The object of the invention is an active chair, which, with its construction allows movement of the seat in all directions, thus enabling active seating and eliminating all shortcomings of healthy and correct posture while seating, known until now, including a stabillity ball and a chair spring.

The invention successfully solves problems of active seating with its unique, simple and clear construction, which allows the optimal condition of the entire body while seating. Its construction is well suited for industrial manufacturing and its use in different areas.

Human balance can be defined as an active compensation, that a person is experiencing, or as anticipation of conflicting external interferences.

Balance of the living body is operated by internal body forces such as muscle tone, changes in muscle tension etc. A human body, which is normally in physically stable balanced position, can often be subject to disruptions. On a disturbed balance, the body can easily react with the increased intimate support such as muscle power, detailed response, and change of position.

Living organisms, including the human body, work in a way, to protect and preserve stability with different mechanisms, i.e. try to withstand the changes. Occasionally, the nerve systems must follow the changes in body position or lead them.

In order to have a good control over the posture, one has to have a good stabilizing mechanism, which preserves and protects stability. It is desirable to have the stabilizing mechanism as active as possible so that possible disturbances are minimized. Disturbances must be as minimal as possible, to prevent the unnecessary lost of energy due to the change. Each body strives towards keeping its internal environment very stable while spending as little energy as possible. This is achieved by recognizing the disturbance as soon as possible and adjusting it. It is very important, that the body remains active; disturbance should be minimized, so that the body doesn't use up too much energy.

It is very important that a person has a good stabilizing mechanism, which preserves and protects stability. That is why the stabilizing mechanism has to be as active as possible so that there would be a low number of disturbances. Disturbances must be as minimal as possible so it wouldn't come to the unnecessary lost of energy because of change. Everybody strives towards keeping its internal environment very stable, while spending as little energy as possible. This is achieved by recognizing the disturbance as soon as possible and adjusting it.

Numerous physical impairments are mainly the consequence of lack of physical activity of people. One of the main reasons is also seating. There are many different types of chairs available, which have one common flaw: they only enable passive sitting. Passive sitting is defined by the supporting points of these chairs: the console, the backrest, legs which provide the body with information about the supporting points. Thus natural information which is pointed towards the constant search for natural stability is distorted.

The body receives information on the achieved balance of the body, which is not correct. The reaction of the body is to minimize the muscle strain and to suspend the activities of the muscles. Thus, muscles become largely inactive in their unnatural position. That is why the weight of the body is borne by vertebrae and the intervertebral discs which if repeated often, gradually lead to defects in the body. On the other side, activation of the muscles of the torso, especially near spine and deep abdominal muscles means, that the weight of the body is mainly borne by muscles, which consequently relieves the spine, that is, the vertebrae and the intervertebral discs, which is beneficial.

Known solutions to the problem of inactive muscles at seating are described in SI20508 and WO 2011/142727.

The back draws of the presented solutions are in the fact that the chair doesn't provoke mechanisms that maintain continuity. Sitting on the known active chairs, leads to a continuous demolition of control over posture, or to distortion of information about it. The chair follows the disruptions and can additionally weaken the control over the posture. The user of known chairs, therefore, can maintain stability without any activity, even if the nerve-muscle activity is equal to the sleeping man since the resistance of the material is enough that the person remains in the chair. This means that on an active chair there is no activation of deep tissue muscles and the resulting stability, which would lead to quality control of posture.

Another known solution is described in the patent SI21 114. The chair has a base designed as a spherical portion, but it is excessively unstable and doesn't allow the adjustment of the surface of the seat to the surface of the ground. The task and object of the invention is such construction of the chair, which would force the user to continuous sensory and muscle activity.

Accordihg to the invention, the problem of no active sensors and muscles in a sitting person is solved by an active chair, according to the independent patent claim.

The invention will be described with embodiments and with figures which show:

Fig. 1 : an active chair according to the invention in a vertical stable position,

Fig. 2: an active chair according to the invention in a tilted position,

Fig. 3: joint in the first embodiment,

Fig. 4: joint in the second embodiment,

Fig. 5.1 : first version of the joint in the second embodiment,

Fig. 5.2: second version of the joint in the second embodiment,

Fig. 5.3: third version of the joint in the second embodiment.

An active chair according to the invention consists of a base 2, a bar 3, a joint 4 and a seat 5. The chair is positioned on the ground 1.

In the embodiment the lower part of the base 2 is formed as a spherical cap with a radius of 31 to 50 cm, and with the curved part facing the ground 1. The mentioned length of the radius provides that the distance of the seat 5 from the ground 1 is always the same or the distance changes negligibly, when the chair is moved from its central position. The lower part of the base 2 is axially symmetric. The upper surface of the base 2 is designed arbitrarily, but preferably axially symmetric. This means that the upper surface can be flat, conical, pyramidal, round or in various other forms. In the middle, i.e. in the axis of the base 2 on the upper surface of the base 2, the bar 3 is attached. The bar 3 is firmly attached to the base but preferably removable.

