US3309290A - Method of forming electrotypes - Google Patents

Method of forming electrotypes Download PDF

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Publication number
US3309290A
US3309290A US266748A US26674863A US3309290A US 3309290 A US3309290 A US 3309290A US 266748 A US266748 A US 266748A US 26674863 A US26674863 A US 26674863A US 3309290 A US3309290 A US 3309290A
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United States
Prior art keywords
shell
electrotype
depressions
lead
alloy
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Expired - Lifetime
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US266748A
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English (en)
Inventor
Blackmore Roy Clifford
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Purnell and Sons Ltd
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Purnell and Sons Ltd
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D1/00—Electroforming
    • C25D1/10—Moulds; Masks; Masterforms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
    • B41C—PROCESSES FOR THE MANUFACTURE OR REPRODUCTION OF PRINTING SURFACES
    • B41C3/00—Reproduction or duplicating of printing formes
    • B41C3/08—Electrotyping; Application of backing layers thereon

Definitions

  • the mould is first taken from the original which is to be duplicated.
  • the mould may be made of a number of materials, including lead, wax, Tenaplate or plastic sheet.
  • the mould is placed in an elec trolytic. deposition tank for the electrolytic deposition of a shell of copper on to the surface of the mould.
  • the thickness of this copper shell is determined by the rate of deposition of copper on to .the mould and the time the mould is kept in the tank.
  • the shell thickness generally lies between 0.010" and 0.020".
  • the copper shell with its edges turned upwards in the form of a tray is then backed-up with lead in the molten state, an operation which can be carried out by the open pan method in which the molten lead is poured into the copper shell in the form of a pan or tray or with the assistance of a pressure caster.
  • the flatness of the printing surface of the electrotype will vary from plate to plate but almost without exception will require further mechanical or hand slabbing, or both, in order to provide the electrotype with as nearly as possible a perfectly level printing surface.
  • the Whites or nonprinting areas of the electrotype tend to be forced upwardly towards the printing surface and then subsequently have to be routed out of the electrotype.
  • Curved electrotypes are of three well-known kinds:
  • the electrotype can be left as it is if required for compression lock-up on a rotary printing machine, or if tension lockup is required, the electrotype can be bored to a thinner gauge and the lead which has been removed can be replaced by a sheet of pre-curved aluminium bonded to the electrotype.
  • cold curved electrotypes suffer from the same disadvantages as the flat electrotype. Furthermore the curved electrotype stretches when curved and is subjected to heavy stress and pressure, which is most undesirable, particularly when close-register colour Work is involved.
  • the electrotype In plastic-backed electrotypes, if the electrotype is required to be chrome-faced, it either has to be routed after chroming which, due to the hardness of the chrome, is troublesome, or links have to be left to carry the current all over the surface of the electrotype and these links finally removed.
  • This invention has among its objects to mitigate the disadvantages of known processes as hereinbefore described and to provide a simple method of producing electrotypes which will obviate the necessity for the adjustments essential in such known processes.
  • sufficient metal or alloy of relatively low melting point is caused to flow into the depressions in the back or non-printing side of the electro-deposited shell, of copper or nickel for example, to eliminate sharp depressions or crevices, after which the shell is backed-up by the electrolytic deposition of a metal or alloy, preferably lead or an alloy of lead and tin.
  • the electrolytic deposition of the backing layer takes place at ambient temperature or at a slightly elevated temperature so that the distortion produced by application of the backing in molten form is avoided.
  • the use of pressure is also avoided; no Whites are forced up and as packing is unnecessary, the step of routing away of packing metal does not arise.
  • the metal of relatively low melting point employed may, for example, be tin or a tin-lead alloy and a 50-50 alloy of tin and lead has been found to be suitable.
  • the melting point of this metal or alloy employed advantageously lies within the range 69-235" C. and preferably not above 200 C.
  • the relatively low melting point of the metal or alloy and the relatively small amount of the metal or alloy needed are such that substantially no distortion of the copper shell occurs in the process of so removing the sharp depressions.
  • the shell may itself be electrolytically deposited on to a curved mould after which the metal or alloy of relatively low melting point is applied to eliminate sharp or relatively deep depressions in the back of the shell before the backing-up layer is formed by electrolytic deposition.
  • the mould may be formed to the required curve, fixed to a suitable carrier, and then be suspended in a copper or nickel vat and a copper or nickel shell be deposited on the curved surface of the mould.
  • the curved shell is removed from the mould and a small amount of a relatively low melting point metal or alloy is caused to flow into the depressions on the non-printing side of the shell to eliminate sharp depressions and crevices.
  • the modified back or non-printing side of the shell is then backed up by the electrolytic deposition of a metal or alloy.
  • a curved electrotype may, in another method according to the invention, be made from a flat shell, the flat shell being formed to the required curvature either before or after the relatively low melting point metal or alloy is caused to flow into the depressions in the back of the shell, after which the backing-up layer of metal is applied electrolytically.
  • the invention also comprises an electrotype which is a product of the method, that is to say, an electrotype having a copper face, an electrolytically deposited backing layer and an intervening layer of a metal or alloy of relatively low melting point, the intervening layer being only of such thickness that sharp depressions present in the back of the copper shell are much less sharp in that surface of the intervening layer which lies adjacent to the electrolytically deposited backing layer.
  • FIGURE 1 is a cross section of part of an electrodeposited electrotype shell of copper
  • FIGURE 2 is a section corresponding to FIGURE 1 showing strips of a low melting alloy placed on the back of the shell;
  • FIGURE 3 is a corresponding section after the low melting alloy strips shown in FIGURE 2 have been rendered molten and have flowed into the depressions;
