Method for reducing equipment damage of pulp line double-disc refiner in papermaking industry

Abstract

The invention discloses a method for reducing equipment damage of a pulp line double-disc refiner in the papermaking industry, and relates to the technical field of papermaking double-disc refiner, the double-disc refiner comprises the following steps: step 1, a tool retracting motor is connected with a three-phase voltage through a frequency converter, U, V and W terminals of the frequency converter are connected with the tool retracting motor, and R, S and T terminals of the frequency converter are connected with a phase line; 2, coils of the intermediate relays K1, K2 and K5 are all connected with a DCS and used for controlling rapid forward and reverse rotation of a tool retracting motor; 3, one end of a contact switch of the intermediate relay K1 is connected with a Di0 terminal of the frequency converter, and the scheme solves the problems that in the prior art, when a DCS system of a refiner breaks down and cannot receive signals fed back by a field sensor, or the sensor breaks down and cannot feed back the signals to the DCS, transmission equipment cannot stop and output the signals all the time, and consequently a transmission mechanism is twisted off, and the transmission efficiency of the refiner is affected. And economic loss and safety production hidden dangers are easy to occur.

Description

Technical Field

[0001] The invention relates to the technical field of papermaking double-disc refiner, in particular to a method for reducing equipment damage of a double-disc refiner in a pulp line of the papermaking industry. Background Art

[0002] The pulping machine is the most basic instrument used in the field of pulp and paper industry testing and research. The pulping machine can make wood chips into pulp, improve pulp or make wood chips into synthetic fiber, glass fiber and carbon fiber. The main circuit of the high-voltage motor of the double-disc mill pulping machine is controlled by a vacuum circuit breaker. The DCS system collects the actual power of the equipment fed back by the high-voltage cabinet and compares it with the set power. The DCS control system remotely outputs signals to control the forward and reverse rotation of the feed and retract frequency converter to adjust the grinding disc gap size and realize constant power automatic control. For example, the Chinese authorized patent with announcement number CN214459167U (a pulping knife for a fine pulping machine): includes a coarse pulping knife assembly, a half pulping knife assembly and a fine pulping knife assembly, wherein the coarse pulping knife assembly includes a coarse pulping knife fixed knife and a coarse pulping knife rotating knife, the half pulping knife assembly includes a half pulping knife fixed knife and a half pulping knife rotating knife, the fine pulping knife assembly includes a fine pulping knife fixed knife and a fine pulping knife rotating knife, the pulp is processed by the coarse pulping knife assembly, the half pulping knife assembly and the fine pulping knife assembly in sequence, wherein the blade angles in the coarse pulping knife assembly and the half pulping knife assembly gradually increase, or the blade angles in the half pulping knife assembly and the fine pulping knife assembly gradually increase, the blade angle in the coarse pulping knife assembly is 4 degrees; the blade angle in the half pulping knife assembly is 8 degrees; the blade angle in the fine pulping knife assembly is 8 degrees.

[0003] However, in the above-mentioned prior art, when the DCS system of the pulping machine fails, it cannot receive the signal fed back by the on-site sensor, or the sensor fails and cannot feed back the signal to the DCS, the transmission equipment cannot stop and keeps outputting, resulting in a twisting accident of the transmission mechanism, which is prone to economic losses and safety hazards in production. Therefore, it does not meet the existing needs. In this regard, we propose a method for reducing equipment damage to the double-disc refiner in the pulp line of the papermaking industry. Summary of the invention

