JP6863759B2 - Parison controller for hollow molding machine and hollow molding machine equipped with it - Google Patents

Description

The present invention relates to a ball screw drive circuit, a parison controller for a hollow molding machine, and a hollow molding machine including the same.

A ball screw consists of a screw shaft and a nut member that is screwed onto the screw shaft via a plurality of balls (steel balls or steel balls), and the rotational output of an electric motor is driven by the screw shaft or the nut member with low friction. It is a mechanism that can be converted into displacement, and is also used, for example, as a drive mechanism for a wall thickness adjusting mechanism of a ballison in the hollow forming machine described in Patent Documents 1 and 2.

The ball screw has a small frictional force because a plurality of balls as rolling elements are interposed between the screw shaft and the nut member, but the machine is between the screw shaft and the ball and between the nut member and the ball. There is no change in the relative movement, and frictional force acts on each contact surface, and the contact surface wears and generates heat. Therefore, lubrication is performed to form an oil film of grease on the contact surface.

In a hollow molding machine as described in Patent Documents 1 and 2, a parison is pushed out from a gap between a die and a core at the lower end of an extrusion head and hung down, and the parison is sandwiched in a pair of dies. A hollow molded product is formed by blowing compressed air, and a ball screw is used as a drive mechanism for adjusting the wall thickness of the parison by adjusting the gap between the die and the core based on the relative ascending / descending movement. Has been done.

Japanese Unexamined Patent Publication No. 5-92481 Japanese Unexamined Patent Publication No. 7-227900

The ball screw used as the drive mechanism of the parison wall thickness adjustment mechanism in such a parison extrusion head is a ball screw because the relative movement amount between the die and the core required for the parison wall thickness adjustment is small. The operating stroke of the screw shaft is as small as several millimeters, and the relative rotation amount between the screw shaft and the nut member is only a minute angle. Moreover, under the condition that the hollow molding machine is continuously operating, the wall thickness of the parison based on the operation of the ball screw is not adjusted at least until the predetermined operation cycle of the hollow molding machine is completed.

Therefore, if the ball screw is used for a long period of time under such a situation, the grease may not sufficiently reach the contact surface between the screw shaft and the nut member and each ball, which may lead to malfunction due to wear, and as a result, the ball screw. It is not preferable because it leads to an early life.

The present invention has been made by paying attention to such a problem, and lubrication with grease can be sufficiently and smoothly performed on the contact surface between the screw shaft and the nut member and each ball even under a usage state in which the operating stroke is extremely small. as there is provided a blow molding machine provided with the parison controller and for it empty molding machine in which the.

Further, the parison controller for blow molding machine according to claim 1 of the present invention, is suspended by extruding a parison from a gap between the die and the core of the lower end of the extrusion head, upper sandwiching the parison within a pair of molds When molding a hollow molded product by blowing compressed air in, a parison controller for a hollow molding machine that controls the wall thickness of the parison by adjusting the gap between the die and the core based on the relative ascending / descending movement. It is assumed.

Then, of the screw shaft constituting the ball screw and the nut member screwed to the screw shaft via a plurality of balls, one of them is used as a driving side member and the other is used as a driven side member of the die or core. By rotating the drive side member in connection with the above, the die or core can be moved up and down together with the driven side member based on the screwing action of the ball screw, and the cooperation between the die and the core. When the operation of the hollow molding machine for which the wall thickness adjustment by the operation is completed is stopped, the die or core is moved up and down with forward and backward movements by a stroke equal to or more than the rotational movement amount of one rotation of each ball.

Further, the hollow molding machine according to claim 2 of the present invention is provided with the parison controller according to claim 1.

Here, in the inventions according to claims 1 and 2, the stroke for operating the ball screw extra is as a stroke equal to or more than the rotational movement amount of one rotation of each ball interposed between the screw shaft and the nut member. It is based on the finding that if the ball makes at least one rotation, the contact surface between the screw shaft and nut member and each ball can be evenly lubricated with an oil film of grease. Therefore, the upper limit of the stroke equal to or greater than the rotational movement amount of one rotation of each ball is basically not particularly limited as long as it is within the range of the maximum stroke of the ball screw itself.

According to the present invention, it is sufficient that the oil film of grease can be evenly distributed to the contact surface between the screw shaft and the nut member and each ball even when the ball screw is used, which is premised on operation with a minute stroke. Since various grease lubrication can be performed, it is possible to suppress wear and malfunction of the ball screw component due to insufficient lubrication, and to extend the life of the ball screw.

