CN116730245A - Lead screw assemblies, linear actuators and lifting equipment - Google Patents

Abstract

The present invention provides lead screw assemblies, linear actuators and lifting equipment. The screw assembly includes a center screw, a main nut engaged with the center screw to convert rotational motion of the center screw into translational motion, and a safety nut engaged with the center screw upon failure of the main nut, wherein, The screw assembly further includes a clutch mechanism disposed between the main nut and the safety nut, the clutch mechanism being configured such that when the center screw rotates in one direction, the safety nut engages with the safety nut. The main nut is coupled to drive the main nut to move. When the center screw rotates in a direction opposite to the one direction, the safety nut is disengaged from the main nut without driving the main nut to move. The screw assembly according to the present invention has a simple structure, low cost and high reliability.

Description

Lead screw assemblies, linear actuators and lifting equipment

Technical field

The present application relates to a screw assembly, as well as a linear actuator and a lifting device including such a screw assembly.

Background technique

Lifting equipment such as operating tables, aerial work platforms, cranes or scissor lifts often use linear actuators to drive the corresponding load-bearing platforms. A linear actuator generally includes an electric motor, a transmission mechanism such as a gearbox, and a screw assembly connected to the rotating shaft of the motor through the transmission mechanism. The screw assembly includes a center screw, a main nut engaged with the center screw to convert rotational motion of the center screw into translational motion, and a safety nut engaged with the center screw upon failure of the main nut.

When the main nut is working normally, the safety nut does not contact the center screw. However, once the thread of the main nut fails due to abnormal wear or material defects, the ball between the main nut and the center screw falls off, or other faults cause the main nut to malfunction. During operation, the safety nut engages with the center screw and carries the load under the action of a load ("load" in this application may include the load-bearing platform and people and objects on it). Because the friction between the safety nut and the center screw is relatively large, it can jam the center screw. When the safety nut engages the center screw, the screw assembly has failed or been damaged. In this case, for example, in the case of aerial work platforms, if the screw assembly extends the push tube of the screw assembly outward relative to the protective tube and pushes the load, this may cause serious safety hazards; and for example, in automobiles When repairing the lifting frame, if the screw assembly retracts the push tube of the screw assembly inward relative to the protective tube, it may also cause serious safety hazards. Since the driving power efficiency of the linear actuator becomes significantly worse when the safety nut is engaged with the center screw, an electronic control system has been proposed that uses a controller to monitor changes in the driving power efficiency of the linear actuator to determine linearity Whether there is a fault in the actuating device, when it is judged that there is a fault, the operation of the motor is controlled so that the push tube of the screw assembly can only be lowered but not raised. The electronic control system based on controlling the operation of the motor to control the movement of the push tube is not only complex in structure and high in cost, but also has low reliability. It still cannot completely eliminate the safety risks that exist during the operation of the linear actuator.

Therefore, there is a need to improve existing lead screw assemblies for linear actuators.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned defects in the prior art and provide a screw assembly, as well as a linear actuating device and lifting equipment including such a screw assembly, which can be used when the main nut fails and cannot operate normally. The mechanical structure ensures that the screw assembly can only extend the push tube outward or retract inward relative to the protective tube.

According to one aspect of the present invention, a screw assembly is provided, including:

center screw;

a main nut engaged with the center screw to convert rotational motion of the center screw into translational motion; and

a safety nut that engages the center screw upon failure of the main nut;

Wherein, the screw assembly further includes a clutch mechanism disposed between the main nut and the safety nut, the clutch mechanism is configured such that when the center screw rotates in one direction, the safety nut and The main nut is coupled to drive the main nut to move. When the center screw rotates in a direction opposite to the one direction, the safety nut is disengaged from the main nut without driving the main nut. sports.

Preferably, the clutch mechanism is arranged radially between the main nut and the safety nut.

Preferably, the screw assembly further includes a tail cap disposed around the central screw, the tail cap being fixedly connected to the main nut so as to define a space with the main nut for retaining the safety nut. space.

Preferably, a receiving cavity is formed at one end of the main nut, and the safety nut is partially held in the receiving cavity.

Preferably, a receiving cavity is formed at one end of the main nut, and the safety nut is completely disposed in the receiving cavity and is retained by a bearing radially disposed between the safety nut and the main nut. in the receiving cavity.

Preferably, the screw assembly further includes a spring member disposed against the safety nut to axially urge the safety nut onto the main nut.