[0004] The object of the present invention is to provide a method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry, so as to solve the problem in the prior art proposed in the above background technology that when a DCS system of the refiner fails, it cannot receive the signal fed back by the on-site sensor, or the sensor fails and cannot feed back the signal to the DCS, the transmission equipment cannot stop and keeps outputting, resulting in a twisting accident of the transmission mechanism, which is prone to economic losses and safety hazards in production.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry, comprising the following steps: Step 1: First, connect the knife-retracting motor to the three-phase voltage through the inverter, connect the U, V, and W terminals of the inverter to the knife-retracting motor, and connect the R, S, and T terminals of the inverter to the phase line; Step 2: The coils of the intermediate relays K1, K2, and K5 are all connected to the DCS, and are used to control the fast forward and reverse rotation of the knife retracting motor; Step 3: Connect one end of the contact switch of the intermediate relay K1 to the Di0 terminal of the inverter, and connect one end of the contact switch of the intermediate relays K2 and K5 to the Di1 terminal of the inverter; Step 4: Connect the other end of the contact switch of the intermediate relay K1 to the other end of the contact switch of the intermediate relay K2 and then connect to the +24V terminal of the inverter through the travel switch; Step 5: The travel switch is installed at the limit position of the retracting knife of the pulping machine to control the limit position of the retracting knife.

[0006] Preferably, the DCS in the above step 2 includes a control cabinet, a DCS system is arranged inside the control cabinet, a tool retraction module, a relay module, a frequency converter module and a travel switch module are arranged inside the DCS system, and relays K1, K2, K3, K4 and K5 are arranged inside the relay module.

[0007] Preferably, the tool retraction module, relay module, inverter module and travel switch module are electrically connected to a DCS system, and the DCS system is electrically connected to a communication module.

[0008] Preferably, a base is provided at the bottom of the control cabinet, a cabinet door is installed on the front end surface of the control cabinet, and a door handle is installed on one side of the front end surface of the cabinet door.

[0009] Preferably, a monitoring device is provided on the front face of the cabinet door, an observation port is provided below the monitoring device, a heat dissipation device is provided on the top of the control cabinet, a heat dissipation port is provided on the upper surface of the heat dissipation device, and a plurality of heat dissipation ports are provided.

[0010] Preferably, a partition plate is provided inside the control cabinet, a plurality of air holes are provided inside the partition plate, a mounting frame is provided on the rear end surface inside the control cabinet, and a plug-in slot is provided on the front end surface of the mounting frame.

[0011] Preferably, the retraction of the pulping machine in the above step five includes a retraction limiting component and a fixed frame, a first fixed plate is arranged on the retraction limiting component, fixing screws are arranged around the front end surface of the first fixed plate, a connecting port is arranged inside the first fixed plate, a scale rod is arranged inside the connecting port, a connecting plate is arranged on the front end surface of the scale rod, a support plate is arranged on one side of the first fixed plate, a controller is arranged on the upper surface of the support plate, and a bracket is arranged on one side of the controller.

[0012] Preferably, a second rotating seat is provided on the upper surface of the bracket, a connecting rod is provided on one side of the second rotating seat, the other end of the connecting rod is fixedly connected to the connecting rod, and a first rotating seat is provided inside the connecting rod.

[0013] Preferably, a connecting groove is provided inside the fixing bracket, a fixing hole is provided inside the connecting groove, mounting holes are provided at the upper and lower ends of the front end surface of the fixing bracket, a second fixing plate is provided at the front end of the fixing bracket, and a control switch is provided on the front end surface of the second fixing plate.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention sets a knife retraction module, a relay module, a frequency converter module, and a travel switch module in a DCS system, collects signals of the states of the controller, the communication module, and the input and output cards in the DCS system, and adds a safety control loop. When any hardware failure occurs in the third or fourth level of the system, the frequency converter is controlled by hard-wire interlocking to realize emergency retraction of the knife advance and retraction motor, and a mechanical travel switch is installed at the limit position of the knife retraction. When the DCS system, the proximity sensor, and the position photoelectric switch controlling the knife retraction fail to function and cause the knife retraction limit inhibition to fail, the travel switch can directly disconnect the knife retraction motor. The source effectively reduces the probability of equipment damage and avoids safety hazards. It has a low investment cost, effectively avoids the failure rate of electronic components of inductive proximity switches, reduces safety risks, and effectively reduces the significant economic losses caused by equipment damage accidents caused by control system failures by collecting the underlying data of the software and hardware of the control system. It solves the problem in the prior art that when the DCS system of the pulping machine fails, it cannot receive the signal fed back by the on-site sensor, or the sensor fails and cannot feed back the signal to the DCS, the transmission equipment cannot stop and keeps outputting, resulting in a twisting accident of the transmission mechanism, which is prone to economic losses and safety production hazards.

