The transmission assembly and linear lifting device of the linear lifting device

Abstract

This utility model discloses a transmission assembly and linear lifting device for a linear lifting device, belonging to the technical field of mechanical transmission devices. The transmission assembly includes a lead screw, a transmission nut, a tubular component, and a safety nut. The safety nut is sleeved on the lead screw. The transmission nut has a cavity for receiving the safety nut, with an inner conical surface. The safety nut has an outer conical surface. One of the inner and outer conical surfaces is provided with a rib, and the other with a groove. Under normal conditions, the rib and groove cooperate to restrict the relative rotation of the transmission nut and the safety nut. Under the condition of transmission nut failure, the rib and groove disengage, and the inner and outer conical surfaces press together to form a friction pair for static self-locking or dynamic friction between the transmission nut and the safety nut. By adding a safety nut, the object supported by the linear lifting device is prevented from falling rapidly in the event of transmission nut failure, greatly eliminating safety hazards and improving safety in use.

Description

Technical Field

[0001] This utility model relates to the field of mechanical transmission device technology, and in particular to a transmission assembly for a linear lifting device. In addition, this utility model also relates to a linear lifting device using this transmission assembly. Background Technology

[0002] Linear lifting devices are common components of linear drive equipment, widely used in intelligent office equipment such as electric height-adjustable desks and electric height-adjustable platforms, as well as in intelligent medical equipment. Taking an electric height-adjustable desk as an example, it includes a tabletop and two linear lifting devices located beneath it. The height of the tabletop can be adjusted by controlling the raising or lowering of these devices through a controller installed on the crossbeam or other locations.

[0003] Existing linear lifting devices generally include a drive assembly, a transmission assembly, and a tube structure. The tube structure includes an inner tube, a middle tube, and an outer tube that are nested and can extend or retract relative to each other. The tube structure has a fixed end and a telescopic end. The drive assembly is located inside the fixed end of the tube structure. The telescopic end of the tube structure is connected to the linear moving end of the transmission assembly. The drive assembly drives the tube structure to extend or retract through the transmission assembly.

[0004] The transmission assembly of a linear lifting device typically employs a lead screw and nut structure, with the nut contacting the lead screw and bearing the load. Due to the limited lifting speed of older products, lead screws with small leads were generally used, resulting in a small thread helix angle between the lead screw and nut. Therefore, the threaded pair between the lead screw and nut possessed a certain degree of self-locking. When the nut failed, the self-locking property of the nut bearing the load prevented a rapid fall. However, when the lifting speed increases or a lead screw with a larger lead is used, the thread helix angle between the lead screw and nut becomes larger. In this case, the self-locking force between the lead screw and nut is smaller, or even nonexistent. When the nut fails, the nut bearing the load will fall rapidly relative to the lead screw, causing the entire device to fall quickly. This poses a significant safety hazard and compromises operational safety. Utility Model Content

[0005] To address the shortcomings and deficiencies in the existing technology, this utility model provides a transmission assembly for a linear lifting device. By adding a safety nut, it prevents the object supported by the linear lifting device from falling rapidly in the event of transmission nut failure, thereby greatly eliminating safety hazards and improving safety in use.

[0006] To achieve the above technical objectives, the transmission assembly of the linear lifting device provided by this utility model includes:

[0007] Lead screw;

[0008] A transmission nut, which is fitted onto the lead screw and is restricted from rotation;

[0009] A tubular component, which is fitted onto the outside of the lead screw and is driven by a transmission nut to reciprocate along the axial direction of the lead screw;

[0010] The transmission assembly also includes a safety nut fitted on the lead screw. The transmission nut has a cavity for receiving the safety nut at one end facing the safety nut. The cavity has an inner conical surface, and the safety nut has an outer conical surface. One of the inner conical surface and the outer conical surface is provided with a rib, and the other is provided with a groove.

[0011] Under normal conditions, the rib and groove of the transmission nut cooperate to restrict the relative rotation of the transmission nut and the safety nut.

[0012] When the transmission nut fails, the rib and the groove disengage, and the inner conical surface and the outer conical surface press together to form a friction pair, which is used for static self-locking or dynamic friction between the transmission nut and the safety nut.

[0013] Preferably, the transmission nut and the lead screw form a first threaded pair, and the safety nut and the lead screw form a second threaded pair. The thread fit clearance of the second threaded pair is greater than that of the first threaded pair. Under normal conditions, the transmission nut is supported by the first threaded pair, and under the failure condition, the transmission nut is supported by the second threaded pair.

[0014] Preferably, the inner conical surface and the outer conical surface have the same cone angle.

[0015] Preferably, in the normal state of the transmission nut, there is an axial gap between the end face of the safety nut facing the transmission nut and the bottom wall of the cavity, and there is a conical normal gap between the inner conical surface and the outer conical surface. The rib and the groove both extend along the axial direction of the lead screw, so that the two form a fit that allows axial relative displacement.

[0016] Preferably, there is a circumferential gap between the rib and the groove.

[0017] Preferably, there is a radial gap between the rib and the groove.

