Elastic strip feeding process and device thereof

Abstract

The invention discloses an elastic strip feeding technology and device, the device comprises a material frame, a dynamic storage unit and a deviation rectifying unit, the elastic strip is folded and flatly laid on a conveying belt through the dynamic storage unit to release tension, the conveying belt drives the elastic strip to be conveyed in the flow direction, and the deviation rectifying unit is used for rectifying deviation of the elastic strip. The sensor detects the position of the elastic strip on the conveying belt in real time and controls the speed of the conveying belt to be matched with the discharging speed, it is guaranteed that the tension of the elastic strip on the conveying belt can be fully released, then the elastic strip is output in a tension-free state, the defects that the thighs, the shanks and linings are curled due to unstable tension in the follow-up machining process of materials are overcome, and the production efficiency is improved. The method can be widely applied to the processing fields of sanitary products, clothes and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of flexible material processing, and particularly to a feeding process for an elastic flexible strip and a corresponding device. Background Art

[0002] In the processing of disposable underwear, the elastic strip needs to release tension before lamination so that it can be laminated with another material in a state close to zero tension. Since the elasticities of the two materials are different, if the tension is not fully released, it is very easy to cause shrinkage and curling deformation after lamination. Therefore, during the unwinding and feeding process of the elastic strip, a series of devices and methods are required to release the tension of the elastic strip to ensure that it will not shrink and deform due to tension after lamination.

[0003] To solve this problem, Chinese Patent Application No. CN202410461382.1 discloses a method, system and short pants processing method for non-tension lamination of elastic strips. This method unwinds an elastic material roll by configuring a feeding mechanism; multiple tension rollers are arranged in the transmission path of the elastic strip for support, and a tension control component is used to control the tension of the elastic strip in a hierarchical manner; the control component is configured to include a traction roller group and a tension controller. The traction roller group adjusts the transmission speed of the elastic strip according to the detected tension signal, so that the tension of the elastic strip in its transmission section tends to be in a non-tension state and is laminated with a non-elastic sheet without tension.

[0004] However, adopting the above method, since the elastic material roll often has tension when it is wound, during the transmission process, the tension value collected by the signal unit is unstable, which easily causes the tension control component to be unable to collect data and respond in real time, affecting the product qualification rate. If the tension is not fully released, after passing through the lamination unit subsequently, it will cause wrinkles to appear after the lining and the elastic strip are laminated; defects such as thighs and calves will appear after arc cutting. Therefore, it is necessary to improve the existing process equipment to further ensure that the material tension is fully released, thereby improving the product qualification rate. Summary of the Invention

[0005] The purpose of the present invention is to provide a feeding process and device for an elastic strip, which solve the problem that the existing feeding equipment and method cannot fully release the tension of the elastic strip.

[0006] The technical solution adopted by the present invention to solve its technical problems is as follows: A feeding process for an elastic strip is used to fully release the tension of the elastic strip from an elastic coil and output it in a tension-free state. This process sets a dynamic storage unit on the traveling path of the elastic strip, and uses the dynamic storage unit to transport the elastic strip and complete the tension release of the elastic strip; the dynamic storage unit includes a second dynamic storage unit, and the second dynamic storage unit includes a conveyor belt. The elastic strip enters the conveyor belt vertically from the upstream side. While the elastic strip enters, the moving speed of the conveyor belt is controlled so that the elastic strip is laid on the conveyor belt in a tension-free state.

[0007] Further, the dynamic storage unit includes a first dynamic storage unit and a second dynamic storage unit. The first dynamic storage unit is arranged on the upstream side of the second dynamic storage unit; the elastic strip from the elastic coil is received by the first dynamic storage unit and the elastic strip is reciprocally transported on the first dynamic storage unit to achieve a primary tension release of the elastic strip. The elastic strip after the primary tension release enters the second dynamic storage unit vertically for a secondary tension release.

[0008] To control the conveying speed of the conveyor belt and ensure full release of the secondary tension, the second dynamic storage unit further includes sensors. At least two sensors are provided. By detecting the extreme motion states of the elastic strip near the conveyor belt outlet and a preset lifting point, the speed of the conveyor belt is adjusted to match the traction speeds of the upstream and downstream.

