From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Description of an indicating mechanism for recording pressure variations in a combustion chamber using an oscillograph.
| Identifier | ExFiles\Box 165\4\ img048 | |
| Date | 28th March 1928 guessed | |
| -3- of the rigid arm 24, frame 16, terminal 54, conductor 66, and oscillograph element 68. Current is supplied to the Wheatstone bridge from battery 72 through variable resistance 74 and conductors 76 and 78. The oscillograph element, which is but diagrammatically indicated, produces movement of a mirror in synchronism with the current fluctuations in the bridging circuit, causing a light ray to be projected and recorded on a traveling photographic roll. The operation of the indicating mechanism is as follows: Pressure variations in the combustion chamber cause movement of the diaphragm 26 which is transmitted through the tubular thrust member 30 to the rigid arm 24. Movement of the arm effects variations in the pressure applied to the carbon pile rheostats 34 and 36, and this results in corresponding variations in their resistance and, consequently, in the potential at that end of the bridging circuit, causing flow of current through the bridging circuit which operates the oscillograph element 68. The movement of the element is recorded on the photographic roll and gives an accurate record of pressure variations in the combustion chamber. Within the tubular thrust member 30 there is arranged an insulator 80 surrounding the central electrode 82 of the spark plug. At the upper end of the bore there is provided a second insulator 84 surrounding the first insulator and centering it in the bore of the member 16. The central electrode is provided with the usual terminal 86 which may be connected in the usual manner to the ignition system. The side electrode 88 which co-operates with the central electrode is preferably mounted on the diaphragm 26 although it might, if preferred, be mounted directly on the member 16. I have shown at 90 a bore communicating with the central bore 20 and connected at 92 to a conduit leading to a source of compressed air. A cooling blast of air is thus directed against the diaphragm, the air escaping through the clearance provided between the tubular thrust member 30 and the bore 20 into the chamber 22 from which it may escape through suitable apertures, not shown, into the atmosphere. The cooling blast not only cools the diaphragm but also cools the central electrode and its insulator, preventing preignition. Having now particularly described and ascertained the nature of our said invention, and in what manner the same is to be performed, we declare that what we claim is:- | ||