Turning – Lathe – With work feeder or remover
Reexamination Certificate
2000-10-11
2003-06-10
Tsai, Henry W. H. (Department: 3722)
Turning
Lathe
With work feeder or remover
C082S126000, C082S162000
Reexamination Certificate
active
06575063
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a bar supporting apparatus for a lathe (which will be simply referred to as a bar supporting apparatus hereinafter) which supports a long circular work piece such as a bar or tube which is subjected to lathe work (it will be generically referred to as a bar hereinafter in the present specification) on a extended line of a main spindle of an automatic lathe.
BACKGROUND ART
This type of the bar supporting apparatus is provided in the vicinity of the automatic lathe and rotatably supports a portion of a long bar projecting from a head stock in order to prevent the bar from generating rotation oscillation. For example, as shown in
FIG. 28
, the prior art bar supporting apparatus
100
comprises: a case
111
having a predetermined length; a guide tube
113
whose diameter is slightly larger than an external diameter of a bar
117
which is to be supported in the case
111
; and a hydraulic unit
114
which supplies a large amount of oil for supporting the bar
117
in the guide tube
113
, and it causes the bar
117
to float in the guide tube
113
by the dynamic pressure of the oil involved by rotation of the bar
117
so that the bar is rotatably supported. It is to be noted that the bar
117
is gripped by a chuck
125
of a main spindle
124
of the automatic lathe so as to be processed. Since the rear end of the case
111
is sealed to avoid leakage of the oil in the bar supporting apparatus
100
, the bar
117
is inserted after moving the front end side (the automatic lathe side) of the case
111
to the side with a supporting base
115
on the rear side as a supporting point. After inserting the bar
117
into the case
111
, the case
111
is returned to its original position to be supplied to the main spindle
124
side (FIG.
29
and FIG.
30
).
Here, although the oscillation of the bar
117
can be suppressed all the more as a gap between the external diameter of the bar
117
and the guide tube
113
is smaller, the bar
117
oscillates due to rotation during processing, and a narrow gap hence disadvantageously causes the bar
117
to come into contact with the guide tube
113
to generate heat. Therefore, the optimum gap between the internal diameter of the guide tube
113
and the external diameter of the bar
117
is determined to be approximately 1 mm in case of the bar having the external diameter of not more than 30 mm; approximately 2 mm in case of the bar having the external diameter of 31 mm to 65 mm; and approximately 3 mm in case of the bar having the external diameter of 66 mm to 69 mm. The quantity of the gap is also a problem of design, and these are approximate values. Thus, the guide tube
113
is replaced in accordance with the external diameter of the bar
117
, or a guide tube having a small diameter is provided on the inner side of the guide tube
113
so as to cope with the bar
117
having a different external diameter.
In this case, in order to set an optimum gap between the guide tube
113
and the bar
117
, the inner peripheral surface of the long guide tube
113
must be processed so as to obtain a straight axial center with the high accuracy, but it is very difficult to accurately process the inside of the long guide tube
113
with the current processing technology such as boring. Further, although the processing must be carried out with low-speed rotation depending on the bar
117
which is a target of processing, the dynamic pressure to be generated becomes small even if an appropriate gap is formed between the bar
117
and the guide tube
113
in this case, and the bar
117
does not float by oil but comes into contact with the guide tube
113
to cause the oscillation or noise.
In addition, a bend of the bar
117
is remedied by a straightening machine in the final step of the manufacturing process even if the bar
117
is made of a mill scale material or a polishing material and the bend is straightened to some degree, but the slight deflection is generated by its own weight and the like because it is actually long. Therefore, it is very difficult to inspect the bend of the bar
117
, and the bend is often missed in the inspection even if the bar
117
is actually bent. The slightly bent bar
117
has to be supported by the bar supporting apparatus
100
. Thus, the bar
117
oscillates more than necessary to come into contact with the guide tube
113
depending on the bend of the bar
117
which can not be found in the inspection, or the bar
117
may be deflected to be brought into contact with the guide tube
113
by the centrifugal force in the high-speed rotation, even if the bar
117
is not bent thereby generating oscillation or noise.
As a countermeasure, there is developed a bar supporting apparatus
100
A which does not use the guide tube. As shown in
FIGS. 31 and 32
, the bar supporting apparatus
100
A mounts on a counter
118
a plurality of supports
119
each consisting of a bearing having oil supplying means at predetermined intervals. An upper support
119
A and a lower support
119
B of the support
119
are disposed to the respective halves of the bearing
123
, and the bar is inserted and removed by oscillating the upper support
119
A around an upper frame pivot
120
. The upper support
119
A opens and closes by using a cylinder
122
. The bearing
123
has a diameter slightly larger than that of the bar
117
and supports the bar
117
by generating the dynamic pressure between itself and the bar
117
with a large amount of oil being supplied to the bearing surface. Thus, since the oil supplied from the hydraulic unit to the bearing
123
of the support
119
spatters or leaks, the entire apparatus is covered with a large casing, thereby enlarging the size of the apparatus. It is to be noted that a plurality of the supports
119
are provided on the counter
118
at predetermined intervals. The apparatus is assembled so that all the upper and lower bearings
123
disposed to the multiple upper and lower supports
119
A and
119
B provided at predetermined intervals can have the axial centers accurately matched with each other.
However, since the bearing
123
is split in two to be supported by the upper and lower supports
119
A and
119
B and others, the shapes of components of the bearing
123
are complicated and hard to be processed. Further, it is very difficult to perform accurate centering on all the bearings
123
disposed to the upper and lower supports
119
A and
119
B due to an attachment error and others of the respective supports.
Moreover, when the gap between the bar
117
and the half bearing
123
is narrowed to approximately 1 mm or less, the bar
117
can be further rotated with no noise. However, since the upper and lower supports
119
A and
119
B are separately disposed, they can not be disposed to the same accurate straight axial center but attached with the respective axial centers being slightly shifted. Taking the axial center shift of the respective upper and lower supports
119
A and
119
B into consideration, it is extremely hard to reduce the gap between the bar
117
and the respective upper and lower supports
119
A and
119
B. This can not completely eliminate the noise depending on the situations.
Furthermore, in the bar supporting apparatus which supplies a large amount of oil and causes the bar to float by the supplied oil, the large amount of oil is used to enable rotation without noise even if the rotating bar oscillates, but the oil may disadvantageously spatter when the large amount of oil is supplied from an oil supplying device provided to the large hydraulic unit to the respective supports. Accordingly, it is necessary to manufacture an apparatus which is entirely covered with a cover so that the spattered oil is collected to be returned to the hydraulic unit for circulation, which may result in the expensive bar supporting apparatus.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a bar supporting apparatus which can accurately match axial centers of plural supports supporting a rotatin
Notaro & Michalos P.C.
Tsai Henry W. H.
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