US1728420A - Ruler - Google Patents

Description

Sept. 17, 1929.

c. H. LITTLE 1,728,420

RULER Filed April 6, 1925 2 Sheets-Sheet l Erg Z- Sept. 17, 1929. C. H |TT| E 1,728,420

RULER Filed April 6, 1925 2 sheets-sneer 2 rmvaraaalarammvmnamm Patented Sept. 17, 19.29

UNITED STATES CHARLES' H. lLITTLE, 0F EAST- CLEvELAND,` OHIO RULEB.

Application led April 6, 1925. Serial No. 20,934.

This invention relates to rulers ordrafting toolsl such as scales, straight edges, tri-l In general, it is the object of the present j linvention to provide certain improvements or features of construction which impart to the rulers the chief advantages of both l wooden and metal rulers asheretofore commonly employed, and at the same time to eliminate certain well-knowndisadvantages of bothl types. More particularly, it is the aim of the invention to provide rulers which have substantially the lightness and the legibility and certain other desirable characteristics ot' wooden rulers, but do not possess the warping characteristic and lack of permanency and accuracy characteristic of wooden rulers, but which also possess the stiffness, accuracy and permanency of metal rulers, but not their poor legibility, tendency to Isoil the drafting paper, and certain other undesiralde features or characteristics of metal rulers as heretofore employed.

Still further the invention aims to accomplish the above objects more effectively than in my prior Patents Nos. 1,274,291 and L27-1.292, granted July 30, 1918.

Still further objects are to provide a nonwooden and non-warping core, preferably a light, solid metal core, wholly enclosed in a non-metallic, preferably celluloidal covering formed and appliedA in a new and inexpensive manner, which will admit of the rulers being constructed cheaply but accurately and otherwise satisfactorily, and so as to provide a celluloidal covering having distinct advantages over that in my Patent No. 1,274,292.

.A still further object is to provide certain improvements in connection with graduated rulers, which in'iprovements facilitate the use of such rulers by permittingr exact measuref ments or dimensions to be laid out more readily and quickly, and with less strain on the eyes, than if the graduations alone are relied on.

The above and other objects are attained by my invention, which may be here summarized as consisting in certain novel details of construction, and combinations and arrangements of. parts, all of which will be described in the specification and set forth in the appended claims. e

In the accompanying sheets of drawings wherein I have illustrated rulers in the form of a scale and straight edge embodying my invention in its preferred form, Fig. lis a plan view with a portion broken away; having a metal core, wholly encased in a tightly fitting non-metallic covering, the core being formed and the covering being .formed and applied in accordance with my invention; Fig. 2 is a cross-sectional view of the same; Fig. 3 is a cross-sectional view through dies' closed onto the ruler, which is also shown in cross-section, this view illustrating the preferred way in which the covering or shell is applied to the core so as to wholly enclose the latter; Fig. 4 is a .cross-sectional view of the solid metal core for the scale; Fig. 5 is a perspective view of a portion of the scalewlth one corner in section to illustrate the homogeneous or seamless character of the covering which is applied to the core; Fig. 6 is an enlarged view showing a portion of the scale partly in` end elevation and partly in section to illustrate notches which may be applied in the working edges of the scale and into which the point of the pencil may be placed by the draftsman so as to permit the desired dimensions to be marked on paper with more accuracy and speed than is the case if graduat-ions and characters alone are relied on; Fig. 7 is a fragmentary edge view of the same; Fig. 8 is a similar view illustrating a slight modification in the form of the notches and in their arrangement with respect to the graduations; Fig. 9vis a perspective and more or less diagrammatic view illustrating in separated fashion the two parts of the non-metallic shell and the solid core of which the scale is composed; Fig. 10 is a plan view of a portion of the scale, the same being provided with a chuckplate to adapt it for use in a drafting machine; Fig. 11 is a plan view of a straight edge embodying my invention; Fig. 12 is is a partialllongitudinal sectionalview 'of the same; Figs. 14 .and 15,are respectively a transverse sectional view and a. partial longitudinal,` sectional view, showing the vparts which form the straight edge, separated as in Fig. 9; andFlg. 16 1s a v1ew similar to Fig. 5 showing a portion-of the straight edge.

