Abstract:
In order to improve workability of an operation to adjust the interval between two members, leveling devices ( 3 ) support an air rail ( 2 ) on base frames ( 1 ), and adjust the height of the air rail ( 2 ) with respect to the base frames ( 1 ). The leveling devices ( 3 ) have: disc spring groups ( 31 ) which expand and contract in the height direction of the air rail ( 2 ) with respect to the base frames ( 1 ); a columnar indenter ( 32 ), in which a stepped through-hole ( 324 ) for inserting a bolt ( 4 ) is formed from one end face ( 321 ) to the other end face ( 323 ), with a first edge part ( 322 ) formed outward on the one end face ( 321 ) side; a columnar spring guide ( 33 ), in which a through-hole ( 334 ) for inserting the bolt ( 4 ) is formed from one end face ( 331 ) to the other end face ( 333 ), with a flange part ( 332 ) formed outward on the one end face ( 331 ) side; and a tubular housing ( 34 ) in which a second edge part ( 342 ) is formed inward at one opening ( 341 ) thereof.

Description:
This application is the U.S. national phase of International Application No. PCT/JP2013/059019 filed 27 Mar. 2013 which designated the U.S. and claims priority to Japanese Patent Application No. 2012-092788 filed 16 Apr. 2012, the entire contents of each of which are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to an interval adjustment device, and particularly to structure of a leveling device suitable for a floating transportation apparatus that transports an object of transportation in a floated state. 
     BACKGROUND ART 
     As a floating transportation apparatus that transports an object such as a substrate used for a flat-panel display (FPD) in a state of being floated above a transportation surface, a substrate transportation apparatus described in the Patent Document 1 is known. 
     This floating transportation apparatus transports a substrate in the direction of transportation while floating the substrate as the object of transportation by blowing compressed air from transportation surfaces of arranged floating blocks. Here, to allow adjustment of respective heights and flatness of the floating blocks, the floating blocks are fixed on respective movable plates by screws, so that an interval between each movable plate and a fixed plate can be adjusted at three points. 
     In detail, a movable plate, which projects from both sides of the bottom of each floating block, has female threads at three positions in total. The fixed plate has female threads at positions opposite to the female threads of each movable plate, and a pitch of the female threads of the fixed plate is different from that of the female threads of the movable plate. Further, an adjust screw, which has male thread portions screwable into the female threads of the movable plate and the fixed plate, is screwed into each pair of opposite female threads in a state that the adjust screw is inserted in a spring placed between the movable plate and the fixed plate. A worker can adjust the interval between a movable plate and the fixed plate by inserting a tool between adjacent floating blocks and turning an adjust screw so as to increase or decrease the interval by the distance corresponding to the difference between the pitches of the female threads of both the plates. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Laid-Open No. 2009-229258 
     SUMMARY OF INVENTION 
     Technical Problem  
     In the substrate transportation apparatus described in the Patent Document 1, to fix a movable plate to the fixed plate, a worker has to place a spring around an adjust screw inserted in a female thread of the movable plate, and has to position the tip of the adjust screw at the corresponding female thread of the fixed plate while holding the spring to keep them from dropping off. Thus, its workability is not good. 
     Further, it is necessary to ensure space on both sides of a floating block for a worker to do fastening or loosening work on an adjust screw, and thus it is impossible to narrow the gap between adjacent floating blocks further and to make adjacent floating blocks contact closely with each other. Accordingly, at a location of a gap between adjacent floating blocks, it is impossible to blow compressed air onto an object of transportation under good conditions, and it can lead to an unstable floating state of the object of transportation. 
     The present invention has been made considering the above situation. And an object of the present invention is to provide a technique that improves workability of adjustment of an interval between two members. 
     Solution to Problem 
     To solve the above problem, the present invention provides an interval adjustment device for adjusting an interval between two members, in which a plurality of component parts including an elastic body or the like has unit structure that allows easy assembling, and which fixing of one member to the other member and adjusting of the interval between the two members can be performed by using one bolt. 
     For example, the present invention provides an interval adjustment device, which is placed between two members for adjusting an interval between the two members, comprising: 
     an elastic body, which expands and contracts in a direction of the interval; 
     a presser of a tubular shape, which comprises: a stepped through-hole formed from one end face toward other end face to have a large-diameter portion on a side of the one end face and a small-diameter portion on a side of the other end face; and a first edge portion formed outward on the side of the one end face; 
     a guide member of a tubular shape, which comprises: a columnar portion having a through-hole formed to run from one end face to other end face, a side of the other end face being inserted into the large-diameter portion of the stepped through-hole; and a flange portion formed outward at the one end face of the columnar portion; and 
     a housing of a tubular shape, in which a second edge portion is formed inward at one opening portion; and wherein, 
     the housing is placed between the two members such that other opening portion on an opposite side to the one opening portion faces one member between the two members; 
     the presser is housed in the housing such that the first edge portion is in contact with the second edge portion and the other end face of the presser projects from the one opening portion of the housing to abut against the other member between the two members; 
     the side of the other end face of the columnar portion of the guide member is inserted into the large-diameter portion of the stepped through-hole of the presser housed in the housing, so that an axis of the through-hole coincide with an axis of the stepped through-hole, and a hollow portion of a tubular shape is formed by an inner surface of the housing, a side surface of the guide member, the first edge portion, and the flange portion; and 
     the elastic body is placed in the hollow portion so that the guide member is biased in the direction of being pushed out from the other opening portion of the housing so as to be pressed against the one member between the two members. 
