Abstract:
A vacuum apparatus has a recessed portion which is provided at an appropriate position of a fan casing. When incoming materials frequently pass through the fan casing, the recessed portion wears more quickly than the rest of the inner surface of the fan casing. Hence, a user of the vacuum apparatus can easily know when to replace the fan casing by visually checking the recessed portion from outside the fan casing.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a vacuum apparatus and, more particularly, to a vacuum cleaner used for cleaning up, for example, fallen leaves, wooden chips, and waste, and to a fan casing for the same. 
     2. Description of the Related Art 
     In a vacuum cleaner used for cleaning up fallen leaves, wooden chips, waste, and other items (U.S. Pat. No. 5,245,726 is an example of such a device), incoming materials are passed through a fan casing while sliding against an inner surface of the fan casing; hence, the inner surface of the fan casing is apt to wear due to the contact with the incoming materials. If the fan casing is subjected to continued use for an extended period of time without being replaced at appropriate intervals, then the fan casing may incur serious damage or incoming materials may leak out, or other problems may arise during operation of the device. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention has been made with a view toward solving the problems associated with the related art, and it is an object thereof to provide a vacuum apparatus that enables a user to easily check from outside a degree of wear on an inner surface of a fan casing that is caused by frictional contact with incoming materials so as to allow the user to easily know the appropriate time to replace the fan casing. 
     To this end, the present invention provides a vacuum apparatus equipped with a fan casing through which an incoming material passes, wherein an outer surface of the fan casing is provided with a recessed portion that extends toward the inner surface of the fan casing. The recessed portion has the appearance of a protrusion when viewed from inside the fan casing. 
     According to the present invention, if incoming materials frequently pass through the fan casing, then the recessed portion wears more quickly than the rest of the inner surface of the fan casing. Therefore, the user will be able to easily know when to replace the fan casing by visually checking the recessed portion from outside the fan casing. If the wear on the recessed portion advances until a hole finally opens in the recessed portion, then a noise (e.g. a whistle-like noise) that is different from normal operating noises will be produced, so that the time to replace the fan casing can be known audibly as well as visually. 
     In a preferred embodiment of the present invention, the depth of the recessed portion can be set so that an outer surface of the recessed portion reaches the inner surface of the fan casing, or the outer surface of the recessed portion is positioned farther inward than the inner surface of the fan casing. 
     Furthermore, the number of the protrusions is not limited to one; any appropriate number of recessed portions may be provided along the outer periphery of the fan casing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective general view of a vacuum cleaner in accordance with an embodiment of the present invention. 
     FIG. 2 is a front view showing a fan casing of the vacuum cleaner of FIG.  1 . 
     FIG. 3 is an enlarged sectional view of an essential section of the fan casing of FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, a vacuum apparatus in accordance with one embodiment of the present invention is a vacuum cleaner used for cleaning up fallen leaves, wood chips, waste, and other materials. A main body  1  of the vacuum apparatus is integrally equipped with an air-cooled two-cycle gasoline engine  2  working as a driving motor, a recoil starter  3  for starting the engine  2 , a fuel tank  4 , a fan casing  5 , and operating handles  9  and  10  that provide grasping portions for an operator. The upper operating handle  9  is provided with an output control lever  15  for the engine  2 . A suction pipe  6  is detachably coupled to an intake opening  5   d  of the fan casing  5 , while a blowout pipe  7  is detachably coupled to an outlet opening  5   a  of the fan casing  5 . A dust bag  8  having appropriate air permeability is detachably connected to a downstream or blowout end of the blowout pipe  7 . 
     In the vacuum apparatus, the fan casing  5 , the suction pipe  6 , and the blowout pipe  7  are formed of, for example, a plastic constituent to minimize the weight of the apparatus. 
     Referring to FIG. 2, the fan casing  5  is removably attached to one side surface of the main body  1  by a plurality of attaching sections  5   c  provided along an outer periphery thereof. A cutter  11  and a fan  12  are positioned in the fan casing  5 , and the cutter  11  and the fan  12  are also mounted on an output shaft  14  of the engine  2 . The suction pipe  6  is detachably coupled to the intake opening  5   d  of the fan casing  5 . 
     When the fan  12  rotates, incoming materials such as fallen leaves, wood chips, and waste are drawn into the fan casing  5  through the suction pipe  6 , smashed by the cutter  11 , guided in slidable contact with an inner surface  5   b  of the fan casing  5  that is smoothly curved, blown out through the blowout pipe  7 , and accommodated in the dust bag  8 . 
     In this embodiment, a recessed portion  13  that extends toward the inner surface  5   b  of the fan casing  5  is formed along the outer periphery of the fan casing  5 . The recessed portion  13  is provided at a location in the fan casing  5  that is prone to be worn due to frictional contact with incoming materials. Preferably, an appropriate number of the recessed portions  13  are provided at appropriate locations, instead of providing just one. 
     As shown in an enlarged view of FIG. 3, an outer surface  13   a  (the surface facing the outside of the fan casing  5 ) of the recessed portion  13  extends inward, and beyond the inner surface  5   b  of the fan casing  5 . In other words, the depth of the recessed portion  13  is set so that the outer surface  13   a  of the recessed portion  13  is positioned farther inward than the inner surface  5   b  of the fan casing  5 . 
     Most incoming materials drawn into the fan casing  5  through the suction pipe  6  when the fan  12  rotates are fed from the intake opening  5   d  toward the outlet opening  5   a  while being held firmly in frictional contact with the inner surface  5   b  of the smoothly curved outer periphery of the fan casing  5  by a centrifugal force produced by the rotation of the fan  12 . Therefore, in a prolonged use, the inner surface  5   b  of the fan casing  5  gradually wears from the frictional contact with the incoming materials. In this case, since the recessed portion  13  is provided in the fan casing  5  at a location prone to wear, the recessed portion  13  wears more quickly than other portions of the fan casing  5 . As a result, the wall of the recessed portion  13  becomes thin, allowing the operator to visually check the degree of wear of the inner surface  5   b  easily from outside the fan casing  5 . Generally, materials appear either lighter in color or more transparent as they become thinner due to wear. Thus, the operator can easily know the appropriate time to replace the fan casing  5 . 
     Moreover, when the wear of the recessed portion  13  advances until a hole opens therein, then the hole will produce a noise (e.g. a whistle-like noise) that is different from normal operating noises, so that the proper time to replace the fan casing  5  can be known audibly as well as visually from outside the fan casing  5 . An appropriate number of recessed portions  13  distributed at appropriate locations in the fan casing  5  permits more reliable check of wear. 
     The wall thickness, depth, and other characteristics of the recessed portion  13  may be set according to the desired replacement interval of the fan casing  5 . If the foregoing whistling effect is not mandatory, then the outer surface  13   a  of the recessed portion  13  does not have to be deep enough to reach the inner surface  5   b  of the fan casing  5 ; the recessed portion  13  may have a depth that makes a thinner wall portion that corresponds to an allowable amount of wear. Alternatively, the recessed portion  13  may be filled with a transparent constituent such as a synthetic resin to prevent materials from exiting out of the holes created by a worn recessed portion  13  although this prevents the whistling effect.