Patent Description:
The rotor blades of reaction jet or "tip jet" helicopters are powered by forcing air through nozzles at the blade tips, resulting in reactive forces powering rotation of the blades and providing lift and propulsion. Powering rotation of the rotor blades at their tips as opposed to from a central shaft overcomes issues with the torque of the central shaft causing rotation of the fuselage in an opposite direction to the rotation of the rotor. Accordingly, reaction-jet helicopters do not require an antitorque rotor (tail rotor). A considerable amount of helicopter accidents results from malfunctioning tail rotors and so obviating their requirement provides improved safety over shaft-driven helicopters. Reaction jet helicopters are also substantially less complex than central shaft helicopters as none of the machinery to operate a tail rotor is required. This reduces manufacturing cost and complexity, overall cost, and the amount of skill and training required to operate. Maintenance costs are also significantly reduced which accounts for a large proportion of the ongoing ownership costs of helicopters. Pressure-jet helicopters utilize compressed air forced out of the rotor blade nozzles to power rotation. Typically, these helicopters have an engine which powers a compressor to force air through a duct to a distribution hub where it is then distributed into and along cavities within the rotor blades and out through the nozzles.

Reaction-jet helicopters are known, yet production and usage of reaction-jet helicopters remains much lower than that of central shaft helicopters. The control of output air pressure from the compressor is managed by adjustment of the compressor blade angle, which requires constant pilot input to balance the air demand. The rotor blade nozzles are custom converging-diverging nozzles which operate at an optimal pressure ratio to maximize thrust. In some instances, the air pressure in the duct can exceed a threshold amount, resulting in excess pressure at the nozzle inlet. This reduces thrust efficiency and can induce compressor stall and back flow surge.

<CIT> discloses a rotary wing aircraft that includes a fuselage, a gas turbine engine operated air compressor within the fuselage, and a jet nozzle driven rotor assembly situated over the fuselage and including a plurality of jet nozzle driven rotor blades having air conduit means extending there through. A propulsion nozzle is located at the tip of each rotor blade for exhausting gases to produce rotation of the rotor assembly. A braking nozzle also is located at the tip of each rotor blade for exhausting gases to produce a braking action on the rotor assembly. A diverter valve is operatively associated with the propulsion and braking nozzles for alternately directing the exhausting gases into one of the nozzles. A cover is provided for closing the open end of the braking nozzle to eliminate drag on the rotor assembly when the rotor assembly is being rotated by exhausting gases through the propulsion nozzle. Other rotor blades of the prior art are known from <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>.

It is an object of the invention to obviate or mitigate the problems with reaction jet helicopters outlined above.

It is a further object of the invention to reduce the frequency of or prevent stalling in reaction jet helicopters.

According to a first aspect of the invention there is provided a rotor blade for a reaction jet helicopter, as defined in claim <NUM>.

The invention will now be described with reference to the accompanying drawings, which show one embodiment of the invention by way of example only:.

In the drawings there is shown a reaction jet helicopter according to the invention indicated generally by reference numeral <NUM>. The helicopter <NUM> has a fuselage <NUM>, engine <NUM>, tail boom <NUM> and rudder <NUM>. The propulsion system of the helicopter <NUM> has a compressor <NUM>, duct <NUM>, distributor hub <NUM>, rotor blade <NUM> and jet nozzles <NUM>. Compressor <NUM> is used to convert atmospheric-pressure air, input via a compressor inlet pipe (not shown), into compressed gas. When compressed gas from compressor <NUM> is exhausted into a lower-pressure atmosphere, a flow of gas is produced. In the preferred embodiment compressor <NUM> is a turbine-driven air compressor and is powered by a primary power source in the form of engine <NUM>. The flow of air travels through the duct <NUM> and into the rotor blade cavity <NUM> in the rotor blade <NUM>.

Referring more particularly <FIG>, there is shown a rotor blade <NUM>, the rotor blade <NUM> having a cavity <NUM> and nozzles <NUM> for the expulsion of compressed air from the rotor blade cavity <NUM> thereby resulting in rotation of the rotor blade <NUM>. The rotor blade <NUM> further has a pressure regulating arrangement indicated generally by the reference numeral <NUM>. The pressure regulating arrangement <NUM> is operable to release compressed air from the cavity <NUM>. The pressure regulating arrangement <NUM> has twenty valves <NUM> operable to release air from the blade cavity <NUM>. It will of course be appreciated that twenty valves are described with reference to the drawings however the invention is no way limited by the number of valves and any number of valves suitable to carry out the function of pressure regulation is encompassed within the scope of the invention. By valve <NUM> we mean any mechanical device capable of regulating the flow of fluid. This means that air can be released from the blade cavity <NUM> via the valves <NUM> to reduce pressure in the event of buildup of excess pressure. This reduces backflow of air towards the compressed air source <NUM> so that reduction in lift is minimized and the risk of engine stall is reduced or prevented.

The pressure regulating arrangement <NUM> has a plurality of valves <NUM>. The plurality of valves <NUM> enables pressure regulation to occur at a plurality of locations, for example, at twenty or more points along the rotor blade <NUM>. The valves <NUM> are mounted in the rotor blade <NUM>. The rotor blade <NUM> has twenty outlet apertures <NUM> The pressure regulating arrangement <NUM> has twenty outlet apertures <NUM>. This means that the outlet apertures <NUM> provide an outlet for high pressure air, via the movement of the valve, thereby reducing choke. The outlet apertures <NUM> are in fluid communication with the valves <NUM> via one or more pathways indicated generally by the reference numeral <NUM>. In this embodiment, each outlet aperture <NUM> is in fluid communication with a corresponding valve <NUM>. In this embodiment, adjacent outlet apertures are in a V-shape, as illustrated in <FIG> and <FIG>. The outlet apertures <NUM> are located on the rotor blade <NUM>, most preferably on the upper surface. Orientation of the outlet apertures <NUM> relative to the surface of rotor blade <NUM> accelerates flow over the upper surface of rotor blade <NUM> towards the trailing edge of the rotor blade <NUM>. The outlet apertures <NUM> are located at any distance between the leading edge and trailing edge of the rotor blade <NUM>. The outlet apertures <NUM> are located at or about the leading edge of the rotor blade <NUM>. The outlet apertures <NUM> are located at a distance of at least <NUM>% to at least <NUM>% of the total distance from the leading edge to the trailing edge of the rotor blade <NUM>. The outlet apertures <NUM> are integrated into inserts mounted on the rotor blade <NUM>. The pressure regulating arrangement has one or more plenum chambers <NUM>. The one or more pathways <NUM> have a plenum chamber <NUM>. Each pathway <NUM> has a plenum chamber <NUM>. Each plenum chamber <NUM> equalizes the air pressure supplied to an individual outlet aperture <NUM> along the rotor blade <NUM> upper surface. The one or more plenum chambers <NUM> are in fluid communication with the outlet apertures <NUM>. Each plenum chamber <NUM> is in fluid communication with a corresponding outlet aperture <NUM>.

Each plenum chamber <NUM> is in fluid communication with a corresponding valve <NUM>. The outlet apertures <NUM> have an outlet channel <NUM>. The pressure regulating pathways <NUM> have an outlet channel <NUM> in fluid communication with the plenum chamber <NUM> and the outlet aperture <NUM>. The valves <NUM> having a closed configuration and an open configuration. The valves <NUM> have an inlet aperture <NUM> and a valve body for releasably blocking the inlet aperture <NUM> and releasably blocking the flow to the leading edge outlet apertures <NUM>. The valves <NUM> have a shaft <NUM> sized to pass through the inlet aperture <NUM>. The valves <NUM> have a head <NUM> sized such that it cannot pass through the inlet aperture <NUM>. Therefore, the head <NUM> stops movement of the valves <NUM> in at least one direction. The valves <NUM> have a biasing arrangement <NUM> for biasing the valves <NUM> towards the closed configuration. The biasing arrangement <NUM> is a spring in this instance although it will be appreciated that other biasing arrangements are suitable for use with the valves. Therefore, the biasing arrangement <NUM> urges the valves <NUM> into the closed configuration, as illustrated in <FIG> and <FIG>, without manual input. In the embodiment shown, the spring <NUM> is a coiled spring <NUM>. The shaft <NUM> is connected at one end to the head <NUM>. A portion of the shaft <NUM> faces into the rotor blade cavity <NUM> at the other end. The head <NUM> is connected at one end to the shaft <NUM> and is operably engaged at the other end to the biasing arrangement <NUM>.

At least part of the valves <NUM> are formed, most preferably shaped, to be moveable by air especially high-pressure air. In this embodiment, at least part of the valves <NUM> are formed, most preferably shaped, to be moveable via direct actuation by air especially compressed air. The compressed air directly actuates movement of the valve <NUM> when the pressure in the cavity <NUM> exceeds a desirable preset value.

The pressure regulating arrangement <NUM> is configured so that the valves <NUM> are actuated at a pre-determined compressed air pressure. This enables air in the rotor blade cavity <NUM> to open the valves <NUM>, against the force of the biasing arrangement <NUM>, when the air pressure is at or above a pre-determined level. The inlet aperture <NUM> provides fluid communication between the blade cavity <NUM> and the pathways <NUM>. Therefore, the inlet aperture <NUM> allows compressed air flow to exit the rotor blade cavity <NUM> into the pathways <NUM>. The inlet aperture <NUM> is sealable by the head <NUM>. Therefore, the head <NUM> prevents air from exiting the rotor blade cavity <NUM>, which is the normal operation of the valves, when air pressure is below a pre-determined level in the rotor blade cavity <NUM>.

The valves <NUM> are adjustable to open at a range of pre-determined levels of air pressure. The valves <NUM> are manually adjustable. The valves <NUM> are manually adjustable, prior to installation, by tightening, loosening, adding, removing or replacing component parts, such as a spring or springs of the biasing arrangement <NUM>. The adjustability of the valves <NUM> enables a range of preset air pressure to open the valves <NUM>. This provides a range of preset valves to match a range of flight conditions.

