Patent GB-663766-A (GB)
Title: Improvements in or relating to automatic weighing gear
IPC: G01G19/16
Filed: 1948-09-06
Abstract: 663,766. Weighing apparatus. WILLIAMS & SONS, Ltd., S., and GAMBLE, F. D. M. Aug. 26, 1949 [Sept. 6, 1948], No. 23438/48. Class 143 An automatic weigning device for use with a crane comprises a load balancing unit A which transmits fluid at a pressure proportional to the gross load to a weighing unit B which converts this pressure into a force approximately proportional to the gross load, a compensating mechanism C for converting movements of the weighing unit into movements accurately proportional to the gross load, and an apparatus D which automatically deducts the tare weight from the gross weight and is associated with a weight integrating and printing mechanism E which serves to totalize and record the net weights lifted. The load balancing unit is connected with the load by sheaves 15 and members 61, 48 the combined weight of which is counterbalanced by springs 51 which, together with the member 48, operatively engage the lower portion of a piston 16. This piston is in contact with a diaphragm 17 and the annular space between the piston and a fixed diaphragm retaining ring 50 is bridged by a member 20 forming a flexible support for the diaphragm where it overlies this gap, the member 20 being in the form of a series of discs, annular sector pieces or a complete annulus having radial slots around its periphery. Fluid is contained in the space 18 between the diaphragm and a fixed cylinder 19, and, through a slide valve 52, the space 18 may be connected with either a continuously running pump feeding a port 24, or a reservoir connected to an outlet port 24<SP>1</SP>, the arrangement being such that as the member 48 lifts the piston 16 it also causes valves 52 to admit fluid to the space 18 at an increased pressure, and, when the member 48 is lowered, the pressure of the fluid is similarly reduced, so that the diaphragm is maintained at a'constant level. The fluid in space 18 is in communication through a pipe 25 with the weighing unit B which comprises an axially fixed but continuously rotating piston 26 and a cylinder 3 which is axially movable against the resistance of a spring 8. Movement of this cylinder is communicated by a rod 2, a bell crank 1 and an arm 4, connected to an endless band' 5<SP>1</SP>, to an indicator shaft 28<SP>1</SP>, and, to compensate for inaccuracies which would produce non-proportionality between the movement of the indicator shaft and the gross load, the crank 1 is also moved by a cam member 6 co-operating with rollers 5, 7 on said crank. The angle of the cam member 6 is automatically adjusted by nuts 9, 10 and screws 11, 12 driven through a differential (not shown) connected with the luffing and hoisting mechanisms, in such a manner that the cam also compensates for the weight of the cable supported by the jib.. When the load is being discharged a shaft 55 driving a totalizer 31 is automatically coupled to the shaft 28<SP>1</SP> in its gross load indicating position by a clutch 54, similar to that described in Specification 653,997, [Group XXIV], until shaft 28<SP>1</SP> has returned to its tare load indicating position whereupon a gravity operated rod 33 is raised by the arm 4 from a switch 32 which then de-energises the clutch and brakes the shaft 55. Printing wheels are associated with the totalizer and at the end of the operation a printed record is taken. Means are provided to ensure that the crane is not hoisting or luffing when the weighing mechanism is in operation, and further means are provided to ensure that one weighing- only is made on each lift. Visual indicators 28 and 34 are also provided, the former serving to indicate the gross weight of each load and the latter the total net load handled since the last re-setting thereof, contacts 36 being provided to indicate when a predetermined load has been handled. The sequence of operations is as follows: with a load greater than tare, contacts 32<SP>1</SP> and 32<SP>2</SP>, Fig. 2, are closed in the switch 32 so that when push button 37 is operated its hold-on coil 37' is energised so maintaining a closed circuit through this switch and thus when the transformers 39, 391 are automatically de-energised by the commencement of luffing and hoisting movements, a continuously energised, but anti-phase, transformer 40 closes lock out relay contacts 381 so energising a time delay unit 41, a lock out relay 42 and the stamper 43. The hoisting and luffing motors are then de-energised due to the opening of contacts 42<SP>1</SP> and the stamping mechanism is cocked. Coil 58 is energised after a time delay dependent upon the time constant of resistance 59 and condenser 60, and closes contacts 41<SP>1</SP>, 41<SP>2</SP> so energising the clutch coil 56 <SP>1</SP> and de-energising the brake coil 57<SP>1</SP>, and de-energising the lock out relay 42 which then allows hoisting and luffing to re-start. On discharge of the load, switch 32 drops so disconnecting the clutch coil 56<SP>1</SP> and energising the brake coil 57<SP>1</SP>, disconnecting the hold on coil 37<SP>1</SP> so allowing button 37 to re-set, and disconnecting the time delay and stamper so that the printed record is made. Switch 32 is vertically adjusted at the correct tare position by putting it in such a position that when the crane supports the tare weight alone, neither of lamps 46, 47 is illuminated. Specifications 663,767, [Group XXXV], and 663,768 are referred to.