EP0894199B1

EP0894199B1 - Impeller

Info

Publication number: EP0894199B1
Application number: EP97921050A
Authority: EP
Inventors: Edgar Säterdal
Original assignee: Flaekt Woods AB
Current assignee: Flaekt Woods AB
Priority date: 1996-04-26
Filing date: 1997-04-23
Publication date: 2003-06-25
Anticipated expiration: 2017-04-23
Also published as: HUP9901664A2; PL182685B1; BG62900B1; AU2719897A; DE69723065D1; NO984955L; HUP9901664A3; SK144098A3; EP0894199A1; PL329515A1; NO984955D0; CZ287283B6; SK282927B6; SE9601589D0; RU2184275C2; DK0894199T3; ES2202610T3; TR199802138T2; CZ335298A3; ATE243812T1

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

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 require, when manufacturing impellers having different diameters and/or different numbers of blades for each individual impeller variant, specially designed components, 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 US 4.877.376 an attaching means for a blade of fiber material, more particularly for a propeller of a propfan to a metallic hub which will satisfy the requirements of substantially different cross-sections of the two components and achieve a favorable transfer of the forces caused by centrifugal effect and impact from foreign bodies while reducing the weight is revealed.

The blade is formed with an integral shank and the hub comprises a metal body having a bore receiving the shank and tensioning means connects the shank and the body for applying tensile force to the shank, the blade and its shank being integrally formed of a fiber-reinforced synthetic resin material. The blade is connected to a flange on the metal body by means of bolts or screws.

The construction of the invention permits the manufacture of the assembly to be advantageously simplified and the weight to be reduced while providing a consistently high rate of force transfer.

In CH 601 675 A5 an impeller for an axial flow fan is revealed. It comprises a hub and two ring-shaped carrier elements, preferably made of a polymer material. In the carrier elements a plurality of indentations are made for the attachment of radially orientated fan blades. The object of the invention is to make it possible to use the same ring-shaped elements for different number of blades and different lengths of the blades.

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 positioned 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 mountings. 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 circumference 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 impeller according to the invention with the blades removed,

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 impeller,

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 keyway 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, preferably 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 C1, 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 integrally 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 mountings 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 positioned 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 circumference 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 sufficient 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 claims. 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

An axial impeller, for an axial flow fan, having
a hub (1) for attaching the impeller to a shaft,
a plurality of blade mountings (12),
and a plurality of essentially radial blades (4), which are each connected to the hub (1) by means of the blade mounting (12) and turnably attached to the respective blade mountings,
characterised by two parallel discs (5) which are arranged in front of each other, have essentially the same diameter and are provided with bolt holes (10, 11),
in that the hub (1) supports the two parallel discs (5) which are bolted to the hub (1),
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),
in that the blade mountings (12) are arranged between the discs (5), and
in that the blade mountings (12) are attached to the discs (5), by means of bolts (17, 18), which extend through bolt holes (10, 11) in the respective discs (5) and through through bolt holes (15, 16) in the respective blade mountings (12).
An axial impeller as claimed in claim 1, characterised in that the discs (5) are made of metal sheet.
An axial impeller as claimed in any one of claims 1-2, characterised 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 undisturbed by the blade mountings (12).
An axial impeller as claimed in claim 3, characterised in that the border (30) has internal disc mountings (32), which are uniformly distributed 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.
An axial impeller as claimed in claim 4, characterised in that the disc mountings (32) are yieldable in a limitedly elastic manner in the radial direction of the discs (5).
An axial impeller as claimed in any one of claims 3-5, characterised in that the border (30) is made of metal sheet.