US2774122A - Die-casting machine - Google Patents

Description

Dec. 18, 1956 F. HoDLER DIE-CASTING MACHINE 7 Sheets-Sheet l Filed Feb. 5, 1953 INVENTOR Fritz'` Hodler Dec. 18, 1956 F. HODLER 2,774,122

DIE-CASTING MACHINE Filed Feb. 5, 1955 7 sheets-sheet 2 INVENTOR Fritz Hodler' Dec. 18, 1956 F. HODLER 2,774,122

DIE-CASTING MACHINE Filed Feb. 5, 1953.

7 Sheets-Sheet 5 INVENTOR Fritz Hodler Dec. 18, 1956 F. HODLER DIE-CASTING MACHINE 7 Sheets-Sheet 4 Filed Feb. 5, ,1953

INVENTOR Fritz Hdler F. HODLER DIE-CASTING MACHINE Dec. 18,` 1956 '7 Sheets-Sheet 6 Filed Fab. 5, 1953 llllllllll INVENTOR Fritz Hodler Dec. 18, 1956 F. HODLER 2,774,122

DIE-CASTING MACHINE Filed Feb. 5, 1953 7 Sheets-Sheet '7 INVENTOR Fritz Hodler United States Patent O DIE-CASTING MACHNE Fritz Hodier, Territet, Switzerland Application February 5, 1953, Serial No. 335,215

Claims priority, application Switzeriand February 7, 1952 8 Claims. (Cl. 22-5S) The invention relates to die-casting machines.

The known methods, particularly the cold-chamber process, consist in forcing into a die under elevated pressure a molten metal charge which corresponds to a metal volume which is considerably greater than the volume of the finished casting. f

The cold-chamber process is generally carried out as follows:

A molten metal charge is poured into an injection cylinder a plunger reciprocating in this cylinder is then pushed under strong pressure, i. e. with high speed, into said cylinder, so as to inject the molten metal contained in the cylinder into the die cavity adjacent the cylinder.

This process is not fully satisfactory. As prior to the injection stroke a certain amount of air is entrapped in the cylinder, it frequently happens that the castings contain blowholes and that a substantial percentage of the castings have to be discarded for this reason.

It has been attempted to obviate this drawback by lowering the injection speed in order to give the air entrapped in the die and in the injection cylinder time to escape before the metal is completely forced into the die cavity. This however, introduces another drawback. Because of the low injection speed, certain parts of the casting freeze before the whole structure is cast. This produces surface irregularities which are not permissible.

In order to overcome the recited defects, at least in part, cold-chamber machines have been designed wherein a higher pressure is exerted on the injecting piston after a part has been cast in the usual manner. The purposeV is to compress the air mixed with the molten metal to such an extent that the air inclusions which may occur are ot' small size; in this way, the surface properties of the castings are improved. However, the use of very high pressures requires the construction of very heavy machines, which have a mediocre output from the point of view of their production cycle; in addition, the blow-holes, though smaller, remain nonetheless in the castings.

An object of the invention is to provide a cold-chamber machine suitable to carry out my new process.

Another object of the invention is to provide a suitable control mechanism for governing the injection velocity applied to the machine.

Other objects and advantages will become apparent from a consideration of the specification and claims.

The process according to the invention consists in effecting the injection of the charge in two principal steps whereby the rst injection step is carried out at a lower speed than the second step; in this way, the air entrappedin the injection cylinder is evacuated during the rst step and the die cavity is completely filled by the metal in the second step.

A cold-chamber machine for carrying out the process is provided with an automatic control adjusted to secure the injection movement in two principal distinct steps; in the iirst step a relatively slow movement is imparted to the plunger to allow the air entrapped in the injection cylinder to escape; the second step consists in a quick dis- 2,774,122 Patented Dec. 18, 1955 ice placement of the plunger causing the injection proper of the metal into the die. i

Some preferred forms of the invention are shown, by way of example, in the drawingin which Fig. l is a sectional side elevation of a cold-chamber die casting machine, showing diagrammatically the arrangement of a control mechanism according to the invention;

Fig. 2 shows a detail of a control mechanism;

Fig. 3 is similar to Fig. 1 and shows diagrammatically another form of a control mechanism;

Fig. 4 shows constructional details of a control mechanism according to Fig. 3;

Fig. 5 is, on large scale, an elevational View of a part ot the mechanism of Fig. 3;

Fig. 6 shows a construction detail of the injection cylinder;

Fig. 7 is a diagram representing a complete machine in another embodiment of the invention;

Fig. 8 is a partial section of the die of the machine o Fig. 7;

Fig. 9 shows elements of Fig. 8 viewed from the die cavity;

Fig. 10 is a similar view taken from the die cavity and showing the displaceable die section;

Fig. 11 is a time diagram illustrating the injection stroke; this diagram contains also a curve of the speed variations of the injection plunger as a function of its travel;

Fig. 12 shows diagrammatically the various injection phases during one injection stroke; and

Fig. 13 is a partial diagram of still another modification of a machine embodying the invention.

