Abstract: A chair having a backrest having an upper backrest section and a lumbar section, wherein the lumbar section is provided with a plurality of perforations and is elastically deformable to allow a backward tilting movement of the upper backrest section under a backward thrust applied from a user's back, and wherein the perforations stop the backward tilting movement of the upper backrest section in a position of maximum backward tilt of the upper backrest section.

Abstract: A body support structure includes a pair of laterally extending load bearing support segments each having an outer portion coupled to a support structure and an inner portion. Each of the load bearing support segments extends laterally inwardly from the outer portion, and the inner portions are laterally spaced apart so as to define a gap therebetween. A body support member is spaced forwardly from the pair of load bearing support segments. A plurality of links connect the load bearing support segments to the body support member.

Abstract: A seating arrangement includes a back arrangement movable between upright and reclined positions, a linkage arrangement including a first link member comprising a portion of a seat arrangement, a second link member supported on a base, flexibly resilient front link members extending between forward portions of the first and second link members and being integral with the second link member, and a rigid rear link member extending between rearward portions of the first and second link members including a separate piece from the first or second link members, wherein the rearward portion of the first link member extends laterally in a first plane when the back arrangement is upright, and laterally in a second plane when the back arrangement is reclined, where the second plane is angled with respect to the first plane, and is positioned farther away from the base when the back arrangement is reclined than when upright.

Abstract: In the vehicle seat, rear suspension members are provided at two positions spaced away from each other in a lateral direction on an edge of a seat cushion near a seatback, and support the seat cushion while the seat cushion is suspended from a seat cushion support frame so that the seat cushion is movable in the lateral direction. A front suspension member is provided at one position or two positions spaced away from each other in the lateral direction on ahead of the rear suspension members, and supports the seat cushion while the seat cushion is suspended from the seat cushion support frame so that the seat cushion is movable in the lateral direction.

Abstract: Disclosed is a vehicle seat (1) comprising a seat cushion (2) and a seat back (4), wherein the seat cushion and the seat back are comprised of: a frame structure (8) to be fixed to the vehicle body; and a seating member (10) supported by the frame structure having an elastic deformation property and a vibration damping property and allow an occupant to be seated therein, and wherein the vehicle seat satisfies the following relationship: DS/DF?20, where DS denotes a deformation amount of the seating member itself in a situation where a load W is applied at a position XS of the seating member, and DF denotes a displacement of a position XF of the frame structure corresponding to the position XS, in a situation where the frame structure is fixed to the vehicle body, and the given load W is applied at the position XF.

Abstract: A vehicle seat includes a first seat component such as a seat pan or seat frame, and a second seat component such as a seat back. The first seat component is rotatably coupled to the second seat component by a rotatable coupling, and a laterally oriented vibration isolator is positioned between the first seat component and the second seat component at the rotatable coupling. Transmission of vibration from the first seat component to the second seat component through the rotatable coupling is suppressed by the vibration isolator. In some cases, the vibration isolator is a quazi-zero-stiffness (QZS) isolator.

Abstract: A kinetic seat assembly that rotates based on a force applied on an occupant seated therein is provided. The kinetic seat assembly includes a primary seat cushion frame, a primary seat back frame, a secondary seat cushion frame pivotally connected to the primary seat cushion frame, and a secondary seat back frame pivotally connected to the primary seat back frame. The kinetic seat assembly further includes a front pivot mechanism for damping movement between the primary seat cushion frame and the secondary seat cushion frame in a kinetic seat vertical direction, and an upper pivot mechanism for damping movement between the primary seat back frame and the secondary seat back frame in a kinetic seat longitudinal direction.

Abstract: A seat includes a support having a first coupling hole and a second coupling hole disposed therein. The seat also includes a seat cradle having a back, a bottom, a first side fixedly connected to the back and the bottom, and a second side fixedly connected to the back and the bottom. The seat cradle has a neutral position in which a top portion of the back is positioned forward of a bottom portion of the back, and a rear portion of the bottom is positioned below a forward position of the bottom. The seat also has a first cradle coupler extending from the first side of the seat cradle, such that the first cradle coupler cannot rotate with respect to the first side. The seat further includes a second cradle coupler extending from the second side of the seat cradle, such that the second cradle coupler cannot rotate with respect to the second side. The first cradle coupler is received in the first coupling hole and the second cradle coupler is received in the second coupling hole.

