Technical Field The present invention relates to a transporter, and more particularly, to a transporter capable of smoothly and safely running over roads, ramps, stairways and the like.

Background Art Various kinds of vehicles, transporters, etc. (hereinafter, referred to as "transporter") capable of running over roads, ramps, stairways and the like with freight and a person loaded thereon have been developed. It is important to ensure safety in the transport of the freight and person along the ramps and stairways by using the transporter. Furthermore, there have been developed elevators, lifters and the like for transporting a wheelchair with a wheelchair user who cannot ascend the stairways due to his/her physical handicap sat thereon. Such these elevators and lifters are utilized in only a restricted region since they have many difficulties in their installation and maintenance because of their innate fixed structures.

Therefore, researches for developing the transporter capable of guaranteeing the safety of the user upon transport of the user through the ramps, stairways and the like have been vigorously performed.

As an example of these researches, U. S. Patent No. 5,676,215 discloses a transporter wherein a pair of crawlers having driving wheels, idle wheels, grounding wheels, and crawler belts wrapped around the wheels for running the transporter are installed on both sides of a body of the transporter. Further, belt supporting devices are constructed to support the crawler belts in cooperation with a gas spring.

The transporter of this patent can ascend a stairway by means of operation of the crawlers and the belt supporting devices. However, since an upper part of the body is tilted by the gas spring and the belt supporting devices interlocked with the crawler belts when the transporter ascends and descends the stairway, there is a

disadvantage in that it is highly likely that the freight or occupant fall off from the body. In particular, since the crawler belts positioned between the idle wheels and the grounding wheels collide with the ground when the transporter descends from the lowermost step of the stairway, landing of the transporter onto the ground becomes unstable and it is difficult for the transporter to travel. Thus, it is likely that a serious safety accident occurs. On the other hand, as the crawler belts of the crawlers become lengthened, a contact area thereof with the steps of the stairway increases, and thus, ascending and descending stability is ensured. However, an overall length of the transporter is increased and traveling resistance for the transporter increases due to the increased contact area upon travel on the roads.

As a result, there is a problem in that more power is required in driving the crawlers.

Disclosure of Invention Accordingly, the present invention is contemplated to solve several problems in the prior art. An object of the present invention is to provide a transporter capable of smoothly and safely traveling over roads, ramps, stairways and the like.

Another object of the present invention is to provide a transporter having an excellent capability to ascend the ramps, stairways and the like.

A further object of the present invention is to provide a transporter capable of always keeping a stage in a horizontal state to ensure stability thereof.

A still further object of the present invention is to provide a transporter capable of conveniently loading freight and an occupant thereon.

A still further object of the present invention is to provide a transporter wherein its traveling capability can be enhanced since crawler belts thereof can accurately come in contact with the ground or edges of steps of the stairway, and damage to the crawler belts can be effectively avoided.

A still further object of the present invention is to provide a transporter capable of stably keeping balance of a frame thereof to prevent the transport from being overturning.

A transporter of the present invention for achieving the above objects comprises a frame; a stage movably disposed on the frame; a pair of parallel main crawlers installed on the left and right sides of the frame; a pair of parallel front arms extending forward at the left and right sides of a leading end of the frame; A pair of front crawlers installed on the front arms to be moved in synchronism with the main crawlers; a front arm actuating means for actuating the front arms; and a leveling means for keeping the stage in a horizontal state by moving the stage with respect to the frame.

Brief Description of Drawings FIG. 1 is a perspective view showing the whole constitution of a transporter according to a first preferred embodiment of the present invention.

FIG. 2 is a perspective view of the transporter with a stage removed therefrom according to the first embodiment of the present invention.

FIG. 3 is a perspective view showing the constitution of a main crawler and a front crawler of the transporter according to the first embodiment of the present invention.

FIG. 4 is a perspective view showing the constitution of front arms, the front crawlers and a front arm actuating device of the transporter according to the first embodiment of the present invention.

FIG. 5 is a partial sectional view showing the constitution of a driving wheel of the main crawler, a driving wheel of the front crawler and the front arm actuating device of the transporter according to the first embodiment of the present invention.

FIG. 6 is a perspective view of a stage leveling device of the transporter according to the first embodiment of the present invention.

FIG. 7 is a sectional view of a feeding threaded shaft, a front slider, a rear slider and a restraint mechanism of the stage leveling device in the transporter according to the first embodiment of the present invention.

FIG. 8 is a side view illustrating an operation of the leveling device of the transporter according to the first embodiment of the present invention.

FIG. 9 is a block diagram illustrating a control means of the transporter according to the first embodiment of the present invention.

FIGS. 10a and 10b are sectional views showing the constitution of a tilt sensor of the transporter according to the first embodiment of the present invention.

FIG. 11 is a side view illustrating an operation of a tailgate of the transporter according to the first embodiment of the present invention.

FIGS. 12a to 12c are side views illustrating an operation of the transporter when ascending a stairway according to the first embodiment of the present invention.

FIGS 13a to 13c are side views illustrating an operation of the transporter when descending the stairway according to the first embodiment of the present invention.

FIGS. 14a and 14b are side views schematically showing a state where main crawler belts of the main crawlers of the transporter operates at edges of the stairway according to the first embodiment of the present invention.

FIG. 15 is a perspective view showing the whole constitution of a transporter according to a second embodiment of the present invention.

FIG. 16 is a side view of the transporter according to the second embodiment of the present invention.

FIG. 17 is a perspective view of the transporter with a stage removed therefrom according to the second embodiment of the present invention.

FIG. 18 is a perspective view showing the constitution of one of main crawlers, one of front crawlers and one of rear crawlers of the transporter according to the second embodiment of the present invention.

FIG. 19 is a sectional view showing the constitution of a driving wheel of the main crawler, a driving wheel of the front crawler, a traveling motor, a reducer, one of rear arms and the rear crawler.

FIG. 20 is a sectional view showing the constitution of a driven wheel of the main crawler, one of front arms and a driven wheel of the front crawler of the transporter according to the second embodiment of the present invention.

FIG. 21 is a sectional view showing the constitution of an outer idle wheel of the main crawler in the transporter according to the second embodiment of the present invention.

FIG. 22 is a sectional view showing the constitution of a main belt supporting device of the transporter according to the second embodiment of the present invention.

FIG. 23 is a sectional view showing the constitution of a front belt supporting device of the transporter according to the second embodiment of the present invention.

FIGS. 24a to 24c are views schematically showing an operation of a tailgate, rear arms, the rear crawlers and rear arm actuating devices of the transporter according to the second embodiment of the present invention.

FIG. 25 is a view schematically showing an operation of the stage and the rear arm actuating devices in the transporter according to the second embodiment of the present invention.

FIG. 26 is a block diagram illustrating a control means of the transporter according to the second embodiment of the present invention.

FIGS. 27a to 27c are side views showing an operation of the tailgate of the transporter according to the second embodiment of the present invention.

FIGS. 28a to 28c are side views illustrating an operation of the transporter when ascending a stairway according to the second embodiment of the present invention.

FIGS. 29a to 29c are side views illustrating an operation of the transporter when descending the stairway according to the second embodiment of the present invention.

FIGS. 30a and 30b are side views schematically showing a state where main crawler belts of the main crawlers of the transporter operates at edges of the stairway according to the second embodiment of the present invention.

Best Mode for Carrying Out the Invention Hereinafter, preferred embodiments of a transporter according to the present invention will be described in detail with reference to the accompanying drawings.

First, FIGS. 1 to 14 show a transporter of a first preferred embodiment of the present invention. Referring to FIGS. 1 and 2, the transporter according to the first embodiment of the present invention comprises a frame 10. The frame 10 includes a pair of left-hand and right-hand frames 11 disposed parallel to each other in a lengthwise direction, and first to third cross members 12a to 12c for fixedly connecting front, middle and rear portions of the side frames 11. A front portion of the bottom of each side frame 11 is formed with a cut-away recess ll a for preventing interference with the ground or edges or steps of stairways. Batteries 13 as a power source are mounted between the second and third cross members 12b, 12c.

Referring to FIGS. 1,2 and 8, a plate-shape stage 20 capable of loading freight, a person or the like thereon is disposed over the frame 10 so that the stage can be freely moved. A fence 21 is fixed to surround front and side portions of the stage 20 in order to protect the freight or person. A guard 22 is mounted to a leading end of the stage in order to protect the stage 20 from being damaged due to collision. Further, a plurality of shock absorbers 14 for supporting a bottom surface of the stage 20 are installed at front and rear corners of the side frames 11.

In the preferred embodiment of the present invention, the shock absorbers 14 may be replaced with stoppers for constraining a motion of the stage 20.

Referring to FIGS. 1 to 5, a pair of main crawlers 30 for traveling the transporter, each of which can be driven independently with respect to each other, are installed on the side frames 11 of the frame 10, respectively. Each main crawler 30 includes a driving wheel 31 mounted at a front portion of the side frame 11; a driven wheel 32 mounted at a rear portion of the side frame 11; an intermediate wheel 33 mounted at a portion of the side frame 11 between the driving wheel 31 and the driven wheel 32 so that it is aligned with the driven wheel 32 at a predetermined interval therefrom; and a main crawler belt 34 wrapped

around the driving wheel 31, the driven wheel 32 and the intermediate wheel 33.

The driving wheel 31 is mounted to be able to rotate about a fixed shaft 35 secured at the front portion of the side frame 11.

Further, an inner idle wheel 36 of the main crawler 30 serves to support an inner surface of the main crawler belt 34 to guide travel of the main crawler belt 34 between the driving wheel 31 and the driven wheel 32. An outer idle wheel 37 is mounted to a position adjacent to the recess 1 la of the side frame 11. The outer idle wheel 37 serves to guide the travel of the main crawler belt 34 between the driving wheel 31 and the intermediate wheel 33 and simultaneously to support an outer surface of the main crawler belt 34 to define an inverted V-shaped recess 34a in the main crawler belt 34. A belt guide 38 for supporting the inner surface of the main crawler belt 34 to cause the main crawler belt 34 to come into close contact with the ground is mounted at a portion of the side frame 11 between the driven wheel 32 and the intermediate wheel 33.

Referring to FIGS. 1 to 4, a pair of front arms 40 extend forwardly parallel to each other from leading ends of the side frames 11. A pair of front crawlers 50 are mounted on inner surfaces of the front arms 40, respectively. Each front crawler 50 includes a driving wheel 51 mounted at a rear portion of the front arm 40 to be coaxial with the driving wheel 31 of the main crawler 30, a driven wheel 52 mounted at a front portion of the front arm 40, and a front crawler belt 53 wrapped around the driving wheel 51 and the driven wheel 52. A belt guide 55 for supporting an inner surface of the front crawler belt 53 to cause the front crawler belt 53 to come into close contact with the ground is mounted at a portion of the front arm 40 between the driving wheel 51 and the driven wheel 52.

As shown in FIGS. 4 and 5, the transporter of the present invention includes a pair of traveling motors 60 as a driving means for driving the driving wheels 31 of the main crawlers 30 and the driving wheels 51 of the front crawlers 50, respectively ; and a pair of reducers 61 for reducing rotational speeds of the traveling motors 60, respectively. Each traveling motor 60 and each reducer 61 are fixedly installed within a casing 15 mounted to one of the side frames 11 of the frame 10.

An output shaft 61a of the reducer 61 is aligned to be coaxial with the fixed shaft 35 of the main crawler 30, and a boss 5 la of the driving wheel 51 of the front crawler 50 is fitted over and overlapped with the fixed shaft 35 of the main crawler 30 and the output shaft 61a of the reducer 61. Further, the driving wheel 31 of the main crawler 30 and the driving wheel 51 of the front crawler 50 are fixed to each other by a key 62 in order to move together.

Referring to FIGS. 2,4 and 5, a boss 41 fitted over the boss 51a of the driving wheel 51 of the front crawler 50 is formed at a rear end of the front arm 40.

A pair of front arm actuating devices 70 are operatively connected to the bosses 41 of the front arms 40. Each front arm actuating device 70 serves as a driving means, and includes a single arm motor 71, and a reducer 72 for reducing driving force rotational speed of the arm motor 71. The arm motor 71 and reducer 72 of the front arm actuating device 70 are fixedly installed to the casing 15.

