JP2014079913A - Hollow-molding method - Google Patents

Abstract

Previously, a flow rate proportional valve with a free flow rate control pattern was used in the compressed air supply line for preliminary blow, and the flow rate was switched and controlled using a timer or the like. A method for controlling the flow rate of compressed air has been desired.
SOLUTION: Lines 20 to 23 for supplying compressed air for pre-blowing and solenoid valves 44 and 45 are used, and the solenoid valves 44 and 45 are turned ON / OFF at every point where one molding cycle is equally divided into a desired number. Preliminary blow is performed by changing the amount of air from the compressed air supply lines 20-23. Thus, preliminary blow can be performed using a general-purpose solenoid valve, and a hollow molding method that meets market needs for a general-purpose flow rate control method can be provided. Since the flow rate switching point is set at an equally divided point in one molding cycle, it is handled in the same way as general parison wall thickness adjustment by a parison controller, and the setting is easy to understand and simple, thereby shortening the molding condition setting time.
[Selection] Figure 7

Description

The present invention relates to a hollow molding method for performing preliminary blowing.

In the hollow molding method, a heated and melted thermoplastic resin is extruded from a die head and a parison is dropped between a pair of mold dies, compressed air is blown from a blowing nozzle, and a pair of closed molds are closed. Expand to form a hollow molded product.

In such a direct blow molding method, conventionally, a low flow rate air is generally blown into a parison before mold closing in order to make the thickness distribution of a hollow molded product uniform and improve the insertability of a blow pin for forming a mouth. It is generally known to improve the property and thickness accuracy. For example, as disclosed in Patent Document 1, a parison hangs down from a die head, and when the parison reaches a predetermined length, the lower part of the parison is pinched by a lower part of a mold or a pinch device, and in this pinched state, Preliminary blow is performed by supplying compressed air.

The preliminary blow of the parison having a pinch seal at the lower part of the parison may be performed using a compressed air amount based on software set in advance depending on the resin material of the parison, the cavity shape of the molding die, and the like.

JP2007-152866A

Conventional preliminary blow uses a flow rate proportional control valve that can freely adjust the flow rate of compressed air in the compressed air supply line, and controls the flow rate using a timer or the like. Although the flow rate proportional control valve is easy to adjust, it is expensive, and while the cost reduction for the hollow molding machine is becoming more and more recent, another method for adjusting the flow rate of the preliminary blow compressed air has been desired. In addition, simplification of the flow rate control setting has been desired.

An object of the present invention is to solve the above problems and to provide a hollow molding method capable of adjusting the flow rate of compressed air for preliminary blowing without using a flow proportional valve.

In order to achieve the above object, the present invention is such that the outer surface of a bottomed parison formed by hanging a parison from a die head in a state where the molding die is opened and cutting and closing the lower portion of the parison is used as the mold of the molding die. Hollow molding that performs preliminary blow to supply compressed air into the bottomed parison so as not to contact the inner surface, and then closes the molding die and drives a blow nozzle to supply compressed air into the bottomed parison to perform hollow molding In the method, two or more compressed air supply lines for supplying pre-blowing compressed air and two or more solenoid valves for opening and closing each line are used, and the molding cycle is divided into the desired number at each point. The hollow molding method is characterized in that the preliminary blow is performed by changing the amount of compressed air for preliminary blow from the compressed air supply line by opening and closing two or more solenoid valves. One molding cycle refers to a process from a process of cutting a parison after closing a mold to a process of cutting a parison after closing the next mold. The desired number is 30 to 100 points, and the number of control points that is generally the same as the number of control points used in the parison thickness controller is desirable because it is easier to set and relate to the parison thickness control. .

The second problem-solving means is a hollow molding method according to the above-described problem-solving means, wherein the flow rate of the compressed air is different in each of the two or more compressed air supply lines.

The third problem-solving means is supplied for the preliminary blow in the bottomed parison so that the inner surfaces and the outer surfaces of the bottomed parisons do not contact the inner surface of the mold of the molding die in both the problem-solving means described above. A hollow molding method is characterized in that a part of compressed air is exhausted.

The operation of the first problem solving means is as follows. In other words, since the preliminary blow flow rate can be adjusted for each point obtained by dividing one molding cycle by the desired number, it is related to the set point of the parison wall thickness controller compared to the case where the flow rate was adjusted with the previous timer. Since the flow rate can be set with ease, the setting becomes simple and the preliminary blow flow rate can be adjusted without any inferiority. Also, compared to the hollow molding method using preliminary flow using a flow rate proportional control valve, preliminary blow can be performed using a more general-purpose electromagnetic valve, so that a hollow molding method meeting recent market needs can be provided. .

