US1746830A - Drafting machine - Google Patents

Description

v'. S. HARMON DRAFTING MACHINE Feb, 11, 1930.

Filed Nov. ll 1927 2 Sheets-Sheet @1 0%. wm, QM QW QNI hm,

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DRAFTING MACHINE Filed Nov. 11. 1927 2 sheets-sheet 2 7@ "#*fff-wm Patented Feb. i1, 1930 UNITED STATES WINFIELD S. HARMON, OF CHICAGO, ILLINOIS DRAFTING MACHINE Application led November 11, 1927. Serial No. 232,490.

This invention relates to drafting machines and has for an object to provide meansfor adjustably supporting a straight edge in operable relation with a drawing board. An-

other object of the invention is to provide a carriage for the straight edge, movable in a track for maintaining the straight edge in true alignment. A further object is4 to provide a mechanism that is self-adjusting for 1o taking up the wear of the movable parts so as to permit precise and accurate work at all times. A further object is to provide novel clutch means for securing the carriage in a definite position relative to the board, but

permitting of angular adjustment of the straight edge and especially adapted to support the carriage kand straight edge `when mounted on an inclined board. It consists in certain features and elements of construction,

2o herein shown and described and as indicated by the claims.

In the drawings:

Figure 1 is a plan view of a drawing board equipped with my improved drafting machine.

Figure 2 is an enlarged view in side elevation of the drafting machine mounted on a drawing board, the free end of the straight edge being broken away to show the bearing 3o support.

Figure 3 is a bottom plan view of a straight edge, showing the clutch mechanism mounted thereon.

Figure 4 is an enlarged vertical longitudinal section through the carriage and straight edge taken at line 1 -4, Figure 1.

Figure 5 is an end view 0f the carriage, showing the relative positions of the track rollers and the tapered bearing for the pivotal support of the straight edge.

Figure 6 is a vertical section through the auxiliary carriage and the transverse straight edge, taken at line 6-6 on Figure 1.

Figure-7 is-a cross section through the end of the transverse straight edge, taken at line 7 7 on Figure 1.

As shown in the drawings, a drawing board is indicated at l, having a longitudinally extending straight edge, 2, and a transversely straight edge, 3, slidably supported on the straight edge, 2, and movable therewith over said drawing board. For convenience and for carrying out certain conventional methods of drafting, the longitudinally extending straight edge, 2, is adjustably secured at its left-hand end to avcarriage or head, 4,' mounted for rolling support in a track or guideway, 5, secured to the left-hand end of said board. These straight edges are preferably of metal so as to provide suiiicient 50 rigidity to overcome flexing when the free ends of said straight edge members are grasped for movement as well as to insure at all times a substantially true working edge. The longitudinally extending straight edge, 2, is pivotally connected to and removably mounted on the carriage plate, 6, for providing angular adjustment of the straight edge on the board; the range of such adjustment being limited to the particular requirements 7o of the user. This pivotal connection, which is centrally aligned over the track, 5, comprises a tapered stud, 7, secured to and projecting from the underside of said straight edge, 2, having journaled support in anv internally tapered bearing boss, 8,secured to the lower side of the carriage plate, 6. It is apparent that the weight of the straight edge will normally tend to seat the stud, 7, tightl in its bearing and eliminate practically all play at this connection. Further, the gradual wear of the pivotal connection is compensated for by the tapered stud seating itself deeper into the bearing, which provides for a true pivotal swinging movement of the as straight edge indefinitely. l It is desirable to pivot the straight edge, 2, to the carriage as close as possible to the edge of the board so that the extension arm, 2a, of said straight edge, 2, beyond said pivot, is of 9o a maximum length. This arm, 2, may be any shape and as herein shown is cut back to provide an indicating edge, 2b, for alignment with certain scale marks on the graduated sector, 11, of the carriage plate, 6, for accurately positioning said straight edge at various angular adjustments. Circumscribing said sector and in radial alignment with the points thereof, is a segment of teeth, 12, on the upper surface of plate, 6, adapted to be selectively engaged by teeth, 13, on the underside and at the outer end of the arm, 2, for securing said straight edge in the various positions of angular adjustment on the carriage. The graduation of the sector and the teeth of the segment are radially aligned with respect to the tapered pivot, of the straightedge. It is preferable that the arm, 2, be as long as possible so that the radius of the sector may be at a maximum to provide precise and exact angular adjustment of the straight edge about its tapered pivot. The straight edge, 2, is adapted to be locked to the carriage, (with teeth, 12 and 13, intermeshed at any of the various positions of adjustment,) by a clamping plate, 14, fixed to the lower end of a non-circular stud, 15, which extends upward through the outer end of the arm, 2a, and is threaded at its upper end to receive a wing nut, 16. This stud is positioned so that the upper surface of the clamping plate, 14, will be moved into clamping engagement with the underside of the ca rriage plate, 6, as the wing nut, 16, draws said stud through the plate, 6, and the adj ustnient is rendered positive by the interengagement of the Segment teeth, 12, with the teeth, 13.

