Patent Publication Number: US-2023147877-A1

Title: Seat device

Description:
TECHNICAL FIELD 
     The present invention relates to a seat device that can convert the state of a seat. 
     BACKGROUND ART 
     Conventionally, there are seats of a stool type mounted in, for example, railroad cars, which are long in both directions and can seat a plurality of persons, and are generally installed along walls in cabins. As for this seat, a rotary seat is known that can be rotated about a rotation axis in the center of the seat to convert the orientation between a long state where the back of the seat is parallel to and along a wall, and a cross state where the back of the seat is orthogonal to the wall. 
     As for such a rotary seat, a seat device has been proposed that includes a sliding mechanism in addition to a rotation mechanism of the seat, and further includes a transmission mechanism for interlocking each mechanism, so that the trajectory (turning radius) of the seat does not interfere with a wall, when rotating the seat from the long state along the wall to the cross state. Refer to, for example, Patent Literature 1. 
     That is, in the rotary seat, in order to expand the aisle width between seats on both sides in a cabin as much as possible to obtain a comfortable space, the rotation axis of the seat is located near a wall in the long state, while the rotation axis of the seat is slid to an aisle side in the cross state, so that the seat does not interfere with the wall. Therefore, in the rotary seat, in order to prevent the interference with the wall in the long state, it was necessary to regulate the rotation of the seat by operations by a seated person. 
     Here, as for a lock mechanism for regulating the rotation of the seat, a common configuration is a lock pin that is protruded toward the seat side from a fixed side of the seat. In this lock mechanism, as a configuration to prevent the seated person from performing a lock release operation only in the long state, it was insufficient to merely store a pedal for performing the lock release operation (refer to paragraph 0062 of Patent Literature 1). Therefore, for example, the technology has been known that provides a difference between an electric operation and a manual operation for the stroke of a lock pin from a locking position to a lock release position (refer to paragraph 0053 of Patent Literature 2). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Patent No. 3431772 
         Patent Literature 2: Japanese Patent Laid-Open No. 2018-016217 
       
    
     SUMMARY OF THE INVENTION 
     However, in conventional rotating apparatuses, in the lock mechanism for regulating the rotation of the seat, the configuration for preventing a seated person from performing the lock release operation only in the long state includes many parts and is complicated, and it has been desired to further reduce the cost. Additionally, it has been troublesome to achieve accuracy between parts, and there has also been a risk that malfunctions occur. 
     The present invention has been made by focusing on the problems of the related art as described above, and an object of the present invention is to provide a seat device that can reliably prevent a rotation operation of a seat by a seated person when the seat is in a specific state (long state), with a simple configuration, and without causing an increase in the cost. 
     In order to achieve the aforementioned object, in one aspect of the present invention, 
     a seat device that can convert a state of a seat includes 
     a rotation lock mechanism that can restrain a seat at each of a plurality of rotation angles, the seat being rotatable about a rotation axis, 
     a rotation operation unit that performs a release operation of restraint by the rotation lock mechanism, and 
     a rotation operation prevention mechanism that disables the release operation in the rotation operation unit, when the seat is in a specific state of one of the rotation angles, 
     the rotation operation prevention mechanism including 
     an engaging unit provided on a fixed side of the seat, and 
     an engaged unit that is provided in the rotation operation unit on a movable side of the seat, and disables the release operation in the rotation operation unit by being engaged with the engaging unit when the seat is in the specific state. 
     With the seat device according to the present invention, in a case where the state of the seat can be converted, the rotation operation of the seat can be reliably prevented when the seat is in the specific state, with a simple configuration, and without causing an increase in the cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 ( a )  is a perspective view of an entire seat,  FIG.  1 ( b )  is an enlarged perspective view of a reclining operation unit, and  FIG.  1 ( c )  is an enlarged perspective view of a rotation operation unit, showing a cross state of a seat device according to an embodiment of the present invention. 
         FIG.  2 ( a )  is a perspective view of the entire seat,  FIG.  1 ( b )  is an enlarged perspective view of the reclining operation unit, and  FIG.  1 ( c )  is an enlarged perspective view of the rotation operation unit, showing a long state of the seat device according to the embodiment of the present invention. 
         FIG.  3    is a perspective view showing an internal structure of the seat device according to the embodiment of the present invention. 
         FIG.  4    is a front view showing the cross state of the seat device according to the embodiment of the present invention. 
         FIG.  5    is a side view showing the long state of the seat device according to the embodiment of the present invention. 
         FIG.  6    is a perspective view showing a leg stand, a movable stand, and an underframe of the seat device according to the embodiment of the present invention. 
         FIG.  7    is a side view showing an initial position of the reclining operation unit of the seat device according to the embodiment of the present invention. 
         FIG.  8    is a side view showing an operation position of the reclining operation unit of the seat device according to the embodiment of the present invention. 
         FIG.  9    is a side view showing an initial position of each part of the reclining operation unit of the seat device according to the embodiment of the present invention. 
         FIG.  10    is a side view showing a state where each part of the reclining operation unit of the seat device according to the embodiment of the present invention is restrained in the initial position to disable the operation. 
         FIG.  11    is a side view showing a state where the rotation operation unit of the seat device according to the embodiment of the present invention is not restrained to disable the operation by the rotation operation prevention mechanism. 