  • FIGURE 4 is a section according to FIGURE 3 showing the electrotype after it has been backed electrolytically with a lead/ tin layer;
  • FIGURE 5 is a section corresponding to FIGURE 4 showing the backed electrotype after the backing has been planed flat.
  • FIGURE 1 shows, in cross section, part of an electrotype shell of copper after removal from the mould on which the copper was electro-deposited, the thickness of the copper shell being approximately 0.015 inch.
  • shell 10 has a printing face 11 and a non-printing side or rear face 12.
  • the rear face 12 is fiuxed and strips 13 of a 40/60 lead tin foil of about 0.05 inch in thickness are laid over the depressions in the rear face 12 of the shell 10.
  • the shell whilst perfectly fiat, is then heated to approximately 200 C. to melt the strips of lead-tin foil.
  • the molten lead-tin alloy flows in the depressions 14 in the rear face 12 of the shell 10.
  • the lead-tin alloy forms solid masses 15 in the depressions 14.
  • the lead-tin alloy forming the masses 15 do not completely fill the depressions 14 but they greatly reduce the depth of the depressions, the residual depressions being then very much shallower than the original sharp and relatively deep depressions 14.
  • the front or printing face 11 of the shell 10 is brushed with a shellac solution to form a protective coating on that face, and the shell is then suspended in a carrier in a lead-tin depositing tank or bath.
  • a lead-tin backing 16 is then electro-deposited on the back of the shell, part of the lead-tin backing 16 being directly in contact with the rear face 12 of the copper shell 10 and the remainder of the lead-tin backing 16 being in contact with the intervening layer 15.
  • the electrotype is removed from the bath and the rear surface of the backing 16 is planed to a fiat surface 17. The electro was then bonded through the surface 17 to aluminium of inch thickness in known manner.
  • Example 1 A laminated plastic mould was secured by adhesive to a sheet of plate glass in order to keep the mould perfectly fiat during the copper-depositing process. The edges of the mould were sealed to the plate glass with wax in order to prevent the plating solution making contact with the adhesive and possibly rendering it less effective. After the mould has been silvered, it was suspended in a copperdepositing tank and a copper shell of 0.020 thickness was grown. The copper shell was carefully removed from the mould and fiuxed on the back, and a 40/60 lead/tin foil of 0.005" thickness was laid on the back of the shell wherever the depressions (caused by the relief printing image on the face of the shell) occurred.
  • the shell with foil in position and lying perfectly flat was then heated to 200 C. (which is the preferred highest temperature) in an oven, which caused the tin/lead foil to flow into the depressions, making the back of the shell very much smoother and free from any deep or sharp crevices or depressions.
  • the printing face of the shell was then brushed with a shellac solution for protection and, after being placed in a suitable carrier, the shell was suspended in a lead/tin depositing tank containing, per gallon, 1% ozs. stannous tin, 14 /2 ozs. lead, 6 /2 ozs. free fluoboric acid, plus additives. At a current density of 50 amps per sq. ft.
  • Example 2 A thermoplastic mould having a smooth back was placed in hot water at 70 C. and pressed into a former having the required curvature.
  • the former with the mould was then placed in cool water and the mould was found to have the required curve and to be quite rigid.
  • the mould had been silvered it was placed in a suitable carrier and suspended in a copper-depositing tank and a copper shell 0.020" thick was grown.
  • the shell was carefully removed from the mould and fluxed on the non-printing side.
  • a 40/60 lead/tin foil of 0.005" thickness was laid on the back of the shell wherever deep depressions (caused by the relief printing image on the face of the shell) occured.
  • the shell with foil in position was heated by radiation in 2" strips to approximately 200 C. which caused the lead/ tin foil to flow into the depressions, making the back of the shell very much smoother and free from any deep or sharp crevices or depressions. It was found necessary to limit the heating to strips, otherwise the tin/ lead would flow to the lowest part of the curved shell rather than just into the depressions.
  • the printing face of the shell was then brushed with a shellac solution for protection, and, after being placed in a suitable carrier, the shell was suspended in a lead/ tin depositing tank containing, per gallon, 1 ozs. stannous tin, 14 /2 ozs. lead, 6 /2 ozs. free fiuoboric acid and additives.
  • Example 3 A laminated plastic mould was attached to a sheet of plate glass by strong rubber bands in order to keep the mould perfectly flat during the copper-depositing process. After the mould has been silvered it was hung in a copper-depositing tank and a copper shell of 0.030" deposited on the silvered surface of the mould. The mould with the copper shell deposited thereon was then removed from the tank and the visible or non-printing side of the copper shell was fiuxed. Pieces of foil of an alloy of lead, tin, bismuth and cadmium having a melting point of 70 C. were laid on the non-printing side of the shell wherever the depressions occurred, the thickness of the foil being 0.005".
  • the pieces of foil were heated by radiation, the heating being only that required to permit the alloy to flow into the depressions.
  • the sharp corners of the depressions were thus eliminated and the depressions were made shallower and relatively broader.
  • the mould with the modified copper shell was placed in a lead-tin depositing tank and left in the 6 tank until a deposit of 0.045" of lead-tin had deposited electrolytically on the surface of the copper.
  • the electrotype was then bonded in known manner to a sheet of aluminium of a thickness of 0.100" to provide an electrotype of an overall thickness of 0.166" (Pica plate thickness).
  • a method for the production of an electrotype from an electrotype shell which comprises placing a pre-selected amount of alloy in the form of strips and having a melting point in the range of 200 C. over the sharp depressions in the non-printing side of said electrotype shell, heating said shell and alloy strips to melt the strips and cause the molten alloy to flow into said sharp depressions said pre-selected amount of alloy being insuflicient to completely fill the depressions and crevices, and then electroplating a layer of a mixture of metals containing lead onto the non-printing partially-filled side of the shell to form an electrotype.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Printing Plates And Materials Therefor (AREA)
US266748A 1961-08-28 1963-03-20 Method of forming electrotypes Expired - Lifetime US3309290A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB30197/61A GB931309A (en) 1961-08-28 1961-08-28 Electrotypes
GB1108462 1962-03-22

