Technical Field
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The object of the invention is a unit for changing the position of the wheelchair rear wheels. Thesolution is found useful in wheelchairs, in particular when the wheelchair is provided with a front drive. The invention increases stability of the wheelchair, thus increasing the safety of the person travelling in the wheelchair considerably, in particular when using a front drive.
Prior Art
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Front drives mounted to wheelchairs are well known from prior art. Mounting such drives to wheelchairs is beneficial to person with disabilities, providing them with the ability to move more quickly, as well as with certain independence of their relatives and urban transport. However, the assembly of such drives results in raising the front part of the wheelchair, thus causing a shift in its centre of gravity, which may be very dangerous to a person with disabilities, as it increases the risk of tipping over the wheelchair along with the drive, due to reduced stability of the wheelchair.
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Methods of shifting the centre of gravity of a wheelchair are known from prior art. Document
US5294142A may be an example of such a solution, disclosing a wheelchair in which the position or the angle of inclination of the rear wheels can be corrected. The document discloses construction of an adjustable wheelchair having a support frame, a drive wheels mount connected to the support frame at each side thereof, each mount comprising a base, a cylindrical axle bracket rotatably mounted on the base, and a bore in the axle bracket inclined at a fixed angle to the axis of the cylindrical axle bracket. The axle is fixed in the bore for one of the wheels, with means for securing the cylindrical axle bracket in the bores at each side of said frame. Such design enables adjustment of the inclination of the wheels mounted in the bores at each side of said frame. In the adjustable wheelchair, by loosening the bolts mounting the axle bracket, it is possible to move the rear wheels axle upwards and downwards or frontwards and rearwards, and to correct the angular position of the wheels. These bolts are tightened following the adjustment. The document also discloses the ability to attach drive wheels mounts on longitudinal horizontal tubes of the frame in order to permit a horizontal adjustment of the rear wheels. However, changing the direction of adjustment requires repositioning a mounts, thus hindering quick change in the position of the wheelchair rear wheels. Also, such a manner of adjusting the centre of gravity and the inclination of the wheels requires dedicated design of the wheelchair.
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In prior art, there are also known methods for changing the centre of gravity by mounting special units to the wheelchair support frame , for example as disclosed in document
WO2002085658A1 . The unit has the form of two coupled mounting plates, which are mounted on both sides of the support frame tube of the wheelchair and form a single unit. The final setup includes two units, each one mounted on one side of the support frame of the wheelchair. A single unit is provided with a saddle made by the mounting plates, which rests against the first support frame tube, and mounting holes with bolts mounting the unit to the second support frame tube passing there through. The unit is provided with holes in mounting plates, which allow for repositioning the wheelchair axle. The unit can be mounted in various positions, providing vertical or horizontal adjustment. However, changing the direction of adjustment requires repositioning a mount, thus hindering quick change in the position of the wheelchair rear wheels. Also, the solution according to
WO2002085658A1 does not allow for adjustment of the inclination angle of the wheelchair rear wheels with respect to the frame.
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Document
WO2001032119A1 discloses an unit in the form of axle plates bolted to the support frame of the wheelchair. The unit comprises a left and right axle plate, each of which is adapted to be mounted in the joints corners of the wheelchair support frame by means of bolts. Each axle plate comprises adjustment holes both in the vertical and the horizontal axis. However, similarly to document
WO2002085658A1 , the rear wheels axle unit requires moving the entire wheels axle to different position, which may be difficult for a person with disabilities.
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Document
US20150123446A1 discloses an unit mounting the wheelchair wheel in an adjustable manner. The unit comprises two clamps mounted on the wheelchair frame, connected by a coupling comprising teeth. The teeth allow for vertical change in the position of the rear wheel's axle. Depending on the mounting place of the clamps, it is also possible to adjust the rear wheels axle horizontally. Horizontal adjustment is limited by the dimensions of the wheelchair support frame. Each unit enables adjustment of the axis of a single wheel. Therefore, it is possible to adjust the wheels in a noncoaxial manner.
