Knocked-down fan for engine cooling and other applications

Abstract: An engine cooling-system fan (10) formed by combining two fan assemblies (12, 12') of like construction. Each fan assembly (12, 12') comprises a sheet-metal hub (14) with radiating spokes (20), and a set of fan blades (16) fastened one to each spoke (20). The hubs (14) of both fan assemblies (12, 12') are riveted or otherwise joined together in axial alignment, with the two sets of fan blades arranged alternately at constant angular spacings. Preferably, the spokes (20) of either one of the fan assemblies (12, 12') are offset to provide the same plane of rotation for the two sets of the blades (16).

Description: This invention relates generally to fans, and particularly to those of the class used for engine cooling and like applications. By the term "fan" as used herein and in the claims attached hereto is meant any propeller-type device for imparting motion and acceleration to air or other gases and operating on the centrifugal principle. Thus the invention should be construed to comprehend devices that may be commonly classified as blowers. Internal-combustion engines such as those used on motor vehicles are normally equipped with a fan as a part of the engine-cooling system. Normally mounted on the water-pump shaft driven from the engine via a fan belt, the engine fan functions to provide a powerful draft of air through the radiator. A typical construction of the engine fan according to US-A-3 147 811 or US-A-2 140 017 is such that a set of fan blades have been attached, in the case of US-A-2 140 017 by riveting respectively to arms or spokes radiating from a hub. The hub and spokes are a unitary piece of sheet metal. This type of engine fan, as so far constructed, has had some shortcomings. Such shortcomings arise from the fact that the fan blades should not overlap, as seen in a front view, to such an extent as to interfere with the riveting of the successive blades to the spokes. Limitations have therefore been imposed on the shape, size and number of fan blades that could be employed. The number of fan blades has had to be reduced if they are each increased in size for higher rates of air delivery. Conversely, if the number of fan blades is increased, the size of each blade has had to be reduced. Such limitations on the prior art have made it difficult to make the rate of air delivery as high as can be desired, and the air pressure has been liable to pulsate. It might be contemplated to drive the fan at higher speeds for higher rates of air delivery. This solution would not be realistic because, driven at high speeds. the engine fan would generate inconveniently large amounts of vibrations and noise, particularly if it had a relatively small number of blades. US-A-2 098 640 discloses a fan construction with two fan assemblies which have an unequal number of blades with the angles between each pair of blades being different from that of any other adjacent pair of blades, whereby the two fan assemblies are statically balanced. Blades attached to corresponding arms radially extending from a hub member may be arranged in such a way that the arms of the separate assemblies overlap or even are arranged one above the other. SUMMARY OF THE INVENTION Starting from a fan of the type disclosed by US-A-3 147 811 or US-A-2 140 017 it is an object of the present invention to provide a fan of a so-called knocked-down construction whereby any desired practical number or size of fan blades can be employed without the possibility of interfering with the assemblage of the fan. This object is solved according to the features of claim 1. The fan blades are attached to spokes radially extending from a hub before the fan assemblies are joined together. In each such fan assembly the angular distances between the fan blades are twice as much as those between the fan blades of the assembled fan. Each blade can therefore be attached to the spoke of its respective fan assembly without being hampered by the neighbouring blades. Thus, the fan can be readily assembled with practically any desired number or size of blades to provide a desired rate of air delivery at constant pressure. The spokes of one of the fan assemblies are offset into coplanar relation with those of the other fan assembly so that the blades of the two combined fan assemblies rotate in the same plane. The performance of the resulting fan would then be totally free from any adverse effect that might be feared to arise from the joining of the two fan assemblies in axial alignment. Advantageous embodiments are disclosed by the dependent claims. The above and other features and advantages of this invention and the manner of realising them will become more apparent, and the invention itself will best be understood, from a study of the following description and dependent claims, with reference to the attached drawings showing some preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front elevation of a knocked-down engine fan embodying the principles of this invention, the fan comprising two fan assemblies disposed one behind the