Patent Description:
A common goal in the field of seating apparatuses, particularly office chairs and the like, is to improve the comfort and fit for the occupant. Reclinability is a key feature for providing a chair that can be utilized for an entire workday without discomfort. There have been a variety of approaches employed in order to provide reclinability. Such chairs are known for example from <CIT>, <CIT> and <CIT>.

Conventional reclining chairs utilize one or more springs to bias the backrest in the upright position and provide resistance to the reclining motion. Springs, by their very nature, exhibit a linear increase in the output force as the spring is deformed. Thus, because a spring can only provide a singular recline curve across its range of motion, designers of conventional reclining chairs typically select a spring that accommodates the size and weight of the median occupant. At the extremes of the population, the recline resistance force provided by the spring will not match the force being applied by the occupant during the reclining motion, thus preventing the occupant from comfortably utilizing the recline mechanism. Large occupants will find the resistance force to be too weak and thus find the reclinable chair too prone to recline. Conversely, small occupants will find the resistance force to be too strong and thus have difficulty utilizing the recline mechanism at all.

Weight-sensitive reclinable chairs have been developed in order to address the shortcomings of conventional reclining chairs. Weight-sensitive reclining chairs feature recline mechanisms that cause the seat to rise against the weight of the occupant as the backrest is reclined. In this manner, the occupant's own weight provides at least a portion of the recline-resistance force, thereby customizing the counterbalancing force provided by the chair's recline mechanism to the occupant. Many commercially-available weight-sensitive reclinable chairs utilize a combination of the occupant's weight and one or more conventional springs to provide the overall recline-resistance force.

Weight-sensitive reclinable chairs aim to provide a chair whose recline action parallels the natural body action during recline. However, with many weight-sensitive reclinable chairs, there is a tendency for the occupant's legs to be lifted from the floor during recline, thereby causing the underside of the occupant's legs to be supported solely by the forward edge of the seat. This phenomenon creates a pressure point for the occupant's legs that can cause discomfort. To overcome this problem, the pivot point of the reclining mechanism may be moved forward (i.e., towards the front edge of the seat) to reduce the front seat lift at full recline sufficiently to permit the occupant's feet to stay on the floor. The undesirable effect of this arrangement is that the body angle between the occupant's torso and legs is unchanged and as a result, the occupant's eye level drops undesirably when the chair is reclined. Moreover, if you move the pivot point too far forward, the center of gravity of the occupant's back tends to fall too much during reclining actions, making it difficult for the occupant's weight to counterbalance the reclining force.

For the foregoing reasons, weight-sensitive reclinable chairs typically have their backrest pivotally attached to the seat at a position below the seat and proximate to the user's hip joints. However, when the backrest pivot is located in this position, the pivot point is displaced from its ideal position during reclining actions. An improved weight-sensitive reclinable chair is needed that maintains the most ergonomic relationship as possible between the seat and the backrest throughout its range of motion.

A reclinable seating apparatus is as set out in independent claim <NUM>.

The accompanying figures, together with the detailed description below, are incorporated in and form part of the specification, serve to illustrate further various exemplary embodiments and to explain various principles and advantages in accordance with the present invention:.

Detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Alternate embodiments may be devised without departing from the scope of the invention. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention. While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward.

As used herein, the terms "a" or "an" are defined as one or more than one. The term "plurality," as used herein, is defined as two or more than two. The term "another," as used herein, is defined as at least a second or more. The terms "comprises," "comprising," or any other variation thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises. a" does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element. The terms "including," "having," or "featuring," as used herein, are defined as being synonymous with the term "comprising" (i.e., open language). The term "coupled," as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. As used herein, the term "about" or "approximately" applies to all numeric values, whether or not explicitly indicated. These terms generally refer to a range of numbers that one of skill in the art would consider equivalent to the recited values (i.e., having the same function or result). The terms "motion-facilitating component(s)" and "roller(s)" are used synonymously herein and should be understood to encompass any motion-facilitating component, such as rollers, glides, wheels, spherical balls, or any other structure capable of engaging with an adjacent surface and moving forwards and rearwards along the surface. For the sake of simplicity, the motion-facilitating components may be referred to herein only in terms of rollers unless otherwise specified. The terms "front", "rear," "side", "forwardly", "rearwardly", "upwardly" and "downwardly" as used herein are intended to indicate the various directions and portions of the chair as normally understood when viewed from the perspective of a user sitting in the chair. The terms "longitudinal" and "lateral" as used herein are intended to indicate the direction of the chair from front to rear and from side to side, respectively. For the avoidance of doubt, the "rear" or "rear portion" of the seat assembly should be understood to refer to the area of the chair's seat assembly proximate to the backrest as indicated in <FIG>. The "front" or "front portion" of the seat assembly should be understood to refer of the area of the chair's seat assembly proximate to a user's knee joints when seated on the seating apparatus as indicated in <FIG>.

