GB1216654A - Apparatus for cracking a structure - Google Patents

Abstract

1,216,654. Heating and cracking concrete and rock surfaces. A. MALET, A. WATSON and A. J. CHABOWSKI. 19 March, 1968 [19 Dec., 1966], No. 56838/66. Headings E1F and E1G. [Also in Divisions H3-5] In the event of excessive force e.g. due to explosion, on the radiating end 27, 28 of the waveguide 30 of a microwave concrete or brick cracking apparatus, the waveguide 30 is swung clear of the structure being cracked to prevent damage. The apparatus comprises two wheeled vehicles one, not shown, acting as a power pack for the other 2 which carries the magnetron 4, a traction motor and the remainder of the equipment. The vehicle 2 may be driven in forward or reverse through a clutch, pulley 48 and belt 47 or may be oscillated backwards and forwards through the clutch, crank 53, link 52 and adjustable pin 51A on wheel 51. The magnetron 4 is water cooled, the water being passed through a radiator 6 which is cooled by air from a fan 8. A thermostat switches the magnetron off should it become overheated and a regulator controls the power supplied. Microwave energy is passed from the magnetron through a system of rectangular waveguides 5, a flexible waveguide 21, a block 22, waveguide 35 to waveguide 30. Waveguide 35 can be omitted. The block 22 Fig. 4 is apertured at 34A and contains a cylinder 34 having a diametral passage therethrough. The passage contains one end of waveguide 35 and normally communicates through an aperture 22A in the block with flexible waveguide 21. The cylinder 34 is rotable about the axis 34B so that waveguides 35, 30 may occupy the position shown in chain lines. A snap-action tension spring 60 and hydraulic damper not shown controls the pivotal movement and the waveguides are arrested in a vertical position by spring biased stops 22B. A microswitch 33 actuable by the waveguide 35 switches the magnetron off as soon as the'waveguide 35 is raised. An eccentric 32 adjusts the height of the head 27, 28 above the structure being worked on. In an alternative construction waveguides 30 and 21 are pivoted together, directly and waveguide 30 is raised against the action of a dashpot on the occurrence of an explosion. The end of the waveguide 30 is inclined at an acute angle to the horizontal and microwave energy is directed downwardly through a hole in a metal plate inserted in the end. An asbestos sheet covers the hole and prevents dust &c entering the waveguide. The end of the waveguide is surrounded by a horizontal circular array of square copper gauze to prevent lateral microwave leakage. A skirt 28 of brass wires brushes the surface of the structure being cracked to prevent radiation leakage. A microswitch carried by the waveguide 30 turns off the magnetron should the head 27, 28 be excessively raised from the structure.