     Advantageous Effects of Invention 
     The present invention can improve workability of operation of adjusting an interval between two members. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an external view showing a general configuration of a transportation platform  100  of a floating transportation apparatus according to an embodiment of the present invention; 
         FIG. 2(A)  is an external view showing a base frame  1 , and  FIG. 2(B)  is an A-A cross-section view of the base frame  1  shown in  FIG. 2(A) ; 
         FIG. 3(A)  is an external view showing an air rail  2 , and  FIG. 3(B)  is an enlarged B-B cross-section view of the air rail  2  shown in  FIG. 3(A) ; 
         FIG. 4(A)  is an external view showing a leveling device  3 , and  FIG. 4(B)  is a C-C cross-section view of the leveling device  3  shown in  FIG. 4(A) ; 
         FIG. 5(A)  is an external view showing a hexagon socket head bolt  4 , and  FIG. 5(B)  is a cross-section view of a T-nut  5 ; 
         FIG. 6(A)  is a cross-section view for explaining assembling work of the leveling device  3 , and  FIG. 6(B)  is a cross-section view for explaining work of fixing the leveling device  3  to the air rail  2 ; and 
         FIG. 7  is a cross-section view for explaining work of fixing the air rail  2  to the base frame  1 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS  
     In the following, one embodiment of the present invention will be described. 
       FIG. 1  is an external view showing a general configuration of a transportation platform  100  of a floating transportation apparatus according to one embodiment of the present invention. 
     As shown in the figure, the floating transportation apparatus of the present embodiment comprises the transportation platform  100  for transporting an object such as a glass substrate used for an FPD, a solar battery panel or the like in a state of floating from a transportation surface  21 . The transportation platform  100  comprises: two base frames (for example, aluminum frames)  1  of rectangular column shapes, which are arranged side by side with a prescribed space between them; an air rail  2  of a plate shape, which is placed to extend over the two base frames  1 ; and two leveling devices  3  (partially not shown) for each base frame  1  (namely, four leveling devices  3  in total). The present embodiment shows an example in which one air rail  2  is placed over two base frames  1 . However, in practice, a plurality of air rails  2  are placed over two base frames  1  each having the length of the transportation distance for example, being placed side by side in the longitudinal direction (Y direction in  FIG. 1 ) of the base frames  1 . Further, although in the present embodiment one air rail  2  is supported by the four leveling devices  3 , it is sufficient to use the leveling devices  3  to the number that can support the air rail  2  stably. 
     Although not shown in  FIG. 1 , the transportation platform  100  further comprises: bolts  6  for fixing the leveling devices  3  to the air rail  2 ; hexagon socket head bolts  4  and T-nuts  5  for fixing the air rail  2  to the base frames  1  via the leveling devices  3  (See  FIG. 7 ). As for the bolts  6 , two bolts  6  are used for each leveling device  3 . Further, a hexagon socket head bolt  4  and a T-nut  5  are used as a pair for each leveling device  3  (i.e. four pairs in total are used in one air rail  2 ). 
       FIG. 2(A)  is an external view of a base frame  1 , and  FIG. 2(B)  is an A-A cross-section view of the base frame  1  shown in  FIG. 2(A) . 
     As shown in the figure, in each of four outer surfaces (an upper surface  12 A, a left side surface  12 B, a lower surface  12 C and a right side surface  12 D) of the base frame  1 , is formed a T-shaped groove  11  for placing a T-nut  5  at a desired position in the longitudinal direction of the base frame  1 . The T-shaped groove  11  has a T-shaped cross-section including a step  113  at which the groove width changes from s1 to s2 (&gt;s1) between a groove edge  112  and a groove bottom  111 . The T-shaped groove  11  continues from one end face (a face perpendicular to the longitudinal direction)  13  of the base frame  1  to the other end face  14 . By this T-shaped groove  11 , are formed T-shaped openings in both end faces  13 ,  14  of the base frame  1 . Thus in each of the four outer surfaces  12 A- 12 D, an opening of the groove width s1 continuing from the one end face  13  to the other end face  14  is formed. 
     As the base frame  1 , the present embodiment uses a four-grooved-surface type frame, which has four outer surfaces  12 A- 12 D in each of which the T-shaped groove  11  is formed. However, as the base frame  1 , it is possible to use a frame in which the T-shaped groove  11  is formed at least in the upper surface  12 A facing the air rail  2 . 
       FIG. 3(A)  is an external view of the air rail  2 , and  FIG. 3(B)  is an enlarged B-B cross-section view of the air rail  2  shown in  FIG. 3(A) . 
