Dustproof construction for slider unit

Details Dustproof construction for slider unit Dustproof construction for slider unit

2001-10-25

2003-09-30

Footland, Lenard A. (Department: 3682)

Bearings

Linear bearing

Combined with seal or guard

C384S045000

Reexamination Certificate

active

06626571

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dustproof construction for a slider unit, which is envisaged to close effectively any clearance between a track rail and a slider unit to thus prevent foreign materials such as dust and dirt, oil mist and so on from entering into the slider unit and also keep debris, metal cuttings, oil contamination and so on owing to the slider unit itself against escape outside the slider unit through there.
2. Description of the Prior Art
Referring first to
FIGS. 18 and 19
, there is shown an example of prior slider units conventionally used in various fields such as semiconductor manufacturing apparatus, machine tools, assembling apparatus, testing instruments and so on, which are needed to work in any clean room. The slider unit is primarily comprised of an elongated track rail
2
opened upwardly at
27
to provide an U-shaped traverse cross-section to make a recess
5
, and a slider
2
fitting snugly in the recess
5
of the track rail
2
for sliding movement relatively to the track rail
2
, a recirculating-ball screw shaft
4
mating with the slider
3
, and a driving motor
4
to turn the recirculating-ball screw shaft
4
. The recirculating-ball screw shaft
4
is supported for rotation on the track rail
2
at both of a first bearing member
11
installed in an lengthwise end near the driving motor
9
and a second bearing member
12
installed in the lengthwise opposite end of the track rail
2
, which is fastened to any basement by means of suitable fastener means such as screws. The slider
3
is installed to move linearly along the track rail
2
through rolling elements. A bottom
6
and a pair of upright side walls
7
define in combination the upwardly opened recess
5
in the track rail
2
. The side walls
7
are provided on their widthwise opposing inner surfaces with raceway grooves
8
that extend in parallel with each other lengthwise along the track rail while the sliding element
3
has raceway grooves confronting the raceway grooves
8
to define a load raceway between them. Rolling elements may run through the load raceway, thereby making the slider
3
move smoothly along the track rail
2
.
The slider
3
has a pair of widthwise opposing upright flanges
13
, which are to mount an object such as a workpiece table on the slider. The flanges
13
are made with threaded holes
14
for fixture means such as bolts to hold any object thereto. A dustproof cover
15
is attached to the bearing members
11
,
12
so as to shield the track rail
2
with the exception of sidewise clearances
33
where the flanges
13
are allowed to move back and forth through there. Thus, the dustproof cover
15
is arranged above all of the slider
3
and the recirculating-ball screw shaft
4
, which constitute in combination a torque-to-thrust conversion system for the slider unit, thereby keeping dust and debris against entering into and also coming prom inside the track rail
2
. A pair of the upright flanges
13
, on which the object to be moved is loaded, should be formed so as to be unobstructed with the dustproof cover
15
. To this end, the upright flanges
13
each extend widthwise outwardly of the slider
3
and then turn upwardly to thereby provide a substantially L-shape in front view. The slider
3
has a nut
17
made therein with an internal helical groove that will mate with an external helical groove provided around the recirculating-ball screw shaft
4
. The combination of the screw shaft
4
with the nut
17
constitutes a torque-to-thrust conversion system in which the rotation of the screw shaft
4
results in driving linearly the nut
17
along the track rail
2
. The lengthwise opposite bearing members
11
,
12
are mounted on railheads
20
of the upright side walls
7
,
7
of the track rail
2
. The railheads
20
are finished in parallel with the raceway grooves a of the track rail
2
.
Sensor rails
22
are disposed on sidewise outsides of the upright side walls
7
of the track rail
2
, each to side wall. The sensor rails
22
are each provided with a limit sensor
23
at any preselected place to sense the associated flange
13
, followed by issuing the detected signal to a controller through a lead wire
24
and a sensor connector
25
. The driving motor
9
is energized depending on any control signal applied through a motor connector
28
to produce a torque transmitted to the recirculating-ball screw shaft
4
via a coupling
30
. A fore-and-aft range over which the slider
3
is allowed to travel is defined with stoppers
31
,
32
that are secured to the bearing member
11
,
12
, each to each bearing member.
In Japanese Patent Laid-Open No. 325070/1999 there is disclosed a sealing construction for the slider unit constructed as stated earlier, in which bellows-like sealing means are installed to keep foreign matter such as dust, debris and so on against entering into and coming from inside the slider unit through the sidewise clearances
33
. The bellows-like sealing means are each composed of at least one sealing member expansible owing to its own elasticity, which is secured to anyone of the confronting lengthwise edges of the track rail
2
and the dustproof cover
15
to close the associated clearance
33
. When the slider
3
travels along the track rail
2
, the flanges
13
extending across the clearances
33
are allowed to move smoothly because the sealing members are easily subject to the elastic expansile and collapsed deformation and thus thrust aside by the action of the moving flanges
13
.
Another example of the sealing constructions for the slider unit made as stated earlier is disclosed in Japanese Patent Laid-Open No. 27235/2001, in which expansible sealing members are arranged in gaps between the track rail
2
and the dustproof cover
15
in a manner allowing the flanges
13
to travel through the gaps on the sliding movement of the slider
3
along the track rail. Each expansible sealing member is composed of upper and lower sealing parts that are urged elastically against each other to close the associated gap. When the flange travels across the associated gap, the upper and lower sealing parts are shoved apart from each other at only a region closely neighboring the moving flange to allow it to travel between the sealing parts, with keeping a sliding contact with the opposite surfaces of the moving flange. At the residual regions before and after the moving flange, however, the upper and lower sealing parts are kept in abutment against each other due to their own elasticity. Moreover, the upper and lower sealing parts are made in an elongated configuration that is attached at one lengthwise side thereof to any one edge of the gap and abutted against the counterpart with their own elasticity. The lower sealing part is made greater in elastic force than the upper sealing part to compensate the influence of gravity.
With most prior slide units, any elongated slits or clearances
33
are left uncovered between the dustproof cover
15
and the track rail
2
to allow the flanges
13
for supporting thereon a workpiece table to travel back and forward integrally with the slider
3
along the clearances
33
, with extending sidewise across the clearances
33
. This means many conventional slider units should not be able to effectively prevent foreign materials such as dust and dirt, and so on from entering into the slider unit through the clearances
33
and also keep debris, metal cuttings, and so on owing to the slider unit itself against scattering all around through the clearances
33
in the clean room where the semiconductor manufacturing machines are installed. To cope with this, various ways constructed as stated earlier have been proposed to keep dust and debris against entering into and escape out of the dustproof cover through slits, clearances
33
and so on. Nevertheless, the major obstacles to all the sealing constructions in which the bellows-like expansible sealing members are installed to close the sidewise clearances
33
and

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