Chairs and seats – Rest for knee – leg – or foot – For occupants knee or shin
Patent
1992-07-09
1993-11-16
Trettel, Michael F.
Chairs and seats
Rest for knee, leg, or foot
For occupants knee or shin
297316, 297319, A47C 1032
Patent
active
052617270
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a chair as defined in the introductory portion of claim 1, i.e. a chair which can be converted from one state where a person can traditionally sit on the approximately horizontal seat of the chair, to another state where the person can sit on the now inclined seat of the chair, one and the same means being used as a back rest in said one state and as a knee rest in said other state.
Such a convertible chair is known e.g. from the U.S. Pat. No. 4 793 655. To lock the movable part of this chair in the traditional state with approximately horizontal seat and with back rest, there is in one embodiment provided a hook below the seat, and to convert the chair to the other state with inclined seat and with knee rest some dexterity must be exercised to find and to release the hook, and the person must moreover bend to be able to see the hook below the seat. In the other state of said chair with inclined seat and with knee rest, the seat and the knee rest are not locked in this state, which is therefore unstable. The chair therefore involves the risk that the seat and the knee rest will tilt in case of certain loads with unfortunate consequences for the seated person. In another embodiment a toothed rack is journalled to the bottom of the seat and extends into the supporting column. The arm of the back rest carries a pinion engaging the rack so that a vertical movement of the rack effects a pivoting of the arm with the back rest. The rack may be locked in various different vertical positions by a short rack member which is mounted in the supporting column and carries a knob. When the chair is to be converted the user may disengage the rack member by pulling in the knob whereafter the rack may be displaced to the new setting position. This chair is very difficult to convert because the knob is positioned below the seat and near the floor so that the user of the chair will have to bend down or kneel on the floor in order to pull the knob. Further, there is no means for determining the correct position of the back rest. Consequently, the user may either have to adjust the chair several times at each conversion or have to accept a somewhat wrong sitting position which impairs the ergonomical advantages of the convertible chair.
The U.S. Pat. No. 4 736 982 discloses a convertible chair where a transverse rod on a two-armed lever, which carries the back/knee rest, is to be positioned in a specific gap between downwardly facing teeth on an open rack on the lower side of the seat. The conversion is difficult to perform and involves some uncertainty, and great care is to be exercised in practice to localize the rod in precisely the tooth gap giving the desired angular position between the seat and the rest. The great drawback of this chair is that it is potentially unstable in both of its positions. If a person sitting on the chair places his weight on the seat toward the back/knee rest, the seat can unintentionally tilt toward the back/knee rest with the unfortunate consequence that the seat with the rack will be lifted out of engagement with the rod, so that the back/knee rest falls down, and the seat loses its support. The same risk exists when the chair is in the traditional sitting position with back rest, and the person intends to move the chair and therefore naturally lifts and pulls the front edge of the seat. This can entail that the seat tilts upwardly, and that the transverse rod thereby disengages from the adjusted engagement, following which the back rest swings downwardly.
When the chair has been converted for knee rest use, and the person wants to sit on it, he will initially straddle the knee rest and can hereby unintentionally apply a downward pressure to the seat end most adjacent to the knee rest, so that the seat and thereby the engagement means and the arm are tilted out of the preadjusted knee rest position. This involves the risk of the user sitting down on a seat which is not locked in the angular position and will consequently tilt forwardly, while the knee rest disappears rea
REFERENCES:
patent: 2471024 (1949-05-01), Cramer
patent: 4629249 (1986-12-01), Yamaguchi
patent: 4650249 (1987-03-01), Serber
patent: 4736982 (1988-04-01), Hwang
patent: 4765684 (1988-08-01), Kvalheim et al.
patent: 4793655 (1988-12-01), Kvalheim et al.
patent: 4834454 (1989-05-01), Dicks
patent: 5054857 (1991-10-01), Kvalheim
Space International ApS
Trettel Michael F.
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