WO2005107678A2

WO2005107678A2 - Kerb climbing device, its use and walking aid provided with a kerb climbing device

Info

Publication number: WO2005107678A2
Application number: PCT/NL2005/000348
Authority: WO
Inventors: Jan Corné VAN DONGEN; Gijs Hofman; Martijn Schaaper; Arijanneke Anna Gerda Jozephina Baptist
Original assignee: BOB BEWEGINGSTECHNOLOGISCH ONTWERP BUREAU
Current assignee: BOB BEWEGINGSTECHNOLOGISCH ONTWERP BUREAU
Priority date: 2004-05-12
Filing date: 2005-05-09
Publication date: 2005-11-17
Anticipated expiration: 2006-11-12
Also published as: NL1026176C2; WO2005107678A3

Abstract

Kerb climbing device (1), which is suitable for passing height obstacles (50) by means of a movable carriage (42), the kerb climbing device (1) comprising a displacement mechanism in the form of a quadrilateral linkage which comprises a suspension part, a foot part (9) and rotatable connecting arms, which connecting arms are provided between the foot part (9) and the suspension part for displacing the foot part (9) with respect to the suspension part between a climbing position and an end position, and the displacement mechanism being provided with adjustment means for adjusting the foot part (9) in the climbing position.

Description

Short title: Kerb climbing device, its use and walking aid provided with a kerb climbing device

