US2782474A

US2782474A - Apparatus for casting electrotypes

Info

Publication number: US2782474A
Application number: US285818A
Authority: US
Inventors: Homer L Bishop
Original assignee: CLARK PATTON; EARL E STANSELL; HOMER L BISHOP; RALPH H DAUGHERTY
Current assignee: CLARK PATTON; EARL E STANSELL; HOMER L BISHOP; RALPH H DAUGHERTY
Priority date: 1952-05-02
Filing date: 1952-05-02
Publication date: 1957-02-26
Anticipated expiration: 1974-02-26

Description

Feb. 26, 1957 H. L. BISHOP APPARATUS FOR CASTING ELECTROTYPES 6 Sheets-Sheet 2 Filed May 2, 1952 IN V EN TOR.

Feb. 26, H. L. BISHOP 2a782474 APPARATUS FOR CASTING ELECTROTYPES Filed May 2, 1952 e Sheefs-Sheet s ZN V EN TOR.

Feb. 26, 1957 H. L., BISHOP APPARATUS FOR CASTING ELECTROTYPES 6 Sheets 4 Filed I Ma 2 1952 Om N6 INVENTOR, Z fl fl Feb. 26, 1957 H. BISHOP APPARATUS FOR CASTING ELECTROTYPES 6 She ets-Sheet 5 Filed May 2, 1952 IN V EN TOR.

Feb. 26, 1957 H. BISHOP APPARATUS FOR CASTING ELECTROTYPES 6 Sheets-Sheet 6 Filed May 2, 1952 mom United States Patent APPARATUS FOR CASTING ELECTROTYPES Application May 2, 1952, Serial No. 285,818

8 Claims. (Cl. 22-58) This invention relates to an apparatus for manufacturing electrotype plates from a shell having backing metal applied to the rear thereof.

This application is a continuation-in-part of my copending application Serial No. 758,515, filed July 2, 1947, for Process of Producing Electrotypes, now abandoned.

In the printing industry electrotype plates are used for printing various types of publications, advertising material, posters, et cetera. A great number of electrotype plates are required for each edition of magazines having circulations in the millions, and especially magazines having a number of illustrations. Due to the fact that some of these magazines are published weekly, the problem of producing the electrotype plates promptly and efiiciently is what might be referred to as one of the bottle-necks in the industry.

In the first place, it is necessary to make a mat for use from copper that may have the face electroplated with some other metal that is harder and somewhat more wear resistant, as for example, nickel or chrome. The rear side of the shell is then tinned, so as to cause the backing metal, usually consisting of lead, antimony and tin, to adhere thereto. In other words, the tin coating forms a bond.

A number of problems are presented in casting the backing metal upon the rear side of the shell. Asis well known to those skilled in the art, lead has a very high specific gravity. It is very heavy. Copper, the principal metal used in the shell, is much lighter. By placing the shell in the bottom of the mold cavity and then applying backing metal to the rear thereof, the shell wants to float, unless some precautionary measure is taken to prevent the shell from rising upwardly in the backing metal. Various modes have been used in attempting to prevent the shell from lifting up from the bottom of the mold cavity. In the past, it has been rather common practice to pour the backing metal on the rear of the shell by means of a ladle. This takes time and requires a considerable amount of skill. Furthermore, if the shell is not perfectly flat and in intimate contact with the bottom of the mold cavity, the heavy molten metal will flow under the shell, destroying at least a part of the printing area.

When casting electrotype plates by the methods formerly used, the electrotype warps and is drawn out of shape when solidification takes place. By pouring molten metal on the rear of the shell in a cold mold, tremendous stresses are set up in the cast metal, in that the solidification is not uniform. The portions of the molten metal coming in contact with the cold walls of the mold solidify almost instantly, whereas other portions of the molten metal remain molten for a longer period of time. This uneven solidification of the metal results in warping of the electrotype plate. Furthermore, stresses are set up between the cold shell and the molten metal, in that the shell absorbs heat, thereby expanding, while the molten metal coming in contact with the rear cold shell contracts,

in electrodepositing the shell. This shell is usually made" 2,782,474 Patented Feb. 26, 1957 setting up opposing forces tending to warp the finished product and also tending to cause a rupture between the shell and the backing metal. Furthermore, there are no forces counteractingthe tendency to warp, for the reason that the shell and the backing metal lie loosely in the bottom of the mold cavity. In view of this situation, it has been the practice in the past to first submit the plate to a pressure so as to straighten the shell, forcing the printing surface into a common plane. This is followed by shaving the rear of the electrotype plate, so as to reduce' it to the desired thickness.

