EP2213268B1

EP2213268B1 - Frame member and frame for a personal conveyance, e.g. a wheelchair

Info

Publication number: EP2213268B1
Application number: EP09151784A
Authority: EP
Inventors: Michael Knopf
Original assignee: Sunrise Medical GmbH and Co KG
Current assignee: Sunrise Medical GmbH and Co KG
Priority date: 2009-01-30
Filing date: 2009-01-30
Publication date: 2013-01-30
Anticipated expiration: 2029-01-30
Also published as: ES2401682T3; EP2213268A1

Description

The invention relates to a frame for a personal conveyance and to a personal conveyance, e.g. a wheelchair.
An example of such a frame is known. WO 98/16182 discloses a wheelchair having a frame to which is connected a pair of wheels. The frame comprises a seat support, a backrest support and a lower leg support. The seat support comprises a pair of longitudinal bars, which are interconnected by a rear brace, a front brace and an axle. The axle is mounted on a pair of axle supports. Each axle support has a lower horizontal support bar which supports an axle clamp. The lower support bar is connected to a pair of uprights which engage within telescopic outer sleeves which have apertures for setting height using adjustment screws. A problem of the known wheelchair is that the configuration of the axle supports and the manner in which they are attached to the longitudinal bars mean that a separate lower horizontal support bar and axle clamp are required to make the longitudinal position of the axle adjustable relative to the seat. This in turn necessitates the use of two uprights which engage within telescopic outer sleeves, so that the axle supports are relatively heavy.
US 6,302,429 B1 discloses a wheelchair having a pair of side frame assemblies, spaced from each other and including a generally horizontal top tube and a generally horizontal bottom tube below the top tube. The top tube has a row of holes for seat attachment when converted to a rigid frame wheelchair. An optional wheel attachment consists of an axle plate tube mounted between the top frame tube and the bottom frame tube. The axle plate tube is secured to the frame tubes with connecting fittings at both ends.
It is an object of the invention to provide a frame for a personal conveyance, that allows for a transfer of weight from a first frame member supporting a part such as a seat via a second frame member to an axle of a main wheel in a predominantly longitudinal direction along the second frame member, wherein the second frame member can depend freely from the first 2 frame member, and the connection between the two frame members is relatively impervious to forces transverse to the longitudinal axis of the second frame member.
This object is achieved by the frame according to claim 1.
Preferred frame members according to the invention are described in claims 2 to 7.
Furthermore, the elongated section may be of tubular configuration at least the first end, and arranged to receive an inner member at the first end.
Also, the elongated section may have a non-circular cross-section with a major diameter of which at least a projection into a plane containing a longitudinal axis of a frame member received in the saddle is generally parallel to that longitudinal axis.
In an embodiment, a longitudinal axis of the elongated section, at least at the second end, is at an angle of less than 90°, in particular at an angle in the range from 85° to 75°, to a longitudinal axis of the saddle.
In a further embodiment, the saddle is comprised in a device for holding the saddle at an adjustable position on a frame member received in the saddle.
In a variant of this embodiment, the saddle is comprised in a clamp collar shaped to extend over more than 180° around an inserted frame member received in the saddle.
According to another aspect, a personal conveyance with a frame according to the invention is defined in claim 8.
The invention is based on the surprising insight that, because the frame member widens at a second, opposite end, into an end part including a saddle for receiving a further frame member at a predominantly transverse orientation to the elongated section, a relatively large contact area with the further frame member is provided, which area extends beyond the diameter of the elongated section in at least one direction. Thus, the end part including the saddle maintains the angle between the elongated section and the further frame member relatively well. An elongated section arranged to engage a member in a telescoping relation is a typical example of a frame member that is generally provided in a predominantly upright orientation in a personal conveyance, thus transferring forces along its length that are due to the weight of the occupant.
