BRIER PETER (NL)
EP0491650A2 | 1992-06-24 | |||
US5827593A | 1998-10-27 | |||
DE4213466A1 | 1993-10-28 |
PATENT ABSTRACTS OF JAPAN vol. 1997, no. 06 30 June 1997 (1997-06-30)
1. | A method for manufacturing an injection molded product, wherein, utilizing the same injection mold, injection molded products of a different final form are made, wherein the injection mold bounds a mold cavity, of which mold cavity the shape can be varied in that at least a part of the injection mold disposes of a movable wall part, wherein operating means are provided by means of which the position of the respective movable wall part can be influenced, wherein these operating means are operated to provide in a first injection molding processing step an injection molded product having a first final form and wherein the operating means are operated in a second injection molding processing step to provide an injection molded product having a second final form, deviating from the first final form. |
2. | A method according to claim 1, wherein after removing the first injection molded product from the injection mold, the operating means for influencing the movable wall part are brought in another condition, after which the plastic for the second injection molded product is subsequently injected into the injection mold. |
3. | A method according to claim 1 or 2, wherein the operating means comprise a pressure chamber in which fluid is present, wherein the pressure is measured in the mold cavity and the pressure chamber, and wherein depending on the desired position of the respective wall part the pressure in the pressure chamber is controlled. |
4. | A method according to any one of claims 13, wherein the movable wall part is formed by a flexible wall part which is engaged at the rear side by said operating means. |
5. | A method for manufacturing an injection molded product according to any one of claims 14, wherein the first injection molded product manufactured in the first injection molding processing step is a first substantially plateshaped optical registration carrier part, while the second injection molded product manufactured in the second injection molding processing step is a second substantially plateshaped optical registration carrier part, wherein the first registration carrier part is provided with a surface structure which simplifies unstacking of the finished optical registration carriers, such as, for instance, a stacking ring or stacking bumps, and wherein the second registration carrier part is substantially smooth, such that the surface is printable. |
6. | A method according to claim 5, wherein the first and the second registration carrier parts, after being removed from the injection mold, are bonded together. |
7. | A method according to claim 6, wherein, before the first and the second registration carrier parts are bonded together, the first registration carrier part is provided with a reflective coating, such as, for instance, a metallic coating. |
8. | A method according to any one of claims 57, wherein the second registration carrier part is provided with an imprint. |
9. | A method according to any one of the preceding claims, wherein a number of movable wall parts are provided which are individually operable, wherein by means of said number of movable wall parts, a coding, such as, for instance, a dot matrix coding, is provided in the injection molded product.. |
10. | A method according to any one of the preceding claims, wherein a said movable wall part, in addition to two extreme positions, can further assume a large number of intermediate positions. |
11. | An injection mold provided with two mold halves which, in a closed condition, jointly bound an injection mold cavity, wherein at least one of the injection mold halves is provided with a movable wall part which bounds the mold cavity, wherein furthermore operating means are provided for influencing the position of the movable wall part, wherein these operating means are connectible to, and controllable by, a control, wherein the control is arranged to operate the operating means in a first injection molding processing step for keeping the movable wall part in a first condition for manufacturing a first injection molded product, wherein the control is arranged to operate the operating means in a second injection molding processing step for keeping the movable wall part in a second condition for manufacturing a second injection molded product. |
12. | An injection mold according to claim 11, wherein the control is arranged to have the transition of the operating means for bringing the movable wall part from the first condition to the second condition take place after the removal of a first injection molded product manufactured in the first injection molding processing step and before the second injection molding processing step is performed. |
13. | An injection mold according to claim 11 or 12, wherein the movable wall part is formed by a flexible wall part which bounds a part of the mold cavity. |
14. | An injection mold according to any one of claims 1113, wherein the operating means comprise a pressure chamber which is filled with fluid whose pressure is controllable, wherein one of the walls of the pressure chamber is formed by said movable wall part, wherein the pressure chamber is provided on the side of the movable wall part remote from the mold cavity. |
15. | An injection mold according to claim 14, wherein a controllable plunger is provided for controlling the pressure of the fluid in the pressure chamber. |
16. | An injection mold according to claim 14 or 15, wherein in the pressure chamber and in the mold cavity pressure sensors are arranged which communicate with a control which, depending on the signals provided by the pressures sensors, controls the pressure in the pressure chamber. |
17. | An injection mold according to any one of claims 1113, wherein the operating means are designed as an actuator, such as, for instance, an electromagnetic or piezoelectric actuator. |
18. | An injection mold according to at least claim 13, wherein the flexible wall part has been formed in that in the respective mold half, on the side remote from the mold cavity, at the location of the flexible wall part, a chamber has been formed which extends virtually up to the mold cavity bounding wall of the mold half, such that there only a very thin, flexible wall part remains. |
