JPS61148026A - Bubble guide device of inflation film molding machine - Google Patents

Abstract

PURPOSE:To constitute the titled device that creases or slackening is not generated at the time of folding of a cylindrical bubble in a flat state by a pinch roll, by a method wherein a sliding contact face of a film guide is made into a three-dimensional curved surface through which respective lengths of moving loci extending from arbitrary position on the circumference of the cylindrical bubble to gearing tangents become equal with each other. CONSTITUTION:Resin which has been heated and softened is cooled by air blown off through a slit of a die 8 and an air ring 10, the air is blown into the inside, formed into a cylindrical bubble 9, and the tip of the same is pulled upward by pinch rolls 15, 15. an inflation film is guided by each of rollers running along a three-dimensional curved surface Q of a film guide 20 of an expanded bubble guide device 16, cooled, deformed into a sheetlike state in order from a cylindrical cross-sectional part and then folded. In addition to the above, a nut plate 29 can be moved vertically and opening angles of the film guides 20, 20 can be varied.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a bubble guide device for guiding bubbles extruded from a die in a blown film forming machine to pinch rolls.

(Prior Art) In order to mold a thermoplastic resin such as polyethylene, vinyl chloride, polypropylene, etc. into a cylindrical thin film, an inflation molding method is usually used, and a blown film molding machine is used for this.

This inflation molding machine, as shown in Figure 8,
A frame (C) located above the die (<1)) of the extruder (a) is provided with a pair of pinch rolls (d) facing each other, and the extruder is extruded upward from the annular slit of the die (b). The cylindrical molten resin is cooled by an annular nearing (θ) to form a cylindrical bubble (f), and after inflation molding, the upper end is pivoted to the frame (C) and the lower part expands. The pinch roll ((L
).

This blown film is made from the pinch roll (
After being folded flat in a), it is wound up in a winder (h).

(Problems to be Solved by the Invention) As described above, the conventional blown film guide device has a pair of flat stabilizers facing each other,
In addition, since the structure is such that the lower part expands and is suspended from the frame, after the cylindrical bubble is folded flat, the inflation film (j) is opened as shown in Figures 9 and 10. There was a problem that sagging (j) or wrinkles (j) were likely to occur at intervals in the center, making subsequent printing difficult.

Especially, the inner thickness of the blown film is thick or wrinkles occur frequently.

Further, when the winding speed is increased in order to increase the production amount, this phenomenon becomes more noticeable.

(Means to Solve the Problem) The present inventor (c) analyzed the cause of wrinkles or sag in the inflation film and found that this was caused by the shape of the sliding surface of the stabilizer plate. Based on the analysis results, the present invention attempts to solve the problem by providing a bubble guide device for a blown film forming machine in which the sliding contact surface of the film with the film is an ideal three-dimensional curved surface.

In other words, the sliding surface of the film guide is a three-dimensional curved surface such that the lengths of the travel trajectories from any point on the circumference of the cylindrical bubble to the meshing tangent of the pinch roll are equal to each other. This prevents wrinkles or sagging from occurring when the cylindrical bubble is folded flat with pinch rolls.

Next, in order to clarify the principle underlying the present invention, the occurrence of wrinkles in the blown film will be analyzed based on FIGS. 1) to 20.

As shown in Figure 1), the blown film (2) extruded from the die (1) of the blown film molding machine is cooled by nearing (3), becomes a cylindrical bubble (2a), and then a pair of bubbles are formed. Information board (41
(After passing between 41 and 41, it is folded into a flat shape by pinch rollers (5) (5) and becomes a sheet) (2b).

In order to calculate the change in the external dimensions of such a blown film (2+), the radius of the bubble (2a) at the base line AB, where the change in the circular cross section of the bubble (2a) begins, as shown in Figures 12 and 16. R1 is the diameter, D1 is the width of the sheet (2b) at the tangent EF of the pinch roll (5), W is the height between AB and EF (H), and is the length of the side edge seen from the side between them (S). , the length of each of the front and rear edges as seen from the front is (L), and assuming that the inflation film (2) in these parts has already hardened and is not considered to stretch, each part can be expressed by the following formula. be done.

