Patent GB-730087-A (GB)
Title: Improvements in automatic weighing machines
Inventor: HOWARD THOMAS PARKER
IPC: G01G13/26
Filed: 1951-06-05
Abstract: 730,087. Automatic feed weighers. PNEUMATIC SCALE CORPORATION, Ltd. June 5, 1951, No. 13335/51. Class 143. [Also in Group XXIX] In an automatic feed batch weigher a fluid pressure servomotor system controls the automatic cut-off of the feed of material and comprises a jet 95 the escape of compressed air from which is controlled by an obturating member 99 connected with a pair of parallel vertically-spaced cantilever leaf springs 10, 12 of equal length on the free ends of which the weighing vessel 18 is supported. Deflection of the springs mounting is thus independent of the position of the material in the weigh receptacle. As shown, Figs. 10 and 11, the jet 95 is connected to a primary air chamber 89 connected with the compressed air source through a restricted throat member 91 and variations in the pressure in the primary air chamber 89 are communicated to a bellows 103 of large cross-section operating a spring-controlled piston 113. Connected to the latter is a valve 123 controlling a second jet 127 so that a considerably amplified variation in pressure in a secondary air chamber 131 connected with the jet 127 and through a restricted throat 133 with the compressed air supply is produced. This amplified pressure variation is applied to a further spring- controlled piston 82 to operate a U-shaped member 84 coacting with the lower end of a lever 88 pivoted on a rocking shaft 90, an arm 96 on the shaft, and a spring-controlled latch member engaged by the arm 96 to release under its own weight a gate 60, rapidly cutting off the feed. A cam 102 on the same pivot 64 as the feed gate at the same time operates through a roller 108 a resilient switch arm 106 of a switch 100 to de-energize a motor 56 and stop vibration of a conduit 40 supported on flexible steel straps which receives material from the supply tube 42 and supplies it to a feed hopper 58. Further, the cam 102 operates through linkage 160, 154 to free the tail end of a spring-loaded pawl 146 mounted on a normally stationary disc 144 to engage it with a constantly rotated ratchet 142 so that a shaft 132 secured to the disc rotates and cams on it operate respectively through linkage a lever 122 which opens the spring controlled door 110 of the weigh receptacle 18 to discharge the latter, then allows it to close again, and a shaft 168 connected to a bell crank lever pivoted coaxially with and on the other side of the feed gate pivot 64, the other arm of which has connected to it an extension arm positioned underneath a bracket 184 of the gate 60 which raises the gate 60 and resets the spring-loaded latching device, and a new weighing cycle commences. The raising of the feed gate 60 at the same time retracts the rod 160 and through linkage projects a rod 148 so that it engages the tail end of the pawl 146 after one revolution of the ratchet clutch and thereby disengages the pawl and ratchet. The pawl engaging linkage may be provided with a depending rod 186 and handle 188 engageable in a slotted lug 190 so that the pawl may be locked free of engagement with the ratchet when the machine is not in use. The pawl engaging linkage may also be coupled to a carton feed mechanism to ensure a carton being automatically positioned under the delivery chute 114. The feed gate 60 may engage a resiliently faced stop 63 in its closed positon. The movement of the spring weighbeam is limited by adjustable upper and lower stops 155, 165 respectively. A coil spring 20 secured at its upper and lower ends to adjustable bolts exerts 'an adjustable counter force on the spring beam, and a secondary light coil spring 30 with screw adjustment secured to the beam permits fine weight adjustments.