Patent GB-730557-A (GB)
Title: A new or improved process and apparatus for coating surfaces with liquid compositions containing solid matter in suspension
Inventor: HAWES ALBERT HENRY
Filed: 1951-04-27
Abstract: Surfaces are coated with liquid compositions containing solid matter in suspension, by mixing successive batches of the composition to be coated, circulating each batch in turn around a closed feeding circuit from which the composition is discharged directly on to the surface to be coated, and simultaneously with the circulation of one batch around the feeding circuit, mixing the next batch and circulating it around a further circuit so as to maintain the solid constituents in suspension in the liquid vehicle until required to be supplied to the feeding circuit on utilization of all or part of the previously mixed batch.  The process is particularly applicable to the coating of walls and other surfaces with a suspension in water of cement, plaster and similar material.  As shown in Fig. 6, two similar containers 11, 12 are provided, each having an agitator comprising spaced paddles on a vertical tubular shaft 14 <PICT:0730557/III/1> connected to a short spindle which is rotatably mounted in bearings in a sleeve 16 and carries a worm-wheel 17 driven by a worm 18.  A further worm-wheel 28, driven by a worm 27, is connected through an overload clutch to a shaft 32, concentric with the tubular shaft 14, and driving a pump 34 mounted on the base 37 of the container 11 or 12.  The pump may be similar to that described in Specification 599,315, but is mounted with the rotor axis vertical. Pipes 39 connect the outlets of the pumps 34 to the inlet ports 40, 41 of a four-way rotary valve 43, one outlet port 44 of which is connected to a mixing circuit flexible hose 63, the end 64 of which may be directed into either of the containers 11 or 12, the other outlet port 45 being connected to the inlet port 50 of a three-way valve 51.  One outlet port 53 of the valve 51 is connected to a flexible circulating hose 55, the end 56 of which may be inserted in either of the containers 11 or 12; the other port 52 is connected to a flexible hose 54 through which the mixture may be supplied to a spray gun 57, which is preferably of the form described in Specification 627,440.  Part of this mixture is sprayed by the gun, the remainder being returned through a flexible hose 59 to one of the containers 11 or 12.  According to the positions of the valves 43 and 51, the contents of either container may follow a mixing circuit through the hoses 39 and 63 or 55, or they may be directed to the spray gun 57.  An alternative arrangement is described in which the outlet port of each pump is connected to one part of a separate three-way valve, the other two ports of each of which are connected respectively to a return pipe and to one of two ports of a third three-way valve, the remaining port of which is connected to the inlet port of the feeding circuit.  The apparatus described above is mounted on a wheeled platform on which is also mounted an internal combustion engine which drives the worms 18 and 27 and a compressor supplying air through a hose 68 to the spray gun 57 and, through a branch 69, bifurcating at 70, valves 71 and 72 and pipes 73, to casings 16 surrounding the hollow agitator shafts 14, into the interior of which the air passes through radial holes therein; the air emerges from the bottom ends of the spindles and aerates the mixture.  A water tank 75 is connected through pipes 76, embodying control valves 77, 78, to each of the pipes 73, permitting controlled amounts of water to pass to the interior of the agitator shafts 14. In operation, the valves 43 and 51 are set to the position shown, and the engine started to drive the agitators and the pumps.  Each container 11 or 12 is now partially filled with water and the desired quantity of cement added.  The aerating valves 71, 72 are now opened, then sand is added.  After a suitable period of mixing, the valve 51 is operated to cause the mixture from the container 11 to be p circulated past the spray gun, part being discharged therefrom and the remainder returned to the container 11.  When the contents of this are exhausted, the valve 43 is turned to connect the container 12 with the feeding circuit, and the end 60 of the feeding circuit return hose is placed in the container 12.  The end 64 of the mixing circuit hose is placed in the container 11, which is now re-charged. Specification 644,638 also is referred to.