Specification for visors for non-metal police and firemen's helmets

IS 9995: Scope Key Points

• Scope: Specifies requirements and test methods related to optical instruments (e.g., telescopes) and materials like phenolic and polyethylene moulding materials, firemen's helmets, and cast acrylic sheets for luminaires.

• Telescope Specs (Clause 1.1):

  • Magnification: 7.5 to 20 (recommended 15)
  • Aperture: 15 to 20 mm
  • Eye-piece: Adjustable with graticule; example: thiodolite adjustable vertically and laterally
  • Quality check: Use a 5 mm aperture to detect image doubling or aberrations within a 20 mm diameter field

• Calibration (Clause 2.1):

  • Setup telescope and target optical system coaxially
  • Distance: 4.6 ± 0.1 m
  • Use parallel beam light of adjustable intensity for trans-illumination
  • Focus reticule and target pattern; zero point of diopter scale set here
  • Telescope focusing calibrated to measure power increments of 0.01 m⁻¹

Summary Table: Telescope Parameters

flowchart LR
    A[Telescope Setup] --> B[Align on Same Optical Axis]
    B --> C[Trans-illuminate Target with Parallel Beam]
    C --> D[Adjust Distance to 4.6 ± 0.1 m]
    D --> E[Focus Reticule & Target]
    E --> F[Set Zero Point on Diopter Scale]
    F --> G[Calibrate for 0.01 m⁻¹ Power Measurement]

This ensures precise optical measurements as per IS 9995 scope.

IS 9995 - Key Definitions & Specifications

• Visor Screen (Clause 2.2):
  A curved transparent polycarbonate sheet designed to protect eyes and face.

• Telescope (Clause 1.1 B-1.1):

  • Magnification: 7.5 to 20 (recommended 15)
  • Aperture: 15 to 20 mm
  • Adjustable eye-piece with graticule (e.g., thiodolite adjustable vertically and laterally)
  • Quality check: No image doubling or aberrations; tested with 5 mm aperture if needed.

Polycarbonate Sheet Requirements (Clause 3.1 A-1)

• Must meet physical requirements (clarified in the code).
• Transparent, impact-resistant, curved for visor use.

Rounding off Numerical Values

• Follow revised rules as per the standard (precise rounding not detailed here).

Summary Table (Conceptual)

flowchart LR
    A[Visor Screen] --> B[Polycarbonate Sheet]
    B --> C[Physical Requirements]
    A --> D[Eye & Face Protection]
    E[Telescope] --> F[Magnification 7.5 - 20]
    E --> G[Aperture 15-20 mm]
    E --> H[Adjustable Eye-piece]
    H --> I[Graticule (e.g., Thiodolite)]

This summary captures the key definitions and specifications from IS 9995 relevant to visors and telescopes.

IS 9995 - Material Requirements for Polycarbonate Sheet (Clause 3.1 & Appendix A)

Key Specifications:

• Relative Density:
  ≥ 1.2 (as per IS 2530-1963)

• Tensile Strength:
  ≥ 600 kgf/cm² (tested as per IS 2530-1963)

• Thickness of Visor Screen:
  3.0 ± 0.2 mm polycarbonate sheet

Additional Notes:

• The polycarbonate sheet must be optically clear and transparent.
• Material must comply with physical properties in Appendix A of IS 9995.
• Testing methods for density and tensile strength are based on IS 2530-1963.

Summary Table:

This ensures the visor screen is durable, strong, and visually suitable for use in protective helmets or similar applications.

IS 9995: Key Construction Specifications

1. Relative Density (Clause 1.1)

• Minimum relative density of material: ≥ 1.2
• Test method: As per IS 2530-1963

2. Light Transmission (Clause 2.5)

• Minimum light transmission: 80%
• Test method: Appendix G of IS 7569-1975

3. Visor Screen (Clause 3.1)

• Material: Optically clear, transparent polycarbonate sheet
• Thickness: 3.0 ± 0.2 mm
• Compliance: Must meet Appendix A physical requirements

4. Physical Requirements of Polycarbonate Sheet (Clause 3.1, Appendix A)

• Should ensure optical clarity, impact resistance, and durability
• Must conform to mechanical and optical standards detailed in Appendix A

Summary Table

flowchart TD
    A[Material Selection] --> B[Check Relative Density ≥ 1.2]
    B --> C[Polycarbonate Sheet: Thickness 3.0 ± 0.2 mm]
    C --> D[Light Transmission ≥ 80%]
    D --> E[Physical & Optical Tests as per Appendix A]

This ensures compliance with IS 9995 construction requirements for visor screens and related components.