The present invention relates to a kerb climbing device, for passing height obstacles by means of a carriage movable by manpower which is provided with at least one wheel, the kerb climbing device comprising a displacement mechanism in the form of a linkage which comprises a suspension part, a foot part and rotatable connecting arms, which connecting arms are provided between the foot part and the suspension part for displacing the foot part with respect to the suspension part between a climbing position and an end position, and the displacement mechanism being provided with adjustment means for adjusting the foot part in the climbing position. A kerb climbing device of this type is presented in British Patent GB 2237250, and its operation is illustrated for a three- wheeled vehicle, such as an electric scooter for people who have difficulty in walking. The kerb climbing device comprises a linkage which, at the front wheel, is secured to a front fork in which the front wheel is secured. The section of the front fork at which the connecting arms are connected is referred to in the context of this description as the suspension part. Connected to the connecting arms is a foot part for climbing a height obstacle, such as for example a kerb, which is approached from a roadway. The foot part basically consists of two parts, namely a climbing element and a leg fixedly secured to it, the connecting arms being rotatably secured to the leg. When the climbing element is in contact with the height obstacle during climbing, the obstacle exerts a force on the climbing element, which force is transmitted via the leg to the three-wheeled vehicle connected to the kerb climbing device. The connecting arms are held, under stress from a tension spring, in a position which is such that the foot part is in the climbing position, i.e. in a position in which the climbing element of the foot part is at a suitable angle to climb up the obstacle. Therefore, unlike in the situation in which the kerb climbing device is absent - the height obstacle is climbed gradually, in the sense that the vertical component of the climbing movement is relatively small compared to the horizontal component. However, although the kerb climbing device allows the height obstacle to be passed over gradually, so that the height obstacle is no longer taken so violently, this solution has a number of drawbacks, in particular with a view to its use for a walking aid. The foot part of the kerb climbing device described in GB 2237250 comprises a linkage which is secured to the fork of the swivel front wheel of the three-wheeled vehicle. This has the inherent drawback that the front wheel has to be accurately aligned so that the kerb climbing device comes into contact with the obstacle to be climbed in the right direction. Moreover, it is difficult to keep the kerb climbing device in the correct direction during climbing, on account of the front fork being rotatable, with the result that the kerb climbing device can unintentionally start to pivot and can even shoot out of the climbing position. Therefore, considerable skill is required on the part of the driver to use the kerb climbing device, with the result that the ease of use decreases. If the kerb climbing device is used in combination with, for example, a walking aid, which has more swivel front wheels, it is even more difficult for the user to direct the front wheels. These drawbacks apply to an even greater extent if the front wheels can pivot freely. Another drawback of the kerb climbing device described in GB 2237250 is associated with the use of the kerb climbing device for carriages which are moved by manpower, in particular for walking aids, such as rollators. These walking aids are constructed from a frame and, connected to it, wheels and grip means for the user, the weight of the frame being relatively low compared to the weight of the user. When the user is supporting himself on the grip means - generally designed as handles - by means of his own weight, he exerts a force which is relatively high compared to the weight of the rollator, which force, when the rollator is kept in a horizontal position, does not cause a moment of force on account of the positioning of the wheels of the rollator with respect to the frame and the grip means. This is because this positioning is generally as follows: the rollator has two front wheels and two rear wheels which, when seen from above, are arranged at the corners of an imaginary rectangle, while the frame and the handles are located above and inside the imaginary rectangle. In particular when negotiating height obstacles, such as pavements or doorsteps, it is because of the inclined position of the rollator, of importance that the user of the walking aid has to exert as little force as possible on the handles, so that the risk of the rollator undesirably tipping over is minimized. In addition, it is in general advantageous in regard of ease of use for the climbing of an obstacle requires as little force as possible. A kerb climbing device in accordance with GB 2237250, when used on a rollator, has the drawback that pushing the rollator over the height obstacle still takes a relatively large amount of force, with the result that the stability of the rollator when negotiating the obstacle is also adversely affected. A further drawback of the kerb climbing device according to the prior art is that the suspension part forms a non-releasable part of the three-wheeled vehicle. Therefore, fitting a kerb climbing device to an existing three-wheeled vehicle which does not yet have the features for fitting the connecting arms to the suspension part entails additional installation time. It is an object of the invention to completely or partially resolve one or more of the above drawbacks, so as to provide an improved kerb climbing device with an increased ease of use when passing over height obstacles. To this end, the kerb climbing device of the type described above, according to a first aspect of the invention, comprises as connecting arms a front arm and a rear arm, a top end of the front arm being rotatably connected to the suspension part via a first rotation point, a top end of the rear arm being rotatably connected to the suspension part via a second rotation point, and a bottom end of the front arm being rotatably connected to the foot part via a third rotation point and a bottom end of the rear arm being rotatably connected to the foot part via a fourth rotation point, wherein the connecting lines between the first and second rotation points, between the second and fourth rotation points, between the fourth and third rotation points and between the third and first rotation points, when seen from the side, form a quadrilateral, the corners of which are located at the rotation points, and wherein the suspension part comprises a connecting member for releasably connecting it to the abovementioned carriage, in such a manner that, when seen from the side, the angle of the suspension part with respect to the carriage can be adjusted with the aid of the connecting member. A kerb climbing device of this type comprises a linkage which, when fitted to a walking aid, allows the walking aid to perform a gradual climbing movement when climbing, with the vertical component of the climbing movement being relatively small compared to the horizontal component, certainly when compared to the prior art. The fact that the linkage is in the form of a quadrilateral has the first advantage that, when the foot part comes into contact with the obstacle while the point of contact is between the third and fourth rotation points of the foot part, a lever effect is exerted by the force which the kerb climbing device exerts on the obstacle via the front arm, and vice versa also by the normal force which is exerted by the obstacle on the contact point of the foot part and which acts on the suspension part via the rear arm. This considerably reduces the force which is required to overcome the obstacle, on account of the fact that the forces which are transmitted via the front arm and rear arm interact when climbing the obstacle. A kerb climbing device of this type therefore needs less force when a user is climbing a height obstacle using a defined walking aid compared to a kerb climbing device according to