Abstract:
An adjustable armrest assembly for a stool or chair comprises an armrest base, an armrest support member and an adjustment assembly. The armrest base is connectible to the stool or chair and has a first opening. The armrest support member has a first end with a second opening. The first end is positionable with the second opening aligned with the first opening. The armrest support member has a second end opposite the first end and extending distally to support an armrest. An adjustment assembly is positionable to extend through the second opening and the first opening to define a pivot axis and an adjustable pivot connection between the support member and the base. The assembly is movable within at least one of the first opening and the second opening to laterally reposition the pivot axis. A variable friction member applies a selected degree of resistance to the adjustable pivot connection.

Description:
BACKGROUND 
       [0001]    Dental practitioners typically practice from a seated position in which they lean forwardly to access the patient, and in particular, the patient&#39;s oral cavity. In addition to providing adequate support, dental operatories and other dental work spaces are often confined, so seating for practitioners needs to have a small form factor and be highly mobile. Moreover, stools or other seating for practitioners needs to allow easy ingress and egress, particularly because a practitioner attending to multiple patients in several different operatories concurrently throughout an entire day may enter and exit a seated position 100 times or more. Further, practitioners range in sizes, practice styles and preferences, so any seating solution useful to a practice with multiple practitioners needs to allow for a range of adjustment that can be performed simply and quickly. 
       SUMMARY 
       [0002]    Described below are embodiments of an armrest assembly and an associated practitioner&#39;s stool that address some of the drawbacks of conventional seating for practitioners. 
         [0003]    According to a first implementation, an adjustable armrest assembly for a stool or chair comprises and armrest base, an armrest support and an adjustment assembly. The armrest base is connectible to the stool or chair and has a first opening. The armrest support member has a first end with a second opening. The first end is positionable with the second opening aligned with the first opening in the armrest base. The armrest support member has a second end opposite the first end and extending distally to support an armrest for pivoting. The adjustment assembly is positionable to extend through the second opening and the first opening to define a pivot axis and an adjustable pivot connection between the armrest support member and the armrest base. The adjustment assembly is movable within at least one of the first opening and the second opening to laterally reposition the pivot axis, and the adjustment assembly has a variable friction member that applies a selected degree of resistance to the adjustable pivot connection. 
         [0004]    The adjustment assembly can include a hand knob tightenable to position the axis of rotation within the first and second openings. In some implementations, the first opening in the armrest base is circular, and the second opening in the armrest support is slotted such that the armrest support can be moved laterally relative to the armrest base while the slotted opening is aligned with the circular opening to reposition the pivot axis. 
         [0000]    The armrest support member can be adjustable to change a height of an armrest attached to its distal end. The armrest support can comprises a mounting section and yoke connectible to the mounting section to mount the armrest support to a shaft of a chair or stool. 
         [0005]    The variable friction member can comprise a threaded member and a nut. In some implementations, the adjustment assembly can comprise a threaded extension having a hand knob positioned to extend along the pivot axis and the variable friction member comprises a threaded member positioned to extend in the axial direction and tightenable to exert an axial force on the threaded extension. 
         [0006]    In some implementations, the threaded extension can be configured to extend through the first and second openings and be received in a pivot hub positioned on a lower side of the armrest support, and the variable friction member can include a friction adjustment screw positionable to bear against the pivot hub. There can be a friction isolation bearing positioned between the friction adjustment screw and the pivot hub. In some implementations, a backer plate is configured for attachment to the armrest support to hold the friction adjustment screw in place. The backer plate can comprises apertures for fasteners to attach the backer plate to a lower surface of the armrest support. 
         [0007]    In some implementations, there is at least one thrust bearing, at least one thrust washer and/or at least one low friction washer, positioned around the threaded extension. In some implementations, the friction isolation bearing includes a thrust bearing, a first thrust washer on a first side of the thrust bearing and a second thrust washer on a second side of the thrust bearing opposite the first side. 
         [0008]    According to one implementation, a stool for dentistry includes a leg assembly with multiple feet, a seat assembly supported by the leg assembly, the seat assembly including a seat, a seat back support assembly extending from a rear area of the seat and a seat back coupled to the seat back support, an armrest base, at least one armrest support member and an armrest. The armrest base is connectible to the leg assembly at a height below the seat and has at least one first opening. The armrest support member has a first end with a second opening, the first end being positionable with the second opening aligned with the first opening in the armrest base, and a second end opposite the first end and extending distally. The armrest is connectible to the distal end of the armrest support. A variable friction adjustment assembly is positionable to extend through the second opening and the first opening to define a pivot axis and an adjustable pivot connection between the armrest support member and the armrest base, the adjustment assembly being movable within at least one of the first opening and the second opening to laterally reposition the pivot axis. 