Preferably, the screw assembly further includes a plurality of balls disposed between axially opposing surfaces of the main nut and the safety nut.

Preferably, the clutch mechanism includes:

A plurality of wedge-shaped grooves circumferentially spaced apart are formed on the outer circumferential surface of the safety nut, the wedge-shaped grooves having a straight bottom surface; and

rollers disposed in each of said wedge-shaped grooves;

Wherein, when the center screw rotates in the one direction, the safety nut and the tail cover are locked together by the roller, and when the center screw rotates in the opposite direction to the one direction, the safety nut and the tail cap are locked together by the roller. When the safety nut and the tail cap are separated.

Preferably, the clutch mechanism includes:

A plurality of wedge-shaped grooves circumferentially spaced apart are formed on the outer circumferential surface of the safety nut, the wedge-shaped grooves having a straight bottom surface; and

rollers disposed in each of said wedge-shaped grooves;

Wherein, when the center screw rotates in the one direction, the safety nut and the main nut are locked together by the roller, and when the center screw rotates in the opposite direction to the one direction, the safety nut and the main nut are locked together by the roller. When the safety nut and the main nut are separated.

Preferably, an axial groove is formed on the bottom surface close to the end with a greater depth of the wedge-shaped groove, a torsion spring is provided in the axial groove, and one end of the torsion spring abuts the roller. The other end of the column is against the wall of the wedge-shaped groove.

Preferably, the clutch mechanism includes:

A plurality of mounting grooves formed on the outer circumferential surface of the safety nut at circumferential intervals;

A pawl is provided in each of the mounting grooves, and the free end of the pawl extends outside the outer circumferential surface under the action of a spring piece; and

a plurality of inclined pawl receiving grooves formed on the inner circumferential surface of the tail cap at circumferential intervals;

Wherein, when the central screw rotates along the one direction, the pawl engages with the pawl receiving groove, and when the central screw rotates along the opposite direction to the one direction, the pawl engages with the pawl receiving groove. Disengage from the pawl receiving groove.

Preferably, the clutch mechanism includes:

A plurality of mounting grooves formed on the outer circumferential surface of the safety nut at circumferential intervals;

A pawl is provided in each of the mounting grooves, and the free end of the pawl extends outside the outer circumferential surface under the action of a spring piece; and

a plurality of inclined pawl receiving grooves formed on the inner circumferential surface of the main nut at circumferential intervals;

Wherein, when the central screw rotates along the one direction, the pawl engages with the pawl receiving groove, and when the central screw rotates along the opposite direction to the one direction, the pawl engages with the pawl receiving groove. Disengage from the pawl receiving groove.

Preferably, the clutch mechanism includes:

A plurality of cam wedges are spaced apart along the circumferential direction between the outer circumferential surface of the safety nut and the inner circumferential surface of the tail cover, and the major diameter of the cam wedges is larger than all the lengths of the safety nut. The distance between the outer circumferential surface and the inner circumferential surface of the tail cap, the short diameter of the cam wedge is smaller than the distance; and

Annular coil springs are connected end to end, and the coil springs are arranged on the fulcrum of each cam wedge to reset the cam wedge;

Wherein, when the center screw rotates along the one direction, the safety nut and the tail cover are locked together by the cam wedge, and when the center screw rotates along the direction opposite to the one direction, the safety nut and the tail cover are locked together by the cam wedge. When rotating in the opposite direction, the safety nut is separated from the tail cap.

Preferably, the clutch mechanism includes:

A plurality of cam wedges are spaced apart along the circumferential direction between the outer circumferential surface of the safety nut and the inner circumferential surface of the main nut, and the major diameter of the cam wedges is larger than all of the safety nut. The distance between the outer circumferential surface and the inner circumferential surface of the main nut, the short diameter of the cam wedge is smaller than the distance; and

Annular coil springs are connected end to end, and the coil springs are arranged on the fulcrum of each cam wedge to reset the cam wedge;

Wherein, when the center screw rotates along the one direction, the safety nut and the main nut are locked together by the cam wedge. When the center screw rotates along the direction opposite to the one direction, the safety nut and the main nut are locked together by the cam wedge. The safety nut is separated from the main nut when rotated in the opposite direction.

Preferably, an annular groove for receiving the cam wedge is formed on the outer circumferential surface of the safety nut.

