Adjustable chair

Abstract

An adjustment mechanism 15 of an adjustable chair 10 comprising: a fore-aft frame 20a pivotally connected to a leg 25a and seat 30 of the chair; a lift actuator 35 pivotally attached at ends to the le

Description

Technical Field The present disclosure relates to an adjustable chair, particularly, but not exclusively, to an electrically adjustable chair. Background Many people around the world require assistance with tasks such as movement around a premises or standing up. Currently, when a person’s mobility decreases to the point where they have difficulty moving around or standing up, they have the choice of various aides to help them depending on their personal requirements. These can include walking stick, self-propelled wheelchairs, electric wheelchairs, adjustable commode chairs, etc. Adjustable chairs are available but have limited range of movement and can require significant maintenance, particularly on any software components. Many of these solutions are limited in the adjustability they provide their users and can be quite arduous to use. There is therefore a requirement for an adjustable chair that is both easier to use and provides the user with a wide range of adjustability. Summary There is provided an adjustment mechanism of an adjustable chair, the adjustment mechanism comprising a fore-aft frame pivotally connected to a leg of the chair and pivotally connected to a seat of the chair. The adjustment mechanism may further comprise a lift actuator pivotally attached to the leg of the chair at a first end of the lift actuator and pivotally attached to the fore-aft frame of the chair at a second end of the lift actuator. The adjustment mechanism may further comprise a tilt actuator pivotally attached to the fore-aft frame at a first end of the tilt actuator and pivotally attached to the seat of the chair at a second end of the tilt actuator, the second end being attached forward of the first end. Optionally, the adjustable chair may be a commode chair, for example an adjustable shower commode chair. The adjustable chair may be an electrically adjustable chair. The actuators may be controlled electronically. Optionally, the leg may be a member upstanding from the base of the chair. The base of the chair may comprise a plurality of wheels, such that the chair may is moveable on the wheels. Optionally, when the tilt and lift actuators are extended by the same distance, a shape formed between the lift actuator, the leg and the fore-aft frame is the same as a shape formed between the tilt actuator, the fore-aft frame, and the seat of the chair. Optionally, the shape may be reflected or rotated. The same shape refers to the lengths of the sides and angles between the sides. This beneficially provides an adjustable chair wherein the lift actuator and tilt actuator can both be extended by the same distance to achieve a vertical lift of the chair, thereby simplifying the mechanism by which a vertical lift of the chair can be achieved. Furthermore, Simple hardware can therefore be utilised to control the movement of the seat via the tilt and lift actuators. The geometry of the tilt and lift actuators further enables provision of a chair with increased manoeuvrability. The pivotal attachment of the actuators may be achieved via a mechanical pivoting connection, a flexible joint, a spring, or by other means. Optionally, the lift actuator may be configured to predominantly act as a lifting means to raise / lower the seat relative to the base in a vertical direction. The lift actuator and tilt actuator may be a linear actuator, the linear actuator being operable to move between a retracted configuration and an extended configuration wherein a distance between a first end and a second end of the actuator has a lower limit and an upper limit, and when the distance between the first and second end is at the lower limit, the actuator is in its retracted configuration, and when the distance between the first and second end is at the upper limit, the actuator is in its extended configuration. Optionally, the lift actuator and the tilt actuator are configured to perform the same action when they receive the same input. The geometry of the shapes formed by the tilt and lift actuators in the chair allow the tilt actuator and lift actuator to both extend at the same speed to achieve vertical lift of the seat. As such, provision of the same input to both actuators simultaneously will result in vertical