Screw connecting device

Abstract

The invention belongs to the technical field of injection molding machines, and particularly relates to a screw connecting device. Comprising a shell, a glue melting motor, a transmission wheel, a transmission shaft, a belt and a cushion cover, the glue melting motor is arranged on the shell, an output shaft of the glue melting motor is in transmission connection with the transmission wheel through the belt, the transmission shaft is rotationally arranged in the shell, the transmission wheel is in transmission sleeve connection with the front end of the transmission shaft, and the rear end of the transmission wheel abuts against a shaft shoulder at the front end of the transmission shaft; the front end of the transmission shaft is provided with a front-end butt-joint opening, the rear end of the transmission shaft is provided with a rear-end butt-joint opening, the cushion sleeve is slidably arranged in the front-end butt-joint opening, a cushion sleeve shaft shoulder abuts against the front end of the transmission wheel, the screw is in transmission connection in the cushion sleeve, and the cushion sleeve and the transmission shaft clamp the transmission wheel and are connected through a bolt. An output shaft of the glue injection motor is coaxially connected with the screw rod, the screw sleeve is connected with the shell and used for supporting the shell, the screw rod is sleeved with the screw sleeve in a transmission mode, the front end of the screw rod penetrates through the screw sleeve and is rotationally arranged in the butt joint opening in the rear end, and the screw rod can be prevented from deviating after being used for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of injection molding machines, and in particular relates to a screw rod connecting device. Background Art

[0002] Injection molding machines are usually composed of injection systems, mold clamping systems, hydraulic transmission systems, electrical control systems, heating and cooling systems, lubrication systems, and safety monitoring systems. Among them, the injection system is one of the most important components of the injection molding machine, which is responsible for injecting the molten plastic into the mold cavity. The injection molding system includes a screw and a drive shaft. The connection between the injection molding machine screw and the drive shaft is usually achieved through a specific transmission device or coupling. These connecting components are responsible for effectively transmitting the rotational force of the drive shaft to the screw, thereby driving the screw to rotate in the barrel.

[0003] The screw of an injection molding machine is generally driven by a belt or directly. In large injection molding machines, the belt drive has a certain overload protection capability. When the injection molding machine encounters an overload during operation, the belt may slip and act as a buffer, thereby protecting the screw and other transmission components from damage; compared to the direct motor drive, the belt drive can respond more quickly and stop running when encountering abnormal situations, such as blockage or overload, thereby reducing the risk of accidents. For example, a mobile base for injection molding of an injection blow molding machine in Chinese patent CN210634101U includes a processing table, a base and a driving motor, a dual-axis motor is installed in the processing table, and a gear is connected to the output end of the dual-axis motor, the base is arranged on the top of the processing table, and a limit seat is fixed at the bottom of the base, the limit seat is located in the limit groove, and the limit groove is opened on the upper end face of the processing table, a docking block is arranged at the bottom of the limit seat, the driving motor is fixed at the top edge of the base, and a barrel is arranged on the upper end face of the base, and a hopper is connected to the top of the barrel, a plasticizing screw is installed in the barrel, a guide rod is connected to the inner shaft of the hopper, and a material dividing plate is fixed on the guide rod, and one end of the guide rod passes through the hopper and is connected to the driving motor through a belt. The mobile base for injection molding of the injection blow molding machine is convenient for driving the automatic and smooth movement of the injection molding component, and can separate the materials and prevent them from being blocked.

