In an injection molding apparatus, wherein a plasticizing chamber has a nozzle attached to one end thereof, with the nozzle having a passageway therein and being in communication with the sprue of a mold, the improvement which constitutes a compact, pneumatically-powered, reciprocable spool-type device having a passageway therein, operated by alternately actuated opposed pistons, interposed between the nozzle and the plasticizing chamber, in one position blocking the communication between the plasticizing chamber and the nozzle and in the other position allowing molten material to enter the nozzle.
|
1. In an injection molding apparatus comprising a chamber having a nozzle attached near one end thereof, means for forcing molten material from said chamber through a passageway formed in said nozzle, a mold having a sprue formed therein, which sprue is in communication with the passageway formed in said nozzle, and a nozzle shut-off device interposed between said nozzle and said chamber the improvement comprising:
(a) a body for said device having a first passageway in communication with both said chamber and the passageway formed in said nozzle and a second passageway intersecting said first passageway; (b) a spool reciprocal in the second passageway of said body and having a third passageway capable of communicating with the first passageway of said body; (c) a piston attached to each end of said spool; (d) a cylinder encompassing each of said pistons, said cylinders each having a closed end and an open end, with said open end being adjacent to said body and said cylinders being attached to said body; (e) a source of fluid pressure; and (f) means to connect said source of fluid pressure alternately to said cylinders to pressurize one and vent the other of said cylinders, thus causing said spool to reciprocate, thereby in one position blocking the first passageway in said body and in the other position connecting the third passageway in said spool with the first passageway in said body, thus allowing molten material to pass from said chamber into said nozzle.
2. In an injection molding apparatus comprising a plasticizing cylinder having a nozzle attached near one end thereof, means for forcing molten material from said cylinder through a passageway formed in said nozzle, a mold having a sprue formed therein, which sprue is in communication with said passageway formed in said nozzle, and valve means interposed between said nozzle and said cylinder the improvement comprising:
(a) a valve body having a first passageway in communication with said cylinder and in axial alignment with the passageway formed in said nozzle and a second passageway intersecting said first passageway; (b) a valve spool reciprocable in the second passageway of said valve body and having a third passageway capable of axial alignment with the first passageway of said valve body; (c) a piston attached to each end of said valve spool; (d) a cylinder encompassing each of said pistons, said cylinders each having one closed end and one open end, with said open end being ajacent to said valve body and said cylinders each being attached to said valve body; (e) a source of fluid under pressure; and (f) means to connect said source of fluid under pressure alternately to said cylinders to pressurize one and vent the other of said cylinders, thereby causing said pistons and valve spool to reciprocate, thus in one position blocking the first passageway in said valve body and in the other position axially aligning the third passageway in said valvespool with the first passageway in said valve body, thereupon allowing molten material to enter said nozzle from said plasticizing cylinder.
3. In an injection molding apparatus comprising a temperature controllable cylinder having a nozzle attached to one end thereof, means for forcing molten material from said cylinder through a passageway formed in said nozzle, a platen with a mold having a sprue formed therein, which sprue is in communication with said passageway formed in said nozzle, and a nozzle shut-off valve interposed between said nozzle and said chamber, the improvement comprising:
(a) a valve body having a first passageway in axial alignment with both said cylinder and the passageway formed in said nozzle and a second passageway intersecting said first passageway; (b) a valve spool reciprocable in the second passageway of said valve body and having a third passageway parallel to and capable of axial alignment with the first passageway of said valve body; (c) a piston attached in an axial direction to each end of said valve spool; (d) a cylinder peripherally encompassing each of said pistons and having one closed end and one open end with said open end being adjacent to said valve body and said cylinders each being attached to said valve body; (e) a source of fluid under pressure; and (f) means to connect said source of fluid under pressure alternately to said cylinders, to pressurize one and vent the other of said cylinders, thereby causing said pistons and valve spool to reciprocate in unison, thus in one position blocking the first passageway in said valve body and in the other position axially aligning the third passageway in said valve spool with the first passageway in said valve body, thereupon allowing molten material to enter said nozzle from said temperature controllable
cylinder. 4. The injection molding apparatus of claim 3 11 wherein the second passageway in said valve body is substantially perpendicular to the first passageway in said valve body. 5. The injection molding apparatus of claim 3 11 wherein the second passageway of said valve body and said valve spool are substantially circular in cross-section and of substantially equal diameters. 6. The injection molding apparatus of
