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A Winder for Small Inductances
739
As illustrated this result is obtained by the ratio of the gears A and B. The gear A being on the same shaft with the coil, its rotating is the same as that of the coil, while the gear B being larger than the gear A, turns more
BRASS BUSHING PRESS FIT IN CAM
PITCH SPIRAL THROUGH 180°
FIG. 5
A working sketch of the cam, the most important unit of the entire device
slowly. Fastened to the gear B is a cam which operates the nozzle C. The shape of this cam is very important. The rate of travel of the nozzle should be constant with practically no time-interval at the end of the travel when the direction is reversed. Therefore, the ideal shape of the cam is that of a straight spiral through 180° and the reverse spiral through the remaining 180°. There is absolutely ho way that this cam can be cut except on an end milling machine with a double motion. Any up-to-date machine shop has this equipment and the actual cutting of the cam is a very short process after the milling machine is set up. Fig. 5 is a working sketch of this cam. Its lateral reciprocating action is plainly illustrated in Fig. 6.
THE WINDING MACHINE
OF COURSE, it is absolutely necessary that there is no end play in the mechanism. The shaft on which the coil is wound must run absolutely true in order to prevent
— GEAR AND CAM BOTH /'PRESS FIT ON BUSHING
GUIDESft
ROD FREE TO TURN ,' AS COIL BUILDS UP
O rfWWWWWW J
SPRING TO KEEP ROD AGAINST FACE OF CAM
LATERAL MOVEMENT
FIG. 6
Illustrates the function of the cam and nozzle
the wire from slipping on the edges of the coil while it is being wound. D in Fig. 2 represents a counter which counts the number of turns being wound. This is likewise almost a necessitv because it is verv casv to make an
error in attempting to count and wind by hand. The writer used a motor with a worm drive with a gear on the main shaft, but an> form of drive would serve the purpose.
In using the machine, the wire is first fastened on the end of the shaft and allowed to wind twenty or thirty turns on the bushing D which is clamped on the end of the shaft \vith a nut. At this point the machine is stopped and a piece of adhesive tape f of an inch wide is laid across the bushing with the sticky side up as in Fig. 7. Then the counter is set at zero and the desired number
FIG. 7 Preparing the coil for binding with adhesive tape
of turns are wound on. After this, the adhesive tape is brought up over the outer edge of the coil to hold the last turn and the bushing with the coil on it is removed from the shaft. After driving the bushing out of the coil the first twenty or thirty turns are removed from the inside and the finished coil is dipped in a mixture of acetone and celluloid.
By varying the shape of the cam which con
COIL
ROLLER
FIG. 8
A detail showing how the roller with spring tension keeps the layers in place