19. | An injection mold according to claim 13, wherein the flexible wall part is part of an insert which is included in the respective mold half. |
20. | An injection mold according to any one of claims 1119, wherein the mold cavity in the first condition of the movable wall part is designed for forming a first substantially plateshaped optical registration carrier part, while the mold cavity in the second condition of the movable wall part is designed for forming a second substantially plateshaped optical registration carrier part, wherein the first registration carrier part is provided with a surface structure which simplifies unstacking of the finished optical registration carriers, such as, for instance, a stacking ring or stacking bumps, and wherein the second registration carrier part is substantially smooth, such that the surface is printable. |
21. | An injection mold according to any one of claims 1120, wherein a number of said movable wall parts are provided which are individually operable for applying a coding on the injection molded product. |
22. | An injection mold according to any one of claims 1121, wherein the operating means of a said movable wall part are arranged to keep said movable wall part, in addition to said first and second conditions, in a number of intermediate conditions. |
23. | An injection molding apparatus provided with an injection mold according to any one of the preceding claims. |
24. | Apparatus for manufacturing DVDs, provided with an injection molding apparatus according to claim 23, and with a control and a number of successive processing stations, among which a processing station for bonding together first and second injection molded products, wherein the control is designed to arrange for alternate manufacture of first and second injection molded products by means of the respective injection molding apparatus and for driving the processing station for bonding together successively produced first and second injection molded products. |
25. | Apparatus according to claim 24, provided with a processing station for providing the first injection molded product with a reflective coating. |
26. | Apparatus according to claim 24 or 25, provided with a processing station for applying an imprint on the second injection molded product. |
27. | An injection molded product obtained with the method according to any one of claims 110, utilizing an injection mold according to any one of claims 1122. |
28. | An injection molded product according to claim 27, wherein the injection molded product is an optical registration carrier provided with two registration carrier parts which have both been manufactured in the same mold cavity of the same injection mold, wherein the first registration carrier part has a relief structure, for instance in the form of a stacking ring or stacking bumps, and wherein the second registration carrier part does not have such a relief structure. |
The invention relates to a method for manufacturing an injection molded product. The invention further relates to an injection mold, an injection molding apparatus provided with such an injection mold and to apparatus for manufacturing DVDs provided with such an injection molding apparatus.
In practice, there is sometimes a need to manufacture several injection molded products in random order in one process with one injection molding machine. This can evidently be done by incorporating different mold cavities in the injection mold. However, in the case of products where accuracy is of major importance, such a multiple mold sometimes cannot provide relief. To be considered in this connection are, for instance, products which need to be interconnected afterwards. By way of example, one can think of DVDs, more particularly DVD-5. Such DVDs consist of two disks of which at least one is provided with an information-containing layer in the form of a pit pattern.
After one of the disks has been provided with a reflective coating, the disks are connected with each other and optionally further provided with an imprint. In the case of DVD-5, sometimes the second disk is manufactured in the same mold cavity as the first disk. Accordingly, this second disk, designated in practice as dummy disk, also contains the information- containing pit pattern, but this pit pattern does not have any function and is not read out. It is well known that CDs, but also DVDs, are provided with stacking rings or stacking bumps. This involves a relief structure which is annular and comprises bumps, respectively, on a main surface of the disk, which relief structure provides that the disks when stacked onto each other can easily be unstacked again. This as a consequence of the fact that the relief structure provides for a small contact surface between disks stacked
onto each other. In the use of the known method (in that connection, see US-5, 827,593 ; column 2, lines 21-24), the DVD thereby obtained will have such relief structure on both surfaces. This is undesired because one of the surfaces is often provided with a printing, which is rendered considerably more difficult by the presence of such a relief structure.
Accordingly, the invention contemplates a method wherein using a single injection mold, different injection molded products can be manufactured in the same mold cavity.
To that end, the invention provides a method wherein, utilizing the same injection mold, injection molded products of a different final form are made, wherein the injection mold bounds a mold cavity, of which mold cavity the shape can be varied in that at least a part of the injection mold disposes of a movable wall part, wherein operating means are provided by means of which the position of the respective movable wall part can be influenced, wherein these operating means are operated to provide in a first injection molding processing step an injection molded product having a first final form and wherein the operating means are operated in a second injection molding processing step to provide an injection molded product having a second final form, deviating from the first final form.
