Patent Publication Number: US-9844268-B2

Title: Sitting apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to sitting apparatus and, more particularly, to a sitting apparatus having at least one armrest assembly upon which a user in a sitting position can support his/her arm. 
     Background Art 
     There are currently many different types of sitting apparatus that incorporate an armrest assembly to allow a user in a sitting position thereon to support his/her arm(s). The sitting apparatus with the arm supports may be in the form of a task chair, a lounger, etc. The sitting apparatus may be floor mounted, wall mounted, or even ceiling mounted. For simplicity, the basic function and deficiencies of existing armrest assemblies will be described with respect to a conventional task chair, with it being understood that the design criteria and objectives are the same for basically all types of sitting apparatus that incorporate one or more armrest assemblies. 
     The conventional task chair has a frame with a wheeled pedestal upon which a seat assembly is supported. The chair may be provided with or without a backrest assembly. Laterally spaced armrest assemblies are provided at the sides of the seat assembly. Each armrest assembly has a surface to support the elbow and forearm regions of a user in a sitting position on the seat assembly. Typically, the surface on each armrest assembly is nominally flat with a reference plane thereon generally parallel to a subjacent support surface. The armrest assemblies are constructed so that the respective surfaces thereon can be raised and lowered to accommodate a particular user size and/or to assist the performance of different tasks. Normally, the surfaces are also movable selectively towards and away from each other and each may be repositionable around a vertically extending axis. 
     More and more, users utilize laptop computers, tablets, PDAs, etc, while sitting in this type of chair. Generally, the user will hold the particular device with both hands while supporting the elbow and/or forearm regions on the spaced surfaces on the armrest assemblies. 
     The horizontal orientation of the armrest assembly surfaces does not result in the particular device being optimally positioned with the user&#39;s forearms and/or elbows supported thereon. Consequently, the user will generally exercise one of three options with this conventional chair construction. 
     The first option is to simply observe the screen/monitor of the device from a somewhat awkward angle. This can eventually lead to eye strain and generally detracts from an otherwise potentially enjoyable activity. 
     The second option is for the user to lift his/her arms off of the armrest assemblies to place the particular device in a better location in terms of allowing easier observation of the screen/monitor and facilitating operation of the device as through a touch screen or keyboard. When the latter option is exercised, the armrest assemblies essentially become functionless other than to provide a resting place for a user periodically after his/her arms become fatigued. 
     The third option is to rest only the elbows on the armrest assembly surfaces. This requires hinging of each hand at the wrist and each forearm at the elbow to optimize a viewing angle. This can become fatiguing in a short period of time since the wrists and forearms remain unsupported and may be placed at awkward angles. 
     If the user wishes to have the benefit of an inclined backrest, the above problems may be aggravated since the user becomes further distanced from the held device and is placed at an even more inconvenient angle with respect thereto from the standpoint of both viewing and operation thereof. 
     In spite of the ever increasing use of laptop computers, tablets, smart phones, and other screen based technology, the industry has offered users thereof no reasonable alternative to basic task chair designs to facilitate use of that technology in a sitting position. 
     SUMMARY OF THE INVENTION 
     In one form, the invention is directed to a sitting apparatus including: a frame configured to be situated at a sitting location; a seat assembly on the frame defining a support for a user in a sitting position; and at least one armrest assembly having at least one surface to support an arm of a user in a sitting position on the seat assembly. The at least one armrest assembly is configured to be changed between first and second states. The at least one surface changes in angular relationship to a horizontal reference plane as an incident of the at least one armrest assembly changing between the first and second states. 
     In one form, the sitting apparatus has a front and rear and laterally spaced sides. A lateral inclination of the at least one surface changes as the at least one armrest assembly is changed between the first and second states. 
     In one form, the sitting apparatus has a front and rear and laterally spaced sides. A front-to-rear inclination of the at least one surface changes as the at least one armrest assembly changes between the first and second states. 
     In one form, the armrest assembly is configured so that the at least one surface follows movement of a part of the at least one armrest assembly that pivots around a laterally extending axis as the at least one armrest assembly is changed between the first and second states. 
     In one form, the laterally extending axis is located at least approximately where one of: a) a shoulder joint; and b) an elbow joint of a user in the sitting position is located. 
     In one form, the laterally extending axis extends through, or is adjacent to, the part of the at least one armrest assembly. 
     In one form, the at least one surface follows movement of a part of the at least one armrest assembly as the at least one armrest assembly is changed between the first and second states. The part of the at least one armrest assembly is connected to the frame through a mechanical linkage. 
     In one form, the part of the at least one armrest assembly defines a link member in the mechanical linkage. 
     In one form, the mechanical linkage has a projected pivot located at least approximately where one of: a) a shoulder joint; and b) an elbow joint of a user in the sitting position is located. 
     In one form, the sitting apparatus further includes a locking assembly that is operable to selectively maintain the at least one armrest assembly in at least one of the first and second states. 
     In one form, the locking assembly has an actuator that is configured to be moved by a user. The actuator consists of at least one of: a) a component that is movable independently of the at least one surface on the at least one armrest assembly; and b) a part of the at least one armrest assembly that moves with the at least one surface as the at least one armrest assembly is changed between the first and second states. 
