JPH1158262A - Percussion tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively restrain impact at the time of returning from a no-load striking preventive state. SOLUTION: Front blowholes 31, 31... and rear blowholes drilled with the front blowholes 31, 31... slipped in the axial direction are respectively arranged at a position of an air chamber 25 on a cylinder 8, and three auxiliary holes 33a-c are drilled in order in the axial direction in front of the air chamber 25. Consequently, at the time when a slide sleeve 17 retreats from a no-load stroking preventive state, the auxiliary holes 33a, 33b, the front blowholes 31, the rear blowholes and the auxiliary hole 33c are blocked in sequence, and air spring work of the air chamber 25 stepwisely returns.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a striking tool such as an electric hammer and a hammer drill, which is provided with an idling prevention device for coping with idling under no load.

[0002]

2. Description of the Related Art As the above-mentioned idle hit prevention device, Japanese Utility Model Laid-Open No.
1 shows an electric hammer disclosed in JP-A-174887. This is, as shown in FIG.
And a striker 43 interlocked with a piston 41 via an air chamber 42, which is slidable in the axial direction in a cylinder 40 provided inside, and which is slid forward (bit 47 side) by a compression spring 44.
The slide tube 45 urged to the outside is externally fitted. According to this configuration, at the retracted position of the bit 47 for pressing the bit 47 against the ground or the like, the slide tube 45 is retracted together with the meson 46 disposed between the bit 47 and the cylinder 4.
Air hole 4 that is formed in the air chamber 4 and communicates the air chamber 42 with the outside air.
8 is closed to cause the air chamber 42 to function as an air spring. On the other hand, when the bit 47 is not pressed against the ground or when the bit 47 is not mounted, the slide tube 45 moves forward together with the meson 46 to open the air hole 48 and loses the action of the air spring, thereby causing the piston 41 to lose its function. And striker 4
3 is interlocked and the idle hit prevention state is maintained.

[0003]

When the above-described idle hit prevention device operates, the striker 43 together with the bit 47 and the meson 46 are operated.
Is also located in front of the cylinder 40, but at the time of return from the idling prevention state, the bit 47 is pressed against the ground or the like, so that the bit 47 and the meson 46 are retracted, the slide tube 45 is retracted, and the air hole is formed. 48 is closed. Accordingly, the striker 43 is also pushed rearward by the retreating intermediate element 46, and interlocks with the piston 41 by the return of the air spring due to the closing of the air hole 48.
The impact spring 43, which starts interlocking with the piston 41, is suddenly retracted rearward by the air spring of the air chamber 42 which is suddenly closed, so that the impact (reaction) due to the impact at the start of the impact is large, and the impact causes an impact. There has been a problem that the workability and operability of the impact tool at the start are deteriorated.

[0004] Therefore, the invention according to claim 1 aims at preventing idle hit using such a slide tube.
It is an object of the present invention to provide a striking tool that effectively suppresses an impact at the time of starting striking to return from an idling prevention state and does not impair workability or operability.

[0005]

According to a first aspect of the present invention, the air hole is formed continuously or intermittently at a desired length in the axial direction of the cylinder. The air hole is gradually closed when the slide tube retreats from the time of the idling prevention. The invention according to claim 2 is
In addition to the object of the present invention, in order to more effectively buffer at the time of starting a blow obtained by the air hole, the opening / closing state is changed by forward and backward movement of the striker ahead of the air hole in the cylinder. An auxiliary hole for communicating the air chamber with the outside air is provided at least for a predetermined period from the time when the slide tube is completely retracted by the slide tube when the air tube is retracted from the time of the idling prevention.

[0006]

