US3074128A

US3074128A - Casting stereotype plates

Info

Publication number: US3074128A
Application number: US858626A
Authority: US
Inventors: Brockel Ernst
Original assignee: MAN Maschinenfabrik Augsburg Nuernberg AG
Current assignee: MAN AG
Priority date: 1958-12-11
Filing date: 1959-12-10
Publication date: 1963-01-22
Anticipated expiration: 1980-01-22

Description

Jan. 22, 1963 E. BROCKEL 3,074,128 CASTING STEREOTYPE PLATES Filed Dec. 10, 1959 rates Patent 3,:ii745l28 Patented Jan. 22, 1953 hoe 3,074,128 CASTHNG STEREQTYPE PLATES Ernst Broekel, Augsburg, Germany, assignor to Maschinenfabrik Augshurg-Nurnberg A.G., Augsburg, Germany, a corporation of Germany Filed Dec. 10, 1959, Ser. No. 858,626 Claims priority, application Germany it, 1958 tilaimst (Cl. 22-4) This invention relates to the casting of stereotype plates for rotary printing presses and the like wherein the cast ing operation includes forcing molten metal into the plate mold through a gate in contact with a molten metal outlet and, more particularly, to producing such cast plates with continuous circulation of molten metal past the metal outlet and where the metal outlet is positioned at a level above the level of molten metal in the supply reservoir or kettle.

As is well understood, stereotype plates for use on rotary printing presses may be produced by casting type metal in a generally cylindrical mold against a matrix or mat of the type matter to be reproduced on the stereotype plate, and, since a plurality of duplicate or different stereotype plates are conventionally made in sequence in the mold, there is usually provided means whereby a reservoir or a heated kettle of molten metal is maintained from which sequential injections or feedings of molten metal are pumped or otherwise ejected from a metal outlet in flow of communication with a gate or inlet to the mold cavity of the stereotype plate mold. Also as will be understood, with such types of apparatus, means may be provided for intermittently withdrawing molten metal from a reservoir thereof (as by pumps or suction) for injection into the stereotype molds intermittently for the repeated and intermittent casting of plates in the plate mold.

With such an arrangement, it may be desired to incorporate at the metal outlet adjacent the gate of the mold a valve or stop cock for controlling the metal flow into the mold and for preventing passage of molten metal through the outlet during the intermittent periods of time when the mold is moved away from the outlet for removal of the molded stereotype plate, etc., in known manner, and to incorporate in the apparatus means for heating the stop cock and the conduits leading thereto from the molten metal kettle to avoid solidification of metal therein during the pauses between successive molding operations.

If it is desired, however, to utilize such an arrangement whereby periodic or intermittent injections of molten metal are supplied from the molten metal kettle or reservoir to the gate of the stereotype plate mold, difficulty may be experienced from the accumulation of metal oxides, carbonaceous deposits, and the like, in the conduits leading to the cut-off cock at the metal outlet and in the cut-off cock itself, notwithstanding provision of heating elements therein, with resultant non-uniformity of temperature distribution and gradual clogging or throttling of the various feed lines, as, for example, when the molten metal flows but intermittently through the feed conduits and metal outlet for each molding or casting operation and then recedes therefrom back into the kettle upon the completion thereof.

According to this invention, however, production of stereotype plates is provided for whereby the molten metal flows continuously through a feed line, past the cut-off cock or valve at the metal outlet therefrom, and back to the molten metal reservoir or kettle, providing a continuous, rather than intermittent, and more or less uniform flow of molten metal at all times through the feed conduits and past the cut-off cock for continuous circulation of molten metal and for continuously flushing from the conduits of impurities deposited therein, to maintain a flow of metal of substantially uniform temperature and quality, from which continuous flow or recirculation is intermittently drawn off the metal for each molding operation; and, as further features of this invention, there are provided means for maintaining an ejecting pressure on the molten metal flowing out of the feed outlet for injection into the mold, and for maintaining a negative pressure upstream of the feed outlet during the periods between successive molding or casting operations to prevent dripping of molten metal from the feed outlet when the stereotype plate mold gate is out of contact therewith.

