Description:FIELD OF THE INVENTION
The present invention relates to high-pressure composite overwrapped pressure vessels (COPVs), particularly Type IV cylinders used for the storage and transportation of compressed natural gas (CNG) and gaseous hydrogen (H₂). More specifically, the invention pertains to a novel blank end boss design that is geometrically identical to the threaded valve boss but devoid of any internal bore, thereby providing enhanced structural support, manufacturing uniformity, and operational reliability.

BACKGROUND OF THE INVENTION
Type IV COPVs are widely adopted in industrial, vehicular, and stationary energy storage applications due to their lightweight design and high-pressure resistance. These vessels consist of a polymeric liner overwrapped with resin-impregnated composite fibers, with metallic end bosses inserted at both ends to interface with external devices.
In conventional configurations, one boss (the valve boss) is threaded and functional, while the opposite end is typically closed by molding or using a plug, lacking structural complexity. This asymmetry can introduce several drawbacks:
• Uneven stress distribution during internal pressurization, particularly at the dome ends.
• Inconsistencies during the filament winding process, which relies on uniform end profiles for fiber tensioning.
• Liner deformation or displacement due to lack of rigid support at the non-valve end.
• Handling and balancing difficulties in robotic and vehicular integration.
There exists a need for a structurally symmetric design that eliminates these limitations without adding excessive cost or weight.

Key Patent References (Patent Literature)
US 8047396 B2 – “End boss and composite pressure vessel”
This patent pertains to COPVs with detail on end bosses—particularly methods of attaching bosses or caps to liners. It covers features such as molded/flanged sealing and composite overwrap bonding around the bosses.
US 9,829,153 B2– Composite pressure vessel and method of construction
Describes a vessel with a pipe sealed at both ends using internal plugs or compression caps. One cap may include a port; the opposite cap is non-functional.
WO 2015/130599 A1 – Pressure vessel
Focuses on COPV liners and composite wrapping but does not explicitly describe blank geometric bosses. Nonetheless, its modular liner constructions and fiber winding considerations are relevant.
Other Relevant Applications
Patents such as US 2011/0309074 A1 and US 2025/0122976 A1 discuss composite vessel manufacturing methods, winding on mandrels, cap assembly, and sealing techniques—background technology that relates to your boss integration approach.

Non Patent Literature (NPL) & General References
• Wikipedia: Composite overwrapped pressure vessel
Provides technical background on COPV construction—liner function, fiber overwrap, boss structures, and general manufacturing considerations—helpful for context and broader state of the art framing.
• Reddit discussion on COPV fabrication (ISRO forum)
Offers technical description of liner winding, fiber tensioning, and structural challenges during manufacturing—useful for describing process context and problems your invention addresses.

SUMMARY OF THE INVENTION
The present invention provides a Type IV composite cylinder comprising a polymeric liner and two end bosses—one functional and the other non-functional (blank). The blank end boss is externally identical to the valve boss in geometry, size, and interface characteristics but lacks any internal threading, bores, or flow paths.
This design provides multiple advantages:
• Geometrical and mechanical symmetry during manufacturing and operation.
• Structural support at both ends during filament winding, resulting in uniform fiber tension and composite layer buildup.
• Resistance to deformation under winding loads.
• Reinforced structural termination under high internal pressure.
• Balanced mass distribution, improving handling, mounting, and alignment.
The blank boss may also serve as a sealed port for future modifications, non-destructive inspection, or RFID integration.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: Isometric view of the Type IV composite cylinder with both end bosses.
Figure 2: Cross-sectional view showing the polymeric liner, composite overwrap, and end bosses.
Figure 3: Detailed sectional view of the blank end boss integrated into the liner.
Figure 4: Diagram showing filament winding process with support at both ends.
Figure 5: Stress distribution schematic showing balanced load paths across symmetric end bosses.