     In one form, the at least one armrest assembly has first and second laterally spaced armrest assemblies. 
     In one form, the first and second armrest assemblies are configured so that the at least one surface on the first and second armrest assemblies can be relatively moved to change a lateral spacing between the at least one surface on the first and second armrest assemblies. 
     In one form, the first and second armrest assemblies are configured so that the at least one surface on each of the first and second armrest assemblies can be selectively raised and lowered relative to the frame. 
     In one form, the first and second armrest assemblies are configured so that the at least one surface on each of the first and second armrest assemblies can be selectively moved around a respective vertically extending axis. 
     In one form, the sitting apparatus further includes a backrest that is configured to be moved relative to the frame so as to thereby change an angular orientation of the backrest relative to the frame. 
     In one form, the sitting apparatus further includes a wheeled support for the frame. 
     In one form, the at least one armrest assembly has first and second riser components that are configured to be placed in different vertical relationship to thereby change the at least one armrest assembly between the first and second states. 
     In one form, at least one of the first and second riser components is mounted to a part of the at least one armrest assembly that moves with the at least one surface for pivoting movement around an axis. 
     In one form, each of the first and second riser components is mounted to a part of the at least one armrest assembly that moves with the at least one surface for pivoting movement around a respective axis. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of one form of sitting apparatus, according to the present invention, and including at least one armrest assembly with at least one arm supporting surface thereon for a user in a sitting position; 
         FIG. 2  is a schematic representation showing additional details for the inventive sitting apparatus in  FIG. 1 ; 
         FIG. 3  is a partially schematic, side elevation view of a user in a sitting position on the inventive sitting apparatus and with the user&#39;s forearm supported on the surface of the armrest assembly with the armrest assembly in a first state; 
         FIG. 4  is a view corresponding to that in  FIG. 3  with the armrest assembly changed to a second state; 
         FIG. 5  is a schematic representation of a 3-axis reference system for describing the inventive structure; 
         FIG. 6  is a side elevation view of one exemplary form of sitting apparatus with one exemplary form of armrest assembly incorporated therein; 
         FIG. 7  is an enlarged, side elevation view of the armrest assembly in  FIG. 6  in its first state; 
         FIG. 8  is a view as in  FIG. 7  with the armrest assembly in its second state; 
         FIG. 9  is a view as in  FIG. 8  with the surface on the armrest assembly lowered; 
         FIG. 10  is a schematic representation of a drive for changing the state of the inventive armrest assembly; 
         FIG. 11  is a schematic representation of an armrest assembly as in  FIG. 10  with a locking assembly thereon and an associated actuator therefor; 
         FIGS. 12 and 13  are side elevation views of a modified form of armrest assembly in first and second states, respectively; 
         FIGS. 14 and 15  are side elevation views of another modified form of armrest assembly in first and second states, respectively; 
         FIGS. 16 and 17  are side elevations views of a further modified form of armrest assembly in first and second states, respectively; 
         FIG. 18  is side elevation view of an armrest assembly and schematically showing a mechanism for effecting repositioning of the arm supporting surface thereon; 
         FIGS. 19 and 20  are side elevation views of a modified form of armrest assembly in first and second states, respectively; 
         FIGS. 21 and 22  are side elevation views of a further modified form of armrest assembly in first and second states, respectively; 
         FIGS. 23 and 24  are side elevation views of a still further modified form of armrest assembly in first and second states, respectively; 
         FIG. 25  is a schematic representation of a mechanical linkage connecting between an armrest assembly part, defining an arm resting surface, and a frame; 
         FIGS. 26 and 27  are schematic representations of a further modified form of armrest assembly incorporating one form of mechanical linkage, as in  FIG. 25 , and in first and second states, respectively; 
         FIGS. 28 and 29  show a modified form of linkage similar to that in  FIGS. 26 and 27  and in corresponding first and second states, respectively; 
         FIG. 30  is a further modified form of armrest assembly with a linkage as in  FIGS. 26-29  in a first state and with a projected pivot coinciding with a sitting user&#39;s elbow; 
         FIG. 31  is a view as in  FIG. 30  wherein the armrest assembly has a projected pivot coinciding with a sitting user&#39;s shoulder; 
         FIG. 32  is a side elevation view of a further modified form of armrest assembly incorporating a mechanical linkage; 
         FIG. 33  is a side elevation view of a further modified form of armrest assembly including a modified form of mechanical linkage; 
         FIG. 34  is a side elevation view of a further modified form of armrest assembly with a spring assist; 
         FIGS. 35 and 36  are schematic representations of a further modified form of armrest assembly in first and second states, respectively; 
         FIGS. 37 and 38  are schematic representations of a further modified form of armrest assembly, similar to that in  FIGS. 35 and 36 , in first and second states, respectively; 
         FIG. 39  is a side elevation view of an armrest assembly with a generic form of locking assembly to fix a desired position of the armrest support surface; 
         FIG. 40  is a side elevation view of another form of armrest assembly with a specific form of locking assembly incorporated; 
         FIGS. 41-43  are underside schematic representations of riser components in  FIG. 40  in different positions relative to a part on which the armrest surface is defined to place the arm support surface in different positions; 
         FIG. 44  is a partially schematic, perspective view of a modified form of armrest assembly with a locking assembly thereon; and 
         FIG. 45  is an enlarged, perspective view of a mounting system, for the part of the armrest assembly in  FIG. 44  defining the arm support surface, that allows repositioning of the part of the armrest assembly to operate a locking assembly thereon. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In  FIG. 1 , a sitting apparatus, according to the present invention, is shown in schematic form at  10 . The sitting apparatus  10  consists of a frame  12  configured to be situated relative to a support  14  at a sitting location. The support  14  may be any type of support commonly used for sitting apparatus—including a subjacent surface upon which the frame  12  can be placed, a vertically extending structure upon which the frame  12  is mounted, an overhead structure from which the frame  12  is suspended, etc. 
