JP4082788B2 - Drill tool - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drill bit having a drill blade portion at both ends, and a drill tool including the drill bit.
[0002]
[Prior art]
A general drill tool has a configuration in which a drill blade portion and a shank portion are integrally formed. However, in this configuration, if the drill blade is damaged, it cannot be used thereafter, and thus there is a disadvantage that a long life cannot be expected.
[0003]
Therefore, in recent years, for the purpose of improving the life of a drill tool, a combination of a drill bit having a drill blade portion at both ends and a drill bit holder for detachably holding the drill bit has been developed.
[0004]
For example, in Japanese Patent Publication No. 8-18213, a hexagonal torque receiving portion is formed in an intermediate portion of a drill bit having drill blade portions at both ends, and a cylindrical shape between the torque receiving portion and each drill blade portion. An annular groove is formed in the centering shaft portion of the drill bit holder, while the drill bit holder has a drill bit insertion hole that can accommodate the drill blade portion, a circular cross-sectional insertion hole that can fit the centering shaft portion, A hexagonal fitting hole into which the torque receiving portion can be fitted is provided, and torque transmission from the drill bit holder to the drill bit is enabled by fitting the hexagonal fitting hole with the torque receiving portion, and the annular groove In this case, a drill bit is prevented from coming off from the drill bit holder by fitting a ball with a spring force. According to such a drill tool, even if one of the drill blades is damaged, the drill bit is once removed from the drill bit holder at that stage, and then reattached to the drill bit holder in the opposite direction. The drilling operation can be continued using the other drill blade portion that is not damaged. Therefore, the tool life is greatly improved.
[0005]
[Problems to be solved by the invention]
The drill tool has the following problems to be solved.
[0006]
a) In addition to forming a hexagonal torque receiving portion for transmitting torque at the intermediate portion of the drill bit, a cylindrical centering shaft portion is formed at both ends thereof, and the centering shaft portion An annular groove must be formed, and the shape of the drill bit is complicated. On the other hand, on the drill bit holder side, a hexagonal insertion hole into which the torque receiving portion can be inserted must be formed, and the process is considerably complicated as compared with the case where only the circular hole is formed. Therefore, it is difficult to reduce the cost of the entire drill tool.
[0007]
b) To reliably prevent the drill bit from swinging, increase the axial length of the centering shaft portion as much as possible, and ensure a large fitting area between the centering shaft portion and the circular insertion hole on the holder side. However, when the centering shaft portion is lengthened, the overall length of the drill bit is inevitably increased. Therefore, it is difficult to perform reliable centering with a compact structure.
[0008]
In view of such circumstances, an object of the present invention is to provide a drill tool including a drill bit that can be attached and detached with a simple and inexpensive structure and that can be reliably centered.
[0009]
[Means for Solving the Problems]
As means for solving the above-mentioned problems, the present invention provides a drill having a drill blade portion at both ends and a portion to be locked to be locked to a drill bit mounting portion between the drill blade portions. A drill bit holder having a bit, a circular drill accommodating hole that can accommodate one drill blade portion of the drill bit, and a circular insertion hole having a circular cross section into which both circular portions of the locked portion can be fitted. A drill tool, wherein both end portions in the axial direction of the locked portion of the drill bit are circular shapes having the same shape and larger diameter than the drill blade portion, and a portion between the circular portions is a circle of the circumscribed circle. A step portion between the rear circular portion and the deformed portion on the peripheral wall surrounding the insertion hole in the drill bit holder, which has a polygonal or substantially polygonal cross-sectional shape whose diameter is equal to or less than the diameter of the circular portion. Engaged with the drill A locking portion movable between a locking position for preventing the bit from coming off and rotating and a releasing position for retracting the drill bit from the locking position to the outside in the radial direction; and A holding portion that can be switched between a state of being restrained at the locking position and a state of being released is provided .
