A high-strength plate electrically assisted straightening device and straightening process

Abstract

The present invention provides an electrically assisted straightening device and straightening process for high-strength plates, belonging to the field of straightening technology. It comprises an upper roller group and a lower roller group which are arranged correspondingly up and down, a gap is formed between the upper roller group and the lower roller group for plates to enter, the upper roller group has a plurality of upper roller bodies which can be lifted and lowered in the vertical direction and can rotate circumferentially, and the lower roller group has a plurality of lower roller bodies which can rotate circumferentially. The upper roller group cooperates with the lower roller group to mechanically straighten the plates, and the pulse power supply can apply a pulse current to the plates through the upper roller group and the lower roller group to improve the plasticity of the high-strength plates, thereby achieving the purpose of straightening the high-strength, warped, and wavy plates after heat treatment at room temperature.

Description

Technical Field

[0001] The invention belongs to the technical field of straightening, and relates to a high-strength plate electric-assisted straightening device and a straightening process. Background Art

[0002] At present, the widely used stretch bending straightening machine for cold-rolled strip straightening stretches and bends the strip with a certain tension along the roller surface of the working roll. After repeated bending and straightening, the plate and strip undergo plastic deformation. After the tension is removed, the plate and strip remain straight. The roller straightening machine is a straightening device for continuous and repeated bending. Through a number of parallel straightening rollers arranged in a staggered manner, the plate is continuously and repeatedly bent and straightened in a certain pressing mode (large deformation or small deformation mode) to achieve the purpose of straightening. However, for steel plates that have undergone heat treatment such as quenching, because they have a high yield strength and a large resilience after straightening, conventional roller straightening machines are difficult to straighten, and the plate needs to be heated to a certain temperature before straightening. However, it is still impossible to straighten such high-strength, warped, and wavy plates after heat treatment at room temperature.

[0003] In order to overcome the shortcomings of the existing technology, people have proposed various solutions through continuous exploration. For example, a Chinese patent discloses a cold-hardened strip steel plate straightening process [application number: 201510878218.1], which includes a stretching and bending straightening process and a multi-roller continuous straightening process. The cold-hardened strip steel is subjected to stretching and bending straightening and multi-roller continuous straightening in sequence, including the following steps: installing the unit: setting an inlet tension roller group in the process section of the unit, and also setting an outlet tension roller group, and setting a composite straightener between the inlet tension roller group and the outlet tension roller group; assigning the total elongation setting value to the tensile straightening unit and the multi-roller straightening unit of the composite straightener; comparing the actual elongation of the strip steel with the total elongation setting value, and dynamically adjusting the tension value. This solution has the advantages of simple structure, convenient operation, better control of the elongation of the steel plate, and can significantly improve the quality of the cold-hardened strip steel plate shape and improve the product quality level. However, it also has the disadvantage of being unable to straighten high-strength, warped, and wavy plates after heat treatment at room temperature;

[0004] For example, a Chinese patent discloses a high-efficiency electroplastic stamping forming device [application number: 200920134044.8], which includes a punch, a die, a pressure device for pressing the stamped metal sheet against the die, and a high-energy pulse power supply; it also includes: two electrical connection devices, which are respectively installed on both sides of the pressure device and insulated from the pressure device; the two electrical connection devices are respectively connected to the two output ends of the high-energy pulse power supply; and an insulating film for insulating the metal sheet from the die. This solution has the advantages that when the die is closed to punch the metal sheet, the high-energy pulse power supply introduces pulse current to the metal sheet through the electrical connection device insulated from the pressure device, and the electroplastic treatment and forming of the metal sheet can be completed simultaneously at room temperature, the forming temperature is reduced, the surface quality of the product is improved, and the yield rate is increased; it is also easy to install, safe to use, and avoids the loss of electric energy in the pressure device and the die, so that the utilization rate of electric energy is further improved. However, this aspect has not been used in the field of sheet straightening. Summary of the invention

[0005] The object of the present invention is to provide a high-strength plate electrically assisted straightening device in view of the above problems.

