Patent Description:
As shown in <FIG>, an existing wheelchair <NUM> includes a main seat body <NUM> and an anti-tip apparatus <NUM>. The main seat body <NUM> has a seat frame <NUM>, two front wheels <NUM>, and two rear wheels <NUM>. The front and rear wheels <NUM>, <NUM> are connected to the seat frame <NUM> in a front-rear manner. The anti-tip apparatus <NUM> is integrally fixed to and is inclined rearwardly and downwardly relative to a lower part of the seat frame <NUM> to prevent the wheelchair <NUM> from tipping backwards for enhancing safety of a user (not shown). Another existing wheelchair with an anti-tip apparatus is disclosed in <CIT>.

However, because the anti-tip apparatus <NUM> is integrally fixed on the main seat body <NUM>, when the wheelchair <NUM> needs to be moved from a lower ground (e.g., a street) to a higher ground (e.g., a raised sidewalk), lifting the front wheels <NUM> while using the rear wheels <NUM> as a fulcrums is impeded by abutment of the anti-tip apparatus <NUM> against the lower ground. As a result, the wheelchair <NUM> is unable to be tilted further backwards. Hence, there is still room for improvement in the wheelchair <NUM>.

Therefore, an object of the disclosure is to provide an operable anti-tip assembly that can alleviate the aforesaid drawback of the prior art.

According to the disclosure, an operable anti-tip assembly is adapted for a wheelchair, and includes a control mechanism and an anti-tip mechanism.

The control mechanism includes a mounting unit and a positioning unit. The mounting unit is adapted to be mounted at a rear end portion of the wheelchair in a removable manner, extends in a first direction, and defines a mounting space. The positioning unit is disposed in the mounting space in a resiliently restorable manner and includes a first engaging portion.

The anti-tip mechanism includes an anti-tip strut unit and a resilient member. The anti-tip strut unit is movably inserted through the mounting unit in a second direction inclined with respect to the first direction, and includes a second engaging portion. The resilient member is connected to the mounting unit and the anti-tip strut unit, and urges the anti-tip strut unit to move away from a ground surface.

The positioning unit is changeable within the mounting space between a locking state, where the first engaging portion engages the second engaging portion to prevent the anti-tip strut unit from moving relative to the mounting unit in the second direction, and an unlocking state, where the first engaging portion disengages from the second engaging portion to allow the anti-tip strut unit to be urged by the resilient member to move relative to the mounting unit in the second direction and away from the ground surface.

Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment(s) with reference to the accompanying drawings. It is noted that various features may not be drawn to scale.

Referring to <FIG> and <FIG>, two operable anti-tip assemblies <NUM> according to a first embodiment of the disclosure are adapted for a wheelchair <NUM>. The wheelchair <NUM> includes a seat body <NUM>, two front wheels <NUM> connected to a front end of the seat body <NUM>, and two rear wheels <NUM> connected to a rear end of the seat body <NUM>. The seat body <NUM> includes two frame members <NUM> that are disposed at a bottom side of the seat body <NUM> and that extend in a front-rear direction. In this embodiment, the two operable anti-tip assemblies <NUM> are respectively assembled to rear end portions of the frame members <NUM>. Since the two operable anti-tip assemblies <NUM> are identical, only one of the two operable anti-tip assemblies <NUM> is to be described hereinafter.

In this embodiment, the wheelchair <NUM> is a manual wheelchair. In variant embodiments, the wheelchair <NUM> may be a power wheelchair. The number of the anti-tip assemblies <NUM> may be one as long as a rear end portion of the wheelchair <NUM> allows installation thereof.

Referring to <FIG>, the operable anti-tip assembly <NUM> includes a control mechanism <NUM> and an anti-tip mechanism <NUM>. The control mechanism <NUM> includes a mounting unit <NUM>, a positioning unit <NUM>, and a control member <NUM>.

