Patent Publication Number: US-10765573-B2

Title: Wheelchair brake system

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a National Stage Application of PCT International Patent Application No. PCT/KR2015/012553 filed on Nov. 20, 2015, under 35 U.S.C. § 371, which claims priority to Korean Patent Application Nos. 10-2014-0162755 filed on Nov. 20, 2014, 10-2014-0174131 filed on Dec. 5, 2014, and 10-2015-0018616 filed on Feb. 6, 2015, which are all hereby incorporated by reference in their entirety. 
     TECHNICAL FIELD 
     The present invention relates to a wheelchair brake system, and more particularly to a wheelchair brake system which is in a brake lock mode as usual as when a user stands up from a wheelchair, but automatically releases a brake only if a user sits down on the wheelchair or folds up the wheelchair, so that the wheelchair can move only when a user sits down thereon or it is folded, thereby preventing a user from getting hurt from a fall at a moment when the user sits down on and stands up from the wheelchair. 
     BACKGROUND ART 
     In general, a wheelchair refers to a means of transportation for a less able-bodied person, which is pushed by a person who is sitting down thereon or by an assistant from behind. 
     Since a user who needs the wheelchair is the less able-bodied person, it is very dangerous at a moment when s/he sits down on or stands up from the wheelchair. The wheelchair can move while the user is sitting down on or standing up from the wheelchair, and thus often cause accidents where the user gets hurt from a fall. 
     To solve the foregoing problems, there has been developed a wheelchair with a brake. However, a conventional wheelchair brake system still has a problem of causing the fall accidents since artificial control is needed to actuate the brake of the wheelchair like that of a bicycle. 
     DISCLOSURE 
     Technical Problem 
     The present invention is conceived to solve the foregoing problems, and an aspect of the present invention is to provide a wheelchair brake system which is in a brake lock mode to stop if no one sits down on a wheelchair, but releases a brake to move only if a user properly sits down on the wheelchair, thereby preventing a user from getting hurt from a fall due to movement of the wheelchair at a moment when the user sits down on and stands up from the wheelchair. 
     Technical Solution 
     A wheelchair brake system according to the present invention comprises; a brake which is provided in a wheel of a wheelchair; and a brake actuation controller which connects with the brake and locks and releases the brake, wherein the brake is usually in a lock mode, but the brake actuation controller controls the brake to be switched over from the lock mode to a release mode if sensing that a user sits down on the wheelchair or the wheelchair is folded up. 
     The brake actuation controller comprises: a connection member which has a first end elastically connecting with the brake; a brake switching member to which a second end of the connection member is fixed, and which actuates the connection member connecting with the brake to release the brake when a user sits down on the wheelchair, but returns the connection member to switch the brake over to the lock mode when the user stands up from the wheelchair. 
     The connection member comprises a cable or a bar; the brake switching member is non-motorized or motorized for automatic actuation. 
     The non-motorized brake switching member comprises: a sensing frame which is provided beneath a seat of the wheelchair, and accommodates a second end of the cable therein to be fixed and connected thereto; and an upper plate which couples with the sensing frame and changes tension of the cable by pressing the cable accommodated in the sensing frame when a user sits down on the seat. 
     The upper plate comprises a cable accommodator; the cable accommodator does not press the cable when no one sits down on the wheelchair, but presses the accommodated cable as the upper plate moves down when a user sits down on the wheelchair; and the brake is released since the cable is tensed in a direction opposite to the brake when the cable is pressed. 
     The sensing frame and the upper plate are divided into a plurality of units; at least one of cables is connected to the respective units is connected to the brake; and the brake is switched over from the lock mode to the release mode when at least one among the plurality of units is actuated. 
     The motorized brake switching member comprises: a sensing frame which is provided beneath a seat of the wheelchair, accommodates a second end of the cable therein to be fixed and connected thereto, and comprises an electric driver to electrically wind the cable to change tension; and an upper plate which couples with the sensing frame and comprises a sensor to sense whether a user sits down on the seat. 
     The electric driver comprises: an electric pulley for changing a winding direction of a cable, and winding the cable; a motor for providing torque to drive the electric pulley; and a driving controller for controlling the torque of the motor, and the electric driver drives the motor to rotate the electric pulley to make tension act in an opposite direction of the brake and release the brake when a pressure sensor provided in the upper plate senses that a user sits down on the wheelchair, but drives the motor to rotate in an opposite direction to rotate and return the electric pulley to its original position, to make the tension act toward the brake and to lock the brake when the user stands up from the wheelchair. 
