JPS6343214B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a stretching device that can properly stretch plastic films and the like with a simple device. Conventionally, this type of stretching apparatus for plastic film, etc., has generally been divided into two types: a clip tenter system, in which both sides of the flat film are gripped with clips, etc., and stretched uniaxially in the width direction while being fed in the longitudinal direction; A tubular inflation method is used in which the above-mentioned film, etc. is stretched simultaneously in vertical and horizontal directions by applying expansion force from inside, but the former method requires large-scale and expensive heating furnaces and other equipment. , and a large amount of unstretched parts remain on both sides of the film that is held with clips, etc.Although the equipment cost of the latter method is relatively low, it is difficult to control the stretching, and it is difficult to control the stretching ratio and film thickness. There were problems in that variations were likely to occur and it was difficult to obtain a high quality stretched product. The present invention solves the above-mentioned problems of the conventional art, and provides a pair of left and right stretching pulleys that rotate in opposite directions, and a pair of belts individually engaged with both pulleys, in order to properly stretch the film, etc., with a simple device. This invention provides a new type of so-called belt-type stretching device that grips and stretches both sides of the above-mentioned film, etc., and is particularly designed to prevent sag in the longitudinal axis direction of the material to be stretched or shrinkage during high-magnification stretching. The purpose is to prevent the occurrence of wrinkles and to obtain a high quality stretched product. In the present invention, a pair of stretching pulleys are disposed in a heating area of a material to be stretched so as to rotate in opposite directions with a predetermined distance left and right in substantially the same plane, and a pair of endless stretching belts are arranged in a heating area of a material to be stretched. By individually engaging the stretching pulleys in a rotating range of less than half a circumference that diverges toward each other along the rotation direction and disposing them symmetrically, the material to be stretched is placed in the engagement area between both pulleys and both belts. gripping portions are formed between the both side portions for stretching the material while gripping both side portions of the material and feeding the material along an arcuate trajectory having a radius of less than a semicircle that widens toward each other; The present invention is characterized in that a guide member is disposed to apply tension to the intermediate portion of the material by causing the intermediate portion of the material to bulge outward from the surface connecting both gripping portions at the folded portion. With this configuration, the material to be stretched such as plastic film can be stretched appropriately. In particular, the material to be stretched can be smoothly folded back by the guide member during stretching, and horizontal wrinkles due to sagging or shrinkage in the longitudinal direction of the material can be avoided. This can be prevented, the stretching ratio can be improved, the film thickness can be made uniform, and highly accurate stretching can be performed. Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an example of a stretching device for stretching a tubular film. This device has a pair of stretching pulleys 2, 2' in a heating chamber 1 with a shaft 21,
21' on the same plane with a predetermined interval left and right, and a pair of endless stretching belts 3, 3' are individually engaged with approximately the lower half of each stretching pulley 2, 2'. The guide pulleys 41 to 44 and 41' to 44' are stretched as shown in the figure. Of the guide pulleys, the guide pulleys 41 and 41' located above the stretching pulleys 2 and 2' are supported by the upper end of the support column 4, and the other guide pulleys 42 to 44 and 42' to 44' is supported by a fixed frame inside the heating chamber 1. Then, both stretching pulleys 2, 2' are connected to the shaft 2.
A driving device (not shown) connected to belts 1 and 21' rotates them in opposite directions in the directions of arrows A and A', so that each stretching belt 3 and 3' circulates in the directions of arrows B and B'. comprising the stretching pulley 2,
2' and the stretching belts 3, 3' are formed with gripping parts 31, 31' along arcuate orbits that diverge toward each other in the rotational direction. Furthermore, guide members 5 and 5' are provided at positions that protrude forward and backward from the front and rear surfaces of the stretching pulleys 2 and 2', respectively, between the lowermost folding points B and B' of both gripping parts 31 and 31'. It is placed.
