A universal shaft hoisting device for a vertical rolling mill

Abstract

The utility model discloses a kind of vertical rolling mill universal shaft hoisting devices, it is related to hoisting equipment technical field, to solve the problem of poor flexibility of existing equipment, insufficient stability, complex operation and low degree of automation. The equipment includes hoisting crossbeam, vertical mounting bracket, position adjusting mechanism, end clamping piece, electric push rod and bottom end push plate;Hoisting crossbeam is balanced suspension by four corner hoisting cable, vertical mounting bracket sets vertical mounting groove, position adjusting mechanism is driven by first speed reducer motor screw rod to adjust the height of end clamping piece;End clamping piece is clamped universal shaft top end by double-end screw rod and second speed reducer motor drive side clamping assembly, electric push rod drives bottom end push plate to right universal shaft. It can be adapted to different specifications universal shaft, ensure hoisting vertical stability, simplify operation, improve hoisting efficiency and safety, suitable for vertical rolling mill universal shaft installation, maintenance and replacement.

Description

Technical Field

[0001] This utility model relates to the field of hoisting equipment technology, and in particular to a novel hoisting equipment for vertical rolling mill universal joints. It is specifically applicable to hoisting operations during the installation, maintenance and replacement of vertical rolling mill universal joints in the steel smelting and processing industry. It can achieve precise and stable hoisting of universal joints of different lengths and diameters, significantly improving the safety and efficiency of hoisting operations. Background Technology

[0002] In the steel smelting and processing industry, the vertical rolling mill is one of the core pieces of equipment for steel rolling. The universal joint, as a key connecting and supporting component of the vertical rolling mill, plays a crucial role in transmitting torque and compensating for installation deviations. Its performance directly affects the stability of the rolling process and the quality of the steel. Due to the working characteristics of the vertical rolling mill, the universal joint is usually designed as a long shaft structure (often 1-3m in length), and its outer wall needs to fit precisely with other components of the rolling mill. This results in extremely high requirements for hoisting operations during installation, maintenance, and replacement—not only must the universal joint be kept vertical throughout its length (verticality error ≤0.5°), but hoisting tools must also be prevented from scratching or deforming the surface of the universal joint.

[0003] Currently, the mainstream vertical rolling mill universal joint lifting equipment on the market is mainly divided into two categories: one is a fixed clamping lifting device, which uses bolt-locked clamping blocks to fix the top of the universal joint and achieves lifting through a simple lifting frame; the other is a simple lifting frame, which only uses hooks or clamps to initially fix the universal joint, relying on manual assistance to adjust its posture. However, these devices have the following significant drawbacks in practical applications: Extremely poor flexibility: The clamping dimensions and lifting height of existing equipment are mostly fixed designs. If it is necessary to lift universal joints of different lengths (such as 1.2m and 2.8m) or different diameters (such as 150mm and 280mm), it is necessary to disassemble and replace the clamping blocks and adjust the hanger structure. The entire adjustment process takes 1-2 hours, which is inefficient and cannot meet the needs of rapid switching of multiple specifications of universal joints in steel workshops.

[0004] Insufficient hoisting stability: Fixed clamping devices use single-point or two-point clamping, resulting in uneven clamping force distribution and a lack of anti-slip design. During hoisting, the universal joint is prone to slippage due to its own weight. Simple hoisting frames lack an active straightening mechanism, and the universal joint is prone to tilting due to airflow in the workshop or slight swaying of the hoisting rope. This can increase the difficulty of subsequent installation and alignment, or even cause a safety accident where the universal joint collides with the mill gearbox.

[0005] High operational complexity: Existing equipment requires at least 2-3 operators to work together – 1 person controls the crane lifting, and 1-2 people on the ground manually adjust the attitude of the universal joint using crowbars and ropes. The operation steps are cumbersome and rely on personnel experience, which not only increases labor costs, but also easily causes safety hazards due to personnel coordination errors (such as being hit by the shaking universal joint during manual adjustment).

[0006] Low level of automation: Lacking intelligent adjustment and feedback mechanisms, the height adaptation of the universal joint, clamping force control and verticality adjustment all rely on manual judgment, making it impossible to achieve integrated operation of "parameter input - automatic adjustment - precise hoisting". The hoisting accuracy is greatly affected by the skill of the personnel, making it difficult to meet the automated production needs of modern steel workshops.