With the foregoing and other objects in view, an embodiment of this invention will now be further described, and other objects and advantages of this invention will be apparent from the following description, the accompanying drawings, and the appended claims.

In the drawings:

KG. 1 is a somewhat diagrammatic view in vertical section showing a portion of the molten metal kettle and casting apparatus embodying and for practising this invention taken along the line 1-i of FIG. 2;

PEG. 2 is a vertical section through the apparatus of FIG. 1 and in a plane substantially perpendicular to that of PEG. 1 taken along the line 2-2 of FIG. 1 and including a portion of the mold and mold-supporting elements of apparatus embodying and for practising this invention; and

FIG. 3 is a fragmentary view in vertical section similar to PEG. 1 of an alternative modification of a portion of the apparatus shown in FIGS. 1 and 2.

Referring to the drawings, in which like characters of reference refer to like parts of the several views thereof, stereotype plate molding or casting apparatus embodying and for practising this invention is indicated as comprising a main support or base i, on which is movably or pivotally supported in known manner a frame 2, to which is attached a semi-cylindrical core 3 about which a curved stereotype plate is to be molded or cast, with frame 2 being mounted, in known manner, to swing about pivot point 2a. A curved outer mold or casting shell member 4 is also provided for cooperation with core 3 to provide therebetween a mold cavity or casting space 5 into which molten metal is injected through the gate 5a to form or mold a stereotype plate therein, and, also in known maner, casting shell 4 is mounted on a linkage indicated generally by 4a whereby shell 4 can be retracted from core 3 when a casting operation is completed. Similarly, also in known manner, frame 2 can be swung downwardly from the position shown in FIG. 2 about pivot 2a upon completion of the molding operation.

When the foregoing parts are in the position illustrated in FIG. 2, mold gate 5a is in communication with molten metal outlet 8:: of a feed channel 8 in stop cock housing 6, which feed channel and outlet are controlled by stop cock '7. Channel 8 leads to molten metal outlet 84! through stop cock 7 from a manifold or intermediate circulating chamber 9 to which molten metal is supplied from melting kettle or reservoir 11 through feed line or riser 12. Preferably, heating elements it? are also provided in the walls of cock housing 6 so that this housing, as well as manifold 9, channel 8, and stop cock 7, may be readily and controllably maintained at a temperature which is slightly above the melting point of the molten metal from kettle 11. Thus, when cock 7 is in the open position shown in FIG. 2, molten metal can readily flow from manifold 9, through channel 8 and outlet 8a thereof, into gate 5a of mold cavity 5 to form therein the desired stereotype plate.

Both ends of manifold 9 in housing 6 are connected in flow communication in accordance with this invention with the lower part of melting kettle 11 by riser 12 and return conduit 13. At the lower end of feed riser 12 there is provided means, such as centrifugal pump 14 driven by motor 15, for continuously pumping and recirculating molten metal from kettle 11 up riser 12 through manifold 9, and back into kettle 11 through return conduit 13. If desired, electric heating elements 30 and 31 may be provided in riser 12 and/ or in return line 13 to maintain the molten metal from kettle 11 at a desirably fluid flowing temperature in use, and as also will be understood, satisfactory results are obtained by providing a plurality of feed conduits 8, each leading, through a stop cock 7, into a plurality of gates 5a in mold cavity 5, or gate 5a may be a continuous slot across the apparatus, as with feed channels 8. Similarly, as will be noted particularly in FIG. 1, it is preferred that stop cock 7 be constructed with a gradually increasing diameter or tapered configuration with regard to the flow of metal from riser 12, through manifold 9', back into kettle 11 through return pipe 13.