It is noted that forged head-set stems with saddle clamps are known in the field of bicycle technology, but that these are always used in a predominantly horizontal orientation. They do not include an end arranged to engage a further member in a telescoping relation. Furthermore, the clamp is forged in order to counter twisting forces exerted on the head (i.e. a moment around the longitudinal axis of the elongated section), which occur when cyclists pull the handlebars as they go uphill.
If the transition between the end part and the elongated section is forged, then the transition will be able to withstand forces exerting a moment in the plane containing the elongated section and the frame member received in the saddle without tearing. This connection between the end part and the elongated section is much stronger than a welded connection between two parts that are not integral components of a single metal part. There is no weakening as would occur due to localised heating in a welding step. This reduces the risk of tearing in the transition. Moreover, to obtain a smooth appearance, it is not necessary to include a grinding step in the manufacturing process. Using at least one forging tool comprising a die, as well as controlled temperature and forces, the frame member can be produced in series with relatively low tolerances. Compared to a cast frame member, the forged connection allows the use of a hollow elongated section with a relatively thin wall.
If the elongated section is of tubular configuration at at least the first end, and arranged to receive an inner member at the first end, then the part with the largest diameter is also the part that extends from the predominantly transversely oriented frame member and that further widens into the saddle. Thus, greater resistance to moments in a plane containing the elongated section and the predominantly transversely oriented frame member is achieved.
If the elongated section has a non-circular cross-section with a major diameter of which at least a projection into a plane containing a longitudinal axis of a frame member received in the saddle is generally parallel to that longitudinal axis, then the frame member is further strengthened in the plane containing the elongated section and the predominantly transversely oriented frame member.
If a longitudinal axis of the elongated section, at least at the second end, is at an angle of less than 90°, in particular at an angle in the range from 85° to 75°, to a longitudinal axis of the saddle, then the first end can be placed at a longitudinal end of the frame member received in the saddle without having to place the saddle at that end. This is of use in e.g. wheelchairs, where the frame member can be used to carry an axle tube beneath a longitudinal frame member carrying the seat. The axle is placed as far to the rear as possible without positioning the saddle at the very end of the frame member carrying the seat. This leaves space for the connection to a backrest, for example. A further effect is that the slight elasticity of the elongated section allows for vertical shocks to be absorbed.
In an embodiment, the saddle is comprised in a device for holding the saddle at an adjustable position on a frame member received in the saddle. An effect is to make the frame comprising the frame member more versatile, since the frame member can be re-positioned relative to the frame member received in the saddle. If the saddle is comprised in a clamp collar shaped to extend over more than 180° around an inserted frame member received in the saddle.
If, in the method of manufacturing a member for a frame of a personal conveyance, e.g. a wheelchair, the step of providing the end part includes at least one forging step for forming at least a transition between the elongated section and the end part, then a relatively strong connection between the end part and elongated section is provided. This connection is resistant to tearing due to forces tending to exert a moment on the elongated section in a plane comprising the elongated section and the frame member received in the saddle.
If the method further includes forging at least the first end of the elongated section into a tubular form, then a drilling operation to provide the tubular form can be dispensed with. This saves material and a separate manufacturing step. The tubular form allows the use as an outer tube of a telescopic connection to an inner member. It generally saves weight.
The invention will be explained in further detail with reference to the accompanying drawings, in which:

