JP3074720U - Screw linear actuator - Google Patents

Abstract

(57) [Summary] [Purpose] It has a security function and is mechanically simple.
Provided is a linear actuator that is short, easy to process, and can reduce cost. SOLUTION: Even if the nut portion of the safety nut is damaged, it can be engaged with the screw shaft, and the work can be quickly lowered by free sliding with each other to prevent injury to the worker. A safety screw is provided to engage with the screw groove of the screw shaft. Further, by manufacturing the safety nut with a material having high strength in order to reduce the space occupied by the safety nut, sufficient strength can be provided even if the thickness of the safety nut is reduced. Further, in order to simplify the production and reduce the cost, the thickness of the safety nut can be reduced by a mechanism for connecting with a pin or a split pin between the safety nuts. Further, the stroke affected by the screw shaft is short, and the manufacturing and assembly costs can be reduced.

Description

[Detailed description of the invention]

[0001]

[Technical field to which the invention belongs]

 The present invention relates to a linear actuator, and more particularly to a linear actuator that is driven by a motor and a screw and that can receive an external axial load even when a nut used in accordance with the screw is broken.

[0002]

[Prior art]

 As is well known, the actuator is composed of an outer case, a motor, a transmission shaft and an output shaft. The rotation force of the motor is transmitted to the output shaft via the transmission shaft. The output shaft includes a bolt and an extension tube, the screw has a screw shaft and a nut, and the bolt has a screw shaft and a nut. The rotation of the screw shaft can be switched to linear thrust by the nut, and the work can be operated because the extension pipe is connected to the nut. However, when the linear actuator is used for a long period of time and the output shaft receives an inappropriate external force, the nut may be damaged, leading to the loss of the thrust of the linear actuator. At this time, without protection by a safe mechanism, the linked work would quickly lose weight, leading to severe destruction.

[0003] There are mainly two types of screws used in linear actuators: ball screw shafts and ACME screws. The damage to the ball screw shaft is caused by wear or detachment of the ball, and in the case of the ACME screw, the screw tooth of the plastic nut used is broken. At this time, if no special protective measures are taken, the workpiece is dropped by external force and may be damaged or may cause injury to workers.The safety nut is the most commonly used design for safety protection. You.

In a conventional ball screw safety nut, as shown in FIG. 6, in a general situation, power is transmitted between a screw shaft 32 and a nut 33 by a ball 30. If the ball 30 is damaged, the power of the ball 30 cannot be transmitted, so that the load is applied to the safety screw portion 331 of the safety nut 33 instead. Since the safety screw portion 331 is located near the inner diameter of the nut 33 and extends between the screw grooves of the screw shaft 32, it can receive a load when the ball (30) is damaged or comes off. . However, while such safety nuts are suitable for use in large industrial rolling ball screws, the small ball screws used in linear actuators are clearly too long, complicated and difficult to machine. Not easy and the available strokes are reduced shortly.

[0005]

[Problems to be solved by the invention]

 The present invention mainly has a safety protection function in view of the drawbacks that the safety nut mechanism in the prior art as described above is too long, is complicated, and is difficult to machine and manufacture. It is an object of the present invention to provide a linear actuator that is short, easy to process, and capable of reducing costs.

[0006]

[Means for Solving the Problems]

 The design of the safety nut in the present invention has a hollow shape, and the inside of the safety nut can engage with the screw shaft even if the nut is damaged in the safety nut, and can slide freely with each other. A safety screw is provided to engage with the screw groove of the screw shaft to prevent the workpiece from dropping rapidly and injuring the operator. In order to reduce the space occupied by the safety nut, the safety nut is made of a high-strength material (for example, metal material) so that sufficient strength can be obtained even if the thickness of the safety nut is reduced. Can be provided. In addition, in order to simplify the production and reduce the cost, the safety nut can be made thinner by connecting it with a pin or split pin between the safety nut and the nut. Also, the stroke affected by the screw shaft is short, and the manufacturing and assembly costs can be reduced.

[0007] Most linear actuators receive an operating force in a specific direction, and one direction is sufficient for safe protection. However, if a portion of the linear actuator requires safety protection in both the push and pull directions, the present invention provides a method to partially secure the linear actuator when it receives tensile stress. A design with a protective effect is provided. With this design, the safety nut and the pin fixing hole on the nut are positioned perpendicular to the screw axis, and when the linear actuator is subjected to tensile stress and the nut breaks, the pin is considerably The danger of damaging the workpiece by receiving the load is eliminated. Further, in order to improve the receiving force of the pin, the diameter of the pin can be increased or the material of the pin can be changed so as to conform to design safety.