Abstract: A kinetic seat back assembly that rotates based on a force applied on an occupant seated therein is provided. The kinetic seat back assembly includes a primary seat back frame, a secondary seat back frame, a seat back tilt mechanism coupling the secondary seat back frame to the primary seat back frame such that the secondary seat back frame is movable with respect to the primary seat back frame, and an upper pivot mechanism that pivotally couples an upper portion of the primary seat back frame to an upper portion of the secondary seat back frame.

Abstract: A vehicle seat includes a seat base, a backrest connected to the seat base and an leg rest assembly, also referred to as a leg rest assembly. The leg rest assembly includes a deflectable leg support panel pivotably connected to the seat base. The deflectable leg support panel and deflects under a load of legs of the user and returns with a restoring force back to an initial position upon removing the load of the legs of the user. The leg rest assembly may be connected to the vehicle seat by a pivoting structure, that allows the leg rest assembly to be pivoted to a non use position. The leg rest assembly may also be fixedly connected to the vehicle seat a support base front cross structure. This fixed connection then forms an only pivot axis of the leg rest assembly.

Abstract: A backrest includes a frame having a pair of laterally spaced upright members connected with longitudinally spaced upper and lower members. A flexible shell has opposite sides coupled to the upright members and upper and lower portions coupled to the upper and lower members. The shell includes first and second slots extending longitudinally along opposite sides of the shell inboard of locations where the shell is connected to the upright members, and one or more third slots extending laterally along the lower portion of the shell above a location where the shell is connected to the lower member. Terminal ends of the one or more third slots are spaced apart from lower terminal ends of the first and second slots. In other embodiments, the shell is a three-dimensional molded component having a plurality of openings. In various embodiments, the slots and/or openings provide different levels of compliance to the backrest.

Abstract: The present invention relates to a spine orienting device for integration into a variety of types of seats, for example, automotive seats or office type seating, in order to properly position the sacrum of the individual using the seat, which in turn will properly pivot the pelvis to assist in maintaining the spine in equilibrium.

Abstract: An adjustable bench has a frame with a seat support pivotably coupled to the frame. The seat support includes a slide assembly which allows the seat to be slidably positioned relative to the frame. A back support is also pivotably coupled to the frame.

Abstract: A seating arrangement includes a base, a lower shell having a portion fixedly coupled to the base, and an upper shell supported entirely by the lower shell, the upper shell comprising a seating portion, a backrest portion moveable between an upright position and a reclined position, and a curved transition portion extending between the seating portion and the backrest portion, wherein a pair of laterally spaced longitudinal slots are located in portions of the seating portion and the transition portion thereby defining a central region and laterally spaced side regions, wherein the central region moves up relative to the side regions during recline.

Abstract: A spacer (40) comprising a generally planar body portion (44) and one or more channels (42) defined by one or more unitary channel walls (48), channel wall segments (52), or both extending from the generally planar body portion (44); and one or more flexing regions (74) defined by two or more juxtaposed channel wall segments (52) separated by a gap (54) for providing flexibility to the spacer (40).

Abstract: A seat assembly having a seat back and a bolster subassembly. The bolster subassembly may have a bolster frame and a bolster trim subassembly. The bolster frame may be mounted to a back panel of the seat back. The bolster trim subassembly may be received between the bolster frame and the back panel when the bolster subassembly is mounted to the seat back.

Abstract: A reconfigurable apparatus having: a frame; at least a first component on the frame upon which a force is applied in a first manner in using the apparatus for its intended purpose; and at least a second component on the frame that is movable relative to the at least first component and/or the frame and upon which a force can be applied in a second manner to reconfigure the apparatus by moving the at least second component relative to the at least first component and/or the frame. An adjusting assembly cooperates between the at least first component and the at least second component and is configured so that as an incident of the force being applied in the first manner changing, the force being applied in the second manner required to reconfigure the apparatus changes.

Abstract: A seating assembly for a vehicle includes a base. A seatback having a lower portion is rotatably coupled to the base and an upper portion is pivotably coupled to the lower portion by at least one pivot joint. The at least one pivot joint is disposed on a front portion of the seatback. A guide bracket is disposed on a rear portion of the seatback and is configured to guide the upper portion of the seatback between a resting position and a deployed position. A resilient member provides a resistance to pivoting of the upper portion of the seatback and the resilient member is operably coupled to the upper portion of the seatback and the lower portion of the seatback. The upper portion of the seatback pivots from the resting position to the deployed position during a frontal collision of the vehicle.