As noted, substantially continuous circulation of the molten metal from kettle 11 is maintained by pump 14 through manifold to maintain the quality and fluidity of the molten metal therein, and also to help maintain, in connection with heating elements 10, a uniformity of temperature in housing 6 and the channels 8, etc., while keeping these various passage free of accumulations of deposited metal or impurities therefrom. It is to be understood, of course, that ejection of molten metal through cock '7 into mold cavity 5 is also accomplished under the pressure of pump 14 on the molten metal in the circulation system, although such molding injections are intermittent.

Accordingly, a smaller quantity or throughput of molten metal need be circulated through manifold 9 to maintain the desired temperature and other conditions therein between molding injections than is necessary when a portion of this metal is being drawn off through channels 8 and stop cock 7 for a molding injection into mold cavity 5. For accomplishing such variation in the throughput quantity of molten metal circulated through manifold 9 from a higher quantity during molding injection to a lower quantity between injections, motor is provided as a variable speed motor, with means such as a limit switch (not shown) in known manner, automatically to shift motor 15 to a higher speed upon closing of molding shell 4 into the injection or molding position shown in FIG. 2 for a molding operation, and to shift motor 15 automatically to a reduced speed upon completion of the molding operation, so that a smaller throughput quantity of molten metal is forced through manifold 9 between molding injections.

As a result of such reduced speed of motor 15 and, consequently, a smaller throughput of metal and/or a slower flow rate thereof as pumped by pump 14 up riser 12 through manifold 9 and back through return pipe 13, a partial vacuum is present, upon reduction of throughput quantity between molding injections, above the level of the molten metal in kettle 11. Hence between molding injections, cutoff cock 7, being positioned above the level of metal in kettle 11, is under partial vacuum or negative pressure, as a result of the lower throughput of metal being forced up riser 12 and siphoning effect of gravity return pipe 13, thus minimizing the tendency of molten metal in channel 8 to drip out of metal outlet 8a during periods of operation between molding injections when molding shell 4 is retracted and not in casting position. On the other hand, when molding shell 4 closes into casting position, the above noted limit switch causes motor 15 to operate pump 14 at a higher speed for delivering a greater quantity of metal into manifold 9 for injection, under the pressure of pump 14, into mold cavity 5.

As will be understood, the increase in throughput occasioned by such increase of speed of motor 15 upon closing of molding shell 4 also provides for the purging of air from manifold 9 prior to each molding operation or injection. Similarly, as soon as the molding shell 4 is in molding position (as moved by the linkage 4a thereof) to receive a casting injection, cutoff cock 7 starts to rotate into the open position illustrated in FIG. 2 under the action of lever 16 driven by a connecting rod 17 and an appertaining linkage (not shown) including a lost motion arrangement, in known manner, activated by the motion of linkage 4a and/or molding shell 4 to provide for opening stop cock 7 only after molding shell 4 is in casting or injecting position.

On one end of the plug of cock 7 (e.g., the right hand end in FIG. 1) there is provided another lever 18 which, upon the rotation of cutolf cock '7 to the open position shown in FIG. 2 moves a push rod 19 to the right in FIG. 2. This motion, acting through bell crank IMP-21, and the linkages 2223, closes a rotatable flap valve 24 in return line 13, thus blocking return of molten metal from manifold 9 back into kettle 11 through return pipe 13 and, accordingly causes the entire force of pump 14 to force molten metal from manifold 9, through feed channel 8 and stop cock 7, into the gate 5a of molding cavity 5 to perform a molding or casting operation. As will be understood, the adjustment of the several foregoing levers, linkages, and motor speed switch are correlated so that, sequentially, upon closing of mold shell 4 into molding position, the throughput of molten metal is increased to purge the last traces of air from manifold 9, and flap valve 24 closes, so that, upon opening of cutoff cock 7, the full pressure of pump 14 and full quantity of liquid metal in manifold 9 are available for providing the desired molding injection into the mold cavity 5 with full pressure and fastest rate of flow.