W=πD (1) L odor 7T ma (2) Next, the shape of the inflation film (2) in contact with the guide plates f4) and f4) will be considered.

When a cylinder as shown by the broken line in FIGS. 14 and 15 is cut along an inclined plane, the cross section becomes a quadratic curve that approximates a parabola and an ellipse.

A quadratic curve (U
) 4 widths of the cut plane appearing between A (M) on the center line and the point (OI) on the center line, point (1) on the quadratic curve If the angle of (is,
7=2Rgtnθ...(4) Also, the intersection of the central longitudinal section and the circle with radius (R) is (03)
Then, the circular arc PM becomes: /'l PM=27=2Rθ (5).

Inflation film (tri for 2+, 14th
It is represented by a quadratic curve (U) shown by the solid line in the figure, and the height is h).
The width (y) at is also slightly larger than the width (7).

Here, assuming that the quadratic curve (U) is a parabola, y=cJF
Then, when h=4(, =rcfl, so "!'
= cJF.

πR However, 9te・C=了πR 7=云i% -----(6) Next, the distance from any position of the cylindrical inflation film to the pinch roll is as shown in FIG. 16, however, From Dan = Yu, n = nR1h m = R - m = R (1-, H) Therefore, l = h + (1--) L ...... (7
).

If the mutual opening angle of the stabilizing plates is 2φ, then dan=μsφ, so the shea plexusφ...(8)L
H F2 1 = correction - h (-1) = Hsec φ - h (see φ - 1) ---- (91 Length relative to the coordinates that equally divided the bride from the center (G) of the tangent line of the pinch roller) A value For example, W=80
0mic, n=250mm, n=1,980mm
In the case of , it becomes as follows.

Thin φ = 1 gloss = 0.125 1.980 Also, from equation (3), S=1.985 dragons.

In this case, <d) and (
The value of L/H) is calculated from the equations (8) and (9) as follows.

When each of the above tables is represented in a graph, it becomes as shown in FIG. 17.

As is clear from this graph, the larger the value of φ, the more
The difference in l becomes large.

That is, when the stabilizer is flat, the central portion is sagging and both ends are tensed, which causes wrinkles or sag in the blown film. As long as the stabilizer plate is flat, this phenomenon cannot be eliminated.

In order to eliminate this drawback, the inner surface of the stabilizer plate should be curved so that the distance traveled by any point during deformation from a cylindrical shape to a flat shape, that is, the length of e in the above equation, is equal. 0 Next, an example of this curved surface is obtained by calculation.

In FIG. 18, if S=2αrH''2rsinα, then δ=r(1 part α) (10) holds true.

Therefore, in the case of Table 2, that is, φ-7°10'W
= 800 mm, H = 2000 mm, and calculate the sag value (δ) of each trajectory line on the right half that runs through 10 equally divided positions when viewed from the front of the stabilizer, Table 4 is obtained.

Further, if the front shape of l in the width direction is drawn from these values, it will be as shown in FIGS. 20(a) to 20(f).

Thus, when the blown film is folded into a pinch roll, there is a difference in travel distance between the center and both ends in the region guided between the stabilizers.

As a result, the center part sag, which is considered to be the cause of wrinkles.

Table 4 Therefore, in order to keep the tension constant when the blown film is folded, the center part of the stabilizer plate is made into a curved surface.
If the stabilizing plate is provided with a curved surface (Q) and guided so that the lengths of the travel trajectories from any point on the circumference of the cylindrical bubble to the meshing tangent of the pinch roll are equal, wrinkles can be eliminated. Alternatively, it is presumed that the occurrence of sagging can be prevented.

(Example) An example in which the present invention is applied to a blown film forming machine will be described below with reference to FIGS. 1 to 7.

(6) is an inflated film forming machine (7) an extruder, (8) is a die having an annular slit forming a bubble (9) on the upper surface, and (10) is an annular near ring. At the upper end of the support column 1) 1 that stands up from the base (not shown),
A frame (12+), which faces the guide (8) and has a rectangular frame shape when viewed from above, protrudes horizontally.
+ is provided with a bearing (131).
3), a pinch roller α5) (151) is attached with a pair of front and rear shafts 1) 41, and is rotationally driven by a drive source (not shown).