[0010]
According to this drill tool , the drill bit can be prevented from coming off by locking the step between the rear circular portion of the drill bit and the deformed portion having a smaller cross-sectional shape, and the rotation of the drill bit is restricted. Torque transmission can be performed.
[0011]
And as a drill bit holder for holding this drill bit, a circular drill storage hole in which one drill blade part can be stored and a circular insertion hole having a circular cross section in which both circular parts of the locked part can be inserted The drill bit holder has a peripheral wall that surrounds the fitting hole and engages with a step portion between the rear circular portion and the deformed portion to prevent the drill bit from coming off and preventing rotation. A locking part movable between a locking position and a releasing position for retracting radially outward from the locking position to release the drill bit, and a state in which the locking part is restrained to the locking position and the release What is necessary is just to provide the holding | maintenance part which can be switched to the state to perform. That is, it is not necessary to form a hole having an irregular cross section on the drill bit holder side as in the prior art, and the drill bit can be held only by providing a drill storage hole and a fitting hole having a circular cross section. Therefore, the manufacturing process of the drill bit holder is greatly simplified.
[0012]
And centering can be performed using this to-be-latched part by inserting both the circular parts of to-be-latched part in the common insertion hole. Therefore, reliable centering can be achieved with a compact structure.
[0013]
Furthermore, while forming a cylindrical centering shaft portion having a diameter larger than the drill blade portion and smaller than the circular portion between each drill blade portion and the locked portion of the drill bit, If the drill bit holder is provided with a centering insertion hole for centering the drill bit by inserting the centering shaft part, the fitting is made in two places (the insertion hole and the circular part). And the fitting of the centering shaft and the centering insertion hole), the centering of the drill bit becomes more reliable.
[0014]
Note that, in the locked portion of the drill bit, the cross-sectional shape of the deformed portion may be slightly smaller than the cross-sectional shape of the circular portion, but the shape of the locked portion is the drill blade portion. If the shape of the cylindrical part with a larger diameter than the axial direction of both ends is cut out with a plane at a plurality of locations in the middle between them, the above-mentioned excellent processing can be achieved by simply cutting a part of the cylinder. A locked portion having a function can be easily manufactured.
[0015]
Further, the cross section of the deformed portion may be substantially polygonal, but in particular, when it has a substantially rectangular shape, a large torque transmission force can be secured, and an advantage of easy manufacture can be obtained.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of the present invention will be described with reference to the drawings.
[0017]
The drill bit 10 shown in FIG.1 and FIG.2 has the to-be-latched part 12 in the axial direction intermediate part, and the drill blade part 14 is formed in the both ends. Both end portions in the axial direction of the locked portion 12 are circular portions 18 having the same shape and a larger diameter than the drill blade portion 14, and the four flat surfaces 15 are circumferential in the intermediate portion sandwiched between the circular portions 18. The deformed portions 16 are arranged in a substantially square shape. In this embodiment, the four corner portions of the deformed portion 16 are arcuate and are continuous with both circular portions 18. That is, the locked portion 12 has a shape in which a plurality of circumferential portions at an intermediate portion thereof are cut off by the plane 15 while leaving both ends of the cylinder in the axial direction (circular portion 18).
[0018]
A cylindrical centering shaft portion 19 having a diameter larger than that of the drill blade portion 14 and smaller than that of the circular portion 18 is formed between the locked portion 12 and both drill blade portions 14.
[0019]
A drill bit holder 20 to which the drill bit 10 is attached is shown in FIGS. The drill bit holder 20 integrally includes a shank portion 22 connected to a rotational drive source (not shown) and a drill bit mounting portion 24 to which the drill bit 10 is mounted. The drill bit mounting portion 24 is formed with a drill blade portion accommodation hole 26 having a circular cross section, and one drill blade portion 14 can be accommodated in the drill blade portion accommodation hole 26, and the drill blade portion accommodation hole 26. The drill bit 10 is centered by the centering shaft portion 19 being fitted therein with almost no gap. That is, in this embodiment, the drill blade storage hole 26 also serves as a centering insertion hole.
