GB2242271A - Monitoring particle flow - Google Patents

Abstract

Particle flow monitoring apparatus for use, for example, in an agricultural seed drill to warn of impairment or cessation of particle flow in any one of a plurality of pipes defining flowpaths for the particles, includes a transducer 18 for detecting the noise produced by the particles as they move relative to one another and to surfaces e.g. of a rigid tube 14 contacted by the particles, along each flowpath. Means responsive to an output signal generated by the transducer indicate when the flow of particles is adversely affected. The indication may be by means of variable intensity LED displays and an alarm circuit is also disclosed. <IMAGE>

Description

FWW MONITORING APPARATUS This invention relates to particle flow monitoring apparatus.

It is applicable generally to monitoring the operation of a device in which particles are caused to flow along a flowpath, for example, through a pipe, and more particularly though not exclusively to the monitoring of a device such as an agricultural air seed drill having a rank of pipes through which seeds are delivered into furrows in the ground.

One problem encountered in the use of such drills is to ensure that all pipes in the rank are operating effectively. A single blocked pipe in a four metre drill represents a 3% loss in seeded crop area; a loss higher than the 2~% (20 metre) tramline loss. Early detection of a blockage is therefore important. Further, should a blockage occur, as it often does in practice because of soil in a drilling end of the pipe, low air pressure or a foreign body in the seed metering system, an operator must dismount from the tractor to clear the blockage before proceeding.

A previous attempt to solve this problem involves the use of a capacitive detector positioned so as to detect seeds passing through the pipe. This is not entirely satisfactory, however, at least in so far that such a detector is incapable of distinguishing between a flow of seeds and seeds blocking the pipe.

One object of the present invention is to enable monitoring the flow of seeds through a drill pipe in a relatively cheap, simple and convenient manner.

According to the present invention, we propose a method and apparatus for monitoring the flow of particles or a fluid along a flowpath, wherein a transducer is disposed to detect movement of the particles, more particularly by detecting vibration preferably acoustic vibration (i.e. noise) caused by said flow, and generates in response thereto an output signal to drive flow indicator means. It is preferred to arrange or mount the transducer to detect the percussive effect produced by particles in collision with one another and/or impinging upon a surface which may be the surface of a baffle or other partial obstruction placed in the path of the particles but is preferably a flowpath boundary surface.In the case of a device wherein particles are entrained in a turbulent air stream, impingement of the particles with the pipe wall may generate sufficient noise, depending upon the sensitivity of the transducer used, the nature of the pipe wall and the type of seed.

The invention also includes a device, more particularly a seed drill comprising monitoring apparatus according to the invention.

For monitoring flow through a plurality of pipes as in an agricultural seed drill, a separate transducer and associated indicator means are provided for each pipe or group of pipes.

The indicator means in such multi-channel apparatus may conveniently comprise indicators arranged in an array corresponding to the arrangement of the pipes themselves so as to assist the operator in identifying which pipes are blocked or otherwise ineffective.

The number of channels will vary according to the type and size of device to be monitored. Typically 32 channels are required for a 4 metre corn drill and 50 channels for a 6 metre drill.

Many corn drills have pipes made of soft flexible material tending to damp the noise or vibration caused by seeds flowing therethrough making detection difficult even when the flow is turbulent. To enhance the percussive effect and hence increase the noise generated the flowpath boundary surface may include a resonant or sounding surface portion associated with the transducer and upon which the particles impinge as they travel along the flowpath. The resonant or sounding surface portion may comprise a taut diaphragm or rigid plate-like member set in the wall of the pipe or may be the active or sensitive surface of the transducer.In the preferred embodiment, however, each channel has a sensor comprising a rigid tube of say plastics material, for insertion between two drill pipe portions or in the end of a drill pipe so as to form a continuation of or an extension of the flow path therethrough, the transducer being mounted on or adjacent the wall of the tube. Seeds impinging upon the wall of the rigid tube give rise to sufficient noise and/or vibration to be detected by even the most simple transducer. We have found the use of a crystal microphone entirely satisfactory.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings in which: Figure 1 shows schematically the display panel of multichannel seed drill monitoring apparatus according to the present invention; Figure 2 is a diagram of a single monitoring channel circuit in the apparatus shown in Figure 1; Figure 3 is a longitudinal cross-section through a flow monitoring sensor; Figure 4 schematically illustrates a flow monitoring sensor such as shown in Figure 3 inserted to communicate between two portions of a seed drill pipe; and Figure 5 is a diagram of a modified channel circuit of a seed drill monitor which includes a universal alarm to warn of a blockage occurring in any of the pipes of a seed drill.

