US3539220A

US3539220A - Seat tilting chair

Info

Publication number: US3539220A
Application number: US772262A
Authority: US
Inventors: Henry Aguilar
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-10-31
Filing date: 1968-10-31
Publication date: 1970-11-10
Anticipated expiration: 1987-11-10

Description

United States Patent [72] Inventor Henry Aguilar 1309 27th Ave., San Francisco, California 94131 21 Appl. No. 772,262 [22] Filed Oct. 31, 1968 [45] Patented Nov. 10, 1970 [54] SEAT TILTING CHAIR 12 Claims, 11 Drawing Figs.

[52] U.S. Cl 297/320 [51] Int. Cl A47c U032 [50] Field oiSearch 297/316, 320, 338, 345; 5/81 [56] References Cited UNlTED STATES PATENTS 689,942 i2/l90l Wright 297/320 3,000,668 9/1961 Croy 3,337,266 8/1967 Burns Primary ExaminerReinaldo P. Machado Attorney-Boyken, Mohler, Foster and Schwab ABSTRACT: A chair having a generally horizontally disposed seat pivotally mounted for tilting about an axis parallel with its forward edge under a continuously applied force of progressively decreasing strength proportionate to progressive changes in the position of the center of gravity of the body of a person rising in a normal manner from a fully seated position on said seat, and which seat is returnable from tilted position under progressively increasing resistance as the weight of said person is applied to said seat in a normal seating operation.

Patented Nov. 10, 1970 v 3,539,220

INVENTOR. HEMP) Aka/44? lrrdi/vifi SEAT 'IILTING CHAIR SUMMARY The employment of electric motors and power transmission means, including links and gears for tilting chair seats, is expensive and adds appreciably to the weight of the chair. Also, in the event of accidental slippage by the person rising from the chair, and a sudden backward movement of such person when the seat is )artially or wholly tilted, may result in the person sliding onto the floor, causing injury, since the seat will continue its movement in the direction in which its tilting movement is started, or will stop.

Other attempts to solve the problem of assisting persons to rise from seated positions in chairs without employing a motor, have involved the requirement of one or more manually actuatable levers that are intended to tilt the seat proportionate to the degree of manual force applied to the levers, and hydraulic means has been connected to the seat. which means must be manually actuated to provide the force for tilting the seat.

The normal manner in which most persons rise from arm chairs is to lean forward in the chair and to place their hands on the arms of the chair at the same time. This results in movement of the center 'of gravity of the body forwardly to approach the position in which the center of gravity is over the feet and by slight downward pressure of the hands against the arms, combined with the employment of the leg muscles, the body moves to an upright standing position.

Those persons, such as invalids, elderly persons and others, whose leg and arm muscles are weakened, normally have little difficulty in rising if some assistance is given to getting the body over the legs, and due to these weaknesses in the legs and arms, a sudden and unexpected application of force, or lack of such application, may result in serious injury unless provision is made for counteracting such application of force or lack of the latter.

One of the objects of the present invention is the provision of a tilting chair seat in a chair that is provided with means arranged and constructed to automatically be cooperative with the normal actions of a seated person in rising to provide substantial assistance to such person, and which means is ofa type that is free from the use of auxiliary power-driven elements, such as electric motors or the like, and also free from means that must be manually operated to transmit power to the seat, and an added object is the provision of such chair seat that is readily adapted to use by persons of different weights and strengths.

A still further object of the present invention is the provi sion of a chair adapted to accomplish the foregoing objects, and which chair includes safety means to prevent accidental and unexpected operation of the seat in the event the sitter should make moves that would normally effect tilting of the seat when no such tilting was desired.

An additional object is the provision of an armchair in which the seat and back are connected and simultaneously movable, solely under the influence ofa force applied thereto, from a normal angular position of said seat and back relative to each other, to a position in which said seat is tilted about a horizontal axis parallel with its forward edge, until the person that was seated thereon is in a substantially upright position or in a position in which the legs are substantially straight and upright, and which force is continuously applied and is of progressively decreasing strength proportionate to progressive changes in the center ofgravity of the body ofa person during the act of rising in a normal manner from a fully seated position on said seat, and resting against said back, with the hands of said person resting on the arms of said chair.