The mounting unit <NUM> is fixed to the rear end portion of the frame member <NUM> in a removable manner by a bolt <NUM> and a nut <NUM>, and includes a first mounting tube <NUM> and a second mounting tube <NUM>. The first mounting tube <NUM> is in the form of a round tube that extends in a first direction (T1) parallel with the front-rear direction, and defines a mounting space <NUM> extending in the first direction (T1). The second mounting tube <NUM> is fixedly connected to an outer peripheral surface of the first mounting tube <NUM>, extends in a second direction (T2) inclined with respect to the first direction (T1), and is internally in communication with the first mounting tube <NUM>. The second mounting tube <NUM> has an abutment surface portion <NUM> that extends radially inwardly from an inner circumferential surface of the second mounting tube <NUM> in a position below a top end of the second mounting tube <NUM>, and that faces upwardly toward the top end of the second mounting tube <NUM>.

The positioning unit <NUM> is disposed in the mounting space <NUM> in a resiliently restorable manner, and includes a positioning member <NUM>, a fixed plate <NUM>, and a springy member <NUM>. The positioning member <NUM> is disposed in the mounting space <NUM> and is movable in the first direction (T1) relative to the mounting unit <NUM>. The fixed plate <NUM> is fixed in the mounting space <NUM> adjacent to the frame member <NUM>, and is spaced apart from the positioning member <NUM>. The springy member <NUM> is disposed between and abuts against the positioning member <NUM> and the fixed plate <NUM>.

The positioning member <NUM> is disposed between the control member <NUM> and the springy member <NUM>, and has an abutting portion <NUM> and a first engaging portion <NUM>. The abutting portion <NUM> in a cylinder form extends in the first direction (T1) and abuts against the springy member <NUM>. The first engaging portion <NUM> protrudes and is narrowed from the abutting portion <NUM> in a manner away from the frame member <NUM>. The springy member <NUM> is a compression spring that urges the positioning member <NUM> to move away from the fixed plate <NUM>. Specifically, the frame member <NUM> is inserted into the first mounting tube <NUM> in the first direction (T1) and communicates with the mounting space <NUM>. In some embodiments, the fixed plate <NUM> and the springy member <NUM> may be disposed in the frame member <NUM> as long as the springy member <NUM> is disposed between the positioning member <NUM> and the fixed plate <NUM> to urge the positioning member <NUM> to move away from the fixed plate <NUM>.

In this embodiment, the positioning member <NUM> further has a first limiting hole <NUM> that extends through the abutting portion <NUM> and that is elongated in the first direction (T1). A bolt <NUM> extends through the first mounting tube <NUM> and the first limiting hole <NUM> and is fixed onto the first mounting tube <NUM> by a nut <NUM> so that movement of the positioning member <NUM> is limited to a length of the first limiting hole <NUM> that is movable in the first direction (T1) relative to the bolt <NUM>. In other embodiments, the positioning member <NUM> may further have a limiting component (not shown), such as a slot or a protrusion. The first mounting tube <NUM> may have a corresponding limiting component (not shown), such as a corresponding protrusion or a corresponding slot, to engage with the limiting component of the positioning member <NUM> so that the positioning member <NUM> may move in the first direction (T1) within the first mounting tube <NUM>.

