JPH0731976Y2 - 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 a hammering tool having an intermediate hammer 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.

As shown in FIG. 6, in the conventional rotation transmitting portion, the rotation locking portion 19 between the cylinder 9 and the intermediate impacting element 13 is slidable in the axial direction, but is fitted with almost no gap. Since it is a minute gap, it is easily sealed with grease and air circulation is hindered. Further, as shown in FIG. 5, when the intermediate striker 13 moves forward, the spline troughs on the outer periphery 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]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, prevent the hitting tool of this kind from idling, and 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, the positional relationship between the hob run-up position of the spline trough on the outer circumference of the intermediate striker and the cylinder end is devised so as to secure the air flow path.

[Example of device]

 An embodiment of the present invention will be described with reference to FIGS.

A motor (not shown) in the housing 1 forming the body frame
The crankshaft 4 is rotatably supported in the crankcase 2 fixed to the housing 1. Further, in the cylinder case 3 fixed to the crank case 2, there are a cylinder 7 rotatably supported by a shaft support 7 and a shaft support 14 via a gear 5, and the cylinder 9 is rotatably supported from the crankshaft 4 side. Piston 8, striker 11, intermediate striker 13
Are slidably fitted together. A first air chamber 10 is provided between the piston 8 and the striker 11, and a second air chamber 12 is provided between the striker 11 and the intermediate striker 13. The intermediate striker 13 is rotationally locked to the cylinder 9 by a spline having a large gap flow passage 21 on the non-contact surfaces 27, 28 side as shown in FIG. The tip tool 17 is directly inserted into the intermediate striker 13, and the intermediate striker 13 strikes the cylinder 9 via the washer 15. 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 hob cut-up position 25 of the spline trough portion 22 on the outer periphery of the intermediate striker 13 is positioned outside the tip end surface 23 of the cylinder 9. Has been formed.

The state at the time of working with the impact tool will be described with reference to FIG.
When the tip tool 17 is pushed in the D direction and abutted against the work material 18, the intermediate striker 13 also abuts the washer 15 and stops at the position shown in the figure. On the other hand, when the crankshaft 4 is rotated by the motor, the piston 8 reciprocates in the cylinder 9, and due to the fluctuation in the compression of the first air chamber 10, the striker 11 also reciprocates to move the intermediate striker 13. Hit. Therefore, the impact is transmitted from the intermediate striker 13 to the tip tool 17, and the tip tool 17
Hits. Further, the gear 5 is rotated by the motor and the rotation is transmitted to the cylinder 9 via the key 6. Cylinder 9
This rotation 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 main body is pulled up in the F direction to remove the load on the tip tool 17, the tip tool 17,
The intermediate striker 13 moves in the D direction, and the air in the second air chamber 12 passes through the flow path 21 of the rotation locking portion 19 and then flows along the spline portion 24 on the outer periphery of the intermediate striker 13 to produce the intermediate strike. Flows to the third air chamber 20 through the hob cut-up position 25 of the spline valley 22 on the outer periphery of the child 13. 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 the first air chamber
The pressure fluctuation of 10 disappears, and the striker 11 also stops the impact without reciprocating.

[Effect of device]

According to the present invention, since the return of the intermediate striking element is prevented, it is possible to prevent idle driving, and vibration and noise due to idle driving,
Also, the main body can be prevented from being damaged.

[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. FIG. 4 is a side sectional view of a main part of the tool, FIG. 4 is an enlarged side sectional view showing an embodiment of an engaging portion between a cylinder and an intermediate impactor according to the present invention, and FIG. 5 is a relationship between a conventional cylinder and an intermediate impactor. FIG. 6 is an enlarged side sectional view of the joint portion, and FIG. 6 is a sectional view taken along the line CC of FIG. 1 of a conventional striking tool. In the figure, 8 is a piston, 9 is a cylinder, 10 is a first air chamber, 11 is a striker, 13 is an intermediate striker, 19 is a rotation locking portion,
Reference numeral 21 is a flow path, 25 is a hob rising position of a spline trough on the outer periphery of the intermediate striker, and 17 is a tip tool.

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 The hitting tool idle prevention structure characterized in that the hob rising position of the valley portion of the spline engaging portion on the outer periphery of the intermediate hitting element is extended in the direction of the tip tool.