GB2256623A - Mounting a device above a helicopter rotor. - Google Patents

Abstract

A helicopter having a main sustaining rotor and internal pitch control means comprising a tubular control spindle 19 rotatable with a rotor hub 14 for controlling the pitch of rotor blades both collectively and cyclically includes attachment means for attaching a device above the main sustaining rotor and comprising a lower rigid tube 34 protruding from both ends of the control spindle 19, retention means 36, 37 for preventing rotation of the lower tube 34 with the control spindle whilst permitting relative axial movements, a first apertured universal joint 42 for attaching an upper end of the lower tube 34 to the lower end of an upper rigid tube 35 and a second apertured universal joint 43 for attaching an upper end of the upper tube 35 to mounting means for attaching the device, whereby services 33 may be routed through the tubes and universal joints to said device. The device may be an above-rotor aerial or weapons sight. <IMAGE>

Description

Description of Invention HELICOPTERS This invention relates to helicopters and particularly to helicopters adapted to support a device such as an aerial or weapons sight above a main sustaining rotor.

It is known to mount a device such as an aerial or weapons sight above a helicopter main sustaining rotor. Such installations usually have a stationary mounting shaft that extends through the rotor head, and may be also the gearbox, and which must also house necessary services such as electrical supplies to the device. This dictates the requirement for a hollow rotor drive shaft having the necessary vertical internal space to accommodate the mounting shaft and, whilst this is often practical in a rotor having an external control system (e.g. a conventional swashplate system), difficulty is experienced in installing such a mounting arrangement on a helicopter sustaining rotor having an internal control system that utilises a hollow rotor drive shaft to accommodate control system components.

A prior apparatus addressing this problem is disclosed in EP-A-0064346.

That apparatus comprises first and second ring gears located respectively above and below the rotor, the first gear being supported from helicopter structure concentrically of an axis of rotation of the sustaining rotor, support means supporting the second gear and attached device above the rotor and synchronising means comprising a pair of spaced apart gear wheels rotationally fixed to each other and supported at the end of a yoke member extending radially from a fixed attachment to the rotor hub. Aligned external transmitter/receiver units are located on the device and the first gear and are operatively connected using laser or micro-wave signal means.

This arrangement is complex and heavy and tends to be unstable in operation, and the external location of the parts and the transmitter/ receiver units makes the apparatus vulnerable to damage.

An objective of this invention is to provide a helicopter having an internal control system and attachment means for supporting a device above a sustaining rotor which overcomes the problems associated with the prior art arrangement.

Accordingly, this invention provides a helicopter having a main sustaining rotor comprising a hollow rotor hub and a plurality of radially extending rotor blades for rotation about a generally vertical axis, internal pitch control means including a tubular control spindle rotatable with the rotor hub for controlling the pitch of the rotor blades both collectively and cyclically and attachment means for attaching a device above the main sustaining rotor, the attachment means comprising a lower rigid tube protruding from both ends of the tubular control spindle, retention means at a lower end of the lower tube for preventing rotation of the lower tube with the control spindle whilst permitting relative axial movements, a first apertured universal joint for attaching an upper end of the lower tube to the lower end of an upper rigid tube and a second apertured universal joint for attaching an upper end of the upper tube to mounting means for attaching said device.

The universal joints preferably comprise Hookes joints having a radiussed aperture extending through the cruciform portion thereof.

The retention means may comprise a tubular sleeve rotationally fixed concentrically of the lower end of the lower tube and having external axial splines engaged in internal splines of a support member rotationally fixed to a stationary housing. Conveniently said stationary housing may be rotationally mounted at the lower end of said control spindle for attaching said spindle to cyclic and collective input control means.

The mounting means may comprise an annular housing located in bearings carried in a support housing rotationally fixed above the rotor hub concentrically of the axis of rotation.

The invention will now be described by way of example only and with reference to the accompanying drawings in which Figure 1 is a fragmentary sectioned view of part of a helicopter illustrating one embodiment of the invention; Figure 2 is a view taken on lines A-A of Figure 1; Figure 3 is a fragmentary sectioned view of part of Figure 1 on an enlarged scale; Figure 4 is a sectioned view taken on lines B-B of Figure 3; and Figure 5 is a fragmentary sectioned view similar to Figure 3 illustrating an operational feature of the invention.

