TILT-IN-SPACE WHEELCHAIR WITH DYNAMIC TILT RANGE

Abstract

A wheelchair provides a tilt function characterized by tilt-in-space behaviour in the posterior tilt range and wherein in the anterior tilt range, the seat to backrest angle opens as the seat tilts forward.

Claims

1. A wheelchair having a tilt function comprising a guide plate having a slot that tracks the movement of an upper frame during posterior tilt of said upper frame, and wherein during anterior tilt of said upper frame, a force is applied against said guide plate to cause a cylinder assembly that is attached to said guide plate to actuate recline of a backrest.

2. The wheelchair of claim 1 wherein said cylinder assembly is attached to selectively recline a backrest, said cylinder assembly being lockable during tilting of said upper frame and further comprising: a rod of said cylinder assembly being attached to said plate; said plate being pivotally attached to said upper frame; a pin depending from said upper frame, said pin defining a path as said upper frame is tilted; said pin extending into and being retained in said slot; said slot being configured not to exert substantial resistance to said pin along said path as said upper frame is tilted in a posterior range of tilt; said slot further being configured to cause said pin to pull said plate forward as said upper frame is tilted in the anterior direction while said cylinder assembly is locked, said plate thereby exerting a forward force on said locked cylinder assembly; whereby posterior tilting of said upper frame does not cause said backrest to substantially recline but anterior tilting of said upper frame causes said backrest to recline.

3. A wheelchair having a tilt function comprising: a cylinder assembly attached to selectively recline a backrest, said cylinder assembly being lockable during tilting of an upper frame of said wheelchair; a member pivotally attached to said upper frame at a tilt pivot axis; said cylinder assembly having a rod pivotally attached to said member at a point that is spaced from said tilt pivot axis; a longitudinal axis of said cylinder assembly and a spacing of said point from said tilt pivot axis being selected so that said backrest does not substantially recline during posterior tilting of said upper frame but said backrest reclines during anterior tilting of said upper frame.

4. The wheelchair of claim 3 wherein a point of attachment of a cylinder of said cylinder assembly to a backrest assembly defines a path of travel during posterior tilting of the upper frame that is approximately parallel to a tilt arc of the upper frame during posterior tilting of said upper frame, said spacing being effective to cause said path of travel to deviate from said tilt arc to a greater extent than during posterior tilting so as to exert a recline force on said cylinder assembly during anterior tilting of said upper frame.

5. The wheelchair tilt mechanism of claim 4 wherein said longitudinal axis of said cylinder assembly aligns with said pivot axis at a tilt angle that is located between 10 and 20 of posterior tilt of said upper frame.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] At least one mode for carrying out the invention in terms of one or more examples will be described by reference to the drawings thereof in which:

[0031] FIG. 1 is a front and bottom isometric view of the structural components of a wheelchair according to the preferred embodiment of a first approach of the invention;

[0032] FIG. 2 is a front view of the preferred embodiment of a first approach of the invention;

[0033] FIG. 3 is a side sectional view taken along line 3-3 of FIG. 2, with the upper frame being in a neutral seated position;

[0034] FIG. 4 is the same view as FIG. 3 but with the chair in posterior tilt;

[0035] FIG. 5 is the same view as FIG. 3 but with the chair in anterior tilt;

[0036] FIG. 6 is a partially exploded side elevation of the chair of FIG. 3;

[0037] FIG. 6A is an enlarged side elevation of the guide plate;

[0038] FIG. 7 is a partially exploded isometric view of the chair of FIG. 3;

[0039] FIG. 8 is a bottom view of the chair of FIG. 2;

[0040] FIG. 9 is a front view of the structural components of a wheelchair according to the preferred embodiment of a second approach of the invention, with the right rear wheel removed;

[0041] FIG. 10 is a side sectional view taken along line 10-10 of FIG. 9;

[0042] FIG. 11 is the same view as FIG. 10 but with the chair in posterior tilt;

