US2462271A - Drafting machine - Google Patents

Description

Feb. 22, E949. c. H. LITTLE ET AL. 2,462,271

` DRAFTING MACHINE Filed sept. 22 1944 4 sheets-sheet 1 m f l4 P7; \V l Q. `\/f"| i r l 'I lr I l l* ll i |I i;

INVENToR mais Haw/ey nv-e j@ Pkw/@Wam Fell 22, 9j49- c. H. LITTLE ET AL 2,4629271 DRAF'TING MACHINE Filed sept. 22, 1944 4 sheets-sheet? Trae/YE yg Feb. 22, 1949. C, H. .TTLE ET AL 1462,27@

DRAFTING MACHINE Filed Sept. 22, 1944 4 Sheets-Sheet 3 M /1 Trae/V575 Feb; 22, w49, C. H. LITTLE Em 2,462,27l

DRAFTING MACHINE Filed Sepi. 22, 1944 4 Sheets-Sheet 4 I .l INVENTORS CHARLES Ha/e y fue 1 ByC/#mss #aaa/wohn@ 1 Q wf/WWW@ www atented Feb. 22, 1949 UNITED STATES ATENT OFFICE DRAFTING MACHINE Charles Henry Little, Cleveland Heights, and Charles Hubbard Little, Cleveland, Ohio 19 Claims. l

The present invention relates to drafting machines and similar devices comprising a parallel motion mechanism or arm, one end of which is secured to or is adapted to be secured to a table, drafting board or like device, affording a Working surface over which the free end of the arm provided with some suitable instrument is adapted to be moved and the instrument carried thereby maintained parallel in successive positions.

Where the working surface is inclined, the parallel motion arm, which usually comprises two relatively movable sections, will not remain in any predetermined position without being held therein by the operator. In an attempt to overcome this difficulty, various counterpoise mechanisms have been proposed but none of the counterpoise mechanisms heretofore employed have been entirely satisfactory for various reasons, such as, that they give the machine a bulky and ungainly appearance, impose limitations upon the otherwise normal range of movement of the parallel motion arm, are not effective for all board angles, etc.

One of the principal objects of the present invention is the provision of a novel and improved drafting machine or similar device, including a parallel motion arm and counterpoise mechanism therefor, which machine is so constructed and arranged that it will be accurate in operation and will not have the appearance of being bulky and ungainly, and in which the counterpoise mechanism will not interfere with the otherwise normal range of movement of the parallel motion arm and will counterbalance or counterpoise the same in all positions.

Another object of the invention is the provision of a novel and improved drafting machine or like device comprising a parallel motion arm and counterpoise mechanism therefor effective to balance the parallel motion arm at all board angles from zero to ninety degrees.

Another object of the invention is the provision of a novel and improved drafting machine or like device comprising a parallel motion arm and counterpoise mechanism therefor, which counterpoise mechanism is automatically adjustable for dierent board angles.

Another object of the invention is the provision of a novel and improved drafting machine or like device comprising a parallel motion arm and counterpoise mechanism including a helical-type contractional spring for counterbalancing the parallel motion arm.

Another object of the invention is the provision of a novel and improved drafting machine or Another object of the invention is the provision of a novel and improved drafting machine or similar device comprising a parallel motion arm and counterpoise mechanism therefor including a helical-type contractional spring adapted to be located at the side of the drafting board opposite the arm, and means independent of the spring for varying the counterpoising effect thereof to balance the arm at different board angles.

Another object of the invention is the provision of a novel and improved drafting machine or similar device comprising a wheel and band type parallel motion arm and counterpoise mechanism for the parallel motion arm including a counterpoise force producing mechanism located underneath or behind the working surface or drafting board and connected to the arm by means permitting the arm to be adjusted angularly relative to the counterpoise force producing mechanism.

Another object of the invention is the provision of a novel and improved drafting machine or similar device comprising counterpoise mechanism for the parallel motion arm, which counterpoise mechanism includes a counterbalancing device, such as a spring or weight located underneath or behind the drafting board or other working surface and connected to the arm by means comprising an eccentric o1' substantially eccentric cam and a lever interposed between the counterbalancing force producing device and the cam for changing the amount of counterpoising force applied to the arm so as to provide for different board angles.

Another object of the invention is the provision of a novel and improved drafting machine or similar device comprising a multi-section parallel motion arm of the wheel and band type and including means located at the side of the drawing board opposite the arm for counterbalancing the lower or instrument section of the arm independently of the bands of the parallel motion mechanism.

