US2984267A - Device for continuous feeding of nonfree flowing powdery materials - Google Patents

Description

May 16, 1961 G. A. GROSS 2, 67

DEVICE FOR CONTINUOUS FEEDING OF NON-FREE FLOWING POWDERY MATERIALS Filed Feb. 6, 1959 2 Sheets-Sheet 1 II YIIIIIJVIIIIIIIIIIII,

INVENTOR. Gusmv Aoou= 6205s 111W, ma; mam m A TTORNEVS May 16, 1961 G. A. GROSS DEVICE FOR CONTINUOUS FEEDING OF NON-FREE FLOWING POWDERY MATERIALS 2 Sheets-Sheet 2 Filed Feb. 6, 1959 INVENY OR. oou Gnoss GusrAv A BY g M zm diMia ATTOQNEYS Patented May 16, 1961 hire DEVICE FGR CONTINUOUS FEEDING OF NON- FREE FLOWING POWDERY MATERIALS Gustav Adolf Gross, Basel, Switzerland, assignor to Cilia Limited, Basel, Switzerland, a Swiss firm Filed Feb. 6, 1959, Ser. No. 791,660

9 Claims. (Cl. 141-71) This invention relates to a hopper apparatus and feed shoe design for the feeding of light density, non-free flowing, powder-like materials to the dies of tablet presses.

In the manufacture of tablets today of the so-called compressed type where powder is compressed into tablet form such as, for example, aspirin tables, the problem of output capacity has become critical and it has become necessary to increase the speed of operation of rotary presses materially to obtain the output desired. With this increase in speed, one of the problems to be met has been the feeding of the powder-like material, which is introduced into the dies for compression. The material is not free flowing and tends to accumulate and arch and otherwise block flow toward the dies, thus creating air pockets preventing proper continuous operation of the machines.

The object of the present invention is to provide a mechanism which insures continuous free flow of these light density materials. This has been accomplished by a series of moving devices directly in the path of the powder so designed and constructed that the powder will be moved on its way in such a manner that the flow is even and uninterrupted to any die pockets that are being fed.

It is an object to provide a device which assures positive die fill at high speeds and eliminates tablet capping and lamination due to air entrapment. Hard tablets of uniform density are consistently produced. In many cases material of the type to be handled has been preslugged and granulated to insure free flow. With the present device this intermediate process can be eliminated for most materials. The improved device also provides superior results on granulated materials.

It is also an object to provide a machine which produces tablets of consistent weight by introducing the same quantity of fill into each die. A gentle downward pressure of material into the die is achieved which fills the dies with uniformity and wherein balance is achieved between in-fiowing and out-flowing material.

Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claims.

Drawings accompanying the disclosure and the various views thereof may be briefly described as:

Figure 1, a perspective elevation of a tablet forming machine showing the outside contours of the hopper.

Figure 2, sectional view on line 22 of Figure 1.

Figure 3, a horizontal sectional view on line 3--3 of Figure 2.

Figure 4, a partial section on line 44 of Figure 3.

Figure 5, a sectional view showing a double hopper unit on a rotary press.

Figure 6, a horizontal section on line 66 of Figure 5.

Referring to the drawings:

In Figure 1 a rotary compression machine is shown having a hopper 20 on a suitable base 22, the hopper leading to a feed shoe 24 shown in greater detail in Figure 2. The hopper has an entrance tube 26 shown in Figure 1 and gradually ensmalls from the top toward the throat portion 28. A suitable supporting housing is provided on the machine as shown by the bracket 30. The feed shoe 24 has a circular chamber 32 with an opening 34 connected to the throat 28 of the hopper 20. To the right of the feed shoe 24, as viewed in Figure 2, is a toe portion 36 which overlies a rotating die pocket ring 38 on the machine. This die ring is of standard construction; and suitable die punches 40 are provided to rotate with the ring and to be moved into the die pockets after they are loaded.

