US3029483A - Fluid pressure operated die casting machines, presses, moulding machines and the like - Google Patents

Description

p 1962 I A. R. MILLS ETA]. 3,029,483

FLUID PRESSURE o PERATED DIE CASTING MACHINES, PRESSES, MOULDING C ES AND E LIKE Fil March 1959 Zfl/fl 01 mm: 40 IM 0. g 42 i Z5 i.i.:. ;::j'jt.i 12 47/ 27 76 g. 11 z -15 14 1g 24' P I v 3 jNI/F VT PS United States Patent Ofiice 3,029,483 Patented Apr. 17, 1962 FLUID PRESSURE OPERATED DIE CASTING MA- CHINES, PRESSES, MOULDING MACHINES AND THE LIKE Aubrey Robert Mills and Eric Arthur Roy Mace, London, England, assignors to Die Casting Machine Tools Limited, London, England, a British company Filed Mar. 10, 1959, Ser. No. 793,551 Claims priority, application Great Britain Mar. 13, 1958 6 Claims. (Cl. 22-68) This invention relates to fluid pressure operated die casting machines, presses, moulding machines and like apparatus in which two moulds or dies are brought t getherand moved apart by fluid e.g. hydraulic or pneumatic pressure acting on a piston in a cylinder. Such machines will hereinafter be referred to as machines of the kind described.

The invention has for its principal object to provide an improved safety arrangement for stopping the closing movement of the dies or moulds in the event of any obstruction being positioned between the dies or moulds.

According to this invention, in a machine of the kind described there are provided pressure responsive means responsive to the fluid pressure in the cylinder, or in the feed thereto, operative to inhibit further closing movement of the dies or moulds if the pressure exceeds a predetermined value together, with over-ride means preventing such inhibition of closing movement if the pressure should exceed such predetermined value during the initial and final stages of the closing movement. While the dies or moulds are being brought together, which is usually efiected by moving one die or mould while keeping the other fixed, the fluid pressure drops substantially below the supply pressure to a value which may be determined empirically and which remains substantially constant. If the moving die or mould should meet any obstruction however, the pressure will rise above this value and so, by the arrangement described above, further closing movement is inhibited. This predetermined pressure, however,

is substantially exceeded during the initial part of the stroke as the die or mould begins to move and also as the dies or moulds finally close together and the over-ride means prevent any interruption of operation due to this increased pressure. The over-ride means need only to over-ride thepressure responsive means for a distance at each end of the stroke which is very short compared with the length of the die closing stroke; the exact distances required for the over-ride means can readily be determined empirically for the particular apparatus used. Over the greater part of the stroke, if the moving die or mould should meet any obstruction, the pressure in the cylinder or in the feed thereto will rise and will inhibit further closing movement.

Conveniently the aforementioned pressure responsive means are arranged to control or produce an electric signal in a control circuit, for example the pressure responsive means might comprise a diaphragm or the like adapted to be deflected under the fluid pressure to open or close an electrical circuit. In such an arrangement an override means may conveniently comprise switches which are mechanically operated. The over-ride means may conveniently remain operative during the whole time that the dies or mouldsare fully open or fully closed and hence the pressure responsive means may be arranged not only merely to inhibit closing of the dies or moulds but to interrupt the main electric supply circuit to the machine so as to remove all power from the machine. The fluid pressure in this case may be controlled by a spring loaded solenoid valve or valves arranged so that, on failure or interruption of the electric power supply, the fluid pressure is cutoff from the machine. It is preferred however for the die or mould movement that the solenoid should control a reversing valve so that failure or interruption of the electric power supply will cause the dies or moulds to move apart.

The over-ride means may comprise any convenient type of electric switch, for example a fixed rod or rods may be provided with contacts arranged to co-operate with a contact or contacts or a moving part of the machine (e.g. a die or a die-carrying platen) or the rod or rods may be moved to co-operate with fixed contacts.

It will be appreciated that the fluid pressure means might be a switch which is operative to make a circuit when the pressure exceeds the aforementioned predetermined value, in which case the over-ride means may comprise switches electrically in series with the fluid pressure responsive switch, Preferably, however, in order to ensure that the system fails safe on interruption of the electric supply, the pressure responsive means is made a switch operative to interrupt said control circuit and the over-ride means comprise electrical switches in parallel with one another and with the pressure responsive switch.

Such a circuit may include in series the operating coil of a relay and also a self-holding contact of the relay so that even a momentary interruption of the circuit will cause the relay to release and keep the circuit open. A re-set switch, for example a push-button switch, may be provided across the relay contact for enabling the relay to be re-set when it is required to return the machine to operation.

The following is a description of one embodiment of the invention, reference being made to the accompanying drawings in which:

FIGURE 1 illustrates diagrammatically certain components of a die casting machine; and

FIGURE 2 is a circuit diagram.

Referring to FIGURE 1, there are illustrated diagrammatically certain components of a die casting machine including a fixed die 10 and a movable die 11. The fixed die 10 is secured to a platen 12 mounted on a base 13, while the movable die 11 is mounted on a platen 14 which is moved towards and away from the fixed die 10 by means of a piston operating in a cylinder 15. The piston and cylinder assembly may be pneumatically or hydraulically operated, and conventional exhaust means (not shown) are provided whereby, upon movement of the piston, spent fluid is exhausted from the cylinder. For clarity in the present description only the essential features are shown and it will be understood that, in accordance with well known practice, the movable platen 14 would be operated from the piston cylinder assembly 15 by means of a toggle linkage which serves to lock the movable die plate in position tightly against the fixed die plate 10 when the dies are closed. A pneumatic or hydraulic cylinder (not shown) is provided for injecting the molten metal through an injection nozzle 16 into the die cavity when the dies are closed. The present invention is concerned primarily with the provision of safety means for ensuring that the closing movement of the dies is stopped in the event of any obstruction being positioned between the dies or the moulds. The fluid pressure supply for op.- erating the cylinder 15 is led through a pipe 20 to a solenoid operated spring-loaded reversing valve 21 which controls the darnission of the fluid under pressure to one or other end of the cylinder 15 according to the required direction of movement of the die plate 11. This valve 21 is indicated diagrammatically as having a spring 22 urging the valve in one direction and a solenoid operating coil 23 which, when the solenoid is energised, moves the valve in the opposite direction against the spring pressure. The valve is arranged so that the spring pressure normally urges the valve in the direction such as to tend to open pressure supply line 28 will increase. Connected to this supply line 28 is a chamber 24-, one wall of which is' bounded by a flexible diaphragm 25 which is connected to a rod 26 for operating an electrical switch 27. This switch is normally closed but is opened when the pressure 7 in the chamber 24 exceeds some predetermined value. This pressure-operated switch is adjusted so that the switch does not operate during the normal opening and closing movement of the dies but will be operated if the pressure rises appreciably above the normal value during such movement.

As shown in FIGURE 2, the switch 27 is connected in a series circuit from main supply input terminals 30, 31 to the operating coil 32 of a relay. This relay has first normally open contacts 33 which control the application of electric power supply to terminals 34, 35 leading to the machine so that when the relay is unenergised, there is no electric power supply to the machine. The relay also has a self-holding contact 36 which is normally open and it is connected in series with the relay operating coil 32.. A normally-open push-button re-set switch 37 is connected across the contacts '36 so that, by pushing the button 37, a circuit can be completed through the coil 32 whereupon the relay will operate and close the self-holding contact 36 to maintain the circuit, so holding the relay operated and putting power on the machine.

The pressure in the supply line 28 will rise at the beginning and end of the closing movement of the movable die plate 11 and over-ride switch means are provided for preventing the pressure-operated switch 27 from cutting ofi power to the machine during the initial and final stages of the die closing movement. The over-ride means need only be operative for a distance at each end of the stroke which is very small compared with the length of the die closing movement. These over-ride means comprises two normally-open micro-switches 40, 41 which, as shown in FIGURE 2, are connected in parallel with one another and in parallel with the switch 27. The switches are illustrated diagrammatically in FIGURE 1 as being op erated by a striker 42 attached to the movable platen 14.

It will be readily appreciated that many other mechanical arrangements for the construction and operation of such over-ride switches might be used and that FIGURE .1 merely illustrates diagrammatically the manner of operation of the switches. For example, a fixed rod or rods might be provided with contacts arranged to co-operate with a contact or contacts on the movable die 11 or the die-carrying platen 14. Alternatively a rod or rods mounted'on a moving part of the machine may be arranged to cooper-ate with fixed cont-acts.