The present invention is directed to a weight-sensitive, reclinable seating apparatus that features a backrest pivot mechanism capable of providing a virtual pivot for the backrest that is projected above the seat surface. In preferred embodiments, the backrest pivot mechanism is positioned entirely within the seat assembly of the seating apparatus and is designed to minimize the vertical drop of the backrest during the recline motion, which in turn minimizes the seat lift during the recline motion. By minimizing the magnitude of the backrest drop and the seat lift during a recline operation, the seating apparatus of the present invention reduces the displacement of the functional pivot from the ideal pivot point as the chair reclines. Ideally, to maintain the most ergonomic relationship as possible between the seat and the backrest during reclining actions, the virtual backrest pivot should be located just behind and just below the center of an occupant's lumbar region. However, when located at this position, an occupant experiences a sensation of the backrest pivoting around their lumbar region as opposed to a natural recline sensation. Thus, in order for the occupant to experience a suitable recline sensation, the virtual pivot must be projected above the seat surface at a position between the occupant's hip joint and the occupant's lumber region. If the virtual pivot is projected to far above the seat surface, the occupant will experience a sensation of the backrest pivoting around their back. If the virtual pivot is projected too far forward, it will cause the center of gravity of the occupant's back to fall too much during reclining actions and therefore make it difficult for the occupant's weight to counterbalance the reclining force. In a particular preferred embodiment, the virtual pivot is projected <NUM> ± <NUM> above the seat surface and <NUM> ± <NUM> forward of the backrest, which is approximately <NUM>-<NUM> above and <NUM>-<NUM> behind the median user's hip joint (which itself is generally located approximately <NUM>-<NUM> above the seat surface and approximately <NUM> forward of the backrest) when the median user is seated in the chair in the upright position. Most preferably, the virtual pivot is projected <NUM> above the seat surface and <NUM> forward of the backrest. The seating apparatus preferably exhibits a front seat lift of approximately <NUM>" ±. <NUM>" and a rearward seat pitch of approximately <NUM>-<NUM> degrees between the upright position and the fully reclined position.

In embodiments exemplifying the principles of the present invention, the backrest pivot mechanism comprises a plurality of motion-facilitating components and corresponding ramps positioned within the seat assembly for providing the virtual pivot for the seating apparatus' backrest assembly. The seating apparatus beneficially takes advantage of the weight of the user to facilitate both a reclining motion and a seat lifting motion, as well as to provide for ease of return to the upright, seat lowered position. The interaction of the motion facilitating components and ramps dictate the rearward motion of the backrest and the upward motion of the seat during recline. The combination of the recline geometry with the shape and angle of the ramps is preferably calculated to cause the seated weight of the occupant to be transferred proportionally as a counter-balance to the recline force. As a seated user leans backward in the chair to recline, the load from the user's body weight transitions from being almost exclusively supported by the seat to being at least partially supported by the backrest. Thus, as the angle of the recline increases, the load (i.e., the force) being applied against the backrest increases. Accordingly, in preferred embodiments of the invention, the ramps are beneficially designed such that the gradient or incline of the ramps (referred to herein as the "ramp angle") changes as the reclining action of the chair increases to account for the increasing load exerted by the occupant's upper body as the backrest is reclined. By varying the ramp angle across the ramp's length, the seating apparatus can be optimized to offset and counterbalance the increasing force being applied to the backrest during recline so that the seating apparatus reclines in a controlled fashion. Moreover, the combination of the recline geometry with the shape and angle of the ramps is also preferably calculated to minimize the vertical drop of the backrest during the recline motion, which in turn minimizes the seat lift during the recline motion.

