JPH09136273A - Hammer drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide idle hammering preventing device preventing a forward/ backward movement of a cylinder so as to improve durability. SOLUTION: A cylinder 7 rotated by the rotation transmitted from a motor and a tool holder 11 fitted around the cylinder 7 are connected together so as to be rotated integrally by means of a ball 17, while between the cylinder 7 and the tool holder 11, a slide sleeve 21 is arranged. The slide sleeve 21, which can be moved backward until its folded part, 22 is brought into contact with a cylinder 7 front end and can be moved forward until a washer 27 and a rubber 28 are brought into contact with the tool holder 11, is energized forward with a receiving ring 24 on the rear side by means of a compression spring 26. In the position corresponding to an air chamber 29 in the cylinder 7, air holes 34, 34... are bored, while vent holes 35, 35... are bored in the second air chamber 31, and the air holes 34 are closed by means of the receiving ring 24 only in the retraction position for the slide sleeve 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hammer drill equipped with an idle-driving prevention device for dealing with idle-driving operation under no load.

[0002]

2. Description of the Related Art As a hammer drill equipped with the above-mentioned blank hitting prevention device, in Japanese Patent Publication No. 4-500043, a piston which moves forward and backward and a striker which works with the piston via an air chamber are internally provided. The cylinder is rotatably supported by the rotation transmission from the motor and can be moved back and forth in the axial direction. The cylinder is urged toward the bit side to provide an air hole at the position of the air chamber. The cylinder is in the retracted position and the air hole is closed by the inner surface of the casing by the bit that is pushed in during operation, and when idle, the cylinder is in the advanced position and opens the air hole, and the air spring of the air chamber acts. A structure that eliminates

[0003]

In the above structure, the cylinder moves forward and backward to prevent idling, and also transmits rotation to the bit through the tool holder. In the front, it is necessary to provide a connecting means such as a gear that connects with the tool holder and rotates integrally with it, but since the cylinder makes sliding contact by moving back and forth, wear at the meshing part of the gear etc. is rapid and deterioration of durability is reduced. Invited.

[0004]

SUMMARY OF THE INVENTION Therefore, the present invention provides a hammer drill designed to reduce the load on the cylinder and improve its durability. The structure of the hammer drill is such that the tool holder is coaxial with the cylinder. A slide tube that is movable forward and backward in the axial direction is provided between the tool holder and the cylinder by urging the slide tube forward, while the cylinder has an air hole for ventilating the air chamber and the outside of the cylinder. The slide tube retreats to close the air hole at the time of striking operation, and the slide tube moves forward to open the air hole at the time of idle driving. Further, by forming a slit in the peripheral wall of the slide tube in the axial direction,
The connecting means may be provided through the slit. Further, the connecting means may be a ball provided so as to extend between the cylinder and the tool holder.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial vertical cross-sectional view of the hammer drill 1. Here, the left side will be described as the front and the right side will be described as the rear. A motor (not shown) arranged at the rear of the hammer drill 1 rotates a crankshaft 3 which is axially supported at the rear of the crank housing 2, but an eccentric pin 4 protruding from the crankshaft 3 has a The piston 6 is connected via the connecting rod 5, where the rotation of the motor is converted into reciprocating motion of the piston 6. A cylindrical cylinder 7 in which the piston 6 is installed is loosely inserted into a bevel gear 9 which is pivotally supported by the crank housing 2 by a needle bearing 8, and a pinion 7a provided around a rear portion of the bevel gear 9 and a bevel gear 9 are provided. The cylinder 7 can rotate integrally with the bevel gear 9 by meshing with the engagement teeth 9a on the inner circumference. On the other hand, the bevel gear 9 is meshed with the tip of a shaft 10 to which the rotation of the motor is arbitrarily switched and transmitted by switching of a transmission mechanism (not shown). Here, the rotation of the motor is transmitted from the shaft 10 to the cylinder 7 via the bevel gear 9. It can also be transmitted to. Furthermore, in the front part of the cylinder 7,
The large diameter portion 14 of the tool holder 11 which is axially supported by the ball bearing 2a in the crank housing 2 is coaxially fitted on the outside, and the cylinder 7 and the tool holder 11 are, as shown in FIGS. , The concave portion 1 on the outer circumference of the cylinder 7
5 and 15 and through holes 16 and 16 of the tool holder 11
.A plurality of balls 17, 17 that are fitted across and
Are connected so as to be integrally rotatable. This ball 1
Reference numeral 7 denotes a sleeve 1 fitted around the tool holder 11.
It is prevented from coming off by 8.

