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United States Patent 3,664,495
Graham ,   et al. May 23, 1972



An economical locking capsule is provided having telescopically joinable cap and body parts adapted to be joined together in a prelocking position and optionally in a more fully joined position. The capsule, for packaging of medicaments and the like, is produced by the dip-molding technic on conventional automatic machinery and can be printed, filled, etc., using standard equipment.

Inventors: Graham; Richard J. (Grosse Pointe, MI), Mottin; Ralph E. (Grosse Pointe Park, MI), Noren; Oscar B. (Grosse Pointe Farms, MI)
Assignee: Parke Davis & Company (Detroit, MI)
Appl. No.: 05/100,303
Filed: December 21, 1970

Current U.S. Class: 220/8 ; 220/DIG.34
Current International Class: A61J 3/07 (20060101); A61b 019/02 ()
Field of Search: 220/6R,42A 206/63.2R,56AA

References Cited

U.S. Patent Documents
691687 January 1902 Wilson
3258115 June 1966 Kath
3285408 November 1966 Carnaghi et al.
3399803 September 1968 Oglevee et al.
3584759 June 1971 Lorincz
Primary Examiner: Knowles; Allen N.


We claim:

1. A hard shell pharmaceutical locking capsule having cylindrical, telescopically joinable, coaxial cap and body parts each having a side wall, an open end and a closed end, the cap and body being adapted to be mutually joined in a first pre-locking position and optionally in another more completely joined position,

the cap and body side walls each having an inner surface and an outer surface and the cap side wall also having a pair of diametrically opposed integral indents extending radially inwardly from the sides of the wall,

the profile of each indent including two indent slopes separated at a distance of about 0.030 to 0.040 inch by an indent flat, the slopes joining the flat at an angle of about 8.degree.-12.degree.,

the diametral spacing of the indents being less than the outside diameter of the open end of the body by an approximate constriction distance differing according to capsule size, as set forth below, such that the body can enter into the cap to the pre-locking position and yet the cap and body at this position mutually engage in an elastic frictional fit,

the center line of the indents being located axially from the inner surface of the closed end of the cap at a distance permitting optimum wall flexibility and pre-locking strength, the location differing according to capsule size approximately as follows:


This invention relates to hard shell locking capsules of the type having a cap part and a body part adapted to be telescopically joined together to provide a container for substances such as pharmaceutical preparations intended for oral administration. More particularly, the invention relates to capsules of the kind described which can be manufactured, printed, filled and joined on modern high-production machinery and can be locked in the closed position, as desired, in a partial lock or pre-lock, and optionally in a more completely joined lock.

The conventional locking pharmaceutical capsules consist of a tubular or cylindrical cap part closed at one end with the opposite end open to telescopically receive a closely fitting body part of like conformation having contacting inner surfaces which provide a locking action to prevent separation of the cap and body parts. In general, the known types of locking capsules are constructed to provide both a temporary lock (sometimes referred to as a semi-lock or pre-lock) when partly joined and a more secure lock when more fully joined. One such type of capsule, for example, is known from British Pat. specification No. 1,108,629 and Italian Pat. No. 789,324. The prior art locking capsules have in general been satisfactory but some types have occasionally malfunctioned or failed from time to time in finishing, distribution, etc. In particular, the cap and body parts have sometimes tended to "pop apart" when joined on the production line; also, empty capsules in the pre-lock position prior to filling or subsequently, as in shipment to the customer, have sometimes pulled apart especially in a case where the cap has been insufficiently advanced onto the body. Also, capsules in the fully locked position have sometimes been known to pull apart and become separated due to severe vibration. Capsules of the friction lock type, that is capsules locked with the capsule walls under distortion, have been known to crack and fail, especially under excessive drying conditions as when filled with hygroscopic powders or other desiccating substances. The failures are not uncommon, especially during the printing operation using equipment which calls for precise length control of the pre-lock capsule. Separation failures are also likely to occur during the filling steps, particularly where, as in standard machinery, the capsules are delivered from the supply hopper by oscillatory movements tending to cause the capsule parts to separate. A separated part undesirably can cause the magazine tube to be blocked, or a free cap, for instance, can seat on a joined capsule body and form a "double-cap" which may jam the rectifying mechanism. Also, the loose part can crowd the filling ring chamber so that the intended body part does not seat properly in the filling ring. As will be appreciated, each malfunction constitutes an economic loss whether of production time, capsule material, medicament, etc.