After at least partial solidification of the metal in mold cavity 5 under the molding pressure, the plug of cock 7 is rotated from the open position shown in FIG. 2 to a closed position cutting off flow of metal and fluid pressure through outlet 3a into gate 5a of mold cavity 5, and flap valve 24 in return pipe 13 is opened (as by the reverse action of the lovers and linkages 1823) to permit return of liquid metal from manifold 9 back into kettle 11, thus resulting in somewhat of a surge of liquid metal from manifold 9 back into kettle 11. This momentary surge of metal is utilized to purge or flush from manifold 9 air bubbles which may have arisen thereinto during the injection of molten metal into the previously empty mold cavity 5. Thereafter, upon the complete rotation of cock '7 to closed position (or shortly before the complete closing thereof), motor 15 is again switched to a reduced speed by a limit switch (not shown) in known manner so that the continued circulation of molten metal by pump 14 from kettle 11 up riser 12, through manifold 9, and back to kettle 11 through return line 13 is again conducted at a lower throughput rate, which lower rate continues while mold shell 4 opens for the removal of the stereotype plate and until mold shell 4 again closes into the injecting or molding position shown in FIG. 2 for the subsequent casting 'of the next stereotype plate, at which time the foregoing sequence of operations is automatically repeated. Preferably, at the end of a molding injection operation, the time between complete opening of valve 24 in return line 13 and the switching of motor 15 from high speed to reduced speed is provided in known manner (as by a time delay relay not shown) to be about one to three seconds for the flushing action in manifold 9 by molten metal being pumped therethrough at high speed.

Satisfactory results are also achieved in accordance with this invention by providing for the differential flow rate or throughput quantity of the molten metal during high flow of molding injection and lower flow in the periods between molding or casting operations by utilizing, instead of the variable speed motor control arrangement previously described, an arrangement as indicated in FIG. 3. In this case, pump 14 and motor 15 operate at a continuous rate of speed, volume throughput, rate of flow, and fluid pressure. In order to produce the differential flow desired, and, especially, the vacuum or negative pressure suggested above in manifold 9 between molding injection operations, a throttle valve 25 is provided in riser 12, satisfactorily in substantially the same form as flap valve 24 in return pipe =13, although flap valve 25 is provided with an aperture or bore 26, the diameter of which permits the passage of a controlled quantity of fluid metal through the valve even when it is in closed position, so that the valve 25, with its aperture 26, has the effect of a throttling valve in riser l2 controlling the passage of fiuid metal therethrough from the outset side of pump 14.

In operation and during a molding injection or casting, valve 25 is open (i.e., brought to a position as shown by the dotted circle in FIG. 3 where it has substantially no throttling eifect upon the stream of molten metal being passed upwardly through riser 12 under the action of pump 14), while, during the same casting operation, valve 24 in return line 13 is closed, as previously described. Thus, in accordance with the foregoing, the entire pressure and fluid flow of molten metal under the action of pump 14 acts, through manifold 9 to flow through channels 8 and cook 7 into the mold cavity 5. After solidification, at least partially, of the meta in mold cavity 5 and as the plug of stop cock 7 is rotated to the closed position, throttle valve 25 closes under the mechanical action, as indicated in FIG. 3, of a lever member 27 afiixed to the plug of stop cock 7 and the linkage 28-29, in much the same manner as valve 24 is operated in return line 13.

