Patent Application
20080175947
1. Field of the Invention
The present invention relates to cut structures for molds and, particularly, to a cut structure for a plastic molding mold.
2. Discussion of the Related Art
Most products made of polymers or other plastics are usually formed using injection molding. During a typical injection molding process, a molten material is injected into a mold cavity via a runner. The molten material in the cavity is cooled to form the molded product.
However, if the molten material is directly injected into the mold cavity, resistance from the mold cavity will affect the molten material resulting in flow marks appearing in the final product. Therefore, it is necessary to adopt a gating structure for molded product so as to eliminate defects. The gating structure is generally a structure that connects the runner and the mold cavity.
One kind of typical molded product with a gating structure is represented in
In order to reduce working steps, a method is adopted to design the position of the gate in a side of a mold cavity. Referring to
Therefore, an improved cut structure is desired in order to overcome the above-described problems.
A cut structure for a mold apparatus, which the cut structure is configured to connect to a mold cavity, includes a first hole, a cut punch and a draw pin. The first hole is configured to communicate with the mold cavity. The cut punch is movably received in the first hole for cutting a portion of a molded product. The cut punch defines a second hole; and the draw pin is movably received in the second hole of the cut punch. The draw pin has a wedge cutout configured for drawing the portion of a molded product from the mold apparatus.
Other advantages and novel features of the present cut structure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawing.
The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present cut structure. Moreover, in the drawings, like reference numerals designate corresponding parts.
Referring now to the drawings in detail,
The injection mold apparatus 100 includes an upper mold 10, a lower mold 20, an ejector structure 30, and a cut structure 40. The upper mold 10 and the lower mold 20 may be separable from each other. When the upper and lower molds 10, 20 are engaged together, a parting plane 120 is formed therebetween.
The upper mold 10 includes an upper fixed plate 12, an upper mold part 14, and an upper mold core 16. The upper fixed plate 12, the upper mold part 14, and the upper mold core 16 are fixed together with screws. The upper mold 10 is fixed to a fixed side of the injection mold apparatus 100.
The upper fixed plate 12 is substantially square, and may be fixed to attach with the injection mold apparatus 100. The upper fixed plate 12 defines an opening 122 in a central area thereof. The opening 122 includes a first hole 1222 and a second hole 1224. A diameter of the first hole 1222 is larger than that of the second hole 1224. The upper mold part 14 defines a recess, and the upper mold core 16 is engaged in the recess. The upper mold part 14 and the upper mold core 16 respectively define a common through hole 140 in central areas thereof. The through hole 140 communicates with the opening 122 of the upper mold core 16.
A bush 18 is inserted into the through hole 140. A bottom end of the bush 18 is received in the through hole 140, and a top end of the bush 18 is received in the second hole 1224. The bush 18 has a sprue 182, a gate 184 and a runner 186 defined in a central area thereof. The sprue 182 is used for seating a nozzle (not shown) of the injector mold apparatus 100, and the molten material may flow into the mold cavity 210 through the runner 186 and the gate 184.
A positioning ring 19 is engaged in the first hole 1222 of the opening 122. The positioning ring 19 may resist the bush 18 so as to prevent the bush 18 breaking off from the opening 122. The positioning ring 19 may help to align the nozzle with the runner 182 of the bush 18.
The lower mold 20 includes a lower fixed plate 22, two spaced blocks 24, a support plate 26, a lower mold part 28, and a lower mold core 29. The lower fixed plate 22, the spaced blocks 24, the support plate 26, the lower mold part 28 and the lower mold core 29 are fixed together with screws. The lower mold 20 is fixed to a movable side of the injection mold apparatus 100.
The lower fixed plate 22 is substantially square-shaped, and fixed to a movable disk (not shown) of the injection mold apparatus 100. Each spaced block 24 is substantially rectangular-shaped, and supported on one of two ends of the lower fixed plate 22. The spaced blocks 24, beneficially, has sufficient height to provide a desired distance between the lower fixed plate 22 and the support plate 26. The support plate 26 is fixed on the two spaced blocks 24. The lower mold part 28 is fixed on the support plate 26. The lower mold part 28 defines a recess, and the lower mold core 29 is engaged in the recess. When the upper and lower mold cores 16 and 29 are engaged together, it cooperatively forms a mold cavity 210 therebetween. The runner 128 communicates with the mold cavity 210 so that molten material such as molten plastic may flow along the runner 128 into the mold cavity 210.
The ejector structure 30 is movably positioned above the lower fixed plate 22, between the two spaced blocks 24. The ejector structure 30 includes an upper ejector plate 32, a lower ejector plate 34, and a plurality of ejector pins 36.
The upper ejector plate 32 defines a plurality of stepped holes 322. The support plate 26, the lower mold part 28 and the lower mold core 29 cooperatively define a plurality of common through holes 362. Each ejector pin 36 extends through a corresponding stepped hole 322, and is movably received in a corresponding through hole 362. The lower ejector plate 34 is fixed on a bottom side of the upper ejector plate 32. Thus one end of each ejector pin 36 is locked into the corresponding stepped hole 322 by the lower ejector plate 34, so as to fix all the ejector pins 36 in the ejector structure 30.
