Specification for visors for scooter helmets
1981 Edition

This section defines the extent and application of the specification, emphasizing terminologies related to eye protection and optical testing procedures. It includes calibration details such as aligning the telescope and target along the same axis with a parallel light beam at 4.6 ± 0.1 meters, establishing zero dioptre scale, and setting the sensitivity to detect prismatic power down to 0.01 dioptres. Prismatic power tests are conducted by positioning the visor orthogonal to the telescope axis, with acceptance criteria capped at 0.5 dioptres. The section ensures precise optical calibration following IS 7524 (Part II).

Clarifies key terms such as 'visor screen,' described as a curved transparent plastic shield for eye and face protection. It explains the prismatic power test where the visor is placed normal to the telescope axis, with prismatic power considered excessive if reticule intersection falls outside a designated annulus. Methods to detect spherical and cylindrical optical errors are included, with limits established to minimize distortion, ensuring visors meet transparency and impact criteria.

Details the optical and physical requirements for visor materials, highlighting the necessity for a minimum of 80% light transmission tested per Appendix G of IS 7569-1975. It also outlines test procedures for spherical and cylindrical errors as described in Appendix A, ensuring materials deliver adequate clarity without distortion. Materials such as cast acrylic sheets are typical, meeting the defined optical and mechanical properties.

Focuses on performance criteria of visors rather than detailed structural design computations. Requirements include clear, impact-resistant materials providing protection from environmental elements. Testing for optical clarity and mechanical strength is mandatory. References to related standards such as IS 4151-1982 for helmet specifications are provided for comprehensive design guidance.

Specifies minimum performance thresholds, including at least 80% light transmission and adherence to optical error limits for spherical and cylindrical refractive distortions. Testing methods from Appendices A and G ensure visors meet these optical standards, guaranteeing clear visibility and minimal distortion for users.

Mandates that visors must be optically clear and free from defects such as scratches, bubbles, and surface irregularities. Edges should be smooth and free from burrs or protrusions to prevent discomfort or injury. Field of vision requirements align with IS 4151-1982. The section also reiterates the necessity for minimum light transmission and optical error testing to maintain quality.

Limits the complete visor weight to a maximum of 350 grams. If the visor exceeds this weight, the exact mass, rounded to the nearest 10 grams, must be clearly labeled on the product. The section also references flammability and light transmission standards to ensure overall safety compliance.

Provides guidance for proper cleaning and upkeep of visors, emphasizing avoidance of scratches and dirt accumulation. It prohibits the use of organic solvents such as metal polishes or waxes, recommending gentle cleaning with a soft cloth. The section advises on labeling requirements related to visor mass and stresses practices that prolong visor clarity and durability.

Requires each visor to bear the manufacturer's name or trademark and the year of production. The ISI certification mark is optional but regulated. Specifications for the target plate used in optical tests are detailed, including dimensions and mounting. Flammability criteria are also reiterated to ensure safety and traceability.

Describes the calibration and testing methodology for optical errors. The setup involves a telescope and target spaced 4.6 ± 0.1 meters apart with aligned axes, using a parallel light beam for illumination. The telescope is focused to zero dioptre, and standard lenses with ascending powers are inserted to measure spherical and cylindrical refractive errors. This method ensures precise detection and quantification of optical distortions.

Summarizes the burning rate test as per Appendix F of IS 2925-1975, requiring that the material’s combustion rate does not exceed 3 centimeters per minute. The procedure includes exposing the sample to flame, measuring the burnt length, and calculating the burning speed. Compliance with this limit confirms the material's flame safety.

Outlines the procedure for determining total and diffuse light transmission using spectrophotometric equipment as per Appendix G of IS 7569-1975. The visor material must transmit at least 80% of visible light with diffuse transmittance under 5%. Samples must be clean and properly calibrated instruments used to ensure accuracy.