US2368734A - Method of making laminated wooden propeller blades - Google Patents

Description

atented Feb. 6, 1945 OFFlCE METHOD OF MAKING LAMINATED WGUDEN PROPELLEE BLADES 4 Fred E. Weick, College Park, Md., asslg-nor to Englneering and Research Corporation, Riverdale, Md., a corporation of Maryland No Drawing."

Application October 30, 1942, Serial No. 463,949

1 Claim. (Cl. 144-309) This invention relates to the'manufacture of articles and devices, such as propeller blades, which are made of wood which has been impregnated and' compressed. For purposes of illustration only, the invention will be described as applied to the manufacture of propeller blades.

In the manufacture of many articles and devices, such as the so-called "Compreg propellers, laminae of wood are first impregnated with a. material, such as a phenolic condensation product which hardens and solidifies when heated. A number of these laminae are then superposed and are subjected to heat and a predetermined pressure in order to compress them and harden the binder, thereby forming a slab. A number of these slabs are then superposed and united, as by glueing, in order to form a block from which an article such as a propeller blade, may be out.

It is usually found that each of the separate laminae which are combined to form a slab'is not of the same density throughout whereby, for example, one endof a lamina will be heavier than the other. It is also found that the total weight of one lamina will be heavier than that of another. 'I'hese phenomena almost invariably result in the formation of slabs and blocks which differ in total weight or in the location of the density.

center of gravity, or in both, and each of which slabs or blocks is of non-uniform density throughout. It is, of course, desirable to eliminate these variations from slabs and blocks regardless of the intended use thereof but their elimination is of particular importance when the slabs and blocks are to be used in the manufacture of propeller blades, which must be dynamically and statically balanced. Various expedients, such as local weighting, are now resorted to in the manufacture of propeller blades to correct the effects of the non-uniformity of the laminae and slabs.

It is the princip l object of this invention to provide an improved method of making slabs and blocks of the described type in general accordance with the described procedure, but which will result in the formation of slabs and blocks of equal total weight and each of which will be. of constant average density.

In manufacturing such blocks and slabs in acweight. Laminae of varying thickness and weight may be added or substituted for one of the superposed laminae in order to provide a slab of the predetermined weight. The superposed, impregnated laminae. are then subjected to heat and pressure in accordance with known practice but, in distinction to known practice, are compressed to a predetermined thickness, which is preferably the same for all slabs which are to be included in the same block, instead of being subjected to a predetermined pressure as in the prior art. I thus produce slabs of constant weight and thickness and consequently of constant average These slabs may be superposed and united to form a block, which may be carved into any desired shape, such as that of a propeller blade, in accordance with known practice. special cases the lateral edges of the superposed laminae may be confined while compressing the laminae into a slab in order to produce a slab of which the blades are out are of equal weight.

The method according to this invention may be applied to the manufacture of the root portions of blades of the so-called Schwarz type, in which blades only the root portion is formed of cordance with my invention, I first form laminae -o make p a slab of approximate predetermined 6 skilled in the art that modifications thereof, both I by addition and deletion of steps and change in theorder thereof, may be made without departing* in any Way from the spirit or scope of the .40

invention, for the limits of which reference must be had to the appended claim. 1 What is claimed is:

'I'he'method of forming a block of impregnated and compressed wood of approximately constant density throughout, which comprises the steps of impregnating separate wood laminae of substantially equal area with a material which hardens and solidifies when heated, superposing a plurality of said laminae having a predetermined total weight, simultaneously heating the superposed laminae and compressing them to a predetermined thickness to form a slab, and uniting a plurality of slabs of approximately equal weights to form a block.

FRED E. WEICK.