|Publication number||US2555319 A|
|Publication date||Jun 5, 1951|
|Filing date||Aug 17, 1944|
|Priority date||Apr 19, 1943|
|Publication number||US 2555319 A, US 2555319A, US-A-2555319, US2555319 A, US2555319A|
|Inventors||Cross Bert S|
|Original Assignee||Minnesota Mining & Mfg|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Referenced by (37), Classifications (7)|
|External Links: USPTO, USPTO Assignment, Espacenet|
June 5, 1951 B. s. cRoss 2,555,319
BEAD COATED TYMPAN SHEET 7l/fa wwf/)fg INI/ENToR.
MMV?? TTRNEY June 5, 1951 B, s, CROSS 2,555,319
BEAD COATED TYMPAN SHEET Filed Aug. 17, 1944 2 Sheets-Sheet 2 INVENTOR.
M/MMLW Patented June 5, 1951 UNITED STATES TENT OFFICE BEAD COATED TYMPAN SHEET Application August 17, 1944, Serial No. 549,906
This invention relates broadly to the provision of a composite sheet material having a surface composed of a multiplicity of substantially spherical protuberances. More specifically this invention relates to such sheet material comprising a backing sheet to a surface of which a plurality of substantially spherical particles of material are securely bonded by an adhesive material to provide a substantially uniform but discontinuous surface wherein the advantageous physical characteristics of spherical particles as a surfacing material for sheet material as such and in combination with selected backing sheet ma terials and selected adhesive coating materials are made available for various uses hereinafter more specically designated.
Among the important elds of use for the composite sheet material of my invention are the printing industry where it is used as a durable cover or blanket for the press rolls and bed and as a tympan sheet to prevent olset and to improve the quality of the printing and the paper and fabric coating industries where my material is used as a facing for those elements oi the coating machine which make contact with the freshly coated surfaces of the paper or fabric for supporting and guiding purposes and to minimize the transfer of the wet coating substances to such machine elements. In these and other applications it is important to provide a multiplicity of points of contact which are uniformly spaced at a common level and the contact points and adjacent areas in most cases must be either nonadherent or of such character that they may be cleaned readily. Moreover, in many applications 'v the bead coated material must withstand high iocalized pressures and severe impact and rubbing forces tending to dislodge and crush the indivdual beads.
I have discovered that minute spherical or sphercidal bodies, when bonded and arranged as erein described, impart unique and astonishing qualities to contact surfaces for many purposes. Among 'their outstanding characteristics for my purposes are their great strength to resist crushing force, their uniformity in size which can be controlled within narrow limits, as compared with granular or crushed materials, and their smooth rounded surfaces which are easy to clean and have no abrasive projections. They possess the further advantage for my purposes in that each bead presents a single point of contact at a controlled elevation and at a controlled distance laterally from the contact points formed by the adjacent beads at substantially the same elevation or level. As compared with granular or crushed material such minute globular bodies presenta more dilrcult problem of bonding where they are subjected to severe impact and rubbing forces since they have no reentrant or concave surfaces to interlock with the adhesive and they tend to roll free of their support under tangentially directed force. For my purposes the backing and bonding materials, as well as the spheroidal bodies, must in some cases withstand localized rolling and/or impact pressure of the order of magnitude of three to five tons per square inch.
I-leretofore transparent beads have been attached to various materials, for the purpose of ornamentation and to reflect or diffuse light, but to my knowledge none of the previously known beaded materials have either had the high degree of uniformity in the projecting segments oi the beads or the great strength to resist severe impact, rubbing and other forces tending to crush and dislodge the beads required for my purposes.
In the iield of printing accessories it has been proposed to. use granular or rough surfaced paper of the type sometimes called sandpaper for the facing of tympan rolls and for other purposes. rlhis type of paper offers relatively irregular points of contact, the grits tend to break down under the applied pressures, they are relatively dimcult to clean and the degree of frictional re,- sistance to slippage of the work in contact with the grits cannot be controlled within wide limits as in the ease of my product. Various attempts have been made to control the grit shape and thereby prolong the useful life of the product, but since they are produced by a crushing operation the shape of the individual particles cannot be accurately controlled and a large proportion of the particles have strain lines which cause them to break down under the printing or other applied pressures. By the comparative tests more fully hereinafter described it has been shown that my bead coated product is far superior to the prior grit coated materials in the matter of durability, elimination of offset, ease ci' cleaning and in improving the quality of the printing.
lt is an object of my invention to utilize the unique properties of minute spherical or spheroidal bodies herein described as the contact facing of exible materials adapted to withstand the destructive forces to which they are subjected in the lields of use described and for analogous and other purposes.