The carriage plate, 6, is provided with a pair of fixed transversely spaced, downwardly depending tapered studs, 20, on which are joui'- naled tapered rollers, 21. Theserollers are positioned for movement in a guideway, 22, of tapered cross section, formed in the track, 5, on the edge of said board. Said guideway comprises a pair of outwardly diverging walls, 22a, inclined at an angle substantially equal to the taper of the rollers so that when said rollers are positioned therein they tend to seat themselves tightly, whereby the carriage may be moved to various positions in substantially a true plane. The tapered rollers will seat deeper in the groove, as they gradually wear and so with respect to the tapered stud, the roller will be forced farther onto the tapered shank as the bore is gradually worn larger. The walls, 22, of the guideway, 22, terminate in vertical walls, 22", parallel to each other and provide rolling contact for the cylindrical parts, 21a, of said rollers which are slightly less in diameter than the distance between said walls, 22h, to provide rolling clearance. It has been found that in using machines of this character it is the tendency of the average draftsman to grasp the' straight edge when it is desirous of moving the same across the board. Thus the present construction particularly reacts to this sort of treatment; by grasping the straight edge at most any point (preferably near'the right hand end) and moving it in a desired direction the tapered surfaces of the rollers tend to climb the tapered or diverging walls, 22, until the cylindrical part, 21a, contacts with the vertical walls, 22h, providing rolling support for the carriage and straight edge during the transverse movement. It will be seen that by grasping the outer end ot' the straight edge for moving the saine, the force transmitted thereby will be divided into two component forces, one acting to force a roller against one side of the guideway, and the other forcing the secon-d roller against the opposite side of the guideway which is permitted by the clearance of the cylindrical parts, 21a, of said rollers between walls, 22, of the guideway. When the movement of the cariiage is arrested, the cylindrical paits of said rollers are freed from the vertical guideway surface, 22", and the rollers are permitted to seat tightly between the tapered or divering walls, 22, due to the weight of the carriage and partial weight of the straight edge, 2. It will now be clear that regardless of the position of movement the carriage will always be aligned in a true plane and consequently maintain precise alignment of the straight edge. As may be noted from the drawings, the pivotal connection of the straight edge to the carriage is over the guideway, 22, and the bearing boss, 8, in alignment with the rollers and positioned for sliding freely between the walls of the gui'deway as the carriage is moved thereover.

A pair oi stop brackets, 24, are secured to the upper and lower edges of the board adjacent the left end, and have curved stop extensions, 24a, extending around the end of the track, 5, for limiting the movement of the carriage in the track.

