US3604499A

US3604499A - Diecasting machine with force-balanced reciprocation apparatus and transferring means

Info

Publication number: US3604499A
Application number: US882021A
Authority: US
Inventors: Franck M Picker
Original assignee: PIC AIR Inc
Current assignee: PIC AIR Inc
Priority date: 1969-12-04
Filing date: 1969-12-04
Publication date: 1971-09-14
Anticipated expiration: 1988-09-14

Abstract

A fast-acting diecasting machine including in combination, a die having at least one die platen which is reciprocatable between open and closed positions, a prime mover, reciprocation means disposed between said movable die platen and said prime mover for selectively and intermittently reciprocating said movable die platen between open and closed positions, transfer means for moving castings from said die cooperatively connected to said reciprocation means, means selectively and intermittently connecting said transfer means to said prime mover, means maintaining said reciprocation apparatus in a substantially force-balanced state during at least a major part of a platen reciprocation cycle, and means for injecting liquid matter into the die when it is closed. There is also disclosed a novel method for die casting.

Description

United States Patent Inventor Franck M. Picker Oak Ridge, Tenn. Appl. No. 882,021 Filed Dec. 4, 1969 Patented Sept. 14, 1971 Assignee Pic-Air Inc.

Oak Ridge, Tenn.

DIECASTING MACHINE WITH FORCE- BALANCED RECIPROCA'I'ION APPARATUS AND [56] References Cited UNITED STATES PATENTS 2,848,770 8/ 1958 Schuchardt 164/344 UX Primary Examiner-Robert D. Baldwin Artorney- Paul E. Hodges ABSTRACT: A fast-acting diecasting machine including in combination, a diehaving at least one die platen which is reciprocatable between open and closed positions, a prime mover, reciprocation means disposed between said movable die platen and said prime mover for selectively and intermittently reciprocating said movable die platen between open and closed positions, transfer means for moving castings from said die cooperatively connected to said reciprocation means, means selectively and intermittently connecting said transfer means to said prime mover, means maintaining said reciprocation apparatus in a substantially force-balanced state during at least a major part of a platen reciprocation cycle, and means for injecting liquid matter into the die when it is closed. There is also disclosed a novel method for die casting.

l 5 CONTROL 68 TO INJECTION SYSTEM 51 BRAKE CLUTCH SYSTEM PATENTED SEP] 4 |97| SHEET 1 BF 9 uxaim INVENTOR.

Franck M. Picker ATTORNEY.

PATENTEU SEPI 41911 3,604,499

sum 2 or 9 INVENTOR.

, Franck M. Picker ATTORNEY.

PATENIEU SEP14|97| 3 604L499 sum 5 [IF 9 PLATEN FORCE OMBINATION 6.C.+ G.C.0UTPUT TORQUE I CRANK) AT CONSTANT INPUT PLATEN SPEED (COMBiNATION G.C.+

2/1 CRANK) PLATEN SPEED AT CONSTANT CRANK INPUT=2 Edouwm SPEED AT \CONSTANT 0 INPUT some.

- --1aocnmx 1 PLATEN l RECIPROCATION CYCLE Fig.6

INVENTOR.

Franck M. Picker ATTORNEY.

PATENIEDSEPMIQ?! I 3504,4299 sum 7 or 9 INVENTOR. Franck M. Picker BY 2., a. 7 46 ATTORNEY.

PATENIEBsEPMnm 3,604,499

sumaurs INVENTOR. Franck M. Picker ATTORNEY.

PATENTED sP14|91| 3.604.499

SHEET 9 OF 9 INVENTOR. Franck M. Picker QIEXQ ATTORNEY.

DIECASTING MACHINE WITH FORCE-BALANCED RECIPROCATION APPARATUS AND TRANSFERRING MEANS This invention relates generally to die casting and diecasting machines employing he method of injecting molten metal, under pressure, into a die cavity defined by a closed die.

Speaking generally, in die casting of metals or other materials, the molten metal is usually injected under pressure into a cavity defined by two or more closed die platens in accordance with the geometry of the desired cast product. The injected molten metal is maintained within the closed die until solidification occurs to at least the extent that the metal becomes self-sustaining. Thereupon, the die is opened and the solidified product, termed a casting, is transferred out of any away from the die.

Rapidly and repeatability are two major concerns in the field of die casting. Manufacturing economics, enhanced by employing die casting, clearly, are further enhanced by fast diecasting operations. The prior art diecasting technology suffers the lack of fast diecasting techniques and apparatus which will withstand repeated use over extended periods of time. For example, prior to the present invention, a diecasting machine in the 30-ton class capable of performing 6 to 10 acceptable casting cycles per minute over extended periods was deemed extraordinary as respects speed of casting. Fatigue and component wear resulting from multitudinous die openings and closings under the relatively large die-closing pressures routinely incurred accounted for a large portion of the prior art apparatus failures.

ln diecasting methods employing a die platen movable between open and closed positions, apparatus is required to move the die platen rapidly and repetitively along a reciprocation path. in such a method the die platen must reverse its direction at least twice during a casting cycle. Also, the die platen must remain stationary in the closed position for a time sufficient to permit solidification of the metal in the die cavity. Consequently, the apparatus which moves the die platen is subjected during a platen reciprocation cycle, to the force and stress attending movement of the die platen toward a closed position, followed by a greatly increased force and stress as a large die-closed holding force is applied, followed by a relaxation of the die-closed holding force, and a reversed force and stress attending movement of the die platen toward an open position. in the prior art, this cyclic stressing of the apparatus resulted in frequent failure of the apparatus which reciprocated the die platen, such failure occurring even more quickly as the frequency of die platen reciprocation increased.

The large die-closing forces present in diecasting molten metal have heretofore dictated the necessity of massive components in the die platen reciprocation apparatus and/or other portions of the diecasting machine Massive machine components possess great inertia. Accordingly, powerful prime movers were required and great forces and stresses were developed within the diecasting apparatus when these components were placed into motion, accelerated and stopped. in fast diecasting, these forces and stresses reached enormous proportions which contributed to early failure of the apparatus. Further, due to the great inertia of the massive components of the prior art diecasting machines, such machines were not subject to fine control and were expensive to fabricate. Additionally, the prior art prime movers were necessarily of great capacity, hence very expensive.

