Chair having a leaf spring with a fulcrum point that moves to shorten a working length of the leaf spring and increase resistance to tilting of a backrest portion of the chair relative to a column portion of the chair

Abstract

Disclosed herein is a chair that includes a backrest portion, a seat portion coupled with the backrest portion, a column portion coupled with the seat portion, a linkage coupled with the backrest portion, a leaf spring in direct contact with the linkage, an arc-shaped toothed structure fixed translationally relative to the column portion, and a different toothed structure in contact with the arc-shaped toothed structure. The chair is also configured such that when a weight is applied to the seat portion, a fulcrum point of the leaf spring moves as the different toothed structure moves along the arc-shaped toothed structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest portion relative to the column portion. A process for assembling the chair and a weight-based tilt-resistance assembly for use with the chair are also described herein.

Claims

1. A chair, comprising: a backrest portion; a seat portion coupled with the backrest portion; a column portion coupled with the seat portion; a linkage coupled with the backrest portion; a leaf spring in direct contact with the linkage; an arc-shaped toothed structure fixed translationally relative to the column portion; and a different toothed structure in contact with the arc-shaped toothed structure, and wherein: when a weight is applied to the seat portion, a fulcrum point of the leaf spring moves as the different toothed structure moves along the arc-shaped toothed structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest portion relative to the column portion.

2. The chair of claim 1, wherein the linkage includes one or more pivotal connections at which the backrest portion is configured to tilt about, the one or more pivotal connections being distinct from a contact point between the linkage and the leaf spring.

3. The chair of claim 2, wherein a respective pivotal connection of the one or more pivotal connections at which the backrest portion is configured to tilt about is located at a location beneath the seat portion.

4. The chair of claim 3, wherein the respective pivotal connection is configured to be closer to the seat portion as compared to the contact point between the linkage and the leaf spring.

5. The chair of claim 1, further comprising a weighing spring configured to weigh the weight that is applied to the seat portion.

6. The chair of claim 5, wherein the weighing spring is configured to measure weight applied across an entirety of the seat portion.

7. The chair of claim 1, further comprising another arc-shaped toothed structure, distinct from the arc-shaped toothed structure, the other arc-shaped toothed structure having a size that is different than a size of the arc-shaped toothed structure.

8. The chair of claim 7, wherein the arc-shaped toothed structure is associated with a smaller diameter facilitating movement associated with the arc-shaped toothed structure as compared to a larger diameter facilitating movement associated with the other arc-shaped toothed structure.

9. The chair of claim 1, wherein the leaf spring is configured to be hidden within a housing for a height-adjustment mechanism of the chair.

10. The chair of claim 1, wherein the linkage includes a first part in direct physical contact with the backrest portion and a second part in direct physical contact with the leaf spring.

11. The chair of claim 1, wherein the leaf spring is oriented within a same horizontal plane as the seat portion.

12. The chair of claim 1, wherein the linkage is configured to be in direct contact with an additional leaf spring, distinct from the leaf spring, the additional leaf spring configured to provide an additional resistance to tilting of the backrest portion relative to the column portion, and the leaf spring and the additional leaf spring are each in contact with an elongate, wedge-shaped actuating component that is configured to assist in providing a resistance to tilting of the backrest portion related to the column portion.

13. The chair of claim 1, wherein the column portion is coupled with one or more wheels for moving the chair.

14. The chair of claim 1, wherein: the working length of the leaf spring is between the fulcrum point of the leaf spring and a contact point between the leaf spring and the linkage.

15. The chair of claim 1, wherein, when the weight is applied to the seat portion, the different toothed structure, a pivot point at which the backrest portion is configured to tilt relative to the column portion, and the linkage are configured to move at a same point in time.

16. The chair of claim 1, wherein the chair is configured such that: before the fulcrum point of the leaf spring moves, the fulcrum point of the leaf spring is configured to be between (i) a pivot point at one end of the linkage, the pivot point being a point at which the backrest portion is configured to tilt relative to the column portion and (ii) another end of the linkage at which the linkage contacts the backrest portion.

17. The chair of claim 16, wherein the chair is configured such that: after the fulcrum point of the leaf spring moves, the fulcrum point of the leaf spring is configured to remain between (i) the pivot point at the one end of the linkage and (ii) the other end of the linkage.

18. A process for assembling a chair, the process comprising: providing a backrest portion; coupling a seat portion with the backrest portion; coupling a column portion with the seat portion; coupling a linkage with the backrest portion; placing a leaf spring in direct contact with the linkage; providing an arc-shaped toothed structure that is fixed translationally relative to the column portion; and providing a different toothed structure in contact with the arc-shaped toothed structure, and wherein: after the chair has been assembled, it is configured such that when a weight is applied to the seat portion, a fulcrum point of the leaf spring moves as the different toothed structure moves along the arc-shaped toothed structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest portion relative to the column portion.

19. A weight-based tilt-resistance assembly configured for use in a chair, the weight-based tilt-resistance assembly comprising: a linkage coupled with a backrest portion of a chair, the chair also including a seat portion coupled with the backrest portion and a column portion coupled with the seat portion; a leaf spring in direct contact with the linkage; an arc-shaped toothed structure fixed translationally relative to the column portion; and a different toothed structure in contact with the arc-shaped toothed structure, and wherein: the weight-based tilt-resistance assembly is configured such that when a weight is applied to the seat portion, a fulcrum point of the leaf spring moves as the different toothed structure moves along the arc-shaped toothed structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest portion relative to the column portion.

20. The weight-based tilt-resistance assembly of claim 19, wherein the linkage includes one or more pivotal connections at which the backrest portion is configured to tilt about, the one or more pivotal connections being distinct from a contact point between the linkage and the leaf spring.

21. The weight-based tilt-resistance assembly of claim 20, wherein a respective pivotal connection of the one or more pivotal connections at which the backrest portion is configured to tilt about is located at a location beneath the seat portion.

22. The weight-based tilt-resistance assembly of claim 21, wherein the respective pivotal connection is configured to be closer to the seat portion as compared to the contact point between the linkage and the leaf spring.

23. The weight-based tilt-resistance assembly of claim 19, further comprising a weighing spring configured to weigh the weight that is applied to the seat portion.

24. The weight-based tilt-resistance assembly of claim 23, wherein the weighing spring is configured to measure weight applied across an entirety of the seat portion.

25. The weight-based tilt-resistance assembly of claim 19, further comprising another arc-shaped toothed structure, distinct from the arc-shaped toothed structure, the other arc-shaped toothed structure having a size that is different than a size of the arc-shaped toothed structure.

26. The weight-based tilt-resistance assembly of claim 25, wherein the arc-shaped toothed structure is associated with a smaller diameter facilitating movement associated with the arc-shaped toothed structure as compared to a larger diameter facilitating movement associated with the other arc-shaped toothed structure.

27. The weight-based tilt-resistance assembly of claim 19, wherein the leaf spring is configured to be hidden within a housing for a height-adjustment mechanism of the chair.

28. The weight-based tilt-resistance assembly of claim 19, wherein the linkage includes a first part in direct physical contact with the backrest portion and a second part in direct physical contact with the leaf spring.

29. The weight-based tilt-resistance assembly of claim 19, wherein the leaf spring is oriented within a same horizontal plane as the seat portion.

30. The weight-based tilt-resistance assembly of claim 19, wherein the linkage is configured to be in direct contact with an additional leaf spring, distinct from the leaf spring, the additional leaf spring configured to provide an additional resistance to tilting of the backrest portion relative to the column portion, and the leaf spring and the additional leaf spring are each in contact with an elongate, wedge-shaped actuating component that is configured to assist in providing a resistance to tilting of the backrest portion related to the column portion.

