WO2019068183A1

WO2019068183A1 - Anti-tipper mechanism for wheelchair

Info

Publication number: WO2019068183A1
Application number: PCT/CA2018/051240
Authority: WO
Inventors: Mikael PROUS
Original assignee: Motion Composites Inc.
Priority date: 2017-10-02
Filing date: 2018-10-02
Publication date: 2019-04-11

Abstract

An anti-tipper mechanism for a wheelchair comprises an arm having a first end adapted to provide anti-tipper contact with a ground. An indexing mechanism operatively connects the arm to the wheelchair, and displaces the arm reciprocally between a deployed orientation and a stowed orientation as a response to a manual force applied onto the anti-tipper mechanism.

Description

ANTI-TIPPER MECHANISM

FOR WHEELCHAIR

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority of United States Patent Application No. 62/566,786, filed on October 2, 2017 and incorporated herein by reference.

TECHNICAL FIELD

[0002] The present application relates to wheelchairs and, more particularly, to an anti-tipper mechanism for wheelchairs.

BACKGROUND OF THE ART

[0003] Wheelchairs are commonly equipped with anti-tippers, often in the form of rearwardly projecting arms at the end of which are provided casters or casters wheels. These anti-tippers, also known as anti-tipper mechanisms or anti-tipping mechanisms decrease the chance of an accidental tipping over backwards of a wheelchair, as they block a rearward rotation of the wheelchair.

[0004] Such anti-tippers are often removable from a remainder of the wheelchair, for instance to facilitate the stowing of a wheelchair as the anti-tippers increase the footprint of the wheelchair. Moreover, some wheelchair users may not always need anti-tippers, for example when a wheelchair is pushed from the back by a caretaker. In such a case, the anti-tippers may even be cumbersome. However, the removal of anti-tippers is not always an ergonomic procedure, as the anti-tippers must often be pulled away from a remainder of the wheelchair.

SUMMARY

[0005] It is an aim of the present disclosure to provide an anti-tipper mechanism for wheelchairs that addresses issues associated with the prior art.

[0006] Therefore, in accordance with the present disclosure, there is provided an anti-tipper mechanism for a wheelchair comprising: an arm having at least a first end adapted to provide anti-tipper contact with a ground; and an indexing mechanism operatively connecting the arm to the wheelchair, and displacing the arm reciprocally between a deployed orientation and a stowed orientation as a response to a manual force applied onto the anti-tipper mechanism.

[0007] Further in accordance with the present disclosure, the indexing mechanism has for instance a housing for receiving a second end of the arm, a joint with a rotational degree of freedom and a translational degree of freedom being formed by the housing and the arm.

[0008] Still further in accordance with the present disclosure, the indexing mechanism has for instance a guide and a follower, the follower being on the arm.

[0009] Still further in accordance with the present disclosure, the follower includes for instance a pin connected to the arm inside the housing.

[0010] Still further in accordance with the present disclosure, the follower includes for instance a bearing rotatably mounted to the pin.

[0011] Still further in accordance with the present disclosure, the guide includes for instance a pathway for the follower defined in a wall of the housing.

[0012] Still further in accordance with the present disclosure, the pathway is for instance defined in a structural tube of the housing.

[0013] Still further in accordance with the present disclosure, the pathway has for instance an inverted chevron shape.

[0014] Still further in accordance with the present disclosure, the housing has for instance a structural tube.

[0015] Still further in accordance with the present disclosure, the housing has for instance a sleeve inserted inside the structural tube, the pathway of the guide being defined in a sleeve window of the sleeve.

[0016] Still further in accordance with the present disclosure, the sleeve is for instance made of a polymer, and the structural tube is made of a metal.

[0017] Still further in accordance with the present disclosure, the housing has for instance a clip mounted to an outer surface of the structural tube opposite a tube window in the structural tube, the clip having a guide projection passing through the tube window and inserted into the sleeve window to form the guide with the sleeve window.

[0018] Still further in accordance with the present disclosure, the guide projection and the sleeve window each have for instance an inverted chevron shape.

[0019] Still further in accordance with the present disclosure, the clip is for instance made of a polymer.

[0020] Still further in accordance with the present disclosure, a biasing spring biases for instance the translational degree of freedom in a direction.

[0021] Still further in accordance with the present disclosure, the biasing spring is for instance a coil spring located in an annular space between the housing and the second end of the arm.

