the second motor 9 is connected to a second wiring board 21 as shown in fig4 the brush board 18 of the first motor 8 and the brush board 20 of the second motor 9 are connected to each other through an electronic control circuit of the first wiring board 19 and the second wiring board 21 connected to each other the first motor gear 14 for decreasing the rotational speed of the first motor 8 is provided with an operation cam 22 and the first wiring board 19 is connected to a first motor brake sensor 23 which are disposed in a gear box of the motor gear 14 so that the operation cam 22 is engaged with the first motor brake sensor 23 by the rotation of the motor gear 14 the motor gear 15 for decreasing the rotational speed of the second motor 9 is provided with an operation cam 25 and the second wiring board 21 is connected to a brake sensor 26 which is disposed in a gear box of the motor gear 15 so that the operation cam 25 is engaged with the brake sensor 26 by the rotation of the motor gear 15 as shown in fig3 the first wiring board 19 of the electronic control circuit is connected to the brush board 18 of the first motor 8 and the brake sensor 23 disposed in the gear box of the motor gear 14 and has a normal rotation relay a a reverse rotation relay b and a time relay c the normal rotation relay a of the first wiring board 19 is connected to a signal generating circuit 30 and the brush board 18.