Further, the front arm actuating device 70 includes a first power transmitting device 80 for transmitting the driving force from the reducer 72 to any one of the front arms 40, and a second power transmitting device 90 for transmitting the driving force from the reducer 72 to another front arm 40. The first power transmitting device 80 comprises a driving sprocket 81 mounted to an output shaft 72a of the reducer 72, a driven sprocket 82 mounted to the boss 41 of the front arm 40, and a chain 83 wrapped around the driving and driven sprockets 81,82. The second power transmitting device 90 comprises an intermediate shaft 92 which is disposed parallel to the output shaft 72a of the reducer 72 and of which both ends are rotatably supported to the casing 15 through bearings 91, a first driving sprocket 93 mounted to the output shaft 72a of the reducer 72, a first driven sprocket 94 mounted to one end of the intermediate shaft 92, and a first chain 95 wrapped around the first driving and driven sprockets 93,94. In addition, the second power transmitting device 90 comprises a second driving sprocket 96 mounted to the other end of the intermediate shaft 92, a second driven sprocket 97 mounted to the boss 41 of the front arm which is disposed on the side opposite to the arm motor 71, and a second chain 98 wrapped around the second driving and driven sprockets 96,97.

Referring to FIGS. 6 to 8, the transporter of the present invention includes a leveling device 100 for always keeping the horizontality of the stage 20 by causing the stage 20 to move with respect to the frame 10. The leveling device 100 includes a feeding threaded shaft 101 disposed below the stage 20 along the lengthwise direction of the frame 10, and a pair of guide bars 102 disposed parallel to each other on both sides of the feeding threaded shaft 101. First and second unthreaded shaft portions 101a, 101b are formed at both ends of the feeding threaded shaft 101, respectively. The central portions and both ends of the feeding threaded shaft 101 and the guide bars 102 are supported by Plummer blocks 101 c, 102a fixed to a bottom surface of the stage 20, respectively. Front and rear sliders 103, 104 of the leveling device 100 reciprocate along the lengthwise direction at the front and rear of the stage 20, respectively. In the central portions of the front and rear sliders 103,104 are mounted feeding nuts 103a, 104a which are threadedly moved along the feeding threaded shaft 101, while at both ends thereof are mounted a pair of guide blocks 103b, 104b which linearly reciprocate along the guide bars 102.

Further, the leveling device 100 includes a stage motor 105 for rotating the feeding threaded shaft 101, a reducer 106 for reducing the rotational speed of the stage motor 105, and first and second gears 107a, 107b for transmitting the driving force outputted through an output shaft 106a of the reducer 106 to the feeding threaded shaft 101. One side ends of a pair of front rods 108 and a pair of rear rods 109 are pivotably connected to the guide blocks 103b, 104b of the front and rear sliders 103,104 through first joints 108a, 109a, respectively. At this time, the pair of front rods 108 are fixedly connected to each other by a supporting bar 108c.

In addition, the other side ends of the front and rear rods 108,109 are pivotably connected to fixed shafts 110 through second joints 108b, 109b, respectively.

Both ends of each fixed shaft 110 are fixed to the side frame 11 of the frame 10 and the second cross member 12b through first and second brackets 110a, 110b, respectively.

A restraint mechanism 120 of the leveling device 100 includes first and

second actuating pieces 121,122 for restraining lateral sides of the feeding nuts 103a, 104a of the front and rear sliders 103,104, and the first and second actuating pieces 121,122 are fixedly connected to each other by means of a connecting bar 130. Any one of the feeding nuts 103a, 104a of the front and rear sliders 103,104 restrained by the first and second actuating pieces 121,122 of the restraint mechanism 120 is positioned at any one of the first and second unthreaded shaft portions 101a, 101b of the feeding threaded shaft 101 to be idling, while the other feeding nut is positioned at the feeding threaded shaft 101.

Referring to FIGS. 6 and 7, the feeding nut 103a of the front slider 103 is placed onto the first unthreaded shaft portions 101a of the feeding threaded shaft 101, and the feeding nut 104a of the rear slider 104 is placed close to the second unthreaded shaft portion 101b of the threaded shaft 101. Under these circumstances, the front rod 108 and the rear rod 109 are spaced apart from each other with respect to the fixed shaft 110, and the stage 20 is supported by the shock absorbers 14 of the frame 10. Thus, as shown in FIG. 11, the stage 20 defines a horizontal surface parallel to the ground 1.

Referring to FIGS. 1 and 11, a tailgate 130 is installed at a rear portion of the stage 20 so that it is opened and closed by a geared motor 131. An upper end of the tailgate 130 is a free end, and it is in contact with the ground 1 when the tailgate is completely opened. Thus, a bridge for assisting freight to be loaded and a person to get on the stage is formed between the ground 1 and the stage 20.

Alternatively, when the tailgate 130 is closed, the tailgate 130 blocks a rear portion of the fence 21. Thus, the freight and the occupant can be safely protected by the closed tailgate.

As shown in FIGS. 1 and 13c, rearward extending tail supporters 140 are fixedly mounted at rear ends of the side frames 11 of the frame 10. A free end of the tail supporter 140 is sloped to face upwardly.

FIG. 9 shows a block diagram for illustrating a control process of the transporter according to the first embodiment of the present invention. Referring to FIG. 9, the transporter of the present invention includes the traveling motors 60;

the arm motor 70; a controller 150 which outputs signals for driving the stage motor 105 and the geared motor 131 and controls the motors 105,131; a control panel 160 which can be manipulated by an operator or occupant; a sensing unit 170 for sensing a traveling state of the transporter and inputting the sensed state into the controller 150, a display unit 180 such as a LCD or monitor for displaying the traveling state of the transporter, and a sound output unit 181 such as speakers for outputting sounds. In FIG. 9, the traveling motors 60 are denoted as a left traveling motor 60-1 and a right traveling motor 60-2 for independently driving the left and right main crawlers 30 and the left and right front crawlers 50.

As shown in FIG. 1, the control panel 160 is installed on the fence 21, and it comprises a power switch for turning on/off electric power from the batteries 13, and a manipulating lever or joystick and button switches for inputting direction control signals related to a forward movement, a backward movement, left turn and right turn of the transporter.

Referring to FIG. 9 again, the sensing unit 170 includes left and right speed sensors 171a, 171b for detecting a traveling speed of the transporter by sensing rotational speeds of the left and right traveling motors 60-1, 60-2, respectively; and a tilt sensor 172 mounted at the bottom surface of the stage 20 for sensing an angle of the stage 20 with respect to the frame 10.

Referring to FIGS. 10a and lOb, the tilt sensor 172 includes a housing 173 and a cover 174 for covering the housing 173, which are in turn mounted to the bottom surface of the stage 20 by a bolt 175. A weight 176 which swings on a hinge shaft 176a, and first and second switches 177a, 177b which are contacted with the weight 176 to output switching signals are installed within the housing 173.

