This invention relates to an office-type chair, and more specifically relates to a synchrotilt mechanism having an improved tilt tension mechanism coupled to the seat and back of the chair.
Office chairs conventionally provide some type of rearward tilting movement. In its simplest variations, the rear tilting involves solely the back, or the seat and back as a unitary construction. To provide improved and more desirable tilting movement and seating comfort, however, many office-type chairs employ a synchrotilt mechanism coupled between the chair base and the seat-back assembly, for permitting the seat and back to simultaneously tilt at different rates, with the tilt rate and maximum tilt angle of the back typically being about twice the tilt rate and maximum tilt angle of the seat.
Chairs employing synchrotilt mechanisms for permitting simultaneous but relative tilting of the seat and back are well known, and numerous mechanisms have been developed for performing this function. Additionally, such synchrotilt mechanisms include a subassembly, namely a tilt tension mechanism that includes a resilient biasing arrangement which permits rearward tilting or reclining of the seat and back while generating a resilient restoring force to bias the seat and/or back upwardly or forwardly to a normal, unreclined position. Known biasing arrangements typically include a spring mechanism such as a coil spring or torsion bar which provide the resilient restoring force.
For those types of chairs having a torsion bar, such torsion bars typically include an arm projecting radially therefrom which is swingable circumferentially about an elongate axis of the torsion bar. This drive arm controls the deflection within the torsion bar, and as such, the amount of displacement of the drive arm controls the restoring force. Known chair arms have used various drive mechanisms for displacing the drive arm pursuant to a manual actuator that is controlled by the chair occupant.
For example, U.S. Pat. No. 5,772,282 (Stumpf et al.) discloses a driving arrangement having a upwardly extending threaded drive shaft which is rotatably mounted to a control body of the tilt tension mechanism. A block member engaged with the distal end of the radial arm of a torsion spring moves up and down the threaded shaft in response to rotation thereof. The mechanism of the '282 patent includes a bevel gear on the upper end thereof which cooperates with a cooperating bevel gear that meshes therewith and is driven by a rotatable handle.
The invention relates to a chair having an improved drive mechanism for driving the drive arm of a torsion bar by manual rotation of an actuator handle. The tilt tension mechanism of the invention includes a threaded drive shaft rotatably mounted on the control body of the tilt tension mechanism and a follower nut which rides vertically along the drive shaft in response to shaft rotation.
To drive the shaft, an improved gear drive arrangement is provided comprising a drive gear and a sidewardly-oriented actuator shaft having a pinion section with spiral threads thereon which mate with corresponding spiral gear teeth on the face of the drive gear. Rotation of the actuator shaft effects rotation of the drive gear, and the gear and pinion have a spiral teeth arrangement to provide continuous engagement between multiple teeth in an effort to reduce tooth stress and loading, reduce backlash and improve the overall operation of the gear drive.
Other objects and purposes of the invention will be apparent to persons familiar with constructions of this general type upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience in reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. These latter terms will also refer to the normal directions and positional orientations associated with a person sitting in the chair. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the chair and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.
Referring to
The seat assembly 18 includes a rigid seat frame or cradle 21 defined by a generally rectangular ring-shaped top frame 22 (
The seat assembly 18 defines thereon an upper seat cushion 28 disposed for contacting engagement with a chair occupant. The seat cushion 28, when engaged with a seated occupant, resiliently deforms downwardly so that the upper surface thereof, at least in the main central region of the cushion 28 where engaged with the occupant, is deflected downwardly from the non-deformed position indicated in
The back assembly 19 is supported on a generally rigid upright structure 31 which is defined by a pair of generally parallel and sidewardly positioned L-shaped side upright elements or members 32, each of which has a lower lever arm portion 33 positioned below the seat cushion 28 and which, at a rearward end, is joined through an integral bend to an upper arm portion 34 which is cantilevered upwardly and has the back assembly 19 mounted thereon. The sidewardly spaced uprights 32 are, adjacent the lower ends of the upper arm portions 34, rigidly joined by a cross member 35 extending therebetween.
The forward ends of the lower lever arm portions 33 are nonrotatably connected to a tilt shaft 42 which defines a rotational axis 43 extending generally horizontally in transverse relationship relative to the seat assembly 18. The tilt shaft 42 is rotatably supported within a housing or support arm 41 which is fixed to the upper end of the height-adjusting pedestal 13, with the housing 41 being cantilevered forwardly from the pedestal so that the tilt shaft 42 is positioned under but more closely adjacent the front edge of the seat surface.