The operation of the second problem solving means can adjust the flow rate of the preliminary blow in a finer flow rate setting range as compared with the case where a line having the same flow rate is provided.

The action of the third problem solving means is that a part of the compressed air of the pre-blowed parison is exhausted, the mold is closed after the exhaust is completed, and the blow nozzle is driven to form a hollow mold, so that the parison touches the cavity surface when the mold is closed. There is an effect that the surface skin can be prevented from becoming rough.

According to the hollow molding method according to the present invention as described above, preliminary blow can be performed using a general-purpose solenoid valve, and therefore further versatility can be achieved.

FIG. 1 is a front view of a hollow molding machine used in one embodiment of the present invention. FIG. 2 is a plan view of the hollow molding machine shown in FIG. FIG. 3 is a side view in which a part of the hollow molding machine shown in FIG. 1 is omitted. FIG. 4 is an enlarged front view of the die head of the hollow molding machine shown in FIG. 5 is an enlarged cross-sectional view taken along the dashed line AA in FIG. FIG. 6 is an enlarged side view of the die head and the parison cutting device in the hollow molding machine shown in FIG. FIG. 7 is a schematic view showing a preliminary blow line in the die head shown in FIG. FIG. 8 is a graph showing the preliminary blow flow rate according to the dividing point of one molding cycle. FIG. 9 is a graph showing the ON / OFF state of the suction pump according to the division point of one molding cycle. FIG. 10 is a graph showing the outer shape of the parison according to the length of the drooping parison.

The hollow molding machine used in an embodiment of the present invention is of a so-called double station type, and in the drawings, the description of the same member and the same device that perform the same operation is omitted as appropriate. 1 to 3, a main extruder 1, a first sub-extruder 2, a second sub-extruder 3, a third sub-extruder 4, and a die head for melting and extruding a resin composition. 5, a parison cutting device, which will be described later, two right and left molding dies 6 and 7, left and right blowing devices 8 and 9 for compressed air, and a mold clamping device 10 for opening and closing the molding dies 6 and 7 and clamping them. 11, 11, and moving devices 12 and 13 for molding dies and clamping devices for laterally moving the molding dies 6 and 7 in the side-by-side direction thereof.

The main / sub extruders 1, 2, 3 and 4 are used for feeding, kneading, melting and discharging resin compositions into the resin composition hoppers 1a, 2a, 3a and 4a, respectively. Is omitted.

As shown in FIGS. 4 and 5, the die head 5 is for four heads, and is connected to the tips of the extruders 1 to 4, and four die heads 5 using the molten resin composition supplied from these extruders. The arranged cylindrical parisons are formed by hanging from the four head tips 5a, 5b, 5c, 5d at the lower end of the die head. Each of the tips 5a to 5d is composed of a die 5e and a core 5f, and the die 5e and the core 5f adjust the sectional area of the tip of the resin flow path 5g to adjust the thickness of the parison. Yes.

4 and 5, reference numerals 20, 21, 22, and 23 are preliminary blow compressed air supply lines, and mandrel shafts 20a, 21a, and 22a connected to the respective cores 5f of the head tips 5a, 5b, 5c, and 5d. The preliminary blow air is supplied by a pipe joint screwed and fixed to the upper part of 23a. 4 and 5, reference numeral 24 is a die body, reference numeral 25 is a servo motor, reference numeral 26 is a guide shaft, and reference numeral 28 is lifted and lowered by the servo motor 25 and a ball screw (not shown) rotated by the servo motor 25. An elevating plate 28 that moves, and a guide shaft 26 guides the elevating motion.

The mandrel shafts 20a, 21a, 22a, and 23a are in a hollow state, and the preliminary blow air supplied from the pipe joint is supplied into the parison from the tip of the core 5f through the hollow hole of the mandrel shaft. ing. The mandrel shafts 20a, 21a, 22a and 23a are fixed to the elevating plate 28, and the servo motor 25 is operated by the control profile of the parison thickness controller (not shown), and the elevating plate 28 moves up and down to move the die 5e and the core 5f. The desired parison wall thickness can be obtained by adjusting the gap.

