U.S. patent application number 09/733895 was filed with the patent office on 2001-08-23 for circular hole cutting devices.
Invention is credited to Ajimi, Kunio, Uemura, Akihito.
Application Number | 20010016152 09/733895 |
Document ID | / |
Family ID | 26585683 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010016152 |
Kind Code |
A1 |
Ajimi, Kunio ; et
al. |
August 23, 2001 |
Circular hole cutting devices
Abstract
A circular hole cutting device (1) for making a circular hole in
an object comprises a bit holder (3) which can be attached to a
drive shaft of an electric power tool in such a way that the bit
holder (3) with a bit (2) attached to a far end of the bit holder
(3) rotates together with the drive shaft on a common axis, a cover
(4) which is fitted to the bit holder (3) relatively rotatably
about its axis, and a radial rod (5) attached to the cover (4) such
that the amount of projection of the radial rod (5) in a direction
intersecting the bit (2) can be varied. The physical size of the
cover (4) is determined such that the bit (2) projects from a far
end of the cover (4). The radial rod (5) has a pivot shaft (52)
having a pointed end formed by bending a terminal part of the
radial rod (5) approximately at right angles.
Inventors: |
Ajimi, Kunio;
(Higashiosaka-shi, JP) ; Uemura, Akihito;
(Kasugai-shi, JP) |
Correspondence
Address: |
Smith Patent Office
Suite 200
1901 Pennsylvania Ave., N.W.
Washington
DC
20006
US
|
Family ID: |
26585683 |
Appl. No.: |
09/733895 |
Filed: |
December 12, 2000 |
Current U.S.
Class: |
409/179 ;
30/310 |
Current CPC
Class: |
B23B 51/05 20130101;
Y10T 409/30644 20150115 |
Class at
Publication: |
409/179 ;
30/310 |
International
Class: |
B23C 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 2000 |
JP |
2000-41598(PAT.) |
Jul 19, 2000 |
JP |
2000-219284(PAT.) |
Claims
What is claimed is:
1. A circular hole cutting device which makes a circular hole in an
object when turned about a center hole formed in the object, said
circular hole cutting device comprising: a bit holder adapted for
being attached to a drive shaft of an electric power tool in such a
way that the bit holder with a bit attached to a far end rotates
together with the drive shaft on a common axis; and a relatively
rotatable part fitted to the bit holder and relatively rotatable
about the axis of the drive shaft, the relatively rotatable part
having a pivot shaft which is located at a position offset from the
bit in its radial direction and can be inserted into said center
hole formed by the bit.
2. A circular hole cutting device according to claim 1, wherein
said relatively rotatable part has a contact portion which goes
into contact with a surface to be worked of the object.
3. A circular hole cutting device according to claim 2, wherein
said relatively rotatable part is constructed such that the
position of its contact portion can be adjusted in an axial
direction.
4. A circular hole cutting device according to claim 1, wherein
said relatively rotatable part is formed with a cavity which
receives chips cut by said bit is formed.
5. A circular hole cutting device according to claim 1, wherein
said relatively rotatable part is provided with a radial member
which extends parallel to a radial direction of said bit and has
said pivot shaft at a far end.
6. A circular hole cutting device according to claim 5, wherein
said radial member is constructed to allow adjustment of the
distance from its pivot shaft to the bit.
7. A circular hole cutting device according to claim 1, wherein
said relatively rotatable part is provided with a plurality of
radial members each of which extends parallel to a radial direction
of said bit when fitted to said relatively rotatable part and has
said pivot shaft at a far end, said radial members allowing a
choice of different distances from the pivot shaft to the bit.
8. A circular hole cutting device according to claim 1, further
comprising a bearing which is fitted between said bit holder and
said relatively rotatable part.
9. A circular hole cutting device according to claim 1, wherein
said relatively rotatable part includes a cover having a peripheral
wall and an internal cavity which receives chips cut by said bit
and a radial member fitted to the cover, wherein said radial member
has at its far end said pivot shaft extending parallel to said bit
and is fitted to the cover in such a way that the distance from the
pivot shaft to the bit can be adjusted, and said peripheral wall is
formed with a cutout which makes it possible to retract the pivot
shaft into the cavity of the cover.
10. A circular hole cutting device according to claim 9, wherein
said cover includes a first cylindrical part in which said cavity
and said cutout are formed and a second cylindrical part which is
detachably fitted to the first cylindrical part in such a way that
the second cylindrical part covers at least part of said
cutout.
11. A circular hole cutting device according to claim 10, wherein
said second cylindrical part has a contact portion which goes into
contact with a surface to be worked of the object, and is mounted
on the first cylindrical part such that the position of the contact
portion can be adjusted in an axial direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to circular hole cutting
devices which are used for making holes for passing electric wires
or water pipes, for instance, in ceilings, walls or floors in a
building or house.
[0003] 2. Description of the Background Art
[0004] FIG. 14 shows an example of a conventionally known circular
hole cutting device 100. This circular hole cutting device 100
comprises a cylindrical attachment 101, a guide rod 102 passing
through the cylindrical attachment 101 at right angles to but at a
slight distance from its central axis, and a stopper 103 which is
screwed into a curved wall of the cylindrical attachment 101 at
right angles to the guide rod 102 in such a way that an extreme end
of the stopper 103 comes into contact with the guide rod 102.
[0005] The cylindrical attachment 101 is securely attached to an
electric power tool 105 as one end of the cylindrical attachment
101 is fitted over a far end of the electric power tool 105 as
illustrated. A bit 104 which is turned at high speeds about a
central axis of the electric power tool 105 is detachably fitted to
its far end. The physical size of the cylindrical attachment 101 is
determined such that the bit 104 protrudes to the outside of the
cylindrical attachment 101 when the cylindrical attachment 101 is
mounted on the electric power tool 105.
[0006] The guide rod 102 has a pivot shaft 102a at one end formed
by bending a terminal part of the guide rod 102 at right angles to
its main part. The extreme end of the pivot shaft 102a is sharply
pointed.
