Patent Publication Number: US-2005135795-A1

Title: Heat insulating structure for hot air blower

Description:
FIELD OF INVENTION  
      The present invention relates to safety mechanisms of a hot air blower, and more particularly to a heat insulating structure for hot air blower including a heat insulating member locked between a inner barrel and the outer cover of a hot air blowers for preventing heat from being conducted toward the outer cover.  
     DESCRIPTION OF THE PRIOR ART  
      A conventional hot air blower for industrial use comprises a fan motor assembly, an inner barrel, a heating element, a nozzle and an outer cover. The fan motor assembly drives airflow to pass through the inner barrel, the airflow being heated by the heating element and ejected from the nozzle. Since the working temperature in the inner barrel is approximately 500-600 hundred degrees Celsius, the inner barrel is usually made of metals, which will conduct heat efficiently to the outer cover. After a time period of operation, the outer cover will be so hot so that it becomes hazardous to people who touches it. Also, the heat accumulated on the inner wall of the outer cover due to conduction will also damage the inner wall.  
      As shown in  FIG. 1 , a hot air blower  1  according to U.S. Pat. No. 6,370,326 to Cheng includes a nozzle  13  connected to the front end of an inner barrel  11 . An outwardly extending flange  131  disposed at the rear end of the nozzle  13  is provided with a plurality of radially arranged through holes  132 . The flange  131  supports against the inner wall of the outer cover of the hot air blower  1 , so as to insulate the outer cover from the hot nozzle  13 . A fan motor assembly  12  mounted at the rear end of the inner barrel  11  drives airflow through the inner barrel  11 , mainly passing through the nozzle  13  with a minor portion passing through the through holes  132  for cooling the flange  131 . As shown in  FIG. 2 , a hot air blower  1  according to U.S. Pat. No. 6,460,272 to Cheng includes a positioning ring  22  around an inner barrel  21 . The positioning ring  22  is provided with a plurality of support pieces cast on the inner wall thereof for defining a gap between the positioning ring  22  and the inner barrel  21 . A fan motor assembly  24  drives airflow through the inner barrel  21  as well as the gap between the positioning ring  22  and the inner barrel  21 , thereby cooling the positioning ring  22 .  
      The aforecited inventions provides a cooling mechanism that prevents efficient heat conduction from the interior heated parts of a hot air blower to its outer cover. However, it is discovered that the conventional mechanism cannot prevent the outer cover of a hot air blower from overheating under longtime operation. Therefore, a more efficient mechanism that insulates the heat produced in the inner barrel is necessary.  
     SUMMARY OF THE INVENTION  
      Accordingly, the primary object of the present invention is to provide a heat insulating structure for hot air blower wherein a heat insulating member sandwiched by the inner wall of the outer cover and a flange on the outer wall of the inner barrel. The heat insulating member stops heat from being conducted toward the outer cover and thus achieves effects of enhancing user&#39;s safety and protecting the outer cover from burning out.  
      The secondary object of the present invention is to provide a heat insulating structure for hot air blower wherein the heat insulating member encloses the outer rim of the flange and is embedded in an annular groove around the inner wall of the outer cover, so that airflow between the inner barrel and the outer cover passes through the holes on the flange only. Furthermore, since the heat insulating member has a low heat expansion coefficient, it provides a better positioning effect for the inner barrel.  
      The various objects and advantages of the present invention will be more readily understood from the following detailed description of preferred embodiments, when read in conjunction with the appended drawings. 
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded perspective view of the invention disclosed in one prior art.  
       FIG. 2  is a perspective view of the invention disclosed in another prior art.  
       FIG. 3  is an exploded perspective view of the first preferred embodiment according to the present invention.  
       FIG. 4  is a perspective view showing the combination of the flange and the heat insulating member in the first preferred embodiment.  
       FIG. 5  is a cross-sectional view of the first preferred embodiment.  
       FIG. 6  is an exploded perspective view of the second preferred embodiment according to the present invention.  
       FIG. 7  is a cross-sectional view of the second preferred embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring to  FIGS. 3 and 5 , a heat insulating structure for hot air blower according to the present invention comprises an inner barrel  30 , an outer cover  34 , a tapered nozzle  31  and a heat insulating member  33 . The inner barrel  30  contains a high-impedance resistance heating element therein, which is not shown in the figures. The tapered nozzle  31  includes a positioning flange  32  extending outwardly from a rear end thereof. The rear end of the nozzle  31  is connected to the front end of the inner barrel  30 . The flange  32  is further provided with a plurality of circularly arranged through holes  321  for passing cooling airflow. The outer cover  34  is provided with a substantially annular groove  341  molded on an inner wall thereof. The heat insulating member  33 , being substantially annular, is sandwiched by the flange  32  and the outer cover  34 , the inner rim of heat insulating member  33  enclosing the outer rim of the flange  32 , and outer rim of the heat insulating member  33  being embedded in annular groove  341 . The heat insulating member  33 , secured between the inner barrel  30  and the outer cover  34 , therefore stops heat generated inside from being conducted toward the outer cover  34  and achieves effects of enhancing user&#39;s safety and protecting the outer cover from burning out.  
      Referring to  FIGS. 6 and 7 , another preferred embodiment of a heat insulating structure for hot air blower according to the present invention comprises an inner barrel  40 , an outer cover  44 , a positioning flange  42  and a heat insulating member  43 . The positioning flange  42 , surrounding the lateral wall of the inner barrel  40 , is provided with a plurality of positioning pieces  421  for supporting against the outer wall of the inner barrel  40 . The heat insulating member  43  is of substantially annular shape and has its outer rim embedded in a substantially annular groove  441  molded on the inner wall of the outer cover  44 . The heat insulating member  43  is therefore secured between the flange  42  and the inner wall of the outer cover  44 . The heat insulating member  43 , sandwiched by the inner barrel  40  and the outer cover  44 , stops heat generated inside from being conducted toward the outer cover  44  and achieves effects of enhancing user&#39;s safety and protecting the outer cover from burning out.  
      The present invention is thus described, and it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.