Means for holding stamper plate in molding metal die

Abstract: A means for holding a stamper plate 32 in a molding metal die according to the present invention comprises a cavity center hole 37 defined at the center of a cavity plate 36, a stamper plate press member 31 including a flange portion 35 having a portion larger than the center hole of the stamper plate 32 at an end thereof and loosely inserted into the cavity center hole 37 from the other end thereof, a vacuum evacuation device 50, a compressed air supply device 51, and switching/connecting means 53, 54 for switching and connecting the bottom of the cavity center hole to the vacuum evacuation device and the compressed air supply device. When the stamper plate is to be mounted, the stamper plate press member 31 is inserted into the cavity center hole 37 in the state that the other end of the stamper plate press member 31 is inserted into the center hole of the stamper plate, a space between the other end and the cavity center hole is connected to the vacuum evacuation device by the switching/connecting means 53, 54 and when the stamper plate is to be removed, the space between the other end and the cavity center hole is connected to the compressed air supply device by the switching/connecting means 53, 54 to thereby push out the stamper plate press member.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a means for holding a stamper plate in a molding metal die according to the precharacterising part of claim 1 and of claim 4 respectively. 2. Description of the Related Art There is known an optical disk substrate injection molding metal die for moving a stamper plate press bush using a cam shaft. Refer to, for example, Japanese patent Application Laid-open No. H2-295726. FIG. 4 is a cross sectional view showing an injection molding state of a conventional optical disk substrate injection molding metal die for moving the stamper plate press bush using the cam shaft. FIG. 5 is a schematic cross sectional view showing a state that the stamper plate press bush is moved by the conventional apparatus. Note, although these drawings show that a fixed side molding metal die is located on an upper side, there are also cases that the fixed side molding metal die is used laterally so that the center axis of a cavity is disposed horizontally and that the position of the fixed molding metal die is vertically reversed with respect to the above case. A fixed side disk cavity plate 4 is disposed to a fixed side plate 6 and a hole 5 is defined at the center of the fixed side disk cavity plate 4 to receive a stamper plate press bush 2. A flange 3 having an outside diameter larger than the center hole of a stamper plate 1 is disposed at the lower end of the stamper plate press bush 2. Further, a cutout 9 is defined to the upper end of the stamper plate press bush 2. The fixed side plate 6 rotatably supports two engaging rods 7, 7 to be engaged with the cutout 9 of the bush 2. These two engaging rods 7, 7 have planes 8, 8 each having a semi-circular cross section and are connected to each other so as to rotate in synchronism. A spool bush 10 is inserted into the center hole of the stamper plate press bush 2 and has an injection hole 11 for molten resin defined at the center thereof. Ring-shaped cooling water passages 12 are disposed to the fixed side disk cavity plate 4 in contact with the fixed side plate 6. A movable side disk cavity plate 17 is fixed to a movable side plate 19. A punch 18 is upward and downward movably supported at the center of the movable side disk cavity plate 17 to punch the center hole of a disk substrate. When injection molding is effected, the stamper plate 1 is engaged with the stamper plate press bush 2 so that the outer periphery of the hole of the stamper plate is pressed by the flange 3 of the bush 2. In the injection molding, the stamper plate press bush 2 is engaged with the planes 8, 8 of the semi-circular cross sections of the two engaging rods 7, 7 and pressed thereby, as shown in FIG. 4. Next, steps of procedures for removing the stamper plate 1 will be described with reference to FIG. 5. A molded disk substrate member 20 is removed by opening the die. When the two engaging rods 7, 7 are turned in the direction of an arrow in the drawing as shown in FIG. 5, the planes 8 of the engaging rods 7 are disengaged once from the cutout 9 of the stamper plate mounting bush 2 and pushes the upper surface of the bush 2 in the drawing. With this operation, the stamper plate mounting bush 2 is pushed out from the center hole 5 of the fixed side disk cavity plate 4 as shown in the drawing. Thus, the operator can take out the stamper plate 1 by hand while holding the stamper plate press bush 2. Since the conventional example is a system for mechanically mounting and removing the stamper plate 1 by the stamper plate mounting bush 2, the stamper plate can be securely mounted. However, since the above two rods 7, 7 are used and a driving unit for driving them are needed, the following problems arise. The use of the two rods and the provision of the driving unit for driving them disposed in relation to the molding metal die prevent the reduction of size and weight of the die. Further, the provision of the above rods and driving unit in relation to the die restricts the design of the cooling water passages. Further, a certain degree of skill is required to mount and remove the stamper plate. Similar devices are known from EP-A 0 177 991 and the Japanese patent publication No. 02 276610 in which the stamper plate mounting bush is held by mechanical means. These devices have the same