Stretching device

Abstract

In a biaxial stretching device (1), stretching mechanisms (10) provided at the four edges of a to-be-processed sheet (S) each comprise: a slider box (11) that comprises rails (12) which are provided parallel to the corresponding edge for the stretching mechanism and two sliders (13) on which the rails (12) slide; chucks (14) that are respectively provided to the two sliders (13) and that are for grasping the corresponding edge of the to-be-processed sheet (S); and a drive mechanism (19) that pulls the slider box (11) in a direction perpendicular to the corresponding edge. The rails, which are constituent elements for adjusting the interval between the chucks, are provided parallel to the corresponding edge of the to-be-processed sheet such that a space occupied by the device in a direction perpendicular to the corresponding edge can be suppressed, and as a result the entirety of the device can be downsized.

Description

Stretching device

[0001] The present invention relates to a stretching device such as a biaxial stretching device that stretches a sheet to be processed made of a thermoplastic resin or the like in two directions.

[0002] Biaxial stretching devices are used to produce a sheet product thinner than the original sheet by stretching the sheet to be processed. For example, the biaxial stretching device described in Patent Document 1 has multiple arms attached to each side of a square sheet to be processed by clips (chucks), and the multiple arms on each side are connected to each other by pantographs.

[0003] In this state, if the arms on the four sides are moved outward, the processed sheet is stretched in two directions. As the processed sheet is stretched, the spacing between the arms on each side inevitably increases, but the pantographs installed between the arms on each side absorb the expansion between the arms on that side and adjust the expansion so that it is even.

[0004] Japanese Patent Application Laid-Open No. 2005-199617

[0005] In the biaxial stretching apparatus described in Patent Document 1, the pantograph is longest in the direction perpendicular to each side of the processed sheet in the initial state (when the processed sheet has not yet been stretched), and is longest in the direction parallel to each side when the processed sheet is stretched to its maximum. The size of the pantograph is determined by the length of each side of the processed sheet at its maximum stretching. Therefore, the greater the stretch ratio of the processed sheet is attempted to be, the greater the length of the pantograph in the direction perpendicular to each side in the initial state becomes, resulting in a larger overall apparatus.

[0006] The problem to be solved by the present invention is to provide a stretching apparatus such as a biaxial stretching apparatus that can be made compact.

[0007] The biaxial stretching device according to the first aspect of the present invention, which has been made to solve the above-mentioned problems, is characterized in that each of the stretching mechanisms provided on the four sides of the processed sheet comprises: a) a slider box having a rail provided parallel to the corresponding side of the stretching mechanism and two sliders that slide on the rail; b) a chuck provided on each of the two sliders for gripping the corresponding side of the processed sheet; and c) a drive mechanism that pulls the slider box in a direction perpendicular to the corresponding side.

[0008] In the biaxial stretching apparatus according to the present invention, the stretching mechanism for each side (corresponding side) is equipped with two sliders, and a chuck provided on each slider grips the corresponding side. The slider boxes of the stretching mechanisms for that side and the opposite side (opposing side) are pulled in opposite directions by their drive mechanisms, so that the processed sheet is pulled in the direction connecting those sides (the direction perpendicular to those sides).

[0009] At the same time, the processed sheet is pulled in the same way on the two adjacent sides by the stretching mechanisms. As a result, the two sliders slide on the rails, widening the gap between the two chucks provided on each of the two sliders and gripping the processed sheet on the corresponding and opposite sides. In the biaxial stretching device according to the present invention, the sliders slide within the slider boxes to absorb the widening gap between the two chucks.

[0010] According to the biaxial stretching device of the present invention, the rails, which are components for adjusting the spacing between the chucks, are arranged parallel to the corresponding sides of the processed sheet, thereby reducing the space occupied by the device in the direction perpendicular to the corresponding sides, thereby making it possible to make the entire device smaller.

[0011] The biaxial stretching apparatus according to the present invention may further include: d) racks with the same pitch fixed to each of the two sliders; e) pinions with the same number of teeth meshing with each of the two racks; and f) a synchronization mechanism that rotates the two pinions in synchronous with each other in opposite directions.

[0012] According to the biaxial stretching device of this aspect, the two sliders slide in opposite directions in synchronization, so that it is possible to prevent the problem that one of the sliders gets stuck and cannot move.

[0013] The biaxial stretching device according to the present invention may further include: g) a synchronous expansion mechanism that rotates the two pinions of the stretching mechanism in synchronization with the movement of the drive mechanism of the stretching mechanism corresponding to the adjacent sides of the processed sheet.

[0014] According to this embodiment of the biaxial stretching device, the two sliders are driven to slide in opposite directions so as to synchronize with the drive speed of the adjacent sides, i.e., the pulling speed of the two adjacent sides, so that the pulling speeds of the four sides are synchronized, enabling smooth biaxial stretching of the processed sheet.