other in axial alignment; Fig. 2 is a front elevation of the front fan assembly of the engine fan; Fig. 3 is a front elevation of the rear fan assembly of the engine fan; FIG. 4 is a side elevation of the sheet-metal hub members or spiders of the engine fan, shown together with only one of the fan blades attached thereto for illustrative convenience; FIG. 5 is a front elevation of the spider of the rear fan assembly of FIG. 3; FIG. 6 is an enlarged fragmentary section through the spider of FIG.5, taken along the line VI-VI therein; and FIG. 7 is a front elevation of the spider of the front fan assembly of FIG. 2. DESCRIPTION OF THE PREFERRED EMBODIMENTS The knocked-down fan of this invention will now be described more specifically as adapted for use as an engine cooling-system fan. Generally designated 10 in FIG. 1, the knocked-down engine fan exemplifying the invention is shown as a combination of two fan assemblies 12 and 12' of like construction disposed one behind the other. The front fan assembly 12 is shown by itself in FIG. 2, and the rear fan assembly 12' in FIG. 3. It will be seen that FIGS. 2 and 3 show the fan assemblies 12 and 12' in the same angular positions about their axes as they are depicted in FIG. 1. As will be understood from FIG. 2, the front fan assembly 12 comprises a hub member 14 known to the specialists as a spider because of the resemblance of its appearance, and a plurality of, four in this embodiment, fan blades 16 fastened to the spider 14. This spider takes the form of a sheet-metal punching integrally comprising a hub 18 and a set of four arms or spokes 20 extending radially from the hub with a constant angular pitch spacing of 90 degrees. The fan blades 16 are riveted at 22 to the respective hub spokes 20 via sheet-metal retainers 24, with each fan blade engaged between one hub spoke 20 and one retainer 24. It will be appreciated that the four fan blades 16 of the front fan assembly 12 employed in this embodiment are angularly spaced from one another much more widely than the eight fan blades of the complete fan 10 of FIG. 1. Therefore, if the fan blades 16 are riveted to the hub spokes 20 before the two fan assemblies 12 and 12' are joined together, the riveting of each fan blade will not be hampered by the neighboring fan blades of the same fan assembly. It will also be understood that the width, or dimension in the circumferential direction of the fan, of each fan blade 16 can be far greater than if the fan 10 were not divided into the two separate assemblies 12 and 12', as has been the case heretofore. The hub 18 has a mounting hole 26 of relatively large diameter formed centrally therethrough for use in mounting the fan 10 on, for example, the water-pump shaft of an internal-combustion engine. An annular row of six additional mounting holes 28 of smaller diameter are formed concentrically around the central mounting hole 26 for use in fastening the fan 10 to, for example, a fan pulley on the water-pump shaft. Another annular row of eight holes 30 in the hub 18, also centered about the hub axis, are rivet holes for use in fastening together the two fan assemblies 12 and 12'. Despite the showing of FIG. 2, it is not essential that the holes 26, 28 and 30 be formed in the hub 18 before the front fan assembly 12 is combined with the rear fan assembly 12' as in FIG. 1. The rivet holes 30, in particular, should preferably be formed after the two fan assemblies 12 and 12' are held together in the correct axial and angular positions as in FIG. 1, in order to firmly unite the fan assemblies in the required relative positions. The construction of the front fan assembly 12 as so far described with reference to FIG. 2 applies to that of the rear fan assembly 12' illustrated in FIG. 3. Therefore, in this and other drawings, the various parts of the rear fan assembly 12' are indicated by priming the reference numerals used to denote the corresponding parts of the front fan assembly 12. No repeated explanation of such parts of the rear fan assembly 12' is considered necessary. As will be understood by referring back to FIG. 1, taken together with FIG. 4, the two fan assemblies 12 and 12' are fastened together by rivets 32 passing through the rivet holes 30 and 30' in the hubs 18 and 18'. The fan assemblies are united in alignment about the hub axis X-X but with an angular difference equal to half the pitch of the fan blades 16 and 16' of each fan assembly. Since each fan assembly 12 or 12' has four blades with a pitch angle of 90 degrees in this particular embodiment, the two fan assemblies 12 and 12' are joined with an angular displacement of 45 degrees from each other about the hub axis X-X, providing a total of eight fan blades 16 and 16' with an equal pitch spacing of 45 degrees. Incidentally, FIG. 4 shows only the spiders 14 and 14' of the fan assemblies 12 and 12' in their correct relative positions, together with only fan blade 16' in order to reveal the twist imparted to each hub spoke 20 or 20'. Such twist of the hub spokes 20 and 20', and the resulting angles of the fan blades 16 and 16' with respect to the