[0018] Preferably, a predetermined fracture portion is formed at the root of the rib, and the predetermined fracture portion undergoes shear fracture when the rib is subjected to a torque exceeding a threshold, thereby disengaging the rib from the groove.

[0019] Preferably, in the case of failure of the transmission nut, the relative displacement to the safety nut causes the rib to move axially out of the groove, thereby disengaging the fit.

[0020] This utility model also provides a linear lifting device, including an actuation unit and a telescopic sleeve assembly composed of at least two sleeve sections. The actuation unit includes a motor and a reduction mechanism. The linear lifting device also includes the transmission assembly described above. The motor drives the lead screw to rotate through the reduction mechanism. One end of the tubular component is connected to a transmission nut, and the other end is non-rotatably connected to the telescopic sleeve assembly.

[0021] Preferably, the actuation unit is provided with a self-locking mechanism, which is used to restrict the lead screw from being driven to rotate by the load when the motor is not running. The self-locking mechanism is configured with one of the following structures:

[0022] The motor shaft is equipped with a braking device. When the motor is not running, the braking device restricts the rotation of the motor shaft caused by the lead screw being driven by the load.

[0023] The reduction mechanism includes a worm and a worm wheel. The worm is driven by the output shaft of the motor, and the worm wheel is driven by the lead screw. The helical teeth of the worm and the teeth of the worm wheel form a one-way friction self-locking mechanism, so that the worm can drive the worm wheel but the worm wheel cannot drive the worm.

[0024] By adopting the above technical solution, this utility model has the following advantages:

[0025] 1. The transmission assembly of the linear lifting device provided by this utility model includes a lead screw, a transmission nut, a tubular component and a safety nut. One end of the transmission nut is provided with a cavity for receiving the safety nut. The cavity is provided with an inner conical surface, and the safety nut is provided with an outer conical surface. Mutual ribs and grooves are provided between the inner conical surface and the outer conical surface.

[0026] When the drive nut is in its normal position, the safety nut is positioned in the recessed cavity with the rib inserted into the groove. The engagement of the rib and the groove restricts the relative rotation of the drive nut and the safety nut, meaning the two nuts are mutually circumferentially limited. The two nuts can rotate synchronously relative to the lead screw, allowing the drive nut to smoothly drive the tubular component in axial reciprocating motion. At this time, the drive nut in its normal state bears the load, while the safety nut has no load-bearing capacity and is in a redundant state. The threads of the drive nut bearing the load abut against the threads of the lead screw. When the lead screw is stationary, the drive nut is also stationary, thus ensuring the tubular component driven by the drive nut remains stably in a certain position, thereby allowing the object supported by the linear lifting device to be stably maintained at a certain height.

[0027] When the transmission nut is in a failed state, the fit between the rib and the groove is released, meaning the circumferential restraint between the two nuts is released, allowing them to rotate relative to each other. Simultaneously, the inner and outer conical surfaces press against each other, forming a friction pair. When there is no self-locking force or a small self-locking force between the transmission nut and the lead screw, the friction pair formed by the two conical surfaces subjects the failed, rotating transmission nut to a certain frictional force. This frictional force effectively reduces the rotational speed of the failed transmission nut, preventing it from driving the safety nut to rotate or only driving it to rotate at a low speed. This avoids the tubular component from rapidly retracting due to the rapid rotation of the failed transmission nut, and consequently, prevents the object supported by the linear lifting device from falling rapidly. When a self-locking force exists between the transmission nut and the lead screw, the load force borne by the transmission nut after its failure is transferred to the safety nut through the conical surface fit. That is, the safety nut takes over the load when the transmission nut fails. The threads of the safety nut bearing the load abut against the threads of the lead screw, utilizing the self-locking force between the safety nut and the lead screw to replace the self-locking force between the transmission nut and the lead screw. This self-locking force prevents the safety nut bearing the load from momentarily moving axially relative to the lead screw, thus avoiding rapid retraction of the tubular component due to transmission nut failure, and consequently preventing the object supported by the linear lifting device from falling rapidly. When the lead screw actively rotates, causing the tubular component to retract, the friction generated between the safety nut and the failed transmission nut through the conical surface fit treats the two nuts as a single unit. The actively rotating lead screw causes both nuts to move axially synchronously, allowing the object supported by the linear lifting device to descend at a stable and controllable speed. When the lead screw rotates actively to extend the tubular component, the friction between the safety nut driven by the lead screw and the failed transmission nut is insufficient to cause the safety nut to drive the transmission nut to move axially relative to the lead screw synchronously. That is, the safety nut and the transmission nut are in a slipping state, and the object supported by the linear lifting device cannot be raised or lowered, thereby playing a safety role and an abnormality warning role.

[0028] In summary, the addition of a safety nut can prevent objects supported by the linear lifting device from falling rapidly in the event of a failure of the transmission nut, greatly eliminating safety hazards and improving operational safety.

