Fluid reaction surfaces (i.e. – impellers) – Working member foldable – pivotable or collapsible to non-use... – Member movement in rotation plane
Reexamination Certificate
2001-06-07
2002-09-10
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Working member foldable, pivotable or collapsible to non-use...
Member movement in rotation plane
C416S21000A, C416S21000A
Reexamination Certificate
active
06447249
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a rotorcraft rotor in which the blades are, at least some of them, folding blades and equipped with an electric deicing or anti-icing device, entailing the routing of electrical energy to the blades from a collector placed at the centre of the hub of the rotor. This routing of electrical energy is performed using an electrical connection installation consisting essentially of an electric wiring harness and comprising, for each blade, at least one electric connecting cable connected to a member for connecting the corresponding blade to the hub of the rotor and equipped with connectors at its ends in order to make an electrical connection between the collector and the blade.
More specifically, the invention relates to a rotorcraft rotor, particularly a helicopter main rotor, of the type comprising:
a hub intended to be driven in rotation about an axis of the hub which is the axis of rotation of the rotor,
at least three blades, each of which is connected to the hub by a connecting member which is substantially radial with respect to the axis of rotation, and the outer radial end of which is shaped as a clevis in which the corresponding blade has its root retained by two blade pins each passing through aligned bores in the clevis and the blade root, the two blade pins being substantially mutually parallel, at least one blade being foldable on one side of the rotorcraft and having at least one removable blade pin, so that withdrawal of said removable blade pin from the blade root and from the clevis of the connecting member allows the blade to be pivoted about the other blade pin, and
an electrical connection installation comprising, for each blade, at least one electrical connecting cable connecting a first connector, carried by the hub and powered by at least one supply conductor, to a second connector mounted on the blade and connected to at least one electric conductor of an electric device for deicing or preventing the icing of said blade.
Rotorcraft rotors of this type are known, in particular, from EP 0 754 623 and FR 2 781 198.
For at least one folding blade of a rotor according to EP 0 754 623, the connecting cable comprises a first length, radially towards the outside, arranged as an overhead hook stretching from this blade to the corresponding connecting member and connecting the second connector on this blade to a first end, in an outer radial position, of a second length of connecting cable held substantially radially on this connecting member.
This overhead hook of the connecting cable has a rounded cross section, possibly a screened structure, and is connected to a plug of the second connector, which plug connects to a socket of this second connector, this socket being fixed to the blade and connected to the deicing conductor for this blade.
When a blade is folded, the pivotings of the blade root in the outer radial clevis of the corresponding connecting member may introduce damaging tension into the overhead hook and the second length of the connecting cable and into the second connector and/or this overhead hook may oppose the full folding of the blade.
To remedy this drawback, EP 0 754 623 makes provision for the plug of the second connector, on the corresponding end of the overhead hook of the connecting cable, to connect removably to the socket of the second connector, which is fixed to the blade. Giving this overhead hook a long enough length to allow the full folding of the blade without disconnecting the plug and socket of this connector is not advisable because an overhead hook of such a length would be subjected to significant forces and would undergo fairly high-amplitude whiplash movements encouraging it to catch unintentionally on nearby components, such as pendular blade root antivibrators or drag dampers, on a rotating rotor, the corresponding blade then making its angular excursions in pitch, flapping and drag.
If the blades are folded manually, it is therefore not possible to avoid manual disconnections and connections between the plug and the socket of the second connector, the former before folding and the latter after returning a blade to a flight configuration, if the advantages afforded by the other characteristics of the connection installation described in EP 0 754 623 are to be maintained.
By contrast, on a rotor whose blades can be folded “automatically”, using actuators mounted on the connecting members, EP 0 754 623 proposes for the overhead hook between the blade and the connecting member to extend from the second connector, on the blade, to a rotating part of a rotary coupling, of which a stationary part, on the connecting member, is connected to the second length of cable held thereon, the rotating part of the rotary coupling being mounted to rotate coaxially with the pivoting connection between the blade and the connecting member so that the automatic foldings and unfoldings of the blade can be brought about without disconnections or connections having to be performed at either of the two connectors of the installation.
FR 2 781 198 proposes improvements to folding-blade rotors with the electric deicing installation according to EP 0 754 623, particularly in order to diminish the stresses and/or displacements of the connecting cable in its overhead hook length connecting the connecting member to the second connector on the blade when the rotor is turning and during operations of folding the blades back and forth.
To this end, according to FR 2 781 198, part of this overhead hook is held in at least one retaining member mounted in the substantially axial continuation of the folding axis. This technical step affords the following advantages: it is no longer necessary for the connection between the overhead hook and the deicing device to be disconnected at the second connector before the blade is folded and when this overhead hook is of a relatively short length. The retaining member thus prevents displacements of this overhead hook on each side of the folding axis, during the folding or unfolding of the blade, thus avoiding prejudicial twisting of this length of the connecting cable, provided that this overhead hook is long enough, and in order for this overhead hook of the connecting cable to itself adopt the position in which it is mechanically stressed the least, when a blade is being folded or unfolded, the retaining member can be mounted so that it swivels freely coaxially on the axis of folding.
Whether this rotating member is fixed or whether it swivels on the folding axis, it may be arranged as a fork in which an elongate part of this overhead hook, with a cross section substantially in the shape of a flattened rectangle, is engaged and held by at least one elastic tab.
However, the improvements proposed in FR 2 781 198 are not enough to avoid disconnections and connections between the connecting cable and the second connector on the blade during manual foldings and unfoldings of the blades when the foldings are performed using a manual folding device as described in EP 0 888 964.
What happens is that, to fold manually a folding blade, the two blade pins of which are removable, the device according to EP 0 888 964 comprises a removable spacer piece which spaces the root of the folding blade away from the corresponding connecting member, the spacer piece comprising a journal through which a first bore passes and a clevis with a second bore, the spacer piece being, once a first blade pin has been withdrawn and the blade has been pivoted with respect to the connecting member and about the second blade pin, able to be mounted in terms of rotation on the connecting member by the retaining of the spacer piece journal in the clevis of the connecting member using a pin (tooling) that can be engaged in the first spacer piece bore and in the bore, previously containing the first blade pin, of the clevis of the connecting member, and the spacer piece being capable of retaining the blade root in terms of rotation in the spacer piece clevis by engaging another pin in the second bore of th
Eurocopter
Kenaga Michael L.
Nguyen Ninh
Rudnick Piper
LandOfFree
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