CA1294753C - Gas venting device for molding operations - Google Patents
Gas venting device for molding operationsInfo
- Publication number
- CA1294753C CA1294753C CA000546463A CA546463A CA1294753C CA 1294753 C CA1294753 C CA 1294753C CA 000546463 A CA000546463 A CA 000546463A CA 546463 A CA546463 A CA 546463A CA 1294753 C CA1294753 C CA 1294753C
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- valve
- valve body
- gas venting
- inlet
- venting arrangement
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Abstract
ABSTRACT
A gas venting device for molding operations is disclosed having a valve for closing off a gas evacuation system from a mold when the mold cavity is filled with melt.
A positive drive mechanism is provided for closing the valve, and a mechanism is provided for allowing the valve body to close more rapidly by action of the melt itself against the valve body in the event the melt advances more rapidly through the gas vent passage than expected.
A gas venting device for molding operations is disclosed having a valve for closing off a gas evacuation system from a mold when the mold cavity is filled with melt.
A positive drive mechanism is provided for closing the valve, and a mechanism is provided for allowing the valve body to close more rapidly by action of the melt itself against the valve body in the event the melt advances more rapidly through the gas vent passage than expected.
Description
GAS VENTING DEVICE FOL~ MOLDING OPERATIONS
BACKGROUND OF THE INVENTION
This invention relates to a gas venting arrangement for use with a molding machine, such as one used in die-casting operations.
In die-casting operations a quantity of molten metal is injected into a die cavity which has a shape corresponding to the shape of the final die-cast product. In order to ensure a substantially void-free die casting, the mold cavity is placed under vacuum throughout the melt injection process to remove as much gaseous material as possible from the mold cavity. One type of commonly used gas evacuation or venting arrangement incorporates a shut-off valve for controlling gas flow out of the mold cavity through a gas vent passage. The valve remains open during injection and, when the mold cavity is filled with melt~ the valve closes to prevent the vacuum source from ingesting any excess melt which may flow out of the mold and through the gas vent passage.
Valved gas venting devices of the prior art generally are of two typesl both typically involving a reciprocating valve body which cooperates with an annular seat. In one type the movement of the valve body tc its closed position 12~3~7~3 is accomplished by a positive drive mechanism which is synchronized with melt injection so as to close when the mold cavity is full. Morton U S. 3,121,926 discloses one example of this type of arrangement, wherein a trigger switch actuated by the injection ram initiates valve closure. Thurner U.S. 4,463,793 discloses another example of this type of arrangement. These types of positively driven gas vent valves, while effective, are not Eoolproof, inasmuch as rapidly advancing melt in some ins-tances may reach the valve body before it is completely closed, thereby fouling the valve and seat, preventing full closure and clogging the evacuation system.
The other type of valve arrangement used in the prior art involves a melt-driven valve body wherein movement of the valve body to its closed position is effected by pressure or dynamic forces exerted by the melt itself directly on the valve body. In many situations, such as that disclosed by Takeshima U.S. 4,431,047, the valve body is spring-biased to its open position, dynamic melt forces supposedly being sufficient to overcome the spring force and move the valve body to its closed position. However, as recognized by Takeshima in his later U.S. Patent No.
4,489,771, such an arrangement is not foolproof because the valve body can oscillate due to serial impingement of discontinuous melt (i.e, having one or more voids) which momentarily relieves pressure on the valve body and allows ~L~gA~7~3 it to re-open. Momentary opening of the valve in the presence of the melt can lead to fouling of the sealing surfaces and invasion of melt into the evacuation chamber.
Accordingly, Takeshima in U.S. 4,489,771 provides a complex biasing and triggering mechanism which reverses the bias on the valve body (i.e., towards its closed position) upon initial impingement of the melt. While this arrangement may preclude valve body oscillation, it is not clear whether the closing spring force on the valve body is sufficient in all instances to seal the valve body against the valve seat if some melt has reached the valve seat and interferes with closure. Hodler U.SO 3,885,618 discloses a melt-actuated valve body which floats freely in the valve chamber (when the mold is closed). Hodler relies on the configuration of the valve body to make an effective seal when it retracts within the seat, but there is no guarantee that the pressure of the melt itself acting on the valve body can overcome ar.y obstruction that may be present between the sealing surfaces caused by solidified melt which may have splashed past the valve body and into the seat.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to overcome the above-noted and shortcomings and disadvantages oE the prior art by providing a gas venting device for molding operations which reliably isolates the vacuum system .
47~3 from the mold cavity when the mold cavity is filled with melt with virtually no invasion of melt into the evacuation system prior to valve closure.
Another object of the invention is to provide such a gas venting device having a positive valve closure mechanism which will overcome any obstruction between the valve body and the valve seat.
Another object oE the invention is to provide -such a gas venting device wherein the valve body is more rapidly advanced toward closure by the melt itself if melt advancing through the gas vent passage overtakes the positively driven valve body, virtually precluding invasion of melt into the evacuation system under all circumstances.
These and other objects of the invention are accomplished by a gas venting arrangement for use with molding apparatus including a mold having a cavity to be filled with melt, means for injecting melt into the mold cavity and a gas vent passage communicating with the mold cavity for evacuating gas from the mold cavity ahead of advancing melt as it fills the mold cavity. The gas venting arrangement comprises a housing having a valve chamber with an inlet adapted to be placed in fluid communication with the gas vent passage, and an exhaust port for evacuating gas from the valve chamber. An annular valve seat adjacent the inlet cooperates with a valve body coaxial with the valve chamber and the valve seat, the valve body having a valve 1L2~7~3 stem extending rearwardly through the valve chamber away from the mold. The valve body is axially movable forwardly, toward the mold, to open the inlet, and movable rearwardly, away Erom the mold, to close the in]et in cooperation with the valve seat.
An detecting and producing means is provided for detecting an injecting ram to reach a predetermined set position on the stroke of the ram in the injection operation thereof, and for producing a signal in response to said detecting means.