Fig. 1: is a perspective view of a wheelchair with the seat and backrest removed for clarity;
Fig. 2: is a front view of the wheelchair of Fig. 1;

Fig. 3: is a rear view of the wheelchair of Figs. 1 and 2;
Fig. 4: is a side view of the wheelchair of Figs. 1-3;
Fig. 5: is a perspective view of some parts of the frame of the wheelchair of Figs. 1-4;
Fig. 6: is a perspective view of the wheelchair of Figs. 1-4 with rear wheels removed to show an interconnection between frame members for supporting the seat and an axle tube;
Fig. 7: is a perspective view corresponding to that of Fig. 6, but with a spacer added to the interconnection;
Fig. 8: is a perspective view corresponding to that of Figs. 6 and 7, but with a further spacer added;
Fig. 9: is a perspective view from another angle of the wheelchair of Figs. 1-8, with one rear wheel removed for clarity and in the configuration of Fig. 7;
Fig. 10: is a perspective view of a tubular member of one of the assemblies interconnecting a frame member for supporting the seat and the axle tube;
Fig. 11: is a further perspective view of the tubular member of Fig. 10;
Fig. 12: is a cross-sectional view of the tubular member of Figs. 10 and 11;
Fig. 13: is a bottom view of the tubular member of Figs. 10-12;
Fig. 14: is a perspective view of an intermediate product for forming the tubular member of Figs. 10-13; and
Fig. 15: is a detailed exploded view of the axle tube and two assemblies interconnecting the axle tube and respective frame members for supporting the seat.

