Abstract:
A latch device includes a display apparatus having a display apparatus body installed in the ceiling portion or the like of a vehicle and a display section retracted so that it can be developed from the display apparatus body. A plunger section is fixed to the display apparatus body for driving an actuator section on the basis of input signals. A pressing structure is bent by the driving of the actuator section. Movement of a sliding structure is restricted by the bending of the pressing structure. A latch section projects toward the display section retracted in the display apparatus body in accordance with the movement of the sliding structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of Co-pending U.S. patent application Ser. No. 10/111,352, filed Apr. 22, 2002, which is now U.S. Pat. No. 6,811,129, and which is a Section 371 of International Application No. PCT/JP01/07071 filed on Aug. 16, 2001, the disclosures of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a fixture device for fixing a display apparatus on the ceiling portion of a vehicle, such as an aircraft, and to a fixture apparatus for fixing a display section to the display apparatus. 
     2. Background Technology 
     In recent years, entertainment systems for providing music, video images, etc. to passengers are provided in the cabin of a vehicle, such as a passenger aircraft; for this purpose, a display apparatus for displaying video images are installed. In particular, a display apparatus for the entertainment system of an aircraft is herein taken as an example to describe. 
       FIGS. 14(   a ) and ( b ) are perspective views showing a display apparatus body  4  having a display section  6 , such as an LCD display apparatus, installed in the ceiling portion and the lower portion of a baggage rack  5  in the cabin of a passenger aircraft.  FIG. 14(   a ) shows the retracted state (the state of nonuse) of the display section  6  of the display apparatus body  4 , and ( b ) of the same figure shows the state of use. In  FIGS. 14(   a ) and ( b ), the display apparatus body  4  is arranged at the lower portion of the baggage rack  5  of the passenger aircraft, and comprises the display section  6  and an open/close operation portion  7 . The display section  6  has a display member  8 , such as an LCD flat panel. The display member  8  is held by the open/close operation portion  7  so as to keep the most suitable angle to a passenger. The opening in the display apparatus body  4  is covered with a cover  9  to prevent dirt and dust from entering during the use of the display section  6 . 
     The display apparatus body  4  is fixed to the inside of a ceiling portion  3  at the lower portion of the baggage rack  5  by a fixture device that will be described below. 
       FIG. 15  is a sectional view showing the baggage rack  5  and the ceiling portion  3  below the lower portion thereof perpendicular to the direction from the rear to the nose of the aircraft (hereafter referred to as “nose direction”). In  FIG. 15 , the nose direction is a direction which is perpendicular to the face of the paper. Two rail installation stands  12  and  13  being parallel in the nose direction are fixed on the ceiling face  3 A of the ceiling portion  3 . A rail  14  is fixed to the lower face of the rail installation stand  12 , and a rail  15  is fixed to the lower face of the rail installation stand  13 . A left block  16  is attached to the rail  14 , and a right block  17  is attached to the rail  15 . As shown in  FIG. 19 , the left end portion  4 A of the display apparatus body  4  is supported by the rail  14  (not shown) via the two left blocks  16  installed with a predetermined distance therebetween in the nose direction indicated by an arrow  68 . In a similar way, the right end portion  4 B of the display apparatus body  4  is supported by the rail  15  (not shown) via the two right blocks  17  installed with a predetermined distance therebetween in the nose direction. In other words, the display apparatus body  4  is installed on the ceiling face  3 A via the two left blocks  16  and the two right blocks  17 . The fixture device that will be described below comprises the left blocks  16 , the right blocks  17  and a fixture block  25  that will be described later. 
     The display apparatus body  4  is required to be installable and removable on and from the rails  14  and  15  by simple operation so as to be replaced promptly at the time of a breakdown or the like.  FIGs. 16(   a ), ( b ), and ( c ) are perspective views showing the conventional left block  16  configured so as to be installable and removable easily.  FIGs. 16(   a ) to ( c ) show steps of installing the left block  16  on the rail  14  shown partially cut away. In  FIG. 16(   a ), the left block  16  is inserted into the rail  14  from the opening  14 A of the rail  4 . Next, as shown in  FIG. 16(   b ), a bar wrench  20  having a hexagonal cross-section is inserted into the hexagonal hole in a hexagonal socket head bolt  18  in the left block  16 , and turned about 90° in a direction indicated by an arrow  29 A as shown in (c) of the same figure. As a result, a nut plate  22  fixed to the tip of the hexagonal socket head bolt  18  is turned about 90°, whereby both the tip portions  22 A thereof engage the bent portions  14 B of the rail  14 . One left block  16  has two hexagonal socket head bolts  18 ; hence, by turning four hexagonal socket head bolts  18  in total for the two left blocks  16  about 90°, the two left blocks  16  are installed on the rail  14 . In this state, the left blocks  16  can be moved along the rail  14 . 
     As shown in  FIGS. 17(   a ) and ( b ), the fixture block  25  to be connected to the left block  16  is provided on the left end portion  4 A of the display apparatus body  4 .  FIG. 17(   a ) is a perspective view showing a state before the fixture block  25  is connected to an attachment window  24  formed in the left block  16 . The fixture block  25  has an arm  28  rotatably supported by a shaft  27  on a base plate  26 . The arm  28  is thinned like the shape of a comb to reduce its weight. A projection plate  29  is provided at the end of the arm  28 . The base plate  26  is fixed to the left end portion  4 A of the display apparatus body  4  by three sets of bolts and nuts  30 . The fixture blocks  25 , two in number, as many as the left blocks  16 , are fixed to the left end portion  4 A.  FIG. 17(   b ) shows a state wherein the projection plate  29  is inserted into the attachment window  24  of the left block  16  as will be described later in detail. 
     Next, description is made as to the right blocks  17  for supporting the right end portion  4 B of the display apparatus body  4  shown in  FIG. 15 . As shown in  FIG. 19 , the two right blocks  17  are fixed in advance with the predetermined distance therebetween on the right end portion  4 B of the display apparatus body  4 . 
       FIGS. 18(   a ) to ( c ) show steps of attaching the right block  17  of the display apparatus body  4  to the right rail  15 . Before these steps, at least two workers lift the display apparatus body  4 , and insert the projection plate  29  of the arm  28  of the fixture block  25  into the installation window  24  as shown in  FIG. 17(   a ). While one of the workers holds the display apparatus body  4  so that the projection plate  29  does not come out from the installation window  24 , the other worker connects the connector (not shown) of a connection cable, which supplies electrical power and signals to the display apparatus body  4 , to the display apparatus body  4  by using both hands. Subsequently, the right block  17  fixed to the right end portion  4 B of the display apparatus body  4  is inserted into the inside of the rail  15  from the opening  15 A of the rail  15  as shown in  FIG. 18(   a ). At the time of the insertion, a triangular guide plate  33  of the right block  17  facilitates the insertion of the right block  17  into the opening  15 A. The distance between the left and right rails  14  and  15  is not always constant but varies at various portions of the aircraft body. However, the projection plate  29  of the arm  28  shown in  FIG. 18(   a ) moves in and out from the insertion window  24  depending on the variation, whereby the installation of the right block  17  is done without causing problems in spite of some variations. 