With reference to Fig. l, the machine comprises aV frame 1 on which the casting die is fastened. An injection cylinder 3 is located in the frame 1, and an injection plunger 4 is mounted for sliding movement in said cylinder 3. A moving mechanism, in this case a piston 5, operated by a fluid under-pressure, is provided to displace the plunger 4 in the cylinder 3. The uid under pressure is fed into the cylinder 6, in which the piston 5 slides, through a feed line 7 which is controlled by the main gate valve 8. The feed line 7 contains, in addition, a valve 9 for regulating the admission of the pressure fluid to the cylinder 6 and thereby controlling at the same time the displacement speed of the piston 5 and of the injection plunger 4.

The feed line is provided with a by-pass 10, which also feeds the piston 5. This by-pass is controlled, on the one hand, by an automatic stop valve 11 and, on the other hand, by a regulating valve 12 of the same type as the valve 9.

The machine represented in Fig. l operates as follows:

After a molten metal charge has been poured into the cylinder 3 through the pouringV hole. 13, the main gate valve 8 is opened. The fluid under pressure passesthrough the regulating valve 9 and is directed into the cylinder '6. As the valve 11 is closed, only the ratey of feed of the fluid through the va1ve9 determines the speed of displace.- ment of the piston 5 and plunger 4.

This. speed is made rather slow so that the air entrapped in the die 2 and the cylinder 3, above the molten metal, may escape through the vents provided in the die 2.V

After the piston 5 and plunger 4 have traveled for a: sulhcient distance to expel the ent-ire air entrapped in the cylinder 3 and before the molten metal enters the die, the valve 11 is automatically opened, whichy produces an additional supply of huid under pressure to the; cylinder 6 and consequently an increased velocity of the piston 5 and plunger 4. .The injection proper of' the molten metal then takes place at high speed, so that the casting freezes only after it has been completely cast. This two- Y 3 step injection, Where the first injection Vis slower than the second step corresponding to the injection proper, allows of obtaining castings which are free of blow-holes or air inclusions and whichjhave la perfectnsurfa'ce. As thev process permits of working at lowerp'ressures than those conventionally employed, the risk'of accidents due to opening of the die and ejectionv of the molten metal is eliminated.

The automatic opening of the valve 11 to start the second injection step may be brought about in various ways.

For instance, valve 11mayA be `controlled by a timer which is started with the opening of the main valve 9 and actuates the opening of valve 11 after a predetermined interval Whichv is chosen'in accordance with the feed of valve 9. In practice, the point at which the plunger 4 'on'its' forward stroke will have completely expelled the air entrapped in cylinder 3 will be calculated and the timer will be set accordingly. l

It is to be understood that other devices can be provided for controlling the automatic opening of the valve 11.VV SuchV devices may be operated mechanically, pneumatically, hydraulically, electrical-ly or by a combination of such means and beractuated either by theplunger 4 or by the molten metal in the injection cylinder.

A mechanical control device for opening the valve 11 by the movement of the piston and plunger 4 is shown,

by way of example, in Fig. 2. vThis device comprises a roller 14 mounted for movement with the piston 5V and plunger 4. 'Ihe valve 11 is actuated by a rod 15. A lever 16 is, at 17, pivotally mounted on the framey 1 and connected by a pin 18 to the push-rod 15. The lever presents -to the roller 14 a sloped track 19 which constitutes a kind of cam. Y i

` V'Ihe device is shown on Fig. 2 at the beginning of theV stroke of the plunger 4. When, after the first injection step, the roller 14 abuts against the shoulder 20, it rocks the lever 16, which then assumes the position shown Vin vdotted lines. This position of the lever 16 corresponds tothe open position of the Valve 11. YThe device allows of selecting the point Vof shifting from the first injection step into the second step by loosening the screws 21 and changing the position of the rol1er-14 withv respect to the'plunger 4.

The Yoperation of the gate valve 11 may be adjusted to a sudden or gradual opening by imparting aY suitable Y form and grade tothe slope 19.

Fig. 3 shows diagrammatically a modification of the Vinvention where the opening of the valve 11 is controlled valve 27, the air pressure opens the gate valve 11, by

means of apiston or a membrane. After opening of the main Valve 3, the plunger 4 ad vances in the cylinder 3 at a relatively low speed. When the molten metal reaches ythe level of the contact 23, a

embodiment, one of the electric conductors leading to the amplifier 25 is connected to the mass of the machine whereas the other conductor is connected to said terminal. Y

It is obvious that also two terminals, insulated against the die 2, can be provided in the chamber 22 and electrically connected with the amplifier 25. y

Instead of providing electrical contact between the two conductors leading to the amplifier 25 throughV the molten metal itself, the contact can be established by Van intermediary metal piece which is displaced by the molten metal when it reaches the level of the contact 23 in the chamber 22.4 For instance, a cylindrical hole can be provided in the wall of the chamber 22 andv a plunger can be slidably mounted in said hole. The terminals of the electrical conductors to the kamplifier 25 are located at the bottom of V-said hole, and contact between said terminals is established by the plunger when the -latter is pushed bythe molten metal into the hole.