The display panel 2 of Figure 1 is intended to be located in the cab of a tractor within sight of the driver and preferably on the dashboard. It incorporates indicators 4 which, in the preferred embodiment, are light emitting diodes (LED), arranged in two staggered rows 6,8 so as to correspond to an array of seed pipes in a seed drill towed behind the tractor.

In fact the rows of LED's are contained within an outline 10 (in plan view) of the seed drill to give a clearer indication of the position of each pipe and the circulation of the drill.

A flow monitoring sensor including an acoustic transducer such as a crystal microphone is provided in association with each seed pipe, the individual sensors together with corresponding indicators being connected in separate circuits or channels to provide an indication of the flow conditions in each piper and further in such a way that should a blockage occur or flow be otherwise impaired causing this to be indicated on the display, the relevant pipe or pipes can readily be identified with reference to the position of the corresponding indicator in the display panel. A multi-core cable extending between the tractor and the trailer connects the individual sensors and associated to separate circuit boards in the display panel.

In a typical monitoring channel circuit such as shown in Figure 2, the monitoring sensor 12 output signal is applied to an operational amplifier OAl connected via transistor T1 to drive transistor T2 connected in series with the associated indicator including a light emitting diode LED visible on the display unit 10. An output signal from the sensor is amplified by the operational amplifier OAl and applied to switch on the transistor T2 to activate the LED whenever at a signal level above a predetermined threshold level adjustable by means of variable resistor.

The sensor 12 shown in Figure 3 is in the form of a rigid tube 14 of plastic, glass or metal or other suitable material, to which is attached a boss 16 carrying a crystal microphone 18 disposed parallel with the tube wall 20. The sensor is fitted between two lengths of rubber pipe which together from a seeddrill pipe and is located typically 15cm from the outlet of a seed metering hopper 30. As will be understood from Figure 4 when seed falling from the seed drill hopper 30 is entrained in the flow of air emerging from a source of air under pressure (not shown) through a venturi 32, seeds indicated by arrows 34 flow along the pipe and at some stage impact on the internal wall of the rigid tube 14. Noise generated is detected by the crystal microphone in the sensor 12 producing an output signal which (see Figure 2) is amplified and applied to activate the light emitting diode LED.The light intensity of the diode is proportional to the noise generated and hence to the quantity of seed flowing through the pipe. Thus the dimming or even extinguishing of one or more lights in the display 10 indicates to the operator that corresponding pipes are no longer effective.

It may be desirable to provide an audible alarm to alert the tractor driver when a blockage or other fault occurs. This would avoid the need for constant observation of the display unit. Furthermore, it has been found useful to provide separate alarms, usually visual indicators for sub-groups of pipes in an array so that activation of one such alarm would warn that a blockage has occurred, for example, in-a pipe on one or other side of the seed drill; to the left or right of the tractor.

Figure 5 shows a circuit arrangement suitable for this purpose.

The upper part of the figure represents one of the circuits in a group A corresponding to the group of seed drill pipes to say the left hand side of the tractor and the lower part to one of the circuits or channels in group B corresponding to the group if pipes to the right. All of the circuits or channels in group A are connected at A' as illustrated to an alarm circuit and similarly group B channels are connected thereto at B', Each of the monitoring channel circuits shown in Figure 5 incorporates a second operational amplifier OA2 which controls a universal audible alarm circuit, the audible alarm being provided by a piezzo-electric buzzer PB connected in parallel with additional visual alarm indicators in the form of LED's corresponding to the two pipe groups A and B.

A signal received from the microphone 18 when a seed is detected in the flow monitoring sensor 12 (see Figure 3) is amplified and inverted by the first operational amplifier OA1 as in the circuit of Figure 2, to switch a transistor T1 and via the transistor T2, activate the channel indicator LED.