         [0009]    The stool may have right and left armrests that are positionable independently of each other. In some implementations, the seat back support of the stool is tilt adjustable. In some implementations, the seat back support is height adjustable. 
         [0010]    The foregoing and other features and advantages of the disclosed embodiments will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIGS. 1A and 1B  are perspective views of a practitioner&#39;s stool according to a first implementation. 
           [0012]      FIG. 2A  is an exploded perspective view of an adjustment assembly for changing a height of a seat back on the stool of  FIG. 1 . 
           [0013]      FIG. 2B  is an enlarged perspective view showing part of the stool of  FIG. 1  with portions of the adjustment assembly cutaway to show its internal components. 
           [0014]      FIGS. 3A-3C  are front elevation views of a stool similar to the stool of  FIG. 1 , but having adjustable armrest assemblies and armrests. 
           [0015]      FIG. 4  is an exploded perspective view of a portion of the adjustable armrest assemblies. 
           [0016]      FIG. 5  is an enlarged section view in elevation of a portion of one adjustable armrest assembly of  FIG. 4 . 
           [0017]      FIGS. 6A-6D  are schematic plan views of a stool having two adjustable armrest assemblies and showing various positions in which the armrests can be positioned relative to each other and the rest of the stool. 
           [0018]      FIG. 7  is a perspective view of a stool according to another implementation. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]      FIGS. 1A and 1B  are perspective views from different sides of an embodiment of a practitioner stool  100 . The stool  100  has a seat back assembly  102 , which extends from a seat assembly  104 . The seat back assembly  102  and the seat assembly  104  are supported by the leg assembly  106 . As shown, the leg assembly  106  has a center support from which multiple legs with casters extend. 
         [0020]    The seat assembly  104  includes a seat  108  shaped to support a practitioner in a seated position. The seat back assembly  102  is adjustable to change a height of a seat back  110  coupled to its upper end. At a lower end, the seat back assembly  102  has a support  112  (also referred to as a support member) that is connected to a rear area of the seat assembly  104 . 
         [0021]      FIG. 2A  is an exploded perspective view of an embodiment of the seat back assembly  102 , which is also referred to herein as a height adjust mechanism. As shown in  FIG. 2 , the support  112  in the illustrated implementation has a lower end  114  and an opposite upper end  116 . The lower end  114  can have apertures  118  for receiving fasteners  120  to secure the support  112  in place. In the illustrated implementation, there are optional spacers  122  through which the fasteners  120  are threaded. The lower end  114  can be angled as shown to suit the particular configuration, or it may have another suitable shape. As is described in more detail below, a movable portion, or movable height adjusting assembly, is movable relative to the support  112  which is stationary (unless provided with an optional tilt capability, as is described below). 
         [0022]    The support  112  includes at least one generally upright guiding feature, such as one or more guide grooves or slots. In the illustrated implementation, the support  112  includes a pair of parallel through slots  124  configured to be positioned generally vertically when assembled. The support  112  is constructed to have a robust configuration that does not yield. In some implementations, the support  112  is machined from solid bar stock steel. 
         [0023]    The slots  124  receive guide members, which in the illustrated implementation are the respective guide members  126  extending from an inner surface  127  of an outer cover  150 . Each guide member  126  has a lateral width shaped to be slidingly received in one of the slots  124 , respectively, and a substantial length so as to ensure that the movable assembly can be extended and retracted smoothly without excess play. The guide members  126  are secured in the respective slots  124  by a plate  134  on an inner side, which is secured by fasteners  136  that extend through apertures  135  and are received in threaded holes or bores  137  in the guide members  126 . In the illustrated implementation, there are two fasteners  136  securing the left side of the clamp plate  134  to a left guide member  126 . There are also two fasteners  136  securing a right side of the clamp plate  134  to a right guide member  126 , but the right side of the clamp plate  134  has a cut-out or opening  142  shaped to receive an actuator  140  accessible from an exterior surface of the seat back assembly  102  (see, e.g.,  FIG. 1 ) that the user can depress or otherwise manually actuate to allow the user to adjust the position of the seat back  110 , i.e., to move it upward or downward. In some implementations, the actuator  140  is a pushbutton actuator. 
         [0024]      FIG. 2B  is a perspective view of the seat back assembly  102  from a rear side with a portion of the outer cover  150  cut away to show the interaction of the guide members  126  in the slots  124  and an engagement member  144 . As illustrated, a distal end  145  of the engagement member  144  is positioned into one of a series of spaced recesses  147  formed in the support  112 , such as by being spring-biased in a direction towards the support  112 . The spaced recesses  147  define a height adjustment range for the seatback  110 . In the illustrated implementation, the engagement member  144  is attached at its lower end to the inner surface  127  with fasteners  146  ( FIG. 2A ). 
