GB2060419A

GB2060419A - Improvements in or relating to mixing and conveying apparatus

Info

Publication number: GB2060419A
Application number: GB7935840A
Authority: GB
Original assignee: HAMPTONS AERCRETE Ltd
Current assignee: HAMPTONS AERCRETE Ltd
Priority date: 1979-10-16
Filing date: 1979-10-16
Publication date: 1981-05-07
Also published as: GB2060419B

Abstract

Mixing and conveying apparatus e.g. for mixing cement, sand and water, has an outer helix (17) extending at one end, the inlet end, beyond an inner helix (16) so as to closely surround an internal sleeve (4) which rotates with the inner helix at a different speed (in the same or opposite sense) from that of the outer helix. An outer casing (10) affords a mixing trough. The effect of the different rotation between the outer helix and internal sleeve is to squeeze, roll out and flatten cement and water (which is added as a spray (13) over the length of the internal sleeve) to provide thorough mixing and wetting prior to the addition (12) of a foamed mixture of air, water and a foaming agent. <IMAGE>

Description

SPECIFICATION Improvements in or relating to mixing and conveying apparatus This invention relates to mixing and conveying apparatus especially for mixing cement and water with or without a filler such as sand and comprising an elongated casing, a double helix conveyor rotatably mounted in the casing to feed material to the outlet end thereof, said conveyor comprising an inner helix surrounded by an outer helix and means for rotating the helices at different speeds from each other. Such an apparatus is described and claimed in Patent No.

1336143.

While this apparatus provides efficient mixing for certain materials some difficulty has been experienced in mixing water with neat cement or with cement and a minimal proportion of sand and it has been found that too much water has to be added to ensure adequate mixing.

Aerated neat cement mixes are required for insulation for example for of walls and roof screeds. Aerated neat cement mixes provide a low thermal conductivity at low densities thus being suitable as an insulant. Unfortunately, to mix neat cement in a known mixer requires more than normal amounts of water, and it is the use of "extra" water that causes excessive hydraulic shrinkage and vapour blisters which detract from the materials functional value.

According to the present invention an apparatus as described is provided with a drum within a part of the outer helix which extends beyond the inner helix adjacent to an entry opening for the materials to be mixed, the drum having a diameter only slightly less than the outer helix and rotating at a speed different from that of the outer helix.

The drum and inner helix may be fixed to rotate together about a central shaft.

A stream of cement may be fed from a continuous metering system with a minimum proportion of water. A foamed mixture of air, water and foaming agent may also be fed after the drum so as to produce an aerated cement mixture.

The invention will be further described by way of example with reference to the accompanying diagrammatic drawing in which Fig. 1 is a side elevation of an apparatus made in accordance with the invention with part of the casing omitted, and Fig. 2 is an end view of the drum and outer helix.

The apparatus comprises a casing 10 of trough shape into which cement can be introduced at the position 11 together with a fine spray of water which may extend over the length of the drum from a nozzle 13. A foamed mixture of air water and foaming agent can be added at about the position 12 on to the beginning of the double helix.

Mounted in the casing longitudinally thereof is a shaft 1 5 which extends out of one end of the casing at 1 SA and is driven by a motor (not shown). An inner helix 1 6 is located within an outer helix 1 7 and spaced a small distance from it diametrically. These helices are made from round rod and the outer helix is spaced a small distance from the casing. The outer helix is driven from the shaft 15A through a gearbox 1 8 at a speed less than that of the inner helix e.g. at 100 r.p.m.

compared with the inner helix rotating at 1 50 r.p.m. in the same or opposite direction.

The outer helix extends beyond one end of the inner helix to form in effect a third helix 1 7A within which is located a drum 20 which is fixed to the inner helix and to the shaft 1 5.

The drum may have a diameter about 0.2 to 0.4 inch less than the inner diameter of the helix 1 7A.

The cement, and water are squeezed and rolled out and flattened so that a thorough and uniform wetting of the cement is effected before aerating and mixing with foam.

The drum may be 4 to 10 inches in length e.g. 6 inches.