Other objects of my invention are to provide novel bead coated materials which are adapted to overcome various defects and shortcomings of the prior materials used for like purposes; to provide such coated material with a contact surface made up of a single layer of globular bodies of substantially uniform diameter and having the tops of the bodies uniformly spaced in a common plane; to afford a bond of great strength between minute spheroidal facing bodies and a flexible backing therefor, and to control the tendency of contacting substances to adhere to the beads or support therefor by appropriate selection of the component materials or finishing treatment.
According to the present invention I utilize as the facing material a single layer of globular bodies of substantially uniform diameter and having the requisite strength and surface characteristics. These bodies are securely bonded individually to a strong, flexible backing, leav ing a somewhat less than half the diameter of each body projecting for contact with the work.
Both breakage and loss of beads must be prevented in a product of this class because serious deterioration of the work may result from even slight irregularities in the contact surface. To
insure an adequate bond I carefully select the adhesive for its resistance to impact as well as its adhesion to the beads and backing and, in the manufacturing operation, great care is exercised to submerge each bead in the adhesive to a depth of not less than half its diameter to the end that a strong embracing socket covering from to 75% of the bead area is formed by the adhesive. For many uses about submergence in the adhesive is preferable to afford adequate capacity in the depressions for the applied substance or particles of the work, as the case may be, combined with high bonding strength.
I thereby not only prevent appreciable loss of beads but also make the entire surface of the depressions between beads accessible for cleaning. rIhis is of considerable importance where some transfer` of ink or other substance to the beaded surface is unavoidable or desirable and the transferred substance is to be removed later. Smooth hard bead surfaces are provided for most uses. Vitreous, glass or glass-like surfaces formed on beads of adequate toughnes are eX- cellent where, as in the tympan sheet and press roll blanket field, an unyielding face to oppose the type is usually beneficial. For such purposes have successfully used beads formed from a lime soda glass such as that commonly used in the construction of glass containers and window panes. However, since the optical characte 1istics of the material are not involved, the beads may be formed from iron, steel or other metals or alloys, or from ceramic material, mineral, synthetic resin, or other materials having the required surface quality and toughness combined with cheapness commensurate with the intended use.
Inexpensive methods of forming spheroidal bodies of adequate strength are well known to those skilled in the art. According to one suitable method, crushed and roughly sized particles of the material are projected into a body of air or inert gas which has been heated to the melting temperature of the particles and the latter, while in suspension, are allowed to cool and harden while the phenomenon of surface tension retains them in the desired spherical or spheroidal shape. Thereafter the globular bodies are accurately graded for size by methods known to be suited to the range of sizes required. Another method that has been used for forming the minute globular bodies involves preliminary heating of a suitable material to a molten condition, then breaking it up into minute globules by the application of a jet of high velocity fluid, then allowing the particles to solidify while in suspension and finally grading them for size. Either of these methods produces beads which are inherently strong as compared with relatively irregular particles of crushed material because the resulting beads are devoid of the strain lines produced by crushing. Comparative tests have shown that such fused globular bodies have vastly superior resistance to crushing. For example, average specimens of glass beads and of glass particles, called cullets, and abrasive grits of silicon carbide (SiC) and aluminum oxide (A1203) all of the same mesh or bead size, were tested by successively placing the individual particles between the at, hardened steel jaws of a testing machine adapted to indicate the pressure in pounds exerted between the jaws and having means for progressively increasing the pressure applied to the particle under test. In this series of tests the pressures in pounds required to crush the several beads or particles (ten specimens of each composition) were recorded as follows:
[All particles #10 bead or 80 mesh size (values in pounds required to crush) .1
Gloss Glass Bead SIC Cullets A1203 8. 0 5. 75 75 4. 0 4. 5 2. 75 75 3. 5 5. 0 l. 75 l. 25 5 9. 0 2. 50 5() l. 5 8. 0 1. 25 50 25 7. 0 50 1. 75 l. 25 8. 0 1. 75 50 75 8. 0 17. 00 75 4. 00 6. 0 50 50 l. 5 5.0 4.00 l. 25 1. 75
case of the glass beads is much more uniform than that of the other particles tested.