     Next, as shown in  FIG. 18(   b ), a hexagonal socket head bolt  18  is turned by about 90° by using the wrench  20  in the direction indicated by an arrow  20 A as shown in (c) of the same figure. As a result, a nut plate  22  fixed to the tip of the hexagonal socket head bolt  18  is turned about 90°, whereby both the tip portions  22 A thereof engage the bent portions  15 B of the rail  15 . Two nut plates  22  are provided for one right block  17 ; hence, by turning four hexagonal socket head bolts  18  in total for the two right blocks  17  about 90°, the two right blocks  17  are attached to the rail  15 . By turning the four bolts  18  further by a number of turns, the bent portions  15 B are held between the tip portions  22 A of the nut plates  22  and the right blocks  17 , whereby the display apparatus body  4  is firmly fixed to the rail  15 . 
     The right block  17  shown in  FIG. 18  will be described further in detail. In the following explanations, the right block  17  is referred to as a fixture device  110 . 
       FIG. 20  is an external view of a conventional fixture device  110 . The fixture devices  110  are installed on the display apparatus body  4  as shown in  FIG. 21 . Next, as shown in  FIG. 22 , the display apparatus body  4  is fixed to the rails  111  on the body side in the ceiling portion of a vehicle by turning hexagonal socket head bolts  116  by using a bar wrench  112  having a hexagonal cross-section as shown in  FIGS. 25(   a ) to ( d ).  FIG. 23 , an exploded view, shows the configurations of the components of the conventional fixture device  110 .  FIGS. 24(   a ), ( b ), ( c ) and ( d ), elevation views, and  FIGS. 25(   a ), ( b ), ( c ) and ( d ), perspective view, show the sequence of the installation work. 
     A nut plate  114  shown in  FIG. 23  has an internal thread at its center, and installed between the rib  113   x  of a height X and the rib  113   y  of a height Y of a block  125 , by using bolts  116  each passing through a washer  117  and a highly flexible coil spring  120 . The following relationships are selected among the height X of the rib  113   x , the height Y of the rib  113   y  and the thickness (hereafter simply referred to as the thickness of the rail  111 ) of the rack portions  111   m  and  111   n  of the rail  111  shown in  FIG. 24 . Namely, the relationships are as follows: the height X ≦ the thickness of the rail  111  and the height X &lt; the height Y. 
     A nut  121  is engaged with the tip of the bolt  116  and fixed to the bolt  116  with an adhesive. At this time, as shown in  FIG. 24(   b ) and  FIG. 25(   b ), the nut  121  is turned when the bar wrench  112 , having a hexagonal cross-section, for example, is inserted into the hexagonal hole in the bolt  116  and raised and turned clockwise. As a result, the nut plate  114  passes the rib  113   x  ( FIG. 23)  having the height X of the block  113  and is turned clockwise. It is fixed to the bolt  116  so as to have a height making contact with the rib  113   y  having the height Y of the block  113 , and thereby not turning, if the wrench is turned counterclockwise. The block  113  is connected to the base  115  via a through shaft  123 , and the through shaft  123  is fixed by a split pin  124  inserted into the rear (right) end thereof. 
     In this configuration, the wrench  112  is inserted into the hexagonal hole of the bolt  116  and raised and turned clockwise. At this time, the nut plate  114  passes over the rib having the height X of the block  113 , turns clockwise and makes contact with the inner walls  111   w  ( FIG. 24  and  FIG. 25 ) of the rail  111  having a frame shape in cross-section, and then stops. The display apparatus  4  has nut plates at eight positions in total, and all of them are set in this state. However, when the bolts  116  are loosened slightly from its completely tight position, the display apparatus  4  can be moved slightly along the rail  111 , whereby positional adjustment is made possible. 
     By tightening the bolts  116  further as shown in  FIG. 24(   c ) and  FIG. 25(   c ), the conventional fixture device  110  is fixed to the rail  111 . By completely fastening the nut plates at all the eight positions in a similar way, the display apparatus  4  can be fixed completely to the rails  111  on the aircraft body in the ceiling portion. When removing the display apparatus  4 , the nut plate  114  is released by turning the bolt  116  counterclockwise, thereby releasing the friction force with the rack-shaped portions  111   m  and  111   n  of the rail  111 . The nut plate  114  is turned counterclockwise depending on the turning of the bolt  116  and makes contact with the higher rib on the upper face of the block  113 , that is, the rib  113   y  having the height Y. In this state, when the bolt  116  is turned counterclockwise further until the nut plate  114  is raised by the bolt  116  to a position making contact with the nut  121 , the nut plate  114  is moved beyond the rib  113   y  and becomes parallel with the opening groove  111   g  ( FIG. 25)  of the rail  111 . In a similar way, all the nut plates  114  at all the eight positions are turned counterclockwise so that the nut plates  114  become parallel with the opening grooves  111   g , whereby the display apparatus  4  can be removed from the rails  111  of the aircraft body in the ceiling portion. 
     Next, a latch device for fixing the display section  6  having the display member  8  to the display apparatus body  4  in a retracted state will be described. The display section  6  is retracted into the display apparatus body  4  during takeoff and landing. The display apparatus body  4  is provided with the latch devices to prevent the display section  6  from jumping out because of shocks and the like during takeoff and landing. 
     A conventional latch device will be described referring to  FIGS. 14(   a ) and ( b ) and  FIGS. 26(   a ) and ( b ).  FIGS. 26(   a ) and ( b ) show the latch operation of the conventional latch device. A conventional latch device  230  shown in  FIG. 26(   a ) is disposed on the display apparatus body  4  and engages the display section  6  retracted into the display apparatus body  4 , thereby preventing unnecessary opening of the display section  6 .  FIG. 26(   a ) shows the state of the engagement, and ( b ) thereof shows an intermediate state in an opening operation. Furthermore,  FIGS. 26(   c ) and ( d ) show intermediate states in the retraction. 
     The operation of the conventional latch device will be described below in accordance with an operation sequence shown in  FIGS. 26(   a ) to ( d ).  FIG. 26(   a ) shows a state wherein the display section  6  is retracted into the display apparatus body  4 , and the engagement protrusion  236  of the rotary shaft  234  of the latch device  230  engages the recessed section  260  formed at the bottom face of the display section  6 . The rotary shaft  234  is combined with a rotary plate  232  so as to be rotatable about a shaft  235 . The rotary shaft  234  is held by an elastic plate spring  237  that is bent slightly with respect to the rotary plate  232 . When the engagement protrusion  236  of the rotary shaft  234  engages the recessed section  260  of the display section  6 , a slide shaft  233  is inserted into a hole formed on the side face of the rotary plate. As a result, the rotary plate  232  is prevented from rotating, and the engagement state of the engagement protrusion  236  and the recessed section  260  is maintained. As a result, the display section  6  is prevented from jumping out from the display apparatus body  4  because of shocks and the like. 
       FIG. 26(   b ) shows a state wherein the opening operation is performed, that is, the display section  6  is rotated with respect to the display apparatus body  4  and opened. The open/close operation portion  7  ( FIG. 14)  controls a direct current applied to a plunger  238  by an opening command from a microcomputer provided outside the apparatus so that the opening operation is performed, that is, the display section  6  is rotated and opened. When the direct current flows through the plunger  238 , the slide shaft  233  disengages the hole in the rotary plate  232 . As a result, the rotary shaft  234  and the rotary plate  232  become integrally rotatable about the shaft  235 . Hence, the rotary shaft  234  is rotated by the opening operation of the display section  6 , and the engagement projection  236  disengages the recessed section  260 . 
