WO1996019668A1

WO1996019668A1 - Pump drive

Info

Publication number: WO1996019668A1
Application number: PCT/NL1995/000436
Authority: WO
Inventors: Augustinus Wilhelmus Maria Bertels
Original assignee: Helpman Intellectual Properties B.V.
Priority date: 1994-12-22
Filing date: 1995-12-20
Publication date: 1996-06-27
Also published as: AU4401896A; TW327670B; NL9402188A

Abstract

The invention relates to a pump for medium, for instance a liquid pump or a fan, comprising: a central hub (2); a plurality of blades (3) to this hub (2), which blades (3) take a form such that when driven rotatably round the axis of the hub (2) a medium displacement occurs; and drive means (8) for rotatably driving the hub round the axis of the hub (2). The pump according to the invention has the feature that the outer end zones of the blades (3) are connected by a ring (5), which ring (5) is supported rotatably in a housing (7); and the drive means comprise a motor (8) which is placed at a distance from the hub (2) outside the medium flow generated by the driven blades (3), which motor (8) is connected to the hub (2) by means of a flexible shaft (10).

Description

PUMP DRIVE

The invention relates to a pump for medium, for instance a liquid pump or a fan, comprising: a central hub; a plurality of blades connected to this hub, which blades take a form such that when driven rotatably round the axis of the hub a medium displacement occurs; and drive means for rotatably driving the hub round the axis of the hub.

Such a pump is known. The drawback of the known pump is that it comprises a relatively wide central hub, the diameter of which lies in the same order of magnitude as the centrally placed, comparatively large motor. The motor supports the hub via its output shaft and drives it directly. As a consequence of this structure the medium flow generated by the pump cannot be prevented from being seriously affected by the presence of the motor and the relatively large hub.

It is the object of the invention to embody the pump of the described type such that the medium flow generated by the pump is affected to only negligible extent by the drive means.

A further object of the invention is to embody the pump such that its efficiency compared to known pumps is increased considerably. With a view to the above stated objectives the pump according to the invention has the feature that the outer end zones of the blades are connected by a ring, which ring is supported rotatably in a housing; and the drive means comprise a motor which is placed at a distance from the hub outside the medium flow generated by the driven blades, which motor is connected to the hub by means of a flexible shaft.

A very simple embodiment has the special feature that the flexible shaft comprises a plastically twisted strip. Surprisingly, such a strip with helical torsion is capable of excellent energy transfer with very small losses.

A preferred embodiment has the special feature that the strip consists, at least to a mechanically predomi¬ nant extent, of metal.

Diverse metals can be considered suitable for the material of the metal strip, in particular steel, for instance stainless steel, or preferably spring steel. In this latter case the strip can for instance have a thickness of (0.5 ± 0.2) mm.

Another embodiment has the special feature that the strip consists, at least to a mechanically predominant extent, of plastic optionally reinforced with fibres, such as of glass, carbon, boron or aramid.

An embodiment is recommended in which the plastic is reinforced with fibres. A good energy transfer can be achieved hereby, while the strip is nevertheless rela¬ tively inexpensive and can be manufactured easily. The latter described embodiment in particular can have the feature that the proportion of fibres with a length of more than 5 mm amounts to more than 20%. This ensures a very great mechanical strength. In addition, such a structure is little susceptible to failure due to ageing. The pump can further display the special feature that the strip is manufactured by extrusion from thermo¬ plastic material.

This latter variant preferably has the special feature that prior to substantial cooling after the extrusion the strip is subjected to a twisting treatment, followed by substantial cooling. The twisting treatment can take place very simply by supplying hot air to the flat extrudate in a manner which is preselected and adjusted during the production process. This air is blown at the strip by nozzles such that the still warm strip is subjected to a twisting couple. The torsion is fixed in the structure by the substantial cooling subsequent to the said treatment. For good vibration damping the embodiment is recom¬ mended in which the strip comprises a laminate consisting of at least two alternating layers of a metal, particu¬ larly steel, and a plastic, particularly an elastomer. An alternative has the special feature that the flexible shaft is embedded and enveloped by a co-rotating jacket.

This variant can have the special feature that the jacket consists of an elastic mass, consisting for in- stance of a foamed material such as silicone rubber, polypropylene, polyurethane or a rubber.

An alternative has the special feature that the jacket comprises a sleeve. For still greater vibration damping this latter embodiment can have the special feature that the sleeve is filled with a vibration-damp¬ ing mass, for instance a viscous liquid.

In order to prevent unintended yielding and prema¬ ture ageing of the flexible shaft in the case of heavy mechanical loads, use can be made of an embodiment in which the flexible shaft is locally mounted for rotation. A specific embodiment displays the special feature of tensioning means for at least locally placing and holding the flexible shaft under tension prestress within the elastic range of the or each material which this shaft contains. Herewith can be realized an effective vibration suppression with associated suppression of radiated sound.

This embodiment can advantageously have the special feature that the tensioning means comprise at least two mutually displaceable and fixable bearings.

