US 2664818 A
Description (OCR text may contain errors)
C. K. HEASLEY STENCIL AND BACKING UNIT Filed Dec. 15, 1944 INVENTOR.
y f MWMW Patented Jan. 5, 1954 STENCIL AND BACKING UNIT Charles K. Heasley, St. Paul, Minn., assignor to Minnesota, Mining & Manufacturing Company, St. Paul, Minn., a corporation of Delaware Application December 15, 1944, Serial N 0. 568,313
This invention relates to the art of forming stencils such as those used in duplicator machines and particularly to a stencil and composite backing sheet wherein a surface composed of a multiplicity of minute, substantially spherical protuberances affords a substantially uniformly level but discontinuous support for the stencil during the typing and other stencilizing operations.
Most of the commercial stencil sheets for use in duplicator machines have been composed of thin tissue paper, such as Yoshino, coated with a wax or other pressure displaceable composition to render them impervious to ink. During the stencilizing of such sheets it has been customary to place a cushion of tissue paper, either plain or coated, in contact with the back face of the sheet and to back the cushion in turn with a smooth, hard surfaced film or sheet of paper. The group of sheets thus arranged is placed in a typewriter which is operated to cause the type to strike the stencil sheet and thereby dislodge the wax or other ink-impervious substance from the areas of the impressions. From these areas the inkimpervious substance is either displaced laterally or is caused to adhere to the cushion, leaving the stencil characters permeableto ink.
By the present invention I obviate a number of difiiculties which are attendant upon the use of such backing materials. Due to the relatively irregular fibrous consistency of the cushion sheet the resulting stencil characters are not uniformly clear and the quality of the work subsequently performed by the duplicator machine through the stencil is also relatively irregular. There is also atendency for the type to cut through the fibers of the stencil sheet where there is a continuous, relatively hard surfaced backing, thus completely separating the areas bounded by the closed loops of characters such as a, e, 0, etc. The wax or other coating for stencils of this kind is usually dyed a dark color and enough of the displaced colored material remains on the areas of the impressions to make the stencil characters poorly legible until after the cushion carrying the dislodged material has been separated from the stencil sheet. Consequently the stencil is not easily legible for proof-reading without removal from the typewriter and this makes it relatively diflicult to correct errors. Further difiiculties are sometimes encountered when it is attempted to write or draw with a stylus on the stencil sheet because of the softness of both this sheet and the cushion tissue. 7
It is an object of the present invention to provide a stencil with an improved backingin which a multiplicity of substantially uniform, smoothly substantially uniform size.
2 rounded segments are utilized to support the sheet during the stencilizing operation.
. A particular object is to produce more clearly defined stencil characters by providing a stencil backing having directly opposed to each type face a multiplicity of substantially uniformly spaced, smooth, spheroidal protuberances in contact with the stencil sheet and having recesses between the several protuberances into which all of the pressure-displaceable, ink-impervious material from the stencil will pass readily in the stencilizing operation,
Another object is to provide a stencil backing of such durable character that it may be used a large number of times, having durable, smooth,
spheroidal glass or vitreous protuberances from which the wax or other substance displaced from the stencil sheet may be readily removed by the application of a solvent. 3
A further object is to provide a stencil backing from which sufficient light is reflected through the porous areas of the impressions to render the stencil characters easily legible without separation of the stencil sheet from the backing.
Other objects are to provide a stencil backing which minimizes the cutting of the stencil fibers, minimizes damage to the type during the cutting operation, facilitates free-hand writing and drawing on the stencil sheet and affords a durable, permanent record of the document reproduced on the stencil.
My composite backing has a facing composed of a single layer of hard, globular particles of These particles are securely bonded individually to a flexible backing by a suitable adhesive. To insure an adequate bond the adhesive is carefully selected for its resistance to impact as well as its adhesion to the particles and backing sheet. Care is exercised to submerge each spheroidal particle in the adhesive to a depth not exceeding one-half its diameter and preferably between 30% and 50% of its diameter. This affords recesses of adequate capacity between the protruding segments to receive the wax or other material dislodged from the stencil. It will thus be evident that a large number of the recesses extend beneath the overhanging peripheries of the spheroidal particles. The facing layer is preferably composed of particles of one of the smaller sizes, for example, bead sizes No. 15 to No. 19. Equivalent average particle diameters are approximately as follows:
Bead size: Diameter in microns 15 .58 17 .43 19 .24.
Facing particles of these sizes, ranging from approximately .001 inch to .003 inch, are particularly adapted for use where the stencilizing is to be performed on a typewriter having type faces ranging from about .01 to .015 of an inch in width.