Another object of the invention is the provision ofa method of assisting a person seated in an armchair, to rise from the latter, and an added object includes the method ofsal'ely seating a standing person.

Other objects and advantages will appear in the description and drawings.

In the drawings:

FIG. I is a perspective view showing the rear and one side of a chair embodying one form of the invention, minus conventional upholstering of the seat and back and arms, or where such upholstering is desired.

FIG. 2 is a view of the chair of FIG. I showing the front and one side.

FIG. 3 is a side-elevational view of the chair of FIG. 1, shown in full line, and the seat and back are shown in elevated position in broken lines.

FIG. 4 is a fragmentary enlarged isometric view of a portion of the chair detached from the latter.

. FIG. 5 is a fragmentary enlarged elevational view of a portion of the device shown in FIG. 4 detached from the latter, with a portion of the chair shown in cross section.

.FIG. 6 is an isometric view of a portion of the seat lifting device of the chair separate from the latter.

FIG. 7 is an elevational view of one of the seat lifting elements of FIG. 6.

FIG. 8 is an isometric view of a modified form of seat and back elevating structure apart from the chair, except for the seat.

FIGS. 9, ll), ll are diagrammatic views illustrating the manner of operation of the invention in successive steps dur ing rising of a person from the chair, the modified form of the chair being shown for clarity, in which weights are used instead of springs.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION The chair illustrated comprises front legs 1 (FIG. 2), rear legs 2, (FIG. 1), front cross frame member 3, upper rear cross frame member 4, (FIG. 1), and a lower rear cross frame member 5. Extending between, and secured to the front cross frame member 3, and to the lower cross frame member 5, are spaced parallel frame members 6 (FIGS. l3).

A generally horizontally disposed seat 7 has forward extensions 8 (FIG. 2) rigid therewith, which extensions are pivotally connected at 9 to brackets 10 that are secured to the upper ends of legs I. Said seat is supported on the lower frame members 6 when the seat is in its lowermost position, and conventional upholstery or a cushion, not shown, may be part of the seat, and secured thereto for movement therewith.

The use of the words forward," forwardly, rearward," and rearwardly," and words of similar import, are used with reference to the seat and back of the chair against which the back of a person is adapted to rest. Said back is generally designated 13 and extends upwardly from the rear edge of the seat 7. The seat extends forwardly from the lower edge of the back 13. The back, like the seat, may be upholsteredin the usual manner. This invention is not concerned with the type of upholstery, if any.

The back 13 includes upwardly extending side frame pieces 14, the lower ends of which are pivotally connected to brackets 15 secured to the rear end of seat 7 at opposite sides ofthe latter by coaxial pivots 17 (FIGS. 2, 3).

Rigidly connected to the rear ends of the side frame members 6 and to upper cross frame member 4 are a pair of vertically extending uprights 18 that terminate at their lower ends adjacent the rear edge of seat 7, and at their upper ends below an upper horizontal piece 19 (FIG. I) on said seat, which piece 19 extends between, and is rigid with the upper ends of the side pieces 14.

Parallel chair arms 20 extend forwardly past the side pieces 14 of the back 13 and are rigidly secured to the upper ends of legs I and 2, the rear ends of said arms projecting rearwardly past the back 13, saidprojeeting rear ends being rigidly connceted by a horizontal back frame member 23, (FIG. I). The forward ends of said arms may project forwardly of the upper ends of legs I.

The back l3 includes a rigid panel having an upper section 25 (FIG. I that is parallel with side pieces 14 along the forward edges of the latter, and a lower panel 26 that may incline slightly rearwardly in a downward direction from the lower edge of the upper section (FIGS. 2, 3).

Said

sections

25, 26 extend to and are rigidly connected with the side pieces 14, and the upper ends of the uprights 18 are rounded at 27 (FIG. 3) and slidably support the back I3, the latter being inclined rearwardly from its lower end when the seat is in its lowermost position. The forward faces 28 of the upper portions of uprights 18 are inclined to lie flat against the rear side of section 25 when the seat is in said lowermost position, and the rounded upper edges 27 of the panel 25 uprights I8, is a horizontal cylindrical bar 33 (FIGS. I, 3, 6)

on which is swingably supported the upper end of a flattened housing 34 carrying a plurality of sets 3 5 (FIG. 6) of pairs of conventional spring tension pulleys 37 (FIG. 7) respectively enclosing a spring 38 of the clock spring-type each stationarily held at one end and connected at its opposite end with a wire rope or cord 39, shown in single lines in FIGS. I, 6, that is adapted to extend downwardly from the spring of each pair. A hook 40 is provided at the lower end of each rope 39.

