Patent Publication Number: US-9429266-B2

Title: Brake mechanism of robot using multi-output differential gear

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority under 35 U.S.C. §119(a) of Korean Patent Application No. 10-2013-0144560 filed on Nov. 26, 2013 and Korean Patent Application No. 10-2013-0165596 filed on Dec. 27, 2013, with the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference. 
     FIELD 
     The present invention relates to a brake mechanism of a robot using a multi-output differential gear, and more particularly, to a brake mechanism of a robot using a multi-output differential gear, capable of forcibly blocking driving force transferred from the multi-output differential gear. 
     BACKGROUND 
     Piping installations, industrial infrastructures, may be distributed all over the country like blood vessels in a human body, and be established as supply routes for various energy resources. However, such piping installations are mostly buried in the underground, and thus, when corrosion occurs in an inside wall of a pipe by the elapse of time and the inside wall is broken due to impacts of external environmental conditions; it may be difficult to inspect and replace the broken component. 
     Thus, piping installations are continuously being deteriorated, and various defects occurring in this process may cause various pipe-related accidents every year. However, due to insufficient supplies of manpower and technological methods, it difficult to conduct regular, systematic inspections on the piping installations. 
     In this regard, robots capable of inspecting the inside of the pipe have been developed, and currently, research thereon has been variously conducted. However, the related art robots needs to be equipped with a driving unit (an actuator) for every wheel to separately adjust the movement state of each wheel according to the shape of the pipe, thereby leading to an increase in the size of the robots. 
     As a result, attention to robots capable of adjusting the speed of each movement unit according the shape of the pipe using only one driving unit has been increasing. 
     Further, research into methods allowing a robot capable of inspecting the inside of a pipe to a point thereof required by a user or apparatuses of blocking power from being transferred and collecting the power when the robot abnormally moves has been ongoing. 
     SUMMARY 
     Therefore, an aspect of exemplary embodiments of the present invention is to provide a brake mechanism of a robot using a multi-output differential gear, capable of blocking or applying driving force to a differential gear unit as needed, by controlling a spaced distance between a driving unit and the differential gear unit. 
     In addition, an aspect of exemplary embodiments of the present invention is to provide a brake mechanism of a robot using a multi-output differential gear, capable of interrupting movements of the robot by forcibly blocking driving force transferred from the multi-output differential gear. 
     According to an embodiment of the present invention, there is provided a brake mechanism of a robot, using a multi-output differential gear, the brake mechanism including: a differential gear unit receiving driving force and generating at least three outputs differentiated from the driving force while being linked with the driving force; a driving unit transferring the driving force to the differential gear unit and moving in a direction away from or approaching the differential gear unit to thereby be detachably provided in the differential gear unit; and a rescuing unit controlling a spaced distance between the driving unit and the differential gear unit to attach and detach the driving unit to and from the differential gear unit. 
     The differential gear unit may include: a driving transferring part rotating by receiving the driving force from the driving unit; a first differential gear part disposed on one surface of the driving transferring part and including a first output gear generating a first output having a rotational speed different from that of the driving transferring part when external resistance is applied to the first output gear and an intermediate gear linked with the first output gear to generate an intermediate output; and a second differential gear part receiving the intermediate output from the first differential gear part and including a second output gear generating a second output having a rotational speed different from that of the intermediate output when external resistance is applied to the second output gear and a third output gear linked with the second output gear and generating a third output having a rotational speed different from that of the second output. 
     The driving unit may have a sliding gear on a rotational axis thereof, and the driving transferring part may include a plurality of connection gears arranged on a virtual circle centered on the rotational axis, the sliding gear being detachably provided between the connection gears according to movements of the driving unit. 
     The rescuing unit may include: a frame part extended from an outer surface of the driving unit in a radial direction of the rotational axis; and an axial member passing through the frame part and connected to the sliding gear, wherein a spaced distance between the driving transferring part and the driving unit is controlled by applying a load to the axial member. 
     The rescuing unit may further include: a handle part provided on an end portion of the axial member adjacent to the frame part and preventing the axial member from being separated from the frame part during the applying of the load to the axial member. 
     The rescuing unit may further include: an elastic member provided on an end portion of the axial member adjacent to the sliding gear and applying elastic force to the axial member 
     The break mechanism may further include: a plurality of moving units respectively linked with the outputs generated by the first output gear, the second output gear, and the third output gear, receiving external resistance, and transferring the external resistance to at least one of the first output gear, the second output gear and the third output gear. 
     The break mechanism may further include: an interval adjusting unit controlling a spaced distance between the moving units and the differential gear unit so as to maintain a state of contact between the moving units and a movement surface. 
     The interval adjusting unit may include: a sliding element disposed on an outer surface of the driving unit and movably provided in a length direction of the driving unit; a first connection member extended from the sliding element and connected to one of the pair of moving units; and a second connection member extended from the sliding element and connected to the other of the pair of moving units, the first connection member and the second connection member allowing the pair of moving units to move in a direction approaching or away from each other according to the movement of the sliding element. 
     The first differential gear part may include: a plurality of output gears generating a plurality of outputs respectively having a rotational speed different from that of the driving force provided from the driving transferring part when external resistance is applied. 
     According to another embodiment of the present invention, there is provided a brake mechanism of a robot, using a multi-output differential gear, the brake mechanism including: a driving unit; a differential gear unit receiving driving force and generating at least three outputs differentiated from the driving force while being linked with the driving force when external resistance is applied; an output transferring unit connected to the differential gear unit and linked with the respective outputs generated by the differential gear unit; and a braking unit provided in a state of contact or non-contact with one end of the output transferring unit to interrupt or allow for the movement of the output transferring unit. 
     The differential gear unit may include: a driving transferring part rotating by receiving the driving force from the driving unit; a first differential gear part disposed on one surface of the driving transferring part and including a first output gear generating a first output having a rotational speed different from that of the driving transferring part when external resistance is applied to the first output gear and an intermediate gear linked with the first output gear to generate an intermediate output; and a second differential gear part receiving the intermediate output from the first differential gear part and including a second output gear generating a second output having a rotational speed different from that of the intermediate output when external resistance is applied to the second output gear and a third output gear linked with the second output gear and generating a third output having a rotational speed different from that of the second output. 
     Sawtooth portions may be formed on an outer circumferential surface of the first output gear, the output transferring unit may include a first output transferring part including a first transfer gear engaged with the first output gear, a first axial member extended from the first transfer gear in a direction of a central axis of the first transfer gear, and a first brake gear provided on the first axial member and linked with the braking unit, and the braking unit may include a first locking member movably provided in a direction approaching or away from the one end of the output transferring unit to selectively contact the one end of the output transferring unit; a driving motor allowing for movements of the first locking member; and a link part connecting the first locking member and the driving motor to each other. 
     Sawtooth portions may be formed on a surface of the first locking member opposed to the first brake gear, the sawtooth portions being engaged with the braking unit. 
     The braking unit may further include: a second locking member opposed to the first locking member with the first brake gear interposed between the locking members, and having sawtooth portions formed on a surface thereof opposed to the first locking member, the second locking member approaching or being apart from the first locking member while being linked with the movement of the first locking member. 
     The first differential gear part may further include: a plurality of output gears generating a plurality of outputs respectively having a rotational speed different from that of the driving force when external resistance is applied. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view schematically illustrating a brake mechanism of a robot using a multi-output differential gear according to a first exemplary embodiment of the present invention; 
         FIG. 2  is an exploded perspective view schematically illustrating the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 ; 
         FIG. 3  is a perspective view schematically illustrating a differential gear unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 ; 
