Patent Publication Number: US-8109342-B2

Title: Beach-cleaning system for separating litter from sand, trailer incorporating same, and method of using same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority under 35 USC 119 based on Japanese patent application No. 2008-243936, filed on Sep. 24, 2008. The entire subject matter of this priority document, including specification claims and drawings thereof, is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a beach-cleaning system and method. The system includes a trailer which is loaded with, and which collectively carries a plurality of beach-cleaning apparatus for collecting litter from sandy beach areas, and a collection station in which the litter collected by the beach cleaner is accumulated. More particularly, the present invention relates a system and method for separating litter of various sizes and shapes from sand, and to a trailer incorporating the system. 
     2. Description of the Background Art 
     There is a known beach cleaner for collecting various kinds of litter scattered on the sandy beach areas, such as bathing beaches. When towed by a vehicle, during operation thereof, the beach cleaner travels on the sands of the beach to rake the sand and litter together, and collect only the litter by separating the litter from the sand. Further, when towed by the vehicle, the beach cleaner carries the litter collected thereby to a collection station, and operations for moving out the litter form a trailer are performed at the collection station. 
     The known trailer for beach cleaning is towed by a vehicle. The trailer has an accommodation portion, which is loaded with the beach cleaner and the collection station, and is used to collectively carry them to the beach. The trailer is also used as a part of the collection station (see, for example, the Japanese Patent Application Publication No. 2007-303087). 
     However, conventionally there has not been a trailer, as the one described above, which is used for collecting litter, and also for separating the collected litter from accompanying sand. 
     The known beach cleaner and the collection station offer advantages for collecting litter on sandy beach areas where the vehicle can travel. However, such beach-cleaning equipment and collection stations cannot perform the litter collection on areas where the vehicle cannot travel, such as sandy areas with large rocks. On such areas, litter has to be collected through a manual separation of litter from sand. 
     The present invention has been made in consideration of the above circumstances. Accordingly it is one of the objects of the present invention to provide a beach-cleaning trailer which allows easy collection (and separation) of litter even on areas where the beach cleaner towed by a vehicle cannot be used to collect the litter without collecting sand therewith. 
     SUMMARY OF THE INVENTION 
     In order to achieve the above objects, the present invention according to a first aspect thereof provides a beach-cleaning trailer apparatus including equipment for beach cleaning. The trailer is a box-shaped trailer formed by sidewalls, and having an opening on a top portion thereof. The trailer includes wheels arranged at side wall portions thereof. The beach-cleaning trailer is loaded with, and collectively carries, a beach cleaner and a litter collection station. The beach-cleaning equipment are towable by a vehicle so as to collect litter on the sands. The litter collected by the beach-cleaning equipment is accumulated in the litter collection station. 
     The beach-cleaning trailer includes a pair of rail members disposed on upper edges of the respective side wall portions, respectively, such that they face each other with the opening in between. A sieve unit is detachably mounted on the rail members, and is operable to reciprocally move in a back-and-forth direction along the rail members. 
     With this structure, for example, sieving can be performed with the sieve unit by placing litter along with sand on the sieve unit using a scoop or the like and reciprocally moving the sieve unit to and fro (in a back-and-forth direction) on the rail members. 
     The present invention according to a second aspect thereof, in addition to the first aspect, is characterized in that, the beach-cleaning trailer may include a driving mechanism that transmits rotary power of the wheels of the trailer to the sieve unit to move the sieve unit to and fro (in a back-and-forth direction) along the rail members based on the rotary power of the wheels. 
     With this structure, when the wheels rotate by the trailer traveling, the sieve unit can move to and fro. 
     Further, the present invention according to a third aspect thereof, in addition to the second aspect, is characterized in that the driving mechanism may be a crank mechanism including a drive wheel arranged on an axle of the wheels, a driven wheel driven in accordance with rotation of the drive wheel, and a connecting rod for operatively connecting the sieve unit with the driven wheel. 
     With such structure, rotary power of the drive wheel or the driven wheel can easily be converted to power moving the sieve unit in a back-and-forth direction. 
     The present invention also relates to a method of cleaning a sandy area, as further described herein. 
     EFFECTS OF THE INVENTION 
     The beach-cleaning trailer according to the present invention includes the pair of rail members provided on the upper edges of the respective side wall portions forming the box shape, respectively, in such a manner so as to face each other with the opening in between; and the sieve unit being capable of moving along the rail members and being detachably attached onto the rail members. 
     Accordingly, sieving can be performed by placing litter along with sand on the sieve unit using a scoop or the like, and by moving the sieve unit in a back-and-forth direction along the rail members. Therefore, the litter and the sand can easily be separated from each other, and only the litter can be collected. Thus, even on an area where litter collection is impossible using a beach cleaner, the litter can be separated and collected mechanically without collecting the litter through manual separation. 
     Moreover, the beach-cleaning trailer includes the driving mechanism that transmits rotary power of the wheels to the sieve unit to move the sieve unit in a back-and-forth direction along the rail members in accordance with the rotary power. Accordingly, when the wheels rotate during operation of the trailer, the sieve unit can move in a back-and-forth direction along the rail members. Such movement of the sieve unit allows the sieving to be performed mechanically by the sieve unit, and also makes it unnecessary to collect the litter through manual separation. 
     Furthermore, the driving mechanism is a crank mechanism to which the sieve unit is connected, by the connecting rod, to one of the drive wheel provided on the axle of the wheels and the driven wheel that rotates in accordance with the drive wheel. Accordingly, rotary power of the drive wheel or the driven wheel can easily be converted to power moving the sieve unit a back-and-forth direction, allowing the sieving to be performed by the sieve unit with a simple structure. 
     For a more complete understanding of the present invention, the reader is referred to the following detailed description section, which should be read in conjunction with the accompanying drawings. Throughout the following detailed description and in the drawings, like numbers refer to like parts. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side plan view of beach-cleaning equipment and a litter collection station loaded on a beach-cleaning trailer according to an illustrative embodiment of the present invention. 
         FIG. 2  is a top plan view of the litter collection station, in an assembled state thereof. 
         FIG. 3  is a side plan view of the litter collection station, in an assembled state thereof. 
         FIG. 4  is a side plan view a secondary beach cleaner in a state towed by a vehicle during litter collecting operation. 
         FIG. 5  is a partial top plan view of the secondary beach cleaner. 
         FIG. 6  is a side plan view of a sieve unit is attached to a trailer. 
         FIG. 7  is a top plan view of a driving mechanism shown in  FIG. 6  (the sieve unit is not shown). 
         FIG. 8  is a side plan view of a trailer provided with no driving mechanism, according to a modified embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     An embodiment of the present invention will now be described, with reference to the drawings. Throughout this description, relative terms like “upper”, “lower”, “above”, “below”, “front”, “back”, and the like are used in reference to a vantage point of an operator of the vehicle to which the inventive trailer is connected, where the operator is seated on the driver&#39;s seat and facing forward. It should be understood that these terms are used for purposes of illustration, and are not intended to limit the invention. 
     With reference to the drawings, a preferred embodiment of the present invention will be described below. 
       FIG. 1  is a side view of beach-cleaning equipment and a litter collection station loaded on a beach-cleaning trailer according to an illustrative embodiment of the present invention. 
     As shown in  FIG. 1 , a vehicle  1  includes a vehicle body, and left and right front wheels  2  and rear wheels  3  arranged at front and rear of the vehicle body. The vehicle body is generally small and lightweight. The front and rear wheels  2  and  3  are low-pressure balloon tires of relatively large diameter. 
     The vehicle  1  is an all terrain vehicle (ATV) having a large ground clearance thereby having an improved ability to especially travel on rough terrain. The vehicle includes a body frame  4  having a long box-shaped structure at a center portion of the vehicle  1  in a width direction thereof. An engine  5 , which is a prime motor of the vehicle  1 , is mounted on the body frame  4  substantially at a center portion thereof. 