     The electric driver further comprises a sensor unit such as an acceleration sensor and a tilt sensor, and the sensor unit is provided to make the brake be not only simply switched over between the lock mode and the release mode, but also automatically actuated for safety when the wheelchair moves at an excessively high speed or on a slope. 
     Advantageous Effects 
     According to an embodiment of the present invention, a wheelchair brake system has an effect on preventing a user from getting hurt from a fall due to movement of the wheelchair at a moment when the user sits down on and stands up from the wheelchair since it is in a brake lock mode to stop if no one sits down on a wheelchair, but releases a brake to move only if a user properly sits down on the wheelchair. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  schematically shows a wheelchair according to an embodiment of the present invention. 
         FIG. 2  schematically shows a wheelchair according to another embodiment of the present invention. 
         FIG. 3  schematically shows sensing frames and upper plates which are divided into four units according to an embodiment of the present invention. 
         FIG. 4  schematically shows sensing frames and upper plates which are divided into two units according to an embodiment of the present invention. 
         FIG. 5  schematically shows actuation of a brake in the wheel chair of  FIG. 3 . 
         FIG. 6  schematically shows that the wheelchair is folded up. 
         FIG. 7  schematically shows a wheelchair brake system according to still another embodiment of the present invention, and  FIG. 8  is a detailed view of  FIG. 7 . 
         FIG. 9  schematically shows a motorized wheelchair brake system according to an embodiment of the present invention. 
         FIG. 10  schematically shows a brake according to an embodiment of the present invention. 
         FIG. 11  schematically shows that a switching member according to an embodiment of the present invention is a safety device given in the form of a safety bar or a seat belt, 
         FIGS. 12 to 15  are detailed views of the safety bar provided as the switching member of  FIG. 11 , and 
         FIG. 16  to  FIG. 18  are detailed views of the seat belt provided as the switching member of  FIG. 11 . 
         FIGS. 19 to 21  schematically show a structure where a footrest is used as a switching member for the brake according to an embodiment of the present invention. 
     
    
    
     BEST MODE 
     To achieve the foregoing object, a wheelchair brake system according to the present invention includes a brake provided in a wheel of a wheelchair, and a brake actuation controller connected to the brake and locking and releasing the brake, in which the brake is usually in a lock mode but is released from the lock mode in sync with actuation of a safety device sensed by the brake actuation controller when a user sits down on the wheelchair. 
     MODE FOR INVENTION 
     Below, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  schematically shows a wheelchair according to an embodiment of the present invention. 
     Referring to  FIG. 1 , a wheelchair brake system according to an embodiment of the present invention includes a brake  20  provided in a wheel of a wheelchair, and a brake actuation controller  10  connected to the brake and locking and releasing the brake  20 , in which the brake is usually in a lock mode but is released from the lock mode by the brake actuation controller  10  when a user properly sits down on the wheelchair or when the wheelchair is folded up. 
     The brake actuation controller  10  may include a connection member  110  having a first end connected to the brake, and a brake switching member  120  coupled to a second end of the connection member  110  and actuating the connection member  110  connected to the brake to release the brake when a user sits down on the wheelchair but return the connection member  110  to switch the brake over to the lock mode when a user stands up from the wheelchair. 
     In other words, the brake switching member  120  switches the brake over to a release mode if a user sits down on the wheelchair, and returns the connection member  110  to an original state to switch the brake over to the lock mode if a user stands up from the wheelchair or the wheelchair is unfolded. 
     In more detail, the connection member  110  may be achieved by a cable or bar, and the cable is set to give tension to the brake so that the brake can keep the lock mode if no one sits down on the wheelchair. Here, the cable refers to a member made of a wire (or a string). 
     That is, the brake is usually locked since the cable is kept to give tension so that the brake can be locked. However, the cable is automatically pulled in an opposite direction when a user sits down on the wheelchair, and thus the brake is released. 
     The brake switching member  120  may be non-motorized or motorized. 
