DESCRIPTION TYPIST'S OFFICE CHAIR WITH SWIVEL COLUMN ON RAY BASE WITH WHEELS Technical field This invention has as object a typist's office chair with swivel column with ray base having adjustable seat and back. Background Art At the present stage of technology, typist's office chairs with swivel column with ray base on wheels, having adjustable seat and back are well known. The drawback of these types of chairs consists essentially in the respective regulation commands that are protruding, therefore cumbersome and dangerous besides being aesthetically unpleasant. Furthermore the actual commands of seat height regulation are not simple or practical for use considering that these must be operated whilst one is seated. Other aims of the present invention regard the strengthening of the seat, which as known in chairs of this type deteriorate easily. In fact the seat of these types of chairs are generally realized in a wooden frame appropriately covered and padded. The anchorage of the seat to the upper part of the column is achieved by means of screws that loosen easily, furthermore the wooden structure has uncontrolled areas of reduced resistance, wherefore it is easy that after considerable use, it subsides and breaks. Problems finally determine the support system and regulation of the back, that finds anchorage to the seat unreliable and unrational regulation systems.

One of the principal means of back regulation consists in fact in the regulation of the pliability of the back, but with use it has demonstrated that this is not useful, on the contrary it is harmful and tiring for the user. The present invention according to the characteristics of the included claims solves the problem by means of a typist's office chair with swivel colunm with ray base, having adjustable seat and back, characterized in that the command of raising and lowering of the seat consists in a button enclosed on the side, under the seat, which interacts with a lever with intermediate fulcrum, also enclosed within the seat, the extremity of which goes to the center of the seat and interacts with the command means of the underlying column for its lengthening or shortening. Advantageously said seat regulation command is placed along a diagonal of the seat. Advantageously said positioning is placed in the zone corresponding to a front corner of the seat. In this way the command is positioned with the maximum functionality and agility, without protrusions from the seat and the raising and lowering of the chair is a great deal easier and more practical, also operating whilst one is seated. Advantageously for greater sturdiness, reliability and duration of the seat, it is made in plastic material injected in a single piece with underlying rib finnings, all fully padded and covered. In this way one has a robust and light seat. Advantageously the seat structure in plastic material involves the inclusion, at least in the connecting zone of the back

1 support stanchion, of a metallic plate with incision for the passage

2 of screw means for the anchorage of the back stanchion, that

3 extends to the center of the seat for the anchorage to the

4 respective stanchion.

5 In this way the anchorage of the back stanchion is safe

6 avoiding breakages and also giving maximum reliability against

7 loosening.

8 For a more rational support of the back, a crushed tubular

9 stanchion essentially "L" shaped is furthermore utilized with a

I 0 plurality of holes in the upright section of the "L" shape in order

I I to allow an easy and convenient correction in height of the back. 1 2 In this way the back stanchion, besides being easy to 1 3 remove, is robust and at the same time light.

1 4 Furthermore the upper extremity of the back's upright

1 5 support stanchion is guided within the fully covered back,

1 6 whereupon the chair may be easily transformed into a typist's

1 7 chair and seat and with the advantage of not having dangerous and

1 8 unattractive protrusions of the stanchion out of the back.

1 9 Finally the back involves sliding guide means on the

20 upright of the stanchion with hooking system on said holes by 2 1 means of intermediate hinged lever and involving on the one side 22 an insertion peg into said holes of said stanchion and on the other 2 3 a pressure button for the disengagement, said button being 24 subsequently enclosed in said back.

2 5 These and other advantages will appear from the subsequent

2 6 description of illustrative preferential solutions of realization in

27 connection with the drawings enclosed.

2 8 Figure 1 is a schematic view from the underside of the seat frame.

Figure 2 is a diagonal cross sectional view in connection with the height regulation lever of the same seat structure. Figure 3 is a back view of the hooking system of the back to the stanchion that departs from the seat. Figure 4 is a side view of the device in Figure 3. Figure 5 is a perspective view of the chair ensemble with visualization of its exterior conformation and position of the respective regulation commands. Figure 5 illustrates the chair in which 1 indicates the height regulation button of the back 5 sliding within a crushed tubular stanchion (3) essentially "L" shaped in which the elevation inserts itself within the back 5 and is blocked with the button dorsally enclosed 1 which operates a lever 41 hinged 419 to a square metallic guide 4 with peg 411 that enters into correspondent holes 31 of the stanchion 3; and the base is inserted between the seat 6 where it is fixed by a screw handle 8 through a groove 69 in the structure of the seat frame in plastic die-cast 6 with sheetplate insert 7 that extends up to the center 63 for a solid anchorage to the stanchion column 9. The structure of the seat frame is in a single piece in pressure injected plastic material 6 with underlying reinforcement fins 60, and ribs always having a finning form 61, 62, 63, 64 also having a cylindric form 62, 63, 66. The regulation of the chair's height 6 happens by means of a front button on the diagonal enclosed underneath the seat 2 cutout from the ribbing 62 that operates a second type of lever 20 (boxed laterally by two opposite ribbed- wings 61 wtih intermediate swivel 21 and the extremity of which brings it to the center of the seat 63

to operate the command pole of the column 9 for the height regulation.