US2801451A - Method of and apparatus for making printing plates - Google Patents

Description

Aug. 6, 1957 v E. L. GEIGER 2,801,451

METHOD OF AND APPARATUS FOR MAKING PRINTING PLATES Filed April 4, 1956 I lhlm J mmvrox Unitd ews Patent METHOD OF AND APPARATUS FOR MAKING PRINTING PLATES Earl L. Geiger,Daytn, Ohio Application April 4, 1956, Serial No. 576,167

11 Claims. (Cl. 22-72) This invention relates to methods of and apparatus for making printing plates. In stereotype casting, a matrix made of a relatively soft fibrous material is prepared by pressure rolling, or the like, from a composed assembly of type. The matrix is dried and shrunk and is then placed in the mold of a casting box wherein molten metal is poured in such manner that as the metal hardens a surface thereof is formed with the stereo likeness of the matrix impression.

The prepared matrix has type high areas corresponding approximately to the full thickness of .the matrix and has bolster .or bolstered areas or depressions which are required to be maintained in the completed plate. In the casting box, the bolster areas are subject to collapse by the weight and pressure of the molten metal. To avoid this it is conventional practice to pack the reverse face of the matrix with strip material, in an effort to provide a substantially continuous even surface over the reverse side of the matrix for constant support and resistance to the metal pressure.

The co-called packing of the'matr'ix thus is a regular part of stereotype practice. It requires a not inconsiderable amount of skill and adeptness since the strip material is selected for use in compensation with the varying depth of the bolster areas. It is, moreover, a time consuming operation which it would'be desirable to dispense with, particularly in newspaper plants wherein the saving of process time between the composing room and the press room is greatly to be desired.

An object of this invention is to improve the art of stereotype practice by eliminating, or substantially eliminating, the need for packing of the matrix, it being contemplated that no packing should be required save possibly in marginal areas of the matrix.

Another object of the invention is to provide support for the bolster areas of a matrix in a casting box by means other than packing strips.

A further object of the invention is to achieve support as described above without change in the methods of making the printing plate, except for omission of the packing step, and with little or no modification of existing apparatus.

A further object of the invention is to utilize a principle of pressure fluid support of the bolster areas, it being proposed to supply compressed air to the rear face of the matrix in a timed relation with the operation of pouring the metal.

A still further object of the invention is to provide certain automatic acting controls regulating the supply of pressure fluid as described.

Other objects and structural details of the invention will appear from the following description when read in connection with the accompanying drawing, which is a view in diagram of stereotype casting apparatus embodying the instant invention in its illustrated form.

Referring to the drawing, a casting box as used in stereotype work, is here shown in fragmentary and diice agrammatic form, and is seen to comprise a cope 10 and a core 11 in relatively spaced relation. Secured to and in effect forming a part of the cope 10 is a platen member12 in parallel laterally spaced apart relation to the wall of the cope proper to define therebetween a chamber 13. A matrix 14 is inserted in the casting box between the core 11 and the platen 12 and is adapted to seat on the platen, leaving an intermediate space 15 which is the molding chamber. Into the space 15 molten metal is poured by way of a spout 16 which is in overhanging relation to the casting ,box and extends from a reservoir 17. As diagrammatically indicated herein, the reservoir 17 contains molten metal and in addition to the outer shell thereof may comprise an inner cylinder 18 receiving a piston 19 through its open upper end and having a lateral opening 21 near its lower end communicating with the interior of the reservoir outside the cylinder. The piston 19 is connected by a rod 22 with a lever 23 having a fixed pivot point 24 near its one end. The rod 22 is attached to the lever 23 on one side of the pivot point 24 while on the opposite side of such point there is pivotally attached to the lever a rod 25 extending from a hydraulic or compressed air actuating cylinder 26. The rod 25 is extensible from and retractable in the cylinder 26, under control of the operator and by means which it is unnecessary here to consider, whereby to rock the lever 23 about its pivot point 24. According to the construction and arrangement of parts, a retracting motion of the rod 25 rocks the lever 23 in a counterclockwise direction as viewed in Fig. 1 causing the piston 19 to descend in the cylinder 18 substantially to the position shown in full lines. As the piston passes the opening 21, on its downward stroke, the interior of the cylinder 18 above the piston is permitted to fill with molten metal from the reservoir 17. Now as the rod 25 moves in an extending direction from the cylinder 26, the lever 23 rocks in a clockwise direction to lift the piston 19, which, as it rises in the cylinder 18, expels the molten metal trapped above the opening 21, causing it to overflow from the cylinder 18 through an opening 27 into the spout 16 whence it is delivered to the molding chamber 15.

Within the chamber 15, the molten metal flows into intimate contacting relation to the outwardly facing surface of the matrix 14, and, as it hardens, takes on a surface configuration corresponding to that of the matrix. The metal plate, so formed, is removed by opening the casting box, as by a swinging movement by the cope 10 or core 11.

