JP2000042947A - Bit coming-off preventing mechanism for power tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bit coming-off preventing mechanism for a power tool by surely preventing switching by mistake from a fixed condition to an opened condition so as to improve reliability. SOLUTION: A bit coming-off preventing mechanism is provided with a roller 2, arranged capable of protruding/sinking in a roller hole 1a formed in a cylindrical drill holder 1 to penetrate in a radial direction thereof, to engage with a recessed part of a bit 11 inserted in the drill holder 1 in a condition protruded to an internal peripheral surface side of the drill holder 1, to hold the bit 11 incapable of rotating relating to the drill holder 1, and a sleeve S assembled outside the drill holder 1 coaxial thereto and rotatable in a peripheral direction to protrude/sink the roller 2 in accordance with its rotational position in the roller hole 1a. The sleeve S is arranged slidably in an axial direction relating to the drill holder 1. A lock means L impeding rotation in the peripheral direction of the sleeve S relating to the drill holder 1, in a condition that the sleeve S is slid in one side, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mechanism for preventing a bit from being removed from a power tool such as a hammer drill.

[0002]

2. Description of the Related Art In general, an electric motor is housed in a housing of an electric tool, and the power of a motor shaft of the motor is transmitted to a drill holder via a power transmission mechanism. This type of power tool is provided with a bit removal prevention mechanism for detachably attaching a bit to the drill holder.

Referring to FIG. 8, a power tool as a hammer drill provided with a conventional bit removal prevention mechanism B will be described below. This power tool is used for hanging and drilling operations. A cylinder (not shown) is arranged in the housing 9 so as to be rotatable in the circumferential direction. Inside the rear end side of the cylinder, a piston (not shown) and a striker (not shown) are respectively slidably disposed so as to form an air chamber therebetween. On the other hand, a cylindrical drill holder 1 is integrally formed at the tip of the cylinder. A bit (not shown) is attached to the drill holder 1 via a bit removal prevention mechanism B so as to be non-rotatable in the circumferential direction and slidable in the axial direction.

[0004] A pinion (not shown) is formed at one end of an electric motor (not shown) disposed in the housing 9, and power generated from this pinion is transmitted via a power transmission mechanism (not shown). At the same time as being transmitted to the cylinder and rotating it with the drill holder 1 in the circumferential direction,
The power of the electric motor is also transmitted to the piston, and the piston is reciprocally slid in the axial direction, and the striking element is resiliently and intermittently moved by using the air chamber as an air spring. As a result, the drill holder 1 resiliently and intermittently moves in the axial direction in conjunction with the above-described movement of the striker while rotating.

[0005] The bit removal mechanism B includes a pair of rollers 2 and 2 and a sleeve S. That is, a pair of roller holes 1a, 1a penetrating in the radial direction are formed at opposing positions of the drill holder 1, and a pair of rollers 2, 2 are respectively disposed in the pair of roller holes 1a, 1a so as to be able to protrude and retract. Have been. When the pair of rollers 2, 2 protrude toward the inner peripheral surface of the drill holder 1, the rollers engage with the recesses of a bit (not shown) inserted into the drill holder 1, and transfer the bit to the drill holder 1. In order to prevent rotation. Here, the recess of the bit is a pair of rollers 2,
Since the bit is longer than the length 2, the bit can slide in the axial direction with respect to the drill holder 1.

Further, on the outer peripheral surface of the drill holder 1,
Between a pair of rollers 2, 2, a steel ball 6 described later is provided.
1st stopper groove 1b and 2nd stopper groove 1c for receiving selectively.

[0007] The sleeve S is mounted on the outside of the drill holder 1 coaxially and rotatably in the circumferential direction, and the rollers 2, 2 are made to protrude and retract in the roller holes 1a, 1a according to the rotational position. That is, in consideration of the assemblability of the annular spring 5 described later, the sleeve S is provided on the outside of the drill holder 1 so as to be coaxially rotatable with the collar 3 so as to be rotatable in the circumferential direction. It comprises a collar 3 and an operating ring 4 attached to the collar 3 so as to rotate integrally with the collar 3 at its rear end.