     First, if the brake switching member  120  is non-motorized, the brake switching member  120  is placed beneath a seat of the wheelchair, and includes a sensing frame  121  holding, accommodating and connecting with a second end of the cable, and an upper plate  122  coupled to the sensing frame and pressing the cable accommodated in the sensing frame to switch a direction of applying the tension to the cable when a user sits down on the seat. 
     Specifically, the sensing frame  121  includes a cable accommodator, so that the cable accommodated in the cable accommodator can be free from pressure of the cable accommodator when no one sits down on the wheelchair, but be pressed by the cable accommodator as the upper plate moves down when a user sits down on the wheelchair. 
     If the cable is pressed as described above, the cable is tensed in an opposite direction to the brake and thus the brake is released from the lock mode. 
     Therefore, the brake is always kept in the lock mode if no one sits down on the wheelchair, but released only when a user sits down on the wheelchair. 
       FIG. 2  schematically shows a wheelchair according to another embodiment of the present invention. 
     Referring to  FIG. 2 , the connection member  110   a  is achieved by not the cable but a bar, in which the connection member has a first end connected to the brake actuation controller  122   a  and includes a plurality of joints. 
     The actuation controller  122   a  is elastically coupled as a plate to a bottom of the seat of the wheelchair, and is thus elastically disposed downward when a user sits down on the wheelchair and returns to an original position when the user stands up from the wheelchair. 
     Further, the connection member  110   a  includes a central shaft aligned with a central shaft of the wheel, so that the central shaft thereof can connect with the brake of the wheel by the cable. 
     Therefore, when no one sits down on the wheelchair, the brake is in the lock mode by initial tension. On the other hand, when a user sits down on the wheelchair, the actuation controller  122   a  is elastically displaced downward and the connection member  110   a  integrally coupled to the actuation controller  122   a  is also displaced by the elastic displacement, thereby actuating the cable connected to the brake in the opposite direction to the initial tension and thus releasing the brake from the lock mode. 
       FIG. 3  schematically shows the sensing frames and the upper plates which are divided into four units according to an embodiment of the present invention. 
     In this embodiment, the upper plate is divided into four units, but not limited thereto. Alternatively, the upper plate may be divided into two units as shown in  FIG. 4 . Likewise, it will be appreciated that the upper plate may be designed to be divided into various numbers of sections. 
     Referring to  FIG. 3 , the sensing frame  210  is sectioned into four units, and each unit is formed with a pulley assembly, thereby connecting with the connection member of the cable through the pulley assembly. 
     The pulley assembly may include a main pulley  211   a  for directly affecting the lock/release of the brake, and a sub pulley  211   b  for changing a direction of the cable without directly affecting the lock/release of the brake lock. 
     In each of four units, two main pulleys  211   a  are spaced apart at a predetermined distance and form a pair, and the cable is at least once wound on one main pulley and connected to the brake via the sub pulley  211   b.    
     Like the number of divided units, there may be four cables. One cable is coupled to each unit, and two cables among four cables form a pair. Thus, the pair of cables is connected to each of two brakes. 
     In this embodiment, a first cable coupled to a first unit and a fourth cable coupled to a fourth unit form a pair and are connected to a first brake, and a second cable coupled to a second unit and a third cable coupled to a third unit form a pair and are connected to a second brake. 
     To adjust the tension of each cable, a screw adjuster  212  is provided at each starting point of the four cables. 
     Likewise, the upper plate is divided into four. Each of the upper plates includes the cable accommodator  221  placed beneath the plate, and a coupling member  222  for coupling with the sensing frame. 
     The coupling member  222  is provided as a spring for elastically coupling with the sensing frame so that the upper plate can move up and down in accordance with whether a user sits down on the wheelchair. 
     Further, the cable accommodator  221  includes a protrusion bar protruding from the bottom of the plate, and a cable groove formed in the protrusion bar. 
     To accommodate the cable wound on a pair of main pulleys, two cable grooves are formed as shown in  FIG. 3 . 
     As described above, the upper plate is divided into four sections, and a pair of brakes connects with two cables, so that the brake can be released when at least one among four units is pressed by adjusting the tension of the brake connected to the cable. 
     For example, the brake is released if one unit connected to the pair of brakes is pressed by adjusting the tension of the cable. Alternatively, the brake may be released if four units are all pressed. 
