Pilot test type synchronous stretcher and stretching method thereof

Abstract

The invention provides a pilot-scale type synchronous stretcher and a stretching method thereof, and relates to the technical field of film stretching devices.The pilot-scale type synchronous stretcher is characterized in that two sets of mirror curve rails are arranged on the upper portion of a support, each curve rail comprises an inner annular rail and an outer annular rail, and a driving chain wheel is arranged on the inner side of one end of each curve rail; a driven chain wheel is arranged on the inner side of the other end of the curve track, the driving chain wheel is in transmission connection with a driving motor, a plurality of chain clip mechanisms are slidably connected to the curve track, and the driving chain wheel is used for driving the chain clip mechanisms. The technical problem that in the prior art, a film stretching device cannot achieve roll-to-roll continuous stretching in a laboratory and meanwhile can achieve accurate stretch ratio control in a small stretch ratio application scene is solved.

Description

Technical Field

[0001] The invention relates to the technical field of film stretching devices, in particular to a pilot-type synchronous stretching machine and a stretching method thereof. Background Art

[0002] Synchronous film stretching is a processing method for manufacturing plastic films, which involves simultaneous longitudinal and transverse stretching during the film production process to obtain a film product with specific mechanical properties and dimensional stability. Synchronous film stretching technology is usually used in the production or experiment of biaxially stretched plastic films, such as biaxially stretched polypropylene (BOPP) film, biaxially stretched polyester (BOPET) film, and biaxially stretched nylon (BOPA) film; by precisely controlling the temperature, speed and stretching ratio during the stretching process, the film is uniformly stretched in two perpendicular directions, thereby obtaining a film with good optical properties, mechanical strength and thermal stability. Synchronous film stretching is achieved by clamping both sides of the film in the jaws of the chain clip, and then changing the lateral spacing between the jaws on both sides and the longitudinal spacing to synchronously achieve transverse and longitudinal stretching of the film.

[0003] There are two types of devices for synchronous film stretching methods. One is the laboratory biaxial stretching instrument (handkerchief machine) used in the laboratory. The handkerchief machine can only stretch thick sheets cut into 100mm×100mm square blocks into handkerchief-shaped stretched films. The thickness uniformity and performance of the film cannot be adjusted. Therefore, the handkerchief machine can only obtain sheet samples, which are mainly used for raw material and formula testing, and cannot achieve film roll-to-roll stretching. The other is a large-scale synchronous stretching machine for industrial use. Its overall large structure is expensive and is suitable for application scenarios with a longitudinal stretching ratio greater than 3; when facing application scenarios with a longitudinal stretching ratio less than or equal to 2 times, due to the design of the chain clip structure, it is easy to have a large longitudinal stretching ratio error.

[0004] However, the stretching device in the prior art lacks a synchronous stretching machine that is between a laboratory biaxial stretching machine and an industrial synchronous stretching machine, which can be used to achieve roll-to-roll continuous stretching in the laboratory, and can also be used in small stretching ratio application scenarios where the longitudinal stretching ratio is less than 2 (especially the longitudinal stretching ratio is less than 1.5), thereby achieving precise stretching ratio control. Summary of the invention

[0005] The object of the present invention is to provide a pilot-scale synchronous stretching machine and a stretching method thereof, so as to alleviate the technical problem that the film stretching device in the prior art cannot realize continuous roll-to-roll stretching in the laboratory, and at the same time can realize precise stretching ratio control in the application scenario of a small stretching ratio of less than 2 in the longitudinal stretching ratio.

[0006] The present invention provides a pilot-scale synchronous stretching machine, comprising: a bracket, a curved track, a driving sprocket, a driven sprocket, a driving motor and a chain clip mechanism;

[0007] Two sets of mirror-inverted curved tracks are provided on the upper part of the bracket, each curved track includes an inner ring track and an outer ring track, a driving sprocket is provided on the inner side of one end of the curved track, and a driven sprocket is provided on the inner side of the other end of the curved track, the driving sprocket is connected to the drive motor, and a plurality of chain clip mechanisms are slidably connected to the curved track, and the driving sprocket is used to drive the chain clip mechanism to move.

