IMPELLER

Abstract: An axial impeller has a hub (1) for attaching the impeller to a shaft and a plurality of essentially radial blades, which are connected to the hub (1) by means of blade mountings (12). The hub (1) supports two parallel discs (5) which are arranged in front of each other, have essentially the same diameter and which are provided with through bolt holes. The blade mountings (12) are arranged between the discs (5). The discs (5) are attached to the blade moutings (12) and pressed against these by means of bolts (17, 18), which extend through bolt holes in the respective discs (5).

Description: IMPELLER The present invention relates to an axial impeller having a hub for attaching the impeller to a shaft and a plurality of essentially radial blades, which are each connected to the hub by means of a blade mounting and turnably attached to the respective blade mountings. Normally used prior art axial impellers, which are of this type and in which the blades are turnable for adjusting the capacity of the impeller, have a cast rim of the centre, which is accurately machined. Each blade is turnably arranged on a substantially radial blade shaft, which is nonrotatably anchored in the rim of the centre, e.g. screwed into accurately machined holes in the rim. The rim is connected to the shaft hub, which is cast, by means of components which are cast integrally with the hub and the rim. Other prior art axial impellers, which are of the type mentioned by way of introduction and in which the blades are turnable for adjusting the capacity of the impeller, have a forged rim, which is connected to the shaft hub by means of a sheet metal cone which is welded to the rim and the hub. These two types of prior art axial impellers have a complicated design and are difficult to manufacture since extremely accurate and expensive machining operations are required for the type of impeller as first described above, and time-consuming and costly welding operations are required for the type of impeller as last described above. Thus, both types of axial impellers are expensive. Moreover, owing to the above-described design, they re- quire, when manufacturing impellers having different diameters and/or different numbers of blades for each individual impeller variant, specially designed compo¬ nents, such as hub with rim and blade mountings for the first-mentioned type of impeller, and rim, cone and blade mountings for the last-mentioned type of impeller. In view of that stated above, the object of the present invention is to provide an axial impeller, which is simple and inexpensive to manufacture and is of simple design, which does not require the stock-keeping of a plurality of expensive components, which are individually adapted to a number of impeller variants, e.g. impellers having different diameters and/or different numbers of blades . According to the present invention, this object is achieved by an axial impeller, which is of the type stated by way of introduction and which is characterised in that the hub supports two parallel discs which are arranged in front of each other, have essentially the same diameter and are provided with through bolt holes, that the blade mountings are arranged between the discs, and that the discs are attached to the blade mountings and pressed against these by means of bolts, which extend through bolt holes in the respective discs. In a preferred embodiment, the bolt holes in the one disc are positioned in front of the bolt holes in the other disc, and the bolts extend through through bolt holes in the respective blade mountings. In this case, the bolt holes in each disc are suitably arranged in pairs, one of the bolt holes in all pairs being posi- tioned on an outer circle which is concentric with the disc and the other of these bolt holes being positioned on an inner circle which is concentric with the disc, and each blade mounting has two through bolt holes, which are located in front of the bolt holes in a pair of bolt holes in each disc. The discs are preferably made of metal sheet. In a preferred embodiment, a circumferential border surrounding the two discs and having through holes for the blades is attached to the discs to produce a flow which is aerodynamically undisturbed by the blade mount¬ ings. The border suitably has internal disc mountings, which are uniformly distributed along the circumference of the border and have pins, which are inserted into pin holes formed in the discs in the vicinity of the circum¬ ference thereof. The disc mountings are