[0007] The circular hole cutting device 100 thus constructed is
used as follows. First, a small center hole is made by the bit 104
at the center of a circular hole to be formed in a ceiling, for
instance, operating the electric power tool 105. Then, with the
pivot shaft 102a fitted into the center hole, the electric power
tool 105 is turned about the pivot shaft 102a while turning the bit
104 at a high speed. As the bit 104 moves in a circle all around
the pivot shaft 102a, the ceiling is cut by the bit 104 so that the
circular hole for passing an electric wire or a water pipe, for
instance, is made therein.
[0008] In the conventional circular hole cutting device 100, the
cylindrical attachment 101 is mounted on the electric power tool
105 as described above. It is to be noted, however, that different
types of electric power tools have different shapes. Accordingly,
one problem of the conventional circular hole cutting device 100 is
that it lacks flexibility in use due to the need to prepare various
cylindrical attachments specially designed for use with different
types of electric power tools.
[0009] Furthermore, when turning the electric power tool 105 about
the pivot shaft 102a, it is necessary to continuously turn the
electric power tool 105 about its own axis so that an operator has
to change his or her working posture. This poses another problem of
the conventional circular hole cutting device 100 that it involves
low labor efficiency.
SUMMARY OF THE INVENTION
[0010] This invention is intended to solve the aforementioned
problems of the prior art. It is therefore an object of the
invention to provide a circular hole cutting device featuring high
flexibility in use with adaptability to various types of power
tools and ease of operation.
[0011] According to a principal feature of the invention, a
circular hole cutting device which makes a circular hole in an
object when turned about a center hole formed in the object
comprises a bit holder which can be attached to a drive shaft of an
electric power tool in such a way that the bit holder with a bit
attached to a far end rotates together with the drive shaft on a
common axis, a relatively rotatable part fitted to the bit holder
relatively rotatably about the axis of the drive shaft, and a pivot
shaft which can be inserted into the center hole formed by the bit,
wherein the pivot shaft connected to the relatively rotatable part
is located at a position offset from the bit in its radial
direction.
[0012] With this circular hole cutting device, it is possible to
form a circular hole whose radius corresponds to the distance
between the bit and the pivot shaft in the object by inserting the
pivot shaft in the center hole, activating the electric power tool
to turn the bit at a high speed, and slowly turning the electric
power tool about the pivot shaft with the bit passing through the
object so that the bit turning at the high speed cuts the object
along a circular path.
[0013] The drive shaft of the electric power tool usually has a
chuck complying with industrially standardized dimensional
specifications. Therefore, the circular hole cutting device of this
invention can be connected to practically any electric power tool
regardless of its manufacturer or type, so that the circular hole
cutting device provides great flexibility in application.
[0014] Furthermore, since the relatively rotatable part and the bit
holder are connected relatively rotatably with each other, the
relatively rotatable part does not rotate together with the drive
shaft of the electric power tool even when the relatively rotatable
part is turned about the pivot shaft. Accordingly, it is not
necessary for an operator to change his or her working posture to
turn the circular hole cutting device about its own axis when
making a hole in a ceiling, for instance. This would help increase
labor efficiency in hole-cutting operation.
[0015] These and other objects, features and advantages of the
invention will become more readily apparent from the following
description and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a partially cutaway exploded perspective diagram
showing a circular hole cutting device according to a first
embodiment of the invention;
[0017] FIG. 2 is a partially cutaway perspective assembly diagram
of the circular hole cutting device of FIG. 1;
[0018] FIG. 3 is a cross-sectional diagram taken along lines 3-3 of
FIG. 2;
[0019] FIG. 4 is a cross-sectional diagram taken along lines 4-4 of
FIG. 2;
[0020] FIG. 5A is a diagram showing a radial rod whose effective
length is variable;
[0021] FIG. 5B is a diagram showing radial rods whose effective
lengths are fixed;
[0022] FIG. 6A is a side view showing a state where a center hole
has just been made at the center of a hole to be formed in a
ceiling by turning a bit;
[0023] FIG. 6B is a side view showing a state where a pivot shaft
of the radial rod has been fitted into the center hole;
[0024] FIG. 7A is a perspective view showing a state where the hole
is being cut in the ceiling by turning the circular hole cutting
device clockwise about the pivot shaft;
[0025] FIG. 7B is a perspective view showing a state where the hole
has just been cut in the ceiling by turning the circular hole
cutting device all around the pivot shaft;
[0026] FIG. 8 is a perspective view showing an example of a hole
formed in a board using a combination bit;
[0027] FIG. 9 is an exploded perspective view showing a circular
hole cutting device according to a second embodiment of the
invention;
[0028] FIG. 10 is a perspective assembly diagram of the circular
hole cutting device of FIG. 9;
[0029] FIG. 11 is a view of the circular hole cutting device taken
in the direction of arrow D of FIG. 10;
[0030] FIG. 12 is a bottom view showing a circular hole cutting
device according to a third embodiment of the invention;
[0031] FIG. 13 is a cross-sectional diagram taken along lines 13-13
of FIG. 12; and
[0032] FIG. 14 is a perspective view of a conventionally known
circular hole cutting device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
[0033] FIG. 1 is a partially cutaway exploded perspective diagram
showing a circular hole cutting device 1 according to a first
embodiment of the invention, FIG. 2 is a partially cutaway
perspective assembly diagram of the circular hole cutting device 1
of FIG. 1, FIG. 3 is a cross-sectional diagram taken along lines
3-3 of FIG. 2, and FIG. 4 is a cross-sectional diagram taken along
lines 4-4 of FIG. 2. As depicted in these Figures, the circular
hole cutting device 1 is a tool for making circular holes in an
object like a ceiling or a wall (hereinafter represented by the
ceiling as a typical object in which the holes are to be made) for
passing electric wires or installing lighting fixtures.
[0034] The circular hole cutting device 1 comprises in its basic
construction a bit 2 having cutting blades, such as an end mill or
a router bit, a bit holder 3 which can be attached to a drive shaft
D1 of an electric power tool D in such a way that the bit holder 3
with the bit 2 attached to a far end of the bit holder 3 rotates
together with the drive shaft D1 on a common axis, a cover
(relatively rotatable part) 4 which is fitted to the bit holder 3
and is relatively rotatable about its axis, and a radial rod
(radial member) 5 attached to the cover 4 such that the amount of
projection of the radial rod 5 in a direction intersecting the bit
2 can be varied.
