Patent GB-1228875-A (GB)
IPC: B61B13/10
Filed: 1967-07-19
Abstract: 1,228,875. Controlling vehicles; vehicle wheels. EMI ELECTRONICS CANADA Ltd. 15 July, 1968 [19 July, 1967], No. 33059/67. Headings B7C and B7H. [Also in Division H5] A weld-inspection trolley for carrying a radiographic camera along the inside of a pipe comprises driving wheels 14 connected to an electric motor 15, a retrieval cable 50 anchored to the trolley for pulling the trolley backwards along the pipe, and a pair of auxiliary wheels 68 which are lowerable under the control of a backward pull on the cable 50 to lift the driving wheels 14 and allow the trolley free backward movement independently of the motor 15. The motor 15 is supplied by a saddle-shaped battery pack carried on supports 2 and is connected to the driving wheels 14 through a belt drive and worm gearing. The auxiliary wheels 68 are carried by levers 63 fixed to a shaft 62 carrying an arm 51 to which the cable 50 is secured. One end of each lever 63 is engaged with an adjustably spring-loaded latch 64 to retain the wheels 68 in a retracted position until sufficient pull is exerted by the cable to forceably release the latches and lower the wheels 68 to lift the driving wheels 14. A spring-loaded lever 70 on one driving wheel 14 engages a recocking lever 71 when the driving wheels rotate to reset the latch 64 if the pull on the cable is relaxed. Compound guiding wheels 13 at the front of the trolley each comprise a basic wheel made up of two segments 21 connected by a bar 22, and two barrel-shaped subsidiary wheels 23 rotatable about axles 24 lying in the plane of the basic wheel. The subsidiary wheels 24 allow the trolley to roll back to its lowest position in the pipe if the wheels 13 attempt to climb the pipe wall due to an obstruction or unbalance at the driving wheels 14. The radiographic camera comprises a shield 3 from which extends a flexible tube 4 to a vertically-adjustable isotope receptacle 4, and a cross-head 10 to which is attached a flexible rod for pushing a radio-active source from a position within the shield 3 to the receptacle 4. The cross-head 10 is displaceable along a slide 8 by cords 42, pulleys 43 and electric motor drive mechanism 45. A spring motor connected to the cross-head 10 provides for automatic retraction of the radio-active source into the shield 3 if the motor 15 or the motor of the mechanism 45 fails. A knocking device 72 on the trolley imparts to the pipe an acoustic signal having a sound pattern which varies with the operational state of the trolley. The signal is heard from a safe distance by an operator having a hand-held code selector and power unit which generates coded signals which are transmitted to the pipe by a hammering device attached to the outside of the pipe. A transducer on the trolley converts the signals into commands for control mechanism on the trolley. In operation, the trolley is started down the pipe by manual switch mechanism thereon and stops automatically at each weld for the operator to order exposure of an X-ray film wrapped around the weld to the radio-active source for a predetermined time. If the trolley is moving towards a blind end or it meets an obstacle or breaks down it can be recovered by means of the cable 50.