Technical Field The present invention relates to a wing body trailer, and more particularly to the wing body trailer having a double-deck type loading box, in which a upper loading box a nd a bottom frame are simultaneously raised or lowered by means of a lifting machine i n order to achieve easy loading in dock-loading circumstances as well as in the flat grou nd circumstances.

Background Art Generally, many types of the wing body trailers are disclosed, wherein one side or both sides of the loading box may be opened to load cargo and wherein a variable ty pe loading box for loading the cargo on an upper section and a lower section in a mid p art of the loading box. For example, Figures 1a and 1b shows Korean Utility Model application entitled with "Wing body trailer having variable loading box" filed on 30 August 2001 by the appli cant of the present application. The application was registered as Korean Utility Model Registration No. 0273150 dated 11 April 2002. Referring to figures, the wing body trailer having the conventional variable loadin g box includes a main frame 10 comprising: a tow section 11 with a king pin 11a for bei ng coupled to a tow vehicle (not shown) so as to perform traction; a traveling section 12 with a plurality of wheels 12a provided behind the tow section 11 for being traveled or braked on a road by the tow vehicle; and lower loading boxes 13 provided between the traveling section 12 and the tow section 11. Also, a wall frame 20 is provided at a central part along the main frame 10 so as to divide a left and right sides of the wing body trailer 1 and to support a side of the load ed cargo. With reference to the wall frame 20, lift units 31 are disposed at both sides of up per parts of the lower loading box 13. The lift unit 31 includes a first, a second and a third posts P1 , P2 and P3, which are telescopically inserted and extended. The first post P1 is installed on the bottom s urface of the lower loading box 13 and the second and the third posts P2 and P3 are in serted into the first post P1 one after another. Four corners of an upper loading box 30 are supported on upper ends of the thir d post P3 so as to enable loading the cargo in two-step manner. A support frame SF i s horizontally disposed on upper ends of the second post P2. A lift cylinder LC is disp osed under the support frame SF. On the other hand, one end of a wire rope WR is connected to the lower end of t he first post P1 and the other end of the wire rope is connected to the lower end of the t hird post P3. Accordingly, when the second post P2 is lifted by the operation of the lift cylind er LC, the third post P3 connected through the wire rope WR is simultaneously lifted, so that lower space of the upper loading box 30, in other words, the space for loading the lower loading box 13 is formed. Further, although not seen in the figures, the conventional wing body trailer 1 incl udes a fall prevention unit in longitudinal outward direction. The fall prevention unit mak es lengthwise-located cams to rotate in either one or the other direction by forward and backward movement of a laterally-disposed cylinder (not shown). Thus, it causes the I oaded cargos, upper surface of which are protruded or depressed, to incline toward the wall frame 20, so that it prevents the cargos from falling outwardly during the traveling. Also, a fixing bracket 21 formed with a plurality of apertures 21a in the upper and the lower direction is disposed on an upper side of the wall frame 20. In the upper Io ading box 30 disposed on the upper side of the third post P3, a cylinder CD is horizonta Ny disposed. A front end of the cylinder rod CR has a fixing axis FS. Accordingly, when the loading of the cargos on the upper side of the upper loadi ng box 30 is completed, the cylinder CD operates to move the fixing axis FS in the horiz ontal direction so as to let the latter penetrate the apertures 21a, so that the upper loadi ng box 30 can be fixed. At the same time, the lower end of the second post P2 is supported by inserting a fixing pin FP into a pin aperture FH, which is formed at the lower end of the first post P1 mounted to the lower loading box 13. However, because only the upper loading box can move upward and downward i n the conventional wing body trailer, it is possible to load the cargo only in the plane gro und. On the other hand, it is not possible to load the cargo onto the upper side of the I ower loading box at the warehouse wherein docks are formed at a certain height to load the cargo. Furthermore, the aforementioned fall prevention unit cannot prevent the cargo fr om falling when the trailer runs along sharp curve road. It is because the heavier load exerts on the cam rotating under the cargo and the inward inclination of the cargo, whic h can prevent the outward movement of the cargo leading to fall, is not formed by the c onventional fall prevention unit. Also, if the apertures formed at the wall frame are not centrally coincident with ce nter of the cylinder, which is disposed at the upper loading box and has the penetrating axis at front end of cylinder rod, exact fixation is not achieved. Also, the fixing pin inserted into the second post from the outside of the first post escapes from the position due to vibration generated during the traveling of the trailer. Thus, the lift cylinders and the wire ropes supporting the second and the third posts ex perience overload, so that the upper loading box with cargo may be collapsed. Also, since a user should manually insert the fixing from the outside of the secon d post, time for loading and the inconvenience of the user will be increased.

