IMPELLER FOR CENTRIFUGAL PUMP

Abstract: An empeller for a centrifugal pump comprises a disc (1) and blades (2), which comprise a number of band elements (4'), each formed by a length of a band (4) and finished at each end with band loops (42). The loops (42) are slipped over consoles, rigidly and with equal spacing fastened to said disc along its perimeter and the band elements (4') are stretched towards the centre of the disc by means of tension devices (5).

Description: Impeller for centrifugal pump. The present invention relates to an impeller for centrifugal pump comprising a disc and radial blades. The invention is intended for centrifugal acceleration of a fluid, that may be either a liquid or a gas or a mixture between a liquid and a gas. By known impeller designs the discs and blades are rigid constructions with a given performance for ench shaping, in order to fill a spectrum of pressures and mass flows impellers are built with blades, that are straight, bent back or forward, with a varying num¬ ber of blades, with varying blade geometry, with varying disc diame¬ ter etc. In spite of this it may be hard to find an optimally desig¬ ned pump for a specific purpose. The manufacturing process for the impellers as a rule requires serial production, for which reason some standard impeller often must be chosen, that is oversized end will give unneccesary cost for purchase and operation. A first purpose with the invention is a esign of im¬ pellers with few and simple components, that allow an exceptionally large variation of flow properties. Impellers may with good economy be custom made for their task as a single specimen or as small series. A second purpose is to use as power transmitting devices bands with high tensile strength only exposed to membrane forces. High strength may thus be combined with low weight, which favourably decreases starting momentum for the impeller and load on its bearings. Vibrations that create noise and exhaust in rigid blades, are also avoided. Said purposes are met with an impeller further charac¬ terized in that said blades comprise a number of band elements, either formed by a lenght of a band finished by loops, formed by joining the band ends to the band by a joint, that it further comprises a double said number of consoles, rigidly and with equal spacing fastened to said disc along its perimeter and further comprises said band loops slipped over said consoles and the band elements stretched inwards towards the centre of said disc by means of tension devices. The invention is described in the following in relation to the drawings. Figures 1 and 2 show an impeller in elevation and section. Figure 3 illustrates in perspective a blade forming band ele- ment.Figure 4 shows a design of a console and figure 5 design of a disc. Figures 6 a-d show in elevation different flow geometries, formed by varied mounting of the band elements to a disc. Figures 7 a-c illustrate further variations of flow geometry, achieved by variation of the number of band elements per disc. In referanoe to figures 1 and 2 an impeller disc is marked 1 and connected radial blades marked 2. By 6 is marked an inlet opening in a pump house for a fluid 7, centrifugally accelerated in the impeller. The blades 2 comprise a number of band elements 4'* further illustrated in figure 3 . each formed by a length of a band 4 and finished with band loops 42 formed by joining the band ends with the band by a joint 41 • The joint 41 may he a seam or a weld for a weldable band material. The blades 2 comprise further a double num¬ ber of consoles 3» rigidly and with equal spacing fastened to the disc 1 along its perimeter. The band loops 4 are slipped over the consoles 3 and the band elements 4' are stretched inwards towards the centre of the disc 1 by means of tension devices » In a preferred design according to figure 4 the con¬ soles 3 consist of cylinders 3 t preferably of thin wall tubes. Each cylinder 3 has a slit 32, cut to approx. half the cylinder diameter and well fitted to the thickness of the edge 13 of th«. disc 1, thus counter sinkable over the edge 13 to the half cylinder diameter. The edge 13 has further equidistant hacks 11, which penetrate over a short end 321 of the slit 3 and thus lock the cylinders 31 into position along the edge 13 * The console height H of the cylinder 3 is essentially equal to the width B of the band 4» As a tension device 5 is preferred for each band element 4' a supporting bolt 51* supporting and tensioning the band 4 and tightened into a centre part 4 of the disc 1. This centre part is pre erably increased in thickness relative the edge 13 for increased stiffness of the disc 1 and for rigid fastening of the bolts 51 and a driving shaft 12. With the above described design the cylinders 3 1 are locked into their positions by a tension force in the bands 4 with¬ out any further fastening. The cylinders 3 and the band elements 4' may thus be simply mounted or dismounted by mounting or dismounting the bolts 51. Power transmitted from the disc 1 to the pumped fluid flow 7 results in a membrane tension in the bands 4 with a minimum of vibration, noise and exhaust of the band material. The band 4 may be a fiber material of high strength for instance a weld- able fibre reinforced plastic material, such as marqee canvas or by metal, such as thin stainless steel. The diameter of' the inlet opening 6 is related to the disc, so that the joints 41 hut not the loops 42 are exposed in the opening. In flow channels enclosed by straight, tensioned band parts of the loops 4 is caused the essential acceleration of the fluid 7» while a starting retardation and pressure increase is caused along the cylindric band parts of the band loops 42, supported by the cylin¬ ders 31 * According to experiance good flow properties are obtained, if circumference proportions between the loop 4 and the cylinder 3 are in the order of 1,2 - 1,3. The geometric line for positioning the bolts 5 is an elipse with two cylinders 31 as focal points. According to posi¬ tion pump geometry may with the same band elements be varied between back bent, straight or forward bent blades as according to figures 6 a - c. A futher variation is illustrated by figure 6 d with inclined bolts and twisted band elements 4' . that influence the feeding of the fluid flow 7. Figures 7 - c illustrate how flow properties of the impeller further may be varied by an increased number of band elements. With increasing number turbulence will be reduced in the accelerated fluid flow and consequently noise level and power consumtion. Is to above described variations with given construc¬ tion elements added a kit with compatible elements in different sizes, such as cylinders 31 with a few variations of console height H, bands 4 with corresponding variations of width B and discs 1 with some differant diameters and perimeter speeds, a very large spectrum of flow properties may be covered by a simple building technique.

Claims: Claims 1. An impeller for centrifugal pumps comprising a disc (1) and radial blades (2) c h a r a c t e r i z e d i n that said blades (2) comprise a number of band elements H') . either formed by a length of a band (4) finished by loops (42), formed by joining the band ends to the band by a joint (41), that it further comprises a doubl said number of consoles (3) » rigidly and with equal spacing fastene to said disc (1) along its perimeter and further comprises said band loops (42) slipped over said consoles and the band elements (4') stretched inwards towards the centre of said disc (1 ) by means of tension devices (5). 2. An impeller according to claim l c h a r a c t e r i z e d i n that said console (3) is comprised of a cylinder (31 ) preferably of a thin wall tube, having a slit (32) cut to essentially half the cylinder diameter with a good fitting to thickness of the edge (13) of said disc (1) and said cylinder (31) countersunk over said edge (15) to essentially half the cylinder diameter. 3. An impeller according to claims 1-2 c h a r a c t e r i z e d i n that said disc (1) comprises along said edge (13) equidistant hacks (11), penetrating over a short end (321 ) of said slits (32). 4» An impeller according to claims 1-3 c h a r a c t e r i z e d i n that perimeter proprtions between said band loop (42) and said cylinder (3 ) are in the order 1,2 - 1,3. 5. An impeller according to claims 1-4 c h a r c t e r i z e d i n that said tension devices (5) comprise a bolt ( 1 ) for each said band element (4 ! ) t tensioning said band (4) and fastened into a centre part (14) of said disc.

Inventors: ZEILON STEN, ZEILON, STEN
Applicants: ZEILON STEN, ZEILON, STEN
Application year: 1992
Main classification: F04D17
IPC codes: F04D29, F04D31