the prior art. On account of the linkage forming a quadrilateral, the kerb climbing device according to the invention also has the advantage that, when the foot part comes into contact with the obstacle, the force which the obstacle exerts on the foot part is transmitted with better support to the walking aid compared to the prior art, in which the force is transmitted via a single leg. In addition, the shape of the linkage makes it possible for the foot part to execute a compact travel in the horizontal direction between the climbing position and end position for a defined height difference which has to be bridged. This makes the kerb climbing device according to the invention very suitable for combining with a wide range of types of carriages, since only a limited amount of space has to be kept clear for the travel of the foot part of the kerb climbing device. In particular, the kerb climbing device is suitable for walking aids, such as a rollator, in which in use it is advantageous to minimize the travel of the foot part, for example in order to reduce the number of unintentional collisions and because the user himself is less likely to knock against the kerb climbing device as a result of his own movement. The kerb climbing device according to the invention has the additional advantage that the suspension part comprises a connecting member for releasably connecting it to the carriage, the connecting member allowing the angle at which the suspension part is connected to the carriage, as seen in side view, to be adjusted. By way of example, this angle can be defined as the angle of the suspension part with respect to the ground surface on which the carriage is resting, when seen from the side. On account of the kerb climbing device being releasable, it is easy to fit to a carriage without the carriage itself having to be modified or adjusted, as in the case of the kerb climbing device being fixedly connected to the carriage. As a result, a kerb climbing device can easily be transferred to another carriage and can also easily be replaced. Further practical advantages ensue from the fact that the connecting member enables to adjust the angle at which the suspension part is fitted with respect to the carriage. Since there are various types of carriages, which vary in terms of wheel height, and since the height at which the kerb climbing device is connected to the carriage via the connecting member may also vary, the angular adjustability makes it easy to adapt the kerb climbing device to the type of carriage. In the context of the invention, the kerb climbing device is suitable in particular for wheelbarrows, prams, rollators, etc. By way of example, the kerb climbing device is fitted to a transverse tube of the frame of a rollator between the front wheels. Furthermore, in practice it has been found that the angle adjustment also offers a solution for other variables, such as the bearing load of the carriage, the standard forward speed of the carriage, and the mean height of common obstacles which have to be passed over. The connecting member is preferably a clamping structure by which the kerb climbing device can be secured to the frame of the carriage. In the present description, the top side and underside of the components of the kerb climbing device are defined with respect to the line on which the first and second rotation points lie when this line is parallel to the horizontal. Therefore, in a kerb climbing device the front arm and the rear arm are respectively beneath the first and second rotation points, and beneath that is the foot part, which is connected via the third and fourth rotation points. The front and rear sides of the kerb climbing device are defined with reference to the front arm and the rear arm, the front arm, when the kerb climbing device is in use, passing over the obstacle earlier than the rear arm. In the climbing position, the third rotation point is in an advanced position with respect to the first rotation point (i.e. the third rotation point passes over the height obstacle earlier than the first rotation point) , and the foot part is at an angle to the horizontal plane, on account of the fact that the third rotation point is in a higher position than the fourth rotation point. The end position is adopted by the kerb climbing device when the foot part, after it has negotiated the obstacle, comes free of the contact point by virtue of the wheel of the carriage finding support on the obstacle. When climbing an obstacle, the contact point between the foot part and the obstacle is virtually fixed. It is preferable for the third and fourth rotation points to be present in the vicinity of the front and rear ends of the foot part. In a preferred embodiment of the kerb climbing device according to the invention, the first rotation point, the second rotation point, the third rotation point and the fourth rotation point respectively comprise a first axle, a second axle, a third axle and a fourth axle, these axles being substantially parallel to one another. An embodiment of this type has the advantage that the rotation points offer a robust structure both with respect to the bearing load and with respect to transverse forces exerted on the kerb climbing device. The fact that the movement of the kerb climbing device is limited to a single degree of freedom (i.e. a movement within one plane) by the use of the axles makes a contribution to this. The axles are preferably designed as a steel clamping bush axle with plastic sliding-contact bearings. In this case, by way of example, the axles are fixedly connected to the connecting arms, and the axles are accommodated rotatably in corresponding bushes provided in the suspension part and the foot part, respectively. It is advantageous for the kerb climbing device to be formed in such a manner that the suspension part, the foot part and the connecting arms have a width which is comparable to the length of the four axles, since this considerably strengthens the structure and at the same time keeps the dimensions compact. It is preferable, in the kerb climbing device according to the invention, for the distance dl between the first and second rotation points to be shorter than the distance d2 between the third and fourth rotation points. The result of this is that, for a given length of the front arm and rear arm, the foot part executes a movement with respect to the suspension part, wherein the amplitude of the foot part is relatively large compared to the dimensions of the suspension part. A further result of this is that the extent to which the angle of the foot part with respect to the horizontal plane can vary is relatively large. Consequently, the foot part can remain of relatively small dimensions, with the result that the kerb climbing device takes up a relatively small amount of space, which promotes ease of use. As an alternative, the distances between the first and second rotation points, on the one hand, are equal to the distance between the third and fourth rotation points. It is advantageous for the dimensions of the kerb climbing device to be such that the distances between the first and second rotation points, third and fourth rotation points, first and third rotation points and second and fourth rotation points differ by a factor of no more than 3, preferably a factor of no more than 2. It is advantageous for the size of the kerb climbing device to be comparable to the wheels of the carriage for which it is used, in which case in particular the rear arm of the kerb climbing device is of a length which is comparable to the diameter of the wheel. Therefore, the dimensions of the kerb climbing device are such that it does not project far beyond the circumference of the wheels, resulting in the abovementioned advantage that the kerb climbing device causes few unintentional collisions during use. In a preferred embodiment of the kerb climbing device according to the invention, in the climbing position, the extension of the connecting line between the first rotation point and the third rotation point, on the one hand, and the extension of the connecting line between the second rotation point and the fourth rotation point, on the other hand, intersect one another at an intersection point which lies above and behind the first rotation point. This