A synchronous-tilt reclining office chair includes a seat, a backrest interconnected to the seat, and an arrangement providing a synchronous-tilt mechanism that controls synchronous movement of the backrest and seat between a normal non-reclined position and a reclined position. Recline tension provided by the arrangement is a function of a force required to compress at least one tensioning spring mounted below the seat, a weight applied on the seat by a seat occupant, and a location of the weight on the seat relative to front and rear portions of the seat, whereby, as the weight is applied toward the front portion of the seat, recline tension is reduced and, as the weight is applied toward the rear portion of the seat, recline tension is increased.

BACKGROUND

The present invention relates to chairs, such as task and side office chairs, and more particularly, to an office chair that can be reclined.

Office chairs are known to include a seat, a reclinable backrest, and a mechanism that enables synchronous movement of the seat with the backrest as the backrest is reclined from a generally upright position or returned to the upright position from a reclined position. Recline tension provided by the chair may be automatically set as a function of a weight applied to the chair by the occupant seated in the chair. Thus, when a person is sitting with good posture, and at their healthiest position for maximum core strength, the recline tension is set in balance with the occupant's weight. This automatic weight-sensing feature eliminates the need to manually adjust tension each time a different user sits in the chair. Accordingly, the chair may be automatically tensioned correctly for each occupant.

An occupant of a chair may assume a sitting position with a relatively poor posture (i.e., may be slid forward in the seat in a relatively slouched position). This is generally considered an unhealthy sitting position. A problem in particular with a slouched seating position in a reclinable chair that automatically adjusts recline tension based on occupant weight is that the automatically adjusted recline tension necessarily applies a relatively high amount of pressure on the lower back when the occupant attempts to recline the chair. This provides risk for injury.

The above referenced weight sensing chairs typically use some form of a parallelogram, or four-bar linkage, to raise and lower the seat. Thus, as the backrest is caused to be moved to a reclined position, the front and rear of the seat may be caused to move upward. However, this results in a further problem in that lifting of the front of the seat may impinge upon the underside of the occupant's knee and restrict blood flow to the legs of the occupant to some extent.

Accordingly, a self-tensioning reclinable office chair that addresses at least some of the above referenced problems is desired.

SUMMARY

According to an embodiment, a chair is provided having a seat base, a backrest interconnected to the seat base via a hinge connection and movable relative to the seat base about a backrest pivot axis between a normal non-reclined position and a reclined position, and a seat supported on the seat base and having a rear portion adjacent the backrest and a front portion defining a front edge of the seat. The rear portion of the seat is interconnected to the backrest via a hinge connection such that as the backrest is pivoted to the reclined position, the rear portion of the seat pivots relative to the backrest of the seat and is elevated. The front portion of the seat is interconnected to the seat base via a hinge connection such that the seat is movable about a seat front pivot axis and such that as the backrest is pivoted to the reclined position and the rear portion of the seat is elevated, the seat pivots about the seat front pivot axis thereby causing the front edge of the front portion of the seat to be lowered.

The chair may include a tensioning spring, a plunger for engaging the tensioning spring, and a front support bar that interconnects to the plunger and defines the seat front axis pivot axis about which the seat pivots. The tensioning spring may be mounted on the seat base beneath the seat such that a rear end of the tensioning spring is mounted to the seat base in a stationary position relative to the seat base. The front support bar extends within at least one slot formed by the seat base such that, as the backrest is pivoted to the reclined position, the rear portion of the seat is elevated, and the front portion of the seat is lowered, the front support bar moves to a rearward location within the at least one slot causing the plunger to compress the at least one tensioning spring.

According to an embodiment, recline tension provided by the chair is a function of a force required to compress the at least one tensioning spring mounted below the seat, a weight applied to the seat by a seat occupant, and a location of the weight applied to the seat relative to front and rear portions of the seat. Accordingly, as the weight is applied toward the front portion of the seat (such as by an occupant in a slouched seated position), the recline tension is reduced and, as the weight is applied toward the rear portion of the seat (such as by an occupant seated in an upright position with good posture), recline tension is increased.

DETAILED DESCRIPTION

A chair10, which may be a task office chair, is shown inFIGS.1and2. The chair10includes a seat12and a backrest14. In addition, for this embodiment, the chair10includes armrests16and support structure18including a central support post20and four lower legs22each having a wheel24.

The chair10can be positioned in an upright position (as shown in dark grey inFIGS.1and2) and a reclined position (as shown in light grey inFIGS.1and2). This can be accomplished by the seated occupant leaning backward against the backrest14of the chair10to exert a force on the backrest14that is sufficient to cause the backrest14to pivot in a rearward direction. The recline motion provided by chair10is capable of being started with ease and can stop softly for every sized person and can provide fluidic, responsive movement.