The electrotype plate may then be solidified by a device disclosed in my Patent No. 2,580,723, issued January 1, 1952, for Preliminary Finishing Machine. Treatment may be placed in the electrotype plate by the use of make-readies made according to the processes disclosed in my Patent No. 2,088,398, issued July 27, 1937, for Printing Process and my Patent No. 2,256,921, issued September 23, 1941, for Make-ready. Due to the fact that the electrotype plate may be solidified very rapidly and treated efficiently and speedily, it is desirable to improve upon the methods of casting the electrotype plates, so as to produce the electrotype plates more rapidly in readiness for the subsequent operations and at the same time produce a better product.

An object of this invention is to provide a machine for automatically submerging the molds in molten metal while the shell is physically held in intimate contact with the bottom of the mold cavity, then a device is used for compressing the cast metal during the solidification thereof, so as to insure the face of the electrotype plate coming out of the mold in a flat condition to eliminate the step of flattening the plate, so that as the finished electrotype plate comes out of the casting machine, it is ready for solidification.

Other objects and advantages reside in the construction of parts and the combination therof, as will become more apparent from the following description.

In the drawings, Figure 1 is a top plan view of the machine for casting the electrotype plates and carrying out the process.

Figure 2 is a side elevational view of the machine shown in Figure 1.

Figure 3 is a top plan view of a mold provided with means for retaining the shell in the bottom thereof.

Figure 4 is a cross sectional view taken substantially on line 4-4 of Figure 3.

Figure 5 is a top plan view of a mold cavity shown without the device for exertingpressure upon the rear of the shell. p

Figure 6 is an end elevational view of the mold showing a portion of the conveyor in section.

Figure 7 is an enlarged fragmentary and detail view of the mechanism for causing the mold to travel downwardly into the vat of molten metal.

Figure 8 is a sectional view taken substantially on the line 88 of Figure 7.

Figure 9 is an enlarged, fragmentary, side elevational view of the mechanism for holding the mold down in the molten metal vat.

Figure 10 is a fragmentary, cross sectional view taken substantially on the line 1010 of Figure 9.

Figure 11 is an enlarged, fragmentary view of a portion of the side of the machine showing the mold in a tilted position as it advances out of the vat.

Figure 12 is a fragmentary, cross sectional view taken substantially on the line 1212 of Figure 11.

Figure 13 is an enlarged, top plan view of a mold having the cast backing metal therein and having mounted thereon a metal compressing device.

spasms Figure 14 is a cross sectional view of the mold taken substantially on the line 1414 of Figure 13.

Figures 3-5 have been drawn on a larger scale than Figures 1 and 2 and on a smaller scale than Figures 7-14 inclusive.

Referring to the drawings, the reference character 20 indicates a plurality of supports located on each side of the machine. These supports 20 on each side cooperate to support a laterally disposed frame member 22, shown in Figure 8, there being one frame member on each side. End posts 24 are mounted adjacent the ends. The sides of the machine are enclosed by a suitable apron 26. The frame structure is adequately braced in any suitable manner.

A pair of sprocket wheels 28 is journaled in bearings 30 adjustably mounted upon the frame member 22. The bearings 30 are mounted for adjustment and held in adjusted position by screws 32 threadedly engaging suitable supports 34. The opposite end of the frame supports a pair of sprocket wheels 40 mounted upon a drive shaft 42 journaled in suitable bearings 44. The drive shaft 42 is driven from an electric motor 46 through a suitable gear box, not shown.