[0035] In one alternative arrangement, a combination bit 2a having
a straight bit portion 21 and a spot facing portion 22 provided
between the straight bit portion 21 and a shank may be used instead
of the bit 2, the spot facing portion 22 having a cylindrical shape
whose diameter is larger than that of the straight bit portion 21.
The combination bit 2a thus constructed is convenient when making a
hole of a later-described type because it makes it possible to
simultaneously cut a peripheral edge of the hole to make spot
facing.
[0036] The bit holder 3 is constructed of a generally cylindrical
bit-holding part 31 having a stepped stage in longitudinal cross
section and a connecting shaft 34 detachably connected to a rear
end of the bit-holding part 31 such that they are aligned on a
common axis. The bit-holding part 31 has a large-diameter portion
32 provided immediately adjacent to the rear end of the bit-holding
part 31 and a small-diameter portion 33 concentrically extending
from a forward end of the large-diameter portion 32. A bearing B is
fitted around a rear end (right end as illustrated in FIG. 3) of
the small-diameter portion 33. The bearing B is located between the
bit-holding part 31 and the cover 4. When a force pushing the
bearing B toward the large-diameter portion 32 is exerted via the
cover 4, the bearing B is prevented from moving onto the
large-diameter portion 32 since the bearing B is pressed against
the stepped stage between the small-diameter portion 33 and the
large-diameter portion 32.
[0037] The bit-holding part 31 has a bit-fitting hole 33a formed
concentrically in a far end surface of the bit-holding part 31 as
well as a screw hole 33b tapped from a curved outer surface of the
small-diameter portion 33 all the way to the bit-fitting hole 33a.
The bit 2 is fixed to the bit-holding part 31 as a shank of the bit
2 is inserted into the bit-fitting hole 33a and a set screw 33c is
screwed into the screw hole 33b so that an extreme end of the set
screw 33c pushes tightly against a peripheral surface of the bit
2.
[0038] A screw hole 32a for attaching the connecting shaft 34 is
formed in a rear end surface (right side as illustrated in FIG. 1)
of the large-diameter portion 32 concentrically around a
longitudinal axis of the bit-holding part 31.
[0039] The connecting shaft 34 is formed of a main shaft portion 35
which is linked to the drive shaft D1 of the electric power tool D
(FIG. 2), a flange 36 provided at a forward end (left side as
illustrated in FIG. 1) of the main shaft portion 35, and an
externally threaded part 37 projecting forward from the flange 36
on a common axis. The connecting shaft 34 is joined to the
bit-holding part 31 as the externally threaded part 37 is screwed
tightly into the screw hole 32a.
[0040] The main shaft portion 35 has three straight flutes 35a
grooved in a peripheral surface of the main shaft portion 35 all
the way along its longitudinal axis at equal angular intervals
around its circumference. On the other hand, the electric power
tool D is provided with a chuck D2 having three jaws at a far end
of the drive shaft D1. The flutes 35a of the main shaft portion 35
are fitted onto the jaws of the chuck D2 and the main shaft portion
35 is fastened by making a specific action, whereby the connecting
shaft 34 is connected to the drive shaft D1.
[0041] The cover 4 is constructed of a first cylindrical part 41
having a closed end and a second cylindrical part 42 slidably
fitted over the first cylindrical part 41. The second cylindrical
part 42 is enables adjustment of a contact area between the first
cylindrical part 41 and the second cylindrical part 42 in their
axial direction. The first cylindrical part 41 is formed of a
cylindrical wall 41a and a bottom plate 41b which closes one end of
the cylindrical wall 41a. In the illustrated example, the inner
diameter of the cylindrical wall 41a is made approximately three
times larger than the outer diameter of the bit-holding part 31 and
the length of the cylindrical wall 41a is made slightly smaller
than the length of the small-diameter portion 33 of the bit-holding
part 31. A space surrounded by the cylindrical wall 41a and the
bottom plate 41b constitutes a chip retaining space 40 for
capturing and retaining chips cut by the bit 2.
[0042] A through hole 41c whose diameter is slightly larger than
the outer diameter of the small-diameter portion 33 of the
bit-holding part 31 is made in the bottom plate 41b of the cover 4
at its center, the through hole 41c being located concentrically
with respect to the bit-holding part 31. A bearing-fitting hole 41d
whose diameter is larger than the diameter of the through hole 41c
is formed on the outside of the through hole 41c. When the
bearing-fitting hole 41d is fitted over the bearing B which has
been force-fitted to the rear end of the small-diameter portion 33
of the bit-holding part 31, the first cylindrical part 41 is fitted
on the bit-holding part 31.
[0043] There is formed a circular groove 41e in an appropriate
position of an inner surface of the bearing-fitting hole 41d all
the way along its circumference. A C-ring 43 is fitted into the
circular groove 41e with the bearing-fitting hole 41d fitted over
the bearing B, whereby the first cylindrical part 41 fitted onto
the bit-holding part 31 is prohibited from coming off.
[0044] A rod-passing hole 41f for fitting the radial rod 5 is
formed in the bottom plate 41b of the first cylindrical part 41.
The rod-passing hole 41f passes through the bottom plate 41b across
the first cylindrical part 41 without intersecting the
bearing-fitting hole 41d. Further, a first screw hole 41g is formed
in the bottom plate 41b in its radial direction at right angles to
the rod-passing hole 41f, the first screw hole 41g passing from a
curved outer surface of the first cylindrical part 41 (bottom plate
41b) into the rod-passing hole 41f. A first fixing part 44 is
screwed into the first screw hole 41g.
[0045] The first fixing part 44 is made of a generally disk-like
knob 44a and a fixing screw 44b having a pointed tip and projecting
from the center of an inside surface of the knob 44a. When the
fixing screw 44b is screwed into the first screw hole 41g with the
radial rod 5 inserted into the rod-passing hole 41f, the pointed
tip of the fixing screw 44b goes into contact with the radial rod
5, forcing the radial rod 5 inward. As a consequence, the radial
rod 5 is prevented from sliding along the rod-passing hole 41f and
set in a fixed position.
