US2682708A - Portable drafting machine - Google Patents

Description

y 1954 G. c. LUEBKEMAN 2,682,708

PORTABLE DRAFTING MACHINE Filed May 3, 1952 INVENTOR.

. E Gem-ye C. Luefemarz WM xi"? Patented July 6, 1954 PORTABLE DRAFTING MACHINE George C. Luebkeman, Cincinnati, Ohio Application May 3, 1952, Serial No. 285,879

9 Claims.

This invention relates to drafting machines and has for an object the provision of a primarily portable device which can be conveniently carried in the coat pocket or in the briefcase and which is primarily adapted for comfortable and accurate use and ambulatory adjustment with one hand without necessitating the employment of fastening means on the drawing surface.

Another object of the invention is to provide a simple, reliable and relatively inexpensive device for the stated purposes which device affords to the user an exceptionally easy and rapid adjustment to the requirements in making or check- 7 ing a drawing of any size.

A further object of the invention is to provide a machine of this character which is provided with means adapting it to use in environments other than on a drawing board without loss of its advantages of easy and extremely flexible ambulatory and swinging adjustments.

These and other important objects, hereinafter made apparent, are attained by the means described herein and exemplified in the accompanying drawings, in which:

Fig. 1 is a perspective view of a pocket drafting machine embodying the invention operatively held by the users hand.

Fig. 2 is a top plan view of the device, partly broken away.

Fig. 3 is a cross sectional view taken on line 33 of Fig. 2. s

Fig. 4 is a cross sectional view taken on line 4-4 of Fig. 2.

Fig. 5 is a cross sectional view taken on line 5--5 of Fig. 2. V

Fig. 6 is a cross sectional view taken on line .65 Of Fig. 2.

Fig. 7 is a cross sectional view showing a means for securing the machine to a small portable drawing board.

It is known in the art to employ a jointed parallel arm assembly having at its opposite ends a drafting square and a base or another drafting instrument, the base forming portion being either permanently or temporarily secured to the drawing board in use.

It is the particular object of the invention to provide a drafting machine that is primarily adapted for convenient and accurate use without the necessity of employing any securing means, but is nevertheless capable of exceptionally easy adjustment which affords the operator a reliable, comfortable and very flexible control of the machine in its desired relation to any portion of a drawing surface. The manipulation is under practically all circumstances controlled by one hand of the user while the users other hand is free to execute the drawing or checking of lines with a pencil or comparable instrument.

In its preferred form the drafting machine employs as a base or normally stationary memher a protractor 8, which may be of transparent plastic material, having a true diameter line 9 thereon which is parallel to a straight edge In of the protractor. At the true radial center of the protractor 8 there is provided a finger piece II with a reduced cylindrical stem [2 which may turn freely and reciprocate slightly in a bore l3 that is centered exactly at the true radial center of the protractor. Counterbores I4 and 15 are provided in the top and. bottom faces of the protractor to selectively receive the upper and lower disc-like enlargements I6 and I1 respectively on the ends of stem l2 which spaces said enlargements from each other at a distance sufficient to allow the enlargement I! to shift into or slightly out of counterbore I5 and selectively engage the antiskid surface l8 of enlargement I! on a drawing surface when digital pressure is applied on top of piece H and to thus permit the protractor 8 to be adjusted about its true radial center. The finger piece II also has an axial bore [9 to admit a pencil point or a push pin for marking or for temporarily holding the true radial center on the drawing if desired when the drawing and the device are left idle. The

vbase or protractor 8 also has bores 20-20 adjacent opposite ends of the true diameter line 9 for marking or securing purposes if desired. A suitable clamp such as 2| may be employed having a slender lug 22 for entry into one of the bores [9 or 20 for temporarily fixing the machine on a small drawing board 23 if such a combination is wanted.

The semicircular margin of protractor 8 is suitably graduated as at 24 through one hundred eighty degrees on one side of diameter line 9 and is provided in known manner with reversely readable indicia 25 and 26.

The important feature of the present drafting machine of the invention is its combination of simple means which afford an improved maneuverability of the machine in a stepwise ambulatory fashion over successive areas of a drawing surface and the relative adjustment of its members on opposite ends of the jointed arm assembly 21 to carry on the drafting or checking operaticns without the use of fastening means. An L-square indicated generally at 2B or any other drawing implement is pivotally connected at one end of the arm assembly 27, which assembly is pivoted at its opposite end to the base or protractor member 8.

As shown in the drawings, assembly 21 comprises an annular joint member 29 which has .the ends of a pair of parallel links 3D-3| pivoted on its top at diametrically opposite sides thereof .by means of rivets at 32 and 33. The links 30 and 3| have their remaining ends pivoted on top of the L-square on rivets 34 and 35 that are located on the longitudinal center of the drawing scale 36 which may be an integral or a removable part of said'L-square 28. An upstanding finger knob 3.1 is mounted between. the pivots 34 and 35 and relatively closer to the pivot 34 so that the stem of the knob 31 serves as a stop for arm to limit the pivotal movement of L-square-28- in one direction about its pivots 34 and 35. A

stop pin 38 (or in lieu thereof another knobsimilar to 31) located relatively. elose-tothe pivot.