31. The weight-based tilt-resistance assembly of claim 19, wherein the column portion is coupled with one or more wheels for moving the chair.

32. The weight-based tilt-resistance assembly of claim 19, wherein: the working length of the leaf spring is between the fulcrum point of the leaf spring and a contact point between the leaf spring and the linkage.

33. The weight-based tilt-resistance assembly of claim 19, wherein, when the weight is applied to the seat portion, the different toothed structure, a pivot point at which the backrest portion is configured to tilt relative to the column portion, and the linkage are configured to move at a same point in time.

34. The weight-based tilt-resistance assembly of claim 19, wherein the weight-based tilt-resistance assembly is configured such that: before the fulcrum point of the leaf spring moves, the fulcrum point of the leaf spring is configured to be between (i) a pivot point at one end of the linkage, the pivot point being a point at which the backrest portion is configured to tilt relative to the column portion and (ii) another end of the linkage at which the linkage contacts the backrest portion.

35. The weight-based tilt-resistance assembly of claim 34, wherein the weight-based tilt-resistance assembly is configured such that: after the fulcrum point of the leaf spring moves, the fulcrum point of the leaf spring is configured to remain between (i) the pivot point at the one end of the linkage and (ii) the other end of the linkage.

36. The process of claim 18, wherein the linkage includes one or more pivotal connections at which the backrest portion is configured to tilt about, the one or more pivotal connections being distinct from a contact point between the linkage and the leaf spring.

37. The process of claim 36, wherein a respective pivotal connection of the one or more pivotal connections at which the backrest portion is configured to tilt about is located at a location beneath the seat portion.

38. The process of claim 37, wherein the respective pivotal connection is configured to be closer to the seat portion as compared to the contact point between the linkage and the leaf spring.

39. The process of claim 18, further comprising: coupling a weighing spring to the seat portion, wherein the weighing spring is configured to weigh the weight that is applied to the seat portion.

40. The process of claim 39, wherein the weighing spring is configured to measure weight applied across an entirety of the seat portion.

41. The process of claim 18, further comprising: providing another arc-shaped toothed structure, distinct from the arc-shaped toothed structure, the other arc-shaped toothed structure having a size that is different than a size of the arc-shaped toothed structure.

42. The process of claim 41, wherein the arc-shaped toothed structure is associated with a smaller diameter facilitating movement as compared to a larger diameter facilitating movement associated with the other arc-shaped toothed structure.

43. The process of claim 18, wherein the leaf spring is configured to be hidden within a housing for a height-adjustment mechanism of the chair.

44. The process of claim 18, wherein the linkage includes a first part in direct physical contact with the backrest portion and a second part in direct physical contact with the leaf spring.

45. The process of claim 18, wherein the leaf spring is oriented within a same horizontal plane as the seat portion.

46. The process of claim 18, wherein the linkage is configured to be in direct contact with an additional leaf spring, distinct from the leaf spring, the additional leaf spring configured to provide an additional resistance to tilting of the backrest portion relative to the column portion, and the leaf spring and the additional leaf spring are each in contact with an elongate, wedge-shaped actuating component that is configured to assist in providing a resistance to tilting of the backrest portion related to the column portion.

47. The process of claim 18, further comprising: coupling one or more wheels to the column portion for moving the chair.

48. The process of claim 18, wherein: the working length of the leaf spring is between the fulcrum point of the leaf spring and a contact point between the leaf spring and the linkage.

49. The process of claim 18, wherein, when the weight is applied to the seat portion, the different toothed structure, a pivot point at which the backrest portion is configured to tilt relative to the column portion, and the linkage are configured to move at a same point in time.

50. The process of claim 18, wherein the chair is configured such that: before the fulcrum point of the leaf spring moves, the fulcrum point of the leaf spring is configured to be between (i) a pivot point at one end of the linkage, the pivot point being a point at which the backrest portion is configured to tilt relative to the column portion and (ii) another end of the linkage at which the linkage contacts the backrest portion.

51. The process of claim 50, wherein the chair is configured such that: after the fulcrum point of the leaf spring moves, the fulcrum point of the leaf spring is configured to remain between (i) the pivot point at the one end of the linkage and (ii) the other end of the linkage.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic representation of a reconfigurable apparatus, according to the present invention;

(2) FIG. 2 is a side elevation view of a task chair, that is one representative form of apparatus as shown in FIG. 1, and incorporating an adjusting assembly according to the present invention;

(3) FIG. 3 is a partially schematic representation of one specific form of adjusting assembly, integrated into the apparatus in FIGS. 1 and 2;

(4) FIG. 4 is a fragmentary view of a part of the adjusting assembly in FIG. 3, which utilizes a leaf spring, and from a different perspective;

(5) FIG. 5 is an enlarged, fragmentary view of a modified form of a leaf spring utilized on the apparatus in FIGS. 3 and 4;

(6) FIG. 6 is an enlarged, fragmentary, elevation view of a linkage, modified from a corresponding linkage as used on the apparatus in FIGS. 3 and 4;

(7) FIGS. 7-16 are partially schematic representations of apparatus incorporating different forms of adjusting assemblies, according to the invention;

(8) FIG. 17 is a schematic representation of a further modified form of reconfigurable apparatus, according to the present invention;

(9) FIG. 18 is a schematic representation of adjusting assemblies, according to the invention, acting between separate components on a frame;

(10) FIG. 19 is a schematic representation of a modified form of apparatus, according to the present invention, and including an adjusting assembly with separate first and second subassemblies;

(11) FIG. 20 is a schematic representation of the first subassembly in FIG. 19 in a form that is operable independently of the second subassembly;

(12) FIG. 21 is a schematic representation of a form of the second subassembly in FIG. 19 that is operable independently of the first subassembly therein;

(13) FIG. 22 is a schematic representation of one form of the first and second subassemblies in FIG. 19 that share at least one component;

(14) FIG. 23 is a schematic representation of one form of the apparatus in FIG. 19 used for sitting;

(15) FIG. 24 is a schematic representation of additional details on the apparatus in FIG. 23;

(16) FIG. 25 is a schematic representation of different actuators for manual operation of the second subassembly;

(17) FIG. 26 is a schematic representation of another form of actuator for the second subassembly;

(18) FIG. 27 is a schematic representation showing a portion of an apparatus with one form of the inventive first and second subassemblies;

(19) FIG. 28 is a sectional view of the apparatus taken along line 28-28 of FIG. 27;

(20) FIG. 29 is a view as in FIG. 27 and showing portions removed/separated to identify details of the second subassembly;

(21) FIG. 30 is a view as in FIGS. 28 and 29 and showing a modified form of apparatus;

(22) FIG. 31 is a sectional view of the apparatus taken along line 31,31 of FIG. 30;

(23) FIG. 32 is a schematic representation of a modified form of apparatus with a first form of subassembly according to the invention;

(24) FIG. 33 is a view as in FIG. 32 of a slightly modified form of the apparatus with a second subassembly incorporated;

(25) FIG. 34 is a view as in FIG. 33 with a different form of the second subassembly incorporated;

(26) FIG. 35 is a fragmentary elevation view of a linkage as in FIG. 6;

(27) FIG. 36 is a view as in FIG. 35 with a second subassembly incorporated;

(28) FIG. 37 is a view as in FIGS. 35 and 36 with a different form of second subassembly incorporated;

(29) FIG. 38 is a schematic representation of first and second subassemblies, according to the invention, and the second subassembly in the form in FIG. 37;

(30) FIG. 39 is a view as in FIG. 38 with a modified form of the subassembly;

(31) FIG. 40 is a partially schematic representation of a second subassembly, according to the present invention, with one form of manual actuator;

(32) FIG. 41 is a view as in FIG. 40 with another form of actuator; and

(33) FIG. 42 is a schematic representation of a part of a seat with another form of actuator shown schematically on a peripheral edge of the seat.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(34) In FIG. 1, a reconfigurable apparatus, according to the present invention, is shown in schematic form at 10. The apparatus 10 consists of a frame 12 and at least a first component 14 on the frame 12 upon which a force is applied in a first manner in using the apparatus 10 for its intended purpose.

