The present invention relates in general to rotor blades of a lift rotor. In the context of the present invention, a “lift rotor” is a rotor providing lift force to a flying vehicle, such as for instance a helicopter, or a gyrocopter. The invention relates particularly to the field of convertible vehicles that have a flying condition and a road traffic condition.
Generally, the length of a rotor blade is much longer than the width or length of the vehicle concerned. Such length translates to an amount of floor space occupied by the vehicle when standing still. In certain circumstances, it is desirable to reduce that space, for instance when being parked in a shelter or when being transported in a truck or airplane.
For rotors having two blades, it is possible to reduce the width of the overall vehicle by aligning the rotor blades with the longitudinal direction of the vehicle. If that does not suffice, it is known to remove the rotor blades, which does however require hoisting equipment and/or the need for personnel to climb on top of the vehicle.
Solutions such as described above are not suitable for convertible vehicles. By the very nature of such vehicles, it is essential that they can be converted from a flying condition to a road traffic condition in a relatively simple and quick manner, by a single person remaining standing on the floor. Further, in the road traffic condition, it is not intended that the rotor blades are left behind, hence removing the blades is not a preferred solution.
Further, in the road traffic condition, merely positioning the rotor such that the rotor blades are aligned longitudinally in opposite direction is not a suitable solution. The vehicle as a whole should, in the road traffic condition, comply with road traffic regulations, have a low centre of gravity, have a low air resistance, etc.
Said requirements can, up to a point, be met if the rotor blades are hinged to a central rotor hub, and are with respect to this central hub hinged to a mutually parallel position, i.e. in the same direction parallel to the longitudinal direction of the vehicle.
Nevertheless, for performing in flying condition, a relatively large blade length is desirable, while the vehicle body is desirably compact so that large blades would, apart from being an aerodynamic problem, pose the problem of projecting beyond the vehicles contours. Therefore, the present invention proposes to have each rotor blade be foldable.
In the following, a virtual plane defined by the chord 14 and the blade centre line 13 will be indicated as a chord plane 17. It is noted that, in operation, the rotor blade 10 will be rotating around a substantially vertical rotation axis, with the chord plane 17 directed substantially horizontally.
According to an important aspect of the present invention, the rotor blade comprises, between its proximal end and distal free end, a hinge structure having a hinge axis substantially parallel to the chord plane 17, perpendicular to the blade centre line 13. Such hinge structure allows the rotor blade to be folded about an axis substantially parallel to chord 14.
In an operational position, the rotor blade 10 is positioned at a relatively large height above ground, if only to provide sufficient ground clearing. Chord 14 will be substantially horizontal. Folding the rotor blade while being in this operational position would require a hinging action in a vertical plane, which would be difficult if not impossible for a person standing on the ground. In a vehicle according to the present invention, a rotor hub is mounted at the top of a mast positioned above the vehicle. The lower end of the mast is hinged with respect to the vehicle, so that the mast can be lowered to a substantially horizontal position. The rotation axis of the rotor hub is fixed with respect to the mast, so that, with the mast in its lowered horizontal position, the rotation axis of the rotor hub is also directed horizontally. While the mast is being lowered, the two rotor blades are held parallel to the hinge axis. After the mast has been lowered, the two rotor blades still extend substantially horizontally, but now the chord plane 17 has rotated over about 90° to a substantially vertical orientation, so that the chord 14 is directed substantially vertically.
Folding the rotor blade about said axis parallel to chord 14 now involves hinging about a substantially vertical axis, i.e. a displacement in a horizontal plane, which can easily be accomplished by a single person.
When folding the rotor blade 10, it is desired that the two blade segments can be laid parallel to each other, i.e. a hinge angle of 180° should be achieved. It is possible to use a single-axis hinge, but in such case the hinge axis must be arranged outside the aerodynamic wing contour of the blade, which is not desirable since it increases aerodynamic drag. If the hinge would be located entirely within the aerodynamic wing contour of the blade, it is not possible to hinge over 180°.
To overcome these problems, the present invention proposes that the hinge structure has at least two hinge axes arranged in parallel.
These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which:
The vehicle 100 accommodates an engine (not shown for sake of simplicity). In drive mode, the engine power is transferred to the rear wheels for propelling the vehicle as a normal car on a road. In fly mode, the engine power is transferred to the propeller 130 for providing propulsion in air.