A slide sleeve 21 is interposed between the cylinder 7 and the tool holder 11 so as to be movable back and forth. The slide sleeve 21 can be retracted until the folded-back portion 22 formed at the front end contacts the front end of the cylinder 7, and forwardly, the washer 27 and the rubber 28 provided in the large-diameter portion 14 of the tool holder 11 are used as tools. Holder 1
It is possible to move forward until it comes into contact with the medium diameter portion 13 of 1.
The first half portion is provided with a plurality of slits 23, 23 ... In the axial direction so as not to interfere with the ball 17,
7 is a form that connects the cylinder 7 and the tool holder 11 through the slit 23. A receiving ring 24 is attached to the rear of the slide sleeve 21 so as to be movable back and forth, and a compression spring 26 between the receiving ring 24 and a fixed ring 25 on the outer circumference of the cylinder 7 causes the slide sleeve 21 to move forward. Energized. .. formed on the outer periphery of the cylinder 7 in the axial direction, and ridges 20, 20 formed on the inner periphery of the tool holder 11 in the axial direction. Are respectively inserted by half width, and here, the slide sleeve 21 is arranged so as to straddle the cylinder 7 and the tool holder 11. Further, in the cylinder 7, a striker 30 is arranged in front of the piston 6 via an air chamber 29 so as to be movable back and forth, and a second air chamber 31 is formed in front of the striker 30, while a medium diameter portion of the tool holder 11 is formed. An intermediate member 32 is arranged in the inner ring 13, and this intermediate member 32 also comes into contact with the small diameter portion 12 into which the bit 40 is inserted and in a rear position with which the washer 27 of the large diameter portion 14 and the rubber 28 are brought into contact. It can be moved back and forth between and. Furthermore, at the position of the air chamber 29 of the cylinder 7,
Two replenishment holes 33, 33 and six air holes 34, 34.
Are provided in the second air chamber 31, and six ventilation holes 35, 3 are provided in the second air chamber 31 at the position of the slit 23 of the slide sleeve 21.
.. are drilled (FIG. 4). The replenishment hole 33 on the side of the air chamber 29 replenishes the air loss of the air chamber 29, and the air hole 34 is at the retracted position where the folded portion 22 of the slide sleeve 21 abuts on the tip of the cylinder 7 (see FIG. 1). Only at the position), the receiving ring 24 is retracted at the same time. Similarly, in the large-diameter portion 14 of the tool holder 11, six through holes 36, 36 ... Are provided at the outer peripheral position of the vent hole 35 of the cylinder 7, respectively.
It communicates with the outside of 1. 37, 37 are rollers, 3
Reference numeral 8 denotes a chuck sleeve that is biased forward and causes the roller 37 to project in the axial direction.
The bit 40 is fitted in the locking grooves 39, 39 formed in the axial direction of the bit 40 to be inserted into the small-diameter portion 12 so that the bit 40 and the tool holder 11 can be integrally rotated.

Hammer drill 1 constructed as described above
First, in the hitting mode, the bit 40 is inserted from the tip of the tool holder 11 and the bit 40 is pressed against the work. Thereby, the meson 32 is pushed in, and the meson 32
Moves the washer 27, the rubber 28, the slide sleeve 21, and the receiving ring 24 backward against the bias of the compression spring 26. At this time, as shown in FIG. 1, the air holes 34, 34 ...
Is closed by the receiving ring 24, so that when the piston 6 moves back and forth due to the rotation of the motor, the air chamber 2
9 acts as an air spring to interlock the striker 30, and strikes the rear end of the meson 32 protruding into the second air chamber 31,
The striking action is transmitted to the bit 40. On the other hand, in the rotation + striking mode in which the shaft 10 meshing with the bevel gear 9 is rotated by switching the transmission mechanism, the cylinder 7 is rotated by the rotation of the bevel gear 9, and the tool holder 11 integrated via the ball 17 is rotated. Then, the rotation operation is applied to the bit 40. In both of these two modes, however, the second air chamber 31 includes the vent hole 35, the slit 23 of the slide sleeve 21, and the large diameter portion 14.
Since it is communicated with the outside through the through hole 36, there is no repulsion of air here and no loss of striking force occurs. The washer 27 and the rubber 28 cushion the recoil from the bit 40 at the time of striking operation and soften the rearward impact. And the bit 40 is not pressed against the work as shown in FIG.
Alternatively, during idle driving in a state where the bit 40 is not inserted, the intermediate member 32 is moved toward the small diameter portion 12 as the striking member 30 advances.
Move forward until it touches. By the forward movement of the intermediate member 32, the washer 27, the rubber 28, the slide sleeve 21
The receiving ring 24 also advances to the position shown in FIG. 5 by the urging force of the compression spring 26, but the air hole 34 that has been closed by this is opened to the atmosphere, so the action of the air spring of the air chamber 29 is lost, The interlock between the piston 6 and the striker 30 is cut off, and the striker 30 stops at the position where it abuts the rear end of the advanced intermediate member 32, so that the idle driving thereafter is prevented. Even if the slide sleeve 21 advances at this time, the slits 23 allow the ventilation holes 35 and the through holes 36 to pass through.
Since the communication with the outside of the second air chamber 31 by the is secured, the air does not repel here and the striker 30 is not pushed back to the piston 6 side.