         FIG.  12    is a side view showing a state where the rotation operation unit of the seat device according to the embodiment of the present invention is restrained to disable the operation by the rotation operation prevention mechanism. 
         FIG.  13    is a perspective view showing a rotation lock mechanism of the seat device according to the embodiment of the present invention. 
         FIG.  14    is a perspective view showing a state where the rotation lock mechanism of the seat device according to the embodiment of the present invention is seen from the bottom. 
         FIG.  15    is an explanatory diagram showing processes of converting the seat into the long state, one cross state, and a reverse cross state in the seat device according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, an embodiment representing the present invention will be described based on the drawings. 
       FIG.  1    to  FIG.  15    show one embodiment of the present invention. 
     A seat device  10  according to the present embodiment can convert the state of a seat  1 . Here, the state of the seat  1  is a concept including not only the orientation of the seat  1  by rotation, but also the change in the front and back position of the seat  1 , etc. Additionally, although the kind of the seat  1  is not particularly limited, a case will be described below as an example where the seat  1  is applied to a stool for two persons mounted in a cabin of a railroad car. Note that, in each figure, a slight difference in the shape of an identical part is merely a design change (for example, the difference in the shape of an underframe  30  in  FIG.  1    and  FIG.  6   , etc.). 
     &lt;Outline of Seat Device  10 &gt; 
     As shown in  FIG.  6   , the seat device  10  includes a leg stand  11  fixed on a floor surface, a movable stand  20  supported by the leg stand  11  so as to be able to advance and retract in front and back directions, and the underframe  30  of the seat  1  supported by the movable stand  20  so as to be rotatable in forward and backward directions. Here, the leg stand  11  is “a fixed side of the seat  1 ”, and the movable stand  20  and the underframe  30  are “a movable side of the seat  1 ”. Note that the seat device  10  is arranged on the floor surface near a wall (window) in the cabin of the railroad car, and “A” in  FIG.  6    is a part of the wall parallel to the moving direction of the railroad car. 
     In the seat device  10 , the underframe  30  of the seat  1  is supported on the movable stand  20  to be rotatable about a rotation axis via the rotation mechanism  40 . The movable stand  20  is supported on the leg stand  11  together with the rotation mechanism  40  via a sliding mechanism  14  so as to be able to advance and retract. Additionally, although an illustration is omitted, the seat device  10  includes an interlocking mechanism in order to interlock the rotation of the seat  1  by the rotation mechanism  40  with the advancement and retraction of the seat  1  by the sliding mechanism  14 . 
     &lt;Regarding Seat  1 &gt; 
     As shown in  FIG.  1   , the seat  1  is formed as a stool for two persons by arranging two seating portions  2  and backrests  3  side by side in both directions. A pair of sleeve portions  4  covering the seating portions  2  from the sides are provided on both sides of the seat  1 . An upper end side of each sleeve portion  4  serves as an armrest  5  that extends substantially horizontally in front and back directions. A lower end side of the backrest  3  is supported at a rear end side of the seating portion  2  via a reclining mechanism  50  (refer to  FIG.  3   ) in a tiltable manner. 
     &lt;Reclining Mechanism  50 &gt; 
     As shown in  FIG.  3   , the reclining mechanism  50  supports the backrest  3  with respect to the seating portion  2  in a predetermined angular range in a tiltable manner. The reclining mechanism  50  includes, for example, a damper  51  such as a gas spring. The damper  51  is configured such that a piston rod  53  is inserted into its cylinder body  52  so as to be able to protrude, and is arranged on the underframe  30  to be parallel to the front and back directions. Although the damper  51  is urged in a direction in which the piston rod  53  is housed in the cylinder body  52 , the piston rod  53  can be fixed in a state where only an arbitrary amount of the piston rod  53  is projected. 
     A rear end of the cylinder body  52  is connected to a lower end of a frame  3   a  of backrest  3  so as to be able to be pushed and pulled. On the other hand, a tip of the rod  53  that protrudes from a front end of the cylinder body  52  is connected to a proper place of a front end side of the underframe  30 . With such a damper  51 , the backrest  3  can be held at an arbitrary tilt angle. That is, when the damper  51  is a locked state, the piston rod  53  is fixed in a state where only a predetermined amount of the piston rod  53  is projected from the cylinder body  52 , so that the backrest  3  can be held at an arbitrary tilt angle. 
     When the locked state of the damper  51  is released, the backrest  3  returns to a most upright initial position by the biasing force with which the piston rod  53  is housed in the cylinder body  52 . When a seated person presses the backrest  3  backward against the restoring force of the damper  51  in this lock released state, the backrest  3  can be adjusted to an arbitrary tilt angle. 
     Although a detailed description of the lock mechanism of the damper  51  is omitted since the lock mechanism is common, a release button  54  for releasing the locked state is provided near the piston rod  53 . A reclining operation unit  100  for pressing this release button  54  to release the locked state is provided in a front end of the armrest  5 . Note that the reclining operation unit  100  corresponds to an “operation unit” of the present invention. 
     &lt;Reclining Operation Unit  100 &gt; 
     As shown in  FIG.  1   , in the reclining operation unit  100 , each component is incorporated and unitized in one housing  101 , and is incorporated inside the front end of the armrest  5 . The reclining operation unit  100  performs an operation (reclining operation) for tilting the backrest  3  by the reclining mechanism  50 . 
