GB1603697A - Apparatus for and a method of monitoring the flow of material - Google Patents

Description

(54) APPARATUS FOR AND A METHOD OF MONITORING THE FLOW OF MATERIAL (71) We, DENNIS WILLIAM HOLDSWORTH, residing at 33 Old Farm Road, Dover, Massachusetts, United States of America and Ernst Adler, residing at Woodchester Drive, Chestnut Hill (Newton), Massachusetts 02167, United States of America, both citizens of the United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to apparatus for, and a method of, monitoring or controlling the flow of material.

According to the present invention there is provided apparatus for monitoring the flow of material as it is caused to be delivered from a container to a receiving station and flows by gravity through a flow path from the container to the receiving station; said apparatus comprising an inclined surface supported for movement and situated in the flow path and over which the material slides and sensing means for sensing a quantity dependent on the movement of the inclined surface and substantially representative of the mass of said material sliding over the surface, and hence the rate of mass flow along the path at any given instant, wherein material is deposited on the inclined surface such that the sensing means is substantially insensitive to impact forces due to said flow.

The sensing means would normally produce a signal indicating the aforesaid sensed quantity and means may be provided to smooth out rapid fluctuations in said signal. The signal can be utilzed in various ways. For example, integrating means can be responsive to the signal to denote the total mass of material moving along the path over any period of integration.

The invention also provides a method of monitoring the flow of material comprising causing the material to flow by gravity along a flow path from a container to a receiving station depositing the material on an inclined movable support surface in the flow path and sensing the rate of mass flow along an inclined support surface in said path with the end of sensing means responsive to the movement of the support surface caused by the mass of material sliding over the surface but rendered substantially insensitive to impact forces due to said flow by the deposition of the material on the support surface.

In another aspect the invention provides apparatus for controlling the delivery of material from a hopper to a distributor; said apparatus comprising means for delivering material from the hopper to a flow path for gravitational delivery to the distributor, means including an inclined support surface supported for movement and situated in the flow path to sense the weight of material flowing on said support surface under gravity to produce a signal substantially proportional to the mass of material flowing on the support surface and hence the rate of mass flow an any instant the material being received by the support surface in a manner such that said signal is substantially independent of impact forces due to said flow and means operated by said signal to alter the speed of the delivery means to maintain a predetermined selected flow of material along the flow path.

A method of controlling the delivery of material from a hopper or container to a distributor may comprise operating delivery means to cause the material to flow by gravity along a flow path from the hopper to the distributor, depositing the material on an inclined support surface in the flow path, sensing the weight of material flowing on the support surface with the aid of sensing means which produces a signal representing the movement of the support surface and the rate of mass flow along the support surface at any instant but rendered by the deposition of the material on the support surface substantially insensitive to impact forces due to said flow and utilizing said signal to control the speed of the delivery means to maintain a predetermined selected flow of material along the flow path.

Monitoring apparatus constructed in accordance with the invention may be incorporated in equipment embodying a container for flowable material and delivery means for initiating or causing the material to flow from the container to a recovery station or distributor under the influence of gravity.

The inclined surface can be defined by an inclined sensing plate supported on a pivot axis, the sensing means then senses pivoting of the sensing plate and material is deposited on said surface adjacent said pivot axis to render the sensing means substantially insensitive to impact forces due to said flow.

The equipment disclosed hereinafter is in the form of a vehicle which incorporates apparatus constructed in accordance with the invention. The vehicle is specifically designed to spread a mass of sand and/or salt on highways, airport runways and the like; however, it is to be understood that it may be used for spreading fertilizer and other material over areas other than paved surfaces. Equipment of this general type has been disclosed in United States Patent Specifications 2,256,655; 3,744,993, 3,232,626; 3,550,866; 3,677,540; 3,756,509; 2,600,439 and 3,768,737. The equipment described in the foregoing patent specifications operates to effect uniform distribution by increasing the speed of a conveyor by means of which the material is delivered to a distributor in proportion to any increase in the ground speed of the vehicle. The effectiveness of such equipment depends upon the conveyor delivering a constant predetermined volume of material. As a practicing matter, the conveyor will not always deliver the same mass for a given speed of the conveyor due to the fact it is a volume system, also the material may cake in the hopper and not flow freely onto the conveyor due to the fact that obstructions such as frozen chunks of salt and sand and/or rocks may hold back the material on the conveyor, so the conveyor will not deliver the required amount of material. Such a system is an "open loop" control since no error signal is derived from the actual material being handled.