[0008] Rollers 2 and 2 are provided with roller holes 1 at opposite positions on the inner peripheral surface of the collar 3 in accordance with the rotational position of the collar 3.
a, a pair of cam grooves 3
d and 3d are respectively formed. Further, between the pair of cam grooves 3d, 3d of the collar 3, a ball hole 3e penetrating the collar 3 in the radial direction is formed.

In the ball hole 3e, a steel ball 6 is arranged so as to be able to come and go. Further, an annular spring 5 is fitted on the outer peripheral surface of the collar 3 so as to press the steel hole 6 inward.

The operation ring 4 is rotatably mounted on the drill holder 1 so as to cover the collar 3.
The operation ring 4 rotates integrally with the collar 3. Therefore, one of the operation ring 4 and the collar 3 is provided with an engagement recess, and the other is provided with an engagement protrusion engaging with the engagement recess.

At the tip of the drill holder 1 described above, FIG.
As shown in FIG. 1, an annular stopper member 10 is attached.

The conventional bit loss prevention mechanism B having the above-described structure is used as follows. That is, when attaching a bit to the drill holder 1, first, the operation ring 4
To rotate the collar 3 to one side so that the steel ball 6 is placed in the second stopper groove 1c of the drill holder 1 as shown in FIG. 9, and the rollers 2 are deepest in the cam grooves 3d and 3d. Part. Thereby, the rollers 2, 2
Are immersed in the roller holes 1a, 1a.

In this state, a bit (not shown) is inserted into the inside of the drill holder 1 and then the operation ring 4 is inserted.
To rotate the collar 3 to the other side so that the steel ball 6 is housed in the first stopper groove 1b of the drill holder 1. As a result, the rollers 2, 2 are pushed toward the center of the drill holder 1 along the cam grooves 3d, 3d, and engage with the recesses of the bit.

Here, the recess of the bit is the roller 2,
2 longer than the length. Therefore, the bit is held so as to be non-rotatable in the circumferential direction and slidable in the axial direction with respect to the drill holder 1.

When the steel ball 6 is thus housed in the second stopper groove 1c, a state where the bit can be attached to and detached from the drill holder 1 (hereinafter referred to as an "open state") is maintained. When the steel ball 6 is housed in the first stopper groove 1b, the state of attachment of the bit to the drill holder 1 (hereinafter, referred to as "fixed state") is maintained.

[0016]

However, in the above-mentioned conventional bit removal prevention mechanism B, the open state and the fixed state are held only by the elastic force of the annular spring 5. Accordingly, when the power tool is driven in a state where the bit removal prevention mechanism B is placed in a fixed state, a rotational force exceeding the elastic force of the annular spring 5 is applied to the collar 3 and / or the operation ring 4 by the action of the inertial force. Then, the collar 3 and the operation ring 4 rotate, the bit removal prevention mechanism B is switched from the fixed state to the open state, and there is a possibility that the bit comes off.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a bit removal prevention mechanism for an electric power tool, which reliably prevents erroneous switching from a fixed state to an open state and improves reliability.

[0018]

In order to achieve the above object, according to the present invention, there is provided a cylindrical drill holder (1) which projects into and out of a roller hole (1a) formed through the cylindrical drill holder (1) in a radial direction thereof. The bit (11) is engaged with the recess (11a) of the bit (11) inserted into the drill holder (1) in a state where the bit (11) protrudes toward the inner peripheral surface of the drill holder (1). A roller (2) for holding the rotor in a non-rotatable manner with respect to the drill holder (1), and the drill holder (1)
And a sleeve (S) which is mounted coaxially with the outer periphery of the roller so as to be rotatable in the circumferential direction, and which has a sleeve (S) for allowing the roller (2) to protrude and retract in the roller hole (1a) according to the rotational position. In the detachment prevention mechanism, the sleeve (S) is disposed so as to be slidable in the axial direction with respect to the drill holder (1), and in a state where the sleeve (S) slides to one side, the drill holder ( Locking means (L) for preventing circumferential rotation of the sleeve (S) with respect to 1) is provided.

