US2228140A - Drafting machine - Google Patents

Description

4 c. H. LITTLE arm. 2,228,140,

' DRAFTING MACHINE Filed Dec. 27, 1937 s Sheets-Sheet 1 INVENTOR. Camus Hmzv LITTLE 01424:: Hueamep 0745 ATTORNEYS Jan. 7, 19,41- c. H. LITTLE ETALI DRAFTING MACHIN E Filed Dec. 27, 1937 8 Sheets-Sheet 3 Ja n.' 7, 1941. CH. LITTLE Em. 4

' DRAFTING MACHINE Filed Dec. 27,. 1937 8 Sheets-Sheet 5 INVENTOR.

Claus: A's/my 4/772: amass Mzaamo- A an:

/ ATTO 5 Jan. 7, 1941. c .H 2,228,140

DRAFTING MACHINE Filed Dec. 27, 1937 BSheets-Sheet 6 INVENTCR. Canaan l/ENEY Z/rrLE F765 76 {a CHHELEJ fluaaazo Um:

ATTORNEY:

Jan. 7, 1941. H. LITTLE ETAL DRAETING MACHQINE 27, 19 37 8 Sheets-Sheet 7 Filed Dec.

- :iiii! isiik 13111 7, 19 1 c. H. LITTLE HAL ,228,140 v DRAFTING nmcxmu:

Filed Dec. 27, 1915"!- 8 Sheets-Sheet. 8

1 {IV km all CHARLES llsnevl/rnf C/l 021.5: fiuaenea llrms fund Armani arsresrea Jan. 1, 1941 i x 7 233 140 UNITED STATES. PATENT OFFICE) Charles Henry Little and Charles Hubbard Little,

Cleveland Heights, Ohio K Application December 27,1937, Serial No. 181,790

21 Claims. (01. 33-79) The present invention relates to drafting mathe bands extend and wherein the tension of the chines and more particularly to drafting mabands can be adjusted by means of nuts threaded chines of the wheel and band type wherein the onto the tubes and engaging against the end parallel motion mechanism or arm comprises a members or yokes.

plurality of parallelograms comprising wheels 7 Another object of the present invention is toheld in spaced relation by struts and operatively provide a novel and improved drafting machine connected together by flexible bands. of the type referred to comprising struts or strut An object of the present invention is to provide frames for maintaining the wheels in spaced relaa novel and improved drafting machine of the tion including parallel tubes through which the 1 type referred to which will be light inweight and bands extend and end members so constructed embody the desired characteristics of stiffness and reenforced as to obtain ,maximum stren h and flexibility, and in which the wheels of the with minimum weight. parallelograms are held in spaced relation by Another object of the present invention is to struts or strut frames which wholly enclose the provide a novel and improved drafting machine 1? wheels and the bands encircling the same.-- of the type referred to comprising a cou'nterpoise Another object of the present invention is to for each arm including means for adjusting the provide a novel and improved drafting machine tension of the counterpoise springs. of the type referred to in which the struts'or Another object of the present invention is to strut frames entirely enclose the wheels and provide anovel and improved drafting machine of bands, and include parallel tubes through which the character referred to comprising a spring the bands extend but which will permit the bands counterpoise and an offset anchor forming a cover to be readily assembled or removed, and tuned. or housing for the. counterpoise spring.

Another object of the present invention is to Another object of the present invention is to provide a novel and improved drafting machine provide a novel and improved drafting machine of the type referred to-wherein the struts or strut or the type referred to comprising a flexible band frames comprise parallel tubes through which encircli'ng'the wheels thereof the ems-sectional the hands extend and removable covers for the area of which band is increased in the portionwheels and that part of the band adjacent the thereof intermediate the wheels. latter. Another object of the present invention is to 0 Another object of the present invention is to Provide anovel and improve il f m r m ly provide a novel and improved drafting machine for a drafting'machine including a spring-pressed of the type referred to having a parallel motion pawl or detent cooperating with an internally mechanism comprising two pivoted unitary sec notched plate.

" tions connected together at the center of the The presentinven'on resides in certain novel 35 wheels. 1 V details of construction, and combinations and Another object of the present invention is to arrangements of -parts,'and further objects and provide a novel and improved drafting machine of advantages will be apparent to those skilled in the type referred to wherein the protractor is the art to which the invention relates from the concentric with the wheel at the protractor end following description of the preferred embodi- 40' of theparallel motion mechanism or arm, and merits thereof described with reference to the comprising an oifset anchor so as to extend the accompanying drawings forming a part of this range of unobstructed operation of the machine specification in which similar reference characters at the left part of the board. I designate corresponding parts, and in which:

Another object of the present invention is to v 'Fig. 1 is a plan view of a drafting machine emprovide a novel and improved drafting machine bodying the present invention; I g

of the type referred to including struts or strut Fig. 2 is an enlarged plan view of a portion of frames comprising parallel tubes through which the anchor end of the drafting machine shown 7 I the bandsextendwhereintheparalleltubesare inFig.l;

rotatably connected to the end members or yokes Fig. 3 is a section with portions in elevation on ofthestrutssoastoimpartdesiredflexiblechar- 'thelineHofrlg z;

acterlstlcs to the drafting machine. A Fig. 4 isan enlarged plan view of the elbow por- Another object of the present invention is to tion of the parallel motion mechanism or arm provide tunnel and improved drafting machine ofthedrafting machine showninrigJ;

ofthetypereferred to comprising struts or strut Fig.6 is a section with portions in elevation tubeathroughwihich' takeaonthelineHofFlgd;

