DESC:FIELD OF INVENTION
The present disclosure relates to the fields of mechanical engineering and automobile engineering. More particularly, the present disclosure relates to spun yarn braided multi-layer (FKM/ECO/Spun Polyester Braiding) fuel return line hose. More particularly, the present disclosure relates to spun yarn braided multi-layer fuel return line hose and method of manufacture.
BACKGROUND
In the realm of mechanical and automobile engineering, considerable attention is dedicated to the development and enhancement of vehicle components that contribute to operational efficiency, durability, and environmental sustainability. One such component of significant interest is the fuel return line hose, a critical part in automotive fuel systems. These hoses must withstand various internal and external stresses, including chemical exposure, temperature fluctuations, and mechanical wear. Traditionally, these hoses are constructed from materials that resist fuels, oils, and other chemicals. Advances in material science have led to the development of multi-layered hoses that utilize a combination of different materials such as Fluoro elastomers (FKM), Epichlorohydrin (ECO), and spun polyester braiding to achieve superior performance in terms of flexibility, chemical resistance, and overall durability. These innovations aim to meet the stringent requirements of modern internal combustion engines and evolving automotive standards.

In current practices, the available 2L FRL hose does not completely satisfy DIN 73379 fuel hose standards, indicating a lack of full compliance with prescribed performance requirements. Also, its production cost is relatively high, which hinders competitiveness as compared to other available solutions that use clamp application methods. When it comes to co-extrusion processes for hose manufacturing, it generally involves extruding two distinct types of rubber compounds together to create a single tube. Post extrusion, this tube is then subject to knitting or spiraling or braiding processes before a rubber cover is extruded over it. This multi-stage process contributes to additional time and cost involved in manufacturing, reducing overall efficiencies.

The technical realm of mechanical engineering and automobile engineering has seen the surge of innovative technologies aimed at enhancing the efficiency, reliability, and safety of automotive machinery. A key segment within this field concerns the design and production of fuel return line hoses, which serve the pivotal function of transporting fuel residue from the engine back to the fuel tank. An essential component of a vehicle's fuel system, the fuel return line hose has considerable bearing on the overall performance and fuel efficiency of the vehicle. As such, the development of technologies related to fuel return line hoses, particularly those involving spun yarn braided multi-layer constructions, have drawn considerable interest. This realm encompasses both the product's physical structure and the methodologies for its fabrication, revealing the potential for varied and multifaceted improvements.

Current hose manufacturing techniques have demonstrated certain drawbacks. These methods often make it difficult to produce hoses in complete adherence with the prevalent fuel hose standards, posing potential regulatory compliance issues. Additionally, the existing techniques can introduce substantial manufacturing costs, making wide-scale implementation a challenge for many enterprises. Furthermore, these practices have struggled to deliver the desired production efficiency, often resulting in prolonged manufacturing timelines.

Given these constraints prevalent in the existing hose manufacturing methodologies, there emerges a necessity for an invention that could potentially address these challenges. A method that could bridge these gaps would offer an effective alternative to the current industry practices, facilitating compliance with fuel hose standards, optimizing production costs, and bolstering operational efficiency.

SUMMARY
One or more of the problems of the conventional prior art may be overcome by various embodiments of the present disclosure.

In one aspect of the present disclosure, a multi-layer fuel return line hose is provided that comprises an innermost layer made of PFAS-free Fluoro elastomer (FKM), an intermediate layer made of Epichlorohydrin (ECO) rubber, and an outermost reinforcement layer consisting of polyester spun yarn braiding. The hose is configured to withstand fuel compositions and pressures up to 70 BAR.

In another aspect of the present disclosure, the polyester spun yarn braiding in the multi-layer fuel return line hose comprises a 12 counts 3-ply yarn, designed to provide application pressure of up to 20 BAR.

In another aspect of the present disclosure, the adhesion strength between the layers in the hose is particularly strong, reaching at least 4.73 N/mm between the FKM and ECO layers, and at least 2.5 N/mm between the ECO and polyester yarn layers.