[0046] A second screw hole 41h opening into the rod-passing hole
41f is formed in an outer flat surface of the bottom plate 41b. The
second screw hole 41h accommodates a click mechanism 45 which is
provided to produce a click, or tactile response, when the radial
rod 5 is slid across the first cylindrical part 41. The click
mechanism 45 includes a set screw 45a which is screwed into the
second screw hole 41h, a coil spring 45b pushed into the second
screw hole 41h by the set screw 45a, and a steel ball 45c located
between the coil spring 45b and the radial rod 5.
[0047] When the click mechanism 45 is fitted in the second screw
hole 41h, the steel ball 45c is forced against the radial rod 5 by
a pushing force exerted by the coil spring 45b. When the radial rod
5 is slid across the first cylindrical part 41, the steel ball 45c
drops into later-described click-producing indentations 54 (FIG. 4)
which are formed in a sliding arm 51 of the radial rod 5. This
action of the steel ball 45c produces clicks which are perceptible
by an operator.
[0048] When cutting a hole with the circular hole cutting device 1,
a far end surface (contact portion) 42b of the second cylindrical
part 42 is held in contact with the surface of an object in which
the hole is to be made. A slot 42a is formed in a cylindrical wall
of the second cylindrical part 42 at its appropriate position. The
slot 42a extends parallel to the axial direction of the second
cylindrical part 42. A third screw hole 41i is formed in the
cylindrical wall 41a of the first cylindrical part 41 at a position
corresponding to the slot 42a in the cylindrical wall of the second
cylindrical part 42. The third screw hole 41i and the slot 42a are
used for fitting a second fixing part 46 to the cover 4.
[0049] The second fixing part 46 is made of a generally disk-like
knob 46a and a fixing screw 46b projecting from the center of an
inside surface of the knob 46a. The second fixing part 46 is fixed
to the cover 4 when the fixing screw 46b is tightly screwed into
the third screw hole 41i through the slot 42a. When the second
fixing part 46 is loosened, the second cylindrical part 42 can be
moved in its axial direction relative to the first cylindrical part
41 as much as the length of the slot 42a. This makes it possible to
adjust the amount of projection of the second cylindrical part 42
from the first cylindrical part 41.
[0050] If the fixing screw 46b is screwed into the third screw hole
41i by turning the knob 46a after the amount of projection of the
second cylindrical part 42 has been properly set, the knob 46a goes
into contact with a curved outer surface of the second cylindrical
part 42, whereby the set amount of projection of the second
cylindrical part 42 is fixed.
[0051] Although the knob 44a of the first fixing part 44 and the
knob 46a of the second fixing part 46 for fixing the radial rod 5
and the second cylindrical part 42, respectively, have a generally
star-shaped structure in the present embodiment, wing nuts having
wing-like projections may be employed instead of the knobs 44a,
46a.
[0052] The radial rod 5 has approximately the same diameter as the
bit 2. One end of the radial rod 5 is bent at right angles to the
sliding arm 51. This bent portion extending from the sliding arm 51
constitutes a pivot shaft 52. The length of the pivot shaft 52 is
made larger than the distance between a far end of the cover 4 and
the sliding arm 51 when the second cylindrical part 42 is most
extended from the first cylindrical part 41.
[0053] As can be seen from FIG. 4, the aforementioned multiple
click-producing indentations 54 are formed in a curved outer
surface of the sliding arm 51 in a radial direction opposite to the
direction in which the pivot shaft 52 extends in such a way that
each of the click-producing indentations 54 would align with the
second screw hole 41h when the radial rod 5 is slid across the
first cylindrical part 41. Further, a plurality of rod-fixing
indentations 53 are formed in the curved outer surface of the
sliding arm 51 in a radial direction perpendicular to the
click-producing indentations 54 in such a way that each of the
rod-fixing indentations 53 would align with the first screw hole
41g. The pointed tip of the fixing screw 44b of the first fixing
part 44 fits into one of the rod-fixing indentations 53 while the
steel ball 45c of the click mechanism 45 fits into one of the
click-producing indentations 54. When the operator slides the
radial rod 5 across the first cylindrical part 41 to adjust the
extending length of the sliding arm 51, the steel ball 45c forced
against the radial rod 5 by the coil spring 45b drops into the
click-producing indentations 54. This action produces clicks
perceptible by the operator and makes it easy to set the effective
length of the radial rod 5 (or the distance between the axial
center of the bit 2 and the pivot shaft 52).
[0054] A fourth screw hole 41j is formed in a forward perimetric
surface of the first cylindrical part 41. The fourth screw hole 41j
is provided for fitting a second pivot shaft 47, which is used for
providing a pivot about which the bit 2 is turned when cutting a
hole whose diameter is equal to the diameter of the second
cylindrical part 42.
[0055] Now, the radial rod 5 and its variations are described in
detail referring to FIGS. 5A and 5B which illustrate various types
of radial rods. FIG. 5A shows the radial rod 5 whose effective
length is variable, and FIG. 5B shows seven radial rods 5a-5g
having fixed effective lengths.
[0056] The radial rod 5 shown in FIG. 5A is of a type whose
effective length (the distance between the axial center of the bit
2 and the pivot shaft 52) can be varies by sliding the radial rod 5
across the first cylindrical part 41 as already stated. Seven
rod-fixing indentations 53 including the first rod-fixing
indentation 531 which provides a minimum effective length to the
seventh rod-fixing indentation 537 which provides a maximum
effective length are formed in the curved outer surface of the
sliding arm 51. It is therefore possible to obtain a desired
effective length with the single radial rod 5 by selecting one of
the rod-fixing indentations 531-537.
[0057] In contrast, the first to seventh radial rods 5a-5g shown in
FIG. 5B individually provide the fixed effective lengths.
Specifically, the first radial rod 5a has one indentation which
corresponds to the first rod-fixing indentation 531 of FIG. 5A, the
second radial rod 5b has one indentation which corresponds to the
second rod-fixing indentation 532 of FIG. 5A . . . , and the
seventh radial rod 5g has one indentation which corresponds to the
seventh rod-fixing indentation 537 of FIG. 5A.
