Abstract:
A tumble dryer includes a housing, which has an enclosable drying chamber, a heater mounted in the enclosable drying chamber, a gate for closing/opening the enclosable drying chamber and a tumbler rotatably mounted in the drying chamber, an intake pipeline equipped with an intake control valve for guiding outside air into the drying chamber, an exhaust pipeline equipped with an exhaust control valve for guiding air out of the drying chamber to the atmosphere, an air-suction pipeline equipped with a pipeline control valve and having a pump installed therein for pumping air out of the drying chamber to the atmosphere.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to drying machines and more particularly, to a high-efficiency tumble dryer that draws moisture away from washing rapidly. 
     2. Description of the Related Art 
     A regular tumble dryer generally comprises a tumbler for turning washing over and over, means to blow warm air onto washing, and vent system to carry air moisture away from the machine. In order to improve the drying efficiency, two methods may be selected. One method is the use of a thermostat to avoid overhead. The other method is the use of a moisture sensor to avoid continuous working after washing having been dried. These two methods are not good methods to effectively improve the drying efficiency. They cannot reduce energy consumption significantly. Due to the principle of using fresh (dry) air to replace old (wet) air in the tumble dryer, conventional tumble dryers cannot draw air moisture away from the machine effectively. 
     Therefore, it is desirable to provide a tumble dryer, which eliminates the drawbacks of conventional designs. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a tumble dryer, which draws air moisture rapidly away from the machine so that the low-pressure dry environment left thereafter provides very dry air to facilitate quick evaporation of the water molecules in washing, allowing evaluation of the dry rate of washing subject to the evaporation speed of the water molecules. 
     To achieve this and other objects of the present invention, a tumble dryer comprises a housing, an intake pipeline, an exhaust pipeline and an air-suction pipeline. The housing comprises an enclosable drying chamber, a heater mounted in the enclosable drying chamber, a gate disposed at one side of the enclosable drying chamber for access control and a tumbler rotatably mounted in the drying chamber for turning washing over and over. The intake pipeline extends from the outside of the housing to the drying chamber for guiding outside air into the drying chamber, comprising an intake control valve controllable to open/close the intake pipeline. The exhaust pipeline extends from the drying chamber to the outside of the housing for guiding air out of the drying chamber to the atmosphere, comprising an exhaust control valve controllable to open/close the exhaust pipeline. The air-suction pipeline is disposed in communication between the drying chamber and the space outside the drying chamber, comprising a pipeline control valve controllable to open/close the air-suction pipeline and a pump controllable to pump air out of the drying chamber to the atmosphere. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional side view of a tumble dryer in accordance with a first embodiment of the present invention. 
         FIG. 2  is a schematic sectional side view of a tumble dryer in accordance with a second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 1 , a tumble dryer in accordance with a first embodiment of the present invention is shown comprising a housing  10 , an intake pipeline  20 , an exhaust pipeline  30  and an air-suction pipeline  40 . 
     The housing  10  comprises a drying chamber  12  that can be closed, a heater  13  mounted in the drying chamber  12  and adapted for heating the air in the drying chamber  12 , a gate  14  arranged at one side of the drying chamber  12  and openable for enabling the during chamber to be in communication with the outside space, and a tumbler  15  rotatably mounted in the drying chamber  12  for holding things to be dried. Further, a barometer  16 , a thermostat  17  and a timer  18  are mounted on the top side of the housing  10 . The barometer  16  can indicate the value of the air pressure in the drying chamber  12 . The timer  18  is adapted for setting the operation time of the tumbler  15 . The thermostat  17  is adapted for controlling the setting of the heating temperature of the heater  13 . 
     The intake pipeline  20  extends from the outside of the housing  10  to the drying chamber  12 , having installed therein an intake lint screen  21  and an intake control valve  22 . The intake control valve  22  can control open/close of the intake pipeline  20 . Further, an intake fan  23  is mounted to the entrance of the intake pipeline  20  and adapted for drawing outside air into the inside of the intake pipeline  20 . 