     When the display section  6  no longer contacts the engagement protrusion  236 , the rotary shaft  234  and the rotary plate  232  are pressed by a spring  231  and return to a position shown in  FIG. 26(   a ). At this time, no direct current flows through the plunger  238 , and the slide shaft  233  is moved to its original position by a spring that is not shown. Therefore, the slide shaft  233  is inserted into the hole formed on the side face of the returned rotary plate  232  to obtain engagement of the display section  6  with the engagement protrusion  236  again. When the slide shaft  233  is inserted into the hole of the rotary plate  232  as described above, the engagement protrusion  236  of the rotary shaft  234  is held by the plate spring  237  so as to be rotatable about 40 degrees counterclockwise. 
     As described above, in the retraction state of the display section  6 , the slide shaft  233  is inserted into the hole in the rotary plate  232 . For this reason, the engagement protrusion  236  of the rotary shaft  234  does not rotate clockwise in  FIG. 26(   a ). Incidentally, in this retraction state, the engagement protrusion  236  is rotatable counterclockwise in  FIG. 26(   a ), but does not rotate further since the display apparatus body  4  is disposed above the display section  6 . 
       FIGS. 26(   c ) and ( d ) show the state of retracting the display section  6 . At this time, the engagement protrusion  236  of the rotary shaft  234  makes contact with the display section  6  and rotates counterclockwise. Then, when the engagement protrusion  236  engages the recessed section  260  of the display section  6 , the engagement protrusion  236  is returned to its original position by the plate spring  237 , and the display position  6  is securely retracted and held in the display apparatus body  4 . 
     The conventional fixture device has the following problems. When installing the display apparatus body  4  on the left and right rails  14  and  15 , at least two workers are required. Hence, one problem of the conventional fixture device is that the labor cost for the installation is high. 
     The present invention is intended to provide a fixture device for a display apparatus body, capable of being installed by one worker. 
     Furthermore, when an attempt is made to place the nut plate  114  on the rack-shaped portions  111   m  and  111   n  by inserting the wrench  112  into the hole in the bolt  116  and by raising and turning the wrench clockwise in this kind of conventional fixture device, if the nut plate  114  is not sufficiently raised, the nut plate  114  will not clear the rib  113   x , having the height X, of the block  113 . When the bolts are tightened in this state wherein the nut plate is present between the rib  113   x  and the rib  113   y  of the block  113 , having the height X and the height Y, respectively, as shown in  FIG. 24(   d ) (when the bolts are tightened at improper positions), both ends of the nut plate  114  are not placed properly on the rack-shaped portions  111   m  and  111   n  of the rail  111 . Hence, even when tightened, the nut plate  114  is only engaged with the upper face of the block  113  as shown at the upper right in  FIG. 25(   d ) and  FIG. 24(   d ). If both the nut plates  114  are in this state, the fixture device  110  disengages from the rail  111 . However, at this time, the bolts  116  are completely tightened and secured, just as in the case shown in  FIG. 24(   c ) wherein the bolts are tightened at proper positions. 
     Although one fixture device has two nut plates  114 , even if both of the bolts  116  are tightened firmly, this state is not reliable. This is because it is impossible to determine whether both of the nut plates  114  are installed at their proper positions because the state of the installation is unable to be seen from the outside. If all of the nut plates  114  are not placed on the rack-shaped positions  111   m  and  111   n  at the proper positions, proper strength cannot be obtained. Hence, if vibrations are encountered for an extended time, an improperly installed apparatus, such as a display apparatus, could potentially fall from the fixture device and land on a passenger seat below, presenting a very dangerous situation. 
     The present invention intends to solve the above-mentioned problem by detecting a wrong installation in the case that the nut plates are tightened at the improper positions. 
     Furthermore, in the conventional latch device, the rotary shaft  234  is rotated so that the engagement protrusion  236  engages the recessed section  260  in the display section  6 . Therefore, it is required that the size of the recessed section  260  in the display section  6  is made larger than the shape of the engagement protrusion  236  so as to give a clearance therebetween. As a result, a problem of the conventional latch device is that the retracted display section  6  rattles depending on the clearance when it receives shocks and the like. Furthermore, another problem of the apparatus is that, since the drive shaft of the plunger  238  is linearly connected to the slide shaft  233  in the drive direction thereof, the apparatus is relatively large. Still further, the conventional latch device comprises many components having complicated shapes, which increase the cost of production and cause the problem of raising the cost of the apparatus. 
     The present invention is intended to provide a latch device comprising a reduced number of components having simple shapes, wherein the latch devices provided for a display section and a display apparatus body are fitted securely without wobble in the retracted state, and the display apparatus provided with the latch devices can be made compact. 
     BRIEF SUMMARY OF THE INVENTION 
     A latch device in accordance with the present invention includes a display apparatus having a display apparatus body installed in the ceiling portion or the like of a vehicle and a display section retracted so that it can be extended from the display apparatus body. A plunger section, fixed to the display apparatus body, drives an actuator section on the basis of input signals. A pressing means is bent by the driving of the actuator section. A sliding means, that has its motion restricted by the bending of the pressing means, and a latch section that projects toward the display section retracted in the display apparatus body in accordance with the movement of the sliding means. 
     The latch device configured as described above comprises fewer number of components having simple shapes, and the display section can be securely fitted into the display apparatus body in its retraction state, whereby the display apparatus provided with the latch device can be made compact. 
     A latch device in accordance with another aspect of the present invention is configured so that the latch section has an upper latch and a lower latch, so that the upper latch and the lower latch are engaged with each other via balls so as to interlock with each other, and so that projection section fitted into the recessed section in the display section and inclined section making contact with the end portion of the sliding means are formed on the upper latch and the lower latch, and the upper latch and the lower latch of the latch section move in response to the movement of the sliding means. With this configuration, when the display section is retracted in the display apparatus body, the tip of the latch section of the latch device in accordance with the present invention is fitted in the recessed section in the display section, whereby the display section is prevented from jumping out from the ceiling portion or the like in which the display apparatus body is provided, owing to vibration, shocks and the like; when the display section is opened to a given angle by drive means, such as an electric motor or when the display section is retracted from its open state by elastic means, such as a spring, the latch section is pushed back, thereby not preventing the operation of the display section. 
     A latch device in accordance with another aspect of the present invention is configured such that holes engaging the balls in the upper latch are slots extending in the projection direction of the latch section, and holes engaging the balls in the lower latch are round holes preventing the rolling of the balls, when the upper latch moves in a direction opposite to its projection direction, the lower latch also moves horizontally, and when the lower latch moves in a direction opposite to its projection direction, the upper latch starts moving after the lower latch has moved by a predetermined distance. With this configuration, the latch device in accordance with the present invention does not prevent the operation of the display section when the display section is opened to a given angle by drive means, such as an electric motor, by components having simple shapes, and the latch device does not prevent the operation of the display section either when the display section is retracted from the open state into the ceiling portion having the display apparatus body by elastic means, such as a spring. 
     A latch device in accordance with another aspect of the present invention is configured such that when the display section is retracted in the display apparatus body, the projection sections of the upper latch and the lower latch are fitted into the recessed section in the display section, the upper latch is prevented from moving by the sliding means, and the inclined section of the lower latch makes contact with the end portion of the sliding means. With this configuration, the latch device in accordance with the present invention can reduce a clearance (a rattle) when the projection sections of the latch section are fitted into the recessed section in the display section. 