Equipment made in accordance with the present invention preferably utilizes a closed loop" feed back control system incorporating the sensing means for delivering a selected mass of material per unit of target area to be covered in spite of such obstructions in the delivery of material to the distributor. The error signal to close the loop can be derived from a continuous measurement of the actual rate of mass flow of material as compared with the desired or computed rate of mass flow for a range of vehicle speeds. The vehicle speed can be measured and used to modify the desired rate of mass flow in order to achieve a controlled mass per unit area of ground surface.

As herein illustrated, a preferred form of equipment comprises in combination with the monitoring or delivery control apparatus a power-driven vehicle and a chassis which embodies or supports the material container which may be in the form of a hopper. The receiving station can then be a distributor likewise supported for movement with the chassis. The delivery means may be a conveyor or conveying means such as an endless belt or which may be an auger of the Archimedean screw variety. The speed of the delivery means may be operator-controlled. The distributor serves to distribute the material along a surface over which the vehicle travels.

Means is provided to produce a signal proportional to the speed of travel of the vehicle and means serves to compare the signal from the sensing means indicating the flow of material to the distributor and the vehicle speed-indicating signal. Means is then responsive to the compared signals to change the speed of the delivery means so as to compensate for changes in the speed of the vehicle. In this way, a substantially uniform distribution can be achieved independent of the vehicle speed.

Manually-operable means can serve to increase or decrease the mass per unit area of distributed material at any predetermined speed of the vehicle. Means can be provided for nullifying signals of short duration due to sudden acceleration or deceleration of the vehicle and/or temporary obstructions in the feed from the conveyor and means can be provided for effecting a temporary increase or decrease in the feed flow rate to provide for extraordinary conditions. Visual signal lights and/or audible warnings can also be provided to indicate such conditions as failure of the feed due to obstructions or a depleted hopper and to indicate the total weight of material distributed at any given time.

An inclined deflector plate can be supported adjacent the delivery means with its upper end at the delivery end thereof.

This deflector plate guides material onto the inclined support surface defined by a pivotably supported sensing plate. The sensing means senses pivotal displacement of the sensing plate and the lower end of the deflector plate is positioned such that the material is deposited onto the sensing plate support surface sufficiently adjacent the pivot axis thereof to inhibit the sensing means from responding to impact force. The sensing plate is preferably inclined in the opposite direction from the direction of inclination of the deflector plate and the deflector plate and the sensing plate can be inclined at approximately 45 degrees. The effect of the deflector plate, in addition to directing the flow of material to the correct part of the sensing plate, is to nullify the effect of impact forces on the rate of mass flow measurement, since, for different sizes of vehicles, the height of free fall from the delivery means to the sensing plate will vary considerably. The delivery means or conveyor is supported below the hopper with its receiving end in a position to gravitationally receive material from the hopper. A vertically disposed discharge chamber can be provided. This chamber can be supported with its upper end adjacent the hopper and its lower end adjacent the distributor. The chamber contains at its upper end a side wall opening through which the discharge end of the conveyor extends by means of which the material withdrawn from the hopper is delivered into the upper end of the chamber. The deflecting plate and the sensing plates are then situated within the chamber below the discharge end of the conveyor and are inclined in opposite directions.

The invention will now be described in greater detail with reference to the accompanying drawings, wherein: Figure 1 is an elevation diagrammatically illustrating equipment incorporating apparatus constructed in accordance with the invention.

Figure 2 is a diagrammatic plan view of Figure 1; Figure 3 is a vertical fragmentary section showing a portion of the conveyor, the deflector plate, the sensing plate and the distributor; Figure 4 is a view corresponding to a section taken at right angles on line 3-3 of Figure 3; Figure 5 is a horizontal section taken on the line 5-5 of Figure 3; Figure 6 is a vertical section taken on line 66 of Figure 3; Figure 7 is a block diagram of the control means; and Figure 8 is a schematic wiring diagram of the control means of Figure 7.

Referring to the drawings, Figs. 1 and 2, there is diagrammatically illustrated in elevation and plan view a motor-driven vehicle comprising a chassis 10, front and rear wheels 12 and 14 and a power plant in the form of a motor E. A wide-mouthed hopper 16 is mounted on the chassis rearwardly of the cab 18 and rearwardly of the hopper there is a vertically disposed chamber 20 of substantially rectangular horizontal section to which the material to be spread is delivered by a conveyor 22 underlying the hopper. At the lower end of the chamber 20, there is a distributor 24 onto which the material is deposited.