     The air rail  2  blows compressed air from a plurality of air blowing holes (not shown) of the transportation surface  21  through an air supply path (not shown) in the inside of the air rail  2 . Here, the compressed air is supplied from the outside of the air rail  2  to an air supply opening (not shown) of the air rail  2 . 
     As shown in the figure, at mounting positions (four positions in the present embodiment) of the air rail  2  to the base frames  1 , are formed height-adjustment bolt holes  23  for inserting hexagon socket head bolts  4  from the transportation surface  21  toward the back surface (i.e. the surface on the opposite side from the transportation surface  21 )  24 , respectively. In each height-adjustment bolt hole  23 , is formed a step  25  to come in contact with a seating surface  412  (See  FIG. 5 ) of a hexagon socket head bolt  4  which is inserted into this height-adjustment bolt hole  23  from the side of the transportation surface  21 . The diameter r1 in the area (a large-diameter portion)  28  from the transportation surface  21  to the step  25  is larger than the diameter r2 in the area (a small-diameter portion)  27  from the step  25  to the back surface  24 . 
     Further, in the back surface  24  of the air rail  2 , on both sides of each height-adjustment bolt hole  23 , are formed threaded holes  26  into which bolts  6  are respectively screwed. 
     In the present embodiment, the height-adjustment bolt holes  23  are formed at the mounting positions of the air rail  2  to the base frames  1 . However, to make the mounting positions of the air rail  2  to the base frames  1  adjustable, stepped elongate holes of any length having a cross-sectional shape similar to that of the height-adjustment bolt hole  23  may be formed for example in the longitudinal direction of the air rail  2 . 
       FIG. 4(A)  is an external view of the leveling device  3 , and  FIG. 4(B)  is a C-C cross section view of the leveling device shown in  FIG. 4(A) . 
     Each leveling device  3  supports the air rail  2  on the base frames  1 , and adjusts the height of the air rail  2  relative to the base frames  1 . 
     As shown in the figure, each leveling device  3  comprises: a disc spring group  31  that expands and contracts in the height direction (Z direction in  FIG. 1 ) of the air rail  2  relative to a base frames  1 ; a presser  32  of a tubular shape with an edge portion, which is biased by the disc spring group  31  to be pressed against the upper surface  12 A of the base frame  1 ; a spring guide  33  of a tubular shape with a flange portion, which is pressed against the back surface  24  of the air rail  2  biased by the disc spring group  31 ; and a housing  34  of a tubular shape with a flange portion and a edge portion, which houses these parts  31 - 33 . 
     The housing  34  comprises: a tubular portion  343 ; a second edge portion  342  formed along the inner periphery of an opening portion  341  on the side of one end face (the bottom surface  348  of the housing  34 ) of the tubular portion  343  so as to protrude toward the inside of the tubular portion  343 ; and a flange portion  349  formed on the side of the other end face (the upper surface  346  of the housing  34 ) of the tubular portion  343  so as to protrude outward from the outer periphery of the tubular portion  343 . 
     The housing  34  is placed between the base frame  1  and the air rail  2 , such that the upper surface  346  comes in contact with the back surface  24  of the air rail  2  in a state that an opening portion  344  on the side of the upper surface  346  faces a height-adjustment bolt hole  23  of the air rail  23 . Further, in the flange portion  349 , at positions corresponding to threaded holes  26  in the back surface  24  of the air rail  2 , are formed through-holes  347  into which bolts  6  are inserted respectively. 
     The presser  32  comprises: a circular-cylinder portion  325 , which protrudes toward the side of the base frame  1  from the opening portion  341  on the side of the bottom surface  348  of the housing  34 ; and a first edge portion  322  formed on the side of one end face (the upper surface  321  of the presser  32 ) of the circular-cylinder portion  325 , so as to protrude outward from the outer periphery of the circular-cylinder portion  325 . In the circular-cylinder portion  325 , a stepped through-hole  324  is formed from the one end face (the upper surface  321  of the presser  32 ) toward the other end face (the bottom surface  323 ). And the stepped through-hole  324  has an axis in common with the circular-cylinder portion  325 . This stepped through-hole  324  has a large-diameter portion  327  on the side of the one end face  321  and a small-diameter portion  328  on the side of the other end face  323 . In the inside of the large-diameter portion  327  of the stepped through-hole  324 , is inserted the below-described circular-cylinder portion  335  of the spring guide  33 . The large-diameter portion  327  guides this circular-cylinder portion  335  in the direction (Z direction in  FIG. 1 ) of expansion and contraction of the disc spring group  31 . Further, a hexagon socket head bolt  4  is inserted through the small-diameter portion  328  (See  FIG. 7 ). 
     The presser  32  is housed in the housing  34  in a state that the lower surface  326  of the first edge portion  322  is in contact with the upper surface  350  of the second edge portion  342  of the housing  34 , and the bottom surface  323  projects toward the base frame  1  from the opening portion  341  on the side of the bottom surface  348  of the housing  34 . 