     The engine  5  is a water-cooled single-cylinder engine, and outputs rotary power of the crankshaft to front and rear propeller shafts  6   a  and  6   b  via a gear-mesh-type transmission. The engine  5  may be air-cooled single-cylinder or a multi-cylinder engine. The rotary power thus outputted to the front and rear propeller shafts  6   a  and  6   b  is then transmitted to the left and right front wheels  2  and rear wheels  3  via front and rear speed reducers  7   a  and  7   b , respectively. 
     The vehicle  1  is a semi-automatic vehicle capable of changing the gear ratio of the transmission electrically. Through, for example, a centrifugal clutch, the gear ratio can be changed without clutch operations but only with operations such as pushing a change button. Such semi-automatic vehicle  1  is suitable for travel with heavy load as well as for travel at constant speed, compared to a vehicle including a belt-type transmission. 
     The left and right front wheels  2  are suspended on a front portion of the body frame  4  via a front suspension  8   a , which is an independent suspension. The left and right rear wheels  3  are suspended on a rear portion of the body frame  4  via a swing arm type rear suspension  8   b . A rear end portion of a swing arm  9  of the rear suspension  8   b  has a trailer hitch  11  for towing a trailer  13 . Moreover, as shown in  FIG. 1 , a front carrier  12   a  is supported on a front portion of the body frame  4 , and a rear carrier  12   b  is supported on a rear portion of the body frame  4 . 
     The vehicle  1  is capable of towing the trailer  13  carrying a primary beach cleaner (a first beach cleaner)  20 , a secondary beach cleaner (a second beach cleaner)  50 , a litter collection station  40 , and a sieve unit  205 , which are described later. 
     The trailer  13  is a box-shaped trailer, i.e., the trailer  13  includes a vertical shallow box having an open top. The trailer  13  has a pair of left and right wheels  15  at a substantially center portion thereof in a front-rear direction of the vehicle body. A loading unit  16  is arranged in the vertical shallow box. The trailer  13  includes a tow arm  17  extending frontwardly from a lower front portion thereof. The tow arm  17  includes a hitch coupler  17   a  arranged at front end portion thereof. The hitch coupler  17   a  corresponds to the trailer hitch  11 . 
     A portion of the litter collection station  40  (a part of separated bodies constituting the litter collection station  40 ) is accommodated in the loading unit  16 . The first and second beach-cleaning equipment  20  and  50  and the portion of the litter collection station  40  are mounted on the loading unit  16 . The beach-cleaning equipment  20  and  50  and the litter collection station  40  can be carried to a work place by the vehicle  1  towing the trailer  13  as loaded above. The frame of the loading unit includes left and right side edge members  16   b  and  16   c , respectively. 
       FIG. 1  shows a state in which the beach-cleaning equipment  20  and  50  and the litter collection station  40  are loaded in the trailer  13 .  FIG. 2  and subsequent drawings show states in which the beach-cleaning equipment  20  and  50  and the litter collection station  40  are being used on the sands, unless otherwise noted. Moreover, the state shown in  FIG. 1 , specifically, a state in which the trailer  13  has both wheels  15  on the ground and the loading unit  16  maintained at a certain height horizontally, is called a towed state of the trailer  13 . 
     In addition, in the drawings, a line GL indicates a ground surface (an upper surface of the sands), and a line CL (in  FIGS. 2 and 5 ) indicates the transverse center of the vehicle  1 , the beach-cleaning equipment  20  and  50  towed by the vehicle  1 , and the litter collection station  40  between which the vehicle  1  and the beach-cleaning equipment  20  and  50  pass through (the vehicle, beach-cleaning equipment, and litter collection station are collectively called the vehicle and the like below). 
     Moreover, an arrow FR indicates the front of the vehicle and the like in the traveling direction (front-rear direction). An arrow UP indicates the upside of the vehicle and the like in the vertical direction. An arrow LH (in  FIGS. 2 and 5 ) indicates the left side of the vehicle. 
     The beach-cleaning equipment  20  and  50  each collect various kinds of litter scattered on the sands while traveling on the sands (beach) on a coast or the like by being towed by the vehicle  1 . The litter collected by the beach-cleaning equipment  20  and  50  is collected together at the litter collection station  40  set up at a certain place on the sands. The beach-cleaning equipment  20  and  50  and the litter collection station  40  are each formed by appropriately assembling multiple types of steel product, such as stainless steels, with bonding means such as welding, for example. It may be noted that the beach-cleaning equipment  20  and  50  may be towed by a tractor. 
       FIG. 2  is a plan view showing the primary beach cleaner  20  lifted up on the litter collection station  40 .  FIG. 3  is a left-side view of the primary beach cleaner  20  lifted up on the litter collection station  40  shown in  FIG. 2 . 
     The primary beach cleaner  20  is formed as follows. Specifically, as shown in  FIG. 2 , multiple (e.g., 15) longitudinal members  21  extending in the traveling direction of the vehicle  1  are arranged in the width direction (left-right direction) at substantially equal intervals thereby forming frame  22  shaped like a duckboard with parallel slats. Moreover, multiple sand pins  23  are detachably attached to each of the longitudinal members  21  in such a manner as to protrude downward. It may be noted that the primary beach cleaner  20  has a left-right symmetric structure. 
     The longitudinal members  21 , for example, are circular steel pipes (or may be square steel pipes), and are arranged extending in the front-rear direction. Each longitudinal member  21  has a front end portion curved obliquely upward and frontward, and a rear end portion curved obliquely upward and rearward. 
     Front and rear transverse members  24   a  and  24   b  extend transversely further beyond the outermost longitudinal members  21 . A side longitudinal member  21   a  is arranged between left end portions of the respective front and rear transverse members  24   a  and  24   b . Similarly, another side longitudinal member  21   a  is arranged between right end portions of the respective front and rear transverse members  24   a  and  24   b . The side longitudinal members  21   a  have a curvature similar to a curvature of the longitudinal members  21 . 
     Further, a brace-shaped assist member  21   b  is arranged across a front portion or rear portion of the rightmost longitudinal member  21 , and across a portion that the front or rear transverse member  24   a  or  24   b  extends further rightward. Another brace-shaped assist member  21   b  is arranged across a front or rear portion of the leftmost longitudinal member  21  and a portion that the front or rear transverse member  24   a  or  24   b  extends further leftward. 
     The frame  22  formed of these has a transversely-long rectangular shape, when viewed in a top view. The left-right width of the frame  22  is greater than a width of the vehicle  1  (see  FIG. 2 ), and is also greater than a distance between left and right side structure bodies  41 R and  41 L of the litter collection station  40  (described later). 
     Accordingly, when the primary beach cleaner  20  towed by the vehicle  1  enters between the left and right side structure bodies  41 R and  41 L, left and right side portions of the frame  22  of the primary beach cleaner  20  climb up on the respective left and right side structure bodies  41 R and  41 L. Therefore, the primary beach cleaner  20  is lifted up to a certain height. It may be noted that, since the left-right width between the left and right side structure bodies  41 R and  41 L is greater than that of the vehicle  1 , the vehicle  1  can pass through between the left and right side structure bodies  41 R and  41 L. 
     When the primary beach cleaner  20  travels on the sands, the sand pins  23  catch or hitch scattered litter of relatively large size (such as ropes, nets, and driftwoods) thereby raking such litter. 
     In the frame  22 , a tow member  37  is arranged to a front portion of the longitudinal member  21  on, for example, the third from the leftmost longitudinal member  21  and that from the rightmost longitudinal member  21 . The tow members  37  allow the vehicle  1  to tow the primary beach cleaner  20 , and are shaped as thick plates extending perpendicular to the left-right direction. A connection hole (not shown) is formed in each of the tow members  37  at a front end portion thereof. A tow rod  38  is connected to the trailer hitch  11  of the vehicle  1  at one end, and to the connection hole at the other end thereof. The primary beach cleaner  20  is towed by the vehicle  1  via the tow rod  38 . 