       FIG. 5  schematically shows actuation of a brake in the wheel chair of  FIG. 3 . 
     Referring to  FIG. 5 , the brake keeps the lock mode since the tension of the cable is applied to the brake in an initial state where no one sits down on the wheelchair. 
     Here, the cable has the first end connected to the brake, and the second end connected to a cable adjuster  212  of the sensing frame. The cable adjuster  212  is an element of using an adjusting screw to adjust the tension of the cable, and serves as a fixed end. The first end of the cable coupled to the brake serves as an elastic end to reverse the direction of the tension by external forces. 
     When a user sits down on the wheelchair, the upper plate elastically coupled to the sensing frame moves down and the cable accommodated in the cable groove of the cable accommodator is pressed downward. 
     As described above, if the cable is pressed downward, the main pulley rotates as much as the displacement of the pressed cable. At this time, since the second end is the fixed end, pulling tension is generated at the elastic end coupled to the brake, thereby reversing the tension of acting toward the brake and thus releasing the brake from the lock mode. 
     Here, the upper plate is divided into four units, and one brake connects with two cables connected to two units, so that the direction of the tension acting on the brake can be reversed to release the brake if at least one among four units is pressed, thereby releasing the brake only when a user sits down on the wheelchair. 
     By adjusting the tension of the cable, it will be freely determined how many units among four units have to be pressed to release the brake. 
       FIG. 6  schematically shows that the wheelchair is folded up. 
     Referring to  FIG. 6 , when the wheelchair is folded, bending causes tension to be generated to pull the cable. Since the second end is the fixed end, the pulling tension is generated at the elastic end coupled to the brake, thereby reversing the direction of the tension acting toward the brake and thus releasing the brake from the lock mode. 
       FIG. 7  schematically shows a wheelchair brake system according to still another embodiment of the present invention, and  FIG. 8  is a detailed view of  FIG. 7 . 
     Referring to  FIGS. 7 and 8 , the wheelchair brake system according to the present invention employs a blocking bar  20   a  as a brake. When no one sits down on the wheelchair, the blocking bar  20   a  passes through and is caught in spokes of the wheel, thereby making the wheelchair be in the lock mode. 
     On the other hand, when a user sits down on the wheelchair, the blocking bar  20   a  elastically moves to the inside of the wheel and is thus released from the lock mode. 
     Here, the brake actuation controller  10   a  includes a flat spring formed beneath the seat of the wheelchair, a gear box for changing elasticity of the flat spring into mechanical displacement, and an elastic member formed behind the gear box, so that the blocking bar can move inward as the elastic member is compressed as much as the displacement caused by the gear box. 
     Further, when a user stands up from the wheelchair, the elasticity of the flat spring is removed to cause the mechanical displacement of returning a gear assembly to its original position, and the compressed elastic member returns to its original position by restoring force, thereby making the blocking bar pass through the spokes of the wheel and enter the lock mode. 
     Below, an embodiment where the brake switching member is motorized will be described. 
       FIG. 9  schematically shows a motorized wheelchair brake system according to an embodiment of the present invention. 
     Referring to  FIG. 9 , the brake switching member in this embodiment includes a sensing frame provided beneath the seat of the wheelchair, fixing and accommodating the second end of the cable therein, and having an electric driver electrically winding the cable to reverse the direction of the tension; and an upper plate coupling with the sensing frame, and having a pressure sensor  221  to sense whether a user sits down on the wheelchair. 
     The electric driver may include an electric pulley for winding the cable, a motor for providing torque to drive the electric pulley, and a driving controller for controlling the torque of the motor, and reverse a direction of winding the cable. 
     The driving controller controls the motor to turn the electric pulley in an opposite direction to the tension when the pressure sensor  221  installed in the upper plate senses that a user sits down on the wheelchair. 
     With this, the tension acting toward the brake is reversed, and thus the brake is released from the lock mode. Since detailed principles of locking and releasing the brake are the same as those of a mechanical brake, detailed descriptions will be omitted. 
     Then, if a sensed value of the pressure sensor is changed as a user stands up from the wheelchair, the driving controller returns the electric pulley to its original position, thereby changing the direction of the tension again toward the brake and thus switching the brake over from the release mode to the lock mode. 
     Here, the sensing frame and the upper plate may be divided into a plurality of units so that the brake can be switched over between the release mode and the lock mode like the mechanical brake only when a user properly sits down on or stands up from the wheelchair. 
     Further, the electric driver may further include a sensor unit  230  such as an acceleration sensor and a tilt sensor. 
     With this sensor unit  230 , the brake is not only simply switched over between the lock mode and the release mode, but also automatically actuated for safety when the wheelchair moves at an excessively high speed or on a slope. 
     In other words, if the sensor unit senses that the wheelchair moves at a high speed or on a downhill road, the brake is not fully switched over to the lock mode, but partially actuated to provide braking force, thereby decreasing the speed for safe movement. 
     Further, the acceleration sensor is additionally provided to sense the speed of the wheelchair, so that the electric pulley can be driven to actuate the brake if the sensed speed exceeds a specific speed (e.g. set within a range of 5˜10 km per hour). 
     Here, a locking level of the brake is adjusted in accordance with the exceeded speed, thereby controlling the actuation of the electric pulley and thus securing safe movement. 
       FIG. 10  schematically shows a brake according to an embodiment of the present invention. 
     According to the present invention, the brake may be variously classified into (a) a brake pad type, (b) a caliper type generally used for a baby carriage, (c) a rim brake type generally used for a bicycle, (d) a band brake type, etc. In case of a motorized brake system, the band brake type is recommended since it is easy to adjust the locking level of the brake. 
       FIG. 11  schematically shows that a switching member according to an embodiment of the present invention is a safety device given in the form of a safety bar or a seat belt,  FIGS. 12 to 15  are detailed views of the safety bar provided as the switching member of  FIG. 11 , and  FIG. 16  to  FIG. 18  are detailed views of the seat belt provided as the switching member of  FIG. 11 . 
     Referring to  FIG. 11 , the wheelchair brake system according to the present invention may be configured to release the brake only when the safety bar or the seat belt is fastened after a user sits down on the wheelchair. 
     The wheelchair brake system according to the present invention includes a brake  20  provided in a wheel of a wheelchair, and a brake actuation controller  10  connected to the brake  20  and locking and releasing the brake  20 , in which the brake is usually in a lock mode but is released from the lock mode by the brake actuation controller  10  interlocking with the safety bar or the seat belt as the brake actuation controller  10  automatically senses that a user sits down on the wheelchair and fastens the safety bar or the seat belt. 
     The brake actuation controller  10  includes a connection member  110  connected to the brake, and a brake switching member  120  coupled to a second end of the connection member  110  and actuating the connection member  110  connected to the brake to release the brake when a user sits down on the wheelchair and fasten the safety device but return the connection member to its original position to switch the brake over to the lock mode when a user unfasten the safety device. 
     In other words, the brake switching member  120  switches the brake over to a release mode by pressing the connection member and reversing the direction of the tension acting on the brake if a user fastens the safety device after sitting down on the wheelchair, but returns the connection member to its original position of applying the tension toward the brake with restoring force to switch the brake over to the lock mode if a user sitting down on the wheelchair unfastens the safety device. 
     In more detail, the connection member  110  may be achieved by a cable or string, the tension of which is adjustable, and the cable is set to give the tension to the brake so that the brake can keep the lock mode if no one sits down on the wheelchair. Here, the cable refers to a member made of a wire (or a string). 
     That is, the brake is usually locked since the cable is kept to give tension so that the brake can be locked. However, the cable is automatically pulled in an opposite direction as much as displacement of the pressed connection member when a user sits down on the wheelchair and fastens the safety bar or the seat belt, thereby releasing the brake. 
     The brake switching member  120  may be non-motorized or motorized. 
     The brake switching member  120  in this embodiment using the safety bar, the seat belt or a footrest to be described later has the same operations and effects as those of adjusting the tension of the cable to lock and release the brake. 
       FIG. 12  shows the wheelchair with the safety bar, in which, in which the safety bar  121  serves as the brake switching member  120 , and the brake keeps the lock mode since the tension of the cable acts toward the brake before fastening the safety bar  121 . 
     The cable has a first end as a fixed end since it is fixed to the brake, and a second end for adjusting tension since it is coupled to a tension adjusting member  122 . 
     Further, the cable has the first end coupled to the brake and connected to the inside of the safety bar, and is also connected to a tension adjusting member  122  through a pulley. 