The invention resides in certain constructions and combinations and arrangements of parts and further objects and advantages will be apparent to those skilled in the art to which it relates from the following description of the preferred embodiment with reference to the accompanying drawings forming a part of this specification in which similar reference characters designate corresponding parts, and in which Fig. 1 is a View of a drafting machine embodying the present invention attached to a Hamilton Auto-shift drafting table;

Fig. 2 is a fragmentary sectional view of the device shown in Fig. 1, approximately on the line 2-2 of Fig. 1, with both sections of the parallel motion arm positioned at right angles to the upper edge of the drawing board;

Fig. 3 isa fragmentary sectional view, with portions in .,eievation, approximately on the line 3-3 of Figs. 1 and 5, with the drafting board in a vertical position and the parallel motion arm in the position shown in Fig. 2;

Fig. 4 is a fragmentary sectional view approximately on the line 4 5 of Fig. 3; and

Fig. 5 is a fragmentary rear view of the device shown in Fig. 1, with the various parts in the positions shown in Fig. 3.

The drafting machine shown comprises a jointed two-section parallel motion mechanism orA arm of the wheel and bandtype having an instrument or ,protractor head A at the free end and .theother end xedly secured, as by wood screws l0, to the drafting board B of a Hamilton "Autoshiit drawing table, designated generally bythe referencechara-cter C. The instrument head A is adapted to be moved about the Working surface of the drawing board B and the rulers or other instruments forming a part thereof maintained parallel by the parallel motion mechanism in successive positions to which they are moved.

As previously stated, one of the objects of the present invention is the provision of a drafting machine comprising counterpoise mechanism effective to balance the parallel motion arm at all board angles without attention on the part of the operator as the drawing board is moved from one angle to another; therefore, the drawings show the drafting machine applied to an adjustable drawing board. The Hamilton Auto-shift drawing table referred to is of commercial construction and the drawing board B thereof can be realily located in either a` horizontal or a vertical position or in any intermediate position. vA complete description of the table is not necessary to a full understanding of the present invention. Suffice it to say that the drafting board B is pivotally connected, as by bolts Il, to vertical upriglits i2 located adjacent to opposite ends of the table and vertically adjustable relative to the table proper by mechanism not shown but wellknown in the art.

`The parallel motion mechanism or arm shown, which is the preferred construction, comprises two angularly movable sections, each compri-sing a pair of wheels of equal diameter encircled by a ilegible band and held in spaced relation with the band under tension by a strut so constructed as to enclose the band and wheels. The upper or anchor section of the parallel motion mechanism or arm comprises the wheels I3 and I4 encircled by an endless band l5 and held in spaced relation by a strut D comprising yokes or yoke members i5 and i7 connected by tubular side menibers 20 and 2l. The upper yoke l5 is pivotally connected to the anchor assembly E, of which the upper wheel 3 is a part and through the medium of which the parallel motion arm is connected to the drawing board -B by being fixedly secured to the upper or left-hand end oi an elongated bolt or spindle 22 rotatably supported in the anchor bracket by anti-friction bearings 23 and 2G, 25, '25 adiacent to the upper, intermediate and lower parts thereof, respectively. The

tubelike nut members rotatable in one direction to expand the strut and tense the band and in the opposite direction to release the same so that they can befmoved along the side members to lexposes. portionor portions of the band.

The protractor section of the parallel motion arm is of similar construction and comprises equal diameter wheels 30 and 3l encircled by an endless band 32 and held in spaced relation by a strut comprisingl yoke members 33, 34 connected by ` tubular side members 35, 36 including Itulziular nut members similar to the tubular `rmt.rnezn bcrspreviously referred to. The wheels [Land at the elbow of thearm are preferably` formed integral and are operatively. connectedto therespectivc struts by anti-friction bearings respectively. The wheel .3| located-attire free end of the parallelmotion arm forms apart of the instrument head A. The construction. ofthe protractor strut is such that it enclosesthe wheels and band of the protractorsection.

The instrument A is similarin constructionto that disclosed and claimed in our copending application Serial No. 555,268, filed SeptembergZ,

1944, entitled Drafting machine, and is-not here in shown and described in detail. :Reference is made tothe aforesaid application foiwacomplete disclosure thereof. Suflice it to saythat the-instrument head A comprises a rulerlassembly F including a normally rotatable member .45 forming one'element of the.protractorpropersandv one or more rulers 4| detachably secured to.a.ruler or chuck arm-42. In addition to the aforementioned elements, the instrument head comprises a normally stationary protractor .element 43, which cooperates with the rotatable protraetor element previously referred to, to indicatethe angular :position of the ruler or rulers, 4index mechanism including the thumb piece Mge protractor clamp 55,. and a ruler assembly: clamp d6.

The counterpoise mechanism-showncomprises two helical-type contractional springs A5l), .-.Sl locatedbehind or underneaththe drawing" board B for counterbalancing the anchor.1 and-:protractor sections of the'parallelmotion arm, respectively. VThe,.contractional springs 50,'.5l1are.p1'eloaded at the Vtime of assembly andi-are'- housed within a. double-'walled tubular member 52, the lower endof-.which is closed by -a member 53 securely fixed to both tubes.V The=doublewa1led tubular member-52 extends generally'infadirecn tion at right' angles Vto the upper edge of vthe drawing board and is pivotally connected 'to,`,a bracket 54 through the medium lof a memberjSS fixed to'the member'52 Vand pivotally connected tothe bracket Slby a pin 56. Asy shown, the bracketA 54 is connected to the anchor. bracket -E by machine screwsf'l and to the undersideof the drawing board by wood screws58. )The constructionris such that the tubular member .452 is'supported underneath the drawing board B for rotation Vabout thepin 56 as an .axis, which axis is fixed withrespecttothe anchor bracket.