         FIG. 4  is an exploded perspective view schematically illustrating the differential gear unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 ; 
         FIG. 5  is a plan view schematically illustrating a first differential gear part in the differential gear unit of  FIG. 3 ; 
         FIG. 6  is an exploded perspective view schematically illustrating a second differential gear part in the differential gear unit of  FIG. 3 ; 
         FIG. 7  is a cut-away perspective view schematically illustrating coupling relationships between a second output gear, a third output gear, a second epicycle gear, and a third epicycle gear in the second differential gear part of  FIG. 6 ; 
         FIG. 8  is a graph schematically illustrating linkage relationships between the respective output gears in the differential gear unit of  FIG. 3 ; 
         FIG. 9  is a front view schematically illustrating a state of a rescuing unit before the rescuing unit is operated in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 ; 
         FIG. 10  is a front view schematically illustrating a state of the rescuing unit during the operation of the rescuing unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 ; 
         FIG. 11  is a perspective view schematically illustrating moving units in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 ; 
         FIG. 12  is a front view schematically illustrating a state in which the moving units of  FIG. 11  are spaced apart from each other; 
         FIG. 13  is a front view schematically illustrating a state in which the moving units of  FIG. 12  move in directions in which they approach each other by an interval adjusting unit; 
         FIG. 14  is a perspective view schematically illustrating a brake mechanism of a robot using a multi-output differential gear according to a second exemplary embodiment of the present invention; 
         FIGS. 15A and 15B  is a plan view schematically illustrating an operation of a braking unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 14 ; 
         FIG. 16  is a perspective view schematically illustrating a differential gear unit in a brake mechanism of a robot using a multi-output differential gear according to a third exemplary embodiment of the present invention; and 
         FIG. 17  is an exploded perspective view schematically illustrating the differential gear unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The disclosure may, however, be exemplified in many different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. 
     In various exemplary embodiments, the same reference numerals will be used throughout to designate the same or like elements, and a configuration of elements will be representatively described in a first exemplary embodiment and other configurations different from those of the first exemplary embodiment will be described in further exemplary embodiments. 
     Hereinafter, a brake mechanism of a robot using a multi-output differential gear according to a first exemplary embodiment of the present invention will be described in detail. 
     For convenience of explanation, the following description is made on the assumption that a robot using a multi-output differential gear is an in-pipe robot moving along an inside wall of a pipe. 
     However, a robot according to exemplary embodiments of the present invention is not limited to the in-pipe robot, and examples thereof may include a robot capable of entering into an internal space to which the access of a human is unfeasible to inspect damage to the space, a robot capable of conveying a certain product to an internal space, a robot capable of repairing the interior of the space, and the like. 
       FIG. 1  is a perspective view schematically illustrating a brake mechanism of a robot using a multi-output differential gear according to a first exemplary embodiment of the present invention.  FIG. 2  is an exploded perspective view schematically illustrating the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 . 
     Referring to  FIG. 1 or 2 , a brake mechanism  100  of the robot using the multi-output differential gear according to the first exemplary embodiment of the present invention may include a differential gear unit  110 , a driving unit  150 , a rescuing unit  160 , moving units  170 , and an interval adjusting unit  180 , and may be configured in such a manner that respective output gears of the differential gear unit  110  may be linked with each other to control speeds thereof according to an internal state of a pipe, thereby allowing for stable driving of the robot and if necessary, driving force applied to the differential gear unit  110  may be blocked. 
       FIG. 3  is a perspective view schematically illustrating a differential gear unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 .  FIG. 4  is an exploded perspective view schematically illustrating the differential gear unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 . 
     Referring to  FIG. 3 or 4 , the differential gear unit  110  may be configured to receive driving force from the driving unit  150  to be described later, transfer outputs to three output gears, and generate a differential operation by external resistance applied to the moving units  170  to be described later. The differential gear unit  110  may include a driving-force transferring part  120 , a first differential gear part  130 , and a second differential gear part  140 . 
     In the first exemplary embodiment of the present invention, the first differential gear part  130  and the second differential gear part  140  may have the same central axis  105 . 
     The driving unit  150  to be described later may be detachably provided in the driving-force transferring part  120 . When the driving unit  150  is mounted in the driving-force transferring part  120 , the driving-force transferring part  120  may receive driving force from the driving unit  150  to transfer the driving force to the first differential gear part  130 . When the driving unit  150  is separated from the driving-force transferring part  120 , the driving force applied to the first differential gear part  130  may be blocked. The driving-force transferring part  120  may include a housing  121  and connection gears  123 . 
     The housing  121  may perform as a main frame of the driving-force transferring part  120  and have an insertion groove  122  formed in a surface of the housing  121  facing to the driving force  150 . A sliding gear  152  of the driving unit  150  may be inserted into or separated from the driving-force transferring part  120  through the insertion groove  122 . 
     The connection gears  123  may be engaged with the sliding gear  152  of the driving unit  150 , and depending on whether or not the connection gears  123  are engaged with the sliding gear  152 , driving force may be transferred to the first differential gear part  130 , or may be blocked. 
     That is, the connection gears  123  may be accommodated in the interior of the housing  121  and may be arranged on a virtual circle centered on a rotational axis  151  of the driving unit  150 . Here, a diameter of the virtual circle on which the connection gears  123  are disposed may be variously set according to a diameter of the sliding gear  152 . 
     The connection gears  123  according to the first exemplary embodiment of the present invention may be installed on a first finishing member  115   a  to be described later and may rotate together with rotation of the sliding gear  152  to transfer driving force to the first differential gear part  130 . 
       FIG. 5  is a plan view schematically illustrating a first differential gear part in the differential gear unit of  FIG. 3 . 
     Referring to  FIG. 5 , the first differential gear part  130  may transfer driving force received from the driving-force transferring part  120  to the moving units  170  and at the same time, when external resistance is applied thereto from the moving units  170 , the respective gears of the first differential gear part  130  may be linked with each other, generate a first output having a rotational speed different from that of the driving force applied from the driving unit  150 , and transfer the first output to the moving units  170 . In addition, an intermediate output having a rotational speed lower than that of the driving force may be transferred from an intermediate gear  133  to the second differential gear part  140 . The first differential gear part  130  according to the first exemplary embodiment of the present invention may include a first output gear  131 , three first epicyclic gears  132 , and the intermediate gear  133 . 
     Meanwhile, first finishing members  115  may be mounted on opposing surfaces of the first differential gear part  130  to fix locations of the first output gear  131 , the three first epicyclic gears  132 , and the intermediate gear  133 . 
     In the first exemplary embodiment of the present invention, the connection gears  123  may be installed on an outer surface of the first finishing member  115   a  and the housing  121  may be provided to cover outer surfaces of the first finishing members  115  to configure the driving-force transferring part  120 . 
     Meanwhile, the first differential gear part  130  may generate the first output having a rotational speed different from that of the driving force and the intermediate output having a rotational speed lower than that of the driving force, upon receiving external resistance applied from the moving units  170 . 
     Here, a reduction ratio of the rotational speed may be varied depending on a ratio of gears engaged with each other. That is, when a linkage movement is made from the first output gear  131  to the intermediate gear  133 , the first output may be transferred to the intermediate gear  133 , in an amount corresponding to a ratio of the number of sawtooth portions formed on an inner circumferential surface of the first output gear  131  versus the number of sawtooth portions of the intermediate gear  133  (That is, a ratio of the number of sawtooth portions formed on an inner circumferential surface of the first output gear  131 : the number of sawtooth portions of the intermediate gear  133 ). The formula will be described in detail in an operating method according to the first exemplary embodiment of the present invention to be described later. 
     The first output gear  131  has sawtooth portions formed on the inner circumferential surface and an outer circumferential surface thereof, and the sawtooth portions of the inner circumferential surface are engaged with the first epicyclic gears  132 , and the sawtooth portions of the outer circumferential surface may transfer the first output to a first moving unit  171  to be described later but receive external resistance. 
     That is, the sawtooth portions of the outer circumferential surface may receive external resistance from the first moving unit  171  and at the same time, transfer the first output having a rotational speed different from that of the driving force to the first moving unit  171 , depending on the external resistance. 