Rotatably carried by, and projecting through, the rear ends of arms (FIGS. 4, 6) is a horizontal bar 43 that, in turn, is parallel with the bar 33 that extends between and is carried by the upper ends of the uprights 18 (FIG. 6). Eye members 45 extending longitudinally of the bar 43 project upwardly from the latter and are rigid with and extend longitudinally thereof. One eye 45 is on each of the projecting end portions of bar 43 that project oppositely outwardly of the pair of arms 30, and two corresponding eyes are between the arms30. These eyes are vertically below the sets of spring tension devices so one or both of the wire cords 39 may be detachably connected with each eye by a hook 40.

The sets 35 of spring tension pulleys are readily available in any desired strength. Thus the spring in each pulley may exert approximately a It) pound pull on each cord, when the hook is at the pulley, or more, according to the lifting force desired, the degree of pull being progressively increased as each hook is pulled outwardly of the housing 34. Thus, the total amount of yield-able tension applied to the ends of arms 30 depends upon the number of cords connected with bar 43.

When the seat and back of the chair are in the full line posi tion, as seen in FIG. 3, the cords 39 that are connected with g bar 43 will be tensioned to the maximum degree for moving the seat and back to the broken line position 47, in which the seat has swung about pivots 9 and the back and seat have moved about pivots [7.

When the seat and back are in the broken line position 47 (FIG. 3) it is seen that the springs 38 in sets35 are at their minimum tension (but which is still quite substantial) as the bar 43 and the said springs are relatively close together. The decrease in the lifting power exerted on the seat by the springs and the mechanical or leverage advantage become progressively less as the seat tilts to its maximum tilted position, said maximum tilted position occurring when the seat 7 and the back are substantially in alignment with the cords 39, and at this point the substantial force of the spring is fully transferred to the pivots 9.

Supported at the underside of each arm 20 of the chair is a horizontally-extending rod 49 terminating at its forward end in a button 50 (FIGS. 1, 3) readily accessible to the finger of the hand of a person seated in the chair for pushing therod rearwardly by such finger. Each rod slidably extends through openings in the upper portions of

legs

2, 3 and through the upper rear cross frame member 4, and terminates at its rear end rearwardly of cross frame member 4 (FIG. I). The forward end of each rod 49 projects forwardly from the upper portion ofeach leg I,

The horizontally aligned bars 51 (FIG. I) of a pair thereof are spaced slightly rearwardly of the upper rear cross frame member 4, each bar being swingable about a vertical pivot 52 (FIGS. I, 3) supported at its ends by the back frame member 23, and a member 53 rigid with and projecting rearwardly from the upper cross frame member 4.

The ends of bars 51 (FIG. I) opposite the ends that are engaged by the push rods 49 terminate centrally between the sides ofthe chair and engage the forward side of the upper end of a generally vertically extending strip 54. Horizontal coaxial pivots 55 intermediate the upper and lower ends of said strip pivotally support saidspring on a pair of horizontally spaced, vertically extending frame members 56, rigidly secured at their upper ends to the back frame member 23 and to the lower rear cross frame member 5.

The lower portion.58 (FIGS. 4, 5) of strip 54 is yieldably held in engagement with the rear arcuate surface of a horizontal element 59 that, in turn, is secured at its ends against the terminal rear end surfaces of the arms 30. These arms 30 are the ones that are secured to and extend rearwardly and downwardly from seat 7.

The lower end portion of strip 54 adjacent to and above portion 58 thereof, said strip is formed with an upper and a lower pair of forwardly and downwardly projecting teeth 60, the lower pair of which are spaced above the element 59 (FIG. 5) a distance enabling them to clear said element 59 when the lower end of the strip is moved rearwardly, so that the element 59, and consequently seat 7, may swing upwardly. However, unless said lower end of strip 54 is moved rearwardly, the lower pair of teeth 60 will engage the element 59 to prevent upward movement of the seat. The dotted line position of element 59 (FIG. 5) shows the latter in engagement with the lower pair of teeth.

