Patent GB-1387411-A (GB)
Title: Weighing machines
IPC: B65B1/32
Filed: 1971-02-25
Abstract: 1387411 Weighing machines IMPERIAL CHEMICAL INDUSTRIES Ltd 17 Feb 1972 [25 Feb 1971 (3)] 5411/71 5412/71 and 5413/71 Heading G1W A weighing machine for delivering predetermined quantities of powder to racks comprises a fluidizer 1 for the powder, a valve for controlling the flow of powder, a two compartment weigh bucket oscillatable between two positions such that one compartment is in the charge position while the other is in the discharge position, and an outlet shoot. The fluidizer (Fig.2) comprises a cylinder 1 having flexible walls of polyurethane coated nylon fabric.. Air is introduced into cylinder 1 and into the discharge tube 3 respectively by a porous cone 2 and a porous probe 8 to fluidize the powder. Powder enters the cylinder 1 from a mass flow hopper 11, and the head of the fluidized powder is maintained constant by a cone 12 connected by a vent pipe 13 to the space above the powder in the hopper, the position of the cone 12 being adjustable. The flow central valve (Figs.3 and 7) comprises a resilient flexible tube 21 through which the powder flows and pairs of pinch bars 22 and 27 which are actuated by pneumatic rams to pinch the tube. The bars 22 pinch only part of the tube to slow the flow rate, and the bars 27 pinch the whole tube to stop the flow. Springs 31 cause the bars 27 to pinch the tube in the event of a power failure. The weigh bucket is mounted on struts 46 by trunnions, and may be moved between its two positions by a pneumatic ram 49. The struts 46 depend from a horizontal frame pivoted on a weigh beam, the axis of the pivoting of the frame being parallel to the beam pivot axis but perpendicular to the axis of rotation of the weigh bucket. The pivots may be knife edge or flexure pivots. Movement of the weigh beam is detected by proximity switches, and the beam is arrested during the initial loading of the bucket. The weigh beam and the flow control valve are both housed in housing 33, and a flexible casing 51, Fig.10 (not shown) of polyurethane coated nylon fabric surrounds the weigh bucket. Suction air knives are provided to return any powder which misses the bucket to the supply hopper. Two forms of weigh bucket and associated outlet shoot are described. In the first form for use with normal racks, the glass fibre reinforced polyester weigh bucket Fig.9 (not shown) consists of two compartments diametrically opposite each other and is oscillated through 180 degrees by ram 49. The glass fibre reinforced polyester shoots (Fig. 12) has a circular upper end tapering to a lenticular outlet, and is provided with venting channels 63. The shoot is suspended from a fixed frame 72 by means of a harness 71 and resilient suspension means 73. A pair of clamping jaws for the racks is provided, each jaw comprising a pair of members pivoted on brackets 75 of the harness and carrying a webbing strap 83 (Fig.1). Pneumatic cylinders 89 are provided to pull the jaws towards each other to clamp the racks against a rubber sleeve 88. Two out of balance electric motors 91 are secured to the brackets 75 to jig the rack being filled. The two motors may rotate in opposite directions. Deflector plates may be provided above the outlets of the venting channels 63, Fig.15 (not shown), and a discharged compartment of the bucket may be scoured by four moist air jets Figs. 15 and 16 (not shown) provided on the shoot. In the second form (Fig.17) for use with valve racks, the mouths of the compartments of the weighing bucket are less than 180 degrees apart, and are arranged to discharge' into individual outlet shoots, the bucket oscillating through an angle smaller than 180 degrees. Each outlet shoot consists of an upper part (Fig.19) and a lower part (Fig.21). The upper parts are constituted by a hopper split into two by a weir 184 and 185. A slot 188 at the top of the weir is supplied with compressed air or suction to prevent powder crossing the weir. Each lower part comprises a porous fluidizing pad 213 and a rotated impeller 215 to ease the flow of the powder (Fig.21). A vent pipe 216 is connected to a vent pipe (Fig.20, not shown) venting into the upper part of the shoot, a deflector plate being provided above the opening of the vent pipe. Each rack is clamped to a lower part by means of a pneumatically operated clamp pad 222, (Fig.22) and is supported on a supporting cradle 223 vibrated during filling of the rack by an out of balance motor 229. The cradle 223 may be rotated between a filling and a discharge position by a pneumatic ram 228.