Patent Publication Number: US-2023134654-A1

Title: Flow path switching valve, and construction machine equipped with same

Description:
TECHNICAL FIELD 
     The present invention relates to a flow path switching valve preferably used in an oil path configuration of a hydraulic oil for operating a work attachment of a construction machine and also relates to the construction machine equipped with the flow path switching valve. 
     BACKGROUND ART 
     Conventionally, for example, among excavating work machines as one type of construction machines, there is one that has a configuration where a work attachment is detachably installed on an arm that constitutes an excavating unit as a front work unit. As attachments, a bucket for the excavating work and a crushing unit (breakers) for crushing work are attached depending on the nature of work. 
     In this configuration where the attachment is detachably installed on the arm, there is one that is equipped with a switching valve in an oil path which is a flow path of a hydraulic oil to operate the attachment. Patent Literature 1 discloses a configuration where a so-called stop valve that opens and closes a flow path is installed, as a switching valve, on the side of an arm. In this configuration, when replacing the attachment, the stop valve closes the oil path to the attachment, and after the attachment is removed and another attachment is installed, opening the stop valve again opens the oil path. 
     Regarding the switching valve installed on the front work unit in this way, a configuration equipped with a so-called three-way valve, which is a flow path switching valve that has three opening portions (ports) to receive connections of oil pipes such as hydraulic hoses and selectively communicates two opening portions with each other, is known (see, for example, Patent Literature 2). The above flow path switching valves are installed on the respective oil paths for supplying and discharging the hydraulic oil to the attachment, and are placed, for example, on both the right and left sides of the arm. 
     In a configuration with a thumb (also referred to as a bucket fork, etc.) used together with a bucket, as disclosed in Patent Literature 2, the three-way valve simplifies the work of replacing the attachment. Specifically, as described as follows. 
     That is, in the case of a switching valve having only two opening portions, when the attachment is to be replaced from the bucket to the crushing unit, it is necessary to remove the oil pipe from a hydraulic cylinder used to operate the thumb and to connect the oil pipe to the crushing unit. In contrast, according to the three-way valve, the oil pipe connected to one opening portion is left connected to the hydraulic cylinder that operates the thumb, while the other one opening portion is used as an opening portion to connect the oil pipe to operate the crushing unit. 
     In order to securely switch the flow path in the flow path switching valve, Patent Literature 2 discloses the following technology concerning three opening portions formed in a block-shaped body and three oil paths communicated to respective opening portions. That is, the other two oil paths are formed at an angle of 120° respectively to the one oil path, and these two oil paths are formed in the shape of an arc. The opening portions through which the two arc-shaped oil paths are communicated have respective axial centers parallel to each other and open on a common face. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2015-140810 
     Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2013-217424 
     DISCLOSURE OF INVENTION 
     Problems to be Solved by the Invention 
     According to the conventional three-way valve configuration described above, it is necessary to form the oil path, which is communicated to each of the opening portions, in a curved or bent shape. This makes it difficult to form the flow path to the body, causing a problem of increasing the cost for forming the flow path. In addition, two of the three opening portions are configured to open on the common face in the body, thus making it difficult to make the body compact. 
     The present invention has been made in view of the above problem, and therefore, it is an object of the present invention to provide a flow path switching valve that facilitates the formation of a flow path to the body, can be manufactured at a low cost, and is able to be made compact, and to provide a construction machine equipped with the flow path switching valve. 
     Means for Solving the Problems 
     A flow path switching valve according to the present invention is a flow path switching valve for switching a flow path, including: a block-shaped body having a first opening portion and a second opening portion which open on faces which are opposite to each other and communicate with each other via a linear first oil path, and a third opening portion opening which opens on a face different from the faces which are opposite to each other and communicates via a linear second oil path to the first oil path; a valve body that is rotatably installed on the body, and that is formed with a communicating flow path which communicates, depending on a rotation position, two of the three opening portions including the first opening portion, the second opening portion, and the third opening portion with each other; and a selecting portion that, by regulating a rotation range of the valve body, selects the rotation position of the valve body as any of a rotation position where the opening portions of a first combination of combinations of the two opening portions selected from the three opening portions communicate with each other by the communicating flow path, and a rotation position where the opening portions of a second combination that is the combination different from the first combination communicate with each other by the communicating flow path. 
     In the flow path switching valve according to another mode of the present invention, the selecting portion is equipped by mounting a rotation regulating member, which is a member detachably attached to the body, on the body, and the body has, as mounting portions of the rotation regulating member, a first mounting portion that causes the first combination to include the first opening portion and the second opening portion, and causes the second combination to include the first opening portion and the third opening portion, and a second combination that causes the first combination to include the first opening portion and the second opening portion, and causes the second combination to include the second opening portion and the third opening portion. 
     In the flow path switching valve according to still other mode of the present invention, the valve body has a valve body protruding portion which is a portion protruding from the body, and the valve body protruding portion is formed with a hole portion passing through in a direction along a plane perpendicular to a rotation axis direction of the valve body. 
     A construction machine according to the present invention is a construction machine equipped with the flow path switching valve, including: a traveling unit; a front work unit that is installed in front of the traveling unit and that includes an arm portion by which a work attachment is detachably supported; and a hydraulic driving unit that is provided on the arm portion and operates by receiving a supply of a hydraulic oil, wherein the construction machine, as the flow path switching valves, includes: a first flow path switching valve which is mounted to one of right and left sides of the arm portion, and which receives a connection of a supply oil pipe that is extended, to the first opening portion, from the traveling unit side, and that is for supplying the hydraulic oil to the hydraulic driving unit or to the attachment, and a second flow path switching valve which is mounted to another of right and left sides of the arm portion, and which receives a connection of a discharge oil pipe that is extended, to the second opening portion, from the traveling unit side, and that is for returning the hydraulic oil discharged from the hydraulic driving unit or from the attachment. 
     Effect of the Invention 
     According to the present invention, a flow path switching valve facilitates the formation of a flow path to the body, can be manufactured at a low cost, and is able to be made compact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a left side view of a construction machine according to one embodiment of the present invention. 
         FIG.  2    is a perspective view of the construction machine, viewed from a left side, according to the one embodiment of the present invention. 
         FIG.  3    is a left side view of a part of an excavating unit according to the one embodiment of the present invention. 
         FIG.  4    is a right side view of a part of the excavating unit according to the one embodiment of the present invention. 
         FIG.  5    is a left side view showing a crushing unit installed in place of a bucket in the excavating unit according to the one embodiment of the present invention. 
         FIG.  6    is a front view showing a state of a flow path switching valve being installed according to the one embodiment of the present invention. 
         FIG.  7    is a top view of a state of the flow path switching valve being installed according to the one embodiment of the present invention. 
         FIG.  8    is a front view showing the flow path switching valve according to the one embodiment of the present invention. 
         FIG.  9    is a top perspective view showing the flow path switching valve according to the one embodiment of the present invention. 
         FIG.  10    is a bottom perspective view showing the flow path switching valve according to the one embodiment of the present invention. 
         FIG.  11    is a cross-sectional view of A-A in  FIG.  12   . 
         FIG.  12    is a cross-sectional view of B-B in  FIG.  7   . 
         FIG.  13    is a perspective view showing a valve body according to the one embodiment of the present invention. 
         FIG.  14    is a perspective view showing the valve body according to the one embodiment of the present invention. 
         FIG.  15    shows a state of switching the flow path switching valve according to the one embodiment of the present invention.  FIG.  15 A  shows a state of the valve body in a second rotation position, and  FIG.  15 B  shows a state of the valve body in a third rotation position. 
         FIG.  16    shows one example of a connection mode of a hydraulic hose to a left flow path switching valve according to the one embodiment of the present invention.  FIG.  16 A  shows a breaker in use, and  FIG.  16 B  shows a bucket in use. 
