subject to minor divisions depending upon whether the work is heavy, or medium, or light. The different qualities which are necessary for the various classes of work are so well understood by foundrymen as to need no explanation here. However, in order to properly understand the problem of foundry sand handling it is necessary to have some idea of the character of the work for which the sand is being used. For light castings of gray iron, brass and aluminum, the sand should contain a high percentage of clay as a binder, whereas the requirement for steel castings is a sand which is almost pure silica, with the addition of such materials as will give it the proper consistency for the work in hand. As malleable iron requires somewhat higher temperatures than ordinary gray iron, the sand for this work should. contain a trifle more silica than is necessary for gray iron castings. Screening and Treating Sand Given the proper sand for any particular class of work, the first operation is the proper screening and treatment of the sand, so as to enable the molder to use it in the production of castings. The manual processes in use for many years consist principally of the addition of water to the sand on the floor of the foundry, either before or after hand screening, and then the cutting over of the sand with a shovel or other tool, and allowing the sand to stand over night so that the water became thoroughly associated with the various particles by capillary attraction. This method requires considerable floor space for the storage of sand, and usually makes it necessary for the sand to be worked over by a night force after the day's product has been poured. It also involves the shoveling of the sand many times before it is placed in the mold. Such methods cannot be economical in foundries of large production which handle many tons of sand every day. The mechanical problems to be met depend very largely upon the nature of the work to be done, and whether or not it is desirable to reclaim the core sand as well as the mold sand. Different problems are encountered in handling dry sand molds. and in handling green sand molds. The most of these problems are essentially similar in that the sand is of such a nature as to render it practically impossible to divert it from one place to another by means of chutes. The sand must be picked up and carried from one place to another. It must be thoroughly cleaned. The proper amount of moisture must be added, FIG. 2-CONVEYOR UNDER FOUNDRY FLOOR FOR REMOVING USED SAND beaten thoroughly into the sand and then allowed sufficient time. for final, even, distribution throughout the mass. Equipment for Gray Iron Foundry Various mechanical methods are being used for handling sand in foundries. Fig. 1 shows the interior of a foundry engaged in casting light gray iron parts, practically all of which are being made in snap flasks of such size as to be readily handled by one man. In this particular installation molding machines are operated in pairs, about 6 feet 6 inches apart, one molder working on a drag and the other on a cope for the same job. As rapidly as molds are made they are laid out on the floor directly back of the molders, where a separate pouring crew attends to the pouring of the metal and the shaking out of the molds. In order to facilitate the prompt return of the sand in this installation, a pan or apron type conveyor runs underneath the floor of the foundry extending the entire length of the center of the molding bay. Over this conveyor, at intervals, there FIG. 3-CLOSE-UP VIEW OF USED SAND CONVEYOR SHOWING HOPPER FROM FOUNDRY FLOOR are receiving hoppers and on top of the hopper there are gratings to prevent castings and matter other than sand from getting onto the conveyor. The conveyor delivers the sand to what is called the scalping or roughing screen which removes pieces of coke and such small foreign substances which get into the sand. The screened sand then drops into an elevator and is carried to the top of the treating building where it is again screened. After screen ing, water is added and the water and sand are thoroughly milled in a centrifugal machine which produces a uniform product. The control of the water supply is in the charge of an operator who is held responsible for adding the proper amount to put the sand in ideal condition. From the milling process the sand drops into a storage bin where it is allowed to rest for a definite period in order that capillary action may take place and the moisture become thoroughly distributed through the particles of sand. From this point the sand is fed onto FIG. 4-SCALPING OR ROUGHING SCREEN FOR PRELIMINARY SCREENING OF USED SAND belt conveyors and distributed to the molders, the hopper for each molder being placed above his machine, so that he can drop the sand directly on the mold if he desires. Fig. 5 shows the gate and hopper used in the installation which has just been described. Molds May be Handled Mechanically This is by no means the only method which can be economically followed in the handling of sand. Frequently it becomes desirable to convey molds for pouring either on a conveyor, or on cars, or by other means, to a central pouring station and from there to a dumping position where the hot |