GB2121014A - Discharging apparatus for e.g. a silo - Google Patents

Abstract

A grain silo discharging apparatus comprises a shell 1 disposed in the silo throat and movable between a position in which the throat is closed and a position in which a gap is defined between the walls of the throat and the lower edge of the shell 1 through which grain may fall under gravity. The width of the gap is determined by regulating the supply of air to an air cushion 4 supporting the shell 1 and which in turn sets the height of the shell 1. The air supply to the cushion is controlled by a cam operated valve 26 or a whisker valve to maintain the shell at a predetermined height as grain flows out. Grain outflow is monitored and, if it ceases, air is supplied to the cushion 4 to raise the shell 1 to its full height to impart a bridge breaking action to the grain. Vibrators 8 may be mounted on the shell. <IMAGE>

Description

SPECIFICATION Discharging apparatus The present invention relates to apparatus for discharging the contents of a container. The type of containerto which the invention is particularly, but not exclusively, applicable is a bulk storage bin such as, for example, a grain silo.

In such silos a throat informed leading to an outlet through which the grain is directed. As the grain is confined by the throat on its passage to the outlet there is a tendency for a jam to occur as a result of which the flow is halted. In effect the grain forms a bridgespanningtheoutletpastwhich no grain can flow. Such an occurrence is extremely inconvenient, can result in additional and expensive processing time and may require a person to constantly monitor the silo outflow in order to reduce the risk of that happening.

According to the present invention, there is provided apparatus for discharging the contents of a container comprising a body, a support for supporting the body atthe outlet of a container to be discharged, meansfor moving the body relative to the support between a first position in which the body is operative to closethe outletfromthecontainerand a second position in which the outlet is opened and control meansforcontrolling the means for moving.

A preferred embodiment of the invention may comprise any one or more ofthe following advantageous features: (a) The means for moving the body are pressure fluid operable, (b) The pressure fluid operable means for moving the body comprises an air cushion (spring), (c) The control means are pressure fluid operable, (d) The pressure fluid operable means and control means are pneumatic, (e) The control means comprises means enabling the body to be moved relative to the support to a third position on that side of the second position remote from the outlet to enable the body, in operation, to perform a bridge breaking function, (f) Thecontrol meanscomprisesadetectorfor detecting outflow of contents from a container said detector being associated with the means for enabling the body to be moved to a third position and operative to trigger such a move should a cessation in outflow be detected, (g) The control means comprises an actuator for actuating the detector, (h) The detector is an electrical capacitive detector and the actuator is an air/electrical actuator operative to supply electrical power to the detectorwhen air is supplied to the pneumatic control means.

(i) The control means enabling the bodyto be moved to a third position comprises a pressure fluid operabte valve, (j) Means are provided enabling the pressure fluid operable valve to be manually operated.

(k) Means for vibrating the body are provided operative to vibrate the body when the body is in the second or third positions.

(I) The control means comprises means for limit- ing movement ofthe bodyfrom the second position due to a reduction oftheforce acting on the body experienced as the contents flow from the container.

In orderthatthe invention may be more clearly understood, one embodimentthereof will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a side elevational view in section of apparatus for discharging a grain silo, Figure 2 shows a pneumatic circuit forming part of the apparatus of Figure 1, and Figure 3 is a modification ofthe apparatus of Figure 1.

Referring to the drawings, the apparatus comprises a discharge body in the form of a shell 1 of inverted V-shaped cross-section. The shape of this shell 1, which is made of sheet steel or synthetic plastics material, may be chosen as desired. Ifthe grain silo in which the apparatus is to be used is of rectangular or square horizontal cross-section,then the shell 1 will also be correspondingly rectangular our square in horizontal cross-section and therefore exhibit a pyramid shape externally. Similarly, if the grain silo is substantially cylindrical, the shell 1 will be correspondingly circular in horizontal cross-section and therefore exhibit a conical external shape.

