WO2006019294A1

WO2006019294A1 - Method and device for removing a disc-shaped information carrier from a mould

Info

Publication number: WO2006019294A1
Application number: PCT/NL2005/000594
Authority: WO
Inventors: Joseph Johannes Jacobus Janssen
Original assignee: F.T.Engineering B.V.
Priority date: 2004-08-18
Filing date: 2005-08-17
Publication date: 2006-02-23
Also published as: NL1026860C2

Abstract

Method and installation for removing a disc-shaped information carrier moulded by injection moulding and possibly subsequent pressing from a mould cavity. Removal takes place, inter alia, by blowing in air from one mould section. This blown air is blown from the central punch member from the centre of the disc towards the outside. According to the invention it is proposed to close off the opening in the disc-shaped information carrier during this operation. Preferably this is effected by leaving the punch member in the opening when blowing out the gas, such as air. The characteristics of the core of the disc-shaped information carrier can be optimised by this means.

Description

Method and device for removing a disc-shaped information carrier from a mould

The present invention relates to a method for the production of a disc-shaped information carrier, comprising delimiting a mould cavity using two mould halves, introducing and dispersing fluid plastic into said cavity, when forming said information carrier making an opening therein by inserting a punch member into said mould cavity from one mould half, moving said mould halves apart and removing said infoπnation carrier using an ejector member. Such a method is generally known in the art and is used, for example, in the production of CDs and DVDs. In such information carriers the information density is continually increasing, as a result of which increasingly more stringent requirements are being imposed on the refractive/light transmitting properties of the material of the information carrier and the accuracy with which elevations and depressions are made. Furthermore, increasingly more stringent requirements are being imposed on the flatness of the disc-shaped information carrier. As a result the heart of the disc-shaped information carrier, that is to say the region around the central opening, must comply with increasingly more stringent requirements. There must be no visible stresses and stresses must not lead to warping of the core. A construction for moving both the punch member and the ejector member is known in the state of the art. With this construction, after an opening has been made by means of the punch member and the core or sprue thus produced has been removed when the ejector member moves outwards, the punch member is withdrawn. That is to say the punch member first executes a movement in the direction away from said one mould part, into which this has been introduced, and then executes a return movement back into the one mould part, the optical information carrier or other injection moulded product still being on the punch member during the return movement. By moving the ejector sleeve outwards at the same time, (stripping) of the optical information carrier from the punch member takes place and this can be removed.

Efforts are being made to shorten the cycle time for a product as much as possible. On the other hand the intention is to be able to control the conditions during the removal of the optical information carrier from the punch member as closely as possible. This is important, inter alia, if use is made of air blown between the optical information carrier and the one mould half when opening the mould. Apart from being better able to remove the optical information carrier from the one mould as a result, the mechanical properties of the product are also effected by influencing the cooling behaviour of, in particular, the core of the product or optical information carrier.

The aim of the present invention is to provide an improved method.

This aim is realised with a methods as described above, in that the removal of said information carrier comprises moving said punch member further in said direction for punching out said opening at a first speed while at the same time moving said ejector member in the same direction at a second speed, wherein said second speed is higher than said first speed.

In contrast to the state of the art, according to the present invention after punching the punch member is not moved back into the mould half in which it was accommodated, but the ejector member is moved at a higher speed than the punch member after removal of the sprue from the injected product by the punch member. That is to say, after punching the opening, the ejector sleeve or the ejector member overtakes the punch member during this movement, so that the optical information carrier or other product is pushed off the punch member. This is a very gradual movement because the punch member is still continuing to move in the same direction during this operation. As a result, on the one hand, shocks are avoided and, on the other hand, for example when feeding a cooling gas, accurate control of the gas flow can take place because accurate adjustment of the gap between the product and the one mould half is possible. Moreover, it is possible to separate injected product a greater distance away from the one mould half as a result of which it is easier to grasp this product for the removal thereof. Overall a more stable construction is obtained, which results in fewer faults and the cycle time can be shortened because it is not necessary that the direction of movement of the punch member is reversed. As a result there is also no risk that the sprue or core that has been pushed outwards by the punch member is moved back onto the optical information carrier, with, as a consequence, the danger there will be particles on the optical information carrier, as a result of which this no longer meets the specification.

With this arrangement it is possible to move the ejector member at the same time as the punch member. If, however, the ejector member is close to the disc-shaped information carrier such a simultaneous movement would lead to an undesired effect. In such a case it is necessary for the ejector member to be activated with some delay relative to the movement of the punch member.

It is possible to move the punch member back only after the ejector sleeve has overtaken the punch member to such an extent that the disc is completely free of the punch member. However, it is also possible to initiate the return movement of the punch member at an earlier point in time. However, the start of the "stripping movement" for the optical information carrier by the punch member will always be carried out with the punch member and the ejector member moving in the same direction.

