The present Invention provides a furniture unit to sit on it; it is designed for application when resting or performing office work.

One of the known solutions of such furniture units to sit-on is disclosed in the international invention description under the Patent No. WO 95/16374. It is a chair with a seat fixed to the frame in a manner permitting the frame to move in all directions. For this purpose, the seat is mounted to the frame using a spiral spring, a ball joint, or any other adequate mechanism. Such a seat is reposed on a ball-shaped head having a relatively large radius and placed within the concave bottom plane of a cylinder encompassing the entire head. The cylinder height determines the inclination angle; additionally, this angle may be properly adjusted using a screw mechanism or through the diameter of a hole in the cylinder lid. Such a chair allows for the increased mobility of the upper body part of a person working in a sitting position; it also enables the improvement of the chair's user posture. Moreover, the stimulation of the nerve at the end of the spinal column enhances the physical state.

Another known chair solution is disclosed in the invention description under the Patent No. WO 2009157148. The solution cited comprises a rocking chair equipped with a seat with a lower convex part forming a spherical surface with its central point set above the seat. The rotating rollers contacting the lower convex surface allow for the convex part to move along the spherical surface and the chair supporting part. Another chair is known from WO 90/14031.

The hitherto used furniture units designed for sitting on allow that the following movements of the sitting person's body are possible: leaning, vibrations, rocking or driving, but the individual body parts move toward each other only accidentally.

The objective of the Invention is, on the one hand, to ensure, while sitting, the stabilization of specific body axes. On the other hand, the objective is to concurrently ensure a motion around those axes in order to enable the controlled rotational movements of torso since they determine the frequent and easy changing of the workload of particular surfaces and capsules, ligaments, and muscles.

According to the present Invention, the furniture unit to sit-on comprises the features of claim 1.

Preferably, the backrest frame is equipped with three independent movable rest elements; the middle rest element may be embedded in the frame using a ball joint, and, additionally, both the upper and the lower rests can be made of two independent elements placed parallel toward each other and symmetrically, towards the vertical axis, to the backrest frame.

Preferably, one embodiment variant of the furniture unit to sit-on is equipped with a footrest with two movable props for feet; the props are pivotally connected with the frame of the footrest using a crank assembly.
Additionally, in the upper part of the backrest frame, an element may be fixed and serve as a rest for raised upper extremities.

The furniture unit may be also equipped with an armrest mounted to the base of the backrest frame. To this base, either a work surface or a top for a monitor can be fixed, or those two elements. Owing to this specific construction, the applied Invention as shown above makes it possible to comfortably perform any office work.

A small diameter of the ball joint guarantees that the body rotation axis agrees with or is close to agree with the spinal column axis, therefore, the destructive transverse forces are eliminated. The inter-segmental mobility of spinal column is guaranteed by the stability of specific axes of the sitting person's body (spinal column axis, lateral axis at the head base, and lateral axis of pelvis), and by the possible motion of the body around those axes; the Invention simultaneously ensures both the necessary stability and the motion potential.

When a person's back is supported point wise in one or more points, the sitting and working person can comfortably rest and it a rigid, unchangeable position of his back during a longer period of time.

The use of footrest with movable props for the feet makes it possible that the lower extremities work continuously while the person sits, and, thus, the muscle pump of lower extremities is activated; this prevents varices.

The subject under this Invention is exemplified in the drawings attached to this Application. They show one embodiment of the Invention. In Fig. 1, there is a diagrammatic drawing of a side-view of the furniture unit to sit-on, whereas in Fig. 2, there is a diagrammatic drawing of the furniture unit without its seat.

The furniture unit to sit-on has a main frame 2 connected by a joint with the frame base of the backrest 3. Above the main frame 2, a seat 1 is placed; it is fixed to the main frame 2 or, alternatively, to the frame base of the backrest 3 by a ball joint A. The said connection is made so that a bearing A1 of the ball joint A is mounted to the seat 1, and the ball A2 of the ball joint A is fixed onto the main base 2 or, alternatively, onto the frame base of the backrest 3. The frame base of the backrest 3 has armrests 11 mounted to an adjustable jib, as well as a working surface or a top 12 for a computer keyboard, mounted onto an another jig 13. An arm for securing a top for LCD monitor or PC screen is mounted to the jib 13 that fixes a working surface or a top 12 for keyboard.

The backrest frame 4 has a durable connection with the frame base of the backrest 3 and those two elements have jointly a possibility to adjust the up or down position and/or the inclination angle. The backrest frame 4 is equipped with three (3) independent movable rests: an upper headrest 5, a middle chestrest 6, and a lower backrest 7. The middle chestrest 6 is secured to the backrest frame 4 using a ball joint C whereas the upper rest 5 and the lower rest 7 are connected with the backrest frame 4 in a way that makes it possible to slightly (within a short distance range) move them forwards and backwards, or up and down, or aside. The rest elements 5 and 7 may be coupled with the backrest frame 4 using a spring-loaded telescopic mechanism. In the upper part of the backrest frame 4, a rest element 10 for lower extremities is placed on a jib.

To the main frame 2, a footrest 8 is secured; it has two movable props for feet, which are connected by a flexible joint with the footrest frame using a crank assembly 9. The foot props can move up and down, as well as rotate. The footrest 8 is secured so that it can be freely pulled out and placed in a position allowing to place his/her feet thereon or it can be placed under the main frame 2 when not used. The footrest 8 can be situated using, for example, a rail, or it can have a telescopic connection. The latter makes it possible to adjust the distance between the footrest and the main frame 2.