Backqround to the Invention Cotton buds are typically harvested from their plants by a mechanical harvesting unit having one or more (typically two) rotary picker drums, each comprising a spaced array of spindles. As the harvesting unit is driven along rows of cotton plants the spindles catch the cotton buds removing them from their plants.

The cotton buds are removed from the spindles as the rotary picker drum rotates and fall into a conveyor system that transports the cotton buds to a bin. The bin is usually a separate unit and is emptied when full while the harvesting unit is stopped. The conveyor system is almost always based upon the flow of air through a number of ducts.

Typically, there is one ducted conveyor (or chute) per rotary picker drum.

It is desirable to be able to monitor the amount of cotton being harvested in a continuous manner. Prior art monitoring techniques have been directed to the detection of blockages in the ducts but the inventor is not aware of any prior art systems that allow the continuous monitoring of the volume flow of cotton.

One monitoring technique for detecting duct blockages is described in United States Patent No 4961304 assigned to

J.I. Case Company. Duct blockage can occur when the cotton buds aggregate and snag on imperfections within the duct.

Cotton buds have a tendency to aggregate due to the nature of the fibres and the oil content. J.I. Case teaches the use of acoustic sensors to detect the sound of cotton seeds impacting the walls of the ducts. When the noise drops below a given level it is assumed that the cotton flow has stopped.

A further monitoring system is described in United States Patent No 4068223 assigned to Dickey-John Corporation. The Dickey-John device monitors the flow of air in each duct and provides an indication to the harvester operator if the air flow drops below a predetermined level.

While these prior art monitors can indicate the existence of a blockage, they cannot provide continuous volume monitoring of harvest yield.

Summary of the Invention The present invention was conceived with the aim of providing continuous volume monitoring for harvested cotton, embodiments can be applied to any type or form of particulate or clumpy material.

It is an object of the present invention to provide a volume monitoring apparatus for a flow of particulate or clumpy material.

According to the present invention there is provided an apparatus for monitoring the volume of a flow of particulate or clumpy material, the apparatus including: transmitter means for transmitting a signal across a flow path of a particulate or clumpy material; receiver means opposite the transmitter means for receiving the signal after transmission across said

path and providing a data signal related to the volume of material flowing through the path; and, controller means adapted to analyse the data signal to produce an output indicative of the volume of material flowing through the path.

The controller means is suitably a programmable logic controller or other processor that controls the operation of the transmitter means and receiver means. There is preferably a clock means that provides timing for the pulsing of the transmitter means and synchronous sampling of the receiver means. The clock may be integral to the controller or external.

Preferably the transmitter means is in the form of a linear array of separate transmitting units and the receiver means is in the form of a linear array of separate receiving units equal in number to the transmitting units and wherein individual units of one array align with individual units of the other array across the path.

Preferably the respective arrays are dimensioned and juxtaposed so that all material flowing through the flow path must pass between the arrays.

Preferably the transmitter means is pulsed at a frequency in the range of 200 Hz to 2000 Hz.

More preferably the transmitter means is pulsed at a frequency of approximately 1700 Hz.

Preferably the receiver means is sampled synchronously with the pulsing of the transmitter means.

Preferably the data signal is a number S in the form of a digital word number being indicative of the number of receiving units whose input of a signal from a

corresponding transmitting unit is blocked or otherwise attenuated by the material at the time of sampling of the receiver means.

Preferably the controller calculates the instantaneous volume of material flowing through the flow path by application of the algorithm F=KS where F is the calculated instantaneous volume, S is the data signal and K is a calibration constant.

Preferably the controller is further adapted to provide an accumulated volume of material by generating a running sum of F.

Brief Description of the Drawinqs To assist in understanding the invention preferred embodiments will now be described with reference to the following figures in which: Figure 1 is a representation of a cotton harvester; Figure 2 illustrates a longitudinal section of a chute of the cotton harvester a chute including a cotton volume monitoring apparatus; Figure 3 is a cross-section of Figure 2 showing the positions of a transmitter array and a receiver array of the volume monitoring apparatus; Figure 4 is a block circuit diagram of the volume monitoring apparatus; Figure 5 is a schematic circuit diagram of the transmitter array;

Figure 6 is a schematic circuit diagram of the receiver array; Figure 7 is a schematic circuit diagram of a controller incorporated in the volume monitoring apparatus; Figure 8 is a schematic representation from the side of part of the volume monitoring apparatus applied to a grain elevator; and, Figure 9 is a partial front view of the grain elevator shown in Figure 8.

