BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sub-suction pipe assembly for a vacuum cleaner. 
     2. Description of the Prior Art 
     Generally, as shown in FIG. 1, a vacuum cleaner, such as a canister vacuum cleaner, includes a suction brush  3 , which is connected to a body  1  of the vacuum cleaner. The suction brush  3  moves along a cleaning surface during a cleaning operation. The body  1  of the vacuum cleaner is divided into a dust collecting chamber, which houses a dust filter or the like, and a motor driving chamber, which houses a motor for generating a suction force. Further, the cleaner body  1  is connected to an air suction pipe  6 , which includes a flexible hose  4  and a handle  5 . The handle  5  of the air suction pipe  6  is detachably connected to a suction extension pipe  7 , which in turn is connected to the suction brush  3 . 
     When cleaning a large area such as a floor of a living room, hallway, etc., the suction extension pipe  7  is connected to the handle  5 . The suction extension pipe  7  can be removed from the handle  5  and replaced with a smaller, sub-section pipe  9  to clean smaller areas, such as a desk, table, etc. The sub-suction pipe  9  has a brush  9   a , which is mounted at one end thereof, for passing across a smaller surface area. Accordingly, in order to use the suction extension pipe  7 , after cleaning with the brush  9   a  of the sub-section pipe  9 , the sub-suction pipe  9  must first be detached from the handle  5 . When removed from the handle  5 , the sub-suction pipe  9  must be stored in a separate place. 
     Since the sub-suction pipe  9  is stored separate from the vacuum cleaner body  1 , the sub-suction pipe  9  is often lost. This results in an inconvenience to a user, as the user must first find the sub-suction pipe  9  in order to use it. As a result, the sub-suction pipe  9  may not be readily accessible to the user when needed. 
     Another inconvenience that a separately stored sub-suction pipe  9  creates for the user is that user must switch back and forth between connecting and disconnecting the extension pipe  7  and the sub-suction pipe  9  to and from the handle  5  when cleaning large and small surface areas. 
     SUMMARY OF THE INVENTION 
     The present invention has been made to overcome the above-problems of the prior art. Accordingly, it is an object of the present invention to provide a sub-suction pipe assembly for a vacuum cleaner that has an improved structure, which facilitates exchange between the sub-suction pipe and suction extension pipe. 
     The above object is accomplished by a sub-suction pipe assembly for a vacuum cleaner that includes an air suction pipe connected to a vacuum cleaner body, and a sub-suction pipe movably connected to the air suction pipe and movable with respect to an end of the air suction pipe. The sub-suction pipe includes a brush attached to an end thereof. The sub-suction pipe assembly further includes a suction extension pipe detachably connected to the air suction pipe and locking/unlocking means for locking and unlocking the suction extension pipe with respect to the air suction pipe. 
     The locking/unlocking means includes a plate spring disposed in the suction extension pipe, a locking hole, a release button and a spring. The plate spring has a locking protrusion protruding from an outer wall of the suction extension pipe through a passing hole formed therein. The locking hole is formed in the air suction pipe to receive the locking protrusion. The release button, which is mounted on the sub-section pipe, removes the locking protrusion from the locking hole. The release button is biased away from the locking hole by the spring. 
     An aligning means is further provided for aligning the locking hole with the locking protrusion when connecting the suction extension pipe to the air suction pipe. The aligning means includes an alignment groove formed lengthwise in an inner wall of the air suction pipe, and an alignment protrusion extending from the outer wall of the suction extension pipe. The alignment groove receives the alignment protrusion when the suction extension pipe is aligned with and inserted into the air suction pipe. 
     A rotation preventing means is further provided for guiding the sub-suction pipe along the air suction pipe and preventing rotation of the sub-suction pipe. The rotation preventing means includes a guide protrusion protruding from the outer wall of the air suction pipe, and a guide groove formed in the inner wall of the sub-suction pipe. 
     The sub-suction pipe includes an elastic connecting portion connected to the outer wall of the air suction pipe. The elastic connecting portion generates a friction force between the air suction pipe to restrict movement of the air suction pipe. The elastic connecting portion includes a protrusion that is received in one of a plurality of inserting holes formed in the outer wall of the air suction pipe. 
     The ends of the sub-suction pipe and the brush are at a predetermined angle with respect to a central axis of the sub-suction pipe. 
     The air suction pipe includes a handle portion having a pipe type connecting portion, which is movably connected to the sub-suction pipe, and a flexible hose portion connecting the handle and the cleaner body. 