     When viewed in a top view, the tow rod  38  has a shape in which the other ends extend from the one end connected to the trailer hitch  11 , toward the respective left and right tow members  37  in a V or Y shape ( FIG. 2 ). The one end is provided with the hitch coupler  17   a  corresponding to the trailer hitch  11 . 
     As shown in  FIG. 3 , when the primary beach cleaner  20  is lifted up on the litter collection station  40 , as discussed above, the sand pins  23  are spaced away from the upper surface of the sands enough in order to drop the litter raked by the sand pins  23 . Accordingly, the litter can be collected collectively with the sand. 
     As shown in  FIGS. 2 and 3 , the litter collection station  40  is constructed by integrally connecting the left and right side structure bodies  41 R and  41 L to each other with a pair of front and rear connection members  42 . The litter collection station  40  has a left-right and front-rear symmetric structure, except for, for example, the structure of a center portion in the front-rear direction of each of the left and right side structure bodies  41 R and  41 L. 
     Each of the left and right side structure bodies  41 R and  41 L is shaped as a trapezoid by arranging a ground member  43  and a guide member  44 . The ground member  43  is formed of, for example, a circular steel pipe. The ground member  43  extends in the front-rear direction. The guiding member  44  is formed of, for example, a circular steel pipe and shaped as a mountain of gradual slope, when viewed in a side view. The guiding member  44  is positioned above the ground member  43 . The front end portions of the ground member  43  and the guiding member  44  are connected to each other integrally. Also, rear end portions of the ground member  43  and the guiding member  44  are connected to each other integrally. 
     A foot member  45  is detachably attached to each of front and rear portions of the left and right ground members  43 . When viewed in a top view, the foot members  45  attached to the front portions is arranged such that they incline leftward and rightward, respectively, as they extend frontward; and the foot members  45  attached to the rear portions incline leftward and rightward, respectively, as they extend rearward. The foot members  45  are placed on the sands together with the corresponding ground members  43 . Therefore, the litter collection station  40  can be stably set up with its widened ground contact area. 
     The connection members  42  are each formed of, for example, a circular steel pipe and extended in the left-right direction. The connection members  42  integrally connect the left and right side structure bodies  41 R and  41 L to each other with the end portions of the connection members  42  detachably inserted into corresponding connection pipes  46  provided under front portions and rear portions of the ground members  43 . The litter collection station  40  being relatively large can be divided into multiple separate bodies (the left and right side structure bodies  41 R and  41 L and the front and rear connection members  42 ). 
     Further, each of the left and right side structure bodies  41 R and  41 L can be separated into three separate bodies, i.e., the front, middle, and rear bodies. Specifically, the left side structure body  41 L can be separated into a left front separate body  41   a , a left middle separate body  41   c , and a left rear separate body  41   b . Similarly, the right side structure body  41 R can be separated into a right front separate body  41   a , a right middle separate body  41   d , and a right rear separate body  41   b.    
     The connection pipes  46  at the front and rear of the ground members  43  are each formed of a relatively short circular steel pipe and extends in the left-right direction. Each of the connection pipes  46  is integrally connected to the corresponding ground member  43  by fitting its upper circumference into a notch formed in a lower part of the ground member  43 . Accordingly, the connection pipe  46  protrudes downward from the lower face of the ground member  43 , and is therefore buried in the sand when the litter collection station  40  is set up on the sands, preventing the litter collection station  40  from moving. 
     A locking pin  47  is inserted through each pair of the connection member  42  and the connection pipe  46 . The locking pin  47  protrudes downward into the sand at a certain degree. In other words, the locking pins  47  prevent the litter collection station  40  getting displaced (moved away) from a certain place where it is set up. The litter collection station  40  can be separated into the left and right side structure bodies  41 R and  41 L and the front and rear connection members  42  by removing the locking pins  47 , and thus separating the connection members  42  from the corresponding connection pipes  46 . 
     The front separate body  41   a  of each of the left and right side structure bodies  41 R and  41 L mainly includes a front inclination member  44   a  of the guiding member  44 , a front horizontal portion  43   a  of the ground member  43 , and a substantially-vertical front support member  48   a . The front horizontal portion  43   a  is located below the front inclination member  44   a . The front support member  48   a  arranged between a rear end portion of the front inclination member  44   a  and that of the front horizontal portion  43   a.    
     On the other hand, the rear separate body  41   b  of each of the left and right side structure bodies  41 R and  41 L consists mainly of a rear inclination member  44   b  of the guiding member  44 , a rear horizontal member  43   b  of the ground member  43 , and a substantially-vertical rear support member  48   b . The rear horizontal member  43   b  is located under the rear inclination member  44   b . The rear support member  48   b  arranged between a front end portion of the rear inclination member  44   b  and that of the rear horizontal member  43   b . It may be noted that the front and rear separated bodies  41   a  and  41   b  have the substantially similar shape in the present embodiment, and that they can be switched from front to rear. 
     In the present embodiment, the trailer  13  in the towed state constitutes the left middle separate body  41   c . Specifically, the right side wall portion  16   c  of the loading unit  16  of the trailer  13  in the towed state is formed as a single substantially-horizontal bar, and constitutes a substantially-horizontal top edge portion  44   c  of the guiding member  44 . When the trailer  13  is in the towed state and the litter collection station  40  is set up on the sands, the height of the right side wall portion  16   c , which is a right top edge portion of the loading unit  16 , is substantially similar as the height of the top edge portion  44   c  of the guiding member  44  (in an in-use state). It may be noted that, in the towed state, the trailer  13  can stand alone using a supporting leg (not shown). 
     The front inclination member  44   a  of the front separate body  41   a  can be attached and detached at a rear end portion thereof to and from a front end portion of the right side wall portion  16   c . Similarly, the rear inclination member  44   b  of the rear separate body  41   b  can be attached and detached at front end portion thereof to and from a rear end portion of the right side wall portion  16   c . The front end portion and the rear end portion of the right side wall portion  16   c  are connected, by using certain retaining mechanisms, to the rear end portion of the front inclination member  44   a  and the front end portion of the rear inclination member  44   b , respectively, while not allowed to be taken further in or out. The front and rear inclination members  44   a  and  44   b  can be separated from the right side wall portion  16   c  by removing the retainer mechanisms. 
     With such a configuration, since the right side wall portion  16   c  of the trailer  13  constitutes a portion of the left side structure body  41 L, the trailer  13  is located to the immediate left of the litter collection station  40  in a set-up state. 
     On the other hand, the right middle separate body  41   d  mainly includes the substantially-horizontal top edge portion  44   c  of the guide member  44 , a middle horizontal portion  43   c  of the ground member  43 , and multiple (a pair, in this embodiment) substantially-vertical middle support members  48   c . The middle horizontal portion  43   c  is located under the top edge portion  44   c . The middle support members  48   c  are arranged between the top edge portion  44   c  and the middle horizontal portion  43   c . The right middle separate body  41   d  is shaped like a ladder, when viewed in a side view. 
     The front inclination member  44   a  of the front separate body  41   a  can be attached and detached, at its rear end portion, to and from a front end portion of the top edge portion  44   c . Likewise, the rear inclination member  44   b  of the rear separate body  41   b  can be attached and detached, at its front end portion, to and from a rear end portion of the top edge portion  44   c.    
     Further, the front horizontal portion  43   a  of the front separate body  41   a  can be attached and detached, at its rear end portion, to and from a front end portion of the middle horizontal portion  43   c . The rear horizontal member  43   b  of the rear separate body  41   b  can be attached and detached, at its front end portion, to and from a rear end portion of the middle horizontal portion  43   c.    
     The front end portion and the rear end portion of the top edge portion  44   c  are connected, using certain retaining mechanisms, to the rear end portion of the front inclination member  44   a  and the front end portion of the rear inclination member  44   b , respectively, while allowed to be taken further in or out. The front and rear inclination members  44   a  and  44   b  can be separated from the top edge portion  44   c  by removing the retaining mechanisms. 