In further aspects of the present disclosure, the hose exhibits resistance to extreme environmental conditions, including temperatures as low as -30°C and ozone concentration up to 500 ± 50 ppb, with no visible cracks or breaks.

The current disclosure also provides a method of manufacturing the multi-layer fuel return line hose, including steps of co-extruding two rubber compounds, FKM and ECO, applying polyester spun yarn braiding around the formed tube, under specifically defined conditions.

In another aspect of the present disclosure, the hose is subjected to curing under steam pressure of 116 ± 0.3 PSI for 50 minutes and post-curing at 150°C for 2 hours.

The invention also extends to a hose assembly, including the multi-layer fuel return line hose and a nozzle configured to provide a secure fit with the hose without additional clamping, wherein the assembly withstands burst pressure of up to 70 BAR.

In yet another aspect, the hose may comprise an adhesion promoter selected from silane coupling agents, titanate coupling agents, and epoxy silanes to enhance bonding between the layers.

In another embodiment of the invention, the method of manufacturing the hose includes a water medium leakage test under 40 BAR pressure for at least 1 minute to ensure no leaks.

Lastly, in one aspect of the invention, the hose is designed to resist shrinkage or expansion in axial directions under pressure, maintaining its structural integrity without external clamping.

DETAILED DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part of this specification, show certain aspects of the subject matter disclosed herein and, together with the description, help explain some of the principles associated with the disclosed implementations. In the drawing,

In one embodiment, the present invention pertains to a multi-layer fuel return line hose designed to withstand various fuel compositions and pressure levels of up to 70 BAR. The hose comprises three principal layers: an innermost layer made of Fluoro elastomer (FKM) especially, PFAS-free Fluoro elastomer (FKM) which directly encounters and resists the fuel, an intermediate layer made of Epichlorohydrin (ECO) rubber, and an outer reinforcement layer of polyester spun yarn braiding. The polyester spun yarn braiding, employing a 12 counts 3-ply yarn, is particularly designed to endure application pressure reaching up to 20 BAR. The respective adhesion strengths between the layers are key in maintaining the structural integrity of the hose, where the strength between the FKM and ECO layers is at least 4.73 N/mm, and between the ECO and polyester yarn layers is at least 2.5 N/mm. This layered construction confers resistance to extreme environmental conditions, including temperatures as low as -30°C and ozone concentrations up to 500 ± 50 ppb, such that the hose remains without visible cracks or breaks under these conditions.

Continuing with the same embodiment, the invention includes a method of manufacturing this multi-layer fuel return line hose. The method involves co-extruding the two rubber compounds, FKM and ECO, to form a single tube, then the polyester spun yarn braiding is applied around this tube. The braiding process is under a tension of 1.5 Kg and includes a braid design choice from 2 over 2, 1 over 1 full, or 1 over 1 half braiding. Ensuring quality and structural integrity, the hose is subjected to a curing process under steam pressure of 116 ± 0.3 PSI for 50 minutes and post-curing at 150°C for 2 hours. The assembly of the hose includes a nozzle which provides secure and clamping-free hose fitting, maintaining an enduring resistance to a burst pressure of up to 70 BAR. Furthermore, the hose can optionally include an adhesion promoter from a selection of silane coupling agents, titanate coupling agents, and epoxy silanes to enhance the bonding amongst the FKM, ECO, and polyester yarn layers. To ensure zero leaks, the hose is subjected to a water medium leakage test under 40 BAR pressure for at least 1 minute. The hose's construction is intricately planned and executed to resist any shrinkage or expansion in axial directions when under pressure, maintaining its structural integrity without needing external clamping.

