Description:4. DESCRIPTION

Title of The Invention
Leak-proof , Tamper-evident, Self Sealing, two-Piece Hard Capsule

Field of The Invention

Embodiments of the present invention generally relate to leak-proof tamper-evident capsules. More specifically, the invention pertains to a two-piece hard shell capsule that gets sealed on its own without the use of external sealing operations, providing a completely leak-proof functionality, and completely leak-proof tamper-evident seal. The invention also includes a method for manufacturing such capsules. These capsules are suitable for encapsulating pharmaceutical, nutraceutical, cosmetic, or food supplement formulations.

Background of the Invention
Oral solid dosage forms are among the most commonly used formats in pharmaceutical formulations. Hard capsules, a type of oral solid unit dosage form, are widely utilized in the pharmaceutical industry due to advantages such as ease of large-scale manufacturing, administration, stability, and transportation. Compared to tablets, hard capsules typically require fewer excipients, exhibit reduced interaction with active ingredients, and achieve desired functionality in a cost-effective and globally accepted format.
The basic design of the two-piece hard capsule has remained largely unchanged for over a century. While this design is simple and effective for many applications, it exhibits certain limitations when a completely sealed, tamper-evident, or hermetically protected product is required. Such formulations opt for sealed two-piece hard capsules or softgels to meet these requirements. However, two-piece hard capsules are increasingly being considered to replace softgels, wherever possible, due to its ease of manufacturing.
Conventional two-piece capsules rely on a friction fit between the cap and body, which is generally adequate for solid fills but is insufficient for moisture-sensitive, hygroscopic, fine powders, or liquid or semi solid formulations that require a secure, leak-proof seal.
To mitigate these limitations, various post-filling sealing techniques have been developed, including:
• Gluing: Using hydroalcoholic solutions or polymer-based adhesives, often followed by drying.
• Band Sealing: Applying a gelatin or polymer band at the cap-body junction, which also serves as tamper-evident feautre.
• Fusing: Employing heat or solvents to melt and bond the cap and body together.
Although effective, these additional sealing steps introduce several drawbacks:
1. Susceptibility to leakage before sealing :
The manufacturing process usually requires capsules to be filled at one station and then transported to a separate sealing station. This physical transfer introduces a time lag, during which the capsules remain unsealed. This increases the risk of leakage or spillage, especially for liquid or semi-solid contents.

2. Leakage due to improper or inadequate sealing:
There remains a possibility of occasional leakage even after sealing. Also, the excess air in the sealed capsule attempts to escape, creating bubbles in the band that may potentially create tracks in the seal, affecting the integrity of the seal.

3. Compromised product quality:
Any leakage exposes sensitive formulations to moisture and air, potentially causing degradation, oxidation or microbial contamination. Such instability can shorten the product’s shelf life, alter its chemical or physical properties, and diminish its overall quality and consistency.

4. Reduced dosage accuracy:
The amount of active material and the resulting dosage delivered in each capsule may be lower than intended due to leakage, reducing the product’s efficacy where dosages have narrow therapeutic windows. In nutraceuticals, this may undermine consumer trust and product reliability.

5. Higher rejections:
Leakage also causes contamination of capsules within the same batch or container, causing rejection, material waste and increased production costs, necessitating additional quality control measures.

6. Safety concerns:
Leakage of potentially irritating or hazardous substances can pose safety risks for end-users.

7. Material compatibility requirements
The sealing process usually involves applying a sealant to close the capsule shells securely. The sealant must be chemically and physically compatible with both the capsule shell and the encapsulated contents. Incompatible sealants may degrade the capsule shell or alter the fill material’s properties. Identifying and validating suitable sealants adds complexity to product development.

8. Process compatibility constraints
Sealing techniques that involve heat, pressure or solvents must not weaken the capsule shell, cause unintended chemical reactions, or degrade sensitive fill materials (eg. vitamins or pharmaceuticals). These constraints limit the range of applicable sealing technologies and require extensive testing to ensure product reliability.

