Blade for a wind motor

A blade for a wind motor comprises a load-bearing structure and an external covering of plastic material. The load-bearing structure is of flat tubular form and is composed of a pair of facing half shells constituted by sheet metal pressings of substantially channel section. Flat-bottomed impressions are provided along the edges of the shells. The shells are joined together by spot welds welding the bottoms of the impressions of one shell to the bottoms of corresponding impressions of the other shell.

The present invention relates to a blade for a wind motor, the blade being 
of the type comprising a load-bearing structure attachable at the root end 
of the blade to a rotary mounting, and an outer covering of plastic 
material carried by the load-bearing structure. 
The object of the present invention is to provide a blade of the aforesaid 
type which is robust yet light, and is both simple and economical to 
produce. 
In order to achieve this object, the present invention provides a blade of 
the type indicated above, in which the load-bearing structure comprises an 
elongate reinforcing element of flat tubular form which tapers towards the 
free end of the blade, the said tubular reinforcing element being composed 
of a pair of facing half shells constituted by sheet metal pressings of 
substantially channel section, said shells being provided along their 
edges with a plurality of separate impressions each with a flat base with 
dimensions sufficient to accommodate a spot weld, the flat base of each 
impression of one half shell being joined by means of a spot weld to the 
flat base of a corresponding said impression of the other half shell. 
The blade is therefore composed of only a small number of parts which can 
be assembled together relatively quickly and economically due to the 
simple assembly techniques involved. 
The impressions formed in the edges of each half shell, are preferably 
substantially semi-circular in profile and ensure stable and effective 
retention of the external plastic covering by the load-bearing structure. 
Preferably, the tubular reinforcing element has a hollow axial stub of 
rectangular cross-section which projects through the covering of plastic 
material and which is provided on two opposite faces with stiffening 
plates, said hollow stub being arranged to receive therewithin a 
rectangular portion of a shaft carried by said rotary support, and said 
plates and stub being formed with aligned holes through which bolts can be 
passed to secure the blade to said rectangular shaft portion. 
Due to this arrangement, the mounting of the blade on the rotary support of 
the wind motor can be carried out quickly and easily.

The blade 10 shown in the drawings is intended for use in a wind motor, 
that is a motor designed to convert the energy of the winds into a form in 
which it can be used to drive a machine. 
The blade 10 is composed of a metallic load-bearing structure 12 surrounded 
by an external covering 14 of plastic material. The external covering 14 
is shaped like a wing with an aerofoil cross-section and a plan profile 
which is trapezoidal in form and tapers towards the free end 10a of the 
blade. 
The load-bearing structure 12 consists of a tubular reinforcing element 
which has a flat profile in cross section and which tapers towards the 
free end 10a of the blade 10. This reinforcing element is formed by a pair 
of facing, symmetrical half shells of pressed metal sheet, each of which 
presents a substantially similar channel profile in cross-section. The 
half shells 16, 18 are provided along their facing edges, in corresponding 
axial positions, with a plurality of impressions 16a, 18a of semi-circular 
profile; one such impression 16a is illustrated in detail in FIG. 3. The 
impressions 16a, 18a each have a flat base 16b, 18b with dimensions 
corresponding to the dimensions of a spot weld. The base 16b of each 
impression 16a is joined to the base 18b of the corresponding impression 
18a by means of a spot weld 20. 
In addition to enabling the half shells 16 and 18 to be joined together by 
spot welding, the impressions 16a and 18a serve to positively locate 
internal projections on the external plastic covering 14 and thereby 
ensure accurate and secure anchoring of the covering 14 to the 
load-bearing structure 12. 
In correspondence to the root 10b of the blade 10, the load-bearing 
structure 12 has a tubular axial stub 22 protruding through the plastic 
covering 14. In the region of the axial stub 22, the half shells 16, 18 
have flanged edges 16c, 18c which are joined together by means of spot 
welds 20. As can be seen in FIG. 4, the axial stub 22 is of rectangular 
cross-section and is arranged to receive the rectangular end 24a portion 
of a shaft 24. The shaft 24 is supported by a rolling bearing 26 in a 
rotary support 28 of the wind motor. The shaft 24 and the axial stub 22 
together support a centrifugal mass 30 which serves to orientate the blade 
10, in the usual manner. The rectangular end 24a of the shaft 24 is 
secured inside the axial stub 22 by means of a pair of radial through 
bolts 32 which pass through transverse holes 34 formed in the end 24a of 
the shaft 24 and through corresponding holes formed in the half shells 16 
and 18. The bolts 34 also pass through holes 36 a, 38a formed in two 
rectangular stiffening plates 36, 38 welded to opposite outer faces of the 
stub 22.