You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
     The present invention relates to a scraper for snow removal machines for scraping snow lying on road surfaces. 
     BACKGROUND OF THE INVENTION 
     A scraper for a snow removal machine of this kind is disclosed, for example, in Japanese Utility Model Laid-Open Publication No. SHO-51-34105 entitled “Snow Removing Case for Snow Removal Machine”, and in Japanese Utility Model Laid-Open Publication No. SHO-52-14347 entitled “Bottom Scraping Blade for Snow Removal Machine”. 
     SHO-51-34105 includes an auxiliary ground plate fastened with bolts to a lower end portion of the snow removing case. The ground plate is adjustable up and down as desired. When lowered, the plate prevents an auger from contacting the ground. When raised, the plate allows the auger to crush frozen snow, thus avoiding any large resistance which would otherwise be applied to the lower end portion of the snow removing case. 
     SHO-52-14347 includes a bottom scraping blade movably fitted in an arc-shaped long groove formed in a lower portion of an auger case. The scraping blade can be shifted upward and downward along the groove. To remove hard snow, the bottom scraping blade is held higher than the bottom of the auger so that the auger alone scrapes snow under reduced propulsion resistance, resulting in an efficient snow removal operation. 
     Augers can scrape frozen snow or trampled hard snow. When an auger contacts a surface of a roadway, a sidewalk or the like, it may scratch or damage the surface. For preventing such scratching, the auxiliary ground plate and the bottom scraping blade may be lowered. However, the ground plate and the scraping blade are generally made from steel plates and hence still have the possibility of scratching the ground. 
     To prevent such damage to a road surface, it is possible to replace a steel plate with a resin plate. In this case, however, it is troublesome to demount the auxiliary ground plate and the bottom scraping blade of one material and then mount those of the other material each time this becomes necessary. 
     Further, if the auxiliary ground plate and the bottom scraping blade are lowered to any unsuitable levels, they may strike road surfaces or hard objects such as stones and thus be damaged. It is quite hard to replace the damaged auxiliary ground plate and the bottom scraping blade with new ones on the spot. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a scraper for a snow removal machine, which enables improved snow removal performance and easy blade change. 
     According to an aspect of the present invention, there is provided a scraper for a snow removal machine, mountable to a lower end portion of a snow removing plate, for scraping snow on a road surface, which comprises: a polygonal prism member rotatably mountable to the snow removing plate; a plurality of blades detachably attached to respective surfaces of the polygonal prism member; and a rotation prevention member for preventing rotation of the polygonal prism member. 
     The blades may be of the same material, or may be made from different kinds of material. 
     It is desired that the scraper has the blades attached to respective surfaces of the polygonal prism member. One of the blades is selected for use in accordance with snow quality, the kind of a pavement to be cleared of snow, and the condition of each blade. This enables efficient snow removing operation and protection of the pavement surface, thereby improving snow removing performance of the machine. The scraper has the blades provided on the polygonal prism member, and the rotation prevention member for preventing rotation of the polygonal prism member. The rotation prevention member prevents rotation of the polygonal prism member which has been rotated at a desired angle to select a desired blade. Thus, the change of blades is facilitated. When the blades are made of the same material and one of the blades used is deformed or damaged and becomes unusable, that blade can be replaced with another blade of the same material in a short time. Thus the change of blades of the same material is facilitated. When the blades are made of different kinds of material, one of the blades can be selected in accordance with snow quality or the kind of a pavement to be cleared of snow. For example, a steel blade is used to scrape hardened snow, and a resin blade is used to protect a pavement from being scratched. Such blades of different kinds of material enable selection of one of the blades in a short time. Thus the change of blades of different kinds of material is facilitated. 