drawbacks. To solve the above problems, there is proposed an optical disk substrate injection molding metal die provided with a vacuum suction type stamper plate press unit. Refer to, for example, Japanese Patent Publication No. H2-60502. As shown FIG. 3, concentric circular grooves 22, 23 are defined around the central portion and outer peripheral portion of a stamper plate side disk cavity plate 21. These concentric circular grooves are connected to an external vacuum suction unit (not shown) through a communication hole 24. A circumferential portion 27 to be inserted into the center hole of a stamper plate 25 is disposed at the extreme end of a cylindrical bush 26. A cylindrical bush 28 disposed at the center of the cylindrical bush 26 is a punch for punching the center hole the stamper plate 25. A spool bush 30 is disposed at the center of a fixed side disk cavity plate 29. In the molding metal die arranged as described above, the stamper plate 25 can be simply removed from the disk cavity plate 21 by stopping vacuum suction. However, this type of the apparatus also has a drawback. In the optical disk substrate injection molding metal die, the interior of the cavity is often filled with molten metal in the state that it is evacuated to vacuum to provide the density of the molten resin in the cavity with improved uniformity. In this case, however, since the rear surface of the stamper plate 25 and the cavity are evacuated to the same level, no suction force acts on the rear surface of the stamper plate 25. Therefore, there is a possibility that the stamper plate 25 falls away from the cylindrical bush 26 by the vibration and impact of a molding machine operating at a high speed. Further, a vacuum pump must be operated so far as the stamper plate 25 is mounted even if a molding operation is interrupted. An object of the present invention is to provide a means for holding a stamper plate in a molding metal die capable of securely holding the stamper plate in the molding metal die by a simple arrangement without employing a special support structure in the molding metal die and permitting the stamper plate to be easily replaced. SUMMARY OF THE INVENTION The above object is achieved according to the present invention by the means for holding a stamper plate as defined in claim 1 and by the means as defined in claim 4. Particular embodiments of the invention are the subject of the dependent claims. The means for holding a stamper plate in a molding metal die according to the present invention comprises a cavity center hole defined at the center of a cavity plate, a stamper plate press member including a flange portion having a portion larger than the center hole of the stamper plate at an end thereof and loosely inserted into the cavity center hole from the other end thereof, a vacuum evacuation device, a compressed air supply device, and switching/connecting means for switching and connecting the bottom of the cavity center hole to the vacuum evacuation device and the compressed air supply device. When the stamper plate is to be mounted, the stamper plate press member is inserted into the cavity center hole in the state that the other end of the stamper plate press member is inserted into the center hole of the stamper plate and a space between the stamper plate press member and the bottom of the cavity center hole is connected to the vacuum evacuation device by the switching/connecting means and when the stamper plate is to be removed, the space between the stamper plate press member and the bottom of the cavity center hole is connected to the compressed air supply device by the switching/ connecting means to thereby push out the stamper plate press member. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view showing a main portion of a first embodiment of an optical disk substrate injection molding metal die according to the present invention; FIG. 2 is a cross sectional view showing a main portion of a second embodiment of an optical disk substrate injection molding metal die according to the present invention; FIG. 3 is a cross sectional view showing a main portion of an embodiment of a conventional optical disk substrate injection molding metal die for pressing a stamper plate by vacuum evacuation; FIG. 4 is a cross sectional view showing an injection molding state of a conventional optical disk substrate injection molding metal die for moving a stamper plate press bush using a cam shaft; and FIG. 5 is a schematic cross sectional view showing the state that the stamper plate press bush is moved by the conventional apparatus shown in FIG. 4. DESCRIPTION OF PREFERRED EMBODIMENTS A means for holding a stamper plate in a molding metal die according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a view schematically showing the cross section of a main portion of an optical disk substrate injection molding metal die using an embodiment of the means for holding the stamper plate in the molding metal die according to the present invention and an air pressure device. Information to be transferred is held on the upper surface of the stamper plate 32 in the drawing. A stamper plate press member 31 has an outside diameter to be accurately engaged with the center hole 33 of the stamper plate 32 as well as is provided with a flange portion 35 larger than the center hole 33 of the stamper plate at the extreme end thereof. A fixed side disk cavity plate 36 has a through hole 38 defined thereto which has a hole 37 for accurately and detachably receiving the stamper plate press member 31. Further, a fixed side disk cavity plate 36 has a hole 39 defined