US3029457A - Cleaning sheet for typewriter type - Google Patents

Description

April 1962 R. A. HUNDER ETAL 3,029,457

CLEANING SHEET FOR TYPEWRITER TYPE Filed July 30, 1959 Layer of erecf f/ock fibers 400%0' W/W? norma/(y-fac/(y A va raps Q40 4 flu/voae 5/ 7x 1500025 5UCHHOL rz ater 3,629,457 Patented Apr. 1 7, 1962 3,029,457 SHEET FOR TYPEWRITER TYPE Ray A. Huntler, White Bear Lake, and Theodore Buchholtz, Maplewood, Minn, assignors to Minnesota Mining and Manufacturing Company, St. Paul, Minn, a corporation of Delaware Filed July 30, 1959, Ser. No. 830,601 3 Claims. (Cl. 15-210) CLEANING This invention relates to a flexible cleaning sheet adapted to be inserted in a typewriter for cleaning the type when struck against the sheet; the ink ribbon having been shifted so as not to interfere. The product in sheets or tapes of suitable size can be similarly employed for cleaning the type of other typing machines, such as printing calculating machines a A flexible nonsticky cleaning sheet or tape is provided, having a nonsticky ink-receptive and ink-retentive flocked face side, so constructed that the sheet or tape can be directly fed into a typing machine with the flocked face side exposed to impact of the type, without sticking to the machine, and be employed to eifectively clean the type by the mere striking of type thereagainst. The flocked face side is comprised of a fuzzy layer of erect spacedapart short-staple rayon (or equivalent) flock fibers that are coated with an ink-receptive adhesive which, although it is normally tacky, does not render the sheet or tape sticky to the touch on ordinary handling. This latter feature results from the extreme thinness of the adhesive coating on the fibers and is obtained even when the adhesive is of a type employed in aggressively tacky pressure-sensitive adhesive tapes. I

The cleaning expedients heretofore commonly used by typists have been inefficient, inconvenient and messy. It has been diflicult to clean type without ending up with soiled fingers. Painstaking elfort has been required to thoroughly clean all of the type-particularly letters and numerals having small loops-so that a uniform sharp imprinting or stencil cutting performance of the machine would be obtainable. In some typing devices the type is not conveniently accessible to cleaning by conventional methods.

The use of solvents, as in using a brush that has been dipped in solvent, is hazardous and is objected to by manufacturers of electric typewriters owing to risk of harming the mechanism into which the dirtied solvent may be splattered or dripped. Cleaning putties are ineflicient and become fouled with repeated use so as to dirty the fingers. The use of pins or picks or the like for cleaning out looped type is tedious and may result in specks of dirty ink getting into the mechanism or onto the fingers, and may result in scratching or otherwise damaging the type characters. Dry brushing causes flicking of ink particles and is ineffective because of the tenacity with which accumulated ink deposits cling in the type recesses. The labor cost of maintaining an ofiice typewriter in really good writing condition throughout a years time, by use of prior expedients, has been considerable.

The present cleaning sheet may be conveniently provided in common letter size (e.g., 8% x 11") for typewriter usage. It has a flexibility and thickness comparable to a set of paper sheets interleaved with copying tissues as commonly inserted into a typewriter. It is not sticky and sheets can be kept in a drawer without sticking to each other or to other objects.

To clean the type of a typewriter, the typist merely feeds the cleaning sheet into the machine in the usual manner and types upon it, the ribbon having been shifted out of the way so that the type will directly strike against the surface of the sheet. Each key is depressed one or more times depending upon how dirty the particular type character is, the movement of the carriage automatically bringing a fresh portion of the sheet into position for each type impact, and the paper being advanced after each line is typed. Removed ink is retained in the body of the sheet and firmly held, and provides a tell-tale mark, after each type impact. When no appreciable mark is left, the typist knows that effectively complete cleaning of the particular type character has been achieved. In the case of an electric typewriter, it is a convenient procedure for the typist to run her finger down each row of keys until no marking of the sheet is observed.

A typewriter can be easily and continually maintained in good typing condition by cleaning it in this way at the beginning of each Work day, in which case only a minute or two is required, the type never having a chance to become badly fouled.

Upon completion of each cleaning job, the sheet is removed and is kept for further use unless it has been used up. The utilized portion can be easily cut off with a pair of scissors and discarded. A transversely perforated sheet can be provided so that successive strips of the sheet can be torn off as they are used from time to time. Removal of the used portion of the sheet after a cleaning operation is desirable when badly fouled type have been cleaned and have left heavy deposits of ink material. But there is no need of so doing when relatively clean type have been cleaned as the ink deposits will be light and will be retained by the sheet so as to avoid smudging. One letter size sheet suflices for a number of cleaning operations, depending on how dirty the type are each time the sheet is used.