[0043] FIG. 12 is the same view as FIG. 10 but with the chair in anterior tilt;

[0044] FIG. 13 is an isolated view of the upper frame, backrest assembly, sub-frame and recline cylinder assembly of FIG. 10, with the chair in a neutral tilt position;

[0045] FIG. 14 is an isolated view of the upper frame, backrest assembly, sub-frame and recline cylinder assembly of FIG. 10 with the chair in posterior tilt;

[0046] FIG. 14A is an isolated view of the upper frame, backrest assembly, sub-frame and recline cylinder assembly of FIG. 10 with the chair in posterior tilt and showing a path of travel of a backrest connection point and an arc of travel of the upper frame during tilting; and,

[0047] FIG. 15 an isolated view of the upper frame, backrest assembly, sub-frame and recline cylinder assembly of FIG. 10 with the chair in anterior tilt.

DETAILED DESCRIPTION OF AT LEAST ONE MODE FOR CARRYING OUT THE INVENTION IN TERMS OF EXAMPLE(S)

[0048] Referring to FIGS. 1 and 6, the wheelchair of the preferred embodiment generally comprises a lower frame assembly 10 that provides mounting locations 12 for the large rear wheels 14 and mounting locations 16 for the small casters 18 which support the wheelchair. A sub-frame assembly 20 is fixedly bolted to the lower frame member 11 by means of two of several attachment positions 13, the plurality of which facilitates height adjustability of the sub-frame relative to the ground. The sub-frame 20 can be considered a sub-component of the lower frame assembly 10. It is attached by mounting plates 15 to the frame member 11.

[0049] An upper frame 22 bolts to the sub-frame through a rotatable bolted connection 24, enabling the tilting of the upper frame relative to the sub-frame. The bolted connection 24 is preferably positioned in a location that is sufficiently forward on the chair that when tilting, the vertical movement (rise or drop) of the front of the upper frame is minimized.

[0050] A tilt hydraulic cylinder assembly 30 bolts rotatably to the upper frame at its rearward end 31 (best seen in FIG. 8) and to the sub-frame at its forward end 34. Extension and retraction of the tilt rod 33 actuates rotation of the upper frame relative to the sub-frame about the pivot point 24 to tilt the upper frame. In the preferred embodiment, the tilt cylinder assembly 30 is mounted to the sub-frame 20 such that the seat is in a neutral position)(tilt=0 when the tilt rod 33 is approximately halfway extended. The tilt cylinder assembly 30 further provides an elastic locking function through its travel allowing the upper frame 22 to be parked or locked in a given position relative to the sub-frame 20. According to the preferred embodiment, the upper frame can be positioned from 20 to the posterior to 30 to the anterior direction relative to the sub-frame.

[0051] The backrest assembly 40 bolts rotatably to the upper frame near the upper frame's rear end at 42 enabling backrest rotation relative to the upper frame 22. The connection 42 is positioned in a location to minimize shear of the seat and back surfaces. Shear refers to the difference developed between the combined lengths of the seat and back surfaces of the wheelchair and the combined length of the occupant's upper leg and torso, created during the recline motion. If the backrest pivot 42 is located at or very near the occupant's hip joint there will be no shear (or no differential length developed). As the backrest pivot moves away from the hip joint the shear will increase, which is not desirable as the occupant will lose proper alignment with the backrest surface and headrest if there is a headrest. A backrest recline hydraulic cylinder 49 is attached to the backrest assembly 40 at 45 with its rod 51 being attached according to whether the first or the second approach of the invention is being implemented.

[0052] According to the preferred embodiment of the first approach to the invention illustrated in FIGS. 2-8, a guide rail or plate 50 is rotatably attached to the upper frame 22 (preferably one guide plate on each of the port and starboard sides of the wheelchair) and is attached by means of a backrest recline cylinder assembly (cylinder 49 and rod 51) to the backrest assembly 40.