[0007] In summary, existing vertical rolling mill universal joint lifting equipment can no longer meet the steel industry's demand for "high efficiency, stability, and automation" in lifting operations, and there is an urgent need for a new type of lifting equipment that can overcome the above-mentioned shortcomings. Summary of the Invention

[0008] The technical problem to be solved by this utility model is to provide a new type of vertical rolling mill universal joint hoisting device that is compact in structure, highly adaptable, stable in hoisting and highly automated, in contrast to the above-mentioned prior art.

[0009] The technical solution adopted by this utility model to solve the above problems is as follows: a vertical rolling mill universal joint hoisting device, including a hoisting beam, a vertical mounting frame, an adjustment mechanism, a hinge seat, an end clamping piece, an electric push rod, a bottom push plate, and a PLC control system. The connection relationship and structural design of each component are as follows: hoisting crossbeam Material: Made of Q345B high-strength alloy steel, welded and formed with an I-shaped cross section and a length of 2-3m, ensuring a load-bearing capacity of ≥5t (meeting the weight requirements of mainstream universal joints). Balanced suspension structure: Reinforcing lugs are welded to the four corners of the lifting beam. Each reinforcing lug is connected to a lifting cable made of steel wire rope through a shackle. The tops of the four lifting cables converge and are connected to the crane hook to form a "four-point suspension" structure, which ensures the horizontal balance of the overall lifting system and avoids the beam tilting during the lifting process.

[0010] Vertical mounting bracket Fixing method: The vertical mounting frame is a rectangular steel structure, which can be detachably fixed to the front end of the hoisting beam with high-strength bolts (M20 bolts, 4-6 bolts in total, to ensure connection strength). The connection between the two is equipped with positioning pins to prevent the mounting frame from shifting laterally. Guide structure: The inner side of the vertical mounting frame is provided with a vertical mounting groove along the height direction (groove width 80-120mm, groove depth 50-80mm), and the groove wall is provided with a wear-resistant lining plate (material is 45# steel quenched and treated, hardness HRC40-45), which provides a stable moving track for the adjustment mechanism.

[0011] Positioning mechanism Core components include the first geared motor, lead screw, first lead screw sleeve, and bearing housing; Connection relationship: The first geared motor (power 0.75kW, speed 100r / min, with braking function) is fixed to the top of the vertical mounting slot through the motor base. One end of the lead screw (diameter 30-50mm, lead 10-16mm) is connected to the output shaft of the first geared motor through a coupling, and the other end is rotatably connected to the bottom end of the vertical mounting slot through a deep groove ball bearing seat. The first lead screw sleeve (internal thread adapted to the lead screw) is sleeved on the outside of the lead screw, and its outer wall is slidably fitted with the wear-resistant liner of the vertical mounting slot. The outer wall of the sleeve is also provided with a guide protrusion, which is adapted to the guide groove of the inner wall of the vertical mounting slot to prevent the sleeve from rotating synchronously with the lead screw. Function: The first reducer motor drives the lead screw to rotate forward and backward, which in turn moves the first lead screw sleeve up and down along the vertical mounting groove, thereby adjusting the height of the end clamping part and adapting to universal shafts of different lengths (height adjustment range 0-1500mm, adjustment accuracy ±1mm).

