A linear actuator and power equipment based on face gear transmission

Abstract

The present invention discloses a linear actuator and power equipment based on face gear transmission. The linear actuator includes a power output device, the end of which is connected to a face gear transmission box; a reciprocating motion component, one end of which is connected to the top of the face gear transmission box, and the other end is provided with a guide device; a stroke detection component, one end of which is connected to the face gear transmission box, and the other end is connected to the guide device; a dustproof component is arranged on the guide device. The face gear transmission structure has a high meshing overlap, which can effectively reduce the noise of the electric cylinder, reduce vibration, and has higher safety and reliability. The face gear transmission is basically not affected by the ambient temperature and can meet the use of special occasions with high load-bearing capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of drive devices, and in particular relates to a linear actuator and a power device based on face gear transmission. Background Art

[0002] The servo electric cylinder, as a modular product that combines a servo motor with a lead screw, converts the rotational motion of the servo motor into the linear reciprocating motion of the push rod with the help of a lead screw pair, thereby achieving high-precision displacement and speed control. It is used in industrial scenarios with high requirements for precision and automation.

[0003] Existing servo electric cylinders have two structural types: linear and parallel. Linear electric cylinders often use planetary gear transmission, and the motor, transmission device and cylinder body are coaxially installed. Although it is easy to install, the overall length is large. Although the planetary gear reduction device used can achieve a larger transmission speed ratio and stronger load-bearing capacity, the planetary gear transmission structure is complex and requires high manufacturing precision. The transmission efficiency will decrease as the transmission ratio increases.

[0004] Parallel electric cylinders are usually driven by synchronous belts or cylindrical gears. The motor, transmission device and cylinder body are installed in parallel, which is suitable for installation locations with limited space. When synchronous belts are used for transmission, the transmission is stable and the service life is long, but the input power is small and the load capacity is limited. Under heavy load conditions, the synchronous belt will have problems such as overload and slippage. At the same time, under extreme temperatures, the properties of the synchronous belt material will change, affecting the transmission efficiency and life. It is not suitable for use under heavy load conditions and harsh environmental conditions. When cylindrical gear transmission is used, although the input power is large and a large thrust output is required, multi-stage transmission is required to improve the transmission ratio and increase the output torque, but this will cause the electric cylinder structure to be complex and the overall size to become larger, which is not suitable for occasions with limited space.

[0005] With the rapid development of industry, the trend of servo electric cylinders is mainly towards high precision, high load, high speed, miniaturization, integration and intelligence. At the same time, it is urgent to develop new transmission forms to meet the special occasions of large stroke and high load-bearing capacity. Summary of the invention

[0006] The purpose of the present invention is to provide a linear actuator and power equipment based on face gear transmission, so as to solve the technical defects of the servo electric cylinder in the prior art that it cannot be used in harsh environments with heavy loads and limited installation space.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: In a first aspect, a linear actuator based on face gear transmission is provided, comprising: A power output device, the end of which is connected to a face gear transmission box; A reciprocating motion assembly, one end of which is drivingly connected to the top of the face gear transmission box, and the other end of which is provided with a guide device; A stroke detection assembly, one end of which is connected to the face gear transmission box, and the other end of which is connected to the guide device; The dustproof component is arranged on the guide device.

[0008] Further, the face gear transmission box includes a box body, the power output device is arranged on one side of the box body, and its driving end extends into the box body; A cylindrical gear is provided in the box body on one side close to the driving end, the cylindrical gear is installed on the outside of the driving end, a face gear is meshed with the bottom of the cylindrical gear, and the cylindrical gear is axially perpendicular to the face gear; One end of the reciprocating motion component is connected to the face gear, and the other end is connected to the guide device. The reciprocating motion component and the face gear are axially overlapped.

[0009] Furthermore, a bearing mounting seat is provided on the inner bottom surface of the box body, and a first bearing is provided in the bearing mounting seat; The reciprocating motion assembly includes a lead screw, one end of which passes through a face gear and is connected to a first bearing; the other end of the lead screw is provided with a second bearing and a nut, and the second bearing and the nut cooperate with the guide device.

[0010] Further, the guide device includes a cylinder body and a push rod; The cylinder body is arranged on the top of the box body, and one end of the cylinder body connected to the box body is provided with a bearing seat, a second bearing is installed in the bearing seat, and the second bearing is installed on the lead screw; One end of the push rod is slidably connected to the cylinder body, and the other end extends to the outside of the cylinder body. The nut is installed on the end of the push rod slidably connected to the cylinder body and is located above the second bearing.

