Airplane window construction

. Application filed August 27,

This invention relates to improvements in the window construction of airplane fuselages, and the primary object thereof is to provide a window construction consisting of 6 a pair of spaced transparent panels, between which panels a partial vacuum is maintained while the airplane is in flight for the purpose of preventing the transmission of motor and propeller noises from the exterior to the in'10 terior of the fuselage.

It is well known that the noise produced by the rapidly whirling propellers of airplanes is highly objectionable to the occupants of such planes. Airplane designers IB have made serious efforts in the matter of reducing or minimizing this annoyance by forming the walls of the fuselage from sound insulating materials so that the noise.of the motors and the propellers associated there20 with will be prevented'from reaching the interior of the machine. To the best of my knowledge little or no effort has been made to prevent the transmission of sound through the windows, and since most closed bodies.of ²⁵ airplanes are provided with appreciable window area it follows that irrespective of the sound insulating materials employed in the walls of the body a very large proportion of sound will enter the body by transmission 30 through the windows.

Therefore in accordance with the present invention I aim to overcome this condition by constructing each window to include a pair of spaced transparent panels and the ³⁶ space between the panels is closed on three sides but is open along the rear edge or side, whereby as the machine moves in the air suction forces are developed which remove the air in the space between said transparent pan⁴⁰ els to produce a partial vacuum in order to minimize or prevent the transmission of sound vibration from the outer of said panels to the inner. By this arrangement there is a marked reduction in the transmission of ⁴⁸ sound energy to the interior of the machine with the result that the comfort of the occupants is materially increased and an outstanding objection on the part of the general public to airplane travel alleviated.

⁸⁰ For a further understanding of the inven2

1,853,317 of the frame 3 produces suction forces which result in withdrawing air from the space 9, leaving as a result a partial vacuum in the space 9. Since the physical intensity of a ⁵ sound varies as the energy of the vibrating particles of the medium, it follows that due to the presence of the partial vacuum in the space 9 there will be little or practically no . noise transmitted to the interior of the ve10 hide by reason of the window area when the present invention is employed. The present invention in combination with fuselage walls constructed from a sound proof material produces a very marked diminution in noise usu15 ally present in airplane bodies. I am aware of the fact that efforts have been made to muffle or quiet the noise of the engines employed in airplane operations, but tests have disclosed that most of the noise is attributable ²⁰ to the exposed rapidly .whirling propellers, and therefore to obtain a quiet interior not only are sound proof body walls necessary but also sound proof windows.

I have described what I consider to be a ²⁵ practical and simple way of attaining a sound proof window construction, and while I consider the form of the invention illustrated to be a preferred one, nevertheless it will be understood that it is within the prov³⁰ ince of the invention to maintain a partial vacuum between the spaced panels by any other appropriate means, and the present invention is therefore to be considered in this broader sense.

³⁵ With regard to the matter of ventilation, the inner panel 6 may be provided with an ordinary form of crank lift to raise and lower it vertically in a manner common to the adjustment of automobile windows.

⁴θ However, it is considered more practicable to have the panels 5 and 6 stationarily mounted and well set in felt or other nonvibrating material in order to make possible the greatest amount of vacuum between said 45 panels, and to provide for ventilation by means of muffled filters for air inlet and outlet in the fore and aft parts of the airplane cabin.