JPS5833067B2 - impact tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry striking prevention device for preventing the movement of a striking element during idle rotation in a structure in which the striking element is operated via an air spring, such as in an electric hammer.

In the conventional case, an air bleed hole is provided in the cylinder to prevent dry firing.

However, when idling, the striker hits the shaft sleeve with the first hit, and when working upward, the striker lowers due to its own weight, so the striker returns to the striking state.

This causes large vibrations in the main body, and the striker hits each part, causing damage.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art by utilizing an air cushion, thereby improving operability and service life.

The present invention focuses on the configuration of an air spring between the cylinder and the striker, and uses the compressed air spring to consume the energy of the first advance of the striker during idling, and when the forward energy decreases, the compressed air is This prevents impact from being transmitted to each component.

In addition, in the case of upward work, the striker tends to descend from the above state, so it becomes negative and positive, thereby preventing the striker from descending and preventing the striker from returning to the striking state.

The present invention will be explained below with reference to illustrated embodiments.

In the figure, 1 is an electric motor, 2 is a first gear extending to this rotor, 3 is a second gear that reduces the rotation speed of the rotor 2, 4 is a crankshaft integrally connected to this gear, and 5 is an eccentric pin attached to an eccentric position of this crankshaft, to which one end of the connecting rod 6 is pivotally attached.

7 is a cylinder with a ball bearing 9 in the cylinder case 8
It is rotatably supported by a needle bearing 24 via a gear 10.

Reference numeral 11 denotes a slide shaft whose back and forth movement is regulated by a sleeve 12 coupled to the cylinder 7I, a hole 14 in the sleeve, and a ball 13 fitted in a long groove 15 provided in the slide shaft 11.

A holding portion 16 is fixed to the tip of the slide shaft 11 to insert and hold the tool 17 therein.

Reference numeral 18 denotes a striker slidably fitted into the cylinder, reference numeral 19 indicates a groove provided in the striker 18, and reference numeral 20 indicates a groove 19.
A vent hole 21 connecting the tool-side end surface of the striking element 18 is a piston fitted in the cylinder 7 so as to be freely movable, and is pivotally connected to the other end of the connecting rod 6 by a piston pin 211.

22 is an exhaust hole provided in the cylinder 7, 23 is a similar exhaust hole, 25 is a transmission air chamber constituted by the cylinder 7 and the striker 18, and 26 is an exhaust hole formed by the cylinder 7, the sleeve 12, the slide shaft 11, and the striker 18. It is a structured air chamber.

The positional relationship between the air chamber 26 and the ventilation hole 23 is as follows.

That is, as shown in FIG. 1, when the tool 17 is inserted to drill a hole in a workpiece, the exhaust hole 23 is in a position facing the air chamber 26, and the air chamber 26 is located in the cylinder. In ventilation with the outside.

Further, when the striker 18 strikes the slide shaft 11 and approaches the sleeve 12 as shown in FIG. 2, the striker 18 is located outside the air chamber 26 and seals the air chamber 17.

Furthermore, as shown in FIG. 3, the striker 18 moves forward and the sleeve 12
When it reaches just before, the compressed air in the air chamber 26 is discharged through the exhaust hole 23 facing the ventilation hole 20 and groove 19 of the striker 18.

The configuration is as described above, so when drilling a hole, when the piston 21 moves in the direction of the striker 18 as shown in Figure 1 (hereinafter this movement will be referred to as forward movement and the opposite as backward movement), the air in chamber 25 will be compressed. This creates a positive pressure, which causes the striking element 1 to
8 and strike the rear end of the slide shaft 11.

Next, when the eccentric pin 5 rotates about half a turn from the state shown in FIG. 1 and the piston 21 retreats, the striking element 18 retreats due to the repulsive force at the time of striking and the negative pressure in the air chamber 25.

During the above operation, the air chamber 26 is in communication with the outside air, and there is no problem with the striking operation.

By repeatedly and continuously performing this type of striking action,
The concrete or the like pressed against the tip of the tool 17 is crushed.

Immediately after crushing, the resistance at the tip of the tool 17 disappears, the slide shaft 11 is struck out by the striker 18 as shown in FIG. 2, and the striker 18 itself approaches the sleeve 12.

At this time, the air chamber 26 is cut off from ventilation with the outside, and the air in the air chamber 26 is compressed when the striker 18 moves forward, so it functions as an air spring and absorbs the striking force of the striker 18. Furthermore, just before contacting the sleeve 12, the compressed air is discharged and comes into contact with the sleeve 12.

Even if the groove 1 of the striker 18 is idly rotated upward in the state shown in Fig. 3,
At the position where the air chamber 9 and the exhaust hole 23 are no longer opposed to each other, the air chamber 26 becomes a negative pressure, and the striker 18 does not move back.

If it is desired to restore the striking action, this can be done by pressing the tip of the tool 17 against the milled material.

The groove 19 of the striking element 18 may be a recess or a hole instead of a groove.

As described above, according to the present invention 1, the air chamber 26 formed between the cylinder 7 and the striker 18 is sealed only when the striker 18 is not in the normal striking position, and the sleeve The exhaust hole 23 and the ventilation hole 2 of the striking element 18 are arranged so that the air in the air chamber 26 is exhausted just before the striking element 12 and the striking element 18 come into contact with each other.
0. Since the groove 19 is provided, a more effective buffering effect can be obtained than in the conventional case, and the time of the striking element 18 can be reliably maintained during idling.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view showing an embodiment of the entire village prevention device for an electric hammer drill according to the present invention; FIG. 2 is a partial longitudinal sectional side view showing the state of the device just before the tool is released from the workpiece; FIG. 3 is a partial longitudinal sectional side view of the engine in a stopped state. FIG. 4 is a partially vertical side view of a conventional electric hammer drill. 7...Cylinder, 11...Slide shaft, 12...Sleeve, 18...
Striker, 20... Ventilation hole, 22, 23...
...Exhaust hole, 26...Air chamber.

Claims (1)

[Claims] 1. A device comprising a sleeve into which a slide shaft is inserted and held, a cylinder section housing a striking element for striking the slide shaft, and a drive device for driving the striking element, in which the striking hole corresponds to the exhaust hole of the cylinder. When the striker approaches the sleeve within a predetermined range, a sealed air chamber is formed, and a vent hole for discharging the compressed air from the air chamber immediately before contacting the sleeve is bored through the side wall from the bottom of the tip of the striker. A striking tool characterized by the following features: