EP0059091A1

EP0059091A1 - Flow control devices

Info

Publication number: EP0059091A1
Application number: EP82300863A
Authority: EP
Inventors: Leslie Stott
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-02-25
Filing date: 1982-02-19
Publication date: 1982-09-01

Abstract

A device (10) for controlling the flow of powdered or granular material out of a storage device such as a hopper (11) comprises a body (12,13) for mounting underneath the storage device and defining at least one outlet passage (17, 18) for the material and at least one control member (20,21). The device has at least one material support surface (30) adjacent to the outlet passage (17, 18), the support surface (30) being positioned and shaped to support a substantial part of the pressure head exerted by the material, thus substantially reducing the pressure head acting on material tending to flow through the outlet passage (17, 18) and making it easier for the control member (20, 21) to control the flow of material through the outlet passage (17,18). The control member (20, 21) has a surface which faces upwardly at an inclined angle to the horizontal when the control device (10) is mounted underneath the storage device (11), and the control member (20,21 ) is movable across the outlet passage (17, 18) transversely to the direction of flow, to control the flow.

Description

The invention relates to flow control devices, and particularly to devices for controlling the flow of powdered or granular material out of a storage device such as a hopper or silo. ,
According to a first aspect of the invention, a device for controlling the flow of powdered or granular material out of a storage device, the flow control device comprising a body arranged for mounting underneath the storage device and defining an outlet passage for the material, a control member for the outlet passage, the device having at least one material support surface adjacent the outlet passage, the support surface being positioned and shaped to support a substantial part of the pressure head exerted by the material, thus substantially reducing the pressure head acting on material tending to flow through the outlet passage and making it easier for the control member to control the flow of material through the outlet passage.
There may be a support surface at each side of the aperture.
A first support surface at one side of the aperture may comprise a surface sloping downwardly towards the aperture.
A second support surface at the opposite side of the aperture may comprise a surface sloping downwardly towards the aperture at a steeper angle than the first support surface.
The lowermost edge of the second support surface is preferably positioned below the level of the lowermost edge of the first support surface.
The first support surface preferably has an undercut lip at its lowermost edge.
There may be a plurality of outlet apertures, the first support surface adjacent one aperture combining with the second support surface adjacent the adjacent aperture to present to the material in the storage device an upwardly facing ridge-like surface.
Between each pair of adjacent,apertures each first support surface and adjacent second support surface may be formed as an integral unit.
The unit may be of plastics clad metal, e.g. steel clad with high density polyethylene.
Other parts of the device may also be made of plastics clad metal, thus reducing weight.
According to a second aspect the invention provides a device for controlling the flow of powdered or granular material out of a storage device, the flow control device comprising a body arranged for mounting underneath the storage device and defining an outlet passage for the material, and a control member for the outlet passage, the control member having a surface which faces upwardly at an inclined angle to the horizontal when the control device is mounted underneath the storage device,' the control member being movable across the outlet passage transversely to the direction of flow, to control the flow.
Preferably the control member is such that during the said transverse movement the angle of the said surface to the horizontal varies.
Preferably the control member is movable, from a position in which it closes the outlet passage, to progressively open the outlet passage, such movement causing the angle of the said surface to the horizontal to progressively increase.
Preferably the direction of flow through the outlet passage is also inclined to the horizontal.
The outlet passage may be such that when material is moving towards the control member it travels along a path which is inclined in a similar direction to the said surface but after passing the control member it changes direction to follow a path inclined in the opposite direction, the outlet passage thus being of a zig-zag configuration.
The control member may be mounted on a slide for movement across the outlet passage.
The control member may comprise a flat plate pivotally mounted on the slide.
The slide may be operated by a fluid controlled ram.
Preferably the control member is such that the change in angle of inclination as the control member moves enables the said surface to maintain contact with a closed side of the outlet passage so that flow takes place only past that side of the control member which is remote from the closed side of the outlet passage.
The closure member may be spring loaded into engagement with the said closed side.
The said closed side may be shaped to accommodate more of the control member in the upward direction as the control member moves towards the closed side, so that the change in angle of the said surface is brought about by the spring means moving the leading edge of the control member progressively upwardly as the control member moves towards the closed side.
There may be a plurality of outlet passages each having its associated closure member.
The closure members may be mounted on a common slide for movement in synchronism.
The body is preferably vibratable to promote the flow of material through the or each outlet passage.
The control member of the first aspect of the invention may be as defined according to the second aspect of the invention.
The invention includes a storage device, e.g. a hopper or silo, fitted with a flow control device as described above.
The term 'storage device' is intended to include any device which supports a column of material above the control device and hence gives rise tα a pressure head of material, and may include devices other than hoppers and silos, for example feed pipes.
By way of example, specific embodiments of the invention will now be described, with reference to the accompanying drawings, in which:-

