GB2060421A - Mixing and conveying apparatus - Google Patents

Abstract

Mixing and conveying apparatus has two helices in a container one helix (3) being located within the other (2) and both helices being mounted on a single shaft (1) and running in the same direction as each other but with the inner helix tapered from the input end, enlarging to the output end. Also, the inner helix has a longer pitch than the outer. An initial part (4) of the outer helix is of strip steel, the remainder being of round rod. In use, with the shaft inclined to the horizontal, a trough-like casing (5) around the lower regions of the helices is afforded by a flexible sheet secured releasably in position by clips. <IMAGE>

Description

SPECIFICATION Mixing and conveying apparatus This invention relates to mixing and conveying apparatus and is more particularly although not solely, intended for mixing cement with water and a foaming agent with or without sand or other filters to produce settable aerated cement or concrete.

Various forms of helical devices have heretofore proposed including location of one helix within another but with certain materials such- as foaming agents it is difficult to achieve completely intimately mixed products. For example with two round rod helices each of constant diameter, one within the other attached to one shaft and therefore running with the same rotation, the moment, sand, cement, water and foam is introduced, two flow patterns one inner and one outer are conveyed to the outlet so that the contents are not properly mixed to give homogeneous aerated mix. This disadvantage was overcome by the device disclosed in the specification of patent No. 1336143 which used two helices, one within the other, but with the inner helix mounted on an independent shaft running half as fast again as the outer helix.

This design although it greatly increased the cost of production resulted in extra maintenance with one shaft running concentrically through the other.

According to the present invention two rod helices are provided within a container one helix being located within the other, mounted on a single shaft running in the same direction but with the inner helix tapered from the input end enlarging to the output end.

Due to the small diameter of the taper at the input end, much space is created between the inner and outer helices so that with the mixer running inclined at about 10 to 20% to the horizontal e.g. 1 50, a tumbling action of the materials is induced and due to the increasing diameter of the taper helix towards the output the materials are forced back towards the outside thus merging the flow patterns to afford a perfect continuous homogeneous mix of sand cement water and a foam formed by mixing water with a foaming agent.

The invention will now be further described by way of example with reference to the accompanying diagrammatic drawings wherein: FIGURE 1 is an elevational view of a mixing apparatus made in accordance with the invention; FIGURE 2 is a sectional view on the plane marked 2-2 on Figure 1; FIGURE 3 is a sectional view on the plane marked 3-3 on Figure 1; and FIGURE 4 shows the apparatus enclosed in a casing mounted at an angle to the horizontal.

The mixer comprises a central shaft 1 around which, fixed concentrically, are two helices of differing diameters and pitches. The pitch of the inner helix is greater than the outer helix pitch. The first part 4 (e.g. 12) of the outer helix 2 is of ribbon or steel strip construction, the remainder being round steel rod e.g. 0.75 inch diameter. The inner helix 3 is made of round steel rod and is tapered for 75% of its length. The remaining 25% is parallel and runs towards the discharge end of the mixer.

The mixer assembly is ball bearing mounted and is driven by a hydraulic motor 4 or other power sources. A trough 5 (Figure 4) which contains the mix material may be made of a sheet of rubber or other tough flexible sheet which wraps around the underside of the mixer helices and is fastened with clips at its outer edge. This arrangement facilitates cleaning after completing the work at the end of the day. The sheet forms a U-shaped casing open at the top with the inner helix running close to the sheet e.g. about an inch or even less from the sheet. The clips at one end are released so that the sheet falls down as a more or less flat sheet which can be readily hosed down.

In operation the material to be mixed is fed into the right hand side of the mixer and comes under the influence of the ribbon part 4 of the outer helix and the small diameter of the inner helix. Rotation of the helices drives the material along the shaft length and the differing pitches and diameters of the helices disturb its pattern of movement, thoroughly mixing the ingredients by the time they reach the discharge end where a suitable discharge chute 6 (Figure 4) is provided.

1. A mixing and conveying apparatus having two rod helices in a container one helix being located within the other mounted on a single shaft running in the same direction as each other but with the inner helix tapered from the input end enlarging to the output end.

2. A mixing and conveying apparatus as claimed in claim 1 wherein the pitch of the inner helix is greater than the outer helix pitch.

3. A mixing and conveying apparatus as claimed in claim 1, 2 or 3 wherein the first part of the outer helix is of ribbon steel construction, the remainder being round rod, and having part of its length of constant diameter at the inlet end of the apparatus.