A pair of conveyors consisting of

chains

48 and 50 extend throughout the length of the machine and pass over the

sprocket wheels

28 and 40. By this arrangement it can readily beseen that when the motor 46 is energized, the

chains

48 and 50 will be driven by the sprocket wheels 40. These chains are tightened or tensioned by the adjusting screws 32. The two

chains

48 and 50 have the same number of links, so that the two chains will rotate in unison. The rate of travel ofthe chains is quite slow, in that it takes several minutes for a chain to make a complete revolution. Furthermore, the rate of travel of the conveyors may be changed by changing the speed of the motor or by changing the gear ratio of the gear box.

A plurality of molds 60 are mounted on crank arms 62, there being four crank arms for supporting each mold, two crank arms on each side. These crank arms are provided with pins 64 extending at right angles to the length of the machine and are pivotally mounted in the sides of the mold 60. In the end of the crank arms opposite the pins 64 are mounted pins 66 pivotally journaled in suitable sockets in lugs 67 attached to the

conveyor chains

48 and 50. The pins 66 also extend at right angles to the longitudinal length of the machine, but in the opposite direction from the pins 64. There is considerable clearance between the

pins

64 and 66 and the apertures, recesses or sockets therefor in the molds and the lugs respectively to allow for free movement of the mold into the various levels and inclinations without binding.

As may best be seen by referring to Figure 4, one end of the mold is provided with a transverse recess or aperture 70. The opposite end of the mold is-provided with an inclined aperture or recess 72. As the molds are advanced into a horizontal position shown to the extreme left of Figures 1 and 2, the operator places a shell 80 in the bottom of the mold. This shell 80, as seen in Figure 4, consists of a sheet of copper that has been electrodeposited and has an irregular surface forming the printing surface. This printing surface may be protected by suitable hard metal, such as nickel or chrome, electroplated on the printing side of the shell. The printing surface is placed in the bottom of the mold cavity. The rear of the copper shell has been tinned, the tinned surface forming a bond between the shell and the backing metal of the finished electrotype plate, as is wellknown to those skilled in the art.

Due to the fact that the backing metal consists of lead, antimony and tin, the lead predominating, it can readily be seen that the shell, which has a much lower specific gravity, wil tend to float or raise upwardly from the bottom of the mold cavity when the mold is submerged in molten backing metal. That being the case, the submerging of the mold with the shell in the bottom thereof presents a problem, in that the shell tends to rise upwardly, so that backing metal will flow under the shell. Furthermore, in the event there are any kinks or wrinkles or bulges in the margins of the shell, the molten metal will flow under these raised portions.

As may best be seen by referring to Figure 4, a plurality of springs 82, arranged in close proximity to each other throughout the entire area of the shell, are compressed against the rear of the shell by a capping member 84 provided with a marginal flange 86 along one side thereof. This flange 86 is provided with a pair of projections 88 extending into the aperture 70 in the end of the mold. A lever 90 is pivotally attached to member 84 on the end opposite the projections 88. The lever 90 is provided with a prong or projection 92 hooked into the aperture 72. Member 84 together with the springs 82are placed in position on the mold immediately after the shell is laid in position. The springs 82, engaging the shell in a number of areas throughout the rear of the shell, exert a pressure on the rear of the shell, flattening the shell out, removing wrinkles and bulges therein, and firmly hold the shell in the bottom of the mold. The strength of the springs is such that when engaging the rear surface of the shell the force exerted upon each area of the shell is greater than the weight of a column of metal extending from the shell to the top of the vat which will be described more fully hereinafter. By this arrangement the force exerted by the springs pressing the shell against the bottom of the mold is sufficient to more than offset the buoyancy of the shell submerged in a vat of molten metal.

Member 84 is open along the

margins

94 and 96, so that there is a gap 98 between member 84 and the top margin 100 on the one side of the mold and a similar gap between the top margin 102 on the opposite side of the mold, which top margins are best seen in Figures 5 and 6. The distance from the top of the margin 102, which is the trailing margin of the mold, to the bottom of the mold cavity is held within predetermined tolerances for reasons that will appear more fully later.