(16) is a bubble guide device, which consists of a pair of upper and lower adjustment screw rods anan (front and rear) that penetrate the side surface of the frame +t41 and are rotatably provided, and each of these adjustment screw rods C17) ( 17) Upper and lower parts 1 joined to the middle part of
It consists of a pair of slide stands α (to) (18) and a pair of left and right film guides whose upper ends are pivoted with a horizontal shaft (1gl) on the slide stand side.

The film guide (2υ, as shown in FIG. 2, has a frame circle having a rectangular shape when viewed from the side and having side plates (21a) (21a) that curve inward when viewed from the front;
Both ends are supported by the front and rear plates (21a), and the frame body [21
), the horizontal axis L22+ (g612s・
......, and each of these horizontal axes L27J (24
(gS... has a large number of rollers e, 31 disposed along its axial direction via a collar (2).

Each roller 123) is coated with a heat insulating coating (23a) as shown in FIG.

The surface connecting the tangents on the inner surface of each roller constitutes a three-dimensional curved surface, and this curved surface is defined by I)
From the formula 00), δ=r, (lcosα) so that the values of =Hsecφ−h(seeφ−1) are equal.
A three-dimensional curved surface (Q) having a sag is formed.

(29 is a pair of left and right adjusting tools for adjusting the opening angle of the group of film guides, and the vertical plate QO hanging down from the front and rear walls of the frame [14], and the inner part of the lower part of this vertical plate ω, A set of support plates (271
A threaded rod Q81 having upper and lower ends having a handle (28a) at its lower end, which is pivotally connected to the screw rod, a Nand plate screwed into the middle part of this screw rod, this nut plate, and the film guide. ■It consists of a pair of links Iida connecting the.

Note that 6D is a guide roller provided on the top left side surface of the support column (1) 1.

(Function) After the heated and softened resin is blown out from the slit of the gooey (8), it is cooled by the near ring (101).
Air is blown into the inside to form a cylindrical bubble (9), the tip of which is pulled upward by a pinch roll (151 (15)).

For this reason, the blown film is guided by each roller along the three-dimensional curved surface (ψ) of the film guide ω of the expanded bubble guide device (16) and is cooled. It is transformed into a shape and folded.

By turning the handle (28&) of the adjustment tool (c), the nut plate can be moved up and down, and the opening angle of the film guide ω can be changed. In the example, 1
The most preferable condition was obtained between 0° and 20°.

(Effects) As explained in detail above, in the present invention, the film guide of the bubble guide device has a guide surface consisting of a contact surface that matches a three-dimensional curved surface (Q) that changes from a cylinder to a sheet shape. Because of this, it is possible to prevent sagging and wrinkles from occurring on the surface of the blown film even after it is folded into a sheet.

In particular, even when the drawing speed is increased or the cooling is strengthened, wrinkles can be prevented from forming, which has the advantage of improving production efficiency.

(Modification) In the above embodiment, the film guide Q1 has a frame body and a number of rollers pivotally attached to a plurality of horizontal shafts provided on the frame body, and has a three-dimensional curved surface (forming ψ) that guides the film. However, sliding guide members can be used instead of rollers.

Figure 21 shows a bubble guide in which a three-dimensional guide curved surface (32a) is formed from a single synthetic resin plate 04 and is attached to a rectangular frame membrane. It has the advantage of being easy to mold.

The bubble guide shown in Fig. 22 has a rectangular frame (34).
are respectively curved with different curvatures on their inner surfaces, and
Horizontal bars 051c4c whose surfaces are covered with a heat insulating material are arranged vertically at intervals to form a three-dimensional guide curved surface. In this case, there is an advantage that the cooling effect of the blown film is improved. This is because the spacing allows heat to be dissipated.

In addition, the bubble guide shown in FIG.
. . ., a roller 01c1jr that can rotate in a curved state, consisting of rollers each having a different curvature,
A three-dimensional guide surface (31) is formed with hja...... Each of these rolls o wholesale!j (3s...
... are each rotationally driven by a drive source provided at the upper end of the frame (37), that is, a motor (41).