IS 9995 - Workmanship and Finish: Key Points

1. Workmanship (Clause 5)

• Visors must be adjustable and securely bolted to the helmet shell (Clause 4.1).
• All components should be free from defects like cracks, sharp edges, or burrs.
• Surfaces must be smooth, uniform, and free from stains or discoloration.
• Assembly should ensure durability and maintain functional integrity under normal use.

2. Polycarbonate Sheet Specifications (Clause 3.1 & Appendix)

• Physical Requirements:
  • Flammability: Must be self-extinguishing per IS 2745:1969 (Appendix H).
• Optical Requirements:
  • Minimum Light Transmission: ≥ 80% as per IS 7569:1975 (Appendix G).

Summary Table:

Illustration of Visor Attachment (Conceptual)

graph LR
A[Helmet Shell] -- Bolted connection --> B[Adjustable Visor]
B -- Smooth finish --> C[Polycarbonate Sheet]
C -- Optical clarity --> D[Light Transmission ≥ 80%]

This ensures safety, durability, and user comfort as per IS 9995 standards.

IS 9995 — Weight Specifications for Visors

• Maximum Mass: Clause 6.1 states the complete visor mass ≤ 350 g.
• If mass > 350 g, it must be labeled with the exact mass (nearest 10 g).

Key Related Material Properties (for weight considerations):

Weight Calculation (if dimensions known):

[ \text{Weight} = \text{Volume} \times \text{Density} \times g ]

• Density = Relative Density × Density of Water (≈ 1 g/cm³)
• Use relative density ≥ 1.2 → Density ≥ 1.2 g/cm³

Summary:

• Keep visor weight ≤ 350 g for compliance.
• Use relative density ≥ 1.2 to estimate material density.
• Label visor if weight exceeds 350 g.

flowchart TD
    A[Material Properties] --> B[Relative Density ≥ 1.2]
    B --> C[Calculate Density]
    C --> D[Calculate Volume]
    D --> E[Compute Weight = Volume × Density]
    E --> F{Weight ≤ 350 g?}
    F -- Yes --> G[No Label Required]
    F -- No --> H[Label Weight on Visor]

IS 9995 - Key Instructions Summary

• Mass Limit:
  The complete visor mass ≤ 350 g (Clause 6.1).
  If mass > 350 g, show exact mass (nearest 10 g) on the visor label.

• Material Specification:
  Visor screen must be made of curved transparent polycarbonate (Clause 2.2).
  This ensures adequate protection for eyes and face.

• Rounding Off:
  Numerical values in the standard should follow revised rounding rules (exact rules not specified here).

Important Notes:

• The visor must be lightweight for comfort and safety.
• Polycarbonate sheets must meet physical and optical clarity requirements (Clause 3.1).
• Labeling is mandatory if visor mass exceeds the prescribed limit.

If you need formulas or detailed tables for physical properties or testing methods, please specify.

IS 9995 Marking Key Points

Target (Clause 1.2.1)

• Target plate: Black plate with cut-out pattern per Fig. 1 of IS 7524 (Part II)-1979.
• Bar width: 2 mm.
• Annulus dimensions:
  • Bigger annulus diameter: 46 mm, aperture: 0.6 mm.
  • Smaller annulus diameter: 23 mm.
• Central aperture diameter: 0.6 mm.
• Mounted on a glass plate.

Visor Marking (Clause 8.1)

• Must include:
  • Manufacturer's name or trademark.
  • Year of manufacture.
• Optional: ISI Certification Mark (Clause 8.1.1) following ISI rules.

Visor Dimensions (Fig. 1 Highlights)

• Radius to suit helmet shell.
• Transparent polycarbonate sheet.
• Fixing hole diameter: ≥ 6 mm.
• All dimensions in millimeters.

Additional Notes

• Flammability (Clause 1.9): Must be self-extinguishing per IS 2745 Appendix H.
• Optical requirements are covered under Clause A-2.

Summary Table

flowchart LR
    A[Target Plate] --> B[Black plate with cut-out pattern]
    B --> C[Bars 2 mm wide]
    C --> D[Bigger annulus 46 mm dia, 0.6 mm aperture]
    C --> E[Smaller annulus 23 mm dia]
    C --> F[Central aperture 0.6 mm]
    G[Visor] --> H[Polycarbonate sheet]
    H --> I[Fixing hole ≥ 6 mm dia]
    G --> J[

IS 9995: Physical Requirements for Polycarbonate Sheet (Visor Screen)

Key Specifications (Clause 3.1 & Appendix A)

• Material: Optically clear, transparent polycarbonate.
• Thickness: 3.0 ± 0.2 mm.
• Properties: Must comply with optical clarity and impact resistance as per Appendix A (not fully detailed here).

