US2226882A - Drafting machine - Google Patents

Description

Dec. 3 1, 1940. v. B. WALLACE DRAFTING MACHINE Filed Jan. 9, 1959 s sheets-sheet 2 i226. 5'

/M/wae wea i 42465 ATTORNEY.

V. B. WALLACE' DRA FTING MACHINE Filed Jan'. "9, 1959 3 Sheets-Sheet 3 Z22-6. IZ

Patented Dec. 31, 1940 l EJNiTED STATES PATENT OFFICE Damme MACHINE Vard B. Wallace, Sierra Madre, Calif., assigner to Vani Mechanical Laboratories, a partnership composed of Vard B. Wallace and Paul H. Ford y Application January 9, 1939, serial No. 249,889

17 Claims. My invention relates to drafting machines and has particular reference to a new and improved construction of the device disclosed/in my patent No. 2,051,115, issued August 18, 1936. This application is a continuation, in part, of my co-pending application, Serial No. 207,015, filed May 10, 1938 and entitled Drafting machine". l

In the art oi drafting, itis the common practice to use drafting machines which will sup port one or more straight edges or scales in such manner that, though they may be moved to various positions over the drawing board or drawing paper, the straight edges may be maintained at a ilxed angle relative to a base line on the drawing board. l

Two common types of such machines are in general use, one of which is of the pantograph type includinga plurality of parallel bars or rods fixed atA one end to a base member to be permanently or detachably secured to the drawing board while the opposite ends of the bars o r rods are connected to an articulation plate ort frame. The second set of parallel bars or rods extend between and are connected to the articulation plate and a scale or straight edge supportng frame, the iixed base, the articulation plate and the frame dening parallelograms so tha", the frame may he moved to various positions over the drawing board without change of its angular relation relative toa predetermined base line on the board. ,s K

The other of these types of machines isknown as the find and pulley type wherein pulleys mounted, respectively, on the fixed base, the articulation member, and the scale supporting frame are intercoupled by means of endless metal bands in such manner that the scale supporting frame will maintain a deiinite angular position relative to a base line on the drawing board regardless of the position of the frame upon the board. L

1n both of these types of machines it is the common practice lto mount the scales or straight edges upon a scale support, which is in turn mounted upon the frame to permit of its rotation relative thereto and to thus permit the straight edges or scales to be set at any desired angle relative to the base line and when so set thereafter maintain that same angular position during all `movements of the scales or straight edges over the board.

Protractors are also usually provided upon the frame and scale support arranged in such manner as to permit the ready selection of any desired angularl relation between" the scales and the base line. Again it is common practice in these machines to provide pawls or other spring pressed latching devices receivable in notches or holes when the scales are at certain commonly employed angles relative to the base line and 5 to permit of adjustment of the angular position of the scales by retraction of the pawl, rotation of the scale supporting plate and the insertion of the pawl in a newly selected one of the notches orholes. It frequently occurs, however, that the particular angle at which it is desired to set the scales or straight edges does not coincide with the position of any of the notches or holes and under such circumstances it is desirable that the pawl or latch be locked in a retracted position and that the scale support. be clamped in such desired angular position upon the frame.

One of the primary difficulties which have been encountered in the use of such drafting machines having adjustment for the angular positions of the scales has been that, due to the construction of the machines, the scope of rotational movement between the scale supporting plate and the parallel mechanism frame has been `limited to a relatively small portion of a complete circle whereas it isv frequently desired to move the scales to positions beyond this limit; namely, at

` any position throughout a complete circle. Again -another difficulty which has heretofore been encountered has been that the pawls and releasing devices employed for releasing the pawls from their notches or holes have been so inconveniently and awkwardly located that it has been necessary for the draftsman using the machine to drop pencils, dividers o r other instruments which he is then using and to employ both hands for, the adjustment or repositioning of the scales and frame. A

It is therefore an object of my invention to provide a mounting for the scales on parallel 40 mechanism drafting machines in which the scales may be ro'tated through a complete 360 of rotation relative to the parallel mechanism frame.

Another object of my invention is to provide a device of the character set forth in the pre- `ceding paragraph which is equally adaptable to either the parallel bar type of drafting machine -and to the band and pulley type machine.

Another object -oi my invention is to provide a scale support and parallel mechanism-frame mounting in which a pawl or latch may be employed to adjustably fix the angular relation between the supporting plate and the frame and in which release devices for the latch are so conveniently mounted that a person manipulating the machine may with a single hand release the latch and turn or adjust the scales to the. new` desired position.