Publications (1)

Publication Number Publication Date
US3309290A true US3309290A (en) 1967-03-14

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US266748A Expired - Lifetime US3309290A (en) 1961-08-28 1963-03-20 Method of forming electrotypes

Country Status (5)

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US (1) US3309290A (fr)
BE (1) BE636483A (fr)
DE (1) DE1257161B (fr)
FR (1) FR1351255A (fr)
GB (1) GB931309A (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US287617A (en) * 1883-10-30 Process of preparing rubber plates or sheets for graining
US385519A (en) * 1888-07-03 Setts
US994705A (en) * 1901-03-08 1911-06-06 Alexander Elliott Electrotype and process of making same.
US1720430A (en) * 1928-04-20 1929-07-09 Bartholomew J O'brian Process of manufacturing curved electrotype plates
US2172564A (en) * 1934-05-04 1939-09-12 Tablet fob use in fabricating

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US287617A (en) * 1883-10-30 Process of preparing rubber plates or sheets for graining
US385519A (en) * 1888-07-03 Setts
US994705A (en) * 1901-03-08 1911-06-06 Alexander Elliott Electrotype and process of making same.
US1720430A (en) * 1928-04-20 1929-07-09 Bartholomew J O'brian Process of manufacturing curved electrotype plates
US2172564A (en) * 1934-05-04 1939-09-12 Tablet fob use in fabricating

Also Published As

Publication number Publication date
GB931309A (en) 1963-07-17
FR1351255A (fr) 1964-01-31
BE636483A (fr)
DE1257161B (de) 1967-12-28

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