The conveyor 22 is an endless belt, comprised of spaced, parallel slats 26, entrained about longitudinally spaced, parallel rollers 28-28, one of which is driven by a motor M2. Alternatively an auger screw feed can be employed as before mentioned. The upper run of the belt enters the left-hand end of the hopper as shown in Fig 1 through a slot 30, travels along the bottom 32 of the hopper and leaves the hopper through an opening 34 at the righthand end of the hopper. The vertical height of the opening 34 is preset by means of a doctor blade 36. In the case of the auger screw feed, the exit orifice is fixed and only the feed rate can be controlled.

The chamber 20, Figs 3 and 4, has near its upper end an opening 38 through which extends the delivery end of the conveyor belt 22 so that rotation of the belt carries the material from the bottom of the hopper into the upper end of the chamber 20 where it is discharged and falls gravitationally downwardly within the chamber 20 toward the distributor 24.

The distributor 24 is in the form of a flat disk, having on its upper surface radially disposed vanes 40 Figs. 3 and 4 secured to the lower end of a shaft 42, the latter being rotatably supported in suitable bearings within the chamber 20 at the geometrical center thereof. A motor M3 connected to the shaft 42 provides for rotating the distributor.

In accordance with this invention, there is provided in the chamber 20, Figs. 1, 3 and 4, an inclined deflector plate 44 and an inclined sensing or sensor plate 46. The inclined deflector plate 44 as shown in Figs.

3 and 4 is fixed at its upper end to a bar 48 just below the inwardly projecting end of the conveyor belt with its lower end projecting downwardly toward the opposite wall at an angle of approximately 45 degrees. The lower portion of the deflector plate 44 contains an opening 50 for receiving the shaft 42. The sensor plate 46 is mounted below the deflector plate at the opposite side of the chamber from the deflector plate on a bracket member generally designated 52 having a part 54 located within the chamber to which the sensor plate is secured by fastening means 56 and a part 58 which extends through an opening 60 in the wall of the chamber and is pivotally supported by a shaft 61, the ends of which are fixed in space by parallel, vertically disposed bracket plates 6262 at the outer side of the chamber. The sensor plate 46 is normally supported at an inclination of substantially 45 degrees by a vertically disposed plunger element 64 which protrudes from the lower end of a hydraulic cylinder 66 supported for adjustment laterally with respect to the part 58 of the bracket 52 by a plate 68 containing slots 7(1--70 for receiving bolts 72-72 by means of which it is fastened to one of the plates 62. The lower end of the sensor plate 46 contains an opening 74 for receiving the shaft 42. Desirably, the outwardly protruding part 58 of the bracket, the plunger 64 and hydraulic cylinder 66 are enclosed within a housing member 76 attached to the outer side of the chamber 20. It is to be understood that this is only one type of transducer which can be operated by the part 58. The transducer used preferably senses force without appreciable deflection. The objective is to measure the pressure due to the mass of material sliding down the plate without producing appreciable deflection of the plate since this will produce an error in measurement proportional to tangent theta 8 which must be corrected.

The deflector plate 44 and sensor plate 46 are dimensioned so as to extend the full width of the chamber, that is, from side-toside as shown in Fig. 4, and to overlap to such an extent that the lower end of the deflector plate 44 is closely adjacent the upper end of the sensor plate 46 and the lower end of the sensor plate 46 terminates substantially at the center of the chamber.

The material which is to be distributed is delivered through the side wall opening 38 at the top of the chamber 20 and falls freely onto the upper sloping surface of the deflector plate 44 whereupon it slides downwardly thereon onto the oppositely inclined, upwardly facing support surface of the sensor plate 46. Because of the arrangement of the plates 44 and 46, the material sliding down from the deflector plate 44 onto the sensor plate 46 is deposited on the sensing plate sufficiently close to the axis of the shaft 61, which is the pivot axis on which the sensor plate 46 is pivotally supported, to substantially inhibit pivoting torque due to impact forces.

Following deposit on the sensor plate 46, the material slides downwardly thereon and gravitationally falls onto the upper side of the distributor 24. In order to redirect any of the material which is projected beyond the lower end of the sensor plate 46, there is provided at the bottom of the chamber a reversely inclined apron 78.

The plunger 64 and hydraulic cylinder 66 constitute one form of sensing means which is operative by pivotal means of the sensor plate 46 in response to the weight of the mass deposited thereon to send a signal by way of a conductor 67 Fig 1 proportionate to the mass on the sensing plate at any given time to a comparator unit 78, Figs. 1, 2 and 7. Since, as related above, the material is deposited sufficiently close to the pivot axis of the sensor plate 46 substantially to nullify the effect of impact forces, the sensor device will only reflect changes in mass.