     A latch device in accordance with another aspect of the present invention is configured such that when the display section is developed from the display apparatus body, the actuator section is driven by the plunger section, the fixed state of the sliding means by the pressing means formed of a plate spring is released, and the sliding means is made movable so that the upper latch can move in the direction opposite to its projection direction. With this configuration, the latch device in accordance with the present invention does not prevent the extending operation of the display section when the display section is opened to a given angle by drive means, such as an electric motor, by components having simple shapes. 
     A latch device in accordance with another aspect of the present invention is configured such that when the display section is retracted into the display apparatus body, the display section makes contact with the lower latch, the lower latch is pushed back, the sliding means is driven by the movement of the lower latch, and the end portion of the sliding means makes contact with the inclined section of the upper latch so that the upper latch can move in the direction opposite to its projection direction. With this configuration, the latch device in accordance with the present invention does not prevent the operation of the display section when the display section is retracted into the display apparatus body, whereby the display section is retractable securely. 
     A latch device in accordance with another aspect of the present invention is characterized in that the plunger section and the sliding means are disposed so that the movement direction of the actuator is substantially perpendicular to the movement direction of the sliding means. With this configuration, the depth of the display apparatus body provided with the latch device in accordance with the present invention can be reduced. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1(   a ) is a perspective view showing a state before the connection of a left block  36  and a fixture block  45  in accordance with a first embodiment of the present invention; 
         FIG. 1(   b ) is a perspective view showing a state after the connection of the left block  36  and the fixture block  45 ; 
         FIG. 2  is an exploded perspective view showing the fixture block in accordance with the first embodiment of the present invention; 
         FIG. 3(   a ) is a sectional view taken on line III—III of  FIG. 1 , showing the connection state of the left block  36  and the fixture block  45  in accordance with the first embodiment of the present invention and also showing a state wherein the cut-and-raised portion  52 A of a release lever  52  falls in a latch hole  44 A; 
         FIG. 3(   b ) is a view showing a state wherein the cut-and-raised portion  52 A comes out from the latch hole  44 A; 
         FIG. 4  is a side sectional view showing a state wherein a display apparatus body hangs down from the left blocks; 
         FIG. 5  is a perspective view showing a fixture device in accordance with a second embodiment of the present invention; 
         FIG. 6  is an exploded perspective view showing the fixture device in accordance with the second embodiment of the present invention; 
         FIGS. 7(   a ), ( b ), ( c ) and ( d ) are sectional views showing a state wherein a display apparatus is fixed to a rail by the fixture device in accordance with the above-mentioned second embodiment; 
         FIGS. 8(   a ), ( b ), ( c ) and ( d ) are perspective views showing the installation steps of the fixture device in accordance with the above-mentioned second embodiment; 
         FIGS. 9(   a ), ( b ), ( c ), ( d ) and ( e ) are partially sectional views showing the display apparatus body and the display section provided with a latch device in accordance with a third embodiment of the present invention; 
         FIG. 10(   a ) is a plan view showing the latch device in accordance with the third embodiment;  FIG. 10(   b ) is a right side view;  FIG. 10(   c ) is a front view;  FIG. 10(   d ) is a left side view; and  FIG. 10(   e ) is a rear view; 
         FIG. 11(   a ) is a sectional view showing the latch device in accordance with the third embodiment, showing the retracted state of the display section; and  FIG. 11(   b ) shows the extended state of the display section; 
         FIG. 12(   a ) is an exploded perspective view showing the upper latch, lower latch, balls and latch springs of the latch device in accordance with the third embodiment;  FIG. 12(   b ) is a sectional view; and  FIG. 12(   c ) is a plan view of opposed faces of the upper latch and the lower latch; 
         FIG. 13(   a ) is a left side view showing a state wherein the latch device in accordance with the third embodiment is installed on the display apparatus;  FIG. 13(   b ) is a plan view;  FIG. 13(   c ) is a right side view of the opened display section; and  FIG. 13(   d ) is a front view of the opened display section; 
         FIG. 14(   a ) is a perspective view showing a state wherein the display section  6  of the display apparatus body  4  in accordance with the conventional example and the present invention in the ceiling portion of the cabin of a passenger aircraft is not used; and  FIG. 14(   b ) is a perspective view showing a state wherein the display section  6  is used; 
         FIG. 15  is a cross sectional view showing the ceiling portion of the cabin of the passenger aircraft provided with the display apparatus body in accordance with the conventional example and the present invention, viewed from the rear to the nose of the aircraft; 
         FIGS. 16(   a ), ( b ) and ( c ) are perspective views showing steps of installing the conventional left block  16  on the left rail  14 ; 
         FIG. 17(   a ) is a perspective view showing a state before the conventional left block  16  is connected to the fixture block  25 ; and  FIG. 17(   b ) is a perspective view showing a state after the connection; 
         FIGS. 18(   a ), ( b ), and ( c ) are perspective views showing steps of installing the conventional right block  17  on the right rail  15 ; 
         FIG. 19  is a bottom view showing the display apparatus body  4  in the ceiling portion of the cabin of the passenger aircraft, viewed from below; 
         FIG. 20  is a perspective view showing the conventional fixture device; 
         FIGS. 21(   a ), ( b ) and ( c ) are a bottom view, a front view and a side view, respectively, showing the display apparatus installed in the ceiling of the cabin; 
         FIG. 22  is a cross sectional view showing the ceiling portion of the cabin; 
         FIG. 23  is an exploded perspective view showing the components of the conventional fixture device; 
         FIGS. 24(   a ), ( b ), ( c ) and ( d ) are sectional views showing the operation steps for the conventional fixture device; 
         FIGS. 25(   a ), ( b ), ( c ) and ( d ) are perspective views showing the operation sequence at the time when the conventional fixture device is installed; and 
         FIGS. 26(   a ), ( b ) ( c ) and ( d ) are partial side views showing the operation of the conventional latch device. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Preferred embodiments of the present invention will be described referring to  FIG. 1  to  FIG. 13 . 
     First Embodiment 
     A fixture device in accordance with a first embodiment of the present invention will be described referring to  FIG. 1  to  FIG. 4 . The fixture device of the present invention is an improvement of the conventional fixture device comprising the left block  16  and the fixture block  25  for supporting the left end portion  4 A of the display apparatus body  4  in  FIG. 17  of the conventional technology. Since the configurations other than the left block and the fixture block are the same as those in the description of the above-mentioned conventional technology, the components are designated by the same reference numerals and described simply. 
       FIG. 1(   a ) is a perspective view showing the fixture device in accordance with the present invention, and shows a state before the projection plate  49  of a fixture block  45  is inserted into the installation window  44  of a left block  36  so as to couple both.  FIG. 1(   b ) shows a state after both have been coupled by the insertion. The left block  36  is attached to a rail  14  that is not shown, in accordance with steps similar to those for the conventional technology shown in  FIG. 16 . The base plate  46  of the fixture block  45  is fixed to the display apparatus body  4  with three sets of the bolts and nuts  30 . 
