GB1297777A - - Google Patents

Abstract

1297777 Step-by-step jacks N H AHLGREN and O TAHR 8 Dec 1969 [21 Feb 1969] 59759/69 Heading B8J A jack assembly comprises a gripper 8 for a loaded rod 15 raised by pressure fluid admitted below a piston 5 through rods 6 engaging a ball holder 7. As shown slides 3 are restrained from rising by stop bolts 1 so that balls 10 retain their illustrated position in the holder 7 holding knockout sleeve 11 of a gripper opening means away from wedges 12 urged by springs 14 into contact with the rod 15. The assembly can operate with a similar jack or with a gripper fixedly mounted in relation to the jack housing 2, the return stroke being made under the action of return spring 9 and return piston 35 when the load has been transfered, the wedges 12 sliding over the rod 15. When the loaded rod 15 is to be lowered the stop bolts 1 are removed and a friction device 16 set by tightening a set screw 17. From the position shown, when another gripper has taken over the load the rod 15 is lifted slightly causing the device 16 to lift the slides 3. The balls 10 are thus released from the sleeve 11 under the lower bevel on the slides 3 by the action of knock-out spring 13 which strikes the wedges 12 and opens the gripper 8. When the opened gripper 8 is now raised by the piston 5 and catches up with the slides 3 the balls 10 are again forced into the holder 7 by the bevelled surface, but are located below the bead on the sleeve 11, thus preventing the sleeve 11 from being returned by distance spring 23 when the sleeve 11 is clear of the knock-out spring 13. After the initial slight lift, when the gripper of the other jack starts lowering the rod 15, the device 16 returns the slides 3 to their initial position. When the lowering jack has reached its final position the opened gripper 8 is moved towards its upper extreme position, knock-in spring 36 being compressed by the wedges 12 and the balls 10 on arrival at the upper bevelled surface of the slides 3 are urged out of the holder 7 by the distance spring 23, the wedge springs 14 and the knock-in spring 36, the stroke being set by adjustment of an abutment 4. The wedges 12 are then urged against the rod 15 by the springs 14 and the knock-in spring 36. As the piston 5 continues to raise the gripper 8 the wedges 12 engage the rod 15 and take over the load from the other jack. On lowering the load the balls 10 are urged by the upper bevelled surface of the slides 3 into the holder 7 above the bead of the sleeve 11. The final stage of lowering compresses the spring 13 and returns the device to the initial position. When several jacks co-operate in lowering the load a stop device 37 arresting the return movement of the gripper 8 until the pressure has risen to a value dependent on the setting of the stop device ensures that all the jacks simultaneously come into fresh engagement.