Distance-multiplying telescopic mechanism and control method thereof

Abstract

The invention relates to the technical field of operation and transportation, in particular to a multiple-distance telescopic mechanism and a control method thereof.The multiple-distance telescopic mechanism comprises a telescopic arm, and the telescopic arm is composed of a first telescopic square pipe, a second telescopic square pipe and a third telescopic square pipe; the first telescopic square pipe, the second telescopic square pipe and the third telescopic square pipe are sequentially arranged in a stacked mode from top to bottom, and guide assemblies are connected among the first telescopic square pipe, the second telescopic square pipe and the third telescopic square pipe. A synchronous belt driving assembly driving the first telescopic square pipe and the second telescopic square pipe to stretch out and draw back is connected to one side of the first telescopic square pipe and the second telescopic square pipe. Clamping assemblies used for adjusting the rotating output rate of the synchronous belt driving assembly are further arranged between the first telescopic square pipe and the second telescopic square pipe and between the second telescopic square pipe and the third telescopic square pipe, and the telescopic arm is driven by the synchronous belt driving assembly to stretch or retract in the sliding direction of the guide assembly. The multiple-distance telescopic mechanism can provide a longer conveying distance and a smaller space proportion, so that the transportation efficiency of the tray is improved.

Description

Technical Field

[0001] The invention relates to the technical field of operation and transportation, and in particular to a multiple-distance telescopic mechanism and a control method thereof. Background Art

[0002] With the rapid development of e-commerce and modern logistics, pallets, as the basic carrier of cargo transportation, have a direct impact on the cost and efficiency of the overall supply chain with their loading, unloading, storage and distribution efficiency. Therefore, the existing pallet production line system is usually equipped with multiple production lines to carry out a series of automated operations such as loading, unloading, storage and distribution of pallets. In order to coordinate and connect multiple production lines, a telescopic translation mechanism is usually used to complete the transfer of pallets, which means that the space required to place the production line during production is relatively large.

[0003] Moreover, the telescopic translation mechanism in the prior art can generally extend a stroke that is about 0.6 to 0.7 times the length of the telescopic translation mechanism's body. If a telescopic translation mechanism with a longer telescopic stroke is required, its body will occupy more space and the transmission speed will be slower, which not only affects the layout of the on-site space, but also affects production efficiency. Summary of the invention

[0004] In order to solve the technical defects raised in the above-mentioned background technology, the purpose of the present invention is to provide a double-distance telescopic mechanism, aiming to provide a longer conveying distance and less space occupation, thereby effectively improving the transportation efficiency.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: A double-distance telescopic mechanism comprises a telescopic arm, which is composed of a first telescopic square tube, a second telescopic square tube and a third telescopic square tube; the first telescopic square tube, the second telescopic square tube and the third telescopic square tube are stacked in sequence from top to bottom, and a guide assembly is connected between the first telescopic square tube, the second telescopic square tube and the third telescopic square tube; a synchronous belt drive assembly for driving the first telescopic square tube and the second telescopic square tube to extend and retract is connected to one side of the first telescopic square tube and the second telescopic square tube; a clamping assembly for adjusting the rotational output rate of the synchronous belt drive assembly is also arranged between the first telescopic square tube and the second telescopic square tube and between the second telescopic square tube and the third telescopic square tube, and the telescopic arm is folded and contracted or extended and stretched along the sliding direction of the guide assembly under the driving action of the synchronous belt drive assembly.

[0006] Preferably, the guide assembly includes a linear guide rail, a slider and a guide plate, the linear guide rail is respectively arranged at the bottom ends of the first telescopic square tube and the second telescopic square tube; the slider is slidably connected to the linear guide rail, the guide plate is fixedly connected to the slider, and one side of the guide plate is respectively connected to the second telescopic square tube and the third telescopic square tube.

[0007] Preferably, the synchronous belt drive assembly includes a synchronous wheel, a synchronous belt and a drive motor, the synchronous wheel consists of a driving wheel and a driven wheel, and there are multiple driving wheels and driven wheels, and the multiple driving wheels are transmission connected by chains and sprockets; the driven wheels are respectively arranged at both ends of the first telescopic square tube and the second telescopic square tube, and the driven wheel and the driving wheel are rotationally connected by a synchronous belt; the output end of the drive motor is transmission connected to the driving wheel.

