Patent GB-704421-A (GB)
Title: An improved check-weighing machine
IPC: B07C5/32
Filed: 1952-01-04
Abstract: 704,421. Weighing-apparatus. ARNOLD, J. C. (Pneumatic Scale Corporation, Ltd.). Jan. 4, 1952, No. 365/52. Class 143 [Also in Groups XIX and XXXV] A check-weighing machine comprises weighing means for determining the variation of the weight of an article from a predetermined weight, said weighing means controlling pneumatic means for operating indicating means whereby the average algebraic deviation of a plurality of the weighed articles from the aforesaid predetermined weight is ascertained. Means may also be provided for correcting the operation of a load-forming machine when the average deviation varies beyond predetermined amounts. As shown in Fig. 2, the packages for checkweighing are transferred by a pusher 18 from the delivery belt 16 on to. a receiving plate, and are moved by arms 22 to. the scale pan 26 of the check-weigher scale beam. The check-weighing unit comprises upper and lower horizontal relatively stiff leaf springs 126, 128, which are attached at one end to a block 130 secured to the machine frame, the other ends of the springs being secured to a block 132 to which the scale pan 26 is attached. A coil spring 134 connected between the weighing unit and the machine frame is adjusted so that the deflection of the leaf springs is proportionate to the weight of the package above a predetermined minimum weight limit. A rod 143 secured to a projection 142 of the member 132 carries a piston extending into a dash pot 145. The weighing unit co-operates with pneumatically operated gauging means 144 comprising a chamber 152, Fig. 3, through which air under pressure may flow to be discharged through an orifice 154 which co-operates with a valve 156 adjustably mounted on a rod 158 attached to the projection 142. A flexible hose 160 supplies the chamber with air through a restricted throat portion 162. The weighing unit is normally maintained in a locked position with the valve member 156 spaced from the orifice 154 so that a relatively low pressure is maintained in the chamber 152 during the package moving operation, the beam being unlocked after a package is placed on the platform 26. A small deflection of the spring beam. due to a load in excess of the predetermined minimum, causes the valve 156 to move towards the orifice 154, thereby effecting a substantial pressure increase in the chamber 152 which is utilized to operate the indicating mechanism. The unit 144 is connected by a flexible hose 164 to an expansible tube 166 supported at one end in a collar 168 attached to the machine frame, and connected at its other end to an adapter 174 which is attached to a bracket 176 carrying a pivotally mounted pawl 148. When the pressure in the tube 166 is increased the tube is elongated and moves the bracket 176 to the right, retracting the pawl relative to the rack 150. A subsequent decrease in pressure when the spring beam is again locked moves the bracket 176 to the left to advance the rack an increment of movement proportional to the weight of the load in excess of the predetermined minimum. The bracket 176 is supported on vertical leaf springs 182 supported at their lower ends in a bracket attached to the frame, and is normally urged to the left by a spring 186. The rack 150 is normally urged to the right by a spring 192, but a holding pawl retains the rack in its advanced position until subsequently released. A vertically reciprocal rod 200 maintains the spring beam 28 in a locked position during the package moving operation and is operated by a lever 206 co-operating with a cam 212. At the completion of a predetermined number of cycles of operation of the check weigher the average algebraic deviation of the weight of a plurality of packages from a predetermined weight, as shown by the position of the rack 150, is recorded on a roll 228 of graph paper, which has a central line 227 indicating that the group of packages conforms to the predetermined weight, any deviation from such weight being indicated by marks on one or other side of the central line. The recording mechanism is supported between sideplates 218, 220, which are secured to a rocker plate pivotally mounted on the frame so that the roller 230, over which the recording paper is passed, may be moved toward a pen 238 carried by the rack 150, for the marking operation, the paper being moved continuously by a motor 234. The rocker plate is moved by an electromagnet 240 which is energized when a switch 248 is closed by means of a member 252 on the disc 254, after, for example, five packages have been check weighed. To maintain the check weigher inoperative to move the rack 150 during the recording a vertically reciprocable rod 262 operated from the cam 273 through a lever 267 engages a stud 265 on the projection 142. After the recording has been made a bell crank 258 is operated by an electromagnet 291 when a switch (not shown) arranged beside the switch 248, is closed by a member 299 on the disc 254, and extends under and lifts the rack holding pawl and the rack advancing pawl to allow the rack to return to its initial position at the right. For the purpose of detecting when the recordings on the paper fall outside the limit lines X, Y, a switch is mounted on each of the side plates 218, 220, carried by the rocker plate. When the plate is rocked to make the recording the switches are moved toward the rack 150, and if the recording is outside the limit lines a lug carried by the rack engages the respective switch. By this means the check weigher may be used to correct the operation of a gross-weight weighing machine, a netweight weighing machine, and a volumetric filling machine as described in Specification 707,748. Fig. 15 shows a modified form of indicating and recording mechanism, in which the pneumatically operated gauge 144 is connected by an air line 512 to a conventional pressure transmitter 514 which is provided with a high-pressure air supply through a line 515. The pressure transmitter is connected via a pipe 516 to a rolling tube bellows unit which comprises a cylindrical rubber tube 517 attached by means of a flanged fitting 519 to the bottom wall of a bored out portion of the block 518. The outer end of the tube is turned inwardly upon itself and secured to a movable member 524 attached to a member 526 mounted upon vertical leaf springs 530 for horizontal reciprocation. Upon increase or decrease in air pressure effected by the gauging unit 144 the tube 517 rolls on or off the restraining surfaces of the block 518 to move the member 526 which carries a lower air brake unit 504, the member 526 being normally urged to the left by a compression spring 534. The lower pair of opposed air brakes 504 engage opposite sides of a slide member 508 to move it at the proper time in the cycle of operations. A bracket 546 attached to the slide carries the marking pen 510 which co-operates with the graph paper 228, and an upper pair of air brakes 506 engage opposite sides of the slide to hold it in the position to which it is moved by the lower brakes 504. Compressed air is supplied to .the lower air brakes through a line 562 and to the upper brakes through a line 574. The slide plate 508 is initially moved to the right against a stop 548 by a piston and cylinder unit 580 carried in the bearing arm 542 and supplied with compressed air by a pipe 584. When the check-weighing unit 28 is unlocked to perform the check-weighing operation the pressure in the unit 144 is increased and the rolling bellows are elongated to move the member 526 and the brake 504, which is in its open position, to the right a distance proportionate to the weight of the package in excess of the predetermined minimum. During this movement the brake 506 holds the slide 508 stationary. When the member 526 comes to rest the brake 504 engages and the brake 506 disengages the slide 508, the spring beam 28 is again locked, effecting reduced pressure in the unit 144, and the spring 534 moves the member 526 together with the slide 508 to the left until the stop 540 engages the block 518. The brake unit 506 is then engaged to hold the slide 508 in its moved position and the brake 504 disengaged ready for the next cycle of operation. After a predetermined number of cycles the recording paper 228 is rocked upwardly into engagement with the pen 510, and the slide 508 is then returned to its initial position to the right by the piston 580 both brake units being disengaged and the upper unit 506 engaging the slide when it has moved against the stop 548. To automatically effect engagement and disengagement of the brake units in the correct sequence solenoid operated air valves 586, 588, are included in the air lines 562, 574 respectively, and are operated by switches controlled by cams on the main cam shaft of the check-weighing machines, Fig. 17 (not shown). A solenoid operated valve 598 controls the resetting cylinder 582. Specifications 222,166, [Class 94(1)], and 663,229 also are referred to.