[0058] When this type of radial rods 5a-5g are provided, the
operator just need to select one of the radial rods 5a-5g that
provides the desired effective length. It is possible to cut a hole
of the correct diameter only if the operator selects the
appropriate radial rod 5a-5g. The radial rods 5a-5g having the
fixed effective lengths may be supplied as accessories to the
circular hole cutting device 1.
[0059] Operation of the circular hole cutting device 1 provided
with the radial rod 5 of the type shown in FIG. 5A is described
referring to FIGS. 6A-6B and 7A-7B which illustrate how the
circular hole cutting device 1 works. FIG. 6A is a side view
showing a state where a center hole C1 has just been made at the
center of a hole C2 (FIG. 7B) to be formed in a ceiling C by
turning the bit 2, and FIG. 6B is a side view showing a state where
the pivot shaft 52 has been fitted into the center hole C1. FIG. 7A
is a perspective view showing a state where the hole C2 is being
cut in the ceiling C by turning the circular hole cutting device 1
clockwise about the pivot shaft 52, and FIG. 7B is a perspective
view showing a state where the hole C2 has just been cut in the
ceiling C by turning the circular hole cutting device 1 all around
the pivot shaft 52.
[0060] The above operation of the circular hole cutting device 1 is
explained in further detail below. To cut the hole C2 (FIG. 7B) in
the ceiling C, the first fixing part 44 is loosened until the
pointed tip of the fixing screw 44b is located outside of an inner
surface of the rod-passing hole 41f, and the sliding arm 51 of the
radial rod 5 is inserted into the rod-passing hole 41f from the
right side (as illustrated in FIG. 1) in such a way that the
sliding arm 51 is properly positioned in the rod-passing hole 41f
to obtain a desired effective length and the pivot shaft 52 becomes
parallel to the bit 2 (or the rod-fixing indentations 53 are
directed toward the first screw hole 41g). The operator can check
out whether the pivot shaft 52 has been set to the desired
effective length (cutting radius) by feeling clicks produced when
the steel ball 45c drops into the click-producing indentations
54.
[0061] When the pivot shaft 52 has been set to the desired
effective length, the operator turns the knob 44a of the first
fixing part 44 so that the fixing screw 44b is screwed into the
first screw hole 41g. Consequently, the pointed tip of the fixing
screw 44b fits into one of the rod-fixing indentations 53 and the
first fixing part 44 is secured in position. The sliding arm 51 of
the radial rod 5 is set to the length corresponding to the radius
of the hole C2 to be cut in the ceiling C in this fashion. Next,
the second fixing part 46 is loosened to allow the second
cylindrical part 42 to move relative to the first cylindrical part
41, and the amount of projection of the second cylindrical part 42
from the first cylindrical part 41 is adjusted such that the bit 2
would project from the second cylindrical part 42 by an amount
appropriate for drilling a through hole in the ceiling C. When the
amount of projection of the bit 2 has been properly adjusted in
this fashion, the second fixing part 46 is fastened to secure the
second cylindrical part 42 to the first cylindrical part 41.
[0062] Subsequently, a tip end of the bit 2 of the circular hole
cutting device 1 is positioned at the center of hole C2 to be
formed in the ceiling C and the electric power tool D is activated,
whereby the bit 2 turns at a high speed and drills the center hole
C1 in the ceiling C as shown in FIG. 6A. Upon completion of this
drilling operation, the bit 2 is pulled out of the center hole
C1.
[0063] Next, the sliding arm 51 of the radial rod 5 is fitted in
the center hole C1 and the electric power tool D is turned on so
that the bit 2 turning at the high speed drills a hole in the
ceiling C at a distance corresponding to the effective length of
the sliding arm 51 from the center hole C1 as shown in FIG. 6B.
[0064] After confirming that the bit 2 has drilled through the
ceiling C, the operator turns the circular hole cutting device 1
clockwise about the pivot shaft 52 while maintaining the high
turning speed of bit 2 as depicted in FIG. 7A. Since the bit 2
turns at the high speed, its blades cut the ceiling C along a
circular path whose radius corresponds to the effective length of
the sliding arm 51 as shown in FIG. 7A. Chips produced during this
hole-cutting operation drop from the ceiling C into the cover 4,
which prevents downward dispersion of the chips.
[0065] When the circular hole cutting device 1 has been turned
clockwise all around the pivot shaft 52, a circular portion of the
ceiling C having the radius corresponding to the effective length
of the sliding arm 51 is cut away and the hole C2 of the desired
diameter is made in the ceiling C as shown in FIG. 7B.
[0066] As shown in the foregoing discussion, the circular hole
cutting device 1 of the invention can be attached to the drive
shaft D1 of the electric power tool D in such a way that the bit
holder 3 fitted with the bit 2 rotates together with the drive
shaft D1 on the common axis. The circular hole cutting device 1
comprises the bit holder 3 with the bit 2 attached to a far end of
the bit holder 3 on the common axis, the cover 4 fitted to the bit
holder 3 relatively rotatably about its axis, and the radial rod 5
having the sliding arm 51 and the pivot shaft 52 attached to the
cover 4 such that the amount of projection of the sliding arm 51 in
the direction intersecting the bit 2 can be varied. With this
construction, it is possible to form the circular hole C2 whose
radius corresponds to the effective length of the sliding arm 51 in
the ceiling C by drilling the center hole C1 for fitting the pivot
shaft 52 at the center of hole C2 to be formed in the ceiling C,
inserting the pivot shaft 52 in the center hole C1, activating the
electric power tool D to turn the bit 2 at the high speed, and
slowly turning the electric power tool D about the pivot shaft 52
with the bit 2 passing through the ceiling C so that the bit 2
turning at the high speed cuts the ceiling C along the circular
path.
[0067] Since the far end of the cover 4 is held in sliding contact
with the ceiling C during the hole-cutting operation, the cover 4
captures the chips, preventing their dispersion in a reliable
fashion. Accordingly, the chips would not fall on the operator and
this serves to greatly improve work environment.
