Abstract:
A method and apparatus for fabricating reinforcing bands for strengtheningarts to be subjected to high centrifugal stresses. The reinforcing bands are made of coiled wire with a high modulus of elasticity and with a matrix of light metal or light-metal alloy. The coil, hoop or blank so formed is compacted in a direction parallel to its axis under high pressure and heat by an annular metal ram in a mold or die consisting of a bottom member, an inner ring, and an outer ring which are constructed so that the blank or coil does not undergo any radial stresses.

Description:
BACKGROUND 
     1. Field of the Invention 
     This invention concerns a process and apparatus for manufacturing wound wire reinforcing bands and the product so obtained. 
     2. Description of the Prior Art 
     The high mechanical strength of boron or silicon carbide wire suggests utilizing such wire for fabricating bandlike reinforcing memebers intended for strengthening high-speed rotating parts or components subjected to high centrifugal stresses. Such reinforcing bands are made by coiling the wires and joining them to each other by means of a metallic matrix preferably consisting of light metal or a light metal alloy such as aluminum. 
     SUMMARY OF THE INVENTION 
     A new process and apparatus is here disclosed for producing such band-like reinforcing members. According to the invention, the high-strength wire is spirally wound on a mandrel and is covered by a foil of light metal, the wire being spaced at intervals of between 0.3 and 2.0 &#34;d &#34;(d being the diameter of the wire). The material used as matrix is then deposited on the single layer of wire obtained as above. This procedure is then repeated as many times as desired. Finally, the blank so formed is subjected to high pressure and heat in a mold wherein the direction of such pressure is parallel to the axis of the blank. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The drawing shows a view, partly in section and partly in side elevation, of the device for carrying out the process of the invention and the product thereby in a certain stage of formation. 
    
    
     DETAILED DESCRIPTION 
     To facilitate understanding of the invention, a specific example is given below, but the invention, of course, is not restricted in any way to this example. 
     The present example relates to the fabrication of a reinforcing band according to the invention wherein a tungsten core coated with silicon carbide is used as coil wire and wherein aluminum is used as matrix. The finished band is then obtained by use of high pressure in a power press as shown in part in the drawing. 
     The wire utilized as the starting material has a diameter of about 0.100 mm. This wire is wound on a mandrel (outer diameter 146 mm) and covered by aluminum foil in such manner that the spacing between each wire is about 0.100 mm. By means of a plasma torch, the aluminum used as matrix is projected on the single layer of wire, and the quantity of aluminum is such that it completely covers the coil of wire and forms a continuous aluminum surface. 
     This surface is suitably finished to provide a nearly plane surface on which a new layer of wire is coiled at the same pitch as the first layer. Then, another matrix of aluminum is again welded to the second layer. 
     This results finally in a coil or blank of 18 successive layers of wire with an approximate thickness of 2.85 mm. The volume of the blank consists of 64% aluminum, 20% wire and 16% &#34;voids&#34;. The blank is then subjected to high pressure by being placed in a mold (shown in the attached sheet of drawing). The mold includes: 
     - a bottom member 1; 
     - an inner ring 2; 
     - an outer ring 3, which defines, together with ring 2, an annular space in which the blank is inserted; and 
     - a metal ram 4, which enters the top of the annular space and which exerts high pressure on the blank. 
     The mold is then heated to such a temperature that the matrix, under the influence of the ram pressure creeps into and fills the voids in the blank. When the matrix is of aluminum, as it is in this example, the press may be operated at 500° C and a pressure of 40 × 10 3  &#34;kPa&#34; or 600° C at a pressure of 3 × 10 3  &#34;kPa&#34;. It is generally preferable to work at a relatively low temperature in order to avoid degrading the matrix (e.g., by oxidation). 
     During the above compaction of the blank, there occurs simultaneously &#34;creepage&#34; of the matrix into the voids of the blank and a shrinkage of the spirals of the wire. Such shrinkage, however, should not be too great, and, in any event, the spacing of the spirals must not be less than 0.2 &#34;d&#34;, where d is the diameter of the wire. 
     It must be kept in mind that the only stress exerted on the blank must be the stress in a direction parallel to the axis of the coil (i.e., parallel to the layers of the wire spirals). Specifically, it is necessary to prevent any radial stress which might develop (e.g., during heating and/or cooling of the mold containing the blank). 
     Consequently, the coefficients of expansion of the several components of the mold must be selected as a function of the coefficients of expansion of the blank. For example, when the coefficient of expansion of the blank in the example above is 6.5 × 10 -6 , steel with a coefficient of expansion of 14.2 × 10 -6  may be employed for the inner ring 2, and graphite with a coefficient of expansion of 4 × 10 -6  may be employed for the outer ring 3 of the mold. Considering that the mechanical strength of graphite may be insufficient, it is preferable to strengthen this part of the mold itself by way of a reinforcing band as is shown by reference numeral 5 in the drawing. 
     After compaction, there results a finished reinforcing band, totally compacted, in which the voids now represent a volume of less than 0.1%. 
     The detailed example above provides an understanding of the process, apparatus, and product as well as their particular features, but it is not in any way intended to be restrictive. 
     Numerous recently developed materials may be used such as tungsten wire coated with boron or silicon carbide, boron nitride, or with more than one of these materials. Such wire generally has a diameter between 0.075 and 0.200 mm. 
     The layers are coiled layer after layer with a pitch such that the spacing of the wires is between 0.3 and 2.0 times the diameter of the wire. In the example, each layer has the same spiral pitch as the next layer, but this is not necessary. According to the invention, it is possible to produce windings where each layer has a different spiral pitch. 
     The metal used as matrix must be compatible with the coating substance of the wire and will be a light metal or a light-metal alloy. In the example described above, the matrix is deposited on the wire coils preferably by means of a plasma torch. However, it is also possible to place aluminum foil as the matrix around each layer of spirals. 
     In the example given, the blank has voids of 16% of the entire volume before compaction. It is obvious that the percentage of voids of the blank will vary as a function of a) the material used as the matrix, b) the conditions under which the matrix is applied, and c) the manner of application of the matrix. The percentage of voids of the blank may therefore vary between about 15% and 25%. 
     The reinforcing bands produced in accordance with the invention have the special advantage that the strands do not undergo radial stresses at any time (i.e., along a radius of the band). 
     Only the electrolytic process of depositing the matrix permits the fabrication of reinforcing members with similar properties. However, with electrolysis, it is not possible to use other than pure aluminum or, at most, a binary alloy as the matrix. 
     Consequently, the method according to the invention is much more flexible, and this method makes it possible to obtain new materials due to a larger choice among available matrix substances. 
     The reinforcing bands according to the invention have the form of a torus with rectangular cross section and may have a number of possible uses, as, for example: 
     - drums, disks, shafts; 
     - parts of ultracentrifuges; 
     - flywheels; and, in general, as reinforcing bands for all parts and components subjected to very high centrifugal forces.