Prior to the present invention, it was common practice to remove, or attempt to remove heat from the molten metal within the die cavity as rapidly as possible by subjecting the molten metal to a temperature as far below the solidification temperature of the metal as practicable. For example, when casting a zinc alloy whose melting point is about 740 F., it has been the practice heretofore to pass through the die a coolant maintained at a temperature of about 320 F. By this technique, there was developed a very large temperature gradient between the coolant than did smaller temperature gradients.

It is noted that the relatively cold coolant of the prior art continued to remove heat from the die, including the die cavity wall at all times, even when the die was open. The die cavity wall was thus very cool when the die was once again closed. When the molten metal was then injected into the closed and cooled die, the die cavity wall underwent an immediate and drastic increase in temperature. The net effect of these large temperature gradients on the die itself and more especially on the die cavity wall was to subject the die metal to many cyclic temperature changes of great magnitude with concomitant metal fatigue and consequent failure of the die metal. This deleterious effect upon the die metal was compounded in the prior art by the relatively long time which elapsed between opening and closing of the die during a casting cycle. in addition to the continued cooling effect on the die by the coolant, the longer the die remained open during a casting cycle, the longer the time during which heat was being transferred from the die cavity surfaces to the circulating coolant.

I Thus in the prior art, at all times when the die was open there occurred a continuing transfer of heat from the die cavity wall to the coolant, i.e., a cooling of the die cavity wall. Of course, when the die was again closed and molten metal injected into the die cavity, there occurred the above-described rapid and drastic increase in the temperature of the die cavity wall. Repeated cooling and heating of the die cavity wall produced metal fatigue and resultant cracks in the die cavity wall, thereby effectively destroying the die.

it is important to successful die casting that at the time molten metal is injected into the die that the die cavity wall be at a temperature as near the melting temperature of the metal as possible for the reason that a cool die cavity wall will instantaneously remove excessive amounts of heat from the molten metal in contact with the cool wall in preference to removal of heat from the remainder 6 of the molten metal. This preferential cooling of the molten metal results in premature solidification of portions of the injected metal and resultant chill marks on the metal casting. Moreover, where the casting has a thin wall thickness in part or in whole, premature solidification frequently precludes complete filling of the die cavity in the area of the thin wall portion and produces a defective casting. In any event, the prior art taught that where thin wall thicknesses are involved, one should use very fast injection and large pressures. Such conditions of casting caused one to lose control over the injection operation and increased the frequency with which defective castings occurred.

l-lydraulically operated diecasting machines are common in the prior art and have been employed in attempts to provide the large forces required to operate prior art machines. These hydraulic systems, however, are subject to many faults including their complexity and great cost of manufacture and maintenance.

It is therefore an object of this invention to provide a method and apparatus for fast, repetitive and controllable die casting especially such a method and apparatus wherein the useful life of the diecasting apparatus and the die is extended beyond the useful life of the apparatus and die obtainable in the prior art. It is is another object to provide a diecasting machine for rapid diecasting wherein the die platen reciprocation apparatus is maintained under substantially balanced forces during a major part of a platen reciprocation cycle. It is a further object to provide a diecasting machine wherein molten metal may be injected into the die cavity at relatively slower rates and under relatively lower pressure while simultaneously substantially decreasing the total casting cycle time over the time heretofore obtainable. It is a further object to provide a diecasting machine wherein the die is not subjected to large temperature changes during a casting cycle. It is a still further object to provide a nonhydraulically operated diecasting machine.

Other objects and advantages of the present invention will be evident from the following description of the invention including the figures.

For present purposes, the discussion herein will be restricted to diecasting metal, but is not intended to so limit the invention. It will be recognized by those skilled in the art of diecasting that the present concepts are useful in casting metals, alloys, plastics, and/or other materials, substances, etc.

FIG. 1 is a representation of one diecasting apparatus in accordance with the present invention;

FIG. 2 is an exploded view of the means employed in the present invention to intermittently connect the several components of the casting transfer mechanism to the prime mover;

FIG. 3 is a graphic representation of one casting cycle and depicting the preferred cyclic positions of certain apparatus functions and their relative magnitudes, assuming a constant prime moving input throughout the cycle;

FIG. 4 is an expanded graphic representation of that portion of the casting cycle of FIG. 3 which occurs between 67 and l57% and depicting the torque output and several corresponding rotational positions of the cam of the-present invention;

FIG. 5 is an expanded graphic representation of that portion of the casting cycle of FIG. 3 which occurs between 202% and about 292 /z and depicting the torque output and several corresponding rotational positions of the cam of the present invention;

FIG. 6 is a graphic representation of a typical output speed and torque of the Geneva Cross mechanism of this invention and of a typical linear speed and torque of the die platen as moved by the combined actions of the Geneva Cross and crank mechanism (including the 2:1 gear ratio discussed hereinafter) of this invention;

FIG. 7 is a representation of one embodiment of a die employed in the present invention and depicting various features of such die;

FIG. 8 is an illustration of one embodiment of the cam and cam follower apparatus of this invention;

FIG. 9 and 9A are representations of several rotational and translational positions of the transfer and strip feed arms of the transfer mechanism of this invention.

In accordance with the concepts of the present invention, the present diecasting machine comprises in combination a prime mover, a die having at least one die platen which is reciprocatable between open and closed positions, reciprocation means disposed between the movable die platen and the prime mover for selectively and intermittently reciprocating the movable die platen between its open and closed positions, means operatively associated with the reciprocation means and maintaining it in a substantially force-balanced state during the major part of a platen reciprocation cycle, transfer means cooperatively connected with the platen reciprocation means for moving castings from the die, and means for injecting liquid matter into the die when it is closed whereby there is formed a cast product upon solidification of such liquid matter. As desired, the casting apparatus may include means for performing an operation upon the casting such as dressing, trimming, or the like, such means being coordinated in function with the casting apparatus, particularly the casting transfer means.

It has been found possible in the present invention to obtain enhanced speed and controllability of casting through coordinated functioning of the several elements of the casting machine as will appear more fully hereinafter.