intersection point is also referred to as the momentary rotation centre (MRC) . On account of the fact that the MRC is located behind and above the first rotation point, it is in the vicinity of the grip means of the carriage. It has been found that shortening the distance between the MRC and the location where the user exerts a force on the carriage lowers the force which is required to climb a height obstacle. In addition, the abovementioned interplay of forces of the front arm and rear arm are well matched to one another in a configuration of this type, since the force components involved have the desired interacting effect to a high degree. In addition, it has proven important for the direction of the reaction force or normal force exerted by the obstacle on the foot part during climbing to be on a line located behind the MRC. It should be noted that the MRC plays a role not only when the kerb climbing device comes into contact with the obstacle. In fact, during the movement of the kerb climbing device from the climbing position to the end position as it passes over the obstacle, the MRC changes position with respect to the first rotation point. During this movement, the MRC follows an arc in which the MRC moves upwards and forwards. It is assumed that this movement of the MRC, since it has the same components (forward and upward) as the carriage moving over an obstacle, makes a contribution to further increasing the ease for a user to pass over the obstacle. In a further preferred embodiment of the kerb climbing device according to the invention, the foot part comprises a contact surface which is concave in form. The contact surface is the surface which makes contact with the obstacle and is located on the underside of the foot part. A concave form enables the foot part to move between the end position and climbing position without the contact surface rubbing on the obstacle, which is of benefit to the durability of the contact surface. As an alternative, the contact surface of the foot part is of flat design, and the same effect is achieved by adapting the other parts of the linkage. If the other parts permit, it is also possible for the foot part to be convex in form. In the kerb climbing device according to the invention, it is preferable for the foot part to comprise a friction-increasing contact surface. A contact surface of this type increases the friction at the point of contact between the foot part and the obstacle during climbing, so that the slipping of the foot part over the obstacle is minimized. This is of benefit both to the lever effect of the interacting connecting arms and to lowering the wear on the contact surface. The contact surface is made, for example, of wear-resistant material, such as rubber, if desired provided with ribs or some other form of relief pattern. More preferably, in the kerb climbing device according to the invention, the adjustment means comprise a torsion spring which engages on one of the connecting arms, and a stop for one of the connecting arms. This means that the foot part is always held in the climbing position when the kerb climbing device is not executing the climbing movement. Consequently, the kerb climbing device reverts to the climbing position immediately after an obstacle has been climbed, which increases the ease of use. The stop is advantageously adjustable, so that the kerb climbing device can be set to a position which has been adjusted to the obstacles most frequently encountered by the particular user. It is preferable for the length of the front arm and/or rear arm of the kerb climbing device according to the invention to be adjustable. This offers the advantage that, as has already been noted above, the position of the foot part of the kerb climbing device can easily be adapted to changing conditions, such as the type of carriage, the mean obstacle height, the bearing load of the carriage, etc . In a subsequent embodiment of the kerb climbing device according to the invention, it comprises an auxiliary front arm, which is telescopically displaceable in the longitudinal direction, and a front arm which is composed of a main front arm and a collapsible front arm, the auxiliary front arm being rotatably connected, at a top end via a fifth rotation point, to the suspension part in a position between the first and second rotation points, and being rotatably connected, at a bottom end via a sixth rotation point, to the foot part in a position in front of the main front arm, and the collapsible front arm, in the climbing position, resting on the foot part between the sixth rotation point and the main front arm, the collapsible front arm being rotatably connected, at a first end, to the foot part via the third rotation point and, at a second end, to the main front arm via a seventh rotation point, the collapsible front arm being rotatably connected, via the third rotation point to the foot part, said third point being in a fixed position with respect to the foot part, while the seventh rotation point can move with respect to the foot part . The advantages of a kerb climbing device of this type relate to the final phase of the movement from climbing position to end position, in which phase, at a given instant, the auxiliary front arm moves into the fully retracted position, and then, in the event of a further movement, the collapsible front arm pivots open, with the result that the front arm as a whole in fact becomes longer. This lengthening of the front arm results in the foot part only moving a small amount upward in the final phase of the climbing movement, or even not being moved any further upward at all. This is important since it becomes difficult or impossible to release the kerb climbing device from the obstacle if the foot part is in a relatively high position with respect to the wheel. A height difference of 5 cm between the foot part and the contact point between the wheel and the ground is enough to cause problems of this nature. This difference in height plays an important role in particular if, in the climbing position, the configuration of the main front arm and the rear arm is such that, when seen in side view, they are virtually parallel. This degree of parallelism may be necessary if the MRC of the kerb climbing device has to be at a relatively high position, for example in the case of a rollator. It should be noted that before the fully retracted position of the auxiliary front arm is reached, the MRC is determined by the directions of the main front arm and the rear arm with respect to one another. As soon as the collapsible front arm pivots open, this is no longer the case and the MRC is determined by the directions of the auxiliary front arm and the rear arm with respect to one another. The above explanation will be clarified further with reference to the description of the figures below. More preferably, in the kerb climbing device having an auxiliary front arm and a front arm composed of a main front arm and a collapsible front arm, the third axle and sixth axle are combined to form a single axle. This offers a simpler design, with advantages in terms of production, maintenance, etc. More preferably, the kerb climbing device according to the invention comprises an auxiliary piece for coupling the connecting member to the carriage. If the frame of the carriage offers insufficient options for connecting the kerb climbing device via a clamping structure, an auxiliary piece offers the option of still effecting a connection between the frame of the carriage and the kerb climbing device without having to alter the dimensions of the kerb climbing device. With the aid of this auxiliary piece, it is advantageously possible to adjust the distance of the connecting member with respect to the carriage. By way of example, the auxiliary piece is a transverse rod which is coupled to the carriage at the location of the suspension part for the two front wheels. The kerb climbing device according to the invention advantageously comprises parallel front arms, the top end of which is rotatably connected to the suspension part via the first axle, and the bottom end of which is rotatably connected to the foot part via the third axle, and/or parallel rear arms, the top end of which is rotatably connected to the suspension part via the second axle and the bottom