Chair control with tilt lock

A chair control comprising a frame structure adapted to be supported on a conventional chair base, a chair seat support pivotally mounted on the frame structure for fore and aft tilting movement relative to the frame structure, a biasing structure such as a torsion bar biasing the seat support to a position corresponding to a normal seating position of a chair seat, and rotatable blocking members mounted on the seat support for movement, in a tilted position of the seat support, to a position engaged with the frame structure so as to block return movement of the seat support to the normal position. The blocking members are operable by an actuating knob conveniently located close to the seat for operation by the seat occupant and are moveable to a plurality of positions corresponding to various tilted positions of the chair. This tilt lock structure enables the chair occupant to sit comfortably in the chair in a tilted position of the seat without having to fight the continuous tendency of the chair to return to the normal seating position.

SUMMARY OF THE INVENTION 
It is desirable, from the standpoint of comfort, to be able to retain a 
tiltable chair in a tilted position, and some tilting chairs have included 
structure for maintaining the chair in a tilted position. However, it is 
now recognized that the seating comfort of the chair occupant is improved 
if the occupant is enabled to still move the chair seat in a fore and aft 
direction even when the chair seat is blocked against returning to its 
normal seating position. It is an object of the present invention, 
therefore, to provide an improved chair control in which in a given tilted 
position of the chair seat, the seat is blocked against return movement to 
its normal position, but the occupant is permitted to tilt the chair 
further back from the tilt lock position and thence forward again to the 
tilt lock position so that occupant movement is not totally restricted in 
any tilt lock position of the chair. 
The chair control of this invention comprises a frame structure supportable 
by the usual chair base, seat support members pivotally mounted on the 
frame structure for tilting movement relative to the frame structure, bias 
means, such as a torsion bar, operatively associated with the frame 
structure and the seat support members biasing the seat support members to 
normal positions relative to the frame structure, and blocking means 
movably mounted on the seat support members for movement in a tilted 
position of the seat support members to positions engaged with the frame 
structures so as to block return movement of the seat support members to 
the normal position. When the blocking members block return movement of 
the seat support members, the seat occupant does not have to fight the 
normal tendency of the chair to return to a normal seating position, thus 
improving occupant comfort. In addition, the occupant is allowed to tilt 
the seat further back and return the seat forwardly as far as the position 
in which it is blocked. This ability of the seat occupant to more or less 
rock the chair back and forth from its tilt lock position further improves 
occupant comfort. The seat locking means consists of a pair of rotatably 
mounted members, each of which has a plurality of surfaces engageable with 
the frame structure to block return movement of the seat to the normal 
position from a plurality of tilted positions that are selectable by the 
chair occupant. The blocking members are mounted on a shaft which is 
operable by rotating an actuating knob conveniently positioned for the 
seat occupant immediately below and adjacent one edge of the chair seat. 
The tilt lock chair control of this invention thus achieves increased chair 
occupant comfort in tilting seat chairs of the type that are in common use 
.

