US 3837705 A
An office chair in which the seat height and back inclination and height are adjustable and having a frictional pivotal coupling between the back and the back supporting member. The adjustment of the back inclination is accomplished with a hub affixed to the back supporting member and a slider disposed for axial motion within said hub and angularly fixed with respect to the chair seat. A pair of projections in the slider ride in helical grooves in the hub so that as the slider is moved axially the back is rotated. A rack attached to the back and slidable in the back supporting member is engaged by a spiral gear member attached to the back supporting member for controlling the height of the back.
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Description (OCR text may contain errors)
ilnited States Patent n 1 Marraccini I 51 Sept. 24, 1974 OFFICE CHAIR  Inventor:
22 Filed: Jan. 24, 1973 21 Appl. 1 Io.:326,334
Franco Marraccini, Massa, ltaly  US. Cl 297/353, 297/339, 297/361, 297/374, 297/410  Int. Cl. A47c 1/00  Field of Search 297/339, 347, 353, 410; 168/147; 248/404-406, 157
 References Cited UNITED STATES PATENTS 128,775 7/1872 Archer et al 108/147 360,855 4/1887 Cooper 297/353 X 779,633 1/1905 Wustner 108/147 X Primary Examiner-James C. Mitchell Attorney, Agent, or Firml. J. Schaefer [5 7] ABSTRACT An office chair in which the seat height and back inclination and height are adjustable and having a frictional pivotal coupling between the back and the back supporting member. The adjustment of the back inclination is accomplished with a hub affixed to the back supporting member and a slider disposed for axial motion within said hub and angularly fixed with respect to the chair seat. A pair of projections in the slider ride in helical grooves in the hub so that as the slider is moved axially the back is rotated. A rack attached to the back and slidable in the back supporting member is engaged by a spiral gear member attached to the back supporting member for controlling the height of the back.
4 Claims, 9 Drawing Figures OFFICE CHAIR BACKGROUND OF THE INVENTION The present invention relates generally to office chairs and more particularly to secretarial chairs, having adjustable seat heights and back supports.
A secretarys work area generally includes a desk with one or more telephones, a table for a typewriter and one or more shelves or filing cabinets for documents. A secretarial chair must therefore be easily movable on the floor and must have a seat which is adjustable in height and a back which is adjustable both in height and in inclination, so as to adapt itself to the various working positions adopted by the users.
A number of chairs are known on which one or more adjustments can be made. The inclination of the back or its support with respect to the seat is generally effected by means of snap detent elements or by means of differential-type gears, for example of the type with internally toothed wheels. These structures are generally unsatisfactory since the making of adjustments with them is complicated and they are costly in construction.
SUMMARY OF THE INVENTION According to the present invention Applicant provides a chair having an improved mechanism for adjusting the angle of a back supporting member which includes a hub proximate the lower end of the back supporting member and fixedly attached thereto and a slider mounted within the hub for axial motion with respect to the hub, the slider including a threaded aperture. Also included are means for preventing angular motion of the slider with respect to the seat and a screw engaging the slider at the threaded aperture. Cooperating projecting and recessed portions carried, one each, by the slider and the internal face of the hub angularly lock the hub with respect to the slider, the portion carried by the internal face of the hub extending helically along the internal face relative to the axis of the hub. Also included in the chair according to the invention are means for adjusting the height of the back with respect to the seat which include a rack attached to the back and slidable in a hollow portion of the back supporting member and a spirally threaded element rotatably mounted on the hollow member and an inclination with the rack for engaging a tooth of the rack with only the portion of the spiral thread inclined toward the rack.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a side view from the right ofa chair embodying the invention;
FIG. 2 is a plan view of the chair of FIG. 1;
FIG. 3 is a section of the device for adjusting the inclination of the support for the back of the chair of FIG. 1;
FIG. 4 is a section on the line lV-IV of FIG. 3;
FIG. 5 is a section of the device for adjusting the height of the back support;
FIG. 6 is a section on the line VI-VI of FIG. 5;
FIG. 7 is a section of the device for angular adjustment of the chair back;
FIG. 8 is a section of the device for adjusting the height of the seat; and
FIG. 9 is a section on the line IXIX of FIG. 8.
DETAILED DESCRIPTION Referring to FIG. 1 of the drawings, the office chair according to the invention essentially comprises a supporting structure 1, a seat 2 and a back 3. The supporting structure 1 is formed by a vertical sleeve member 4 supported by a horizontal cross having four arms 6 radiating from the sleeve at intervals of degrees and each carrying a castor 7 for facilitating movement of the chair.