       FIG. 2  is an exploded perspective view of the fixture block  45 . In this figure, an arm  48  thinned like the shape of a comb has the projection plate  49  to be inserted into the installation window  44  of the left block  36 . As shown in the sectional view of  FIG. 3  (the cross-section III—III of  FIG. 1 ), the projection plate  49  has a hollow portion  57  having an opening in its lower face. A guide hole  58  communicating with the above-mentioned hollow portion  57  of the projection plate  49  is provided at the center portion of the arm  48  shown in  FIG. 2 . An L-shaped release lever  52  is inserted into the guide hole  58 . A plate spring  53  for applying a rotation force to the release lever  52  in a direction indicated by an arrow  60  and a holder  54  are placed upon the lever section  52 B of the release lever  52 , and fixed with two male screws  55  to the female threads  56  in the arm  48 . Hence, the release lever  52  is biased in the direction indicated by the arrow  60  in  FIG. 3(   a ). A cut-and-raised portion  52 A is provided at the tip of the release lever  52 . The cut-and-raised portion  52 A is a tongue-shaped section projecting downward from the lower face of the release lever  52  as shown in  FIG. 3(   a ). When the projection plate  49  is inserted into the installation window  44  of the left block  36  shown in  FIG. 1(   a ), the cut-and-raised portion  52 A falls into a latch hole  44 A in the installation window  44  as shown in  FIG. 3(   a ), thereby preventing the projection plate  49  from escaping from the installation window  44 . 
     When removing the projection plate  49  from the installation window  44 , the bent portion  52 B of the release lever  52  is pressed in a direction indicated by an arrow  66  as shown in  FIG. 3(   b ). As a result, the release lever  52  rotates in a direction opposite to the direction of the arrow  60  shown in  FIG. 3 , whereby the cut-and-raised portion  52 A is removed from the latch hole  44 A. When the arm  48  is pulled to the right in the figure in this state, the projection plate  49  comes out from the installation window  44 . Since the width of the latch hole  44 A is larger than the width of the cut-and-raised portion  52 A, the projection plate  49  can move slightly side-to-side with respect to the left block  36  in the state shown in  FIG. 3(   a ). 
     In  FIG. 2 , by passing a shaft  47  through holes  61 ,  63  and  64  in the base plate  46  and a hole  62  in the arm  48 , the arm  48  can be rotatably mounted on the base plate  46 . A split pin  62  is inserted into a fastening hole  59  formed at the right end of the shaft  47 , thereby preventing the shaft  47  from escaping. 
     Description is made as to steps of installing the display apparatus body  4  provided with the fixture devices in accordance with this embodiment on the left and right rails  14  and  15  shown in  FIG. 15  by one worker referring to  FIG. 1 ,  FIG. 3 ,  FIG. 4 ,  FIG. 16  and  FIG. 18 . The worker attaches the left blocks  36  to the rail  14  in accordance with steps similar to those for the conventional left blocks  16  shown in  FIG. 16 . The fixture blocks  45  in accordance with this embodiment are attached beforehand to the left end portion  4 A of the display apparatus body  4  by using the bolts and nuts  30 . Blocks similar to the conventional right blocks  17  shown in  FIG. 18  are attached beforehand to the right end portion  4 B of the display apparatus body  4 . The worker lifts the display apparatus body  4  configured as described above and inserts the projection plates  49  of the fixture blocks  45  into the installation windows  44  of the left blocks  36 . As shown in  FIG. 3(   a ), the cut-and-raised portion  52 A of the release lever  52  falls into the latch hole  44 A of the installation window  44  as shown in  FIG. 3(   a ), thereby preventing the projection plate  49  from being removed from the installation window  44 . When the worker releases his hands from the display apparatus body  4  in this state, the display apparatus body  4  hangs from the left blocks  36 , as shown in  FIG. 4 . The worker can connect connectors of connection cables, which supply electrical power and signals to the display apparatus body  4 , with both of his free hands. 
     After completion of connection of the connectors, the worker lifts the right end portion  4 B of the display apparatus body  4 , inserts the right blocks  17  into the openings  15 A of the rail  15  as shown in  FIG. 18 , and mounts the right blocks  17  on the rail  15  by using the wrench  20  in a method similar to the conventional method. Since the hole  44 A is made wider than the cut-and-raised portion  52 A, the projection plate  49  can move slightly with respect to the left block  36 , whereby the right block  17  can be inserted easily into the opening  15 A of the rail  15  even when a slight positional deviation is present between the rail  15  and the right block  17 . By turning the hexagonal socket head bolts  18  about 90° by using the wrench  20 , the right block  17  can be mounted on the rail  15 . 
     In this state, the left blocks  16  and the right blocks  17  are supported by the rails  14  and  15  via only the tip portions  22 A of the nut plates  22 . Hence, the display apparatus body  4  can be moved and positioned at a desired position by sliding the left blocks  36  and the right blocks  17  inside the rails  14  and  15 . After completion of the positioning of the display apparatus body  4 , the four hexagonal socket head bolts  18  for the two left blocks  36  and the four hexagonal socket head bolts  18  for the two right blocks  17  are turned by a number of turns in the direction indicated by the arrow  20 A shown in  FIG. 16  and  FIG. 18 . As a result, the bent portions  14 B of the rail  14  are held between the tip portions  22 A of the nut plates  22  and the upper face of the left block  36 , thereby fixing the left block  36  to the rail  14 . In a similar way, the bent portions  15 B of the rail  15  are held between the tip portions  22 A of the nut plates  22  and the upper face of the right block  17 , thereby fixing the right block  17  to the rail  15 . 
     Second Embodiment 
     A second embodiment of the present invention will be described referring to  FIG. 5  to  FIG. 8 ,  FIG. 14 ,  FIG. 20  and  FIG. 22 . The present embodiment relates to an improvement in a fixture device for fixing a display apparatus to a ceiling portion. 
     In the fixture device of the present embodiment, the nut plates of the fixture device are pushed upward, rotated into contact with the rail of the ceiling portion of a vehicle, and then tightened using bolts. Hence, the nut plates are fixed to the rail, thereby fixing the display apparatus to the ceiling portion. In a state before the bolts are tightened completely, the display apparatus can be moved to a desired position along the rail. 
     In the device of the present embodiment, when the bolt is tightened at an improper position such that the nut plate of the above-mentioned fixture device is not placed properly on the rack-shaped section of the rail at the ceiling portion of the vehicle, a wobble (play) occurs in the axial direction of the bolt. The fact that the device is improperly installed is identifiable by this wobble. Hence, the heavy display apparatus can be fixed securely on the ceiling portion of the vehicle, thereby enhancing safety and reliability. 
     Hereafter, the present embodiment will be described referring to  FIG. 5  to  FIG. 8 .  FIG. 14  and  FIG. 22  are also used in this explanation.  FIG. 14  shows the ceiling portion of a passenger aircraft and the display apparatus body  4  disposed therein.  FIG. 21  is a view showing the fixture positions of the fixture devices on the display apparatus.  FIG. 22  shows a state wherein the display apparatus shown in  FIG. 21  is fixed to the ceiling portion.  FIG. 5  is a perspective view showing the fixture device in accordance with this embodiment of the present invention.  FIG. 6  is an exploded perspective view showing the components configuration of the fixture device shown in  FIG. 5 .  FIGS. 7(   a ) to ( d ) are views showing the sequence of the installation operations of the device in this embodiment.  FIGS. 8(   a ) to ( d ) are perspective views showing the sequence of the operations in  FIGS. 7(   a ) to ( d ). 