Valve actuation means is associated with the housing and is operatively coupled to the valve stem for positively driving the valve body rearwardly to positively close the inlet, in response to the signal from the producing means, before the advancing melt reaches and contacts the undersurface of che valve body. Valve actuation means is associated with the housing and is operatively coupled to the valve stem for positively driving the valve body rearwardly to positively close the inlet when the mold is full of melt.
Preferably, the valve actuation means also positively -drives the valve body forwardly to forcibly open the inlet before melt is injected into the mold cavity. This may include a double-acting fluid cylinder and piston assembly acting on a reciprocable drive member which is operatively coupled to the valve stem. The coupling arrangement 12~4~7~3 provides for free valve body movement between the open and closed positions when the fluid cylinder is not pressurized.
This enables the operator to check for obstructions when the mold is open.
BRIEF DESCRIPTION OF THE DRAWINGS
Other Eeatures and advantages of the invention can be more fully understood from the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings, in which:
Figures 1, 2 and 3 are schematic representations of die-casting apparatus incorporating the gas venting device according to the invention, showing progressive phases of the die-casting and gas venting operation; and Figures 4, 5 and 6 are vertical sectional views of the gas venting device according to the invention shown in different phases of the die-casting and gas evacuation operation.
Figures 7a through 7d are vertical sectional views of valve body and valve seat in other embodiments of the present invention.
DETAILED DESCRIPTION
Referring to Figures 1, 2 and 3, die casting apparatus is schematically shown which comprises a die or mold having stationary and movable mold sections 2, 3, ~2~L7~3 respectively, which define a mold cavity 4 therebetween. An injection chamber 5 communicates with mold cavity 4 through an inlet passage 6. Injection chamber 5 is charged with molten metal 7 from a crucible 8 or other source of melt through funnel 9. An injection ram 10 drives an injection piston 11 through injection chamber 5 to force melt 7 into mold cavity 4.
A gas venting device 100 according to the invention and associated evacuation equipment serve to remove gases from mold cavity 4 during the injection process through a gas vent passage 12. As seen more clearly in Figures 4, 5 and 6, gas vent passage 12 branches into two by-pass gas vent passages 13 and a main gas vent passage 14. A valve chamber 102 houses a valve seat 104 which cooperates at its lower end with a reciprocable valve body 106 to open and close a gas inlet 108 at the lower end of valve chamber lQ2. A gas evacuation port 110 is connected to a vacuum source or pressure reducing device (not shown~ for drawing gases through gas vent passages 12 and 13 and inlet 108 when valve body 106 is in its lower or open position, blocking the upper end of main gas vent passage 14. Valve body 106 is connected as described below to a pneumatic cylinder and piston assembly 112 which effects forward (i.e., toward the mold) and rearward (i.e., away from the mold) movement of valve body 106 to open or close inlet 108.
Referring again to Figures 1, 2 and 3, pneumatic cylinder and piston assembly 112 is controlled through a solenoid valve 15 connected at 16 to a source of compressed air. The position of solenoid valve 15 is determined by a control circuit incorporating DC voltage source 17 and a limit switch 18 which senses the predetermined set position of injection piston 11 by interaction with cam 19 located on the drive shaft of injection ram 10.
The molding or die-casting operation now will be generally described with reference to Figures 1, 2 and 3.
Figure 1 illustrates the configuration of the system just prior to injection of melt into mold cavity 4. As descri-bed in more detail below, compressed air from source 16 delivered to the upper port of pneumatic cylinder and piston assembly 112 keeps valve body 106 in its lowermost or open position, poised for positive upward movement by pneumatic cylinder and piston assembly 112 when mold cavity 4 is filled with melt. Limit switch 18 is open in this configuration. Figure 2 illustrates the configuration of the molding equipment when mold cavity 4 is substantially filled with melt. At this point, the melt is just beginning to rise into main gas vent passage 12, and limit switch 18 has just been tripped to a closed position by cam 19, causing solenoid valve lS to deliver compressed air to the underside of the piston in pneumatic cylinder and piston assembly 112, driving valve body 106 upwardly toward its ~Z~7C3 closed position. By the time inlet 108 is closed by valve body 106 (Fig. 3), injection piston 11 has moved a little farther to the left and melt has risen through main gas vent passage 12 into by-pass gas vent passage 13. The forceful upward movement of valve body 106 is sufficient to close inlet 108 before melt advancing through by-pass gas vent passages 13 has a chance to invade valve chamber 102.
Once molding has been completed, movable die portion 3 is opened, the molded part is removed and excess melt is cleared from the gas vent passages and the lower face of valve body 106. With solenoid valve 15 in the position illustrated in Figure 1, compressed air supplied at 16 again will force valve body 106 downwardly to its open position, facilitating cleaning of the valve body and adjacent surfaces. With cleaning complete and the mold reassembled, the molding process then may be repeated.
Referring to Figures 4, 5 and 6, the gas venting device according to the invention now will be described in detail.
Valve chamber 102 is contained within a housing 114, at the top or rear end of which is located pneumatic cylinder and piston assembly 112. This assembly comprises a cylinder 116 housing a piston 118 which is connected to a drive member or rod 120 extending forwardly into a coupling chamber 122. A
piston-engaging coil`spring 124 within cylinder 116 exerts a rearward bias on piston 118 and drive rod 120. Valve body 106 is mounted at the end of a valve stem 126 which extends _ g _ ~;29~753 rearwardly through valve chamber 102 into coupling chamber 122. The position of valve seat 104 is adjustable by means of tapered seat adjusting blocks 128 which can be externally manipulated by means of adju.sting screws ].30.
~ rive rod 120 and valve stem 126 are coaxial and their distal ends are coupled by a sliding joint 132 located in coupling chamber 122. A valve stem nut 134 is threaded onto the end of valve stem 126 and has a forwardly facing shoulder 136 which cooperates with a rearwardly facing shoulder 138 at the forward end of sliding joint 132.