As can best be seen by Figures 3 and 4, the

top margins

104 and 106 of the ends of the mold are exposed when member 84, together with the springs thereon, is locked in position. The mold, as it advances, is guided upon a pair of rails 108, so as to be maintained in a horizontal position. The rails 108 terminate near the edge of a vat or tank 110. A rail or guide 112, which is arranged at an angle, is used to support the leading edge of the mold 60, as shown in Figure 7.

A cam 114 actuated by a sprocket wheel 116 driven by the conveyor chain 48 is mounted in a position such that the cam 114 rides on the margin 106 and a like cam on the opposite end of the shaft 118 contacts the margin 104, so as to tip the mold downwardly into the molten metal found in the vat 110. The cam 114 rotates through one revolution or multiple thereof in the distance equal to the spacing of the molds on the conveyor, so that the cam is properly synchronized with the travel of the molds. The mold advances under the

friction wheels

120 and 122 that hold the mold cavity on rails 124 horizontally disposed in the bottom of the vat 110. The top of the mold is below the level of the liquid in the vat, so that the shell mounted in the bottom thereof is submerged in the molten metal.

The

wheels

120 and 122 are journaled upon stub shafts 126 secured into lateral frame members 128 secured to the frame member 22. An arcuate member 130 is used in supporting the shaft 126 in a horizontal position. There is a considerable upward pressure on the

wheels

120 and 122, in that the material used in producing the mold and the parts in the mold are much lighter than the molten metal. That being the case, there is a tendency for the mold and the contents thereof to rise upwardly and float on the molten metal.

A rail or guide 140 pivotally attached to the horizontal rail 142 extending beyond the vat is used in guiding the mold out from the molten metal. This rail 140 is adjustably mounted, so that the angle of inclination thereof may be adjusted. This adjustment is accomplished by means of a shaft 144 positioned in the slot 146 in member 140. The shaft 144 is fixedly mounted in a gear 148 meshing with a gear 150 controlled by a suitable hand wheel 152, so that by rotating the hand wheel 152, the gear 150 actuates the gear 148 to raise or lower the lower end of the rail 140. The shaft 144 extends through the opposite side of the vat, so as to actuate the rails on both sides in unison. The lower end of the rail 140 is attached by a suitable pivot 160 to a rail segment 162 in the bottom of the vat, so that as the angle of inclination of the rail or member 140 is raised, the one end of the rail 162 is adjusted upwardly or downwardly, so as to cause the leading edge of the mold cavity as it advances towards the rail 140 to actually engage this rail.

As the mold is advanced by the

chains

48 and 50 advancing, the mold is gradually withdrawn from the vat of molten metal. The inclination of the rail 140 is such that as the mold is guided out of the vat, the surplus molten metal will be spilled out over the top margin or trailing edge 100 of the mold. The inclination of the rail 140 is so adjusted that the proper amount of molten metal will remain in the mold to provide the proper thickness of the backing metal when the mold is advanced into horizontal position.

In the event the backing metal is too thick, the angle of inclination of the rail 140 is increased to empty more metal out of the mold when withdrawn from the vat. On the other hand, if the backing metal is too thin, the angle of inclination of the rail 140 is decreased so as to leave more metal in the mold. All of the molds are sub stantially identical, so that the same quantity of metal remains in each successive mold passing through the vat with the same setting of the guide rails 140.

The molten metal in the vat 110 is maintained in a molten state by a plurality of gas fired burners 170 automatically controlled by the automatic controls 172. The molten metal is maintained at a temperature slightly above the melting point of the metal, so that shortly after the mold is withdrawn from the vat, the metal begins to solidify. In order to prevent too rapid a solidification of the metal coming in contact with the walls of the mold, the molds are also heated by the burners 170, in that the burners supply heat in the compartment for the return of the molds, so that the molds are maintained hot and raised to the desired temperature while returning, so that the temperature of the mold upon being submerged in the vat is substantially equal to the temperature of the molten metal. A cover is mounted between the upper and lower track for the chains, so as to reduce the heat losses and so as to supply heat to the returning molds.