It is therefore an object of the present invention to provide a locking capsule of a novel type having an improved pre-lock construction for optimum performance during finishing, distribution, etc.

It is also an object of the invention to provide an improved capsule having cooperating elements for the partial and complete locking of the body and cap parts.

Still another object of the invention is to provide an improved capsule having pre-lock means assuring the partial joining of the capsule parts in a constant pre-determined length.

Yet another object of the invention is to provide pre-lock means for capsules which prevents or minimizes the occurrence of popping apart of the capsule parts as they are being assembled.

Other objects, features and advantages of the invention will be seen in the following specification with reference to the accompanying drawings in which:

FIG. 1 is a side view of an assembled capsule according to the invention;

FIG. 2 is a section taken on axis line 2--2 of FIG. 1, of the upper part of a capsule of the invention in a full lock position;

FIG. 3 is a similar view in the pre-locked or partly closed position;

FIG. 4 is a transverse section of a capsule taken on line 4--4 of FIG. 1;

FIG. 5 is a plan view in section of the indented pre-lock contour of the cap mold pin, the pin contour being covered over with a capsule shell coating;

FIG. 5a is a section of the pre-lock position of a capsule shown in contact according to the invention with the capsule body;

FIG. 6 is an elevational view of the contour represented in FIG. 5; and

FIGS. 7a, 7b and 7c are sectional views illustrating the stepwise migration of the capsule liquid onto the shaped contours of a capsule mold pin as the pin is dipped increasingly deeper into the capsule liquid.

Referring to FIG. 1, the capsule of the invention 10 includes a cap 11 and a body 12 with closed ends 13 and 14, the parts being readily molded, stripped, etc., on standard capsule-making machinery and assembled easily, as desired, in either locked or semi-locked position. The cap 11 includes a cap end 18 with a suitable opening and a pair of capsule indents 24 (FIGS. 2, 3 and 4).

The cap 11, in greater detail as seen in FIGS. 2 and 3, has an inner wall 16 and an outer wall 17. The closed end 13 is preferably rounded or hemispherical but the shape is not critical. If desired, the cap end can have other shapes. The inner cap wall 16 proceeding from the open end 18 to the line 23, which is the shoulder line, has a slight narrowing diametral taper of the order of 0.010 inch per inch exclusive of indent means 24. In FIG. 2 the cap and body parts are shown in the fully locked position whereas in FIG. 3 the cap and body parts are shown in partly closed or pre-locked position. The body has a standard tapered side wall and is generally conventional. In FIG. 2, as indicated, the cap and body have been pressed together from the partly closed pre-locked or semi-locked position into the fully closed, locked position. In this position the open body end has advanced into the cap to a point near or preferably just beyond the shoulder line 23. The body like the cap is tapered in the same degree and in the direction from its open end to its closed end. The body taper and the body dimensions are such as to provide an ample entrance of the body into the cap. The body taper and the body dimensions in relation to the taper and dimensions of the cap also are such as to provide an elastic frictional fit in the pre-locked position shown in FIG. 3; the fit between adjacent wall surfaces of the cap and body advantageously permits the passage of air particularly around the periphery of the flat and along a gap 24c at the slopes 24b. By contrast the body wall is in close conformity with the indent flat 24a and edges 24d (FIGS. 5a and 6). The pre-locked fit in the area of the indent 24 is a friction fit wherein the capsule parts are elastically distorted--the cap undergoing "ovalling" and the body "dimpling"--making for increased passage means or air vent means so as to permit the escape of compressed air contained within the capsule occasioned, for example, by the sudden joining of the body and cap parts into locked position. Thus, the release of air advantageously avoids any tendency of the cap and body to pop apart. The mentioned construction unexpectedly provides performance characteristics (in joining, separation, printing, filling, etc.) which are wholly acceptable by comparison with any prior art capsule heretofore produced. Thus, there is little tendency under the conditions obtaining in capsule manufacture for the pre-locked capsule parts in accordance with the invention to become separated inadvertently or to become joined together farther than intended.