     As shown in  FIG.  9    and  FIG.  10   , the rotation operation unit  100  includes an operation lever  104  that is swingably supported by a supporting bracket  102  fixed to the housing  101  via an axis  103 . A lower end side of the operation lever  104  can be swung in front and back directions with the axis  103 , to which an upper end side of the operation lever  104  is pivotably supported, being the swing center. The operation lever  104  is swung between an initial position (refer to  FIG.  7   ) where the lower end side is housed in the housing  101 , and an operation position (refer to  FIG.  8   ) where the lower end side is pulled out forward. 
     A receiving member  105  of a reclining operation lock mechanism  110 , which will be described next, is fixed to a back side of the operation lever  104 . One end side of a reclining operation cable  106  extended to the release button  54  side is connected to the receiving member  105 . Here, by pulling the operation lever  104  forward to the operation position, a link on the release button  54  side is pulled via the reclining operation cable  106  to push the release button  54 , and the locked state of the damper  51  is released. Note that the operation lever  104  is normally urged backward to be housed at the initial position via the reclining operation cable  106 . 
     &lt;Reclining Operation Lock Mechanism  110 &gt; 
     Additionally, the reclining operation unit  100  is provided with the reclining operation lock mechanism  110  that can restrain the reclining operation unit  100  in an inoperable manner. The reclining operation lock mechanism  110  restrains the reclining operation unit  100  in an inoperable manner, when the seat  1  is in a long state (specific state), which will be described later. Note that the reclining operation lock mechanism  110  corresponds to a “lock mechanism” of the present invention. 
     As shown in  FIG.  9   , the reclining operation lock mechanism  110  includes a substantially L-shaped link  112  supported by the housing  101  via an axis  111  so as to be swingable in the front and back directions. In the link  112 , a lock pin  113  is further supported upward in one end side from the axis  111 . The lock pin  113  is disposed such that its upper end side penetrates through a guide hole  102   a  in the supporting bracket  102 , and protrudes in up-and-down directions with the swing of the link  112 . 
     The receiving member  105  on the back side of the operation lever  104  is provided with a lock hole  105   a  into which a tip of the lock pin  113  can protrude and fit, the lock hole  105   a  being provided at a lower location to which the lock pin  113  opposes when the operation lever  104  is in the initial position. Here, the link  112  that moves the lock pin  113  is normally urged by a spring member  114  in the clockwise direction around the axis  111  in  FIG.  9   , so as to be in a state where the lock pin  113  is disengaged from the lock hole  105   a  of the receiving member  105 . 
     One end side of a reclining lock cable  115  is connected to the other end side of the link  112  from the axis  111  via a connector  116 . The other end side of the reclining lock cable  115  is extended to a rotation operation unit  200  side, which will be described later. When the seat  1  is in the specific state (the long state, which will be described later), the reclining lock cable  115  restrains the reclining operation unit  100  in an inoperable manner by being pulled from the rotation operation unit  200  side. 
     That is, the reclining lock cable  115  swings the link  112  in the counter clockwise direction around the axis  111  in  FIG.  9    and  FIG.  10    by resisting the biasing force of the spring member  114 . Accordingly, since the lock pin  113  fits into the lock hole  105   a  of the receiving member  105 , the operation lever  104  is restrained in an inoperable manner. Note that the reclining lock cable  115  corresponds to “transmission means” of the present invention. 
     As shown in  FIG.  7    and  FIG.  8   , component parts of the reclining operation lock mechanism  110  arranged on the housing  101  are covered by a cover-like lid  101   a . An arc-shaped guide groove  101   b  centered on the axis  111  of the link  112  is formed in the housing  101  and the lid  101   a . An axis  117 , which pivotably supports the connector  116  to the other end of the link  112 , movably fits into the guide groove  101   b , and a swing centered on the axis  111  of the link  112  is regulated. 
     &lt;Regarding Orientation of Seat  1 &gt; 
     The seat device  10  can convert the state of the seat  1  between the long state (refer to  FIG.  6   ,  FIG.  2   ) in which the back of the seat is substantially parallel to and along a wall A, and a cross state (refer to  FIG.  1   ) in which the back of the seat is substantially orthogonal to the wall A. Here, for the cross state, there are one cross state (refer to  FIG.  1   ), and a reverse cross state that is 180 degrees in the opposite direction to the one cross state. As shown in  FIG.  15   , when it is assumed that the long state of the seat  1  has a rotation angle of 0 degrees as an original position, the rotation angle of the one cross state is 90 degrees, and the rotation angle of the reverse cross state is −90 degrees. Note that the back of the seat is synonymous with the back of the backrest  3 . Hereinafter, when collectively referring to the one cross state and the reverse cross state, they are merely written as the cross state. 
     &lt;Leg Stand  11 &gt; 
     As shown in  FIG.  6   , the leg stand  11  is fixed onto the floor surface near the wall A in the cabin. The leg stand  11  is formed by combining frame members into the shape of a stand that is long in the direction (front and back direction) substantially orthogonal to the wall A. Although an upper surface side of the leg stand  11  is substantially horizontal, and this upper surface side is surrounded by both side ends  12  and  12 , forming the long sides, and a rear end portion, forming a short side on the rear side (wall A side), the front side (aisle side) is opened. 
     The leg stand  11  is arranged so that its rear end portion is close to and substantially parallel to the wall A, and both side ends  12  and  12  are substantially orthogonal to the wall A and extend toward the aisle side. Note that, in addition to the sliding mechanism  14 , which will be described next, related parts such as a stopper for regulating the advance and retract range and the rotation direction of the underframe  30  are provided in the upper surface side of the leg stand  11 . 