On the supporting structure 1 there is located a device 8 for adjusting the height of the seat 2. This device 8 is constituted by a screw and nut connection in which the screw 9 (FIG. 8) which is fixed to a support plate 11 (FIG. 1) for the seat 2, engages a nut 12 fitted to the sleeve 4. A ring 13 disposed between a shoulder 14 of the nut 12 and the sleeve 4 of the supporting structure 1 is provided with three lugs 16 (FIG. 9) spaced from one another at intervals of degrees. The ring 13 is moreover provided with a tooth 17 projecting inwardly and cooperating with a longitudinal groove 18 (FIG. 8) with which the screw 9 is provided. Each of the three lugs 16 is furnished with a dog 19 projecting above the surface of the ring 13 and adapted to engage a corresponding radial groove 21 formed in the shoulder 14 of the nut 12.
The screw 9 is covered by a corrugated sheath of a flexible plastic material engaged between a shoulder 23 of the nut 12 and a flange, not visible in FIG. 1, carried at the bottom of the support plate 11 (FIG. 1).
The ring 13 (FIG. 8) is held angularly fast with the screw 9 by the keying action of the tooth 17 in the groove 18. It is also normally held angularly fast with the nut 12 by the engagement of the grooves 21 of the nut 12 by the dogs 19. This prevents any rotation of the nut 12 under the weight of the user, and holds the screw 9 fast with the nut 12 thereby preventing any variation in the height of the seat 2.
Adjustment of the height of the seat 2 is effected by turning the nut 12 manually in one direction or the other when the chair is not occupied. The dogs 19 then disengage themselves from the grooves 21, as a result of which the ring 13 and the screw 9 are angularly released by the nut 12. This therefore causes raising or lowering of the screw 9 and, consequently, also of the seat 2. The tooth 17 of the ring 13 slides along the groove 18.
The support plate 11 (FIG. 1) has a forked extension arm 24 having two symmetrical lugs 26 (FIG. 2). Each lug 26 has a recess 27 (FIG. 3) of substantially circular form. Between the two lugs 26 there is arranged a device 28 for adjusting the inclination of the back. The lugs 26 have three pairs of holes in alignment with one another, namely central hole 29 and two pairs of holes 31 symmetrical with respect to holes 29. The holes 31 permit the passage of two guide pins 33. These two guide pins 33 are fixed in one of the lugs 26 by means of milled portions 34 having a diameter slightly greater than that of the respective pin 33 so as to become jammed in the corresponding hole 31.
Each end portion 36 of the control screw 32 has a bore 37 into which there is inserted a pin 38 which is locked at the ends in two slots in a washer 39. The washer 39 is fixed together with the terminal portion 36 of the control screw 32 in the inner part of a corresponding knob 41. The two knobs 41 are thus held fast with one another and with the screw 32.
The control screw 32 has a threaded central portion screwed through a slider 42. The slider 42 is provided with two opposite notches 43 (FIG. 4) fitting slidably over the two guide pins 33, and with two inclined projections 44 mating in two helical grooves 46 (FIG. 3) formed in the inner part of a hub 47. This hub is rigid with the lower terminal portion of a bar 48 of rectangular cross section supporting the back 3. Set into the hub 47 are two washers 49 of antifriction material for reducing the friction between the hub 47 and the lugs 26. The washers 49 are both drilled to permit the passage of the guide pins 33 and the control screw 32.
Adjustment of the inclination of the back is effected by manually rotating one or the other of the two knobs 41. The rotation of the knobs 41 is transmitted to the control screw 32, which causes the slider 42 to shift axially on the guide pins 33. During the shifting of the slider 42, the projections 44 engaged in the oblique grooves 46 cause the hub 47 to rotate and with it the bar 48 and the back 3 (FIG. 1). Adjustment of the inclination of the bar 48 supporting the back 3 is effected between the extreme positions indicated by the dash lines in FIG. 1 which form an angle of about 40 degrees containing the vertical position. More particularly, by causing the slider 42 to shift to the right the back is brought to the rear.
Moreover, a position of the back 3 is provided in which the bar 48 of the back 3 is free and can turn freely to the rear. This position is used for reducing the over-all dimensions of the chair for packing. This position is reached by shifting the slider 42 (FIG. 3) completely to the right into correspondence with a recess 45 of the hub 47. The slider 42 then disengages the projections 44 from the grooves 46 and therefore the hub 47 and the bar 48 of the back 3 are free to turn.
On unpacking the chair, in order to find again the exact point at which the inclined projections 44 are to re-enter the oblique grooves 46 two inclined stops 51 are provided in the recess 47, these stops forming an extension of one side of the oblique grooves 46.
The bar 48 of the back 3 (FIG. 1) is provided with a device 52 for adjusting the height of the back 3. To this end, the bar 48 (FIG. is a hollow and has at the top an axial opening 53 in which there is engaged a guide element 56 in which a rod 57 is slidable. The guide element 56 is clamped to the bar 48 by an extension thereof extending into a hollow 54 in the bar 48. The rod 57 has in its central portion a rack 58 which is engaged by a spiral projecting rib 59 (FIG. 6) of a knob 61 rotatable in a seat 62 (FIG. 5) formed in the guide element 56. The knob 61 is in an inclined position with respect to the rack 58, in such manner that only the upper portion of the projecting spiral rib 59 engages a tooth of the rack 58. The height of the rib 59 increases from the periphery towards the center of the knob 61 so as to keep the inner turn of the rib 59 in mesh with the rack 58. Moreover, the beginning and end of the projecting rib 59 (FIG. 6) are adapted to engage simultaneously with the rack 58 (FIG. 5), that is the pitch of the rack is equal to the radial pitch of the spiral, as a result of which a uniform and continuous movement of the rod 57 is obtained during the rotation of the knob 61. To the rotation of the knob 61 in one sense or the other there corresponds a raising or lowering of the rack 58,- and, consequently, also of the back The guide element 56 has a tooth 63 (FIG. 5) engaging an annular groove 64 in the knob 61 for preventing the knob 61 leaving its seat. The knob 61 is mounted on the element 56 from the right-hand side thereof, in FIG. 5, before the element 56 is fitted on the bar 48.
A friction device 66 (FIG. 7) is used for the angular adjustment of the back 3 with respect to the rod 57 and includes a hub 67 integral with the rod 57 (FIG. 5). The hub 67 (FIG. 7) is disposed between two lugs 68 integral with a supporting structure 69 for the back 3. Each lug 68 is provided with a recess 71 at the base of which there is provided a hole 72 of rectangular form with two circular sides, while the hub 67 is provided with a hole 73 of circular section.
In each pair of holes 72 and 73 there is housed a stem 74 of a corresponding knob 76. Provided in the stem 74 are four longitudinal slots 77 which define four bendable axial portions 75, while internally it is adapted to house a resilient member 78 having a C-shaped cross section and forming a spring which acts to spread the bendable portions of the stem 74 apart. On the stem 74 there is moreover an annular portion 79 projecting to the inside to retain the resilient member 78 and having a substantially square form on the outside, so as to clamp the stem 74 in the hole 72 and render the knobs fast with the structure 69. The portions 75 of the stem 74 of the knob 76 tend to expand under the thrust of the profile 78, producing a frictional engagement between the stem 74 and the hole 73 and, therefore, the structure 69 and the rod 57. Because of the aforesaid frictional engagement, the back 3 is not free to turn or pivot, but can nevertheless be brouhgt into the desired position by exerting a force sufficient to overcome the friction between the stem 74 of the knobs 76 and the hole 73.
What is claimed is:
l. A chair comprising: a seat; a back; and means connecting the seat and the back for selectively adjusting the distance between the seat and the back, said means comprising a hollow member, a toothed rack connected to said back and slidable in said hollow member, a rotatable disc having an annular groove on the periphery thereof, a projection extending from one side of said disc for manually rotating same, a spiral rib projecting from another side of said disc opposite to said one side, means mounting said disc in an inclined position with respect to said rack to enable a tooth of said rack to engage with only the portion of said spiral rib inclined towards said rack, and means solely in contact with said disc for rotatably mounting same on said hollow member comprising a guide element fixed to said hollow member and engaging said annular groove on the periphery of said disc.
2. A chair according to claim -1, wherein the height of said spiral rib from said disc increases towards the center thereof.
3. A chair according to claim 1, wherein said guide element comprises an annular tooth which engages said annular groove.
4. A chair according to claim 2, wherein said hollow element is disposed adjacent to said back at a predetermined distance therefrom and said projection extends between said hollow element and said back less than said predetermined distance.
v I UNITED STATES PATENT OFF ICE- CERTIFICATE OF CORRECTION Patent No. 3,837,705 4 Dated September 24 1974 Inve t Franco Marraccini It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
on the first page after " appln. No.: 326,334" insert V--[3O] Foreign Application Priority Data January 31, 1972" Italy. .672 6,7- A/72--.
Signedatid sealed this 17th day of December 19 74.
McCOY M. GIBSON JR.
0. MARSHALL DANN Attesting Officer Commissioner of Patents F ORM F'O-1050 (10-69) USCOMM'D C GO BYS-PBQ 9 [1.5. GOVIII I II ENT HUNTING OFFICE ISIS 03ii-33b