Similarly, a drive rod nut 140 threaded onto the end of drive rod 120 has a rearwardly facing shoulder 142 which is adapted to mate with a forwardly facing shoulder 144 at the rear end of sliding joint 132. A joint-engaging coil spring 146 in coupling chamber 122 exerts a forward bias on sliding joint 132 toward its foremost position against the fron~ end 148 of coupling chamber 122. The forward biasing force of spring 146 is greater than the rearward biasing force of spring 124. Thus, with valve body 106 in its foremost or open position and cylinder 116 unpressurized, the working parts are in the configuration shown in Figure 6, with a spacing Sl between the ends of valve stem nut 134 and drive rod nut 140. In this "check" position valve body 106 and valve stem 126 are freely movable, which allows the operator to manually check the freedom of movement of valve body 106 before the mold is reclosed for further molding. As ~Z~47~3 explained more fully below, this free play in the coupling mechanism also permits melt-driven movement of valve body 106 during valve closure in the event melt advances more rapidly than normal toward valve chamber 102.
The sizing and spacing of the various working components of the gas venting device preferably is as follows. Valve body 106 (and valve stem 126) must undergo a stroke S defined by the fully open position shown in Figures 4 and 6 (blocking main gas vent: passage 14) and the fully closed position shown in Figure 5 (retracted within valve seat 104). The shoulder 150 on valve stem 126 is located at a spacing Ss from the rear end of valve seat 104 with the valve in the open position, where Ss i9 equal to or greater than stroke S. This spacing of course allows valve body 106 to move through a complete stroke when closing. Similarly, with sliding joint 132 in its foremost position (see Figure 4), the spacing S4 between its rear end and the rear end of joint chamber 122 must be equal to or greater than stroke S.
This also holds true for the spacing S6 between the rear end of piston 118 and the rear end of cylinder 116, since rearward movement of piston 118 causes drive rod nut 140 to lift sliding joint 132 and, in turn, lift valve stem nut 134 along with valve stem 126 and valve body 106. Gap G between the front and rear shoulders 138, 144 of sliding joint 132 must exceed the minimum spacing between shoulder 142 on drive rod nut 140 and shoulder 136 on valve stem nut 134 ~ 2g47~3 (S3) by a distance S2 which is at least equal to stroke S.
Of course, spacing Sl (Figure 6) must equal spacing S2.
Certain ancillary control elements may be used to provide data on the positions of certain working parts of the gas venting device, which can be utilized for automatic control, if desired. Thus, a magnetic or optical position sensor 152 detects the position of valve stem nut 134, while magnetic limit switches 154, 156 detect the position of piston 118 within cylinder 116. Other position detectors and controllers may be provided as necessary for indicating the condition of the various working elements of the gas venting device.
The operation of the gas venting device according to the invention now will be described in detail, with reference to Figures 4, 5 and 6. Figure 4 illustrates the configuration of the device when cylinder 116 is pressurized to drive valve stem 126 forwardly to force valve body 106 to its open position. This typically would be done after the mold has been opened to return valve body 106 to its open position for cleaning and inspection. Before the mold is reclosed cylinder 116 is depressurized which permits the working parts to assume the "check" configuration shown in Figure 6. As explained above, because of the relative biasing forces of springs 124 and 146, sliding joint 132 assumes its foremost position while drive rod nut 140 abuts the rear shoulder 144 of sliding joint 132. This leaves t2~9L7~3 valve body 106 free to move so that the operator can manually check for any obstructions in or around inlet 108 and insure freedom of movement of valve body 106.
Figure 4 also illustrates the configuration of the device during the melt injection phase, when gases are evacuated through gas vent passage 12 and 13, inlet 108 and exhaust port 110. In this configuration pneumatic cylinder and piston assembly 112, while maintaining valve body 106 in the open position, remains poised to drive valve stem 126 and valve body 106 rearwardly to the closed position when compressed air is supplied to the lower port of cylinder 116. When this occurs (Figure 5) valve stem 126 and valve body 106 are driven rearwardly at a rapid rate.
As illustrated in Figure 4, 5 and 6, the forward face of valve body 106 and the forward end of valve seat 104 are machined at a slight angle to a plane perpendicular to the axis of the valve body and valve stem. This facilitates removal of melt which may have adhered to these surfaces.
Cleaning also may involve complete removal of the gas venting device from the portion of the mold to which it is bolted.
Figures 7a through 7d illustrate other preferred embodiments of the present invention. Those parts which are identical to those of the previous embodiment are denoted by identical reference numerals, and will not be described in detail.
~IL29~7~3 As shown in Figures 4, 5 and 6, the forward face of valve body 106 and the forward end of valve seat 104 are machined at a slight angle to a plane perpendicular to the axis of the valve body and valve stem. However, in the present embodiments, the forward face of valve body 106 is machined at an angle different from that of the forward end of valve seat 104. Further, the Eorward face o~ the valve body 106 and/or the forward end of the valve seat 104 are machined to provide a notch portion. Thereby it ensures to open the mold without undercut and to extrude the product therefrom.
Especially, Figure 7a illustrates that a notch or step is provided at inlet portion 108a of valve sheet 104~
According to the present configuration, a molten metal solidified in the gas vent passages 13 and/or 14 will be displaced with the movable mold section 3 in right direction in Figure 7a when opening the mold or extruding the product.
In this stage, a half of the forward face 106a of the valve body 106 is appeared out of the inlet 108a whereas the remaining half thereof is within the inlet 108a thereby being able to open the mold without any undercut and to extrude the product easily therefrom.
Figure 7b illustrates a configuration in which the forward face of the valve body 106 is machined to be a different angle of the step provided in the inlet 108b of the valve seat 104.
.
~;~9~7~3 Further~ Figure 7c illustrates a configuration in which a notch with step is provided in the forward face 106c of the valve body 106. The inclined angle of the notch will be approximately same to that of the step of inlet 108c.
Furthermore, Figure 7d shows a configuration in which the inclined angle of forward face 106d of the valve body 106 is different from that of forward end of the inlet 108d.