[0029] 2. The clearance of the second threaded pair between the safety nut and the lead screw is preferably greater than the clearance of the first threaded pair between the transmission nut and the lead screw. By reasonably setting the size relationship of the clearances of the two threaded pairs, the safety nut is basically not in contact with the lead screw when the transmission nut is not in failure. On the one hand, this avoids the safety nut interfering with the normal transmission between the lead screw and the transmission nut. On the other hand, it ensures that the wear of the safety nut before the transmission nut fails is basically zero. Under the condition that there is a self-locking force between the lead screw and the two nuts, the self-locking performance between the safety nut and the lead screw is guaranteed.

[0030] 3. The inner and outer conical surfaces are preferably set with the same cone angle, that is, the two conical surfaces are preferably set in parallel, so that the inner and outer conical surfaces can make full contact after the engagement of the rib and the groove is released. This ensures the contact area between the transmission nut and the safety nut. On the one hand, it can increase the friction between the two when the transmission nut fails. On the other hand, it can improve the load-bearing stability of the safety nut after it takes over the load, so that the transmission assembly can better meet the requirements of keeping the object stable or descending slowly when the transmission nut fails.

[0031] 4. Under normal conditions, the transmission nut has an axial clearance between its end face and the bottom wall of the cavity, and a normal clearance between the inner and outer conical surfaces. Both the rib and the groove extend axially along the lead screw and can undergo relative displacement along the axial direction. Furthermore, there is a circumferential clearance between the rib and the groove, and a radial clearance between them. A reasonable design of the fit between the transmission nut and the safety nut reduces the assembly difficulty of both nuts with the lead screw, and also reduces the difficulty of fitting the two nuts together. This ensures that after assembly, both nuts are mutually circumferentially limited while maintaining a good threaded fit with the lead screw. Additionally, the reserved assembly clearance provides some deformation space for the heated lead screw and also provides an escape channel for minor deformations or impurities, preventing the safety nut from jamming and preventing the transmission nut from being driven by the lead screw.

[0032] 5. A predetermined fracture section can be formed at the root of the rib. When the transmission nut fails and the torque borne by the rib exceeds the threshold, the predetermined fracture section undergoes shear fracture under the action of torque, thereby releasing the fit between the rib and the groove, so that the inner conical surface of the cavity and the outer conical surface of the safety nut can be pressed into contact and the two nuts can rotate relative to each other.

[0033] 6. When the transmission nut fails, the transmission nut under force may move axially, causing the rib to move axially out of the groove, thereby releasing the fit between the rib and the groove, thus releasing the circumferential limit between the transmission nut and the safety nut, so that the inner conical surface of the cavity and the outer conical surface of the safety nut can press into contact and the two nuts can rotate relative to each other. Attached Figure Description

[0034] Figure 1 This is an axial sectional view of the transmission assembly in Embodiment 1;

[0035] Figure 2 This is a partial structural diagram of the transmission assembly in Example 1;

[0036] Figure 3 This is a structural diagram of the transmission nut of the transmission assembly in Example 1;

[0037] Figure 4 This is a structural diagram of the safety nut of the transmission assembly in Example 1;

[0038] Figure 5 This is an axial sectional view of a partial structure of the transmission assembly in Example 1 when the transmission nut is in a normal state.

[0039] Figure 6 This is a cross-sectional view of the transmission assembly in Embodiment 1 at the point where the transmission nut and the safety nut meet, perpendicular to the axial direction.

[0040] Figure 7 This is an axial sectional view of a portion of the transmission assembly in Example 1 when the transmission nut is in a failed state.

[0041] Figure 8 This is an axial sectional view of the linear lifting device in Embodiment 1;

[0042] Figure 9 This is a structural diagram showing the cooperation between the actuation unit and the transmission assembly of the linear lifting device in Embodiment 1;

[0043] Figure 10 This is a diagram showing the fit between the rib and the groove perpendicular to the axial direction when a thinning groove is provided at the root of the rib in Embodiment 1.

[0044] Figure 11 This is an axial sectional view of a partial structure of the transmission assembly in Example 2 when the transmission nut is in a failed state.

[0045] In the diagram, 100-transmission assembly, 110-lead screw, 111-screw section, 112-polished section, 113-external thread, 120-transmission nut, 121-cavity, 122-inner conical surface, 123-first internal thread, 130-tubular component, 140-safety nut, 141-outer conical surface, 142-second internal thread, 151-rib, 1511-predetermined fracture section, 1512-thinning groove, 152-groove, 160-joint, 171-first threaded pair, 172-second threaded pair, 180-transmission sleeve, S1-axial clearance, S2-conical surface normal clearance, S3-circumferential clearance, S4-radial clearance.

[0046] 10-Linear lifting device,

[0047] 200-Actuation unit, 210-Motor, 220-Reduction mechanism, 221-Housing housing, 222-Drive shaft, 223-Worm gear, 2231-Gear tooth, 224-Worm, 2241-Helical tooth, 225-Driving gear, 226-Driven gear.

