GB577933A - An improved means for the protection of aerodromes, aircraft landing fields and other situations - Google Patents

Abstract

577,933. Fortifications. PICKETT, F. N., and HAMILTON, D. St. A. July 12, 1940, No. 11615. [Class 20 (i)] Means for use in the protection of aerodromes, roads, and like situations comprises a pit sunk into the ground and a hollow head normally resting with its upper surface level with the ground, so that vehicles may pass over it, and adapted to be raised by means of hydraulic, air or screw pressure so as to form a combined fort and an obstruction against the landing of aircraft. In one form a pit is sunk into the ground and is lined with a casing 1 of concrete and an upper sleeve 11 forming a recess to receive the projecting edge of the upper end 3 of an inverted hollow hood with open bottom. The hollow hood is adapted to be raised and lowered by a jack 7 which may be actuated pneumatically by the use of compressed air bottles adapted to be positioned around the jack, and is provided with firing apertures 4 disposed around its surface and a guide roller 12 to engage a groove 13 in the lining. Pedestals 9 supporting firing platforms 5 are in turn supported by the concrete base 8, and a pump 19 is provided to pump out any water which may collect in the base of the cavity. Ventilation apertures 24, 26 are provided in the hood and sleeve respectively and drainage grooves 23 are provided in the sleeve. In a modification, Fig. 6, the raisable hood is counterbalanced by a weight 32 which is adapted to constitute the firing platform and which is attached to the hood by means of a rope over a pulley, so that as. the hood falls the platform rises into a position within the hood. The pulley is supported by one of three uprights 36 projecting upwardly from the base; and which form guides for the hood and counterbalance weight. Manholes 39 are provided to give access to the hood.