US2697315A - Vacuum strip retention - Google Patents

Description

Dec. 21, 1954 F s l N ETAL 2,697,315

VACUUM STRIP RETENTION Filed Nov; 3, 1950 2 Sheets-Sheet 1 4 INVENTORS F/Pfi/YA" A. ST/P/V,

ATTORNEY i p Dec. 21, 1954 F. E. STIRN ETAL 2,697,315

VACUUM STRIP RETENTION Filed Nov. 3, 1950 2 Sheets-Sheet 2 Jaw Mfzlkv- ATTO R N EY United States Patent VACUUM STRIP RETENTION Frank Edwin Stirn, Pearl River, and Arthur Sinclair Taylor, Spring Valley, N. Y., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine Application November 3, 1950, Serial No. 193,946

3 Claims. (Cl. 53--10.5)

This invention relates to improvements in a method and mechanisms for forming and filling capsules from soft elastic strip material such as gelatin, whichcapsules may be filled with any desired material, and relates particularly to a method of retaining the strip on the surface of the die, in such fashion as to avoid slippage and to prevent variations in size of the capsule and to permit the obtaining of straight, evenly-formed capsules.

In the past, it has been found that in standard capsuling machines, in which a gelatin film is held against the surface of a die roll, the vacuum to force the gelatin strip down into the individual cavities on the die roll for the formation of capsules has been applied solely to the area in which it was desired to cause the gelatin film to be pressed downward or held against the die roll. Also, it has been customary to use a certain amount of lubrication to prevent the gelatin strip from adhering to the die roll and to make it easier to handle. As a result of these combined actions, capsules have been produced but all too frequently there has been a previously unexplained variation in the size and also an unexplained irregularity in shape, particularly in the long cylindrical form of capsules with rounded ends referred to in the trade as flat ovals. They frequently have had a heliform or worm-shape; they have come out with various types of configurations like a kidney bean or a jelly bean, rather than a straight, symmetrical, evenlyformed capsule as is desired.

We have found that these irregularities result from the skidding of the gelatin on the surface of the die roll during its formation into the capsules. Surprisingly, we have found that by the use of a vacuum on both the inside and the outside of the capsule forming cavities, it is possible to draw the gelatin film towards the surface of the die roll, both inside and outside of the cutting-out edges and both inside and outside of the capsule-forming cavities, and thereby provide a means whereby the gelatin film, being more evenly retained, does not tend to skid or slide in and out of the capsule-forming cavities, nor otherwise on the roll, and accordingly, it is evenly and symmetrically held in position. The strip is normally thus held during the filling and up until the time of sealing or cut-out. The capsules, when formed, also develop an even, symmetrical and uniform configuration.

We have found that by varying the relative internal and external tensions and the exact moment of application of the various vacuums, it is possible to obtain a variation in the size of the capsules formed with a particular size of die. This is most desirable in the pharmaceutical profession because it is frequently found that the strength of the encapsulated material may vary from batch to batch, or various materials are to be used which give a variation in the size of the capsules. To avoid an unnecessary large inventory of capsuling dies, it is. highly desirable that more than one size may be formed from a single die roll. In the past, a variation in strip thickness has been used, as for example by Weclte'sser 2,323,582. Such a system uses more gelatin, and the variation in wall thickness gives an undesirable lack of uniformity in the product.

We have found it desirable in the formation of capsuling dies to leave or form small grooves or vents between the cavity die insert and the main body of the roll, whereby the vacuum which operates inside the gelatin cavity operates also outside the cavity. 1

For greater flexibility, it is desirable that separate vacuum hold-down connections or bleed passages be used to the inside and the outside of the capsule-forming cavities, whereby it is possible to control the vacuum independently.

For large production runs, where but a single capsule size is desired, and a uniformity of composition of the filling contents is to be expected, it is possible to use but a single manifold system with air leads to both the inside and the outside of the cavity ledge, and thereby attain satisfactory results with a more easily formed capsuling die.

Our method of retaining the strip in position is of particular value if the strip is coated on what is to become the inside of the capsule with an adhesive material such as a silicone resin or gum benzoin, or shellac, etc. If such a coating is used, it is desirable that none of the feeding or forming mechanisms contact the strip after the coating is applied. Our method of strip retention is particularly useful under such circumstances.

Our new type of hold-down dies may be used to position the strip in capsuling machines like those shown in our co-pending application Serial No. 164,426 filed May 26, 1950 for use with a single die roll against the fiat sealing roll.

Our vacuum strip hold-down may be used in machines like those shown by Scherer 1,970,396 to retain the strip in position while the capsule cavities are being formed. Our vacuum strip hold-down may be used also in machines like those shown in Weckesser 2,323,581 and those shown by Cowley 2,387,747. Such machines are doublesided and vacuum strip retention is preferably to be used I on each roll.