     Although the block  113  and the like of the fixture device in accordance with this embodiment appear similar to those of the conventional fixture device in their external appearances, their main structures will be described below. The nut plate  114  has a threaded hole  241  having an internal thread in the center thereof. The tip portion of the hexagonal socket head bolt  116  passing through a washer  117 , a spring washer  118  having a predetermined compression deformation amount and placed thereon, a sleeve  119  having a predetermined length and placed thereon, and the flexible coil spring  120  outside the sleeve  119  are screwed into the threaded hole  241  in the nut plate  114 . Above the nut plate  114 , the nut  121  is screwed and bonded to the tip of the bolt  116 . The nut plate  114  is disposed between the lower rib (a small protrusion)  113   x  of a height X and the higher rib  113   y  of a height Y on the upper face of the block  113 . The following relationships are selected among the height X of the rib  113   x , the height Y of the rib  113   y  and the thickness D ( FIG. 7 ) (hereafter simply referred to as the thickness of the rail  111 ) of the rack portions  111   m  and  111   n  of the rail  111 . In other words, the relationships are as follows: [the height X]≦[the thickness D of the rail  111 ] and [the height X]&lt;[the height Y]. 
     At this time, as shown in  FIGS. 8(   b ) and ( c ), the nut  121  is turned when the bar wrench  112  having a hexagonal cross-section is inserted into the hexagonal hole in the bolt  116  and raised and turned clockwise, and the nut plate  114  passes the rib  113   x  ( FIG. 6) , having the height X, of the block  113  and turns clockwise. However, the nut plate  114  is fixed to the bolt  116  so as to have a height making contact with the rib  113   y , having the height Y, of the block  113  and thereby not turning when the wrench  112  is turned counterclockwise. The block  113  is connected to the base  115  by a through shaft  123 , and the through shaft  123  is fixed by the split pin  124  inserted into the rear (right) end thereof. 
     In this configuration, the wrench  112  is inserted into the hole in the bolt  116  and turned clockwise about 90° (substantially 90°) while the wrench  112  is raised. At this time, the nut plate  114  passes over the rib  113   x  having the height X of the block  113  and turns clockwise. Both end portions thereof make contact with the inner walls  111   w  of the frame-shaped rail  111  in cross-section ( FIG. 7  and  FIG. 8 ) and then stop. The eight nut plates in the display apparatus  4  are set in this state. However, when the bolts are loosened slightly instead of being tightened completely, the display apparatus  4  can be moved slightly along the rail  111 , whereby positional adjustment is made possible. 
     By tightening the bolts  116  completely as shown in  FIG. 7(   c ) and  FIG. 8(   c ), this fixture device  110  is fixed to the rail  111 . By completely fastening the nut plates  114  at all the eight positions in a similar way, the display apparatus  4  can be fixed completely to the rails  111  on the aircraft body in the ceiling portion. When removing the display apparatus  4 , the nut plate  114  is released by turning the bolt  116  counterclockwise, thereby releasing the friction force with the rack-shaped portions  111   m  and  111   n  of the rail  111 . 
     In  FIG. 6 , the nut plate  114  is turned counterclockwise as the bolt  116  is turned and makes contact with the higher rib on the upper face of the block  113 , that is, the rib  113   y  having the height Y. In this state, the bolt  116  is turned counterclockwise until the nut plate  114  is raised by the bolt  116  to a position making contact with the nut  121 . As a result, as shown in  FIG. 7(   d ), the nut plate  114  is moved beyond the rib  113   y  and becomes parallel with the opening groove  111   g  of the rail  111 . By a similar operation, all the eight nut plates  114  are turned counterclockwise. Hence, all the eight nut plates  114  become parallel with the opening grooves  111   g , whereby the display apparatus  4  can be removed from the rails  111  on the aircraft body in the ceiling portion. 
     In  FIG. 7(   d ) and  FIG. 8(   d ), when the wrench  112  is turned clockwise while pushing the bolt  116  upward, if the nut plate  114  is insufficiently raised, the nut plate  114  will not pass over the rib  113   x , having the height X, of the block  113 . Therefore, the nut plate  114  does not rotate and does not become perpendicular to the opening groove  111   g . (This also occurs when the nut plate  114  is rotated from a position other than its original position.) If fastening is carried out when the nut plate  114  is present between the rib  113   x  and the rib  113   y  of the block  113 , having the height X and the height Y, respectively, or, in other words, when the nut plate  114  is parallel with the opening groove  111   g  (if the fastening is carried out at an improper position) as described above, the nut plate  114  is only fastened to the upper face of the block  113  as shown in  FIG. 7(   d ) and is not fastened to the rack-shaped portions  111   m  and  111   n  of the rail  111 . 
     In the present embodiment, the length of the firmly fastened integration, comprising the head (the flange-shaped portion at the lower end in  FIG. 6 ) of the tightened bolt  116 , the washer  117 , the spring washer  118 , the sleeve  119 , and the nut plate  114 , is longer than the depth of a loose-fitting hole  113   u  for inserting the bolt of the block  113 . 
     In  FIG. 7(   d ), the diameter of the loose-fitting hole  113   u  in which the bolt and the coil spring are inserted is larger than the diameter of the sleeve  119  except proximate the upper face of the block  113 , whereby the sleeve  119  can move freely inside the loose-fitting hole  113   u . The diameter of the spring washer is selected so that the spring washer  118  can be inserted in the lower portion of the loose-fitting hole  113   u . In  FIG. 7(   d ), since the nut plate  114  does not project up to the upper faces of the rack-shaped portions  111   m  and  111   n  of the rail  111 , the lower face of the nut plate  114  does not rise from the upper face of the block  113  to a level to contact with the rack-shaped portions  111   m  and  111   n.    
     Hence, in this case, a clearance exists between the upper face of the nut plate  114  and the lower portion of the nut  121 . Furthermore, a clearance Z exists between the upper face of the washer  117  and the lower end of the loose-fitting hole  113   u  as shown in  FIG. 7(   d ). Therefore, when the wrench  112  is pushed up, the bolt  116  and the washer  117  are lifted while compressing the coil spring  120 . However, when the pushing force of the wrench  112  is released, the bolt  116  is pushed back downward by the recovery force of the coil spring  120 . 
     The relationship between the above-mentioned clearance Z and the dimension of each part and the actions thereof are described below. 
     (a) A condition wherein the bolt  116  is tightened sufficiently and properly: 
     [The thicknesses of the rack-shaped portions  111   m  and  111   n  of the rail  111 ]≧[The entire length of the sleeve  119 +the thickness of the flat washer  117 +the compressed thickness of the spring washer  118  reduced from that in the free state thereof] Furthermore, as shown in  FIG. 7(   d ), 
     (b) When constant play (clearance Z) occurs after improper and/or insufficient tightening, the dimension of the clearance Z is: 
     [The entire length of the sleeve  119 +the thickness of the flat washer  117 +the thickness of the compressed and flattened spring washer  118 ]−[the thickness of the block  113 ]=the clearance Z 
     The above-mentioned relationships (a) and (b) are arranged as follows: 
     [The thickness D of the rack-shaped portions  111   m  and  111   n  of the rail  111 ]&gt;the clearance Z 
     Since the clearance Z is formed by the above-mentioned configuration, when the wrench  112  is moved up and down by increasing or decreasing the upward pushing force, the flange face of the head of the bolt  116  strikes the step portion  113   d  of the block  113 , thereby causing rattling that can be heard and vibrations that can be felt. From this, it is understood that both end portions of the nut plate  114  are improperly coupled to the rack-shaped portions  111   m  and  111   n  of the rail  111 . In other words, the rattle heard and the vibrations felt, which occur when the washer  117  makes contact with the lower step portion  113   d  of the loose-fitting hole  113   u  of the block  114  because of the up-down movement of the bolt  116  from the deformations of the spring washer  118  and the coil spring  120 , are used as a means for indicating improper installation. 