Another object of my invention is to provide a mechanism of the character set forth in the preceding paragraph wherein a simple locking means is provided for locking the pawl or latch in its free position whenever it is desired either ito move'the scales to some uncommon angle for which no notch or hole is provided, or when it is desired to leave the scales in a condition to be freely rotated relative to the parallel mechnismframa fOther objects and advantages of my invention will be apparent from a study of the following speciilcatlons, read in connection with the accompanying drawings, wherein:

Fig. 1 is a fragmentary plan view illustrating one form of the protractor head of my invention as being employed on a drafting machine of the endless band type;

Fig. 2 is a vertical section taken substantially` along the line Ii-II of Fig. l and illustratingv the construction ofthe protractor head shown in Fig. l:

Fig. 3 is a horizontal section taken as indicated by the line VIII-III of Fig. l to show additional details of construction ofthe protractor head and release mechanism;

Fig. 4 is a vertical section taken along the line IV-IV of Fig. 3 and illustrating a clamping mechanism employed for locking the protractor head in any set position:

Fig. 5 is a plan view similar to Fig. 1 but illustrating the application of a protractor head embodying the principles of my invention to a drafting machine of the parallel varm or rod type;

Fig. 6 is an enlarged plan view of an alterna-` tive form of protractor head with certain parts broken away to show the construction of the release mechanism;

Fig. 7 is afvertical section taken along the line VII-VII of Fig. 6 and showing additional details of construction of the release mechanism employed in the typer of prctractor` head illustrated in Fig. 6; v

Fig. 8 is an elevational view partly in section taken as indicated by the line VIII-VIII-of Fig. 6 and showing` the construction oi' a Ilocking device employed for locking the aforementioned release mechanism in the released position;

Fig. 9 is a plan view illustrating a still further modified form of protractor release mechanism;

Fig. 10 is a plan view similar to Fig. 9 showing a an additionalmodiilcation oi' the release mechanism of my invention;

Fig. l1 is a vertical sectional view taken as Y indicated by the linen-XI of Fig. l0 and illustrating the details of construction of this form of release mechanism; and y Fig. l2 is a fragmentaryperspective view showing the construction and inter-relationship of' the control knob and release levere'mployed in the form of my invention which is illustrated inl Fig. 9. f

Referring .to thedrawings, I have illustrated in Fig. 1 a typical Yendless band type'oi'x drafting machine which includes a pair of arms or struts i Aand 2, 'each of which is constructed to include a pivot head at each of its ends held apart by an extensible and eontractible rod mechy anism. The arm i includes a pivot head la at one end of the rod Ib which in .turn carries the pivot head ic at its opposite end. A mounting bracket 9 secured or clamped. upon the edge of a drawingboard 4 constitutes a pivotal mounting for arm Lupen which bracket the pivot head la of that arm may be rotatably secured for moveV rotated about the bracket 9 the! p ulley 1 will maintain the same angular position relative to the board as that of theilxed pulley l. l

An arm 2 likewise includes a pivot head 2a pivotally connected to the head Ic of arm i for rotation relative thereto in a plane parallel to the board, head 2a being mounted at one end of a rod Ibfthe opposite end of which carries pivot head 2c. l

A second endless band or belt 9 extends about a pair of pulleys on arm 2, one of these pulleys indicated at 9 being rotatably mounted upon the head 2c of arm 2 while the other may be the same pulley 'I which forms a part of arm i. Thus. as either or both of the arms or struts I and 2 are moved over the board, the pulley 9 will always maintain a ilxed'angular position' relative yto a base line on the board.

As is fully shown and described in my More! mentioned patent, No. 2,015,115, adjustment ofV the tension exerted upon the band 9 is permitted by forming the pivot heads with shanks I9 having sockets il formed therein to receive the ends of the rod Ib, at least one -of the sockets having an adjusting screw i2 therein which threadedly engages the rod lb such that by rotating the rod about its longitudinall axis the effective spacing of the pulleys 1 and 9 may be changed. A similar construction embodied in'arm I may be used to adjust the tension of the band 9. Ifdesired. a knurled or hexagonal handle portion I3 may be formed upon rods ib and 2b to facilitate turning them.

It will be readily observed that the aforementioned pulleys 5, 'I and 9 and' the endless bands 9 and 9 cooperating therewith function in combination with the p ivoted Joints of the struts Il and 2 to maintain the pulley 9 in axed angular location relative to the pulley. I and the drawing board 9 so that while thepulley 9 may be moved to any desired position on the drawing board l, it will at al1 times maintain a fixed angular relationship to the base line il while so doing and pulley'sfmay constitute a support for scales or straight edges to be used in making drawin on the boardl. i f

I provide a protractor plate i9 'whichvis securely attachedto the pulley 9 and rotatably supports co-axially' therewith a head plate." which is provided'with a protra'ctor index I9. The head board 9.

As illustrated in Figs. 2 and 3, the pu1ley 9 maybe rigidly secured theprotractor plate i9 by providing/a'recess `2| therein which will accommodate the protruding portion of an attaching means which. as shown in Fig. 2,` may comprise machine screws 23 passed through suit' able openings 23 in the body portion of the pulley 3 and threadedly engaged with the protractorr V.plate I6. The assembled pulley V3 and vprotractor plate I6 may be secured on a sleeve 21 which extends upwardly from the vprotractor plate I3 by providing a hub 21a for engaging the underside of the protractor plate I3 anda means to be described hereinafter for. forcing the. pulley' and the protractor plate I3 against said hub. An

-inner race 28 of a ball vbearing is preferably mounted on, the central portion of the sleeve 21, and an outer race 29 of said ball bearing is rotatably secured to the inner racef-asby means of balls or rollers 30 and secured in a flxed po-I sition relative to a body portion 3| oi.' the shank Il as by providing a press iit between the outer race 23 and a recess 32 provided therefor. "I

provide a nut 21bvwhich is threaded upon the upper end ofthe sleeve 21 and arranged to clamp base line I4, I provide another sleeve 33 which.

is inserted within the aforementionedsleeve 21 and adapted to rotate therein. The sleeve 33 is provided with a flanged baseportion 3l which is secured to the head plate I1 as by means of suitable attaching means 35 which may be, as illustrated in- Fig. 2, headless rivets. The head plate I1 is'provided with a circular recess 33 adapted to contain the protractor plate I8 so that the upper surfaces of the protractor plate I3 and the head plate I1 may lie in the same plane while the body portion of the head plate I1 may pass under the protractor plate I6 so as to establish the aforementioned engagement between the head plate I1 and the flanged portion 34 of the inner sleeve 33.

