JPS6343215B2 - - 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 such as 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. The present 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 in particular, prevents the material to be stretched from sagging in the longitudinal axis direction during stretching, and prevents the generation of horizontal wrinkles. The purpose of this is to prevent such problems and to obtain high-quality stretched products. 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. A gripping part is formed to extend between the both sides while gripping both sides of the material and feeding it along an arcuate trajectory of less than a semicircle that widens toward each other, and the material is folded back at the folding point of both gripping parts. A fluid ejecting means for ejecting fluid onto the inner surface of the material to apply outward expansion force to the material is disposed at a position facing the inner surface of the material, and facing the fluid ejecting means to the outside of the material. The device is characterized in that a backup guide member having a U-shaped cross section is arranged to regulate the expansion force of the device. With this configuration, it is possible to properly stretch a material to be stretched such as a plastic film. In particular, during stretching, heated fluid is ejected from the fluid jetting means to apply an outward expansion force to the material to be stretched that has been folded at a folding point. At the same time, by mechanically regulating the expansion force using the back-up guide member, the material to be stretched is properly expanded and folded back smoothly at the folding part, and sag or shrinkage in the longitudinal direction of the material is prevented. The occurrence of horizontal wrinkles due to the film is reliably prevented, and it is possible to improve the stretching ratio and make the film thickness uniform.
High-precision stretching is 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' at a predetermined interval on the left and right on the same plane, and a pair of endless stretching belts 3, 3' are individually engaged with substantially 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. In addition, jet pipes 5, 5' for spouting fluid such as heated air (hot water or steam may be used) are arranged opposite to each other on both front and rear sides between the folding points B and B' at the bottom of both gripping parts 31 and 31'. It is placed. The jet pipes 5, 5' have jet ports 51, which open in the direction between the turning points B, B'.
51' are provided at predetermined intervals in the longitudinal direction, and are supported in a suspended position by support frames 52, 52' provided in the heating chamber 1 via support/fluid supply pipes 53, 53'. Backup guide member 6,
6' is formed to have a substantially U-shaped cross section so as to be located across the front and rear between the turning points B and B', and is connected to a position opposite to the fluid ejection pipes 5 and 5' via struts 61 and 61'. I support it. In addition, feeding nip rolls 71, 71' are arranged near the raw film feeding port 7 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 72, 72' are arranged near C' to divide the stretched tubular film into front and back parts, and the stretching pulley 2,
Turn rolls 73, 73' 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 73, 73', there are nip rolls 74, 74 for taking off the film, respectively. 74' (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 _O is fed into the heating chamber 1 by feeding rolls 71 and 71'.
The guide pulleys 41, 41' and the stretching belts 3, 3' are placed over the introduction paths that are substantially parallel to each other,
The tips of the opposite sides F ₁ and F ₂ of the original film F _O in the folding diameter direction are sandwiched between the engagement starting points A and A' between 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 _O 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 O is fed out to the outside by the gripping parts 31, 31' which widen towards each other, and as a result, the film F _O 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 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 folded back at turning points B and B' so that it is turned inside out. From these turning points B and B', the pulley 2, 2' and belts 3 and 3' until the separation point C, C', the belt is further expanded and stretched while being sent upward along an arcuate trajectory that expands upward in the remaining approximately 1/4 rotation range. At this time, fluid such as heated air is jetted from the support/fluid supply pipes 53, 53' through the fluid jet pipes 5, 5' into the inside of the film folded back at the folding points B, B'. pressure expands the film outwardly, and
The expansion force is mechanically properly regulated by the backup guide members 6, 6', and the expansion force acts as a stretching tension in the longitudinal direction of the film, and the film is stretched while preventing sagging and horizontal wrinkles in the longitudinal direction. In other words, when considering the advancing speed of the film in the longitudinal direction (vertical axis direction) in the above stretching process,
Initially, the film is fed at a predetermined feeding speed v between the engagement start points A and A' of the stretching pulleys 2 and 2' and the belts 3 and 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 turning points B and B', and then gradually increases from turning points B and B' to separating points C and C', and between separating points C and C', the feed speed v and 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,
From A' to turning point B, from B' to separation point C,
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, without using the fluid ejection pipes 5, 5' and the backup guide members 6, 6' described above, the film can be passed along both the front and rear sides of the stretching pulleys 2, 2' at the folding points B, B'. When folded back, due to the change in the traveling speed in the vertical axis direction, the seventh
As shown in the figure, sag occurs in the longitudinal axis direction of the film before and after the folding points B and B', and conversely shrinkage occurs during high-magnification stretching, resulting in horizontal wrinkles _F.sub.X. 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 horizontal stripes and cracks. However, as mentioned above, fluid such as heated air is ejected from the fluid ejection pipes 5 and 5' provided on both the front and back sides between the turning points B and B', and the film that is turned back at the turning points B and B' is exposed to the air. By applying an expansion force in this direction, horizontal wrinkles caused by sagging or contraction in the longitudinal direction are eliminated. Moreover, at this time, the expansion force is properly regulated by the backup guide members 6, 6'.