The present cleaning sheet comprises a flexible backing (paper or film) carrying a flexible binder coating on the face side which bonds the inner tips of a fuzzy layer of erect spaced-apart flock fibers (such as short-staple viscose-rayon flock fibers). This flocked side of the sheet is coated with a normally-tacky ink-receptive rubbery adhesive so as to size or thinly coat the fibers, Without filling the interstices, leaving voids larger than the fibers between the fibers and providing a porous fibrous layer. The tacky erect adhesive-coated free fibers are of sufiicient length, stilfness and pliancy to reach and scrape the base and side areas of the type characters impacted against the sheet, so that ink deposits can be loosened and removed from all portions and the type will be effectively cleaned.

The tacky ink-receptive adhesive coating thereon enables the fiock fibers to more readily remove, and also to retain, the ink when a type character is struck against the sheet. The etficiency and convenience are vastly greater than is obtainable in the absence thereof. The tacky fibers are bent down by the type impact and cohere together so that most of the removed ink becomes absorbed into the fibrous layer below the plane of the outer tips of the surrounding fibers. This aids in minimizing subsequent smudging. The adhesive is highly cohesive and leaves no residue upon the type or on parts of the typewriter that it contacts. Rolling of the cleaning sheet through the typewriter also serves to clean the platen pressure rollers which bear against the sized flock surface, and which are normally inaccessible to cleaning and are not cleaned by typists. A water-soluble or .markedly oleophobic type of adhesive would not be compatible with the oily ink and hence would not be ink-receptive and would not be suitable for present usage.

Although the fiber-sizing adhesive may be of the kind used in aggressively-tacky pressure-sensitive adhesive tapes, the fuzzy flocked structure and the extreme thinness of the adhesive coating on the fibers, prevents the sheet from having a tacky feel when handled and from sticking to the back of another sheet, or to other objects, that it may contact. It would not be apparent on ordi-,

nary scrutiny and handling that such an adhesive coating is employed. However, if a forefinger is firmly pressed against the flocked face of the sheet so as to mash down the fibers, a tacky feel can be readily detected.

A fuzzy layer of short-staple flock fibers, as employed in the present product, is quite different from a bristly or brush-like layer formed of bristles. The present cleaning sheet does not perform the function of a brush but operates on a disparate principle.

The structure of this cleaning sheet is illustrated in the accompanying diagrammatic drawing of a greatly enlarged section.

A flexible backing 1 (such as a sheet of dense paper), preferably provided on the back side with an antislip backsize coating 2, carries on its face side a flexible binder coating 3 which securely holds a layer 4 of erect spacedapart flock fibers whose inner tips are embedded therein and which are thinly coated with a normally-tacky inkreceptive rubbery adhesive. This fiber-sizing adhesive covers the exposed surfaces of the fibers (and also the underlying binder coating) without clogging up the interstices between the fibers, thereby providing a porous layer of adherent free fibers.

The adhesive coating operation may result in some of the fibers being adhered to contiguous fibers to form bundles or clumps of two or a few fibers, as indicated in the drawing, but these function in substantially the same manner as do the individually coated free fibers and it is not necessary to avoid formation thereof in the manufacture of the product. Nor is it necessary that the coating operation result in complete coating of all fibers from tip to base. It is not necessary that the fibers stand perfectly straight and erect. An approximation of the ideal is satisfactorily useful.

Example A dense wet-strength kraft paper web, having a basis weight of about 150 lbs. per thousand square yards (about 80 kgs. per thousand square meters) and a caliper thickness of approximately 5 mils (0.13 mm), is given a thin sizing coating on the back of synthetic rubber (such as a butadicne-styrene copolymer) to provide an antislip back surface. A coating of colloidal silica in a binder may alternatively be employed to roughen the back surface and provide an antislip surface. The purpose of this backsize is to provide the back surface of the product with an antislip characteristic that facilitates rolling the sheet into and through a typewriter. A backsize may be selected which also serves to clean the platen roll as the sheet is rolled through the typewriter.

This backing sheet web is continuously coated on the face side with a binder resin solution or dispersion. While this coating is still soft and tacky, the web is passed through a flocking machine where short-staple viscoserayon flock fibers are flocked into the surface in the desired density so as to embed the inner ends of the erect fibers in the binder coating. The web is then passed through an oven to dry or cure the binder coating and set the fibers. As flocking machines and procedures are well known in the textile industry, a detailed description unnecessary.