DETAILED DESCRIPTION OF THE INVENTION
The invention relates to an improved Type IV pressure vessel comprising:
• A polymeric liner formed from thermoplastics such as high-density polyethylene (HDPE), polyamide (PA), or polyethylene terephthalate (PET).
• A composite overwrap made from continuous fibers (e.g., carbon, aramid, glass) applied through filament winding and impregnated with epoxy or thermoset resin.
• A first end boss—a functional valve boss that includes an internal bore and threads for pressure fittings.
• A second end boss—a blank end boss that is externally identical to the valve boss but completely solid and sealed.
Symmetrical End Boss Design:
The blank end boss features the same external dimensions, flanged engagement, and outer profile as the threaded boss. Both bosses are integrated into the liner via:
• Mechanical interference fit,
• Over-molding,
• Or thermal bonding.
This results in geometric and mechanical symmetry, improving stress distribution during pressurization and reducing localized stress risers at the dome ends.
Support During Filament Winding:
During filament winding, continuous fibers are laid over the liner under high tension. The blank end boss:
• Acts as a rigid structural termination.
• Prevents liner deformation or collapse under tension.
• Enables even composite layering, improving strength and reliability.
Pressure Performance and Structural Integrity:
The blank end boss contributes to structural reinforcement, acting as a closed-end load distributor. When pressurized (e.g., up to 700 bar or more), the boss shares axial and hoop stresses, minimizing deformation and elongation at the closed end. This supports long-term fatigue resistance and dimensional stability.
Operational and Handling Advantages:
The identical bosses at both ends:
• Allow robotic grippers and fixtures to interface with either end.
• Simplify vehicular mounting and balancing.
• Aid in dynamic loading applications by preventing mass asymmetry-induced vibration.
Optional Features:
The blank boss may further include:
• Embedded RFID tags or serial code inserts.
• Structural ribs or webs for internal reinforcement.
• Optional sealed ports for pressure testing or future functional conversion.
Materials:
Both bosses may be fabricated using:
• Aluminum alloys (e.g., 6061, 7075),
• Stainless steel (e.g., SS304, SS316),
• Titanium or high-performance alloys compatible with liner and resin systems.
The integration method ensures that both bosses anchor securely, forming hermetic seals and maintaining mechanical load paths during operation.
The present invention relates to an improved structural design of Type IV Composite Overwrapped Pressure Vessels (COPVs), particularly CNG and H2 cylinders, which incorporates a blank end boss on the side opposite the primary valve boss. This blank end boss is identical in external geometry and structural profile to the valve-side end boss but does not have any internal bore or port. Instead, it is fully solid or sealed, serving a non-functional, yet highly beneficial mechanical and structural role in the cylinder assembly.
During the manufacturing of Type IV cylinders, a polymeric liner is overwrapped with high-strength composite fibers to create a lightweight yet pressure-resistant vessel. End bosses are inserted at both ends of the liner to interface with external fittings such as valves. In conventional designs, only one boss is functional — the one housing the valve. The opposite end is often closed off by molding the liner directly or inserting a plug-type structure. However, such asymmetry can introduce issues related to unbalanced stress distribution, structural non-uniformity, and complications during the composite overwrapping process.
In this invention, the blank end boss mirrors the main valve boss in every respect except for the internal threading or flow path. This means that it features a matching flange, shoulder, neck, and outer profile, allowing for symmetrical integration with the liner. This symmetry is essential for high-performance pressure vessels, as it ensures that both ends of the liner receive equal mechanical support, preventing distortion during manufacturing and operation.
One of the critical advantages of this blank end boss design is the support it provides during the filament winding process. Filament winding involves wrapping continuous fibers, such as carbon or glass, over the liner under tension. Without adequate structural backing, the open or weak end of the liner may deform, collapse, or shift, leading to uneven layering and unpredictable strength. The blank end boss acts as a rigid internal mandrel at the rear end, maintaining shape fidelity throughout the winding process. This ensures that the composite layers are evenly applied, thereby enhancing the mechanical performance and reliability of the cylinder.
Additionally, this configuration contributes to the structural performance of the finished vessel. Since the blank boss is mechanically bonded or molded into the liner, it behaves as a load-sharing structural termination. Under high internal pressure, the boss resists axial loads and hoop stress by transferring forces between the liner and the composite shell. This reduces stress concentrations, particularly at the end dome regions, which are typically the weakest points in pressure vessels.
Furthermore, the symmetry introduced by having matching bosses on both sides facilitates better handling, assembly, and system integration. It allows automated and manual processes to grip and position the cylinder more easily. In vehicular applications, the balanced design also aids in dynamic loading conditions, where imbalances can lead to wear, vibration, or mounting challenges.
The blank end boss may also serve as a platform for optional enhancements. It can incorporate embedded identifiers such as RFID tags or barcodes, and in some versions, be used as a backup port for pressure testing or future connectivity, while still maintaining its sealed nature during normal use. The boss can be manufactured from the same materials as the primary boss — typically aluminum, stainless steel, or high-strength alloys — ensuring compatibility with the liner and composite matrix.
Therefore, the incorporation of a blank, sealed end boss that mirrors the main boss in form but not function results in a safer, more reliable, and more manufacturable Type IV cylinder. It addresses key issues faced during winding, enhances the structural symmetry and pressure tolerance of the vessel, and simplifies operational processes. This innovation represents a valuable evolution in the design of high-pressure COPVs for CNG and related applications.
, Claims:1. A Type IV composite overwrapped pressure vessel, comprising:
o a polymeric liner;
o a first end boss including a threaded or ported interface for mounting a valve or pressure fitting;
o and a second, blank end boss disposed on the opposite end of said liner, said blank end boss having an external geometry identical to that of the first end boss but devoid of any internal bore, threading, or flow channel.
2. The vessel of claim 1, wherein both end bosses are secured to the liner via mechanical or thermal flanged integration.
3. The vessel of claim 1, wherein the blank end boss acts as a structural support during a filament winding process.
4. The vessel of claim 1, wherein the blank end boss contributes to pressure containment by reinforcing the closed end under axial and hoop stresses.
5. The vessel of claim 1, wherein the symmetrical geometry of the two bosses enables uniform composite overwrapping, reducing stress discontinuities.
6. The vessel of claim 1, wherein the blank end boss includes embedded structural ribs while maintaining a sealed configuration.
7. The vessel of claim 1, wherein the blank end boss is capable of housing embedded identifiers, RFID tags, or sealed instrumentation ports.