[0015] The biaxial stretching device according to the present invention can be configured such that, in addition to the two rack-equipped sliders, rails for sliding two additional rack-equipped sliders are provided within the slider box, and each of the two additional rack-equipped sliders is provided with an additional chuck and an additional pinion for gripping the corresponding edge of the processed sheet, and the additional racks and additional pinions of the two additional rack-equipped sliders are set to move in opposite directions to each other at speeds that correspond to the gripping positions of the two chucks and the two additional chucks on the corresponding edges.

[0016] In this embodiment of the biaxial stretching device, each side of the processed sheet is pulled by four chucks, and the spacing between these four chucks can be widened synchronously depending on the pulling speed of the adjacent side and the position of each chuck, allowing for smoother biaxial stretching processing.

[0017] The drive mechanism used in the biaxial stretching apparatus according to the present invention can also be suitably used in stretching apparatuses other than biaxial stretching apparatuses. A stretching apparatus according to a second aspect of the present invention comprises: two rod-shaped gripping members that grip two opposing sides of a rectangular processed sheet along each of the sides; two first gripping member holding portions that rotatably hold one end of each of the two gripping members; two second gripping member holding portions that rotatably hold the other end of each of the two gripping members; and a drive mechanism that pulls the two first gripping member holding portions and the two second gripping member holding portions in directions perpendicular to the two sides at different speeds.

[0018] In the stretching device of the second aspect, two opposing sides of a rectangular processed sheet before stretching are gripped by two rod-shaped gripping members along each side, and then the drive mechanism pulls the two first gripping member holding portions and the two second gripping member holding portions in a direction perpendicular to the two sides at different speeds. As a result, the two gripping members rotate relative to the first gripping member holding portion and the second gripping member holding portion, respectively, while one end side and the other end side move apart at different speeds. As a result, the processed sheet is stretched non-uniformly in the direction perpendicular to the two sides so that the stretch ratio (the ratio of the length after stretching to the length before stretching) varies depending on the position between the one end and the other end.

[0019] This state in which a rectangular processed sheet is stretched non-uniformly so that the stretching rate varies depending on the position corresponds to the transient state that occurs in a mass production device for sheets, in which the processed sheet is stretched by holding two opposing edges of the processed sheet with clips that move along two rails that are provided so that the gap between them gradually increases in a certain section, as described in, for example, Patent Document 2. The stretching device of the second aspect can be suitably used as a test machine for investigating the state of polymers and the like in the processed sheet in the transient state in such a mass production device.

[0020] In the stretching device according to the second aspect, the speed at which the drive mechanism pulls the two first gripping member holding parts may be 0. In this case, the two first gripping member holding parts may be fixed directly or via another member.

[0021] The stretching device of the second aspect can be configured as an option for the stretching device of the first aspect by attaching second gripping member holders to two of the four slider boxes facing each other. In this case, the remaining two slider boxes, the two drive mechanisms that pull them, and the chucks provided on all slider boxes are not used. Alternatively, the stretching device of the second aspect may be a separate device from the stretching device of the first aspect.

[0022] According to the present invention, a stretching device such as a biaxial stretching device can be made smaller.

[0023] 1 is a schematic top view showing one embodiment (first embodiment) of a biaxial stretching apparatus according to a first aspect of the present invention; FIG. 2 is a perspective view showing the biaxial stretching apparatus of the first embodiment; FIG. 3 is a top view showing a slider box provided in the biaxial stretching apparatus of the first embodiment; FIG. 4 is a bottom view showing the biaxial stretching apparatus of the first embodiment with the upper and lower plates of the slider box removed; FIG. 5 is a top view showing the biaxial stretching apparatus of the first embodiment with the upper and lower plates of the slider box and the 0th chuck removed; FIG. 6 is a side view showing the biaxial stretching apparatus of the first embodiment with the plate on one side of the slider box removed; FIG. 7 is a top view showing the initial position of the chuck when using the biaxial stretching apparatus of the first embodiment; FIG. 8 is a top view showing an example of the position of the chuck during use of the biaxial stretching apparatus of the first embodiment; FIG. 9 is a top view showing the state in which a processed sheet has been stretched by the biaxial stretching apparatus of the first embodiment, and the position of the chuck at that time. 1 is a schematic top view showing the state of the entire apparatus excluding the control unit when a processed sheet is stretched by the biaxial stretching apparatus of the first embodiment. FIG. 2 is a schematic top view showing another method of using the biaxial stretching apparatus of the first embodiment. FIG. 3 is a schematic top view showing an embodiment (second embodiment) of a stretching apparatus according to the second aspect of the present invention. FIG. 4 is a partially enlarged top view of the stretching apparatus of the second embodiment. FIG. 5 is a bottom view (a) showing the configuration of a gripping member of the stretching apparatus of the second embodiment, and a bottom view (b) showing a state in which the gripping member has been rotated around the pivot pin of the second gripping member holding unit. FIG. 6 is a top view showing a state in which a processed sheet has been stretched by the stretching apparatus of the second embodiment. FIG. 7 is a top view showing a slider box in a biaxial stretching apparatus of a modified example of the first embodiment. FIG. 8 is a top view showing a slider box in a biaxial stretching apparatus of another modified example of the first embodiment.

[0024] An embodiment of a stretching device according to the present invention will be described with reference to FIGS.

[0025] (1) One embodiment of the biaxial stretching device according to the first aspect of the present invention (first embodiment) As shown in Figures 1 and 2, the biaxial stretching device 1 of the first embodiment includes four stretching mechanisms 10 provided corresponding to the four sides of the sheet S. In Figures 1 and 2, these four stretching mechanisms are denoted by the reference numerals 10A, 10B, 10C, and 10D in counterclockwise order, but all of them have the same configuration.

[0026] The stretching mechanism 10 includes a slider box 11, a chuck 14, a drive mechanism 19, and the like.

[0027] The slider box 11 is a rectangular box having a shape such that the direction parallel to the side of the processed sheet S corresponding to the stretching mechanism 10 (hereinafter referred to as the "corresponding side") (hereinafter referred to as the "longitudinal direction") is larger than the width and height directions. As shown in FIG. 3, four rails 12 consisting of slits parallel to the corresponding side are provided on the top surface of the slider box 11. These four rails 12 are referred to as the first rail 121, the second rail 122, the third rail 123, and the fourth rail 124, in order from the side closest to the processed sheet S. The first rail 121 and the second rail 122 have the same length, while the third rail 123 and the fourth rail 124 have the same length but are shorter than the first rail 121 and the second rail 122. The first rail 121 extends from a position near one end in the longitudinal direction to a position closer to the other end than the center in the longitudinal direction. The second rail 122 extends from a position near the other end to a position closer to the one end than the center. The third rail 123 extends from a position closer to the one end than the midpoint between the one end and the center to a position closer to the other end than the center, and the fourth rail 124 extends from a position closer to the other end than the midpoint between the other end and the center to a position closer to the one end than the center.

[0028] The slider box 11 accommodates one slider 13 for each rail 12, which slides along the rail 12 (FIG. 3). Hereinafter, the sliders 13 provided for the first rail 121, second rail 122, third rail 123, and fourth rail 124 will be referred to as the first slider 131, second slider 132, third slider 133, and fourth slider 134, respectively. The flat upper surface of each slider 13 is flush with the upper surface of the slider box 11, and a rack 15 (described below) is fixed to the lower surface.

[0029] One chuck 14 is fixed to the upper surface of each slider 13. The chucks 14 are arranged outside the slider box 11. The chucks 14 fixed to the first slider 131, second slider 132, third slider 133, and fourth slider 134, respectively, are called the first chuck 141, second chuck 142, third chuck 143, and fourth chuck 144. Each chuck 14 has a base 1491 whose underside is fixed to the corresponding slider 13, and a gripping portion 1492 that grips the processed sheet S. A portion of the base 1491 protrudes further than the upper surface of the slider box 11 toward the corresponding side of the processed sheet S, and the gripping portion 1492 is provided on that protruding portion. These first chuck 141 to fourth chuck 144 all move in the longitudinal direction of the slider box 11 as the first slider 131 to fourth slider 134 slide along the first rail 121 to fourth rail 124 .

[0030] In addition to the first chuck 141 to the fourth chuck 144, a zeroth chuck 140 is fixed to the center of the longitudinal direction of the top surface of the slider box 11 outside the slider box 11. The zeroth chuck 140 does not have the slider 13 or a rack 15 (described later) fixed thereto, and does not move from the center of the longitudinal direction.

[0031] The chucks 14 are arranged in the order of the first chuck 141, the third chuck 143, the zeroth chuck 140, the fourth chuck 144, and the second chuck 142 from one end in the longitudinal direction, and this arrangement does not change even if the chucks 14 move in the longitudinal direction.

[0032] A rack 15 is provided on the underside of each slider 13 (inside the slider box 11). To facilitate understanding of the configuration of the rack 15 and the pinion 16 (described later), the following description will be made with reference to FIG. 4 , a bottom view showing the slider box 11 with the top and bottom plates removed, and FIG. 5 , a top view. FIG. 5 also shows the state with the 0th chuck 140 removed. The racks 15 fixed to the first slider 131, second slider 132, third slider 133, and fourth slider 134, respectively, are referred to as the first rack 151, second rack 152, third rack 153, and fourth rack 154. Each rack 15 extends in the longitudinal direction of the slider box 11, has a gear formed on its underside ( FIG. 4 ), and has a flat upper surface ( FIG. 5 ). This flat upper surface is fixed to the underside of the slider 13. Each rack 15 is movable in the longitudinal direction. The gear teeth of each rack 15 have the same pitch.