[0004] However, when the screw is driven by a belt, the driving position is generally at the end of the screw, a melt barrel is arranged outside the screw, and the melt barrel injection port at the front end of the screw is far away from the end of the screw. The vibration of a large injection molding machine is inevitable during operation, which causes a small vibration at the end of the belt-driven screw, resulting in a small displacement. The injection port at the front end of the screw has a large displacement, which leads to a decrease in the docking accuracy between the melt barrel injection port and the injection port of the mold, and the problem of poor product quality is prone to occur. Based on this, in order to avoid the problem of displacement of the screw when the screw is driven by a belt, a screw connection device is proposed. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a screw connecting device.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A screw connection device comprises a screw, a rotating assembly and a pushing assembly, wherein the rotating assembly comprises a housing, a melt-melt motor, a transmission wheel, a transmission shaft, a belt and a bushing, wherein the melt-melt motor is arranged on the housing, the output shaft of the melt-melt motor is connected to the transmission wheel through the belt transmission, the transmission shaft is rotatably arranged in the housing, the transmission wheel is transmission-sleeved on the front end of the transmission shaft, and the rear end of the transmission wheel abuts against the front end shoulder of the transmission shaft, the front end of the transmission shaft is provided with a front end docking interface, and the rear end is provided with a rear end docking interface, the bushing is slidably arranged in the front end docking interface, and the bushing shoulder abuts against the front end of the transmission wheel, the screw is transmission-connected in the bushing, the bushing shoulder and the front end shoulder of the transmission shaft clamp the transmission wheel and are connected by bolts;

[0008] The pushing assembly includes a screw rod, a wire sleeve and an injection motor. The output shaft of the injection motor is coaxially connected to the screw rod. The wire sleeve is connected to the housing and is used to support the rear end of the housing. The wire sleeve is transmission-sleeved on the screw rod. The front end of the screw rod passes through the wire sleeve and is rotatably disposed in the rear end docking port.

[0009] Furthermore, the front end of the shell body abuts against a first bearing, the rear end shoulder of the transmission shaft abuts against the first bearing, the rear end of the shell body abuts against a second bearing, a retaining ring is detachably installed on the transmission shaft, the retaining ring abuts against the other end of the second bearing, and the retaining ring is used to limit the transmission shaft.

[0010] Furthermore, the first bearing is an axial contact ball bearing, and the second bearing is a tapered roller bearing.

[0011] Furthermore, it also includes two half-moon rings. The rear end of the screw is provided with a shaft shoulder. The two half-moon rings abut against the shaft shoulder at the rear end of the screw and are detachably connected to the bushing for axial limitation of the screw.

[0012] Furthermore, the two half-moon rings are mutually clamped to form a fastening ring, the inner side wall of the fastening ring is provided with an internal thread, the annular groove of the screw is provided with an external thread, the side wall of the fastening ring is provided with a plurality of bolt holes at equal intervals, and the side wall of the large column section of the sleeve is provided with a plurality of bolt holes correspondingly, the fastening ring is used to adjust the tightness of the screw and the sleeve, and the sleeve and the bolt holes on the fastening ring are connected by bolts to fix the adjusted fastening ring.

[0013] Furthermore, a washer is provided at the bottom of the circular groove of the transmission shaft, the outer side wall of the washer is an inclined surface, the outer side wall of the washer abuts against the bottom of the sleeve, and the end face of the washer abuts against the end face of the screw.

[0014] Furthermore, the transmission shaft and the transmission wheel are connected by a key, and the screw rod and the bushing are connected by a spline.

[0015] The beneficial effects of the present invention are:

[0016] (1) By making the screw drive the thread sleeve and the rotating assembly to reciprocate, on the one hand, the thread sleeve is connected to the housing, so that the injection motor, the screw and the thread sleeve can serve as the support points of the rear end of the rotating assembly, and the screw displacement caused by vibration is reduced by increasing the support points. On the other hand, the screw can always slide and rotate back and forth in the rear end docking port, so that the screw and the transmission shaft and the screw always remain coaxial, thereby improving the stability of the screw and the rotating assembly during injection, thereby improving the docking accuracy between the injection port of the melt tube and the injection port of the mold;

[0017] (2) The use of the bushing as an intermediate layer can disperse the load and stress between the screw and the drive shaft. When the screw is subjected to loads from plastic melting, conveying and injection, these loads first act on the bushing and are then transmitted to the drive shaft by the bushing. In this way, direct contact and head-on collision between the screw and the drive shaft are avoided, thereby reducing wear. The addition of the bushing also allows for more flexible adjustment of the fit clearance between the screw and the drive shaft. Even if wear occurs, it is mainly the wear of the bushing, not the wear of the screw or the drive shaft. By reducing wear, the bushing indirectly extends the service life of the screw and the drive shaft. When the bushing is worn to a certain extent, it can be easily removed and replaced with a new bushing without the need for large-scale disassembly and repair of the entire transmission system.

[0018] (3) A complete tightening ring can be formed by two half-moon rings. The two ends of the middle fixed section of the half-moon ring have connecting sections. A protruding male joint is provided on the inner side of the connecting section of one of the half-moon rings, and a recessed female joint is provided on the connecting section of the other half-moon ring. The male joint and the female joint are connected to each other to form a complete tightening ring, and the inner side of the tightening ring is provided with a thread. When in use, the two half-moon rings are respectively attached to the annular groove from both sides, and then the two half-moon rings are buckled together to form a tightening ring, and then the tightening ring is tightened toward the side of the sleeve to make the connection between the screw and the sleeve tighter. After long-term use causes the connection between the screw and the sleeve to wear, the tightening ring is used to reinforce it again to avoid loosening. At the same time, the relatively tight connection between the screw, the sleeve and the transmission shaft can also reduce wear, thereby reducing the frequency of maintenance and replacement and increasing the service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0020] Figure 1 It is a schematic diagram of the internal structure of the present invention;

[0021] Figure 2 It is a partial side view structural schematic diagram of the present invention;

[0022] Figure 3 It is a schematic diagram of a partial three-dimensional structure of the present invention;

[0023] Figure 4 It is a structural schematic diagram of the half-moon ring of the present invention.

[0024] Legend: 1. Screw; 11. Half-moon ring; 12. Washer; 2. Melt-melting motor; 3. Transmission shaft; 4. Transmission wheel; 5. Injection motor; 6. Screw; 7. Thread sleeve; 8. Housing; 81. First bearing; 82. Second bearing; 83. Retaining ring. DETAILED DESCRIPTION

[0025] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0026] like Figure 1-4 As shown, a screw connection device of the present invention comprises a screw 1, a rotating assembly and a pushing assembly, the rotating assembly comprises a housing 8, a melt glue motor 2, a transmission wheel 4, a transmission shaft 3, a belt and a bushing, the melt glue motor 2 is arranged on the housing 8, the output shaft of the melt glue motor 2 is connected to the transmission wheel 4 through a belt transmission, the transmission shaft 3 is rotatably arranged in the housing 8, the transmission wheel 4 is transmission sleeved at the front end of the transmission shaft 3, and the rear end of the transmission wheel 4 abuts against the front end shoulder of the transmission shaft 3, the front end of the transmission shaft 3 is provided with a front end docking interface, and the rear end is provided with a rear end docking interface, the bushing is slidably arranged in the front end docking interface, and the bushing shoulder abuts against the front end of the transmission wheel 4, the screw 1 is transmission-connected in the bushing, the bushing shoulder and the front end shoulder of the transmission shaft 3 clamp the transmission wheel 4 and are connected by bolts;

[0027] The push assembly includes a screw rod 6, a wire sleeve 7 and an injection motor 5. The output shaft of the injection motor 5 is coaxially connected to the screw rod 6. The wire sleeve 7 is connected to the housing 8 and is used to support the rear end of the housing 8. The wire sleeve 7 is connected to the screw rod 6. The front end of the screw rod 6 passes through the wire sleeve 7 and is rotatably arranged in the rear end docking port.

[0028] Working principle of screw 1, rotating assembly and pushing assembly: the output shaft of melt-melting motor 2 drives transmission wheel 4 through belt, the belt is a toothed belt, and the rim surface of transmission wheel 4 is provided with teeth, the teeth of the belt mesh with the teeth of transmission wheel 4 for driving, since transmission wheel 4 is transmission connected with transmission shaft 3, screw 1 is transmission connected with the front end docking interface of transmission shaft 3 through a bushing, therefore, when transmission wheel 4 rotates, transmission shaft 3 and screw 1 rotate synchronously, and the output shaft of injection motor 5 of pushing assembly drives lead screw 6 to rotate, so that lead screw 6 pushes silk sleeve 7 to reciprocate, thereby driving reciprocating motion of rotating assembly and screw 1, in the process of driving silk sleeve 7 to reciprocate motion, since the rear end docking interface is provided on the transmission shaft 3, lead screw 6 can always slide and rotate reciprocatingly in the rear end docking interface.