[0053] The connection of the guide plate 50 to the upper frame 22 causes the guide plate to move with the upper frame 22 during tilting of the upper frame 22. The guide plate 50 includes a slot 56 for receiving a slide arm or pin 58 that is mounted onto the sub-frame 20. As discussed in the Summary of the Invention, the shape, location and curvature of the slot 56 determines the behaviour of the backrest 54 as the sub-frame 20 reacts to the tilting of the upper frame 22. The backrest is connected to the guide plate 50 by means of the recline cylinder assembly 49, 51, the latter being locked during tilting of the upper frame. As the upper frame 22 is tilted through the posterior range, the movement of the pin 58 that is mounted on the sub-frame 20 matches the path and radius of curvature of the portion 59 (the posterior range) of slot 56. While in posterior tilt, portion 59 of the slot 56 effectively matches the normal movement of the pin 58. The result is no relative movement between the guide plate 50 and the upper frame 22. The slot 56 therefore accommodates the movement of the pin 58 through the posterior range so that there is no net force on the guide plate 50 and therefore no force on the locked recline rod 51 or on the backrest mounting plate 60.

[0054] When the tilt angle reaches the anterior range, the slot 56 changes direction (61) so that tilting of the chair causes the pin 58 to now urge the guide plate 50 to pull against the locked recline rod 51. The backrest 54 is thereby urged to open its angle to the seat. More specifically, the guide pin 58 follows the slot 56 in the guide plate 50 in portion 61 of the slot in such a way as to pull the recline rod 51 and therefore the backrest pivot member 60. That in turn causes the backrest 54 to recline in relation to the upper frame 22. The backrest thereby reclines with an anterior tilt. Selecting different shapes and curvatures of the slot 56 can result in different recline behaviour of the backrest.

[0055] The recline cylinder assembly 49, 51 further provides an elastic locking function through its travel allowing the backrest 54 to be locked in a position relative to the upper frame 22 for a given upper frame position. The backrest can be positioned from 90 to 130 posterior recline depending on the upper frame position, 90 being a standard perpendicular backrest position.

[0056] According to the preferred embodiment of the second approach, illustrated in FIGS. 9-15, a backrest recline hydraulic cylinder assembly 49, 51 bolts rotatably to the sub-frame 20 at its forward end 34 and to the mount 60 of the backrest at its rearward end 45. Extension and retraction of the recline rod 51 allows rotation of the backrest relative to the upper frame 22 about pivot axis 42. As will be discussed below, it is primarily the alignment of the longitudinal axis of the recline cylinder assembly 49, 51 with the upper frame tilt axis 24 and the spaced location of the sub-frame recline rod mount 34 in relation to the tilt pivot axis 24 that develop the desired differential backrest angles for the posterior and anterior tilt ranges of the upper frame 22. A parallelogram arrangement of the points 24, 34, 45 and 42 govern the relative movement of the points. According to the preferred embodiment illustrated in the drawings, the backrest angle to the seat/upper frame remains substantially constant (2 of recline over 20 of tilt) in the posterior tilt range and the angle opens in the anterior tilt range (12 of recline over 30 of tilt).

[0057] The recline rod mount 34 on the sub-frame 20 is positioned in a location such that for the posterior tilt range it emulates the recline rod 51 having an upper frame mount (in which case there would be no force on the rod during tilting of the upper frame) while for the anterior tilt range it acts according to the relative positions of the upper frame (to which the backrest is mounted) and the sub-frame 20 on which the rod mount is actually located. When the longitudinal axis of the recline cylinder 49, 51 is broadly in alignment with the upper frame tilt pivot axis 24, the assembly 49, 51 effectively behaves as if it were mounted at the upper frame pivot 24. If the assembly 49, 51 were actually mounted at the upper frame pivot location 24 it would provide no relative movement between the backrest 54 and the upper frame 22 (which is the desired behavior for the posterior tilt range only).