Figure 1 is a side view, partially in section, of an embodiment of flow control device according to the invention;
Figure 2 is a front view, also partially in section; and
Figure 3 is a schematic view of an alternative embodiment.

The flow control device indicated generally at 10 in Figures 1 and 2 is intended, in use, to be bolted to the bottom of a hopper 11 or similar storage device for powdered or granular material.
The device 10 comprises a body having a fixed frame made up of two elongate members 12 and two shorter cross members 13.
Suspended from the members 12 by means of flexible bushes 14 is a movable frame 15. This frame 15 houses a casting 16 which, as best shown in Figure 1, defines the upper part 17 and 18 of two outlet passages. Each passage is provided with a control member in the form of a plate 20, 21 and the passages continue below the plates with portions 22 and 23, defined by the lower part of the movable frame 15. It will thus be seen from Figure 1 that each outlet passage has a first part which is inclined to the left as the passage extends downwardly, and after passing the associated control member the passage changes direction and is inclined to the right, so that the passage has a zig-zag configuration.
The parts of the casting adjacent to the passages have the affect of reducing the pressure head acting in the vicinity of the passages, in the manner described in more detail with respect to the embodiment shown schematically in Figure 3.
Mounted on the movable frame 15 is an electric vibrator 24, operable to cause the movable frame 15 to vibrate in the direction of the arrows 25 shown in Figure 1.
The movable frame 15 is sealed to the upper frame by means of a flexible sleeve 26.
Each plate 20, 21 is.pivotally connected to a slide member 27 which can be moved horizontally by means of a linear actuator 28. Each plate 20, 21 is fitted with a leaf spring 29 which urges the plate into contact with part 30 of the casting 16.
In the position shown in Figure 1, the outlet passages are closed, and no material can flow out of the hopper 11.
If it is desired to open the outlet passages, the actuator 28 is operated to move the plates 20 and 21 to the right as viewed in Figure 1. This means that the left hand side of each outlet passage opens progressively, so that material can pass along each zig-zag outlet passage, for example into a waiting container.
Because of the action of the spring 29, each plate 20 and 21 maintains contact with the associated portion 30 of the casting, so that the outlet passage remains closed at this side. This has the advantage that material cannot get between the plates and the casting, thus adversely affecting the smooth pattern of flow along the zig-zag path, and also avoiding the possibility of a build-up of material between the plates and the parts 30 of the casting, thus possibly preventing the plates from returning to the position shown in Figure 1.
Because the casting is hollowed out upwardly at 31, the action of the springs causes the leading edge of each plate to rise as the plate moves to the right as shown in Figure 1. This means that as each plate moves to the right, the angle of inclination of the plate to the horizontal increases. In the fully open position of the device, the plates take up the dotted line positions shown in Figure 1.
Turning now to Figure 3, there is shown an alternative embodiment of device according to the invention.
The device is generally very similar to that shown in Figures 1 and.2, although the frame made up of members 12 and 13 is mounted on suspension springs and is sealed to the hopper 11 by means of a flexible cushion 26a.
A vibrator 24 is again provided, and there are three spring loaded plate-like control members 20, mounted on a common slide, although the slide has not been shown in Figure 3 for the sake of simplicity.
In this embodiment, the casting has been replaced by three first support devices 32a, 32b and 32c, and three second support devices 33a, 33b, and 33c. It will be seen that devices 32b and 33a are combined to form an integral unit, as are devices 32c and 33b. The devices provide a generally similar structure to the casting 16 of Figures 1 and 2, but if the devices are analysed in more detail it will be seen that for each aperture, there is at each side of the aperture a first downwardly sloping support surface 34 and a second, more steeply inclined, downwardly sloping support surface 35. The lowermost edge 36 os each second support surface is positioned below the level of the lowermost edge 37 of each first support surface 34. Each first support surface 34 has a lip at its lowermost edge 36 undercut at 38.