[0048] 300 - Telescopic sleeve assembly, 310 - Fixed end, 320 - Movable end, 330 - Sleeve. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the terms "upper," "lower," "left," "right," "longitudinal," "lateral," "inner," "outer," "vertical," "horizontal," "top," and "bottom," etc., which indicate orientation or positional relationship, are based solely on the orientation or positional relationship shown in the accompanying drawings and are used only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device / component referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0050] Example 1

[0051] Combination Figures 1 to 7 The linear lifting device transmission assembly 100 provided in Embodiment 1 of this utility model includes a lead screw 110, a transmission nut 120, a tubular component 130, and a safety nut 140. The transmission nut 120 is sleeved on the lead screw 110 and its rotation is restricted. The tubular component 130 is sleeved outside the lead screw 110 and is driven by the transmission nut 120 to reciprocate along the axial direction of the lead screw 110. The safety nut 140 is sleeved on the lead screw 110. The end of the transmission nut 120 facing the safety nut 140 has a cavity 121 for receiving the safety nut 140. The cavity 121 has an inner conical surface 122, and the safety nut 140 has an outer conical surface 141. One of the inner conical surface 122 and the outer conical surface 141 is provided with a rib 151, and the other is provided with a groove 152. Under normal conditions, the rib 151 and the groove 152 cooperate to restrict the relative rotation of the transmission nut 120 and the safety nut 140. When the transmission nut 120 fails, the rib 151 and the groove 152 disengage, and the inner conical surface 122 and the outer conical surface 141 press together to form a friction pair, which is used for static self-locking or dynamic friction between the transmission nut 120 and the safety nut 140.

[0052] The addition of a safety nut 140 in this application can prevent objects supported by the linear lifting device from falling rapidly in the event of failure of the transmission nut 120, thereby greatly eliminating safety hazards and improving safety in use.

[0053] Combination Figure 1 , Figure 2 In this embodiment, the lead screw 110 is long and includes a coaxial screw portion 111 and a smooth portion 112. The smooth portion 112 is located at the rear end of the screw portion 111. The screw portion 111 and the smooth portion 112 are integrally formed or separately formed and then fixed together. The outer circumferential surface of the screw portion 111 is provided with a spirally extending external thread 113. The inner circumferential surface of the transmission nut 120 is provided with a first internal thread 123 that mates with the external thread 113. The transmission nut 120 is sleeved on the screw portion 111 through the engagement of the first internal thread 123 and the external thread 113. The engagement of the first internal thread 123 and the external thread 113 forms a first threaded pair 171.

[0054] Combination Figure 3 In this embodiment, the cavity 121 is located at the rear end of the transmission nut 120. Specifically, the cavity 121 extends forward from the rear end of the transmission nut 120 to a certain depth, and its inner diameter gradually decreases from rear to front. The cavity 121 is a tapered cavity that is narrower at the front and wider at the back. The circumferential inner wall of the cavity 121 forms an inner conical surface 122. Furthermore, a rib 151 is provided on the inner conical surface 122 of the cavity 121. The rib 151 protrudes radially from the inner conical surface 122 toward the central axis of the transmission nut 120. The rib 151 extends axially to a certain length. Additionally, one or several ribs 151 are provided circumferentially along the inner conical surface 122.

[0055] Combination Figure 4 In this embodiment, the safety nut 140 is a flat-topped cone shape. The inner circumferential surface of the safety nut 140 is provided with a second internal thread 142 that mates with the external thread 113. The outer circumferential surface of the safety nut 140 forms an outer cone surface 141. A groove 152 is provided on the outer cone surface 141, and it is distributed one-to-one with the rib 151. The groove 152 is recessed radially from the outer cone surface 141 toward the central axis of the safety nut 140, extending from the front end face to the rear end face of the safety nut 140. The safety nut 140 is fitted onto the screw portion 111 through the engagement of the second internal thread 142 and the external thread 113. The second internal thread 142 and the external thread 113 form a second threaded pair 172. Simultaneously, the safety nut 140 is housed within the cavity 121, and the rib 151 is embedded within the groove 152.

[0056] Combination Figure 5In this embodiment, the depth of the cavity 121 is preferably greater than the axial length of the safety nut 140, so that the entire safety nut 140 can be completely contained within the cavity 121, thereby increasing the axial length of the engagement between the rib 151 and the groove 152. When the transmission nut 120 is in its normal state, there is a certain axial gap S1 between the front end face of the safety nut 140 contained within the cavity 121 and the bottom wall of the cavity 121, and a certain cone surface normal gap S2 between the inner conical surface 122 and the outer conical surface 141 in a direction perpendicular to the conical surface. In addition, since both the rib 151 and the groove 152 extend a certain length along the axial direction of the lead screw 110, the rib 151 and the groove 152 form a fit that allows for relative axial displacement. By rationally designing the mating relationship between the transmission nut 120 and the safety nut 140, the assembly difficulty of the two nuts and the lead screw 110 is reduced, as is the mating difficulty of the two nuts. After assembly, the two nuts can be mutually circumferentially restrained by the rib 151 and the groove 152, while maintaining a good threaded fit with the lead screw 110. Furthermore, the reserved mating clearance provides a certain deformation space for the heated lead screw 110 and also provides an escape channel for minor deformations or impurities, preventing the safety nut 140 from jamming with the lead screw 110 and thus preventing the transmission nut 120 from being driven by the lead screw 110. In other embodiments of this invention, the safety nut 140 may also be partially housed within the cavity 121.