The purpose of the aforesaid pivotal construction will be hereinafter referred to.

The counterpoise springs 58, 5l are located between the inner and outer walls of the member 52 and are concentrically arranged with respect to each other with their upper ends abutting against the lower ends of two concentric members 60, 6l, respectively. The upper ends of the members 60, 6l are provided with rollers 62, 63 continuously in contact with the lower or front sides of levers 64, 65, respectively. The lower or front ends of the members 60, 6I are provided with downwardly extending tubular members 66, 61, respectively, xedly secured thereto. The tubular members 66, 61 extend between the counterpoise springs 58, 5I and in addition to forming guides for the members 60, 6l separate the springs, thus preventing one from interfering with the other. The upper ends of the tubes of the member 52 are flared towards each other in such a manner that the counterpoise springs will be retained therein even though the inembers 60, 6I and their respective tubes 66, 61 are withdrawn. This construction facilitates assembly as the counterpoise springs can be assembled with the member 52 prior to the assembly of the members 60, 6I therewith.

The levers 64, 65, previously referred to, are interposed between the rollers B2, 63, respectively, and ball bearing eccentric cams, designated generally by the reference characters 10, 1|, which cams are similar to the ball bearing eccentric cams shown and described in our copending application Serial No. 555,267, filed September 22, 1944 and, as shown, comprise commercial ball bearings fixed to eccentrics 12, 13. The levers 64, 65 are pivotally connected to the anchor bracket E by a pin 14 fixed in said bracket to one side of the center of the spindle or bolt 22 and so located with respect to the eccentric cams that the levers extend generally parallel with the upper edge of the drawing board.

The lower or right-hand cam 1l! which forms a part of the counterpoise mechanism for the anchor section of the parallel motion arm is keyed or otherwise non-rotatably fixed to the 1bolt 22 adjacent to its lower or right-hand end with its center oiset from the center of the bolt 22 along the center line of the anchor section of the arm and in the direction in which the f arm extends. The ball bearing eccentric cam 1| which forms a part of the counterpoise mechanism for the protractor or instrument section of the parallel motion arm is rotatably supported on the bolt 22 by an anti-friction bearing 15 with its center oiset with respect to the center or axis of the bolt 22 in a direction generally parallel with the length of the instrument section or strut of the arm and to the side thereof corresponding to the direction in which the section extends from the elbow of the arm.

The eccentric cam 1I is operatively connected to the strut of the instrument section of the arm by a gear 16 xed to a flange 11 formed integral with the eccentric 13 of the ball bearing eccentric cam 1|. The gear and flange are concentric with the bolt 22 and the gear is continuously in mesh with a pinion 18 fixed to the lower end of a shaft 80 rotatably supported in the bracket E by anti-friction bearings 8|, 82. The upper or left-hand end of the shaft 80 is provided with a pinion 83 continuously in mesh with an internal gear 84 xed to the lower or right-hand side of a pulley 85 rotatably supported on the upper member 21 of the bracket E by an anti-friction 6 bearing 86. The pulley is operatively co'ii-f nected to an equal diameter pulley 81 formed integral with or attached to the upper side of the yoke member 33 of the instrument strutby a cable 88 encircling both pulleys and provided with turnbuckles 89 for tensioning the same and adjusting the section angularly relative to the counterpoise mechanism proper, as will be hereinafter more specifically referred to. Preferably, the cable 88 is connected to the pulleys 85 and 81 by screws 90, thus reducing the amount of tension which would otherwise be necessary to prevent them from slipping on the pulleys. Any rotation of the instrument section of the parallel motion arm relative to the drafting board or any force tending to rotate the same is transmitted by the cable 88, pulley 85, etc., to the ball bearing eccentric cam 1I.

The construction is such that when the parallel motion arm is at right angles to the upper edger of the drawing board, that is, in the position' shown in Figs. 2, 3 and 4 of the drawings, the centers of the eccentrics 12, 13 are in line with the points of Contact between the levers 64, 65 and the ball bearing cams 10, 1I, respectively, and the center of the bolt 22, with the result that the forces of the counterpoise springs are applied in line with the center of the bolt 22 and the springs have no tendency to rotate the eccentrics "i2, "i3,` As either section of the parallel motion arm is moved out of the aforesaid position, the eccentric associated therewith is rotated with it and its center moved to one side or the other of the center of the bolt 22 depending upon the direction in which the section is moved, with the result that the respective spring associated therewith tends to rotate the eccentric and thus counterbalance or counterpoise the section.

