JP2797705B2 - Mold clamping method and apparatus for blow molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method and an apparatus for blow molding, and more particularly to a method and an apparatus for blow molding that allow a parison injected from a die to be properly aligned with a mold cavity.

[Prior art]

In a general blow molding method for molding a hollow product using a thermoplastic resin, a resin is plasticized by an extruder, extruded into a die by an injection device, and a tubular parison is injected from the die. The injected parison hangs down from the die, hangs between the male and female molds that are installed below the die and opposes, is sandwiched in the mold before cooling and solidifying, and blows air inside to expand, Molding is performed by pressing against the inner wall of the cavity and solidifying by cooling. In this type of blow molding machine, when a parison that is injected from a die and hangs down is inserted into a mold, when the lower end of the parison protrudes from the mold, the amount of burrs increases and the yield deteriorates. If the mold is clamped before the lower end of the mold does not hang down sufficiently, the molding will be defective. For this reason, conventionally, when the mold clamping is completed, the parison lower end is adjusted so as to have a proper amount of burr such that the lower end of the parison does not largely protrude outside the mold. The most general conventional method which can be performed for setting the mold clamping timing is to start the mold clamping after the injection is completed as shown in FIG.
Is output, the injection is completed by detecting the position of the plunger or the like of the injection device (step 110), and a preset mold closing timing timer is started and counted (step 120). It is determined whether or not the value has reached (step 130), and a mold clamping start command is output (step 140). Normally, the set value of the timing timer is set to “0”, and the mold clamping is started immediately after the injection is completed. The flowchart shown in FIG. 5 is applied to a blow molding machine having a hydraulic circuit capable of performing a parallel operation of injection and mold clamping.
At the same time, start the mold closing timing timer (step 21
0), the count value of the timer is a preset value (injection time 1
It is determined whether or not the value has reached (a value several seconds shorter than 0 to 20 seconds) (step 220), and mold clamping is started (step 230).

[Problems to be solved by the invention]

However, in the above conventional method, in any case, a timer for inputting and counting the injection signal of the parison is used,
In order to start mold clamping by this time up,
There were the following problems. In other words, recently, in the case of engineering plastics that have been heavily used due to the expansion of applications, the dripping speed of the parison injected from the die is large,
Moreover, since the solidification speed is high, high-speed injection is performed. However, when injection is performed at a high speed, the error (variation) in the parison position after a certain period of time has elapsed immediately after the start of injection is large, and if the mold clamping is started by a timer count from the start of injection, the timing will match. In many cases, the parison is too fast or too slow with respect to the lower end of the parison, resulting in a problem that satisfactory molding cannot be performed. In other words, in the conventional method, the mold closing timing is a method of counting the timer from the start of the injection or after the completion of the injection. In addition, by uniquely performing mold clamping with a timer count irrespective of the actual parison position and state, mold clamping that accurately corresponds to the parison position is not performed, resulting in excessive burr and poor molding due to unfilled This is the cause of the problem. For this reason, the setting of the timer requires a very complicated setting operation, and in practice, a plurality of shots must be performed by trial and error to set the mold closing timing. The present invention focuses on the above-mentioned conventional problems, and does not need to set the mold clamping timing for each molding of individual products due to differences in resin material and mold replacement, when the parison reaches the proper position accurately. To provide a mold-closing method and apparatus for a blow molding machine capable of eliminating complicated preparation work, improving product yield, and performing good molding. Aim.

[Means for Solving the Problems]

In order to achieve the above object, a mold clamping method for a blow molding machine according to the present invention detects a hanging speed of the parison at a fixed position in the middle of a hanging path of a parison injected from a die of the blow molding machine, The time required for the lower end of the parison to reach the lower end of the mold is calculated based on the detected speed, thereby controlling the speed of the hydraulic cylinder device for closing the mold to complete the closing of the mold immediately after the lower end of the parison reaches the lower end of the cavity. It was configured as follows. Further, the mold clamping device of the blow molding machine according to the present invention is a speed detector that is disposed at a fixed position in the middle of the hanging path of the parison ejected from the die of the blow molding machine and detects the hanging speed of the parison, and a mold. A flow control valve disposed on a hydraulic pressure supply path to a mold clamping cylinder connected to the mold; calculating a time required to reach a lower edge of the mold cavity at the lower end of the parison based on a detection signal from the speed detector; Control means for controlling the flow control valve to set and output the mold clamping speed so that the mold clamping is completed immediately after the lapse of time.