Abstract: A seating arrangement includes a seat arrangement that includes first, second, third and fourth link members coupled to one another, a back arrangement movable between an upright position and a reclined position and coupled to the seat arrangement such that the first link member moves between forward and rearward positions as the back arrangement is moved between the upright and reclined positions, and a stop arrangement including a stop link coupled to at least one of the first link member, the third link and the fourth link member such that the stop link moves with the associated link member as the back assembly moves between the upright and reclined positions, wherein travel of the stop link is limited with respect to the second link member thereby limiting a rearward movement of the back arrangement toward the reclined position.

Abstract: A chair back height adjustment mechanism comprises a guide having an abutment surface at a lateral side of the guide which extends along an adjustment direction. The chair back height adjustment mechanism comprises an adjusting device supported on the guide so as to be displaceable along the adjustment direction. The adjusting device comprises a carrier, a coupling member which is moveably supported on the carrier, and a bias mechanism. The coupling member has a contact face shaped to abut on the abutment surface of the guide and a slanted face. The bias mechanism is operative to apply a force onto the slanted face to urge the contact face of the coupling member against the abutment surface of the guide.

Abstract: A chair comprising: a support structure including a rigid front fixing element, and an essentially L-shaped seating element, including a seat portion and a backrest portion connected to each other via an arcuate connecting portion, wherein the seat portion comprises a front fixing section fixed to said rigid front fixing element, a main seat section having a concave cross-section and a planar bending section located between said front fixing section and said main seat section and having a flat cross-section.

Abstract: Chair, more especially an office chair, comprising a seat plate (34) which is arranged on an undercarriage (12) and a backrest (14) which in the manner of a so called synchronous mechanism permit a synchronous movement of seat plate (34) and backrest (14), characterized in that the seat plate (34) is mounted laterally tiltable and the backrest includes two backrest supports (22, 24) whose lower ends are mounted pivotally independently of each other on the undercarriage (12) and are coupled in movement to the seat plate (34) in such a manner that by rearward pivoting of the support (22, 24) one side of the seat plate (34) is pressed down on the same side and the opposite side thereof is raised.

Abstract: A banquet chair comprises a seat and a backrest carried by a plurality of legs. A pair of arcuate leaf springs flexibly couples the backrest to the plurality of legs. The pair of arcuate leaf springs is spaced-apart, and each is located closer to a different outside edge of the seat and the backrest than to each other or a middle of the seat and the backrest. Each of the pair of arcuate leaf springs has an outermost edge exposed through a lateral perimeter of the backrest.

Abstract: A chair assembly includes a seat support structure, a back support structure, a back tensioning assembly adjustable between low and high tension positions, an actuator assembly adapted to adjust the back tensioning assembly between the low and high tension positions, a control input assembly actuable by rotating the portion of the control input assembly, and a control link assembly operably coupling the control input assembly with the actuator assembly to adjust the back tensioning assembly between the low and high tension positions upon rotation of the portion of the control assembly by a seated user, wherein a number of rotations of the portion of the control input assembly is not limited by the control link.

Abstract: A chair back assembly includes a back shell member including laterally extending top, bottom and side portions cooperating to define an open space therebetween, where a portion of the back shell member is located in a lumbar region, a cover having a first surface and a second surface opposite the first surface, wherein the cover covers at least a portion of the open space, and a back frame assembly operably supporting the back shell member and movable between upright and reclined positions, wherein the back frame assembly causes the back shell to flex in a fore-to-aft direction as the back frame assembly is moved between the upright and reclined positions independent of an external force being exerted on the back shell member, and where the lumbar portion of the back shell member remains spaced from the back frame as the back frame is moved between the upright and reclined positions.

Abstract: A vehicle seating assembly including a lower seatback. An upper seatback is operably coupled to the lower seatback. The upper seatback is pivotally mounted to the lower seatback at a pivot axis. An arcuate back support bar is disposed in the upper seatback and is configured to rotate the upper seatback between forward and rearward positions. The arcuate support bar includes first and second generally linear members and an arcuate intermediate portion disposed between the first and second generally linear members. An articulation assembly operably couples the lower seatback with the upper seatback.