cylinders. 7. The injection molding apparatus of claim 11 wherein the piston-stroke adjusting means comprises a nut and bolt assembly incorporated in the closed end of at least one of said cylinders. 8. The injection molding apparatus of claim 3 11 wherein the fluid under pressure which causes said pistons and valve spool to reciprocate is air. 9. The injection molding apparatus of
recess in said platen. 10. The injection molding apparatus of claim 3 11 with the addition of at least one internal heating element incorporated into said valve body. 11. In an injection molding apparatus comprising a temperature controllable cylinder having a nozzle attached to one end thereof, means for forcing molten material from said cylinder through a passageway formed in said nozzle, a platen with a mold having a sprue formed therein, which sprue is in communication with said passageway formed in said nozzle, and a nozzle shut-off valve interposed between said nozzle and said cylinder, the improvement comprising: (a) a valve body having a first passageway in axial alignment with both said cylinder and the passageway formed in said nozzle and a second passageway intersecting said first passageway; (b) a valve spool reciprocable in the second passageway of said valve body and having a third passageway parallel to and capable of axial alignment with the first passageway of said valve body; (c) a piston attached in an axial direction to each end of said valve spool; (d) a cylinder peripherally encompassing each of said pistons and having one closed end and one open end with said open end being adjacent to said valve body and said cylinders each being attached to said valve body; (e) a piston-stroke adjusting means incorporated in at least one of said cylinders; (f) a source of fluid under pressure; and (g) means to connect said source of fluid under pressure alternately to said cylinders, to pressurize one and vent the other of said cylinders, thereby causing said pistons and valve spool to reciprocate in unison, thus in one position blocking the first passageway in said valve body and in the other position axially aligning the third passageway in said valve spool with the first passageway in said valve body, thereupon allowing molten material to enter said nozzle from said temperature controllable cylinder. 12. In an injection molding apparatus comprising a temperature controllable cylinder having a nozzle attached to one end thereof, means for forcing molten material from said cylinder through a passageway formed in said nozzle, a platen with a mold having a sprue formed therein, which sprue is in communication with said passageway formed in said nozzle, and a nozzle shut-off valve interposed between said nozzle and said cylinder, the improvement comprising: (a) a valve body having a first passageway in axial alignment with both said cylinder and the passageway formed in said nozzle and a second passageway intersecting said first passageway; (b) a valve spool reciprocable in the second passageway of said valve body and having a third passageway parallel to and capable of axial alignment with the first passageway of said valve body; (c) a piston attached in an axial direction to each end of said valve spool; (d) a cylinder peripherally encompassing each of said pistons and having one closed end and one open end with said open end being adjacent to said valve body and said cylinders each being attached to said valve body; (e) said platen having a recess therein located and sized to substantially contain said nozzle shut-off valve; (f) said nozzle shut-off valve being disposed substantially within said recess; (g) a source of fluid under pressure; and (h) means to connect said source of fluid under pressure alternately to said cylinders, to pressurize one and vent the other of said cylinders, thereby causing said pistons and valve spool to reciprocate in unison, thus in one position blocking the first passageway in said valve body and in the other position axially aligning the third passageway in said valve spool with the first passageway in said valve body, thereupon allowing molten material to enter said nozzle from said temperature controllable cylinder. |
|||||||||||||||||||
This invention relates to injection molding machines in general, but particularly to the reciprocating screw or plunger type machine suitable for the injection molding of plastic and elastomeric materials. Conventional molding apparatus of the reciprocating-rotating screw type usually includes a plasticizing cylinder or chamber having a bore, wherein the plasticizing screw rotates in such a manner so as to allow the solid molding material to enter the cylinder and be plasticized as it advances in the direction of screw feed. Attached on one end of the plasticizing cylinder is a nozzle in communication with a mold sprue. As the plasticized material is deposited at the metering or front end of the screw, it developes a back pressure that forces the screw to retract in the cylinder bore and when the plasticized material reaches a predetermined volume, or shot size, the retracting screw contacts a limit switch and stops its rotation. At this stage, the shot is ready for injection into the mold, generally upon receipt of a signal from the clamp, whereupon the screw is driven forward hydraulically to inject the shot. Upon receipt of another signal, the plasticizing screw again starts to rotate and gradually retract as a fresh shot is built up in the plasticizing cylinder. Thus, the screw reciprocates once per machine cycle to plasticize and inject a shot of material.