Anybody of the above illustrated embodiments performs same function and same effectiveness to the configuration illustrated in Figure 7a.
From the foregoing it will be seen that the gas venting device according to the invention efficiently accomplishes its objectives. Pneumatic cylinder and piston assembly 112 provides a positive closing force for the valve which helps valve body 106 overcome any obstruction. The ability of valve body 106 to undergo more rapid, melt-driven closure ensures that virtually no melt can find its way through inlet 108 into valve chamber 102. Although disclosed as usable in connection with die-casting operations, the gas venting device according to the invention is equally applicable to other types of molding operations involving gas evacuation, such as the injection molding of plastic or other types of materials. ModiFications to the disclosed preferred embodiment will be apparent to those skilled in the art. For example, cylinder and piston assembly 112 may be hydraulically driven, rather than pneumatically actuated.
lZ~ 3 Coupling means other than that illustrated and described in coupling chamber 122 may be provided which performs substantially the same function. Other modifications will be apparent to those skilled in the art without departing from the true scope of the invention which is defined by the appended claims.
~ ' .
;~
BACKGROUND OF THE INVENTION
This invention relates to a gas venting arrangement for use with a molding machine, such as one used in die-casting operations.
In die-casting operations a quantity of molten metal is injected into a die cavity which has a shape corresponding to the shape of the final die-cast product. In order to ensure a substantially void-free die casting, the mold cavity is placed under vacuum throughout the melt injection process to remove as much gaseous material as possible from the mold cavity. One type of commonly used gas evacuation or venting arrangement incorporates a shut-off valve for controlling gas flow out of the mold cavity through a gas vent passage. The valve remains open during injection and, when the mold cavity is filled with melt~ the valve closes to prevent the vacuum source from ingesting any excess melt which may flow out of the mold and through the gas vent passage.
Valved gas venting devices of the prior art generally are of two typesl both typically involving a reciprocating valve body which cooperates with an annular seat. In one type the movement of the valve body tc its closed position 12~3~7~3 is accomplished by a positive drive mechanism which is synchronized with melt injection so as to close when the mold cavity is full. Morton U S. 3,121,926 discloses one example of this type of arrangement, wherein a trigger switch actuated by the injection ram initiates valve closure. Thurner U.S. 4,463,793 discloses another example of this type of arrangement. These types of positively driven gas vent valves, while effective, are not Eoolproof, inasmuch as rapidly advancing melt in some ins-tances may reach the valve body before it is completely closed, thereby fouling the valve and seat, preventing full closure and clogging the evacuation system.
The other type of valve arrangement used in the prior art involves a melt-driven valve body wherein movement of the valve body to its closed position is effected by pressure or dynamic forces exerted by the melt itself directly on the valve body. In many situations, such as that disclosed by Takeshima U.S. 4,431,047, the valve body is spring-biased to its open position, dynamic melt forces supposedly being sufficient to overcome the spring force and move the valve body to its closed position. However, as recognized by Takeshima in his later U.S. Patent No.
4,489,771, such an arrangement is not foolproof because the valve body can oscillate due to serial impingement of discontinuous melt (i.e, having one or more voids) which momentarily relieves pressure on the valve body and allows ~L~gA~7~3 it to re-open. Momentary opening of the valve in the presence of the melt can lead to fouling of the sealing surfaces and invasion of melt into the evacuation chamber.
Accordingly, Takeshima in U.S. 4,489,771 provides a complex biasing and triggering mechanism which reverses the bias on the valve body (i.e., towards its closed position) upon initial impingement of the melt. While this arrangement may preclude valve body oscillation, it is not clear whether the closing spring force on the valve body is sufficient in all instances to seal the valve body against the valve seat if some melt has reached the valve seat and interferes with closure. Hodler U.SO 3,885,618 discloses a melt-actuated valve body which floats freely in the valve chamber (when the mold is closed). Hodler relies on the configuration of the valve body to make an effective seal when it retracts within the seat, but there is no guarantee that the pressure of the melt itself acting on the valve body can overcome ar.y obstruction that may be present between the sealing surfaces caused by solidified melt which may have splashed past the valve body and into the seat.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to overcome the above-noted and shortcomings and disadvantages oE the prior art by providing a gas venting device for molding operations which reliably isolates the vacuum system .
47~3 from the mold cavity when the mold cavity is filled with melt with virtually no invasion of melt into the evacuation system prior to valve closure.
Another object of the invention is to provide such a gas venting device having a positive valve closure mechanism which will overcome any obstruction between the valve body and the valve seat.
Another object oE the invention is to provide -such a gas venting device wherein the valve body is more rapidly advanced toward closure by the melt itself if melt advancing through the gas vent passage overtakes the positively driven valve body, virtually precluding invasion of melt into the evacuation system under all circumstances.
These and other objects of the invention are accomplished by a gas venting arrangement for use with molding apparatus including a mold having a cavity to be filled with melt, means for injecting melt into the mold cavity and a gas vent passage communicating with the mold cavity for evacuating gas from the mold cavity ahead of advancing melt as it fills the mold cavity. The gas venting arrangement comprises a housing having a valve chamber with an inlet adapted to be placed in fluid communication with the gas vent passage, and an exhaust port for evacuating gas from the valve chamber. An annular valve seat adjacent the inlet cooperates with a valve body coaxial with the valve chamber and the valve seat, the valve body having a valve 1L2~7~3 stem extending rearwardly through the valve chamber away from the mold. The valve body is axially movable forwardly, toward the mold, to open the inlet, and movable rearwardly, away Erom the mold, to close the in]et in cooperation with the valve seat.
An detecting and producing means is provided for detecting an injecting ram to reach a predetermined set position on the stroke of the ram in the injection operation thereof, and for producing a signal in response to said detecting means.
Valve actuation means is associated with the housing and is operatively coupled to the valve stem for positively driving the valve body rearwardly to positively close the inlet, in response to the signal from the producing means, before the advancing melt reaches and contacts the undersurface of che valve body. Valve actuation means is associated with the housing and is operatively coupled to the valve stem for positively driving the valve body rearwardly to positively close the inlet when the mold is full of melt.