At substantially the same time as throttle valve 25 closes in riser 12, under the action of the rotating plug of stop cock 7, flap valve 24 in return line 13 is opened by virtue of the previously described similarly driven arrangement of lever 18 and the linkage 19-23 appertaining thereto. In this way, after a molding injection at the full throughput of metal flow up riser 12, through open throttle valve '25 (and into mold cavity 5) and against the closed off effect of flap valve 24 under the full pressure of pump 14, upon the completion of a molding injection and when stop cock 7 is rotated into a closed position, throttle valve 25 is rotated, through the linkage 27--29, into a closed position, more or less simultaneously with the opening of valve 24, so that the flow past throttle valve 25 is controlled by the size of aperture 26 therein, whereas the return flow from manifold 9 to return line 13 is virtually unrestricted by the opening of flap valve 24 therein. As a result of this condition, a reduced flow of fluid material, under the pumping action of pump 14, is restricted by the aperture 26 in closed throttle valve 25, so that a reduced amount of fluid metal flows up riser 12 and through manifold 9, after the closing of stop cock 7. Such immediate reduction of flow (somewhat in the same manner as was achieved by a reduction of pumping speed described previously in connection with FIGS. 1 and 2), coupled with the full opening of flap valve 24 in return line 13, produces the desired partial evacuation and/or flushing or purging of manifold 9 and, indeed, maintains the desired continuous circulation of metal sufiicient to keep the various passages free of occluded deposits or solidification of metal therein and to keep them at the desirably controlled temperature with constant circulation of a small but sufficient quantity of metal through the aperture 26 in throttle valve 25, until the mold shell 4 is again in position for a subsequent molding injection into the mold cavity 5, at which time, as driven by the rotation of the plug of stop cock 7 toward open position, throttle valve 25 is opened to permit free passage of material therethrough under the force of pump 14, which open position of throttle valve 25 is, as noted, indicated by the dottle circle in FIG. 3.

As will be understood by men skilled in this art, then, there is provided, in accordance with the foregoing,

6 production of stereotype plates by the intermittent molding thereof, whereby there is constantly circulated a quantity of molten metal from a reservoir or melting kettie through a manifold adjacent a metal outlet, and such continuous circulation serves to control the temperature in the various feeding ducts, outlets, etc, while also, by continuous flow, maintaining the several channels or conduits substantially free of occluded or other deposition of solidified metal or impurities. Similarly, as noted, the flow rate or quantity of fluid metal flow is automatically increased to a desired maximum during that portion of the cycle where metal is withdrawn from the continuously flowing stream and/or injected into the molding cavity of the stereotype plate mold, while, in accordance with the foregoing, providing for the differential control of throughput or flow rate as between the periods of metal injection and the periods between injections of molten metal into the molding cavity, and such differences or variances, as predetermined, in flow rate or quantity of metal or throughput are specifically correlated and automatically controlled with regard to the opening and closing of the metal ejection outlet stop cock to provide for purging the metal manifold of bubbles of air introduced thereinto during the injection molding operation as well as maintaining a throughput quantity of liquid metal for uniform metal consistency and fluidity during the molding operation and the period between molding operations.

While the forms of apparatus herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

I claim:

1. In apparatus for the automatic production of stereotype plates and the like by injecting molten metal through a metal outlet from a molten metal reservoir into a plate mold for intermittent casting of plates in said plate mold, the combination which comprises a header spaced from said metal outlet, means for circulating metal from said metal reservoir through said header in a closed system and substantially in the absence of exposure to air during and between said intermittent casting operations, a plurality of channels means in fiow communication between said header and said metal outlet for conducting molten metal from said header to said metal outlet during said intermittent casting operations, cutofi valve means at said metal outlet for selectively controlling and interrupting flow of molten metal from said channels through said outlet into said plate mold for said intermittent casting operations, and bypass means adjacent said cutoff valve at said metal outlet establishing a recirculation path for molten metal when said cutofi? valve is closed and between said valve and said header and through said channel means for maintainin sulficient partial circulation of metal in said channels between said intermittent casting operations to avoid accumulation of oxide encrustants therein.

2. Apparatus as recited in claim 1 in which said header and said metal outlet are disposed above said plate mold for gravity fiow of liquid metal between said header and said outlet and through said outlet into said plate mold during said intermittent casting operations.

3. Apparatus as recited in claim 1 in which said header and said molten metal continuously circulating therethrough are spaced from said metal outlet and said plate mold sufficiently to avoid heat transfer from said circulating molten metal in said header to cast metal in said mold interfering with the substantially instantaneous solidification of metal at said metal outlet after each of said intermittent casting operations and notwithstanding the continuous circulation of molten metal through said header.

