Patent GB-707748-A (GB)
Title: Improvements in check weighing machine
Inventor: HOWARD THOMAS PARKER
IPC: G01G13/00
Filed: 1951-06-05
Abstract: 707,748. Weighing-apparatus. PNEUMATIC SCALE CORPORATION, Ltd. June 5, 1951, No. 13336/51. Class 143 [Also in Groups XVII and XXX] In a check-weighing machine the checkweighing mechanism includes means for determining the variation in weight of an article from a predetermined weight, means operatiyely connected with and controlled by said variation-determining means for ascertaining the average algebraic deviation of a plurality of the weighed articles from the predetermined weight, and indicating means for indicating such average algebraic deviation. Check-weighing and recording apparatus. As shown in Figs. 1 and 2 a check-weighing apparatus 10 is operatively connected to a gross weight weighing and packaging machine 12 from which the filled packages 14 are delivered by a conveyer belt 16. A pusher 18 transfers alternate packages from the belt 16 to a plate 20 and intermittently movable arms 2 on an endless chain 24 move the package on to a scale pan 26 of the check-weigher, the preceding package being thereby moved on to a discharge conveyer 30. A counter 32 is actuated to close a switch 36 when the arm 34 is engaged by alternate packages. The main cam shaft 44 of the check-weigher is driven by a motor 40 through a pulley 42 loosely mounted on the shaft. 44 and integral with a ratchet 46 which cooperates with a pawl carrier disc 48 fast on the shaft 44 and carrying a pawl 50 to form a one revolution clutch. When the switch 36 is closed an electromagnet 62 is energized and causes the spring-loaded pawl 50 to engage with the ratchet 46 to cause one revolution of the cam-shaft. Upon initiation of the operation of shaft 44 the pusher 18 tranfers a package to the plate 20. The pusher 18 is supported on parallel links and is operated through a rod 72 and cam roller 78 which co-operates with a cam 80 attached to the shaft 44. The chain 24 is carried by sprockets 84, 86 on shafts 88, 90 respectively and driven from the shaft 44 through a cam 110, unidirectional clutch 102, horizontal shaft 96, and shaft 88, and by this means the packages are advanced one station by the arms 22, and the clutch is then disengaged to prevent reverse rotation of the shaft 88. In order to rock the arm 22 away from the package at the check-weighing station; the arms 22 are carried bv members 116 which co-operate with a cam piece 120 provided with a low spot 124. The check-weighing scale beam 28 is mounted on knife edges 126 and is provided with an adjustable counterweight 130, the beam resting on a stop 132, and the counterweight being so adjusted that the scale beam is in balance when the minimum weight limit is applied to the scale pan 26. A coil spring 134 attached to the scale beam and the machine frame acts as an additional counterweight, the extension of the spring being proportional to the excess of the load being weighed over the minimum weight limit. The scale beam carries a pawl 138 which co-operates with a frictionally held and vertically movable rack 140 during the return movement of the scale beam after each check-weighing operation, the scale beam being returned by a cam-operated vertically reciprocating locking rod 142. At its upper end the rod 142 is attached to a cam lever 146 which co-operates with a cam 152 driven from the main shaft 44. In operation the scale beam is maintained in a locked position until a package has advanced, on to the scale pan when it is unlocked to perform the check-weighing. The pawl 138, which is normally disengaged' from the rack 140, is then engaged therewith by means of an electromagnet 168, and the beam is returned to its initial position moving the rack a distance proportionate to the deviation from the counterweight of the weight of the article being check-weighed. The electromagnet 168 is energized through a switch 174 which is closed by a cam 176. Successive increments of movement made by the scale beam in returning to its position against the stop 132 after each check-weighing of the individual loads comprising a group sample are added, the total excess of the group over the minimum weight limit being indicated by the extent of movement of the rack 140. The stylus 182 carried by the rack co-operates with a roll 188 of graph paper provided with a zero line 238 and plus and minus control limits represented by lines 244 and 246 are provided by pens 240, 242. The paper is guided by an idler roll 192 supported by a pivotally mounted plate 200, the plate being rocked by a cam 204 through a lever 