[0012] End clamping parts Connection method: Hinged to the first lead screw sleeve via a hinge seat (the hinge seat adopts a cross shaft structure, allowing the end clamping parts to be finely adjusted within ±5°, adapting to the slight tilt of the universal joint top). Overall structure: includes a clamping frame, a clamping drive unit, and two sets of symmetrically arranged side clamping assemblies; Clamping frame: A rectangular welded frame (made of Q235 steel) used to support the clamping drive and side clamping components; Clamping drive components include a double-ended lead screw, a second geared motor, and a support base; the two ends of the double-ended lead screw (diameter 25-40mm, threads at both ends in opposite directions, lead 8-12mm) are fixed in the clamping frame via sliding bearing seats; the second geared motor (power 0.5kW, speed 80r / min) is fixed to one side of the clamping frame via a motor base, and its output shaft is connected to one end of the double-ended lead screw via a coupling. Side clamp assembly: Each side clamp assembly includes a vertical support rod (made of 45# steel, with a square cross-section), an arc-shaped clamping plate, and a polyurethane anti-slip coating; one end of the vertical support rod is fixedly connected to the nut of the double-ended screw, and the other end is detachably connected to the arc-shaped clamping plate by bolts; the curvature of the arc-shaped clamping plate is designed according to the diameter of the universal joint (available in five specifications: 100mm, 150mm, 200mm, 250mm, and 300mm, which can be quickly replaced), and its inner wall is sprayed with a 2-3mm thick polyurethane anti-slip coating (friction coefficient ≥0.8), which enhances the clamping force and avoids scratching the surface of the universal joint; Function: The second geared motor drives the double-ended lead screw to rotate. Since the threads at both ends of the double-ended lead screw rotate in opposite directions, the two sets of side clamping assemblies move synchronously towards the center or outward to clamp the top of the universal joint (clamping stroke 0-200mm, clamping force can be adjusted by controlling the motor output torque through PLC, range 1-3kN).

[0013] Electric push rod and bottom push plate Electric actuator: An electro-hydraulic actuator (thrust 5kN, stroke 0-500mm, response time 0.5s, with position feedback function) is used and fixed to the ground base or the auxiliary crossbeam of the workshop crane by a bracket (the installation position can be adjusted according to the site conditions). Bottom push plate: It is an arc-shaped steel plate (Q235 steel, 10-15mm thick), with an arc-shaped groove on its inner side that matches the outer wall of the universal joint (the arc of the groove matches the arc-shaped clamping plate). A 5-10mm thick rubber anti-slip pad is pasted on the inner side of the groove. The bottom push plate is fixedly connected to the front end of the piston rod of the electric push rod through a flange. Function: The electric push rod pushes the bottom push plate through the extension and retraction of the piston rod, adjusts the position of the bottom end of the universal joint, corrects the tilt of the universal joint in real time, and ensures that the universal joint remains vertical during the hoisting process.

[0014] PLC control system Core components: Siemens S7-200 SMART PLC, equipped with a 7-inch touchscreen as the human-machine interface; Connection relationship: The PLC is electrically connected to the first geared motor, the second geared motor, and the electric push rod, and is also connected to a laser verticality sensor (installed on the side of the end clamping part, with a detection accuracy of ±0.1°). Function: After the operator inputs the length and diameter parameters of the universal joint via the touch screen, the PLC automatically controls the first geared motor to adjust the height of the end clamping parts and controls the second geared motor to adjust the spacing of the side clamping components and clamp the universal joint. During the hoisting process, the verticality sensor detects the verticality of the universal joint in real time. If tilt is detected (error > 0.3°), the PLC immediately controls the electric push rod to push the bottom push plate to correct the posture, realizing the integrated operation of "automatic adaptation - automatic clamping - real-time straightening".

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. Significantly improved flexibility, adaptable to multiple sizes of universal joints. The longitudinal height of the end clamping piece can be adjusted from 0 to 1500 mm via the adjustment mechanism, which is compatible with universal shafts of 1-3 m in length; the transverse clamping stroke of the interchangeable arc-shaped clamping plate (five specifications) and the side clamping assembly is 0-200 mm, which is compatible with universal shafts of 100-300 mm in diameter. The adjustment process does not require disassembling the equipment; it only requires inputting parameters via PLC or manually replacing the arc-shaped clamp (replacement time ≤ 5 minutes). The adjustment efficiency is more than 10 times higher than that of existing equipment, meeting the rapid switching needs of various specifications of universal joints in steel workshops.

[0016] 2. Lifting stability is greatly enhanced, and safety is improved. The end clamping component adopts a design of "double-headed screw synchronous drive + arc-shaped clamping plate + polyurethane anti-slip coating", which ensures uniform clamping force distribution and a friction coefficient ≥0.8, effectively preventing slippage of the top of the universal joint. The bottom end is aligned in real time via an electric push rod and a bottom push plate with anti-slip pads. Combined with closed-loop control of a laser verticality sensor, it ensures that the verticality error of the universal joint is ≤0.5°, completely avoiding the risk of collision and damage caused by tilting of existing equipment, and improving the safety of hoisting by more than 90%.