end of which is rotatably connected to the foot part via the fourth axle. Designing the front arm and rear arm in duplicate in this way makes the structure as a whole more resistant to forces which act transversely with respect to the direction of movement of the foot part. A second aspect of the invention relates to the use of the kerb climbing device according to the invention, in which the latter is releasably connected to the carriage. The use of the kerb climbing device in combination with the carriage provides the advantages which have already been indicated above. It is preferable for the kerb climbing device to be connected to the carriage at a position at the level of the front wheels and in the centre at the front side of the frame. The kerb climbing device is advantageously used on a rollator. A third aspect of the invention relates to a walking aid which comprises a frame and, connected to it, wheels and grip means for the user, which is provided with a kerb climbing device according to the invention. A walking aid, such as in particular a rollator, which is provided with a kerb climbing device according to the invention provides the advantages which have already been indicated above. The kerb climbing device can be secured to the walking aid in any suitable way, for example via the abovementioned connecting member. According to a preferred embodiment of the walking aid according to the invention, the walking aid comprises a frame and, connected to it, wheels and grip means for the user, which walking aid is provided with a kerb climbing device according to the invention, wherein, when the kerb climbing device is in the climbing position, the extension of the connecting line between the first rotation point and the third rotation point, on the one hand, and the extension of the connecting line between the second rotation point and the fourth rotation point, on the other hand, intersect one another at an intersection point which is in the vicinity of the grip means of the walking aid. A walking aid of this type has the advantage that the proximity of the intersection point and grip means in practice lowers the force which is required to negotiate a height obstacle. For the sake of clarity, it should be noted that the linkage and the axles of the kerb climbing device are advantageously made from rigid materials, such as strong plastics or metals. More advantageously, these rigid materials are lightweight. The suspension part, the arms and the foot part are designed, for example, as elongate plates or tubes. The length of the front arm and rear arm may vary within the conditions imposed on the kerb climbing device. These lengths are selected as a function of the mounting height on a walking aid. In this context, it is preferable for it to be possible to climb height obstacles starting from 2 cm. The choice of the lengths with regard to the dimensions of the suspension part and the foot part can be determined by the person skilled in the art on the basis of his specialist knowledge, taking account of the abovementioned characteristics of the kerb climbing device according to the invention. A fourth aspect of the invention relates to a carriage comprising a frame, at least one wheel which is connected to the frame, and grip means for the user, which carriage is movable by manpower and is provided with a kerb climbing device for passing height obstacles, the kerb climbing device comprising a displacement mechanism in the form of a linkage which comprises a suspension part, a foot part and rotatable connecting arms, which connecting arms are provided between the foot part and the suspension part for displacing the foot part with respect to the suspension part between a climbing position and an end position, and the displacement mechanism being provided with adjustment means for adjusting the foot part in the climbing position, wherein the connecting arms comprise a front arm and a rear arm, a top end of the front arm being rotatably connected to the suspension part via a first rotation point, a top end of the rear arm being rotatably connected to the suspension part via a second rotation point, and a bottom end of the front arm being rotatably connected to the foot part via a third rotation point and a bottom end of the rear arm being rotatably connected to the foot part via a fourth rotation point, wherein the connecting lines between the first and second rotation points, between the second and fourth rotation points, between the fourth and third rotation points and between the third and first rotation points, when seen from the side, form a quadrilateral, the corners of which are located at the rotation points, and wherein the suspension part is an integral part of the frame of the abovementioned carriage. A carriage of this type has the abovementioned advantages of an improved climbing action, on account of the quadrilateral shape of the linkage. Where swivel castors are used, the suspension part should form part of the connecting part of the frame which pivots with the wheel. In the carriage according to the invention, in the climbing position, the extension of the connecting line between the first rotation point and the third rotation point, on the one hand, and the extension of the connecting line between the second rotation point and the fourth rotation point, on the other hand, preferably intersect one another at an intersection point which lies above and behind the first rotation point. This type of configuration of the linkage provides an advantageous position of the MRC in the climbing position, with the associated advantages referred to above. The invention will be explained below with reference to the appended drawings, in which: Fig. 1 shows a diagrammatic side view of a kerb climbing device in accordance with a preferred embodiment of the invention; Fig. 2 shows a three-dimensional reproduction of a walking aid provided with a kerb climbing device in accordance with a preferred embodiment of the invention; Fig. 3 shows a side view of a walking aid provided with a kerb climbing device in accordance with a preferred embodiment of the invention, with the kerb climbing device in contact with a height obstacle in the climbing position; Fig. 4 shows a simplified side view of the climbing position of a kerb climbing device in accordance with a preferred embodiment of the invention; Fig. 5 shows a simplified side view of the end position of the kerb climbing device in accordance with a preferred embodiment of the invention; Fig. 6 shows a side view of the climbing position of a kerb climbing device which comprises an auxiliary front arm in accordance with a preferred embodiment of the invention; Fig. 7 shows a perspective view of the end position of a kerb climbing device which comprises an auxiliary front arm in accordance with a preferred embodiment of the invention; Fig. 8 shows a representation of a detail of a carriage in accordance with a preferred embodiment of the invention, in which the suspension part of the kerb climbing device is an integral part of the frame of the abovementioned carriage. Fig. 1 diagrammatically depicts a kerb climbing device 1, in which the displacement mechanism 2 is in the form of a linkage 3 which forms a quadrilateral. The linkage 3 comprises a suspension part 5 made from aluminium, a foot part 9 made from aluminium which is provided with a rubber contact surface 11 with a concave underside 12, a front arm 13 and a rear arm 15, the arms 13 and 15 being designed as aluminium plates. The top end of the front arm 13 and the top end of the rear arm 15 are rotatably connected to the suspension part 5 via a first axle 20 and a second axle 22, respectively. The first and second axles 20 and 22 are located at the two longitudinal ends of the suspension part 5. The foot part 9 is rotatably connected to the bottom end of the front arm 13 via the third axle 24 and to the bottom end of the rear arm 15 via the second axle 26. The third and fourth axles 24 and 26 lie at the two longitudinal ends of the foot part 9. The distance dl between the first and second axles 20 and 22 is shorter than the distance d2 between the third and fourth axles 24 and 26. At the second axle 22 there is a torsion spring 30, the ends of which engage on the one hand on the rear arm 13 and on the other hand on the