     &lt;Sliding Mechanism  14 &gt; 
     As shown in  FIG.  6   , the movable stand  20  is attached to the upper surface side of the leg stand  11  via the sliding mechanism  14 , so as to be able to advance and retract in the direction substantially orthogonal to the wall A. The sliding mechanism  14  includes a pair of guide rails  14   a  and  14   a  that are provided inside both side ends  12  and  12  of the leg stand  11 . The pair of guide rails  14   a  and  14   a  are parallel to and oppose to each other along both the long sides of the upper surface of the leg stand  11 , and both side portions  21  and  21  of the movable stand  20 , which will be described next, directly and slidably fit inside the respective guide rails  14   a.    
     &lt;Movable Stand  20 &gt; 
     As shown in  FIG.  6   , the movable stand  20  is substantially horizontally arranged on the upper surface side of the leg stand  11 , and is formed by combining frame members into a rectangular framework shape. Both side ends  21  and  21 , forming the long sides of the movable stand  20 , slidably fit inside the aforementioned pair of guide rails  14   a  and  14   a . Thus, the movable stand  20  can be slid so as to advance or retract in the direction substantially orthogonal to the wall A. The rotation mechanism  40  that rotates the seat  1  about the rotation axis is provided at a substantially center of the movable stand  20 . 
     &lt;Rotation Mechanism  40 &gt; 
     The rotation mechanism  40  supports the underframe  30  of the seat  1  on the movable stand  20  so as to be rotatable in the forward and backward directions in a substantially horizontal surface. The rotation mechanism  40  is formed as a unit in which, for example, a pair of inner and outer ring-shaped turntables are rotatably combined with each other by interposing a bearing, etc. between them. In this rotation mechanism  40 , the outer turntable is fixed to the moving table  20 , and the inner turntable is fixed to the underframe  30 . 
     The rotation axis, which serves as the rotation center of the seat  1 , is the center line of the rotation mechanism  40 , and does not have a physical substance in the present embodiment. As shown in  FIG.  4   , the rotation mechanism  40  includes a motor  41 , which is a power source. The motor  41  is provided with a reducer, and a drive gear in its output axis is rotatably engaged with a sprocket  42  centered on the rotation axis provided in the underframe  30  side. Note that the rotation mechanism  40  also allows the seat to be manually rotated. 
     &lt;Underframe  30 &gt; 
     As shown in  FIG.  6   , the seat  1  is attached to the underframe  30 , and the underframe  30  is supported by the rotation mechanism  40  on the movable stand  20 . The underframe  30  is formed by, for example, a metal plate that corresponds to a bottom surface of the seating portion  2 . Although described above, the sprocket  42  with which the drive gear of the motor  41  rotatably engages is integrally provided in the bottom surface side of the underframe  30 . 
     &lt;Interlocking Mechanism&gt; 
     Additionally, the seat device  10  includes an interlocking mechanism (not shown) that interlocks the rotation and advancement and retraction of the seat  1 , so that the seat  1  does not interfere with the wall A, when converting the seat  1  to the long state, the one cross state, and the reverse cross state. 
     When the seat  1  is rotated with the underframe  30 , the interlocking mechanism converts the rotation of the underframe  30  into linear motion, transmits the linear motion to the movable stand  20 , and makes the movable stand  20  move in a linear direction so as to be close to or separated from the wall A together with the underframe  30 . Although the kind of such an interlocking mechanism is not particularly limited, specifically, for example, the invention already proposed by the present applicant and described in Japanese Patent Laid-Open No. 2018-187971 may be utilized, or, although not published, the invention proposed in Japanese Patent Application No. 2019-239066, etc. may be utilized. 
     &lt;Rotation Lock Mechanism  60 &gt; 
     The seat device  10  includes a rotation lock mechanism  60  that unrotatably restrains the underframe  30  (seat) in each rotation position of the long state, the one cross state, and the reverse cross state. Since the rotation lock mechanism  60  unrotatably locks the underframe  30  to the leg stand  11 , the movable stand  20  is also inevitably restrained to the leg stand  11  so as not to be able to advance and retract. 
     As shown in  FIG.  6   , the rotation lock mechanism  60  includes a lock pin  61  that can protrude up and down from the leg stand  11  side to the underframe  30 , and locking holes  62   a ,  62   b , and  62   c  that are provided in the underframe  30 , and with and from which the lock pin  61  are engaged and released. A total of three locking holes  62   a ,  62   b , and  62   c  are provided in a long side along the back of the seat, and both short sides along the seat of the substantially rectangular underframes  30 , respectively. 
     The lock pin  61  is incorporated in a unit  60   a , and the unit  60   a  is fixed near the rear end of the upper surface side of the leg stand  11 . The lock pin  61  is operated between a lock position at which the lock pin  61  can protrude upward from the upper surface side of the leg stand  11  to project upward and fit into the locking holes  62   a ,  62   b , and  62   c , and a lock release position at which the lock pin  61  retracts downward to be released from the locking holes  62   a ,  62   b , and  62   c.    
