Patent GB-870520-A (GB)
Title: Gravity-operated device for weighing granular or like material in batches
IPC: B65B1/32
Filed: 1958-09-01
Abstract: 870,520. Automatic feed weighers. THOMPSON (AUSTRALIA) PTY Ltd., JOHN. Sept. 1, 1958 [Sept. 3, 1957; Jan. 13, 1958], No. 27963/58. Class 143 An automatic feed weigher for granular or powdery materials comprises a weigh bucket 24 tiltable between a receiving position below a feed hopper 10, Fig. 11, and a discharge position, Fig. 12, under the weight of material therein and having a balance weight 50 for gravity return to the feed position, the bucket being suspended from a main weigh beam 25 which is associated with an auxiliary weight-controlled system 51, 52, 53, which applies a force to the beam 25 to increase its speed of tilting during a first phase of the weighing, the force being removed in a subsequent phase of the weighing during which the rate of feed to the bucket is automatically reduced and eventually cut off when the beam 25 reaches a predetermined tilt, there being means 65-70 allowing the bucket to tilt to discharge position when such point of balance is reached, and means 21, 22, 23 controlled by the bucket to restore the feed when the bucket returns to its feed position. As shown the bucket 24 is of irregular shape with a feed aperture 45 in its normally upper surface aligned with the outlet chamber 11 of the hopper 10, and a discharge opening 46 at one side extending to the bucket base 47 and normally closed by a hinged flap 48 which swings open when the bucket is tilted to discharge position. The hopper outlet chamber 11 has a pair of nesting flaps 18, 19 hinged to its sides by arms 16, 17 respectively, the inner flap 19 having an aperture 20 and serving to reduce the flow from the hopper, and the outer flap 18 being a closure flap. One arm 17 of the inner flap 19 has a pin 21 extending laterally through a recess in the adjacent arm 16 of flap 18 to cooperate with an arm 23 on the bucket 24 operative thereby to open the flaps as the bucket swings into the feed position, Fig. 10, and to release the flow reducing flap 19 when the bucket sinks a predetermined distance under initial loading, Fig. 15, the closure flap 18 being held open by an additional latch mechanism releasable only on full loading of the bucket. The bucket 24 is suspended from and between corresponding ends 32 of a pair of centrally pivoted main weigh beams 25 by means of hangers 26 which support knife edges 27 projecting one from each side of the bucket. The ends 40 of the weigh beams 25 pivotally support a cradle 43 receiving replaceable weights 44 against which the loaded bucket is balanced. At least one of the beams 25 has an auxiliary beam 53 pivoted thereon on a pin 54 vertically aligned with the main beam pivot 37, the auxiliary beam having a long arm supporting a small slidable weight 52 and a larger weight 51 at its end, and a short arm supporting a weight 57 at its end which serves merely to balance the long arm. The weight 51, Fig. 11, is vertically slidable in a guide 58 and rests freely on the arm end which is vertically movable in a slot in the weight 51 and the guide 58, the guide having a platform 62 which serves to support the weight 51 after a predetermined lowering of the beam arm whereupon the arm is relieved of the weight. The short arm of the beam has a bearing 64 to engage a knife edge 63 on the main beam 25 so that the weights 51 and 52 apply a movement to the beam 25 tending to augment the bucket load. In operation with the empty bucket in the feed position holding the flaps 18, 19 open, material falls into the bucket from the hopper 10 causing it eventually to swing the beams 25 about the pivots 37 with consequential lowering of the bucket until the auxiliary beam 53 is relieved of the weight 51. Thereupon only the weight 52 on the auxiliary beam is effective to augment the movement of the bucket and movement of the beams 25 is retarded. At about the same time the arm 23 of the lowered bucket disengages from the pin 21 and allows the flow reducing flap 19 to swing over the hopper outlet and reduce the feed rate, the closure flap being held by the additional latch mechanism. This comprises a pin 73 on the flap arm 16 which is held captive in a recess 79 of a freely hanging lever 75 the lower end 77 of which provides an arcuate track for the pin 73. The lever 75 is biased towards the pin 73 by a weight 78 and is additionally held in engagement therewith by one end 81 of a bell-crank lever 82 the other end of which is movable by a pin 85 on a scale pointer when the latter reaches the point of balance of the beam 25 from which it depends. When this point is reached the bell-crank lever is tripped from engagement with the lever 75 and the weight of the flap 18 disengages the pin 73 from the recess 79 to permit closing of the flap. The arcuate end 77 of the lever 75 ensures repositioning of the pin 73 in its recess when the flaps are subsequently swung open on return of the bucket to feed position. Simultaneously with closing of the flap 18, a latch member 67, carried by a hanger 26 to engage a knife edge 70 on the bucket to hold it against tilting, is lifted clear of the knife edge by a fixed detent 65 to permit tilting of the bucket to discharge position. When the bucket has emptied its contents, the weight 50 therein swings it back to feed position at the same time as the beams 25 swing back, thereby re-engaging the weight 51 on the auxiliary beam and opening the flaps 18, 19 to commence another weighing cycle. To ensure that the hangers 26 remain vertical during the weighing, they are connected at their lower ends by links 89 to points on the main frame 39 vertically aligned with the beam pivots 37, each link having a pair of vertically aligned knife edges at each end to engage corresponding bearing surfaces on the hanger 26 or main frame 39. A counter 113 having a lever 114 actuated by a pin 115 on the bucket 24 provides a record of the number of weighings, and a latch 88 pivoted on the main frame may be used to engage the knife edge 70 and lock the bucket in the discharge position. For adjustment purposes the auxiliary beam 53 may be relieved from its main beam pivot 54 and rested on a pin 111 on the main frame 39 by means of rod 106 vertically adjustable in the guide 58 to lift the long arm of the auxiliary beam. Adjustment of the apparatus may be effected by movement of the weight 52 along the auxiliary beam.