(35) At least a second component 16 is provided on the frame 12 and is movable relative to the at least first component and/or the frame 12. A force can be applied in a second manner upon the at least second component to reconfigure the apparatus 10 by moving the at least second component 16 relative to the at least first component and/or the frame 12.

(36) An adjusting assembly 18 cooperates between the at least first component 14 and the at least second component 16 and is configured so that, as an incident of the force being applied in the first manner changing, the force applied in the second manner required to reconfigure the apparatus 10 changes.

(37) The adjusting assembly 18 includes a spring assembly 19. The spring assembly 19 is configured to exert a force that resists movement of the at least second component 16 that varies as a magnitude of the force applied in the first manner varies.

(38) The generic showing of the apparatus 10 is intended to encompass a wide range of different products and different applications. The inventive concepts can be used in virtually any system or apparatus wherein its normal intended use requires the application of a force on a first component and wherein that force on the first component impacts a force required to be applied to a second component to reconfigure the apparatus as contemplated during use.

(39) While not intended to be limiting, the detailed description herein will be focused upon furniture and, more particularly, a chair construction. This application of the inventive concepts is intended to be exemplary in nature only and should not be viewed as limiting the inventive concepts to the specific type of apparatus described in detail herein. Further, the schematic showing in FIG. 1 is intended to encompass not only a wide range of different systems/apparatus, but different forms of components and their interaction for each such system/apparatus.

(40) For example, interlocking toothed components are described, in exemplary forms below. The invention contemplates not only different types of toothed components, such as gears, differential gears, epicyclic gears, rack and pinion arrangements, etc., but also virtually an unlimited number of different interengaging components, such as sprockets and chains, pulleys and cables, mechanisms using levers, pistons, different types of linkages, etc.

(41) In FIG. 2, one exemplary apparatus 10 is shown in the form of a task chair, in this case without armrests. Of course, armrests might be incorporated and might also have parts thereof movable in different manners depending upon the weight of the user, as hereinafter explained.

(42) The chair 10 has a wheeled frame 12 with a vertically extending pedestal assembly 20. The first component 14 is in the form of a conventional-type seat with an upwardly facing user support surface 22. In this case, the aforementioned force applied in the first manner is the weight of the user exerted downwardly on the support surface 22 as he/she sits on the chair 10.

(43) A corresponding second component 16 is in the form of a back rest against which a seated user leans to exert the aforementioned force in the second manner to reconfigure the chair 10. That is, the back rest moves relative to the frame 12 and first component 14, as the user leans back and forth while seated, generally in a manner as indicated by the double-headed arrow 23.

(44) The adjusting assembly 18, as shown schematically in FIG. 2, acts between the first component/seat 14 and second component/back rest 16 directly and/or through the frame 12. The adjusting assembly 18 may be added to the frame 12 by attachment thereto, virtually anywhere thereon, or integrated thereinto, as by being constructed within a hollow 24 on the pedestal assembly 20.

(45) The chair 10 may incorporate one or more adjusting features other than one that permits reconfiguration by changing the angle of the second component/back rest 16. The adjusting assembly 18 may be integrated into the mechanisms associated with these other features. Alternatively, the other features may operate without effect by the adjusting assembly 18.

(46) For purposes of simplicity, the second component/back rest 16 will be shown as repositionable relative to the first component/seat 14 to reconfigure the chair 10 by movement of the second component/back rest 16 relative to the first component/seat 14 and frame 12 around a pivot axis 26. This particular connection should not be viewed as limiting.

(47) Exemplary specific forms of the adjusting assembly 18 will now be described. As noted above, virtually an unlimited number of different variations of adjusting assembly are contemplated within the generic showing of FIGS. 1 and 2. These specific forms are exemplary in nature only. These particular mechanisms will also be described with respect to the apparatus in the form of a chair as shown in FIG. 2. Again, the particular nature of the apparatus is not limited to a chair or furniture, although it has particular applicability in this category of product.

(48) In FIGS. 3 and 4, the first component/seat 14 (hereinafter referred to only as the representative chair “seat 14”) is integrated into a support 28 that has a depending post 30 that is slidable guidingly vertically, as indicated by the double-headed arrow 32, in a guide channel 34 on the frame 12. A biasing assembly, shown in one exemplary form as a coil spring 33, normally biasably urges the seat 14 upwardly relative to the frame 12.

(49) A generally U-shaped member 36 has one leg 38 of the “U” mounted on a frame part 40. The other leg 42 of the “U” has an offset bracing end 44.

(50) For purposes of simplicity, the support 28 and member 36 can be considered to be part of the frame 12 and/or the adjusting assembly 18. Similarly, the component 58 can be considered to be part of the back rest 16 and/or the adjusting assembly 18.

(51) The spring assembly 19 in this embodiment is in the form of a leaf spring. The leaf spring 19 has an elongate body 46 with a length L between spaced ends 48, 50, a width W, and a thickness T.

(52) The leaf spring end 19 is anchored in the member 36 to project in cantilever fashion vertically upwardly therefrom. In this embodiment, the body 46 of the leaf spring 19 is preloaded so that it naturally assumes the dotted line shape and position.

(53) The bracing end 44 of the member 36 is bifurcated, as seen in FIG. 4, with spaced edges 52 (one shown) at the extremity of the bracing end 44 engageable with one surface 54 of the leaf spring body 46 to maintain the body 46 in the straight vertical orientation, as shown in FIG. 3.

(54) A part of the second component/back rest 16 (hereafter referred to only as the representative chair “back rest 16”) is connected to the support 28 for movement relative thereto around the axis 26 as seen in FIG. 2. As a user situated on the seat 14 leans against the back rest 16, a force is generated as shown by the arrow 56 on the back rest component 58 that tends to pivot the component 58 in the direction of the arrow 60 around the axis 26.

(55) The component 58 is configured so that an edge 61 on a cantilevered part 62 thereof bears against the leaf spring surface 54. In the depicted state, this produces a force upon the leaf spring body 46, at a location A along the length of the body 46, that tends to bend the body 46 in the direction of the arrow 64 around a fulcrum location at 66 where the body 46 projects away from the part of the member 36 in which it is anchored. The leaf spring 19 thus biasably resists movement of the component 58, and the back rest 16 of which the component 58 is a part, with a first force.

(56) The configuration in FIG. 3, while it could show a starting state without any force application on the seat 14, is also representative of the overall state of the apparatus 10 with an individual of a first weight seated thereon. This is an equilibrium position for the chair 10 resulting from the balancing of the user's weight and the upward biasing force generated by the spring 33 acting between the frame 12 and the seat 14 through the support 28.