[0006] The purpose of the present invention is to provide a high-strength plate electrically assisted straightening process in view of the above problems.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A high-strength plate electrically assisted straightening device comprises an upper roller group and a lower roller group which are arranged correspondingly up and down, a gap is formed between the upper roller group and the lower roller group for plates to enter, the upper roller group has a plurality of upper roller bodies which can be lifted and lowered in the vertical direction and can rotate circumferentially, the lower roller group has a plurality of lower roller bodies which can rotate circumferentially, and the outermost upper roller body in the upper roller group and the outermost lower roller body in the lower roller group are arranged correspondingly up and down, and the remaining upper roller bodies in the upper roller group and the remaining lower roller bodies in the lower roller group are staggered one by one, and the upper roller body and the lower roller group are both connected to a pulse power supply.

[0009] In the above-mentioned high-strength plate electric-assisted straightening device, the ends of the roller bodies in the upper roller group and the lower roller group are connected to electrodes, and a knife switch is provided between the electrode and the pulse power supply. The knife of the knife switch is connected to the electrode through a wire, the negative pole of the knife switch is connected to a No. 1 wire, and the end of the No. 1 wire away from the negative pole of the knife switch is connected to the negative pole of the pulse power supply, and the positive pole of the knife switch is connected to a No. 2 wire, and the end of the No. 2 wire away from the positive pole of the knife switch is connected to the positive pole of the pulse power supply.

[0010] In the above-mentioned high-strength plate electric assisted straightening device, the electrode is cylindrical, and a spherical connector is connected to the end of the electrode away from the knife switch. The spherical connector is inserted into the rolling roller body corresponding to the spherical connector and is movably connected to the rolling roller body.

[0011] In the above-mentioned high-strength plate electric assisted straightening device, the several upper roller bodies in the upper roller group can be raised and lowered in the vertical direction and the several upper roller bodies are independent of each other, and the outermost upper roller body in the upper roller group and the outermost lower roller body in the lower roller group can be clamped together.

[0012] In the above-mentioned high-strength plate electrically assisted straightening device, the ends of the upper roller bodies in the upper roller group away from the pulse power supply are respectively connected to reducers, and the ends of the reducers away from the upper roller bodies are connected to motors.

[0013] In the above-mentioned high-strength plate electrically assisted straightening device, the plurality of lower rolling roller bodies in the lower rolling roller group are arranged in parallel and at even intervals.

[0014] A high-strength plate electrically assisted straightening process using a high-strength plate electrically assisted straightening device is as follows: A high-strength plate electrically assisted straightening process comprises the following steps:

[0015] Step 1: driving the upper roller group to move upward so that the distance between the upper roller group and the lower roller group becomes larger;

[0016] Step 2: Turn on the pulse power supply to apply pulse current to the upper roller group and the lower roller group;

[0017] Step 3: Feed the end of the plate to the outermost roller bodies of the upper roller group and the lower roller group and drive the outermost upper roller body of the upper roller group to move downward to clamp the plate, and then drive the remaining upper roller bodies in the upper roller group to move downward to the corresponding positions according to the bending condition of the plate;

[0018] Step 4: driving the upper roller body in the upper roller group to rotate, thereby driving the plate forward for straightening through friction, and the plate undergoes elastic-plastic deformation during the process;

[0019] Step 5: Drive the upper roller group to move upward to make the plate rebound to a free state. At this time, the straightening is completed, the pulse power supply is turned off, and a straightening cycle is completed.

[0020] In the above-mentioned high-strength plate electrically assisted straightening process, step 2 further includes the following steps:

[0021] Step a: measuring the properties of the board;

[0022] Step b: manually and selectively setting the knife of the knife switch connected to the upper roller group to be connected to the positive pole of the knife switch, and the knife of the knife switch connected to the lower roller group to be connected to the negative pole of the knife switch;

[0023] Step c: Turn on the pulse power supply and apply pulse current to the upper roller group and the lower roller group.

[0024] In the above-mentioned high-strength plate electrically assisted straightening process, in step a, the model of the plate is 630 / 17-4PHPLATE, and the plate has a yield strength of 1000 MPa after quenching heat treatment.

[0025] In the above-mentioned electrically assisted straightening process for high-strength plates, in step three, the distance between the remaining upper roller bodies in the upper roller group except the outermost upper roller body and the lower roller group can be adaptively adjusted according to the bending conditions of the plate, and the closer the upper roller bodies in the upper roller group are to the outermost upper roller body, the larger the gap between the upper roller body and the lower roller group.