     When the seat  1  is converted into the long state, the one cross state, and the reverse cross state, the lock pin  61  unrotatably restrains the seat  1  by fitting into the locking holes  62   a ,  62   b , and  62   c  on the underframe  30  side to which the lock pin  61  vertically corresponds at the respective positions. That is, in the long state, the lock pin  61  fits into the locking hole  62   a  in one long side of the underframe  30 . Additionally, in the one cross state, the lock pin  61  is inserted into and engaged with the locking hole  62   b  in one short side of the underframe  30 . Furthermore, in the reverse cross state, the lock pin  61  fits into the locking hole  62   c  in the other short side of the underframe  30 . 
     As shown in  FIG.  13    and  FIG.  14   , the unit  60   a  in which the lock pin  61  is incorporated is provided with each of a spring member (not shown) that always urges the lock pin  61  to project upward to the lock position, and a link  60   b  that makes the lock pin  61  resist the biasing force of the spring member to retract to the downward lock release position. 
     The lock pin  61  is configured to be normally maintained in the lock position by the biasing force of the spring member, but to retract in the lock release position against the biasing force of the spring member, when the link  60   b  is pulled by each operating cable. Here, the other end side of the operating cable for manual operation is extended to the rotation operation unit  200  provided in the leg stand  11  side. Although described later, when the operating cable  206  (refer to  FIG.  11   ) is pulled by an operation in the rotation operation unit  200 , the restraint of the rotation lock mechanism  60  is released. 
     On the other hand, for example, the motor  41  of the rotation mechanism  40  also serves as the power source for pulling the operating cable for electric operation. That is, the motor  41  includes a clutch, and is configured to be able to switch between an operation for rotating the seat by the rotation mechanism  40 , and an operation for retracting the lock pin  61  to release the lock, by switching of the clutch. Note that a detailed description of the clutch of the motor  41  is omitted, since the configuration regarding the clutch of the motor  41  is common. 
     The rotation lock mechanism  60  according to the present embodiment is configured such that, when the seat  1  is in the long state, the restraint by the rotation lock mechanism  60  cannot be released by a manual operation in the rotation operation unit  200 , and can be released only by an electric operation by the motor  41 . Here, the electric operation is performed by a crew or station employee of a vehicle, and the manual operation is mainly performed by a passenger. 
     &lt;Rotation Operation Unit  200 &gt; 
     Additionally, the rotation lock mechanism  60  is provided with the rotation operation unit  200  for performing a release operation of the restraint by the lock pin  61 . As shown in  FIG.  1   , the rotation operation unit  200  is unitized by incorporating each part in one housing  201 , and is fixed to an attaching portion  22  (refer to  FIG.  6   ) hanging from the front end side of the movable stand  20 . 
     As shown in  FIG.  1  ( a ) ,  FIG.  2  ( a ) ,  FIG.  11   , and  FIG.  12   , the rotation operation unit  200  includes a step pedal  204  swingably supported by a lower end of a supporting bracket  202  fixed to the front surface side of the housing  201  via an axis  203 . A tip side of the step pedal  204  can be swung in the front and back directions, with the axis  203 , to which its base end side is pivotably supported, being the swing center. Note that the step pedal  204  corresponds to a “pedal” of the present invention. 
     The step pedal  204  is swung between a using position (refer to  FIG.  11   ) at which the tip side protrudes forward of the housing  201 , and a housing position (refer to  FIG.  12   ) at which the tip side withdraws upward. The step pedal  204  is normally urged to protrude forward to be in the using position via the spring member  205 . Here, when the step pedal  204  is in the using position, an operation of stepping on this to release the restraint by the rotation lock mechanism  60  is enabled, but when the step pedal  204  is in the housing position, the operation of releasing the restraint by the rotation lock mechanism  60  is disabled. Note that the spring member  205  corresponds to “biasing means” of the present invention. 
     The base end side of the step pedal  204  is connected to the other end side of the operating cable  206  for manual operation extended to the rotation lock mechanism  60  side via a connector. Here, when the step pedal  204  in the using position is stepped downward, the operating cable  206  is pulled and the lock pin  61  (refer to  FIG.  13   ) is retracted downward, and the locked state of the rotation lock mechanism  60  is released. 
     Additionally, a pin-shaped engaged portion  207  projecting in both directions at a position eccentric from the axis  203  is fixed to the base end side of the step pedal  204 . The engaged portion  207  is connected to the other end side of the reclining lock cable  115  extending from the reclining operation lock mechanism  110  side via a connector. Here, when the engaged portion  207  is engaged with an engaging portion  211 , which will be described next, the reclining lock cable  115  is pulled, and the lock pin  113  of the reclining operation lock mechanism  110  projects upward, and the reclining operation unit  100  is restrained to disable the operation. 
     &lt;Rotation Operation Blocking Mechanism  210 &gt; 
     Additionally, the rotation operation unit  200  is provided with a rotation operation prevention mechanism  210  that disables the release operation of the restraint by the rotation operation unit  200 . The rotation operation prevention mechanism  210  disables the operation of the step pedal  204  when the seat  1  is in the long state. The long state here corresponds to a “specific state where the seat  1  is at one rotation angle” in the present invention. 
     As shown in  FIG.  11    and  FIG.  12   , the rotation operation prevention mechanism  210  includes the engaging portion  211  provided in the leg stand  11 , which is the fixed side of the seat  1 , and the engaged portion  207  provided in the rotation operation unit  200  in the movable side of the seat  1 . The engaging portion  211  is arranged in the front end of the bottom surface side of the leg stand  11 , and is formed in a bracket shape that protrudes diagonally upward toward the front. 
