US2825944A - Controls for printing plate casting apparatus - Google Patents

Description

Match 11, 1958 s. TYMA ET AL 2,

CONTROLS FOR PRINTING PLATE CASTING APPARATUS Filed Nov. 50, 1955 6 Sheets-Sheet 1 M ,f z/W m gg w m,

March 11, 1958 V L. s. TYMA ET AL 2,825,944

CONTROLS FOR P RINTING PLATE CASTING APPARATUS 6 Sheets-Shee't 2 Filed Nov. 30, 1955 ENTORS.

March 11, 1958 2,825,944

CONTROLS FOR PRINTING PLATE cAsTING APPARATUS L. s. TYMA E1: AL

6 Sheets-Sheet 5 Filed Nov. 30, 1955 mm: ii MAM IN VENTORS.

March 1953 L. s; TYMA ET AL 2,825,944

CONTROLS FQR PRINTING PLATE CASTING APPARATUS Filed Nov. 39, 1955 6 Sheets-Sheet 4 March 11, 1958 s. TYMA ETAL 2,825,944

CONTROLS FOR PRINTING PLATE CASTING APPARATUS Filed Nov. 30, 1955 e She ets-Sheet 5 23y: A-QA.

March 11, 1958 s. TYMA ET AL 2,825,

CONTROLS FOR PRINTING PLATE CASTING APPARATUS P 6 Sheets-Sheet 6 Filed Nov. 30, 1 955 5 z 12 9 1% v -J 151- fl INVENTORS.

United States Patent CONTROLS FOR PRlNTllNG PLATE CASTING APPARATUS Louis S. Tyma, Hinsdale, John Gvozdjak, Cicero, and Corson Walter Chase, Oak Park, 111., assignors to Miehle-Goss-Dexter, Incorporated, Wilmington, Del., a corporation of Delaware Application November 30,1955, Serial No. 549,959

12 Claims. (Cl. 22-2) This invention relates to apparatus for casting printing plates, such for example as curved stereotype plates, and is particularly concerned with improvements in safety and protective controls for such apparatus. Plate casting apparatus of the type here considered usually includes a closable mold box adapted to receive and hold a type matrix or mat, together with a pump for supplying molten metal from a heated pot to the box, the pump being operated by a suitable power actuator such as a fluid pressure ram.

It is the general aimv of the invention to make it virtually impossible for an operator to inadvertently misuse plate casting apparatus of the type described, thereby protecting the operator from injury and the apparatus from damage.

More specifically, it is an object of the invention to positively prevent operation of the metal pump, even though theactuator therefor should be energized, unless the mold box is in proper condition to receive molten metal.

In this respect, it is another object of the invention to automatically block movement of a metal pump unless the casting box is closed, and unless a mat is held therein by the vacuum means, thereby preventing spilling of hot metal onto the floor or the entry of such metal into the vacuum means.

Still another object is to automatically block movement of the metal pump after it has completed one cycle of operation and until the casting box is first opened to remove the completed plate, thereby preventing the supply of molten metal to the box while it is full and preventing the consequent spilling or overflow of molten metal.

Other objects and advantages will become apparent as the following description proceeds, taken in conjunction with the accompanying drawings, in which:

Figure l is aside elevation of exemplary plate casting apparatus equipped with safety controls embodying the features of the present invention;

Fig. 2 is a front elevation of the mold box shown in Fig. 1; v

Fig. 3 is an enlarged fragmentary elevation corresponding to a part of Fig. l and showing details of the metal Fig. 9 is an enlarged fragmentary view, partially in 70 section, corresponding to a part of Fig. 8;

Fig. 9A is a fragmentary detail view taken substantially along the line 9A9A in Fig. 9;

Fig. 10 is a detail plan view taken along the line 1010 in Fig. 8;

Figs. 11-14 are similar to Fig. 10 and illustrate successive steps in the operational cycle of the control means; and

Fig. 15 is a schematic electrical diagram for the controls illustrated in Figs. 8-14.

While the invention has been shown and is described in some detail with reference to particular embodiments thereof, there is no intention that it thus be limited to such detail. On the contrary, it is intended here to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention as defined by the appended claims.

Referring now to the drawings, an exemplary metal melting pot 20 and a mold box 21 have been illustrated (Figs. 1 and 2) to make clear the environment of the invention. The mold box itself may take any one of a variety of forms known to those skilled in the art. That here shown comprises a base casting 22 supporting an upright jacket 24 which is formed to have a generally semi-cylindrical inner surface. Mounted on the jacket 24 by suitable hinges 25 is a front portion or door 26, also generally semi-cylindrical on its inner surface and swingable into closing relation with the jacket 24 to define a generally upright mold cavity. The door 26 may be locked closed by means such as a cam type latch 28 in response to movement of a hand lever 29.