InFIG.1, the occupant26of the chair is seated upright with good posture in the chair10, and inFIG.2, the occupant26is shown slouched within the chair in relatively poor posture. Accordingly, as shown inFIGS.1and2with the designation “KG”, the weight (i.e., center of gravity) of the occupant26applied to the chair10is applied to the rear portion28of the seat12inFIG.1, whereas the weight (i.e., center of gravity) of the occupant26is centered and applied on the front portion30of the seat12inFIG.2.

According to an embodiment, the chair10is configured to provide synchronous-tilting that not only is able to account for the occupant's weight applied to the seat12, but also able to account for the occupant' posture in the chair10to automatically adjust recline tension. Here, recline tension refers to the amount of force required to be applied to the backrest by the occupant of the chair to cause the backrest to recline. Recline tension must be sufficiently strong so as to prevent unwanted recline movement by an upright seated occupant.

By way of example, for a given occupant of a given weight, recline tension is automatically set at an appropriate level (i.e., a level that prevents unintended reclining, but that is not too strong as to cause injury to an occupant attempting to recline the chair) based on occupant weight when the occupant has good upright seating posture as shown inFIG.1. This is accomplished by a synchronous-tilt configuration that takes into account the weight of the occupant and that the weight of the occupant is being applied essentially to the rear portion28of the seat12. However, if the same occupant (i.e., the same weight is being applied to the seat) assumes a slouched position on the chair10as shown inFIG.2and the weight of the occupant is shifted and applied to the front portion30of the seat12, recline tension is automatically reduced by chair10. For instance, see arrow32inFIG.1which shows that the reline tension is relatively high for the occupant seated with good posture, and see the arrow34inFIG.2which shows that recline tension is relatively less when the same occupant (i.e., of the same weight) is seated with poor posture.

Thus, when the occupant26is sitting with good posture, at a healthy position for maximum core strength, the recline tension provided by the chair10is automatically set to appropriately balance recline tension with occupant weight. This weight-sensing feature does not require manual recline tension adjustment and is automatically tensioned correctly for each user.

In comparison, when the occupant26is sitting with poor posture (i.e., slid forward in the seat and slouched), the occupant26is considered to be at a relatively unhealthy sitting position. If recline tension remains the same for the same occupant seated as shown in bothFIGS.1and2, too high an amount of pressure will be exerted on the lower back of the occupant inFIG.2when the occupant attempts to recline the chair. Thus, according to an embodiment, the amount of recline tension provided by the chair10automatically decreases as the occupant's weight is shifted forward on the seat12. This reduces pressure applied to the occupant's lower back upon recline and thereby reduces risk of injury.

Accordingly, the chair10provides seating that is healthy even when users or occupants slouch throughout the day. In addition, the above referenced feature results in providing the occupant with subtle feedback to which the occupant can react. For instance, as recline tension drops, the occupant's reaction is typically to scoot back in the seat thereby promoting and creating a more upright and healthy posture.

Further, the motion of the seat12when the backrest14is reclined, relieves pressure under the legs of the occupant behind his/her knees to prevent any restriction of blood flow to the legs. For instance, as shown inFIG.3, when the chair10is an upright, normal, or non-reclined position (as shown in dark grey inFIG.3), the front edge36of the seat12is higher in elevation then when the chair10is in a reclined position (as shown in light grey inFIG.3). Thus, this automatic drop in elevation of the front edge36of the seat12during recline, relieves pressure under the legs of the occupant supported on the front edge36.

According to an embodiment, the recline tension of the chair10is controlled by the amount of weight being applied to the seat12and where on the seat12the weight is being applied (i.e., toward the rear or front of the seat12) along with a force provided by a helper or tensioning spring38. For instance, as shown inFIG.4, when the weight is applied over the rear portion of the seat12, recline tension is relatively high (see arrow40). In contrast, when the same weight is applied over the center of the seat12, recline tension becomes relatively less (see arrow42), and when the same weight is applied over the front portion of the seat12, recline tension is further reduced (see arrow44).

In comparison, weight sensing chairs using some form of a parallelogram, or four-bar linkage46, to raise and lower the seat is shown inFIG.5. When the weight of the occupant is centered over the rear portion of the seat, the center of the seat, or the front portion of the seat, reline tension (see arrows48,50and52) remains the same for the same occupant weight. Also, the front edge of the seat inFIG.5is raised when the backrest is reclined and thereby undesirably exerts pressure under the legs of the occupant which can restrict blood flow to the legs of the occupant.

A sliding-block linkage54according to an embodiment is shown inFIG.4. The sliding block linkage54includes a front pivot point or axis56that remains fixed in height from the floor on which the chair10is supported. Accordingly, the seat front edge36(i.e., the part of the seat at or extending forward of the front pivot point56) is not lifted or elevated during incline. The front edge36of the seat12forward of the front pivot point56lowers or drops in elevation when the backrest14is reclined and thereby automatically relieves pressure behind the knees of the occupant.

