Calibration weight arrangement for an electronic balance

Abstract

A calibration weight arrangement ( 4, 104 ) for an electronic balance with a force-transmitting mechanism ( 1 ) has a calibration weight ( 3, 103 ) adapted to be coupled to the force-transmitting mechanism. The arrangement also has a transfer mechanism and a drive source to manipulate the calibration weight in a guided movement. The drive source includes an actuator ( 18 ) cooperating with the transfer mechanism and at least one piezoelectric element ( 19 ) which drives the movement of the actuator. The piezoelectric element interacts with a drive wheel ( 17, 117 ) that is centrally positioned relative to the calibration weight arrangement and drives a likewise centrally positioned shaft ( 16, 126 ). The interaction between the piezoelectric element and the drive wheel occurs during the advance movement in one direction through the repeated engagement and release of a frictional contact force.

1 . A calibration weight arrangement for an electronic balance comprising a force-transmitting mechanism, the calibration weight arrangement comprising:
 a calibration weight adapted for coupling to the force-transmitting mechanism;   a transfer mechanism to manipulate the calibration weight in a guided movement, and   a drive mechanism, comprising an actuator that cooperates with the transfer mechanism, the actuator comprising:
 a piezoelectric element; 
 a drive wheel which interacts with the piezoelectric element, the drive wheel being centrally positioned relative to the calibration weight arrangement; and 
 a centrally-positioned shaft that cooperates with the drive wheel in producing a linear advance movement, the interaction between the piezoelectric element and the drive wheel occurring during the linear advance movement in one direction through the repeated engagement and release of a frictional contact force. 
   
   
   
       2 . The arrangement of  claim 1 , wherein:
 the transfer mechanism comprises:
 a lifting element; 
 a calibration weight seat; and 
 a guiding device. 
   
   
   
       3 . The arrangement of  claim 2 , further comprising:
 an external screw thread on the shaft, which can be set into rotation by the actuator, and   a lifting- or guide platform, comprising an internal screw thread and arranged for linear displacement along the shaft.   
   
   
       4 . The arrangement of  claim 2 , wherein:
 the guiding device comprises:
 two guide posts arranged laterally of the shaft; and 
 a guide platform having a guiding brace formed on each side thereof, the guiding brace sized so that the guide platform can glide along the guide posts almost free of loose play. 
   
   
   
       5 . The arrangement of  claim 4 , wherein:
 the calibration weight seat is materially integrated in one piece with the guide platform.   
   
   
       6 . The arrangement of  claim 3 , wherein:
 the drive mechanism is self-locking, such that the lifting- or guide platform is immobilized in a current position when there is no current flowing to the drive mechanism.   
   
   
       7 . The arrangement of  claim 1 , wherein:
 the piezoelectric element comprises an integral means for sensing at least one of: the proper functioning of and the actual position of the transfer mechanism.   
   
   
       8 . The arrangement of  claim 1 , further comprising:
 a pusher finger, moved by the piezoelectric element on an elliptic path, the pusher finger acting as an actuator that, while moving on the path, periodically contacts the drive wheel in the sense of a frictional or form-fitting connection.   
   
   
       9 . The arrangement of  claim 1 , further comprising:
 a base plate on which the force-transmitting device is arranged, the base plate having a recess on which the drive mechanism is arranged.   
   
   
       10 . The arrangement of  claim 9 , wherein:
 an area of the recess has a reduced thickness and an opening for the passage of at least a part of the lifting element.   
   
   
       11 . A calibration weight arrangement for an electronic balance comprising a force-transmitting mechanism, the calibration weight arrangement comprising:
 a calibration weight adapted to be coupled to the force-transmitting mechanism;   a transfer mechanism to manipulate the calibration weight in a guided movement; and   a drive mechanism, comprising an actuator cooperating with the transfer mechanism, the actuator comprising:   a shaft equipped with an external screw thread, can be set into rotation by means of the actuator, and that a lifting- or guide platform comprising an internal screw thread is arranged for linear displacement along the shaft.   
   
   
       12 . The arrangement of  claim 11 , wherein:
 the transfer mechanism comprises:
 a lifting element; 
 a calibration weight seat; and 
 a guiding device. 
   
   
   
       13 . The arrangement of  claim 11 , wherein:
 the guiding device comprises:
 two guide posts arranged laterally of the shaft; and 
 a guide platform having a guiding brace formed on each side thereof, the guiding brace sized so that the guide platform can glide along the guide posts almost free of loose play. 
   
   
   
       14 . The arrangement of  claim 13 , further comprising:
 a calibration weight seat that is materially integrated in one piece with the guide platform.   
   
   
       15 . The arrangement of  claim 11 , further comprising:
 a base plate on which the force-transmitting device is arranged, the base plate having a recess on which the drive mechanism is arranged.   
   
   
       16 . The arrangement of  claim 15 , wherein:
 an area of the recess has a reduced thickness and an opening for the passage of at least a part of the lifting element.   
   
   
       17 . An electronic balance, comprising:
 a calibration weight arrangement according to  claim 1 .   
   
   
       18 . An electronic balance, comprising:
 a calibration weight arrangement according to  claim 11 .