     The three first epicyclic gears  132  may be engaged with the inner circumferential surface of the first output gear  131  and be disposed to form angles of 120 degrees with respect to the central axis  105  of the first differential gear part  130 . The first epicyclic gears  132  may transfer the first output generated in consideration of external resistance received from the first output gear  131 , to the intermediate gear  133 . 
     However, the number and arrangements of the first epicyclic gears  132  are not limited thereto, and if necessary, may be freely selected. 
     The intermediate gear  133  may not rotate in the case of no external resistance, and when external resistance is applied thereto, may transfer the intermediate output having a rotational speed reduced as compared to that of the driving force, to the second differential gear part  140 . 
     Re-explaining coupling relationships of the first differential gear part  130 , the three first epicyclic gears  132  may be engaged with the inner circumferential surface of the first output gear  131 , and the intermediate gear  133  may be disposed inwardly of the first epicyclic gears  132  such that the outer circumferential surface thereof may be engaged with the first epicyclic gears  132 . 
     In other words, the three first epicyclic gears  132  may be engaged with the outer circumferential surface of the intermediate gear  133 , and the first output gear  131  may be disposed such that the sawtooth portions formed on the inner circumferential surface thereof are engaged with the first epicyclic gears  132 . Here, the first output gear  131  and the intermediate gear  133  may have the same central axis  105 . 
     As described above, according to the first exemplary embodiment of the present invention, the first finishing members  115   a  and  115   b  may be formed between the driving unit  150  and the first differential gear part  130  to fix the locations of the first epicyclic gears  132  so as to allow the first epicyclic gears  132  to individually rotate, and may perform a connector of transferring the driving force received from the driving unit  150  to the first epicyclic gears  132 . 
       FIG. 6  is an exploded perspective view schematically illustrating a second differential gear part in the differential gear unit of  FIG. 3 .  FIG. 7  is a cut-away perspective view schematically illustrating coupling relationships between a second output gear, a third output gear, a second epicycle gear, and a third epicycle gear in the second differential gear part of  FIG. 6 .  FIG. 8  is a graph schematically illustrating linkage relationships between the respective output gears in the differential gear unit of  FIG. 3 . 
     Referring to  FIGS. 6 through 8 , the second differential gear part  140  may receive the intermediate output from the intermediate gear  133  to generate an output externally through a second output gear  141  and a third output gear  142 . When external resistance is applied from the moving units  170  to the second differential gear part  140 , gears of the second differential gear part  140  may be linked with each other and generate a second output having a rotational speed different from that of the intermediate output and a third output having a rotational speed different from that of the second output through the second output gear  141  and the third output gear  142 . 
     According to the first exemplary embodiment of the present invention, the second differential gear part  140  may include the second output gear  141 , the third output gear  142 , second epicycle gears  143  and third epicycle gears  144 . 
     In a case in which external resistance is not applied to a second moving unit  172  or a third moving unit  173  to be described later, each of the second output gear  141  and the third output gear  142  may generate an output the same as the intermediate output. In a case in which external resistance is applied to the second output gear  141  or the third output gear  142 , the second output gear  141  may generate a second output having a rotational speed different from that of the intermediate output and the third output gear  142  may be linked with the second output gear  141  and generate a third output differentiated from the second output. 
     In addition, in the case that the intermediate output is not present, when external resistance is applied to the second output gear  141 , the second output gear  141 , the second epicycle gears  143  and the third epicycle gears  144  may be linked with each other, and the third output gear  142  may rotate in a direction opposite to a direction of the rotation of the second output gear  141 . 
     The second output gear  141  may have sawtooth portions formed on an inner circumferential surface and an outer circumferential surface thereof. The sawtooth portions of the inner circumferential surface may be engaged with the second epicycle gears  143  and the sawtooth portions of the outer circumferential surface may transfer the second output to the second moving unit  172 . That is, the sawtooth portions formed on the outer circumferential surface of the second output gear  141  may receive external resistance from the second moving unit  172  and at the same time, transfer the second output having a rotational speed different from that of the intermediate output to the second moving unit  172 , depending on the external resistance. 
     The third output gear  142  may have sawtooth portions formed on an inner circumferential surface and an outer circumferential surface thereof. The sawtooth portions of the inner circumferential surface may be engaged with the third epicycle gears  144  and the sawtooth portions of the outer circumferential surface may transfer a third output to the third moving unit  173 . That is, the sawtooth portions formed on the outer circumferential surface of the third output gear  142  may transfer the third output having a rotational speed different from that of the second output to the third moving unit  173  using external resistance, upon receiving the external resistance from the third moving unit  173 . 
     The second epicycle gears  143  may be engaged with the inner circumferential surface of the second output gear  141  and also be engaged with the respective third epicycle gears  144 . The three second epicycle gears  143  may be disposed to form angles of 120 degrees with respect to the central axis  105  of the second differential gear part  140 . The second epicycle gears  143  may transfer the external resistance received from the second output gear  141  to the third epicycle gears  144  to be described later. 
     However, the number and arrangements of the second epicycle gears  143  are not limited thereto, and if necessary, may be freely selected. 
     The third epicycle gears  144  may be engaged with the inner circumferential surface of the third output gear  142  and also be engaged with the second epicycle gears  143 . The three third epicycle gears  144  may be disposed to form angles of 120 degrees with respect to the central axis  105  of the second differential gear part  140 . The third epicycle gears  144  may transfer the external resistance received from the third output gear  142  to the second epicycle gears  143 . 
     However, the number and arrangements of the third epicycle gears  144  may preferably be selected to correspond to those of the second epicycle gears  143 . 
     In a case in which external resistances may be applied simultaneously from the second moving unit  172  and the third moving part  173 , since the second output gear  141 , the third output gear  142 , the second epicycle gears  143 , and the third epicycle gears  144  configuring the second differential gear part  140  may be linked with one another, external resistance applied from the second moving unit  172  and external resistance applied from the third moving part  173  may be offset from each other or may complement each other, such that it is considered that a single external resistance is applied. Thus, the said case is identical to the case of having external resistance applied from one of the second moving unit  172  or the third moving part  173 . 
     Re-explaining the coupling relationships of the second differential gear part  140  with reference to  FIGS. 6 through 8 , the sawtooth portions formed on the inner circumferential surface of the second output gear  141  may be engaged with the second epicycle gears  143 , and the second epicycle gears  143  may be engaged with the respective third epicycle gears  144  corresponding thereto. In addition, the third epicycle gears  144  may be engaged with sawtooth portions formed on an inner circumferential surface of the third output gear  142 . 
     However, since lower portions of the second epicycle gears  143  may be engaged with upper portions of the third epicycle gears  144 , the second epicycle gears and the third output gear  142  may not be directly engaged with each other or the third epicycle gears  144  and the second output gear  141  may not be directly engaged with each other. 
     Even with the coupling relationships, the second output gear  141  and the third output gear  142  may be preferably disposed not to directly influence each other. 
     Meanwhile, according to the first exemplary embodiment  100  of the present invention, second finishing members  145   a  and  145   b  may be preferably formed to fix locations of the respective gears of the second differential gear part  140  thereto. 
     The second finishing members  145   a  and  145   b  may be connected to the intermediate gear  133  and fix the locations of the second epicycle gears  143  and the third epicycle gears  144  so as to allow the epicycle gears to individually rotate. When the intermediate output is generated, the second finishing members  145   a  and  145   b  may transfer the intermediate output to the second epicycle gears  143 . 
     In addition, an output transferring unit  111  may be further provided between the differential gear unit  110  and the driving unit  150 , the output transferring unit  111  transferring outputs generated by the output gears  131 ,  141  and  142  to the moving units  170 . 
     The output transferring unit  111  may include spur gears  112   a  (not shown),  112   b  and  112   c  engaged with the respective output gears  131 ,  141 , and  142 , output transferring shafts  113   a ,  113   b  and  113   c  receiving the outputs generated by the output gears  131 ,  141 , and  142  from the spur gears  112   a ,  112   b  and  112   c , and bevel gears  114   a ,  114   b  and  114   c  connected to the output transferring shifts  113   a ,  113   b  and  113   c  to rotate in the same manner as those of the spur gears  112   a ,  112   b  and  112   c.    
     However, the present invention is not limited thereto, any configuration may be included, as long as it may provide a mechanism capable of delivering the outputs generated by the output gears  131 ,  141  and  142 . 