     The scraper may further comprise a guiding/gap-closing member mountable to a lower end portion of the snow removing plate for closing a gap between the scraper and the snow removing plate and guiding transfer of snow from the scraper to the snow removing plate. The guiding/gap-closing member attached to the snow removing plate abuts against the scraper at the opposite side. Thus, a gap between the scraper to be rotated and the snow removing plate can be closed to prevent snow removed from leaking rearwards from the boundary between the scraper and the snow removing plate. When the scraper is rotated, part of the guiding/gap-closing member opposite to the scraper is pushed and bent by the scraper, not interfering with the scraper, and thereby allowing the scraper to rotate easily. Further the guiding/gap-closing member is mounted to guide transfer of snow from the scraper to the snow removing plate, enabling smooth transfer of snow, and thereby improving the snow removing performance of the machine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a snow removal machine according to the present invention; 
     FIG. 2 is a perspective view illustrating on an enlarged scale part of a snow removing plate shown in FIG. 1; 
     FIG. 3 is an exploded view of a scraper according to a first embodiment shown in FIG. 2; 
     FIG. 4 is a side view of the snow removing plate shown in FIG. 2 with its part cutaway; 
     FIGS. 5A and 5B are functional diagrams showing the mounting and changing of a plurality of blades of the scraper; 
     FIGS. 6A to  6 C are functional diagrams of the scraper according to the present invention in a snow removing operation; 
     FIG. 7 is a side view of a scraper according to a second embodiment; and 
     FIG. 8 is a cross-sectional view of the scraper shown in FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1, a snow removal machine  10  has a body frame  11 , left and right crawler belts  14 ,  14  mounted to the left and right sides of the body frame  11  via left and right drive wheels  12 ,  12  and driven wheels  13 ,  13  (the right drive and driven wheels  12 ,  13  are invisible in the figure), an engine  15  mounted to the body frame  11 , a control handle  16  mounted rearward of the body frame  11 , a control panel  17  provided to an upper portion of the control handle  16 , left and right grips  18 ,  18  provided to rear ends of the control handle  16 , and a snow removing attachment mounted to the front of the body frame  11  via a supporter  21 . 
     The snow removing device comprises a snow removing plate  22  having a plate body  23  formed in a sectionally arch shape, reinforcing plates  26 ,  27  mounted to left and right ends  24 ,  25  of the plate body  23 , a guiding/gap-closing member  31  and a scraper  32  mounted to a lower end portion of the plate body  23 . 
     In FIG. 2, the snow removing plate  22  is shown in perspective. The reinforcing plate  26  is attached to the left end  24  of the plate body  23 . The guiding/gap-closing member  31  and the scraper  32  are attached to the lower end portion of the plate body  23 . The snow removing plate  22  is symmetrical with respect to the centerline C. The plate body  23  has a closing member mounting part  33  at its lower end portion. 
     The scraper  32  has a polygonal prism member  41  rotatably mounted to the snow removing plate  22 , a first blade  42 , a second blade  43 , and a third blade  44  mounted to the polygonal prism member  41 , and a rotation prevention device comprising a pair of rotation prevention members  45  for preventing rotation of the polygonal prism member  41 . Reference numeral  46  denotes a ring. 
     One of the rotation prevention members  45  is provided on the left side of the scrape  32  and includes a fixed plate  51  mounted to the reinforcing plate  26 , a tubular spindle retaining part  52  provided at a lower portion of the fixed plate  51 , and a pin  53  to be inserted into the spindle retaining part  52 . In this embodiment, the spindle retaining part is generally cylindrical-shaped. The fixed plate  51  is mounted to the reinforcing plate  26  with a plurality of bolts  54 . The other rotation prevention member  45  is provided on the right side of the scraper  32  and includes a fixed plate  51  mounted to the reinforcing plate  27  (See FIG.  1 ), a spindle retaining part  52  and a lock member in the form of a pin  53 . The spindle retaining part  52  has a pinhole  55  for receiving the pin  53 . 
     Reference is now made to FIG. 3 showing the scraper in an exploded state. The polygonal prism member  41  has a body  56  of a generally triangular prism made from a steel material in this embodiment. A hole  57  is formed centrally of the body  56  in the longitudinal direction. A support shaft in the form of a spindle  58  is inserted into the hole  57  and fixed to the body  56  by welding. The body  56  has a first surface  61 , a second surface  62  and a third surface  63  which constitute the outer periphery thereof. Those surfaces are in a curved shape. The surfaces  61 ,  62  and  63  are formed with a plurality of female threads  64 , respectively. 
     The spindle  58  has, at each of the opposite ends, as shown in FIGS. 5A and 5B, a first angle setting hole  66 , a second angle setting hole  67 , and a third angle setting hole  68  provided as through holes, which are arranged at intervals of 120 degrees. 
     Description will now be made as to the blades  42 ,  43  and  44  of the scraper  32 . 
     The first blade  42 , the second blade  43 , and the third blade  44  are made from different kinds of material. Specifically, the first blade  42  is made from a steel material, the second blade  43  a resin material, and the third blade  44  rubber. 
     The first blade  42  has a plurality of mounting holes  42   a  corresponding to the female threads  64  formed in the polygonal prism member  41 , and is fixed to the first surface  61  of the polygonal prism member  41  with bolts  65  screwed through the mounting holes  42   a  into the female threads  64 . The first blade  42  has a cutting edge  71  in the longitudinal direction. 
