A large charging screw is placed directly in the top of the gas chamber. Into this is screwed a tee and short nipple, or it may be a special fitting made for that purpose. On this tee or special fitting a pressure gauge is screwed, and a float valve is attached on the branch. Into the gas chamber or as close to the partition as possible an angle valve is placed.
To Operate.
To charge the apparatus the safety valve is removed and the amount of the charge of acidulated water having been previously ascertained, the charge is poured into the acid chamber through the air pipe. The charge of spelter or zinc is placed in the gas chamber through the charging screw on top of the gas chamber. The pump is now attached to the air inlet cock with a short hose, and a few strokes of the pump will force the acid up into the gas chamber until the zinc is completely submerged. The generation of gas will begin at once.
The cock on the burner is then closed until the necessary working pressure is obtained, when it is ready for use. The pressure of gas can be regulated by setting the safety valve to blow off at a greater or less pressure, as desired. The use of the float valve is to prevent acid from being forced out of the gas chamber and into the tube. If this happens, the valve floats up and instantly closes the outlet, in which condition the valve remains until sufficient gas is generated to force the acid back into the acid chamber. When first charging the machine, acid should be forced up into the gas chamber until this valve closes, as that will force all of the air contained in the gas chamber out through the tube, leaving only pure gas in the generator. When the acid is spent it is easily removed from the generator by attaching the pump to the air inlet cock and forcing the acid up into the gas chamber. The angle valve is then opened, when the spent acid can be drawn off into a pail or other receptacle. This will not drain the acid chamber absolutely dry, but practically so.
When the operator ceases work, as for dinner or for any purpose, all that is necessary is to open the air inlet cock and detach the hose from the gas outlet. The acid will return by gravity to the acid chamber when generation ceases. When the operator is ready to resume work a few strokes of the pump will start generation again.
The Burner.
The burner, shown in Fig. 46, which is the most important part of the apparatus, is also constructed on a principle not heretofore used on a lead burning apparatus. It consists of a small tube, to one end of which is screwed a small cock, similar to a pet cock. To the other end, at a convenient angle, is brazed the burner proper. This consists of a needle point valve. The needle point, being about ½ inch long, is arranged so that the point can pass through the gas outlet about 1-16 inch. This seems to spread the flame in such a manner that it absorbs sufficient air to reduce the flame. It can be regulated by drawing the needle in or out, as the work requires. There is also a tube arranged to act as a by-pass or subflame. By opening the valve on this by-pass a pilot or subflame is maintained, which does away with the annoyance of having the flame pop out or become extinguished, as it is instantly ignited again by the subflame. In operating, the flame is held at such a distance from the work as experience will teach to be proper, or until the lead starts to melt. It should fuse with that well-known and instantly recognized bright appearance which indicates the nonoxidizing flame.
Any one who is used to handling the blow pipe can easily familiarize himself with this blow pipe. The maker claims that 2 quarts of vitriol will serve to operate the apparatus for a day of 8 hours on lead as heavy as 12-pound. I have no doubt that it will do even more than the makers claim for it. The apparatus is made in three sizes, adapted for different classes of work. After the experience I have had with it, I feel sure that any beginner can use this apparatus safely if he uses ordinary judgment and care in handling a gas apparatus that needs common sense treatment.
CHAPTER XIII.
SOFT SOLDERING WITH THE MOUTH BLOW PIPE.
The common blow pipe is a simple little tool that is used in connection with an alcohol torch for soldering the finest and most delicate pieces of jewelry, and constitutes the sole method of soldering used by Britannia workers and jewelers, and the fact that such a varied assortment of articles are soldered by the blow pipe process leads one to surmise that it can be used to advantage on coarser work. Though it is a familiar tool to gas fitters, plumbers as a rule are ignorant of its use, and it is hard work to find one who ever saw a blow pipe used on lead work. It is an easy matter to become proficient in its use, and the trick of keeping up a steady blast, and breathing regularly at the same time, is soon learned, and, when once acquired, stays with you always. This trick consists of making a bellows of your cheeks and using your tongue as a valve to close the entrance to the throat, leaving the passage from the nostrils to the lungs clear for breathing purposes. The only things necessary to purchase for practice are a common bent blow pipe, which can be had for about 15 cents, and a common candle.