The valves <NUM> are mechanically operated. The valves <NUM> are electrically operated such as a solenoid valve. The valves <NUM> are operated through a closed loop control system. The valves <NUM> are operated through a closed loop control system for various parts of flight envelope. This enables a range of air pressures to open the valves <NUM> according to the various parts of flight envelope. The valves <NUM> have one or more actuators <NUM> to actuate electrical or electronic opening and/or closing of the valves <NUM> during various parts of flight envelope. The valves <NUM> have one or more actuators <NUM> to automatically actuate electrical/electronic opening and/or closing of the valves <NUM> during various parts of flight envelope. The actuators are operably coupled to pressure sensors <NUM>.

The pressure regulating pathways <NUM> extends from the rotor blade cavity <NUM> through the body of the leading-edge spar portion and out through the upper surface of the leading-edge spar portion. The shaft <NUM> is formed to move through the inlet aperture <NUM> when the valves <NUM> move between an open and closed configuration. The shaft <NUM> is coaxial or substantially coaxial with the inlet aperture <NUM>. The valves <NUM> have a seat <NUM> for engaging with the head <NUM>. Therefore, the seat <NUM> limits movement of the head <NUM> in one direction. The seat <NUM> is disposed within the inlet aperture <NUM>. The seat <NUM> further prevents the head <NUM> from passing through the inlet aperture <NUM>. The seat <NUM> has one or more engaging faces. Therefore, the engaging faces enable optimum engagement of the seat <NUM> with the head <NUM> thereby enabling the head <NUM> to seal the inlet aperture <NUM>.

The head <NUM> is shaped to engage with the seat <NUM> when the valves <NUM> are in the closed position. The engaging faces taper towards the inlet aperture <NUM>. The engaging faces of the seat <NUM> guides the head <NUM> into position when the head <NUM> is urged towards the inlet aperture <NUM>, via the biasing arrangement <NUM>, as in the closed configuration of the valves <NUM>. The head <NUM> has a tapered face shaped to correspond with the engaging face of the seat <NUM>. Therefore, in the closed configuration, the corresponding shape of the head <NUM> provides maximum engagement of the head <NUM> with the seat <NUM> and thereby provides maximum seal and prevents the head <NUM> from sliding or moving laterally.

When air pressure in the rotor blade cavity <NUM> exceeds a pre-determined level, it forces the head <NUM> away from the seat <NUM> against the force of the biasing arrangement <NUM> thereby opening the valves <NUM>, as illustrated in <FIG> and <FIG>. Opening the valves <NUM> allows compressed air to escape from the rotor blade cavity <NUM> and thereby minimizes thrust reduction and compressor stall when pressure exceeds a safe level within the rotor blade cavity <NUM>.

When the valves <NUM> are in an open position the compressed air flows from the rotor blade cavity <NUM> through the inlet aperture <NUM> into the plenum chamber <NUM> to the outlet channel <NUM> and through the outlet apertures <NUM> on the upper surface of rotor blade <NUM>. When the compressed air pressure is below the pre-determined level, the biasing arrangement <NUM> urges the head <NUM> against the seat <NUM> thereby closing valves <NUM>, as illustrated in <FIG> and <FIG>. When the valves <NUM> are in a closed position the inlet aperture <NUM> is closed and there is no air flow from the rotor blade cavity <NUM> to the pathway <NUM>.

Various modifications will be apparent to those skilled in the art. For example, the biasing means may be formed from different springs or a plurality of springs. The valves can be any type of one-way valve provided it is operable at the high-pressures of the blade cavities. The shape of the pathways can be altered and the location and number of the valves along the blade may also be altered.

In the preceding discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of the values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of the parameter, lying between the more preferred and the less preferred of the alternatives, is itself preferred to the less preferred value and also to each value lying between the less preferred value and the intermediate value.

Claim 1:
A rotor blade (<NUM>) for a reaction jet helicopter (<NUM>), the rotor blade (<NUM>) comprising a cavity (<NUM>) and one or more nozzles (<NUM>) for the expulsion of compressed air from the rotor blade cavity (<NUM>) thereby resulting in rotation of the rotor blade (<NUM>), the rotor blade (<NUM>) further comprises a pressure regulating arrangement (<NUM>), the pressure regulating arrangement (<NUM>) being operable to release compressed air from the rotor blade cavity (<NUM>), wherein the rotor blade (<NUM>) comprises one or more outlet apertures (<NUM>), wherein the pressure regulating arrangement (<NUM>) comprises one or more fluid pathways (<NUM>), characterised in that each pathway (<NUM>) comprises a plenum chamber (<NUM>), each plenum chamber (<NUM>) being configured to equalize the air pressure supplied to an individual outlet aperture (<NUM>) of the one or more outlet apertures (<NUM>) along a rotor blade upper surface.