     The second blade  43  has a plurality of mounting holes  43   a  corresponding to the female threads  64  and is fixed to the second surface  62  of the polygonal prism member  41  with bolts  65  screwed through the mounting holes  43   a . The second blade  43  has a cutting edge  72  in the longitudinal direction. 
     The third blade  44  has a plurality of mounting holes  44   a  corresponding to the female threads  64  and is fixed to the third surface  63  of the polygonal prism member  41  with bolts  65  screwed through the mounting holes  44   a . The third blade  44  has a cutting edge  73  in the longitudinal direction. 
     Reference is made next to FIG. 4 showing in side elevation the snow removing plate  22 , with the scraper  32  and its surroundings shown in cross-section. The scraper  32  is mounted to a rear lower portion of the snow removing plate  22 . The guiding/gap-closing member  31  is mounted to the closing member mounting part  33 . 
     The guiding/gap-closing member  31  has an upper-half mounting part  75  mounted to the closing member mounting part  33  with bolts  77 , and a lower-half seat part  76 . 
     The guiding/gap-closing member  31  is mounted to the closing member mounting part  33  in a manner that a surface  82  of the guiding/gap-closing member  31  is coplanar with a surface  81  of the snow removing plate  22 . The upper edge of the first blade  42  of the scraper  32  substantially abuts against the lower edge of the seat part  76 . The seat part  76  also substantially abuts against the second blade  43  and the third blade  44  when the scraper  32  is rotated as described later. 
     Now, an operation of the scraper for the snow removal machine will be described with reference to FIGS. 5A to  6 C. 
     FIG. 5A shows that one of the three blades  42 ,  43  and  44  attached to the scraper  32  is selected for use in accordance with the state of snow on a road surface. The first angle setting hole  66 , the second angle setting hole  67 , and the third angle setting hole  68  are provided in the spindle  58  with 120 degree pitches as described above. When the pin  53  is inserted into the spindle retaining part  52 , passing through the first angle setting hole  66 , the first blade  42  of steel material is selected and locked for use. To change the blade, the pin  53  is pulled out as shown by arrow {circle around (2)} to release the lock, thereby making the scraper  32  rotatable. 
     FIG. 5B shows that the scraper  32  is rotated counter-clockwise in the figure (in the direction of arrow {circle around (3)}) at a predetermined angle, making the second angle setting hole  67  communicate with the pinhole  55 . The pin  53  is inserted into the spindle retaining part  52 , passing through the second angle setting hole  67  as shown by arrow {circle around (4)}. In this state, the second blade  43  of resin material is selected and is locked for use. 
     To select the third blade  44 , the pin  53  is pulled out and inserted similarly. 
     Thus, with the first, second and third blades  42 ,  43  and  44  mounted to the polygonal prism member  41  and the pin  53  of the rotation prevention member  45  pulled out from the retaining part  52 , the scraper  32  can be rotated for blade change. This facilitates the change of blades of the scraper  32 . 
     In FIG. 6A, the snow removal machine  10  is propelled (in the direction of arrow {circle around (5)}) with the scraper  32  cutting through snow S on road surface R, scraping the snow S for removal. In this case, the first blade  42  of the scraper  32  is used to relatively easily scrape hardened snow with the cutting edge  71  of steel. The scraper  32  can thus handle hardened snow. 
     When the seat part  76  of the guiding/gap-closing member  31  is made to substantially abut against the scraper  32 , closing a gap between the scraper  32  and the snow removing plate  22 , any gap hardly remains between the scraper  32  and the plate body  23 . As a result, the snow removing plate  22  can remove snow without leaking rearward, thereby improving efficiency in snow removing operation. When the first blade  42  is replaced with the second blade  43 , the guiding/gap-closing member  31  also substantially abuts at the seat part  76  against the second blade  43 . 
     Since the guiding/gap-closing member  31  is mounted to the closing member mounting part  33  at the lower end of the snow removing plate  22 , and the surface  82  of the guiding/gap-closing member  31  is set coplanar with the surface  81  of the snow removing plate  22 , and the guiding/gap-closing member  31  guides the transfer of snow S from the scraper  32  to the snow removing plate  22  as shown by arrow {circle around (6)}, the snow S can be smoothly transferred, resulting in improved snow removing performance of the machine  10 . 