     A seat assembly  16  is situated on the frame  12  and defines a support  18  for a user in a sitting position. 
     At least one armrest assembly  20  has at least one surface  22  to support an arm of a user in a sitting position on the seat assembly  16 . While typically two such armrest assemblies  20  are incorporated, it is possible that a single armrest assembly  20  might be provided on one side of the seat assembly  16  or in a more laterally centered position. 
     The at least one armrest assembly  20  is configured to be changed between first and second states. The at least one surface  22  is changed in angular relationship to a horizontal reference plane as an incident of the at least one armrest assembly changing between the first and second states. 
     The sitting apparatus  10  may further include a backrest  24  that is configured to be moved relative to the frame  12  so as to thereby change an angular orientation of the backrest  24  relative to the frame  12 . 
     The seat assembly  16  may have a fixed orientation or may be adjustable relative to the frame  12 . The backrest  24  may be mounted to the frame  12  independently of the seat assembly  16 . Alternatively, as shown in dotted lines in  FIG. 1 , the backrest  24  and seat assembly  16  may be interconnected so that the seat assembly  16  and backrest  24  move in a coordinated manner. 
     As also shown in dotted lines in  FIG. 1 , the backrest  24  may be interconnected to the at least one armrest assembly  20  so that changing of the angular position of the backrest  24  effects a predetermined movement of the at least one armrest assembly  20  to thereby reorient the surface(s)  22  thereon. 
     The schematic showing of the components in  FIG. 1  is intended to encompass specific components as described in exemplary embodiments hereinbelow, and virtually an unlimited number of variations in those components and their interaction that would be obvious to one skilled in the art with the teachings herein in hand. 
     Generally, as shown also in schematic form in  FIG. 2 , the sitting apparatus  10 , in a form with separate and laterally spaced armrest assemblies  20  on the frame  12 , utilizes an armrest assembly construction and connecting structure  26  between each armrest assembly  20  and frame  12  that allows each of the surfaces  22  to be moved relative to each other and the frame  12  in multiple dimensions. While in its most basic form, only a single change in angular orientation of the surfaces  22  relative to a horizontal reference plane might be allowed, as through a front-to-rear change in inclination, in other preferred forms, the surfaces  22  thereon are at least one of: a) movable towards and away from each other in a lateral direction; b) movable vertically relative to the frame  12 ; c) angularly repositioned around a fore-and-aft axis; and d) movable around a vertically extending axis. The primary movement of the armrest assembly surfaces  22  that is desired is relative to the frame  12  in a manner that front-to-rear inclination of the surfaces  22  changes as the armrest assemblies are changed between the aforementioned first and second states. 
     As seen in  FIGS. 3 and 4 , this primary desired movement of the surfaces  22  on the armrest assemblies  20  involves repositioning at least a part  28  of each armrest assembly  20 , that defines its respective surface(s)  22 . For simplicity, each armrest assembly  20  will be described with a single surface  22 . In the first state for the representative armrest assembly  20 , as shown in  FIG. 3 , the surface  22 , while potentially contoured, approximates a flat support surface that is substantially parallel to a horizontal reference plane HP. As shown in  FIG. 4 , in the second state for the armrest assembly  20 , the surface  22  is at an angle α to the horizontal plane HP with the front of the surface  22  inclined relative to the rear thereof. 
     Different angles α may be selectively settable. It is conceivable that the angle α may be as great as 75° or more. 
     As can be seen in  FIGS. 3 and 4 , the surface  22  will generally support primarily forearm and elbow regions FA, E on a user U with the user U in a sitting position on the seat assembly  16 /support  18 . 
     The schematic showing of the inventive structure is intended to encompass a wide range of different capabilities. For example, in one form, the armrest assembly surfaces  22  are movable only as in  FIGS. 3 and 4 . This movement may be effected either by manually grasping the parts  28  to effect movement thereof or, more preferably, simply by causing movement in response to movement of the user&#39;s forearm region and/or in response to other weight shift and/or force application by the user. The position of the armrest assembly surfaces may be maintained by forces applied by the user or may be mechanically fixed by appropriate structure, as described below. 
     In one preferred form, the various dimensions of movement of the surfaces  22 —lateral and front-to-rear inclination around front-to-rear and laterally extending axes respectively, movement towards and away from each other, vertical movement, etc.—may be effected in one fluid motion by reason of the adjustment of the user&#39;s body to which the sitting apparatus  10  automatically responds. The various dimensions of movement may alternatively be effected through automated mechanisms or manually by separate manipulation of the parts, with the different configurations maintained automatically, or through one or more separate locking assemblies as shown generically at  30  in  FIG. 2 . Each locking assembly  30  may be operable through one or more actuators  32 . The locking assemblies  30  can be used to maintain one or both of the aforementioned first and second states or other states resulting from repositioning of the surfaces  22  relative to the frame  12 . 