From the foregoing it will be apparent that for proper operation, a certain predetermined angular relationship must be maintained between the struts and the eccentric cams associated therewith. This does not present any particular problem in so far as the anchor strut is concerned because the desired angular relationship therebetween and the eccentric cam which forms a part of the connection between the strut and the counterpoise force producing mechanism can be readily eiected at the time of assembly and with the construction shown the relationship thereafter remains fixed. However, because the connection between the protractorstrut and the eccentric cam associated therewith includes the cable 88 which must be tightened at assembly and at various times thereafter, provision must be made for adjusting the angular relationship between the protractor or lower strut and its eccentric cam. In the present instance this adjustment is effected by the provision of the two turnbuckles 89, one in each of the two reaches of the cable 88. Without further description, it will be apparent that if only one turnbuckle was employed, the angular relationship between the strut and the eccentric cam would be changed every time the cable was tightened. However,

once the desired relationship is obtained by turn.

ing one or the other of the turnbuckles, the cable can be tightened without disturbing the relationship by turning each turnbuckle an equal amount. Alternatively, other means may be provided for adjusting the angular relationship between the strut'and the eccentric cam eitherl at assassin.

the vtime of assembly or subsequent `.,therfeiio, .if desired.

Because different.counterbalancing forces .are required to balance the arm at anyigiven pos tion .on the drawing board for different board angles, provision is made for changing the counterbalancing Veiect of the counterpoise springs as .the board angle is changed. vIn .the present instance this uis accomplished withoutadjusting the springsor, in other words,independentlyoi the springs by changing the point of application of the force of the springs .tothe ileversl, '6i interposed 'between the rollers 52, and -the ballbearing eccentriccams fifi, `lll. As shown, the point o application ofthe counterpoise spring pressures againstthe levers EsLfSf-is-varied in accordancewith the board `angle by moving the member 512 about the pin 56, previously referred to, as a pivot, thus moving the rollers 62, 68 along the levers Gil, e5. The construction is such that the rollers 62, 63 caribe located at any den sired position along the levers Bil, inter-mediate a line through the pivot 'lll or through-the bolt.

Preferably the member 52 is moved automatically with a change in the board angle. .As shown, this is accomplished by a roller 32 connected to the upper or front side of a lever $3 intermediate the ends of the lever, which roller engages within a cam slot S4 in the member 5. One end of the lever 93 is pivotally connected by a'pin S5 to a'projection on the bracket and the other end thereof is pivotally connected by a pin 95 to the upper or rear end of a rod 91, the lower or front end of which rod is pivotally connected'by'apin '33 to a bracket Se 'fixed to a channel member i953 bolted to the upright-s S2 and which channel member is a part of the Autoshift table, previously referred to. The length of I-tl'ie rod `97 can be adjusted by a turnbnckle lOl. In view of the fact that the force-requirer to balance the parallel motion arm does not vary directly with the board angle, the slot S!! assumes the curved 4shape shown in the dra-Wings when itis desired that the counterpoise mechanism balance the arm at all board angles between zero and ninety degrees. rEhe shape can be computed by measuring the force required to coi-.interbelance the arm at different board angles or by the cut-and-try method. The relative positions of the member 52, etc., when the board is in a vertical position, is that shown in full lines in Fig. 5. The relative positions of the various parts with the board in a horizontal position is shown in dot-dash lines and it YWill Ybe understood that Vfor intermediate board angles the parts will assume intermediate positions.

The following table gives approximately the counter-balancing force required for different board-angles in percent of that required With the While the preferredmeans for Varying the counterpoising, force at an accelerated rate relative to the rate `at which the angle of thel board is-Ivaried has been described with considerable 8 detail, it. is to :be :understood `that the :present invention contemplatesthe use .of means Aother than thecurved slotlconstruction shown.

.es previouslyfstated, ,the/counterpoise springs arepreloadednt `the time 'of assemblyand the -truction employed permits the use of relay heavy, substantially constant pressure springs,lthussredueing the dimensional requirements oflthe deviceand making amore compact zonstruction. The fact that the counterpoise springs -are housed within the member 52 pro- :luces a Very safe construction and one wherein the counterpoise mechanism 4is at leastpartially operable even thoughone vor both of the counterpoise springs may break.

Front the foregoingV description of the' preferred embodiments of the'invention, it will belapparert that the Vobjects'lieretofore enumeratedjand others have'been accomplished and that a novel Vand lfnproved drafting machine or like device `has been provided comprising counterpoise mecha- 'a vin of improved design andconstructiomwhich counterpoise mechanism does not 'interfere .with *be otherwise ull movement of the parallel moarm, doesnot give the device a bulky and -niy appearance', isout of the Way ofthe op ator, and is effective throughout the ran'ge i .iovernent por the parallel` motion Varmand for all `diierent board angles.

While .the preferredembodiments of the invenfion'have been ,described with considerable the invention islnot limited to ther particuconstruction shown and. it is our intention Yto "by cover all adaptations, niodications and es thereof which come Withintlie Vpracticeof those skilled in the art to which .the invention relates and ,within the spirit and scope of the appended claims.