For defining an annular space within the box when the door is closed and to afford convenient removal of completed printed plates, a generally cylindrical plunger 30 is pivoted on a shaft 31 to swing between a vertical position within the box and an outwardly inclined position shown by dashed lines in Fig. 1. be moved to its vertical position by stepping on a foot pedal 32 connected with a lever 34 and having a cam therefore, it is but a simple matter for an operator to tilt the plunger 30 forwardly and remove a completed plate therefrom. The plunger may be returned to its position within the box by depressing the foot pedalj32. The door 26 may then be reclosed for casting the succeeding plate.

To hold a matrix within the box 21 in proper position to produce an accurate printing plate, vacuum means are preferably employed. As here shown, a series of ports 40 open into the inner surface of the jacket 24 and door 26 and are connected with a suitable vacuum source such as a vacuum pump 41 driven by an electric motor 42. A mat (not shown) placed in covering relation to the ports 40 is thus securely held in place.

For supplying molten type metal from the pot 20 to the mold box 21, a metal pump 44 is immersed in the metal contained by the pot and connected by a trough or suitable conduit 45 to discharge into the open, upper end of the box. Preferably, the pump 44 is of the single, linear stroke type, having a piston 46 slidable within a cylinder 48 and connected with an externally projecting piston rod 49. It will be understood that upon upward movement of the piston 46 metal is pumped through the conduit 45, while upon downward movement of the piston suitable valve means (not shown) permit molten metal to fiow to the upper side of the piston.

To operate the pump 44, a suitable power actuator is,

operatively connected therewith. In the apparatus here shown, a linear actuator in the form of a double-acting fluid pressure ram 50 is connected with the pump piston 46 by means of a lever 51. The lever is fulcrumed at 52 (Fig. 1) on a bracket 54 extending upwardly from the pot 20 and is pivotally connected at 55 to the upper 7 end of the piston rod 49. The lever 51 is also pivotally Patented Mar. 11,1958

The plunger 30 may connected as at 56 with a piston rod 68 projecting from a cylinder 69 for the ram 50. Pressure fluid such as air supplied by an air compressor is admitted to and vented from the ram 50 under the control of a four-way valve 70 which is preferably one of the type operated upon energization of a solenoid 71. The solenoid may be energized by any suitable means such as a manually depressed push button switch.

In the use of plate casting apparatus such as that described above, it is vitally necessary that the box 21 be completely closed and a mat held therein by a vacuum existing in the ports 40 before metal is pumped into the mold space. Otherwise, the metal would simply spill onto the floor if the door 26 were open, or it would be sucked into and clog the ports 40 if the door were closed without a mat having been properly placed in the box. Moreover, it is necessary to prevent the pump 46 from operating through two successive working strokes without the box having been opened and the completed plate removed prior to the second stroke. Unless the first plate is removed, the metal pumped by the second stroke would simply spill out of the box, perhaps burning an operator and damaging the equipment.

In accordance with the present invention, a movable abutment is held normally disposed to block movement of the pump piston 46 even though the actuator therefor should be energized, unless conditions exist which satisfy all of the requirements set forth above. Means are provided to shift the abutment out of blocking relation with the actuator and pump only if the box is closed and vacuum present in the mat-holding ports, together with means for shifting the abutment back into blocking position upon the completion of a pumping stroke and main taining it there until the box is fully opened for removal of a completed plate.

In the embodiment illustrated by Figs. 1-6, a member such as a rod or bar 75 is connected fast to the lever 51 as by a pivot connection at 76 (Fi s. 1 and 3) to move in unison with the actuator piston rod 68. A movable abutment in the form of a plunger 77 is disposed in the path of the rod 75 when the latter is in its raised or uppermost position. As shown in Fig. 5, the rod 75 is mounted to slide through an opening 78 in a partition 79 forming part of a bracket 80 rigidly bolted to the upper surface of the pot 20. The abutment 77 is horizontally slidable through openings 81 in the bracket 80 and biased to its blocking position (i. e., to the right as viewed in Fig. by a suitable compression spring 82 bearing against a collar 84. For retracting the abutment 7'7 clear of the rod 75, it is opcratively connected as by a pin at 85 with the armature 86 of a suitable electro-magnetic solenoid 88 mounted in a housing 89 fixed to the bracket 80. Energization of the solenoid moves the armature 86 and the abutment 77 to the left (Fig. 5) against the biasing force of the spring 82.

