GB2158728A - Mixing plant - Google Patents

Abstract

A plant for cementitious mixes has a single, compact silo 10 which is divided internally to form two or more compartments for solid components of the mix. Each compartment 46, 48 is served by a screw conveyor 62, 68 which directs material gravitating from the compartment to a mixing chamber 54 where mixing of the solid components takes place. The silo can be charged with solid materials away from the construction site, loaded horizontally onto a transport vehicle, and off-loaded at the site, where it is used to prepare a mix continuously. Control means are provided for controlling the mix proportions at site. <IMAGE>

Description

SPECIFICATION Batching system Background to the invention This invention relates to a batching system for cementitious materials. In one embodiment, the system can be used for batching mortar.

At present in the preparation of mortar, the sand and other additives, without cement, are mixed under controlled conditions away from the construction site where the mortar is to be used. The mix is then delivered to the construction site, where the cement is added separately.

There are a number of problems with this conventional system. In the first place, the addition of cement on site is usually done manually, and is difficult to control with the required degree of accuracy. Also, before off-site mixing of the sand and other additives, the sand usually has to be dried completely so that the correct mix proportions can be achieved. The drying of the sand is a time-consuming and costly process. Transportation is also a problem in many cases. The cement has to be supplied separately on site, only the sand and other additives being prepared off-site.

Some solutions to the problems mentioned above are to be found in the prior art. US Patent 4,298,288 describes a truck-mounted system in which concrete can be prepared on site for subsequent distribution in a guniting process. The apparatus of the system is permanently mounted on a trailer, and is bulky.

In US patent 3,456,925, a batching apparatus is permanently fixed to the bed of a truck and is again bulky. The same may be said of the invention disclosed in US patent 3,310,293.

The apparatus disclosed by US patent 3,305,222 is extremely bulky in nature and is not designed for ready transportation. US patent 2,285,765 also describes a non-transportable system.

It is an object of the present invention to provide a batching system for cementitious mixes which is compact in nature and which is transportable.

Summary of the invention The invention provides a compact batching system for cementitious mixes, the system including a single elongate silo having legs for supporting it at a vertical attitude and which can be laid horizontally on the bed of a vehicle for transportation thereof, the silo being divided internally to provide separate, internal compartments for the solid componets, including cement, of the cementitious mix, the compartments having closable charging openings through which they can be charged with the mix components at a location away from a site where the cementitious mix is to be used and from which location the charged silo can be transported to the site, the compartments also having discharge outlets situated in use at their bottom ends through which the components can exit under gravity, a mixing container situated in a position operatively beneath the silo, screw conveyors actuable to direct the mix components to the mixing container in desired proportions, a water feed device for feeding water into the mixing container at a desired rate, means within the mixing container for mixing the components and the water and for discharging the resulting aqueous cementitious mixture continuously from the mixing container.

Preferably, the screw conveyors are driven by separate motors and the rate of feed by each screw conveyor is individually controllable. The silo may be divided internally into two separate compartments, one for sand and the other for cement or for cement-containing solids. At least the sand compartment may be provided with one or more baffle plates in the vicinity of the discharge opening to prevent bridging in the relevant component as it gravitates from its compartment.

Brief description of the drawings Figure 1 shows a side view of a batching silo in a system according to the invention; Figure 2 shows another side view of the silo, this time in the direction of the arrow A in Figure 1; Figure 3 shows another side view of the silo, this time in the direction of the arrow B in Figure 1; Figure 4 shows a plan view on the silo; Figure 5 shows a section at the line 5-5 in Figure 2; Figure 6 shows a partial view of a modified silo; and Figure 7 shows a section at the line 7-7 in Figure 6.

Specific description A batching system according to the invention includes a single, elongate silo 10 which is supported on legs 12, 14, 16 and 18 fitted with feet 20.

Braces 22 are provided as shown to rigidify the structure.

The silo 10 includes a round cylindrical upper portion 24 and a conical lower portion 26 tapering to a discharge outlet 28. There is a domed roof 30 on top of the portion 24. The roof 30 has two charging openings 32, 34 which are provided with hatch covers 36, 38 respectively, and with air vents 40, 42 leading to the ambient atmosphere.

Internal walls 44 divide the interior of the silo 10 into two separate compartments 46 and 48, the compartment 46 being served by the charging opening 32 and by the discharge outlet 28, and the compartment 48 being served by the charging opening 34 and by a discharge outlet 50. The outlet 28 communicates with the inlet section 52 of a mixing chamber 54 within which is mounted a shaft 56 driven in rotation by a motor 58 through a gearbox 60. In the inlet section 52, the shaft 56 carries a spiral screw conveyor flight 62. In the remaining section 63 of the mixing chamber 54, the shaft 56 carries a series of radially extending paddles 64.