Referring now to FIG. 1, the diecasting machine of the present invention is depicted schematically and comprises a prime mover 12 providing the driving force for operation of a die reciprocation subassembly and a transfer subassembly which will be more fully described hereinafter. Also depicted in FIG. I is a molten metal injection subassembly indicated generally at 37 and a trim-press subassembly indicated generally at 47.

Referring further to FIG. 1 representative of a diecasting machine comprising one embodiment of the present invention, power for driving the die platen reciprocation apparatus of the present invention is derived from a single motor l2 a conventional clutch and brake system 20 interposed within its length. This drive shaft terminates in a sprocket 14 around which is trained a chain 21, the chain also being trained around a second sprocket 22 keyed to a stub shaft 23 which in turn carries a worm 24. Accordingly, worm 24 is positively and mechanically connected in driven relationship with motor 12 except as clutch 20 may be disengaged.

Worm 24 serves as the driving gear for a Geneva Cross mechanism indicated generally at 11. Specifically, worm 24 engages the cam gear 25 of the Geneva Cross mechanism such that rotation of worm 24 will rotate gear 25. This gear 25 is provided with two

convex cam sections

45, 46, two concave cam sections 26, 27 and two lugs 28, 29 for cooperatively engaging the cross 30 of the mechanism. The periodic motion imparted to the cross 30 is further transferred by the cross to a shaft 31 to which the cross is keyed. Shaft 31 carries a sprocket 32 keyed thereto so that each movement of cross 30, effected by rotation of gear 25, results in a corresponding rotation of sprocket 32. This sprocket 32 is drivingly connected to a further sprocket 33 spaced apart from sprocket 32 and keyed to a further shaft 6. Sprocket 32 is chosen in the depicted embodiment to be twice the diameter of sprocket 33 such that each rotation of sprocket 32 results in two rotations of sprocket 33 hence two rotations of shaft 6. There is provided on shaft 6 a crank arm 7 which is rotatable 360 with rotation of shaft 6. Crank arm 7 extends perpendicularly from a shaft 6 and its outboard end receives, in pivotal connection, one end of a link 8. The other end of link 8 is pivotally connected to a ram 9 to which is secured the movable die platen 10. Appropriate mounting means is provided for reciprocatably mounting this ram.

During each reciprocation cycle of the die platen, it may be visualized that worm 24 rotates gear 25 one revolution. For each such one revolution there occurs two equal periodic rotational movements of cross 30.

Each of these equal movements results in one quarter turn of cross 30, the cross being stationary during the intervals between the aforesaid two equal movements of the cross. The duration of the two nonactive intervals are established by the arcuate lengths of the respective

convex cam sections

45 and 46. From FIG. 1 it can be seen that each one-fourth turn of cross 30 results in a one-fourth turn of sprocket 32. By virtue of the size relationship between

sprocket

32 and 33, each onefourth rotation of sprocket 32 results in one-half rotation of sprocket 33, hence one-half rotation of shaft 6 and movement of arm 7 through an arc of 180. Each 180 movement of arm 7 moves ram 9 through one-half of a platen reciprocation cycle. That is, for each one-fourth turn of cross 30 there occurs movement of die platen 10 from a position of fully closed to fully opened or from fully opened to fully closed, as the case may be.

It will be realized that when either of the cam lugs 28 and 29 of gear 25 initially engages a slot 34 (typical) of the cross, the lug makes first contact nearest the peripheral end of the slot. Maximum torque and minimum speed were imparted to cross 30 at this point of contact. Further, at this rotational position of cross 30, it is assumed for present purposes that the die platen is in its full open position. As the cross is rotated, the cam lug moves radially inward and the torque and speed imparted to the cross by the lug, decreases and increases, respectively, through each one-half platen reciprocation cycle. The rotational speed of the cross reaches a maximum and the torque imparted to shaft 31 by cross 30 reaches a minimum when the lug reaches its most radially inward position. At the point when the lug escapes the slot, the torque and speed of cross 30 are again maximum and minimum, respectively. At this latter point, the die platen is in its fully closed position. The profile of the Geneva Cross outputs during both the opening and closing halves of such platen reciprocation cycle are depicted graphically in FIGS. 3, 4, 5 and 6.

Simultaneously with the mechanical advantages developed by the Geneva Cross mechanism, a similar mechanical advantage, having similar torque and speed profiles, is developed by crank arm 7 and link 8 as arm 7 is rotated by shaft 6. The torque and speed components of this crank mechanism and the Geneva Cross mechanism combine additively and are imparted to ram 9. The resultant linear speed of the die platen l affixed to ram 9 is depicted graphically in FIGS. 3 and 6.

Referring specifically to FIG. 6, assuming a constant input (speed and torque) to the Geneva Cross mechanism (G.C.), its output speed over 90 (one-fourth of a casting cycle or onehalf of a die platen reciprocation cycle) is shown by the line labeled G.C. Output Speed at Constant Input. It is noted that upon actuation of the G.C. its output speed increases slowly from dead stop (left of FIGURE), then accelerates rapidly to a maximum, followed by a rapid decrease in speed and a slow approach to dead stop. Whereas this G.C. output itself has been found to provide a desirable output speed pattern for movement of a die platen, to use a G.C. alone for reciprocating the die platen is impracticable in that an inordinately massive G.C., superstructure, prime mover, etc. would be required. Moreover, a G.C. alone would be subject to the hereinbefore described large cyclically changing forces with concomitant wear, tear, failure, inability to control, slow action etc. of the diecasting apparatus.

Presently, it has been found that advantage can be taken of the G.C. output in diecasting by combining it with a crank mechanism indicated generally at connected between the G.C. and a movable die platen such that the G.C. and crank outputs are combined to impart linear motion to the die platen. The combined output speed from the G.C. and crank are depicted in FIGS. 3 and 6. In the figures this output is shown as being increased by the 2:l gear ratio between

sprockets

32, 33. It is recognized that other gear ratios could be chosen and the 2:1 ratio discussed herein is not to be deemed limiting of the invention.

Review of FIGS. 3 and 6 shows that, in the present invention, at any time during a casting cycle whereupon power from he prime mover is applied to move the die platen, the apparatus is subjected to force and stress very slowly at first (left to right in the FIGURES), such force then accelerating rapidly to a maximum and then decelerating in a substantially identical, but reverse, manner. In the absence of the present invention, the platen, in a typical one-half platen reciprocation cycle, e.g., open to close or close to open, would experience an increase and decrease in speed as shown in FIG. 6, by the line labeled Platen Speed at Constant Input" (assuming a 2:1 gear ratio as discussed hereinbefore). It is noted that the present invention provides a significantly flatter curve at the beginning and end of the indicated period. This flatter curve portions are indicative of the relatively slow rate of approach of the platen to its open or closed position as the case may be, and its similar slow rate of movement away from either its open or closed position. Consequently, in the present invention the platen reciprocation apparatus is not subjected to the large shock or stress which attend the prior art machines due to their abrupt change in direction when they move the platen through its open or closed positions (i.e., where the direction of travel reverses). In the present invention the platen recipro cation apparatus moves the platen very rapidly through a reciprocation cycle but it approaches and leaves an end point (open or closed) at almost zero speed to thereby avoid the opening and closing shock referred to above with resultantly reduced wear and tear of the machine. It is to be noted that this reduction in opening and closing shock is in addition to the force and stress reduction afforded by the cam-cam follower concept to be discussed hereinafter, these two concepts functioning simultaneously to enhance the overall diecasting operation.

Also in accordance with the present invention, it has been discovered that the die platen reciprocation apparatus of the present diecasting machine can be maintained under conditions of balanced force and stress, through the use of a combination including a cam 38 secured to a shaft 6 disposed within and being an element of the die reciprocation apparatus, and a spring-loaded cam follower 39 riding against the cam surface such that rotation of the shaft and cam causes preselected transfer of energy from the die reciprocation apparatus to the spring of the cam follower and subsequent transfer of the energy from the spring back to the reciprocation apparatus. It is important for reasons which will appear hereinafter that the energy transfers be programmed and not allowed to occur in an unordered manner.

It has been further found that selective compression of the spring associated with the cam follower provides a means for controlling the magnitude of energy accumulation and dispensation. Only that quantity of energy is accumulated which is excess in the system. This energy is dispensed only when such serves a useful purpose in the overall scheme of the apparatus functioning.

One suitable physical arrangement of the cam-cam follower mechanism is shown in FIGS. l and 2 wherein there is provided a shaft 6 with cam 38 keyed to and rotatable therewith. As provided for in the present invention, shaft 6, by virtue of its position in the reciprocation apparatus, experiences as a torque force impressed thereupon, any stress present in the die reciprocation apparatus directed toward movement of the movable die platen 10 toward either an open or closed position. Consequently, it has been found possible to manipulate the torque forces experienced by shaft 6 in a manner so as, at substantially all times during a platen reciprocation cycle, to impose on such shaft a countertorque force by means of cam 38 and its spring loaded follower 39, which is slidably mounted as by cylindrical housing 44. That is, in accordance with the present concepts, spring 40 is cyclically compressed and expanded, hence the torque experienced by shaft 6 is controlled in accordance with a planned program selected to develop torque values which are opposite in direction but of approximately equal magnitude as the torque values impressed upon the shaft by the platen reciprocation apparatus during a platen reciprocation cycle. Accordingly, at all times during a casting cycle, the present invention provides a proper force to shaft 6 which will balance the cumulative force ahead of the shaft (toward the die 13) against he cumulative force behind the shaft (toward the prime mover 12), thereby achieving a balanced system.

It is important to note that the present invention provides for full utilization of both the force provided by the prime mover and the several other forces and mechanical advantages associated with opening and closing the die platen. Such use of these forces is accomplished while at the same time the heretofore expected wear and tear of the mechanical apparatus and superstructure is substantially minimized through the balancing of such forces in a programmed manner. Still further, all the while the total system functions at a faster cycling rate than the prior art. Speaking generally therefore, the present invention provides a diecasting method and apparatus wherein the apparatus functions faster, longer, and with less prime moving force than heretofore has been possible.

The advantages provided by the present invention are myriad. Aside from the aforementioned large decrease in wear and tear, this invention makes it possible to construct less massive casting apparatus components thereby decreasing the initial cost of fabricating a diecasting machine. Because the platen reciprocation apparatus is balanced, less prime-moving power is required, for example it has been found satisfactory to utilize a 5 hp. motor as the prime mover under circumstances which in the prior art required a 50 hp. motor.

Very importantly and contra to the prior art, the balanced platen reciprocation apparatus of the present invention renders the diecasting machine amenable to fine control. This factor is of significance in that fine control permits the elimination of lost time between steps of a casting cycle, thus minimizing the total cycle time and significantly increasing the productive output of a given machine. In addition, accurate control of the timing of cycle steps reduces defective castings due to irregular apparatus functioning, with resultant economic savings.

In one preferred embodiment of the present invention, shaft 6 is provided with a cam having the configuration depicted in FIG. 8. The tension on spring 40 retaining the cam follower 39 against the circumference 41 of cam 38 is adjusted so as to provide an optimum constant force base, specific for individual machines and desired casting cycles. From a knowledge of the casting cycle and the forces developed in the course of such cycle, an appropriate contour is determined and provided on cam 38.

Referring to FIGS. 3, 4 and 5, a typical casting cycle and the rotational attitudes of the cam at several points during the cycle are depicted. In any given casting cycle employing the present invention, the movable die platen 10 is moved to a closed position (the closed position being defined as the point in the cycle where the two die platens contact without significant concomitant stress of the platen or their supporting superstructure), the platens and their supporting superstructure are then forced into a stressed state (termed the stressedclosed position for purposes this disclosure), the molten metal is injected into the die cavity and allowed to solidify, the closing stress on the die is relaxed, and the movable die platen is moved to an open position to permit extraction of the casting, thereby completing a cycle. As desired, of course other machine functions can be interposed within the cycle. The movable die platen preferably is moved rapidly and without stopping or interruption from its stressed-closed position, through its closed position, through its open position, through its closed position, and return to its stress-closed position. When the die is in the latter position, the die reciprocation apparatus may be deactivated for that period of time during which the die remains stressed-closed.