[0015] 2. A tool retraction limiting component is provided, a scale rod and a controller are provided on the tool retraction limiting component, a connecting plate of the scale rod is connected to the first rotating seat and the second rotating seat through a connecting rod, and the connecting rod is rotatably connected to the first rotating seat and the second rotating seat, and it is installed on the device through a first fixed plate and a support plate. When the tool retraction module drives it to operate, the scale rod corresponds to the maximum limit position to ensure that the equipment will not exceed the limit.

[0016] 3. By placing a wire from the tool retraction limit component from the site to the inside of the control cabinet as a signal feedback line, the start and stop operation control of the advance and retraction motor is realized by the on and off of the signal, and a K5 relay is added in the control cabinet to connect the normally closed point to the fast retraction node when abnormalities occur in the hardware, software, and network communication of the DCS control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the control cabinet of the present invention; Figure 2 It is an enlarged schematic diagram of the local structure inside the control cabinet of the present invention; Figure 3 It is a schematic diagram of the structure of the tool retraction limiting component of the present invention; Figure 4 It is an enlarged schematic diagram of the local installation structure of the control switch of the present invention; Figure 5 It is a schematic diagram of the system principle of the present invention; Figure 6 is a circuit diagram of the present invention; In the figure: 1. control cabinet; 2. base; 3. cabinet door; 4. door handle; 5. monitoring device; 6. observation port; 7. heat dissipation device; 8. heat dissipation port; 9. partition plate; 10. ventilation hole; 11. mounting frame; 12. plug-in slot; 13. first fixing plate; 14. fixing screw; 15. connecting port; 16. scale rod; 17. connecting plate; 18. connecting rod; 19. first rotating seat; 20. supporting plate; 21. controller; 22. bracket; 23. second rotating seat; 24. fixing frame; 25. connecting slot; 26. fixing hole; 27. mounting hole; 28. second fixing plate; 29. ​​control switch; 30. DCS system; 31. retracting module; 32. relay module; 33. inverter module; 34. travel switch module; 35. retracting limit assembly. DETAILED DESCRIPTION