lift of the chair. The tilt and lift actuators may be voltage-controlled actuators. The geometry described above in combination with the use of voltage-controlled actuators means that the same voltage can be applied to the two actuators to achieve a vertical lift of the seat. Optionally, the lift actuator and tilt actuator may be controllable independently of each other. Independent control of the lift actuator and tilt actuator may provide a wider range of movement of the seat, providing the user with more control over the positioning of the seat, including the ability to tilt the chair at a range of heights. Optionally, the voltage applied to each one of the tilt actuator and lift actuator may be tuned to compensate for load differences on each of the lift actuator and tilt actuator and / or manufacturing tolerances. This may be achieved by using resistors on each of the lift actuator and tilt actuator. Optionally, the lift actuator may be indirectly attached to the leg of the chair. Optionally, the tilt actuator may be attached to the fore-aft frame via a branch member, the branch member fixedly attached to the fore-aft frame and pivotally attached to the tilt actuator. The branch member may be a downwardly extending branch member, optionally the branch member downwardly extending from a tilting pivot connection between the fore-aft frame and the seat. The branch member may be a longitudinal member. The shape formed by the tilt actuator may be between the branch member, fore-aft bar and tilt actuator. Optionally, the fore-aft frame may comprise a first fore-aft bar to which the lift and tilt actuators are attached. Optionally, the fore-aft frame may comprise at least one load transfer member configured to transfer load applied by the lift and tilt actuators widthways across the fore-aft frame. Optionally, the fore-aft frame may comprise a second fore-aft bar and the first and second fore-aft bars are on opposing lateral sides of the chair. Optionally, the at least one load transfer member may comprise a front load transfer member fixedly coupled to the first fore-aft bar and optionally fixedly coupled to the second fore-aft bar. Optionally, the at least one load transfer member may comprise a rear load transfer member fixedly coupled to the first fore-aft bar and optionally fixedly coupled to the second fore-aft bar. Optionally, the load transfer member(s) may each comprise a first load transfer bar and a second load transfer bar, the first load transfer bar being fixedly attached to the leg of the chair or the seat of the chair and the second load transfer bar being rotatably coupled to the first load transfer bar and fixedly coupled to the first fore-aft bar and optionally the second fore-aft bar. Optionally, the first load transfer bar may be bolted and / or welded to the leg of the chair or the seat of the chair. Optionally, the second load transfer bar may be bolted and / or welded to one or both of the fore-aft bars. Optionally, the first load transfer bar and the second load transfer bar may be concentric, for example, the first bar or the second bar may be hollow and the other of the first load transfer bar and the second load transfer bar may be within the hollow load transfer bar. Optionally, the first load transfer bar and / or the second load transfer bar may be tubes. Optionally, a central region of the rear load transfer member may be positioned higher than a lowest part of the seat. This allows the chair to be moved, rear first, into alignment with a toilet, the seat being positioned over a toilet. The seat once aligned may be lowered over the toilet using the lift and tile actuators if desired. Optionally, the first load transfer bar and second load transfer bar may be positioned above the lowest part of the seat. Optionally, the fore-aft frame may be a metal frame. Optionally, a diameter of the or each load transfer member may be at least 50mm. Optionally, the adjustment mechanism may further comprise a controller configured to transmit inputs to the lift and tilt actuators, wherein the controller comprises hardware components configured to receive user input, convert the user input to actuator input signals, and transmit the actuator input signals to the lift and tilt actuators. An adjustment mechanism formed of hardware, rather than software results in less required maintenance of the adjustment mechanism. There is further provided a method of raising an adjustable chair comprising applying