The housing 173 is filled with nonconductive oil 178 for damping vibration of the weight 176 and external vibration and keeping an operation of the weight 176 stable, and a gasket 179 is interposed between the housing 173 and the cover 174 in order to become airtight therebetween. In the preferred embodiment of the present invention, in order to sense an angle of the stage 20 to be tilted forwardly and rearward, the tilt sensor 172 is installed such that the first and second switches 177a,

177b are disposed in a fore and aft direction of the stage 20. Further, in order to sense an angle of the stage 20 to be tilted from side to side, the tilt sensor 172 may be installed such that the first and second switches 177a, 177b are disposed in a right and left direction of the stage 20.

Hereinafter, the operation of the transporter according to the first embodiment of the present invention constructed as such will be described.

Referring to FIG. 11, in order to load freight or a person onto the stage 20 of the transporter according to the first embodiment of the present invention, the closed tailgate 130 is first rotated and opened by means of actuation of the geared motor 131. Then, since the free end of the tailgate 130 comes into contact with the ground 1 to form the bridge, it is convenient to load the freight and person. In particular, a wheelchair user who sat in the wheelchair 3 can get on the tailgate 130.

The user can conveniently move toward and get on the stage 20 after leveling the stage 20 and the tailgate 130 with each other through actuation of the geared motor 131.

Referring to FIGS. 1 and 12a, when the transporter travels along a road, the stage 20 is supported by the shock absorbers 14 of the frame 10 to maintain the horizontality thereof. Leading ends of the front arms 40 are lifted up from the ground, while only the front crawler belts 53 wrapped around the driving wheels 51 of the front crawlers 50 are in contact with the ground. Therefore, since the contact area between the transporter and the ground is decreased, travelling resistance for the transporter that travels along the road is also decreased, and thus, travelling capability is improved.

On the other hand, as for the travel of the transporter, when the traveling motor 60 is driven by means of manipulation of the control panel 160, the rotational speed of the traveling motor 60 is reduced by the reducer 61. Then, the driving wheel 51 of the front crawler 50 is rotated through the output shaft 61a of the reducer 61. The driving wheel 51 of the front crawler 50 is rotated in synchronism with the driving wheel 31 of the main crawler 30. By means of the rotation of the driving wheel 31 of the main crawler 30, the main crawler belt 34 travels

sequentially along the inner idle wheel 35, the first driven wheel 32, the intermediate wheel 33 and the outer idle wheel 35 to cause the transporter to travel.

Referring to FIG. 9, when the left and right traveling motor 60-1,60-2 are driven together, the transporter can move forward or backward. If the left traveling motor 60-1 is stopped and the right traveling motor 60-2 is driven, the transporter can turn left. Alternatively, if the right traveling motor 60-2 is stopped and the left traveling motor 60-1 is driven, the transporter can turn right.

Next, the operation of the transporter when ascending a stairway will be described with reference to FIGS. 12a to 12c. As shown in FIG. 12a, when the transporter moves forward by means of the main crawler belts 34 of the main crawlers 30 in the state where the front arms 40 are lifted up from the ground, the front crawler belts 53 of the front crawlers 50 come in contact with an edge 2a of the lowermost step 2-1 and starts to ascend the lowermost step 2-1. When the front crawler belts 53 of the front crawlers 50 ascend a second step 2-2 beyond the lowermost step 2-1 of the stairway, the front arms 40 are rotated to be gradually lowered by means of actuation of the arm motor 71. As the front arms 40 are lowered, the front crawler belts 53 of the front crawlers 50 and the main crawler belts 34 of the main crawlers 30 are gradually aligned with each other, and thus, the transporter can ascend the second step 2-2.

As shown in FIG. 12b, when the main crawler belts 34 of the main crawlers 30 ascend the stairway 2 halfway beyond the second step 2-2, the main crawler belts 34 of the main crawlers 30 and the front crawler belts 53 of the front crawlers 50 are perfectly aligned with each other to be in contact with a plurality of positions of the stairway 2. Accordingly, the transporter can smoothly and stably ascend the stairway 2.

Referring to FIGS. 12c and 14a, when the front crawler belts 53 of the front crawlers 50 pass through a second step 2-3 from a top end of the stairway and an edge 2a of the uppermost step 2-4 of the stairway, the edge 2a of the uppermost step 2-4 is positioned in the recesses 34a of the main crawler belts 34 of the main crawlers 30. At this time, since the main crawler belts 34 of the main crawlers 30

come into contact with the two positions of the ground 1 and the stairway 2, the transporter passing through the edge 2a of the uppermost step 2-4 of the stairway can be prevented from being subject to abrupt change of slope thereof. Thus, a pitching phenomenon of the transporter around the edge 2a of the uppermost step 2- 4 as a fulcrum can be avoided. Accordingly, the transporter can smoothly and stably pass through the edge 2a of the uppermost step 2-4, and particularly, the transporter can be prevented from overturning. These recesses 34a of the main crawlers 30 can prevent the pitching of the transporter from occurring even when the transporter travels along rough roads or runs over the edges. Thereafter, as the transporter moves forward, the front arms 40 are gradually lowered by driving the arm motor 71. Then, the front crawler belts 53 of the front crawlers 50 come in contact with the ground to facilitate the forward movement of the transporter.

The operation of the transporter when descending the stairway will be described with reference to FIGS. 13a to 13c. When the front crawlers 50 approach to the edge 2a of the uppermost step 2-4, the front arms 40 are gradually lowered by means of actuation of the arm motor 71 so that the front crawler belts 53 of the front crawlers 50 come in contact with the edge 2a of the uppermost step 2-4, as shown in FIG. 13a. The front crawler belts 53 of the front crawlers 50 to come into contact with the edge 2a of the uppermost step 2-4 allow the following main crawler belts 34 of the main crawlers 30 to approach to the uppermost step 2-4.

When the front crawler belts 53 of the front crawlers 50 pass through the uppermost step 2-4 and the second step 2-3 from the top end of the stairway, the edge 2a of the uppermost step 2-4 is placed in the recesses 34a of the main crawler belts 34 of the main crawlers 30. In the same way as the ascending operation of the transporter, these recesses 34a of the main crawlers 30 prevent the pitching of the transporter around the edge 2a of the uppermost step 2-4 which serves as a fulcrum, as shown in FIG. 14b.

