GB2077609A - Hopper assembly with agitator at discharge outlet - Google Patents

Abstract

The agitator is in the form of a flexible, resilient member (30) fixed so that a marginal edge (36) is normally in contact with and defines an interface (38) with an associated inner surface (24) of the hopper (10). Air under pressure is fed to the interface in such fashion as to cause the marginal edge of the resilient member to flutter and allow the air to escape in randomly directed "puffs". The fluttering movement combined with the intermittent puffs of air causes pulverulent material to be agitated, aerated and/or fluidized as it passes to the discharge opening (12). <IMAGE>

Description

SPECIFICATION Aerator Pulverulent materials are commonly transported in and discharged from tank vehicles, the discharge being effected through a closed system to minimise contamination of the atmosphere by dust. The discharge of powdered materials such as cement is much easier if the material is aerated or fluidized before entering a piping system through which the product is pneumatically conveyed. The vehicles may be in the form of elongate, substantially horizontal tanks with one or more discharge hopper devices along their lower sides through which the product may migrate by gravity to the pneumatic conveying piping system, a portion which may be carried by the vehicle itself.The interior of the tank may be pressurized to facilitate the discharge, and as above noted, the discharge is easier if the material is aerated or fluidized before entering the pneumatic conveying pipe system. A common means of achieving fluidization is to introduce air into the hopper of the tank through porous or similar elements, fluidization of the material adjacent the discharge mouth assisting in conveying the material to the discharge port.

These porous elements or pads exhibit certain undesirable characteristics, in particulartheir propensity to blinding due to the fact that the air passed therethrough normally contains a certain amount of foreign material or dust which gradually fills the pores of the material, which may be, for example, canvas.

Also, these porous pads make it difficult to clean the hopper assembly.

However, without some form of aid, bulk products such as cement when discharged through the narrowed hopper outlet mouths tend to pack or bridge at these outlets and it is therefore relatively essential that some means be provided to aid in this discharge.

Accordingly, it is an object of the invention to provide means for decreasing the tendency of bulk products being discharged from a hopper structure to pack or bridge at the outlet.

The invention provides a hopper assembly for storing pulverulent material an interior surface of which is arranged to channel the material to a discharge mouth through which the material may flow out of the hopper, the assembly comprising a flexible, resilient annular agitating member fixed within and surrounding the discharge mouth and having a marginal portion contacting the said interior surface over an area but free to flutter with respect to the supporting surface, and means for supplying airto the agitating member at a superatmospheric pressure, the arrangement being such that, in use, the marginal portion of the agitating member is caused to flutter so that at least a part of it is intermittently out of contact with the supporting surface to allow air to escape past the supporting surface in discrete bursts.

An annular manifold preferably surrounds the discharge mouth, the discharge mouth being provided with a series of openings leading from the annular manifold to the interface.

The invention also provides a hopper assembly comprising at least one device in accordance with the invention.

The invention also provides avehiclefortransport- ing pulverulent material, which comprises at least one such hopper assembly. The vehicle may further comprise valve means for selectively opening and closing the discharge mouth, and a discharge line communicating with the discharge mouth through the valve means, the discharge line being arranged to receive pressurized airto convey material through the discharge line.

One form of device constructed in accordance with the invention will now be described by way of example with reference to the accompanying drawing, in which: Fig. 1 is a vertical section taken through the hopper outlet of a tank vehicle and through one form of the device; With reference to Fig. 1, an outlet hopper indicated generally by the reference numeral 10, which, it is to be understood, is of a construction conventional in bulk product tank vehicles, is provided with a discharge mouth 22 and as is indicated in phantom lines in Fig. 1, associated therewith is a valve indicated generally by the reference numeral 14 which permits selective opening of the discharge mouth 12 to allow discharge of the material contained in the tank vehicle.The hopper structure 10 is usually one of several which are provided along the underside of thetankvehicle and the valve 14 forms an integral part of the vehicle structure as does a distribution pipe 16. The structure also includes a pipe stub 18 which discharges into the main line 16, all of which is conventional in the art. It is also conventional in these tank vehicles to provide a motor driven blower which not only discharges air into the outlet line 16 to allow fluid conveying of the material but also pressurizes the interior of the tank, thereby aiding in the expulsion of the material from the tank. It will be appreciated that at one end the distribution line 16 is connected to the user's distribution system for delivering the material to the desired site.