Figure 1 illustrates a cross-section of a hose construction with three layers. The innermost layer 1 and made of FKM (Fluoro elastomer), the intermediate layer 2 made of ECO (Epichlorohydrin rubber), and the outermost reinforcement 3 consist of polyester spun yarn braiding. The layers should be circular and concentric, with the reinforcement layer appearing as a braided pattern around the two inner layers. Each layer should be clearly defined and distinct from the others. Include annotations for each layer with their respective labels.

Figure 2 illustrates a hose with a longitudinal and a cross-sectional view. The longitudinal view shows the length of the hose labeled as 'L'. The hose appears as a cylindrical object, with the outer and inner boundaries represented by solid lines, while the longitudinal section in the middle is marked with dashed lines indicating the internal layers or structure. The cross-sectional view, placed to the right of the longitudinal section, provides detailed measurements of the hose's dimensions. The outer diameter of the hose is specified as 7.0 mm with a tolerance of ±0.3 mm, while the inner diameter is indicated as 3.2 mm with a tolerance of ±0.15 mm. These measurements are annotated clearly on the cross-sectional view, with lines extending from the diameter points to the respective measurements. The overall design emphasizes the precise dimensions and construction of the hose, showcasing both its external and internal features.

Figure 3 illustrates a graph of analysis of multi-peak traces obtained in determinations of adhesion strength is done as per ISO 6133. ISO 6133, Method B is followed to figure out the separation resistance between the different layers.

Figure 4 illustrates a segment of the hose, which corresponds to the reinforcement layer braided with spun polyester yarn. This braiding is essential for providing the hose with strength and flexibility, allowing it to withstand high pressures.

Figure 5 illustrates a graph likely depicts the force (N) versus displacement (mm) during this separation test, ensuring that the adhesion between the ECO and yarn layer meets the required performance standards for durability and operational integrity in the hose construction. The results from such tests are essential for verifying that the multi-layer structure, especially the ECO to yarn adhesion, can withstand mechanical stresses during use.

Figure 6 illustrates different braiding patterns used in the construction of the spun yarn braided multi-layer hose, which aligns with the description from the document. Specifically, the document references 2 over 2, 1 over 1 full, and 1 over 1 half braiding patterns that are used in the reinforcement layers of the hose

DETAILED DESCRIPTION OF THE INVENTION
Various embodiments of the disclosure are discussed in detail below. While specific implementations are discussed, it should be understood that this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without parting from the spirit and scope of the disclosure. Thus, the following description and drawings are illustrative and are not to be construed as limiting. Numerous specific details are described to provide a thorough understanding of the disclosure. However, in certain instances, known details are not described in order to avoid obscuring the description.
References to one or an embodiment in the present disclosure can be references to the same embodiment or any embodiment; and such references mean at least one of the embodiments.
Reference to "one embodiment", "an embodiment", “one aspect”, “some aspects”, “an aspect” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others.
The terms “layer (s) or two layer or three layer” used in this specification generally have their ordinary meanings in the art, within the context of the disclosure, and in the specific context where each term is used. Alternative language and synonyms may be used for any one or more of the terms discussed herein, and no special significance should be placed upon whether or not a term is elaborated or discussed herein. In some cases, synonyms for certain terms are provided.
A recital of one or more synonyms does not exclude the use of other synonyms.
The use of examples anywhere in this specification including examples of any terms discussed herein is illustrative only and is not intended to further limit the scope and meaning of the disclosure or of any example term. Likewise, the disclosure is not limited to various embodiments given in this specification. Without intent to limit the scope of the disclosure, examples of instruments, apparatus, methods, and their related results according to the embodiments of the present disclosure are given below. Note that titles or subtitles may be used in the examples for convenience of a reader, which in no way should limit the scope of the disclosure. Unless otherwise defined, technical and scientific terms used herein have the meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. In the case of conflict, the present document, including definitions will control.
Additional features and advantages of the disclosure will be set forth in the description which follows, and in part will be obvious from the description, or can be learned by practice of the herein disclosed principles. The features and advantages of the disclosure can be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. These and other features of the disclosure will become more fully apparent from the following description and appended claims or can be learned by the practice of the principles set forth herein.
As mentioned before, there is a need for a method that delivers a product fully compliant with prevailing fuel hose standards, is cost-effective, and most importantly, enhances production efficiency. Such an invention could potentially streamline the hose manufacturing processes and provide an advantageous alternative to existing solutions in the market.