As shown FIG. 13b, when the main crawler belts 34 of the main crawlers 30 pass through the uppermost step 2-4, the front arms 40 are gradually lifted by means of actuation of the arm motor 71 so that the main crawler belts 34 of the main

crawlers 30 and the front crawler belts 53 of the front crawlers 50 are aligned with each other. Therefore, the main crawler belts 34 of the main crawlers 30 and the front crawler belts 53 of the front crawlers 50 come in contact with a plurality of positions of the stairway 2. Accordingly, the descending operation of the transporter can be smoothly and stably performed.

Further, after the leading ends of the front crawler belts 53 of the front crawlers 50 pass the lowermost step 2-1 and then come in contact with the ground, the front arms 40 are lifted by means of actuation of the arm motors 71 so that the contact area of the front crawler belts 34 with the ground is decreased and the contact area of the main crawler belts 34 with the ground is increased. As shown in FIG. 13c, at the final stage of the stairway descending operation of the transporter, the tail supporters 140 are supported by the edge 2a of the lowermost step 2-1 to assist the main crawler belts 34 of the main crawlers 30 to come in contact with the ground. Thus, the transporter can come in contact with the ground in a stable posture without colliding with the ground and be prevented from overturning due to its unstable contact with the ground.

On the other hand, referring to FIGS. 6 to 9, when the transporter ascends or descends the stairway 2 or the ramps, the stage 20 is tilted with respect to the horizontal surface. The tilt sensor 172 senses a tilted angle of the stage 20, and the controller 150 outputs control signals for the stage motor 105 and drives the stage motor 105 in response to the signals inputted from the tilt sensor 172. The driving force from the stage motor 105 is reduced by the reducer 106. Then, the feeding threaded shaft 101 is rotated by means of the first and second gears 107a, 107b connected to the output shaft 106a of the reducer 106. At this time, the stage motor 105 is driven forward or backward according to the control signals of the controller 150, and consequently, the feeding threaded shaft 101 is rotated forward or backward.

Referring to FIGS. 7,8,12b and 12c, when the feeding threaded shaft 101 is rotated forward, the feeding nut 103 of the front slider 103 placed on the unthreaded shaft portion 10 la of the feeding threaded shaft 101 is idling at the position where it

was. Further, the feeding nut 104a of the rear slider 104 is threadedly moved along the feeding threaded shaft 101 to convey the rear slider 104 toward the center of the feeding threaded shaft 101. As the rear slider 104 is moved, the rear rods 109 connected to guide blocks 104b of the rear slider 104 are raised upright so that it causes the stage 20 to form the horizontal surface by lifting the rear portion of the stage 20 with respect to the frame 10.

Referring to FIGS. 7 and 13 a to 13c, when the feeding threaded shaft 101 is rotated backward, the feeding nut 104a of the rear slider 104 engaged with the feeding threaded shaft 101 is conveyed to the second unthreaded shaft portion 101b by means of the threaded movement, and is then idling at that position. The feeding nut 104a of the rear slider 104 to be conveyed pushes and conveys the second actuating piece 122 of the restraint mechanism 120. The first actuating piece 121 of the restraint mechanism 120 restrains the feeding nut 103a of the front slider 103 and conveys the feeding nut 103a from the first unthreaded shaft portion 101a of the feeding threaded shaft 101 to the center of the shaft 101. As the feeding nut 103a of the front slider 103 is conveyed to the center of the feeding threaded shaft 101, the front rods 108 are raised upright so that it causes the stage 20 to form the horizontal surface by lifting a front portion of the stage 20 with respect to the frame 10. That is, when the transporter ascends or descends the stairway 2 or ramps, the stage 20 is always kept horizontal in cooperation with the leveling device 100, the controller 150 and the tilt sensor 172. Therefore, the freight and occupant can be kept in their stable posture.

FIGS. 15 to 30 show a transporter according to a second embodiment of the present invention. Referring to FIGS. 15 to 18, the transporter according to the second embodiment of the present invention comprises a frame 210. The frame 210 includes a pair of left-and right-hand side frames 211 disposed parallel to each other in a lengthwise direction, and first to fifth cross members 212a to 212e for fixedly connecting the pair of side frames 211. A front portion of the bottom of each side frame 211 is formed with a cut-away recess 211a for preventing interference with the ground, or edges or steps of stairways. Batteries 213 as

power sources are mounted on the second and third cross members 212b, 212c. A freely movable plate-shaped stage 220 capable of loading freight, a person or the like thereon is disposed on the frame 210. A fence 221 is built around the front and side portions of the stage 220 in order to protect the freight or person.

Further, a pair of main crawlers 230 for traveling the transporter, which can be driven independently of each other, are installed on the side frames 211 of the frame 210, respectively. Each main crawler 230 includes a driving wheel 231 mounted at a rear portion of the side frame 211; a driven wheel 232 mounted to be rotatable about a fixed shaft 232a secured at a front portion of the side frame 211; an intermediate wheel 233 mounted at a portion of the side frame 211 between the driving wheel 231 and the driven wheel 232 so that it is aligned with the driven wheel 232 with a predetermined interval therebetween; and a main crawler belt 234 wrapped around the driving wheel 231, the driven wheel 232 and the intermediate wheel 233.

As shown in FIGS. 16 and 21, an outer idle wheel 235 is mounted to be rotatable about a fixed shaft 23 5 a in vicinity of the recess 211 a of each side frame 211. The outer idle wheel 235 serves to guide traveling of the main crawler belt 234 between the driven wheel 232 and the intermediate wheel 233 and simultaneously to support an outer surface of the main crawler belt 234 to define an inverted V-shaped recess 234a in the main crawler belt 234. A belt guide 236 for supporting an inner surface of the main crawler belt 234 and guiding the traveling thereof is mounted at a portion of the side frame 211 between the intermediate wheel 233 and the outer idle wheel 235.

Referring to FIGS. 15 to 18 and 20, a pair of parallel front arms 240 extend forward from leading ends of the side frames 211, respectively. A boss 241 formed at a rear end of each front arm 240 can be rotated about the fixed shaft 232a.

Leading ends of the pair of the front arms 240 are fixedly connected by an arm cross member 242. A pair of front crawlers 250 are installed on outer surfaces of the front arms 240. Each front crawler 250 includes a driving wheel 251 mounted at a rear portion of the front arm 240 to be coaxial with and operated in

synchronism with the driven wheel 232 of the main crawler 232, a driven wheel 252 mounted at a front portion of the front arm 240, and a front crawler belt 253 wrapped around the driving wheel 251 and the driven wheel 252. FIG. 20 shows that the driven wheel 232 of the main crawler 230 and the driving wheel 251 of the front crawler 250 are integrally constructed together. However, it is merely illustrated by way of example, and thus, the driven wheel 232 of the main crawler 230 and the driving wheel 251 of the front crawler 250 may be constructed separately.