Preferably, the valve actuation means also positively -drives the valve body forwardly to forcibly open the inlet before melt is injected into the mold cavity. This may include a double-acting fluid cylinder and piston assembly acting on a reciprocable drive member which is operatively coupled to the valve stem. The coupling arrangement 12~4~7~3 provides for free valve body movement between the open and closed positions when the fluid cylinder is not pressurized.
This enables the operator to check for obstructions when the mold is open.
BRIEF DESCRIPTION OF THE DRAWINGS
Other Eeatures and advantages of the invention can be more fully understood from the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings, in which:
Figures 1, 2 and 3 are schematic representations of die-casting apparatus incorporating the gas venting device according to the invention, showing progressive phases of the die-casting and gas venting operation; and Figures 4, 5 and 6 are vertical sectional views of the gas venting device according to the invention shown in different phases of the die-casting and gas evacuation operation.
Figures 7a through 7d are vertical sectional views of valve body and valve seat in other embodiments of the present invention.
DETAILED DESCRIPTION
Referring to Figures 1, 2 and 3, die casting apparatus is schematically shown which comprises a die or mold having stationary and movable mold sections 2, 3, ~2~L7~3 respectively, which define a mold cavity 4 therebetween. An injection chamber 5 communicates with mold cavity 4 through an inlet passage 6. Injection chamber 5 is charged with molten metal 7 from a crucible 8 or other source of melt through funnel 9. An injection ram 10 drives an injection piston 11 through injection chamber 5 to force melt 7 into mold cavity 4.
A gas venting device 100 according to the invention and associated evacuation equipment serve to remove gases from mold cavity 4 during the injection process through a gas vent passage 12. As seen more clearly in Figures 4, 5 and 6, gas vent passage 12 branches into two by-pass gas vent passages 13 and a main gas vent passage 14. A valve chamber 102 houses a valve seat 104 which cooperates at its lower end with a reciprocable valve body 106 to open and close a gas inlet 108 at the lower end of valve chamber lQ2. A gas evacuation port 110 is connected to a vacuum source or pressure reducing device (not shown~ for drawing gases through gas vent passages 12 and 13 and inlet 108 when valve body 106 is in its lower or open position, blocking the upper end of main gas vent passage 14. Valve body 106 is connected as described below to a pneumatic cylinder and piston assembly 112 which effects forward (i.e., toward the mold) and rearward (i.e., away from the mold) movement of valve body 106 to open or close inlet 108.
Referring again to Figures 1, 2 and 3, pneumatic cylinder and piston assembly 112 is controlled through a solenoid valve 15 connected at 16 to a source of compressed air. The position of solenoid valve 15 is determined by a control circuit incorporating DC voltage source 17 and a limit switch 18 which senses the predetermined set position of injection piston 11 by interaction with cam 19 located on the drive shaft of injection ram 10.
The molding or die-casting operation now will be generally described with reference to Figures 1, 2 and 3.
Figure 1 illustrates the configuration of the system just prior to injection of melt into mold cavity 4. As descri-bed in more detail below, compressed air from source 16 delivered to the upper port of pneumatic cylinder and piston assembly 112 keeps valve body 106 in its lowermost or open position, poised for positive upward movement by pneumatic cylinder and piston assembly 112 when mold cavity 4 is filled with melt. Limit switch 18 is open in this configuration. Figure 2 illustrates the configuration of the molding equipment when mold cavity 4 is substantially filled with melt. At this point, the melt is just beginning to rise into main gas vent passage 12, and limit switch 18 has just been tripped to a closed position by cam 19, causing solenoid valve lS to deliver compressed air to the underside of the piston in pneumatic cylinder and piston assembly 112, driving valve body 106 upwardly toward its ~Z~7C3 closed position. By the time inlet 108 is closed by valve body 106 (Fig. 3), injection piston 11 has moved a little farther to the left and melt has risen through main gas vent passage 12 into by-pass gas vent passage 13. The forceful upward movement of valve body 106 is sufficient to close inlet 108 before melt advancing through by-pass gas vent passages 13 has a chance to invade valve chamber 102.
Once molding has been completed, movable die portion 3 is opened, the molded part is removed and excess melt is cleared from the gas vent passages and the lower face of valve body 106. With solenoid valve 15 in the position illustrated in Figure 1, compressed air supplied at 16 again will force valve body 106 downwardly to its open position, facilitating cleaning of the valve body and adjacent surfaces. With cleaning complete and the mold reassembled, the molding process then may be repeated.
Referring to Figures 4, 5 and 6, the gas venting device according to the invention now will be described in detail.
Valve chamber 102 is contained within a housing 114, at the top or rear end of which is located pneumatic cylinder and piston assembly 112. This assembly comprises a cylinder 116 housing a piston 118 which is connected to a drive member or rod 120 extending forwardly into a coupling chamber 122. A
piston-engaging coil`spring 124 within cylinder 116 exerts a rearward bias on piston 118 and drive rod 120. Valve body 106 is mounted at the end of a valve stem 126 which extends _ g _ ~;29~753 rearwardly through valve chamber 102 into coupling chamber 122. The position of valve seat 104 is adjustable by means of tapered seat adjusting blocks 128 which can be externally manipulated by means of adju.sting screws ].30.
~ rive rod 120 and valve stem 126 are coaxial and their distal ends are coupled by a sliding joint 132 located in coupling chamber 122. A valve stem nut 134 is threaded onto the end of valve stem 126 and has a forwardly facing shoulder 136 which cooperates with a rearwardly facing shoulder 138 at the forward end of sliding joint 132.
