US130140A - Improvement in forming curved electrotypes - Google Patents

Description

Improvement in Forrrt'i'g Curved Electrotypes.

N0. 130,140, Patentd Aug. 67,1872.

UNITED STATES PATENT OFFICE.

ANSON JUDSON, OF BROOKLYN, NEW YORK, ASSIGNOR TO HIMSELF AND NATHAN S. CLEMENT, OF NORTIIAMPTON, MASSACHUSETTS.

IMPROVEMENT IN FORMING CURVED ELECT'ROTv'PES.

Specification forming part ofLettcrs Patent No. 130,140, dated August 6, 1872.

` Specification describin gan ImprovedMethod of Forming Curved Elect-rotypes, invented by ANSON JUDSON, of Brooklyn, in the county of Kings and State of New York.

The purpose of the invention is to avoid the faults due to wrinkling andirregular contraction in the present mode of producing curved electrotypes. These electrotypes, it will be understood, are produced on molds impressed on flat forms and then curved to a large radius to adapt them for use on a cylinder-press.

In the ordinary method, anv impression having been taken from a flat form in gutta-percha or the like, the extended flat mold is laid across a properly-curved metallic bed, and is partially melted by a gradual rise of temperature until its gravity causes it to sink into and conform to the curvature of its support. It is allowed to cool in this curved condition, and is afterward immersed in the bath and the. electrotypeproduced with, of course, a corresponding curvature. The partial melting to which the mold is subjected in this process is highly objectionable. Beside the delay occasioned in the gradual warming and cooling there is a liability and almost a certainty to produce several Wrinkles and irregular contractions at different points. Myimproved method saves time a-nd produces more perfect work. I can by its means produce not only letter-press, but even engravings, with a high degree of perfection and with very great rapidity, with a small outlay for apparatus. I employmechanical force through the intervention of a iuid to compel the straight mold to bend to the curvature of its bed. This may be done either by inducing a vacuum underneath or by inducing a surplus pressure of atmosphere or other gas above; or

` the curve may, under proper conditions, be induced by the pressure of water or other dense liquid.

The following is a description of what I consider the best means of carrying out my invention.

Figure 1 is a vertical section, showing the apparatus ready to curve a mold 5 and Fi g. 2 is a vertical section at right angles to the irst.

A is a table adapted to support and allow the ready introduction and removal of the other parts represented. B is a curved iron plate or removable shell of suflcient thickness to give stiffness and support to the delicate material sustained thereby. This piece B may be the same as is ordinarily employed for this purpose.

- (l is a cover or top piece, of iron or other suitable material, adapted to press rml y and make a tight joint upon thepedges of the delicatelymolded material D, to be described further on.

O is a broad' backing-piece, which may be formed in a continuous plate or more open work,

.or may be formed entirely of one or more simple cross-bars. Its function is to hold down the cover O firmly upon the bed B and the intermediate molded piece D. E E are bolts littingin T-shaped grooves and carrying nuts E', which hold down the whole and liberate them easily. The flat mold may be formed, in gutta-percha, as usual, it" preferred, but I believe it better to employ wax, ordinary bees-wax, either alone or mixed in ordinary proportions with other materials to form a plastic mass capable of receiving sharp impressions. I back it with a sheet of stout cartridge or other paper. The wax adheres strongly and naturally to the paper, and the back of the paper, as also the hollow face of the iron mold B, is coated with anadhesive cement. The impression is produced from the dat form (not represented) on the upper face of the delicate wax surface D, in the ordinary manner. The broad sheet of wax, with the paper beneath, is then laid on the hollow bed B and the cover C applied to form a tight t around the edges. The lower edge of the cover C maybe expanded to make a broad bearing, or it may be contracted to make a sharp edge, or there may be several ridges or sharp edges parallel to each other extending around.` The latter construction is probably preferable, but I believe either will succeed. The most serious difficulty involved is in forming a tight joint at the ends, so to speak. I esteem it preferable to make the ends with a curved outline corresponding to the form which the delicately-molded wax layer is to assume after it has been bent, and to press it down rmly to a bearing by force in applying the cover and making the joint. The result is a distortion of the plate D along the lines where the edge is thus applied and pressed down, and this distortion extends a little ways inward toward the middle of the mold; but by forming the mold,with a broad edge this distortion will not extend into the type surface. VThe surface which has received the impression of the type will remain up in a fiat or plane condition, or nearly so, while the edges will bepressed down and held air-tight against the supporting-piece B. Having secured the cover by means of the bolts E andl nuts E the bein g employed, (not represented,) air is forced in gently through the pipe m, and the pressure over the wax plate D is gradually increased until the yielding character of the wax and of the paper backing thereon is not sufficient to resist the strain. It yields gradually, and, the air beneath escaping through the aperture represented in the bed-piece B, the wax is soon pressed down fairly to the curvature of the latter. The moment the cemented surface at the back of the paper meets the cemented hollow face of the iron shell B they adhere firmly, and, the pressure being now let off, the bolts E may be released, the cover G lifted, and the shell B, with its now closely-fitting impressed material Dmay be lifted ofi', from the table A, and the electrotype produced thereon by depositing from a solution in the ordinary manner, while the table A receives another shell, B, another ilat wax surface, D, with its paper and cement, and again receives the cover C and the blast of air. I esteem it but little different to leave the bolts E and the cross-bars orother top work C off, and having fitted the cover C tightly upon the waxedcoat, pressing it down around all its edges, apply the force of an air-pump, or analogous device, to eX- haust the air from below the impressed layer C by exhausting it through the apertures in the shell B. This mode of operation allows only a maximum pressure of about fourteen pounds per square inch, while the other plan is unlimited 3 but it Will ordinarily require much lesspressure than fourteenpounds toinduce the prompt and true curvature desired. There is no particular skill or variation of the treatment required in obtaining the impression from the type surface on the wax or in the subsequent deposit of the copper coating. I

I do not consider it absolutely essential to success that the backing of the plastic layer D shall be formed of paper, or that the cement shall be applied on both it and the shell B, but I esteem this the preferable mode of working. The backing up and subsequent use of the curved electrotypes may be in the ordinary or any suitable manner.

It will be understood that, when used With the plus pressure above, the holes in the curvedv piece B serve to allow the free escape of the air which might otherwise be imprisoned below the paper. The bed A should be grooved or rou'ghened to allow its ultimate release. It may be practicable to allow sufficiently for this escape of air by merely groovin g or rou ghening the inn er face of the piece B.

I claim as my invention- The within-described method of producing curved electrotypes-that is to say, molding from the flat form in wax or analogous yielding material and forcibly bending it into a curved form by fluid pressure and afterward holdingit in the curved formall substantially as herein specified.

In testimony whereof I have hereunto set my name in presence of two subscribing witnesses.

- ANSON J UDSON. Witnesses:

THoMAs D. STETsoN, ARNOLD HOERMANN.

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