and has an efficient agitating device for keeping the brine in motion. The brine acts as a medium for the transfer of the heat from the distilled water within the cans to the expanding ammonia in the expansion coils, which are placed longitudinally of the tank and between which the cans are inserted.

The ice when frozen is hoisted out of the tank by means of the hoisting apparatus (No. 19). The ice is loosened from the cans by the use of warm water from the condenser, either by employing a sprinkling apparatus (No. 20) or by dipping the can bodily into a tank.

TABLE 20.

TABLE GIVING NUMBER OF CUBIC FEET OF GAS THAT MUST BE PUMPED PER MINUTE AT DIFFERENT CONDENSER AND SUCTION PRESSURES, TO PRODUCE ONE TON OF REFRIGERATION IN TWENTY-FOUR HOURS.

Temperature of the Gas in Degrees F.

65° 70° 75° 80° 85° 90° 95° 100° 105°

Corresponding Condenser Pressure (gauge), lbs. per Sq. In.

103 115 127

139

153 168

184 200 218

In the De La Vergne refrigerating machine the cooling of the heated gas is effected by passing it through pipes surrounded by running water. The characteristic feature of this machine consists in the patented system for preventing the occurrence of any leakage of gas taking place past the stuffing box, piston, and valves, and of extracting the heat from the gas during compression, by the simple device of injecting into the compressor, at each stroke, a certain quantity of oil or other suitable lubricating fluid. By means of this sealing, lubricating and cooling oil, not only are the stuffing box, piston, and

valves effectually sealed, and the heat developed during compression taken up, but all clearances are entirely. filled up. This latter is a matter of great importance, as it ensures a complete discharge of the gas from the pump cylinder, and obviates the above-mentioned loss of power and efficiency.

This method of sealing the stuffing box and piston prevents leakage and consequent introduction of air into the pump, or wasting of the refrigerating gas at each alternate stroke of the piston without necessitating the

packing of piston so tightly as to cause excessive fricion. Fig. 167 shows a sectional view of a double acting De La Vergne compressor fitted with Louis Block's arrangement of valves, the main object of which is to secure the discharge of the oil at the lower end of the cylinder taking place immediately after all the gas is gone and not before, as in the latter case re-expansion will take place, resulting in loss of efficiency of the pump. To effect this, two valves are provided in the lower end of the compressor cylinder, one above the other.

Either or both of these valves may open on the down stroke of the piston, until the latter covers the upper one, when only the lower one is left open to the condenser. During the remainder of the stroke of the piston, after the lower valve is also closed, the other or upper one opens communication with an annular chamber formed in the said piston. In the bottom of this annular chamber are provided, moreover, valves which open as soon as all the other outlets from the underside of the piston are closed, to ensure which they are loaded with springs, so arranged as to require somewhat more pressure to open them than the discharge valves on the side of the cylinder. The gas, and afterwards the oil, then all pass out through the piston, no trace of the former being present at the completion of the down stroke. In this manner the oil system of sealing can be advantageously retained, and the pump will work as well at the lower side as the upper.

Fig. 168 shows a complete installation of a refrigerating plant on the De La Vergne system, the vertical compressor being driven by a horizontal engine. The circulation of the ammonia, and the sealing oil is as follows:

A is the compressor cylinder, double acting, and