Disclosure of the Invention The present invention is provided in order to solve the above-mentioned problem s. Accordingly, one object of the present invention is to make it possible to load cargo not only on the plane ground, but also in a warehouse wherein docks are formed at a c ertain height. Another object of the present invention is to provide a fall prevention unit, which avoids the heavier load and forms the inclination of the loaded cargo in natural manner. Another object of the present invention is to solidly fix an upper frame loaded wit h the cargo, so that life span of wire ropes for supporting third post may be extended. Another object of the present invention is to improve loading productivity and ach ieve solid fixation without causing overload of cylinder supporting cylinder by means of automatic coupling of fixing pin supporting lower end of the second post. Another object of the present invention is to increase convenience for user by e mploying the above-mentioned automatically coupled fixation unit.

In order to achieve the above objects, the present invention provides a wing bod y trailer comprising: a main frame having a tow section at the front end and a traveling s ection at the rear end and a lower loading box downwardly formed between the tow sec tion and the traveling section; wall frames longitudinally installed in central part of the m ain frame; an upper loading box disposed at both upper sides of the lower loading box with reference to the wall frames and including lift units at both ends thereof, wherein sa id wing body trailer further comprises: a deck unit including posts disposed at front and rear ends of the upper loading box to extend upward and downward and bottom frame having four corners mounted to the lower end of the posts; and lift units disposed at bot h mid locations between the front end and the rear end for raising and lowering the dec k unit.

Brief Description of the Drawings Figure 1a is a side view of a wing body trailer with a variable-type loading box of t he prior art. Figure 1 b is a cross-sectional view along the line A-A of Figure 1a. Figure 2 is an extracted side view of a deck unit of a wing body trailer with a dou ble-deck-type loading box according to the present invention. Figure 3 is a plane view illustrated in a direction of the arrow B as in Figure 2. Figure 4a is an enlarged side view illustrating the circle C as shown in Figure 2, which represents a lift unit according to the present invention. Figure 4b is a plane view illustrated in a direction of D as in Figure 4a. Figure 5 is a longitudinal cross-section view illustrated along the line E-E as sho wn in Figure 2, which represents an upper loading box according to the present inventio n. Figure 6 is a longitudinal cross-section view illustrated along the line F-F as show n in Figure 2, which represents a deck unit according to the present invention. Figure 7 is an extracted side view of a fall prevention unit according to the prese nt invention. Figures 8 and 9 are enlarged side views illustrating the circle G as shown in Figu re 7, which sequentially represent operations of the fall prevention unit according to the present invention. Figure 10 is a cross-sectional view illustrated along the line H-H as shown in Figu re 9, which represents operation of the fall prevention unit according to the present inve ntion. Figure 11 is a longitudinal cross-section view illustrating a fixation unit according to the present invention. Figure 12 is a perspective view of a fixation unit for the upper loading box accordi ng to the present invention. Figure 13 is a cross-sectional view illustrated along I - I as shown in Figure 12. Figure 14 is an exploded perspective view of a post fixation unit according to the present invention. Figure 15 is a side view sequentially representing operations of the post fixation unit according to the present invention. Figure 16 shows another embodiment of the fixation unit for the upper loading bo x according to the present invention.