According to another aspect of the present invention, a linear actuator is provided, comprising:

electric motor;

A lead screw assembly as described above; and

A transmission mechanism that connects the rotating shaft of the motor and the central screw of the screw assembly.

Preferably, the linear actuating device further includes an electromagnetic brake having a release handle, the electromagnetic brake being configured to brake the electric motor in the event of a power outage.

According to yet another aspect of the present invention, a lifting device is provided, wherein the lifting device includes a lead screw assembly as described above or a linear actuating device as described above.

According to the present invention, when the main nut fails, when the center screw rotates in the one direction, the safety nut and the main nut are locked together through a clutch mechanism to drive the main nut and the push tube to move. , thereby retracting the push tube or extending the push tube relative to the protective tube; when the center screw rotates in the direction opposite to the one direction, the safety nut and the main nut are separated, and the safety nut rotates in place. , will not cause the main nut and push tube to move, and the push tube and load will remain in place relative to the protective tube. Therefore, the screw assembly according to the present invention completely uses the mechanical structure to control the movement of the main nut and the push tube without requiring a complex electronic control system. Therefore, the structure is simple, the cost is low, and the reliability is high, so that it can maximize Minimize or eliminate safety risks during operation of linear actuators.

In order to explain the structural features and functions of the present application more clearly, the present application will be described in detail below with reference to the drawings and specific embodiments.

Description of drawings

Figure 1 is a cross-sectional view schematically showing the linear actuator of the present application;

Figure 2 is a cross-sectional view schematically showing the screw assembly of the first preferred embodiment of the present application;

Figure 3 is a cross-sectional view taken along line 3-3 of Figure 2;

Figure 4 is a cross-sectional view taken along line 4-4 of Figure 2;

Figure 5 is a cross-sectional view taken along line 5-5 of Figure 2;

Figure 6 is a cross-sectional view taken along line 6-6 of Figure 2;

Figure 7 is a cross-sectional view schematically showing the screw assembly of the second preferred embodiment of the present application;

Figure 8 is a cross-sectional view taken along line 8-8 of Figure 7;

Figure 9 is a cross-sectional view taken along line 9-9 of Figure 7;

Figure 10 is a cross-sectional view taken along line 10-10 of Figure 7;

Figure 11 is a cross-sectional view taken along line 11-11 of Figure 7;

Figure 12 is a cross-sectional view schematically showing the screw assembly of the third preferred embodiment of the present application;

Figure 13 is a cross-sectional view taken along line 13-13 of Figure 12;

Figure 14 is a cross-sectional view taken along line 14-14 of Figure 12;

Figure 15 is a cross-sectional view taken along line 15-15 of Figure 12;

Figure 16 is a cross-sectional view taken along line 16-16 of Figure 12; and

17 is a cross-sectional view schematically showing a screw assembly according to a fourth preferred embodiment of the present application.

Detailed ways

Specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but it should be understood that the accompanying drawings are only used to illustrate the present invention and do not constitute limitations to the present invention.

Figure 1 is a cross-sectional view schematically showing the linear actuator of the present application. As shown in Figure 1, the linear actuator 1 generally includes a motor 3 for providing power, a transmission mechanism 5 such as a gearbox, a belt drive, and a chain drive, and a screw assembly connected to the rotating shaft of the motor 3 through the transmission mechanism 5. 7. The screw assembly 7 includes a center screw 9 , a main nut 11 engaged with the center screw 9 to convert the rotational motion of the center screw 9 into a translational motion, and a safety nut 13 engaged with the center screw 9 when the main nut 11 fails. The screw assembly 7 may also include a push tube 15 arranged around the central screw 9. The push tube 15 is rigidly connected to the main nut 11 at the proximal end, and a rotatable joint 17 is provided at the distal end to rotatably connect the push tube 15. to the carrying platform (not shown). The screw assembly 7 may also include a protective tube 19 arranged around the central screw 9, the main nut 11, the safety nut 13 and the push tube 15. The proximal end of the protective tube 19 is fixed on the transmission mechanism 5, and the distal end of the protective tube 19 is provided with Opening 21 is configured to slidably receive push tube 15 .

When the motor 3 rotates forward, the transmission mechanism 5 connected to the rotating shaft of the motor 3 and the central screw 9 of the screw assembly 7 respectively transmits the rotational motion of the rotating shaft of the motor 3 to the central screw 9 at a reduced speed, and interacts with the central screw 9 The engaged main nut 11 converts the rotational motion of the central screw 9 into a translational motion, thereby pushing the push tube 15 to extend outward relative to the protective tube 19 to push or lift the load far away. When the motor 3 rotates reversely, the main nut 11 drives the push tube 15 to retract inward relative to the protective tube 19 to retract or lower the load.

