Mold clamping device and method

Abstract

Moving servo motors of molds in synchronization with the operations of platens which enables fine patterns or shapes to be formed even on a large molded article. A mold clamping device forms patterns or the like on a molded article by detecting a mold position of a second platen among first, second, third platens with digital mold opening/closing position detector, and driving servo motors for molds of the molds in synchronization with a digital mold opening/closing position signal from the digital mold opening/closing position detector.

Claims

1. A mold clamping device that moves, with an actuator, at least a second platen among first, second, and third platens provided on a base via a tie bar, and closes and opens first and second molds provided on the second and third platens, respectively, the mold clamping device comprising: servo motor(s) for the molds provided in at least one or both of the respective molds; and digital mold opening/closing position detection means provided on the base and detecting a mold position of the second platen, wherein one or both of the servo motors for the first and second molds are configured to be driven in synchronization with a digital mold opening/closing position signal from the digital mold opening/closing position detection means.

2. The mold clamping device according to claim 1, wherein the first and third platens are configured to move with the second platen.

3. The mold clamping device according to claim 1, wherein the digital mold opening/closing position detection means is formed from a combination of any of an encoder, a resolver and a magnetic encoder, and a rack-and-pinion.

4. The mold clamping device according to claim 1, wherein the mold clamping device is combined with a blow molding machine.

5. The mold clamping device according to claim 1, wherein the digital mold opening/closing position detection means is formed from a servo motor with a rotation detector, and a ball screw.

6. A mold clamping method for moving, with an actuator, at least a second platen among first, second, and third platens provided on a base via a tie bar, and closing and opening first and second molds provided on the second and third platens, respectively, the mold clamping method comprising: using servo motor(s) for the molds provided in at least one or both of the respective molds and digital mold opening/closing position detection means provided on the base and detecting a mold position of the second platen; and driving one or both of the servo motors for the first and second molds in synchronization with a digital mold opening/closing position signal from the digital mold opening/closing position detection means.

7. The mold clamping method according to claim 6, wherein the first and third platens move with the second platen.

8. The mold clamping method according to claim 6, wherein the digital mold opening/closing position detection means is formed from a combination of any of an encoder, a resolver and a magnetic encoder and a rack-and-pinion.

9. The mold clamping method according to claim 6, wherein the mold clamping method is combined with a blow molding machine.

10. The mold clamping method according to claim 6, wherein the digital mold opening/closing position detection means is formed from a servo motor with a rotation detector, and a ball screw.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic construction diagram showing a mold clamping device and a mold clamping method according to this invention.

(2) FIG. 2 is a schematic construction diagram showing the mold opening state of FIG. 1.

(3) FIG. 3 is a block diagram of a construction in which a conventional hydraulic mold clamping device is modified.

(4) FIG. 4 is a block diagram in which the mold clamping device according to this invention is configured as a hydraulic type.

(5) FIG. 5 is a schematic construction diagram showing the mold closing state of another embodiment of the mold clamping device according to this invention.

(6) FIG. 6 is a schematic construction diagram showing the mold opening state of FIG. 5.

(7) FIG. 7 is a schematic construction diagram showing the mold opening state of a conventional mold clamping device.

(8) FIG. 8 is a schematic construction diagram showing the mold clamping state of FIG. 7.

(9) FIG. 9 is a block diagram showing a conventional electric mold clamping device.

(10) FIG. 10 is a block diagram showing a conventional hydraulic mold clamping device.

(11) FIG. 11 is a schematic cross-sectional construction diagram showing the essential portions of a conventional blow molding machine.

(12) FIG. 12 is a schematic cross-sectional construction diagram showing the state of starting the mold clamping in FIG. 11.

(13) FIG. 13 is a cross-sectional diagram showing the state of completing the mold clamping and the state of injecting air in FIG. 12.

EMBODIMENTS OF THE INVENTION

(14) A mold clamping device and a mold clamping method according to this invention use a digital mold opening/closing position signal from digital mold opening/closing position detection means during mold clamping to enable servomotors provided in molds or the like to operate in synchronization with the digital mold opening/closing position signal.

Embodiment

(15) Hereinafter, a description will be given of preferred embodiments of a mold clamping device and a mold clamping method according to this invention with reference to the drawings.

(16) Note that portions the same as or equivalent to those of a conventional example will be shown by the same reference signs to be described, portions same as those of FIGS. 7 to 13 representing a conventional example will be shown by the same reference signs and their descriptions will be incorporated and omitted in order to avoid duplication, and only different portions will be described.

(17) A description will be given of portions different from the conventional construction (FIGS. 7 and 8) described above in the mold clamping device of FIG. 1 and FIG. 2 according to this invention. Note that in the construction of FIGS. 1 and 2, platens 5, 6, and 7 are movable like the construction of FIGS. 7 and 8.

