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 



Press-buffon. 



la/ch 



C/oc/r 



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- 



Wincfoiv jojh 



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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