Apart from the ejector member described above that can comprise an ejector sleeve, according to a further advantageous embodiment of the invention there can also be a further ejector member that can be an ejector pin. Such a further ejector member is fitted for the removal of the part punched out by the punch member.

Preferably this moves at the same speed as the ejector member. However, the delay, described above, when starting the movement of the ejector member is not necessary, that is to say the further ejector member or the ejector pin can move at the same time as the punch member.

The construction described above can be used with both horizontally and vertically operating injection moulding installations.

The invention also relates to an installation for carrying out the method described above. According to the present invention this installation for the production of a disc¬ shaped information carrier comprises two mould halves that can be moved relative to one another, which delimit a mould cavity between them, wherein one mould half is provided with a punch member and an ejector member, wherein there are control means in the mould cavity for moving said punch member and ejector member relative to said one mould half, wherein said control means are embodied such that when said mould opens said punch member is moved in the direction away from said one mould at a first speed and said ejector member is moved in the same direction at a second speed, higher than said first speed.

The movement of both punch member and the ejector member can be executed by the control means in any manner known in the art. According to an advantageous embodiment of the invention, the control means consist of a construction operating with a screw thread. The complex movement of ejector sleeve and punch can be obtained by a single drive with various threaded rods of different pitch. Moreover, this can be combined with combination of the movement of a central ejector pin that has been fitted for ejection of the sprue. It will be understood that other techniques can also be used for moving both the punch member and the ejector. What is important according to the invention is that the mutual movement of these parts takes place in a coordinated manner, wherein the punch member with the disc-shaped information carrier preferably moves away from the mould section concerned and separation of the disc from the punch member takes place only after the passage of a specific quantity of gas that flows over the surface of the disc that has just been produced. Moreover, with such a construction it is possible, by means of a suitable embodiment thereof, to adjust the position of the punch with respect to the drive of the control described above. Adaptation to the thickness of the punched articles can be provided by this means. This applies, for example, to the production of CDs or DVDs, where a DVD (half) is appreciably thinner than a CD.

The invention will be explained in more detail below with reference to an illustrative embodiment shown in the drawing. In the drawing;

Fig. 1 shows, diagrammatically, a front and sectional view of the combination of a mould assembly and control means;

Figs 2 - 5 show, in detail, the various positions that the ejector pin, punch member and ejector can assume with respect to one another when the injection moulded product is removed from the mould cavity.

In the drawings a mould assembly is indicated by 1. This consists of two mould halves or mould sections 2, 4. It will be understood that the mould can have more than two sections.

2 indicates a stationary mould provided with an injector nozzle 3. The movable mould 4 is provided with an ejector or ejector sleeve 5 within which a punch 6 is arranged. An ejector pin 9, for removing the sprue that partly extends into the cavity of the injector nozzle 3, is arranged inside punch 6. The mould cavity is indicated by 7 and the desired pattern of elevations and depressions is produced with of stamper 8.

An air inlet, to which a source of compressed air not shown in more detail is connected, is indicated by 10. Air can move via air inlet 10 in the direction of arrows 19 between the ejector sleeve 5 and the mould 4 so as to flow over the information carrier formed. Ih Figs 2 - 4 this information carrier is indicated by 29 (shown in part).

A return spring 15, which drives the ejector pin towards the left in the drawing, back into the second mould half 4, engages on the central ejector pin 9. Driving of pin 9 is effected by means of pressure cup 12. Pressure cup 12 is also provided with pushers 13 and after bridging the free space 14 these bear on the ejector sleeve 5. The ejector sleeve 5 is driven back into the second mould half with spring 11. Punch 6 is connected to a pressure sleeve 17. This is provided with slots, as a result of which this has no effect on the movement of the pressure cup 12.

The control for moving the pressure sleeve 17 and the pin 16 engaging on pressure cup 12 is indicated by 30. This consists of a housing 20. Inside this there is a shaft 22 that can be driven with a pulley 21 on which a servomotor not shown in more detail acts via a transmission. Shaft 22 is mounted in bearings 23. Shaft 22 is provided with a screw thread 24 on which a first nut-like construction 25, which merges into sleeve 17, engages. Sleeve 17 is fitted such that it cannot turn but can execute translational movement, so that on rotation of shaft 22, sleeve 17 executes translational movement. Shaft 22 is connected in a non-turnable manner to a second nut-like construction 28. This engages on a second screw thread 27 made in pressure pin 16. Pressure pin 16 is also fitted such that it cannot turn, so that on rotation of the second nut-like construction 28 pin 16 executes a translational movement. The pitch of the second screw thread 27 is much greater than the pitch of the first screw thread 24, so that the pin 16 will move much "faster" than the pressure sleeve 17.

Before the position in Fig. 2 is reached, the information carrier 29 is injection moulded with the mould halves closed and the punch member is moved through the information carrier while the mould halves are still closed. The mould halves are then opened and the situation as shown in Fig. 2 is obtained. In this situation the punch member 6 has moved somewhat beyond the free end of information carrier 29. In the situation according to Fig. 2 ejector pin is not in contact with the punched-out core 18.