     Similarly, the front end portion and the rear end portion of the middle horizontal portion  43   c  are connected, using certain retaining mechanisms, to the rear end portion of the front horizontal portion  43   a  and the front end portion of the rear horizontal member  43   b , respectively, while allowed to be taken further in or out. The front and rear horizontal members  43   a  and  43   b  can be separated from the middle horizontal portion  43   c , by removing the retaining mechanisms. It may be noted that a member corresponding to the middle horizontal portion  43   c  can be provided to the left side structure body  41 L. 
     The substantially-horizontal left side edge member  16   b  of the loading unit  16  of the trailer  13  can be used as the top edge portion  44   c  of the guide member  44 , like the right side edge member  16   c . The left-right width between the left and right side edge members  16   b  and  16   c  are substantially the same as that between the left and right side structure bodies  41 R and  41 L. Accordingly, when a front end portion of the rear inclination member  44   b  of each of the rear separated bodies  41   b  is connected to a corresponding rear end portion of the left and right side edge members  16   b  and  16   c  of the loading unit  16 , the same structure as the rear portion of the litter collection station  40  in the set-up state can be reproduced. 
     This allows the primary beach cleaner  20  (and the secondary beach cleaner  50 ) loaded on the loading unit  16  to be unloaded on the sands by sliding it down along the top edge portions  44   c  and the rear inclination members  44   b  of the left and right guide members  44 . On the other hand, the primary beach cleaner  20  (and the secondary beach cleaner  50 ) on the sands can be loaded onto the loading unit  16  by sliding it up along the rear inclination members  44   b  and the top edge portions  44   c  of the left and right guide members  44 . The above state of the trailer  13  in which the left and right side edge members  16   b  and  16   c  are connected to the respective rear separated bodies  41   b  is called a load-unload operation state. 
       FIG. 4  is a side view showing a state of the secondary beach cleaner  50  during towing thereof by the vehicle.  FIG. 5  is a plan view of the secondary beach cleaner  50 . 
     The secondary beach cleaner  50  has a frame  53  which mainly includes multiple (e.g., 3) longitudinal members  51  and front and rear transverse members  52   a  and  52   b . The longitudinal members  51  extend in the vehicle traveling direction. The front and rear transverse members  52   a  and  52   b  extend in the width direction (left-right direction) while intersecting the longitudinal members  51  substantially at right angles. The frame  53  has keels  54  and scrapers  55  at a front portion thereof, and a mesh body  56  (described later) at a rear portion thereof. It may be noted that the secondary beach cleaner  50  has a left-right symmetric structure, too. 
     The longitudinal members  51  are each formed of, for example, a circular steel pipe, and are arranged extending in the front-rear direction. Each of the longitudinal members  51  is moderately cranked at longitudinal-center portion thereof, when viewed in a side view, such that rear portion thereof may be displaced slightly higher than the front portion. 
     Further, by moderately bending a longitudinal-center portion of a front portion of the longitudinal member  51 , a front half of the front portion inclines frontward and upward slightly. The front half of the front portion of the longitudinal member  51  is called a front inclination portion  57 . On the other hand, the rear end portion of the longitudinal member  51  curves upwardly. 
     The multiple longitudinal members  51  are transversely arranged parallel to each other so that they overlap, when viewed in a side view. The front and rear transverse members  52   a  and  52   b  are each formed of, for example, a steel pipe, and extend in the left-right direction. Front ends of the respective longitudinal members  51  are brought to the front transverse member  52   a  from rear and thus connected thereto. 
     Similarly, rear ends of the respective longitudinal members  51  are brought to the rear transverse member  52   b  from below and thus connected thereto. The frame  53  mainly including the longitudinal members  51  and the transverse members  52   a  and  52   b  is shaped substantially square, when viewed in a top view. It may be noted that the left-right width of the frame  53  is less than a distance between the left and right side structure bodies  41 R and  41 L of the litter collection station  40 . 
     A plural (e.g., 3) scraper frames  58  are transversely arranged parallel to each other, between the transverse-center longitudinal member  51  and the left longitudinal member  51 , as well as between the center longitudinal member  51  and the right longitudinal member  51 . The scraper frames  58  incline so that they can overlap with the front inclination portions  57  of the longitudinal members  51 , when viewed in a side view. The scraper frames  58  are each formed of a circular steel pipe (or may be a square steel pipe) having the same or similar diameter as the longitudinal member  51 . 
     Front ends of the respective scraper frames  58  are brought to the front transverse member  52   a  from rear, and thus connected thereto. On the other hand, rear ends of the respective scraper frames  58  are free ends, i.e., rear end of the scrapper frames  58  are not connected to any other component. It may be noted that, while the scraper frames  58  are arranged at substantially equal intervals from the center longitudinal member  51 , a smaller interval is provided between the leftmost scraper frame  58  and the left longitudinal member  51 , and between the rightmost scraper frame  58  and the right longitudinal member  51 . 
     The keels  54  and the scrapers  55  are attached to the front inclination portions  57  of the longitudinal members  51  and the scraper frames  58 . The keels  54  and the scrapers  55  are churn-up members. The keels  54  and the scrapers  55  rake sand and relatively small litter (such as beverage containers, wastepaper, and cigarette butts) during moving the secondary beach cleaner  50  on a beach when towed by a vehicle. 
     The keels  54  are detachably attached to a rear portion of respective front inclination portions  57  of the longitudinal members  51 , and to respective the scraper frames  58  ( FIG. 5 ). The keel  54  includes a plate member  61 , a C-shaped pin  62 , and a keel body  63 . The plate member  61  curves so that it can fit around the lower outer surface of the front inclination  57  or of the scraper frame  58 . The C-shaped pin  62  is shaped like a squared C having an opening at the top, when viewed in a side view, and both sides of the C-shaped pin  62  penetrate the plate member  61 . The keel body  63  is shaped like a plate perpendicular to the left-right direction, and extends downward from a lower end edge of the plate member  61 . 
     Each keel  54  (keel body  63 ) has multiple scraper support holes  66  formed in the rear end portion thereof, and each of the scrapers  55  is inserted into these scraper support holes  66  and supported thereby. The scrapers  55  are each shaped like, for example, a bar having a circular cross section, and supported by the upper and lower scraper support holes while extending in the left-right direction across the keels  54  by being inserted into the respective upper and lower scraper support holes  66 . The number of the scrapers  55  to be supported can be selected depending on the beach and litter conditions, and multiple scrapers  55  can be supported as well. 
     Both the ends of the scrapers  55  are subjected to a certain retaining measure, such as insertion of a locking pin, to prevent the scrapers  55  from falling off from the keels  54 . It may be noted that the sectional shape of the scraper  55  is not limited to a circle, and may be a semicircle having a top face inclined frontward and downward, or other shape. The number of the scrapers  55  may be one or more than three, and the scrapers  55  may be arranged not only in a manner that one is arranged above another, but in a manner that one is arranged on the right or left of another, or in a manner extending obliquely. 
     The secondary beach cleaner  50  is configured such that the keels  54  and the scrapers  55  are buried in the sand to an appropriate degree. When the secondary beach cleaner  50  travels in such a state, the keels  54  rake the sand and litter and then the scrapers  55  scrape them up. Accordingly, the sand and litter thus churned up are thrown up into the mesh body  56  at the rear portion of the frame  53 . 
     A tow member  67  is provided at a front of each of the scraper frames  58  which are, for example, the second ones from the leftmost edge and the rightmost edge, respectively, of the frame  53 . The tow members  67  allow the vehicle  1  to tow the secondary beach cleaner  50 , and are shaped as thick plates extending perpendicular to the left-right direction. 
     A plural (e.g., 4) connection holes  67   a  are formed in each of the tow members  67  in a vertically-arranged manner. The tow rod  38  connected to the trailer hitch  11  of the vehicle  1  at one end thereof is connected to any one pair of these connection holes  67   a  at the other end. The secondary beach cleaner  50  is towed by the vehicle  1  via the tow rod  38 . 
     An optimal towing position depends on the clearance between the secondary beach cleaner  50  and the ground. An optimal towing position can be set by adjusting and selecting a pair of the connection holes  67   a  to be connected the other end of the tow rod  38 . It may be noted that the left-right interval between the left and right tow members  67  is substantially the same as that between the left and right tow members  37 . 
     A front ski support pipe  72  is provided at a front of each of the scrape frames  58  which are, for example, the leftmost one and the rightmost one, respectively, of the frame  53 . The ski support pipes  72  support respective front ski legs  71 . The front ski support pipes  72  are each formed of, for example, a square steel pipe, and penetrate the front transverse member  52   a  vertically. 
     A leg member  73  of each of the front ski legs  71  is also formed of a square steel pipe. The leg member  73  is supported by the corresponding front ski support pipe  72  by being inserted into it. The front ski legs  71  allow the front portion of the secondary beach cleaner  50  to be positioned at a certain height from the ground (height from an upper surface of the sands), and also improve the ability to slide on the sands. Each of the front ski legs  71  is formed by placing the leg member  73  upright on a front ski plate  74  having a front portion curved frontward and upward, and having a predetermined width. 
     The front ski support pipes  72  each have left and right through-holes  72   a  formed therein. The leg member  73  has a plural (e.g., 4) pairs of left and right through-holes  73   a  corresponding to the left and right through-holes  72   a . The pairs of the through-holes  73   a  are arranged vertically. A locking pin or the like is inserted into a hole obtained by overlapping the left and right through-holes  72   a  of the front ski support pipe  72  with a pair of the left and right through-holes  73   a.    
     The height of the front portion of the frame  53  from the front ski leg  71  is thus determined, so that the height of the front portion of the secondary beach cleaner  50  to the ground is set to a certain height. In other words, the height of the front portion of the secondary beach cleaner  50  from the ground is adjustable by selecting a pair of the left and right through-holes  73   a  of the leg member  73  to insert the locking pin or the like into. Therefore, the degree to which the keels  54  and the scrapers  55  are buried in the sand is adjustable. 
     Rear legs  76  are supported at both sides of a rear portion of the rear transverse member  52   b . Each of the rear legs  76  includes an extension frame  75 , a rear leg support pipe  77 , a leg member  78 , an arm member  100 , a left or right wheel  106 , and a rotating shaft  104 . The extension frame  75  extends from either side of a rear portion of the rear transverse member  52   b , and the rear leg support pipe  77  is provided at a rear end portion of the extension frame  75 . 
     The leg member  78  penetrates the rear leg support pipe  77 . The arm member  100  includes an arm  100   a  extending rearward, from a top part of the leg member  78  and an arm  100   b  extending inward in the vehicle width direction, from a rear end portion of the arm  100   a . The centers C of the left and right wheels  106  are connected to each other with an axle  108 . 
     The rotating shaft  104  is inserted into the arm  100   b , which is de-centered from the wheel center C. The rear leg  76  is used for setting the height of a rear portion of the secondary beach cleaner  50  from the ground (height from the upper surface of the sands) to a predetermined height and for vibrating the rear portion of the frame  53  vertically. 
     Front lift arms  81   a  are arranged at a front portion of the frame  53 , each on the outer left side and the outer right side from which they extend leftward and rightward, respectively. Similarly, rear lift arms  81   b  are arranged at a rear portion of the frame  53 , each on the outer left side and the outer right side from which they extend leftward and rightward, respectively. The front and rear lift arms  81   a  and  81   b  are each shaped like, for example, a frame of transversely-long square, when viewed in a top view. A transverse-middle portion of each lift arm is substantially horizontal. 
     A transverse-inner portion and a transverse-outer portion of each lift arm are formed bending inward and downward, and bending outward and downward, respectively. The left-right width between the transverse-outer edges of the respective front lift arms  81   a , and the left-right width between the transverse-outer edges of the respective rear lift arms  81   b  are larger than a distance (width) between the left and right side structure bodies  41 R and  41 L of the litter collection station  40  (i.e., substantially the same as the left-right width of the frame  22  of the primary beach cleaner  20 ). Accordingly, when the secondary beach cleaner  50  enters between the left and right side structure bodies  41 R and  41 L, the lift arms  81   a  and  81   b  climb up on the respective left and right side structure bodies  41 R and  41 L. Therefore, the secondary beach cleaner  50  is lifted up to a certain degree. 
     When the secondary beach cleaner  50  is lifted up on the litter collection station  40 , as discussed above, the mesh body  56  at a rear portion of the frame  53  rises to a certain height. Work of collecting litter collected in the mesh body  56  can be easily performed by rotating the mesh body  56  via a hinge  82  provided on its left. Since the trailer  13  is adjacent to the left of the litter collection station  40 , the litter is directly thrown into the loading unit  16  of the trailer  13 . 
     The rear lift arm  81   b  on the left side of the frame  53  is provided with a rear hinge bracket  83  which constitutes a part of the hinge  82  rotatably supporting a left side portion of the mesh body  56 . The rear hinge bracket  83  arranged across foot ends of the rear lift arm  81   b . A rear hinge pipe  85  corresponding to the rear hinge bracket  83  is provided at the left side of the mesh body  56 . The rear hinge pipe  85  is rotatably supported in a pivoting manner by the rear hinge bracket  83  via a hinge pivot  82   a  extending in the front-rear direction. 
     Further, a frame-shaped support arm  86  is located at a position slightly forward of the lift arm  81   b . A width in a left-right direction for the support arm  86  is less than a width of the lift arm  81   b . The support arm  86  supports a front hinge bracket  87  having a structure similar to a structure of the rear hinge bracket  83 . A front hinge pipe  89  corresponding to the front hinge bracket  87  is provided at the left side of the mesh body  56 . The front hinge pipe  89  is rotatably supported by the front hinge bracket  87  via the hinge pivot  82   a  extending in the front-rear direction. It may be noted that that the hinge pipes  85  and  89  and the hinge pivot  82   a  are coaxially provided. 
     The mesh body  56  is shaped as a box having open top and front. For example, the mesh body  56  is formed by attaching a metal mesh having a certain mesh size to a frame formed mainly of steel pipes. The positioning of the mesh body  56  in the front-rear direction is performed such that the mesh body  56  covers from a position a little forward of the front-rear center of the frame  53  to a vicinity of a rear end portion of the frame  53 . As to the positioning in the left-right direction, the mesh body  56  is positioned to have substantially the same left-right width as the frame  53 . 
     The mesh body  56  includes a bottom wall portion  92 , a rear wall portion  93 , and left and right side wall portions  94 . When viewed in a top view, the bottom wall portion  92  is shaped transversely-long rectangular. The rear wall portion  93  extends substantially vertically from a rear edge of the bottom wall portion  92 . The left and right side wall portions  94  extend from the respective side edges of the bottom wall portion  92  while moderately inclining leftward and rightward, respectively, as they extend upwardly. The rear wall portion  93  and the left and right side wall portions  94  form a fence member  91  that fences round the bottom wall portion  92 , opening only the front side of the bottom wall portion  92 . The fence member  91  allows litter churned up by the keels  54  and the scrapers  55  to be collected onto the bottom wall portion  92 . 
     The bottom wall portion  92  includes an inclination portion  92   a  moderately inclining frontward and downward at a front portion thereof. A portion rearward of the inclination portion  92   a  is a horizontal portion which is substantially horizontal. The horizontal portion is sectioned into a front horizontal portion  92   b  and a rear horizontal portion  92   c  by a transverse member extending in the left-right direction. 
     Each of the side wall portions  94  of the mesh body  56  has a side wall body  94   a  and a rear protruded portion  94   b . The side wall body  94   a  is a longitudinally-long rectangular in a side view and located on a corresponding one of the sides of the bottom wall portion  92 . The rear protruded portion  94   b  is trapezoid-shaped, when viewed in a side view, and is located on a rear of the side wall body  94   a.    