'I'o assist the draftsman in moving the scales over the board 4 and to make such rotational adiustment between the scales and pulley 8 as he may desire. I provide a. handle or control knob 31 securely attached to the upper end of the inner sleeve 33 as by providing a mounting plate 33 which may be threadedly engaged with a threaded upper portion 39 and'locked in the desired position by means of jarnb nuts 43 and 6I. The control knob 31 may be attached to the mounting plate 38 as by means of machine screws l2 engaging the knob 31 and threadedly engaged with the mounting platey 38. An operator may therefore, by grasping the knob 31, rotate the head plate I1 relative to the protractor plate I8 (protractor plate I6 being in a xed angular position relative to the base line 23) so as to establish any desired angular relationship between the scales zi and 22 attached to the head plate l1 and the base line 23. t

In order that the protractor `plateV I6 and the' I1 at such angular positions and for holding the protractor plate I6 in such position. This mechanism includes a notch plate 5I which is disposed immediately below'the protractor. plate I6 and securely attached thereto by the aforementioned f fastening means 25. The notch plate II is pro' vided with a plurality` of notchesV 82 disposed about theperiphery of the notch plate in such location that vwhen said notches register with a pawl I3, the scales' 2I kand 22 will occupy one of the aforementioned frequently used angular po' sitions. Such angular positions may include a positionin which the scale 22 is disposed parallel- -to the base line 23 and other positions at angles of 15, 30,' 45, 60 land 90 degrees thereto.

The pawl 53 is pivotally secured to the head plate I1l as by means of a pin or bolt 54 and confined' in a recess 54a provided therefor in the head plate I1. A spring B6 is gprovided. which is anged' to normally urge the pawl 53 toward the notch plate 5I so that whenever the head plate I1 is rotated to a position in which a notch engaging end 63 of the pawl '63 registers with one of the notches v52, the spring will urge the` pawl 53 into engagement with that notch so as to lntertie the head plate I1 to the'notch plate 5I and the protractor plate I3 attached thereto. v

' I prefer to locate the pivot'point Il appro'ximately on a line tangential to the notch plate 5I at the.point of engagement of the pawl 53 with the notch plate 5I so that any tendency of the head plate I1 'and the pawl 53 carried thereby to rotate relative to the notch .plate'l will provide no component of force tending to dislodge the pawl 33 from engagement with the notch E2 of the notch plate 5I. l

In order that the pawl 33 may be readily and with cylindrical gear rack .teeth SI which are `arranged to be operably engaged with similar gear teeth 62 provided in a gear sector 63. The

gear sector 63 is attached to a shaft 3| whichA is inserted within .the inner sleeve 33 and is rotatable relative thereto. The gear sector 33 is attached to .the shaft 34 by means of 4a nut 35 which operates in conjunction with a threaded end 3B of the shaft 34 toiorce the sector 63 into intimate engagement with a shoulder 61 provided on theupper end of the shaft 34. The shaft N is providedy with a horizontal ange portion 61a which vis disposed immediately below the previously described flange portion 34 of the inner rotatable sleeve 33.

I provide a connecting link 68 which is con- .fined in a recess 63a in .the head plate I1 and pivotally secured to the flange 61a as by means of a pivot pin S9 located near the periphery of the flange 61a. The other end of the link B3 is pivotally secured to the notch engaging end 56 of the pawl 53 as by means of a suitable pivot pin 1d.

I prefer .to arrange the previously described parts in such a manner .that should the plunger Iili Si be moved to the left, as illustrated in Fig. 3,

to rotatelthe shaft tl, the linir 38 Twill be moved 53`away from the notch .plate 5i against' the i restoring action of the spring 55. It will. be observed that this operation Aof disengaging the pawl from the notch with which lit is engaged y will 4then allow .the drattsman to change the relative location of the head plate I1 with respect to the protractor plate I6 by turning the control knob in a manner previously described. It also follows, if during this operation the draftsman removes the pressure fromthe plunger 51 that as soon as the head plate I1 and the protractor plate I5 are rotated relative to each other to a position in which .the notch engaging end 58 of the pawl 53 registers with another of the notches 52, the spring 55 will force the pawl 53 into engagement therewith and through the interaction of the link 88 and Athe gear sector 63 return the plunger 51 to the position'it occupied prior to the above described operation.

In performing certain drafting operations it may be desired to have the scales freely rotatable to various positions without interference by the locking pawl 53. I have accordingly provided means for holding the operating plunger 51 in pawl releasing position as byforming a projection 1I on the control knob 31 which depends downwardly and is arranged to engage' a bayonet recess 12 provided 'in the upper surface of the plunger 51. A thumb piece 14 is formed on one end of the plunger 51 and is preferably cylindrical in shape so that it may be grasped by the draftsman and rotated after it has been moved to disengaged position so as lto cause the projection 1I to engage a toe portion 13 of the bayonet recess 12 and prevent the operation of the spring l55 from restoring the parts to their original or non-operated position. l

I prefer to-provide a bottom cover plate 15 which is disposed below the head .plate I1 and substantially in the plane of the iiange 81a so as to provide a cover for .the linlr 68 and the pawl 53.` The cover plate 15 maybe attached to the head plate I1 in anysuitable manner. It will be observed that by ,utilizing the arrangements of parts described hereinbefore that thedraftsman may, by placing .the plunger 51 in an operated position so as to disengage'the pawl 53 from the notches 52 `provided in the notch plate 5I, rotate the head plate I1 and the scales attached thereto to any desired angular position relative to the base line 23.

lt will be further noted that this operation of rotating the scales 2l and 22 may be continued throughout a full circle of 360 degree movement without interfering or coming into contact with the parallel mechanism attached to the shank I and 'the body portion 3| thereof.

In order that the head plate I1 may be securely locked in any desired angular position relative to thefprotractor plate I6, particularly when such desired position is different from the positions provided bythe previously described pawl type locking device, I provide a clamping mechanism which,A in the preferred form of my invention,y is constructed as illustrated in Fig. 4. The clampingy mechanism includes an upstanding threaded rod or machine screw 15a which is threadedly secured to the hea'd plate I1 and arranged to extend thereabove and be loosely encircled by 'af clamping member 15b which is provided with a tapered face 15c arranged to extend beneath a similar beveled edge of the protractor plate IB and over the upper surface of the notch plate I. The clamping member 15b is nonrotatably seated in a recess d and adapted to have its outer edge rest upon a projection 15e disposed in the bottom of said recess so that a nut threaded on to the screw 15a may be rotated as by a handle 1li to force the clamping member' 15b downwardly. Downward movement of i the clamping member 15b willcause it to pivot,

on the projection 15e and clamp the edge of the notch plate 5I between the member 15b and the head plate I1.. Inasmuch as the notch plate 5I is rigidly secured to the protractor plate I5, it will be seen that this operation will lock the protractor plate I8 and the head plate I1 securely together.

I have illustrated in Fig. 5 a second type o1' drafting machine which also employs a protraetorA and scale supporting head of my invention. This machine may be attached to the drawing board or table 4 by means of the supporting or clamping bracket 3. A hinge member 15 is plvotally attached to the bracket member 3 as by means of a pivot 11 which lies substantially in the plane of the drawing board 4. This type of parallel mechanism includes a pair of arms 18 and 19 which are pivotally attached to the hinge member 16 as by means of pivots 80 and 8l. The arm members 18 and 19 extend from the hinge member 16 in a parallel relation relative to each other and are separately and independently pivotally secured to a ring member 82 as by means of pivot pins 83 and 84. 'Ihe pins 83 and 84 are spaced apart a distance equal to the spacing between the pivots 89 and BI and the rod members 18 and 19 are made of equal length as measured between the pivot points provided at each'end thereof. The ring member 82 carries a second pair of pivot pins 85 and 8S which are disposed Y in right angle locations relative to the locations of the previously described pivot pins 83 and 84,

and pivotally attach to said ring member 82 another pair of parallel rod members 81 and 88. ' Ihe rod members 81 and 88 are also pivotally attached to a protractor head frame member 89 as by means of pivot pins 99 and 9I.

The pivot pins 80, BI, 83, etc., may be constructed in the same manner as the construction of pivot point 98 which is illustrated in Fig. '1. Such pivot point may include a bolt or other suitable fastening means 92 which is threadedly engaged with the protractor head frame member 89 and is employed to secure thereto a ball bearing 93 through clamping action exerted on the inner race 94 thereof between the head of the Abolt 92 and a washer 95 disposed between the innerA race 94' and the protractor head frame member 89. An outer race 96 of the ball bearing 93 is secured in a recess 91 provided in the end of the arm 88 by means of a turned in liange 9B provided around the lower edge of the recess 91 and further by means of a snap ring 99 which mutually engages an annular recess |00 and the outer race 95 of the ball bearing 93. `I prefer to employ a snap cover IOI which is carried by a ledge. |02 in the recess 91 for covering the bolt 92 and providing a nished exterior appearance.

In view of the fact that each-rod of a pair is of the same effective length as the companion rod, and in'view of the fact that the spacing between the pivot pins 80 and 8l is made the same as the spacing between the pivot pins 83 and 84 and that the spacing between the pivot pins 85 and 85 is'made equal to the spacing of the pivot pins 9II and 9|, it follows that the protractor head frame member 89 may be moved in a translatory fashion' over the surface of the drawing board 4, such movement being permitted by the the latter carrying supporting members I9 and 20 to which are attached the drafting scales or straight edges 2| and 22. In order that the protractor plate I6 may be maintained at a fixed angular position with respect to` the base line Iii, I securely attach said protractor plate I6 to the body portion 3| of the protractor head frame member 80 as by means of screws or bolts 25,. The heads of the screws 25 are included in the recess 24 formed in the body portion 3| and the screws extend through suitable holes 26 and into threaded .engagement with the protractor plate I6. It follows therefore that the protractor plate I6 must be maintained in a fixed angular position relative to the base line' i4 since the protractor head frame member 80 to which it is securely attached is, as has been previously shown, maintained in such xed location.