The described example of the invention which follows isforacylindrical silo and the shell 1 is externally conical. The shell 1 is supported through a bracket 2 on resilient mountings 3 which are all housed within the shell 1. These mountings 3 are in turn mounted on the pneumatic air spring or cushion 4 which is made of natural or synthetic rubber. The cushion 4 is supported on a beam which, in use of the apparatus, is bolted to the sides ofthethroat 5 of the apparatus just above the outlet 6 that it spans this outlet. A pneumatic supply duct to the cushion 4 is shownat7.Two pneumaticallyoperablevibrators8 are attached to the underface of the shell. Pneumatic supply ducts to these vibrators are shown at 9.In the position shown in double full-line in Figure 1, the shell 1 makes sealing contact at 10 with the sides of the throat in order to seal off passage to the outlet 6 to preventflow of grain therethrough. To allowflowto the outlet 6, the shell 1 is vertically raised a distance h sothatan annulargap,through which grain may flow, is produced between the lower circular edge ofthe shell 1 and the adjacent surface ofthe throat 5. The raised position of shell 1 is shown in single line in Figure 1. In orderto raisetheshell 1 air is supplied to the pneumatic air spring 4via the duct 7 and the height to which the shell is raised and therefore the width of the annular gap is controlled by controlling the position of the cam.

To promoteflowthroughtheannulargapthe vibrators 8 are operated to impart a vibratory motion to the shell 1 and therefore to the grain in contact with the shell 1. As the grainflows out ofthe silo, theweight of grain pressing down on the shell 1 progressively reduces. If no compensatory action were taken, the shell 1 would gradually rise progressively opening the annular gap between the shell and the sides of the throat causing the outflow of grain to increase still further. To avoid this, upward movement ofthe shell 1 is limited. Should a bridge form in the grain spanning the outlet from the container outflow ceases. To restore the outflow, the shell 1 is pushed up into the grain from its normal open position to break the bridge (in this particular example the shell 1 is pushed up 150mm).This bridge breaking function may be manually or automatically actuated aswill bede- scribed in more detail later.

Movement of the shell 1 in the manner described above is controlled by the pneumatic control circuit.

This circuit is illustrated in Figure 2. In this figure electric lines are shown dotted and pneumatic lines are shown in full-line. Referring to Figure 2 the circuit comprises a plurality of pneumaticvalves 21 to26 controlling the supply of airfrom an air supply 27. On leaving the supply, the air passes through a filter 28to remove moisture, an oil bath 29 to lubricate it and, in turn, the devices through which it passes, and a pressureregulatorto regulatethe air pressure within the range 0 to 100 p.s.i. Valve 21 is effectively an on/off valveforthe circuit. This valve 21 is a three port valve, is operated by a manually operable lever 21 a and is shown in the off position.In the on position (as shown in the upper part ofthe diagrammatic representation) thevalve permits airtoflowto valve 22 and valve 37.

Valve 37 is a lever operated 3 port valve which in the on position allows airto pass through regulator38 and associated gauge 39to the vibrators 8. Valve 22 is a five port spring return valve shown in its normal operating condition in which it permits airto flow from valve 21 to valve 23. In its other position, this valve 22 permits airto flow from valve 21 to bypass valve 23 for a purpose to be described later. Valve 23 is a five port manually operable lever operated valve (lever is referenced 23a). This valve 23, in the position shown, permits airto be fed at mains pressure via two shuttle valves 30 and 31 to the air spring or cushion 4.In this other position (which is the position for normal operation) valve 23 permits airto befed to an automatic section of the pneumatic control circuitry indicated generally by the reference numeral 32 via a pressure regulator 33 and associated pressure meter 34. Airfrom valve 23 passes to valves 24 and 25. Valve 25 is athree port pilot actuated valve and is shown in the position in which it permits airto flow via a shuttle valve 31 to air spring or cushion 4.Valve 24 is a three portspring return valve which is shown in the spring position in which air is passed to the pilot 25a of valve 25to shut offthatvalve and to allow airto exhaustto atmosphere from the air spring or cushion via shuttle valve 31.An air relaytimer35 delays operation of valve 24to its operating position shown and therefore prevents supply of airvia valve 25to cushion 4for a set time period. Avalve 26 is a cam operated three port roller valve (cam referenced 26a) which is shown in its non-operative position. When the cam 26a is actuated air is supplied to the pilot 25a of valve 25 via a shuttle valve 36to exhaust airfrom cushion 4. When air is suppliedto air cushion 4 it is also supplied to an air to electrical switch valve 40.This valve 40, when switches nc, supplies currentto a capacitive grain level probe 41 which detects outflow of grain from the silo as previously mentioned. The signal from this probe 41 is in turn used to control valve 22.