Referring now to <FIG>, an exemplary embodiment of a seating apparatus <NUM> (e.g., an office chair) embodying features of the present invention is depicted. The chair <NUM> comprises a base assembly <NUM>, a seat assembly <NUM>, and a backrest assembly <NUM>. The seat assembly <NUM> is mounted to the base assembly <NUM>, while the backrest assembly <NUM> is mounted to the seat assembly <NUM>.

The base assembly <NUM> may comprise any base known in the art for supporting a seat at a sufficient height for a user. In the depicted embodiment, the base assembly <NUM> comprises a base <NUM>, a plurality of casters <NUM>, and a column <NUM>. The base <NUM> comprises five legs with individual casters <NUM> pivotally attached to the distal end of each leg. The column <NUM> comprises a height-adjustable, gas cylinder attached to the center of the base <NUM> to provide a pedestal on to which the seat assembly <NUM> may be mounted. In alternative embodiments, other known base assemblies may be utilized. For example, the base assembly <NUM> of the chair <NUM> may comprise four legs, a swivel pedestal, a cantilever base, or other known base assemblies commonly used with a seating apparatus.

The seat assembly <NUM> may comprise a housing subassembly <NUM>, a connector subassembly <NUM>, a seat plate subassembly <NUM>, a shroud <NUM>, a seat casing <NUM>, and a seat <NUM>. The housing subassembly <NUM> may be mounted to the column <NUM> using a fastener or other known means in the art. A handle subassembly <NUM> may be attached to the housing subassembly <NUM> and operatively coupled to the column <NUM> to provide a means for adjusting the level of extension of the column <NUM> and, consequently, the height of the seat <NUM>. The connector subassembly <NUM> depicted in <FIG> comprises a generally L-shaped connector <NUM> and functions to connect the backrest <NUM> to the seat <NUM>. In the depicted embodiment, the vertical extension of the connector <NUM> may be partially disposed within a cavity formed within the backrest <NUM>, and the horizontal extension of the connector <NUM> may be partially disposed with the housing <NUM>. The seat plate subassembly <NUM> may be pivotally connected to the connector <NUM>, with an optional shroud <NUM> being positioned over the seat plate subassembly <NUM>. The bottom of the seat casing <NUM> may be mounted to the seat plate subassembly <NUM>, and the seat <NUM> may be mounted to the top of the seat casing <NUM>. The connector subassembly <NUM>, the housing subassembly <NUM> and the seat plate subassembly <NUM> function together to provide the pivot mechanism for the backrest assembly <NUM>.

The backrest assembly <NUM> may comprise a backrest <NUM> and optional armrests 330a, 330b attached thereto. The backrest <NUM> may be operatively coupled to the vertical extension of the connector <NUM> such that when a rearward force is applied to the backrest, it is transferred to the connector <NUM>. In certain embodiments, the backrest <NUM> is fixedly attached to the vertical extension of the connector <NUM> such that the backrest <NUM> does not pivot relative to the vertical extension of the connector <NUM>. In alternative embodiments, the backrest <NUM> may be pivotally coupled to the vertical extension of the connector <NUM>. The armrests 330a, 330b may be mounted to the left and right sides of the backrest <NUM>, respectively.