(18) In FIG. 1, a servo motor 42 with a rotation detector in which a rotation detector 40 such as an encoder and a servo motor 41 are integrated with each other is provided on a base 1. A tip end 43a of a ball screw 43 provided in the servo motor 42 with the rotation detector abuts with the second movable platen 6.

(19) A bearing (not shown) is provided at the tip end 43a of the ball screw 43, and the tip end 43a is configured to be rotatable while abutting with the second movable platen 6.

(20) The servo motor 42 with the rotation detector and the ball screw 43 described above constitute digital mold opening/closing position detection means 100, and a digital mold opening/closing position detection signal 100a is configured to be output from the digital mold opening/closing position detection means 100 as shown in FIG. 3.

(21) Generally, the rotation detector 40 of the servomotor 42 with the rotation detector uses a count value, which is obtained by counting the pulse-shaped rectangular wave of an encoder with a counter after shaping waveform thereof, as the digital mold opening/closing position detection signal 100a. Therefore, the communication speed thereof is faster than the output signal of a conventional linear scale or potentiometer.

(22) Further, the digital mold opening/closing position detection means 100 is not limited to the combination with the ball screw 43 described above. If the ball screw 43 is replaced by a rod-shaped rack (not shown) and any of an encoder, a resolver, and a magnetic encoder is connected to a pinion provided in the rack (i.e. a well-known rack-and-pinion), the same functions and effects as those of the construction using the ball screw 43 described above can be obtained.

(23) That is, the resolver described above is configured to be extremely stable as a rotation detector, capable of obtaining a two-phase output even under unfavorable conditions, and capable of obtaining the digital mold opening/closing position detection signal 100a having faster communication speed by an A/D convertor, and is used in, for example, detecting the rotation of a hybrid vehicle.

(24) Further, the magnetic encoder can also output a pulse-shaped rectangular wave as a count value and is used in, for example, detecting the speed of a Japanese bullet train.

(25) Servo motors 45, 46 for first and second molds having first and second movable elements 44, 44A, respectively, are provided in first and second molds 11, 11A described above, respectively, and configured to be used to form irregularities, patterns, or the like on the shape of a parison 33 during molding like respective movable elements 31 described in FIGS. 11 to 13 representing a conventional construction.

(26) The construction of FIG. 1 shows a state in which the respective molds 11, 11A are being clamped with a protrusion element 11 of an actuator 12 protruded. In this case, however, the respective movable elements 44 and 44A are not protruded from the molds 11, 11A, respectively. Therefore, a parison (not shown) sandwiched between the molds 11, 11A is molded into the shape of the cavity of the molds 11, 11A.

(27) Further, in the construction of FIG. 2, the servomotors 45, 46 for the respective molds are operated to protrude the respective movable elements 44, 44A. From this state, both sides of the parison (not shown) are pressed in the way described above in FIG. 12, whereby concave portions can be formed on a molded article (not shown).

(28) A state in which the operation of the actuator 12 is controlled by a hydraulic unit 10 like the construction of FIGS. 1 and 2 described above is shown in FIGS. 3 and 4.

(29) That is, in the control construction of FIG. 3, a conventional hydraulic mold clamping device is so modified that a conventional analog linear-motion detector 16 is used, that the digital mold opening/closing position detection means 100 formed from the ball screw 43 and the servo motor 42 with the rotation detector having the rotation detector 40 according to this invention is added, and that the digital mold opening/closing position signal 100a from the servomotor 42 with the rotation detector is input to the control board 20.

(30) In the construction of FIG. 3, the digital mold opening/closing position detection signal 100a from the servomotor 42 with the rotation detector can be obtained via the ball screw 43 as the platens 5, 6, 7 are opened/closed, and the operations of the servo motors 45, 46 for the respective molds can be controlled in synchronization with content thereof.

(31) That is, the encoder 40 of the servo motor 42 operates as a high-speed position detector for opening/closing of the molds in a hydraulic mold clamping mechanism and converts position information on the platen 6 measured by the encoder 40 of the servo motor 42 into a speed during the opening/closing of the molds, so that the positions and the speeds of the servo motors 45, 46 in the molds 11, 11A are synchronized with each other during the opening/closing of the molds to enable the servo motors 45, 46 in the molds and other places to be synchronously operated by a programmable logic controller (PLC) in the control board 20.

(32) Note that since the existing hydraulic mold clamping device is modified in the construction of FIG. 3, a mold opening/closing position detection signal 25 of the built-in analog linear-motion detector 16 is not used due to its slow communication speed.

(33) The construction of FIG. 4 is different from the modified type of FIG. 3 and is a construction in which only the digital mold opening/closing position detection means 100 formed from the ball screw 43 and the servo motor 42 with the rotation detector 40 according to this invention is used as a completely new type without using the analog linear-motion detector 16 to detect the position of the second platen 6 to enable the control of the synchronization between the second platen 6 and the servo motors 45, 46 for the respective molds.

