Chairs and seats – Rocker-mounted – With means to limit or inhibit rocking motion
Patent
1988-09-20
1989-10-31
McCall, James T.
Chairs and seats
Rocker-mounted
With means to limit or inhibit rocking motion
297302, A47C 302, A47C 300
Patent
active
048772909
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a rocker mechanism for chairs and the like which incorporates a locking facility to anchor the seat in different tilt positions relative to the underpart.
It has become very popular in recent times to equip seating furniture, and in particular revolvable armchairs, with some form of rocker mechanism. Such rocker mechanisms enable one to sit in the armchair and rock back and forth, or to tilt the armchair, by shifting one's weight, and to remain seated in the chair with the chair thus inclined. The drawback with such mechanisms, however, is that the chair will not remain in the tilted or inclined position to which it has been adjusted, but will move to a new position as soon as the weight of the body is shifted.
To overcome this drawback there is proposed in Norwegian Patent No. 125568 a rocker mechanism locking facility which comprises an arm which projects out from the underpart of the mechanism and which carries a vertical, planar locking plate. The plate is embraced by two clamping jaws which are manipulated with the aid of a locking bar or rod provided with a righthand and a lefthand screwthread.
This known arrangement is encumbered with a number of drawbacks. For example, clamping jaws, or plates, which abut a flat counter-pressure plate do not lock the mechanism reliably. If an attempt is made to overcome this, by tightening the clamping plates still harder, the screwthreads and the locking rod bearings are liable to become worn, and the locking arrangement may even be broken as a result of excessive tightening of the plates. Furthermore, because no hole is provided in the plate for throughpassage of the locking rod, there is obtained a complicated construction when the load applied thereto is uneven, which further increases the risk of wear and poor locking qualities. In addition, because the plate is located on an arm which projects laterally outwards from the underpart of the rocker mechanism, the arm is subjected to vertically acting torque, which leads to high stress concentrations and the risk of fatigue fractures at the point at which the arm is attached to said underpart. Because the clamping jaw attachments are not centred exactly in relation to the plate, the arm may also be subjected to laterally acting forces.
U.S. Pat. No. 3,101,971 proposes a locking arrangement for rocker mechanisms having a holder arm which is pivotally mounted on the underpart of the mechanism and which presents an elongated opening for accommodating the shaft or axle of the locking arrangement. The shaft presents a nut which is held by a lock-nut and which forms a fixed abutment for a washer or plate which acts against the holder arm. The shaft extends through the elongated opening and a hole in the upperpart of the rocker mechanism and is screwed into a non-rotatably positioned nut. When tightening the shaft the holder arm is held clamped between the aforesaid plate and the side of said upperpart.
This arrangement also incorporates flat abutment surfaces with a subsequent risk of wear, damage and slipping. The pivotal attachment of the holder arm results in play and instability, which unavoidably results in wear and other damage. Furthermore, the holder arm is mounted on one side of the mechanism, which causes unequal load distribution and, with time, results in warping of the chair and other damage.
The purpose of the invention is therefore to provide a rocker mechanism with an improved locking arrangement which will ensure positive locking with no play when applying but a low tightening force; which will avoid unequal load distribution and unfavourable loading conditions; which is self-centering and does not need to be manufactured to high precision standards nor yet particular accuracy in assembly; and which is of simple construction with regard to its function and can be manufactured at low costs.
To this end there is proposed in accordance with the invention a rocker mechanism with locking facility that has a holder and clamping plates with arcuate clamping surfaces conforming
REFERENCES:
patent: 2698649 (1955-01-01), Hopkes
patent: 2907373 (1959-10-01), Katz
patent: 3101971 (1963-08-01), Hampton
patent: 4099775 (1978-07-01), Mizelle
patent: 4198094 (1980-04-01), Bjerknes et al.
patent: 4438898 (1984-03-01), Knoblauch et al.
patent: 4664445 (1987-05-01), Groseth
McCall James T.
Swing-Matic AB
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