Horizontally supported planar surfaces – Power driven
Reexamination Certificate
2002-05-10
2004-04-20
Chen, Jose V. (Department: 3637)
Horizontally supported planar surfaces
Power driven
C108S022000, C074S016000
Reexamination Certificate
active
06722289
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a table system with angular position controls, which can be used in fields as diverse as semiconductor manufacturing equipments, precision machines, machine tools, and so on to provide accurate position control of tiny angles in circular direction for an object such as a work mounted on a table.
2. Description of the Prior Art
Linear motion guide units constructed as shown in
FIG. 7
are commonly known to those skilled in the art. The prior linear motion guide unit
40
is mainly comprised of an elongated track rail
41
and a slider
42
fitting astride over the track rail
41
for linear movement. The track rail
41
is made on widthwise opposing sides thereof with lengthwise raceway grooves
49
, one to each side. The slider
42
is allowed to move along the track rail
41
in sliding way through rolling elements running in the grooves
49
. The track rail
41
is made on a lengthwise upper surface thereof with bolt holes that are arranged lengthwise at a fixed interval. The track rail
41
is fastened down to any mounting base such as a bed, machine bed, working bench, and so on with fastening bolts that extend through the bolt holes in the track rail
41
to be screwed into the threaded holes in the mounting base. The slider
42
includes a casing
43
, and end caps
44
secured to forward and aft ends of the casing
43
, one to each end. The casing
43
is provided on an upper surface thereof with bolt holes that are used to fasten any other appliance, machine component, chuck, clamping jaw, and so on to the slider
42
.
All the casing
43
and the end caps
44
are made with recesses that are formed forward and aft to fit over and conform to the track rail
41
to be allowed to move astride the track rail
41
. Inside the recesses there are formed raceway grooves
50
that extend forward and aft in opposition to the raceway grooves
49
on the track rail
41
to cooperate with their confronting raceway grooves
49
, defining load raceways between the confronting raceway grooves
49
,
50
where rolling elements
46
such as balls or the like run through there. Moreover, a retainer band
47
is attached to the casing
43
to embrace the rolling elements
46
lest they fall away from the casing
43
. The end caps
44
each has a turnaround where the rolling elements
46
are allowed to turn round for recirculation, and a claw to scoop the rolling elements
46
out of the raceway grooves
49
on the track rail
41
at any one of the forward and aft ends of the slider
42
.
Also mounted on the end caps
44
are end seals
45
, one to each end cap, for keeping sealing function between the track rail
41
and the lengthwise opposing ends of slider
42
. The end caps
44
are fastened to the forward and aft end faces of the casing
43
, one to each end face, with more than one fastening bolt that are tightened through bolt holes in the end caps
44
. With the prior linear motion guide unit stated earlier, a ball-recirculating circuit for the rolling elements
46
is made up of the load raceway defined between the confronting raceway grooves
49
and
50
, the turnarounds formed in the end caps
44
, and a return passage
51
formed in the casing
43
to extend in parallel with the raceway groove
50
. The slider
42
is allowed to move smoothly in and out relatively to the track rail
41
as more than one rolling element
46
runs through the load raceway with keeping rolling contact with the raceway grooves
49
,
50
, even under a considerably loaded condition. The linear motion guide unit of the sort stated above is applied with lubricant; usually grease to lubricate the rolling elements
46
in the recirculating circuit. To this end, there is provided a grease nipple
48
to supply lubricant to the recirculating circuit in which the rolling elements
46
run through there.
Moreover referring to
FIG. 8
, there is shown a prior rotary table system in which a servo-actuator is connected directly to a motor
60
in direct-drive manner to provide very fast, highly accurate position control in circular direction with no backlash or no lost motion. The servo-actuator to turn a table
52
in any circular direction to a desired angular position is mainly comprised of the motor
60
, an optical encoder
59
and a rolling-contact bearing
55
. The motor
60
is comprised of a rotor
54
fixed to the table
52
, and a stator
53
mounted on a housing
61
. With the rotary table system stated earlier, the table
52
is encased in the housing
61
for free rotation through the rolling-contact bearing
55
that is composed of an inner ring
56
, an outer ring
57
and rolling elements of cylindrical rollers
58
. The rolling-contact bearing
55
is constructed with a crossed-roller bearing in which the rollers
58
are arranged circumferentially with their axes intersecting alternately one another in such a manner that each roller can carry the table
52
against any load in every direction, either radial or axial.
Angular position control means in circular direction or &thgr;-direction for a table supporting a work thereon is disclosed in Japanese Patent Laid-Open No. 238232/2000, where there is provided a linear motion guide unit of recirculating-ball nut and screw set comprising a screw shaft driven by a motor, and a ball nut fitting around the screw shaft for linear movement along the axial direction of the screw shaft as the screw shaft turns on its own axis. The ball nut has thereon a lug that makes engagement with a cam follower of forked rollers on a bracket arm, which extend out of the work table in a way the forked rollers coming in pinch engagement with the opposite sides of the lug. The linear motion guide unit is arranged flanking the work table while the bracket arm integral with the cam follower of forked rollers supports the work table for free rotation. With the position control means in &thgr;-direction stated earlier, when the linear motion guide unit is energized, the lug communicates the linear motion along the axis of the screw shaft to the cam follower, which in turn moves the work table in &thgr;-direction through the bracket arm to an angular position complying with the linear motion of the lug.
Disclosed in Japanese Utility Model Laid-Open No. 133540/1992 is a moving table system in which a ball thrust bearing is interposed between a base and a movable stage lying on the base, while actuators are arranged to move the stage relatively to the base in the horizontal towards any desired position. The movable stage lying on the base through the thrust bearing is connected at any side thereof to the actuators. With the moving table system cited earlier, moreover, linear guide members are mounted to the upper surface of the base and any side surface of the movable stage, one to each surface, in a relation that they extend in perpendicular to one another, while slide members articulated with each other through a hinged pin fit in the linear guide members for free sliding motion, one to each guide member. The conjugated slide members, upon movement of the stage, move along their associated guide members, with crooking on the hinged pin to follow easily the movement of the stage, thereby keeping the stage against a warp that might otherwise occur due to any eccentric load.
With the rotary table system as shown in
FIG. 8
, nevertheless, the rotor
54
of the motor
60
is arranged overall around the periphery of the table
52
while the stator core
53
is installed circumferentially in an annular groove in the housing
61
in opposition to the rotor
54
. This type of the prior rotary table system results in becoming tall in height and a corresponding increase in dimensions, and also would get complicated in construction itself.
In the position control means in &thgr;-direction stated in the former citation, the forked rollers of the cam follower, when having moved over any amount of angle, will interpose aslant the lug between them so that the engagement of the lug with the forked
Browdy and Neimark
Chen José V.
Nippon Thompson Co. Ltd.
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