Excellent results have been obtained by forming the globular particles for my .purpose from a lime soda glass, such as that commonly used in the manufacture of glass containers and window panes. Other materials having suitable surface qualities and adequate resistance to crushing ;for my purpose are metals, metal alloys, ceramic material and. synthetic resins. As the support or backing for the globular particles a' pa-per maybe used, such as wood pulp or rope paper of twenty pound or heavier weight, aseventy pound paper being preferred for use with most wax coated stencil sheets. It will be understood that such Weight designation represents the weight of a :ream of the paper,'i. e.,480 sheets-of size 24 inches by 36 inches. Other materials which may be substituted for the "paper backin are sheets of rubber or rubber derivative "or-a suitable synthetic resin film.
Where the-composite sheet'is to be used with a stencil sheet impregnated with a wax or other material of dark color, -I provide either a backing 'or an adhesive containing a white pigment or of a'light color and I use .clear or light colored glass :or white particles'as a facing, thus affording maximum contrast between the dark wax or other substance displaced "and the backing to which such substance adheres. dark backing or dark adhesive is supplied for use with white or light tinted stencil sheets. This improves the legibility of the stencil character when read against the backing for the detection of errors and also the legibility of the characters on the backing when the latter is used as a permanent record sheet.
The adhesive may comprise a suitable glue or a rubber or synthetic elastomer composition, or a thermo-setting synthetic resin, such as phenolaldehydes, urea-formaldehyde, melamine aldehyde, thio urea-formaldehyde, alkyd resins, etc., or mixtures of such resins or a suitable thermoplastic resin. Most highly plasticized resins and unmodified starches have insufii'cient bonding strength for my purposes. 'The adhesive must be chemically "inert with respect to the stencil sheet with which it may be in contact for long periods of time.
In cases where the backing is to be used repeatedly its components comprising the supporting sheet, adhesive and globular particles must be chemically inert with respect to the solvents that may be used in removing the wax or other deposits from previous sten'ciling operations. For example, with wax coated stencils ether or alcohol may be applied to the glass sphere .coated backing to remove deposits of wax therefrom and in this case the adhesive bond and supporting sheet or film must be inert to these solvents.
My improved stencil backing material may be prepared by either of several known methods which have been employed in the manufacture of coated abrasive material. For example, the solid globular particles may be dropped upon a flexible backing 'upon which there is a surface coating of a suitable adhesive of the requisite thickness and the excess particles may then be removed. As the next step, before the adhesive has set, the coated web may be passed between accurately spaced nip rolls which level the tops of the globular particles and submerge them'to ;or by spraying with a sizing solution, or by any other suitable means.
:Other methods -of applying solid particles to a backing which may be adapted to the manufacture of my composite stencil backing are those described generally in Carlton Patent No. 2,318,570. Such methods are particularly adapted to secure uniform spacing of the particles by reason of the dispersing action resulting from the electrical charges imposed upon the particles. "To accurately level the "tops of all particles and to submerge their lower portions to the required depth in adhesive the freshly coated web may then be passed beneath a nip rolliwhich I is accurately spaced from another machine element in :contact with the fle'x ible backing so that the spacing of these machine elements corresponds to the overall thickness of the product. Finally the globular particles are retained at this controlled depth in the adhesive and with their tops uniformly level during the setting-cf :the adhesive.
Where, as is usually the case, closely spaced point for contact with the stencil are desirable, care is taken to crowd the particles together leaving only a thin film o'f 'a'dhesi'vebetweeh their adjoining peripheries. The resulting product possesses the highest degree of uniformity because the number .of :points of contact afforded by the protruding spherical segments-Over a given area is determined by the accurate grading of the particles themselves, for size.
To illustrate an exemplary embodiment of the invention, and not to limit it, reference is had to the accompanying drawing in which:
Figure 1 is 'a plan view showing my improved stencil sheet and backing unit;
Fig. :2 is a magnified plan view showing a fragmen-tary portion of the stencil sheet and backing on which a type impression has been made;
.Eig. :3 -is a further magnified section takenpn the line 3-3 of Fig. 2 and illustrating the coaoperative relationship between the stencil and :backing, as well as prefer-red details of the backmg, and
Fig. 4 is a fragmentary plan view showing a fragment of the face of the backing on which 'wax or other ink-impervious material from a stencil has been impressed by a type, also on an enlarged scale.
the drawing a stencil sheet, indicated 'generally by the numeral 5, is shown in assembled relation to my improved backing, indicated generally by the numeral "These elements may be joined together in the usual manner by a narrow band of adhesive 3 extending along the upper margin of the sheet 5, in spaced relation to the upper edge 'of the backing 16, thereby leaving a margin 8 of the backing 6 which projects to facilitate the fastening of the stencil sheet to its support in the duplicator machine. Keyhole shaped perforations 9 in the margin 18 are provided to receive lugs on the cylinder or other stencilysupporti-ng element of the machine. To
facilitate the necessary separation of the impression part of the backing B from its margin 8 aline of perforations If? is formed therein, be-
low and adjacent to the band of adhesive I.