     The driving unit  150  may move in a direction approaching or away from the differential gear unit  110  and be detachably provided in the driving-force transferring part  120 . When the driving unit  150  is mounted in the driving-force transferring part  120 , the sliding gear  152  may be provided on the rotational axis  151  to provide driving force to the differential gear unit  110 . 
     The sliding gear  152  may be provided on the rotational axis  151  and rotate together with the rotational axis  151 . The sliding gear  152  may be detachably provided between the connection gears  123  according to the movement of the driving unit  150  so as to transfer or block the driving force of the driving unit  150  to the differential gear unit  110 . 
     That is, the driving unit  150  may move in a direction approaching or away from the differential gear unit  110 , and through the movement, the sliding gear  152  of the driving unit  150  may be detachably provided between the connection gears  123  to thereby block or transfer the driving force of the driving unit  150  to the differential gear unit  110 . 
       FIG. 9  is a front view schematically illustrating a state of a rescuing unit before the rescuing unit is operated in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 .  FIG. 10  is a front view schematically illustrating a state of the rescuing unit during the operation of the rescuing unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 . 
     Referring to  FIG. 9 or 10 , the rescuing unit  160  may control a spaced distance between the differential gear unit  110  and the driving unit  150  to block or transfer driving force generated by the driving unit  150  to the differential gear unit  110 , and may include a frame part  161  and an axial member  162 . 
     The frame part  161 , a plate member provided on an outer surface of the driving unit  150  and extending in a radial direction with respect to the central axis  151 , may be provided with a groove formed in a direction of the movement of the driving unit  150  so as to guide movements of the axial member  162  to be described later. 
     In addition, the frame part  161  may simultaneously serve as a main frame of the interval adjusting unit  180  movably provided in a length direction of the driving unit  150  on the outer surface of the driving unit  150  in a state in which a first connection member  181  and a second connection member  182  are installed on the frame part  161  to thereby control a spaced distance between the driving unit  150  and the differential gear unit  110 . 
     The axial member  162  may have one end connected to the sliding gear  152  and be disposed to pass through the frame part  161 . The axial member  162  may be pushed or pulled to slide the sliding gear  152  along the rotational axis  151 , thereby detachably providing the sliding gear  152  between the connection gears  123 . 
     In the first exemplary embodiment of the present invention, when the axial member  162  is pulled, the sliding gear  152  may be detached from the connection gears  123 , such that the transfer of driving force may be blocked. However, the present invention is not limited to such a structure and when the axial member  162  is pushed, the sliding gear  152  may be detached from the connection gears  123 , such that the transfer of driving force may be blocked. 
     Meanwhile, even in the case that the sliding gear  152  may slide on the rotational axis  151  of the driving unit  150 , the sliding gear  152  and the rotational axis  151  may rotate together. 
     Meanwhile, in the first exemplary embodiment of the present invention, an elastic member  163  may be further included on an end portion of the axial member  162  adjacent to the driving-force transferring part  120 , and may apply elastic force to the axial member  162  to allow the axial member  162  to return back to an initial state thereof when the axial member  162  is pushed or pulled. 
     In addition, a handle part  164  may be further included on the other end of the axial member  162  so as to prevent the axial member  162  from being separated from the frame part  161  when the axial member  162  is pushed or pulled. 
     Here, the handle part  164  may have a width greater than a diameter of the axial member  162  or a length greater than the axial member  162  to prevent the axial member  162  passing through the frame part  161  from being separated from the frame part  161 . In addition, the handle part  164  may serve as a handle portion able to facilitate the pulling or pushing of the axial member  162 . 
       FIG. 11  is a perspective view schematically illustrating moving units in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 1 . 
     Referring to  FIG. 11 , the moving units  170  may be linked with the output gears and receive the outputs generated by the output gears to perform movements thereof, while receiving external resistance generated during the movements thereof to transfer the external resistance to the respective output gears. The moving units  170  may include the first moving unit  171 , the second moving unit  172 , and the third moving unit  173 . 
     The first moving unit  171  may receive driving force or the first output from the first output gear  131  to perform the movement thereof and at the same time, may transfer the external resistance to the first output gear  131  in a case in which external resistance factor is generated such as cases in which a rotating section is formed or obstructions are formed in a movement path in the interior of a pipe. 
     According to the first exemplary embodiment  100  of the present invention, two first moving units  171  are provided as a pair of first moving units  171 , and one of the first moving units  171  may be disposed toward a front end portion of the robot while the other of the first moving units  171  may be disposed toward a rear end portion of the robot. Each of the first moving units  171  may include a gear mechanism  1711  engaged with the bevel gear  114   a , receiving the first output from the output gear  121 , and transferring the first output to a wheel part  1713 , the wheel part  1713  moved by receiving the first output from the gear mechanism  1711 , and support parts  1712  supporting the wheel part  1713 . 
     The gear mechanism  1711  may be configured to include a plurality of spur gears  1711   a  and a bevel gear  1711   b  that are spaced apart from each other and engaged with each other, and one of the spur gears  1711   a  may have the same axis as that of the bevel gear  1711   b  and rotate together therewith. 
     Here, the bevel gear  1711   b  of the gear mechanism  1711  may be engaged with the bevel gear  114   a  of the output transferring unit  111  to receive the first output, and the bevel gear  1711   b  may sequentially transfer power to the plurality of spur gears  1711   a  and transfer the first output to the wheel part  1713 . 
     The support parts  1712 , members supporting the wheel part  1713 , may be provided on both opposing surfaces of the wheel part  1713 . Here, the support part  1712  installed on one side of the wheel part  1713  may be provided to cover both sides of the spur gears  1711   a  so as to fix relative locations of the plurality of spur gears  1711   a  configuring the gear mechanism  1711  thereto. 
     That is, one of the support parts  1712  may support the wheel part  1713  and fix the relative locations of the plurality of spur gears  1711   a.    
     In addition, the support part  1712  may be classified as a pivoting part  1712   a  having the same pivot axis as the central axis of the spur gear engaged with the bevel gear  114   a  among the plurality of spur gears  1711   a  configuring the gear mechanism  1711 , and an extension part  1712   b  extending from the pivoting part  1712   a  to the wheel part  1713 . 
     Here, the pivoting part  1712   a , a circular member, may be rotatably provided about the pivot axis and control a spaced distance between a pair of first moving units  171 , whereby the first moving units  171  may be maintained in a state in which they come into contact with the inside wall of a pipe. 
     Meanwhile, the extension part  1712   b  may be a member extending from the pivoting part  1712   a  to the wheel part  1713  and factors thereof such as a length or the like may be differently set in consideration of an inner diameter of the pipe. 
     However, such a configuration may be provided as an example of a structure configured to deliver an output from the differential gear unit  110  to the moving units  170  according to the first exemplary embodiment  100  of the present invention. Thus, the present invention is not limited to the configuration as described above. 
     In addition, since the second moving units  172  and the third moving units  173  may be configured in the same manner as that of the first moving units  171 , a detailed description thereof will be omitted. The second moving units  172  may receive the second output and transfer external resistance through the second output gear  141 , and the third moving units  173  may receive a third output and transfer external resistance through the third output gear  142 . 
     Meanwhile, re-explaining disposition relationships of the first moving units  171 , the second moving units  172  and the third moving units  173  according to the first exemplary embodiment  100  of the present invention, the respective moving units may be disposed to form angles of 120 degrees with respect to the central axis of the differential gear unit  110 . The moving units  171   a ,  172   a  and  173   a  disposed on a front surface of the differential gear unit  110  may be arranged on a common concentric circle, and the moving units  171   b ,  172   b  and  173   b  disposed on a rear surface of the differential gear unit  110  may also be arranged on a common concentric circle. 
     In addition, the concentric circle formed by the moving units  171   a ,  172   a  and  173   a  disposed on the front surface of the differential gear unit  110  may have a diameter the same as that of the concentric circle formed by the moving units  171   b ,  172   b  and  173   b.    
     However, the dispositions of the moving units are not limited thereto and may be differentially set according to a user&#39;s intention. 
       FIG. 12  is a front view schematically illustrating a state in which the moving units of  FIG. 11  are spaced apart from each other.  FIG. 13  is a front view schematically illustrating a state in which the moving units of  FIG. 12  move in directions in which they approach each other by an interval adjusting unit. 
     The interval adjusting unit  180  may be connected to the pivoting part  1712   a  of the support part  1712  and may pivot the pivoting part  1712   a  to control the spaced distance between the moving units  170  and the differential gear unit  110 . The interval adjusting unit  180  may include the first connection member  181  and the second connection member  182 . 