     The locking/unlocking means includes a plate spring disposed in the suction extension pipe. The plate spring has a locking protrusion protruding from the outer wall of the suction extension pipe through the passing hole formed therein. A locking hole is formed in the air suction pipe for receiving the locking protrusion when the suction extension pipe is connected to the air suction pipe, and an elastically deformable elastic portion is disposed between the air suction pipe and the sub-suction pipe. The elastic portion has a release protrusion that is selectively inserted in the locking hole to disengage the locking protrusion from the locking hole. 
     The sub-suction pipe has a sloping groove formed lengthwise along an inner wall of the sub-suction pipe at a predetermined angle, and the elastic portion of the locking/unlocking means is elastically deformed by the sloping groove as the sub-suction pipe moves with respect to the air suction pipe. 
     Each of the air suction pipe and the sub-suction pipe includes a locking elevation for engagement with each other to restrict movement and separation of the sub-suction pipe from the air suction pipe. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will become readily apparent by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is an exploded perspective view of a conventional vacuum cleaner including a suction extension pipe and a sub-suction pipe; 
     FIG. 2 is an exploded perspective view of a sub-suction pipe assembly for a vacuum cleaner in accordance with the present invention; 
     FIG. 3 is a partial cross-sectional view taken generally along the line III—III of FIG. 2; 
     FIG. 4 is a cross-sectional view taken generally along the line IV—IV of FIG. 3; 
     FIG. 5 is a cross-sectional view taken generally along the line V—V of FIG. 4; 
     FIG. 6 is a partial cross-sectional view showing an air suction pipe connected to the suction extension pipe; 
     FIG. 7 is a partial cross-sectional view showing a locking protrusion engaged in a locking hole; 
     FIG. 8 is a partial cross-sectional view showing a release button of FIG. 7 being depressed; 
     FIG. 9 is a partial cross-sectional view showing the suction extension pipe being separated from the air suction pipe, while the release button is depressed; 
     FIG. 10 is an exploded perspective view of a sub-suction pipe assembly of a vacuum cleaner in accordance with another preferred embodiment of the present invention; 
     FIG. 11 is a partial sectional view of the sub-suction pipe assembly of FIG. 10; 
     FIG. 12 is a partial perspective view showing the sub-suction pipe and the air suction pipe being connected together; 
     FIG. 13 is a front sectional view showing an end of the sub-suction pipe; 
     FIG. 14 is a sectional view of the air suction pipe of FIG. 10; 
     FIG. 15 is a cross-sectional view taken generally along the line VI—VI of FIG. 10; 
     FIG. 16 is a cross-sectional view showing the air suction pipe in connection with the suction extension pipe; 
     FIG. 17 is a partial sectional view showing the air suction pipe, with the suction extension pipe removed from the air suction pipe; 
     FIG. 18 is a partial cross-sectional view showing the suction extension pipe connected to the air suction pipe; and 
     FIG. 19 is a partial cross-sectional view showing the locking protrusion disengaged from the locking hole. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 2, in accordance with one preferred embodiment of the present invention, a sub-suction pipe assembly for a vacuum cleaner includes an air suction pipe  10 , a sub-suction pipe  20  movably connected to an end of the air suction pipe  10 , a suction extension pipe  30 , and a locking/unlocking means. 
     The air suction pipe  10  includes a hose  11  that is connected to the body  1  of the vacuum cleaner (see FIG.  1 ), and a handle portion  13  that is connected to the hose  11 . The hose  11  is made of a flexible material, such as a rubber, etc., and connects the handle portion  13  to the vacuum cleaner body  1 . The handle portion  13  includes a handle  13   a , which a user can grasp to direct the appropriate brush of the vacuum cleaner across a cleaning surface. A drive switch  13   c  is formed on the handle  13   a  to turn on/off the vacuum cleaner. The handle portion  13 , which further includes a pipe type connecting portion  13   b , is preferably formed of plastic. 
     The sub-suction pipe  20  is provided for cleaning a small or narrow surface area, such as a niche, table, cupboard, etc., or an area at a certain height from a floor. As shown in FIGS. 3 and 4, the sub-suction pipe  20  is movably connected to the connecting portion  13   b  of the handle portion  13 . The sub-section pipe  20  slides over the connecting portion  13   b , such that the two overlap by a certain distance. In order to clean using the sub-suction pipe  20 , a user advances the sub-suction pipe  20  in a direction indicated by an arrow B in FIG. 3 over the connecting portion  13   b . On the other hand, in order to store the sub-section pipe  20  and use the suction extension pipe  30 , the user retracts the sub-suction pipe  20 , by sliding it in a direction indicated by an arrow A in FIG.  3 . 
