Bearings – Linear bearing – Recirculating
Reexamination Certificate
2002-05-21
2004-03-23
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
C384S051000
Reexamination Certificate
active
06709158
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, inspection equipment, 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 rollers that are allowed to run through recirculating circuits, together with separators each interposed between any two adjacent rollers.
2. Description of the Prior Art
Although current linear motion guide units have been used extensively in diverse fields of machinery such as semiconductor manufacturing machines, measuring/inspection instruments, 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, versatile 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.
Disclosed in Japanese Patent Laid-Open No. 132745/2001 is a linear motion rolling guide unit in which flanged separators are each interposed between any two adjoining rollers, with their flanges coming into engagement with axially opposite ends of the rollers to keep the separators against axial deviation or offset thereby to make certain of smooth sliding movement with no noise of the separators. With the prior linear motion rolling guide unit recited earlier, the separators are each composed of a major body made concaved at opposite sides thereof to accommodate therein the adjacent rollers in a rolling contact relation, one to each side, and flanges arranged at the axial opposite ends of the major body, one to each end, in a way extending in opposite directions to each other along the moving direction of the rollers to come into face-to-face engagement with their associated axial ends of the adjacent rollers. The separator constructed as stated just above may be well kept against any offset in axial direction of the roller with no need of specific guide member, because the roller rolls in a condition that they are regulated at their axial opposite ends to run through a recirculating circuit. In the prior linear motion rolling guide unit in which the separators have flanges on their axial ends, there is a major drawback that the recirculating circuit has to be made large in width by thickness of the flanges on the separators, compared with the linear motion guide unit of the sort having no separator. Moreover, the separator recited earlier is disadvantageously made too smaller in outside periphery diameter than the roller to embrace the associated rollers therein.
In Japanese Patent Laid-Open No. 26017/1989 there is disclosed a rolling means to guide parts in linear direction, in which many rollers are held by means of spacers that come in engagement at their sidewise ends thereof with recesses formed in skids. The spacers are each made sidewise extended beyond opposite axial ends of the roller to form sidewise opposed lugs, which come in engagement with the recesses formed inside recirculating grooves in the skids, thereby holding the rollers in place. With the rolling means constructed as recited earlier, the troublesome work must be done to provide sidewise lugs for the spacers. Moreover, the recesses in which the lugs of the spacers fit in a sliding engagement have to be cut into the overall inside of the recirculating grooves. The lugs of the spacers are sensitive to be subject to damage such as wear that might be caused by the continuous sliding engagement with the inside surfaces of the recesses.
Another prior linear motion system disclosed in Japanese Patent Laid-Open No. 314420/2000 has spacers for linear motion, which are each interposed between any two adjoining rollers. The spacer is made hollow to experience elastic deformation in moving direction of the rollers and also is provided at the center thereof with a guide plate extending radially outwardly into a guide channel that is cut in the moving direction in an inside periphery of a recirculating circuit where the rollers run through there. In this prior linear motion guide unit, however, the spacer has to be designed lest it comes in interference at any edge thereof with the inside surface of the roller-recirculating circuit. The troublesome work is further needed to cut the guide channel, in which the guide plate fits for free movement, in the overall inside surface of the roller-recirculating circuit. Moreover, the guide plate is apt to be subject to damage such as wear, since the guide plate comes most often in sliding engagement with the walls in the associated guide channel, but not always.
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 quietness, high accuracy and wear proof in operation. With the prior linear motion guide unit having any separator interposed between two adjoining rollers, moreover, any construction that the separator travels with keeping to fit snugly over the rollers flanking the forward and aft ends of the separator is critical for making sure of steady movement of the rolling elements throughout the roller-recirculating circuit even under modern high-speed operation. For allowing the separator in the linear motion guide unit to move with fitting over the associated rollers, it will be sufficient only to get the separator concaved on the forward and aft sides thereof flanking the adjacent rollers and made large in outside diameter to what extent the separator may fit over the overall roller.
As the separator travels in a sliding manner as opposed to the roller that moves in rolling manner, however, the separators made large in outside diameter would pose a major problem that they, when traveling through a turnaround in the recirculating circuit, might tend to experience an interference with an inside surface of the turnaround, incurring travel failure. Thus, it remains a major challenge to provide the separator that, even though made large in outside diameter enough to fit over the overall roller, is allowed to recirculate steady, smoothly together with the rollers flanking the forward and aft sides of the separator through, especially, the turnaround in the roller-recirculating circuit.
Recently many types of linear motion guide units have been developed in which separators are each interposed between any two adjoining rollers to lessen noise and wear, and increase life span of the associated parts. Especially the present inventor has already developed a linear motion guide unit in which more than one separator made large in outside diameter thereof is interposed between any two adjoining rolling elements of balls. This linear motion guide unit was filed in Japan in the name of the present applicant under Patent Application No. 2001-391276. With the linear motion guide unit that the separator made large in outside diameter are interposed between any two adjoining balls as recited just above, the turnaround is made on a radially inside curved surface thereof with a gutter for relief to make certain that the separator is allowed to travel through the turnaround without seeing any interference with the inside surface of the turnaround. Application of the technical conception developed earlier to a linear motion guide unit using rollers rather than balls for the rolling elements has resulted in the development of the present invention about how to define the relation of the separator with the turnaround in the roller-recirculating circuit.
SUMMARY OF THE INVENTION
The present invention, therefore, has as its primary object to overcome the major problem d
Browdy and Neimark , P.L.L.C.
Hannon Thomas R.
Nippon Thompson Co. Ltd.
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