[0009] Specifically, the first dynamic storage unit includes a set of top guide rollers and a set of bottom guide rollers, and the elastic strip shuttles back and forth between the top guide rollers and the bottom guide rollers; a driving roller is arranged at the feeding end of the second dynamic storage unit, and the driving roller is located above the conveyor belt. The driving roller drives the elastic strip of the first dynamic storage unit to move forward, and the elastic strip enters the conveyor belt in a free-falling manner after passing through the driving roller.

[0010] To fully release the tension of the elastic strip, the elastic strip is folded and laid flat on the conveyor belt.

[0011] The feeding device for the elastic strip of the present invention includes: a material rack for supporting an elastic strip coil; a first dynamic storage unit for receiving the elastic strip from the elastic coil and performing a primary tension release; a second dynamic storage unit for receiving the elastic strip from the first dynamic storage unit and performing a secondary tension release; the second dynamic storage unit includes a conveyor belt for placing the elastic strip and driving the elastic strip to move forward. The elastic strip enters the conveyor belt from top to bottom and is laid on the conveyor belt in a tension-free state; a deviation correction unit is arranged on the downstream side of the second dynamic storage unit for controlling and adjusting the traveling direction of the elastic strip.

[0012] To further form a folded and flattened state of the elastic strip on the conveyor belt, a swinging mechanism that swings back and forth in the horizontal direction is provided between the conveyor belt and the driving roller. The swinging mechanism acts on the elastic strip to drive the freely falling elastic strip to deflect in the horizontal direction, so that the elastic strip forms a folded and flattened state after falling onto the conveyor belt.

[0013] Advantages of the present invention: The conveyor belt on the second dynamic storage unit drives the elastic strip to be conveyed forward in the present invention, so that the elastic strip can fully release the tension on the conveyor belt, and the speed of the conveyor belt is controlled by the sensor to match the discharging speed, so as to ensure that the elastic strip is output in a tension-free state after the tension on the conveyor belt is fully released, avoiding defects such as thigh and calf curling and inner lining curling caused by unstable tension in the subsequent processing of the material, and improving the processing qualification rate of the product. To shorten the length of the conveyor belt, the present invention also adopts the cooperation of the first dynamic storage unit and the second dynamic storage unit. First, the elastic strip is subjected to a primary tension release through the first dynamic storage unit, and then the elastic strip is subjected to a secondary tension release through the second dynamic storage unit, so that the tension of the elastic strip can be fully released after being output from the material roll. In the second dynamic storage unit, the elastic strip enters the conveyor belt in a freely falling manner and there is no other additional traction force when entering the conveyor belt. Therefore, it will not cause an increase in the tension of the elastic strip on the conveyor belt. At the same time, the free fall helps to release the tension of the elastic strip. A deviation correction area is provided on the conveyor belt, which can give a certain stabilizing force to the elastic strip to avoid excessive left and right deviation of the elastic strip during the conveying process, affecting the subsequent processing. At the same time, a deviation correction unit is provided downstream of the conveyor belt for further deviation correction, so as to ensure the accuracy of the conveying direction of the elastic strip.

[0014] The present invention will be described in more detail below with reference to the drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention.

[0016] Figure 2 It is a three-dimensional structural diagram of the second dynamic storage unit in the present invention.

[0017] Figure 3 It is a schematic diagram of the elastic strip discharging when the conveyor belt speed is fast in the present invention.

[0018] Figure 4 It is a schematic diagram of the elastic strip discharging when the conveyor belt speed is slow in the present invention.

[0019] Figure 5 It is a schematic structural diagram of Embodiment 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] Embodiment 1: AsFigures 1 to 4 As shown, a feeding process and device for an elastic strip. Through the improvement of the feeding process and the innovation of the device of the present invention, the tension of the elastic sheet on the material roll can be fully released, thereby avoiding the defects such as wrinkles and thigh and calf problems after arc cutting when the non-elastic sheet and the elastic sheet of the disposable sanitary product prepared are compounded due to the insufficient release of the stress of the elastic strip before compounding.