Clutching mechanism is mounted on the underside of the straight edge, 2, for locking the carriage in a fixed position along the track, 5, irrespective of the position of the straight edge to the carriage. The underside of said straight edge is suitably recessed for the clutch mechanism, which comprises a tapered movable clutch jaw, 30, integral with a clutch bar, 31, slidably supported in a bearing, 32, secured to the underside of said straight edge, 2. Said clutch jaw is curved and comprises a sector, concentric with the tapered pivot, 7, so as to have engagement at any position of angular adjustment with a reversely tapered, fixed clutch'jaw, 33, extending substantially across the end of the board and integral with the track, 5, as shown in Figure 1. The clutch jaw, 30, is adapted to be normally held in yielding engagement with clutch jaw, 33, by a sprin 34, secured at one end to the underside o the straight edge, the other end engaging in a groove, 35, of the clutch bar, 31. The tapering surface of these jaws serves as a wedge when in contact with each other and as may be seen in Figure 4, tends to force the carriage downwardly, thereby seating the tapered rollers tightly in the guideway, 22, also assisting in aligning the carriage and straight edge in a true plane. The clutch mechanism' is aligned with and as vclose as possible to the pivotal connection, 7, so that the diameter of the curved surface of said clutch aw, 30, will be at a minimum. The size of said clutch jaw sector, 30, is governed by the limits of angular adjustment of the straight edge, and must at least be equal to the maximum angular swing, so as to provide sufiicient clutching contact with jaw, 33, to lock the carriage in fixed position at any angular position of the straight edge.

The clutch jaws are preferably maintained in engagement during the preparation of a drawing and as previously stated, if the straight edge, 2, is to be moved, it is usually grasped by the draftsman and to this end I have arranged to operate the clutch to free the carriage for movement in the track, 5, by providing an operating bar, 35, extending substantially the length of said straight edge, 2, set in a recess, 36, in the lower edge of said straight edge. The end of said bar, 35, adjacent the clutch is pivotally connected to one end of a bell crank lever, 37, pivoted at 38; the opposite end of said lever, 37 ,engages the clutch bar, 3l, while the opposite end of said operating bar is pivotally connected to a link, 39, extending parallel to the connecting arm of the bell crank lever to said bar, whereby a force applied to any point along said bar, 35, moves the same toward the straight edge in parallel relation for moving the clutch jaw, 30, away from the clutch jaw, 33, to free the carriage. Manifestly the movement of the straight edge from place to place maybe had by simply grasping the straight edge and bar, 35, and yet when the operating bar is released, the straight edge is positively held in fixed position by engagement of the clutch requiring practically no thought for manipulation and expediting the preparation of drawings. There are occasions when it is desirous to slide or move the straight edge so frequent that it would be advantageous to have the clutch permanently disengaged, for which I provide a wing nut, 40, on the lower edge of the straight edge, 2, adapted to be moved to engage the outer edge of the operating bar, 35, when the bar is in clutch-disengaging position.

For various reasons it may be desirable to remove the carriage from the track; this is possible by moving the carriage to either extreme end of the track, so that the clutch jaw, 30, will be freed from clutch jaw, 33,

due to the recesses, 33, enabling the carriage and straight edge to be bodily removed. Also there areinstances when it is desirable to remove the straight edge from the carriage, which is possible by swinging it upwardly about its pivot until the clamping plate, 14, is freed from carriage plate, 6.

The transverse straight edge, 3, is carried by an auxiliary carriage or head, 45, movable on the straight edge, 2. Said auxiliary carriage comprises a plate member, 46, having tially the entire length thereof. The guideway, 49, comprises a pair of oppositely diverging side walls, 49, and the rollers are somewhat spherical so as to have substantially a line contact with the walls of said guideway. This construction also enables the auxiliary carriage to be maintained in true alignment and the wear of the various parts to be compensated for, as for the carriage, 4.

