US 2785448 A
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March 19, 1957 F HODLER 2,7
APPARATUS FOR THE AUTOMATIC EXPULSION OF AIR FROM THE DIE-CAVITY OF HOT AND COLD CHAMBER DIE-CASTING MACHINES Filed June 14, 1955 :z: VACUUM PUMP Frp'iz Hodler.
ATTORNEY a 2,785,448 Ice Patented Mar. 19, 1957 APPARATUS FOR THE AUTOMATIC EXPULSION OF AIR FROM THE DIE-CAVITY OF HOT AND COLD CHAMBER DIE-CASTING MACHINES Fritz Hodler, Territet, Switzerland Application June 14, 1955, Serial No. 515,385
Claims priority, application Switzerland June 29, 1954 4 Claims. (Cl. 22-68) This invention relates to a method of and apparatus for the automatic expulsion of air from the die-cavity of hot and cold chamber die-casting machines.
It relates more particularly to pressure die-casting machines in which the expulsion of the air from the diecavity is effected automatically and as far as timing is concerned in such a manner, that all conditions for the complete filling of said cavity are fulfilled, said expulsion being efiected by means of a valve, mounted on one of the die-halves.
According to the invention a maximum degree of homogeneousness and surface quality, as not obtained by other known means, is made possible and this also in the case of intricate castings, difficult to produce by other methods.
Pressure die-casting machines with air removal means, with or without control-devices attached to the die are known. However all these devices have intricate control mechanisms, operated by mechanical, pneumatic or electrical means, or by a combination of these, which are not satisfactory in practical use also because of the fact that they are not suitable for effecting the required synchronisation of the various operations to be controlled. In the case of the present invention, this synchronisation is effected automatically and in a simple manner by the utilisation of an increase of pressure occurring during the casting operation. In order to explain the requirements which must be met by an air-expulsion valveof this type, as far as its effective and reliable operation are concerned, the following conditions, prevailing during the casting operation must be taken into consideration.
The time required for the filling of the die-cavity, i. e. the time lapse from the moment the metal reaches the point of inlet, in other words the actual entrance .to the die-cavity till the complete filling of the latter, should not exceed the mean valve of /100 of a second, failing this, the surface quality of the casting will deteriorate because of unfavourable cooling conditions. On the other hand, in order to allow air and gases contained in the die-cavity to be exhausted as completely as possible, the valve must reach its final closing position only when the metal has filled the die-cavity completely, provided always that the timing of the closing operation is such as not to allow the molten metal to pass through the valve.
Apart from meeting the requirements for the proper timing of the closing operation, mentioned before, the section of free passage of the valve must be as large as possible in order to reduce the air-resistance to a minimum.
Since it has been found in practice that occasional sticking of metal to the contact surfaces of the closing organ of the valve-mechanism (fusion) is inevitable, and since this may make its proper operation impossible, the closing force of the valve must be large enough to prevent trouble of this nature under all circumstances.
The above requirements cannot be met by known devices, which have control means operated by intricate mechanical, pneumatic or electrical means or by a com- T bin'ation thereof and it was therefore necessary to find means to solve the above problems in a simple, reliable and technically sound manner.
The solution according to the invention utilises the increase of pressure, which is inevitable during the casting operation for the direct operation of a simple and foolproof valve Without mechanical, pneumatic or electrical auxiliary means. i
In order to enable the invention to be more readily understood reference is made to the accompanying drawing, which illustrates diagrammatically and by way of example an embodiment thereof and in which:
Fig. 1 shows diagrammatically a partialview in section of the machine. I
Fig. 2 shows a partial internal view of the die.
The machine according to Fig. 1the casing of which is omitted-shows a die consisting of the parts 1 and 2. Part 2 shows an inner article forming cavity or recess 3 which represents the form of the piece to be cast. In part 1 of the die a material inlet 4 is provided in the form of an injection sleeve, said sleeve having the opening 5 through which the molten metal can be poured. This metal is then pressed into the die-cavity 3 by the action of the primary fluid piston means which includes 6, 7, 8, 9 and 10. The injection piston is 6, said piston being capable of sliding in sleeve 4. The injection piston 6 is connected by the rod 7 to the main piston 8 sliding in the cylinder 9. Said piston 8 is actuated by hydraulic pressure which is controlled by the operator through the feed pipe 10.
As shown in Fig. l, the die has a channel 11 through which the air contained in the die-cavity and in the injection sleeve 4 can escape. The valve 12 enables the channel 11 to be closed, as soon as the die-cavity 3 is filled with molten metal. Said valve 12 comprises a cylindrical shaft 13 capable of sliding in a bore 14 provided in the part 2 of the die. Said shaft 13 is secured to a piston 15 capable of sliding in the cylinder 16. Said cylinder 16 is secured to the die part 2, for instance as shown by means of the flange 17 and the screws 18 or by any other means serving the same purpose. The piston 15 is held in the rear position (to the left on the accompanying drawing) in which position the valve 12 is open, allowing the air to pass freely through the channel 11 by the force of the spring 19 or of any other means serving the same purpose. The piston 15 is provided with a fluidtight lining.
in the embodiment of the invention shown by way of example the cylinder 16 is connected with the control cylinder 9 of the injection piston 6 by means of the pipe 21.
