Chairs and seats – Movable bottom – Tiltable
Patent
1998-12-15
1999-11-30
Barfield, Anthony D.
Chairs and seats
Movable bottom
Tiltable
297320, 297330, 29735413, A47C 1024
Patent
active
059929340
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a dental patient chair having a mechanism for the constraint-coupled adjustment of seat and backrest of the chair. The mechanism includes a seat carrier or frame which is connected to an upper part for pivotable movement around a backrest proximate axis so that when the backrest is inclined backwards, the seat carrier with a seat and leg support is tilted upward around the backrest proximate axis and when the backrest is raised upward, the carrier is tilted downward.
A patient chair having such a mechanism is disclosed, for example, by European Letters Patent 0 373 245. Even though the mechanism disclosed therein allows the seat to be brought into a relatively low limit position, the parts provided for the inclination of the backrest and for tilting the seat relative to the upper part occupy a relatively large space.
DE-A1 3 018 684 discloses another patient chair wherein the seat support is divided into a seat part carrying the buttocks and thighs and a calf support arranged pivotable relative to the seat part. So that the calf support can be designed short and pivoted down into a vertical position when the seat part is lowered far, the calf support contains a support part that can be telescopically extended and retracted in its longitudinal direction. The support part is adjusted along the calf support with the assistance of a cable that is arranged in the fashion of a block and pulley and runs over three rollers when it is adjusted with the assistance of an actuating drive that acts between seat part and calf support.
SUMMARY OF THE INVENTION
The invention is based on the object of creating a mechanism of the species initially cited that allows a lower, flatter structure of the seat overall, particularly of the seat carrier. The improvement in the mechanism comprises the backrest at a lower end adjacent the seat being guided in a curved guide which is provided in the seat carrier and a flexible, bendable force transmission element has one end secured to a first fastening point on the upper part and another end secured to the backrest at a second fastening point adjacent the lower end, the transmission element is guided over three rollers in the fashion of a block and pulley with a first roller being mounted at a projection on the seat carrier to form a first variable spacing between the first fastening point and the first roller, the second roller mounted on the upper part adjacent the lower end of the backrest to form a second variable spacing between the second roller and the second fastening point and the third roller being mounted on the upper part spaced from the second roller toward the first roller so that a shortening of the first spacing causes a lengthening of the second spacing and vice versa.
The inventive constraint-coupling of seat and backrest is advantageously achieved with a roller chain and three chain wheels, whereby the one chain wheel represents the "loose roller" of the "inverse block and pulley" and the two other chain wheels merely serve for the deflection of the chain force.
The overall arrangement is advantageously undertaken so that the backrest is inclined approximately twice as fast as the seat is tilted. This is achieved in that, as a result of the arrangement in the fashion of a block and pulley, the adjustment paths and, thus, the adjustment rates between the fastening points of the force transmission element, for example the roller chain, at the seat-side or lower end of the backrest on the one hand and at the upper part on the other hand are brought into a specific relationship relative to one another. The aforementioned motion relationship can be achieved on the basis of the selection of the spacings.
Other advantages and objects of the invention will be readily apparent from the following description of the preferred embodiments, the drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view with portions removed for purposes of illustration of a dental patient chair in a position that corresponds to a lying po
REFERENCES:
patent: 3578379 (1971-05-01), Talor
patent: 3866973 (1975-02-01), Heubeck
patent: 3873152 (1975-03-01), Garas
patent: 4572573 (1986-02-01), Yoshikawa et al.
patent: 4988145 (1991-01-01), Engel
patent: 5015035 (1991-05-01), Stoeckl et al.
Gehrig Hermann
Moritz Gunther
Barfield Anthony D.
Sirona Dental Systems GmbH & Co. KG
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