Patent GB-567649-A (GB)
Title: Improvements in or relating to the drying of moulded contact masses
IPC: F26B17/02
Filed: 1943-03-16
Abstract: 567,649. Drying systems. HOUDRY PROCESS CORPORATION. March 16, 1943, No. 4266. Convention date, April 2, 1942. [Class 34 (ii)] [Also in Group V] Moulded units of. wet material, such as a paste containing water and synthetic inorganic gel, are converted into solid pellets suitable for use as contact masses by being subjected to a special drying process which consists in heating a localized surface of each unit while simultaneously maintaining, in portions of each unit adjacent to all other surfaces, enough water to maintain said portions flowable until they are hardened by the removal of water through the localized surface. That is, only one surface is heated, and drying proceeds progressively through the unit, whereby cracking due to uneven drying is prevented ; the other surfaces may contain enough water in the portions adjacent thereto, to maintain flowability, or water may be added thereto for that purpose. Fig. 1 shows apparatus comprising a link-plate type belt 5 having perforations extending therethrough, into which the contact masses are cast from a hopper 6. The belt passes through a drying chamber B, the units in the perforations being wetted on one side by a device 17. In the chamber the first two runs of the belt are heated on one side only by hot gases from ducts 16 (or by electrical units or steam coils), baffles (not shown) being disposed to prevent or minimize access of the hot gases to the other side of the belt. In the lower part of the chamber, drying is completed by impinging hot gases on both sides of the belt. Instead of open-ended apertures, the moulds may comprise a series of cups or closedend apertures provided in partly-drilled plates or in embossed plates or belts, in which case drying proceeds from the open end, the closed end being cooled as by water sprays. The paste may be thin enough to flow into the belt apertures or thick enough to necessitate forcing thereinto. In the arrangement shown in Fig. 1, a roller 7 feeds thick paste to the belt and forces it into the perforations, and a squeegee or knife blade 10 removes extruded excess from the underside of the belt ; spring-loaded rolls 11 further compress the paste, or an additional roller may be placed under the belt opposite roller 7. In an alternative arrangement, Fig. 3, an adjustable knife 8 controls the thickness of the sheet fed from the hopper by the roller 7, and the latter is spaced from the belt so as not to compress the material. The material passes into a casting chamber defined by retaining members 13, 14 and is wiped into the belt apertures by a squeegee 15. Another squeegee 15a disposed under the belt has two functions : to wipe off excess material and to push the units partly through the belt, whereby application of pressure to the protruding ends thus formed facilitates or effects discharge. To facilitate discharge also, the perforations are tapered and a third squeegee 15b pushes the units back again so that the protrusions are at the narrow ends of the apertures and may, when the belt emerges from the chamber B, be engaged by a roller which pushes the units out of the belt. Alternatively, and as shown, the belt is subjected to simultaneous pressure and vibration by rotating beaters 18. Rolls 19 prevent excessive vibration. The discharged units may be further dried in chamber B or belt 20. The belt may be cleaned by a rotating wire brush 24, washed with alkali, acid, salt, &c. from nozzles 21a, dried by vacuum jets at 23 and washed with water and/or lubricated at 22a. Specification 553,736, [Group V], is referred to.