FIG. 1 is a longitudinal sectional view of an electric hammer 1, and FIG. 2 is an enlarged sectional view of a cylinder 8 portion. A motor shaft 2 of a motor (not shown) arranged behind the hammer drill 1 rotates a crank shaft 4 which is provided in a crank housing 3 and is supported in a direction orthogonal to the axial direction of the hammer drill 1. An eccentric pin 5 protruding from the crankshaft 4 is connected to a piston 7 in a cylinder 8 via a connecting rod 6. Here, the rotation of the motor shaft 2 is converted into a reciprocating motion of the piston 7. . Also, cylinder 8
Is a barrel 1 connected to the front of the crank housing 3.
2, a front flange 9 is gripped and fixed to a barrel 12. A tool holder 13 having a large-diameter portion 14, a middle-diameter portion 15, and a small-diameter portion 16 formed in accordance with the difference in the inner diameter is coaxially disposed in front of the flange portion 9, and the large-diameter portion 14 is connected to the flange portion 9. ing. Are accommodated in the small-diameter portion 16 of the tool holder 13 in the circumferential direction, and these balls 37 project into the small-diameter portion 16 by a lock sleeve 38 urged forward. Thus, the bit 36 interferes with the front and rear ends of the constricted portion 39 of the bit 36, and the bit 36 is prevented from coming off and the front and rear strokes are restricted. Further, a slide sleeve 1 as a slide tube is provided on a cylinder body 10 of the cylinder 8.
7 is externally slidably fitted back and forth. At the front end of the slide sleeve 17, as shown in FIG. 3, four inserts 18, 18,... Project forward, respectively.
Four slits 1 in the circumferential direction formed at the connection part with
Slide sleeve 1
The rotation of 7 is regulated.

On the other hand, a receiving ring 19 is fixed to the rear of the cylinder body 10 and a compression spring 20 is disposed between the cylinder ring 10 and the rear end of the slide sleeve 17 to urge the slide sleeve 17 forward. I have. A ring-shaped receiving member 21, an O-ring 22, and a guide sleeve 23, which are disposed between a striker 26 and a middle element 29, which will be described later, are provided in the large-diameter portion 14 of the tool holder 13 in front of the slide sleeve 17. Each of the slide sleeves 17 is provided so as to be movable back and forth.
The stoppers 2 are provided so that the gaps 8, 18,... Have a space that can enter between the inner periphery of the flange portion 9 and the inner periphery of the large diameter portion 14.
4 are provided around. Therefore, the slide sleeve 17 urged forward projects in a normal state to a position where the insertion pieces 18, 18... Abut against the stopper 24 of the guide sleeve 23. A striker 26 is accommodated in the cylinder 8 in front of the piston 7 via an air chamber 25 so as to be movable back and forth, and forms a second air chamber 27 in front of the piston 7 with the guide sleeve 23. . The striker 26 has a forwardly projecting distal end shaft 26a which can be freely inserted into the guide sleeve 23, and an O-ring 28 which can grip the loosely inserted distal end shaft 26a on the inner periphery of the guide sleeve 23. Is provided. On the other hand, in the middle diameter portion 15 of the tool holder 13,
The meson 29 is also accommodated so as to be able to move back and forth, and a rear end shaft 29a that can be loosely inserted into the receiving member 21 is provided at the rear.

Further, at the position of the air chamber 25 in the cylinder 8, there are provided air replenishing holes 30, 30, and three front air holes 31, 31,...
As shown in FIGS.
··· and the rear air holes 32, 32 ··· which are equally spaced by three so as to be positioned between the front air holes 31, 31 in the circumferential direction, while being shifted in the axial direction by H. Have been. Similarly, three auxiliary holes 33 are provided in front of the air chamber 25.
a, 33b, 33c are bored side by side in the axial direction, while the second air chamber 27 also has four ventilation holes 34, 34,.
Are drilled. First, the air supply hole 3 on the air chamber 25 side
0, 30 is to supplement the air loss of the air chamber 25,
The front air hole 31 and the rear air hole 32 are
At the retracted position in FIGS. 1 and 2 that abut against the flange portion 9, and is closed by the slide sleeve 17 that is simultaneously retracted. Next, the auxiliary holes 33a to 33c always hold the striker 2 during normal striking operation.
6 forward of the rear end 26b (however, the position of the rear end 26b of the striker 26 at the foremost position during the normal striking operation is
(Substantially coincides with the position of the rear auxiliary hole 33c).
It is not communicated with the air chamber 25, and communicates with the air chamber 25 by the striking element 26 that advances (by passing the rear end 26 b of the striking element 26 through the auxiliary holes 33 a to 33 c) at the time of idle hitting to be described later. And, the ventilation hole 34, at the time of the normal striking operation,
Insertion pieces 18 of the slide sleeve 17 at the retracted position
Between them (shown in FIG. 3) to allow the second air chamber 27 to communicate with the outside air. At the time of idling, the second air chamber 27 is closed by the advancing slide sleeve 17 and seals the second air chamber 27. . Reference numeral 35 denotes a moving hole formed from the rear of the slide sleeve 17, and the moving hole 35 is located at a position where all three auxiliary holes 33a to 33c communicate with the outside air at the time of idle hitting. In operation, the last auxiliary hole 33c
Only at a position exposing only the outside of the cylinder 8.