The different operating modes ofthe apparatus are as follows. When the silo outlet is closed bythe shell 1 valve 21 is in the off position and no air is supplied to the pneumatic circuitry. To open the silo outlet valve 21 is opened and air is supplied via valve 23, regulator 33, valve 25 and shuttle valve 31 to the cushion 4. This raises the shell 1 to produce the annular opening through which grain can flow. There is a time delay governed bytimer35 before valve 24 actuates valve 25 to its operative position via shuttle valve 36 and pilot 25a. Air is also supplied to switch 40 to powerthe probe 41.The pressure ofthe air supplied to the cushion 4 and therefore the heightofthe shell 1 is determined by the regulator33 in dependance upon the grain outflow required which is in turn determined from material throughput graphs. Asthe grain flows out ofthe silo the weight of grain bearing down on the shell 1 reduces and the shell rises until it actuates cam 26a ofthe valve 26. This switches over the valve 26 from the position shown which in turn switches over valve 25 via shuttle valve 31. The shell 1 therefore drops, valve 26 resets itself causing valve 25 to switch back and resupplyairto cushion 4as a resultofwhich the cycle repeats itself. Cycle repetition is continuous until the silo is empty or until a bridge occurs or until the silo outlet 6 is closed by switching valve 21.

Alternatively, by restricting air escaping from spring 4via port25aofvalve25theshell 1 will remain atthe set heightwithoutthe annular gap increasing unless a bridge occurs.

If a grain bridge occurs in the silo, grain ceases to flow pastthe probe 41 and solenoid operated valve 22 is switched via an electronictimer in this valve to its other operating position as a result of which air at mains pressure is supplied via shuttle valves 30 and 31 directto cushion 4. This raises the shell 1 above its normal operating height and forces it into the grain mass to breakthe bridgetoallowgrainflowto resume, whereupon the probe once again detects the flow resets valve 22 and the circuit returns to its normal operating mode previously described after lapseofa presettime. Manual (as opposed to the above described automatic) bridge breaking is provided by lever operated valve 23.When this valve is operated (into the bridge breaking mode shown) air at mains pressure isfedvia shuttlevalves 30 and 31 directto the air cushion 4. In both automatic and manual bridge breaking modes, the normal automatic operation ofthe control circuitry is effectively isolated.

Normal operation is restored byreturningvalve23to its other position. Discharge from the silo can be suspended at anytime simply by operating valve 21 to exhaust all airfrom the circuit and allowthe shell to close the silo outlet.

As mentioned above, a time delay is provided by timer 35 before normal operation is restored after a bridge breaking operation. The timer prevents restoration ofairsupplyto cushion 4by holding valve 25 in the off position through valves 24 and 36forthat period after air is supplied to section 32. This delay enables shell 1 to fall past cam 26a before resumption of normal operation, so that the limiting function of this cam 26a can once more be brought into play.

Because of its construction, the above described discharger may easily be sized to suit any size of silo from 600mmto3000mm and eithersquare or round in section.Asimple bolt on design doesawaywith flexible sleeves and support rods which usually cause trouble. In addition, lower capital outlay, plus reduced operating costs make the unit very economical in terms of commissioning and running costs. The unit enables a controlled flow of the product and provides for change of flow rate as required and for remote control facilities, bridge breaking when needed, discharge on demand, a positive shut off at start and end of cycle and is mechanically stable. The unit may be sealed against material or purging pressure is of relatively low capital cost and requires relatively little maintenance.

Itwill be appreciated thatthe above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention. For example, the cam 26a, the position of which may be adjusted to alter the point at which the valve 26 is operated, is not readily accessible from outside the apparatus to enable such adjustment to be made. The point at which valve 26 is operated determines the height ofthe shell 1 and therefore the width ofthe annular gap. The valve 26, cam 26a arrangement may be replaced by an adjustment mechanism accessible from outside the apparatus. Such a mechanism is illustrated in Figure 3. It comprises a pushrod 50 fixed to the underside ofthe shell 1 and a pivot bar 51 pivotally mounted on a bracket 52.One end of the pivot bar 51 is urged against the lower end of the pushrod 50 by means of a spring 53 connected between the other end of the pivot bar 51 and an anchor point 54. Pivot bar 51 also has a counterweight55 at its end remote from the pushrod 50.

The valve 26 is replaced by a whisker valve 56 which, like valve 26, controls flow of airto the air cushion 4.