Best mode for carrying out the Invention

Herein below, a preferred embodiment of the wing body trailer in accordance wit h the present invention will be fully described with reference to the attached drawings. Referring to Figures 2 and 3, a wing body trailer 1 with a double-deck type loadin g box according to the present invention comprises: a deck unit 100 formed by an uppe r loading box 30 and a lower loading box 13 for being shaped into a box with left and rig ht sides opened; and elevator units 200 uprightly disposed at the central location betwe en the front and the rear of the deck unit 100. The deck unit 100 includes the upper loading box 30; and a bottom frame 110 ho rizontally disposed under the upper loading box 30 and having lift units 31 integrally inst ailed on four corners thereof. The upper loading box 30 and the bottom frame 110 have quadrilateral planes fo r loading cargos. The lift units 31 for connecting the upper loading box 30 to the botto m frame 10 includes first, second and third posts P1 , P2 and P3, all of which are telesc opically connected to each other as mentioned before regarding the prior art. Lower e nds of the first posts P1 are installed to four corners of the bottom frame 10 and upper ends of the third posts P3 inserted into the first posts P1 are mounted to four corners of the underside of the upper loading box 30. On the other hand, as described before, the elevator units 200 are uprightly disp osed at the central location between the front and the rear of the box-shaped deck unit 100. Referring to Figures 4a and 4b, the elevator 200 of the present invention include s a screw block 210, a housing bracket 220, a slider 230, a guider 240, a screw 250 an d a rotation machine 260. The screw block 210 forms an outer shape and is formed with a thread portion 2 11a in a perpendicular direction. The screw block 210 has a housing bracket 220 at th e rear part. The housing bracket 220 is bent into a predetermined shape as can be seen in F igure 4b. The housing bracket 220 is formed with a support portion 221 having thread s 221a at its end so as to be inserted into an end plate 101 under the deck unit 100 and coupled to the nut block 223. Also, the housing bracket 220 is formed at its front with a concave groove 220a t o allow the upper and the lower sides of the screw block 210 to be inserted therein for t he purpose of support. On the other hand, the slider 230 is installed at both sides of the screw block 210 , so that upward and downward sliding of the guider 240 may be facilitated inside of the slider bracket 243. The slider is preferably made of engineering plastic capable of being self lubhcati on and wear-resistant, so that life span of the slider 230 can be extended. Also, the guider 240 is uprightly disposed at the central location of side walls CB, which are symmetrically formed at the front and the rear of the lower loading box 13. The guider 240 includes a main plate 241 installed on the side wall CB, a slide bracket 243 disposed at a side of the main plate 241, and a support bracket 245 symmetrically disposed at upper and lower locations of the slider bracket 243 and supporting upper a nd lower ends of a screw 240 as described herein below. Also, an upper and a lower ends of a screw 250 coupled to the thread portion 21 1a of the screw block 210 are supported by the support bracket 245. The lower end of the screw 250 is axially connected with a rotation machine 260. The rotation machin e 260 may be a hydraulic motor capable of obtaining strong torque at an initial moment of starting. The operations of the deck unit 100 and the elevator unit 200 according to the pr esent invention will be detailed with reference to Figures 5 and 6. Figure 5 illustrates the operation of loading the cargo onto the bottom frame of th e deck unit 100 in a plane ground. When the cylinder LC installed at the center of the lift unit 31 begins to operate, t he upward movement of the support frame SF coupled to the cylinder rod LCR of the cy under LC causes the second post P2 to move upward. Accordingly, since an end of the wire rope WP is connected to the first post P1 a nd the other end thereof to the third post P3, the third post P3 moves upward. Thus, t he upper loading box 30 supported by the third post P3 moves upward, so that the spac e may be obtained for loading the cargo onto the bottom frame 110 located there-under

Figures 4b and 6 illustrate that the deck unit 100 according to the present inventi on operates in the dock formed with a certain height for easy loading of the cargo in th e warehouse. After finishing entrance of the wing body trailer 1 into the dock D, the rotation ma chine 260 of the elevator unit 200 begins to rotate in a direction. Then the screw 250 coupled to the rotation machine 260 will rotate. Accordingly, the screw block 210 coupled to the screw 250 and the housing brae ket 220 coupled to the screw block 210 move upward. Then the bottom frame 110 a nd the upper loading box 30 coupled to the support portion 221 of the housing bracket 220 moves upward. As a result, the deck unit 100 of the present invention moves up ward as a whole. Thus, it is possible to readily load the cargo onto the bottom frame 110 using a fo rk lifter (not shown) since the level of the bottom frame