9. Process complexity: Additional sealing process involves coordinating multiple stations adding to logistical complexity, making the process less efficient.

10. Additional infrastructure costs:
a. Most of sealed capsules for Liquid filled hard capsules are specially designed. These require special machines for filling, which is additional cost.
b. Sealing operations require additional specialized machinery distinct from filling equipment, along with dedicated systems for inspecting and testing sealed capsules.
This amounts to increased capital investment, costs for maintaining and calibrating these systems with added operational complexities.

11. Dependence on Skilled Labor
Sealing process demands trained personnel to operate machinery, monitor quality, and troubleshoot issues. This reliance on skilled labor poses additional challenges related to manpower, potentially leading to production delays or quality inconsistencies.

12. Lower profits
The special filling and sealing steps drives up overall manufacturing costs, extended production time, more equipment, space and manpower, increased energy consumption, higher rejection rates and lower profitability and lower price competitiveness.

13. Reduced manufacturing throughput
The sealing process is often slower than the filling process, creating a bottleneck in the production line. This mismatch in speed further limits the output rate, reducing overall productivity. It hinders the manufacturer’s ability to meet high demand or maintain cost-effective operations.
Furthermore, most two-piece capsules are designed with air vents that allow entrapped air to escape before closure. While this feature facilitates smooth locking of the capsule halves, it also presents potential leakage points—especially problematic in liquid-filled capsules.
While softgel is popularly used in many nutraceutical companies, this technology has its own set of limitations.

When compared to softgels, two-piece hard capsules have distinct advantages, few of these are as below:

• The unified manufacturing process of softgel capsules offers immediate hermetic sealing of the encapsulated ingredient. However, it also involves wastage of the very expensive active ingredient.
• Hard capsules have thinner walls and need much lesser gelatin / HPMC / Pullulan etc which are expensive materials.
• Hard capsules are better suited to encapsulate substances with low melting point, hygroscopic and oxidation sensitivity.
• It is not possible to fill hot melts or emulsions with very small particle size in Sofgels.
• Hard capsules have lower weight variation.
• Cross-contamination is virtually eliminated in hard capsules.
• Hard capsules have much lesser migration of components between the shell and the fill, leading to better product life and dosage efficacy.
• Hard capsules exhibit lower permeability and hence apt for encapsulation of highly odorous products.
• Hard capsules offers easy flexibility of filling combinations in the form of beads, micro-tablets, and pellets in combination with
liquid formulation.
• Softgels are sensitive to variations in temperature and humidity, leading to reduced shelf-life and microbiological issues; therefore demanding special storage conditions.
• Manufacturing and filling of hard capsules is an easily scalable process.
• Hard capsules require fewer excipients than other solid dosage forms. And hence is preferred for product development of nutraceutical products, with reduced cost and reduced time to market.

With enhanced bio-availability of drugs through lipid-based (LBDDS) or self-emulsifying (SEDDS, SMEDDS) systems, hard capsules becomes a highly appealing alternative to softgel capsules.

Accordingly, there remains a need for a two-piece hard capsule design that:
• Retains the benefits of venting for air escape during closure,
• Ensures a reliable leak-proof seal suitable for sensitive, fine, or liquid formulations,
• And eliminates the need for post-filling sealing operations.

Summary of the invention
The present invention relates to a two-piece hard capsule, and more particularly, to a completely leak-proof and tamper-resistant capsule featuring an enhanced multi-level interlocking design and integrated air vents for improved closure dynamics.
Conventional hard capsules, especially when used to contain liquids or semi-solids, are susceptible to leakage, separation during handling, or pressure build-up during filling operations. These issues can affect dosage accuracy, product stability, and user safety.
The capsule of the present invention incorporates a specially engineered interlocking structure that engages the cap and body at multiple points along their circumference and length. This design ensures a firm and secure closure, making it resistant to accidental opening or tampering. Furthermore, the capsule includes one or more air vents positioned in such a manner that they allow the escape of air during the closing process, thereby minimizing internal pressure and facilitating smooth assembly on high speed capsule filling machines. Yet, they do not cause the encapsulated ingredients to leak.
The invention provides improved sealing integrity, enhances product protection, and enables reliable use in pharmaceutical and nutraceutical applications, particularly for formulations sensitive to moisture, oxidation, or spillage.