The tilt shaft 42 projects outwardly through openings 44 (
Referring to
This torsion bar 51, as it projects outwardly from opposite sides of the drive arm 52, has an interior bar 53 telescoped within the interior of coaxially aligned shaft segments 56 which define the main tilt shaft 42, wherein the bar 53 is resiliently connected to the shaft segments 56 to permit relative rotation between the shaft segments 56 and the bar 53 with the resilient restoring force resisting this relative rotation.
The shaft segments also have radially-projecting stop members or projections 60 fixed thereto and cooperating with opposed stops (not shown) associated with the control housing 41 for defining the permissible angle of movement of the shaft 42 and of the back arrangement 19 as coupled thereto through the upright structure 31. The shaft segments 56 further include radially-projecting connector brackets 61 disposed outside of the control housing 41 which connect to the forward ends of the lower lever arm portions 33 such that rearward tilting of the back assembly 19 effects rotation of the shaft segments 56 relative to the interior bar 53 resiliently connected thereto. Thus, the resilient restoring force of the torsion bar 51 applies the restoring force to the upright structure 31 to resist rearward tilting or reclining of the back assembly 19 and return the back assembly to the initial unreclined position generally illustrated in
To adjust the magnitude of the restoring force, the gear drive mechanism 55 is connected to the outer, free end 63 of the radial drive arm 52. By displacing the drive arm 52 upwardly or downwardly, the relative position of the interior bar 53 relative to the shaft segments 56 is adjusted which thereby adjusts the restoring force in direct relation to the resiliency of the resilient connection between the bar 53 and the shaft segments 56. The gear drive mechanism 55 generally is manually actuatable by the chair occupant to effect this adjustment of the drive arm 52.
More particularly as to the gear drive mechanism 55, this mechanism includes a main upright drive shaft 65 having a lower end 66 rotatably connected to the control housing 41 and an upper end 67 projecting upwardly therefrom. Referring to
The drive shaft 65 projects vertically and includes a threaded section 72 with circumferential threads that extends along a substantial intermediate portion of the shaft length. The threaded section 72 has a block-like follower nut 74 which is formed with an internal threaded bore that is threadedly engaged with the threads 73 of the threaded section 72. The follower nut 74 travels upwardly and downwardly along the threaded section 72 in response to controlled rotation of the drive shaft 65.
Referring to
As to the control housing 41, this housing further includes a top plate 78 which is rigidly affixed to and overlies the open interior 47 of the control housing 41. The top plate 78 includes a downwardly-curving arcuate front portion 79 which is adapted to fit over the torsion bar 51 and secure the torsion bar 51 in position. The top plate 79 includes semi-circular side portions 80 in the sides thereof which define the upper halves of the openings 44 wherein the opposite ends of the torsion bar 51 project outwardly therefrom.
The front portion 79 as illustrated in
To accommodate the gear drive mechanism 55, the side wall of the control housing 41 includes an actuator shaft notch 87, while the top plate 78 includes a circular opening 88. Still further, the top plate 78 has downwardly projecting connector blocks 89 which are each adapted to engage a pair of fasteners 90 as generally illustrated in
Referring more particularly to the gear drive mechanism 55, this mechanism generally comprises a face-type, drive gear 90 and an actuator shaft 91 which shaft 91 extends sidewardly and is rotated manually to effect driving rotation of the face gear 90. The gear 90 further is coupled to and rotatably drives the drive shaft 65 to effect adjustment of the torsion bar 51.
More particularly, the gear 90 as illustrated in
Additionally, the gear 90 includes a mounting hub 100 which projects from the primary gear face 92 and includes a circular outer circumference 101. A central opening 102 extends vertically through the entire thickness of the gear 90 including the mounting hub 100 to permit engagement with the drive shaft 65. More particularly, the central opening 102 includes arcuate portions 103 which essentially define opposite sides of a circle which said circle has a diameter slightly larger than the outer diameter of the upper end 67 of the drive shaft 65 so as to snugly receive the drive shaft 65 therein. As such, the upper shaft end 67 slidably fits within the central opening or passage 102.
To define a non-rotatable connection between the drive shaft 65 and the mounting hub 100, the central opening 102 includes flat lands 104 which flat lands are adapted to abut against a pair of flats 105 (
Additionally to secure the gear 90 to the top plate 78, the mounting hub 100 also includes squared vertical channels 106 which extend vertically along the length of the opening 102 and open interiorly or sidewardly into the opening 102. A channel 106 is located between each pair of flat lands 104.