PFAS-free materials provide significant advantages, encompassing health, environmental, and regulatory benefits. By eliminating PFAS (per- and polyfluoroalkyl substances), known for their persistence and potential health risks such as cancer and hormone disruption, these materials contribute to enhanced safety and reduced health hazards. Their use mitigates environmental pollution associated with PFAS, often referred to as "forever chemicals" due to their inability to break down easily. This ensures a reduced long-term environmental footprint. Additionally, PFAS-free materials facilitate compliance with increasingly stringent regulations worldwide, thus safeguarding against potential legal and financial repercussions. They also bolster consumer trust, as growing awareness drives demand for safer, eco-friendly products. Furthermore, these materials align with sustainability objectives, enabling responsible production processes and promoting a positive environmental impact

Figure 1 illustrates a cross-section of a hose construction with three layers. The innermost layer 1 and made of PFAS free FKM (Fluoro elastomer), the intermediate layer 2 is made of ECO (Epichlorohydrin rubber), and the outermost reinforcement 3 consists of polyester spun (staple) yarn braiding, which is meant for Automotive LCV & PV fuel hose return line application where common rail injectors are used in the engines. This hose can work under any composition of diesel & petrol with different ethanol content, but validations are necessary according to the application actual conditions. The inner most layer which is FKM is validated according to the DIN 73379 requirements, also the ECO compound is validated according to the FKM requirements, and it is meeting the requirements, it gives additional safety to our product during the application. ECO compounds are validated according to the intermediate layer test requirements too. The layers should be circular and concentric, with the reinforcement layer appearing as a braided pattern around the two inner layers. Each layer should be clearly defined and distinct from the others. Include annotations for each layer with their respective labels.

Figure 2 illustrates a hose with a longitudinal and a cross-sectional view. The longitudinal view shows the length of the hose labeled as 'L'. The hose appears as a cylindrical object, with the outer and inner boundaries represented by solid lines, while the longitudinal section in the middle is marked with dashed lines indicating the internal layers or structure. The cross-sectional view, placed to the right of the longitudinal section, provides detailed measurements of the hose's dimensions. The outer diameter of the hose is specified as 7.0 mm with a tolerance of ±0.3 mm, while the inner diameter is indicated as 3.2 mm with a tolerance of ±0.15 mm. These measurements are annotated clearly on the cross-sectional view, with lines extending from the diameter points to the respective measurements. The overall design emphasizes the precise dimensions and construction of the hose, showcasing both its external and internal features.

The following table 1 exhibits the practical result of the proposed invention.
Table 1
Test ID Testing Parameters Units Results / Remarks
1 Hose Construction -- OK
2 Color -- OK
A1 FKM to ECO N/mm 4.73 OK
A2 ECO to YARN N/mm 2.5 OK
B1 Min. BAR BAR 78.67 OK
C1 Water Medium BAR No Leak OK
D1 Max. N N 129 OK
E1 Min. N N 291.67 OK
F1 Max. % % -2.9 OK
G1 Min. N N 11.83 OK
H1 Min. N N 369 OK
I1 -30 Deg.C -- No Crack OK
J1 Ozone concentration: (500 ± 50) ppb -- No Crack OK

