US2701918A

US2701918A - Adjustable straightedge

Info

Publication number: US2701918A
Application number: US238703A
Authority: US
Inventors: Phelps Glenn
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-07-26
Filing date: 1951-07-26
Publication date: 1955-02-15
Anticipated expiration: 1972-02-15

Description

Feb. 15, 1955 Filed July 26, 1951 G. PHELPS 2,701,918

ADJUSTABLE STRAIGHTEDGE 3 Sheets-Sheet l 4 :CENVIIIIIIIIII: u\\\ FIG. 4.

INVENTOR.

GLENN DI-IELPS BY an)? ATTORNEY Feb. 15, 1955 G. PHELPS ADJUSTABLE STRAIGHTEDGE 3 Sheets-Sheet 2 Filed July 26, 1951 JNVENTOR. LBNN PHELPS H. II

ATTORNE Feb. 15, 1955 Filed July 26, 1951 G. PHELPS 2,701,918

ADJUSTABLE STRAIGHTEDGE 3 Sheets-Sheet 5 FIG. 9.

INVENTOR. PHELPS ATTORNEY GLENN BY United States PatentfO ADJUSTABLE STRAIGHTEDGE GIennPhelps, New York, N. Y. Application Jul'y- 26, 1951, Serial No. 238,703 6' Claims; (Cl. 33-80) Thisinvention relates to an improvement in combined Jdraftingboards and straight-edges and, more. particularly, to a straight-edge articulated to a drafting board so that they'may be relatively adjusted.

'The subject improvement is intended particularly for combined" straight edges and drafting boards wherein, conventionally, the board has toothed tracks along op- 'p'o'sit'e. side edges and wherein a straight edge extending crosswise between the opposite edges of the board is carried by an axle geared at each end to the tracks, thereby insuring that the straight edge will remain transverse to the length of the board at all times. The main problem solved by the improvement arises from the virtual. impossibility of securing a sheet of drawings to the board. so that the longitudinal and transverse lines of the drawing run exactly lengthwise and transversely of the board, and once secured the almost negligible chance that the common T-square will align with all the longitudinal linesbecause of imperfections (be they ever so slight) in the drawing board edges and/or the T- square. head; and weakness, flexibility and lack of support of the T-square blade ends. This problem arises particularly in working on drawings which may be removed from and replaced on the board from time to time, and similar difficulties arise in re-working large drawings having parts slightly out of line. The object ow is. to provide a straight edge geared to a drafting board. sothat it always lies substantially parallel to the length of and at an angle of 90 with respect to the breadth of the board, but with an arrangement whereby the. angularity of the straight edge can be adjusted above or. below 90 so as. to compensate for out-of-trueness of the. drawing sheet or for previous discrepancies. More particularly, it is intended to provide for an ample range of. angular adjustment, from a relatively wide angle, for the above named discrepancies, down to the narrowest. line-breadth. And, once adjusted, it is intended to provide a straight-edge that is securely anchored to the drawing. board and firmly supported at both ends, that always. moves in dependable and accurate parallelism throughout the extent of the drawing board; and one with which the most minute and accurate parallel spacing can be obtained by a slight movement of knurled thumb turns attached to and which actuate an, equally slight movement of the spur gears.

In. accordance with the broad objectives of the invention, it is proposed now to provide a drafting board having toothed tracks along opposite edges, a straightedge guided by a transverse axle, track-engaging spur gears normally fixed on opposite ends of the axle, and an adjusting mechanism for one of the spur gears so that it may be angularly adjusted with respect to the axle. Since the spur gears remain engaged with the track, it is thus apparent that the angularity of the straightedge with respect to the board will vary with the angulari'ty of one of the spur gears with respect to the ax e.

Another object of the invention is to provide for "maintammg a gear-track straight edge engaged at all desired times with the drafting board while nevertheless providing for easy assembly and dis-assembly of the 'parts. In the subject device it is intended also to provide for pivotally lifting the straight-edge about the axle upwardly from the board without disturbing the work, or the longitudinal or angular setting or the straight-edge. in anyway. Yet another object is to provide-a gear-track straight-edge with. both a. primarily justment of the straight-edge is achieved by adjusting one of the toothed tracks longitudinally along the board edge with which it is associated. In addition to the generic concept of adjusting one end only of the straightedge the second embodiment has, in common with the first, previously mentioned improvements in the straight-edge per se. In both embodiments, whether the adjusting member be a toothed track or a spur gear, the spur gears should have beveled shoulders so that they can run at angles with respect to the tracks without climbing off.