The outlet 50 communicates with a conveyor chamber 66 within which is located a screw conveyor 68 the shaft 70 of which is driven through a gearbox 72 by a motor 74. An inclined chute 76 extends from the end of the conveyor chamber 66 to an opening 78 in the upper wall of the remaining section 63 of the mixing chamber 54.

The mixing chamber 54 has an end plate 80 fitted with a hinged hatch 82, the hatch 82 being shown in the open position in Figure 1.

Extending vertically down one side of the silo 10 is a robust bracket 84 formed from channel sections 86. A cross-beam 88 spans between the webs of further, short channel sections 87 secured to the channel sections 86 of the bracket 84 via a beam 85. A further bracket 90 is fixed to the underside of the conical portion 26 of the silo 10. Suitable vibratory motors (not shown) are mounted in use to the bracket 90, which is seen in Figure 5.

The bracket 84, channel sections 87 and crossbeam 88 permit loading and unloading of the silo from a suitably adapted flat bed of a vehicle. This will be achieved by means of a crane or other lifting arrangement which engages the silo at the cross-beam 88. The lifting arrangement will be such that the silo can readily be lifted from the vertical position seen in Figures 1 to 3 and laid horizontally on the flat bed of the vehicle.

In use of the silo during mortaring operations, the compartments 46 and 48 are charged through the openings 32 and 34 with sand and cement or a cement-containing composition respectively. A typical cement-containing composition would be a mixture of cement and ash. The charging of the compartments will be carried out with the silo standing vertically at a central supply location remote from the site at which the mortaring is actually to take place. Note that it is not necessary to dry the sand at the central supply location. Damp sand can be used, as long as its moisutre content is known.

Once charged with sand and cement or the cement-containing composition, the hatches 36 and 38 are battened down, and the whole silo is then lifted from its vertical position and laid horizontally on the flat bed of a vehicle, which is driven to the mortaring site. At the site, the reverse procedure is followed, and the silo is lifted off the vehicle and reinstated on a suitable supporting surface in its vertical position. Mortaring operations can now begin.

The motors 58 and 74 are started up. Sand gravitates from the compartment 46, through the discharge outlet 28 and onto the screw conveyor 62 which conveys it downstream from the section 52 of the mixing chamber 54 to the remaining section 63 thereof.

At the same time, cement or the cement-containing composition gravitates from the compartment 48, through the discharge outlet 50 and onto the screw conveyor 68 which conveys it to the entrance of the chute 76. The cement or cement-containing composition falls through the chute into the remaining section 63 of the mixing chamber 54.

A water spray head 92 extends into the mixing chamber 54 at the upstream end of the remaining section 63 i.e. at the position where the sections 62 and 63 meet one another.

In the section 63, the paddles 64 act to mix the solid components arriving from the compartments 46 and 48 with the water sprayed from the spray head 92. The resulting aqueous cementitious mix migrates under the action of the screw conveyor 62 towards the end of the mixing chamber 54 where it forces open the hatch 82 and drops out for immediate use in mortaring.

In order to achieve the correct mortar mix, it is important that the rates of feed of the sand, cement or cement containing composition and water be closely controlled. A control panel 94 (seen in Figure 3 only) is provided for controlling the motors 58 and 74. Also, the gearboxes 60 and 72 can be of variable speed type to permit variations in the rotational speed of the shafts 56 and 70 and hence the screw conveyor feed rates.

The vibratory motors mounted to the bracket 90 serve to impart high-speed vibrations to the silo 10 to discourage material in either compartment 46 or 48 from sticking on the internal walls of the silo or on the walls 44. These vibratory motors, which will be of conventional type, will also be controlled from the control panel 94.

Figure 3 also illustrates air nozzles 96 and 98 communicating with the interiors of the compartments 46 and 48. If material should lodge in the compartments, compressed air can be fed through the nozzles to disturb it.

Figures 6 and 7 illustrate an important modification of the silo 10. These Figures only illustrate the relevant parts of the silo 10 and the numerals used are the same as those used in previous Figures.

Secured to the conical wall of the portion 26 inside the compartment 46 are converging baffle plates 96 and 98 which meet at an apex 100. These plates are situated below the level of the conveyor chamber 66 and above the discharge outlet 28.