Abstract: A motion setting method that can set motions to a standing and sitting motion-supporting robot so that a care receiver can make standing and sitting motions comfortably is provided. The motion setting method is a motion setting method of a standing and sitting motion-supporting robot that supports standing and sitting motions being at least one of a standing motion and a sitting motion of a care receive. The motion setting method includes a custom tracking path acquisition step. In the custom tracking path acquisition step, a custom tracking path is obtained by correcting a base tracking path of the standing and sitting motions in accordance with the position of a predetermined body portion of each care receiver.

Abstract: A chair back assembly includes a substantially rigid peripheral frame defining a central opening, and a substantially flexible back shell coupled to the peripheral frame and spanning at least a portion of the central opening, wherein a first portion of the back shell is fixed with respect to the frame at a first position, a second portion of the back shell is fixed with respect to the frame at a second position that is different than the first position, a third portion of the back shell is constrained with respect to the frame in at least one direction of motion at a third position located between the first position and the second position, and wherein a fourth portion of the back shell is free from constraint with respect to the frame at a fourth position located between the third position and the second position.

Abstract: A seat back for vehicles including a seat back pad having supporting bodies fixed on a periphery of an opening or a seat frame, or formed integrally with the periphery of the opening by one or multiple-point support, the supporting bodies aligned at predetermined intervals, each arranged in a direction between periphery portions opposite to each other of the opening at a front surface portion formed as a backrest surface for a seated person, the supporting bodies being independent of each other in rod or plate form, each made of a synthetic resin foam having 20 mm or larger in bending deflection amount and 2 to 100 N in load when deflected by 20 mm measured in accordance with a method defined by JIS K7221-2:2006, and having an interspace portion configured such that the supporting bodies are allowed to be deformed by bending in a rear direction.

Abstract: A wheelchair (10) comprising:—a seat module (10) including a seat frame (11) supporting a seat (12);—a backrest module (20) including a backrest frame (21) connected to said seat frame (11) and supporting a backrest (22);—a front frame module (30) including a front frame (31), said front frame (31) including left and right bended legs (31a, 31b) removably connected at their upper end to said seat frame (11) and at their lower end to a footrest (32), said bended legs (31a, 31b) being supported by caster wheel assemblies (35, 36) via caster support (34);—a rear wheel module (40) including left and right rear wheels (41a, 41b) pivotally connected to an axle (42), said rear wheel module (40) being removably connected to said seat module (10) through left and right connecting elements (43a, 43b); wherein said seat frame (11) consists in left and right longitudinal profiles (11a, 11b) extending in the same plane.

Abstract: A chair back that includes a back support, an upright frame, and at least one flex wing. The back support is substantially flexible and has a first side portion and a second side portion. The upright frame is substantially rigid and has a first frame side and a second frame side. The flex wing is located between the first frame side and the first side portion, where the flex wing includes a front portion coupled to the first side portion, a back portion coupled to the first frame side, and a web portion interconnecting the front portion and the back portion. The flex wing flexes during engagement by a user.

Abstract: A lightweight self-reclining chair for outdoor having a skid-like to stand over any ground. The chair variable geometry frame comprising an articulated arched-shaped seat panel with an hinged back-rest panel and an hinged leg-rest panel clamped over upper ends of front-leg and rear-leg of a U-shaped chair support base; lower end of rear-leg U-shaped form chair support base being fitted with spring-hinge to pull back the seat in a reclined motion. The chair is equipped with hand-operable tension mechanism having integrated stopper to provide incremental adjustment on chair reclined a seat back angle with auto-pivoting of a leg-rest panel.

Abstract: A control assembly for a chair including a base structure including a first pivot point and a second pivot point spaced from the first pivot point, and a seat support structure directly pivotably coupled to the base structure for rotation about the first pivot point, a back support structure pivotably coupled to the base structure for rotation about the second pivot point, wherein the back support structure is adapted to move between a first and second position, a control link having a first end operably coupled to the seat support structure, and a second end operably coupled to the back support structure, and a biasing assembly exerting a biasing torque about the second pivot point that biases the back support structure from the second position toward the first position, wherein the biasing torque is adjustable between first and second magnitudes when the back support structure is in the first position.