principal plane of the fan 10, is of course needed for the air-moving function of the fan. Although the two fan assemblies 12 and 12' are nearly identical in construction, a slight difference exists in order to make the fan blades 16 and 16' of both fan assemblies rotate in one and the same plane. Toward this end the hub spokes 20' of the rear fan assembly 12' are offset into coplanar relation with the hub spokes 20 of the front fan assembly 12, as discussed in more detail in the following. As will be noted from FIGS. 5 and 6, the hub spokes 20' of the rear fan assembly 12' are each twisted at its region Y, in the immediate vicinity of the hub 18', to hold the associated fan blade 16' at the required angle set forth with reference to FIG. 4. At this twisted part Y each hub spoke 20' is offset forwardly a distance equal to the thickness T of the sheet metal of which the spiders 14 and 14' are made, into coplanar relation with the hub spokes 20 of the front fan assembly 12. With the hub spokes 20 and 20' of the two fan assemblies 12 and 12' thus disposed in coplanar relation to each other, the fan blades 16 and 16' rotate in the same plane just like those of the conventional undivided fan. It will, of course, be understood that the hub spokes 20 of the front fan assembly 12 could be offset into coplanar relation with the hub spokes 20' of the rear fan assembly 12'. As has been mentioned, the mounting holes 26, 26', 28 and 28' and rivet holes 30 and 30' need not necessarily be formed in the hubs 18 and 18' before the fan assemblies 12 and 12' are united as shown in FIG. 1. Only the central mounting holes 26 and 26' may be preformed in the hubs 18 and 18' to facilitate the boring and other operations to be performed subsequently on the hubs. However, in some instances. it may be desirable to preform all such holes in the hubs 18 and 18', as in the quantity production of the fan assemblies 12 and 12' including those to be held in stock for future use as replacements. In such cases the holes may be arranged as shown in FIG. 5 in the hub 18' of the rear fan assembly 12' and as shown in FIG. 7 in the hub 18 of the front fan assembly 12. Since each hub has four spokes in this embodiment, the eight rivet holes 30 and 30' can be of the same arrangement in each hub 18, 18'. The arrangement of the six mounting holes 28, 28' must differ between the hubs 18 and 18'. The angle Z, FIG. 7, between one of the mounting holes 28 in the hub 18 and the centerline of the adjacent spoke 20 is 15 degrees whereas the angle Z', FIG. 5, between one of the mounting holes 28' in the hub 18' and the centerline of the adjacent spoke 20' is 30 degrees. Although the present invention has been shown and described in very specific aspects thereof and as embodied in engine cooling-system fans, it is not desired that the invention be limited by the exact details of the illustrated embodiments. For example, the number of fan blades of each fan assembly could be greater or smaller than four. Still further, the two or more fan assemblies could be united by screwing or bolting.

Claims: A fan for engine cooling or other applications, comprising two preassembled fan assemblies (12, 12') each of which comprises a plurality of equally angularly spaced spokes (20, 20') radially extending from a hub (18, 18'), and a plurality of identical fan blades (16, 16') riveted or otherwise attached radially to the spokes (20, 20'); the angular spacing of the spokes of one fan assembly being the same as that of the other fan assembly; the fan blades (16, 16') of one fan assembly being the same as these of the other fan assembly; the fan assemblies (12, 12') being arranged in axial alignment and angularly displaced from each other by half the angular spacing of the fan blades (16, 16') of one assembly, and joined together by riveting, bolting or screwing to form a knocked-down fan with neighbouring blades (16, 16') of the different fan assemblies partly overlapping; and the spokes (20, 20') of one fan assembly differing from those of the other fan assembly only in that the spokes (20') of one fan assembly (12') are offset a distance equal to the thickness of a sheet material of which the spokes (20, 20') are made, for rotation of the blades (16, 16') of the fan assemblies in the same plane. The fan according to claim 1, characterised in that each blade (16, 16') is engaged between a sheet metal retainer (24, 24') and the corresponding spoke (20, 20'). The fan according to claim 1 or 2, characterised in that the spokes (20') of one fan assembly (12') comprise a twisted part (Y) in the immediate vicinity of the hub (18') for the offsetting of the spokes. The fan according to claims 1 to 3, characterised in that an annular row of mounting holes (28, 28') and/or an annular row of rivet holes (30, 30') are arranged concentrically around a central mounting hole (26, 26') of the hub (18, 18').

Inventors: MASATSUGU TOMOMI, MATOBA YOSHIAKI, MASATSUGU, TOMOMI, MATOBA, YOSHIAKI
Applicants: CATERPILLAR MITSUBISHI LTD, SHIN CATERPILLAR MITSUBISHI LTD.
Application year: 1989
Main classification: F04D29
IPC codes: F04D29