Referring now to Figure 1, a helicopter gearbox 11 supports a main sustaining rotor 12 for rotation about a generally vertical axis 13.

Sustaining rotor 12 includes a hollow rotor hub 14 rotationally attached to a gearbox output shaft 15 supported in bearings 16, and includes a plurality of radially extending arms 17 each adapted to support a rotor blade (not shown).

The pitch of the rotor blades is controlled by an internal pitch control system generally indicated at 18 and comprising an axially extending tubular control spindle 19 which rotates with the rotor hub 14 about the axis of rotation 13. A lower end of the spindle 19 is supported by bearings 20 in a stationary housing 21 having forked connection means 22 adapted for connection to cyclic and collective input pitch control means 22a operable by the pilot.

An upper end of the spindle 19 supports radially extending spider arms 23 equal in number to the number of rotor blades and located through holes 24 in the rotor hub 14. Outer ends of the spider arms are connected by adjustable connecting rods (not shown) to pitch change means associated with each rotor blade.

Control spindle 19 is supported intermediate its upper and lower ends by support means 25 comprising a gimbal joint 26 which permits pivotal movement in any direction about control pivot point 27 to effect cyclic pitch changes of the rotor blades. The gimbal joint 26 is supported internally of a sleeve 28 rotatably supported internally of the rotor hub 14 and having external vertical splines 29 engaged by a splined ring 30 supported from the rotor hub 14 so as to permit vertical movement of the control spindle 19 to effect collective pitch changes of the rotor blades.

Torque is transmitted through the ring 30, splines 29 and gimbal joint 26 to rotate the control spindle 19.

The internal control system described above is known in the art and forms no part of this invention.

The helicopter of this invention includes attachment means generally indicated at 31 for attaching a stationary device 32 such as an aerial or a weapons sight above the sustaining rotor 12. The problems faced by the inventor were twofold, namely the provision of a stationary attachment above the rotor hub 14 and the routing of services such as electric power supplies to the device 32. Such services are depicted in the attached drawings as a bundle of cables designated by the numeral 33.

Attachment means 31 includes a lower rigid tube 34 and an upper rigid tube 35 through which the cable bundle 33 is routed to the device 32.

Lower tube 34 is located concentrically through the control spindle 19 and protrudes from both ends thereof. A lower end of lower tube 34 is rotationally fixed to retention means comprising a sleeve 36 having external axially extending splines 37 engaged by internal splines at one end of a support member 38 (Figures 1 and 2) whose other end is rotationally fixed to the stationary housing 21. Sleeve 36 is connected to cabin roof structure 39 by a flexible rubber boot 40.

Lower tube 34 is supported intermediate its ends in a plain bearing 41 located adjacent an upper end of control spindle 19 so as to permit relative rotational and axial movements.

An upper end of lower tube 34 is connected to a lower end of upper tube 35 through a first universal joint 42 immediately above the spider arms 23, and an upper end of upper tube 35 is connected through a second universal joint 43 to mounting means comprising an annular housing 44 located in bearings 45 carried in a support housing 46 rotationally fixed above the rotor hub 14 concentrically of axis 13. Annular housing 44 provides attachment for the device 32 by way, in the illustrated embodiment, of an annular flange for bolted attachment to the device 32.

Universal joints 42 and 43 are similar in construction and will be described with reference to Figures 3 and 4 which show details of the first universal joint 42. Universal joint 42 is a Hookes joint having a central cruciform 47 located respectively in diametrically opposed bearing pairs 48 and 49 secured by retainer plates 50 respectively in yokes 51 and 52. Yoke 51 is rotationally fixed to the upper end of lower tube 34 and yoke 52 is rotationally fixed to the lower end of upper tube 35.

An essential feature of the illustrated embodiment is that the cruciform 47 of both universal joints 42 and 43 has a central aperture 53 having a radiussed surface as indicated by broken line in Figure 3 to accommodate the cable bundle 33.

In operation of the helicopter of this invention, collective pitch changes of the rotor blades are accomplished by vertical movements of the control spindle 19 on splines 29, and cyclic pitch changes are accomplished by pivoting the control spindle 19 in any direction on gimbal joint 26 about pivot point 27.

The mated splined end of support 38 with the splines 37 on sleeve 36 serves both to permit relative vertical movement between control spindle 19 and lower tube 34, and to maintain lower tube 34 stationary through the connection of support 38 to non-rotating housing 21. The plain bearing 41 permits relative axial and rotational movements.

Collective pitch change inputs to the rotor blades therefore simply result in sliding movement of control spindle 19 on splines 37 and bearing 41 relative lower tube 34. However, cyclic pitch change inputs resulting from tilting of control spindle 19 about axis 27 result in a cocking motion of the universal joints 42 and 43 as illustrated in Figure 5 in respect of universal joint 42. Thus, universal joint 42 is shown cocked through an angle 54 which causes bending of the cable bundle 33 where it passes centrally through the aperture 53 in the cruciform 47 of universal joint 42.

It will be apparent that the second universal joint 43 will be cocked in the other direction and will result in a further bend of cable bundle 33.

Apart from permitting the aforementioned cocking movements, universal joint 42 retains upper shaft 35 stationary and universal joint 43 retains annular housing 44 stationary whilst support housing 46 rotates with the rotor 12 on bearings 45. Device 32 is attached to annular housing 44 and is therefore also retained stationary.

Thus, the present invention provides a helicopter having an internal control system and attachment means for attaching a device above a sustaining rotor. The attachment means includes tubular means for retaining the device stationary and for routing services to the device that is simple, lightweight and is located internally of the helicopter and therefore protected from damage.

Whilst one embodiment has been described and illustrated it will be understood that many modifications may be made without departing from the scope of the invention. For example, annular housing 44 will necessarily be adapted to suit the attachment features of the particular device 32 to be fitted in individual installations. Whilst described with reference to the mounting of a stationary device 32 above a sustaining rotor it will be understood that the attachment means could be adapted to mount an independently rotatable device above the sustaining rotor, and the mechanism for independently rotating the device could be installed in the support housing 46. Consequently, the use of the term stationary herein in relation to the device 32 is to be construed as including an independently rotatable device. Similarly, suitable forms of universal joint other than the Hookes joint of the described and illustrated embodiment could be used provided the joint can cope with the required cocking motions as herein described and has a central aperture for passage of the cable bundle 33. For example, a flexible metal bellows type joint may be used and the term universal joint is to be construed accordingly.

Claims (5)

1. A helicopter having a main sustaining rotor comprising a hollow rotor hub and a plurality of radially extending rotor blades for rotation about a generally vertical axis, internal pitch control means including a tubular control spindle rotatable with the rotor hub for controlling the pitch of the rotor blades both collectively and cyclically, and attachment means for attaching a device above the main sustaining rotor, the attachment means comprising a lower rigid tube protruding from both ends of the tubular control spindle, retention means at a lower end of the lower tube for preventing rotation of the lower tube with the control spindle whilst permitting relative axial movements, a first apertured universal joint for attaching an upper end of the lower tube to the lower end of an upper rigid tube and a second apertured universal joint for attaching an upper end of the upper tube to mounting means for attaching said device.

2. A helicopter as claimed in Claim 1, wherein said universal joints are Hookes joints having a radiussed aperture extending through the cruciform portion thereof.

3. A helicopter as claimed in Claim 1 or Claim 2 wherein said retention means comprise a tubular sleeve rotationally fixed concentrically of the lower end of said lower tube and having axial splines engaged in internal splines of a support member rotationally fixed to a stationary housing.

4. A helicopter as claimed in Claim 3, wherein said stationary housing is rotationally mounted at the lower end of said control spindle and serves for attaching said spindle to cyclic and collective input control means.

5. A helicopter as claimed in any preceding Claim, wherein said mounting means comprise an annular housing located in bearings carried in a support housing rotationally fixed above the rotor hub concentrically of the axis of rotation.