Abstract: A seating support includes a lumbar support portion having first and second lumbar supports. The lumbar support portion defines at least a portion of a channel extending between the first and second lumbar supports. The channel is sized to substantially preclude contact with an occupant of the seating support. Such a seating support also includes a coccyx support portion having first and second coccyx supports. The coccyx support portion is disposed substantially perpendicular to the lumbar support portion and is in communication therewith such that the channel extends from the lumbar support portion between the first and second coccyx supports.

Abstract: A chair assembly including a first chair structure, a second chair structure, an actuator assembly coupled to the second chair structure to move the second chair structure between the first and second positions, a control input assembly coupled to the first chair structure, and a control link assembly coupling the control input assembly with the actuator assembly to move the second chair structure between first and second positions, and including a first shaft operably coupled to the control link, and rotatable about a second axis that is substantially orthogonal to the first axis and to the first direction, and first and second universal joint assemblies coupling the first shaft member to the second shaft, wherein actuation of the control input moves the second chair structure between the first and second positions.

Abstract: A chair assembly includes a back shell member including a laterally-extending top portion, a laterally-extending bottom portion and a pair of longitudinally-extending side portions extending between the top portion and the bottom portion and cooperating therewith the defined open space therebetween, and a cover having a first surface adapted to support a seated user and a second surface opposite the first surface, wherein the cover is positioned over the back shell member to cover at least a portion of the open space, and wherein the cover comprises an elastomeric material having a longitudinal direction compliance to lateral direction compliance ration of at least 3:1.

Abstract: According to the present invention a back for a seating unit is provided. The back comprises a plurality of flexible finger elements. Each of the plurality of flexible finger elements has a distal end. The back further comprises a retainer connecting at least two of the flexible finger elements proximate their distal ends. When a load is applied to a flexible finger element, the retainer distributes at least a portion of the load to at least one adjacent flexible finger element.

Abstract: Vehicle seat (1), with a seat part (2) and a backrest (3), which comprises a lumbar support (7), wherein the lumbar support (7) has a lumbar apex (7.1) towards the back of a seat occupant and tapers from there and that the lumbar support comprises a suspension 9, 11, 12) that results in load distribution with a primery load uptake (8. 1) at the lumbar apex (7.

Abstract: A chair with a tilting backrest including two flexible supporting sectional elements set at a distance from one another in a transverse direction, wherein each of said supporting sectional elements is provided with a plurality of through notches that form respective points of localized bending that enable bending backwards of the supporting sectional element, and wherein each of said notches has a first contact surface and a second contact surface that, in the position of maximum inclination backwards of the backrest, come to bear upon one another to stop bending backwards of the sectional element, wherein the projections of said first and second contact surfaces in a vertical plane parallel to the longitudinal axis of the chair are at least partially superimposed on one another in such a way as to prevent visual communication through said notches in a direction orthogonal to said vertical plane.

Abstract: A chair chassis includes a base, a warped plate, a first adjustment member and a second adjustment member. The base including an upper cover, a lower cover and a front cover is arranged at a bottom surface of a seat of a chair. The warped plate is disposed under the upper cover of the base for connecting to a seat back of the chair. Two compression springs arranged in parallel with a certain interval are disposed between the first adjustment member and the warped plate for adjusting travel distance of the compression springs and changing a force of the seat back. The second adjustment member is used for lifting the chair by rotation of a second adjustment shaft. The chair chassis is fastened and adjusted by operating the second adjustment shaft to move along an axial direction. The chair chassis has simple structure, easy operation and improved applicability.

Abstract: A chair back that includes a back support, an upright frame, and at least one flex wing. The back support is substantially flexible and has a first side portion and a second side portion. The upright frame is substantially rigid and has a first frame side and a second frame side. The flex wing is located between the first frame side and the first side portion, where the flex wing includes a front portion coupled to the first side portion, a back portion coupled to the first frame side, and a web portion interconnecting the front portion and the back portion. The flex wing flexes during engagement by a user.

Abstract: The present invention relates to a vehicle seat having a seat part and having at least one backrest part which is pivotable about an axis of rotation relative to the seat part, and having a spring means which is effective between the seat part and the backrest part, wherein the backrest part comprises at least a backrest rear wall, backrest upholstery and a backrest cover. According to the invention, a spring means designed as a torsion spring is in each case arranged completely within the corresponding backrest part, is supported at the first end thereof on the backrest rear wall and acts at the second end thereof opposite the first end on an intermediate piece or on a stop of the intermediate piece, wherein the intermediate piece is arranged on the axis of rotation and is fastened to a bearing in a manner fixed relative to the frame.