From the foregoing discussion, it will be noted that the reciprocation apparatus for the movable die platen undergoes severe changes in load during a single casting cycle. Specifically, assuming a die-open starting position, the reciprocation apparatus starts a cycle with a zero load, i.e. no force or stress is imposed thereupon. The load of die reciprocation in a positive direction (acceleration) is them immediately placed on the apparatus, such load increasing to a maximum at the midpoint between open and closed positions of the die and abruptly changing to a negative load (deceleration) which load decreases to zero at the closed position whereupon the reciprocation apparatus is required to supply a very sudden, large, positive, stress-closing force to the die and retain such load during injection and solidification of the casting metal. The reciprocation apparatus is also required to absorb (in a negative direction) this large stress-closing force when the die is relaxed. During the die-opening half of a cycle, the reciprocation apparatus is subjected to loads which are the reverse of the aforedescribed closing loads. Clearly the wear and tear on the reciprocation apparatus can be severely great and good reason exists for the massiveness and frequent breakdowns common in the prior art which was not afforded the benefits of the present invention.

It has been found, however, that the energy cam of the present invention will maintain the reciprocation apparatus for the movable die platen in a substantially force-balanced state during a casting cycle. This result is accomplished by employing the cam and its spring-loaded cam follower to absorb energy during those parts of a casting cycle when excess energy is present, such as during relaxation of the die from its stress-closed position, and dispensing such accumulated energy during those parts of a casting cycle when extra" energy is needed, such as during acceleration of the movable die platen.

In FIG. 8, cam 38 is shown as contoured for one typical casting cycle. The cam surface 41 in the depicted embodiment is of generally elliptical geometry but in other cycles it may assume other configurations. At one apex of the ellipse, there is provided a notch 42 including within its extent about 16 of the cam circumference. Accordingly, the cam follower 39 abruptly enters the notch and equally abruptly exits the same as the cam rotates. Of course, while the follower resides in the notch, it neither imparts energy to nor absorbs energy from the cam. In Position 1 of FIG. 4, the cam follower resides in notch 42 and the die platen is in its stressed-closed position. In the stress-closed position of the die platen, the die is not merely in contact with the other die section or sections as the case may be. Rather, the die is in a compressed state and the framework of the die-casting machine is also stressed, i.e. there is a large quantity of energy stored in the die and its supporting structural framework. I-Ieretofore, upon movement of the die platen from its stress-closed position toward its open position, this stored energy was necessarily assumed by the die reciprocation apparatus. In the present invention, this stored energy is absorbed by the spring 40 associated with the cam follower. This result is accomplished by the follower moving out of the notch 42 and compressing the spring as the die is relaxed from its stressed-closed position and is depicted by the negative" (indicative of die opening) curve between 67 W of 157% in FIG. 4.

As shown in FIG. 4 and the reference to FIGS. 3 and 6, the energy absorbed in spring 40 is returned to the system as the die platen is moved halfway (Position IV) toward its open position (Position VI). This return of energy enables the die reciprocation apparatus to overcome the inertia of the apparatus component and accelerate halfway between closed and open positions of the platen. It is noted that the energy dispensed by the spring increases immediately upon the die platen leaving its closed position, achieves a maximum, and then becomes less as the platen progresses along its cycle, becoming minimum at the aforesaid halfway point. The die platen speed (FIGS. 3 and 6) increases to a maximum at this halfway point, whereupon the cam and its follower cause the spring to commence absorbing energy with resultant deceleration of the die platen, rapidly at first but decreasing to minimum deceleration as the platen achieves its fully open positions.

In FIG. 3, there is depicted a dwell time (IS'IW-ZOZW when the platen is in its fully open position. The duration of such dwell time being accomplished and established by the movement of the G.C. convex cam section 45 interacting with cross 30 of the G.C. Position VI of FIG. 3 depicts the follower at the unnotched apex 43 of the elliptical cam where it will be observed that continuous rotation of the cam would result in immediate changeover of the spring from its open position toward its closed position and reduce the total casting cycle time. During the closing half of a casting cycle, the pattern of energy control by the spring is repeated as for the opening half of the cycle (see Positions VI-X and I, FIG. 5). In FIGS. 3-5, die platen closing forces are depicted as positive" to indicate that they are opposite to the negative" opening forces.

In atypical casting cycle, the platen makes contact with the stationary die platens about 8 prior to the stress-closed point in a platen reciprocation cycle. At this point, there is needed a large and sudden force to stress-close the die. In the present invention, this force is supplied by spring 40 moving into a notch 42 and thereby in a brief span of time imparting a large quantity of energy to the ram 9 of the platen reciprocation apparatus as is depicted in FIG. 5. For purposes of clarity, the abscissa scales of FIGS. 4 and 5 are taken as representing a constant input rotation force so as to expand the scale in a linear manner. If the mechanical advantages of the G.C. and crank were interjected into the FIGURES, the scale would not be linear across a platen reciprocation cycle.

When a powerful prime mover is imparting large quantities of energy to a mechanical system, any severance of the connection such as disengaging a clutch to separate the prime mover from its load, results in severe stresses, i.e. shock, within the mechanical apparatus, especially if the apparatus must be braked. Because the die reciprocation apparatus of the present invention is in a balanced state, it may be disconnected at any point during the platen reciprocation cycle from the prime mover and braked to a stop without introducing abrupt force imbalances which exert great strain and wear upon the apparatus. This capability provides the further benefit of fine control of the movement (or nonmovement) of the die reciprocation apparatus. That is, because the apparatus is maintained in a force-balanced state, it may be stopped or put in motion with only a relatively small force which results in an excellent degree of controllability. When the die is in its stressed-closed position the prime mover may be disconnected and, in effect, the die reciprocation apparatus hardly experiences the change.