     Here, a case in which the first connection member  181  and the second connection member  182  are connected to the first moving units  171  is described, and the first connection member  181  and the second connection member  182  may be applied to the second moving units  172  and the third moving units  173  in substantially the same manner as that of the first moving units  171 . 
     The first connection member  181  may have one end connected to the frame part  161  and the other end connected to a lower end portion of the pivoting part  1712   a  of the support part  1712  finishing the gear mechanism  1711 . 
     The second connection member  182  may have one end connected to the frame part  161  and the other end connected to an upper end portion of a pivoting part  1712   a  of a support part  1712 ′ opposed to the support part  1712  to which the first connection member  181  is connected. 
     Here, when the frame part  161  moves in a direction away from the differential gear unit  110 , the first connection member  181  may rotate the support part  1712  in a counterclockwise direction, and the second connection member  182  may rotate the support part  1712 ′ in a clockwise direction, whereby a spaced distance between the pair of the first moving units  171  may be reduced. 
     Conversely, when the frame part  161  moves in a direction approaching the differential gear unit  110 , the first connection member  181  may rotate the support part  1712  in a clockwise direction, and the second connection member  182  may rotate the support part  1712 ′ in a counterclockwise direction, whereby the spaced distance between the pair of the first moving units  171  may be increased. 
     That is, the interval adjusting unit  180  according to the first exemplary embodiment of the present invention may freely control the spaced distance between the pair of the first moving units  171  through the movement of a single frame part  161  to provide easiness and convenience of operations. 
     Meanwhile, unlike the first exemplary embodiment of the present invention, the first connection member  181  and the second connection member  182  may not be connected to the frame part  161  but may be installed on a sliding element (not shown), a separate constitution. 
     The sliding element (not shown) may be movably provided in the length direction of the driving unit  150  on the outer surface of the driving unit  150 . Here, a screw thread may be formed on the outer surface of the driving unit  150  and another screw thread corresponding to the screw thread of the driving unit  150  may be provided on an inside wall of the sliding member (not shown). However, the present invention is not limited thereto. 
     Meanwhile, the movements of the second and third moving units  172  and  173  may be controlled by the interval adjusting unit  180  in the same manner as that of the first moving units  171 . 
     Further, according to the first exemplary embodiment of the present invention, a plurality of guiding units  184  may be provided in a circumferential direction of the driving unit  150  to guide the frame part  161  in the movement direction thereof. 
     In order to simultaneously control the spaced distance between the first moving units  171 , a spaced distance between the second moving units  172 , and a spaced distance between the third moving units  173  using a single frame part  161 , the frame part  161  may need to maintain a state thereof in parallel with an initial state thereof and may need to move in a direction far away from or approaching the differential gear unit  110 . 
     To this end, the plurality of guiding units  184  penetrating through the frame part  161  and disposed to be perpendicular with respect to the frame part  161  may be installed, whereby the movement direction of the frame part  161  may be easily controlled. 
     Hereinafter, operations of the brake mechanism of the robot using the multi-output differential gear according to the first exemplary embodiment of the present invention as described above will be described. 
     First, in the brake mechanism of the robot using the multi-output differential gear according to the first exemplary embodiment of the present invention, operations of the differential gear unit  110  receiving driving force and external resistance to perform a differential operation and transferring differential outputs to the respective moving units will be described. 
     First, an operation of the driving-force transferring part  120  will be explained. Only in a case in which the sliding gear  152  is installed between the connection gears  123  of the driving-force transferring part  120 , the driving force of the driving unit  150  may be transferred to the differential gear unit  110 . In a case in which the sliding gear  152  is separated from the connection gears  123 , the transfer of driving force from the driving unit  150  may be blocked. 
     Here, whether or not the sliding gear  152  is installed between the connection gears  123  may be determined by an operation of the rescuing unit  160 . When the handle part  164  of the rescuing unit  160  is directly pulled by a user or is drawn through an automatic driving scheme, the driving unit  150  may move away from the differential gear unit  110 . 
     In this case, the sliding gear  152  provided on the rotational axis  151  of the driving unit  150  may be separated from the connection gears  123 , simultaneously with the driving unit  150 , and in this case, the driving force of the driving unit  150  may not be transferred to the differential gear unit  110 . The said case may be defined as “a driving force cut-off state” 
     The “driving force cut-off state” may be provided in a case in which an operation of the robot in a moving state needs to be stopped, for example, in a case in which the robot moving through the interior of a pipe may be caught by obstacles and may not be movable, or in a case in which the robot arrives at a target point in the interior of the pipe and thus, it is necessary to be removed from the pipe. 
     However, in the “driving force cut-off state”, since the driving force may not be transferred to the first differential gear part  130 , an operation of the first differential gear part  130  will be explained on the assumption that the sliding gear  152  is installed between the connection gears  123 , that is, “a driving force transfer state” is provided. 
     Here, since the driving-force transferring part  120  may merely transfer the driving force received from the driving unit  150  and does not increase or attenuate a magnitude of the driving force, the driving-force transferring part  120  may deliver driving force having the same magnitude as that of the driving force received from the driving unit  150  to the first differential gear part  130 . 
     A case in which the driving force is received from the driving-force transferring part  120  and at the same time, external resistance is not applied from the first moving units  171  to the first output gear  131  will be described as follows. The driving force received from the driving-force transferring part  120  may be delivered to the first epicyclic gears  132 , and the first epicyclic gears  132  may rotate while being engaged with the outer circumferential surface of the intermediate gear  133  to thereby allow the first output gear  131  to rotate in a direction of the rotation of the driving unit  150 . In this case, the rotational speed may be varied depending on a ratio of a sawtooth number of the first epicyclic gears  132  versus a sawtooth number of the first output gear  131  (That is, a ratio of a sawtooth number of the first epicyclic gears  132 : a sawtooth number of the first output gear  131 ). 
     In this case, since the intermediate gear  133  is in a stationary state, a value of the intermediate output may be “0” and the second differential gear part  140  may be in a stationary state when external resistance is not applied thereto. 
     When external resistance is applied to the first output gear  131 , the first output gear  131  may generate a first output having a rotational speed different from that of external power by using the external resistance, the gears of the first differential gear part  130  may be linked with each other, and the intermediate gear  133  may generate an intermediate output. Accordingly, the intermediate gear  133  may perform a differential function for external power. 
     Meanwhile, an operating method of the second differential gear part  140  will be described. When a value of the intermediate output transferred to the second differential gear part  140  is “0”, a second output and a third output generated by the second output gear  141  and the third output gear  142  may be affected depending on whether or not the external resistance is applied to the gear. In a case in which external resistance is not applied, since the intermediate output may not be transferred to the second differential gear part  140  as described above, all of the second output and the third output may not be generated. Meanwhile, in a case in which external resistance is applied to the second output gear  141  or the third output gear  142 , the second output gear  141  and the third output gear  142  may rotate together to thereby generate the second output and the third output, respectively. 
     Here, when the intermediate output is applied to the second differential gear part  140  and external resistance is applied to the second output gear  141 , the second output gear  141  may generate a second output having a rotational speed different from that of the intermediate output, and the third output gear  142  linked with the second output gear  141  may generate a third output having a rotational speed different from that of the second output. 
     Conversely, in a case in which external resistance is applied to the third output gear  142 , an operation may be performed in the same manner as that of a case in which external resistance is applied to the second output gear. When external resistances are applied to both the second output gear  141  and the third output gear  142 , the external resistances may be offset from each other and may complement each other, such that it is considered that a single external resistance is applied and thus, the operation as described above may be performed. That is, all of the second output gear  141  and the third output gear  142  may perform a differential function. 
     The first output gear  131 , the second output gear  141 , and the third output gear  142  may have rotational speeds varied according to sawtooth numbers of the gears linked with one another, but may rotate in the same direction. In a case in which three output gears need to rotate at the same rotational speed in the same direction, relative speeds of the gears within the first differential gear part  130  may be 0. In a case in which the three output gears need to rotate at different rotational speeds, that is, in a case in which the output gears perform a differential function, the relative speeds of the respective output gears may be varied, which will be explained by the following formula: 
     