The linear actuator 1 may also include an electromagnetic brake 25 with a release handle 23. The electromagnetic brake 25 is configured to be in a braking state when the power is off, so as to brake the motor when the motor 3 is suddenly powered off, thereby blocking the central screw. 9 to prevent the push tube 15 from retracting into the protective tube 19 under external pressure in the event of a power outage or other failure. When it is necessary to retract the push tube 15 to lower the load, due to a power outage, the operator can release the braking state of the electromagnetic brake 25 by pulling the release handle 23, so that the push tube 15 retracts into the protective tube 19 under the load. . In a preferred embodiment, the electromagnetic brake 25 is provided at the end of the opposite side where the motor 3 is connected to the transmission mechanism 5 to brake the rotating shaft of the motor 3 in the event of a power outage or other failure.

Although the screw composed of the center screw 9 and the main nut 11 can be a trapezoidal screw, due to the low transmission efficiency of the trapezoidal screw, ball screws or roller screws are more commonly used in practice. Due to abnormal wear or material defects of the trapezoidal screw, the thread of the main nut fails, the balls between the main nut and the center screw of the ball screw fall off, and the rollers between the main nut and the center screw of the roller screw appear. When the main nut fails to work normally due to falling off or other faults, the safety nut engages with the center screw under load and carries the load. According to the present invention, the screw assembly 7 further includes a clutch mechanism 29 disposed between the main nut 11 and the safety nut 13 , and the clutch mechanism 29 is configured such that when the center screw 9 rotates in one direction, the safety nut 13 and the main nut 11 are combined together to drive the main nut 11 to move together. When the central screw 9 rotates in the opposite direction to the one direction, the safety nut 13 is disengaged from the main nut 11 and will not drive the main nut 11 to move together. In this way, when the main nut 11 fails and cannot work normally, when the center screw 9 rotates in one direction, the safety nut 13 and the main nut 11 are combined together to drive the main nut 11 and then the push tube 15 to move together. Thereby, the push tube 15 is retracted or extended relative to the protective tube 19; when the central screw 9 rotates in the opposite direction to this direction, the safety nut 13 is disengaged from the main nut 11, and the safety nut 13 is rotated relative to the main nut 11. When the nut 11 rotates idling, it will not drive the main nut 11 and the push tube 15 to move together. The push tube 15 and the load remain in place relative to the protective tube 19 .

Figure 2 is a cross-sectional view schematically showing the screw assembly of the first preferred embodiment of the present application. Figure 3 is a cross-sectional view taken along the center line 3-3 of Figure 2. Figure 4 is a cross-sectional view taken along the center line 4-4 of Figure 2. 5 is a cross-sectional view taken along line 5 - 5 of FIG. 2 , and FIG. 6 is a cross-sectional view taken along line 6 - 6 of FIG. 2 . As shown in FIG. 2 , a receiving cavity 31 is formed at the proximal end of the main nut 11 (ie, the end far away from the end connected to the push tube 15 ) for at least partially receiving the safety nut 13 arranged around the central screw 9 . The tail cap 33 arranged around the central screw 9 is fixedly connected to the main nut 11 by a connecting device 35 such as a screw to retain the safety nut 13 in the space 37 defined by the main nut 11 and the tail cap 33 . A disc spring 39 may be provided between the tail cap 33 and the safety nut 13 to axially push the safety nut 13 onto the main nut 11 . The disc spring here can also be replaced by a wave spring. As long as the safety nut can be axially pressed onto the main nut, the type of the spring component is not limited. Preferably, a plurality of balls 41 may be provided between axially opposite surfaces of the main nut 11 and the safety nut 13 to facilitate the safety nut 13 to rotate smoothly relative to the main nut 11 . As shown in FIGS. 2-6 , according to the first preferred embodiment of the present invention, the clutch mechanism 29 includes a plurality of wedge-shaped grooves 45 circumferentially spaced apart and formed on the outer circumferential surface 43 of the safety nut 13 . The wedge-shaped grooves 45 have a generally flat shape. Straight bottom surface 47 so as to have a gradually varying radial depth along the circumference. The clutch mechanism 29 also includes a roller 49 provided in each wedge-shaped groove 45 .

