Rem Technologies, Inc.

Enprotech Corp.

William H Miller

Warren R Brook

Rodolfo Palma

James Jonathan Grant

Timothy P Mannix

Scott E Thibault

An improved apparatus and method for determining the existence and severity of a crack in a shaft system is provided. The apparatus includes means for mounting multiple vibration responsive output transducers around an outer circumference of the shaft system, allowing simultaneous measurements of vibrational response of the shaft system when multiple vibration responsive output transducers are mounted to the mounting means. In a first approach, the mounting means comprises a collar having two connected arcuate members, with drilled milled and tapped apertures for mounting radial input and output transducers. Torsional input and output transducers may also be mounted tangentially on the collar in drilled milled and tapped heads of bolts used to connect the two arcuate members. In a second approach, the mounting means comprises a plurality of support blocks disposed substantially symmetrically around and protruding outward from the outer collar circumference with each of the blocks orienting at least one transducer in a radial direction and at least one transducer in a tangential direction. Each block may further orient another transducer in an axial direction.

Multiple axis transducer mounting collar

A heart pump having a housing with a central longitudinal axis, inlet means and an outlet means is disclosed. A stationary shaft extends axially within the housing and the means are provided for supporting the shaft centrally located within the housing. A stator assembly is mounted about the stationary shaft and a shell assembly is rotatable about the stator assembly and shaft. The shell assembly is located between the housing and stator assembly and includes a spiral ridge located on the outerside thereof for pumping blood through the housing between the housing and shell assembly as the shell assembly rotates. Rotor laminations are located on an innerside of the shell assembly. The rotor laminations have a plurality of axially extending permanent magnets therebetween which are circumferentially spaced about the stationary shaft. A damper winding means is mounted within the rotor laminations. Blood may flow between the shell assembly and housing without exposure to magnetic fields.

Heart pump

A rotor for a dynamoelectric machine, without windings and rotatable about a central longitudinal axis, having an axially extending rotatable body and a toroidal magnet coaxially mounted on the body is constructed to provide magnetic exitation for the rotor. The rotatable body contains a first set of circumferentially spaced axially extending salient poles with circumferentially spaced recesses therebetween and a second set of similar poles at an opposite axial location. The toroidal magnet is coaxially mounted on the body between the first and second set of salient poles. A second toroidal magnet may also be mounted on the body and a magnetic spacer placed in between both toroidal magnets.

Rotor with hollow cylindrical permanent magnet

The presence, size and location of a crack in a shaft is determined by comparing actual measured natural frequencies of the operating shaft system with the results of an analytical model. From a multi-station analytical model of an uncracked operating shaft system, natural frequencies and associated mode shapes are derived. A suspected axial location of a crack is defined, and a natural frequency of interest is selected which has an associated mode shape exhibiting significant localized bending at the suspected axial location of the crack and at a site of response measurement. The analytical model is modified to include a representation of an asymmetric crack at the suspected crack location. A predicted split and downward shift of a lateral natural frequency of interest as a function of crack depth and/or a predicted downward shift of a torsional natural frequency of interest as a function of crack depth is calculated from the modified model. The actual shaft system is subjected to an operating force excitation, and vibrational response measurements are taken with strain gages and then output through a short range telemetry system. A fast Fourier transform analyzer derives frequency response spectra from the measurements which indicate the actual natural frequencies of the shaft system. A comparison of actual natural frequency(s) in the region near the natural frequency of interest with frequency values predicted by the modified model is employed to determine the presence and severity of a crack in the shaft.

Crack detection method for operating shaft

The presence, size and location of a crack in a shaft is determined by comparing actual measured natural frequencies of the shaft system with the results of an analytical model. From a multi-station analytical model of an uncracked shaft system, natural frequencies and associated mode shapes are derived. A suspected axial location of a crack is defined, and a natural frequency of interest is selected which has an associated mode shape exhibiting significant localized bending at the suspected axial location of the crack and at a site of response measurement. The analytical model is modified to include a representation of an asymmetric crack at the suspected crack location, and a predicted split and downward shift of a lateral natural frequency of interest and/or a predicted downward shift of a torsional natural frequency of interest as a function of crack depth is calculated from the modified model. The actual shaft system is subjected to an excitation force, and vibrational response measurements are taken. A fast Fourier transform analyzer derives a frequency response function from the measurements which indicates the actual natural frequencies of the shaft system. A comparison of actual natural frequency(s) in the region near the natural frequency of interest with frequency values predicted by the modified model is employed to determine the presence and severity of a crack in the shaft.

Crack detection method for shaft at rest

A homopolar, transverse pole rotor (14) having a central cylindrical body (24) with a set of circumferentially spaced, axially extending salient poles (28) at each end thereof, is constructed to reduce windage losses. Integral shrouds (29, 31) are placed on either side of each set of salient poles, and a relief is machined into the outer surface of each shroud to form an accentuated pole tip (64) which ensures magnetic centering of the rotor. To further minimize windage losses, the diameter of the central cylindrical body (24) can be reduced, and non-magnetic material can be secured within interpole recesses. Mechanical fasteners (66), dove tails (72) or tensioned circumferential banding (82) can be used to secure the non-magnetic interpole pieces to the rotor.

Rotor with reduced windage losses

The presence, size and location of a crack in a shaft is determined by comparing actual measured natural frequencies of the shaft with the results of an analytical model. From a multistation analytical model of an uncracked shaft, natural frequencies and associated mode shapes are derived. A suspected axial location of a crack is defined and a natural frequency of interest is selected which has an associated mode shape exhibiting maximum deflection at the supected axial location of the crack and at a site of excitation. The analytical model is modified to include a representation of an asymmetric crack, at the suspected crack location, and the predicted split and downward shift of the natural frequency of interest as a function of crack depth is calculated from the modified model. The actual shaft is subjected to a radial excitation force, and vibrational response measurements are taken with an accelerometer along multiple radial directions. A fast Fourier transform analyzer derives a frequency response function from the measurements for each radial direction. The frequency response functions indicate the actual natural frequencies of the shaft. A comparison of these actual natural frequencies with those predicted by the modified model is employed to determine the presence and severity of a crack in the shaft.

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Loudonville, NY, United States of America

William H Miller