JPS6327153B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a safety device for pneumatic tools, which stops the air motor when the rotation speed reaches the stop valve setting even if the governor device malfunctions or malfunctions. This prevents the pneumatic tool from rotating excessively beyond the set rotational speed, thereby preventing damage to the grinding wheel attached to the main shaft due to excessive rotation.

Conventionally, in pneumatic tools, a safe maximum rotational speed is determined depending on the model, and safety is ensured by a governor device. However, the governor device may not operate safely due to moisture or particulate dust mixed into the high-pressure air supplied to the tool, or due to other reasons. For this reason, pneumatic tools may exceed the safe maximum rotational speed for various reasons, which is dangerous. In particular, in the case of an air grinder, if the rotation speed exceeds the set value, there is a risk that the grinding wheel will be sheared by the strong centrifugal force and be scattered all around.

Therefore, in the unlikely event that the governor device malfunctions and reaches the maximum allowable rotation speed (hereinafter simply referred to as the set rotation speed) exceeding the safe rotation speed, the air passage is shut off and the air motor is stopped. Attempts have been made to provide a device for this purpose, but blocking the air passage against the flow of high-pressure supply air has problems such as considerable air pressure resistance, making the device large and expensive. .

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a novel safety device for a pneumatic tool, which operates a stop valve using the air pressure and spring pressure of the supplied pressure air itself to ensure that the air passage is shut off. . Hereinafter, the present invention will be explained based on illustrated embodiments.

In the figure, 1 is the main body of the pneumatic tool, and the high pressure air supplied to the slot is introduced into the governor chamber 5 through the air introduction passage 2 and air hole 3 formed in the main body by opening the valve V. Air is supplied from the governor chamber 5 to the air motor 6. Inside this governor shaft chamber 5,
One end of a motor shaft 7 of the air motor 6 is protruded, and a governor device A is provided at this shaft end. The governor device A includes a governor frame 11 formed by a governor shaft 10 whose one end is screwed onto the axis of the motor shaft 7 and the motor shaft 7.
is clamped, a governor pendulum 12 is eccentrically supported on the governor frame 11 by a support shaft 13, and a governor valve 14, which is fitted into the governor shaft 10, is provided opposite to the pawl 12a of the governor pendulum 12. The governor valve 14 is fitted into the axial center of the governor shaft 10, and is inserted into the inner hole 7a of the motor shaft 7 by the main spring 15.
The governor valve 14 is engaged with the pilot shaft 16, which is biased in the direction, via a pin 17, and is constantly pressed against the pawl 12a of the governor pendulum 12 by the main spring 15.

As a result, as the motor shaft 7 rotates, the governor pendulum 12 is swung around the support shaft 13 by centrifugal force, and the claw 12a moves the governor valve 14 into the air between the air hole 3 and the governor chamber 5. The air is pushed toward the passageway 4 side against the main spring 15 to throttle the supplied air and control the rotation of the air motor 6.

B is a safety device, and the governor valve 14
The stop valve 20 is fitted into the stop valve 20, a spring 21 urges the stop valve 20 toward the air hole 3, and a locking means 22 locks the stop valve 20 in the lowered position against the spring 21. In the stop valve 20, a head 20a facing a valve seat 23 attached to the air hole 3 is squeezed inward to form a spring seat 20b on the inner surface, and the inner diameter is larger than the air hole 3. ing.

The locking means 22 has a guide hole 25 bored in the radial direction at one or more places in the governor frame 11, and a ball guide 26 that slides while maintaining airtightness is fitted into the guide hole 25. The ball guide 26 is equipped with a ball 28 that is engaged with an engagement hole 27 drilled in the stop valve 20, and is biased toward the stop valve 20 by a pressure spring 29, so that the stop valve 20 is not normally held. It is placed in the lowered position (FIG. 2) against the force of the spring 21, and is engaged and held by the locking means 22. Note that the pressure spring 29 is pressed against the ball 28 during normal rotation.
is engaged and held in the engagement hole 27 of the stop valve 20, but when the air motor 6 reaches the set rotation speed that exceeds the safe rotation speed, the ball 28 and the ball guide 26 resist the pressing spring 29 due to centrifugal force. The strength of the pressure spring 29 is set so that the pressure spring 29 is moved and disengaged from the stop valve 20. In the figure, 30 is a seat for fixing the pressure spring 29.

