US2041743A - Printing plate matrix - Google Patents

Description

May 26, 1936. T. c. BROWNE PRINTING PLATE MATRIX Filed May 7, 1934 FIG 2 Z8 IIIIIIIIIA xmN F l G. 3

FIG. 5

e 0 mw m L M m m m an 6 f wk m5 w Patented May 25, 1936 UNITED STATES PATENT OFFICE PRINTING PLATE MATRIX Theodore C. Browne, Hinsdale, Ill. Application May 7, 1934, Serial.No."I24,273 5 Claims. (01. 41-25) This invention relates to the graphic arts and is particularly directed to the production of a matrix in which resinous or resin-like rlmning plates may be molded.

In my copending application Serial No. 670,238, filed May 10, 1933, I showed how resinous bodies might be cured under considerable pressureand formed into hard, dense masses conforming exactly to the-original shape of the mold, even if the mold or matrix, as it is commonly called in the graphic arts, be of a soft, yielding nature.

In an application of Gilbert C. Waters, Serial N0. 724,280, filed May 7, 1934, entitled Art of producing printing plates and matrices, a type or type-containing matrix was disclosed which because it is yieldable, extensible, but self-restoring, always can be removed from the type form no matter how broken the composition or deep the spaces between the type. It has the further ad} vantages not found in previous matrices that the full shoulder depth of the type is always reproduced, that no surfacegrain or structure is introduced, and that shrinkage is practically eliminated. In fact,the shrinkage is so negligible that such a matrix retains multi-color registration in 133 line screen work perfectly.

This invention may beconsidered an improvement upon the processes set forth in the above applications and has for its objects to produce matrices from mixed forms containing a number of metals, to reduce the possibility ofchemical damage to expensive half-tone originals; to prevent such chemical action as will render the production of a running plate in such-a matrix difficult or impossible, and to produce matrices by "closed moulding.

Still other objects and advantages of my invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its fundamental principles and. as to its particular embodiments will best be understood by reference to the specification and accompanying drawing in which Fig. l givesaperspective view of the form showing the chase modified according to my invention.

Fig. 2 is a transverse sectional view through the mould,

3 is a sectional view of one form of matrix,

Fig. 4 is a similar section through an alternative form of matrix, and

Fig. 5 illustrates the method of manufacture, showing the'press diagrammatically.

above.

under the name of Duprene.

In the above identified wat ers application the, direction is given to plate the illustrations with some suitable metal such as tin, although nickel also is generally suitable.

Although the procedure outlined by Waters 5 .produces consistently excellent results when clean,

fresh type metal makes up the form, it sometimes happens that the resin duplicates made in matrices formed on plated originals or electros, or from dirty, much-used type are full of minute blisters. In some cases, both the matrix and the resin running plate are full of small pits.

A chemical investigation of such matrices shows them to be poisoned with copper. From the exaggerated cases, intentionally produced in the 15 experimental work on this invention I have found that copper-rubber, and particularly the copperrubber-sulphur complexes, of whatever nature they may be, act like cement, in that they cause the sticking of resinous or resin-like masses to 20 rubber. In some cases, it is impossible to separate the two without destroying either or both the plate and the matrix when the matrix bears even a very small amount of copper.

' Sticking is not confined to one group of resins 2.5

or even to resins, such very diverse chemical substances as phenol-formaldehyde resins, ureaformaldehyde resins, vinyl resins, chlorinated rubber, chlorinated rubber glucose mixtures, and

the resin-like derivatives known as plioform 30 Successful matrices have been made contain- 40 ing, rubber pts., 1, 3, 5 tri-nitro-benzol 2' pts., aniline, 1 pt., and carbon black pts. which were cured 40 minutes in direct contact with copper, without any of the defects noted I much prefef because of greatly improved mechanical and surface characteristics obtainable, to make matrices having a working face of polymerized chloroprene, obtainable commercially tion about this substance is available. It is well to point out, however, that its base substance bearssuch a resemblance to isoprene, the base substance of rubber. that great physical resemblance is to be expected.

If the matrix is to be 35 Much informa- 50 Neither does it pick up from the copper the ex-' tremely small amounts of poison which are sufiicient to ruin a sulphur-bearing rubber matrix.

As the foregoing applications have pointed out,

lateral deformation of the subsequent moldings or pressings is difiicult to prevent in a rubber or rubber-like matrix, unless the rubber be cemented rigidly to a non-extensible member, preferably a thin sheet of spring brass. v Preferably also, the union of rubber to brass should occur as the matrix is being formed. "Duprene will adhere to rubber when both are simultaneously cured and the rubber in turn will adhere to the prepared brass.