,Such plunger can be replaced by any other metallic im plement capable of being displaced by the molten metal yon filling the chamber 22.

a predetermined level in the chamber 22 located at the i exit end of the injection cylinder 3.

The detector device is also a contact 23 shown on anY v enlarged scale in Fig. 5. Y

According to Fig. 4, a transformer 30 -is connected withV its terminals 31 to the lines of the supply circuit. This transformer is provided to maintain the terminals 32 of the secondary circuit under low tension. A relay 33 and the contact 23 are placed in the secondary circuit.

VThe contacts 34 of Vthe relay 33 control the feed circuit of an electromagnet 35 controlling a first valveV 36.

The first Valve 36 is held by a spring 37 on its closed position at rest and actuates a hydraulic servomotor 38 consisting of a cylinder'39 in which a piston V40 isA slidably arranged.- This piston Vcarries a valve disc 41 which is held in its position `of rest yon a seat 42 by aspring 43. The disc 41 controls the conduit 10, which constitutes the by-pass feed line for the piston 5 during the second Y second step.

current is produced,.whic'h, jamplified by the device 25,

closes the relay 24; The electromagnet 26 is then energized'and causes the opening of the gate valve 11 by the intermediary of the valve 27. Thus, the second injection step is started and the molten metal is forced at great speed into `the die 2,. l Y

The electrical contact 23 may be, for,instance,.a'ter minal insulated against the die 2 and the machine frame -1 and ending flush with awall of the chamber 22. In this case, the electrical contact is established by the' I the chamber 4S.

It is to be noted that'in the diagrammatic representaV tion of this embodiment (Fig. 4) the gate valvesV for the hydraulic kcontrol are shown von a larger scale than theY Y die andthe injection plunger. The yoperation yof the mechanism shown in Pig. is `as follows: After the molten metal has been poured into the cylinder 3, the operator 'opens the main valve lS'to the desiredV extent. A'part of the compressed fiuid passes Y through the conduitV 7 and the regulating valve ,9 into :the cylinder '6 and pushes the piston 5 and injection plunger 4. Y This movement of the plunger 4 corresponds `to the first injection step.

During this first step, the Ycompressed fluid acts vonV either side of the disc 41 in the chamber 44'as well'as in ,It acts also in the chamber 46 on top of the first disc 36, through a channel 47.

The remainder of the control mechanism for l As soon as the molten metal reaches the level of the Contact 23, lthe secondary circuit of the transformeri) is closed and the relay 33 is energized. The contacts 34 join and the iirst disc 36 is raised from its seat by the `electromagnet 35.

The compressed iiuid can now act in the `cylinder 39 and push the piston 40 downwardly, which displaces the valve disc 41 from its seat 42 against the pressure of the spring 43.

The iuid under pressure flows `then out toward the cylinder 6 through the conduit 10 and the regula-ting valve 12, which produces the second step of rapid injection.

Instead of using a sou-rce of alternating current in this last modification, a source of direct current can -be employed, it is sufficient for this purpose to replace the transformer 30 by a commutator for direct current.

Such an installation operated with direct current has Ithe advantage that it insures ythat the reaction time for the opening of the valve 41 is always exactly the same.

If, in the last described embodiment, a suiiiciently strong electromagnetic valve control is employed, it is possible -to omit the servomotor 38 and to actuate the rvalve disc 41 directly bythe electromagnet 35.

According to Fig. 5, the contact 23 can be designed as an electrode 48 of which the tip located lin the chamber 22 is surrounded by a cone 49 of insulating refractory material `of t-he type used for spark plugs of explosion engines. Said cone 49 is held laterally in ia sleeve 50 disposed in a conforming seat 51 of `the die. A second sleeve 52 is arranged ybehind the cone 49 to ensure its axial position in spite of the high injection pressures, These sleeves 50 and 5-2 are held in the die Iby a threaded member 53 screwed into the die. An insulating sheath 54 is provided around the electrode 43. The outer end of the electrode carries a `terminal '5 for a connection with the secondary of the transformer 30.

The electrode 48 can also be mounted in the sleeve 5t), eccentrically to its axis. In this way, it is possible to adjust the height of the electrode 48 by turning the sleeve 50 on its seat 5'1. Such an adjustment of the position of the electrode 48 permits of varying the starting time of the second injection step by some thousandths of a second.

In lorder to prevent a too strong attack of the contact 23 by the high `temperatures of the molten metal, the contact may .be arranged in an appendage of the chamber 22, provided, for instance, at the side thereof. This appendage needs only have a width of several tenths of a millimeter in the separation plane of the two parts of the die. After lthe molten metal has entered said appendage and established the lcontact closing ythe relay circuit '.33, it freezes quickly, which prevents any injury or smearing of the contact v23.