Referring to Figs. 1-4 in particular, a wheelchair 1 shown here by way of example is supported by left and right rear main wheels 2,3 and left and right caster wheel assemblies 4,5, comprising caster wheels 6,7. The wheelchair 1 comprises a base frame and a backrest frame 8 (see Fig. 5).
The base frame comprises left and right side frame members 9,10, arranged on opposite sides of a central axis (not shown) aligned with a direction d of forward displacement of the wheelchair 1. The left and right side frame members 9,10 are generally L-shaped. In other words, the wheelchair 1 has an open frame. The side frame members 9,10 each terminate longitudinally in a first leg 11,12 and a second leg 13,14. Each first leg 11,12 transitions into a second leg 13,14 via a respective curved section 15,16. The first legs 11,12 extend generally horizontally, and the second legs 13,14 depend downwardly. It is noted that the angle of the first legs 11,12 to the horizontal can be adjusted by adjusting the rear height of the first legs 11,12 above ground. They are thus only predominantly oriented in a horizontal direction, not exclusively.
The first legs 11,12 are arranged for supporting a seat (not shown) of the wheelchair 1. In particularly, a seat sling (not shown) can be slung between the first legs 11,12 of the side frame members 9,10, on top of which a seat cushion (not shown) of any shape or configuration can be placed.
With particular reference to Figs. 2 and 5, the curved sections 15,16 of the side frame members 9,10 are curved in multiple planes, such that the second legs 13,14 are separated from each other by a shorter distance than the first legs 11,12 of the side frame members 9,10. Thus, the seat can be relatively wide, whereas the second legs 13,14 of the side frame members 9,10 provide support for the wheelchair occupant's legs.
The second legs 13,14 are supported by the caster wheel assemblies 4,5 via caster struts 17,18 in which the caster wheel assemblies 4,5 are partially accommodated. The caster struts 17,18 are attached with respective longitudinal ends to the sides of the respective second legs 13,14 at a position removed from the (lower) ends of the second legs 13,14 corresponding to the ends of the side frame members 9,10. The caster struts 17,18 place the caster wheels 6,7 at a wider distance from the longitudinal central axis of the wheelchair 1, to provide stability. They are also attached to second legs 13,14 of the side frame members 9,10 at an angle thereto so as to be oriented at least partly in a direction opposite to the direction d of displacement of the wheelchair 1, i.e. closer to the rear wheels 2,3. This makes the manoeuvrability of the wheelchair 1 relatively good, by shortening the wheelbase. Because the wheelchair 1 has an open frame, it is supported by the caster wheels 6,7 only via the caster struts 17,18 and second legs 13,14. There is no other connection between the caster wheel assemblies 4,5 and the first legs 11,12 of the side frame members 9,10. Similarly, the caster struts 17,18 form the only connections between the caster wheel assemblies 4,5 and the side frame members 9,10.
It is desirable to place the rear wheels 2,3 as close together as possible in view of the width of the seat, and thus also as close to the side frame members 9,10 as possible. The seat should be wide enough to accommodate an occupant comfortably, but, overall, the wheelchair 1 should be narrow for better manoeuvrability and access to buildings, transport means and the like. This is only possible if the set camber of the rear wheels 2,3 is maintained when the wheelchair 1 is occupied. There must be no "sagging" of the frame, in particular rotation or torsion of the side frame members 9,10, under the weight of the occupant. Otherwise, the wheels 2,3 would angle inwards at the top towards the first legs 11,12, and run against them or against side guards 19,20 mounted to the first legs 11,12 of the side frame members 9,10. To prevent this, the first legs 11,12 are directly connected by a first cross-brace 21, and indirectly by an axle tube 22. Additionally, a foot rest assembly with left and right foot rest frame members 23,24, in general alignment with and connected to the second legs 13,14, includes at least a first cross-member 25 interconnecting the left and right foot rest frame members 23,24. A further cross-member 26 is situated below a foot plate (not shown), in use.
For adjustment of the height of the foot rest assembly, it is contemplated that the left and right foot rest frame members 23,24 of the foot rest assembly be accommodated within the second legs 13,14 in telescoping manner. Means for arresting telescopic movement of the left and right foot rest frame members 23,24 in one of a number of positions will generally be provided, e.g. in the form of biased pins in the foot rest frame members 23,24, arranged to cooperate with any of a series of holes in the second legs 13,14 of the side frame members 9,10. In the illustrated embodiment, the foot rest frame members 23,24 are clamped within the second legs 13,14 of the side frame members 9,10.
