JPS6337179Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a support device for rotatably supporting a drill bit in a hammer drill configured to perform drilling operations by the striking and rotational movements of the drill bit. The object is to provide a support device for a drill bit in a hammer drill that can securely grip the drill bit and enhance the effect of transmitting rotation to the drill bit.

An embodiment of the present invention will be described below with reference to the drawings.

A substantially cylindrical drill holder 1 rotatably supported by the body H of the hammer drill is rotationally driven via a drive mechanism (not shown) built into the body H, and the vicinity of its tip is inserted into the shaft hole 1a of the drill holder 1. It projects forward of the main body H to support the drill bit 2, which is reciprocated in the front and back direction for a striking action with a striking member (not shown) that is inserted and removed and inserted into the shaft hole 1a.

A pair of key holes 4, 4, which are opened opposite to each other near the center of the protrusion of the drill holder 1, are recessed along the axial direction near the base end of the drill bit 2, and are recessed at the front and rear ends. It has the same width as a pair of key grooves 3, 3 having curved end surfaces 3a, 3a, and has a substantially trapezoidal side cross section tapering inward, and is formed in the shape of a long hole along the axial direction. Further, on one side of the key hole 4, a recess is formed near the outer periphery of the one side, and hook portions 5, 5 are formed in a rotationally symmetrical manner, respectively.
The other side surfaces of the keyhole 4 facing both the hooking portions 5 serve as pressing surfaces 4a, 4a, respectively.

The positioning holes 6 to 6 recessed near the tip of the drill holder 1 are respectively arranged at positions dividing the circumference of the outer peripheral surface of the drill holder 1 into four equal parts.

Keys 7, 7, which are movable in the radial direction of the drill holder 1 and are fitted into both key holes 4 of the drill holder 1 in an almost tight fit, are attached to the side surfaces to prevent them from falling into the shaft hole 1a. has a substantially trapezoidal shape similar to the key hole 4, and is formed such that its inner end 7a protrudes into the shaft hole 1a, and when the drill bit 2 is inserted into the shaft hole 1a, the inner ends of both keys 7 The portions 7a are respectively engaged in the key grooves 3 of the drill bit 2, and the drill bit 2 is supported for rotation with the drill holder 1. The inner end portions 7a of both keys 7 are located at both end surfaces 3a with respect to the inside of both key grooves 3, respectively.
The drill bit 2 is fitted in such a manner that a clearance is formed between the drill bit 2 and the drill bit 2 to allow the drill bit 2 to move back and forth, thereby transmitting rotational motion and striking motion to the drill bit 2.

Protrusions 7b, 7b, which are approximately crescent-shaped in the front and are provided on one side of both keys 7, respectively, prevent the key 7 from moving into the shaft hole 1a when the key 7 tilts within the key hole 4 when inserting or removing the drill bit 2. In order to prevent the key 7 from falling off and to maintain the fitted position of the key 7, the two locking parts 5 are disposed opposite to each other so as to be able to come into contact with both hooking parts 5 of the drill holder 1.

A substantially cylindrical chain ring 8 is slidably fitted onto the outside of the drill holder 1, and a ring-shaped chain ring 8 is inserted into a through hole 8a that is penetrated near the tip of the chain ring 8, facing the positioning hole 6 of the drill holder 1. spring 9
A spherical lock member 10 biased inwardly is removably fitted into each positioning hole 6, while a drill bit 2 is inserted into the shaft hole 1a of the drill holder 1 on the inner peripheral surface of the change ring 8. In order to allow the key 7 to move in the radial direction when it is inserted or removed from the keyway 3, relief parts 8b, 8b are recessed to face each other, and the change ring 8 is rotated 90 degrees at a time. When the lock member 10 is rotated and engaged with each positioning hole 6, the change ring 8 is moved to a position where both relief portions 8b are opposite to both keys 7 (see Fig. 4), or both relief portions 8b are positioned opposite to both keys 7. It can be selectively locked at a position rotated by 90 degrees with respect to 7 (see Fig. 3), and when both relief parts 8b are retracted from both keys 7, both keys 7 are locked between both change ring 8 and drill bit 2. While being held between the key groove 3,
When both escape portions 8b are opposed to both keys 7, the drill bit 2 can be inserted into and removed from the shaft hole 1a of the drill holder 1.