As shown in FIGS. 17 and 19, the transporter includes traveling motors 260 as a driving means for driving the driving wheels 231 of the main crawlers 230, reducers 261 for reducing the rotational speeds of the traveling motors 260, and brakes 262 for braking the traveling motors 260. Each traveling motor 260 and its reducer 261 are fixedly installed on the side frame 211 of the frame 210. The driving wheel 231 of the main crawler 230 is fixed to an output shaft 261a of the reducer 261.

Referring to FIGS. 15 and 17, the arm cross member 242 of the front arm 240 is operatively connected to a front arm actuating device 270. The front arm actuating device 270 includes a pair of arm hydraulic actuators 271 disposed at the left and right sides of the front portion of the frame 210. A cylinder 27 la of each arm hydraulic actuator 271 is pivotably connected to the frame 210 through a first joint 272a, and a cylinder rod 271b of the arm hydraulic actuator 271 is pivotably connected to the arm cross member 242 through a second joint 272b.

Referring to FIGS. 17 to 19 and 22, the transporter includes main belt supporting devices 280 for supporting the traveling of portions of the main crawler belts 234 which were in contact with the ground between the driving wheels 231 and the intermediate wheels 233 of the main crawlers 230. Each main belt supporting device 280 includes a roller chain 283 wrapped around first and second wheels 281,282 formed at the driving wheel 231 and the intermediate wheel 233 of the main crawler 230, respectively, and a chain cover 284 mounted on the roller chain 283 to support the inner surface of the main crawler belt 234. A slip pad 286

having a guide groove 285 for guiding the traveling of the roller chain 283 is mounted between the driving wheel 231 and the intermediate wheel 233 of the main crawler 230. The slip pad 286 is fixed to the side frame 211 of the frame 210 through a bracket 287.

The roller chain 283 and the chain cover 284 of the main belt supporting device 280 travels along the guide groove 285 and simultaneously support the inner surface of the main crawler belt 234 to prevent deformation of the main crawler belt.

Thus, the main crawler belt 234 can be kept in a stable traveling state without any deformation even when passing through edges of stairways or rough roads. In addition, it is possible to prevent vibration and damage due to the deformation of the main crawler belt 234.

Referring to FIGS. 17,18,20 and 23, the transporter includes front belt supporting devices 290 for supporting the traveling of portions of the front crawler belts 253 which were in contact with the ground between the driving wheels 251 and the driven wheels 252 of the front crawlers 250. In the same way as the main belt supporting device 280, each front belt supporting device 290 includes a roller chain 293 wrapped around first and second wheels 291,292 formed at the driving wheel 251 and the driven wheel 252 of the front crawler 250, respectively, and a chain cover 294 mounted on the roller chain 293 to support the inner surface of the front crawler belt 253. Further, a slip pad 296 having a guide groove 295 for guiding the traveling of the roller chain 293 is mounted between the driving wheel 251 and the driven wheel 252 of the front crawler 250. The slip pad 296 is fixed to the front arm 240 through a bracket 297.

Referring to FIGS. 17, 28a to 28c and 29a to 29c, the transporter includes a leveling device 300 for always keeping the horizontality of the stage 220 by moving the stage 220 with respect to the frame 210. The leveling device 300 includes a pair of front hydraulic actuators 301 disposed at the left and right sides of a front portion of the frame 210 and operatively connected to a front portion of the stage 220, and a pair of rear hydraulic actuators 302 disposed at the left and right sides of a rear portion of the frame 210 and operatively connected to a rear portion of the

stage 220. Cylinders 301a, 302b of the front and rear hydraulic actuators 301, 302 are pivotably connected to the frame 210 through first joints 303a, 304a, respectively. Cylinder rods 301b, 302b are pivotably connected to the stage 220 through second joints 303b, 304b, respectively. Furthermore, the leveling device 300 includes a pair of support bars 305 for restraining the movement of the stage 220 by connecting the left and right rear portions of the frame 210 with the stage 220. A lower end of each support bar 305 is pivotably connected to the third cross member 212c of the frame 210 through a first joint 306a, and an upper end thereof is pivotably connected to the stage 220 through a second joint 306b. As shown in FIGS. 16 and 17, a pair of stoppers 307 are mounted at the left and right sides of a rear portion of the frame 210 to restrain the stage 220 by supporting a rear portion of the bottom surface of the stage 220.

Referring to FIGS. 15 to 17, and 27a to 27c, a tailgate 310 is installed at a rear portion of the stage 220 so that a hinge bracket 311 of the tailgate 310 is opened and closed while rotating about a hinge 312 mounted at a lower rear end of the stage 220. Side portions of the tailgate 310 are surrounded by a fence 313.

The tailgate 310 is configured such that it can be opened and closed by means of actuation of a gate hydraulic actuator 314 as a driving means. A cylinder 314a of the gate hydraulic actuator 314 is pivotably connected to the bottom surface of the stage 220 through a first joint 315a, and a cylinder rod 314b of the gate hydraulic actuator 314 is pivotably connected to a lower end of the tailgate 310 through a second joint 315b.

Referring to FIGS. 15 to 19, a pair of rearward extending rear arms 320 are mounted at rear ends of the side frames 211 of the frame 210. A leading end of each rear arm 320 is a free end, and a boss 321 disposed at a rear end of the rear arm 320 is mounted to be rotated about a boss 261b of the reducer 261. A pair of rear crawlers 330 are mounted on outer surfaces of the rear arms 320. Each rear crawler 330 includes a driving wheel 331 mounted to be moved in synchronism with driving wheel 231 of the main crawler 230, a driven wheel 332 mounted at a front portion of the rear arm 320, and a rear crawler belt 333 wrapped around the

driving wheel 331 and the driven wheel 332. A belt guide 334 for supporting an inner surface of each rear crawler belt 333 to cause the rear crawler belt 333 to be in close contact with the ground is mounted at a portion of the rear arm 320 between the driving wheel 331 and the driven wheel 332. FIG. 19 shows the constitution in which the driving wheel 231 of the main crawler 230 and the driving wheel 331 of the rear crawler 330 are integrally formed together. However, it is merely illustrated by way of example, and thus, the driving wheel 231 of the main crawler 230 and the driving wheel 331 of the rear crawler 330 may be constructed separately.

