AU621848B2 - Adjustable chair - Google Patents

Description

4 Form PATENTS ACT 19520 COMPLETE SPECIF0,Tq 0

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Ark,: Name of Applicant: TO BE COMPLETED BY APPLICANT SCH-IAVELLO BROS, (VIC. PTY. LTD. a Victorian company, of Tullamarine Park Road, Tullamarine, Victoria 3043, Australia.

Address of Applicant: Actual Inventor: Address for Service: ANTONINO SCHIAVELLO Care of: COWIE, CARTER HENDY, Patent Attorneys, 71 Queens Road, Mel~bournie, Vic., 3004, Australia.

Complete Specification for the invention entitled: O~ F X) F %_ADJUSTABLE CHAIR The following statement is a full description of this invention, including the best method of performing it known to -1 Note: The description Is to be tytqed In double spacing, pica type face, In an area not exceeding 250 mm in depth and 160 mm In width, on tougih white paper of good quality and It Is to be Inserted Inside this form.

1 4599/78-L. Printed by C. J. TnompsoN Commonwealth 0overnmnt Printer, Canberra I is the actual inventor(s) of the invention and the facts upon which the applicant is entitled to make the application are as follows:- The said company is the assignee of the 1 Sinvention from the said actual inventor.

I 1 'his invention relates to an adjustable chair and relates particularly to an adjustable chair having a relative movable seat and backrest.

Adjustable chairs are known in which both the seat and the backrest are adjustable either individually or together. With individually adjustable seat and backrequiring at least two adjusting mechanisms which are operated independently. A further height adjusting mechanism is also usually incorporated into such a chair which may be used, for example, as an office chair, Chairs which have the seat and backrest interconnected so as to be adjusted together, in rtc synchronism, utilize an arrangement whereby tilting 15 movement of the seat about a substantially horizontal pivotal axis causes a related movement of the backrest.

However, the mechanisms which permit such a synchronous movement of the seat and backrest either involve movement of the front of the seat in conjunction with movement 20 of the backrest or utilize sliding mechanisms which are subject to wear and deterioration.

It is desirable to provide an improved mechanism for the synchronous adjustment of a seat and backrest of a chair. It is also desirable to provide a chair the construction of which is relatively simple and economical to manufacture.

It is also desirable to provide an improved construction of synchronous chair mechanism which can be utilized in a variety of chairs.

It is also desirable to provide an improved construction of chair in which the relative positions of the seat and backrest can, selectively, be fixed or be floating.

It is also desirable to provide an improved construction of chair having a tiltable seat and a synchronized movable backrest in which the adjusting mechanism can be varied to accommriodate users of different body weight. -2- I 1 j 3 According to one aspect of the invention there is provided a chair adjustment mechanism for enabling adjustment of the relative positions of a chair seat and backrest comprising a chair support, a main frame structure carried by the support, a chair seat frame pivotally mounted at a forward position to the main frame whereby a rear end of the seat frame is movable vertically relative to the main frame, a backrest frame pivotally connected to the rear end of the seat frame, and a pair of spaced control link members pivotally mounted at their upper ends to the rain frame, lower ends of the link members being connected to a lower end of the backrest frame.

In its preferred form, the chair adjustment mechanism is utilized in a chair with a chair support having a height adjustment, such as a gas spring.

Further, in its preferred form, the chair adjustment mechanism is utilized with an adjustable backrest wherein the height, at ieast, is variable. In the most preferred form, the backrest comprises an assembly nivotally mounted to the upper -r •end of the backrest part so that the inclination as well as the 20 height of the backrest is adjustable relative to the backrest part.

p The chair adjustment mechanism of the invention preferably o includes locating means to selectively locate the positions of the seat part, the control link and the backrest part relative to the body part. The locating means may comprise an adjustable gas spring which extends between the pivotal mounting of the seat part to the body part and the pivotal mounting of the control link to the backrest part. Such an adjustable gas spring is preferably provided with a locking arrangement to lock the relative length of the gas spring at the appropriate location to thus provide a desired relative position of the parts, thus fixing the relative position of the seat part and the backrest part. The spring locking arrangement can be released, if desired, to enable the seat part and backrest part to "float" which enables the seat part and backrest part to follow the movement of the user anywhere between an upright and a reclining position.