Referring now to <FIG>, embodiments of the various components of the seat assembly <NUM> are depicted. The seat apparatus <NUM> features a backrest pivot mechanism comprising a connector <NUM> that interfaces with the seat assembly's housing <NUM> via a plurality of motion-facilitating components and corresponding ramps (each motion-facilitating component/ramp pairing referred to herein as a "ramp assemblage") positioned within the seat assembly <NUM> for providing a virtual pivot <NUM> for the backrest assembly <NUM>. In the depicted embodiment, the backrest pivot mechanism comprises front, central and rear ramp assemblages, with the central and rear ramp assemblages operating in cooperation to provide the virtual pivot <NUM> for the backrest that is projected above the seat surface and forward of the backrest. The front ramp assemblage comprises right and left front glides 272a, 272b that engage right and left front housing ramps 215a, 215b. The central ramp assemblage comprises right and left central rollers 222a, 222b that engage arcuate connector ramps 255a, 255b. The rear ramp assemblage comprises right and left rear rollers 252a, 252b that engage right and left rear housing ramps 217a, 217b.

As shown in <FIG> and <FIG>, the housing subassembly <NUM> can comprise a housing <NUM>, right and left front housing ramps 215a, 215b positioned in the front portion of the housing <NUM>, right and left rear housing ramps 217a, 217b positioned in the rear portion of the housing <NUM>, a central post <NUM> positioned in the central portion of the housing <NUM>, and right and left central rollers 222a, 222b mounted to the central post <NUM>. The housing <NUM> can take the form of a generally rectangular tub defined by a bottom floor, two substantially parallel sidewalls, and a sloping front wall. Right and left front housing ramps 215a, 215b may be mounted to the front of the housing <NUM> in a position adjacent to the sloping front wall, while right and left rear ramps 217a, 217b may be mounted to the rear portion of the bottom floor of the housing <NUM>. In certain embodiments, the front and rear ramps 215a, 215b, 217a, 217b may be separate components attached to the housing <NUM> using one or more fasteners. In other embodiments, and particularly where the housing <NUM> is constructed from molded plastic, the front and rear ramps 215a, 215b, 217a, 217b may be integrally formed into the housing <NUM> during the molding process. In the particular embodiment depicted in Figure <FIG>, the front housing ramps 215a, 215b are separate components fixedly attached to the housing <NUM>, while the rear housing ramps 217a, 217b are integrally formed into the housing <NUM>.

Still referring to <FIG> and <FIG>, a central post <NUM> may be attached to, or integrally formed with, the bottom floor of the housing <NUM> at a position between the front and rear of the housing <NUM>. The central axle <NUM> may be positioned in a channel seat <NUM> (see <FIG>) formed in the central post <NUM>, with the axle cap <NUM> positioned over the front axle <NUM> to hold the central axle <NUM> in the seat <NUM>. Right and left central rollers 222a, 222b may be attached to the right and left ends, respectively, of the central axle <NUM>. In alternative embodiments, the right and left central rollers 222a, 222b may take the form of other motion-facilitating components, such as glides, spherical balls, or any other structure capable of moving forwards and rearwards along the arcuate connector ramps 255a, 255b.

The handle subassembly <NUM> may be operatively coupled to the central post <NUM> to provide a means for adjusting the level of extension of the column <NUM> and, consequently, the height of the seat <NUM>. The handle subassembly <NUM> may comprise a height adjustment pivot lever <NUM> pivotally mounted to the central post <NUM>. The second end of the pivot lever <NUM> is operatively coupled to the upper end of the column <NUM> (e.g., a gas cylinder) to selectively adjust the extension of the column <NUM>. A handle <NUM> can be attached to the first end of the pivot lever <NUM> and extend through an aperture in the housing <NUM> to allow the user to toggle the handle subassembly <NUM> and adjust the height of the chair <NUM>. A spring <NUM> can be operatively coupled to the first end of the pivot lever <NUM> to bias the pivot lever <NUM> in a first direction. A column fastener <NUM> can be utilized to secure the top end of the column <NUM> to the housing <NUM> (see <FIG>).

