GB2148817A

GB2148817A - Helicopter countertorque rotor assembly

Info

Publication number: GB2148817A
Application number: GB08426450A
Authority: GB
Inventors: Emilio Pariani
Original assignee: Costruzioni Aeronautiche Giovanni Augusta SpA
Current assignee: Agusta SpA
Priority date: 1983-10-26
Filing date: 1984-10-19
Publication date: 1985-06-05
Also published as: DE3437396A1; JPS60166594A; FR2554080A1; IT1161529B; GB8426450D0; IT8368107A0

Abstract

A fixed tubular rod (9), inside which extends part of a drive shaft (7) integral with a rotor (50), supports in sliding manner a slide (12) supporting in rotary manner a ring (38) turned by the drive shaft (7) by means of calipers (58) and connected with pitch-change connecting rods (55); axial displacement of the said slide (12) being controlled by a servocontrol (27). <IMAGE>

Description

SPECIFICATION Helicopter countertorque rotor assembly The present invention relates to a helicopter countertorque rotor.

Helicopter countertorque rotor assemblies are known on which a drive shaft, turning round its own axis and projecting from a drive box, is fitted on its free end with a rotor having its blades connected to a pitch-change device.

The latter normally comprises an annular plate connected to the said drive shaft by means of a splined coupling which, while making the said plate and drive shaft angularly intergral, at the same time enables the plate to slide axially a given distance along the drive shaft.

Axial slide of the said plate is controlled by a servo-control and converted into corresponding pitch variations of the rotor blades by means of connecting rods connected, on one side, to the said plate and, on the other, to a respective blade.

A major drawback on the aforementioned countertorque rotor assembly is its relatively high maintenance cost, mainly due to the fact that, during operation, the drive shaft tends to bend under the strain imparted on it by the rotor. Any deflection on the drive shaft is automatically accompanied by deflection on the splined drive section of the said plate, as well as by severe wear on the splined coupling connecting the plate to the drive shaft.

The aim of the present invention is to provide a helicopter countertorque rotor assembly involving none of the aforementioned drawbacks.

With this aim in view, the present invention relates to a helicopter countertorque rotor assembly comprising a drive box, a rotary drive shaft projecting from the said box, a rotor fitted on to an end section of the said shaft, a pitch-change servocontrol and drive means for connecting an output on the said servocontrol to each blade on the said rotor, characterised by the fact that the said drive means comprise a fixed support extending along a mid portion of the said shaft, a slide moved along the said fixed support by the said servocontrol, a ring coaxial with the said drive shaft and assembled on the said slide so as to turn round its own axis, while at the same time being axially fixed in relation to the slide, caliper connecting means between the said drive shaft and the said ring for connecting them angularly integral with each other, and a pitch-change connecting rod extending between the said ring and each said blade.

A non-limiting arrangement of the present invention will now be described with reference to the attached drawings in which: Figure 1 shows an axial section, with parts removed for clarity, of a first portion of a helicopter countertorque rotor assembly according to the present invention; Figure 2 shows a side elevation of a second portion of the Figure 1 assembly; Figure 3 shows a section along line Ill-Ill in Figure 1; Figure 4 shows a section along line IV-IV in Figure 1.

Number 1 in Figures 1 and 2 indicates a helicopter countertorque rotor assembly comprising an essentially cylindrical drive box 2 fitted, at one end, with a connecting plate 3 for connecting it to a fixed support (not shown) and closed off, at the other end, by a cover 4 made integral with box 2 by screws 5.

Cover 4 presents a centre through hole 6 through which extends, in watertight manner, drive shaft 7. The latter projects from box 2 by which it is supported in rotary manner by means of bearings 8 only one of which is shown in Figure 1.

Part of shaft 7 outside box 2 extends inside tubular rod 9 integral with cover 4 and coaxial with both shaft 7 and hole 6. Rod 9 presents a cylindrical outer surface on which are fitted two sliding bushes, 10 and 11, integral with the inner surface of an essentially cylindrical sleeve 12 coaxial with rod 9 and shaft 7 and forming a slide mounted so as to slide along rod 9.

Any angular displacement of sleeve 12 in relation to rod 9 is arrested by a rocker arm 13, shown in detail in Figures 2 and 3, having two cylindrical, coaxial, centre recesses 14 engaged by opposite ends of hinge pin 15. A centre portion of pin 15 engages, in rotary manner, a through hole 16 in one end of link 17, the other end of which is hinged by pin 18 to a side ear 19 on box 2. Rocker arm 13 presents, on one end, a fork 20 the arms of which present respective through holes 21 coaxial with each other and engaged by pin 22 hinging rocker arm 13 to one end of connecting rod 23. The other end of the latter is hinged by pin 24 to the end of lever 25 fitted on to shaft 26, which constitutes the output shaft of pitch-change servocontrol 27 and is supported in rotary manner by ear 28 integral with plate 3.