The control member <NUM> is assembled to the mounting unit <NUM>, is disposed distally from the positioning member <NUM> opposite to the frame member <NUM>, and is operable to move in the first direction (T1). The control member <NUM> includes a pressing portion <NUM>, a restricting portion <NUM>, and two pushing portions <NUM>. The pressing portion <NUM> is in the form of a button and is disposed outside the first mounting tube <NUM>. The restricting portion <NUM> extends from the pressing portion <NUM> into the mounting space <NUM> in the first direction (T1). The two pushing portions <NUM> extend from the restricting portion <NUM> in the first direction (T1), and are spaced apart from each other and disposed in the mounting space <NUM>. The restricting portion <NUM> has a second limiting hole <NUM> extending therethrough. The second limiting hole <NUM> is elongated in the first direction (T1). A bolt <NUM> extends through the first mounting tube <NUM> and the second limiting hole <NUM> and is fixed to the first mounting tube <NUM> by a nut <NUM> so that movement of the control member <NUM> is limited to a length of the second limiting hole <NUM> that is movable in the first direction (T1) relative to the bolt <NUM>. Each pushing portion <NUM> is in the form of a long sheet. The pushing portions <NUM> abut against the abutting portion <NUM> of the positioning member <NUM>, and the first engaging portion <NUM> of the positioning member <NUM> is disposed between the pushing portions <NUM>. When the control member <NUM> is operated to move toward the frame member <NUM>, the positioning member <NUM> is pushed by the control member <NUM> to move toward the frame member <NUM>. In practice, the control member <NUM> may be a steel cable directly connected between the positioning member <NUM> and the seat body <NUM> of the wheelchair <NUM> to drive the movement of the positioning member <NUM> toward the frame member <NUM>.

The anti-tip mechanism <NUM> includes an anti-tip strut unit <NUM> and a resilient member <NUM>.

The anti-tip strut unit <NUM> is movably inserted through the mounting unit <NUM> in the second direction (T2), and includes an anti-tip strut <NUM> and a cap member <NUM>. The anti-tip strut <NUM> is movably inserted through the first and second mounting tubes <NUM>, <NUM> in the second direction (T2) and extends movably between the pushing portions <NUM>. The anti-tip strut <NUM> has an insertion portion <NUM>, a connection portion <NUM>, an anti-tip portion <NUM>, and a second engaging portion <NUM>. The insertion portion <NUM> is hollow and is movably inserted through the first and second mounting tubes <NUM>, <NUM> in the second direction (T2). The connection portion <NUM> is disposed below the first mounting tube <NUM> and is fixedly connected to a bottom end of the insertion portion <NUM>. The anti-tip portion <NUM> is connected to a bottom end of the connection portion <NUM> and is movable to touch the ground surface for preventing the wheelchair from tipping backwards. The second engaging portion <NUM> is disposed on a front outer peripheral surface of the insertion portion <NUM>. A top end of the insertion portion <NUM> of the anti-tip strut <NUM> and the second mounting tube <NUM> are radially spaced apart from each other to define an accommodating space <NUM> therebetween. The cap member <NUM> fixedly covers a top end of the anti-tip strut <NUM>. The cap member <NUM> has an annular end wall <NUM> that is sleeved fixedly on the top end of the insertion portion <NUM> of the anti-tip strut <NUM>, and a tubular portion <NUM> that extends downwardly from an outer periphery of the annular end wall <NUM> in the second direction (T2). The annular end wall <NUM> has an inner surface <NUM> facing downwardly. The tubular portion <NUM> is sleeved movably on the second mounting tube <NUM>. In this embodiment, the first engaging portion <NUM> of the positioning member <NUM> is a protruding tongue that extends from the abutting portion <NUM> of the positioning member <NUM> toward the anti-tip strut unit <NUM> and that is engageable with the second engaging portion <NUM> of the anti-tip strut <NUM>. The second engaging portion <NUM> of the anti-tip strut <NUM> is an engaging hole for engagement of the first engaging portion <NUM> therewithin.

The resilient member <NUM> is sleeved around the top end of the insertion portion <NUM> of the anti-tip strut <NUM> and is accommodated within the accommodating space <NUM>. Two opposite ends of the resilient member <NUM> respectively abut against the abutment surface portion <NUM> of the second mounting tube <NUM> and the inner surface <NUM> of the cap member <NUM>. The resilient member <NUM> urges the anti-tip strut unit <NUM> to move away from the ground surface.