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From prior art, there are also known detachably mounted units ensuring coaxiality of wheels, like those disclosed in document
EP1799536A2 . The unit comprises two clamps adapted to be mountable on the wheelchair frame, mutually connected by a bar for mounting the wheelchair rear wheels slidably with respect to the clamps on the protruding elements of the clamps. The bar along with the clamps provide the ability to adjust the position of the height of the bar with respect to the clamps by sliding it over the protruding elements of the clamps. The construction of the clamps themselves allows for mounting them in various places of the wheelchair frame, thus adjusting the position of the axis in a horizontal plane. However, the scope of adjustment of the position of the rear wheels axle in a horizontal plane is limited by the wheelchair frame design. The unit bar comprises inserts on its ends, in which a thread adapted to mount the rear wheels may be made at an angle with respect to the bar axis. The inserts made in such a manner allow for mounting the wheelchair rear wheels at an angle, thus increasing its stability. The invention disclosed in document
EP1799536A2 provides adjustment of the rear wheel's axle in both planes-vertical and horizontal, as well as mounting the rear wheels at an angle. However, it should be noted that the assembly of the unit requires the use of a large number of bolts, and the scope of adjustment of the axle in a horizontal plane is rather limited.
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The purpose of the invention is to solve the technical problem which involves providing an unit for changing the position of the wheelchair rear wheels, enabling coaxial adjustment of the position of the rear wheels. The purpose of the invention is also to provide simple and quick mounting of the unit. The purpose of the invention is also to enable a person with disabilities to change the position of the wheels on their own, without much effort and with no need to reposition the entire wheelchair wheels axle, which often entails disassembly of the entire structure of the wheelchair chassis.
The Essence of the Invention
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The object of the invention is an unit for changing the position of a wheelchair rear wheels, comprising brackets connected to a bar for mounting the wheelchair rear wheels. The essence of the invention is in that the brackets are adapted to be seated on the wheelchair rear wheels axle while mounting the unit on a wheelchair chassis, and in that the unit comprises at least one coupling and blocking element for blocking the position of the unit on the wheelchair chassis.
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The unit according to the invention enables coaxial adjustment of the position of the rear wheels by providing the ability to move the wheelchair rear wheels to the bar of the unit for mounting the wheelchair rear wheels. Moving the wheelchair rear wheels to the bar of the unit for mounting the wheelchair rear wheels causes change in the position of the centre of gravity, thus increasing stability of the wheelchair and minimising the risk of the wheelchair tipping over rearwards.
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Preferably, at least one coupling and blocking element is seated in at least one bracket.
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Preferably, the coupling and blocking element has the form of an extension rod, an extension rod with a spring, a spring bolt, or a spring latch, thus enabling simple and quick mounting of the unit, with no need for the use of tools.
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Equally preferably, the brackets of the unit are detachably connected to the bar for mounting the wheelchair rear wheels, which allows for detaching the bar when not used to change the position of the wheelchair rear wheels.
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Preferably, the bar for mounting the wheelchair rear wheels comprises spacer elements slidably connected to the brackets. Slidable connection of the brackets to the spacer elements allows for adjusting the rearward extension of the wheelchair rear wheels, thus increasing the adjustment range of the centre of gravity of the wheelchair, and therefore increases stability of the wheelchair.
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Equally preferably, the unit comprises a system for blocking the mutual positioning of the brackets and the spacer elements of the bar, thus allowing for permanent fixing of the mutual positioning of these elements, with no need for the use of tools.
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It is good when the system for blocking the mutual positioning of the brackets and the spacer elements of the bar has the form of a spring-loaded blocking mechanism, the spring-loaded blocking mechanism preferably comprising a flat spring with a blocking pin placed in the brackets or spacer elements, and fixing holes located in the spacer elements or brackets, respectively. Such a solution is characterised by simple, durable and failure-free design.
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Preferably, the brackets of the unit comprise at least two rotatably connected arms, which also constitute a shock-absorbing component of the bar for mounting the wheelchair rear wheels. The use of the shock-absorbing component ensures more comfortable and safer travelling on an uneven ground.
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Preferably, the bar for mounting the wheelchair rear wheels comprises inserts for mounting the wheelchair rear wheels. It is recommended for the inserts to comprise a mounting hole for mounting the rear wheels, wherein the mounting hole for mounting the rear wheels being made at an angle with respect to the longitudinal axis of the inserts at the angle ranging from 0° to 6°. Holes made at an angle with respect to the longitudinal axis of the inserts allow for tilting the wheels inwards with respect to the frame of the wheelchair, thus increasing stability and improving stability of the wheelchair on the curves. Equally preferably, the inserts are externally threaded, which allows for their easy mounting and quick replacement.