`Having thus described our invention, ,what we .-iaimds:

V1. ln a counterpoise mechanism fora draft-4 ing machine or like deviceincluding aparallel motion mechanism orarm adapted tobe connected to a drawingboardor 'thelike formovel:nent overv at least'a portion of Oneside. thereof, a contractional helical springlocated-atthe side of said drawing board .opposite ,said arm for counterpoising said arm, Yand means .automaticallyY )perabie upon variation. of the board .angle or varying the i counterpoising eiect of said spring.

2. In `a counterpoise mechanism. fora drafting nine or likedevice including a parallelmoriechanismcr ,arm-adapted.Y to be connected to adrawing board or the like for movement over. atleast-a portionor'. oneiside thereof, a contractional helical spring located Vat ther-side of saiddrawing Vboard opposite'said arm forcounerpoising said ,arm. and means automatically operable .upon variation of the boardangle for varyingthe -counterpoising eifectof said spring anaccelerated rate assaid board angle increases.

,3..In a counter-poise mechanism for a drafting machine Lor .like device including a multi-section, parallclmotion mechanisnror arm adapted tobe connected to adrawing board or-the like for movement ovenat least'a `portion thereof, a contractionallhelical-spring located at the side of said drawing' board opposite said arm for `counterbalancing asection of said arm, an eccentric cam,: means'a'dapted to operatively connect said eccentricV cam tothe section of said ,arm tolbe balanced-by said-spring,-a :lever interposedbetween said spring and said eccentric cam. means for pivotally supporting said lever at one side of said eccentric cam, and means for changing the point of application of the force of said spring to said lever.

4. In a counterpoise mechanism for a drafting machine or like device including a multi-section, parallel motion mechanism or arm adapted to be connected to a drawing board or the like for movement over at least a portion thereof, a contractional helical spring located at the side of said drawing board opposite said arm for counterpoising said arm, an eccentric cam, means for operatively connecting said eccentric cam to a section of said arm, a lever interposed between said spring and said eccentric cam, means for pivotally supporting said lever at one side of said cam, a member enclosing said spring, means for pivotally supporting said member, and means for rotating said member about said pivot for changing the point of application of the force of said spring to said lever.

5. In a counterpoise mechanism for a drafting machine or like device including a multi-section, parallel motion mechanism or arm adapted to be connected to a drawing board or the like for movement over at least a portion thereof, a contractional helical spring adapted to be located at the side of said drawing board opposite said arm for counterpoising a section of said arm, an eccentric cam, means for operatively connecting said eccentric cam to a section of said arm, a lever pivotally supported at one side of said eccentric cam and having a part thereof interposed between said spring and said cam, a member for enclosing said spring, means for pivotally supporting said member, and means actuated by a change in board angle for rotating said member to change the point of application of the force of said spring to said lever.

6. In a counterpoise mechanism for a drafting machine or like device including a multi-section, parallel motion mechanism or arm adapted to be connected to a drawing board or the like for movement over at least a portion of one side thereof, means comprising counterpoise force producing mechanism adapted to be located at the side of said drawing board opposite said paralle] motion arm, and means including two internal gears located at opposite sides of the drawing board and connected by a shaft provided with pinions for operatively connecting said counterpoise force producing means with a section of said parallel motion arm to be counterbalanced thereby.

7. In a counterpoise mechanism for a drafting machine or like device, including a multi-section, Wheel and band type, parallel motion mechanism or arm adapted to be connected to a drawing board or the like for movement over at least a portion of one side thereof, means comprising counterpoise force producing mechanism adapted to be located at the side of said drawing board opposite said parallel motion arm, means including two relatively rotatable members for operatively connecting said counterpoise force producing mechanism to a section of said parallel motion arm to be counterbalanced thereby, and means for adjusting said members angularly relative to each other.

8. In a counterpoise mechanism for a drafting machine or like device, including a multi-section, parallel motion mechanism or arm .adapted to be connected to a drawing board or the like for movement over. at least a portion of one side thereof, a contractional helical spring adapted to be located at the side of the drawing board opposite said arm for counterpoising a section thereof, means including two relatively rotatable members for operatively connecting said spring to the section of said parallel motion arm to be counterbalanced thereby, and nieans'for adjusting said members angularly relative to each other.

9. In a drafting machine or like device adapted to be used on an inclined drawing board or the like, an anchor member adapted to be connected to a drawing board or the like, a wheel fixed with respect to said anchor member andA adapted to be located at one side of the drawing board to which the anchor member is attached, a strut rotatably supported concentric with said wheel, a second wheel spaced from said first wheel, means for pivotally connecting said second wheel to said strut, a flexible band encircling said wheels, a third wheel concentric with said second wheel and fixed with respect thereto, a'second strut, means for pivotally connecting said second strut to said third wheel for rotation about an axis concentric therewith, a fourth wheel spaced from said third wheel, means for pivotally con-v necting said fourth wheel to said second strut, a flexible band encircling said third and fourth wheels, a member located adjacent. to said rst wheel, means for supporting said member for rotation about an axis concentric with the axis of said first strut, means for operatively connect' ing said member with said second strut, force producing means for counterpoising said second strut and adapted to be located at the side of the drawing board opposite said wheels, and means for operatively connecting said force producing means to said member. v

