Mold opening and closing device

Abstract

A mold opening and closing locking device belongs to the technical field of plastic product molding equipment. It includes a dead-point overrunning self-locking mechanism located between a swing arm connecting frame and a left mold frame. The dead-point overrunning self-locking mechanism comprises a motor, a gearbox, a swing arm, a pull arm, and a right hinge seat for the pull arm. The motor is horizontally fixed to the front of the gearbox and drives the gearbox. The gearbox shaft faces rearward. The left end of the swing arm is hinged to the upper right side of the swing arm connecting frame. The gearbox shaft is hinged to the left end of the swing arm on the upper right side of the swing arm connecting frame. The left end of the pull arm is hinged to the right end of the swing arm. The right end of the pull arm is hinged to the right hinge seat for the pull arm. The right hinge seat for the pull arm is fixed to the middle left side of the left mold frame in the height direction. Advantages: The dead-point overrunning self-locking mechanism can achieve dead-point mold locking, generating a strong self-locking force to ensure the quality of plastic products; it saves energy, avoids oil leakage, and embodies clean production; it eliminates problems such as mold frame deformation caused by eccentricity.

Description

Technical Field

[0001] This utility model belongs to the technical field of plastic product molding equipment, specifically relating to a mold opening and closing locking device. Background Technology

[0002] As is known in the industry, for each product molded by a plastic product molding machine, the left and right mold frames (also called "left and right half molds") open and close once. Opening the mold allows the molded product to leave the mold, while closing the mold involves introducing molten plastic into the left and right half molds and allowing the product to solidify within the required molding time. Taking hollow plastic products such as various sizes of gallon barrels, stackable barrels, IBC containers, and water tanks for blow molding (also called "blow molding") as an example, with the left and right mold frames and the left and right molds mounted on them in the closed state, a robotic arm or other similar device introduces the molten plastic billet obtained from the previous process between the left and right half molds. Then, the blow molding device's blow needle performs the blow molding. Throughout the blow molding process, the left and right half molds remain in a reliable closed state, which is commonly referred to in the industry as the locked state.

[0003] In existing mold-closing and clamping devices, the power mechanism almost universally uses hydraulic cylinders. However, using hydraulic cylinders has at least the following drawbacks: First, the clamping force cannot meet industry expectations, as the quality of the clamping effect and / or the strength of the clamping force affects product quality. For hollow plastic products, insufficient clamping force can leave flash at the joint surface, a major quality concern. Flash often requires removal by subsequent equipment, which is labor-intensive, inefficient, and of questionable quality, wasting valuable labor resources. Second, it lacks energy-saving benefits. During the pressure-holding phase after clamping (also known as the "pressure-holding period"), the clamping cylinder, like a hydraulic press, must continuously operate a high-pressure oil pump, increasing energy consumption. Third, it fails to meet clean production requirements. Hydraulic cylinder clamping inevitably leads to oil leakage, impacting the work environment. Furthermore, the need for frequent hydraulic oil changes during shutdown increases operating costs and affects the efficiency of the plastic molding machine. Utility Model Content

[0004] The objective of this invention is to provide a mold opening and closing device that helps to provide excellent clamping force to ensure pressure holding during the molding process of plastic products and avoid the production of defective products; facilitates the elimination of the use of hydraulic cylinders to significantly reduce energy consumption and avoid oil leakage to achieve clean production; and helps to ensure the ideal uniformity of clamping force to eliminate problems such as mold frame deformation caused by eccentric torque.

[0005] The present invention accomplishes its objective as follows: a mold opening and closing locking device includes a dead-point overrunning self-locking mechanism disposed between a swing arm connecting frame and a left mold frame. The dead-point overrunning self-locking mechanism comprises a motor, a gearbox, a swing arm, a pull arm, and a right hinge seat for the pull arm. The motor is fixed to the front of the gearbox in a horizontal position and engages with the gearbox in transmission. The gearbox shaft faces rearward. The left end of the swing arm is hinged to the upper right side of the swing arm connecting frame. The gearbox shaft is hinged to the left end of the swing arm on the upper right side of the swing arm connecting frame. The left end of the pull arm is hinged to the right end of the swing arm, and the right end of the pull arm is hinged to the right hinge seat for the pull arm. The right hinge seat for the pull arm is fixed to the middle left side of the left mold frame in the height direction.