As shown inFIG.4, as the backrest14is rotated rearward (see arrow58), the angle of the seat12changes (i.e., it tilts about the front pivot point or axis56). Thus, the seat12lifts in the rear and drops in the front. In addition, the further the occupant's weight (i.e., center of gravity) is located rearward on the seat12, the higher the amount of recline tension will be automatically generated by the chair10to balance the backrest14.

An embodiment of a side office chair100is shown inFIGS.6A-9C. As best shown inFIG.6A, chair100includes a seat102, a backrest104, and four legs106, one at each corner of the seat102. In addition, as best shown inFIGS.6B and6D, the seat102includes an upper seat section110providing a seating surface108and a lower seat section or seat base112.

FIGS.6A and6Bshow the chair100in an upright, normal, non-reclined position. In contrast,FIGS.6C and6Dshow the chair100in a reclined position. The legs106and the seat base112remain stationary regardless of the chair100being in the non-reclined or reclined position. As best shown inFIG.6B, in the recline position, the backrest104pivots rearward and the upper seat section110moves such that the rear of the upper seat section110is lifted upward and the front edge114of the upper seat section drops slightly in elevation.

The mechanism116includes a pair of tensioning springs118contained within the seat102. The springs118extend parallel to each other and in a direction from front-to-back of the chair. The rear of the springs118are mounted in a stationary position to the seat base112and the front of springs118interconnect to a bar120or the like extending in front of and perpendicular to the springs118. A tensioning screw122is connected to the bar120and permits some manual fine adjustment to the amount of recline tension provided by the mechanism116.

The mechanism116defines a seat front pivot axis124about which the upper seat section110pivots relative to the stationary seat base112adjacent the front of the seat102, a seat rear pivot axis126about which the rear of the upper seat section110pivots relative to the backrest104, and a stationary backrest pivot axis128about which the backrest104pivots.

The bar120can define the seat front pivot axis122and hinge connection used to connect the upper seat section110to the seat base112. The opposite ends of the bar120can extend within relatively short travel slots130. Accordingly, as shown inFIG.7B, the seat front pivot axis124is located forward within the travel slot130when the chair100is in the normal, non-reclined position, and as shown inFIG.7D, the seat front pivot axis124is located rearward in the travel slot130when the chair100is in the recline position. With this mechanism or arrangement116, the recline tension automatically increases when occupant weight increases and reduces when occupant weight decreases. In addition, the recline tension automatically reduces when an occupant slouches forward in the chair100such that occupant's weight (i.e., center of gravity) is centered over a forward part of the seat102as discussed above.

FIGS.8A and8Bshow a cross-section of the chair100in a normal, non-reclined position and in a reclined position. The springs118are acted upon by a plunger132interconnected to the bar120. When the chair100is in the non-reclined position of the chair100(seeFIG.8A), the plunger132presses against the springs118, and when the chair100is in the reclined position (seeFIG.8B), the plunger132is forced further toward the springs118to further compress the springs118. This force combined with the occupant's weight and occupant's position on the seat defines the sets tension. As the backrest104is pivoted rearward about the stationary backrest pivot axis128, the rear of the upper seat section110becomes elevated as is the seat rear pivot axis128and the springs118become compressed. In addition, the front edge114of the upper seat section110is lowered as the upper seat section110pivots about the front seat pivot axis124. The force of the springs118position the chair100in the normal, non-reclined position when there is no occupant in the chair or when the occupant no longer leans rearward in the chair.

FIG.9Ashows the upper seat section110in the non-reclined position. The upper seat section110provides an upper covering for the seat102and moves as discussed above.FIG.9Bshows the mechanism116with the upper seat section110removed and with the chair in the normal, non-reclined position.FIG.9Cshows the mechanism116with the upper seat section110removed and with the chair100in the reclined position. By comparingFIGS.9B and9C, it is shown that the backrest104pivots about the stationary backrest pivot axis128and that the rear of the upper seat section110is connected to and pivots relative to the backrest104about the seat rear pivot axis126and is thereby elevated when the chair100is reclined. In addition, it is shown that the seat front pivot axis124travels rearward in the travel slot130during chair recline, but remains at about the same height above the floor. Thus, the upper seat section110pivots about the seat front pivot axis124and therefore the front edge114of the upper seat section110drops in elevation during chair recline. Also, due to the rearward movement of the seat front pivot axis124, the springs118(which are mounted in a stationary position to the seat base112) become further compressed as the chair is reclined and provides a force in an opposite direction that urges the seat front pivot axis toward the front of the travel slot130.