advantageously yieldable in a limitedly elastic manner in the radial direction of the discs. The border is preferably made of metal sheet. The invention will now be described in more detail with reference to the accompanying drawings, in which Fig. 1 is a perspective view and shows an axial im- peller according to the invention with the blades re¬ moved, Fig. 2 illustrates the impeller according to Fig. 1 from the side, i.e. in axial direction, the impeller being provided with one blade only, Fig. 3 is a sectional view along line III-III in Fig. 2, Fig. 4 is a perspective view of a blade mounting, Fig. 5 is a side view of a disc included in the im¬ peller, Fig. 6 illustrates the impeller in the direction of the arrow VI in Fig. 2, and Fig. 7 is an enlarged sectional view along line VII- VII in Fig. 6 and shows the attachment of the blade to the blade mounting. The axial impeller shown in the drawings has a hub 1 for attaching the impeller to a shaft (not shown) . To this end, the hub 1 has an axial centre hole 2 and a key- way 3 formed therein. In a manner that will be described in more detail below, the hub 1 supports a plurality of essentially radial blades 4, of which only one is shown in Figs 2 and 6. The hub 1 supports two discs 5 which are arranged in front of each other and are made of metal sheet, prefer¬ ably cor-ten metal sheet. The two discs 5 are concentric with the hub 1 and perpendicular to the axis thereof. Each disc 5 has a centre hole 6, which has a smaller diameter than the hub 1 but a greater diameter than the centre hole 2 thereof, and a plurality of bolt holes 7, which are positioned in the vicinity of the centre hole 6 and are uniformly distributed around this. Each disc 5 is attached to the hub 1 by means of bolts 8, which extend through the holes 7 and are screwed into corresponding threaded holes 9 in the hub 1 (Fig. 3) . Each disc 5 has two series of through bolt holes 10 and 11, the bolt holes 10 in one series being positioned on and uniformly distributed along an outer circle Cl, which is concentric with the disc 5, and the bolt holes 11 in the other series being positioned on and uniformly distributed along an inner circle C2 , which is concentric with the disc 5. The bolt holes 10 and 11 are positioned radially in front of each other and form pairs of holes 10, 11. The number of pairs of holes 10, 11 is identical with the number of blades 4. Each blade 4 is, in a manner that will be described in more detail below, attached to a cast blade mounting 12, which is arranged between the discs 5. Each blade mounting 12 has a main part 13 and a pivot pin 14 integ¬ rally cast therewith. The main part 13 has two parallel through bolt holes 15 and 16, each positioned axially in front of a bolt hole 10, 11 in a pair of holes 10, 11 in each disc 5. The discs 5 are attached to the blade mount- ings 12 and pressed against the main part 13 thereof by means of bolts 17 and 18, which extend through the holes 10, 11 in the discs 5 and the holes 15, 16 in the blade mountings 12. To each blade mounting 12, there is fixed a ring 19 consisting of two ring halves which are interconnected by means of bolts 20 (Fig. 4) . The ring 19 has an internal circumferential shoulder 21 engaging in a circumferential groove 22 in the pivot pin 14 of the blade mounting 12, and is turnable about the pivot pin 14 for adjustment of the blade 4. The outer surface of the ring 19 is posi¬ tioned at the same level as the free end surface of the pivot pin 14. The ring 19 has four threaded bolt holes 23, which extend in the axial direction of the pivot pin 14 and which are uniformly distributed along the circum¬ ference of the ring 19. Each blade 4 has a blade base 24 in the form of a disc, which abuts against the outer surface of the ring 19 and the end surface of the pivot pin 14. An annular groove 25 is formed in the end surface of the pivot pin 14 and receives a cup spring 26, against which the blade base 24 abuts in the area of the groove 25. The blade 4 is attached to the blade mounting 12 with the aid of four bolts 27, which each extend through a hole 28 in the blade base 24 and are each screwed into one of the bolt holes 23 in the ring 19 so as to press the base 24 of the blade 4 against the blade mounting 12. As will be apparent, the ring 19 is turnable for adjusting the blade 4 merely when the bolts 27 are not tightened. A border 30 of metal sheet, preferably cor-ten metal sheet, surrounds the two discs 5 to produce a flow which is aerodynamically undisturbed by the blade mountings 12. The border 30 has