According to a second aspect of the present invention, in the bit-preventing mechanism of the first aspect, an elastic means (8) for urging the sleeve (S) to the one side is provided. And

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A bit removal prevention mechanism A for a power tool according to an embodiment of the present invention applied to a hammer drill will be described below with reference to FIGS. The hammer drill as an electric tool to which the present invention is applied is used for hanging and drilling work, similarly to the above-mentioned hammer drill to which the conventional bit removal prevention mechanism B is applied. (Not shown) is rotatably arranged in the circumferential direction. Inside the rear end side of the cylinder, a piston (not shown) and a striker (not shown) are respectively slidably disposed so as to form an air chamber therebetween. On the other hand, a cylindrical drill holder 1 is integrally formed at the tip of the cylinder. A bit 11 (see FIG. 7) is attached to the drill holder 1 via a bit removal prevention mechanism A so as to be non-rotatable in the circumferential direction and slidable in the axial direction.

A pinion (not shown) is formed at one end of an electric motor (not shown) disposed in the housing 9, and the power generated from this pinion is transmitted via a power transmission mechanism (not shown). At the same time as being transmitted to the cylinder and rotating it with the drill holder 1 in the circumferential direction,
The power of the electric motor is also transmitted to the piston, and the piston is reciprocally slid in the axial direction, and the striking element is resiliently and intermittently moved by using the air chamber as an air spring. As a result, the drill holder 1 resiliently and intermittently moves in the axial direction in conjunction with the above-described movement of the striker while rotating.

The bit removal prevention mechanism A according to the present invention includes a pair of rollers 2 and 2 and a sleeve S, similarly to the above-described conventional bit removal prevention mechanism B. That is, a pair of roller holes 1a, 1a penetrating in the radial direction are formed at opposing positions of the drill holder 1, and a pair of rollers 2, 2 are respectively disposed in the pair of roller holes 1a, 1a so as to be able to protrude and retract. Have been. When the pair of rollers 2, 2 protrude toward the inner peripheral surface of the drill holder 1, the recesses 11 a, 11 of the bit 11 inserted into the drill holder 1
a, the bit 11 is non-rotatably held with respect to the drill holder 1. Here, the recess 11 of the bit 11
Since a and 11 a are longer than the length of the pair of rollers 2, 2, the bit 11 can slide in the axial direction with respect to the drill holder 1.

Further, on the outer peripheral surface of the drill holder 1,
Between a pair of rollers 2, 2, a steel ball 6 described later is provided.
1st stopper groove 1b and 2nd stopper groove 1c for receiving selectively.

The sleeve S is mounted on the outside of the drill holder 1 coaxially and rotatably in the circumferential direction and slidably in the axial direction. Appear at 1a, 1a. That is, the collar S is attached to the outside of the drill holder 1 so as to be rotatable coaxially and circumferentially and slidable in the axial direction in consideration of the assemblability of the annular spring 5 described later. 3 and an operation ring 4 which is rotatably and axially slidably disposed outside the drill holder 1 at a front end portion and is attached to the rear end portion so as to rotate integrally with the collar 3. It is composed of

Rollers 2 and 2 are provided at the opposite positions on the inner peripheral surface of the collar 3 in accordance with the rotational position of the collar 3.
a, a pair of cam grooves 3
d and 3d are respectively formed. Further, between the pair of cam grooves 3d, 3d of the collar 3, a ball hole 3e penetrating the collar 3 in the radial direction is formed.

In the ball hole 3e, a steel ball 6 is arranged so as to be able to come and go. Further, an annular spring 5 is fitted on the outer peripheral surface of the collar 3 so as to press the steel hole 6 inward.

The operation ring 4 is rotatably mounted on the drill holder 1 so as to cover the collar 3.
The operation ring 4 rotates integrally with the collar 3. Therefore, an engagement concave portion 3c is formed by cutting out a part of the periphery of the distal end portion of the collar 3, while a corresponding position of the operation ring 4 can be engaged with the engagement concave portion 3c. An engagement protrusion (not shown) is formed. The engaging recess may be formed on the operation ring 4 and the engaging protrusion may be formed on the collar 3. The form of connection between the collar 3 and the operation ring 4 is not limited as long as they can be integrally rotated.