Means are provided for energizing the solenoid 88 only whenever the box is fully closed and a vacuum is present in the mat-holding ports 40. For this purpose, a limit switch LS1 is mounted on the box in a manner such that its contacts are closed whenever the box is closed. As shown in Fig. 1, the limit switch LS1 may be of the type having normally open contacts and mounted such that its yieldable actuator LSlb is depressed upon movement of the hand lever 29 to its latching position. For sensing the presence of a vacuum in the ports 59' holding a matwithin the box, a vacuum switch 5 0 is mounted within thehousing 89 and connected by a suitable conduit 91 to the manifold formed within the box jacket 24. The vacuum switch may be of the type which has normally open contacts which are closed when a vacuum is present in the conduit 91.

'Means are also provided to cause deenergization of the solenoid 88 whenever the pump 44- has completed one working stroke, and to maintain that solenoid deenergized until the box is fully opened for removal of a completed plate. For this purpose, a second limit switch LS2 (Fig. 1) is suitably mounted on the box 21 so that it is actuated only when the box is open and the plunger lowered to its inclined position. As here shown, the limit switch LS2 may be mounted on the underside of the base casting 22 with its yieldable actuator LSZb disposed in the path of the cam 36. When the plunger 30 is disposed as shown by dashed lines in Fig. 1, the cam 36 depresses the actuator LS2!) and closes the normally open contacts of the switch LS2.

Additionally, a third limit switch LS3 is mounted within the housing 89 with its yieldable actuator LS3b adjacent a pin 94 slidably disposed in openings 95 formed in the bracket 36 and biased away from the actuator L331) by a suitable compression spring 95. The free end of the 94 is disposed in the path of a frusto-conical cam 98 carried by the rod 75. Upon downward movement of the rod 75 as the pump moves through a working stroke, the cam 98 urges the pin 94 to the left (Fig. 5) against the biasing of the spring 96 so that the actuator LS3b is depressed and the normally closed contacts of the switch LS3 are opened.

The limit switches and vacuum switch described above are associated in an electric control circuit illustrated diagrammatically in Fig. 6. As there shown, the solenoid 71 for controlling the valve 70 may be connected directly across a suitable voltage source through a normally open manual push button switch 100. It is thus possible to energize the solenoid 71, open the valve 70 and supply fluid pressure to the ram 50 at any time. However, such energization of the ram 50 will result in pumping of metal only if the conditions previously specified are To bring this about, a control relay R having a coil and two sets of normally open contacts R1, R2 is employed together with the limit switches LS1, LS2, LS3 and vacuum switch 90 described above. The normally open contacts R1, the solenoid 88, the normally open vacuum switch 90, and the normally open limit switch LS1 are connected in series relation across a suitable voltage source as shown in Fig. 6. The normally open limit switch LS2 is connected in series with the coil of the relay R across the voltage source, and the normally closed limit switch LS3 is connected in series combination with the normally open contacts R2, the series combination being connected in parallel with the limit switch LS2.

The operation of this control arrangement is thus as follows. The mold box 21 must be first opened by pulling the plunger 30 forwardly (Fig. 1) in order to close the limit switch LS2. This energizes the relay R which then remains energized, even when the plunger 30 is raised, by current flow through the normally closed limit switch LS3 and the now closed relay contacts R2. However, the solenoid 88 is not yet energized, so that the abutment 77 is disposed in blocking relation with the rod and the pump cannot be operated even though the push button switch 100 is depressed to energize the solenoid valve 71.

With closure of the mold box 21, the limit switch LS1 closes; and with the application of a vacuum to the ducts 40 to hold a mat thereagainst, the vacuum switch closes. At this time, the solenoid 88 is energized so that the abutment 77 is retracted clear of the bar 75. It is now possible to actuate the metal pump 44 by closing the push button switch to open the valve 70 and supply pressure fluid to the ram 50,

As the ram operates the pump, the cam 98 strikes the pin 94 when the rod 75' reaches the end of its downward stroke, thereby actuating the limit switch LS3 and opening its contacts. Since the limit switch LS2 is now open, the relay R is dropped out. With this, the contacts R1 open and the solenoid 88 is deenergized so that the abutment 77' is urged by the spring 82 into abutting, sliding engagement with. the. rod 75. When the pump stroke is complete, and thepush. button 100 is released, the ram 50 will return the pump to its original position thereby raising the bar 75 and permitting the abutment 77 to snap under its lower end.

Under these conditions, it is impossible to actuate the pump 44 a second time by closing the push button switch 100. The abutment 77 effectively blocks movement of the rod 75 and thus movement of the lever 51 and the pump 44. However, when the box is re-opened and the plunger 30 again lowered to remove the completed plate, the limit switch LS2 will be reclosed and the relay R energized. The control means are thus returned to their original condition ready for another cycle of operation.