Detailed Description of the Preferred Embodiments In the drawings, like reference numerals refer to like parts. The preferred embodiment is described in relation to its use with a flow of cotton through a cotton harvester 10. However it is to be understood that embodiments of the invention may be applied to a flow of other particulate of clumpy material. Additionally the term "flow" is used throughout this specification, including the claims in a very broad sense to include material which is caused to flow by being entrained in a moving fluid such as air or water or material which is moved by mechanical agents such as by a conveyor, auger, paddle wheel etc.

Referring to Figure 1, there is shown a sketch of a front end of a cotton harvester 10. The cotton harvester 10 includes a cabin 12 for an operator and ground engaging wheels 14.

A cotton harvesting unit 16 is mounted towards the front of the harvester 10. Although the sketch shows only a single cotton harvesting unit it will be appreciated that a cotton harvester will have a plurality of such units disposed

across the front of the harvester. Within the cotton harvesting unit 16 is mounted one or more rotary picker drums (not shown) and collection assemblies (not shown) that collect the cotton from the tines of the drums. A chute 18 conveys the picked cotton from the cotton harvesting unit 16 to a bin 20.

The chute 18 is shown in a greater detail in Figure 2. An air jet 22 is located at a lower part of the chute 18 and directs a stream of air into the chute to convey clumps of cotton 24 along the chute and into the bin 20. The chute 18 defines a flow path for the cotton clumps 24.

Referring to Figure 4 it is seen that an apparatus 26 for monitoring the volume of cotton 24 flowing through chute 18 includes transmitter means in the form of an infrared transmitter array 28 located on the chute so as to transmit infrared radiation across the path of the cotton, and receiver means in the form of infrared receiving array 30 located opposite the infrared transmitting array for producing a data signal related to the volume of cotton 24 flowing through the chute 18. (Infrared radiation is preferred to minimise the effect of ambient light however operation of the apparatus 26 is not otherwise dependent on the nature of the radiation. Visible radiation could be suitable with appropriate lock-in detection techniques.) Controller means 32 analyses the data signal to produce an output indicative of the volume of material (ie cotton 24) flowing through the path.

The positioning of the transmitter array 28 and receiver array 30 is shown most clearly in Figure 3. The arrays are located towards the top of the chute 18 to minimise the amount of ambient light present. As shown in figure 2 it is advantageous to position the receiver array 30 on the inside of the curve of the top of the chute 18 so that no ambient light can directly impinge on the receiver array

30.

The transmitter array 28 consists of eight light emitting diodes (LED's) 34 transmitting a plane of light across the chute. The receiver array 30 consists of eight corresponding photodiodes 36 monitor light that crosses the chute. The degree of attenuation of light is proportional (and thus related) to the quantity of cotton 24 in the path at the instant of sampling the receiver array 30. The signals from the photodiodes 36 are analysed in controller 32 to determine an instantaneous measured volume of cotton.

By making a series of measurements over time the volume flow rates and accumulated volume is determined.

Figure 4 shows a block diagram of a system incorporating two apparatuses 26 and 26' fitted to two chutes on a cotton harvester. The first apparatus 26 for chute one comprises the transmitter array 28 and receiving array 30. The transmitting array 28 is pulsed according to signals 38 sent by the controller 32. The receiver array 30 is read synchronously with the transmitter array 28. Cotton 24 blocks a proportion of the radiation emitted by the transmitter array 28.

Signals from the receiver array 30 are passed to the controller 32 on data bus 40 for calculation of the volume and/or flow rate. The pulsing of the transmitter array and the receiver array provides a time base for the calculation of flow rate as well as reducing the overall power consumption of the sensor. A suitable pulse frequency is in the range 200 Hz to 2000 Hz. At a pulse frequency of 1700 Hz the cotton will travel approximately 1 cm in chute 18 between readings in a typical harvester. The sampling frequency is chosen having regard to ground speed of the harvester and the flow speed of cotton 24 through chute 18.

At 200 HZ sampling would occur approximately every 5 cm of ground traversed by the harvester but the cotton 24 would

traverse about 8 cm along chute 18. With a sampling frequency of 1700 HZ the cotton will traverse about 1 cm in chute 18 and the harvester, travel about 1/2 cm across the ground.

The second apparatus 26' for chute two comprises identical components to the apparatus 26, namely a transmitter array 28', receiver array 30' and controller 32'. Each apparatus 26 and 26' is self contained and modular allowing as many apparatuses 26 as there are chutes. The controllers 32, 32 are in signal connection with a common data logger 42 via bus 44. Although any manner of data logger 42 could be used a suitable data logger is the "Data Tracker" made by Micro Trac. The output from each controller 32, 32' is modulated at a unique frequency recognised by the data logger 42.