As soon as the mold advances into the horizontal position immediately past the vat, the springs 82 and the capping member 84 are removed. This may be accomplished by the use of a bar 180 shown in Figures 13 and 14. One end of the bar 180 is provided with a deflected portion 182 projecting into an aperture in the capping member 84. By pressing downwardly on the outer end of thebar 180, the lever or latch member 90 may be rotated in a counter-clockwise direction, so as to permit the prong or projection 92 to clear the aperture 72. The capping member 84 and the springs 82 may then be raised and the lower ends of the springs 82 lifted out of the molten metal. However, due to the fact that the rear of the shell is completely covered with molten metal, the shell remains in the bottom of the mold cavity. The mold, together with the shell and the backing metal,

moves slowly towards the right, as viewed in Figures 1 and 2. The metal soon begins to solidify.

At the proper time ametallic shim 200 is laid on top of the freshly cast backing metal 202, as best seen in Figure 14. The capping member 84 and the springs 82 are then again inserted into position, as shown in Figure 14, by projecting the projection 88 into the aperture 70 and latching the projection 92 carried on the lever into the aperture 72. The springs are now in greater compressicn than they were when holding down the shell, in that the springs have been compressed an additional distance equal to the distance from the top of the shell to the top of the shim.

The springs 82 cooperate with the shim 200 to exert a pressure over the entire rear area of the backing metal, so as to firmly press the shell into contact with the bottom of the mold cavity. By this arrangement, warping of the shell and the backing metal is deterred and practic'ally eliminated. Furthermore, by'exerting the pressure upon the rear of the shim overlying the metal that is being solidified, the pressure exerted on this metal tends to eliminate or reduce blow holes and voids in the backing metal and thereby tends to reduce the undesirable effect caused by what is generally referred to in the trade as soft spots in the finished electrotype plate.

When the mold approaches the sprocket wheels 40, the capping member '84, the springs 82, and the shim 200 are removed. The period of time that it takes for the mold to travel from the molten metal to the sprocket wheel 40 is sufiicient to permit solidification of the cast metal, so that as the mold is carried over the end of the machine, the mold is inverted and the cast electrotype plate drops out of the mold and may be carried away on a suitable conveyor not shown.

The mold has not cooled so very much, in that it takes only a few degrees temperature drop to cause the metal to solidify, and that being the case, in returning in the compartment located below the top of the lower tier of the conveyor, the mold absorbs sufficient heat from the gas burners, so that when it returns -to the horizontal position on the left-hand end of the machine, asviewed in Figures 1 and 2, the temperature of the mold is substantially the same as the temperature of the molten metal. The distance from the left end of the machine to the vat for the molten metal is quite short as compared to the distance from the vat to the sprocket wheel 40 on the opposite end of the machine.

Mode of operation While the mold is advancing into the horizontal position on the left-hand end of the machine, as viewed in Figures 1 and 2, a shell is placed in the bottom of the mold. This shell is preferably centered with respect to the mold. The springs 82 are then placed on top of the shell and the capping member 84 locked in position, the springs exertinga uniform pressure in numerous uniformly spaced areas throughout the entire rear of the shell.

Due to the fact that the mold is hot as it advances into the horizontal position to the left of the machine, as viewed in Figures 1 and 2, the shell absorbs heat from the mold. Copper being a good conductor causes the shell to heat rapidly, so that by the time that the mold and the shell reach the vat, the shell has a temperature substantially equal to the temperature of the molten metal.

The mold dips into the vat so that the mold cavity is completely submerged in the molten metal. The level of the metal in the vat is preferably maintained auto matically at a constant height. The mold, advancing into the molten metal at an angle, tends to expel all air as the mold gradually advances into the vat, thereby reducing the possibility of blow holes. Furthermore, the mold travels through the molten metal for a considerable period of time, which permits any gas bubbles or air bubbles to rise to the surface while the mold is traveling through the molten metal.

The mold being withdrawn from the molten metal is withdrawn at a predetermined angle, so as to maintain a predetermined amount of molten metal in the mold cavity. This molten metal is, so to speak, located in one corner of the mold while the mold is being withdrawn from the molten metal. As the mold advances into the horizontal position, the molten metal spreads uniformly throughout the area of the mold, so as to cause the molten metal to have a uniform depth.