(57) In the event that an individual of greater weight assumes a sitting position on the seat 14, the support 28 and component 58 will translate further downwardly against the force of the spring 33, which causes the edge 61 on the back rest component 58 to bear upon the leaf spring 19 at a location below the location A. As a result, a shorter moment arm is established between the location where the edge 61 on the part 62 contacts the surface 54 and the fulcrum location at 66. Thus, the leaf spring 19 has an effectively shorter length, whereby a greater force is required to be applied to the leaf spring 19 to effect bending thereof as would in turn allow movement of the back rest 16 to reconfigure the chair 10.

(58) To stabilize the support 28, a depending arm 70 thereon connects to the frame part 40 through a link 72. One link end 74 moves about an axis 76 that is fixed relative to the frame part 40. The other link end 78 pivotally connects to the arm 70 for movement about an axis 80.

(59) The bifurcated configuration of the leg 42 allows the part 62 on the component 58 to move in an opening 82 through the region at the offset bracing end 44 so that the member 36 does not interfere with the back rest component 58 as the back rest component 58 lowers under increasing user weight.

(60) Accordingly, an increase in the weight of a user causes the leaf spring 19 to produce a greater resistance to movement of the back rest 16 relative to the frame 12. As a result, the chair is self-adjusting. The parts thereof can be engineered so that a desired relationship between the user's weight and the force required to move the back rest 16 are appropriately established.

(61) In designing the chair 10 using a leaf spring component, the leaf spring body 46 may have a uniform cross-sectional shape as viewed orthogonally to its length. Alternatively, this shape may be non-uniform over at least a portion of its length. For example, as shown for a portion of the length of a modified form of body 46a, as shown in FIG. 5, the cross-sectional area varies progressively.

(62) Tapering the cross-sectional area of the leaf spring over its length may allow further tuning of performance. Thickened regions may be provided to produce larger resistance forces for users at the higher weight end of the functional range.

(63) The leaf spring material may be metal, plastic, a composite, etc. The leaf spring may be straight, curved, with changing cross-sectional shapes, etc. Changing shapes, pre-loading, changing dimensions, etc., are just examples of options that might be practiced to design and tune the adjusting assemblies so that they adapt more appropriately to users throughout a workable user weight range.

(64) In a still further modified form of the structure in FIG. 3, as shown in FIG. 6, the link 72a, corresponding to the link 72, can be connected to the frame 12 for pivoting movement about an axis 84 between its ends 74a, 78a. Accordingly, as the arm 70a moves downwardly under increasing user weight, link 72a pivots around the axis 84 so that the member 36a simultaneously moves upwardly. Thus, for each incremental movement of the seat 14 downwardly, there is a greater movement of the edge 61 on the part 62 toward the fulcrum location 66 for the leaf spring 19 than occurs with the design in FIGS. 3 and 4.

(65) In FIG. 7, a modified form of chair is shown at 10′, with elements corresponding to those in FIGS. 3 and 4 identified with like reference numerals and a “′” designation.

(66) The chair 10′ has a back rest component 58′ that acts against a leaf spring 19′ that is anchored in a component 36′.

(67) In this embodiment, the leaf spring body 46′ is mounted at a slight angle a to vertical. Accordingly, the part 62′ of the component 58′ tends to bind more with the leaf spring 19′ as it slides downwardly thereagainst under increasing user weight. This binding creates frictional forces that augment the upward balancing force produced by the spring 33′.

(68) Additionally, the chair 10′ utilizes cooperating toothed elements 86, 88, 90 that interact to cause movement of the frame part 40′, arm 70′ and leg 38′ relative to each other and the frame part 40′ that replicates the relative movement that occurs with corresponding elements in the embodiment shown in FIGS. 3 and 4. The toothed element 88 is in the form of a differential pinion that turns around an axis 92. Larger and smaller diameter toothed portions 94, 96, respectively, engage toothed racks 98, 100, respectively on the leg 38′ and arm 70′. Turning of the toothed element 88 in the direction of the arrow 102 under increasing user weight causes simultaneous upward movement of the member 36′ and downward movement of the support 28′.

(69) In FIG. 8, a further modified form of chair, according to the present invention, is shown at 10″. The chair 10″ incorporates a back rest component 58″ that interacts with a leaf spring 19″ and leg 42″ in the same way that the corresponding components interact on the chair 10 in FIGS. 3 and 4.

(70) Further, the chair 10″ incorporates toothed elements 86″, 88″, 90″ which function essentially in the same manner as the corresponding components on the chair 10′ in FIG. 7. The primary difference between these embodiments is that the leg 38″ has a curved shape that moves in a complementarily-curved channel 104 on the frame part 40″. Whereas the support 28′ associated with the seat 14 and member 36′ move relative to each other in parallel, straight paths, the member 36″ moves in a curved path, as dictated by the curvature of the leg 38″ and cooperating channel 104. This curvature nominally matches the curved shape of the leaf spring 19″ which is pre-loaded from the dotted line position to the operative, solid line position in FIG. 8. Accordingly, the relative movement of the member 36″ and support 28″ causes the part 62″ that engages the leaf spring 19″ to generally follow the pre-loaded curvature of the leaf spring 19″.

(71) In a further modified form of chair, as shown at 10′″ in FIG. 9, the basic construction of FIGS. 3 and 7 is utilized with the exception that the leaf spring 19′″ is fixedly mounted to the component 58′″ and acts against the member 36′″, i.e., this component arrangement is reversed from that in the earlier embodiments. The leaf spring 19′″ is pre-loaded from the dotted line position into the solid line position which is maintained by the abutment thereof to the member 36′″.

(72) In FIGS. 10 and 11, a further modified form of chair, according to the invention, is shown at 10.sup.4′. In this embodiment, multiple leaf springs 19a.sup.4′, 19b.sup.4′, 19c.sup.4′, 19d.sup.4′ are utilized, each with an end anchored in a block 105.

(73) In this embodiment, the post 30.sup.4′ has a toothed rack 100.sup.4′ that cooperates with a toothed, differential pinion element 88.sup.4′, that cooperates in turn with a toothed rack 98.sup.4′ making up part of a toothed element 86.sup.4′ on a member 36.sup.4′.

(74) Downward movement of the post 30.sup.4′ under the weight applied to the seat 14 causes the toothed rack 100.sup.4′ and toothed element 88.sup.4′, and separately the toothed elements 88.sup.4′, 86.sup.4′, to interact to translate the member 36.sup.4′ in the direction of the arrow 106.

(75) As the weight on the seat 14 is increased, the member 36.sup.4′ will move continuously in the direction of the arrow 106 to successively engage free ends of angled extensions 108a, 108b, 108c at the ends of leaf springs 19a.sup.4′, 19b.sup.4′, 19c.sup.4′, successively. The extensions 108a, 108b, 108c and one surface 110 on the leaf spring 19d.sup.4′ reside in a reference plane P. As user applied weight increases, a surface 112 on the member 36.sup.4′ moves along this plane P to successively engage the extensions 108a, 108b, 108c and eventually the surface 110, whereby the surface 112 defines separate fulcrum locations, corresponding to the fulcrum location 66, for the free ends of the leaf springs 19a.sup.4′, 19b.sup.4′, 19c.sup.4′, 19d.sup.4′. In other words, the leaf springs 19a.sup.4′, 19b.sup.4′, 19c.sup.4′, 19d.sup.4′ are successively operatively engaged under increasing user weight. As a result, the resistance force to the applied leaning force on the back rest 18 in the direction of the arrow 114 is generated by some or all of the leaf springs 19a.sup.4′, 19b.sup.4′, 19c.sup.4′, 19d.sup.4′ as they are borne against the surface 112 under the user leaning force.