In the event of failure of the main nut 11 , the safety nut 13 engages the central screw 9 . Due to the large friction between the safety nut 13 and the center screw 9, when the motor 3 drives the center screw 9 to rotate in one direction, the safety nut 13 tends to rotate clockwise in Figure 3-6, and the rollers 49 will be locked with the safety nut 13 and the tail cap 33, so that the tail cap 33 has a tendency to rotate clockwise. Since the tail cap 33 and the main nut 11 are connected together through the connecting device 35 , the main nut 11 and the push tube 15 are eventually driven to move together, thereby allowing the push tube 15 to retract or extend relative to the protective tube 19 . When the motor 3 drives the center screw 9 to rotate in the other direction, the safety nut 13 tends to rotate counterclockwise in Figure 3-6, and the roller 49 separates from the safety nut 13 and the tail cover 33. Under the action of the pretightening force of the disc spring 39, the safety nut 13 rotates in place with the help of the ball 41. Therefore, the main nut 11 and the push tube 15 do not move, and the push tube 15 and the load remain in place relative to the protective tube 19 . In this way, after the safety nut 13 is engaged with the center screw 9, the main nut 11 can only be driven to move in one direction by means of the clutch mechanism 29.

An axial groove 51 can be formed on the bottom surface 47 at one end of the wedge-shaped groove 45 with a larger depth, and a torsion spring 53 is provided in the axial groove 51. One end of the torsion spring 53 abuts the roller 49, and the other end abuts the wedge-shaped groove. 45's wall. In this way, the position of the roller 49 in the wedge-shaped groove 45 can be limited, thereby improving the response speed of the clutch mechanism 29 when it switches from the disengaged state to the locked state.

Figure 7 is a cross-sectional view schematically showing the screw assembly of the second preferred embodiment of the present application. Figure 8 is a cross-sectional view taken along line 8-8 in Figure 7. Figure 9 is taken along line 9-9 in Figure 7. 10 is a cross-sectional view taken along line 10 - 10 in FIG. 7 , and FIG. 11 is a cross-sectional view taken along line 11 - 11 in FIG. 7 . For the sake of brevity, the description of the same elements in the second preferred embodiment of the present application as those in the first preferred embodiment of the present application will be omitted below.

As shown in FIGS. 7-11 , according to the second preferred embodiment of the present invention, the clutch mechanism 29 includes a plurality of mounting grooves 55 circumferentially spaced apart and formed on the outer circumferential surface 43 of the safety nut 13 , and each mounting groove 55 has a A pawl 57 is provided, and the free end of the pawl 57 extends outside the outer circumferential surface 43 of the safety nut 13 under the action of a not-shown elastic piece. The clutch mechanism 29 also includes a plurality of inclined pawl receiving grooves 59 circumferentially spaced apart and formed on the inner circumferential surface of the tail cover 33 so that the tail cover 33 forms an inner ratchet.

When the safety nut 13 has a tendency to rotate clockwise in Figures 8-11, the pawl 57 on the safety nut 13 engages with the pawl receiving groove 59 on the inner circumferential surface of the tail cover 33 and is locked in place. Together, the main nut 11 and the push tube 15 are finally driven to move together, thereby allowing the push tube 15 to retract or extend relative to the protective tube 19 . When the safety nut 13 tends to rotate counterclockwise in FIGS. 8-11 , the pawl 57 on the safety nut 13 disengages from the pawl receiving groove 59 on the inner circumferential surface of the tail cover 33 . Under the action of the pretightening force of the disc spring 39, the safety nut 13 rotates in place with the help of the ball 41. Therefore, the main nut 11 and the push tube 15 do not move, and the push tube 15 and the load remain in place relative to the protective tube 19 . In this way, after the safety nut 13 is engaged with the center screw 9, the main nut 11 can only be driven to move in one direction by means of the clutch mechanism 29.

Figure 12 is a cross-sectional view schematically showing the screw assembly of the third preferred embodiment of the present application. Figure 13 is a cross-sectional view taken along the center line 13-13 of Figure 12. Figure 14 is a cross-sectional view taken along the center line 14-14 of Figure 12. 15 is a cross-sectional view taken along line 15 - 15 of FIG. 12 , and FIG. 16 is a cross-sectional view taken along line 16 - 16 of FIG. 12 . For the sake of brevity, description of the same elements in the third preferred embodiment of the present application as in the first preferred embodiment of the present application will be omitted below.