Referring to <FIG> in combination with <FIG> and <FIG>, the positioning unit <NUM> is changeable within the mounting space <NUM> between a locking state (see <FIG>), where the first engaging portion <NUM> of the positioning member <NUM> engages with the second engaging portion <NUM> of the anti-tip strut <NUM> to prevent the anti-tip strut unit <NUM> from moving relative to the mounting unit <NUM> in the second direction (T2) so that the anti-tip strut <NUM> is disposed adjacent to the ground surface, and an unlocking state (see <FIG>), where the first engaging portion <NUM> disengages from the second engaging portion <NUM> to allow the anti-tip strut unit <NUM> to be urged by the resilient member <NUM> to move relative to the mounting unit <NUM> in the second direction (T2) and away from the ground surface. When the positioning unit <NUM> is in the unlocking state, the connection portion <NUM> of the anti-tip strut <NUM> abuts against the first mounting tube <NUM>, thereby preventing the anti-tip strut <NUM> from upward movement relative to the mounting unit <NUM>. Specifically, the control member <NUM> is operable to move in the first direction (T1) so that the positioning unit <NUM> may be switched between the locking and unlocking states.

In this embodiment, the anti-tip portion <NUM> of the anti-tip strut <NUM> is, but not limited to, a caster. In other variant embodiments, the anti-tip portion <NUM> may be a block to prevent the wheelchair <NUM> from tipping backward when the positioning unit <NUM> is in the locking state.

As shown in <FIG> and <FIG>, during regular use, the positioning unit <NUM> is in the locking state to prevent backward tipping of the wheelchair <NUM>. In such a case, the first engaging portion <NUM> engages the second engaging portion <NUM>, and the anti-tip portion <NUM> is adjacent to the ground surface. When the wheelchair <NUM> tilts backward, the anti-tip portion <NUM> touches the ground surface to prevent the wheelchair from tipping backward.

As shown in <FIG> and <FIG>, when the wheelchair <NUM> needs to move from a lower ground (e.g., a street) to a higher ground (e.g., a raised sidewalk), a user (not shown) may press the control member <NUM> in the first direction (T1) to move the positioning member <NUM> toward the frame member <NUM> so that the first engaging portion <NUM> of the positioning member <NUM> may disengage from the second engaging portion <NUM> of the anti-tip strut <NUM> and so that the positioning unit <NUM> is changed to the unlocking state. The anti-tip strut <NUM> is urged by the resilient member <NUM> to move automatically upwardly away from the ground surface in a manner that the anti-tip portion <NUM> is situated on a radially inward side of one of the rear wheels <NUM>. When the wheelchair <NUM> is rotated backward about the rear wheels <NUM>, which together serve as a fulcrum, the anti-tip strut unit <NUM> would not touch the ground surface. In other words, when the positioning unit <NUM> is in the unlocking state, the wheelchair <NUM> is not limited by the anti-tip strut <NUM> to rotating backward only by a small degree. As a result, the wheelchair <NUM> may easily rotate backward about the rear wheels <NUM>, which serve as the fulcrum, until the front wheels <NUM> are raised and touch the higher ground, thereby transferring the whole wheelchair <NUM> onto the higher ground.

After the whole wheelchair <NUM> is transferred onto the higher ground, the user may step on a top end of the cap member <NUM> to move the anti-tip strut <NUM> downwardly until the second engaging portion <NUM> of the anti-tip strut <NUM> engages with the first engaging portion <NUM> of the positioning member <NUM>, thereby changing the positioning unit <NUM> to the locking state to immobilize the anti-tip unit <NUM>.