In the embodiment shown in FIGS. 1 to 4, the guide members 5, 5' are made of plate material and have a substantially U-shaped longitudinal cross section.
A support frame 51 having a substantially trapezoidal planar shape and having the members 5 and 5' disposed within the heating chamber 1;
51 via support rods 52, 52 in a suspended position. In addition, feeding nip rolls 61, 61' are arranged near the raw film feeding port 6 at the upper end of the heating chamber 1, and the separation point C, between the drawing pulleys 2, 2' and the drawing belts 3, 3' is A pair of cutters 62, 62' are arranged near C' to divide the stretched tubular film into front and back parts, and the stretching pulley 2,
Turn rolls 63, 63' for leading out the stretched and divided film to the front and back of the film are disposed before and after the film 2', and in front and behind the turn rolls 63, 63', there are nip rolls 64, 64 for taking off the film, respectively. 64' (the rear part is not shown). Next, a case will be described in which a tubular film is stretched using the stretching apparatus configured as described above. First, a tubular raw film F ₀ is fed into the heating chamber 1 by feeding rolls 61, 61'.
Cover the guide pulleys 41, 41' and the stretching belts 3, 3' with their introduction paths that are substantially parallel to each other,
The tips of the opposite sides F ₁ and F ₂ of the raw film F ₀ in the folding diameter direction are sandwiched between the engagement start points A and A′ of the stretching pulleys 2 and 2′ and the belts 3 and 3′. In this state, live steam or the like is supplied into the heating chamber 1 to heat the film F ₀ to a temperature suitable for stretching, while the stretching pulleys 2 and 2' are connected to the shafts 21 and 21. It is rotated in the directions of arrows A and A' by a drive device (not shown) connected to '. As a result, the stretching belts 3, 3' move as shown in FIG.
As the film circulates in the direction _F1 , _F2 , the stretching pulleys 2, 2', the belt 3,
3', the film F 0 is fed out to the outside by the gripping parts 31, 31' which widen toward each other, and as a result, the film F ₀ is held by the gripping parts 31, 31'. In between, first, there is a circular arc that expands downward in approximately 1/4 rotation range from the engagement start points A, A' of the stretching pulleys 2, 2' and the belts 3, 3' to the lowest turning points B, B'. While being sent downward along the track, it is expanded and stretched into a flat morning glory shape, and then from the turning points B, B' to the separation point C, between the pulleys 2, 2' and the belts 3, 3'.
In the remaining approximately 1/4 rotation range up to C', it is further enlarged and stretched along an upwardly expanding arcuate trajectory while being turned inside out. In such a stretching process, considering the speed at which the film advances in the longitudinal direction (vertical axis direction), the film initially moves between the engagement starting points A and A' between the stretching pulleys 2 and 2' and the belts 3 and 3'. is fed at a predetermined feeding speed U, but the gripping parts 31, 3
1' are circular arc trajectories that diverge toward each other, so the advancing speed of the film in the longitudinal axis direction gradually decreases from between the engagement starting points A and A' to between the turning points B and B'. It becomes 0 between the turning points B and B', and then gradually increases from the turning points B and B' to the separation points C and C', and between the separation points C and C', the feeding speed becomes 0. Almost equivalent. In this way, the advancing speed of the film in the longitudinal axis direction during stretching changes, and the joining starting point A,
Turning point B from A', distance point C across B',
The average traveling speed of the film in the longitudinal direction until it reaches C′ is approximately

[Formula] is smaller than the above-mentioned feeding speed and sending speed, especially 0 between turning points B and B'.
