JPH0141547Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a screw tightening device that rotates and tightens a screw while lowering the screw using air pressure.

FIG. 1 is a front view showing an example of a conventional screw tightening device. In the figure, 1 is the driver body, 2
3 is a feeding air cylinder that raises and lowers the driver body 1, 3 is a damper that adjusts the tightening speed, 4 is a moving shaft that moves in the same way as the driver, and 5 is a base to which these are attached. 6 is a mounting bracket for fixing the driver, 7 is a screw supply section, 8 is a DC motor brush, and 9 is a clutch.

According to the conventional device as described above, the driver main body 1 is rotated by electricity and lowered by the feeding air cylinder 2. At the same time, a driver bit (not shown) is rotated, and the screw supply section 7 receives the screw and tightens the screw. The damper 3 also adjusts the speed and pressing force when tightening the screws. After the screw tightening is completed, the driver body 1 is returned quickly, and the clutch 9 stops the rotation of the driver body 1 when the screw tightening is completed.
Figure 2 is a configuration diagram of a vane motor, which is a typical rotation method of an air driver, in which 50 is an inlet pipe;
1 is an outlet pipe, 52 is a vane, 53 is a cylinder, and 54 is a rod.

According to the conventional screw tightening device configured as described above, the screw rotation part and the pressing part are separated, and the pressing force is also adjusted by the pressure of the air cylinder, so it is easy to damage the threads and cause screw tightening failures. Also
DC motors require brush replacement, and air drivers have drawbacks such as exhaust noise and shock when tightening.

This idea was made to solve the above-mentioned drawbacks, and not only does it have low noise and almost no shock when tightening, it is also less likely to cause screw tightening errors, is extremely compact, and does not require brush replacement. The purpose is to obtain a screw tightening device that does not

In order to achieve the above object, this device is a screw tightening device that uses pneumatic pressure as a power source to tighten screws. a piston having a rotation prevention mechanism; a ball screw having one end of a screw shaft rotatably attached to the lower side of the piston, and a ball nut that engages with the threaded portion of the screw shaft fixed to the inner wall of the cylinder; A driver bit is attached to the other end of the screw shaft of the ball screw via a clutch mechanism; the longitudinal length of the threaded portion of the screw shaft of the ball screw is set to be longer than the tightening length of the screw to be tightened. The present invention provides a screw tightening device characterized by the following. This idea will be explained below using the drawings.

FIG. 3 is a longitudinal sectional view showing an embodiment of this invention. In the figure, 15 is a rapid-feeding cylinder (second pneumatic cylinder), 14 is a rapid-feeding piston, and 13
is a rapid-feeding piston rod, and a screw tightening cylinder (first pneumatic cylinder) 26 is provided at its tip. A seal 38 is inserted into the outer peripheral groove of the rapid-feeding piston 14, and a seal 39 is also provided on the rapid-feeding cylinder wall 40. 11 and 1
Reference numeral 2 denotes an air inlet/outlet pipe, which is an inlet/outlet of compressed air for raising and lowering the rapid-feeding piston 14. 16 is an inlet pipe for lowering the screw tightening piston 21, and 19 is an outlet pipe thereof. Also 1
8 is an inlet pipe for raising the screw tightening piston 21, and 17 is its outlet pipe. A bearing 22 is fitted into the screw tightening piston 21 and rotatably supports a screw shaft 23, which will be described later. 23 is a screw shaft, and as shown in FIG. 4, a threaded portion 23a with the same pitch as the screw to be tightened is carved in the longitudinal direction of this screw shaft 23, and the length of this threaded portion is as follows. It is set longer than the tightening length of the screw that should be tightened. Furthermore, a ball nut 24 is engaged with the threaded portion of the screw shaft 23, which is provided with a threaded portion 24a having the same pitch as that of the screw to be tightened. These screw shafts 23 and ball nuts 24 are combined to form a ball screw. A ball nut 24 is fixed to the inner wall of the screw tightening cylinder 26. 25
is a gasket, and 20 is a seal for the piston 21. 32 is a driver bit, 33 is a feeder that supplies screws, and 34 is a workpiece to be screwed. 35 is a seal for preventing air from escaping into the ball nut portion, and 36 is a seal wall for this purpose. Note that the screw tightening piston 21 is prevented from rotating due to the friction of the seal 20. Further, as shown in FIG. 5, the detection plate 28 is attached to the screw shaft 23 and also serves as a guide for the sleeve 27. Further, the spring 41 has one end fixed to the end surface of the sleeve 27 and the other end fixed to the detection plate 28, and serves to prevent the sleeve 27 from falling, escape the sleeve 27, and hold down the workpiece. 27 is a sleeve, 31 is a clutch, 30 is a light sensor for the mounting bracket 29, and 28 is a detection plate of the light sensor 30. Note that the mechanism of the clutch 31 is configured as shown in FIG. 6, for example.
Since it is not related to the essence of this invention, various conventionally known methods can be used. FIG. 6a is a front sectional view, and FIG. 6b is a side view. Numeral 46 is a pin fitted into the driver bit 32, and is adapted to engage with a groove 23a formed in the end surface of the screw shaft 23. Reference numeral 47 denotes a screw that is attached to the hole 23b of the screw shaft 23 and abuts one end of the driver bit 32. 48 is a pedestal for receiving the pin 46, and is fixed to the driver bit 32.