[0022] Still further in accordance with the present disclosure, a bearing is for instance at an end of the coil spring in the annular space.

[0023] Still further in accordance with the present disclosure, a push sleeve is for instance at the second end of the arm, the push sleeve mounted over the housing.

[0024] Still further in accordance with the present disclosure, a cap is for instance mounted to the push sleeve, and a bearing between the cap and the push sleeve.

[0025] Still further in accordance with the present disclosure, the guide is formed for instance into at most 185 degrees in a surface of the housing, whereby the arm rotates reciprocally in a range of at most 185 degrees between the deployed orientation and the stowed configuration.

[0026] Still further in accordance with the present disclosure, a clamp is for instance adapted to connect the housing to the wheelchair, the clamp being clamped around an assembly of the clip, the structural tube and the sleeve.

[0027] Still further in accordance with the present disclosure, a clamp is for instance adapted to connect the indexing mechanism to the wheelchair. [0028] Still further in accordance with the present disclosure, the clamp has for instance a clamp end being tightened on an outer surface of the indexing mechanism.

[0029] Still further in accordance with the present disclosure, the clamp end has for instance a C-shaped clamp with at least one fastener to tighten the C-shaped clamp.

[0030] Still further in accordance with the present disclosure, the clamp has for instance a quick-release unit adapted to releasably connect the clamp to a tube of the wheelchair.

[0031] Still further in accordance with the present disclosure, at least one caster is for instance at the first end of the arm.

[0032] Still further in accordance with the present disclosure, a lockable telescopic joint is for instance in the arm between the first end and a junction with the indexing mechanism.

[0033] Still further in accordance with the present disclosure, the arm has for instance a L-shape.

[0034] Still further in accordance with the present disclosure, the L-shape has for instance an angle ranging between 90 degrees to 155 degrees inclusively between its two segments.

[0035] In accordance with another embodiment, there is provided a wheelchair comprising: a frame defining a seat portion and a backrest portion; rear wheels connected to the frame; front casters connected to the frame; at least one of the anti-tipper mechanism as described above, the at least one anti-tipper mechanism being connected to the frame.

DESCRIPTION OF THE DRAWINGS

[0036] Fig. 1 is a perspective view of a wheelchair featuring anti-tipper mechanisms in accordance with the present disclosure;

[0037] Fig. 2 is a perspective view of a rear end of the wheelchair of Fig. 1 , showing one anti-tipper mechanism of the present disclosure; [0038] Fig. 3 is an exploded view of the anti-tipper mechanism similar to that of Fig. 2;

[0039] Fig. 4 is an exploded view of a clamp of the arm of Fig. 2;

[0040] Fig. 5 is an axial section view of the anti-tipper mechanism of Fig. 2;

[0041] Fig. 6 is a perspective view of a pathway clip of the anti-tipper mechanism of Fig. 2;

[0042] Fig. 7 are perspective views of a pathway sleeve of the anti-tipper mechanism of Fig. 2;

[0043] Fig. 8 is an assembly view of the pathway clip and pathway sleeve of the anti-tipper mechanism of Fig. 2; and

[0044] Fig. 9 is a flattened view of pathways of the pathway clip and pathway sleeve of the anti-tipper mechanism of Fig. 2

[0045] Fig. 10 is a flattened view of a pathway of the pathway sleeve of the anti- tipper mechanism of Fig. 2, in accordance with another embodiment of the present disclosure.

DETAILED DESCRIPTION

[0046] Referring to the drawings and, more particularly, to Figs. 1 and 2, a wheelchair with an anti-tipper mechanism is generally shown at 10. The wheelchair 10 has rear drive wheels 1 1 and a frame 12 having for example a plurality of tubular frame members, the frame 12 forming the structure supporting a plurality of components, such as rear wheel mounting brackets, a brake system, foot rests, etc. While not described in full detail, the frame 12 interfaces the wheels 1 1 to a seat 13, a backrest 14, armrests 15 and/or caster assemblies 16, among other components. For clarity, the rolling direction of the wheel 1 1 in a forward movement of the chair is illustrated by A. While the frame 12 has tubular frame members, it may formed of other types of structural members as an alternative or as a complement to tubular members. For example, plates may be used.

