EP0279615A1

EP0279615A1 - Apparatus for producing aerated cementitious material

Info

Publication number: EP0279615A1
Application number: EP88301242A
Authority: EP
Inventors: William Thomas Williams
Original assignee: WORCESTER Ltd
Current assignee: WORCESTER Ltd
Priority date: 1987-02-13
Filing date: 1988-02-15
Publication date: 1988-08-24
Also published as: GB2206059B; ZA88969B; HU199905B; ZA881026B; GB8703318D0; HUT46749A; GB2206059A

Abstract

Apparatus for producing aerated cementitious material includes first and second hoppers (12 and 13) for cement and sand respectively. The material is delivered by constant speed screw conveyors and the wall (21) of the second hopper (13) is inclined to overhang the adjacent screw conveyor.

Description

This invention relates to apparatus for producing aerated cementitious material.
Apparatus according to the present invention feeds and mixes cement with water and a foaming agent, with or without fillers such as sand and pulverised fuel ash, to produce aerated cementitious material. Without fillers the material is especially suitable for filling spaces in double walls of buildings because of its heat insulation, fireproof and vermin proof properties. It can also be used for covering roofs. The addition of fillers is desirable for making bricks, beams, floors, road paving and swimming pools.
In order to produce continuously aerated cementitious material of high and predictable quality it is essential that the proportions of the different ingredients are accurately controlled, and that these ingredients are thoroughly mixed.
The present invention is apparatus for producing aerated cementitious material, including a first hopper for cement, means for conveying cement from the first hopper to a mixing means, a second hopper for a filler material and means for conveying filler material from the second hopper to the mixing means, said conveying means including a first screw conveyor in the first hopper and a plurality of screw conveyors in the second hopper, each of said screw conveyors having its respective constant speed drive means, and said second hopper having a sidewall which is inclined inwardly to overhang the adjacent screw conveyor.
An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Fig. 1 is a side elevation of apparatus according to the present invention for making aerated cementitious material;
Fig. 2 is a rear end elevation of the apparatus of Fig., 1;
Fig. 3 is a front end elevation of the apparatus of Fig. 1;
Fig. 4 is a plan view of the apparatus; and
Fig. 5 is a side view of the mixing chamber of the apparatus on an enlarged scale.

Referring now to the drawings, apparatus for making aerated cementitious material comprises a chassis 10 having road wheels 11 arranged to serve as a trailer to a road vehicle. The road wheels 11 are retractable to enable the chassis 10 to be lowered to the ground for stability and to facilitate supply of materials to the apparatus when in use on site.
The apparatus includes a first hopper 12 for cement, and a larger second hopper 13 for sand or other filler such as pulverised fuel ash for example.
The cement is metered through a circular aperture 14 in the front wall of the hopper assembly by means of a round rod helix conveyor 18 whilst the filler is metered through circular apertures 15, 16 and 17 in the front wall by means of respective round rod helix conveyors 19. The helices of the conveyors 18 and 19 are mounted for rotation on shafts whose diameters decrease towards the apertures 14, 15, 16 and 17. This construction ensures a uniform flow of material over the length thereof of the hoppers into helices along the lengths thereof, and significantly reduces torque load. The common wall 21 between the hoppers 12 and 13 is inclined into the hopper 13. In the embodiment illustrated the wall 21 is at right angles to the inclined base 22 of the hopper to provide an acute angle to the vertical and overhang the adjacent conveyor 19 allowing it to be used on its own without cavitation. The conveyors 18 and 19 have individual constant speed drive motors 24, 25, 26 and 27.
Accurate control of the flow of material through the apertures 14 to 17 is obtained by metering valves in the form of respective conical plugs 29, 30, 31 and 32 which can be advanced into the apertures 14, 15, 16 and 17 respectively or retracted therefrom to a desired extent by individual control levers (not shown). The plugs have axial bores to accommodate the ends of the conveyor shafts therein.
Generally it will be sufficient for each plug 29 to 32 to be set in one of three positions giving full flow, half flow and no flow respectively enabling most commonly required mixes of cement to filler such as 1:1, 1:2, 1:3, or 1:4 to be obtained by suitable selection of the plug positions and proper control of the number of conveyors 19 in operation.
Additional control can be had by provision of bulkhead s 34 and 35 slidable over the respective lengths of the hoppers 12 and 13, thereby varying the effective lengths of the hoppers and the amount of the filler and cement entering the helices of the conveyors.
Materials delivered by the conveyors through the apertures 14, 15, 16 and 17 are delivered to a transverse endless band conveyor 36 which carries them to a mixing chamber 37.
Water from a tank 39 and liquid foaming agent from a tank 38 are supplied by independent pumps 45 and 47 to a foam injection gun 40, which, receiving compressed air from a compressor 60, provides foam having 20 micron independent air cells to the chamber 37.
The various ingredients are conveyed from the chamber 37 and thoroughly mixed in an upwardly inclined cylindrical mixing chamber 41 comprised by a flexible tube 42 (typically rubber or P.V.C) supported within a steel cage 43.
A shaft 44 driven by a motor 49 extends axially through the chamber 41 and carries a short section of two-start full flight helical conveying screw 46 at its lower end for rapid removal of material from the chamber 37, thus to prevent any damming of the incoming materials. Following the screw 46 is an extended length of ribbon helix 48 connected to the shaft 44 by struts 50.
Axially extending bars 52 are provided at intervals between struts 50 to carry freely rotatable round rod helices 53 which contact the inner periphery of the chamber 41. Regardless of the amount of material input the mixing chamber 41 has to be filled completely before any delivery occurs at the outfall.
This arrangement provides for a thorough mixing of the ingredients, regardless of throughput, as they pass upwardly through the chamber 41 for delivery to a placing pump 55.
Through put may be as little as 0.05m³/min for spray applications and as high as 0.3³/min for bulk pouring, for example.
The pump 55 is a peristaltic pump whose resilient delivery tube 54 and motor 56 are disposed susbstantially horizontally. The motor 56 includes a reversing switch to facilitate the replacement of delivery tubes and the clearing of any blockage in the delivery tube. The roller carriage 57 is readily removed to simplify the removal of any material allowed to solidify and impeding the rollers.
The electric drive motors in the machine are constant speed motors and the startup sequence is pump motor 56, mixer motor 49, solution pump 47, compressor 60 for supplying air to the foam gun 40, water pump 55, conveyor 30 and the selected combination of conveyors 18 and 19.
Water, solution and air are metered through flow controls to chamber 37 in accordance with the mix control and density desired.
A control panel contains all the switches, power/on lights, and circuit breakers for the protection of all motors, the panel being mounted in a hinged blister cabinet 65, to be closed at night for protection against vandalism and against freezing of liquids in flow controls.
The control panel is mounted on the right side of the machine, and provides motor controls, a flowmeter to monitor the mixing water flow, and air and solution, and three on/off ball valves which control water, air, and solution respectively.

Claims

1. Apparatus for producing aerated cementitious material, including a first hopper for cement, means for conveying cement from the first hopper to a mixing means, a second hopper for a filler material and means for conveying filler material from the second hopper to the mixing means, said conveying means including a first screw conveyor in the first hopper and at least one screw conveyor in the second hopper, each of said screw conveyors having its respective constant speed drive means, and said second hopper having a sidewall which is inclined inwardly to overhang the adjacent screw conveyor.

2. Apparatus as claimed in claim 1, in which said sidewall is common to both hoppers.

3. Apparatus for producing aerated cementitious material, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.