A partially cutaway front view showing an embodiment of a hollow molding machine provided with a ball screw drive circuit and a parison controller of the present invention. FIG. 3 is an enlarged cross-sectional view of a discharge port in the extrusion head shown in FIG. Explanatory drawing which shows the detail of the parison controller of this invention shown in FIG. An enlarged cross-sectional view showing an example of another discharge port different from the discharge port shown in FIG. An enlarged cross-sectional view showing an example of yet another discharge port different from the discharge port shown in FIG. FIG. 3 is a side view of a ball screw used in the extrusion head shown in FIG. FIG. 6 is a vertical cross-sectional view of a part of the ball screw shown in FIG. Flow chart at the time of coarse movement of the ball screw. Timing chart during the coarse movement of the ball screw.

Hereinafter, embodiments of a ball screw drive circuit according to the present invention, a parison controller using the same, and a hollow molding machine including the parison controller will be described with reference to the drawings.

The hollow molding machine shown in FIG. 1 has a hopper 2 for charging solid resin pellets, and is connected to an extruder (not shown) in which the resin pellets are softened and melted by a screw and sent out to the front side, and the tip of the extruder. Then, the molten resin sent out from the extruder is extruded from the die 13 at the tip as a tubular (tube-shaped) parison P and hung down, and a molding die sandwiching the extruded head 1 and the parison P extruded from the extrusion head 1. 3. A mold clamping device 6 provided with a molded product holder 5 attached to the platen 4, an electric motor for molding and opening the platen 4 and the molding die 3, and a parison P having a predetermined length. A parison cutting device (not shown), a mold transfer device 7 for moving the molding die 3 under a predetermined stroke, and an air blowing nozzle 8 for blowing compressed air into the parison P are provided. It is equipped with a nozzle driving device 9 and the like. Reference numeral 10 in FIG. 1 indicates a base.

Further, the hollow molding machine shown in FIG. 1 is accompanied by a handling device 11. The handling device 11 has an opening / closing type gripper portion 12 at the tip thereof, and has a function of receiving the hollow molded product S held by the molded product holder 5 and carrying it out to the outside.

The outline of the molding procedure in the hollow molding machine configured in this way is as follows.

The molten resin sent from the extruder (not shown) toward the extrusion head 1 is extruded as a tubular parison P from the die 13 at the tip of the extrusion head 1 and hangs down onto the mold 3 which is open. It is accommodated and sandwiched in the molding die 3 by being molded by the mold clamping device 6. After that, the mold transfer device 7 transfers the molding die 3 together with the nozzle driving device 9 directly below the nozzle driving device 9. The nozzle driving device 9 lowers the air blowing nozzle 8 to drive the air into the parison P in the molding die 3, and then blows compressed air into the parison P to expand the parison. The expanded parison P is pressed against the cavity on the inner surface of the molding die 3 and molded into a predetermined molded product shape.

After molding, the molding die 3 opens, and the opened molding die 3 moves to the original position directly under the extrusion head 1 by the movement of the mold transfer device 7, while the molded product S after molding moves. After being lifted by the air blowing nozzle 8, it is transferred to the molded product holder 5 by the gripping operation of the molded product holder 5. Further, the molded product S held by the molded product holder 5 is transferred to the gripper portion 12 of the handling device 11 and then carried out to the outside.

FIG. 2 is an enlarged cross-sectional view showing the details of the die 13 in the extrusion head 1 shown in FIG. 1, and FIG. 3 shows the details of the extrusion head 1 and the structure of the parison controller 14 attached thereto.

As shown in FIGS. 1 and 2, the die 13 at the lower part of the extrusion head 1 has a small diameter portion 13a protruding downward, and the core 15 as a moving body is concentrically inserted into the small diameter portion 13a. There is. At the tip of the small diameter portion 13a, as shown in FIG. 2, a tapered opening 17 formed so as to spread downward in a skirt shape at the lower end of the straight passage 16 on the small diameter portion 13a side, and a core 15 An annular discharge port 18 for extruding the parison P is formed by a substantially tappet-shaped tapered shaft portion 15b formed at the lower end portion of the straight shaft portion 15a on the side so as to spread downward in a skirt shape. Has been done. Then, as will be described later, if the small diameter portion 13a side of the die 13 is the fixed side and the core 15 is the movable side, the core 15 is moved up and down with respect to the small diameter portion 13a in the axial direction to eject. The opening width dimension G of the outlet 18, and eventually the wall thickness of the parison P to be extruded from the discharge port 18 can be variably controlled.