[0018] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0019] See also Figure 1-6 The present invention provides an embodiment: a method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry, comprising the following steps: Step 1: First, connect the knife-retracting motor to the three-phase voltage through the inverter, connect the U, V, and W terminals of the inverter to the knife-retracting motor, and connect the R, S, and T terminals of the inverter to the phase line; Step 2: The coils of the intermediate relays K1, K2, and K5 are all connected to the DCS, and are used to control the fast forward and reverse rotation of the knife retracting motor; Step 3: Connect one end of the contact switch of the intermediate relay K1 to the Di0 terminal of the inverter, and connect one end of the contact switch of the intermediate relays K2 and K5 to the Di1 terminal of the inverter; Step 4: Connect the other end of the contact switch of the intermediate relay K1 to the other end of the contact switch of the intermediate relay K2 and then connect to the +24V terminal of the inverter through the travel switch; Step 5: The travel switch is installed at the limit position of the knife retraction of the pulping machine to control the limit position of the knife retraction; by setting the knife retraction module 31, the relay module 32, the frequency converter module 33, and the travel switch module 34 in the DCS system 30, by collecting signals of the states of the controller 21, the communication module, and the input and output cards in the DCS system 30, a safety control loop is added, and when any of the third or fourth level hardware in the system fails, the frequency converter is controlled by hard-line interlocking to realize the emergency retraction of the knife advance and retraction motor, and a mechanical travel switch is installed at the limit position of the knife retraction. When the DCS system 30, the proximity sensor and the position photoelectric switch that control the knife retraction fail to cause the knife retraction limit suppression to fail, the travel switch can directly disconnect the power supply of the knife retraction motor, effectively reducing the probability of equipment damage and avoiding safety hazards. The investment cost is small, the failure rate of the electronic components of the inductive proximity switch is effectively avoided, and the safety risk is reduced. By collecting the underlying data of the software and hardware of the control system, the significant economic losses caused by equipment damage accidents caused by the failure of the control system are effectively reduced, and the existing technology solves the problem of the pulping machine when the DCS The system 30 fails and cannot receive the signal fed back by the field sensor, or the sensor fails and cannot feed back the signal to the DCS, the transmission equipment cannot stop and keeps outputting, resulting in a twisting accident of the transmission mechanism, which is prone to economic losses and hidden safety hazards in production. By setting a tool retraction limiting component 35, a scale rod 16 and a controller 21 are set on the tool retraction limiting component 35, and the connecting plate 17 of the scale rod 16 is connected to the first rotating seat 19 and the second rotating seat 23 through the connecting rod 18, and the connecting rod 18 is connected to the first rotating seat 19 and the second rotating seat 23 is rotatably connected, and it is installed on the device through the first fixed plate 13 and the support plate 20. When the retracting module 31 drives it to operate, the scale rod 16 corresponds to the maximum limit position to ensure that the equipment will not exceed the limit. By placing a line from the retracting limit component 35 from the site to the inside of the control cabinet 1 as a signal feedback line, the start and stop operation control of the advance and retracting motor is realized by the on and off of the signal, and a K5 relay is added in the control cabinet 1 for the DCS control system hardware, software, and network communication. When an abnormality occurs, the normally closed point is connected to the fast retracting node.

[0020] See also Figure 1-Figure 6 In the above step 2, the DCS includes a control cabinet 1, a DCS system 30 is arranged inside the control cabinet 1, a tool retraction module 31, a relay module 32, a frequency converter module 33 and a travel switch module 34 are arranged inside the DCS system 30, and relays K1, K2, K3, K4 and K5 are arranged inside the relay module 32.

[0021] See also Figure 1-Figure 6 The knife retraction module 31, the relay module 32, the inverter module 33 and the travel switch module 34 are electrically connected to the DCS system 30, and the DCS system 30 is electrically connected to the communication module. By setting the knife retraction module 31, the relay module 32, the inverter module 33 and the travel switch module 34 in the DCS system 30, by collecting signals of the states of the controller 21, the communication module and the input and output cards in the DCS system 30, a safety control loop is added. When any hardware failure occurs in the third or fourth level of the system, the inverter is controlled by hard-line interlocking to realize emergency retraction of the knife advance and retraction motor, and a mechanical travel switch is installed at the extreme position of the knife retraction. When the DCS system 30, the proximity sensor and the position light controlling the knife retraction fail, the knife advance and retraction motor is controlled to be in emergency retraction. When the electric switch fails and the knife retraction limit suppression fails, the travel switch can directly disconnect the knife retraction motor power supply, effectively reducing the probability of equipment damage and avoiding safety hazards. The investment cost is low, and the failure rate of electronic components of the inductive proximity switch is effectively avoided, reducing safety risks. By collecting the underlying data of the control system's software and hardware, the significant economic losses caused by equipment damage accidents caused by control system failures are effectively reduced. This solves the problem in the prior art that when the DCS system 30 of the pulping machine fails, it cannot receive the signal fed back by the on-site sensor, or the sensor fails and cannot feed back the signal to the DCS, the transmission equipment cannot stop and keeps outputting, resulting in a twisting accident of the transmission mechanism, which is prone to economic losses and safety production hazards.

[0022] See also Figure 1-Figure 6 A base 2 is provided at the bottom of the control cabinet 1, a cabinet door 3 is installed on the front end surface of the control cabinet 1, and a door handle 4 is installed on one side of the front end surface of the cabinet door 3.