As shown in FIGS. 12-16 , according to the third preferred embodiment of the present invention, the clutch mechanism 29 includes a plurality of devices spaced apart along the circumferential direction between the outer circumferential surface 43 of the safety nut 13 and the inner circumferential surface of the tail cover 33 . A cam wedge 61. Each cam wedge 61 has two diameters of different sizes. The long diameter is larger than the distance between the outer circumferential surface 43 of the safety nut 13 and the inner circumferential surface of the tail cover 33 , while the short diameter is smaller than the outer circumferential surface of the safety nut 13 . The distance between the circumferential surface 43 and the inner circumferential surface of the tail cover 33. The coil springs 63 connected end to end to form an annular shape are arranged on the fulcrum of each cam wedge 61 to allow the cam wedge 61 to return to its original position. In a preferred embodiment, an annular groove 64 may be formed on the outer circumferential surface 43 of the safety nut 13 for receiving a plurality of cam wedges 61 . In addition, in the preferred embodiment, two circles of cam wedges 61 are provided between the outer circumferential surface 43 of the safety nut 13 and the inner circumferential surface of the tail cover 33 . It should be understood that only one circle of cam wedges 61 may be provided. Or more turns of the cam wedge 61.

When the safety nut 13 has a tendency to rotate clockwise in Figures 13-16, since the long diameter of the cam wedge 61 is greater than the distance between the outer circumferential surface 43 of the safety nut 13 and the inner circumferential surface of the tail cover 33 , the cam wedge 61 is stuck between the tail cover 33 and the safety nut 13, so that the safety nut 13 and the tail cover 33 are locked together, and finally drive the main nut 11 and the push tube 15 to move together, thereby allowing the push tube 15 to move relative to each other. The protective tube 19 retracts or extends. When the safety nut 13 tends to rotate in the counterclockwise direction in Figures 13-16, since the short diameter of the cam wedge 61 is smaller than the distance between the outer circumferential surface 43 of the safety nut 13 and the inner circumferential surface of the tail cover 33 , the cam wedge 61 will not be stuck between the tail cover 33 and the safety nut 13, and the safety nut 13 will be separated from the tail cover 33. Under the action of the pretightening force of the disc spring 39, the safety nut 13 rotates in place with the help of the ball 41. Therefore, the main nut 11 and the push tube 15 do not move, and the push tube 15 and the load remain in place relative to the protective tube 19 . In this way, after the safety nut 13 is engaged with the center screw 9, the main nut 11 can only be driven to move in one direction by means of the clutch mechanism 29.

In the above-mentioned preferred embodiments, the clutch mechanism 29 is configured to drive the tail cap 33 and the main nut 11 to move together when the clockwise rotation trend in Figures 3-6, Figures 8-11 and Figures 13-16 is shown. It is understood that the clutch mechanism 29 can be configured as needed to drive the tail cap 33 and the main nut 11 to move together during the counterclockwise rotation trend in these figures.

In the first to third preferred embodiments, the safety nut 13 is only partially disposed in the receiving cavity 31 at the proximal end of the main nut 11 , but it should be understood that the safety nut 13 can be completely disposed in the proximal end of the main nut 11 . in the receiving cavity 31 at the end. 17 is a cross-sectional view schematically showing a screw assembly according to a fourth preferred embodiment of the present application. The fourth preferred embodiment is substantially the same as the first preferred embodiment, except that the safety nut 13 is completely disposed in the receiving cavity 31 at the proximal end of the main nut 11, and there is also a gap between the safety nut 13 and the main nut 11 at the open end of the receiving cavity 31. Bearings 65 such as deep groove ball bearings are arranged radially therebetween. On the one hand, the bearing 65 can prevent the safety nut 13 from falling when the linear actuator is set vertically, and on the other hand, it can prevent the safety nut 13 and the main nut 11 from rotating at the same time. Of course, the clutch structure in the fourth preferred embodiment can also be replaced by the clutch structures in the second preferred embodiment and the third preferred embodiment. It should be understood that the tail cap in the second and third preferred embodiments can also be replaced by bearings. In addition, it is also feasible that the receiving cavity 31 is not formed at the proximal end of the main nut 11. In this case, the safety nut 13 is generally held in the receiving cavity formed by the cup-shaped tail cap.

