Patent GB-913085-A (GB)
Title: Weighing scales
Inventor: FARMER EDWARD BALDWIN
IPC: G01G23/18
Filed: 1960-06-20
Abstract: 913,085. Weighing-apparatus. FAIRBANKS, MORSE & CO. June 20, 1960, No. 21559/60. Class 143. [Also in Group XL (b)] A scale for weighing and recording the weight of a load on the scale comprises means for sensing the weight of a load on the scale, a printer operatively connected to the scale for recording in permanent form the weight of a load on the scale, means for sensing the rate of movement of said scale and control means connected to the rate-sensing means and to said printer to prevent operation of the printer until a selected delay has occurred, following occurrence of a selected rate of movement of the scale. The control means generally comprises a capacitor whose charge through a photo-electric cell arrangement operated by movement of the scale member can be adjusted by a potentiometer, and whose complete charge time to effect delay of the printing operation can also be adjusted by a further potentiometer. These operative elements appear in the circuit arrangement, Fig. 6. A body placed on a scale pan 10, Fig. 1, actuates weight-determining mechanism 15 operating through a link 17 to rotate a shaft 20 carrying notched discs providing units, tens and hundreds indications of the weight. When the equilibrium position has been attained, the energization of a motor 39 operates through a connection 40, 42 a detent member 30 engaging a serrated positioning or indexing disc 28 and print control members 35, 36, 37 to derive selective movement of type-bearing members 45, 46, 47 against the lower surface of which a tape is pressed. The shaft 20 also carries a disc 54 with a toothed periphery 55, 56 disposed between a light-source 60 and a photoelectric cell 61. The operation of the motor 39 is controlled by the operation of a solenoid 81, Fig. 2, which rooks a pivoted lever 103 to the position shown to close contacts 73 in the circuit of the motor 39. The lever 103 has a finger 109 normally engaging in a recess 118 of a flange on a cam member 115 and in engagement with a projection 128 of a pivoted dog member 125 associated with a ratchet wheel 123 on a shaft 122 driven by the motor 39. The operation of the solenoid 81 initiates rotation of the motor 39 through one revolution during which the finger 109 rides on the flange until it again enters aperture 118 to allow lever 103 to open contacts 73 and to rock the pivoted dog 125 to disconnect the cam member 115. A further microswitch 135, Fig. 3, operated during a portion of a revolution of the motor 69 is connected to the control circuit 67 via a contact arm 139 actuated by an arm 141 rocked by a cam surface 145 mounted on an arm 147 connected to a member on the shaft 120. Main control circuit, Fig. 6. Operating voltage for the circuit is derived from a source 152 and a transformer 180 with a secondary winding 184 connected to a rectifier bridge 186 illuminating the light source 60 and a secondary winding 183 providing voltage for two twin triodes 192, 193 operating in response to the light fluctuations impressed on the photocell 61 and controlling a relay 162 in the anode circuit of the second section 193b of the triode 193. During rotation of the chopper disc 54, the positive pulses from the cell 61 are amplified by the sections 192a, 192b of the valve 192 and both sections of the valve 193 conduct, thereby holding relay 162 energized and a capacitor 258 generally discharged, but the amount of charge can be adjusted by a potentiometer 233. When the rotation of the shaft 20 conveying the disc 54 ceases, section 193a of valve 193 no longer conducts, capacitor 258 begins to charge or to increase its charge without interruption and temporarily holds triode section 193b conducting, the time constant of the charging cycle of capacitor 258 being adjustable by a potentiometer 260. Subsequently, the charged condition of capacitor 258 effects the cutting-off of triode 193b, but a diminishing charging current still flows through relay 162 from capacitor 258 until finally it is reduced to a value allowing the release of the relay 162 which closes contact 162a of the printing-control circuit including the motor 39. Printing-control circuit, Fig. 4. With switch 160 against contact 158 the closure of contacts 162a of relay 162, Fig. 6, energizes over normally closed contacts 164a of relay 164 the winding 85 of solenoid 81 which closes contacts 73 to allow the motor 39 to effect a revolution during which the indication of the weight is printed. During the rotation of the shaft 120 the contacts 137 of the microswitch 135 are closed, and relay 164 operates to open the normally closed contacts 164a and locks up over holding contacts 164b and contacts 162a. When the weight is removed from the pan 10, Fig. 1, the disc 54 again rotates and effects the energization of relay 162 so that contact 162a opens the locking circuit of relay 164 which releases. When the disc 54 again comes to rest corresponding to the position of zero weight, relay 162 again releases to operate the printer to record the zero indication. For manual control of the printing operation the switch member 160 is moved against contact 168 operating relay 166 to close contacts 166b to prepare an energizing circuit for the motor by manual operation of the solenoid cap 95, Fig. 1, to close the contacts 73, and to open contacts 166a to isolate the remainder of the circuit. A further printer-control circuit, Fig. 5 (not shown), is modified to prevent the printing of the zero indication after the weight has been removed from the scale pan 10, but includes a relay operated by a switch to include the feature of zero recordation, if so desired.