     For purposes of the description hereinbelow, a reference system as shown in  FIG. 5  will be utilized. A three axis reference arrangement is shown with the X axis extending laterally in the direction of the double-headed arrow  34 , the Y axis extending in a front-to-rear direction, as indicated by the double-headed arrow  36 , and a Z axis extending in the vertical direction, as indicated by the double-headed arrow  38 . 
     Referring to  FIG. 6 , one more specific exemplary form of sitting apparatus  10  is shown. The support  14  is in the form of a pedestal  40  projecting upwardly from a wheeled carriage  42 . The seat assembly support  18  is located at the top of the support  14 . The support  18  may be at a fixed vertical height or may be vertically adjustable relative to the support  14 . 
     A backrest  24  is connected to the support  18 . 
     The frame  12  includes a fixed base  44  at one side of the frame  12  through which the exemplary armrest assembly  20  is operatively mounted. In this embodiment, like armrest assemblies  20  are provided at each side of the sitting apparatus  10 . 
     Details of one exemplary armrest assembly  20  are shown in  FIGS. 7-9 . In this embodiment, the armrest assembly  20  has first and second riser components  46 ,  48  that are configured to be placed in different vertical relationships to thereby change the armrest assembly  20  between its first state, as shown in  FIG. 7 , and its second state, as shown in  FIG. 8 . As noted above, in the first state, the surface  22 , approximated as a generally flat surface, resides in a plane that is substantially parallel to the horizontal reference plane HP. In the second state, as shown in  FIG. 8 , the surface  22  is angled in relationship to the horizontal reference plane HP. In this case, the surface  22  makes an angle α with respect to the horizontal reference plane HP. 
     The riser components  46 ,  48  are substantially straight and may be abutted to each other, in which relationship they can slide vertically together guidingly within the frame base  44  and relative to each other in the vertical direction—along the Z axis. 
     The upper ends of the riser components  46 ,  48  are respectively joined to a part  50  of the armrest assembly  20 , defining the surface  22 , for pivoting movement about axes  52 ,  54 , respectively. The axes  52 ,  54  extend laterally parallel to the X axis. 
     With the armrest assembly  20  in its first state, the axes  52 ,  54  are at the same height, as seen in  FIG. 7 . By advancing the first riser component  46  upwardly relative to the second riser component  48  and/or the second riser component  48  downwardly relative to the first riser component  46 , the relationship in  FIG. 8  is realized wherein the riser components  46 ,  48  and part  50  cooperate to incline the surface  22  from rear to front. 
     The riser components  46 ,  48  are also movable together guidingly within the base  44  in a vertical direction to change the height of the surface  22  relative to the frame  12  with the armrest assembly  20  in either its first or second states, as shown in  FIG. 9 . 
     The riser components  46 ,  48  also cooperate with the frame base  44  to be guided together in movement around a vertical axis  56 . This allows the fore-and-aft length of the part  50  to be selectively either aligned with the Y axis or angled with respect thereto. 
       FIG. 8  discloses a generic form of a drive or drives  58  that are configured to effect relative movement between the riser components  46 ,  48  and base  44  to allow the armrest assembly  20  to be moved relative to the frame  12  in the various manners described above. The drive(s)  58  could be automated or simply respond to different weight shifting and movements of the user&#39;s limbs. 
     In one exemplary form, as shown additionally in schematic form in  FIG. 10 , the drive  58  consists of one or more toothed members  60  that cooperate with one or more drive gears  62 . One or more toothed members  60  can be associated with the frame  12  and/or components making up the armrest assembly  20 . One or more drive gears  62  effect appropriate movement of the toothed member(s)  60  to change the state of the armrest assembly  20  and cause the other movements of the surface  22 , as described above. 
     The drive gear(s)  62  can be moved through an appropriate actuator  64 . The change of state may be accomplished automatically in response to operation of the actuator  64  and/or may result from a shifting of the user&#39;s limbs and weight. 
     In the embodiment shown in  FIGS. 7-9 , one toothed member is shown on the riser component  48  which cooperates with a drive gear  62  that is on the riser component  46  and turned to effect relative vertical movement between the riser components  46 ,  48 . 
     The generic showing of the drive  58  in  FIG. 8  is intended to encompass virtually an unlimited number of other drive transmission structures/mechanisms, including crank-and-slot arrangements, screw gear arrangements, rack-and-pinion arrangements, etc. 
     As noted above, a particular configuration of the sitting apparatus  10 , including the armrest assemblies  20 , can be maintained by forces applied by a user. The aforementioned locking assemblies  30  can be utilized to maintain any desired state of the armrest assemblies  20 , including the first and second states described above. 