An embodiment of a task office chair200is shown inFIGS.10A-13C. As best shown inFIG.10A, chair200includes a seat202, a backrest204, armrests206, a central support post208that extends to at least four legs210having wheels212. In addition, as best shown inFIGS.10B and10D, a seat support plate or seat base214is connected to the upper end of the support post208.

FIGS.10A and10Bshow the chair200in an upright, normal, non-reclined position. In contrast,FIGS.10C and10Dshow the chair200in a reclined position in which the backrest204is pivoted rearward and the rear of the seat202elevates while front edge216of the seat202drops slightly in elevation.

As shown inFIGS.12A and12B, the mechanism218includes a pair of tensioning springs220contained on the seat base214. The springs220extend parallel to each other and in a direction from front-to-back of the chair200. The rear of the springs220are mounted in a stationary position on the seat base214and the front of the springs220interconnect via a plunger224to a bar222or the like extending in front of and perpendicular to the springs220. A tensioning screw234can be connected to the bar222to permit some manual fine adjustment to the amount of recline tension provided by the mechanism218.

The mechanism218defines a seat front pivot axis226about which the seat102pivots adjacent the front of the seat102, a seat rear pivot axis228about which the rear of the seat102pivots relative to the backrest204, and a stationary backrest pivot axis230about which the backrest204pivots.

The bar222can define the seat front pivot axis226and provide a hinged connection. The ends of the bar222can extend within a relatively short stationary travel slots132. Accordingly, as shown inFIG.11B, the seat front pivot axis226is located forward within the travel slots232when the chair is in the normal, non-reclined position, and as shown inFIG.11D, the seat front pivot axis226is located rearward in the travel slots232when the chair200is in the recline position. With this mechanism218, the recline tension automatically increases when occupant weight increases and reduces when occupant weight decreases. In addition, the recline tension automatically reduces when an occupant slouches forward in the chair200such that occupant's weight is centered over a forward part of the seat202as discussed above.

FIGS.12A and12Bshow a cross-section of the chair200in a normal, non-reclined position and in a reclined position. The springs220are acted upon by the plunger224that is interconnected to the bar222. When the chair200is in the non-reclined position (seeFIG.12A), the plunger224lightly press against the springs220, and when the chair200is in the reclined position (seeFIG.12B), the plunger224is forced further toward the springs220to compress the springs220. The force generated by the springs220combined with the occupant's weight and occupant's position on the seat102automatically adjusts the recline tension. As the backrest204is pivoted rearward about the stationary backrest pivot axis230, the rear of the seat202is elevated as is the seat rear pivot axis228and the springs220become compressed. In addition, the front edge216of the seat202is lowered as the seat202pivots about the front seat pivot axis226. The force of the springs220position the chair in the normal, non-reclined position when there is no chair occupant or the occupant ceases to lean rearward in the chair.

FIG.13Ashows a top of the seat202in the non-reclined position.FIG.13Bshows the mechanism218beneath the seat202and with the chair200in the normal, non-reclined position.FIG.13Cshows the mechanism218beneath the seat202and with the chair200in the reclined position. By comparingFIGS.13B and13C, it is shown that the backrest204pivots about the stationary backrest pivot axis230and that the rear of the seat202is connected to and pivots relative to the backrest204about the seat rear pivot axis228and is thereby elevated when the backrest204is reclined. In addition, it is shown that the seat front pivot axis226travels rearward in the travel slots232during chair recline, but remains at about the same height above the floor. Thus, the seat202pivots relative to the seat front pivot axis226and therefore the front edge216of the seat202drops in elevation during chair recline. Also, due to the rearward movement of the seat front pivot axis226, the springs220(which are mounted in a stationary position to the seat base214) become compressed as the chair200is reclined and provides a force in an opposite direction that urges the seat front pivot axis226toward the front of the travel slots232.

The task chair200may be provided with additional features. A handle underneath the seat may be provided to enable the seat to be slid forward for manual seat depth adjustment. Thus, as needed by the end user, the seat can be positioned closer to or further away from the backrest. In addition, a further handle located underneath the seat may adjust the chair height, (i.e., to effectively increase or decrease the length of the support post). These handles may be on opposite sides of the seat underneath the seat. Further, the arm rests may be adjustable so that they can be raised and lowered in height via a trigger under the arms of the arm rests.

The various components described above may be made of metallic, non-metallic, wooden, plastic, resins, composite, fabric or like materials. The above description illustrates embodiments of how aspects of the present invention may be implemented, and are presented to illustrate the flexibility and advantages of particular embodiments as defined by the following claims, and should not be deemed to be the only embodiments. One of ordinary skill in the art will appreciate that based on the above disclosure and the following claims, other arrangements, embodiments, implementations, and equivalents may be employed without departing from the scope hereof as defined by the claims.

Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims.