GB1361832A - Apparatus for controlling the velocity of motion of a supporting beam such as an extensible mast ladder or the like - Google Patents

Abstract

1361832 Luffing arm apparatus CARL METZ GmbH 7 July 1971 [7 July 1970] 31952/71 Heading B8H [Also in Division E1] A mobile extension ladder or other rescue apparatus with a telescopic boom, or a crane with a variable length arm, is provided with apparatus for modifying the velocity of extension, slewing or raising of the extensible arm, boom or ladder in dependence on the relationship between the tilting moment at any instant and a pre-defined tilting moment which is less than the critical tilting moment. The moment is measured by a balance 13 and when it reaches the pre-defined value an electric or other equivalent circuit (Fig. 2) provides an automatic lowering of the velocity range of at least one of the motions. In one embodiment, an extra resistor is added to the control circuit so that all motions except retraction of the ladder are slowed. When the critical moment is reached, all movements, except such retraction are prevented. Before the pre-defined moment is reached, a control pulse I 601 alone exists, and a programme transmitter 305, in the pilot control unit, remains stationary and all motions can be carried out up to their maximum velocities. When the pre-defined moment is exceeded, pulses I 601 and I 602 co-exist, and the transmitter 305 is driven to the right by a motor M, and an extra resistance is added to the circuit indicated at I 170, and hence into each control circuit except that relating to the retraction of the boom or arm (I 116). This movement is stopped by a sensing element 310 mounting a cam. The movement is reversed by a change back to I 601 alone, but continues if the change is to I 602 alone, whereupon eventually contact 304 is made, circuit I 170 is interrupted, and all control circuits except I 116 are blocked.