Electric vacuum cleaner

Abstract

In an electric vacuum cleaner including a communicating tube forming an air trunk which communicates to a suction opening which suctions dust and a vacuum cleaner main body having a communicating tube attachment member attaching the communicating tube, a strain gauge is attached to a floor surface side of the communicating tube attachment member. This strain gauge is connected to one side of a resistor bridge circuit. Tension acts on the strain gauge due to an operation of the communicating tube during the cleaning so that an output is generated at the resistor bridge circuit. After being amplified, this output is differentiated in a condenser. This differentiated voltage signal is compared to a threshold level voltage in a comparator. A running motor is driven only in a period that the voltage signal exceeds the threshold level voltage.

1 . An electric vacuum cleaner comprising: 
 a communicating tube forming an air trunk which communicates to a suction opening which suctions dust; and    a vacuum cleaner main body having a suction motor and a communicating tube attachment member which attaches the communicating tube so as to communicate the communicating tube to the suction motor,    wherein the vacuum cleaner main body including:    a wheel for running on a floor;    driving means for driving the wheel;    detecting means for detecting with a sensor a pulling tension given to the communicating tube during a cleaning operation with the communicating tube gripped, and outputting a voltage signal depending on the detected pulling tension;    differentiating means for differentiation-processing the voltage signal from the detecting means; and    control means for controlling the driving means depending on a period when a signal level of a differentiation signal differentiated and output by the differentiating means exceeds a predetermined threshold level.    
   
   
       2 . The electric vacuum cleaner according to  claim 1 , wherein the driving means has a motor as a driving source, and the control means has a comparator for comparing a signal level of the differentiation signal to the threshold level and outputting a driving signal in a period when the signal level exceeds the threshold level, and a driving circuit for driving the motor of the driving means in accordance with the driving signal from the comparator.  
   
   
       3 . The electric vacuum cleaner according to  claim 1 , wherein the sensor comprises a strain gauge, and this strain gauge is attached to the communicating tube attachment member.  
   
   
       4 . The electric vacuum cleaner according to  claim 3 , wherein the communicating tube attachment member is fixedly attached to the vacuum cleaner main body, and the strain gauge is attached to a floor surface side of the communicating tube attachment member.  
   
   
       5 . The electric vacuum cleaner according to  claim 3 , wherein the communicating tube attachment member is attached to the vacuum cleaner main body so as to rotate upward and downward a front end of the communicating tube attachment member, and the strain gauge is attached to a floor surface side or an opposite upper side of the communicating tube attachment member.  
   
   
       6 . The electric vacuum cleaner according to  claim 4 , wherein the communicating tube attachment member has, on the floor surface side, a deformable member which deforms towards a pulling direction when a tense along the pulling direction occurs due to an operation of the communicating tube, and the strain gauge is attached on the deformable member.  
   
   
       7 . The electric vacuum cleaner according to  claim 5 , wherein, when the strain gauge is attached to the floor surface side of the communicating tube attachment member, the communicating tube attachment member has, on the floor surface side of the communicating tube attachment member, a deformable member which deforms towards a pulling direction when a tense along the pulling direction occurs due to an operation of the communicating tube, and the strain gauge is attached on the deformable member.  
   
   
       8 . The electric vacuum cleaner according to  claim 2 , wherein the communicating tube has a gripper to be gripped in an operation and grip detecting means, provided at the gripper, for detecting a state of gripping, and the motor of the driving means is forced to halt when the grip detecting means does not detect the state of gripping.