[0029] Since vibration is inevitable during the operation of large injection molding machines, the end of the belt-driven screw 1 produces a small vibration, resulting in a small displacement. The injection port at the front end of the screw 1 has a large offset, which leads to a decrease in the docking accuracy between the injection port of the melt tube and the injection port of the mold, which is prone to poor product quality.

[0030] Therefore, in the process of driving the threaded rod 6 to drive the threaded sleeve 7 and the rotating assembly to reciprocate, on the one hand, the threaded sleeve 7 is connected to the housing 8, so that the injection motor 5, the threaded rod 6 and the threaded sleeve 7 can be used as the support points of the rear end of the rotating assembly, and the displacement of the screw 1 caused by vibration is reduced by increasing the support points. On the other hand, the threaded rod 6 can always slide and rotate back and forth in the rear end docking port, so that the threaded rod 6 always remains coaxial with the transmission shaft 3 and the screw 1, thereby improving the stability of the screw 1 and the rotating assembly during injection, thereby improving the docking accuracy between the injection port of the melt cylinder and the injection port of the mold.

[0031] At the same time, the use of the bushing as an intermediate layer can disperse the load and stress between the screw 1 and the transmission shaft 3. When the screw 1 is subjected to the load from the melting, conveying and injection of plastic, these loads first act on the bushing, and then are transmitted to the transmission shaft 3 by the bushing. In this way, direct contact and hard collision between the screw 1 and the transmission shaft 3 are avoided, thereby reducing wear. The addition of the bushing also allows for more flexible adjustment of the matching clearance between the screw 1 and the transmission shaft 3. By selecting the appropriate bushing thickness and material, it can be ensured that the clearance between the screw 1 and the transmission shaft 3 is neither too large nor too small, thereby reducing wear while ensuring transmission efficiency. The presence of the bushing reduces the direct contact area between the screw 1 and the transmission shaft 3, thereby reducing the risk of wear. Even if wear occurs, it is mainly the wear of the bushing, not the wear of the screw 1 or the transmission shaft 3. By reducing wear, the bushing indirectly extends the service life of the screw 1 and the transmission shaft 3. This can not only reduce the maintenance cost of the equipment, but also improve the reliability and stability of the equipment. The material and thickness of the bushing can be selected according to different working conditions and requirements. For example, for injection molding machines working in high temperature, high pressure or corrosive environments, high temperature and corrosion resistant bushing materials can be selected to ensure the normal operation of the equipment and reduce wear. As a consumable part, the bushing is relatively simple and quick to replace. When the bushing is worn to a certain extent, it can be easily removed and replaced with a new one without large-scale disassembly and repair of the entire transmission system.

[0032] Since the housing 8 is pushed to reciprocate by the screw rod 6 and the screw sleeve 7, and the large injection molding machine is heavy, there is a large inertia during the start and stop process of the reciprocating motion. At the same time, in order to make the transmission shaft 3 rotate more smoothly inside the housing 8, in one embodiment, the front end of the housing 8 abuts against the first bearing 81, the rear end shoulder of the transmission shaft 3 abuts against the first bearing 81, and the rear end of the housing 8 abuts against the second bearing 82. A snap ring 83 is detachably installed on the transmission shaft 3, and the snap ring 83 abuts against the other end of the second bearing 82. The snap ring 83 is used to limit the transmission shaft 3; wherein the first bearing 81 is an axial contact ball bearing, and the second bearing 82 is a tapered roller bearing;

[0033] The two outer rings of the axial contact ball bearing are respectively in contact with the shoulder at the rear end of the transmission shaft 3 and the front end of the housing 8, which can reduce the friction between the transmission shaft 3 and the housing 8 when subjected to axial impact; while the tapered roller bearing can withstand large radial loads and axial loads, and is particularly suitable for occasions that need to withstand radial and axial combined loads at the same time. The line contact design of this bearing reduces the contact stress between the roller and the raceway, thereby improving the load-bearing capacity and extending the service life. The tapered roller bearing has greater rigidity and can withstand greater impact and vibration loads, so it can be used in large injection molding machines. In order to prevent the tapered roller bearing from relative displacement with the housing 8, the front end of the housing 8 is limited by the first bearing 81 and the shoulder at the rear end of the transmission shaft 3, and then the second bearing 82 is connected to the transmission shaft 3 and abutted against the rear end of the housing 8, and then fixed to the transmission shaft 3 by the snap ring 83 and abutted against the second bearing 82, so that the transmission shaft 3 will not have relative displacement in the housing 8.