[0047] Anti-tipper mechanisms in accordance with the present disclosure are shown at 20. In Fig. 1 , the wheelchair 10 has two of the anti-tipper mechanisms 20, whereas one is shown in Fig. 2. The wheelchair may have one or more anti-tipper mechanism 20. The expression "anti-tipper mechanism" is used herein, but other names could be used as well to identify the mechanism, such as anti-tippers or anti- tipping mechanisms. It is contemplated to use a wheelchair with a pair of anti-tipper mechanisms 20 for balance and optimal roll over protection, but a wheelchair may also operate with a single anti-tipper mechanism 20. The anti-tipper mechanisms 20 project rearwardly in conventional fashion, to increase the footprint of the wheelchair

10 to which they are connected. Increasing the footprint does not imply that the anti- tipper mechanism(s) 20 is in contact with a ground simultaneously with the wheels

1 1 and the casters of the caster assemblies 16, though the wheelchair 10 may have all of these in simultaneous contact with a floor. The anti-tipper mechanism 20 increases the footprint of the wheelchair in that, from a bird's eye top plane view, the wheelchair 10 has a greater length when the anti-tipper mechanism 20 is deployed in an anti-tipping orientation.

[0048] For simplicity, the anti-tipper mechanisms 20 will be mostly described in the singular hereinafter, to simplify the text. However, both anti-tipper mechanisms

20 have a similar construction (e.g., identical, or symmetric with one for the left and one for the right), whereby the components described in the singular may be present in both of the anti-tipper mechanisms 20. The anti-tipper mechanism 20 has an arm

21 that is releasably connected to the frame 12, and projects rearwardly. As in Fig. 2, the arm 21 may have a first portion 21 A and a second portion 21 B telescopically connected to the first portion 21A, with a collar 23 blocking the portions 21 A and 21 B together when tightened. Casters 22 (a.k.a., wheels, rollers, etc) may be at a free end of the second portion 21 B, to contact the ground and block a roll over of the wheelchair 10 if the frame 12 tips or rotates rearwardly about the axis of the wheels 1 1 . Figs. 1 and 2 show pairs of casters 22, but a single caster 22 may suffice for each anti-tipper mechanism 20. Moreover, it is possible also to have an arm 21 without any caster 22, for instance by a contact pad (e.g, polymer, PTFE) or like end component configured to contact the ground. In such a case, the end of the arm 21 would simply contact the ground and block a roll over. As a direction of the telescopic joint formed concurrently by the portions 21 A and 21 B is transverse relative to the horizon (between 0 and 60 degrees when the wheelchair 10 is horizontal), a displacement of the second portion 21 B relative to the first portion 21 A may adjust a height of the casters 22. The adjustment of height of the casters 22 may be determined by the user, as a preference for the maximum permissible rearward roll angle. The telescopic joint may be optional. Referring to Fig. 3, the arm 21 may have another shape than that shown in Figs. 1 and 2. In Fig. 3, the arm has a L shape, formed of a pair of tubes, for instance welded to one another. Other shapes may also be used, including with a L shape that has an angle ranging from 90 degrees to 155 degrees, with the shape at 155 degrees being akin to a chevron. As shown in Fig. 3, a pin 24 supports a cam 24A projecting from the arm 21 . The pin 24 may alternatively be used as cam. In an embodiment, the cam 24A is rotatably mounted to the pin 24, for easing a following action of the cam 24A along guideways, as explained hereinafter. For example, the cam 24A is a bearing on the pin 24. As another example, the cam 24A is a low friction sleeve. Although the expression "cam" is used, the principle is that of a following component, or follower, that cooperates with a guideway, so as to follow a movement direction imparted by the guideway. As the pin 24/follower/cam 24A is connected to the arm 21 , the movement of the arm 21 Is guided by the pin 24/follower/cam 24A following (rolling along, sliding along) the guideway. The guideway is described hereinafter.

[0049] Referring to Figs. 2 and 3, the anti-tipper mechanism 20 may have a clamp 25 by which the arm 21 is connected to the frame 12. The clamp 25 may be of any appropriate type, but is shown as having a C-shaped connector 26 having a C-shaped body 26A, with a vertical slit 26B (a.k.a., gap). The C-shaped body 26A is configured to elastically deform when a fastener(s) 26C closes the slit 26B. An annular channel 26D may be provided in the connector for receiving a circlip 26E to block movement of the component of the anti-tipper mechanism 20 received in the clamp 25.

