Combustion process observation element construction

The combination of a combustion chamber formed in a structural block (2, 22) particularly for observation of combustion within the cylinder block of an internal combustion engine to monitor combustion occurring therein,

• a combustion process observation element for observation of combustion within the combustion chamber,
• wherein
• the block is formed with an opening (3, 3') through which the observation element is introducible, and for retention therein, the opening including
• a stepped bore, having an inner portion (3a) adjacent the combustion chamber (1) of a predetermined diameter, and an outer portion (3b) remote from the combustion chamber, and which has a diameter larger than said predetermined diameter of the inner portion,
• and a seating surface (4) separating said inner and outer portions;
• and wherein the observation element includes
• a separable assembly comprising
• a tubular housing (11) and light-sensitive pick-up means (12) located in the housing;
• a window (5) closing off the opening and separating the interior of the combustion chamber (1) from the light-sensitive means (12),
• the window having an inner portion (5a) having a cross section to fit into the inner portion (3a) of the opening, and an outer flange (6) having a cross section larger than said cross section of the inner portion and fitting against said seating surface (4) of the opening (3, 3') in the block;
• the tubular housing (11) being formed with a flange (11b) fitting against the flange (6) on the window;
• and releasable positioning means (7, 14) securing and clamping the window and the housing in position with one surface of the flange (6) on the window fitting against the seating surface (4) of the opening (3), and one surface of the flange (11b) of the tubular housing (11) seated against an opposite surface of the flange (6) of the window (5), the releasable positioning means (7, 14) bearing against the opposite surface of the flange (11b) of the tubular housing,
• the tubular housing providing an unobstructed light path between the window and the light-sensitive pick-up means (12) and being separable from the window to permit separate, individual removal and replacement of the window, and of the housing with the light-sensitive pick-up means therein, respectively.