[0006] In a specific embodiment of this utility model, a pair of horizontally cantilevered hinge lugs of the swing arm connecting frame are fixed to the upper right side of the swing arm connecting frame, and are parallel to each other and have the same shape and size. A swing arm connecting frame hinge lug bearing receiving hole is opened on each pair of swing arm connecting frame hinge lugs at corresponding positions. A swing arm connecting frame hinge lug bearing is provided in the swing arm connecting frame hinge lug bearing receiving hole. The left end of the swing arm is inserted between the pair of swing arm connecting frame hinge lugs, and a swing arm transmission connection hole is opened at the left end of the swing arm. The swing arm transmission connection hole corresponds to the bearing inner ring hole of the swing arm connecting frame hinge lug bearing. The gearbox shaft is inserted into the swing arm transmission connection hole at the position corresponding to the bearing inner ring hole and is connected to the swing arm transmission.

[0007] In another specific embodiment of this utility model, a flat key is formed on the gearbox shaft, and a flat keyway is formed on the wall of the swing arm transmission connection hole, and the flat key and the flat keyway are fixed together.

[0008] In another specific embodiment of this utility model, the motor is a servo motor with forward and reverse rotation functions.

[0009] In another specific embodiment of this utility model, a pair of swing arm bearings are provided at the right end of the swing arm, which are positioned in a front-to-back correspondence and spaced apart from each other. Each of the pair of swing arm bearings is provided with a left hinge shaft bearing. The left end of the swing arm is inserted between the pair of swing arm bearings and is hinged to the pair of swing arm bearings at the position corresponding to the left hinge shaft bearing via the left hinge shaft. A pair of right hinge ears are provided on the left side of the right hinge seat in a horizontal cantilever state, which are both corresponding to and spaced apart from each other. A right hinge shaft bearing is provided on each pair of right hinge ears at a corresponding position. The right end of the swing arm is inserted between the pair of right hinge ears and is hinged to the pair of right hinge ears at the position corresponding to the right hinge shaft bearing via the right hinge shaft.

[0010] In another specific embodiment of this utility model, a left hinge shaft anti-movement plate for preventing the left hinge shaft of the pull arm from moving back and forth is fixed on each of the opposite sides of the pair of swing arm shaft seats; and a right hinge shaft anti-movement plate for preventing the right hinge shaft of the pull arm from moving back and forth is fixed on each of the opposite sides of the pair of right hinge ears of the pull arm.

[0011] In a further specific embodiment of this utility model, the right hinge seat of the pull arm is fixed to the left side of a right hinge seat fixing plate of the pull arm, and the right hinge seat fixing plate of the pull arm is fixed to the middle of the left side of the left mold frame in the height direction.

[0012] In a further specific embodiment of this utility model, a left threaded head is formed at the left end of the pull arm, and a right threaded head is formed at the right end of the pull arm. A left hinge shaft connector is threaded onto the left threaded head of the pull arm, and a left hinge shaft hole is formed at the left end of the left hinge shaft connector. A right hinge shaft connector is threaded onto the right threaded head of the pull arm, and a right hinge shaft hole is formed at the right end of the right hinge shaft connector. The left hinge shaft is hinged to the pair of swing arm bearings at a position corresponding to the left hinge shaft hole, and the right hinge shaft is hinged to the pair of right hinge lugs at a position corresponding to the right hinge shaft hole.

[0013] In yet another specific embodiment of this utility model, a left locking nut for the pull arm is threaded onto the left threaded head of the pull arm, and a right locking nut for the pull arm is threaded onto the right threaded head of the pull arm.

[0014] The technical solution provided by this utility model is that the dead-point overrunning self-locking mechanism, composed of a motor, a gearbox, a swing arm, a pull arm, and a right hinge seat of the pull arm, can achieve dead-point mold locking and generate a strong self-locking force, ensuring the quality of plastic products. Since only a very small force is needed to ensure mold locking during the dead-point mold locking and pressure holding stage, it is not necessary to use a high-pressure oil pump to continuously operate to meet the cylinder pressure as with a hydraulic cylinder, thus significantly saving energy consumption and avoiding oil leakage, thereby achieving clean production. Since the center mold locking can fully ensure the ideal uniformity of the mold locking force, problems such as mold frame deformation caused by eccentricity can be eliminated. Attached Figure Description

[0015] Figure 1 This is a structural diagram of an embodiment of the present utility model;

[0016] Figure 2 for Figure 1 A preferred embodiment of the pull arm is shown in the diagram;

[0017] Figure 3 This is a schematic diagram illustrating an application example of this utility model.