[0011] Furthermore, the cylinder body and the push rod are both hollow rectangular structures, and guide plates are provided around the outer side of the push rod, and the guide plates cooperate with the inside of the cylinder body.

[0012] Furthermore, the guide plate has a guide surface, and a lubricating layer is provided on the guide surface.

[0013] Furthermore, lubricating particles are provided in the lubricating layer.

[0014] Furthermore, the stroke detection component includes a displacement sensor, which is arranged on the top of the face gear transmission box, and the end of the displacement sensor is connected to the guide device through a pull wire.

[0015] Furthermore, the dustproof assembly includes a dustproof plate and a pressure plate, the dustproof plate is arranged on the top of the guide device, and the pressure plate is arranged on the top of the dustproof plate.

[0016] In a second aspect, a power device is provided, comprising a device body, on which the linear actuator based on face gear transmission as described above is mounted.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The face gear transmission structure has a high meshing overlap, which can effectively reduce the noise of the electric cylinder and reduce vibration, with higher safety and reliability. The face gear transmission is basically not affected by the ambient temperature and can meet the special occasions with high load-bearing capacity.

[0018] 2. The meshing of cylindrical gears and face gears realizes the efficient transmission of power from the power output device to the reciprocating motion component. This vertical meshing method not only saves space, but also makes the transmission structure more compact. Secondly, the axially perpendicular layout of the cylindrical gears and face gears helps to reduce friction and wear during the transmission process and improve the efficiency and stability of the transmission. The design of axial overlap between the reciprocating motion component and the face gear ensures that the rotational motion of the face gear can be accurately converted into the linear motion of the reciprocating motion component, reducing the error in the transmission process and improving the accuracy of displacement conversion.

[0019] 3. The setting of the bearing mounting seat provides stable support for the first bearing, ensuring that one end of the screw can be firmly connected to the box, which helps to reduce the shaking and deviation of the screw during operation and improve the stability and accuracy of the transmission. The cooperation between the second bearing and the nut and the guide device provides precise guidance and support for the other end of the screw, which not only ensures the linear motion of the screw, but also reduces friction and wear and prolongs its service life.

[0020] 4. As the main component of the guide device, the cylinder body provides stable guidance and support for the push rod. The firm connection between the cylinder body and the box ensures the stability and reliability of the entire guide device. The setting of the bearing seat provides a precise installation position for the second bearing, further enhancing the stability and rigidity of the screw in the cylinder body, helping to reduce the shaking and deviation of the screw during operation, and improving the accuracy and stability of the transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 A three-dimensional schematic diagram of a linear actuator based on face gear transmission provided by the present invention; Figure 2 A cross-sectional view of a linear actuator based on face gear transmission provided by the present invention; Figure 3 A three-dimensional schematic diagram of a face gear transmission housing in a linear actuator based on face gear transmission provided by the present invention; Figure 4 A three-dimensional schematic diagram of a push rod in a linear actuator based on face gear transmission provided by the present invention; Figure 5 A three-dimensional schematic diagram of a guide plate in a linear actuator based on face gear transmission provided by the present invention; Figure 6 A cross-sectional view of a guide device in a linear actuator based on face gear transmission provided by the present invention; Wherein: 1. power output device; 2. face gear transmission box; 21. box body; 211. motor mounting hole; 212. motor mounting stop; 213. bearing mounting seat; 214. top plate mounting hole; 215. electric cylinder mounting hole; 22. cylindrical gear; 23. face gear; 24. first bearing; 25. second bearing; 26. bearing seat; 27. upper cover plate; 3. nut; 4. lead screw; 5. cylinder body; 6. push rod; 61. sensor wire mounting hole; 62. nut mounting hole; 63. groove; 64. guide plate mounting hole; 7. dustproof component; 71. dustproof plate; 72. pressure plate; 8. limit nut; 9. guide plate; 91. countersunk hole; 92. guide surface; 10. displacement sensor; 101. sensor body; 102. wire. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0024] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0026] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0027] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] The servo electric cylinder, as a modular product that combines a servo motor with a lead screw, converts the rotational motion of the servo motor into the linear reciprocating motion of the push rod with the help of a lead screw pair, thereby achieving high-precision displacement and speed control. It is used in industrial scenarios with high requirements for precision and automation.

[0029] Existing servo electric cylinders have two structural types: linear and parallel. Linear electric cylinders often use planetary gear transmission, and the motor, transmission device and cylinder body are coaxially installed. Although it is easy to install, the overall length is large. Although the planetary gear reduction device used can achieve a larger transmission speed ratio and stronger load-bearing capacity, the planetary gear transmission structure is complex and requires high manufacturing precision. The transmission efficiency will decrease as the transmission ratio increases.