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It is recommended for the brackets to comprise recesses or holes for seating the brackets on the wheelchair rear wheels axle when mounting the unit on the wheelchair chassis.
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The object of the invention is also a wheelchair comprising the unit according to the first aspect of the invention.
Advantages of the Solution
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The invention allows for simple and quick change in the position of the rear wheels, which results in shifting the centre of gravity of the wheelchair. Change in the position (rearwards movement) of the rear wheels is particularly important when using a wheelchair with a front drive, which results in raising the front wheels of the wheelchair, increasing the risk of tipping over the vehicle rearwards. The unit according to the invention enables proper movement of the rear wheels when a front drive is attached to the wheelchair. Moving the rear wheels axle rearwards changes the position of the centre of gravity, and reduces the risk of tipping over the wheelchair.
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The invention also allows to setup negative camber angle on the wheels, towards the frame of the wheelchair (inwards with respect to the frame), thus increasing stability of the wheelchair on the curves. Inclination of the wheels additionally reduces the risk of tipping over a wheelchair with a front drive attached thereto.
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The use of at least one coupling and blocking element for blocking the position of the unit on the wheelchair chassis ensures simple assembly of the unit on the wheelchair chassis, without the use of screws or additional tools, which are usually not carried by a person with disabilities. The unit according to the invention may be mounted and demounted at any time; it is not necessary for it to be mounted on the wheelchair permanently.
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The use of at least one coupling and blocking element for blocking the position of the unit ensures secure mounting of the unit on the wheelchair chassis. Due to the coupling and blocking element, the unit according to the invention does not rotate once mounted, and it is stably mounted on the wheelchair chassis.
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The unit according to the invention enables adjustment of the position of the centre of gravity of the wheelchair with no need to reposition the entire rear wheels axle of the wheelchair. Moving the rear wheels to the bar of the unit for mounting the wheelchair rear wheels does not require additional tools, and a person with disabilities may perform such replacement by themselves, with little effort.
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The bar used for mounting the wheelchair rear wheels, which is longer than the wheelchair rear wheels axle, allows for moving the rear wheels downwards and sideways, thus increasing stability of the wheelchair considerably. Such a system prevents the inserts of the unit from blocking the movement of the rear wheels in the wheelchair, when the wheels are mounted on the wheelchair rear wheels axle. Likewise, the rear wheels axle does not block the movement of the wheelchair rear wheels when the rear wheels are mounted on the bar of the unit.
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Due to the use of detachable connection, in particular a slidable connection between the mounting brackets and the bar of the unit for mounting the wheelchair rear wheels, it is possible to adjust the distance between the unit and the wheelchair rear wheels axle, thus allowing for more precise adjustment of the position of the centre of gravity of the wheelchair.
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Moreover, this adjustment may be provided in an ergonomic manner, so that the person with disabilities could adjust the distance of the bar of the unit for mounting the wheelchair rear wheels from the wheelchair rear wheels axle by themselves, with no additional tools. Such adjustment may be provided by blocking pins connected to a flat spring inside the elements of the detachable connection, and holes in these elements which correspond to the pins. Such a solution also provides the ability to safely block the position of the wheel's axle of the unit with respect to the wheelchair rear wheels axle, and prevents detachment of the elements of the wheel unit of the wheelchair when driving.
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The use of replaceable inserts with holes made at various angles allows for easy and quick change of the angle of inclination of the wheels towards the wheelchair frame. The tilting of wheels by the inserts allows a person with disabilities to adjust the wheels camber angle.