     The sub-suction pipe  20  includes a pipe type suction pipe body  21 , a brush  23  mounted on a leading end of the suction pipe body  21 , and an elastic support portion  25 , which extends from a rear end of the suction pipe body  21 . The leading end of the sub-suction pipe  20  is formed at a predetermined sloping angle, preferably at 45°, with respect to an axis X of the air suction port. It is further preferable that the end of the brush  23  that is attached to the suction pipe body  21  is at the same angle as the suction pipe body  21 . The elastic supporting portion  25  elastically supports an outer wall or circumference of the connecting portion  13   b  and generates a frictional force between the sub-suction pipe  20  and the connecting portion  13   b . Further, as illustrated in FIG. 4, the elastic supporting portion  25  includes a protrusion  25   a  that is selectively inserted into insertion holes H 1  and H 2  formed in the connecting portion  13   b . That is, by retracting the suction pipe body  21  in the direction indicated by the arrow A, the protrusion  25   a  is received in the insertion hole H 1 . Then by advancing the suction pipe body  21  in the direction indicated by arrow B, the protrusion  25   a  is received in the insertion hole H 2 . As described, the protrusion  25   a  is inserted in either one of the inserting holes H 1  and H 2 , and accordingly prevents a movement of the sub-suction pipe  20 . 
     A rotation preventing means is provided to prevent rotation of the sub-suction pipe  20  with respect to the connecting portion  13   b . The rotation preventing means further acts to guide movement of the sub-suction pipe  20 . As shown in FIG. 5, the rotation preventing means includes a guide protrusion  13   d , and a guide groove  26  for receiving the guide protrusion  13   d . The guide protrusion  13   d  extends from the outer wall of the connecting portion  13   b , and the guide groove  26  is formed in an inner wall or circumference of the sub-suction pipe  20 . Alternatively, the guide protrusion may be formed on the inner wall of the sub-suction pipe  20  and the guide groove formed in the outer wall of the connecting portion  13   b.    
     The suction extension pipe  30  is removably mounted to the connecting portion  13   b  of the handle portion  13  of the air suction pipe  10 . Accordingly, an outer diameter of the suction extension pipe  30  corresponds to an inner diameter of the sub-suction pipe  20 . One end of the suction extension pipe  30  is connected to a suction brush  50  (see FIG.  2 ), which draws in foreign substances, such as dust, on the cleaning surface into the vacuum cleaner. 
     A locking/unlocking means locks or unlocks the suction extension pipe  30  with respect to the air suction pipe  10 . The locking/unlocking means includes a plate spring  40  disposed in the suction extension pipe  30 , a locking hole H 3  formed in the connecting portion  13   b  of the air suction pipe  10 , a release button  60  movably disposed on the sub-suction pipe  20 , and a spring  63 . The plate spring  40  is disposed along an inner wall or circumference of the suction extension pipe  30  and has a locking protrusion  41 . The locking protrusion  41  projects out of the suction extension pipe  30  through a passing hole  31  formed therein. The elastic plate spring  40  deforms or recovers as the locking protrusion  41  moves in the passing hole  31 . The locking hole H 3  of the connecting portion  13   b  receives the locking protrusion  41 , when the suction extension pipe  30  is inserted into the connecting portion  13   b . Accordingly, when the locking protrusion  41  is engaged with the locking hole H 3 , the suction extension pipe  30  cannot be separated from the air suction pipe  10 . 
     The sub-suction pipe  20  also includes passing hole H 4 . The passing hole H 4  is in alignment with the locking hole H 3 , when the sub-suction pipe  20  is in its retracted position (e.g., when the protrusion  25   a  of the elastic supporting portion  25  of the sub-suction pipe  20  is in the insertion hole H 1 ). The release button  60  is aligned with the passing hole H 4  of the sub-suction pipe  20 . The release button  60  includes a button portion  61  and a release bar  62  extending from the button portion  61  to the locking hole H 3 . The button portion  61  is movably mounted in a connecting portion  64 , which is mounted on an outer wall or circumference of the suction pipe body  21 . A spring  63  is disposed in the connecting portion  64 . The spring  63  biases the release button  60  outward, such that the release bar  62  of the release button  60  does not extend into the locking hole H 3 . When a user depresses the button portion  61 , the release bar  62  passes through the passing hole H 4  and into the locking hole H 3 . There, the release bar  62  pushes the locking protrusion  41  out of the locking hole H 3 , enabling the user to detach the suction extension pipe  30  from the air suction pipe  10 . 