It is also preferred that a tensioning device _T

O

L. i g j t i ai fl f _:1 7 I be located between the pivotal mounting of the seat part to the body part and the mounting of the control link to the backrest part whereby the force required to adjust the relative positions of the parts may be varied. Such an adjusting arrangement enables the mechanism to be adjusted to suit weights of different users.

In order that the invention will be more readily understood, one embodiment thereof will now be described with reference to the accompanying drawings wherein Figure 1 is a diagrammatic illustration of the SC operation of the mechanism of the present invention, I Figure 2 is a view similar to that of Figure 1 but showing the backrest in an upright position, Figure 3 is a cross-sectional elevational view taken along the lines of 3-3 on Figure 5 and showing one Sembodiment of an adjustable mechanism in accordance with the invention with the mechanism in a reclined position, 4 Figure 4 is a cross-sectional elevational view taken along the lines 4-4 of Figure 5 and showing the mechanism in an upright position, and Figure 5 is a top plan view of the mechanism of this embodiment.

Referring to Figures 1 and 2 of the drawings there is schematically illustrated the concept of the mechanism of this invention which utilizes four links of appropriate dimensions and relative locations to provide the desired synchronous movement for the adjusting mechanism. The body link AB is fixed in position, preferably by being fixed to a chair support, while the links AD, BC and CD all move relative to link AB. Thus, the other links alter their angle and position relative to the fixed link AB.

The adjustable link AC is provided to control the relative angle and position of the movable links. In the preferred form of the invention to be described hereinafter, the adjustable link AC comprises a combination of a gas spring and a spring tensioning device. However, any form of adjustable link may be utilized for the adjusting link AC. Thus, a simple threaded rod or the like may be used -4i---4 as the adjusting link.

It will be seen from Figgure 1 that with the link BC approaching a vertical position, the backrest, which comprises an extension of the link CD, takes up a reclining position. Referring to Figure 2, movement of the link BC about the point B by extending the length of link AC causes the backrest to move to an upright position. At the same time, the link AD, which is the link to which the seat is attached, moves from a backward tilting position to a substant-ally horizontal position. Thus, .oo by a single movement produced by variation of the length of link AC, both the seat and backrest of a chair are o' °moved in synchronism.

oo Referring to Figures 3 to 5, the embodiment 0 B 15 illustrated comprises a chair support 12 which includes o a height adjustable gas spring 14 which is mounted on a five leg chair base 16 of known construction.

o.th The mechanism comprises a body part 17 fixed to the upper end of the gas spring 14. A height adjusting 20 pver 18 (Figure 5) is mounted on the body part 17 and a extends tc one side thereof to facilitate adjustment of the height of the chair support 12, in a known manner.

A seat plate 19 is mounted to the forward end Soa of the body part 17 by pivotal mounting 21. The seat 25 plate 19 carries a resilient seat member 22 nounted on flexible mounting blocks 23 carried by supports 24.

At a rear end of the body part 7 is a pair of downwardly extending control links 26 connected to the body part 17 by pivots 27. The lower ends of the control links 26 are pivotally attached by the shaft 25 to a lower end of a backrest part 28 which extends rearwardly and upwardly to intersect, and be pivotally attached as at to a rear part of the seat plate 19. The backrest part 28 then extends upwardly to a backrest assembly (not shown), the assembly carrying a backrest member 29 which may be pivotally mounted to the backrest part 28 and may have a height adjusting mechanism thereon to permit vertical height adjustment of the backrest member 29.

:i ik The backrest assembly is well known in the art and does not form a part of this invention, An adjusting gas spring 31 is connected at its lower end to the pivot 27 and extends towards the pivotal mounting 21 of the seat part on the body part. At the upper end, the adjusting gas spring 31 is fixed to a mounting bracket 32 which is connected to the pivotal mounting 21. The mounting bracket 32 also carries an adjusting trigger 33 operable by the trigger lever 34 10 which extends from one side of the mechanism. Operation o a G On °ono of the trigger lever 34 enables the length of the gas :o o spring to be adjusted thus varying the distance between oaf the pivotal mounting 21 and the pivot pin 27.

01 A trigger lever lock 36, which is pivoted to the 15 trigger lever 34, may be operated to lock the trigger can move freely under tile influence of forces on the seat 0oQoo member and backrest membr. Thus, in the lock position, 000 o oO 00 a person using the chair can move the seat and backrest members as desired between the upright and reclined ooo positions. When the lock is released, the adjusting gas spring 31 is locked in position to prevent substantial relative movement of the parts, although the nature of S 25u the gas spring is such that small movements may occur due to gas compression.