As shown in FIG. 6, the parison sealing device 30 also serving as parison cutting cuts the upper part of each cylindrical parison P hanging from the head tips 5 a to 5 d of the die head 5 and seals the lower part of the next cylindrical parison. The cutter 31 and the seal member 32 are provided. The rod tip of the air cylinder 33 is fixed to the rear cutter arm 35 via an extension rod 34. The rear cutter arm 35 has a rear cutter 31 and a seal member 32 attached thereto, and the front cutter arm 36 has a front cutter 31 and a seal member 32 attached thereto. The rear cutter arm 35 and the front cutter arm 36 are synchronized with each other by a rack and a pinion (not shown), and the cutter arm 35 is advanced by the air cylinder 33 by a pair of guide shafts 37 so that the front cutter arm 36 is moved forward. Also, the parison can be cut and the upper parison end can be sealed by moving forward in the proximity direction and closing the cutter arms of both.

Each of the left and right molding dies 6 and 7 includes a pair of split molds having cavities matched to the outer shape of the molded product, and the molding die moving devices 12 and 13 having an electric motor directly below the die head 5 and the left and right molds. Between the four rail nozzles 8a and 9a of each of the blower devices 8 and 9 in the horizontal direction on the pair of rails 15 extending in the lateral direction provided in the machine frame of the hollow molding machine. It is designed to reciprocate.

The left and right mold clamping devices 10 and 11 include left and right bases 10a and 11a that move on a pair of rails 15, left and right front platens 10b and 11b, and a rear platen 10c (the left rear platen is not shown), and these platens. And a mechanism for clamping the molding dies 6 and 7 by moving them close to and away from the parting line. The front platens 10b and 11b are attached to the front split mold of a pair of molds 6 and 7, and the right rear platen 10c and the left rear platen (not shown) are attached to the other split mold of the molds 6 and 7. It is like that.

The left and right blowing devices 8 and 9 are for blowing compressed air by blowing the blowing nozzles 8a and 9a from above into four parisons positioned between a pair of split molds of the molding dies 6 and 7, respectively. Blow nozzle drive devices 8b and 9b for raising and lowering the blow nozzles 8a and 9a are provided.

The left and right cooling nozzles 16 and 17 are disposed in the vari punching unit adjacent to the outside of the left and right blowing nozzles 8a and 9a. The cooling nozzles 16 and 17 are fixed by driving the blowing nozzles 8a and 9a so that the number corresponding to the four blowing nozzles 8a corresponds to the arrangement positions of the corresponding blowing nozzles 8a and 9a. It is connected to the parts 8c and 9c, and rapidly cools the mouth of the hollow molded product P after being molded with a water cooling structure. These cooling nozzles 16 and 17 are moved up and down by corresponding air cylinders 18 and 19.

The molded product holder 27 holds the right and left hollow molded products Pr released from the molds 6 and 7 that have been opened after the blow molding is completed. The molded product holders 27 hold the front platens 10b of the mold clamping devices 10 and 11, respectively. 11b and the back platen 10c (the back platen of the mold clamping device 11 is not shown) are provided to extend horizontally and outwardly.

After cooling by the cooling nozzles 16, 17, the bottom burr, shoulder burr, and bottom burr of the bottomed hollow molded product Pr from which the cooling nozzles are separated are cut out in a state of being sandwiched by the molded product holder 27, so that illustration is omitted. A burr separator is provided. The hollow molded product Pr after the burr separation is carried out from the punching unit to the outside of the hollow molding machine by a belt conveyor or the like.

As shown in FIG. 7, the above-described preliminary blow compressed air supply lines 20 to 23 are connected to an air source 40 that outputs compressed air via a preliminary blow compressed air supply source line 41. The original line 41 branches into two compressed air supply branch lines 42 and 43 having the same pressure on the way to the die head 5. The first solenoid valve 44 and the second solenoid valve 45 are interposed in the middle of the branch lines 42 and 43 to open and close the branch lines 42 and 43.

Each of the branch lines 42 and 43 is further divided into four lines 42a, 42b, 42c, 42d and lines 43a, 43b, 43c, 43d on the downstream side of the solenoid valves 44, 45, and these lines 42a-42d and 43a. ˜43d can respectively change the flow rate of the compressed air by the flow rate control valves 46 and 47. On the downstream side of the flow control valves 46 and 47, the lines 42a and 43a, the lines 42b and 43b, the lines 42c and 43c, and the lines 42d and 43d are joined together, and the corresponding preliminary blow compressed air supply lines 20, 21, 22 and 23 are connected. In FIG. 7, reference numerals 48 and 49 denote pressure reducing valves that adjust the preliminary blow pressure.

The electromagnetic valves 44 and 45 can be turned on (opened) and turned off (closed) at each point obtained by dividing one molding cycle by a desired number, for example, 40. Both the first electromagnetic valve 44 and the second electromagnetic valve 45 are provided. OFF, the first solenoid valve 44 is ON, the second solenoid valve 45 is OFF, the first solenoid valve 44 is OFF, the second solenoid valve is ON, and the first solenoid valve 44 and the second solenoid valve 45 are both ON. Can be operated in combination.