[0057] In this embodiment, the cone angles of the inner cone surface 122 and the outer cone surface 141 are preferably the same, so that the inner cone surface 122 and the outer cone surface 141 are arranged parallel to each other. When the nut is in the normal state, a relatively stable cone surface normal gap S2 can be formed between the parallel inner cone surface 122 and the outer cone surface 141, avoiding friction between the two nuts. When the nut fails, the parallel inner cone surface 122 and the outer cone surface 141 can be in complete contact after the engagement of the rib 151 and the groove 152 is released, ensuring the contact area between the transmission nut 120 and the safety nut 140. On the one hand, this can increase the friction between the two when the transmission nut 120 fails, and on the other hand, it can improve the load-bearing stability of the safety nut 140 after it takes over the load, so that the transmission assembly 100 can better meet the requirements of keeping the object stable or descending slowly when the transmission nut 120 fails.

[0058] In this embodiment, the shape of the protruding rib 151 is preferably smaller than that of the groove 152, thereby reducing the installation difficulty of the safety nut 140, so that the safety nut 140 can be accommodated in the cavity 121 of the transmission nut 120 and can also be sleeved on the lead screw 110. Furthermore, in combination with... Figure 6The thickness T of the rib 151 is slightly less than the groove width W of the groove 152, so that the rib 151 and the groove 152 can form a certain circumferential gap S3. In addition, the protrusion height H of the rib 151 is slightly less than the radial depth D of the groove 152, so that the rib 151 and the groove 152 can form a certain radial gap S4.

[0059] Combination Figure 5 In this embodiment, to ensure that the safety nut 140 does not substantially contact the lead screw 110 when the transmission nut 120 is not faulty, the thread fit clearance of the second thread pair 172 is greater than that of the first thread pair 171. Specifically, there is a very small unilateral radial fit clearance G1 between the root of the external thread 113 and the crest of the first internal thread 123, and a very small unilateral axial fit clearance G2 between the thread surfaces of the external thread 113 and the first internal thread 123. There is a very small unilateral radial fit clearance G3 between the base of the external thread 113 and the crest of the second internal thread 142, and a very small unilateral fit clearance G4 between the thread surfaces of the external thread 113 and the second internal thread 142. By setting the appropriate clearance between the two threaded pairs (G1 < G3 and G2 < G4), the safety nut 140 is kept essentially out of contact with the lead screw 110 when the transmission nut 120 is functioning properly. This avoids interference between the safety nut 140 and the normal transmission between the lead screw 110 and the transmission nut 120, and also ensures that the wear of the safety nut 140 is essentially zero before the transmission nut 120 fails. This also guarantees the self-locking performance between the safety nut 140 and the lead screw 110 when there is a self-locking force between the lead screw 110 and the two nuts.

[0060] In this embodiment, a predetermined fracture portion 1511 is formed at the root where the rib 151 connects with the inner conical surface 122. When the torque borne by the rib 151 exceeds the threshold, the predetermined fracture portion 1511 of the rib 151 undergoes shear fracture under the action of torque, thereby releasing the fit between the rib 151 and the groove 152, so that the inner conical surface 122 of the cavity 121 and the outer conical surface 141 of the safety nut 140 can press against each other to form a friction pair.

[0061] Combination Figure 1 In this embodiment, the tubular component 130 is sleeved on the outside of the lead screw 110 with a certain circumferential gap between them. The rear end of the tubular component 130 is sleeved with the transmission nut 120, and the front end of the tubular component 130 can be connected to the driven member through the connector 160. The driven member, connector 160, tubular component 130, and transmission nut 120 are circumferentially limited. Specifically, the rear end of the tubular component 130 can be fixedly sleeved on at least a portion of the outer periphery of the transmission nut 120 by means of threaded engagement, snap-fit ​​engagement, or interference fit.

[0062] Combination Figure 8 , Figure 9 This embodiment also provides a linear lifting device 10, including an actuation unit 200, a telescopic sleeve assembly 300 composed of at least two sleeve sections 330, and the aforementioned transmission assembly 100. The actuation unit 200 includes a motor 210 and a reduction mechanism 220. The motor 210 drives the lead screw 110 to rotate through the reduction mechanism 220. One end of the tubular component 130 is connected to the transmission nut 120, and the other end is non-rotatably connected to the telescopic sleeve assembly 300. Specifically, the actuation unit 200 and the transmission assembly 100 are located inside the telescopic sleeve assembly 300. The axial direction of the transmission assembly 100 is substantially consistent with the length direction of the telescopic sleeve assembly 300, that is, the axial direction of the transmission assembly 100 is consistent with the lifting direction of the device. The actuation unit 200 is relatively fixedly located at the fixed end 310 of the telescopic sleeve assembly 300. The tubular component 130 of the transmission assembly 100 is non-rotatably connected to the movable end 320 of the telescopic sleeve assembly 300 through a connector 160. The telescopic sleeve assembly 300 can have two or more sleeves 330, with each sleeve 330 inner and outer sleeves together and movable relative to each other. The specific structure of the telescopic sleeve assembly 300 can be referred to in the prior art, and will not be repeated here. In the specific solution of this embodiment, the connector 160 at the end of the tubular component 130 and the movable end 320 of the telescopic sleeve assembly 300 can be connected in a non-rotatable manner by means of a pin engagement or other engagement methods.