A plurality of guide rods 19 are arranged above the die 13 in the extrusion head 1 shown in FIG. 3, and the slider 20 is guided and supported by the guide rods 19 so as to be able to move up and down. Further, the core 15 shown in FIGS. 1 and 2 is connected to the slider 20, and the servomotor 21 and the speed reducer 22 are coaxially arranged above the extrusion head 1. A ball screw 23 is arranged between the speed reducer 22 and the slider 20. As is well known, the ball screw 23 includes a screw shaft (screw shaft) 24 and a nut member 25 screwed onto the screw shaft 24 via a plurality of balls (steel balls or steel balls) (not shown). Has been done.

In FIG. 3, the screw shaft 24 of the ball screw 23 is connected to the output shaft of the speed reducer 22 via the coupling 26, while the nut member 25 screwed to the screw shaft 24 is connected to the upper part of the slider 20. There is. As a result, when the screw shaft 24 of the ball screw 23 is rotationally driven as a drive side member by the servomotor 21, the nut member 25 screwed to the screw shaft 24 functions as a driven side member, and the nut member Together with the 25, the slider 20 moves up and down in a form guided by the guide post 19. Then, as described above, since the core 15 shown in FIGS. 1 and 2 is connected to the slider 20, the core 15 moves up and down together with the slider 20. As a result, as shown in FIG. 2, the opening width dimension G of the discharge port 18, and thus the wall thickness of the tubular parison P extruded from the discharge port 18, changes. Here, the amount of movement that moves the core 15 as a moving body up or down when adjusting the wall thickness of the parison P is defined as a normal stroke or a normal elevating stroke.

On the other hand, instead of the shape of the discharge port 18 shown in FIG. 2, the shape of the discharge port 18 formed by a combination of the tapered opening 17a and the tapered shaft portion 15c as shown in FIG. 4 and the shape of the discharge port 18 as shown in FIG. The shape of the discharge port 18 composed of a combination of the tapered opening 17b and the tapered shaft portion 15d may be adopted.

In the shape of the discharge port 18 shown in FIG. 2, the wall thickness of the parison P extruded from the discharge port 18 becomes thinner as the core 15 rises, whereas the thickness of the discharge port 18 shown in FIGS. 4 and 5 becomes thinner. On the contrary, as the core 15 rises, the wall thickness of the parison P extruded from the discharge port 18 becomes thicker. Here, the former aspect shown in FIG. 2 is referred to as "die shape is diverge", and the latter aspect shown in FIGS. 4 and 5 is referred to as "die shape is converge".

A rotation detector 27 such as a rotary encoder is attached to the servomotor 21 shown in FIG. 3, and forms a feedback loop with the servo amplifier 28. A servo control controller 29 is connected above the servo amplifier 28, and a sequencer (also referred to as a programmable controller or PLC) 30 that controls comprehensive control is connected above the servo control controller 29. Further, the sequencer 30 is provided with an operation panel 31 provided with a monitor 31a for various settings and displays. A parison controller 14 is formed by adding an operation panel 31 to the servo amplifier 28, the servo control controller 29, and the sequencer 30. Then, when the core 15 shown in FIGS. 1 and 2 is moved up and down to control the wall thickness of the parison P, the servomotor 21 is rotationally driven via the servo control controller 29 and the servo amplifier 28 by a command from the sequencer 30. Will be done.

As is clear from the above description, in addition to the die 13 in the extrusion head 1 shown in FIGS. 1 and 3 and the core 15 inserted in the small diameter portion 13a of the die 13, the slider 20, the ball screw 23, and the servomotor The parison wall thickness adjusting mechanism 31 is formed by 21 and the like.

6 and 7 show the details of the ball screw 23 shown in FIG. 3, FIG. 6 is a side view thereof, and FIG. 7 is a vertical sectional view of FIG. As shown in FIGS. 6 and 7, the ball screw 23 includes a screw shaft 24 on the male screw side, a nut member 25 externally inserted into the screw shaft 24 and on the female screw side, and a screw shaft 24 and a nut member 25. It is composed of a plurality of balls 32 as rolling elements interposed between the balls. A spiral (screw groove shape) ball rolling groove 24a is formed on the screw shaft 24, and similarly, a spiral (thread groove shape) ball rolling groove 25a is formed on the nut member 25. Then, by interposing a plurality of balls 32 between the ball rolling grooves 24a and 25a so as to mesh with each other, the screw shaft 24 and the nut member 25 can be smoothly screwed. Are screwed together via the balls 32.

A return pipe 33 is attached to the nut member 25 as shown in FIG. The return pipe 33 forms an endless ball circulation path together with a part of the ball rolling grooves 24a and 25a, and a plurality of balls 32 circulate in the ball circulation path. Reference numerals 34 and 35 in FIGS. 6 and 7 indicate end caps screwed to both ends of the nut member 25.