suspension part 5. Consequently, the torsion spring 30 holds the kerb climbing device 1 in a climbing position, a stop block 34 being provided at the underside of the suspension part in order to limit the maximum travel of the rear arm 13 under stress from the torsion spring 30. Furthermore, in the suspension part 5 there is a connecting member 36, which comprises a clamping structure for securing to the frame of a walking aid, which can be tightened using pins 38. When the connecting member 36 is clamped onto a tube of the frame of a carriage, it is possible to adjust the angle of the kerb climbing device, since the connecting member 36 can easily be rotated with respect to the tube by virtue of the round opening. The linkage 3 itself has one degree of freedom of movement according to this embodiment. Fig. 2 shows a subsequent embodiment of a kerb climbing device 1 according to the invention, which has been secured to a front transverse tube of the frame 40 of a rollator 42, with the kerb climbing device 1 positioned between the front wheels 44. The corresponding components of the kerb climbing device which are shown in Fig. 1 are provided with identical reference numerals. In the case of walking aids without a transverse tube of this type, the kerb climbing device may comprise an auxiliary piece in the form of a transverse tube of this type, which can be secured between the upright tubes of the frame. For the sake of clarity, it should be noted that the kerb climbing device 1 is secured to the frame 40 via the clamping structure 36 and that the kerb climbing device 1 is designed with a double front arm 13 and a double rear arm 15. The walking aid 42 is provided with grip means in the form of handles 46. Fig. 3 shows a side view of the combination of a kerb climbing device 1 with a rollator 42 in accordance with Fig. 2. The kerb climbing device 1 is in a climbing position, and the foot part 9 is in contact with the height obstacle 50 that is to be passed over. The dashed auxiliary lines 52 and 54 represent extensions of the connecting lines 28 between the first and third axles 20 and 24, on the one hand, and between the second and fourth axles (not indicated) on the other hand. It will be clear that the intersection point 56 is located behind and above the first axle 20. Consequently, the intersection point 56 is located closer to the grip means 46 of the rollator 42 than if the intersection point were to lie below the first axle 20 or in front of the first axle 20. The arrow F denotes the normal force which is exerted on the foot part 9 by the obstacle 50. Fig. 4 shows a simplified illustration of a detail of the climbing position of the kerb climbing device 1 when it is used for a rollator. A front wheel 44 of the rollator is indicated by dashed lines, as is a part of the frame 40 which is connected to the kerb climbing device 1 via the connecting member 36. The foot part has a fixed point of contact 60 on the height obstacle 50 in the climbing position. It can be seen from the figure that a force FI pushing forwards will cause the linkage to move forwards in a counterclockwise direction, in a similar manner to a caterpillar track. Consequently, the forces in the front arm will be directed primarily towards the threshold which is to be surmounted, and the forces in the rear arm will be directed away from the threshold. It is precisely this forwards movement which results in a climbing movement by means of the linkage 3 which requires less force, while the vertical component of the movement is relatively small compared to the horizontal component. Fig. 5 shows a simplified illustration of a detail of the end position. of the kerb climbing device 1 after it has passed over the height obstacle proceeding from Fig. 4. The wheel 44 has reached the height obstacle 50, and from this moment on the foot part 9 is released again from the obstacle 50. Then, once the foot part is released from the obstacle 50, the linkage 3 will be moved back into a climbing position under the influence of the torsion spring (not shown) . Fig. 6 shows a side view of the climbing position of a kerb climbing device 1 which comprises an auxiliary front arm 60 in accordance with a preferred embodiment of the invention. Corresponding components to those shown in the previous drawings are provided with corresponding reference numerals. The auxiliary front arm 60 comprises an inner part 62 and an outer part 64, which are telescopically displaceable with respect to one another, the outer part 64 determining the length of the auxiliary front arm 60 in the fully retracted position. The inner part 62 is rotatably connected to the suspension part via a fifth axle 66 at a position behind the connecting member 36. The outer part 64 is rotatably connected to the foot part 9 via a sixth axle 68. The front arm 13 is composed of a main front arm 70 and a collapsible front arm 72, the collapsible front arm 72 resting on the foot part 9 in the climbing position. At the front end, the collapsible front arm is rotatably connected to the foot part 9 via a third axle 24, which in this embodiment is the same as the sixth axle 68. The construction is designed in such a manner that the collapsible front arm 72 can rotate about the same sixth axle 68 independently of the outer part 64 of the auxiliary front arm 60. At the rear end of the collapsible front arm 72, the latter is connected to the main front arm 70 via a seventh axle 74. Where the main front arm 70 and the auxiliary front arm 60 cross one another there is a slot in the main front arm 70, inside which slot the auxiliary front arm 60 can move, as illustrated in more detail in the following figure. It can be seen from this figure that the direction of the front arm 13 and the rear arm 15 only deviate to a limited extent from the parallel, with the result that the MRC of the kerb climbing device is at a relatively high level, and consequently this device is suitable for rollators. To provide a clearer illustration of this kerb climbing device, the first axle (20) , second axle (22), third axle (24) and fourth axle (26), which together form a quadrilateral, are indicated by their reference numerals . Fig. 7 shows a perspective view of the end position of a kerb climbing device, the climbing position of which is illustrated in Fig. 6. Components which correspond to those shown in previous drawings are provided with corresponding reference numerals. The main front arm 70 is provided with a slot 80 inside which the auxiliary front arm 60 moves. In the position of the kerb climbing device 1 illustrated, the auxiliary front arm 60 is fully retracted, with the result that it is now the outer part 64 which determines the length of the auxiliary front arm. At the same time, the main front arm 70 has moved towards the rear to such an extent that the collapsible arm 72 is partially free of the foot part 9, in which position, therefore, the front arm 13 as a whole is lengthened since the distance between the sixth axle 68 and the first axle 20 increases. It is precisely this lengthening which results in the effect in the end position of the kerb climbing device 1 whereby the height of the foot part 9 does not differ much from the tread of a wheel of the carriage on which the kerb climbing device is fitted. It should be noted that in the end position illustrated the foot part is supported on the rear arm 15 and the auxiliary front arm 60, and therefore the direction of these two arms is the determining factor for the MRC of the kerb climbing device 1. Fig. 8 shows a perspective illustration of a detail of a rollator 42 in accordance with a preferred embodiment of the invention, in which the suspension part 5 of the kerb climbing device 1 is an integral part of the frame of the abovementioned carriage 42. Components which correspond to those shown in the previous drawings are provided with corresponding reference numerals. A part of the pivotable front wheel suspension 90 is used on both sides of the front wheel 44 as suspension part 5 for the kerb climbing device 1. A front arm 13 and a rear arm 15 are rotatably connected to the suspension part 5 on both sides of the wheel 44 via axles, and the foot part 9 is designed in a U shape, so that the construction which surrounds the wheel 44 can move without impeding the wheel 44.

