GB2293312A

GB2293312A - Chair with synchronised seat and back movement

Info

Publication number: GB2293312A
Application number: GB9415689A
Authority: GB
Inventors: Crispin Hall; Paul Brooks
Original assignee: Individual
Current assignee: Individual
Priority date: 1994-08-03
Filing date: 1994-08-03
Publication date: 1996-03-27
Anticipated expiration: 2014-08-03
Also published as: GB2293312B; GB9415689D0

Abstract

A chair, especially of the "office" type, has a seat squab and a seat back which can be tilted. The tilting movements are linked, eg via a pin engaged in an "L" shaped slot so that in tilting the seat from a forward tilting sitting position to a level sitting position, the back moves through the same angle as the seat, but on further, reclining movement backwards the seat back moves through a greater angle than the seat squab, eg in a ration of at least 1:1.4. The increase in movement of the back can be made gradual by use of a cam or curved slot. The mechanism is spring loaded to the level position. <IMAGE>

Description

VARIABLE RATIO SYNCHRONISED CHAIR MOVEMENT This invention relates to a reclining chair movement found in office (work) chairs.

Office chair which have a 'free floating' movement which allows the user to recline by the use of body weight are well known. There is a special type of chair movement which is known as a synchronised movement which provides a fixed ratio of movement between the back and seat pan when pressure or weight is applied to the back-rest. Usually this movement in contained under the seat within a cowl although some chairs have more 'designed' movements which are more ascetically pleasing and exposed.

Synchronised movements however offer one fixed ratio of movement and do not address the issue of providing back support and a 'free floating' movement in both the forward and level working positions. In some chairs 'bolt on' additional movements attempt to resolve the requirement for both forward and level working positions. This is either done by a separate control which allows the whole seat and back to tilt forward or by a seat pan which 'free floats'. The first instance does not offer continuous free floating movement through the range and the second does not provide back support.

If a synchronised movement is mounted onto the chair base at such an angle as to provide a forward tilting seat pan when the user reclines in the chair to a position where the seat pan angle is level the angle between the backrest and seat is too wide to provide back support.

According to the present invention there is a chair movement with continuos movement (with 2 different movement ratios between the seat and back) which allows the user to move between a forward and level sitting position at ratio of 1:1 before reclining at a movement ratio of 1:1.4 or greater.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which: SKO1 shows in section, the movement in a forward sitting position SK02 shows in a section, the movement in a level sitting position SK03 shows in section, the movement in a reclining sitting position SK04 shows in section, the chair mechanism in a forward sitting position SK05 shows in section, the chair mechanism in a level sitting position SK06 shows in section, the chair mechanism in a reclining sitting position The movement is designed to give 2 different ratios of movement to the back and seat of a reclining office chair with a forward tilting seat pan.Referring to the SK05 and the Key on DWG sheet 05 the movement comprises of 3 pivot points (1 and 8) and a slot (4 and 12) which (by it's shape) determines the ratio of movement between the seating surfaces (back and seal pans).

The movement is also designed to allow the seat angle to be preset (in any or a predetermined number of positions) between level and forward tilt by, for example, a return stop (shown in SKO1) which operates on the chassis, the vertical part of the slot (4 and 12 on SK05) or similar means (not shown). The return stop does not affect the "free floating" motion provided by the movement upon reclining.

A locking mechanism (not shown but common on many synchronised chairs) could be fitted to allow the movement to be locked in any (or a predetermined number of) position.

Their are alternative methods of providing the geometry of movement which is an essential ingredient of the current invention. For example cams could be used to change the ratio of seat to back angle instead of an "L" shaped slot. The mechanism could equally apply to single or split shell chairs.

In order to achieve a reclining position the chair user must lean back on the back-rest. The amount of backward movement is determined by the range (in degrees) provided by the chair movement and the amount of pressure (weight) applied on the backrest by the user.

As the chair movement is under tension in all but its most forward position the chair returns to an upright position when the pressure or weight of the user is removed from the back rest. This type of movement is achieved by a variety of existing tension mechanism which include: a gas assisted spring with a preset tension, a tension adjustable spring, a sprung chair shell or similar means (not shown) and provides what is commonly known as "permanent contact".