Our vacuum strip retention may also be used for submerged filling like that shown by Pittenger 2,219,578 and may be used with either the double roller or the roll and flat die form shown by him.

Other modifications for use with other machines will be obvious to those skilled in the art.

Having thus described certain advantages thereof, certain modifications of our invention are shown in detail by the following drawings.

Figure l is a surface view of a capsule die roll for flat oval capsules.

Figure 2 is a sectional view along line 2-2 of Figure 1 showing the manifold passages.

Figure 3 is a modification of our invention showing round capsule dies.

Figure 4 is a modification of our invention showing a separate vacuum system for the hold-down.

Figure 5 is a sectional view along line 5-5 of Figure 4 showing a manifold system for use with separate holddown ducts, showing the strip with the retention vacuum applied, before the application of the capsule cavityforming vacuum.

In Figure 1 there is shown a cavity die roll 11 having in its surface capsule cavity inserts 12. These inserts may be a press fit in insert slots 13. Each of the capsule cavity inserts has a cutting out rim 14 over which a deformable strip material 15 is placed. Normally a soft gelatin film is preferred for capsule work; various substitutes for gelatin may be used for this strip. Under the capsule cavity inserts, there may be a capsule ejector piston cylinder 16 in which fits a capsule ejector piston 17 to which is attached a capsule ejector plug 18. To the cylinder 16 is connected a manifold 19 which connects the cylinders with a valve seat surface 20 of the cavity die roll. On this surface rests a valve plate 21 in which there is a vacuum chest 22 to which a vacuum connection 23 is attached. This general form of die roll is described in our earlier applications, Serial Nos. 164,426 and 174,748.

A restricted passage, 24 serves as a vacuum bleed during the forming cycle of capsuling operations. This passage should be very small, but in the drawings is accen: tuated so as to be visible. A partial vacuum applied through the vacuum connection to the vacuum chest, in turn through the manifold 19, past the capsule ejector pis' ton and plug and hence to the cavity die underneath the strip material, holds the strip material against the surface of the cutting out rim and pulls this deformable strip material down into the capsule cavity preparatory to its being filled.

In the past the strip material has skidded on the surface off'tlie-caps'ule cavity insert and'has accordingly permitted a variable...amountof..the...strip..material toslideinto the. capsule cavity. Previously, this movement of the film over the die rim has been considered to be an advantage. Note for: example, column. 1,.lines ,20-25 ,of the :patent to;C.oWley 2,387,747. We have found that the. irregularities in this skidding causes irregularities in the capsule. Our, restricted .passage. or vacuum bleed permits the vacuum; to operate outside ofthe capsule ,die. insert and outside ofjth'e cutting out rinrand hold the. gelatin .film towardsthe surface of the cavity die roll as is shown in Figure, 2. It'lis, important that the vacuum bleed be of .Tsuchsiz'eas to not admit enough air to break the vacuum or1overtaxthe capacity. of the passages and yet at the.-san1e.tirne, it is necessary that it be sufiiciently large to .be..eff'ctive.., Asthe. gelatin film feeds towards the surfacetofthe .cavitydie roll, ,it hasthe tendency to lay fiatonithesurfaces .of-Ithe rims and must be pulled down intorcontact with the die roll.-both.inside and outside'of thecavities by the reduction of'pressure under the strip; It is desirablelthat the passages be ofsuch size as .to give a reduced pressure zone over the entire arc oficontact, anfparti'cularly; at ithepoint of actual. fill.,

The exact size and shape of this vacuum bleed passage.

maygvary over; awide "range depending upon its relationship'with' the other elements present, the capacityof'the vacuum pump, etc.

From the above description, to those skilled in the art the-relative proportions required will be obvious. By way ofexample; it has been found that with a flat oval cavity which-is 1" widesand whose end centers are .682" apart that a vacuurn bleed formed by a /8 iameter end millcuttingai slot 0.20" deep into the end ofthe slot and"i003"' below theb'ottom of the insert slot forms a very eifective vacuum bleed. A A3" manifold passage leading'to arvalve platewith'a vacuum chest 0.2" wide and-0.15.' deep-connected to a /s" pipe tap as a vacuum connection is a desirable'arrangement. Multitudinous variationsfrom these particular sizes are possible, as above mentioned.

It is also convenient when formingqthe insert slots-to form--them'slightly longer thanrequired for the capsule cavity insert and then nick'one end at the bottom to provide the vacuum bleed.

Ah independent'hole to the'surface of the cavity die roll from the manifold passage 19 may be used. For this'purpose a"#44 drill'gives a proper size of bleed for the particularsize capsule mentioned above.