The Table 1exhibits that the hose and its components have met all specified test requirements, indicating high quality and compliance with necessary standards. The hose construction and color passed the visual inspections, as both were marked "OK." Adhesion tests showed that both the FKM to ECO and ECO to YARN connections exceeded the minimum required strength, with values of 4.73 N/mm and 2.5 N/mm respectively. The hose also performed well under pressure, withstanding 78.67 BAR without any clamping in hose nozzle assembly and showing no leakage under 40 BAR. Additionally, the Nozzle assembly force & Nozzle plug off force tests revealed that the hose Assembly met or exceeded all specified requirements, with the assembly force of maximum reaching 150 N and Plug off force of 369 N under different conditions. Finally, the hose demonstrated excellent performance in low temperature behavior and ozone resistance tests, with no cracks observed, thereby confirming its robustness and durability

Regrading the Adhesion Strength Analysis, the test of the separation resistance is carried out according to DIN 53530 with strip samples or closed ring samples. Analysis of multi-peak traces obtained in determinations of adhesion strength is done as per ISO 6133. ISO 6133, Method B is followed to figure out the separation resistance between the different layers.
From the following tables related to the analysis of delamination stability results, between the ECO (Epichlorohydrin) layer and the yarn in the spun yarn braided multi-layer hose, as described here. The table and graph represent the peaks in adhesion force (N) and delamination stability (N/mm), which are critical factors in determining the performance and durability of the hose.

From the document, it can be inferred that the delamination stability and adhesion strength between layers, particularly between ECO and yarn, are tested according to ISO 6133 and DIN 53530 standards. The table records the median, range, and peak forces during these tests, which ensure that the hose can withstand the mechanical stresses of its operational environment without layer separation

Figure 3 illustrates a graph of analysis of multi-peak traces obtained in determinations of adhesion strength is done as per ISO 6133. ISO 6133, Method B is followed to figure out the separation resistance between the different layers.

Figure 4 illustrates a segment of the hose, which corresponds to the reinforcement layer braided with spun polyester yarn. This braiding is essential for providing the hose with strength and flexibility, allowing it to withstand high pressures.

Figure 5 illustrates a graph likely depicts the force (N) versus displacement (mm) during this separation test, ensuring that the adhesion between the ECO and yarn layer meets the required performance standards for durability and operational integrity in the hose construction. The results from such tests are essential for verifying that the multi-layer structure, especially the ECO to yarn adhesion, can withstand mechanical stresses during use.

Figure 6 illustrates different braiding patterns used in the construction of the spun yarn braided multi-layer hose, which aligns with the description from the document. Specifically, the document references 2 over 2, 1 over 1 full, and 1 over 1 half braiding patterns that are used in the reinforcement layers of the hose

