US1902914A - Duplicating stencil - Google Patents

Description

. to provide a duplicating stencil for type- P'atented Mar. 28, 1933 UNITED STATES PATENT oEFicE ms 'smon, or woman, GERMANY, nssren'on. 'ro 13mm wnonnia'or mom.

onmumr, A conrona'non on (mam a a DUPLIGATIN G STENCIL H6 Drawing. Application am June 15, 1931, Serial No. 544,701, and' in Germany April a0, 1631.

This invention relates to improvements in duplicating stencils and a method for producin the same.

t has been known to use, as a duplicating stencil, a fibrous and porous Japanese paper coated with a layer of hardened or nonhardened roteins to which softening agents such as ycerine, sugar, fats, fatty acids, etc. haveieen added. Suzh duplicating sten- 1o oils have, hgvever, the drawback that the softening agent added to the proteins is 1iable, during the storage of the stencil, to be exuded at the surface of the coating in such quantities that the stencil will become sticky 15 and consequently useless.- It is not possible to eliminate this drawback by diminishing the amount of the softening agents added to the proteins because a certain amount of said I softeners is required to keep the coating plastic. If the amount of the softeners added to the proteins is less than a certain positive value, the coating will become hard and full of cracks after a certain period of storage, so that it will be impracticalto use it. Nor is it possible to eliminate completely this precipitation of softeners in the coating by mixing inorganic fillers therewith, consisting, for instance, of bentonit or kaolin, as has been proposed in prior art, because such pastes cannot prevent, with certainty, this exudation for a sufliciently long time." The main object of this invention is to eliminate the above-mentioned drawback and to provide a duplicating stencil which can be safely stored for a considerable period of time and which has a coating that remains soft and plastic during this storage.

A further object of this invention is to provide a stencil coating comprising pro- 40 teins and softeners mixed with substances b means of which said softeners may be'equa 'ly distributed in the coating and securely bound therewith.

' A still further object of this invention is' fectivel writing and duplicating machines, which will not smear the types or case and dirty the caoutchouc rollers .of sairfiiachines.

The above-mentioned objects can be realized b adding organic fillers as distinguishe from inorganic fillers heretofore used, to the coating, such organic fillers consisting, for instance, of a very finely ground wood-flour, such as beechwood. Fugue sylvatica) or bamboo-wood (Am 0 bambos), or of horn-dust, Lycopodium dust or other substances.

Horn dust is derived by powdering or grindigg the horn material of animals, while Lycop ium dust (lycopode) is a yellow powder derived from the spores of the club moss, especially L. claoatum, L. selago, L. phlegmasia, L. mbmm, L. saussum, etc.

An or anic filler of this kind will efind the softeners within the coating an will further the even distribution of such softeners. Duplicating stencils provided with a c'oatingin accordance with this invention remain uniformly soft and flexible even after having been stored for a very long time and the precipitation of softeners is totally prevented. This is not the case with duplicating stencils provided with a protein coating as known in prior art, which become sticky after a certain period of, storage or hard when the coating does not contain a sufiicient amount of softeners.

' A further advantage of adding an organic paste to the stencil coating resides in the fact that when the duplicating stencil is used in connection with a typewriter the types will not become dirty or locked. Furthermore, the softeners forming partof the coating and consisting of oils or fats will not be deposited on the rubber rollers of the typewriters and v duplicating mechanisms.

I have found thatthebest resultsare obtained when an organicfiller consisting of a wood-dust is addedto the coating substance and used in connection with other substances. u I

An example of a mixture which may be emplayed 1s as follows: Puts Water 200 This liquid mixture is applied in the usual way onto a sheet of Japanese paper at the usual temperature, of about 50 C. and is dried then at the same temperature so that the water. evaporates.

The advantageous results obtained from the use of organic fillers, such as Wood flour, are achieved owing to the fact that the wooddust comprises a certain small amount of coagulating or tanning substances which have a slight hardening efiect on the proteins contained in the coating substance.

It is possible to increase the hardening efiect by adding another substance, for instance, a formaldehyde, to the'coating.

I claim: I

. l, A process for manufacturing duplicat- Y ing stencils, comprising the steps of adding a substantially insoluble organic filler to'a coating mixture containing proteins and softening agents, and then applying said coating mixture onto a fibrous and porous sheet 2; A process for manufacturing duplicating stencils, comprising the steps of adding a a wood-dust to a coating mixture containing proteins and softening agents, and then applying said coating mixture; onto a fibrous and porous sheet.

3. A process for manufacturing duplicat-v ing stencils, comprising the steps of adding horn-dust to a coatingmixture containing proteins and softening agents, and then applymg said coating mixture onto a fibrous and porous sheet.

4. A process for manufacturing duplicating stencils, comprising the steps of adding a substantially insoluble organic filler to a coating mixture containing proteins and softening agents then adding a formaldehyde to the mixture, and then applying said coating mixture onto a fibrous and porous sheet.

7. A coating for duplicating stencils, comprising a mixture of petroleum jelly, a sul= phonated non-mineral oil, gelatine, a wooddust, g'lycerine, castor oil, olive oil, methylene blue and sodium para chlorbenzoate.

8. A coating for duplicating stencils com prising, 60 parts by weight of petroleum jelly, 18 parts by weight of a sulphonated non-mineral oil, 10 parts by Weight of gela-z tine glue, 10 parts by weight ofa Wood-dust,

3 parts by Weight of glyc'erine, 2 parts by weight of castor oil, 2 parts by Weight of olive oil, .7 5 part by weight of methylene blue and 35 part by weight of sodium parachlorbenzoate. p 9. A coating for duplicating stencils comprising a mixture of hardened gelatin, a softening agent and a permanent finely divided substantially insoluble organic filler.-

10. A coating for duplicating stencils comprising a mixture of hardened gelatin, a softening agent and a powdered organic filler containing small quantities of a tanning ma terial. i

11. A coating for duplicating stencils comprising a mixture of hardened gelatin, a softening agent and a powdered cellulose filler.

12. A coating for duplicating stencils com prising a mixture of hardened gelatin, a softening agent and one of a group of powdered organic fillers, said group including beechwood flour and bamboo wood flour.

In testimony whereof I have aifixed my Lycopodium dust to a coating mixture containing proteins and' softening agents, and then applying said coating mixture onto a fibrous and porous sheet,

5. A process for manufacturing duplicating stencils, comprising the steps of adding a substantially insoluble organic filler to a coating mixture containing proteins and softening agents, then adding a hardening agent to the mixture, and then applying said coating mixture onto a fibrous andporous sheet. 7

6. A process for manufacturing duplicat-