Air is then introduced between the ejection sleeve 5 and mould section 4 while the punch member 6 moves further outwards. This is indicated by arrow 19. Ejector pin 9 moves faster than punch member 6 and will hit core 18. This is shown in Fig. 3.

The movement of ejector pin 9 is exactly synchronised with movement of the ejector sleeve 5 except for the fact that as a result of the gap 14, ejector sleeve 5 becomes effective only after some time. This has been drawn in Fig. 4, where ejector sleeve 5 has partly overtaken punch member 6. Because pin 9 moves at the same point in time as punch member 6 with a higher speed than the ejector member 5, the free end thereof has already been brought appreciably beyond the free end face of the punch member 6 and the core 18 has already been brought an appreciable distance into the gap between the two mould halves.

In Fig. 5 it is then shown that the punch member has been completely overtaken by the ejector sleeve 5, where the information carrier 29 has been stripped from the punch member 6.

The difference in the movement pattern between the punch 6, ejector sleeve 5 and ejector pin 9 described above is determined by the different pitch of the first screw thread 24 and second screw thread 27 as well as the size of the gap 14. Preferably the speed at which ejector sleeve 5 and the ejector pin coupled thereto moves is at least three times and preferably approximately six times as high as the speed of punch 6. As a result detachment of the disc will be effected within a relatively short path without the position of ejector pin 9 becoming such that the part 18 moves back onto the optical information carrier that has just been injection moulded, as a result of which the danger of contamination with particles is avoided. As a result of the gap 14, the ejector sleeve 5 will move with a delay relative to the punch 6, while this does not apply for the ejector pin 9.

Although the invention has been described above with reference to a preferred embodiment, it will be clear to those skilled in the art that numerous variations are possible. For instance, the drive for the punch, the ejector sleeve and ejector pin, respectively, can be constructed in any other way known from the art. It is, in particular, the pattern of movement of punch and ejector sleeve that is important for the invention, the punch continuing the previously initiated pumping movement and the optical information carrier ultimately being removed as a result of the rapid movement of the ejector sleeve. This inventive concept can be employed with other injection moulding installations with the same effect and such variants therefore fall within the scope of the appended claims.

Claims

Claims:

1. Method for the production of a disc-shaped information carrier, comprising delimiting a mould cavity (7) using two mould halves (2, 4), introducing and dispersing fluid plastic into said cavity, when forming said information carrier making an opening therein by inserting a punch member (6) into said mould cavity from one mould half, moving said mould halves apart and removing said information carrier using an ejector member (5), characterised in that the removal of said information carrier comprises moving said punch member (6) further in said direction for punching out said opening at a first speed while at the same time moving said ejector member (5) in the same direction at a second speed, wherein said second speed is higher than said first speed.

2. Method according to Claim 1, wherein the ejector member is arranged next to the information carrier and the further movement of said punch member comprises a first phase in which said ejector member is stationary and a second phase in which said ejector member (5) moves faster than said punch member.

3. Method according to Claim 1, wherein said second speed is at least three times higher than said first speed.

4. Method according to one of the preceding claims, wherein when said punch member moves a gas is blown in between said punch member, said moulded information carrier and said one mould half.

5. Method according to Claims 1 - 3, wherein said gas is air.

6. Method according to one of the preceding claims, wherein there is a further ejector member (9) for removing the part (18) of said information carrier punched out by the punch member, wherein said further ejector member moves in concert with the ejector member (5).

7. Installation for the production of a disc-shaped information carrier comprising two mould halves (1; 4) that can be moved relative to one another, which delimit a mould cavity (7) between them, wherein one mould half is provided with a punch member (6) and an ejector member (5), wherein there are control means (30) in the mould cavity for moving said punch member (6) and ejector member (5) relative to said one mould half (4), characterised in that said control means are designed such that when said mould opens, said punch member (6) is moved in the direction away from said one mould at a first speed and said ejector member is moved in the same direction at a second speed, higher than said first speed.

8. Installation according to Claim 7, wherein said control means are designed to set the movement of the ejector member with a delay relative to the movement of said punch member.

9. Installation according to Claim 7 or 8, comprising a further ejector member for removing the portion of said information carrier punched out by the punch member, wherein said further ejector member (9) is arranged such that it moves synchronised with said ejector member (5).

10. Installation according to Claim 9, wherein said further ejector member moves when said punch member moves.

11. Installation according to one of Claims 7 - 10, wherein said ejector member comprises a sleeve (5) arranged around the punch member.

12. Installation according to Claim 7 - 11, wherein said control means comprise a mechanical coupling of the drive for said punch member and ejector member.

13. Installation according to Claims 7 - 12, wherein the control means comprise a linear drive for said punch member and said ejector member.

14. Installation according to Claim 13, wherein said linear drive comprises a screw drive.

15. Installation according to Claim 14, wherein said screw drive is common to the punch member and said ejector member.