35, limits pivotal movement of arm 3| in the opposite direction. The links 3ll'and 31. cannot approach each other closely enough toimpair the accuracy of their parallel relation.

The remaining links 39 and 40 respectively have ends pivoted on rivets 4| and 42 to the lower face of joint member 23 atdametrically opposite sides. thereof. I preferably dimple the-member 29 to provide shallow dished places inits top face to receive the heads of the pivot forming rivets 4! and 42' in substantially countersunkrelation with the top face. of. member 29. The member 2'9'has the. heads of rivets 32' and 33 substantially countersunk in shallow dished places in the bottom face of said member 29. This arrangement affords a sturdy mounting. and. interference free operation of the pivoted links on the annular joint member 29.

The remaining ends of links 39' and 40: are pivotally connected to the top face of the protractor or base member 8 by means of rivets 43 and 44. The L.-square 28' is thusshiftable relative to the straight edge IU of the protractor with the scale arm 36 in parallel relation in known manner of'operation of a drafting machine;

In order to enable the, user. to holdthe pro.- tra-ctor 8' in non-shifting. relation at a selected place on the drawing with one hand and also permit the same hand to manipulate the L-square 28 throughout an area of the drawing sheet adjacent the protractor I have provided'on the bottom face of 'the. protractor. or base 8; sufficient antiskid surface.45.to,enab1e saidbase to beheld in position. on the drawing while the weight oil the users-left-hand rests the-top ofthe said base. For this purpose several patches-or areas 45 of "antiskid surfacing may be used. and may be formed of dried rubber cement. film. or, fine grit abrasive. suitably fixed. on the base.

A.- slightly cupped hand rest indicatedgenera-lly at. 46 is mountedv for rotation on. top. of base-8 and in parallelism. with the latter. The hand rest 46 comprises an upper disc portion. which overhangs a considerable areaof the base 8 and is dished or cupped at 48. in. the upper center thereof so that the heel or outer bottom carpal portion 49 of a users hand 50 may comfortably and non-shiftably rest thereon while permitting the hand toswivel with its supporting rest relative to the base 8 while. the latter is held against sliding or turning on the drawing under the weight of the hand 50 on said hand rest. The disc 41 has an integral hub 5| on the bottom and is rotatably held in slightly spaced relation by a center pin or rivet 52, A simple ball race 53 is interposed between base 8 and disc 4! and it turns freely about the circumference of hub 5|. Bea-ring balls 54-disposed in individual holes in theball race 53 afford a free turning and steady support for the disc as the hub and disc may turn on the ball bearing support with a minimumof wear. on the center pin 52. Disc 4'! may be of a diameter sufficient to overhang the finger piece II by peripherally cutting or notching the disc as at 55. The notch can be brought into registry with the top of the finger piece to render the latter accessible when desired.

It istobe: observed thatithe outer circumference of the race member 53 serves as a limit stop for either the link 39 or the link 48 when said links are turned on their pivots 43 and 45. The links-39-and40 are thus also prevented from so closely approaching each other in their movements as to impair the parallel positioning.

The holdingof the protractor 8 with its straight edge l0..on a given line will be readily understood'since either the heel of the hand or one or more fingers of the hand 50 may comfortably rest in the cupped center 48 of the hand rest 46 while the index finger ofthe same-hand may seat in the cupped top 56-of-the finger knob 3-? on the L-square 28. The index finger may be extended or retracted to'shift the L-square relative to the protractor and that part ofv the hand which rests on member may turn and swing as the hand rest 46-rotates on itsbearing support without relaxingthecomfortable resting of the weightof the handon said support and without danger of accidental shifting of the protractor base 8 on the-drawingsurface. The ability of different users 'witheitherlarge or, small hands to quickly adapt themselves to an individually comfortable, rapid and easy mode of operation is to be noted. It'willbe-understood. the usualoperations'of shifting the L-sq-uare to successive positions in'the fieldofadjustment of-the L-square about theprotractor; base 8" may be advantageously performed: by the same hand which rests on" member 46 and: thus holds the protractor against shifting on' the drawing. When lines are to bedrawn the l.--square is heldfirmly by digital. pressure on knob 31 while the position of the base-8 ismaintained bytheweight of the users'hand on member 461 In order that. the digital;holding of, the L- square- 28*and the" shifting of said" square rela tive to the protractor may be suited'to the greatest ease andcomfort'for the bandit of 'theuser I prefer to. providethedrawing scale members 36 and 36l' of the' l.'-square and also the link 3.3 with tappedbores 310 located at suitable distances away from' the finger knob 37 and one or more optionally. employed finger knobs 310i) are provided for selective mounting in one or more of. said bores, Inthisway thedisposition of'the finger knobor knobs may be accommodated to facile operation by almost any person regardless of thesize or of the normal or handicapped condition of, the. hand. to be used for controllingv the machine. The selectively employedifinger knobsf31'00i are desirably lower than the finger knob 31 but all of said knobs have concaved tops toafford easy digital control of the machine and. a. maximum. comfortable support for. the, entire hand.