In a fourth preferred embodiment, the clutch mechanism 29 is arranged radially directly between the safety nut 13 and the main nut 11 . In the first to third preferred embodiments, the clutch mechanism 29 is radially directly disposed between the safety nut 11 and the tail cover 33 . Since the tail cover 33 is connected with the main nut 11 , the clutch mechanism 29 can also be understood. It is arranged between the safety nut 13 and the main nut 11. Therefore, in the present invention, the clutch mechanism 29 radially disposed between the safety nut 13 and the main nut 11 should be understood to include the situation where the clutch mechanism is directly disposed between the safety nut 13 and the main nut 11 and the clutch mechanism indirectly. is disposed between the safety nut 13 and the main nut 11. Furthermore, although in the preferred embodiment, the clutch mechanism 29 is radially disposed between the safety nut 13 and the main nut 11 , it should also be understood that the clutch mechanism 29 may be axially disposed between the safety nut 13 and the main nut 11 space, for example, can be provided between the axially opposite surfaces of the main nut 11 and the safety nut 13 . In the latter case, the individual components of the clutch mechanism 29 can be adapted. Therefore, in the present invention, the clutch mechanism 29 disposed between the safety nut 13 and the main nut 11 should be understood to include the situation where the clutch mechanism is radially disposed between the safety nut 13 and the main nut 11 and the clutch mechanism axially. It is provided between the safety nut 13 and the main nut 11 .

The preferred embodiments of the present invention have been described above, but the spirit and scope of the present invention are not limited to the specific embodiments disclosed here. Those skilled in the art can make more modifications and substitutions based on the teachings of the present invention, and these modifications and substitutions are within the spirit and scope of the present invention. The spirit and scope of the present invention are not limited by the specific embodiments, but by the claims.

Claims (18)