[0021] The process method of the present invention includes receiving the elastic strip 10 from the elastic material roll 401 through the second dynamic storage unit 200 and releasing the tension of the elastic strip 10. After the tension of the elastic strip is released, it is output after being adjusted by the deviation rectifying unit 300 and then compounded with other sheets. The corresponding feeding device for the elastic strip includes a material rack 400 for supporting the elastic material roll and a second dynamic storage unit 200 arranged behind the material rack 400, and a deviation rectifying unit 300 arranged behind the second dynamic storage unit 200.

[0022] The concept of the present invention will be specifically described below through the structure and the corresponding method.

[0023] The elastic strip is wound and stored on the elastic material roll 401. When in use, the elastic material roll 401 is mounted on the material rack 400 and unrolled through the material rack 400. The elastic strip 10 enters the second dynamic storage unit 200 in the horizontal direction after being unrolled from the elastic material roll 401, and the tension is fully released on the second dynamic storage unit 200. The second dynamic storage unit 200 includes a driving roller 201 that applies a traction force to the elastic strip 10 output from the elastic material roll 401, and a conveyor belt 202 for placing the elastic strip 10 and driving the elastic strip 10 to be conveyed forward.

[0024] Under the action of the driving roller 201, the elastic strip 10 output from the elastic coil 401 enters the driving roller 201 at a speed V1. The conveyor belt 202 is located below the driving roller 201. After the elastic strip 10 passes through the driving roller 201, it falls onto the conveyor belt 202 in a vertically free-falling manner. The free-falling manner enables the elastic strip 10 to have no traction force, and the elastic strip 10 can continue to release stress during the falling process. During the falling process of the elastic strip 10, the conveyor belt 202 moves slowly forward, so that the elastic strip 10 is laid flat on the conveyor belt 202 in a tension-free state, and the tension is fully released. The tension-free conveyance of the elastic strip 10 here means that the elastic strip 10 does not deform due to external force stretching in both the length direction and the width direction, but is conveyed under the traction of the conveyor belt while maintaining a basically non-stretched state. During this process, the self-tension of the elastic strip 10 can be fully released. The length and speed of the conveyor belt 10 can be set according to the time required for the stress release of the elastic strip 10. Under the condition of meeting high-speed conveyance, the length of the conveyor belt 10 can be extended to obtain sufficient stress release time.

[0025] The conveyor belt 202 is a rotary conveyor belt and is driven by a driving mechanism. To ensure that the discharge amount of the elastic strip 10 on the conveyor belt 202 matches the downstream driving traction speed V3 and to avoid a change in the tension of the elastic strip 10 when it leaves the conveyor belt 202, a sensor 203 for sensing the moving position of the elastic strip 10 on the conveyor belt 202 is provided on the downstream side of the conveyor belt 202. The sensor 203 is a photoelectric sensor. By detecting the extreme motion state of the elastic strip near the outlet of the conveyor belt 202 and the preset lifting point, the speed of the conveyor belt is adjusted to match the upstream and downstream traction speeds. The upstream traction speed of the conveyor belt 202 refers to the speed V1 obtained through the driving roller 201.

[0026] Specifically, two sensors 203 are provided, which are respectively located on the left and right sides of the material lifting point A along the conveying direction of the conveyor belt 202. For the convenience of description, they are defined as the left sensor 2031 and the right sensor 2032. The material lifting point A refers to the best position point where the elastic strip leaves the conveyor belt 202 in a tension-free state and is conveyed obliquely upward along the set direction, that is, the normal conveying position of the elastic strip 10. When the conveying speed V2 of the conveyor belt 202 is too fast and the downstream driving traction speed V3 cannot take away the elastic strip 10 separated from the conveyor belt 202 in time, the elastic strip 10 will sag at the discharge end, as Figure 3As shown in the figure, when the sag exceeds the set position point b, at this time, the left sensor 2031 will sense the presence of the elastic strip 10, indicating that the elastic strip 10 output by the conveyor belt 202 is excessive, and the elastic strip 10 accumulates downstream of the discharge end of the conveyor belt 10. The accumulation may cause a change in the tension of the elastic strip 10. Therefore, it is necessary to control the conveyor belt 202 to reduce the speed. When the conveying speed V2 of the conveyor belt 202 is too slow and cannot meet the demand for the output volume of the elastic strip by the driving traction speed V3 downstream of the second dynamic storage unit, the elastic strip 10 will be pulled away from the conveyor belt 202 before reaching the material lifting point A, as Figure 4 shown in the figure. When the elastic strip 10 at the position point c detaches from the conveyor belt 202, at this time, the right sensor 2032 cannot sense the presence of the elastic strip 10, and the elastic strip 10 is output in advance, which will also cause a change in the tension of the elastic strip 10. Then, it is necessary to increase the conveying speed of the conveyor belt 202. By the cooperation of the left sensor 2031 and the right sensor 2032, the conveying speed of the conveyor belt 202 is adjusted to ensure the normal output of the elastic strip 10 and avoid changes in the tension of the elastic strip 10 during output.