The pulverulent materal contained in the tank vehicle may be a relatively fine powder such as cement and, forthis season, it may tend to back or bridge over the discharge mouth 12, thus interrupting the efficient and steady flow of material to the discharge conveying pipe 16.

The hopper structure 10 is provided with a manifold formed by wall means 20 and having an interior 22 which is provided with a suitable connection (not shown) with the pressurized air system to maintain air under the requisite pressure within the manifold interior 22. Around the periphery of the hopper wall 24 is provided a series of circumferentially spaced openings 26 through which air may escape from the manifold.

Cooperatively associated with the discharge opening 26 is an agitating and aerating means which is indicated generally by the reference character 28 and which, in this form of device, takes the form of a frustoconical section of rubber or like material 30 engaging in face-to-face contact with the interior of the hopper wall 24 just adjacent to the discharge opening 12 and further including a central portion 32 which extends radially outwards in the form of an annular flange around the discharge opening 12.

Thus, the member 30 includes an intermediate portion 34 which normally closes the manifold openings 26 and a marginal edge portion 36 lying flat against the interiorofthe hopper wall 24to define an interface 38. If the pressure of the air within the manifold interior 22 is maintained art a propervalue, air will be supplied to the interface 38 at a pressure suf ficientto cause the marginal edge 36 of the agitating and aerating means 28 to flutter or vibrate with a consequent periodic or interrupted escape of air in the form of air jets directed upwardly along the inner surface of the hopper wall 24 and at random circumferential spacings therearound.The pressure of air maintained within the interior of the manifold 22 will ordinarily be of the order of 1 to 10 pounds per square inch gauge (7 to 70 kPa) if the interior of the tank vehicle is under normal atmospheric pressure.

If the interior of the tank vehicle is maintained under some higher pressure in order to expedite the discharge, then the pressure in the manifold 22 will ordinarily be of the order of 1 to 10 psi (7 to 70 kPa) higher than that internal pressure. ln either case, the air flow rate pastthe agitating and aerating means 28 will be of the order of from 10 to 400 standard cfm (5 to 200 dm3/s).

As described above, the agitating and aerating means 28 causes the escaping air to flow in random, interrupted fashion by the fluttering or vibrating action of the marginal edge portion 36 which occurs randomly around the periphery of the edge portion 36. As a result not only is the pulverulent material agitated in the immediate vicinity of the discharge mouth 12, but also an aerating or fluidized effect is produced, the net result being that a steady and efficient discharge flow of material is achieved.

Claims (8)

1. A hopper assemblyforstoring pulverulent material an interior surface of which is arranged to channel the material to a discharge mouth through which the material may flow out of the hopper, the assembly comprising a flexible, resilient annularagi- tating member fixed within and surrounding the discharge mouth and having a marginal portion contacting the said interior surface over an area but free to flutter with respect to the supporting surface, and means for supplying air to the agitating member at a superatmospheric pressure, the arrangement being such that, in use, the marginal portion of the agitat ing member is caused to flutter so that at least a part of it is intermittently out of contact with the support ing surface to allow air to escape past the supporting surface in discrete bursts.

2. A hopper assembly as claimed in claim 1, wherein the agitating member is in the form of a frustoconical sleeve fitted within the discharge mouth of the hopper.

3. A hopper assembly as claimed in claim 2, including an annular manifold surrounding the discharge mouth, the discharge mouth being provided with a series of openings leading from the annular manifold to the interface.

4. A hopper assembly for storing pulverulent materials substantially as hereinbefore described with reference to, and as shown in, Fig. 1 of the accompanying drawing.

5. A hopper assembly as claimed in any one of claims 1 to 3, which is formed by a closed body of a', vehicle for transporting pulverulent material.

6. Avehiclefortransporting pulverulent material which comprises at least one hopper assembly as claimed in any one of claims 1 to 4.

7. Avehicle as claimed in claim 6, which further comprises a valve means for selectively opening and closing the discharge mouth, and a discharge line communicating with the discharge mouth through the valve means, the discharge line being capable of receiving pressurized air to convey material through the discharge line.

8. A flexible, resilient annular member suitable for use as the said agitating member in a hopper assembly as claimed in any one of claims 1 to 5.