Referring now of the composite ruler. The shape of the core will depend, of course, upon-the type or kind of ruler toiwhich my invention is applied, but it is a characteristic of all my resent improved rulers that thecoreis ormed of solid metal, and in this respect 1t differs from 'the rulers of vmy prior patents, before referred to, wherein the core, for the sake uof li htness is formed of sheet metal and is ho ow. To permit .the use of a solid core which has lthe desired degree of stiff- 'may be emplo ed.

ness and is suiliciently light in .weight to answer the requirements, special metals or alloys are necessari, and several of which or example, I have used advantageous y for this purpose, magnesium and a magnesium-aluminum alloy consisting chiefly o magnesium, and containing a small percentage of aluminum,v as for exy ample, approximately 92% to 96% of magnesium and 8% to 4% of aluminum, or duralumin may be used advantageously. These metals or alloys not only have a Sulliciently low specific gravity, but what is more important, t ey can be drawn or extruded to the exact cross-sectional dimensions and to the desired shape that the core is to assume in the ruler, which shape, as already stated, will depend upon the particular ruler in which the core is to be employed. I prefer to produce the core in the desired shape by the drawing or` extruding process, not only because of the relatively low cost of this process, but a drawn or extruded core is peculiarly fitted for this purpose in view of the fact that in the process offorming it, it receivesa skin or surface hardening which adds to the stiffness of the core, and. furthermore, it is relieved lof bending or in ternal stresses which may, and generally do occur in machining.

In the case of the scale, the solid core 10 has a flat bottom 10, and a top having the middle portions 10b parallel with the bottom, and tapered portions 10c leading from the top surface portion 10b substantially, but not quite to the lower face 10B, leaving narrow, flat edges of approximately one-siXty-fourth of an inch (more or less) in width, which edges are straight and parallel for the entire length of the scale.

The core for the straight edge is somewhat differently shaped, as illustrated in Figs. 11, 12 and 13, this core, designated 11,

' strai htfed l' trauen which is, of course, alsosolid, and is formed inthe same manner as the core of the scale, havin parallel top and bottom faces which vexten 1n arallel planesjto the side edges which are ormed'square and parallel. The K Y are frequently of considerable lengt an vthe thickness may bevaried in v :cordan'ce with the length 'of the straight to the drawings, reference will first be made to the core or metallic part ge, to provide increased stiffness if the same should be found desirable. v The core of either the scale or straight edge may'r be provided with tapped openings td accommodate screws 12 for securin to the finished ruler, chuck-plates 13 (see ig 10), these chuck-plates when employed, adapting the ruler for use with a drafting machine, although it is immaterial whether these openings are provided in the core before or after the enclosing covering is, applied to it. This connection of the chuckplate to the solid metal gives a substantial hold at the end o f the ruler which practically does away with any slightmotion at this point, this being especially desirable in long rulers or straight edges. It is understood also, that the chuck-plates will be -omitted in the` event that the ruler is intended to be used as a separate tool independently of the drafting machine.

After the core of theruler is formed into the right length it is encased in a non-metallic .covering or shellwhich entirely encloses the core, is tightly fitted thereon, and is mechanically held by the core against movelment in any direction.

The shell or covering 'is preferably formed of sheet celluloid, or some other suitable nitroderivative of celluloid, or possibly of some other substance having certain wellknownproperties or characteristics of celluloid, i. e. which in its inished state is hard, smooth, easily movable over drafting paper, and will not soil the paper; which is tough in the sense that it will not chip olf and can be liexed without liability of breakage or tearing; which 4has cohesive properties such that fine, smooth lines or characters can be formed therein, which undergoes llO shrinkage that will cause the covering to l' everywhere maintain the initial tight gripping relationship between the core and cover and will retain permanently its shape and accuracy; and which for use in producing certain rulers such as straight edges can be lmade in transparent form thereby providing transparent edges which are very desirable for straight edges. Inasmuch as celluloid, and particularly sheet Celluloid has Aall these properties and characteristics, and others which admirably adapt it for this use, sheet celluloid is the preferred' material for this covering, and the word Celluloid is used in this specification as applicable to any material having the above characteristics, or a suiiicient portion of them to adapt it for be formed of several parts, a seamless covering is produced-directly on the core, preferably by heat and pressure, the latter causing a true welding of theparts and making a ho,-

mogeneous unitary or monolithic covering' which tightly grips and wholly'encloses the core. In the case of the scale, the covering, which is designated as a whole by the reference character 14, is preferably formed of two pieces or strips of sheet celluloidf consisting of a top piece 14, and a bottom piece 14h, one of these pieces, in this instance the bottom piece 14h, being provided with bentup tabs 14c to form the covering for the ends of the core. A

After these pieces are blanked out from sheet Celluloid, slightly longer and also slightly wider than the core which they are to enclose, the two pieces with the' core beneath them are placed between the heated dies of a press, and are subjected to severe pressure and to heat for a sulici'ent length of time to weld the two parts together and form a one-piece or seamless covering or shell completely enclosing the core. Dies suitable for this purpose are indicated conventionally at 15 and 16 in Fig. 3, these dies, as shown, being hollow or having interior spaces lawand 16ay for the circulation of a heating medium.