Referring to FIGS. 15,24a to 24c and 25, the transporter includes a rear arm actuating device 340 for interlocking the stage 220, the tailgate 310 and the rear arms 320. The rear arm actuating device 340 includes a pair of guides 341 each of which is mounted at a rear upper portion of the side frame 211 of the frame 210 and has a substantially vertical slot 341a, first links 343 each of which has one end connected to one side of each rear arm 320 through first pivots 342a and the other end having a second pivot 342b movably inserted into the slot 341 a of the guide 341, second links 344 each of which has one end kept in slidable contact with the second pivot 342b of the first link 343 and is formed with a slot 344a in vicinity of the other end thereof, third links 345 each of which has one end with a third pivot 343c for moving along the slot 344a of the second link 344, and fourth links 346 each of which has one end connected to the other end of the third link 345 through a fourth pivot 342d and the other end fixed to a lower end of the tailgate 310.

Although it has been described that the fourth link 346 of the rear arm actuating device 340 is fixed to the lower end of the tailgate 310, the fourth link may be connected to the rear end of the stage 220.

The rear arm actuating device 340 further includes compression springs 347 for returning the respective rear arms 320 to a lifted position. One end of each compression spring 347 is connected to the side frame 211 of the frame 210 and the other end thereof is connected to the rear arm 320. Herein, the lifted position of the rear arm 320 means a position where the rear arm 320 is tilted at an angle of 45

degrees with respect to the frame 210. The rear arm 320 moves between the lifted position and a ground contacting position where the rear crawler belt 333 of the rear crawler 330 is aligned with the main crawler belt 234 of the main crawler 230 to be in contact with the ground.

FIG. 26 shows a block diagram for illustrating control of the transporter according to the second embodiment of the present invention. Referring to FIG.

26, the transporter includes a controller 350 which outputs control signals for driving the traveling motors 260 and controls the traveling motors 260, a control panel 360 manipulated by an operator or occupant, a sensing unit 370 for sensing a traveling state of the transporter and inputting the sensed state into the controller 350, a display unit 380 such as a LCD or monitor for displaying the traveling state of the transport, and a sound output unit 381 such as speakers for outputting sounds.

In FIG. 26, the traveling motors 260 are denoted as a left traveling motor 260-1 and a right traveling motor 260-2 for independently driving the left and right main crawlers 230.

As shown in FIG. 16, the control panel 360 and the display unit 380 are installed on the fence 221, and include a power switch for turning on/off the electric power from the batteries 213, and a manipulating lever or joystick, button switches and the like capable of inputting direction control signals related to a forward movement, a backward movement, left turn and right turn of the transporter. The sensing unit 370 includes left and right speed sensors 371a, 371b for detecting a traveling speed of the transporter by sensing rotational speeds of the left and right traveling motors 260-1, 260-2, and a pair of tilt sensors 372 mounted at front and rear portions of the bottom surface of the stage 220 for sensing a tilted angle of the stage 220 with respect to the frame 210. In this embodiment, each tilt sensor 372 is a 2-axis sensor of which one axis is used to sense the tilted angle of the stage 220 with respect to a horizontal plane and the other axis is used to sense the speed.

Since the structure and operation of such a 2-axis sensor have been well known, the detailed description thereof will be omitted.

Referring to FIGS. 17 and 26, the transporter includes a hydraulic pressure

supplying device 390 for controlling the arm hydraulic actuators 271, the front hydraulic actuators 301, the rear hydraulic actuators 302 and the gate hydraulic actuator 314 in accordance with the control signals from the controller 350 of the transporter. A hydraulic pressure controller 391 of the hydraulic pressure supplying device 390 is connected to a hydraulic pump unit 392 for generating hydraulic pressure, a valve unit 393, and an accumulator 394. The hydraulic pressure supplying device 390 is mounted between the second and third cross members 212b, 212c of the frame 210. Since the structure and operation of the hydraulic pressure supplying device 390 have been well known, the detailed description thereof will be omitted.

Hereinafter, the operation of the transporter according to the second embodiment of the present invention constructed as such will be described.

Referring to FIGS. 27a to 27c, in order to load freight or a person onto the stage 220 of the transporter, the closed tailgate 310 is first opened by means of actuation of the gate hydraulic actuator 314. The free end of the tailgate 310 is supported by the ground 1 to form a bridge. A wheelchair user can get on the tailgate 310 in a state where the user sits on the wheelchair 3. The user can easily get on the stage 220 by moving onto the stage 220 after leveling the stage 220 and the tailgate 310 by means of the actuation of the gate hydraulic actuator 314.

As shown in FIGS. 24a to 24c, when the tailgate 310 is opened, the fourth links 346 and the third links 345 of the rear arm actuating device 340 connected to the rear end of the tailgate 310 are articulately moved to pull up the folded second links 344 which in turn are unfolded. At this time, the first links 343 pressed down by means of the contact with the second links 344 are relieved from the restraint.

At the same time, the compression springs 347 are stretched and the rear arms 320 are pushed and rotated toward the ground, so that the rear crawler belts 333 of the rear crawlers 330 come in contact with the ground. Therefore, it is prevented that the center of gravity of the transporter is shifted rearward while the tailgate 310 is opened and that a front portion of the frame 210 is lifted while freight is loaded onto or a person gets on the transporter through the tailgate 310.

As shown in FIG. 16, when the transporter travels along a road, the main crawler belts 234 of the main crawlers 230 are in contact with the ground, and the leading ends of the front arms 240 and the rear arms 320 are lifted up from the ground. Therefore, the front crawler belts 253 of the front crawler 250 and the rear crawler belt 333 of the rear crawler 330 are not in contact with the ground. When the traveling motor 260 is driven by means of manipulation of the control panel 360, the rotational speed of the traveling motor 260 is reduced by the reducer 261, and then, the driving wheels 231 of the main crawlers 230, the driving wheels 251 of the front crawlers 250, and the driving wheels 331 of the rear crawlers 330 are rotated in synchronism with one another. By means of the rotation of the driving wheels 251 of the front crawlers 250, the main crawler belts 234 travels along the driven wheels 232, the intermediate wheels 233 and the outer idle wheels 235 to move the transporter.

Next, the operation of the transporter when ascending a stairway will be described with reference to FIGS. 28a to 28c. When the transporter moves forward by means of the main crawler belts 234 of the main crawlers 230 in the state where the front arms 240 and the rear arms 320 are lifted up from the ground, the front crawler belts 253 of the front crawlers 250 come in contact with an edge 2a of the lowermost step 2-1 and ascends the lowermost step 2-1, as shown in FIG.