The invention will now be elucidated with reference to the annexed drawings. Herein: figure 1 shows a partly broken away perspective view of a fan according to the invention; figure 2 shows a partly broken away perspective view of an alternative flexible shaft; figure 3 shows a schematic perspective view of an apparatus for manufacturing a twisted strip consisting for at least a major part of plastic- figure 4 shows a perspective view of a flexible shaft consisting of a twisted laminate; and figure 5 shows a schematic perspective view of tensioning means with two mutually displaceable and fixable bearings for tensioning at least locally a flexi¬ ble shaft according to the invention. Figure 1 shows a fan 1 according to the invention which comprises: a central hub 2; eight aerodynamically formed blades 3 connected to this hub 2 and extending at least more or less in radial direction, which blades take a form such that during rotary driving round the axis of hub 2 an air displace¬ ment occurs; and drive means to be described hereinbelow for rota¬ tably driving the hub round the axis of the hub. The outer end zones 4 of blades 3 are joined by a ring 5 which is supported in a housing 7 by means of bearings 6.

The drive means comprise a motor 8 which is fixed to a frame 9 which also supports housing 7. Motor 8 is connected via a twisted spring steel strip 10 to the central hub 2 for driving the rotor 2,3,4,5. Strip 10 has a thickness in the order of 0.5 mm.

Figure 2 shows in partly broken away perspective view a twisted spring steel strip 10 of the same type as shown in figure 1 which in this specific embodiment, however, is embedded and enveloped by a substantially cylindrical jacket 11 consisting of an elastic poly- urethane mass. An excellent vibration damping is obtained with this embodiment. Figure 3 shows schematically the manner in which a twisted strip, which consists for at least a major part of plastic and which can serve as flexible shaft, can be manufactured. An extrusion head 12 provides a plastic strip 13. Before this strip is substantially cooled it is subjected to a twisting couple by two nozzles 13, 14 which direct respective hot air streams 15, 16 at a position relative to the axis 17 of the extrudate 18 such that a twisting couple is thus exerted. The twisted form drawn downstream of the nozzles 13, 14 is thus obtained. This twisted form is subsequently fixed in the structure in that the twist¬ ed strip 19 is guided through an annular cooler 20 which directs cold air onto strip 19 via a ring of nozzles 21 whereby it is cooled and the twisted form fixed. The cooled twisted strip 19 is then wound onto a reel 22.

Figure 4 shows a twisted strip 23 consisting of the twisted spring steel strip 10 and an elastomer layer 24 adhered thereto. An excellent vibration damping is also obtained with this structure. It is noted that the lami¬ nate can consist of a number of layers, for instance alternatingly spring steel and an elastomer.

Figure 5 shows that the twisted strip 10 can be mounted locally by rotation bearings 25, 26 located at mutual axial distances. By moving these bearings away from each other an effective tensile force can be exerted on strip 10 which is active during rotation of strip 10. The bearings 25, 26 can be displaced and fixed relative to each other.

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Claims

1. Pump for medium, for instance a liquid pump or a fan, comprising: a central hub; a plurality of blades connected to this hub, which blades take a form such that when driven rotatably round the axis of the hub a medium displacement occurs; and drive means for rotatably driving the hub round the axis of the hub, characterized in that the outer end zones of the blades are connected by a ring, which ring is supported rotatably in a housing; and the drive means comprise a motor which is placed at a distance from the hub outside the medium flow generated by the driven blades, which motor is connected to the hub by means of a flexible shaft.

2. Pump as claimed in claim 1, wherein the flexible shaft comprises a plastically twisted strip.

3. Pump as claimed in claim 2, wherein the strip consists, at least to a mechanically predominant extent, of metal.

4. Pump as claimed in claim 2 , wherein the metal is steel.

5. Pump as claimed in claim 4, wherein the metal is stainless steel.

6. Pump as claimed in claim 4, wherein the metal is spring steel.

7. Pump as claimed in claim 6, wherein the strip has a thickness of (0.5 ± 0.2) mm.

8. Pump as claimed in claim 2, wherein the strip consists, at least to a mechanically predominant extent, of plastic optionally reinforced with fibres, such as of glass, carbon, boron or aramid.

9. Pump as claimed in claim 8, wherein the plastic is reinforced with fibres.

10. Pump as claimed in claim 9, wherein the propor¬ tion of fibres with a length of more than 5 mm amounts to more than 20%.

11. Pump as claimed in claim 8, wherein the strip is manufactured by extrusion from thermoplastic material.

12. Pump as claimed in claim 8, wherein prior to substantial cooling after the extrusion the strip is subjected to a twisting treatment, followed by substan¬ tial cooling.

13. Pump as claimed in claim 2 , wherein the strip comprises a laminate consisting of at least two alternat¬ ing layers of a metal, particularly steel, and a plastic, particularly an elastomer.

14. Pump as claimed in claim 1, wherein the flexible shaft is embedded and enveloped by a co-rotating jacket.

15. Pump as claimed in claim 14, wherein the jacket consists of an elastic mass, consisting for instance of a foamed material such as silicone rubber, polypropylene, polyurethane or a rubber.

16. Pump as claimed in claim 14, wherein the jacket comprises a sleeve.

17. Pump as claimed in claim 16, wherein the sleeve is filled with a vibration-damping mass, for instance a viscous liquid.

18. Pump as claimed in claim 14, wherein the flexi¬ ble shaft is locally mounted for rotation.

19. Pump as claimed in claim 1, comprising tension¬ ing means for at least locally placing and holding the flexible shaft under tension prestress within the elastic range of the or each material which this shaft contains.

20. Pump as claimed in claims 18 and 19, wherein the tensioning means comprise at least two mutually displace- able and fixable bearings.

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