The backing material for my product must have moderately good resistance to shear and tension combined with sumcient flexibility to permit the material to conform t/o the machine elements or other support on which it is to be mounted and to withstand the local flexing incident to its use. A backing comprising a good grade of wood pulp or rope paper of twenty pound or heavier weight is suitable for many uses, although woven fabric, rubber sheeting, rubber coated fabric, suitable synthetic resin sheets, or other materials or combinations of materials having adequate strength may be employed as the bead backing in other or special applications. It will be evident that the requirements of strength and other characteristics of the backing vary widely depending on the iield of use. For some purposes the backing must be hard and unyielding, ywhereas in other cases a degree of compressibility and elasticity is desirable to allow the bead coated material as a whole to be compressed under locally applied pressures. Thus when the material is used as a press blanket or tympan sheet for newsprint presses the backing for the bead coat may be made sufficiently compressible to compensate for ordinary inequalities in the type face level or slight variations in cylinder face and to obviate the need for make-ready adjustments. A porous, somewhat absorbent backing may be provided for some specialties but for most uses the material should be impervious to the ink or other applied substance. This quality may be provided either by coating the front or back face of the backing with an impervious composition or by providing an interior layer which cannot be penetrated by the ink or other applied substance or by the cleaning fluid which is to be used. Such coating or interior layer may comprise ,a glue and glycerine composition or a resin such as an alkyd resin or a synthetic rubber which is nonreactive to the ink or other applied substance and insoluble in the cleaning iluid that may be applied in use. With fibrous or other porous backing materials the impervious composition may be caused to saturate or impregnate the backing or an interior or exterior layer thereof.
Examples of suitable adhesive for bonding the globular bodies to the backing are proteinaceous adhesive, such as glue, or `a suitable rubber or synthetic elastomer composition, or a thermosetting synthetic resin, such as phenol-aldehydes, urea-formaldehyde, melamine aldehyde, thio urea-formaldehyde, alkyd resins, etc. and mixtures of such resins or a suitable thermoplastic resin. Most highly plasticised resins and unmodi-` ed starches have insulcient bonding strength for my purposes.
It is to be understood that the spheroidal or globular bodies constituting the facing of my products are herein sometimes called beads for convenience of reference only, not to limit the subject-matter to conventional bead sizes or materials which are designed to produce various optical or ornamental effects.
My improved material may be prepared by either of several known methods which have been employed in the manufacture of coated abrasive material. For example, the small solid globular bodies may be dropped upon the flexible backing upon which there is a surface coating of a suitable adhesive of the requisite thickness. The spheres may be sprinkled or spread upon the web, for example by gravity, the excess 'spheres being then removed. As the next step,
before the adhesive has set, the coated web is passed between accurately spaced nip rolls which level the tops of the beads and submerge them to the required depth in the adhesive. After the adhesive has set, a second or sizing coat may be spread over the spheres in order to more firmly secure them to the flexible backing or to impart a surface which will control the tendency of the ink or other substance encountered in a particular use to wet or adhere to the finished material. In many situations it is advantageous to provide a beaded surface or sizing therefor which is either repellent or non-adhesive and non-absorbent with respect to the applied substance. The sizing coat may be applied by means of a roll partially immersed and revolving in a pan of sizing material `and contacting with the bead coated surface of the web, 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 by the additional procedure herein described to the manufacture of my products, are those described generally in Carlton Patent No. 2,318,570, which is particularly .adapted to secure uniform spacing of the beads by reason of the dispersing action resulting from the electrical charges imposed upon the particles. The additional procedure includes treatment to accurately level the tops of all beads and to submerge their lower portions to the required depth in adhesive. As hereinbefore indicated this may be accomplished by passing the freshly coated web beneath a nip roll which is accurately spaced from another machine element in contact with the backing. The spacing of these machine elements corresponds to the overall thickness of the product and the globular bodies are retained at this controlled depth in the adhesive and with their tops uniformly level during the setting of the adhesive. Caliper tests of my improved bead coated material for tympan sheet use show uniformity in overall thickness within approximately one-thousandth of an inch.