The backrest frame 8 is pivotably connected to the base frame by a connection mechanism that enables left and right backrest frame members 27,28 to be arrested in a generally upright position at any of several angles to the first legs 11,12 of the side frame members 9,10. This connection mechanism comprises left and right hinge plates 29,30, that connect the left and right backrest frame members 27,28 to the left and right side frame members 9,10, respectively. The connection to the left and right backrest frame members 27,28 is fixed. The hinge plates 29,30 are pivotably connected to the side frame members 9,10. A retractable pin (not shown in detail) engages one of an array 31 of apertures in the left hinge plate 29 to arrest the pivoting motion of the hinge plate 29 and left backrest frame member 27, and a similar locking mechanism is provided on the right side of the wheelchair 1. With the pin or similar engagement member retracted from the hinge plates 29,30, the backrest frame members 27,28 can be folded and arrested in a position in which their longitudinal central axes are predominantly parallel to and positioned along longitudinal central axes of the first legs 11,12 of the side frame members 9,10. In this configuration, the wheelchair 1 can be transported easily, e.g. in the boot of a car. It can be carried with one hand by the first cross brace 21 between the side frame members 9,10 or a similar second cross-brace 32 provided between the backrest frame members 27,28.
With reference to Fig. 5, the first cross-brace 21 is comprised of a tubular structure having, seen in longitudinal direction, a central section 33 and first and second end sections 34,35. The end sections 34,35 terminate at the ends of the cross-brace 21 with which it is connected to the left and right side frame members 9,10. They each have a central longitudinal axis angled away from a plane defined by the first legs 11,12 of the left and right side frame members 9,10, at least where they join the left and right side frame members 9,10. Thus, the central section 33 lies in a plane parallel to the plane defined by the first legs 11,12. There is therefore space between the central section 33 and a seat supported by the left and right first legs 11,12. By angling the end sections 34,35 in this way, the central section 33 can be relatively long, and need not be held exactly under the middle of the seat. In an alternative embodiment, the end sections 34,35 are in the plane of the left and right first legs 11,12, and curved sections angling out of this plane are provided between the central section 33 and the end sections 34,35.
In a similar manner to the first cross-brace 21, the second cross-brace 32 is comprised of a tubular structure having, seen in longitudinal direction, a central section 36 and first and second end sections 37,38. The end sections 37,38 terminate at the ends of the cross-brace 21 with which it is connected to the left and right side backrest frame members 27,28. They each have a central longitudinal axis angled away from a plane defined by the backrest frame members 27,28, at least where they join the left and right backrest frame members 27,28. Thus, the central section 36 lies in a plane parallel to the plane defined by the backrest frame members 27,28. There is therefore space between the central section 36 and a backrest (not shown) supported by the left and right backrest frame members 27,28. By angling the end sections 37,38 in this way, the central section 36 can again be relatively long.
The axle tube 22 is connected to the base frame via left and right axle tube clamps 39,40 (see Figs. 2, 3, 6-9 and 15). The axle tube 22 accommodates camber tubes (not shown in detail) for holding axles of the rear wheels 2,3. The camber tubes are also held in position by the axle tube clamps 39,40. At least one of the camber tube and the axle is removable from the axle tube 22, so that the rear wheels 2,3 can be taken off the wheelchair frame when the wheelchair 1 needs to be transported. Thus, the (open) ends of the axle tube 22 provide housings for removably accommodating rear wheel axles.
The interconnection between the axle tube clamp 39,40 and the first legs 11,12 allows for movement of the axle tube 22 between the different pre-determined positions at varying distances to the first legs 11,12 of the side frame members 9. The positions are at varying distances to the seat. In this manner, the rear seat height can be adjusted.
The interconnection between the axle tube 22 and the first legs 11,12 of the side frame members 9,10 comprises two assemblies of a tubular member in form of an upright tube 41,42 and an inner member in form of an upright post 43,44. Each upright post 43,44 is telescopically inserted into an upright tube 41,42, so as to extend over only part of the latter's length, because the upright posts 43,44 are substantially shorter than the upright tubes 41,42. In the illustrated embodiment, the upright tubes 41,42 depend downwardly from the side frame members 9,10. In fact, the upright tubes 41,42, in particular, elongated sections 45,46 thereof, are not precisely at right angles to the first legs 11,12 of the side frame members 9,10. Instead, they are at an angle of less than 90°, in particular at an angle in the range from 85° to 75°, to a longitudinal axis of the first legs 11,12. This angle is on the side facing away from the front wheels 6,7. It is noted that the upright tubes 41,42 may still be generally vertically oriented, because the first legs 11,12 need not be exactly horizontal. Generally, they will be angled slightly downwards towards the rear, so that an occupant of the wheelchair 1 will be kept in the seat.
