Abstract:
An impeller for a fan comprising a hub for rotation by a drive rotor and a plurality of fan blades for rotation with the hub, the impeller further comprising a support or guide member supporting or connecting fan blades of said plurality, and wherein one or more pockets are provided in said support or guide member and open axially of the fan for receiving balance weights.

Description:
This is a continuation of application Ser. No. 07/787,409, filed Nov. 4, 1991, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to an impeller for a blower, for example for a radial fan. 
     In radial fans, the air or the like is sucked in axially and blown out radially. Generally, the impellets of such fans are made from sheet metal. For example, a blade ring or rim is positioned between two guide rings and is connected thereto, for example, by bending over sheet metal tabs or by pinned fitting. If in the case of larger impeller diameters balancing of the impeller Is necessary, then balancing weights are fixed by clips to appropriate points of the impeller. It is also possible to balance the impeller by a planned milling away of parts of the impeller. Such techniques are also used with other types of blowers, for example, with axial-flow fans. 
     It is an object of the present invention to simplify the manufacture and balancing of impellers for fans, particularly for radial fans, end to cut down production costs. 
     SUMMARY OF THE PRESENT INVENTION 
     According to the present invention there is provided an impeller for a fan comprising a hub for rotation by a drive rotor and a plurality of fan blades for rotation with the hub, the impeller further comprising a support or guide member supporting or connecting fan blades of said plurality, and wherein one or more pockets are provided in said support or guide member and open axially of the fan for receiving balance weights. 
     In an embodiment, for a radial fan, said support or guide member is a guide ring arranged coaxially of said hub and supporting said plurality of fan blades. 
     For example, an impeller for a radial fan may have at least one of the guide rings provided with pockets. Preferably, said guide rings are arranged coaxially, and each is equipped with pockets, so as to permit complete dynamic balancing. The pockets may be in the form of axially open grooves, grooved sectors or bores. 
     In order to permit the insertion of balancing weights in simple manner on both guide or support rings without impediment by the other guide ring, both guide rings preferably have different diameters, the diameter steps being towards the open side of the pockets and the pockets of both guide rings being open to the same side. This makes it possible for the insertion of balancing weights from one side to not only take place without impediment on the front guide ring, but also on the larger diameter guide ring positioned behind it. However, it is also possible to construct the pockets so as to be open to both sides. 
     The impeller can be manufactured particularly inexpensively, if it comprises a plastics injection moulding, which encloses in one-piece manner the two guide rings and the interposed blade ring, as well as a sheet metal disk forming the hub and fixed to the plastics injection moulding by hot crimping of pins of the plastics part inserted in holes in the sheet metal disk. The one-piece injection moulding of this part is made particularly easy in that both guide rings have different diameters, which facilitates the design of the mould. 
     In a particularly advantageous development of the invention the pins for fixing to the sheet metal disk are located on lateral faces of the blades of the blade ring and the larger diameter guide ring is connected by connecting webs injection moulded onto the blades to the ends of the latter. This makes it possible to produce the plastics injection moulding with only two mould halves and without requiring slides. The sheet metal disk is preferably located within the associated guide ring and its inner face is aligned with the inner face of the guide ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the present invention will hereinafter be described, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 shows a longitudinal section through a radial fan having an impeller of the invention, 
     FIG. 2 shows a side view of the radial fan of FIG. 1, 
     FIG. 3 is en end view of the impeller of the radial fan shown in FIGS. 1 and 2, 
     FIG. 4 shows an axial section through the impeller of the fan of FIG. 3, 
     FIG. 5 shows a detail of the impeller of FIG. 4 showing on a larger scale pockets for the insertion of balancing weights, and 
     FIG. 6 is a view similar to that of FIG. 5 showing a detail of another embodiment of an impeller. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The radial fan shown in FIG. 1 and 2 has a fan casing 17, an impeller 16 end a drive motor 15. In the illustrated embodiment, the drive motor 15 is constructed as an external rotor-type motor having a centrally arranged stator surrounded by an external rotor. A hub portion 3 of the impeller 16 is pressed onto the rotor or a rotor hub such that the impeller 16 rotates with the rotor. Upon rotation of the impeller 16, the radial fan is arranged to suck in air from above, as illustrated in FIGS. 1 and 2, and blow it out radially. 