[0033] Furthermore, four pinions 16 are provided inside the slider box 11, one for meshing with each rack 15. The pinions 16 provided corresponding to the first rack 151, second rack 152, third rack 153, and fourth rack 154 are referred to as the first pinion 161, second pinion 162, third pinion 163, and fourth pinion 164, respectively. The first pinion 161 and the second pinion 162 have the same number of teeth and the same diameter. The third pinion 163 and the fourth pinion 164 have the same number of teeth and the same diameter, but the number of teeth and diameter are half that of the first pinion 161 and the second pinion 162.

[0034] The second pinion 162 and the fourth pinion 164 rotate about a main rotation shaft 184, while the first pinion 161 and the third pinion 163 rotate about a driven rotation shaft 173. The main rotation shaft 184 and the driven rotation shaft 173 extend to the outside of the slider box 11 by penetrating the side surface of the slider box 11 opposite to the corresponding side. A main gear 171 that rotates about the main rotation shaft 184 is provided on the main rotation shaft 184 at a position outside the slider box 11. A driven gear 172 that rotates about the driven rotation shaft 173 is provided on the driven rotation shaft 173 at a position outside the slider box 11. The main gear 171 and the driven gear 172 have the same number of teeth and are in mesh with each other.

[0035] The main rotating shaft 184 is rotated by the rotation mechanism 18, which will be described later. At this time, the driven rotating shaft 173 and the driven gear 172 rotate in opposite directions at the same speed (number of rotations per unit time) as the main rotating shaft 184 and the main gear 171. As a result, the first pinion 161 and the second pinion 162, which have the same number of teeth, rotate in opposite directions at the same speed (same as above), and the first rack 151 and the second rack 152 move in opposite directions at the same speed (linear movement distance per unit time). Furthermore, the third pinion 163 and the fourth pinion 164, which have the same number of teeth but half the number of teeth of the first pinion 161, etc., rotate in opposite directions at the same speed as the first pinion 161, etc., and the third rack 153 and the fourth rack 154 move in opposite directions at half the speed of the first rack 151, etc. As a result, the chucks 14 fixed to each rack 15 move in opposite directions at the same speed as each other, with the first chuck 141 and the second chuck 142, and the third chuck 143 and the fourth chuck 144 moving in opposite directions at the same speed as each other but half the speed of the first chuck 141, etc.

[0036] The main gear 171 and the driven gear 172 operate as described above, and therefore correspond to the aforementioned "synchronization mechanism that rotates two pinions in synchronous directions in opposite directions."

[0037] The main rotating shaft 184 and the driven rotating shaft 173 are located at the same height, and as described above, the third pinions 163 and the fourth pinions 164 have smaller diameters than the first pinions 161 and the second pinions 162. Therefore, as shown in FIG. 6 , the upper ends of the first pinions 161 and the second pinions 162 are higher than the upper ends of the third pinions 163 and the fourth pinions 164. Accordingly, the first rack 151 and the second rack 152 that mesh with these pinions 16 are located higher than the third rack 153 and the fourth rack 154. To accommodate these height differences and align the positions of the upper surfaces of the sliders 13 with the upper surface of the slider box 11, the third slider 133 and the fourth slider 134 are taller than the first slider 131 and the second slider 132.

[0038] The rotation mechanism 18 has a first base 181, a first motor 182 provided on the first base, a first transmission mechanism 183, and the main rotation shaft 184. The first base 181 is connected to the slider box 11 by a connecting rod 196 provided in the drive mechanism 19 described below. The first base 181 can move back and forth in a direction perpendicular to the corresponding side of the sheet S to be processed, and moving the first base 181 back and forth moves the entire rotation mechanism 18 and the slider box 11 back and forth in that direction. The first transmission mechanism 183 is a mechanism that transmits the rotation of the shaft of the first motor 182 to the main rotation shaft 184, and a known mechanism can be used.

[0039] The drive mechanism 19 includes a second base 191, a second motor 192, a second transmission mechanism 193, a screw shaft 194, a second base upper rail 195, and the connecting rod 196. The second transmission mechanism 193 transmits the rotation of the shaft of the second motor 192 to the screw shaft 194. The screw shaft 194 extends in a direction perpendicular to the corresponding side of the sheet S. The second base upper rail 195 is provided on the upper surface of the second base 191 and extends in a direction perpendicular to the corresponding side. A screw member (not shown) that engages with the thread of the screw shaft 194 is fixed to the first base 181, and the first base 181 is placed on the second base upper rail 195. As the screw shaft 194 rotates, the first base 181 advances and retreats along the second base upper rail 195 in a direction perpendicular to the corresponding side.

