JP2004001141A - Bit holding mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bit holding mechanism for performing an excellent attaching/detaching work without problems, even if using any of stepped bits having dispersion in dimension. <P>SOLUTION: This bit holding mechanism is provided with: an output shaft 2 having a hexagonal hole 3; a through hole 4 formed in a radial direction from an outside surface of the output shaft 2 to the hexagonal hole 3; a steel ball 8 arranged within the through hole 4; and a sleeve 5 located on the outside surface of the output shaft 2 and switching whether the steel ball 8 is pushed out into the hexagonal hole 3 from the inside of the through hole 4 in a partially projected state. The mechanism prevents the bit from falling from the inside of the hexagonal hole 3 by an engagement to the steel ball 8 pushed out into the hexagonal hole 3 and partially projected by the sleeve 5. At a bottom part of the hexagonal hole 3, a first butting surface 41 for butting a double ended bit 30 and a second butting surface 43 for butting the stepped bit 32 are separately formed so that the first butting surface 41 may be located more closely to the bottom side than the second butting surface 43. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a bit holding mechanism, and more particularly, to a technique for satisfactorily holding either a double-ended bit or a stepped bit.
[0002]
[Prior art]
FIG. 9 shows a driver 1 that uses, for example, electricity as a power source. Such a driver 1 has a structure as shown in FIGS. 11 and 12 as a bit holding mechanism. That is, a hexagonal hole 3 for insertion of a bit is formed in a portion on the front end side (that is, the front side) of the output shaft 2 which is rotationally driven by the power source, in the axial direction. A through hole 4 is formed in the radial direction from the outer surface to the hexagonal hole 3, and a steel ball 8 is held in the through hole 4. A substantially cylindrical sleeve 5 is axially slidably fitted on the outer surface of the output shaft 2 so as to cover the through hole 4. At the rear end of the inner surface of the sleeve 5, a locking portion 6 protrudes in the center direction, and the outer surface of the output shaft 2 has a stepped portion 7 formed so that the front side is one step lower than the rear side. The locking portion 6 locks to limit the retreat of the sleeve 5.
[0003]
A convex portion 9 is formed at a substantially central portion of the inner surface of the sleeve 5 in the front-rear direction, and a ring 10 is fixed to the front end of the outer surface of the output shaft 2 by fitting. A spring 11 and a washer 12 are interposed between the convex portion 9 of the sleeve 5 and the ring 10 fixed to the output shaft 2, and the front end face of the washer 12 is brought into contact with the ring 10 so that the rear end of the spring 11 is in a compressed state. The end is brought into contact with the front end face of the projection 9 and the front end is brought into contact with the rear end face of the washer 12 to apply a rearward urging force by the spring 11 to normally engage the sleeve 5 with the step 7 as shown in FIG. The stop portion 6 is held at a position where it cannot be further retracted by the locking of the stop portion 6.
[0004]
In this normal state, the protrusion 9 of the sleeve 5 is located at a position facing the through hole 4 of the output shaft 2, and the protrusion 9 hits the steel ball 8 held in the through hole 4, and the steel ball 8 is removed from the through hole 4. It is configured to be pushed out toward the center to a state where it partially projects into the hexagonal hole 3. For example, a double-ended bit 30 is inserted into the hexagonal hole 3 as a bit. At a position where one head of the double-ended bit 30 is abutted against an abutting surface 14 formed at the rear part of the hexagonal hole 3, a predetermined position of the double-ended bit 30 is set. The part of the steel ball 8 protruding as described above is engaged with the locking groove 31 formed in a concave shape as a small diameter, thereby preventing the double-ended bit 30 from falling out of the hexagonal hole 3.
[0005]
Further, a portion sandwiched between the locking portion 6 protruding from the rear end portion on the inner side surface of the sleeve 5 and the substantially central portion of the convex portion 9 is a concave steel ball escape portion 13. As shown in FIG. 12, the steel ball escape portion 13 is located instead of the convex portion 9 at the position facing the through hole 4 by pulling forward against the urging force of the spring 11. The ball escape portion 13 is in a state of communicating with the radial direction. Accordingly, at the time of pulling out, the steel ball 8 partially protrudes into the steel ball escape portion 13 and is movable in the radial direction to a position where it does not protrude into the hexagonal hole 3. Since the state is not fixed, the double-ended bit 30 becomes detachable.