the same input to a lift actuator and a tilt actuator to cause a seat of the chair to rise without changing its incline. There is further provided an adjustable armrest for a chair, the adjustable armrest comprising a mount, an arm pivotally attached to the mount, an upper stop rotatably attached to the mount and positioned to contact a top surface of the arm when the arm is pivoted to a forward position, and a lower stop rotatably attached to the mount and positioned to contact a bottom surface of the arm when the arm is pivoted to the forward position. The lower stop may comprise a set of lower recesses spaced around a circumference of the lower stop, each lower recess configured to support a bottom surface of the arm when the arm is pivoted to the forward position, and the upper stop may comprise a set of upper recesses spaced around a circumference of the upper stop, each upper recess configured to support the top surface of the arm when the arm is pivoted to the forward position and wherein each upper recess is paired with a respective one of the lower recesses and each pair of recesses are configured to support the arm at a different angle in the forward position. When the armrest is in the forward position, the armrest extends from a back rest of the seat such that it is in a substantially horizontal position, substantially perpendicular to the back rest. Alternatively, when the armrest is in an upright, or stowed position, the armrest is in a substantially vertical position, substantially parallel to the back rest of the seat. Optionally, the adjustable armrest for a chair may comprise a coupling mechanism configured to transfer rotation of one of the upper and lower stops to the other of the upper and lower stops. The upper and lower stops may be rotated to choose between the angles provided by the recesses for the forward position of the armrest. The angles may be between 70 and 110 degrees. The upper and lower stops may be easily rotatable between different angles. Optionally, the coupling mechanism may comprise a belt, optionally, a toothed belt. Optionally, the couple mechanism may comprise a set of gears. Optionally, the set of upper recesses may consist of four upper recesses and the set of lower recesses may consist of four lower recesses. Optionally, an edge of one or both of the stops may protrude from a cover of the mount permitting a user to rotate the stops by rotating the protruding edge, for example by hand. Optionally, each stop may comprise between two and eight recesses. Optionally, the mount may be attached to a back rest of the chair. There is further provided an adjustable chair comprising a seat, a leg, a base, supporting the leg, and the adjustment mechanism as described above, and / or an armrest as described above. Optionally, two armrests are provided on the chair. By using the same set of recesses on each armrest, the same angle can easily be selected between the left arm and the right arm. There is further provided a computer-readable medium having computer-executable instructions adapted to cause a 3D printer to print an armrest mount as described above. Brief Description of Drawings Embodiments of the present disclosure will now be described by way of example only, with reference to the following diagrams, in which:- Figure 1 shows a perspective view of an adjustable chair comprising an adjustment mechanism; Figure 2 shows a perspective view of the adjustable chair of Figure 1 from a different orientation; Figure 3 shows a perspective view of a second adjustable chair comprising an adjustment mechanism; Figure 4 shows a top view of the adjustable chair of Figure 3; Figure 5 shows a cross-sectional side view of the adjustable chair of Figure 3 along cut Z-Z of Figure 4; Figures 6a-c show perspective views of the adjustable chair of Figure 3 in three different seat positions (a: raised seat; b: seat tilted backwards; and c: seat tilted forwards); Figures 7a shows a perspective view of an armrest mount on the adjustable chair of Figure 3; Figure 7b shows a perspective view of the armrest mount of Figure 7a without its cover with the armrest arm in an extended position; and Figure 7c shows a perspective view of the mount of Figure 7a without its cover with the armrest arm in a retracted position. Detailed Description Turning now to Figure 1, there is shown an adjustable chair 10 that can be adjusted to suit the user's requirements. In use, the adjustable chair 10 can be adjusted to