These and other objects will be apparent fromthe following specification and drawings, in which:

Fig. l is a plan view of the preferred embodiment, broken away to reduce the size and to show certain parts in section;

Fig. 2 is a vertical cross section taken along the line 22 of Fig. 1, and broken away along lines corresponding to the break-away lines of Fig. 1;

Fig. 3 is a fragmentary side elevation as seen from the line 3-3 of Fig. l, but with the handle removed;

Fig. 4 is a vertical longitudinal section taken along the lines 44 of Fig. I looking in the direction of the arrows;

Fig. 5 is an elevation of an alternate form of spur gear usable with either embodiment of the invention;

Fig. 6 is an isometric view of the assembly shown in Figs. 1 to 4, inclusive, showing the straight-edge angularly adjusted, and with a part of the adjusting mechanism shown in exploded view at the right-hand end of the figure;

Fig. 7 is an exploded isometric view of the adjusting mechanism;

Fig. 8 is a fragmentary isometric view of a second embodiment of the invention; and

Fig. 9 is a fragmentary side elevation of the-embodiment shown in Fig. 8.

Referring first to Figs. 1 to 7, inclusive, of the drawings, in which like reference numerals denote similar elements, the straight-edge indicated generally at 10 is mounted for movement at a fixed angle along drawing board 12. It will be understood that the assembly is particularly, although not exclusively, adapted for working out drawings which may be as much as eight feet wide, with which parallelism, or lack of it, is a problem.

Along the

opposite side edges

14 and 16 of board 12 are mounted similar

toothed tracks

18 and 20, respectively, each including a depending flange 22 secured by screws 24 to the board edge, and a laterally projecting track 26. The bottom of each track 26 constitutes a downwardly-facing, smooth shoulder 28 whereas along its top runs a series of regularly spaced teeth 30 which form a linear gear. Preferably on at least one end of a track there is aflixed a spring stop pin 32, as shown at the lower left-hand corner of Figs. 1 and 6.

Straight-edge It) is a composite. member composed of a flat, relatively thin blade 34 having hard, straight ruling edge 36 preferably of suitable plastic material, and a similar hard, straight rear edge 38; a housing, described later, to guard the axle 54; and a secondary straight-edge member 43 super-imposed upon the blade 34. Over each end of blade 34 are

end pieces

44 and 46, secured as by screws 48.

End pieces

44 and 46 are formed preferably of metal, such as aluminum, and are bored at 50 so that they form bearings fitting snugly but revolvably about axle 54. Preferably about the middle of the assembly there is a bearing strap, or more than one such strap if an excessive length of'the blade dictates, which rotates snugly about the axlev 54 and axle.

has its ends secured to blade 34 in order to hold the .long and small, and therefore flexible, axle 54 in its proper alignment with the blade. Over the entire portion of the axle 54 that reaches between the

end pieces

44 and 46 is a housing 40, the purpose of which is to act as a guard for the rotating axle and a ready thumb bearing against which to actuate the hand movement of the straight-edge assembly upward on the drawing board, the downward movement being actuated by the fingers against the shoulder 41. This housing, as the best means of manufacture may dictate, may be made a single casting of a homogeneous material such as a plastic, or it may be made up of composite members such as is shown, a thin metallic shaped member 40 bent to form a U with its bight fitting over axle 54, with its shape sustained by the wood filler member 52. On the underside of the housing member 40 is a rabbet so shaped that the blade edge 38 will fit flush in it and the two are secured together with the screws 42.

Referring particularly to the left-hand portions of Figs.l, 2 and 6, and to Figs. 3 and 4 on axle 54 near its left-end there is aflixed a spur gear 58 having teeth 60 meshing with the teeth 30 on track 18. Gear 69 has a long hub 62 over which fits a knurled thumb turn 64, both being non-rotatably affixed on axle 54 by a set screw 66 which goes through gear hub 62 to the A spring hold-down clip 68 slidably fitting over hub 62 between teeth 60 and knurled thumb turn 64 has free ends 70 engaging with moderate tension beneath the smooth, downwardly facing shoulder 28. There is a corresponding hold-down clip 68 on the opposite end of the assembly.