Where, as is usually the case, closely spaced points for contact with the work are desirable care is taken to crowd the spheres together leavinfY only a thin film of adhesive between 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 beads themselves. Methods for con trolling the distribution or spacing of the beads in the manufacturing operation are known in the grit coating art and such methods are employed to obtain any desired spacing of the globular bodies on the adhesive coated backing for my purposes.
After the spheres have been deposited and followed by the application of a final sizing coat (if one is used), the sizing may be set or cured, for example, by passing the sheet through an oven in `the form of festoons, similar to the method used in the curing or setting of coated abrasive webs, well known in the coated abrasive K art, where a heat-maturable, thermosetting synthetic resin is used as the adhesive and/or the sizing coat, the resin may be cured by any of the methods known to the art. The resulting web may be cut into sheets of varying size den pending on the particular field in which it is to be used. For use on large tympan rolls it has been found that 8 sheets size 22 inches by 36 inches are necessary to cover the roll.
To illustrate exemplary embodiments of the invention, and not to limit it, reference is had to the accompanying drawing in which:
Figure l is a magnified section through a bead coated material made according to the present invention, wherein the contacting surface is formed by a layer of small, solid, globular bodies secured to a backing by means of an adhesive coating;
Fig. 2 is a diagrammatic vertical section of a printing apparatus illustrating a method of printing on both sides of a paper web in which the supporting rolls opposed to the type cylinders are shown covered with material embodying my invention;
Fig. 3 is a fragmentary enlarged sectional View showing the action of the printing type on the web and showing the small globular bodies in contact with the portion of the web to be printed;
Fig. 4 is a diagrammatic vertical section of cloth coating or finishing apparatus in which my bead coated material is used as a facing for certain of the rolls supporting the freshly coated fabric;
Fig. 5 is a diagrammatic sectional view showing paper coating apparatus wherein my improved material is used on an idler roll in contact with the freshly coated paper;
Fig. 6 is a magnified sectional view showing an embodiment of my invention wherein spherical bodies of one of the larger sizes are relatively widely spaced on the backing and also showing a nlm for controlling the wetting properties of the contact face;
Fig. 7 is a magnified sectional view showing my bead coating on a cloth or textile fabric backing, and
Fig. 8 is a similar view showing a form of the invention wherein the backing comprises a com-- bination of paper and textile fabric.
Referring in detail to the drawing (in the several figures of which like reference characters denote similar parts), in Fig. l a sheet Z is shown in which small solid globular bodies Iii are secured to a iiexible backing I I by means of an adhesive I2. The bodies I are approximately uniformly spaced and substantially spherical. in shape. These bodies are shown submerged in the adhesive to a depth somewhat in excess of one-half their diameters so that each is positively confined in a strong socket wherein surface adhesion alone is not depended on to anchor it.
In Fig. 2 the numeral I3 represents a blank sheet 01 web, such as paper, which is fed in the direction of the arrow from a supply roll (not shown) between the print roll I4, inked by means of ink roll I5, and the first tympan or impression roll I which is preferably faced with my bead coated material. The paper I3, thus printed on its lower side, is then fed between a second print roll I1, similarly inked by an ink roll I8, and a second tympan or impression roll I9, faced with a tympan sheet indicated generally by the numeral 20. Other modifications whereby the tympan sheet may be used in the form of a belt which passes around. the tympan roll I9 and idler rolls (not shown) will be readily apparent. Other modifications, such as the addition of wiper rolls (not shown) to meisten the tympan sheet with a suitable ink solvent, may be used, and are hereby comprehended.
Figure 3 illustrates further and more in detail a part of the printing process with which this invention is particularly concerned. The paper I3, after it has been printed on its lower side, is fed between a printing roll Ii, having type 2I, and a tympan roll I3, faced with a tympan sheet 2E). The tympan sheet comprises a fiexible base II and small solid globular bodies Il, such as glass beads, secured to the backing II by means of an adhesive I 2.
