# Patent

## Title
Armrest assembly and stool for dental practitioner

## 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.

## Background
BACKGROUND
Dental practitioners typically practice from a seated position in which they lean forwardly to access the patient, and in particular, the patient'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
Described below are embodiments of an armrest assembly and an associated practitioner's stool that address some of the drawbacks of conventional seating for practitioners.
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.
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. The armrest support member can be adjustable to change a height of an armrest attached to its distal end. The armrest support can comprise a mounting section and yoke connectible to the mounting section to mount the armrest support to a shaft of a chair or stool.
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.
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.
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.
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.
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.
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
FIGS. 1A and 1B are perspective views of a practitioner's stool according to a first implementation.
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.
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.
FIGS. 3A-3C are front elevation views of a stool similar to the stool of FIG. 1, but having adjustable armrest assemblies and armrests.
FIG. 4 is an exploded perspective view of a portion of the adjustable armrest assemblies.
FIG. 5 is an enlarged section view in elevation of a portion of one adjustable armrest assembly of FIG. 4.
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.
FIG. 7 is a perspective view of a stool according to another implementation.



DETAILED DESCRIPTION
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.
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.
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).
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.
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.
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).
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.
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.
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' 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.
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.
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'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.
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'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's size and current activity, which may require leaning over the torso bar 302 to access a patient's oral cavity. The assistant'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's feet when the stool 300 is used at greater heights.
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'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's specific activities, as well as ingress and/or egress.
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.
Referring to FIGS. 4 and 5, the armrest assembly 160 has an adjustment knob 172a with a shaft that extends through a slot 184a in a support member 170a that supports the armrest 162 and through an aligned opening 186a in the armrest base 158. The distal end of the shaft is received in a pivot hub 190a. A backer plate 197a is secured to a lower side of the armrest base with fasteners 198a. There is a friction adjustment screw 196a with a threaded end extending outwardly through the backer plate 197a that receives a nut 199a for adjusting the amount of friction experienced during movements. If necessary, the friction adjustment screw 196a can be held in place while the nut 199a is rotated by inserting an appropriate tool in a slot or recess provided at an end 201a of the friction screw 196a. 
In the illustrated implementation, there is a series of components positioned between the adjustment knob 172a and the armrest base 158, namely a thrust washer 174a, a thrust bearing 176a, a thrust washer 178a, a low friction (e.g., nylon plastic) washer 180a and another low friction (e.g., nylon plastic) washer 182a. Similarly, there are similar components in the assembly below the armrest base 158, including a friction washer 188a positioned over the pivot hub 190a, and a friction isolation bearing stack comprising a thrust washer 192a, a thrust bearing 194a and a thrust washer 195a positioned between the pivot hub 190a and the friction adjustment screw 196a. A slight gap is maintained between the support member 170a and the armrest base 158.
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 feel for how components of the stool move relative to each other.
The adjustment knob 172a 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 armrest base 158 to part of the chair, such as, e.g., a shaft of the chair.
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.
Commonly assigned and concurrently filed applications entitled “SEAT ASSEMBLY FOR TASK-ORIENTED SEATING” (U.S. patent application Ser. No. 14/639,959) and “HEIGHT ADJUSTING MECHANISM AND STOOL FOR DENTAL PRACTITIONER” (U.S. patent application Ser. No. 14/639,932) are incorporated herein by reference.
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.

## Claims

1. An adjustable armrest assembly for a stool or chair, comprising:
an armrest base having an armrest base mounting section shaped to connect to a shaft of the stool or chair and a mounting section retainer securable to the arm rest base to retain the armrest base in position on the shaft, the armrest base having a first opening;
an armrest support member having 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, the armrest support member having a second end opposite the first end and extending distally to support an armrest;
an adjustment assembly 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, wherein 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.

2. The adjustable armrest assembly of claim 1, wherein the adjustment assembly comprises a hand knob tightenable to position the axis of rotation.

3. The adjustable armrest assembly of claim 1, wherein the first opening in the armrest base is circular and wherein the second opening in the armrest support is slotted, and wherein 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.

4. The adjustable armrest assembly of claim 1, wherein the armrest support member is adjustable to change a height of an armrest attached to the distal end.

5. The adjustable armrest assembly of claim 1, wherein the variable friction member comprises a threaded member and a nut.

6. The adjustable armrest assembly of claim 1, wherein the adjustment assembly comprises a threaded extension with a hand knob, the threaded extension being positioned to extend along the pivot axis, and wherein 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.

7. The adjustable armrest assembly of claim 6, wherein the threaded extension is 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 wherein the variable friction member comprises a friction adjustment screw positionable to bear against the pivot hub.

8. The adjustable armrest assembly of claim 7, further comprising a friction isolation bearing positioned between the friction adjustment screw and the pivot hub.

9. The adjustable armrest assembly of claim 8, wherein the friction isolation bearing comprises 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.

10. The adjustable armrest assembly of claim 7, further comprising a backer plate configured for attachment to the armrest support to hold the friction adjustment screw in place.

11. The adjustable armrest assembly of claim 10, wherein the backer plate comprises apertures for fasteners to attach the backer plate to a lower surface of the armrest support.

12. The adjustable armrest assembly of claim 6, further comprising a nut, wherein the threaded member comprises an exposed end sized to receive the nut, and the nut can be tightened or loosened relative to the exposed end to vary the friction applied to the pivot connection.

13. The adjustable armrest assembly of claim 6, further comprising at least one thrust bearing positioned around the threaded extension.

14. The adjustable armrest assembly of claim 6, further comprising at least one thrust washer positioned around the threaded extension.

15. The adjustable armrest assembly of claim 6, further comprising at least one low friction washer positioned around the threaded extension.

16. The adjustable armrest assembly of claim 1, wherein the mounting section retainer is securable to the armrest base with threaded fasteners to retain the armrest base in position relative to the shaft of the chair or stool.

17. A stool or a chair having the adjustable armrest assembly of claim 1.