The upright posts 43,44 are directly connected to the axle tube clamps 39,40. The upright posts 43,44 thus extend upwardly from the axle tube clamps 39,40. In the illustrated embodiment, the upright posts 43,44 and respective tube clamps 39,40 are in fact integral parts of a single component. This is a cast or forged component. There is thus no interface between the upright posts 43,44 and respective tube clamps 39,40. The latter provide bases with support surfaces 47,48 (Fig. 15) for first spacers 49,50 of stacks of spacers 49-54 for transferring a longitudinal force from a respective lower end of the vertical tubes 41,42 to a respective support surface 47,48.
Because the axle tube clamps 39,40 are provided at the longitudinal ends of the upright posts 43,44, the axle tube clamps 39,40 are situated immediately below the first legs 11,12 of the side frame members 9,10, right at the ends of the axle tube 22. Thus, the wheels 2,3 can be placed close to the side frame members 9,10, but there is a relatively low moment arm on the axes that would tend to tilt them and thereby affect the camber of the wheels 2,3. Because there is a single axle tube 22 interconnecting the upright tubes 41,42, they will have less tendency to bend.
The elongated, tubular sections 45,46 of the upright tubes 41,42 are non-circular, in this case oval, in cross-section (see Fig. 13). An axis 55 aligned with a major diameter of the non-circular cross-section is predominantly aligned with the longitudinal central axes of at least the first legs 11,12 of the side frame members 9,10. This provides extra rigidity to prevent bending in a direction parallel to the direction d of displacement of the wheelchair 1. Other non-circular cross-sections will also provide this effect.
At a top end, the upright tubes 41,42 are connected to double tube clamps 56,57. The double tube clamps 56,57 are integral parts of the upright tubes 41,42, meaning that there is no internal or external interface between the tube clamps 56,57 and elongated tubular sections 45,46 of the upright tubes 41,42. The double tube clamps 56,57 are movable along the first legs 11,12 of the side frame members 9,10, so that the distance between the caster wheels 6,7 and the rear wheels 2,3 can be changed. Because the upright tubes 41,42 are interconnected by the axle tube 22, the distance between the left caster wheel 6 and rear wheel 2 and the distance between the right caster wheel 7 and rear wheel 3 remains the same. The double tube clamps 56,57 also contribute to maintaining the distance between the front wheels 6,7 and rear wheels 2,3 constant.
Each double tube clamp 56,57 comprises a saddle 58,59, which, in use, supports the respective first leg 11,12 of a side frame member 9,10. In the illustrated embodiment, the saddle 58,59 is comprised in each of two clamp collars 60-63 extending over more than 180° around the side frame member 9,10 when inserted into the double tube clamp 56,57. In an alternative embodiment (not shown), the saddles can be comprised in tube clamps comprising opposite clamp halves that are held together by bolts or similar fastening devices. However, the illustrated embodiment allows one to loosen the double tube clamps 56,57 to move the upright tubes 41,42 in longitudinal direction (parallel to the direction d of displacement), without risk of the upright tubes 41,42 coming off.
For further rigidity, the first legs 11,12 are also of non-circular, e.g. oval, cross-section. The double tube clamps 56,57, in particular also the saddles 58,59 are appropriately configured for this cross-sectional shape.
It will be apparent, in particular from Figs. 12 and 13, that the upright tubes 41,42 widen at the transition between the elongated sections 45,46 to the double tube clamps 56,57. Thus, the minimum diameter of the elongated sections 45,46 can be lower than the minimum diameter of the first legs 11,12, if required. Moreover, the first legs 11,12 of the side frame members 9,10 are supported over a longer distance by the saddles 58,59. Thus, the widening is at least in the cross-sectional plane through a longitudinal axis 64 of the saddle 58,59 and parallel to or through a longitudinal axis of the elongated section 45,46.
In the illustrated embodiment, the basic configuration of the upright tubes 41,42 is provided by forging. Fig. 14 shows an intermediate frame member 65 after the forging steps have been carried out. Further stages of the manufacturing process involve milling and cutting to provide the double tube clamps 56,57. The forging steps involve the use of one or more tools which are negatives of the shape of the intermediate frame member 65. These are used to provide the hollow tubular elongated section 45 and the transition between the elongated section 45 and the end part that will finally comprise the saddle 58 of the double tube clamp 56. Forging is carried out under controlled conditions. The temperature is controlled to a point at which the material of the upright tubes 41,42 is quite ductile. The force with which the tools are applied to the workpiece is controlled relatively precisely. Afterwards, a heat treatment can be carried out. The forged nature of the transition between the elongated section 45 and the end part that will finally comprise the saddle 58 of the double tube clamp 56, means that the upright tubes 41,42 are able to withstand jolts in the direction d of displacement relatively well. There is little risk of tearing at the upper ends of the elongated sections 45,46. This effect is achieved without having to provide the elongated sections 45,46 with relatively thick walls.
