Patent GB-763622-A (GB)
Title: Improvements in or relating to jet-propulsion nozzles
Inventor: BRITT JACK
IPC: F02K1/12
Filed: 1954-01-01
Abstract: 763,622. Jet propulsion nozzles. ROLLSROYCE, Ltd. Jan. 3, 1955 [Jan. 1, 1954], No. 88/54. Class 110 (3). A variable-area jet propulsion nozzle comprises a fixed annular nozzle which defines the maximum area of the nozzle, a plurality of overlapping nozzle elements arranged around the outside of the fixed nozzle and movable axially relative thereto by a motor between a retracted and extended position in which the elements project partly beyond the end of the fixed nozzle and cam means, operative on the nozzle elements to cause the downstream edges of the elements to move inwards when the elements are extended, including tracks on the elements and a load-carrying structure and roller elements cooperating with the tracks. The variable-area propelling nozzle, Figs. 2 and 3, comprises a jet pipe 10 having at its outlet a part-spherical ring 10a defining the maximum possible outlet area of the nozzle surrounded by a plurality of overlapping alternately arranged main nozzle elements 13, Fig. 2, and auxiliary nozzle elements 23. Each main nozzle element 13 comprises a rectangular sheet metal wall 14 reinforced by a pair of sheet metal ribs 16 to each side of which are welded racks 17. An outer sheet metal wall 15 is pivoted to the wall 14 by a pivot 18a and a link 19. Rams 24 pivoted to brackets 25 mounted on a box girder 26 fixed to the outer casing 11 are provided to move each of the nozzle elements 13 axially. Each auxiliary nozzle element 23, Fig. 6, comprises a sheet metal wall 28 reinforced by a box-shaped rib 30 to which is pivoted the outer sheet metal wall 29. Flanges 37, 39 formed on the wall 29 engage flanges 38, 40 of the wall 14 so that when the main nozzle elements move axially the auxiliary nozzle elements move with them. The inner walls 14, 28 of the nozzle elements 13, 23 slide on a braided metal strip 41 located in a channel ring 42 welded to the jet pipe through another channel ring 43. Associated with each nozzle element 13, there is a bobbin 44 formed at its ends with pinions 44a. These pinions mesh with the racks 17 and a pair of racks 46 mounted on a rack carrier 45. Each rack carrier is pivoted through lugs 48 and brackets 49 on the box girder 26 and comprises a pair of limbs 47 of channel section sheet metal construction. The bobbins 44 run in the channel formed be. tween the limbs and the racks 46 are secured at each side of the base of the channel. The ribs 16 fit neatly in the mouth of this channel and ribs 30 fit neatly in the space between the downstream ends of adjacent rack carriers so that the nozzle elements are restrained against circumferential movement. The downstream ends of the rack carriers are encircled by a continuous thick metal band 52 which is attached to the rack carriers by setscrews 55 passing through lugs attached to the rack carrier 45 and band 52 respectively. The racks 46 are inclined inwards towards the jet pipe axis so that rearward movement of the nozzle elements 13, 23 causes the downstream edges to move inwards and thus reduce the effective outlet area of the nozzle. The pinions 44a are arranged to be just upstream of the centre of pressure of the gases on the walls 14, 28 so that these walls are held in contact with the sealing ring 41. To assist in assembly of the nozzle, strips 51 forming part of the nozzle elements have downstream-projecting hooked tabs 56, 57, 61 which engage the upstream edge of the band 52. The tabs 56, 61 are also used to retain bowed-springs 59, 62 which urge the outer walls 15, 29 outwardly with respect to the band 52 so that contact is maintained between the pinions 44a and the racks 17, 46 when there are no gas loads on the nozzle elements. An annular spring metal seal 63 is carried on the inner surface of the casing 11 so as to constrain any cooling air flowing through the space 12 to pass out from the space between the inner and outer walls of the nozzle elements.