thereto through which air is evacuated and supplied. A cylindrical cut bush 40 is a cut bush for punching the center hole of a disk substrate. A spool bush 41 is disposed at the center of the cylindrical cut bush 40. A fixed side plate 42 has an externally connecting hole 43 defined thereto which corresponds to the air evacuation and supply hole 39. The externally connecting hole 43 is connected to a vacuum evacuation device 50 and a compressed air supply device 51 through connecting means 53, 54. Note, numerals 44a - 44d denote air tight seal members such as O rings and the like. Next, a mechanism for mounting and removing the stamper plate 32 of an embodiment of the optical disk substrate injection molding metal die will be described. First, the stamper plate 32 is mounted in such a manner that the stamper plate press member 31 on which the stamper plate 32 is mounted is manually inserted into the center hole 37 of the disk cavity plate 36. Continuously, the vacuum evacuation device 50 is operated by opening the valve 53 so that the air in the space of the center hole 37 is evacuated to vacuum though the externally connecting hole 43 as shown by an arrow and the pressure in the space is instantly reduced to vacuum. Therefore, the stamper plate press member 31 is strongly sucked to the center hole of the fixed side disk cavity plate 36 and held thereby. Next, the stamper plate 32 is removed in such a manner that when the compressed air supply device 51 is operated by opening the valve 54, the stamper plate press member 31 is pushed out from the center hole 37 of the disk cavity plate 36 by an air pressure. At the time, the operator can simply remove the stamper plate 32 by hand while supporting the stamper plate press member 31 once. Note, although a means for sucking the stamper plate 32 to the surface of the disk cavity plate 36 is not shown in this example, it may be separately formed as necessary. FIG. 2 schematically shows the cross sectional view of a main portion of an optical disk substrate injection molding metal die making use of a second embodiment of the means for holding a stamper plate in a molding metal die according to the present invention and an air pressure circuit. This embodiment is provided with a means for sucking a stamper plate 32 onto the surface of a disk cavity plate 46 in addition to a stamper plate press member 31. Since the main components of this embodiment are common to those of the aforesaid first embodiment, the common components are denoted by the same numerals as used in the embodiment 1 and the description thereof is omitted. A cylindrical member 45 for sucking the stamper plate has an inside diameter which can be accurately received by the outside diameter of the stamper plate press member 31. Then, the outside diameter of the cylindrical member 45 has a plurality of stripe-shaped rim portions which are accurately engaged with the inside diameter of a center hole 47 and a portion for forming a multiplicity of arc-shaped interval portions 48 in a radial portion which is 0.02 mm or more smaller than the radius of the above center hole. The above rim portions are accurately engaged with the above center hole to thereby form a suction passage. Next, operation of the second embodiment of the optical disk substrate injection molding metal die will be described. First, the stamper plate press member 31 on which the stamper plate 32 is mounted is attached to the inner diameter surface of the cylindrical ring 45 disposed to the center hole 47 of the disk cavity plate 46 by vacuum evacuation. At the same time, the air on the back surface of the stamper plate 32 and on the disk cavity plate 46 is evacuated by a vacuum evacuation device 50 from the above intervals 48 to thereby cause the stamper plate 32 to come into intimate contact with the surface of the disk cavity plate 46. Note, the stamper plate 32 may be inserted into the center hole 47 of the disk cavity plate 46 after it is coupled with the stamper plate press member 31 and the stamper plate press member 31 is engaged with the cylindrical member 45. The stamper plate 32 can be removed in such a manner that a compressed air supply device 51 is operated by actuating a valve of a connecting device after a die is opened to thereby forcibly float the stamper plate press member 31 and the cylindrical member 45 for sucking the stamper plate at the same time and then they are drawn out once and held. Various modifications may be made within the scope of the present invention with respect to the embodiments described above in detail. The optical disk substrate injection molding metal die using the means for holding the stamper plate in the molding metal die according to the present invention arranged as described above has the following advantages. The optical disk substrate injection molding metal die does not need an actuator driving mechanism as used in the conventional optical disk substrate injection molding metal die shown in FIG. 4 and FIG. 5. As a result, the reduction in size and weight of the molding metal die can be achieved as well as the number of components can be reduced and a wider degree of freedom of design can be obtained. Thus, an optical disk substrate injection molding metal die having more excellent characteristics can be manufactured. The optical disk substrate injection molding metal die according to the present invention solves all the problems such as the removal of a stamper plate caused by vibration and the like which arise in the conventional optical disk substrate injection molding metal die shown in FIG. 3 employing only vacuum evacuation.