     The spring guide  33  comprises: a circular-cylinder portion  335 , which is inserted into the disc spring group  31  in the housing  34  and the large-diameter portion  327  of the stepped through-hole  324  of the presser  32 ; and a flange portion  332 , which is formed on the side of the one end face (the upper surface  331  of the spring guide  33 ) of the circular-cylinder portion  335  so as to protrude outward from the outer periphery of the circular-cylinder portion  335 . And the flange portion  332  presses the disc spring group  31  between the flange portion  332  and the upper surface  321  of the presser  32  in the housing  34 . The flange portion  332  is formed into a disk shape concentric with the circular-cylinder portion  335 , and has an outer diameter r8 (See  FIG. 6 ) that is smaller than the inner diameter r7 of the tubular portion  343  of the housing  34  to the extent that the flange portion  332  is smoothly guided in the direction of expansion and contraction of the disc spring group  31  in the inside of the tubular portion  343 . In the circular-cylinder portion  335 , is formed a through-hole  334  through which the hexagon socket head bolt  4  is inserted from the upper surface  331  of the spring guide  33  toward the bottom surface  333  so as to be concentric with the circular-cylinder portion  335 . The circular-cylinder portion  335  has an outer diameter r9 that is set smaller than the inner diameter r5 (See  FIG. 6 ) of the large-diameter portion  327  of the stepped through-hole  324  of the presser  32  to the extent that the circular-cylinder portion  335  is smoothly guided in the direction of expansion and contraction of the disc spring group  31  in the inside of the large-diameter portion  327 . Further, the inner diameter r4 of the through-hole  334  of the circular-cylinder portion  335  is set larger than the inner diameter r6 of the small-diameter portion  328  of the stepped through-hole  324  of the presser  32 . In the present embodiment, the inner diameter r4 of the through-hole  334  is set as nearly same as the inner diameter r6 of the small-diameter portion  328  of the stepped through-hole  324 . 
     When the circular-cylinder portion  335  of the spring guide  33  is inserted into the large-diameter portion  327  of the stepped through-hole  324  of the presser  32  housed in the housing  34 , then a hollow portion  337  of a tubular shape is formed by the outer peripheral surface  339  of the circular-cylinder portion  335 , the lower surface  336  of the flange portion  332 , the inner surface  345  of the housing  34 , and the upper surface  321  of the presser  32 . Although details will be described later, only by inserting the flange portion  332  of the spring guide  33  into the inside of the tubular portion  343  of the housing  34 , the circular-cylinder portion  335  of the spring guide  33  can be positioned relative to the large-diameter portion  327  of the stepped through-hole  324  of the presser  32 . By this, the circular-cylinder portion  335  is smoothly inserted into the large-diameter portion  327 , and the axis of the through-hole  334  of the circular-cylinder portion  335  becomes almost coincident with the axis of the stepped through-hole  324  of the presser  32 . Accordingly, at the time of fixing the air rail  2  to the base frame  1 , it is possible to eliminate operation for center alignment of insertion holes (the through-hole  334  of the spring guide  33  and the small-diameter portion  328  of the stepped through-hole  324  of the presser  32 ) for the hexagon socket head bolt  4 . 
     Here, the length k1 between the bottom surface  333  of the circular-cylinder portion  335  of the spring guide  33  and the lower surface  336  of the flange portion  332  is set to a value that allows formation of a gap between the bottom surface  333  of the spring guide  33  and a step surface  329 , when the upper surface  331  of the spring guide  33  is aligned with the upper surface  346  of the housing  34 . The gap is larger than a height-adjusting allowance for the air rail  2 . The step surface  329  is located between the large-diameter portion  327  and the small-diameter portion  328  of the stepped through-hole  324  of the presser  32 . 
     The disc spring group  31  consists of a plurality of disc springs  311  that are layered in the hollow portion  337  of the tubular shape in the height direction of the air rail  2  in relation to the base frame  1 . The disc springs  311  are layered to the number at which the free height of the disc spring group  31  is larger than the distance between the lower surface  336  of the flange portion  332  and the upper surface  321  of the presser  32 , in the case where the upper surface  331  of the spring guide  33  is aligned with the upper surface  346  of the housing. Namely, the disc springs  311  are layered to the number at which the upper surface  331  of the spring guide  33  projects from the opening portion  334  on the side of the upper surface  346  of the housing  34  in an unloaded state of the disc spring group  31 . In the present embodiment, disc springs  311  are layered such that adjacent disc springs  311  are directed in opposite directions (the so-called serial combination system). Alternatively, however, the plurality of disc springs  311  may be layered such that adjacent disc springs  311  are directed in the same direction (the so-called parallel combination system), or a combination of the serial system and the parallel system may be employed. Further, although six disc springs  311  are layered in the present embodiment, the number of disc springs for use can be changed suitably as far as the disc spring group  31  is compressed between the lower surface  336  of the flange portion  332  and the upper surface  321  of the presser  32  when the spring guide  33  is pressed until the upper surface  331  of the spring guide  33  is aligned with the upper surface  346  of the housing  34 . 