By virtue of the positioning unit <NUM> being changeable between the locking and unlocking states, the anti-tip strut unit <NUM> is either immobilized or movable relative to the mounting unit <NUM>. When the wheelchair <NUM> needs to be stabilized, the anti-tip strut unit <NUM> is immobilized by changing the positioning unit <NUM> to the locking state. When the wheelchair <NUM> needs to rotate backward, the anti-tip strut unit <NUM> is movable by changing the positioning unit <NUM> to the unlocking state. The operable anti-tip assembly <NUM> is relatively practical and convenient to provide the wheelchair <NUM> both safety and mobility. Specifically, the user may directly step on either the control member <NUM> or the top end of the cap member <NUM> so that the anti-tip portion <NUM> of the anti-tip strut <NUM> may move away from or become adjacent to the ground surface; the user does not need to stoop down to operate the operable anti-tip assembly <NUM> using hands, and therefore the operation is relatively convenient.

<FIG> illustrate an operable anti-tip assembly <NUM> according to a second embodiment of the disclosure. The second embodiment is similar in structure and operation to the first embodiment. Only the differences between the second and first embodiments are to be described.

In the second embodiment, the second mounting tube <NUM> of the mounting unit <NUM> is omitted. The first mounting tube <NUM> has a through slot <NUM> disposed above and spatially communicated with the mounting space <NUM>. The through slot <NUM> extends through the outer peripheral surface of the first mounting tube <NUM> and is elongated in the first direction (T1).

Regarding the positioning unit <NUM>, the positioning member <NUM> is rotatably and fixedly disposed in the mounting space <NUM> by a pivot member <NUM>. The positioning unit <NUM> further includes a resilient restoring member <NUM> connected between the first mounting tube <NUM> and the positioning member <NUM>. The first engaging portion <NUM> of the positioning member <NUM> has a barb configuration and extends towards the anti-tip mechanism <NUM>. The positioning member <NUM> further has an arm portion <NUM> connected to and disposed behind the first engaging portion <NUM>. The resilient restoring member <NUM> is sleeved around the arm portion <NUM>. A top end of the resilient member restoring <NUM> is fixedly connected to the positioning member <NUM>. A bottom end of the resilient member <NUM> is fixedly connected to a bottom side of an inner circumferential surface of the first mounting tube <NUM>. The resilient restoring member <NUM> provides a resilient force urging the arm portion <NUM> to move upwardly away from the bottom side of the inner circumferential surface of the first mounting tube <NUM> and toward the through slot <NUM>.

The control member <NUM> extends upwardly from a top end of the positioning member <NUM>. The pressing portion <NUM> of the control member <NUM> extends outside the through slot <NUM>, is thicker than the positioning member <NUM>, and is pressable. The restricting portion <NUM> and the pushing portions <NUM> are omitted from the control member <NUM> in this embodiment.

The control mechanism <NUM> further includes an abutting member <NUM> that is mounted in the mounting space <NUM> in a spaced-apart manner from the positioning member <NUM> of the positioning unit <NUM>.

Regarding the anti-tip mechanism <NUM>, the anti-tip strut unit <NUM> is movably inserted through the mounting unit <NUM> in the second direction (T2), and the resilient member <NUM> is disposed in the anti-tip strut unit <NUM>.

The anti-tip strut <NUM> of the anti-tip strut unit <NUM> is hollow and has a strut portion <NUM>' that extends in the second direction (T2) while the insertion and connection portions <NUM>, <NUM> are omitted from the anti-tip strut <NUM>. The anti-tip portion <NUM> of the anti-tip strut <NUM> is mounted to a bottom end of the strut portion <NUM>'. The cap member <NUM> of the anti-tip strut unit <NUM> covers a top end of the strut portion <NUM>'. A front side of the strut portion <NUM>' is formed with a first elongated opening <NUM> that extends in the second direction (T2). In this embodiment, the anti-tip strut unit <NUM> further includes a mounting member <NUM> that is fixedly disposed within the anti-tip strut <NUM> by a bolt <NUM> and that extends in the second direction (T2). The mounting member <NUM> has a second elongated opening <NUM> that extends in the second direction (T2). The abutting member <NUM> protrudes into the second elongated opening <NUM> through the first elongated opening <NUM>. In order to meet the requirements of different types of wheelchairs, the anti-tip strut <NUM> has a plurality of second engaging portion <NUM>' formed at a rear side of the strut portion <NUM>' so that a distance between the anti-tip strut <NUM> and the ground surface is adjustable. The number of the second engaging portions may be one in some other embodiments.