The purpose of the overall equipment is to deliver a selected mass of material per unit area at whatever ground speed the vehicle is travelling. Accordingly, the rate of delivery of the material to the distributor must be modified with changes in the ground speed of the vehicle. As related, heretofore this has been achieved by correlating the speed of the conveyor with that of the vehicle, but, as also pointed cut, this was predicated on the assumption that there would be a uniform, uninterrupted flow of material from the hopper onto the conveyor and from the conveyor to the distributor. This is not the fact for, even though the conveyor may be moving at a predetermined speed, caking of the material in the hopper may be such that it does not flow uniformly from the hopper onto the conveyor, or chunks of frozen salt and sand and/or rocks may become lodged against the doctor blade so that the entire width of the conveyor is not discharging into the chamber. Consequently, such control is not effective. The control provided herein eliminates the defects of such prior apparatus in that the mass is measured at its place of delivery to the distributor by the sensor plate 46 so that if the mass at the sensor plate 46 changes from what has been determined as desirable per unit of area, a signal will be sent thereby to either increase of decrease the rate of movement of the conveyor to either supply more or less material as required. To achieve this, there is provided speed-sensing means 80, Figs. 1, 2 and 7, which is driven from the drive train D or a vehicle wheel.

The speed-sensing means 80 is connected by a cable 81 to the comparator 78 so as to generate signals which are proportional to the speed of the vehicle. The two signals, the one from the sensing device 64, 66 and the one from the speed-sensing means 80, are combined at the comparator 78 to produce an error signal. The signal from the comparator is transmitted as an electric current through a conductor 82to a valve housing 84 containing valves V1 and V2.

The valve Vl is connected by a supply pipe 86 to a hydraulic pump P which is driven by the engine E and by a supply pipe 88 to the hydraulic motor M2 which drives the conveyor belt. A return pipe 90 connects the hydraulic motor M2 to the hydraulic pump P. The valve V2 is connected by a supply pipe 92 to the hydraulic motor M3 which drives the distributor and this valve V2 may be manually adjusted to increase or decraase the rate of flow to the hydraulic motor M3 and, hence, to increase or decrease the speed of rotation of the distributor. A return pipe 93 connects the hydraulic motor M3 with the pump P.

The comparator 78 is mounted in the cab, together with the control panel on which there is mounted an ON/OFF switch 94 for starting the system in operation or shutting it down. The panel also has on it a blast switch 106 for increasing the rate of delivery of the material for a short period of time to take care of unusual conditions, a lane selector 109 and switch 2 for selecting the number of lanes, and visual and audio signals for indicating failure of delivery of the material, depletion of the supply in the hopper and a total distributed weight indicator.

A block diagram of the control is shown in Fig. 7 and, as indicated therein, signals from the mass and speed-sensing means 64, 66 and 80 are, respectively, preprocessed in first and second mass followers 94, 96 and a speed pulse generator 98 and integrator 100, whereupon they are combined in the comparator circuits 78. The latter, via output circuit 102, actuates the electric gear motor M3 so as to change the hydraulic fluid flow to the conveyor drive motor M3 (and therefore conveyor speed and material flow). Mass information is also applied to a count computer 104 so that the material distributed may be totalized in counter 105.

In the absence of mass flow, a red light R is illuminated. This condition is to be expected when the vehicle is at rest.

When the vehicle is in motion and either (a) the hopper is empty or (b) a blockage is impeding the correct mass flow, the valve Vl will open fully to try to correct this situation. The full open condition in the valve Vl is indicated by the intermittent tones of an audible alarm B. When the valve Vl is in a fully open condition and there is no mass flow, the red light R will flash at the same rate as the alarm B.

Certain conditions require increased spreading rate for a short time. For this purpose, there is provided a push button operator actuate blast switch 106 and timer 108. Momentary depression of the push button will initiate the timer 108 for a period, for example, of 10 seconds during which the spreading rate is increased by 50 percent (for example). Continuous depression of the push button will maintain the increased spread rate and delay the onset of the 10 second period until it is released. An amber signal light A denotes the increased spread rate condition.

Adjustment of the preset spread rate (normally 300 pounds per lane mile) for different road widths is selected for two, three or four lanes by means of a lane selector switch L.

The means illustrated in Figs. 1 to 7 inclusive for sensing the mass if a hydraulically-operated bourdon gauge; however, it is within the scope of the invention to employ other kinds of sensing means such as a servo system, a resistance system or a hydraulic valve system.

Referring now to Fig. 8, the control means will be described in further detail.