Brief description of drawings
Detailed description of the invention will be more readily understood in conjunction with the accompanying drawings, in which:
Fig 1 is an elevation view of a capsule in a fully closed position;
Fig 2 indicates the position and details of the three barriers in the capsule and the air vents with reference to several hypothetical horizontal planes indicated by the dotted lines;
Fig 3 and 4 are the enlarged cross sectional views of the capsule in the Fig 1, along the lines b-b’ and c-c’ indicated on Fig 2, respectively in unclosed and fully closed position indicating the first barrier;
Fig 5 is the expanded view of a portion of the first barrier indicated in Fig 4 in fully closed position;
Fig 6 and 7 are the enlarged cross sectional views of the capsule in Fig 1, between the lines d-d’ and f-f’ indicated in Fig 2, respectively in unclosed and fully closed position indicating the second barrier;
Fig 8 is the expanded view of a portion of the second barrier indicated in Fig 7 in fully closed position;
Figs 9 and 10 are the enlarged cross-sectional views of the capsule in Fig 1, along the lines g-g’, h-h’and i-i’ indicated on Fig 2, in unclosed and fully closed position respectively indicating the third barrier;
Fig 11 is the expanded view of a portion of the third barrier indicated in Fig 10 in fully closed position;
Fig 12 is the cross-sectional view of the capsule in Fig 1, indicating the air vents in fully closed position.
Fig 13 is the expanded view of a cross-sectional view cut through the air vents of the capsule in Fig 1 in fully closed position indicating the two barriers 11 & 16;
Fig 14, 15, 16 and 17 indicate the airflow patterns at first, second, third and final (fully closed) stage of engagement respectively.

Detailed Description of the Invention
The following definitions are provided to facilitate understanding of the invention described herein
Capsule:
A dosage form comprising two cylindrical parts: a cap and a body,fitting together to enclose a substance intended for oral or other administration.