Claims

1. Kerb climbing device, for passing height obstacles by means of a carriage movable by manpower which is provided with at least one wheel, the kerb climbing device comprising a displacement mechanism in the form of a linkage which comprises a suspension part, a foot part and rotatable connecting arms, which connecting arms are provided between the foot part and the suspension part for displacing the foot part with respect to the suspension part between a climbing position and an end position, and the displacement mechanism being provided with adjustment means for adjusting the foot part in the climbing position, characterized in that the connecting arms (13, 15) comprise a front arm (13) and a rear arm (15) , a top end of the front arm (13) being rotatably connected to the suspension part (5) via a first rotation point (20) , a top end of the rear arm (15) being rotatably connected to the suspension part (5) via a second rotation point (22), and a bottom end of the front arm (13) being rotatably connected to the foot part (9) via a third rotation point (24) and a bottom end of the rear arm (15) being rotatably connected to the foot part (9) via a fourth rotation point (26) , wherein the connecting lines (28) between the first and second rotation points, between the second and fourth rotation points, between the fourth and third rotation points and between the third and first rotation points, when seen from the side, form a quadrilateral, the corners of which are located at the rotation points (20, 22, 24, 26) , and wherein the suspension part (5) comprises a connecting member (36) for releasably connecting it to the abovementioned carriage (42) , in such a manner that, when seen from the side, the angle of the suspension part (5) with respect to the carriage (42) can be adjusted with the aid of the connecting member (36) .

2. Kerb climbing device according to claim 1, characterized in that the first rotation point (20) , the second rotation point (22) , the third rotation point (24) and the fourth rotation point (26) respectively comprise a first axle (20), a second axle (22), a third axle (24) and a fourth axle (26), these axles (20, 22, 24, 26) being substantially parallel to one another.

3. Kerb climbing device according to one of the preceding claims, characterized in that the distance (dl) between the first and second rotation points (20, 22) is shorter than the distance (d2) between the third and fourth rotation points (24, 26) .