As shown particularly in Figure 4, also extending between the pivotal mounting 21 and the pivot pin 27 is an adjustble tensioning spring 37 which acts to vary the forces necessary to cause relative movement between i the seat member and backrest member. The tensioning spring 37 is mounted on a threaded support 38 which is rotatable by a hand wheel 39 which drives through a right angle gear box 41. Rotation of the threaded support 38 causes the nut 42 to move longitudinally therealong thus varying the tension in the spring 37.

In use, if a person of relatively light weight is ising the chair, the hand wheel 39 is rotated to release tension on the spring 37 thus making it easier to adjust -6- J4 the relative positions of the seat member 22 and backrest member 29 against the restraining forces of the adjusting gas spring 31. When a heavier person uses the chair, the hand wheel 39 may be rotated to increase the tension in the spring 37. This "fine tuning" of the spring tension enables the free float mechanism to be used to its optimum capability. At the same time, with the gas spring 31 in its locked position, readjustment of the relative position of the seat and backrest is facilitated.

A feature of the present invention is that the ,oc mechanism design enables a substantially constant dimension o o° to be maintained between the lumbar region of the backrest ooO o member 29 and the centre of the seat member. By maintain- O 1 ing such a substantially constant dimension throughout 15 the range of relative movement, a tendency to disarrange o 0 oo clothing, which occurs with other synchro mechanisms, is avoided. This constant dimension also makes the chair oO4 more comfortable to use.

2 While the relative dimensions and angles of the o 00 20 various parts may be varied in accordance with desired design parameters, it is preferred that, when the mechanism is in a fully reclined position, the seat plate is set at between 5 and 120 to the horizontal, sloping rearwardly, o o and the backrest is at between 105 and 1200. In the 25 upright position, the seat is preferably between rearwardly and 50 forwardly and the backrest at between 84 and 920. In the most preferred embodiment, the seat has an adjustment of 8' and the backrest an adjustment of 14.

Many modifications may be made in the design and/or construction of an adjustable chair mechanism in accordance with the present invention and all such modifications which come within the scope of the invention shall be deemed to be within the ambit of the above description.

I

Claims (9)

1. A chair adjustment mechanism for enabling adjustment of the relative positions of a chair seat and backrest comprising a chair support, a main frame structure c Lrried by the support, a chair seat frame pivotally mounted at a forward position to the main frame whereby a rear end of the seat frame is movable vertically relative to the main framB, a backrest frame pivotally connected to the rear end of the seat frame, and a pair of spaced control link members pivotally mounted at their upper ends to the main frame, lower ends of the link members being connected to a lower end of the backrest frame. S2. A mechanism according to claim 1 wherein the main frame is fixed to the chair support.

3. A mechanism according to claim 1 or claim 2 wherein an adjusting means is mounted to the control link members to enable the relative position of the control link members to be i adjusted.

4. A mechanism according to claim 3 wherein a lockable i control strut extends between the lower ends of the link I I I 20 members and the main frame, the control strut being selectively adjustable in length to selectively fix the relative position of the link members and, thus, the seat and backrest positions.

5. A mechanism according to claim 4 wherein the lockable control strut comprises a gas spring extending between the link members and the main frame, and a lock is operable to selectively lock the gas spring in a desired position thus locating the relative positions of the control link members, seat frame and backrest frame.

6. A mechanism according to any one of the preceding claims wherein adjustable spring means is located between the main frame and the link members to adjustably bias the link members to a position at which the backrest is substantially upright.

7. A mechanism according to any one of the preceding claims wherein the backrest frame includes a height adjuster.

8. A mechanism according to any one of claims 1 to 6 wherein the backrest frame includes a height adjuster and a pivot adjuster.

9. A chair adjustment mechanism substantially as hereinbefore described with reference to the accompanying drawings. ,f 9 An adjustable chair incorporating a chair adjustment mechanism in accordance with any one of the preceding claims.

11. An adjustable chair according to claim 10 wherein the chair support includes a height adjuster. DATED: 3 December 1991 CARTER SMITH BEADLE Fellows Institute of Patent Attorneys of Australia Patent Attorneys for the Applicant: SCHIAVELLO BROS (VIC) PTY LTD *r I 9 4 4; 4 444 **G /4 .fI1"~r