Patent GB-1299082-A (GB)
Title: Blending method and apparatus
IPC: H01Q15/08
Filed: 1969-11-12
Abstract: 1299082 Moulding dielectric lenses ARMSTRONG CORK CO 12 Nov 1969 [12 Nov 1968] 29856/69 Heading B5A [Also in Divisions B1 and H4] In the moulding of a mass of material having a parameter gradient, e.g. dielectric microwave lenses wherein the dielectric constant varies with two-dimensional or with three-dimensional lens co-ordinates, first and second particulate, or liquid, or mixed material of differing dielectric constant are respectively loaded between a cylindrical mould 10 and the exterior wall of a differently shaped tubular form 22, and to the same height within at least a portion of the form 22, and the form 22 is then displaced within the mould 10 to dispense the second material, from within the form 22, to be located in a predetermined shape adjacent the first material and after repeating the loading and dispensing steps, the material within the mould 10 is blended into the desired parameter gradient by stirring about a plurality of concentric circles. In the preferred embodiment the first and second materials are dielectrics which respectively comprise particulate expanded polystyrene of low dielectric constant and aluminium sliver loaded polystyrene beads of high dielectric constant. The bottom of the mould 10 is closed by a composite layer 11 of expanded metal and fine mesh screening which permits the passage of steam for fusion of the particles after dispensing from the form 22, which is heart-shaped and with the junction 23 of the lobes thereof located on the axis of the mould 10, and which form 22 is positioned therein by attached support screens 24, 25 of a mesh sufficiently large to permit passage of the particles. Cylindrical sleeves 13, 19, are slidingly displaceable within the mould 10 and are respectively provided with mesh screens 14 and 20, the screen 20 being of larger mesh than screen 14 which is slightly larger in mesh than the particles. In moulding a lens which exhibits a radial Luneberg gradation in two dimensions, the form 22 is sequentially displaced to the top of the mould 10 to dispense the second material, which has been located in the entire volume therein, within the first material, which has been loaded between the form 22 and the mould 10. After removal of the form 22 from the mould 10, a support 18 is bolted to a flange 21 of sleeve 19 and a support shaft 18a is then attached to a driving mechanism whereby the sleeve 19 is slowly rotated and raised, and preferably vibrated, so that the screen 20 blends the particles from within and without the form 22 in a circular direction around the axis of the mould 10. Sleeve 13 is then slowly drawn out of the mould, without rotation and preferably vibrated, by the support 18 attached to a further mechanism, to ensure randomization of the blended particles. In the moulding of a spherical lens having a substantially uniform Luneberg gradation in all radial directions, a layer of the first material is located on the base of sleeve 19 whereafter, for each of successive dispensing displacements of the form 22, the second material is dispensed from the volume between the form 22 and the upper side (as viewed in Fig. 3) of a different divider 30-35, the first material also being dispensed from the volume between the form 22 and the lower side of the divider 30-35 and, after the dispensing displacement using the last divider 35, the first material is dispensed over the entire area within the mould 10, whereafter successive dispensing displacements of the form 22 employ the dividers in the reverse sequence 35-30 terminating, after removal of the form 22, in a final layer of the first material located over the entire area of the mould 10. The spherical lens is obtained by machining, preferably after establishing the electrical equator of the cylindrical moulded configuration by application of microwave energy thereto. The use of the six dividers 30-35 facilitates the production of lenses of six to twelve inches diameter, but for lenses of 18 to 24 inches diameter 12 dividers may be employed, and 22 dividers may be employed for 44 inch diameter lenses. The dividers may also be of differing heights.