     The spring washer  118  is used in the above-mentioned configuration to reliably turn the nut plate  114  substantially 90° by rotating the bolt  116  while pushing it up. As described above and as shown in  FIG. 7(   d ), in the present invention, play, that is, the clearance Z, is formed between the head (in reality, the washer  117  disposed just above it) of the bolt  116  and the lower face (in reality, the lower step portion  113   d  of the loose-fitting hole u) of the block  113 . To form this clearance Z, a loose-fitting cylinder having a predetermined length, that is, the sleeve  119 , is loosely fitted between the coil spring  120  and the bolt  116 . In this case, as shown in  FIG. 7(   b ), in a state wherein the bolt  116  is gently pushed up by using the wrench  112  or the like, the upper end of the sleeve  119  does not yet reach the lower face of the nut plate  114 . In other words, when the bolt is just pushed up with a gentle force, the sleeve  119  does not contact the nut plate  114 , as shown in  FIG. 7(   b ). If the sleeve  119  does not contact the nut plate  114  and the bolt  116  is pushed up and rotated, the nut plate  114  slides with respect to the bolt  116  and is not rotated accurately (the nut plate  114  remains even if the bolt  116  is rotated). However, when the spring washer  118 , having a predetermined compressive elastic force, is provided and the bolt  116  is pushed up by the predetermined compressive force to compress the spring washer  118 , as in the present invention, the nut plate  114  and the sleeve  119  are kept in contact by virtue of the upward pushing force. Consequently, friction increases between the nut plate  114  and the sleeve  119  and between the nut plate  114  and the bolt  118  connected thereto. For this reason, when the bolt  116  is pushed up and rotated, the nut plate  114  is turned securely without slipping. 
     In the above description, an example configured by using the spring washer  118  is described. However, even when a wire spring is used instead of this, this embodiment is realizable. Furthermore, even when only a wire spring is used instead of the configuration of the spring washer and the sleeve, this embodiment is realizable. 
     Third Embodiment 
     A latch device in accordance with a third embodiment of the present invention will be described referring to  FIG. 9  to  FIG. 13 . 
     The latch device described in this embodiment is disposed in the ceiling portion of a passenger aircraft and is used for a display apparatus for displaying video images. Therefore, since the latch device in accordance with this embodiment is used in a situation similar to that of the above-mentioned conventional display apparatus shown in  FIG. 14 , the latch device in accordance with this embodiment will be described referring to the reference numerals for the display apparatus used in  FIG. 14 . 
     As shown in  FIG. 14 , the display apparatus  3  is arranged in the lower portion of the baggage rack  5  in the ceiling portion  2  of the passenger aircraft, and comprises the display apparatus body  4 , the display section  6  is configured to be retractable into the display apparatus body  4 , and the open/close operation section  7  is used for opening/closing this display section  6 . The display section  6  is provided with the display member  8 , such as an LCD (liquid crystal display), serving as a flat panel display means. The display member  8  is supported at the most suitable angle. 
       FIGS. 9(   a ) to ( e ) are sectional views illustrating the engagement operation between the display apparatus body  4  provided with a latch device  250  in accordance with this embodiment and the display section  6  retracted into the display apparatus body  4 . The latch device  250  in accordance with this embodiment is disposed on the display apparatus body  4 , and is configured so that a latch section  300  having an upper latch  210  and a lower latch  211  is fitted into a recessed hole  214  formed on a side face of the retractable display section  6 . As shown in  FIG. 9(   a ), inside the display apparatus body  4 , a plunger  215  is disposed above the display member  8  of the retracted display section  6 . An actuator  216  serving as the drive shaft of this plunger  215  is driven in the leftward and rightward directions of the figure. When the plunger  215  is energized, the actuator  216  is moved rightward. As this actuator  216  is moved, a slide shaft  219  is configured to move up and down via a plate spring  218 .  FIG. 9(   a ) shows a state wherein the slide shaft  219  is pushed by the plate spring  218  and is moved downward.  FIG. 9(   b ) shows a state wherein the plate spring  218  is no longer pushing the slide shaft  219  and the slide shaft  219  is pushed up by a coil spring  220 . The coil spring  220  is provided between the rim  221  of the slide shaft  219  and the frame of the display apparatus body  4  and biases the slide shaft  219  upwardly at all times. 
       FIG. 10  is a view showing the latch device  250  provided for the display apparatus body  4 , wherein (a) is a plan view, (b) is a left view, (c) is a front view, (d) is a right view, and (e) is a rear view.  FIG. 11  is a side view of the internal mechanism of the latch device shown in  FIG. 10 , wherein (a) shows a state wherein the actuator  216  is moved leftward and (b) shows a state wherein the plunger  215  is energized and the actuator  216  is moved rightward. 
     As shown in  FIG. 10  and  FIG. 11 , one end of the plate spring  218  is fixed to the frame of the display apparatus body  4 , and the other end slidably engages an arm  217  attached nearly perpendicular to the tip of the actuator  216 . Therefore, with the leftward and rightward movements of the actuator  216 , the plate spring  218  presses the upper end of the slide shaft  219  and drives it upwardly and downwardly. In  FIG. 10 , open/close signals are sent from the open/close operation portion to the plunger  215  via a signal cable  222 . Furthermore, a hook  223  provided at the lower end of the latch device  250  engages the frame of the display apparatus body  4  to facilitate positioning thereof. 
       FIG. 12(   a ) is an exploded perspective view of the latch section  300 . The latch section  300  comprises the upper latch  210 , the lower latch  211 , four balls  212 , and two latch springs  213 .  FIG. 12(   b ) is a sectional view showing the latch section  300 , and ( c ) is a plan view showing the shapes of the opposed faces of the upper latch  210  and the lower latch  211 .  FIG. 12(   b ) is a sectional view taken along the line B—B of the plan view in ( c ). 
     As shown in  FIG. 12(   a ), in the latch section  300 , the upper latch  210  is attached to the lower latch  211  with the balls (steel balls)  212  held therebetween. Projection sections  210   p  and  211   p  are formed on the upper latch  210  and the lower latch  211  to fit into the recessed hole  214  in the display section  6 . A protrusion  211   b  is formed to protrude from a face of the lower latch  211  opposed to the upper latch  210 . The lower latch  211  and the upper latch  210  are positioned with respect to each other using the protrusion  211   b . Furthermore, holes for holding the balls  212  are formed on the mutually opposed faces (see  FIG. 12(   c )) of the projection sections of the upper latch  210  and the lower latch  211 . As shown in  FIG. 12(   c ), four round holes  211   c , for fixing and holding the balls  212 , are formed in the lower latch  211 . Slots  210   c  are formed in the upper latch  210  to hold the balls  212  so that the balls  212  are movable parallel to the projection direction (the X direction in  FIG. 12(   a )) of the projection section by a predetermined distance (about 0.5 mm). Furthermore, the upper latch  210  is pressed at all times by the latch springs  213  in a direction (the Y direction in  FIG. 12(   a )) opposite to the projection direction. 