The electric hammer 1 configured as described above is
During a normal operation, the bit 36 is inserted into the small diameter portion 16 of the tool holder 13 and the tip of the bit 36 is pressed against the ground or the like. As a result, the meson 29 is pushed, and the meson 2
9 is a receiving member 21, an O-ring 22, a guide sleeve 2.
3, and slide sleeve 17 into compression spring 20
(FIG. 2). At this time the front air hole 3
1. Since the rear air holes 32 are all closed by the slide sleeve 17, when the piston 7 moves forward and backward, the air chamber 25 acts as an air spring, causing the striking element 26 to interlock in the full load state, and The rear end shaft 29a is hit by 29 to transmit a hitting action to the bit 36. Here, the rear end 26b of the striker 26 at the forefront position is located on the rearmost auxiliary hole 33c, but since the striker 26 that has hit the meson 29 rebounds and the rear end 26b immediately closes the auxiliary hole 33c, There is no problem in interlocking with the piston 7. The second air chamber 27 is provided with the ventilation hole 34 and the insertion piece 1 of the slide sleeve 17.
Since the air is communicated with the outside air between 8, 18, there is no rebound of air here, and no loss of impact force occurs.

Next, when the bit 36 is not pressed against the ground or the like, as shown in FIG. 2, or when the bit 36 is not inserted, the intermediate member 29 moves the tool holder 13 as the striker 26 advances. Forward until it comes into contact with the small-diameter portion 16. Due to the advance of the meson 29, the receiving member 2
1, the O-ring 22, the guide sleeve 23, and the slide sleeve 17 also advance to the positions shown in FIG. At this time, the striker 26 that moves forward is
Each of which passes through the auxiliary holes 33a to 33c and communicates with the air chamber 25,
The tip shaft 26a is inserted into the guide sleeve 23 and is held by the O-ring 28 as it is. Next, as the slide sleeve 17 advances, the rear air holes 32, 32,.
Release them in the order of 1. Therefore, the piston 7
, The air spring does not operate and the striker 26 does not move, and subsequent idle hit is prevented. At this time, in the second air chamber 27, the cylinder body 10 closes the ventilation holes 34, 34,.
In order to cut off the communication with the outside, the air in the second air chamber 27 sealed here weakens the momentum of the striking element 26 that advances, and at the same time the striking element 26 that has been fitted into the O-ring 28 moves toward the piston 7. Return (bounce) is effectively prevented by negative pressure.

When the bit 36 inserted into the tool holder 13 is pressed against the ground or the like when returning from the idling prevention state, the intermediate member 29 is pushed in as described above, and the intermediate member 29 is attached to the receiving member 21 and the O-ring. 22, the guide sleeve 23 and the slide sleeve 17 are retracted.
Then, the retreating slide sleeve 17 closes the auxiliary holes 33a, 33b and the front air holes 31, 31,... In that order, and the tip shaft 26a of the striker 26 is pressed rearward by the rear end shaft 29a of the intermediate member 29. To escape from the O-ring 28. However, as shown in FIG.
Are not closed yet, and the rear end 26b of the striker 26 has not reached the rearmost auxiliary hole 33c.
The air chamber 25 has rear air holes 32, 32,.
5. It communicates with the outside air via the auxiliary hole 33c. Even in this state, the striking element 26 is pulled backward by the reciprocating piston 7, but the stroke of the reciprocating movement of the striking element 26 is small because the air spring action is small. Subsequently, when the slide sleeve 17 is retracted until the rear air holes 32, 32,... Are closed, the air chamber 25 is further hermetically sealed, and the striker 26
The reciprocating stroke becomes longer, but the rear auxiliary hole 3
Since 3c is not yet closed by its position setting, it does not reach the full load state. Finally, when the rear end 26b of the striker 26 which is pushed in and retreated while reciprocating returns to the position of the rearmost auxiliary hole 33c in FIG.
Is restored, and the striker 26 interlocks with the piston 7 in a normal stroke.