     As shown in  FIGS. 14 and 15 , the cable includes brake cables connecting with two brakes, and a control cable connecting with the a tension adjusting member  122 , in which the brake cable and the control cable are coupled by a coupler. Through the coupler, two brake cables and the control cable are operated as a single body. 
     When a user sits down on the wheelchair and fastens the safety bar  121 , the control cable placed in the safety bar is pressed and the cable in the direction of the brake cable is pulled since the tension adjusting member  122  connected through the pulley is fixed, thereby generating tension in the opposite direction to the brake cable. Thus, the tension of the cable toward the brake is reversed so that the brake can be released from the lock mode. 
     On the other hand, if the safety bar  121  is unfastened, the tension acting on the cable inside the safety bar is removed and thus the tension of the cable is applied again toward the brake, thereby switching the brake over from the release state to the lock mode. 
     Therefore, the brake is released only when a user sits down on the wheelchair and fastens the safety bar  121 , and it is thus possible to further secure user safety. 
       FIG. 13  shows the wheelchair with the seat belt, in which the seat belt  122  serves as the brake switching member  120 , and the brake keeps the lock mode since the tension of the cable acts toward the brake before fastening the seat belt  122 . 
     The embodiment of  FIG. 13  has the same principle as the embodiment of  FIG. 11 , and different in that the tension of the cable connected to the brake is changed in direction in accordance with whether the seat belt is fastened or not, so that the brake can be switched over between the lock mode and the release mode. 
     In  FIGS. 12 and 13 , the seat belt is achieved by a buckle, in which the cable connecting with the brake is positioned inside a fastening frame, i.e. a buckle inlet to which a buckle  122  is fastened, and thus the cable is pressed when the buckle  122  is coupled to the buckle inlet of the fastening frame in order to fasten the seat belt. As the cable is pressed, the tension acting toward the brake is reversed to thereby release the brake from the lock mode. 
     Here, the cable is coupled to the inside of the fastening frame through a plurality of pulleys, and thus pulled as much as inward displacement of the cable when the buckle  122  presses the cable, thereby reversing the tension acting toward the brake and releasing the brake. On the other hand, if the buckle  122  is separated from the fastening frame, the cable is returned to its original position and force of pulling the cable is removed, thereby returning the tension of the cable toward the brake and locking the brake. 
       FIG. 18  schematically shows a seat belt according to another embodiment of the present invention. 
     Referring to  FIG. 18 , a guide member  123   c  for switching over the tension direction of the cable is provided inside a fastening frame  123   b . As a buckle  123   a  is inserted in and fastened to the fastening frame  123   b , the guide member  123   c  causes displacement of the cable and thus pulls the cable, thereby reversing the tension acting on the brake and releasing the brake from the lock mode. 
     In more detail, the guide member  123   c  includes two opposite guide grooves A and B respectively formed in front and rear sides thereof, and a moving member  1231  having a front projection C protruding above from the front guide groove A and a rear projection D protruding below from the rear guide groove B and coupling with the cable, which are formed as a single body so that the front projection and the rear projection can relatively move along the guide grooves, and mounted to the guide member. 
     The moving member  1231  rotates with respect to a rotary axis. The moving member has elasticity based on a spring so that the front projection can be set to be positioned by the elasticity on the top of the front guide groove. Therefore, the moving member  1231  returns to its original position by restoring force when the buckle  123  is unfastened even though it moves down in the front guide groove when the buckle  123   a  is fastened. 
     Here, the buckle  123   a  is provided to be inserted on the front side of the moving member. Therefore, if the buckle  123   a  is inserted in the fastening frame  123   b , the buckle  123   a  is inserted pushing the front projection C down, and thus the front projection C moves down along the front guide groove A. 
     At this time, the rear projection D moving relative to the front projection C moves up along the rear guide groove B as the front projection C moves down. 
     Therefore, the cable coupling with the rear projection D moves upward and is thus pulled to reverse the tension of the cable acting toward the brake, thereby switching the brake over from the lock mode to the release mode. 
     On the other hand, if the buckle  123   a  is separated from the fastening frame  123   b , the moving member  1231  returns to its original position by the restoring force of the spring, and the rear projection relatively moves and returns to its original position, thereby returning the direction of the tension of the cable toward the brake again and thus switching the brake over from the release mode to the lock mode. 
       FIGS. 19 to 21  schematically show a structure where a footrest is used as a switching member for the brake according to an embodiment of the present invention. 
     In this embodiment referring to  FIGS. 19 to 21 , the footrest serves as the brake switching member, in which the brake keeps the lock mode since the tension of the cable acts toward the brake when the footrest is folded up. 
     When a user sits down on the wheelchair and opens the footrest, the cable provided in the footrest is pressed to generate tension in an opposite direction and thus the tension of the cable acting toward the brake is reversed, thereby switching the brake over from the lock mode to the release mode. 
       FIG. 19  shows the simplest embodiment, in which so that the brake is in the lock mode since the tension of the cable is adjusted to act toward the brake when a footrest  124  is folded up, but the brake is released from the lock mode since the cable is pulled to make the tension of the cable act in an opposite direction to the brake and a brake pad is spaced apart from the brake when the footrest  124  is opened. 
     In more detail, two cables may be provided as the connection member  110 , and a first cable (refer to a blue line) and a second cable (refer to a green line) are tensed relative to each other as the footrest is folded up and down or left and right. In the state that the footrest is folded, the first cable has no tension but only the second cable is tensed so that the brake can keep the lock mode. On the contrary, if the footrest is opened, the first cable is tensed but the second cable has no tension so that the brake can be released from the lock mode as the tension acting on the brake is changed. 
       FIG. 20  shows an embodiment where a footrest  125  serves as the brake switching member  120 , and a tension adjuster  60  connecting with the cable is further provided in between the footrest and the brake. 
     The tension adjuster  60  is connected to the brake  20  by a brake cable  115 , and is also connected to the footrest  125  by a control cable  116 . 
     The tension adjuster  60  may include a guide rail  610  installed beneath the seat, and a sliding member  620  moving along the guide rail  610 . 
     The sliding member  620  has a first end connecting with the control cable  116 , and a second end connecting with the brake cable  115 . 
     Here, the brake cable  115  is installed to be tensed in the direction of the brake and therefore the sliding member  620  is affected by the tension of the brake cable. That is, the brake cable is tensed in the direction of the brake when the footrest  125  is folded up, thereby keeping the brake in the lock mode. 
     On the other hand, if the footrest  125  is opened from the folded state, the length of the brake cable  115  is increased in a direction opposite to the brake, and thus tension is generated in the direction opposite to the brake, thereby pressing and pulling the control cable, moving the sliding member  620  toward the front of the wheelchair along the guide rail  610  so that the brake cable  115  can be also pulled, making the tension act in the direction opposite to the brake, and switching the brake over from the lock mode to the release mode. 
     Here, the tension adjuster  60  is connected to two footrests  135  by one brake cable  115 , and therefore actuated only when both the footrests are all opened, thereby releasing the brake. 
     On the other hand, if the footrests  125  are folded up again, the increased length of the brake cable  115  is decreased to remove the tension and thus force acting on the control cable  116  is also removed to return the sliding member  620  to its original position by restoring, thereby changing the tension acting on the brake cable  115  in the direction of the brake and pressing the brake pad to switch the brake over from the release mode to the lock mode. 
     Here, the sliding member  620  may couple with the guide rail  610  by an elastic spring in order to provide elasticity and restoring force to move or return to an original position when the tension is applied or removed. 
       FIG. 21  shows an embodiment where a footrest  126  serves as the brake switching member  120 , and a gear assembly  70  is further provided in between the footrest and the brake and connected by the cable. 
     Referring to  FIG. 21 , the gear assembly  70  may include a first axis rotary gear unit  710  rotated connecting with a control cable  118 , a second axis rotary gear unit  720  engaged with the first axis rotary gear unit and rotating with respect to a second axis, and a brake control unit  730  coupling with a brake cable  117  and pressing the brake cable while rotating with respect to the first axis along the second axis rotary gear unit. 
     The first axis rotary gear unit  710  includes a cable connecting portion  711  formed at a first end with regard to the axis, connecting with first and second control cables  118   a  and  118   b  and rotating in a first axial direction; and a first gear  712  formed at a second end, engaged with the second axis rotary gear unit and transmitting rotary force to the second axis rotary gear unit. Two first axis rotary ear units  710  may form a pair to couple with the respective footrests  126 . 