     In one exemplary form, shown schematically in  FIG. 11  with a part  66  of the armrest assembly having teeth  68 , as on the member  60  in  FIG. 10 , the locking assembly  30  may have a component  70  that is moved between adjacent teeth  68  with the locking assembly in a locked state. Disengagement of the components  70  from between the teeth  68  places the locking assembly in an unlocked state. Repositioning of the components  70  can be effected directly or indirectly through the aforementioned actuator  32 , that may be a dedicated component. Alternatively, movement of another component, such as the part  50 , as described below, may effect changing of the locking assembly  30  between locked and unlocked states. In that event, the part  50  serves as the actuator  32 . 
     The component  70  may be movable through a pivoting action, through translation, or in another manner to effect changing of the state of the locking assembly  30 . 
     It is not necessary that the component  70  interact with existing components, as a dedicated locking structure might be incorporated as an alternative. 
     A number of different embodiments are described below. Corresponding parts on the various embodiments will be identified with the same reference numerals and differentiated with different “′” designations. 
     In  FIGS. 12 and 13 , one modified form of armrest assembly is shown at  20 ′. The armrest assembly  20 ′ has riser components  46 ′,  48 ′ that cooperate with a fixed frame base  44 ′. 
     The part  50 ′, defining the surface  22 ′, is connected to the riser component  48 ′ for pivoting movement relative thereto around a laterally extending axis  54 ′. 
     A cam component  72  is mounted to the riser component  48 ′ for pivoting movement around a laterally extending axis  74 . The cam component  72  is also connected to the riser component  46 ′ for pivoting movement about a laterally extending axis  76  that is offset from the axis  74 . 
     Upward movement of the riser component  46 ′ within the frame base  44 ′ and relative to the riser component  48 ′ causes the cam component  72  to act against an underside surface  78  of the part  50 ′ forwardly of the axis  54 ′, thereby causing pivoting of the part  50 ′ around the axis  54 ′ between the position shown in  FIG. 12  and that in  FIG. 13 . This corresponds to a change between first and second states for the previously described armrest assembly  20 . 
     In  FIGS. 14 and 15 , a further variation of the inventive armrest assembly is shown at  20 ″ with riser components  46 ″,  48 ″ between which a third riser component  80  is provided that is in a fixed position relative to the frame  12 ″. The riser components  46 ″,  48 ″,  80  cooperate with a fixed frame base  44 ″. 
     The upper ends of the riser components  46 ″,  48 ″ each is pivotally connected to the part  50 ″ for relative movement around laterally extending axes  52 ″,  54 ″, respectively. The upper end of the riser component  80  is connected to the part  50 ″ for pivoting movement around a laterally extending axis  82 , that is between the axes  52 ″,  54 ″. As depicted, the axes  52 ″,  54 ″,  80  reside in a common plane. 
     The lower region of the riser component  80  is fixed to the frame base  44 ″. As the riser components  46 ″,  48 ″ are moved up and down relative to each other and the riser component  80 , the part  50 ″ pivots about the axis  82  whereby the part  50 ″ is changed between the positions shown in  FIG. 14  and  FIG. 15 . The  FIG. 14  state for the armrest assembly  20 ″ corresponds to the first state for the armrest assemblies  20 ,  20 ′, previously described, with the state of the armrest assembly  20 ″ in  FIG. 15  corresponding to the second state for the armrest assemblies  20 ,  20 ′. 
     In  FIGS. 16 and 17 , a further modified form of armrest assembly is shown at  20 ′″. The primary difference between the armrest assemblies  20 ,  20 ′″ is that the riser component  46 ′″ is made from two pieces  84 ,  86  with adjacent ends joined for pivoting movement around a laterally extending axis  88 . 
     As the armrest assembly  20 ′″ is changed from a first state into a second state, corresponding to those shown for the armrest assembly  20 , by upward movement of the riser component  46 ′″ relative to the riser component  48 ′″, the riser component pieces  84 ,  86  pivot, as shown in  FIG. 17 , thereby avoiding any friction or binding that might interfere with the transition of states. The operation of the armrest assembly  20 ′″ is otherwise the same as that for the armrest assembly  20 . 
     In  FIG. 18 , a further modified form of armrest assembly is shown at  20   4′ . The armrest  20   4′  has a single riser component  90  that cooperates with a fixed frame base  44   4′ . An upper region of the riser component  90  is connected to the part  50   4′  so that the part  50   4′  moves relative thereto around a laterally extending axis  82   4′ , which allows the part  50   4′  to pivot between the solid lines and dotted line positions, respectively representing first and second states for the armrest assembly  20   4′ . 
     An appropriate mechanism  92  connects between the part  50   4′  and at least one of the riser component  90  and fixed frame base  44   4′  to allow automated changing of the state of the armrest assembly, permit user limb movement to effect this reconfiguration, effect locking, etc. 
     In  FIGS. 19 and 20 , a further modified form of armrest assembly, according to the present invention, is shown at  20   5′ . The armrest assembly  20   5  has a part  50   5′ , which defines the surface  22   5′ , that is fixed to a guide piece  94 . The guide piece  94  has a curved length, with the curvature thereof matched to the curvature of a passage  96  for the guide piece  94  defined by a support  98 . 
