Chairs and seats – Chair hardware or attachment
Reexamination Certificate
2000-11-15
2003-02-04
Brown, Peter R. (Department: 3636)
Chairs and seats
Chair hardware or attachment
C297S300300, C297S302200
Reexamination Certificate
active
06513879
ABSTRACT:
FIELD OF INVENTION
The present invention relates generally to a mechanism for the control of seated body support and more specifically to the adjustment movements of an ergonomically correct chair.
BACKGROUND OF THE INVENTION
Ergonomically correct seating for work has been of concern for many years. It not only reduces the fatigue at the end of the day but it also contributes to the long-term health of the spinal column. Given the importance of proper posture while sitting, it is not surprising that many different mechanisms have been developed to accommodate the three most important seating adjustments: seat height, seat inclination, and the back support adjustment.
The prior art patents, dating back to 1947, are typical for the style and technology of the day. The technology disclosed is outdated and does not meet today's product safety requirements. The adjustments proposed by Harman in 1947 (U.S. Pat. No. 420,7452) and by Hamilton in 1966 (U.S. Pat. No. 3,338,626) are based on hand wheels, worm gears, and cylindrical springs in which fingers can get caught. In 1968, Hasbrouck (U.S. Pat. No. 3,361,472) introduced a stool with an adjustable semi-circular back support that can also serve as armrest, though it does not offer a seat tilt adjustment. Interesting is the Scheben design of 1975 (U.S. Pat. No. 3,880,465) that was the first to introduce gas springs for seat height and back support adjustment with a single lever; however, the design does not provide for an adjustment of the seat tilt and uses separate levers for the two adjustments.
The 1981 patent of Aaras et. al. (U.S. Pat. No. 4,277,102) introduces the unchanged seat-to-backrest relation throughout the range of adjustment. It also introduces the concept of armrests being adjustable in all directions. The embodiment shown invites further development to bring the revealed ideas to fruition.
The 1982 Meiller patent (U.S. Pat. No. 4,364,605), referring back to the Scheben patent, proposes a more elegant arrangement of gas springs for height and backrest adjustment activated by a single lever. Meiller did not follow Aaras' idea of an unchanged seat-to-backrest relation when the seat inclination is changed. By contrast, in 1987 Steifensand (U.S. Pat. No. 4,682,815) introduces the combination of gas springs with an unchanged seat-to-backrest relation. In 1995, Dauphin was granted the U.S. Pat. No. 5,447,357 for an adjustment mechanism that uses one lever to activate a clutch-like release and lock arrangement for the seat inclination and seating height and a second lever for the gas spring adjustment of the back support. This patent, first applied for in Germany in 1992, uses a different approach to maintain the seat-to-backrest relation. Dauphin calls it a “synchronous” mechanism.
Since then, several mechanism have come onto the market that use a single lever for the adjustments of seating height, seat inclination, and backrest, apparently not all being covered by patents.
Today, the value of maintaining the seat-to-back relation throughout the adjustment range of the seat inclination is being reconsidered for the simple reason that the body posture changes with the inclination of the seat. For this reason, the present invention by Stem keeps the backrest floating while the seat tilt is being adjusted. When the seat is properly tilted for the work at hand and locked into position, the backrest can still be adjusted to a comfortable position and then be locked by releasing the lever into its resting position. Both these adjustments and the seat height positioning are accomplished by means of a single lever and are executed by lever motions that are analogous to the specific adjustment movement to avoid confusion. Earlier designs that offered no analogy between control motions and adjustment motions often created problems, especially in dental or surgical situations where seating adjustments must be made quickly and safely.
SUMMARY OF THE INVENTION
The chair adjustment mechanism, subject of this invention, is based on the use of three gas springs for the three adjustments, all activated by a single lever by means of a central multi-action cam.
The multi-action cam allows for a design more compact than any design previously patented. Most importantly, the lever movements correspond logically to the adjustment movements to avoid erroneous manipulations that could result in accidents. Medical professionals, especially dentists and surgeons, must be able to adjust their stools quickly and without thinking about the coordination of non-coordinated movements. At present, even high-end chairs do not offer easy-to-understand adjustment features. The preferred embodiment of the multi-action cam features three distinct cams each of which controls a different adjustment movement. The subject invention works logically: (1) Lift the lever to adjust the seat height. (2) Push the lever backwards to adjust the back support. (3) Push the lever even further back, beyond a certain resistance, to adjust the seat tilt. When the tilt is in the desired position, it will be locked when the lever moves forward to the intermediate position. At this point, the back support can still be adjusted. Then, when the lever returns to the resting position, all three adjustments seat height, seat tilt, and back support are locked in place.
Additionally, due to the symmetry of the multi-action cam, the adjustment lever can be mounted on the right side for right-handed persons, or on the left side for left-handed persons.
The seat can be inclined, using the lever, for a 10° range for a fine adjustment. In addition, it can be set in one of two basic positions that are 10° apart for a coarse adjustment, thus offering a total adjustment range of 20° to accommodate different work habits and regional preferences.
The use of the multi-action cam can also be designed to activate electrical switches or additional levers or mechanical functions if needed.
REFERENCES:
patent: 4364605 (1982-12-01), Meiller
patent: 4408800 (1983-10-01), Knapp
patent: 4589697 (1986-05-01), Bauer et al.
patent: 4743065 (1988-05-01), Meiller et al.
patent: 4838510 (1989-06-01), Holstensson
Brown Peter R.
Fulcrum Product Development Inc.
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