Although the open moulding procedure shown in the above identified applications is a great advantage where an enormous number of different sizes of forms are to be handled as in a jobbing electrotypers establishment, it is not so certain as is, closed moulding in producing a flat, fully filled matrix. It is possible to secure closed moulding advantages in establishments such as book, magazine and catalog printing houses where a relatively few sizes of forms cover all needs by the following procedure.

The chase, [0, (Fig. 1) is of the ordinary cast iron or welded steel variety. It is surface ground to some convenient exact thickness and is provided with four locating holes II, II drilled through the pads at the corners. The form is composed in the conventional manner except that wide, accurate type high steel bearers surround the composition and the furniture I3, is preferably of metal instead of wood. The form is held in place by the quoins M.

I then provide a nest I5, which is an accurately ground plate of steel having a central moulding aperture Hi. It carries four locating pins I1, I! which engage the holes II, II. If the chase I0, is exactly type high (0.918) the shim I8 is unnecessary. Otherwise it is adjusted to bring the outside bearing for the nest exactly type high. The plunger I9 is a flattened T having a leg or plunger portion 2| which fits within the aperture l6 with about .005" clearance, and a head 22.

In moulding the matrix, the chase Ill and the nest l5 are placed on the lower platen of a press 23, as shown in Fig. 5. A laminated sheet of gum stock having a polymerized chloroprene face and a; backing layer of rubber gum stock is placed in the aperture l6. On this is placed a thin sheet of spring brass (covered with a cement to promote adhesion to the rubber) or a sheet of resin-cement covered resin-impregnated paper.

Then the plunger I 9 is put in place and the press closed against the top platen 24. Steam is admitted through the conduits 25, 25.

Under ordinary circumstances the inner face 26 of the head 22 engages the top surface 21 at the nest IS. The depth at the plunger section 2| controls the thickness at the matrix. If adjustments of thickness are necessary, they may be compounding. In the example given, the cure is complete in ten minutes at eighty pounds steam.

I have found it advantageous to use as the backing layer a rubber compound which commercially is designated as non-sulphur. The vulcanizing agent in this case is actually an organic sulphur compound which releases sulphur upon heating. So active, however, is the released sulphur that full cure is effected with as little as .017% combined sulphur.

With such a rubber, extremely thin layers of polymerized chloroprene are all that is necessary (a great advantage, since Duprene is as yet an expensive substance).

When ordinary sulphur rubber compounds are used (2%,; to 3% sulphur) the excess sulphur is active and dangerous. Then thicker polymerized chloroprene is required to insulate and guard the copper from any possibility of sulphur attack.

The physical similarity of polymerized chloroprene to rubber is close. It is resilient, deformable, self-restoring after deformation, and produces a matrix which has many of the advantages of rubber. It may be pulled loose from any type form, however complicated, and restores itself so completely to the original size that registration of multicolor fine-screen,-half-tone plates is easily secured.

A considerable number of rubber printing plates are now manufactured by moulding a thermo-setting resin matrix upon the type surface and thereafter moulding rubber therein. The mould herein described is adapted for the production of such matrices and I have produced extremely accurate and entirely satisfactory thermo-setting matrices therein.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention as will be evident to those skilled in the art.

I claim:

1. A matrix for the production of printing plates from molded plastics having an impression-bearing face comprising a layer of a sulphur-free resilient compound capable of relatively large deformation within its elastic limit, an intermediate layer of rubber, and a metallic back vulcanized and united together to form a unitary matrix element.

2. A flexible matrix comprising an impression-bearing face of a sulphur free chloroprene polymer, an intermediate layer of rubber and a reinforcing element which is substantially nonextensible under the pressures to which the matrix is designed to be subjected bonded together to form a single unitary structure.

3. A mold liner comprising an impressionbearing surface of a cured;fiexible,@ielding sulphur-free resilient substance capable of relatively large deformation within its lastic limit, an intermediate layer of vulcanized soft rubber and a reinforcing member.

4. A non-sticking mold liner for heat reactive resin molding which comprises a resilient, yield.- ing, surface of a substantially sulphur-free chloroprene polymer, a backing layer of rubber, and

reinforcing member having substmtiany zero 5 lateral stretch.

5. A matrix tor molding comprising snimpression-bearing face of a siflphur-tree resilient com-

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