[0063] In this embodiment, in order to reduce the overall thickness of the device, the actuation unit 200 and the transmission assembly 100 are arranged in a U-shape. Specifically, the axial direction of the motor 210 is arranged along the length direction of the telescopic sleeve assembly 300, that is, the axial directions of the motor 210 and the lead screw 110 are parallel and staggered by a certain distance. The reduction mechanism 220 is located between the rear end of the motor shaft and the rear end of the lead screw 110. Specifically, the reduction mechanism 220 includes a fixed housing 221, a rotatable drive shaft 222 mounted inside the housing 221, a worm gear 223 sleeved on one end of the drive shaft 222, a worm 224 driven by a motor 210 and meshing with the worm gear 223, a driving gear 225 located at the other end of the drive shaft 222, and a driven gear 226 meshing with the driving gear 225. The worm 224 is connected to the motor shaft of the motor 210 and the two are coaxial. The worm gear 223 is located inside the housing 221 and its axial direction is approximately perpendicular to the axial direction of the worm 224. The drive shaft 222 is rotatably mounted in the housing 221 via bearings and is coaxial with the worm gear 223. The drive gear 225 is connected to the drive shaft 222 and the two are coaxial. The smooth rod portion 112 of the lead screw 110 extends into the housing 221 and is provided with a drive sleeve 180. The drive sleeve 180 and the smooth rod portion 112 can be integrally formed or separately formed and then fixedly sleeved together. The drive sleeve 180 and the smooth rod portion 112 are rotatably supported by bearings. The driven gear 226 is sleeved on the drive sleeve 180 through a non-circular shaft hole fit structure or a keyway fit structure.

[0064] When motor 210 is running, the motor shaft drives worm 224 to rotate. Worm 224 drives lead screw 110 to rotate forward or reverse via worm wheel 223, transmission shaft 222, drive gear 225, and driven gear 226. A forward-rotating lead screw 110 drives transmission nut 120 to move tubular component 130 forward, causing the telescopic sleeve assembly 300 to extend and the object supported by linear lifting device 10 to rise. A reverse-rotating lead screw 110 drives transmission nut 120 to move tubular component 130 backward, causing the telescopic sleeve assembly 300 to shorten and the object supported by linear lifting device 10 to descend.

[0065] In this embodiment, the worm 224 and worm wheel 223 of the reduction mechanism 220 constitute a self-locking mechanism. When the motor 210 is not in operation, the load force is transmitted to the lead screw 110 through the telescopic sleeve assembly 300, the joint 160, the tubular component 130 and the transmission nut 120. The lead screw 110 transmits the load force it bears to the worm wheel 223. Under the action of the load force, the helical teeth 2241 of the worm 224 and the gear teeth 2231 of the worm wheel 223 abut against each other to form a one-way friction self-locking mechanism. This allows the motor 210 to drive the worm wheel 223 to rotate through the worm 224 and output actuation torque to the lead screw 110. However, the lead screw 110 cannot transmit the reverse torque generated by the load to the worm 224 through the worm wheel 223, so as to avoid the situation where the motor shaft rotates under the torque generated by the load, causing the linear lifting device 10 to fall back.

[0066] Combination Figure 5 When the transmission nut 120 is in the normal state, the safety nut 140 is housed in the cavity 121 of the transmission nut 120 and the rib 151 is embedded in the groove 152. There is an axial gap S1 between the end face of the safety nut 140 and the bottom wall of the cavity 121, and a conical normal gap S2 between the inner conical surface 122 and the outer conical surface 141. The safety nut 140 and the transmission nut 120 are mutually circumferentially limited by the cooperation of the rib 151 and the groove 152. The two nuts can rotate synchronously relative to the lead screw 110, so that the transmission nut 120 can drive the tubular component 130 to move axially and reciprocally smoothly. At this time, the load force of the object supported by the linear lifting device 10 is transmitted to the transmission nut 120 through the joint 160 and the tubular component 130. The transmission nut 120, which bears the load force, transmits the load force to the lead screw 110 through the contact between the first internal thread 123 and the external thread 123. Under the unidirectional friction self-locking action of the self-locking mechanism, the lead screw 110, which bears the load force, is in a stationary state. The transmission nut 120 is also in a stationary state when the lead screw 110 is stationary. At the same time, the safety nut 140 has no load-bearing function and is in a redundant state. The transmission nut 120 and the tubular component 130 are stably in a certain position, thereby enabling the object supported by the linear lifting device 10 to be stably maintained at a certain height. When the lead screw 110 is actuated to rotate, the lead screw 110 drives the transmission nut 120 and the safety nut 140 to move linearly along the axial direction in a roughly synchronous manner through the first threaded pair 171 and the second threaded pair 172. The linearly moving transmission nut 120 drives the linear lifting device 10 to extend or shorten through the tubular component 130 and the connector 160, thereby driving the object supported by the linear lifting device 10 to rise or fall.