1. A screw assembly, including: Center screw (9); a main nut (11) engaged with the central screw (9) to convert the rotational motion of the central screw (9) into a translational motion; and a safety nut (13) that engages the center screw (9) when the main nut (11) fails; Wherein, the screw assembly also includes a clutch mechanism (29) disposed between the main nut (11) and the safety nut (13), and the clutch mechanism (29) is configured to operate when the center When the screw (9) rotates in one direction, the safety nut (13) and the main nut (11) are combined to drive the main nut (11) to move. When rotating in the opposite direction, the safety nut (13) is disengaged from the main nut (11) and does not drive the main nut (11) to move. 2. The screw assembly according to claim 1, wherein the clutch mechanism (29) is arranged radially between the main nut (11) and the safety nut (13). 3. The screw assembly according to claim 2, further comprising a tail cap (33) arranged around the central screw (9), the tail cap (33) being fixedly connected to the main nut ( 11) so as to define with the main nut (11) a space (37) for holding the safety nut (13). 4. The screw assembly according to claim 3, wherein a receiving cavity (31) is formed at one end of the main nut (11), and the safety nut (13) is partially retained in the receiving cavity (31). 31) in. 5. The screw assembly according to claim 2, wherein a receiving cavity (31) is formed at one end of the main nut (11), and the safety nut (13) is completely disposed in the receiving cavity (31). ) and is held in the receiving cavity (31) by a bearing (65) arranged radially between the safety nut (13) and the main nut (11). 6. The screw assembly according to claim 3 or 5, further comprising a screw assembly arranged to abut the safety nut (13) to axially urge the safety nut (13) to the main nut (13). 11) on the spring piece (39). 7. The screw assembly according to claim 3 or 5, further comprising a plurality of balls (41) disposed between axially opposite surfaces of the main nut (11) and the safety nut (13) ). 8. The lead screw assembly of claim 3, wherein the clutch mechanism (29) includes: A plurality of wedge-shaped grooves (45) are circumferentially spaced and formed on the outer circumferential surface (43) of the safety nut (13), the wedge-shaped grooves (45) having a straight bottom surface (47); and Rollers (49) provided in each wedge-shaped groove (45); Wherein, when the center screw (9) rotates in one direction, the safety nut (13) and the tail cover (33) are locked together by the roller (49). When the screw (9) rotates in the opposite direction to the one direction, the safety nut (13) and the tail cap (33) are separated. 9. The lead screw assembly of claim 5, wherein the clutch mechanism (29) includes: A plurality of wedge-shaped grooves (45) are circumferentially spaced and formed on the outer circumferential surface (43) of the safety nut (13), the wedge-shaped grooves (45) having a straight bottom surface (47); and Rollers (49) provided in each wedge-shaped groove (45); Wherein, when the center screw (9) rotates in one direction, the safety nut (13) and the main nut (11) are locked together by the roller (49). When the screw (9) rotates in the opposite direction to the one direction, the safety nut (13) and the main nut (11) are separated. 10. The screw assembly according to claim 8 or 9, wherein an axial groove (51) is formed on the bottom surface (47) close to the end with a greater depth of the wedge-shaped groove (45), A torsion spring (53) is provided in the axial groove (51), one end of the torsion spring (53) is against the roller (49), and the other end is against the wall of the wedge-shaped groove (45) . 11. The lead screw assembly of claim 3, wherein the clutch mechanism (29) includes: A plurality of mounting grooves (55) formed on the outer circumferential surface (43) of the safety nut (13) at circumferential intervals; A pawl (57) is provided in each mounting groove (55), and the free end of the pawl (57) extends outside the outer circumferential surface (43) under the action of a spring piece; and A plurality of inclined pawl receiving grooves (59) formed on the inner circumferential surface of the tail cover (33) at circumferential intervals; When the central screw (9) rotates along the one direction, the pawl (57) engages with the pawl receiving groove (59). When rotating in the opposite direction, the pawl (57) is disengaged from the pawl receiving groove (59). 12. The lead screw assembly of claim 5, wherein the clutch mechanism (29) includes: A plurality of mounting grooves (55) formed on the outer circumferential surface (43) of the safety nut (13) at circumferential intervals; A pawl (57) is provided in each mounting groove (55), and the free end of the pawl (57) extends outside the outer circumferential surface (43) under the action of a spring piece; and A plurality of inclined pawl receiving grooves (59) formed on the inner circumferential surface of the main nut (11) at circumferential intervals; Wherein, when the central screw (9) rotates along the one direction, the detent (57) engages with the detent receiving groove (59), and when the central screw (9) rotates along the When rotating in the opposite direction, the pawl (57) is disengaged from the pawl receiving groove (59). 13. The lead screw assembly of claim 3, wherein the clutch mechanism (29) includes: A plurality of cam wedges (61) spaced apart along the circumferential direction between the outer circumferential surface (43) of the safety nut (13) and the inner circumferential surface of the tail cover (33), the cam The long diameter of the wedge (61) is greater than the distance between the outer circumferential surface (43) of the safety nut (13) and the inner circumferential surface of the tail cover (33). The cam wedge (61) The minor diameter is less than the spacing; and Annular coil springs (63) are formed end to end, and the coil springs (63) are arranged on the fulcrum of each cam wedge (61) to reset the cam wedge (61); Wherein, when the central screw (9) rotates in one direction, the safety nut (13) and the tail cover (33) are locked together through the cam wedge (61). When the central screw (9) rotates in the opposite direction to the one direction, the safety nut (13) is separated from the tail cap (33). 14. The lead screw assembly of claim 5, wherein the clutch mechanism (29) includes: A plurality of cam wedges (61) spaced apart along the circumferential direction between the outer circumferential surface (43) of the safety nut (13) and the inner circumferential surface of the main nut (11), the cam The long diameter of the wedge (61) is greater than the distance between the outer circumferential surface (43) of the safety nut (13) and the inner circumferential surface of the main nut (11). The cam wedge (61) The minor diameter is less than the spacing; and Annular coil springs (63) are formed end to end, and the coil springs (63) are arranged on the fulcrum of each cam wedge (61) to reset the cam wedge (61); Wherein, when the center screw (9) rotates in one direction, the safety nut (13) and the main nut (11) are locked together through the cam wedge (61). When the center screw (9) rotates in the opposite direction to the one direction, the safety nut (13) is separated from the main nut (11). 15. The screw assembly according to claim 13 or 14, wherein an annular recess for receiving the cam wedge (61) is formed on the outer circumferential surface (43) of the safety nut (13). slot(64). 16. A linear actuating device, comprising: motor(3); The screw assembly according to any one of claims 1-15; and The transmission mechanism (5) connects the rotating shaft of the electric motor (3) and the central screw (9) of the screw assembly (7). 17. The linear actuating device of claim 16, wherein the linear actuating device further comprises an electromagnetic brake (25) having a release handle (23), the electromagnetic brake (25) being configured to Brake the electric motor (3). 18. A lifting device, wherein the lifting device includes a screw assembly as claimed in any one of claims 1 to 15 or a linear actuating device as claimed in claim 16 or 17.