         FIG.  17    shows one example of a connection mode of the hydraulic hose to a right flow path switching valve according to the one embodiment of the present invention.  FIG.  17 A  shows the breaker in use, and  FIG.  17 B  shows the bucket in use. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention, in a flow path switching valve used in an oil path configuration of a hydraulic oil (pressure oil) to operate a work attachment of a construction machine, for example, seeks to reduce costs and make the unit more compact by devising a flow path configuration formed by a body and a valve body installed on the body. A description will hereinafter be made on an embodiment of the present invention with reference to the drawings. 
     In the present embodiment, a description will be made on an excavating work machine t, which is a turning work vehicle, as an example of a construction machine according to the present invention. However, the construction machine according to the present invention is not limited to the excavating work machine, but can be widely applied to any other construction machine, such as a crane work machine and a wheel loader, for example. 
     A description will be made on an overall configuration of an excavating work machine  1  according to the present embodiment with reference to  FIG.  1    and  FIG.  2   . As shown in  FIGS.  1  and  2   , the excavating work machine  1  includes a traveling unit  2  as a self-propelled traveling body, and an excavating unit  3  and a soil removal unit  4 , each of which is a work portion mounted to the traveling unit  2 . 
     The traveling unit  2  is a part constituting a main machine of the excavating work machine  1  and has a pair of crawler-type traveling portions  5 ,  5  on right and left, a machine body frame  6  as a base stand installed between the right and left traveling portions  5 ,  5 , and a turn stand  7  installed on the machine body frame  6 . The turn stand  7  is configured in a substantially circular shape in plan view, and can turn in any of right and left directions around a vertical axis. 
     On the turn stand  7 , there is installed a driving portion  8 . In the latter half portion on the turn stand  7 , there is installed a prime mover portion  9  that includes an engine and the like. 
     The driving portion  8  is for driving and operating the traveling unit  2 , the excavating unit  3 , and the soil removal unit  4 , and is installed on a cabin  10  installed for the turn stand  7 . The cabin  10  has a frame that forms an outline thereof and a plurality of window portions made of glass or other transparent member, and is configured as a whole in a substantially box shape. In the left side portion, the cabin  10  has an open/close door  10   a  that opens and closes an operator&#39;s entrance to and exit from the driving portion  8 . 
     In the driving portion  8 , a driver&#39;s seat support stand is installed on a floor portion, and a driver&#39;s seat  8   a  is installed on the driver&#39;s seat support stand. In the driving portion  8 , a pair of right and left traveling levers is installed in front of the driver&#39;s seat  8   a,  extending upward from the floor portion, and a plurality of work operation pedals is placed on both right and left sides of the traveling levers on the floor portion. In the driving portion  8 , the driver&#39;s seat  8   a  is surrounded by work operation levers for operating the work portion (excavating unit  3  or soil removal unit  4 ) and an operation panel portion having various actuator portions, such as switches, etc. 
     A base end portion of the excavating unit  3  is mounted to the right/left center portion of the front end of the turn stand  7 . The soil removal unit  4  is mounted to the front side of the machine body frame  6  via between the right and left traveling portions  5 ,  5 . 
     The soil removal unit  4  has a support frame  11  that includes a pair of right and left arms, each of which extends in a front-rear direction, at a position between the right and left traveling portions  5 ,  5 , a blade  12  as a soil removal plate that is installed on a tip side of the support frame  11 , and a blade cylinder  13  that lifts/lowers the blade  12  via the support frame  11 . 
     In a manner to be rotatably lifted and lowered, the support frame  11  is mounted to the machine body frame  6  by having the right and left arms rotatably supported to a support bracket installed on the front portion of the machine body frame  6  with the right/left direction as a rotation axis direction. The blade  12  is installed in a manner to be supported to the front end portion of the support frame  11 . The blade  12  extends in the right/left direction in a manner to have a width that is substantially the same as the right/left width of the right and left traveling portions  5 . The blade cylinder  13  is equipped in a state of being bridged between the machine body frame  6  and the support frame  11 . 
     In the excavating work machine  1  that has the configuration as described above, a desired operation or work is performed when an operator who is seated on the driver&#39;s seat  8   a  appropriately operates the traveling lever, the work operation lever, or the like. Specifically, by the operating of the traveling lever, for example, the traveling unit  2  makes the forward/rearward linear travel or right/left turn travel. In addition, operating the work operation lever performs the excavating work by the excavating unit  3 , or the soil removal work or leveling work by the soil removal unit  4 . 
       FIGS.  1  through  4    are to be used to describe the excavating unit  3 . The excavating unit  3  is a front work unit that is installed on a front side of the traveling unit  2 . Specifically, a support bracket  15  is protruded forward at the right and left center portion of the front end of the turn stand  7 , the base end portion of the excavating unit  3  is mounted to the support bracket  15 . The excavating unit  3  has a boom support bracket  16  as a member of the base end portion thereof. The excavating unit  3  has the boom support bracket  16  rotatably supported to the support bracket  15  on the main machine side with the vertical direction as a rotation axis direction. 
     The excavating unit  3  is so installed as to swing right and left with respect to the turn stand  7  by means of a swing cylinder (not shown) placed on the right side of the boom support bracket  16 . The swing cylinder is placed between the boom support bracket  16  and the turn stand  7 . 
     The excavating unit  3  has a boom  17  that constitutes the base end portion thereof, an arm  18  that is coupled to a tip side of the boom  17 , and a bucket  19  that is mounted to a tip portion of the arm  18 . The excavating unit  3  also has a boom cylinder  21  that causes the boom  17  to be rotationally operated, an arm cylinder  22  that causes the arm  18  to be rotationally operated, and a work tool cylinder  23  that causes the bucket  19  to be rotationally operated. 
     The boom  17  has a boomerang-shaped bent shape in side view, and is rotatably supported to the boom support bracket  16  with the right/left direction as a rotation axis direction. The boom cylinder  21  is placed on the front side of the erect boom  17 , and is bridged between the boom support bracket  16  and a bracket  17   a  protruding on the inside of a bent portion of the boom  17 . 
     The arm  18  is rotatably connected to the tip portion of the boom  17  with the right/left direction as the rotation axis direction. The arm cylinder  22  is placed on the upper side (back side) of the erect boom  17 , and is bridged between a bracket  17   b  protruding on the outside of the bent portion of the boom  17  and an end portion on a rear side (upper side) of a bracket  18   a  protruding on the rear end portion of the arm  18 . 
     The bucket  19  is connected to the tip portion of the arm  18  via an attachment bracket  24 . The attachment bracket  24  is a fitting member of the work attachment, and is installed by means of an axle portion  25  to the tip portion of the arm  18  in a manner to be rotated with the left/right direction as the rotation axis direction. The work tool cylinder  23  is placed on the front side (back side) of the arm  18  which hanging down from the upper end of the boom  17 . 
     The work tool cylinder  23  has a cylinder  23   a,  and a cylinder rod  23   b  that has a piston on one end side and is slidably installed in the cylinder  23   a  via the piston. The work tool cylinder  23 &#39;s end portion on the bottom side (cylinder  23   a  side) as an end portion on one side is supported to an end portion on the front side (lower side) of the bracket  18   a  in a rotatable manner with the right/left direction as the rotation axis direction. 
     Meanwhile, the work tool cylinder  23 &#39;s end portion on the rod side (cylinder rod  23   b  side) as an end portion on the other side is connected to the attachment bracket  24  via a first link  26 . Via a second link  27 , the work tool cylinder  23 &#39;s end portion on the rod side is supported to a site near the tip portion of the arm  18 . 
     The first link  26  is rotatably connected to the work tool cylinder  23  and the attachment bracket  24  respectively, with the left/right direction as the rotation axis direction. The second link  27  is rotatably communicated to the work tool cylinder  23  and the arm  18  respectively, with the left/right direction as the rotational axis. A portion to support the second link  27  to the arm  18  is positioned more on the base end side of the arm  18  than the axle portion  25 . 
     In this configuration, the extending and contracting of the work tool cylinder  23  causes the attachment bracket  24  to rotate with the axle portion  25  as the rotation axis, the bucket  19  rotates in unison with the attachment bracket  24 . 