It is desirable that the matrix 14 take up and maintain a position upon the platen 12 which will avoid relative movement of the matrix while the metal is being poured and while it hardens; To aid this action, the platen 12 is formed with perforations 28 and means are provided for exhausting the chamber 13 whereby to exert through the platen a vacuum pressure upon the matrix 14 causing the matrix to be drawn back upon and firmly to seat upon the' platen. In accordance with the instant invention, a further use of the perforations 28 is made in that a reversal of pressure forces is contemplated to supply the chamber 13 with fluid under pressure at approximately the conclusion of the filling of molding chamber 15. Thus, it is proposed that at this time the exhausting of the chamber 13 be dicontinued and a pressure fluid, such as compressed air, be supplied the chamber 13, which pressure fluid passes through the openings 28 and 'fills or floods bolster areas 29 of the matrix, supporting such areas against collapse under the weight and pressure of the metal in chamber lS.

While the vacuum pressure and the oppositely acting supportnig pressure may be separately applied and con trolled in any convenient manner, manually or automatically, they are in the illustrated embodiment of the invention combined in a single system intended to be largely automatic in its action. Referring to the drawing, the chamber 13 in the cope of the casting box communicates through a conduit 30 with a distributor-like valve 31 which is connected also by a conduit 32 communicating with a pump 33 discharging to atmosphere. Also connected to the valve 31 is a conduit 34 extending from a source 35 of compressed air. The conduit 30 is alternately exhausted and energized with compressed air, under control of the valve 31 which occupies alternate positions of adjustment in response to the energizing of an electromagnetic device 36. With the device 36 deenergized, the valve 31 is positioned to disconnect the conduit 30 from the conduit 34, the conduit 32 being open. Accordingly, when the pump 33 operates, the conduit 29 and therefore the chamber 13 are exhausted for creation of the vacuum pressure above described. Energizing of the electromagnet 36 results in opening the conduit 30 to communication with conduit 34 and the source 35 of compressed air and may also be utilized to close conduit 32. In this position of the parts, therefore, the conduit 30 and chamber 13 is supplied with compressed air for support of the bolster areas of the matrix as described.

Further in the latter described adjustment, the operation of pump 33 may be discontinued. Thus, the pump 33 is driven by an electric motor 37 disposed in power conductors 38 and 39. In the conductor 38 is an on-oif switch 41 as well as a switch assembly 42. The latter includes a contact arm 43 settable to alternate positions of adjustment to engage either a contact 44 or a contact 45. The arm is biased normally to engage the contact 44 but may be depressed by an insulating pin 46 to leave contact 44 and engage contact 45. The contact 44 is connected directly to the conductor 39 while contact 45 is connected to the conductor 39 indirectly by way of a lead 47 passing through the electromagnetic device 36.

Thus, in the operation of the system when the switch 41 is closed, the motor 37 tends constantly to be in operation, driving the pump 33 and exhausting the chamber 13 of the casting box. The switch 41 may, for example, be closed immediately that the casting box has been closed up upon a newly inserted matrix 14 whereupon the matrix will be pulled to and firmly seated upon the platen 12. The operating pin 46 for the switch assembly 42 is arranged for actuation by the lever 23 of the metal pumping mechanism in such manner as to be depressed as the lever reaches a position raising the piston 19 to its upper limit of movement in the cylinder 18. This position of the piston coincides approximately with completion of filling of the molding chamber 15, so that actuation of the switch 42 may be said to take place as the molding chamber is filled. With such actuation, the switch arm 43 is moved out of engagement with contact 44 and into engagement with contact 45. As a part of such motion, the motor 37 is deenergized to stop operation of the pump 33. Application of the vacuum pressure is accordingly interrupted. As another part of such actuation, the electromagnetic device 36 is energized to cause valve 31 to shift communication of the conduit from conduit 32 to conduit 34. Compressed air from the source accordingly is free to flow to the chamber 13 of the casting box and thence through the holes 28 in the platen 12 to the matrix 14, filling and reenforcing the bolster areas 29 thereof. Upon retraction of the rod 25 in the cylinder 26, the lever 23 is raised and the switch assembly 42 released and permitted to reassume its normal illustrated position wherein the contact arm 43 is in engagement with contact 44 and wherein valve 31 is positioned to close conduit 34.

The platen 12 is formed with a relatively large number of closely spaced apart openings 28. The printing portions of the matrix'are of maximum thickness and seat on and close the platen openings which register therewith.

The depressed or bolster areas of the matrix are open to receive the air pressure which floods these areas exerting a pressure counter to the collapsing pressure exerted by the metal on the opposite side of the matrix. The matrix requires the support of the compressed air only momentarily since the metal in chamber 15 sets very rapidly. The pressure value of the air may be regulated by interposing in the conduit 34 a pressure reducing valve 48, as

indicated, which valve may be adjusted to suit the physical I properties of different matrices.