The invention further provides an injection mold which is suitable and intended for performing the above-described method. To that end, according to the invention, the injection mold is provided with two mold halves which, in a closed condition, jointly bound an injection mold cavity, wherein at least one of the injection mold halves is provided with a movable wall part which bounds the mold cavity, wherein furthermore operating means are provided for influencing the position of the movable wall part, wherein these operating means are connectible to, and controllable by, a control, wherein the control is arranged to operate the operating means in a first injection molding processing step for keeping the movable wall part in a first condition for manufacturing a first injection molded product, wherein the
control is arranged to operate the operating means in a second injection molding processing step for keeping the movable wall part in a second condition for manufacturing a second injection molded product.
It is noted that the first and the second injection molding processing steps do not need to follow each other directly. The concept of the invention should be understood to encompass a method in which, for instance, first ten first injection molded products are manufactured and subsequently ten second injection molded products are manufactured. However, it will be evident that the concept of the invention should also be understood to encompass a method in which alternately first and second injection molded products are manufactured. In particular when in a following path the first and the second injection molded product are to be jointly processed further, for instance in that the injection molded products are to be bonded together, the method according to the invention has the advantage that the process can be completed with just one injection molding apparatus. This results inter alia in a considerable saving on the investment for a production line for the respective process. Moreover, the dimensions and dimensional tolerances of the first and the second injection molded product will accurately correspond with each other, obviously apart from the portion where the shape of the injection molded product is determined by the movable wall part. In particular in the case of objects to be subsequently interconnected, such accurately corresponding dimensions and dimensional tolerances are of great importance.
According to a further elaboration of the invention, after removing the first injection molded product from the injection mold, the operating means for influencing the movable wall part are brought in another condition, after which the plastic for the second injection molded product is subsequently injected into the injection mold. To that end, according to a further elaboration, the injection mold is characterized in that the control is arranged to have the transition of the operating means for bringing the
movable wall part from the first condition to the second condition take place after the removal of a first injection molded product manufactured in the first injection molding processing step and before the second injection molding processing step is performed.
This has as a consequence that the formation of a respective injection molded product is not, at least not actively, influenced by the movable wall part during the injection of the plastic into the injection mold or during curing. Incidentally, this conclusion does not exclude the possibility that the operating means for influencing the movable wall part, in one of the conditions allow movement of the wall part under the influence of the pressure prevailing in the injection mold, which is exerted by the liquid plastic on the wall part; in that case, however ; this movement is passive and not active.
In a particularly favorable further elaboration of the invention, the movable wall part is formed by a flexible wall part which is engaged at the rear side by the operating means. The flexible wall part bounds a part of the mold cavity.
Such an embodiment has the advantage that there are no parts present in a mold half that slide relative to the mold half, which reduces the chances of trouble. This is because plastic might flow into the slits between parts sliding relative to each other, which might adversely affect, or actually block, their slidability relative to each other. In the case of flexible wall parts, such slits are not present and accordingly the operating means for moving the flexible wall part are inaccessible to liquid plastic. Such an injection mold is therefore much less sensitive to trouble and needs less servicing. An additional advantage of this embodiment is that not even the smallest"flashes"occur, which flashes might lead to contamination or damage of the printing equipment.
According to a further elaboration, the first injection molded product manufactured in the first injection molding processing step can be a first
substantially plate-shaped, optical registration carrier part, while the second injection molded product manufactured in the second injection molding processing step is a second substantially plate-shaped optical registration carrier part, wherein the first registration carrier part is provided with a surface structure which simplifies unstacking of the finished optical registration carriers, such as, for instance, a stacking ring or stacking bumps, and wherein the second registration carrier part is substantially smooth, such that the surface is printable. Evidently, the mold cavity of the injection mold should define a shape appropriate therefor and should contain inter alia a stamper for forming the pit pattern containing the information.
Such injection molded products can be used-for manufacturing DVDs which are properly unstackable owing to the presence of a stacking ring or stacking bumps and whose other side is yet properly printable in that this side does not have any stacking ring or stacking bumps. The dimensions of the two injection molded products, incidentally, correspond accurately with each other, and only one injection molding apparatus and one injection mold need to be deployed for manufacturing both registration carrier parts.