     The disc spring group  31  biases the presser  32  in the direction of pushing out from the opening portion  341  on the side of the bottom surface  348  of the housing  34  so as to press the presser  32  against the upper surface  12 A of the base frame  1 . At the same time, the disc spring group  31  biases the spring guide  33  in the direction of pushing out from the opening portion  344  on the side of the upper surface  346  of the housing  34  so as to press the spring guide  33  against the back surface  24  of the air rail  2 . Further, the disc spring group  31  has the allowable load and the spring constant which are sufficient for stably supporting a load (such as loads of the transported object, the air rail  2  and the like on each leveling device  3 ) to bear during transportation of the object. Instead of the disc spring group  31 , another elastic body (such as a coil spring, rubber of a tubular shape, or the like) can be used as far as the elastic body has such elasticity. 
     The present embodiment uses the spring guide  33  of the tubular shape with flange portion, the presser  32  of the tubular shape with edge portion, and the housing  34  of the tubular shape with flange portion and edge portion. However, it is possible to use a spring guide  33 , a presser  32  and a housing  34  of other three-dimensional shapes that prevent displacement of the axis of the disc spring group  31 . 
       FIG. 5(A)  is the external view of a hexagon socket head bolt  4 . 
     As shown in the figure, in the upper surface  411  of a head portion  41  of the hexagon socket head bolt  4 , is formed a hexagon socket  43  for a hexagon wrench. The diameter r3 of the head portion  41  of the hexagon socket head bolt  4  is smaller than the diameter r1 of the large-diameter portion  28  of the height-adjustment bolt hole  23  of the air rail  2  and larger than the diameter r2 of the small-diameter portion  27 . Further, the thickness k2 of the head portion  41  of the hexagon socket head bolt  4  is smaller than the length k3 (See  FIG. 3(B) ) of the large-diameter portion  28  of the height-adjustment bolt hole  23  of the air rail  2 . As a result, when the hexagon socket head bolt  4  is inserted into the height-adjustment bolt hole  23  from the side of the transportation surface  21  of the air rail  2 , the seating surface  412  of the head portion  41  comes in contact with the step  25  of the height-adjustment bolt hole  23  in the position where the head portion  41  is under the transportation surface  21 . Thus the head portion  41  is completely contained in the large-diameter portion  28  of the height-adjustment bolt hole  23 . 
     Further, the length k4 from the seating surface  412  of the hexagon socket head bolt  4  to a threaded portion  42  of the hexagon socket head bolt  4  is smaller than the sum of the length k5 (See  FIG. 3(B) ) of the small-diameter portion  27  of the height-adjustment bolt hole  23  of the air rail  2  and the height (the length from the opening portion  341  to the opening portion  344 ) k6 (See  FIG. 4(B) ) of the housing  34  of the leveling device  3 . Further, as shown in  FIG. 4(B) , in a state that the first edge portion  322  of the presser  32  is in contact with the second edge portion  342  of the housing  34  and the bottom surface  323  of the presser  32  projects from the opening  341  of the housing  34 , the length k7 from the seating surface  412  of the hexagon socket head bolt  4  to the tip  421  of the threaded portion  42  is bigger than the sum of the length k8 from the bottom surface  323  of the presser  32  to the upper surface  346  of the housing  34 , the length k5 of the small-diameter portion  27  of the height-adjustment bolt hole  23  of the air rail  2  and the depth k10 (See  FIG. 2(B) ) from the groove edge  112  of the T-shaped groove  11  of the base frame  1  to the step  113 , and the length k7 is smaller than the sum of the above-mentioned k8 and k5 and the depth k11 (See  FIG. 2(B) ) from the groove edge  112  of the T-shaped groove  11  of the base frame  1  to the groove bottom  111 . 
       FIG. 5(B)  is a cross-section view of the T-nut  5 . 
     As shown in the figure, the T-nut  5  has a T-shaped cross-section including a step  52  at which the width changes from s3 to s4 (&gt;s3) between one end face (the upper surface  51 ) and the other end face (the bottom surface  53 ). Further, in the T-nut  5 , there is formed a threaded hole  54  running through from the upper surface  51  to the bottom surface  53 , into which the threaded portion  42  of the hexagon socket head bolt  4  is screwed. The width s3 in the area from the upper surface  51  to the step  52  is smaller than the groove width s1 (See  FIG. 2(B) ) of the T-shaped groove  11  of the base frame  1  in the area from the groove edge  112  of the T-shaped groove  11  to the step  113 . The width s4 in the area from the step  52  to the bottom surface  53  is larger than the groove width s1 of the T-shaped groove  11  of the base frame  1  in the area from the groove edge  112  of the T-shaped groove  11  to the step  113 , and smaller than the groove width s2 (See  FIG. 2(B) ) in the area from the step  113  of the T-shaped groove  11  to the groove bottom  111 . Further, the height k9 from the step  52  to the upper surface  51  is not larger than the depth k10 (See  FIG. 2(B) ) from the groove edge  112  of the T-shaped groove  11  of the base frame  1  to the step  113 . Thus, the T-nut  5  can be placed at a desired position in the T-shaped groove  11  of the base frame  1 . Further, when the threaded portion  42  of the hexagon socket head bolt  4  is screwed into the threaded hole  54  so as to apply force in the direction from the groove bottom  111  of the T-shaped groove  11  to the groove edge  112 , the step  52  comes in contact with the step  113  of the T-shaped groove  11  and is fixed to the base frame  1 . 