A coil spring 61 (FIG. 3) reacts between the lower portion of strip 54 and the lower rear frame member 5 to yieldably urge the lower end 58 of said strip against the arcuate rear side of element 59.

The provision of the teeth 60 and the release means comprising a finger actuated rod 49 and its connection with strip 54 to release the seat for upward tilting movement, is to prevent accidental tilting of the seat 7, should a person seated in the chair lean forward when not intending to rise. The position of the push buttons 50 under both arms, where one may readily be pushed rearwardly, by a finger of either hand, when desired, are not accessible to accidental actuation that would likely release the seat for tilting when not intended, and the second, upper pair of teeth is to insure against accidental tilting of the seat when a person is being seated, but is not fully seated to the degree where the lower set of. teeth are operative for holding the seat down. Some persons, in being seated, may shift themselves, and lift their bodies slightly just before being fully seated, and with the upper set of teeth 60 automatically operative to hold the seat down unless one or the other of rods 49 are actuated, the person is not unexpectedly given an upward push by the seat. Both sets of teeth automatically move to hold-down" positions when the seat is lowered under the weight ofa person.

Substantially the same manner of operation may be effected by the substitution of a pulley and weights for the spring sets 35, as shown in FIGS. 811, in which the same numerals will be used for elements corresponding to those shown in FIGS. 1- -7.

In FIGS. 8-1! a horizontal differential pulley 64 is rotatably supported between the upper ends of upright 18 and arms 30 project downwardly and rearwardly below seat 7.

The central portion 67 (FIG. 8) of pulley 64 is of reduced diameter, while the end portions 68 are of substantially greater diameter. Cords 69, secured to and extending around portions 68, depend from said portions 68 and carry removablc weights 7() at. their lower ends, while a single cord 7I extends around and is secured to the reduced diameter central portion 67 of pulley 64 and depends therefrom for connection with the bar 72 extending between and connecting the rear ends of arms 30 that are connected with seat 7. The seat 7 is pivoted at its forward end to the chair at 9. A back 13. (FIGS. 9l I corresponding to back I3. may be pivotally connected to the seat 7 by pivots 17. The bar 72. it should be noted. substitutes for bar 43 in FIG. 6.

The differential pulley 64 and its connection to the seat provides a substantial power advantage that enables a relatively compact arrangement of weights while applying the desired lifting effect on the seat. and the relationship between the arms and pulley 64 is such that the maximum upward force on the seat is applied when the seat is in its lowermost position. corresponding to the full line position of the seat 7 in FIG. 3. or in FIGS. 8-l0 while the minimum force is exerted when the cord 71 is generally in alignment with the seat. and the seat and back 13 (FIG. 9) are in a position corresponding to the broken line position 47 in FIG. 3, or in full line in FIG. 11.

Arms (FIGS. 9- l l) are the same as shown in FIG. 3 and the push rods and spring and hook structure 49 to 61 are understood to all present in the form of invention semidiagrammatically illustrated in FIGS. 9--l 1.

In both forms of the invention, the upward force applied to the seat is progressively reduced as the seat rises. The employment of the sets of springs instead of the use of weights substantially reduces the weight of the chair; however, in both forms. the degree of upward force applied to the seat and back may be quickly and easily varied to suit the weight of the person. and to the degree of lifting force that is desired by the sitter.

Persons using the chair may be elderly and merely weakened to a degree that their legs lack sufficient strength to lift the body to a standing position. but are capable of walking. once they have risen. or they may be partially incapacitated through illness. accident or for other reasons so that control of the limbs during rising from a chair may be somewhat uncertain. For safety reasons in such instances, a foot pad 76 (FIGS. 1, 2) of fabric or suitable material having a roughened upper surface may be provided for the feet of the user. Openings 77 in said pad for the lower ends of the front legs 2 of the chair is provided to prevent slippage of the chair rearwardly in the event the chair is pushed rearwardly when the person on the pad is rising or is being seated. An upturned portion 78 (FIG. I) of the pad at the rear edge of each opening will still further prevent accidental rearward slippage of the chair and pad. The weight of the person on the pad will hold the pad down.