The invention further provides an injection molding apparatus provided with an injection mold according to the invention. In particular the control of such an injection molding apparatus should be arranged to be able to drive, at least to operate at the right moment, the operating means of the movable wall part. What can thus be accomplished is that the transition of the movable wall part from one condition to the other condition does indeed occur between two injection molding processing steps and not during the injection or the curing of the plastic in the mold.
According to a further elaboration, the first and the second registration carrier part, after being removed from the injection mold, can be connected with each other. Here, before the first and the second registration carrier part are connected with each other, the first registration carrier part can be
provided with a reflective coating, such as, for instance, a metallic coating.
Further, the second registration carrier part can be provided with an imprint. This step can take place before the registration carrier parts are connected with each other or afterwards.
For the purpose of performing these next steps, the invention further provides apparatus for manufacturing DVDs, the apparatus being provided with an injection molding apparatus according to claim 23, and with a control and a number of successive processing stations, among which a bonding station for bonding together first and second injection molded products, wherein the control is designed to arrange for alternate manufacture of first and second injection molded products by means of the respective injection molding apparatus and for driving the processing station for interconnecting successively produced first and second injection molded products. Here, the apparatus may be provided with a processing station for providing the first injection molded product with a reflective coating and optionally with a processing station for applying an imprint on the second injection molded product. Evidently, also transport means will be present in the apparatus, for moving the registration carrier parts and the interconnected registration carrier parts from and to the different processing stations.
The invention further relates to an injection molded product obtained with the method according to the invention, utilizing an injection mold according to the invention. More particularly, the invention relates to an optical registration carrier provided with two registration carrier parts, wherein both parts have been manufactured by means of the method and injection mold according to the invention.
Further elaborations of the invention are described in the subclaims and will be further clarified hereinafter with reference to the drawing.
Fig. 1 shows a top plan view of a registration carrier part with stacking ring;
Fig. 2 shows a top plan view of a registration carrier part with stacking bumps ; Fig. 3 shows a cross-sectional view along line III-III from Fig. 1 in combination with a similar cross-sectional view of a registration carrier part without relief structure ; Fig. 4 shows a schematic cross-sectional view of an injection mold according to the invention; Fig. 5 shows a detail of the cross-sectional view from Fig. 4; Fig. 6 shows a similar cross-sectional view to that represented in Fig. 5, of a second exemplary embodiment of an injection mold ; Fig. 7 schematically shows apparatus for manufacturing DVDs.
Although hereinafter an exemplary embodiment is discussed which relates to the manufacture of DVDs, it is important to note that the invention is not limited to a method, an injection mold and an injection molding apparatus for manufacturing optical registration carrier parts for the purpose of the manufacture of DVDs. With the method, injection mold and injection molding apparatus according to the invention, totally different products can be manufactured as well. To be considered, by way of example, are products which are otherwise identical in shape but are only distinguished from each other by a relief code, mutually different in each case, such as, for instance, a dot code matrix. Thus, injection molded products can be individualized. Also other uses where products differing from each other only by small variations in shape can be realized by means of a method, injection mold and injection molding apparatus according to the invention.
To clarify the present exemplary embodiment, Figs. 1 and 2 show a top plan view of a disk-shaped optical registration carrier part 1 and 51, respectively, which is provided with a stacking ring 2 and with stacking bumps 52, respectively. Such a stacking ring 2 or stacking bumps 52 serve to simplify the unstacking of a number of optical registration carriers
stacked onto each other; this as a consequence of the fact that the contact surface between optical registration carriers stacked onto each other is considerably reduced by the presence of the stacking ring or stacking bumps. Registration carriers with such stacking rings or stacking bumps are known per se.
As already indicated in the introduction of this specification, DVD can be manufactured from two optical registration carrier parts. The first registration carrier part is then preferably provided with a stacking ring or stacking bumps. The other registration carrier part is preferably not provided with such relief structures, so as to enable a fine, undisturbed imprint to be applied over the entire surface.
Fig. 3 shows a cross section taken along line Ill-Ill from Fig. 1 of a first registration carrier part 1 provided with a relief structure in the form of a stacking ring 2 or stacking bumps 52 and, arranged under it, a second registration carrier part 3, in which such a relief structure 2,52 is absent.
The two registration carrier parts, optionally after undergoing a number of intermediate processing steps, are bonded together to form a DVD.
According to an elaboration of the invention, the first and the second registration carrier parts 1,3 are manufactured in the same injection mold.