It will be understood that the electrical and flow diagrams here presented are for purposes of illustration only and that various forms of control may be provided to secure the alternating vacuum and pressure forces in the casting box which are contemplated by the instant invention. For example, stereotype casting methods as now known and practiced include the use of a perforated platen 12 and of a vacuum pump for exhausting the space to the rear of the platen for better seating of the matrix. Without alteration in this method or apparatus, a practice of the present invention might involve merely the making of a separate connection to the .casting box of a compressed air line, with the operator selectively actuating the controls for exhaust or pressure. The invention is not understood to require a modification of the casting box although more consistent results may be obtained with a platen having a larger number of holes or perforations therein than is the case in the casting boxes conventionallynow in use.

The valve 31 may be a simple solenoid operated shut off valve in the compressed air line, with the vacuum line joined thereto for convenience, or it may provide also for positive opening and closing of the vacuum line in an inverse relation to the opening and closing of the compressed air line. Commercially available multi-way valves are known for performing either function.

What is claimed is:

1. In the making of poured metal printing plates, the steps of placing a matrix within a casting box having a perforated plate in adjacent parallel relation to the reverse face of the matrix, creating a vacuum in the casting box applied in a direction to seat the matrix on said perforated plate, pouring metal into said casting box, and at about the same time that the metal is poured applying fluid under pressure through said perforated plate to the bolstered areas of the matrix to inhibit collapse thereof by said metal.

2. A method of casting a printing plate in a mold having spaced apart walls, one of which is perforated, the matrix being received between said walls and molten metal being poured between the matrix and the other one of said walls, including the steps of exerting a vacuum pull upon the matrix through said perforated wall whereby to seat said matrix on said perforated wall, pouring molten metal as described and of reversing the vacuum pull action to supply fluid under pressure through said perforated wall to support bolstered portions of the matrix against poured molten material.

3. A method of casting a printing plate in a mold providing a perforated backing plate for seating of the matrix thereon, including the steps of pouring a molten metal into said mold and of alternately exerting a suction upon the matrix through said plate for firm seating of the matrix thereon and of applying a pressure through said plate in the opposite driection to support bolstered portions of the matrix against poured molten metal.

4. A method of casting a printing plate from a matrix having bolstered portions, including the steps of mounting the matrix for seating on a perforated backing plate, drawing the matrix firmly to a seat on said plate, pouring molten metal in such manner that the weight of the metal is exerted in a direction to seat the matrix upon said plate, and supplying pressure fluid through said perforated plate to said bolstered portions for support thereof.

5. A method of casting a printing plate, including the steps of placing a matrix in a mold wherein the reverse side of the matrix is backed up by a perforated plate member, applying a vacuum pressure through said member to the matrix for seating thereof on said member, pouring molten metal into said mold, and reversing the applied pressure forces within the mold to supply fluid under pressure through said plate member to support bolstered portions of the matrix against crushing by the metal.

6. A method according to claim 5, characterized in that the reversal of said pressure forces is timed approximately to coincide with the filling of the mold by the molten metal.

7. A combination of the kind described, including a mold for printing plates, a cope in said mold providing a perforated plate for seating of the matrix thereon and a chamber to the rear of said plate, means for pouring the molten metal into said mold, and means for alternately exhausting said chamber and for connecting it to a source of fiuid under pressure.

8. A combination of the kind described, including a mold having a cope and a core receiving a matrix therebetween, means for pouring molten metal into said mold between said core and one side of the matrix, a perforated plate member providing support for the other side of said matrix on said cope, and means operative in a timed relation to the pouring of said molten metal for supplying fluid under pressure through said plate member to the said other side of the matrix for support of bolstered areas thereof.

9. A combination according to claim 8, characterized in that said last named means is operative by said means for pouring molten metal.

10. A combination of the kind described, including a casting box providing a mold defined by acore and a cope, a perforated plate member providing support for the reverse side of the matrix and defining with said cope a chamber in said box, means for exhausting said chamber to create a vacuum pulling the matrix to a seat on said plate member, means to connect said chamber to a source of fluid under pressure to flood bolstered areas of the matrix with pressure fluid for support thereof, means for pouring molten metal into said casting box in a space between said core and the matrix, and means operated by said last namd means concomitantly to discontinue application of the vacuum in said chamber and to supply pressure fluid thereto.

11. A combination according to claim 10, characterized in that said last named means is operated in predetermined timed relation to the pouring of the metal so that the described pressure reversal occurs approximately at the conclusion of the pouring of the metal.

References Cited in the file of this patent UNITED STATES PATENTS 1,153,220 Grey Sept. 14, 1915 2,109,206 Bungay Feb. 22, 1938 2,109,207 Bungay Feb. 22, 1938 2,141,802 Temte Dec. 27, 1938 2,173,990 Wood Sept. 26, 1939 2,242,943 Clark May 20, 1941 2,297,739 Blackley Oct. 6, 1942 2,461,151 Foster Feb. 8, 1949 FOREIGN PATENTS 298,111 Germany May 30, 1917

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