Other means may be provided to ensure and control the injection `in two distinct steps. For instance, the valve 12 may 'be omitted, in which case the maximum opening of the gate valve 111 is regulated in accordance with the injection speed chosen for the second step.

In another modiiication, the by-pass may be omitted. The shift from the first to the second injection step is then carried out by acting directly on the gate valve 9, i. e. by increasing the efiective cross l.section for passage of the compressed fluid at the end of the rst injection step. This control of the valve 9 can lbe effected in the same way as described with respect to the valve 111, i. e. by means of a timer 'or mechanically from the 'plunger 4 or by pneumatic, hydraulic or electric means.

lFig. 6 shows a modification of the injection cylinder 3 and its plunger 4 which can be applied to all embodiments of the invention described hereinbefore. According to this modification, a passage 28 is provided in the cylinder 3 to allow the air entrapped in said cylinder to v escape directly from the cylinder into the atmosphere in the first par-t of the injection stroke of the plunger 4.

Said passage is preferably construed in 'form of a E? groove extending in a wall of the cylinder 3 over part of its length from the admission end inwardly. As will be noted in viewing the drawing, the bottom of said groove is inclined with respect to the axis of the cylinder 3.

In lall the described embodiments of the invention, the injection plunger 4 is always controlled by a shot piston 5 actuated by a fluid -under pressure. However, it is .to be understood that my two-step injection process can also be applied to machines in which the injection plunger is mechanically or electrically actuated.

My new process is applicable not only to cold-chamber injection machines but also to hot-chamber injection machines where the metal held in the molten state in a pot is expelled in successive charges of an injection plunger through Ia conduit in form of a gooseneck carrying the molten metal to a die.

On the other hand, the new process can be applied not only to machines using the horizontal shot end but also to vertical type shot end machines. The machines for carrying out the process may be machines of the construction described or old type transformed machines, which are provided with an automatic control valve of the type of the gate valve l11.

The two modifications shown in Figs. 7 to 13 are also cold-chamber die casting machines suitable for carrying out the process o f the invention.

In these latter machines, however, the evacuation of the air contained in the die prior to the injection proper 4of the molten metal is improved and rendered still more effective, due to the provision of auxiliary air suction means.

These machines 'operate according to an improved process in which, after the injection cylinder has been iilled and at the en-d of the first of the principal operative phases, a supplemental air suction phase is automatically triggered, whereby the injection proper of the metal into the die is also automatically started successively to saidV air suction phase. These machines are of the same type as those previously described herein, but are provided, in addition, with a suction pump so as to remove the air entrapped in the die already, prior tothe second phase of operation, i. e. the injection phase.

The evacuation of the air by suction from the dies of pressure-operated die casting machines, before the metal is cast, has not found general acceptance due tothe -diiiiculties met in the `operation of, such machines. In such machines, it is necessary to adjust with great precision the start and stop of the air suction phase with respect to the metal injection phase proper so as to prevent any access of molten metal particles into the air pump.

The machines illustrated in the drawings avoid this difiiculty. They are distinguished from the known machines of this type by the provision of a detector element which is responsive to the absolute pressure in the die and allows the commencement yof the `second phase, i. e., the phase of rapid injection, only after a predetermined vacuum has been obtained in the die. The air suction conduit is controlled by a valve which automatically closes the air exhaust port of the die before the molten metal comes in contact therewith.

In the die-casting machine shown in Fig. 7, the reference numeral 69 designates the frame on which a die 61 formed by the two sections 62 and 3 is mounted. A locking mechanism is provided to press said two halves tightly against each other. in the shown embodiment, this locking mechanism comprises a hydraulically operated piston 64, which actuates, by means of toggles 66, a rod 65 and has the function of pressing a locking plate 67 against the die section 62 so a-s to maintain said part in contact with the other section 63. The locking plate 67 is supported by shafts 68 which reciprocate in supportsk 69 provided at lthe left hand side of the machine frame. An linjection cylinder 70 is located in the right hand portion of the frame 69. An injection plunger 71 is avverse" mounted for reciprocating movement in cylinder Y70' and is. operated by a driving mechanism. In the showniembodiment, said driving mechanism consist-s in a hydraulically actuated piston 72. Said piston 72 is displaced by the action of the hydraulic liquid in a cylinder 73, which is fixedly arranged in a support76 secured to the base 7S of the machine. Y 1

The hydraulic liquid for the actuation of the pistons 64 and 72 is delivered by a pump 77 driven by a motor 78. Said pump withdraws the liquid from a reservoir 79 and returns it to said reservoir through the general feed circuit 80 of the machine.