[0023] See also Figure 1-Figure 6 A monitoring device 5 is provided on the front face of the cabinet door 3, an observation port 6 is provided below the monitoring device 5, a heat dissipation device 7 is provided on the top of the control cabinet 1, a heat dissipation port 8 is provided on the upper surface of the heat dissipation device 7, and a plurality of heat dissipation ports 8 are provided.

[0024] See also Figure 1-Figure 6 A partition plate 9 is provided inside the control cabinet 1, and a plurality of air holes 10 are provided inside the partition plate 9. A mounting frame 11 is provided on the rear end surface inside the control cabinet 1, and a plug-in slot 12 is provided on the front end surface of the mounting frame 11, so as to facilitate the disassembly and assembly of the internal modules and ensure the flexibility and practicality of the components during use.

[0025] See also Figure 1-Figure 6In the above step 5, the retracting of the fine pulping machine includes a retracting limiting component 35 and a fixing frame 24, a first fixing plate 13 is arranged on the retracting limiting component 35, fixing screws 14 are arranged around the front end surface of the first fixing plate 13, a connecting port 15 is arranged inside the first fixing plate 13, a scale rod 16 is arranged inside the connecting port 15, and a connecting plate 17 is arranged on the front end surface of the scale rod 16, the retracting motor is connected to the three-phase voltage through the inverter, the U, V, and W terminals of the inverter are connected to the retracting motor, and the R, S, and T terminals of the inverter are connected to the phase line; the coils of the intermediate relays K1, K2, and K5 are all connected to the DCS, which are respectively used to control the fast forward and reverse rotation of the retracting motor; One end of the contact switch of the intermediate relay K1 is connected to the Di0 terminal of the inverter, one end of the contact switches of the intermediate relays K2 and K5 is connected to the Di1 terminal of the inverter, the other end of the contact switch of the intermediate relay K1 is connected to the other end of the contact switch of the intermediate relay K2 and then connected to the +24V terminal of the inverter through the travel switch; the travel switch is installed at the extreme position of the retraction of the pulping machine, which is used to control the extreme position of the retraction, increase the safety protection logic and control, and collect signals from the status of the controller 21, communication module, and input and output cards in the DCS system 30 to ensure that the equipment protection function can be realized under abnormal circumstances.

[0026] See also Figure 1-Figure 6 A support plate 20 is disposed on one side of the first fixing plate 13 , a controller 21 is disposed on the upper surface of the support plate 20 , and a bracket 22 is disposed on one side of the controller 21 .

[0027] See also Figure 1-Figure 6 A second rotating seat 23 is provided on the upper surface of the bracket 22, a connecting rod 18 is provided on one side of the second rotating seat 23, the other end of the connecting rod 18 is fixedly connected to the connecting rod 18, and a first rotating seat 19 is provided inside the connecting rod 18, so that the connection of the scale rod 16 can avoid jamming when it is extended or retracted.

[0028] See also Figure 1-Figure 6The fixing frame 24 is provided with a connecting groove 25 inside, a fixing hole 26 is provided inside the connecting groove 25, and mounting holes 27 are provided at the upper and lower ends of the front end surface of the fixing frame 24. The front end of the fixing frame 24 is provided with a second fixing plate 28, and the front end surface of the second fixing plate 28 is provided with a control switch 29. By setting a tool retraction limiting component 35, a scale rod 16 and a controller 21 are provided on the tool retraction limiting component 35, and the connecting plate 17 of the scale rod 16 is connected to the first rotating seat 19 and the second rotating seat 23 through the connecting rod 18, and the connecting rod 18 is connected to the first rotating seat 1 9 is rotatably connected to the second rotating seat 23, which is installed on the device through the first fixed plate 13 and the support plate 20. When the retracting module 31 drives it to operate, the scale rod 16 corresponds to the maximum limit position to ensure that the equipment will not exceed the limit. By placing a line from the site of the retracting limiting component 35 to the inside of the control cabinet 1 as a signal feedback line, the start and stop operation control of the advance and retracting motor is realized by the on and off of the signal, and a K5 relay is added in the control cabinet 1 for the DCS control system hardware, software, and network communication. When an abnormality occurs, the normally closed point is connected to the fast retracting node.

