US2720353A - Method of uniform powder filling - Google Patents

Description

m. W 19% EWIWN m METHOD OF UNIFORM POWDER FILLING 2 sheets shee't 1 Filed Jan. 29, 1952 bbbwk INVENTORS F/amv/r 1 677 EN ,4/?7w /A 5. 714/4 0/ 5 BY 7% f ATTORNEY Oct. 11, 1955 F. E. STIRN ETAL METHOD OF UNIFORM POWDER FILLING 2 Sheets-Sheet 2 Filed Jan. 29, 1952 llllll I' V I J/VVE/VTORS FHA Mr E. sr/mv, ARTHUR s. TAYLOR,

BY 4mm; M "144M ATTORNEY METHOD OF UNIFORM POWDER FILLING Frank E. Stim, Evans Park, Pearl River, and Arthur S. Taylor, Spring Valley,N. Y., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application January 29, 1952, Serial No. 268,834

1 Claim. Cl. 226-71) This present invention relates to a method of filling more nearly uniform weights of a powder whose apparent density may vary slightly. By compacting the powder into a standard container and varying the vacuum slightly, it is possible to adjust the degree of compaction to compensate for non-homogeneity in a powder.

This application is a continuation-in-part of our copending applications, Serial No. 62,012 filed November 26, 1948, entitled Method and Apparatus for Filling Powder in Capsules, and Serial No. 164,426, filed May 26, 1950, entitled Method and Apparatus for Forming Combination-Filled Capsules.

Another continuation-in-part application of Serial No. 164,426, filed May 26, 1950, as Serial No. 399,130 has since issued as Patent No. 2,697,317, December 21, 1954 entitled Capsule Forming Die Roll. This patent shows details of an entire encapsulation procedure in which may be utilized the present invention.

More particularly, in filling powders by volumetric measurement, as for example disclosed in our Patent 2,540,059, entitled Method of and Apparatus for Measuring and Filling Powders Volumetrically, or in filling powders into capsules as disclosed in our co-pending application, Serial No. 62,012 and our co-pending case, Serial No. 164,426; there are disclosed methods for compacting a uniform powder into charge chambers as a method of uniformly measuring a powder. Unfortunately, in filling of powders into containers or capsules, it is often found that even though a batch of powder is uniformly blended, changes in weather conditions, or humidity, or compaction due to standing, or electrostatic charges and other causes, causes the powder to become non-uniform, so that in the actual filling operation small variations occur due to non-homogeneity in the powder being filled.

We find that by varying the vacuum causing the compaction of the powder into charge chambers, it is possible to slightly vary the charge, and by weighing occasional charges and adjusting the vacuum in accordance with these Weight determinations, it is possible to obtain a greater degree of uniformity than has been previously possible.

It is, of course, very preferable to use a powder of uniform characteristics but the characteristics of most powders to be filled will not remain uniform over prolonged periods. Our new method of varying the vacuum permits adjusting the charge rapidly and readily to maintain a high order of accuracy.

In pharmaceutical work particularly, it is highly desirable that each individual charge be measured as accurately as is possible. The physician in administering to the patient desires to know just exactly how much is being administered. In production, it is necessary that the charge to each container be at least as great as the labelled weight. To be sure that the final containers have at least the labelled weight, it is necessary and customary to use an overage of at least three times the average variation in fill. In other words, if a machine will fill to an average variation of 2% from the mean value, it is necessary to have an overage of at least 6% in the fill to insure that at least 99% of the containers have the labelled weight. It can be seen that a small increase in accuracy will give a disproportionately large saving in that the overage can be reduced and also provide a much more desirable package in that the superior uniformity permits a more accurate administration to a patient.

We find that in operation, many pharmaceutical powders will vary several percent in apparent density. By varying the vacuum used in the apparatus of our prior inventions, above referred to, over limits in the neighborhood of from 5 to 25 inches of mercury, it is possible to compensate for the usual changes in powder density which may be experienced during a prolonged filling run and achieve both a saving in cost of production and superior quality of product.

The exact ratio of the change of the powder charge in a standard charge chamber with a variation in vacuum will vary with the powder to be filled. However, by weighing occasional charges in the filling operation, it is possible to determine the direction and degree of change required. The relative rate of change for a given type of powder remains substantially constant.

A different calibration curve is required for each powder but may be readily prepared in a few minutes time by an operator for the specific charge chamber and the spe cific powder which is being used.

By way of illustration, a curve and figures for a particular powder are given.

Figure 1 shows a plot of the vacuum in inches of mercury against the weight of the charge in milligrams for a particular vitaminaceous powder used for filling soft gelatin capsules.

Figure 2 is a view showing a charge chamber with a forarninous area such as may be used in practicing the present invention. Details of machines embodying such charge chambers are embodied in our earlier applications of which this is a continuationin-part.

Figure 3 is a view of a powder measuring roll having therein a plurality of charge measuring chambers, a powder containing hopper, and part of a cavity die roll.

Figure 4 is a sectional view of the measuring roll along line 44 of Figure 3.

As shown in Figure 1, measurements of the weight of a charge for a particular vitaminaceous powder show the following:

Weight in Vacuum, inches of mercury: milligrams 4 495 A charge decrease of 25 milligrams in the weight of the powder being filled at a vacuum of 10 inches of mercury caused by non-homogeneity of the powder may be compensated by increasing the vacuum to 15 inches of mercury.