Similarly, a drive rod nut 140 threaded onto the end of drive rod 120 has a rearwardly facing shoulder 142 which is adapted to mate with a forwardly facing shoulder 144 at the rear end of sliding joint 132. A joint-engaging coil spring 146 in coupling chamber 122 exerts a forward bias on sliding joint 132 toward its foremost position against the fron~ end 148 of coupling chamber 122. The forward biasing force of spring 146 is greater than the rearward biasing force of spring 124. Thus, with valve body 106 in its foremost or open position and cylinder 116 unpressurized, the working parts are in the configuration shown in Figure 6, with a spacing Sl between the ends of valve stem nut 134 and drive rod nut 140. In this "check" position valve body 106 and valve stem 126 are freely movable, which allows the operator to manually check the freedom of movement of valve body 106 before the mold is reclosed for further molding. As ~Z~47~3 explained more fully below, this free play in the coupling mechanism also permits melt-driven movement of valve body 106 during valve closure in the event melt advances more rapidly than normal toward valve chamber 102.
The sizing and spacing of the various working components of the gas venting device preferably is as follows. Valve body 106 (and valve stem 126) must undergo a stroke S defined by the fully open position shown in Figures 4 and 6 (blocking main gas vent: passage 14) and the fully closed position shown in Figure 5 (retracted within valve seat 104). The shoulder 150 on valve stem 126 is located at a spacing Ss from the rear end of valve seat 104 with the valve in the open position, where Ss i9 equal to or greater than stroke S. This spacing of course allows valve body 106 to move through a complete stroke when closing. Similarly, with sliding joint 132 in its foremost position (see Figure 4), the spacing S4 between its rear end and the rear end of joint chamber 122 must be equal to or greater than stroke S.
This also holds true for the spacing S6 between the rear end of piston 118 and the rear end of cylinder 116, since rearward movement of piston 118 causes drive rod nut 140 to lift sliding joint 132 and, in turn, lift valve stem nut 134 along with valve stem 126 and valve body 106. Gap G between the front and rear shoulders 138, 144 of sliding joint 132 must exceed the minimum spacing between shoulder 142 on drive rod nut 140 and shoulder 136 on valve stem nut 134 ~ 2g47~3 (S3) by a distance S2 which is at least equal to stroke S.
Of course, spacing Sl (Figure 6) must equal spacing S2.
Certain ancillary control elements may be used to provide data on the positions of certain working parts of the gas venting device, which can be utilized for automatic control, if desired. Thus, a magnetic or optical position sensor 152 detects the position of valve stem nut 134, while magnetic limit switches 154, 156 detect the position of piston 118 within cylinder 116. Other position detectors and controllers may be provided as necessary for indicating the condition of the various working elements of the gas venting device.
The operation of the gas venting device according to the invention now will be described in detail, with reference to Figures 4, 5 and 6. Figure 4 illustrates the configuration of the device when cylinder 116 is pressurized to drive valve stem 126 forwardly to force valve body 106 to its open position. This typically would be done after the mold has been opened to return valve body 106 to its open position for cleaning and inspection. Before the mold is reclosed cylinder 116 is depressurized which permits the working parts to assume the "check" configuration shown in Figure 6. As explained above, because of the relative biasing forces of springs 124 and 146, sliding joint 132 assumes its foremost position while drive rod nut 140 abuts the rear shoulder 144 of sliding joint 132. This leaves t2~9L7~3 valve body 106 free to move so that the operator can manually check for any obstructions in or around inlet 108 and insure freedom of movement of valve body 106.
Figure 4 also illustrates the configuration of the device during the melt injection phase, when gases are evacuated through gas vent passage 12 and 13, inlet 108 and exhaust port 110. In this configuration pneumatic cylinder and piston assembly 112, while maintaining valve body 106 in the open position, remains poised to drive valve stem 126 and valve body 106 rearwardly to the closed position when compressed air is supplied to the lower port of cylinder 116. When this occurs (Figure 5) valve stem 126 and valve body 106 are driven rearwardly at a rapid rate.
As illustrated in Figure 4, 5 and 6, the forward face of valve body 106 and the forward end of valve seat 104 are machined at a slight angle to a plane perpendicular to the axis of the valve body and valve stem. This facilitates removal of melt which may have adhered to these surfaces.
Cleaning also may involve complete removal of the gas venting device from the portion of the mold to which it is bolted.
Figures 7a through 7d illustrate other preferred embodiments of the present invention. Those parts which are identical to those of the previous embodiment are denoted by identical reference numerals, and will not be described in detail.
~IL29~7~3 As shown in Figures 4, 5 and 6, the forward face of valve body 106 and the forward end of valve seat 104 are machined at a slight angle to a plane perpendicular to the axis of the valve body and valve stem. However, in the present embodiments, the forward face of valve body 106 is machined at an angle different from that of the forward end of valve seat 104. Further, the Eorward face o~ the valve body 106 and/or the forward end of the valve seat 104 are machined to provide a notch portion. Thereby it ensures to open the mold without undercut and to extrude the product therefrom.
Especially, Figure 7a illustrates that a notch or step is provided at inlet portion 108a of valve sheet 104~
According to the present configuration, a molten metal solidified in the gas vent passages 13 and/or 14 will be displaced with the movable mold section 3 in right direction in Figure 7a when opening the mold or extruding the product.
In this stage, a half of the forward face 106a of the valve body 106 is appeared out of the inlet 108a whereas the remaining half thereof is within the inlet 108a thereby being able to open the mold without any undercut and to extrude the product easily therefrom.
Figure 7b illustrates a configuration in which the forward face of the valve body 106 is machined to be a different angle of the step provided in the inlet 108b of the valve seat 104.
.
~;~9~7~3 Further~ Figure 7c illustrates a configuration in which a notch with step is provided in the forward face 106c of the valve body 106. The inclined angle of the notch will be approximately same to that of the step of inlet 108c.
Furthermore, Figure 7d shows a configuration in which the inclined angle of forward face 106d of the valve body 106 is different from that of forward end of the inlet 108d.
Anybody of the above illustrated embodiments performs same function and same effectiveness to the configuration illustrated in Figure 7a.