The preferred embodiment of the invention is shown by Figs. 1-5 and 7. Referring now to Fig. 7, a modified control circuit is there shown using the same control components previously described except for the addition of another control relay. The addition of this relay positively prevents partial pumping strokes. That is, in the arrangement shown by Fig. 6 it might be possible for for the operator to hold the push button switch 100 closed only long enough to permit the pump 44 to operate partially through a pumping stroke. Release of the push button switch 100 would then cause the pump to return to its original position and a second closure of the push button switch 100 would result in a second partial pumping stroke.

As shown in Fig. 7, this remote possibility is eliminated by a modified circuit employing a second control relay S having two sets of normally open contacts S1, S2 and one set of normally closed contacts S3. The second limit switch LS2 is connected in series with the normally closed contacts S3 and the coil for the relay R across a suitable voltage source. The normally open relay contacts R2 are connected in series combination with the normally closed limit switch LS3, the combination being connected in parallel with the limit switch LS2 to provide a seal-in circuit for the relay R. As before, the first limit switch LS1, the normally open relay contacts R1, the vacuum switch 90, and the solenoid 88 are connected in series relation across the voltage source. A normally open push button switch 10017 is connected in series combination with the relay coil S, the combination being in parallel across the vacuum switch 90 and the solenoid 88. Thus, it is possible to energize the relay S by momentarily closing the switch after the limit switch LS1 has been closed and the relay R energized. Moreover, the normally open relay contacts S1 are connected in parallel relation across the contacts R1 and. the push button switch 1013b so that once the coil S has been energized, it will remain energized as long as the limit switch LS1 remains closed. In lieu of direct energization of the solenoid 71 for the ram controlling valve 70, the solenoid 71 is connected in series combination with the normally open contacts S2, the series combination being in parallel with the relay coil R. Thus whenever the relay coils R and S are both energized, the solenoid 71 will be energized to open the valve 70 and supply pressure fluid to the ram 50.

In operation, therefore, the mold box 21 must be first opened and the plunger 30 lowered to close the limit switch LS2 (Fig. 1). This energizes the relay coil R through the contacts S3, closure of the contacts R2 sealing in that relay through the normally closed limit switch LS3. Then, the box must be closed to actuate the limit switch LS1, and thevacuum switch 90 closed in response to the presence of a vacuum in the ports 40 holding a mat in place. With this, the solenoid 88 is energized so that the abutment 77 is retracted from the path of the rod 75. A pilot lamp 102 may be connected in parallel with the solenoid 8%, if desired, to indicate to an operator that the apparatus is in readiness for the pumping operation.

To eflect such pumping, the operator momentarily de presses the push button switch 10%. This energizes the relay coil S through the now closed limit switch LS1 and. the new closed relay contacts R1, the contacts S1 thus- 6 closing to maintain the coil S energized even though the contacts R1 should later open. Pick-up of the relay S also closes the contacts S2 so that the valve solenoid 71 is energized through the now closed contacts R2 and the normally closed limit switch LS3. The pump thus opcrates through one complete stroke.

At the end of the stroke, the cam 98 shifts the pin 94 to actuate and open the normally closed limit switch LS3. As a result, the valve solenoid 71 is deenergized and the pump returns to its original position. The relay R is also deenergized so that its contacts R1, R2 open. With the opening of the contacts R1, the blocking solenoid 88 is deenergized, permitting the abutment 77 to return to blocking engagement with the rod 75. The relay S, however, remains energized. With the relay S energized, its contacts S3 remain open so that it is now impossible to energize the relay R by closure of the contacts LS2. Moreover, closure of the push button switch 10Gb at this time will have no effect whatever. It cannot cause the pump to operate through another cycle or a partial cycle.

When the mold box is opened, the limit switch LS1 is deactuated and its contacts open to drop out the relay S. As the plunger 30 is pulled outwardly, the limit switch LS2 again closes and picks up the relay R through the now reclosed contacts S3 to prepare the circuit for another cycle of operation.

Referring now to Figs. 8-l5, a modified form of the invention is there illustrated which provides substantially the same protective blocking action of the metal pump and its actuator. Since the plate casting apparatus previously described is the same, like parts have been identified by the reference characters previously employed, but with the addition of the distinguishing sufiix a.