As shown in detail in Fig. 3, my improved backing sheet has a facing composed of a single layer of minute, spheroidal particles II which are secured by means of a coat of adhesive I2 to a flexible supporting sheet I3. As hereinbefore described, the particles II preferably comprise ininute spherical or spheroidal glass particles of substantially uniform size, substantially uniformly distributed to afford a level but discontinuous surface for contact with the stencil sheet 5. Each of these particles is submerged in the adhesive I2 to a depth of from to 50% of its diameter so-that recesses are provided between their protruding segments of sufficient capacity to receive all of the ink-impervious coating material that is to be displaced from the stencil sheet 5 over the areas of the impressions. The stencil sheet 5 has a tissue paper base i4, composed of long fibers and coated on its face adjacent the particles. II with an ink impervious material I5 which may be a wax, a mixture of waxes or other suitable pressure displaceable substance.
To prepare the stencil sheet 5 to duplicate typewritten matter the assembly comprising this sheet and the backing 6, shown in Fig. 1, is placed on the platen of a typewriter'as for ordinary typing and, with the inking mechanism inoperative, the machine is operated in the usual manner to type the subject-matter on the uncoated face of the stencil sheet. During this operation the keys apply suflicient pressure upon the areas of the type characters to displacethe ink-impervious material I5 from the fibrous base l4 into the recesses between the protruding segments of the spherical particles II. This is illustrated in detail in Fig. 3'wherein a fragmentary portion of a type is indicated at I6 in cross section and greatly magnified. A face Isa of the type is shown withdrawn slightly from the area of the impression and is representative of the width, usually .01 to .015 inch, ofthe ordinary type faces approximately to the same scale as that of the backing 6 which is also shown in this view. Pressure thus applied causes the coating material I5 to be displaced into the recesses between the globular particles II, as indicated at IT, leaving the fibrous stencil area I 8 pervious to ink. In Fig. 2 this pervious area I8 of one of the type characters, viz.: the letter t, is shown in plan view and in Fig. 4 the displaced material I"! is indicated on the sphere coated backing sheet 6.
Uniformly well defined stencil characters are obtained by reason of the fact that the ink-impervious material is allowed to escape from the entire area of each impression into the uniformly distributed recesses of adequate capacity between the rounded protuberances of the facing particles. This will be understood when it is considered that the face Ilia of each type character is opposed by a large number of minute, smoothly rounded protuberances which support the fibers of the stencil base I4 without cutting them, while directing the displaced material I5 into the immediately adjoining recesses. Damage to the typewriter keys is prevented not only by the cushioning effect of the stencil material but also by the smooth, nonabrasive character of the protuberances and the large number of them which oppose each type face,
My improved backing coacts with the stencil sheet in a similar manner to produce clearly defined, pervious areas when the impressions are made by a stylus, as in free hand writing and drawing on the sheet 5. In this case the smoothly rounded, hard surfaced, protuberances formed by the particles I I afford a support which allows the stylus to glide smoothly over the stencil With-,- out severing or detrimentally disturbing the flbers comprising the base I4.
As long as the backing remains in contact with the stencil the work thereon is clearly legible by reason of the fact that my preferred transparent glass particles are excellentreflectors of light which coact with the white or light colored back-:- ing to illuminate the pervious areas formed by the impressions, notwithstanding the presence of the network of fibers remaining in these areas. Moreover, legibility is improved even when the spheroidal particles are composed of opaque material of a color which contrasts with that of the stencil sheet because the smoothly rounded pro tuberances deflect the displaced wax into the adjoining recesses which are uniformly distributed and have suificient capacity to insure exposure of the tops of the particles in contact with the fibrous network of the stencil. Consequently proof-reading and the making of corrections without removing the stencil and backing from the typewriter is facilitated by the present invention.