Leak-proof Capsule:
A capsule specifically designed to prevent leakage of its contents, particularly suitable for liquids, semi-solids, or powders prone to seepage, through the use of multiple locking mechanisms and geometric seals.
Tamper evident:
Tamper evident describes a device or packaging system designed to show a visible indication of unauthorized access or manipulation of a product or its container, thereby protecting the product's integrity and ensuring its safety for the consumer.
Interference Fit:
A type of mechanical fit where the dimensions of the cap and body are such that they create frictional engagement, ensuring a tight and secure closure.
Air Vents:
Openings strategically placed to facilitate the escape of air during capsule closure, aiding smooth engagement of capsule halves and ensuring proper seating without deformation or pressure buildup.
Pharmaceutical Composition:
A formulation comprising one or more active pharmaceutical ingredients (APIs) along with suitable excipients, intended for therapeutic or prophylactic use.
Nutraceuticals:
Substances derived from food sources that provide health benefits, including prevention and treatment of disease, but are not strictly classified as pharmaceuticals.
Cosmetic Composition:
A formulation intended for application to the human body for cleansing, beautifying, promoting attractiveness, or altering appearance.
Food Supplement:
A concentrated source of nutrients or other substances with a nutritional or physiological effect, intended to supplement the normal diet.
Hard Gelatin/Vegetarian Capsule:
A capsule made from gelatin or plant-based polymer alternatives, having rigid structural characteristics suitable for encapsulating solid, semi-solid, or liquid contents.
The invention will now be described in detail with reference to various embodiments. It should be understood that these embodiments are illustrative and not limiting, and that various modifications may be made without departing from the scope of the invention.
Fig 1 represents a hard shell capsule 1. It comprises of a tubular hollow cap (2) and a tubular hollow body (3), wherein the inner diameter of the cap is slightly larger than the outer diameter of the body and the length of the body is slightly larger than the length of the cap. The body (3) is partially inserted inside the cap (2) along the insertion axis y-y’ until a fully closed final position is achieved. At fully closed position the cap and body form an internal container like structure allowing to enclose powders/ liquids or semi-solids. The particular closure of the cap and body described in this invention is best suitable for enclosing liquids and semi-solids. However, it is equally suitable to be used for enclosing solids. The capsules are made from natural, synthetic or semi-synthetic materials like gelatin, pullulan, cellulose derivatives, starch or starch derivatives or any other polymer. Both the body and cap are made separately by dipping molds in the solution of the material from which they are being made. The capsule depicted in the figure is not true to dimensions. The curved portions of the wall, the cut edges, grooves and any other recessed and protruding portions are emphasized.
The cap (2) has a circular open end (4) and a curved closed end (5). Similarly, the body (3) has a circular open end (6) and a curved closed end (7). The outer diameter of the body is slightly less than the inner diameter of the cap (2). The difference between the diameters of the cap and body are just enough to ensure a snug fit when the open circular end of the body (6) is inserted inside the open circular end of the cap (4) along the axis y -y’. The cap has in general a cylindrical wall (8) extending from open end (4) to closed end (5). The closed end (5) may be hemispherical or dome shaped and the radius of the dome may vary. The body has in general a cylindrical wall (9) extending from open end (6) to closed end (7). The closed ends may be hemispherical or dome shaped. The shapes of closed ends of the body and cap are preferably identical in a particular embodiment. Both the cap and body are slightly flexible in nature and can elastically deform at the time of insertion to ensure a snug fit. The insertion length of the body inside the cap at the time of complete closing is such that the tapered portion (19) of the open end of the body coincides with the taper portion (18) of the cap, the locking groove (12) of the cap coincides with the locking groove (14) of the body and the annular ridge (13) of the cap coincides with the annular ridge (15) of the body. At the partial closure or pre-lock position, the open end (6) of the body is located just adjacent to the locking groove (12) of cap, towards the open end (4) of the cap. The cap and body have complementing locking mechanisms at three positions, first barrier (10), second barrier (11) and third barrier (16).
Fig 2 indicates the different barriers in the capsule when the cap and body are fully engaged. The cap has variable diameters at different planes as indicated by hypothetical lines b-b’, c-c’, d-d’, e-e’, f-f’, g-g’, h-h’, i-i’ and j-j’. All these hypothetical lines divide the cap into 7 sections. The first section is the closed end of the cap indicated by the line b-a-b’. This section has a smooth curved profile. At the hypothetical horizontal line b-b’, the wall of the cap turns slightly outward. The portions b-c and b’-c’ are preferably tapered. The degree of taper can be a variable aspect. The cap wall then straightens between horizontal lines cc’ and d-d’. After the horizontal line d-d’, the wall turns inwards up to e-e’, preferably in a linear fashion and the portions d-e and d’-e’ are straight slanting lines. The cap wall then turns slightly outwards in the region between e-e’ and f-f’, preferably in a linear fashion. This region is the locking groove (12) of the cap. Between f-f’ to g-g’, the wall is relatively straight. Between g-g’ and i-i’, it forms a annular ridge (13) which is deepest at h-h’. After the groove ends at i-i’ the cap wall straightens again upto j-j’. The portions of the cap between f-f’ to g-g’ and i-i’ to j-j’ are reasonably cylindrical in form. The body wall (9) has regions with variable diameters complementary to the cap wall, as indicated in the figure, with certain regions of the cap and the body designed to ensure a snug fit. The open end of the body is inserted into cap along the insertion axis y-y’ and at the fully closed position, the open end of the body aligns with the line b-b’.
In between the horizontal lines b-b’ to c-c’ where the cap wall has an outward taper, the open end of the body (6) has a complimenting inward tapered portion, which matches with the outward taper of the cap at fully closed final position.
Fig 3 represents a section of the cap and body portion along the lines b-b’ and c-c’ in unclosed position and Fig 4 represents the same section in fully closed position, forming the first barrier (10). Fig 5 is the enlarged view of Fig 4 at first barrier. Barrier (10) is created at the mating surfaces of the tapered end (18) of the cap and complimenting taper (19) of the body. This geometry, at fully closed position, ensures a 3600 uninterrupted circular contact area of sufficient width with an interference fit between the complementary mating portions of the cap and body creating barrier (10). This forms the first barrier to avoid the leakage of the encapsulated contents.