[0026] Compared with the prior art, the advantages of the present invention are:

[0027] 1. The upper roller group cooperates with the lower roller group to mechanically straighten the plate. The pulse power supply can apply pulse current to the plate through the upper roller group and the lower roller group to improve the plasticity of the high-strength plate, thereby achieving the purpose of straightening the high-strength, warped, and wavy plates after heat treatment at room temperature.

[0028] 2. When pulse current passes through metal materials, a large number of free electrons with directionally drifting will be generated. When pulse current is applied, electrical energy, thermal energy and stress are instantaneously input into the material. The random thermal motion of atoms obtains enough kinetic energy to leave the equilibrium position under the instantaneous impact force of the pulse current. The diffusion ability of atoms is enhanced, and dislocations are more likely to slip and climb, thereby improving the plasticity of the metal.

[0029] 3. Straightening the high-strength plate at room temperature greatly saves energy consumption compared with the prior art of straightening the high-strength plate after high-temperature heating.

[0030] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a circuit connection schematic diagram provided by the present invention;

[0032] Figure 2 It is a schematic diagram of the structure when the plate is clamped in step three;

[0033] Figure 3It is a schematic diagram of the structure when the plate is advancing and straightening;

[0034] Figure 4 is a schematic diagram of the structure of the plate and the roller body in step 4;

[0035] Figure 5 It is a schematic diagram of the structure of the plate after straightening;

[0036] Figure 6 It is a schematic diagram of the structure where the rollers and electrodes are connected.

[0037] In the figure, there are a lower roller group 10, an upper roller group 11, a pulse power supply 12, a motor 13, a reducer 14, an electrode 15, a knife switch 16, a No. 1 wire 17, a No. 2 wire 18, and a spherical connector 19. DETAILED DESCRIPTION

[0038] like Figure 2-Figure 4 As shown, there are seven rollers, including two rollers 1 and 2 for clamping in the feeding stage, and the remaining five rollers are used to straighten the repeated bending of the sheet, among which rollers 2, 3, and 4 can be adjusted in the height direction to adjust the gap between them and rollers 1, 7, 6, and 5. The upper roller bodies in the upper roller group 11 are numbered 2, 3, and 4 from left to right, and the lower roller bodies in the lower roller group 10 are numbered 1, 7, 6, and 5 from left to right.

[0039] like Figure 1-Figure 5 As shown, a high-strength plate electrically assisted straightening device includes an upper roller group 11 and a lower roller group 10 which are correspondingly arranged in the upper and lower parts, a gap for plates to enter is formed between the upper roller group 11 and the lower roller group 10, the upper roller group 11 has a plurality of upper roller bodies which can be lifted and lowered in the vertical direction and can rotate circumferentially, the lower roller group 10 has a plurality of lower roller bodies which can rotate circumferentially, and the outermost upper roller body in the upper roller group 11 and the outermost lower roller body in the lower roller group 10 are correspondingly arranged in the upper and lower parts, and the remaining upper roller bodies in the upper roller group 11 and the remaining lower roller bodies in the lower roller group 10 are staggered one by one, and the upper roller bodies and the lower roller group are both connected to a pulse power supply 12.

[0040] In this embodiment, the upper roller group 11 cooperates with the lower roller group 10 to mechanically straighten the plate, and the pulse power supply 12 can apply pulse current to the plate through the upper roller group 11 and the lower roller group 10 to improve the plasticity of the high-strength plate, thereby achieving the purpose of straightening the high-strength, warped, and wavy plates after heat treatment at room temperature.

[0041] Secondly, straightening the high-strength plate at room temperature greatly saves energy consumption compared with straightening the high-strength plate after high-temperature heating in the prior art.

[0042] Those skilled in the art should understand that when a pulse current passes through a metal material, a large number of free electrons with directionally drifting will be generated. When a pulse current is applied, electrical energy, thermal energy and stress are instantaneously input into the material. The random thermal motion of atoms obtains sufficient kinetic energy to leave the equilibrium position under the instantaneous impact force of the pulse current. The diffusion capacity of atoms is enhanced, and dislocations are more likely to slip and climb, thereby improving the plasticity of the metal.

