Chairs

Details Chairs Chairs

1997-04-18

2001-09-25

Barfield, Anthony D. (Department: 3636)

Chairs and seats

Bottom or back

Contoured bottom

C297S452260, C297S452230

Reexamination Certificate

active

06293625

ABSTRACT:

TECHNICAL FIELD
This invention relates to improvements to chairs and in particular to an improved meet design and support therefore. The present invention has particular but not exclusive application to chairs of the type which have a forwardly tilted seat or a seat which allows for some degree of forward tilting movement.
A seated person's weight is largely born on, and balanced over the Ischial Tuberosities of the pelvis and their posture is largely determined by the front to rear rotation of the pelvis. If the knees are elevated higher than the hips, the pelvis is tilted back and a less desirable posture results.
BACKGROUND ART
Chairs of many different designs are currently available. In many chair designs, the most common seat configuration in one in which the seat Is substantially flat and disposed with a slight backward tilt. This configuration induces an undesirable seated posture and creates a transverse pressure ridge against the underside of the user's legs.
In improved chair designs, the seat is provided with a forward tilt to encourage a more erect posture and the correct lordosis of the lower back. When using such chair designs, the knees are lower than the hips and the normal curve of the spine is encouraged. As the tilt of the chair seat increases however, means are required to be provided to prevent a person seated on the chair from sliding off the seat.
The use of knee rests is common for such purposes, however knee rests create certain difficulties as considerable pressure Is applied to the knees which can thus be aggravated. Furthermore, chairs of this design reduce the freedom of movement of the person's posture and additionally the chairs themselves are more cumbersome
Various seat contours have also been proposed to prevent sliding from a tilted seat. Most however have as their principal object the restraint of sliding and thus are not adapted for comfortable effective seating. For example, one earlier proposal utilises a seat contour formed with a transverse V-shaped recess which would not be particularly comfortable in use. Others provide a forward-elevating central ridge which would also be uncomfortable for many users.
Furthermore, these arrangements do not maintain a desired posture wherein the skull, neck, lower backbone and Ischial Tuberosities of the pelvis are substantially maintained in vertical alignment while the user's weight is transferred to a relatively flat horizontal surface.
Also, in many prior proposals tilting seats are considered desirable. In this respect it is believed that small amplitude tilting movements of the spine stimulate nutrient secretion to the spine. However most use conventional tilting arrangements which result in the user's body being raised and lowered with the tilting action This changes the body's height in relation to the desk which is most undesirable. Thus the desired relationship between hip and knees and the desk at which the person is seated is varied with the tilting. Furthermore when in a tilted position, offset pressure must be applied to the seat in order to maintain the desired tilted attitude. This further reduces the relaxed attitude of the user's body and increases stress.
The present invention aims to alleviate one or more of the above disadvantages.
SUMMARY OF THE INVENTION
The present invention in one aspect thus provides a seat for a chair having:
a rigid base formed with a front edge portion which curves downward relative to a main supporting portion;
a layer of padding covering the base, and
mounding means disposed in the front portion of the base and forming a low mound in the upper surface of the padded covering in front of each Ischial Tuberosities which tapers forwardly towards the front edge portion and rearwardly towards the back portion of the base and against which respective opposed forward portions of a user's Ischial. Tuberosities may engage.
This arrangement provides a dished supporting portion beneath the Ischial Tuberosities which maintains a substantially level supporting surface beneath the Ischial Tuberosities and a forward-elevating surface in front of the Ischial Tuberosities when the base is tilted forwardly. Thus the seat base may be tilted forwardly through a limited angle while maintaining a desirable supporting contour for the user.
Preferably the mounding means forms respective laterally spaced apart mounds providing a gap or trough therebetween to prevent excess pressure being applied to the front of the centre of the pelvis and adjacent body parts. The mounding means in cross-section suitably has a curved upper surface forming an external substantially convex configuration.
The mounding means Is suitably formed as spaced part cylindrical sections disposed with their longitudinal axes either substantially transversely aligned with each other or angled to each other such that their axes extend from the sides of the seat towards the front of the seat.
The mounding means may be provided by the base of the seat, by an Insert or inserts in or on the seat or by a suitably shaped cushion on the base of the seat. Where defined by the base of the seat, the base may be shaped to incorporate the mounding means and be covered by suitable cushioning such as a constant thickness foam plastics sheet or other resilient material. Where defined by an insert or inserts, the insert or inserts are suitably interposed between the base of the seat and cushioning. Where defined by the cushioning applied to the base of the seat, the cushioning is suitably shaped to define the mounding means.
The seat configuration of the invention may be applied to chairs having a seat of fixed inclination or of a variable inclination. Preferably the seat is applied two a variable inclination support in which the seat is supported for fore and aft tilting motion about a transverse pivot which, in use, may be substantially in vertical alignment with the skull, neck, lower backbone and Ischial Tuberosities of a user comfortably seated upon the seat. This arrangement has the advantage that the user's body is not significantly raised and lowered with the tilting action. Thus the user adjusted relationship, by seat height adjustment, between hip and knees is maintained. In addition as the user's weight is applied through the pivot offset pressure need not be applied to the seat in order to maintain the desired tilted attitude.
In a further aspect, this invention resides in a chair seat support of the type utilising a leaf or torsion spring having upper and lower end portions which connect to the seat bass and the support means respectively to springedly support the seat base relative to the support means, and hereinafter referred to collectively as “U-shaped spring means”, said chair support including:
support means providing an elevated seat support;
U-shaped spring means having a lower end portion fixed to the support means and an upper end portion fixed to the seat base, and characterised in that the portion of the U-shaped spring means which spans between the upper and lower end portions, hereinafter referred to as the spanning portion, is disposed substantially centrally of the seat base to permit a user to move when supported by the seat bass to a position at which the seat base is tilted forwardly while its medial position above the spanning portion remains at a substantially constant elevation.
Preferably the support means is a central strut type support which is height adjustable and the U-shaped spring means comprises a pair of laterally spaced apart U-shaped springs in which the spanning portion between the upper and lower end portions is a substantially part-cylindrical springing portion. The use of U-shaped springs is preferred over the use of torsion springs as, in addition to providing spring for the tilting action, U-shaped springs also provide minimal vertical springing for the supported seat.
Suitably the substantially part-cylindrical spanning portion has a radius of between 1 ⅛″ and 3 ¼″. In a preferred embodiment each

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