     The rear side of the side wall body  94   a  and the rear side of the rear protruded portion  94   b  extend substantially vertically, and are continuous in a substantially straight line, when viewed in a side view. The continuous rear sides are the sides of the rear wall portion  93  of the mesh body  56 . The top edge of each of the side wall portions  94  (rear protruded parts  94   b ) has substantially the same height as the top edge of the rear wall portion  93 . 
     Front and rear hinge plates  95   a  and  95   b  are arranged on the respective front and rear portions of the left side wall portion  94  of the mesh body  56 . The front and rear hinge plates  95   a  and  95   b  are arranged across a middle frame and a bottom frame of the left side wall portion  94 . Each of the hinge plates  95   a  and  95   b  is a substantially square-shaped plate, when viewed in a side view, and is lightened through a cut-out, leaving an outer edge portion and diagonal-line portions. Each of the hinge plates  95   a  and  95   b  curves inward transversely at front and rear edge portions and serves as an enforcement flange. Front and rear hinge pipes  89  and  85  are integrally joined to outer faces of the hinge plates  95   a  and  95   b , respectively. 
     As described above, the left side portion of the mesh body  56  is rotatably connected to, and supported by the left side portion of the frame  53  via the hinge  82 . When rotated via the hinge  82  by raising the right side of the mesh body  56  upwardly, the mesh body  56  is in a raised state in which the bottom wall portion  92  is substantially upright. Then, litter collected in the mesh body  56  falls onto the left side wall portion  94 , and is discharged to the outside of the mesh body  56  via the left side wall portion  94 . 
     Here, inclusion of handles  96   a  and  96   b  to certain parts (or at least a part on the opposite side of the hinge  82 ) of the fence member  91  of the mesh body  56  facilitates the work of collecting the litter collected in the mesh body  56  performed by rotating the mesh body  56 . Further, by providing the hinge  82  to only one of the short sides (the left side) of the laterally-long mesh body  56 , a distance from the rotating shaft (hinge pivot  82   a ) to the operation part (the right one of the handles  96   a  and  96   b ) is secured when the mesh body  56  is to be raised. The operation of rotating the mesh body  56  is thus facilitated. 
     The left side wall portion  94  of the mesh  56  (in other words, the wall portion of the fence wall  91  on the hinge  82  side) is a wall portion in which a plate member is fixed to allow favorable litter discharge. It is designed so that the top edge portion of the left side wall portion  94  of the mesh body  56  may extend more leftward than the left side structure body  41 L of the litter collection station  40  in the raised state. 
     Thus, the litter collected in the mesh body  56  is directly thrown onto the loading unit  16  of the trailer  13  adjacent to the left of the litter collection station  40 , using the left side wall portion  94  as a slope. It may be noted that the right side wall portion  94  and the rear wall portion  93  are mesh members in which, for example, a metal mesh having a rough mesh is fixed to prevent the litter thrown into the mesh body  56  from falling down. 
     Front-edge and rear-edge stoppers  97   a  and  97   b  are arranged on each of the left and right longitudinal members  51  in the frame  53  and used for positioning of the front and rear edges on the left and right sides of the mesh body  56 . Each of the stoppers  97   a  and  97   b  has a substantially-vertical position restriction face and a rotation guide face continuous with the position restriction face from its top and inclining with the face up. The position restriction face abuts the front or rear edge of the mesh body  56 . The stoppers  97   a  and  97   b  are detachably attached to the longitudinal members  51  by using, for example, bolts or the like. 
     When the mesh body  56  is in use (when the bottom wall portion  92  is set substantially horizontal and abuts the frame  53  from above), the mesh body  56  abuts, at its front edges on both sides, the position restriction faces of the left and right front-edge stoppers  97   a . At the same time, the mesh body  56  when in use abuts, at rear edges on both sides thereof, the position restriction faces of the left and right rear-edge stoppers  97   b . Therefore, the positioning of the mesh body  56  with respective to the frame in the front-rear direction is performed. 
     For the mesh body  56  to go back to the in-use state from the raised state by being rotated, the front and rear edges on both sides of the sides of the mesh body  56  are guided by the guide faces of the stoppers  97   a  and  97   b , and thereby the mesh body  56  smoothly goes back to a certain position on the frame  53 . Note that it may be designed such that the attachment positions for the stoppers  97   a  and  97   b  on the longitudinal members  51  are movable frontward and rearward to allow the mesh body  56  to be movable frontward and rearward. 
     Next, a description of an outline of procedures of cleaning the beach by using the beach-cleaning equipment  20  and  50  is provided. 
     As shown in  FIG. 1 , the beach-cleaning equipment  20  and  50  and the litter collection station  40  are first loaded in the trailer  13  and carried to a certain cleaning place. At this time, the beach-cleaning equipment  20  and  50  are each loaded in the trailer  13  in an integrally-assembled state, while the litter collection station  40  is loaded in the trailer  13  in a state separated into left and right pairs of the front and rear separated bodies  41   a  and  41   b , the right middle separate body  41   d , the front and rear connection members  42 , and the foot members  45 . 
     More specifically, first, one of the pairs of the front and rear separated bodies  41   a  and  41   b  (or a pair of the front or rear separated bodies) is mounted in the trailer  13  (is accommodated in the loading unit  16 ), and then the beach-cleaning equipment  20  and  50  are mounted. Here, the primary beach cleaner  20  is loaded in the following state. 
     The front and rear transverse members  24   a  and  24   b  of the frame  22  are mounted with their side parts on the left and right side edge members  16   b  and  16   c  of the loading unit  16  (the left and right side edge members  16   b  and  16   c  are namely the top edge portions  44   c  of the guide member  44  of the litter collection station  40 ). The rearward movement of the primary beach cleaner  20  is restricted by the leftmost and rightmost sand pins  23  at the rearmost row abutting, from front, respective outer faces of wheel cavities  16   a  of the loading unit  16 . 
     On the other hand, the secondary beach cleaner  50  is loaded in the following state. 
     The longitudinal members  51  of the frame  53  are mounted on the front and rear transverse members  24   a  and  24   b  of the primary beach cleaner  20  in the aforementioned loaded state. Here, the secondary beach cleaner  50  is moderately inclined rearward and downward. The rearward movement of the secondary beach cleaner  50  is restricted by the keels  54  abutting the front transverse member  24   a  of the primary beach cleaner  20  from front. 
     Then, the other pair of the front and rear separate bodies  41   a  and  41   b  (or the other pair of the front or rear separate bodies) and the right middle separate body  41   d  of the litter collection station  40  are mounted in such a manner as to overlap over the front inclination portions  57  and the scraper frames  58  of the secondary beach cleaner  50  in the loaded state. Moreover, the connection members  42  are mounted on, for example, the right side on the loading unit  16  in a state inclining frontward and downward. The foot members  45  are accommodated at, for example, the left side on a rear of the loading unit  16 . 
     It may be noted that the state how the litter collection station  40  is loaded is not limited to the one described above, and may be alternatively loaded in the following manner. 
     Specifically, only the right middle separate body  41   d  is mounted over the front inclination portions  57  and the scraper frames  58  of the secondary beach cleaner  50  in the loaded state. Then, for example, one pair of the front and rear separated bodies  41   a  and  41   b  is mounted on a rear of the secondary beach cleaner  50  in such a manner that they are arranged along the left and right direction. The other pair of the front and rear separated bodies  41   a  and  41   b  is mounted in the loading unit  16 . The foot members  45  are appropriately distributed and accommodated on the loading unit  16  at its rear on the left and right. 
     Next, the beach-cleaning equipment  20  and  50  in the loaded state are unloaded on the ground. At this time, the rear separated bodies  41   b  are connected to the respective left and right side edge members  16   b  and  16   c  of the loading unit  16  of the trailer  13 . Therefore, the trailer  13  is now in the load-unload operation state. 
     Then, the beach-cleaning equipment  20  and  50  in the loaded state are unloaded on the ground by sliding them along the left and right guide members  44 . Accordingly, even when the beach-cleaning equipment  20  and  50  are each integrally assembled, they can be unloaded on the ground relatively easily. Moreover, speedy transition to the litter collection operations can be accomplished. 
     Subsequently, a set-up operation is performed in which the litter collection station  40  is set up at a certain place on the beach. First, the right side structure body  41 R is formed in the following manner. 
     One of the rear separated bodies  41   d  which is connected to the left side edge member  16   b  of the loading unit  16  of the trailer  13  in the loading-unloading operation state is removed from the left side edge member  16   b . Then, the rear separate body  41   b  thus removed, the right middle separate body  41   d , and one of the front separated bodies  41   a  are connected to one another. Further, the left side structure body  41 L is formed by connecting the other front separate body  41   a  to the right side wall portion  16   c  of the loading unit  16  of the trailer  13 . 
     Then, the left and right side structure bodies  41 R and  41 L are connected to each other with the front and rear connection members  42 . The foot members  45  are attached to corresponding places. The litter collection station  40  is thus assembled and is now in the set-up state. 
     Since the relatively large size litter collection station  40  is separated into the multiple separated bodies and the like and then loaded on the loading unit  16  in such a state, the operation of loading and unloading the litter collection station  40  in and from the trailer  13  can be easily performed. 
     Next, in order to collect relatively large size litter on the beach, the primary beach cleaner  20  is towed by the vehicle  1  to travel on the beach at a constant speed. The primary beach cleaner  20  collects the relatively large size litter on the beach while the sand pins  23  are buried in the sand. Accordingly, the primary beach cleaner  20  has a relatively large travel resistance and a travel speed set as low as 5 to 10 km/h. 
     When a certain amount of litter is collected under the frame  22  by traveling on the beach, as described above, the primary beach cleaner  20  is brought to the litter collection station  40 . Then, the operation of collecting the litter thus collected is performed. After the vehicle  1  passes through between the left and right side structure bodies  41 R and  41 L of the litter collection station  40 , the primary beach cleaner  20  enters between the left and right side structure bodies  41 R and  41 L. 
     At this time, the left and right side portions of the frame  22  climb up on the respective left and right side structure bodies  41 R and  41 L, and the primary beach cleaner  20  is thus lifted up by a certain degree (see  FIG. 3 ). The vehicle  1  and the primary beach cleaner  20  are stopped when the primary beach cleaner  20  is on the top edge portions  44   c  of the guiding members  44  of the respective left and right side structure bodies  41 R and  41 L. Then, the operation of collecting the litter is performed. 
     Thereafter, the vehicle  1  and the primary beach cleaner  20  are operated on the beach to repeat the litter collection operations. 
     After a certain area is cleaned by the primary beach cleaner  20 , the secondary beach cleaner  50  is towed to travel on the beach in the certain area (cleaned by the primary beach cleaner) to collect relatively small size litter on the beach. Use of the secondary beach cleaner  50  after the primary beach cleaner  20  in this manner prevents breakage of the keels  54 , the scrapers  55 , the mesh body  56 , and the like which are configured to handle small size litter. When the secondary beach cleaner  50  travels, the beach has been ploughed up by the operation of the primary beach cleaner  20  and thus softened. 
     In addition, the secondary beach cleaner  50  needs to churn up the sand and litter with its keels  54  and scrapers  55 . For these reasons, the travel speed of the secondary beach cleaner  50  is set to 15 to 25 km/h which is a little faster than that of the primary beach cleaner  20 . 
     The secondary beach cleaner  50  churns up relatively small size litter along with sand with its keels  54  and the scrapers  55  by traveling on the beach, and the litter and the sand are collected in the mesh body  56  at a rear of the frame  53 . Here, the metal mesh of the bottom wall portion  92  of the mesh body  56  is configured such that the mesh size may become smaller and smaller from its front to rear, i.e., the mesh size becomes gradually smaller from front to rear of the bottom wall portion  92 . Such configuration substantially prevents the collected litter from falling down, and also prevents clogging of the metal mesh. 
     When a certain amount of litter is collected in the mesh body  56  by traveling on the beach as described above, the secondary beach cleaner  50  is returned to the litter collection station  40 . Then, the operation of collecting the litter thus collected is performed. After the vehicle  1  passes through between the left and right side structure bodies  41 R and  41 L of the litter collection station  40 , the secondary beach cleaner  50  enters between the left and right side structure bodies  41 R and  41 L. At this time, the left front and rear lift arms  81   a  and  81   b  and the right front and rear lift arms  81   a  and  81   b  of the secondary beach cleaner  50  climb up on the respective left and right side structure bodies  41 R and  41 L. 
     The secondary beach cleaner  50  is thus lifted up by a certain degree. The vehicle  1  and the secondary beach cleaner  50  are stopped when the secondary beach cleaner  50  is on the top edge portions  44   c  of the guiding members  44  of the respective left and right side structure bodies  41 R and  41 L. Then, the operation of collecting the litter is performed by rotating the mesh body  56 . Thereafter, the vehicle  1  and the secondary beach cleaner  50  again operated on the beach to repeat the litter collection operations. 
     When the operation of collecting the collected litter is performed by rotating the mesh body  56 , the litter is directly thrown onto the loading unit  16  of the trailer  13  adjacent to the left of the litter collection station  40 . The loading unit  16  can therefore be used as a litter collection container. Accordingly, the collected litter can be carried with the trailer  13  after completion of the cleaning operation, and there is no need to perform the operation of collecting the litter fallen on the ground, which allows reduction in the number of cleaning operation steps. 
       FIG. 6  is a side view showing a state in which the sieve unit  205  is attached to the trailer  13 .  FIG. 7  is a top view of a driving mechanism shown in  FIG. 6  (the sieve unit  205  is omitted). 
     As discussed above, the trailer  13  is shaped as a shallow box. The body frame  14  is shaped substantially square, when viewed in a top view, and the loading unit  16  is provided in such a manner as to substantially overlap with the body frame  14  in a top view. The loading unit  16  is constituted of side wall portions  201  on the respective front and rear of the vehicle body, left and right side wall portions  202 , and a bottom wall portion  203 . Plate members are fitted onto the body frame  14  to form the side wall portions  201  and  202 . The bottom wall portion  203 , on the other hand, is placed on the body frame  14 , and is detachable from the trailer  13 . 
     In addition, the wheel cavities  16   a  are formed, in an upward cup shape, on the left and right of the bottom wall portion  203  at places corresponding to the left and right wheels  15 . 
     Rail members  204  are attached to the respective top edges (the left and right side edge members  16   b  and  16   c ) of the respective left and right side wall portions  202  of the body frame  14 . The rail members  204  are arranged in parallel to each other and extend in the front-rear direction of the vehicle body. The sieve unit  205  is placed on these rail members  204 . 
     The sieve unit  205  is shaped substantially rectangle shape, when viewed in a top view. The sieve unit includes an outer frame portion  205   a  forming the outer frame and a mesh member  205   b  surrounded by the outer frame portion  205   b . The sieve unit  205  has auxiliary wheels  206  at bottom four corners thereof. The auxiliary wheels  206  engage with the rail members  204  for allowing the sieve unit  205  to move in the front-rear direction through guidance of the rail members  204 . 
     Each of the rail members  204  is formed, for example, by laying a pipe member having a circular section in the front-rear direction of the vehicle body. The traveling face of each of the auxiliary wheels  206  guided by the rail members  204  is formed in such a manner that a middle portion of the diameter of the wheel in the width direction of the vehicle body is constricted to be in contact with an upper semi-circle of the pipe member. Such semi-circle of the pipe member shape restricts the positions of the auxiliary wheels  206  in the width direction of the vehicle body, and allows the auxiliary wheels  206  to move on the rail members  204  in the front-rear direction of the vehicle body. 
