Patent GB-1291727-A (GB)
Title: A method of and an apparatus for making blocks
Inventor: WIENAND MICHAEL
IPC: D06N7/00
Filed: 1969-10-13
Abstract: 1291727 Moulding patterned thermoplastics material DYNAMIT NOBEL AG 13 Oct 1969 50234/69 Heading B5A [Also in Division E1] Blocks of patterned thermoplastics material are moulded from a uniform sintered stack, of a size approximating that of the block, of superimposed layers of rectangular chips which are produced in a continuous layer by cutting longitudinally and transversely of a sheet calendered from granules. In the Fig. 1 embodiment, multi or different coloured granules 3 are cut from one or more extruders 1 by devices 2, and fall on to a conveyer 4 wherefrom they are transported by a conveyer 5 to a calender 7 which produces the sheet 8. Transverse pieces 11 which are cut by a device 10 from the sheet 8, delivered through guide rolls 9, are transported by a conveyer 12 to a device 13 which cuts the pieces longitudinally into the chips 14 which are collected as a layer on an endless belt 15, which is driven at the same speed as a reciprocatory carriage 16, on which it is mounted, is driven towards an endless belt 18, and at twice the speed thereof, during the return movement of the carriage 16, whereby uniformly distributed layers of the chips 14 are successively deposited into a stack 20 on the endless belt 18. The stacked chips 20 are sintered in respective high frequency and hot air ovens 19, 21, intermediate which they are cut by a device 22 to a size approximating that of a mould 23 in which they are moulded, within a press 25, covered by a toothed plate 24 which retains the cooled moulded block to facilitate the cutting thereof into panels. It is stated that the width of the stack preferably exceeds that of the moulded block by approximately half the width of a chip, and the orientation of the chips may be altered, e.g. by 90 degrees, from that of the sheet during transfer from the cutter 13 to the belt 15 and thence to the belt 18. Separate sheets may be laminated between opposed rolls, Fig. 3 (not printed), and an electrically conductive paste, Fig. 4 (not printed), may be incorporated between the laminated sheets and hardened during passage through an infra-red heating zone prior to the transverse cutting. Alternatively, Fig. 5 (not printed), two calendered sheets may be similarly but separately cut either into different transverse widths, or into both different transverse and longitudinal widths, prior to superimposition on a conveyer to form the chip layer. In the Fig. 7 embodiment, the chip layers are stacked on an endless belt 43 advanced into a heating tunnel 41 at a uniform speed until the necessary amount for a sheet has been deposited thereon, whereafter the belt is rapidly advanced, optionally through precompression rollers 44, into a second tunnel 21 where the stack is sintered at a higher temperature to form a sheet which is wound to a cylindrical configuration around a mandrel 46 under the compression of an endless belt. In this embodiment, several of the endless belts 43 may be juxtaposed and operated synchronously to ensure continuity in the deposition of successive stacks. In this embodiment, the chips 14 are deposited from an endless belt 15 driven by rollers 40 at a constant speed towards the belt 43, with the carriage 16 on which it is mounted reciprocating at the same speed towards the belt 43 and away therefrom to deposit the stack layers, each layer either comprising a planar, or overlapping form (Figs. 9 and 10, not shown) depending on the speed at which the carriage 16 is retracted. The wound sheet upon the mandrel 31, Fig. 8, is put under slight axial compression during the attachment by bolts 37 of mould endplates 36, prior to insertion into a mould 48 in which it is radially compressed to a cylindrical block upon admitting cooled compressed air or liquid to tubular diaphragms located externally, e.g. 49, and/or internally. Additional cooling may be effected by fluid circulated through the mandrel 46. The moulded cylindrical block is circularly slit to produce a sheet floor covering. An electrically conductive sheet flooring may be produced employing electrically conductive paste or powder laminated between two sheets, or applied to the exterior thereof. In the latter case the stack comprises inclined layers of chips to ensure uniform electrical properties are obtained by cutting across the plane of the chips to produce the sheet, in which electrical continuity may additionally be enhanced by a conductive adhesive, or by coating the earth side with a conductive paste.