With particular reference to FIGS. 1 and 2, the transfer subassembly of the present die-casting machine comprises a Geneva Cross mechanism 52 receiving driving power from a wonn 50 interposed along the length of drive shaft 19 and meshing with gear 51 of the Geneva Cross mechanism. Laterally on opposite sides of gear 51 there are provided

crosses

53 and 54 keyed to

respective shafts

55, 56 which are keyed to

sprockets

57 and 58 respectively. As is more particularly pointed out in FIG. 2, gear 51 has provided on the opposite flat surfaces thereof

respective cam sections

59 and 60 and lugs 61 and 62. It will be realized that upon rotation of gear 51, lugs 61 and 62 respectively engage the slots 63 and 64 (typical) of

crosses

53 and 54 to effect periodic rotation of said crosses in accordance with the circumferential spacing of lugs 61 and 62 on gear 51 and the rotational speed of gear 51.

Referring again to FIG. 1, sprocket 58 has trained therearound a chain 65 which is further trained around sprocket 66 fixedly secured to tubular shaft 67 whereupon rotation of cross 54 imparts rotation to shaft 67 as modified by the gear ratio between

sprockets

58 and 66. Sprocket 57 has trained therearound a chain 68 which is further trained around sprocket 69 keyed to shaft 70 which is coincident along a major portion ofits length with shaft 67 but independently rotatable thereof.

Preferably shaft 67 is hollow and shaft 70 extends therethrough to terminate in a crank 71 operatively inserted within a slot 72 of the central portion 73 of a strip feed arm 74 which is reciprocatably mounted by mounting

means

75 and 76 secured on opposite ends of a transfer arm 93, provided on the terminal end of shaft 67. It may be realized, therefore, that rotation of the strip feed arm 74 is affected through rotational movement of shaft 67 and translational reciprocation of the strip feed arm is affected through rotational movements of shaft 70.

As indicated in FIG. I, strip feed arm 74 is provided at either of its ends with a

core

77, 78 designed to be inserted within the die cavity 16 during a casting operation. These cores are fixedly secured to the ends of the transfer arm.

Referring again to FIG. 1, it may be seen that shaft 67 is mechanically connected by

links

79 and 80 to ram 9 of the die reciprocation subassembly. The respective ends 81, 82 (82 not visible) of

links

79 and 80 contact and ride against a circumferential shoulder 83 provided on shaft 67. These

links

79 and 80 are rotatably retained by an appropriate means such as

blocks

84, 85, 86, 87. The opposite ends 88 and 89 of

links

79 and 80, respectively, are disposed in a contoured slot 90 provided on ram 9 and movable therewith. It will be noted from observing the contour of slot 90 that upon the movement of ram 9 from a closed die position toward an open die position, ends 88 and 89 of

links

79 and 80 will be carried with ram 9 during the initial interval of movement of the ram by virtue of end 88 being contacted by surface 98. Thereupon link 75 is caused to rotate thereby causing end 81 of link 79 to bear against the annular shoulder 83 on shaft 67 and move shaft 67 along its longitudinal axis a distance equal to the distance which ram 9 moves while end 88 of link 79 is in contact with surface 98 of slot 90. As link 75 is rotated, its end 88 slides into portion 91 of slot 90 and the movement of shaft 67 ceases while ram 9 continues its longitudinal movement. Thus the movable die platen l and core 78 move simultaneously as the platen moves part way open. When ram 9 moves toward the closed die position, end 89 of link 80 contacts end 92 of slot 90, causing the link 80 to rotate and its end 82 (not visible in FIGURE to bear against one side of the annular shoulder 83 on shaft 67 and move shaft 67 along its longitudinal direction concurrently with ram 9 moving toward a closed die position. Accordingly, ram 9 and shaft 67 move at the same time and speed toward the die-closed position causing transfer arm 93, hence strip feed arm 74, also to move such that a core (78 or 77 as the case may be) is in position to be inserted into the closed die through an appropriate opening provided therein. Upon ram 9 moving die platen 10 to its closed position, and with the strip feed arm in the appropriate lateral attitude with respect to the closed die, cross 53 is activated and shaft 70 thereby rotated to cause crank 71 to become activated and effect translational movement of strip feed arm 74 to the left in FIG. 1 hence position core 78 within the die 13.

Upon completion of the die injection operation and after the casting has solidified to the extent that it is self-supporting, ram 9 is moved toward an open die position. By design, end 88 of link 79 contacts surface 98 of slot but its movement into portion 91 is delayed until ram 9 has moved the die platen 10 to an open position sufficient for extraction of the casting by rotational movement of the transfer arm 93.

Precise coordination of the axial movements of ram 9 and shaft 67 is highly desirable for the rapid machine movements contemplated in the present invention. With reference to FIG. 1, it may be seen that in the depicted embodiment link 79 comprises two elongated sections indicated at 79' and 70" which are joined by a helically coiled spring having one of its end secured to section 79 and its other end secured to section 79". Spring 100 is strongly torsion loaded at assembly thereby causing sections 79' and 79" to tend to rotate in opposite direction. Such rotation is restrained by end 88 bearing against end 98 of slot 90 (which tends to move ram 9 axially toward die 13) and by end 81 bearing against shoulder 83 (which tends to move shaft 67 axially also but in the opposite direction from ram 9). The directional urging imparted to shaft 67 is transferred through shoulder 83 to end 82 (not visible), thence to link 80, and thence to end 89 which bears against end 92 of slot 90 thereby creating a force loop whereby the ends 81, 88, 82, 89 are at all times retained in intimate contact with their respectively adjacent bearing surfaces. When so maintained in position by the strong torsion force of spring 100, these ends of the links cause the desired precise and definite axial movement of shaft 67 is response to axial movement of ram 9. It is recognized that other linkage arrangements could be made between ram 9 and shaft 67 which would bring about the desired coordinated axial movements. For example, a single link having its ends fitted in appropriate slots provided on ram 9 and shoulder 83 could be employed but such requires more precise fitting between the ends and their respective contact surfaces than does the depicted arrangement.