[0067] Combination Figure 7When the transmission nut 120 fails, the transmission nut 120 bearing the load reverses relative to the lead screw 110, causing the rib 151 to be subjected to a large torque. When the torque rib 151 bears exceeds the threshold, the predetermined fracture part 1511 undergoes shear fracture under the action of torque. The fractured rib 151 detaches from the inner conical surface 122, and the limiting fit between the rib 151 and the groove 152 is released, that is, the mutual circumferential limiting between the two nuts is released, and the two nuts can rotate relative to each other. At the same time, the inner conical surface 122 and the outer conical surface 141 press against each other to form a friction pair. When there is no self-locking force or the self-locking force is small between the transmission nut 120 and the lead screw 110, the friction pair formed by the two conical surfaces causes the failed rotating transmission nut 120 to be subjected to a certain friction force. This friction force can effectively reduce the rotation speed of the failed rotating transmission nut 120, so that the transmission nut 120 cannot drive the safety nut 140 to rotate or can only drive the safety nut 140 to rotate at a low speed. This avoids the tubular component 130 from rapidly retracting due to the rapid rotation of the failed transmission nut 120, and thus avoids the object supported by the linear lifting device 10 from falling rapidly. When there is a self-locking force between the transmission nut 120 and the lead screw 110, the load force borne by the transmission nut 120 after its failure is transmitted to the safety nut 140 through the conical surface fit. That is, the safety nut 140 takes over the load when the transmission nut 120 fails. The safety nut 140 bearing the load causes the second internal thread 142 to abut against the external thread 123. The self-locking force between the safety nut 140 and the lead screw 110 replaces the self-locking force between the transmission nut 120 and the lead screw 110. Through the self-locking force between the safety nut 140 and the lead screw 110, the safety nut 140 bearing the load will not make instantaneous axial movement relative to the lead screw 110, thereby avoiding the rapid retraction of the tubular component 130 due to the failure of the transmission nut 120, and thus avoiding the rapid fall of the object supported by the linear lifting device 10. When the lead screw 110 rotates actively, causing the tubular component 130 to retract, the friction between the safety nut 140 and the failed transmission nut 120, generated by their conical engagement, treats the two nuts as a single unit. The actively rotating lead screw 110 causes the two nuts to move axially synchronously, allowing the object supported by the linear lifting device 10 to descend at a stable and controllable speed. When the lead screw 110 rotates actively, causing the tubular component 130 to extend, the friction between the safety nut 140 driven by the lead screw 110 and the failed transmission nut 120 is insufficient to cause the safety nut 140 to drive the transmission nut 120 to move axially relative to the lead screw 110 synchronously. In other words, the safety nut 140 and the transmission nut 120 are slipping, and the object supported by the linear lifting device 10 cannot be raised or lowered, thus serving a safety function and an abnormality warning function.

[0068] In other embodiments of this invention, the positions of the ribs 151 and the grooves 152 can be interchanged. That is, a plurality of outwardly protruding ribs 151 are provided on the outer conical surface 141 of the safety nut 140, and grooves 152 corresponding to the ribs 151 are provided on the inner conical surface 122 of the cavity 121.

[0069] Combination Figure 10 In other embodiments of this invention, a thinning groove 152 can be provided at the root of the rib 151. The thinning groove 152 reduces the stress threshold at which the rib 151 will break under torque, so that the rib 151 can break in time when the transmission nut 120 fails.

[0070] In other embodiments of this invention, the motor 210 of the reduction mechanism 220 and the lead screw of the transmission assembly 100 can also be arranged in an L-shape. In this case, the reduction mechanism 220 can only use a worm and a worm wheel. The worm is connected to the motor shaft of the motor, and the axial direction of the worm is approximately perpendicular to the axial direction of the lead screw. The worm wheel 223 is directly or indirectly sleeved on the smooth part 112 of the lead screw 110. The worm wheel and the worm mesh and form a self-locking mechanism. The motor shaft of the motor 210 can output actuation torque to the lead screw 110 through the meshing worm and worm wheel. However, the lead screw 110 cannot transmit the reverse torque generated by the load to the motor shaft.

[0071] In other embodiments of this invention, the self-locking mechanism can also be a braking device mounted on the motor shaft. When the motor 210 is not in operation, the braking device locks the motor shaft. The clamping force of the braking device on the motor shaft is greater than the reverse torque force transmitted to the motor shaft by the lead screw 110 under load, thereby preventing the motor shaft from reversing under the torque generated by the load. This allows the object supported by the linear lifting device 10 to be stably positioned at a certain height. The braking device can employ existing methods such as electromagnetic braking or back EMF short-circuit braking, which will not be elaborated here.