Fig 6 represents a section of the cap and body portion between the horizontal lines d-d’ and e-e’ in unclosed position and Fig 7 is the same section in fully closed final position forming second barrier (11). Fig 8 is an enlarged view of Fig 7 at the second barrier (11) marked by a circle. Barrier (11) is created at the mating surfaces of the locking groove (12) of the cap and a complimenting locking groove (14) of the body. This geometry, at fully closed position, ensures an interference fit between complementary mating portions of the locking grooves of the cap and body creating barrier (11). This forms the second barrier to avoid the leakage of the encapsulated contents.

The profile of the cap between d-d’ to e-e’ and a complimenting profile in the body creates 3600 uninterrupted interference barrier (11). Barrier (11) is created due to the engagement of the locking groove (12) of the cap and (14) of the body. The illustrated annular locking groove (12) on the cap has an angular profile. The two arms of this angular profile forming the groove (12) are not symmetrical. The angular groove (12) formed in the region between d-d’ and f-f’ is deepest at e-e’. This groove may have a small radius. The body has a similar complementary groove. Fig 8 is an expanded view of barrier (11). The illustrated annular groove (12) on the cap has a V-shaped angular profile. ¬
As indicated in Fig 8, the angle formed between the two straight portions e-e’ to f-f’ and f’f’ to g-g’ of the cap is the entry angle θ. Similarly there is another angle formed between the two straight portions e-e’ to d-d’ and d-d’ to c-c’of the cap which is the disengagement angle Ɣ. Angle θ is much narrower than angle Ɣ . When the body is inserted along axis y-y’, the annular ridge (12) of the cap causes an obstruction to the movement of open end 6 of body, due to reduction in the diameter, smallest being at e-e’. Because of the flexible elastic deforming nature of the cap and the body and entry angle θ being narrow, the cap and body reach the fully closed position with minimal resistance to this enagagement process. Once engaged in the fully closed position, any attempt to open the locked capsule meets with a high resistance due to the much higher disengagement angle Ɣ. It is almost impossible to disengage the cap and the body without damaging the capsule. Now the angular locking grooves (12) and (14) are engaged in an interference fit to form barrier 11, which is difficult to open. This contributes to the tamper-evident feature to the capsule.
Fig 9 represents a section of the cap and body portion between horizontal lines axis g-g’ and i-i’ in unclosed position and Fig 10 represents the same section in fully closed position forming the third barrier (16). Fig 11 is the enlarged view of Fig 10 at this third barrier (16), marked by a circle. Barrier (16) is created at the mating surfaces of the annular groove 13 of the cap and a complementary annular groove (15) of the body. This geometry, at fully closed position, ensures a 3600 uninterrupted circular contact area of sufficient width, with an interference fit between complementary mating portions of the annular ridges of the cap and body creating barrier (16). This forms the third barrier to the leakage of the encapsulated contents. There can be a plurality of such ridges running around the circumference in between f-f’ and j-j’.
Fig 12 indicates the air vents (17) in fully closed position. These are axial recesses on the outer surface of the body (3). There can be a plurality of such air vents to facilitate required air flow. Their shape and dimensions can vary and they serve the same function irrespective of the shape of the recesses. The air vents may be located anywhere between the first barrier (10) and closed end (7) of the body (3).