The gear 90 is rotatably mounted to the top plate 78 by a plastic isolator bushing 108 (
The hub portion 109 also includes a pair of cantilevered, resiliently flexible connector fingers 111 which project downwardly away from the opening 88 and are received axially within the channels 106 of the gear 90. The lowermost ends of the connector fingers 111 include radial projections 112 (
Since the gear 90 rotates relative to the top plate 78, a low-friction thrust washer 113 is supported within the gear recess 99 so as to be sandwiched between the bearing face 98 and the opposing lower surface 78A of the top plate 78.
Additionally, an arcuate, plate-like isolator bearing 114 also is positioned or sandwiched between the bearing face 98 and the opposing surface 78A of the top plate 78 near the outer gear circumference 94. The isolator bearing 114 is located in the right rear quadrant of the gear 90. This isolator bearing 114 is located directly below the engagement location between the gear 90 and the actuator shaft 91 as will be discussed in further detail herein to thereby provide low-friction, vertical support to the bearing face 98 and help maintain the outer circumference of the gear 90 in engagement with the actuator shaft 91. The bearing 114 is made of a suitable low-friction material.
When the top plate 78 is mounted in position on the control body 41, the gear mounting hub 100 slips downwardly onto the upper end 67 of the drive shaft 65 wherein rotation of the gear 90 effects a corresponding rotation of this drive shaft 65. However, since the top plate 78 is fixed to the control body 41, it is not necessary to permanently fasten the gear 90 to the shaft 65 wherein the gear 90 therefore is removable in unison with the top plate 78.
More particularly as to the actuator shaft 91, this actuator shaft 91 also is mounted to the top plate 78 as illustrated in
The outer circumference 121 effectively defines an axle by which the gear section 116 may be rotatably supported on the top plate. In this regard, a generally U-shaped clamp bracket 122 fits over the outer gear end 119 and is fixed to one of the connector blocks 89 of the top plate 78 by a pair of the above-described fasteners 90.
The gear section 116 further includes a reduced diameter section 123 which defines an additional axle section that is rotatably mounted on the top plate 78 by a further clamp bracket 124 which said clamp bracket 124 is affixed to the other connector block 89 by a respective pair of fasteners 90. The annular shaft wall 125 defining the side of the reduced diameter portion 123 effectively defines a stop that abuts against an adjacent edge of the clamp bracket 124 and prevents inward movement of the actuator shaft 91.
The gear section 116 also includes a threaded section 126 which has an increased diameter relative to the outer section end 119 to effectively define an additional stop surface that faces axially and abuts against the adjacent clamp bracket 122 to prevent inward displacement of the shaft 91.
More particularly as to the threaded section 126, this section has spiral gear teeth extending circumferentially around the entire circumference of the threaded section 126 which gear teeth have a spiral shape and mate with the corresponding spiral gear teeth 93 formed on the gear 90. As to the formation of the individual gear teeth, these gear teeth are formed by annular grooves extending about the circumference thereof with each groove defining opposed gear faces 130 and 131 as seen in
During assembly, the gear 90 is rotatably mounted on the top plate 78 by the bushing 108 and thereafter the actuator shaft 91 is rotatably mounted in place by the clamp brackets 122 and 124. It is noted that the isolator bearing 114 is located generally above the pinion gear section 116 to accommodate any vertically directed forces acting on the outer gear circumference 94 as a result of the meshing engagement of the gear teeth on the pinion gear section 116 with the spiral gear teeth 93.
The top plate assembly then is mounted in place on the control body 41 with the gear 90 being fitted downwardly onto the upper end 67 of the drive shaft 65. With this arrangement, during operation, the actuator shaft 91 is manually rotated to effect driven rotation of the shaft 65 and move the torsion bar drive arm 52 upwardly or downwardly.
The biasing mechanism 46 represents one arrangement for effecting biasing of the chair into its normal upright position. It will be recognized that other biasing mechanisms employing other types of spring devices such as coil springs are well known and hence could be usable with the chair of the present invention. For example, the legs of coil springs could cooperate with the follower nut 74 to adjust the deflection thereof and thereby adjust the restoring force.
Although a particular preferred embodiment of the invention has been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention.
Number | Date | Country | |
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60571231 | May 2004 | US |