     The left and right wheels  15  of the trailer  13  are connected to each other with an axle  207  extending transversely along the bottom face of the bottom wall portion  203 . The wheels  15  rotate when the trailer  13  towed by the vehicle  1  traveling. As shown in  FIGS. 6 and 7 , a left end portions  207   a  of the axle  207  and the outer frame  205   a  of the sieve unit  205  are connected to each other via a driving mechanism  208  to move the sieve unit  205  frontward and rearward. 
     As shown in  FIG. 6 , the driving mechanism  208  includes a drive wheel  210  attached to the axle  207 , a driven wheel  211  attached to the trailer  13 , and a connecting rod  212  connecting the driven wheel  211  to the sieve unit  205 . 
     The drive wheel  210  is attached to the left end portion of the axle  207 , outside of the trailer  13  in a width direction thereof. The drive wheel  210  is arranged coaxially with the axle  207 , and rotates in synchronization with rotation of the wheel  15 . 
     The driven wheel  211  is rotatably attached, via a bearing or the like, to a shaft  213  protruding outward of the vehicle, from the left side wall portion  202  of the trailer  13 . The driven wheel  211  and the drive wheel  210  are V-belt pulleys around which a V belt  214  is wound. The driven wheel  211  is attached on the same plane as the drive wheel  210  so that the core of the V belt  214  around the drive wheel  210  aligns with the core of the V belt  214  around the driven wheel  211  (see  FIG. 6 ). Accordingly, the driving power of the drive wheel  210  is transmitted to the driven wheel  211  via the V belt  214 , rotating the driven wheel  211  along with the drive wheel  210 . 
     The connecting rod  212  is rotatably attached, at its one end  212   a , to a position de-centered from the rotational center of the driven wheel  211 , and at the other end  212   b , to a rotating shaft  206   a  of the auxiliary wheel  206  positioned at the left rear side of the sieve unit  205 . Accordingly, when the driven wheel  211  rotates, the sieve unit  205  is pushed (or pulled) in the longitudinal direction of the connecting rod  212 . At this time, the rotation of the end portion connected to the connecting rod  212  allows the sieve unit  205  to move to and fro (back-and-forth) in the front-rear direction of the vehicle body along the rail members  204 . 
     When the wheels  15  rotate by the trailer  13  during towing operation, the sieve unit  205  moves to and fro in the front-rear direction of the vehicle body via the driving mechanism  208 . 
     It may be noted that the bottom wall portion  203  of the trailer  13  is removed when sieving is performed using the sieve unit  205  by moving the sieve unit  205  to and fro. In this manner, sand fallen down through the sieve unit  205  is discharged outside of the trailer  13  through the bottom portion of the trailer  13 , thereby sand does not remain inside the trailer  13 . 
     The beach-cleaning trailer according to the embodiment of the present invention is shaped as a box having an open top, and has the wheels  15  at the left and right side wall portions  202 . The beach-cleaning trailer  13  is loaded with, and collectively carries, the beach-cleaning equipment  20  and  50  (which are towed by the vehicle  1  to collect litter on the sands) and the litter collection station  40  with which the litter collected by the beach-cleaning equipment  20  and  50  is accumulated. 
     The beach-cleaning trailer  13  includes a pair of rail members  204  disposed on the upper edges (side edge members  16   b  and  16   c ) of the left and right side wall portions  202  respectively. The rail members  204  face each other with an opening in therebetween. The beach-cleaning trailer also has the sieve unit  205  adapted to move along the rail members  204  and adapted to detachably attach to the rail members  204  by placing the sieve unit  205  on the rail members  204 . 
     Accordingly, sieving can be performed with the sieve unit  205  by placing litter along with sand on the sieve unit  205  using a scoop or the like, and moving the sieve unit  205  to and fro on the rail members  204 . 
     Therefore, the litter and the sand can easily be separated from each other, and only the litter can be collected. Also, even on an area where litter collection is impossible using the beach-cleaning equipment  20  and  50 , the litter can be separated and collected mechanically without collecting the litter through manual separation. 
     Moreover, since the sieve unit  205  is detachable, the beach-cleaning trailer  13  can be used as a trailer having functions of both carrying the beach-cleaning equipment  20  and  50  and the like including the litter collection station  40 . 
     Further, the trailer  13  includes the driving mechanism  208  that transmits rotary power of the wheels  15  to the sieve unit  205  to move the sieve unit  205  to and fro along the rail members  204  in accordance with the rotary power of the wheels. Accordingly, when the wheels  15  rotate, during operation thereof, the sieve unit  205  can move to and fro along the rail members  204 . Therefore, the sieving operation of the sieve unit  205  can be performed mechanically, making the litter collection through manual separation unnecessary. 
     Furthermore, the driving mechanism  208  is a crank mechanism in which the drive wheel provided on the same axis as the axle  207  of the wheels  15  is connected to the sieve unit via the connecting rod  212 . Accordingly, the rotary power of the axle  207  can easily be converted to power moving the sieve unit  205  to and fro, allowing the sieving with the sieve unit  205  to be performed with a simple structure. 
     In addition, the crank mechanism includes the driven wheel  211  around which and the drive wheel  210  the V belt  214  is wound, and the driven wheel  211  is rotatably attached to one end part of the connecting rod  212 . Accordingly, the length of the connecting rod  212  and the distance in which the sieve unit  205  moves to and fro can be restricted according to the position to which the driven wheel  211  is attached, improving flexibility of designing the driving mechanism  208 . 
     Furthermore, the bottom wall  203  of the trailer  13  is only placed on the body frame  4 . Therefore, the bottom wall  203  can be removed easily. Accordingly, when the sand and litter are sieved with the sieve unit  205 , the sand falling down from the sieve unit  205  can fall down through the trailer  13 . 
     The embodiment of the present invention has been described above. However, various modifications and alternations can be made based on the technical concept of the present invention. 
     For example, although the driving mechanism  208  has the driven wheel  211  around which and the drive wheel  210  the V belt  214  is wound in the present embodiment, the driven wheel  211  does not have to be provided. The sieve unit  205  can move to and fro in the front-rear direction by, for example, rotatably attaching the one end part  212   a  of the connecting rod  212  to a position de-centered from the center of the axle  207  of the drive wheel  210 . Thus, by performing the sieving through the to-and-fro movement of the sieve unit  205  on the rail members  204 , the sand and litter can easily be separated from each other, and only the litter can be collected. 
     Moreover, power transmission is performed between the drive wheel  210  and the driven wheel  211  by using the V belt  214 , but it is not limited to this. A suitable mechanism can be employed as long as it can transmit rotary power from the drive wheel  210  to the driven wheel  211 . For example, such mechanism includes a transmission mechanism using a chain and a sprocket, a transmission mechanism using a spur gear, and the like. 
     Further, although provided to a position on the left of the trailer  13 , the driving mechanism  208  may also be provided on the right or to both sides of the trailer  13 . Also in this case, by performing the sieving through the to-and-fro movement of the sieve unit  205  on the rail members  204 , the sand and litter can easily be separated from each other, and only the litter can be collected. 
     Further, an alternative structure may be employed by transmitting the rotation driving power of the wheels  15  by 90° with a bevel gear or the like to move the sieve unit  205  to and fro in the width direction of the vehicle body. 
     As shown in  FIG. 8 , the sieving with the sieve unit  205  may be performed manually without providing the driving mechanism  208  to the trailer  13 . 
     In such a case, stoppers  300  are provided to both ends of the rail member  204  in the front-rear direction of the vehicle body. The stoppers  300  restrict the movement range of the sieve unit  205 . As shown in  FIG. 8 , each stopper  300  is formed by covering an L-shaped support member  301  with an elastic body  302 . The stopper  300  is placed so that the elastic body  302  may face the sieve unit  205 , and is detachably fixed to the rail part  204  with a bolt  303 . 
     In other words, although the present invention has been described herein with respect to a number of specific illustrative embodiments, the foregoing description is intended to illustrate, rather than to limit the invention. Those skilled in the art will realize that many modifications of the illustrative embodiment could be made which would be operable. All such modifications, which are within the scope of the claims, are intended to be within the scope and spirit of the present invention.