Hydraulic sensing means 64, 66 operates to vary a pressure sensitive variable resistor Rm which decreases in resistance as the mass on sensor plate 46 increases. This resistance variation in the voltage divider circuit R1, Rm applies a voltage signal representing instantaneous mass flow rate to operational amplifier U2 which has an adjustable voltage from potentiometer R5 applied to set the output voltage to zero at zero mass flow rate on sensor plate 46. The output of U2 is applied to a unity gain op amp U2-2 having RC feedback via capacitor C2 and resistor R14 to smooth out short rapid mass signal fluctuations. Op amp U2-2 has accessible jumpers 111, 112 which can be replaced by resistors to calibrate the actual mass flow to the magnitude of the mass flow signal and signal variation. Thus delivery rates for the material distributed by the system other than the previously described 300 Ibsflane mile can be selected.

The output of U2 is also applied to the count computer 104 which is comprised of op amps U4, U4--1, U-2, U4--3. U4 references the zero mass flow rate signal to V/2, half the supply voltage, and has a gain of 1/3. U4-1 is an integrator having an integration feedback capacitor C3 which is shunted by an FET switch Q1. U42 has a gain of 3 for the integrated signal and applies its output to voltage comparator U4--3 which is referenced to an voltage such that it toggles, i.e., produces a comparison output, each time the integrator U4-l has accumulated a signal representing distribution of a predetermined mass of material, for example, 10 Ibs. A comparison output from U4--3 operates through transistor Q2 to make Ql conduct thereby resetting integration capacitor C3 to zero and thus returning the output of comparator U4--3 to logic zero. The comparison pulse from U W 3 also is applied to transistor Q3 which has a pulse stretching coupling circuit driving a Darlington pair Q4, Q5 which registers the pulse as a counter in the counter 105 preferably calibrated in weight of material distributed.

A speed sensor 112 connected to the vehicle drive train is arranged to produce a predetermined number of switch closures or other pulse actuations per road mile. In the present system the switch 112 is arranged to produce 6,000 pulses per road mile. Hence at 30 mph there are 6000 30x -50 pulses per second.

60x60 The pulses produced by road speed are standardized in op amp U3 and applied to an integration circuit associated with op amp U3-1 having capacitor C8 on the input thereof and feedback capacitor C9.

The pulses which are so applied are standardized in width by op amp U3 and the width is adjustable by means of selector switch 113. The resistors introduced and removed by selector switch 113 are calibrated as part of a voltage divider input to the reference input terminal of U3 to correspond to 2, 3 and 4 lane widths of the road. Thus the control 113 is available in the cab for the driver of the vehicle to select whether he is spreading material on two lane of the road or whether he is covering 3 or 4 wanes. Similarly, the feedback ratio for op amp U3--1 can be modified by FET switch U18 in response to a signal on solenoid line 114 which feature is utilized in vehicles equipped with variable ratio differentials in response to operation of gear change to modify the scaling function of op amp U3-l to correspond to the different road miles covered for particularly selected gear ratio in the differential. Thus the output signal from integrator C8, R98, R99 applied to U3--1 is proportional to road speed and can be compensated for both selected travel lanes or road widths to be covered and for the gear differential ratio of the drive train.

The pulse width which is integrated to obtain a voltage proportional to road speed can be overridden by actuation of FET switch Q17 in response to closure of blast switch 106 which is available in the cab.

Closure of switch 106 grounds an input to op amp U3-2, the output of which is applied through transistor Q6 to make Q17 non-conductive. Upon release of blast switch 106 the timing circuit comprising resistor R-39 and capacitor C5 at the input of U3-2, maintains switch Q17 nonconductive for predetermined time while capacitor C5 recharges. Thus a momentary closure of blast switch 106 provides a predetermined timing of additional material flow and holding switch 106 depressed maintains the increased rate of material distribution for as long as it it depressed. As previously described during operation with blast switch conditions for high mass material flow, amber indicating light A in the cab is energized to indicate such condition.

The combining of the mass delivery signal and the road speed signal is accomplished in op amp U2-3. The signal from the second mass follower U2-2 is applied as one input to op amp U2-3 and the other input is supplied as the road speed signal from op amp U3--1. For standard road speed and standard mass delivery these signals balance and the output of op amp U2-3 is logic zero. The output of U2-3 is applied to opposite polarity inputs of a voltage comparator U1--l, Ul-2, which are op amps biased at their other inputs to be nonconductive over a suitable deadband interval provided by voltage divider resistors R56, R58. Thus for logic zero signal from U2-3 the comparator op amps Ul-l and Ul-2 both have logic zero outputs and beacuse of the opposite polarity connection for the input signals thereto, only one of the op amps Ul-l or <RT per road mile, the circuit operates to reduce the output of signal comparator U2-3 to within the deadband of comparators Ul-l and Ul-2 and the valve position remains as set until further changes in operating conditions, either road speed or material delivery from the conveyor to the mass sensor 46 occurs. Similarly, movement toward closure of valve Vl is controlled by op amp U1--4. To prevent continued operation of valve motor M4 when valve Vl is fully open, an end stop position of potentiometer RV supplies a voltage signal to op amp Ul-3 to make its output logic zero. The prevent any delivery of material at zero road speed, potentiometer RV has a bottom end stop position, selected by a trimmer RW, to exactly close valve Vl at zero road speed condition by means of op amp U1---4.

