Milling of cereals and the like

A process and apparatus is disclosed for milling cereal in a milling plant having a control device, such as a computer device, for controlling various process elements of the plant and the operative parameters of those process elements, in which the characteristics of the material to be milled are established together with the characteristics of the required finished product and from those characteristics desired operating parameter values for one or more selected process elements are determined bearing in mind the characteristics of the process elements of the plant, and those parameter values are stored in the control device to be used as control signals for the process elements, and in which such control signals are determined and stored in groups associated with required combinations of material and finished product characteristics, and an appropriate group of parameter values is selected by means of the control device to provide process control signals for controlling the operative parameters of said process elements.

BACKGROUND OF THE INVENTION 
This invention relates to a control system for apparatus used in cereal 
milling plants. 
The invention finds particular application in a mill for producing flour, 
more particularly baking flour, semolina and medium ground flour in a 
series of progressive stages. 
Modern cereal mills are largely automatic. The heart of the mill, i.e. the 
milling portion, and more particularly the mill rolls and the cleaning 
installations are interconnected and actuated via electrical interlocking 
to such an extent that operation during the starting, operating and output 
phase can be regarded as completely automatic. The entire stream of 
product, starting from the raw grain, is automatically conveyed through 
all the milling stages. 
White flour which is one of the main objectives of cereal milling must have 
a very low ash content. A low ash or husk content is directly contrary to 
maximum recovery of the endosperm. A large number of factors, e.g. the 
feel of the flour, the baking properties, taste and smell of the bread, 
are checked and constantly monitored by the miller and his laboratory 
assistants, using in many cases their own unaided senses. The reliability 
of the individual machines, mechanical conveying elements, actuating 
means, etc. has now been brought to such a high standard that a single man 
(i.e. the miller or head miller) can without aid, monitor a large mill 
with a daily output of some 300-400 tonnes. 
In recent times, many proposals have been made for further automation of 
mills. The most obvious idea of all would be simply to control the mill by 
a computer. However, a single miller is still required. As a result the 
computer, with the necessary computer expert, is a retrograde step, and 
likely to lead to over-control of the mill and may endanger the present 
high level of automation as faults in the computer result in complete shut 
down of the plant. Although laboratory work has been going on for almost 
two decades, the computer has not been accepted in milling practice, 
except for "book-keeping" tasks, where it only collects the necessary 
information and processes or stores it for accounting and other 
book-keeping purposes. A yield computer is an example of the book-keeping 
computer. A yield computer is arranged to continuously monitor the weights 
of raw flour supplied and the products obtained therefrom, i.e. medium 
ground flour, bran, etc. from which it calculates the yield for a 
particular time or from a given load. Mill experts have not so far 
accepted a central control computer to supervise a mill because they know 
only too well that it may fail, resulting in complete shut down of the 
mill. 
An important concept in the background of the invention is that a cereal 
mill should be treated in a manner appropriate to itself and not like a 
chemical factory or cement factory. animals will not accept fodder except 
in a form which appeals to them, and the same applies even more to man in 
his acceptance of flour. A purpose of the mill, therefore, must be to 
produce flour which meets the needs for baking good bread or for making 
good paste products. For this, however, the intervention of the miller 
with his skill and experience is essential. Accordingly an acceptable end 
product can be obtained only by full co-operation between the miller and 
the machinery. 
One interesting discovery is that a mill must be piloted somewhat in the 
manner of a modern passenger aircraft. A mill must have an automatic 
"pilot" which helps the real pilot or miller without replacing him. In 
both the aircraft and the mill, the "take-off", "flying" and "landing" 
process must be assisted, but the head miller remains responsible for 
active guidance and piloting in a supervisory capacity, adding his own 
perception to the control of the mill process. He must, with his unaided 
senses, allow for all the important factors, more particularly those which 
are difficult to measure mechanically but which are critical in the 
process, and he must be able to give suitable control instructions at any 
time. 
OBJECTS OF THE INVENTION 
An object of the invention is to provide a control system for a mill plant 
which can facilitate control thereof by the miller, i.e. a man, using a 
minimum number of technical aids or actuating and control means, and 
guarantee uniform operation so that the mill has optimum efficiency. 
It is a further object of the invention to provide such a control system 
which avoids the shut down of the whole mill plant in the event of a 
failure in the main or subsidiary parts of such a control system. 
SUMMARY OF THE PRESENT INVENTION 
In one aspect the invention provides a process for milling cereal in a 
milling plant having a control device, such as a computer device, for 
controlling various process elements of the plant and the operative 
parameters of those process elements, in which the characteristics of the 
material to be milled are established together with the characteristics of 
the required finished product and from those characteristics desired 
operating parameter values for one or more selected process elements are 
determined bearing in mind the characteristics of the process elements of 
the plant and stored in the control device to be used as control signals 
for the process elements, and in which such control signals are determined 
and stored in groups associated with required combinations of material and 
finished product characteristics, and an appropriate group of parameter 
values is selected by means of the control device to provide process 
control signals for controlling the operative parameters of said process 
elements. 