     The exhaust pipeline  30  extends from the drying chamber  12  to the space outside the housing  10 , having installed therein an exhaust lint screen  31  and an exhaust control valve  32 . The exhaust control valve  32  can control open/close of the exhaust pipeline  20 . Further, an exhaust fan  33  is mounted to the rear end of the exhaust pipeline  30  and adapted for drawing air out of the drying chamber  12 . 
     The air-suction pipeline  40  is disposed in communication between the drying chamber  12  and the space outside the drying chamber  12 , having installed therein an air-suction lint screen  41 , a pipeline control valve  42  and a pump  43 . The air-suction pipeline  40  can be extended directly from the drying chamber  12  to the outside of the housing  10 , or connected between the drying chamber  12  and the exhaust pipeline  30  for communication with the space outside the housing  10  through the exhaust pipeline  30  as shown in  FIG. 1 , the air-suction pipeline  40  is connected with the exhaust pipeline  30  on an outlet side of the exhaust control valve  32 . 
     The tumble dryer of the present invention is to change the drying chamber to a low-pressure or vacuum condition by drawing air out, so that air moisture can be fully drawn away from the drying chamber subject to the physical principle that fluid can be evaporated easily under low pressure. Actually, as shown in  FIG. 1 , outside air can flow through the intake pipeline  20 , the intake lint screen  21  and the intake air control valve  22  into the drying chamber  12 , and then the heater  13  is operated to heat the washing and/or object in the tumbler  15 , causing the water content in washing to be vaporized into air vapor that is then carried away from the drying chamber  12  to the atmosphere through the exhaust lint screen  31  and the exhaust control valve  32 . 
       FIG. 2  shows a tumble dryer in accordance with a second embodiment of the present invention. According to this second embodiment, a pre-heater  50  is mounted on the outside of the housing  10  and adapted for heating intake air so that pre-heated warm air flows through the intake pipeline  20  and the intake lint screen  21  and the intake air control valve  22  into the drying chamber  12  to warm up washing in the tumbler  15 , and then the heater  13  is operated to heat the washing and/or object in the tumbler  15 , causing the water content in washing to be vaporized into air vapor that is then carried away from the drying chamber  12  to the atmosphere through the exhaust lint screen  31  and the exhaust control valve  32 . 
     When sufficient high-density air vapor is produced in the drying chamber  12 , all the control valves  22 ; 32 ; 42  are closed to keep the drying chamber  12  in an enclosed condition, and then open the pipeline control valve  42  and then start the pump  43  to draw air vapor out of the drying chamber  12  through the exhaust lint screen  41  and the pipeline control valve  42  to the atmosphere. During operation, air and moisture can be continuously drawn away from the drying chamber  12 . Alternatively, the pipeline control valve  42  can be closed and the pump  43  can be turned off to keep the drying chamber  12  in a low pressure condition, and then uses the heater  13  to heat the washing and/or object in the drying chamber  12  continuously for causing the water content in washing to be vaporized into air vapor. When the reading of the barometer  16  reaches a predetermined value, open the pipeline control valve  42  and then start the pump  43  to draw air vapor out of the drying chamber  12  through the exhaust lint screen  41  and the pipeline control valve  42  to the atmosphere. Subject to the reading of the barometer  16  and counting of the timer  17  to measure the rising speed of air pressure, the dry rate of washing is evaluated. 
     Further, after drawing of air vapor out of the enclosed drying chamber in the primary state, the rising speed of air pressure in the drying chamber may be excessively high, the dry rate of washing may not reach the desired level, and washing in the tumbler may still contain a certain amount of moisture. At this time, in order to accelerate the heating process of heating the water content in washing into air vapor, the intake control valve  22  can be opened for letting hot air generated by the pre-heater  50  flow through the intake lint screen  21  and the intake control valve  22  into the tumbler  15  in the drying chamber  12  to mix with the air in the tumbler  15  during rotation of the tumbler  15  to turn washing over and over. Thus, the water content in washing in the tumbler  15  can be vaporized into air vapor rapidly, and then drawn away from the drying chamber  12  into the atmosphere. Thus washing in the tumbler  15  can be dried quickly. 
     In conclusion, the invention is to draw air out of the drying chamber  12  continuously or intermittently to keep the drying chamber  12  in a low pressure condition or vacuum condition, facilitating quick dry of washing. Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.