(76) It is important to point out that the rack and pinion components are not restricted to any specific orientation. The cooperating rack and pinion components may be oriented in virtually any orientation that can be adapted to cause movement of the associated parts in the same manner.

(77) Further, one or all of the leaf springs 19a.sup.4′, 19b.sup.4′, 19c.sup.4′, 19d.sup.4′ could be pre-loaded or in curved tracks.

(78) In an alternative form of the basic structure in FIGS. 10 and 11, as shown for the chair 10.sup.5′ in FIGS. 12 and 13, the member 365′ vertically advanced, or advanced in another direction, is caused to interact with some, or all, of a plurality, and in this case three, leaf springs 19a.sup.5′, 19b.sup.5′, 19c.sup.5′, which are arranged to be substantially coplanar, as opposed to stacked as the leaf springs 19a.sup.4′, 191D.sup.4′, 19c.sup.4′, 19d.sup.4′ are on the chair 10.sup.4′.

(79) Under an increasing user weight on the seat 14, a surface 1125′ on the member 365′ engages successively against surfaces 116a.sup.5′, 116b.sup.5′, 116c.sup.5′. As shown in FIG. 12, the particular exemplary weight causes engagement of the surface 1125′ with only two of the leaf springs 19a.sup.5′, 19b.sup.5′.

(80) The leaning force on the back rest 18 is applied on an actuator 118 in a direction into the page, as indicated by the “X” at 120. Resistance to the leaning force is generated in the same manner for the chair 10.sup.5′ as for the chair 10.sup.4′ but with the different arrangement of leaf springs.

(81) In an alternative form, each of the leaf springs in FIGS. 12 and 13 might be substituted for by coil springs, compression/tension springs, or a torsion rod of the type described in an additional embodiment below. One or more springs might be utilized. More springs allow for finer control. Each spring can be individually tuned.

(82) In FIG. 14, a further modified form of chair, according to the invention, is shown at 10.sup.6′. A post 30.sup.6′ has a toothed rack 100.sup.6′ that cooperates with a differential pinion/toothed element 886′. The toothed element 88.sup.6′ moves together with a component 58.sup.6′ that is part of the back rest 16 or otherwise moves in response to movement thereof. The component 58.sup.6′ is mounted for pivoting movement relative to a frame part 122 around an axis 124 as the post 30.sup.6′ raises and lowers as different weight forces are applied to and removed from the seat 14.

(83) The leaning force on the back rest 16 is applied to an arm 126 on the component 58.sup.6′ in the direction of the arrow 128.

(84) The frame part 122 has a “U” shape with spaced legs 130, 132. The component 586′ is mounted on the leg 130.

(85) The toothed element 88.sup.6′ cooperates with a separate toothed element 134 that moves guidingly in a channel 136 on the component 58.sup.6′. In this embodiment, the toothed element 134 and cooperating channel 136 have a curved shape so that the toothed element 134 is movable guidingly in an arcuate path. A row of teeth 138 on one side of the toothed element 134 engage teeth 140 on the toothed element 88.sup.6′ so that the toothed element 134 moves back and forth within the channel 136 as the toothed element 88.sup.6′ is rotated in opposite directions around its axis 124.

(86) The adjusting assembly 18.sup.6′ in this embodiment consists of an elongate spring assembly 19.sup.6′, in this particular embodiment shown as a coil spring under tension. The spring 19.sup.6′ is connected between an end location at 144 on the toothed element 134 and the leg 132 on the frame part 122.

(87) As a user sits on the seat 14, without leaning against the back rest 16, the post 30.sup.6′ moves against the force of the spring 33.sup.6′ downwardly, thereby turning the toothed element 88.sup.6′ in the direction of the arrow 146, which causes the toothed element 134 to move in the direction of the arrow 148 in the channel 136. The precise position of the toothed element 134 in the channel 136 is dictated by the weight of the user.

(88) Once the user is seated and leans back against the back rest 16, separate teeth 150, 152, on the toothed element 134 and component 58.sup.6′, within the channel 136, engage, thereby to fix the position of the toothed element 134 within the channel 136.

(89) Under an applied leaning force in the direction of the arrow 128 on the arm 126, the component 58.sup.6′, and the associated back rest 16, tend to pivot around the axis 124, which is resisted by the force in the spring 142. Because the distance between the axis 124 and end location 144 where the resistant spring force is applied is increased with increasing weight of a user, the resistant force generated by the coil spring 19.sup.6′ is likewise increased.

(90) The chair 10.sup.7′ in FIG. 15 operates on the same basic principles as the chair 10.sup.6′ in FIG. 14.

(91) More particularly, a toothed element 1347′ moves in a channel 1367′ having an arcuate shape. A coil spring 197′ connects between the toothed element 1347′ and a leg 132.sup.7′ on a U-shaped frame part 1227′.

(92) The primary difference between the structure in FIG. 15, compared to that in FIG. 14, is that the toothed element 1347′ is part of, and moves with, an elongate component 154 that is pivoted about an axis 156 that is the approximate location at which the spring 197′ connects to the leg 132.sup.7′. The component 154 has a curved edge 158 with a constant radius R centered on the axis 156. That edge 158 has teeth 160 which mesh with teeth 162 on a post 307′ that has a toothed rack 100.sup.6′ where the teeth 162 are located.

(93) Increased weight of a user on the seat 14 pivots the component 154 in the direction of the arrow 164 around the axis 156 to move the toothed element 1347′ in the direction of the arrow 166 in the channel 1367′. In so doing, the distance between the spring mount location at 1447′ on the toothed element 1347′ and the pivot axis 1247′ for the component 587′ increases, thereby to cause an increase in the resistance to tilting of the back rest 16 in the same manner as occurs with the chair 10.sup.6′.

(94) In FIG. 16, a further modified form of chair is shown at 108′ wherein the spring assembly 198′ includes an elongate torsion component 168 with a lengthwise axis 170. The adjusting assembly 188′ further includes an actuating component 172 that has a portion 174 keyed to the periphery of the torsion component 168 to move slidingly axially therealong in the same angular orientation. With the torsion component 168 fixed in relationship to the frame 12.sup.8′, a user's weight on the seat 14 causes movement of the actuating component 172 through cooperation between a toothed rack 176 thereon and intermediate input structure 178 of suitable construction. Increased weight on the seat 14 causes the actuating component 172 to shift closer to a base 180 of the torsion component 168 closer to where it is anchored to the frame 12′″.

(95) A leaning force on the back rest 16 is applied to the torsion component generally in the direction of the arrow 182, tending to turn the torsion component 168 around the axis 170. For the back rest 16 to reposition, the torsion component 168 must be twisted around the axis 170. This twisting action is resisted to a greater degree with the actuating component 172 closer to the base 180 under a heavier user weight.

(96) On the other hand, with the actuating component 172 shifted towards its free end 184, as occurs with a lighter user, the torsion component 168 can be more readily twisted about its length and the axis 170.

(97) In FIG. 17, a still further modified form of chair, according to the invention, is shown at 10.sup.9′ with an adjusting assembly 18.sup.9′ cooperating between a seat 14 and back rest 16. A spring assembly 199′ is mounted to a frame 129′ and consists of separate leaf springs with bodies 469′ each with spaced ends supported by blocks 186, 188 on the frame 129′. With this arrangement, the bodies 469′ and blocks 186, 188 cooperatively extend around an opening 190 with a width W.

(98) An elongate, wedge-shaped actuating component 192 with a uniform width Wi, slightly less than the width W, extends through the opening 190.