different heights and different inclinations. The adjustable chair 10 comprises an adjustment mechanism 15 which can adjust the height and inclination of a seat of the adjustable chair 10. In this particular embodiment, the adjustment mechanism 15 is located on one side of the adjustable chair 10. The adjustment mechanism comprises a first fore-aft bar 20a. The first fore-aft bar 20a is pivotally attached at a first end to a leg 25a of the chair 10. By being pivotally attached, an angle between the fore-aft frame 20a and the leg 25a can be adjusted. The leg 25a of the chair is fixedly attached to a base 80 of the chair. The leg 25a of the chair 10 holds the seat 30 above the base 80. The first fore-aft bar 20a forms part of a fore-aft frame of the chair 10. The first fore-aft bar 20a is pivotally attached at a second end to a seat 30 of the chair 10, the second end of the first fore-aft bar 20a being located at a rearward facing side of the chair 10. The adjustment mechanism 15 further comprises a lift actuator 35, the lift actuator 35 being pivotally attached to the leg 25a at a first end, and pivotally attached to the first fore-aft bar 20a at a second end. The lift actuator 35 can be extended any distance between its fully retracted configuration and its fully extended configuration. By being pivotally connected to both the leg 25a and the first fore-aft bar 20a, the lift actuator 35 can change the angle at the connection between the leg 25a and the first fore-aft bar 20a, thereby raising the height of the seat 30 relative to the base 80 of the chair 10. The adjustment mechanism 15 further comprises a tilt actuator 40. The tilt actuator 40 is pivotally connected to the seat 30 at a first end and is pivotally connected to the first fore-aft bar 20a at a second end. The tilt actuator 40 may be pivotally connected to the first fore-aft bar 20a via branch member 45 that extends downwardly from the second end of the first fore-aft bar 20a. By being pivotally connected to both the first fore-aft bar 20a and the seat 30, the tilt actuator 40 can change the angle between the first fore-aft bar 20a and the seat 30, changing the inclination of the seat 30 relative to the base 80 of the chair 10. When the lift actuator 35 and the tilt actuator 40 are extended by the same distance, the seat 30 can be raised relative to the base 80 without the inclination of the seat 30 changing (i.e. maintaining the same angle between the seat 30 and the base 80). A shape formed between the lift actuator 35, the leg 25a and the first fore-aft bar 20a is the same as a shape formed between the tilt actuator 40, the first fore-aft bar 20a and the branch member 45. A system wherein the lift actuator 35 and the tilt actuator 40 can be extended by the same amount to raise the seat 30 relative to the base 80 without altering the inclination of the seat 30 means that the same voltage can be provided to both actuators 35, 40 in order to the raise the seat 30, thus simplifying the mechanism by which the actuators are controlled. The adjustable chair 10 further comprises a first load transfer member 55 at a forwardfacing side of the chair 10, and a second load transfer member 65 at a rearward facing side of the chair 10. The first and second load transfer members 55, 65 are configured to transfer the loads from the lift actuator 35 and tilt actuator 40 from one side of the chair 10 to the other side of the chair 10. As shown in more detail in Figure 5, the first load transfer member 55 comprises a first load transfer bar 70 and a second load transfer bar 75. The first load transfer bar 70 is bolted to the leg 25 of the chair 310. The second load transfer bar 75 is rotatably coupled to the first load transfer bar 70 and bolted to the fore-aft bar 20a and the second fore-aft bar 20b. One of the first load transfer bar 70 and the second load transfer bar 75 is hollow and the other of the first load transfer bar 70 and the second load transfer bar 75 is within the hollow load transfer bar. The second load transfer member 65 comprises a first load transfer bar 71 and a second load transfer bar 76. The first load transfer bar 71 is bolted to the seat 30 of the chair 310. The second load transfer bar 76 is rotatably coupled to the first load transfer bar 71 and bolted to the fore-aft bar 20a. The first load transfer bar 71 is at least partially hollow and the second load transfer bar 76 is at least partially within the hollow part of the first load transfer