From the foregoing it will be seen that the gas venting device according to the invention efficiently accomplishes its objectives. Pneumatic cylinder and piston assembly 112 provides a positive closing force for the valve which helps valve body 106 overcome any obstruction. The ability of valve body 106 to undergo more rapid, melt-driven closure ensures that virtually no melt can find its way through inlet 108 into valve chamber 102. Although disclosed as usable in connection with die-casting operations, the gas venting device according to the invention is equally applicable to other types of molding operations involving gas evacuation, such as the injection molding of plastic or other types of materials. ModiFications to the disclosed preferred embodiment will be apparent to those skilled in the art. For example, cylinder and piston assembly 112 may be hydraulically driven, rather than pneumatically actuated.
lZ~ 3 Coupling means other than that illustrated and described in coupling chamber 122 may be provided which performs substantially the same function. Other modifications will be apparent to those skilled in the art without departing from the true scope of the invention which is defined by the appended claims.
~ ' .
;~
Claims (21)
1. A gas venting arrangement for use with molding apparatus including a mold having a cavity to be filled with a melt, means for injecting melt into the mold cavity and a gas vent passage communicating with the mold cavity for evacuating gas from the mold cavity ahead of advancing melt as it fills the mold cavity, said gas venting arrangement comprising:
a housing having a valve chamber with an inlet adapted to be placed in fluid communication with the gas vent passage, and an exhaust port for evacuating gas from said valve chamber;
an annular valve seat adjacent said inlet;
a valve body coaxial with said valve chamber and said valve seat and having a valve stem extending rearwardly through said valve chamber away from the mold, said valve body being axially movable forwardly, toward the mold, to open said inlet, and movable rearwardly, away from the mold, to close said inlet in cooperation with said valve seat;
means for detecting that an injecting ram reaches a predetermined set position on the stroke of the ram in the injection operation thereof, and for producing a signal in response to said detecting means;
Valve actuation means associated with said housing and operatively coupled to said valve stem for positively driving said valve body rearwardly to positively close said inlet, in response to said signal from said producing means, before said advancing melt reaches and contacts the undersurface of said valve body.
a housing having a valve chamber with an inlet adapted to be placed in fluid communication with the gas vent passage, and an exhaust port for evacuating gas from said valve chamber;
an annular valve seat adjacent said inlet;
a valve body coaxial with said valve chamber and said valve seat and having a valve stem extending rearwardly through said valve chamber away from the mold, said valve body being axially movable forwardly, toward the mold, to open said inlet, and movable rearwardly, away from the mold, to close said inlet in cooperation with said valve seat;
means for detecting that an injecting ram reaches a predetermined set position on the stroke of the ram in the injection operation thereof, and for producing a signal in response to said detecting means;
Valve actuation means associated with said housing and operatively coupled to said valve stem for positively driving said valve body rearwardly to positively close said inlet, in response to said signal from said producing means, before said advancing melt reaches and contacts the undersurface of said valve body.
2. A gas venting arrangement according to claim 1, wherein said valve actuation means positively drives said valve body forwardly to forcibly open said inlet before melt is injected into the mold cavity.
3. A gas venting arrangement according to claim 1, wherein said valve actuation means comprises a positively driven, reciprocable drive member and coupling means interconnecting said drive member and said valve stem for transmitting rearward movement of said drive member to said valve stem.
4. A gas venting arrangement according to claim 3, wherein said valve actuation means also positively drives said drive member forwardly against said valve stem to forcibly open said inlet before melt is injected into the mold cavity.
5. A gas venting arrangement according to claim 3, wherein said drive member comprises an elongated, axially reciprocable drive member positioned rearwardly of and coaxial with said valve stem.
6. A gas venting arrangement according to claim 5, wherein said coupling means comprises a forwardly facing shoulder on the distal end of said valve stem, a rearwardly facing shoulder on the distal end of said drive member, and a sliding joint embracing the distal ends of said valve stem and said drive member and having front and rear mutually facing shoulders which mate respectively with said forwardly and rearwardly facing shoulders on said valve stem and said drive member, the gap between said front and rear shoulders of said sliding joint being greater than the minimum spacing between the shoulders on the distal ends of said valve stem and said drive member.
7. A gas venting arrangement according to claim 6, wherein said gap between said front and rear shoulders of said sliding joint exceeds the minimum spacing between the shoulders on the distal ends of said valve stem and said drive member by at least the stroke of said valve body between its fully open and fully closed positions.
8. A gas venting arrangement according to claim 7, wherein said valve actuation means also positively drives said drive member forwardly through said sliding joint and into engagement with said valve stem to forcibly open said inlet before melt is injected into the mold cavity.
9. A gas venting arrangement according to claim 6 or 7, wherein said coupling means further comprises a joint-engaging spring exerting a forward bias on said sliding joint.
10. A gas venting arrangement according to claim 9, wherein said valve actuation means comprises a fluid cylinder and piston assembly operatively coupled to and driving said drive member, said cylinder and piston assembly including a piston-engaging spring in said cylinder exerting a rearward bias on said drive member, said forward bias on said sliding joint exceeding said rearward bias on said drive member whereby, when said cylinder and piston assembly is not pressurized, said sliding joint is kept in its foremost position with said inlet open and the shoulder on said drive member is engaged with said rear shoulder on said sliding joint.
11. A gas venting arrangement according to claim 10, wherein said cylinder and piston assembly is double-acting and also positively drives said drive member forwardly, against the action of said piston-engaging spring, through said sliding joint and into engagement with said valve stem to forcibly open said inlet before melt is injected into the mold cavity.
12. A gas venting arrangement according to claim 1 or 7, wherein said valve body and said valve seat are cylindrical and are dimensioned so that said valve body can retract fully within said valve seat to close said inlet.
13. A gas venting arrangement according to claim 12, wherein the forward face of said valve body and the forward end of said valve seat are angled slightly with respect to a plane perpendicular to the axis of said valve body.
14. A gas venting arrangement according to claim 13, a step portion is provided at the forward end of said valve sheet, of which angle of inclination is almost same to the inclined angle of forward face of said valve body.