FIGS. 9 and 9A depicts, in steps, the several relative movements of the transfer mechanism of this invention. Generally, shaft 67 is rotatable and axially slidable, its rotation being effected by intermittent connection to motor 12 as brought about by lug 61 (FIGS. 1 and 2) or gear 51 engaging cross 54 which is mechanically joined to shaft 67 and its axial movement being effected by

links

79, 80 as described above. Shaft 70 is likewise rotatable and axially slidable, its axial movement arising only as its connected strip feed arm 74 is moved axially (of the shaft) by axial movement of shaft 67 whose transfer arm 93 carries the strip feed arm 74. Shaft 70, however, is rotatable in two separate increments, once simultaneously and coextensively with shaft 67 by virtue of lug 61 of gear 51 acting in common with crosses 53, 54 (FIGS. 1 and 2) and once independently of shaft 67 by lug 62 of gear 51 engaging cross 53 and rotate shaft 70. The purposes of these several movements will become apparent from FIGS. 9 and 9A. Specifically, in Step A, die 13 is shown to be fully open. With the die so positioned, strip feed arm 74 is positioned so as to feed a casting 97 (from previous cycle) within a trimming press 47. The casting is frozen onto core 77. Core 78 on the opposite end of arm 74 is completely withdrawn from die 13. Also in Step A, shaft 67 is disposed at one of its limits of longitudinal travel (in the up" direction of the FIGURE).

Step B of FIG. 9 shows the relative positions of the several components as die 13 is moved toward its closed position and shaft 67 is moved therewith. In Step C, the die is fully closed and the casting is in position for trimming. To this point, shaft 67 and arm 74 have only moved longitudinally but have reached their other longitudinal limit (in the down direction in the FIGURE). In Step D, arm 74 is translated laterally to strip core 77 from casting 97 and feed core 78 into die 13. This translational movement is accomplished by lug 62 of gear 51 engaging cross 53 and resultant rotation of shaft 70. As noted hereinbefore in connection with FIG. 1, shaft 70 is provided at one of its ends with a crank 71 through whose action, rotation of shaft 70 is converted into lateral translational movement of strip feed arm 74.

Upon completion of the strip feed action, molten metal is injected into the die. As the metal solidifies, Step E, the trimming operation is completed, the trim press opens and in Step F the die platen 10 is moved toward its open position, carrying with it the casting and shaft 67, hence arm 74 and core 87. In Step G, shaft 67 reaches its limit of longitudinal travel and platen 10 continues its movement so as to become separated from the casting. As desired, an appropriate ejector pin 99 may be provided to assist extraction of the casting. As platen 10 moves away from the casting,

shafts

67 and 70 are simultaneously activated to rotate equally, thereby simultaneously rotating transfer arm 93 and strip feed arm 74 (Step H). By this means, there is no rotation of arm 74 relative to arm 93, hence no lateral translational movement of arm 74 as it is swung 180 to move casting 97 away from die 13 and into trim press 47 to complete the cycle. In the absence of such simultaneous rotation of

shafts

67 and 70, there would occur relative rotation therebetween the movement of crank 71 such as would move arm 74 laterally and result in casting 97 being out of position for trimming without further complicated coordination of movements.

Additionally, the benefits of the present invention have been found best achieved by continuously subjecting the die 13 (FIG. 7) to a coolant maintained at a temperature of at least between about room temperature and 50 percent of the solidification temperature of the casting metal. Preferably this coolant is circulated through a network of coolant channels 94 (shown in section) within the die platens l0, l and very close to the die cavity wall 16. Still further enhancement of benefits has been found possible by providing the strong die platens with an insert 95 of less strength but having greater thermal conductivity than the platens. In this scheme of things, heat is rapidly withdrawn from the molten cast metal and the casting is caused to solidify very quickly yet the die cavity wall never cools below about 50 percent of the solidification temperature of the casting metal. It is of significance in the present invention that during the time that the die is open, heat is rapidly transferred to the die cavity wall to minimize cooling of the wall during the open interval.

Suitably, the channel system may be disposed about oneeighth inch from the die cavity wall 16. Water coolant maintained at a constant temperature of about 70 F. to 360 F. may be continuously circulated through the channel system when casting products having melting points as high as about 730 F. Other coolants, if desired, may be substituted for the water.

Conventional metal injection apparatus 37 (FIG. 1) comprising a pump 96 for moving molten metal 35 from a heated vessel 36 to the die may be employed in this invention.

Employing the present concepts, it has been possible, using a single cavity die, to repetitively cast in excess of 60 acceptable products per minute each having a mass on the order of ounces. Because of the capability of the present invention to maintain the die cavity wall at or near the desired casting temperature, products having about 0.030 inch thin walls can be successfully cast at the aforesaid rate while maintaining a structurally sound casting having negligible chill marks.

Further, the hot die cavity wall and increased speed of platen reciprocation obtained with the present method permit the use of lower molten metal injection pressures and slower injection rates, all with an overall increase in the rapidity and repeatability of the casting operation. For example, the present invention has been successfully employed to produce castings at the rate of 60 per minute, the castings have wall portions of 0.100 inch thickness.

Whereas the present invention has been described by referring specifically to the preferred crank and Geneva Cross mechanisms, other mechanical arrangements performing like functions could be substituted without departing from the scope of this invention.

What Is Claimed Is: 1. Apparatus for die casting comprising a multisection die having at least one die section which is reciprocatable between open and closed positions and in cooperation with the remainder of the die defining a casting cavity when said movable die section is in its closed position, a prime mover, reciprocation apparatus interposed between said movable die section and said prime mover adapted to intermittently and cyclically move said die section between its open and closed positions and including torque-manipulating means adapted to maintain said reciprocation apparatus in a substantially force-balanced state during a major portion of a reciprocation cycle of said die section,

injection means adapted to admit liquid matter into said casting cavity when said die section is in its closed position where said liquid matter solidifies into a self-supporting casting, core mount means including core members disposed thereon each movable by said core mount means between a position at least partially within said casting cavity and a position external of said casting cavity whereby said liquid matter substantially solidifies about that portion of said core positioned within said cavity and is subsequently moved away from said die with said core member,

transfer means connected with said core mount means so as to move said core mount means and said core members between the several positions of said core members, and

means connecting said transfer means to said reciprocation apparatus so as to move said transfer means and said core members in coordination with reciprocation of said die section whereby one of said core members is positioned in register with said casting cavity when said die section is in its closed position.