[0040] The slider boxes 11 of the stretching mechanisms 10A and 10C are arranged at the same height with their longitudinal directions parallel to each other. The slider boxes 11 of the stretching mechanisms 10B and 10D are arranged at the same height with their longitudinal directions substantially parallel to each other, but are arranged at a lower position with their longitudinal directions substantially perpendicular to the slider boxes 11 of the stretching mechanisms 10A and 10C.

[0041] The slider boxes 11 of each of the four stretching mechanisms 10A, 10B, 10C, and 10D, the various components provided within the slider boxes 11, the chucks 14, the main gears 171, the driven gears 172, and the driven rotation shafts 173, as well as parts of the main rotation shafts 184 and connecting rods 196, are all housed in a single (common) thermostatic chamber 20 (see FIG. 1; the thermostatic chamber 20 is omitted in FIG. 2). Holes are provided in the side walls of the thermostatic chamber 20 through which the main rotation shafts 184 and connecting rods 196 pass. A heater 21 is provided within the thermostatic chamber 20. By heating with this heater 21, the temperature within the thermostatic chamber 20 can be maintained at a temperature at which the sheet S to be processed softens. The top plate (not shown) of the thermostatic chamber 20 can be opened and closed, and when the sheet S to be processed is attached to the chuck 14 or when the sheet S to be processed after the stretching process is removed from the chuck 14, the top plate is opened to perform the work.

[0042] The biaxial stretching apparatus 1 further includes a control unit 25 that controls the rotation of the first motor 182 and the second motor 192 of each stretching mechanism 10, as well as the output of the heater 21. Focusing on stretching mechanism 10A, for example, the speeds of the first motor 182 of stretching mechanism 10A and the second motors 192 of stretching mechanisms 10B and 10D are controlled so that the chucks of stretching mechanism 10A move at a speed synchronized with the speed at which the corresponding edge of the processed sheet S in stretching mechanism 10A is stretched in accordance with the rotation of the second motors 192 of stretching mechanisms 10B and 10D adjacent to each other on both sides of stretching mechanism 10A. The speeds of the first motor 182 of each stretching mechanism and the second motors 192 of the adjacent stretching mechanisms on both sides are controlled in a similar manner for each of stretching mechanisms 10B to 10D. The first motor 182, the second motor 192 and the control unit 25 correspond to the aforementioned "synchronous extension mechanism that rotates the two pinions of the stretching mechanism in synchronization with the movement of the drive mechanism of the stretching mechanism corresponding to the adjacent sides of the processed sheet."

[0043] The method of using the biaxial stretching apparatus 1 of the first embodiment will now be described. In the initial state, the first motor 182 is rotated to position the chucks 14 so that adjacent chucks 14 are closest to each other, as shown in Figures 1 and 7. In this state, the top plate of the thermostatic chamber 20 is opened, and the four sides of the rectangular sheet S to be processed are gripped by the chucks 14. Thereafter, the top plate of the thermostatic chamber 20 is closed.

[0044] The control unit 25 controls the temperature in the thermostatic chamber 20 by passing current through the heater 21 and adjusting the magnitude of the current to maintain the temperature within the thermostatic chamber 20 within a predetermined temperature range in which the sheet S softens. After the temperature in the thermostatic chamber 20 reaches this temperature range, the control unit 25 rotates the second motor 192 of each stretching mechanism 10 to move the slider box 11 toward the side opposite the corresponding edge of the sheet S (vertical arrow in FIG. 8 ). At the same time, the control unit 25 rotates the first motor 182 of each stretching mechanism 10. As described above, the rotation of the first motor 182 causes the first chuck 141 and the second chuck 142 to move in opposite directions at the same speed (horizontal arrow in FIG. 8 ), and the third chuck 143 and the fourth chuck 144 to move in opposite directions at the same speed but half the speed of the first chuck 141 (same). The zeroth chuck 140 does not move. Here, the control unit 25 controls the rotation speed of the first motor 182 and the second motor 192 of each stretching mechanism 10 so that the movement of each chuck 14 is synchronized with the speed at which the corresponding edge of the processed sheet S is stretched by the adjacent stretching mechanisms 10 on both sides.

[0045] By the above operation, the processed sheet S is stretched in four directions. Figure 8 shows the processed sheet S stretched to about half of its maximum stretching, while Figures 9 and 10 show the processed sheet S in its maximum stretched state. The degree to which the processed sheet S is stretched (the distance the slider box 11 is moved) is arbitrary.