     In FIG. 6B, the scraper  32  is rotated counterclockwise (in the direction of arrow {circle around (3)}), the first blade  42  being replaced with the second blade  43 . At this time, the second blade  43  comes into contact with the seat part  76  of the guiding/gap-closing member  31 . The guiding/gap-closing member  31  bends as shown by arrow {circle around (7)}, avoiding interfering with the scraper  32 , and thereby not preventing the rotation of the scraper  32 . 
     In FIG. 6C, the blade of the scraper  32  is changed to the second blade  43  with the cutting edge  72  of resin for removing snow on sidewalk H surfaced with a relatively sensitive material such as tiles or lumber. When pushed onto the surface of the sidewalk H, the cutting edge  72  is resiliently deformed, reducing pushing force F, and thereby causing no scratches on the sensitive surface of the sidewalk H. 
     When the third blade  44  is set as the blade of the scraper  32 , the cutting edge  73  of rubber can scrape relatively hard snow, and scraping noise can be reduced. This allows snow removal with the machine to be performed even during early mornings and late nights without annoyance. 
     Since the first blade  42  of steel, the second blade  43  of resin, and the third blade  44  of rubber are thus attached to the polygonal prism member  41 , and the polygonal prism member  41  is supported by the rotation prevention member  45 , a desired blade can be selected for use in a short time in accordance with a road surface to be cleared of snow and the state of snow. As a result, the scraper  32  can efficiently remove snow of different states, from hardened snow to soft snow, alone, while avoiding scratching the surface of a roadway or sidewalk, thereby improving the snow removing performance of the machine  10 . 
     Now, a scraper according to a second embodiment will be described with reference to FIGS. 7 and 8. 
     Like elements as in FIGS. 2 to  5 B of the first embodiment are referred with like reference numerals to omit the description thereof. 
     FIG. 7 shows a scraper  32 A according to the second embodiment having all blades made from the same material. Specifically, a first blade  42 , a second blade  42 , and a third blade  42  are all made of steel material. These three blades  42 ,  42 ,  42  are provided on a polygonal prism member  41 A. The scraper  32 A has a positioning hole  84  formed in an end face of the polygonal prism member  41 A (See FIG. 8) and a rotation prevention member  45 A. The rotation prevention member  45 A includes a fixed plate  51 , a supporting member  85  attached to the fixed plate  51 , a locking bolt  86 , and mounting bolts  87 ,  87 . 
     In FIG. 8, the supporting member  85  is fitted into a central hole  57  of the polygonal prism member  41 A, a pin  88  of the locking bolt  86  is fitted into the positioning hole  84 , and the mounting bolts  87  are tightened, thereby attaching the scraper  32 A to the snow removing plate  22 . 
     In the second embodiment, since the three blades of the scraper  32 A are made of the same steel material, if the first blade  42  is deformed or damaged, rotation of the scraper  32 A is all that is needed to replace the blade with the second blade  42  attached to a second surface  62 . This enables replacement with a new blade of the same material to occur in a short time, resulting in very easy blade change. 
     In the embodiment shown in FIGS. 7 and 8, the three blades are made of the same steel material. These blades may be made of resin material, rubber, or other material. 
     The polygonal prism member  41  having the blades of different kinds of material attached thereto and the rotation prevention member  45 A using the bolts as shown in FIGS. 7 and 8 may be combined. Also, the pin  53  and the polygonal prism member  41 A having the blades of the same material attached thereto may be combined. 
     The present disclosure relates to the subject matter of Japanese Patent Application No. 2000-381434, filed Dec. 15, 2000, the disclosure of which is expressly incorporated herein by reference in its entirety.

Summary:
A scraper is mountable on a snow removing machine for scraping snow on a road surface. The scraper has a polygonal prism member rotatably mountable to a lower end portion of a snow removing plate of a snow removing machine. The polygonal prism member has a first end, a second end disposed opposite the first end, surfaces disposed between the first and second ends, and a central hole extending throughout a length of the polygonal prism member from the first end to the second end. The scraper also has blades each removably connected to respective ones of the surfaces of the polygonal prism member. A rotation prevention device has a pair of rotation prevention members for preventing rotation of the polygonal prism member. Each of the rotation prevention members has a plate disposed on a respective one of the first and second ends of the polygonal prism member and fixedly mountable to the snow removing plate, a support shaft extending through the central hole of the polygonal prism member and connected to the polygonal prism member for rotation therewith, and a lock member for releasably locking the plate and the support shaft to one another to prevent rotation of the polygonal prism member.