[Action]

The hanging speed of the parison changes depending on the set value of the injection speed, the type of resin, the resin temperature, and the like, and also changes depending on the die gap. Moreover, the droop speed often changes for each shot. In the present invention, since the droop speed of the parison ejected from the die is detected, it is possible to directly grasp the droop speed of the parison that changes individually. The detection of the speed is realized by a photoelectric sensor arranged along the hanging direction, but this can also be realized by a magnetic sensor, an ultrasonic sensor, or the like. When the parison's drooping speed is detected, the mold sandwiching it is movable in the horizontal direction, but its position is fixed with respect to the drooping direction, and the time for the parison to reach the lower edge of the cavity can be easily calculated. You. On the other hand, the mold is waiting at a predetermined position, and the distance from that position to the mold clamping completion position is given as an initial value. In addition, a flow control valve is provided in a hydraulic path to a hydraulic cylinder that provides a mold clamping operation to the mold, and the time required for the mold to reach the mold clamping position from the standby position can be controlled by adjusting the supply flow rate to the cylinder. The control means opens the supply flow path from the hydraulic pressure source to the cylinder according to the time when the parison reaches the lower edge of the cavity, and at the same time, controls the opening of the flow control valve to adjust the moving speed of the mold, thereby closing the parison with the mold. Is controlled so that the mold clamping is completed immediately after the lower end of the parison has passed the lower edge of the mold cavity. Therefore, in the above invention, the mold clamping speed is controlled in accordance with the actual hanging speed of the parison, and even if the parison sagging speed fluctuates due to changes in the injection speed, resin temperature, etc., the mold clamping is performed accurately, and Not only does the setting work become very simple, but it also prevents the yield from dropping due to burrs,
In addition, the rate of occurrence of molding defects due to unfilled cavities and the like can be greatly improved.

【Example】

Hereinafter, specific examples of a method and an apparatus for clamping a blow molding machine according to the present invention will be described in detail with reference to the drawings. 1 and 2 are a side view and a plan view of a blow molding machine provided with a mold clamping device according to an embodiment. The blow molding machine has a die portion 10 for receiving a supply of molten resin from an injection device (not shown), and a parison 12 is extruded in a tube shape from a die opening on the lower surface of the die portion 10 so that the parison 12 hangs down. A pair of dies 14R and 14L are disposed opposite to each other with the parison 12 interposed therebetween at a position below the die portion 10, and these are formed in a cavity (not shown) formed by joining the two as male and female dies. The parison 12 can be inserted therebetween. The pair of dies 14 (14R, 14L) has a platen 16 on the back.
(16R, 16L) are mounted, and on the back surface thereof, a hydraulic cylinder device 18 (18) for moving the mold 14 toward and away from each other.
R, 18L). For this reason, by supplying and discharging the hydraulic oil to and from the hydraulic cylinder device 18, the pair of dies 14 approach each other to close the mold or open the mold. The direction in which the mold 14 approaches and separates is horizontal movement orthogonal to the direction in which the parison 12 hangs. For this reason, a carriage 22 (22R, 22L) that runs on a base 20 is attached to each platen 16, and the hydraulic cylinder The device 18 is also supported by support frames 24 (24R, 24L) erected at both ends of the base 20 so that each platen 16 and thus the mold 14 are horizontally moved by expansion and contraction to perform mold clamping and mold opening. ing. In order to perform the mold clamping and mold opening of the mold 14, hydraulic pipes 26 and 28 are connected to the pump 30 and the tank 32 in each hydraulic cylinder device 18, and an open / close switching electromagnetic valve 34 for each pipe 26 and 28 is provided. It is interposed. The solenoid valve 34 drives the hydraulic cylinder device 18 by selectively switching between holding the position of the mold 14, supplying pressure oil in the mold clamping direction, and supplying pressure oil in the mold opening direction by a switching signal. Here, of the hydraulic pipes 26 and 28, a flow control valve 35 is interposed in the pipe 26 connected to the pump 30 at the time of mold clamping. The flow control valve 35 arbitrarily sets and controls the degree of opening to adjust the amount of pressurized oil supplied to the hydraulic cylinder device 18, thereby varying the speed at which the mold 14 reaches the mold clamping position from the standby position. Thus, the arrival time from the standby position to the mold clamping position can be controlled. In such a blow molding machine, a speed detector 36 for detecting the hanging speed of the parison 12 is mounted at a fixed height position at an intermediate position of the hanging path of the parison 12 in order to properly perform mold clamping. ing. The speed detector 36 includes an upper photoelectric sensor 38 and a lower photoelectric sensor 40,
As shown in FIG. 2, each sensor 38, 40 has an emitting element
The optical axes of 38A and 40A and the light receiving elements 38B and 40B are arranged so as to pass through the hanging center of the parison 12. As a result, when the parison 12 is ejected and hangs down, the upper photoelectric sensor 38 detects first, whereby the lower photoelectric sensor 40 disposed below by a certain distance detects the parison 12. Therefore, the hanging speed of the parison 12 can be detected based on the time difference between the two sensors 38 and 40. On the other hand, a control device 42 for inputting the detection signals of the two sensors 38 and 40 is provided.
The droop speed calculator 44 is provided. The calculator 44 counts down the time of signal input from the sensors 38 and 40, reads the set distances of the upper and lower sensors 38 and 40 from the memory 45, and reads the actual parison 12 Is calculated. Then, the calculation result is output to the mold clamping speed setting unit 46. In the mold clamping speed setting section 46, the parison 12
Is calculated based on the input speed signal. Since the distance between the cavity of the mold 14 and the photoelectric sensors 38 and 40 is determined in advance, the distance can be easily calculated by reading the distance from the memory 45. Further, the distance from the standby position of the hydraulic cylinder device 18 to the mold clamping position and the cylinder capacity are known, and the relationship between the flow rate supplied by the flow control valve 35 and the moving speed draws a constant characteristic line. Therefore, it is possible to arbitrarily set the time required for the mold 14 to move from the standby position to the mold clamping position by adjusting the opening of the flow control valve 35. Therefore, the calculated arrival time of the parison 12 to the lower edge of the cavity is obtained based on, for example, the parison detection time of the upper photoelectric sensor 38,
Hydraulic cylinder device 18 so that mold clamping is performed immediately after arrival
It adjusts the drive speed. Since there is a fixed relationship between the driving speed of the cylinder and the supply flow rate,
It is set to 45, and the opening of the flow control valve 35 is calculated in relation to the parison arrival time. Then, the calculation result is output to the valve driver 48, and the mold is clamped so that the time for the mold 14 to reach the mold clamping position coincides with the time immediately after the lower end of the parison 12 has passed the lower edge of the cavity. is there. FIG. 3 shows a flowchart of the mold clamping process performed by the apparatus configured as described above. First, when an injection command is output (step 300), the parison 12 is ejected from the die unit 10 and hangs down. Since the parison 12 descends continuously, it first blocks the optical path of the upper photoelectric sensor 38 and then blocks the optical path of the lower photoelectric sensor 40. Therefore, it is determined whether or not the tip of the parison 12 is detected by the upper photoelectric sensor 38 (step 310), and when it is detected, time measurement (t = 0) is started (step 320). Subsequently, it is determined whether or not the tip of the parison 12 has been detected by the lower photoelectric sensor 40 (step 330), and when it is detected, time measurement (t = t ₁ ) is completed (step 340). This is input to the speed calculator 44 of the controller 42, where the parison droop speed v = 1 / t ₁ (where 1 is the distance between the photoelectric sensors 38 and 40) is calculated (step 350). This calculation result is input to the mold clamping speed setting unit 46, and the time T during which the parison 12 reaches the cavity lower edge position is calculated (step 360). Then, since the proper insertion state is a state in which an appropriate amount of burr is generated by adding the short time α to the time T, the mold clamping speed V is calculated so that the mold clamping is completed after this time (T + α) ( Step 370). Since the supply flow rate at which the speed V is obtained is known in advance, it is stored in a memory.
The flow is read from 45, the corresponding opening of the flow control valve 35 is set, and this is output to the valve driver 46 (step 380). By such a series of processes, the mold 14 is completely closed when the parison 12 reaches an appropriate position (step 390). According to such an embodiment, as long as the same mold 14 is used, even if the injection speed of the parison 12 is changed, or the dripping speed is changed due to a change in the resin temperature, the parison 12 is always properly adjusted. When the position is reached, the mold clamping is completed, so that the cavity is not filled or excessive burr does not occur. That is, even if the droop speed of the parison changes due to conditions and the environment, the actual droop speed is detected and the mold is clamped, so that the timing shift is eliminated and the mold 14 is fastened to the position of the parison 12 at an early stage. In other words, there is no delay, and there is no molding failure, so that the yield is greatly improved. In addition, since the photoelectric sensors 38 and 40 for detecting the parison drooping speed are arranged on the axis in the direction of drooping, no matter what the shape of the parison tip, accurate molding timing requires less molding timing. Provides configurable benefits.

【The invention's effect】

As described above, according to the mold clamping method and apparatus of the blow molding machine according to the present invention, since the mold clamping speed is controlled according to the hanging speed of the parison, differences in molding conditions and environments, resin Even if you do not set the mold closing timing for each material molding due to the difference in material and the mold change, the mold clamping is completed when the parison reaches the appropriate position accurately, and complicated preparation It is possible to obtain an excellent effect that the work can be eliminated, the product yield can be improved, and good molding can be performed.

[Brief description of the drawings]

FIG. 1 is a side view of a blow molding machine provided with a mold clamping device according to an embodiment. FIG. 2 is a plan view of the same, FIG. 3 is a flowchart of a mold clamping process, FIG. 4 is a flowchart of a mold clamping process according to a conventional example, and FIG. 5 is a flowchart of a mold clamping process according to another conventional example. . 10 ... Die, 12 ... Parison, 14 ... Mold, 16 ...
Platen, 18 hydraulic cylinder device, 20 base, 2
6, 28 ... hydraulic piping, 30 ... pump, 34 ... open / close switching solenoid valve, 36 (38, 40) ... parison droop speed detector (photoelectric sensor), 42 ... control device, 44 droop speed Arithmetic unit, 46
…… Molding speed setting section, 48 …… Valve driver.

Continuation of front page (56) References JP-A-56-96560 (JP, A) JP-A-56-96561 (JP, A) JP-A-63-262225 (JP, A) , U) (58) Fields surveyed (Int. Cl. ⁶ , DB name) B29C 49/02-49/06 B29C 49/48-49/56 B29C 49/78 B29L 22:00

Claims (2)

(57) [Claims] 1. The method according to claim 1, wherein a droop speed of said parison is detected at a fixed position in the middle of a droop path of the parison ejected from a die of a blow molding machine. And calculating the speed of the mold-clamping hydraulic cylinder device to terminate the mold-clamp completion immediately after the lower end of the parison reaches the lower end of the cavity. 2. A speed detector for detecting a hanging speed of a parison, which is arranged at a fixed position in a hanging path of a parison injected from a die of a blow molding machine, and a speed detector for detecting a speed of a parison cylinder connected to a mold. A flow control valve disposed in a hydraulic pressure supply path, and a time required to reach the lower edge of the mold cavity at the lower end of the parison is calculated based on a detection signal from the speed detector, and the mold clamping is completed immediately after the cavity lower edge elapses. And a control means for controlling the flow control valve to set and output a mold closing speed.