GB2139912A - Mixing and feeding device - Google Patents

Abstract

In the mixing of materials such as lightweight concrete a rotatable member is mounted in a chamber 9, the member having a shaft 10 with a continuous series of helical flights, 11, 12, at least some of which are hollow. Additionally, paddles 13 are mounted on the shaft 10 and disposed at an angle of opposite sense to the helix angle of the flights 11, 12. <IMAGE>

Description

SPECIFICATION Helical mixing and feeding devices This invention relates to devices for mixing and feeding granular, liquid, semi-liquid or materials in other forms, whether wet or dry, by means of a rotatable screw-like helically bladed member or members. Materials which may be mixed and fed include concrete or food products.

There are in existence many helical mixing and feeding devices, being often referred to as augers, and they usually operate within a chamber which provides relatively small clearance between the blade or flight periphery and the chamber wall.

While the conventional helical auger device is quite satisfactory for feeding material along the length of the chamber, the mixing of the materials during transport through the device is often rather unsatisfactory, the ingredients tending to remain in layers which may not be greatly disturbed during travel through the device.

There have therefore been proposed various flight or blade configurations which improve mixing but none of these is particularly satisfactory, some being efficient in mixing the materials but having impaired transporting efficiency.

It is therefore the object of the invention to provide a helical mixing and feeding device having good mixing characteristics as well as being efficient in feeding material lengthwise of the device.

In accordance with the invention there is provided a mixing and feeding device comprising a rotatable member mounted in a chamber, the member having helical flights, at least some of which have hollow interiors, at least one paddle being located within or adjacent to at least one of the hollow flights, said paddle being disposed at an angle of opposite sense to the helix angle of the flights.

The invention will now be described by way of example, with reference to the accompanying drawings, in which Figure lisa side elevation view of the rotatable member of a mixing and feeding apparatus construction in accordance with the invention, Figure 2 is a cross-sectional scrap view of the device and Figure 3 is a side elevation cross-sectional view The apparatus shown is intended for use in a machine for producing mixed concrete in quantity and therefore the machine may have provision for storage of the ingredients to be mixed and means for feeding these to a chamber in which they are mixed together in appropriate proportions. Provision may be made for altering the relative quantities of the materials through valves or other controls and there is also included pumping apparatus whereby the mixed material is delivered out of the machine.

In one example such a machine is mounted on wheels and has its own prime mover.

The invention is concerned with the portion of the machine which mixes the ingredients together and delivers them to an outlet from the machine. From this portion of the machine, the material may be pumped to the outlet which may have a flexible hose connected to it whereby the material can be delivered at a position relatively remote from the machine.

Furthermore the material may have to be elevated to a delivery position which may be substantially above the machine.

The apparatus for mixing and feeding comprises a rotatable member contained within a chamber formed by a generally U-shaped trough 9. The arcuate base of the trough has a radius only a little larger than the overall diameter of the rotatable member so that there is relatively small clearance between the lower curved wall portion of the trough and said rotatable member.

Material is fed into the top of the trough and, also for example, a foaming agent is added at the start end of the device through a supply nozzle. The mixed material leaves at the opposite or delivery end of the device through an outlet 8, to which an outlet pipe or other fitting may be attached.

The rotatable member comprises an elongated shaft 10 with provision (not shown) whereby it is rotated through a suitable drive train. The ends of the shaft are mounted in bearings in the trough or associated with the ends thereof.

Fixed on to the shaft is a continuous helical blading arrangement made up from a continuous number of flights which all have substantially the same helix angle as shown. Some of the flights are of solid form at 11 and some are hollow as indicated at 12. The solid flights have their internal peripheries secured to the shaft 10, as by welding, and the hollow flights are of square or rectangular crosssection and are carried by adjacent solid flights, to which their ends are connected. As shown, the solid and hollow flights are arranged in alternating sequence. At the right-hand end of the shaft shown in Figure 1 there are three solid flights, adjacent to which there are two hollow flights. A single solid flight is fixed near the centre of the shaft and there are then alternating hollow and solid flights.Two hollow followed by one solid flight may alternate along the shaft to the opposite end (not shown) at which further solid flights may be provided.

With this arrangement efficient feeding of material from one end of the device to the other is possible.

Hollow flights will feed horizontally or at an upward angle but if a significant angle of elevation is required, greater reliance is placed upon the solid flights to achieve this.

In order to improve mixing of the ingredients as they are conveyed from one end to the other of the device, there are provided, within the zone at which hollow flights are fitted, paddles 13. Each paddle is secured to the shaft 10 and has a blade positioned so that it lies at an angle opposite to the helix angle of the adjacent flight. As shown, the paddles 13 may be mounted in pairs disposed at opposite sides of the shaft respectively and occupying the space within the hollow flights 12. The reverse angle of the paddles 13 causes some reversing of the flow of the material and creates turbulence which gives good mixing characteristics.

In one example, the paddles are simply fixed, as by welding, to the shaft 10. However, they may be fixed in such a way as to be adjustable. By means of this adjustment it is possible to vary the angles of the paddles. This is particularly useful when a foaming agent is to be added to a material such as concrete since if the angle of the paddles is increased, there is greater turbulence and therefore more foaming and thus a concrete is produced with a low density.

Conversely if it is required to increase the concrete density the paddle angles may bedecreased.

The mixing and feeding device illustrated is particularly suitable for producing lightweight concrete which is aerated during the mixing process but is applicable to other products such as food products, and it is suitable for use with granular or liquid or semi-liquid materials.

The distribution of solid and hollowflights may be varied as may be the position of the paddles. It is possible to dispense with solid flights and to use only hollow flights. Furthermore, there may be one paddle for each hollow flight or one paddle for a number of adjacent flights. The form of the hollow flights and of the paddles may be varied to suit different types of materials.

Claims (6)

1. A mixing and feeding device comprising a rotatable member mounted in a chamber, the member having helical flights, at least some of which have hollow interiors, at least one paddle being located within or adjacent to at least one of the hollow flights, said paddle being disposed at an angle of opposite sense to the helix angle ofthe flights.

2. A mixing and feeding device as claimed in claim 1 wherein the member comprises a shaft on which are mounted a continuous series of flights having a predetermined helix angle, some of the flights being hollow and some solid, and a number of paddles disposed within or adjacent to at least some of the hollow flights.

3. A mixing and feeding device as claimed in claim 2 wherein the paddles are mounted in opposed pairs on the shaft.

4. A mixing and feeding device as claimed in any one of the preceding claims wherein the paddles are mounted in such a manner that their angles can be adjusted relatively to the helix angle of the flights.

5. A mixing and feeding device as claimed in any one of the preceding claims in which the chamber has an internal wall of a dimension only slightly larger than the external diameter of the helical flights.

6. A mixing and feeding device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.