[0008] Further, the chain clip mechanism includes a clip head assembly, a clip body and a chain link assembly;

[0009] A first cylindrical through hole is provided at the center of the clip body, a front drive shaft is inserted into the first through hole, and positioning bearings are provided at both ends of each front drive shaft and are slidably connected to the outer annular rail. A clip head assembly is provided at the clamping end of the clip body, and a second through hole is passed through the connecting end of the clip body, a connecting shaft is inserted into the second through hole, a chain link assembly is sleeved on the outside of the connecting shaft, and the chain link assembly is slidably connected to the inner annular rail;

[0010] Further, the clip head assembly includes a clip handle and a clip cover;

[0011] The clamp handle is arranged at the clamping end of the clamp body and is hinged with the clamp body, the bottom end of the clamp handle is connected with the clamp cover, and the clamp cover is fitted with the clamp body to clamp the film;

[0012] Further, the chain link assembly includes a first chain plate, a second chain plate, a third chain plate, a fourth chain plate, a rear drive shaft and a rolling bearing;

[0013] One ends of the first chain plate, the second chain plate, the third chain plate and the fourth chain plate are sequentially sleeved on the connecting shaft, the other ends of the first chain plate and the third chain plate are penetrated in the rear drive shaft together with the second chain plate and the fourth chain plate in the previous adjacent chain link assembly, the other ends of the second chain plate and the fourth chain plate are penetrated in the rear drive shaft together with the first chain plate and the third chain plate in the next adjacent chain link assembly, and both ends of each rear drive shaft are provided with rolling bearings slidably connected to the inner annular rail.

[0014] Further, the chain clip mechanism includes a positioning plate;

[0015] The positioning plate is in the shape of a long strip and is used to make the chain link assembly move symmetrically along the central axis of the clip body. A first arc groove and a second arc groove are provided on the surface of the positioning plate. The transverse length of the first arc groove is not less than the diameter of the front drive shaft, and the first arc groove is used to pass through the front drive shaft. The transverse length of the second arc groove is not less than the diameter of the connecting shaft, and the second arc groove is used to pass through the connecting shaft.

[0016] Further, the tracks on opposite sides of the two curved tracks are divided into a preheating and stretching section, a heat setting and cooling section, and a rotating section;

[0017] Further, the diameter and number of teeth of the driven sprocket are the same as those of the driving sprocket;

[0018] The present invention also provides a stretching method of a pilot-scale synchronous stretching machine, comprising the following steps:

[0019] Step 1: The driving motor drives the driving sprocket to rotate, thereby causing the chain clamp mechanism to move along the curved track, and clamping the pre-processed thick sheet with a thickness of 50 μm to 600 μm through the chain clamp mechanism;

[0020] Step 2, the longitudinal length of the thick sheet before processing when clamped by the chain clip mechanism is the center distance MD1 of the clamping points of the chain clip mechanism, and due to the movement of the chain clip mechanism on the curved track, the longitudinal length of the thick sheet before processing is also stretched to MD2 along with the center distance of the clamping points of the chain clip mechanism; and due to the expansion of the two curved tracks, the transverse length of the thick sheet before processing is also stretched from TD1 to TD2 along with the chain clip mechanisms at two opposite ends, so as to obtain a stretched film;

[0021] Step 3: The stretched film with a thickness of 2 μm to 200 μm will continue to be transported on the curved track to be heat-set and cooled, completing the synchronous stretching of the film.

[0022] Furthermore, the longitudinal tensile ratio of the stretched film is λ MD =MD2 / MD1, the transverse pull ratio of the stretched film is λ TD =TD2 / TD1.

[0023] Beneficial effects:

[0024] The present invention provides a pilot-scale synchronous stretching machine, including two sets of mirror-inverted curved tracks on the upper part of a bracket, and the bracket supports the upper curved tracks. The curved tracks are calculated by combining precise geometry and kinematics to achieve synchronous longitudinal and transverse stretching; each curved track includes an inner annular track and an outer annular track, and the double-track design allows multiple chain clip mechanisms to be slidably connected to the curved track, and the chain clip mechanisms clamp the film. The shape of the curved track is used to force the lateral spacing between two adjacent chain clip mechanisms and the longitudinal spacing between two relative chain clip mechanisms to expand, thereby achieving synchronous bidirectional stretching of the film after sufficient preheating.

[0025] A driving sprocket is arranged on the inner side of one end of the curved track, and a driven sprocket is arranged on the inner side of the other end of the curved track. The driving sprocket is connected to the driving motor, and the driving sprocket is used to drive the chain clip mechanism to move. The power system is set by a set of simple driving sprockets and driven sprockets, so that the chain clip structure can move smoothly and stretch the thick sheet on the curved track while saving costs.