Two types of rubber compounds (1, 2) are extruded together to form a single tube (3), followed by knitting or spiraling or braiding. The co-extruded tube (3) is braided over with spun polyester yarn (4). FKM uses 99.995% pure ZnO, sieved to 500 mesh to avoid metal traces. A special epoxy resin-based adhesion promoter ensures strong bonding between the FKM (1) and ECO (2) layers and between ECO (2) and the spun polyester yarn (4). A precise process ensures a maximum wall thickness variation of 0.4 mm. The adhesion promoter enhances the interlayer bonding, ensuring that the multi-layer hose can withstand the harsh environments typical in mechanical and automobile applications. This improved adhesion prevents delamination, increases the durability and lifespan of the hose, and maintains its structural integrity under demanding operational conditions.
Wherein the adhesion promoter may be selected from the following groups or may be compositions, like Silane coupling agents, such as amino silanes, vinyl silanes, epoxy silanes, and methacryloxy silanes, are commonly used to enhance adhesion between organic polymers and inorganic materials like glass and metals. In cases where silane agents may not be effective, titanate coupling agents, including isopropyl tri(dioctyl)phosphate titanate and neopentyl(diallyl)oxytri(dioctyl)phosphate titanate, serve as excellent alternatives by improving filler dispersion and bonding. Zirconate coupling agents, such as neopentyl(diallyl)oxytri(dioctyl)phosphato zirconate, are another option, particularly effective in high-temperature applications or combination of organic tetrafunctional acrylate ester, Toluene & Poly epoxides with modified and controlled alpha glycol content.
For polyolefins, maleic anhydride grafted polymers like maleic anhydride-grafted polypropylene (MAH-PP) are used to promote adhesion with polar substrates. In applications requiring strong urethane linkages, polyurethane-based adhesion promoters, including isocyanate-terminated prepolymers and moisture-curable polyurethane promoters, are highly effective. Similarly, acrylic-based adhesion promoters, such as methacrylate esters and acrylate oligomers, are widely used in paints, coatings, and adhesives.
Phosphate esters, including alkyl phosphate esters and aryl phosphate esters, are often employed to improve adhesion in coatings and sealants, especially on metal substrates. Epoxy silanes, such as glycidoxypropyltrimethoxysilane (GPTMS), are commonly used in epoxy-based adhesives and coatings due to their ability to bond with both epoxy resin and inorganic substrates. For polyolefins, chlorinated polyolefins like chlorinated polypropylene and chlorinated polyethylene are particularly effective in automotive applications. Finally, organosilicon compounds, such as hexamethyldisiloxane (HMDS) and trimethylsilyl chloride, are frequently used to improve adhesion in silicone-based coatings and adhesives by creating chemical bonds between organic and inorganic phases.
The co-extrusion process uses a mandrel let-off unit, tube winding unit, in between them a caterpillar for pulling the mandrel from mandrel let off unit & a caterpillar for pulling the co-extruded tube from the extruder and both the caterpillars are synchronized in ratios, so that the desired tube OD can be achieved by altering the synchronization ratio ensuring uniform tension and precise dimensions. The OD of the tube is also controlled by relatively changing the extruder RPM & Mandrel travelling speed (Line Speed). Cooling of the tubes is achieved using RO water at temperatures below around 15 to 20°C.
The tube ID is in the range from 2.9mm to 3.5mm with the 1st layer wall thickness range from 0.2mm to 0.8mm and the final co extruded tube wall thickness is 1.05+/- 0.1 mm.
Polyester spun yarn (4) of 12 counts 3 ply is used, twisted for optimal performance. Twenty carrier vertical braiders apply 1.5 Kg braid tension for clamp-free applications. The braiding pattern ensures automatic locking with the nozzle under pressure, maintaining structural integrity without additional clamps.
The material used in the reinforcement layer is Polyester spun (staple) black doped yarn, which is formed of staple yarns, that have not been treated with any special chemicals which aid bonding to the rubber compounds. So in this case, here the rubber compounds are specially designed to get the bonding with this yarn. This study proposes to capitalize the different denier & count yarns to achieve the desired properties. In this aspect different count yarns are tried, and process & finished product behaviors are studied.

S.No Yarn Description Denier Count Nec. Ply (No of strands) strand Count TPM
1 Poly ester spun (staple) black doped yarn 1330 3.90 3 12 320 +/- 20

Some other reinforcement materials available in the market already are Filament yarns, which are completely different from the current claimed yarn in terms of manufacturing method and application usage conditions.
Based on the carrier insertion method in the Braiding machine, it is possible to have different types of braiding pattern. Different braiding patterns are 2:1 (2 over 2), 1:1 (1 over 1 full), 1:1 half full (1 over 1 half). In our study we opted for 2 over 2 braid designs to assist the application requirements, which are tabulated.
From figure 6 the reinforcement layers are braided over the tubes with specific pitch. This braid pitch defines the finished hose properties, such as burst pressure, Change in OD under pressure, Shrinkage or expansion in axial directions. Based on the application needs and process requirements, this Pitch can be finalized.
The braided tubes are cured under steam pressure of 116 ± 0.3 PSI for 50 minutes. Curing occurs with the tubes wound over specific SS Reels to protect the braiding during the process.
Extraction uses RO water at 80 Bar pressure, ensuring no clamping is required due to the nozzle design. Leakage testing is conducted at 40 Bar and length measurement at 6 Bar.
Post curing involves maintaining the hose at 150°C for 2 hours, enhancing assembly over the nozzle.
Table 2. Performance Under Pressure
Testing Parameter Units Specification Sample 1 Sample 2 Sample 3 Average Result
Minimum Burst Pressure BAR = 50 74 77 85 78.67 OK
Water Medium Leakage Test BAR 40 (1 minute) No Leak No Leak No Leak No Leak OK
The table 2 focuses on the adhesion strength of different layers of the hose. It shows that the adhesion between the FKM (Fluoro elastomer) and ECO (Epichlorohydrin) layers, as well as the ECO to spun polyester yarn braiding, exceeds the required specification of 2 N/mm, with averages of 4.73 N/mm and 2.5 N/mm respectively. These results confirm strong bonding between the materials, which is critical for ensuring the hose’s durability and resistance to delamination under pressure. This ensures the hose’s reliability in fuel return line applications.