(99) A toothed rack 194 is provided on the actuating component 192 and moves therewith. In response to a weight force being applied to the seat 14, and through an appropriate force transfer structure 196, the toothed rack 194 and actuating component 192 are shifted in the direction of the arrow 198.

(100) By reason of the wedge shape, the actuating component 192 has oppositely facing actuating surfaces S1, S2, each with one dimension D1 at one end and a larger dimension D2 at its opposite end, that abut to, or reside adjacent to, facing surfaces S3, S4, respectively, on the bodies 469′. As the actuating component 192 shifts in the direction of the arrow 198, a progressively larger area of the surfaces S1, S2 confronts the leaf spring bodies 469′.

(101) The back rest 16 imparts a force to the actuating component 192 through a suitable force transfer structure at 202 tending to turn the actuating component 192 around an axis 204.

(102) Accordingly, a user leaning force generates a force on the actuating component 192 that bears the surfaces S1, S2 simultaneously against the surfaces S3, S4 of the leaf spring bodies 469′ between the spaced supported ends. The larger the area of the surfaces S1, S2 in contact with the bodies 469′, the more resistant the bodies 469′ are to deformation. This translates into a greater resistance to the repositioning of the back rest 16 for a larger weight application on the seat 14.

(103) Further, as the actuating component 192 turns around the axis 204, the force transfer between the actuating component 192 and bodies 469′ occurs primarily at corners C1, C2, C3, C4 of the actuating component 192, which bear against reinforced and thus more rigid parts of the bodies 469′ adjacent to the blocks 186, 188 as more user weight is applied. Thus, greater resistance to back rest movement results.

(104) In a still further alternative form, as shown in FIG. 18, multiple adjusting assemblies 18 are utilized between a cooperating first component(s)/seat 14 and second component(s)/back rest 16 on a frame 12.

(105) Ideally, the apparatus/chair 10 will adapt to users weighing as much as 350 pounds, or more. While one spring assembly might be designed for a total desired weight range to be accommodated, two or more spring assemblies might be utilized and their function and operation coordinated.

(106) Further, different spring assemblies might be utilized with coordinated operation. For example, one spring assembly may cover a range of 30-175 pounds with a second spring assembly operational for user weights in the range of 175-350 pounds. More springs/spring assemblies might be added to further split up the weight ranges.

(107) The spring assemblies may be designed in relationship to seat movement. For example, one spring assembly may be operational for 0-0.5″ of seat movement with a separate spring assembly operational for seat movement of 0.5″-1″, where 1″ is the seat movement for the maximum weight for which the apparatus is designed.

(108) The examples herein of spring assembly/spring construction should not be viewed as limiting. Different spring types and combinations are contemplated. For example, the springs may be curved, coiled with different turn diameter and rise, hybrid shapes, concentric arrangements, etc. Coil springs, or the like, may produce forces under either compression or tension.

(109) In FIG. 19, another form of the inventive apparatus is shown at 10.sup.10′ consisting of a frame 12.sup.10′ and at least a first component 14.sup.10′ on the frame 12.sup.10′ upon which a force is applied in a first manner in using the apparatus 10.sup.10′ for its intended purpose.

(110) At least a second component 16.sup.10′ is provided on the frame 12.sup.10′ and is movable relative to the at least first component 14.sup.10′ and/or the frame 12.sup.10′. A force can be applied in a second manner upon the at least second component 1610′ to reconfigure the apparatus 1010′ by moving the at least second component 16.sup.10′ relative to the at least first component 14.sup.10′ and/or the frame 12.sup.10′.

(111) An adjusting assembly 18.sup.10′ is provided to cooperate between the frame 12.sup.10′, first component(s) 14.sup.10′, and second component(s) 16.sup.10′, potentially in different manners.

(112) The adjusting assembly 18.sup.10′ in turn consists of a first subassembly 310 and a second subassembly 312. The first and second subassemblies 310, 312 are usable independently or cooperatively to thereby change a resistance to movement of the second component(s) 16.sup.10′ relative to the first component(s) 14.sup.10′ and/or frame 12.sup.10′. The first and second subassemblies 310, 312 may cooperate between any of the frame 12.sup.10′, first component(s) 14.sup.10′, and second component(s) 16.sup.10′ in any combination and in different manners.

(113) In one form, as shown in FIG. 20, the first subassembly 310 cooperates between the second component(s) 16.sup.10′ and first component(s) 14.sup.10′/frame 12.sup.10′ through at least one component 314 independently of the second subassembly 312.

(114) Similarly, as shown in FIG. 21, the second subassembly 312 may cooperate between the second component(s) 16.sup.10′ and the first component(s) 14.sup.10′/frame 12.sup.10′ through one or more components 316 independently of the first subassembly 310.

(115) Alternatively, as shown in FIG. 22, the first subassembly 310 and second subassembly 312 cooperate between the second component(s) 16.sup.10′ and the first component(s) 14.sup.10′/frame 12.sup.10′ through one or more components 318, 320, respectively on the first subassembly 310 and second subassembly 312, and further share at least one component 322.

(116) While the apparatus 10.sup.10′ is not so limited, it will be described hereinbelow using an exemplary seating apparatus/chair construction, as shown schematically in FIG. 23, wherein the first component(s) is in the form of a seat 14.sup.10′ on the frame 12.sup.10′ with the second component(s) consisting of a back rest component 16.sup.10′ that is mounted to the seat 14.sup.10′ and/or frame 12.sup.10′ to be movable relative thereto.

(117) It should be understood that the backrest 16.sup.10′ may be made of a single component or multiple independently movable or cooperating parts that might be adjusted together or independently through the adjusting assembly 18.sup.10′. For purposes of simplicity, a representative single back rest component 16.sup.10′ will be described hereinbelow.

(118) The reconfigurable apparatus/chair 10.sup.10′, without limitation, may have the same basic construction as any of the apparatus/chairs 10-10.sup.9′, as described above.

(119) The first subassembly 310 corresponds generally to the adjusting assembly 18-18.sup.9′, as shown in each of FIGS. 1-17. The first subassembly 310 operates principally, or exclusively, in response to movement of the seat 14.sup.10′ between: a) a first position in which the seat 14.sup.10′ resides with no user sitting on the seat 14.sup.10′; and b) a loaded position into which the seat 14.sup.10′ moves from the first position as the incident of the user sitting on the seat 14.sup.10′, to thereby change a resistance to changing of the angular orientation of the back rest component 16.sup.10′ from a starting angular position a predetermined amount, related to user weight.

(120) The second subassembly 312 is configured to be manually operable by a user to change its state.

(121) With the second subassembly 312 in a first state and no user sitting in the seat 14.sup.10′, a first leaning force is required to be applied to the back rest component 16.sup.10′ to change the angular orientation of the back rest component 16.sup.10′ from a starting angular position relative to the at least one of the seat 14.sup.10′ and frame 12.sup.10′.

(122) With the second subassembly 312 in the first state, a user sitting on the seat 14.sup.10′ applies a first force to the seat 14.sup.10′ whereupon the resistance to changing of the angular orientation of the back rest component 16.sup.10′ from the starting orientation increases a predetermined amount, related to a user's weight.

(123) By manually changing the second subassembly 312 from a first state into a second state, upon a user sitting and applying the first force to the seat, the second subassembly 312 causes the resistance to changing of the angular orientation of the back rest component 16.sup.10′ such that with a user sitting in the seat 14.sup.10′ and applying the first force, the second subassembly 312 in the second state causes the resistance to changing of the angular orientation of the back rest component 16.sup.10′ from the starting position to be one of greater than or less than the predetermined amount added to the final leaning force.