[0043] The ends of the roller bodies in the upper roller group 11 and the lower roller group 10 are connected to electrodes 15, and a knife switch 16 is provided between the electrode 15 and the pulse power supply 12. The knife of the knife switch 16 is connected to the electrode 15 through a wire, and the negative pole of the knife switch 16 is connected to a No. 1 wire 17, and the end of the No. 1 wire 17 away from the negative pole of the knife switch 16 is connected to the negative pole of the pulse power supply 12, and the positive pole of the knife switch 16 is connected to a No. 2 wire 18, and the end of the No. 2 wire 18 away from the positive pole of the knife switch 16 is connected to the positive pole of the pulse power supply 12.

[0044] In this embodiment, combined with Figure 1-Figure 5 As shown, the electrodes are connected to an external switch and a pulse power supply through wires, and the switch is set to positive and negative poles, so that the positive and negative properties of each roller can be manually adjusted during operation.

[0045] The electrode 15 is cylindrical, and one end of the electrode 15 away from the knife switch 16 is connected to a spherical connector 19 . The spherical connector 19 is inserted into the roller body corresponding to the spherical connector 19 and is movably connected to the roller body.

[0046] In this embodiment, combined with Figure 6 As shown, the electrode 15 is connected to the roll body through a spherical connector 19 so that the electrode will not rotate when the roll body rotates.

[0047] The plurality of upper roller bodies in the upper roller group 11 can be lifted and lowered in the vertical direction and are independent of each other. The outermost upper roller body in the upper roller group 11 and the outermost lower roller body in the lower roller group 10 can be clamped together.

[0048] In this embodiment, combined with Figure 1-Figure 5 As shown, the upper roller bodies 2, 3 and 4 in the upper roller group 11 can be independently lifted and lowered in the vertical direction to facilitate adjustment of the gap between the upper roller bodies 2, 3 and 4 and the lower roller group 10, so as to facilitate adjustment of the straightening gap according to different plate conditions.

[0049] The ends of the upper roller bodies in the upper roller group 11 away from the pulse power supply 12 are respectively connected to reducers 14, and the ends of the reducers 14 away from the upper roller bodies are connected to motors 13.

[0050] In this embodiment, combined with Figure 1-Figure 5As shown, the motor 13 and the reducer 14 are connected to the upper roller bodies 2 and 3. When the motor is turned on, the upper roller bodies 2 and 3 can be driven to rotate, thereby using friction to drive the plate forward.

[0051] The plurality of lower roll bodies in the lower roll group 10 are arranged in parallel and at even intervals.

[0052] The high-strength plate electrically assisted straightening process includes the following steps:

[0053] Step 1: driving the upper roller group 11 to move upward so that the distance between the upper roller group 11 and the lower roller group 10 becomes larger;

[0054] In this embodiment, combined with Figure 2-Figure 5 As shown, the distance between the upper roller group 11 and the lower roller group 10 becomes larger to facilitate the loading of the plate.

[0055] Step 2: Turn on the pulse power supply 12 to apply pulse current to the upper roller group 11 and the lower roller group 10; in this embodiment, combined with Figure 1 As shown, the pulse power supply 12 applies pulse current to the upper roller group 11 and the lower roller group 10 to improve the plasticity of the plate, thereby achieving the purpose of straightening the high-strength, warped, and wavy plate after heat treatment at room temperature.

[0056] Step 3: Feed the end of the plate to the outermost roller bodies of the upper roller group 11 and the lower roller group 10 and drive the outermost upper roller body of the upper roller group 11 to move downward to clamp the plate, and then drive the remaining upper roller bodies in the upper roller group 11 to move downward to corresponding positions according to the bending condition of the plate;

[0057] Step 4: driving the upper roller body in the upper roller group 11 to rotate, thereby driving the plate forward through friction to be straightened, and the plate undergoes elastic-plastic deformation during the process;

[0058] Step 5: Drive the upper roller group 11 to move upward to make the plate rebound to a free state. At this time, the straightening is completed, and the pulse power supply 12 is turned off to complete a straightening cycle.