The way in which the pressure head of a column of powdered or granular material acts is different to that of a column of liquid. Powdered or granular material receives a certain amount of side support and the extent to which material in the column contributes to the pressure head at the bottom of the column reduces as one moves up the column. For example, in Figure 3, the two V-shaped areas of material 39 do not apply any pressure to the flow control device at all, since these areas are entirely supported by the side walls of the hopper 11 and by side pressure from the central bulk of material 40.
The pressure exerted by the bulk of material 40 is substantially taken by the support surfaces 34 and 35 and so the only material that actually applies pressure in the immediate vicinity of the outlet passages is the material in the areas designated by the reference numeral 41.
Thus the arrangement of the support surfaces reduces the pressure head in the vicinity of the outlet passages substantially, and this has two important advantages. It makes it easier for the control members 20 to operate,and completely cut off flow if necessary, since they do not have to work against a substantial pressure head.
Even more importantly, since the rate of flow through the outlet passages, for a given material and a given size of outlet opening, is dependent on the pressure head created by the material in the regions 41, the rate of flow will be substantially constant irrespective of the height of material above the flow control device. The rate of flow will only change when the device is practically empty and the surface level of the material reaches the level of the regions 41.
This ability to provide a constant rate of flow, which can easily be controlled, is extremely important for many applications, for example for use in feeding material to a weighing appliance. Furthermore, since the rate of flow is substantially constant across the device, in other words the rate of flow through each outlet aperture is identical to the rate of flow through the other outlet apertures, the device can be used when it is desired to feed equal quantities of material from one storage device into a plurality of other storage devices. For instance if each of the three apertures shown in Figure 3 were arranged to feed material to each of three separate containers positioned under the device, each container would receive an equal quantity of material. Although the three control members 20 are shown in : different positions in Figure 3 for the purposes of illustration, the control devices will of course in use all have the same position, since they are each spring loaded and all mounted on the-same support carriage.
The rate of flow through the apertures is governed by three factors. Firstly, the extent to which the passages are opened by movement of the control members; secondly, the angle of inclination of the upper faces of the control members; and thirdly, the amplitude of the vibration applied by the vibrator 24. The above described embodiments enable the first two of these factors to be controlled simultaneously, using a very simple mechanical arrangement having very few moving parts. It is thus possible to provide very accurate and fine control over the flow of material, particularly since the effective pressure head is only that applied by the material in the areas 41, and when flow is no longer required, flow can be shut off positively with ease by returning the plates to the fully closed position.
It will be noted also that the embodiment shown in Figure 3 does not have the lower portions 22 and 23, since it has been found with the embodiment shown in Figure 3 that a zig-zag path is not essential.
It has been found to be advantageous to fabricate the device from components such as those shown in Figure 3. The support devices, and the support frame if desired, may be manufactured from plastics material which is clipped into position over metal supports. The supports may for example be of stainless steel, the plastics parts.being of high density polyethylene. This provides a structure which may be one-third of the weight of an equivalent all-metal structure, and this has the advantage that a less powerful vibrator can be used.
The invention is not restricted to the details of the foregoing embodiments. For instance, any desired number of outlet passages may be provided, from one upwards. A device having the desired number of outlet passages may be built up either by fabrication, or by the use of modular castings or mouldings.