Referring to Fig. 15, at the opposite ends to the tube clamps 56,57 of the upright tubes 41,42, there are provided vertical tube clamps comprising respective collars 66,67 and bolts 68,69 for engaging respective ones of a plurality of internally threaded bores 70-75. It is noted that the bores 70-75 extend only a short distance into the solid upright posts 43,44. They are thus not through-holes. The bolts 68,69 are inserted through bores 76,77 in the collars 66,67 and apertures 78,79 in the upright tubes 41,42.
It is observed that, in the illustrated embodiment, the insides of the internally threaded bores 70-75 do not provide support surfaces, and the bolts 68,69 do not function as elements for transferring a longitudinally directed force from an end of the upright tubes 41,42 to the upright posts 43,44, because the spacers 49-54 perform this function. In other embodiments, however, this need not be the case.
Aside from the one aperture 78,79, the upright tubes 41,42 are smooth. The absence of an array of apertures through the walls of the upright tubes 41,42 makes them stronger.
Although the elongated sections 45,46 of the upright tubes 41,42 have a generally oval cross-sectional shape, also on the inside, the upright posts 43,44 have a different cross-sectional shape, so that a certain amount of play exists. Due to the use of clamps to clamp the upright tubes 41,42 to the upright posts 43,44, this does not matter greatly. On the other hand, manufacture of the components comprising the upright posts 43,44 is thereby simplified, because the tolerance ranges can be larger. It is noted, however, that the upright posts 43,44 also have a non-circular cross-sectional shape, so that twisting of the upright posts 43,44 within the upright tubes 41,42 is prevented due to a shape-lock that is established when the collars 66,67 are tightened. In this case, the upright posts 43,44 are cylindrical with an octagonal cross-sectional shape. The sides of the octagon are alternately short and long, defining a shape corresponding to that of a rectangle with truncated corners. When the bolts 68,69 are tightened, the collars 66,67 act on the surfaces defined by the short sides that form the truncations. Two such surfaces 80,81 are indicated in Fig. 15.
As far as the spacers 49-54 are concerned, at least one, smaller spacer 49,50 comprises a non-metal material, e.g. plastic, rubber or artificial rubber. This spacer 49,50 may be reinforced by metal components for further structural rigidity. The non-metal surface of the spacer prevents metal-on-metal contact between the upright posts 43,44 and upright tubes 41,42. It is envisaged that at least the smaller spacer 49,50 will always be present, even with the wheelchair 1 in the lowest position, so that a quiet ride is ensured.
Top surfaces 82,83 of the upper spacers 53,54 abut and support end faces 84,85 of the upright tubes 41,42 as well as lower surfaces of the collars 66,67. Thus, the walls of the upright tubes 41,42 are generally subjected to longitudinal forces. There is no force on the edges of the apertures 78,79.
In the illustrated embodiment, the spacers 49-54 are of cylindrical configuration with generally identical cross-sectional shapes, at least where the outer circumference is concerned. Thus, a smooth appearance is created, with no sharp edges at interfaces between spacers 49-54. This is continued due to the fact that the outer circumference of the cross-sectional shape of the spacers 49-54 is generally identical to that of the collars 66,67.
In general, the wheelchair 1 will be provided with a set of spacers 49-54 for adjustment by the user. The user may select an appropriate number of spacers of an appropriate type from the set. In an alternative embodiment, the set of spacers differs in at least one of dimensions and composition. In the illustrated embodiment, the heights of the larger spacers 51-54 correspond to the distances between the successive internally-threaded bores 70-75 in the upright posts 43,44. They may be equidistant or be placed at different intervals, so that either spacers of the same height or spacers of different height will be used.
The spacers 49-54 transmit the longitudinal forces between the upright tubes 41,42 and upright posts 43,44, so that the apertures 78,79 and threads of the bores 70-75 are not subjected to damaging forces under the weight of the occupant of the wheelchair 1. The upright posts 43,44 lend extra rigidity to the upright tubes 41,42.
The invention is not limited to the embodiments described above, which may be varied within the scope of the claim. The features mentioned in the description, claims and drawings can be essential to the invention in its various implementations.
The members of the wheelchair frame can be made of a composite material or a metal or metal alloy. Suitable materials in particular also for the forged upright tubes 41,42, include aluminium-scandium alloys, aluminium alloys from the 7000 series, particularly aluminium 7003, or aluminium from the 6000 series. Aluminium 7000 has a relatively high tensile strength.