15. A gas venting arrangement according to claim 13, inclined surfaces are provided at the forward face of valve body and the forward end of valve seat, respectively, both angles of inclined surfaces are different from each other.
16. A gas venting arrangement according to claim 13, step portions are provided at the forward face of valve body and the forward end of valve seat, of which angles of inclination are almost same each other.
17. A gas venting arrangement for use with molding apparatus including a mold having a cavity to be filled with a melt, means for injecting melt into the mold cavity and a gas vent passage communicating with the mold cavity for evacuating gas from the mold cavity ahead of advancing melt as it fills the mold cavity, said gas venting arrangement comprising:
a housing having a valve chamber with an inlet adapted to be placed in fluid communication with the gas vent passage, and an exhaust port for evacuating gas from said valve chamber;
a cylindrical valve seat adjacent said inlet;
a cylindrical valve body coaxial with said valve chamber and said valve seat and having a valve stem extending rearwardly through said valve chamber away from the mold, said valve body being axially movable forwardly, toward the mold, to open said inlet, and movable rearwardly, away from the mold, to retract fully within said valve seat and thereby close said inlet;
means for detecting that an injecting ram reaches a predetermined set position on the stroke of the ram in the injection operation thereof, and for producing a signal in response to said detecting means;
a double-acting fluid cylinder and piston assembly at the rear of said housing having a drive rod coaxial with and extending forwardly toward said valve stem; and coupling means in said housing, intermediate said valve chamber and said cylinder and piston assembly, interconnecting said drive rod and said valve stem for transmitting rearward movement of said drive rod to said valve stem to positively close said inlet, in response to said signal from said producing means, before said advancing melt reaches and contacts the undersurface of said valve body, and for transmitting forward movement of said drive rod to said valve stem to forcibly open said inlet before melt is injected into the mold cavity.
said coupling means comprising a forwardly facing shoulder on the distal end of said valve stem, a rearwardly facing shoulder on the distal end of said drive rod, and a sliding joint embracing the distal ends of said valve stem and said drive rod and having front and rear mutually facing shoulders which mate respectively with said forwardly and rearwardly facing shoulders on said valve stem and said drive rod, the gap between said front and rear shoulders of said sliding joint being greater than the minimum spacing between the shoulders on the distal ends of said valve stem and said drive rod.
a housing having a valve chamber with an inlet adapted to be placed in fluid communication with the gas vent passage, and an exhaust port for evacuating gas from said valve chamber;
a cylindrical valve seat adjacent said inlet;
a cylindrical valve body coaxial with said valve chamber and said valve seat and having a valve stem extending rearwardly through said valve chamber away from the mold, said valve body being axially movable forwardly, toward the mold, to open said inlet, and movable rearwardly, away from the mold, to retract fully within said valve seat and thereby close said inlet;
means for detecting that an injecting ram reaches a predetermined set position on the stroke of the ram in the injection operation thereof, and for producing a signal in response to said detecting means;
a double-acting fluid cylinder and piston assembly at the rear of said housing having a drive rod coaxial with and extending forwardly toward said valve stem; and coupling means in said housing, intermediate said valve chamber and said cylinder and piston assembly, interconnecting said drive rod and said valve stem for transmitting rearward movement of said drive rod to said valve stem to positively close said inlet, in response to said signal from said producing means, before said advancing melt reaches and contacts the undersurface of said valve body, and for transmitting forward movement of said drive rod to said valve stem to forcibly open said inlet before melt is injected into the mold cavity.
said coupling means comprising a forwardly facing shoulder on the distal end of said valve stem, a rearwardly facing shoulder on the distal end of said drive rod, and a sliding joint embracing the distal ends of said valve stem and said drive rod and having front and rear mutually facing shoulders which mate respectively with said forwardly and rearwardly facing shoulders on said valve stem and said drive rod, the gap between said front and rear shoulders of said sliding joint being greater than the minimum spacing between the shoulders on the distal ends of said valve stem and said drive rod.
18. A gas venting arrangement according to claim 17;
wherein said gap between said front and rear shoulders of said sliding joint exceeds the minimum spacing between the shoulders on the distal ends of said valve stem and said drive rod by at least the stroke of said valve body between its fully open and fully closed positions.
wherein said gap between said front and rear shoulders of said sliding joint exceeds the minimum spacing between the shoulders on the distal ends of said valve stem and said drive rod by at least the stroke of said valve body between its fully open and fully closed positions.
19. A gas venting arrangement according to claim 18, wherein said coupling means further comprises a joint-engaging spring exerting a forward bias on said sliding joint.
20. A gas venting arrangement according to claim 19, wherein said cylinder and piston assembly includes a piston-engaging spring in said cylinder exerting a rearward bias on said drive rod, said forward bias on said sliding joint exceeding said rearward bias on said drive rod whereby, when said cylinder and piston assembly is not pressurized, said sliding joint is kept in its foremost position with said inlet open and the shoulder on said drive rod is engaged with said rear shoulder on said sliding joint.
21. A gas venting arrangement according to claim 20, wherein the forward face of said valve body and the forward end of said valve seat are angled slightly with respect to a plane perpendicular to the axis of said valve body.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000546463A CA1294753C (en) | 1987-09-09 | 1987-09-09 | Gas venting device for molding operations |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000546463A CA1294753C (en) | 1987-09-09 | 1987-09-09 | Gas venting device for molding operations |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1294753C true CA1294753C (en) | 1992-01-28 |
Family
ID=4136406
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000546463A Expired - Fee Related CA1294753C (en) | 1987-09-09 | 1987-09-09 | Gas venting device for molding operations |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1294753C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114367641A (en) * | 2020-10-16 | 2022-04-19 | 丰田自动车株式会社 | Mold pressure measuring device and mold pressure measuring method |
-
1987
- 1987-09-09 CA CA000546463A patent/CA1294753C/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114367641A (en) * | 2020-10-16 | 2022-04-19 | 丰田自动车株式会社 | Mold pressure measuring device and mold pressure measuring method |
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