Fig. 16.
There are several forms of these burners, but the principle of all is the same. A gas burner protrudes from the top of a brass case which encloses the actuating mechanism. This mechanism consists generally of two electro-magnets, the armature of one opening the valve and allowing the gas to flow, at the same time vibrating a platinum-tipped rod against an electrode upon the burner collar. This produces a series of sparks at the burner tip which ignites the gas. A second magnet is provided which shuts the valve and extinguishes the gas. Some devices use one electro-magnet to both open and close the valve, but the majority have double electro-magnets. The circuit is worked from a push button, Fig. 16, situated wherever desired; pressure on a white button lights the gas and on a black one shuts it off.
Bartholdi Automatic Burner.
Instead of a rotating stop-cock, as in other automatics, a gravity valve is employed in the Bartholdi, which is held to its seat by the weight of the armature and connecting stem, as shown in figure 17. When the gas is turned off the valve rests upon its seat, as indicated in the cut. By a closure of the electric circuit at the turn-on button, two of the helices M P are energized, causing the armature J to be lifted, thus, by means of the stem H, raising the valve G from its seat into the dotted position, and opening the gas way so that the gas may issue to the tip, as shown by the arrows. At the same time, the top of the valve strikes against the end of the lever W, causing the circuit to be broken at the spark points T U, resulting in a continuous sparking as long as the finger presses the button. The magnet when raising the armature has also twisted or partially revolved it, so as to bring the notch d in the armature over the end of the hook e, as shown in the dotted lines. When the circuit is broken by lifting the finger from the button, the notch falls into the hook and the valve is locked open.
Fig. 17.
To extinguish the flame, the turn-off button is pressed, when a second magnet (not shown in cut) lifts the armature and twists it in the opposite direction, so that when the circuit is broken the armature falls free to its normal position, closing the valve.
Fig. 18.