As shown in Fig. 8, the rod or bar 75a is movable in unison with the piston rod 68a of the ram 50a, as before, except that in this instance it is rigidly bolted to a flange 11th carried by the upper end of the piston rod. At its lower end, the bar 75a is formed with a notch 111. When the bar 75a is at its upper travel limit, the notch 111 is disposed opposite an abutment plate 112 which is slidable transversely to the bar. As here shown, the abutment plate 112 is horizontally slidable in slotted supports 114 mounted on flange member 115 rigidly fixed to and extending transversely from the ram cylinder. An opening 116 (Fig. 9) in the flange 115 permits the bar 75a to move downwardly when the piston rod 68a is drawn into the ram 50a. As seen best in Fig. 10, the abutment plate 112 is cut out at 118 to embrace the rod 75a. A comparison of Figs. 10, 11 and 12, will reveal that the abutment plate is slidable between a center position and first and second deflected positions to the right and left of such center position. The abutment plate is of such thickness that with the rod 75a in its uppermost position and that plate 112 in one of its deflected positions, the latter enters the notch 111 and effectively blocks movement of the rod, the piston rod 68a, the lever 51a and the pump which is associated with the lever as shown in Fig. 1.

For yieldably retaining the abutment plate 112 in each of its three positions, spring means are provided. To shift and yieldably hold the abutment plate 112 in either of its deflected positions once it is moved from its center position, a pair of upright pintles 120, 121 (Fig. 9) are rotatably inserted into vertical bores in the flange 115 and the plate 112, respectively. A connecting pin 122 is horizontally inserted through the two pintles and surrounded by a compression spring 124. This arrangement thus creates a spring toggle which urges the abutment plate 112 either to the extreme left or the extreme right.

To retain the plate 112 in its center position, a small recess 125 in its underside cooperates with a rounded detent pin 126 biased upwardly by a compression spring 128 contained within a vertical sleeve 129 fixed to the support 115 (Fig. 9). Whenever the abutment plate is 7 centered, the detent 126 snaps into the recess 125 and thus yieldably holds the plate 112 in its centered position.

Means are provided for shifting the abutment plate 112 from its centered position to its first deflected position, i. e., to the right as viewed in Fig. 11, as an incident to downward movement of the rod 75:: as the actuator 56a operates through a working stroke. In the present instance, such means are provided by a wedge-shaped cam 131 (Fig. 9A) which is fixed, as by welding, to the rod 75a at a location spaced above the notch 111. As the rod 750 moves downwardly, therefore, the cam 131 cugages the edge of the cutout 118 in the plate 112 thereby shifting the latter from dead center against the retaining force of the detent 126 so that the toggle spring 124 positively urges the plate toward its first deflected position. At this point the plate 112 rides against the side of the rod 75a. When pumping stroke is completed and rod 75a returns to starting position, the spring toggle snaps the plate to the right into notch 111 (Fig. 11).

In order to shift the abutment plate 112 from its first position to its second deflected position when and only when the mold box 21 has been opened, a solenoid 135 is suitably mounted on the flange 115 to the right of the plate 112, such solenoid having an armature 136 carrying a plunger 13.8. The plunger is normally retracted by a suitable tension spring 139, and the solenoid 135 is connected in series across voltage supply lines L1, L2 (Fig. 15) through a normally open limit switch LS2a which is mounted and arranged as shown for the switch LS2 (Fig. l) on the mold box. Whenever the mold box is open and the plunger 30 pulled outwardly therefrom, the switch LS2a is closed to energize the solenoid 135, thus shifting the plunger 138 to the left (Fig. 12) so that it engages and urges the abutment plate 112 toward its second deflected position, i. e., to the extreme left as viewed in Fig. 12.

Provision is made to positively latch the abutment plate 112 in its second deflected position so long as the mold box 21 (Fig. 1) remains open. For this purpose, the abutment plate 112 is formed with a latch slot 146 in one side thereof located to receive a latching plunger 141 carried by the armature 142 of a solenoid 144. The plunger is normally biased against the side surface of the abutment plate 112 so that it will snap into the recess 140 when the plate reaches its second position (Fig. 12). As here shown, the plunger 14?. carries a collar 14-5 engaged by a compression spring 146. Energization of the solenoid 144 retracts the armature 142 and the plunger 141 against the biasing force of the spring 146 (Fig. 13). Th solenoid 144 is arranged to be energized only when the mold box is closed by virtue of its connection across the voltage supply lines L1, 1.2 (Fig. 15 through the normally open limit switch 1281a. The latter switch is mounted on the mold box 21 as shown for the limit switch LS1 in Fig. 1 so that it will be actuated by the manual lever 29 only when the box door 26 is closed and locked.

