Bearings – Linear bearing – Recirculating
Reexamination Certificate
2002-09-10
2004-05-04
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Recirculating
Reexamination Certificate
active
06729761
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a linear motion guide unit envisaged to treat well high speed and high cycle in modern advanced machines such as semiconductor manufacturing equipments, industrial robots, engines, and so on, and more particularly a linear motion guide unit in which sintered resinous material of porous structure is installed in a carriage to provide a return passage therein while a joint tube communicates the return passage with turnarounds formed in the end caps.
2. Description of the Prior Art
The conventional linear motion guide units are commonly so constructed that a slider is movable relatively of an elongated track rail through many rolling elements, which are allowed to run through recirculating circuits comprised of load areas of raceways defined between the track rail and the slider, and non-loaded areas including turnarounds in end caps and return passages in a carriage in the slider. To help prevent metal-to-metal direct contact between the rolling elements and the recirculating circuits thereby to make certain of the rated durability of the linear motion guide units, it is necessary to continue constantly supplying the rolling elements and the recirculating circuits with lubricant to ensure keep lubrication between the rolling elements and the recirculating circuits. Secure lubrication between the recirculating circuits and the rolling elements is usually realized by periodic replenishment of lubricant.
Recently remarkable needs in reduction of expenditure on maintenance activities as well as in energy savings have given birth to various advanced machines such as semiconductor manufacturing equipments, industrial robots, engines, and so on, which can operate on maintenance-free. Correspondingly, the linear motion guide units to be used in the machinery are also counted on meeting with needs of maintenance-free lubrication. Especially, the linear motion guide units expected incorporated in the semiconductor manufacturing equipment, and so on, which conform the clean-room specifications must meet demands to adopt specific substances and/or designs that might yield little or no debris or cutting. Moreover, it is inevitable to limit the amount of lubricant used as least as possible since fine mist of lubricant might contaminates the atmosphere in the clean room.
A prior linear motion guide unit is disclosed in Japanese Patent Laid-Open No. 161354/2000, in which a ball-recirculating circuit is composed of a linear area bored in a carriage of a slider, and a curved area formed in an end cap, and the linear area is connected with the curved area through a socket-and-spigot joint that is made up of a hollow spigot end to extend an open end of the curved area into the linear area of the carriage, and a receptacle formed in an open end of the linear area to receive and fit over the spigot end. With the prior linear motion guide unit constructed as stated above, the end cap is made with a roughly cylindrical spigot while the carriage is made with a roughly socket to receive therein the spigot to communicate the linear area in the carriage with the curved linear area in the end cap to complete the ball-circulating circuit. In the prior linear motion guide unit, however, the linear area in the ball-recirculating circuit has no sintered resinous material as will be recited later, and moreover a guide member to define a radially inside curved area, because made apart from the end cap, has to be assembled into the end cap in conformity with the curved area in the end cap. It will be said this construction is unfit for the machines that need maintenance-free operation.
Another conventional linear motion guide unit is disclosed in Japanese Patent Laid-Open No. 136805/1986, in which a circulating circuit provided by combination of a slider with a guide rail is made up of a load raceway defined between a raceway groove on the guide rail and a raceway groove in a carriage of the slider, a return passage bored in the carriage in parallel with the load raceway, and curved ways formed in end caps of the slider one to each end cap. The return passage is made with a tube fit forcible into a hole drilled through the carriage. However, since the tube for the return passage is forcibly fit in the through-hole in the carriage, replacement with new one is very tough job.
Although but the prior linear motion guide units recited just above can operate successfully with no application of lubricant so long as used under light loads in the clean room specifications, they do not always serve well for the recently advanced machinery that has become increasingly higher in speed and oscillation. With the prior lubricant-containing polymer member availed for the conventional linear motion guide units, the polymer should be molded while being mixed with lubricating oil. In addition, the lubricant-containing polymer member, because of lacking the necessary strength in itself and of itself, has to be reinforced when incorporated really in the linear motion guide units. To cope with these disadvantages, the linear motion guide unit has inevitably become sophisticated in construction and highly advanced technology has been needed. With the construction in which the lubricating plates were mounted on the slider to make sliding engagement with the track rail, there is the problem that the slider has caused large frictional resistance when it was applied to machinery high in speed and oscillation.
Modern advanced machinery has a tendency to get higher in working speed and oscillation. These days, to deal with the tendency, the linear motion guide unit in which a return passage is made with a sintered resinous material of porous structure has been used in practice. An example of the linear motion guide unit having the return passage of sintered resinous material of porous structure stated just above is disclosed in, for example Japanese Patent Laid-Open No. 82469/2001, which is a senior application of the same applicant. With the linear motion guide unit recited earlier, the return passage bored in the slider is lined with sintered resinous material of porous structure, which can make certain of supplying the rolling elements with lubricant for a prolonged period, refining the slider in durability. The slider movable relatively to the track rail by virtue of the rolling elements is made therein with a through-hole in which a sleeve of the sintered resinous material having porous structure fits to form a return passage encircled with the sintered resinous material. Grease, lubricating oil and so on is absorbed in the porous structure of the sintered resinous material in a way continuing to be supplied for a long period onto the rolling elements running through the return passage, thereby lubricating the raceway via the rolling elements to improve the slider in durability as well as reduce the sliding resistance that is encountered when the slider moves on the track rail.
Thus, it may be worthwhile developing a linear motion guide unit continuing to supply the rolling elements with lubricant, thereby making certain of smooth running of the rolling elements for a prolonged period. To this end, it remains a major challenge to provide a linear motion guide unit in which the rolling elements running through the return passage in the slider are allowed to roll smoothly at a joining area of the return passage together with the associated turnaround, and the material fit in the through-hole in carriage of the slider to define the return passage has a property of self-lubrication of lubricating oil onto the rolling elements and also a strength enough of itself to need not to be reinforced with any other means.
SUMMARY OF THE INVENTION
The present invention has for its primary object to overcome the challenge as described just above, especially provide a linear motion guide unit in which a sleeve of sintered resinous material capable of impregnated with lubricant fits in a through-hole bored in a carriage to form a return passage, and a joint tube is app
Ishihara Toyohisa
Itabashi Shigemasa
Matsui Takeshi
Browdy and Neimark , P.L.L.C.
Hannon Thomas R.
Nippon Thompson Co. Ltd.
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