     The support  98  has a bent shape with a lower portion  100  that cooperates with a fixed frame base  44   5′  to allow the support  98  to be moved guidingly upwardly and downwardly relative to the frame base  44   5′ . As depicted, the lower part  100  and frame base  44   5′  make a telescoping connection. As with all such connections incorporated in any embodiments, the invention contemplates that the inside/outside relationship of telescoped components can be reversed. 
     In  FIG. 19 , the guide portion  94  is shown extended a predetermined amount into the passage  96 , which represents a first state for the armrest assembly  20   5′ . Because of the complementary curvatures of the guide portion  94  and passage  96 , upward movement of the guide portion  94  relative to the support  98  causes the part  50   5′  to incline from rear to front until the corresponding second state for the armrest assembly  20   5′ , as shown in  FIG. 20 , is achieved. 
       FIGS. 21 and 22  show an armrest assembly at  20   6′  that is a refinement of the more generic version shown in  FIGS. 19 and 20  for the armrest assembly  20   5′  therein. The armrest assembly  20   6′  utilizes the same type of support  98   6′  that cooperates with a fixed frame base  44   6  and guide piece  94   6′  on a part  50   6′  that defines the armrest surface  22   6′ . 
     In this embodiment, the curvatures of the passage  96   6′  and guide piece  94   6′  are approximated by an arc with a radius R that is centered at approximately the location of a user&#39;s elbow, indicated at  102 , with the user in a sitting position. Thus, as a user, in a sitting position with his/her forearms resting on the surface  22   6′ , bends his/her arm at the elbow, the part  50   6′  of the armrest assembly  20   6′  comfortably follows that path. That is, the surface  22   6′  follows the natural pivot path of a user&#39;s forearm as it hinges at the user&#39;s elbow. 
       FIGS. 23 and 24  show a further modified form of armrest assembly at  20   7′  that has the same basic components as the armrest assembly  20   6′ —notably, a support  98   7′  defining a curved passage  96   7′  that cooperates with both a fixed frame base  44   7′  and a guide piece  94   7′  with a part  104  having a curvature matched to that of the passage  96   7′ . 
     The primary difference between the armrest assemblies  20   6′  and  20   7′  is that the curvature of the guide piece  94   7′  and that of the passage  96   7′  is greater than that for the corresponding parts on the armrest assembly  20   6′ . 
     In a preferred form, the curvature of each of these components is approximated by an arc with a radius R 2  centered approximately where a user&#39;s shoulder pivots with the user U in a sitting position, as shown in  FIG. 23 . This arc center location is indicated at  106 . Accordingly, movement of the part  50   7′  defining the surface  22   7′  comfortably follows the pivoting movement of the entire arm of the user as it is repositioned while generally maintaining the bent shape shown in  FIG. 23 . 
     Essentially, for the armrest assemblies  20   6′  and  20   7′ , the pivot axes for the parts  50   6′  and  50   7′  are moved from a location adjacent to the parts  50   6′  and  50   7′  to be at or adjacent elbow and shoulder joints for a user. 
     In  FIG. 25 , another generic type structure for connecting the exemplary arm assembly part  50 , with the surface  22  thereon, to the fixed frame  12 , is shown. The connecting structure is a mechanical linkage  108 . This mechanical linkage  108  is part of the generic connecting structure  26  identified in  FIG. 2 . Specific exemplary forms of the mechanical linkage  108  will now be described, with it being understood that these are exemplary in nature only as virtually an unlimited number of different mechanical linkages might be devised that facilitate movement of the arm rest assembly part  50  relative to the frame  12  to change the associated armrest assembly between first and second states therefor. 
     In  FIGS. 26 and 27 , an armrest assembly according to the present invention is shown at  20   8′  with one form of the mechanical linkage  108   8′  incorporated. While not required, this mechanical linkage uses four link members L 1 , L 2 , L 3 , L 4 , with the front and rear of the armrest assembly  20   8′  identified at F and R, respectively. The link members L 1 , L 2 , L 3 , L 4  pivot where connected to each other about parallel axes extending into the page. The link member L 1  is the part  50   8′  that defines the arm support surface  22   8′ . The link member L 3  is fixed to, or part of, the frame  12   8′ . 
     Through this linkage arrangement, the link member L 1  can be controllably repositioned to change the armrest assembly  20   8′  between the  FIG. 26  and  FIG. 27  states, corresponding to the aforementioned first and second states therefor. 
     Changing of the states of the armrest assembly  20   8′  can be effected by any means or mechanism herein described or mentioned. 
       FIGS. 28 and 29  show a modified form of mechanical linkage  108   9′  on an armrest assembly  20   9′  with four link members L 1   9′ , L 2   9′ , L 3   9′ , L 4   9′  corresponding to the link members L 1 , L 2 , L 3 , L 4 , successively on the armrest  108   8′ . The armrest assembly  20   9′  has a front F and rear R. 
     The transverse orientation of the fixed link member L 3   9′ , compared to the corresponding link member L 3 , and the L-shaped configuration of the link member L 1   9′ , allow an inverted configuration for the link L 1   9′  having the associated armrest surface  22   9′ . 
     Again, the linkage  108   9′  allows changing of the armrest assembly  20   9′  between first and second states as shown respectively in  FIGS. 28 and 29 . 