[0027] To better release the tension of the elastic strip 10 on the conveyor belt 202, the elastic strip 10 is folded and laid flat on the conveyor belt 202. The folding and laying flat method of the elastic strip 10 is beneficial to the tension release of the elastic strip 10. To further form a folded and laid flat state, a swing mechanism 204 that swings back and forth in the horizontal direction is provided between the conveyor belt 202 and the driving roller 201. The swing mechanism 204 acts on the elastic strip 10 to drive the freely falling elastic strip 10 to deflect in the horizontal direction, so that the elastic strip 10 forms a larger folded and laid flat state after falling onto the conveyor belt 202, better releases stress, and reduces the offset amount of the elastic strip 10 on the conveyor belt 202.

[0028] As Figure 2 shown in the figure, the swing mechanism 204 includes a left swing arm 2041, a right swing arm 2042, and a swing rod 2043 disposed between the left swing arm 2041 and the right swing arm 2042 and located below the driving roller 201. The swing rod 2043 rotates around its own axis while swinging, and the rotation speed is consistent with that of the driving roller 201. By the rotation of the swing rod 2043, the pulling force of the swing rod 2043 on the elastic strip 10 is reduced, preventing the elastic strip 10 from increasing its own stress due to the swing rod 2043.

[0029] To reduce the problem of excessive offset of the elastic strip 10 on the conveyor belt 202 due to the release of its own stress, a deviation rectifying structure 205 for reducing the offset of the elastic strip 10 is provided on the conveyor belt 202. The deviation rectifying structure 205 acts on a local area of the elastic strip 10 to apply a certain positioning and holding force to the local area of the elastic strip 10. This deviation rectifying structure 205 can not only not affect the release of the tension of the elastic strip 10, but also reduce the offset of the elastic strip 10.

[0030] Preferably, the deviation rectifying structure 205 is not limited to a group of negative pressure adsorption areas scattered on the conveyor belt 202. A negative pressure device is correspondingly provided below the negative pressure adsorption areas to provide negative pressure for the negative pressure adsorption areas, and to give a downward suction force to the elastic strip 10 located on the negative pressure adsorption areas, so as to reduce the offset of the elastic strip 10. The negative pressure device can adopt a structure in which a negative pressure pipeline is connected to a vacuum pump, and the pipe orifice of the negative pressure pipeline corresponds to the negative pressure adsorption areas. The number and size of the negative pressure adsorption areas can be adjusted according to the actual situation, so as to use a relatively small number and negative pressure area to ensure that the elastic strip 10 can fully release the tension while reducing the offset.

[0031] The elastic strip 10 discharges from the discharge end of the conveyor belt 202 in an inclined upward manner, and a deviation rectifying unit 300 is provided on the discharge path to rectify the elastic strip 10 and control and adjust the traveling direction of the elastic strip 10. The deviation rectifying unit 300 can select a common BST deviation rectifying system in the market, and will not be specifically described here.

[0032] Embodiment 2: As Figures 2 to 5 shown, a feeding process and device for an elastic strip are used to fully release the tension of the elastic strip from an elastic material roll and output it in a tension-free state. By adopting a combination of a first dynamic storage unit 100 and a second dynamic storage unit 200 to release the tension of the elastic strip, the layout distance required for the stress release of the elastic strip is reduced. This process method includes receiving the elastic strip 10 from the elastic material roll 401 through the first dynamic storage unit 100 and performing a first tension release on the elastic strip 10. The elastic strip 10 after the first tension release is subjected to a second tension release through the second dynamic storage unit 200; the elastic strip after two tension releases is adjusted by the deviation rectifying unit 300 and then output for compounding with other sheets and other processes. The corresponding feeding device for the elastic strip includes a material rack 400 for supporting the elastic material roll, a first dynamic storage unit 100 for realizing the first tension release, a second dynamic storage unit 200 provided after the first dynamic storage unit 100, and a deviation rectifying unit 300 provided after the second dynamic storage unit 200.