The transverse straight edge is secured to a supporting plate, 50, which is pivotally connected to the auxiliary carriage plate, 46, to permit a relatively wide range of angular adjustment of said straight edge. This pivotal connection, comprises an upwardly extending sud, 5l, on plate, 46, having an enlarged, upwardly tapering portion, 52,.

adapted to be journaled in a tapered bore, 53, in said plate, 50. The upper end of said stud, 5l, is threaded for a thumb screw, 54, which is adapted to compress a yielding washer, 55, such as of rubber, so as to obtain sufficient frictional engagement of the supporting plate, 50, on the tapered stud to position the straight edge. The extreme end of the supporting plate, 50, beyond the pivotal connection, is provided with an indicating mark for alignment with the different degree points of a graduated sector, 56, secured tothe top of the plate, 46, and concentric with the pivotal connection so that the straight edge may be adjusted to various angular positions. Said straight edge is held in fixed positions of adjustment by clamping means analogous to that employed on the carriage, 4, and comprises a circular clamping plate, 57, interposed between plates, 46 and 50, and secured to the lower end of a nonrotatable` bolt, 58, extending upwardly through plate, 50, and having a wing nut, 59, threaded thereon. Said clamping plate is beveled at, 60, for detachably engaging an oppositely tapered surface, 61, on the sector, 56, for locking the straight edge in position. A hand knob, 63, is secured to the upper side of supporting plate, 50, for conveniently moving the transverse straight edge across the board or for bodily removing it from the straight edge, 2.

It is preferable that the guideways, 22 and 49, are of a relatively hard metal and the co-operating rollers of soft metal so. as to reduce adhesion and frictional resistance between the parts.

The outer or free ends of the straight edges, 2, and 3, are supported by rollers so as to be clear from the drawing board and permit easy movement thereover. At the end of straight edge, 2, a curved tread roller, 65,

is set in a recess, 66, and journaled on a pin, 67, as seen in Figure 2. At the end of the transverse straight edge, a ball, 68, is mounted in a socket, 69, which is recessed into said straight edge. A curved tread or spherical roller provides substantially a line contact for support on the board, affording minimum frictional resistance.

The straight edges, 2 and 3, are provided with rules, or graduated measuring members, and '71, respectively, having a dove-tail tongue, 72, slidably removable in dove-tail grooves, 73, in said straight edges. For convenience in usage these rules are positioned along the top edge of straight edge, 2, and left-hand edge of straight edge, 3; a rule having a different scale may be desired for use in conjunction with one of another scale, therefore another dove-tail groeve is provided at the right hand edge of straight edge 3. These rules may be of wood, metal or composition and several rules of varied scales may be provided, so as to be quickly interchangeable with those in use. The dove-tail grooves are recessed at, 73a, opening at the end of the straight edges to guide the tongue of the rules into the groove.

A drafting machine constructed in accordance with the present invention will provide precise and accurate work and may be made for relatively large drawing boards and still retain the precision and exactness of movements. Further, this machine may be so mounted as to utilize practically the entire effective drawing area of the board.

I claim:-

1. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge thereof comprising a guideway of tapered cross-section, a movable carriage provided with a straight edge extending over the board, and having transversely spaced tapered rollers arranged, for movement in said guideway, adapted to fit snugly therein under downward pressure to position the straight edge accurately for work, said rollers being journaled on downwardly tapering studs secured to the carriage.

2. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge thereof comprising a guideway of tapered cross-section, a movable carriage provided with a straight edge extending over the board, and having transversely spaced taperedrollers arranged for movement in said guideway, adapted to fit snugly therein under downward pressure to position the straight edge accurately for work, normally engaged selflocking clutch means for holding the straight edge in fixed position on the board and tending to seat the tapered rollers in the guideway. l

3. In a drafting device of the character described, the combination of a drawing board` a track mounted adjacent one edge thereof comprising a guideway of tapered cross-section, a movable carriage provided with a straight edge extending over the board, and having transversely spaced tapered rollers arrangedv for movement in said guideway, adapted to fit snugly therein under downward pressure to position the straight edge accurately for work, clutch means for holding the straight edge in fixed relation to the board, said means including an inclined jaw on the straight edge, adapted to be moved into and out of engagement with a co-operating jaw on the board, and means normally maintainingsaid jaws in engagement whereby the engagement of said jaws tends to force the carriage downwardly thereby seating the rollers in a wedging manner in the guideway.

4. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge of the board having a guideway designed with upwardly diverging sides with parallel upper portions, a movable carriage provided with transversely spaced rollers each havin a lower tapered part and an upper cylindrical part fitting with clearance inthe guideway, and a stra-ight edge extending across the board and secured to the carriage; the tapered parts of said rollers being formed to seat between the diverging sides of the guideway for securing substantially true alignment of said carriage and its straight edge at various positions of adjustment with respect to the board.

5. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge of said board, a movable carriage provided with rollers positioned for movement over said track, a straight edge extending over the board and secured at one end to the carriage, and movable therewith, clutch means for holding said straight edge in fixed position on the board, Comprising a aw on the straight edge yieldingly held in engagement with a jaw on the board, and release means for said clutch to free the straight edge and carriage from the board, said release means including a bar connected to and extending parallel to said straight edge, and operatively connected to the clutch jaw whereby actuation of said bar yieldingly shifts said jaw out of Contact with the jaw on the board to permit the carriage and straight edge to be moved freely.

6. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge thereof comprising a guideway of tapered cross-section, a movable carriage provided with a straight edge extending over the board, and having transversely spaced tapered rollers arranged for movement in said guideway, adapted to fit snugly therein under downward pressure to position the straight edge accurately for work, means for holding the straight edge in fixed relation to the board, comprising a beveled rail on the board extending adjacent the track and a jaw on the carriage having an inclined face movable into and out of engagement with the beveled edge of the rail for gripping the latter to hold the carriage and force it downward for engagement of its tapered rollers in the tal pered guideway.

P In the combination defined in claim 6, yielding means for holding said jaw normally against the beveled rail, and means accessible throughout a substantial portion of the length of the straight edge operatively connected for releasing said jaw to permit movement of the carriage and straight edge over the board.

8. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge of said board, a movable carriage provided with guide means engaging said track, a straight edge extending over the board and pivotally connected at one end to said carriage on an upwardly extending axis to permit adjustment of said straight edge at various angular positions, said pivotal connection comprising a tapered stud j ournaled in a tapered bore.

9. In a drafting device of the character described, the combination of a drawing board, a track mounted adjacent one edge thereof, having a tapered guideway, a movable carriage including a pair of transversely spaced, tapered rollers positioned for movement in said guideway, a straight edge extending over the board having one end secured to said carriage for movement therewith, said straight edge being provided with a longitudinally extending tapered guideway, a movable head having spaced tapered rollers arranged for movement in said guideway of the straight edge, and a second straight edge connected at one end to said head and extending transversely of said first straight edge.

10. In a described, the combination of a drawing board, a track mounted adjacent one edge thereof having a tapered guideway, a movable carriage provided with transversely spaced tapered rollers positioned for movement in said guideway, a straight edge extending over the board having one end pivotally connected to the carriage for adjustment into a plurality of angular positions, said straight edge being provided with a 1ongitudinally extending tapered guideway, a movable head having spaced tapered rollers arranged for engagement in said guideway of the straight edge, and movable with said straight edge and carriage with respect to said track, and a second straight edge pivotally connected at one end to said head and drafting device of the character adjustable to a plurality of angular positions relative to said head.

l1. In the combination defined in claim 10, said pivotal connections of the straight edges to the carriage and head respectively comprising a tapered bearing and a tapered stud having journal support therein, to take up wear and maintain true alignmentat the pivot-al connections.

12. In the combination defined in claim l0, said pivotal connections of the straight edges to the carriage and head each comprising a tapered stud seated in a tapered bearing and arranged to permit ready removal of the straight edges upwardly from the carriage and head respectively.

13. In the combination defined in claim 10, said carriage and head being removable bodily from their respective guideways.

14. In the combination defined in claim 5, means operable at will for locking said bar in clutch-releasing position.

WINFIELD S. HARMON.

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