[0018] In the diagram: 1. Swing arm connecting frame; 11. Swing arm connecting frame hinge lug; 111. Swing arm connecting frame hinge lug bearing receiving hole; 1111. Swing arm connecting frame hinge lug bearing; 11111. Bearing inner ring hole; 2. Left mold frame; 3. Dead point overrunning self-locking mechanism; 31. Motor; 32. Gearbox; 321. Gearbox shaft; 3211. Flat key; 33. Swing arm; 331. Swing arm transmission connecting hole; 3311. Flat keyway; 332. Swing arm shaft seat; 3321. Pull arm left hinge shaft bearing; 3322. Pull arm left hinge shaft anti-slip plate; 34. Pull arm; 341. Pull arm left hinge shaft; 342. Pull arm right hinge shaft; 343. Pull arm left threaded head; 3431. Pull arm left hinge shaft connector; 34311. 3432. Left hinge shaft hole of the pull arm; 344. Left locking nut of the pull arm; 3441. Right threaded head of the pull arm; 3441. Right hinge shaft connector of the pull arm; 34411. Right hinge shaft hole of the pull arm; 3442. Right locking nut of the pull arm; 35. Right hinge seat of the pull arm; 351. Right hinge ear of the pull arm; 3511. Right hinge shaft bearing of the pull arm; 3512. Anti-movement plate of the right hinge shaft of the pull arm; 352. Fixing plate of the right hinge seat of the pull arm; 4. Base; 5. Left pull arm; 6. Right pull arm; 7a. Upper pull rod; 7b. Lower pull rod; 8. Right mold frame; 9. Synchronization mechanism. Detailed Implementation

[0019] In order to better understand the technical essence and beneficial effects of this utility model, the applicant provides a detailed description below by way of embodiments. However, the description of the embodiments is not intended to limit the solution of this utility model. Any formal but not substantive equivalent transformations made based on the concept of this utility model should be considered within the scope of the technical solution of this utility model.

[0020] In the following description, all directional or positional concepts involving up, down, left, right, front, and back are based on the current position. Figure 1 The location is based on the position, and therefore should not be construed as a special limitation on the technical solution provided by this utility model.

[0021] Please see Figure 1 This illustrates a dead-point overrunning self-locking mechanism 3 positioned between the opposing sides of the swing arm connecting frame 1 and the left mold frame 2.

[0022] The key technical points of the technical solution provided by this utility model are as follows: The aforementioned dead-point overrunning self-locking mechanism 3 includes a motor 31, a reduction gearbox 32, a swing arm 33, a pull arm 34, and a pull arm right hinge seat 35. The motor 31 is fixed to the front side of the reduction gearbox 32 in a horizontal position and is in transmission cooperation with the reduction gearbox 32. The reduction gearbox shaft 321 of the reduction gearbox 32 faces backward. The left end of the swing arm 33 is hinged to the upper right side of the swing arm connecting frame 1. The aforementioned reduction gearbox shaft 321 is hinged to the left end of the swing arm 33 on the upper right side of the swing arm connecting frame 1. The left end of the pull arm 34 is hinged to the right end of the swing arm 33, and the right end of the pull arm 34 is hinged to the pull arm right hinge seat 35. The pull arm right hinge seat 35 is fixed to the middle left side in the height direction of the left mold frame 2.

[0023] A pair of horizontally cantilevered hinge lugs 11, which are parallel to each other and have the same shape and size, are fixed on the upper right side of the aforementioned swing arm connecting frame 1. A swing arm connecting frame hinge lug bearing receiving hole 111 is opened on the pair of swing arm connecting frame hinge lugs 11 at corresponding positions. A swing arm connecting frame hinge lug bearing 1111 is provided in the swing arm connecting frame hinge lug bearing receiving hole 111. The left end of the aforementioned swing arm 33 is inserted between the aforementioned pair of swing arm connecting frame hinge lugs 11, and a swing arm transmission connection hole 331 is opened at the left end of the swing arm 33. The swing arm transmission connection hole 331 corresponds to the bearing inner ring hole 11111 of the swing arm connecting frame hinge lug bearing 1111. The aforementioned gearbox shaft 321 is inserted into the aforementioned swing arm transmission connection hole 331 at the position corresponding to the bearing inner ring hole 11111 and is connected to the swing arm 33 for transmission.