A flat handle 72 rigid with and extending outwardly from straight edge blade 34 may be grasped for lifting up the straight-edge, handle 72 being cut-away to accommodate spur knurled thumb turn 64 and recessed at 76 to guard spur gear 58.

Referring now to the right-hand portions of Figs. 1, 2, 6 and to Fig. 7, angular adjustment of straightedge 10 is obtained by an ular adjustment of spur gear 581: with respect to axle 54. Spur gear 58a is similar in all respects to its counterpart 58 except that it is not directly held tight on axle 54 but, on the contrary, is free to rotate on the axle under certain conditions.

Near the right-hand end of axle 54 there is a fixed thrust collar 78 and against it rests spur gear 58a. The right-hand knurled thumb turn is divided into two parts, 64a and 64b, respectively, part 64a having its hub fitting over gear hub 62a and held on by a set screw 66a extending only to the periphery of gear hub 62a. Thus, thumb turn part 64a and spur gear 58a at all times rotate together. The other part, 64b, of the thumb turn, has an internally threaded hub 86 engaging threads 82 on the end of axle 54. By screwing on thumb turn part 64b, spur gear 58a is tightly clamped against thrust collar 78 so that now, thumb turn parts 64b, 64a, spur gear 58a, and axle 54 all turn together.

An alternate form of spur gear is illustrated in Fig. 5. It will be noted that its teeth. 58a have the beveled shoulders prescribed for the straight-cut spur gears previously detailed.

In addition, the teeth in this form are provided with arcuate sides so as to enhance its tracking properties under all conditions of angular adjustment.

In operating the embodiment of the invention detailed above the straight-edge 10 is pivoted upwardly about axle 54, as diagrammatically indicated by the dash lines and curved arrow of Fig. 4, and the work sheet S is installed on board 12, straight-edge 10 then being lowered to its normal working position with ruling edge 36 against sheet S. At all times, spring clips 68 keep the annular spur gears 58, 58a in constant mesh with the linear gear teeth 30. The chances are that the horizontal line or lines of sheet S will be other than exactly transverse to board 12. The dash lines A, A and A" in Fig. 6 illustrate the typical source of adjustment required to compensate for erroneously angled drawing sheets or mis-drawn lines. To establish the necessary correction, part 64b of the right-hand knurled thumb screw is unscrewed to back it off from spur gear hub 62a. Knurled thumb turn part 64a is then turned in .the appropriate direction to roll spur gear 58a up or down track 22. Meanwhile, the left-hand knurled thumb turn 64 is held stationary so that adjustment of the right-hand end changes the transverse angularity of straight-edge 4 10. Thus, the thrust collar 78, threaded axle end 82, and internally threaded part 64b constitute a quick release for connecting spur gear 58a and axle 54 for co-joint rotation.

The embodiment illustrated in Figs. 8 and 9 is similar in many respects to the one of Figs. 1 to 7, inclusive. The elements immediately recognizable as corresponding to those previously described are similarly numbered except that the hundreds prefixes are added. For example, straight-edge slides along board 112. However, the mechanism for angular adjustment of the straight-edge assumes a somewhat different form.

In the Figs. 8 and 9, structure spur gears 158 are afiixed on both ends of axle 154 by set screws 166. Angular adjustment is obtained by adjusting the one track lengthwise of board edge 116. This is accomplished by providing slots 121 through which nicely fit bearing screws 123, track 120 being thereby held against wobble or vertical movement, but being permitted limited lengthwise movement along board edge 116. An apertured end projection 125 on track 120 is internally threaded to engage a headed adjusting screw 127, the latter having a neck rotatably caught in a forked projection 129 affixed on board 112. Thus, when the head of adjusting screw 127 is rotated in one direction or the other track 120 is correspondingly moved lengthwise of board 112 and, of cgurse, straight-edge 110 is thereby angularly aduste In all forms of the invention, it is apparent that a triangle T or other drafting aid may be placed either against ruling edge 36 or, if it is desired to limit its contact with sheet S, triangle T may be placed over straight-edge blade 34 and against the secondary shoulder 41. As shown best in Figs. 1 and 4, secondary shoulder 41 is the free edge of a plastic strip 43 aflixed along the front of axle guard 40. If disassembly of the mechanism is required, the free ends 70 of spring clips 68 can be run off from beneath shoulders 28 by removing stop pin 32.