[0017] 3. Simple operation, reducing reliance on manual labor With PLC automated control, the operator only needs to input the universal joint parameters (length, diameter) on the touch screen, and the equipment can automatically complete the height adjustment, clamping, and straightening operations. A single person can complete the entire hoisting process. No manual adjustment using crowbars or ropes is required, reducing the number of operators (from 2-3 people to 1 person), lowering labor costs, and avoiding safety hazards caused by personnel coordination errors.

[0018] 4. High degree of automation, improving hoisting efficiency and precision. It integrates a closed-loop control logic of "parameter input - automatic adjustment - real-time detection - dynamic correction", eliminating the need for manual judgment and ensuring that the hoisting accuracy is not affected by personnel skills (verticality error ≤0.5°, clamping force control accuracy ±0.1kN). The time for a single hoisting operation is reduced from 30-60 minutes with existing equipment to 10-15 minutes, increasing efficiency by 2-3 times. It is especially suitable for maintenance and replacement of multiple batches of universal joints in steel workshops.

[0019] 5. Compact structure and strong adaptability Each component is modularly designed, the vertical mounting frame and the lifting beam are detachably connected, and the electric push rod installation position is adjustable, making it easy to arrange in the confined space of the rolling mill workshop; Core components (such as geared motors and electric actuators) all use industrial-grade standard parts, making maintenance and replacement convenient. The overall service life of the equipment can reach 8-10 years, reducing later maintenance costs. Attached Figure Description

[0020] Figure 1 is a schematic diagram of the overall structure of this utility model; Label 1 - Lifting beam, 11 - Lifting cable, 2 - Vertical mounting frame, 21 - Vertical mounting slot, 3 - Adjustment mechanism, 4 - Hinge seat, 5 - End clamping piece, 6 - Electric push rod, 7 - Bottom push plate.

[0021] Figure 2 is a schematic diagram of the adjustment mechanism of this utility model; Label 31 - First geared motor, 32 - Lead screw, 33 - Bearing housing.

[0022] Figure 3 is a schematic diagram of the end clamping component structure of this utility model; Label 51 - Clamping frame, 52 - Clamping drive, 53 - Side clamp assembly.

[0023] Figure 4 is a schematic diagram of the clamping drive component of this utility model; Label 521 - Double-ended lead screw, 522 - Support base, 523 - Second geared motor.

[0024] Figure 5 is a schematic diagram of the side clamp assembly structure of this utility model; Label 531 - Vertical support rod, 532 - Clamping plate fixing plate, 533 - Curved clamping plate. Detailed Implementation

[0025] The technical solution of this utility model will be described in more detail below with reference to preferred embodiments. However, these embodiments are merely descriptions of preferred implementations of this utility model and should not be construed as limiting the scope of this utility model in any way.

[0026] (a) Preparations before implementation Equipment inspection: Confirm that the hoisting beam, vertical mounting frame, adjustment mechanism, end clamps, electric push rods and other components are free from deformation and damage; check whether the circuit connections of the PLC control system, verticality sensor, geared motor and electric push rod are normal; Parameter confirmation: Obtain the parameters of the universal joint to be hoisted: length L=2.2m, diameter D=200mm; Component replacement: Select an arc-shaped clamp with the corresponding curvature according to the diameter D=200mm, and fix it to the vertical support rod of the side clamp assembly with bolts (replacement time is about 3 minutes).

[0027] (II) Lifting Operation Procedure System suspension and initialization Connect the top ends of the four hoisting cables to the crane hook, start the crane to lift the entire hoisting system to a height of 1.5m above the ground, and make minor adjustments to the length of the hoisting cables to ensure that the hoisting beam is level (levelness error ≤0.2°). The operator inputs the universal joint parameters (length 2.2m, diameter 200mm) on the PLC touch screen and clicks the "Initialize" button. The PLC automatically controls the first geared motor to start, drives the lead screw to rotate, and moves the first lead screw sleeve downward along the vertical mounting groove, adjusting the height of the end clamping part to the preset position of "suitable for 2.2m long universal joint" (the initial distance between the end clamping part and the bottom push plate is set to 2.1m, with a 100mm adjustment margin).