In order that the head plate I1 and the scales 2| and 22 carried thereby may be manually rotated to any desired angular position relative to the base line I4, I secure the head plate I1 to the sleeve 33 and attach the control knob 31 thereto in the same manner as described hereinbefore.

In this form of the device of my invention, I also incorporate the spring pressed pawl 53 which is arranged to engage each of the, plurality of notches 52 provided in the notch plate 5| disposed immediately below and attached to the protractor plate I6. The mechanism for operating the pawl 53 is similar to that previously described in that it includes the shaft Btwhich is operably connected to the pawl 53 by the link 68.

Rotation of the shaft 64 will actuate the link 83 so as to move the pawl 53 out of engagement y with the notches 52 against the action of the spring opposing this movement. In this ernv bodiment of my invention, illustrated in Figs. 5 through 8, I prefer to employ an alternative means for rotating the shaft 64. This means may portion of the control mob 31.

The lever |03 is preferably provided with a hand contacting portion |06 `which may be of-a suitable thermo-plastic material, such as Bakelite, molded about the edge of the lever |03 and arranged to protrude from the horizontal recess so as to provide a smooth and comfortable handle by which the lever |03 may be rotated' about its pivot pin |04. In order that movment of the lever |03 may rotate the shaft 03, I provide a link III extending between the lever |03 and one end of a bell crank |01 which is secured to the upper end of the shaft 84 as by means of a pair of nuts |08 and |00. The link III may be attached to the bell crank |01 by a pivot pin I|0 and to the lever |03 by means of a pivot I l2.

It will be seen that movement of the lever |33 in an inward direction with respect to the control knob 31 will move the link III and the recess |23 in one side of the lever |20 near the bell crank |01 so as' to impart a rotary motion to the shaft 04 to disengage the pawl 53 from the notches 52 in the notch plate 5l. It will be further observed that the action of the spring 55 tending to restore the pawl 53 into a notch 5 engaging position will also rotate the shaft 64 in a direction reverse to that Just described so as to return the lever |03 to a non-operated position.

For the reasons hereinbefore stated,'I prefer to arrange the mechanism so that the protractor release device may be locked in `a released position. This may be accomplished, as illustrated in Figs. 6 and 8, by the employment of a locking plunger |I3 which is slidably mounted in a hole I I4 and normally urged upwardly by means of a spring IIS contained in a recess IIS provided in the control knob 31 and confined between the bottom of the recess IIS and a knob or thumb piece ||1 aiilxed to the upper end of 20 the locking plunger II3. The locking plunger I|3 is provided at its lower end with an annular recess I I 8, the plunger being located in such aposition as to lie directly over a notch I|0 provided inthe outer edge of the lever |03 when said lever is moved to its operated position. c

It will, be observed that 'should the plunger I 3 be depressed when the lever |03 is moved inward to its operated position, the lower end of the plunger II3 will be inserted into the notch |I9 provided in the platev |03 and thereby prevent the outward movement of the lever |03 as a result of the force of the spring 55. The annular recess IIB is made, with a width slightly in excess of the thickness of the lever |03 so that when the plunger I I3 is depressed with the lever |03 in its operated position and thelever |03 is ,then released, the side of the notch IIIl provided therein will engage the annular recess |I8 and prevent the spring H5 from moving the plunger II3 upwardly to release the lever |03.

It will be observed therefore that this operation will lock the lever |03 and the pawl 53 connected thereto in a disengaged position with respect to the locking plate El. It will be further observed that in order to release the locking plunger I|3 it is only necessaryl to move the lever |03 in the releasing direction and thereby disengage the edge of the notch IIO from the annular recess |I8 to allow the spring IIS to move the locking. plunger H3 upwardly vinto a disengaged position. This type of protractor head may also include the clamping device 15b and the bottom cover plate 15.

I have illustrated in Figs. 9 and 12 an alternative method of operating the release mecha nism for the protractor head as including a lever |20 which may be used to rotate the shaft '04 and thereby actuate the pawl 53. As .illusshaft ,64. The lever |20 is arranged to protrude through a suitable slot. |22 provided irlr the periphery of the control knob 31' so as -to have ag the end thereof disposed exteriorly of said knob and be readily accessible to a draftsman employing this machine. I provide a notch or finger',

protruding end thereof and provide a boss or protuberance |26 on the periphery -of the control knob 31 so that the lever |20 may be actuated by an operator thereof placing a thumb to the left of the boss |24 and a ilnger to the right ofthe lever |20 to engage the recess |2375 provided therein and moving the lever |20 toward the boss |24 by exerting pressure between the thumb and finger. Inasmuch' as the lever |20 is keyed to the shaft 5I, it will be observedl that such operation will rotate the shaft and.

the notch plate will restore the lever |20 tol its non-operated position whenever it is released by the draftsman. l

1n order that the lever m may be locked in' an operated position corresponding to the released position of the protractor head, I prefer,

to form the previously described slot |22 which is provided in the periphery of the control knob 01 with a J or bayonet shape which includes a toe portion |25. I prefer to make thelever |20 of relatively thin and resilient material so that when moved to the operated position it may be deflected -or sprung downwardly to engage the toe portion |25 of the J slot and be held thereby in the operated position corresponding to thereleased `position of the` protractor head.

