Chairs and seats – Bottom or back – Contoured bottom
Reexamination Certificate
1999-09-29
2002-01-08
Brown, Peter R. (Department: 3636)
Chairs and seats
Bottom or back
Contoured bottom
C297S452210
Reexamination Certificate
active
06336681
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a chair and in particular a seat cushion for a chair that allows a person occupying the chair to sit with good posture while also maximising blood circulation in the lower limbs.
BACKGROUND ART
The human body evolved for the purposes of running and walking and not prolonged sitting. Sitting originated as a function related to status and as such chairs were designed to reflect the status of the sitter. The combination of poor chair design with an increase in sedentary lifestyle has lead in modern times to an increase in spinal and other problems resulting from the body being seated for long periods of time.
It is known that the adoption of an upright seating posture can prevent and help alleviate some spinal conditions that lead to back pain. One type of chair that does encourage correct seating posture is those chairs having a seat portion that slopes forwardly. Such chairs can sometimes have a knee rest that helps prevent the person sitting in the chair from sliding forwardly off the seat member. One disadvantage of this known seat is that the pressure exerted on the knees by the knee rest can result in discomfort for the sitter.
An example of an alternative type of chair that is described as encouraging good seating posture is the chair described in Australian patent specification AU-B-73415/87. This chair has a seat member including at least forward and rear support portions separated by a crevice. The rear support portion is described as having a relatively low resistance to resilient deformation compared to that of the forward support cushion. The combination of this difference in relative resistance to resilient deformation of the forward and rear support portions and the crevice therebetween serves to locate the sitter's ischial tuberosities behind the forward support portion so that the forward portion can exert a rearwardly directed pressure on the ischial tuberosities. This in turn is described as resulting in the sitter being supported in an ergonomically correct posture. One perceived disadvantage with the seat member described in AU-B-73415/87 is that the relatively higher resistance to resilient deformation of the forward support cushion can exert a level of pressure on the back of the thighs that leads to at least some impedance of the peripheral blood circulation in this area with its attendant consequences. A further potential disadvantage is that depending on the sitter's anthropometrics, a sitter may have no choice but to sit in a position where their ischial tuberosities are not positioned behind the crevice thereby negating any perceived benefit that the chair might normally provide to the posture of a sitter.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention consists in a seat member for a chair, the seat member including a forward supporting portion and an adjacent rear supporting portion, wherein the rear supporting portion has a high resistance to resilient deformation and the forward supporting portion has a low resistance to resilient deformation, the resistance to resilient deformation of each portion being relative to the other portion.
The seat member preferably includes a base member that supports the forward and rear supporting portions.
In one embodiment, the forward and rear supporting portions can comprise separate cushions supported by the base member.
In another embodiment, the forward and rear supporting portions can comprise separate cushions that are in abutment with each other.
In a still further embodiment, the forward and rear supporting portions can comprise cushions that are affixed to each other, such as by a suitable adhesive.
In yet a further embodiment, the forward and rear supporting portions can be integral.
In still yet a further embodiment, the forward and rear supporting portions are formed by the insertion of a partition into a cushion cover that allows the cushion cover to be divided into areas that when filled have respectively a lower and higher resistance to resilient deformation relative to each other.
The cushions in this embodiment preferably have a fabric cover. Covers made of other suitable materials, including vinyl and leather can be readily envisaged.
The forward supporting portion can in one embodiment occupy between 30 and 70% of the area defined by the seat member and the rear supporting portion between 70 and 30% of this area. In a preferred embodiment, each occupy about 50% of the area defined by the seat member. In other embodiments, the forward supporting portion can occupy more of the area of the seat member than the rear supporting portion and in another embodiment the inverse can be the case.
The forward and rear supporting portions can be formed from a foam material. For example, the foam material can comprise cut foam or molded foam. While other foams such as rubber latex foams can be utilised, the foam material is preferably a polyurethane foam. Flexible polyurethane foam is made up of a network of cellular shapes comprised of tiny struts and cell windows. The struts form the exterior support structure of the cells, while the windows are voids which are created as foam bubbles burst during the foam production process. Common struts are shared among cells to create a unified material with good structural integrity and handing strength. This structure complements the elasticity of the plastic material allowing polyurethane cells to compress and recover on response to applied load.
If required, the foam material can incorporate fillers or additives. For example, additives are sometimes incorporated to improve the combustion performance of the foams.
In a preferred embodiment, the rear supporting portion is formed from a foam material having a firmness greater than that of the foam material comprising the forward supporting portion. In one embodiment, the rear supporting portion can be formed from polyurethane foam having a measured Indentation Force Deflection (25% IFD) greater than that of the forward supporting portion. The rear supporting portion preferably has a 25%, IFD of between about 85 to 105 Newtons and the forward supporting portion a 25% IFD of between about 70 to 90 Newtons.
Further, the rear supporting portion can be formed from a foam material having a density substantially the same or greater than the density of the foam material comprising the forward supporting portion.
One particularly suitable polyurethane foam for use as the rear supporting portion is sold under the name Dunlop Enduro—EN36-130 by Dunlop Flexible Foams. This flexible foam has the following characteristics:
Density:
36-38 kg/m
3
IFD:
25%
40%
65%
Minimum
85
110
205
Maximum
105
140
250
Indentation Factor:
2.39
A particularly suitable foam for use as the forward supporting portion is sold under the name Dunlop Enduro—EN36-100 by Dunlop Flexible Foams. This flexible foam has the following characteristics:
Density:
36-38 kg/m
3
IFD:
25%
40%
65%
Minimum
70
95
170
Maximum
90
120
220
Indentation Factor:
2.44
Both the forward and rear supporting portions each have a forward edge, a rearward edge and side edges.
In another embodiment of the invention, the density of one or both of the forward and rear supporting portions can vary from the forward edge to the rearward edge. For example, the density of the portion might decrease from its rearward edge to its forward edge.
In a still further embodiment, the resistance to resilient deformation of one or both of the forward and rear supporting portions may vary from the forward edge to the rearward edge. For example, the resistance to resilient deformation of the portion might decrease from its rearward edge to its forward edge.
In a still further embodiment, the rear supporting portion may comprise at least two layers, one upper layer disposed above a lower layer. In this embodiment, the upper layer can have a low resistance to resilient deformation and the upper layer a high resistance to resilient deformation, the resistance to resilient deformation of each layer being relative to the o
Browdy and Neimark
Brown Peter R.
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