1. A mixing and conveying apparatus comprising a casing having an entry opening near one end for entry of solid material, means for supplying water to the drum near said entry opening, an inner helix within the drum, an outer helix between the inner helix and the drum, the end of the inner helix at the entry end being spaced from the positions for entry of solid material and water, the outer helix continuing at that end to the end of the drum, means for rotating the helices at different speeds from each other, and a drum within that part of the outer helix that extends beyond the inner helix, the drum having a diameter only slightly less than the outer helix, and means to rotate the drum and helices such that the drum rotates at a speed different from that of the outer helix.

2. A mixing and conveying apparatus as claimed in claim 1 wherein the drum and inner helix are fixed to rotate together about a central shaft.

3. A mixing and conveying apparatus as claimed in claim 2 wherein the outer helix is driven through a gearbox.

4. A mixing and conveying apparatus as claimed in claim 1, 2 or 3 having a central shaft to which the drum and inner helix are fixed.

5. A mixing and conveying apparatus as claimed in any of claims 1 to 4 wherein the helices are made of round rod.

6. A mixing and conveying apparatus as claimed in any of the preceding claims wherein

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to mixing and conveying apparatus This invention relates to mixing and conveying apparatus especially for mixing cement and water with or without a filler such as sand and comprising an elongated casing, a double helix conveyor rotatably mounted in the casing to feed material to the outlet end thereof, said conveyor comprising an inner helix surrounded by an outer helix and means for rotating the helices at different speeds from each other. Such an apparatus is described and claimed in Patent No. 1336143. While this apparatus provides efficient mixing for certain materials some difficulty has been experienced in mixing water with neat cement or with cement and a minimal proportion of sand and it has been found that too much water has to be added to ensure adequate mixing. Aerated neat cement mixes are required for insulation for example for of walls and roof screeds. Aerated neat cement mixes provide a low thermal conductivity at low densities thus being suitable as an insulant. Unfortunately, to mix neat cement in a known mixer requires more than normal amounts of water, and it is the use of "extra" water that causes excessive hydraulic shrinkage and vapour blisters which detract from the materials functional value. According to the present invention an apparatus as described is provided with a drum within a part of the outer helix which extends beyond the inner helix adjacent to an entry opening for the materials to be mixed, the drum having a diameter only slightly less than the outer helix and rotating at a speed different from that of the outer helix. The drum and inner helix may be fixed to rotate together about a central shaft. A stream of cement may be fed from a continuous metering system with a minimum proportion of water. A foamed mixture of air, water and foaming agent may also be fed after the drum so as to produce an aerated cement mixture. The invention will be further described by way of example with reference to the accompanying diagrammatic drawing in which Fig. 1 is a side elevation of an apparatus made in accordance with the invention with part of the casing omitted, and Fig. 2 is an end view of the drum and outer helix. The apparatus comprises a casing 10 of trough shape into which cement can be introduced at the position 11 together with a fine spray of water which may extend over the length of the drum from a nozzle 13. A foamed mixture of air water and foaming agent can be added at about the position 12 on to the beginning of the double helix. Mounted in the casing longitudinally thereof is a shaft 1 5 which extends out of one end of the casing at 1 SA and is driven by a motor (not shown). An inner helix 1 6 is located within an outer helix 1 7 and spaced a small distance from it diametrically. These helices are made from round rod and the outer helix is spaced a small distance from the casing. The outer helix is driven from the shaft 15A through a gearbox 1 8 at a speed less than that of the inner helix e.g. at 100 r.p.m. compared with the inner helix rotating at 1 50 r.p.m. in the same or opposite direction. The outer helix extends beyond one end of the inner helix to form in effect a third helix 1 7A within which is located a drum 20 which is fixed to the inner helix and to the shaft 1 5. The drum may have a diameter about 0.2 to 0.4 inch less than the inner diameter of the helix 1 7A. The cement, and water are squeezed and rolled out and flattened so that a thorough and uniform wetting of the cement is effected before aerating and mixing with foam. The drum may be 4 to 10 inches in length e.g. 6 inches. CLAIMS

6. A mixing and conveying apparatus as claimed in any of the preceding claims wherein the drum diameter is 0.2 to 0.4 inch less than the inner diameter of the outer helix, the drum being 4 to 6 inches in length.

7. A mixing and conveying apparatus as claimed in claim 1 substantially as described with reference to the accompanying drawings.