[0024] Depend on Figure 1 As shown, a flat key 3211 is formed on the aforementioned gearbox shaft 321, and a flat keyway 3311 is formed on the hole wall of the aforementioned swing arm transmission connection hole 331. The flat key 3211 and the flat keyway 3311 are key-fitted and fixed.

[0025] In this embodiment, the aforementioned motor 31 is a servo motor with forward and reverse rotation functions.

[0026] See you later Figure 1Extending from the right end of the aforementioned swing arm 33 are a pair of swing arm bearing seats 332 that are positioned opposite each other and spaced apart. Each of the pair of swing arm bearing seats 332 is provided with a left hinge shaft bearing 3321. The left end of the aforementioned pull arm 34 is inserted between the pair of swing arm bearing seats 332 and is hinged to the pair of swing arm bearing seats 332 at a position corresponding to the left hinge shaft bearing 3321 via the left hinge shaft 341. Extending horizontally in a cantilevered state from the left side of the aforementioned right hinge seat 35 are a pair of right hinge ears 351 that are both opposite each other and spaced apart. Each of the pair of right hinge ears 351 is provided with a right hinge shaft bearing 3511 at a position corresponding to the right hinge shaft bearing 3511. The right end of the pull arm 34 is inserted between the pair of right hinge ears 351 and is hinged to the pair of right hinge ears 351 at a position corresponding to the right hinge shaft bearing 3511 via the right hinge shaft 342.

[0027] See you later Figure 1 On each of the two opposing sides of the aforementioned pair of swing arm bearing seats 332, a left hinge shaft anti-movement plate 3322 for preventing the left hinge shaft 341 of the aforementioned swing arm from moving back and forth is fixed; on each of the two opposing sides of the aforementioned pair of right hinge ears 351, a right hinge shaft anti-movement plate 3512 for preventing the right hinge shaft 342 of the aforementioned swing arm from moving back and forth is fixed.

[0028] Preferably, the aforementioned right hinge seat 35 of the pull arm is fixed to the left side of a right hinge seat fixing plate 352 of the pull arm, and the right hinge seat fixing plate 352 of the pull arm is fixed to the middle of the left side of the aforementioned left mold frame 2 in the height direction.

[0029] Please see Figure 2 A left threaded head 343 is formed at the left end of the aforementioned pull arm 34, and a right threaded head 344 is formed at the right end of the pull arm 34. A left hinge shaft connector 3431 is threaded onto the left threaded head 343, and a left hinge shaft hole 34311 is formed at the left end of the left hinge shaft connector 3431. A right hinge shaft connector 3441 is threaded onto the right threaded head 344, and a right hinge shaft hole 34411 is formed at the right end of the right hinge shaft connector 3441. The left hinge shaft 341 is hinged to the aforementioned pair of swing arm bearings 332 at the position corresponding to the left hinge shaft hole 34311, and the right hinge shaft 342 is hinged to the aforementioned pair of right hinge ears 351 at the position corresponding to the right hinge shaft hole 34411.

[0030] As can be seen from the above description, the aforementioned pull arm 34 can be adjusted as needed to make adaptive compensation adjustments for factors such as mold errors.

[0031] A left locking nut 3432 is threaded onto the left threaded head 343 of the aforementioned pull arm, and a right locking nut 3442 is threaded onto the right threaded head 344 of the aforementioned pull arm.