FIGS. 9. 10, 11 best illustrate the manner of operation of the invention, whether springs or weights are used to apply the upward force to the seat 7. The structure employing the pulley 64, cords 69. H and weights 70 is shown in FIGS. 9II for clarity. It is obvious that the spring sets of FIG. 6 may be substituted for the length of cord 71 (FIG. 9) that extends between the arms 30 and the pulley 64.

The center ofgravity of a person 80 fully seated in the chair. as seen in FIC. 9 is approximately at line 8I. In an adult. the upper and lower legs articulate about a point that is close to the axis of pivots 9. The forward extensions 8 on the seat 7 position the pivots 9 of the chair at approximately the level of the knee joints so that the scat legs will swing about approximately the same horizontal axis. The arms 83 of the person 80 are shown resting on arms 20 ofthe chair.

FIG. 10 shows the initial movement of the person 80 in rising. The upper body moves forward to gain lifting power in the upper and lower arms and at the same time the center ofgravity moves a substantial distance forwardly to approximately line 84, (FIG. 10) which is appreciably closer to pivot 9, with the result of decreasing the degree of force required to tilt the seat to the point where any desired degree of lifting force may be applied according to the number of cords 39 (FIG. 6) or weights 70 (FIGS. 8-11) are employed.

In most instances. and for purposes of safety, the springs or weights are so adjusted that some use of the arms 83 or downward pressure of the hands on arms 20 of the person is desirable to effect a tilting of the seat and to raise the body to the position of FIG. 11 and the lifting force applied to the seat progressively decreases as the sitter rises to a standing posisively increasing resistance to lowering the seat as the seat moves to the full line position of FIGS. 3, 9 from the position 47 of FIG. 3 or the full line position of FIG. ll. Were there no decrease in the lifting power as the seat tilts to the position shown in FIG. 11. and the person using the chair would slip, such person would slide off the seat and onto the floor. with the likelihood of receiving an injury.

The automatic, gentle return of the seat to its generally horizontal position solely under the influence of the weight of a person. where there is insufficient downward pressure of the hands on the arms of the chair to reduce the gravitational force of the body below the ever present upward force applied to the seat by the springs or weights, enables the person using the chair to have full control of the operation of the seat at all times.

The automatic progressive reduction in the degree of upward force applied to the seat as the center of gravity of the body moves forward until the person is standing. and the automatic progressive increase in said upward force as the person resumes a seated position insures the safety of the person using the chair. The body is not propelled upwardly at a rate of speed that is independent of the desires of the person using the chair. and at any time during said movement the person may be reseated by merely moving his body from the forward leaning position to the normal rearward leaning seating position, or by ceasing to exert downward pressure of the hands on the arms. according to how the springs or weights may be ad justcd.

Normally. where a person is fully seated in an arm chair. the center of gravity is approximately along a vertical line 81 (FIG. 9), extending generally from or through the horizontal axis of the hip joints 85. although it may vary slightly forwardly or rearwardly of such line according to the erectness of the body of the sitting person.

The lower legs of such sitting person would under any circumstance be approximately vertical. and the upper legs would be approximately at right angles to the lower legs, and the forearms would rest substantially horizontally on the rigid arms ofthe chair, with the hands stationary on the latter.

The foregoing is the normal position a seated person, particularly when such person were prepared to rise, but had made no movement of the body from a fully seated position. As applied to a person in substantially the foregoing position, the preferred method of elevating such person in accordance with the present invention, may be said to comprise the steps of applying an upwardly and forwardly directed force against the buttocks of the seated person along line 81, which force is insufficient to elevate such person to a standing position. and then progressively moving said center of gravity forwardly by bending the body above said axis of said hip joints forwardly about said axis whereby the difference between the degree of force required to overcome the influence of gravity and to elevate said person becomes progressively less, and then overcoming the latter difference by application of a downward pressure of the hands against the arms of said chair while said lower legs remain substantially stationary whereby the body of such person will automatically be elevated to standing position. and at the same time progressively decreasing the strength of said upwardly directed force along said line.