I pr'efer to form the toe portion |25 of the J shaped'slot |22 with an undercut portion |26 adapted to receive the lever |20 when it is pressed into the locked position so as to lprevent the resilience of .the lever |20 from disengaging said lever from the toe portion of the J slot.

In Figs. and 1l, I have illustrated another alternative form of the protractor releasing mechanism of my invention which will find favor in those applications where a lever protruding from the side of the control knob 31 is undesirable. In this modification, I prefer to effect the release of the pawl 53 from the notch plate 5| in the manner previously described; namely, by rotating the shaft 64. In this form of my invention I prefer to accomplish this by means of an auxiliary control knob |21 which may be attached Ato an extension |20 of the shaft 00 Vby means of nuts |29 and |30 positioned above and below the knob |21. I prefer to ilt the knob |21 into a recess |3| provided in .the upper surface of the control knob 31 and to provide a finished i It will be observed in this form of my invention that, the auxiliary control knob |21 is placed in 'a position where it may be readily and easily 1manipulated by a draftsman employing this macations of the mechanism of my invention which I I have illustratedv herein, the scales 2| and 22 and the head plate -|1 to which they are amxed are positioned below the -lower-most portion of the mechanism attached to the parallel mechanism regardless of whether said parallel mechanism is of the endless band type or of the parallel arm type, and thatas a" result of this construction the scales may be moved to any desired position in a full circle without interfering .or coming into contact with said parallel mechanism.

It will also be noted that Ihave provided a number of` types of release devices for the prqtractor head, each of which overcomes the primary disadvantagesl found in drafting machines in current use today: that is to say, that each of y the release mechanisms which I have provided is so positioned and of such type as to be readily operable by a draftsman using the machine without requiring that the draftsman employ both hands ,for this operation, the devices of my invention each being readily manipulated in4 con- `iunction with the operation of rotating the protractor head by means of the saine hand which is employed to effect said rotation. I have also provided a means for locking said mechanisms in actuated by the same hand of the operator as is employedv to operate the release mechanism and to rotate the protractor head assembly.

While I have shown and described the preferred embodiment 'of my invention, I do not desire to be limited to. any of the details of construction shown or described herein, except as defined in the appended claims.

I claim:

1. A drafting machine comprising a'supporting head adapted for free movementabove a drawing board in a plane parallel thereto, frame means -extending below and rotatably supported by said their released position, said means being readily i ing said tool against rotation with respect to said frame, control means above the level of said head for actuating said locking means, in which said locking means comprises a pawl on said tool mov- `:able into and out of engagement with a portion of said frame, means guiding said pawl for movement in a fixed path toward and away from said frame. shaft means rotatable with respect to said frame and handle and extending therebetween, means adjacent said handle for rotating said shaft relative to the handle, and means for moving said pawl between released and engaged positionsin response to rotary movement of said shaft. i

2. A drafting machine comprising a supporting head. adapted for free movement above a drawing board in a plane parallel thereto, frame means extending below and rotatably supported by said head. means for maintaining said frame in fixed angular relation with respect to said 'board irrespective of movement of said head and frame over said board, a drafting tool below said head. means rotatably supporting said drafting tool from said head, a handle positioned above said head and secured to said drafting tool for rotation therewith, releasable locking means for locking said tool against rotation with respect to said frame. control means'above the level of said head for actuating said locking means. in which said locking means comprises a pawl on said tool movable into and out of engagement with a portion of said frame, means guiding said pawl for movement in a fixed path toward and away from said frame, shaft means rotatable with respect to said frame and handle and extending therebetween. means adjacent said handle for rotating said shaft relative to the handle. a mechanism 7o ing head adapted for -free movement above a 7g means extending below and rotatably supported by said head, means for-maintaining said frame in xed angular relation with respect to said board irrespective of movement of said head and frame over said board, a drafting tool below said v head, means rotatably supporting .said drafting tool from said head, a handle positioned above said head and secured to said drafting tool for rotation therewith, releasable locking means for locking said tool against rotation with respect to said frame, control means above the level of said head for actuating said locking means, in which said locking means comprises a pawl on said tool movable into and out of engagement with a portion of said frame, means guiding said pawl for movement in a fixed path toward and away from said frame, shaft means rotatable with respect to said frame and handle and extending therebetween, means adjacent said handle for rotating said shaft relative to the handle, a mechanism for transmitting rotary'motion of said shaft into reciprocating motion of said pawl, spring means urging said pawl into locking position, a notched disk included in said frame memberhaving notches at predetermined angular spacings thereon into which said pawl ts to positively restrain said tool in predetermined angular positions with respect to said frame,` said pawl being slidable on said disk between said notches therein, whereby said spring members are effective to automatically engage said pawl with a notch in said disk when said notch reaches said pawl.

