Patent GB-989516-A (GB)
Title: Control means for use in building construction
Inventor: DOUGLAS JOHN ROBERT TOMKYS
IPC: E04B1/35
Filed: 1962-11-20
Abstract: 989,516. Rotary hydraulic motors. BRITISH LIFT SLAB Ltd. Jan. 29, 1964 [Nov. 29, 1962], No. 43796/62. Heading F1F. [Also in Division B8] A plurality of devices are used for raising at least one floor slab, formed around a number of vertical columns, to the position the slab is to occupy in a finished structure, and each device comprises a pair of nuts 1 drivable through a chain 2 by an hydraulic motor 3. Control means for the motor 3 consists of a valve 4 operable by a differential controller 5 which is coupled to the motor 3 and to a synchronous electric motor 6. The nuts 1, the motors 3, 6 and the controller 5 constitute a lifting unit, and a plurality of the units are mounted on a slab to be lifted, adjacent the columns respectively. Pairs of screwthreaded members 7 attached at their upper ends to the columns coact with the pairs of nuts 1. The synchronous motor 6 drives a pinion 9 having a screw-thread central bore and the hydraulic motor 3 drives a pinion 11 which is engaged by a splined portion of a spindle 12. The spindle also has a screw-thread portion engageable with the screw-thread bore of the pinion 9. The spindle, which is vertically movable, is connected to a lever 15 for controlling a switch 16 in the circuit of the motor 6. The lower end of the spindle is connected to a lever 13 which controls a valve 4 for the hydraulic motor 3. The synchronous motors 6 of all the lifting units are connected in series with a common generator 17 drivable by a variable speed driving unit 18. The motors 3 are connected to a common pump. In use, the pump is set in motion but, assuming all the valves 4 are closed, no rotation of the nuts 1 occurs. The motors 6 are next energized by starting the generator 17 and, since the nuts 1 are stationary, the pinions 11 are stationary. The pinions 9 are rotated by the motors 6 and the spindles 12 are displaced to open the valves 4 thus causing rotation of the nuts 1 by the motors 3. While the generator 17 is accelerated, the nuts 1 lag behind the motors 6 but when the motors 6 reach a steady speed, the supply of fluid to the motors 3 is such that they will be rotated slightly faster than the motors 6, owing to displacement of the spindles 12. The lag is thus reduced until the total angular displacements of the nuts 1 and the associated motor 6 are the same. The angular position of the shafts of the synchronous motors 6 provides a continuously advancing datum position which is the same for each motor. In the event of one of the pairs of nuts 1 lagging behind or leading the motors 6 by a predetermined distance sufficient for the associated switch 16 to be opened by the lever 15, the supply from the generator 17 is terminated so that all the motors 6 are stopped. The spindles 12 are then displaced to close all the valves 4 and stop all the motors 3 so that further operation of the lifting units is prevented until the fault is corrected. Alternative lifting means (not shown) may comprise a number of hydraulic jacks controlled by a pair of series circuits each including a plurality of normally open switches operable by the jacks. The switches of the first circuit are closed only when the jacks are fully extended and the switches of the second circuit are closed only when the jacks are fully retracted. The first circuit controls a normally shut solenoid valve in the line supplying fluid for retracting the jacks. Similarly, the second circuit controls a second solenoid valve in the line supplying fluid for extending the jacks. Manually operated switches are also provided, the arrangement being such that when one of the manual switches is operated, e.g. to extend the jacks, the second solenoid valve is not opened unless all the switches of the second circuit are closed, that is unless all the jacks have been fully retracted.