Figure 2 shows such a charge chamber 11, containing a powder charge 12. The powder charge may be drawn into the chamber by the variable vacuum acting through the foraminous area 13 through vacuum line 14. As shown in Figures 3 and 4, a machine for using the present invention includes the measuring roll 15, which has therein a series of charge chambers 11. These charge chambers are spaced about the periphery of the measuring roll. Each charge chamber, as shown in Figure 2, may consist of a tapered chamber with rounded corners and conical bottom, 16, a portion of the bottom of which is a foraminous area 13.

The foraminous area 13 should be of such porosity that the application therethrough of a partial vacuum (or sub-atmospheric pressure) will suck powder into the charge chamber compacting the powder therein, and yet be sufiiciently fine in texture that the particular powder being filled will not pack or bind into the interstices of the foraminous material thereby unduly obstructing the flow of gases through the forarninous material. pharmaceutical products, a good grade of fine felt, such as is used for wick oilers in electric motors is eminently satisfactory. As shown in Figure 2, the foraminous area may be formed by a foraminous material 17 fastened firmly into position at the bottom portion of the charge chamber. A short threaded portion 18, with a retaining shoulder 19, will serve to hold the foraminous material firmly in place. The felt may be twisted and screwed thereinto permitting the felt to be readily removed and yet not permitting undue leaks around the edges. Knurled or grooved surfaces may be used with appropriate methods of inserting the felt, or a turned edge may be used to retain the felt. multiple part chambers may be used, wherein the felt is placed under a detachable charge chamber so that only the working portion is exposed, or the foraminous material may consist of sintered metals, sintered glass, fine metallic screens, multiple finely spaced edges or other such material as will suggest itself, depending upon the porosity and type of powder which is to be filled. The suitability of pore size may be easily tested by inserting a test portion of the material placed over a vacuum orifice into the powder which is to be filled and then reversing the flow of gas to check and see that the material does not pack or block passages in the material and at the same time suflicient gas is permitted to flow therethrough to insure proper transfer and packing of the charged material.

The under-portion of the foraminous material opens on to a vacuum line 14, which, as shown in Figures 3' and 4, connects to the manifold passages 20, which in turn lead to the respective faces of the measuring roll. Adjacent to each of the faces of the measuring roll is a stationary valve plate 21. The valve plates have therein a vacuum chest 22 connected to a vacuum through the vacuum connection 23; a discharge pressure chest 24 connected to a suitable source of gas pressure by pressure connection 25, and a cleaning pressure chest 26 in turn connected to a cleaning pressure connection 2'2. The valve plates may be held against the sides of the measuring roll by springs 28, which in turn bear against the frame or other portion of the mechanism.

A powder hopper 29 is positioned over the measuring roll 15. A powder 30 is fed through the hopper into the charge chambers 11. The powder is fed down through the hopper, and by the vacuum acting through the vacuum connection 23, and vacuum chest 22, manifold passage 20', vacuum line 14, and the foraminous area 13, is compacted into the charge chamber 11, to a desired density. As each individual charge chamber passes under the front edge of the hopper, the front edge serves as a doctor 31, to cut ofi the powder charge at the level of the surface of the For many.

If desired, other retaining means such as measuring roll. The powder charge is retained in the chamber by the vacuum until it reaches a point in juxtaposition to powder receiving containers which may be gelatin strip lined cavities 32 in the cavity die roll 33 at which point the manifold passage passes from its connection to the vacuum chest 22 to the discharge pressure chest 24 through which the gas pressure acting through the pressure connection 25 builds up a gas pressure behind the individual charge and uniformly and effectively forces it out of the charge chamber into a container or capsule forming cavity 32.

A series of running checks on the weight being filled permits the operator to vary the vacuum so as to obtain uniform charges in spite of changes in the apparent density of the powder. The range over which variations in weight may be compensated by the change in vacuum is normally sufficiently large to compensate for any changes in a batch of powder that will be encountered in pharmaceutical practice.

It is convenient to. have a gauge on the vacuum line. Any standard type of vacuum regulating device 34 may be used to control the vacuum used in compacting the powder. with or without a bleed furnishes an economical method of such control. An adjustable automatic vacuum valve of any of the known types may be used, one such device being described in U. S. Patent 2,482,167 to Gilmont, entitled Manostat.

The size of the charge chamber may vary over a wide range depending upon the quantity of powder which is to be filled. Either charge chambers of variable size, such as are disclosed in our U. S. Patent 2,540,059, or nonadjustable charge chambers as disclosed in application Serial No. 62,012 and application Serial No. 164,426 may be used in the practicing of our present invention.

Having described our invention, we claim:

The method of volumetrically measuring substantially uniform chargesof a slightly non-uniform powder which comprises in succession passing a series of charge'chambers under a powder-containing hopper, withdrawing at least a part of the gas present in the charge chambers through foraminous material forming a part of the chamber wall by operation of an adjustable vacuum, successively moving the charge chambers past a doctor means and ejecting the powder by means of gas pressure into successive containers, determining the weight of at least some of the powder charges and adjusting the vacuum to such a negative pressure that the degree of compaction of powder into the charge chamber is adjusted to compensate for non-uniformity of the powder.

References Cited in the file of this patent UNITED STATES PATENTS 1,052,653 Crowley Feb. 11, 1913 2,282,477 Joa May 12, 1942 2,488,395 Goldberg Nov. 15, 1949 2,540,059 Stirn et a1. Jan. 30, 1951 A needle valve or throttling arrangement either

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