[0068] Moreover, the circular hole cutting device 1 is connected to
the electric power tool D by attaching the bit holder 3 to the
drive shaft D1 of the electric power tool D. The drive shaft D1 of
the electric power tool D designed to hold a drill bit normally has
a chuck mechanism at the far end. The drive shaft D1 of this kind
is usually designed to hold various types of drill bits. This means
that the circular hole cutting device 1 can be connected to
practically any electric power tool D having a chuck mechanism
regardless of the manufacturer or type of the electric power tool
D. It would be recognized that the circular hole cutting device 1
of the invention provides great flexibility in application.
[0069] When using one of the radial rods 5a-5g shown in FIG. 5B
having the fixed effective lengths, the operator should select the
proper one according to the diameter of the hole C2 to be formed in
the ceiling C and perform the same operation as described above
with the selected radial rod fitted to the cover 4.
[0070] FIG. 8 is a perspective view showing an example of a hole B0
formed in a board Bd using the aforementioned combination bit 2a.
The combination bit 2a shown in FIG. 1 is used when making the hole
B0 surrounded by spot facing B2 in the board Bd having a plurality
of parallel ridges B1 formed on a drilling surface. The spot facing
B2 is often made on the surface of the board Bd on which the ridges
B1 are formed for installing a lighting fixture, for instance.
[0071] If the combination bit 2a is attached to the circular hole
cutting device 1 instead of the bit 2 and the amount of projection
of the spot facing portion 22 from the second cylindrical part 42
is made equal to the height of the ridges B1, it is possible to cut
a peripheral part of the hole B0 to be made in the board Bd with
the straight bit portion 21 and cut the ridges B1 with the spot
facing portion 22 to form the spot facing B2.
[0072] It is possible to make the spot facing B2 having a flat
surface which facilitates installation of a lighting fixture using
the combination bit 2a as discussed above. Since both the drilling
and spot facing operations can be carried out in a single process,
the use of the combination bit 2a is extremely convenient.
[0073] FIG. 9 is an exploded perspective view showing a circular
hole cutting device 1a according to a second embodiment of the
invention, FIG. 10 is a perspective assembly diagram of the
circular hole cutting device 1a of FIG. 9, and FIG. 11 is a view of
the circular hole cutting device 1a taken in the direction of arrow
D of FIG. 10. In this embodiment, a first cylindrical part 410 of a
cover 4a has a large-diameter portion 411 formed from a rear end
(right end as illustrated in FIG. 9) of the first cylindrical part
410 and having the same outer diameter as a second cylindrical part
42, and a small-diameter portion 412 formed from a forward end of
the first cylindrical part 410 and having an outer diameter
slightly larger than the inner diameter of the second cylindrical
part 42.
[0074] A radial rod 5 is provided with a spherical knob 55 which is
screwed onto an end of a sliding arm 51 opposite to its end from
where a pivot shaft 52 extends. More specifically, one end of the
sliding arm 51 is externally threaded and an internally threaded
hole is made in the spherical knob 55 so that the spherical knob 55
can be fitted to the sliding arm 51 of the radial rod 5 by screwing
the spherical knob 55 onto the threaded end of the sliding arm 51.
The provision of the spherical knob 55 makes it easier to slide the
pivot shaft 52 across the cover 4a by hand when adjusting the
amount of projection of the sliding arm 51, or its effective
length.
[0075] The sliding arm 51 of this embodiment has an innermost
rod-fixing indentation 530 formed closer to the pivot shaft 52 than
the first rod-fixing indentation 531 of the first embodiment (FIG.
5A). With the provision of the innermost rod-fixing indentation
530, a pointed tip of a fixing screw 44b of a first fixing part 44
fits into the innermost rod-fixing indentation 530 with the pivot
shaft 52 retracted into an internal space (chip retaining space 40)
of the cover 4a as shown by alternate long and two short dashed
lines in FIG. 9.
[0076] An elongate cutout 413 is made in the first cylindrical part
410 of the cover 4a. This cutout 413 extends from one end of a
rod-passing hole 41f formed in a ring-shaped bottom plate 41b of
the large-diameter portion 411 toward the small-diameter portion
412 and through the small-diameter portion 412 in a direction
parallel to the longitudinal axis of a bit 2. The width of the
cutout 413 is made slightly larger than the diameter of the pivot
shaft 52.
[0077] To retract the pivot shaft 52 from a position shown by the
alternate long and two short dashed lines of FIG. 9 to a position
shown by solid lines in FIG. 9, an operator removes the second
cylindrical part 42 from the small-diameter portion 412 of the
first cylindrical part 410 after loosening a second fixing part 46
and pulls the radial rod 5 by holding the spherical knob 55 such
that the pivot shaft 52 is pulled toward the cover 4a and retracted
into its internal space passing through the cutout 413.
[0078] The operator turns a knob 44a of the first fixing part 44
such that the pointed tip of the fixing screw 44b is forced into
the innermost rod-fixing indentation 530, fits the second
cylindrical part 42 over the small-diameter portion 412 of the
first cylindrical part 410 and secures the second cylindrical part
42 by tightening the second fixing part 46, whereby the radial rod
5 is set in position with the pivot shaft 52 accommodated in the
chip retaining space 40 as shown by solid lines in FIG. 10.
[0079] Further, a first screw hole 41g in which the fixing screw
44b of the first fixing part 44 is screwed is formed in the bottom
plate 41b of the first cylindrical part 410. In this embodiment,
the first screw hole 41g is made at a position slightly offset from
line extended from a longitudinal axis of a bit-holding part 31 of
a bit holder 3, which is perpendicular to the sliding arm 51,
toward the spherical knob 55 as shown in FIG. 11. Therefore, the
pivot shaft 52 can be retracted all the way into the cover 4a
without interfering with the fixing screw 44b.
[0080] Further, in the second embodiment, a third screw hole 41i in
the small-diameter portion 412 of the first cylindrical part 410
and a slot 42a in the second cylindrical part 42 for fitting the
second fixing part 46 are located opposite to the first fixing part
44 with respect to the bit 2. This arrangement makes it possible to
manipulate the second fixing part 46 without interfering with the
spherical knob 55.