The bar 3 can be of any shape. Its length is such, that, together with the base 2, the joint 3 and the seat 5 a suitable height for the sitting person is provided. The bar 3 can be, by known methods, adjustable in its length to provide the adjustment of the height of the chair to the height of the user. The joint 4 is inserted between the bar 3 and the seat 5 and enables the change of the angle between the direction of the bar 3 and the surface of the seat 5. The joint 4 enables the change of the. angle between the direction, of the bar 3. and the surface of the seat 5 preferably up to 16°. The joint 4 is designed in a way that by increasing the angle between the bar 3 and the surface of the seat 5 the retraction force of the joint 4 is increased. This means that the force, with which the joint 4 attempts to return the chair in a vertical position, increases by the angle of deflection from the vertical.

In the first embodiment, according to the figure 3, the joint 4 is made with a bearing wherein through a central opening in a sphere 6, a mount 8 is provided, which is with its upper side attached to the seat 5 and with its lower side to a spring rod 9. The sphere 6 is rotatable secured to a frame 7. The spring rod 9 reaches in the interior of the bar 3. In the interior of the bar 3 a regulator 10 is provided. The form of the external surface, of the regulator 10 is adjusted to the form of the interior surface of the bar 3 so that the regulator 10 can easily move within the bar 3 along its length. The regulator 10 has in its centre a bore, which is with its form adjusted to the form of the spring rod 9 so that the regulator 10 can easily be moved on spring rod 9. The rod 9 is inserted into the bore of the regulator 10. The regulator 10 is controllably movable along the length of bar 3 and can be fix at the wanted position on bar 3, for instance by a screw, which is movable in the groove along the rod 3. The joint 4 is a standard spherical bearing with the axial capacity more than 100kg. The spring rod has a typical radius of 6 mm and is preferably made of steel.

When the person using the chair sits on the seat 5 and causes the tilting of the chair, the mount 8 in the sphere 6 moves for a certain angle from the vertical. The sphere 6 rotates in the frame 7. The spring rod 9 bends between the mount 8 and the regulator 10 and attempts to return the seat to the right angle between the surface of the seat and the rod and thereby return the chair to a vertical position. The force, which returns the chair to a vertical position, can be regulated by the position of the regulator 10. Moving of the regulator 10 in the direction of the mount 8 can increases this force, and the movement of the regulator 10 in the direction of the base 2 decreases it.

In the second embodiment according to figure 4, a joint 4 is made of elastic material, thus the angle between the direction of the bar 3 and the surface of the seat 5 is automatically returned to the starting angle, preferably the right angle. On the joint 4 the seat surface 5 is firmly, but preferably removable attached. The joint 4 is therefore embedded between the seat 5 and the bar 3. The seat 5 is any known suitable seat.

The elastic joint according to the second-embodiment can be in different forms. On figure 5 1 an elastic joint in the form of a body with a radical symmetry about its central axis with a concave form of its side area is presented. On figure 5.2 an elastic joint in the form of a cylinder is presented. On figure 5.3 an elastic joint in the form a body with a radical symmetry about its central axis with a concave form of its side area and with an elastic ring 11 attached over said body is presented. The force which returns the chair in a vertical position is the smallest in the example of an elastic joint in the form of a a body with a radical symmetry about its central axis with a concave form of its side area, and the largest in the example of a joint in the form a body with a radical symmetry about its central axis with a concave form of its side area and with an elastic ring 11 attached over said body. The joint 4 is made of rubber of hardness of 50 to 110 SHOR.

The lower part of the base 2 is in a form of a spherical cap. The problem of that form is stability of the chair during non-usage. The chair is overturned so that the bar 3 is almost parallel with the ground 1. One solution to this turning over is the weighting of the base 2 in its central lower part. The other solution is non spherical form of the lower part of the base 2. In central part of the base the radius of the sphere is very large but decreases rapidly toward the edges of the base. So the lower part of the base 2 is in this way almost flat but gets increasingly rounded towards the edge. Nevertheless the lower part of the base 2 is always round and axially symmetric. In any case, the lower part of the base 2 is a rotating shape of a round form.

The joint 4 automatically aligns the seat 5 in a correct horizontal position, which also represents the optimal seating position. The joint 4 further offers a progressive resistance during seating: the more the chair and the position of sitting are moved away from the centre, the bigger force is necessary for the seat 5 to be aligned in a horizontal position. The resistance of the joint can be adjusted to the weight of any person. The resistance should be sufficient to stimulate the muscles of the core as much as possible and to give the body a signal, where the centre of the seating is and, consequently, subconsciously stimulate the body to tend to be in a right position. For security reasons the limitation of mobility of the joint from the right angle between the direction of the bar 3 and the surface of the seat 5 is limited to 16 degrees at most. The mobility is limited either with a special edge, on which the seat surface 5 leans on or with the mechanism in the joint 4. The lower part of the base 2 in the embodiment is in the form of a spherical cap with a radius from 31 to 50 cm, thus the base 2 is touching the ground at one point only or at a very small part of the circumference of the sphere. The tilting of the base 2 is, due to safety reasons, limited by a ring around the circumference of the base 2, which only permits tilting up to 30°.