Means are provided, additionally, to shift the abutment plate 112 from its second deflected position back to its center position whenever a vacuum is present in the mat-holding vacuum ducts 4d, and provided that the mold box is closed. For this purpose, a small vacuumresponsive ram 151) is mounted on the flange 115 to the left of the plate 112, the ram having an internal piston 151 carrying a piston rod 152 and being equipped with a conduit 154 which is connected into the manifold for the ducts 40. The piston 151 is normally urged to the left (Fig. by a suitable biasing means such as a tension spring 155. Upon application of a vacuum to the ducts 4t) and through the conduit 154, however, the piston 151 is shifted to the right (Fig. 14) against the force of the spring 155 so that the plunger 152 engages the abutment plate 112 and shifts the latter back to its center position where the detent pin 126 snaps into the recess 125. It will be observed that the vacuum ram 150 cannot produce this shifting of the abutment 112 unless the plunger 141 is first retracted from the latch slot 140 as shown in Fig. 13.

In considering the operation of this control arrangement, assume first that the abutment 112 has been shifted to its center position and is retained there by the detent 126 as shown in Fig. 10. Assume, further, that the box has been closed and that a vacuum is present in the ducts 40 due to the presence of a mat. To initiate the pumping operation, an operator depresses a push button switch 1013a in series with the solenoid 71a for the valve 70,0 across the lines L1, L2 (Fig. 15 This, as explained previously, causes the solenoid valve a to supply pressure fluid to the ram 50a so that the latter moves through a working stroke and causes the metal pump to supply molten metal to the mold box. As the piston rod 68:: for the actuator 5% moves downwardly, and the rod a moves with it, the cam 131 on the latter engages the abutment plate 112 and shifts the latter to the right, the toggle spring 124 holding it there. The edge of the cutout 118 will thus ride along the external surface of the rod 75a as the latter returns to its original position. When the rod 75a is thus returned, the toggle spring 124 causes the abutment plate 112 to snap into the notch 111 (Fig. 11), thereby positively locking the rod 75a and thus the ram 50a from further movement. It is thus impossible for a second pumping stroke to take place, even though the push button switch a is closed, until the abutment plate is returned to its center position.

When the mold box 21 is opened and the plunger 30 pulled outwardly to remove the completed printing plate, the limit switch LSZa is closed. This, in turn, energizes the solenoid so that its plunger 138 moves to the left (Fig. 12), thereby shifting the abutment plate beyond its center position to the extreme left. Since, with the box open, the limit switch LSla is now open, the solenoid 144 is now deenergized so that its plunger 141 is biased against the side surface of the abutment plate 112. When the latter reaches its second deflected position as shown in Fig. 12, the plunger 141 snaps into the latching recess 140, preventing movement or" the abutment plate until that plunger is retracted. It will also be observed that the abutment plate in its left position also enters the notch 111 in the rod 75:: so that operation of the actuator 50a and the metal pump cannot occur. This is true, even though the push button switch 100:: should be closed and the solenoid 71a energizer to open the valve 70a.

Now, as soon as the mold box is reclosed, the limit switch LSM is opened, thus causing the plunger 138 to be retracted by its spring 139. Additionally, the limit switch LSla is closed, thereby energizing the solenoid 144 and retracting the latch plunger 141. As a vacuum builds up in the ducts 4%, indicating a mat properly held in the box, the vacuum ram 151 will be actuated so that its plunger 152 moves to the right and returns the abutment plate 112 to its centered position where it is retained by the detent 126. The apparatus is then in condition for operation of the pump to cast a second plate.

In summary, it may be observed that the pump-actuating ram in each instance is prevented from movement even though it is energized by supply of pressure fluid thereto. Once a pumping stroke has been made, the ram is blocked from a second pumping stroke until the box has been opened for the removal of the completed plate. Pumping still cannot occur until the box is first closed and a vacuum is present in the mat-holding ducts.

We claim:

1. For use with printing plate casting apparatus including a clcsable mold box having vacuum holding means for retaining a mat and a linear stroke pump for delivering molten metal into the box, improved controls comprising, in combination, a linear actuator, a lever connecting said actuator to operate said pump, a member physically connected to and movable with said lever, a movable abutment normally disposed in the path of movement of said member to block movement of the latter and thus block movement of said actuator, first and second limit switches and means causing them respectively to be open and closed when the mold box is open and to be closed and open when the mold box is closed, means responsive collectively to the presence of a vacuum in the holding means and the closure of said first limit switch for shifting said abutment clear of said member, means for returning said abutment into blocking engagement with said member as the pump is returned after one pumping stroke, and means for preventing said abutment from again being shifted clear of said member until said first switch is closed by opening of the mold box.

2. For use with printing plate casting apparatus including a closable mold box and a pump for supplying molten metal to the box, improved controls comprising, in combination, a power actuator operatively connected with the pump, a member physically connected to and movable with said actuator, an abutment movable into and out of blocking engagement with said member to respectively prevent or permit movement of said actuator when it is energized, means for shifting said abutment out of blocking relation with said member only when the box is closed, means for causing return of said abutment into blocking relation with said member upon return of the pump after a single working stroke, and means for preventing shifting of said abutment out of blocking relation with said member a second time until said box has first been opened.