[0081] According to the circular hole cutting device 1a of the
second embodiment, the pivot shaft 52 can be retracted into the
first cylindrical part 410 through the cutout 413 by pulling the
spherical knob 55 with the second cylindrical part 42 removed from
the first cylindrical part 410. Compared to the circular hole
cutting device 1 of the first embodiment without the provision of
the cutout 413, the distance between the bit 2 and the pivot shaft
52 can be made much smaller in this embodiment. Consequently, it is
even possible to make a hole having a diameter smaller than that of
the small-diameter portion 412 of the first cylindrical part 410
using the circular hole cutting device 1a. It would therefore be
appreciated that the circular hole cutting device 1a of the second
embodiment provides even great flexibility in application.
[0082] Although the second cylindrical part 42 is a straight
cylinder member having the same diameter along its length in both
the first and second embodiments, the second cylindrical part 42
need not necessary be the straight cylinder member according to the
invention. For example, the second cylindrical part 42 may have a
stepped cylinder structure with its forward portion having a larger
diameter. This modified structure would serve to capture and retain
drill chips in the second cylindrical part 42 in a more reliable
fashion since it has the increased diameter.
[0083] FIG. 12 is a bottom view showing a circular hole cutting
device 1b according to a third embodiment of the invention, and
FIG. 13 is a cross-sectional diagram taken along lines 13-13 of
FIG. 12. According to this invention, the bit holder 3 need not
necessarily be arranged on a common axis with the cover 4. The
circular hole cutting device 1b of the third embodiment is an
example having an eccentric arrangement. Specifically, the circular
hole cutting device 1b of this embodiment differs from the circular
hole cutting devices 1, 1a of the first and second embodiments in
that a bit holder 3 is located at a position offset from a central
axis O of a cover 4b and a radial rod 5 is attached to the cover 4b
in such a way that the radial rod 5 passes close to the central
axis O of the cover 4b, as illustrated in FIGS. 12 and 13. A cutout
413 is formed in a first cylindrical part 415 so that a pivot shaft
52 of the radial rod 5 can be retracted into an internal space
(chip retaining space 40) of the cover 4b in a manner similar to
the circular hole cutting device 1a of the second embodiment.
[0084] In the circular hole cuffing device 1b of the third
embodiment, the first cylindrical part 415 which is one constituent
part of the cover 4b is characterized in that a through hole 41c
formed in a bottom plate 41b of the first cylindrical part 415 for
fitting the bit holder 3 is offset from the central axis O of the
cover 4b to make the aforementioned eccentric arrangement. Further,
the first cylindrical part 415 has a bit holder retaining boss 416
projecting rearward (leftward as illustrated in FIG. 13) from the
bottom plate 41b on a common axis with the through hole 41c.
[0085] The bit holder retaining boss 416 is also offset from the
central axis O of the cover 4b. A rear end of a small-diameter
portion 33 of the bit holder 3 is rotatably supported by the bit
holder retaining boss 416 with a bearing B placed in between as
illustrated in FIG. 13. Generally, the circular hole cutting device
1b of the third embodiment has otherwise the same construction as
the foregoing embodiments.
[0086] In this embodiment, the bit holder 3 is offset to a
direction opposite to the pivot shaft 52 with respect to the
central axis O of the cover 4b, so that the chip retaining space 40
has an open area extending toward the pivot shaft 52 from a bit
2.
[0087] Since the bit holder 3 is fitted at the position offset from
the central axis O of the cover 4b, the radial rod 5 can be located
closer to the central axis O of the cover 4b in the circular hole
cutting device 1b of the third embodiment. This makes it possible
to increase the distance between two contact points between an
sliding arm 51 of the radial rod 5 and a cylindrical wall 41a of
the first cylindrical part 415 and, as a consequence, the first
cylindrical part 415 can support the radial rod 5 in a more stable
manner.
[0088] As so far described, a circular hole cutting device in one
form of the invention which makes a circular hole in an object when
turned about a center hole formed in the object comprises a bit
holder which can be attached to a drive shaft of an electric power
tool in such a way that the bit holder with a bit attached to a far
end rotates together with the drive shaft on a common axis, and a
relatively rotatable part fitted to the bit holder relatively
rotatably about the axis of the drive shaft, the relatively
rotatable part having a pivot shaft which is located at a position
offset from the bit in its radial direction and can be inserted
into the center hole formed by the bit.
[0089] According to the invention, it is possible to form a
circular hole whose radius corresponds to the distance between the
bit and the pivot shaft in the object by inserting the pivot shaft
in the center hole, activating the electric power tool to turn the
bit at a high speed, and slowly turning the electric power tool
about the pivot shaft with the bit passing through the object so
that the bit turning at the high speed cuts the object along a
circular path.
[0090] The circular hole cutting device of the invention is
attached to the electric power tool by fixing the bit holder to the
drive shaft of the electric power tool. The electric power tool has
a chuck at a far end of the drive shaft and the chuck is usually
designed to hold various types of drill bits. Accordingly, as long
as the drive shaft is of a type to which the bit holder of the
circular hole cutting device can be attached, it is possible to
connect the circular hole cutting device to practically any
electric power tool regardless of its manufacturer or type, so that
the circular hole cutting device provides great flexibility in
application.
[0091] The cylindrical attachment (cover) 101 of the
earlier-mentioned conventional circular hole cutting device 100 is
designed to be mounted on a casing of the circular hole cutting
device 100, and this casing is made in different shapes depending
on its manufacturer and type. Therefore, the cover designed to fit
a specific type of circular hole cutting device can not usually be
attached to other circular hole cutting devices and, as a
consequence, the conventional circular hole cutting device 100 can
only be used with only the specified type of circular hole cutting
device, providing extremely low flexibility in use. In contrast,
the aforementioned circular hole cutting device of the invention is
not associated with such inconvenience because it is constructed
such that the bit holder is attached to the drive shaft of the
electric power tool.