Fig. 6 is an enlarged plan view of the protractor end of the drafting machine shown in Fig. 1;

Fig. 7 is a section on the line 1-1 of Fig. 6;

Fig. 8 is an enlarged view of a portion of Fig. 6 withparts broken away;

Fig. 9 is a perspective view of the 'protractor assembly shown in Fig. 6;

Fig. 10 is a section on the line ||l||| of Figs. 6 and 8;

Fig. 11 is a section on the line of Figs. 6 and 8;

Fig. 12 is'a section on the line "-42 of Fig.

Fig. 13 is an enlarged perspective view of the upper end member or yoke of the strut for the anchor parallelogram;

Fig. 18 is a section on the line l8-l8 l6;

Fig. 19 is a plan view of the anchor shown in Fig. 1 with portions thereof broken away;

Fig. 20 is a section on the line 20-20 of Fig. 19 with portions in elevation;

Fig. 21 is aplan view of the anchor end of a Fig.1! is a section approximately on the line drafting machine of modified constructionemallelograms, the'upper end of which arm is conbodying the present invention; and Fig. 22 is a section on the line 22-22 of Fig. 21 with portions in elevation.

Referring to the drawings, the drafting machine shown therein comprises a. parallel motion mechanism or arm of the wheel and band type, including two angularly movable sections or pernected to the drafting board A through the medium of an anchor assembly designated in' general by the reference character B, while the lower end thereof is provided with a protractor assembly, designated generally by the reference character C, which protractor assembly includes a ruler assembly D. Generally speaking, each of the sections or parallelograms of the parallel motion mechanism or armcomprises a pair of wheels of equal diameter encircled by a flexible band and held in spaced relation by struts or strut frames. In the present instance, the struts or strut frames are so constructed and arranged that they completely encircle the bands and wheels, thereby producing a neat appearance and protecting the prises the wheels l0 and H,

operator from any possible injury in the event that a band should break during operation, or the like. The construction is also such that dirt,

etc, is excluded from the bearings.

The anchor section or parallelogram com atively connected to the wheels in a manner hereinafter referred to,-and a band designated generally by the reference characterF encircling the wheels. The upper wheel l0, which in. some respects forms apart of the anchor mechanism,

,is connected vsto a bracket member or casting H which forms the anchor proper and constitutes a housing for a counterpoise mechanism hereinafter referred to, through the medium of a hub I3 formed integral with the wheel Ill. The lower end M of the hub I3 is reducedand threaded into a tapped aperture in the top of a boss l5 formed integral with the member l2. The upof Fig. A

' friction bearing 25.

the strut E oper per side of the wheel i0 is provided with a plurality of apertures IQ for the reception of a spanner wrench used in securing the wheel to the member l2. The huh I! of the wheel l0 and the boss l5 of the member, l2 are concentric with and form a support for the inside race ll of an anti-frictionbearing 8, the outside race I! of which is fixed in the upper end member or yoke 20 of the strut E. The inside race I! of the anti-friction bearing I8 is securely clamped between thewheel l0 and a shoulder formed on the member 2 by the boss l5, and the wheel III is held flxed to the member l2 of theanchor through the medium of friction alone.

The lower wheel ll of the anchor parallelogram or section of the arm is held in spaced relation with respect to wheel l0 through the medium of the strut or strut frame E consisting in general of parallel tubes 2| through which the straight portions of the band F extend, and upper and lower end members or yokes 20 and 22. The upper ends of the tubes 2| extend into suitable cylindrical sleeves formed in the yoke 20 and are held therein and adapted to be adjusted longitudinally of the yoke member through the medium of nuts' 23 threaded on the ends of the tubes and engaged within suitable slots 24 in the yoke 20. The lower ends of the tubes 2| extend into suitable cylindrical apertures in the lower end member or yoke 22. As previously stated, the upper end member or yoke 20 is rotatably supported 'coaxially with the upper -wheel -Hl through the medium of the anti-friction bearing l8 and the lower wheel II is rotatably supported in the yoke 22 through the medium of an anti The wheels are operatively connected together by the band F which, as previously stated, ex-

tends through the tubes 2|. In the embodiment of the invention shown, the band F consists of two flexible flat steel sections 21 and 28 encircling I the wheels l0 and H,

creased cross-section. The rods 29 form those parts of the band which are not required to bend respectively, and opera- 'tively connected by sections or rods 29 of inabout the wheels, and the flexible fiat steel bands are connected thereto by connectors 30, see Fig. 4, located at opposite ends of the rod sections 29 and having threaded engagement therewith. The threads at opposite ends of the rod sections 29 are right-hand and left-hand, on the order of a turnbuckle, and function in a similar manner.

Holes 3| ,at opposite ends of the rods 29 facilitate the manipulation of,,the rods. The flat steel sections of the bands are lorig enough to permit the wheels to rotate through at least about 270. In

other words, they should not'be less than about one and one-quarter times the circumference of the wheels. In the embodiment of the invention shown, the wheels are three and one-half inches in diameter, the flat sections of'band are onequarter of an inch wide and twenty-thousandths of an inch thick, and the cross-sectional area of the rods is about three times as great as that of the flat sections of the band.