     The engaged portion  207  is provided in the pin shape at the position eccentric from the axis  203  in the base end side of the step pedal  204  as described above. This engaged portion  207  is set to precisely engage with the engaging portion  211  when the seat  1  in the long state (specific state). Since the step pedal  204  is swung to be in the housing position against the biasing force of the spring member  205  when the engaged portion  207  is engaged with the engaging portion  211 , the release operation in the rotation operation unit  200  is disabled. At the same time, the reclining operation unit  100  is restrained to disable the operation. 
     &lt;Operation of Seat Device  10 &gt; 
     Hereinafter, based on  FIG.  15   , the operation of converting the state of the seat  1  will be described. First, as shown in  FIG.  15  ( a ) , when the underframe  30  (seat  1 ) is in the long state, the rotation axis (rotation mechanism  40 ) of the underframe  30  is most retracted (close) to the wall A side. Here, the long side of the underframe  30  (the back of the seat) is substantially parallel to and along the wall A, and the rotation angle is 0 degrees. 
     &lt;&lt;Restraint of Rotation Operation of Seat  1 &gt;&gt; 
     When the seat  1  is in the long state, the underframe  30  is restrained to disable the rotation with respect to the movable stand  20  by the rotation lock mechanism  60 . That is, as shown in  FIG.  6   , the lock pin  61  of the rotation lock mechanism  60  fits into the locking hole  62   a  in the one long side of the underframe  30 . Here, since the lock pin  61  protrudes from the leg stand  11 , which is the fixed side of the seat  1 , the seat  1  is not only restrained to disable the rotation, but also simultaneously restrained to disable advancement and retraction. 
     As shown in  FIG.  2   , when the seat  1  is in the long state, the release operation in the rotation operation unit  200  is disabled by the rotation operation prevention mechanism  210 . That is, in the long state, the movable stand  20  is most retracted (close) to the wall A side, and the front end side of the movable stand  20  overlaps with the front end side of the leg stand  11 . With this positional relationship, as shown in  FIG.  2  ( c ) , the engaged portion  207  of the step pedal  204  in the movable stand  20  is engaged with the engaging portion  211  in the leg stand  11 . Then, the step pedal  204  is swung to be in the housing position at which the step pedal  204  is upright against the biasing force of the spring member  205 , and is restrained in the housing position. 
     Accordingly, when the seat  1  is in the long state, the step pedal  204  is not only displaced to the housing position at which the operation is disabled, but also firmly held in the housing position by the engagement relationship between the engaging portion  211  and the engaged portion  207 . Thus, in the long state, the release operation in the rotation operation unit  200  is disabled. With such a simple configuration, the rotation operation of the seat  1  by a seated person can be reliably prevented in the long state. 
     &lt;&lt;Restraint of Reclining Operation of Backrest  3 &gt;&gt; 
     Additionally, when the seat  1  is in the long state, the reclining operation in the reclining operation unit  100  is disabled by the reclining operation lock mechanism  110 . To be more specific, when the step pedal  204  is swung upward by the engagement of the engaged portion  207  to the engaging portion  211 , the reclining lock cable  115  connected to the engaged portion  207  is pulled, and the reclining operation unit  100  is restrained to disable the operation. 
     That is, as shown in  FIG.  10   , when the reclining lock cable  115  is pulled, the link  112  is swung in the counter clockwise direction around the axis  111  in  FIG.  10    against the biasing force of the spring member  114 . Then, the lock pin  113  in the one end side of the link  112  projects upward to fit into the lock hole  105   a  in the receiving member  105  integrated with the operation lever  104  in the initial position. 
     Accordingly, when the seat  1  is in the long state, the reclining operation by the reclining operation unit  100  is disabled, and the backrest  3  cannot be tilted by the reclining mechanism  50 . With such a simple configuration, in the long state, the reclining operation of the backrest  3  by a seated person can be reliably prevented, and the backrest  3  can be prevented from being carelessly tilted to interfere with the wall A. 
     &lt;&lt;Conversion from Long State to One Cross State&gt;&gt; 
     As shown in  FIG.  15  ( a )  to  FIG.  15  ( c ) , in order to convert the underframe  30  (seat  1 ) into the one cross state from the long state (the rotation angle 90 degrees), first, it is necessary to release the restraint of the rotation by the rotation lock mechanism  60 . Here, the operation of disengaging the lock pin  61  from the locking hole  62   a  cannot be performed by the operation of the step pedal  204  as described above, and is performed by the electric operation utilizing the power of the motor  41 . 
     In the long state shown in  FIG.  15  ( a ) , when the underframe  30  is rotated by the motor  41  to the forward direction (the counter clockwise direction in  FIG.  15   ) as shown in  FIG.  15  ( b )  after releasing the restraint by the rotation lock mechanism  60 , the underframe  30  is rotated while moving forward by interlocking mechanism. That is, the underframe  30  is rotated while being rotated in the forward direction and moving forward to the aisle side, so as not to interfere with the wall A. 
     As shown in  FIG.  15  ( c ) , when the underframe  30  reaches the one cross state (the rotation angle 90 degrees), in  FIG.  6   , the lock pin  61  of the rotation lock mechanism  60  fits into the locking hole  62   b  in the one short side of the underframe  30 . Accordingly, the underframe  30  (seat  1 ) is unrotatably restrained in the one cross state. 