The film is stretched along the guides 6, 6' while being smoothly folded back. After stretching the film in this manner, both sides F ₁ , F of the film held by the gripping portions 31, 31′ near the separation points C, C′ between the stretching pulleys 2, 2′ and the belts 3, 3′. ₂ is cut in the longitudinal direction by a pair of cutters 72 and 72' 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 F after division is ₃ , F ₄ is turn roll 73, 73' and nip roll 7
4, 74' to the outside. At this time,
Stretched films F ₃ and F ₄ are on turn rolls 73 and 7
3' and Nipprol 74, 74' 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 portions 31 and 31' are taken out unstretched and cut into strips by the pair of cutters 72 and 72'. The film is led outward and upward along each stretching belt 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 _O 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,
A feeding guide roll 81 is installed on the back side of the film introducing path which is substantially parallel to each other on the belts 3 and 3'.
and a film guide frame 8 are arranged, and on the back side of the pulleys 2, 2', a fluid jet pipe 5' similar to the above and a backup guide In addition to disposing the members 6' and the like, a take-out turn roll 75 is disposed at the rear between the separation points C and C'. In addition, 1' is a heating bath filled with hot water, etc., and the stretching pulley 2,
Substantially the lower half of the film 2' is immersed in the heating bath 1', and during stretching, the film is immersed in the heating bath 1' and heated to a temperature suitable for stretching. According to this device, flat raw film can be
Feed f _O from the back side of the belts 3, 3', bend both sides (edges) f ₁ , f ₂ by the guide frame 8, and stretch it along the inner surface of each belt 3, 3'. The pulleys 2, 2' and the belts 3, 3' are fed into engagement starting points A, A', gripped by the gripping parts 31, 31', and the pulleys 2, 2' are rotated in the directions of arrows A and I'. By doing so, the film is stretched using the same principle as the tubular film described above. In this case as well, during the stretching process, fluid such as heated air is ejected from the fluid ejection pipe 5' to apply an outward expansion force to the film folded between the folding points B and B', and to By properly regulating the expansion force with the guide member 6', it is possible to prevent the film from sagging in the longitudinal direction and from generating horizontal wrinkles, and also to smoothly fold and stretch the film. The stretched film _f3 is taken out to the back side of the pulleys 2 and 2' by a take-out turn roll 75. FIG. 6 shows annular bulges 22, 2 protruding in the axial direction on the periphery of the back surfaces 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 and the film can be prevented from sagging in the longitudinal direction. Therefore, by using this pulley with a bulging portion in combination with the guide member, it is possible to more reliably prevent the film from sagging in the longitudinal axis direction and from forming horizontal wrinkles. In the case of a tubular film, annular bulges 22, 22' projecting in the axial direction may be provided on the peripheral portions of both the front and back surfaces of the stretching pulleys 2, 2'. 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'. In addition, the pressure of the fluid ejected from the fluid ejection pipes 5, 5' and the shape of the backup guide members 6, 6' are determined according to the stretching ratio.
Determine size, curvature, etc. 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. 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, fluid such as heated air is ejected from a fluid ejection tube to apply outward expansion force to the stretched material that has been folded at the folding point, thereby eliminating sagging and horizontal wrinkles in the longitudinal direction of the material. In addition, the expansion force can be properly regulated mechanically by the back-up guide member, and the material can be folded and stretched smoothly, making the stretching ratio and film thickness uniform. It is possible to stretch with high precision and 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, Figure 6 is a cross-sectional plan view of main parts showing an embodiment in which a bulge is provided on the stretching pulley, and Figure 7 is a guide. FIG. 6 is an explanatory diagram of a state in which wrinkles occur in the film when there is no member. 1...Heating chamber, 2,2'...Stretching pulley,
3, 3'...Stretching belt, 31, 31'...Gripping part, 41-46, 41'-46'...Guide pulley, 5,5'...Fluid ejection pipe, 6,6'...Back Up 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 The inner surface of the material is folded at the folding point of both gripping parts, and the inner surface of the material is folded at the folding point of both gripping parts. A fluid ejection means for ejecting fluid onto the inner surface of the material to apply an outward expansion force to the material is disposed at a position facing the material, and a fluid ejection means for applying an outward expansion force to the material is arranged opposite to the fluid ejection means to apply an outward expansion force to the material. 1. A stretching device for plastic film, etc., characterized in that a back-up guide member having a U-shaped cross section is arranged to regulate the back-up guide member.