Patent GB-260679-A (GB)
Title: Improvements in or relating to weighing scales
IPC: G01G1/28
Filed: 1925-08-05
Abstract: 260,679. White, A. E., (Dayton Scale Co.). Aug. 5, 1925. Loose-weight apparatus. - A loose-weight weighing-scale is provided with automatically operated, weight-changing mechanism which selects, and applies to or removes from the weigh-beam, one or more factored combinations of weights to balance the load. As shown in Figs. 1 and 3, the weigh-beam 30 of a weighing- scale is adapted to carry on one side of the fulcrum 31 a weigh-pan 33, and on the other side. one or more of a series of four removable weights 39 capable of counterbalancing respectively, loads of 1, 2, 2 and 4 units of weight. The weights are applied and removed by bell-crank levers 40 actuated by cams 44 mounted on a shaft 45. In one revolution of the cam-shaft weights are applied and removed to balance successively loads of 0, 1 - - - 9 units, the load being printed by any known means, or indicated by a drum 47 connected to the cam-shaft. The camshaft is driven by an electromotor 48 through a one-revolution clutch 51 which is controlled by a magnet 57 and beam-contacts 59, 60. Two pilot weights 61, 64 are disposed adjacent the end of the beam and prevent the closure of either of the beam-contacts unless the beam is out of balance by an amount exceeding one unit. The starting-switch of the motor is closed by a cressbutton or by a draw-rod switch 68<a>, and is maintained in closed position by an auxiliary circuit established through a contact 75. The contact 75 is controlled by a mechanically-delayed relay, Fig. 13, comprising a magnet 86 arranged in series with the magnet 57 and adapted upon energization to draw a plunger 88, pivoted to the armature 86<a>, out of engagement with a threaded part of a slowly rotating shaft 89, and thereby allow the contact 75 to close. Upon the deenergization of the magnet 86 by the opening of the beam-contacts, the plunger re-engages the screw thread and is thereby fed to the right until, after an interval of time, it opens the contact 75 and stops the motor. The cam-shaft is adapted to rotate in one direction only, so that in the event of the load being less than the counterbalancing weights, the position of balance is obtained after the weight-changing mechanism has passed through the maximum counterbalancing position and the zero position. In order to prevent continuous rotation of the cam-shafts when the load exceeds the capacity of the machine, two contacts 78, 78a, Fig. 4, arranged in series with the beam-contacts 59, 60, respectively, are provided, and adapted to be operated by a cam 90 on the cam-shaft. At the zero position of the cam-shaft, contact 78 is closed and contact 78<a> open; at the maximum position contact 78<a> is closed and contact 78 open; for intermediate positions both contacts are'closed. Thus the cam-shaft cannot pass from the maximum position to the zero position unless beamcontact 60 is closed, i.e., unless the load is less than the counterbalancing weight. In order to keep the open circuit voltage across the beamcontacts low, these circuits are supplied from tappings across a resistance in the motor-control circuit. In a modification, two sets of removable weights are provided, one set corresponding to the pounds of the load and the other to the ounces. Two pairs of pilot weights are provided, the beam having a certain travel limited only by the ounce pair and free of the pound pair. The arrangement is such that the weight-changing mechanism for the ounce weights does not come into action until the major part of the load is balanced. Specification 259,340 is referred to.