GB2196546A

GB2196546A - Multi-purpose mixer

Info

Publication number: GB2196546A
Application number: GB08715477A
Authority: GB
Inventors: Kenneth Wright
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-07-02
Filing date: 1987-07-01
Publication date: 1988-05-05
Anticipated expiration: 2007-07-01
Also published as: GB8715477D0; GB2196546B; GB8616142D0

Abstract

A mixer, e.g. for concrete, embodying the basic mixing principle of a flow of initially dry granular components (11) hitting a swirling funnel-shaped wall of liquid (17) and being vortex-mixed with that liquid, is characterised by the feature that the mixer incorporates nozzles (23) which open on to the inside wall of the casing and through which fluid-in this case air-under pressure impinges on the mixture of liquid and granular components to reduce wear of the casing wall. <IMAGE>

Description

SPECIFICATION Multi-purpose mixer Field of the Invention The invention relates to mixers of the kind ("the kind in question") embodying the basic mixing principle of a flow of initially dry granular components hitting a swirling funnelshaped wall of liquid and being vortex-mixed with that liquid.

Review of Art Known to the Applicants Mixers of the kind in question are known for example from the following UK patent specifications: 1 453 469 1 465 919 1 486 840 1 520 482 1 523 404 2 025 427 2 067 908 The last two of these neatly summarise the basic mixing principle, and 1 486 840 also describes and illustrates the concept of the funnel-shaped liquid vortex being generated by a ring of sprays.

Mixers of the kind in question as disclosed in these published UK patent specifications have found wide use, but the wear on the mixer casing from the swirling fluid and granular inflow can be excessive. Where a concrete aggregate is being mixed, for example, the mixer casing can be scarred within a very short time.

It is known to line the mixer casing with a wear-resistant material which, when worn, can be replaced. But there is clearly a continuing need for some means of extending the life of the casing wall beyond that which is already obtainable by the known linings.

Summary of the Invention In one advantageous aspect of the invention, a mixer of the kind in question incorporates nozzles which open onto the inside wall of the casing and through which fluid impinges on the mixture of liquid and granular components.

In another advantageous aspect of the invention, a mixer of the kind in question has its liquid-spraying nozzles all circumferentially spaced about the casing in substantially the same plane.

In another broad aspect of the invention, a mixer of the kind in question has its non-liquid fluid-spraying nozzles opening onto the inside wall of the mixer casing non-tangentially when the casing is viewed from above.

In a further advantageous aspect of the invention, a mixer of the kind in question has its non-liquid fluid-spraying nozzles fed from a plenum defined by an annuiar gap between the mixer casing and a funnel-shaped liner onto which the mixture of liquid and components impinges.

In another advantageous aspect, the invention is embodied in a mixer of the kind in question in which the non-liquid fluid-spraying nozzles open onto the inside wall of the mixer casing at an angle other than a right angle when the casing is viewed from the side and in cross-section.

In another broad aspect, the invention is embodied in a mixer of the kind in question combined with a discharge chute in the form of a vibrator.

The scope of the invention is defined in the claims.

Brief Description of the Drawings The accompanying drawings show the best way currently known to the applicant of putting the invention into practise.

In these drawings: Figure 1 is a schematic sectioned side elevation showing the way the mixer works; Figure 2, enlarged in scale, is a side elevation of the mixer; Figure 3, drawn to the same scale as Figure 2, shows the mixer in plan; Figure 4, drawn to a smaller scale than any of the previous figures, shows the mixer mounted on a lorry and combined with a feed conveyor and cone and a discharge chute; and Figure 5, drawn approximately to the same scale as Figure 4, shows the lorry-mounted mixer and other components of Figure 4 in perspective.

Description of the Preferred Embodiment The mixer shown in the drawings is fed via a screw conveyor with correctly proportioned initially dry components, for example cement, sand and gravel, through a cone ring feeder which deposits them into the mixer casing.

As they enter the casing, the dry granular components come into contact with a veil of liquid-in this case water-which initiates a swirling action of the liquid-granular mixture.

As the mixture drops further into the mixer, fluid-in this case air-fed into the mixer from a hydrovane compressor speeds up the swirling action and creates a directional vortex.

The air space created at the wall of the mixer inner cone (the mixer lining) considerably reduces the wearing frictional contact between the inner cone and the abrasive mixture. This enables the inner cone:to be produced in materials, such as NYLATRON (RTM) or NYLON BEETLE 666 compound, which are relatively easily mouldable and which, whilst being abrasion-resistant, need not necessarily be as abrasion resistant as the linings of conventional mixers of the kind in question.

The mixture is discharged at the base of the mixer into a discharge chute lined with the same material as the mixer inner cone is com posed of. A vibrator unit is located at the centre i.e. half way along the length-of this discharge chute, to assist the flow of the mix and at the same time to de-aerate the mix.

In Figure 1, initially dry granular components of (for example) cement, sand and gravel emerge in a mixed stream 11 from the discharge end of a screw conveyor 12 and fall under gravity into a cone ring feeder whose casing 13 is frusto-conical and is inverted over the cone 14.

The cone ring feeder spreads the dry granular stream 11 in circular fashion into the mixer itself. The mixer casing, like the feeder casing, is an inverted frusto-cone and is co-axial with the feeder casing 13. The cone 14 is held by struts 15, each equally circumferentially spaced about the same plane circle at 120" spacing. The incoming dry mix flows over and around the cone 14 and the struts 15 under gravity.