[0059] Step 2 also includes the following steps:

[0060] Step a: measuring the properties of the board;

[0061] Step b: manually and selectively setting the knife of the knife switch 16 connected to the upper roller group 11 to be connected to the positive electrode of the knife switch 16, and the knife of the knife switch 16 connected to the lower roller group 10 to be connected to the negative electrode of the knife switch 16;

[0062] Step c: Turn on the pulse power supply and apply pulse current to the upper roller group 11 and the lower roller group 10.

[0063] In this embodiment, combined with Figure 4As shown, at this time, the current flowing through the billet is divided into six sections, and the current directions are 2→8→1, 2→8→7, 3→8→7, 3→8→6, 4→8→6, 4→8→5. At this time, the billet current is the most stable and the current density is the largest.

[0064] In step a, the model of the plate is 630 / 17-4PH PLATE, and the plate has a yield strength of 1000 MPa after quenching heat treatment.

[0065] In this embodiment, the plate needs to be heated at high temperature before mechanical straightening can be performed in the prior art, which consumes a lot of energy. This process can achieve straightening at room temperature, saving a lot of energy.

[0066] In step three, the distance between the remaining upper roller bodies in the upper roller group 11 except the outermost upper roller body and the lower roller group 10 can be adaptively adjusted according to the bending condition of the plate, and the closer the upper roller bodies in the upper roller group 11 are to the outermost upper roller body, the larger the gap between the upper roller body and the lower roller group 10.

[0067] In this embodiment, combined with Figure 2-Figure 5 As shown, the upper roller body farthest from the outermost one in the upper roller body is numbered 2, and the gap between roller 3 and the lower roller group 10 is larger than the gap between roller 4 and the lower roller group 10, so that the plate can be gradually straightened, and the friction between the roller and the plate can be prevented from preventing the plate from passing through roller 3 due to excessive warping of the plate.

[0068] The working principle of the present invention is: driving the upper roller group 11 to move upward to increase the distance between the upper roller group 11 and the lower roller group 10, measuring the performance of the plate, manually and selectively setting the knife of the knife switch 16 connected to the upper roller group 11 to be connected to the positive pole of the knife switch 16, and the knife of the knife switch 16 connected to the lower roller group 10 to be connected to the negative pole of the knife switch 16, turning on the pulse power supply and applying a pulse current to the upper roller group 11 and the lower roller group 10, sending the end of the plate to the outermost roller body of the upper roller group 11 and the lower roller group 10 and driving the outermost upper roller body of the upper roller group 11 to move downward to clamp the plate, and then driving the remaining upper roller bodies in the upper roller group 11 to move downward to the corresponding position according to the bending condition of the plate to drive The upper roller body in the upper roller group 11 rotates, thereby driving the plate forward through friction for straightening. During the process, the plate is driven by elastic-plastic deformation, and the upper roller group 11 moves upward to make the plate rebound to a free state. At this time, the straightening is completed, and the pulse power supply 12 is turned off to complete a straightening cycle. The upper roller group 11 cooperates with the lower roller group 10 to mechanically straighten the plate. The pulse power supply 12 can apply a pulse current to the plate through the upper roller group 11 and the lower roller group 10 to improve the plasticity of the high-strength plate, thereby achieving the purpose of straightening the high-strength, warped, and wavy plates after heat treatment at room temperature. Straightening the high-strength plate at room temperature greatly saves energy compared to the high-strength plate that is straightened after high-temperature heating in the prior art.

[0069] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0070] Although the terms such as lower roller group 10, upper roller group 11, pulse power supply 12, motor 13, reducer 14, electrode 15, knife switch 16, No. 1 wire 17, No. 2 wire 18, ball connector 19 are used more frequently in this article, the possibility of using other terms is not excluded. The use of these terms is only for more convenient description and explanation of the essence of the present invention. It is contrary to the spirit of the present invention to interpret them as any additional limitation.

