GB2217221A

GB2217221A - Apparatus for preparing foamed concrete or other foamed products

Info

Publication number: GB2217221A
Application number: GB8809284A
Authority: GB
Inventors: Gary Kenneth Busch
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-04-20
Filing date: 1988-04-20
Publication date: 1989-10-25
Anticipated expiration: 2008-04-20
Also published as: WO1989010247A1; GB8809284D0; GB2217221B

Abstract

An apparatus for producing foamed concrete by continuously mixing the ingredients comprises, mounted on a road vehicle chassis, a mixing section of two similar chambers (26, 28), each having a pressure-resistant outer casing, an inlet (29, 30), for supply of compressed air from a compressor, and containing an inner mixing vessel (32, 34) tapering downwardly and having a plurality of spaced through-holes (35, 36), preferably arranged at an angle of about 45 DEG to the horizontal, and preferably also at an angle to the radius of the chamber (see Fig. 4), the holes allowing pressurised gas to mix the contents of the chamber. The apparatus may include containers for sand, cement and any other optional ingredients (Fig. 2) and means for supplying them to the top of the mixing chamber via motor-driven helices within supply lines (10, 11, 12). In use, a pre-mix is formed in the upper chamber, and water and foaming agent are supplied through nozzles (44) in a collar connecting the chambers, and the mixture is further mixed and aerated in the lower chamber (28) by air passing through the holes (36), and the resulting foamed concrete mixture is sucked out of a lower outlet (40) by a jet pump (46). Alternatively, the two mixing chambers are placed side by side on the chassis, with a further jet pump to convey the premix to the top of the second chamber. The self-contained apparatus is mobile and easily operated, and the foamed concrete thus produced is light-weight, resistant to water and fire, and strong and stable.

Description

APPARATUS FOR PREPARING FOAMED CONCRETE OR OTHER FOAMED PRODUCTS This invention relates to apparatus for producing foamed concrete by continuously mixing the various con stituents, including solids such as cement and sand, and water and a foaming agent to form a light-weight foamed product. The concrete products thus formed can be easily pumped over long distances for any desired use.

A distinctive feature of the invention is the mixing means and method, wherein pressurised gas such as air is used to intimately mix the ingredients and to provide an aerated or foamed product, and the method is also applicable to the production of mixed or foamed plastics, or food products such as dough or confectionery.

The production of light-weight foamed concrete has hitherto usually been carried out batchwise. Although mixing devices such as described in GB-A-20998079 have been proposed for continuously mixing foamed concrete by mechanical means, production therewith has tended to be erratic. I have devised a new apparatus and method for such purpose, which is carried out continuously and uniformly.

The present invention provides apparatus for preparing a foamed product, which comprises: two pressure-resistant chambers each having an inlet for supply of a stream of pressurised gas and each containing an inner mixing vessel shaped to taper downwardly and having a plurality of spaced through-holes to allow pressurised gas passing through said holes to mix the intents of the vessel; the first chamber having means for supply of desired solid ingredients to the top of the mixing vessel and having an outlet at the bottom thereof for the aerated mixture produced, and the second chamber being arranged to receive the mixture leaving the outlet of the first chamber and having one or more inlet for receiving foaming agent and having an outlet at the bottom of the mixing vessel for delivery of the foamed product formed.

Preferably the form of each of the mixing vessels is that of an inverted truncated cone.

The through-holes are preferably at an angle to the radius of the mixing vessel, which angle decreases for the holes closer to the outlet; the holes are also preferably at the angle to the vertical and they taper inwardly towards the inside surface of the vessel.

For the mixing of cement, an inlet for foaming agent and water is preferably provided at a collar around the base of the first chamber, in which collar these ingredients become mixed.

The method of use of this apparatus comprises supplying the various ingredients including pressurised gas (normally air) to the respective inlets of the two chambers, causing the solid ingredients to be mixed in the first chamber by the action of the air, supplying foaming agent and water or other desired ingredients to mix with the pre-mix leaving the first chamber and supplying the resultant mixture to the second mixing chamber, and then removing the mixed finished aerated product from the outlet of the second chamber.

In this method, the pressurised gas entering each mixture has the effect of causing centrifugal turbulence in each mixing vessel. The use of pressurised air for mixing has the advantages of eliminating the need for moving mechanical parts and reducing wear on the surfaces of the apparatus; the quantities of ingredients of the mixture can be metered so as to accurately determine the composition of the foamed product and thus the relative strength and weight thereof. The apparatus can be totally enclosed and virtually dust-free.

The invention is illustrated by way of example in the accompanying drawings, in which: Fig. 1 is an elevation of an entire mobile apparatus for making foamed concrete, viewed from one side; Fig. 2 is a view of the apparatus of Fig. 1 seen from above; Fig. 3 is a sectional view' along the line III-III of Fig. 2; and Fig. 4 is a fragmentory horizontal cross-section of part of a mixing vessel of Fig. 3.