[0046] After the stretching of the processing target sheet S is completed, the heater 21 is stopped, the upper plate of the thermostatic chamber 20 is opened, and the processing target sheet S is taken out.

[0047] According to the first embodiment of the biaxial stretching device 1, the rail 12, which is a component for adjusting the spacing between the chucks 14, is arranged parallel to the corresponding edge of the processed sheet S, so that the space occupied by the device in the direction perpendicular to the corresponding edge can be reduced, thereby making the entire device smaller.

[0048] Since the entire device can be made smaller in size, the volume of the thermostatic bath 20 can also be made smaller, and the power consumption of the heater 21 can also be reduced.

[0049] In the examples shown so far, all four sides of the processed sheet S are expanded equally, but the degree of expansion may be different between two opposing sides. For example, two opposing sides of the four sides of the processed sheet S may be gripped by the chucks 14 of only two of the four stretching mechanisms 10 (e.g., stretching mechanisms 10A and 10C), and the slider boxes 11 of one or both of the two stretching mechanisms 10 may be moved in a direction perpendicular to the corresponding sides of the processed sheet S, while the chuck 14 of only one of the stretching mechanisms 10 may be moved. In these cases, the chuck 14 of the stretching mechanism 10 whose slider box 11 moves does not need to be synchronized with the slider boxes 11 of the remaining two stretching mechanisms 10 (in the previous example, all stretching mechanisms 10 move simultaneously, but in this example, none of the slider boxes 11 move). Therefore, the slider boxes 11 can be moved independently of the slider boxes 11. That is, the slider boxes 11 and chucks 14 may be moved simultaneously, or only one of them may be moved first. In either case, the processed sheet S is ultimately stretched into a trapezoidal shape as shown in FIG.

[0050] (2) One embodiment of the biaxial stretching apparatus according to the second aspect of the present invention (second embodiment) As shown in Fig. 12, the stretching apparatus 3 of the second embodiment is obtained by adding an additional mechanism 30 as an option to the biaxial stretching apparatus 1 of the first embodiment. The additional mechanism 30 is detachably attached to the upper surface of the slider box 11 of each of two opposing stretching mechanisms 10B and 10D among the four stretching mechanisms 10A to 10D of the biaxial stretching apparatus 1. The slider boxes 11 of the two stretching mechanisms 10A and 10C to which the additional mechanism 30 is not attached are not used in the stretching apparatus 3 of the second embodiment, and are therefore moved backward by operating the drive mechanisms 19 provided for those two stretching mechanisms 10A and 10C, as shown by the dashed lines in Fig. 12. In addition, the chucks 14 provided in the biaxial stretching device 1 are removed from the slider boxes 11 of the stretching mechanisms 10B and 10D to which the additional mechanism 30 is attached (the chucks 14 of the slider boxes 11 of the stretching mechanisms 10A and 10C that are not in use may remain attached).

[0051] As shown in an enlarged view in FIG. 13, the additional mechanism 30 has two gripping members 31 , two first gripping member holding portions 32 , and two second gripping member holding portions 33 .

[0052] The gripping member 31 is a rod-shaped member that is rectangular when viewed from above, and a clip 311 is provided on one of the long sides of the rectangle to grip the long side of the rectangular processing sheet S over a linear range. The two gripping members 31 are arranged so that the clips 311 face each other. The bottom surface of the gripping member 31 is provided with a groove 312 that extends in the longitudinal direction.

[0053] In this embodiment, the two first gripping member holding portions 32 are members fixed to stand apart from each other on the surface of a single (common) plate-like member 320, and are inserted into holes provided at one end (the end on the stretching mechanism 10C side in this example) of each of the two gripping members 31. As a result, each of the two first gripping member holding portions 32 rotatably holds the gripping member 31 that has been inserted therethrough.

[0054] The two second gripping member holders 33 are fixed to the upper surfaces of plate-shaped fixtures 330, which are fixed with screws to the upper surfaces of two opposing slider boxes 11, respectively. Each of the second gripping member holders 33 has a cam follower at its tip that rotates around an axis perpendicular to the upper surface of the fixture 330. The two second gripping member holders 33 are inserted into grooves 312 formed in the two gripping members 31. At the other end of the gripping member 31 (the end toward the stretching mechanism 10A in this example), a stopper 313 is provided in the groove 312 to prevent the second rotation shaft 332 from disengaging. This configuration allows the second gripping member holder 33 to slide relative to the groove 312 of the gripping member 31. The gripping member 31 can be rotated while sliding until it abuts against the stopper 313 ( FIG. 14( b) ). The cam follower provided in the second gripping member holder 33 allows the gripping member 31 to rotate smoothly. The second gripping member holding portion 33 may be formed of a pin instead of a cam follower.

