BRIEF DESCRIPTION OF THE DRAWINGS
The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:
FIG. 1A is a general perspective view an exemplary rotary wing aircraft rotor head embodiment for use with the present invention;
FIG. 1B is a general perspective view a servo flap rotor blade for use with the present invention;
FIG. 2A is a sectional view of heatable elastomeric bearing;
FIG. 2B is an expanded sectional view of a heatable shim layer within the heatable elastomeric bearing;
FIG. 3 is a perspective view of heatable elastomeric bearing;
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1A illustrates a general perspective view of a rotor system 10 which includes a rotor shaft 12 driven in conventional fashion by an engine through a reduction gearing for rotation about an axis of rotation A. A rotor hub 14 is mounted to the rotor shaft 12 for rotation therewith about an axis of rotation to support a multiple of rotor blade assemblies 16 (illustrated schematically) therefrom.
Each blade assembly 16 is mounted to the rotor hub 14 so as to be flexible about a pitch change axis P. It should be understood that various attachment systems and rotor blade pitch change systems are usable with the present invention. Pitch change loads are imparted to each rotor blade assembly 16 by pitch control rods 18 which are articulatably connected at one end to the rotor blade assembly 16 at a pitch horn 20. The opposite end of the pitch control rod 18 is articulately connected to a swash plate assembly 22.
As shown, a heatable elastomeric bearing 24 may be utilized in the rotor system 10 at a multitude of locations for a multitude of purposes. Typical applications include spherical rod end elastomeric bearings for pitch control rods and dampers, spherical blade retention elastomeric bearings for fully articulated rotors, and cylindrical bearings for semi-articulated rotors and fluid-elastic damper seals as well as other locations.
It should be understood that although the elastomeric bearings in the illustrated embodiment are depicted within a rotor system 10, the elastomeric bearings of the present invention are not limited to just rotor head applications but may be in any location in which elastomeric bearings are utilized such as in substitution for non-lubricated or self-lubricated bearings such as Teflon fabric lined bearings. The heatable elastomeric bearings 24 are most preferably utilized in rotor systems which are of the fully articulated rotor system type with servo flap control 16S (FIG. 1B) as such rotor systems have spherical elastomeric blade retention bearing 24S which are not readily exercised through pilot control during conventional preflight procedures.
Referring to FIG. 2A, the heatable elastomeric bearing 24 generally includes a plurality of shear deformable elastomeric material layers 30 separated by heatable shim layers 32 formed of high-stiffness constraining material such as composite or metallic layers. Each heatable shim layer 32 preferably includes a first outer shim 34 and a second outer shim 36 which are preferably manufactured of a metallic material to sandwich a heater mat layer 38 therebetween to conduct thermal energy therefrom (FIG. 2B). Preferably, the insulators electronically insulate the thermal element 40 but conduct thermal energy to the shims 34, 36. The heater mat layer 38 is preferably a wire or heating foil thermal element 40 encapsulated between a first insulator 42 and a second insulator 44 typically manufactured of a non-metallic material such as fiberglass (FIG. 2B). Preferably, the heatable shim layers 32 are equally spaced throughout the heatable elastomeric bearings 24 stack-up, but need not be utilized in every shim layer. Most preferably, a heatable shim layer inner endplate 46 and a heatable shim layer outer endplate 48 mount the heatable elastomeric bearing 24 to a first member A and a second member B (FIG. 3).
Referring to FIG. 2B, an electrical jumper 50 preferably connects each thermal element 40 within the heatable elastomeric bearing 24 to a power supply P. Each electrical jumper 50 extends from the heatable elastomeric bearing 24 to provide slack which permits free relative movement of the deformable elastomeric material layers 30.
It should be understood, however, that various shim materials of differing rigidity will also benefit from the present invention such that an alternate design would integrate the insulating layers into two composite shim layers.
Referring to FIG. 3, the heatable elastomeric bearing 24 operates as a coupler between the first member A and the second member B. During operation, the shear deformable elastomeric material layers 30 shear within the constraints of the shim layers 32. The shim layers 32 guide the elastomeric shear deformation such that the displacement trajectory of the first member A relative to the grounding member B is a predefined movement. The heatable shim layers 32 facilitate the maintenance of a constant bearing spring rate to prevent an increase to bearing loads and reduced strength that may otherwise occur at cold temperatures. In the illustrated aircraft rotor head embodiment, the heatable elastomeric bearing 24 are heatable using on-board or external power sources prior to rotor start-up. In-flight, the power need only be selectively applied as strain energy will to warm the elastomeric material layers 30.
Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.
The foregoing description is exemplary rather than defined by the limitations within. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For that reason the following claims should be studied to determine the true scope and content of this invention.
Patent Application
20080044283