The displacement of the wax or other ink-impervious substance into the recesses of the backing 8 is so uniform and complete that this product is adapted to constitute a clearly legible, permanent record of the subject-matter impressed on the stencil. It is more durable than most record papers and ordinary rubbing of the sphere coated face does not remove or otherwise affect the legibility of the impressed deposits. In the event that the backing is not needed as a permanent record, a substantial saving in the cost of the duplicating may be effected by repeated use of the same sphere coated backing sheet. To remove previous deposits it is only nec-i essary to apply a solvent for the wax or other deposited substance by suitable mean such as a cloth or brush. Such cleaning is greatly facilitated where the surface to be cleaned is composed of my preferred, smooth, spheroidal protuberances of glass or of other globular particles which are similarly devoid of abrasive points and edges.
The discontinuous nature of the surface of my improved stencil backing affords a multitude of minute recesses between the adjacent spherical particles and when the stencil sheet is hit by the type face or otherwise impressed as by a stylus these recesses serve to accommodate the fibers of the stencil sheet and to prevent the cutting of these fibers, thus eliminating the cutting out of closed loops of characters such as the letter O, which is one of the above noted defects of the prior constructions utilizing a smooth backing sheet. Accordingly the use of my improved stencil backing not only results in improved stencils when used with stencil sheets of special long fiber tissue paper, but also make possible the use as a stencil sheet of less expensive tissue paper with shorter fibers which would not be satisfactory for use with the smooth continuous surfaces of the backing sheets previously used.
What I claim is:
1. In combination, a stencil sheet upon which pervious areas may be formed by the application of pressure and without perforating the sheet and 4a aback-mg ifor said sheet comprising a meniplicity er minute globular particles of substanmay funisiorm :si'ze having rounded segirient's protruiimg in contact with said sheet and in relation to :each other, a flexible support in said particles and an adhesive bonding said particles to said support, said. particles be ing submerged in the ia'dh'esive to a depth knot exceeding :ene ha lf their :diameters.
2. in combination, :a stencil sheet upon which pewious areas may be formed by the application 56f pressure and a :backing for said "sheet com"- pixising a multipli'city of minute globular, glass narticlesr l'iaving :rou'n'ded segments protruding in contact with said sheet and .in spaced relation to'each other, "afiording a substantially level but discontinuous -supporting surface for saidstencil sheet, :a flexible support \for said particles and an adhesive bonding said particles "to said support.
3. combination, a stencil sheet upon which penvious areas may be formed the application of pressure and :a backing for said sheet comprising :a single layer of substantially spherical particles "of substantially uniform size, the diameters :of which do not exceed .-003 inch and each having a rounded segment protruding in contact with the stencil sheet, affording a substantially level but discontinuous supporting :surface ifor sa-i'd stencil sheet, a flexible support for said particles and an adhesive @bonding said particles l-to said support.
4.;11-1 combination, a-stencil sheet composed of a fibrous base carrying pressu-re-displaceahle costing ia-nd a backing for 'said shee't comprising 2. single compact layer of spheroidal particles of substantially uniform size having smooth, rounded segments :pr'ot-rud-ing in contact with said sheet, affording a substantially level but discontinuous supporting surface for said stencil sheet, the diameters of said particles being not 'laaiger than @093 inch, =a flexible support for said particles and an adhesive bonding said particles to said support and submerging them to a depth not exceedingone-half their diameters, the space between mmtruding segments of said particles being adaiotei'l to receive the coating displaced from said sheet by steno'il i'zin'g pressure.
'5. In combination, a stencil sheet composed of a fibrous bas'e earry mg a coating of ressure- 'displaceable wax and a backing for said sheet comprising a single compact layer or spheroidal glass particles of substantially uniform sizeflea'ch having a sm'ooth, rounded seg r'nen't protruding in oontact with the wax "coated surface of said sheet, "a flexible support for said particles and an adhesive bondin'g 's'a-id particles to sai'd support and submergin'g them to a depth of from 30% to or their diameters, the space between protruding segments "of said particles having capacity sufficient to contain allof the was displaoed from said sheet by stenc'iliz'ing pressure.
'6. A stem-d1 sheet assembly comprising a type and styms i mpfESSible =st'enei1-sheetnaving a. base tissue of interlaced fibres impregnated wl'th a p'ressui e dis'pl'aceable coating, and a backing for said stencil sheet having one surface foiimed by a =layer of small, hard, elastic-bodies set in spaced relati'onin ='a :plasti'cally deformable adhesive, said bodies having rounded projections adapted to oontaot the'stencil sheet and defining inter'sp'ac'es for reception of thefibr'es and oi coating material expressed during 's'tenciliza'tion.
*CHARLES 'K. References Cited In the file of This patent UNITED STATES PATENTS