JP2991976B2 - Core drill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core drill for drilling a large-diameter hole, and more particularly, to a method in which a center drill is preceded by a center drill, and thereafter a large-diameter hole concentric with the center hole is drilled by a core body. More particularly, the present invention relates to a core drill suitable for drilling a large-diameter hole in concrete or the like by using a rotary hammer drill.

[0002]

2. Description of the Related Art Conventionally, various types of drills for drilling large-diameter holes have been developed and marketed. In order to smoothly perform such a large-diameter hole drilling operation, a center drill is combined with a cylindrical core body having a drilling blade formed at a lower end edge thereof. A core drill having a configuration in which a large-diameter hole is formed later by a core body is widely used.

[0003] In this type of core drill, a configuration is usually adopted in which a center drill and a core body are separately provided and these are detachably attached to a base having a shank. A configuration in which the upper end of the center drill is inserted into a drill mounting hole provided at the center of the lower surface of the, and a set screw is screwed to the base, and the tip is pressed against a flat holding surface formed on the upper surface of the center drill and fixed. There are many things.

In such a configuration in which the center drill is fixed to the base with the set screw, a tool for loosely tightening the set screw is required for attaching and detaching the center drill. Also, when a large diameter hole is drilled in concrete or masonry, etc. using a rotary hammer drill, in a configuration where the center drill is fixed to the base with set screws, the center drill is directly connected to the center drill from the base side. Because it is a perforation that simultaneously gives both effects of vibrational striking force in the center direction and rotational torque,
The set screw may become loose during drilling.

[0005]

SUMMARY OF THE INVENTION Accordingly, the present invention relates to a method of engaging and disengaging an engagement projection projecting from a wall of a drill mounting hole of a base with an engagement groove provided at an upper end portion of a center drill under the bias of a spring. It is intended to provide a core drill that can be attached and detached to the base in a simple operation without using a tool by a simple operation to be performed, and that does not have trouble such as loosening of the set screw when used for a rotary hammer drill. It is.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a base having a shank on an upper portion is provided with a center drill and a drilling blade on a lower edge. A cylindrical core body is attached to the bottom of the base.
Push the center drill into the bottom of the drill mounting hole
In a core drill provided with a spring for biasing in a dispensing direction, an engagement protrusion is provided on a wall of the drill mounting hole, and a guide groove is formed on a peripheral surface of an upper end portion of the center drill corresponding to the engagement protrusion.
Is formed in a hook shape with a vertical groove portion and a horizontal groove portion, and is formed in a horizontal groove portion of the guide groove.
A long groove-shaped engagement groove is continuously provided in a T-shape in the generatrix direction.
Spring accommodation with a stepped spring at the bottom of the drill mounting hole
Housed in the hole and pushed the center drill against the spring
Sometimes the upper end of the center drill contacts the bottom of the drill mounting hole.
And the engaging projection is located at the middle of the engaging groove .

Here, in attaching the core body to the base,
A well-known screw connection structure in which a male screw portion provided at the lower part of the base is screwed into a female screw hole provided at the center of the top of the core body.

When the center drill is attached to the base, the engaging projection projecting from the wall of the drill mounting hole provided at the center of the lower surface of the base is provided for the drill mounting hole in the base. A bottom hole is provided, the bottom of the hole with respect to the mounting hole is appropriately formed, and the bottom of the hole is extruded from the outside of the base to the side of the mounting hole, so that the engagement projection can be formed in a spherical shape. With this configuration, the engaging projection can be formed by processing a part of the base, so that there is no loosening structure like a set screw, and the number of parts can be reduced, and the workability is excellent. .

The spring for biasing the center drill in the pushing direction is provided with a stepped spring receiving hole at the bottom of the drill mounting hole and is accommodated in the spring receiving hole. In the fully extended state, a part (lower end) of the spring is projected into the drill mounting hole. And as for the strength of this spring, when you hold the center drill in your hand and insert the upper end into the drill mounting hole,
It should be strong enough to be reduced by being pushed by hand.