[0055] The control unit 25 controls the operation of the second motor 192 of the stretching mechanisms 10B and 10D and the output of the heater 21. In the stretching device 3 of the second embodiment, it is not necessary to control the second motor 192 of the stretching mechanisms 10A and 10C and the first motor 182 of each stretching mechanism 10, which are not used.

[0056] The operation of the stretching device 3 of the second embodiment will be described. First, the control unit 25 operates the drive mechanisms 19 provided in the stretching mechanisms 10B and 10D to bring the two gripping members 31 closer to each other to a distance slightly shorter than the length of the two of the four sides of the processed sheet S that are not gripped by the gripping members 31. Next, the two gripping members 31 are slid to an appropriate position in the longitudinal direction (where the user can easily work). Then, the user grips two of the four sides of the processed sheet S with the clips 311 of the different gripping members 31.

[0057] Next, the control unit 25 controls the temperature by passing an electric current through the heater 21 and adjusting the magnitude of the current so that the inside of the thermostat 20 is within a predetermined temperature range in which the workpiece sheet S softens. After the inside of the thermostat 20 reaches this temperature range, the control unit 25 rotates the second motors 192 of the stretching mechanisms 10B and 10D to move the two slider boxes 11 in opposite directions (directions perpendicular to the two sides of the workpiece sheet S held by the gripping members 31). Then, the two gripping members 31 are pushed by the second gripping member holders 33 fixed to the slider boxes 11 via the fixtures 330 and move in opposite directions. As a result, the two gripping members 31 rotate in opposite directions about the first gripping member holder 32 and slide while being guided in the grooves 312 until the second gripping member holder 33 abuts against the stopper 313. When the second gripping member holder 33 abuts against the stopper 313, the two gripping members 31 further rotate in opposite directions about the second gripping member holder 33.

[0058] Through the above operations, as shown in FIG. 15, the two gripping members 31 move such that the distance between the other ends opens while the distance between the one ends remains unchanged, and are arranged in the shape of the Chinese character "八" (eight). By the movement of the gripping members 31, the workpiece sheet S is stretched in a direction perpendicular to the two sides held by the gripping members 31 as a whole, but the stretching rate is non-uniform, being the largest near the other end and approximately 1 (almost no stretching) near the one end. The shape of the workpiece sheet S after stretching is trapezoidal.

[0059] According to the stretching device 3 of the second embodiment, in a sheet mass-production device including a uniaxial stretching device or a sequential biaxial stretching device using two rails provided so that the interval gradually expands in a part of the section, a sheet reproducing a transient state can be obtained. By investigating the state of polymers and the like in the sheet thus obtained, the phenomenon occurring in the sheet in the mass-production machine can be confirmed.

[0060] (3) Modifications The present invention is not limited to the above embodiments, and various modifications are possible.

[0061] For example, in the biaxial stretching apparatus 1 of the first embodiment, the 0th chuck 140 may be omitted as shown in FIG.

[0062] 17, the third chuck 143 and the fourth chuck 144 may be omitted from the biaxial stretching apparatus 1 of the first embodiment. In that case, the third rail 123, the fourth rail 124, the third slider 133, the fourth slider 134, the third rack 153, the fourth rack 154, the third pinion 163, and the fourth pinion 164 are not required. Alternatively, in the configuration shown in FIG. 17, the zeroth chuck 140 may be omitted.

[0063] 16 and 17 show an example in which the number of chucks 14 is reduced compared to the above embodiment. Conversely, the number of chucks 14 may be increased compared to the first embodiment. In this case, the number of rails 12, sliders 13, racks 15, and pinions 16 are also increased by the same amount. The number of teeth on each pinion 16 is set so that each chuck 14 moves in synchronization with the speed of stretching of the corresponding edge of the sheet by the stretching mechanism 10 adjacent to the corresponding edge. For example, two chucks may be added to both outer sides of the five chucks (0th chuck 140 to 4th chuck 144) shown in the above embodiment, and two rails, two sliders, two racks, and two pinions may be added corresponding to the two chucks. The number of teeth on the two pinions may be 3 / 2 times that of the first pinion 161. This allows for a configuration in which a total of seven chucks are provided per slider box. The same applies when the number of chucks is further increased (to 9, 11, etc.) or when the 0th chuck 140 is omitted (to make a total of 6, 8, 10, etc.).

[0064] If the frictional resistance to the slider 13 generated when moving on the rail 12 is made sufficiently small, it is possible to move each chuck 14 in synchronization with the speed of stretching of the corresponding edge of the processed sheet by the stretching mechanism 10 adjacent to the corresponding edge, without using the rack 15, pinion 16, etc. In this case, the rack 15, pinion 16, and rotation mechanism 18 may be omitted in the biaxial stretching apparatus 1 of the first embodiment.