[0030] Parallel electric cylinders are usually driven by synchronous belts or cylindrical gears. The motor, transmission device and cylinder body are installed in parallel, which is suitable for installation locations with limited space. When synchronous belts are used for transmission, the transmission is stable and the service life is long, but the input power is small and the load capacity is limited. Under heavy load conditions, the synchronous belt will have problems such as overload and slippage. At the same time, under extreme temperatures, the properties of the synchronous belt material will change, affecting the transmission efficiency and life. It is not suitable for use under heavy load conditions and harsh environmental conditions. When cylindrical gear transmission is used, although the input power is large and a large thrust output is required, multi-stage transmission is required to improve the transmission ratio and increase the output torque, but this will cause the electric cylinder structure to be complex and the overall size to become larger, which is not suitable for occasions with limited space.

[0031] With the rapid development of industry, the trend of servo electric cylinders is mainly towards high precision, high load, high speed, miniaturization, integration and intelligence. At the same time, it is urgent to develop new transmission forms to meet the special occasions of large stroke and high load-bearing capacity.

[0032] In order to solve the above technical defects, the inventor provides a linear actuator and a power device based on face gear transmission.

[0033] The present invention is further described in detail below in conjunction with the accompanying drawings: like Figure 1-Figure 6 As shown, in the first aspect, an embodiment of the present invention provides a linear actuator based on face gear transmission, including a power output device 1, whose end is connected to a face gear transmission box 2; a reciprocating motion component, one end of which is transmission-connected to the top of the face gear transmission box 2, and the other end of which is provided with a guide device; a stroke detection component, one end of which is connected to the face gear transmission box 2, and the other end of which is connected to the guide device; and a dustproof component 7, which is arranged on the guide device. Since this solution adopts a face gear transmission structure with a high meshing overlap, it can effectively reduce the noise of the linear actuator, reduce vibration, and make its use safer and more reliable. In addition, the face gear transmission is basically not affected by the ambient temperature and can meet the needs of special occasions with high load-bearing capacity. Figure 1 and Figure 2 As shown, the face gear transmission box 2 includes a box body 21, which is a rectangular structure with an opening on the top and a hollow interior; the power output device 1 is preferably a servo motor, and the power output device 1 is arranged on one side of the box body 21. The driving end extends into the housing 21; inside the housing 21, a cylindrical gear 22 is provided on one side close to the driving end of the power output device 1, and the cylindrical gear 22 is installed on the outside of the driving end of the power output device 1; at the bottom of the cylindrical gear 22, a face gear 23 is meshed, and the cylindrical gear 22 and the face gear 23 are axially perpendicular; the meshing of the cylindrical gear 22 and the face gear 23 realizes the efficient transmission of power from the power output device 1 to the reciprocating motion component, which not only saves space but also makes the transmission structure more compact. At the same time, the layout of the cylindrical gear 22 and the face gear 23 axially perpendicular helps to reduce friction and wear during the transmission process and improve the efficiency and stability of the transmission; and, as a key component in the transmission process, the face gear 23 has a strong load-bearing capacity. By meshing with the cylindrical gear 22, the face gear 23 can withstand a large load, thereby ensuring the stability of the transmission system. Furthermore, as Figure 3As shown, the housing 21 is provided with a motor mounting hole 211, a motor mounting stop 212, a bearing mounting seat 213, a top plate mounting hole 214, and an electric cylinder mounting hole 215; wherein the power output device 1 is installed in the motor mounting hole 211, the end of the power output device 1 with the driving end is against the motor mounting stop 212, the bearing mounting seat 213 is used to install the first bearing 24, the top plate mounting hole 214 is used to connect the guide device to the housing 21, and the electric cylinder mounting hole 215 is used to install the entire linear actuator on other power equipment. Figure 2 As shown, one end of the reciprocating assembly is connected to the face gear 23, and the other end is connected to the guide device. The reciprocating assembly and the face gear 23 are axially overlapped. The reciprocating assembly includes a lead screw 4, one end of which passes through the face gear 23 and is connected to the first bearing 24; the other end of the lead screw 4 is provided with a second bearing 25 and a nut 3, and the second bearing 25 and the nut 3 cooperate with the guide device. First, the face gear 23 transmission can reduce the weight while still maintaining a large load-bearing capacity, improve the overall performance and efficiency of the mechanical equipment, and has high reliability and good interchangeability; because the face gear 23 transmission has high reliability and good interchangeability, the cost and difficulty of maintenance and replacement of the entire linear actuator are reduced; finally, the face gear 23 transmission does not generate axial force when transmitting power and motion, which helps to reduce the wear and vibration of the mechanical equipment and improve the stability of the transmission. The lead screw 4 in the reciprocating assembly can be converted into linear motion through rotational motion, realizing precise transmission and positioning functions, and can respond quickly and operate efficiently.

