Device with rotor, stationary part or stator, and different types of liquid pocket sliders with respective specific functions

Abstract

A device includes a rotor ( 5 ), a stator ( 2 ) and different types of liquid pocket sliders ( 3; 4; 10 ), each type with different and specific functions, the liquid pocket sliders preferably being mounted at the outermost surface of the rotor. The device can include ordinary pocket sliders ( 3 ), with the function of load support and bearing self-centering on the rotor ( 5 ); “sentinel” pocket sliders ( 4 ) having the function of predicting failures and/or monitoring the distribution of the load around the rotor; preload pocket sliders ( 10 ), with the function of compensating for possible unbalance of the rotor at a given velocity.

1 . Rotation device comprising:
 a rotor ( 5 ) integral with a rotation shaft ( 1 ), a stator ( 2 ) coaxial with the rotor ( 5 ) and which faces directly on the external periphery of the rotor ( 5 ), forming an annular interspace with respect to the latter, liquid pocket sliders ( 3 ;  4 ;  10 ) comprising a membrane ( 8 ) for containing a liquid and functioning as radial bearings during the rotation of the rotor ( 5 ), said membrane ( 8 ) being characterized by a tension (τ) and by a high elastic modulus (E), i.e. substantially rigid upon traction, said rotation device providing for means for preloading the liquid pocket sliders ( 3 ;  4 ;  10 ) against a respective relative slide surface,   characterized in that said liquid pocket sliders ( 3 ;  4 ;  10 ) are mounted inside said peripheral annular interspace by fixing the edge of their membrane ( 8  or  9 ) to a mounting surface inside the stator ( 2 ) or to a mounting surface outside the rotor ( 5 ), the surface opposite the mounting surface constituting said relative slide surface; and wherein, given an estimated maximum of the possible unbalance (e) of the rotor ( 5 ), and given a maximum design angular velocity (ω M ) of the rotor ( 5 ), the centripetal reaction force exerted by said liquid pocket sliders ( 3 ;  4 ;  10 ) on the rotor ( 5 ) is such to prevent resonances by limiting the amplitude of the oscillations due to possible small misalignments between the rotor ( 5 ) and the stator ( 2 ) and/or due to the centrifugal force Mω 2 e for each rotation velocity ω≦ω M , given that “M” is the mass of the rotor ( 5 ) including the shaft ( 1 ); and wherein the elastic rigidity (dW/dδ) of said liquid pocket sliders ( 3 ;  4 ) is such that the total force (f T ) acting on the rotor has a local minimum at d=0.   
     
     
         2 . Device according to  claim 1 , characterized in that at least one of said liquid pocket sliders ( 3 ;  4 ) constitutes a sentinel cell ( 4 ) adapted to detect an excessive load or an excessive wear which has possibly caused the breakage of its membrane ( 9 ) over time. 
     
     
         3 . Device according to  claim 2 , characterized in that said at least one sentinel cell ( 4 ) is associated with a pressure sensor ( 7 ) for continuously or intermittently measuring the internal pressure of the liquid retained by the membrane ( 9 ), so as to verify possible liquid losses outside the relative liquid pocket slider ( 4 ). 
     
     
         4 . Device according to  claim 2 , characterized in that at least one of said sentinel cells ( 4 ) has smaller size than that of the other liquid pocket sliders ( 3 ) of ordinary type, which do not have the function of predicting possible device failures, and therefore such sentinel cell ( 4 ) supports a smaller percentage of the total load with respect to a liquid pocket slider ( 3 ) of ordinary type. 
     
     
         5 . Device according to  claim 2 , characterized in that said sentinel cells ( 4 ) are arranged in strategic positions for constantly or intermittently monitoring the possible non-uniform distribution of the load on the rotor, i.e. around the rotor itself, given that they are preferably arranged at regular intervals from each other and between the liquid pocket sliders ( 3 ) of ordinary type. 
     
     
         6 . Device according to  claim 2 , characterized in that each of said sentinel cells ( 4 ) is associated with one or more sensors ( 7 ) of different type, adapted to detect the breakage thereof and/or the variation of the sustained load, said sensors ( 7 ) being selected for example from among the following types:
 pressure sensors;   load cells;   optical sensors;   temperature sensors.   
     