According to the provisions of the present in-. venticn, the struts or strut frames and covers entirely enclosethe wheels and bands. As previously stated, the straight sections of the band F extend through the parallel tubes 2|, and in order to enclose the wheels ill and H and the fiat parts 2'! and 28 of theband which encircles the wheels, the yoke members 20 and 22 are provided with removable covers 32 and 33, respectively. Enlarged detail views of the yoke member 20 and the cover 32 therefor are shown in Figs. 13, 14, and 15. As shown in Figs. 13 and 14, the upper yoke member comprises two offset sections 23' and 34, the former of which is comparatively heavy and oifset vertically about the lower thinner section 14. The latter section 34 has the hub 25 formed integral therewith, projecting above and below the plane thereof within which hub the outside race I! of the anti-friction bear- .ing it is fixed. The upper heavy section 28 of the yoke member extends toward the left as viewed in Figs. 3 and 13.to closely adjacent the wheel I, and conforms with the circumference thereof. That part of the lower thinner section tion between the part 25 of the yoke member and the reenforcing projection is strengthened and reenforced by a projection or pad 31 cast integral with the yoke member onthe under side thereof as viewed in the drawings. The side of the-member 31 adjacent the hub 35 is curved about the hub in a manner similar to that .in which the end of the member 3! remote from the hub is shaped, but the two reenforcing members overlap, see Fig. 3. The cup-shaped wheel III is as shown in Fig. 3 and the projection 36 extends closely adjacent the inside edge of the wheel and conforms thereto. The construction is such as to produce a uniformly strong section, to the right of the hub 35, as viewed in Fig. 13, even though the upper part of the yoke member has what resembles a cut-out portion 32 to accommodate the rim of the wheel II. A section similar to that shown in Fig. 14 will embrace the ends of the section 26 and of the reenforcing member 31.

while still including the reenforcing member 38. The particular yoke shown is made of cast aluminum and 'the shape of the reenforcing members or sections formed integral therewith is clearlyshown in the drawings.

42 about the periphery of the section 34 of-the yoke 20 while the latter engages within a groove 42 formed in the section 2 of the yoke. The construction is such that the yoke 22 together with the cover 32 form a complete cover for the wheel II and that part of the band encircled 1 ..thereby.' '1he un er Dirt 01' the hub of the yoke member and the adjacent part 45 of the member 12 are so constructed and arranged that the opening or clearance therebetween forms an irregular path or labyrinth, as shown in Fig. 3,

which prevents the entrance of dirt. etc; into the Thelower end 'member or'yoke 22 of the an chor parallelogram is similar in construction to the upper yoke member 2. just described. with the exception that the lower ends of the parallel rods 2| merely abut against shoulders in the ends of the apertures or sleeves inthe yoke member within which they are'positioned instead of incorporating adjusting means,. and the section 44 which on to the section 24 of the yoke member 2| isnot quite as thick as the section 24 because thisryokememberisnot required to carrythe samewcishtnoris it subjected great astrainastheyokememberat the anchor endof the arm. The wheel H and the section of flexible band 22 extending about the periphery thereof is enclosed by a cover 32 similar to the cover 32 previously referred to and detachably connected to the yoke member 22 in alike manner.

The left-hand wheel 48 of the protractor section or parallelogram and the wheel 'll of the anchor parallelogram are similar in construction formed integral with the hubs 5| and-52 of the wheels II and .40, respectively. The threaded portions 49 and 50 are threaded into opposite ends of a suitably tapped aperture in a spacer member 53 interposed between the wheels. Both wheels II and 48 are provided with apertures similar to the apertures IS in the wheel Ill, adapted to receive spanner wrenches through the medium of which the wheels may be relatively rotated to assemble and disassemble the same with the space member 53. The construction is such that the wheels are held in fixed relation, with reference to the spacer member 53 and each other, by friction only.

' The wheel ll of the anchor section or parallelogram is rotatably supported in the strut E through the medium of th anti-friction bearing 25, previously referred to, the inside race 54.

wheel 48 of the protractor section or parallelogram through the medium of an anti-friction bearing 58, the inside race 59 of which is fixed to the hub 52 of the wheel 48, while the outside race ill thereof is fixed withinthe hub 5| of the yoke 51. Adjacent parts of the spacer member 53, the yokes 22 and 51 .are so'constructed that the clearance therebetween is in the form of an irregular path or labyrinth, as clearly shown in Fig. 5, so as to prevent the entrance of dirt into the bearing's. Washers i2 and 63 interposed between the spacer member 53 and the bearings 25 and 58, respectively, assist in preventing the entrance of dirt, etc. into the bearings.

,The band operatlvely connecting the wheel 48' of the protractor parallelogram at the elbow of the arm and the wheel 64 at the protractor end of the arm is similar in construction to the band.

F already described, and will not be referred to in detail. Suillce it to say that the corresponding parts thereof are designated by similar reference characters.