     Next, operation of fixing the air rail  2  to a base frame  1  will be described. 
       FIG. 6(A)  is a cross-section view for explaining assembling work of the leveling device  3 , and  FIG. 6(B)  is a cross-section view for explaining work of fixing the leveling device  3  to the air rail  2 . Further,  FIG. 7  is a cross-section view for explaining work of fixing the air rail  2  to the base frame  1 . 
     (1) Assembling of a Leveling Device  3   
     The leveling devices  3  of the number (four in the present embodiment) required for fixing the air rail  2  to the base frames  1  are previously assembled. Details will be described in the following. 
     As shown in  FIG. 6(A) , the presser  32  is inserted into the tubular portion  343  of the housing  34  from the side of the bottom surface  323  so that the first edge portion  322  of the presser  32  abuts against the second edge portion  342  of the housing  34 . The circular-cylinder portion  325  and the stepped through-hole  324  of the presser  32  are formed to be concentric with each other. Thus when the presser  32  is simply inserted into the tubular portion  343  of the housing  34 , the inner peripheral surface of the second edge portion  342  of the housing  34  comes in contact with the outer peripheral surface of the circular-cylinder portion  325  of the presser  32 . By this, the stepped through-hole  324  of the circular-cylinder portion  325  of the presser  32  is axially aligned with the tubular portion  343  of the housing  34 . Next, a plurality of disc springs  311  are layered on the presser  32  housed in the housing  34 , such that adjacent disc springs  311  are directed in opposite directions. Then, the spring guide  33  is inserted into the housing  34  from the side of the bottom surface  333  so that the circular-cylinder portion  335  of the spring guide  33  is inserted into the disc spring group  31  and the large-diameter portion  327  of the stepped through-hole  324  of the presser  32 . Here, the circular-cylinder portion  335  and the flange portion  332  of the spring guide  33  are formed to be concentric. Thus when the spring guide  33  is simply inserted into the tubular portion  343  of the housing  34  up to the flange portion  332  of the spring guide  33 , the circular-cylinder portion  335  of the spring guide  33  is positioned relative to the large-diameter portion  327  of the stepped through-hole  324  of the presser  32 . Thus, the circular-cylinder portion  335  of the spring guide  33  can be smoothly inserted into this large-diameter portion  327 . Here, the circular-cylinder portion  335  and the through-hole  334  of the spring guide  33  are formed to be concentric. Thus when the circular-cylinder portion  335  of the spring guide  33  is inserted into the large-diameter portion  327  of the stepped through-hole  324  of the presser  32 , the presser  32 , the disc spring group  31  and the spring guide  33  are housed in this order in the housing  34  in a state that the through-hole  334  of the spring guide  33  is axially nearly aligned with the stepped through-hole  324  of the presser  32 . By this, the leveling device  3  as shown in  FIGS. 4(A) and 4(B)  is completed. 
     (2) Fixing of the Leveling Devices  3  to the Air Rail  2   
     As shown in  FIG. 6(B) , for each leveling device  3 , two bolts  6  are screwed into threaded holes  26  in the back side  24  of the air rail  2  through the through-holes  347  of the housing  34 . As a result, the upper surface  346  of the housing  34  abuts against the back surface  24  of the air rail  2  in a state that the axes of the through-hole  334  of the spring guide  33  and the stepped through-hole  324  of the presser  32  are nearly aligned with the axis of the height-adjustment bolt hole  23  of the air rail  2 . By this, the leveling device  3  is fixed to the back side  24  of the air rail  2 . 
     As a result, the spring guide  33  is pushed into the housing  34  so that the upper surface  331  of the spring guide  33  comes to the same level as the upper surface  346  of the housing  34 , and preload is applied on the disc spring group  31 . In this state, the length of the projected portion of the presser  32  out of the bottom surface  348  of the housing  34  is referred to as c1, and the length from the bottom surface  333  of the spring guide  33  to the step surface  329  between the large-diameter portion  327  and the small-diameter portion  328  of the presser  32  is referred to as c2. 
     (3) Fixing of the Air Rail  2  to the Base Frames  1  and Height Adjustment 
     The air rail  2  is placed so as to bridge between two base frames  1 . Two T-nuts  5  are inserted in the T-shaped groove  11  on the side of the upper surface  12 A of each base frame  1 , and located at positions corresponding to height-adjustment bolt holes  23  of the air rail  2 . Next, as shown in  FIG. 7 , for each height-adjustment bolt hole  23  of the air rail  2 , the hexagon socket head bolt  4  is inserted from the side of the transportation surface  21  of the air rail  2  through the height-adjustment bolt hole  23 , the through-hole  334  of the spring guide  33 , and the small-diameter portion  328  of the stepped through-hole  324  of the presser  32 . Then, the threaded portion  42  of the hexagon socket head bolt  4  is screwed into the threaded hole  54  of the T-nut  5  by using a hexagon wrench  7 . Thus, the air rail  2  is fixed to the base frames  1  through the leveling devices  3  in a state that, for each leveling device  3 , the bottom surface  323  of the presser  32  (which projects from the opening portion  341  on the side of the bottom surface  348  of the housing  34  toward the base frame  1 ) abuts against the upper surface  12 A of the base frame  1 . 
