The subject of the invention is a convertible dual function chair for sitting and kneeling, which gives the possibility of changing the position and relieving the spinal column during a prolonged work in a sitting position.

A kneeling chair is known from the description of the Polish utility model no. 64081. It is a rehabilitation chair, intended mainly for kneeling, without a backrest, built in the shape of the letter X.

Another solution with a similar purpose is also known, such as a convertible piece of furniture from the Polish patent application P.390736, intended for sitting and kneeling, in which a two-piece set of kneelers is supported on the arms pivotally mounted, in the brackets of the crosspiece.

Other solutions with a similar application are known, such as the solution from European patent specification no. EP 0570550, in which a seat, a knee-brace and a backrest are suspended on a cantilever column supported on a wheeled base. These mechanisms are levers that allow the usable surfaces of the chair to be moved in space, depending on the needs. This is how the chair is processed into sitting, sitting-kneeling and similar positions. The position of the seat, kneeler and backrest is fixed by means of locking and ratchet mechanisms.

Furniture of a similar type is also known from the Polish patent application no. P.387898. The chair described there has a seat, a two-piece kneeler, a backrest and armrests. The kneeler unit consists of two parts, each of which has the ability to tilt the kneeler and move it backwards.

Moreover, the solution from the application of the invention PCT/IB2013/000114 is known, in which the chair seat is divisible, its front part is transformed into a kneeler, the chair has a two-arm support for the seat, one movable arm which supports the front part of the seat that can be converted into a kneeler, and the other arm which supports the rear part of the seat and the backrest.

From a US patent no. 7,946,972 B2, a multi-functional yoga chair solution is known, in which the kneeler is lowered over the seat column.

Patent EP2816932 discloses a specially shaped base which allows the feet to move freely in the kneeling position within a limited range, when the arms of the base are parallel to the side edges of the seat.

A dual function chair for sitting and kneeling, with a seat, backrest and a kneeler.

The chair, according to the invention, is provided with a backrest support and a movable headrest, shaped in such a way that its displacement changes the size of the chair simultaneously vertically and horizontally, adapting it to the size of the user.

The chair, according to the invention, is provided with a backrest sliding-rotary-return device, which causes the backrest to follow the user's back when the backrest is tilte and, at each angle of inclination of the backrest, it accurately supports the back. The device causes the backrest to return to its original position automatically.

The chair, according to the invention, is provided with a sliding-return backrest device, which causes it to follow the user's back when tilting the backrest and accurately support the back at each angle of inclination of the backrest. The device causes the backrest to return to its original position automatically.

The chair, according to the invention, is provided with a headrest through a rotary-sliding mechanism connected to the headrest arm, which rotationally connects to the backrest support, and the distance between the headrest rotation axis and the headrest rotation axis is greater than 200 mm.

The chair, according to the invention, has a specially shaped five-arm base, the arms of which, apart from the area above the wheels, are maximally flattened and located as low as possible above the ground, with the clearance between the lower plane of the arms being only slightly greater than the thickness of the floor coverings used in offices.

It is advantageous when the dual function chair for sitting and kneeling, which includes a seat, a backrest and a kneeler, is provided with a movable backrest and headrest support, shaped in the lower part in such a way that its displacement changes the size of the chair both vertically and horizontally, adjusting it to the size of the user, because the chair with the highly developed ergonomics must respond to the differences in height and body built. The solution by obliquely positioning the backrest frame sliding line changes the depth of the seat and the height of the backrest at the same time.

It is advantageous when the chair for sitting and kneeling is provided with a sliding-rotary- return device of a pivoting back, which causes the backrest to follow the user's back when tilting the backrest, and at every angle of inclination of the backrest, it accurately supports the back, which is particularly important for the lumbar part of the spine, which is most often subject to damages due to poor support.

It is advantageous when the chair for sitting and kneeling is provided with a sliding-return backrest device, which causes the backrest to follow the user's back when tilting the backrest, and at every angle of inclination of the backrest, it accurately supports the back, which is particularly important for the lumbar part of the spine, which is most often subject to damages due to poor support.

It is advantageous when the chair for sitting and kneeling is provided with a headrest through a rotary-sliding mechanism connected to the headrest arm, which rotationally connects to the backrest support, in which the distance between the axis of rotation of the headrest and the axis of rotation of the headrest arm is greater than 200 mm.

Low location of the axis of rotation of the headrest arm makes the headrest properly support the head in every position of the chair backrest.

It is advantageous when the chair for sitting and kneeling has a specially shaped five-arm base, the arms of which, apart from the part above the wheels, are maximally flattened and located as low as possible above the ground, because such low-lying arms allow free movement of the feet in the kneeling position. It is not necessary to orient the base in relation to the desk.

The object of the invention, in its embodiment, has been illustrated on the drawing: Fig. 1 illustrates the chair for sitting and kneeling in the sitting position, provided with a movable backrest and headrest support, shaped in the lower part so that its displacement changes the size of the chair simultaneously vertically and horizontally, provided with a sliding-rotating-return pivoting backrest device which causes that when the backrest is tilted, it follows the user's back and at every angle of the backrest inclination it accurately supports the back, equipped with a headrest through a rotary- sliding mechanism connected to the headrest arm, which rotationally connects with the backrest support, and provided with a specially shaped five-star base, in which the arms, apart from the part above the wheels, are maximally flattened and located as low as possible above the ground.

