Two-surface constrainable tool

Details Two-surface constrainable tool Two-surface constrainable tool

1999-09-17

2001-05-15

Howell, Daniel W. (Department: 3722)

Gear cutting, milling, or planing

Milling

With cutter holder

C408S23900A, C409S232000

Reexamination Certificate

active

06231282

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a tool to be fitted to a spindle included in a machine tool, such as a machining center and, more particularly, to a two-surface constrainable tool having a bottom grip taper shank (BT shank) with a conical taper shank and a flange to be constrained.
2. Description of the Related Art
BT shanks are used widely as shanks for standard tools for machining centers. The BT shank is mounted on a spindle with its taper shank fitted closely in the conical taper bore of the spindle. The recent progress of machining centers which achieve high performance in spindle speed and machining efficiency has brought about new problems in BT shanks. For example, a front end portion of the spindle surrounding the conical taper bore is caused to expand because of its high speed rotation and the tool holding firmness of the spindle is reduced. Consequently, the tool becomes unstable and chatters, and the positional accuracy of the cutting edge of the tool is deteriorated.
A new tool which has a BT shank with a taper part and a flange has been developed to solve such a problem. The taper part of the BT shank is fitted closely in the conical taper hole of a spindle and the flange is brought into contact with the end surface of the spindle to hold the tool securely on the spindle in a state of two-surface constraint. Known two-surface constrainable tools are shown in
FIGS. 6 and 7
.
FIG. 6
shows a two-surface constrainable tool known as a collar adjustment type. In
FIG. 6
indicated at
30
is a spindle and at
32
is a BT shank. A taper part
33
of the BT shank
32
is fitted in a conical taper bore
31
formed in the spindle
30
. A collar
35
is inserted into a clearance between the end surface of the spindle
30
and the end surface of a flange
34
. According to the collar adjustment type, the taper part
33
of the tool is constrained by the inner surface of the conical taper bore
31
, and the flange
34
of the same is constrained by the collar
35
in close contact with the end surface of the spindle
30
.
FIG. 7
shows a two-surface constrainable tool known as of a century type. This tool has a BT shank
32
having a short taper part
36
and a flange
34
. A disk spring
37
is placed in a clearance between the flange
34
and the end surface of a spindle
30
to facilitate pushing the short taper part
36
of the BT shank
32
into a taper bore formed in the spindle
30
and to enhance cutting vibration damping effect.
As to the BT shank
32
of the collar adjustment type retained in the two-surface constrained state, the collar
35
subjected to the centrifugal force is caused to loosen and the stiffness of contact between the collar
35
and the end surface of the spindle
30
decreases when the spindle
30
rotates at a high rotating speed.
On the other hand, the taper part
36
of the tool of the century type does not have a enough contact area to keep reliable contact with the surface of taper bore
31
, and the tool is liable to play axially. There is an opinion that the tool of a century type is unsuitable for high-speed heavy machining.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to solve those problems in the prior art and to provide a two-surface constrainable tool capable of securely holding a collar between the end surface of a spindle and the end surface of the flange without allowing the collar to loosen or fall off and of being used for high-speed machining.
According to one aspect of the present invention, a two-surface constrainable tool having two constrained surfaces on an end portion of a spindle provided with a conical tapered bore and an end surface, said two-surface constrainable tool comprises a bottom grip taper shank having a taper part provided with a first constrained surface and capable of being closely fitted in the conical tapered bore of the spindle, and a flange provided on one end surface thereof facing the end surface of the spindle with a groove; and a collar to be interposed between the end surface of the flange and the end surface of the spindle, having a ridge to be fitted in the groove of the flange, and a second constrained surface to be brought into close contact with the end surface of the spindle.
When the bottom grip taper shank is mounted on the spindle, the tapered conical surface of the taper part in close contact with the inner conical surface of the taper bore of the spindle serves as a first constrained surface, and the end surface of the flange resting through the collar on the end surface of the spindle serves as a second constrained surface. Since the two-surface constrainable tool thus retains itself by the two retaining surfaces on the spindle, the tool holding firmness of the spindle is not reduced even if the spindle rotates at a high rotating speed.


REFERENCES:
patent: 4673319 (1987-06-01), Ishikawa
patent: 4714389 (1987-12-01), Johne
patent: 4840520 (1989-06-01), Pfalzgraf
patent: 4902177 (1990-02-01), Burnett
patent: 5118231 (1992-06-01), Daniels
patent: 5322304 (1994-06-01), Rivin
patent: 5595391 (1997-01-01), Rivin
patent: 5775857 (1998-07-01), Johne
patent: 5975816 (1999-11-01), Cook

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