Claims

1. A high-strength plate electrically assisted straightening device, comprising an upper roller group (11) and a lower roller group (10) arranged correspondingly above and below, wherein a gap is formed between the upper roller group (11) and the lower roller group (10) for the plate to enter, characterized in that: The upper roller group (11) comprises a plurality of upper roller bodies that can be lifted and lowered in a vertical direction and can rotate in a circumferential direction, the lower roller group (10) comprises a plurality of lower roller bodies that can rotate in a circumferential direction, and the outermost upper roller body in the upper roller group (11) and the outermost lower roller body in the lower roller group (10) are arranged in correspondence with each other in the upper and lower directions, and the remaining upper roller bodies in the upper roller group (11) and the remaining lower roller bodies in the lower roller group (10) are arranged in a staggered manner, and the upper roller bodies and the lower roller group are both connected to a pulse power supply (12); The ends of the roller bodies in the upper roller group (11) and the lower roller group (10) are connected to electrodes (15), and a knife switch (16) is provided between the electrode (15) and the pulse power supply (12). The knife of the knife switch (16) is connected to the electrode (15) through a wire, the negative pole of the knife switch (16) is connected to a first wire (17), and the end of the first wire (17) away from the negative pole of the knife switch (16) is connected to the negative pole of the pulse power supply (12), and the positive pole of the knife switch (16) is connected to a second wire (18), and the end of the second wire (18) away from the positive pole of the knife switch (16) is connected to the positive pole of the pulse power supply (12); The electrode (15) is cylindrical, and one end of the electrode (15) away from the knife switch (16) is connected to a spherical connector (19), and the spherical connector (19) is inserted into a roller body corresponding to the spherical connector (19) and is movably connected to the roller body; The plurality of upper roller bodies in the upper roller group (11) can all be raised and lowered in the vertical direction and are independent of each other, and the outermost upper roller body in the upper roller group (11) and the outermost lower roller body in the lower roller group (10) can cooperate to be clamped.

2. The high-strength plate electrically assisted straightening device according to claim 1, characterized in that: The ends of the plurality of upper roller bodies in the upper roller group (11) away from the pulse power supply (12) are respectively connected to reducers (14), and the ends of the reducers (14) away from the upper roller bodies are connected to motors (13).

3. The high-strength plate electrically assisted straightening device according to claim 2, characterized in that: The plurality of lower rolling roller bodies in the lower rolling roller group (10) are arranged in parallel and at even intervals.

4. A high-strength plate electrically assisted straightening process using the high-strength plate electrically assisted straightening device according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step 1: driving the upper roller group (11) to move upward so that the distance between the upper roller group (11) and the lower roller group (10) becomes larger; Step 2: Turn on the pulse power supply (12) to apply a pulse current to the upper roller group (11) and the lower roller group (10); Step 3: feeding the end of the plate to the outermost roller bodies of the upper roller group (11) and the lower roller group (10) and driving the outermost upper roller body of the upper roller group (11) to move downward to clamp the plate, and then driving the remaining upper roller bodies in the upper roller group (11) to move downward to corresponding positions according to the bending condition of the plate; Step 4: driving the upper roller body in the upper roller group (11) to rotate, thereby driving the plate forward through friction to be straightened, and the plate undergoes elastic-plastic deformation during the process; Step 5: Drive the upper roller group (11) to move upward to make the plate rebound to a free state. At this time, the straightening is completed, and the pulse power supply (12) is turned off to complete a straightening cycle.

5. The high-strength plate electrically assisted straightening process according to claim 4, characterized in that: Step 2 also includes the following steps: Step a: measuring the properties of the board; Step b: manually and selectively setting the knife of the knife switch (16) connected to the upper roller group (11) to be connected to the positive electrode of the knife switch (16), and the knife of the knife switch (16) connected to the lower roller group (10) to be connected to the negative electrode of the knife switch (16); Step c: Turn on the pulse power supply and apply pulse current to the upper roller group (11) and the lower roller group (10).

6. A high-strength plate electrically assisted straightening process according to claim 5, characterized in that: In step a, the model of the plate is 630 / 17-4PH PLATE, and the plate has a yield strength of 1000 MPa after quenching heat treatment.

7. The high-strength plate electrically assisted straightening process according to claim 4, characterized in that: In step three, the distance between the remaining upper roller bodies in the upper roller group (11) except the outermost upper roller body and the lower roller group (10) can be adaptively adjusted according to the bending condition of the plate, and the closer the upper roller bodies in the upper roller group (11) are to the outermost upper roller body, the larger the gap between the upper roller body and the lower roller group (10).

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