As described above, according to the present embodiment, at the time of the start of a blow returning from the idling prevention state, the air chamber 2
5 are mainly the front air holes 31, 31.
By closing in three steps in the order of 2... The auxiliary hole 33c and gradually shifting to the closed state, it is not possible to switch to the full load hitting state at once. Therefore, the impact element 26 does not suddenly retract, the impact due to the impact at the start of the impact is effectively suppressed, and a soft start can be realized. Therefore, workability and operability of the impact tool are improved. Also, here, since the plurality of auxiliary holes 33a to 33c are arranged so as to be shifted in the axial direction, the auxiliary holes 33a
a, 33b are sequentially closed, and the front air hole 31 is closed.
The soft start at the time of transition from the idle hit by the rear air hole 32 and the auxiliary hole 33c to the normal hit can be effectively assisted when the slide sleeve 17 starts to retreat.

The number of front air holes 31 and rear air holes 32,
The axial interval is not limited to the above embodiment,
It can be changed as appropriate, and three or more rows may be provided instead of two rows before and after, or the opening area may be gradually changed. Others
If it is a form that can gradually return the sealing of the air chamber 25,
Instead of the air holes separately arranged before and after in the axial direction, a long hole may be formed in the axial direction, and the air spring function may be continuously returned by the long hole. Further, in the above-described embodiment, the air spring action is mainly restored in three stages by the front air hole 31, the rear air hole 32, and the auxiliary hole 33c.
Ｃc can be eliminated and a soft start can be obtained in two stages only by the front and rear air holes 31 and 32. Further, in the above embodiment, the present invention is applied to the electric hammer using the meson 29. However, the present invention can also be applied to a type in which the hammer directly hits the rear end of the bit without using the meson.
Of course, the present invention is not limited to the electric hammer, and may be applied to a hitting tool such as a hammer drill.

[0014]

According to the first aspect of the present invention, the air hole is formed continuously or intermittently at a desired length in the axial direction of the cylinder, so that the slide tube prevents the idle hit. By gradually closing the air hole when retreating from time, the impact due to the impact at the start of the impact is effectively suppressed, and a soft start can be realized. Therefore,
Workability and operability of the impact tool are improved. Claim 2
According to the invention described in (1), in addition to the effect of claim 1, by providing the auxiliary hole in the cylinder, the recovery action of the air spring by the air hole is further performed stepwise,
Buffering at the start of the impact can be more effectively performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an electric hammer during a normal striking operation.

FIG. 2 is an enlarged sectional view of a cylinder portion of FIG.

FIG. 3 is an explanatory view of the cylinder as viewed from the front.

FIG. 4 is an enlarged sectional view of a cylinder portion when idling is prevented.

FIG. 5 is an enlarged sectional view of a cylinder part in which a slide sleeve closes only a front air hole.

FIG. 6 is an enlarged sectional view taken along line AA.

FIG. 7 is an enlarged sectional view taken along line BB.

FIG. 8 is an explanatory view of a conventional hitting prevention device for a hitting tool.

[Explanation of symbols]

1. Electric hammer, 7 Piston, 8 Cylinder, 10 Cylinder body, 13 Tool holder, 1
7. Slide sleeve, 20 Compression spring, 2
5 air chamber, 26 air striker, 27 air chamber,
29 ... meson, 31 ... front air hole, 32 ... rear air hole, 33a-c ... auxiliary hole, 34 ... vent hole, 36 ...
bit.

Claims (2)

[Claims] 1. A reciprocating motion of a piston in a cylinder is interlocked with a striking element via an air chamber so that a striking operation can be transmitted to a bit mounted in front of the striking element. The slide tube, which is movable and urged forward, is fitted over the slide tube, and the slide tube retreats at the time of transmitting the striking operation to close an air hole provided at the position of the air chamber of the cylinder. A striking tool that moves forward when idling is prevented to open the air hole, wherein the air hole is formed continuously or intermittently at a desired length in the axial direction of the cylinder, Wherein the air hole is gradually closed when retracting from the time of the idling prevention. 2. An opening / closing state is changed by forward and backward movement of the striker ahead of the air hole in the cylinder,
2. The impact tool according to claim 1, further comprising: an auxiliary hole for communicating the air chamber with the outside air at least for a predetermined period from a time when the slide pipe is completely closed by the slide pipe when retracted from the time of the idling prevention. 3.