The cycle of operation in the case of the embodiment of the invention shown by way of example is as follows:
When a piece is to be cast under pressure in the die 3, the required quantity of molten metal is introduced into the sleeve 4 through the opening 5. The machine is now put into operation by allowing a liquid under pressure, for example water, to be introduced through the pipe 10 into the cylinder 9. The pistons 8 and 9 then move to the left (relatively to the drawing). The molten metal in the sleeve 4 is at first forced into transfer chamber 22 of the feed channel to the die-cavity 3. The force exercised by the spring 19 or by other means serving the same purpose must be such as to maintain the valve 12 in its open position during this first injection phase, which is intended to fill the sleeve d and the chamber 22, in spite of the pressure occurring in the cylinder 9, the pipe 21 and the cylinder 16.
When however the molten metal reaches the constricted throat 23 of the feed channel to the die-cavity 3 (this 0 constricted throat 23 constituting the mouth of the feed 22 to the die-cavity 3), the pressure increases considerably,
on the one hand in the sleeve 4 and on the other hand in the cylinder 9 due to the obstruction to the flow of metal caused by said contraction. This increase of pressure is transmitted to the cylinder 16, through the pipe 21., which causes the piston 15 to move and the valve 12 to begin its closing operation. In order to also allow the masses of air and gases contained in the die-cavity to escape before said cavity is filled with the molten metal, suitable means must be provided for regulating the closing time of the valve in such a manner as to cause the final closing stage of the valve to co-incide with the complete filling of the die-cavity. This can, for
instance, be effected by giving the pipe .21 suitable dimensions or by providing it with a regulating valve 24 of known construction and therefore not shown in detail, or by any other means serving the same purpose.
After the metal in the die has solidified, it is removed in known manner and the cycle of operation as described can be repeated. It will be understood, that modifications may he made without departing from the spirit of the invention and that the utilisation of the increase of pressure caused by the contracted part 23 for the direct operation of valve-mechanism, is not limited to the way in which this is eflected in the embodiment shown. This increased pressure can also be utilised for the indirect operation of regulatingor valve-mechanisms, in which case for instance mechanical, pneumatic or electrical auxiliary means may be used.
It will also be understood that the point at which this increased pressure is utilised is not limited to the point at which this is effected in the embodiment shown by Way of example. Since the increase of pressure does not only occur in the cylinder 9 but also in the various organs of the hydraulic system, for instance in the pipe 19, the utilisation of the increased pressure is not limited to the point shown in the embodiment described, and therefore the pipe 21 (Fig. 1) can also be connected to the supply line 10. It will further be understood, that the advantages of the invention are not limited to the use of the valve for allowing the air to escape as described. It is for instance possible to combine the action of the valve with means for exhausting the masses of air and gases contained in the die-cavity and free channels, at any suitable point, by known means for instance by connecting the air escape-channel 11 with an exhaust system or a vacuum pump of known construction and therefore not shown.
It will also be understood that the invention is not limited to the horizontal type pressure die-casting machine shown by way of example, but that .it can be modified to he used on other types, for instance on vertical hotand cold-chamber pressure die-casting machines, provided that the ejection stroke of such machines is eifected by hydraulic means.
What I claim is:
1. Die-casting apparatus, comprising, a die having a die-casting material inlet and an article cavity, said cavity communicating with the constricted throat of a material transfer chamber which receives discharge from said inlet, said cavity also communicating with an escape channel, a valve for controlling the escape of .air and gas from the die-cavity through said channel, said valve having a spring normally biasing it to open position and a piston responsive to hydraulic pressure for moving it to closed position, hydraulic primary piston means including a cylinder and main piston for forcing casting material through said inlet, and pipe means establishing communication between the fluid pressure side of the valve piston and the main piston of the said primary piston means, whereby, as the main piston of the primary piston means moves through the initial portion of its stroke to inject material through the inlet and into the transfer chamber, the fluid pressure on the valve piston wi l not overcome the force of the valve spring and the valve will remain open to permit escape of air from the die-cavity until the material reaches the constricted throat of the transfer passage and pressure builds up behind the main piston whereupon increasing pressure on the valve piston will progressively cause the valve to close the escape channel until the latter is fully closed when. the die-cavity is filled.
2. Die-casting apparatus, comprising, a die casing having a die-cavity communicating with an air escape channel and a material transfer chamber, the latter having a constricted throat where it joins the die-cavity, a material inlet sleeve for the casing and discharging into the transfer chamber, a valve for controlling the escape of air from .the die cavity through said channel, said valve having a spring normally biasing it to open position and a piston responsive to hydraulic pressure for moving it to closed position, hydraulic primary piston means including a cylinder and main piston for forcing casting material through said inlet sleeve, and pipe means establishing communication between the fluid pressure side of the valve piston and the main piston of the said primary piston means, whereby, as the main piston moves through its stroke to inject material through the sleeve and into the transfer chamber the valve will remain open until the material reaches the constricted throat whereupon the increased fluid pressure on the main piston to overcome the resistance created by the constricted throat will cause a rise in pressure in the cylinder of the primary piston means, said rise in pressure being communicated through pipe means to the valve piston to progressively move the valve to closing position until the valve is fully and automatically closed when the cavity is filled.
3. Die-casting apparatus according to claim 2, wherein the pipe means is provided with a device for regulating the closing of the valve.
4. Die-casting apparatus according to claim 2, wherein, the valve in the escape channel is in the fiorm of a rod about which the spring is coiled.
References Cited in the file of this patent UNITED STATES PATENTS 1,912,981 Hoy June 6, 1933 2,079,936 Gastrow May 11, 1937 2,243,835 Brunner June 3, 1941 2,484,907 Purcell Oct. 18, 1949 2,634,468 Holder Apr. 14, 1953 2,668,985 Babbitt Feb. 1 6, 1954 FOREIGN PATENTS 848,689 Germany -a Sept. 8, 1952