Here, as shown in FIG. 2, the amount of vertical movement of the core 15 (the above-mentioned normal stroke or the normal elevating stroke) when adjusting the wall thickness of the parison P is extremely small, and the core 15 inevitably moves linearly. The amount of operation of the ball screw 23 that controls the drive is also very small, and even when converted into the amount of rotational movement of each ball 32, it is less than the amount of movement equivalent to one rotation of each ball 32. In such a usage pattern, the oil film of grease between the ball rolling grooves 24a and 25a and each ball 32 is likely to run out, and if the use is continued as it is, early wear is likely to occur due to insufficient lubrication at the contact surface between the two. Is as described above.

As a countermeasure, in the present embodiment, for example, on condition that the operation cycle of the hollow molding machine is stopped, a preset coarse movement distance (coarse) is used as the coarse movement operation of the ball screw 23 regardless of the wall thickness control of the parison P. It is assumed that the ball screw 23 is operated greatly by the amount of movement). The above-mentioned coarse movement distance is an amount of movement that does not cause the grease oil film to run out between the ball rolling grooves 24a and 25a and each ball 32, or the amount of movement that can recover the oil film running out, and the movement of each ball 32. When converted into an amount, the amount of movement is equal to or greater than the amount of movement corresponding to one rotation of each ball 32. This coarse movement distance shall be set in advance in the sequencer 30 shown in FIG. The upper limit of the coarse movement distance is not particularly limited as long as the stroke of the ball screw 23 has a margin.

Since the value of this coarse movement distance depends on the specifications of the ball screw 23, the diameter D1 of the ball 32 used for the ball screw 23, the lead (screw pitch) LD of the screw shaft 24, and the screw shaft 24 It can be calculated based on each value of the diameter D2.

First, the moving distance L1 when the ball 32 rotates N is calculated from the following equation 1. Here, N is the number of rotations of the ball 32 and is an integer of 1 or more, D1 is the diameter of the ball 32, and π is the pi.

L1 = N × D1 × π (1)
Next, the circumference length L2 of the screw shaft 24 is obtained from the following equation (2). Here, D2 is the center diameter of the screw shaft 24.

L2 = D2 × π ‥‥‥ (2)
Further, the angle DG based on the moving distance L1 of the ball 32 is obtained from the following equation (3).

DG = D1 / D2 x 360 ... (3)
Finally, the moving distance (operating distance) of the ball screw 23 based on the N rotation of the ball 32 is calculated as the coarse movement distance L3 from the following equation (4). Here, the LD is a lead of the screw shaft 24.

L3 = LD x DG / 360 ... (4)
The coarse movement distance L3 of the ball screw 23 thus obtained is set and stored in advance in the storage unit of the sequencer 30 shown in FIG. For the setting / storage of the coarse movement distance L3, the value calculated on the desk based on the above equations (1) to (4) is set / stored in the storage unit of the sequencer 30 by the operation on the operation panel 31. In addition, the above equations (1) to (4) are input to the sequencer in advance, and then the diameter D1 of the ball 32 and the lead LD of the screw shaft 24, which are the specifications of the ball screw 23 described above, are input. By inputting the respective values of the diameter D2 of the screw shaft 24 and the screw shaft 24, the value automatically calculated and obtained by the sequencer 30 may be set and stored in the storage unit of the sequencer 30.

Further, on condition that the operation cycle of the hollow forming machine is stopped, it is assumed that the sequencer is programmed in advance so that the operation in the above-mentioned coarse movement operation mode is performed.

The flow chart in FIG. 8 is a detailed description of the movement in the coarse movement mode.

On condition that the operation cycle of the hollow molding machine in step S1 of FIG. 8 is stopped, the operation of the ball screw 23 in the next step S2 in the coarse motion operation mode is executed.

In this coarse movement mode, first, in step S3, it is determined whether or not the die shape is diverge, and if the die shape is diverge, the process proceeds to the next step S4, and if the die shape is not diverge. Is nothing but a converged die shape as described above, so the process proceeds to the next step S5.

In step S4, the coarse movement of the ball screw 23 starts. Specifically, as shown in the next step S6, by starting the servomotor 21, the ball screw 23 moves the core 15 shown in FIG. 2 downward by the coarse movement distance L3 set in advance (forward movement). Let me. When the core 15 moves downward by the coarse movement distance L3, in the next step S8, the core 15 shown in FIG. 2 is moved upward by the coarse movement distance L3 in which the ball screw 23 is preset due to the reversal of the servomotor 21. Move (recover). With one reciprocating movement of the ball screw 23 based on the coarse movement distance L3, the core 15 returns to the original position, and the hollow forming machine is completely stopped in that state.