Abstract: A reclining chair has a base coupled to a chair back. The chair back is adapted to recline from an upright position to a reclined position. To accommodate that reclining motion, the chair back includes a flex zone formed with notches extending through an inner portion of the flex zone. Those notches narrow as the chair back reclines from the upright position to the reclined position. The flex zone also includes an outer portion that is separated from the inner portion by a gap, the outer portion having one or more notches extending through the outer portion. Those notches also narrow as the chair back reclines from the upright position to the reclined position.

Abstract: A chair system according to embodiments of the present invention includes a base comprising a seat for a user and one or more support legs, a back, and a flexible back support element rigidly coupled to the back and to the base, the flexible back support element comprising a flex zone, the flex zone comprising one or more notches, wherein the back is reclinable from an upright position to a reclined position, wherein the one or more notches are configured to narrow as the back reclines from the upright position to the reclined position, and wherein the one or more notches are open in the upright position and closed in the reclined position.

Abstract: The invention relates to an item of seating furniture (2), in particular an office chair, with a substantially curved supporting shell (14) which has two raised, curved, flexible curved arms (24) and a rigid central piece (16) arranged between said curved arms. Furthermore, the item of seating furniture (2) comprises a covering (30) which is clamped in the manner of a secant between the curved arms (24) of the supporting shell (14), wherein, when the covering (30) is loaded, at least one curved arm (24) is at least partially increasingly raised and/or is at least partially curved in the direction of the central piece (16).

Abstract: A flexible resilient seat back, a chair including the seat back and methods of using the chair. The seat back includes an integral sheet material having rigidity sufficient to maintain its shape absent a deforming force; the sheet material having relatively upper and lower portions considered in a direction from top toward bottom, an area of the sheet material approximately at the juncture of the upper and lower portions protruding more forwardly than the major extent of the upper and lower portions, and the sheet material resiliently flexible permitting limited (controlled) deformation during use generally in a prescribed manner in response to force to bend the upper portion of the sheet material relative to the lower portion in a direction front to back and/or in a sidewise direction while supporting the back of the user. A method using and exercising using the chair with seat back.

Abstract: A backrest inclination structure for lumbar support enables a backrest to enter a free state when a user sitting at any position of a chair lifts a lever of a spring continuous control unit, such that the backrest fits the user's moving back when the backrest is configured for movable inclination. Hence, the backrest can move together with the user's back ergonomically to provide lumbar support. Accordingly, the user can sit comfortably on the chair and be free from lumbago and kyphosis which are common among sedentary individuals.

Abstract: A chair including a dynamically-flexible back and seat having a shape that adjusts to the movements of a user seated in the chair to enhance user comfort. Each of the back and seat has an air gap formed therewithin and a resilient frame or liner with a spring memory. The resilient liner is adapted to flex in response to compressive forces that are generated as the user slides his body back or from side-to-side in the chair. Accordingly, some of the chair back and some of the chair seat move into respective air gaps so that the shapes of the back and seat change to conform to the movements of the user. The air gaps also establish air flow ventilation channels which run laterally through the back and seat of the chair.

Abstract: A chair with a back-and-forth moving backrest comprises a seat and a backrest, the lower end of the backrest is separated from the seat; both sides of the lower end of the backrest are respectively connected with both sides of the back end of the seat by a rotating mechanism; the lower end of the rotating mechanism can be rotatably regulated relatively to the seat; the upper end of the rotating mechanism can be rotatably regulated relatively to the backrest; during the rotating regulation of the rotating mechanism, the backrest only moves back and forth relatively to the seat without changing the vertical state of the backrest.

Abstract: A chair system according to embodiments of the present invention includes a base comprising a seat for a user and one or more support legs, a back, and a flexible back support element rigidly coupled to the back and to the base, the flexible back support element comprising a flex zone, the flex zone comprising one or more notches, wherein the back is reclinable from an upright position to a reclined position, wherein the one or more notches are configured to narrow as the back reclines from the upright position to the reclined position, and wherein the one or more notches are open in the upright position and closed in the reclined position.