becomes. Therefore, if the film is folded back at the folding points B and B' along both the front and rear sides of the stretching pulleys 2 and 2' without using the guide members 5 and 5' described above, the film will not advance in the longitudinal axis direction. Due to the change in speed, as shown in FIG. 11, sagging occurs in the longitudinal axis direction of the film before and after folding points B and B', and shrinkage occurs during high-magnification stretching, resulting in horizontal wrinkles F _x
occurs. If the film is stretched with horizontal wrinkles as described above, the thickness of the film will be non-uniform, the orientation will be poor, and the film will have a horizontal striped pattern. However, as described above, if the guide members 5 and 5' are arranged on both sides of the front and rear sides between the turning points B and B', the film can be moved to the turning points B and B as shown in FIGS. 2 to 4. After the film is folded back at ', the intermediate part of the film bulges forward and backward along the guide members 5 and 5' to absorb the slack in the longitudinal axis direction, and when the stretching ratio is large and shrinkage occurs. shrinkage is suppressed, horizontal wrinkles are eliminated, and the film can be folded and stretched smoothly. After stretching the film in this manner, both sides of the film held by the gripping portions 31, 31' F ₁ , F ₂ is cut in the longitudinal direction by a pair of cutters 62 and 62' respectively, and the films F ₃ and F ₄ stretched between the both sides F ₁ and F ₂ are divided into front and back parts, and each stretched film after division is _F3 , _F4
is taken out to the outside by turn rolls 63, 63' and nip rolls 64, 64'. At this time,
Stretched films F ₃ and F ₄ are turned on rolls 63 and 6
3' and Nipprol 54, 54' is the cooling chamber 10,
10' and is cooled by suitable means.
On the other hand, both sides F ₁ and F ₂ of the film held by the gripping parts 31 and 31' are taken out unstretched and cut into strips by the pair of cutters 62 and 62'. The film is led outward and upward along the stretching belts 3, 3' and wound up by an unstretched film winding device (not shown). Next, another example will be described. FIG. 5 shows an embodiment in which a flat film f ₀ is stretched. In this apparatus, a pair of endless stretching belts 3, 3' are connected to a pair of stretching pulleys 2, 2'. Guide pulley 45, 46
and 45', 46' as shown in the figure, and a film guide frame 7 is disposed on the back side in the middle of the film introduction path of the belts 3, 3' which are substantially parallel to each other, and the pulleys 2, 2 ′ on the back side of
A guide member 5' similar to that described above is arranged behind the folding points B and B' of the gripping parts 31 and 31', and
A take-out turn roll 65 is installed at the rear between separation points C and C'.
are placed. Note that 1' is a heating bath filled with hot water, etc., in which almost the lower half of the stretching pulleys 2, 2' is immersed, and during stretching, the film is immersed in this heating bath 1' to maintain a temperature suitable for stretching. It is heating up to . According to this device, the raw film f ₀ is supplied from the back side of the belts 3, 3', and
The portions f ₁ and f ₂ are bent by the guide frame 7 and placed along the inner surface of each belt 3, 3', and the stretching pulleys 2,
2' and the engagement start points A, A' of the belts 3, 3', gripped by the gripping parts 31, 31', and rotated the pulleys 2, 2' in the directions of arrows A and I'. Then, it is stretched using the same principle as the tubular film. In this case as well, during the stretching process, the guide member 5' allows the film to be folded smoothly between the folding points B and B', thereby preventing the occurrence of sagging or horizontal wrinkles. The stretched film _f3 is taken out to the back side of the pulley by a take-out turn roll 65. In each of the above embodiments, the guide members 5, 5' are made of plate material, but the guide members have a rod-shaped guide bar 5a and an arcuate guide bar 5b inside and outside, as shown in FIGS. 6 and 7. Alternatively, the arcuate guide bar 5b may be arranged at predetermined intervals.
Alternatively, as shown in FIGS. 8 and 9, a guide roll 5c may be rotatably supported between the tips of support rods 52' and 52' via a shaft 53. good. Note that FIGS. 6 to 9 illustrate the case where each guide member 5a, 5b, 5c is arranged on the back side of the stretching pulley 2, 2' for stretching the flat film _f0 . When the aforementioned tubular film F ₀ is targeted, it goes without saying that the guide members are arranged symmetrically before and after the stretching pulleys 2, 2'. FIG. 10 shows annular bulges 22, 2 protruding in the axial direction on the periphery of the back surface of the stretching pulleys 2, 2'.