Further, the guide groove provided on the peripheral surface of the upper end portion of the center drill and the engagement groove continuous with the guide groove are both formed in an arc-shaped cross section corresponding to the engagement protrusion, so that the engagement protrusion is free. The upper end of the vertical groove portion of the guide groove reaches the upper end of the center drill so that the engaging projection can come and go. Then, at the time of drilling, the engaging projections engage with the engaging grooves to transmit the rotational torque from the base to the center drill.

The center drill is attached to and detached from the base body by holding the center drill and inserting the upper end of the center drill into the drill mounting hole under the bias of a spring. When attaching the center drill to the base, push the center drill against the spring and rotate the center drill when the engaging projection reaches the end of the vertical groove of the guide groove to disengage the engaging projection from the lateral groove. Move to the groove. Here, when the center drill is released, the center drill is pushed out by the force of the spring, and the engagement projection is settled on the upper end of the engagement groove under the bias of the spring (normal position). Is separated from the bottom of the drill mounting hole, and the engaging projection on the base side is accommodated in the upper part of the engaging groove of the center drill and does not come off.

In the above configuration, in the drilling operation,
The center drill is pushed in against the spring and
The upper end of the rill comes into contact with the bottom of the drill mounting hole, and the rotation torque from the base side to the center drill is transmitted from the engagement projection via the engagement groove, and the hole is drilled. The striking force is transmitted through the upper end of the center drill which is in contact with the bottom of the drill mounting hole. At this time, the engaging projection is located between the engaging grooves.
And the striking force from the base side is
It is not transmitted to the center drill from the lower end of the engaging groove
Things.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

In the drawings, FIG. 1 is a front view of a core drill according to the present invention with a part thereof removed, FIG. 2 is an enlarged sectional view of a main part, FIG. 3 is a front view and a plan view in which an upper end of a center drill is enlarged, 4 is an enlarged cross-sectional view of a main part in a state where a center drill is attached to a base body, and FIG. 5 is an enlarged cross-sectional view of a main part in a state in which the upper end of the center drill in FIG. 4 is in contact with the bottom of a drill mounting hole.

In the figures, 1 is a base, 2 is a core body, and 3 is a center drill.

The base 1 has a shank 4 supported by a chuck of a drive shaft at the center of the upper surface. To attach the core body 2 to the base 1, a male screw portion 5 provided at the lower part of the base is attached to the core body 2. Is screwed into a female screw hole 6 provided at the center of the top plate. The core body 2 has a cylindrical shape,
It has a well-known configuration in which a perforated blade 7 is provided at the lower edge.

To mount the center drill 3 on the base 1, a drill mounting hole 8 is provided at the center of the lower surface of the base 1, and an engaging projection 9 is projected from the wall of the drill mounting hole 8. In this embodiment, a bottomed hole 10 is provided as the engagement projection 9 leaving a hole bottom having an appropriate thickness for the drill mounting hole 8, and the bottom of the hole is extruded in a manner of driving a sharp end pin into the mounting hole 8 side. Thus, the engagement projection 9 is formed in a spherical shape. in this way,
When the engaging projections 9 are formed by processing the base 1, there is no configuration that is loosened like a set screw, and the number of parts can be reduced, resulting in excellent workability.

On the peripheral surface of the upper end portion of the center drill 3 corresponding to the engagement projection 9, an engagement groove 12 having a long groove shape is provided in the generatrix direction continuously with the hook-shaped guide groove 11. Both the guide groove 11 and the engagement groove 12 allow the engagement protrusion 9 to move freely. The guide groove 11 is formed around the lower end of the vertical groove 11a in the generatrix direction whose upper end reaches the upper end of the center drill 3. A horizontal groove 11b is formed in the direction, and is formed in a hook shape, and is continuous with the horizontal groove 11b in a T-shape in the middle of the engaging groove 12.

A spring 13 for biasing the center drill 3 in the pushing direction is provided at the bottom of the drill mounting hole 8. The spring 13 is provided with a stepped spring accommodation hole 14 having a smaller diameter than the drill attachment hole 8 at the hole bottom 8 a of the drill attachment hole 8, and is accommodated in the spring accommodation hole 14 so as to be expandable and contractible. In the state in which is fully extended, a part (lower end) of the spring 13 is projected into the drill mounting hole 8. Also,
The strength of the spring 13 is set to such a level that the center drill 3 can be contracted and pushed by hand when the upper end thereof is inserted into the drill mounting hole 8 while being held by the hand.