KEY TO SKOS ON DWG SHEET 03 1 BACK PIVOT 2 SEAT MOUNTING PLATE 3 ACTION CHASSIS - MhlN PART 4 "L" SHAPED SLOT. SYNCHRONOUS RECLINING MOVEMENT SECIION 5 "L" SHAPED SLOT PIN 6 SPRING MOUNIING BAR AND PLATE 7 SPRING 8 FRONT PIVOT 9 JBAR FLXING 10 BACK BAR 11 SPINDLE TAPER 12 "L"SLOT - NON SYNCHRONOUS FORWARD TILT SECTION 13 ACTION CHASSIS FRONT PART 14 TENSION WHEEL KEY TO SK01, SK02 AND SK03 ON DWG SHEET 01 SK01 SHOWS A CHAIR IN A FORW ARD SITTING POSITION. SK02 SHOW A CHAIR IN A LEVEL SITTING POSITION, SK03 SHOWS A CHAIR IN A RECLINING POSITION.

1 BACK PIVOT 8 FRONT PIVOT 15 PLANE OF BACK.REST 16 SEATTO BACK ANGLE-INDICITIVE AT 95 DEGREES 17 PLANE Or; SEAT PAN 18 SIIOWS SEAT PAN WITH 5 DEGREES OF FORWARD TILT 19 ADJUSTABLE SEAT PAN ANGLERETURN STOP 20 CHASSIS CONNECTION POINT TO GAS LIFT 21 "L" SHAPED SLOTTED PIVOT 22 SHOWS SEAT PAN IN LEVEL POSITION - 0 DEGREES OF TILT 23 SEAT TO BACK ANGLE. INDICITIVE AT 100 DEGREES.

(CHANGE IN SEAT TO BACK ANGLE BETWEEN SK02 AND SK03 INDICATES A 2:1 (BACK:SEAT) MOVEMENT RATIO ONCE THE SEAT MOVES PAST THE LEVEL. POSITION. RATIO COULD BE GREATER OR LESS THAN 2:1 24 SHOWS SEAT PAN WTTH 5 DEGREES OF BACKWARD TILT

Claims

Claims 1 A chair movement with continuos movement (with 2 different movement ratios between the seat and back) which allows the user to move between a forward and level sitting position at ratio of approximately 1: 1(seat:back) before reclining at a movement ratio of 1:1.4 or greater.
2 A chair movement as claimed in Claim 1, wherein the ratio between forward and level sitting (or thereabouts) position is approximately 1:1 whilst the reclining movement ratio is 1:1.4 or greater.
3 A chair movement as claimed in Claim 1 or Claim 2, wherein the 2 ratios of movement can be varied by varying the shape of slot C.
4 A chair movement as claimed in any proceeding claim, wherein an "L" shaped slot with a curve between the 2 planes will change the ratio gradually between 1:1 and 1:1.2 or greater.

This gradual change between the 2 ratios of movement could also be achieved by using a cam or other means.
5 A chair movement as claimed in any proceeding claim, wherein a return stop allows the seat angle to be preset for individual use. i.e. the seat angle can be set at any angle between forward tilt and level without affecting the 'free floating' reclining movement.
6 A chair movement as claimed in any proceeding claim, wherein a locking mechanism allows the movement to be locked in any position.
7 A chair movement as claimed in any proceeding claim with the exception of Claim 5, wherein the range of movement between forward tilt and level provides seat 'bounce' to reduce 'bottoming out' and thereby ensure the spine is not jarred upon sitting down.
8 A chair movement as claimed in Claim 5, wherein a return stop allows the seat angle to be preset for individual use. When load is removed from the seat pan any preset on the return stop is lost.
9 A chair movement as claimed in any proceeding claim where the location of the pivot points is varied but the ratio of movements is substantially as described herein.
10 A split or single shell chair movement which provides the ratio of movements as described in Claim 1 11 A chair movement substantially as described herein with reference to SKO1 through SK06 of the accompanying drawing or the accompanying supporting text.