Construction Details (Clause 2.2)

• The visor is a curved transparent polycarbonate sheet designed to protect eyes and face.
• Radius of curvature must suit the helmet shell for proper fit.
• Fixing holes: Diameter ≥ 6 mm for fixture attachment.

Marking Requirements (Clause 8.1)

• Manufacturer's name or trademark.
• Year of manufacture.

Summary Table

Visualization of Visor Attachment

graph LR
A[Helmet Shell] --> B[Curved Polycarbonate Visor]
B --> C[Fixing Hole ≥ 6 mm]

This ensures proper fit, clarity, and protection per IS 9995 standards.

IS 9995: Optical Testing Methods - Key Points

1. Telescope Specifications (Clause 1.1)

• Magnification: 7.5 to 20 (Recommended: 15)
• Aperture: 15 to 20 mm
• Eye-piece: Adjustable with graticule (e.g., thiodolite adjustable vertically & laterally)
• Quality Check: Use 5 mm aperture to detect image doubling or aberrations; focometer can be used.

2. Calibration & Test Setup (Clause 2.1)

• Align telescope and target optical axis.
• Use parallel beam light of adjustable intensity to trans-illuminate target (per IS: 7524 Part II - 1979).
• Distance: 4.6 ± 0.1 m between telescope and target.
• Focus reticule and target; set this as zero diopter scale.
• Calibration sensitivity: measure power changes as small as 0.01 m⁻¹.

3. Astigmatism Recording (Clause 2.4)

• Measure max difference in refractive powers resolving horizontal & vertical bars.
• Rotate test lens around axis to record variations.

4. Standard Lenses (Clause 1.2.2)

Summary Diagram: Optical Test Setup

graph LR
A[Telescope] -- Align optical axis --> B[Target with reticule]
B -- Trans-illuminated by --> C[Parallel beam of light]
A -- Distance 4.6 ± 0.1 m --> B

This ensures precise optical measurement and calibration per IS 9995.

IS 9995 - Light Transmission Test Method (per IS 7569-1975 Appendix G)

Key Specifications:

• Minimum Light Transmission: 80%
• Maximum Diffuse Transmittance: 5%

Test Method Summary:

• Use the procedure in Appendix G of IS 7569-1975, which specifies measuring light transmission through acrylic sheets.
• Light transmission (T) is measured using a spectrophotometer or photometer.
• Diffuse transmittance is measured to ensure clarity, limiting haze.

Important Notes:

• Test specimens should be free of defects.
• The telescope used for optical assessment should have:
  • Magnification: 7.5 to 20 (recommended 15)
  • Aperture: 15 to 20 mm
  • Adjustable eyepiece with graticule for precise observation.

Formula for Light Transmission (%):

[ T = \frac{I_t}{I_0} \times 100 ] Where:

• (I_t) = transmitted light intensity
• (I_0) = incident light intensity

Summary Table:

flowchart LR
    A[Incident Light \(I_0\)] --> B[Specimen]
    B --> C[Transmitted Light \(I_t\)]
    C --> D[Measure Intensity]
    D --> E[Calculate Transmission \(T = \frac{I_t}{I_0} \times 100\%\)]
    E --> F{Is \(T \geq 80\%\)?}
    F -- Yes --> G[Pass]
    F -- No --> H[Fail]

This ensures optical clarity and safety compliance for cast acrylic sheets used in luminaires as

IS 9995 — Flammability Test Method Summary

Flammability (Clause 1.9, Appendix H of IS 2745:1969)

• Test Method: As per Appendix H of IS 2745:1969.
• Requirement: The material shall be self-extinguishing.
• Procedure Highlights:
  • A specimen is exposed to a flame for a specified time.
  • The flame is removed, and the time taken for the specimen to self-extinguish is recorded.
  • No sustained burning or dripping of flaming particles is allowed.

Optical Requirements (for context)

• Diffuse Transmittance: ≤ 5% (Appendix G, IS 7569:1975)
• Light Transmission: ≥ 80% (Appendix G, IS 7569:1975)

Key Points for Flammability Test (IS 2745:1969, Appendix H)

Summary Diagram: Flammability Test Flow

flowchart TD
    A[Prepare specimen] --> B[Expose flame for 10 sec]
    B --> C[Remove flame]
    C --> D{Does specimen self-extinguish?}
    D -- Yes --> E[Test Passed]
    D -- No --> F[Test Failed]

Note: For exact test setup and detailed procedure, refer directly to Appendix H of IS 2745:1969.