[0026] The pilot-scale synchronous stretching machine of the present invention can not only perform roll-to-roll film sample test analysis on a wide variety of additives and formulations in the laboratory, but also serve as an industrial production machine for small-batch production of high-value-added films, thereby reducing equipment costs. Compared with large-scale industrial production devices, the chain clip structure in the present application can achieve uniform synchronous stretching, and can ensure that the chain links composed of the chain plates always move symmetrically along the central axis of the clip body. Therefore, the pilot-scale synchronous stretching machine provided by the present invention is very suitable for application scenarios with a small stretching ratio of ≤2 times and requiring a precise stretching ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 A schematic diagram of the structure of a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of the connection between the driving sprocket and the chain clip mechanism in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0030] Figure 3 A schematic diagram of two sets of curved tracks and chain clamps in the preheating and stretching section and the return stroke in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0031] Figure 4 A schematic structural diagram of a chain clip mechanism in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0032] Figure 5 A schematic diagram of a chain clip mechanism in a preheating zone of a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0033] Figure 6 A schematic diagram of a chain clip mechanism in a stretching zone of a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0034] Figure 7 A schematic diagram of the structure of a positioning plate in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0035] Figure 8 A flow chart of a stretching method of a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0036] Fig. 9 A graph showing the variation of the chain link spacing of a chain clip mechanism in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention after one cycle of operation;

[0037] Fig.10 A graph showing the variation of the distance between the clip heads of the chain clip mechanism of the pilot-scale synchronous stretching machine provided in the embodiment of the present invention after one cycle of operation;

[0038] Fig.11 A schematic diagram of the center distance of a chain link assembly in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention;

[0039] Fig.12 A schematic diagram of the variation in spacing of curved tracks in a pilot-scale synchronous stretching machine provided in an embodiment of the present invention.

[0040] Icons: 1-bracket; 2-curved track; 21-inner annular track; 22-outer annular track; 23-preheating and stretching section; 24-heat setting and cooling section; 25-rotating section; 3-driving sprocket; 4-driven sprocket; 5-driving motor; 6-chain clip mechanism; 61-clip head assembly; 611-clip handle; 612-clip cover; 62-clip body; 621-first through hole; 622-front drive shaft; 623-positioning bearing; 624-second through hole; 625-connecting shaft; 63-chain link assembly; 631-first chain plate; 632-second chain plate; 633-third chain plate; 634-fourth chain plate; 635-rear drive shaft; 636-rolling bearing; 64-positioning plate; 641-first arc groove; 642-second arc groove. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0044] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0045] In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are required to be absolutely horizontal or overhanging, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0046] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0048] like Figure 1 , Figure 2 and Figure 3 As shown, the present invention provides a pilot-scale synchronous stretching machine, comprising: a bracket 1, a curved track 2, a driving sprocket 3, a driven sprocket 4, a driving motor 5 and a chain clip mechanism 6;

[0049] Two sets of mirror-inverted curved tracks 2 are provided on the upper part of the bracket 1, and each curved track 2 includes an inner annular track 21 and an outer annular track 22. A driving sprocket 3 is provided on the inner side of one end of the curved track 2, and a driven sprocket 4 is provided on the inner side of the other end of the curved track 2. The driving sprocket 3 is transmission-connected to a driving motor 5, and a plurality of chain clip mechanisms 6 are slidingly connected to the curved track 2. The driving sprocket 3 is used to drive the chain clip mechanism 6 to move.

[0050] Specifically, the bracket 1 is made of an iron frame or other metal materials, and two sets of curved mirror-shaped tracks 2 are arranged in parallel on the upper surface of the bracket 1 to play a supporting role. Each curved track 2 includes two sets of annular guide rails arranged on the surface of the bracket 1, namely, an inner annular track 21 and an outer annular track 22, and a matching curved track A (partially shown in the figure) is also arranged on the top of the curved track 2; the shape of the curved track A and the curved track 2 is a mirror image up and down; through the matching of the curved track A and the curved track 2 and the inner annular track 21 and the outer annular track 22, a sliding path is provided for the chain clip mechanism 6, the chain clip mechanism 6 is clamped from top to bottom, and the chain clip mechanism is driven in cooperation with the active sprocket 3. During the synchronous stretching process, the fully preheated thick sheet realizes the synchronous longitudinal and transverse stretching of the film in the synchronous stretching section with the help of the expansion of the curved track 2 and the curved track A and the movement of the synchronous chain clip mechanism 6 to gradually increase the spacing.