The strut frame G of the protractor parallelogram is similar. in construction to that of the anchor parallelogram and comprises parallel rods 85' similar to the rods 2| through which! the straight sections r the band extend. The left hand ends of the rods 55 are connected toithe yoke member 51 in a manner similar to that. in

which'the upper ends of the rods 2| are connected to the yoke member 20. In other words, the same provision is made for adjusting the rods relative to the yoke members in the protractor parallelogram as has been heretofore described with reference to the anchor parallelogram. The right-hand ends of the rods 55 project into suitable apertures formed in the yoke member 54 in a manner similar to ,thatin which the lowerends oftherods project into similar apertures in the yoke member 22. In order'to enclose the wheel 48 and the thin flexible part of the band encircling the same, while permitting access thereto for the purpose of assembly, re-

7 The wheel 64 of the protractor parallelogram which forms a part of the protractor assembly is rotatably supported in the yoke 66 at the free end of the strut G throughthe medium of antifriction bearings 00, the inside race 60 of which is secured on the hub 10 of the wheel 04 by a flanged nut 1| threaded onto the lower end of the hub. The outside race 12 .is fixed in the righthand yoke member of the protractor strut G, which yoke member 00 is similar in construction to the other yoke members previously de-' scribed but, in view of the fact that it is at the 2 free end of the arm where it is not subjected to as much strain, it is not necessary to make the same quite as heavy or as strong as the other yoke members. The cover for the yoke member 66 is necessarily diiferent from the other covers referred to, since the wheel 00 forms a part of the protractor assembly, as will be hereinafter apparent. Both the ,nut 1I and the wheel ,ldare provided with suitable apertures for the reception of spanner wrenches to facilitate tightening the nut 1|,and the construction is such by friction alone.

arranged that the clearance therebetween is in the form of an irregular path or labyrinth, see Fig. '7, which prevents the entrance of dirt, etc.. into the bearing.

The protractor in the present instance comprises a disk '13 rotatably supported on an intermediate member or ring 14, which ring 1| is in turn rotatably supported on the upper side of an annular flange" formed integral with the wheel 64, which flange is hereinafter referred to as the holding plate '15. The ring 14 has. a PXOJBQ-r tion 16 formed integral therewith, to the upper side of which is secured a member 11 upon which the dead line is formed, and a pair of lugs 10 projecting from opposite sides thereof spaced 90 from the dead line 10. The ring member 14 is adapted to be adjusted angularly about the axis of the wheel'N, and' clamped in any desired position by a pair of clamp members 00 carried by screws 0|, the shanks of which project upward through the lugs or projections 19 where they plate 15.

are provided with knurled thumb nuts 02.. The radial inner edges of the clamp members 80 are adapted to engageover'an annular flange formed 4 on the periphery of the holding plate and the radial outer ends of the clamp members have slight projections or ridges 03 adapted to en- The protractor plate 13 of the ruler assembly D is rotatably supported coaxial with the wheel 64 through the medium ofa bolt 05 having an enlarged head 06 and a knurled cylindrical section 81 below the head 86'. The bolt 05 is rotatably supported in the wheel 04 through the medium of an anti-friction bearing 00, the inside race of which surrounds the shank of the bolt 05 directly above the head 88 while the outside race thereof is fixed in the hub 10 of the wheel GI. A washer 80 located directly above the bearing It prevents the entrance of dirt into the bearing. The hub of the protractor plate 13 is clamped between the washer. 09 and a member 00 located directly above the protractor plate by a nut 0| threaded onto the upper end of the bolt 05. The ruler plate 02, which carries the horizontal and vertical rulers 93 and 04, consists of a flat plate secured to the knurled part 01 of the bolt 05, and comprises horizontal and vertical arms 05 and 00. The under sides or the rulers ll and 04 are provided with tapered dovetailed grooves 01 into which similarlyshaped ends of the arms 05 and 00 project, see Fig. 12. The

' construction is such that the rulers can be readily chucked to or removed from the ruler arms.

The ruler assembly D includes the usual hand grasp'08 which, in the present instance, is connected to the stud "through the medium of the member 00 secured under the nut 0i and having upturned ends 00 to which the hand grasp is connected by screws I00. To facilitate the setting of the ruler'assembly to the angles of the protractor most commonly used, that is, 0", 30, 45, 60, and 90, the ruler assembly D in the presentinstance includes a spring-pressed pawl designated generally by the reference character H which cooperates with suitable notches I06, formed in the ring member 14. In the present instance the ruler assembly is adapted to be rotated through 360", and the notches I06 are formed in each of the four quadrants of the protractor." The pawl H ;comprises two plates I01 and I00 suitably secured together as by rivets I 09. The lower plate I00 is slidably supported on the upper surface of the protractor plate 13 and has a tongue or projection I II formed integral therewith which extends down through a suitable aperture H2 in the protractor plate where it is provided with a reduced end H3 adapted to engage within the notches I06. The lower end of the plate I08, as viewed in Fig. 8, is provided with a thumb grasp H4 secured thereto by a screw 5. The upper plate I01 is pivotally connected to a member H6 through the medium of a ball pivot H1. The plates I01 and H0 are preferably made pf hardened steel so as to reduce the wear in the pivot to a minimum. The plate H0 is shaped as shown in Fig. 8 and has socuredto the upper side thereof a similarly shaped plate N0, the lower right-hand end H9 of which isoifset and projects above the plate I01, thus securely holding the pivot assembled. The pawl H is continuously urged in a counterclockwise direction about the pivot I-I1, as viewed in Fig. 8, by a tension spring I20, one end of which is connected to a projection I2I formed integral with the plate I00 while the other end is connected to a projection I22 formed integral with the member 90.

