GB761910A - Selective cam transmission - Google Patents

Abstract

761,910. Directive aerial systems. WADE, O. R. May 12, 1954, No. 13919/54. Class 40(7) [Also in Group XXIV] In a selective cam mechanism wherein a link 61 is reciprocated on rotation of a driving shaft 16, the shaft 16 is coupled to a cylindrical cam unit 14 having one or more differently-contoured continuous cam grooves around its periphery each engaged by a respective follower, and manual or power-operated selector means are provided whereby the link 61 may be releasably locked to a selected one of the followers to take up the particular movement thereof without interrupting the rotation of the driving shaft. As shown, the cylindrical cam unit 14 is rotatable in a frame 7 and has three cam grooves 18, 19, 20 disposed to give different throws. The grooves are engaged by three roller followers mounted on studs 29, 34, 39 carried by respective strip members slidable side by side in an opening in a housing 21. Surrounding the housing 21 is a sleeve 41 to which the link 61 is secured, said sleeve being formed with three notches 52, 53, 54 which are shaped as shown and co-operate with the three studs 29, 34, 39 so that the sleeve 41 may be selectively coupled to any one of the reciprocating studs by angular positioning of the housing 21, the later having for the purpose a hand lever 42 and ball detent 47. In the position shown, stud 39 is in the narrow portion of its notch 54 so that the sleeve 41 and link 61 are locked to the follower driven by the cam 20, while the 'studs 29 and 34'reciprocate idly in the wide portions of their respective notches. An additional notch 51 co-operates with a stud '24 on the housing 21 to hold the sleeve 41 in a rest position. The link 61 may oscillate a radar antenna through rack gearing, and in order to mtaintain the same central zero position in each of the three arcs of oscillation determined by the cams 18, 19, 20 the frame 7 is longitudinally slidable on its base 6 and is controlled by a compensating cam comprising a slotted arcuate segment 72 on the housing 21, said cam engaging a, roller on a stud fixed to the base 6 so that angular adjustment of the housing 21 to vary the throw of the link 61 also causes a longitudinal shift of the frame 7 compensating for the change in mid-position of the throw. The manual actuation of the housing 21 may be replaced by power-driven means operating in synchronism with the movement of other elements.