[0050] A coupler 27 projects from the clamp 25, and is for insertion in an open tube of the frame 12, in the manner shown in Figs. 1 and 2. The coupler 27 may be in the form of a tube as in Fig. 4. The connection may be permanent, or may be releasable as well. The coupler 27 may be part of a quick-release unit. According to such an embodiment, the coupler 27 is hollow as it is a tube, and has a hole 27A for receiving a pin 28A of a spring 28. Another pin 28B is on the spring 28, and is received in a hole 29A of the C-shaped body 26A having a detent 29. The spring 28 is a U-shaped spring that is inserted into the inner cavity of the coupler 27, with the pins 28A and 28B respectively received in the holes 27A and 29A, respectively. Therefore, by pressing on the detent 29, the pin 28A may move downwardly relative to the hole 27A through entrainment of the pin 28B. Hence, the pin 28A may move in and out of engagement with a corresponding hole of a tube in the frame 12 matingly receiving the coupler 27. This is one configuration among others as it is also contemplated to have the clamp 25 bolted directly to the frame 12, for releasable engagement. Moreover, some alternatives to the clamp 25 may be used to secure the anti-tipper mechanism 20 to the frame 12, such as brackets, collars, etc. The clamp 25 or equivalent may also be part of the frame 12, instead of being a part of the anti-tipper mechanism 20.

[0051] Referring to Figs. 2 and 3, the anti-tipper mechanism 20 has an indexing mechanism 30. The indexing mechanism 30 is clamped to the frame 12 by the clamp 25, and supports the arm 21 , in such a way that the arm 21 may rotate from the deployed orientation shown in Figs. 1 and 2 (a.k.a., anti-tipping orientation), to a stowed configuration (Fig. 2 in phantom lines) under the seat 13. The arm 21 has a vertical end extending into the indexing mechanism 30. In an embodiment, the stowed configuration is about 180 degrees (e.g., between 160 and 185 degrees) inward of the orientation shown in Figs. 1 and 2. The indexing mechanism 30 is configured for the arm 21 to be in either one of the deployed and stowed orientations only, with the displacement between orientations resulting from a downward push thereon by a user. Due to the placement of the anti-tipper mechanism 20, a wheelchair occupant may even activate the displacement from a seated position in the seat 13.

[0052] According to an embodiment shown in Figs. 3 and 5, the indexing mechanism 30 has a housing for receiving an end of the arm 21 and guiding its movements between orientations, as described below. In accordance with an embodiment, the housing includes structural tube 31 upon which numerous of the components of the indexing mechanism 30 are mounted. The structural tube 31 is received in the clamp 25, and is therefore immovably fixed to the frame 12 of the wheelchair 10 when the anti-tipper mechanism 20 is fixed to the wheelchair 10. A channel, shoulder or like abutment may be present on the surface of the structural tube 31 for receiving the circlip 26E if present, and block axial movement between the clamp 25 and the tube 31 , though a tightening of the clamp 25 may suffice in blocking the axial movement. The structural tube 31 has a window section 31A in which a window 31 B is defined (Fig. 3). The window 31 B is present for the interaction between the cam 24A and a pathway clip 40 and pathway sleeve 50, as explained in full details below. The pathway clip 40 and pathway sleeve 50, though optional, may also be part of the housing with the structural tube 31 . The structural tube 31 may also have a notch 31 C at its bottom edge for proper alignment of the pathway sleeve 50. As an alternative, visual markers could be used. The structural tube 31 may further include surface depressions 31 D at the window section 31 A, notably to allow the pathway clip 40 to be attached in the window section 31 A and/or for collaborating with the circlip 26E and block axial movement. The surface depressions 31 D may result from a thinning portion of the structural tube 31 . When positioned in the window section 31A, the pathway clip 40 is in the recess formed by the window section 31 A such that the outer surface of the structural tube 31 and of the pathway clip 40 form a generally continuous surface of generally constant diameter, except if the surface depressions 31 D are present.