In addition to the compressed air supply lines 20 to 23, an exhaust line 50 for forcibly exhausting part of the compressed air that is being pre-blowed from the parison is connected. The exhaust line 50 is connected to the dry pump 51, and the exhaust timing is adjusted by an electromagnetic valve 52 interposed in the middle of the exhaust line 50.

The air source 40 further includes a blow compressed air supply line 60 connected to the blow nozzle 8a of the right blow device 8 in FIG. 1 and a blow compressed air connected to the blow nozzle 9a of the left blow device 9 in FIG. Connected to the supply line 61. The compressed air supply lines 60 and 61 include low pressure blowing lines 60a and 61a and high pressure blowing lines 60b and 61b.

The hollow molding machine of the present invention is not limited to the double station type shown in the drawings, but is a so-called single station type hollow molding machine comprising one molding die and one mold clamping device, and other types of hollow molding machines. It can be applied to a molding machine.

Next, an embodiment of the present hollow molding method using the above-described hollow molding machine will be described. First, the molten resin extruded from each of the extruders 1 to 4 is introduced into the die head 5, and the parison P is extruded from the head tips 5a to 5d of the die head 5, as shown in FIG.

In the parison P, the upper end of the parison P in the previous step is cut by the cutter 31 of the parison cutting device 30, and the portion Pb above the cut portion Pa is sealed by the seal member 32 and pushed out from the die head 5.

Compressed air is supplied to these parisons P from the preliminary blow compressed air supply lines 20 to 23, and preliminary blow is performed as shown in FIGS.

FIG. 8 shows that when one desired molding cycle is 20 seconds and the required parison length is 400 mm at this time, one molding cycle is divided into 1 to 40 and 40P is set as the vertical axis, and the compressed air for preliminary blow is used. 2 represents a preliminary blow flow graph with the horizontal axis representing the supply amount (liter / minute) of.
FIG. 9 is a graph showing a pump suction state in which 40P is the vertical axis, and the dry pump 51 is in the ON (operation) / OFF (rest) state. FIG. 10 is a graph in which the vertical axis represents the parison length (mm) and the horizontal axis represents the external shape of the parison hanging from the tip 5a of the die head 5 for each parison length. The outer shape of the parison hanging from the other tips 5b to 5d of the die head 5 is the same.

As shown in FIG. 8, the first solenoid valve 44 is turned on, the second solenoid valve 45 is turned off, and the parison is suspended to 25P while the solenoid valve 52 is turned off as shown in FIG. Perform preliminary blow with compressed air. The bottomed cylindrical parison at 12.5 seconds (corresponding to a length of 250 mm) is in an outer shape having a substantially constant waist as shown by A in FIG.

Next, in FIG. 8, the first solenoid valve 44 and the second solenoid valve 45 are turned on in the range from 26P to 36P, and in FIG. 9, the solenoid valve 52 is turned on in the range from 29P to 35P. While sucking, preliminary blow is performed at a compressed air supply rate of 8 l / min. Initially, in the parison, the upper trunk portion swells in comparison with the lower trunk portion in the range from 26P to 28P in FIG.

Then, as shown in FIG. 10, when the parison reaches 17.5 seconds (corresponding to a length of 350 mm), both the upper trunk portion and the lower trunk portion are in a thin flat C state.

In FIG. 8, the first solenoid valve 44 and the second solenoid valve 45 are turned on until 36P, the solenoid valve 52 is turned off at the point of 36P in FIG. 9, and then the first solenoid valve 44 is turned off until 39P. 2 The electromagnetic valve 45 is turned on and preliminary blow is performed at a compressed air supply amount of 5 l / min. In the parison, when the length reaches 19.5 seconds (corresponding to a length of 390 mm) in FIG. 10, the upper torso swells slightly as in the D state.

Further, when the first solenoid valve 44 is turned on and the second solenoid valve 45 is turned off while the solenoid valve 52 is kept off, and preliminary blow is performed at a compressed air supply amount of 3 l / min up to 40P, the parison is shown in FIG. As shown in the E state, the upper body of the parison is slightly thinner.

Each parison subjected to the preliminary blow is inserted into the cavity of the mold 6 or 7 that is open, and simultaneously with the insertion of the parison, the mold 6 or 7 is closed and held in the cavity. Is done.