     The excavating unit  3  is equipped with a thumb  28  used together with the bucket  19 . The thumb  28  is also called a bucket fork, etc., and is so installed as to face the open side of the bucket  19  in a state of being rotatably supported by the arm  18 . With the thumb  28 , in addition to the excavating work by the bucket  19 , it is possible to sandwich logs, rocks, etc. between the bucket  19  and the thumb  28  and convey the same, making it possible to expand applications of the bucket  19 . 
     The thumb  28  has a pair of right and left claw portions  28   a  and a support plate portion  28   b  linking the right and left claw portions  28   a.  The claw portion  28   a  is a longitudinal plate-like portion with the right/left direction as a plate thickness direction. A serrated concave/convex portion  28   c  is formed on the bucket  19  side of the tip portion of the claw portion  28   a.  The support plate portion  28   b  is a plate-like portion installed in the mode of being bridged between the right and left claw portions  28   a,  and is installed between the middle portions of the right and left claw portions  28   a  in the longitudinal direction. 
     The thumb  28  is configured as an integrated member including the right and left claw portions  28   a  and the support plate portion  28   b.  The thumb  28 &#39;s base end portion, which is on the opposite side of the right and left claw portions  28   a&#39; s concave/convex portion  28   c  side, is supported to the tip portion of the arm  18  in a manner to rotate at the axle portion  25  with the right/left direction as the axis direction. 
     The thumb  28  is rotated around the axle portion  25  by a thumb cylinder  29  of the excavating unit  3 . The thumb cylinder  29  is placed at the rear side (ventral side) of the arm  18  hanging down from the upper end of the boom  17 , i.e., on the side opposite to the work tool cylinder  23  with respect to the arm  18 . 
     The thumb cylinder  29  has a cylinder  29   a,  and a cylinder rod  29   b  that has a piston on one end side and is slidably installed in the cylinder  29   a  via the piston. The inner space of the cylinder  29   a  is divided by the piston into a bottom-side chamber which is a space on the cylinder  29   a  side (bottom side), and a rod-side chamber which is a space on the cylinder rod  29   b  side (rod side). Supplying and discharging of the hydraulic oil to and from the bottom-side chamber and rod-side chamber, respectively, moves the cylinder rod  29   b  relative to the cylinder  29   a,  extending and contracting the thumb cylinder  29 . 
     The thumb cylinder  29 &#39;s end portion on the bottom side as an end portion on one side is supported to a support bracket  18   b,  which is protruding on the rear side of the arm  18 , in a manner to be rotated by a bottom-side axial support portion  29   c  with the right/left direction as the rotation axis direction. Meanwhile, the thumb cylinder  29 &#39;s end portion on the rod side as an end portion on the other side is supported to a cylinder support portion  28   d,  which is protruding on the inside of the support plate portion  28   b  of the thumb  28 , in a manner to be rotated by a rod-side axial support portion  29   d  with the right/left direction as the rotation axis direction. The extending and contracting of the thumb cylinder  29  causes the thumb  28  to rotate with the axle portion  25  as the rotation axis. 
     In the excavating unit  3  with the above configuration, the bucket  19  as a work attachment is detachably mounted to an arm portion, and the bucket  19  is replaced by another device such as a rock excavating device or a crushing unit depending on the nature of work. Thus, the excavating unit  3  includes the arm portion by which the work attachment is detachably supported, and the arm portion, via the attachment bracket  24  installed at the tip portion of the arm portion, receives mounting of the attachment that accords to the nature of work. In the present embodiment, the arm portion of the excavating unit  3  is the support arm portion including the boom  17  and the arm  18  which are connected and supported on the front side of the machine body frame  6  of the traveling unit  2 . 
     In the excavating unit  3 , the thumb cylinder  29  which is a hydraulic cylinder and the thumb  28  rotated by its extending and contracting, as a hydraulic driving unit that operates by receiving a supply of the hydraulic oil, are installed on the arm portion. That is, in the present embodiment, the hydraulic driving unit provided on the arm portion of the excavating unit  3  and operated by receiving a supply of the hydraulic oil is a unit configuration including the thumb cylinder  29  and the thumb  28 . 
       FIG.  5    shows a state where, in the excavating unit  3 , instead of the bucket  19 , a breaker  30  which is a crushing unit is installed as the work attachment. The breaker  30  can be used with the thumb  28  installed on the arm  18 . The breaker  30  has a device body portion  31  with a driving portion and the like built in a casing, and a rod portion  32  which is an action portion protruding from one side of the device body portion  31 . 
     The breaker  30 , like the bucket  19 , is detachably mounted to the attachment bracket  24 . By extending and contracting of the work tool cylinder  23 , the breaker  30 , with the axle portion  25  as the rotation shaft, rotates integrally with the attachment bracket  24  thereby to change a posture. 
     The breaker  30  is a so-called hydraulic breaker that has a drive source such as a hydraulic motor and operates by receiving a supply of the hydraulic oil. Receiving a supply of the hydraulic oil, the breaker  30  is operated by hydraulic pressure. The breaker  30  receives the connection of one end side of each of a supply breaker hose  34  and a discharge breaker hose  35 . The supply breaker hose  34  is a supply oil pipe for supplying the hydraulic oil to the breaker  30 . The discharge breaker hose  35  is a discharge oil pipe for returning the hydraulic oil, which is discharged from the breaker  30 , to a predetermined location such as an oil tank. 
     In the excavating unit  3  with the above configuration, the oil path, which is the flow path of the hydraulic oil for operating the thumb cylinder  29  and the breaker  30 , is equipped with a flow path switching valve  50 . The flow path switching valve  50  is a so-called three-way valve that has three opening portions (ports) to receive connections of hydraulic hoses which are oil pipes, and selectively communicates the two opening portions to each other. With the flow path switching valve  50 , the hydraulic hose connected to the one opening portion is left connected to the thumb cylinder  29 , while the other one opening is used to connect the hydraulic hose to operate the breaker  30 . 
     For the breaker  30 , the flow path switching valves  50  are installed on the respective oil paths for supplying and discharging the hydraulic oil. In the present embodiment, the flow path switching valves  50  are installed for the left and right sides  41  ( 41   a,    41   b ) of the arm  18 . That is, one of the flow path switching valves  50  ( 50 L) installed on the oil path for supplying the hydraulic oil is mounted for a left side  41   a  of the arm  18 . The other flow path switching valve  50  ( 50 R) installed on the oil path for discharging the hydraulic oil is mounted for a right side  41   b  of the arm  18 . 
     Thus, the excavating unit  3  is equipped, as the flow path switching valves  50 , with a left flow path switching valve  50 L which is a first flow path switching valve installed on the supply path of the hydraulic oil to the breaker  30 , and a right flow path switching valve  50 R which is a second flow path switching valve installed on the discharge path of the hydraulic oil from the breaker  30 . The left flow path switching valve  50 L and the right flow path switching valve  50 R have a configuration common to each other. 
     A bottom-side hydraulic hose  44 , one end of which is connected to a bottom-side port  42  of the thumb cylinder  29 , extends from the left flow path switching valve  50 L. A rod-side hydraulic hose  45 , one end of which is connected to a rod-side port  43  of the thumb cylinder  29 , extends from the right flow path switching valve  50 R. 
     The bottom-side port  42  is a connection port that communicates to a bottom-side chamber in the cylinder  29   a,  and is installed on the left side in the end portion on the bottom side of the cylinder  29   a.  The rod-side port  43  is a connection port that communicates to a rod-side chamber in the cylinder  29   a,  and is installed on the right side in an end portion of the rod of the cylinder  29   a.    
     A description will be made on a configuration of the flow path switching valve  50  with reference to  FIG.  6    to  FIG.  17   . As shown in  FIGS.  6  to  17   , the flow path switching valve  50  is a flow path switching valve for switching the flow path of the hydraulic oil to the thumb cylinder  29  and breaker  30 , and is equipped with a block-shaped body  51  and a valve body  52  that is rotatable relative to the body  51 . The flow path switching valve  50  is symmetrical in the right/left direction. 