Claims: Means for holding a stamper plate (32) in a molding metal die having a cavity center hole (37) defined at the center of a cavity plate (36), a stamper plate press member (31) including a flange portion (35) having a portion larger than the center hole of said stamper plate at an end thereof and loosely inserted into said cavity center hole (37) from the other, end thereof, a vacuum evacuation device (50), a compressed air supply device (51), characterized in that said means further comprises: switching/connecting means (53, 54) for switching and connecting the bottom of said cavity center hole (37) to said vacuum evacuation device (50) and said compressed air supply device (51); wherein when said stamper plate (32) is to be mounted, said stamper plate press member (31) is inserted into said cavity center hole in the state that the other end of said stamper plate press member is inserted into the center hole (33) of said stamper plate and a space between said stamper plate press member and the bottom of the said cavity center hole is connected to said vacuum evacuation device (50) by said switching/connecting means; and wherein when said stamper plate (32) is to be removed, said space between said stamper plate press member and the bottom of said cavity center hole is connected to said compressed air supply device by said switching/connecting means to thereby push out said stamper plate press member. Means for holding a stamper plate (32) in a molding metal die according to claim 1, wherein said stamper plate is disposed in a molding metal die apparatus so that the upper surface thereof on which information is contained is disposed horizontally. Means for holding a stamper plate (32) in a molding metal die according to claim 1, wherein said stamper plate is disposed in a molding metal die apparatus so that the surface thereof on which information is contained is disposed vertically. Means for holding a stamper plate (32) in a molding metal die having a cavity center hole (47) defined at the center of a cavity plate (46), a stamper plate press member (31) including a flange portion larger than the center hole of said stamper plate at an end thereof, a vacuum evacuation device (50), and a compressed air supply device (51), characterized in that said means further comprises: a stamper plate sucking cylindrical member (45) having a stamper plate sucking air passage (48) forming portion which is defined around the outer periphery thereof and parallel with a center axis and inserted into said cavity center hole from the other end thereof so that an end thereof coincides with the surface of said stamper plate; switching/connecting means (53, 54) for switching and connecting the bottom of said cavity center hole to said vacuum evacuation device and said compressed air supply device; wherein when said stamper plate is to be mounted, said stamper plate press member is inserted into the center hole of said stamper plate sucking cylindrical member (45) which is inserted into said cavity center hole (47) in the state that the other end of said stamper plate press member is inserted into the center hole of said stamper plate and a space between the respective ends of said stamper plate press member and said cylindrical members and the bottom of said cavity center hole is connected to said vacuum evacuation device (50) by said switching/connecting means (53, 54) and wherein when said stamper plate (32) is to be removed, said space between the respective ends of said stamper plate press member (31) and said cylindrical members (45) and the bottom of said cavity center hole is connected to said compressed air supply device by said switching/connecting means (53, 54) to thereby float said stamper plate press member (31) and said cylindrical member (45). Means for holding a stamper plate (32) in a molding metal die according to claim 4, wherein said air passage forming portion (48) between said cavity center hole (47) defined at the center of said disk cavity plate (46) and said stamper plate sucking cylindrical member (45) is arranged to hold an interval of 0.02 mm or more.

Inventors: TAKAHASHI MITSUO, TAKAHASHI, MITSUO
Applicants: SEIKO GIKEN KK, SEIKOH GIKEN CO., LTD.
Application year: 1996
Main classification: B29C45
IPC codes: B29C45, G11B7, B29L17