bar. A central region of the second load transfer member 65 is positioned at a greater vertical height above the base than an upward facing surface of the seat 30, such that the chair 10 can be reversed over a toilet and the seat 30 can then be lowered onto the toilet seat. The inner rim of the seat can then sit within the toilet bowl improving hygiene. Alternatively, the second load transfer members 6 5 can be positioned directly between the second ends of the two first fore-aft bars 20a, 20b as shown in Figure 3. The adjustable chair 10 further comprises an adjustable armrest 85 and a backrest 130 that extends upwardly from a rearward end of the seat 30. The adjustable armrest comprises a mount 90 for attaching the adjustable armrest to the chair 10. The mount 90 is attached to the backrest 130 of the chair 10. The armrest 85 further comprises an arm 95 that is connected to the mount 90. The mount 90 pivotally connects the arm 95 to the backrest 130 of the chair such that it can be moved between an extended orientation wherein the arm 95 is substantially perpendicular to the backrest and a retracted orientation wherein the arm 95 is substantially parallel with the backrest. Turning now to Figure 2, there is shown a perspective view of the adjustable chair 10 of Figure 1 from a different orientation. The side of the chair 10 opposite the lift actuator 35 and tilt actuator 40 comprises a second fore-aft bar 20b and a second leg 25b. The adjustable chair 10 further comprises a plurality of wheels 145a, 145b, 145c, 145d that are connected to the base 80 of the chair 10. The plurality of wheels 145a, 145b, 145c, 145d may be castor wheels which permit the user to move the chair 10 freely in all directions. The adjustable chair further comprises a pair of footrests 140a, 140b that extend downwardly from a forward-facing side of the seat 30, such that the user can place their feet into the footrests 140a, 140b. The pair of footrests 140a, 140b are adjustable in length to the user’s preferences. The chair further comprises a handlebar 150 on an upper end of the backrest 130 such that the chair 10 can be pushed. Figure 3 shows a perspective view of a second embodiment of an adjustable chair 310. The components of chair 310 are structured as described above in relation to the chair 10 except the differences described below. The chair 310 comprises a second load transfer member 365 that connects the second ends of the two fore-aft bars 20a, 20b. In this embodiment, the second load transfer member 365 is positioned directly between the second ends of the two fore-aft bars 20a, 20b. Turning now to Figure 4, there is shown a schematic downward view of the adjustable chair 310. The chair 310 comprises two armrests 85 located on opposing sides of the chair 310 such that the user is provided with support on both sides of the chair 310. Turning now to Figure 5, there is shown a schematic cross-sectional cut view of the adjustable chair 365 of Figure 3 along line Z-Z of Figure 4. The first load transfer member 55 comprises a first load transfer bar 70 and a second load transfer bar 75. The first load transfer bar 70 is bolted to the leg 25 of the chair 310. The second load transfer bar 75 is rotatably coupled to the first load transfer bar 70 and bolted to the fore-aft bar 20a and the second fore-aft bar20b. One of the first load transfer bar 70 and the second load transfer bar 75 is hollow and the other of the first load transfer bar 70 and the second load transfer bar 75 is within the hollow load transfer bar. The second load transfer member 365 comprises a first load transfer bar 71 and a second load transfer bar 76. The first load transfer bar 71 is bolted to the seat 30 of the chair 310. The second load transfer bar 76 is rotatably coupled to the first load transfer bar 71 and bolted to the fore-aft bar 20a and the second fore-aft bar 20b. One of the first load transfer bar 71 and the second load transfer bar 76 is hollow and the other of the first load transfer bar 71 and the second load transfer bar 76 is within the hollow load transfer bar. Turning now to Figures 6a-c, there are shown three perspectives views of the adjustable chair 310 in three different positions. The lift actuator 35 and tilt actuator 40 are configured to work together to achieve the different positions displayed in Figures 6a-c. Figure 6a shows the seat 30 of the chair 310 in a raised position. In Figure 6a, the lift actuator 35 and tilt actuator 40 are both