     The body  51  has a front face  51   a,  a rear face  51   b,  a right face  51   c,  a left face  51   d,  a top face  51   e,  and a bottom face  51   f  each of which is a flat face, and these faces form a rectangular outline. In the flow path switching valve  50 , the side that appears in the side view of the excavating unit  3  (the bottom side in  FIG.  7   ) is defined as the front side and the opposite side is defined as the rear side, and the longitudinal direction (right and left in  FIG.  8   ) in the front view of the flow path switching valve  50  is defined as the right/left direction, and the short direction (up and down in  FIG.  8   ) in the same front view is defined as the up/down direction. The body  51  defines the right/left direction as the longitudinal direction relative to the front-back and vertical directions, respectively. 
     The body  51  has three opening portions (ports) including a first opening portion  61 , a second opening portion  62 , and a third opening portion  63 . Each of the opening portions of the body  51  is a circular opening part that receives the connection of a coupling for connecting the hydraulic hose. The three opening portions of the body  51  have an identical or a substantially identical hole diameter. 
     In the body  51 , the first opening portion  61  and the second opening portion  62  are side opening portions formed in a manner to open facing the right face  51   c  as one side and the left face  51   d  as the other side, which are opposite faces to each other. In the body  51 , the first opening portion  61  and the second opening portion  62  are communicated with each other via a linear first oil path  71 . The first opening portion  61  and the second opening portion  62  are formed at a position closer to the upper side than the center in the vertical direction, and both opening portions are formed at the same height position relative to the bottom face  51   f  of the body  51 . 
     In the body  51 , the third opening portion  63  is a bottom opening portion formed in a manner to open facing the bottom face  51   f  which is a face different from the right face  51   c  and the left face  51   d.  In the body  51 , the third opening portion  63  communicates to the first oil path  71  via a linear second oil path  72 . The third opening portion  63  is formed in the center portion of the bottom face  51   f  of the body  51 . 
     In the examples shown in  FIGS.  6  and  7   , a first coupling  64  is mounted to the first opening portion  61 , a second coupling  65  is mounted to the second opening portion  62 , and a third coupling  66  is mounted to the third opening portion  63 , respectively. Each coupling is screw-fastened to the opening portion via an oil seal or the like. Due to this, the inner peripheral faces of the respective opening portions have female thread portions  61   a,    62   a,    63   a.    
     In the body  51 , the first oil path  71  is formed along the right/left direction in a manner to be along the cylindrical inner peripheral face coaxial with the first opening portion  61  and the second opening portion  62 . The first opening portion  61 , the second opening portion  62 , and the first oil path  71  form a flow path portion passing through the body  51  in the right/left direction. In the present embodiment, the first oil path  71  has a predetermined inner diameter (flow path diameter) that is reduced relative to the inner diameters (hole diameters) of the first opening portion  61  and the second opening portion  62 . 
     In the body  51 , the second oil path  72  is formed along the vertical direction in a manner to be along the cylindrical inner peripheral face coaxial with the third opening portion  63 . In the body  51 , the third opening portion  63  and the second oil path  72  form a flow path portion communicating from the bottom side to the first oil path  71 . In the present embodiment, the second oil path  72  has a predetermined inner diameter (flow path diameter) that is reduced relative to the inner diameter (hole diameter) of the third opening portion  63  and has an identical or a substantially identical hole diameter with that of the first oil path  71 . 
     In the body  51 , the first oil path  71  and the second oil path  72  are formed along a substantially T″ shape in frontal cross-sectional view. At a merging part of the first oil path  71  and the second oil path  72 , a valve body support hole  73  for through-supporting the valve body  52  is formed in the front-back direction. The valve body support hole  73  is formed along the cylindrical face. In the body  51 , the three opening portions ( 61 ,  62 ,  63 ) as well as the first and second oil paths  71  and  72  are formed so that their respective central axes are placed on a common plane perpendicular to the front-back direction. 
     The valve body  52  is an axial member having a substantially cylindrical outline as a whole, as shown in  FIGS.  13  and  14   , and has a communicating flow path  85  that selectively communicates the opening portions where the body  51  is present. The valve body  52  has a body shaft portion  81  which is a portion forming the communicating flow path  85 , an actuator portion  82  which is the end portion on the front side of the valve body  52 , and a protruding edge portion  83  which is a flange-like portion installed between the body shaft portion  81  and the actuator portion  82 . 
     The body shaft portion  81  is a cylindrical part having an outer circumferential face  81   a  along the cylindrical face, making up the majority on the rear side of the valve body  52 . The actuator portion  82  has a substantially hexagonal cylindrical shape similar to the head portion of a hexagonal bolt, and has a side portion  82   a  having six planar sides that form a hexagonal shape in the axial view of the valve body  52 , and an end face portion  82   b  that forms the end face on the front side of the valve body  52 . The protruding edge portion  83  is a part enlarged in diameter relative to the body shaft portion  81  and the actuator portion  82 , and is a plate-like portion with the valve body  52 &#39;s axial direction as a plate thickness direction. The protruding edge portion  83  has a substantially circular shape in the axial view of the valve body  52 . 
     Being inserted into the valve body support hole  73 , with the front-back direction as the axial direction, and penetrating the body  51  in the front-back direction, the valve body  52  is installed on the body  51  in a manner to be rotated around the central axis. The valve body  52  is equipped in a state that substantially the entirety of the body shaft portion  81  is positioned within the valve body support hole  73 . The outer diameter of the body shaft portion  81  is substantially the same as the inner diameter of the valve body support hole  73  of the body  51 ; concerning the rotation of the valve body  52 , the outer circumferential face  81   a  of the body shaft portion  81  serves as a face for sliding relative to the inner peripheral face of the valve body support hole  73 . 
     Thus, the valve body  52  has the central axis thereof aligned with the central axis of the valve body support hole  73 , and in a fixed position inserted into the valve body support hole  73 , is installed on the body  51  in a manner to rotate with the central axis as a rotation axis. The valve body  52 , depending on the rotation position thereof, changes the direction around the central axis. 
     The valve body  52  has the protruding edge portion  83  positioned on the front face  51   a  of the body  51 , and has a rear face  83   a  of the protruding edge portion  83  in contact or substantially in contact with the front face  51   a.  Meanwhile, the valve body  52  has the rear end portion thereof protrude from the rear face  51   b  of the body  51 , and has a “C” shaped retaining ring  75 , as a member locking to the rear face  51   b,  fit over the rear end protruding portion thereof. The rear end portion of the body shaft portion  81  has an outer groove  81   b  for fitting the retaining ring  75 . 
     Between the body shaft portion  81  of the valve body  52  and the body  51 , a plurality of oil seals  76 ,  77  are interposed (see  FIG.  12   ). For the body shaft portion  81 &#39;s portion on the front side of the communicating flow path  85 , two oil seals  76  are equipped that fit with two outer peripheral grooves  81   c  formed in the body shaft portion  81 . For the body shaft portion  81 &#39;s portion on the rear side of the communicating flow path  85 , a single oil seal  77  is equipped that fits with an inner peripheral groove  73   a  formed in the site where the valve body support hole  73  is formed in the body  51 . 
     To the body  51 , the valve body  52  is rotatably supported at such a strength that the valve body  52  is not rotated by an action of the pressure oil passing through the communicating flow path  85 . In the present embodiment; to the body  51 , the valve body  52  is rotatably supported at such a strength that the valve body  52  cannot be easily rotated by a direct operation by a human hand. 
     Depending on the direction changed by the valve body  52 &#39;s rotation position, that is, the valve body  52 &#39;s rotation relative to the body  51 , the communicating flow path  85  causes two of the three opening portions including the first opening portion  61 , the second opening portion  62 , and the third opening portion  63 . The communicating flow path  85  is formed in the axial center portion of the body shaft portion  81  in a manner to correspond to the first oil path  71  and the second oil path  72  which are formed in the body  51 . 