The air vents (17) do not start at the cut open end of the body. It may begin in the region below the open end 6 of the body, such that it leaves an uninterrupted 3600 circular area of sufficient width in the region which will form the first barrier (10) along with the complementary mating area on the cap in the fully closed position. It may extend across the regions which will form barriers 11 and 16 in the fully closed position. The depth of the air vents may vary at different positions along it’s length. It may be lower than the depth of grooves which the air vents may extend across, such that there always remains an uninterrupted 3600 circular contact area of sufficient width in the regions forming barriers with the complementary mating areas on the cap in the fully closed position. The function of the air vents is to allow air movement between the inner chamber of the capsule and the atmosphere outside allowing passage for air escape at the time of final closure of the capsule.
Fig 13 is an enlarged view of Fig 12 indicating the position of the air vent (17), the second barrier (11), and the groove forming the third barrier (16).
Fig 14 is a diagrammatic representation of the air-flow pattern in the first stage of engagement of the cap and body. This is the pre-lock position where the ridge (13) of the cap engages with the locking groove (14) of the body. This sectional view cuts through the air vents, offering a clear understanding of how the air vents facilitates free flow of air. At this position there is enough gap between the cap and the body, to allow free flow of air through the air vents.
Fig 15 is a diagrammatic representation of the air-flow pattern as the cap and the body move beyond the first stage of engagement. This is the second stage of engagement. When the open cut end of the body (6) approaches e-e’ of the cap; the taper provided at the open cut end of the body comes in contact with the angular profile of the locking groove (12) on the cap. This causes a momentary stoppage of air flow. The sectional view cuts through the air vents.
Fig 16 is a diagrammatic representation of the air-flow pattern, capturing the moment when the cap and body have moved further towards each other. This is the third stage of engagement. The outer diameter of the body is larger than the minimum inner diameter of the locking groove (12) of the cap. At this stage, both the cap and the body undergo elastic deformation. The cap is momentarily under tensile stress and the body is under compression, till such time d-d’ of the body crosses over e-e’ of the cap. With changing motion dynamics, at this stage, the air vent once again provides route to facilitate air passage just before reaching final lock position.
Fig 17 is a diagrammatic representation of fourth stage of engagement of the cap and the body, which is the final closed and locked position. The moment the cap and the body are in the final closed and locked position, the air flow is completely blocked as all the three barriers are now fully engaged and activated, blocking all routes for air passage and renders the capsule completely sealed and totally leak- proof. This sectional view shows the fully locked capsule, the air vents and three completely engaged barriers, with no passage for air flow.
Examples
Example 1: Leak integrity test for hard capsules under vacuum
Objective: To evaluate and compare the leak-proof sealing capability of the inventive capsule design with that of three commercially available two-piece hard gelatin capsules of reputed brands designed for liquid filling application.

Method: Three marketed hard gelatin capsule types (A, B, and C) were tested and compared with the inventive capsule. Ten empty capsules of each type were placed in a perforated plastic container and immersed in 1 litre of light liquid paraffin contained within the desiccator chamber of a vacuum leak testing apparatus. A 50gm metal dead weight was placed atop the plastic container to ensure submersion. The chamber was sealed with a transparent lid and subjected to a vacuum of 625 mm Hg, held for 180 seconds. Upon completion, the vacuum was released, and the capsules were retrieved and examined for:
a) opening of capsules before completion of test
b) presence of air bubbles on the paraffin surface during vacuum hold (indicative of leakage), and
c) presence of liquid paraffin inside the capsule shells post-experiment

Observations:
Capsule type Bubbles observed No.of capsules popped open No of capsules found to contain paraffin No. of capsules that passed the test
A Yes 1 7 2
B Yes 2 7 1
C Yes 4 4 2
Inventive capsule No 0 0 10