[0020]
Further, an insertion hole 27 having a circular cross section into which both the circular portions 18 of the locked portion 12 can be inserted with almost no gap is formed on the inlet side of the drill blade portion accommodation hole 26, and the drill bit 10 is also inserted by this insertion. Centering is performed. A lock portion 30 for locking the mounting state of the drill bit 10 is provided around the insertion hole 27.
[0021]
Specifically, as shown in FIGS. 4 and 5, the peripheral wall of the drill bit mounting portion 24 surrounding the insertion hole 27 has a plurality of (two in the illustrated example) through-holes 28 penetrating in the radial direction. Are provided at equal intervals (180 ° intervals in the figure), and balls (locking portions) 32 are accommodated in the respective through holes 28. Each ball 32 has a diameter larger than the wall thickness of the peripheral wall provided with the through hole 28, and projects into the insertion hole 27 as shown in FIGS. 3 and 4A and 4B. It is movable between a stop position and a release position that retracts radially outward from the locking position. Then, as shown in FIGS. 3 and 4 (a) and 4 (b), when the circular portions 18 are fitted into the fitting holes 27 and the balls 32 are located at the locking positions, the balls 32 are deformed. The arrangement positions of the through hole 28 and the ball 32 are set so as to engage with the step 17 between the portion 16 and the rear circular portion 18.
[0022]
The outer peripheral surface of the peripheral wall is a small-diameter portion 25 having a slightly smaller diameter than the other outer peripheral surfaces of the drill bit mounting portion 24, and a holding sleeve (holding portion) 34 is slidable in the axial direction on the small-diameter portion 25. It is fitted outside without any gaps.
[0023]
On the inner circumferential surface of the holding sleeve 34, a circumferential groove 34a that is open to the front end side and a space from the circumferential groove 34a to the rear (rightward in FIGS. 4 (a) and 5 (a)) are formed. The circumferential groove 34b is formed. A compression coil spring 36 is housed in the circumferential groove 34 a, and a leading end side (left side in FIGS. 4A and 5A) is fixed to the outer peripheral surface of the drill bit mounting portion 24. Is regulated by. The holding sleeve 34 is urged rearward by the elastic force of the compression coil spring 36, and the rear end of the holding sleeve 34 is held at a position where it contacts the step 25a at the rear end of the small-diameter portion 25 in a state where no external force is applied. It has become so. In this state, the portion of the holding sleeve 34 between the circumferential grooves 34a and 34b restricts the ball 32 from the outside and restrains it at the locking position shown in FIGS. 4 (a) and 4 (b). a) (b)) On the other hand, when the external force is applied to the holding sleeve 34 from the state and the sleeve 34 moves forward, the ball 32 is retracted in the circumferential groove 34b, and FIG. 5 (a) (b). The shape of the holding sleeve 30 is set so that it can move to the release position shown in FIG.
[0024]
Next, the operation of this drill tool will be described.
[0025]
First, in the state where the drill bit 10 is mounted on the drill bit holder 20 as shown in FIGS. 3 and 4 (a) and 4 (b), the ball 32 restrained at the locking position is formed by the deformed portion 16 and the rear circular portion. The drill bit 10 is prevented from coming off by engaging with the step 17 with respect to 18. In addition, since the rotation of the locked portion 12 in the insertion hole 27 is prevented by the presence of the ball 32, when torque is applied to the drill bit holder 20 from the rotational drive source in this state, the torque is reliably ensured. It is transmitted to the drill bit 10 and the entire drill tool rotates together. For this reason, a good drilling operation can be performed using the drill blade portion 14 on the distal end side of the drill bit 10.
[0026]
When the drill blade portion 14 being used is damaged or the like and the drilling operation becomes impossible, the drill bit 10 is once removed from the drill bit holder 20. Specifically, by holding the holding sleeve 34 with a finger or the like, an external force is applied to the distal end in the axial direction, and the holding sleeve 34 is slid to the position shown in FIG. 5A against the elastic force of the compression coil spring 36. . As a result, the ball 32 can escape into the circumferential groove 34b, and the restraint to the locking position is released. In this state, the drill bit 10 can be extracted from the drill bit holder 20.