The springs 82 and the capping member 84 have been held in position during the entire travel of the mold through the vat of molten metal. Immediately upon the mold being removed from the vat, the capping member 84 and the springs 82 are removed before the backing metal begins to solidify. As soon as the backing metal has cooled sufliciently so as to support the shim 200, the shim is placed on top of the backing metal and the capping member 84 together with the springs 82 are inserted on the rear of the shim to exert a force on top of the shim, clamping the shell flat against the bottom of the mold cavity. The tension of the springs holding the shim in position is far greater than the tension used when engaging the shell in the bottom of the mold during submersion of the mold. The compressive force of the springs has been so chosen that the proper force is exerted on the rear of the electrotype plate.

The springs 82 and the capping member 84 remain in position until the mold reaches the extreme right of the machine, as viewed in Figures 1 and 2, when the capping member 84 and the springs 82 together with the shim 200 are removed. As the mold travels around the end of the path of the conveyors or

chains

48 and 50, the electrotype plate automatically drops out of the mold upon a suitable ledge or conveyor in readiness for the subsequent operations.

The electrotype plate produced by this method need not first be compressed so as to flatten the shell, but it may be treated in the solidifying machine disclosed in my Patent No. 2,580,723, thereby eliminating the step of flattening the shell or removing the irregularities out of the electrotype plate after it is removed from the mold.

Instead of one shell being located in the bottom of the mold cavity, several small shells may be inserted in the bottom of the mold cavity side by side, so as to provide a backing metal for a plurality of electrotype plates in the same mold cavity. The size of the mold cavity is a matter of choice, depending upon the requirements of the particular machine.

The temperature of the molten metal may be adjusted, so that the temperature of the molten metal is slightly above the melting point thereof. In the event the ingredients of the molten metal are changed, resulting in a change in the melting point, the controls for the heating elements used in heating the vat are adjusted automatically. Instead of utilizing gas burners, electric burners could be used, the type of burners or heating elements being determined by the available source of heat and the cost thereof.

Each mold together with the electrotype plate thereon is heavy. That being the case, as the molds travel over the

rails

108 and 109, there is considerable friction and the parts wear rather rapidly. Instead of using

solid rails

108 and 109, the molds preferably travel over rollers arranged in tandem, so that the molds roll across the rollers. This reduces wear on the parts, thereby retaining the dimensions of the molds substantially uniform throughout a longer period of time. When the bottoms of the molds wear, it is then necessary to adjust the angle of inclination of rails 140, so as to tilt the molds to the proper angle to pour out the surplus metal.

The height of the end flanges or

top margins

104 and 106 of the molds is preferably sufiiciently high, so as to be located above the level of the molten metal in the vat when the molds are traveling through the vat. The height may be increased, if necessary, to obtain sufficient head pressure of the column of molten metal above each square inch of shell.

The molds travel rather slowly, so that ample time is provided for solidification of the metal from the time that the molds are withdrawn from the molten metal until the molds are tipped to dump the electrotype plates. If it is found desirable to increase the output of the machine, the conveyor may be lengthened and the rate of travel of the molds may be increased so that suflicient time elapses between the time that the mold is withdrawn fro-m the molten metal until the electrotype plate is dumped to permit solidification of the backing metal. By doubling the speed at which the molds travel, the length of the conveyor beyond the vat to the position where the electrotype plate is dumped should be doubled in order to allow the same time for the solidification of the molten metal.

Although the preferred embodiment of the device has been described, it will be understood that within the purview of this invention various changes may be made in the form, details, proportion and arrangement of parts, the combination thereof and mode of operation, which generally stated consist in a device capable of carrying out the objects set forth, as disclosed and defined in the appended claims.