     In addition, the vacuum cleaner includes an aligning means to align the locking protrusion  41  with the locking hole H 3  as the suction extension pipe  30  is inserted in the connecting portion  13   b . The aligning means includes an alignment groove  13   e  formed in the inner wall of the connecting portion  13   b  and an alignment protrusion, i.e., the locking protrusion  41 , that is received in the alignment groove  13   e . The alignment groove  13   e  extends from one end of the connecting portion  13   b  to the locking hole H 3 . When the suction extension pipe  30  is inserted in the connecting portion  13   b , the locking protrusion  41  slides along the alignment groove  13   e . When the locking protrusion  41  reaches the locking hole H 3 , the plate spring  40  biases the locking protrusion  41  into engagement with the locking hole H 3 . 
     Although the locking protrusion  41  serves as the aligning protrusion in this embodiment, it is only one example. Another possibility is to include a plurality of alignment grooves in the connecting portion  13   b  with corresponding alignment protrusions on the suction extension pipe  30 . 
     Use of the sub-suction pipe assembly for the vacuum cleaner, in accordance with one preferred embodiment of the present invention will be described below. 
     First, in order to clean a small or narrow area, such as a niche, table, or the like, the sub-suction pipe  20  is used. Accordingly, as shown in FIG. 3, the suction extension pipe  30  is detached from the connecting portion  13   b , and the sub-suction pipe  20  is advanced in the direction indicated by the arrow B until the protrusion  25   a  of the elastic supporting portion  25  engages the inserting hole H 2 . With the sub-suction pipe  20  in its extended state, the user can remove foreign substances, such as dust, etc., from the surface of a desk or wall. The foreign substances are drawn into the cleaner body  1  through the air suction portion of the sub-suction pipe  20 . 
     In order to use the suction brush  50  of FIG. 2, the user retracts the sub-suction pipe  20  in the direction indicated by the arrow A, until the protrusion  25   a  engages the inserting hole H 1 . Accordingly, as shown in FIG. 4, the protrusion  25   a  of the elastic supporting portion  25  is inserted in the inserting hole H 1 , securing the position of the sub-suction pipe  20 . Then, as shown in FIG. 5, the user aligns the locking protrusion  41  with the alignment groove  13   e . In this state, the user can then move the suction extension pipe  30  in the direction indicated by the arrow A in FIG. 4, into the connecting portion  13   b . As shown in solid line of FIG. 6, the alignment groove  13   e  depresses the locking protrusion  41 . Once the suction extension pipe  30  is fully inserted in the direction indicated by arrow A to the position indicated by the dashed line in FIG. 6, the locking protrusion  41  extends outward into the inserting hole H 3 . With the locking protrusion  41  in engagement with the locking hole H 3 , the connection between the connecting portion  13   b  with the suction extension pipe  30  is secure. In this state, the user can use the suction brush  5  to vacuum a large cleaning surface, such as a floor or the like. 
     As described above, unlike a conventional vacuum cleaner, the suction extension pipe  30  of the present invention is directly connected to the handle portion  13  at the same time that the sub-suction pipe  20  is connected to the handle portion  13 . Accordingly, any inconvenience in having to remove and store the sub-suction pipe  20  in a separate place is eliminated. 
     The process of detaching the suction extension pipe  30  from the sub-suction pipe  20  is shown in FIGS. 7-9. The user first presses down on the release button  60 . As the release button  60  is depressed, the release bar  62  is passes through the passing hole H 4  and into the locking hole H 3 . There, the release bar  62  pushes the locking protrusion  41  out of the locking hole H 3 . The suction extension pipe  30  can then be moved in the direction indicated by the arrow B in FIG. 9 to disconnect the suction extension pipe  30  from the connecting portion  13   b.    
     Referring now to FIGS. 10 and 11, a brush assembly for a vacuum cleaner according to another preferred embodiment of the present invention is shown. The brush assembly includes an air suction pipe  110 , a sub-suction pipe  120  movably connected to an end of the air suction pipe  110 , a suction extension pipe  130 , and a locking/unlocking means. 
     The air suction pipe  110  includes a hose  111  that is connected to the cleaner body  1  (see FIG.  1 ), and a handle portion  113  that is connected to the hose  111 . The handle portion  113  includes a handle  113   a  and a pipe type connecting portion  113   b , which is connected to the handle  113   a . The connecting portion  113   b  can be separately manufactured and connected to the handle  113   a.    