[0033] Specifically, the elastic strip is wound and stored on the elastic coil 401. During use, the elastic coil 401 is mounted on the coil rack 400, and unwinding is performed through the coil rack 400. After the elastic strip 10 is unwound from the elastic coil 401, it enters the first dynamic storage unit 100 in the horizontal direction, and a primary tension release is performed through the first dynamic storage unit 100. The first dynamic storage unit 100 includes a set of top guide rollers 101 arranged side by side at intervals and a set of bottom guide rollers 102 arranged side by side at intervals. The elastic strip 10 shuttles back and forth between the top guide rollers 101 and the bottom guide rollers 102. As Figure 5 shown, the top guide rollers 101 include top guide rollers 101A, 101B, 101C, 101D, and 101E arranged at intervals in sequence, the bottom guide rollers 102 include bottom guide rollers 102A, 102B, 102C, 102D, and 102E arranged at intervals in sequence. After the elastic strip 10 enters the bottom guide roller 102A horizontally, it runs vertically upward into the top guide roller 101A. The elastic strip 10 bypasses the top guide roller 101A and runs vertically downward into the bottom guide roller 102B, bypasses the bottom guide roller 102B and then runs vertically upward into the top guide roller 101B, and so on. The elastic strip passes through the bottom guide roller 102C, the top guide roller 101C, the bottom guide roller 102D, the top guide roller 101D, and the bottom guide roller 102E in sequence, and finally is output from the top guide roller 101E. The elastic strip 10 realizes a primary tension release by shuttling back and forth between the top guide rollers 101 and the bottom guide rollers 102. The first dynamic storage unit can refer to the prior art such as CN111527038B, US11679951B2, etc., and will not be elaborated here.

[0034] After the elastic strip 10 is output from the top guide roller 101E, it enters the second dynamic storage unit 200, and a secondary tension release of the tension is realized on the second dynamic storage unit 200, and the tension of the elastic strip 10 is fully released. The second dynamic storage unit 200 includes a driving roller 201 that docks with the first dynamic storage unit 100 to apply a traction force to the elastic strip 10 output from the top guide roller 101E, and a conveyor belt 202 for placing the elastic strip 10 and driving the elastic strip 10 to be conveyed forward. The specific structure of the second dynamic storage unit 200 is the same as that of Embodiment 1.

[0035] The elastic strip 10 is discharged from the discharge end of the conveyor belt 202 in an inclined upward manner, and a deviation correction unit 300 is provided on the travel path of the discharge to correct the elastic strip 10 and control and adjust the travel direction of the elastic strip 10. The deviation correction unit 300 can select a common BST deviation correction system in the market, and will not be specifically described here.

[0036] Through the structural design of the first dynamic storage unit 100 and the second dynamic storage unit 200 and their mutual cooperation, before the elastic strip 10 is compounded, its own stress can be fully released, so as to ensure that the sheet after compounding will not be deformed, thereby improving the qualified rate of product processing. At the same time, the layout distance can be shortened, and the compactness of equipment layout can be improved.

[0037] The present invention has been described exemplarily in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited by the above methods. As long as various non-substantive improvements are made by adopting the method concept and technical solution of the present invention; or without improvement, the above concept and technical solution of the present invention are directly applied to other occasions, they are all within the protection scope of the present invention.

Claims

1. A feeding process for an elastic strip, which is used to fully release the tension of the elastic strip from an elastic coil and output it in a tension-free state, characterized in that, By setting a dynamic storage unit on the traveling path of the elastic strip, the elastic strip is transported by the dynamic storage unit and the tension release of the elastic strip is completed; the dynamic storage unit includes a second dynamic storage unit, which has a conveyor belt, and the elastic strip enters the conveyor belt vertically from the upstream side. While the elastic strip enters, the moving speed of the conveyor belt is controlled so that the elastic strip is laid on the conveyor belt in a tension-free state and is driven forward by the conveyor belt.