4. A drafting machine comprising a supporting head adapted for free movement above a drawing board in a'plane parallel thereto, frame means extending below and rotatably supported by said head, means for maintaining said frame in fixed angular relation with respect to said board irrespective of movement of'said headand frame over said board, a drafting tool below said head, means rotatably supporting said drafting tool from said head, a handle positioned above said head and secured 'to said drafting tool for rotation therewith, releasable locking means for locking `said tool against rotation with respect to said frame, controlmeans -above the level of pawl for movement in a xed path toward and away from said frame, shaft means rotatable with respect to said frame and handle and extending therebetween, gear teeth on said shaft, a rack engaging' therewith andv etxending transversely in said handle for rotating said shaft, Aand means for moving said pawl between released and engaged positions in response to rotary movement of Said shaft. l

5. A drafting machine comprising a supporting head adapted for free movement above a drawing board in a plane parallel thereto, frame means extending below and rotatably supported by said head, means for maintaining said frame inv xed angular relation with respect to said board irrespective of movement of said head and frame over said board, a drafting tool below said head, means rotatably supporting said drafting tool fromsaid head, a handle positioned above said head and secured to said drafting tool for rotation therewith, releasable locking means for movable into and out of engagement with a portion of said frame, means guiding said pawl for movement in a ilxed path toward and away from said frame, shaft` means rotatable with respect to said frame and handle and extending therebetween, gear teeth on said shaft,'a cylindrical rack engaging therewith and extending trans'- versely in said handle for rotating said shaft, said rack being rotatable in said handle, and means for locking said rack against longitudinal movement with respect to said handle in response parallel thereto; means for maintaining said head in a fixed angular position relative to said drawing board irrespective of said translatory movement; 'a drafting tool disposed below Isaid head; pivot means mounting said drafting tool on said head for free rotation thereabout; a handle secured to said pivot means and disposed above said head for manually rotating said drafting tool; a pawl on said tool; meansmounting said pawl for movement into and out of engagement with said head; shaft means supported for rotary movement relative to said head and relative to said tool; means carried bysaid handle in a position to be operated by the same hand of an operator as is used to grasp said handle andl '7. In a drafting machine, thel combination of:

a drafting head supported for free translatory movement relative to a drawing boardin a plane parallel thereto; means for maintaining said head in a fixed angular position relative to said drawing board irrespective of said ktranslatory movement; a drafting tool; pivot means rotatably supporting said drafting tool from said head; a handle secured to said pivot means for manually rotating said drafting tool; a pawl on said .tool means mounting said pawl'for movement into and out of engagement with said head; spring means normally urging said pawl into engagement with said head; shaft means supported for rotaryv movement relative to said head and relative to said tool; means carried by said handle in a position to be operated bythe same hand of an operator as is used to grasp said handle and coupled to move said rotatable shaft; and means inter-engaging said pawl and said shafttfor moving said pawl out of engagementl with said' head in response to -rotary motion of said shaft.

8. In a drafting machine, the combination of: a drafting head supported for free translatory movement relative to a drawing board ina plane parallel thereto; means for maintaining said head in a fixed 'angular position relative to said drawing board irrespective of said translatory movement; a drafting tool; pivot means rotatably supporting said drafting tool from said head; a handle secured to said pivot means for manually rotating said drafting tool; a pawl on said tool; means mounting said pawl for movement into and out of `engagement with said head; shaft means supported for rotary movement relative to said head and relative to said tool; gear teeth on said shaft; a gear rack engaging said gear teeth for moving said shaft and mounted for slidable movement in said handle in a position to bemoved by the same hand of said locking means comprises a pawl on said tool A an operator as is used to grasp said handle; and means coupling said pawl to said shaft for moving said pawl out of engagement with said head in response to movement of said shaft.

9. In a drafting machine, the combination of: a -drafting head supported for free translatory movement relative to a drawing board in a plane parallel thereto; means for maintaining said head in aviixed angular positionvrelative to said drawing board irrespective of said translatory movement; a drafting tool; pivot meansy rotatably supporting said drafting tool from said head; a. handle secured to said `pivot means for manually rotating said drafting tool; a pawl on said tool; means mounting said pawl formovement into and out of engagement with said head; shaft means supported for rotary movement relative to said head and relative to said tool; means carried by said handle for moving said rotatable shaft comprising a bell crank secured to said shaft, a lever pivotally secured to said handle in Aa position to be moved by the same hand of an operator as is used to grasp said handle, and a link coupling said lever to said bell crank; and means coupling said pawl to said shaft for moving said pawlout of engagement with said head in response to movement of said shaft.

10. In a drafting machine. the combination of: a drafting head supported for free translatory movement relative to a drawing board in a plane parallel thereto; means for maintaining saidhead in anxed angular position relative to said drawing board irrespective of said translatory movement; a drafting tool; pivot means rotatably supporting said, drafting tool 'from said head: a handle secured to said pivot means for manually'rotating said drafting tool; a pawl on said tool; means mounting said pawl for movement into and out of engagement with said head; shaft means supported for rotaryA `movement relative to said head and relative to said tool; lever means carried by said shaft and disposedadjacent said handle in a position to be moved by the same hand of an operator as is used to grasp said handle and coupled to rotate said shaft; and means coupling said pawl to said shaft for moving said pawl out ,of engagement with said head in response to movement of said shaft. i il. In a drafting machine, the combination of: a drafting head supported for free translatory movement relative to a drawing board in a plane parallel thereto; means for maintaining said head in a fixed angular positionrelative to said drawing board irrespective of said translatory movement; a drafting tool; pivot means rotatably supporting said drafting tool from said head; a handle securedv to said pivot means for manually rotating said drafting tool; a pawl on said tool; means mounting said pawl for movement into and out of engagement with said head; shaft means supported' for rotary move- -ment relative `to said head and relative to said tive thereto having a drafting tool pivotally se-l cured to said head for manual rotation relative to said head and relative to said tool; means coupling said pawl to one end of said shaft for moving said pawl between said engaged and disengaged positions in response to movement of said shaft; `control means for moving said shaft carried by said handle in a position to be operated by the same hand of an operator as is used to grasp said handle and coupled to the other end of said rotatable shaft; and manually operable restraining means' 'associated with said control means for restraining said shaft in a position corresponding to the disengaged position of said pawl.

