Patent GB-502261-A (GB)
Title: Improvements in weighing machines
IPC: G01G23/18
Filed: 1937-09-30
Abstract: 502,261. Photo-electric control of weighing-machines. SILCOCK & SONS, Ltd., R., and BROADHEAD, F. G. Sept. 30, 1937, No. 26448. [Class 40 (iii)] [Also in Group XVIII] In a recording steelyard apparatus of the kind which is enclosed or may be enclosed and wherein a control member (e.g. a ticket-slot obstructing member) is operatively interlocked with the steelyard to prevent the printing or delivery of a record card unless the steelyard is in equilibrium, the steelyard and control member are electrically interlocked by an electromagnetic device the current through which is controlled by means removed from, but governed by the movement of the steelyard in such a manner as not to influence the movement of the steelyard adjacent to the equilibrium position. The current control means for the electromagnetic device may include a photo-electric cell. As shown in Fig. 1, where a printed record is made by means of a printing handle 65, the steelyard 10 is enclosed in a casing having a semi-cylindrical door 19 to give access to the steelyard poise 11. A control shutter 15 operated by an electromagnet 22, through members 42, 43, 44 closes a ticket slot 13 except (as described below) when the steelyard is in equilibrium and the door 19 is closed. The end of the steelyard is loosely embraced by the forked end 37 of a lever connected by a link to a pivoted mercury switch which breaks the circuit through the electromagnet 22 unless the steelyard is in equilibrium. In series with the mercury switch is a second switch 24 closed by the closure of the door. The closure of the two switches energizes the electromagnet 22 for moving the control shutter to open the ticket slot. A bolt 52 engaging a collar 53 on the rod 42 also prevents the opening of the ticket slot even if the switch 24 is fraudulently closed. The bolt is withdrawn upon closure of the door, by a spring 60, Fig. 3, rendered effective when a bent-out extension 59 of the door permits sufficient movement of intermediate members 54, 56. The control shutter when clear of the ticket slot engages an abutment 50 on the door 19 to prevent the opening thereof until the current is switched off after making a record. A lamp in parallel with the electromagnet 22 indicates that printing may be effected and a second lamp controlled by a switch 62 and collar 53 indicates that the steelyard is not in poise. In a modification, Fig. 6 (not shown) the mercury switch operated by the fork 37 is replaced by a photo-electric circuit influenced by a part of the steelyard interposed between the light source and the cell to vary the light intensity falling on the cell. A similar photoelectric arrangement may also be used instead of the door switch 24. In a further modification, Fig. 7 (not shown), the casing is normally permanently closed and the poise is moved along the steelyard by an external handle projecting through a longitudinal slot in the casing. In further arrangements the control shutter 15 instead of obstructing the ticket slot may be arranged to prevent operation of the printing mechanism, or when the invention is applied to a machine wherein the record is printed on a ticket delivered 'from a stack, the shutter may be arranged to deflect a wrongly printed ticket into an inaccessible box. Instead of giving a printed record, the mechanism may be arranged to emboss or punch the card or give a photographic record. The control shutter may be in the form of an interposer providing an operative connection between the printing handle and the printing mechanism.