Task chair with adjustable seat depth

Details Task chair with adjustable seat depth Task chair with adjustable seat depth

1999-07-07

2001-02-20

Nelson, Jr., Milton (Department: 3624)

Chairs and seats

Bottom or back with means to alter contour

Located at the front of the seat bottom

C297S284100

Reexamination Certificate

active

06189971

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a task chair with a support and with a seat that supports the buttocks and at least the part of the thigh near the buttocks.
2. Background Information
A conventional task chair has a standardized seat depth of approximately 40 to 43 cm. There is space on the seat surface for the buttocks and, depending on the size of the person sitting on the chair, a variable length of the thigh. For shorter persons, the front edge of the chair is often too far forward, so that the blood vessels in the legs are compressed by the front edge, thus hindering the blood supply to the legs. The unpleasant and unhealthy consequences are cold feet and varicose veins.
To correct the seat depth, in some task chairs, the position of the backrest is adjustable; that is, the person sitting in the chair can choose how great the distance between the front edge of the chair and the backrest should be. However, if the seat surface is physiologically shaped, then a shorter person sits too far forward or a tall person sits too far to the rear on the seat surface.
From German Patent DE 196 17 689 C (Faure), a seat depth adjustment for motor vehicle seats is known. In it, the seat region at the front of the seat is movable in the longitudinal direction of the vehicle. The front seat region is secured to the seat by two parallel retaining arms, which can be swivelled about a horizontal shaft fixed to the seat. Its top side is located partly under the seat surface. The retaining arms are articulated in the rear end of the moveable seat region, and a further, adjustable-length arm is pivotably secured to the seat at a rear shaft and articulated to the front end of the seat region. A disadvantage of this seat depth adjustment is that the retaining arms and the adjustable-length arm require shafts secured to the seat, which are disposed below and at a distance from the seat surface. Such a construction is unacceptable for task chairs for use in the office, because these arms under the seat surface are not only unattractive but do not guarantee enough space for the legs below the seat surface.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to create a task chair, for instance for work at a desk or computer screen, that is adjustable to the body size of the person using the chair. The adjustment should be accomplished with the simplest and most-aesthetic possible means, and the chair adjusted to the person should be physiologically adapted as optimally as possible. In particular, the seat depth should be adjustable.
According to the invention, this is attained by a seat surface which has a buttocks portion large enough for the buttocks alone and a thigh support, which is separate from the buttocks portion and can be displaced to at least partway under the bearer part and be pulled forward while under the buttocks portion.
A task chair accordingly has a support, and on the support at least the following chair elements are secured:
a) a rear buttocks portion of the seat surface, with a depth adapted to a human bottom and in which a physiologically shaped seat depression is embodied, and
b) a front thigh support of the seat surface, the thigh support being separate from the buttocks portion and supported such that it can be displaced in a circularly curved rail forward and backward relative to the support and the buttocks portion;
and on the underside of the seat surface, the arc of the rail runs past the seat surface under the buttocks portion and is curved toward the task chair so that the thigh support can be displaced to at least partway under the buttocks portion in the rail and can be pulled forward while under the buttocks portion.
Separating the actual seat surface for the buttocks, which must bear the load of the upper body of a person sitting on it, from the thigh support, which if the seat is in the correct position supports only the legs, makes it possible for the thigh support to be variable in length, because the thigh support can be put into positions with different spacings between the front edge and the buttocks portion. As a result, the total length of the seat surface can be changed, without this change in length changing the shape of the seat depression in the buttocks portion or its position with respect to an optional backrest or lumbar support. A person sitting on the chair always sits on the right spot in the seat depression and can have his legs supported as desired. The unused length of the thigh support, being under the buttocks portion, is not a hindrance in any way. Thanks to the lengthening of the thigh support by displacement, rather than for instance adding successions of parts, a seamless, continuous thigh support can be used. Furthermore, the specially shaped front edge remains at the very front in every position.
The thigh support is guided with a circularly curved displacement path. A curved guide on the one hand enables a physiological design of the thigh support with an upward-oriented rounding and a sloping front edge. In addition, the rounding makes space free under the buttocks portion, because thanks to the rounding, the spacing between the surfaces of the thigh support and the depression for the buttocks becomes all the greater, the farther the rounding or the thigh support extends to below the buttocks portion. This space is either needed or readily usable for the construction of the buttocks portion.
Thus a shallow transition from the buttocks portion to the thigh support can be made. To make the transition as imperceptible as possible, the buttocks portion in the front region is advantageously formed so that it tapers in wedgelike fashion. If at least the buttocks portion is padded, then the wedge-like front region of the padded buttocks portion expediently forms a cushion, which rests under load on the thigh support. The transition between the buttocks portion and the thigh support is thus fluid and virtually imperceptible. This makes it possible to dispense with a supporting construction, connected to the substructure of the buttocks portion, for padding the front edge of the buttocks portion. Such a supporting construction would surely be perceptible in the case of padding that tapers to a point or is wedge-like at the front. At the transition between the buttocks and the thigh, which is also the point of transition between the buttocks portion and the thigh support, great pressure on the cushion is not expected, if the seat is in the correct position, and a transition designed in this way is thus not perceived, at least when the seat is in an upright position.
Advantageously, the thigh support can be locked in various displacement positions. The displacement position can be locked by the load of the person sitting on the chair. This can be achieved by providing teeth or zigzags along a guide, both on the displaceable part and on the part guiding it; these teeth or zigzags mesh with one another when a load is put on the thigh support and thus make displacement at least more difficult, yet in the unloaded state, under tension or pressure, they slide easily past one another in the displacement direction on the displaceable part.
Expediently, two bearer parts bear the buttocks portion on both sides, and a guide in which the thigh support is displaceably supported is made in each of these bearer parts.
A lumbar support is preferably provided on the task chair, and its spacing from the seat surface is adjustable. This makes it possible to react to the body size of the user. The lumbar support can be performed by a support cushion that is rotatable about a horizontal axis and has at least three seat surfaces. These seat surfaces each have a different spacing from the pivot axis of the supporting cushion in the plane of symmetry of the chair, so that depending on the rotary position the support of the small of the back or lumbar spine of a user is provided farther forward or farther forward to the rear with respect to the seat depression or seat surface.
Advantageously, a ba

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