     The sub-suction pipe  120  surrounds an outer wall or circumference of the connecting portion  113   b  and reciprocates with respect to the connecting portion  113   b  by a certain distance. The sub-suction pipe  120  includes a suction pipe body  121  and a brush  123 , which is provided at one end of the suction pipe body  121 . Here, the brush  123  is formed at a predetermined angle. 
     Referring to FIG. 12, the connecting portion  113   b  and the sub-suction pipe  120  include first and second locking elevations  113   c  and  121   a , respectively, for preventing separation of the sub-suction pipe  120  from the connecting portion  113   b . The first locking elevation  113   c  is formed at an open end of the connecting portion  113   b  as an extension of the outer wall, such as a flange. The second locking elevation  121   a , which corresponds to the first locking elevation  113   c , protrudes from an inner wall or circumference of the connecting end of the suction pipe body  121 . A plurality of second elevations  121   a  are formed on the inner wall of the suction pipe body  121  in a non-continuous pattern. Further, a third locking elevation  115  (FIG. 11) protrudes from the outer circumference of the connecting portion  113   b  to limit movement of the sub-suction pipe  120  in the direction indicated by the arrow A. The third locking elevation  115  has a height approximately equal to a thickness of the suction pipe body  121 . The third locking elevation  115  is preferably made of a plastic and bonded to the connecting portion  113   b . Alternatively, the third locking elevation  115  may be integrally formed with the connecting portion  113   b.    
     In addition, a rotation limiting means is provided to prevent rotation of the sub-suction pipe  120  with respect to the connecting portion  113   b . As shown in FIGS. 13 and 14, the rotation limiting means includes a locking protrusion  113   d  that extends from an outer circumference of the first locking elevation  113   c , and a rotation prevention groove  121   b  that is formed in an inner wall or circumference of the suction pipe body  121  and corresponding to the locking protrusion  113   d . The rotation prevention groove  121   b  extends lengthwise a certain distance along the suction pipe body  121 . In addition, the rotation prevention groove  121   b  slopes in the lengthwise direction of the suction pipe body  121 , such that the groove  121   b  is deepest at the end of the connecting portion  113   b  and becomes more shallow as it approaches the center of the connecting portion  113   b . The rotation prevention groove  121   b  will hereinafter be referred to as a “sloping groove.” 
     Since the construction of the suction extension pipe  130  is identical that of the suction extension pipe  30  shown in FIG. 2, its description will be omitted. 
     As illustrated in FIG. 11, the locking/unlocking means includes a plate spring  150  disposed in the suction extension pipe  130 , a locking hole hl formed in the connecting portion  113   b  of the air suction pipe  110 , and an elastic piece  170  attached to the outer wall of the connecting portion  113   b . As shown in FIG. 15, the plate spring  150  is disposed in the suction extension pipe  130 , and has a locking protrusion  151 , which is projects through the passing hole  131  of the suction extension pipe  130 . The locking hole h 1  is designed to receive the locking protrusion  151 . When the suction extension pipe  130  is inserted in the connecting portion  113   b , the locking protrusion  151  is inserted into and thus engaged with the locking hole h 1 . 
     The elastic piece  170  includes a fixed end that is secured by a fixing pin  171  to the outer wall of the connecting portion  113   b . The elastic piece  170  further includes a free end that extends from the fixed end and is elastically deformable. A release protrusion  170   a  extends from the free end of the elastic piece  170 . The release protrusion  170   a  is adapted to fit into the locking hole h 1 . The elastic piece  170  is elastically deforms when it contacts the sloping groove  121   c  (FIG.  11 ). When the sub-suction pipe  120  moves in the direction indicated by arrow A of FIG. 11, the elastic piece  170  is pressed within the shallow (e.g., vertically narrower) part of the sloping groove  121   c , and accordingly, the release protrusion  170   a  of the elastic piece  170  is inserted into the locking hole h 1 . 
     Additionally, an aligning means is provided to align the locking hole h 1  with the locking protrusion  151  during connection of the air suction pipe  110  and the suction extension pipe  130 . As shown in FIG. 16, the aligning means includes a guide groove G 1  that extends lengthwise along the inner wall of the connecting portion  113   b  toward the locking hole h 1 . 