[0008] Preferably, a protective cover is further provided on the outer sides of the driving wheel and the driven wheel, and the protective cover is fixedly connected to the first telescopic square tube.

[0009] Preferably, the clamping assembly includes a clamping seat, a telescopic flat pressure plate and a telescopic tooth pressure plate, one end of the clamping seat is fixed on the telescopic arm, and the other end is connected to the synchronous belt; one end of the telescopic flat pressure plate is connected to a rotating shaft, and the telescopic flat pressure plate is rotatably connected to both sides of the clamping seat through the rotating shaft; the telescopic tooth pressure plate is fixed on the telescopic flat pressure plate, and a gap for clamping the synchronous belt is retained between the telescopic tooth pressure plate and the telescopic flat pressure plate.

[0010] Preferably, a plurality of pressing teeth are densely distributed on one side of the telescopic tooth pressure plate facing the telescopic flat pressure plate, and the plurality of pressing teeth are respectively in contact with two sides of the synchronous belt to clamp and fix the two ends of the synchronous belt.

[0011] Preferably, the first telescopic square tube is also provided with an anti-collision seat for preventing the clamping assembly from colliding during transfer. The anti-collision seat is fixed at both ends of the first telescopic square tube, and a buffer rubber pad is connected to the anti-collision seat.

[0012] A control method for a multiple-distance telescopic mechanism comprises the following steps: a. Initial state: After the pallet arrives at the designated station, the controller detects the in-position signal and prepares to start the telescopic mechanism to grab the pallet; b. Extension process: The driving motor drives the driving wheel to rotate clockwise, and transmits the power to the driven wheel through the synchronous belt, and at the same time transmits the power to each telescopic square tube through the synchronous belt. During the synchronous driving process, the clamping assembly will be driven to move to the left, so that the second telescopic square tube and the third telescopic square tube slide forward along the length direction of the first telescopic square tube; c. Grabbing and transporting: When the third telescopic square tube is fully extended and the clamping assembly reaches the maximum extension state, the moving distance of the third telescopic square tube is exactly three times the moving distance of the clamping assembly. The second telescopic square tube and the third telescopic square tube stop sliding, and the pallet is grabbed by the grabbing mechanism set on the third telescopic square tube; d. Recovery stage: After the grabbing is completed, the synchronous belt drive assembly and the clamping assembly are operated in reverse to gradually retract the second telescopic square tube and the third telescopic square tube to their original positions to complete the transfer of the pallet; e. Cycle repetition: Repeat the above stretching and recovery process continuously to achieve continuous conveying of pallets.

[0013] In summary, the beneficial effects of the present invention are: The present invention arranges guide components on the first telescopic square tube, the second telescopic square tube and the third telescopic square tube for cooperative sliding, so that the sliding process is smoother and faster; at the same time, a synchronous belt driving component and a clamping component are arranged to drive the second telescopic square tube and the third telescopic square tube to slide and extend outward, thereby realizing rapid transfer of the pallet; in addition, by setting the pitch circle ratio of the synchronous wheel to 1:1, the moving distance of the third telescopic square tube is three times the moving distance of the clamping component, that is, when the telescopic arm is unfolded, its maximum outward extending transport stroke can reach about three times, thereby realizing long-distance transportation and effectively improving transportation efficiency; and when stored, the second telescopic square tube and the third telescopic square tube only occupy the area occupied by the first telescopic square tube, and the storage space is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the double-distance telescopic mechanism of the present invention in a folded state; Figure 2 It is a structural schematic diagram of the double-distance telescopic mechanism of the present invention in an expanded state; Figure 3 yes Figure 2 A magnified view of the structure at a in the middle; Figure 4 It is a structural schematic diagram of the clamping assembly in the present invention.