List of references numerals

1: Wheelchair
2: Left rear wheel
3: Right rear wheel
4: Left caster wheel assembly
5: Right caster wheel assembly
6: Left caster wheel
7: Right caster wheel
8: Backrest frame
9: Left side frame member
10: Right side frame member
11: Left first leg
12: Right first leg
13: Left second leg
14: Right second leg
15: Left curved section
16: Right curved section
17: Left caster strut
18: Right caster strut
19: Left side guard
20: Right side guard
21: Cross-brace
22: Axle tube
23: Left footrest frame member
24: Right footrest frame member
25: 1^st Footrest cross-member
26: 2^nd Footrest cross-member
27: Left backrest frame member
28: Right backrest frame member
29: Left hinge plate
30: Right hinge plate
31: Aperture array
32: Back cross-brace
33: Central section

34: 1^st End section
35: 2^nd End section
36: Central section
37: 1^st End section
38: 2^nd End section
39: Left tube clamp
40: Right tube clamp
41: Left upright tube
42: Right upright tube
43: Left upright post
44: Right upright post
45: Elongated section of left upright tube
46: Elongated section of right upright tube
47: Left first surface
48: Right first surface
49: Left small spacer
50: Right small spacer
51: Left lower spacer
52: Right lower spacer
53: Left upper spacer
54: Right upper spacer
55: Axis aligned with major diameter of cross-section of upright tube
56: Left double tube clamp
57: Right double tube clamp
58: Saddle of left upright tube
59: Saddle of right upright tube
60: First collar of left double tube clamp
61: Second collar of left double tube clamp
62: First collar of right double tube clamp
63: Second collar of right double tube clamp
64: Longitudinal axis of saddle
65: Intermediate frame member
66: Left collar
67: Right collar
68: Left bolt
69: Right bolt
70: 1^st Left bore
71: 2^nd Left bore
72: 3^rd Left bore
73: 1^st Right bore
74: 2^nd Right bore
75: 3^rd Right bore
76: Left collar bore
77: Right collar bore
78: Left aperture
79: Right aperture
80: Surface on left post
81: Surface on right post
82: Top surface of left upper spacer
83: Top surface of right upper spacer
84: Left end face
85: Right end face

Claims

Frame for a personal conveyance (1), e.g. a wheelchair, including:
- at least one first frame member (9,10) for supporting a part for occupation by a user;

- at least one second frame member (41,42) for transferring weight from the first frame member (9,10) to an axle of a main wheel (2,3) and arranged to support the first frame member (9,10) at a predominantly transverse orientation to the second frame member (41,42), wherein
the second frame member (41,42) includes an elongated tubular section (45,46) and widens at a second end of the elongated tubular section (45,46) into an integral end part including a saddle (58,59) for receiving the first frame member (9,10), and

- at least one further frame member (39,40,43,44), wherein
the elongated tubular section (45,46) being arranged to engage the further member (39,40, 43,44) in a telescoping relation at a first end of the second frame member (41, 42),
charactere in that
the further member is provided in form of an upright post (43,44) directly connected to an axle tube clamp (39,40), with the upright post (43,44) and the tube clamp (39,40) being a single cast or forged component.
Frame according to claim 1, wherein the transition between the end part and the elongated section (45,46) is forged.
Frame according to claim 1 or 2, wherein the elongated section (45,46) is of tubular configuration at least the first end, and arranged to receive the upright post (43,44) at the first end.
Frame according to any one of the preceding claims, wherein the elongated section (45,46) has a non-circular cross-section with a major diameter of which at least a projection into a plane containing a longitudinal axis of a frame member (9,10) received in the saddle (58,59) is generally parallel to that longitudinal axis.
Frame according to any one of the preceding claims, wherein a longitudinal axis of the elongated section (45,46), at least at the second end, is at an angle of less than 90°, in particular at an angle in the range from 85° to 75°, to a longitudinal axis (64) of the saddle (58,59).
Frame according to any one of the preceding claims, wherein the saddle (58,59) is comprised in a device (56,57) for holding the saddle (58,59) at an adjustable position on a frame member (9,10) received in the saddle (58,59).
Frame according to claim 6, wherein the saddle (58,59) is comprised in a clamp collar (60-63) shaped to extend over more than 180° around an inserted frame member (9,10) received in the saddle (58,59).
Personal conveyance, e.g. a wheelchair, including a frame according to any one of claims 1-7.