the specific seat construction described herein is given as an example of the use of the control and to illustrate its advantages . the control is useful with many other seat and support shapes and configurations . a seat 10 according to this invention is intended to rest firmly on a floor 11 , or if desired to be tilted and moved around the floor on rollers . it is intended to be lightweight , but strong enough to support even a very heavy person , still without appearing to be , and certainly not being , a heavy article of furniture . its intended function is not only to be comfortable and affordable , but also to be attractive , without the appearance of an “ institutional ” piece of furniture . accordingly it is principally made of castings , extrusions which can be slim and unobtrusive , and of fabric which is suitably flexible and thin . this combination enables the chair or furniture group to be cleaned without damage . a base 15 comprises a pair of struts 16 , 17 . strut 16 has two legs 18 , 19 . strut 17 has two legs 20 , 21 . they are mirror images of one another , so only strut 16 will be described in detail . its rear leg 19 and forward leg 18 meet at a junction 22 that is forward of the mid - point 23 ( see fig3 ) between the lower ends 24 , 25 of the legs . accordingly , the rear leg 19 makes a smaller angle with the floor than forward leg 18 . a pad 26 is attached to the bottom end of the forward leg . preferably it is screw - mounted to the leg so it can be raised or lowered to compensate for irregularities in the floor . the bottom end of rear leg 19 has a pad 27 mounted where it will contact the floor when the base is fully in contact with the floor . rollers 28 are rotatably mounted to the rear legs , but are spaced from the pad so that when the pad contacts the floor , the rollers do not . when the seat is to be moved , the base is tilted around the bottom of the rear legs . this moves the rollers into contact with the floor , and moves the pads out of contact with the floor . the seat can then readily be wheeled to a new location . a rearward first cross beam 29 rigidly interconnects the rear legs of the two struts . a forward second cross beam 30 rigidly interconnects the struts near the junctions of the legs . cross beam 29 resists spreading of the rear legs . cross beam 30 is more substantial for reasons which will become apparent . it must resist stronger bending and torsional forces than the cross beam 29 . the seat further includes a support 35 , that receives and supports the person . it includes a bottom 36 and a back 37 . rails 38 , 39 are provided at opposite sides of the back . rails 40 , 41 are provided at opposite sides of the bottom . the respective rails are strong and provide support for webs 42 , 43 which the user rests on . the webs are strongly held to the rails by means of no importance to this invention . the bottom has a gradually convex upward contour extending from its rear end to a forward lip 45 . this lip is arcuate , with an approximate center of curvature 46 , whose location will further be discussed below . while the contour of the back is arbitrary , a convex lumbar portion 47 is preferably provided for comfort , and on taller seats , also a convex head rest 48 ( fig4 ). this type of back is most useful for a “ patient ” chair , in which an indisposed person must rest for a considerable time . a fabric web will provide a comfortable fit . instead of a fabric web , inflexible pieces such as slats may be used , or more rigid , perhaps molded plastic shapes can be used when long - term comfort and attractiveness are of less importance . a control 60 ( fig5 and 6 ) interconnects the base and the support . its purpose is to mount the support for a knee action tilt ( convexly upward ) rocking motion . its lower arm 61 ( or “ jaw ”) is bolted to forward cross beam 30 . it will be observed that cross beam 30 has a very strong cross - section to resist both bending from the weight of the occupant and twisting when the occupant rocks forwardly or backwardly . the upper arm 62 ( or “ jaw ”) of the control is pivotally mounted to lower arm 61 by a pivot pin 63 ( fig6 ). pin 63 is on or near the center of curvature 46 of forward lip 45 of the bottom of the support . the upper arm of the control is firmly attached to a support beam 64 . the shallow u shape of beam 64 provides deflection room for a flexible seat bottom when occupied , and also provides minor side wise springiness , which will be slight , but often appreciated . the support beam at its center is fixed to the upper arm so the support beam and the support rotate when the upper arm rotates . as shown , the arms 70 and 71 of the seat are pinned to the support beam . a limit pin 65 establishes the maximum downward tilt of the control . it may conveniently be attached to the upper jaw . when it strikes the lower jaw , the seat can not tilt farther back . the control may be disabled by an optional lock which can prevent any relative motion between the arms of the control . such a lock 66 is shown in fig1 and 13 . it includes a shank 67 and a head 68 . it is mounted to the lower arm and passes through it . it may be pressed in to prevent a downward movement of the upper arm by blocking it as shown by placing the shank between the two jaws so they cannot move closer together . when pulled out , the shank is pulled out and rocking motion is again enabled . the arrangement of the two pivoted arms 61 and 62 of the control allows the support to tilt . the support is held in its uppermost , forwardly tilted position by the control when there is no load on the support . it is maintained in this condition by a pair of cantilever blade - like flexures 73 , 74 which are rigidly mounted to the lower jaw , held between plates 75 by bolts 76 . the flexures have a free end 77 and a fixed end 78 . a contactor rod 80 extends across and rests on top of the flexures away from the fixed end . this rod is rigidly mounted to the upper arm at its lateral extremes and extends across the upper arm above and in contact with the flexures . a tongue 81 depends downwardly from the upper arm and fits in the space between the flexures to exclude fingers . a load on the support will cause the support to rotate counterclockwise in fig1 . weight on the support causes the control rod to deflect the flexures , and the flexures in turn will exert an upward resilient force tending to resist this weight . the support will assume a position respective to the force on it . an occupant can cause a rocking movement by leaning forwardly or rearwardly on the support . by selecting various thicknesses or lengths of flexures , or properties of the material of construction , the rocking characteristics can be established for a given chair . the control and thereby also the support are attached to beam 30 by a post 85 fixed to the bottom of the bottom arm . it fits in a socket 81 a in cross beam 30 . a curved portion 86 of the bottom arm conforms to the outside of the beam . the post passes through a socket 87 in the top of the beam . it will be seen that the control and support are thereby readily attached to the beam wherever there are a pair of aligned holes . the illustrated example is for a single patient chair . its contours are selected to provide long term comfort for the occupant , and can be placed in any suitable location . in fact , fig1 and 11 show the use of this control along with another amenity . in fig1 , a support 100 having struts 101 and 102 has a cross beam 103 which extends far to one side of chair 104 . the post 105 of control 106 is placed in a socket 107 as before , and the chair is the same functionally as in fig1 . notice , however the different shape of its back , without a head support . a table top 111 also has a post 112 , which is inserted in socket 113 . a second support 114 supports the far end of the cross beam . now the entire system has additional advantage places not only to sit , but to put things on or even to receive another seat . this is a profoundly useful basic device . the flexure can be made of any material which is springly bendable . composite fabric reinforced organic plastic bars are suitable . instead , metal flexures may be used , as desired . modification of the control allows for more or less tilting , and even for no tilting at all . this invention is not limited by the embodiments shown in the drawings and described in the description , which are given by way of example and not of limitation , but only in accordance with the scope of the appended claims .
a control for a seat , and a seat in combination with the control and a base , said control comprising an upper and a lower arm pivotally joined , with a flexure extending as a cantilever between them , such that a contactor contacts the flexure , and both permits and limits the tilting movement of the seat .