Description of the Drawings
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The invention is presented in embodiments and in the drawing, in which:
- Fig. 1 -
- presents a perspective view of an unit for changing the position of the wheelchair rear wheels according to a first embodiment;
- Fig. 2 -
- presents a perspective view of a wheelchair with a mounted unit for changing the position of the wheelchair rear wheels according to the first embodiment, and the wheelchair rear wheels moved to the bar of the unit for mounting the wheelchair rear wheels;
- Fig. 3 -
- presents a partial view of the wheelchair with the mounted unit for changing the position of the wheelchair rear wheels according to the first embodiment;
- Fig. 4 -
- presents the bar of the unit in a cross-section with inserts for mounting the wheelchair rear wheels, and a detail revealing an insert for mounting the wheelchair rear wheels;
- Fig. 5a -
- presents a perspective view of the unit for changing the position of the wheelchair rear wheels according to a second embodiment;
- Fig. 5b -
- presents an exploded view from the perspective of the unit for changing the position of the wheelchair rear wheels according to the second embodiment;
- Fig. 6 -
- presents the bar of the unit in a cross-section with inserts for mounting the rear wheels in the wheelchair, and a detail revealing an insert for mounting the wheelchair rear wheels;
- Fig. 7 -
- presents a side view of a wheelchair with a mounted unit for changing the position of the wheelchair rear wheels, with the rear wheels mounted on the bar of the unit for mounting the wheelchair rear wheels;
- Fig. 8 -
- presents a side view of a wheelchair with a front drive and a mounted unit for changing the position of the wheelchair rear wheels, with the rear wheels mounted on the bar of the unit for mounting the wheelchair rear wheels;
- Fig. 9a -
- presents a perspective view of an unit for the wheelchair wheels according to a third embodiment;
- Fig. 9b -
- presents an exploded view from the perspective of detachable connection of mounting brackets and wheels axles of the wheelchair unit according to the third embodiment;
- Fig. 10a -
- presents a perspective view of an unit for the wheelchair wheels according to a fourth embodiment;
- Fig. 10b -
- presents an exploded view from the perspective of detachable connection of mounting brackets and wheels axles of the wheelchair unit according to the fourth embodiment;
- Fig. 11 -
- presents a front view of a wheelchair according to any embodiment, with the wheels tilted inwards.
Detailed Description of the Invention
First embodiment
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Fig. 1 presents an unit 1 for changing the position of the wheelchair rear wheels, comprising brackets 2 connected to a bar 3 for mounting the wheelchair rear wheels. The brackets 2 may be detachably connected to the bar 3, which allows for detaching the bar 3 when not used to change the position of the wheelchair rear wheels.
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The brackets 2 have the form of flat bars connected to sleeves. The brackets 2 have a recess 4 whose shape is adapted to be seated on the wheelchair rear wheels axle 21 while mounting the unit on the wheelchair chassis.
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The bar 3 for mounting the wheelchair rear wheels comprises spacer elements 5 which connect the bar 3 to the brackets 2.
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The bar 3 also comprises inserts 6 for mounting the rear wheels in the wheelchair, like for example presented in Fig. 4. The inserts 6 comprise mounting holes 7, in which the rear wheels are mounted. The mounting holes 7 for mounting the rear wheels are made at an angle with respect to the longitudinal axis of the inserts 6 at the angle ranging from 0° to 6°. Holes made at an angle with respect to the longitudinal axis of the inserts 6 allow for change wheels camber angle with respect to the frame of the wheelchair (Fig. 11), thus increasing stability and improving safety of the wheelchair on the curves. The inserts 6 may be replaceable inserts, thus allowing for their quick replacement and adjustment of wheels camber angle of the wheelchair with respect to the frame to the current needs of the user. In this embodiment, the inserts 6 are externally threaded and screwed into the bar 3. In other embodiments, the inserts 6 may be mounted in the bar 3 in other known manners.
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The unit 1 also comprises a coupling and blocking element 8 for coupling and blocking the position of the unit 1 on the wheelchair chassis. The coupling and blocking element 8 have form of an extension rod, preferably an extension rod with a spring. The ends 9a, 9b of the extension rod passing through holes 10 in the brackets 2 are intended to be seated in holes in the wheelchair chassis, for blocking the position of the unit 1, and therefore its stable mounting.
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In order to mount the unit 1 on the wheelchair chassis, the recesses 4 of the brackets 2 become seated on the wheelchair rear wheels axle 21, with simultaneous compression of the coupling and blocking element 8 in the form of an extension rod in order to insert the brackets 2 of the unit 1 between elements of the wheelchair chassis, for example rear wheel brackets 23. Then by expanding the extension rod 8 and placing the ends 9a, 9b in holes 22 in the wheelchair chassis, due to which the unit is blocked and stably mounted on the wheelchair chassis.
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Once the unit 1 has been mounted on the wheelchair chassis, the user is able to move the rear wheels axle rearwards by moving the wheels from the wheelchair axle 21 to the bar 3, as presented in Fig. 2. This allows for shifting wheels axle backward from the centre of gravity of the wheelchair, thus increasing stability of the wheelchair and reducing the risk of tipping over the wheelchair rearwards. This is particularly important when a front drive is attached to the wheelchair, causing the front wheels of the wheelchair to raise and increasing the risk of tipping over the vehicle.