Theembodiment'sh'own in Figures 4 and 5 has a separate vacuum bleed leading to a bleed port passage 26 which leads to the valve seat-surface adjacent a separate bleed vacuum chest 27'in the valve plate to which is connected a' separate'bleed vacuum connection 28. In-'Fi'gure'-5the gelatin strip is shown with the holding vacuumapplied; thus'retaining the strip in position, but before'the shell forming vacuum is applied, hence the gelatin strip is not yet pulled into the capsule cavity to formt'the capsule'shell. This modification is of particularradvantage when it is desired to vary the size of the capsule'formedby a particular die roll.

Theoseparatevacuum chest'and passages permit the holdingtvacuum to be'independentlyapplied, prior to, simultaneously with, orrsubsequentto --the.;.capsule shell formingsvacuumrin the cavity die' inserts... With zaisingle. vacuum. .chest, and a single manifoldsystem, the 1 capsule shellj forming-- vacuum;.which .pulls; the gelatin 1 strip into the-:cap'sule :cavity, is 5 simultaneous with. the strip hold down vacuum.

Itais .notrnecessary that aebleedpassagebe adjacent .to each capsule.formingcavitycutting out rim. As shown.

in figure 3-, .the.vacuum..bleedsmay be;p resentadjacent only certainof the roWs:of-;the.cavities.or.may be present;

at .alternat'e;..cavit.ie.s;.in. alternate rows, or, as .desired... It.

iszppssiblezttolobtain .a..pr.oper;.vacuum. by using fewer bleedfipass'a'ges; and; making ,them.. slightly 7 largerwell asifthose joff built-up' construction.

A variation in the bleed vacuum applied through the bleed. vacuum. connection. can..increase or. decreasecthe...

holding action on the strip material outside of the capsule cavity inserts and therefore influences the tension of the gelatin film in the capsule cavity inserts, and this in turn permits a variation in thersizepof the capsules formed. An increase in this bleed vacuum decreases the diameter of the capsule. To thoseskilled in .capsulemaking procedures, this modification which permits a variation in.

to thesurface of a capsule-::dieroll, which comprisesplacing the-strip adjacent the-surface of-the'die-roll' and* reducing the-pressure in" capsule-cavities in th'e'die' roll' surface, therebyformingpockets' inthe strip, and-in dependently and separately controllably' reducing the pressure under theportion ofi'the strip outside ofthecapsule cavities, thereby-retaining thestrip in position;

2; The method of forming; soft elastic capsules from a soft elastic strip which comprises uniformly and con-v tinuously feeding at least one-strip of elastic strip adja cent to a capsule die roll surface which has thereon aplurality of-capsule-forming cavities, eachof which has a cutting out rim, sequentiallyreducing the pressure with in a series ofsaid capsule-formingcavities thereby cans-"- ing the elastic strip material to: form shell's'within the cavities and independently and-.separately controllablyreducing the pressure under'the :portion of the-strip outside of the capsule cavities, thereby holding theelastic. strip down to and adjacent th'e dierrollsurface, thereby: preventing the slipping of.theestripmaterial on the.cutting out rims, placing capsule: contentsserially in the thus formed shells, placing asecondclayer.of'elasticstrip adjacent the first strip and .cuttingoutcand. sealingv capsules.

from the thus filled-shells.

3. A die roll for formingusoft elastic capsules from; an elastic stripwhich. comprises"v a. cylindrical die rolll. I

blank, in the cylindrical periphery-thereof,.a-series of capsule-forming cavities eachconsisting of, a; raised rim insert fittedintothe periphcry of 'said cylindrical roll,. and in av recess undersaid insert at least one ejector plug, said ejector plug-having thereon a piston head, whereby said plug may be, byairpressure, raised to substantially the top of said cavity, apiston cylinder, azmanifolding passage from an end of .saidcylinder to:a valve surfaceof said roll, sufiicient clearancesbetween the piston and the plug that anyyarration-in pressure within said manifold passage is permitted to communicate itself around the plug and the piston into the-.capsuleforming cavity,

and a second 'manifoldingpassage-from awalvesurfacei ofsaid roll to a location on the cylindrical surface of the die 'roll blank which .is outside of the-.capsuleforming.

cavities, whereby pressure between theelasticstrip and the die roll blank. but outside: of .the capsule forming cavities may be independently controlled..-

References Cited ;in;the.-.file of. this patent UNITED STATES? PATENTS" Number Name: Date 1,629,154 De :Ybarrondo c-....- .May 1-7, l927' 1,654,647 Heist F .Jan..3, 1928' 2,152,101. Schcrer Mar. 28,. 1939: 2,219,578; Pittenger. ,Oct. 29, 1940, 2,308,453. Plotchen.. Jan. 12,1943. 5 2,376,805.v Peacockcwpn-unhe.. .May,22, 19.45,. I 2,524,419.? Billner. ..Oct... 3', 1950.

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