[0051] By respectively arranging a driving sprocket 3 and a driven sprocket 4 at both ends of the curved track 2 and the curved track A, compared with the stretching machine used in industrial production, which needs to be equipped with two active driving sprockets at the entrance and the exit, the present application can achieve a compact mechanical layout, save equipment costs and space, and is suitable for environments with limited space to achieve the effect of a pilot test. The two drive motors 5 provide power for the entire stretching machine, provide a rotating force for the driving sprocket 3, and make the chain clip mechanism 6 contact the sprocket teeth on the driving sprocket 3, so that the chain clip mechanism 6 moves along the curved track.

[0052] It should be noted that the curved track 2 and the curved track A are optimized by precise geometry and kinematics calculations, and are precisely machined by a CNC machining center. The curves are strictly symmetrical up and down, and the machining errors and assembly errors are strictly controlled to ensure stable operation.

[0053] In an embodiment of the present invention, Figure 4 , Figure 5 and Figure 6 As shown, the chain clip mechanism 6 includes a clip head assembly 61, a clip body 62 and a chain link assembly 63;

[0054] A first cylindrical through hole 621 is provided at the center of the clip body 62, a front drive shaft 622 is inserted into the first through hole 621, and both ends of each front drive shaft 622 are provided with positioning bearings 623 slidably connected to the outer annular rail 22. A clip head assembly 61 is provided at the clamping end of the clip body 62, and a second through hole 624 passes through the connecting end of the clip body 62, a connecting shaft 625 is inserted into the second through hole 624, and the chain link assembly 63 is sleeved on the outside of the connecting shaft 625, and the chain link assembly 63 is slidably connected to the inner annular rail 21.

[0055] Specifically, the chain clip mechanism 6 includes a clip head assembly 61, a clip body 62 and a chain link assembly 63, wherein the cross section of the clip body 62 is an inverted H-shape, one end of which is connected to the clip head assembly 61 as a clamping end to clamp the fully preheated film, and the other end of which is clamped to the chain link assembly 63 as a connecting end, thereby contacting the driving sprocket 3 and moving on the curved track 2.

[0056] A circular first through hole 621 is opened at the center position of the clip body 62 from top to bottom. The first through hole 621 is used to insert a front drive shaft 622 with both ends extended outward, and positioning bearings 623 are fixedly connected to both ends of the front drive shaft 622, wherein the upper part of the positioning bearing 623 at the top moves along the concave track on the curved track A matching the outer annular track 22; the positioning bearing 623 at the bottom end is slidably installed in the concave track of the outer annular track 22 in the curved track 2, providing a moving route for the chain clip mechanism 6; a clip head assembly 61 is clamped at the center position of the clamping end of the clip body 62, and the clip head assembly 61 is hinged to the clamping end opening of the clip body 62 through a pin shaft or a positioning shaft, and the film can be clamped and released through the clip head assembly 61. The tail connection end of the clip body 62 passes through a second circular through hole 624, and a connecting shaft 625 is inserted into the second through hole 624. The longitudinal length of the connecting shaft 625 is the same as the longitudinal length of the clip body 62, so as to prevent the connecting shaft 625 from extending too long out of the clip body 62 and getting stuck in the curved track 2 and the curved track A. The outer sleeve of the connecting shaft 625 is provided with a chain link assembly 63, which is a chain link rolling type, and is ensured by precision machining, and has good interchangeability.

[0057] In an embodiment of the present invention, the clip head assembly 61 includes a clip handle 611 and a clip cover 612;

[0058] The clamp handle 611 is clamped at the clamping end of the clamp body 62 and is hinged to the clamp body 62 . The bottom end of the clamp handle 611 is connected to the clamp cover 612 . The clamp cover 612 fits the clamp body 62 and is used to clamp the film.