Where my improved material is to be used as a tympan sheet the globular bodies and bonding adhesive therefor must be chemically inert to the action of the printing ink and to the solvents used therewith. In practice, glass spheres having a diameter in the neighborhood of .U01- .005 inch, e. g., .003 inch, corresponding to Number bead size and 220 grit size, is suitable for many applications, but smaller or larger sizes may be employed as desired. If small solid globular bodies other than glass spheres are used, the diameter of the individual globular bodies may be as above indicated for glass spheres. The
exible backing may be made of cloth, paper, or other material, or combinations of suitable materials, and may be sized or unsized, and, for example, of a thickness of the order of .004 to .016 inch. An excellent tympan sheet has been obtained by the use of Number l5 lime soda glass spheres, corresponding to 220 mesh size, adhesively secured to a pound Fourdrinier paper. As is well known in the papermaking art, 130 pound paper means a paper of Such weight that a ream thereof, i. e. 480 sheets, 24 x 36" in size, weighs 130 pounds. Any cf the ordinary backings used in coated abrasive sheets may be used. If it is desired to have the backing less absorbent, a highly calendered paper, such as 130 pound cylinder paper, may be used. If desired, a paper which has been treated with suitable material such as glue, zein, etc. to render it oil and grease proof may also be used. However, if it is preferred to have a more absorbent backing, paper such as 130 pound Fourdrinier paper may be used. In high class printing jobs, e. g. in printing the better magazines involving precision work in controlling the depth of shade of portions of halftone cuts, etc., it is sometimes desired to have the backing and/or bond absorptive but to have the backing backsized or comprising a ply on the back or interior of the same which will prevent the ink and/or cleaning fiuid from going completely through the tympan sheet or blanket.
Referring to Fig. 4 of the drawing, a web 22 of cloth to be finished or coated is fed from a receptacle 23 upon suitable guide rolls to the periphery of a drum 2li which is partially submerged in a vat 25 containing starch, glue or other coating or finishing substance in liquid form. The wet face of the freshly coated or impregnated fabric then passes over idler rolls 25 which are faced with my bead coated material 3G and thence to the drying section of the machine indicated generally by the numeral 21, wherein the first roll 28 which makes Contact with the coated side of the fabric is also provided with a blanket of the material 3G to minimize both transfer of the coating substance and smearing of the coated face. For this purpose, in case the coating substance is a starch, the spherical bodies It 0f the material Se may be bonded to the backing by employing an adhesive of the phenolic resin type to which the wet starch on the cloth does not readily adhere. The spheroidal segments projecting from the material 3Q may also be covered with a phenolic resin lm or Sizing. In general, spheroidal bodies of the larger sizes ranging from bead sizes l() to 5 are better suited for minimizing offset in the field of cloth finishing and wider spacing of the globular bodies is preferable in this field in order to compensate for the tendency of the protuberances to penetrate relatively deeply into the softer, more yielding fabrics and their coating.
In Fig. 5 an application of the invention to paper coating is illustrated diagrammatically. In this case the paper is fed from a roll 3i over suitable guide rolls and its bottom face is brought into contact with a coating roller 32 submerged in a pan 33 containing the coating substance. The web 3d is then guided to the drying section 35 and any supporting machine element, such as the roller 36, which makes contact with the wet face of the web, is preferably covered with my bead coated material 36 having beads, adhesive and backing which are correlated to the particular substance carried by the web Sli as hereinbefore described.
Referring to Fig. 6, the material indicated generally by the numeral 3o has the globular bodies il! of one of the larger sizes bonded to the backing ll in relatively widely spaced relation to each other and a film of sizing 3l is shown covering the protruding surfaces of the bodies lil and intervening exposed surface of the adhesive l2. As hereinbefore indicated, the iilm 3l increases the bond and may be of such character as to repel or minimize adherence of the particular substance that is to be encountered in use. Penetration of the wetting substance completely through the sheet may be prevented by the appli cation of an impervious composition to the back face of the backing Il as shown, or otherwise as hereinbefore described,
As shown in Fig. '7, the globular bodies forming the contact face may be bonded to a backing i le. comprising a textile fabric having the required strength and flexibility. Material of this character is well adapted for a number of special uses including the construction of upholstery coverswherein the protruding globular segments composed of glass or other smooth durable material minimize wear on the clothing coming in Contact with the upholstery. When used as the seat covers in vehicles this material facilitates sliding movements of the occupants of the vehicles, to and from the seats, and in moving about within the vehicles.
Fig. 8 shows the globular bodies lil forming the contact facing on a composite backing which may comprise a layer of paper Hb and a cloth layer 3d bonded together by a layer di] of glue or other suitable adhesive. Such a backing affords great strength combined with flexiblity and a degree of compressibility. Other combinations of backing materials as well as variations in the bead sizes, materials and spacing and use of other bonding materials and siaing'lms and treatment to control surface characteristics within the scope of my invention will be understood from the foregoing and following specification.