extended by the same amount, causing the seat 30 to remain horizonal whilst being raised relative to the base 80 of the chair 365. Figure 6b shows the chair 310 in a rearward tilted position wherein the seat 30 is reclined. In Figure 6b, the tilt actuator 40 is extended by a greater distance than the lift actuator 35, causing the seat 30 to tilt rearwards. Figure 6c shows the chair 310 in a forward tilted position wherein the seat 30 is tilted forward. In Figure 6c, the lift actuator 35 is extended by a greater distance than the tilt actuator 40, causing the seat 30 to tilt forwards. The lift actuator 35 and tilt actuator 40 are controlled by supplying a voltage to each actuator, the voltage corresponding to a speed and direction (extension or retraction) of movement. As such by adjusting the voltage applied to the tilt and lift actuators, the position and orientation of the seat 30 is controlled. Turning now to Figure 7a, there is shown a perspective view of the mount 90 for affixing the armrest 85 to the adjustable chair 10. The mount 90 comprises a cover 92 that protects the internal features of the mount 90. The cover 92 is removable and can be affixed to the armrest by using one or more screws. Turning now to Figure 7b, there is shown a perspective view of the mount 90 of Figure 7a with its cover 92 removed and with the arm 95 in a forward position. The arm 95 is pivotally attached to the mount 90 such that it can rotate between a forward position and a retracted position. The mount 90 comprises an upper stop 100 rotatably attached to the mount 90. The upper stop 100 is positioned such that a top surface 120 of the arm 95 contacts a lower surface of the upper stop 100 when the arm 95 is in its forward position. The mount 90 also comprises a lower stop 101 rotatably attached to the mount 90. The lower stop 101 is positioned such that a bottom surface 110 of the arm 95 contacts an upper surface of the lower stop 101 when the arm 95 is in its forward position. The upper stop 100 comprises a set of upper recesses 115 spaced around a circumference of the upper stop 100. Each upper recess 115 is configured to support the top surface 120 of the arm 9 5 when the arm 95 is pivoted to the forward position. Each of the upper recesses 115 on the upper stop 100 has a different depth such that when the upper stop 100 is rotated, the arm 95 contacts a different recess 115. This permits the arm 95 to be orientated at different angles in the forward position depending on the user’s preference. The lower stop 101 comprises a set of lower recesses 105 spaced around a circumference of the lower stop 101. Each lower recess 105 is configured to support a bottom surface 110 of the arm 95 when the arm 95 is pivoted to is forward position. Each of the lower recesses 105 on the lower stop 101 has a different depth such that when the lower stop 101 is rotated, the arm 95 contacts a different recess 105. This permits the arm 95 to be orientated at different angles depending on the user’s preference. The mount 90 is configured such that each of the lower recesses 105 has a corresponding upper recess 115 which it is paired to. The upper stop 100 and lower stop 101 are connected via a coupling mechanism 125 configured to transfer rotation of one of the upper 100 and lower 101 stops to the other of the upper 100 and lower 101 stops. The coupling mechanism 125 is a belt system, wherein each of the upper stop 100 and lower stop 101 have a plurality of teeth onto which the toothed belt 125 is mounted. Turning now to Figure 7c, there is shown a perspective view of the mount 90 of Figure 7a with its cover 92 removed and with the arm 95 in a vertical retracted position. When the arm 95 is pivoted into its vertical retracted position, the top surface 120 of the arm 95 is in contact with a forward-facing recess 115 of the upper stopper 100. Likewise, when the arm 95 is pivoted into its vertical retracted position, the bottom surface 110 of the arm 95 is in contact with a backward facing recess 105 of the lower stopper 101. Although particular embodiments of the disclosure have been disclosed herein in detail, 5 this has been done by way of example and for the purposes of illustration only. The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims. It is contemplated by the inventors that various substitutions, alterations, and 10 modifications may be made to the invention without departing from the scope of the invention as defined by the claims.

Claims

1. An adjustment mechanism of an adjustable chair, the adjustment mechanism comprising:a fore-aft frame pivotally connected to a leg of the chair and pivotally connected to a seat of the chair,a lift actuator pivotally attached to the leg of the chair at a first end of the lift actuator and pivotally attached to the fore-aft frame of the chair at a second end of the lift actuator,a tilt actuator pivotally attached to the fore-aft frame at a first end of the tilt actuator and pivotally attached to the seat of the chair at a second end of the tilt actuator, the second end being attached forward of the first end.

2. An adjustment mechanism according to claim 1, wherein, when the tilt and lift actuators are extended by the same distance, a shape formed between the lift actuator, the leg and the fore-aft frame is the same as a shape formed between the tilt actuator, the fore-aft frame and the seat of the chair.

3. An adjustment mechanism according to claim 1 or claim 2, wherein the lift actuator and the tilt actuator are configured to perform the same action when they receive the same input.

4. An adjustment mechanism according to any preceding claim wherein the lift actuator and tilt actuator are controllable independently of each other.

5. An adjustment mechanism according to any preceding claim wherein the tilt actuator is attached to the fore-aft frame via a branch member, the branch member fixedly attached to the fore-aft frame and pivotally attached to the tilt actuator.

6. An adjustment mechanism according to any preceding claim wherein the fore-aft frame comprises a first fore-aft bar to which the lift and tilt actuators are attached.

7. An adjustment mechanism according to claim 6, wherein the fore-aft frame comprises at least one load transfer member configured to transfer load applied by the lift and tilt actuators widthways across the fore-aft frame.

8. An adjustment mechanism according to claim 6 or 7, wherein the fore-aft frame comprises a second fore-aft bar and the first and second fore-aft bars are on opposing lateral sides of the chair.

9. An adjustment mechanism according to claim 8, wherein the at least one load transfer member comprises:a front load transfer member fixedly coupled to the first fore-aft bar and optionally fixedly coupled to the second fore-aft bar and,a rear load transfer member fixedly coupled to the first fore-aft bar and optionally fixedly coupled to the second fore-aft bar.

10. An adjustment mechanism according to any of claims 7 to 9 wherein the load transfer member(s) each comprise a first bar and a second bar, the first bar being fixedly attached to the leg of the chair or the seat of the chair and the second bar being rotatably coupled to the first bar and fixedly coupled to the first fore-aft bar and optionally the second fore-aft bar.

11. An adjustment mechanism according to claim 10, wherein one of the first bar and the second bar is hollow and the other of the first bar and the second bar is within the hollow bar.

12. An adjustment mechanism according to claim 9, or claims 10 or 11 when dependent on claim 9, wherein a central region of the rear load transfer member is positioned higher than a lowest part of the seat.

13. An adjustment mechanism according to any preceding claim wherein the fore-aft frame is a metal frame.

14. An adjustment mechanism according to any preceding claim wherein a diameter of the or each load transfer member is at least 50mm.

15. An adjustment mechanism according to any preceding claim, the adjustment mechanism further comprising a controller configured to transmit inputs to the lift and tilt actuators, wherein the controller comprises hardware components configured to:receive user input,convert the user input to actuator input signals, andtransmit the actuator input signals to the lift and tilt actuators.

16. An adjustable chair comprising:a seat,a leg,a base, supporting the leg, andthe adjustment mechanism of any of claims 1 to 15.

17. A method of raising an adjustable chair comprising applying the same input to a lift actuator and a tilt actuator to cause a seat of the chair to rise without changing its incline.

18. An adjustable armrest for a chair, the adjustable armrest comprising: a mount,an arm pivotally attached to the mount,an upper stop rotatably attached to the mount and positioned to contact a top surface of the arm when the arm is pivoted to a forward position, anda lower stop rotatably attached to the mount and positioned to contact a bottom surface of the arm when the arm is pivoted to the forward position,wherein the lower stop comprises a set of lower recesses spaced around a circumference of the lower stop, each lower recess configured to support a bottom surface of the arm when the arm is pivoted to the forward position, andthe upper stop comprises a set of upper recesses spaced around a circumference of the upper stop, each upper recess configured to support the top surface of the arm when the arm is pivoted to the forward position andwherein each upper recess is paired with a respective one of the lower recesses and each pair of recesses are configured to support the arm at a different angle in the forward position.

19. An adjustable armrest according to claim 18, further comprising a coupling mechanism configured to transfer rotation of one of the upper and lower stops to the other of the upper and lower stops.

20. An adjustable armrest according to claim 19, wherein the coupling mechanism comprises a belt, optionally, a toothed belt.

21. An adjustable armrest according to any of claims 18 to 20, wherein the set of upper recesses consists of four upper recesses and the set of lower recesses consists of four lower recesses.

22. An adjustable chair comprising the armrest of any of claims 18 to 21, wherein the mount is attached to a backrest of the chair.

23. An adjustable chair according to claim 16, the adjustable chair further comprising an armrest according to any of claims 18 to 20.

24. A computer-readable medium having computer-executable instructions adapted to cause a 3D printer to print an armrest mount according to any of claims 18 to 20.

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