[0027]
Next, the drill bit 10 is directed in the opposite direction (that is, the undamaged drill blade portion 14 that has been accommodated in the drill bit mounting portion 24 is directed toward the distal end side), and the damaged drill blade portion 14 is turned to the drill blade portion. After inserting into the storage hole 26 and inserting the centering shaft part 19 and the circular parts 18 into the drill blade part storage hole 26 and the insertion hole 27, respectively, the holding sleeve 34 is released. As a result, the holding sleeve 34 is retracted to the position where it hits the step 25a by the elastic force of the compression coil spring 36, and the ball 32 is again restrained to the locking position. The mounting state of the drill bit 10 is locked again by the ball 32, and the drilling operation can be resumed using the new drill blade portion 14.
[0028]
In this structure, it is only necessary to form a substantially rectangular deformed portion 16 in the intermediate portion of the locked portion 12 in the drill bit 10, and a peripheral groove or the like for fitting a retaining ball as in the prior art is provided. There is no need to form. On the other hand, in the drill bit holder 20, it is only necessary to form the drill blade portion accommodation hole 26 and the insertion hole 27 with a circular cross section, and it is not necessary to form a polygonal hole as in the prior art. The bit holder 20 can be manufactured. Therefore, the cost of the entire drill tool can be significantly reduced.
[0029]
In particular, in this embodiment, the overall shape of the locked portion 12 is a shape in which a plurality of circumferential portions of the intermediate portion are cut out by the plane 15 except for both ends (circular portions 18) in the axial direction of the cylinder. Therefore, it is possible to easily form the locked portion 12 simply by excising a plurality of portions in the circumferential direction of the cylindrical portion by a removal process such as cutting, and the drill bit while having such a simple shape. 10 can be prevented from coming off and non-rotating (torque transmission) at the same place.
[0030]
Moreover, the circular portions 18 have the same shape, and the drill bit 10 can be centered by inserting the circular portions 18 into the insertion holes 27 having a circular cross section. That is, since the locked portion 12 is also used as the centering shaft portion, reliable centering can be achieved with a compact structure. Further, as shown in this embodiment, the centering shaft portion 19 different from the locked portion 12 is formed, whereby the centering becomes more reliable.
[0031]
In addition, embodiment of this invention is not limited to this, For example, it can also take the following forms.
[0032]
(1) The cross-sectional shape of the deformed portion 16 is not limited to a substantially square shape, and may be a substantially hexagonal shape as shown in FIG. Although the amount of removal processing increases, as shown in FIG. 5B, it is possible to make the deformed portion 16 a complete polygon (square in the figure) that is slightly smaller than the circular portion 18. However, as shown in FIG. 5C, at least a part of the plane 15 may be replaced with a concave surface 15 ′. However, as the number of vertices of the polygon increases, the torque transmission force becomes weaker as it approaches the circle. Therefore, it is preferable that the number of the vertices is small. .
[0033]
(2) The drill blades 14 at both ends of the drill bit 10 do not necessarily have the same shape. For example, the diameters of the two drill blades may be different from each other.
[0034]
(3) The centering shaft portion 19 of the drill bit 10 can be omitted as appropriate. When the centering shaft portion 19 is formed, in the above-described embodiment, the drill blade portion accommodation hole 26 of the counterpart drill bit holder 20 is also used as a centering insertion hole. And the centering insertion hole may be formed separately.
[0035]
(4) The number and shape of the locking portions (the balls 32 in the above embodiment) in the drill bit holder 20 are not particularly limited and can be set as appropriate. For example, only the inner end of the locking member (the end contacting the drill bit 10 side) may be spherical, and the portion housed in the through hole 28 may be columnar. The specific structure of the holding portion is not particularly limited, and the locking portion may be constrained to the locking position from the outside by, for example, a ring-shaped spring.
