US2056427A - Stencil - Google Patents

Description

Oct. 6, 1936. A M GOMES 2,056,427

STENCIL Filed- Feb'. 28, 1933 INVENTOR 44.55970 M Q0/1455.

Patented Oct. 6 1936 UNITED STATES PATENT orrlca This invention relates to new and useful improvements in stencils and more particularly it pertains to stencils of the type employed in cornneetion with duplicating machines, sills screen stencil frames and similar duplicating apparatus.

The stencil forming the subject of thisinvention is intended in its ultimate form to be of the sensitized type and although I am aware that sensitized stencils have been heretofore manufactured, all such stencils with which I am familiar have many disadvantages.

' sensitized stencils with which I am familiar are completed in their sensitized form at the time of their manufacture. Such stencils are subject to rapid deterioration as a result of atmospheric, temperature and other conditions and under certain conditions are unfit for use a month after their manufacture. Also, such stencils are de veloped after exposure, by means of heated solu= tions which invariably causes expansion of the stencil which isfollowed by contraction as the finishing steps are carried out. These inherent conditions render such stencils practically useless for the productionof multi-colored work since to produce such work a number of stencils must be employed and inasmuchas they cannot be .uniformly manufactured perfect registration cannot be obtained. Furthermore, the several solutions with which these stencils are treated have a tendency to render the stencils more or less rigid and unpliable, thus rendering them liable to damage in use.

A feature of the invention resides in a novel method of manufacturing sensitized stencils which method permits of the ultimate user performing for himself the sensitizing step of the method or process.

' Another feature of the invention resides in a novel method whereby stencils which are of uniform character may be produced. This feature is particularly important for the reason that uniform stencils permit of obtaining perfect registration therefore making possible the attainment of perfect results with said stencils in multicolor work.

A further feature of the invention resides in the provision of a sensitized stencil in which it is not necessary to protect the stencil from the action of light except over extended periods. Such a stencil may be prepared and handled in lights of ordinary intensity without de v2w. effects. 1. Still a further feature of my improved stencil resides in the fact that the stencil duringmanw facture, developing and fixing, is not subjected to 5 temperatures which cause expansion and com traction thereof.

Still a further feature of the invention resides in a novel construction whereby the stencil may be used to take an impression either by a photo- 19 graphic process or by direct printing contact.

Other features of the invention will appear as I the nature thereof is understood for which purpose reference will be had to the following specification and the accompanying drawing. 15

In the drawing; I Figure l is a perspective view of a completed stencil constructed in accordance with the present invention,

Figures 2, 3 and ii illustrate one manner in 20 which my improved stencils may be formed, and v Figure 5 is a perspective longitudinal sectional view illustrating a finished stencil blank before it has been sensitized.

indicated by the reference character In and in Figure 2 the strip of cardboard by which the base material is manipulated is designated I I.

The reference numeral "designates a suitable receptacle preferably in the form of a relatively '40 shallow tray such as used for containing various solutions in the photographic art and it is this type of receptacle which Iprefer to use in carrying out my improved method or process.

After the strip 'of base material has been at- 45 tached to the manipulating strip of cardboard, the same is treated by floating it upon the surface of a suitable solution which prepares the base material for taking a sensitizing solution to be subsequently applied thereto. This step of the 50 process is illustrated in Figure 2 of the drawing.

The solution with which the base material I0 is impregnated .by the foregoing step is designated ii in Figure 2 of the drawing and one 'example of such a solution which I have successfully employed in the manufacture of stencils is as follows:

Egg albumin (dry flakes) 2 ounces Gum arabic in tears 2 ounces orn syrup or glycerol 1 ounce Sodium chloride 1 percent Sodium borate 5 percent Chloride of lime percent alcohol in order to impart to the base material the desired color or tint.

The special ,pieces of base material which form the stencils are treated as heretofore described with said compound, after which they are allowed to dry. Since the compound or emulsion with which they are treated is a cold liquid the base material is not subjected to expansion or contraction due to changes in temperature during either the impregnating or drying steps.

After the stencils have been thus far completed they are stripped from the manipulating cardboard strip and attached to the regular perforated strip of cardboard material, which strip adapts them for use in connectionwith duplicating machines, except that it is provided with a relatively stifi backing it formed with a dark or black field or area l'l which prevents deflection of light thus eliminating fog or halation, more especially when the impression is made by the photographic process. This is accomplished by gluing or otherwise fastening the stencils to the strips. In Figures 3 and 4 this strip is designated l5 and is printed with suitable instructions for use in the ordinary manner.

The stencils as now described are packed and are ready for sale to the ultimate consumer. In this form the stencils will keep indefinitely without deterioration and they will not be affected in this condition by changes in temperature, atmospheric or other conditions.