[0032] Please see Figure 3 ,exist Figure 3 The diagram shows a base 4, left and right pull arms 5 and 6, upper and lower pull rods 7a and 7b, a right mold frame 8, and a pair of synchronization mechanisms 9. The base 4, in its operational state, is mounted on a raised platform (like a floor) above the ground, on the ground itself, or on a similar carrier based on the ground. The left pull arm 5 corresponds to the upper left end of the base 4, and the right pull arm 6 corresponds to the upper right end of the base 4 and is opposite to the left pull arm 5. An upper pull rod 7 connects the upper ends of the left and right pull arms 5 and 6 on opposite sides. a. A lower pull rod 7b is connected between the lower ends of the left and right pull arms 5 and 6 on opposite sides and below the upper pull rod 7a. The upper and lower pull rods 7a and 7b are parallel to each other. The bottoms of the left and right mold frames 2 and 8 each form a sliding pair with the aforementioned base 4, and the center position of the right side of the right mold frame 8 is fixed to the middle left side of the aforementioned right pull arm 6 in the height direction. The upper left side of the aforementioned swing arm connecting frame 1 is fixed to the middle right side of the aforementioned left pull arm 5 in the height direction, and the bottom forms a sliding pair with the aforementioned base 4. A pair of synchronization mechanisms 9 are provided on the aforementioned base 4 at a position between the lower ends of the aforementioned swing arm connecting frame 1 and the left mold frame 2 and are connected to the lower ends of the swing arm connecting frame 1 and the left mold frame 2.

[0033] because Figure 3 In the mold-closed and locked state, the applicant combined Figure 1 To explain: When the mold is closed, the motor 31 of the self-locking mechanism 3 operates, driving the reduction gearbox 32. Since the key 3211 on the reduction gearbox shaft 321 is keyed to the keyway 3311 in the swing arm transmission connection hole 331 at the left end of the swing arm 33, the reduction gearbox shaft 321 drives the swing arm 33. Because the left end of the pull arm 34 is hinged to a pair of swing arm bearing seats 332 at the right end of the swing arm 33, and the right end of the pull arm 34 is connected to the... The left mold frame 2 is hinged to the right hinge seat 35 of the pull arm on the left side. Therefore, when the gearbox shaft 321 drives the swing arm 33 to move, the swing arm 33 drives the pull arm 34. The pull arm 34 acts on the right hinge seat 35 of the pull arm, causing the left mold frame 2 to move to the right. During the rightward movement of the left mold frame 2, the swing arm connecting frame 1 is driven to move to the left through the synchronization mechanism 9. The swing arm connecting frame 1 pulls the right mold frame 8 to the left through the upper and lower pull rods 7a and 7b, thus cooperating with the left mold frame 2 to complete the mold closing. According to professional knowledge, the left half mold and the right half mold (not shown in the figure) are fixed on opposite sides of the left and right mold frames 2 and 8.

[0034] During the aforementioned process, when the axes of the gearbox shaft 321, the left hinge shaft 341 of the pull arm, and the right hinge shaft 342 of the pull arm are on the same horizontal plane, the machine is in a dead-point locking state. That is, the swing arm 33 and the pull arm 34 are on the same straight line, and the right hinge seat 35 of the pull arm presses against the left mold frame 2. In the dead-point locking state, the machine does not need to continuously exert a large force to maintain the locking state, but relies on the self-locking of the mechanical structure. Since mold opening only requires the motor 31 to work in reverse, the movement state of the corresponding components is reversed as described above.

[0035] Figure 3 The diagram illustrates the structure of three templates, namely the left and right mold frames 2 and 8, and the swing arm connecting frame 1 plus the inclined pull arms, namely the left and right pull arms 5 and 6, plus two tie rods, namely the upper and lower tie rods 7a and 7b. The locking point is located at the center of the mold, and the locking force is uniform. The dead point locking can be achieved by electric mold opening and closing. When the dead point locking is performed, the pull arm 34 is flattened, thus reflecting energy saving.

[0036] In summary, the technical solution provided by this utility model makes up for the shortcomings of the prior art, successfully completes the invention task, and faithfully realizes the technical effects described by the applicant in the above technical effect column.

Claims

1. A mold opening and closing locking device, comprising a dead-point overrunning self-locking mechanism (3) disposed between a swing arm connecting frame (1) and a left mold frame (2), characterized in that: The dead-point over-locking mechanism (3) includes a motor (31), a gearbox (32), a swing arm (33), a pull arm (34), and a right hinge seat (35) for the pull arm. The motor (31) is fixed to the front of the gearbox (32) in a horizontal position and is in transmission cooperation with the gearbox (32). The gearbox shaft (321) of the gearbox (32) faces backward. The left end of the swing arm (33) is hinged to the upper right side of the swing arm connecting frame (1). The gearbox shaft (321) is hinged to the left end of the swing arm (33) on the upper right side of the swing arm connecting frame (1). The left end of the pull arm (34) is hinged to the right end of the swing arm (33), and the right end of the pull arm (34) is hinged to the right hinge seat (35) for the pull arm. The right hinge seat (35) for the pull arm is fixed to the middle left side of the left mold frame (2) in the height direction.