With reference to the drawing, the chair control of this invention, 
indicated generally at 10, is illustrated in FIG. 2 secured to the under 
side of a seat 12 and mounted on the upper end of a support pedestal 14 
for a chair, indicated generally at 16 in FIG. 1. As shown in FIG. 1, the 
chair 16 has, in addition to the seat 12 and the pedestal 14, a supporting 
base 18 on which the pedestal 14 is mounted and a seat back 20 located at 
the rear edge of the seat 12. 
A frame structure 22, which includes a pair of angle shaped frame members 
24 that extend fore and aft of the seat 12, is rigidly mounted on the 
upper end of the pedestal 14. A pair of angle shape seat support members 
26 (FIG. 3) parallel to and positioned outwardly of the frame members 24 
are secured to the underside of the seat 12. A conventional torsion bar 
assembly 28 connects the seat support members 26 to the frame members 24. 
The torsion bar assembly 28 consists of an elongated torsion bar 30, 
illustrated as being of rectangular shape in cross-section, which is 
secured at one end by an attachment member 32 to the seat support member 
26. Adjacent its opposite end, the torsion bar 30 is secured by an 
attachment member 34 to one of the frame members 24. The torsion bar 30 
acts as a bias means to bias the seat support members 26 to normal seating 
positions relative to the support structure 18, namely, positions 
corresponding to a normal seating position of the seat 12 untilted with 
respect to the support structure 18 and shown in FIG. 2. When the seat 
support members 26 are tilted upwardly and rearwardly by the seat occupant 
desiring the seat 12 in a tilted position, the torsion bar 30 is twisted 
between the attachment members 32 and 34 and the tendency of the torsion 
bar 30 to return to its untwisted position, corresponding to the normal 
position of the seat 12 shown in FIG. 2, biases the seat support members 
26 toward this position. Thus, in a conventional chair equiped with 
biasing means such as the torsion bar 30, when the seat occupant tilts the 
seat 12 rearwardly, and wants to keep the seat 12 in a rearwardly tilted 
position, the seat occupant must continually fight the tendency of the 
seat 12 to return to its normal position by virtue of the tendency of the 
torsion bar 30 to return to its untwisted position. 
In the chair control of this invention, a shaft 36 which in the illustrated 
embodiment of the invention is of the irregular shape shown in FIG. 3 to 
avoid conflict with other parts of the chair control, is rotatably 
supported on the seat support members 26 so as to extend therebetween. A 
washer assembly 38, consisting of a spring washer 40 engaged with a seat 
support member 26 and a fastener washer 42 engaged with the spring washer 
40, is mounted on the shaft 36 adjacent each of the seat support members 
26 to provide sufficient frictional resistance to rotation of the shaft 36 
to maintain the shaft 36 in a rotated position. Inwardly of and adjacent 
each of the seat support members 26, an irregularly shaped blocking member 
44 is secured to the shaft 36. Each blocking member 44 is provided on its 
circumference with a plurality of blocking surfaces 46 which are located 
at different positions spaced radially outwardly from the shaft 36, the 
magnitude of the radial spacing increasing in a counter-clockwise 
direction on the circumference of the blocking members 44 as viewed from 
FIG. 2. A knurled actuating knob 48, mounted on one end of the shaft 36, 
is located adjacent and immediately below one edge of the seat 12 so that 
the seat occupant can readily grasp the knob 48 and rotate the shaft 36 so 
as to in turn rotate the blocking members 44 for the purpose hereinafter 
described. 
In the operation of the chair control 10, assume that the seat 12 is in its 
normal position shown in FIG. 2. Further assume that the seat 12 is then 
tilted upwardly and rearwardly, as indicated by the arrow 50 in FIG. 4 to 
the tilted position illustrated in FIG. 4. Also assume that the shaft 36 
is in a position in which the blocking members 44 are in the inoperative 
positions illustrated in FIG. 4. These positions are defined by engagement 
of a stop 52 secured to each of the blocking members 44 with a stop 54 
which is struck out of each of the seat support members 26. To place the 
blocking members 44 in the inoperative positions, the handle 48 is grasped 
and rotated in a counter-clockwise direction as viewed in FIG. 4 until the 
stops 52 engage the stops 54. 
Now assume that the chair occupant desires to retain the chair seat 12 in 
the tilted position shown in FIG. 4. The occupant manually grasps the knob 
48 and rotates the knob 48 in a clockwise direction as viewed in FIG. 4 
until the blocking surfaces shown at 46 in FIG. 5 engage the rear edges 56 
of the frame members 24. In these positions of the blocking members 44, 
the seat support members 26 are positively blocked against return 
movement, under the action of the torsion bar 30, to the normal positions 
illustrated in FIG. 2. As shown in FIGS. 4 and 5, each blocking member 44 
has a plurality of blocking surfaces 46 to thus enable the chair occupant 
to lock the seat 12 in a plurality of tilted positions. In the illustrated 
enbodiment of the invention, six surfaces 46 are provided on each blocking 
member 44 and these surfaces 46 correspond to six different tilted 
positions of the seat 12, with about a three degree increment of tilt 
between adjacent tilted positions. 
It is readily apparent that the blocking members 44 can be constructed so 
as to block return movement of the seat 12 from substantially any desired 
tilted position of the seat 12. It is also apparent that when the blocking 
members 44 operate to block return movement of the chair seat 12 to a 
normal position, they do not in any way interfere with further rearward 
tilting of the seat 12 from the tilt locked position, namely, the most 
forwardly tilted position in which the chair seat can be placed. Thus, the 
chair occupant is allowed to tilt the chair back and forth starting from 
the position in which the chair is locked against further forward 
movement. This provides the chair occupant with additional seating comfort 
heretofore unavailable in tilting seat type chairs because the chair is 
not rigidly locked in a tilt lock position. 
From the above description it is seen that this invention provides a tilt 
lock chair control which is selectively operable by the chair occupant to 
block return movement of a tilted chair seat to the normal position. This 
enables the chair occupant to enjoy seating in a reclined position without 
having to fight the tendency of the chair seat to return to the normal 
position. Further, in the chair control of this invention, the chair 
occupant has the opportunity to move the chair fore and aft when the chair 
is in a locked tilted position because only chair movement in the "return 
to normal position direction" is blocked. The chair occupant can still 
rock the chair further back starting from the tilt lock position. Thus, 
the chair control of this invention provides for increased chair occupant 
comfort and with increased chair position options available to the chair 
occupant.