2. The invention of claim 1 wherein said reciprocation apparatus comprises shaft means first mechanical means connecting said shaft means to said prime mover for rotation of said shaft,

second mechanical means connecting said shaft means to said reciprocatable die section,

energy transfer means disposed in energy transfer relationship with said shaft and operative in response to the torque forces imposed on said shaft to exchange torque forces between itself and said shaft so as to reduce the torque force imposed on said shaft.

3. The invention of claim 2 wherein said energy transfer means comprises a cam secured to said shaft and rotatable therewith and a cam follower biased in contact with said cam whereby rotation of said cam results in cyclic change in the degree of bias force exerted against said cam by said cam follower and resultant cyclic change in the torque experienced by said shaft.

4. The invention of claim 1 wherein said transfer means includes a first element adapted to impart rotational movement to said core mount means to swing said core members between their several positions and a second element adapted to effect lateral movement of said core mount means and core members so as to simultaneously move one of said core members to its position within said casting cavity and to extract the other of said core members from a casting which has previously been swung to a stripping position outside said casting cavity.

5. The invention of claim 1 and including a stripping station spaced from said die and including means for grasping a casting attached to a core member swung to said station whereby said casting is retained at said station when said core member is moved away from said station.

6. In a die-casting machine having a multisection die, at least one die section of which is reciprocatable between open and closed positions by a reciprocation apparatus and cooperating with the remainder of the die to define a casting cavity when in its closed stripping position, apparatus for transferring a casting from said die cavity to a position outside said die cavity and comprising core support means rotatably mounted adjacent said die,

first and second core members disposed on said core support means first rotatable and axially movable shaft means carrying said core mount means on one of its ends and connected at its opposite end to a source of power for rotation whereby upon rotation of said shaft means said core support means and said core members are swung about the axis of said shaft means so as to move that core having a casting thereon away from said die cavity and to swing the other of said core members into register with said die cavity,

second rotatable shaft means connected at one of its ends to said source of power for rotation of said second shaft means and connected at its other end to said core support means whereby rotation of said second shaft moves said core support means in a direction substantially perpendicular to the axis of said second shaft means so as to move that core member registered with said die cavity into said die cavity and simultaneously extract the other of said core members from the casting solidified thereon, means cyclically and intermittently connecting said first and second shaft means, respectively, to said source of power, means connecting said first shaft means to said die section reciprocation apparatus so as to move said first shaft means, said core support means and said core members in coordination with the reciprocatory movement of said die section and in a direction parallel to the reciprocatory path of said die section and thereby effecting removal of a solidified casting from that portion of the die which is stationary. 7. The invention of claim 6 wherein said core members are oppositely disposed on said core mount means.

8. The invention of claim 6 wherein said first and second shaft means are coaxial.

9. The invention of claim 6 wherein said second shaft is connected to said core mount means by a crank member.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 604, 499 Dated September 14, 1971 Inventor(s) Franck M. Picker It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line ,2, change "he" to --the--.

Column 1, line 53, following "machine" and before "Massive",

insert a period.

Column 1, line 72, change "320" to --32--.

Column 2, line 36, following "remainder", delete --6--.

Column 10, line 27, change "70" to --79"--.

Signed and sealed this 1 th day of April 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK At testing Officer Commissioner of Patents QM (1069) uscoMM-oc sosnw e a U 5 GOVERNMENT PHINT'NG OFFICE: IQD 0-356-33l

Claims

1. Apparatus for die casting comprising a multisection die having at least one die section which is reciprocatable between open and closed positions and in cooperation with the remainder of the die defining a casting cavity when said movable die section is in its closed position, a prime mover, reciprocation apparatus interposed between said movable die section and said prime mover adapted to intermittently and cyclically move said die section between its open and closed positions and including torque-manipulating means adapted to maintain said reciprocation apparatus in a substantially forcebalanced state during a major portion of a reciprocation cycle of said die section, injection means adapted to admit liquid matter into said casting cavity when said die section is in its closed position where said liquid matter solidifies into a self-supporting casting, core mount means including core members disposed thereon each movable by said core mount means between a position at least partially within said casting cavity and a position external of said casting cavity whereby said liquid matter substantially solidifies about that portion of said core positioned within said cavity and is subsequently moved away from said die with said core member, transfer means connected with said core mount means so as to move said core mount means and said core members between the several positions of said core members, and means connecting said transfer means to said reciprocation apparatus so as to move said transfer means and said core members in coordination with reciprocation of said die section whereby one of said core members is positioned in register with said casting cavity when said die section is in its closed position.

2. The invention of claim 1 wherein said reciprocation apparatus comprises shaft means first mechanical means connecting said shaft means to said prime mover for rotation of said shaft, second mechanical means connecting said shaft means to said reciprocatable die section, energy transfer means disposed in energy transfer relationship with said shaft and operative in response to the torque forces imposed on said shaft to exchange torque forces between itself and said shaft so as to reduce the torque force imposed on said shaft.

6. In a die-casting machine having a multisection die, at least one die section of which is reciprocatable between open and closed positions by a reciprocation apparatus and cooperating with the remainder of the die to define a casting cavity when in its closed stripping position, apparatus for transferring a casting from said die cavity to a position outside said die cavity and comprising core support means rotatably mounted adjacent said die, first and second core members disposed on said core support means first rotatable and axially movable shaft means carrying said core mount means on one of its ends and connected at its opposite end to a source of power for rotation whereby upon rotation of said shaft means said core support means and said core members are swung about the axis of said shaft means so as to move that core having a casting thereon away from said die cavity and to swing the other of said core members into register with said die cavity, second rotatable shaft means connected at one of its ends to said source of power for rotation of said second shaft means and connected at its other end to said core support means whereby rotation of said second shaft moves said core support means in a direction substantially perpendicular to the axis of said second shaft means so as to move that core member registered with said die cavity into said die cavity and simultaneously extract the other of said core members from the casting solidified thereon, means cyclically and intermittently connecting said first and second shaft means, respectively, to said source of power, means connecting said first shaft means to said die section reciprocation apparatus so as to move said first shaft means, said core support means and said core members in coordination with the reciprocatory movement of said die section and in a direction parallel to the reciprocatory path of said die section and thereby effecting removal of a solidified casting from that portion of the die which is stationary.

7. The invention of claim 6 wherein said core members are oppositely disposed on said core mount means.