According to the present invention, the safety protection function of the linear actuator can be realized by using the safety nut. The mechanism separates the nut and the safety nut, and further connects the nut and the safety nut with a pin. . Thus, since the nut is of the conventional type, it is only necessary to increase the pin fixing holes, and the safety screw protruding from the safety nut is processed with a metal material, molded and manufactured, and then the pin is used. Be combined. Both nuts and safety nuts are easy to make. During normal operation, the rotation of the screw shaft linked to the motor is due to the holding and pulling forces generated by the nut on the output shaft. At this time, since the follower of the safety nut follows the movement of the nut, they do not rub against each other. However, if the nut is damaged (ball wear, misalignment, or the plastic nut is broken), the When the safety screw of the safety nut comes into contact with the screw groove of the screw shaft quickly, the external force is received by the safety nut and transmitted from the safety nut to the screw shaft, causing the worker or work to descend quickly. The effect of safety protection is obtained.

[0009]

[Embodiment of the invention]

 For better understanding of the features and technical contents of the present invention, please refer to the following best embodiments of the present invention. These embodiments and drawings are provided for explanation or reference only, and do not limit the present invention in any way.

FIG. 1 is a schematic view of a linear actuator according to an embodiment of the present invention. This linear actuator includes a motor 1, a transmission shaft 2, an output shaft 3, and an outer case 4. The motor 1 provides the rotational power of the linear actuator. One end of the transmission shaft 2 is connected to the output end of the motor 1, and the other end is connected to the output shaft 3. When the screw shaft actuator is driven, the motor 1 rotates to link the transmission shaft 2, and the bevel gear 21 on the transmission shaft 2 is meshed with the bevel gear 34 of the output shaft 3 to output the power of the transmission shaft 2. Transmit to axis 3. The bevel gear 34 is connected to the screw shaft 32 and drives the screw shaft 32. A bearing 35 is attached to the screw shaft 32 in order to reduce rotational resistance. A nut 33 is fastened to the extension tube 31 to limit its rotation. Further, the mutual rotation of the screw shaft 32 and the nut 33 causes the nut 33 to rotate and move, so that the extension tube 31 expands and contracts. The outer tube 41 is fitted on the outside of the extension tube 31 and guides the extension and contraction of the extension tube 31. In a normal situation, the work is raised or lowered by driving the motor 1 and rotating the output shaft 3 to extend or contract. The safety nut 36 connected to the nut 33 only moves according to the nut 33 and does not produce any action with the screw shaft 32.

FIGS. 2 to 5 are views showing details of the vicinity of the nut 33 in FIG. 1 and are for explaining the design of the safety nut 36 of the present invention, and when the nut 33 is damaged. , The operation of the safety nut 36 is shown. FIG. 2 shows a design of a safety nut that can perform a safety protection function only when the extension tube 31 receives a thrust (force for reducing the length of the linear actuator). FIG. 3 is a sectional view of FIG.

One end of the nut 33 is connected to the extension tube 31 by screw teeth, and the other end is connected to a safety nut 36 by a pin 37. Since the nut 33 and the safety nut 36 are connected by the pin 37, the two parts do not rotate with each other, but are allowed to move only in the axial direction. The linear actuator receives the thrust and when the nut 33 is damaged, the weight of the work is transmitted from the extension tube 31 to the nut 33 and pressed onto the safety nut 36. As described above, since the nut 33 does not rotate relative to the safety nut 36, the load on the nut 33 is received by the safety nut 36. Inside the safety nut 36, a safety screw 361 meshed with the screw shaft and a screw 321 of the screw shaft 32 are meshed. Then, by sliding the nut 33 against the screw shaft 32 after the damage, the work can be prevented from being rapidly lowered and damaged, or the worker from being damaged.

The above-described safety nut 36 is made of metal and has a relatively small thickness, so that sufficient strength can be provided. In addition, by designing the mechanism for fixing with the pin 37, the thickness of the safety nut 36 is reduced and the stroke of the screw shaft is occupied shortly, so that the mounting size of the linear actuator can be reduced. When the linear actuator pulls the work, if the nut 33 is broken, the weight of the work separates the nut 33 from the safety nut 36, and the work cannot be quickly performed because the safety nut 36 cannot sufficiently bear the load of the nut 33. Fall to risk of damage. However, linear actuators receive mainly thrust only, which is sufficient for most applications.

FIG. 4 shows another design of a safety nut for a rolling ball screw shaft. When the linear actuator receives thrust and the nut 33 is broken, the weight of the workpiece is transferred from the extension tube 31 to the nut 33. It will be transmitted and will hold down on the safety nut 36. The nut 33 and the safety nut 36 are connected by a pin 37 but do not rotate with respect to each other, and the load of the nut 33 is received by the safety nut 36. Inside the safety nut 36, a safety screw 361 engaged with the screw shaft and a screw 321 of the screw shaft 32 are engaged. Then, it is possible to prevent the workpiece from being rapidly lowered by sliding with the screw shaft 32 after the nut 33 is damaged and from causing injury to the operator.