Insofar as the chair itself is concerned. basically the chair may be said to comprise a rigid frame having a generally horizontally disposed seat providing a forward and a rear edge. and horizontally extending arms at opposite sides of said seat adapted to support the hands of a person seated on said seat with the lower legs of such person extending across said forward edge. Pivot means pivotally supports the seat for swinging upwardly about a horizontal axis parallelwith and adjacent to said forward edge, and seat elevating means is carried by said frame and connected with said seat for yield-ably swinging said seat upwardly about said axis to a position inclined upwardly from the latter for applying an upward force against a person seated on said seat for elevating such person to a standing position, and for yieldably holding said seat in said upwardly inclined position preparatory to receiving the weight of such person upon the latter being reseatcd on said seat. Said elevating means is yieldable, such as the springs or weights, and are variable for application of different degrees of elevating force to said seat. This variability may be by connecting more or fewer of the springs or by increasing or decreasing the weights, or by tensioning or relaxing one or more springs that connect the seat with the frame.

By the present method and structure, the chair is also readily adjusted to the weight of any person using it, and to the capacity of such person to rise. Once adjusted, the application of the desired forces is automatic. Actuation of a push rod 49 to release the seat and back, as heretofore mentioned, is a safety measure, although it is apparent that where the user of the chair desires and requires only a small application of force on the seat to tilt the latter, and the weight of the body is adequate to prevent actuation of the seat where a sudden forward movement ofthc body occurs, it could be omitted.

There is a normal slight forward push on the feet of a person rising from the chair, where the strength ofthc legs is impaired which tends to slide the chair rearwardly. This usually occurs shortly before the person is in the position shown in FIG. I]. The employment of the pad 75 prevents any likelihood ofthe feet or the chair slipping during the operation of rising, although usually, were the feet or chair to slip, the person would automatically resume a seated position, as hereinbefore mentioned.

The absence of a motor, switches, gears, hydraulic means, etc., heretofore employed, materially reduces the cost of manufacture and substantially eliminates maintenance costs.

Although this invention has been described by specific structure, it will be obvious to one skilled in the art that many modifications may be constructed without departing from the invention. The scope of this invention is defined only in the appended claims.

Iclaim:

l. The method of elevating a person seated in an armchair to a standing position, and returning such person from a standing position to a seated position in such chair, in which seated position the hands of said person are on the arms of said chair and the lower legs are approximately vertical at approximately a right angle to the upper legs at the knee joints with the center of gravity of the body along a vertical line that approximately extends through the horizontal axis of the hip joints, which method includes the steps of:

a. applying a generally upwardly directed predetermined amount of force against the buttocks of said person along said line, which force is substantially sufficient to elevate such person from said seated position when said center of gravity is moved forwardly relative to said axis generally toward said knee joints;

b. progressively moving said center of gravity forwardly by leaning the upper portion of his body forwardly about said axis to the point where said degree of upward force is substantially equal to the force of gravity, and then elevating his body about said knee joints to a standing position by said person applying a sufficient downward pressure of his hands on the arms of said chair sufficient to steady his body during rising to a standing position and to overcome said force of gravity;

c. progressively reducing the degree of said upwardly applied force during movement of said body to said standing position to a predetermined degree and ceasing the application of said upwardly applied force at a predetermined point at said predetermined degree when the center of gravity of said body is approximately over the lower legs of said person, and said person is substantially in said standing position:

d. reapplying said generally upwardly directed force against the buttocks of said person at said predetermined point at said predetermined degree upon said person in said standing position moving his body to reseat himself in said chair; and

e. progressively moving the center of gravity of the body rearwardly away from said knee joints about said axis toward said line by rearward movement of the body, and progressively increasing the degree of said upwardly applied force to an amount approximately equal to but less than said force of gravity, until said person is in said seated position, whereby said movements of said body to said standing position and to said seated position are under full control of said person at all times.

2. [n a chair that includes a frame having a forward and rear side:

a. a generally horizontally disposed seat for a person disposed between said forward and rear side for seating a person thereon from said forward side;

b. supporting means on said frame adjacent said forward side supporting said seat for upward movement of the rear end of said seat that is opposite to said forward side from a generally horizontal position of said seat to an elevated position in which said seat is inclined upwardly from said forward sidc relative to horizontal for supporting such person approxin' ately in a standing position;

0. seat elevating means con nectcd with said seat for moving the latter from said 1101 izontal position with a person seated thereon, to said elevated position; and

d. said elevating means including power means automatically operative for applying a progressively diminishing degree of upward force to said seat for moving said seat from said generally horizontal position to said elevated position, when a person is seated thereon.