In a further aspect the invention provides a milling plant for milling 
cereal, having a control device, such as a computer device, for 
controlling various process elements of the plant and the operative 
parameters of those process elements; in which the control device includes 
storage means in which may be stored groups of operative parameter values 
for said process elements, which groups have been determined from the 
characteristics of the raw material to be milled and the desired 
characteristics of the finished product having regard to the 
characteristics of the process elements; and in which the control device 
is arranged to address an appropriate group of operative parameter values 
in response to an input representative of the raw material and required 
finished product characteristics and provide a group of corresponding 
output signals for controlling the operative parameters of said process 
elements. 
In a further aspect the invention provides a control arrangement for 
apparatus for use in cereal milling having at least one variable operating 
parameter, the control arrangement comprising means associated with the 
apparatus for producing a value signal representative of the actual value 
of said parameter, servo-means associated with the apparatus for varying 
the actual value of said parameter in response to an error signal, manual 
means for varying the actual value of said parameter manually, means for 
producing a desired signal representative of a desired value of said 
parameter, comparator means arranged to produce said error signal from a 
comparison between said value signal and said desired signals, and 
switching means arranged to inhibit the servo means in the event of 
failure thereof or otherwise to allow manual variation of said parameter 
by said manual means. 
In a further aspect the invention provides a control arrangement for 
apparatus for use in cereal milling having at least one variable operating 
parameter, the control arrangement comprising means associated with the 
apparatus for producing a value signal representative of the actual value 
of said parameter, servo-means associated with the apparatus for varying 
the actual value of said parameter in response to an error signal, means 
for producing by manual adjustment a first desired signal representative 
of a desired value of the parameter, a computer device including a memory 
means arranged to select from one or more values of said parameter 
prestored in said memory means a chosen value and produce a second desired 
signal representative of a desired value of said parameter, switching 
means arranged to select the first or second desired signals, and a 
comparator arranged to produce said error signal from a comparison between 
said value signal and the selected one of the first and second desired 
signals. 
In a further aspect, the invention provides a cereal milling plant, 
especially for the production of flour, semolina and medium ground flour, 
having a number of process zones for example for cleaning, moistening, 
roller milling, sifting or silo storage of the incoming cereal, 
intermediate or final products, one or more such process zones including a 
process apparatus which includes servo-control means and means for 
interlocking its operation with other apparatus in the milling plant; in 
which the servo-control means includes a set value generator for a process 
parameter of the respective process apparatus, an actual value sensor for 
that process parameter and comparator means with associated drive means to 
operate the servo-control means in a loop to maintain the parameter at a 
chosen value; and in which switching means is provided so that the 
servo-control means of the process apparatus in one or more of said zones 
individually or collectively may be disconnected so that the apparatus may 
operate independently of the servo-control loop. 
In a further aspect the invention provides a cereal milling plant, 
especially for the production of flour, semolina and medium ground flour, 
having a number of process zones for cleaning, moistening, roller milling, 
sifting or silo storage of the incoming cereal, intermediate or final 
products, in which a central control device, such as a computer device, is 
provided to control process apparatus in one or more such process zones, 
such process apparatus including servo-control means and means for 
interlocking its operation with other apparatus in the milling plant; in 
which the servo-control means includes a manually adjustable set value 
generator for a process parameter of the respective process apparatus, an 
actual value sensor for that process parameter and comparator means with 
associated drive means to operate the servo-control means in a loop to 
maintain the parameter at a chosen value; and in which switching means is 
provided so that the comparator means associated with such process 
apparatus in one or more of said zones individually or collectively may be 
connected to either the central control device or the respective set value 
generator so that the servo-loop may operate under the direction of the 
central control device or the associated set value generator.

Referring first to FIG. 1 there is shown in schematic outline the reception 
area of a flour mill. Material to be milled, such as wheat, is brought 
into the reception area by suitable means such as a railway train or road 
vehicles at 100 and placed on a reception conveyor 101. This takes the 
wheat to an elevator 102 by which it is lifted to pass through a weighing 
machine 103, to check the quantity of wheat being taken into the plant, 
and thence to a cleaning and separating sieve arrangement 104 where an 
initial cleaning operation is performed on the wheat. The wheat then 
passes to a further elevator 105 which lifts it to a conveyor system 106. 
