Gear cutting – milling – or planing – Milling – Machine frame
Reexamination Certificate
2002-02-07
2004-06-15
Wellington, A. L. (Department: 3722)
Gear cutting, milling, or planing
Milling
Machine frame
C409S135000, C409S137000, C409S190000, C409S191000
Reexamination Certificate
active
06749378
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a guide apparatus and a machine tool using the guide apparatus, which guides a movable member such as a column of the machine tool in a state of semi-contact.
2. Discussion of the Background
A machine tool has a bed, and a column that is moved on the bed, as main constituent elements. For instance, a workpiece is attached on the bed, and a machining means (a cutting tool) and a drive means (a tool drive motor) that drives the machining means are attached on the column. As a way to movably guide the column on the bed, it is known to supply pressurized lubricant oil between sliding surfaces of the bed and column, to keep a transition state which is intermediate between a state in which the column does not contact the bed (floats) and a state in which the column contacts the bed (does not float), so as to reduce weight of the column acting on the bed. In other words, a machine tool in which the column is moved under a state of semi-contact (semi-float) is known.
FIG. 1
is a side-view of a conventional machine tool. Referring to
FIG. 1
, a column
101
is moved (right and left directions in
FIG. 1
) along a sliding surface
111
of a bed
110
. Lubricant oil is supplied between the sliding surface
111
of the bed
110
and a sliding surface
104
of the column
101
. It is designed such that a product of an area of oil-hold portions (to be described later) which the pressure of the lubricant oil acts on, and the pressure of the lubricant oil, is equal to the weight of the column
101
. Therefore, the column
101
can be guided on the bed
110
in a state of semi-contact (semi-float) by the lubricant oil. The column
101
is moved on the bed
110
in a state of semi-contact (semi-float) by a well known means such as a motor.
A tool spindle
105
supporting a tool, a tool drive means
106
to drive the tool spindle
105
and other elements are attached to the column
101
. Accordingly, the center of gravity of the whole column
101
is unbalanced in a moving direction in most cases. Since such a load unbalanced column
101
inclines on the bed
110
, the column
101
cannot be moved smoothly on the bed
110
.
Therefore, a plural number of the oil-hold portions (for example, quadrangular grooves) to hold the lubricant oil are formed on the sliding surface
104
of the column
101
, and an area of each oil-hold portion is designed according to a load which is acting on the oil-hold portion. For instance, two oil-hold portions
103
a
,
103
b
are formed on the sliding surface
104
of the column
101
along the moving direction of the column
104
. The lubricant oil is supplied to the oil-hold portions
103
a
,
103
b
via throttle nozzles
102
a
,
102
b
. Areas of the oil-hold portions are designed according to the load of the column
101
acting at the location of each oil-hold portion
103
a
,
103
b
. That is, since the center of gravity
100
of the column
101
is located forward (left direction in
FIG. 1
) because of the locations of the tool spindle
105
and the tool drive means
106
, the area of the oil-hold portion
103
a
onto which a heavier load acts is larger than the area of the oil-hold portion
103
b
onto which a lighter load acts. On the other hand, the throttle nozzles
102
a
,
102
b
are designed to have the same opening as each other and are connected to a single oil-supply device.
In the aforementioned machine tool, the same amount of lubricant oil, per unit time, is supplied to the oil-hold portions
103
a
,
103
b
whose areas are different from each other. When the stationary column
101
is moved, the column
101
is floated by an wedge effect of the lubricant oil, and a clearance between the sliding surface
104
of the column
101
and the sliding surface
111
of the bed
110
becomes wider. The wedge effect acting on the column
101
is remarkable in the state of the semi-contact (semi-float). The lubricant oil is supplied into the clearance from the throttle nozzles
102
a
,
102
b
. Since the openings of the throttle nozzles
102
a
,
102
b
are the same, supplying the lubricant oil to the oil-hold portion
103
a
whose area is larger than the area of the oil-hold portion
103
b
is delayed relative to supplying the lubricant oil to the oil-hold portion
103
b
. As the result, the pressure Pa of the lubricant oil in the oil-hold portion
103
a
becomes smaller than the pressure Pb of the lubricant oil in the oil-hold portion
103
b
. Therefore, the column
101
inclines further on the bed
110
and cannot be smoothly moved on the bed
110
.
SUMMARY OF THE INVENTION
In view of the foregoing, it is an object of the present invention to provide an improved semi-contact guide apparatus and a machine tool using the guide apparatus. In order to achieve the above and other objects, the present invention provides a semi-contact guide apparatus comprising a first member, a second member, a plural number of oil-hold portions and an oil-supply device. The second member is movably guided on the first member. A sliding surface is formed on the second member. The plural number of oil-hold portions is formed on the sliding surface. Dimensions of the oil-hold portions are defined according to the load distribution of the weight of the second member. The oil-supply device supplies lubricant oil to the oil-hold portions. The amount of the lubricant oil supplied to the oil-hold portion is defined according to the respective dimensions of the oil-hold portions. Since the dimensions of the respective oil-hold portions are defined according to the load distribution of the weight of the second member, and the amount of the lubricant oil supplied to the oil-hold portions is defined according to the dimensions of the respective oil-hold portions, the second member is prevented from inclining on the first member, and the second member can be smoothly moved on the first member.
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patent: 2869933 (1959-01-01), Bissinger
patent: 3603652 (1971-09-01), Youden
patent: 3781069 (1973-12-01), Gluchowicz
patent: 3903993 (1975-09-01), Vorrhees et al.
patent: 4252381 (1981-02-01), Kimmelaar
patent: 4351574 (1982-09-01), Furukawa et al.
patent: 5104237 (1992-04-01), Slocum
patent: 5694811 (1997-12-01), Tsukada
patent: 6110010 (2000-08-01), Pflager et al.
Saito Toshiyuki
Suzuki Michihiro
Takashima Toshiharu
Teramura Tetsuo
Ross Dana
Toyoda Koki Kabushiki Kaisha
Wellington A. L.
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