(124) As shown in FIG. 24, the components 316 on the second subassembly 312 that act between the back rest component(s) 16.sup.10′ and seat 14.sup.10′/frame 12.sup.10′ may pre-apply a force that resists changing of the angular orientation of the back rest component 16.sup.10′ or may increase resistance in response to a leaning force being applied to the back rest component(s) 16.sup.10′. By changing the second subassembly 312 from its first state into its second state the pre-applied force may changed or the responsive resistance force may be changed.

(125) In one preferred form, the first force generated by the user assuming the sitting position effects a gross change in the resistance to changing of the angular orientation of the back rest component 16.sup.10′ whereas the manual input may be provided for a smaller range of resistance adjustment, which may be considered more as “fine tuning”.

(126) As shown in FIG. 25, the second subassembly 312 has an actuator 324 that is manually operable to change the state of the second subassembly 312. Within the generic showing of the actuator 324 in FIG. 25 are different forms including, without limitation, a knob 324a that is manually turned around an axis, a lever 324b that is manually pivoted around an axis, and a component 324c that is manually translated to change the state of the second subassembly. The actuators 324a, 324b, 324c each requires a manual force input by the user.

(127) Alternatively, as shown in FIG. 26, the second subassembly 312 may have an associated powered drive 326 responsive to manually operation of an input 328. The drive 326 may be a motor, or the like.

(128) The second subassembly 312 is configured to be changed from its first state into a second state either before or after a user assumes a sitting position and is applying the first force to the seat 14.sup.10′.

(129) The change in resistance to changing of the angular orientation of the back rest component(s) 16.sup.10′ can be generated, without limitation, by incorporating the manually operable second subassembly 312 into any of the structures described above. In virtually all of the previously described constructions, the second subassembly 312, in the FIG. 22 form, can be incorporated to coordinate its operation with the first subassembly 310. Generally, the first subassembly 310, corresponding to the adjusting assembly 18-18.sup.9′ in FIGS. 1-17, moves one or more components in controlled/predetermined paths as an incident of the user applying the first force by sitting on the seat 14.sup.10′. The second subassembly 312 may reverse or extend the amount of movement of one or more of such components. This construction should not be viewed as limiting.

(130) Examples of coordinated operation of the second subassembly 312 with adjusting assemblies in exemplary embodiments from FIGS. 1-17 will now be described, with it being understood that with the present teachings in hand, one skilled in the art could utilize the inventive concepts described herein to incorporate a second subassembly 312 into many other different forms of apparatus to coordinate movement with a corresponding adjusting assembly/first subassembly.

(131) In FIGS. 27-29, the first subassembly 310.sup.11′ operates in certain respects similarly to the corresponding structure in FIG. 10. The first force generated by the user's weight is applied in the direction of the arrow 330, thereby causing a post 30″ with a toothed rack 100.sup.11″ to be moved downwardly against a force generated by a spring 33.sup.11″ acting as against a part of the frame 12.sup.11″. The toothed rack 100.sup.11″ cooperates with a differential pinion element 88.sup.11″ which in turn cooperates with a toothed rack 98.sup.11″. The differential pinion element 88.sup.11″ produces a differential movement of associated components as a result of the difference between the radial dimensions D1 and D2, whereby movement of the member 36.sup.11″ in the direction of the arrow 334 is greater than the movement of the post 30.sup.11″ transversely in the direction of the arrow 330, that initiates movement of the overall mechanism.

(132) The member 36.sup.11″ has an upward projection defining a fulcrum at 338.sup.11″. A leaf spring 340.sup.11″ has one end 342.sup.11″ anchored in the frame 12.sup.11″ and cantilevers away therefrom to a free end adjacent to which a component 344.sup.11″ bears such that a force in the direction of the arrow 346 exerted upon the back rest component 16.sup.11″, and applied to the leaf spring 340.sup.11″ by the component 344.sup.11: is resisted by the stiffness of the leaf spring. In other words, the angular repositioning of the back rest component 16.sup.11″ occurs by bending the leaf spring 340.sup.11″ against the fulcrum 338.sup.11′.

(133) As noted above, through the first subassembly 310.sup.11″, the weight of the user will cause location of the fulcrum 338 to be at a predetermined position along the cantilevered length of the leaf spring 340″.

(134) In this embodiment, the aforementioned components correspond to the components 322 shown in FIG. 22.

(135) The second subassembly 312.sup.11′, as shown in FIG. 28, consists of the component 316′″ that is wrapped against the pinion element 88.sup.11″ such that by being manually moved through an actuator 324, the component 316.sup.11″ can be moved in opposite directions, as indicated by the double-headed arrow 350, which causes the pinion element 88.sup.11″ to be moved in opposite directions around its axis 352.sup.11″. This shifts the fulcrum 338 incrementally in distances in opposite directions, indicated by the double-headed arrow 354.

(136) The exemplary component 316.sup.11″ may be an inner core component such as part of a Bowden cable having its end wrapped around a cylindrical portion 356.sup.11″ of the pinion element 88.sup.11′ and anchored thereto at 358.sup.11′.

(137) FIGS. 30 and 31 show a structure corresponding to that in FIGS. 27-29 with the primary exception being that spaced leaf springs 340a.sup.12′, 340b.sup.12′ are cantilever mounted to the frame 12.sup.12′ in spaced relationship, each cooperating with a fulcrum 338a.sup.12′, 338b.sup.12′.

(138) Further, members 36a.sup.12′, 36b.sup.12′ defining the fulcrums 338a.sup.12′, 338b.sup.12′ are curved at bottom sides 360a.sup.12′, 360b.sup.12′ to be guided in a slightly curved path against a complementarily-shaped guide surface 362.sup.12′ on the frame 12.sup.12′.

(139) The curvature of the surface 362.sup.12′ nominally matches the bent shape of the loaded leaf springs 340a.sup.12′, 340b.sup.12′ so as to produce a passageway 364.sup.12′ therebetween with a substantially constant width W within which the free ends 366a.sup.12′, 366b.sup.12′ of the members 36a.sup.12′, 36b.sup.12′ defining the fulcrums 338a.sup.12′, 338b.sup.12′ are guided.

(140) The second subassembly 312.sup.12′, as shown separated in FIG. 30, corresponds substantially to the second subassembly 312.sup.11″ in cooperating with the pinion element 88.sup.12′.

(141) In FIG. 32 a first subassembly 310.sup.13, is shown with some components similar to those in FIG. 15. A component 154.sup.13′ pivots about an axis 156.sup.13′. Under the user's weight on the seat 14.sup.13′, a toothed rack 100.sup.13′ is moved in the direction of the arrow 368, which pivots the component 154.sup.13′ in the direction of the arrow 370 around the axis 156.sup.13′. This causes a pinion gear 372.sup.13′ to move within a curved passageway 374.sup.13′ defined between a leaf spring 376.sup.13′, loaded into the bent solid line shape, and the complementarily-shaped toothed edge 378.sup.13′ in mesh with the pinion gear 372.sup.13′.

(142) A lever component 58.sup.13′ is pivotably mounted to the base 380.sup.13′, on which the component 154.sup.13′ is mounted, for pivoting movement around an axis 382.sup.13′.

(143) One cantilevered arm 384.sup.13′ on the component 58.sup.12′ defines a bearing edge 386.sup.13′ that acts against a surface 388.sup.13′ on the leaf spring 376.sup.13′ facing oppositely to a surface on the leaf spring 376.sup.13′ bounding the passageway 374.sup.13′.