Referring now to <FIG>, <FIG>, and <FIG>, an embodiment of the connector subassembly <NUM> is depicted. The connector subassembly <NUM> may comprise a connector <NUM>, arcuate connector ramps <NUM>, and rear rollers 252a, 252b. As described above, the connector <NUM> may generally be L-shaped with a horizontal extension and a vertical extension. In a preferred embodiment, the L-shaped connector is a rigid member that is substantially non-deformable under forces typically encountered during the seating apparatus' use (i.e., <<NUM> lbs). Arcuate connector ramps 255a, 255b may be attached to, or integrally formed in, the front end of the horizontal extension of the connector <NUM>. The right and left rear rollers 252a, 252b may be rotatably coupled to the bottom of the connector <NUM>. In the depicted embodiment, the right and left rear rollers 252a, 252b are positioned in slots formed in the bottom portion of the connector <NUM> proximate to the rear end of the horizontal extension. The right and left rear axles 253a, 253b extend through the right and left rear rollers 252a, 252b, respectively, to rotatably mount the rollers to the connector <NUM>. The connector subassembly <NUM> is operatively coupled to the housing subassembly <NUM> by seating the right and left central rollers 222a, 222b of the housing subassembly within the right and left connector ramps 255a, 255b, respectively, of the connector subassembly <NUM>. Meanwhile, the right and left rear rollers 252a, 252b of the connector subassembly <NUM> will engage the right and left rear ramps 217a, 217b, respectively, of the housing subassembly <NUM>. Right and left connector retainers <NUM> may be utilized to assist with maintaining the coupling between connector <NUM> and the housing subassembly <NUM>.

In certain embodiments, one or more springs optionally may be attached between the connector <NUM> and the housing <NUM> to bias the seating apparatus in the upright position when the chair is unoccupied. Preferably, the seating apparatus does not rely on a spring to increase or decrease the reclining counterbalance force. Instead, the spring merely provides a secondary force to overcome the weight of the chair components and maintain an unoccupied chair in an upright position. In the depicted embodiment, right and left spring assemblies are utilized and provide approximately <NUM> lbs of recline force at the center of gravity of the occupant's back at full recline. The right spring subassembly comprises a spring piston 265a extending through a helical spring 267a. Similarly, the left spring subassembly comprises a spring piston 265b extending through a helical spring 267b. The right and left spring pistons 265a, 265b each are pivotally attached to the base of the connector <NUM> via right and left pivot rods 266a, 266b. Meanwhile, right and left spring retainers 220a, 220b may be attached to the bottom floor for coupling the distal ends of the right and left pivot rods 266a, 266b to the housing <NUM>.

Referring now to <FIG>, <FIG>, and <FIG>, an embodiment of the seat plate subassembly <NUM> is depicted. The seat plate subassembly <NUM> may comprise a seat plate <NUM>, a seat pivot <NUM>, right and left front glides 272a, 272b, and right and left seat slide bearings 277a, 277b. The seat pivot <NUM> functions to provide a means for pivotally connecting the seat pivot <NUM> to the connector <NUM>. The seat pivot <NUM> may be attached to the rear portion of the seat plate <NUM> at a first position and pivotally attached to right and left finger extensions 257a, 257b of the connector <NUM> at a second position. Right and left front glide members 272a, 272b may be attached to the front portion of the seat plate <NUM> and generally extend downward from the seat plate <NUM> such that the right and left front glides 272a, 272b engage the right and left front ramps 215a, 215b, respectively, of the housing subassembly <NUM>. In alternative embodiments, the right and left front glides 272a, 272b may take the form of other motion-facilitating components, such as rollers, spherical balls, or any other structure capable of moving forwards and rearwards along the ramps. Right and left seat slide bearings 277a, 277b may be attached to the top of the seat plate <NUM>. The seat casing <NUM> may be mounted to seat plate <NUM> by attachment to the slide bearings 277a, 277b, with the seat <NUM> attached to the seat casing <NUM>.

Referring now to <FIG>, section views of the chair <NUM> are depicted in both the upright and reclined states, showing the interaction of the connector subassembly <NUM>, housing subassembly <NUM>, and seat plate subassembly <NUM> to provide the recline mechanism of the present invention.

