Bearings – Linear bearing – Recirculating
Reexamination Certificate
2000-03-29
2001-10-30
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
Reexamination Certificate
active
06309107
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear motion guide unit having wide application in sliding parts incorporated in, for example, machine tools, assembling machines, testing machines and the like. More particularly, it relates to a mounting construction of a linear motion guide unit in which a slider is movable lengthwise along a track rail.
2. Description of the Prior Art
Conventionally, the linear motion guide units have been known for fundamental means applicable universally in various technical fields. Although the linear motion guide units have been now employed extensively in machinery in various fields such as machine tools, semiconductor manufacturing apparatus, testing instruments, industrial robots and the like, the expansion of uses according to the recently remarkable development in technologies requires more and more such linear motion guide unit to deal with the precision, high-speed moving, easy assemblage, wide applicability and the like.
The linear motion guide unit
60
is in general applied between members, as between a stationary bed and a workpiece table as shown in
FIGS. 8 and 9
, which are movable relatively to each other. The linear motion guide unit
60
is comprised of a track rail
61
having a pair of lengthwise side surfaces
63
on which are formed raceway grooves
64
, and a slider
62
mounted on the track rail
61
for sliding movement along the track rail
61
. The track rail
61
is made on the top surface thereof with holes
66
for bolts or screws to fix the track rail
61
to the bed
68
.
The slider
62
mainly comprises a casing
70
riding astride the top surface
65
of the track rail
62
, end caps
71
attached in abutment against lengthwise opposing ends of the casing
70
, each to each end, and end seals
72
arranged on the end caps
71
to seal clearances between the confronting track rail
61
and end caps
71
. Both the end caps
71
and end seals
72
are secured to the casing
70
by means of machine screws
73
. Bottom seals, not shown, are arranged beneath both the end caps
71
and end seals
72
. The casing
70
is provided with raceway grooves
74
confronting the raceway grooves
64
on the track rail
61
, and holes
76
bored through a top face
75
, into which fit machine screws to mount the casing
70
to the workpiece table
78
.
The slider
62
is allowed to move in a sliding manner along the track rail
61
by virtue of rolling elements
81
such as balls, which run through the load areas of raceways
81
defined between the raceway grooves
64
formed on the track rail
61
and the raceway grooves
74
formed in the casing
70
. The rolling elements
80
are held in the casing
70
by retainer bands
84
so as to be kept against disassembling even when the slider
62
is separated from the track rail
61
. The rolling elements
80
may run through endless circulating paths composed of the load raceways
81
, return tunnels
82
bored in the casing
70
to provide non-loaded passages to allow the rolling elements to circulate, and non-loaded turnarounds, not shown, formed in the end caps
71
to interconnect the loaded raceways
81
with their associated non-loaded passages. Moreover, grease nipples
85
to supply lubricant to the endless circulating paths are attached to the end caps
71
and extend outwardly of the end seals
72
.
As shown in
FIG. 9
, the track rail
61
is mounted to the stationary bed
68
by means of bolts
69
that fit into holes
66
in the track rail
61
, which is set in place where a bottom surface
86
of the track rail
61
comes in abutment against a seat surface
90
of the bed
68
while the lower area of any one lengthwise side surface
63
comes in abutment against the confronting side edge
91
of the bed
68
. In contrast, the slider
62
is attached to a workpiece table
78
with bolts
79
that fit in matching holes
76
in the casing
70
. The slider
62
is kept in place with the top face
75
and any one side face
77
thereof being brought into abutment against their confronting bottom surface
92
and a side surface
93
of the workpiece table
78
, respectively. In this manner, the side surfaces
77
of the slider
62
are formed on laterally bulged portions
70
a
to provide sidewise reference surfaces for attachment to the table
78
.
Moreover, another prior linear motion guide unit is disclosed in Japanese Patent Laid-Open No. 347009/1992, which comprises a track rail anchored at lengthwise opposing ends thereof, an upper sliding unit riding astride the track rail, and a lower sliding unit depending from the track rail whereby both the upper and lower sliding units are constituted for a linear motion along the track rail.
In addition, Japanese Utility Model Laid-Open No. 193637/1988 discloses linear motion guide means in which a ball-screw drive is combined integrally with a linear guide. Such prior linear motion guide means integral with the ball-screw drive has a tetragon nut mating with a ball-screw drive, a guide rail made with recessed guiding ways where the tetragon nut comes in loose engagement for linear movement along the guide rail, so that rotating the ball screw allows the tetragon nut to move linearly on the guiding ways of the guide rail by virtue of balls that may run through raceways defined between raceway grooves formed on the widthwise opposing side surfaces of the tetragon nut and raceway grooves formed in the guide rail. The linear motion guide means constructed as described just above is plagued with that the tetragon nut occupies a considerable height above the top level of the guide rail.
Disclosed in Japanese Patent Laid-Open No. 298446/1990 is a worktable traveler in which a worktable is supported for linear movement in a guide rail of U-shape in cross section. The worktable is arranged interposed between widthwise opposing inside walls through rolling elements that are allowed to run through raceways of two rows arranged in vertical juxtaposition, which are defined between confronting raceway grooves formed on the side surfaces of the work table and the inside walls of the guide rail. A screw shaft fits in matching hole that is bored in the worktable at a horizontal plane corresponding substantially center lines of vertical distances spanning between the two raceways vertically juxtaposed on the widthwise opposing side surfaces of the worktable. The guide rail is integrally molded so as to provide raceways in which the rolling elements are held in outwardly-opening contact with the confronting raceway grooves of the worktable and the guide rail, that is, phantom lines linking two points of rolling contact of any rolling element with the confronting raceway grooves of the worktable and the guide rail converge towards the center axis of the screw shaft. As an alternative, the guide rail may be made so as to provide another type of raceways in which the rolling elements are held in inwardly-opening contact, where the phantom lines diverge towards the center axis of the screw shaft.
In the prior linear motion guide unit of the type explained above in which the slider of a nut is driven to move linearly in a lengthwise recess in the guide rail by rotating the ball screw, the worktable is mounted to the flat outer surface of the slider with bolts screwed into their matching holes. Nevertheless, it is common that there is provided no reference means for mounting the worktable onto the slider.
For the linear motion guide unit compact in construction in which the slider is moved linearly in the lengthwise recess in the track rail, thus, it has been desirable to mount the worktable to the slider or mount the stationary bed to the track rail at a preselected mounting position and posture and further ensure the mounting position and posture even after a prolonged period of use.
SUMMARY OF THE INVENTION
The present invention, therefore, has as its primary object to overcome the problem as described just above and more particular to provide an improved linear motion guide unit in which a track rai
Nakano Katsuaki
Ueki Hiroshi
Browdy and Neimark
Hannon Thomas R.
Nippon Thompson Co. Ltd.
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