28a. When the front crawler belts 253 of the front crawlers 250 ascend a second step 2-2 beyond the lowermost step 2-1, the front arms 240 are rotated to be gradually lowered by means of actuation of the arm hydraulic actuators 271. As the front arms 240 are lowered, the front crawler belts 253 of the front crawlers 250 and the main crawler belts 234 of the main crawlers 230 are aligned with each other.

Thus, the transporter can ascend the second step 2-2. As shown in FIG. 28b, when the main crawler belts 234 of the main crawlers 230 ascend the stairway 2 halfway beyond the second step 2-2, the main crawler belts 234 of the main crawlers 230 and the front crawler belts 253 of the front crawlers 250 are perfectly aligned with each other to be in contact with a plurality of positions of the stairway 2.

Accordingly, the transporter can stably and smoothly ascend the stairway.

Referring to FIG. 28c, when the front crawler belts 253 of the front crawlers 250 pass through a second step 2-3 from the top end of the stairway and an edge 2a of the uppermost step 2-4, the edge 2a of the uppermost step 2-4 is positioned in the recesses 234a of the main crawler belts 234 of the main crawlers 230. Thereafter, as the transporter moves forward, the front arms 240 are gradually lowered by driving the arm hydraulic actuators 271. Then, the front crawler belts 252 of the front crawlers 250 come in contact with the ground to facilitate the forward movement of the transporter. At this time, as shown in FIG. 30a, the recesses 234a of the main crawlers 230 prevent pitching of the transporter around the edge 2a of the uppermost step 2-4 which serves as a fulcrum.

On the other hand, when the transporter ascends the stairway 2 or a ramp, the stage 220 is inclined with respect to a horizontal plane. The angle of the stage 220 with respect to the horizontal plane is sensed by the tilt sensors 372. The controller 350 outputs control signals for the rear hydraulic actuators 302 in response to signals inputted from the tilt sensors 372 so as to actuate the rear hydraulic actuators 302. The cylinder rods 302b are extended by means of actuation of the rear hydraulic actuators 302 so that a rear portion of the stage 220 is lifted with respect to the frame 210, thereby making the stage 220 horizontal.

Therefore, even when the transporter ascends the stairway 2, the freight or occupant on the stage 220 can be kept in a stable posture.

As shown in FIG. 25, when the rear portion of the stage 220 is lifted by the rear hydraulic actuators 302, the rear arms 320 are rotated from the lifted position to the ground contacting position by means of the compression springs 347 and the articulate movements of the first to third links 343 to 345 of the rear arm actuating device 340. Thus, the main crawler belts 234 of the main crawlers 230, the front crawler belts 253 of the front crawlers 250, and the rear crawler belts 333 of the rear crawlers 330 come in contact with a plurality of positions of the stairway 2.

Accordingly, the transporter can stably and smoothly ascend or descend the stairway 2.

The operation of the transporter when descending the stairway will be

described with reference to FIGS. 29a to 29c. When the front crawlers 250 approach the edge 2a of the uppermost step 2-4, the front arms 240 are gradually lowered by means of actuation of the arm hydraulic actuators 271 so that the front crawler belts 253 of the front crawlers 250 come in contact with the edge 2a of the uppermost step 2-4, as shown in FIG. 29a. The front crawler belts 253 of the front crawlers 250 to be in contact with the edge 2a of the uppermost step 2-4 allow the following main crawler belts 234 of the main crawlers 230 to approach the uppermost step 2-4.

As shown in FIGS. 29b and 30b, when the front crawler belts 253 of the front crawlers 250 pass through the uppermost step 2-4 and the second step 2-3 from the top end of the stairway, the edge 2a of the uppermost step 2-4 is positioned in the recesses 234a of the main crawler belts 234 of the main crawlers 230. In the same way as the ascending operation of the transporter, the recesses 234a of the main crawlers 230 prevent the pitching of the transporter about the edge 2a of the uppermost step 2-4 which serves as a fulcrum. Subsequently, when the main crawler belts 234 of the main crawlers 230 pass through the uppermost step 2-4, the front arms 240 are gradually lowered by means of actuation of the arm hydraulic actuators 271 so that the main crawler belts 234 of the main crawlers 230 and the front crawler belts 253 of the front crawlers 250 are aligned with each other.

Therefore, the main crawler belts 234 of the main crawlers 230 and the front crawler belts 253 of the front crawlers 250 come in contact with a plurality of positions of the stairway 2. Accordingly, the descending operation of the transporter can be smoothly and stably performed.

Further, after the leading ends of the front crawler belts 253 of the front crawlers 250 pass the lowermost step 2-1 and then come in contact with the ground, the front arms 240 are lifted by means of actuation of the arm hydraulic actuators 271 so that the contact area of the front crawler belts 234 with the ground is decreased and the contact area of the main crawler belts 234 with the ground is increased. As shown in FIG. 29c, at the final stage of the stairway descending operation of the transporter, the rear crawler belts 333 of the rear crawlers 330 are

supported by the edge 2a of the lowermost step 2-1 to assist the main crawler belts 234 of the main crawlers 230 to come in contact with the ground. Thus, the transporter can come in contact with the ground in a stable posture without colliding with the ground and be prevented from overturning due to unstable contact with the ground.

The aforementioned embodiments are merely preferred embodiments of the present invention, and thus, the scope of the invention is not limited to the embodiments described and shown above. Various changes, modifications and substitutions can be made by those skilled in the art without departing from the technical spirit of the invention and the scope defined by the appended claims and should be construed as falling within the scope of the invention.

Industrial Applicability As described above, according to the transporter of the present invention, the transporter can smoothly and stably travel over roads, ramps, stairways, or the like in cooperation with the main crawlers, the front crawlers, and the rear crawlers.

In addition, the transporter has an excellent capability to ascend the ramps, stairways or the like. Furthermore, there are advantages in that since the stage can be always kept in a horizontal state in response to inclination of the frame, safety of freight or an occupant can be ensured and the freight or occupant can be conveniently loaded onto or get on the transporter. Moreover, there are further advantages in that since the transport can travel while accurately coming into contact with the ground or edges of steps of the stairway, its traveling capability can be enhanced, damage to the crawler belts can be effectively avoided, and balance of the frame can be stably kept to prevent the transport from overturning.