JPH088073Y2 - Structure to prevent hitting tools from hitting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Use of the Invention] The present invention relates to an impact tool having an intermediate impactor such as a hammer and a hammer drill.

[Background of the invention]

Generally, a hammer drill having a grease-sealed structure strikes a tip tool 17 via an intermediate striker 13, as shown in FIG. The rotation transmission portion between the cylinder 9 and the intermediate striker 13 has a rotation locking structure such as a spline. The conventional rotation transmitting portion is a rotation locking portion 19 between the cylinder 9 and the intermediate striker 13.
Is slidable in the axial direction, but fitted with almost no gap. Since it is a minute gap, it is easily sealed with grease and air circulation is hindered. Also, when the intermediate striker 13 moves forward, the spline troughs on the outer circumference of the intermediate striker 13
Since the hobbing position 25 of the hob 22 is inside the cylinder 9, the air passage cannot be secured. Then, as shown in FIG. 3, when the loaded state is changed to the unloaded state, the third air chamber 20
Is expanded, a negative pressure is exerted, and a force pulling the intermediate striking element 13 in the F direction is exerted, so that the normal striking position shown in FIG. 1 is easily returned. That is, there is a drawback in that the impact is continued even under a no-load condition (idle condition), vibration and noise are increased, and the life of the tool body is shortened.

[Purpose of device]

The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art,
It is intended to prevent the hitting tool of this kind from idling and to improve the operability and the life of the tool body.

[Outline of device]

In the present invention, if the rotation locking part has a minute gap, it is easily sealed by the surface tension of the grease oil film. If the hob rise position of the spline trough on the outer circumference of the intermediate striker is located inside the cylinder when the intermediate striker moves forward, a small gap will be created between the intermediate striker and the cylinder. Since the flow path is blocked, a plurality of width across flats are arranged around the outer circumference of the intermediate striker to secure the air flow path.

[Example of device]

An embodiment of the present invention will be described with reference to FIGS. 1, 2, 3, 4, and 5. A motor (not shown) is provided in a housing 1 forming a body frame, and a crankshaft 4 is rotatably supported in a crankcase 2 fixed to the housing 1. In the cylinder case 3 fixed to the crankcase 2, bearings A7 and B14 with a gear 5 interposed.
There is a cylinder 9 which is rotatably supported by the cylinder 9. A piston 8, a striker 11, and an intermediate striker 13 are slidably fitted in the cylinder 9 from the crankshaft 4 side. There is a first air chamber 10 between the piston 8 and the striker 11, and the striker 1
1. There is a second air chamber 12 between the intermediate striker 13. The intermediate striker 13 is a spline having a large gap passage 21 on the non-contact surfaces 27, 28 side as shown in FIG. 2, and is rotationally locked to the cylinder 9. The tip tool 17 is directly inserted into the intermediate striker 13, and the intermediate striker 13 is inserted into the cylinder 9 through the washer 15.
Hit against. The front outer peripheral portion of the intermediate striker 13 is slidable in the front cover 16 fixed to the end of the cylinder case 3. Further, as shown in FIG. 4, when the intermediate striker 13 moves forward, the plurality of widths 24 provided on the outer circumference of the intermediate striker 13 connect the second air chamber 12 and the third air chamber 20. It is formed so as to secure a flow path. The state at the time of working with the impact tool will be described with reference to FIG. Tip tool
When 17 is pressed in the D direction and abutted against the work material 18, the intermediate striker 13
Also hits the washer 15 and stops at the position shown. On the other hand, when the crankshaft 4 is rotated by a motor (not shown), the piston 8 reciprocates in the cylinder 9, and the compression fluctuation of the first air chamber 10 causes the hammer 11 to reciprocate. The intermediate striker 13 is hit. Therefore, the impact is transmitted from the intermediate impactor 13 to the tip tool 17, and the tip tool 17 strikes the work material 18. Further, a gear (5) is rotated by a motor (not shown), and the rotation is transmitted to the cylinder 9 via the key 6. The rotation of the cylinder 9 is further transmitted to the intermediate striker 13 by the rotation locking portion 19 to rotate the tip tool 17. In this state, as shown in FIG. 3, when the tool body is pulled up in the F direction and the load on the tip tool 17 is removed, the tip tool 17 and the intermediate striker 13 move in the D direction, and the second air chamber 12 After the air passes through the flow passage 21 of the rotation locking portion 19, it flows along the spline portion 23 on the outer periphery of the intermediate impacting element 13, passes through the spline trough portion 22 on the outer periphery of the intermediate impacting element 13, and the width across flats 24. It flows into the air chamber 20.

In the state shown in FIG. 1, there is no third air chamber 20, and the state is expanded in the state shown in FIG. 3, but since positive pressure is generated by the air flowing in, the intermediate striker 20 is pushed out in the D direction, The intermediate striking element 13 is prevented from returning to the normal striking position shown in FIG. Then, the striker 11 also moves in the D direction and the large breathing port 26 is opened, so that there is no pressure fluctuation in the first air chamber 10, and the striker 11 does not reciprocate and stops the strike.

[Effect of device]

According to the present invention, since the return of the intermediate striker is prevented,
It is possible to prevent blank driving, and to prevent vibration, noise, and damage to the main body due to blank driving.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of a main part of a striking tool in a loaded state according to the present invention, FIG. 2 is a sectional view taken along the line CC of FIG. 1, and FIG. 3 is a striking tool in the same unloaded state. It is a sectional side view of the principal part of a tool. FIG. 4 is an enlarged side cross-sectional view of the engaging portion between the cylinder and the intermediate impactor according to the present invention, and FIG. 5 is a side view of the intermediate impactor according to the present invention. 8 is a piston, 9 is a cylinder, 10 is a first air chamber, 11 is a hitting element, 13 is an intermediate hitting element, 19 is a rotation locking portion, 21 is a flow path, 24
Is the width across flats of the outer circumference of the intermediate striker.

Claims (1)

[Scope of utility model registration request] 1. A reciprocating piston, and a cylinder rotatably supported in a main body frame and guiding the piston.
A striking element that is slidable in the cylinder and is reciprocally driven by the piston through an air chamber, and a striking element that is located at an end portion of the cylinder on the opposite side of the piston and that is in spline engagement with the inner circumference of the cylinder. In a striking tool having an intermediate striker movable in the cylinder axial direction in a different range, a large gap is provided in a spline engagement portion between the cylinder and the intermediate striker in order to secure an air flow path, and A structure for preventing idle hitting of a hitting tool, wherein a width across flats is provided on the outer circumference of the intermediate hitting element.