Bearings – Linear bearing – Recirculating
Reexamination Certificate
1999-10-28
2001-07-03
Marmor, Charles A (Department: 3681)
Bearings
Linear bearing
Recirculating
C384S045000, C384S048000
Reexamination Certificate
active
06254274
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a car and track apparatus such as a sailboat traveler or the like generally comprising a roller car slideably mounted on a track.
A particular type of traveler is generally known as a roller traveler, with an example of such described in great detail in U.S. Pat. No. 4,941,197 issued to Roeser. A roller traveler is characterized in that roller bearing means are used as opposed to ball bearings. Roller bearings generally comprise substantially cylindrical members with rotational engagement occurring on their round sidewalls, and no rotational engagement on their substantially flat endwalls.
Under normal operation, cars of travelers such as that disclosed in the '197 patent do not directly contact the track, but ride on sets of lateral side bearings which engage the track along side grooves. The car ideally distributes loads evenly among its lateral bearings. Prior at travelers, including the traveler of the Roeser patent, however, have some significant problems associated with their use.
When loads are located on either side of the track, as opposed to directly along the plane normal to the track, the cars may disadvantageously distribute an uneven load. This results as loads located to one side or the other of the track tend to bear on the car in that direction, as opposed to the directly forward and rearward load placement along the length of the track in which the car is designed to run. When the load is located to one lateral side of the car, bearings along that side are exposed to increased friction and load. In severe circumstances, the car may tilt to an extent that the lower car side contacts the top of the track causing friction and scraping. These problems are most acute for traveler cars that utilize roller bearings, as opposed to ball bearings, as the roller bearings are able to work only uni-directionally.
Uneven loading on the bearings results in increased friction and decreased bearing, track, and car service life. For roller bearing cars such as that disclosed in the Roeser patent, uneven loading can also lead to the axial end wall of the roller bearing coming into moving contact with non-moving parts.
An unresolved need therefor exists for an improved traveler.
OBJECTS OF THE INVENTION
It is an object of the invention to provide a traveler of the type having a car slideable along a track with improved load distribution under loads directed to one or the other lengthwise side of the track.
SUMMARY OF THE INVENTION
The present invention comprises a traveler of the type generally having a car slideably mounted on a track. The car has two lateral side portions, each having side bearings for engaging lateral side grooves of the track. The car further has a center portion having a bottom wall facing and passing over a track top surface. One example of such a traveler is described in detail in U.S. Pat. No. 4,941,197, herein incorporated by reference.
In addition to having two lateral sets of side bearings for engaging the track side grooves, the car of the present invention further comprises additional thrust bearings in the car center portion bottom wall for engaging the track top surface. These thrust bearings are particularly useful in reducing frictional contact between the track top surface and the car center bottom wall when the car may be tilted to one side, as will occur under a load located to one lengthwise side of the track. The thrust bearings also help to more effectively distribute the load on the two sets of side bearings when the car may be under a laterally non-centered load. Increased traveler efficiency and service life are thereby achieved.
Preferably, the thrust bearings-comprise a plurality of ball bearings rotatable about a substantially oval shaped thrust bearing race in the center portion bottom wall, with elongated race portions along the lateral sides of the bottom wall. The preferred thrust race center portion bottom wall comprises a removable center hub that holds the preferred ball bearings in place, and that may be removed for ball bearing installation, maintenance, and repair. The preferred thrust race has a semicircular cross sectional shape for retaining the ball bearings, with a bottom portion of the bearings exposed beyond the plane of the bottom wall surface for rotational engagement with the track top surface.
When a load is located towards either lateral side of the car, the thrust bearings will help to prevent the car from significantly tilting and thereby will maintain an evenly distributed load on the car lateral side bearings. A compressive load will be placed on the ball bearings along the load bearing lateral side of the oval shaped race, while no corresponding compressive load will be placed on the balls passing along the opposite side of the thrust race. In this manner the thrust bearings rotatably engage the track in the direction of movement along the side of the car, and easily re-circulate around the opposite lateral race portion. This engagement prevents the disadvantageous frictional contact associated with travelers of the prior art, as well as distributing the load on the car and bearings more effectively.
Other embodiments of the thrust bearings of the invention include roller bearings on fixed axles located near the lateral sides of the car bottom wall. These roller bearings on axles may take the form of wheels. They may be partially recessed in a slot in the car bottom wall with only a portion exposed beyond the wall for rotational engagement with the track top surface. Still an additional embodiment of the thrust bearings of the invention comprises a low friction sliding member, such as a layer of polymer. The polymer surface extends beyond the car bottom surface for low friction engagement with the track top surface. The low friction member may comprise two strips of polymer running along the lateral sides of the car bottom wall.
The above brief description sets forth rather broadly the more important features of the present disclosure so that the detailed description that follows may be better understood, and so that the present contributions to the art may be better appreciated. There are, of course, additional features of the disclosure that will be described hereinafter which will further describe the subject matter of the invention. In this respect, before explaining an embodiment of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiments and of being practiced and carried out in various ways, as will be appreciated by those skilled in the art. Also, it is to be understood that the phraseology and terminology employed herein are for description and not limitation.
REFERENCES:
patent: 4375195 (1983-03-01), Tsuboi
patent: 4396235 (1983-08-01), Teramachi
patent: 4659238 (1987-04-01), Teramachi
patent: 4702622 (1987-10-01), Teramachi
patent: 4918846 (1990-04-01), Tsukada
patent: 4941197 (1990-07-01), Roeser
patent: 5123754 (1992-06-01), Tanaka
patent: 6109789 (2000-08-01), Chen
Hanson Thomas
Monahan Kevin
Harken, Inc.
Marmor Charles A
Parekh Ankur
Pyle & Piontek
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