10. In a drafting machine or like device adapted to be used on an inclined drawing board or the like, an anchor inember'- adapted to be connected to a drawing board or the like, a wheel fixed with respect to said anchor member and adapted to be located at one side ofthe drawing board'to which the anchor member is attached, a strut rotatably supported concentric with said wheel, a second wheel spaced from said Ifirst wheel, means for pivotally connecting said second wheel tov said strut, a flexible band encircling said wheels, a third wheel concentric with said second wheel and fixed with respect thereto, a second strut, means for pivotally connecting said second strut to said third wheel for rotation about an axis concentric therewith, a fourth wheel spaced from said third wheel, means for pivotally connecting said fourth wheel to said second strut, a flexible band encircling said third and fourth wheels, a member located adjacent to said first wheel, means for supporting said member for rotation about an axis concentric with the axis of said first strut, means for operatively connecting said member with said second strut, a spring for counterpoising said second strut and adapted to be located at the side of the drawing board opposite said wheels, and means for operatively connecting sa'id spring to said member.

11. In a drafting machine or like device adapted to be used on an inclined drawing board or the like, an anchor member adapted to be connected to a drawing board or the like, a wheel fixed with respect to said anchor member and adapted to be located at one` side of the drawing board lto which the anchormember, is attached; a strut rotatably supported concentric with vsaid wheel,

aprecian second wheel spaced fromk said first wheel, means for pivotallyfconnecting said secondi wheel to said strut; a flexible" band encircling said wheels', a third wheel concentric with said second wheel and fixed' with respect thereto, a second strut', means for pivotallyconnecting said second strutto said thirdY wheel for rotation aboot an axis concentric therewith, a fourth wheelspaced from said third wheel, means for pivotally connectln'g' said fourthwheel tosaid second strutA a liexible band encircling' saidY third and fourth wheels', a memberlo'cated adjacent to said first wheel, means for supporting said member' for rotationabout anaxis concentric with the axis ol said'iirst strut, means for operatively connect-- ing saidA member with saidv second strut, producing'me'ans for counterpoising said second strut and adapted toV be located at the side of the drawing board opposite said wheels, means for operatively connecting said counterpoise force producing meansto said member, and means for aut'omaticallychan'ging the counteipoising effect of said force producing, means upon a change or" board angle.

12; In a drafting machine or like device u adapted to be used on' an inclined drawing board or the like; an anchor'member adapted to be connected to a drawing board or`th'e like, a" wheel fixed with respect'y to said anchor member and adapted to beloc'atedat'oneside of the drawing board' to whichtheanchor member is attached, a strut' rotatably" supported concentric' withA said wheel, a second wheel spaced from said first wheel, means for pivotally connecting saidl second wheeltosaid strut, a flexible band encircling said' wheels, a third wheel concentric with said second4 wheel and fixed with respect thereto, a second strut, means for pivotall'y connecting'said second strut to saidthirdwheel forrotation about an' axis concentric therewith, a fourth wheel spaced' from' said third wheel, means for pivotall'y connecting said'fourthwheel 'to' said second strut, a flexible band* encircling said thirdL and fourth Wheels, a member located adjacent tofv sai'd first wheel, means' for' supporting said' member for rotation about an axis concentric withV the axis of said'flrst strut', means for operatively' connecting said member with said second strut, .a spring for counterpoisi'ng saidy second; strut' andA adapted to be located at the side ci the' drawing boardr op'- p'osite said'A wheels, means for operatively connecting' saidspring to said' member, and means for' automatically changing theY counterpoising eiect of said spring upon a change-of boardlangl'e.

13. In adraf-ting machine or like device adapted' to be used on an inclined drawing board or the like, an anchor member adapted to beV con'- nected to a drawing board or the like, a wheel lxed withx respect to' said anchor member and adapted tobe located at one' sid'e of the drawing board to whichB the anchor member is attached, a strut rotatably: supported concentric with said wheel, a'- secondwheel' spaced from said first wheel, means forI pivotally connecting' said second Wheel toisai'd strut, aflexible band' encircling said wheels, a. third. Wheel. concentric with. said second wheel and xedz with respect thereto, a second` st11utmeans for. pivcta-lly connecting said second-strut to. said third wheel for. rotation about anv axis concentric therewith, a fourth wheel spaced. from: said third4 wheeh means for piyotally connecting. said` fourth wheel to, said; second strut, a flexible band.V encircling, said third and. fourth wheels,.a fth Wheellocated ad'iacent to saldii'rst wheel. means for supportingv said' fth wheel for rotation about an axis concentric with the axis of. said rst strut, a sixth wheel concentric with saidE second and third wheels an-d iixed to said second strut, a flexible band encircling said lth and sixth wheels, counterpoise force producing means'. for counterpoising said second strut and adapted to be located at the side of the `drawing board opposite said wheels, and means for operatively connecting said countcrpoise force producing means to said' fth wheel.