(34) Next, FIGS. 5 and 6 show another embodiment of the mold clamping device according to this invention shown in FIGS. 1 and 2. Besides being applied to the construction of FIGS. 1 and 2 in which all the platens 5, 6, 7 are configured to move horizontally, this invention can also be applied to a mold clamping device in which first and third platens 5, 7 are fixed onto a base and only a second platen 6 moves horizontally, i.e., the second platen 6 is slid back and forth by a protrusion element 12A of an actuator 12.

(35) Note that in the construction of FIGS. 5 and 6, portions same as those of FIGS. 1 and 2 described above are shown by the same reference signs to omit their descriptions, and only different portions are described.

(36) Further, the construction of FIGS. 1 and 2 is slightly different from that of FIGS. 5 and 6, but their functions and effects are the same.

(37) Further, the mold clamping device is disclosed as a hydraulic type in the state described above, but can also be applied to an electric type provided that a large motor having a torque corresponding to the hydraulic type is employed.

(38) Next, the mold clamping device and the method according to this invention described above are summarized as follows.

(39) That is, a mold clamping device that closes and opens first and second molds 11, 11A provided on at least a second platen 5, 6, 7 among first, second, and third platens provided on a base via a tie bar 8 includes: servo motor(s) for the molds provided in at least one or both of the respective molds; and digital mold opening/closing position detection means 100 provided on the base and detecting a mold position of the second platen 6, wherein one or both of the servo motors for the first and second molds are configured to be driven in synchronization with a digital opening/closing position signal 100a from the digital mold opening/closing position detection means 100. Further, the first and third platens 5, 7 are configured to move with the second platen 6.

(40) Further, the digital mold opening/closing position detection means 100 is configured to be formed from a combination of any of an encoder, a resolver and a magnetic encoder, and a rack-and-pinion. Further, the mold clamping device according to any one of claims 1, 2, and 3 is configured to be combined with a blow molding machine.

(41) Further, the digital mold opening/closing position detection means 100 is configured to be formed from a servo motor 42 with a rotation detector, and a ball screw 43.

(42) Further, according to this invention, a mold clamping method for moving, with an actuator 12, at least a second platen 6 among first, second, and third platens provided on a base via a tie bar 8, and closing and opening first and second molds 11, 11A provided on the second and third platens 5, 7, respectively, includes: using servo motor(s) for the molds provided in at least one or both of the respective molds and digital mold opening/closing position detection means 100 provided on the base and detecting a mold position of the second platen 6; and driving one or both of the servo motors for the first and second molds in synchronization with a mold opening/closing position signal 100a from the digital mold opening/closing detection means 100.

(43) In the mold clamping method, the first and third platens 5, 7 move with the second platen 6. Further, the mold clamping method according to any one of Claims 7, 8 and 9 is combined with a blow molding machine. Further, in the mold clamping method, the digital mold opening/closing position detection means 100 is formed from a servo motor 42 with a rotation detector, and a ball screw 43.

INDUSTRIAL APPLICABILITY

(44) Regarding positions of platens upon mold clamping, a mold clamping device and a mold clamping method according to this invention synchronously drive servo motors for respective molds in the respective molds using a digital mold opening/closing position detection signal from digital mold opening/closing position detection means and synchronize the movements of the opening/closing of the molds and the respective molds with each other to enable easy molding of a large and complicated shape or the like.

(45) Further, the mold clamping device may be retrofitted to an existing mold clamping device, and the performance of the mold clamping device can therefore be improved at lower cost than a case in which the mold clamping device is replaced by a new one.

REFERENCE SIGNS LIST

(46) 1 Base

(47) 2 First linear-motion guide

(48) 3 Second linear-motion guide

(49) 4 Third linear-motion guide

(50) 5 First platen

(51) 6 Second platen

(52) 7 Third platen

(53) 8 Tie bar

(54) 9 Nut

(55) 10 Hydraulic unit

(56) 11 First mold

(57) 11A Second mold

(58) 12 Actuator (such as hydraulic cylinder)

(59) 13 First lever

(60) 14 Second lever

(61) 15 Gear

(62) 15A Interlocking mechanism

(63) 16 Analog linear-motion detector

(64) 20 Control board

(65) 40 Rotation detector (such as encoder)

(66) 41 Servo motor

(67) 42 Servo motor with rotation detector

(68) 43 Ball screw

(69) 44 First movable element

(70) 44A Second movable element

(71) 45 Servo motor for first mold

(72) 46 Servo motor for second mold

(73) 100 Digital mold opening/closing position detection means

(74) 100a Digital mold opening/closing position detection signal