     The communicating flow path  85  has a first communicating flow path portion  86  penetrating along the radial direction of the body shaft portion  81 , and a second communicating flow path portion  87  so formed from one side of the body shaft portion  81  in the radial direction as to merge with the first communicating flow path portion  86  in a direction orthogonal thereto. By the first communicating flow path portion  86  and the second communicating flow path portion  87 , the communicating flow path  85  is formed lineally symmetrically along a “T” shape in the axial view of the body shaft portion  81 . 
     In the valve body  52 , the communicating flow path  85  is so formed that the respective central axes of the first communicating flow path portion  86  and the second communicating flow path portion  87  are positioned on a common plane perpendicular to the axial direction of the body shaft portion  81 . The first and second communicating flow path portions  86  and  87  are formed along the cylindrical inner peripheral face and are the same or substantially the same in inner diameter (flow path diameter) as the first oil path  71  and the second oil path  72 . 
     The communicating flow path  85  is open at three locations for the outer circumferential face  81   a  of the body shaft portion  81 . As shown in  FIG.  11   , in a state where the communicating flow path  85  is in an inverted “T” shape in the axial view of the body shaft portion  81 , the opening portion positioned on the right side is defined as a first opening  85   a,  the opening portion positioned on the left side is defined as a second opening  85   b,  and the opening portion positioned on the top side is defined as a third opening  85   c.  The opening portions on both sides of the first communicating flow path portion  86  are the first opening  85   a  and the second opening  85   b,  and the opening portion of the second communicating flow path portion  87  is the third opening  85   c.    
     In the above configuration, the rotation position of the valve body  52  that selectively communicates two of the three opening portions of the body  51  includes the following three. 
     That is, the first rotation position is, as shown in  FIG.  11   , is a rotation position where the valve body  52  turns the first opening  85   a  rightward, the second opening  85   b  leftward, and the third opening  85   c  upward. With the valve body  52  in the first rotation position, the first oil path  71  of the body  51  and the first communicating flow path portion  86  of the valve body  52  form a linear flow path continuous in the right/left direction, and the above flow path allows the first opening portion  61  and the second opening portion  62  to communicate with each other. When the valve body  52  is in the first rotation position, the third opening  85   c  is closed by the upper portion of the inner circumferential wall of the valve body support hole  73 . 
     The second rotation position, as shown in  FIG.  15 A , is a rotation position where the valve body  52  has rotated 90° to the right (clockwise), in the front view, from the first rotation position. That is, the second rotation position is the rotation position where the valve body  52  turns the first opening  85   a  downward, the second opening  85   b  upward, and the third opening  85   c  rightward. With the valve body  52  in the second rotation position, the first oil path  71 &#39;s portion on the first opening portion  61  side and the second oil path  72  in the body  51 , and the second communicating flow path portion  87  and the first communicating flow path portion  86 &#39;s portion on the first opening  85   a  side in the valve body  52  form a right-angled flow path that causes the first opening portion  61  and the third opening portion  63  to communicate with each other. When the valve body  52  is in the second rotation position, the second opening  85   b  is closed by the upper portion of the inner circumferential wall of the valve body support hole  73 . 
     The third rotation position, as shown in  FIG.  15 B , is a rotation position where the valve body  52  has rotated 90° to the left (counterclockwise), in the front view, from the first rotation position. That is, the third rotation position is the rotation position where the valve body  52  turns the first opening  85   a  t upward, the second opening  85   b  downward, and the third opening  85   c  leftward. With the valve body  52  in the third rotation position, the first oil path  71 &#39;s portion on the second opening portion  62  side and the second oil path  72  in the body  51 , and the second communicating flow path portion  87  and the first communicating flow path portion  86 &#39;s portion on the second opening  85   b  side in the valve body  52  form a right-angled flow path that causes the second opening portion  62  and the third opening portion  63  to communicate with each other. When the valve body  52  is in the third rotation position, the first opening  85   a  is closed by the upper portion of the inner circumferential wall of the valve body support hole  73 . 
     The above rotation positions of the valve body  52  are switched by the rotating operation of the valve body  52 . That is, the rotating operation of the valve body  52  switches the communication state between the opening portions, switching the flow path in the flow path switching valve  50 . 
     In the valve body  52 , a “T”-shaped groove portion  82   c  which corresponds to the flow path shape of the communicating flow path  85  is formed in the end face portion  82   b  of the actuator portion  82 . That is, the groove portion  82   c,  corresponding to the “T” shape of the body shaft portion  81  in the axial view, has a linear portion along the first communicating flow path portion  86  and a linear portion along the second communicating flow path portion  87 , forming a “T” shape. The groove portion  82   c  allows the rotation position of the valve body  52 , i.e., the switching state of the flow path in the flow path switching valve  50  (communicating state), to be easily visible from the front side of the flow path switching valve  50 . 
     The valve body  52  has the actuator portion  82  as a valve body protruding portion which is a portion protruding from the body  51  to the front side. The actuator portion  82  has a hole portion  82   d  passing through in a direction along a plane perpendicular to the rotation axis direction of the valve body  52 . 
     The hole portion  82   d  is a linear through hole with a circular hole shape, and is formed along the diameter of the actuator portion  82 . That is, the hole portion  82   d  is so formed that the central axis intersects the central axis of the valve body  52  and is along a plane perpendicular to the axial direction of the valve body  52 . The hole portion  82   d  is opened on two planes positioned on opposite sides of the six planes of the side portion  82   a.    
     At the time of turning the valve body  52 , the hole portion  82   d  is used as an engaging portion to engage a tool or the like with the actuator portion  82 . That is, a rod-shaped tool such as a screwdriver, for example, is used as an operating tool, and penetrating the tool through the hole portion  82   d  cause the operating tool to engage with the actuator portion  82 . In such a state, the operating tool protruding on both sides from the hole portion  82   d  is used as a handle (actuator portion), rotating the valve body  52 . Therefore, the hole portion  82   d  has a hole diameter that can be penetrated by a screwdriver or other commonly used tool. 
     The configuration of mounting the flow path switching valve  50  in the excavating unit  3  is described below. As described above, the flow path switching valve  50  is installed on the right and left sides  41  of the arm  18  included in the excavating unit  3 . The flow path switching valve  50  is mounted at a substantially center position in the direction of extension of the arm  18  (right and left in  FIGS.  3  and  4   ), in a forward inclined orientation in a manner to be forward-descending relative to the direction of extension. The right and left flow path switching valves  50  are each installed on the side  41  of the arm  18  in a similar manner. 
     As shown in  FIGS.  7  and  12   , the flow path switching valve  50  is mounted to the side  41  of the arm  18  via a support plate  91 . The support plate  91  is a rectangular plate-shaped member, with the right/left direction as the longitudinal direction relative to the flow path switching valve  50 , and has dimensions substantially the same as the rightward/leftward dimensions of the body  51  in the right/left direction. The support plate  91  has one-side plate face thereof in contact with the side  41  of the arm  18 , and is fixed in place by welding or the like to the arm  18 . 
     The flow path switching valve  50  is fixed to the support plate  91  by two fixing bolts  92  that pass through the body  51  in the front-back direction. In the body  51 , fixing hole portions  74  for the fixing bolts  92  to pass through are formed in the front-back direction outside the third opening portion  63  on right and left and below the first opening portion  61  and second opening portion  62 , respectively, i.e., at the lower portions on the right and left. The support plate  91  has threaded holes  91   a,  which are female thread portions, at positions corresponding to the right and left fixing hole portions  74 . 
     In a fixed portion by the fixing bolt  92 , a cylindrical spacer  93 , through which the fixing bolt  92  passes, is interposed between the body  51  and the support plate  91 . The fixing bolt  92  is inserted into the fixing hole portion  74  from the front side of the body  51 , penetrates through the body  51  and spacer  93 , and is screwed into the threaded hole  91   a.  The fixing bolt  92  secures the body  51  to the support plate  91 , and the flow path switching valve  50  is mounted to side  41  of the arm  18  via the support plate  91 . 
     The mounting configuration of the flow path switching valve  50  is not limited to the present embodiment. The flow path switching valve  50  may be mounted to the arm  18  by directly fixing the body  51  to the side  41  of the arm  18  by welding, bolting, or the like. 
