Bearings – Linear bearing – Recirculating
Reexamination Certificate
2002-03-07
2004-01-27
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
C384S051000
Reexamination Certificate
active
06682218
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a linear motion guide unit adapted for use in various types of machinery such as semiconductor manufacturing machines, precision measuring instruments, precision assembly machines and, more particularly, to a linear motion guide unit in which a slider is movable on an elongated track rail by virtue of rolling elements that are allowed to run through recirculating passages, together with separating elements each arranged between any adjacent rolling elements.
2. Description of the Prior Art
Although current linear motion guide units have been used extensively in diverse fields of machinery such as machine tools, semiconductor manufacturing equipment, conveying systems, inspection instruments, measuring means, processing systems, assembly machines, various industrial robots, and so on, the scope of their useful applications is still expanding with the development of technology. To this end, the linear motion guide units are seeing growing demands for less noise or vibration, reduction of wear, long-lasting service life, high precision, high-speed sliding motion, easy assembly, generally accepted usage, and so on. In recent years, especially, the linear motion guide unit is much expected in which separators are each interposed between any two adjoining rolling elements to lower noise, reducing wear thereby realizing long-lasting service life.
A linear motion guide unit as shown in
FIG. 16
is disclosed in, for example Japanese Patent Laid-Open No. 12465/2001. The prior linear motion guide unit is generally composed of an elongated track rail
41
and a slider
42
that fits over the track rail
41
for linear movement along the track rail
41
. Raceway grooves
47
are made on lengthwise sides
43
of the track rail
41
, one to each side. Moreover, the track rail
41
is made on a top surface
45
thereof with openings
46
in which bolts fit to fasten the track rail
41
on any of a bed, machine base, and so on. The slider
42
is comprised of a carriage
44
fitting over and conforming to the track rail
41
, end caps
48
secured on forward and aft ends of the carriage
44
, one to each end, and end seals
49
arranged on lengthwise outermost faces of the end caps
48
to close clearances between the track rail
41
and the end caps
48
. Fastening screws
51
are to join together both the end caps
48
and the end seals
49
to the carriage
44
, while sidewise opposing bottom seals
52
are arranged underneath both the carriage
44
and the end caps
48
. The carriage
44
is made therein with raceway grooves
53
confronting the raceway grooves
47
on the track rail
41
. Made open on an upper surface
55
of the carriage
44
are holes
56
having female threads that fit on male threads of associated bolts or screws to fasten the carriage
44
to other component such as a work table and the like. Rolling elements such as balls
58
are arranged in load-bearing raceways
57
, which are defined between the raceway grooves
47
on the track rail
41
and the raceway grooves
53
in the carriage
44
, so as to be allowed to run through the load-bearing raceways
57
, thereby moving the slider
42
in a sliding way along the track rail
41
. Retainer bands
59
serve continuing to keep the rolling elements
58
against escape out of the carriage
44
even after the slider
42
has been detached from the track rail
41
. The rolling elements
58
are charged in the linear motion guide unit in a way allowed to run through a ball-recirculating circuits, each of which includes the load-bearing raceway
58
and a non-loaded raceway that is made up of a return passage
60
bored in the carriage
44
and turnarounds, not shown, formed in the end caps
48
, one to each end cap, to connect at opposite ends thereof with the associated load-bearing raceway
57
and return passage
60
, thereby completing the ball-recirculating circuit. A grease nipple
61
to apply lubricant into the ball-recirculating circuits is attached to the associated end cap
48
in a way extending outside from the end face of the associated end seal
49
.
Nevertheless, the current linear motion guide units, as coming used in the machines that are getting faster in operating speed and cycle, must be further refined on wear proof and quietness in operation. With the prior linear motion guide unit having any separator interposed between two adjoining rolling elements, moreover, any construction that the separator travels with keeping to fit snugly over the associated rolling elements is critical for making sure of steady movement of the rolling elements throughout the ball-recirculating circuit even under modern high-speed operation. For allowing the separator to move with fitting over the associated rolling element, it will be sufficient only to make the separator large in outside diameter, but in this instance it remains a major challenge to make the separators recirculate smoothly together with the associated rolling elements.
Another example of the prior linear motion guide units is disclosed in Japanese Patent Laid-Open No. 281154/1998, in which a separator is arranged between any two adjoining rolling elements to lessen the vibration and noise that might be caused by any regular run of the rolling elements, thus keeping the rolling elements against premature wear. The separator interposed between the two adjoining rolling elements in the linear motion guide unit recited just above, when made large in the outside diameter thereof, is made up of a flat core area and a funnel-shaped peripheral area diverging radially outwardly around the core area. The separator constructed as stated earlier, even though made in the diameter coming into sliding contact with the radially inside curved surface of the associated turnaround, will change place radially outwardly in a direction normal to the running direction of the separator owing to the centrifugal force caused when the separator travels through the turnaround. This behavior will keep the separator from any interference with the radially inside curved surface of the associated turnaround. With the linear motion guide unit stated earlier, however, the separator is apt to experience any wandering in directions normal to the traveling direction of the rolling elements even during the linear travel in any of the load-bearing raceway and return passage because the separator has the flat core area to provide a clearance for allowing the associated rolling element to change place relatively to the concave surface of the separator confronting the rolling element when the separator moves through the turnaround. Thus, the prior linear motion guide unit constructed as stated earlier will get unsteady in the travel of the separator.
Disclosed in Japanese Patent Laid-Open No. 304046/2000 is another example of the prior linear guide bearing arrangement with a separator interposed between any two adjacent rolling elements. With the linear guide bearing arrangement cited above, a curved raceway where the rolling elements are allowed to turn round in sequence is designed to have a radially inside surface of composite curve having more than one curvature different in radius of curvature, rather than an unitary simple semicircular curve. According to the curved raceway constructed as stated earlier, the separator, even if made large in outside diameter, may be kept from any contact at the outside periphery thereof with the radially inside surface of the curved raceway. Nevertheless, the radially inside surface of the curved raceway, because made in the complex shape, introduces expensive machining and forming operations.
Japanese Patent Laid-Open No. 193739/2001 discloses a further another example of the prior linear guide bearing arrangement with a separator interposed between any two adjacent rolling elements, in which balls are accommodated in concaves formed on forward and aft end faces of the associated separator and are allowed to roll with keeping concurrent rolling-contact with b
Browdy and Neimark
Hannon Thomas R.
Nippon Thompson Co. Ltd.
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