A suitable circuit for the transmitter array 28, 28' is shown in Figure 5. All eight LED's 34 are operated at once when voltage is supplied on line 46.

Figure 6 shows a suitable circuit for the receiver array 30, 30'. A bank of phototransistors 36 act as receivers for each of the LED's 34 and are read simultaneously through individual comparators 48. The output from each comparator 48 is a signal indicative of whether the transmitted light is blocked by cotton 24. The signals from the comparators are collated in a multiplexer 50. In the preferred embodiment the eight signals from the comparators are converted to a digital data signal X comprising two two bit words. The two bit words are on lines 52 and 54 and the words are selected by lines 56 and 58. Connection between a transmitter array and a receiver array is via connector A.

A suitable controller 32 is an HC11 reprogrammable logic controller (refer Figure 7), although this can be replaced

by a "burn once" PROM or other suitable controller. The HC11 provides signals on line 60 to pulse the transmitter and receiver arrays. The voltage is controlled by a conventional voltage regulator 62. Timing is provided by a conventional crystal oscillator 64. Interface with the data logger 42 is provided on bus 44 through connector 66.

Connector 68 provides communication to the receiver and transmitter circuits.

In the embodiment described an RS232C port 70 allows reprogramming of the controller 32.

It will be appreciated that the apparatus 26 (or apparatuses when there is more than one operating in series as in the example of Figure 4) must be calibrated for accurate operation. This is achieved in situ using a weighed basket of raw cotton. A calibration number for each apparatus 26, 26' is loaded into the data logger. The apparatuses 26, 26' are nulled for no flow. The inventor has found that calibration errors are insignificant when measuring large cotton volume flows. The instantaneous volume is then calculated by an algorithm of the form F=KS where F is the calculated flow, S is the signal from the receiver array and K is the calibration constant. A flow rate is calculated by monitoring over flow time and an accumulated volume is calculated by simple integration, ie calculating a running sum of instantaneous volumes.

Figures 8 and 9 illustrate the apparatus 26 as applied to a grain elevator 72. The grain elevator comprises an elongated endless chain driven conveyor 74 provided with a plurality of evenly spaced planar paddles 76. The paddles 76 extend perpendicularly to the conveyor 74 to defined catchment areas 78 between the paddles and the conveyor 76 each of which can support a given volume of grain 80. The grain elevator 72 is typically part of a grain harvester and receives clean grain at a bottom end from a cross auger

at the bottom of the harvester and dumps the grain at the top end of the elevator 72 into a grain tank. The transmitter array 28 and receiver array 30 are disposed opposite each other on either side of the upward run of the elevator 72. The arrays 28 and 30 are inclined relative to the plane of the conveyor 74. In this way, the arrays 28 and 30 can form a profile of the heap or pile of grain 80 in each catchment 78. The profile is effectively obtained by reason of having a plurality of individual LED's 34 and photodiodes 36 in the transmitter array 28 and receiver array 30 and by virtue of the inclination of the arrays 28 and 30 relative to the conveyor. At each sampling instance, the arrays 28, 30 look at eight different places in the pile 80. This resolution can of course be increased by increasing the number of separate LED's 34 and photodiodes 36. This level of resolution is particularly beneficial as different types of grains form different shaped heaps in the catchment areas 80 due to the different flowability. It also allows accurate profiles to be taken when the grain harvester is travelling on a hill which would effect the way in which the piles of grain 80 sit in the catchment areas 78. In this instance, zeroing or nulling of the apparatus 26 is achieved by running the elevator 72 without any grain 80. Accordingly, the influence of the paddle 76 as they move between the receiver and transmitter arrays 28 and 30 is negated.

Now that embodiments of the present invention has been described in detail it will be apparent to those skilled in the relevant arts that numerous modifications and variations may be made without departing from the basic inventive concepts. For example, and most notably, embodiments of this apparatus can be applied to any flowing particulate or clumpy material. Other applications include in mineral processing where quantities of minerals are conveyed or transferred along the confined paths by conveyors or say by gravity through chutes. Further, as

previously indicated, the transmitter array 28 can transmit a type of electromagnetic signal essentially dependent only upon the specific application and ability to provide receivers which are capable of receiving that type of radiation. Also the transmitter and receiver arrays can of course have more or less than the eight separate "units" 34 and 36 respectively.

All such modifications and variations together with others which would be obvious to a person of ordinary skill in the art are deemed to be within the scope of the present invention the nature of which is to be determined from the above description and the following claims.