The operation of the foregoing circuit is believed to be clear from the description and will be appreciated to comprise a fully closed loop servo control of the delivery of material to establish a predetermined mass flow rate per unit area which is covered by the vehicle carrying the apparatus. Thus variations in read speed, land widths, gear train ratio and partial blockage of the delivery passage of the material or other mass variations from the source of supply are all automatically compensated to achieve the desired end'of a predetermined mass delivery per unit area covered by the vehicle. Thus the most rigid control to achieve the predetermined delivery rates is automatically accomplished together with various controls, indications and override conditions.

The output signals from the second mass follower U2-2 is also applied to an op amp U2, the output of which is connected through a drive transistor Q20, Q21 to operate the red indicator lamp R. As previously described, illumination of lamp R indicates loss of mass delivery signal from the signal channel originating with mass sensor Rm and indicates either that there is complete blockage from the conveyor or that the hopper supply has been totally depleted.

The movement of the control valve V1 to its fully open (maximum material demand) limit position with the corresponding movement of potentiometer RV to its limit position provides a signal applied to transistor Q22 which is scaled and applied as an enabling input to op amp U3-2 connected as an astable multivibrator to actuate an audible alarm B intermittently as previously described. The signal which actuates the alarm B is also applied to transistor Q20 to energize the visual red indicator R if it is indicating zero flow rate.

Thus loss of mass flow or the condition of end of travel for the adjustment of valve Vl produces visual or audible indications or both.

Special test instruments can be arranged to enable the system to be operated (wholly or in part) without actually moving the vehicle in which it is mounted and/or without actually discharging material. For this purpose special switch/connector jacks 115, 116 are provided which enable speed and/or mass flow rate signals to be injected into the system from the test instruments.

Similarly, critical output signals can be measured and displayed at test points 117, 118. For example, a speed signal could be applied at jack 116 as a pulse generator of suitable pulse repetition rate. A mass flow rate signal can be simulated by a rheostat variable resistance to ground inserted at jack 115.

WHAT WE CLAIM IS: 1. Apparatus for monitoring the flow of material as it is caused to be delivered from a container to a receiving station and flows by gravity through a flow path from the container to the receiving station; said apparatus comprising an inclined surface supported for movement and situated in the flow path and over which the material slides and sensing means for sensing a quantity dependent on the movement of the inclined surface and substantially representative of the mass of said material sliding over the surface, and hence the rate of mass flow along the path at any given instant, wherein the material is deposited on the inclined surface such that the sensing means is substantially insensitive to impact forces due to said flow.

2. Apparatus according to Claim 1, wherein the sensing means produces a signal indicative of said sensed quantity.

3. Apparatus according to Claim 2 and further comprising means for nullifying rapid fluctuations in said signal from the sensing means.

4. Apparatus according to Claims 2 or 3 and further comprising integrating means responsive to said signal from the sensing means to denote the total mass of material moving along the path over any period of integration.

5. Apparatus according to any one of Claims 1 to 4, wherein the inclined surface is defined by an inclined sensing plate supported on a pivot axis, the sensing means senses pivoting of the sensing plate and material is deposited on said surface adjacent said pivot axis to render the sensing means substantially insensitive to impact forces due to said flow.

6. Apparatus according to Claim 5, wherein a hydrauically actuated transducer supports the sensing plate at an angle of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (31)

