System and process for detecting a load of clothes in an automatic laundry machine

Abstract

A system and a process for detecting a load of clothes in an automatic laundry machine, comprising a voltage sensor, a rotation sensor, and a control unit associated with a timer, with the voltage sensor, and with the rotation sensor and which is supplied with data representative of the medium torque Mmot of the electric motor in different voltage ranges and with data representative of the acceleration and deceleration reference times (Ta 1 and Td 1 ) of the electric motor with the basket in the unloaded condition and containing a load of clothes, between two distinct and predetermined rotation values of the electric motor, so as to calculate the moments of inertia (Jv, Jc) of the basket in the unloaded and in the loaded conditions, said control unit calculating the difference between said moments of inertia (Jc e Jv) of the basket and producing a signal representative of the mass of the load of clothes.

1 . A system for detecting a load of clothes in an automatic laundry machine of the type which comprises: 
 a tub, a basket mounted in the interior of the tub and which is dimensioned to receive a load of clothes: and an electric motor which selectively rotatively drives the basket in an operation of the machine, comprising:    a voltage sensor to detect the voltage supplied to the electric motor;    a rotation sensor detect the rotation of the electric motor, and    a control unit operatively associated with a timer, with the voltage sensor, and with the rotation sensor, and which is supplied, in a presetting step of the machine, with data representative of the medium torque Mmot of the electric motor in different voltage ranges, and with data representative of the acceleration and deceleration reference times (Ta 1 , Td 1 ) of the electric motor, with the basket in the unloaded condition, between two distinct and predetermined rotation values of the electric motor, in order to calculate the reference moment of inertia (Jv) of the basket in the unloaded condition, said control unit receiving, selectively, at the beginning of each operation of the machine, data representative of the acceleration and deceleration operation times (Ta 2 , Td 2 ) of the electric motor, with the basket containing a load of clothes, between said rotation values of the electric motor, and processing the data representative of the medium torque Mmot of the electric motor, in the voltage range detected by the voltage sensor, and the data of the acceleration and deceleration reference times (Ta 1 , Td 1 ) and of the acceleration and deceleration operation times (Ta 2 , Td 2 ), in order to determine the moment of inertia (Jc) of the basket with the load of clothes and the difference of said moments of inertia (Jc and Jv) of the basket, and to produce a signal representative of the mass of the load of clothes.    
   
   
       2 . The system according to  claim 1 , wherein the rotation sensor is a tachometer operatively associated with the electric motor.  
   
   
       3 . The system according to  claim 1 , wherein the control unit calculates the reference moment of inertia (Jv) of the basket in the unloaded condition, by means of successive calculations of the moments of inertia of the basket from the data of the acceleration reference time (Ta 1 ) and, subsequently, of the deceleration reference time (Td 1 ), establishing, in the first calculation, zero value for the resistive moment of the basket produced by the friction between the relatively moving parts upon the rotation of the basket.  
   
   
       4 . The system according to  claim 3 , wherein the calculation of the reference inertia moment (Jv) is effected by the control unit ( 20 ) utilizing the formulas:  
     
       
         
           
             
               
                 
                   
                     Ta 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   = 
                   
                     
                       
                         2 
                         ⁢ 
                         πΔ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                       
                       60 
                     
                     × 
                     
                       Jv 
                       
                         Mmot 
                         - 
                         Mres 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
             
               
                 
                   
                     Td 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   = 
                   
                     
                       
                         2 
                         ⁢ 
                         πΔ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                       
                       60 
                     
                     × 
                     
                       Jv 
                       Mres 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
   
   
       5 . The system according to  claim 1  further comprising: 
 an inlet value means, operatively associated with the control unit, to control the supply of the washing liquid to the machine, and    a level meter provided to detect determined levels of the washing liquid within the basket, said control unit associating the signal representative of the mass of the load of clothes with an adequate level of the washing liquid in the basket, so as to produce a blocking signal to the inlet valve means, interrupting the supply of the washing liquid to the machine when the level meter detects said adequate level of washing liquid has been reached.    
   
   
       6 . The system according to  claim 5 , wherein the inlet valve means is an electrovalve that is normally closed.  
   
   
       7 . The system according to  claim 6 , wherein the level meter is a pressure switch mounted to the tub.  
   