A. person. whose hand is supple and. whose fingers are. relatively nimble. can hold the L- square in an adiusteolzposition and'then lightly shift the base 8. to another place for drawing in another area. by manipulation v Withone hand only. The user may. conveniently turn the hand rest to bring. notch 55. in registry. above finger piece ll and then placedigital pressure on the latter and thereafter adjust the protractor about its radial center. Ordinarily. the right. hand or the pencil. in. thesright hand-is employed. in assisting in the last mentioned two operations since the act of drawing is momentarily interrupted.

One who draws with the left hand can manipulate the machine as illustrated with his right hand by disposing straight edge it on the perpendicular instead of horizontal. Obviously the machines can be made for left-handed persons by pivoting links 39 and 40 on the left-hand side of the protractor 8 instead of on the righthand side as herein illustrated.

For adapting the instrument to use on a drawing supported by or scribed on a ferrous metal surface I have provided permanent magnets 5! embedded close to the bottom surface of protractor 8 to materially assist in maintaining the position of the latter. The device is thus made available for use in making original layouts on sheet metal and flat surfaces of castings and in checking the same.

The parts other than the jointed parallel arm assembly are desirably made of transparent plastic materials from which they can be inexpensively formed into light weight drafting machines that can be easily carried about in the monly found on drafting boards, and if a temporary slidable attachment is desired, the holes 20-29 may receive holding lugs on any suitable friction slide to connect said base with the parallel straight edge device carried by the drafting board.

It is to be observed that by moving the links 39 and 40 about their pivots until arm 39 engages the ball race 53 as a stop, the joint member 39 will assume a position below the straight edge l0 and close to the protractor. The arm assembly can then be jack knifed to a folded position with the L-square superposed over the protractor. When thus folded the device occupies a minimum of space and is storable in the briefcase or the pocket without liklihood of accidental damage.

The machine of the invention will be understood to be subject to modification within the spirit of the invention and the scope of the appended claims.

What is claimed is:

1. In a portable drafting machine the combination with a flexible unit comprising a drafting instrument and a jointed parallel arm assembly having said instrument pivotally connected to one end thereof, of a base pivotally connected to the other end of said arm assembly, an antiskid bottom on said base, a hand rest connected to the top of the base for relative swivel movement in parallelism with the top of said base, and a finger knob mounted on said flexible unit.

2. In a portable drafting machine the combination of a base having an antiskid bottom, a swiveled hand rest connected to the top of the base, a jointed parallel arm assembly pivoted at one end on top of the base, a finger piece extending through the base and adapted for relative rotation and limited axial reciprocation therein, said finger piece having an antiskid bottom end, a jointed parallel arm assembly pivoted at one end on the top of said base, a drafting instrument pivotally connected to the opposite end of said arm assembly and a finger knob selectively connected to said arm assembly and said instrument.

3. A portable drafting machine comprising a protractor having an antiskid bottom face, a hand rest swiveled at its center on top of said protractor, a parallel arm assembly including a joint member and two pairs of links each having an end pivotally connected thereto in known manner, a drafting instrument having the remaining ends of one pair of links pivotally connected thereto, the remaining ends of the other pair of said links being pivoted to the top of the protractor, and a finger knob on the drafting instrument.

4. In a device of the class described a protractor having an antiskid bottom face, a hand rest swiveled at its center on top of the protractor,

a drawing instrument, and a parallel arm as-.

sembly connected at its opposite ends on top of said protractor and said instrument respectively.

5. The combination as set forth in claim 4 characterized by the provision of a rotatable finger piece extending through the protractor at the true radial center thereof, said finger piece having an antiskid bottom end adapted to assume a selected position at and slightly below the bottom face of the protractor.

6. The combination as set forth in claim 4 characterized by the provision of a finger piece adapted for rotation and slight reciprocation in the protractor at the true radial center thereof, and by the provision of a notch in the edge of the hand rest adapted for radial alignment with the top of the finger piece and affording digital access to the top of the latter.

7. The combination as set forth in claim 4 characterized by the provision of a finger knob selectively mounted on top of the drawing instrument and arm assembly to permit one part of a users hand to be supported on the hand rest for swiveled movement therewith relative to the protractor for retaining the latter against shifting on a support surface, while a finger of the same hand controls and selectively shifts the drawing instrument relative to the protractor.

8. The combination as set forth in claim 4 characterized by the provision of permanent magnets embedded in the bottom of the protractor.

9. In a portable drafting machine, a base having an antiskid bottom surface, a swiveled hand rest on top of the base, a jointed parallel arm assembly comprising a first pair of parallel links pivoted at one end at relatively opposite sides of the swivel mounting of the hand rest on top of the base whereby the said mounting serves as a stop limiting pivotal movement of the respective links on the protractor, a second pair of parallel links comprising said arm assembly being pivoted in spaced relation on the drawing instrument, and means on said instrument limiting pivotal movement of said second pair of parallel links.

References Cited in the file of this patent UNITED STATES PATENTS Number

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