In this way, each roll is 0 or 31 t3! m...
By rotating these, there is an advantage that the winding resistance of the blown film that is guided in contact with these is reduced.

The three-dimensional guide curved surface is preferably a calculated ideal curved surface, but due to manufacturing problems, a practicable approximated curved surface may be used.

[Brief explanation of drawings]

[1) ri, a front view showing an embodiment in which the present invention is applied to a blown film forming machine, FIG. 2 is a vertical sectional view taken along the line ■-■ in FIG. 1, and FIG. ■－■
4 is a longitudinal sectional view taken along line IV--IV in FIG. 2, FIG. 5 is a cross-sectional view taken along line v-v in FIG. 7 is a longitudinal sectional view showing the roller of FIG. 1, FIG. 8 is a front view showing a conventional blown film forming machine, and FIG. 9 is a conventional sheet forming machine. 10 is a longitudinal sectional view taken along the line X-X of FIG. 9, 1)- is a schematic configuration diagram enlarged from FIG. Figure 16 is a front view, Figure 14 is a side view showing the contact surface between the stabilizer plate and the inflation film, Figure 15 is taken along line XV-XV in Figure 14. 16 is a longitudinal sectional view taken from the line ➝ in Fig. 14, and Fig. 17 is a cross-sectional view showing the angle (φ
Figure 18 is a line graph showing the relationship between shift (δ) and length S), Figure 19 is a line graph showing the relationship between shift (δ) and length S), Figure 19 is a cubic curved surface on the film guide. 20(a) to 20(f) are schematic configuration diagrams showing the state of curved surfaces along the respective cutting lines along the width direction of FIG. 19, and FIGS. 21 to 26 are FIG. 3 is a side view showing other embodiments of the film guide shown in FIG. 2 of the invention. (1) Die (2) I/Frain film (3) Nearing (4) Guide plate (5) Pinch roller (6) Extruder (8) Die
(9) Bubble (1)) Nearing (13
Frame (19 pinch roller ub + bubble guide, do device αη adjustment screw rod aυ slide stand a1
Horizontal axis (21) 1 film guide (2I
) Horizontal shaft of frame (thrower roller)
(24 colors (2 adjustment tools)
Vertical Iida screw rod nut plate (to) link plate (3 force synthetic resin plate 83 (3
4) C3η frame body (3 horizontal bars (to) guide curved surface 1310-141 motor
(Q) Curved surface Fig. 3 Fig. 4 Fig. 5 Fig. 7 Fig. 21 Fig. 22 Fig. 23

Claims (5)

[Claims] (1) After cooling the bubble, which has an annular cross section and is press-formed by a die, it is pinched through a pair of mutually opposing film guides whose upper end is pivoted to a stationary part and whose lower end expands. In a blown film forming machine that guides the film to a roll, flattens it with the pinch rolls, and then winds it up, the inner surfaces of the mutually opposing film guides are guided from any point on the circumference of the cylindrical bubble to the pinch roll. A bubble guide device for a blown film forming machine, characterized in that the sliding surface is a three-dimensional sliding surface in which the lengths of the travel trajectories up to the meshing tangent of the rolls are mutually equal. (2) The sliding surface of the film guide is a convex surface facing inward with respect to the plane connecting the upper and lower edges of the inner surface of the film guide. Bubble guide device for blown film forming machine. (3) The blown film according to claim (1), wherein the sliding surface of the film guide is formed by the outer peripheral surface of a large number of rollers arranged in the vertical direction and the front-back direction. Bubble guide device for molding machine. (4) The sliding surface of the film guide is formed by a frame and the curved surfaces of a plurality of curved horizontal bars each having a different curvature and arranged vertically at intervals on the frame. A bubble guide device for a blown film forming machine according to claim (1). (5) The sliding surface of the film guide is formed by a frame body and a plurality of bending rollers whose both ends are pivotally connected to the frame body and each having a curved outer peripheral surface with a different curvature. A bubble guide device for a blown film forming machine according to claim (1).