[0053] A push sleeve 35 is mounted onto the structural tube 31 , so as to be displaceable at least in translation. In other words, the push sleeve 35 may move up and down along the structural tube 31 . As seen in Fig. 5, the push sleeve 35 has an inner connector 35A by which it is fixed to the end of the arm 21 . The inner connector 35A may include a groove, threading, force fit or friction members, etc. Therefore, the push sleeve 35 and the arm 21 move together, and a pushing action on the push sleeve 35 may result in a downward movement of the arm 21 . The push sleeve 35 has a cap 36 thereon. The cap 36 may be rotatably connected to the push sleeve 35 by way of a bearing 36A, such that the cap 36 may rotate relative to the push sleeve 35, in the embodiment of Fig. 3. Fig. 5 shows a different arrangement, without bearing. A spring 37 surrounds the arm 21 and is in the annular space the arm 21 defines with the structural tube 31 and/or push sleeve 35, and contacts the push sleeve 35, such that the push sleeve 35 and arm 21 are biased upwardly to the position shown in Fig. 5. In the embodiment of Fig. 3, the spring 37 has its lower end against a ring 38 supported by a bearing 39 mounted to an inner shoulder 39A of the structural tube 31 . As the arm 21 and push sleeve 35 may rotate relative to the structural tube 31 , when the arm 21 changes orientation from that shown in Figs. 1 and 2 to the stowed orientation (Fig. 2, phantom lines), the ring 38 and bearing 39 ensure that the spring 37 may also rotate. Moreover, as the user causes this rotation by pressing on the cap 36, the bearing 36A allows the cap 36 not to rotate when manipulated while the arm 21 and push sleeve 35 rotate.

[0054] Referring concurrently to Figs. 6 to 9, the pathway clip 40 and the pathway sleeve 50 are paired to form the pathways of the indexing mechanism 30 that will cause the automatic indexing movement of the arm 21 from the deployed orientation shown in Figs. 1 and 2 to the stowed orientation (Fig. 2 in phantom lines), and vice- versa. Stated differently, it is the pathway clip 40 and/or the pathway sleeve 50 that define the "guide" for the follower (i.e., the pin 24/cam 24A) in the guide-follower pair. The pathway clip 40 has a guide projection 41 having a V shape (trough shaped) so as to define pathways 42A and 42B. Other shapes include a U shape, or separate segments.

[0055] The pathway sleeve 50 has a window 51 whose perimeter defines pathways 52A and 52B. The pathways 52A and 52B meet at receptacle 53 and 54 that are also part of the window 51 . The pathway sleeve may have a block 55 on its outer surface to be received in the notch 31 C for proper alignment of the sleeve 50 with the structural tube 31 . Indeed, for the proper indexing of the arm 21 , the pathways 42A, 42B, 52A and 52B must be aligned in the manner shown in Fig. 9, for the cam 24A to be guided appropriately. While Fig. 9 shows a flat view of the pathways 42A, 42B, 52A and 52B for ease of illustration, in reality the pathways 42A, 42B, 52A and 52B are curved as they are respectively part of the pathway clip 40 and pathway sleeve 50, both of which are arcuate. Fig. 9 shows the flat views for ease of illustration. As observed from Fig. 9, the guide projection 41 and the window 51 may have an inverted chevron shape.

[0056] Now that the various components of the anti-tipper mechanism 20 have been described, an indexing of the arm 21 is set forth.

[0057] Referring to Fig. 9, as a starting point, the cam 24A is in the receptacle 53. At that starting point, the arm 21 and push sleeve 35 are biased to their upmost position, as in Fig. 5. The arm 21 may have the casters 22 deployed or stowed at the starting point.

[0058] As a user presses down on the push sleeve 35, the arm 21 will move downwardly, and the cam 24A will be guided by the pathway 52A to position P1 in Fig. 9. Keeping in mind that the pathways are curved about axis Y, this movement of the cam 24A will cause a rotation of the arm 21 . When reaching position P1 , the arm 21 and push sleeve 35 may no longer move downwardly. This may be felt by the user who will be blocked from pushing the push sleeve 35 further down. The user will release or lessen the pressure on the push sleeve 35 and cap 36. The spring 37 will therefore bias the arm 21 and push sleeve 35 back to the position of Fig. 5. In Fig. 9, this will result in the cam 24A going from position P1 to the receptacle 54. It is observed that an apex 42A' of the pathway 42A is offset rearward of the position P1 , such that the pathway 42A ensures that the cam 24A goes to receptacle 54. Consequently, when the cam 24A reaches the receptacle 54, the arm 21 has reached its other indexed orientation, whether it be with the casters 22 deployed or stowed (i.e., it is the other than at the receptacle 53). A slight curvature is shown in pathway 52A, near the receptacle 54, so that the receptacle 54 is aligned with the pathway 42B. This way, when the arm 21 is pushed down with the pin 24/cam 24A in the receptacle 54, the pin 24/cam 24A comes straight down on the pathway 42B.