     The following is a description of a mode in which the hydraulic hoses are connected to the right and left flow path switching valves  50  according to the present embodiment. 
       FIG.  16 A  shows a state of connecting the hydraulic hose to the left flow path switching valve  50 L when the breaker  30  mounted, instead of the bucket  19 , on the excavating unit  3  is used.  FIG.  16 B  shows a state of connecting to the left flow path switching valve  50 L when the bucket  19  mounted on the excavating unit  3  is used. 
     As shown in  FIGS.  16 A and  16 B , regardless of whether the breaker is in use or the bucket is in use, in the left flow path switching valve  50 L, one end side of a supply hose  101  is connected via the first coupling  64  to the first opening portion  61  positioned on the right side as a base end side of the arm  18 . To the front of the traveling unit  2 , the supply hose  101  extends from a control valve (not shown) installed on the turn stand  7 , etc., in the traveling unit  2 . 
     As shown in  FIGS.  1  and  2   , the supply hose  101  is placed from the front side of the traveling unit  2 , along the boom  17 , is extended along the left side  41   a  of the arm  18 , and is connected to the first opening portion  61  of the left flow path switching valve  50 L. On the left side  41   a  of the arm  18 , a ring-shaped hose guide  95  for the supply hose  101  to pass through is equipped behind the left flow path switching valve  50 L. 
     As shown in  FIGS.  16 A and  16 B , regardless of whether the breaker is in use or the bucket is in use, in the left flow path switching valve  50 L, the other end of the bottom-side hydraulic hose  44  having one end side connected to the thumb cylinder  29  is connected, via the third coupling  66 , to the third opening portion  63  positioned on the bottom side. In the present embodiment, the third coupling  66  is an L-shaped coupling, extending the bottom-side hydraulic hose  44  from the left flow path switching valve  50 L toward the tip side of the arm  18 . 
     As shown in  FIG.  16 A , when the breaker is in use, the other end side of the supply breaker hose  34  having one end side connected to the breaker  30  is connected, via the second coupling  65 , to the second opening portion  62  positioned on the left side of the left flow path switching valve  50 L serving as the tip side of the arm  18  (see  FIG.  5   ). As shown in  FIG.  16 A , when the breaker is in use, the valve body  52  is in the first rotation position (see  FIG.  11   ). 
     As a result, in the left flow path switching valve  50 L, the hydraulic oil supplied from the supply hose  101  flows in from the first opening portion  61  (see arrow A 1 ), flows out from the second opening portion  62  through the first oil path  71  in a communication state via the first communicating flow path portion  86  (see arrow A 2 ), and is supplied to the breaker  30  by the supply breaker hose  34 . Thus, in the left flow path switching valve  50 L with the breaker in use, the linear oil path that is formed when the valve body  52  is in the first rotation position and that is from the first opening portion  61  to the second opening portion  62  is used. 
     Meanwhile, as shown in  FIG.  16 B , when the bucket is in use, the second opening portion  62  of the left flow path switching valve  50 L is not used. Due to this, the second opening portion  62  is closed by a closure member  102 . The closure member  102  has, for example, a head portion  102   a  with a substantially hexagonal shape and a threaded portion  102   b,  and like the second coupling  65 , is screw-fastened to the second opening portion  62  via an oil seal or the like. And, as shown in  FIG.  16 B , when the bucket is in use, the valve body  52  is in the second rotation position (see  FIG.  15 A ). 
     As a result, in the left flow path switching valve  50 L, the hydraulic oil supplied from the supply hose  101  flows in from the first opening portion  61  (see arrow B 1 ), flows out from the third opening portion  63  via the right portion of the first oil path  71 , the second communicating flow path portion  87 , the first communicating flow path portion  86 &#39;s portion on the first opening  85   a  side, and the second oil path  72  (see arrow B 2 ), and is supplied to the thumb cylinder  29  by the bottom-side hydraulic hose  44 . Thus, in the left flow path switching valve  50 L, the bent (right-angled) oil path that is formed when the valve body  52  is in the second rotation position and that is from the first opening portion  61  to the third opening portion  63  is used. 
       FIG.  17 A  shows a state of connecting the hydraulic hose to the right flow path switching valve  50 R when the breaker is in use.  FIG.  17 B  shows a state of connecting to the right flow path switching valve  50 R when the bucket is in use. 
     As shown in  FIGS.  17 A and  17 B , regardless of whether the breaker is in use or the bucket is in use, in the right flow path switching valve  50 R, one end side of a discharge hose  103  is connected via the second coupling  65  to the second opening portion  62  positioned on the left side as a base end portion of the arm  18 . The other end of the discharge hose  103  is connected to an oil tank (not shown) equipped in the traveling unit  2 . That is, the discharge hose  103  is a return pipe to the oil tank, and the hydraulic oil in the oil tank is supplied via a control valve or the like to the supply hose  101 . 
     The discharge hose  103  is placed along the boom  17  from the front side of the traveling unit  2 , is extended along the right side  41   b  of the arm  18 , and is connected to the second opening portion  62  of the right flow path switching valve  50 R (see  FIG.  4   ). On the right side  41   b  of the arm  18 , a ring-shaped hose guide  96  for the discharge hose  103  to pass through is equipped at the position behind the right flow path switching valve  50 R. 
     Also, as shown in  FIGS.  17 A and  17 B , regardless of whether the breaker is in use or the bucket is in use, in the right flow path switching valve  50 R, the other end of the rod-side hydraulic hose  45  having one end connected to the thumb cylinder  29  is connected, via the third coupling  66 , to the third opening portion  63  positioned on the bottom side. In the present embodiment, the third coupling  66  is an L-shaped coupling, extending the rod-side hydraulic hose  45  from the right flow path switching valve  50 R toward the tip side of the arm  18 . 
     As shown in  FIG.  17 A , when the breaker is in use, the other end side of the discharge breaker hose  35  having one end side connected to the breaker  30  is connected, via the first coupling  64 , to the first opening portion  61  positioned on the front side of the right flow path switching valve  50 R (see  FIG.  5   ). As shown in  FIG.  17 A , when the breaker is in use, the valve body  52  is in the first rotation position (see  FIG.  11   ). 
     As a result, in the right flow path switching valve  50 R, the hydraulic oil discharged from the breaker  30  flows in from the first opening portion  61  (see arrow C 1 ), flows out from the second opening portion  62  through the first oil path  71  in a communication state via the first communicating flow path portion  86  (see arrow C 2 ), and is returned to the oil tank by the discharge hose  103 . Thus, in the right flow path switching valve  50 R with the breaker in use, the linear oil path that is formed when the valve body  52  is in the first rotation position and that is from the first opening portion  61  to the second opening portion  62  is used. 
     Meanwhile, as shown in  FIG.  17 B , when the bucket is in use, the first opening portion  61  of the right flow path switching valve  50 R is not used. Due to this, the first opening portion  61  is closed via an oil seal or the like by a closure member  104  having a head portion  104   a  and a threaded portion  104   b,  like the closure member  102 . And, as shown in  FIG.  17 B , when the bucket is in use, the valve body  52  is in the third rotation position (see  FIG.  15 B ). 
     As a result, in the right flow path switching valve  50 R, the hydraulic oil discharged from the rod-side hydraulic hose  45  flows in from the third opening portion  63  (see arrow D 1 ), flows out from the second opening portion  62  via the second oil path  72 , the first communicating flow path portion  86 &#39;s portion on the second opening  85   b  side, the second communicating flow path portion  87 , and the left side portion of the first oil path  71  (see arrow D 2 ), and is returned to the oil tank by the discharge hose  103 . Thus, in the right flow path switching valve  50 R, the bent (right-angled) oil path that is formed when the valve body  52  is in the third rotation position and that is from the third opening portion  63  to the second opening portion  62  is used. 
     As described above, with the flow path switching valve  50 , the bottom-side hydraulic hose  44  and the rod-side hydraulic hose  45 , which are connected to the third opening portion  63 , are left connected to the thumb cylinder  29 , while the other opening portions are used as opening portions to connect hydraulic hoses to operate the breaker  30 . 