The voltage drop across the LED is amplified and inverted by the second operational amplifier OA2, to produce an output signal which switches on a transistor Th so that capacitor C1 begins to charge. A reserve of current during normal operation is provided by capacitor to hold off the alarm via another transistor T4 In the absence of an output signal from the microphone, for example, when a blockage occurs in one of the pipes, the second operational amplifier OA2 provides no output and capacitor C1 begins to discharge.After a certain delay of say five seconds, determined by the time constant (C1R) and which may be adjustable, the voltage drops to a level at which transistor T4 switches off and transistor T5 switches on, so that the universal group alarm is no longer held off and the piezzoelectric buzzer sounds and the appropriate group indicator LED A or LED B lights. The universal audible alarm and the group alarm indicators are located in the display unit in the vehicle cab.

Also contained in the display unit is a light dimming circuit (not illustrated) which automatically adjust the brilliance of the channel indicator LED's as appropriate to the amount of ambient light. During bright daylight the brilliance of the display is at a maximum to make it clearly visible but at night the LED output is reduced to avoid glare.

At normal drilling rates for cereals, (approx 150/200 seeds a second) the individual lED's are highly active, giving the impression of being permanently lit. If a problem occurs producing a partial blockage, and therefore reduced seed flow, the affected LED's will become less active, and be noticeable although the alarm may not sound.

When drilling low rates of small seeds, i.e. oilseed rape, turnips, grass etc. the LED's are less active, and appear to flicker, but the same principle as for corn applies. An occasional check of the display for partial blockages is all that may be needed. The universal alarm will warn of a total blockage of either one pipe or the whole drill.

The seed drill monitoring apparatus described above alerts the operator to all drive train faults, i.e. low hopper seed level, air intake restrictions, low engine RPM, metering system interruptions and bridging in the hopper, all of which result in impairment or cessation of the seed flow. It eliminates the need for continual manual checking of the drill, and redrilling of missed areas due to blockages and breakdowns, therefore time is saved. The drill can be used to its maximum output by monitoring the seed/air flow pattern.

The multiple channel monitoring apparatus described above is also applicable to the monitoring of devices other than seed drills. If, for example, be used to monitor the operation of a multi-spray head for spraying insecticides or the like or indeed to any other application in which fluid is distributed to flow along multiple flowpaths. Laminar flow of fluid may be difficult to detect in view of the low noise generated but it will be understood that the transducers can be located in a position at which the fluid flow becomes turbulent, for example, at exit from or entry to the nozzle. Alternatively, an obstruction to flow amy be introduced to deliberately create turbulence.

Claims (10)

CLAIMS:

1. Apparatus for monitoring the operation of a device in which particles are caused to flow along a flowpath, the apparatus comprising a transducer disposed in relation to the flowpath to detect the noise produced by particles in motion along the flowpath, and means responsive to an output signal from the transducer to indicate impairment or cessation of the flow.

2 Apparatus according to claim I for monitoring the flow of particles along a plurality of flowpaths and comprising separate transducer and indicating means associated with each flowpath.

3. In combination with a seecl drill comprising a plurality of pipes into which seed is distributed and (optionally) entrained in a stream of air, to flow through the pipes for delivery into the ground, apparatus for monitoring the flow of seeds along each of the flowpaths defined by the pipes, the monitoring apparatus comprising for each pipe or group of pipes a transducer for detecting noise generated by the particles in motion along the flowpath, and means responsive to an output signal generated by the detector to indicate impairment or cessation of the flow.

4. Flow monitoring apparatus for monitoring the operation a device having a plurality of flowpaths, the apparatus having multiple monitoring channels each including a transducer disposed or for disposition in relation to one of the plurality flowpaths or a part thereof to detect the noise produced by flow along. the flowpath, and means responsive to an output signal from the transducer to indicate impairment or cessation of the flow.

5. Apparatus according to any one of claims 1 to 3 wherein the transducer is disposed adjacent a flowpath boundary surface to detect impingement of particles thereon.

6. Apparatus according to any one of claims 1 to 3 wherein an active surface of the transducer defines a flowpath boundary surface.

7. Apparatus according to any one of claims 1 to 3 wherein the transducer is mounted on or adjacent a rigid wall providing a boundary surface of the flowpath contacted by particles in motion.

8. Apparatus according to any preceding claim and having a sensor comprising a tubular member of rigid material communicating with the said flowpath, the transducer being mounted to detect impingement of particles flowing through the tubular member on the internal surface thereof.

9. Apparatus according to any preceding claim, wherein the indicator means comprises visual indicators disposed in an array to correspond with the physical arrangement of pipes defining the said plurality of flowpaths.

10.Monitoring apparatus constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.