[0029] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry, characterized in that: The following steps are involved: Step 1: First, connect the knife-retracting motor to the three-phase voltage through the inverter, connect the U, V, and W terminals of the inverter to the knife-retracting motor, and connect the R, S, and T terminals of the inverter to the phase line; Step 2: The coils of the intermediate relays K1, K2, and K5 are all connected to the DCS, and are used to control the fast forward and reverse rotation of the knife retracting motor; Step 3: Connect one end of the contact switch of the intermediate relay K1 to the Di0 terminal of the inverter, and connect one end of the contact switch of the intermediate relays K2 and K5 to the Di1 terminal of the inverter; Step 4: Connect the other end of the contact switch of the intermediate relay K1 to the other end of the contact switch of the intermediate relay K2 and then connect to the +24V terminal of the inverter through the travel switch; Step 5: The travel switch is installed at the limit position of the retracting knife of the pulping machine to control the limit position of the retracting knife.

2. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 1, characterized in that: In the above step 2, the DCS comprises a control cabinet (1), wherein a DCS system (30) is arranged inside the control cabinet (1), wherein a tool retraction module (31), a relay module (32), a frequency converter module (33) and a travel switch module (34) are arranged inside the DCS system (30), and wherein relays K1, K2, K3, K4 and K5 are arranged inside the relay module (32).

3. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 2, characterized in that: The tool retraction module (31), the relay module (32), the frequency converter module (33) and the travel switch module (34) are electrically connected to the DCS system (30), and the DCS system (30) is electrically connected to the communication module.

4. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 3, characterized in that: A base (2) is provided at the bottom of the control cabinet (1), a cabinet door (3) is installed on the front face of the control cabinet (1), and a door handle (4) is installed on one side of the front face of the cabinet door (3).

5. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 4, characterized in that: A monitoring device (5) is provided on the front face of the cabinet door (3), an observation port (6) is provided below the monitoring device (5), a heat dissipation device (7) is provided on the top of the control cabinet (1), a heat dissipation port (8) is provided on the upper surface of the heat dissipation device (7), and a plurality of heat dissipation ports (8) are provided.

6. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 5, characterized in that: A partition plate (9) is arranged inside the control cabinet (1), a plurality of air holes (10) are arranged inside the partition plate (9), a mounting frame (11) is arranged on the rear end surface inside the control cabinet (1), and a plug-in slot (12) is arranged on the front end surface of the mounting frame (11).

7. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 6, characterized in that: In the above-mentioned step 5, the retraction of the pulping machine includes a retraction limiting component (35) and a fixing frame (24), wherein the retraction limiting component (35) is provided with a first fixing plate (13), and fixing screws (14) are provided around the front end surface of the first fixing plate (13), and a connecting port (15) is provided inside the first fixing plate (13), and a scale rod (16) is provided inside the connecting port (15), and a connecting plate (17) is provided on the front end surface of the scale rod (16).

8. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 7, characterized in that: A support plate (20) is provided on one side of the first fixing plate (13), a controller (21) is provided on the upper surface of the support plate (20), and a bracket (22) is provided on one side of the controller (21).

9. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 8, characterized in that: A second rotating seat (23) is provided on the upper surface of the bracket (22), a connecting rod (18) is provided on one side of the second rotating seat (23), the other end of the connecting rod (18) is fixedly connected to the connecting rod (18), and a first rotating seat (19) is provided inside the connecting rod (18).

10. A method for reducing equipment damage of a double-disc refiner in a pulp line in the papermaking industry according to claim 9, characterized in that: A connecting groove (25) is provided inside the fixing frame (24), a fixing hole (26) is provided inside the connecting groove (25), mounting holes (27) are provided at the upper and lower ends of the front end surface of the fixing frame (24), a second fixing plate (28) is provided at the front end of the fixing frame (24), and a control switch (29) is provided on the front end surface of the second fixing plate (28).

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