GB2148818A

GB2148818A - Helicopter countertorque rotor drive

Info

Publication number: GB2148818A
Application number: GB08426451A
Authority: GB
Inventors: Santino Pancotti; Ivan Pergetti
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: FR2554082B1; DE3437582A1; FR2554082A1; IT1161530B; JPS60166595A; GB8426451D0; IT8368108A0

Abstract

Helicopter countertorque rotor drive (1) on which a hollow drive shaft (2) projecting from a drive box (3) houses a pitch-change control shaft (25) mounted in axially-sliding and angularly-integral manner inside the drive shaft (2); one end of the control shaft (25) projecting from the drive box (3) and being connected, in rotary manner, by means of thrust bearings (41) outside the drive shaft (2) and drive box (3), to a tubular output rod (45) on a pitch-change servocontrol (43) located inside the box (3) and housing the said control shaft (25). <IMAGE>

Description

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

On helicopter countertorque rotors, a hollow drive shaft is known to be employed, the said shaft being supported in rotary manner at one end by a casing housing drive components for transmitting rotation to the said drive shaft. The latter is fitted on its free end with a hub, usually provided with two or more variable-pitch, radial blades. On certain known types of countertorque rotors, blade pitch is controlled by a shaft extending inside and projecting from the free end of the said tubular drive shaft so as to support a plate the outer rim of which is connected to each blade by a pitchchange connecting rod.At the end opposite the one connected to the said plate, the said control shaft is connected to the said plate, the said control shaft is connected to the output of an external servocontrol designed to impart axial displacement on the control shaft, the said displacement being transmitted to the blades by means of the said connecting rods for determining the required pitch variation.

On known types of countertorque rotors, the said control shaft is usually divided into two parts, the first connected to the said servocontrol and angularly fixed, and the second turning together with the drive shaft. The said two parts are usually connected to each other by a coupling comprising a thrust bearing designed to render the said two parts axially integral, while at the same time allowing them to turn in relation to each other round their own axes.

The aforementioned known types of countertorque rotors involve a number of drawbacks, partly due to a more or less long section of the control shaft being mounted angularly fixed in relation to the casing supporting the drive shaft, and partly to the location of the said thrust bearing and the said servocontrol.

To be more precise, the said angularly-fixed section of the control shaft is usually supported inside the drive shaft by bearings the working life of which is relatively short on account of the strain they are subjected to, both circumferential, caused by the relative rotation of the said control shaft section in relation to the drive shaft, and axial, caused by axial displacement of the control shaft in relation to the drive shaft. As for the thrust bearing, this is normally located inside the said casing or drive shaft, in such an inaccessible position as to make immediate inspection impossible and routine maintenance or replacement extremely troublesome. As for the said servocontrol, this is usually connected directly to a portion of the helicopter tail, in particular, the fin, to fastening points which, besides being difficult to make, also increase the weight of the fin.

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

With this aim in view, the present invention relates to a helicopter countertorque rotor drive comprising a drive box, a tubular drive shaft projecting from and turning in relation to the said box, a rotor fitted on the free end of the said drive shaft, a pitch-change control shaft partially housed inside the said drive shaft, a servo-control for imparting pitch- change axial displacement on the said control shaft, in relation to the said drive shaft, bearing type connecting means between the said control shaft and said servocontrol, and connecting means for angularly connecting the said two shafts together, characterised by the fact that the said control shaft extends along the said drive shaft and is supported in axially-sliding and angularly-fixed manner by the said drive shaft with the aid of locating means, one end of the said control shaft projecting from the said drive shaft and said drive box and being connected with the said bearing type connecting means, and the said servo-control being tubular in shape, located inside the said box and housing the said control shaft.

The invention will now be described with reference to the attached drawing showing an axial section of one non-limiting arrangement.

Number 1 on the attached drawing indicates a helicopter countertorque rotor drive comprising a tubular drive shaft 2 projecting from a drive box or casing 3 provided with a drive 4 and fitted on its free end with the hub (not shown) of a countertorque rotor indicated as a whole by 5.

Casing 3 consists of two essentially-cup-shaped integral bodies, 6 and 7, arranged with their concave sides facing each other on opposite sides of a bevel gear 8 integral with a portion of shaft 2 inside a casing 3.