The flocked web is then passed through a coating machine adapted to apply a solution of the adhesive to the fibrous face. Any suitable coater may be used, such as a roll coater, knife coater or air knife. A dilute solution of adhesive is applied in a limited amount such that the coating thereof breaks up and thinly coats the individual fibers, and drains down to cover the underlying binder coating. The web is then passed through a drying oven, resulting in the type of product previously described. The dried web can then be cut into sheets of desired size ready for packaging and sale.

Examples of binder compositions for providing the flexible. binder coating are aqueous dispersions of plasticized thermosetting urea-formaldehyde resins, and of polyvinyl acetate. When a paper backing is coated with an aqueous binder composition, a type of paper which includes a wet-strength sizing should be employed so that it will have adequate strength and freedom from distortion during the coating, flocking and drying operations. The coating weight is adjusted so that the flock will be firmly bonded. Only a thin dried coating is needed to anchor the tips of the fibers, thus permitting of a product sheet which is thin enough and flexible enough to be inserted into a typewriter without requiring a leader.

The viscose-rayon flock should have a high enough denier value (indicative of the fiber diameter) to provide adequate stiffness. The denier value should be at least 1.5 and a value of S to 10 is preferred. The flock fibers should have adequate length for eflicient type cleaning action, but should not be so long as to make the sheet too thick for easy passage into and through the typewriter carriage. A length of 30 to 40 mils is desirable and a length of about 35 mils (0.9 mm.) is preferred in making cleaning sheets for conventional typewriters in which the type characters have a height of 25 mils. The density of the flock (number of fibers per unit area) is also related to the type cleaning, and the ink removing and retaining, eficiency of the sheet. The fibers should not be packed together but should be spaced-apart to provide a fuzzy porous layer. This factor is most easily controlled during manufacture by adjustment of the flock coating weight. It is desirable that this weight be in the range of about 125 to 200 lbs. per thousand square yards of sheeting (about 70 to kgs. per thousand square meters), preferably about 160 pounds per thousand square yards (about 90 kgs. per thousand square meters), when using flock fibers of about 5 denier size and 35 mils length.

The preferred fiber-sizing adhesives are pressure-sensitive adhesives such as are well-known in the adhesive tape art. In normal dry form they are aggressively tacky to the touch. They are rubbery (viscoelastic) and highly cohesive. The usual rubber-resin pressure-sensitive adhesives as used in adhesive tapes provide water-insoluble oleophilic coatings. They are compounded from natural rubbery or a rubbery synthetic polymer (elastomer) and an admixed compatible tackifier resin; or formed of a rubbery type of polymer which is inherently aggressively tacky. For present usage, it is preferred to employ a pressure-sensitive adhesive that is stable to long-continued exposure to air and light, since the adhesive coated fibers of the cleaning sheet are accessible to the atmosphere, thereby avoiding loss of tack for at least several months. Adhesives utilizing air and light stable polymers are therefore preferable-such as adhesives embodying polyisobutylene, polyacrylate or polyvinyl ether polymers.

A preferred example of an adhesive coating solution applied by roll coating, has the following formulation (parts by weight):

Parts Rubbery polyisobutylene (such as Vlstanex B) 100 Low molecular weight tacky polyisobutylene (such as Vistac A70) 70 Pure hydrocarbon terpene tackifier resin (such as Piccolyte S85) 45 Rosin ester tackifier resin (such as Hercolyn") 30 Di-tert.-amyl hydroquinone (antioxidant) (such as Santovar A) l Heptane (volatile solvent) 1800 The dried adhesive coating on the fibers is only a thin size coating. Thus in the preferred construction described above (using pounds of flock per thousand square yards), the adhesive may have a dry weight of about 100 pounds per thousand square yards of sheeting (about 55 kgs. per thousand square meters); this includes both the coating on the flock and the coating on the underlying binder layer.

It is not essential that the fiber-sizing adhesive have the aggressive degree of tackiness characteristic of pressure-sensitive tape adhesives. For example, a rubberybase cleaning putty that is slightly tacky to the touch in normal dry form, may be utilized to provide the fibersizing adhesive, being applied to the flocked sheet as a dilute dispersion in water. Such cleaning putty compositions are well-known and may comprise a mixtur of synthetic rubber, factice, oil and inorganic filler, for instance. Use may be made of rubbery polymers, and of rubber and tackifler resin blends, which have a mild degree of tackiness that is less than that of pressure-sensitive tape adhesives. These need only be sufliciently tacky so that the sized flock fibers are rendered ink-receptive.