The following examples carried out on commercial scale printing operations illustrate the superiority and long life of an improved tympan sheet constituting one form of my invention. It will be understood, however, that the following examples are presented merely as illustrations of the utility and characteristics of the invention and are not to be construed as limiting the same.
EXAMPLE I .fi tympan sheet of the old style, i. e. sandpaper type, well known and used commercially, was compared by actual test with the tympan sheet of this invention. The old style sandpaper type tympan sheet, hereinafter called tympan sheet A consisted of a backing of 130 pound cylinder paper to which was adhesively secured a layer of Aiundum abrasive grits of a grit size 2&0. Glue was used as the adhesive bonding material. The tympan sheet of this invention, hereinafter called tympan sheet B consisted of backing of 130 pound Fourdrinier peper to which was adhesively secured a subtially uniform layer of glass beads of a diameter of approximately .003 inch. Glue was also used the adhesive bonding materiaI in this tympan sheet. The glass beads of the size stated are also known as #l5y glass beads which corresponds in size to abrasive grits of #220 grit size. Sheet A used to cover a tympan roll in one large press and sheet B to cover a tympan roll in another. Eight sheets 22 X 36" were needed i l0 in each case to cover each tympan roll. Oil wiper rolls were used. The presses were then put in operation on the printing of a catalogue.
RESULTS or TEST Longevity Tympan sheet A was found no longer serviceable after 35,000 impressions, while tympan sheet B was removed after the run was completed and when 130,000 impressions had been made and was still serviceable.
Microscopic examination of the used sheets disclosed in tympan sheet A, a breakdown of pointed or block surface to a generally at surface in critical areas of heavy form. These heavy form areas are areas in cuts or miscellaneous printed forms which appear especially black or heavy This is the result of continuous or emi-continuous type or cut forms which greatly increase the unit pressures operating upon the tympan surface. Hence the tendency for rapid breakdown of the granules or grits in heavy form areas. Tympan sheet B showed no apparent wearing or breakdown Vof the glass spheres in the critical areas of heavy form.
Offset Half-tone reproductions of the sheets printed on the press using tympan sheet B showed no noticeable offset, while those printed on the press using tympan sheet A showed offset in increasing amounts as the run progressed.
Improvement in printing The halftone reproductions, as well as type areas or areas strictly of printing, were cleaner and sharper where tympan sheet B was used over that of tympan sheet` A. It was thus ap parent that my product improved the general appearance of the printed page throughout the run.
EXAMPLE II Another commercial test run was conducted using only one press wherein the tympan sheets A and B described in Example I, were placed side by side and used to cover half the tympan roll. No oil wiper rolls were used. The job of printing was on newsprint paper. A run of 130,000 impressions was made.
RESULTS or TEST Longevity Both sheets were used over the entire run of 130,000 impressions.
Microscopic examination of the used sheets disclosed in tympan sheet A, a breakdown of pointed or block surface to a generally fiat surface. The breakdown of the granules in areas of heavy form were readily apparent to the eye. Tympan sheet B disclosed no breakdown in heavy form areas and the glass spheres showed no noticeable wearing or breakdown.
Half-tone reproductions of sheets taken from the side or roll covered with tympan sheet B showed no noticeable offset, while those printed on the side of roll covered with tympan sheet A showed offset in increasing amount as the run progressed.
Improvements in printing The half-tone reproductions, as well as type areas or areas strictly of printing, were cleaner and sharper where tympan sheet B was used over that of tympan sheet A, thus indicating that sheet B improved the general appearance of the printed page throughout the run.
EXAMPLE III Another commercial run was conducted using the same type of tympan sheets as described in Example I, which were placed on two tympan rolls in the manner described with reference to Example I. The job to be printed was a commercial seed catalogue.
RESULTS or TEST Longevity 'Iympan sheet A was used for 72,000 impressions, while tympan sheet B was used for 75,000 impressions. The life of sheet A was estimated at an additional 18,000 or a total of 90,000 impressions, while that of sheet B was estimated at 75,000 additional or a total of 150,000 impressions.
Half-tone reproductions of the sheets printed on the press using typmpan sheet B showed no noticeable oset, while those printed on the press using typmpan sheet A showed considerable oifset and in increasing amount as the run progressed.