The proposed hose reveals significant testing results across various parameters, confirming that the hose construction meets industry standards and performance expectations. The material used in the hose includes FKM/ECO/Spun Polyester Yarn Braiding, and the tests were conducted in-house to ensure compliance with DIN 73379, 2014-07 and internal specifications. Each section of the hose construction was tested for critical performance factors, including adhesion strength between the materials, burst pressure, and leakage resistance.

The adhesion strength between the FKM (Fluoro Elastomer) and ECO (Epichlorohydrin) layers was measured, with results of 4.73 N/mm, which exceeded the minimum specification of 2 N/mm. Similarly, the adhesion between the ECO layer and the spun polyester yarn braiding was measured at 2.5 N/mm, indicating strong inter-layer bonding, essential for the hose’s durability under mechanical stress. The hose successfully withstood a burst pressure of 78.67 BAR, which confirms its ability to handle high-pressure fuel return applications, surpassing the minimum requirement of 50 BAR.
Table 3 Adhesion Strength Results
Testing Parameter Units Specification Sample 1 Sample 2 Sample 3 Average Result
FKM to ECO N/mm = 2 4.9 4.5 4.8 4.73 OK
ECO to YARN N/mm = 2 2.4 2.5 2.6 2.5 OK
The above table 3 highlights the hose's performance under pressure. The burst pressure test, which measures the minimum pressure required to cause failure, averaged 78.67 BAR, well above the required 50 BAR. Additionally, the hose passed the water leakage test conducted at 40 BAR for one minute without any leaks. These results indicate the hose’s ability to withstand high-pressure environments, ensuring no fuel leakage even under stressful conditions. This performance meets or exceeds industry standards, making the hose suitable for demanding automotive applications.

Furthermore, leakage tests were conducted under 40 BAR pressure, where the hose exhibited no leaks, validating its structural integrity and reliability in preventing fuel leaks under operational conditions. Additional testing involved determining the maximum force required to insert and secure the nozzle into the hose, which ranged between 125 to 132 N, indicating adequate assembly force within the specified range. The plug-off force was measured at 369 N, ensuring the hose remains securely attached during high-pressure operations without the need for external clamps.

Tests were also performed to evaluate the hose's performance under extreme environmental conditions, such as low temperatures (-30°C) and ozone resistance at a concentration of 500 ± 50 ppb. In both cases, no cracks or breaks were observed, ensuring the hose's resilience in harsh environmental conditions. These results confirm the product’s compliance with both industry standards and specific internal quality requirements, indicating its robustness for automotive fuel return applications.
Table 4. Mechanical and Environmental Resistance
Testing Parameter Units Specification Sample 1 Sample 2 Sample 3 Average Result
Max. Assembly Force N = 150 130 125 132 129 OK
Plug-Off Force N = 350 370 365 372 369 OK
Low Temperature Behavior Visual No Cracks No Crack No Crack No Crack No Crack OK
Ozone Resistance Visual No Cracks No Crack No Crack No Crack No Crack OK