As described above, the sleeve S composed of the collar 3 and the operation ring 4 can slide in the axial direction with respect to the drill holder 1, but when the sleeve S slides to one side, Locking means L for preventing rotation of the sleeve S in the circumferential direction with respect to the drill holder 1 is provided.

The locking means L includes a pair of locking grooves 3b, 3b formed by cutting out opposing portions at the tip of the collar 3, and a locking groove 3b of the collar 3 when the collar 3 slides forward. And a pair of lock pins 7, 7 protruding outward from the outer peripheral surface of the drill holder 1 so as to engage with 3b.

The collar 3 has an outward flange 3a, and a pressing force by an elastic means 8 for urging the collar 3 toward the lock pins 7, 7 is applied to the rear surface of the flange 3a. I have. The elastic means 8 is constituted by a compression coil spring. The type and position of the elastic means 8 are arbitrary as long as they act so as to urge the collar 3 toward the lock pins 7, 7. Flange 3
A tension coil spring may be arranged so as to apply a tensile force to the front surface of a.

As shown in FIGS. 1, 3 and 5, an annular stopper member 1 is provided at the tip of the drill holder 1 described above.
0 is attached.

Next, a method of using the thus configured bit loss prevention mechanism A of the present invention will be described below with reference to FIGS. 2 and 4 show the bit removal prevention mechanism A with the operation ring 4 removed to clearly show the locked state and the unlocked state of the lock means L.

As shown in FIGS. 1 and 2, the collar 3 and the operation ring 4 slide to the left in FIG. By engaging with 7, the locking means L is placed in the locked state.

When mounting the bit on the drill holder 1, the operating ring 4 is first pressed to the right against the elastic means 8 and slid, as shown in FIG. With the sliding of the operation ring 4, the collar 3 also slides in the same direction, so that the lock groove 3b of the collar 3 is separated from the lock pin 7 of the drill holder 1 as shown in FIGS. Is placed in the unlocked state.

In this unlocked state, the operating ring 4 is operated to rotate the collar 3 to one side, and FIG.
As shown in the figure, the steel ball 6 is housed in the second stopper groove 1c of the drill holder 1, and the rollers 2 and 2 are
d, located at the deepest part of 3d. Thereby, the rollers 2 and 2 can be immersed in the roller holes 1a and 1a,
That is, it is placed in an open state.

In this state, the bit 11 is inserted into the inside of the drill holder 1, and then the operating ring 4 is operated to rotate the collar 3 to the other side so that the steel ball 6 is moved to the first stopper of the drill holder 1. Set it in the groove 1b. As a result, the rollers 2 and 2 are pushed toward the center of the drill holder 1 along the cam grooves 3d and 3d, and
1a and 11a.

Here, the recess 11a of the bit 11
11a is longer than the length of the rollers 2,2. Therefore, the bit 11 is held in a state in which the bit 11 cannot rotate in the circumferential direction with respect to the drill holder 1 and can slide in the axial direction, that is, a fixed state.

After the operation ring 4 is released after being held in the fixed state, the operation ring 4 slides together with the collar 3 by the action of the elastic means 8, as shown in FIGS. 1 and 2. In addition, the lock groove 3b of the collar 3 engages with the lock pin 7 of the drill holder 1, so that the lock means L
Is locked again.

In order to switch the bit removal prevention mechanism A from the fixed state to the open state as described above, the operating ring 4 must be pressed in one direction to place the locking means L in the unlocked state. For example, in the fixed state, even if a rotational force exceeding the elastic force of the annular spring 5 is applied to the collar 3 and / or the operation ring 4 by the action of the inertial force,
Unless the above-described pressing operation of the operation ring 4 is performed, the lock means L is not unlocked, and therefore, accidental switching from the fixed state to the open state is prevented.

In the above-mentioned bit detaching prevention mechanism A, the sleeve S is composed of the collar 3 and the operation ring 4, which are connected so as to rotate integrally. After assembling the annular spring 5, the collar 3 and the operation ring 4 may be fixed to each other by screws or the like.