[0065] The stretching device 3 of the second embodiment is the biaxial stretching device 1 of the first embodiment to which an additional mechanism 30 has been added as an option, but it is also possible to use a device separate from the biaxial stretching device 1 of the first embodiment, in which a gripping member 31, a first gripping member holding unit 32, and a second gripping member holding unit 33 are respectively installed on two drive mechanisms, and the gripping members 31 are arranged so as to face each other.

[0066] In the stretching device 3 of the second embodiment, the two first gripping member holding portions 32 are fixed to a single (common) plate-like member 320. Therefore, when the processed sheet S is pulled, they do not move in the pulling direction. Therefore, the processed sheet S is hardly stretched near the one end of the gripping member 31. On the other hand, if it is desired to stretch the processed sheet S unevenly at different stretch rates near one end and the other end while also stretching near one end of the gripping member, the two first gripping member holding portions may not be fixed to each other, and a drive mechanism may be used to pull the two second gripping member holding portions and pull the two first gripping member holding portions at a different pulling speed than the second gripping member holding portions. By thus different pulling speeds for the first gripping member holding portion and the second gripping member holding portion, the processed sheet is stretched unevenly at different stretch rates near one end and the other end of the gripping member. At this time, the stretching rate near the one end can be adjusted by the pulling speed of the first gripping member holding portion.

[0067] DESCRIPTION OF SYMBOLS 1...Biaxial stretching device 10, 10A, 10B, 10C, 10D...Stretching mechanism 11...Slider box 12...Rail 121...First rail 122...Second rail 123...Third rail 124...Fourth rail 13...Slider 131...First slider 132...Second slider 133...Third slider 134...Fourth slider 14...Chuck 140...0th chuck 141...First chuck 142...Second chuck 143...Third chuck 144...Fourth chuck 1491...Base 1492...Gripping part 15...Rack 151...First rack 152...Second rack 153...Third rack 154...Fourth rack 16...Pinion 161...First pinion 162...Second pinion 163...Third pinion 164...Fourth pinion 171...Main gear 172...Driven gear 173...Driven rotating shaft 18...Rotation mechanism 181...First base 182...First motor 183...First transmission mechanism 184...Main rotating shaft 19...Drive mechanism 191...Second base 192...Second motor 193...Second transmission mechanism 194...Screw shaft 195...Second base upper rail 196...Connecting rod 20...Constant temperature bath 21...Heater 25...Control unit 3...Stretching device 30...Additional mechanism 31...Gripping member 311...Clip 312...Groove 313...Stopper 32...First gripping member 320...Fixing device for first gripping member 33...Second gripping member holding part 330...Second gripping member holding part fixing tool S...Sheet to be processed

Claims

1. A biaxial stretching device, characterized in that each of the stretching mechanisms provided on the four sides of the processed sheet comprises: a) a slider box having a rail provided parallel to the corresponding side of the stretching mechanism and two sliders that slide on the rail; b) a chuck provided on each of the two sliders for gripping the corresponding side of the processed sheet; and c) a drive mechanism that pulls the slider box in a direction perpendicular to the corresponding side.

2. The biaxial stretching apparatus according to claim 1, further comprising: d) racks of the same pitch fixed to each of said two sliders; e) pinions having the same number of teeth meshing with each of said two racks; and f) a synchronization mechanism for rotating said two pinions synchronously in opposite directions.

3. The biaxial stretching apparatus according to claim 2, further comprising: g) a synchronous expansion mechanism for rotating the two pinions of the stretching mechanism in synchronization with the movement of the drive mechanism of the stretching mechanism corresponding to the adjacent sides of the processed sheet.

4. A biaxial stretching apparatus as described in claim 2 or 3, characterized in that within the slider box, rails for sliding two additional sliders with additional racks are provided, and each of the two additional sliders with additional racks is provided with an additional chuck and an additional pinion for gripping the corresponding side of the processed sheet, and the additional racks and additional pinions of the two additional sliders with additional racks are set to move in opposite directions to each other at speeds according to the gripping positions of the two chucks and the corresponding sides of the two additional chucks.

5. A stretching device comprising: two rod-shaped gripping members that grip two opposing sides of a rectangular processed sheet along each of the two opposing sides; two first gripping member holding portions that rotatably hold one end of each of the two gripping members; two second gripping member holding portions that rotatably hold the other end of each of the two gripping members; and a drive mechanism that pulls the two first gripping member holding portions and the two second gripping member holding portions in a direction perpendicular to the two sides at different speeds.

6. The stretching device according to claim 5, wherein the speed at which the drive mechanism pulls the two first gripping member holding portions is 0.

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