[0034] like Figure 2As shown, the guide device includes a cylinder body 5 and a push rod 6. The cylinder body 5 is arranged on the top of the box body 21. The end of the cylinder body 5 connected to the box body 21 is provided with a bearing seat 26. The second bearing 25 is installed in the bearing seat 26. The second bearing 25 is installed on the lead screw 4. The cylinder body 5 provides a stable and accurate guide path for the push rod 6 to ensure that the push rod 6 will not deviate or shake during the linear motion, thereby achieving high-precision displacement control. The second bearing 25 not only supports one end of the lead screw 4, but also ensures the stability and accuracy of the lead screw 4 during rotation through its high-precision rotation performance, thereby ensuring the accuracy of the movement of the push rod 6. The rotational motion of the lead screw 4 is directly converted into the linear motion of the push rod 6 through the nut 3. This transmission method is simple and efficient, and can achieve a large transmission ratio, so that a small rotation of the lead screw 4 can produce a large displacement of the push rod 6. Through the mutual cooperation of the above structures, the second bearing 25 reduces the friction resistance, the energy loss in the entire transmission process is greatly reduced, and the mechanical efficiency is improved. One end of the push rod 6 is slidably connected to the cylinder body 5, and the other end extends to the outside of the cylinder body 5. The nut 3 is installed at the end where the push rod 6 is slidably connected to the cylinder body 5, and is located above the second bearing 25. The sliding connection between the push rod 6 and the cylinder body 5 ensures that the push rod 6 can move smoothly and linearly along the cylinder body 5, thereby achieving precise displacement control. The nut 3 is located at the end where the push rod 6 is slidably connected to the cylinder body 5, and is immediately above the second bearing 25, so that the rotation of the lead screw 4 can be directly and efficiently converted into the linear motion of the push rod 6, further improving the accuracy of the displacement control. At the same time, the cooperation between the lead screw 4 and the nut 3 constitutes an efficient transmission mechanism that can convert rotational motion into linear motion, and has a large transmission ratio and high efficiency. It has the characteristics of simple structure, precise transmission, and strong load-bearing capacity. Figure 2-Figure 5 As shown, the cylinder body 5 and the push rod 6 are both hollow rectangular structures. Grooves 63 are provided around the outer side of the push rod 6. A sensor wire mounting hole 61 and a nut mounting hole 62 are provided at the end of the push rod 6. The nut 3 is arranged in the nut mounting hole 62. A guide plate 9 is provided in the groove 63. The guide plate 9 cooperates with the inside of the cylinder body 5. Specifically, the guide plate 9 has a countersunk hole 91 and a guide surface 92. The countersunk hole 91 cooperates with the guide plate mounting hole 64. The guide surface 92 is provided with a lubricating layer. The lubricating layer is provided with lubricating particles, which can release lubricating particles in the absence of external lubrication or poor lubrication conditions to form a stable solid lubricating film, provide effective lubrication, reduce friction, reduce wear, improve the operating reliability and service life of the linear actuator, and reduce maintenance costs. In this solution, Figure 2As shown, the stroke detection assembly includes a displacement sensor 10, and the displacement sensor 10 includes a sensor body 101 and a pull wire 102. The sensor body 101 is located in the cylinder body 5 and is vertically mounted on the top of the upper cover plate 27. The upper cover plate 27 is mounted on the bottom of the box body 21. One end of the pull wire 102 is connected to the sensor body 101, and the other end is connected to the sensor pull wire mounting hole 61. The dustproof assembly 7 includes a dustproof plate 71 and a pressure plate 72. The dustproof plate 71 is arranged on the top of the guide device, and the pressure plate 72 is arranged on the top of the dustproof plate 71; specifically, the dustproof plate 71 is installed at the connection between the cylinder body 5 and the push rod 6, and the pressure plate 72 is installed on the top of the dustproof plate 71 by bolts. The dustproof plate 71 is a flexible material, which can effectively fill the gap between the cylinder body 5 and the push rod 6, prevent pollutants from entering the cylinder body 5, effectively protect the normal operation of the guide plate 9, reduce the wear of the guide plate 9, and improve the life of the linear actuator. The power output device 1 controls the cylindrical gear 22 to rotate in the clockwise direction at a set speed, and drives the lead screw 4 to rotate counterclockwise through the face gear pair. Further, through the nut-screw pair, the rotational motion of the lead screw 4 is converted into the vertical upward linear motion of the nut 3, thereby realizing the extension of the push rod 6. On the contrary, controlling the power output device 1 to rotate counterclockwise can realize the retraction of the push rod 6. Since the transmission ratio of the face gear pair is large, the output torque of the lead screw 4 is large, and the thrust of the push rod 6 is large, which can meet the use of the linear actuator under heavy load conditions. The pull line of the displacement sensor 10 can accurately measure the displacement of the push rod 6. The displacement sensor 10 converts the displacement signal into an electrical signal and feeds it back to the power output device 1 to realize closed-loop control, which can accurately control the displacement accuracy of the linear actuator. The limit nut 8 is installed on the top of the lead screw 4, which can be used as a mechanical limit of the maximum stroke of the linear actuator, and double protection with the set maximum stroke of the displacement sensor 10 to prevent the push rod 6 from detaching from the cylinder 5.