[0059] Specifically, Figure 4 As shown, the clamp handle 611 is clamped at one end of the inverted H-shaped clamp body 62 and is hinged by a pin or a positioning shaft, so that when the clamp handle 611 is pried, the clamp cover 612 and the clamp body 62 are separated and fitted, and the film edge can be clamped and released, and then the center distance between the two adjacent clamp bodies 62 becomes larger and separated, and the film is longitudinally stretched. The bottom end of the clamp cover 612 is also circular in shape. The circular clamping can be more evenly distributed on the film, reducing film damage or deformation caused by excessive local pressure.

[0060] In the embodiment of the present invention, the link assembly 63 includes a first chain plate 631 , a second chain plate 632 , a third chain plate 633 , a fourth chain plate 634 , a rear drive shaft 635 , and a rolling bearing 636 ;

[0061] One ends of the first chain plate 631, the second chain plate 632, the third chain plate 633 and the fourth chain plate 634 are sequentially sleeved on the connecting shaft 625, and the other ends of the first chain plate 631 and the third chain plate 633 are penetrated in the rear drive shaft 635 together with the second chain plate 632 and the fourth chain plate 634 in the previous adjacent chain link assembly 63, and the other ends of the second chain plate 632 and the fourth chain plate 634 are penetrated in the rear drive shaft 635 together with the first chain plate 631 and the third chain plate 633 in the next adjacent chain link assembly 63, and both ends of each rear drive shaft 635 are provided with rolling bearings 636 that are slidably connected to the inner annular rail 21.

[0062] Specifically, one end of the first chain plate 631, the second chain plate 632, the third chain plate 633 and the fourth chain plate 634 are sequentially sleeved on the connecting shaft 625, wherein the first chain plate 631 and the third chain plate 633 serve as a pair of chain links, and the second chain plate 632 and the fourth chain plate 634 serve as a pair of chain links. Figure 5 , Figure 6 As shown, the two pairs of chain links are realized from a close V-shape to a fully opened straight shape through the rear drive shaft 635. Due to the limiting effect of the positioning plate 64, the two pairs of chain links can be jointly opened or folded, thereby realizing that the center distance between the two adjacent chain clip mechanisms 6 is gradually increased, and the film is uniformly and equidistantly stretched longitudinally. Among them, the lengths of the first chain plate 631, the second chain plate 632, the third chain plate 633 and the fourth chain plate 634 are adjusted according to actual needs, and their lengths are determined by the longitudinal stretching multiples. The first chain plate 631, the second chain plate 632, the third chain plate 633 and the fourth chain plate 634 are made of 3mm thick steel plates, which are stamped and polished.

[0063] The other ends of a pair of chain links consisting of the first chain plate 631 and the third chain plate 633 are both inserted into the rear drive shaft 635 together with the second chain plate 632 and the fourth chain plate 634 in the previous adjacent chain link assembly 63, and the other ends of a pair of chain links consisting of the second chain plate 632 and the fourth chain plate 634 are both inserted into the next rear drive shaft 635 together with the first chain plate 631 and the third chain plate 633 in the next adjacent chain link assembly 63. When the two adjacent rear drive shafts 635 are gradually stretched due to the curve of the curved track 2, the two groups of chain links consisting of two chain plates are gradually opened, so that the center distance between the two clip bodies 62 becomes larger, and then the film on the front clip head assembly 61 is longitudinally stretched.

[0064] Both ends of each rear drive shaft 635 are provided with rolling bearings 636 that are slidably connected to the inner annular rail 21; wherein, the upper part of the rolling bearing 636 at the top slides along the concave rail on the curved track A that matches the inner annular rail 21, and the rolling bearing 636 at the top is also sleeved with a shaft sleeve, and contacts the edge sprocket of the driving sprocket 3 to provide power, and the rolling bearing 636 at the bottom is slidably installed in the concave rail of the inner annular rail 21 in the curved track 2, providing a moving route for the chain clip mechanism 6.

[0065] In an embodiment of the present invention, the chain clip mechanism 6 includes a positioning plate 64;

[0066] The positioning plate 64 is in the shape of an elongated strip, and is used to enable the chain link assembly 63 to move symmetrically along the central axis of the clip body. A first arc groove 641 and a second arc groove 642 are provided on the surface of the positioning plate 64. The lateral length of the first arc groove 641 is not less than the diameter of the front drive shaft 622, and the first arc groove 641 is used to pass the front drive shaft 622. The lateral length of the second arc groove 642 is not less than the diameter of the connecting shaft 625, and the second arc groove 642 is used to pass the connecting shaft 625.