       
         
           
             
               
                 
                   
                     [ 
                     
                       
                         
                           
                             ω 
                             1 
                           
                         
                       
                       
                         
                           
                             ω 
                             
                               4 
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                               1 
                             
                           
                         
                       
                       
                         
                           
                             ω 
                             
                               6 
                               / 
                               4 
                             
                           
                         
                       
                     
                     ] 
                   
                   = 
                   
                     
                       
                         [ 
                         
                           
                             
                               1 
                             
                             
                               
                                 
                                   ( 
                                   
                                     
                                       n 
                                       3 
                                     
                                     
                                       n 
                                       2 
                                     
                                   
                                   ) 
                                 
                                 ⁢ 
                                 
                                   ( 
                                   
                                     - 
                                     
                                       
                                         n 
                                         4 
                                       
                                       
                                         n 
                                         3 
                                       
                                     
                                   
                                   ) 
                                 
                               
                             
                             
                               0 
                             
                           
                           
                             
                               1 
                             
                             
                               1 
                             
                             
                               
                                 
                                   n 
                                   6 
                                 
                                 
                                   n 
                                   5 
                                 
                               
                             
                           
                           
                             
                               1 
                             
                             
                               1 
                             
                             
                               
                                 - 
                                 
                                   ( 
                                   
                                     
                                       n 
                                       7 
                                     
                                     
                                       n 
                                       8 
                                     
                                   
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                         ] 
                       
                       
                         - 
                         1 
                       
                     
                     ⁡ 
                     
                       [ 
                       
                         
                           
                             
                               ω 
                               2 
                             
                           
                         
                         
                           
                             
                               ω 
                               5 
                             
                           
                         
                         
                           
                             
                               ω 
                               8 
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   Formula 
                   ] 
                 
               
             
           
         
       
     