     The aligning means includes a guide protrusion  132  and a guide groove G 2  that corresponds with the guide protrusion  132 . The guide protrusion  132  projects from the outer wall of the suction extension pipe  130 , and the guide groove G 2  is formed in the inner wall of the connecting portion  113   b  of the air suction pipe  110 . Alternatively, the guide protrusion may extend from the inner wall of the connecting portion  113   b , and the guide groove may be formed in the outer wall of the suction extension pipe  130 . 
     Use of the sub-suction pipe assembly for the vacuum cleaner, in accordance with the second preferred embodiment of the present invention will be described below. 
     First, in order to use the sub-suction pipe  120 , the suction extension pipe  130  is separated from the rest of the vacuum cleaner. The user then moves the sub-suction pipe  120  in the direction indicated by arrow A of FIG. 11 until the sub-suction pipe  120  contacts the third locking elevation  115 . Then, as shown in FIG. 17, the sub-suction pipe  120  is connected to the connecting portion  113   b  and surrounds the outer circumference of the connecting portion  113   b , contacting the third locking elevation  115 . The return force of the elastic piece  170  restricts movement of the sub-suction pipe  120 . Further, since the first locking elevation  113   c  is inserted in the sloping groove  121   c , rotation of the sub-suction pipe  120  is also prevented. 
     In order to use the suction brush  140 , the user moves the sub-suction pipe  120  in the direction indicated by the arrow B in FIG.  17 . Accordingly, as shown in FIG. 11, the elastic piece  170  recovers its original shape, and the release protrusion  170   a  is separated from the locking hole h 1 . The first locking elevation  113   a  is locked in the second locking elevation  121   a . Accordingly, the sub-suction pipe  120  will not separate from the connecting portion  113   b . In such a state, as shown in FIG. 16, the locking protrusion  151  of the suction extension pipe  130  is aligned with the first guide groove G 1 . Then, the suction extension pipe  130  is moved in the direction indicated by the arrow A in FIG.  11  and inserted into the connecting portion  113   b . The first guide groove G 1  pushes down on the locking protrusion  151  to elastically deform the plate spring  150 . 
     In such a state, the locking protrusion  151  is moved along the first guide groove G 1 , until it reaches the locking hole h 1 . At the locking hole h 1 , the plate spring  150  returns to its normal state to extend the locking protrusion  151  into the locking hole h 1  (see FIG.  18 ). When the locking protrusion  151  is inserted in the locking hole h 1 , the suction extension pipe  130  is fixedly connected to the handle portion  113   b . In such a state, the user can use the suction brush  140  to vacuum the cleaning surface. 
     As described above, the user does not need to detach the sub-suction pipe  120  from the connecting portion  113   b  in order to use the suction brush  140 . 
     In order to separate the suction extension pipe  130  from the connecting portion  113   b , the sub-suction pipe  120  is moved in the direction indicated by the arrow A in FIG.  18 . The elastic piece  170  is pressed within a vertically narrower part of the sloping groove  121   c.    
     When the elastic piece  170  is pressed, the releasing protrusion  170   a  is inserted in the locking hole h 1  (see FIG.  19 ), pushing the locking protrusion  151  out of engagement with the locking hole h 1 . The locking protrusion  151  is then separated from the locking groove h 1 , by moving the suction extension pipe  130  in the direction indicated by the arrow B in FIG. 19 to detach the suction extension pipe  130 . 
     As described above, according to the sub-suction pipe assembly of the present invention, since the sub-suction pipe  120  is movably connected to the connecting portion  113   b , and there is no need to separate the sub-suction pipe  120  from the vacuum cleaner and store it in a separate place, when the sub-suction pipe  120  is not being used. 
     In addition, the sub-suction pipe assembly of the present invention has a much simpler structure, facilitating connection and separation of the suction extension pipe  130  to and from the vacuum cleaner body  1 . 
     As stated above, preferred embodiments of the present invention are shown and described. Although the preferred embodiments have been described, it is understood that the present invention should not be limited to these preferred embodiments. Various changes and modifications can be made by one skilled in the art within the spirit and scope of the present invention as hereinafter claimed.
A sub-suction pipe assembly for a vacuum cleaner includes an air suction pipe connected to a vacuum cleaner body, a sub-suction pipe connected to the air suction pipe and movable along the air suction pipe between a first position and a second position. The sub-suction pipe has a brush attached to an end thereof, a suction extension pipe detachably connected to the end of the air suction pipe, and a lock mechanism for securing the suction extension pipe to the air suction pipe. The sub-section pipe remains coupled to the end of the air suction pipe when the suction extension pipe is connected to the air suction pipe.