At times it is desirable to secure the pawl H in an inoperative position, thus leaving the rulerassembly free to be rotated without the necessity of manually holding the pawl in a position to clear the notches .I0l, and, for this purpose, the present protractor assembly is provided with a latch member I25 'pivotally supported on the uphand end of the latch member I20, as viewed in Fix. a. is adapted to-be encased behind a pro-- of the latch is provided with a raised part m adapted to be engaged by the thumb of the ophis thumb downwardly as viewed in Figs. 8 and 9,

. the anchor and the protractor sections or parwiping the projection I28 with the lower part of his thumb, thus rotating the latch I into enga g position while maintaining the'pawl H in its inoperative or retracted position at the same time.

Provision is made for securely locking the ruler assembly D relative to the protractor plate 13 in the form of a stud I30, the head I3I of which is provided with a groove I32 adapted to engage 'over the radially inward edge of the ring mem ber 14. The shank of the stud I which projccts upwardly through suitable apertures formed in the plates I I6 and H6 is provided with a wing nut .I33 which, upon being tightened, securely clampsrthe protrajctor plate 13 to the ring member 14. The protractor plate 13 is cut out as indicated at I34 to permit free vertical movement of the head I3I of the stud I30. The head I3I of the stud I30 is elongated as shown in Fig. 8, and the groove I32 therein is formed on a radius, as clearly shown in the aforesaid figure, which radius is less than the radius of the inside diameter of the ring member 14 and permits the head I3I to pass over the notches I65 without'engaging therein, thus permitting free rotation of the ruler assembly D. From the foregoing construction it will be apparent that by loosening the knurled nuts 82 the dead line 13 may be moved or set to any desired angle, after which the knurled nuts 82 are tightened, whereupon the protractor readings are reckoned from a new base line of any desired angularity. Also the notches will read from the new base line.

The wheel 54 at the protractor end of the arm and the band adjacent to and engaging the wheel are enclosed'withinthe yoke 66 and a cover I35. The cover I35 is in the form ofa band located radially of the wheel proper and adapted to be clipped or otherwise detachably connected to flanges I35 on the yoke 65 adjacent the cylindrical portions thereof whichreceive .the rods 65 through themedium of reversely bentiianges I31 adapted to engage over the flanges I36. The yoke 55 has a small ridge or tongue I38 formed about the periphery thereof which fits into a groove formed on the cover I35. A small clearance is provided between the upper edge of the cover I35 and the under side of the holding plate 15. The particular construction of the cover I35 referred to is clearly shown in Figs. 16, 1'7, and 18.

shown includes counterpoise mechanism for both allelograms of the arm. For the most part, this mechanism is enclosed within the=member I2 of the anchor and only a small part thereof is ordinarily visible. The member I2v which forms the anchor proper is clamped to the upper edge of the drawing board A in any desired position by clamp screws; I threadedthrough suitable bosses formed on the lower ends of depending projections I42 formed integral with the housing I2. .The counterpoise mechanism for the anchor'parallelogram of the arm comprises two tension springs I45 the left-hand ends of which, as shown. in Figs. 19 and 20', are connected screws I54.

The preferred embodiment of theinvention I41 is secured to the under side of a ring-like member I49 by a screw I56. The upper side of the ring-like member I49 conforms to the shape of the under side of the yoke. surrounds the under part 44 of the hub, and is fixed to the yoke 26 by screws I5I. The under side of the member I49 is flat and, in addition to forming a support for the member I41, forms asupport for a plurality of rollers I52 hereinafter referred to. The

member I4] to which the springs I45 are attached is located to the left and slightly below the axis about which the upper end of the strut or strut frame E is rotatablysupported when the anchor strut is in a vertical position. As the strut frame is rotated during operation, the tension of the spring is increased or decreased as the case might be, the required amount to counterbalance the weight of the arm.

The counterpoise mechanism for the protractor parallelogram comprises the tension springs I53, the left-hand ends of which are connected to a wheel I54 through a connector I55 pivotally connected to the end of a crank member or lever I56 which in turn is pivotally connected to a boss I51 formed on the under side of the wheel I54 by a shouldered screw I58. The boss I51 is located at one side of the axis about which the wheel I54 rotates so as to effect a crank action. The wheel I54 is rotatably connected to the under side of the member I2 by a stud I59 threaded into a suitable aperture in the member I2 and connected to the strut or strut frame G of the protractor parallelogram by a cable I62 one end of which is secured to the under side of the wheel I54 in any convenient manner. From the wheel I54 the cable I62 extends toward the left, see Figs. 1 and 19, passes around a wheel I53 and extends down toward the elbow of the arm underneath the right-hand tube 2|. The wheel IE3 is equal'in diameter to the wheel I0 and is carried by three spacedv rollers I52 secured to the under side of the member I49 by shouldered The rollers I52 engage within a groove I65 formed in the wheel I53 which construction holds the parts assembled while permitting free rotation of the wheel I63. The lower end of the cable I52 is wrapped about and A spacer collar I6l about then secured to a wheel I56 located at the elbow of the arm and fixed to the upper side of the yoke 51 of theprotractor parallelogram by screws I61. The wheels I63 and I55 are of equal diameter.