2. The feeding process of the elastic strip according to claim 1, characterized in that: The second dynamic storage unit further includes sensors, and at least two sensors are provided. By detecting the extreme motion state of the elastic strip near the conveyor belt outlet and the preset lifting point, the speed of the conveyor belt is adjusted to match the traction speeds of the upstream and downstream.

3. The feeding process of the elastic strip according to claim 1, characterized in that: The dynamic storage unit further includes a first dynamic storage unit provided on the upstream side of the second dynamic storage unit; The first dynamic storage unit receives the elastic strip from the elastic coil and the elastic strip is reciprocally transported on the first dynamic storage unit to achieve the first tension release of the elastic strip. After the first tension release, the elastic strip enters the second dynamic storage unit vertically for the second tension release.

4. The feeding process of the elastic strip according to claim 3, characterized in that: The first dynamic storage unit includes a set of top guide rollers and a set of bottom guide rollers, and the elastic strip shuttles back and forth between the top guide rollers and the bottom guide rollers.

5. The feeding process of the elastic strip according to claim 3, characterized in that: A driving roller is provided at the feeding end of the second dynamic storage unit, and the driving roller is located above the conveyor belt. The driving roller drives the elastic strip of the first dynamic storage unit to move forward, and the elastic strip enters the conveyor belt in a free-falling manner after passing through the driving roller.

6. The feeding process of the elastic strip according to claim 1, characterized in that: A deviation rectifying structure is provided on the conveyor belt, and a certain positioning holding force is given to the elastic strip through the deviation rectifying structure to reduce the offset amount of the elastic strip during transportation.

7. The feeding process of the elastic strip according to claim 1, characterized in that: The elastic strip is discharged from the second dynamic storage unit in an inclined upward manner, and a deviation rectifying unit is provided on the discharging traveling path to rectify the elastic strip.

8. The feeding process of the elastic strip according to claim 1, characterized in that: The elastic strip is folded and laid flat on the conveyor belt.

9. A feeding device for an elastic strip, characterized in that, Including: A material rack for supporting the elastic strip coil; A second dynamic storage unit that receives the elastic strip from the elastic coil and releases the tension of the elastic strip; The second dynamic storage unit includes a conveyor belt for placing the elastic strip and driving the elastic strip to move forward. The elastic strip enters the conveyor belt from top to bottom and is laid on the conveyor belt in a tension-free state.

10. The feeding device for elastic strip materials according to claim 9, characterized in that: A first dynamic storage unit is further provided on the upstream side of the second dynamic storage unit. The first dynamic storage unit receives the elastic strip from the elastic coil and performs the first tension release. After the first tension release, the elastic strip enters the second dynamic storage unit for the second tension release.

11. The feeding device for elastic strip materials according to claim 9, characterized in that: A driving roller is provided at the feeding end of the second dynamic storage unit. The driving roller is located above the conveyor belt. The elastic strip enters the driving roller from the discharge port of the first dynamic storage unit and moves forward under the pulling of the driving roller. The elastic strip enters the conveyor belt in a free-falling manner after passing through the driving roller.

12. The feeding device for elastic strip according to claim 9, characterized in that: While the elastic strip is falling, the conveyor belt moves forward slowly, so that the elastic strip is folded and laid flat on the conveyor belt.

13. The feeding device for elastic strip materials according to claim 12, characterized in that: A swing mechanism that swings back and forth in the horizontal direction is provided between the conveyor belt and the driving roller. The swing mechanism acts on the elastic strip to drive the freely falling elastic strip to deflect in the horizontal direction, so that the elastic strip forms a folded and flat state after falling onto the conveyor belt.

14. The feeding device for elastic strip materials according to claim 9, characterized in that: A deviation rectifying structure for reducing the deviation of the elastic strip is provided on the conveyor belt.

15. The feeding device for elastic strip according to claim 14, characterized in that: The deviation rectifying structure is a group of negative pressure adsorption areas scattered on the conveyor belt.

16. The feeding device for elastic strip according to claim 14, characterized in that: Sensors for detecting the limit movement position of the elastic strip are provided near the downstream outlet side of the conveyor belt and the preset lifting point. By detecting the limit movement state of the elastic strip at the corresponding position through the sensors, the speed of the conveyor belt is adjusted to match the traction speeds of the upstream and downstream.

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