Page:Popular Science Monthly Volume 88.djvu/341

 How to Make a Simple, Automatic Window Closing Device

��THE object of this device is to en- able one to sleep in a room with the windows open during cold weather without the disadvantage of having a cold room in the morning. Briefly, it consists of an electro-magnetic latch which holds the window open during the night until at some predetermined hour, early in the morning, an alarm clock ope- rates a switch in the latch circuit which releases the latch and allows the win- dow to close.

The operation of this latch is as fol- lows: When a current passes through the magnet winding (Fig. 1) the arma- ture is drawn in toward the magnet which releases the hook. As the hook falls, the window no longer being sup- ported, closes. It is, of course, neces- sary to fasten a weight to the window, or remove the window weights, so that when it is not supported by the hook it will close because of its weight. When the window is closed the hook remains in the position shown in dotted lines in Fig. 1. As soon as the current ceases to flow through the magnet winding, a spring (not in the drawing) moves the armature back to its original position. When the window is again raised the top of the ring striking against the hook carries it up with it until the hook au- tomatically locks into position. The window will then remain open until a current again passes through the mag- net winding.

The construction is as follows : The yoke piece may be cut out of a piece of iron or cold rolled steel 2/2 ^ iy2 X Vi. Two pole cores of the same material about %'' in diameter are riveted to this yoke piece as shown in the drawing. The magnet spools may

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��Bo/fery Fig. 2. Diagram of connections

��be formed out of brass, or some insulat- ing material, and wound with No. 20 B. & S. gauge single cotton covered wire. About 5 oz. of this wire will be re-

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��Fig. 1. The latch, showing its operation

quired. The armature should be cut out of a piece of 1/16'' sheet iron and bent up at the top to form a bearing and at the bottom to form a support for the hook. The base, the hook, and the ring should be cut out of y^'' sheet brass. A spring must be provided to keep the ar- mature over against the adjusting screw when the magnet is not energized. A suitable .spring for this purpose may be formed by winding No. 23 B. & S. gauge phosphor-bronze wire on a rod 3/16'' in diameter. This spring may be supported on a rod between the two magnet spools. This spring support rod should be just long enough to keep the armature from coming into contact with the pole core ends when the magnet is energized.

For operating this device use an ordi- nary alarm clock, the only requirement being that it shall have an alarm winding kev which rotates as the alarm rings.

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