4. Apparatus as recited in claim 1 which also includes means for automatically controlling and varying said continuous flow of molten metal from said molten metal reservoir through said header whereby a smaller quantity is I! circulated through said header between said intermittent casting operations than during said intermittent casting operations when molten metal is being injected into said plate mold.

5. In apparatus for the automatic production of stereotype plates and the like and including a plate mold which is intermittently brought into flow communication with a metal outlet supplied with molten metal from a molten metal reservoir for intermittent casting operation of said molten metal to form said stereotype plate in said plate mold, the combination which comprises a header spaced from said metal outlet, means for continuously circulating said molten metal from said reservoir through said header during and between said intermittent casting operations, stop cock valve means at said metal outlet for selectively permitting and interrupting flow of molten metal therethrough into said plate mold for said intermittent casting operations, a plurality of channels in flow communication between said header and said valve means for conducting molten metal flowing through said header to said valve means during said intermittent casting operations, and a bypass conduit immediately adjacent said metal outlet and said valve means therefor also interconnecting said plurality of channels whereby circulation of molten metal is maintained by said continuously flowing metal through said header in and through said channels and said bypass conduit even when said valve means are closed between said intermittent casting operations for maintaining said plurality of channels and said valve means free of encrustants of oxidation products formed in said molten metal during said casting operations from reactions between said metal and air entering said metal outlet from said plate mold.

References Cited in the file of this patent UNITED STATES PATENTS 856,026 Brown et a1 June 4, 1907 1,579,991 Winkler Apr. 6, 1926 1,673,857 Wood June 19, 1928 1,887,917 Brockel Nov. 15, 1932 2,058,378 Freund Oct. 20, 1936 2,136,383 Huck Nov. 15, 1938 2,459,892 Palmer et a1 Ian. 25, 1949 2,526,753 Huck Oct. 24, 1950

Claims

1. IN APPARATUS FOR THE AUTOMATIC PRODUCTION OF STEROTYPE PLATES AND THE LIKE BY INJECTING MOLTEN METAL THROUGH A METAL OUTLET FROM A MOLTEN METAL RESERVOIR INTO A PLATE MOLD FOR INTERMITTENT CASTING OF PLATES IN SAID PLATE MOLD, THE COMBINATION WHICH COMPRISES A HEADER SPACED FROM SAID METAL OUTLET, MEANS FOR CIRCULATING METAL FROM SAID METAL RESERVOIR THROUGH SAID HEADER IN A CLOSED SYSTEM AND SUBSTANTIALLY IN THE ABSENCE OF EXPOSURE TO AIR DURING AND BETWEEN SAID INTERMITTENT CASTING OPERATIONS, A PLURALITY OF CHANNELS MEANS IN FLOW COMMUNICATION BETWEEN SAID HEADER AND SAID METAL OUTLET FOR CONDUCTING MOLTEN METAL FROM SAID HEADER TO SAID METAL OUTLET DURING SAID INTERMITTENT CASTING OPERATIONS, CUTOFF VALVE MEANS AT SAID METAL OUTLET FOR SELECTIVELY CONTROLLING AND INTERRUPTING FLOW OF MOLTEN METAL FROM SAID CHANNELS THROUGH SAID OUTLET INTO SAID PLATE MOLD FOR SAID INTERMITTENT CASTING OPERATIONS, AND BYPASS MEANS ADJACENT SAID CUTOFF VALVE AT SAID METAL OUTLET ESTABLISHING A RECIRCULATION PATH FOR MOLTEN METAL WHEN SAID CUTOFF VALVE IS CLOSED AND BETWEEN SAID VALVE SAID HEADER AND THROUGH SAID CHANNEL MEANS FOR MAINTAINING SUFFICIENT PARTIAL CIRCULATION OF METAL IN SAID CHANNELS BETWEEN SAID INTERMITTENT CASTING OPERATIONS SAID CHANNELS BETWEEN SAID INTERMITTENT CASTING OPERATIONS TO AVOID ACCUMULATION OF OXIDE ENCRUSTANTS THEREIN.