GB1001723A - Improvements in precision balances - Google Patents

Abstract

1,001,723. Weighing apparatus. MEPAG A.G. Jan. 7, 1964 [June 28, 1963], No. 731/64. Heading G1W. Relates to a taring and zero adjustment device for a precision balance. A taring spring 26 (Fig. 1) is connected to a weigh beam 6 and to a tensioning member 27. The taring adjustment mechanism includes a drive shaft 13 operated by a knob 12 rotatably mounted in a frame 5 and carrying a toothed wheel 14 which engages a pinion 15 on a lead-screw 16. A thread 17 of the screw is engaged by a travelling nut 18 guided by a fixed rod 19 and connected to the tensioning member 27 by a retaining spring 29 which is able to overcome the effect of the taring spring and press the tension member 27 and its stop 28 against the nut 18. The position of the nut and hence the setting of the taring device is communicated to graduated indicator window 24 by a pin 20, on an extension of the nut, riding in a curved groove or slot 21 of a curved member 22, thereby causing the member 22 to rotate about the shaft 13 while a pointer 23 (Fig. 2) on the member 22 registers on the indicator window 24. OPERATION. With a container to be tared on a weigh pan 10 the tension of the spring 26 is correspondingly reduced by turning the knob 12 causing the nut 18 and tensioning member 27 to move upwards to the position shown in Fig. 1, the pointer 23 moving clockwise and indicating the tare weight. If the pointer moves beyond the range of the tare scale a control weight may be used to keep it within the scale range. To stop the taring effect when the container is removed the knob 12 is rotated so as to move the nut 18 and member 27 downwardly (as in Fig. 3 not shown) until the pointer 23 is in the vicinity of the zero line and a stop 30 on the member 27 comes to a standstill on a leaf spring 35 and thus on the top end 31 of the lead screw. At this position the zero of the beam can be adjusted by displacement of a set screw 32 which slightly alters the axial position of the lead screw 16. This alteration is transferred through the spring 35 and the stop 30 to the tensioning member 27 thereby varying the tension of the taring spring 26 to bring the beam 6 to zero.