[0035] In a second aspect, a power device is provided, including a device body, on which the linear actuator based on face gear transmission as described above is mounted.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. A linear actuator based on face gear transmission, characterized in that: include: A power output device (1), an end of which is connected to a face gear transmission box (2); A reciprocating motion component, one end of which is drivingly connected to the top of the face gear transmission box (2), and the other end of which is provided with a guide device; A stroke detection component, one end of which is connected to the face gear transmission box (2), and the other end of which is connected to the guide device; A dustproof component (7) is arranged on the guide device.

2. The linear actuator based on face gear transmission according to claim 1, characterized in that: The face gear transmission box (2) comprises a box body (21), the power output device (1) is arranged on one side of the box body (21), and the driving end thereof extends into the box body (21); A cylindrical gear (22) is provided on one side of the box body (21) close to the driving end. The cylindrical gear (22) is installed on the outside of the driving end. A face gear (23) is meshed at the bottom of the cylindrical gear (22). The cylindrical gear (22) and the face gear (23) are axially perpendicular. One end of the reciprocating motion component is connected to the face gear (23), and the other end is connected to the guide device; the reciprocating motion component and the face gear (23) are axially overlapped.

3. The linear actuator based on face gear transmission according to claim 2, characterized in that: A bearing mounting seat (213) is provided on the inner bottom surface of the box body (21), and a first bearing (24) is provided in the bearing mounting seat (213); The reciprocating motion assembly comprises a lead screw (4), one end of the lead screw (4) passes through a face gear (23) and is connected to a first bearing (24); the other end of the lead screw (4) is provided with a second bearing (25) and a nut (3), and the second bearing (25) and the nut (3) cooperate with the guide device.

4. The linear actuator based on face gear transmission according to claim 3, characterized in that: The guide device comprises a cylinder body (5) and a push rod (6); The cylinder body (5) is arranged on the top of the box body (21); one end of the cylinder body (5) connected to the box body (21) is provided with a bearing seat (26); a second bearing (25) is installed in the bearing seat (26); and the second bearing (25) is installed on the lead screw (4); One end of the push rod (6) is slidably connected to the cylinder body (5), and the other end extends to the outside of the cylinder body (5). The nut (3) is mounted on the end of the push rod (6) slidably connected to the cylinder body (5) and is located above the second bearing (25).

5. The linear actuator based on face gear transmission according to claim 4, characterized in that: The cylinder body (5) and the push rod (6) are both hollow rectangular structures. Guide plates (9) are provided around the outside of the push rod (6), and the guide plates (9) cooperate with the inside of the cylinder body (5).

6. The linear actuator based on face gear transmission according to claim 5, characterized in that: The guide plate (9) has a guide surface (92), and a lubricating layer is provided on the guide surface (92).

7. The linear actuator based on face gear transmission according to claim 6, characterized in that: Lubricating particles are arranged in the lubricating layer.

8. The linear actuator based on face gear transmission according to claim 1, characterized in that: The stroke detection assembly comprises a displacement sensor (10), the displacement sensor (10) being arranged on the top of the face gear transmission box (2), and the end of the displacement sensor (10) being connected to the guide device via a pull wire (102).

9. The linear actuator based on face gear transmission according to claim 1, characterized in that: The dustproof assembly (7) comprises a dustproof plate (71) and a pressing plate (72); the dustproof plate (71) is arranged on the top of the guide device, and the pressing plate (72) is arranged on the top of the dustproof plate (71).

10. A power device, comprising a device body, characterized in that: The device body is equipped with a linear actuator based on face gear transmission as described in any one of claims 1 to 9.

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