The invention is in the field of mechanical engineering, in particular of micromechanics, and specifically relates to fluid pumps having a rotor and at least one impeller blade for the predominantly axial conveying of a fluid.

Pumps of this kind can be used in different technical fields, particularly where deployment locations are difficult to access and a compressible rotor can be brought onto site in compressed form and can there be expanded for efficient operation.

A particularly advantageous application is in the field of medicine where pumps of this kind can be introduced in particularly small construction into the body of a patient, for example through blood vessels, can be expanded at the deployment location, preferably in a ventricle, and can be operated there.

To remove the pump, it can usually be compressed again and removed through a sluice.

Corresponding compressible pumps are already known in different constructions.

A rotor is, for example, known from WO 03/103745 A2 which has a smaller diameter in a compressed state than in an expanded state and which has an unfoldable rotor blade which unfolds in operation by the fluid counterpressure of the fluid.

WO 03/103475 moreover discloses a rotor which has elements which are axially displaceable with respect to one another and whose mutual displacement accompanies the expansion and compression of a cage surrounding the rotor in the manner of a housing.

Rotors are moreover known from the prior art whose impeller blades are unfoldable for operation and have joints or elastic support parts for this purpose. The use of so-called memory alloys such as Nitinol is in particular known which adopt different geometrical shapes in dependence on the environmental temperature and thereby allow a subsequent deformation of the rotor after the introduction into a body.

A fluid pump is known from WO 99/44651 having a compressible rotor which has a compressible coil which is covered by membrane, comprises a memory alloy and is held together axially by an elastic band. The coil can be compressed by radial pressure thereon.

A fluid pump is known from WO 94/05347 having a rotor which carries conveying elements and is fixedly connected to a shaft, with a sleeve moreover being axially displaceably arranged on the shaft by whose displacement a housing surrounding the rotor can be stretched lengthwise and thus radially compressed. A relative movement of the sleeve to the shaft is converted by a lever mechanism into a radial erection of the conveying elements or into a folding down onto the shaft.

A compressible propeller pump with a rotor is known from WO 99/44651 having a helicoidal coil and an elastic band spanned centrally and coaxially therein as well as a membrane spanned between the named elements as an impeller blade.

Experience has shown that complex constructions for such pumps are also difficult to realize and to operate reliably with the desired service lives due to the small construction.

It is therefore the underlying object of the present invention against this background to provide a fluid pump of the initially named kind which allows a reliable function of the pump both on the introduction and removal and in regular operation with a simple construction design and at low costs.

The object is achieved by the features of the invention in accordance with claim1.

In this respect, the fluid pump in accordance with the invention provides a drivable rotor which is rotatable, about its longitudinal axis and which has at least one impeller, with the rotor at least partly comprising an elastically compressible and expandable material and being elastically stretchable in the direction of its longitudinal axis by elements acting axially on it.

Provision is moreover made in this respect that a push-element and a pull-element engage at different ends of the rotor and/or of a housing of the fluid pump.

A transverse contraction can, on the one hand, be directly realized by the elastic stretchability in the longitudinal direction with such a material-elastic rotor which can, for example, partly comprise an elastomer or a foam. However, different mechanisms within the rotor can also be set into motion by the longitudinal stretching which result in a transverse compression or in an easier transverse compressibility. Provision can e.g. be made for this purpose that the impeller blades are also stretched in the longitudinal direction of the rotor in that they are connected to a hub over a certain extent in the longitudinal direction of said hub. In the non-stretched state, the impeller blades can have a concave or convex or folded form or correspondingly formed support structures in their interior which are stretched by the longitudinal stretching of the rotor. Such geometrical shapes can give the blades additional stability with respect to the fluid pressure in operation, but also with respect to a radial compression, in the non-stretched state. If such structures are elongated by longitudinal stretching of the rotor, a facilitated deformability of the impeller blades results so that the rotor as a whole either becomes more easily radially compressible or automatically at least compresses a little on a longitudinal stretching.

A corresponding facilitation of the radial compressibility can then optionally be utilized by additional mechanisms of the radial compression, for example on moving into a sluice.

The described construction with a connection between the impeller blades and the hub extended in the longitudinal direction is moreover of simple construction to the extent that the rotor and the impeller blades can be manufactured in one piece, for example cast or vulcanized.