Second embodiment
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Figs. 5a and 5b present an unit 1 for changing the position of the wheelchair rear wheels, comprising brackets 2 connected to a bar 3 for mounting the rear wheels in the wheelchair. The brackets 2 are detachably connected to the bar 3, which allows for detaching the bar 3 when not used to change the position of the wheelchair rear wheels.
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The brackets 2 have the form of bent sleeves, with arms 2a, 2b formed by said bend. The arms 2a are connected to C-profiles 11. The C-profiles 11 of the brackets 2 have recesses 4 whose shape is adapted to be seated on the rear wheel's axle 21 of the wheelchair while mounting the unit on the wheelchair chassis. Preferably, the spacing of the arms of the C-profile 11 is adapted to the dimension of the bracket 23 of the wheelchair rear wheels axle 21, which additionally stabilises the position of the unit 1 on the wheelchair chassis.
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The bar 3 for mounting the rear wheels in the wheelchair comprises spacer elements 5 in the form of sleeves which connect the bar 3 to the brackets 2. The spacer elements 5 are slidably connected to the brackets 2, so that the spacer elements 5 are placed in the arms 2b of the brackets 2. The unit also comprises a system 12 for determining the mutual positioning of the brackets 2 and the spacer elements 5 of the bar 3, in the form of a spring-loaded blocking mechanism. This system 12 comprises a flat spring 13 with a blocking pin 14 placed inside the spacer elements 5, and fixing holes 15 in the arms 2b of the brackets 2. The blocking pin 14 is placed in a hole made in the spacer element 5, and it is intended to be inserted into a selected fixing hole 15. A sample spring-loaded blocking mechanism is presented in Fig. 6.
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Determining the mutual positioning of the brackets 2 and the spacer elements 5 involves the insertion of the blocking pin 14 into the selected fixing hole 15. Slidable connection of the brackets 2 with the spacer elements 5 allows for adjusting the rearward extension of the wheelchair rear wheels, thus increasing the adjustment range of the rear wheel's axle position in reference to the centre of gravity of the wheelchair.
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Like in the first embodiment, the bar 3 comprises inserts 6 for mounting the wheelchair rear wheels (for example presented in Fig. 4). The inserts 6 comprise mounting holes 7, in which the rear wheels are mounted. The mounting holes 7 for mounting the rear wheels are made at an angle with respect to the longitudinal axis of the inserts 6 at the angle ranging from 0° to 6°. Holes made at an angle with respect to the longitudinal axis of the inserts 6 allow for tilting the wheels with respect to the frame of the wheelchair, thus increasing stability and improving stability of the wheelchair on the curves. The inserts 6 may be replaceable inserts, thus allowing for their quick replacement and adjustment of the inclination of the wheelchair wheels with respect to the frame to the current needs of the user. In this embodiment, the inserts 6 are externally threaded and screwed into the bar 3. In other embodiments, the inserts 6 may be mounted in the bar 3 in other known manners.
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The unit 1 also comprises a coupling and blocking element 8 for coupling and blocking the position of the unit 1 on the wheelchair chassis. The coupling and blocking element 8 have a form of an extension rod, preferably an extension rod with a spring. The ends 9a, 9b of the extension rod passing through holes 10 made in the C-profiles 11 of the brackets 2 are intended to be seated in holes in the wheelchair chassis, for blocking the position of the unit 1, and therefore its stable mounting.
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In order to mount the unit 1 on the wheelchair chassis, the recesses 4 of the brackets 2 become seated on the wheelchair rear wheels axle, with simultaneous compression of the coupling and blocking element 8 in the form of an extension rod in order to insert the brackets 2 of the unit 1 between elements of the wheelchair chassis, for example rear wheel brackets 23. This is followed by expanding the extension rod 8 and placing the ends 9a, 9b in holes 22 in the wheelchair chassis, due to which the unit is blocked and stably mounted on the wheelchair chassis.
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Once the unit 1 has been mounted on the wheelchair chassis, the user is able to move the rear wheels axle rearwards by reattaching the wheels from the wheelchair axle to the bar 3, as presented in Figs. 7 and 8. This allows for shifting the centre of gravity of the wheelchair, thus increasing stability of the wheelchair and reducing the risk of tipping over the wheelchair rearwards. This is particularly important when a front drive is attached to the wheelchair, causing the front wheels of the wheelchair to raise and increasing the risk of tipping over the vehicle.