         [0025]    When the actuator  140  is depressed with sufficient force, a projection  149  on the actuator contacts the engagement member  144  and moves the distal end  145  away from the support  112  and out of engagement with the recess  147 . While the distal end is disengaged, the user can adjust the height of the seat back  110  by grasping the movable assembly (formed by the outer cover  150 , a mating inner cover  152  and the other associated components coupled thereto) and sliding it upward or downward relative to the support  112  to a new position. Conveniently, the user can reach behind with a right hand, depress the actuator  140  with a thumb, and at the same time use the other four fingers to grasp and move the movable subassembly. Thus, it is possible to adjust the height of the seat back using one hand, which is advantageous, particularly in working environments where frequent changes in seating positions are desirable. 
         [0026]    As shown in  FIGS. 1B and 2B , the actuator  140  can be positioned against the inner cover  152  with a mount  150  held in place to permit the actuator to pivot when depressed. As shown in  FIG. 2A , optional wear pads  130 ,  132  can be assembled in contact with the outer and inner surfaces of the support  112 . The wear pads, which can made of a nylon plastic or other similar material, can be provided to make components of the movable subassembly slide more freely relative to the support  112  and to minimize wear from repeated use. 
         [0027]    When the actuator  140  is in its at rest position, the engagement between the distal end  145  and the selected one of the recesses  147  provides sufficient force to keep the seatback  110  in place and prevent unwanted movement. Of course, other suitable arrangements to provide suitable engagement and/or clamping forces can be used. The height range and adjustment increment are set to accommodate users of a wide range of heights and sizes, as well as to accommodate users&#39; different positions on the stool, including a regular seated position and other positions a practitioner might adopt while working that would cause the practitioner to contact some portion of the seat back assembly  102 . 
         [0028]    As shown in  FIG. 2A , a lower cover  154  can be provided, and it can be secured in place, such as to the outer cover  150  as shown, with fasteners  156 . The outer cover  150  can be formed of extruded aluminum or another suitable material. The inner cover  152  and the lower cover  154  can be formed of injection molded plastic, such as an injection molded polyester and polycarbonate blend, or another suitable material. The inner cover  152  may have a tab  159  or other feature to assist in aligning it with the outer cover  150 . 
         [0029]    As can be seen in  FIGS. 1A, 1B, 2B, 3A-3C , the seat back assembly  102  (as well as the related assembly  102 ′ discussed below) has an exterior configuration that features few surfaces that are generally smooth, few if any sharp corners and substantial generally planar areas. As a result, the actuator  140  can be situated as shown on a forward surface of the assembly adjacent a seat practitioner&#39;s back. This positioning has been found to allow the practitioner to reach back, such as with his or her right hand, to locate the actuator without needing to view it, and to depress it while grasping the surrounding structure, i.e, the relatively smooth and uninterrupted surfaces of the inner cover  152  and the outer cover  150 . In addition, the smooth surfaces of the seat back assembly that are relatively free of interruptions allow for the stool to be cleaned effectively and easily, which is a necessary requirement for the dental operatory environment. 
         [0030]    Although described as a height adjustment mechanism for adjusting the height of the seat back  110 , the same components can be configured for other adjusting functions. For example, as shown in  FIG. 7  for an assistant&#39;s stool  300 , the same assembly as the seat back assembly  102  can be implemented as a torso bar assembly  102 ′ to allow a height of a torso bar  302  to be adjusted upward or downward relative to the seat  108 . This allows an assistant or other occupant to adjust the torso bar  302  for a proper height relative to the assistant&#39;s size and current activity, which may require leaning over the torso bar  302  to access a patient&#39;s oral cavity. The assistant&#39;s stool  300  is generally similar to the stool  100 , which allows common components to be used interchangeably. As illustrated, the stool  300  is fitted with an optional, rotatable foot rest  304  that is useful to support the user&#39;s feet when the stool  300  is used at greater heights. 