The vehicle 100 has a mast 140, having its lower end 141 hinged to the top of the vehicle body 110, at a position close to the rear end of the vehicle body 110. At its top end 142, the mast 140 rotatably carries a lifting rotor 150 which, when rotating, provides a lifting force to the vehicle 100. While it is possible that the rotor 150 receives engine power for rotation, the rotor may also be of gyrocopter type. The rotor 150 comprises a rotor hub 151 and two rotor blades 152, 153.
The vehicle 100 further comprises an extendible tail structure 160, which includes two tail foils 161, 162 mounted to the distal end of an extendible tail boom 163. The tail boom 163 has its proximate end hinged to the mast 140, at a position close to the mast top end 142. At a position rearward from the mast 140, the tail structure 160 comprises a boom support 164, that has its lower end hinged to the vehicle body 110 and its upper end hinged to the tail boom 163.
An important aspect of the present invention concerns the design of the hinge segment 173 in each rotor blade. In the following, a hinge structure for such hinge segment will generally be indicated by reference numeral 200. An objective of the invention is to provide a hinge design such that, in the stretched condition of the rotor blade 152, 153, the blade segments 171, 172 together with the hinge segment 173 provide an aerodynamically continuous outer blade surface, without interruptions, recesses or projections that could interfere with air flow and thus increase drag and reduce efficiency.
The hinge structure 200 comprises a first blade connector 210, a central hinge element 240, and a second blade connector 270.
The central hinge element 240 has a central body 241, a first set of mutually parallel coupling flanges 242 extending away from the central body 241 in a first direction, and a second set of mutually parallel coupling flanges 243 extending away from the central body 241 in an opposite second direction. A first cylindrical hole 244 extends perpendicular through the first flanges 242, a second cylindrical hole 245 extends perpendicular through the second flanges 243. It is noted that the number of coupling flanges is not particularly relevant to the invention, and in fact a hinge with only one coupling flange per direction is also possible.
The first blade connector 210 comprises a blade attachment portion 211 and a hinge portion 212. The blade attachment portion 211 is designed to allow a first blade segment to be attached thereto; the precise shape will be designed in conjunction with the corresponding blade segment. The hinge portion 212 comprises a set of mutually parallel coupling flanges 213 attached to the attachment portion 211, either directly or through an intermediate body part. A cylindrical hole 214 extends perpendicular through the coupling flanges 213. Again, the number of coupling flanges here is not particularly relevant to the invention, and this number may again be as low as one.
The second blade connector 270 has a design comparable to, and possibly even identical to, the first blade connector 210. It comprises a blade attachment portion 271 and a hinge portion 272 with a set of mutually parallel coupling flanges 273 attached to the attachment portion 271, and a cylindrical hole 274 extending perpendicular through the coupling flanges 273.
The flanges 242, 243, 213, 273 have mutually parallel side surfaces extending perpendicular to the axes of the cylindrical holes 214, 244, 245, 275. The flanges match together, i.e. the width of the flanges 213, 273 of the blade connectors 210, 270 corresponds to the distances between the flanges 242, 243 of the central hinge element 240, and conversely the width of the flanges 242, 243 of the central hinge element 240 corresponds to the distances between the flanges 213, 273 of the blade connectors 210, 270.
In the assembled condition (
An important feature of the hinge structure 200 according to the present invention can be seen in
It should be clear that, in the extended state of the hinge, the two blade segments 171, 172 together with the hinge structure 200 define a seamless and flush upper blade surface, without interruptions. This is also illustrated schematically in
Given the fact that the hinge structure 200 has two hinge axes arranged parallel at some distance from each other, with the two blade segments 171, 172 meeting each other at a position in between those two axes, the two blade segments 171, 172 must not be made to hinge simultaneously otherwise they would interfere with each other. This is schematically illustrated in
To avoid this, the present invention provides that the end portions of the two blade segments 171, 172 facing each other, i.e. the proximal end of the distal blade segment 172 and the distal end of the proximal blade segment 171, are shaped so that one allows hinging of the other without interference, as schematically illustrated in
For hinging in the opposite direction, i.e. deploying, the hinging order should be opposite.
From the above, it follows that the two blade segments 171, 172 should be folded and deployed in a correct folding order. It is preferred that the order of folding is not left to the skills of the user, but that the hinge structure 200 is provided with safety features that ensure the correct folding order without the user having to consider.
The angular position of the first recess 311 with respect to the first hinge axle 251 is such that this recess is aligned with a first end of the lock pin 330 when the first blade connector 210 is in the extended condition. The angular position of the second recess 312 with respect to the second hinge axle 252 is such that this recess is aligned with an opposite second end of the lock pin 330 when the second blade connector 270 is in the folded condition.