     As described above, the length k4 (See  FIG. 5(A) ) from the seating surface  412  of the head portion  41  of the hexagon socket head bolt  4  to the threaded portion  42  is smaller than the sum of the length k5 (See  FIG. 3(B) ) of the small-diameter portion  27  of the height-adjustment bolt hole  23  of the air rail  2  and the height k6 (See  FIG. 4(B) ) of the housing  34  of the leveling device  3 . Here, the height k6 is the length from the opening portion  341  to the opening portion  344 . Further, in a state that the first edge portion  322  of the presser  32  is in contact with the second edge portion  342  of the housing  34  and the bottom surface  323  of the presser  32  projects from the opening  341  of the housing  34 , the length k7 (See  FIG. 5(A) ) from the seating surface  412  of the hexagon socket head bolt  4  to the tip  421  of the threaded portion  42  is larger than the sum of the length k8 (See  FIG. 4(B) ) from the bottom surface  323  of the presser  32  to the upper surface  346  of the housing  34 , the length k5 (See  FIG. 3(B) ) of the small-diameter portion  27  of the height-adjustment bolt hole  23  of the air rail  2  and the depth k10 (See  FIG. 2(B) ) from the groove edge  112  of the T-shaped groove  11  of the base frame  1  to the step  113 . And the length k7 is smaller than the sum of the above-mentioned k8 and k5 and the depth k11 (See  FIG. 2(B) ) from the groove edge  112  of the T-shaped groove  11  of the base frame  1  to the groove bottom  111 . 
     Accordingly, by adjusting the degree of screwing of the hexagon socket head bolt  4  into the T-nut  5 , it is possible to adjust the height of the air rail  2  relative to the base frame  1  within the height-adjusting allowance (the smallest length among c1 and c2 shown in  FIG. 6(B)  and the maximum shrinkage of the disc spring group  31 ). Leveling of the transportation surface  21  of the air rail  2  can be performed by doing this height adjustment work for each of the four leveling devices  3  used for fixing the air rail  2  to the base frames  1 . 
     Hereinabove, one embodiment of the present invention has been described. 
     With regard to the leveling device  3  according to the present embodiment, the disc spring group  31 , the presser  32  and the spring guide  33  are housed in the housing  34 , to realize unitization of a plurality of component parts including the disc spring group  31 , the presser  32 , the spring guide  33  and the housing  34 . Accordingly, it is possible to assemble the required number of leveling devices  3  in advance of fixing the air rail  2  to the base frames  1 . Thus, a worker can easily fix the leveling devices  3  to the air rail  2  without caring about falling of some parts, and thus the work efficiency is improved. 
     Further, in assembly work of the leveling device  3 , the circular-cylinder portion  335  of the spring guide  33  is simply inserted into the large-diameter portion  327  of the stepped through-hole  324  of the presser  32  via the disc spring group  31 , so that the through-hole  334  of the spring guide  33  is axially aligned with the stepped through-hole  324  of the presser  32 . Accordingly, there is no need of alignment work of the insertion holes (the through-hole  334  of the spring guide  33  and the small-diameter portion  328  of the stepped through-hole  324  of the presser  32 ) for the hexagon socket head bolt  4 . This allows easy assembling, and the work efficiency of the assembly work is improved. 
     Further, by fixing the leveling device  3  to the air rail  2 , preload is applied on the disc spring group  31  of the leveling device  3 . Accordingly, the air rail  2  can be attached to the base frames  1  only by screwing the hexagon socket head bolts  4  into the T-nuts fewer times in comparison with the case where the disc spring group  31  has not been preloaded. 
     Further, by fixing the leveling device  3  to the air rail  2 , the upper surface  331  of the spring guide  33  is pushed in to the same level as the upper surface  346  of the housing  34 , and preload is applied on the disc spring group  31 . Accordingly, it is possible to apply equal preload on the four leveling devices  3  used for fixing the air rail  2  to the base frames  1  without performing troublesome preload adjustment. 
     Further, the air rail  2  is fixed to the base frames  1  by inserting the hexagon socket head bolts  4  into the height-adjustment bolt holes  23  from the side of the transportation surface  21  of the air rail  2  and by screwing the hexagon socket head bolts  4  into the T-nuts  5  respectively. And, adjustment of the height of the air rail  2  relative to the base frames  1  is performed by adjusting the degree of screwing of each hexagon socket head bolt  4 . As a result, differently from the substrate transportation apparatus described in the Patent Document 1, it is not necessary to ensure gaps for height adjustment at both sides of the air rail  2  in the longitudinal direction (X direction in  FIG. 1 ). Accordingly, in the case where a plurality of air rails  2  are arranged, interval between air rails  2  can be flexibly set considering floating stability and the like of transportation objects. For example, adjacent air rails  2  can be laid in contact. As a result, it is possible to transport objects in a more stable floating state. 
