either end oi the plate which project siishtir not the rear edee oi the hoard for a pin-pose hereinafter apparent. The rear wall of the bracket tit has .two projections tit formed integral therewith, provided with rectangular apertures til within which clamp members m are retained for limited movement. Each of the clamp members includes a bottom arm in which projects underneath the board i9 and engages or is hooked over the iront edge of the plate 2 l3, and a top arm 22! which projects over the bracket 210 at an angle oi about 30 to the worksued the bracket tit is drawn against both the upper side of the hoard l9 and the rear edge of the plate till, find in so doing the machine is securely attached to the board and automatically aligned with the rearedge oi the plate are. Since the plate tit is secureifto the board it at its ends only it will not be. distorted by changes in the board, and'as the anchorfis moved to different positions along the upper edge or the board the machine will always be aligned with the of with the rear edge of the board which is liable to change from time to time.

in adjusting the anchor along the upper edge at the hoard it will he obvious from the conctruction shown that the draitsman need not ienve his position at the trout oi the hoard since the thh screws tilt project above the hoard and are readily accessible from the front. litter the screws tit have heen ted to release the $3 clamp they can he used as handles tor shitting the anchor which inches the operation very simple and reduces the time reenired to a minimum.

the tor-easier description oi the ore Wed or the invention, it will he nareiit the oioiects oi the invention have that novel moo i" art t e r heel ehri'hand type has heen prowherein t ids covered in manner resent it appearance and protect the ldrorisloh has shade for readily adjusting the roe-shine along the upper edge oi the heard and novel means provided tor adjustinr: the tension in the hands. etc. The ruler essentials can 'herotated too and utch settings ohtained at the enrol caries in each of the lone ouorlranto or the protractor. in addition the dead line item which the protractor readings are determined c be adjusted to any desired position about the protractorsince the some is carried on afloating segment.

Numerouschangesin the constmction in additlon tothose already referred to will be apparent to those skilled in the artv to which the invention undistorted rear edge of the plate 2H instead relates, and it ismy intention to cover all variations, adaptations, and uses thereof that come within the practice of those skilled in the art, and I particularly point out and claim as my invention the following:

1. A drafting machine comprising a plurality of wheels, a flexible band enclrclingsaid wheels, and a strut operatively connected to said wheels for maintaining the same in spaced relation, said strut comprising a member including end sections overlying said wheels and connected by a pair of side rods partially enclosing said band and hav-' ing an opening along one side.

2. A drafting machine comprising a plurality of wheels, a flexible band encircling said wheels, and an adjustable strut operatively connected to said wheels, said strut comprising a member having end portions overlying said wheels, a member connected to one of said end portions for adjustment longitudinally of the strut, and means for connecting one of said wheels to said last mentioned member.

3. A drafting machine comprising a plurality 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 member including end sections connected by a pair of side rods of inverted U-shaped section.

4. A drafting machine comprising a plurality of wheels, a flexible band encircling said wheels,- and an adjustable strut pivotally connected to said, wheels for maintaining the same in spaced relation, said strut comprising: a member overlying one of said wheels, a second member slidably supported by said member, one of said wheels being pivotally connected to said second member, and screw means for producing relative movement between said members.

5. A drafting machine comprising a plurality of wheels, a flexible band encircling said wheels, and an adjustable strut rotatably connected to said wheels for maintaining the same in spaced relation, said strut comprising: a member overlying one of said wheels, a second member slidably supported by said member, one of said wheels being rotatably connected to said second member, and a screw located between said wheels in the plane of the band for producing relative linear movement between said members.

6. A drafting machine comprising a plurality of wheels, a flexible band encircling said wheels, and an adjustable strut pivotally connected to said wheels for maintaining the same in spaced relation, said strut comprising: a member overlying one of said wheels, a second member slidably supported by said member, one of said wheels being pivotally connected to said second member, and a screw located within the circumference of the last mentioned wheel for producing relative linear movement between said memhere.

7. A drafting machine comprising a plurality of wheels, a flexible band encircling said wheels, and an adjustable strut rotatably connected to said wheels for maintaining the same in spaced relation, said strut comprising: a member overlying one of said wheels, a second member slidably supported by said member, one of said wheels being rotatably connected to said second member, a plurality of screws for producing relative movement between said members, and means for simultaneously rotating said screws.

8. A drafting machine comprising a plurality of wheels, a flexible band encircling said wheels,

and an adjustable strut rotatably connected to said wheels, said strut comprising a member having an end section overlying one of said wheels and a second member rotatably supported in said end section and operatively connected to said wheel, the relative rotation between said member and said wheel being about an axis eccentric to the axis about which said member is rotatably supported in said end section.

9. A drafting machine comprising an anchor adapted to be attached to a drafting board or the like, a wheel fixed to said anchor, a strut including disk-like end sections connected by side members or rods and a member adjustably connected to one of said disk-like end sections, means for rotatably supporting one end of said strut concentric with said wheel, a second wheel, means for rotatably supporting said second wheel in the other end of said strut, a flexible band encircling said wheels, a third wheel fixed to said second wheel, a second strut including disk-like end sectionsconnected by side members or rods and a member adjustably connected to one of said disk-like end sections, means for rotatably supporting one end of said second strut concentric with said third wheel, a fourth wheel, means for rotatabiy supporting said fourth wheel in the other end of said second strut, and a ruler assembly operatively connected to said fourth wheel.

10. An anchor for a drafting machine comprising a bracket, means for detachably securing said bracket to a drafting board, said means comprising a member on the upper side of said anchor accessible from the draftsmans position at the board for operating said means.

11. An anchor for a drafting machine comprising a bracket, means for detachably securing said bracket to a drafting board so that the anchor can be readily adjusted along the upper or rear edge thereof, said means comprising a member extending above the working surface of said board and accessible from the draftsmans position at the front of the board for operating said means. I

12. '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 located above the working surface of the board and positioned at an angle thereto for drawing the anchor against the upper and rear surfaces of the board.

13. In a device of the character referred to the combination of a drafting board, a metal plate secured at the ends thereof to the underside of said board adJacent the rear edge thereof, a drafting machine comprising an anchor adapted to be detachably connected to said board and adjustable to different positions along the rear edge thereof, said anchor comprising a member adapted to engage the upper surface of said board and the rear edge of said plate, and a clamp adapted to engage said plate and force said member into engagement with both theupper surface of said board and the rear edge of said plate.

14. In a drafting machine the combination of a parallel motion arm, a holding plate operatively connected to one end of said arm, a ruler assembly rotatably supported in the same end of said arm, a protractor plate fixed to said ruler assembly, and a member carried by the periphery of said holding plate and adjustable angularly sembly rotatably supported in the same end of said arm, a protractor plate fixed to said ruler assembly, a member carried by said holding plate and adjustable angularly about the periphery 01 said protractor plate and provided with a dead line mark, said protractor plate having a plurality of apertures therein, and a manually operable pawl carried by said member for engaging 5 in said apertures.

CHARLES H. LI'I'I'LE.

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