13. In combination with a` drafting machine which includes a drafting head supported upon a parallel mechanism for free translatory movement relative to a drawing board in a plane parallel thereto and in a fixed angular position relative thereto having a drafting tool pivotally secured to said head for manual rotation relative thereto by a handle coupledl to said tool and disposed above said head and having a device for securing said tool againstpivotal movement -rel ative to said head comprising a pawl mounted on said tool for movement between a position engaging said head and a position disengaged therefrom, a pawl control. device including: shaft means supported for rotary movement relative to said tool; means coupling said shaft to move said pawl between said engaged and said disengaged positions gear teeth on said shaft; a gear rack; a bore in said handle slidably and rotatably receiving said gear rack for disposing said rack in a position engaging said gear teeth and in a positon to be moved by the same hand of an operator as is used to grasp said handle; pin

means extending into said bore; a slot in said allel thereto and in a nxed angular position rel- A ative thereto having adrafting tool pivotally secured to said head for manual rotation relative thereto by a handle coupled to said tool andl disposed above said head and having a device for securing said tool against pivotal movement rel Aative to said head comprising a pawl mounted on said tool for movement between a position engaging` said head and'- a position disengaged therefrom. a, pawl control device including: a lever carried by said handle in a positionl to be engaged by the same hand of an operator as is used to grasp said handle and mounted for/pivotal movement relative thereto between a securvso ing position and a released positlonfcorresponding, respectively, to said engaged and said disengaged positions of said'l'iawl;` means coupling said lever to said pawl for moving saidpawlf beu tween saidvengaged and said disengaged posimeans mounting said plunger means for movement from a disengaged position to an engaged position extending across the path traversed by said lever in moving from said released position to said securing position, whereby movement of said plunger to said engaged position when said lever is in said released position prevents movement of said lever to said securing position.

15. In combination with a drafting machine which includesl a drafting head supported upon a parallel mechanism for free translatory movement relative to a drawing board in a plane parallel thereto and in a fixed angular position relative thereto having a drafting tool pivotally secured to said head for manual rotation relative thereto by a handle coupled to said tool and disposed above said. headand having a device for securing said tool against pivotal movement relative to said head comprising a pawl mounted on said tool for movement between a position engaging said head and a position disengaged therefrom; a pawl control device including: a slot in said handle; a leverextending through said slot and mounted on said handle for plvotal movement along said slot between a securing position and a released position corresponding, respectively, to said engaged and said disengaged positions of said pawl; means coupling said lever to said pawl for moving said pawl between said engaged and said disengaged positions; and a shoulder formed in said slot near the end thereof corresponding to the released position of said lever for engaging and holding said lever in said released position.

16. In'combinationwith a drafting machine which includes a drafting head supported upon a parallel mechanism for free translatory movement relative to a drawing board in a plane paring said head and a position disengaged therefrom, a pawl control device including: a slot in said handle; a flexible lever extending through said slot and mounted on said handle for pivotal movement along said slot between a securing position andl a lreleased position corresponding, respectively, to said engaged and said disengaged positions of said pawl; means coupling said lever to said pawl for moving said pawl between said engaged and said disengaged positions; a shoulder formed in said slot near the end thereof corresponding to the released position of said lever. whereby'lsaid lever may be moved along said slot to said released position and then flexed to dispose said lever behind said shoulder and prevent a reverse movement of said lever; and an overhanging toe portion associated with said shoulder and disposed in a position to entend over said lever and hold said lever behind said shoulder.

17. In a drafting machine, the combination of: a drafting head supported for free translatory movement relative to a drawing board in a plane parallel thereto: means for maintaining said head in a xed angular position relative to said drawing board irrespective of said translatory movement; a drafting tool; pivot means rotatably supporting said drafting tool from said head; a handle secured to said pivot means for manually rotating said drafting tool; a pawl on said tool; means mounting said pawl for movement into and out of engagement with said head; shaft means below the top of said handle supported for rotary movement relative to said head and relative to said tool; means coupling said shaft to move said pawl out of engagement with said head; a bell crank secured to said shaft; a

lever carriedby said handle in a position to be engaged by 'the same hand of an operator as is used to grasp said handle; means pivotally mounting said lever on said handle for pivotal movement inwardly and outwardly relative to said handle; recess means in the side of said handle for receiving said lever in its inward position; and a link coupling said lever to said bell crank for rotating said shaft in response to pivotalmovement of said lever.

VARD B. WALLACE.

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