[0006]
FIG. 2 shows how the double-ended bit 30 is attached and detached. In this state, the double-ended bit 30 can be inserted into the hexagonal hole 3 from the front with the sleeve 5 pinched and pulled out. The engagement of the double-ended bit 30 from the inside of the hexagonal hole 3 is prevented by the engagement with the steel ball 8 which is partially protruded into the hexagonal hole 3. When the double-ended bit 3 is removed, if the sleeve 5 is pulled out, the fixing of the steel ball 8 in a state of being partially protruded into the hexagonal hole 3 is released, and the double-ended bit 30 can be easily removed.
[0007]
FIG. 13 shows the shape of the hexagonal hole 3 in the conventional bit holding mechanism. The hexagonal hole 3 is a main part 15 which is a hole that is opened in a uniform hexagonal shape in the axial direction as shown in the figure, and a hole that is opened in a circular shape having a diameter larger than the hexagonal circumscribed circle of the main part 15. A piercing portion 17 which is a hole which is formed so as to have a smaller diameter toward the rear by being surrounded over the entire circumference by a certain boring groove portion 16, a tapered butt surface 14, and an escape portion 18 which is a small diameter hole portion. Are sequentially formed from the front side.
[0008]
The abutment surface 14 is formed with an inclination angle slightly larger than the inclination angle of the head shape of the double-ended bit 30 with respect to the axial direction, and the head of the double-ended bit 30 inserted into the hexagonal hole 3 abuts. The dimension A of the double-ended bit 30 in FIG. 15A is set to, for example, 13 mm so that the locking groove 31 of the double-ended bit 30 comes to a position where the locking groove 31 of the double-ended bit 30 is fitted to the steel ball 8 when the double-ended bit 30 comes into contact with the rear end of the surface 14. Is set to
[0009]
The inclination angle of the head shape of the double-ended bit 30 is defined as 26.5 °, and therefore, even when any of the various double-ended bits 30 provided is used, the position where the double-ended bit 30 is inserted into the hexagonal hole 3 and abuts on the hexagonal hole 3 is It is constant, and the attachment / detachment can be performed satisfactorily without any problem at the position where the locking groove 31 is fitted to the steel ball 8.
[0010]
On the other hand, when the stepped bit 32 provided only on one side of the head as shown in FIG. The inclined surface 33 formed by chamfering the corner of the rear end of the stepped bit 32 abuts on the corner 20 formed at the boundary between the side surface and the abutting surface 14. In the stepped bit 32, the dimension B from the rear end to the center of the locking groove 34 is set to, for example, 13 mm, and when the inclined surface 33 abuts as described above, the locking groove 34 It comes to the position where it fits. In this way, if the dimension A and the dimension B match, the same bit holding mechanism can be used for both the double-ended bit 30 and the stepped bit 32.
[0011]
However, in the above-mentioned bit holding mechanism, since the boring groove 16 is formed, the portion where the stepped bit 32 abuts becomes the corner 20, and compared with the case where the boring groove 16 is not formed in this way. It will also hit the rear side. In addition, although the dimension B of the stepped bit 32 is defined and there is no difference, the dimension C of the inclined surface 33 which is the end treatment is not particularly defined and is in the range of 0.5 to 1.5 mm. In a case where the size C is large and the inclined surface 33 is large, the stepped bit 32 is inserted further deeply into the hexagonal hole 3 as shown in FIG. There was a case where it shifted to the rear side from the position fitted with the steel ball 8. In this case, when the stepped bit 32 is pushed in and used, the steel ball 8 bites into the protrusion 9 of the sleeve 5 or the locking groove 34 of the stepped bit 32, and the stepped bit 32 cannot be removed. Such a problem occurred.
[0012]
In order to solve the above-mentioned problem, there is also provided one in which the dimension B is set longer than 13 mm, for example, 14 mm. However, it is difficult for the user to recognize this problem and select an appropriate bit for use. .