     
         7 . Device according to  claim 1 , characterized in that said means ( 11 ) for preloading the liquid pocket sliders ( 3 ;  4 ;  10 ) comprise a movable structure and actuators for causing the relative compression between the slider ( 3 ;  4 ;  10 ) and said relative slide surface, or said preloading means ( 11 ) comprise means for varying the internal pressure of the liquid in the liquid pocket slider ( 3 ;  4 ;  10 ). 
     
     
         8 . Device according to  claim 1 , characterized in that the rigidity (dW/dδ) of said liquid pocket sliders ( 3 ;  4 ;  10 ) is adjusted by employing one or more of the following measures:
 adjusting the internal pressure of the liquid, by acting for example with a small piston that pushes the liquid from a tank communicating with the liquid pocket interior through a respective duct; 
 providing for a surface with curvature that is even non-uniform, but is adapted in the non-stressed rest condition for the surface of the membrane ( 8 ) of the liquid pocket slider ( 3 ;  4 ;  10 ); 
 providing for a suitable squeezing (δ) once the following are set: the materials of the liquid and the membrane ( 8 ) containing it, the internal pressure of the liquid, as well as the shape of the membrane ( 8 ) of the slider ( 3 ;  4 ;  10 ) for δ=0; 
 providing for cage/containment walls/constraints ( 6 ) along the edges of the membrane ( 8 ) at its edge for fixing to the mounting surface. 
 
     
     
         9 . Device according to  claim 8 , wherein said cage/containment walls/constraints ( 6 ) constitute stops that limit the maximum oscillation amplitude of the rotor ( 5 ) and which are formed by materials which minimize the damage to said relative slide surface in case of contact. 
     
     
         10 . Device according to  claim 2 , characterized in that a sufficient number of LPS elements ( 10 ) are fixed on the rotor ( 5 ) so as to be able to introduce a preload in phase with the centrifugal force due to the unbalance “e” of the rotor ( 5 ), capable of balancing said centrifugal force at a specific velocity. 
     
     
         11 . Device according to  claim 2 , characterized in that the membrane ( 9 ) of the sentinel cells ( 4 ) is adapted to be broken before the membrane ( 8 ) of the other types of liquid pocket sliders ( 3 ;  10 ) by virtue of the fact that it has one or more of the following characteristics:
 its thickness is calibrated in a manner so as to be smaller, e.g. 50% smaller, than that of the membrane ( 8 ) of the other types of liquid pocket sliders ( 3 ;  10 );   its material is different and less resistant than that of the membrane ( 8 ) of the other types of liquid pocket sliders ( 3 ;  10 );   it has an anti-wear and/or anti-friction surface coating with calibrated thickness smaller than that of the other types of liquid pocket sliders ( 3 ;  10 );   it has an anti-wear and/or anti-friction surface coating of less resistant material than that of the other types of liquid pocket sliders ( 3 ;  10 ).   
     
     
         12 . Device according to  claim 1 , characterized in that axial thrust bearings are also provided, or simultaneously both radial and axial thrust bearings are provided (radial/axial with regard to the thrust direction), wherein at least one of these, but preferably all, constitute liquid pocket sliders. 
     
     
         13 . Device according to  claim 1 , characterized in that the cage/containment walls/constraints ( 6 ) provided along the edge of the membranes ( 8 ;  9 ) are tangent to the surface of the membranes ( 8 ;  9 ) at their fixing edges or lines. 
     
     
         14 . Device according to  claim 1 , characterized in that it constitutes a so-called CMG (Control Moment Gyro) device for controlling the attitude of a satellite, wherein the rotor ( 5 ) comprises a flywheel ( 5 ) which is driven by a motor. 
     
     
         15 . Device according to  claim 14 , characterized in that said liquid pocket sliders having the function of radial and/or axial thrust bearings during the rotation of the flywheel ( 5 ) are mounted on the external radial surface of the flywheel ( 5 ), which thus constitutes said mounting surface. 
     
     
         16 . Device according to  claim 1 , characterized in that if the device constitutes a part of a turbo machine, a pump, a turbine, a compressor or the like, then the rotor ( 5 ) comprises, in addition to a system of blades or the like, also a ring whose external surface forms a mounting or slide surface for the liquid pocket sliders ( 3 ;  4 ;  10 ). 
     
     
         17 . Device according to  claim 1 , characterized in that at least several liquid pocket sliders ( 3 ;  4 ;  10 ), but preferably all, are pressurized independently from each other, in order to make the device failure-tolerant. 
     
     
         18 . Method for optimizing the functioning of a flywheel of a control moment gyros device and for opportunely preventing the failures thereof which comprises using the device according to  claim 1 .