The dies have a cavity corresponding to the shape of the ruler to be formed, with the result that pressure is exerted between all portions of the core and covering aswell as between the overlapping marginal. portions of the pieces initially forming the covering, that is to say, outside of and along both longitudinal edges of the core, and outside of and along the ends of the core. The result is that not only isa seamless covering or shell formed around the core, with the parts of the covering everywhere welded together along the longitudinal edges and across the ends, but the shell everywhere tightly. engages the core so that the core andl shell are mechanically held together 'and the core holds the shell against movement in an direction. The shrinkage tendency of the ce luloid cannot, therefore, have the effectv of causing ben tween the core and shell any relative movement which could to the slightest degree destroy or affect the accuracy of the device. The only effect of such shrinkage or shrinkage tendency would be to cause the shell, if possible, to more tightlyA grip the core.

I may, if desired', coat the core, or parts of which the shell or covering is composed, or

" both, if desired, with a Celluloid solvent to clean the celluloid, to facilitate the weldingoperation and to enhance the close adherencev between the core and shell. However, the effect of 'this is largelyto bring about the exclusion of air between the parts and prevent the pocketing or trapping of air as the pressure 1s applied.

It is a feature of the process described above, that the scales have thickened edge portions 14a. This not only permits-truing and refinishing in the event that the edges are nicked from use, but also hasa further -advantage in that the edgesmay be notched in a manner and for a urpose to bedescribed present-ly and also improves the welding process.. Additionally it should be noted that the edges are square and straight and parallel when the covering is applied by the above process. lIt might be here mentloned lthat the thickened edge portions and 'square edges, highly desirablel in tools of this kind, are not attainable when the core is formed of sheet metal and the covering applied in liquid form as a coating. y

The same method described above is utilized in forming celluloidal coverings for other forms of rulers, such as for the straight edge, illustrated in Figs. 11, 12, 18, 14, 15 and 16, where the covering is designatedA as a whole by the reference character 17.

In forming this covering, transparent sheet Celluloid is employed so that lines and characters can be seen through the Celluloid, or through those portions thereof which 'project beyond the sides and ends of the core 11, it being -a feature of this process that the transparency or translucency 'of the celluloid is not adversely al'ectedv by the welding Vprocess which forms the parts into a tightly adhering, seamless shell in which the core is in effect embedded.

In forming the covering'17 I prefer to use six pieces, consisting of top and bottom strips l7a'and 17, which extend the` full length of the straight edge, two. longitudinally extending filler strips 17, which engage the longitudial edges of the core 11 and are overlapped by the strips 17a and 17", and two transverse end filler pieces 17 d which en age the ends of the core and are overlappe by the end portions'of the top and bottom strips. These end pieces 17l may extend across the ends of the straight edge from one side edge to the other, in which event they will abut against the ends of the longitudinal filler strips 17, or they may lit in between -the ends of the latter, in which event they will have a lengthequal to the width of the core. The former arrangement is now preferred by me.

These parts are placed in properly assembled relation about the core and are subjected to heat and pressure between dies as in the instance first described, the dies having a cavity correspondin in shape to the finished straight edge, and t e heat and pressure being-continued for a sufficient length of time to weld the parts into a more or less monolithic covering vwhich wholly encloses and everywhere tightly 4grips the core to the same degreeand in the same manner as 1n the case of the scale. may be coated with a solvent for the purposes previously explained, prlor to being subjected to heat and pressure between the dies of the press.

Revel-ting now to the sohd character of the core of each of the several rulers, and to the process in general, I wish to emphasize the importance of the solid core not only as to its utility over a sheet-metal core in a finished ruler, but also in the successful practicing of the above described processes wherein pressure plays an important part in forming the covering. The solid core not only has the important advantage over a thin walled sheet-metal core such as shown in my prior patents that it is not susceptible to crushing in use, as by the elbow of the draftsinan, or to buckling, but a solid core is essential to withstand the severe pressure used in welding together the parts of which the unitary covering is formed, and effectively resists whatever pressure may be necessary in the application ofthe graduations 18 and characters 19 on the scales or'other rulers to which graduations and designating characters may be'applied. In particular, the term solid is employed in describing the core to distinguish from a core such as is formed from relatively thin sheetmetal and is hollow, as in my prior patents, but the term, as herein used, doesnot exclude a core which may be provided along its length with openings formed in the core in case extreme lightness is desired, as long as such a core has the necessary stiffness, solidarity, accuracy and distortion resisting qualities to answer the requirement. This leads to the consideration of some other important features of the present invention both in the article and method aspects thereof.