Claims

1. A device for controlling the flow of powdered or granular material out of a storage device, the flow control device comprising a body (12, 13) arranged for mounting underneath the storage device (11) and defining an outlet passage (17, 18) for the material, and a control member (20, 21) for the outlet passage, characterised in that the device has-at least one material support surface (30) adjacent to the dutlet passage (17, 18) the support surface (30) being positioned and shaped to support a substantial part of the pressure head exerted by the material, thus substantially reducing the pressure head acting on material tending to flow through the outlet passage (17, 18) and making it easier for the control member (20, 21) to control the flow of material through the outlet passage.

2. A device as claimed in Claim 1, in which there is a support surface (34, 35) at each side of the aperture.

3. A device as claimed in Claim 1 or Claim 2, in which a first support surface (34) at one side of the aperture comprises a surface sloping downwardly towards the aperture.

4. A device as claimed in Claim 3, in which a second support surface (35) comprises a surface sloping downwardly towards the aperture at a steeper angle than the first support surface (34).

5. A device as claimed in Claim 4, in which the lowermost edge (36) of the second support surface (35) is positioned below the level of the lowermost edge (37) of the first support surface (34).

6. A device as claimed in Claim 4 or Claim 5, in which the first support surface (34) has an undercut lip (38) at its lowered edge.

7. A device as claimed in any one of Claims 4 to 6, in which there are a plurality of outlet apertures, the first support surface (34) adjacent one aperture combining with the second support surface (35) adjacent the adjacent aperture to present to the material in the storage device an upwardly facing ridge-like surface.

8. A device as claimed in Claim 7, in which, between each pair of adjacent apertures each first support surface (34) and adjacent second support surface (35) are formed as an integral unit.

9. A device for controlling the flow of powdered or granular material out of a storage device, the flow control device comprising a body (12, 13) arranged for mounting underneath the storage device (11) and defining an outlet passage (17, 18) for the material, and a control member (20, 21) for the outlet passage, characterised in that the control member (20, 21) has a surface which faces upwardly at an inclined angle to the horizontal when the control device is mounted underneath the storage device (11), and the control member (20, 21) is movable across the outlet passage (17, 18) transversely to the direction of flow, to control the flow.

10. A device as claimed in Claim 9, in which the control member (20, 21) is such that during the said transverse movement the angle of the said surface to the horizontal varies.

11. A device as claimed in Claim 10, in which the control member (20, 21) is movable, from a position in which it closes the outlet passage (17, 18), to progressively open the outlet passage (17, 18), such movement causing the angle of the said surface to the horizontal to progressively increase.

12. A device as claimed in any one of Claims 9 to 11, in which the control member (20, 21) is mounted on a slide (27) for movement across the outlet passage.

13. A device as claimed in Claim 12, in which the control member (20, 21) comprises a flat plate pivotally mounted on the slide (27).

14. A device as claimed in any one of Claims 10 to 13, in which the control member (20, 21) is such that the change in angle of inclination of the control member (20, 21) as the control member (20, 21) moves enables the said surface to maintain contact with a closed side of the outlet passage (17, 18) so that flow takes place only past that side of the control member (20, 21) which is remote from the closed side of the outlet passage.

15. A device as claimed in Claim 14, in which the said closed side is shaped to accommodate more of the control member in the upward direction as the control member moves towards the closed side, so that the change in angle of the said surface is brought about by spring means moving the leading edge of the control member progressively upwardly as the control member moves towards the closed side.

16. A device as claimed in any one of Claims 10 to 15, in which there are a plurality of outlet passages (17, 18) each having its associated control member (20, 21), the closure members (20, 21) being mounted on a common slide for movement in synchronism.