Referring to Fig. 1, a chassis (1) has road wheels (2) a braking handle (3) and preferably a vehicle body (4), the whole being arranged to serve as a trailer, behind a motor vehicle. As seen in Fig. 2, within the body are are mounted storage containers (5, 6, 7, 8 and 9) for the ingredients sand, cement any other solid additive, water and foaming agent; the solid ingredients are connected by motor-driven helixes within supply lines (10, 11 and 12) to a mixing section, generally indicated as (13), only the top, (14) of which is visible in Fig. 2. Loading ports (15) are provided in the sides of the body.

The apparatus also includes hoses (16, 17) for supply by means of pumps (18, 19) of water and foaming agent respectively from their containers (8, 9).

Also mounted on the chassis (1) is an engine (20) which is connected via a belt (21) to an air compressor (22), and which also drives the pumps (18, 19). On the body (4) is a control panel (25) which controls the engine and includes a flow meter to monitor the pumps (18, 19), an air pressure gauge and regulator and four on/off ball valves which control respectively the inputs of water, foaming agent, sand and cement to achieve desired mixing proportions and the clutches which control the speeds of the respective helices.

Referring to Fig. 3, the mixing section (13) is seen to be made up of two generally similar chambers (25, 28), each being closed to the atmosphere and made of high-density plastics or other suitable strong material resistant to air pressure, and each having an inlet (29 or 30) for supply of compressed air from the compressor (21). Within each chamber is a conical mixing vessel (32 or 34) respectively, each of which is perforated by a plurality of machined through-holes arranged at regular intervals in rows over substantially its entire surface. The spacings between the holes depend on the circumference of the cone.

The holes (35, 36) are preferably arranged at an angle

a of about 45- to the horizontal, so that their upper enas within the cone, and they are preferably also at an angle ss to the radius on the horizontal plane of the respective chamber, as seen in Fig. 4; this angle ss is generally at 30 at the top of each vessel, decreasing towards the bottom of the cone. Moreover the holes taper inwardly towards the internal surface of each cone (32 or 34).

The first, upper mixing chamber is closed at its upper end by the top (14), within which the supply lines (10, 11, 12) for the solid ingredients terminate, and at its lower end it communicates via an outlet (38) with the mixing vessel (34) within the lower chamber, which in turn has an outlet (40) at its lower end. Around the outlet (38) of the upper chamber is a hollow collar (41) which is supplied at its outside with inlets (42, 43) for water and foaming agent, and has nozzles (44) opening around the outlet (38).

Beneath the outlet (40) of the lower mixing chamber is attached a jet pump (46), which can be of a known commercial type, such as supp-lied by Genflo Pumps Limited of Stanford, so that the hopper inlet of the pump encloses the outlet of the lower chamber; the jet pump has a supply (47) for compressed air, and an outlet (48) for delivery of the concrete produced.

In use, sand and cement are fed from their containers (5, 6) via the motor driven helices within the supply lines (10, 11), and any other optional filler such as pulverised fuel ash or polystyrene beads is fed from container (7) via line (12), each to the top of the mixing chamber' (26).

High-pressure compressed air is pumped into the inlets (29 and 30) and causes centrifugal turbulence in each mixing zone, so as to intimately admix the solids as they pass down the upper conical mixing chamber. Water and foaming agent are pumped through hoses (16, 17) into the annular chamber within the collar (41), and are there mixed and delivered through the plurality of nozzles (44) and are sprayed therefrom so as to moisten and mix with the particles of sand/cement pre-mix passing through the outlet (38); this mixture is further mixed and aerated in the lower mixing chamber by the air passing through the respective through holes in the mixing vessel (34) thereof, and the resulting foamed concrete mixture is sucked out of the lower outlet (40) by the jet pump (46), fed by compressed air (47) also from the compressor (22). The mixture formed is pumped from outlet (48) to a location where the concrete is to be used. The jet pump (46) is driven in usual manner by aither a gas or liquid.

The speed of the mixing and the level of the components being mixed inside each of the conical mixing vessels (26, 28) is controlled by the spacing and the angles of the through-holes- 35, 36); the more numerous the holes, the faster the contents are spun, and the closer to 900 is the engle of the hole to the angle ss to the radius of the chambers, the faster does the mixture fall through the n i x i n g vessels.

In an alternative arrangement, the two mixing chambers are placed side by side on the the chassis, if space permits, in which case a further jet pump is required 'at the base Df the first outlet (38) to convey the pre-mix through a suitable conduit to the top of the second mixing chamber.

Also, the inlets (42, 43 ) for the water and foaming agent may be arranged so that a mixture thereof enters the main mixing vessel (34) from above, or a further mixing vessel may be provided separately to pre-mix these components.

The apparatus shown is self-contained mobile, and is easily supplied with the required ingredients, either manually or in conjunction with automatic loading systems.

It can be totally enclosed so as to operate in all weathers and be relatively sound proof. It can be operated by a single person who adjusts the input and output and ensures replenishment of reservoirs, and it is easily constructed, maintained and cleaned.