3. In a chair as defined in claim 2; (e) said power means being operative mainly under the influence of changes in the horizontal position of the center of gravity of a person seated on said seat in a direction toward said forward side.

4. in a chair as defined in claim 3:

f. means for increasing and for decreasing applied by said power means according to the weight of the person seated on said seat, whereby said upwardly applied force may substantially equal the specific gravity of said person at said center of gravity; and i g. the degree at which said upwardly applied force diminishes being proportional to the degree of change in said horizontal position of the center of gravity of said person in a direction toward said forward side of said chair.

5. in a chair as defined in claim 2:

. said power means being continuously operative for applying an upward force to said seat, when said seat is generally horizontal with a person seated thereon, to a degree that is insuffieient to elevate said person when the center of gravity of said person is over the rear portion of said seat with the upper body of said person upright, and which power is substantially suffieient to elevate said seat and the person seated thereon when the center of gravity of said upper body is moved forwardly toward the forward side of said seat a predetermined distance;

f. manually actuatable means for releasably holding said seat against upward movement thereof until manual actuation of said last-mentioned means.

6. In a chair as defined in claim 5:

g. a back extending upwardly from the rear end of said seat having a lower edge pivotally connected with said rear end of said seat; and

h. means supporting said back for upward movement with said seat to a position generally coplanar with the latter when said seat is in its elevated position.

7. In a chair that includes a frame having a forward and a rear side and generally horizontally disposed, horizontally spaced arms in side-by-side relation extending between said the upward force forward and rear sides for supporting the arms of a person seated in said chair:

a. a generally horizontally disposed seat for a person disposed between said forward and rear side and at a level below that of said arms for supporting a seated person thereon, said seat having a forward and a rear end respectively adjacent said forward and rear sides of said frame;

h. supporting means on said frame supporting said seat for upward movement of said rear end about an axis adjacent said forward end from a generally horizontal position of said seat to an elevated position in which said seat is inclined upwardly from said forward side at a sufficient angle relative to horizontal for supporting a person on said seal in approximately a standing position;

cl yieldable elevating means connected with said scat automatically operative for applying a yieldahle upwardly directed force to said seat sufficient for moving the latter from said generally horizontally extending position to said elevated position when a person seated upright on said seat leans his upper body forwardly and applies a relatively slight downward pressure of his hands against said arms, said yieldable means yieldably supporting said body for automatic downward movement of said seat from said elevated position to said generally horizontal position upon such person seating himself from a standing position at said forward side of said frame on said seat substantially free from downward pressure of his hands on said arms, said yieldable means being insufficient to hold said seat in said elevated position under the full weight of a person; and

d. means for increasing and for decreasing the upward yicldahle force applied by said yieldable means according to the weight of the person using said chair.

in a chair as defined in claim 7:

. said yieldable means comprising springs connected with said seat and frame under yieldable tension at all times for applying said upward force to said seat; and

f. means connecting said springs with said frame in a position for progressively diminishing the upward force applied to said seat during movement of the latter to said elevated position, and for progressively increasing the upward force so applied during movement of said seat to said generally horizontal position under the weight of a person on said seat.

. In a chair as defined in claim 8;

. seat holding means on said frame relcasahly connected with said seat for holding said seat in said generally horizontal position against said upward movement thereof under the influence of said yieldable means movable to a position releasing said seat for said upward movement; and

h. manually actuatahle means operably connected with said seat holding means for releasing the latter from seat holding relation upon manual actuation of said manually ac tuatable means.

10. In a chair as defined in claim 9; (i) said manually actuatable means being adjacent each of the arms of said chair and accessible to the hand of either arm of a person seated in said chair for actuation by a finger of either hand.

(g) in a chair as defined in claim 8: g. said supporting means for said seat including pivots spaced forwardly of the forward end of said seat for swinging said seat about a horizontal axis that is approximately coaxial with the knee joints of a person fully seated on said seat, whereby a person being elevated to a standing position will not slide on said seat during movement to said standing position.

12. In a chair as defined in claim 8; (g) said frame including forward and rear legs, and a foot support for the feet of a person-seated on said chair connected with said front legs to prevent sliding of said chair relative to said foot support during rising or seating of a person from said chair having his feet on said foot support