Method and apparatus to check the state of wear in a covering fabric of a driving belt

A method for checking the state of wear of a driving belt, in which said driving belt, provided with a covering fabric treated with electrically conductive charges acting in contact relationship with at least a first pulley and a second pulley which are electrically insulated from each other and the setting in rotation of which brings about the operation of the belt, said method comprising the following steps:

• applying a predetermined electric voltage between the first and second pulleys;
• measuring ma electric resistance value of at least two branches (A, B) of said belt, kept taut between the first and second pulleys;
• comparing the first electric resistance value with a previously input electric resistance value corresponding to a given state of wear of the belt;
• signalling a state of danger when the first electric resistance value is greater than said previously input value, said method further comprising the following steps:
• stopping the belt operation before said step of applying electric voltage is activated;
• detecting the temperature in the vicinity of the belt;
• comparing the temperature value detected in the vicinity of the belt with a previously input reference temperature value;
• enabling the danger signalling when the temperature value detected close to the belt is lower than the reference temperature value, said signalling being kept disabled when the temperature value detected close to the belt is higher than the reference temperature value, as well as during the belt operation.

An apparatus for checking the state of wear of a driving belt comprising:

• a covering fabric treated with electrically conductive charges, applied to said belt and acting in contact relationship with at least a first and a second pulley electrically insulated from each other, the setting in rotation of which brings about the belt operation;
• an electric circuit having respective poles connected to the first and second pulleys respectively for applying a predetermined electric voltage to at least two branches (A, B) of said belt extending between the first and second pulleys;
• detecting means associated with said electric circuit for detecting the electric resistance (Rx) of said belt branches (A, B);
• comparing means to compare the electric resistance (Rx) values detected by the detecting means with a previously input electric resistance value corresponding to a given state of wear of the belt;
• signalling means connected to said comparing means for signalling a state of danger when the detected electric resistance (Rx) value overcomes the preset electric resistance value;
• said apparatus further comprising:
• disabling means connected to deactivate the signalling means during belt operation and for a given waiting time starting from the moment at which the belt stops operation.