in front of each blade mounting 12 a through hole 31 for each blade 4. As will be seen from Figs 1, 3 and 7, the width of the border 30 is greater than the distance between the discs 5. The border 30 has a plurality of internal disc mountings 32 in the form of radially inwardly directed flanges, which are welded to the border and which are uniformly distributed along the circumference thereof. Each mounting 32 has axially directed pins 33, which are inserted in a pin hole 34 (Fig. 5) in the associated disc 5. The pin holes 34 are formed in the discs 5 in the vicinity of the circumference thereof. The disc mountings 32 are provided with axially directed notches 35 (Fig. 3) which enable radial relative motions, which arise between the border 30 and the discs 5 during operation of the impeller, to be received in an elastically yieldable manner. As will be evident from what has been said above, identical blade mountings 12 can be used independently of the number of blades 4 in the impeller. Blade mountings of different types and dimensions thus need not be kept in stock. As to the discs 5 and the border 30, it is suf¬ ficient to keep metal sheets in stock since the machining of a metal sheet for manufacturing discs and border can be effected very easily and quickly once the diameter of the discs and the number of blades have been determined. The machining is suitably carried out as laser cutting. The above-described impeller can be modified in many different ways within the scope of the invention. It should be particularly emphasised that the discs 5 and the border 30 need not be made of cor-ten metal sheet or any other metal sheet, but can be manufactured from, for instance, plastic material.

Claims: CLAIMS 1. An axial impeller having a hub (1) for attaching the impeller to a shaft and a plurality of essentially radial blades (4), which are each connected to the hub (1) by means of a blade mounting (12) and turnably attached to the respective blade mountings, c h a r ¬ a c t e r i s e d in that the hub (1) supports two paral- lei discs (5) which are arranged in front of each other, have essentially the same diameter and are provided with through bolt holes (10, 11), that the blade mountings (12) are arranged between the discs (5), and that the discs (5) are attached to the blade mountings (12) and pressed against these by means of bolts (17, 18), which extend through bolt holes (10, 11) in the respective discs (5) . 2. An axial impeller as claimed in claim 1, c h a r a c t e r i s e d in that the bolt holes (10, 11) in the one disc (5) are positioned in front of the bolt holes (10, 11) in the other disc (5), and that the bolts (17, 18) extend through through bolt holes (15, 16) in the respective blade mountings (12) . 3. An axial impeller as claimed in claim 2, c h a r a c t e r i s e d in that the bolt holes (10, 11) in each disc (5) are arranged in pairs, one (10) of the bolt holes in all pairs being positioned on an outer circle (Cl) which is concentric with the disc (5) and the other (11) of these bolt holes being positioned on an inner circle (C2) which is concentric with the disc (5), and that each blade mounting (12) has two through bolt holes (15, 16) , which are located in front of the bolt holes (10, 11) in a pair of bolt holes in each disc (5) . 4. An axial impeller as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the discs (5) are made of metal sheet. 5. An axial impeller as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that a circumferential border (30) surrounding the two discs (5) and having through holes (31) for the blades (4) is attached to the discs to produce a flow which is aerodynamically undis¬ turbed by the blade mountings (12) . 6. An axial impeller as claimed in claim 5, c h a r a c t e r i s e d in that the border (30) has internal disc mountings (32) , which are uniformly dis- tributed along the circumference of the border and have pins (33), which are inserted into pin holes (34) formed in the discs (5) in the vicinity of the circumference thereof. 7. An axial impeller as claimed in claim 6, c h a r a c t e r i s e d in that the disc mountings (32) are yieldable in a limitedly elastic manner in the radial direction of the discs (5) . 8. An axial impeller as claimed in any one of claims 5-7, c h a r a c t e r i s e d in that the border (30) is made of metal sheet.

Inventors: SAETERDAL EDGAR, SAETERDAL, EDGAR
Applicants: FLAEKT AB, SAETERDAL EDGAR, ABB FLAEKT AB, SAETERDAL, EDGAR
Application year: 1997
Main classification: F04D29
IPC codes: F01D7, F04D29