Bearings – Linear bearing – Alternating roller; or antifriction bearing for auto seat
Reexamination Certificate
2002-11-25
2004-05-18
Footland, Leonard A (Department: 3682)
Bearings
Linear bearing
Alternating roller; or antifriction bearing for auto seat
C384S051000
Reexamination Certificate
active
06736541
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 a variety of machinery such as semiconductor manufacturing machines, precision measuring instruments, precision inspection equipment, precision assembly machines or the like and, more particularly, to a linear motion guide unit that is provided therein with means for keeping a cage against wandering.
2. Description of the Prior Art
In recent years, linear motion guide units of the type hereinafter referred to as “finite linear motion guide unit” because of their construction where rolling elements are allowed to roll over only a definite travel instead of rolling through a recirculating circuit have been used extensively in diverse fields of machinery such as semiconductor manufacturing machines to guide a part in a linear way relatively to any counterpart. Correspondingly, the finite linear motion guide units of the sort recited just above are seeing growing demands for high speed operation and high acceleration/deceleration, with even made slim or compact in construction. At the same time the advanced machinery expects the finite linear motion guide units to be operated with high precision and low-frictional resistance, and so on. Solving the issues stated earlier is needed for further development of the linear motion guide units.
Typically, most prior finite linear motion guide units of the type recited earlier have a mechanism for keeping a cage against wandering, which is a rack-and-pinion arrangement having, for example a rack
41
shown in FIG.
15
. The rack
41
lies in a gutter for relief cut in a raceway groove of a guide rail member in a longitudinal direction thereof, with its tooth bottom part
44
coming into face-to-face contact with a gutter bottom
45
. The rack
41
is slotted at
42
in such a fashion that the rack material remains on the tooth bottom part
44
between the slots
42
in the form of teeth
46
that are arranged successively in the lengthwise direction of the rack
41
at a pitch preselected to mesh with an associated pinion. Moreover, tooth tips
43
of the teeth
46
are made flat, for example as shown at
47
. With the rack
41
constructed as stated earlier, the tooth bottom part
46
can contribute to keeping securely the teeth
46
at their desired positions. Nevertheless, modern tiny linear motion guide unit of the sort recited here can not frequently afford any space to allow the tooth bottom part
44
to have a thickness enough to hold up the teeth.
In Japanese Patent Laid-Open No. 108056/1999, there is disclosed a finite linear motion guide unit of the type recited earlier, which has means for keeping a cage or retainer against wandering to help control certainly the travel of finite guide rail members. The cylindrical rollers held in the cage are placed for rolling between confronting raceway grooves formed on the guide rail members. The cage has supported a pinion for rotation, which comes in mesh with a rack of gear teeth held in a gutter for relief. With the finite linear motion guide unit recited earlier, the rack lies in the gutter for relief cut lengthwise in the raceway groove formed on the guide rail member. The teeth on the rack are made recessed to avoid any interference with the cylindrical rollers. This construction allows the rack of gear teeth to be made in a module large in size, thus increasing the strength in mesh with the pinion thereby to keep the cage against wandering with respect to the associated guide rail members. Thus, the rack-and-pinion mechanism recited just above may be instrumental in keeping the cage against wandering relatively to the guide rail members.
The present assignee has already filed a senior pending Patent Application No. 2001-216235 in Japan relating a finite linear motion guide unit of the sort discussed here in which an earlier developed rack-and-pinion arrangement can serve effective function for keeping the cage against wandering. The finite linear motion guide unit discussed in the earlier pending application, although not shown here, is made shrunken in size and constructed such that a pinion coming into mesh with a rack is installed for rotation in a pinion holder fit in a cage. Especially, the senior application discloses means for keeping the cage against wandering, in which the pinion is held in a pinion chamber made in the pinion holder. The pinion is comprised of a disc having the teeth that are positioned circumferentially at regular intervals around the disc to form tooth spaces or slots each separating any two adjacent teeth, and a shaft carried in the pinion chamber for rotation to provide an axis about which the disc rotates. Moreover, the teeth formed around the disc are each made up of a dedendum part extending radially outwardly out of a curved periphery of the disc, and an addendum part integral with the dedendum part and made in a semicircular configuration. With the finite linear motion guide unit disclosed in the senior pending application, the rack lying lengthwise in the gutter for relief cut in the raceway groove on the guide rail member is made integral with the guide rail member by a molding process in which a powder of metal is formed with a metal injection molding, followed by being subjected to sintering.
With the every prior finite linear motion guide units of the sort discussed here, the rack is made with slots successive in the longitudinal direction thereof with the same pitch as the circular pitch of teeth on the mating pinion. The slots on the rack are each defined between two adjacent projections or teeth integral with a tooth bottom part and also designed to have a circular configuration somewhat larger in radius than the semicircular configuration of the addendum of the pinion tooth, thereby allowing the pinion making certain of sequential mating with the teeth on the pinion to smoothly come into successive mesh with the mating teeth of the rack. Moreover, the prior finite linear motion guide units of the sorts stated earlier, as the rack and the pinion are made relatively complicated in their tooth profile, are apt to encounter large sliding resistance and intermeshing resistance, and also very tough to shrink the guide unit itself down to tiny size in construction.
In most prior finite linear motion guide units of the sort discussed here, the guide rail member is commonly made on sides thereof with bolt holes lengthwise at preselected intervals, which are used to fasten the guide rail member to other object including a table, basement, sliding pedestal, machine bed and so on. When the linear motion guide units must meet an anticipated design demand to shrink them down as tiny as possible in size, nevertheless, the gutter for relief formed in the raceway groove on the guide rail member to fit the rack therein, just as in the conventional constructions, has to be inevitably restricted in depth to the extent where the gutter is allowed to extend around the fastening bolts. This makes the gutter for relief less in depth, thus making it tough to lay the conventional rack in the gutter.
SUMMARY OF THE INVENTION
The present invention, therefore, has as its primary object to overcome the major problems discussed earlier in the finite linear motion guide units of the sort stated earlier, and in particular to provide a finite linear motion guide unit with means for keeping a cage against any wandering, in which a rack has lengthwise side walls opposing widthwise across successive rack teeth to join the teeth together with one another so as to make it possible to keep the teeth between them at a preselected pitch even when any tooth bottom part does not necessarily remain in the rack. The present invention provides the finite linear motion guide unit with means for keeping a cage against wander, in which the tooth bottom part of the rack, if any, can be made as thin as possible to render the rack as slim as possible in depth. According to the present invention especially, the rack used in the means for keeping the c
Kamimura Akihiko
Obara Kouji
Tsuboi Takaaki
Browdy and Neimark , P.L.L.C.
Footland Leonard A
Nippon Thompson Co. Ltd.
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