The hydraulic circuitY 80 is provided with a control valve block 81comprising four valves 82, 83, 84, and 85, all of which are actuated by the same controllever 86. A conduit 87, which is part of the hydraulic circuit 80, feeds the hydraulic liquid into the block 81, and a conduit 88 delivers the hydraulic liquid from the block 81 into the cylinder 73, against the head surface of the piston 72. In the conduit 88, there is a control valve 89, the needle of which is actuated by a pneumatic servomotor 91. Compressed air is supplied to said servomotor 91 through a pipe 92, and an electromagnetically operated four way valve 93 is provided to control the displacement of the lservo-motor 91 in the one or other direction, which ydisplacement determines the closing lor opening of the valve 89. The valve 93 is provided with two solenoids 93a and 9317. Energizing the solenoid 93a by an electric current produces opening, and energizing the solenoid 93b produces closing of the valve 89. It should be noted, however, that the piston of the-servo-motor 91 is not displaced into an intermediary position when the energizing of either of the solenoids 93a and 93b is stopped after the valve 89 has been opened Vor closed. At the contrary, when the energizing current for yone of the solenoids is cut off, the valve 89 remains inV the position into which it has-been brought by the servo-motor on energizing said solenoid.

In addition, a by-pass 94 allows a small amount of hydraulic liquid to flow through the conduit 8S without being subjected to the action of the valve 89. This bypass is provided VVwith a regulating valve 9S. Another regulating valve 96 is provided in the circuit 38 near the cylinder 73.

The feed `of the hydraulic liquid through the conduit 88 into the cylinder 73 i-sintended to vcontrol the first part of each injection stroke of the piston 72.V This first part of they injection'stroke is carried out ,at reduced speed. The second part of the injection stroke, which must be eiected at high speed, is controlled by another hydraulic feed circuit.V Said latter feed circuit is independent of the block S1 and comprises a conduit 97, which is controlled by a'valve 98 of the same' type as valve VS9. Also the needle 99 of this valve vis controlled by a pneumatic servo-motor V100, the movements of which into the 'opening and closing position are determined by energizing the solenoids 100i: and 1001:, respectively.

An air cushion accumulator 101 is provided on the conduit 97 as close as possible to the valve 98 to prevent Y shocks.

. It will be noted that the return strokes of the pistons 72 and 64 are controlled from this conduit 97. A pipeV 102 connects said conduit 97 with the cylinder 73 so asV to feed uid under pressure into the left-hand side of the piston 72. Another pipe 103 is provided to deliverY fluid under pressure onto the right-hand side of the piston 64 soV as to control the opening of the machine by separating the two halves 62 and, 63 of the die.

The machine is provided with an air suction pump 104 driven by an electromotor 105, which pump removes the Y air entrapped in the die 61 prior to the rapid injection of the molten metal. This pump 104 is connected with Vthe die sectiony 62 by means of a pipe 106, which is controlled by an `electromagnetically activated valve 107.

In addition, 1 provide a detector element responsive to the absolute pressure in the die. This detector element 1s aY contactmanometer 108 placed in the conduit106.

A telescopic device 109 allows of prolonging-or-shortening the conduit 106 during the closing and opening of thell tion of rest, its contact piece 112a allows of energizing the solenoids 93a and 100b, which produces the opening of valve 89 and the closing of valve 98.V

The numeral 113 4designates Va transformer, the primary of which is fed through the terminals 111. The secondary feeds a current of low voltage into a circuit 114, which contains in series a relay 115, the contact Vmanometer 108 and a detector device withA contact electrode 116. This detector device 116 acts as an interrupter which is closed -by the molten metal when the metal has completely lled the injection cylinder70. An interrupter 117 allows the Vvoperator to short-circuit the element 116 if the use of the latter is not desired or impossible. Y

A contact 118 is arranged near the rod 119 which rod connects the piston 72 and the plunger 71. 1 This Vcontact 118 is actuated by a nger 120 mounted on the rod 119. It controls a circuit 121 supplied with electric current from the contact piece 112b of the contact 100, which contact piece is only under voltage when the operating lever 8,6 is in position 4, i. e. in the position for performing the injection stroke of the machine. The contact 118 is provided to govern through the circuit 122 onthe one hand the vclosing of the valve89 and on the other hand,

the -opening of the electromagnetick suction controlv valve 107. Y Y Y A Y An interrupter 123, actuated bythe relay 115,-is put into the circuit 121. VSaid interrupter 123, when closed, effects the opening of the valve 93 over the electric conductor 124 and the solenoid 100:1.

'In order to prevent the-risk of entrainingmolten metal particles in the conduit 106 at the end ofthel air suction phase, a valve means 125 is provided in the die section 62V in close proximity to the die cavity, which corresponds tothe form of the castings.

Said valve means V125 is represented on a larger scaleV It closes automatically the air outlet inFigs. 8 and 9, 126 'before the molten metal comes in contact with said outlet. YThe operating principle of such va-lve is described in detail in my application Serial No. 335,216 filed on 'they lsame date as this application.