When the second blade connector 270 reaches its folded condition, the second recess 312 comes into alignment with the lock pin 330. The lock pin 330 is now shifted, with its second end entering the second recess 312 to lock the second blade connector 270 against folding. This condition is illustrated in
When the first end of the lock pin 330 has completely left the first recess 311, the first blade connector 210 is free to hinge up—see
It is noted that the user only needs to take hold of the outer blade segment and push it in the folding direction. In a first hinging stage (typically for the first 90° of hinging), hinging will take place with respect to the second hinge axle 252 as active hinge, after which the first hinge axle 251 automatically becomes the active hinge in a subsequent second hinging stage. In this respect, it does not really matter whether the outer or the inner blade segment is the first to hinge with respect to the central hinge element 240.
For hinging in the opposite direction, for employing the folded blade, the user again only needs to take hold of the outer blade segment and push it in the employment direction. At first, the first hinge axle 251 automatically is the active hinge, so that the first blade connector 210 employs to its extended state—going from
It is possible that shifting the lock pin 330 requires a user action. To assist the user, the folding control arrangement 300 may comprise a bias member 340, for instance a spring, arranged in the chamber 320 or at another suitable position, exerting a bias force on the lock pin 330 for pressing the lock pin 330 towards the second hinge axle 252. Alternatively or additionally, in a preferred embodiment, the second end of the lock pin 330 has a bevelled edge, as does the second recess 312, so that exerting some force on the second blade connector 270 will force the second end of the lock pin 330 out of the second recess 312 while at the same time the first end of the lock pin 330 enters the first recess 311, and the second blade connector 270 can hinge further—going from
It is possible that the extended, deployed state of the hinge structure 200 is defined and secured by a first pin-in-hole arrangement for defining the extended position of the first blade connector 210 with respect to the central hinge element 240, and by a second pin-in-hole arrangement for defining the extended position of the second blade connector 270 with respect to the central hinge element 240, respectively. This would mean that, before the user is able to fold a blade, he would have to remove these two pins, and after deploying the blade he would need to place these pins. In a further elaboration of the present invention, such securing arrangement is not needed, in that the extended, deployed state of the hinge structure 200 is defined by stops, of which the precise design and position is not essential. Such stop may be arranged on the central hinge element, or on a blade connector, or both. A first such stop defines the extended position of the first blade connector 210 with respect to the central hinge element 240, and a second such stop defines the extended position of the second blade connector 270 with respect to the central hinge element 240. For the user, this has an advantage in that he can start folding the blade without first needing to remove a pin, and he can deploy the blade until it reaches the stop(s) without then needing to place any pin. Such pin-in-hole arrangement is not needed for keeping the blades deployed in the operative situation, because forces on the blades are such as to keep them extended automatically.
It is noted that, in an embodiment with the folding control arrangement 300, one of the above-mentioned stops can be dispensed with.
Summarizing, a foldable rotor blade comprises a hinge element defining two hinge axes arranged in parallel, and two blade segments each coupled to the hinge element for hinging with respect to a respective one of said hinge axes. The rotor blade has an extended condition in which the blade segments are substantially aligned with each other; the rotor blade has a folded condition in which each blade segment is hinged with respect to the hinge element so that the blade segments are substantially parallel to each other. The blade has a cord and said hinge axes are substantially parallel to the chord. The blade segments have upper surfaces which in the folded condition are facing each other, and which in the extended condition are flush with each other and the intermediate hinge element.
It should be clear to a person skilled in the art that the present invention is not limited to the exemplary embodiments discussed above, but that several variations and modifications are possible within the protective scope of the invention as defined in the appending claims. For instance, the inventive hinge structure can also be applied to fixed wing airplanes. Further, instead of a hinge structure 200 with blade connectors to be attached to blade segments, it is also possible that a blade connector is integrated with a blade segment, i.e. that the blade segment is provided with a hinge portion such as 212 or 272.
Even if certain features are recited in different dependent claims, the present invention also relates to an embodiment comprising these features in common. Even if certain features have been described in combination with each other, the present invention also relates to an embodiment in which one or more of these features are omitted. Features which have not been explicitly described as being essential may also be omitted. Any reference signs in a claim should not be construed as limiting the scope of that claim.
Number | Date | Country | Kind |
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1043196 | Mar 2019 | NL | national |
Filing Document | Filing Date | Country | Kind |
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PCT/NL2020/000005 | 3/18/2020 | WO | 00 |