     The second axis rotary gear unit  720  includes a second gear  721  engaged with the first gear  712  and rotating in a second axial direction; and a rotary bar  722  integrated with the second gear  721  and rotating in the second axial direction. 
     Like the first axis rotary gear units, two second axis rotary gear units  720  may also form a pair. Two rotary bars  722  and  723  of the second axis rotary gear units  720  are actuated as the footrests  126  are opened in sequence. Therefore, the brake control unit  730  is pressed and rotated only when all the footrests  126  are opened. 
     In more detail, two control cables  118   a ,  118   b  respectively coupling with each footrest  126  are tensed relative to each other in accordance with whether the footrest  126  is opened or folded. The tension is applied to only the first control cable  118   a  when the footrest is folded, but only the second control cable  118   b  when the footrest is opened. 
     In other words, the first control cable  118   a  has the maximum length and is thus tensed in the state that the footrest is folded as shown in  FIG. 21 , thereby pulling the cable connecting portion  711 . On the other hand, the first control cable  118   a  is decreased in length and has no tension in the state that the footrest is opened. The second control cable  118   b  has the maximum length and is thus tensed in the state that the footrest is opened, thereby pulling the cable connecting portion  711 . 
     The cable connecting portion  711  is provided as a perpendicularly bent flange formed with through holes through which the first and second control cables  118   a  and  118   b  are connected. For example, the first control cable  118   a  is coupled to a horizontal flange, and the second control cable  118   b  is coupled to a vertical flange. 
     Therefore, when both the footrests are all folded up, only the first control cable  118   a  is tensed to pull the cable connecting portion  711  as shown in (a) of  FIG. 21 . 
     If one footrest is opened, only the second control cable  118   b  is tensed to pull the cable connecting portion  711  so that the vertical flange coupling with the second the control cable  118   b  can be pulled as shown in (b) of  FIG. 21 , thereby rotating the first axis rotary gear unit  710  in the first axial direction. 
     As the first axis rotary gear unit  710  rotates, the second axis rotary gear unit also rotates in the second axial direction so that the first rotary bar  722  can rotate in the second axial direction as much as displacement. At this time, the first rotary bar  722  rotates and presses the second rotary bar  723 , and thus the second rotary bar  723  is rotated to the brink of pressing the brake control unit  730 . 
     In this state, no forces are transmitted to the brake control unit  730 , and therefore the brake keeps the lock mode. 
     Then, if the other footrest is opened, the second rotary bar  723  of the other second axis rotary gear unit is further rotated by the same operation and presses the brake control unit  730 , thereby rotating the brake control unit  730  in the first axial direction. 
     In more detail, the brake control unit  730  is formed on a central axis, and includes a brake guide bar  731  to which a brake cable  117  is connected. If the second rotary bar  723  rotates and presses the brake guide bar  731 , the central axis of the brake control unit  730  rotates in the first axial direction and the tension of pulling the brake cable  117  down is generated, thereby reversing the direction of the tension acting toward the brake, pulling the brake cable in the direction opposite to the brake, and switching the brake from the lock mode to the release mode. 
     In result, the brake is released from the lock mode only when two footrests are all opened. 
     In this state, if even one of the footrests is folded, the brake guide bar  731  of the brake control unit returns to its original position by reverse action, so that the tension of the brake cable is changed in a direction toward the brake, thereby switching the brake over from the release mode to the lock mode. 
     The brake according to the present invention may be variously achieved by (a) the brake pad type, (b) the caliper type generally used for a baby carriage, (c) the rim brake type generally used for a bicycle, (d) the band brake type, etc. as shown in  FIG. 10 . In case of a motorized brake system, the band brake type is recommended since it is easy to adjust the locking level of the brake. 
     Although a few exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents. 
     INDUSTRIAL APPLICABILITY 
     The present invention relates to a wheelchair brake system, and more particularly to a wheelchair brake system which is in a brake lock mode as usual as when a user stands up from a wheelchair, but automatically releases a brake only if a user sits down on the wheelchair or folds up the wheelchair, so that the wheelchair can move only when a user sits down thereon or it is folded, thereby preventing a user from getting hurt from a fall at a moment when the user sits down on and stands up from the wheelchair.