MOLD CLAMPING APPARATUS

• US 20110052742A1
• Filed: 03/17/2009
• Published: 03/03/2011
• Est. Priority Date: 11/05/2008
• Status: Active Grant

• Current Assignee: Mitsubishi Heavy Industries, Ltd., Mitsubishi Heavy Industries Plastic Technology Co., Ltd. (Ube Machinery Corporation, Ltd.)
• Original Assignee: Mitsubishi Heavy Industries, Ltd., Mitsubishi Heavy Industries Plastic Technology Co., Ltd. (Ube Machinery Corporation, Ltd.)
• Inventors: Kariya, Toshihiko, Kuga, Kazunori, Mizuno, Takashi, Suzuki, Koji, Uchida, Nobuhiro
• Granted Patent: US 8,641,400 B2
• Time in Patent Office: Days
• US Class Current: 425/149
• CPC Class Codes: B29C 45/6728 the separate element consisting of coupling rods
• CPC Class Codes: B29C 45/7653 mould clamping forces
• CPC Class Codes: B29C 45/7693 using rheological models of the material in the mould, e.g. finite elements method

Abstract

There is provided a mold clamping apparatus that can prevent a molding material from spouting from a split surface of a mold even if in-cavity resin pressure causes offset of a mold opening force, and can extend the life of the mold. The mold clamping apparatus includes a control device that estimates a mold opening force by mold internal pressure for molding with mold internal pressure being asymmetrical with respect to a center of a mold block, determines a mold clamping hydraulic value applied to each time bar correspondingly to the estimated mold opening force, and distributes hydraulic pressure supplied to each tie bar so that the determined mold clamping hydraulic value is reached.

Claims

1. A mold clamping apparatus comprising:

a stationary die plate that holds a stationary mold;

a movable die plate that holds a movable mold;

a die plate moving means that moves the movable die plate toward and away from the stationary die plate; and

a mold clamping means that connects and pressurizes the stationary die plate and the movable die plate,

wherein the mold clamping means includes a plurality of mold clamping cylinders provided on one of the stationary die plate and the movable die plate,

a plurality of tie bars each having one end connected to a ram of the mold clamping cylinder, and the other end having a plurality of ring grooves or screw grooves at regular pitches,

a half nut provided on the other of the stationary die plate and the movable die plate and engageable with the plurality of ring grooves or screw grooves,

a hydraulic pipe communicating with each of the plurality of mold clamping cylinders,

a hydraulic source including a hydraulic pump that supplies oil to the hydraulic pipe, and

a control device that controls the supply of the oil from the hydraulic source to the hydraulic pipe,

the control device controls the supply of the oil based on a mold clamping force by each of the plurality of tie bars determined correspondingly to an estimated mold opening force by mold internal pressure for molding with mold internal pressure being asymmetrical with respect to a center of a mold block.

2. The mold clamping apparatus according to claim 1, wherein the mold clamping force by each of the tie bars is determined in such a manner that a flow analysis is previously performed to estimate mold internal pressure and calculate the center of gravity of the mold opening force by the mold internal pressure, and the center of gravity of the mold opening force matches the center of gravity of the mold clamping force by each of the plurality of tie bars.

3. The mold clamping apparatus according to claim 2, wherein the center of gravity of the mold opening force is previously calculated for a progress of an injection process by the flow analysis, and

the mold clamping force by each of the plurality of tie bars is determined so that the center of gravity of the mold opening force that varies with the progress of the injection process matches the center of gravity of the mold clamping force by each of the plurality of tie bars, and the mold clamping force is switching controlled with the progress of the injection process.

4. The mold clamping apparatus according to claim 3, wherein the mold clamping force by each of the plurality of tie bars with the progress of the injection process is switched when a time is up depending on the injection process.

5. The mold clamping apparatus according to claim 1, wherein the mold opening force by the mold internal pressure is estimated based on a measured value of the mold internal pressure in a predetermined position.

6. The mold clamping apparatus according to claim 5, wherein the mold internal pressure in a predetermined position, and the center of gravity of the mold opening force by the mold internal pressure are calculated for the progress of the injection process by a flow analysis, and for a mold internal pressure value, the mold opening force, and the center of gravity of the mold opening force in the predetermined position that varies with progress of the injection process, at a time when the measured value of the mold internal pressure reaches the mold internal pressure in the predetermined position that is previously calculated, a mold clamping hydraulic value applied to each of the tie bars is determined so that the center of gravity of the mold clamping force applied to the die plate by each of the plurality of tie bars matches the mold opening force by the mold internal pressure and the center of gravity of the mold opening force previously calculated by the flow analysis, and hydraulic pressure supplied to each of the tie bars is distributed so that the determined mold clamping hydraulic value is reached.

7. The mold clamping apparatus according to claim 1, wherein the mold clamping apparatus includes a plurality of the hydraulic sources corresponding to the plurality of mold clamping cylinders,

the control device supplies the oil discharged from all the hydraulic sources to each of the mold clamping cylinders through a common pipe at the beginning of pressure increase in supplying the oil to each of the mold clamping cylinders,

at a time when each predetermined mold clamping hydraulic value corresponding to each mold clamping cylinder is reached in a pressure increasing process, the supply of the oil from the hydraulic source through the common pipe to the mold clamping cylinder having reached the predetermined mold clamping hydraulic value is stopped, and the supply of the oil is started from a hydraulic source and a hydraulic pipe independent of the common pipe.

8. A mold clamping apparatus comprising:

a stationary die plate that holds a stationary mold;

a movable die plate that holds a movable mold;

a die plate moving means that moves the movable die plate toward and away from the stationary die plate; and

a mold clamping means that connects and pressurizes the stationary die plate and the movable die plate,

wherein the mold clamping means includes a plurality of mold clamping cylinders provided on one of the stationary die plate and the movable die plate,

a plurality of tie bars each having one end connected to a ram of the mold clamping cylinder, and the other end having a plurality of ring grooves or screw grooves at regular pitches,

a half nut provided on the other of the stationary die plate and the movable die plate and engageable with the plurality of ring grooves or screw grooves,

a hydraulic pipe communicating with each of the plurality of mold clamping cylinders,

a hydraulic source including a hydraulic pump that supplies oil to the hydraulic pipe, and corresponding to the plurality of mold clamping cylinders, and

a control device that controls the supply of the oil from the hydraulic source to the hydraulic pipe,

the control device supplies the oil discharged from all the hydraulic sources to each of the mold clamping cylinders through a common pipe at the beginning of pressure increase in supplying the oil to each of the mold clamping cylinders,

at a time when each predetermined mold clamping hydraulic value corresponding to each mold clamping cylinder is reached in a pressure increasing process, the supply of the oil from the hydraulic source through the common pipe to the mold clamping cylinder is stopped, and the supply of the oil is started from a hydraulic source and a hydraulic pipe independent of the common pipe.