[0015] 1. First telescopic square tube; 2. Second telescopic square tube; 3. Third telescopic square tube; 4. Guide assembly; 41. Linear guide rail; 42. Slider; 43. Guide plate; 5. Synchronous belt drive assembly; 51. Synchronous wheel; 511. Driving wheel; 512. Driven wheel; 52. Synchronous belt; 53. Drive motor; 6. Clamping assembly; 61. Clamping seat; 62. Telescopic flat pressure plate; 63. Telescopic tooth pressure plate; 631. Pressure tooth; 7. Protective cover; 8. Anti-collision seat; 9. Buffer rubber pad. DETAILED DESCRIPTION

[0016] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0017] Those skilled in the art should understand that, in the disclosure of the present invention, the orientation or position relationship indicated by the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc. are based on the orientation or position relationship shown in the drawings, which 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 orientation, be constructed and operate in a specific orientation. Therefore, the above terms should not be understood as limiting the present invention.

[0018] In addition, the terms "installed", "set", "provided with", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0019] In the description of the present invention, if there are words such as "several", it means one or more, "more" means two or more, "greater than", "less than", "exceed" etc. are understood as not including the number itself, and "above", "below", "within" etc. are understood as including the number itself. If there are descriptions of first, second, and third, they are only used to distinguish technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0020] The following is combined with Figure 1-4 , an embodiment of a double-distance telescopic mechanism of the present invention is further described in detail.

[0021] Embodiment 1 A multiple-distance telescopic mechanism, such as Figure 1 , 2 As shown, it includes a telescopic arm, which consists of a first telescopic square tube 1, a second telescopic square tube 2 and a third telescopic square tube 3; the first telescopic square tube 1, the second telescopic square tube 2 and the third telescopic square tube 3 are stacked in sequence from top to bottom, and a guide component 4 is connected between the first telescopic square tube 1, the second telescopic square tube 2 and the third telescopic square tube 3; a synchronous belt 52 driving component 5 for driving the telescopic and retracting thereof is connected to one side of the first telescopic square tube 1 and the second telescopic square tube 2; a clamping component 6 for adjusting the rotation rate of the synchronous belt 52 driving component 5 is also provided between the first telescopic square tube 1 and the second telescopic square tube 2 and between the second telescopic square tube 2 and the third telescopic square tube 3, and the telescopic arm is folded and contracted or extended and stretched along the sliding direction of the guide component 4 under the driving action of the synchronous belt 52 driving component 5.

[0022] Specifically, the synchronous belt 52 driving assembly 5 includes a synchronous wheel 51, a synchronous belt 52 and a driving motor 53. The synchronous wheel 51 is composed of a driving wheel 511 and a driven wheel 512, and there are multiple driving wheels 511 and driven wheels 512. The multiple driving wheels 511 are connected to each other through a chain sprocket; the driven wheels 512 are respectively arranged at both ends of the first telescopic square tube 1 and the second telescopic square tube 2, and the driven wheels 512 are connected to the driving wheels 511 through a synchronous belt 52; the output end of the driving motor 53 is connected to the driving wheel 511 through transmission. Figure 1 When the telescopic arm is in the initial state of contraction, the first telescopic square tube 1 can be fixed on the external machine, and the chain sprockets on the first telescopic square tube 1 are respectively mounted on the driving wheel 511 and the driven wheel 512, that is, the driving motor 53 synchronously drives the driving wheel 511 and the driven wheel 512 to rotate; and the driven wheel 512 on the second telescopic square tube 2 is connected to the driven wheel 512 on the first telescopic square tube 1 through the synchronous belt 52, so that when the driving wheel 511 rotates, the synchronous wheel 51 on the entire first telescopic square tube 1 and the second telescopic square tube 2 is driven to rotate, thereby realizing that the first telescopic square tube 1 drives the second telescopic square tube 2 to slide and retract, and the second telescopic square tube 2 drives the third telescopic square tube 3 to slide and retract, thereby completing the recovery of the telescopic arm.