     Depending on whether the breaker or the bucket is in use, the flow paths of the right and left flow path switching valves  50  are switched by the rotating operation of the valve body  52 . That is, concerning the left flow path switching valve  50 L; when the breaker is in use, the valve body  52  is in the first rotation position, and when the bucket is in use, the valve body  52  is in the second rotation position. Meanwhile, concerning the right flow path switching valve  50 R; when the breaker is in use, the valve body  52  is in the first rotation position, and when the bucket is in use, the valve body  52  is in the third rotation position. 
     Thus, in the present embodiment, the left flow path switching valve  50 L serves as the first flow path switching valve which receives the connection of the supply hose  101  that is extended, to the first opening portion  61 , from the traveling unit  2  side, and that is the supply oil pipe for supplying the hydraulic oil to the thumb cylinder  29  for driving the thumb  28  or to the breaker  30 . In addition, the right flow path switching valve  50 R serves as the second flow path switching valve which receives the connection of the discharge hose  103  that is extended, to the second opening portion  62 , from the traveling unit  2  side, and that is the discharge oil pipe for returning the hydraulic oil discharged from the thumb cylinder  29  or from the breaker  30 . 
     Regarding the rotating operation of the valve body  52 , the flow path switching valve  50  has a selecting portion for selecting the rotation position of the valve body  52  by regulating the rotation range of the valve body  52 . 
     In the left flow path switching valve  50 L, the selecting portion regulates the rotation range of the valve body  52  to be within an angular range of substantially 90° from the first rotation position seen when the breaker is in use (see  FIG.  16 A ) to the second rotation position seen when the bucket is in use (see  FIG.  16 B ). In the right flow path switching valve  50 R, the selecting portion regulates the rotation range of the valve body  52  to be within an angular range of substantially 90° from the first rotation position seen when the breaker is in use (see  FIG.  17 A ) to the third rotation position seen when the bucket is in use (see  FIG.  17 B ). 
     The flow path switching valve  50  has, as the selecting portion, a locking protrusion portion  110  that protrudes from the front face  51   a  of the body  51  and engages with the valve body  52  thereby to regulate the rotation of the valve body  52 . The locking protrusion portion  110  is a protruding portion having a cylindrical outline with the front-back direction as the central axis direction, and when contacting the valve body  52 , functions as a stopper to stop the rotation of the valve body  52  at a predetermined position. Thus, regarding the rotating operation of the valve body  52 , the selecting portion of the flow path switching valve  50  functions as a valve body positioning portion that regulates the rotation range of the valve body  52  thereby to position the rotation position of the valve body  52 . 
     In the present embodiment, the locking protrusion portion  110  is equipped by mounting, to the body  51 , a lock pin  111  as a rotation regulating member which is a member detachably mounted to the body  51 . The lock pin  111  is linear pipe member that is short (e.g., about ¼) relative to the length of the body  51  in the front-back direction (see  FIG.  9   ). 
     The body  51  has a support hole portion  112  that serves as a portion for mounting the lock pin  111  and that is open facing the front face  51   a.  The support hole portion  112  is a cylindrical hole corresponding to the outer shape of the lock pin  111 , and, for the lock pin  111  to be inserted, has an inner diameter (hole diameter) substantially the same as an outer diameter of the lock pin  111 . The support hole portion  112  has a depth equivalent to the length of a substantially half of the lock pin  111 , and substantially half the lock pin  111  protrudes from the front face  51   a.    
     The support hole portion  112  holds the inserted lock pin  111  at such a strength as to prevent the inserted lock pin  111  from being removed by the operation of the excavating unit  3  or by the traveling of the traveling unit  2 . The body  51  has, as the support hole portion  112 , a left support hole portion  112 A as a first mounting portion used in the left flow path switching valve  50 L, and a right support hole portion  112 B as a second mounting portion used in the right flow path switching valve  50 R. 
     In this way, inserting the lock pin  111  into the support hole portion  112  engages the protruding edge portion  83  with the locking protrusion portion  110  installed on the body  51 , causing the valve body  52  to receive the regulation of the rotating. The protruding edge portion  83  has a locking recessed portion  113  as a portion that receives the engaging of the locking protrusion portion  110 . 
     The locking recessed portion  113  is a notch-shaped portion formed in an arc along the circumferential direction of the protruding edge portion  83  at the peripheral edge portion of the protruding edge portion  83 . The locking recessed portion  113  is formed across a substantially 90° angle range, corresponding to the rotation range of the valve body  52  regulated as described above. At both end portions of the locking recessed portion  113 , there are formed locking portions  113   a,    113   b  which are portions engaged with the locking protrusion portion  110 . The locking portions  113   a,    113   b  are formed as arc-shaped recessed portions corresponding to the frontal view outline of the locking protrusion portion  110 . 
     To the above protruding edge portion  83 , the locking protrusion portion  110  is equipped so that at least a portion thereof is positioned within the circular range along which the outer circumference of the protruding edge portion  83  extends. The valve body  52  positions the locking protrusion portion  110  at the site where the locking recessed portion  113  is formed, thereby making it possible to rotate the protruding edge portion  83  without interfering with the locking protrusion portion  110 , due to the locking recessed portion  113 . Then, the valve body  52 , with the locking portions  113   a,    113   b  caused to contact the locking protrusion portion  110 , is locked to the locking protrusion portion  110 , and the rotation is regulated. 
     In the valve body  52  in the first rotation position, the locking recessed portion  113  is formed symmetrically at the lower site of the protruding edge portion  83 . With the valve body  52  in the first rotation position, the left support hole portion  112 A and the right support hole portion  112 B are formed at positions that correspond to the left and right locking portions  113   a,    113   b.  That is, with the valve body  52  in the first rotation position; in the front view, the left and right locking portions  113   a,    113   b  have their arc-shaped concave shapes along the circular support hole portion  112 . 
     With the above configuration, in the left flow path switching valve  50 L, the lock pin  111  is inserted into the left support hole portion  112 A, providing a left locking protrusion portion  110 A as the locking protrusion portion  110 . With the left locking protrusion portion  110 A, as shown in  FIG.  16 A , causing the locking portion  113   a  on one side (left side in  FIG.  16 A ) to contact and engage with the left locking protrusion portion  110 A regulates the counterclockwise rotation (see arrow E 1 ) from the state of being in the first rotation position, positioning the valve body  52  relative to the first rotation position. 
     Also, with the left locking protrusion portion  110 A, as shown in  FIG.  16 B , causing the locking portion  113   b  on the other side (bottom side in  FIG.  16 B ) to contact and engage with the left locking protrusion portion  110 A regulates the clockwise rotation (see arrow E 2 ) from the state of being in the second rotation position, positioning the valve body  52  relative to the second rotation position. 
     Thus, in the left flow path switching valve  50 L, the left locking protrusion portion  110 A serves as the selecting portion that regulates the rotation range of the valve body  52  in a substantially 90° range between the first and second rotation positions, thereby to select the rotation position of the valve body  52  as any of the first rotation position and the second rotation position. 
     Here, the first rotation position is the rotation position where the opening portions including the first opening portion  61  and the second opening portion  62 , as a first combination of combinations the two-opening portions selected from the three opening portions of the body  51 , are communicated with each other by the communicating flow path  85 . The second rotation position is the rotation position where the opening portions including the first opening portion  61  and the third opening portion  63 , as a second combination different from the first combination, are communicated by the communicating flow path  85 . Thus, the left support hole portion  112 A, which constitutes the left locking protrusion portion  110 A by accepting the lock pin  111 , causes the first combination, for the opening portions, to include the first opening portion  61  and the second opening portion  62 , and causes the second combination to include the first opening portion  61  and the third opening portion  63   
     Meanwhile, in the right flow path switching valve  50 R, the lock pin  111  is inserted into the right support hole portion  112 B, providing a right locking protrusion portion  110 B as the locking protrusion portion  110 . With the right locking protrusion portion  110 B, as shown in  FIG.  17 A , causing the locking portion  113   b  on one side (right side in  FIG.  17 A ) to contact and engage with the right locking protrusion portion  110 B regulates the clockwise rotation (see arrow F 1 ) from the state of being in the first rotation position, positioning the valve body  52  relative to the first rotation position. 