On the other hand, when the linear actuator receives the tensile stress and the nut 33 is broken, the tensile stress is transferred from the extension tube 31 to the nut 33, and the nut 33 and the safety nut 36 are connected by a pin 37. Is done. A safety screw 361 that meshes with the screw shaft 32 is provided inside the safety nut 36, and meshes with the screw 321 of the screw shaft 32. Also, to prevent the safety nut 36 from sliding with the screw shaft 32 after breaking, the nut 33 keeps the workpiece from falling until the pin 37 is damaged, and does not cause any injury to the operator. Absent. This structure has the function of safety protection when used for either thrust or pulling force, but has great protection by using thrust. Even with the same structure as in FIG. 3, such a design has a strong and simple structure, and has the effect of reducing the length of the safety nut and reducing the mounting dimensions of the linear actuator. I have.

FIG. 5 shows the design of the safety nut used on the ACME screw shaft. As with the design of FIG. 2, the protection function is exerted only when the extension tube 31 receives thrust. The nut used for the ACME screw shaft has an ACME screw. This nut is made of a material such as metal and plastic. A plastic nut 39 shown in FIG. 5 is connected to the extension tube 31 by a screw on the right side, and is connected to the safety nut 36 by a pin 37 on the left side. It is connected. Since the plastic nut 39 and the safety nut 36 are connected by the pin 37, the two parts do not rotate with each other but are allowed to move only in the axial direction.

When the linear actuator receives the thrust and the plastic nut 39 is broken, the weight of the work is transmitted from the extension tube 31 to the plastic nut 39 and presses the safety nut 36. Further, since the plastic nut 39 and the safety nut 36 are connected by the pin 37 and do not rotate with each other, the load of the plastic nut 39 is received by the safety nut 36. Inside the safety nut 36 is provided a safety thread which meshes with the helical shaft 38 of the ACME screw. Further, when the plastic nut 39 is broken, the plastic nut 39 slides with the spiral shaft 38 to prevent the work from rapidly dropping and injuring the worker. The safety thread 362 has a similar thread shape to the ACME thread.

In order to facilitate the installation of the pin 37 in the embodiment, and to prevent the pin 37, the safety nut 36, and the nuts 33, 39 from being separated from each other, it is preferable to use an appropriate spring pin to have a good connection effect. .

[Brief description of the drawings]

FIG. 1 is a schematic view showing a linear actuator according to an embodiment of the present invention.

FIG. 2 is a sketch drawing of a ball screw including a safety nut.

FIG. 3 is a sectional view of FIG. 2;

FIG. 4 is a sketch of a ball screw including another form of safety nut.

FIG. 5 is a sketch of an ACME screw including a safety nut.

FIG. 6 is a schematic view of a conventional ball screw having a safety nut.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Motor 2 Transmission shaft 3 Output shaft 4 Outer case 21 Bevel gear 30 Ball 31 Extension tube 32 Helical shaft 33 Nut 34 Bevel gear 35 Bearing 36 Safety nut 37 Pin 38 Helical shaft 39 Plastic nut 41 Outer tube 321 Thread groove 331 Safety screw Thread 361 Safety thread 362 Safety thread

Claims (6)

[Utility model registration claims] 1. A screw linear actuator including a motor, a transmission shaft, an output shaft, and an outer case, wherein the motor provides rotational power to the linear actuator, and an output end of the motor is connected to one end of the transmission shaft. By connecting the output shaft of the linear actuator to the end,
Transmitting the rotational power of the motor to an output shaft via a transmission shaft, the output shaft including a screw and an extension tube, the screw having a helical shaft, a nut, a safety nut and a pin; One end is connected to the nut, the other end receives an external force, and has a helical thread groove on the surface of the helical shaft, one end of which is connected to the transmission shaft, and a pin fixing hole on the nut. Is provided, the pin fixing hole has a hollow shape, has a screw on the inner diameter to match the screw groove of the helical shaft, a pin fixing hole is provided on the safety nut, the pin fixing hole is It has a hollow shape, is connected to the nut with the pin, and a safety screw thread is provided inside the safety nut so as to mesh with a screw groove of a helical shaft. Until it breaks Linear actuator, characterized in that not subject to external force from stretching the tube. 2. The linear actuator according to claim 1, wherein said screw is a ball screw. 3. The linear actuator according to claim 1, wherein the screw is an ACME screw. 4. The linear actuator according to claim 1, wherein the pin fixing hole is parallel to a helical axis. 5. The linear actuator according to claim 2, wherein the pin fixing hole is perpendicular to a helical axis. 6. The linear actuator according to claim 1, wherein said pin is a spring pin.