Ordinarily, graduations are cut in the celluloid by a graduating machine,- and the characters are stamped therein, one at a time. The usual cuttlng and stamping processes may be carried out in forming my improved scales, and other graduated rulers, such as protractors, but the process utilized by me in forming the coverings admits of the application of the graduations and characters not only effectively but lin a timesaving manner by. an entirely new method, i. e. by molding the graduations and characters and also notches to be referred to into the celluloidal covering eitherv by the same dies which form or weld together the parts thereof, in which event, one of the die members will be provided in cameo or relief` with graduation and character forming parts which protrude from the face of the If desired, the parts` die, and which in the covering forming process are pressed or embedded in the covering, or the graduations and characters may by suitable dies be simultaneously pressed into the covering in a separate operation subsequent to the cover forming operation.

The severe pressure incident tothisl methodof applying characters and gradua-- tions is readily withstood by the use of a solidl core.

cover, or they may e cut in a subsequent operatlon.

The depressions referred to are in the form of notches, indicated in igs. 5, 6, 7 and 8, and provided on the working edges ofthe rulers, particularly graduated rulers, to receive the point of the pencil in laying off dimensions on paper. These notches, which are molded or cut in the thickened edge portions ofthe ruler. extend back on a diagonal from the face of thefedge, and they vmay be square in outline, as indicated at 20, or they ma be triangular, as indicated at 20a in Fig. 8. urthermore, they are preferably employed in conjunction with the graduations 18, and they may be provided opposite and below all the graduations, as indicated in Fig. 7, or they may occur also between the aduations, in which event fewer graduations may be employed.

The purpose of these notches is to facilitate the laying oi of dimensions as above stated, by acting as centers or positive locating points for the draftsmans pencil,-

which can be moved along the edge of the ruler and dropped into a notch beneath a vgiven graduation, or between two adjacent graduations, so that the draftsman is enabled to locate on the drawing paper `the position of the dimension oint much more quickly and readil than i he were obliged to rely on the gra uations alone.

These notches do not extend in height across` the entire vface of the edge of the ruler, but there is left above the notches an unbroken or smooth'surface along which the pencil can be moved in the usual manner, and to iind or locate a particular dimension point it is only necessary for the draftsman to tip his pencil P forwardly, when it is adjacent the proper notch, in the manner indicated in Fig. 6, in which event the pencil point will nd its way or drop into the notch which accurately locates the dimension -ordinary wooden and metal rulers.

with extreme accuracy, extraordinary speed,

and with relatively little attention on the part of the draftsman.

opposite the graduations, part of the graduations can be eliminated. For instance, .a scale ma be graduated to sixteenths of an inch, an notches cut-to thirty-seconds of an inch. It is then very easy to work to thirtyseconds with a scale that only reads to sixteenths. A scale of this kind is much easier on the eyes and more quickly read. Poor lighting is therefore not so bothersome, and eye-strain is greatly reduced. I might add that I find that notches one-sixty-fourth of an inch in width answer the requirements very effectively, and that the pencil will find its way or drop into the notches more readily if the upright corners formin the sides of the notches are slightly roun ed olf.

One other feature remains -to be explained,

'and that has to do with the equalization of the tension or pull exerted b the celluloidal covering on opposite sides o the ruler when such sides, as the top and bottom of a scale, are unsymmetrical, i. e., are not similarly disposed from' edge to edge. Inasmuch as portions of the top of the scale are beveled or tapered down toward the longitudinal edges, I iind that the tension along the top of the scale, due to the pull created by the shrinking tendency of the celluloid is less than that along the bottom of thescale, which fact would, unless compensated for, cause a bowing of the scale. This, I find can be obviated entirely by making thecelluloid strip forming the to of the scale, somewhat thicker than the strip forming the bottom. I find that by making the top stri l approximately five thousandths of an inc or about 20% thicker than the bottom strip, the stresses along the top and bottom of the scale are exactly balanced. It is unnecessary to employ this expedient in producing the straight edges, for the top and bottom portions ofthe covering or shell are symmetrical, so that the stresses are balanced when top and bottom strips of equal thickness are employed.