In the Table 4, the hose's mechanical and environmental resistance is evaluated. The assembly force for securing the nozzle into the hose averaged 129 N, within the acceptable range. The plug-off force, measuring the strength required to detach the hose from the nozzle, was 369 N, ensuring the hose stays securely attached during use. The hose also performed excellently under low temperature conditions (-30°C) and ozone resistance tests, with no cracks observed. This confirms the hose’s robustness and ability to endure harsh environmental conditions, contributing to its long-term reliability

The hose's optimal performance during cold behavior tests, with minimal dimensional changes under internal pressure, and a strong axial squeeze resistance, further showcasing its durability and structural integrity. Overall, the results from this report strongly validate the innovative design and manufacturing process of the multi-layer fuel hose, ensuring it is fit for high-performance use in automotive applications

ADVANTAGES:
The unique nozzle and hose design eliminates the need for additional clamps, simplifying installation and reducing costs.

The 3-layer construction and high-quality materials provide exceptional resistance to fuel and environmental factors, surpassing existing solutions in durability and performance.

The optimized materials and processes offer a competitive price point while exceeding the performance standards of current market offerings.
,CLAIMS:1. A multi-layer fuel return line hose, comprising:
an innermost layer (1) made of PFAS-free Fluoro elastomer (FKM),
an intermediate layer (2) made of Epichlorohydrin (ECO),
and an outermost reinforcement layer (3) consisting of polyester spun yarn braiding,
wherein the hose is designed to withstand pressures up to 70 BAR without additional clamping mechanisms.
2. The multi-layer fuel return line hose as claimed in claim 1, wherein the reinforcement layer (3) comprises polyester spun yarn with a braid pattern selected from 2 over 2, 1 over 1 full, or 1 over 1 half, providing enhanced structural integrity and pressure resistance.
3. A method of manufacturing a multi-layer fuel return line hose, comprising:
-co-extruding two rubber compounds, Fluoro elastomer (FKM) (1) and Epichlorohydrin (ECO) (2), to form a single tube,
-applying polyester spun yarn braiding (3) around the tube,
wherein the braiding is performed with a tension of 1.5 Kg using a vertical braider to achieve automatic locking with the nozzle.
4. The method of manufacturing a multi-layer fuel return line hose as claimed in claim 3, wherein the hose undergoes a curing process under steam pressure of 116 ± 0.3 PSI for 50 minutes, followed by a post-curing process at 150°C for 2 hours.
5. A fuel return line hose assembly, comprising:
a multi-layer hose as claimed in claim 1,
a nozzle designed to provide a secure connection to the hose without the need for external clamps,
wherein the assembly is capable of withstanding a burst pressure of up to 70 BAR.
6. The multi-layer fuel return line hose as claimed in claim 1, wherein the adhesion strength between the Fluoro elastomer (FKM) layer (1) and the Epichlorohydrin (ECO) layer (2) is at least 4.73 N/mm, and between the Epichlorohydrin (ECO) layer (2) and polyester spun yarn braiding (3) is at least 2.5 N/mm, ensuring durability and resistance to delamination under mechanical stress.
7. The fuel return line hose assembly as claimed in claim 5, wherein the hose includes a leak-proof design, capable of passing a water medium leakage test under 40 BAR pressure for 1 minute without leakage.
8. The multi-layer fuel return line hose as claimed in claim 1, wherein the hose construction is resistant to extreme environmental conditions, including temperatures down to -30°C and ozone concentration of 500 ± 50 ppb, with no visible cracking or damage.
9. The method of manufacturing a multi-layer fuel return line hose as claimed in claim 3, further comprising a step of controlling the braid pitch to optimize burst pressure, shrinkage, and expansion properties under operational pressure conditions.
10. The multi-layer fuel return line hose as claimed in claim 1, wherein the outermost reinforcement layer (3) maintains structural integrity during high-pressure operation due to the precise braiding tension, eliminating the need for additional clamping mechanisms.