14.- In a drafting machine or like device adaptedfto be'used'on an inclined drawing board or the like, an anchor member adapted to be connected to a drawing board or the like, a wheel fixed with respect to said anchor member and adapted to be'located at one side of the drawing board to which the anchor member is attached,

astrut'rotatably supported concentric with said wheel, asecond' wheel spaced from said first wheeli meansfor pivotally connecting said sccond'wheel'to saidv strut, a flexible band encircling said wheels, a third wheel concentric with said second wheel and nxed with respect thereto, a, second" strut, means for pivotally connecting said secondistrut to' saidthird-wheel for rotation about anv axis concentric therewith, a fourth wheel spaced from said third wheel, means for pivotally connectingsaid fourth wheel to said second strut, anexibieband encircling said third and fourth Wheels, ,a ith wheel located adjacent to said rst wheel, means for supporting said fth wheel for rotationl about. an'.y axis concentric with the axis of. saiozfirst-Y strut, a sixth. wheel concentric with said. second and.' third wheels and fixed to said second'st1ut,a-flexible-band encircling said Iifth andsixthwhcels,- a spring foricounterpoising said second strut adapted torbe located at thev side of thedrawing' board' opposite said wheels, means ier operatively connecting said spring tosaid iifth wheel, and means for automatically changing the counterpoising eect of said spring upon a change of boardiangle.

l5, In a vdrafting machine.' or like device adapted to. be used onan inclined drawing board or the like, an anchor member adapted to be connected to' ay drawing board or'the like, a wheel fixed with respect to said anchor member and adapted to be located at one side of the drawing board towhichA the. anchor member is attached, a spindle rotatably supported in said anchor member concentric with said wheel and adapted to extend to opposite sides of the drawing board, a strut xed with respect tosaid spindle, a second wheel spaced. from said iirst Wheel, means for pivctally connecting said second wheel to said strut, a exible band encircling said wheels, a spring adapted to be located at the side of said drawing board opposite said wheels, means for operatively connecting said spring to said spindle, a third wheel concentric with said second wheel and fixed with respect thereto, a second strut, means for. pivotally connecting said second strut to said third'wheel forrotation about an axis concentric therewith, a fourth wheel spaced from said third wheel"l means for` pivotally connecting,r said fourth wheel to said second strut, a exible band encircling said third and fourth wheels. a iifth wheel located adjacent to said first wheel, means for supporting said ith wheel for rotation about an axis concentric with the axis of said spindle, a sixth wheel concentric with said second and third Wheels and fixed to saidv second strut, a exible hand encircling said fth and sixth wheels, a second spring' located adjacent to said first spring,

i3 and means for operatively connecting said second spring to said fifth wheel.

16. In a drafting machine or like device adapted to be used on an inclined drawing board or the like, an anchor member adapted to be connected to a drawing board or the like, a wheel fixed with respect to said anchor member and adapted to be located at one side of the drawing board to which the anchor member is attached, a spindle rotatably supported in said anchor member concentric with said wheel and adapted to extend to opposite sides of the drawing board, a strut fixed with respect to said spindle, a second wheel spaced from said first wheel, means for pivotally connecting said second wheel to said strut, a flexible bandencircling said wheels, a spring adapted to be located at the side of said drawing board opposite said wheels, means for operatively connecting said spring to said spindle,

. a third wheel concentric with said second wheel and xed with respect thereto, a second strut, means f-or pivotally connecting said second strut to said third wheel for rotation about an axis concentric therewith, a fourth Wheel spaced from said third wheel, means for pivotally connecting said fourth Wheel to said second strut, a flexible band encircling said third and fourth wheels, a fthrwheel located adjacent to said rst wheel, means for supporting said fifth wheel for rotation about an axis concentric with the axis of said spindle, a sixth wheel concentric with said second and third Wheels and fixed to said second strut, a flexible band encircling said fifth and sixth wheels, a second spring located adjacent to said first spring, means for operatively connecting said second spring to said fifth wheel, and means for automatically changing the counterpoising effect of said springs upon a change o board angle.

17. In a drafting machine or like device adapted to be used on an inclined drawing board or the like, an anchor member adapted to be connected to a drawing board or the like, a wheel xed with respect to said anchor member and adapted to be located at one side of the drawing board to which the anchor member is attached, a spindle rotatably supported in said anchor member concentric with said wheel and adapted to extend to opposite sides of the drawing board, a strut xed with respect to said spindle, a second wheel spaced from said first wheel, means for pivotally connecting said second wheel to said strut, a flexible band encircling said wheels, a