On the opposite side to fork 20, rocker arm 13 forms a second fork 29 having its arms 30 round sleeve 12 and each having a through hole 31 coaxial with the other hole 31 and with a respective blind axial hole 32 on the end of a respective appendix 33 extending radially outwards from and integral with sleeve 12. Each pair of holes 31 and 32 is engaged by a pin 34 having an end plate 35 secured to its respective arm 30 by eccentric screw 36. On the side of appendixes 33 facing box 2, sleeve 12 is blended to the base of rod 9 by means of a deformable bellows 37, whereas, on the other side, it extends inside a ring 38 coaxial with drive shaft 7 and supported in rotary manner by sleeve 12 with the aid of two bearings 39 between sleeve 12 and a tubular body 40 formed inside ring 39.

The inner ring of bearings 39 is secured axially against a shoulder of sleeve 12 by a ring nut 41 mating with a threaded section of sleeve 12. The outer ring of bearings 39, on the other hand, is secured axially against an annular shoulder inside tubular body 40 by an externally-threaded ring nut 42 mating with a threaded section inside tubular body 40.

The end of tubular body 40, opposite the end facing box 2, projects from ring 38 and is blended, by a flexible, tubular cover bellows 43, to one end of ring 44 fitted on to shaft 7 contacting an annular shoulder 45 of the latter outside the free end of rod 9.

From the end of ring 44 opposite the end facing ring 38, a tubular, axial appendix 45 extends integral with ring 44 and comprising, on its free end, an internally-splined section 46 connected angularly to an externally-splined section 47 on shaft 7.

Splined section 47 extends beyond the free end of splined section 46 on appendix 45 and forms part of a splined coupling 48 connecting shaft 7 and hub 49 on rotor 50, the latter being secured axially against the end of appendix 45 by ring nut 51 fitted on to a threaded end section of shaft 7.

As shown, particularly in Figure 4, from the outer rim of ring 38 extend radially outwards two pairs of diametrically- opposed forks, 52 and 53, arranged alternately and evenly spaced round the axis of shaft 7.

Each fork 52 is connected by pin 54 to one end of pitch-change connecting rod 55, the other end of which is connected, in a manner not shown, to a respective blade 56 on rotor 50 for changing its pitch.

Each fork 53, on the other hand, is connected by pin 57 to one end of articulated caliper 58, the other end of which is connected by pin 59 to fork 60 extending outwards from the outer rim of ring 44.

The foregoing description clearly illustrates how, on assembly 1, any direct connection has been dispensed with between parts called upon to turn and, at the same time, slide axially in relation to one another. Fixed rod 9 inserted between shaft 7 and sleeve 12, in fact, only allows the latter to be slid axially by the servocontrol along the axis of shaft 7, taking ring 38 with it. The latter is turned in relation to sleeve 12 by shaft 7, with the aid of ring 44 and calipers 58, whereas it is axially fixed in relation to sleeve 12 so as to move with it along the axis of shaft 7 and so impart the required pitch variation on blades 56 via connecting rods 55.

Claims

1. Helicopter countertorque rotor assembly comprising a drive box, a rotary drive shaft projecting from the said box, a rotor fitted on to an end section of the said shaft, a pitch-change servocontrol and drive means for connecting an output on the said servocontrol to each blade on the said rotor, characterised by the fact that the said drive means comprise a fixed support extending along a mid portion of the said shaft, a slide moved along the said fixed support by the said servocontrol, a ring coaxial with the said drive shaft and assembled on the said slide so as to turn round its own axis while at the same time being axially fixed in relation to the said slide, caliper connecting means between the said drive shaft and the said ring for connecting them angularly integral with each other, and a pitch-change connecting rod extending between the said ring and each said blade.

2. Assembly according to Claim 1, characterised by the fact that the said fixed support comprises a tubular rod extending from and integral with the said box; the said mid portion of the said drive shaft extending inside and being coaxial with the said tubular shaft.

3. Assembly according to Claim 1 or 2, characterised by the fact that the said slide comprises a sleeve coaxial with the said drive shaft and assembled in sliding manner along the said fixed sup port; the said sleeve being connected to the output of the said servocontrol by a kinematic chain comprising a rocker arm with means for locking the said sleeve angularly in relation to the said fixed support.

4. Assembly according to Claim 3, characterised by the fact that the said locking means comprise a fork supported on the said rocker arm and arranged with its arms on opposite sides of the said sleeve, and on a pin supported on each said arm and engaging in rotary manner a respective radial hole on the said sleeve.

5. Helicopter countertorque rotor assembly constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawings.