Machine element or mechanism – Control lever and linkage systems – Elements
Reexamination Certificate
2000-02-23
2001-02-13
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Elements
C403S365000
Reexamination Certificate
active
06186027
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to improvements in bicycle handlebar stems and more particularly to an improved assembly for securing a bicycle stem to a bicycle fork steerer tube.
DESCRIPTION OF THE PRIOR ART
The handlebar of a bicycle is coupled to the bicycle frame by means of a stem having a vertical tube which is secured to the steerer tube of the fork to which the front wheel is attached. Two different approaches have been used extensively for coupling the bicycle handlebar stem to the steerer tube. One approach involves division of an external screw thread on the upper end of the steerer tube onto which is secured the top race of the upper bearing headset assembly, and a lock nut, with the top end of the steering tube terminating flush with or just below the lock nut. With this approach, the vertical tube of the stem is inserted into the steerer tube and carries a threaded fixing stud which in turn carries a wedge nut at its lower end. The fixing stud has a head that is accessible through the top end of the vertical tube of the stem. When the stud is turned, the wedge nut is pulled upwardly against a compensating tapered surface at the lower end of the vertical tube, causing the wedge to be displaced laterally and to tighten against the inner surface of the steerer tube, whereby the stem acts as an extension of the steerer tube.
The second approach uses a stem that comprises a dual clamp section that surrounds the steerer tube. In this arrangement, the length of the steerer tube is extended so as to accommodate the clamp section of the stem. The upper race of the upper bearing is not screwed to the steerer tube. In order to permit pre-loading the steering headset bearing, a star nut is located inside the steerer tube, and a preload cap is engaged with the upper end of the steerer tube, and a threaded studs extends through the cap and is screwed into the star nut. Turning the threaded stud varies the force with which the cap forces the stem into engagement with the outer race of the upper bearing headset and thereby determines the pre-loading of the bearing.
The first approach is complicated and relatively expensive. The second approach offers the advantage of using a lighter weight stem. However, the second approach suffers from the limitation that it is easy to make a mistake in properly positioning the star nut in the steerer tube, and correcting the mistake is difficult since the star nut, by design, tightly grips the steerer tube. Damage caused by forcing removal of the star nut is especially disadvantageous in the case of expensive light weight bicycle frames. As an alternative to the star nut, a small device which expands radially and has internal threads is inserted into the steerer tube in place of the star nut. The expandable device is more easily removable than the star nut, but it suffers from the disadvantage that it makes a tenuous grip on the steerer tube.
A further problem with the foregoing arrangements is that they make it difficult, if not impossible, to pass a brake cable through and out of the upper end of the steerer tube, thus preventing use of the brake assembly invention disclosed in my U.S. Pat. No. 5,803, 207, issued Sep. 8, 1998.
OBJECTS AND SUMMARY OF THE INVENTION
The primary object of the invention is to provide a new assembly for positively and securely locking a bicycle stem to an unthreaded steerer tube.
Another object is to provide a novel stem-securing means which is simple and inexpensive to manufacture and use.
Still another object is to provide a bicycle handlebar stem having novel means for securing it to a steerer tube.
A further object is to provide a novel bicycle stem/steerer tube combination that facilitates pre-loading of the steerer tube bearings.
Another object is to provide a method of attaching a bicycle stem to a steerer tube which facilitates pre-loading of the upper bearing for the steerer tube.
A more specific object is to provide an arrangement for securing a stem to a bicycle fork steerer tube that allows a brake cable to extend from brake actuating means carried by the fork up through and out of the upper end of the steerer tube.
The foregoing objects are achieved by utilizing with a non-threaded steerer tube a castellated externally-threaded locking bushing that fits onto the upper end of the steerer tube in position to engage the outer race of the upper steering head bearing, and a bicycle stem that comprises a first split clamp section that closely surrounds the tube and is adapted to be compressed into tight engagement with the steerer tube, and a second split clamp section that surrounds and makes a screw thread connection with the castellated bushing and is adapted to be compressed to squeeze the bushing so as to lock it to the steerer tube. The invention includes a method of assembling the stem and bushing with the steerer tube that facilitates pre-loading of the upper bearing associated with the steerer tube. Other features and advantages of the invention are disclosed or rendered obvious by the following detailed specification.
REFERENCES:
patent: 5517878 (1996-05-01), Klein et al.
patent: 5553511 (1996-09-01), Marui
patent: 5588336 (1996-12-01), Chou
Green Mary Ann
Pandiscio & Pandiscio
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