3. In stereotype plate casting apparatus including a closable mold box and a pump for supplying molten metal to said box, improved control means comprising, in combination, a power actuator and a linkage connecting the same to actuate the pump, a member movable with said linkage, a movable abutment normally disposed in the path of said member to block movement of said linkage, a solenoid having an armature connected with said abutment to retract the latter clear of said member when the solenoid is energized, means for permitting energization of said solenoid only when the mold box is closed, a limit switch and cam means'carried by said member for actuating the limit switch as the pump completes a pumping stroke, means responsive to the actuation of said switch for deenergizing said solenoid, and means for preventing energization of said solenoid a second time until the box is first opened.

4. In printing plate casting apparatus including a closable mold box adapted to hold a mat by vacuum means and a linear stroke pump for supplying molten metal to said box, improved control means comprising, in combination, a linear actuator and a lever connecting the same to, actuate the pump, a member movable with said lever, a movable abutment normally disposed in the path of said member to block movement of said lever, a solenoid having an armature connected with said abutment to retract the latter clear of said member when the solenoid is energized, means for permitting energization of said solenoid only when the mold box is closed and a vacuum is present in the vacuum means, means for deenergizing said solenoid when the pump reaches the end of a pumping stroke,

and means for preventing energization of said solenoid a second time until the box is first opened.

5. In printing plate casting apparatus including a closable mold box and a pump for supplying molten metal to said box, improved control means comprising, in combination, a power actuator and means connecting it to actuate the pump, a member movable with said connecting means, a movable abutment normally disposed in the path of said member to block movement of said pump, a solenoid having an armature connected with said abutment to retract the latter clear of said member when the solenoid is energized, means for energizing said solenoid only when the mold box is closed, means for deenergizing said solenoid when the pump completes one pumping operation, and means for preventing energization of said solenoid a second time until the box is first opened.

6. In printing plate casting apparatus including a closable mold box adapted to hold a mat by vacuum means and a linear stroke pump for supplying molten type metal a solenoid having its armature connected with said abutment to retract the latter when the solenoid is energized, and means for energizing said solenoid only when the mold box is closed and a vacuum is present in said vacuum means.

7. In printing plate casting apparatus including a closable mold box adapted to hold a mat by vacuum means and a pumpfor supplying molten type metal to said box, improved control means comprising, in combination, a linear actuator coupled to actuate the pump, a first limit switch and means for causing it to be open and closed when the mold box is open and closed, respectively, a second limit switch and means for causing it to be open and closed when the mold box is closed and open, re-

spectively, a third limit switch and means for causing it to be closed when said actuator is substantially at the end of its stroke, a movable abutment and means for causing it normally to block movement of said linear actuator, a solenoid for retracting said abutment, a vacuum switch coupled to be closed only when a mat is held in the box by the vacuum means, a control relay having a coil and first and second normally open contacts, means for connecting said first switch, vacuum switch, solenoid and first contacts in series across a power source, means for connecting said second contacts and said third switch in series combination and the combination in parallel with said second switch, so that said pump cannot be operated (a) when the box is open, or (b) when the box is closed with no vacuum for holding the mat, and can be operated through but one stroke after the box is closed.

8. In printing plate casting apparatus including a closable mold box having vacuum means for holding a mat and a linear stroke pump for supplying molten metal to the box, improve-d controls comprising, in combination, a double acting fluid pressure ram and a lever operatively connecting it to said pump; a four-way solenoid valve for controlling the supply of pressure fluid to said ram; first and second limit switches and means for causing them to be respectively closed and open when the box is closed and to be respectively open and closed when the box is closed; a vacuum switch and means for causing it to be closed when a vacuum exists in the vacuum holding means; a rod connected to said lever; an abutment and a biasing spring yieldably urging it to a position in the path of said rod to block movement of said lever; a solenoid having an armature connected with said abutment to retract the latter clear of said rod; a third limit switch and means carried by said rod for causing it to be closed when the pump has reached the end of its pumping stroke; a first relay having a coil and two sets of normally open contacts; a second relay having a coil, two sets of normally open contacts, and one set of normally closed contacts, means connecting said first relay coil, said second limit switch, and said normally closed contacts in series and adapting the same for connection to a volt age source; means connecting one of said first relay contacts in series combination with said third limit switch, and the combination in parallel across said second limit switch and said normally closed contacts; means connecting said first limit switch, the other of said first relay contacts, said vacuum switch, and said solenoid in series and adapting the same for connection to a voltage source; a normally open push button switch and means connecting it in series combination with said second relay coil, and the combination in parallel across said vacuum switch and solenoid, means connecting one set of normally open second relay contacts in parallel across said other set of first relay contacts and said push button switch, and means connecting the other set of normally 11 open second relay contacts in series with said solenoid valve and in parallel with said first relay coil.