     Since the latch section  300  is configured as described above, when only the upper latch  210  is pressed and moved in the Y direction ( FIG. 12(   a )), the lower latch  211  connected thereto via the balls  212  also moves simultaneously in the same direction. On the contrary, when only the lower latch  211  is pressed and moved in the Y direction, the upper latch  210  starts moving only after the lower latch  211  has moved by about 0.5 mm. 
     An inclined face  211   d  is formed on the rear side of the latch section  300  to contact the lower end of the slide shaft  219  at all times. The lower end of the slide shaft  219  is formed to have an inclined face to make face-to-face contact with the inclined face  211   d  of the latch section  300 . 
     Next, the operation of the latch device  250 , having the latch section  300  configured as described above, will be described referring to  FIGS. 9(   a ) to ( e ). 
       FIG. 9(   a ) is a state wherein the display section  6  is retracted into the display apparatus body  4 , and the upper latch  210  and the lower latch  211  are fitted into the recessed hole  214  of the display section  6 . At this time, the plate spring  218  presses the slide shaft  219  downwardly by virtue of the arm  217 , the tip of the slide shaft  219  presses the inclined face portion of the lower latch  211 , and the upper latch  210  makes contact with the side face of the slide shaft  219 . As a result, even when the latch section  300  is pressed by the display section  6 , no retraction operation is performed, and the display section  6  does not perform the opening operation by which the display section  6  is rotated with respect to the display apparatus body  4  to open the display section  6 . 
       FIG. 9(   b ) shows an initial state for performing the opening operation by which the display section  6  is rotated with respect to the display apparatus body  4  and is opened. When the display section  6  is subjected to the opening operation, the plunger  215  is energized by an opening command from a microcomputer outside the apparatus, and the actuator  216  is moved rightwardly, as shown in  FIG. 9(   b ). The plate spring  218  is pulled rightwardly by the movement of the actuator  216 , thereby releasing the restriction of the movement of the slide shaft  219 . Hence, the slide shaft  219  is moved upwardly by the elastic force of the coil spring  220 . As a result, the inclined face portion of the upper latch  210  makes contact with the tip of the slide shaft  219 , whereby the upper latch  210  is pushed by the latch spring  213  and moves leftwardly in  FIG. 9(   b ). At this time, the lower latch  211  also moves by the same distance. Hence, the projection distance of the projection section of the latch section  300  is decreased. 
     The state shown by  FIG. 9(   c ) is a state wherein the display section  6  has turned with respect to the display apparatus body  4  from the state shown in  FIG. 9(   b ). In this state, when the display section  6  is subjected to the opening operation, the upper latch  210  and the lower latch  211  are pushed by the display section  6  and moved leftward further. At this time, since the upper latch  210  makes contact with the inclined face of the tip of the slide shaft  219 , the slide shaft  219  is lifted upwardly by the leftward movement of the upper latch  210 . At this time, since the upper end of the slide shaft  219  makes contact with the plate spring  218  that is in a bendable state, the slide shaft  219  upwardly movable. In this state, the lower latch  211  is able to be moved leftward with respect to the upper latch  210 . 
       FIG. 9(   d ) shows a state wherein the display section  6  has turned further from the state in  FIG. 9(   c ) and is completely separated from the latch section  300 . At this time, no direct current flows to the plunger  215 , and the actuator  216  has returned to its original position (the state shown in  FIG. 9(   a )). As a result, the slide shaft  219  is pushed down by the plate spring  218 , and the upper latch  210  and the lower latch  211  return to their original positions. 
       FIG. 9(   e ) shows a state wherein the display section  6  is retracted into the display apparatus body  4 , and the display section  6  makes contact with the lower latch  211 . At this time, the lower latch  211  is pressed by the display section  6  and moved leftwardly. At this time, since the lower latch  211  makes contact with the inclined face of the tip of the slide shaft  219 , the slide shaft  219  is lifted upwardly and the plate spring  218  is lifted upwardly. Since the rotation force at the time when the display section  6  is retracted is sufficiently larger than a load at the time when the display section  6  is displaced because of shocks or the like, the upper latch  210  is also moved leftwardly. 
     In the above-mentioned retraction operation, the lower latch  211  initially moves because of the contact between the display section  6  and the latch section  300 . After the lower latch has moved about 0.5 mm, the slide shaft  219  is pushed upwardly, and the inclined face of the tip of the slide shaft  219  makes contact with the inclined face portion of the upper latch  210 . Since the upper latch  210  makes contact with the inclined face of slide shaft  219 , as described above, when the lower latch  211  is moving, the upper latch  210  starts moving leftward via the balls  212 . The upper latch  210  and the lower latch  211 , moving in this way, are returned to their original positions by the elastic force of the plate spring  218  when they are fitted into the recessed hole  214  in the display section  6 , whereby the display section  6  is securely held in the display apparatus body  4 . 
       FIG. 13  is a view showing a state wherein the latch device in accordance with this embodiment is built in the display apparatus body  4 , wherein (a) is a left side view, (b) is a plan view, (c) is a right side view showing a state wherein the display section  6  is opened, and (d) is a front view showing a state wherein the display section  6  is opened. 
     As described above, in the latch device in accordance with this embodiment, the slide shaft  219  and the actuator  216  of the plunger  215  are disposed in the shape of an L. In this way, it is possible to prevent the apparatus from becoming larger in size because of the mounting of the latch device, and a compact apparatus is achieved. 
     INDUSTRIAL APPLICABILITY 
     As described above in detail in each embodiment, in accordance with the present invention, by inserting the projection plates of the fixture blocks at the left end portion of the display apparatus body into the installation windows in the left blocks attached on the rail, the fixture blocks are fixed to the left block. Therefore, the display apparatus body will not fall even when a worker releases his hands from the display apparatus body. In this way, the worker can carry out necessary cable connection work with both of his free hands. After the completion of the cable connection work, the worker lifts the right end portion of the display apparatus body and fixes the right blocks to the rail. Since these steps of work can be carried out by one worker, the cost of labor for the installation is reduced. 
     In the fixture device in accordance with the present invention, when the nut plate does not pass the rib of the height X of the block but is present between the rib of the height X and the rib of the height Y (in other words, when it is in a state of being fastened at an improper position), the bolt moves up and down and rattles when pushed with a wrench or the like. Because of this, it is possible to detect that the fixture is improperly installed. Hence, the heavy display apparatus can be fixed securely to the ceiling portion of the vehicle, thereby enhancing safety and reliability thereof. 
     In the latch device in the present invention, in the state wherein the display section is retracted into the display apparatus body, the display section and the display apparatus body are fitted securely, whereby rattles due to vibration, shocks, etc. are not caused. 
     Furthermore, in accordance with the present invention, the latch device is configured in the shape of an L, whereby the depth of the display apparatus body provided with the latch device can be reduced. 
     Still further, since the latch device in accordance with the present invention comprises reduced number of components and the shapes of components are simple in comparison with a conventional device, it is easier and less costly to produce than the conventional latch device.