A submersible well pump has diffusers fixed within the housing and an impeller mounted between each of the diffusers. Spacer sleeves located between and in abutment with hubs of adjacent ones of the impellers define a stack wherein the impellers rotate in unison with the shaft and are axially movable in unison with each other relative to the shaft. A stop shoulder on the shaft abuts the lower end of the stack. A spring mounted in compression around the shaft in abutment with the upper end of the stack urges the lower end of the stack against the stop shoulder. Upward movement of the stack requires further compression of the spring. Up thrust and down thrust gaps between each impeller and adjacent diffusers prevent up thrust and down thrust from being transferred to any of the diffusers.

A pump drive for an extracorporeal blood pumping system including an adjustable drive magnet. The pump drive may be coupled to a blood pump which includes a pump impeller. The pump drive may include a stepper motor for dynamically adjusting the position of the drive magnet. The position of the drive magnet may be varied to vary the distance between the drive magnet and an impeller magnet of the pump impeller. Adjusting the position of the drive magnet may include dynamically adjusting the drive magnet and may include axially moving the drive magnet to thereby vary a magnetic attraction force between the drive magnet and the impeller magnet which may thereby minimize forces acting on one or more bearings of a pump impeller.

A pump drive for an extracorporeal blood pumping system including an adjustable drive magnet. The pump drive may be coupled to a blood pump which includes a pump impeller. The pump drive may include a stepper motor for dynamically adjusting the position of the drive magnet. The position of the drive magnet may be varied to vary the distance between the drive magnet and an impeller magnet of the pump impeller. Adjusting the position of the drive magnet may include dynamically adjusting the drive magnet and may include axially moving the drive magnet to thereby vary a magnetic attraction force between the drive magnet and the impeller magnet which may thereby minimize forces acting on one or more bearings of a pump impeller.

A gas turbine includes a main shaft connecting a turbine to a compressor and an additional shaft extending coaxially to the main shaft. The additional shaft has a first shaft section connected to the compressor and a second shaft section connected to the turbine, the shaft sections separated from each other by a gap. At mutually facing ends, the two shaft sections have mutually corresponding structures. The gap been the two shaft sections is dimensioned such that, upon a break of the main shaft, the mutually corresponding structures of the mutually facing ends of the two shaft sections come into interaction and rotate relative to one another as a result of their differing rotational speeds. The mutually corresponding structures are formed such that the two shaft sections are moved away from one other in the event of twisting of the two shaft sections.

A gas turbine includes a main shaft connecting a turbine to a compressor and an additional shaft extending coaxially to the main shaft. The additional shaft has a first shaft section connected to the compressor and a second shaft section connected to the turbine, the shaft sections separated from each other by a gap. At mutually facing ends, the two shaft sections have mutually corresponding structures. The gap been the two shaft sections is dimensioned such that, upon a break of the main shaft, the mutually corresponding structures of the mutually facing ends of the two shaft sections come into interaction and rotate relative to one another as a result of their differing rotational speeds. The mutually corresponding structures are formed such that the two shaft sections are moved away from one other in the event of twisting of the two shaft sections.

A centrifugal pump assembly has an electric drive motor (2) and at least one impeller (10; 10), which is movable in an axial direction (X) between at least two functional positions. In one functional position a flow path through the impeller (10; 10) is essentially closed and in another functional position the flow path through the impeller (10; 10) is opened. The impeller (10; 10) in a first functional position is held by a magnetic force (F.sub.M) or a spring force and in a second functional position is held by a hydraulic force (F.sub.H) produced by a delivered fluid. An impeller is provided for the centrifugal pump assembly.

A centrifugal pump assembly has an electric drive motor (2) and at least one impeller (10; 10), which is movable in an axial direction (X) between at least two functional positions. In one functional position a flow path through the impeller (10; 10) is essentially closed and in another functional position the flow path through the impeller (10; 10) is opened. The impeller (10; 10) in a first functional position is held by a magnetic force (F.sub.M) or a spring force and in a second functional position is held by a hydraulic force (F.sub.H) produced by a delivered fluid. An impeller is provided for the centrifugal pump assembly.

A pump assembly (2) includes an electric drive motor (14) and with at least one impeller (18) which is driven by the motor. The impeller is movable in an axial direction (X) between at least one first and one second position. The impeller in the first axial position is situated in a first flow path through the pump assembly and delivers a fluid through this first flow path. The impeller in the second position is situated in a second flow path through the pump assembly and delivers a fluid through this second flow path. The pump assembly (2) is configured such that a movement of the impeller (18), between the first and the second position at least in one direction, is effected by a hydraulic force which acts on the impeller (18) and is produced by the delivered fluid. A heating installation is provided with such a pump assembly.

A pump assembly (2) includes an electric drive motor (14) and with at least one impeller (18) which is driven by the motor. The impeller is movable in an axial direction (X) between at least one first and one second position. The impeller in the first axial position is situated in a first flow path through the pump assembly and delivers a fluid through this first flow path. The impeller in the second position is situated in a second flow path through the pump assembly and delivers a fluid through this second flow path. The pump assembly (2) is configured such that a movement of the impeller (18), between the first and the second position at least in one direction, is effected by a hydraulic force which acts on the impeller (18) and is produced by the delivered fluid. A heating installation is provided with such a pump assembly.

Apparatus and methods are described including a ventricular assist device that includes an impeller configured to be placed inside a left ventricle of a subject, and a frame configured to be disposed around the impeller. The frame is shaped such that, in a non-radially constrained configuration of the frame, the frame defines a cylindrical central portion, and a distal conical portion that is disposed distally with respect to the cylindrical central portion and that widens from a distal end of the frame to a distal end of the cylindrical central portion. The frame defines struts that define openings therebetween, and all openings that are defined at least partially within the distal conical portion of the frame extend into the cylindrical central portion of the frame. Other applications are also described.