**WARNING** start of CLMS field may overlap end of DESC **. per road mile, the circuit operates to reduce the output of signal comparator U2-3 to within the deadband of comparators Ul-l and Ul-2 and the valve position remains as set until further changes in operating conditions, either road speed or material delivery from the conveyor to the mass sensor 46 occurs. Similarly, movement toward closure of valve Vl is controlled by op amp U1--4. To prevent continued operation of valve motor M4 when valve Vl is fully open, an end stop position of potentiometer RV supplies a voltage signal to op amp Ul-3 to make its output logic zero. The prevent any delivery of material at zero road speed, potentiometer RV has a bottom end stop position, selected by a trimmer RW, to exactly close valve Vl at zero road speed condition by means of op amp U1---4. The operation of the foregoing circuit is believed to be clear from the description and will be appreciated to comprise a fully closed loop servo control of the delivery of material to establish a predetermined mass flow rate per unit area which is covered by the vehicle carrying the apparatus. Thus variations in read speed, land widths, gear train ratio and partial blockage of the delivery passage of the material or other mass variations from the source of supply are all automatically compensated to achieve the desired end'of a predetermined mass delivery per unit area covered by the vehicle. Thus the most rigid control to achieve the predetermined delivery rates is automatically accomplished together with various controls, indications and override conditions. The output signals from the second mass follower U2-2 is also applied to an op amp U2, the output of which is connected through a drive transistor Q20, Q21 to operate the red indicator lamp R. As previously described, illumination of lamp R indicates loss of mass delivery signal from the signal channel originating with mass sensor Rm and indicates either that there is complete blockage from the conveyor or that the hopper supply has been totally depleted. The movement of the control valve V1 to its fully open (maximum material demand) limit position with the corresponding movement of potentiometer RV to its limit position provides a signal applied to transistor Q22 which is scaled and applied as an enabling input to op amp U3-2 connected as an astable multivibrator to actuate an audible alarm B intermittently as previously described. The signal which actuates the alarm B is also applied to transistor Q20 to energize the visual red indicator R if it is indicating zero flow rate. Thus loss of mass flow or the condition of end of travel for the adjustment of valve Vl produces visual or audible indications or both. Special test instruments can be arranged to enable the system to be operated (wholly or in part) without actually moving the vehicle in which it is mounted and/or without actually discharging material. For this purpose special switch/connector jacks 115, 116 are provided which enable speed and/or mass flow rate signals to be injected into the system from the test instruments. Similarly, critical output signals can be measured and displayed at test points 117, 118. For example, a speed signal could be applied at jack 116 as a pulse generator of suitable pulse repetition rate. A mass flow rate signal can be simulated by a rheostat variable resistance to ground inserted at jack 115. WHAT WE CLAIM IS:

1. Apparatus for monitoring the flow of material as it is caused to be delivered from a container to a receiving station and flows by gravity through a flow path from the container to the receiving station; said apparatus comprising an inclined surface supported for movement and situated in the flow path and over which the material slides and sensing means for sensing a quantity dependent on the movement of the inclined surface and substantially representative of the mass of said material sliding over the surface, and hence the rate of mass flow along the path at any given instant, wherein the material is deposited on the inclined surface such that the sensing means is substantially insensitive to impact forces due to said flow.

2. Apparatus according to Claim 1, wherein the sensing means produces a signal indicative of said sensed quantity.

3. Apparatus according to Claim 2 and further comprising means for nullifying rapid fluctuations in said signal from the sensing means.

4. Apparatus according to Claims 2 or 3 and further comprising integrating means responsive to said signal from the sensing means to denote the total mass of material moving along the path over any period of integration.

5. Apparatus according to any one of Claims 1 to 4, wherein the inclined surface is defined by an inclined sensing plate supported on a pivot axis, the sensing means senses pivoting of the sensing plate and material is deposited on said surface adjacent said pivot axis to render the sensing means substantially insensitive to impact forces due to said flow.

6. Apparatus according to Claim 5, wherein a hydrauically actuated transducer supports the sensing plate at an angle of

approximately 450 to the horizontal and constitutes at least part of the sensing means.

7. Apparatus according to Claims 5 or 6, wherein an inclined deflector plate is provided to deposit the material on the inclined surface.

8. Apparatus according to Claim 7, wherein the deflector plate and the sensing plate are inclined at opposite angles of approximately 450 to the horizontal.

9. Apparatus according to any one of Claims 1 to 4, wherein an inclined deflector plate or surface is located in said flow path to direct material onto said inclined surface, the inclined surface is defined by a sensing plate mounted for pivoting about a pivot axis adjacent the lower end of the deflector plate or surface, the sensing means senses pivotal movement of the sensing plate caused by the mass of material sliding over the inclined surface thereof and material is deposited on the inclined surface from the deflector plate in a position adjacent said pivot axis to render the sensing means substantially insensitive to impact forces due to the deposition and flow of the material.

10. Apparatus according to any one of Claims 1 to 9, wherein the sensing means is incorporated in an closed loop rate of mass flow feedback control system.