From the conveyor 106 it may be conducted to a further lower conveyor 
system 107 by which it may be carried to be selectively placed in one or 
more of a series of intake storage silos 108. Five storage silos 108 are 
shown in this embodiment, each of these being of 300 metric tonnes 
capacity and the arrangement of the conveyors is such that any given 
intake batch of wheat can be directed to a chosen one of the silos so that 
different intakes of the same or similar types of wheat can be directed to 
a silo reserved for that type of wheat. Suitable outlet selectors 109 are 
provided at the bottom of the silos 108, so that the wheat may be 
selectively taken from the storage silos 108 for processing, and conveyed 
by a conveyor 110 to the elevator 102 again. The wheat is raised by the 
elevator 102 to pass again through the weigher 103, the cleaner 104 and 
the elevator 105 to the conveyor system 106, and it is this time 
selectively directed to one or more of a group of four temporary storage 
silos 11 (FIG. 2) by means of a conveyor 106A. Wheat would be taken to the 
silos 111 in types and quantities determined by the required end product 
of the mill at a given time. 
While the wheat is stored in the silo 108, it may be dried by hot air or 
other heating devices arranged to operate in the silos in known manner per 
se, resulting in up to 1 to 2 percent reduction in weight, and thus the 
weigher 103 also serves to provide a check on the weight of the material 
taken from the silos for further processing. 
The bottom parts of the temporary storage silos 111 are provided with 
respective feeder devices by which the contents may be fed from the silos 
through flow rate control devices 114 to a conveyor system 112 and thence 
to an elevator 113. The flow control devices 114 may be used to control 
the quantity of wheat taken from each of the silos 111, which may contain 
wheat of different varieties, to provide a blending capability in the 
passage of the wheat to the conveyor 112. In the alternative, a given 
variety of wheat may be taken by the conveyor 112 from a selected one of 
the silos 111 alone, and passed to the elevator 113 for processing as 
discussed below. 
From the elevator 113 the wheat passes by way of a weighing machine 125 
through a sieving arrangement of known design per se indicated at 115 to 
clean the wheat, and passes thence to a de-stoning arrangement 116 of 
known design per se where any entrained stones or similar foreign bodies 
are removed. The wheat then passes to an apparatus 117 of known design per 
se arranged to separate from the wheat seeds of other species of plant and 
like foreign material so that substantially only the wheat to be processed 
is passed on to a further elevator 119, optionally by way of a scouring 
machine (not shown) if this is required in the particular mill. 
The elevator 119 carries the wheat to a station indicated generally at 120 
disposed above a group of four watering silos 121. The station 120 
comprises means arranged to measure the moisture content of the dry wheat 
and to provide a basis upon which the amount of water that must be 
absorbed into the body of the wheat to put it in a suitable condition for 
milling may be calculated in accordance with experience of that type of 
wheat; and to add an appropriate amount of water to the wheat. 
The wheat can pass from the station 120 to any of the silos 121 where it is 
allowed to remain in contact with the added water for a period of time (6 
to 48 hours) which is determined in accordance with the amount of water 
required to be absorbed. The wheat is taken from the bottom of the silos 
121 by way of flow control devices 122 passed to a conveyor 123 and thence 
to an elevator 128. The wheat may be taken if necessary to a further 
watering station disposed above further watering silos for a further 
measurement of the moisture content. The water absorption process may be 
repeated with the wheat remaining in the further watering silos in contact 
with water for a further period of time calculated on the basis of 
measurement at the further watering station before passing by way of 
associated flow control devices to a conveyor and thence to the elevator 
128. It will be appreciated that blending can be carried out between the 
wheat put into the various silos 121 by means of the flow control devices 
122 feeding to their associated conveyors. 
It should be understood that the extent to which moisture must be added is 
dependent on the initial moisture content of the wheat to be processed. 
When the wheat comes from a hot dry climate, more moisture must be added 
to reach the desired moisture content and in such cases the double 
treatment discussed above is needed. If the wheat has a higher initial 
moisture content then only a single treatment is needed and the second 
stage may be dispensed with, the conveyor 123 leading as discussed 
straight to the elevator 128. Again more than four silos 121 may be 
provided in each stage with associated flow control valves to allow for 
blending from more varieties of wheat, or for greater throughput of wheat. 
The elevator 128 carries the wheat up to a machine 129 which scours the 
surface of the wheat in known manner per se. The wheat then passes to a 
surface moisture treatment device indicated at 130 which is arranged in 
known manner per se to spray the wheat surface with water to increase the 
moisture content of the surface bran only of the wheat grains. The wheat 
remains in a dwell silo 131 for a short period of time, which may be some 
10 minutes, to allow that moisture to be absorbed into the surface only of 
the wheat grains whereafter it passes to a weigher of known design per se 
indicated at 132 by which the quantity of wheat passing to the next stage 
in the process may be determined. 