     The impeller 16 of the radial fan is illustrated in FIGS. 3 end 4 and is made of two parts, namely a plastics injection moulding 1 and a sheet metal disk 2. The injection moulding 1 defines two axially spaced, substantially coaxial, Guide range 4 and 5 and a blade ring 10, having blades 11, disposed between said guide rings 4 and 5. On radially extending, axial ends of the blades 11, the plastics injection moulding 1 is provided with pins 12, which each extend through a corresponding bore an the sheet metal disk 2 and which are interconnected by hot crimping the two parts. Preferably, each blade 11 carries several radially spaced pins 12, which are fixed by hot crimping in corresponding bores of the sheet metal disk 2, so as to create a stable impeller and also avoid resonances and vibrations. 
     The plastics injection moulding 1 is constructed in such a way that the two guide rings 4, 5 have different diameters and are arranged in stepped succession. This enables the moulding 1 to be formed in a two-part injection mould without the use of slides and the like. The sheet metal disk 2 is placed within the guide ring 4 and shaped by means of connecting webs 9 onto the outer ends of the blades 11. The inner faces 13 or 14 of the sheet metal disk 2 or the guide ring 4 are aligned with one another, so as not to disturb flow conditions on the impeller 16. FIG. 4 also shows that the sheet metal disk 2 has an inwardly drawn over hub portion 3, which is pressed onto the external rotor of the drive motor 15. 
     It can be seen in FIGS. 3 to 5 that both the guide rings 4 and 5 have pockets 6 or 7 formed therein. These pockets 6, 7 open axially. For balancing purposes it is possible to press into these pockets 6, 7 balancing weights, as 8, which weights, for example, may be of lead, and as a result of the configuration of these pockets adequate fixing against centrifugal forces is obtained. 
     The pockets 6, 7 for receiving the balancing weights 8 are, in the illustrated embodiment, grooved sectors provided on the radially extending, external surfaces of the guide rings 4, 5 and are open axially. The subdivision into grooved sectors increases the stability of the guide rings 4, 5 due to the interposed webs. However, it is also possible to replace the grooved sectors by through grooves or individual bores arranged around the circumference and which are axially open to one side. FIGS. 3 to 5 show that the guide rings 4, 5 have staggered diameters, so that the balancing weights 8 can be inserted from one side without any impediment. This diameter staggering is also appropriate to permit the production of the plastics injection moulding 1 in one piece using a two-part mould. 
     It is also possible, in the case of the embodiment shown in FIGS. 1 to 5, for the pockets 6, 7 to open to both sides (in the axial direction), so that the balancing weights 8 can be inserted from 8 random side. 
     In a further embodiment of an impeller of the invention, which is illustrated in FIG. 6, the two guide rings 4, 5 have the same diameter and the complete impeller 16 comprising the guide rings 4, 5, the fan blades 11 and the hub portion 8 is injection moulded in plastics material in one piece, for example, with the aid of a slide mould. This impeller has no need for a metal part, such as the sheet metal disk 2. 
     As shown in FIG. 6, the pockets 6, 7 in the two guide rings 4, 5 open axially in two opposite directions, but the pockets 6, 7 for the insertion of the balancing weights 8 may be open to the same side (in the axial direction) if required. As previously, the pockets may be continuous grooves or bores or interrupted grooves or spaced recesses. 
     Although the invention has been described and illustrated with respect to a radial fan, it can be used with other fan types. If the fan is, eg an axial blower, then support rings will usually be provided. Such support rings may either carry the fan blades, or, in the case of larger diameter impellers, may be located on the blade tips and interconnect the same. The said support rings may be provided with axially open pockets for the insertion of balancing weights. 
     It will be appreciated that modifications in or variations of the embodiments as described and illustrated may be made within the scope of the appended claims.