[0034] It also includes two half-moon rings 11. A shaft shoulder is provided at the rear end of the screw rod 1. The two half-moon rings 11 abut against the shaft shoulder at the rear end of the screw rod 1 and are detachably connected to the bushing for axial limitation of the screw rod 1.

[0035] Due to wear between the screw 1 and the sleeve after long-term use, a matching gap will appear in the connection part. The injection molding machine has high requirements for the connection between the screw 1 and the transmission shaft 3 to avoid vibration during use. If wear occurs between the screw 1 and the sleeve, the sleeve will be replaced, which not only brings inconvenience in use, but also leads to an increase in the cost of use. Therefore, in order to reduce the cost of maintenance and replacement, in one embodiment, two half-moon rings 11 are clamped together to form a fastening ring, the inner side wall of the fastening ring is provided with an internal thread, the annular groove of the screw 1 is provided with an external thread, the side wall of the fastening ring is equidistantly provided with a number of bolt holes, and the side wall of the large column section of the sleeve is correspondingly provided with a number of bolt holes. The fastening ring is used to adjust the tightness of the screw 1 and the sleeve, and the bolt holes on the sleeve and the fastening ring are connected by bolts to fix the adjusted fastening ring.

[0036] Furthermore, the two half-moon rings 11 each include a fixed section and connecting sections at both ends of the fixed section, wherein the connecting section of one half-moon ring 11 is provided with a male interface, and the connecting section of the other half-moon ring 11 is provided with a female interface, the male interface and the female interface are interlocked to connect the two half-moon rings 11 to form a fastening ring, and the thickness of the fixed section is twice the thickness of the connecting section.

[0037] Specifically, two half-moon rings 11 can form a complete fastening ring, and the two ends of the middle fixed section of the half-moon ring 11 have connecting sections, wherein a protruding male joint is provided on the inner side of the connecting section of one of the half-moon rings 11, and a recessed female joint is provided on the connecting section of the other half-moon ring 11. The male joint and the female joint are connected to each other to form a complete fastening ring, and the inner side of the fastening ring is provided with a thread. When in use, the two half-moon rings 11 are respectively attached to the annular groove from both sides, and then the two half-moon rings 11 are buckled together to form a fastening ring, and then the fastening ring is tightened toward the side of the sleeve to make the connection between the screw 1 and the sleeve tighter. After long-term use causes the connection between the screw 1 and the sleeve to be worn, the fastening ring is used to reinforce it again to avoid loosening. At the same time, the relatively tight connection between the screw 1 and the sleeve and the transmission shaft 3 can also reduce wear, thereby reducing the frequency of maintenance and replacement and increasing the service life.

[0038] At the same time, in order to facilitate installation after connecting the two half-moon rings 11 to form a tightening ring, it is necessary to form an annular groove at the front end of the shoulder of the screw 1. The diameter of the annular groove is smaller than the diameter of other positions of the screw 1, which is used to install the two half-moon rings 11. Then, the annular groove includes a threaded section and a smooth section. During installation, the tightening ring is placed on the smooth section. After connecting the two half-moon rings 11 to form a tightening ring, tighten it toward the sleeve. And after long-term use causes the screw 1 and the sleeve to become loose, there is no need to disassemble the entire device, and only the tightening ring needs to be tightened directly.