Briey, its construction and operation are as follows: f

The yvalve means 125 comprises a piston reciprocating Y in a jbore 127 ofthe die section 62. i The piston'hasat 128 a reduced diameter or a groove V12S to permit freeV passage of the air from the die cavity towards the outlet 126, when the piston is in its right-hand end position shown in Fig'.l 8. VThe closing movement of the piston, i. e. lthe displacement of the valve 125 towards theV lefthandfside of Fig. 8, is brought about by a pis/ton y129,V which -reciprocates in a bore 130 of the die section 62.v

The piston 129. and the check valve 125 are connected by means of a lever 131, which islink'ed at 132'to a support 133 fixed in the die section 62( Said piston 129 is actuf ated -by the molten metal itself when the die cavity is lled.' During the filling .of Vthe die cavity, the air entrapped therein escapes through a channel 134Y opening piston 1,29, said piston is displaced towards the left-'hand side offFig. 8, Which produces the closing movement of the checlevalve 125.` Y

When the operating. lever 86 is in position I, which corresponds to the posii Fig. illustrates, by Way of example, the arrangement of the checa valve 12S in the die section `62. As will be noted on viewing Fig. l0, the channel 135 branches oi the channel for admitting the molten metal into the cavity F, whereas the channel 154 branches o directly from said cavity. According to this arrangement, the mol-ten metal controls the closing of the valve 125 before the die cavity F has been completely tilled.

The operation of the machine represented in Figs. 7 to 10 is as follows:

After a charge of molten metal has been brought into the cylinder 70 through the pouring 4hole 76d, the operator actuates the lever 36 in the direction of the arrow l. ln position i of the shift lever 86, the valves 82 and 33 of the block 81 are closed and the valves S4 and 85 are open; current flows over contacts 11d and 112g; therefore, the valve 89 is opened and the valve 93 is closed. As soon as the lever 36 reaches the position 2, the valves 84 and 35 close and the movable contact 11e disengages the contact 112a. However, though the current energizing the solenoid-s 93a and itlb is cut off, the valve 89 remains open and the valve 98 remains closed. in position 2, `the die is always open and the injection plunger 7l is always in its retracted position.

As soon as the lever reaches the position 2, the valve S2 opens while the valve 83 remains still closed. As the valves S4 and are kept closed, hydraulic uid passes from the conduit S7 through the valve 22 so as to act upon the piston 64, which produces closing of the machine, i. e. the pressing of the two halves o2 and 63 of the die against each other. 1n this position 3, the valve S9 is always open and the valve 9d is closed. The injection plunger 71 is still in its retracted position.

When the lever do comes into the position 4, the valves 82. and 33 are open and the valves 84 and 35 are closed. In addition, the contacts 11G and 112b are closed.

As a result of the opening of valve S3, hydraulic uid hows from the conduit 87 through the pipe S3 and branches into two currents, of which the larger one passes through the valve 89, and the smaller one passes through the valve 95 of the by-pass 94. The flow of the uid in these two lines is then adjusted by the regulating valve 96, the position of which determines the rst slow injection phase of the plunger 71. In the course of this rst main phase of slow injection, the plunger 71 moves from A to B (Fig. 12). The arrival of the plunger 71 at the point B of its course (71b) corresponds to the time of engagement of the finger 120 with the butterfly Contact 118, which produces closing of the valve 89 over the wire 122 and the solenoid 93b, and opening of the valve 167 so as to start the supplementary air suction phase.

The weak flow of fluid through the by-pass 94 continues displacing the plunger 71 at low speed in the direction of the die. This advance, effected at lower speed than that of the rst phase (A to B is represented by the distance B-C in Fig. 12. During this low speed displacement of the plunger 71, the absolute pressure in the die easily decreases and as soon as it has reached a predetermined value, the manometer 198 allows an electric current to pass into the low voltage circuit 114. However, it is to be noted that an electric current can ow only if the molten metal has reached the level of the detector electrode 116. It is therefore necessary that the detector electrode 116, as well as the manometer 198, must be in their circuit closing position to allow a current to how in the circuit 114 and to energize the relay 115. As soon as said relay 115 is energized, the interrupter 123 closes, which produces opening of the valve 9S over the line 12.4 and the solenoid lila. The hydraulic uid passes then from the conduit 97 `through the valve 93 and also through the regulating valve 137 and effects the second lmain operative phase of rapid injection of molten metal into the die. During this phase of rapid injection, the plunger 71 advances from the point vC to 10 the point D ofthe diagram of Fig. l2 (positions '71e and 71d). As soon as the molten metal acts on the piston 129, it actuates the closing of the check valve 125, which prevents any passage of meta-l particles into the air suction pipe 166. (The reference letters: A1, B1, C1, and D1 in the diagram of Fig. l2 indicate the dilerent successive levels of the molten metal in the injection cylinder 70 and in the die cavity F, which levels correspond to the positions 71a, 71b, 71e, and '71d of the plunger 71.