On the other hand, in step S3 of FIG. 8, when the die shape is not diverge, as described above, the die shape is nothing but converged. Therefore, the process proceeds to the next step S5, and the ball screw 23 The coarse movement starts.

Specifically, as shown in the next step S7, by starting the servomotor 21, the ball screw 23 moves upward (forward) the core 15 shown in FIG. 2 by the coarse movement distance L3 set in advance. Let me. When the core 15 moves upward by the coarse movement distance L3, in the next step S8, the core 15 shown in FIG. 2 is moved downward by the coarse movement distance L3 in which the ball screw 23 is preset due to the reversal of the servomotor 21. Move (recover). With one reciprocating movement of the ball screw 23 based on the coarse movement distance L3, the core 15 returns to the original position, and the hollow forming machine is completely stopped in that state.

Then, regardless of whether the die shape is diverged or converged, in the next step S9, the carrier cycle of the hollow forming machine is restarted after waiting for the operation cycle start command.

Here, if the relationship between the movement of each ball screw 23 when the die shape is diverge and converge and the coarse motion signal and the automatic operation signal related to the operation cycle of the hollow molding machine is shown as a timing chart, as shown in FIG. Is.

As described above, according to the present embodiment, the ball screw 23 of the parison wall thickness adjusting mechanism is reciprocated by a preset coarse movement distance L3 each time on condition that the operation cycle of the hollow molding machine is stopped. It was done. Then, the coarse movement distance L3 is equal to or more than one rotation of the ball 32 in terms of the rotational movement amount of the ball 32 interposed in the ball screw 23 so as to be larger than the normal stroke or the normal elevating stroke of the ball screw 23. Since the amount of movement is set to, the oil film running out of grease at the contact portion between each ball 32 and the ball rolling grooves 24a and 25a on the screw shaft 24 side and the nut member 25 side, which are the mating side members, and the accompanying insufficient lubrication are prevented. It can be prevented in advance. Therefore, it is possible to suppress malfunction due to wear at the contact portion between the ball 32 and the mating end member, and to extend the life of the ball screw 23.

Here, in the above embodiment, in the parison wall thickness adjusting mechanism of the hollow molding machine, the die 13 of the extrusion head 1 shown in FIGS. 2 and 4 and 5 is set as a fixed side, and the core 15 inserted therein is set as a fixed side. As the movable side, the core 15 is moved up and down with respect to the die 13, but conversely, even if the core 15 is set as the fixed side and the die 13 on the movable side is moved up and down with respect to the core 15. good. Further, if necessary, both the die 13 and the core 15 may have a structure capable of moving up and down.

Further, in the above embodiment, the screw shaft 24 side of the ball screw 23 is used as the drive side member, and the nut member 25 screwed to the screw shaft 24 is used as the driven side member. It is also possible to use the drive side member as the drive side member and the screw shaft 24 as the driven side member.

Further, in the above embodiment, the ball screw 23 used in the parison wall thickness adjusting mechanism of the hollow molding machine has been described as an example, but the present invention is not limited to this. As is well known, a ball screw is widely used in a drive system for moving parts in various mechanical equipment. Therefore, as long as it does not deviate from the gist of the present invention, the ball screw is often used in various mechanical equipment. Needless to say, the present invention can be applied to the above.

1 ... Extrusion head 3 ... Molding mold 13 ... Die 15 ... Core (moving body)
23 ... Ball screw 24 ... Screw shaft (drive side member)
25 ... Nut member (driven member)
32 ... Ball L3 ... Coarse movement distance P ... Parison S ... Hollow molded product

Claims (2)

When a parison is pushed out from the gap between the die and the core at the lower end of the extrusion head and hung down, the parison is sandwiched between a pair of molds, and compressed air is blown into the hollow molded product, the die and the core are formed. It is a parison controller for hollow forming machines that controls the wall thickness of the parison by adjusting the gap between the two based on the relative ascending / descending movement of the parison.
Of the screw shaft constituting the ball screw and the nut member screwed to the screw shaft via a plurality of balls, one of them is used as a driving side member, and the other is used as a driven side member and connected to a die or a core.
By rotationally driving the drive-side member, the die or core can be moved up and down together with the driven-side member based on the screwing action of the ball screw.
When the operation of the hollow forming machine for which the wall thickness adjustment is completed by the cooperation between the die and the core is stopped, the die or the core is moved up and down with forward and backward movements by a stroke equal to or more than the rotational movement amount of one rotation of each ball. A parison controller for hollow molding machines, which is characterized by being made to rotate. A hollow molding machine comprising the parison controller according to claim 1.

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