[0039] At the same time, when the screw 1 is fixed to the bushing by the tightening ring, only one side is fixed by the tightening ring, which can prevent the screw 1 from moving to one side of the screw 1. However, since the screw 1 is not limited toward the transmission shaft 3 at this time, it can still move. Therefore, it is necessary to connect the side wall of the bushing with the side wall of the transmission shaft 3 so that the end of the screw 1 abuts against the inner wall of the circular groove of the transmission shaft 3 to limit the screw 1. And the tightening is adjusted in sequence according to the wear of the screw 1 and the bushing through the tightening ring. In actual use, the extension length of the screw 1 can be made smaller, and the tightening ring is adjusted according to the actual distance between the screw 1 and the transmission shaft 3 after the bushing is connected to the transmission shaft 3.

[0040] Since it is necessary to form abutment force between the end of the screw 1 and the end of the transmission shaft 3 to tighten the screw 1 and avoid loosening, in one embodiment, a washer 12 is provided at the bottom of the circular groove of the transmission shaft 3, and the outer wall of the washer 12 is an inclined surface. The outer wall of the washer 12 abuts against the bottom of the sleeve, and the end face of the washer 12 abuts against the end face of the screw 1.

[0041] Furthermore, the transmission shaft 3 and the transmission wheel 4 are connected by a key, and the screw rod 1 and the bushing are connected by a spline.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A screw connection device, characterized in that: It includes a screw, a rotating assembly and a pushing assembly, wherein the rotating assembly includes a housing, a melt-melt motor, a transmission wheel, a transmission shaft, a belt and a bushing, wherein the melt-melt motor is arranged on the housing, the output shaft of the melt-melt motor is connected to the transmission wheel through the belt transmission, the transmission shaft is rotatably arranged in the housing, the transmission wheel is transmission-sleeved on the front end of the transmission shaft, and the rear end of the transmission wheel abuts against the front end shoulder of the transmission shaft, the front end of the transmission shaft is provided with a front end docking interface, and the rear end is provided with a rear end docking interface, the bushing is slidably arranged in the front end docking interface, and the bushing shoulder abuts against the front end of the transmission wheel, the screw is transmission-connected in the bushing, the bushing shoulder and the front end shoulder of the transmission shaft clamp the transmission wheel and are connected by bolts; The pushing assembly includes a screw rod, a wire sleeve and an injection motor. The output shaft of the injection motor is coaxially connected to the screw rod. The wire sleeve is connected to the housing and is used to support the rear end of the housing. The wire sleeve is transmission-sleeved on the screw rod. The front end of the screw rod passes through the wire sleeve and is rotatably disposed in the rear end docking port.

2. A screw connection device according to claim 1, characterized in that: The front end of the shell body abuts against a first bearing, the rear end shoulder of the transmission shaft abuts against the first bearing, the rear end of the shell body abuts against a second bearing, a retaining ring is detachably mounted on the transmission shaft, the retaining ring abuts against the other end of the second bearing, and the retaining ring is used to limit the transmission shaft.

3. A screw connection device according to claim 2, characterized in that: The first bearing is an axial contact ball bearing, and the second bearing is a tapered roller bearing.

4. A screw connection device according to claim 1, characterized in that: It also includes two half-moon rings. The rear end of the screw is provided with a shaft shoulder. The two half-moon rings abut against the shaft shoulder at the rear end of the screw and are detachably connected to the bushing for axial limitation of the screw.

5. A screw connection device according to claim 4, characterized in that: The two half-moon rings are mutually clamped to form a fastening ring, the inner side wall of the fastening ring is provided with an internal thread, the annular groove of the screw is provided with an external thread, the side wall of the fastening ring is provided with a plurality of bolt holes at equal intervals, and the side wall of the large column section of the sleeve is provided with a plurality of bolt holes correspondingly, the fastening ring is used to adjust the tightness of the screw and the sleeve, and the sleeve and the bolt holes on the fastening ring are connected by bolts to fix the adjusted fastening ring.

6. A screw connection device according to claim 1, characterized in that: A washer is provided at the bottom of the circular groove of the transmission shaft, the outer wall of the washer is an inclined surface, the outer wall of the washer abuts against the bottom of the washer sleeve, and the end face of the washer abuts against the end face of the screw rod.

7. A screw connection device according to claim 1, characterized in that: The transmission shaft and the transmission wheel are connected by a key, and the screw rod and the bushing are connected by a spline.

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