The resilient member <NUM> is sleeved around the mounting member <NUM>, and abuts against and is disposed between the mounting member <NUM> and the abutting member <NUM>, thereby urging the anti-tip strut unit <NUM> to move away from the ground surface.

<FIG> and <FIG> illustrate the positioning unit <NUM> in the unlocking state and the locking state. When the positioning unit <NUM> is in the locking state (see <FIG>), the first engaging portion <NUM> of the positioning unit <NUM> engages with one of the second engaging portions <NUM>' of the anti-tip strut <NUM> so that the anti-tip strut <NUM> is immobilized in the second direction (T2) in a manner that anti-tip portion <NUM> of the anti-tip strut <NUM> is disposed adjacent to the ground surface. When the positioning unit <NUM> is in the unlocking state (see <FIG>), the first engaging portion <NUM> of the positioning unit <NUM> disengages from the second engaging portions <NUM>' of the anti-tip strut <NUM> so that the anti-tip strut <NUM> is urged by resilient member <NUM> to move away from the ground surface.

When in use, the cap member <NUM> is stepped on by the user until the first engaging portion <NUM> engages with one of the second engaging portions <NUM>' so as to change the positioning unit <NUM> from the unlocking state to the locking state. To change the positioning unit <NUM> from the locking state to the unlocking state, the control member <NUM> is depressed to rotate the positioning member <NUM> of the positioning unit <NUM> in a direction (arrow A, as shown in <FIG>) so that the first engaging portion <NUM> disengages from the second engaging portions <NUM>' and so that the anti-tip strut <NUM> is urged by the resilient member <NUM> to move away from the ground surface. Therefore, the operable anti-tip assembly <NUM> of the second embodiment is capable of achieving the same effect as the first embodiment.

<FIG> illustrate an operable anti-tip assembly <NUM> according to a third embodiment of the disclosure. The third embodiment is similar in structure and operation to the second embodiment. Only the differences between the third and second embodiments are to be described.

Regarding the mounting unit <NUM>, the first mounting tube <NUM> further has an opening <NUM> that opens at a rear end thereof and that communicates with the through slot <NUM>.

Regarding the positioning unit <NUM>, the positioning member <NUM> further has a first pushing portion <NUM> that is disposed on the top end of the positioning member <NUM> and that protrudes backward away from the anti-tip strut unit <NUM>.

The control member <NUM> is rotatably disposed in the mounting space <NUM> of the first mounting tube <NUM> by a pivot member <NUM> and partially extends outside the mounting space <NUM>. In this embodiment, the pressing portion <NUM> of the control member <NUM> extends outside and protrudes backward from the through slot <NUM> and the opening end <NUM>. The control member <NUM> further has a second pushing portion <NUM> that is disposed in the mounting space <NUM> and that is located forwardly relative to the pressing portion <NUM>. The second pushing portion <NUM> is rotatable by pressing the control member <NUM> to push the first pushing portion <NUM> for rotating the positioning member <NUM> about the pivot member <NUM> along a direction reverse to a direction (arrow B), thereby disengaging the first engaging portion <NUM> from the second engaging portion <NUM>.

The resilient restoring member <NUM> of the positioning unit <NUM> is resiliently connected between the positioning member <NUM> and the control member <NUM> to urge rotation of the positioning member <NUM> about the pivot member <NUM> along the direction (arrow B) so that the first engaging portion <NUM> rotates toward the anti-tip strut unit <NUM> to engage the second engaging portion <NUM> and so that the first pushing portion <NUM> is rotated toward the second pushing portion <NUM>.