       FIG. 30  shows another modified form of armrest assembly  20   10′  with a mechanical linkage  108   11′  with four link members L 1   10′ , L 2   10′ , L 3   10′ , and L 4   10′ , with the operative orientation of the mechanical linkage  108   10′  having a front and rear as identified at F and R. 
     The mechanical linkage  108   10′  has a projected pivot location at  110  that corresponds to a user&#39;s elbow joint location with the user&#39;s arm resting on the surface  22   10′ . 
       FIG. 31  depicts a further modified form of armrest assembly  20   11′  with a front F and rear R and corresponding link members L 1   11′ , L 2   11′ , L 3   11′ , and L 4   11′  which cause the projected pivot location at  112  to reside at a user&#39;s shoulder joint with the user in a sitting position and having his/her arm resting on the surface  22   11′ . 
     In each of the embodiments in  FIGS. 26-31 , the part of the armrest assembly that defines each surface  22   8′ ,  22   9′ ,  22   10′ ,  22   11′  defines one of the link members. However, this is not a requirement. 
       FIG. 32  discloses a further modified form of armrest assembly at  20   12′  with a part  50   12′  defining a support surface  22   12′ . The part  50   12′  is part of a mechanical linkage at  108   12′  that is mounted on a support  114  that moves guidingly in a vertical direction relative to a fixed frame base  44   12′ . 
     The mechanical linkage  108   12′  has three link members L 5 , L 6 , L 7  with the link member L 5  being the part  50   12′  defining the surface  22   12′ . The link members L 6 , L 7  each has an end connected to the support  114  for pivoting movement about laterally extending axes  116 ,  118 , respectively. The opposite ends of the links L 6 , L 7  move within horizontally elongate slots  120 ,  122 , respectively on the part  50   12′ . The links L 6 , L 7  are thus allowed to pivot and translate within the slots  120 ,  122 , which thereby allows the surface  22   12′  to be inclined from rear to front as in earlier embodiments. By this reconfiguration, the armrest assembly  20   12′  is changed between corresponding first and second states. The part  50   12′  moves without a fixed pivot axis. Essentially, it pivots and translates simultaneously as the armrest assembly  20   12′  changes states. The armrest assembly  20   12′  is front/rear neutral. 
       FIG. 33  shows an armrest assembly  20   13′  with a front F and rear R and a mechanical linkage  108   13′  with similarities to the mechanical linkage  108   12′  in  FIG. 31 . 
     The mechanical linkage  108   13′  has three link members L 5   13′ , L 6   13′  and L 7   13′ . 
     In place of the slot  122 , the part  50   13′  has a pivot connection to the link member L 7   13′  which allows the link members L 5   13′ , L 7   13′  to move relative to each other around a fixed, laterally extending axis  124 . This linkage arrangement allows reorientation of the part  50   13′  to change the armrest assembly  20   13′  between corresponding first and second states. 
     Both armrest assemblies  20   12′  and  20   13′  can be automatically or manually reconfigured by incorporating an appropriate mechanism and potentially separate actuating structure therefor. 
     In  FIG. 34 , a further modified form of armrest assembly is shown at  20   14′ . The armrest assembly  20   14′  has riser components  46   14′ ,  48   14′  that move vertically relative to each other to effect a change of state of the armrest assembly  20   14′ , as a result of a front inclination of the part  50   14′  defining the armrest surface  22   14′ . 
     Rather than providing fixed pivot locations for the upper regions of the riser components  46   14′ ,  48   14′ , the riser  46   14′  has a component  126  that moves in an elongate slot  120   14′ . Thus, the upper end of the riser component  46   14′  translates and pivots relative to the part  50   14′  as the state of the armrest assembly  20   14′  is changed. 
     In this embodiment, the riser component  48   14′  is normally urged upwardly relative to a fixed frame base  44   14′  by a biasing assembly shown schematically at  130 . An additional biasing assembly  132  urges the riser component  46   14′  upwardly relative to the riser component  48   14′  so that the biasing forces provide a “spring assist” as the armrest assembly  20   14′  is being changed into its second state, as depicted in  FIG. 34 . 
     This structure, among other things, potentially allows for a more comfortable transition between first and second states, regardless of how the transition is effected. 
     In  FIGS. 35 and 36 , a further modified form of armrest assembly is shown at  20   15′ . In this embodiment, a part  50   15′ , upon which the surface  22   15′  is defined, has a guide portion  134  that moves in a track  136  that is on or part of the frame  12   15 . The guide portion  134  and track  136  have a complementary curved shape so that the part  50   15′  is guided around a laterally extending axis  138 . This movement allows the armrest assembly  20   15′  to be changed between the first state in  FIG. 35  and the second state in  FIG. 36 , corresponding to those same states for the various armrest assemblies discussed above. 
     The axis  138  may be located at, or adjacent, a user&#39;s elbow joint with the user in a sitting position. 
       FIGS. 37 and 38  show a further alternative form of armrest assembly at  20   16′ , which utilizes the same basic structure, shown in  FIGS. 35 and 36 , to guide the part  50   16′  with the surface  22   16′  about an axis  138   16′  to place the armrest assembly  20   16′  in first and second states, respectively in  FIGS. 37 and 38 . 
     The armrest assembly  20   16′  is preferably configured so that the axis  138   16′  coincides with, or is adjacent to, a user&#39;s shoulder joint with the user in a sitting position. 