The member I55 is cut out, as shown in Fig. 19,

the wheel I54 by movement of theparallel motion arm. Unless this were done, the tension of the springs I53 would be released when pivot I53 passes deadcenter. In order to permit the device to be adjusted, the under side of the wheel I54 is provided with a plurality of bosses similar to the boss I51." i

The right-hand ends of the springs I45 and;

I53 are connected to opposite ends of a lever I18 pivotaily connected to a flat rectangular end "I of a threaded rod I12. The lever I18 comprises upper and lower plates I18 and I18 one above and the other below the flattened end "I of the member I12. The members I18 and I18 are pivotally connected to the end I'll of the member I12 by means of a shouldered screw I18 which permits free rotation of the levers relative to the member I12. The springs I are connected to the under side of the lever I10 by connector I18 and the springs I53 are connected to the upper side of the opposite end of the lever I10 by connectors I11. The fulcrum or pivot for the lever I10 is not midway between the ends thereof but is closer to theend connected to the springs I88, as shown in Fig. 19, so as to balance the springs in the desired manner.

The'right-hand threaded endof the member I12 projects through suitable apertures I18 and I19, the former of which is formed in a member I80 carried bya'lever I8I fixed to the member The member I12 is adapted to be moved parallel with the top edge of the board A to adjust the tension of the springs I88 and I58 through the medium of a gear I82 rotatably sup- .ported thereby and interposed between the member I80 and the right-hand end of the member I2. Wear plates I 88 and I88 are interposed be- .tween the gear I82 and the members I80 and I2 respectively. a

The right-hand threaded end of the member I12 is enclosed within a tubular projection I88 formed integral with the anchor member I2. The gear I82 is adapted to be rotated in either direction to adjust the tension of the springs depending upon the angle of the drawing board, etc., by .a second gear I88 continuously in mesh with the gear I82 and fixed to the lower end of a shaft I81 rotatably supported in a suitable aperture formed in member I2. A crank I88 fixed to the upper end of the shaft I81 above the member I2 and rotatable in a plane parallel to the working surface of the drawing board provides means for rotating the gears I 82 and I88. Rota tion of the member I12 relative to the member I2 is prevented by cross arm I90 secured to the left-hand end of the member I12, which cross arm is adapted to engage spaced members I9l fixed to the under side of the member I2. The construction is such ,that the cross member I90 is free to slide underneath the members: I8I while preventing rotation of the member I12 relativeto the member I2. Y

In some instances, particularly where the instrument is to be used on a drafting board or table having comparatively little inclination, the counterpoise may be omitted altogether, or may be applied to only one of the sections or parallelograms of the arm. Figs. 21 and 22; show a modification of the embodiment of the invention are designated by the same reference characters I with a prime mark amxed thereto. As shown in these figures, the counterDO S comprises a 'sinle spring I98 the left-hand end of which is connected through the medium of a connector, I98

to the free end of the lever I81 fixedly secured to the under side of the yoke member 28' by screws I'98. The right-hand endofthe spring I88 is pivotally secured to the lower end of a'member I99 through the medium of the connector 288 by a shouldered screw 2". The member I88 is slidably supported in a slot 282 formed in the upper side of the anchor bracket I2 and adapted to be clamped in any adjusted position by means of a knurled nut 288.

In order to facilitate adjustment of the member I99 along the slot 282, the member has formed integral therewith a projection 288 extending upwardly through the slot 282 which projection is adapted to be engaged by the operator in adjusting the tension of the spring I98. The lever I91 is so constructed that when the anchor sec- 'tion of the armis in a horizontal position, that movement of the arm in, a counter-clockwise direction, as viewed in Fig. 21, is continued, the

pivot for the connector I88 will move below the ,axis of rotation of the strut and a counterpois action will be again effected. In both embodiments of the invention shown,

the connection between the parallel motion arm and the anchor is offset to the left a considerable distance-from the point at which the anchor bracket is connected to the board, leaving a clearance for the vertical scale underneath the anchor, as clearly shown in Figs. 20 and 22. This, together with the fact that the protractor is coaxial with the wheel 88 at the free end of the arm,

greatly extends the most convenient range of operation of the drafting machine, that is, at the left end of the board.

The springs are employed in pairs in the preferred embodiment of'the invention so that, in the event one should break while the instrument is being used on a substantially vertical board, the arm will not fall free but will be partially held by the second spring. It will be apparent that two springs may be employed in the embodiment shown in Figs. 21 and 22 if desired. From the foregoing dscription of the preferred embodiments of the invention it will be apparent that the objects heretofore enumerated and others have been accomplished and that a new.

and improved draftingmachine has been provided. The 'fact that each section is a unit facilitates assembly, and enclosing the wheels. bands, bearings, etc. produces a neat appearance andexcludes dirt, etc. from the operating parts. The use of anti-friction bearings permits the me of bands of greater cross-sectional area, thus greatly increasing the stability of the rulers. The fact that the side rods of the struts are rotatably connected to the end members oryokes produces flexibility normal to the working surface of the board, with the result that the rulers always lie flat and the protractor can be lifted without in- Jury to the arm. The central connection at the elbowofthearmpermitsthearmtobeswung through 360', if desired. The counterpoise' Springs for both sections of the armcan be simultaneously adjusted and very little, if any, of thecounterpoise mechanism is ordinarily visible.