[0059] To return the arm 21 and casters 22 to the initial indexed orientation, in the receptacle 53, the user presses down on the push sleeve 35 once more, causing the arm 21 to move downwardly. The cam 24A will be guided by the pathway 42B to position P2 in Fig. 9. As the pathways are curved about axis Y, this movement of the cam 24A to position P2 will cause a rotation of the arm 21 . When reaching position P2, the arm 21 and push sleeve 35 may no longer move downward, and this is felt by the user who releases the pressure on the push sleeve 35 and cap 36. The spring 37 will therefore bias the arm 21 and push sleeve 35 back to the position of Fig. 5. In Fig. 9, this will result in the cam 24A going from position P2 to the receptacle 53. It is observed that an apex of the pathway 52B is offset rearward of the position P2 in a direction of movement, such that the pathway 52B ensures that the cam 24A goes to the receptacle 53, and not back to the receptacle 53. Stated differently, if the user releases the pressure on the push sleeve 35 and cap 36 when the cam 24A is position P2, the cam 24A will move straight up against the pathway 52B, and the cam 24A will slide/roll to the receptacle 53 as biased by the spring 37. Consequently, when the cam 24A reaches the receptacle 53, the arm 21 has returned to its initial indexed orientation.

[0060] The location of the receptacles 53 and 54 define the scope of the angular movement of the arm 21 between the deployed orientation and the stowed orientation. For example, if the receptacles 53 and 54 are diametrically opposed, the arm 21 covers an angular range of 180 degrees. In an embodiment, the angular range of movement is 185 degrees or less, though the angular range of movement can be more.

[0061] Therefore, according to an embodiment, the arm 21 is operatively connected to the housing featuring the structural tube 31 so as to form a two degree-of-freedom (DOF) joint, i.e., a translational DOF and a rotational DOF. The indexing mechanism 30 is configured for constraining the movements of the arm 21 in the two DOFs into a reciprocal rotation between the deployed orientation and the stowed orientation. The indexing mechanism 30 uses the translational DOF for allowing a user to provide a push to index the movements of the arm 21 between the two orientations. A same input by a user on the indexing mechanism 30 results in an automatic movement of the arm 21 between the two orientations. A same input results in a binary output. The indexing mechanism 30 may be described as being a single input, binary output indexing mechanism. The indexing mechanism 30 may also be described as being a translation input, binary rotational output indexing mechanism. The single input may be described as a single degree of freedom input, as a straight push input, as a translation input among other terms.

[0062] The collaboration between the pathway clip 40 and pathway sleeve 50 may simplify the maneuvering done by a user to index the arm 21 between the deployed orientation and the stowed orientation, as a straight downward push may suffice in changing the orientation of the arm. However, other arrangements are considered, without this pair of components. For example, as in Fig. 10, an alternative shape for the window 51 is shown, for an embodiment without the guide projection 41 . In Fig. 10, components similar to the window 51 share like reference numerals. The positions of P1 and P2 are past the apex 52B' of the pathway 52B, in their direction of movement. In such a scenario, the user must give a sufficient push, for instance assisted by the momentum from sliding along the pathway 52A, for the pin 24/cam 24A to reach positions P1 or P2. The push is in the same direction for both directions of movement of the arm 21 , and is for instance straight down on the push sleeve 35 and cap 36.

[0063] According to another embodiment, the window 51 or like guide may be defined in the arm 21 , with the follower (e.g., pin 24, cam 24A) located on the structural tube 31 . The operation of the indexing mechanism 30 would be as described above despite the reversal of the location of the guide and follower.

[0064] In an embodiment, the present disclosure shows the guide portion defined in the pathway sleeve 50 inserted in the structural tube 31 . This may for instance be so as to facilitate part manufacturing and assembly. In such an arrangement, it is contemplated to have the pathway sleeve 50 (and the pathway clip 40) in a low- friction material, such as a polymer (e.g., acetal plastic, etc), while the structural tube 31 may be made of a more rigid material, such as a metal or a composite. However, the window 51 or like guide may be defined directly into the structural tube 31 , instead of having the larger window section 31 A. [0065] The indexing provided by the

Claims

CLAIMS:

1. An anti-tipper mechanism for a wheelchair comprising:

an arm having at least a first end adapted to provide anti-tipper contact with a ground; and

an indexing mechanism operatively connecting the arm to the wheelchair, and displacing the arm reciprocally between a deployed orientation and a stowed orientation as a response to a manual force applied onto the anti-tipper mechanism.