[0028] The top of the universal joint is clamped. The crane moves slowly, aligning the end clamps with the top of the universal joint to be lifted (50mm from the top of the universal joint). The PLC automatically controls the second geared motor to start, driving the double-ended lead screw to rotate (forward). Since the threads at both ends of the double-ended lead screw rotate in opposite directions, the two sets of side clamping components move synchronously towards the center, and the arc-shaped clamping plate gradually fits against the outer wall of the top of the universal joint. When the PLC detects that the output torque of the second geared motor reaches the preset value (2kN, corresponding to a clamping force that meets the anti-slip requirements), the second geared motor stops running, and the end clamping components complete the clamping of the top of the universal joint (the clamping process takes about 20 seconds).

[0029] Universal joint lifting and real-time straightening Start the crane and slowly raise the universal joint (lifting speed set to 0.5m / min); at the same time, the verticality sensor detects the verticality of the universal joint in real time and transmits the detection data to the PLC; When the universal joint is raised to a height of 1m above the ground, the verticality sensor detects that the universal joint is tilted to the left (tilt angle 0.4°, exceeding the threshold of 0.3°). The PLC immediately controls the electric push rod to move (piston rod extends 50mm), pushing the bottom push plate to move to the right to correct the universal joint's posture. After about 0.8 seconds, the verticality sensor detects that the tilt angle has dropped to 0.2°, the PLC controls the electric push rod to stop moving, and the universal joint returns to a vertical state.

[0030] Universal joint positioning and installation The crane continues to lift the universal joint to the installation height of the vertical rolling mill (50mm from the mill connecting flange). The PLC monitors the verticality in real time through a verticality sensor. If a slight tilt occurs (e.g., 0.25°), it immediately controls the electric push rod to make fine adjustments (piston rod extension ≤ 10mm) to ensure that the universal joint is always coaxial with the axis of the mill connecting flange (coaxiality error ≤ 0.3mm). The operator assists in aligning the bottom end of the universal joint with the mounting hole of the mill connecting flange. After confirming the alignment, the operator clicks the "Release Clamp" button on the PLC touch screen. The PLC controls the second geared motor to reverse, driving the double-headed lead screw to rotate. The two sets of side clamping assemblies move outward synchronously, releasing the top of the universal joint. At the same time, the electric push rod piston rod retracts, and the bottom push plate separates from the universal joint. The crane slowly lowered the universal joint and installed it onto the rolling mill connecting flange, completing the hoisting operation (the entire hoisting process took about 12 minutes).

[0031] (III) Post-implementation inspection Equipment reset: After hoisting is completed, the PLC controls the reset of each component (the first geared motor reverses, the end clamping parts rise to the initial height; the electric push rod piston rod retracts to the initial position). Condition check: Check whether the anti-slip coating of the curved clamp is intact, and whether there is any abnormal noise from the electric push rod and the reduction motor to ensure that the equipment is fault-free.

[0032] (iv) Verification of implementation results Adaptability: Successfully adapts to universal joints with a length of 2.2m and a diameter of 200mm, without requiring structural adjustments to the equipment; Stability: During the hoisting process, the universal joint does not slip or shift, and the verticality error is always controlled within 0.5°; Efficiency: Single hoisting time is 12 minutes, a 65% improvement compared to existing equipment (approximately 40 minutes); Human resources: Only one operator completes all operations, reducing reliance on human resources.