While the preferred embodiments of the invention herein shown have been described in considerable detail. it is to be understood that the invention is not limited to the particular construe-- tions shown which may be varied within the scope of this invention. It is our intention to cover hereby all adaptations, modifications, and variations of the aforesaid constructions which come within the practice of those skilled in the art to which the invention relates, and we particularly point out and claim as our invention the follow- 1. A drafting machine having a parallel motion mechanism including a pair of wheels at least one of which has an axially extending annular flange, an endless band extending about the same, and a pivoted strut between the wheels for holding them in spaced relation with the band under tension, said strut comprising a reenforced end member or yoke adjacent one of said wheels and having an arcuate groove therein adapted to receive the annular flange of the wheel and a reenforcing portion opposite said groove.

2. A drafting machine having a paraliehmotion mechanism including a p ir of wheels, a band extending about the same, and a strut between the wheels for holding, them in spaced relation with the band under tension, the strut of one section, being composed of end members and hand encasing side members, said end members having arcuately shaped channels on one side for the reception of thewheels, and reenforcing means directly opposite said channels.

3. A drafting machine having a parallel motion mechanism composed of two pivoted sections each including a pair of wheels, bands ex- 7 tending about the wheels, struts between the wheels for holding them in spaced relation with the bands under tension, an internally notched member connected to the wheel at the protractor end of the parallel motion mechanism and located above the same, a ruler assembly including an angle indicatingmember located above the internally notched member and rotatably supparallel motion mechanism and adjustable within a limit of degrees or more, a pair of clamps for clamping said plate to said wheel, said clamps being diametrically opposite each other, a second plate rotatably supported coaxially with said wheel, and means for clamping theplate to.

said first named Plate, one of said plates having a dead line and the other plate having a co-operating protractor scale.

5. A drafting machine having a parallel motion mechanism composed of two pivoted sections, a protractor assembly including an internally notched plate supported by the parallel motion mechanism, a second plate rotatably'supported coaxially with the internally notched plate, and a clamp carried by the second plate for clamping the same to the internally notched plate, said clamp having a slot therein adapted to receive the inside edge of the internally notched plate, the radius of said slot being less than the internal radius of the notched plate.

6. A drafting machine having a parallel mo' tion mechanism composed of two pivoted sections eachincludingapairofwheelabandsextmding about the wheels, and struts between the wheels for holding them in spaced relation with the bands under tension, an internally notched plate 8 mtat'ably supported by the wheel at the protractor end of the parallel motion mechanism, a pair of clamps for clamping said plate to said wheel, a protractor plate rotatably supported coaxially with the wheel at the protractor end of the parallel motion mechanism, and a clamp carried by said protractor plate for clamping the same to the internally notched plate, said clamp having a slot therein adapted to receive the inside edge of the internally notched plate, the radius or 15 said slot being less than the internal radius of the notched plate.

7. A coimterpoise for a parallel motion mechanism of a drafting machine, said counterpoise comprising a spring one end of which is adapted to be operatively connected to the parallel motion mechanism, a member attached to the other end of the spring, and means for moving said member relativeto the board to which the machine is attached, said last mentioned means a comprising a crank rotatable in a plane substantially parallel with the working surface of the drawing board.

8. A counterpoise for a parallel motion mechanism of a drafting machine, said counter-poise 39 comprising a spring one end of which is adapted to be operatively connected to the parallel motion mechanism, a member attached to the other end of the spring, and means for moving said memoer relative to the board to which the drafting machine is attached, the last mentioned means comprising a gear having threaded engagement with said member and a crank rotatable in a plane substantially parallel with the working surface of the board for rotating the gear.

9. A counterpoise for a parallel motion arm of a drafting machine composed of two pivoted sections, said counterpoise comprising two springs,

'means for connecting one end of one of the springs to one of the sections, means for con- 45 necting the other of said springs to the other of the sections, a lever, means for connecting the other ends of the springs to opposite ends of said lever, and means for moving said lever to adjust the tension of the springs.

10. A counterpoise for a parallel motion arm for a drafting'machine composed of two pivoted sections, said counterpoise comprising two springs, means for connecting one end of one or the springs to one 'or said sections, means forconnecting one end of the other of the springs to the other section, a member adapted to be detachably connected to a drafting board or the like, 7 a threaded rod carried by said member, a lever pivotally connected to said rod, means for connecting the oppositeends of the springs to opposite ends of said lever, a gear having threaded engagement with said rod, a second gear in mesh with said gear, and a crank rotatable in a plane substantially parallel .with the working surface 65 of the board for rotating said seccmd gear.

11. A drafting machine having aparallel mo, tion mechanism composed of two pivoted sections.

' ananchor to which the parallel motion mechanism is'attached, and a counterpoise for said 70 12. A drafting machine having a parallel motion mechanism composed of two pivoted sections each includinga pair of wheels, bands extending about the same, and struts between the wheels for holding them in spaced relation with the bands under tension, an ofiset anchor to which the parallel motion mechanism is attached, and a counterpoise for the parallel motion mechanism, the counterpoise including a spring and the anchor forming a cover for the counterpoise spring. 13. A drafting machine having a parallel motionmechanism composed of two pivoted sections each including a pair of wheels, bands extending about the wheels, struts between the wheels for holding them in spaced relation with the bands under tension, a pulley rotatably supported adjacent the anchor end of the parallel motion mechanism, and a counterpoise for both of the sections, said counterpoise comprising a spring connected to the lower section by a flexible cable encircling said pulley at the anchor, end of the parallel motion mechanism.

