This invention relates to a chair control and to a spring tensioner for a chair control.
A chair control may have a main frame, a seat bracket, and a back bracket. The main frame may be configured for mounting on a seat post and may support the seat bracket. A chair seat may be attached to the seat bracket and a chair back rest may be attached to the back bracket. The back bracket may be hinged to the seat bracket, and a main spring may act between the main frame and the back bracket in order to bias the back bracket toward a rest position. In a typical configuration, the main spring is a helical spring housed in a cylindrical, downwardly projecting, stub of the main frame. A hand wheel extends below the cylindrical stub. When a chair occupant leans back in the chair, the back bracket will pivot against the urging of the main spring so that the back rest tilts backwards. Rotation of the handwheel in one direction compresses the spring in order to increase the urging force applied by the spring. Thus, the occupant can set the force with which the main spring resists tilting of the backrest by turning the handwheel.
This invention seeks to provide an improved mechanism.
A chair control has a threaded element with a thread extending along an axis. A retainer limits axial freedom of the threaded element and a user control rotates the threaded element. A spring backstop is threaded to the threaded element and a spring with a projection has this projection stopped against the spring backstop.
In another aspect of the invention, a spring tensioner for a chair control mechanism has a hand crank, a worm gear rotated by the hand crank, a pinion and captive bolt rotated by the worm gear, a retainer limiting axial freedom of the bolt, and a spring backstop threaded to the bolt.
Other features and advantages of the invention will become apparent from the following description in conjunction with the drawings.
In the figures which illustrate an example embodiment of the invention,
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The back bracket 16 may be pivotably joined to the main frame by shaft 26. A number of user controls may extend from the main frame, namely a spring tension hand crank 30, a gas control paddle 32, and a backrest tilt lock control 34. As is apparent, the paddle 32 may extend from a cylindrical sleeve 36 which is supported for rotation on an arm 38 extending from the hand crank. The hand crank itself may have a depending finger 40 terminating in a rotatable tip 42 which may be grasped by a user.
Turning to FIGS. 3 to 5, a main spring 50 may have two helically wound sections 46a, 46b which each terminate at an inner end in a projection: tangs 52a and 52b. The tangs project from one side of the helically wound sections. Each helically wound section may terminate at its opposite, outer, end in another projection: arms 48a and 48b, which are joined by a bar 54. The arms project from an opposite side of the helically wound sections.
The main spring 50 may be supported in main frame 12 by an annular shaft 56 which extends through the central axis of the helically wound sections of the spring. The annular shaft is carried on shaft 26 (
The bar 54 of the spring abuts the underneath of the back bracket 16 (
A cavity in block 76 is configured to house a pinion 78 and a worm gear 80 so that these gears are held in meshing relation. The pinion 78 may have a hexagonal central bore into which the hexagonal head of bolt 66 is received such that the pinion and bolt have a common central axis and the bolt is constrained to turn with the pinion. The shaft 38 extending from hand crank 30 is joined to the worm gear 80 such that turning the crank turns the worm gear. In this regard, the end of shaft 38 may be hexagonal and fit in a hexagonal opening in the end of the worm gear, as seen in
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An dog 136 may be pivotably joined to a plate 138 proximate one side of the plate 138. Wire 126 may be joined via the dog 136 to the plate 138. The plate may be pivoted to the main frame, proximate the other side of the plate, by a pivot 140. A locking tongue 142 may extend from plate 138 and be received within one of an array of locking receptors in a rack (not shown) extending from the back bracket 16 (
In operation, a user may rotate hand crank 30 to turn worm gear 80. This, in turn, rotates pinion 78 and its captive bolt 66. The bolt is constrained from moving axially upwardly by retainer plate 70. Consequently, when the bolt is rotated in one direction, threaded spring backstop 60 is drawn toward the retainer plate. This moves the tangs 52a, 52b of the springs downwardly thereby increasing the pressure that the bar 54 of the spring exerts on back bracket 16. This increases the force with which the main spring 50 resists backward tilting of any backrest attached to the back bracket. Conversely, if the bolt is rotated in the opposite direction, the spring backstop 60 moves away from the retainer plate 70. This allows the tangs 52a, 52b of the spring to move upwardly thereby decreasing the pressure that the bar 54 of the spring exerts on back bracket 16 and reducing the resistance to backward tilting of the backrest. By providing a thread for bolt 66 that effectively has a low number of turns per inch (e.g., a triple start thread), the user may make a substantial adjustment in the spring tension with a relatively small adjustment to hand crank 30. This therefore makes adjustment of the spring tension quicker and less tiring for the user.
The user may lock the backrest at different tilt angles by rotating the backrest tilt lock control 34 so that cam finger 118 moves from an unlocking position shown in
To unlock the backrest, the user may rotate the backrest tilt lock control 34 so that cam finger 118 moves back to the unlocking position shown in
The user may push paddle 32 in order to cause boss 102 extending from the sleeve 36 joined to the paddle to tilt the control end 90 of lever 86 against the gas control finger. By depressing the gas control finger in this way, the height of the chair may be adjusted.
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Many modifications are possible. For example, pinion 78 and worm gear 80 could be replaced by two bevel gears. Also the spur and worm gears could be reversed so that the bolt 66 is captured by the worm gear. Indeed, if the thread of bolt 66 were provided with a sufficiently large pitch, in place of the gears and hand crank, a lever could be connected directly to the bolt extending at roughly a right angle to the bolt. In this instance, the lever could be rotated to directly rotate the bolt and move the spring backstop. With all of these options, the chair control retains the advantage that an occupant never need reach between their legs to make a chair adjustment. In another embodiment, it would be possible to omit the gears and have the hand crank connected directly to the end of the bolt so that the crank projects downwardly from the chair control. This is not preferred, however, as the chair control would lose its advantage of never requiring an occupant to reach between their legs to make a chair adjustment.
While in the illustrated embodiment, the head of the bolt 66 is captured by a hexagonal bore in the pinion, optionally, the bolt, or any threaded shaft, could be affixed to the pinion in any suitable fashion. In another embodiment, the bolt 66 could be replaced by a nut captured by, or affixed to, the pinion. In this case, the spring backstop could support a threaded shaft which extends downwardly into threaded engagement with the nut.
Other modifications will be apparent to those skilled in the art and, therefore, the invention is defined in the claims.