[0058] In order to maintain such alignment for the posterior range of tilt, consider a nominal line 70 (see FIG. 14A) connecting the tilt pivot axis 24 and the rod mount 34 and consider further an arc 72 through which the rear of the backrest assembly transits in posterior tilt. Where the rod 51 and cylinder 49 completely align with the tilt axis 24, there will be no force applied to the recline mount 60 during tilt in that portion of the arc 72. In the areas immediately adjacent to that zero point, the force on the recline mount 60 will be negligible, and hence effectively zero as well. The selection of the precise location along the arc 72 at which the rod and cylinder are designed to align perfectly with the tilt axis 24 depends on a trade-off between the area of posterior tilt in which zero backrest recline is desired and the degree to which such position accentuates or not the backrest recline in the anterior tilt zone. The inventors have found that the desired behaviour is achieved when the cylinder assembly 49, 51 is mounted such that the assembly aligns with the tilt pivot axis 24 of the upper frame at a posterior tilt angle of between 10 and 20. The preferred angle of alignment is about 16.5.

[0059] The effect of the invention may also be appreciated by considering the path of travel 72 of the connection point 45 between the cylinder 49 and the backrest assembly 40 and the tilt arc 73 of the upper frame during posterior tilting. The path of travel 72 is approximately parallel to the tilt arc 73 during posterior tilting of the upper frame as observed in area 74. However due to the spacing between tilt axis 24 and the rod to sub-frame mount 34, the path of travel 72 during anterior tilting deviates from being parallel to the arc 73 to a greater extent than during posterior tilting as at area 76. That deviation exerts a recline force on the cylinder assembly and therefore causes the backrest to recline (since the cylinder assembly is otherwise locked during tilting).

[0060] Optionally the recline backrest assembly 40 can further provide an elastic locking function through its travel allowing the backrest to be parked in a position relative to the upper frame for a given upper frame position. The backrest can be positioned from 90 to 130 posterior recline relative to the upper frame, 90 being a standard perpendicular backrest position.

[0061] The sub-frame 20 is rigidly fixed in relation to the lower frame 10. The backrest recline rod 51 is rotatably attached to the sub-frame 20 at a point 34 located inboard of the lower/upper frame tilt pivot axis 24. The location of the mount 45 of the cylinder 49 to the backrest assembly is selected such that the recline assembly 49, 51 is generally or nearly aligned with the tilt pivot axis 24 through the posterior tilt range. As a result, upon the upper frame tilting about the tilt pivot axis 24 in the posterior tilt range, there is relatively little change in that alignment angle and therefore little change in distance between the rearward end of the recline assembly 49, 51 and the tilt pivot axis 24 (roughly equivalent to the seat depth and hence no inducement for the backrest to recline). However the rod to sub-frame mount 34 is spaced a sufficient distance from the tilt pivot axis 24 to induce the following behaviour in the anterior range of tilt. The sub-frame 20 is fixed in relation to the lower frame 10 so it does not move as the upper frame 22 tilts. It follows that the location of the recline rod mount 34 to the sub-frame also does not change. It is effectively fixed in space in relation to the lower frame 10. With a sufficient spacing between the tilt pivot axis 24 and the rod to sub-frame mount 34, as the rear of the upper frame 22 crosses over to the anterior range of tilt, the angle of the recline assembly 49, 51 must then move out of alignment with the tilt pivot axis 24 thereby seeking to decrease the distance between the rearward end of the assembly 49, 51 and the tilt pivot axis 24. The distance is maintained by the rod (which is typically locked during the tilt operation) drawing back on the backrest pivot point 45, causing the backrest to recline in the anterior range of tilt.

[0062] The second approach thereby provides a differential backrest recline behaviour according to whether the upper frame is tilting in the posterior range or in the anterior range.

[0063] In the foregoing description, exemplary modes for carrying out the invention in terms of examples have been described. However, the scope of the claims should not be limited by those examples, but should be given the broadest interpretation consistent with the description as a whole. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.