GB2098079A - Improvements in or relating to apparatus for mixing cement with water and foaming agent - Google Patents

Abstract

The invention comprises a helical device for feeding and/or mixing particulate material such as cement, sand and fuel ash in which the helix is round bar. A single helix may be provided or one helix within another. Helices 8, 10, 13, 20-23 may be incorporated in an apparatus for metering sand and cement into a mixing device while also feeding water and foaming agent into the mixing device to produce aerated concrete. <IMAGE>

Description

SPECIFICATION Improvements in or relating to apparatus for mixing cement with water and foaming agent This invention relates to an apparatus feeding cement and/or fillers such as sand and pulverised fuel ash and for mixing cement with water and a foaming agent with or without fillers to produce aerated cementitious material. Without fillers the material especially suitable forfilling spaces in double walls of buildings for its heat insulation properties and forfireproof and vermin proof effect. It can also be used for covering roofs. The addition of fillers is desirable for making bricks, beams, floors, road paving and swimming pools.

According to the invention a conveying and/or mixing device for materials such as cement, sand and fuel ash comprising a casing containing a rotary helix made of round bar.

An improvement to the round rod sand and cement helices is achieved by inserting a coned solid taper diminishing to the outfall end, see Figure 3:20, 21, 22, 23. this allows a bulkhead which can be a sheet of plywood to be placed transversely across the helices at any point along the length of the helices, and accordingly only meters sand or cement consistent with the area of the helix reduced by the area of the taper at that point. In this event, all helices can be run at identical revolutions and obviates clutches and different size sprockets in mechanically driven units and variable speed motors, compensating flow valves and relief valves in hydraulically driven models. By varying the position of the Bulkhead along guide rods within the hopper, any ratio of sand and cement can be achieved and in differing quantities according to production needs all at constant speeds.In parallel rod helices, a full volume of material is taken with the first pitch and conveyed forward, thus the whole length of helix is charged with material taken from point A therefore no other material can enter the whole length of the helix until the material from point A is exhausted, but in the meantime the full weight of the contents of the hoppers bears on the helices and imposes a "brake-drum environment" causing higher horsepower requirement and induces some wear. With this adaption to the round rod helices, increased hopper capacity is possible without increasing the horse-power requirement due to the revolving and conveying potential of the solid taper which as it diminishes in diameter additional material is taken in keeping the whole of mass in the hopper in a "fluid" condition, relieving compaction and cavitation.

The round rod helix can effectively meter moist sand irrespective of normal variations of its water content. The round rod helix cannot convey the sand until it has compressed it sufficiently. This compressing ofthe sand is essential for metering and is not achieved by ribbon type helices. The round rod helix requires a minimum horsepower for its drive and is very little subject to wear by the sand. The round rod helix can equally well deal with other particulate material such as cement and fuel ash.

Also according to the invention an apparatus for mixing cement with water and a foaming agent with or without fillers comprising a container for cement, a round bar helix device for feeding the cement into the lower end of an inclined mixing and conveying device and means for producing a mixture of air, water and foaming agent and feeding it into the lower part of said device so that the aerated mixture is ejected from the upper end of said device.

The apparatus may include a sand hopper and means for feeding the sand also into the lower part of said device.

The cement container and may be also the sand hopper, may be arranged with outlet ports therein above the lower end of said device, so that cement and sand will gravitate into said device.

The feeding of the cement and sand may be effected by helical conveying and metering means.

The apparatus may be in the form of a chassis carrying tanks for water, foam concentrate and solution of water and foam concentrate, means for feeding water and foam concentrate to the solution tank, an engine driving the sand device and driving an air compressor and the helical conveying and metering means, and a foam gun fed with said solution and compressed air from said compressor.

In one form of the invention the cement is (and may be the sand also) fed into a conveyor disposed transversely of the cement feeding means, said transverse conveyor without shaft which makes for easy cleaning, feeding cement and sand and wetted before entering the lower end of said mixing device.

The wetting of the material in the transverse conveyor creates a mortar mix when entering the mixing device so that foam can be administered immediately into the mixing device instead of 12" or so further along. This advantage of entering the foam at the source of the mixing device is that the foam has tremendous lubricating and entraining qualities and reduces wear on the ribbon helix and shaft where the inner shaft of the inner helix passes through the shaft of the outer helix. In this way higher speeds resulting in increased productivity is achieved the mixing device being much more efficient running full or at hydraulic mean flow.In this case to prevent foamed material being thrown out of the U tube of the mixing device due to higher speeds, the U shaped casing of the mixer continues only one-third the length, and converts into a totally enclosed tube for the remaining two-thirds of the mixer, the bottom half retaining the rubber skirt which can be unclasped for ease of cleaning.

The invention will now be described by way of example with reference to the accompanying diag rammatic drawings wherein Figure 1 is a side elevation of one side of a machine made in accordance with the invention; Figure 2 is an elevational view of the other side of the machine; Figures 3 and 4 are a plan view (with upper struc tures removed) and a rear view thereof respectively.

The apparatus comprises a chassis 1 and sub frame 2 having two road wheels 24, and equipped with brakes the whole arranged to serve as a trailer to a motor vehicle.

On this chassis is mounted a two compartment hopper assembly 31. The larger compartment 28, is intended for sand, and the smaller 27, for cement.

The method of conveying and metering the materi als is by round rod helices 20, 21, 22, 23 which are rotatably mounted on shafts at the bottom of their respective compartments. There are three helices to meter sand, and one to meter cement with coned tapers inset. The helices are driven through gears 14.

The cement and sand feed is always constant, but positioned a Bulkhead strategically it is possibl)ato meter 4 parts, 3 parts, 2 parts or 1 part of sand to 5 part cement which is necessary if varying densities of material from 100 Ibs. cu.ft. down to 20 Ibs. cu.ft (neat cement) is required, it is also possible to slow down output without loss of speed.