14. A drafting machine having a parallel motion mechanism composed of'two pivoted sections each including a pair of wheels, bands extending about the wheels, struts between the wheels for holding them, in spaced relation with thebands under tension, a pulley rotatably supported adjaceiit the anchor end of the parallel motion mechanism, a second pulley fixedto the upper side of the strut of the lower section, and a counterpoise for both of the sections, said counterpoise comprising a spring connected to the pulley fixed to the lower section by a flexible cable encircling the pulley at the anchor end of the parallel motion mechanism.

15. A drafting machine for a parallel motion mechanism composed of two pivoted sections each including a pair of wheels, bands extending about the wheels, struts between the wheels for holding them in spaced relation with the bands under tension, a counterpoise for both of the sections.

an anchor to which the parallel motion mech- I anism is connected, said counterpoise comprising a pulley or wheel rotatably supported by the anchor, a spring connected to the pulley or wheel rotatably supported by the anchor to one side of the axis of rotation thereof, a second wheel hired to the upper side of the strut of the lower section, a third pulley or wheel rotatably supported adjacent the anchor end of the parallel motion .mechanismQand a cable connected to the first two mentioned pulleys or wheels and extending aboutthe third mentioned pulley or wheel at the upper end-of the parallel motion mechanism 16. A drafting machine having a parallel motion mechanism composed of two pivoted sections each including'a pair of wheels, bands extending about the wheels. struts between'the wheels for holding them inv spaced relation with the bands under tension, an offset anchor to which the parallel motion mechanism is connecteda pulley or wheel rotatably connected to the under side of mm diameter rotatably supported by a'plurality 'the anchor, a counterpoise for both of the sections, the counterpoise including a spring cohnected to the strut of the upper section at a point located to one side of the pivot therefor, a second spring connected to the pulley or wheel carried by the anchor, a pulley or wheel of uniof rollers adjacent the upper end of the parallel imotion mechanism, and: a flexible cable encircling the last mentioned wheel, one end of-the cable being connected to the pulley or wheel carried by the anchor, the other end of the cable being connected to. the lower section of the parallel motion mechanism.

17. A drafting machine having a parallel motion mechanism composed of two pivoted sections each including a pair of wheels, bands extending about the wheels, struts between the wheels for holding them in spaced relation with the bands under tension, an offset anchor to which the parallel motion mechanism is connected, a pulley or wheel rotatably supported underneath the anchor, a pin projecting to one side of said pulley or wheel coaxial, therewith, a counterpoise for both of the sections, the counterpoise including a spring connected to the strut of the upper section at a point located to one side of the pivot therefor, a second spring connected to the pulley or wheel underneath the anchor, a wheel of uniform last mentioned wheel, one end of the cable being connected to the wheel underneath the anchor, the other end of the cable being connected to the lower section of the parallel motion mechanism, the connection between the second spring and the pulley or wheel underneath the anchor comprising a leverhaving a cutout portion adapted to engage said pin so as to prevent the lever from being carried past deadcenter, and-means for adjusting the connection oi! the lever with the pulley or wheel. I

18. In a protractor assembly for a drafting machine the combination of a ruler having a tapered slot in the under side thereof opening into one end, and a ruler supporting arm or member having a tapered end projecting into and engaging the-sides of the slot in the ruler and lying wholly within the confines of the ruler.

19. In a drafting machine of the wheel and band type the combin tion of: -a pair, of wheels; a flexible band encirc I ng said wheels and engaging the same for maintainingthem in definite angular relationship with respect to each other; and a strut for maintaining said wheels in spaced relation, said strut comprising end members or yokes encasing the wheels and tubular side members encasing the band and extending between said end members for maintaining the same in spaced relation, one of said end members having means aflording access to thebandtherein, said end members and the ends of said tubular side members being in telescopic relationship and having'abutting portions. v

20. In a. drafting machine ofthewheel and band type the combination of: a pairot wheels, a flexlbleband encircling said' wheels and engaging the same for maintaining them'in definite angular relationship with respect to each other; and a strut for maintaining said wheels ins'paced relation, said strut comprising end members or yokes encasing the wheels and having portions extending around the band engaging portions of the wheels and spaced closely thereto, and tubular side members encasingthe portions of the band betweenthe wheels and extending'betweenthe end members so as to maintain them in spaced relation, one of the end members having means aflording access to the band permitting its application or removal, said end members and the ends of the tubular side members being in telescopic relationship and having abutting portions;

a flexible band encircling said wheels and engagimg the same for maintaining them in definite angular relationship with respect to each other;

and a, strut for maintaining said wheels in spaced Q relation, said strut comprising end members or yokes encasing the wheels and tubular side members encasmg the band and extending between said end members for maintaining the same in 7 to the band therein, said end members and the ends of said tubular side members being in telescopic relationship and having abutting portionss 5 CHARLES HENRY CHARLES HUBBARD 11min.-

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