In the upright state depicted in <FIG>, the seat plate subassembly <NUM> (and therefore the attached seat <NUM>) is in a position generally parallel to the bottom floor of the housing <NUM>, while the vertical extension of the connector <NUM>(and therefore the attached backrest <NUM>) is in a position generally perpendicular to the seat plate subassembly <NUM> and the bottom floor of the housing <NUM>. In the upright state, the front, central and rear ramp assemblies are in the following states: the right and left front glides 272a, 272b are positioned at the rear (or bottom) portions of the right and left front housing ramps 215a, 215b; the central rollers 222a, 222b are positioned on the front portions of the right and left arcuate connector ramps 255a, 255b, respectively; and the rear rollers 252a, 252b are positioned on the rear portions of the right and left rear housing ramps 217a, 217b, respectively. In the upright state, the seat pivot <NUM> is positioned rearwardly of the central rollers 22a, 222b relative to the front of the chair <NUM>.

In the reclined state depicted in <FIG>, the vertical extension of the connector <NUM> is pushed rearwards, causing the horizontal extension of the connector <NUM> to be pushed forward relative to the housing <NUM>. As the horizontal extension of the connector <NUM> moves forward, the plurality of motion-facilitating components positioned within the seat assembly <NUM> move along the plurality of corresponding ramps. In the fully reclined state, the front, central and rear ramp assemblies are in the following states: the right and left front glides 272a, 272b are positioned at the front (or top) portions of the right and left front housing ramps 215a, 215b, respectively; the central rollers 222a, 222b are positioned on the rear portions of the right and left arcuate connector ramps 255a, 255b, respectively; and the rear rollers 252a, 252b are positioned on the front portions of the right and left rear housing ramps 217a, 217b, respectively. Through the interaction of the rollers and ramps of each of the front, central, and rear ramp assemblies, the seat plate subassembly <NUM> (and therefore the attached seat <NUM>) is pushed forward and upwards relative to the housing <NUM>.

The recline geometry and the ramp angles are optimized to minimize the vertical drop of the backrest during the recline motion, which in turn minimizes the seat lift during the recline motion. As shown in <FIG>, the virtual pivot <NUM> is projected above the seating surface and is defined by the intersection of imaginary lines extending in a perpendicular fashion from the rear housing ramps 217a, 217b and the connector ramps 255a, 255b. Point <NUM> represents the positioning of a typical user's hip joints when the seating apparatus <NUM> is in the upright position. Arc <NUM> represents the path the rearward movement of the backrest <NUM> during recline, with the left side of the arc <NUM> representing the position of the backrest <NUM> in the upright position and the right side of the arc <NUM> representing the position of the backrest <NUM> in the reclined position. Point <NUM> represents the hip pivot point of the thigh at full reline, and point <NUM> represents the hip pivot point of the back at full recline. It is preferable that the ramp angles and chair geometry are optimized to provide for points <NUM> and <NUM> to remain as close together as possible during a recline action in order to make the reclining action of the seating apparatus <NUM> have a more natural feel and avoid the common shirt-pull problem associated with many reclinable chairs. Moreover, by optimizing the recline geometry and the shape and angle of the ramps, a fully weight-sensitive seating apparatus can be provided that closely mimics the user's natural hip joint articulation during recline.

A preferred embodiment of the seating apparatus <NUM> is depicted in <FIG>. In the depicted embodiment, the right and left rear housing ramps 217a, 217b generally have a rocker-shaped (i.e., reverse camber) side profile, with the ramp angle gradually decreasing from the rear portion of the ramps 217a, 217b to the center of the ramp, and the ramp angle gradually increasing from the center of the ramp to the front portion of the ramps 217a, 217b. The connector ramps 255a, 255b generally have a J-shaped side profile, with the ramp angle gradually increasing from the rear portion of the ramps 255a, 255b to the front portion of the ramps 255a, 255b.

