Patent GB-729636-A (GB)
Title: Improvements in or relating to weighing mechanisms
IPC: G01G13/02
Filed: 1950-05-15
Abstract: 729,636. Weighing-apparatus. LINDARS, H. May 15, 1951 [May 15, 1950], No. 12086/50. Class 143. [Also in Group' XXXVIII] In a weighing apparatus counterbalance weights or springs are applied to the weigh beam by solenoids which may be energized either manually or automatically. As shown in Fig. 1, a beam 1 which supports a receptacle 3 has a number of lugs 4 adapted to support spherical weights 6 when solenoids 9 are energized; and rods 7, urged upwardly by springs 11, are arranged to lift the weights off these lugs into engagement with rings 6a when the solenoids are de-energized. Small moments can also be applied to the beam by a sliding weight (not shown) comprising a lever, one end of which bears on the beam through a roller and the other end of which is pivoted to a carriage movable along fixed horizontal guides by either manual or automatic control means; the carriage being connected with a variable resistance in a bridge circuit which indicates the moment applied by the lever. Alternatively small moments can be applied by a spiral spring acting about the beam fulcrum and having one end anchored to an abutment movable by a servo system calibrated in terms of weight. As applied to an automatic feed weigher the weight of each charge is set by manual operation of one switch 9A ... 9D (Fig. 2) after which, on the actuation of a button 16 the selected solenoid deposits a weight 6 on the beam which then drops and closes contacts 14. Simultaneously relay S/1 operates and locks over contacts S1 and 14, and maintains the circuit to the selected solenoid 9. Operation of button 21 also energizes relay F/2 which closes contacts F2 and energizes a magnet 20 which opens a feed sluice 19. On the charge in pan 3 reaching the selected weight the beam opens contacts 14 so de-energizing relays S/1, F/2, the selected solenoid 9,. and magnet 20, thus cut off is effected, and the circuit returns to normal. Further contacts may be provided to effect a dribble-feed movement of sluice 19. In a modification (Fig. 3, not shown) in which the apparatus is used to weigh loads placed in pan 3 by manual operation of switches 9A ... 9D, these switches are ganged with further switches each in circuit with a resistance, of value corresponding with the amount of the associated weight 6, and an ammeter calibrated in terms of weight. The contacts 14 are then replaced by contact stacks which control "under", "over" and "balance" indicator lamps located, together with the switches, at a station remote from the beam. In the apparatus shown in Fig. 4 the weight of a load in receptacle 3 is ascertained automatically by an electrical system which first deposits weights M100, M200, M300, M400 on the beam, and then removes them one by one to reduce the counter-balancing moment in steps of 100 units of weight until the load is just under balanced, after which groups of weights M10, M20, M30, M40 and M1, M2, M3, M4 are successively deposited on the beam and removed step by step as before until the load is counterbalanced to within one unit of weight. A sliding weight (not shown) as described above is then applied to the beam to accurately ascertain the weight of the load. The operating cycle commences with the closing of key A.W. so energizing a relay A/8 which locks over contact A1, closes contacts A2 so connecting the positive main to levels L1-L4 of uni-selectors U.S., T.S., H.S., opens contacts A3, A4, A5, so breaking the homing circuits of uni-selectors U.S., T.S., H.S., and changes over contacts A7 so stepping uni-selector A.S. one step. Then, through contact 1 on ASL2 the relay B/4 is energized and closes contacts B1, B2, B4 and opens contacts B3. Slugged relays C/l, D/2 then operate over contacts B2, B1, and since contacts Cl are then opened, relay B/4 is de-energized and releases its contacts B1-B4. Over contacts D2 magnet L.M. is energized and locks the beam until after relay D/2 releases. The momentary closing of contacts B4 connects the positive main through contact 1 of uniselector ASL3 to the driving magnet H.S. so stepping uni-selector H.S. one step and, through contacts A2, energizing magnets 9 in the hundreds group and depositing all of weights M100-M400 on the locked beam 1. After a short time delay relay D/2 releases and magnet L.M. is deenergized so allowing the beam to take up a balancing position. Should these weights be too great to balance the load in pan 3, the contacts 14 remain open and relay E/2 is not energized, then after relay C/1 releases, relay B/4 is again energized. A further pulse will then re-energize relays D/2, C/1 and moves uni-selector H.S. on a further step, and since contact 2 of level HSL1 is open circuited, weight M100 is removed. A similar sequence is then repeated with each weight M200-M400 until end 1b rises and closes contacts 14 whereupon relay E/2 is energized. At this stage relay B/4 is de-energized relay D/2 has just released and relay C/l is deenergized but is still operative, and the opening of contacts E1 has open circuited driving magnet H.S. and the closing of contacts E2 has energized driving magnet A.S. On release of relay C/l, relay B/4 is energized, opening its contacts B/3 and so de-energizing the relay E/2. This relay does not immediately release, and consequently, the circuit to the magnet H.S. is not re-made instantly. When relay E/2 does release, relay B/4 is de-energized over contacts Cl, relay E/2 remaining de-energized over contacts D1, and consequently when contacts B4 operate this pulse from relay B/4 does not energize magnet H.S. When relay E/2 releases contacts E2 open thus the wiper of uni-selector A.S. is stepped to contact number 2. The same cycle is then repeated for the tens and unit groups until the load in pan 3 is balanced whereupon the wiper of uni-selector A.S. is moved to contact 4 and the circuit to relays B/4 and E/2 is broken, thus the apparatus is locked. Pointers connected with the spindles of the three uni-selectors indicate the total weight of the load. On the operation of key C.R. relay A/8 is de-energized and so effects homing of uni-selectors U.S., T.S., H.S. and A.S., deenergization of magnets 9, with the result that all the weights 6 are removed from the beam, and open circuiting of relays E/2, B/4. The circuit is then in its original state. Specifications 691,907 and 729,633 are referred to.