Calibration weight arrangement for an electronic balance
View Patent ↗An electronic balance with a force-transmitting device ( 1, 101 ) has a calibration weight arrangement ( 4, 104 ). The arrangement includes a calibration weight ( 3, 103 ) capable of being coupled to the force-transmitting device ( 1, 101 ). It also includes a transfer mechanism and a drive source to effect a guided movement of the calibration weight ( 3, 103 ). The drive source has an actuator ( 16 ) that cooperates with the transfer mechanism and consists, at least in part, of a shape memory alloy. The actuator ( 16 ) moves the calibration weight ( 3, 103 ) through a structural change of the shape memory alloy as a result of a temperature change.
1. A calibration weight arrangement for an electronic balance which has a force-transmitting device, the calibration weight arrangement comprising:
at least one calibration weight, adapted to be coupled to the force-transmitting device;
a transfer mechanism; and
a drive source to guidedly move the at least one calibration weight, the drive source having an actuator comprising a shape memory alloy that cooperates with the transfer mechanism, such that a structural change of the shape memory alloy occurring as a result of a temperature change causes the actuator to move the calibration weight.
2. The calibration weight arrangement of claim 1 , wherein the drive source comprises an electrical heating device that cooperates with the actuator.
3. The calibration weight arrangement of claim 2 , wherein the transfer mechanism comprises:
means for resetting the calibration weight; and
means for lifting the calibration weight.
4. The calibration weight arrangement of claim 3 , wherein the resetting means has a resetting force of sufficient magnitude both to move the transfer mechanism and the calibration weight to their respective rest positions and to return the shape memory alloy to an original shape or length during a cool-down phase thereof.
5. The calibration weight arrangement of claim 3 , wherein the resetting means comprises at least one spring.
6. The calibration weight arrangement of claim 3 , wherein the lifting means is configured either as wedges that move against each other in pairs or in the form of at least one knee-joint linkage.
7. The calibration weight arrangement of claim 3 , wherein:
the lifting means comprises at least two compressive coil springs.
8. The calibration weight arrangement of claim 7 , wherein:
each of the compressive coil springs also serve as the resetting means.
9. The calibration weight arrangement of claim 3 , wherein the transfer mechanism comprises an element serving both as the resetting means and the lifting means.
10. The calibration weight arrangement of claim 9 , wherein the resetting and lifting element has a resetting force of sufficient magnitude both to move the transfer mechanism and the calibration weight to their respective rest positions and to return the shape memory alloy to an original shape or length during a cool-down phase thereof.
11. The calibration weight arrangement of claim 10 , wherein the resetting and lifting element comprises at least one spring.
12. The calibration weight arrangement of claim 11 , wherein the actuator is adapted to perform a function check of the transfer mechanism.
13. The calibration weight arrangement of claim 12 , further comprising at least one means for direction-changing, adapted to change the direction of the actuator force.
14. The calibration weight arrangement of claim 13 , wherein the direction-changing means are rollers, at least one of which comprises a smooth, gliding material.
15. The calibration weight arrangement of claim 14 , wherein the resetting and lifting element is configured either as wedges that move against each other in pairs or in the form of at least one knee-joint linkage.
16. The calibration weight arrangement of claim 14 , wherein:
the resetting and lifting element comprises at least two compressive coil springs.
17. The calibration weight arrangement of claim 1 , wherein the shape memory alloy is selected from the group consisting of: NiTi2, CuZn, CuZnAl, CuZnGa, CuZnSn, CuZnSi, CuAINi, CuAuZn, CuSn, AuCd, AgCd, NiAl and FePt.
18. The calibration weight arrangement of claim 1 , wherein the shape memory alloy comprises a nickel-titanium alloy with a nickel content of at least 40% and with a phase transition temperature of at least 80° C.
19. The calibration weight arrangement of claim 1 , wherein the shape memory alloy in the actuator is configured in wire form.
20. The calibration weight arrangement of claim 1 , wherein the transfer mechanism comprises:
means for resetting the calibration weight; and
means for lifting the calibration weight.
21. The calibration weight arrangement of claim 20 , wherein the transfer mechanism comprises an element serving both as the resetting means and the lifting means.
22. The calibration weight arrangement of claim 1 , wherein the actuator is adapted to perform a function check of the transfer mechanism.
23. The calibration weight arrangement of claim 1 , further comprising at least one means for direction-changing, adapted to change the direction of the actuator force.