[0092] Furthermore, since the relatively rotatable part and the bit
holder are connected relatively rotatably with each other, the
relatively rotatable part does not rotate together with the drive
shaft of the electric power tool even when the relatively rotatable
part is turned about the pivot shaft. Accordingly, it is not
necessary for an operator to turn the circular hole cutting device
about its own axis when making a hole in a ceiling, for instance.
This would help increase labor efficiency in hole-cutting
operation.
[0093] In the aforementioned circular hole cutting device of the
invention, the relatively rotatable part may have a contact portion
which goes into contact with a surface to be worked of the object.
This construction would further facilitates the hole-cutting
operation since fluctuation of the relatively rotatable part is
avoided when its contact portion is kept in close contact with the
surface of the object.
[0094] The relatively rotatable part may be constructed such that
the position of its contact portion can be adjusted in an axial
direction. This would make it easier to set the bit to a position
where it passes through the object when the contact portion of the
relatively rotatable part goes in contact with the object because
the position of the contact portion can be easily adjusted. As a
result, it becomes possible to make a hole according to the
thickness of the object to be worked in an easy and reliable
way.
[0095] In the circular hole cutting device of the invention, a
cavity which receives chips cut by the bit may be formed in the
relatively rotatable part. Since the cavity of the relatively
rotatable part captures the chips cut by the bit during the
hole-cutting operation, the chips would not fall on the operator
and this serves to greatly improve work environment.
[0096] According to the invention, the relatively rotatable part
may be provided with a radial member which extends parallel to a
radial direction of the bit and has the pivot shaft at a far end.
With this arrangement, if the pivot shaft of the radial member is
inserted into the center hole formed in the object before forming
the desired circular hole in the object, it becomes possible to
turn the circular hole cutting device about the center hole in a
stable and reliable fashion and to easily make the circular hole
whose radius is equal to the effective length of the radial member,
or the distance between the bit and the pivot shaft.
[0097] In this case, the radial member may be constructed to allow
adjustment of the distance (effective length) from its pivot shaft
to the bit. This makes it possible to form a circular hole having a
desired diameter in the object.
[0098] Alternatively, the relatively rotatable part may be provided
with a plurality of radial members each of which extends parallel
to a radial direction of the bit when fitted to the relatively
rotatable part and has the pivot shaft at a far end, the radial
members allowing a choice of different distances from the pivot
shaft to the bit. This allows the operator to select a radial
member whose effective length is suited for the radius of the
circular hole to be formed in the object. The radial rods having
the fixed effective lengths may be supplied as accessories to the
circular hole cutting device.
[0099] According to the invention, a bearing may be fitted between
the bit holder and the relatively rotatable part. With this
provision, even when the bit holder is turned at a high speed by
the electric power tool for cutting the circular hole in the
object, the bearing placed between the bit holder and the
relatively rotatable part enables them to turn smoothly relative to
each other, thereby avoiding such an undesirable phenomenon that
the bit holder and the relatively rotatable part turn together with
each other.
[0100] In the aforementioned relatively rotatable part having the
cavity and the radial member, the pivot shaft of the radial member
can not be retracted into the cavity since the pivot shaft is
obstructed by a wall of the relatively rotatable part surrounding
its cavity. The pivot shaft should therefore be located outside the
relatively rotatable part and, as a consequence, the diameter of
the circular hole cut in the object can not be made smaller than
the diameter of the cavity. The invention overcomes this
inconvenience by the following arrangement.
[0101] A circular hole cutting device in another form of the
invention which makes a circular hole in an object when turned
about a center hole formed in the object comprises a bit holder
which can be attached to a drive shaft of an electric power tool in
such a way that the bit holder with a bit attached to a far end
rotates together with the drive shaft on a common axis, and a
relatively rotatable part fitted to the bit holder relatively
rotatably about the axis of the drive shaft, wherein the relatively
rotatable part includes a cover having a peripheral wall and an
internal cavity which captures chips cut by the bit and a radial
member fitted to the cover, wherein the radial member has at its
far end the pivot shaft extending parallel to the bit and is fitted
to the cover in such a way that the distance from the pivot shaft
to the bit can be adjusted, and wherein a cutout which makes it
possible to retract the pivot shaft into the cavity of the cover is
formed in its peripheral wall.
[0102] This construction makes it possible to retract the pivot
shaft into the cavity of the relatively rotatable part by pulling
the radial member in such a way that the pivot shaft passes through
the cutout in the cover, so that the pivot shaft can be located on
either the outside or inside of the cavity. As a result, it becomes
possible to cut a circular hole having a diameter either larger or
smaller than diameter of the cavity using the circular hole cutting
device. This would further enhance the flexibility of the circular
hole cutting device.
[0103] The cover may include a first cylindrical part in which the
cavity and the cutout are formed and a second cylindrical part
which is detachably fitted to the first cylindrical part in such a
way that the second cylindrical part covers at least part of the
cutout. In this construction, the effective length of the radial
member can be adjusted with the second cylindrical part removed
from the first cylindrical part. If the second cylindrical part is
then mounted on the first cylindrical part, the cutout in the first
cylindrical part is covered by the second cylindrical part
regardless of whether the pivot shaft is located on the outside or
inside of the cavity, so that chips produced during the
hole-cutting operation and captured by the cavity in the cover are
prevented from falling through the cutout.
[0104] The second cylindrical part may have a contact portion which
goes into contact with a surface to be worked of the object, and
may be mounted on the first cylindrical part such that the position
of the contact portion can be adjusted in an axial direction. This
construction makes it possible to adjust the amount of projection
of the second cylindrical part from the first cylindrical part
according to the thickness of the object such that the bit passes
through the object. As a result, it becomes possible to make a hole
in an easy and reliable way.
[0105] This application is based on Japanese application Ser. No.
JP2000-41598 filed on Feb. 18, 2000 and Japanese application Ser.
No. JP2000-219284 filed on Jul. 19, 2000, the contents of which are
hereby incorporated by reference.
[0106] Although the present invention has been fully described by
way of examples with reference to the accompanying drawings, it is
to be understood that various changes and modifications will be
apparent to those skilled in the art. Therefore, unless otherwise
such changes and modifications depart from the scope of the present
invention hereinafter defined, they should be construed as being
included therein.
* * * * *