A water inlet 16 feeds a ring 17 of waterspraying nozzles below the rim 18 of the mixer casing 19. As Figure 2 shows, the rim 18 is bolted to the lip of the casing 19 by bolts 21 which ( Figure 3) are spaced at equal circumferential spacings about the rim at 30 spacings.

The casing 19 is lined with a frusto-cone 22 of wear-resistant material. The shape of the casing and the liner is such that they nest, and when the rim 18 is bolted into place then the liner is removably but non-rotatably retained in the casing 19. The liner 22 ends in a circular-cylindrical discharge section 23 of reinforced thickness.

The spray nozzles 17 which feed the water in jets to the inside wall of the liner 22 all occupy substantially the same plane. They direct their jets downwards and towards the centre of the mixer-liner, as shown in Figure 1, to create a funnel-shaped frusto-cone of water and is swirled around by, and mixed into, the water.

Air inlets 24, 25 feed pressurised air to an annular plenum 26 deliberately defined between the mixer casing 19 and the mixer casing liner 22. Nozzles 23 formed in the liner open out onto the inside wall of the liner 22 and jet the air under pressure into the mixing zone.

As Figure 2 shows when viewed in elevation (i.e. as in Figure 2) each of these nozzles 23 runs at 450 to the liner wall. And when viewed in plan (i.e. as in Figure 3) each of the nozzles runs at 450 to a tangent to the liner circumference.

All the air-supplying nozzles thus run nontangentially to the liner wall. Unlike the waterspraying nozzles 17, the nozzles 23 are arrayed over a considerable portion of the wall of the mixer liner 22. They extend from a plane some short way below the water-spraying nozzles 17, in axially successive circular rows, down almost to the discharge section 23 of the liner.

Figure 2 shows that each of these circular rows of nozzles is substantially planar when viewed as in Figure 2. Figure 3 shows that each of the rows of nozzles 23 is linear, and radial with respect to the mixer liner 22, when viewed as in Figure 3.

The vortex-mixing effect of the water and the air sprayed into the mixer liner thoroughly blends the incoming mix 11 by the time it leaves the discharge section 23 of the mixer.

The discharge is taken away by a chute 27 which incorporates a vibrator unit (not shown) to assist the flow of the discharge and at the same time de-aerate it.

Figure 4 shows the mixer and its associated equipment mounted on the back of a lorry 28 to mix and pour concrete into a trench 29.

Figure 5 shows the same lorry in perspective but without the discharge chute 27. A number of features of this mixer and ancillary equipment combination are worth noting.

The screw conveyor 12 pivots half-way along its length into two joined sections 31, 32 for ease of transport and stowage. It can pivot at 33 about the frame 34 to which it and the other major components are secured.

Its air-driven screw 35 is driven by a motor 36 carried at the top end of the portion 31 of the conveyor 12 and supplied from a compressor 37 mounted on the lorry platform.

The supply from compressor 37 to motor 36 is carried by flexible air lines 39.

A water tank 41 on the back of the lorry feeds the water inlet 16 via a pump (not shown); and the air inlets 24, 25 are supplied with air under pressure by the same compressor 37 that supplies the air motor 36 driving the screw conveyor 12.

As Figure 5 shows, the frame 34 carrying the screw conveyor 12, the feeder 13, and the mixer 19, can pivot towards and away from the cab 42 of the lorry 28 about a pivot axis spanning pivots 43 and 44 adjacent the back of the lorry platform. In normal use, as Figure 4 shows, the frame 34 stands substantially upright on the back of the lorry 28; whilst for transport, as shown in Figure 5, it pivots towards the cab 42 once the screw conveyor 12 has been folded and the chute 27 removed.

Claims

1. A mixer of the kind in question incorporating nozzles which open on to the inside wall of the casing and through which fluid under pressure impinges on the mixture of liquid and granular components.

2. A mixer according to Claim 1 in which the liquid-spraying nozzles are all circumferentially spaced about the casing in substantially the same plane.

3. A mixer according to either of the preceding claims in which the non-liquid fluidspraying nozzles open on to the inside wall of the mixer casing non-tangentially when the casing is viewed from above.

4. A mixer according to any of the preceding claims in which the non-liquid fluid-spraying nozzles are fed from a plenum defined by an annular gap between the mixer casing and a funnel-shaped liner on to which the mixture of liquid and components impinges.

5. A mixer according to any of the preceding claims in which the non-liquid fluid-spraying nozzles open on to the inside wall of the mixer casing at an angle other than a right angle when the casing is viewed from the side and in cross-section.

6. A mixer according to any of the preceding claims in which the fluid sprayed through the fluid-spraying nozzles comprises air.

7. A mixer according to any of the preceding claims in which the mixer is combined with a discharge chute in the form of a vibrator.

8. A mixer substantially as described herein with reference to and as illustrated in Figure 1 of the accompanying drawings.

9. A mixer substantially as described herein with reference to and as illustrated in Figures 2 and 3 of the accompanying drawings.

10. A mixer substantially as described herein with reference to and as illustrated in Figures 4 and 5 of the accompanying drawings.