The operation of this device constructed as described above will be explained as follows. First, air pressure is supplied to the air inlet/outlet pipe 11 to lower the fast-forward piston 14, and the screw tightening cylinder 23 attached to the tip of the fast-forward piston rod 13 is lowered.
Next, when air pressure is supplied to the inlet pipe 16 to lower the screw tightening piston 21, since the ball nut 24 is fixed to the wall surface of the screw tightening cylinder 26, when the screw shaft 23 comes into contact with the ball nut 24, Due to the action of the ball screw that converts linear motion into rotational motion, the screw shaft 23 descends while rotating. This provides the torque to tighten the screw. Further, at the same time as the screw tightening cylinder 26 descends, the sleeve 27 suctions the screws on the feeder 33 (the suction tube is not shown). When the screw shaft 23 further descends and reaches the workpiece 34, the sleeve 27
escapes while compressing the spring 41. One screw shaft 2
3 descends while rotating and crushing the spring 47, the pin 46 of the clutch 31 moves into the groove 23a.
When engaged, rotate the driver bit 32 to tighten the screw. In this case, since the pitch of the threads provided on the screw shaft 23 and ball nut 24 is the same as the pitch of the screw to be tightened to the workpiece 34, no force is applied to crush the threads being tightened, and the threads are Since the screw rotates along the same direction and moves forward at the same pitch, the screw is tightened in accordance with the pitch of the screw. When the screw tightening is completed, the screw shaft 23 continues to rotate and tries to further tighten the screw screwed into the workpiece 34, but the rotation of the driver bit 32 is restricted by the screw screwed into the workpiece 34. Therefore, the groove 2 of the screw shaft 23
The pin 46 comes off from 3a, and only the screw shaft 23 rotates idly. On the other hand, at this time, the optical sensor 30
Detects and reacts, momentarily supplies air pressure from the inlet pipe 18 to balance the falling and rising pressures, then stops the supply of air pressure from the inlet pipes 18 and 16, and stops the shock when screw tightening is completed. Eliminate. next,
Air pressure is supplied to the air inlet/outlet pipe 12, the screw tightening cylinder 26 is raised in rapid motion, air is supplied from the inlet pipe 18, the screw shaft 23 is raised, and the screw tightening is completed.

As described above, according to this invention, the force for simultaneously rotating and advancing the screw shaft 23 is obtained by the pressure difference between the upper and lower air pressures of the screw tightening cylinder 26, so that the rotation speed can be lowered. Therefore, over-tightening of the screw (excessive torque) is prevented, and highly accurate tightening torque can be obtained, so that precise tightening can be performed.

In the above description, the inlet pipe 16 and the outlet pipe 17 and the inlet pipe 18 and the outlet pipe 19 have been explained separately, but they may be constructed integrally. Also, a flow control valve can be provided at each inlet, in which case the low rotation speed provides high precision torque.

Note that if the pitch of the ball screw does not match the pitch of the screw to be tightened, it will become a general-purpose screw tightening machine. Also, instead of using the optical sensor 30, a mechanical stopper 42a and a stopper plate 42 as shown in FIG.
b, a limit 43a, and a limit dog 43b may be used. Furthermore, as shown in FIG. 8, the seal 20 can be easily formed by combining a rotation prevention shaft 44 attached to the piston 21 and a rotation prevention plate 45 attached to the cylinder 26.

Further, in the above embodiment, the fast-forwarding cylinder 15 and the screw tightening cylinder 26 are integrally configured, and the screw tightening cylinder 26 is capable of moving in a straight line. The screw tightening device can be configured even if the fast-forwarding piston 14 and the like are omitted.

As is clear from the above explanation, according to this invention, the force that moves the screw shaft forward at the same time as it rotates is obtained by the pressure difference between the upper and lower air pressures of the screw tightening cylinder. Highly accurate tightening torque can be obtained without causing defects, allowing precise screw tightening. In addition, not only can it be configured compactly, but there is no need to replace brushes like with DC motors, and the noise, which was a drawback of air-type screwdrivers, is also reduced.

[Brief explanation of the drawing]

Fig. 1 is a front view showing an example of a conventional screw tightening device, Fig. 2 is a mechanical diagram of a vane motor, Fig. 3 is a longitudinal sectional view showing an embodiment of this invention, and Figs. 4 and 5 are 3 is a sectional view showing the main parts of the clutch, FIG. 6 is a front sectional view and side view showing an example of the clutch, FIG. 7 is a longitudinal sectional view showing another embodiment of this invention, and FIG. It is a sectional view of the main part. 14... Piston for rapid feed, 15... Cylinder for rapid feed, 21... Piston for screw tightening, 23...
...Screw shaft, 24...Ball nut, 31...Clutch, 32...Driver bit.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A screw tightening device that tightens screws using air pressure as a power source, which includes a first pneumatic cylinder and a device that prevents rotation within this pneumatic cylinder and allows only linear movement. a piston having a rotation prevention mechanism; a ball screw having one end of a screw shaft rotatably attached to the lower side of the piston, and a ball nut that engages with the threaded portion of the screw shaft fixed to the inner wall of the cylinder; A driver bit is attached to the other end of the screw shaft of the ball screw via a clutch mechanism, and the longitudinal length of the threaded portion of the screw shaft of the ball screw is set to be longer than the tightening length of the screw to be tightened. A screw tightening device characterized by: (2) The screw tightening device according to claim 1, wherein the pitch of the threaded portion of the screw shaft is the same as the pitch of the screw to be tightened.