Abstract:
An adjustable chair, particularly for the use of attendees at meetings, is disclosed in which a gas cylinder is operatively connected between the underside of the chair seat and a lower cross-member to afford the user control of the lift and tilt of the chair over a range of positions.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to adjustable tilt chairs and, more particularly, to an improved construction of chair with pneumatically controlled back and seat angle adjustment. A large number of adjustable chairs have been designed in the past which are intended for use in the seats of motor vehicles, aircraft, railway cars and buses, exemplified in U.S. Pat. No. 2,132,363 (Thomas et al.) and U.S. Pat. No. 3,810,674 (Svensson). Electrically or hydraulically controlled chairs having occupant assisting features whereby the back and seat members tilt as required to help the user in moving between seated and standing positions (e.g. orthopaedic chairs) are also exemplified in a number of prior patents, e.g. U.S. Pat. No. 4,632,455 (Schiller et al.) and U.S. Pat. No. 5,383,709 (Chaney et al.). 
     None of the existing designs are entirely satisfactory as chairs for use at meetings and lectures. Many known adjustable chairs have large and unwieldy bases which can lead to repetitive contact with and scuffing of the shoes of a user seated in a long and taxing meeting. Many known chairs have a good range of adjustability, but an adjustment mechanism whose use is overly obtrusive and insufficiently silent to lend itself to chairs around a boardroom table, for example. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a readily moveable adjustable chair with a pneumatic action having a simple lift lever manual control. 
     It is a further object of the invention to provide an improved chair as aforesaid which will permit continuous adjustment over a range of comfortable positions from a forward tilt (for poring over documents) to substantial recline for freeform conversation or solitary contemplation. 
     With a view to overcoming the disadvantages of the prior art and achieving the aforementioned objects, according to the invention there is provided a chair with adjustable seating angle which comprises a pair of vertical side walls, having contoured upper edge surface which serve as comfortable arm rests. These sides/arm rests of the chair are supported in spaced parallel relationship by an elongate cross-member extending between the walls below seat level. An integral chair back and seat assembly which is positioned between the side walls and pivotally mounted at the front of the seat portion thereof to the side walls for angular tilting under the action of pneumatic cylinder means connected between the centre of the cross-member and the underside of the seat portion. The tilting of the back/seat assembly is effected by manual actuating or deactuating of the pneumatic cylinder by a conveniently positioned control rod at the front of and just under the seat. 
     These and other objects and advantages of the present invention will be apparent from the detailed description which follows, when considered in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a rear elevational schematic view of a chair according to the present invention; and 
     FIG. 2 is a cross-sectional view taken along line A—A of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A chair according to the invention comprises a spaced pair of vertical side panels  10   a  and  10   b . In what follows,  10   a  and  10   b  will be referred to as the “arms” of the chair since they present contoured upper edge surfaces  11   a  and  11   b  which comfortably support the relaxed arms of the seated user. 
     A one-piece seat/back unit  12  is mounted at each side of the seat portion  12   b  to the arms  10   a  and  10   b  by pivot pins  14  or other suitable means to permit pivoting as the seat portion  12   b  is lifted and the back portion  12   a  tilted forward. In FIG. 2, the extent to which the juncture of back portion  12   a  and seat portion  12   b  may be raised or lowered in use is indicated as h. 
     The lifting of the seat portion and forward tilting of the back portion of the assembly is driven by pneumatic cylinder means which may be actuated or deactuated by control lever  18  which extends forwardly from the cylinder to just under the chair front and acts as a lever for depressing or releasing a control pin on the pneumatic cylinder means. 
     As the pneumatic cylinder means in a chair according to the invention, there may usefully be used a “gas spring”, such as the SUSPA (trade-mark) Series 16. A gas spring is an hermetically-sealed hydropneumatic linear actuator containing a pressurized gas (N 2 ) to provide an output force. The gas spring also contains a specific volume of oil to lubricate the seal, piston and piston rod. The piston rod which moves within the cylinder extends outside of the gas-pressurized cylinder tube when the spring is in its unloaded static state, but as the piston rod is compressed, the piston surface impresses upon the gas cushion in the cylinder causing the internal pressure and output force to be increased according to the volume displacement of the piston rod. Conversely, during extension of the piston rod, the internal pressure and output force decrease, dependent upon the reduction of internal rod volume. 
     Such gas cylinders have been widely used in office chairs, to provide to suitable damped springing effect when someone sits down onto the seat of the chair. In chairs according to the present invention, compactness of structure and ease of use are afforded by providing a tubular cross-member  20  which serves both to support the pneumatic cylinder  16  at its lower end and, by fixed connection to arms  10   a  and  10   b  to provide strength and support for the chair assembly as a whole. 
     The angular tilt of seat portion  12   b  as it is raised by cylinder means  16  over the distance h is compensated by providing a pivotal connection means between the top of the pneumatic cylinder and the underside of the seat portion, such as a swivelling bracket  22 . 
     The flat vertical arms  10   a  and  10   b  of the chair according to the invention allow the ready mounting of any number of accessories to the sides of the chair which are useful in meetings for example a writing tablet, a tote for briefcases, laptops, purses, binders, etc., a cup holder, and so on. A preferred form of construction which lends itself to attractive design is use of a tubular steel body frame molded into CFC-free fire retardant, cold-cured, high resiliency urethane, with rigid urethane glass reinforced arm frame over steel. That affords a lightweight construction so that the chair is readily translatable when provided with conventional casters  24 . 
     Typically, the construction of the chair according to the invention will permit a range of continuous adjustment from a forward tilt of 2° of the back portion  12   a  (for poring over documents) to a full recline of 12° for conversation or contemplation. 
     While a particular form of chair and certain specific arrangement of parts has been illustrated, it will be appreciated that variations to the present arrangement may be used without parting from the spirit of the invention as defined in the appended claims.