[0013]
If the boring groove 16 is not machined, it contributes to solving the above problem. However, as shown in FIG. 16A, a hexagonal columnar shape is formed in a round hole 20 drilled in the output shaft 2. When cutting is performed with the broach cutting tool 21, as shown in FIG. 16 (b), shavings 22 accumulate in the back and clog the feed dimensions of the broach cutting tool 21, or the burrs 23 cannot be removed and processing cannot be performed well. Would. On the other hand, by forming the above-mentioned boring groove portion 16 before cutting with the broach cutting tool 21, the problem of the shavings 22 and the burr 23 can be solved. This is an optimal configuration and indispensable configuration for good and inexpensive manufacturing.
[0014]
[Problems to be solved by the invention]
The present invention has been made in view of the above points, and an object of the present invention is to provide a bit holding mechanism that can perform a good attachment / detachment operation without any problem using any of stepped bits having variations in dimensions. Is what you do.
[0015]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides an output shaft having a hexagonal hole for bit insertion that is axially opened, a through-hole formed radially from an outer surface of the output shaft to a hexagonal hole, A steel ball disposed on the outer side of the output shaft, and a sleeve capable of switching whether or not to extrude the steel ball from the through hole to a state where the steel ball partially protrudes into the hexagonal hole. In a bit holding mechanism for preventing a bit from dropping out of a hexagonal hole by engagement with a steel ball that is extruded into a hole and partially protrudes, a first head in which one head of a double-ended bit is applied to the bottom of the hexagonal hole It is assumed that the abutting surface and the second abutting surface for abutting the root of the stepped bit are separately formed such that the first abutting surface is located on the bottom side of the second abutting surface.
[0016]
By doing in this way, only the stepped bit is further forwardly held against the second abutment surface as compared with the case where the double-ended bit and the stepped bit are held in the hexagonal hole by hitting the same abutment surface. This makes it possible to insert the stepped bit too deeply into the hexagonal hole and use the steel bit properly It is possible to prevent a situation in which it is displaced to the rear side from a proper locking position and a good attachment / detachment becomes impossible.
[0017]
It is also preferable that the inclination angle of the second abutment surface with respect to the central axis of the hexagonal hole is formed smaller than the inclination angle of the first abutment surface with respect to the central axis. The stepped bit hitting the surface can be positioned more reliably in front than in the case where the first abutment surface is extended as it is to serve as a shared abutment surface for the double-ended bit and the stepped bit.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on embodiments shown in the accompanying drawings.
[0019]
1 to 4 show an example of a bit holding mechanism according to the embodiment of the present invention. As shown in the drawing, the configuration of the bit holding mechanism of this example is substantially the same as the configuration of the bit holding mechanism described in the related art. The description will be omitted, and the characteristic configuration of this example will be described in detail below.
[0020]
The characteristic feature of the bit holding mechanism of this example is that the hexagonal hole 3 formed axially symmetrically with respect to the central axis C is formed by the main body 15, the boring groove 16, and the rear end of the stepped bit 32. , The first butting portion 40 to contact one head of the double-ended bit 30, and the relief portion 18 in order from the front side (that is, the tip side) to the rear side (that is, the bottom side). It is formed in communication.
[0021]
As shown in FIG. 4, the first abutting portion 40 becomes smaller in diameter as the rear surround front over the peripheral by the first conditioned abutting surface 41 that is inclined with the inclination angle theta ₁ only tapered relative to the center axis C a form the hole as the second abutment portion 42, as rear surrounds the entire circumference by a second with abutting surface 43 that is inclined to the inclined angle theta ₂ only tapered relative to the center axis C small It is a hole formed so that The rear end portion 43a of the second butting surface 43 is closer to the center axis C than the circumscribed circle of the main body portion 15 and is further away from the center axis C than the front end portion 41a of the first butting surface 41. A step surface 44 facing forward is formed between the front end portion 41a and the rear end portion 43a.
[0022]
Inclination angle theta ₁ of the first abutting surface 41 is formed slightly larger e.g. 30 ° than the inclination angle 26.5 ° of the tip shape of the double-ended bit 30, the inclination angle theta ₂ of the second abutting surface 43 is the smaller form than the inclination angle theta _1. However, the second butting surface 43 interferes with the double-ended bit 30 so that the double-ended bit 30 inserted into the hexagonal hole 3 does not come into contact with the second butted surface 43 before hitting the first butted surface 41. It is formed within the range not to be.
[0023]
According to the above configuration, when the double-ended bit 30 is inserted into the hexagonal hole 3, the rear end of the double-ended bit 30 abuts against the rear end portion 41b of the first attaching surface 41 as shown in FIGS. The locking groove 31 of the double-ended bit 30 is located at a position where it is fitted with the steel ball 8. When the stepped bit 32 is inserted into the hexagonal hole 3, the front end portion of the inclined surface 33 provided at the rear end of the stepped bit 32 as shown in FIGS. You will end up. The abutting position P is determined when the abutting portion 50 is formed by extending the first abutting surface 41 forward without providing the second abutting surface 43 (see the imaginary line in FIG. 2). ′, And is set so as to be located forward by X in comparison with the case where the double-sided bit 30 and the double-sided bit 32 are both stopped on only one surface as in the abutting portion 50. Only bit 32 can be held forward.
[0024]
Therefore, in this example, the locking groove 34 is fitted to the steel ball 8 even when the step C bit 32 having a large dimension C and a large inclined surface 33 is inserted deep into the hexagonal hole 3. The stepped bit 32 is not displaced to the rear side from the mating position and cannot be removed due to the biting of the steel ball 8, and there is no problem with using any of the provided stepped bits 32. It becomes a detachable bit holding mechanism.
[0025]
5 to 8 show another example of a bit holding mechanism according to the embodiment of the present invention. As shown in the figure, the configuration of the bit holding mechanism of this example is substantially the same as the configuration of the bit holding mechanism of the above-described example, and therefore, the basic configuration is denoted by the same reference numeral and the description thereof is omitted. The characteristic configuration of this example will be described in detail below.
[0026]
Bit holding mechanism of the present embodiment as its characteristic configuration, both double-ended bit and an inclined angle theta ₂ inclination angle theta ₁ with respect to the center axis C of the second abutting surface 43 with respect to the center axis C of the first abutting surface 41 30 is slightly larger than 26.5 °, for example, 30 °, and the distance from the center axis C between the front end portion 41a of the first butting surface 41 and the rear end portion 43a of the second butting surface 43. And a step surface 45 facing the center is formed between the front end portion 41a and the rear end portion 43a.
[0027]
In addition, the rear end portion 43a of the second abutting surface 43 is located closer to the center axis C than the circumscribed circle of the main body portion 15, and the double-ended bit 30 inserted into the hexagonal hole 3 is the first abutting surface 41. In order not to hit the second abutting surface 43 before hitting, the bit is formed in a range that does not interfere with the double-ended bit 30.
[0028]
According to the above configuration, when the double-ended bit 30 is inserted into the hexagonal hole 3, the rear end of the double-ended bit 30 abuts against the rear end portion 41b of the first contact surface 41, as shown in FIG. The locking groove 31 of 30 is located at a position where the groove 30 is fitted with the steel ball 8. When the stepped bit 32 is inserted into the hexagonal hole 3, the front end portion of the inclined surface 33 provided at the rear end of the stepped bit 3 as shown in FIGS. You will end up. The abutting position Q is determined when the abutting portion 50 is formed by extending the first abutting surface 41 forward without providing the second abutting surface 43 (see the imaginary line in FIG. 7). ', And only the stepping bit 32 is positioned in comparison with the case where both the double-ended bit 30 and the stepping bit 32 are stopped only on one surface as in the abutting portion 50. Can be held forward.
[0029]
Therefore, even in the present example, even when the stepped bit 32 having a large dimension C and a large inclined surface 33 and a large inclined surface 33 is inserted deep into the hexagonal hole 3, the locking groove 34 is fitted to the steel ball 8. The stepped bit 32 is not displaced to the rear side from the mating position and cannot be removed due to the biting of the steel ball 8, and there is no problem with using any of the provided stepped bits 32. It becomes a detachable bit holding mechanism.
