Pressure Type Bag Filling Machine

Abstract

A pressure type bag filling machine in which a pressure hopper has a downwardly directed air tube supplied with air under pressure to effect the flow of granular material from the hopper through a discharge nozzle and into a valve bag until the bag is filled with a predetermined weight of product. The air tube extends through an inclined orifice plate which extends across the hopper and allows the product to accumulate in a small pile below the orifice plate over the discharge nozzle so that the pressure air can more easily initiate motion of the product and maintain substantially uniform flow of product through the nozzle, resulting in more rapid operation and more accurate weighing.

Description

Valve bag filling machines of the pressure type generally comprise a pressurized hopper containing a supply of granular product and a tube supplying air under pressure to promote the flow of product from the hopper into a valve bag supported on a scale beam until a predetermined weight of product is reached. It is necessary to employ a hopper of a size which will contain sufficient product for any size bag that is conventionally used, such bags generally ranging from 25-pound to 100-pound sizes. When the hopper is completely filled with certain types of material, generally material consisting of larger size particles or particles of irregular shape with rough surfaces, the pressure air from the air tube frequently cannot initiate movement of the particles from the bottom of the column of product in the hopper, and the flow rate from the hopper into the bag is usually quite irregular, which results in inaccurate weighing of the material in the bag.

The present invention provides a bag filling machine of the type described capable of handling granular products of any particle size or shape with greatly increased speed of operation and greatly improved weighing accuracy even when the height of the product in the hopper is at its maximum. The invention contemplates the provision of an inclined orifice plate extending across the hopper and through which the air tube extends, the orifice plate being designed to allow the product to accumulate in a small pile at one side of the bottom of the hopper over the discharge nozzle so that the pressure air can easily initiate motion of the product through the discharge nozzle from this smaller pile of material regardless of the total height of material in the hopper. A further advantage of the provision of the orifice plate is that the pile of product under the orifice plate is continually replenished by a stream of material falling past the plate, and the falling stream of material is easily driven through the discharge nozzle by the air. Since the air reacts against a relatively small pile of product of limited height, the total height of material in the hopper will not affect performance of the machine, and the machine can accommodate the full range of bag weights desired while maintaining substantially uniform flow rates which results in weighing accuracy.

In the drawings:

FIG. 1 is an elevational view, partly in section, of a bag filling machine embodying the present invention; and

FIG. 2 is an elevational view of the orifice plate used in the machine.

The machine comprises a support frame 10 having legs 12 and 14 and a hopper 16 supported on the frame 10. The hopper 16 is adapted to contain a supply of granular material, and the size of the hopper is such as to contain an amount of material at least sufficient to fill the largest size bag that is conventionally filled by machines of this type. The hopper 16 is open at its upper end and is adapted to be supplied with material from a supply bin (not shown). A charging valve 18 is disposed at the upper end of the hopper 16 and is movable by an air cylinder (not shown) or by other means between the closed position shown in FIG. 1 and the open position shown in dotted lines.

The hopper 16 includes a lower portion 20 having a discharge nozzle 22 through which the product is conveyed to a filling tube 24 which is adapted to extend into a valve bag (not shown) to fill the bag with the material contained in the hopper.

A scale beam 26 is movably mounted on a frame member 28 and carries a hanger 30 which at its lower end is pivotally connected to one of the legs 12 of the frame 10 by a link 32. The hanger 30 carries a bag support or plateform 34 on which a bag to be filled is supported with the filling tube 24 extending through the valve opening in the bag.

An air tube 36 enters the side wall of the hopper and extends downwardly along the axis of the hopper. The air tube 36 is supplied with air under pressure by a blower (not shown) through a valve 38. Air may also be supplied through a branch line 40 containing a valve 42 through the bottom wall of the hopper 16 which is closed by a porous pad 44.

A section 46 of the filling tube 24 may consist of a flexible tube which is adapted to be pinched or closed off by a valve 47 operated by an air cylinder 48 or in any other suitable manner. The movable scale beam 26 is adapted to operate a control 50 which controls the cycle of operation of the machine.

When the machine is off, the charging valve 18 is open, the filling tube valve 47 is closed, and the air control valve 38 is closed. The granular product fills the hopper 16 to the required level. The bag is then placed on the bag support 34 and the controls 50 are energized to initiate a cycle of operation, at which time the charging valve 18 closes and valves 38 and 47 are opened. Air under pressure, for example at 10 pounds per square inch, flows through the air tube 36 and effects the flow of the material from the hopper through the filling tube and into the bag.

An orifice plate 52 is disposed within the hopper 16 and may be supported by the air tube 36 or in any other suitable manner. The orifice plate 52 is inclined, as shown in FIG. 1, and the air tube 36 extends downwardly through a central opening 54 in the plate 52. At its lower end the plate 52 is provided with a cut-out portion 56 which allows the material in the hopper above the plate 52 to fall to the bottom of the hopper along one side thereof and to accumulate in a pile over the discharge nozzle 22. The pressurized air from the tube 36 thus reacts against the relatively small pile of material below the plate 52 and can easily initiate flow of the material through the discharge nozzle 22 and through the filling tube 24 into the bag. As the material flows through the discharge nozzle 22, the pile of material below the orifice plate 52 is continually replenished by a falling stream of material which is easily deflected by the air from tube 36 to the nozzle 22 and through the filling tube 24. It will be seen that the provision of the orifice plate 52 prevents the pressure air from having to move the particles against the resistance offered by the head height of the material in the hopper 16 as in conventional machines. The present machine therefore can be used for filling of the largest size bags even though the product may consist of relatively large particles of rough or irregular shape while maintaining very uniform flow rates, which leads to greatly increased weighing accuracy.

As soon as the bag is filled with the proper weight of material, the scale beam 26 tips, thus tripping the main control 50 to stop the cycle of operation, whereupon the air control valve 38 is closed, the filling tube section 46 is closed off, and the charging valve 18 is opened to permit refilling of the hopper 16.

The orifice plate 52 may be provided with a series of small openings 58 on the side thereof opposite the cut-out portion 56. The air tube 36 may also be provided with a number of small openings 60 above the orifice plate 52. Either the plate 52 or the air tube 36, or both, may be provided with openings 58 or 60, respectively, to balance the air pressure on opposite sides of the plate 52 so that the flow of material past the plate 52 is unaffected by air pressure and falls by gravity alone. It is contemplated that the orifice plate 52 may be adjustably mounted on the air tube 36 or within the hopper 16 so that the height of the orifice plate may be adjusted to provide the optimum results according to the type of material being handled.

Claims

What I claim as my invention is:

1. A pressure type bag filling machine for filling a valve type bag with a required weight of granular product, comprising a pressure hopper having a discharge nozzle at its lower end, a filling tube extending from said nozzle, means for supporting and weighing a bag with said filling tube extending into said bag, an air tube in said hopper, means for supplying air under pressure through said tube to promote the flow of product from said hopper through said nozzle and filling tube into said bag, and an orifice plate in said hopper above said discharge nozzle and adapted to support a column of product in said hopper, said orifice plate having an opening therein substantially directly above said discharge nozzle to allow the product to fall freely through said opening to accumulate in a pile over said discharge nozzle, said air tube discharging air under pressure into said hopper below said plate to cause the flow of product from said pile through said nozzle and filling tube, said orifice plate being provided with a series of apertures therein to equalize the air pressure in said hopper on opposite sides of said plate.