[0023] refer to Figure 2 When the telescopic arm is in the unfolded state, the driving motor 53 starts to rotate clockwise to drive the synchronous wheel 51 to rotate, and transmits it to each telescopic square tube through the synchronous belt 52. At the same time, the clamping assembly 6 is driven to move leftward during the transmission process of the synchronous belt 52, so that the second telescopic square tube 2 and the third telescopic square tube 3 move leftward. At this time, the second telescopic square tube 2 moves forward a distance relative to the first telescopic square tube 1. Since the pitch circles of the driving wheel 511 and the driven wheel 512 of the sprocket chain are the same, the second telescopic square tube 2 and the third telescopic square tube 3 move to the left by the same distance. Therefore, the third telescopic square tube 3 also moves forward a distance relative to the second telescopic square tube 2. At this time, the third telescopic square tube 3 moves forward two distances relative to the first telescopic square tube 1; thus, the extension of the telescopic arm is completed. When the servo motor rotates counterclockwise, the synchronous belt 52 on the first telescopic square tube 1 and the synchronous belt 52 on the second telescopic square tube 2 are simultaneously driven in the opposite direction, so that the clamping assembly 6 moves rightward, and the telescopic arm finally returns to the initial position.

[0024] Among them, when the pitch circle of the driving wheel 511 and the driven wheel 512 is 1:1, relative to the first telescopic square tube 1, the moving distance of the third telescopic square tube 3 is three times the moving distance of the clamping assembly 6, which means that when the telescopic arm is unfolded and working, its maximum outward telescopic transport stroke can reach about three times that of the machine, thereby realizing long-distance transportation and occupying less space, effectively improving transportation efficiency.

[0025] In this embodiment, if Figure 3As shown, the guide assembly 4 includes a linear guide rail 41, a slider 42 and a guide plate 43, wherein the linear guide rail 41 is respectively arranged at the bottom ends of the first telescopic square tube 1 and the second telescopic square tube 2; the slider 42 is slidably connected to the linear guide rail, the guide plate 43 is fixedly connected to the slider 42, and one side of the guide plate 43 is respectively connected to the second telescopic square tube 2 and the third telescopic square tube 3.

[0026] Specifically, the linear guide 41 is arranged in parallel on the first telescopic square tube 1 and the second telescopic square tube 2, so that the second telescopic square tube 2 and the third telescopic square tube 3 can slide through the slider 42 installed on the linear guide 41, so that when the drive motor 53 rotates, the synchronous wheel 51 rotates and drives the synchronous belt 52 to move, thereby driving the second telescopic square tube 2 and the third telescopic square tube 3 to perform reciprocating motion along the linear guide 41, so that the telescopic arm can stably perform telescopic work.

[0027] In order to prevent dust or impurities from entering the synchronous wheel 51 and affecting its transmission efficiency, a protective cover 7 is further provided on the outer side of the driving wheel 511 and the driven wheel 512, and the protective cover 7 is fixedly connected to the first telescopic square tube 1; the protective cover 7 can effectively prevent the entry of dust. At the same time, the first telescopic square tube 1 is also provided with an anti-collision seat 8 for preventing the clamping assembly 6 from colliding during the transfer, and the anti-collision seat 8 is fixed at both ends of the first telescopic square tube 1, and a buffer rubber pad 9 is connected to the anti-collision seat 8.

[0028] In this embodiment, if Figure 4 As shown, the clamping assembly 6 includes a clamping seat 61, a telescopic flat pressure plate 62 and a telescopic toothed pressure plate 63. One end of the clamping seat 61 is fixed on the telescopic arm, and the other end is connected to the synchronous belt 52. One end of the telescopic flat pressure plate 62 is connected to a rotating shaft, and the telescopic flat pressure plate 62 is rotatably connected to both sides of the clamping seat 61 through the rotating shaft. The telescopic toothed pressure plate 63 is fixed on the telescopic flat pressure plate 62, and a gap for clamping the synchronous belt 52 is reserved between the telescopic toothed pressure plate 63 and the telescopic flat pressure plate 62.