The locking means L includes a pair of locking grooves 3b, 3b formed by cutting out opposing portions at the front end of the collar 3, and locking the collar 3 when the collar 3 slides forward. Although the lock grooves 3b, 3b are described as comprising a pair of lock pins 7, 7 projecting outward from the outer peripheral surface of the drill holder 1 so as to engage with the grooves 3b, 3b, the lock grooves 3b, 3b are formed in the collar 3. Instead of providing the lock ring, a lock groove may be provided at the tip of the operation ring 4, while a lock pin may be provided in the drill holder 1 at a position corresponding to the lock groove.

In the above description, the operation ring 4 is pressed to the right in the figure to place the lock means L in the unlocked state. However, the operation ring 4 is pressed to the left in the figure to release the lock means L. It is also possible to arrange to put in a state.

Although the description has been made on the assumption that a pair of rollers 2 and 2 are used, the number of rollers is arbitrary and a single roller can be used.
There may be three or more. Further, the lock means L has been described as being constituted by a pair of lock grooves 3b, 3b and a pair of lock pins 7, 7, but the number of these may be arbitrary, and may be single or three or more.

[0044]

According to the first aspect of the present invention, the cylindrical drill holder is disposed so as to be able to protrude and retract from a roller hole formed to penetrate the drill holder in the radial direction, and protrudes toward the inner peripheral surface side of the drill holder. A roller that engages with the recess of the bit inserted into the drill holder and holds the bit non-rotatably with respect to the drill holder, and coaxially and circumferentially rotates on the outside of the drill holder; And a sleeve for allowing the roller to protrude and retract in the roller hole in accordance with the rotational position of the power tool, wherein the sleeve is slidable in the axial direction with respect to the drill holder. A locking means is provided to prevent the sleeve from rotating in the circumferential direction with respect to the drill holder when the sleeve is slid to one side. In, ensures that a switched accidentally from the fixed state to an open state, it is possible to improve the reliability.

[0045] In the bit missing prevention mechanism of claim 1,
If the elastic means for urging the sleeve to the one side is provided, the locking means is automatically placed in the locked state by the elastic means, and the reliability is further improved.

[Brief description of the drawings]

FIG. 1 is a vertical longitudinal sectional view showing a bit removal prevention mechanism of a power tool according to the present invention, in which a locking means is placed in a locked state.

FIG. 2 is a partially sectional front view showing a state where an operation ring and a stopper member are removed from the bit removal prevention mechanism of FIG. 1;

FIG. 3 is a vertical longitudinal sectional view showing the bit removal prevention mechanism of the power tool according to the present invention, in which a lock means is placed in an unlocked state.

4 is a partially sectional front view showing a state in which an operation ring and a stopper member are removed from the bit removal prevention mechanism of FIG. 3;

FIG. 5 is a horizontal vertical sectional view showing a bit removal prevention mechanism of the power tool according to the present invention.

FIG. 6 is a sectional view taken along the line VI-VI of FIG. 5, showing a state where the lock means is placed in an unlocked state;

FIG. 7 is a cross-sectional view similar to FIG. 6, showing a state in which the locking means is placed in a locked state.

FIG. 8 is a vertical vertical sectional view showing a conventional bit dropout prevention mechanism.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 8, showing a state in which a bit can be attached to and detached from a drill holder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill holder 1a Roller hole 2 Roller S sleeve L Lock means 8 Elastic means

Claims (2)

[Claims] 1. A bit inserted in a drill holder in a state that it is disposed so as to be able to protrude and retract from a roller hole formed through a cylindrical drill holder in a radial direction thereof and protrudes toward the inner peripheral surface side of the drill holder. A roller that engages with the recess of the drill holder and holds the bit so as to be non-rotatable with respect to the drill holder. The roller is mounted on the outside of the drill holder so as to be coaxial with and rotatable in the circumferential direction. And a sleeve for allowing the roller to protrude and retract in the roller hole, wherein the sleeve is slidably disposed in the axial direction with respect to the drill holder, and the sleeve is disposed on one side. A lock means for preventing rotation of the sleeve in a circumferential direction with respect to the drill holder in a slid state; Bit missing prevention mechanism. 2. The mechanism as claimed in claim 1, further comprising elastic means for urging the sleeve toward the one side.