In the above configuration, in order to attach the center drill 3 to the base 1, the upper end of the center drill 3 is inserted into the drill mounting hole 8, pushed in and turned, and the engagement projection 9 is turned.
Is moved from the guide groove 11 to the engagement groove 12, and the center drill 3 is released. In this case, the center drill 3 is
, The engaging projection 9 is engaged with the upper end of the engaging groove 12, and the center drill 3 is attached.

In order to remove the center drill 3 from the base body 1, the center drill 3 is pushed against the spring 13 by applying a force to rotate the two in a direction opposite to the drilling rotation direction. Thereafter, the engaging projection 9 is moved to the guide groove 11 in the reverse order, and the center drill 3 is removed.

When the center drill 3 is attached to the base 1 and drilled, the rotation torque from the base 1 to the center drill 3 is transmitted from the engaging projection 9 through the engaging groove 11, and The force is transmitted when the upper end of the center drill 3 abuts on the bottom 8 a of the drill mounting hole 8. Further, since the center drill 3 is always urged in the pushing direction due to the presence of the spring 13, the backlash of the center drill 3 can be prevented, and the effect of preventing noise from this surface can be expected.

[0023]

The present invention is embodied in the form as described above, and according to the present invention, the engaging projection projecting from the wall of the drill mounting hole of the base is attached to the upper end of the center drill under the bias of the spring. The center drill can be attached to and detached from the base in a single operation by a simple operation of engaging and disengaging through the guide groove to the long groove-shaped engaging groove provided in the part, as in the case of attaching and detaching the center drill using the conventional set screw. Simple tools are not required, and handling is simplified. When drilling, the center drill must be
The upper end of the drill
Since it abuts, it is particularly suitable for drilling a large diameter hole in concrete or the like by using a rotary hammer drill.

Further, since the engaging projection protruding from the wall of the drill mounting hole can be easily provided by partially processing the base, the structure can be simplified, the number of parts can be reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a core drill according to the present invention, with a part removed.

FIG. 2 is an enlarged sectional view of a main part of the core drill of the present invention.

FIG. 3 is an enlarged front view and a plan view of an upper end portion of a center drill.

FIG. 4 is an enlarged sectional view of a main part in a state where a center drill is attached to a base.

FIG. 5 is an enlarged sectional view of a main part in a state where the upper end of the center drill is in contact with the bottom of the drill mounting hole in FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base body 2 ... Core body 3 ... Center drill 4 ... Shank 5 ... Male thread part 6 ... Female thread part 7 ... Drilling blade 8 ... Drill mounting hole 8a ... Hole bottom of drill mounting hole 9 ... Engagement protrusion 10 ... Existence Bottom hole 11 Guide groove 11a Vertical groove 11b Horizontal groove 12 Engagement groove 13 Spring 14 Spring receiving hole

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B23B 51/04 B28D 1/14

Claims (2)

(57) [Claims] 1. A base having a shank on an upper part, a center drill and a cylindrical core body having a drilling blade on a lower end edge thereof are attached, and a bottom of a drill mounting hole provided in the center of the lower surface of the base.
A spring that urges the center drill in the pushing direction.
In the core drill provided, an engaging projection is provided on the wall of the drill mounting hole, and a guide groove is formed in a vertical groove and a lateral groove in a hook shape on a peripheral surface of an upper end portion of the center drill corresponding to the engaging projection.
And a long groove-like shape in the generatrix direction continuous with the lateral groove portion of the guide groove.
An engagement groove is provided in a T-shape, and the spring is attached to the bottom of the drill mounting hole.
It is housed in a spring housing hole provided with a step on the center drill.
When the center drill is pressed in against the spring.
Abut on the bottom of the mounting hole, and place the engaging protrusion in the middle of the engaging groove.
Core drill characterized by being located . 2. The core drill according to claim 1, wherein a bottomed hole is provided on the base for the drill mounting hole, and the bottom of the hole is extruded toward the mounting hole to form an engagement protrusion in a spherical shape.