[0072] Example 2

[0073] Combination Figure 11 In this embodiment, the rib 151 is provided on the inner conical surface 122 of the cavity 121, and the groove 152 is provided on the outer conical surface 141 of the safety nut 140. The axial length of the rib 151 is less than the axial length of the groove 152.

[0074] When the transmission nut 120 is in the normal state, the safety nut 140 is housed in the cavity 121 and the rib 151 is embedded in the groove 152. The transmission nut 120 and the safety nut 140 are mutually circumferentially limited by the cooperation of the rib 151 and the groove 152, and the two can move synchronously along the axial direction of the lead screw 110 when the lead screw 110 is actuated.

[0075] When the transmission nut 120 fails, the load-bearing transmission nut 120 moves backward relative to the safety nut 140, causing the rib 151 to move out of the groove 152 axially. That is, the rib 151 and the groove 152 disengage from each other axially, releasing the fit between the rib 151 and the groove 152, thereby releasing the circumferential limit between the two safety nuts 140. At the same time, the inner conical surface 122 and the outer conical surface 141 press together to form a friction pair. This friction pair prevents the tubular component 130 from rapidly retracting due to the rapid rotation of the failed transmission nut 120.

[0076] The other contents of Example 2 are the same as those of Example 1, and will not be repeated here.

[0077] In addition to the preferred embodiments described above, there are other embodiments of this utility model. Those skilled in the art can make various changes and modifications based on this utility model. As long as they do not depart from the spirit of this utility model, they should all fall within the scope defined in the claims of this utility model.

Claims

1. The transmission assembly of the linear lifting device, including: Lead screw; A transmission nut, which is fitted onto the lead screw and is restricted from rotation; A tubular component, which is fitted onto the outside of the lead screw and is driven by a transmission nut to reciprocate along the axial direction of the lead screw; The transmission assembly is characterized in that it further includes a safety nut fitted on the lead screw, and the transmission nut has a cavity for receiving the safety nut at one end facing the safety nut. The cavity has an inner conical surface, and the safety nut has an outer conical surface. One of the inner conical surface and the outer conical surface is provided with a rib, and the other is provided with a groove. Under normal conditions, the rib and groove of the transmission nut cooperate to restrict the relative rotation of the transmission nut and the safety nut. When the transmission nut fails, the rib and the groove disengage, and the inner conical surface and the outer conical surface press together to form a friction pair, which is used for static self-locking or dynamic friction between the transmission nut and the safety nut.

2. The transmission assembly of the linear lifting device as described in claim 1, characterized in that, The transmission nut and the lead screw form a first threaded pair, and the safety nut and the lead screw form a second threaded pair. The thread fit clearance of the second threaded pair is greater than that of the first threaded pair. Under normal conditions, the transmission nut is supported by the first threaded pair, and under the failure condition, the transmission nut is supported by the second threaded pair.

3. The transmission assembly of the linear lifting device as described in claim 1, characterized in that, The inner cone and the outer cone have the same cone angle.

4. The transmission assembly of the linear lifting device as described in claim 1, characterized in that, In the normal state of the transmission nut, there is an axial gap between the end face of the safety nut facing the transmission nut and the bottom wall of the cavity, and there is a cone surface normal gap between the inner cone surface and the outer cone surface. The rib and the groove both extend along the axial direction of the lead screw, so that the two form a fit that allows axial relative displacement.

5. The transmission assembly of the linear lifting device as described in claim 4, characterized in that, There is a circumferential gap between the rib and the groove.

6. The transmission assembly of the linear lifting device as described in claim 4, characterized in that, There is a radial gap between the rib and the groove.

7. The transmission assembly of the linear lifting device as described in claim 1, characterized in that, The root of the rib forms a predetermined fracture portion, which undergoes shear fracture when the rib is subjected to a torque exceeding a threshold, thereby disengaging the rib from the groove.

8. The transmission assembly of the linear lifting device as described in claim 1, characterized in that, In the case of failure of the transmission nut, the relative displacement to the safety nut causes the rib to move axially out of the groove, thus disengaging the fit.

9. A linear lifting device, comprising an actuation unit and a telescopic sleeve assembly consisting of at least two sleeve sections, wherein the actuation unit includes a motor and a reduction mechanism, characterized in that, The linear lifting device further includes the transmission assembly according to any one of claims 1 to 8, wherein the motor drives the lead screw to rotate through a reduction mechanism, one end of the tubular component is connected to a transmission nut, and the other end is non-rotatably connected to the telescopic sleeve assembly.

10. The linear lifting device as described in claim 9, characterized in that, The actuation unit is equipped with a self-locking mechanism, which is used to restrict the lead screw from being driven to rotate by the load when the motor is not running. The self-locking mechanism is configured with one of the following structures: The motor shaft is equipped with a braking device. When the motor is not running, the braking device restricts the rotation of the motor shaft caused by the lead screw being driven by the load. The reduction mechanism includes a worm and a worm wheel. The worm is driven by the output shaft of the motor, and the worm wheel is driven by the lead screw. The helical teeth of the worm and the teeth of the worm wheel form a one-way friction self-locking mechanism, so that the worm can drive the worm wheel but the worm wheel cannot drive the worm.

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