'9. In stereotype plate casting apparatus including a closable mold box and a linear stroke pump for supplying molten metal to said box, improved control means comprising, in combination, a linear actuator and lever connecting the same to actuate the pump, a member movable with said lever, a movable abutment normally disposed in the path of said member to block movement of said lever, a solenoid having an armature connected with said abutment to retract the latter clear of said member when the solenoid is energized, first and second control relays, means energizing said solenoid only when both of said relays are energized, means for energizing and sealing in said first relay only when the mold box is open and said first relay is deenergized, means for energizing said second relay only when the mold box is closed, means for deenergizing said first relay and said solenoid when the pump reaches the end of a pumping stroke while leaving said second relay energized, whereby said solenoid cannot be energized a second time until the box is first opened to deenergize said second relay.

10. In stereotype plate casting apparatus including a closable mold box having vacuum means for holding a mat therein and a linear stroke pump for supplying molten metal to said box, control means comprising, in combination, a linear stroke actuator operatively connected to the pump, a rod movable in unison with said actuator and having a notch cut therein, an abutment plate cut out to embrace said rod and disposed to slide transversely of the rod to slip into said notch from either side when the actuator is retracted to block movement of the latter, a detent for yieldably retaining said plate in a center position free of said notch, a spring toggle for biasing said plate to first and second positions deflected in either direction from the center postion, a cam on said rod for shifting said plate toward its first position from its centered position as said actuator moves through a pumping stroke, a solenoid having an armature disposed to push said plate past center to the second position, means for energizing said solenoid when the casting box is open, a vacuum ram connected to be energized in response to the presence of a vacuum in the mat holding vacuum means and disposed to push said plate from its second position to its center position, a second solenoid having an armature biased to latching engagement with said plate when the latter is in its second position and the solenoid is deenergized, means for energizing said second solenoid when the mold box is closed, whereby after a pumping stroke and return stroke of said actuator the latter is blocked by said plate until the box is opened and reclosed and a vacuum is re-established in the vacuum means.

11. In printing plate casting apparatus including a closable mold box and vacuum means for holding a mat therein and a linear stroke pump for supplying molten metal to the box, control means comprising, in combination, a fluid pressure ram and a lever connecting the same to actuate the pump, a rod fixed to the lever and movable therewith, said rod having a circumferential notch therein, an abutment plate cut out to embrace said rod, means mounting said plate to slide transversely of said rod between centered and first and second deflected positions, said plate entering said notch in its deflected positions when said ram is retracted from a working stroke to block movement of the latter, means for yieldably retaining said plate in each of its positions, a cam carried by said rod for shifting said plate from its center position toward its first position as said ram moves through a Working stroke, a first solenoid and means for energizing the same when the box is opened for shifting said plate from its first to its second position, and means including a vacuum ram responsive to the presence of a vacuum in the mat holding means and a second solenoid energized only when the box is closed for returning said plate to its center position only if the box is closed and a vacuum applied to the that holding means.

12. In printing plate casting apparatus including a closable mold box having vacuum means for holding a mat and a linear stroke pump for supplying molten metal to the box, control means comprising, in combination, a linear actuator and means operatively connecting it to said pump, a rod movable with said actuator and having circumferential notch therein, an abutment plate cut out to embrace said rod, means mounting said plate for sliding movement transverse to said rod between a center position and first and second deflected positions on opposite sides of the center position, said plate entering said notch to block movement of said rod and said actuator When the latter is retracted and the plate is in a deflected position, means for yieldably holding said plate in each of its three positions, means for shifting said plate from its center toward its first position as an incident to movement of said actuator through a working stroke, means for shifting said plate from its first to its second position as an incident to opening of the casting box, means for latching said plate in its second position as long as the box is open, and means for shifting said plate from its second to its center position in response to the presence of a vacuum in the mat-holding vacuum means.

References Cited in the file of this patent UNITED STATES PATENTS 1,514,745 Walser Nov. 11, 1924 1,726,787 Wood Sept. 3, 1929 1,848,593 Wood Mar. 8, 1932 1,856,430 Roesen May 3, 1932 2,173,990 Wood Sept. 26, 1939 2,236,212 Huck Mar. 25, 1941 2,297,739 Blackley Oct. 6, 1942 2,526,753 Huck Oct. 24, 1950 2,619,694 Tornberg et a1. Dec. 2, 1952 2,709,284 Evans et a1. May 31, 1955

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