It has been found according to the invention that the geometry, dimensions and contour of the capsule indents are a critical feature. In particular, the indent slopes 24b must for purposes of the invention be at a relatively low angle. The is required, in respect to the dip-molding method, in order to avoid the excessive formation of air bubbles in the freshly formed capsule wall. Thus, the slopes 24b in relation to the flat 24a (shown in FIG. 5 as angle A and angle B) should form an angle of about 8.degree.-12.degree.. An angle of about 10.degree. is preferred whereas slope angles substantially more than 12.degree. are associated with the formation of excessive numbers of bubbles in the capsule wall portion adhering to the surfaces of the indent slopes and adjacent portions of the indent flat 24a. FIGS. 7a, 7b and 7c illustrate how the capsule making fluid moves in relation to an excessively angular pin contour as the pin 25 is being dipped into the capsule liquid. In FIG. 7a the capsule liquid 26 is rising upward along the pin and is entering the concavity of the pin mold indent. In FIG. 7b the liquid has moved farther past the corner formed by the indent slope and the indent flat without actually wetting the corner so that the air bubble 27 is formed. In FIG. 7c the capsule liquid 26 has moved higher across the capsule indent contour without contacting the innermost corner portions of the contour thereby causing air bubbles 27 in these portions. Subsequently in the molding process while the pin bars are being transported, rotated, subjected to the drying cycle, etc., the air bubbles formed are believed to merge with the liquid film 26 and to migrate in the film until the film sets up and solidifies, whereupon the air bubbles 27 are physically trapped within the capsule wall and particularly with the wall of the capsule indent 24. Such air bubbles tend to cause an undesirable weakness of the capsule. In extreme cases, bubble formation results in formation of holes in the capsule.

The capsule indents 24 of the capsules of the invention must also have a relatively long flat 24a between the indent slopes 24b. In general, a longer flat is associated with fewer, or smaller, air bubbles. It is found that in this regard the length of the indent flat separating slopes 24b should be about 0.030 to 0.040 inch and preferably about 0.035 inch; the width is of the same order and is not particularly critical. The diametral spacing of the capsule indents should be such that the open end of the body can enter into the cap to the pre-locking position and yet the cap and body at this position mutually engage in a frictional fit. In this regard the spacing should preferably be less than the outside diameter of the open end of the body by an approximate distance (designated herein as "constriction") differing according to capsule size, as follows:

Capsule size Constriction, inches __________________________________________________________________________ 0 .0068 1 .0054 2 .0047 3 .0045 4 .0040 5 .0039 __________________________________________________________________________

Shallower capsule indents are less desirable since they give a relatively weak pre-lock, that is, they sometimes fail to properly locate the pre-locked position. On the other hand, where this dimension is deeper the pre-lock tends to be excessive.

The axial location of the indents is also important to insure optimum wall flexibility and pre-locking strength. In this regard, the indents should be located axially from the inside of the closed end of the cap at a distance differing according to capsule size approximately as follows:

Capsule size Indent Location, inches __________________________________________________________________________ 0 .265 1 .250 2 .235 3 .225 4 .210 5 .140 __________________________________________________________________________

Where the indents are located substantially nearer the closed end, the pre-locking engagement is significantly less flexible so that the capability of the capsule parts to accommodate to variable characteristics such as capsule length, wall thickness, etc., is noticeably diminished. On the other hand, where the indents are located nearer the open end, the pre-lock tends to be weaker and therefore less effective.

While gelatin of pharmaceutical grade is a preferred material for the manufacture of the capsules of the invention, other materials having like properties can be substituted in whole or in part for gelatin. It is conventional for capsule mold pins to be made of high-grade stainless steel, and it will be understood that the contour of the mold pins used for making the capsule parts of the invention can be suitably formed by any conventional means such as milling, grinding or the like. It is a significant feature of the invention that the configuration of the indents is such as to require relatively less forming of the standard capsule mold pins. In other words, relatively little metal needs to be taken from the pin to provide the indent grooves and yet the locking action of the resulting molded capsule parts is entirely satisfactory. It will also be understood that the dip-molding process confers the contour of the pin precisely to the inner surface of the molded capsule part. In this respect the capsule cap parts of the invention which include the capsule indent 24 can be readily stripped from the mold pins without difficulty or damage to the capsule part.

While the invention in locking capsules has been described in detail in the foregoing specification, considerable variation in such detail can be made, as will be appreciated by those skilled in the art, without departing from the spirit of the invention.

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