[0029] Specifically, the clamping assembly 6 can drive the synchronous belt 52 transmission assembly to move along the first telescopic square tube 1 or the second telescopic square tube 2 when the synchronous belt 52 transmission assembly rotates, so that the second telescopic square tube 2 and the third telescopic square tube 3 slide relative to the first telescopic square tube 1; and a plurality of pressing teeth 631 are densely distributed on the side of the telescopic tooth pressure plate 63 facing the telescopic flat pressure plate 62, and the plurality of pressing teeth 631 are respectively abutted against both sides of the synchronous belt 52 to clamp and fix the two ends of the synchronous belt 52. The pressing teeth 631 can be used to adjust the tightness of the synchronous belt 52 according to production needs, thereby adjusting the telescopic distance of the telescopic arm.

[0030] Embodiment 2 On the basis of the first embodiment, this embodiment provides a control method of a telescopic mechanism, comprising the following steps: a. Initial state: After the pallet arrives at the designated station, the controller detects the in-position signal and prepares to start the telescopic mechanism to grab the pallet; b. Extension process: the driving motor 53 drives the driving wheel 511 to rotate clockwise, and transmits the power to the driven wheel 512 through the synchronous belt 52, and at the same time transmits the power to each telescopic square tube through the synchronous belt 52. During the movement of the synchronous belt 52, the clamping assembly 6 is driven to move to the left, so that the second telescopic square tube 2 and the third telescopic square tube 3 slide forward along the length direction of the first telescopic square tube 1; c. Grabbing and transporting: When the third telescopic square tube 3 is fully extended, the clamping assembly 6 reaches the maximum extension state. At this time, the moving distance of the third telescopic square tube 3 is exactly three times the moving distance of the clamping assembly 6. The second telescopic square tube 2 and the third telescopic square tube 3 stop sliding, and the pallet is grabbed by the grabbing mechanism arranged on the third telescopic square tube 3; d. Recovery stage: After the grabbing is completed, the synchronous belt 52 drives the assembly 5 and the clamping assembly 6 in the reverse direction, so that the second telescopic square tube 2 and the third telescopic square tube 3 are gradually retracted to their original positions to complete the transfer of the pallet; e. Cycle repetition: Repeat the above extension and recovery process continuously to achieve continuous conveying of pallets.

[0031] Specifically, when the telescopic arm changes from a contracted state to an extended state, the driving motor 53 is controlled to rotate clockwise, and the synchronous wheel 51 is driven to rotate under the action of the driving motor 53, and at the same time, it is transmitted to each telescopic square tube through the synchronous belt 52. During the transmission process of the synchronous belt 52, the clamping assembly 6 will be driven to move leftward, thereby causing the second telescopic square tube 2 and the third telescopic square tube 3 to move leftward. At this time, the second telescopic square tube 2 has advanced a certain distance relative to the first telescopic square tube 1, and since the pitch circles of the driving wheel 511 and the driven wheel 512 of the sprocket chain are the same, the second telescopic square tube 2 and the third telescopic square tube 3 move to the left at the same distance, so the third telescopic square tube 3 has also advanced a certain distance relative to the second telescopic square tube 2. At this time, the third telescopic square tube 3 has advanced two distances relative to the first telescopic square tube 1; thereby completing the extension of the telescopic arm. When the servo motor rotates counterclockwise, the synchronous belt 52 on the first telescopic square tube 1 and the synchronous belt 52 on the second telescopic square tube 2 are simultaneously driven in the opposite direction, so that the clamping assembly 6 moves rightward, thereby driving the telescopic arm to finally return to the initial position.

[0032] The embodiments of this specific implementation are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. The same components are represented by the same figure marks. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A telescopic mechanism, comprising a telescopic arm, characterized in that: The telescopic arm consists of a first telescopic square tube, a second telescopic square tube and a third telescopic square tube; the first telescopic square tube, the second telescopic square tube and the third telescopic square tube are stacked in sequence from top to bottom, and a guide assembly is connected between the first telescopic square tube, the second telescopic square tube and the third telescopic square tube; a synchronous belt drive assembly for driving the first telescopic square tube and the second telescopic square tube to extend and retract is connected to one side of the first telescopic square tube and the second telescopic square tube; a clamping assembly for adjusting the rotation rate of the synchronous belt drive assembly is also arranged between the first telescopic square tube and the second telescopic square tube and between the second telescopic square tube and the third telescopic square tube, and the telescopic arm is folded and contracted or extended and stretched along the sliding direction of the guide assembly under the driving action of the synchronous belt drive assembly.