The whisker 57 of valve 56 extends across the path of movement ofthe pivot bar 51. As material flows out of the silo resulting in a rise in the shell 1, pushrod 50 rises correspondingly allowing pivot bar 51 to pivot underthe action of spring 53. The pivoting pivot bar 51 actuates the whisker 57 of the whisker valve 56 which then releases air from the air cushion 4to permit the shell 1 to fall once again. As the shell falls pushrod 50 again actuates the whisker 57 to open the whisker valveto supply air to the air cushion 4, thus raising the shell until the whisker is actuated to release air of the cushion 4 and the cycle repeats.

The position ofthe whisker valve 56 and associated whicker 57 determines the point atwhich air is supplied or released from the air cushion 4. Acontrol 60 comprising a knurled nut 61 is provided for adjusting this position between outer limits 62 and 63.

The valve 56, whisker 57, outer part of pivot bar 51 and adjustment mechanism 60 are disposed in a subsidiary housing externally of the shell 1. This housing has a hinged lid 64 which may be opened to carry out a requiredwhickervalve adjustment. Most of the mechanism is shown in full outline at one outer limit 62 ofthe adjustment and in dashed outline atthe other outer limit 63 of the adjustment. In this particular example the distance between outer limits 62 and 63 is 50mm but may be other than this.

Claims (19)

1. Apparatus for discharging the contents of a container comprising a body, a supportfor support- ing the body at the outlet of a containerto be discharged, means for moving the body relative to the support between a first position in which the body is operative to close the outlet from the container and a second position in which the outlet is opened and control means for controlling the means for moving.

2. Apparatus as claimed in Claim 1, in which the means for moving the body are pressure fluid operable.

3. Apparatus as claimed in Claim 2, in which the pressure fluid operable means for moving the body comprises an aircushion (spring).

4. Apparatus as claimed in claim 1,2 or 3, in which the control means are pressure fluid operable.

5. Apparatus as claimed in Claim 2 or 3, in which the pressure fluid operable means and control means are pneumatic.

6. Apparatus as claimed in any preceding claim, in which the control means comprises means enabl ingthe bodyto be moved relative to the supportto a third position on that side ofthe second position remote from the outlet to enable the body, in operation, to perform a bridge breaking function.

7. Apparatus as claimed in any preceding claim, in which the control means comprises a detector for detecting outflow of contents from a container said detector being associated with the meansforenabling the body to be moved to a third position and operative to trigger such a move should a cessation in outflow be detected.

8. Apparatus as claimed in claim 7, in which the control means comprises an actuator for actuating the detector.

9. Apparatus as claimed in claim 7 or8, in which the detector is an electrical capacitive detector and the actuator is an air/electrical actuator operative to supply electrical powerto the detector when air is supplied to the pneumatic control means.

10. Apparatus as claimed in claim 7,8 or 9, in which the control means enabling the body to be moved to a third position comprises a pressure fluid operable valve.

11. Apparatus as claimed in claim 10, in which means are provided enabling the pressure fluid operable valve to be manually operated.

12. Apparatus as claimed in any of claims 7 to 11 in which meansforvibrating the body are provided operative to vibrate the body when the body is in the second or third positions.

13. Apparatus as claimed in any preceding claim, in which the control means comprises means for limiting movement of the bodyfrom the second position due to a reduction of the force acting on the body experienced as the contents flowfromthe container.

14. Apparatus as claimed in claim 13, in which the means for limiting movement comprises a valve disposed in a pressure fluid supply circuitto the means for moving, and a control member for controlling the valve, the control member being operative underthe action ofthe bodyto operate the valve to supply or release pressure fluid to or from the means for moving to limit movement of the body from the second position.

15. Apparatus as claimed in claim 14, in which the valve is cam operated and the control member is connected to the body and adjustably positioned for actuating the valve cam.

16. Apparatus as claimed in claim 14, in which the valve is a whiskervalve and the control member comprises a pivotally mounted bar operative to actuate the valve whisker to operate the valve.

17. Apparatus as claimed in claim 16, in which the means are provided for adjusting the position of the whisker valve to adjust the second position of the body.

18. Apparatus as claimed in Claim 17, in which one end ofthe pivotally mounted bar is urged against the body ora member attached to the body and the other end of the bar extends externally of the body adjacentthewhiskervalve and the means for adjusting it which are also disposed externally ofthe body.

19. Apparatus for discharging the contents of a container substantially as hereinbefore described with referenceto Figures 1 and 2 orto these figures with the modification of Figure 3 of the accompanying drawings.