The invention is not limited to the precise structure detailed above, but is intended to cover all modifications, substitutions, and equivalents within the terms and spirit of the following claims.

I claim:

1. In combination, a drawing board having substantially parallel opposite side edges, a pair of similarly toothed linear gear members, support means respectively mounting said linear gear members along said side edges, an axle extending across said board at substantially rightangularity with respect to said edges, a pair of similarly toothed annular ear members respectively meshing with said linear gear members, support means respectively holding said annular gear members on opposite ends of said axle, and an elongate straight-edge member carried by said axle, said straight-edge member comprising a relatively thick strip having an end-to-end bore adjacent one edge thereof rotatably engaging around said axle and a relatively thin bladelike strip rigidly aflixed parallel to said thick strip, said bladelike strip having a free edge constituting a primary ruling abutment, there being a straight upstanding shoulder at the juncture of said thick and thin strips constituting a parallel secondary abutment for engagement by a ruling element.

2. In the combination claimed in claim 1, a handle rigid with one end of said straight-edge member and extending beyond the adjacent edge of said board, whereby said straight-edge member may be pivoted upwardly from said board about said axle.

3. The combination claimed in claim 2, said handle comprising a generally fiat member having a portion thereof overlying the annular gear member and a portion of the linear gear member at that side of the board.

4. In combination, a drawing board having substantially parallel opposite side edges, a pair of similarly toothed linear gears respectively supported on said edges, an axle extending transversely of said board at substantially right-angularity with respect to said edges, a straight-edge member pivotally supported on said axle, a pair of similarly toothed spur gears on opposite ends of said axle and respectively meshing with said linear gears, means fixedly securing one of said spur gears to said axle, the other of said spur gears being rotatably mounted on said axle, thumb turn means rotating .with said other spur gear whereby angularly to adjust the same with respect to said axle so as to adjust the angularity of said straight edge, and quick-release means for connecting said other spur gear and axle for conjoint rotation.

5. The combination claimed in claim 4, said quickrelease means comprising a thrust collar aflixed on said axle on one side of said other spur gear, and a thumbturn part threaded on said axle on the other side of said other spur gear for releasably clamping said other spur gear against said thrust collar.

6. In combination, a drawing board having substantially parallel opposite side edges; a pair of trackways on said edges, each of said trackways having an upwardly disposed series of teeth and a downwardly disposed smooth shoulder running therealong, an axle extending transversely of said board at substantially right-angularity with respect to said edges, a straight-edge member pivotally supported on said axle, first and second similar spur gears on opposite ends of said axle, a toothed portion meshing with one of said liner gears and an axially elongate hub outwardly disposed towards the adjacent of said axle, a first annular thumb-turn member fitting on the hub of the first spur gear, said first spur gear and thumb turn being non-rotatably afiixed on said axle for rotation therewith, the second spur gear being rotatable on said axle, a second annular thumb turn memher aifixed on the hub of said second spur gear, a thrust collar affixed on said axle inwardly of said second spur gear and adjacent thereto, the adjacent outer end of said axle having threads, a third thumb-turn member engaged on said threads for releasably clamping said spur gear against said thrust collar, and a pair of substantially U- shaped spring hold-down clips having their bight portions respectively resting over the spur gear hubs and having their free ends engaged beneath said smooth shoulders.

References Cited in the file of this patent UNITED STATES PATENTS 694,389 Klitsche Mar. 4, 1902 707,165 Schlachter Aug. 19, 1902 1,288,871 Goodspeed Dec. 24, 1918 1,662,490 Cochran Mar. 13, 1928 1,977,213 Slobey Oct. 16, 1934 2,100,114 Walsh Nov. 23, 1937 2,252,535 West et al. Aug. 12, 1941 2,410,559 West Nov. 5, 1946 FOREIGN PATENTS 8,220 Great Britain Apr. 6, 1909 188,214 Great Britain Nov. 9, 1922