[0067] Specifically, Figure 7 As shown, the surface of the positioning plate 64 is provided with a first arc groove 641 and a second arc groove 642. The first arc groove 641 is used to pass through the front drive shaft 622, so the transverse length of the first arc groove 641 is not less than the diameter of the front drive shaft 622; the second arc groove 642 is used to pass through the connecting shaft 625, so the transverse length of the second arc groove 642 is not less than the diameter of the connecting shaft 625, wherein the positioning plate 64 is fixed between the third chain plate 633 and the fourth chain plate 634 on the connecting shaft 625. Through the connection between the positioning plate 64 and the front drive shaft 622 and the connecting shaft 625, the longitudinal movement range of the two is limited, and then cooperates with the clip head assembly 61 and the chain link assembly 63 to achieve uniform synchronous stretching. The design of the positioning plate 64 can ensure that the two chain links coupled to it always move symmetrically along the central axis of the clip body 62; therefore, it is very suitable for applications with a small stretching ratio and requiring a precise stretching ratio, such as a stretching ratio ≤ 2 times, especially a stretching ratio ≤ 1.5 times; in this way, the present invention can overcome the problem of large stretching ratio errors of conventional industrial synchronous production stretching machines in small stretching ratio application scenarios.

[0068] In the embodiment of the present invention, the tracks on opposite sides of the two curved tracks 2 are divided into a preheating and stretching section 23 , a heat setting and cooling section 24 and a rotating section 25 .

[0069] The diameter and the number of teeth of the driven sprocket 4 of the preheating and stretching section are the same as those of the driving sprocket 3 .

[0070] Specifically, the tracks on the opposite sides of the two curved tracks 2 are divided into a preheating and stretching section 23, a heat setting and cooling section 24 and a rotating section 25, that is, the two curved tracks 2 present a mirror image mode, and the chain clip mechanism 6 in the preheating and stretching section 23 of the curved track 2 is in a tightened state, and the adjacent chain clip mechanisms 6 are close. As the chain clip mechanism 6 moves forward to the preheating and stretching section 23, the adjacent chain clip mechanisms 6 gradually separate to a nearly straight line, and while completing the longitudinal stretching, the lateral spacing between the two opposite chain clip mechanisms 6 in the mirror image state also gradually increases, completing the lateral stretching. Next, the chain clip mechanism 6 enters the heat setting and cooling section 24, keeping the spacing unchanged, and after heat setting the film, it passes through the rotating section 25, and the adjacent chain clip mechanisms 6 return to the driving sprocket 3 in an expanded state. After meshing with the chain teeth, the longitudinal spacing of the opposite chain clip mechanisms 6 gradually decreases to a tightened state, preparing for clamping the thick sheet after entering the preheating zone.

[0071] When the number of teeth of the driving sprocket 3 and the driven sprocket 4 is the same, the transmission ratio and the running speed can be kept constant, and the speed of the chain clip mechanism 6 can be accurately controlled.

[0072] The present invention also provides a stretching method of a pilot-scale synchronous stretching machine, such as Figure 8 As shown, the following steps are included:

[0073] Step 1, the driving motor 5 drives the driving sprocket 3 to rotate, thereby causing the chain clamp mechanism 6 to move along the curved track 2, and clamping the pre-processed thick sheet with a thickness of 50 μm to 600 μm through the chain clamp mechanism 6;

[0074] Specifically, the driving motor 5 drives the driving sprocket 3 to rotate. Since the driving sprocket 3 and the driven sprocket 4 are in contact with the chain clip mechanism 6, the chain clip mechanism 6 moves along the curved track 2 and the curved track A, so that the entire pilot-type synchronous stretching machine operates.

[0075] Step 2, the longitudinal length of the thick sheet before processing when clamped by the chain clip mechanism 6 is the center distance MD1 of the clamping points of the chain clip mechanism 6 when they are close together. Due to the movement of the chain clip mechanism 6 on the curved track 2, the longitudinal length of the thick sheet before processing is also stretched to MD2 along with the center distance of the clamping points of the chain clip mechanism 6; and due to the expansion of the two curved tracks 2, the transverse length of the thick sheet before processing is also stretched from TD1 to TD2 along with the chain clip mechanisms 6 at two opposite ends, so as to obtain a stretched film;