     Where, ω 1  indicates a rotational speed of driving force applied from the driving unit  150 , ω 2  is a rotational speed of the first output gear  131 , ω 5  is a rotational speed of the second output gear  141 , ω 8  is a rotational speed of the third output gear  142 , ω 4/1  is a relative speed of the intermediate gear  133  with respect to the driving force, and ω 6/4  is a relative speed of the second epicyclic gear  143  with respect to the intermediate gear  133 . In addition, n 3  indicates the number of sawtooth portions of the first epicyclic gear  132 , n 2  indicates the number of sawtooth portions of the first output gear  131 , and n 4  indicates the number of sawtooth portions of the intermediate gear  133 . Furthermore, n 6  indicates the number of sawtooth portions of the second epicyclic gear  143 , n 5  indicates the number of sawtooth portions of the second output gear  141 , n 7  indicates the number of sawtooth portions of the third epicyclic gear  144 , and n 8  indicates the number of sawtooth portions of the third output gear  142 . 
     First, the rotational speed (ω 2 ) of the first output gear, the rotational speed (ω 5 ) of the second output gear, and the rotational speed (ω 8 ) of the third output gear are denoted by solid lines. The rotational speed (ω 1 ) of external driving power, the relative speed (ω 4/1 ) of the intermediate gear with respect to the external driving force, and the relative speed (ω 6/4 ) of the second epicyclic gear with respect to the intermediate gear are denoted by dots at respective moments of time, the dots being connected to one another. It could be confirmed that a differential operation was made as the relative speeds of the gears are varied depending on a change in angle (θ). 
     On the basis of the operation of the differential gear unit  110 , operations of the brake mechanism of the robot using the multi-output differential gear according to the first exemplary embodiment of the present invention will be described. 
     First, in a case in which the interior of a pipe has a straight form, since it can be assumed that no external resistance is present therein, the first output having a magnitude the same as that of driving force may be transferred from the first output gear  131  to the first moving units  171 . In this case, since the second and third outputs may not be generated by the second output gear  141  and the third output gear  142 , respectively, the second moving unit  172  and the third moving unit  173  may rotate at the same rotational speed as that of the first moving units  171 . 
     Then, in a case in which the interior of a pipe has a curved form or includes obstacles present therein, external resistance may be applied from at least one of the first moving units  171 , the second moving unit  172 , and the third moving unit  173 , and rotational speeds of the respective moving units  170  may be changed by the operation of the differential gear unit  110  as described above. A description thereof has been described in the operation of the differential gear unit  110 , it will be omitted herein. 
     Hereinafter, a process of transferring driving force from the differential gear unit  110  to the moving units  170  will be explained. 
     At least one spur gear of the output transferring unit  111  may be engaged with each output gear  131 ,  141  or  142  included in the differential gear unit  110  and may receive the driving force from the output gear  131 ,  141  or  142 . In this case, rotational speeds of the output gears  131 ,  141  and  142  may be different from those of the spur gears  112  corresponding thereto, which may be determined depending on the numbers of sawtooth portions of the output gears  131 ,  141  and  142  and the spur gears  112 . 
     A description will be made on the basis of the first output gear  131  transferring the first output to the first moving units  171 . The first output gear  131  may be engaged with the spur gear  112   a  of the output transferring unit  111 , and the output transferring shift  113  may be provided on a central axis of the spur gear  112   a.    
     That is, the spur gear  112   a  may be provided on the output transferring shift  113   a , such that the spur gear  112   a  and the output transferring shift  113   a  may rotate together and transfer consequently formed rotational force to the bevel gear  114   a  provided on an end portion of the output transferring shift  113   a.    
     Here, the bevel gear  114   a  may be engaged with the spur gear of the gear mechanism  1711  and finally, the driving force may be transferred to the wheel part  1713 . 
     Since a process of applying external resistance to the wheel part  1713  may be performed in a direction reverse to that of a driving force transferring process, a detailed description thereof will be omitted herein. 
     In addition, such an operation may be performed in the second moving unit  172  and the third moving unit  173  in the same manner as that of the first moving units  173 . 
     Meanwhile, when the robot using the multi-output differential gear according to the first exemplary embodiment of the present invention moves along the interior of a curved pipe, contact between the moving units  170  and an inside wall of the curved pipe may be maintained by the interval adjusting unit  180 . 
     In more detail, when the robot using the multi-output differential gear moves along the interior of a curved pipe, since centrifugal force may act in a radial direction, the robot may be close to a radially-outward wall portion of the curved pipe but may be apart from a radially-inward wall portion thereof. 
     Here, since it is necessary to increase a spaced distance between the moving units  170  adjacent to the radially-outward wall portion, the interval adjusting unit  180  may allow the frame part  161  to move in a direction approaching the differential gear unit  110  to thereby increase the spaced distance between the moving units  170 . 
     In addition, since it is necessary to decrease a spaced distance between the moving units  170  adjacent to the radially-inward wall portion, the interval adjusting unit  180  may allow the frame part  161  to move in a direction away from the differential gear unit  110  to thereby decrease the spaced distance between the moving units  170 . 
     In this manner, the capability of maintaining contact properties between the moving units  170  and the inside wall of the pipe may be improved by properly adjusting the spaced distance between the moving units  170  according to a state of the pipe. 
     Then, a brake mechanism of a robot using a multi-output differential gear according to a second exemplary embodiment of the present invention will be explained. 
       FIG. 14  is a perspective view schematically illustrating a brake mechanism of a robot using a multi-output differential gear according to a second exemplary embodiment of the present invention.  FIG. 15  is a plan view schematically illustrating an operation of a braking unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 14 . 
     Referring to  FIG. 14 or 15 , a brake mechanism  200  of a robot using a multi-output differential gear according to a second exemplary embodiment of the present invention, may promptly block driving force transferred from a differential gear unit to moving units in a case in which the robot moving along an inside wall of a pipe to inspect an interior state of the pipe may malfunction and accordingly, the robot needs to be interrupted. The brake mechanism  200  of the robot using the multi-output differential gear according to the second exemplary embodiment of the present invention may include a driving unit  210 , a differential gear unit  220 , an output transferring unit  250 , moving units  260 , and a braking unit  270 . 
     Referring to  FIG. 15 , the driving unit  210  may apply driving force to the differential gear unit  220  to be described later, and a method of applying force is not particularly limited. 
     That is, the driving unit  210  may be connected to the differential gear unit  220  to directly transfer driving force, and the driving force may be indirectly transferred via a connection element such as a belt portion, a chain portion and the like between the driving unit  210  and the differential gear unit  220 . 
     In addition, in a similar manner to the foregoing first exemplary embodiment, the rescuing unit  160  may be mounted. 
     Since the differential gear unit  220  is identical to the differential gear unit  110  according to the first exemplary embodiment, a detailed description thereof will be omitted herein. 
     The output transferring unit  250  may be connected to a first output gear  231 , a second output gear  241 , and a third output gear  242  and may transfer outputs provided by the first output gear  231 , the second output gear  241 , and the third output gear  242  to a first moving unit  261 , a second moving unit  262  and a third moving unit  263 , respectively. The output transferring unit  250  may include a first output transferring unit  250   a , a second output transferring unit  250   b , and a third output transferring unit  250   c , and each of the output transferring units  250   a ,  250   b  and  250   c  may include a transfer gear  251 , an axial member  252  and a brake gear  253 . 
     The first output transferring unit  250   a  may transfer an output from the first output gear  231  to the first moving unit  261  and at the same time, may transfer external resistance from the first moving unit  261  to the first output gear  231 . The first output transferring unit  250   a  may include a first transfer gear  251   a , a first axial member  252   a  and a first brake gear  253   a.    
     Here, except for a difference in which the first output transferring unit  250   a , the second output transferring unit  250   b , and the third output transferring unit  250   c  are connected to the first output gear  231 , the second output gear  241 , and the third output gear  242 , respectively, configurations of the first output transferring unit  250   a , the second output transferring unit  250   b , and the third output transferring unit  250   c  are identical to one another. Thus, only the first output transferring unit  250   a  may be representatively explained herein. 
     The first transfer gear  251   a  may be engaged with sawtooth portions formed on an outer circumferential surface of the first output gear  231 . The first axial member  252   a , an extension member extended along a central axis of the first transfer gear  251   a , may have one end extended to be linked with the braking unit  270  and the other end extended to be linked with the moving units  260 . The first brake gear  253   a  may be provided on one end of the first axial member  252   a  and be linked with the braking unit  270  to thereby forcibly block a first output provided by the first output gear  231 . 
     That is, the first output gear  231  rotates and accordingly, the first transfer gear  251   a  may rotate, and such an output may be transferred to the first brake gear  253   a  and the first moving unit  261 . 
     Meanwhile, a bevel gear  254  may be provided on the other end of the first axial member  252   a  in order to transfer the first output to the first moving unit  261 . 
     The moving units  260  may be linked to the respective output gears  231 ,  241  and  242  and receive outputs from the output gears  231 ,  241  and  242  to perform movements thereof. Further, the moving units  260  may receive external resistance generated during the movements thereof and transfer the external resistance to the respective output gears. The moving units  260  may include the first moving unit  261 , the second moving unit  262  and the third moving unit  263 . 
     Here, except for a difference in which the first moving unit  261 , the second moving unit  262  and the third moving unit  163  may be connected to the first output transferring unit  250   a , the second output transferring unit  250   b , and the third output transferring unit  250   c , respectively, to receive the first output, the second output, and the third output, respectively, since configurations of the first moving unit  261 , the second moving unit  262  and the third moving unit  263  are substantially identical to one another and are also substantially identical to those of the first moving units  170  according the first exemplary embodiment, a detailed description thereof will be omitted herein. 
     The braking unit  270  may be linked with the output transferring unit  250  and may forcibly block the output received from the differential gear unit  220  from being transferred to the moving units  260 . The braking unit  270  may include a first locking member  271 , a driving motor  272 , a link part  273 , and a second locking member  274 . 
     The first locking member  271  may move in a direction approaching the brake gear  253  in a state in which it is spaced apart from the brake gear  253 . Consequently, the first locking member  271  may come into contact with the brake gear  253  to stop the movement of the output transferring unit  250 . 
     Here, sawtooth portions may be formed on a surface of the first locking member  271  facing the brake gear  253 , the sawtooth portions being engaged with the brake gear  253 . 
     That is, the sawtooth portions of the first locking member  271  may be engaged with the brake gear  253  to stop the brake gear  253  and at the same time, all of the transfer gear  251  and the axial member  252  connected to the brake gear  253  may be stopped and consequently, the transfer of an output to the moving units  260  may be interrupted. 
     The driving motor  272  may be provided to transfer electric power so as to move the first locking member  271  and may be a servo motor according to the second exemplary embodiment of the present disclosure. However, the present invention is not limited thereto. 
     The link part  273 , a member connecting the first locking member  271  and the driving motor  272 , may be provided as a three-fold link structure having one end thereof connected to the driving motor  272  and the other end thereof connected to the first locking member  271 . 
     The second locking member  274 , a member opposed to the first locking member  271  with the brake gear  253  interposed between the locking members, may contact the brake gear  253  to forcibly interrupt the rotation of the brake gear  253 . 
     Here, the movements of the second locking member  274  and the first locking member  271  may be performed in opposite manners. That is, when the first locking member  271  approaches the brake gear  253 , the second locking member  274  may be distant from the brake gear  253 , while when the first locking member  271  is apart from the brake gear  253 , the second locking member  274  may approach the brake gear  253 . 