cam operatively connected to said spindle and J, adapted to be located at the side of the drawing board opposite said wheels, a spring adapted to be located at the side of said drawing board opposite said wheels, means for operatively connecting said spring to said cam, a third wheel concentric with said second wheel and fixed with respect thereto, a second strut, means for pivotally connecting said second strut to said third wheel for rotation about an axis concentric therewith, a fourth wheel spaced from said said third wheel, means for pivotally connecting said fourth wheel to said second strut, a flexible band encircling said third and fourth wheels, an instrument operatively connected to said fourth wheel, a fifth wheel located adjacent to said first wheel, means for supporting said fifth wheel for rotation about an axis concentric with the axis of said spindle, a sixth wheel concentric with said second and third wheels and fixed to said second strut, a exible band encircling said fifth iii) and sixth wheels, a second cam located adjacent to said first cam, means for supporting said second cam for rotation about an axis concentric with the axis of said spindle, means for operatively connecting said fifth wheel and said second whereby they'T rotate in predetermined relation upon rotation of either, a second spring 1ocated adjacent to said first spring, means for operatively connecting said second spring to said second cam, and means adapted to be operatively connected to the drawing board for automatically changing the counterpoising effect of said springs upon variation of the board angle.

18. In a drafting machine or like device 4adapted to be used on an inclined drawing boardor the like, an anchor member adapted to be connected to a drawing board or the like, a wheel fixed with respect to said anchor member and adapted to be located at one side of the drawing board to which the anchor member is attached, a spindle rotatably supported in said anchor member concentric with said wheel and adapted to extend to opposite sides of the drawing board,v

I respect thereto, a second strut, means for pivotally connecting said second strut to said third wheel for rotation about an axis concentric therewith, a fourth wheel spaced from said third wheel, means for pivotally connecting said fourth wheel to said second strut, a flexible band encircling said third and fourth wheels, an instrument operatively connected to said fourth wheel, a fifth wheel located adjacent to said first wheel, means for supporting said fth wheel for rotation about an axis concentric with the axis of said spindle, a sixth wheel concentric with said second and third wheels and fixed to said second strut, a flexible band encircling said fifth and sixth wheels, a second cam located adjacent to said first cam, means for supporting said second cam for rotation about an axis concentric with the axis of said spindle, means for operatively connecting said fifth wheel and said second cam whereby they rotate in predetermined relation upon rotation of either, a second spring located adjacent to said first spring, and means for operatively connecting said second spring to said second cam.

19. In a drafting machine or like device adapted to be used on an inclined drawing board or the like, an anchor 'member adapted to be connected to a drawing board or the like, a wheel ilxed with respect to said anchor member and adapted to be located at one side of the drawing board to which the anchor member is attached, a spindle rotatably supported in said anchor member concentric with said wheel and adapted to extend to opposite sides of the drawing board, a strut fixed with respect to said spindle, a second wheel spaced from said first Wheel, means for pivotally connecting said second wheel to said strut, a flexible band encircling said wheels, a cam operatively connected to said spindle and adapted to be loc-ated at the side of the drawing 12.5 boardiaoppositezsaidfwheels, a compression spring ada-ptewto bef-locatediat theside-of said drawingIrv board-oppositesaid wheels, means `for operatively connecting said. spring; to ,said cam Vcomprising a lever pivotally supported at one side of said cam andoperatively connectedthereto; a third wheel concentric with-said second=whee1 and xed with respecttheretof a secondrstrut, meansfor pivotally connecting said, second strutto said-third Wheelor rotation about an axis concentric therewith,A a'fourth wheel. spaced from said thirdwheel, means forVV pivotall'y` connecting said fourth wheel to said second strut, a exiblefband encircling said vthird and fourth wheels, an instrument operativelyconnected` to said fourth wheeLa fth Wheel .located adjacent to saidvirst wheel, means for. supportingsaidfth wheel forl rotation about an axisconcentric with the axis of said spindle, a'.sixth ,wheel concentric with` said second and thirdw-heels. and Xedto said second strut, a n

flexible band encircling said ifthA and sixth Wheels,.1neans1for adiusting'said wheels angularl'y with respect to each other; a second cam located adjacent to said' first cam, means for supporting1saids'econd cam for rotation about an aXisconc'entric with the aXis of said spindle, an internalgear ii'xed to said fth Wheel, a seco'nditernal gear Xed to said second cam, a second-spindle rotatably supported in said anclior member and provided'w'ith pinion gears in ,niesli Witl saidinternal'gears, a second compress'ion spri'glocated adjacent to said rst spring,

" connected to the drawing board for automatically,v

rotating said springs about said axis upon varia tion of the board angle for increasing thecolun? terpoising effect of said springs at an accelerated rate as the board angle increases.

CHARLES HENRY LITTLE. CHARLES HUBBARD LITTLE.

REFERENCES CITED The following references are of recordin; the le of this patent:

UNITED STATES PATENTS Number Name `Dato 2,164,215 Little ,June 27, 1939 2,228,140 Little ,Jan; 7, 1941 2,330,970 Harriman Oct. 5; 1943 FOREIGN 'PATENTS Number Country Date 175,183V Great Britain Feb. 16, 1922 503,102v Great Britain` i Mar. 31, 19,39

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