Patent GB-892649-A (GB)
Title: Improvements relating to flying helmets
Inventor: LOBELLE MARCEL JULES ODILON
IPC: A62B18/04
Filed: 1959-08-06
Abstract: 892,649. Respiratory appliances. M.L. AVIATION CO. Ltd. July 26, 1960 [Aug. 6, 1959; Jan. 13, 1960], Nos. 26933/59 and 1280/60. Class 81 (2). The vizor of a pressurized helmet is urged into a position in which it closes an opening in the front of the rigid shell of the helmet by springs, one acting on each side arm and extending from the back of the side arm up the side of the shell, each spring also acting through a linkage to pull the vizor rearwardly against the shell to seal the opening. As shown, a vizor 7 is mounted on a pair of arms, each comprising a member 12 pivoted at 9 to the shell 1 and telescopically mounted within a member 13 screwed to the vizor. Pivoted on a lug 14, carried by the member 13, is one member 15 of a toggle linkage, the other link 17 being pivoted at 19 to a lug 20 projecting from the member 12 through a slot 21 in the member 13. Each end of an operating bar 22 comprises a bell-crank lever the junction of which is also pivoted to the lug 20. The link 17 also carries an arm 27 which extends through the slot 21 and lies in front of a sliding plunger 28. A second bellcrank lever is pivoted on a lug 29 on the rear end of the member 12 and has one arm 31 bearing against the plunger 28 and the other arm 32 connected through a link 33 to a spring 34. The vizor is held in the open position by a catch 36 forced into engagement with a latch 37, Fig. 3, by a spring 38. The catch is pivoted to the member 13 at 39 and comprises a projection 41 with a cam surface 42 which is engaged by a roller 43 mounted on the bar 22 so that when the bar is pulled down to close the vizor the roller bears on the surface 42 and releases the catch. The spring 34 through the bell-crank lever 31, 32 urges the plunger 28 forward against the arm 27, thus straightening the toggle linkage and sealing the vizor against a tyre 3 around the opening 2. When the bar 22 is raised, the toggle is broken so that the member 13 carrying the vizor moves forward and the plunger is moved rearwardly by the arm 27. This causes the bell-crank lever 31, 32 to rotate and stretch the spring 34 until a projection 44 comes into contact with a stop 45. The vizor and linkage may then be moved as a unit about the pivot 9 until the catch 36 engages the latch 37. To resist the rearward pull of the spring 34 on the vizor during movement a roller 47 on each side arm runs in an arcuate track 46 mounted on the shell 1 and is retained in a notch 47a when the vizor is in the sealing position. The vizor may be automatically closed by the action of a barometric capsule 57 when the ambient air pressure on a barometric capsule 57, Fig. 3, decreases to a predetermined point. The latch 37 with which the catch 36 engages to hold the vizor open is pivoted on a plate 49 and connected through a bell-crank lever 53, 55 with a collar 56 fixed to the barometric capsule 57. When the vizor is open, abutment of the lever arm 55 against the collar 56 counteracts the pressure of the springs 34 tending through the catch 36 to turn the latch 37 clockwise. When the ambient pressure falls, the capsule expands and moves the collar 56 out of engagement with the arm 55, thus releasing the catch 36. The capsule and collar are adjustably mounted on the plate 49, thus allowing the pressure at which the vizor is automatically closed to be varied. A mouth-piece 6 has a projection 69 which is contacted by the bar 22 to move it to the closed position during manual or automatic closing of the vizor. Specifications 817,167 and 844,060 are referred to.