2. The telescopic mechanism according to claim 1, characterized in that: The guide assembly includes a linear guide rail, a slider and a guide plate. The linear guide rail is respectively arranged at the bottom ends of the first telescopic square tube and the second telescopic square tube; the slider is slidably connected to the linear guide rail, the guide plate is fixedly connected to the slider, and one side of the guide plate is respectively connected to the second telescopic square tube and the third telescopic square tube.

3. The telescopic mechanism according to claim 1, characterized in that: The synchronous belt drive assembly includes a synchronous wheel, a synchronous belt and a driving motor. The synchronous wheel is composed of a driving wheel and a driven wheel, and there are multiple driving wheels and driven wheels. The multiple driving wheels are transmission connected by chains and sprockets; the driven wheels are respectively arranged at both ends of the first telescopic square tube and the second telescopic square tube, and the driven wheel and the driving wheel are rotationally connected by a synchronous belt; the output end of the driving motor is transmission connected to the driving wheel.

4. The telescopic mechanism according to claim 3, characterized in that: A protective cover is also provided on the outer sides of the driving wheel and the driven wheel, and the protective cover is fixedly connected to the first telescopic square tube.

5. The telescopic mechanism according to claim 1, characterized in that: The clamping assembly includes a clamping seat, a telescopic flat pressure plate and a telescopic toothed pressure plate. One end of the clamping seat is fixed on the telescopic arm, and the other end is connected to the synchronous belt. One end of the telescopic flat pressure plate is connected to a rotating shaft, and the telescopic flat pressure plate is rotatably connected to both sides of the clamping seat through the rotating shaft. The telescopic toothed pressure plate is fixed on the telescopic flat pressure plate, and a gap for clamping the synchronous belt is reserved between the telescopic toothed pressure plate and the telescopic flat pressure plate.

6. The telescopic mechanism according to claim 1, characterized in that: A plurality of pressing teeth are densely distributed on one side of the telescopic tooth pressure plate facing the telescopic flat pressure plate, and the plurality of pressing teeth are respectively in contact with two sides of the synchronous belt to clamp and fix the two ends of the synchronous belt.

7. The telescopic mechanism according to claim 1, characterized in that: The first telescopic square tube is also provided with an anti-collision seat for preventing the clamping assembly from colliding during transfer. The anti-collision seat is fixed at both ends of the first telescopic square tube, and a buffer rubber pad is connected to the anti-collision seat.

8. A control method using the telescopic mechanism according to any one of claims 1 to 7, characterized in that: The following steps are involved: a. Initial state: After the pallet arrives at the designated station, the controller detects the in-position signal and prepares to start the telescopic mechanism to grab the pallet; b. Extension process: The driving motor drives the driving wheel to rotate clockwise, and transmits the power to the driven wheel through the synchronous belt, and at the same time transmits the power to each telescopic square tube through the synchronous belt. During the synchronous driving process, the clamping assembly will be driven to move to the left, so that the second telescopic square tube and the third telescopic square tube slide forward along the length direction of the first telescopic square tube; c. Grabbing and transporting: When the third telescopic square tube is fully extended and the clamping assembly reaches the maximum extension state, the moving distance of the third telescopic square tube is exactly three times the moving distance of the clamping assembly. The second telescopic square tube and the third telescopic square tube stop sliding, and the pallet is grabbed by the grabbing mechanism set on the third telescopic square tube; d. Recovery stage: After the grabbing is completed, the synchronous belt drive assembly and the clamping assembly are operated in reverse to gradually retract the second telescopic square tube and the third telescopic square tube to their original positions to complete the transfer of the pallet; e. Cycle repetition: Repeat the above stretching and recovery process continuously to achieve continuous conveying of pallets.

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