[0036]
【The invention's effect】
As described above, the present invention forms a locked portion between the drill blade portions at both ends, and forms both ends in the axial direction of the locked portion as circular portions, and the diameter of the circumscribed circle is between the circular portions. A drill bit having a polygonal or substantially polygonal cross section having a diameter equal to or less than the diameter of the circular part is provided, and a locking part of the drill bit holder is provided at a step between the irregular part of the drill bit and the rear circular part. Since the drill tool enables both the retaining of the drill bit and torque transmission to the drill bit by engaging the drill bit, the retaining of the drill bit and torque transmission are completely different parts as with conventional drill tools. Compared to what was done in the previous section, the drill bit and drill bit holder structure can be made simpler and easier to manufacture to reduce costs, and the drill bit can be centered reliably with a compact structure. There is a kill effect.
[Brief description of the drawings]
FIG. 1 is a perspective view of a drill bit according to an embodiment of the present invention.
2A is a front view of the drill bit, and FIG. 2B is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a cross-sectional front view showing an overall structure of a drill tool including the drill bit and the drill bit holder.
4A is a cross-sectional front view showing a state in which the drill bit is locked in the drill bit holder, and FIG. 4B is a cross-sectional view taken along line BB in FIG.
5A is a cross-sectional front view showing a state where the lock is released, and FIG. 5B is a cross-sectional view taken along the line CC of FIG. 5A.
FIGS. 6A, 6B, and 6C are cross-sectional side views showing modifications of the cross-sectional shape of the deformed portion of the drill bit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Drill bit 12 Locked part 14 Drill blade part 15 Flat surface 16 Deformed part 17 Level difference 18 between deformed part and rear circular part Circular part 19 Centering shaft part 20 Drill bit holder 24 Drill bit storage part 26 Drill blade part storage Hole (also used as centering insertion hole)
30 Locking part 32 Ball (Locking part)
34 Holding sleeve (holding part)

Claims (5)

A drill bit having a drill blade portion at both ends and a portion to be locked to be locked to the drill bit mounting portion between the drill blade portions and one drill blade portion of this drill bit is stored A drill tool comprising a drill bit holder having a possible circular drill storage hole and a circular insertion hole having a circular cross section into which both circular portions of the locked portion can be inserted,
Both ends in the axial direction of the locked part of the drill bit are circular parts having the same shape and larger diameter than the drill blade part, and the diameter of the circumscribed circle is the diameter of the circular part between the circular parts. It is a deformed part having a polygonal or substantially polygonal cross-sectional shape that is the following ,
From the locking position and the locking position for engaging the stepped portion of the rear circular portion and the deformed portion to prevent the drill bit from coming off and preventing rotation on the peripheral wall surrounding the insertion hole in the drill bit holder A locking portion that can move between a release position for retracting radially outward and releasing the drill bit, and a holding mechanism that can be switched between a state in which the locking portion is constrained to the locking position and a state in which the locking portion is released. A drill tool characterized by having a portion . 2. The drill tool according to claim 1, wherein the shape of the locked portion is cut off at a plurality of positions in the circumferential direction in a plane, leaving both axial end portions of a cylinder having a diameter larger than that of the drill blade portion. A drill tool characterized by its shape. According to claim 1 or 2 drilling tool according, drilling tool, characterized in that the said profiled portion with a substantially square shape. The drill tool according to any one of claims 1 to 3, wherein between each drill blade portion and the locked portion, a columnar centering having a diameter larger than that of the drill blade portion and smaller than that of the circular portion. A drill tool characterized in that a shaft portion is formed. The drill tool according to any one of claims 1 to 4, wherein a circle having a larger diameter than the drill blade and a smaller diameter than the circular portion is provided between each drill blade and the locked portion of the drill bit. While forming the columnar centering shaft portion, the drill bit holder is provided with a centering insertion hole for centering the drill bit by inserting the centering shaft portion. Drill tool to do.

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