Cover member 11 fitted onto change ring 8
is formed of a rubber material or the like into a substantially grooved cylindrical shape.

Next, the operation and effects of the embodiment having the above configuration will be explained.

Now, in this example, a pair of keyholes 4 having the same width as the keyway 3 of the drill bit 2 are provided in the drill holder 1, and in both keyholes 4 there are holes for transmitting the rotation of the drill holder 1 to the drill bit 2. A pair of keys 7 whose inner ends 7a are inserted into the keyway 3 are fitted so as to be movable in the radial direction of the drill holder 1 and detachable from the keyway 3. is a relief portion 8 that allows movement of the key 7 in the radial direction.
A change ring 8, which is recessed in the inner circumferential surface, is rotatably fitted onto the outside.

Therefore, by simply rotating the change ring 8, it is possible to easily change the state in which the drill bit 2 is locked to the drill holder 1 and the state in which the drill bit 2 can be attached to and removed from the drill holder 1.
This has the effect of simplifying and smoothing the operation of attaching and detaching the drill bit 2 to the drill holder 1.

Furthermore, when the drill bit 2 is inserted into the shaft hole 1a of the drill holder 1, the drill bit 2 is reliably and stably supported to the drill holder 1 via both keys 7, and the rotation of the drill holder 1 is controlled in both directions relative to the drill bit 2. The information can be reliably transmitted via the key 7.

In particular, the rotational torque of the drill holder 1 is transmitted to the key 7 via the pressing surface 4a of the key hole 4, and is further transmitted to the drill bit 2 via the side surface of the key 7 and the side surface of the keyway 3, so that the rotational torque of the drill holder 1 is transmitted in the pressing direction. Because the rotation is transmitted through a pressing surface and a pressure receiving surface that are perpendicular to each other and in close surface contact with each other, there is no possibility of bite between the members due to local concentration of pressing force during rotation transmission or improper pressing direction. This has the effect of significantly increasing the effect of transmitting rotation to the drill bit 2 by eliminating jamming and twisting.

That is, in the present invention, a substantially cylindrical drill holder rotatably supported by the body of a hammer drill is provided with a keyhole having the same width as the keyway formed in the drill bit that is inserted into and removed from the shaft hole of the drill holder. established,
A key is inserted into the key hole and is movable in the radial direction of the drill holder. A change ring is fitted to the drill holder so as to be removable from the groove, and a change ring is rotatably fitted to the drill holder, and the drill ring has a relief part recessed in the inner peripheral surface to allow movement of the key in the radial direction. By rotating the change ring, it is possible to easily change the state in which the drill bit is locked to the drill holder and the state in which the drill bit can be attached to and removed from the drill holder. This has the effect of simplifying and smoothing the operation of attaching and detaching the drill bit.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a side sectional view of the support device, FIG. XX cross-sectional view, Figure 4 is Y- in Figure 2.
FIG. 5 is a sectional view taken along the Z--Z line in FIG. 1. 1... Drill holder, 1a... Shaft hole, 2... Drill bit, 3... Keyway, 4... Key hole, 7...
...Key, 8...Change ring.

Claims (1)

[Scope of utility model registration request] A nearly cylindrical drill holder rotatably supported by the body of the hammer drill has a keyhole with the same width as the keyway in the drill bit that is inserted into and removed from the shaft hole of the drill holder. A key for transmitting the rotation of the drill holder to the drill bit is fitted in the hole so as to be movable in the radial direction of the drill holder and engageable with and detachable from the key groove, and 1. A support device for a drill bit in a hammer drill, characterized in that a change ring having an inner circumference recessed with a recess for allowing movement of the key in a radial direction is rotatably fitted onto the outside.