[0033] The above are merely specific embodiments of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this invention should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A universal joint hoisting device for a vertical rolling mill, characterized in that, The system includes a lifting beam, a vertical mounting frame, an adjusting mechanism, a hinged seat, end clamps, an electric push rod, and a bottom push plate. Lifting cables are installed at each of the four corners of the lifting beam for suspending and balancing the overall lifting system. The vertical mounting frame is vertically fixed to the front end of the lifting beam, and a vertical mounting groove is formed along the height direction on the inner side of the vertical mounting frame. The adjusting mechanism is located inside the vertical mounting groove and includes a first reduction motor, a lead screw, and a first lead screw sleeve. The first reduction motor is fixed to the top of the vertical mounting groove. One end of the lead screw is connected to the output shaft of the first reduction motor, and the other end of the lead screw is rotatably connected to the bottom of the vertical mounting groove via a bearing seat. The first lead screw sleeve is threadedly engaged with the lead screw. The end clamps are hinged to the first lead screw sleeve via the hinged seat. The end clamps include a clamping frame, a clamping drive component, and two sets of symmetrically distributed side clamps. The clamping assembly includes a clamping drive unit installed within the clamping frame. The clamping drive unit comprises a double-ended lead screw, a second geared motor, and a coupling. The second geared motor is fixed to one side of the clamping frame. The two ends of the double-ended lead screw are rotatably connected to the clamping frame via support seats. One end of the double-ended lead screw is connected to the output shaft of the second geared motor via the coupling, and the threads at both ends of the double-ended lead screw have opposite directions. Two sets of side clamping assemblies are threadedly engaged with the threaded sections at both ends of the double-ended lead screw. Each set of side clamping assemblies includes a vertical support rod and an arc-shaped clamping plate. One end of the vertical support rod is fixedly connected to the nut of the double-ended lead screw, and the other end of the vertical support rod is fixedly connected to the arc-shaped clamping plate. An electric push rod is located below the end clamping member. The front end of the piston rod of the electric push rod is fixedly connected to the bottom push plate. The inner side of the bottom push plate has an arc-shaped groove adapted to the outer wall of the universal joint.

2. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, The lifting beam is made of Q345B high-strength alloy steel and welded into shape with an I-shaped cross section. The load-bearing capacity of the lifting beam is ≥5t. The lifting cable is made of steel wire rope. A reinforcing lug is welded at the connection between the lifting cable and the lifting beam. The reinforcing lug is connected to the lifting cable through a shackle.

3. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, The vertical mounting frame and the lifting beam are detachably connected by M20 high-strength bolts, and a positioning pin is provided at the connection between the vertical mounting frame and the lifting beam; the wall of the vertical mounting groove is lined with a wear-resistant liner plate treated with 45# steel quenching, and the hardness of the wear-resistant liner plate is HRC40-45.

4. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, The outer wall of the first lead screw sleeve is provided with a guide protrusion, and the inner wall of the vertical mounting groove is provided with a guide groove adapted to the guide protrusion; the height adjustment range of the adjustment mechanism is 0-1500mm, and the adjustment accuracy is ±1mm; the power of the first geared motor is 0.75kW, the speed is 100r / min, and the first geared motor has a braking function.

5. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, The inner wall of the arc-shaped clamp is provided with an anti-slip coating. The anti-slip coating is made of polyurethane, with a coating thickness of 2-3mm and a friction coefficient ≥0.

8. The arc-shaped clamp is available in various arc specifications to accommodate universal shafts with a diameter of 100-300mm. The arc-shaped clamp and the vertical support rod are detachably connected by bolts.

6. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, A rubber anti-slip pad is attached to the inner side of the arc-shaped groove of the bottom push plate, and the thickness of the rubber anti-slip pad is 5-10mm; the electric push rod is an electro-hydraulic push rod with a thrust of 5kN, a stroke of 0-500mm, a response time of 0.5s, and the electric push rod has a position feedback function.

7. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, It also includes a PLC control system, which is electrically connected to the first geared motor, the second geared motor, and the electric actuator. The PLC control system uses a Siemens S7-200 SMART PLC and is equipped with a 7-inch touchscreen as the human-machine interface. The PLC control system is also connected to a verticality sensor, which is installed on the side of the end clamping member and has a detection accuracy of ±0.1°. When the verticality sensor detects that the universal joint tilt angle is >0.3°, the PLC control system controls the electric actuator to correct the universal joint posture and ensure that the verticality error of the universal joint is ≤0.5°.

8. The vertical rolling mill universal joint hoisting device according to claim 1, characterized in that, The second geared motor has a power of 0.5kW and a speed of 80r / min; the clamping stroke of the end clamping member is 0-200mm, the clamping force adjustment range is 1-3kN, and the PLC control system controls the clamping force by detecting the output torque of the second geared motor.

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