The rear housing ramps 217a, 217b and the connector ramps 255a, 255b collectively function to provide the virtual pivot <NUM> for the backrest assembly <NUM>. The positioning of the virtual pivot <NUM> is dictated by the ramp angles of the rear housing ramps 217a, 217b and the connector ramps 255a, 255b. Specifically, the virtual pivot <NUM> is projected above the seating surface and its location is defined by the intersection of imaginary lines extending in a perpendicular (i.e., <NUM>°) fashion from the rear housing ramps 217a, 217b and the connector ramps 255a, 255b. In the depicted embodiment, the rear housing ramps 217a, 217b and the connector ramps 255a, 255b have lengths and ramp angles optimized to provide a virtual pivot point <NUM> positioned above the seat <NUM> and forward of the backrest <NUM>. In this manner, the chair <NUM>'s reclining mechanism in preferred embodiments will function to minimize both the vertical drop of the backrest and the lifting of the seat during the recline motion, thereby providing seating apparatus that relies on the user's weight for a vast majority of the recline resistance force (i.e., greater than <NUM>% of the recline resistance force) while also maintaining the most ergonomic relationship as possible between the seat and the backrest throughout its range of motion.

In the embodiment depicted in <FIG> and <FIG>, the width of the housing <NUM> is approximately <NUM>, the length of the housing <NUM> is approximately <NUM>, and the depth of the housing <NUM> is approximately <NUM>. The distance between the central rollers 222a, 222b and the rear rollers 252a, 252b is approximately <NUM>, and the central rollers 222a, 222b are positioned approximately <NUM> above the bottom floor of the housing <NUM> as measured from the central axis of the central rollers 222a, 222b. The roller axle diameters for both the central and rear rollers is approximately <NUM>, while the rollers themselves have diameters of approximately <NUM>. As measured from the horizontal plane, the rear ends of the rear housing ramps 217a, 217b exhibit a ramp angle 217α of approximately -<NUM>°; the center of the rear housing ramps 217a, 217b exhibit a ramp angle 217β of approximately <NUM>°; and the front ends of the rear housing ramps 217a, 217b exhibit a ramp angle 217γ of approximately +<NUM>°. As measured from the horizontal plane, the rear ends of the connector ramps 255a, 255b exhibit a ramp angle 255α of approximately <NUM>°; the center of the connector ramps 255a, 255b exhibit a ramp angle 255β of approximately <NUM>°; and the front ends of the connector ramps 255a, 255b exhibit a ramp angle 255γ of approximately <NUM>°. The range of movement 217θ for the rear housing ramps 217a, 217b and the range of movement 255β for the connector ramps 255a, 255b each are approximately <NUM>° in the depicted embodiment. In alternative embodiments, the range of movement 255β for the connector ramps 255a, 255b may range from approximately <NUM>° to <NUM>° in alternatives. In the depicted embodiment, the virtual pivot <NUM> is projected <NUM> above the seat surface <NUM> and <NUM> forward of the backrest <NUM>. The median user's hip joint <NUM> is located approximately <NUM> above the seat surface <NUM> and approximately <NUM> forward of the backrest <NUM>, which positions the median's user hip joint <NUM> approximately <NUM> behind the column <NUM>. The seating apparatus preferably exhibits a front seat lift of approximately <NUM>" ±. <NUM>" and a rearward seat pitch of approximately <NUM>-<NUM> degrees between the upright position and the fully reclined position. In alternative embodiments, the angles of the central connector ramps and rear housing ramps may be modified such that the virtual pivot <NUM> is projected <NUM> ± <NUM> above the seat surface and <NUM> ± <NUM> forward of the backrest, which is approximately <NUM>-<NUM> above and <NUM>-<NUM> behind the median user's hip joint <NUM>.

The front housing ramps 215a, 215b function to control the lifting of the front portion- and thus the tilt-of the seat plate subassembly <NUM> during recline. Preferably, in the fully reclined state, the front potion of the seat plate subassembly <NUM> is lifted slightly higher than the rear portion of the seat plate subassembly <NUM>. In the depicted embodiment, the front housing ramps 215a, 215b generally have a sloped side profile, with the ramp angle gradually increasing from the rear portion of the ramps 215a, 215b to the front portion of the ramps 255a, 255b. In the embodiment depicted in <FIG> and <FIG>, and as measured from the horizontal plane, the rear ends of the front housing ramps 215a, 215b, exhibit a ramp angle 215α of approximately <NUM>°; the center of the front housing ramps 215a, 215b exhibit a ramp angle 215β of approximately <NUM>°; and the front ends of the front housing ramps 215a, 215b exhibit a ramp angle 215γ of approximately <NUM>°.