Simple experimentation will enable one to arrive at various satisfactory combinations. Although viscoserayon flock fibers are preferred and are readily and eco' nomically available, other equivalent fibers can be used,

such as nylon flock and polyester flock. Equivalent natural fibers may also be used.

The present cleaning sheets and tapes in appropriate sizes can be used for other purposes for which suitable, such as for cleaning suede shoes and felt hats by lightly rubbing.

We claim:

1. A flexible nonsticky cleaning sheet or tape of the character described, having a nonsticky ink-retentive flocked face side, so constructed that the sheet or tape can be directly fed into a typing machine with the flocked face side exposed to impact of the type, without sticking to the machine, and be employed to eflectively clean the type by th mere striking of type thereagainst, comprising a thin flexible backing flocked on the face side with a fuzzy layer of erect spaced-apart short-staple flexible flock fibers of type-cleaning length whose inner tips are bonded to the backing, the flock fibers having a sizing coating thereon of a normally-tacky ink-receptive rubbery adhesive which is so extremely thin that voids larger than the fibers are provided between free fibers, and such that the sheet or tape is'not rendered sticky and the presence of the adhesive is not apparent on ordinary handling not involving a mashing down of the fibers, the flexible adhesive-coated free fibers having a degree of stiflness that permits both of cleaning type and of bending down and cohering together when struck by type.

2. A flexible nonsticky cleaning sheet or tape of the character described, having a nonsticky ink-retentive flocked face side, so constructed that the sheet or tape can be directly fed into a typing machine with the flocked face side exposed to impact of the type, without sticking to the machine, and be employed to effectively clean the type by the mere striking of type thereagainst, comprising a thin flexible backing flocked on the face side with a fuzzy layer of erect spaced-apart short-staple flexible flock fibers of type-cleaning length whose inner tips are bonded to the backing, the flock fibers having a sizing coating thereon of a normally and aggressively tacky inkreceptive rubbery pressure-sensitive adhesive that is stable to long-continued exposure to light and air and which is so extremely thin that voids larger than the fibers are provided between free fibers, and such that the sheet or tape is not rendered sticky and the presence of the adhesive is not apparent on ordinary handling not involving a mashing down of the fibers, the flexible adhesive-coated free fibers having a degree of stiflness that permits both of cleaning type and of bending down and cohering together when struck by type.

3. A cleaning sheet according to claim 2, which is of at least about 8 /2 x ll" size and wherein said flock fibers are viscose-rayon fibers having a denier value of about 5 to 10 and a length of about 30 to 40 mils.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A FLEXIBLE NONSTICKY CLEANING SHEET OR TAPE OF THE CHARACTER SESCRIBED, HAVING A NONSTICKY INK-RENTENTIVE FLOCKED FACE SIDE, SO CONSTRUCTED THAT THE SHEET OR TAPE CAN BE DIRECTLY FED INTO A TYPING MACHINE WITH THE FLOCKED FACE SIDE EXPOSED TO IMPACT OF THE TYPE, WITHOUT STICKING TO THE MACHINE, AND BE EMPLOYED TO EFFECTIVELY CLEAN THE TYPE BY THE MERE STRIKING OF TYPE THEREAGAINST, COMPRISING A THIN FLEXIBLE BACKING FLOCKED ON THE FACE SIDE WITH A FUZZY LAYER OF ERECT SPACED-APART SHORT-STAPLE FLEXIBLE FLOCK FIBERS OF TYPE-CLEANING LENGTH WHOSE INNER TIPS ARE BONDED TO THE BACKING, THE FLOCK FIBRES HAVING A SIZING COATING THEREON, OF A NORMALLY-TACKY INK-RECEPTIVE RUBBERY ADHESIVE WHICH IS SO EXTERMELY THIN THAT VOIDS LARGER THAN THE FIBERS ARE PROVIDED BETWEEN FREE VOIDS FIBRES, AND SUCH THAT THE SHEET OR TAPE IS NOT RENDERED STICKY AND THE PRESENCE OF THE ADHESIVE IS NOT APPARENT ON ORDINARY HANDLING NOT INVOLVING A MASHING DOWN OF THE FIBERS, THE FLEXIBLE ADHESIVE-COATED FREE HAVING A DEGREE OF STIFFNESS THAT PERMITS BOTH OF CLEANING TYPE AND OF BENDING DOWN AND COHERING TOGETHER WHEN STRUCK BY TYPE.

Images