Often, shut-off valves or devices are employed to interrupt the flow of molten material from the nozzle into the mold sprue. These offer the advantages of minimizing or entirely curtailing drool through cut off of material flow at the nozzle and provide the capability to plasticize during periods in which the clamp is open. Generally, plasticizing takes place during part curing to prevent plasticized material from escaping.
Over the years many types of shut-off devices and means to actuate them have been developed and utilized with varying degrees of success. Included among these are, for example, spring operated needle valves such as shown in FIG. 4 of U.S. Patent 3,002,229, which are generally not completely reliable in actual operation; mechanically operated pin valves such as shown in U.S. Patent 3,172,161 which are generally difficult to properly align and have multiple pivot points subject to wear; hydraulically operated rotary valves such as shown in FIG. 3 of U.S. Patent 3,169,275 which are often subject to scoring and difficult to locate near the nozzle because of high nozzle temperatures which make hydraulic operation hazardous; retson reason. However, even in other operating position all leakage is readily removable from cavities 108. In addition, open ended cavities 108 allow visual inspection of valve spool end portions 83, 84 not only for possible molten material leakage but also to determine whether or not valve spool 80 is properly shifting to and from its respective open and closed positions. Another benefit of this construction is that it reduces to a minimum the amount of heat transfer from valve body 51 to cylinders 102, 122, thereby minimizing cylinder and piston distortions.
An examination of FIG. 2 will show that nozzle shut-off valve 50 is so compact as to be substantially contained wholly within recess 24 of platen 22 and is thus located very close to nozzle 34. In addition, penumatic operation is desirable since it presents no difficult or expensive sealing problems as is the case with hydraulic operation, and compressed air is generally readily available, inexpensive, and presents no fire hazards.
While this invention has been described in connection with possible forms or embodiments thereof, it is to be understood that the present disclosure is illustrative rather than restrictive and that changes or modifications may be resorted to without departing from the spirit of invention or scope of the claims which follow.
| Patent | Priority | Assignee | Title |
| 11059208, | May 30 2018 | Ford Global Technologies, LLC | Sprue system for injection-molding processes |
| 4512733, | Feb 04 1982 | Krauss-Maffei Aktiengesellschaft | Adjustable injection molding backflow preventer |
| 4875848, | Feb 29 1988 | Injection molding heated gate insert and method | |
| 5112213, | Feb 26 1991 | VAN DORN DEMAG CORPORATION, A CORP OF DE | Driven ring-type non-return valve for injection molding |
| 5200127, | Dec 17 1990 | BAUER COMPRESSORS, INC | Method and apparatus for gas assisted injection molding |
| 5304058, | Jun 12 1991 | BAUER COMPRESSORS, INC | Injection nozzle |
| 5306134, | Jun 12 1991 | BAUER COMPRESSORS, INC | Fluid forcing nozzle |
| Patent | Priority | Assignee | Title |
| 2443554, | |||
| 2686934, | |||
| 2923031, | |||
| 2936996, | |||
| 2972776, | |||
| 2992455, | |||
| 3354507, | |||
| 3377661, |
| Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
| Feb 13 1978 | Cincinnati Milacron Inc. | (assignment on the face of the patent) | / |
| Date | Maintenance Fee Events |
| Date | Maintenance Schedule |
| Jul 15 1983 | 4 years fee payment window open |
| Jan 15 1984 | 6 months grace period start (w surcharge) |
| Jul 15 1984 | patent expiry (for year 4) |
| Jul 15 1986 | 2 years to revive unintentionally abandoned end. (for year 4) |
| Jul 15 1987 | 8 years fee payment window open |
| Jan 15 1988 | 6 months grace period start (w surcharge) |
| Jul 15 1988 | patent expiry (for year 8) |
| Jul 15 1990 | 2 years to revive unintentionally abandoned end. (for year 8) |
| Jul 15 1991 | 12 years fee payment window open |
| Jan 15 1992 | 6 months grace period start (w surcharge) |
| Jul 15 1992 | patent expiry (for year 12) |
| Jul 15 1994 | 2 years to revive unintentionally abandoned end. (for year 12) |