   
       8 . The system according to  claim 1 , wherein the control unit is programmed to command the energization of the electric motor, accelerating it until reaching a maximum rotation that is higher than said distinct and predetermined rotation values, and then de-energizing the electric motor so that its rotation decelerates to a value that is lower than said distinct and predetermined values, both in the presetting step and in the beginning of each operation of the machine.  
   
   
       9 . The system according to  claim 8 , wherein said maximum rotation is of about 1300 rpm.  
   
   
       10 . The system according to  claim 9 , wherein said distinct and predetermined rotation values maintain a mutual difference of about 460 rpm.  
   
   
       11 . A process for detecting a load of clothes in an automatic laundry machine of the type which comprises a tub; a basket mounted in the interior of the tub and dimensioned to receive a load of clothes; and an electric motor which drives, selectively and rotatively, the basket in an operation of the machine, which comprises the steps of: 
 rotatively driving the electric motor with the basket in the unloaded condition, maintaining its energization until a maximum rotation has been reached, the electric motor being then de-energized and decelerated to a reduced rotation value, as a function of the friction between the movable parts;    detecting the rotation of the electric motor in two distinct and predetermined rotation values, which are lower than the maximum rotation value, both in the acceleration phase and the deceleration phase;    measuring the acceleration and deceleration reference times (Ta 1  and Td 1 ) of the electric motor between said distinct and predetermined rotation values;    calculating a reference moment of inertia (Jv) of the basket in the unloaded condition, in a step of presetting the machine to a posterior operation, by processing the data representative of the acceleration and deceleration reference times (Ta 1  and Td 1 ) and of the known medium torque (Mmot) of the electric motor for the determined voltage;    before each washing operation of the machine, measuring the voltage supplied to the electric motor and rotatively driving the electric motor with the basket containing a load of clothes, maintaining the energization of the electric motor until said maximum rotation has been reached, and de-energizing and decelerating the electric motor by action of the friction between the movable parts;    detecting the rotation of said electric motor in the two distinct and predetermined rotation values in the acceleration and deceleration phases with the load of clothes;    measuring the acceleration and deceleration operation times (Ta 2  and Td 2 ) of the electric motor between said distinct and predetermined rotation values;    calculating the moment of inertia (Jc) of the basket with the load of clothes, by processing the data representative of the acceleration and deceleration operation times (Ta 2 , Td 2 ) and of the medium torque (Mmot) of the electric motor for the detected supply voltage; and    calculating the difference between said moments of inertia (Jc, Jv) of the basket and producing a signal representative of the mass of the load of clothes.    
   
   
       12 . The process according to  claim 11 , wherein the calculation of the reference moment of inertia (Jv) of the basket in the unloaded condition is effected through successive calculations of the moments of inertia of the basket from the data of the acceleration reference time (Ta 1 ) and then of the deceleration reference time (Td 1 ), giving, in the first calculation, zero value to the resistive moment (Mres) of the basket produced by the friction between the relatively moving parts upon the rotation of the basket.  
   
   
       13 . The process according to  claim 12 , wherein the calculation of the reference moment of inertia (Jv) is effected according to the formulas:  
     
       
         
           
             
               
                 
                   
                     Ta 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   = 
                   
                     
                       
                         2 
                         ⁢ 
                         πΔ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                       
                       60 
                     
                     × 
                     
                       Jv 
                       
                         Mmot 
                         - 
                         Mres 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
             
               
                 
                   
                     Td 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   = 
                   
                     
                       
                         2 
                         ⁢ 
                         πΔ 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         rpm 
                       
                       60 
                     
                     × 
                     
                       Jv 
                       Mres 
                     
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
   
   
       14 . The process according to  claim 13 , wherein the processing of the data used for calculating both the reference moment of inertia (Jv) and the moment of inertia (Jc) and for producing the signal representative of the load of clothes is effected by a control unit operatively associated with a voltage sensor, with a timer, and with a rotation sensor coupled to the electric motor.  
   
   
       15 . The process according to  claim 11 , further comprising the steps of: 
 associating the signal representative of the load of clothes with a determined level of the washing liquid in the basket, and    producing a blocking signal, for interrupting the supply of the washing liquid to the machine when the determined level of the washing liquid has been reached.