In alternative embodiments, the ramp angles can vary according to various factors, including the sizing of the various components, the recline geometry, and the resistance provided by the friction introduced by the interaction of the motion facilitating components and the ramps. Because the load (i.e., the force) being applied against the backrest increases as the angle of the recline increases, the ramp angles of the rear housing ramps <NUM>, connector ramps <NUM>, and front housing ramps <NUM> preferably will vary across its length. The shape of the ramps and the motion-facilitating components may also vary. In certain embodiments, the ramps may by substantially linear in shape and the motion-facilitating components be nonuniform in shape. For example, the motion-facilitating components may take the form of substantially oval-shaped rollers. In so further embodiment, the rollers may be spherical, but the ramps may have varying shapes (e.g., partially linear and partial curved), thereby allowing varying lift motions. The motion-facilitating component may take on a variety of forms. For example, the component could be in the form of a roller shaped like a wheel. In one preferred embodiment, the rollers are spherical in nature. Such an embodiment is particularly beneficial for providing stability to the apparatus. The spherical shape increases the surface area of the roller in contact with the ramp, particularly when the ramp comprises a track having a concave shape (e.g., a valley running in the direction of travel) corresponding to the spherical rollers, thereby being particularly adapted for receiving the rollers. Accordingly, the roller becomes self-centering in the track and avoids drifts. Of course, other embodiments of the motion-facilitating components are also encompassed by the invention. For example, the motion-facilitating components could include stationary low-friction glides or ball bearings.

The rollers can be formed from metal or polymeric materials. In certain embodiments, the rollers are formed of low friction, high strength polymeric material, such as polytetrafluoroethylene (PTFE). In further embodiments, the rollers comprise elastomeric materials, such as urethanes, which soften the action of the rolling movement across the ramps, thereby providing a smooth action. The ramps are similarly preferably formed of a material providing strength, durability, and, preferentially, reduced friction during interaction with the rollers. Exemplary materials for use in the ramps include, but are not limited to, high density polyethylene, high density polypropylene, PTFE, and the like.

Claim 1:
A reclinable seating apparatus (<NUM>), comprising:
(a) a seat assembly (<NUM>) comprising a seat housing (<NUM>) and a substantially planar seat plate (<NUM>);
(b) a backrest recline mechanism comprising:
(i) a connector (<NUM>) having a horizontal extension and a vertical extension;
(ii) a central ramp assemblage for operatively coupling the horizontal extension of the connector (<NUM>) to a central portion of the seat housing (<NUM>), wherein the central ramp assemblage comprises: one or more connector ramps (<NUM>) positioned on a front portion of the horizontal extension of the connector (<NUM>); and one or more central rollers (<NUM>) attached to a central post (<NUM>) extending vertically from a floor of the seat housing (<NUM>), wherein the one or more central rollers (<NUM>) operatively engage the one or more connector ramps (<NUM>), and wherein the one or more connector ramps (<NUM>) each have a J-shaped side profile and a ramp gradient defining a connector ramp angle, wherein the connector ramp angle gradually increases from a rear end of each ramp (<NUM>) to a front end of each ramp (<NUM>); and
(iii) a rear ramp assemblage for operatively coupling the horizontal extension of the connector to a rear portion of the seat housing, wherein the rear ramp assemblage comprises: one or more rear housing ramps (<NUM>) positioned on a rear portion of the seat housing (<NUM>); and one or more rear rollers (<NUM>) attached to a bottom portion of the horizontal extension of the connector (<NUM>), wherein the one or more rear rollers (<NUM>) operatively engage the one or more rear housing ramps (<NUM>);
(c) a backrest assembly (<NUM>) attached to the vertical extension of the connector (<NUM>); and
wherein:
a rear portion of the seat plate (<NUM>) is pivotally attached to the connector (<NUM>) and a front portion of the seat plate (<NUM>) is operatively coupled to a front portion of the seat housing (<NUM>), characterized in that the front portion of the seat plate (<NUM>) is operatively coupled to the front portion of the seat housing (<NUM>) via a front ramp assemblage.