There is a tendency for sand to "bridge" across the lower end of a conical container during gravitation thereof towards an outlet. When bridging takes place, the smooth gravitation of sand is disturbed and it is essential to break up the bridge to enable the system to operate accurately again. The problem is especially severe if damp sand is used in the compartment 46.

The baffle plates 96 and 98, which extend into the path of the gravitating sand, have the tendency to prevent bridge formation, since it is impossible for a bridge to form across the plates.

A major advantage of the system described above is its portability. It is obviously desirable to be able to charge up the silo with the necessary components at a central supply location away from the site, and subsequently to transport only the compact silo to the site. There is therefore no need for transportation of individual components, such as cement, to the site with attendant storage and mixing problems there. Once the charges in the compartments 46 and 48 are depleted, the silo is merely re-loaded onto the vehicle and taken back to the central supply location for re-charging. Note also that, because the silo is in no way attached to its vehicle, the vehicle can be used to do other productive work while the silo is in use.

Claims (19)

1. A compact batching system for cementitious mixes, the system including a single elongate silo having legs for supporting it at a vertical attitude and which can be laid horizontally on the bed of a vehicle for transportation thereof, the silo being divided internally to provide separate, internal com partments for the solid components, including cement, of the cementitious mix, the compart ments having closable charging openings through which they can be charged with the mix compo nents at a location away from a site where the ce mentitious mix is to be used and from which location the charged silo can be transported to the site, the compartments also having discharge out lets situated in use at their bottom ends through which the components can exit under gravity, a mixing container situated in a position operatively beneath the silo, screw conveyors actuable to di rect the mix components to the mixing container in desired proportions, a water feed device for feed ing water into the mixing container at a desired rate, means within the mixing container for mixing the components and the water and for discharging the resulting aqueous cementitious mixture contin uously from the mixing container.

2. The compact batching system of claim 1, in which the screw conveyors are driven by separate motors and the rate of feed by each screw con veyor is individually controllable.

3. The compact batching system of either one of the preceding claims, in which the silo is divided internally into two separate compartments, one for sand and the other for cement or for cement-con taining solids.

4. The compact batching system of claim 3, in which at least the sand compartment is provided with one or more baffle plates in the vicinity of the discharge opening to prevent bridging in the rele vant component as it gravitates from its compart ment.

5. The compact batching system of any one of the preceding claims in which the water feed de vice comprises a spray head arranged to spray water into the mixing container at a desired rate.

6. The compact batching system of any one of the preceding claims, in which the container ac commodates a rotatable shaft carrying mixing pad dles for mixing the components and the water.

7. The compact batching system of claim 6 in which the shaft accommodated by the mixing con tainer is the same shaft as forms part of the screw conveyor serving one of the compartments of the silo.

8. The compact batching system of any one of the preceding claims, in which the mixing con tainer has a hinged closure arranged to close un der its own weight and to be pushed open by the cementitious mixture as it is discharged from the mixing container.

9. A compact batching system substantially as described herein with reference to, and as shown in, Figures 1 to 5 or Figures 6 and 7 of the accom panying drawings.

10. A transportable elongate silo having means for supporting it in a vertical position during dis charge of material from the silo and which can be laid horizontally during transport, the silo having at least two internal compartments for solid compo nents of a cementitious mix, each compartment having an inlet and also having an outlet through which the component contained in that compart ment can be discharged when the silo is supported in a vertical position.

11. A silo as claimed in claim 11, wherein one compartment contains sand and a further compart ment contains cement or a cement-containing composition.

12. A silo substantially as described herein with reference to, and as shown in, Figures 1 to 5, or Figures 6 and 7, of the accompanying drawings.

13. A method of preparing a cementitious mix which comprises discharging from a silo as claimed in any one of claims 10 to 12, which silo is supported in a vertical position, the solid components required for the mix, and mixing the components.

14. A method of preparing a cementitious mix which comprises introducing each solid component of the mix into a respective compartment of a silo as claimed in claim 10 or claim 12, the silo being at a location away from the site where the cementitious mix is to be used, transporting the charged silo in a horizontal position to the site, positioning the silo in a vertical position at the site, discharging solid components from the silo, and mixing the solid components.

15. A method as claimed in claim 13 or claim 14, wherein the components are mixed in a mixing container positioned beneath the silo.

16. A method as claimed in any one of claims 13 to 15, wherein the components are discharged from the compartments under gravity.

17. A method as claimed in any one of claims 13 to 16, wherein means are provided for controlling the amount of each component introduced into the mix.

18. A cementitious mix prepared by a method as claimed in any one of claims 13 to 17.

19. Any new and novel feature described herein.