Gear 8 engages with a bevel pinion 9 on shaft 10 of drive 4. Shaft 10 penetrates inside casing 3 through a tubular appendix 11 on body 6, inside which shaft 10 is supported in rotary manner by bearings 12. Body 6 comprises a removable end cover 13 coaxial with shaft 2 and having an outer, axial, tubular appendix 14. Cover 13 is connected integral with a tubular portion 15 of body 6, the said portion supporting a rotary manner one end of shaft 2 with bearing 16 inbetween.

Casing 3 is provided with two side appendixes 17 extending outwards, one from the outer wall of body 6 and the other from tubular appendix 11, and each provided with a hole 18 for securing casing 3 to a tail portion (not shown) on the helicopter.

Body 7 is essentially a truncated cone in shape, comprising a larger end wall 20 facing body 6 and provided with a centre hole 21 aligned with a centre hole 22 through the smaller end wall 23 on the said body. Holes 21 and 22 are engaged in rotary manner, by means of bearings 24, by a centre portion of drive shaft 2.

Through drive shaft 2 extends a pitch-change control shaft 25 consisting of at least two tubular, integral, coaxial segments 26 and 27. Segment 27 is supported in axially-sliding manner by shaft 2 with the aid of locating bush 28 inside body 7 whereas segment 26 extends through body 6 and tubular appendix 14 from the latter of which it projects for engaging the top end portion of a cylindrical pin 29 integral with segment 26.

Pin 29 is engaged inside the inner ring of two thrust bearings 30 secured axially on to pin 29 by nut 31 screwed on to a threaded end section 32 of pin 29.

Pin 29 supports in rotary manner, by means of bearings 30, a bushing 33 having a tubular appendix 34 coaxial with pin 29 and located between the arms of fork 35 constituting one arm of pitchchange control rocker arm 36. Bushing 33 presents two diametrically-opposed, radial holes (not shown) each aligned with a matching hole (not shown) through a corresponding arm of fork 35.

Each pair of the said matching holes (not shown) is engaged by a respective pin 37 extending from a pad 38 connected to the relative arm of fork 35 by screw 39.

Rocker arm 36 is hinged centrally on to the end of an articulated link 40, in turn hinged, at the other end, on to an appendix 41 extending radially outwards of appendix 14.

Appendix 14 forms part of an outer tubular body 42 of a two-part servocontrol indicated as a whole by 43 and integral with cover 13. Servocontrol 43 extends inside casing 3 and is divided into two equal parts by an inner ring 44 secured to the inner surface of tubular body 42 and engaged in sliding manner by a tubular rod 45 one end of which projects from appendix 14 and is connected integral with appendix 34.

Rod 45 is fitted right through with coaxial segment 26 on shaft 25 and is connected externally, in sliding and watertight manner, to two end rings 46 on tubular body 42. Between tubular body 42 and rod 45, rings 44 and 46 define two annular-section cylinders 47 engaged by respective annular pistons 48 on rod 45.

The foregoing description clearly illustrates how, thanks to bearings 30, the whole of shaft 25 is angularly integral with shaft 2 with which it turns so as to exert relatively little strain on bushing 28, the sole function of which is to guide axial slide of shaft 25 along shaft 2.

Furthermore, locating bearings 30 outside casing 3 simplifies inspection of the coupling connection shaft 25 to servocontrol 43, such inspection being performed by simply unscrewing nut 31 for slipping bush 35 and bearings 30 off pin 29.

Claims

1. Helicopter countertorque rotor drive comprising a drive box, a tubular drive shaft projecting from and turning in relation to the said box, a rotor fitted on the free end of the said drive shaft, a pitch-change control shaft partially housed inside the said drive shaft, a servocontrol for imparting pitch-change axial displacement on the said control shaft, in relation to the said drive shaft, bearing type connecting means between the said control shaft and said servocontrol, and connecting means for anguiarly connecting the said two shafts together, characterised by the fact that the said con trol shaft extends along the said drive shaft and is supported in axially-sliding and angularly-fixed manner by the said drive shaft with the aid of lo cating means, one end of the said control shaft projecting from the said drive shaft and said drive box and being connected with the said bearing type connecting means, and the said servocontrol being tubular in shape, located inside the said box and housing the said control shaft.

2. Drive according to Claim 1, characterised by the fact that the said bearing type connecting means comprise at leng and connected to an out put on the said servocontrol.

3. Drive according to Claim 2, characterised by the fact that the said servocontrol comprises a tubular output rod extending through the servocontrol itself and fitted right through with the said control shaft; the said rod being connected at one end to the said bushing.

4. Helicopter countertorque rotor drive constructed and arranged for use and operation substantially as described herein with reference to the accompanying drawing.