coincides with that of the upper surface of the dock D. Figures 7 to 10 are the side view of the fall prevention unit of the trailer 1 accordi ng to the present invention. (The fall prevention units 300 are symmetrically disposed at both sides of extension formed by the tow section 11 , the upper loading boxy 30 a nd the traveling section 12 in a longitudinal direction. Since each of the fall preventio n units has same construction, only the fall prevention unit 300 disposed at the side of the traveling section 12 will be described for the convenience of the description. ) The fall prevention unit 300 includes a guide frame 310, an operation frame 330, a fall prevention member 350 and a cylinder 370. The guide frame 310 is formed by bending metal plate. Periphery of the guide f rame 310 is mounted to a frame FR of the trailer's bottom. At the central portion of th e cross section, the guide frame has a concave groove 311 in a longitudinal direction. On the other hand, an aperture 312 is formed at a center of the concave groove 311 and the operation frame 330 is disposed on a bottom of the concave groove 311. The operation frame 330 is integrally formed with a bottom plate 331 disposed o n the bottom of the concave groove 311 and a plurality of operation cams equidistantly disposed on the bottom plate 331. The bottom plate 331 is a flat bar in the form of long strip. The rod bracket 335 is disposed at a central portion of the bottom plate 331. The rod bracket 335 extends through the aperture 312 and is hinge-coupled to a cylinder rod 373 of the cylinder 37 0. Each of the plurality of the operation cams 333 equidistantly disposed on the bott om plate 331 is formed with a pointed side and an inclined portion 333a. Due to the i nclined portion 333a, the upper surface of the operation cam 333 goes far from the up per surface of the bottom plate 331. A plane portion 333b extends from the inclined portion 333a. At an end of the p lane portion 333b, a latch portion 333c is formed to prevent a guide roller 351 from pa ssing over the operation cam 333. The guide roller 351 is installed at the fall preventi on unit 350. The fall prevention member 350 is disposed above the operation frame 330 inclu ding the operation cam 333 and the bottom plate 331. The fall prevention member 350 has triangular cross-section and has same lengt h as the concave groove 311. The guide roller 351 is hinge-coupled inside of the fall p revention member 350 in such a way that an interval between the guide rollers 351 is e qual to that between the operation cams 333. The guide roller 351 has internal bearings (not shown), so that it can roll on the i nclined portion 333a and the plane portion 333b of the operation cam 333. The cylinder 370 is longitudinally disposed under the guide frame 310, more spe cifically under the concave groove 311. The cylinder 370 is a clevis type cylinder. A clevis disposed at an end of the cyli nder 370 is hinge-connected with a bracket 371a located under the concave groove 31 1. A cylinder rod 373 is hinge-connected with a rod bracket 335 after passing through the aperture 311a of the concave groove 311 to protrude there-under. The operation of the fall prevention unit 300 will be described with reference to th e drawings. Figure 8 illustrate a reversed state of the fall prevention unit 300 according to the present invention. More specifically, the cylinder rod 373 is retracted into the cylinder 370, so that the fall prevention unit is received within the concave groove 311 not to int erfere with the loading of the cargo. Here, the guider roller 351 of the fall prevention member 350 is disposed at the s ideof the inclined portion 333a of the operation cam 333 disposed on the operation fr ame 330. Accordingly, the fall prevention member 350 is received within the concav e groove 311 of the guide frame. When completing the cargo loading, the cylinder rod 373 of the cylinder 373 exte nds forward, so that the rod bracket 335 hinge-connected with the cylinder rod 373 m oves forward. Accordingly, the operation cam 333 integrally mounted to the bottom plate 331 m oves to one side. The rod bracket 335 is installed to the bottom plate 331. Here, the guide roller 351 rolls along the inclined portion 333a of the operation c am 333 to move upward, so that the fall prevention member 350 can be hinge-conne cted with the guide roller 351. As a result, the fall prevention member 350 moves up ward and protrudes above the upper surface of the bottom frame 110 as shown in Fig ure 10. Accordingly, the loaded cargo P inclines with a predetermined angle inside of the wing body trailer according to the present invention. Thus, while the wing body trail er is traveling along the sharp curve, the cargo does not fall and can maintain a firm s tate of loading. Referring to Figure 11 , the wing body trailer 1 of the present invention comprises and upper loading box fixation unit 300 and post fixation units 400. Referring to Figures 11 to 13, the upper loading box fixation unit 300 is disposed at a central position of an upper portion of a wall frame. The wall frame 20 is vertical Iy installed at a central position of the lower loading box 13 in the longitudinal directio n. The post fixation unit 400 is symmetrically disposed to the first post P1 of the lift unit 31. The upper loading box fixation unit 300 includes upper and lower frames 310 an d 320, first and second support brackets 330 and 340, a support bush 350, a connect ing shaft 360, a rotation bush 370, a stopper 380 and a rotation cylinder 390. The upper and the lower frames 310 and 320 are formed by bending metal plate s into a predetermined cross-section. For example, the cross-section is formed in th e shape of "Fl " as shown in Figure 12. The upper and the lower frames 310 and 32 0 are symmetrically disposed at upper and lower ends of the wall frame 20. Within t he upper and the lower frames 310 and 320, the first and the second support bracket s 330 and 340 are vertically disposed. (Since the first and the second support brack ets 330 and 340 have same structure, the first support bracket 330 will be described below.) An upper end and a lower end formed by being the first support bracket 330 are mounted to insides of the upper and the lower frames. The first bracket 330 include s a support 331 and a coupling portion 333 and a mounting portion 335 disposed at e ither sides of the support 331 , respectively. The support portion 331 has a predetermined cross-section, such as "(1 ". The support portion 331 is formed with bush mounting holes 331a, which are horizontally and concentrically disposed. The support bush 350 is mounted into the bush mounti ng hole 331a as described below. The coupling portion 333 formed at a side of the support portion 331 is bent twic e with a right angle from a portion formed with bush mounting hole 331a so as to for m the plane for mounting the rotation cylinder 390. As not seen from the drawings, the coupling portion 333 is formed with a hole co ncentric to the bush mounting hole 331a, so that a rod of the rotation cylinder 390 pa sses there-through so as to facilitate the connection to the rotation cylinder 390. The mounting portion 335 is formed at opposite side of the coupling portion 333. The mounting portion 335 is bent with a right angle from the support portion 331 , s o that when the first and the second brackets 330 and 340 are symmetrically dispose d to each other, a box-type structure may be obtained by crossing each other. Acco rdingly, the durability can be increased. With such structure, the support bush 350 is installed to the support portion 331 of the first support bracket 330. The support bush 350 includes a ring-shaped main body 351 and a mounting por tion 353. The mounting portion 350 has an outer diameter smaller than the diamete r of the main body 351 so as to insert into the bush mounting hole 331a and is conce ntrically and symmetrically disposed with respect to the support portion 331. The first and the second support brackets 330 and 340 are symmetrically dispos ed in the longitudinal direction and the mounting portions 335 and 345 crossed to eac h other are welded, so that each of stoppers is symmetrically disposed. The connecting shaft 360 is axially connected to a side of the supporting bush 35 0. One end of the connecting shaft 360 is axially connected to the rotation cylinder 390. The connecting shaft 360 is formed with a fixing groove 361. The fixing groove 361 is a conventional key groove (KS B 1311-84) for being keyed to the rotation bus h 370 as described herein below. The rotation bush 370 is disposed at a side of the support bush 350 around the p eriphery of the connecting shaft 360. The stopper 380 is integrally mounted to a sid e of the rotation bush 370. The key groove 371 is formed on the inner periphery of t he rotation bush 370 corresponding to the fixing groove 361. The stopper 380 may horizontally extends from the rotation bush 370. A rotatio n prevention member 337, which is longitudinally mounted to the inside of the support portion 331 of the first support bracket 330, is disposed under the stopper 380. Th e rotation prevention member 337 severs to prevent the stopper 380 fixing the upper I oading box 30 from being rotated any further. A latching protrusion 381 is upwardly formed at an end of the stopper 380. The post fixation units 400 are disposed under the upper loading box fixation unit 300. Each of the post fixation units 400 is symmetrically disposed in the first post P1 o f the lift unit 31. Referring to Figures 14 and 15, the post fixation unit 400 includes first and secon d brackets 410 and 420 inwardly and outwardly disposed at a lower part of the first p ost P1 and a locking cylinder 440 with a locking pin 441 disposed at a front end of a r od so as to pass through the first and the second guide brackets 410 and 420. The first guide bracket 410 is inwardly disposed at the lower part of the first post P1 and includes a guide bush 41 at a center thereof. The second guide bracket 420 is outwardly disposed at the lower part of the first post P1 to oppositely correspond to the first bracket 410. A pin hole 421 is formed at a center of the second bracket 420 to concentrically c orrespond to the bush 411 disposed at the center of the first bracket 410. As descri bed herein below, a locking pin 441 at the front end of the locking cylinder passes thr ough the pin hole 421. On the other hand, a cylinder bracket 430 is disposed at a lower side of the first post P1 and the locking cylinder 440 is disposed at a side of the cylinder bracket 430.

