BACKGROUND OF THE INVENTION Generally, widely used chairs and seats comprise a seat portion having a flat surface or a curved surface in order to disperse the pressure. Another type of commonly used chairs or seats adapt a cushion having uniform elasticity in their seat portion. Wile seated, a user's breech gets under most of the pressure arising from his or her upper body's weight, it's the ischium in particular bearing the greatest pressure. In case that a chair has a seat portion having uniform elasticity and a person is seated for hours in the chair, the ischium is overstrained, which causes discomfort of the coccyx and the backbone.

Consequently, it is hard to maintain a fine sitting carriage and a frequent change of sitting posture is imposed, which combines to bring about broken concentration and spinal diseases like spinal curvature to students in a growth period. And if the high pressure has been applied in the ischium for a long time, it may also cause anal, muscular, or urinary diseases because blood circulation of

the breech.

SUMMARY OF THE INVENTION To resolve the problems as described above, the present invention provides a chair having a seat portion with a hole in a predetermined position into which a cushion having multiple elasticity is fitted to disperse the pressure applied on the user's ischium in different directions round the breech. A major advantage of the present invention is that a user can maintain a good posture with blood circulation is not disturbed even if he/she is seated for a long time.

An object of the invention is to provide a seat having a cushioning portion on which a user's breech are placed when he/she is seated. The cushioning portion consists of a first portion corresponding to a user's ischium and a second portion corresponding to the other regions of the hip, wherein, the first portion is of lower elasticity than a second portion so that the pressure exerted on the ischium of a seated person, that is applied on the first portion, can be dispersed to the second portion.

According to the present invention, a hole is provided in the seat portion to fit a first and a second elastic members of the cushion. The first elastic member having a first modulus of elasticity is fitted in the hole, especially corresponding to a first portion of the cushioning portion. The second elastic member is also fitted in the hole, especially corresponding to a second

portion of the cushioning portion, wherein the second elastic member has a higher elasticity than the first elastic one.

According to another aspect of the invention, a pad is provided in the bottom of the hole. The pad could be made of various materials having medicinal effects.

This invention is also to provide a chair or a seat comprising the seat portion mentioned above.

The present chair and the seat comprising: a seat portion having a hole in a place corresponding the ischium of a persion who is seated on the chair; a cushion consists of multi-part and inserted into the hole to disperse the pressure applied on the ischium, wherein the cushion is wrapped with a cover; a pad for improving health which is optionally inserted under the cushion.

The cushion consists of plural elastic bodies having different elasticity respectively. The border of the cushion has a relatively large modulus of elasticity and the center is made of smooth materials having a small modulus of elasticity. The whole cushion is wrapped with a cover. The cover is made of a materials having abrasion resistance and thin enough for the user to fee the elasticity of the cushion.

A pad for improving health having an effect of antibiosis, deodorization, or moisturizing can be optionally used. The pad can be made by covering the materials like charcoal, yellow ocher or bio-ceramic, etc with the cover. Alternately, the pad can be made by foam molding in desired shape after adding polyurethane or

polyester to the materials.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, the invention will be described in greater detail by means of the accompanying drawings, in which: Fig. 1 is a perspective view of a chair according to a first embodiment of the present invention.

Fig. 2 is a longitudinal section view of a seat according to the first embodiment of the present invention.

Fig. 3 is a longitudinal section view of a seat according to a second embodiment of the present invention for showing its'structure.

Fig. 4 is a longitudinal section view of a cushion according to a third embodiment of the present invention for showing its'structure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a first embodiment of the present invention, a chair shown in Fig. 1 comprises a seat portion (12), leg (s) (13) and a backrest (11). The backrest (11) can be formed in flat or in curved. The leg (s) can be one, two or more. Alternatively, the present invention can be embodied without the backrest (11) or the leg.

A hole provided in the seat portion (12) can be any of the shapes like a square, a circle, an oval, a half circle or any other closed line. Preferably, the upper area of the hole is selected between 50 cm2 to 600 cm2

around the spot that the breech are placed when he/she is seated. Generally, the center position of the hole is located with a distance 7 cm to 15 cm from the back end of the chair, but it can be changed in accordance with a chair.

Fig. 2 is a longitudinal section view showing the seat portion (12) having a hole in the place corresponding to the user's breech when he/she is seated, and the cushion (20) that is mounted in the hole. The cushion consists of three parts: a first elastic member (23) having a small modulus of elasticity formed in the center portion of the cushion; a second elastic member (22) having relatively large modulus of elasticity which is formed around the first elastic member and; a cover (21) covered the both elastic members.

When a user seated on a chair according to the first embodiment, the first elastic member (23) that is corresponding to the ischium of a seated person is greatly pressed down, the second elastic member (22) is relatively less pressed down, and the rest part of the. seat portion is not pressed down at all. In a seated condition, the first elastic member (23) that is greatly pressed down, increases the area covering the ischium and transfers the pressure applied on the first elastic member partly to the second elastic member. Therefore, the pressure applied to the ischium is considerably reduced. Since the first elastic member (22) is pressed down a little while its exterior is not pressed at all, the pressure applied on the second elastic member is somewhat transferred to the exterior of the second elastic member.

Accordingly, the high pressure which is applied from the upper body to be applied on the ischium can be transferred to other portion of the breech which is receiving relatively small pressure, so that pressure can be applied evenly throughout the whole breech. Therefore, in case that a user is seated in a long time, he/she may not feel hard on his/her breech without changing a seated posture. Moreover, the present chair is good to health because present chair provides a promotion of blood circulation. It is also possible to add a third and a fourth elastic members to increase the feeling of the seat portion.

Fig. 3 shows a second embodiment of the invention. A chair according to the second embodiment comprises a seat portion (12) having a health pad (24) under a cushion (20), legs (13) and a backrest (13). Preferably, the intensity of the health pad (12) is greater than that of the cushion (20). The health pad (12) can be made of charcoal or mugworts by a compression molding and also can be made of bio-ceramic, yellow soil, or gems. The health pad (12) may improve health of user since the medicinal effects of the materials contained in the pad acts on the user through the cushion, wherein the cushion has permeability.

Alternatively, it is possible to obtaining moisturizing, dampproofing, deodorization or warmth effects by adding an additive having remedial value or emitting far infrared.

It will be helpful especially to a person having anal or urinary diseases.

Fig. 4 shows a chair comprising a cushion (30) formed in integral, a seat portion (12) having the cushion, legs

(13) and a backrest.

It is not shown in the figure, the portion corresponding to user's ischium has small elasticity than the other portion. Therefore, the pressure applied on the ischium can be transferred to the other region of the seat portion same as the first and the second embodiments.

The major principle of the present invention is to provide a seat structure which can disperse the pressure exerted on the region corresponding to the ischium to the other region of the seat.

It should be understood that while the foregoing discussion illustrates a particular embodiment of the present invention, this embodiment merely represents a best mode of currently practicing the invention, and various other modifications and advantages will become apparent to one skilled in the art after having had the benefit of studying the teachings of the specification, the drawings, and the claims, and that such other modifications may be made without departing from the spirit and scope of the invention.

For example, the seat portion could be made without a hole and a cushion but the portion corresponding to the ischium having relatively less elasticity than other portion of the integrally made seat portion. And this seat portion could be incorporated in any type of chair, sofa or means for seat.