[0076] Specifically, at the front end of the preheating zone, the clip opener opens the clip handles 611 in the two adjacent chain clip mechanisms 6, so that the edge of the thick sheet before processing is clamped between the clip cover 612 and the clip body 62. At this time, the longitudinal unit length of the thick sheet before processing is MD1 when the two groups of chain links composed of the first chain plate 631 and the third chain plate 633, the second chain plate 632 and the fourth chain plate 634 in the chain clip mechanism 6 are arranged side by side. Due to the movement of the rear drive shaft 635 on the curved track 2, the two groups of chain links are fully unfolded, and the longitudinal unit length of the thick sheet before processing is also stretched to MD2 along with the clamping point center distance of the clip body 62; and due to the expansion of the two curved tracks 2, the lateral distance of the clip bodies 62 at both ends is gradually increased, stretching from TD1 to TD2, and a stretched film is obtained;

[0077] Step 3: The stretched film with a thickness of 2 μm to 200 μm will continue to be transported on the curved track 2 to be heat-set and cooled, thereby completing the synchronous stretching of the film.

[0078] In an embodiment of the present invention, Fig. 9 and Fig.10 As shown, when the chain clip mechanism 6 runs one circle, the change of the film side spacing and the change of the chain link pitch can be calculated: the longitudinal pull ratio of the stretched film is λ MD =MD2 / MD1, the transverse pull ratio of the stretched film is λ TD =TD2 / TD1; the transverse pull ratio and the longitudinal pull ratio can affect the strength, toughness and ductility of the material; by precisely controlling these two ratios, films with specific performance requirements can be manufactured to meet different needs.

[0079] In an embodiment of the present invention, the working parameters of the pilot synchronous stretching machine are: the maximum temperature of the preheating zone is 250°C; the maximum temperature of the stretching zone is 220°C; the maximum temperature of the heat setting zone is 260°C; the film width at the inlet, i.e., from the clip surface to the clip surface, is 200mm~800mm; the film width at the outlet is 1000mm~1800mm; the outlet speed is 5m / min~100m / min.

[0080] In an embodiment of the present invention, Fig.11 As shown, if the required longitudinal pull ratio is 3.4, in terms of chain clip design, the center distance MD1 of the clamping points of two adjacent clip bodies 62 is set to 20 mm, and the center distances of the first chain plate 631, the second chain plate 632, the third chain plate 633 and the fourth chain plate 634 are designed to be 34 mm;

[0081] In this embodiment, the size of the curved track 2 is as follows: Fig.12As shown, in the preheating and stretching section, from the preheating zone to the end of the stretching zone, the center track width gradually decreases from 34.47 mm to 3.64 mm, thereby forcing the spacing between adjacent clip bodies 62 to gradually increase from 20 mm to 68 mm at the end of the stretching zone, thereby fully matching the size of the chain clip mechanism 6, achieving smooth movement of the chain clip mechanism 6 in the curved track 2 and achieving the required stretching ratio; and in the meshing area between the driving sprocket 3 and the chain clip mechanism 6, the center track width gradually increases, forcing the adjacent chain clip mechanism 6 to tighten and enter the preheating zone.

[0082] The advantages of the present invention are that it fills the gap that the synchronous stretching instrument used in the laboratory can only perform intermittent stretching from sheet to sheet, and can realize continuous stretching from roll to roll in the laboratory; in the application scenario of a small stretching ratio of less than 2 (especially less than 1.5) in the longitudinal stretching ratio, accurate stretching ratio control is achieved.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A pilot-scale synchronous stretching machine, characterized in that: include: A bracket (1), a curved track (2), a driving sprocket (3), a driven sprocket (4), a driving motor (5) and a chain clip mechanism (6); The upper part of the bracket (1) is provided with two groups of mirror-inverted curved tracks (2), each of the curved tracks (2) comprises an inner annular track (21) and an outer annular track (22), the driving sprocket (3) is arranged on the inner side of one end of the curved track (2), the driven sprocket (4) is arranged on the inner side of the other end of the curved track (2), the driving sprocket (3) is transmission-connected to the driving motor (5), a plurality of chain clip mechanisms (6) are slidably connected to the curved track (2), and the driving sprocket (3) is used to drive the chain clip mechanism (6) to move.