Foamed concrete thus produced is light-weight, highly resistant to water and fire, has high strength, exhibits only minute creep or shrinkage is very stable and undergoes very little change in density when it is poured and dried. It also has high compressive and bending strengths, and is thermally and acoustically insulating. It requires a low water content and sets and dries more quickly than known light-weight concrete mixtures and is suitable for many uses, including for the the purposes described in my UK Patent Applications Nos. 8708774 and 8722129. The concrete has low water absorption and can set and be used under water, e.g. for marine construction or in under-water tunnels. It is also useful as a traditional roofing material or for filling moulds either at ground level or at a height, or for building road bases or fabricating lightweight building blocks.

Suitable sizes for the conical mixing vessels (?6 and 27) are, for three sizes of mixing vessel, for the diameters A to D shown in Fig. 3: largest size, A = 51cm, B = 41cm, C = 84cm, D = 68cm middle size, A = 41cm, B = 30.5cm, C = 61cm, D = 46cm smallest size A = 30.5cm, B = 20cm, C = 46cm, D = 30.5cm.

For all these models, the height of the cone is about 30cm and the through-holes (35, 36) can taper from 3mm diameter at the outside of the cone to 1.5mm at the internal surface thereof, for a wall thickness of about 3mm, and with an angle ss which commences at 30 at the top, and decreasing by 50 every 5cm downwardly.

The speed at which the solid components are fed to the top of the first chamber is controlled so as to provide exact desired mixing proportions and thus to allow production of concrete of densities from 2200 kg/m to 400 kg/m on the basis of pure cement, as desired.

The results obtained by the use of varying proportions of ingredients are shown in the following table: Density Cement Sand Water Concentrate Compressive Tensile Mass/vol (Kilos) (Kilos) (Liters) (Liters) Strength Strength 2 (kg/m ) 2200 410 1730 160 .220 30 N/mm2 3.70 N/mm2 2200 410 1530 ,160 .250 26 N/mm2 3.40 N/mm2 1800 400 1340 160 .250 22 N/mm2 3.00 N/mm2 1600 400 1140 160 .350 18 N/mm2 2.50 N/mm2 1400 400 940 160 .450 14 N/mm2 1.90 N/mm2 1200 360 810 140 .550 11 N/mm2 1.20 N/mm2 1000 360 610 140 .650 8 N/mm2 0.80 N/mm2 800 360 410 160 .750 5 N/mm2 0.40 N/mm2 600 360 190 160 .825 4 N/mm2 0.30 N/mm2 400 .360 0 160 .900 3 N/mm2 Oi18 N/mm2 The costs of these mixtures increase with the density thereof.

A suitable foaming agent is a hydrolyzed protein, such as known under the Trade Name "Nicerol", or a known resin soap.

For use in mixing products other than concrete, the number of mixing chambers, angle of the conical mixing vessels, and placing of the through-holes and inlets will be varied as necessary to provide the desired mixing effects and the desired products, whilst the use of the compressed air will again provide an excellent centrifugal mixing effect, The product formed -must remain mobile until it is removed from the apparatus by the jet pump (46).

Claims

CLAIMS:

1. Apparatus for preparing foamed concrete or other foamed products, which comprises: two chambers, each being a pressure-resistant outer chamber having an inlet for supply of a stream of pressurised gas and containing an inner mixing vessel shaped to taper downwardly and having a plurality of spaced through-holes to allow the pressurised gas to mix its contents; the first chamber having means for- supply of desired solid ingredients to the top of the mixing vessel and having an outlet at the bottom thereof; the second chamber- being arranged to receive the mixture leaving the outlet of the first chamber and also having one or more inlet for receiving water and foaming agent, and having an outlet at the bottom of the vessel for delivery of the foamed product formed.

2. Apparatus as claimed in Claim 1, wherein the mixing vessel of either or both of said vessels is in the form of an inverted truncated cone.

3. Apparatus as claimed in Claim 1 or 2, wherein said thr.ough-holes in the mixing vessel are formed at an angle to the radius of the vessel.

4. Apparatus as claimed in any one of the preceding claims, wherein said through-holes in the mixing vessel are formed at an angle to the vertical.

5. Apparatus as claimed in any one of the preceding claims, wherein said through-holes taper inwardly towards the inside surface of the vessel wall.

6. Apparatus as claimed in any preceding claim, which includes containers for supply of compressed air and of the other components to be mixed and pumps and/or motor driven enclosed concentric helixes for delivery of the various materials.

7. Apparatus as claimed in any preceding claim, which includes a jet pump for pumping the foamed product produced.

8. Apparatus according to any preceding claim, which is mounted on a mobile trailer.

9. Apparatus as claimed in Claim 1, substantially as hereinbefore described with reference to the accompanying drawings.

10. A method of mixing concrete or other foamed product, which comprises supplying solid ingredients and water to the respective supply vessels of apparatus according to ' any preceding claim, supplying gas under pressure to the respective gas inlet of each mixing chamber, pre-.mixing the solids in the first mixer, supplying the water and foaming agent to mix with the pre-mix leaving the first chamber and supplying the resultant mixture to the second mixing chamber, then removing the finished product from the outlet of the second chamber.

11. A method as claimed in Claim 10, wherein the pressurised gas causes centrifugal turbulence in each mixing vessel.

12. Foamed concrete or other product produced by the method of Claim 10 or 11.