Results and Conclusion:
The inventive capsule demonstrated complete resistance to paraffin ingress under vacuum, with no bubble formation or internal leakage observed, confirming the effectiveness of its multi-lock sealing mechanism. There was zero instance of popping open of any of the inventive capsules, indicative of a strong tamper-evident locking mechanism. In contrast, the commercially available capsules exhibited leakage indicating insufficient sealing capabilities in absence of an additional sealing operation.
Example 2: Evaluation of opening and closing force at pre-lock position and at final closed and locked position
Objective: To measure and compare the opening and closing forces of the capsules of the present invention with those of four commercially available two-piece hard capsules.
Method:
Capsules A and B (designed for liquid filling) and capsules D and E (standard applications) were tested alongside the inventive capsule. The forces required to reach and overcome both pre-lock and final lock positions were recorded using a force gauge. 10 capsules of each of the four types were tested and the average force with standard deviation was reported.
Observations:
Capsule type Closing force up to pre-lock position
(g)(+S.D.) Opening force from pre-lock position
(g)(+S.D.) Closing force upto final closed & locked position
(g) (+S.D.) Opening force from final closed & locked position
(g) (+S.D.) Difference between final opening and closing force
(g) (+S.D.)
A (for liquids) 15.09(+1.16) 14.51(+1.32) 866.5(+118.6) 969.5(+109.2) 98(+42.5)
B(for liquids) 13.5(+1.06) 13.90(+1.51) 825.0(+135.91) 918(+90.99) 93.0(+61.0)
D(standard) 9.50(+1.29) 9.0(+1.39) 565.0(+118) 588 (+118.0) 23(+5.87)
E(standard) 8.51(+1.29) 8.5(+1.24) 549.5(+125.87) 585.5(+116.83) 29.0(+18.23)
Capsules of the present invention 13.51(+1.65) 14.5(+1.78) 754(+134.5) 1177.5(+149.8) 408.64(+98.77)

Result and conclusion: The capsule of the present invention requires relatively lower closing force yet significantly higher opening force at the final lock position, indicating a secure, tamper-evident seal. The large differential between closing and opening forces minimizes popping open issues and ensures structural integrity post-filling, while also reducing assembly stress and potential damage to the capsule.

Example 3: Impact of a sealing operation on manufacturing efficiency
Objective:
To assess the influence of a secondary capsule sealing operation on overall production throughput.
Method:
The output rates of automatic capsule filling machines and capsule sealing machines were referred from publicly available manufacturer specifications and industry data available online and are indicated in the table below:
Output of a automatic capsule filling machine Average output of a capsule sealing machine Overall output
2,00,000/ hr 50,000/hr 50,000/hr
2,00,000/hr Not required 2,00,000/hr