After the Acastting has been made, the machine may be opened. The opening is effected by returning the manipulating lever S6 into the position 1. During said return movement first to position 3 and then to position 2, the valve S9 remains closed and the valve 98 remains open. The plunger 71 is therefore maintained under pressure and the die halves 62 and 63 are kept tightly pressed against each other. When the manipulating lever 86 reaches the position 1, the valves 82 and 83 are closed and the valves S4 and 85 are opened. On the other hand, the contact of the movable contact with the xed contact 112:1 brings about the opening of the valve 89 and the closing of the valve 98. As a result, the hydraulic fluid from the conduit 97 acts, on the one hand, on the piston 72 so as to return it into the righthand direction with respect to Fig. 7, and, acts, on the other hand, on the piston d4 so as to return it to the left-hand side, which results in the opening of the die, and allows of withdrawing the finished casting. Said return movements of the pistons 64 and 72 are permitted by the escape of the hydraulic liquid acting on their working faces, which liquid ilows through the valves 34 and S5, respectively, towards the reservoir 79.

In Fig, l1, I have shown the time curve t and the speed curve V Vas functions of the advance S traveled by the plunger '71.

A fth embodiment of the invention, as illustrated, in Fig. 13, dilers from the machine shown on Figs. 7 to l() essentially by the control device used for closing the air escape port of the die. This machine is hydraulically operated like the machine described hereinbefore, but it is used for hardened dies where it is not possible to provide automatic valve means like the check valve of the machine shown in Figs. 7-l0. In the machine of Fig. 13, one of the bores 139 provided for the extractors 14? is employed for withdrawing the air from the die. The air escape valve is formed by a piston 125a of similar design as the piston of the valve 125. Said valve 125e is `controlled by an electro-magnet 141, which actuates a lever 142 pivotally linked at 143 to the die section 62. A spring 144 normally holds the valve 125g in open position when no current ows through the electro-magnet. When the electro-magnet is energized, it attracts, against the action of the spring 144, an armature 145, which is linked at 146 to the lever 142, and closes the air exhaust port of the die. A swingable double contact 147 is arranged between the piston 72 and the plunger 71 for automatic actuation by the rod 119 connecting said piston and plunger. For this purpose, a finger 12S is adjustably mounted on the rod 119. Electric current is supplied from the terminals 143. The valves 89 and 98 are represented diagrammatically in a very much simplified form; they function in a manner similar to that described in detail in the preceding embodiment of the invention.

The operation of the machine represented in Fig. 13 is similar to that of the machine described hereinbefore. ln the position 1 of the manipulating lever 86 (not shown in Fig. 13) the valve 39 is kept open by an electric current which is supplied through the terminals 143 and passes through the contact 147 to energize the electromagnet 149. No electric current ows at this time through the electro-magnet 156 which controls the valve 98.

The closing of the machine, i. e. of the die sections 62 and 63 is Yetfected, as in the `preceding modification, by

11 shifting the manipulating lever 86 in the position 3. When the manipulating lever is brought into position 4, hydraulic liquid passes through'the valve 89 so as to act against theV piston 72 and displace said piston towards the' left with respect to Fig. 13. The regulating valve 96 (not shown) allows passage of a fluid flow determining the iirst main operative phase of the machine, i. e. the phase of slow injection.- When the finger 129 Vhas actuated the contact member 147 and shifted it into the position shown in Fig. 13 in dotted lines, the electro-magnet 149 is no longer energized and the valve 89 closes. At this instant, the piston 72 either keeps advancing at a very reduced rate, if a feeble flow of uid takes place, `for instance through a bypass of the type of bypass 94' of Fig. 7, or the piston stops. in the position shown in dotted lines in Fig. 13, the contact lever 147 actuates through the line 151 the opening of the electromagnetically operated valve 167, which starts the suction phase of the machine. When the absolute pressure in the die cavity has reached a predetermined magnitude, the hand of the manometerw108 closes the contact 152 and allows an electric current to ilow in the line 153, which current energizes the electromagnet 141. At the same time, the'manometer 108 allows Y a current to ow in the line 154 and to energize the electro-magnet 150. In other words, as soon as a certain void has beenV obtained in the die cavity, the valve 98 is opened by the action of its electro-magnet 150 Vand the exhaust valve 125a is simultaneously closed by the action of its control electro-magnet 141. The opening of the valve 9S starts, therefore, the phase of rapidrinjection.

After this phase of rapid injection has been terminated, the manipulating lever 86 can be shifted back to position 1 so as to return the piston 72 and the plunger 71 into their positions of rest and to separate the two die halves 62 and 63. During said opening movemenL-theV extractors Y 140 push the casting out of the die.