Having thus described my invention, I claim:

1. A machine for use in the manufacture of electrotype plates, the combination including a continuous length conveyor advancing in one direction in a horizontal plane and in the opposite direction in a horizontal plane on a lower level, a plurality of molds, means for mounting the molds on the conveyor, said means including a plurality of crank arms for supporting each mold, each of said crank arms having one end pivotally mounted on the conveyor and the opposite end pivotally attached to the mold, guide rails for supporting the molds in a horizontal position, a vat for molten metal located between the upper and lower levels of the conveyor, means for tilting the molds downwardly into the molten metal and guiding the molds through the vat of molten metal, and means for raising the molds at an inclined angle from the molten metal, said last mentioned means being adjustable so as to alter the angle of inclination of the mold so that as the mold is removed from the molten metal the quantity of metal remaining in the mold equals the volume of the backing metal desired for the electrotype plate when cast, the conveyor advancing the molds with the molten metal therein horizontally while the metal is being cooled so as to cause the metal to solidify, the conveyor upon advancing from the horizontal position on one level to the horizontal position in the other level tilting the molds so as to permit the cast electrotype plates to drop out of the mold.

2. In a machine for casting electrotype plates utilizing molten metal, the combination including a pair of conveyors, means for driving the conveyors at a uniform rate of speed, said conveyors having bearing seats, a plurality of molds, each of the molds having a plurality of apertures, means for connecting the molds to the conveyors, said means including links extending parallel to the direction of movement of the conveyors, outwardly directed pins for journaling the links in the bearing seats of the conveyors, there being four links for each mold, inwardly directed pins projecting into the apertures in the molds, there being considerable clearance between the pins and the bearing seats in the conveyors and the pins seated in the apertures in the molds so as to prevent bind ing, and cam means for deflecting the path of the molds from a level even with the conveyor to another level below the conveyor without deflecting the conveyors.

3. In a machine for casting electrotype plates according to claim 2, wherein a vat for molten metal is located below the conveyor so that as the molds are deflected by the cam means the molds advance into the vat, rollers engaging the end margins of the molds for guiding the molds in a horizontal position through the vat, and means for withdrawing the molds at a predetermined angle from the vat so as to pour off the surplus metal from each mold, said last mentioned means guiding the molds into a horizontal position.

4. In a machine for casting electrotype plates accord ing to claim 2, wherein dual-functional heating elements are used for heating the molten metal and for heating the molds to a temperature substantially equal to the temperature of the molten metal preparatory to the casting operation.

5. A machine for use in the manufacture of electrotype plates having a shell, the combination including a continuous length conveyor advancing in one direction in a horizontal plane, a plurality of molds, means for mounting the molds on the conveyor, guide rails for supporting the molds in a horizontal position, a vat for molten metal located under the conveyor advancing in said direction, means for tilting the molds downwardly into the molten metal and guiding the molds through the vat of molten metal, means including a rail for raising the molds at an inclined angle from the molten metal, said rail being adjustable so as to alter the angle of inclination of the mold so that as the mold is removed from the molten metal the quantity of metal remaining in the mold equals the volume of the backing metal desired for the electrotype plate when cast, means including a member engaging the tail for adjusting the angle of the mold, and means for advancing the conveyor and the molds with the molten metal therein horizontally while the metal is being cooled so as to cause the metal to solidify.

6. A machine according to claim 5, wherein heating means preheat the molds before advancing into the vat of molten metal.

7. A machine according to claim 5, wherein the conveyor returns on a lower level so that as the conveyor advances to the lower level, the molds are tipped to thereby eject the cast electrotype plates.

8. A machine according to claim 5 wherein a holddown is used in holding the shell in the bottom of the mold while advancing the mold through said vat.

References Cited in the file of this patent UNITED STATES PATENTS 274,358 Menge Mar. 20, 1883 447,683 Hawdon Mar. 3, 1891 539,221 Grossman May 14, 1895 583,424 Acklin May 25, 1897 633,151 Patterson et al Sept. 19, 1899 672,859 Ringler Apr. 23, 1901 1,516,049 Luetscher Nov. 18, 1924 1,559,231 Eckersall Oct. 27, 1925 1,727,259 Turnock Sept. 3, 1929 1,779,253 Temmen Oct. 21, 1930 1,972,945 Nilson Sept. 11,1934

2,182,114 Bungay Dec. 5, 1939 2,222,013 Atwood Nov. 19, 1940 2,253,526 Medsker Aug. 26, 1941 2,294,319 Ringquist Aug. 25, 1942 2,458,410 Parsons Jan. 4, 1949 2,586,134 Winter Feb. 19, 1952 2,611,939 Kux Sept. 30, 1952