Third embodiment
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Figs. 9a and 9b present an unit 1 for changing the position of the wheelchair rear wheels, comprising brackets 2 connected to a bar 3 for mounting the wheelchair rear wheels.
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The brackets 2 have the form of flat bars connected to sleeves. The brackets 2 have holes 16 whose shape is adapted to seat the brackets on the wheelchair rear wheels axle 21 while mounting the unit on the wheelchair chassis.
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The bar 3 for mounting the wheelchair rear wheels comprises spacer elements 5 in the form of sleeves, which connect the bar 3 to the sleeves of the brackets 2. The spacer elements 5 are slidably connected to the brackets 2, so that the sleeves of the brackets 2 are placed in the spacer elements 5. Like in the second embodiment, the unit comprises a system 12 for determining the mutual positioning of the brackets 2 and the spacer elements 5 of the bar 3, in the form of a spring-loaded blocking mechanism. This system comprises a flat spring 13 with a blocking pin 14 placed inside the sleeves of the brackets 2, and fixing holes 15 made in the spacer elements 5. The blocking pin 14 is placed in a hole made in the sleeve of the bracket 2, and it is intended to be inserted into a selected fixing hole 15 in the spacer element 5 of the bar 3.
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Determining the mutual positioning of the brackets 2 and the spacer elements 5 involves the insertion of the blocking pin 14 into the selected fixing hole 15. Slidable connection of the brackets 2 with the spacer elements allows for adjusting the rearward extension of the wheelchair rear wheels, thus increasing the adjustment range of the centre of gravity of the wheelchair, as well as for detaching the bar 3, when not used for changing the position of the wheelchair rear wheels.
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Like in the previous embodiments, the bar 3 comprises inserts 6 for mounting the wheelchair rear wheels (for example presented in Fig. 4). The inserts 6 comprise mounting holes 7, in which the rear wheels are mounted. The mounting holes 7 for mounting the rear wheels are made at an angle with respect to the longitudinal axis of the inserts 6 at the angle ranging from 0° to 6°. Holes made at an angle with respect to the longitudinal axis of the inserts 6 allow for tilting the wheels with respect to the frame of the wheelchair, thus increasing stability and improving stability of the wheelchair on the curves. The inserts 6 may be replaceable inserts, thus allowing for their quick replacement and adjustment of the inclination of the wheelchair wheels with respect to the frame to the current needs of the user. In this embodiment, the inserts 6 are externally threaded and screwed into the bar 3. In other embodiments, the inserts 6 may be mounted in the bar 3 in other known manners.
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The unit 1 also comprises coupling and blocking elements 8 for coupling and blocking the position of the unit 1 on the wheelchair chassis. The coupling and blocking elements 8 are seated in holes made in the flat bars of the brackets 2. The coupling and blocking elements 8 have the form of spring bolts. Alternatively, the coupling and blocking elements 8 can have the form of spring latches. Pins 17 of the spring bolts are intended to be seated in holes in the wheelchair chassis, for blocking the position of the unit 1, and therefore its stable mounting.
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In order to mount the unit 1 on the wheelchair chassis, the bracket 2 is seated on the wheelchair rear wheels axle using holes 16 made in the flat bars of the brackets 2. The coupling and blocking elements 8 in the form of spring bolts are compressed in order to insert the brackets 2 of the unit 1 between elements of the wheelchair chassis, for example rear wheel brackets. Subsequently, the spring bolts are loosened, due to which the pins 17 enter holes 22 in the wheelchair chassis, causing the unit 1 to be blocked and stably mounted on the wheelchair chassis.
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Once the unit 1 has been mounted on the wheelchair chassis, the user is able to move the rear wheels axle rearwards by moving the wheels from the wheelchair axle to the bar 3, as presented in Figs. 7 and 8. This allows for shifting the centre of gravity of the wheelchair, thus increasing stability of the wheelchair and reducing the risk of tipping over the wheelchair rearwards. This is particularly important when a front drive is attached to the wheelchair, causing the front wheels of the wheelchair to raise and increasing the risk of tipping over the vehicle.