The machine shown in Fig. 13 is of somewhat simpler construction than the machine of Fig. 7 insofar as the valves S9 and 98 are not controlled by pneumatic servo'- motors but directly by electro-magnets. Neither does this simplified machine have a detector electrode 116. Nevertheless, the operation of the two machinesis essentially similar. Y

The two last examples of injection machines represented by Figs. 7 to 13 of the drawings are particularly suitable as cold-chamber machines but the new principles applied therein may also be employed for hot-chamberV machines. f

What I claim is:

l. An apparatus for injecting casting material into a die, said apparatus comprising an injection cylinder; an injection plunger; an hydraulically operated piston actuating said injection plunger to deliver shots of molten casting material from the injection cylinder to the-die; a tirst feedline feeding hydraulic fluid under pressure to said piston; a regulating valve in said fcedline for supplying to said piston hydraulic fluid at a rate suflicient only to advance said piston in a first operative main phase; a second Y feed-tine feeding hydraulic iiuid to said piston, said second feedline bypassing said iirst feedline and allowing passage of hydraulic iiuid sufficient to drive thekpiston at high speed for a second operative main phase of rapid shot injection; a valve in said second feedline; an electromagnet actuating said valve; aV suctionpump for withdrawing air from the die, an air suction conduit connecting the die cavity with said pump; a valve controlling the opening of said conduit into the die cavity; a pressure indicating device in said conduit; an electric circuit connecting said pressure indicatingdevice with said electro-magnet actuating said valve in said second feedline; and means on N said pressure indicating device closing said circuit at a predetermined vacuum indicated by saidpressure indicat-Y ing device and opening said valve in said second feedline to initiate a second phase of rapid shot injection. Y

2. An apparatus as claimed in claim 1 including a detector device comprising a contact electrode disposed in the path of the molten casting V'material on its travel from the injection cylinder into the die and arrangedin series with said pressure indicating device in said electric circuit so as to close said circuit on contact with said molten material. Y

3. An apparatus as claimed in-claim 1, including a valve in said air suction conduit; an electro-magnet controlling'said air suction valve; an electric circuit energizing said electro-magnet; a contact in said circuit; and means closing said contact during the forward stroke of said piston, said air suction valve being opened when said contact is closed.

4. An apparatus as claimed in claim l, comprising a I control valve in each of said feed lines; electro-magnets actuating said valves, electric circuits for supplying cur-Vk Y phase of rapid shot injection in closed position and the return valve for the return of the hydraulic fluid from the first feedline in open position; said lever, in another position, closing the electric circuits controlling the closing of the control valve of the iirst feedline controlling the first phase of slow injection and the opening of the control valve of the second feedline controlling the second phase of rapid injection. Y Y Y 5. An apparatus as defined Vin claim 2 comprising a first electric circuit of low voltage connecting said pressure indicating device and said detector device, a second electric circuit of high voltage controlling the valve in the second feedline for the rapid injection phase, Van inter- Y rupter in said high voltage circuit, and a relay in said iirst circuit actuating said interrupter.V

6. An apparatus for injecting casting material into the cavity of a die, said apparatus comprising an injection cylinder, an injection plunger, a piston actuating said injection plunger to deliver shots of molten casting material from the injection cylinder to the die in two phases, means for imparting in the first Vof said phases a relatively slow initial advance to said piston and plunger so as to vacuum producing means for withdrawing air from the Y die prior to said second injection phase, a detector device responsive to the air pressure in the die cavity, said detector device actuating said separate means at a predetermined vacuum in th-e die, an air exhaust ductrconnecting said'vacuum producing means with the die cavity, and a valve in said duct, said valve being automatically closed towards the end of said second injection phase. Y

7. The apparatus defined in claim 6 including means ,Y

actuating said valve in the exhaust duct, said valve actuating means being moved Vinto the valve closing position by the hydraulic pressure of the liquid casting'material injected intovthe die cavity. Y' Y K V8. An apparatus` for injecting casting material into the cavity of a die', said apparatus comprising aninjection cylinder, an injection plunger, ya piston'actuating said injection plunger to deliver shots of molten casting mate-v rial from the injection .cylinder to the die in two phases, means for imparting in the first of'said phases a relatively slowV initial advance to said piston and plunger so as to allow the escape of air entrapped in said injection cylinder, separate means for imparting thereafter in the second of said phases-a rapid further advance torsaid piston and plunger for the injection proper of the shot into the die, vacuum producing means for withdrawing air f 13 from the die prior to said second injection phase, a detector device responsive to the air pressure in the die cavity, said detector device actuating said separate means at a predetermined Vacuum in the die, an air exhaust duct connecting said vacuum producing means With the die 5 cavity, and a valve controlling the opening of said duct into the die cavity, electromagnetic means for controlling said valve, an electric circuit energizing said electromagnetic means, and means operated by the injection plunger actuating said electromagnetic means. 10

References Cited in the file of this patent UNITED STATES PATENTS 1,607,677 Korsmo Nov. 23, 1926 15 14 During et al Apr. 10, 1934 Smith Nov. 28, 1939 Brunner et al June 3, 1941 Tann Aug. 18, 1942 Lyons June 4, 1946 Ernst et al Mar. 29, 1949 Veale Jan. 10, 1950 Holmes Nov. 28, 1950 Schroeder Sept. 16, 1952 Ring Nov. 18, 1952

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