Gear cutting – milling – or planing – Milling – With means to control temperature or lubricate
Reexamination Certificate
2002-04-24
2004-02-17
Cadugan, Erica (Department: 3722)
Gear cutting, milling, or planing
Milling
With means to control temperature or lubricate
C409S136000, C277S549000, C277S551000
Reexamination Certificate
active
06692202
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a spindle protective structure in a spindle-through coolant feeder.
2. Description of Related Art
As a spindle structure for use in a high-speed rotating machine tool such as a drilling machine and a tapping machine or a machining center, there is known a spindle-through coolant feeder for feeding machining fluid to a tip of a tool attached to a spindle through a hole formed axially in the spindle for cooling cutting edges of the tool and removing chips.
Such spindle-through coolant feeders are known as a spindle structure in which a spindle is driven by a spindle motor through a transmission device such as a gear train or a belt and coolant is supplied from the through hole of the spindle, a spindle structure in which the spindle is directly coupled with a rotor shaft of the spindle motor and coolant is supplied through the through hole of the spindle and a through hole formed axially in the rotor shaft, and a spindle structure in which the spindle and the spindle motor are combined to form a built-in motor.
In recent spindle-through coolant feeders, coolant of high pressure is generally used for increasing the efficiency of discharging chips and cooling cutting edges of the tool to improve a finished state of a workpiece. Therefore, if an excessive overflow of coolant is caused at a rotary joint, there is a risk that a large amount of coolant may leak outside in a moment. In the case of the above first mentioned spindle structure, coolant may reach peripheries of the spindle, and in the case of the secondly and thirdly mentioned spindle structures, coolant may directly invade the spindle motor or the built-in motor, to possibly cause serious problems such as rust, abnormal rotation or electrical failure. Further, if coolant is not properly supplied to the tip of the tool, cutting edges of the tool or a workpiece may be damaged.
Thus, it is necessary to prevent the coolant from invading the spindle and the spindle motor. However, if a general oil seal which is an effective measure for preventing fluid leakage is used, a temperature of a lip of the oil seal increases because of heat generated by friction between a surface of the shaft rotating at high-speed and the lip to exceed an allowable temperature range of the general oil seal. Thus, the general oil seal is not used for the above-mentioned spindle structure and only a seal member of non-contact type such as a fringer or labyrinth type has been adopted.
FIG. 6
is a cross-sectional view of a seal stricture in a spindle structure for a machine tool or a machining center with a spindle extending in the horizontal direction, as proposed in U.S. Pat. No. 5,967,716.
A rotary joint support housing
12
is fixed to an end face of a spindle motor
8
by bolts
16
led though holes formed at a flange
14
. The spindle motor
8
and the rotary joint support housing
12
are aligned by engagement of an inner circumferential face of the flange
14
and an outer circumferential face of a spigot
17
provided on the end face of the induction motor
8
.
The interior of the rotary joint support housing
12
is divided into three chambers
12
a
,
12
b
and
12
c
by partition walls
18
and
19
in an axial direction of a rotor shaft
9
. A drain pipe
6
and an auxiliary drain pipe
27
are connected to the housing
12
at the lower portion thereof, to communicate with the chamber
12
a
and the chamber
12
b
, respectively. A fringer
28
is fixed to the rotor shaft
9
in the chamber
12
c
to rotate with the rotator shaft
9
to splash dust and fluid radially outward by centrifugal force of the rotation.
A rotary joint
3
is composed of a nipple-like rotary member
22
which is fixed on a distal end of the rotor shaft
9
and rotates with the rotary shaft
9
, and a stationary member
23
fixed to the housing
12
. A through hole
10
formed axially in the rotor shaft
9
has a tapered pipe thread at its end, and the rotary member
22
is screwed into the through hole
10
to be finely fixed to the rotor shaft
9
. The stationary member
23
is fixed to the housing
12
such that a socket portion
23
a
thereof projects into the chamber
12
a
to be positioned in confronting relation to the rotary member
22
. A pipe
4
for supplying coolant is connected to the stationary member
23
.
Coolant supplied from a pipe
4
is lead through an inner conduit in the stationary member
23
to the socket portion
23
a
and transits from the socket portion
23
a
to a through hole in the rotary member
22
to be introduced into the through hole
10
of the rotor shaft
9
. Coolant leaked out in the transition from the socket portion
23
a
to the rotary side member
22
is discharged by the drain pipe
6
from the chamber
12
a.
A circular groove
24
is formed on an inner surface of the through hole of the partition wall
18
in sliding contact with the circumferential surface of the rotary member
22
. Compressed air or the like is supplied to the chamber
12
a
from an air purge pipe
26
through a thin hole
25
formed in the partition wall
18
in the radial direction and the circular groove
24
, to raise the pressure in the chamber
12
a
so that the coolant overflowed in the chamber
12
a
is reliably discharged through the drain pipe
6
to the outside.
Further, coolant in the chamber
12
b
is discharged through the auxiliary drain pipe
27
, and coolant in the chamber
12
c
is splashed radially outward by the fringer
28
and discharged from cutouts
29
formed at a lower circumference of the housing
12
. Further, a flow rate sensor is provided in a flow passage of the drain pipe
6
so that an alarm is issued when a flow rate of coolant flowing in the pipe
6
exceeds a set value.
As described, for preventing the coolant overflowed from the rotary joint from invading the spindle and the spindle motor, the non-contact type seal structure such as the fringer type or a labyrinth-type is adopted. As described, this is because a general oil seal is not adoptable for such a seal structure because of the high-speed rotation of the spindle.
However, if an excessive overflow is caused in the transition from the stationary member
23
to the rotary member
22
of the rotary joint
3
, there is a risk that discharge by the non-contact seal structure using the fringer
28
may not be enough to prevent the leaked coolant from invading the spindle and the spindle motor.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a spindle protective structure capable of protecting a spindle and a spindle motor from being invaded by leaked coolant in a case where a large amount of coolant overflowed.
A spindle protective structure in a spindle-through coolant feeder of the present invention comprises: a jointing device for feeding coolant into a through hole formed axially in a spindle or a shaft connected to the spindle; a housing for supporting the jointing device; a drain pipe for discharging coolant overflowed in the housing from the jointing device; and a seal member having elasticity for sealing a circumferential surface of a portion of the spindle or the shaft projected into the housing.
The above spindle protective structure is applicable to a spindle structure in which the spindle and a rotor shaft of the spindle motor are connected, to a spindle structure in which the spindle is directly coupled with a rotor shaft of the spindle motor and coolant is fed through the through hole formed axially in the spindle and the through hole formed axially in the shaft, and further to a spindle structure in which the spindle and the spindle motor are combined together to form a built-in motor.
The housing has one or more chambers and the drain pipe and/or the seal member are provided for at least one of the chambers.
The interior of the housing may be divided into a plurality chambers by at lest one partition wall and the seal member may be arranged on the partition wall between the chambers.
A non-contacting seal device such as a fringer or labyri
Katsuzawa Yukio
Nakazawa Yasuyuki
Seki Tomohiro
Cadugan Erica
Fanuc Limited
Ross Dana D
Staas & Halsey , LLP
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