As far as described, however, the stencils have not been sensitized for use and in accordance with the present invention this step is performed by the consumer. In order that the consumer may effectively produce this step he is provided with a sensitizing solution which he may apply to the stencils in a manner to be now described.

This step is illustrated in Figures 3 and 4, which figures disclose a receptacle 20 similar to the receptacle l2 heretofore mentioned in which the sensitizing solution 2| is placed. The sensitizing solution being placed in the receptacle the stencil is grasped as illustrated in Figures 3 and 4 by the strip which forms its attachment to the duplicating machine and is floated over the sensitizing solution until one surface thereof is covered with said solution. This is allowed to dry in a modified light (not necessarily in a totally dark room) after which the stencil is ready for exposure, which may be accomplished either by a photographic process or by direct printing contact with the to be impressed upon the stencil.

In sensitizing the stencils to take the impression I have found that best results are obtained with different solutions, the choice of which is determined by the type of exposure to be employed in the making of the impression. For example, when the impression is to be made by direct printing contact the stencil is sensitized with a composition of one character and when the impression is to be made by a photographic Part Distilled water 1 Acetone... 1 Ethyl alcohol 1 Glycerine Such a sensitizing solution is not sensitive to light in its wet state and therefore sensitizing, exposing and developing can be handled in day light although it is not advisable to subject such a sensitized stencil to direct rays of light.

In making the impression by direct printing contact I prefer to employ a carbon lamp as a source of light and by placing the stencil into direct contact with the. material to be reproduced thereon and'in this position subjecting it to the action of the rays of a carbon lamp, an impression upon the stencil will be had/ While I have stated that I prefer to use a carbon lamp such a light source is not essential and an impression may be obtained upon the stencil by subjecting the assembled apparatus to the action of natural light.

After the exposure is complete whether it is by artificial or natural light, the stencil can be Nitrate of silver recrystalized 560 grains Glacial acetic acid 2 fluid ounces Distilled water 10 fluid ounces Before applying the sensitive solution just mentioned it is necessary to salt the base material by floating it in the following salting solution and drying the same before subjecting it to the sensitizing solution:

Cadmium bromide 25 grains Potassium bromide 50 grains Potassium iodide grains 5 percent albuminized distilled water l0 fluid ounces After the base material has been subjected to this salting solution it is floated on the sensitiz-' 1 ing solution and is then ready for exposure in a camera or similar photographic device in order that the photographic impression may be had.

After the photographic exposure the stencil is immersed in the following solution for catalyzing:

Ounces Ammonium bichromate c. p l Sulphuric acid ,5 Water 70 following:

. Ounces Sodium hyposulphite 6 Formalin 2 Water 70 in which bath it is left for a period of approximately three minutes after which it is thoroughly washed in cold water and dried, after which it is ready for use in the ordinary manner.

From the foregoing it will be apparent that the present invention provides a sensitive stencil which in its original state, however, is not of the sensitive type but is rendered sensitive by the consumer through the medium of certain solutions which are furnished to the consumer.

Inasmuch as the several solutions employed are all employed in the cold state the resulting stencils will be of uniform character since all expansion and contraction of the base material is eliminated. This is important since it permits of the use of a number of stencils for the production of multicolored work all of which stencils will register and produce multicolored work of a very high quality.

While I have stressed the fact that the stencils are preferably sensitized by the user, I wish it understood that stencils for photographic purposes may be manufactured for sale already sensitized with the salting solution and silver nitrate mixed in the coating emulsion and as thus made, offered for sale.

Having thus described the invention, what is claimed as new and what it is desired to secure by Letters Patent oi the United States, is:

1. The method of making duplicating stencils which comprises impregnating a sheet of fibrous base material with a cold protective and presensitizing emulsion, drying the sheet, and subsequently subjecting the sheet to a cold sensitizing bath, the sheet during said steps being subjected to a uniform temperature, and said first mentioned step immunizing the sheet against expansion or contraction due to changes in temperature or other atmospheric conditions during the interval occurring before the subsequent steps.

2. The method of making duplicating stencils which comprises impregnating a sheet of fibrous base material with a cold protective and presensitizing emulsion and drying the sheet at a uniform temperature to render the sheet immune from. expansion or contraction when subjecte to atmospheric or temperature changes durin the interval occurring before subsequent treatment of the sheet, providing a backing for the sheet having a darkened area over its major portion, immersing the sheet in a cold sensitizing bath to prevent physical changes of the sheet and finally removing the backing sheet without injury to the sensitized surface of the sheet.

ALBERTO MARIO GOMES.

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