Note: The above values are indicative and sourced from manufacturer specifications and published industry reports.
Conclusion:
The capsules of the present invention eliminate the need for sealing machines, allowing high-speed operations and improving the net production throughput by around 400%, thus reducing inventory pressure and associated costs. This is over and above the costs saved by eliminating the need for additional plant, machinery and manpower. This results in making available an economical and scalable capsule manufacturing process from the smallest to the largest capsule manufacturer.
, Claims:We claim:
1. A leak-proof, easy-to-close, difficult-to-open, tamper-evident, two-piece hard capsule (1) comprising:
(a) a tubular hollow cap (2), elongated along axis y–y′, having an open end (4) and a closed end (5);
(b) a hollow body (3), which has a diameter slightly larger than the cap to ensure a telescopic fit, having an open end (6) and a closed end (7), configured to telescopically engage with the cap along axis y–y′;
(c) wherein the cap (2) and body (3), upon complete closure, enclose solid, liquid or semi-solid contents in an inner container-like structure rendered leak-proof by three barriers that are 3600 uninterrupted circular contact areas of sufficient width, formed between the complementary mating surfaces of the cap and the body engaging with each other in an interface fit (10, 11, 16):
(i) a first barrier (10), formed between a mating surfaces of the tapered portion (18) of the cap and a complementing taper (19) of the body, with an interference fit, providing a 3600 uninterrupted circular contact area of sufficient width;
(ii) a second barrier (11), formed between the mating surfaces of the locking groove (12) of the cap and the locking groove (14) of the body, with an interference fit, providing a 3600 uninterrupted circular contact area of sufficient width;
(iii )a third barrier (16), which is a singular or plurality of such barriers, located in region covered by the overlapping cylindrical portions(8) of the cap and (9) of the body, between the second barrier (11) and the open cut end (4) of the cap in the fully closed position formed between the mating surfaces of an annular circumferential ridge (13) on the cap and a corresponding annular circumferential ridge (15) on the body, with an interference fit, providing a 3600 uninterrupted circular contact area of sufficient width;
(d) a plurality of air vents (17) enabling fluid communication between the capsule's internal volume and the external environment during the closure process in the form of axial recesses of any shape on the outer surface of the body, located anywhere between the first barrier (10) and the closed end (7) of the body, such that that there always remains an uninterrupted 3600 contact area of sufficient width in the multiple barrier regions formed between the complementary mating areas of the cap and the body in the fully closed position;
characterized in that the air vents (17) begin in the region away from the cut open end(6) of the body such that it leaves an uninterrupted 3600 circular contact area of sufficient width in the region to allow formation of the first barrier (10), with the complementary mating area of the cap in the final closed position of the capsule thereby allowing air escape during the closure process while maintaining the leak-proof nature after final closure;
wherein each of the barriers, singularly or in conjunction with others render the capsules air-tight and completely leak-proof;
and wherein the caps and bodies are suitable to be made on most existing standard two piece capsule making machines including high speed machines;
and wherein these capsules are suitable to be filled on most existing standard two-piece capsule filling machines including high speed machines.
2. The capsule of claim 1, wherein the air vents (17) extend across the locking groove (14) of the body, leaving an uninterrupted 3600 circular contact area of sufficient width in the region to allow formation of second barrier (11) between the locking groove (12) of the cap and locking groove (14) of the body in final closed position of the capsule.
3. The capsule of claim 1 and 2, wherein the air vents (17) extend over the annular ridge (15) of the body, leaving an uninterrupted 3600 circular contact area of sufficient width in the region to allow formation of the third barrier (16) between the annular ridge (13) of the cap and the annular ridge (15) of the body in the final closed position of the capsule.
4. The capsule of claims 1 to 3, wherein the number of air vents (17) is between 1 and 12.
5. The capsule of claims 1 to 3, wherein the number of air vents (17) is preferably between 1 and 8.
6. The capsule of claims 1 to 3, wherein the number of air vents is preferably 4.
7. The capsule of claims 1 to 6, wherein the third barrier (16) is located in the region between the second barrier (11) and the open end of the cap (4) but is not completely overlapped by the air vents.
8. The capsule of claim 1, wherein the two sides of the angle formed by the locking grooves (12) and (14) forming the second barrier (11) are preferably asymmetrical.
9. The capsule of claims 1 to 7, wherein the third barrier (16) comprises of a plurality of annular ridges.
10. The capsule of claims 1 to 7, wherein the third barrier (16) comprises a single annular ridge.

11. The capsule of claim 1 and 8, wherein the entry angle (θ) encountered during the engagement of the cap and the body is narrower than the disengagement angle (γ) encountered during the opening of the cap and body after final closed position, thereby making it easy to close and difficult to open the capsule without damaging it, rendering the capsule tamper-evident.

12. The capsule of claims 1 to 11, wherein the depth of the air vents (17) is less than the depth of the locking groove (14) and annular ridge (15) of the body in the region forming the second and third barrier (16) respectively.

13. The capsule of claim 1 to 12, wherein the capsule is made of a natural, synthetic, or semi-synthetic polymer.

14. The capsule of claims 1 to 13, wherein the polymer is selected from the group consisting of gelatin, pullulan, cellulose derivatives, starch, or starch derivatives.