The cylinder bracket 430 is a metal plate and formed with a coupling hole 431 at a lower end thereof. As described herein below, a connecting bracket 440a dispose d at the front end of the locking cylinder 440 is bolt-coupled to the coupling bracket 4 40a. The coupling bracket 440a is formed with a cross section, such as "π ". One sid e of the connecting bracket 440a is coupled to the cylinder bracket 430 and the other side thereof is coupled to the front end of the locking cylinder 440. The locking cylinder 440 may be a conventional one. A locking pin 441 is dispo sed at the front end of the rod of the locking cylinder 440. The locking pin 441 has a predetermined length in the shape of a rod length to pass through the center of the f irst and the second guide brackets 410 and 420. The operation and advantage of the upper loading box fixation unit 300 and the post fixation unit 400 according to the present invention will be described herein belo W. As illustrated, the second post P2 can be raised by the operation of the lift cylind er LC. Accordingly, the third post P3, one end of which is connected to the wire rop e WR, will be raised and then the upper loading box 30 will be raised thereby. Here, the elevation height of the upper loading box 30 is larger than the operatio n ranges of the fixation units 300 and 400. When the upper loading box 30 is raised higher than the upper loading box fixation unit 300, the rotation cylinder 390 of the u pper loading box fixation unit 300 will be rotated by push of a start button (not shown) included in the controller. Accordingly, the connecting shaft 360 axially connected t o the rotation cylinder 390 will rotate. With this movement, the stopper 380 and the rotation bush 370 keyed to the connecting shaft 360 rotates toward a side and mainta ins the horizontal state. At the same time, the cylinder rod of the locking cylinder 440, which is included i n the post fixation unit 400 disposed under the first post P1 , is forwardly drawn to ins ert into the guide bush 411 of the first guide bracket 410 and the pin hole 421 of the s econd guide bracket 420. With such movement, the locking operation is completed.

After completing the locking of the post fixation unit 400, the lower side of the up per loading box 30 contacts the stopper 380 of the upper loading box fixation unit 300 by slowly lowering the upper loading box 30. By doing so, the fixing operation of th e upper loading box fixation unit 300 is completed. Here, since the latch protrusion 381 formed at the upper side of the stopper 380 supports the frame side of the upper loading box 30, it is possible to prevent the uppe r loading box 30 from being outwardly inclined while the wing body trailer 1 travels alo ng the sharp curve on the road. Furthermore, since the second and the third posts P2 and P3 are operatively eng aged to each other, the lower end of the second post P2 disposed within the first post P1 is supported on the upper portion of the locking pin 441 of the post fixation unit 4 00 when the upper loading box 30 contacts the stopper 380. Thus, the fixation may be fortified. As described herein before, the post fixation unit 400 can prevents the locking pi n 441 from being escaped even if the wing body trailer rocks while traveling on the ro ad. Also, the upper loading box fixation unit 300 for fixing the lower side of the uppe r loading box 30 ensures the reinforced fixation even without erroneous operation. Accordingly, the life span of the wire rope WR and the cylinder LC can be extended. Additionally, a user's convenience may be increased by automatically engaged o peration of the upper loading box fixation unit 300 and the post fixation unit 400, so th at the productivity of the cargo work can be improved. The upper loading box 300 of the present invention may be readily varied in othe r ways with the current technique in the art. For example, as illustrated in Figure 16, the support bush 350, the connecting shaft 360, the rotation bush 370, the stopper 3 80 and the rotation cylinder 390 may be disposed in such a way of two steps, so that either step may be alternatively used depending on the height of the cargo. With su ch operation, the object of the present invention can be achieved. The present invention is not limited to the preferred embodiments as described h erein before. Those skilled in the art may readily vary and modify the embodiments of the present invention without departing from the scope of claims claimed in the pre sent invention. Thus, it should be appreciated that such variation and modification bel ong to the scope of the claimed invention. The present invention has the advantage in that it is possible to load and unload the cargo not only on the plane ground, but also on the dock with a predetermined he ight in the ware house by means of the deck unit capable of moving in the upward an d the downward direction by the elevator unit. Also, the present invention has another advantage in that the cargo is not incline d outwardly by the fall prevention unit acting only in the up-and-down direction, but is inclined inwardly, so that the stable loading of the cargo may be achieved. Also, the present invention has another advantage in that the upper frame loade d with the cargo can be firmly fixed by the upper frame fixation unit, so that the life sp an of the wire rope supporting the third post may be extended. Also, the present invention has another advantage in that the fixing pin supportin g the lower end of the second post may be automatically coupled by means of the po st fixation unit, so that the productivity of the cargo work and the firm fixation can be a chieved. Also, the present invention has another advantage in that the user's convenience may be increase by the upper frame fixation unit and the post fixation unit. Industrial Applicability The present invention may be applied only to the field of the wing body trailer, bu t also to any field related to the cargo work.