(144) A force on the back rest component 16.sup.13′, tending to change the angular orientation of the back rest component 16.sup.13′, is imparted to a cantilevered arm 390.sup.13′ on the component 58.sup.13′ which causes a bending force to be imparted by the edge 386.sup.13′ on the leaf spring 376.sup.13′.

(145) An end 392.sup.13′ on the component 154.sup.13′ defines a fulcrum for the leaf spring 376.sup.13′, the end of which is anchored in the base 380.sup.13′. As the weight of the user increases, the fulcrum 392.sup.13′ advances in the direction of the arrow 394, which shortens the moment arm between fulcrum 392.sup.13′ and the edge 386.sup.13′, thereby creating greater resistance to angular reorientation of the back rest component 16.sup.13′.

(146) The structure in FIGS. 33 and 34 is modified from that in FIG. 32 principally by reason of providing an extended component 396.sup.14′ that shifts the fulcrum location at 398.sup.14′ away from the axis 400.sup.14′ of the pinion gear 372.sup.14′. The first subassembly 310.sup.14′ operates substantially as the first subassembly 310.sup.13′ in FIG. 32.

(147) In FIG. 33, one form of the second subassembly 312a.sup.14′ is shown consisting of a component 316a.sup.14′ that engages the component 154.sup.14′ around a portion of its perimeter at 402.sup.14′ and is connected thereto at 404.sup.14′. By extending and retracting the component 316a.sup.14′, as indicated by the double-headed arrow 406, the component 154.sup.14′ can be pushed/pulled in opposite directions around the axis 156.sup.14′ to thereby change the resistance to movement of the back rest component 16.sup.14′. Whereas the first subassembly 310.sup.14′ moves the component 154.sup.14′ in a predetermined path a first distance, the second subassembly either extends or reverses this movement.

(148) As shown in FIG. 34, the user's weight is applied to the toothed rack 100.sup.14′ which transmits a force to a toothed region 408.sup.14′ on the component perimeter 402.sup.14′ through meshed intermediate gears 410.sup.14′, 412.sup.14′, with the latter in mesh with the toothed region 408.sup.14′. In this embodiment, the second subassembly 312b.sup.14′ has an associated component 316.sup.14′ that wraps against a curved surface on the gear 410.sup.14′ and is extendable and retractable, as indicated by the double-headed arrow 412.sup.14′ to pivot the component 154.sup.14′ in opposite directions around the axis 156.sup.14′.

(149) As noted previously, the above are only representative examples of how the second subassembly might be incorporated, with it being understood that it could be incorporated into the other embodiments herein and virtually any other similarly operating structure using the same principles that is, any construction that has components moving in predetermined/controlled paths by the first subassembly 310 to change resistance forces may be moved further in the paths or moved in reverse directions depending upon how the second subassembly is operated.

(150) In those forms that utilize a fulcrum and a component bendable thereagainst, a relationship between the fulcrum and anchoring point can be changed in the same or different manners by the first and second subassemblies.

(151) In an alternative form, as shown in FIGS. 35 and 36, a first subassembly 310.sup.15′ is shown corresponding to the structure in FIG. 6. A user's weight is directed through the component 70a.sup.15′ in the direction of the arrow 414, which pivots the link 72a.sup.15′ around the axis 84.sup.15′ to in turn advance the link 36a.sup.15′ in the direction of the arrow 418. The link 72.sup.15′ acts as a lever with a built-in differential due to the different pivot axis spacing P1, P2.

(152) The second subassembly 312.sup.15′ has a movable component 316.sup.15′ that is extendable and retractable in the direction of the double-headed arrow 420 to thereby pivot the link 72a.sup.15′ in opposite directions about the axis 84.sup.15′.

(153) In an alternative form, as shown in FIG. 37, the second subassembly 312.sup.16′ has a cylindrical component 422.sup.16′ which is fixed to a link member/lever 424.sup.16′, corresponding to the link member 72a.sup.15′ to move as one piece therewith. A component 316.sup.16′ is wrapped against and fixed to the member 422.sup.16′ whereby extension and retraction in the direction of the double-headed arrow 426 causes the link member 428.sup.16′, corresponding to the link member 36a.sup.15′ to move selectively in opposite directions, which causes the downstream interacting components to increase or decrease resistance to angular reorientation of an associated back rest component.

(154) FIG. 38 discloses an adjusting assembly wherein an elongate toothed member 430.sup.17′ defines a fulcrum 432.sup.17′ against which a cantilevered component/leaf spring 434.sup.17′ is bent under the force of a component 436.sup.17′ urged in the direction of the arrow 438 under a user's sitting weight. The distance Y between the weight force application location and fulcrum 432.sup.17′ is changed by translating the elongate toothed member 430.sup.17′ selectively oppositely, as indicated by the double-headed arrow 440.

(155) As cylindrical member 422.sup.17′ with a fixed link 424.sup.17′, corresponding to like numbered components in FIG. 37, is turned around an axis 442 to thereby advance a gear 444.sup.17′ in mesh with teeth 446. Depending upon the rotational direction, the fulcrum 432.sup.17′ is either advanced towards or away from the location at which the force is applied to the leaf spring 434.sup.17′ through the component 436.sup.17′.

(156) While the first subassembly (not shown in detail) is responsible for a gross movement of the toothed member 430.sup.17′, manual turning of the cylindrical member 422.sup.17′ which is part of the second subassembly 312.sup.17′, through the movement of the member 316.sup.16′ effects finer adjustment.

(157) FIG. 39 shows a structure similar to that in FIG. 38, and which may be part of either first or second subassemblies, with the exception that the corresponding cylindrical member 422.sup.18′ has a perimeter with teeth 448.sup.18′ thereon in mesh with an elongate toothed member 450.sup.18′. Translation of the member 450.sup.18′ in opposite directions, as indicated by the double-headed arrow 452, changes the dimension Y as shown in FIG. 38.

(158) It should be noted that there is no limitation with respect to the degree of change in resistance that the individual first and second subassemblies 310, 312 are responsible for. While preferably the first subassembly 310 accomplishes a gross adjustment, it is possible that the manual adjustment through the second subassembly 312 may be even greater than that achieved through the first subassembly 310. The subassemblies 310, 312 can be complementary in virtually any manner that facilitates convenient setting of an equilibrium state for the apparatus 10.

(159) In FIG. 40, a second subassembly 312.sup.19′ is shown with an actuator 324c in the form of a grippable member 454.sup.19′ that can be grasped and moved guidingly within a slot 456.sup.19′ selectively in opposite directions, as indicated by the double-headed arrow 458, to thereby change the state of the second subassembly 312.sup.19′.

(160) In a further alternative form, as shown in FIG. 41, the actuator 324d is in the form of a graspable knob that is movable around an axis 460 to thereby change the state of the associated second subassembly 312.sup.20′.

(161) Mechanical advantage and strategically controlled differential movement of parts can be incorporated into each actuator so that excessive movement and force application is not required on the user's part.

(162) In another form, as shown in FIG. 42, a seat 14.sup.21′ has a peripheral edge 462 at which an actuator 324e is provided to be accessible at the peripheral edge 462, whereby a user is not required to awkwardly access the actuator as is typical of conventional constructions.

(163) It should also be noted throughout that the back rest component may also be one that engages the neck as well as any discrete location on the user's back region and above.

(164) The foregoing disclosure of specific embodiments is intended to be illustrative of the broad concepts comprehended by the invention.