2. The anti-tipper mechanism according to claim 1 , wherein the indexing mechanism has a housing for receiving a second end of the arm, a joint with a rotational degree of freedom and a translational degree of freedom being formed by the housing and the arm.

3. The anti-tipper mechanism according to claim 2, wherein the indexing mechanism has a guide and a follower, the follower being on the arm.

4. The anti-tipper mechanism according to claim 3, wherein the follower includes a pin connected to the arm inside the housing.

5. The anti-tipper mechanism according to claim 4, wherein the follower includes a bearing rotatably mounted to the pin.

6. The anti-tipper mechanism according to any one of claims 3 to 5, wherein the guide includes a pathway for the follower defined in a wall of the housing.

7. The anti-tipper mechanism according to claim 6, wherein the pathway is defined in a structural tube of the housing.

8. The anti-tipper mechanism according to claim 7, wherein the pathway has an inverted chevron shape.

9. The anti-tipper mechanism according to claim 6, wherein the housing has a structural tube.

10. The anti-tipper mechanism according to claim 9, wherein the housing has a sleeve inserted inside the structural tube, the pathway of the guide being defined in a sleeve window of the sleeve.

1 1. The anti-tipper mechanism according to claim 10, wherein the sleeve is made of a polymer, and the structural tube is made of a metal.

12. The anti-tipper mechanism according to any one of claims 10 and 1 1 , wherein the housing has a clip mounted to an outer surface of the structural tube opposite a tube window in the structural tube, the clip having a guide projection passing through the tube window and inserted into the sleeve window to form the guide with the sleeve window.

13. The anti-tipper mechanism according to claim 1 1 , wherein the guide projection and the sleeve window each have an inverted chevron shape.

14. The anti-tipper mechanism according to any one of claims 12 and 13, wherein the clip is made of a polymer.

15. The anti-tipper mechanism according to any one of claims 2 to 14, further comprising a biasing spring to bias the translational degree of freedom in a direction.

16. The anti-tipper mechanism according to claim 15, wherein the biasing spring is a coil spring located in an annular space between the housing and the second end of the arm.

17. The anti-tipper mechanism according to claim 16, further comprising a bearing at an end of the coil spring in the annular space.

18. The anti-tipper mechanism according to any one of claims 2 to 17, further comprising a push sleeve at the second end of the arm, the push sleeve mounted over the housing.

19. The anti-tipper mechanism according to claim 18, further comprising a cap mounted to the push sleeve, and a bearing between the cap and the push sleeve.

20. The anti-tipper mechanism according to any one of claims 3 to 19, wherein the guide is formed into at most 185 degrees in a surface of the housing, whereby the arm rotates reciprocally in a range of at most 185 degrees between the deployed orientation and the stowed configuration.

21. The anti-tipper mechanism according to any one of claims 12 to 14, further comprising a clamp adapted to connect the housing to the wheelchair, the clamp being clamped around an assembly of the clip, the structural tube and the sleeve.

22. The anti-tipper mechanism according to any one of claims 1 to 20, further comprising a clamp adapted to connect the indexing mechanism to the wheelchair.

23. The anti-tipper mechanism according to claim 22, wherein the clamp has a clamp end being tightened on an outer surface of the indexing mechanism.

24. The anti-tipper mechanism according to claim 23, wherein the clamp end has a C-shaped clamp with at least one fastener to tighten the C-shaped clamp.

25. The anti-tipper mechanism according to any one of claim 21 to 24, wherein the clamp has a quick-release unit adapted to releasably connect the clamp to a tube of the wheelchair.

26. The anti-tipper mechanism according to any one of claims 1 to 25, further comprising at least one caster at the first end of the arm.

27. The anti-tipper mechanism according to any one of claims 1 to 26, comprising a lockable telescopic joint in the arm between the first end and a junction with the indexing mechanism.

28. The anti-tipper mechanism according to any one of claims 1 to 27, wherein the arm has a L-shape.

29. The anti-tipper mechanism according to claim 28, wherein the L-shape has an angle ranging between 90 degrees to 155 degrees inclusively between its two segments.

30. A wheelchair comprising:

a frame defining a seat portion and a backrest portion;

rear wheels connected to the frame;

front casters connected to the frame;

at least one of the anti-tipper mechanism according to any one of claims 1 to 29, the at least one anti-tipper mechanism being connected to the frame.