2. The pilot-scale synchronous stretching machine according to claim 1, characterized in that: The chain clip mechanism (6) comprises a clip head assembly (61), a clip body (62) and a chain link assembly (63); A first cylindrical through hole (621) is provided at the center of the clip body (62), a front drive shaft (622) is inserted into the first through hole (621), and positioning bearings (623) for sliding connection with the outer annular rail (22) are provided at both ends of each front drive shaft (622). The clip head assembly (61) is provided at the clamping end of the clip body (62), and a second through hole (624) passes through the connecting end of the clip body (62), a connecting shaft (625) is inserted into the second through hole (624), and the chain link assembly (63) is sleeved on the outside of the connecting shaft (625), and the chain link assembly (63) is slidably connected to the inner annular rail (21).

3. The pilot-scale synchronous stretching machine according to claim 2, characterized in that: The clip head assembly (61) comprises a clip handle (611) and a clip cover (612); The clamp handle (611) is clamped at the clamping end of the clamp body (62) and is hinged to the clamp body (62). The bottom end of the clamp handle (611) is connected to the clamp cover (612). The clamp cover (612) fits the clamp body (62) and is used to clamp a film.

4. The pilot-scale synchronous stretching machine according to claim 2, characterized in that: The chain link assembly (63) includes a first chain plate (631), a second chain plate (632), a third chain plate (633), a fourth chain plate (634), a rear drive shaft (635) and a rolling bearing (636); One ends of the first chain plate (631), the second chain plate (632), the third chain plate (633) and the fourth chain plate (634) are sequentially sleeved on the connecting shaft (625); the other ends of the first chain plate (631) and the third chain plate (633) are both inserted into the rear drive shaft (635) together with the second chain plate (632) and the fourth chain plate (634) in the previous adjacent chain link assembly (63); the other ends of the second chain plate (632) and the fourth chain plate (634) are both inserted into the rear drive shaft (635) together with the first chain plate (631) and the third chain plate (633) in the next adjacent chain link assembly (63); and rolling bearings (636) slidably connected to the inner annular rail (21) are provided at both ends of each rear drive shaft (635).

5. The pilot-scale synchronous stretching machine according to claim 2, characterized in that: The chain clip mechanism (6) comprises a positioning plate (64); The positioning plate (64) is in the shape of an elongated strip and is used to enable the chain link assembly (63) to move symmetrically along the central axis of the clip body (62). A first arc-shaped groove (641) and a second arc-shaped groove (642) are provided on the surface of the positioning plate (64). The transverse length of the first arc-shaped groove (641) is not less than the diameter of the front drive shaft (622). The first arc-shaped groove (641) is used to pass through the front drive shaft (622). The transverse length of the second arc-shaped groove (642) is not less than the diameter of the connecting shaft (625). The second arc-shaped groove (642) is used to pass through the connecting shaft (625).

6. The pilot-scale synchronous stretching machine according to claim 1, characterized in that: The tracks on the opposite sides of the two curved tracks (2) are divided into a preheating and stretching section (23), a heat setting and cooling section (24) and a rotating section (25).

7. The pilot-scale synchronous stretching machine according to claim 1, characterized in that: The diameter and number of teeth of the driven sprocket (4) are the same as those of the driving sprocket (3).

8. A stretching method based on the pilot-scale synchronous stretching machine according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1, the driving motor (5) drives the driving sprocket (3) to rotate, thereby causing the chain clip mechanism (6) to move along the curved track (2), and clamping the pre-processed thick sheet with a thickness of 50 μm to 600 μm through the chain clip mechanism (6); Step 2, the longitudinal length of the thick sheet before processing when being clamped by the chain clip mechanism (6) is the center distance MD1 of the clamping points of the chain clip mechanism (6) when they are close together. Due to the movement of the chain clip mechanism (6) on the curved track (2), the longitudinal length of the thick sheet before processing is also stretched to MD2 along with the center distance of the clamping points of the chain clip mechanism (6); and due to the expansion of the two curved tracks (2), the transverse length of the thick sheet before processing is also stretched from TD1 to TD2 along with the chain clip mechanisms (6) at two opposite ends, thereby obtaining a stretched film; Step 3: The stretched film with a thickness of 2 μm to 200 μm will continue to be transported on the curved track (2) to be heat-set and cooled, thereby completing the synchronous stretching of the film.

9. The stretching method according to claim 8, characterized in that: The longitudinal pull ratio of the stretched film is λ MD =MD2 / MD1, the transverse pull ratio of the stretched film is λ TD =TD2 / TD1.

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