11. Apparatus according to Claim 10, wherein the sensing means comprises servo means.

12. Apparatus according to any one of Claims 1 to 11, wherein the sensing means comprises resistance means.

13. Apparatus according to any one of Claims 1 to 11, wherein the sensing means comprises a Bourdon gage.

14. Equipment embodying a container for flowable material, delivery means for initiating or causing the material to flow from the container to a receiving station under the influence of gravity and apparatus according to any one of the preceding claims for monitoring said flow.

15. Equipment according to Claim 14 and further comprising operator-controlled means for varying, or initiating a charge in, the operational speed of the delivery means.

16. Equipment according to Claim 15, wherein there is further provided a timer for automatically restoring the speed of the delivery means to an initial value.

17. Equipment according to Claims 14, 15 or 16, wherein the delivery means is an endless belt.

18. Equipment according to Claims 14, 15 or 16, wherein the delivery means is an auger.

19. Equipment according to any one of Claims 14 to 18, wherein a chassis of a motor-driven vehicle forms or supports the container and the receiving station is a distributor mounted to the chassis for movement therewith to distribute the material along a surface over which the vehicle is caused to travel.

20. Equipment according to Claim 14, when appended to Claim 2, wherein a chassis of a motor-driven vehicle forms or supports the container and the receiving station is a distributor mounted to the chassis for movement therewith to distribute the material along a surface over which the vehicle is caused to travel and further comprising means for producing a signal proportional to the speed of travel of the vehicle, means for comparing the speedindicative signal and the signal from the sensing means of the monitoring apparatus and means operably controlled by the comparing means to vary the speed of the delivery means to cause the distributor to effect uniform distribution of material independently of the vehicle speed.

21. Equipment according to Claim 20 and further comprising operator-controlled means for selecting the mass of material to be distributed per unit area.

22. Equipment according to Claim 20 and further comprising operator-controlled means for changing the speed of the delivery means independently of the vehicle speed.

23. Apparatus for controlling the delivery of material from a hopper to a distributor; said apparatus comprising means for delivering material from the hopper to a flow path for gravitational delivery to the distributor, means including an inclined support surface supported for movement and situated in the flow path to sense the weight of material flowing on said support surface under gravity to produce a signal substantially proportional to the mass of material flowing on the support surface and hence the rate of mass flow at any instant, the material being received by the support surface in a manner such that said signal is substantially independent of impact forces due to said flow and means operated by said signal to alter the speed of the delivery means to maintain a predetermined selected flow of material along the flow path.

24. Apparatus for monitoring or controlling the flow of material or equipment including such apparatus substantially as described with reference to, and as illustrated in, any one of more of the Figures of the accompanying drawings.

25. A method of monitoring the flow of material comprising causing the material to flow by gravity along a flow path from a container to a receiving station, depositing the material on an inclined movable support surface in the flow path and sensing the rate of mass flow along an inclined support surface in said path with the aid of sensing means responsive to the movement of the support surface caused by the mass of material sliding over the surface but rendered substantially insensitive to impact forces due to said flow by the deposition of the material on the support surface.

26. A method according to Claim 25 and further comprising utilizing an inclined sensing plate to define the inclined support surface mounting said plate for pivoting, causing the material to be deposited on the support surface adjacent the pivot axis of the plate and sensing the pivotal displacement of the plate about the pivot axis caused by the mass of material passing over the support surface.

27. A method according to Claim 26 and further comprising utilizing a deflector plate positioned in the flow path to cause the material to be deposited on said suppprt surface adjacent the pivot axis of the sensing plate.

28. A method of controlling the delivery of material from a hopper or container to a distributor comprising operating delivery means to cause the material to flow by gravity along a flow path from the hopper to the distributor, depositing the material on an inclined movable support surface in the flow path, sensing the weight of material flowing on the support surface under gravity with the aid of sensing means which produces a signal representing the movement of the support surface and the rate of mass flow along the support surface at any instant but rendered by the deposition of the material on the support surface substantially insensitive to impact forces due to said flow and utilizing said signal to control the speed of the delivery means to maintain a predetermined selected flow of material along the flow path.

29. A method according to any one of Claims 25 to 28 and further comprising incorporating the sensing means in a closed loop rate of mass flow feedback control system.

30. a method according to Claim 28 and further comprising moving a motor-driven vehicle the chassis of which forms or supports the hopper and the distributor over a surface to permit material to be distributed thereover by said distributor, producing a signal proportional to the speed of travel of the vehicle, comparing the speed-indicative signal and the signal from the sensing means and controlling the speed of the delivery means in accordance with the comparison to cause the distributor to effect uniform distribution of material independently of the vehicle speed.

31. A method of monitoring or controlling the delivery of material substantially as described herein with reference to the accompanying drawings.