4. Kerb climbing device according to one of the preceding claims, characterized in that, in the climbing position, the extension (52) of the connecting line (28) between the first rotation point (20) and the third rotation point (24) , on the one hand, and the extension (54) of the connecting line (28) between the second rotation point (22) and the fourth rotation point (26), on the other hand, intersect one another at an intersection point (56) which lies above and behind the first rotation point (20) .

5. Kerb climbing device according to one of the preceding claims, characterized in that the foot part (9) comprises a contact surface which is concave (12) in form.

6. Kerb climbing device according to one of the preceding claims, characterized in that the foot part (9) comprises a friction- increasing contact surface (11) .

7. Kerb climbing device according to one of the preceding claims, characterized in that the adjustment means (30, 34) comprise a torsion spring (30) which engages on one of the connecting arms (13, 15), and a stop (34) for one of the connecting arms (13, 15) .

8. Kerb climbing device according to one of the preceding claims, characterized in that the length of the front arm (13) and/or rear arm (15) is adjustable.

9. Kerb climbing device according to one of the preceding claims, characterized in that it comprises an auxiliary front arm, which is telescopically displaceable in the longitudinal direction, and a front arm which is composed of a main front arm and a collapsible front arm, the auxiliary front arm being rotatably connected, at a top end via a fifth rotation point, to the suspension part in a position between the first and second rotation points, and being rotatably connected, at a bottom end via a sixth rotation point, to the foot part in a position in front of the main front arm, and the collapsible front arm, in the climbing position, resting on the foot part between the sixth rotation point and the main front arm, the collapsible front arm being rotatably connected, at a first end, to the foot part via the third rotation point and, at a second end, to the main front arm via a seventh rotation point, the collapsible front arm being rotatably connected, via the third rotation point, to the foot part, said third point being in a fixed position with respect to the foot part, while the seventh rotation point can move with respect to the foot part.

10. Kerb climbing device according to claim 9, in which the third axle (24) and sixth axle are combined to form a single axle.

11. Kerb climbing device according to one of the preceding claims, characterized in that the kerb climbing device (1) comprises an auxiliary piece for coupling the connecting member (36) to the carriage (42) .

12. Use of a kerb climbing device (1) according to one of the preceding claims, in which the kerb climbing device is connected to the carriage (42) .

13. Walking aid (42) which comprises a frame (40) and, connected to it, wheels (44) and grip means (46) for the user, which is provided with a kerb climbing device (1) according to one of the preceding claims .

14. Walking aid (42) which comprises a frame (40) and, connected to it, wheels (44) and grip means (46) for the user, which is provided with a kerb climbing device (1) according to one of the preceding claims 4-9, wherein, when the kerb climbing device (1) is in the climbing position, the extension (52) of the connecting line (28) between the first rotation point (20) and the third rotation point (24) , on the one hand, and the extension (54) of the connecting line (28) between the second rotation point (22) and the fourth rotation point (26) , on the other hand, intersect one another at an intersection point (56) which is in the vicinity of the grip means (46) of the walking aid (42) .

15. Carriage (42) comprising a frame (40), at least one wheel (44) which is connected to the frame, and grip means (46) for the user, which carriage is by movable manpower and is provided with a kerb climbing device (1) for passing height obstacles, the kerb climbing device (1) comprising a displacement mechanism (2) in the form of a linkage (3) which comprises a suspension part (5), a foot part (9) and rotatable connecting arms (13,15), which connecting arms (13,15) are provided between the foot part (9) and the suspension part (5) for displacing the foot part (9) with respect to the suspension part (5) between a climbing position and an end position, and the displacement mechanism (2) being provided with adjustment means (30,34) for adjusting the foot part (9) in the climbing position, wherein the connecting arms (13, 15) comprise a front arm (13) and a rear arm (15) , a top end of the front arm (13) being rotatably connected to the suspension part (5) via a first rotation point (20) , a top end of the rear arm (15) being rotatably connected to the suspension part (5) via a second rotation point (22) , and a bottom end of the front arm (13) being rotatably connected to the foot part (9) via a third rotation point (24) and a bottom end of the rear arm (15) being rotatably connected to the foot part (9) via a fourth rotation point (26), wherein the connecting lines (28) between the first and second rotation points, between the second and fourth rotation points, between the fourth and third rotation points and between the third and first rotation points, when seen from the side, form a quadrilateral, the corners of which are located at the rotation points (20, 22, 24, 26) , and wherein the suspension part (5) is an integral part of the frame (40) of the abovementioned carriage (42) .

16. Carriage according to claim 14, in which, in the climbing position, the extension (52) of the connecting line (28) between the first rotation point (20) and the third rotation point (24), on the one hand, and the extension (54) of the connecting line (28) between the second rotation point (22) and the fourth rotation point (26), on the other hand, intersect one another at an intersection point (56) which lies above and behind the first rotation point (20) .