The cut structure 40 includes an inner cut hole 42, a first support structure 44, a second support structure 46, an inner cut punch 48 and a draw pin 49.
The inner cut hole 42 is a circular hole, and defined in a central area of the support plate 26, the lower mold part 28, the lower mold core 29, the upper ejector plate 32 and the lower ejector plate 34.
The first support structure 44 and the second support structure 46 are positioned between the two spaced blocks 24, under the lower ejector plate 34. The first support structure 44 includes an upper board 442, a lower board 444, two springs 446 and two screws 448.
The upper board 442 is disposed under the lower ejector plate 34. The upper board 442 defines a received hole 4422. The receive hole 4422 communicates with the inner cut hole 42. One end of the inner cut punch 48 is received in the received hole 4422, the other end of the inner cut punch 48 is received in the inner cut hole 42. The lower board 444 and the upper board 442 are fixed together. The lower ejector plate 34 defines two guide holes 342. A diameter of the guide holes 342 is slightly larger than that of the screws 448. A bottom end of each screw 448 is fixed to the upper board 442, and a top end of each screw 448 is movably received in a corresponding guide hole 342. A portion of each screw 48 below the lower ejector plate 34 is surrounded by a corresponding spring 446. A diameter of each spring 446 is larger than that of each guide hole 342. Accordingly, the springs 446 resist both the lower ejector plate 34 and the upper board 442. If the upper board 442 and the lower board 444 are pressed upward, the upper board 442 and the lower board 444 will move together relative to the upper ejector plate 32 and the lower ejector plate 34, with the screws 48 sliding along the guide holes 342.
The structure of the second support structure 46 is similar to that of the first support structure 44, and includes an upper holder 462, a lower holder 464, two springs 466 and two screws 468. The upper holder 462 is disposed above the lower board 444, and defines a stepped hole 4622. The stepped hole 4622 is configured for receiving one end of the draw pin 49. The lower holder 464 and the upper holder 462 are fixed together, and the lower holder 464 resists the draw pin 49 so as to avoid the drawn pin 49 separating from the second support structure 46. The two springs 466 and the two screws 468 are similar to those of the first support structure 44, which are not detailed herein.
Referring to
The draw pin 49 is substantially a cylinder. One end of the draw pin 49 has a wedge cutout 492, and the other end of the draw pin 49 has a flange 494. The wedge cutout 492 is used for snapping the gate connected with the runner 186. The flange 494 is received in the stepped hole 4622.
In use, the upper mold 10 and the lower mold 20 are closed. When the molten plastic is injected, the molten plastic firstly injects to the mold cavity 210 from the nozzle of the mold apparatus 100. Then, the molten plastic flows into to the runner 186 from the sprue 182 of the bush 18. The molten plastic further flows into the mold cavity 210 from the gate 184. After the molten plastic has filled the whole mold cavity 210, the concave portion 482 and the wedge cutout 482, and when the molten plastic is not completely solidified, the first support structure 44 and the second support structure 46 are driven toward the upper mold core 16 at the same speed so as to move the inner cut punch 48 and the draw pin 49. When the brim portion 4822 of the inner cut punch 48 contacts with the upper mold core 16, the product scrap in the concave portion 482 and the wedge cutout 492 is cut off from the molded product.
After that, the lower mold 20 moves downward. Owing to the molded product scrap with the gate 184 is adhered to the concave portion 482 and the wedge cutout 492, when the lower mold 20 with the cut punch 48 and the draw pin 49 move downward, the molded product scrap is separated from the molded product, and the gate 184 is drawn off from the runner 186. Accordingly, the gate 184 is separated from the upper mold 10. Then, the second support structure 46 is driven so as to make the draw pin 49 move relative to the inner cut punch 48. The wedge cutout 492 extends out from the through hole 486. Accordingly, the product scrap and the gate 184 are drawn from the concave portion 482. Finally, the upper ejector plate 32, the second ejector plate 34 are moved together by a back rod (not shown) of the injection mold apparatus 100 so as to make the ejector pins 36 move up and push the solidified plastic piece. Thus, the molded product is pushed out from engagement with the lower mold core 29.
Referring to
As described above, the cut structure is configured to allow the gate and the scrap in the mold cavity 210 to be cut therein. A main advantage of the cut structure is that the molded product has not only directly achieved the desired structure, it has also achieved a good appearance. In addition, the cut structure is simple and may greatly improve the product quality at relatively little cost.
The above-described cut structure can be used with other kinds of molding apparatuses besides the injection mold apparatus 100 illustrated, or with other kinds of apparatuses that require a cut structure. The products formed can have good mechanical strength as well as a smooth, attractive appearance.
It is believed that the present embodiment and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 200710073000.4 | Jan 2007 | CN | national |
