Light Weight Fan Assembly

Abstract

Disclosed is a fan assembly in which each fan blade is formed by overlying, thin plates which receive, between them, the extending end portion of a fan spider arm, the laminated assembly thus formed being riveted together to provide a light weight, yet rigid, fan spider and blade assembly.

Description

BACKGROUND OF THE INVENTION

Fans of the type under consideration are mass-produced under considerable pressure to keep unit costs for material and assembly at a minimum. While it is advantageous to utilize minimum thickness material in producing the fan spider and attached blades, design movement in this direction is limited by the necessity for strength and rigidity in the assembled fan to fulfill normal performance and durability requirements for the fan.

The structure of the present invention utilizes a laminated form of joining the fan blade to the spider arm permitting use of minimum thickness material in forming the fan blade while retaining the required blade rigidity. Because the blade is very light in weight, centrifugal and vibrational forces acting on the fan assembly, during operation, are reduced and the fan spider itself may be formed of minimum thickness stock thus further decreasing the total weight of the fan assembly. This also results in considerable less stress on the fan elements and fan drive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a fan assembly embodying the present invention.

FIG. 2 is an enlarged, fragmentary plan view of a fan blade attached to the fan spider arm.

FIG. 3 is a sectional view taken generally along the line 3--3 of FIG. 2.

FIG. 4 is an enlarged, fragmentary plan view showing a modified form of attachment of the fan blade to the spider arm.

FIG. 5 is a sectional view taken generally along the line 5--5 of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring initially to FIG. 1, there is shown at 10 a fan spider substantially the same as that disclosed and claimed in my U.S. Pat. No. 3,285,502. The radially extending arms 11 of the fan spider are skewed or twisted somewhat out of the plane of the central portion 10a of the spider and the arms 11 extend at various angles to each other from the central portion of the spider all as described in my patent mentioned above. Attached to the end portions of each of the arms 11 are fan blade elements indicated generally at 12 in FIG. 1.

Referring to FIG. 2, the fan blade elements and the form of their attachment to the end portions 11a of the spider arms 11 will be described in detail. Each of the fan blade elements is formed from a relatively thin plate 13 and an overlying, smaller plate 14. The smaller of the plates identified at 14 lies entirely within the outline of the larger plate 13 and is attached along its marginal area, indicated at 14a, to the plate 13 by any suitable means such as spot welding.

The smaller plate 14 is not attached to the plate 13 along its margin nearest the axis of rotation of the fan assembly and the end portion 11a of the corresponding spider arm 11 extends between the plates 13 and 14 at this portion of the fan blade element. Locating and aligning of the fan blade element with the arm 11 is accomplished by means of an abutment or dimple 16 formed in the plate 14 and extending from the inner surface of plate 14. The protrusion or abutment 16 engages a generally V-shaped notch 17 formed in the end of the arm 11. It will be understood that the dimples 16 might also be formed in the plate 13 rather than in plate 14. Fastening means, in the form of rivets 18 serve to laminate and rigidly fasten the end portion 11a of the spider arm to the plates 13 and 14 between which it extends.

As may best be seen in FIG. 3, the end portion 11a of the spider arm has an arcuate configuration transversely and this provides the desired curvature for the plate 13. The space at the side margins of the arm portion 11a is closed by means of tabs 19 which are integral with the plate 14 and extend generally perpendicular to the plane of the plate 14 and into engagement with the inner surface of the plate 13. These triangularly shaped, inwardly bent tabs 19 serve to aid assembly alignment and to seal the area of entry of the arm portion 11a between the plates 13 and 14 against the entry of dirt or other foreign matter which might, when accumulated, alter the balance of the fan assembly. As will be particularly evident from FIG. 3, the use of the laminated form of attachment of the blade element, composed of the plates 13 and 14, to the spider arm 11a, and the rigidifying effect of the "bracing" action of the plate 14 on the plate 13 provides the fan blade element with the desired rigidity even though the plates 13 and 14 are formed of relatively thin stock.

A modified form of the structure is shown in FIG. 4 and it differs from that previously described only in the means for aligning the fan blade element with the spider arm. Referring to FIGS. 4 and 5, a plate 21 has attached to it a smaller plate 22, the attachment being preferably by means of spot welding along the margin 22a of the plate 22. Accommodated between the plates 21 and 22 is the extending portion 24 of the spider arm 26. The extending portion 24 of the spider arm is identical to the spider arm portion 11a of FIG. 1 except that it does not carry the V-shaped notch but has a rectilinear end margin. The plate 22 is substantially identical to the plate 14 of FIG. 1 except that it carries four abutments or protrusions. Abutments 27 are circular and engage the side margins of arm portion 24 and abutments 27a are L-shaped and engage the corners of the arm portion when it is interposed between the plates 21 and 22. The abutments 27 and 27a serve to align the fan blade element with the spider arm. As was the case with respect to the structure shown in FIG. 1, the laminated construction formed by the plate 22, arm portion 24 and plate 21 is rigidly secured together by means of rivets 28.

From the foregoing it will be evident that the laminated construction described provides the necessary rigidity for the fan blade element but permits utilizing material of minimum thickness in fabricating the blade components. Because of this, the weight and moment of inertia of the fan assembly is relatively low. Because the arrangement permits use of relatively short spider arms, and since the blade components are of minimum weight, the radius of gyration of the assembly is relatively short. Centrifugal force acting on the spider arms is, thus, smaller than in conventional structures permitting safe use of relatively thin cross section configuration for the fan spider. The relatively light weight of the assembly reduces bearing loads and the vibration frequency response of the fan assembly is substantially the same as that of conventional fan assemblies. The protrusions, cooperating with the margin of the spider arm portions provide a quick and positive alignment of the blades with the spider arms, and the tabs bent from the smaller plate component of each of the blade elements serve to prevent entry of foreign matter between the blade components and aid in the assembly alignment.

While two alternate constructions have been described in detail herein, it will be understood that the invention is to be limited only by the appended claims.

Claims

I claim:

1. A fan assembly of the type which includes a fan spider having a plurality of transversely curved radially extending arms with a fan blade attached to each of the arms, wherein the improvement comprises each fan blade being formed by two overlying relatively thin plates, one of said plates having a transverse curvature corresponding to the curvature of said arms and the other of said plates extending across the concave face of said one plate, said other of said plates being attached along its periphery to said one plate but unattached thereto at the end closest the axis of rotation of the fan assembly, the end portion of the corresponding spider arm extending between said plates at their unattached ends, abutment means carried by one of said plates engaging the margin of said extending spider arm portion to locate and align the fan blade on the spider, and fastening means rigidly laminating together said plates and the interposed portion of the spider arm.

2. A fan assembly as claimed in claim 1 in which said abutment means comprises a single protrusion formed at the inner face of one of said plates and the extending tip of said spider arm is provided with a generally V-shaped notch accommodating said protrusion for locating and aligning the fan blade on the spider arm.

3. A fan assembly as claimed in claim 1 in which one of said plates carries tabs on each side of said extending portion of the fan spider, said tabs being bent toward and into engagement with the inner surface of the other plate to thereby substantially seal the space between the plates adjacent the extending portion of the fan spider against the entry of dirt or the like and aiding in the radial alignment of the blade and spider arm.