     Also, with the right locking protrusion portion  110 B, as shown in  FIG.  17 B , bringing the locking portion  113   a  on the other side (bottom side in  FIG.  17 B ) to contact and engage with the right locking protrusion portion  110 B regulates the counterclockwise rotation (see arrow F 2 ) from the state of being in the third rotation position, positioning the valve body  52  relative to the third rotation position. 
     Thus, in the right flow path switching valve  50 R, the right locking protrusion portion  110 B serves as the selecting portion that regulates the rotation range of the valve body  52  in a substantially 90° range between the first and third rotation positions, thereby to select the rotation position of the valve body  52  as any of the first rotation position and the third rotation position. 
     Here, the first rotation position is, like the case of the left flow path switching valve  50 L, the rotation position where the opening portions including the first opening portion  61  and the second opening portion  62  as the first combination are communicated with each other by the communicating flow path  85 . The third rotation position is the rotation position where the opening portions including the second opening portion  62  and the third opening portion  63 , as a second combination different from the first combination, are communicated by the communicating flow path  85 . Thus, the right support hole portion  112 B, which constitutes the right locking protrusion portion  110 B by accepting the lock pin  111 , causes the first combination, for the opening portions, to include the first opening portion  61  and the second opening portion  62 , and causes the second combination to include the second opening portion  62  and the third opening portion  63 . 
     The flow path switching valve  50  according to the present embodiment having the above configuration facilitates the formation of the flow path to the body  51 , can be manufactured at a low cost, and is able to be made compact. 
     That is, in the flow path switching valve  50 , the flow path of the body  51  is so formed as to be along the “T” shape by the first oil path  71  and the second oil path  72  each being a linear flow path, making it possible to easily form the flow path. This will reduce the cost for forming the flow path. 
     The three opening portions of the body  51  are formed in a manner to be distributed to three sides including the right/left sides and bottom side of the body  51 . Since one opening portion is formed on one face of the body  51 , this allows the body  51  to be compact, compared to a configuration with two opening portions formed on one face of the body  51 , for example. 
     With the flow path switching valve  50  according to the present embodiment, the symmetrical flow path can be configured, with a simple configuration, by the rotating operation of the valve body  52 . Therefore, the bucket  19  and the breaker  30  can be separately used with ease by switching the flow path with the flow path switching valve  50 . 
     In the flow path switching valve  50  according to the present embodiment, the locking protrusion portion  110  for positioning the valve body  52  is installed on the body  51  by inserting the detachable lock pin  111  into the support hole portion  112 . The body  51  has, as a portion for inserting the lock pin  111 , the left support hole portion  112 A used in the left flow path switching valve  50 L, and the right support hole portion  112 B used in the right flow path switching valve  50 R. 
     With the above configuration, depending on the mode of switching the flow path in the flow path switching valve  50 , replacing of the lock pin  111  can easily change the position for installing the locking protrusion portion  110 . When the flow paths to be switched are to be limited in different modes in the right and left flow path switching valves  50  by regulating the rotation of the valve body  52 ; depending on the position for mounting the lock pin  111 , the flow paths to be switched can be easily changed. 
     In particular, with the flow path switching valve  50  according to the present embodiment, replacing the lock pins  111  for the two support hole portions  112  can reverse the flow path on right and left in the right and left flow path switching valves  50 , making it possible to accomplish a symmetrical flow path switching configuration, including the mode of regulating the rotation of the valve body  52 . 
     Thus, by merely changing the insertion position of the lock pin  111 , the flow path switching valve  50  according to the present embodiment can be used either the left flow path switching valve  50 L or the right flow path switching valve  50 R. Therefore, all of the components themselves of the right and left flow path switching valves  50  can be common. This allows for lower costs and easier management of parts. In addition, regarding the mounting of the right and left flow path switching valves  50 , it is not necessary to flip the body  51  upside down at the right and left flow path switching valves  50 , for example, and mounting the right and left flow path switching valves  50  in the same mode on both sides can obtain a flow path configuration reversed on right and left, thus making it possible to eliminate any error in mounting the right and left flow path switching valves  50 . 
     In the flow path switching valve  50  according to the present embodiment, the hole portion  82   d  is formed at the actuator portion  82  as the valve body  52 &#39;s portion protruding from the body  51 . 
     With the above configuration, causing a rod-shaped matter such as a screwdriver having a certain rigidity to pass through the hole portion  82   d  can easily rotate, without using a dedicated tool, the valve body  52  for the switching of the flow path. For the outer shape of the hexagonal column-shaped actuator portion  82 , using a spanner, wrench, or other tool can naturally rotate the valve body  52 . 
     Also, the excavating work machine  1  according to the present embodiment has, as the flow path switching valve  50 , the left flow path switching valve  50 L installed on the oil path for supplying the hydraulic oil to the thumb cylinder  29  or the breaker  30 , and the right flow path switching valve  50 R installed on the oil path for discharging the hydraulic oil from the thumb cylinder  29  or the breaker  30 . 
     With the above configuration, a simple, inexpensive, and compact configuration can be achieved for the flow path switching valves  50  to be installed on both the right and left sides of the arm  18  of the excavating unit  3 . And, the flow path switching valve  50  according to the present embodiment is preferably used in the excavating work machine  1  that has the thumb  28  in the excavating unit  3  and replaces the bucket  19  and the breaker  30  depending on the nature of work at the site. 
     The flow path switching valve and construction machine according to the present invention described above are not limited to the embodiment described above, and various modes can be adopted to the extent according to the gist of the present invention. 
     In the embodiment described above, the flow path switching valve  50  is mounted on the side  41  of the arm  18 , but the position of placing the flow path switching valve  50  is not limited. The position of placing the flow path switching valve  50  may be, for example, on the back face or ventral face of the arm  18 , or on the left or right side of the boom  17 . 
     In the embodiment described above, the left flow path switching valve  50 L is the first flow path switching valve that receives the connection of the supply hose  101  at the first opening portion  61 , and the right flow path switching valve  50 R is the second flow control valve that receives the connection of the discharge hose  103  at the second opening portion  62 , but the above flow path switching valves  50  may be placed opposite on right and left. That is, it may be so configured that the right flow path switching valve  50 R is the first flow path switching valve, and the left flow path switching valve  50 L is the second flow path switching valve. 
     In the embodiment described above, the rotation regulating member included in the locking protrusion portion  110  is the lock pin  111  inserted into the support hole portion  112 , but the rotation regulating member may be, for example, a bolt-like member that is screw-fastened to the body. In this case, the bolt-like member is screwed into the threaded hole formed in the body  51  thereby to provide the locking protrusion portion  110 . 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1 : excavating work machine (construction machine) 
           2 : traveling unit 
           3 : excavating unit (front work unit) 
           17 : boom 
           18 : arm 
           19 : bucket 
           28 : thumb 
           29 : thumb cylinder 
           30 : breaker 
           41 : side 
           41   a:  left side 
           41   b:  right side 
           50 : flow path switching valve 
           50 L: left flow path switching valve (first flow path switching valve) 
           50 R: right flow path switching valve (second flow path switching valve) 
           51 : body 
           51   a:  front face 
           51   c:  right face 
           51   d:  left face 
           51   f:  bottom face 
           52 : valve body 
           61 : first opening portion 
           62 : second opening portion 
           63 : third opening portion 
           71 : first oil path 
           72 : second oil path 
           82 : actuator portion (valve body protruding portion) 
           82   d:  hole portion 
           83 : protruding edge portion 
           85 : communicating flow path 
           101 : supply hose 
           103 : discharge hose 
           110 : locking protrusion portion 
           111 : lock pin (rotation regulating member) 
           112 : support hole portion (mounting portion) 
           112 A: left support hole portion (first mounting portion) 
           112 B: right support hole portion (second mounting portion)