Incorporated in the design ofthe hopper, is a water tank 11 which is fitted with a ball type stop cock. This tank provides water for wetting the sand and cement as they enter the transverse conveyor 13, and also for mixing with the foam concentrate.

The tank is connected to a suitable water supply. The mixer has an inlet at its lower end for cement, an inlet at its lower end for liquid foam and an outlet at its upper end. The mixer 9 comprises a U tube 12 one-third the length of mixer and circular tube twothirds containing an inner round bar helix 10 and an outer round bar helix 8. The tube 12 is a rubber sheet which can be opened for washing. The mixer is driven through a bevel gear 19. The inner helix is driven faster than the outer helix. Electric motors when used have stop/start switches and cut out clutches.

An engine 18 is installed at the front of the chassis and provides power to the hopper helices via two clutches 17 and 3, and 2, worm reduction gearboxes 15 and 7. An extension shaft offthe first worm gearbox drives the mixer 9, the placing or delivery pump 5, and the transfer conveyor 13. The engine is also belt 25 connected to a compressor 6, and to two pumps, one 26 for mixing water, and the other 16 for the foam supply.

A control panel is mounted on the right side of the machine, and provides engine controls, a flowmeter to monitor the mixing water flow an air pressure gauge and regulator, and three on/off ball valves which control water, air, and foam respectively.

In operation, the hoppers are filled with sand and cement, the mains or other water source is connected to the water tank. A suction tube is placed into the foam concentrate which is in a container located at the front of the machine.

The engine is started, and the first drive clutch 17 is engaged. This brings into operation the first worm gearbox 15, the transfer conveyor 13, the mixer 9, the compressor 6, the mixing water pump 26, and the foam supply pump 16. Thus wetting water is being supplied at the transverse conveyor and foam is being supplied immediately to the lower end of the mixer. All controls are set to their correct positions, then the second clutch is engaged; or a second electric motor is switched on. Foam is automatically produced to prevent inaccurate metering and contamination or pollution by the use of oil contami nated measureing. The water supplied to pump 16 passes through a circular water meter containing a mercury switch supplied with a 10 milliamp current from a 12 volt battery or supply.The switch is set to pass a signal pulse of 6 pulses per litre of water allowed to passthrough the water meter controlled with a visible flowmeter on the control panel. The pulses travel through a repay to operate a solenoid valve which in turn operated a diaphragm pump powered by compressed airy and depending on the flow rate cum pulses the diaphragm pump injects correct amounts of foam concentrate taken from a sealed container, into a reservoir mixing chamber before the now 2% solution of concentrate and water is pumped to the foam gun where compressed air is added to generate foam through the atomizing gun.

A three-way valve is incorporated in the concentrate line to allow the operator to check the properfunc- tioning of the injection system by exhausting a small amount of concentrate before start-up. An improvement to the foam gun 38521/77 is shown by lengthening the gun some 4" and introducing the foam solution with a dip leg at a lower stage than the compressed air supply. In this way, there is less likelihood of solution back-tracking due to the back pressure in the foam gun, into the air line which can happen and generate foam in the line accidentally and ultimately halts production.

The engagement of the second clutch 3 or electric motor transmits the drive to the sand and cement hopper helices 20 to 23 which meter material on to the transfer conveyor 13 which pre-mixes them, with water and delivers them to the bottom of the mixer tube 9. Here the rotating mixer helices move the material up the tube. Foam is immediately injected into the mix in a precise metered quantity and the mix progresses up through the now enclosed tube to the delivery point. As the double helices of the mixer are just round rods and as they are rotating at different speeds, the material slipstream and is thoroughly mixed before it arrives at the delivery point Now the third clutch 4 or third motor is engaged this operates the placing pump 6. The material is delivered to the placing pump6through a small hopper arrangement and is pumped to the point of use.

The foam may be made by adding foam concentrate to about 25 to 40 parts of water e.g. about 33 parts of water

Claims (10)

1. A conveying and'or mixing device for materials such as cement, sand and fuel ash comprising a casing containing a rotary helix made of round bar.

2. A device as claimed in Claim 1 wherein the casing is a hopper suitable for sand or cement metered by the helix.

3. A device as claimed in Claim 1 comprising an inner round bar helix within an outer round bar helix disposed in a closely fitting casing.

4. A device as claimed in Claim 3 wherein the inner helix is driven faster than the outer helix.

5. A device as claimed in Claim 3 or 4 wherein the casing is inclined and has an inlet at its lower end for cement, an inlet at its lower end for liquid, and an outlet at its upper end.

6. Apparatus for mixing cement with water and a foaming agent with or without fillers comprising a container for cement, a round bar helix device for feeding the cement into the lower end of an inclined mixing and conveying device and means for producing a mixture of air, water and foaming agent and feeding it into the lower part of said device so that the aerated mixture is ejected from the upper end of said device.

7. Apparatus as claimed in Claim 6 wherein said device is constructed in accordance with any of Claims 3 to 5.

8. Apparatus as claimed in Claim 6 having a plurality of round bar metering helices at the lower end of one hopper and at least one round bar metering helix at the lower end of another hopper, said metering helices being parallel to each other means for driving the helices including a clutch for at least one of said plurality of helices, a foam producing device, a round bar conveyor helix transverse to the metering helices and arranged to receive material delivered by said metering helices, a helical mixing device transverse to the conveyor helix and arranged to receive material therefrom, all mounted on a common chassis.

9. Apparatus as claimed in Claim 6 substantially as described and as illustrated in the drawings.

10. Novel features of apparatus as herein described.

New claim filed on 12/2/82 New or amended claim:-Claim 10.