Fourth embodiment
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Figs. 10a and 10b present an unit 1 for changing the position of the wheelchair rear wheels, comprising brackets 2 connected to a bar 3 for mounting the rear wheels in the wheelchair. The brackets 2 are detachably connected to the bar 3, which allows for detaching the bar 3 when not used to change the position of the wheelchair rear wheels.
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The brackets 2 constitute two arms 2a, 2b rotatably connected by a pivot. The arms 2a, 2b constitute a shock-absorbing system for the bar 3 for mounting the rear wheels in the wheelchair. The arms 2a are connected to C-profiles 11. The C-profiles 11 of the brackets 2 have recesses 4 whose shape is adapted to be seated on the rear wheel's axle 21 of the wheelchair while mounting the unit on the wheelchair chassis. Preferably, the spacing of the arms of the C-profile is adapted to the dimension of the bracket 23 of the wheelchair rear wheels axle 21.
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The bar 3 for mounting the rear wheels in the wheelchair comprises spacer elements 5 in the form of sleeves which connect the bar 3 to the brackets 2, whose arms 2b comprise sleeves with fixing holes 15. The spacer elements 5 are slidably connected to the brackets 2, so that the spacer elements 5 are placed in the arms 2b of the brackets 2. Like in the previous embodiments 1, the unit also comprises a system 12 for determining the mutual positioning of the brackets 2 and the spacer elements 5 of the bar 3, in the form of a spring-loaded blocking mechanism. This system comprises a flat spring 13 with a blocking pin 14 placed inside the spacer elements 5, and fixing holes 15 in the arms 2b of the brackets 2. The blocking pin 14 is placed in a hole made in the spacer element 5, and it is intended to be inserted into a selected fixing hole 15. A sample spring-loaded blocking mechanism is presented in Fig. 6.
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Determining the mutual positioning of the brackets 2 and the spacer elements 5 involves the placement of the blocking pin 14 in the selected fixing hole 15. Slidable connection of the brackets 2 with the spacer elements 5 allows for adjusting the rearward extension of the wheelchair rear wheels, thus increasing the adjustment range of the centre of gravity of the wheelchair.
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Like in the first and second embodiments, the bar 3 comprises inserts 6 for mounting the wheelchair rear wheels (like for example presented in Fig. 4). The inserts 6 comprise mounting holes 7, in which the rear wheels are mounted. The mounting holes 7 for mounting the rear wheels are made at an angle with respect to the longitudinal axis of the inserts 6 at the angle ranging from 0° to 6°. Holes made at an angle with respect to the longitudinal axis of the inserts 6 allow for tilting the wheels with respect to the frame of the wheelchair, thus increasing stability and improving stability of the wheelchair while turning. The inserts 6 may be replaceable inserts, thus allowing for their quick replacement and adjustment of the inclination of the wheels of the wheelchair with respect to the frame to the current needs of the user. In this embodiment, the inserts 6 are externally threaded and screwed into the bar 3. In other embodiments, the inserts 6 may be mounted in the bar 3 in other known manners.
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The unit 1 also comprises a coupling and blocking element 8 for coupling and blocking the position of the unit 1 on the wheelchair chassis. The coupling and blocking element 8 have form of an extension rod, preferably an extension rod with a spring. The ends 9a, 9b of the extension rod passing through the holes 10 made in the C-profiles 11 of the brackets 2 are intended to be seated in holes in the wheelchair chassis, for blocking the position of the unit 1, and therefore its stable mounting.
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In order to mount the unit 1 on the wheelchair chassis, the recesses 4 of the brackets 2 become seated on the rear wheel's axle of the wheelchair, with simultaneous compression of the coupling and blocking element 8 in the form of an extension rod in order to insert the brackets 2 of the unit 1 between elements of the wheelchair chassis, for example rear wheel brackets. This is followed by expanding the extension rod 8 and placing the ends 9a, 9b in holes 22 in the wheelchair chassis, due to which the unit is blocked and stably mounted on the wheelchair chassis.
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Once the unit 1 has been mounted on the wheelchair chassis, the user is able to move the rear wheels axle rearwards by moving the wheels from the wheelchair axle to the bar 3. This allows for shifting the centre of gravity of the wheelchair, thus increasing stability of the wheelchair and reducing the risk of tipping over the wheelchair rearwards. This is particularly important when a front drive is attached to the wheelchair, causing the wheelchair front wheels o to raise and increasing the risk of tipping over the vehicle.
Fifth embodiment
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A wheelchair comprising an unit according to any of the described embodiments.