Within the circular chamber 32 of the shoe 24 is a star rotor 42 having radial spokes 44 extending outwardly from the center. Each of these spokes is provided with spaced pins which project to each side of the spoke, the pins projecting downwardly to terminate at a plane which is slightly spaced upwardly from the bottom 46 of the shoe 24 and the top surface of the die ring 38. The upper portions of the pins above the rotor vary in height, the outer pins 56 being of a height to pass underneath the top of the toe portion 36 and the inner pins 52 being of a height to extend upwardly into the shoe chamber around a drive shaft 54 which supports the rotor and causes its rotation through a gear 56 driven from a. gear 58 on a speed reducer shaft 60 driven by a motor 62. The pins on the spokes are staggered in the alternate spokes so that four spokes 90 apart have identically spaced pins and the other four spokes, ofiset 45 from the first, have pins spaced alike but falling about one half the pin spacing radially offset from the first group.

The drive gear 58 also operates a gear 64 which drives the shaft 66 on the bottom of which is a U-shaped rotating member 68 located in the hopper above the throat 28.

Referring to Figure 3, it will be seen that the shoe chamber 32 has a tangential extension housing 70 extending along the contour of the die ring 38. The housing of the shoe chamber is extended at 72 to provide a body portion for supporting two shafts 74 lying substantially radial to the die ring and which have meshing gears 76 at one end driven by a third gear 78 from a speed reducer shaft 80 operated by a reversable motor 82 mounted on an extension of the bottom plate 46. At the other end of the shafts 74 are rotating extensions 84, each of which has cross pins 86 which are spaced to pass each other as they rotate in paths which are in proximity to the walls of the tangential chamber.

The object of the feeding device is to maintain a constant supply of powdered material in the die pockets 90 in the die pocket ring 38. The powdery material is fed through the hopper 20 and moved downwardly through the stirring action of the U-shaped member 68 where the star rotor 42 with its spokes and staggered pins carries the material into the toe portion of the shoe. It is preferred that the direction of motion of the skeleton star wheel be opposite to that of the die ring at the overlap area. Thus if they both operate in a counter clockwise direction, this relative motion will obtain. The pins 86 on rods 34 are moving downward on one side toward the die ring and this action together with the action of the star rotor contributes to a mold packing action of the powder which causes introduction into the die pockets with a slight pressure which insures an even density and eliminates air pockets. The pressure is balanced by constant removal of material from the shoe and the simultaneous action of the rotors prevents packing to a degree of stagnation.

With the embodiment shown in Figures 1 to 4, I have shown that the preferred speeds of operation of the various components are about 60 to rpm. on the rotor 68 and the rotor 42 and about 112 rpm. on the pin shafts 84, the motor 82 having a reversing switch. The speeds are variable to a degree with the speed of operation of the die ring. The direction of the shafts 84 may vary with the material.

In Figures and 6, I have shown a modified version of the device which may be adapted for use with a compression coater needing a hopper on each side of the rotor for the deposit of the base charge and the cover charge of the tablet. As shown in Figure 5, the hoppers 1'00 and 102 are positioned with the throat portions 104 directly above the opening 106 of feed shoes 108. The feed shoes are circular in shape having the relatively high receiving chamber 110 and the lower toe portion 112. A flange plate 114 serves as the bottom of the main portion of the shoe feeder and the toe portion is positioned directly over the top surface of the die ring 116 on each side of the machine, the die pockets 118 being disposed in spaced relation in the ring. Within the shoe feeders are star shaped rotors 120 having radial fingers 112, each provided with a plurality of vertical pins 124, all of which extend downwardly to a point close to the bottom of the shoe feeder, the center pins 126 extending upwardly toward the top of the shoe feeder as dictated by the walls thereof. The rotors are each mounted on shafts 130 which are mounted on a plate 132 above the die ring and punch assembly. On the plate 132 is a motor 134 with a variable speed drive to a speed reducer 136, having an output shaft 138 connected by a chain 140 to the right-hand shaft of Figure 5 and by chain 142 to the left-hand shaft 130. The speed of the motor can be varied by the hand wheel The toe portion of the feed shoe in this case overlies the die pockets 118 and carries the material directly over the die ring 116 and over the pockets.

