JP2933155B2 - Safety device for linear actuator with screw shaft - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a safety device for preventing a linear operating rod of a vertically moving linear operating machine from falling suddenly by a screw shaft.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional linear actuator using a screw shaft has a nut member 2 screwed to a screw shaft 1 driven by a motor, and the nut member 2 is prevented from rotating. A linear moving driven body is connected to the tip of the operating rod 5, and the nut member 2 is excellent in lubricity because the nut member 2 smoothly performs screwing with the screw shaft 1 made of steel. A plastic material having good sliding properties is often used.

[0003]

In the above-mentioned linear actuator in the prior art, since the operating load for linearly operating the driven member is applied to the thread of the nut member, wear due to poor lubrication of the nut member and severe use. Breakage accidents and the like are likely to occur due to breakage or the like under conditions, and particularly when the load applied when the driven body is moved up is excessively large and the nut member is damaged, a fall accident of the linear operating rod occurs.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a linear actuator having a linear operating rod provided with a nut member screwed around a steel driving rotary screw shaft and being prevented from rotating. A steel linear operation rod drop prevention nut loosely screwed to the drive rotary screw shaft is rotationally adjusted so that both threads are continuous and press-fitted, and the steel linear operation rod drop prevention nut is the nut member. By providing the retaining ring so as not to separate more, the above-described problem of the related art is solved.

[0005]

The thrust load of the driven body is applied to the threaded surface of the nut member, and the thrust load is not applied to the threaded surface of the linear actuation rod drop prevention nut loosely engaged with the screw shaft. Therefore, even if the screwing surface of the nut member is damaged by an excessive load or the like and the linear operating rod is about to drop, the floating screwing surface of the linear operating rod drop prevention nut is lowered by the floating gap, and then the screw shaft is rotated. The linear operation rod is received by the screwing surface, and then the linear operation rod is locked to the linear operation rod fall prevention nut via a retaining ring to prevent the linear operation rod from falling.

[0006]

FIG. 1 is a sectional front view of an essential part of a linear actuator having a nut member 2 having a nut 7 for preventing the linear actuation rod from falling, according to the present invention. A nut member 2 is screwed onto the shaft 1, and a proximal end of a linear operating rod 5 is fixed to the nut member 2, and a distal end of the linear operating rod 5 has a connection fitting with a linear moving driven member (not shown). 6 are attached.

The nut member 2 has a screw shaft 1
A linearly actuated rod drop prevention nut (hereinafter simply referred to as a drop prevention nut) 7 which is loosely engaged with the nut is rotationally adjusted so as to form a thread continuous with the thread of the nut member 2, and is press-fitted with a light interference. ing.

FIG. 2 shows a nut member 2 and a fall prevention nut 7.
FIG. 4 is an enlarged cross-sectional view showing a mounting state of the nut member 2. A fall prevention nut 7 that is loosely screwed to the screw shaft 1 is press-fitted into the nut member 2 while being rotationally adjusted so that both threads are continuous. A retaining ring 8 is provided so that the fall prevention nut 7 is not separated from the nut member 2.

FIG. 3A is an enlarged explanatory view of the threaded state of the nut member 2 and the screw shaft 1, and FIG. 3B is an enlarged view of the threaded loosely engaged state of the fall prevention nut 7 and the screw shaft 1. It is an explanatory view. In (A), since both threads are screwed together without loosening, the thrust load of the linear operating rod is applied to both screwing surfaces, and in (B), both threads are screwed. The thrust load is not applied because the threads are loosely engaged by the gap δ.

However, if the thread of the nut member 2 in (A) is damaged due to an excessive load or the like, the fall prevention nut 7 in (B) drops by the gap δ and is received by the threaded surface of the screw shaft. Then, the linear operating rod 5 is locked to the fall prevention nut 7 via a retaining ring 8, and the linear operating rod 5
To prevent falling. Here, the term “fall” means a sharp drop with respect to the rise of the linear operating rod 5.

When the nut member 2 is made of a plastic material and the fall prevention nut 7 is made of a steel material, if the nut member is damaged and the fall prevention nut is received on the threaded surface of the steel screw shaft, the steel material is An abnormal sound is generated by contact between the members, abnormal wear or damage of the plastic nut member can be detected, and the linear operating rod is prevented from dropping. Further, on the screwing surface between the steel drop prevention nut and the screw shaft, frictional heat is generated by the rotation of the screw shaft, seizure occurs, and the rotation of the screw shaft becomes impossible and the linear operation stops.

[0012]

According to the present invention, a steel linear operating rod drop prevention nut which is loosely engaged with the driving rotary screw shaft on a nut member which is screwed with the driving rotary screw shaft is rotated so that both threads are continuous. Adjusted and press-fitted, and a retaining ring is provided so that the steel linear operating rod drop prevention nut does not separate from the nut member, so that even if the threaded surface of the nut member is abnormally worn or damaged, Since the fall prevention nut is received by the threaded surface of the screw shaft and the linear operation rod is locked via the retaining ring to this linear operation rod fall prevention nut, the linear operation rod is prevented from dropping and work safety is reduced. Can be secured,
Even if the material of the nut member is plastic, it is possible to prevent the linear operating rod from falling. In addition, since the fall prevention nut and the screw shaft are made of steel, when the screwing surfaces of the fall prevention nut and the screw shaft come into contact with each other due to abnormal wear or damage of the nut member, the screwing of both screwing surfaces is performed. An abnormal noise is generated due to friction, and abnormal wear or damage of the nut member can be detected.Furthermore, such friction causes seizure of the screw surface due to frictional heat, which stops the rotation of the screw shaft and causes an abnormality. The state is detected and has a remarkable effect as a safety device for the linear actuator.

[Brief description of the drawings]

FIG. 1 is a front view of a partly cross-sectional view of a linear actuator having a safety device according to the present invention.

FIG. 2 is an essential part cross-sectional view showing a screwed state of a screw shaft, a nut member, and a fall prevention nut.

FIGS. 3A and 3B are explanatory views of screwing a nut member and a fall prevention nut to a screw shaft;

FIG. 4 is an essential part cross-sectional view showing a threaded state of a conventional nut member and a screw shaft.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Nut member 3 Outer cylinder 5 Linear operating rod 7 Fall prevention nut

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F16H 25/20-25/24

Claims (1)

(57) [Claims] 1. A linear actuator having a linear actuating rod provided with a nut member screwed around and screwed around a steel drive rotary screw shaft, wherein the nut member is loosely threadedly engaged with the drive rotary screw shaft.
Steel straight-acting rod drop prevention nut has both threads continuous
It is rotated and adjusted so that it is press-fitted and mounted,
The rod fall prevention nut is not separated from the nut member.
The screw shaft is provided with a retaining ring
Linear actuator safety device.