[0030]
Incidentally, further regards inclination angle theta ₂ of the second abutting surface 43, without interfering with the prior double ended bit 30 inserted into the hexagonal hole 3 hits the first abutment surface 41 and the second abutment surface If the first abutment surface 41 is extended forward and the abutment portion 50 is formed without providing the abutment portion 43, the first abutment surface 41 is located at a further forward position within a range where the abutment bit 32 inserted into the hexagonal hole 3 is hit. , it may be each other with an inclination angle theta ₂ of the second abutting surface 43 larger or smaller to form than the inclination angle theta ₁ of the first abutting surface 41.
[0031]
【The invention's effect】
As described above, according to the first aspect of the present invention, only the stepped bit is further moved forward in comparison with the case where the double-ended bit and the stepped bit are held in the hexagonal hole by contacting the same abutting surface. The stepped bit can be held deeply in the hexagonal hole even if a stepped bit with a large size is used, especially if a stepped bit with a large bottom is used. It does not prevent the steel ball from being inserted too far and displaced to the rear side from the appropriate locking position, making it impossible to attach and detach it properly. There is an effect that it is possible to perform an easy attaching / detaching operation.
[0032]
According to the second aspect of the present invention, in addition to the effects of the first aspect, a stepped bit corresponding to the second abutting surface is formed by extending the first abutting surface as it is and forming a double-ended bit. As compared with the case where the attached bit is used as a common abutting surface, there is an effect that the bit can be reliably located at the front.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a state in which a stepped bit is held in an example bit holding mechanism according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is an explanatory diagram showing a state where double-ended bits are held in the bit holding mechanism according to the first embodiment.
FIG. 4 is an enlarged view of a main part of FIG. 3;
5A and 5B show another example of a bit holding mechanism according to the embodiment of the present invention, wherein FIG. 5A is an explanatory diagram and FIG. 5B is a cross-sectional view taken along line DD of FIG.
FIG. 6 is an explanatory view showing a state in which a stepped bit is held in the bit holding mechanism according to the first embodiment.
FIG. 7 is an enlarged view of a main part of FIG. 6;
FIG. 8 is an explanatory diagram showing a state where double-ended bits are held in the bit holding mechanism according to the first embodiment.
FIG. 9 is a perspective view showing a driver.
FIG. 10 is an explanatory diagram showing a bit attaching / detaching method in a driver.
FIG. 11 is an explanatory view showing a bit fixed state in a conventional bit holding mechanism.
FIG. 12 is an explanatory diagram showing a bit fixing release state in the bit holding mechanism of the above.
FIG. 13 is a sectional view showing the bit holding mechanism according to the third embodiment.
FIG. 14 is an explanatory diagram showing a state in which a stepped bit is held in the bit holding mechanism according to the first embodiment.
FIGS. 15A and 15B are side views showing a bit, wherein FIG. 15A shows a double-ended bit and FIG. 15B shows a stepped bit.
16A and 16B are explanatory diagrams illustrating a method of processing the output shaft, wherein FIG. 16A illustrates a state before processing with a broach blade, and FIG. 16B illustrates a state during processing with a broach blade.
[Explanation of symbols]
2 Output shaft 3 Hexagon hole 4 Through hole 5 Sleeve 8 Steel ball 30 Double-ended bit 32 Stepped bit 41 First butting surface 43 Second butting surface

Claims (2)

An output shaft having a hexagonal hole for bit insertion that is open in the axial direction, a through-hole formed radially from the outer surface of the output shaft to the hexagonal hole, a steel ball disposed in the through-hole, and an output shaft. A sleeve positioned on the outer side and capable of switching whether or not to extrude the steel ball from the through hole into a partially protruded state into the hexagonal hole, and a sleeve extruded into the hexagonal hole by the sleeve and partially protruded. In a bit holding mechanism for preventing a bit from falling out of a hexagonal hole by engagement with a ball, a first abutting surface for applying one head of a double-ended bit to a bottom of the hexagonal hole, and a root portion of a stepped bit And a second abutting surface on which the first abutting surface is applied is formed separately such that the first abutting surface is located on the bottom side of the second abutting surface. The bit holding mechanism according to claim 1, wherein the inclination angle of the second abutment surface with respect to the center axis of the hexagonal hole is formed smaller than the inclination angle of the first abutment surface with respect to the center axis.

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