As described above, in the hammer drill 1, the cylinder 7 is stopped only by transmitting rotation without moving back and forth, and opening / closing of the air hole 34 for preventing blank driving is performed.
Since the slide sleeve 21 is moved back and forth, the sliding contact at the meshing portion with the bevel gear 9 is eliminated and the durability is improved. Further, even if the slide sleeve 21 is adopted, since the rotation transmission between the cylinder 7 and the tool holder 11 is possible, a blank driving prevention device suitable for a hammer drill can be constructed. When the slit 23 is used as described above, the connection is rational and the rotation can be smoothly transmitted. Further, here, since the balls 17 are used for the connection, the wear is less than that of the connection by the meshing. In the above embodiment, the ball 1 is used as a connecting means for connecting the cylinder 7 and the tool holder 11.
Although the structure using 7 is described, if the strength and durability are not hindered, the balls 17 and the through holes 16 and the recesses 1 associated therewith are formed.
5 may be eliminated and rotation transmission and idling prevention may be performed only by the slide sleeve 21 interposed between the cylinder 7 and the tool holder 11, in which case the number of parts can be reduced. Other connecting means may be a structure such as a pin.

[0009]

As described above, according to the present invention, since the blanking prevention function is performed by the slide tube provided between the cylinder and the tool holder, it is not necessary to move the cylinder in the axial direction, and the tool holder is eliminated. Since only the rotation transmission to the motor is required, it is possible to suppress wear of the connecting portion with the motor side and improve the durability of the cylinder. Further, if a slit is formed in the peripheral wall of the slide tube in the axial direction and a connecting means for connecting the cylinder and the tool holder is provided through the slit, the connection between the both and the rotation transmission can be smoothly performed even if there is the slide tube. In particular, if the connecting means is a ball straddled between the two, the wear is less than that of the connection by meshing.

[Brief description of the drawings]

FIG. 1 is a partial vertical sectional view of a hammer drill.

FIG. 2 is an explanatory view showing a connecting structure of a cylinder and a tool holder.

FIG. 3 is an enlarged end view taken along line AA.

FIG. 4 is an enlarged end view taken along line BB.

FIG. 5 is an operation explanatory view at the time of idle driving.

[Explanation of symbols]

1 ... Hammer drill, 2 ... Crank housing, 6
..Pistons, 7 ..., Cylinders, 9 ... Bevel gears, 1
1 ... Tool holder, 17 ... Ball, 19 ... Projection,
20 ... Ridge, 21 ... Slide sleeve, 23 ... Slit, 24 ... Receiving ring, 29 ... Air chamber, 30 ...
.Strike element, 31 ... Second air chamber, 32 ... Meson, 34
..Air holes, 35 ... Ventilation holes, 36 ... Through holes, 40 ...
bit.

Claims (3)

[Claims] 1. A piston is provided in a cylinder that rotates by transmission of rotation from a motor, and a forward / backward movement of the piston causes an impact element to interlock through an air chamber, and strikes a bit mounted on a tool holder in front of the impact element. While transmitting the operation,
In a hammer drill in which the tool holder is integrally rotatably connected to the cylinder via a connecting means and the rotation of the cylinder can be transmitted to a bit, the tool holder is coaxially fitted to the cylinder, and the tool holder is A slide tube that is movable back and forth in the axial direction is provided between the cylinder and the cylinder by urging the slide tube forward, while an air hole that allows the air chamber and the outside of the cylinder to vent is formed in the cylinder. A hammer drill characterized in that the slide tube retreats to close the air hole, and when idle, the slide tube advances to open the air hole. 2. The hammer drill according to claim 1, wherein a slit is formed in the peripheral wall of the slide tube in the axial direction, and the connecting means is provided through the slit. 3. The ball according to claim 1, wherein the connecting means is a ball provided between the cylinder and the tool holder.
Hammer drill described in.