The rotor can advantageously be arranged at the distal end of a hollow catheter for the medical deployment of a fluid pump in accordance with the invention in order to be able to transport it with said hollow catheter through a bloodstream into a ventricle, for example.

Provision can advantageously be Made in this case that a pull can be applied in mutually opposite directions to both ends of the rotor by two elements mutually movable and extending along the catheter. The rotor can thus be extended from the proximal end of the catheter along the catheter by different mutually displaceable elements.

Provision can advantageously be made in this respect that one of the elements is a jacket and the other element is a core extending in the jacket. On the provision of a jacket and of a core extending therein, these two elements can support one another against outward kinking. A pull can, on the one hand, by applied by means of the jacket and a pressure in the longitudinal direction can be applied by means of the core, or vice versa.

The hollow catheter can advantageously itself serve as a jacket and, optionally, a drive shaft extending therein can also serve as a core.

Alternatively or additionally to this, however, lines can also be introduced at the outer circumference of the catheter which, with a corresponding stiffness, can transmit both a pull and a compression in the longitudinal direction or corresponding pull-movements and push-movements.

These lines can be introduced along the catheter up to the sluice through which the catheter is introduced into the body and can extend further to the exterior of the body and can be fastened in a fastening ring there so that the lines can be comfortably operated from outside the patient's body.

Provision can be made for the more specific embodiment of the invention that the proximal end of the rotor is connected to the core and the distal end of the rotor is connected to a housing of the rotor in a pull-resistant manner and that the housing is connected in a pressure-resistant manner to the jacket. In this case, the core can apply a pull to the rotor at its proximal end, whereas the other, distal, end of the rotor is held in a housing, for example, in a pull-resistant rotary bearing, which applies a pull in a direction opposite to the core to the rotor which can be realized by a support of the housing at the distal end of the hollow catheter/of the sleeve as a holding force. A compressive force then has to be applied to the sleeve along the catheter and a corresponding pulling force has to be applied to the core.

Provision can also advantageously be made that the proximal end of the rotor is connected directly, or indirectly via the housing, to the sleeve in a pull-resistant manner and that the distal end of the rotor is connected directly, or indirectly via the housing, to the core in a pressure-resistant manner. In this case, a pull-force is applied by the distal end of the jacket two the proximal end of the rotor, for example by a pull-resistant rotary bearing, whereas a pull-force is applied in the distal direction to the distal end of the rotor by the core which transmits a corresponding push-force. The core can for this purpose extend, for example, through the rotor and be connected to the rotor at its distal end. The core can, for example, be formed by a drive shaft of the rotor.

A further embodiment of the invention provides that the rotor is surrounded by a housing likewise stretchable in the direction of the longitudinal axis. In this case, the rotor can in each case be connected rotatably, but in a pull resistant manner, at its two ends to the housing, e.g. in that the rotor is journalled at both sides in the housing in pull-resistant rotary bearings. If a longitudinal stretching is then exerted onto the housing, it is transmitted directly to the rotor. The rotor is thus either compressed directly in the radial direction or it is at least more easily compressible.

Provision can particularly advantageously be made in this respect that the housing automatically undergoes a longitudinal stretching parallel to the longitudinal axis in the case of a transverse compression substantially perpendicular to the longitudinal axis. Provision can advantageously be made in this respect that the housing has a bulbous shape with an inner space sufficient for the expanded rotor in the state in which no forces act on it in the longitudinal direction.

In this case, a longitudinal stretching of the housing and thus a longitudinal stretching of the rotor, associated with a transverse contraction or facilitation of the compressibility of the rotor, can be achieved by application of a radial compression onto the housing, that is, for example, by moving the housing into a funnel-shaped sluice. For this purpose, a corresponding sluice which generates a corresponding radial compression on the withdrawal of the pump housing can be provided, for example, at the end of the hollow catheter. A sluice can, however, also be provided which surrounds the hollow catheter as Stich and into which the hollow Catheter can be withdrawn for the compression of the housing. A corresponding sluice can have an inflow funnel for the pump housing for this purpose.

The invention will be shown and subsequently described in the following with reference to an embodiment in a drawing.