Improvement in printing The half-tone reprodctions, as wel] as type areas or areas strictly of printing, were cleaner and sharper where tympan sheet B was used over that of tympan sheet A thus indicating that my tympan sheet improved the general appearance of the printed page throughout the run.
It will be readily apparent from the foregoing description, that in accordance with this invention a greatly improved tympan sheet has been produced. These superior results are obtained by the use of the small solid globular or spheroidal bodies as a uniform coating in combination with the strong bonding material submerging more than half the surface of each body and providing a surface which does not break down under conditions of use, the points of contact being retained at a uniform elevation. A further advantage is derived from the shape of the protruding surfaces of the spheres and that of the bonding material between protuberances which surfaces lend themselves readily to the action of wiper rolls, hand scrubbing or cleaning with a cloth.
ROCKING DRUM TESTS Embcdiments of the present invention have been further compared with the present commercial products most nearly resembling it by subjecting the several products to the same rubbing tests. For this series of tests the apparatus has included a drum having an unyielding cylindrical surface of 121/2 inches in diameter mounted with its axis horizontal and arranged to be oscillated about its axis. The specimens to be tested were successively attached to the upper periphery of this drum and pressure equal to a two pound weight was applied by means of a hardened steel block having a ilat lower end 13a inch square disposed at an angle of approximately 4 degrees to the beaded or grit coated surface of the material under test so that the Weight was applied to the material along an edge of the block it of an inch long extending parallel to the axis of the drum. An electric motor was connected to the drum to cause the cylindrical supporting surface to be oscillated at the rate of sixty cycles per minute and with a stroke equal to approximately L11/2 inches relative to the contact edge of the stationary pressure block. The edge of the block which made contact with the specimen under test was formed by a sharp right angle corner so that this edge had a tendency to cut into the material under test during the stroke in one direction. Thus the materials under test were subjected to combined scraping and rubbing forces tending to dislodge the surface particles. The machine was provided with an automatic stroke counter and the number of strokes applied in each test were recorded. The weight of the surfacing material removed in each test was nally determined and compared with the weight of the material originally on the corresponding area of the specimen to determine the percentage loss of such surfacing material resulting from the test.
RESULTS 0F RocKINc DRUM TESTS When this test was applied to a specimen of my improved material having a surface composed of #10 lime soda glass beads it was found that only 1.3% of the beads over the area of the rubbing were dislodged by 40 strokes in the testing machine. Operation of the machine was then continued until the same specimen had been subjected to 250 strokes in the machine. This caused a loss of 5.4% of the beads. A second specimen of my product having a facing of #13 lime soda glass beads was subjected to 40 strokes in the machine and showed a loss of 7.74% of the beads over the area subjected to the rubbing. In a third test of my product having a #15 bead coating (also lime soda glass beads) 40 strokes of the machine caused 6.96% bead loss over the area of contact with the block.
As a basis for comparison with my product a commercial tympan sheet like that tested in the printing tests hereinbefore described was subjected to the rocking drum test above referred to. In this case the material to be tested had a coating of 280 mesh aluminum oxide grits of the blocky type particularly adapted for tympan sheet use and it was found that after 40 strokes of the machine the sheet had lost 34.6% of the grits from the area contacted by the steel block. A similar test of a good grade of commercial abrasive paper coated with mesh aluminum oxide grits showed 22.9% loss of grits after 40 strokes in the machine. In another` test of a commercial abrasive sheet coated with 80 mesh silica carbide grits there was a loss of 36.5% of the grits after 40 strokes in the same machine and under con.- ditions identical with those in the other tests. These tests clearly showed that my sphere coated materials are vastly superior to the known grit coated materials in the matter` of resistance to rubbing and cutting forces tending to dislodge the surfacing material.
The resistance of my products to forces tending to dislodge the beads has also been compared with that of other commercially available materials having surface coatings of glass beads, by applying to such commercial products the rocking drum tests hereinbefore described. Among the commercial products so tested were two specimens of a light reflecting material comprising a surface coating of #1l glass beads on a highly plasticised synthetic resin backing. One specimen of such material (white in color) showed a loss of 98% of the beads after 30 strokes said sheet during the printing process, said adhesive being resistant to softening under conditions of use and being non-reactive to printing ink.
8. Tympan material adapted to support a sheet to be printed upon comprising a flexible base member having good resistance to shear and tension and providing a substantially planar and rough surface supporting the sheet to be printed upon, said surface formed by small glass spheres of fairly high frictional resistance to the sliding of the sheet thereon and adapted to support the sheet in the printing plane, said spheres being set in a slightly yieldabie adhesive and defining interspaces for the reception of ink transferred from said sheet during the printing process, said adhesive being resistant to softening under conditions of use and being inert to printing ink.
9. A tympan sheet or printing blanket adapted for use in preventing offset in printing comprising a flexible backing sheet, a substantially uniform coating of approximately uniformly sized small solid substantially globular bodies bonded to said backing by means of an adhesive so as to resist mechanical dislodgment in use and provide an even supporting surface, said adhesive being resistant to softening under conditions of use and said backing sheet including a material serving to prevent ink and cleaning fluid from penetrating completely through the tympan sheet.
10. A tympan sheet or printing blanket adapted for use in preventing offset in printing comprising, a flexible backing sheet, a substantially uniform coating of glass beads and an adhesive coating bonding said beads to said backing sheet and substantially preventing mechanical dislodgment thereof in use, said adhesive coating being inkabsorbent but said backing sheet being treated with a material serving to prevent ink and cleaning uid from completely penetrating the same and said coating of glass beads providing a discontinuous but substantially uniform supporting surface.
11, A tympan sheet or printing blanket adapted for use in preventing offset in printing comprising, a paper backing having a thickness of the order of .004 to .016 inch, a substantially uniform coating of generally spherical glass beads having a diameter of the order of .001 to .005 inch, and a glue coating of less average thickness than the diameter of said glass beads bonding said beads to said paper backing, said coating of glass beads being composed at least substantially completely of a single layer of glass beads, i. e. said layer having a thickness of the order of .O01 to .O05 inch, and providing a substantially plane surface, uniform to within .001 inch to .005 inch.
12. The combination in a machine having a member for supporting a fabric carrying a wet facing material, of a blanket for minimizing transfer of said material interposed between said member and fabric comprising a flexible backing, a coating of minute glass beads of substantially uniform diameter fixed on said backing and having substantially spherical segments projecting therefrom to make contact with the wet facing material at a multiplicity of points which are uniformly spaced in a common plane, said segments having smooth surfaces which are nonadhesive with respect to the wet facing material and a coating of glue bonding said globular bodies to the flexible backing and encasing from 50% to 75% of the surface area of each body, said glue being non-adhesive and inert with respect to the wet facing material.
13. In a printing apparatus comprising, a series of printing elements disposed to successively print on opposite faces of a sheet and tympan rolls cooperating with such cf said printing elements as contact freshly printed surfaces, an improved tympan sheet adapted for use with said tympan roll to prevent offset in printing comprising a composite flexible sheet material comprising a substantially uniform coating of approximately uniformly sized glass beads secured to a flexible backing by means of an adhesive coating suflicient to substantially prevent mechanical dislodgment of said beads in use.
14. In printing apparatus of the character described comprising a series of printing elements disposed to print successively on opposite surfaces of a sheet and tympan rolls or impression cylinders cooperating with said printing elements, an improved tympan sheet adapted for use with said tympan roll or impression cylinder comprising a flexible backing having Substantial resistance to shearing stress, an adhesive coating on said backing and a facing composed of globular bodies the diameters of which are substantially uniform, each body being submerged in said coating to a depth exceeding one-half its diameter and being securely bonded to the exible backing, said bodies having spherical segments protruding from the adhesive at closely spaced points to a substantially uniform elevation for contact with the sheet to be printed upon.
15. In printing apparatus of the character described comprising a printing element and a tympan roll or impression cylinder cooperating with said printing element, an improved tympan sheet for use with said tympan roll or impression cylinder comprising a flexible backing, an adhesive coating on said backing and a durable facing of smooth, tough, globular bodies submerged in said coating to a depth such that from 50% to 75% of the surface area of each body is encased in the adhesive, said bodies having similar spheroidal segments protruding from the adhesive and affording a surface in contact with the paper to be printed upon which is uniform within a few thousandths of an inch.
BERT S. CROSS.
REFERENCES CITED The following references are of record in the file of this patent:
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|U.S. Classification||101/420, 101/422, 226/190|
|International Classification||B41N10/04, B41N10/00|