     This basic concept can be utilized with a number of different interacting components. For example, bearings might be utilized to guide relative movement between the components. Wheels could move in a track. A ball and socket, universal joint, or gimbal arrangement could be utilized. Virtually any type of structure that allows this guided movement of the parts  50   15′ ,  50   16′  is contemplated. 
     The invention contemplates variations of the above structures within the schematic showings thereof. For example, as shown in  FIG. 23 , the base  44   7′ , that is normally a fixed part of the frame, might be movable independently around a laterally extending axis  140  to provide, or augment, the inclination of the surface  22   7′ . 
     With the various embodiments described above, an adjusted position of the armrest surfaces may be maintained either by forces imparted by a user or through mechanical structure that may be operated by the user. The locking assembly/locking assemblies  30  that accomplish this, if manually operated, may utilize a dedicated actuator  32  or may be operated through manipulation of one or more basic components of the particular sitting apparatus that perform the function of a separate actuator. 
     As one example, as shown schematically in  FIG. 39 , the locking assembly  30  on the generically depicted armrest assembly  20   17′  may be actuated by the part  50   17′ , as by turning the part  50   17′  around its fore-and-aft/Y axis  142 . The schematic showing is intended to encompass a locking assembly  30  that might be so actuated to fix the part  50   17′  against some or all of the potential movements permitted by the constructions described above—including front-to-rear/rear-to-front inclination, vertical shifting, pivoting about the vertical/Z axis  144 , etc. This allows a user to effect locking of the part  50   17′  against one or more of the noted movements through the convenient manipulation of the part  50   17′ . The turning of the part  50   17′  around the axis  142  is only one exemplary actuating movement. 
     Turning of the part  50   17′  around the axis  142  introduces the aspect that the part  50   17′  may have an additional degree of adjustment permissible through which the surface  22   17′  may be tipped from side to side. 
     Myriad different structures can be devised to effect locking of the surfaces  22  through the connecting structure  26 , as shown schematically in  FIG. 2 . 
     As noted above, a discrete/dedicated actuator  32  might be provided and accessible to a user to operate the locking assembly  30 . 
     In  FIG. 40 , an armrest assembly is shown at  20   18′  having an overall construction similar to the armrest assembly  20   14′  in  FIG. 33 . Grooves (not shown) may be provided on riser components  46   18′ ,  48   18′  to allow vertical/Z axis turning with respect to a fixed base  44   18′ . Separate sprag clutches  146 ,  148  are provided to make up a locking assembly  30   18′ . 
     The clutch  146  pivots at the riser component  48   18′ . The clutch  148  pivots on the fixed base  44   18′ . 
     As shown in  FIGS. 41 and 42 , the pivoting of riser components  46   18′ ,  48   18′ , as shown in  FIG. 40 , allows different relationships to be set between the riser components  46   18′ ,  48   18′  and the part  50   18′  with which they are associated. Two exemplary relationships are shown in  FIGS. 41 and 42 . The result of changing the relationship of the part  50   18′  and riser components  46   18′ ,  48   18′  is that the lateral position of the part  50   18′  likewise changes. This function can be used to adjust spacing between the surfaces  22   18′  on the laterally spaced armrest assemblies  20   18′  on the particular sitting apparatus. 
     As seen in  FIG. 43 , this same pivoting of the riser components  46   18′ ,  48   18′  relative to the part  50   18′  may effect reorientation of the part  50   18′  around the vertical/Z axis. 
       FIGS. 44 and 45  show a still further embodiment of the inventive armrest assembly  20   19′  that is configured to allow the surface  22   19′  on the part  50   19′  to be repositioned relative to the frame  12   19′  by movement: a) selectively around separate Z axes  150 ,  152 ; b) along a horizontal axis, as indicated by the double-headed arrow  154 ; and c) vertically along the axis  152 , as indicated by the double-headed arrow  156 . 
     The locking assembly  30   19′  is designed to be operated by turning of the part  50   19′  around the Y axis  158 , as indicated by the arrows  160 . The locking assembly  30   19′  includes a rod  162  with ends  164 ,  166  supported for a gimbal-like motion that allows the tilting around the axis  158  through manipulation of the part  50   19′  to thereby actuate the other components making up the locking assembly  30   19′  to fix the surface  22   19′  against movement in one or more manners. 
     Generally, it should be understood that the various components and functions from the different embodiments described above are contemplated to be interchanged to provide additional versatility. 
     The invention is also contemplated to be used with sitting apparatus having all known types of structures to change orientations and positions of arm supporting surfaces on armrest assemblies. 
     The particular mechanisms utilized may be incorporated at least partially within certain components on existing chair technology. Alternatively, the structure can be independently constructed and added to the conventional components. 
     While the second state for the various surfaces  22  is described as inclined at a forward end thereof, opposite inclination is also contemplated. 
     If the actuator for the locking assembly is an existing component, it is not limited to the tilting of the part  50  about the Z axis. Any functional component on a sitting apparatus can be adapted to be an “actuator” through potentially relatively simple and convenient manipulation. 
     The foregoing disclosure of specific embodiments is intended to be illustrative of the broad concepts comprehended by the invention.