... and easy assembly 4.stable operation 5. rich experience SJ series worm ball screw or screw jack•SJ screw jacks are ... without braking device when screw stops traveling. 8. Accessory parts: Motor, hand wheel, rubber bellows, steel cover, frequency inverter and brake ... : Metallurgy, construction, irrigation, chemical industry, healthecare and so on. SJ series worm ball screw or screw jack