The Sprindles Forming The Threads Of The Workpieces Start To Turn One After The Other

In the construction shown in Fig.6.65 the mandrels start to unscrew from the workplece one after the other with the use of spring-actuated clutch.

Operation: following solidification of the workpiece, the mold opens, the built-in electric motor 21 switched together with the gear drive by a limit switch. The motor with bevel gears 23 and 15 starts up the central gear 13 wedged on shaft 8, which turns the gears 12 engaged with it. These gears are connected through spring 10 with the lower end of the thread-forming spindle 25.The number of coils of spring 10 varies at each operating position (in case of many operating positions at each second position). When gear 12 starts to move, it does not carry along the spindle 25 because it begins to turn only when the spring is tensioned. Since however each spring has a different number of coils, the spindles start to turn one after the other. The stripper plate 28 is lifted by springs 6, consequently when mandrels 25 become unscrewed from the piece, the workpieces are lifted axially out of their nests. Workpieces are prevented from turning together with the spindle, by contact with the residual material in the runners. When the workpieces are completely unscrewed from the thread, they are still hanging on the residual material in the sprue and runners, and fall into the box of the machine. The springs become slack again and the mold is ready for the next cycle. It is advisable to wind up the springs directly on the spindle 25, because in this case the recoil will be the same at each operating position.

It is advisable to drive the thread-forming mandrels with an electric motor if the workpiece is ided with a long thread. If there are more than 46 nests in an mold, then driving the mandrels requires considerable torque, i. e a motor with relatively high power.

Advantage: a motor of lower power is sufficient, and the mold is cheaper and the less space is required

Should the residual material in the runners fail to secure the workpieces against turning, the stripper plate 28 is provided with knurls or other small braking notches.