If any obstruction should impede the movement of the die 11 as the latter is closing, the pressure in the line 29 will rise so opening the switch 27 cutting off power to the machine. The supply of fluid pressure to the machine is maintained, however, and as the power supplied to the solenoid 23 is cut oil by the opening of switch 27, the reversing valve 21 operates under the spring pressure to change over. so that, under the fluid pressure, the die plates immediately start to open. Even a momentary interruption of the circuit by the switch 27 will release the relay and open its self-holding contact 36 so that the die plates will move to the fully open position and cannot be closed again until the re-set button 37 is operated.

It will be noted furthermore that any failure of the power supply for any reason whatsoever will also release the relay so causing the die plates to open.

eluding a fluid pressure actuator operable to open and close a pair of molding dies, and a supply of fluid'under pressure: the combination comprising a supply line connected to the actuator for operation thereof in a die closing direction; an electrically controlled valve connected between the supply and said supply line to selectively connect said supply to the supply line for operation.

of the actuator in a die closing direction; a normally closed fiuid pressure operated switch in said supply line opened when the pressure in said supply line exceeds a i pre-set value due to obstruction of closing movement of the dies; a source of electric potential; an energizing circuit for operating said valve to effect operation of said actuator in a die closing direction; said switch controlling connection of said energizing circuit to said source; and a pair of normally opened die operated switches respectively closed during the initial and final increments of the closing movements of the dies; each of said die operated switches being connected in parallel with said fluid pressure switch to over-ride the same at the start and at the termination of the closing movement of the dies.

2. The combination as claimed in claim 1 in which said valve is biased to a position normally disconnecting said supply line from the supply, and is electrically operated to a position connecting said supply line to the supply; whereby, upon opening of said fluid pressure switch, when said die operated switches are open, saidvalve will be de-energized and biased to a position disconnecting said supply line from the supply.

3. The combination as claimed in claim 1 including a V relay having an operating coil in series with said switches; said relay having normally open contact means connected in said energizing circuit in series with' said valve and controlling energization of said valve from said source. 4. The combination as claimed in claim 3 including normally open hold contact means of said relay in series with said relay coil and said switches and closed, upon energization of the latter, to maintain said relay coil energized as long as any of said switches are closed.

5. The combination as claimed in claim 4 including a normally open push button switch connected in shunt with said normally open hold contact means of said relay.

6. In a fluid pressure operated molding apparatus in-.

cluding a fluid pressure actuator operable to open and 1 close a pair of molding dies, and a supply of fluid under pressure: the combination comprising a first supply line connected to the actuator for operation thereof in a die closing directioma second supply line connected to the actuator for operation thereof in a die. opening direction;

an electrically controlled valve connected between the V upon electrical energization thereof, being operated to a position'connecting said first supply line to the supply to operate the actuator in a dieclosing direction, and to disconnect said second supply line from the supply; a normally closed fluid pressure operated switch in said first supply line and opened when the pressure in said supply line exceeds a pre-set value due to obstruction of the closing movement of the dies; a source of electric potential; an energizing circuit for operating said valve to elfect operation of said actuator in a die closing direc tion; said switch controlling connection of said energizing circuit to said source; and a pair of normally open die operated switches respectively closed during the initial 7 and final increments of the die stroke in either direction, each of said die operated switches being connected in parallel with said fluid pressure switch to over-ride the same at the start and at the termination of the die stroke in either direction; whereby said valve, upon opening of said fluid pressure switch when said die operated switches a are open, will disconnect said first supply line from the 5 6 Supply and connect said second supply line to the supply 2,363,759 Waldie NOV. 28, 1944 to interrupt the closing movement of the dies and to open 2,430,935 Klug Nov. 18, 1947 the dies. 2,588,066 Weisberg Mar. 4, 1952 2,786,234 Beyer Mar. 26, 1957 References Clled 1n the file of th1s patent 5 FOREIGN PATENTS UNITED STATES PATENTS 539,748 Canada Apr. 16, 1957 1,511,374 Simmon Oct. 14, 1924 85.590 Netherlands July 15, 1957

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