     &lt;&lt;Release of Restriction of Rotation Operation of Seat  1 &gt;&gt; 
     When the seat  1  is in the cross state, the restraint to disable the operation of the rotation operation unit  200  by the rotation operation prevention mechanism  210  is released. That is, in the cross state shown in  FIG.  15  ( c ) , the movable stand  20  is most advanced (separated) from the wall A side, and the front end side of the movable stand  20  is located farther forward from the front end side of the leg stand  11 . In this positional relationship, as shown in  FIG.  11   , the engaged portion  207  of the step pedal  204  in the movable stand  20  is not engaged with and separated from the engaging portion  211  in the leg stand  11 . Thus, the step pedal  204  protrudes forward to be in the using position by the biasing force of the spring member  205 . 
     At this time, the seated person of the seat  1  can release the restraint by the rotation lock mechanism  60  by stepping on the step pedal  204 . That is, in  FIG.  11   , when the step pedal  204  is stepped on to be swung, the operating cable  206  is pulled, the lock pin  61  (refer to  FIG.  13   ) is retracted downward, and the locked state of the rotation lock mechanism  60  is released. Accordingly, the seated person can manually rotate the seat  1 . 
     &lt;&lt;Release of Restriction of Reclining Operation of Backrest  3 &gt;&gt; 
     Additionally, when the seat  1  is in the cross state, the restraint to disable the operation of the reclining operation unit  100  by the reclining operation lock mechanism  110  is also released. That is, as described above, in the cross state, as shown in  FIG.  11   , the engaged portion  207  of the step pedal  204  in the movable stand  20  is not engaged with and separated from the engaging portion  211  in the leg stand  11 . Thus, the step pedal  204  protrudes forward to be in the using position by the biasing force of the spring member  205 , and the reclining lock cable  115  is in a state where the reclining lock cable  115  is not pulled. 
     Accordingly, as shown in  FIG.  9   , in the reclining operation lock mechanism  110 , the link  112  is in a state where the lock pin  113  is not made to project upward, by the biasing force of the spring member  114 . Thus, the lock pin  113  has come out of the lock hole  105   a  in the receiving member  105  integrated with the operation lever  104 , and the restraint to disable the operation of the operation lever  104  is released to enable the reclining operation. Therefore, the seated person can tilt the backrest  3  to an arbitrary angle by the reclining mechanism  50 , and can improve seating comfort. 
     &lt;&lt;Conversion from One Cross State to Reverse Cross State&gt;&gt; 
     In the one cross state shown in  FIG.  15  ( c ) , when the underframe  30  is rotated to the backward direction (the clockwise direction in  FIG.  15   ) after the restraint of the rotation lock mechanism  60  is released, the underframe  30  advances or retracts while, for example, being rotated by the interlocking mechanism, whose illustration is omitted. Subsequently, as shown in  FIG.  15  ( d ) , in a state where the underframe  30  is temporarily held at the position to which the underframe  30  has advanced in a state parallel to the long state, the underframe  30  is directly rotated to the opposite direction without advancing and retracting. 
     As shown in  FIG.  15  ( e ) , when the underframe  30  reaches the reverse cross state (the rotation angle −90 degrees), the lock pin  61  of the rotation lock mechanism  60  fits into the locking hole  62   c  in the other short side of the underframe  30 , and the underframe  30  is restrained again to disable the rotation. Such conversion of the seat  1  into the reverse cross state from the one cross state can be performed by not only the manual operation, but also by the electric operation. Note that, in order to return the seat  1  from the reverse cross state to the one cross state, and further from the one cross state to the original long state, the inverse operations of the aforementioned conversion from the long state to the one cross state, and from the one cross state to the reverse cross state may be performed, respectively. 
     &lt;Configuration and Effects of Present Invention&gt; 
     Although the embodiment of the present invention has been described above, the present invention is not limited to the aforementioned embodiment. The present invention derived from the aforementioned embodiment will be described below. 
     First, the present invention is 
     the seat device  10  that can convert the state of the seat  1 , including 
     the rotation lock mechanism  60  that can restrain the seat  1  at each of a plurality of rotation angles, the seat being rotatable about the rotation axis, 
     the rotation operation unit  200  that performs the release operation of restraint by the rotation lock mechanism  60 , and 
     the rotation operation prevention mechanism  210  that disables the release operation in the rotation operation unit  200 , when the seat  1  is in the specific state of one of the rotation angles, 
     the rotation operation prevention mechanism  210  including 
     the engaging unit  211  provided on the fixed side of the seat  1 , and 
     the engaged unit  207  that is provided in the rotation operation unit  200  on the movable side of the seat  1 , and disables the release operation in the rotation operation unit  200  by being engaged with the engaging unit  211  when the seat  1  is in the specific state. 
     In the present seat device  10 , when the seat  1  is in the long state, which is the specific state, although the back of the seat is close to the wall A, the rotation of the seat  1  by a passenger is disabled, so that the passenger cannot freely change the position. Here, it is necessary to release the restraint by the rotation lock mechanism  60  by the rotation operation unit  200  for rotating the seat  1 . Therefore, the rotation of the seat  1  can be disabled by disabling the operation of the rotation operation unit  200  by the rotation operation prevention mechanism  210 . 