2' is provided. By providing the bulges 22, 22' in this way, the film can be folded more smoothly at the folding point, and the longitudinal axis of the film can be Therefore, by using this pulley with a bulge in combination with the guide member, it is possible to more reliably prevent the film from sagging in the longitudinal direction and from forming horizontal wrinkles. By the way, in this stretching device, the stretching ratio of the film is determined by the stretching pulleys 2, 2', the belt 3,
3' is determined by the circumferential length and rotation angle of the gripping parts 31, 31' formed from engagement start points A, A' to separation points C, C'. Therefore, the stretching ratio can be freely determined by changing the diameters of the stretching pulleys 2, 2' or by changing the positions of the separation points C, C'. Further, the shape, size, curvature, etc. of the guide members 5, 5', etc. are determined according to this stretching ratio. In the above embodiment, the stretching pulleys 2 and 2' are driven, but the stretching belts 3 and 3' may be driven.
It is also possible to drive both the belts 3 and 3'. Furthermore, radiant heat or the like may be used as a heating means for the film during stretching. Note that the stretching apparatus of the present invention can be used not only for stretching plastic films but also for stretching mesh-like webs of filamentous materials. As explained above, according to the stretching device of the present invention, the stretching path can be made shorter compared to the conventional clip tenter method, the structure of the device can be significantly simplified, and it can be configured compactly, reducing equipment costs. It can be made much cheaper. In addition, a stretched product with a high magnification can be obtained with a simpler operation than with the tubular inflation method. In particular, in the present invention, by providing the guide member, it is possible to smoothly fold back the stretched material, prevent the generation of horizontal wrinkles due to sagging or shrinkage in the longitudinal axis direction of the material, and improve the stretching ratio. In addition, it is possible to make the film thickness uniform and stretch with high precision, making it possible to obtain a stretched product with high commercial value.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an embodiment in which the apparatus of the present invention is applied to stretching a tubular film, FIG. 2 is a cross-sectional plan view thereof, and FIG. 3 is a cross-sectional view taken along the line -
Figure 4 is a perspective view of the main parts showing the state of use, Figure 5
The figure is a perspective view showing an embodiment applied to stretching a flat film, FIG. 6 is a plan view of the main part showing an embodiment using a guide member made of a rod-shaped bar, and FIG. - line sectional view in Figure 6, No. 8
The figure is a plan view of the main parts showing an embodiment in which the guide member is a roll, FIG. 9 is a cross-sectional view taken along the line -- in FIG. 8, and FIG. 10 is an embodiment in which the stretching pulley is provided with a bulge. FIG. 11 is an explanatory diagram of a state in which the film sag when there is no guide member. 1...Heating chamber, 2,2'...Stretching pulley,
3, 3'... Stretching belt, 31, 31'... Grip portion, 41-46, 41'-46'... Guide pulley, 5, 5a, 5b, 5c... Guide member.

Claims (1)

[Claims] 1 A pair of stretching pulleys are arranged in the heating area of the material to be stretched so as to rotate in opposite directions with a predetermined interval left and right in substantially the same plane, and a pair of endless stretching belts are arranged to By individually engaging the pulleys in a rotation range of less than a semicircle that diverges toward each other along the rotational direction and arranging them symmetrically, both sides of the material to be stretched are A gripping part is formed to stretch the material between the both side parts while gripping the material and feeding it along an arcuate trajectory of less than a semi-circumference that widens toward each other, and between the two gripping parts, there is provided an intermediate part of the material being stretched. 1. A stretching device for plastic film, etc., characterized in that a guide member is disposed to apply tension to the intermediate portion of the material by causing the folded portion to bulge outward from a surface connecting both gripping portions.