By way of conclusion I might sum up the advantages inherent in, or derived from the use of rulers formed in accordance with the present invention as compared with the rulers heretofore used, and particularly the l. Accuracy/. The edges remain straight and parallel, which is not true of rulers vhaving a wooden base, because of the latters tendency to warp. 'The graduated scales hold permanently .their overall graduated length, whereas with wooden scales having graduated celluloid strips cemented thereto, tests show a slight shrinkage.

2. legibility/. -Scales formed in accordance with my invention have the permanency and accuracy of metal scales, but be` read much more quickly and easily.

3.. Permammy of )msh-Thc scales which are preferably covered with dull white celluloid have a finish which is pleasing and easy-on theeye, andis muchmore durable than that on metal scales and scales having a wooden base, since in time the finish wears oi 1n laces from both wood and metal.

4. 0 anlz'ness.-The rulers are particularly cleanly due to the inherentl cleanly nature of compressed sheet cellu oid, and due to their light weight. i

5. Lzfghtmss.'-My improved rulers are extremely light in weight, notwithstandingtlie fact that they have solidmetal cores, and

this makes them easy to handle, easy to place at the desired point on the drawing,` and thereis therefore less tendency for the rulers to grind or rub dirt into the drawing -paper when they are moved over it. Light weight metals have heretofore not been satisfactory for rulers because they have either soiled the drawing unduly, or have finishes that would soon wear off.

6. Agreeable to the touch-These rulers are especially agreeable vto the touch, partially because celluloid is not a good con ductor of heat and partially onl account of the smooth, cleanly surface of celluloid. A

metal scale because it is a good conductor of heat is not pleasing to the touch.

7. Durability/. The'se rulers are far more durable than either metal rulers or those having a wooden base. The celluloid will not loosen at any pointnor chip oil', and itprovides a permanent finishv for the metal core, ,while the latter provides permanent'accuracy for the celluloid ed es in the way of Vstraightness and paralle ism, and permanent accurac for'the graduations.v

8. E io'ency.- otv only do these scales and other rulers formed in accordance with my invention have greatutility because ofl their lightness, permanency, accuracy and legibility and for other reasons heretofore mentioned, but the notches provided along the edges of the scales or other graduated rulers greatly enhance the speed and ease with which drawings can be made which require accurately marked oi dimensions, andV they vreduce eye-strain, as already pointed out. -The fact that the ruler has a thickened edge which permits the notches to be formed with a smooth surface above it as well as permitting truing in the event the edge is nicked is a 'decided advantage over rulers having a non-thickened edge as in my prior patents.

9. Low cost of mawufactwre.`-My imr proved rulers, despite ltheir excellency, can

e produced inexpensively, since the heat and pressure and dies used in welding the permits the rapid production of uniformly accurate scales and other rulers'with a minimum of Wastage. On the contrary, in the production of wooden rulers, the wastage is vvery high because of warping. Additionally the cost of production is greatly reduced when the graduations, characters and notches are molded in the Celluloid, particularly during the cover forming process.

While I have illustrated only scales and straight edges, my invention may be utilized also in the production of still other rulers, such as those mentioned in the early part of the specification', and While I have described these rulers in their preferred form, and have specified the preferredmaterials, and thev preferred process of producing the rulers, I do not desire to be confined to the exact details, steps of the method, or materials specified, but aim in my claims to cover all modifications which do not involve a departure from the spirit and scope of my invention in its broadest aspects.

The herein disclosed process of .forming the rulers, including the molding of the graduations, characters and notches, isl

claimed in a divisional application Serial No. 370,220 led June 12, 1929.

I claim:

1. A ruler comprising a core and a unitary seamless welded celluloidal covering completely and tightly enclosing the core including the endsand held from substantial movement thereon in any direction, said covering having a rulingedge held straight by the core.

, 2. A ruler having unsymmetrical opposite sides andprovided with a celluloidal covering thicker on one side than on another to balance theshrinkage stresses.

3. A ruler comprising a core having unsymmetrical op osite sides, and a celluloidal covering tight y enclosing the core and thicker on one side than on the other to balance the shrinkage stresses.

4. A ruler comprising a metal' core and a molded unitary seamless covering completely and tightly enclosing the core including the ends, and having a ruling edge held straight by the core. l l

5. A ruler comprising a metal core and a molded seamless unitary celluloidal covering completely and tightly enclosing the core including the ends, and having a ruling edge held straight by the core.

6. A ruler having graduations extending down to its edge and notches formed along the bottom of the edge in definite spaced relation to the graduations, the intermediate portion of the edge between the ends of the graduations and the notches being smooth.

In testimony whereof, I hereunto affix my signature.

CHARLES H. LITTLE.

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