         [0031]    According to another implementation as shown in  FIGS. 3A-6D , a stool  200  has adjustable armrests, such as a right armrest assembly  160  for supporting a right armrest  162  and a left armrest assembly  164  for supporting a left armrest  166  (for convenience, “left” and “right” as used herein refer the seated occupant&#39;s left and right). The armrest assemblies  160 ,  164  are capable of multiple movements to allow the armrests  162 ,  166  to be independently positioned in a wide variety of positions. Referring to the front side elevation view of  FIG. 3A , the armrests  162 ,  166  are shown in a regular width position.  FIG. 6A  is a plan view of the chair  200  with the armrests  162 ,  166  in the regular width position. In  FIG. 3B , the armrests  162 ,  166  have been moved to a wide position by adjusting each respective armrest assembly  160 ,  164  relative to an armrest base  158 , as is described in detail below.  FIG. 6B  is a plan view of the chair  200  with the armrests  162 ,  166  in the wide position. In  FIG. 3C , the armrests  162 ,  166  have been rotated inwardly to a narrow, elbow support position in which the user can conveniently place his or her elbows on the armrests  162 ,  166 .  FIG. 6D  is a plan view of the chair  200  with the armrests  162 ,  166  rotated to the elbow support position.  FIG. 6C  is a plan view of the chair  200  with the armrests  162 ,  166  rotated to a spread position, which can be used to move the armrests out of the way for the user&#39;s specific activities, as well as ingress and/or egress. 
         [0032]      FIG. 4  is an exploded perspective view of the armrest assembly  160 , the armrest assembly  164  and the armrest base  158 , showing the components that allow the relative movements necessary to permit the armrests  160 ,  166  to be positioned in a wide range of positions.  FIG. 5  is a sectioned elevation view of the armrest assembly  160  for the right side showing the components in an assembled state. 
         [0033]    Referring to  FIGS. 4 and 5 , the armrest assembly  160  has an adjustment knob  172   a  with a shaft that extends through a slot  184   a  in a support member  170   a  that supports the armrest  162  and through an aligned opening  186   a  in the armrest base  158 . The distal end of the shaft is received in a pivot hub  190   a . A backer plate  197   a  is secured to a lower side of the armrest base with fasteners  198   a . There is a friction adjustment screw  196   a  with a threaded end extending outwardly through the backer plate  197   a  that receives a nut  199   a  for adjusting the amount of friction experienced during movements. If necessary, the friction adjustment screw  196   a  can be held in place while the nut  199   a  is rotated by inserting an appropriate tool in a slot or recess provided at an end  201   a  of the friction screw  196   a.    
         [0034]    In the illustrated implementation, there is a series of components positioned between the adjustment knob  172   a  and the armrest base  158 , namely a thrust washer  174   a , a thrust bearing  176   a , a thrust washer  178   a , a low friction (e.g., nylon plastic) washer  180   a  and another low friction (e.g., nylon plastic) washer  182   a . Similarly, there are similar components in the assembly below the armrest base  158 , including a friction washer  188   a  positioned over the pivot hub  190   a , and a friction isolation bearing stack comprising a thrust washer  192   a , a thrust bearing  194   a  and a thrust washer  195   a  positioned between the pivot hub  190   a  and the friction adjustment screw  196   a . A slight gap is maintained between the support member  170   a  and the armrest base  158 . 
         [0035]    The bearings, hub, washers and friction components provide for smooth pivoting and an adjustable degree of friction to prevent unintended rotation of the armrests. Desirably, a range of friction is possible, including sufficient friction to keep the armrests in position after only incidental contact, but allowing the armrest to be moved freely, without manipulation of other components, when pushed or pulled. This provides users with a positive fee for how components of the stool move relative to each other. 
         [0036]    The adjustment knob  172   a  can be tightened to keep the armrest  162  at any desired position. The armrest assembly  164  is a mirror image of the armrest assembly  160 . A yoke  185  and fasteners  187  are used to secure the arm base  158  to part of the chair, such as, e.g., a shaft of the chair. 
         [0037]    The stool can include one or more manual controls, e.g., the levers (or paddles)  201 ,  203  and/or  205 , to allow the user to adjust the positions of portions of the stool. For example, the leg assembly  106  that supports the seat  108  may include a gas cylinder controllable with the lever  201  to assist the user in raising or lowering the seat  108  to a desired height. As another example, the lever  203  may be configured to actuate a tilt adjust mechanism to permit the seat  108  and back  110  to be angled in unison under tension (such as when a seated user leans against it them), to change the tension and/or to lock the seat  108  and back  110  in place and prevent any tilting. The lever  205  may be configured to permit the back  110  to be reclined relative to the seat  108 . 
         [0038]    Commonly assigned and concurrently filed applications entitled “SEAT ASSEMBLY FOR TASK-ORIENTED SEATING” (U.S. patent application No. NOT YET ASSIGNED) and “HEIGHT ADJUSTING MECHANISM AND STOOL FOR DENTAL PRACTITIONER” (U.S. patent application No. NOT YET ASSIGNED) are incorporated herein by reference. 
         [0039]    In view of the many possible embodiments to which the disclosed principles may be applied, it should be recognized that the illustrated embodiments are only preferred examples and should not be taken as limiting the scope of protection. Rather, the scope of protection is defined by the following claims. We therefore claim all that comes within the scope of these claims.