Thereafter, the upper part of the parison is cut by the cutter 31 of the parison cutting device 30 and held in the molding die 6 or 7, and the blowing device 8 or 9 is moved by the moving device 12 or 13 of the molding die / clamping device. It moves directly under the nozzle 8a or 9a. Four blowing nozzles 8a or 9a are driven into the locations corresponding to the mouths of the four parisons that have moved, and compressed air is blown from these nozzles to perform blow molding, which is indicated by a two-dot chain line in FIG. A bottomed hollow molded product Pr is formed.

When the hollow molded product Pr is molded, the molding die 6 or 7 and the molded product holder 16 corresponding to the molding die are opened, and the hollow molded product Pr is attached to the blowing nozzle 8a or 9a and suspended. It becomes the state.

Subsequently, the molding die 6 or 7 in an empty state and the molded product holder 27 corresponding to the molding die are moved directly under the die head 5 and blown by the blowing device 8 by the moving device 12 or 13 of the molding die / clamping device. The parison to be moved next to the nozzle 8a or the blowing nozzle 9a of the blowing device 9 and inserted next is inserted into the molding die 6 or 7, and the molded product holder 27 is molded first and the blowing nozzle 8a or 9a. The hollow molded product Pr adhering to each is gripped. In this state, the blowing nozzle 8a or 9a is lifted by driving the blowing nozzle driving device 8b or 9b and leaves the hollow molded product Pr.

Subsequently, in the state where the next-extruded parison is sandwiched between the molding dies 6 or 7, the blowing nozzle 8a or the blowing device 9 of the blowing device 8 is moved by the moving device 12 or 13 of the molding die / clamping device. While the hollow molded product Pr previously molded is gripped by the molded product holder 27, it moves directly below the four cooling nozzles 16 or 17, respectively. Then, in the same manner as described above, the blowing nozzle 8a or 9a is driven into the parison, compressed air is blown from these nozzles, blow molding is performed, and the hollow molded product Pr is molded.

At the same time, the cooling nozzle 16 or 17 is lowered by the drive of the working air cylinder 18 or 19 corresponding to the cooling nozzle, and is inserted from the respective mouth portions of the previously formed hollow molded product Pr to cool the mouth portion. . After cooling, the cooling nozzle 16 or 17 is raised by the operation of the corresponding air cylinder 18 or 19. In this state, the burr of the hollow molded product Pr with the mouth cooled is cut and separated by a burr separating device (not shown).

While the molding die 6 or 7 and the molding product holder 27 corresponding to the molding die are opened, the hollow molding product Pr is held and rotated by a product take-out device (not shown) having a pair of gripping portions. It is transferred onto a belt conveyor or a shooter, and conveyed outside the molding machine.

By repeating the above steps, a preliminary blow process is performed, and a hollow molded product that has been blown by hollow molding is molded for each molding cycle.

Since the hollow blow molding method according to the present invention can efficiently perform preliminary blow using a general-purpose solenoid valve, it is more easily accepted in the industry and has further versatility. In addition, since the flow rate switching point is set at an equally divided point in one molding cycle, it is handled in the same way as general parison wall thickness adjustment by a parison controller, and the setting is easy to understand and easy to shorten the time required for molding conditions. Become.

5 Die heads 6, 7 Molding die 8, 9 Blowing device 8 a, 9 a Blowing nozzle 10, 11 Mold clamping device 12, 13 Molding die / clamping device moving device 27 Molded product holder 20, 21, 22, 23 Preliminary blow Compressed air supply line 44, 45 Solenoid valve 46, 47 Flow control valve 50 Exhaust line

Claims (3)

The parison is suspended from the die head in a state where the molding die is open, and the outer surface of the bottomed parison formed by cutting and closing the lower portion of the parison is placed in the bottomed parison so as not to contact the inner surface of the molding die. Preliminary blow for supplying compressed air is performed, and then the molding die is closed, a blow nozzle is driven, compressed air is supplied into the bottomed parison, and hollow molding is performed to supply preliminarily blown compressed air. Two or more compressed air supply lines and two or more solenoid valves for opening and closing each line are used, and the compressed air is opened and closed by opening and closing the two or more solenoid valves at each point where one molding cycle is equally divided into a desired number. A hollow molding method, wherein the preliminary blow is performed by changing an amount of compressed air for preliminary blow from a supply line. The hollow molding method according to claim 1, wherein the flow rate of compressed air is different in each of the two or more compressed air supply lines. 2. A part of the compressed air supplied for preliminary blow in the bottomed parison is exhausted so that inner surfaces and outer surfaces of the bottomed parison do not contact the inner surface of the mold. Or the hollow molding method of 2.

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