     Here, sawtooth portions may be formed on a surface of the second locking member  274  facing the brake gear  253 , the sawtooth portions being engaged with the brake gear  253 . 
     That is, when the sawtooth portions of the first locking member  271  or the sawtooth portions of the second locking member  274  are engaged with the brake gear  253 , a sliding movement of the brake gear  253  may be unfeasible and the rotation thereof may be forcibly interrupted. 
     Here, contact between the brake gear  253  and the first locking member  271  or the second locking member  274  may be associated with a direction of the rotation of the brake gear  253 . 
     Re-explaining coupling relationships of the braking unit  270  according to the second exemplary embodiment of the present invention, in a state in which the driving motor  272  and a first stage link  273   a  of the link part  273  are connected to each other, the driving motor  272  may be provided to move in a direction in which it pulls or pushes the link part  273 . 
     Here, the first locking member  271  may have one end thereof connected to a third stage link  273   c  of the link part  273  and the other end thereof rotatably provided while a location thereof is in a fixed state, whereby the first locking member  271  may be adjacent to the brake gear  253  as the driving motor  272  pulls the link part  273 . 
     In addition, the second locking member  274  may have one end thereof connected to a connection portion between a second stage link  273   b  and the third stage link  273   c  of the link part  273  and the other end thereof rotatably provided while a location thereof is in a fixed state, whereby the other end of the second locking member  274  may be distant from the brake gear  253  as the driving motor  272  pulls the link part  273 . 
     In this manner, the movements of the first locking member  271  and the second locking member  274  may be simultaneously determined by a single operation of the driving motor  272 , such that the rotation of the brake gear  253  may be efficiently interrupted. 
     Here, each of the output transferring units  250   a ,  250   b  and  250   c  (that is, the output transferring unit  250 ) may all include the brake gear  253  and the braking unit  270  corresponding to the brake gear  253 . 
     Meanwhile, the brake mechanism  200  of the robot using the multi-output differential gear according to the second exemplary embodiment of the present invention may further include an interval adjusting unit (not shown) controlling the movements of the moving units  260  in order to improve the capability of maintaining contact between the moving units  260  and the inside wall surface of a pipe. 
     The interval adjusting unit (not shown) may be provided in substantially the same manner as that of the first exemplary embodiment. 
     That is, the moving units  260  may move in a direction approaching or away from a central axis  205  of the differential gear unit  220 , whereby the contact between the moving units  260  and the inside wall surface of a pipe may be maintained. 
     Hereinafter, operations of the brake mechanism  200  of the robot using the multi-output differential gear as described above will be described. 
     First, at least one transfer gear  251  of the output transferring unit  250  may be engaged with each output gear  231 ,  241  or  242  included in the differential gear unit  220  and may receive the driving force from the output gear  231 ,  241  or  242 . In this case, a rotational speed of the output gear  231 ,  241  or  242  may be different from that of the transfer gear  251  corresponding thereto, which may be determined depending on the numbers of sawtooth portions of the output gears  231 ,  241  and  242  and spur gears  212 . 
     Explanation is made on the basis of the first output gear  231  transferring the first output to the first moving unit  261 . The first output gear  231  may be engaged with the first transfer gear  251   a  of the first output transferring unit  250   a , and the first axial member  252   a  may be disposed on the central axis of the first transfer gear  251   a  and rotate together with the first transfer gear  251   a.    
     That is, the first transfer gear  251   a  may be provided on the first axial member  252   a , such that the first transfer gear  251   a  and the first axial member  252   a  rotate together, and accordingly formed rotational force may be transferred to a bevel gear  254   a  provided on an end portion of the first axial member  252   a.    
     Here, the bevel gear  254   a  may be engaged with the spur gear of a gear mechanism  2611  and finally, the driving force may be transferred to a wheel part  2613 . 
     Since a process of applying external resistance to the wheel part  2613  may be performed in a direction reverse to that of the driving force transferring process, a detailed description thereof will be omitted herein. 
     In addition, such an operation may be performed in the second moving unit  262  and the third moving unit  263  in the same manner as that of the first moving unit  261 . 
     Meanwhile, in the case that the movement of at least one of the moving units  260  is restricted by obstacles, the braking unit  270  may be operated in order to interrupt the driving force transferred from the differential gear unit  220  to the moving units  260 . 
     Since the first brake gear  253   a  may be provided on the other end of the first axial member  252   a  connected to the first transfer gear  251   a , the first transfer gear  251   a  and the first brake gear  253   a  may rotate together. 
     That is, in the case that the first transfer gear  251   a  may rotate by receiving the first output from the first output gear  231 , the first brake gear  253   a  may also rotate, and in the case that the rotation of the first brake gear  253   a  is interrupted by the braking unit  270 , the rotation of the first transfer gear  251   a  may also be interrupted. 
     That is, when the rotation of the first brake gear  253   a  is interrupted by the braking unit  270 , the rotation of the bevel gear  254   a  may be interrupted and consequently, the transfer of the first output to the first moving member  261  may be blocked. 
     Such an operation of the braking unit  270  may be initiated by the driving motor  272 . The driving motor  272  may move in a state of being connected to the link part  273  and thus, pull the link part  273 . Since the link part  273  may be connected to both the first locking member  271  and the second locking member  274 , both of the first locking member  271  and the second locking member  274  may be driven through the movement of the link part  273 . 
     That is, when the driving motor  272  pulls the link part  273 , the sawtooth portions formed on the first locking member  271  and the second locking member  274  may be simultaneously engaged with the first brake gear  253   a  to thereby interrupt the rotation of the first brake gear  253   a.    
     Then, a brake mechanism of a robot using a multi-output differential gear according to a third exemplary embodiment of the present invention will be explained. 
     A brake mechanism  300  of a robot using a multi-output differential gear according to the third exemplary embodiment of the present invention may include a differential gear unit  310 , a driving unit  350 , a rescuing unit  360 , moving units (not shown), and an interval adjusting unit (not shown), and may be configured in such a manner that respective output gears of the differential gear unit  310  are linked with each other to control speeds thereof according to an internal state of a pipe, thereby allowing for stable driving of the robot and if necessary, driving force applied to the differential gear unit  310  may be blocked. 
       FIG. 16  is a perspective view schematically illustrating a differential gear unit in a brake mechanism of a robot using a multi-output differential gear according to a third exemplary embodiment of the present invention.  FIG. 17  is an exploded perspective view schematically illustrating the differential gear unit in the brake mechanism of the robot using the multi-output differential gear illustrated in  FIG. 16 . 
     Referring to  FIG. 16 or 17 , the differential gear unit  310  may generate a plurality of differential outputs by driving force solely provided. The differential gear unit  310  may include a driving-force transferring part  320 , a first differential gear part  330 , and a second differential gear part  340 . Since the driving-force transferring part  320  and the second differential gear part  340  are identical to those of the first exemplary embodiment  100 , a detailed description thereof will be omitted. 
     The first differential gear part  330  may include a first output gear  331 , three first epicyclic gears  332 , a first intermediate gear  333 , a fourth output gear  334 , three fourth epicyclic gears  335 , a second intermediate gear  336 . 
     In addition, third finishing members  337   a  and  337   b  may be provided between the first intermediate gear  333  and the fourth epicyclic gears  335  to transfer a first intermediate output from the first intermediate gear  333  to the fourth epicyclic gears  335  and may fix locations of the fourth output gear  334 , the three fourth epicyclic gears  335 , the second intermediate gear  336 . However, the present invention is not limited thereto. 
     Disposition relationships of the first differential gear part  330  will be explained. The first differential gear part  130  according to the first exemplary embodiment  100  may be provided as at least two or more first differential gear parts  330  in the third exemplary embodiment of the present invention, and the at least two or more first differential gear parts  330  may be disposed to be adjacent to each other in a direction of the rotational axis  151 . 
     The moving units (not shown) may be linked with the first output gear  331 , the second output gear  341 , the third output gear  342 , and the fourth output gear  334 , may move by receiving the outputs from the respective output gears, and may transfer external resistance to the respective output gears by receiving the external resistance generated during the movements of the moving units  260 . 
     According to the third exemplary embodiment  300  of the present invention, four moving units (not shown) may be provided and disposed such that angles formed by the respective moving units (not shown) centered on a rotational axis  351  of the driving unit  350  may be 90°, equal angles, but the present invention is not limited thereto. 
     Meanwhile, except for the disposition relationships of the respective moving units, since the moving units are the equivalent of the moving units  160  according to the foregoing first exemplary embodiment  100 , a detailed description thereof will be omitted. 
     The interval adjusting unit (not shown) may be provided as four pairs of connection members (not shown) so as to be connected to the respective moving units, and since other configurations thereof are identical to those of the first exemplary embodiment  100 , and accordingly, a detailed description thereof will be omitted herein. 
     That is, according to the third exemplary embodiment  300 , since four output gears may be included in the differential gear unit  310 , fourth moving units (not shown) and four connection members (not shown) of the interval adjusting unit (not shown) may be provided to correspond to the four output gears. 
     Since the differential gear unit  310  may include three output gears, more epicyclic gears and intermediate gears may be further provided to correspond to the output gears, and in addition, more moving units and connection members of the interval adjusting unit may be further provided. 
     Hereinafter, operations of the brake mechanism  300  of the robot using the multi-output differential gear according to the third exemplary embodiment of the present invention as described above will be described. 
     In the configuration of the differential gear unit  310 , operating methods of the driving-force transferring part  320  and the second differential gear part  340  are identical to those of the first exemplary embodiment  100 . In terms of a rescuing unit (not shown), the moving units (not shown), and the interval adjusting unit (not shown), the amounts of the components are merely increased and operating methods thereof are identical to those of the first exemplary embodiment. 
     Operations of the first differential gear part  330  will be explained. The driving force transferred from the driving-force transferring part  320  to the first intermediate gear  333  and a process of generating the first intermediate output may be identical to those of the first exemplary embodiment  100 . 
     First, when the first intermediate output is generated by the first intermediate gear  323 , the first intermediate output may be transferred to the fourth epicyclic gears  335  linked with the first intermediate gear  323  via a second intermediate output transferring part  337 . The first intermediate output transferred to the fourth epicyclic gears  335  may be converted into a second intermediate output by the second intermediate gear  336  depending on whether or not external resistance is applied from the fourth output gear  334  since the fourth epicyclic gears  335  are linked with the fourth output gear  334  and the second intermediate gear  336 . 
     In the case that the second intermediate output is generated from the second intermediate gear  336  due to the external resistance being applied to the fourth output gear  334 , the second intermediate output may be transferred to the second differential gear part  340  to operate the second differential gear part  340 . Since a subsequent operation of the second differential gear part  340  is identical to that of the first exemplary embodiment  100 , a detailed description will be omitted. 
     While this invention has been described in connection with what is presently considered to be practical embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Therefore, the aforementioned embodiments should be understood to be exemplary but not limiting the present invention in any way. 
     According to exemplary embodiments of the present invention as described above, a brake mechanism of a robot using a multi-output differential gear, capable of promptly blocking driving force transferred to moving units in a case in which the robot may malfunction may be provided. 
     In addition, in the brake mechanism of the robot using the multi-output differential gear, a differential operation may be automatically performed at the time of applying external resistance to provide an appropriate level of driving force to the respective moving units, whereby the robot may be stably driven. 
     Further, the capability of maintaining contact between the inside wall of a pipe and the robot may be improved, whereby the robot may be efficiently moved in the interior of the pipe.