Fig. 2 illustrates the chair for sitting and kneeling in the kneeling position, provided with a movable backrest and headrest support, and shaped in the lower part so that its displacement changes the size of the chair simultaneously vertically and horizontally, provided with a sliding-rotating-returning device of an pivoting backrest, which makes it follow the user's back when the backrest is tilted, and at every angle of the backrest inclination it accurately supports the back, equipped with a headrest through a rotary- sliding mechanism connected to the headrest arm, which rotationally connects with the backrest support, and provided with a specially shaped five-star a base, the arms of which, apart from the part above the wheels, are maximally flattened and located as low as possible above the ground.

Fig. 3 illustrates a cross-section of a movable backrest and a headrest support shaped in the lower part in such a way that the displacement changes the size of the chair simultaneously vertically and horizontally.

Fig. 4 illustrates a cross-sectional view of a sliding-rotary-return device for a pivoting backrest, which causes the backrest to follow the user's back when tilting and support it accurately at every inclination angle.

Fig. 5 illustrates a longitudinal section view of a sliding-rotary-return device for a pivoting backrest, which causes the backrest to follow the user's back when tilting and support it accurately at every inclination angle.

Fig. 6 illustrates the chair for sitting and kneeling in the sitting position, provided with a movable backrest and headrest support, and shaped in the lower part in such a way that its displacement changes the size of the chair simultaneously vertically and horizontally, provided with a sliding-return backrest device which makes it follow the user's back when tilting the backrest, and at every angle of the backrest inclination, it accurately supports the back, equipped with a headrest through a rotary-sliding mechanism connected to the headrest arm, which rotationally connects with the backrest support, and provided with a specially shaped five-star base, in which the arms, apart from the fragment above the wheels, are maximally flattened and located as low as possible above the ground.

Fig. 7 illustrates the chair for sitting and kneeling in the kneeling position, provided with a movable backrest and headrest support, and shaped in the lower part in such a way that its displacement changes the size of the chair simultaneously vertically and horizontally, provided with a sliding-return backrest device which causes that when tilting the backrest, it follows the user's back and at every angle of the backrest inclination, it accurately supports the back, equipped with a headrest through a rotary-sliding mechanism connected to the headrest arm, which rotationally connects with the backrest support, and provided with a specially shaped five-star base, in which the arms, apart from the fragment above the wheels, are maximally flattened and located as low as possible above the ground.

Fig. 8 illustrates a longitudinal-section view of a backrest sliding-return device which causes the backrest to follow the user's back when tilting the backrest and support it accurately at any inclination angle.

Fig. 9 illustrates the headrest through a sliding-rotary mechanism connected to the arm of the headrest, which rotary connects to the backrest.

Fig. 10 illustrates a specially shaped five-arm base, the arms of which, apart from the fragment above the wheels, are maximally flattened and located as low as possible above the ground.

Fig. 11 illustrates a plan view of a specially shaped five-arm base, the arms of which, apart from the fragment above the wheels, are maximally flattened and located as low as possible above the ground.

In the example of the implementation, fig. 3 illustrates the movable backrest and headrest support and shaped in the lower part such that its displacement changes the size of the chair simultaneously vertically and horizontally. The backrest support 2 in the lower part is slidably connected with the chair mechanism 17, the sliding is blocked by the lock screw 18, the line of movement runs obliquely to the horizontal axis of the chair.

In the example of the implementation, figs. 1, 2, 4 and 5 illustrates the sliding-rotary- return device of a pivoting backrest, which causes the backrest to follow the user's back when the backrest is tilted and, at every angle of inclination of the backrest, it accurately supports the back. Constructed in such a way that the backrest support 2 is connected with the slider 1 along which the sliding part of the backrest support 3 slides. When the sliding part of the backrest support slides, it compresses the spring 16. The rotating part of the backrest support 4 is connected with the sliding part of the backrest support through the axis 10, which, when rotating, compresses the spring 15.

In the example of the implementation, figs. 6, 7, and 8 illustrates a backrest sliding-return device which causes the backrest to follow the user's back when the backrest is tilted, and at each angle of inclination of the backrest, it accurately supports the back. Constructed in such a way that the backrest support 2 is connected to the slider 1 on which the sliding part of the non-pivoting backrest support 19 slides. The sliding part of the non-pivoting backrest support 19 while sliding, compresses the spring 16.

In the example of the implementation, fig. 9 illustrates the headrest 8 through an axis 14rotary connected to a sliding element 17 slidably connected to the headrest arm 12, which headrest arm 12 is rotary connected via an axis 13 to the backrest support 2.

In the example of the implementation, figs. 10 and 11 illustrates a specially shaped five- arm base, the arms of which, apart from the portion above the wheels, are maximally flattened and located as low as possible above the ground. The base arm is constructed in such a way that in the front part it is above the wheel and then immediately behind the wheel it lowers and flattens so that its upper line is as low as possible above the ground. Markings list

1 - slider

2 - backrest support

3 - the sliding part of the backrest support

4 - swivel part of the pivoting backrest

5 - backrest

6 - seat

7 - armrest

8 - headrest

9 - base

10 - backrest axis

11 - base circle

12 - headrest frame

13 - axis of the headrest arm

14 - headrest axis 15 - backrest spring

16 - backrest sliding spring 7 - chair mechanism 8 - backrest frame sliding lock screw 9 - the sliding part of the non-pivoting backrest support