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).
Specification for an improved combination spark plug and pressure indicator for an internal combustion engine.
| Identifier | ExFiles\Box 165\4\ img046 | |
| Date | 28th March 1928 guessed | |
| COPY. This invention relates to indicating mechanisms and is an improvement in or modification of the invention described in the specification of our prior application for Letters Patent No. 37,024 dated December 14, 1928. While the indicator disclosed in our prior application operates very satisfactorily it is necessary in order to measure therewith pressure variation in the combustion chamber of an internal combustion engine to provide a special hole in the cylinder or cylinder head to receive it. This is not always convenient or desirable and in order to obviate the necessity therefor the present invention consists primarily in combining such an indicator with a spark plug for an internal combustion engine so that in order to make use of the indicator for the purpose mentioned above it is only necessary to replace the conventional spark plug with the combined spark plug and indicator. The invention includes other features hereinafter described and claimed and in order that it may be clearly understood and readily carried into practice reference will now be made to the accompanying drawings wherein a constructional form thereof is illustrated by way of example and wherein:- Figure 1 is a view, partly in section, showing our improved combination spark plug and indicator applied to an internal combustion engine, and also, diagrammatically, the circuit with which the indicator is used. Figure 2 is a view similar to figure 1 but taken at right angles to that figure. Figure 3 is a section on line 3-3 of figure 1. 10 represents a portion of the cylinder head of an internal combustion engine of conventional type and 12 indicates the usual threaded aperture provided in the head for the reception of the conventional type of spark plug. 14 indicates, as an entirety, my combined spark plug and engine indicator. This device comprises a frame 16 provided with a threaded extension 18 for engagement in the aperture 12. The frame 16 is provided with a central bore 20 to receive the central electrode of the spark plug, the spark plug insulator and the rigid thrust member for the indicator. Midway of the length of the bore the frame 16 is provided with a large recess or cavity 22 into which extends a rigid arm 24 integral with the frame. The arm 24 is provided with an aperture in registration | ||