As shown in <FIG>, when the positioning unit <NUM> is in the locking state, because the first engaging portion <NUM> engages with the second engaging portion <NUM>, the anti-tip strut unit <NUM> is immobilized in the second direction (T2) and situated adjacent to the ground surface. As shown in <FIG>, when the positioning unit <NUM> is in the unlocking state, because the first engaging portion <NUM> disengages from the second engaging portion <NUM>, the anti-tip strut unit <NUM> is urged by the resilient member <NUM> to move in the second direction (T2) away from the ground surface.

Referring back to <FIG>, in practice, when the positioning unit <NUM> is in the unlocking state, the top end of the anti-tip strut unit <NUM> is stepped on to move toward the ground surface until the first engaging portion <NUM> is urged by the resilient restoring member <NUM> in rotation along the direction (arrow B) to engage with the second engaging portion <NUM>, thereby changing the positioning unit <NUM> from the unlocking state (<FIG>) to the locking state (<FIG>). As shown in <FIG>, to move the anti-tip strut unit <NUM> away from the ground surface, the control member <NUM> is pressed downwardly to rotate about the pivot member <NUM> along a direction (arrow C) so that the second pushing portion <NUM> is rotated upwardly to push the first pushing portion <NUM> in a manner that the positioning member <NUM> is driven to rotate about the pivot member <NUM> along the direction reverse to the direction (arrow B), thereby disengaging the first engaging portion <NUM> from the second engaging portion <NUM>. As a result, the anti-tip strut unit <NUM> is urged by the resilient member <NUM> to move away from the ground surface, and the positioning unit <NUM> is in the unlocking state.

In summary, because the anti-tip strut unit <NUM> is immobilized or movable relative to the ground surface by the control member <NUM> driving the positioning unit <NUM> to switch between the locking and unlocking states for the first engaging portion <NUM> of the positioning unit <NUM> to engage with or disengage from the second engaging portion <NUM> of the anti-tip strut unit <NUM>, and because the user need not stoop down to operate the operative anti-tip assembly <NUM>, the operative anti-tip assembly <NUM> is convenient to use, not only for effectively preventing the wheelchair <NUM> from tipping backwards but also for allowing the wheelchair <NUM> to cross a tall obstacle, As a result, the wheelchair <NUM> with the operative anti-tip assembly <NUM> may be easily transferred onto grounds with various heights.

Claim 1:
An operable anti-tip assembly (<NUM>) adapted for a wheelchair (<NUM>), and characterized by:
a control mechanism (<NUM>) including
a mounting unit (<NUM>) that is adapted to be mounted to a rear end portion of the wheelchair (<NUM>) in a removable manner, and that defines a mounting space (<NUM>) extending in a first direction (T1), and
a positioning unit (<NUM>) that is disposed in said mounting space (<NUM>) in a resiliently restorable manner and that includes a first engaging portion (<NUM>); and
an anti-tip mechanism (<NUM>) including
an anti-tip strut unit (<NUM>) that is movably inserted through said mounting unit (<NUM>) in a second direction (T2) inclined with respect to the first direction (T1) and that includes a second engaging portion (<NUM>), and
a resilient member (<NUM>) that is connected to said mounting unit (<NUM>) and said anti-tip strut unit (<NUM>) and that urges said anti-tip strut unit (<NUM>) to move away from a ground surface;
wherein said positioning unit (<NUM>) is changeable within said mounting space (<NUM>) between a locking state, where said first engaging portion (<NUM>) engages said second engaging portion (<NUM>) to prevent said anti-tip strut unit (<NUM>) from moving relative to said mounting unit (<NUM>) in the second direction (T2), and an unlocking state, where said first engaging portion (<NUM>) disengages from said second engaging portion (<NUM>) to allow said anti-tip strut unit (<NUM>) to be urged by said resilient member (<NUM>) to move relative to said mounting unit (<NUM>) in the second direction (T2) and away from the ground surface.