Such an injection mold 4 is represented in Fig. 4 and the detail of interest is represented in Figs. 5 and 6.
The detail of Fig. 5 shows mold half parts Ml, M2 in which a movable wall part is formed by a flexible wall part 6. Behind the flexible wall part 6, that is, on the side of the wall part 6 remote from the mold cavity 7, is a pressure chamber 8. The pressure chamber 8 is filled with a fluid, preferably a non-compressible or poorly compressible liquid. Connected to the pressure chamber 8, via a line 9, is a plunger 10 whose position is settable by means of a control 11. By moving the plunger 10, the flexible wall part 6 will assume either the position represented in solid lines 12 or the position represented in dotted lines 13. It is also possible that the
control 11, instead of actively moving the plunger 10, imposes on the plunger either active counterpressure or no active counterpressure, depending on the injection molded product that is desired. With active counterpressure, which is to say that the pressure in the pressure chamber 8 is kept equal to the pressure in the mold cavity 7, a second injection molded product 3 will be obtained without stacking ring 2 or stacking bumps 52. For controlling the pressure in the pressure chamber 8, pressure sensors may be positioned in the pressure chamber 8 and in the mold cavity 7, with which the pressures are measured and on the basis of which the pressures can be tuned to each other. When no active counterpressure is applied, the liquid plastic, when Riling the mold cavity 7, will press the flexible wall part 6 rearwards, and a registration carrier part 1,51 will be formed with a stacking ring 2, or stacking bumps 52, respectively. In Fig. 5, the flexible wall part 6 and the pressure chamber 8 have been formed by milling off material from the mold half.
Fig. 6 shows a variant of Fig. 5 in which the flexible wall part 6 is part of an insert 19 which has been included in the mold half Ml. In addition, the exemplary embodiment of Fig. 6 is distinguished from that of Fig. 5 by the design of the operating means. In the exemplary embodiment of Fig. 6, the operating means are formed by an actuator 20, such as, for instance, an electromagnetic or piezoelectric actuator 20 which is connected directly with the flexible wall part 6.
According to a third variant, the movable wall part can also be formed by a ring arranged slidably in the mold half. Such a mold is known per se from JP-09-035338 (appl. no. 07-200485), but the manner of control of the known mold differs from the control of the injection mold according to the present invention. For in the Japanese publication, with the respective mold, in each case the same injection molded product is manufactured and the slidably arranged ring is present for the purpose of creating a more favorable flow pattern in the mold during the filling of the mold. The ring of
the known mold moves within an injection molding processing step, this in contrast to the movable wall part of the injection mold according to the invention, where the condition of the operating means for determining the position of the movable wall part is changed in between successive injection molding processing steps for forming different products in the same mold cavity. The publication in question does not give the skilled person any hint of manufacturing different products in the same mold cavity by providing a control suitable therefor and performing a method suitable therefor.
Finally, Fig. 7 schematically shows apparatus provided with an injection molding apparatus 14 with an injection mold 4 as described above, as well as a transport system 15 for moving registration carrier parts which are manufactured in the injection molding apparatus 14, to the different processing stations 16-18. The first processing station 16 can for instance serve to apply a reflective coating to the first registration carrier part 1, 51.
The second processing station 17 can for instance be a bonding station for bonding together a first and a second registration carrier part 1, 51, and 3, respectively. The third processing station 18 can be, for instance, a station by means of which the assembly of the two registration carrier parts can further be provided with an imprint. It will be clear that still other processing stations can be part of the apparatus. To be considered here, for instance, are stations for applying supplementary coatings or resist layers for protection of or writable layers for recording data on the registration carrier.
By means of the injection molding apparatus, for instance alternately first and second registration carrier parts are manufactured, which first and second registration carrier parts are led by the transport system through the different processing stations, there to undergo the various necessary processing operations and, at the end of the apparatus, to provide a finished optical registration carrier.
It will be clear that the invention is not limited and that also the variants fall within the framework of the invention as defined by the claims.
The method and the injection mold evidently also comprise the variants where more than two final forms can be realized. Such a variant has already been described in connection with the provision of a coding. However, also the height of the stacking ring on an optical registration carrier could be varied by varying the set position of the respective movable wall part. The height of the stacking ring obtained could then be used as a coding. The terminology of the claims therefore does not exclude the second final form being a different final form in each case. Nor do the claims exclude the possibility, besides the second final form, of a third, a fourth, a fifth through to an n-th final form.
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