     In the rotation operation prevention mechanism  210 , when the seat  1  is in the long state, the release operation of the rotation operation unit  200  is disabled by engaging the engaged portion  207  in the rotation operation unit  200  on the movable side of the seat  1  with the engaging portion  211  in the fixed side of the seat  1 . With such a mechanical engagement relationship between the engaging portion  211  and the engaged portion  207 , the rotation of the seat  1  by a seated person can be disabled only when the seat  1  is in the long state, with a simple configuration, and without using electric power. 
     Additionally, as the present invention, 
     the rotation operation unit  200  can be displaced between the using position at which the release operation is enabled, and the housing position at which the release operation is disabled, and 
     when the seat  1  is in the specific state, the rotation operation prevention mechanism  210  displaces the rotation operation unit  200  from the normal using position to the housing position, and restrains the rotation operation unit  200  in the housing position, by engaging the engaged portion  207  with the engaging portion  211 . 
     In this manner, in the present seat device  10 , when the seat  1  is in the long state, which is the specific state, the rotation operation unit  200  is displaced from the normal using position to the housing position, by engaging the engaged portion  207  with the engaging portion  211 . Therefore, the operation itself of the rotation operation unit  200  by a seated person cannot be performed, and the rotation of the seat  1  can be regulated in a manner that is easily understood by the seated person. 
     Moreover, the rotation operation unit  200  is not only merely displaced to the housing position, but also is restrained so as not to be displaced from the housing position by the engagement relationship between the engaging portion  211  and the engaged portion  207 . Therefore, it is also possible to reliably prevent an erroneous operation of carelessly returning the rotation operation unit  200  to the using position by the seated person. 
     Additionally, the present invention includes 
     the rotation mechanism  40  that rotates the seat  1  about the rotation axis, and 
     the sliding mechanism  14  that advances and retracts the seat  1  together with the rotation mechanism  40  from the fixed side, 
     wherein the state of the seat  1  can be converted by interlocking of the rotation mechanism  40  and the sliding mechanism  14  between 
     the long state where the back of the seat is substantially parallel to and along the wall A, and 
     the cross state where the back of the seat is separated from the wall A in the direction substantially orthogonal to the long state, and 
     the specific state of the seat  1  corresponds to the long state. 
     Accordingly, as described in the above embodiment, it becomes possible to directly apply the present seat device  10  to general rotary seats mounted in railroad cars. 
     Additionally, the present invention includes 
     the leg stand  11  fixed on the floor surface, as the fixed side of the seat  1 , and 
     the movable stand  20 , as the movable side of the seat  1 , the movable stand  20  being supported by the leg stand  11  via the sliding mechanism  14  so as to be able to advance and retract, the seat  1  being rotatably supported by the movable stand  20  via the rotation mechanism  40 , 
     wherein the engaging portion  211  is provided in the leg stand  11 , and 
     the rotation operation unit  200  and the engaged portion  207  are provided in the movable stand  20 . 
     In this manner, in the present seat device  10 , it is possible to achieve the layout that makes the engaging portion  211  and the engaged portion  207  of the rotation operation prevention mechanism  210  the optimum components, among the minimum required components of the seat device  10 . 
     Furthermore, as the present invention, 
     the rotation operation unit  200  includes the pedal  204  that is supported with the base end side being the rotation center, so as to be able to be swung between the using position at which the pedal  204  protrudes forward on the one end side of the movable stand  20 , and the housing position at which the pedal  204  is upwardly upright, 
     the engaged portion  207  is provided at the position eccentric from the rotation center of the pedal  204 , and 
     while the pedal  204  is normally maintained in the using position by the biasing means  205 , when the engaged portion  207  is engaged with the engaging portion  211 , the pedal  204  is swung to be in the housing position against the biasing force of the biasing means  205 , and is restrained in the housing position. 
     In this manner, in the present seat device  10 , among the minimum required components of the seat device  10 , it is possible to easily achieve the rotation operation unit  200 , and the engaging portion  211  and the engaged portion  207  of the rotation operation prevention mechanism  210  with a simple configuration. 
     Although the embodiments have been described above with the drawings, the specific configuration is not limited to these embodiments, and even when there are modification and addition in the scope not departing from the gist of the present invention, they are included in the present invention. 
     For example, the shapes of the leg stand  11 , the movable stand  20 , and the underframe  30  are not limited to those shown. Additionally, although the example of the seat  1  for two persons has been described, the seat  1  may be for three persons or one person. In addition, the conversion of the state of the seat is not limited to the long state, the one cross state, and the reverse cross state. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be widely utilized as a seat device for chairs for theaters, home, and office, in addition to the seat  1  for vehicles installed in cabins of railroad cars, airplanes, automobiles, marine vessels, etc. 
     REFERENCE SIGNS LIST 
     
         
           10  . . . Seat device 
           11  . . . Leg stand 
           14  . . . Sliding mechanism 
           20  . . . Movable stand 
           30  . . . Underframe 
           40  . . . Rotation mechanism 
           50  . . . Reclining mechanism 
           60  . . . Rotation lock mechanism 
           100  . . . Reclining operation unit 
           104  . . . Operation lever 
           105  . . . Receiving member 
           110  . . . Reclining operation lock mechanism 
           113  . . . Lock pin 
           200  . . . Rotation operation unit 
           204  . . . Step pedal 
           207  . . . Engaged portion 
           210  . . . Rotation operation prevention mechanism 
           211  . . . Engaging portion