     Further, the bolts  6  are screwed into the threaded holes  26  formed in the back surface  24  of the air rail  2  via the through-holes  347  formed in the housing  34  of the leveling device  3 , so that the leveling device  3  is fixed to the air rail  2  in a state that the disc spring group  31  is preloaded. Thus, prior to fixing air rails  2  to the base frames  1 , it is possible to perform fixing work of leveling devices  3  to the required number of air rails  2  and preloading work. Thus, work efficiency is improved furthermore. 
     Although, in the present embodiment, the hexagon socket head bolts  4  and the T-nuts  5  are used to fix the air rail  2  to the base frames  1  via the leveling devices  3 , the present invention is not limited to this. For example, in the upper surface  12 A of the base frame  1  at a position corresponding to the height-adjustment bolt hole  23  of the air rail  2 , there may be formed a threaded hole into which the threaded portion  42  of the hexagonal socket head bolt  4  can be screwed, so as to fix the air rail  2  to the base frame  1  without using the T-nut  5 . 
     Further, in the present embodiment, the hexagon socket head bolts  4  are used so that the hexagon wrench  7  can be used from the side of the transportation surface  21  of the air rail  2  so as to perform fixing of the air rail  2  to the base frames  1  and leveling of the transportation surface  21 . However, the present invention is not limited to this. It is possible to employ bolts appropriate to a tool used. For example, it is possible to employ a bolt having a slot or cross slot formed in the upper surface of its head. 
     Further, in the present embodiment, the air rail  2  is fixed to the base frames  1  so as to bridge between two base frames  1  of rectangular columns laid side by side with a given space. However, the present invention is not limited to this. For example, the air rail  2  may be put on and fixed to a sheet of plate-like base frame  1 . 
     The present embodiment has been described taking an example of application to a floating transportation apparatus having a transportation platform  100 . However, the present invention can be applied to another apparatus provided with a table that has a leveling-target surface and is fixed to a base member. 
     Further, the present embodiment has described the leveling devices  3  that support the air rail  2  on the base frames  1  and adjusts the height of the air rail  2  relative to the base frames  1 . The present invention, however, can be widely applied to interval adjustment devices for adjusting an interval between two members. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be applied to fields that require good workability of adjustment of an interval between two members, such as leveling work in an apparatus in which a member having a leveling-target surface is fixed to another member. For example, can be mentioned a transportation apparatus in which a rail having a leveling-target surface is fixed to a base member, and an apparatus in which a table having a leveling-target surface is fixed to a base member. 
     REFERENCE SIGNS LIST 
       1 : base frame;  2 : air rail;  3 : leveling device;  4 : hexagon socket head bolt;  5 : T-nut;  6 : bolt;  7 : hexagon wrench;  11 : T-shaped groove;  12 A- 12 D: outer surface of base frame  1 ;  13 ,  14 : end face of base frame  1 ;  21 : transportation surface;  23 : height-adjustment bolt hole;  24 : back surface of air rail  2 ;  25 : step;  26 : threaded hole;  27 : small-diameter portion of height-adjustment bolt hole  23 ;  28 : large-diameter portion of height-adjustment bolt hole  23 ;  31 : disc spring group;  32 : presser;  33 : spring guide;  34 : housing;  41 : head portion;  42 : threaded portion;  43 : hexagon socket;  51 ,  53 : end face of T-nut  5 ;  52 : step;  54 : threaded hole;  100 : transportation platform;  111 : groove bottom of T-shaped groove  11 ;  112 : groove edge of T-shaped groove;  113 : step;  311 : disc spring;  321 : upper surface of presser  32 ;  322 : first edge portion;  323 : bottom surface of presser  32 ;  324 : stepped through-hole;  325 : circular-cylinder portion;  326 : under surface of first edge portion;  327 : large-diameter portion of stepped through-hole  324 ;  328 : small-diameter portion of stepped through-hole  324 :  329 : step surface between large-diameter portion  327  and small-diameter portion  328  of stepped through-hole  324 ;  331 : upper surface of spring guide  33 ;  332 : flange portion of spring guide  33 ;  333 : bottom surface of spring guide  33 ;  334 : through-hole;  335 : circular-cylinder portion of spring guide  33 ;  336 : under surface of flange portion  332 ;  337 : hollow portion of tubular shape;  339 : outer peripheral surface of circular-cylinder portion  335 :  341 ,  344 : opening portion of housing  34 ;  342 : second edge portion of housing  34 ;  343 : tubular portion of housing  34 ;  345 : inner surface of housing  34 ;  346 : upper surface of housing  34 ;  347 : through-hole;  348 : bottom surface of housing  34 ;  349 : flange portion of housing  34 ;  350 : upper surface of second edge portion;  411 : upper surface of head portion  41  of hexagon socket head bolt  4 ;  412 : seating surface of hexagon socket head bolt  4 ; and  421 : tip of threaded portion  42 .