2. The mold opening and closing device according to claim 1, characterized in that: A pair of horizontally cantilevered hinge lugs (11) of the swing arm connecting frame (1) are fixed to the upper right side of the swing arm connecting frame (1), and are parallel to each other and have the same shape and size. A swing arm connecting frame hinge lug bearing receiving hole (111) is provided on each of the pair of swing arm connecting frame hinge lugs (11) at corresponding positions. A swing arm connecting frame hinge lug bearing (1111) is provided in each of the swing arm connecting frame hinge lug bearing receiving holes (111). The left end of the swing arm (33) is inserted into one of the... A swing arm drive connection hole (331) is provided between the hinge lugs (11) of the swing arm connecting frame and at the left end of the swing arm (33). The swing arm drive connection hole (331) corresponds to the bearing inner ring hole (11111) of the swing arm connecting frame hinge lug bearing (1111). The gearbox shaft (321) is inserted into the swing arm drive connection hole (331) at the position corresponding to the bearing inner ring hole (11111) and is drive-connected to the swing arm (33).

3. The mold opening and closing device according to claim 2, characterized in that: A flat key (3211) is formed on the gearbox shaft (321), and a flat keyway (3311) is formed on the wall of the swing arm transmission connection hole (331). The flat key (3211) and the flat keyway (3311) are key-fitted and fixed.

4. The mold opening and closing device according to claim 1, characterized in that: The motor (31) is a servo motor with forward and reverse rotation functions.

5. The mold opening and closing device according to claim 1, characterized in that: A pair of swing arm bearing seats (332) extend from the right end of the swing arm (33) and are positioned opposite each other and spaced apart. Each of the pair of swing arm bearing seats (332) contains a left hinge shaft bearing (3321). The left end of the pull arm (34) is inserted between the pair of swing arm bearing seats (332) and hinged to the pair of swing arm bearing seats (332) at a position corresponding to the left hinge shaft bearing (3321) via the left hinge shaft (341). The right hinge bearing seat (332)... On the left side of 35), there is a pair of right hinge lugs (351) that are both corresponding to each other and spaced apart. On each pair of right hinge lugs (351) and at corresponding positions, there is a right hinge shaft bearing (3511). The right end of the pull arm (34) is inserted between the pair of right hinge lugs (351) and is hinged to the pair of right hinge lugs (351) by the right hinge shaft (342) at the position corresponding to the right hinge shaft bearing (3511).

6. The mold opening and closing device according to claim 5, characterized in that: On each of the opposite sides of the pair of swing arm bearings (332), a left hinge shaft anti-movement plate (3322) for preventing the left hinge shaft (341) of the pull arm from moving back and forth is fixed; on each of the opposite sides of the pair of right hinge ears (351), a right hinge shaft anti-movement plate (3512) for preventing the right hinge shaft (342) of the pull arm from moving back and forth is fixed.

7. The mold opening and closing device according to claim 5, characterized in that: The right hinge seat (35) of the pull arm is fixed to the left side of a right hinge seat fixing plate (352), and the right hinge seat fixing plate (352) of the pull arm is fixed to the middle of the left side of the left mold frame (2) in the height direction.

8. The mold opening and closing device according to claim 5, characterized in that: A left threaded head (343) is formed at the left end of the pull arm (34), and a right threaded head (344) is formed at the right end of the pull arm (34). A left hinge shaft connector (3431) is threaded onto the left threaded head (343). A left hinge shaft hole (34311) is formed at the left end of the left hinge shaft connector (3431). A right hinge shaft connector is threaded onto the right threaded head (344). The head (3441) has a right hinge shaft hole (34411) at the right end of the right hinge shaft connector (3441). The left hinge shaft (341) is hinged to the pair of swing arm bearings (332) at the position corresponding to the left hinge shaft hole (34311). The right hinge shaft (342) is hinged to the pair of right hinge ears (351) at the position corresponding to the right hinge shaft hole (34411).

9. The mold opening and closing device according to claim 8, characterized in that: A left locking nut (3432) is threaded onto the left threaded head (343) of the pull arm, and a right locking nut (3442) is threaded onto the right threaded head (344) of the pull arm.

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