209, to press the surface of the paper against the stylus 182 to form a mark, at the completion of the check-weighing of a group sample. To render the check-weigher inoperative to move the rack 140 at the end of the checkweighing of a group sample a normally closed switch 222 in the circuit of the pawl electromagnet 168 is opened by a cam 224. Each time the plate 200 is rocked to produce a mark a ratchet is operated to advance the paper a small increment. To reset the rack 140 to its upper position after each recording, a cam 250 co-operates with a roller 252 and arm 254 of a pivoted lever whose second arm is connected by a link to a slidable block 262 which engages the lower end of the frictionally held rack. Automatic weight correcting mechanism. When the underweight or overweight indicated is outside the limit lines 244, 246, provision is made for automatically correcting the operation of the packaging machine. Fig. 3, shows the detecting mechanism which comprises an underweight circuit 266 having a normally open switch 278, and an overweight circuit 270 having a normally open switch 280, each switch being adjustably mounted on a slide member 276 which through a cam 286 and lever 290 moves the switches toward and from the rack 140 during the recording operation to co-operate with a lug 282 on the rack and close the respective switch if the indication is outside the limit lines. The correcting mechanism for the grossweight weighing machine 12, Fig. 1, comprises a coil spring 302, Fig. 9, connected between the counterweight end of the scale beam 296 and a threaded stud 304 which is vertically adjustable, to increase or decrease the effective counterweight, through opposed ratchets 308, 310, which respectively co-operate with pawls 314, 322 which are normally maintained out of engagement. When the overweight circuit 270 is closed a solenoid 320 is energized and through the arm 316 causes the pawl 314 to rotate the ratchet 308 a small increment to contract the spring 302. Similarly, when the underweight circuit 266 is closed the solenoid 328 is energized to cause the spring 302 to be extended. Similar correcting mechanism may be incorporated in a net-weight weighing apparatus, Fig. 11 (not shown). A volumetric filler, Fig. 12, comprises a hopper 400 which feeds the material to revolving telescopically adjustable measuring chambers 402. The upper portion 404 of the chambers is supported by an annular flanged member 406 which rides on rollers 408 carried by an adjustably supported ring 410, and the lower portions 412 are supported on a disc 414 which is attached to a continuously rotated shaft 416. The chambers 402 are provided with camoperated shutters 418 which are closed when the chambers pass under the hopper 400 to be filled, and are e opened to release the measured load through a funnel 420 to a carton 422 when the chambers pass from under the hopper. The cartons are advanced along rails 424 by a flexible metal belt 426 having a series of blocks 427 between which the cartons are engaged. The funnels 420 are supported in alignment with the chambers 402 on a disc 432 attached to the shaft 416. Filled cartons are delivered from the machine to the check-weigher 10 and provision is made for automatically adjusting the upper portion of the measuring chambers when the weight of the filled cartons varies beyond acceptable limits. The adjusting mechanism includes a plurality of screws 438 rotatably mounted in the machine frame, which co-operate with nuts 440 secured in the supporting ring 410, and are connected to rotate together by a chain and sprocket drive 442, one of the screws being provided with a gear 444 co-operating with a gear 446 on the shaft 448. The correcting mechanism, Fig. 13, which is controlled by the check-weighing machine 10. comprises a pair of opposed ratchets 452, 453, attached to the shaft 448 and respectively co-operating with pawls 454,.455, which are carried by arms 456 which are normally held in an elevated position bv latch members operated by solenoids 488, 490, so that the pawls are prevented from engaging with the ratchets by a shield member 480. The arms 456 are pivotally mounted on the shaft 448 and each arm is connected by a. link 458 to cam levers 460 which are pivotally mounted at 462 and through rollers 466 co-operate with cams 468. When one or other of the arms 456 is released by its solenoid the arm is rocked downwardly by its spring 472 allowing the roller 466 to follow its cam 468 the pawl riding off the shield 480 to engage its ratchet to effect rocking of the shaft 448 and adjustment of the measuring chambers 402.