When the slot valve V is operated to supply high-pressure air from the air introduction path 2 through the air passage 4 to the air motor 6, the motor 6 rotates. As a result, the governor device A and the safety device B rotate together with the motor shaft 7, and the governor pendulum 12 swings around the support shaft 13 due to its centrifugal force, and the pendulum claw 12a pushes the governor valve 14 upward. (2nd
figure).

This is because the amount of swing of the governor pendulum 12 differs depending on the rotation speed of the shaft 7, and therefore the amount of upward sliding of the governor valve 14 also differs, which adjusts the size of the gap in the air passage 4 and controls the air opening. 3 to governor room 5
The rotational speed of the air motor 6 is controlled by controlling the amount of air supplied to the air motor 6, so that the air motor 6 rotates at a preset safe maximum rotational speed or lower. At this time, the ball 28 is fitted into the engagement hole 27 of the stop valve 20. However, if the governor device is damaged or malfunctions due to some other reason, the air supply amount is not controlled by the governor device, so the air motor 6 will rotate at the safe maximum rotation speed or higher, and the air motor 6 will rotate at the safe maximum rotation speed or higher. When the set speed exceeds the number of revolutions, the ball 28
The ball guide 26 overcomes the pressing force of the pressing spring 29 due to the centrifugal force and moves toward the outer periphery, and is disengaged from the engagement hole 27 of the stop valve 20. As a result, the stop valve 20 is moved toward the valve seat 23 by the spring 21. will be moved to At the same time, pressurized air from the air hole 3 is introduced into the inner hole of the stop valve 20, and the pressurized air acts on the spring seat 20b on the inner surface of the head of the stop valve 20.
is pressed toward the valve seat 23 by the pressure difference between the inside and outside and the spring 21, and the supply of air to the air motor 6 is therefore cut off (FIG. 3).

In this case, by forming the outer periphery of the head 20a of the stop valve 20 into an inclined surface 20c as shown in the figure, a pressure difference is created between the front and back sides of the head 20a, which is more effective in maintaining airtightness.

Furthermore, when the air motor 6 is instantly stopped from high-speed rotation by the operation of the stop valve 20, the grinding wheel D, which is attached to the lower end of the motor shaft, will continue to rotate due to rotational inertia. There is a risk that the flange E will loosen and the grinding wheel D will come off the shaft 7 along with the flange E, causing a danger. Therefore, a small hole is made in the stop valve, and a small amount of air is supplied to the air motor, causing the air motor 6 to slow down. The rotation may be continued with .

As described above, according to the present invention, the stop valve that is pressed toward the air hole by the spring has a diameter larger than that of the air hole, and is always locked by the locking means apart from the air hole against the spring, so that the stop valve is pressed toward the air hole by the spring. When the rotation speed exceeds the safe maximum speed due to malfunction of the governor device, the locking means is disengaged from the stop valve by centrifugal force, thereby surrounding the stop valve and blocking the air passage. Pressurized air is introduced into the stop valve, and the stop valve is biased in the direction of shutting off the air passage by this air pressure, so shutting off is done quickly and reliably, and even if the operation of the governor device is uncertain, the air passage can be shut off. It has advantages such as maintaining tool safety and simple configuration.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the state when stopped, that is, before air is supplied by operating the lever, Figure 2 is a sectional view of the main parts during normal rotation, and Figure 3 is a cross-section of the main parts when the safety device is activated. It is a diagram. 1... Air tool body, 3... Air hole, 4... Air passage, 6... Air motor, 7... Motor shaft, 10... Governor shaft, 12... Governor pendulum, 14... Governor valve,
20... Stop valve, 21... Spring, 22... Locking means, A... Governor device, B... Safety device.

Claims (1)

[Claims] 1. A governor shaft is provided protruding from the motor shaft, and the governor shaft is equipped with a governor device mainly consisting of a governor pendulum and a governor valve that is moved to the air hole side and narrows the air passage by swinging due to the centrifugal force of the pendulum. In the pneumatic tool, a cylindrical stop valve is provided on the outer periphery of the governor valve, which is always urged toward the air hole by a spring, and has a diameter larger than that of the air hole, and the stop valve is configured to resist the spring pressure by a locking means. The stop valve is locked to the air hole at a predetermined distance, and when the motor shaft exceeds the rotation speed set by the governor valve, the stop valve disengages from the locking means and surrounds the air hole to supply pressurized air. A safety device for a pneumatic tool, characterized in that air is guided into a stop valve and the air passage is blocked by spring pressure.