4. A mixing and conveying apparatus as claimed in claim 1, 2 or 3 wherein the helices are located in a trough made of flexible sheet held in position by releasable clips.

5. A mixing and conveying apparatus substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Mixing and conveying apparatus This invention relates to mixing and conveying apparatus and is more particularly although not solely, intended for mixing cement with water and a foaming agent with or without sand or other filters to produce settable aerated cement or concrete. Various forms of helical devices have heretofore proposed including location of one helix within another but with certain materials such- as foaming agents it is difficult to achieve completely intimately mixed products. For example with two round rod helices each of constant diameter, one within the other attached to one shaft and therefore running with the same rotation, the moment, sand, cement, water and foam is introduced, two flow patterns one inner and one outer are conveyed to the outlet so that the contents are not properly mixed to give homogeneous aerated mix. This disadvantage was overcome by the device disclosed in the specification of patent No. 1336143 which used two helices, one within the other, but with the inner helix mounted on an independent shaft running half as fast again as the outer helix. This design although it greatly increased the cost of production resulted in extra maintenance with one shaft running concentrically through the other. According to the present invention two rod helices are provided within a container one helix being located within the other, mounted on a single shaft running in the same direction but with the inner helix tapered from the input end enlarging to the output end. Due to the small diameter of the taper at the input end, much space is created between the inner and outer helices so that with the mixer running inclined at about 10 to 20% to the horizontal e.g. 1 50, a tumbling action of the materials is induced and due to the increasing diameter of the taper helix towards the output the materials are forced back towards the outside thus merging the flow patterns to afford a perfect continuous homogeneous mix of sand cement water and a foam formed by mixing water with a foaming agent. The invention will now be further described by way of example with reference to the accompanying diagrammatic drawings wherein: FIGURE 1 is an elevational view of a mixing apparatus made in accordance with the invention; FIGURE 2 is a sectional view on the plane marked 2-2 on Figure 1; FIGURE 3 is a sectional view on the plane marked 3-3 on Figure 1; and FIGURE 4 shows the apparatus enclosed in a casing mounted at an angle to the horizontal. The mixer comprises a central shaft 1 around which, fixed concentrically, are two helices of differing diameters and pitches. The pitch of the inner helix is greater than the outer helix pitch. The first part 4 (e.g. 12) of the outer helix 2 is of ribbon or steel strip construction, the remainder being round steel rod e.g. 0.75 inch diameter. The inner helix 3 is made of round steel rod and is tapered for 75% of its length. The remaining 25% is parallel and runs towards the discharge end of the mixer. The mixer assembly is ball bearing mounted and is driven by a hydraulic motor 4 or other power sources. A trough 5 (Figure 4) which contains the mix material may be made of a sheet of rubber or other tough flexible sheet which wraps around the underside of the mixer helices and is fastened with clips at its outer edge. This arrangement facilitates cleaning after completing the work at the end of the day. The sheet forms a U-shaped casing open at the top with the inner helix running close to the sheet e.g. about an inch or even less from the sheet. The clips at one end are released so that the sheet falls down as a more or less flat sheet which can be readily hosed down. In operation the material to be mixed is fed into the right hand side of the mixer and comes under the influence of the ribbon part 4 of the outer helix and the small diameter of the inner helix. Rotation of the helices drives the material along the shaft length and the differing pitches and diameters of the helices disturb its pattern of movement, thoroughly mixing the ingredients by the time they reach the discharge end where a suitable discharge chute 6 (Figure 4) is provided. CLAIMS

1. A mixing and conveying apparatus having two rod helices in a container one helix being located within the other mounted on a single shaft running in the same direction as each other but with the inner helix tapered from the input end enlarging to the output end.

2. A mixing and conveying apparatus as claimed in claim 1 wherein the pitch of the inner helix is greater than the outer helix pitch.

3. A mixing and conveying apparatus as claimed in claim 1, 2 or 3 wherein the first part of the outer helix is of ribbon steel construction, the remainder being round rod, and having part of its length of constant diameter at the inlet end of the apparatus.

4. A mixing and conveying apparatus as claimed in claim 1, 2 or 3 wherein the helices are located in a trough made of flexible sheet held in position by releasable clips.

5. A mixing and conveying apparatus substantially as described with reference to the accompanying drawings.