What is claimed is as follows:

1. A device to facilitate the continuous feeding of non-free flowing powdery materials to die pockets of a tablet forming machine which comprises a feed hopper having a wide mouth and a gradually ensmalling crosssection to a throat area, a feed shoe chamber having a circular body and a raised chamber connected to the throat of the hopper comprising a horizontal toe portion with a closed top, bottom, and sides extending in a direction away from the hopper entrance, a horizontal, continuously rotating die ring having a plurality of circumferentially spaced die pockets moving successively below said horizontal toe portion forming the bottom of that portion of the feed shoe chamber, a star rotor in said feed shoe chamber having a plurality of radial spokes extending to a point in proximity to the outer walls of said chamber, and a plurality of transverse spaced pins on each of said spokes having the ends on one side of said spokes terminating in a plan parallel to and closely spaced to the bottom of said chamber and to said die ring, and means to rotate said rotor in said chamber to fill said die pockets with the material from said chamber.

2. A device as defined in claim 1 in which the feed shoe chamber is extended tangentially to overlie the die ring, and rotating parallel rods are mounted in a body portion of said feed shoe chamber to rotate in opposite directions in said extension portion, each of said rods having interspaced cross pins with ends revolving in a path passing near the other of said rods, and means on said feed shoe chamber for rotating said parallel rods simultaneously with the rotation of said rotor.

3. A device as defined in claim 1 in which the feed shoe chamber is extended tangentially and reduced in height in a portion overlying the die ring, the pins on said spokes being dimensioned to clear the walls of said portion, and one or more rotating rods in said extended portion mounted horizontally over the die table and having cross pins revolving in the confined area of said extended portion.

4. A device for facilitating the continuous feeding of non-free flowing powdery materials through connected chambers to a defined area over a horizontal, continuously rotating die ring having a plurality of circumferentially spaced die pockets which comprises a hopper, a circular chamber positioned below said hopper, said hopper opening into a portion of said circular chamber outside the center thereof and on the side of said chamber opposite to the opening of a horizontal tangential chamber, and rotating means in each of said chambers to move material into said die pockets, said means moving in a path across the intended flow of material through said chambers, said means in said circular chamber comprising a star wheel having spaced spokes radial of said chamber spaced from the walls thereof, and having cross pins parallel to the axis of said wheel extending into proximity to the walls of said circular chamber and to the surface of said die ring.

5. A device as defined in claim 4 in which the rotating means in said tangential chamber comprises parallel members extending across said chamber in a direction substantially radial to said rotating die ring and directly above the successively moving pockets of said ring, said members having interspaced pins revolving to compact the material into the moving die pockets.

6. A device as defined in claim 4 in which the cross pins on alternate spokes of said star wheel are radially staggered relative to pins on adjacent spokes to prevent stagnant areas of material between the circular paths of said pins.

7. A device for facilitating the continuous feeding of a non-free flowing powdery material from a vertical feed hopper, to successive, circumferentially-spaced pockets in the flat horizontal top surface of a continuously rotating die ring, which comprises a horizontal flow chamber having a portion underlying the discharge end of said hopper and a portion overlying successively moving pockets of said rotating die ring and having enclosed side walls and top, and a plurality of spaced skeletal means moving in the enclosed area of said flow chamber to carry material from said hopper to said die ring through said flow chamber, said means creating a gentle pressure on said material to fill said die pockets.

8. A device as defined in claim 7 in which the last means comprises a rotor in said flow chamber having radial spokes and pins on said spokes extending vertically substantially the height of said chamber, said pins being spaced radially to sweep the entire chamber circumferentially.

9. A device as defined in claim 7 in which one of said moving means is housed in said flow chamber overlying the die ring, and comprises a rotating horizontal shaft extending through said chamber having transverse pins to sweep material into the pockets of said die ring.

References Cited in the file of this patent UNITED STATES PATENTS

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