FIG. 3 shows in block schematic outline a typical assembly of roller mills, 
sieving machines and purifiers for processing the wheat leaving the 
weigher 132 of FIG. 2. 
FIG. 5 shows by way of example a flow path for wheat through an assembly of 
six roller mills, six sifters, and two purifiers, so that a typical 
installation may be more readily understood. 
The assembly comprises three breaker roller mills 140, 141 and 142 with 
associated sifters 143, 144 and 145, and three smooth roller mills 146, 
147 and 148 with associated sifters 149, 150 and 151. Interposed between 
the breaker rolls and the smooth rolls are two purifiers 152 and 153. The 
roller mills, sifters and purifiers are all of known design per se, except 
for the adaptation of the roller mills for automatic control in a manner 
to be discussed in more detail below. 
Wheat to be milled passes from the weigher 132 to the first break rolls 140 
and thence to the sifter 143. The sifter 143 comprises two sieves a first 
154 of some thirty wires to the inch and a second 155 of some one hundred 
and fifty microns mesh size. Three outlets from the sieve 143 indicated at 
156, 157 and 158 thus provide over-tailings, semolina, and flour 
respectively. 
The flour from the outlet 158 passes to an outlet line 159 from the 
assembly. The over-tailings from the outlet 156 pass on to the next break 
rolls 141. The semolina from the outlet 157 passes to the purifier 152 in 
which clean semolina or partly ground flour is extracted from the outlet 
160 whereas bran with remaining attached endosperm is separated and leaves 
by the outlet 161 to join with the over-tailings from the outlet 156 of 
the sifter 143 to pass to the break rolls 141. The clean semolina from the 
outlet 160 passes to the first set of smooth rolls 146. 
The material passing through the break rolls 141 continues to the sifter 
144 which contains a first sieve 162 of some thirty-six wires to the inch 
and a second sieve 163 of some one hundred and thirty-two microns mesh 
size, and which has an outlet for over-tailings 164, an outlet for 
semolina 165 and an outlet for flour 166. The flour from outlet 166 passes 
to an outlet 167 from the assembly while the over-tailings from the outlet 
164 pass to the last break rolls 142. The semolina from the outlet 165 
passes to a second purifier 153 which has an outlet 168 for clean semolina 
which passes to the first smooth rolls 146, and an outlet 169 for bran and 
residual endosperm which passes to the last break rolls 142. 
The material from the last break rolls 142 passes to the sifter 145 which 
has a first sieve 170 of some forty wires to the inch and a second sieve 
171 of some one hundred and thirty-two microns mesh size. The sifter 145 
has an outlet 172 for over-tailings which pass to an outlet 173 from the 
assembly which is for course bran. The sifter 145 has an outlet 174 for 
semolina which passes to the second sifter 153, and an outlet 175 for 
flour which passes to an outlet 176 from the assembly. 
The material from the smooth rolls 146 passes to a sifter 149 which has two 
sieving stages 177 operating in parallel, and having a mesh size of some 
one hundred and fifty microns. The sifter 149 has outlets 178 for 
over-tailings which pass to the second smooth rolls 147, and an outlet 179 
for flour which passes to an outlet 180 from the assembly. The sifter 149 
has a preliminary sieve 181 having some forty wires to the inch, and the 
over-tailings from that sieving stage pass to the final sieve 151. The 
over-tailings from the sieve 181 will be largely bran, but will include 
some entrained flour which is separated in the final sifter 151. 
The material from the second smooth rolls 147 passes to the sifter 150 
which has two sieves 182 of some one hundred and thirty-two microns mesh 
size operating in parallel to produce over-tailings at an outlet 183 which 
pass to the last smooth rolls 148, and flour at an outlet 184 which passes 
to an outlet 185 from the assembly. The sifter 150 also has a preliminary 
sieve 186 of some fifty wires to the inch the over-tailings of which pass 
in a similar fashion to the final sifter 151. 
The material leaving the final smooth rolls 148 passes to the sieve 151 
which has two sieves 187 operating in parallel, each of some one hundred 
and thirty-two microns mesh size. The over-tailings from these sieves 
leave by an outlet 188 to pass to an outlet 189 from the assembly which is 
for fine bran. Flour leaves the sifter 151 by an outlet 190 to pass to an 
outlet 191 from the assembly for flour. 
Thus it can be seen that the material entering the first break rolls 140 is 
progressively broken down sifted and purified to produce three grades of 
flour on the outlets 159, 167, 176, 180, 185 and 191 which are labelled in 
FIG. 5 as B1, B2, B3, C1, C2, C3 respectively and the bran is separated to 
leave through outlets 173 and 189. It must be appreciated that FIG. 5 and 
the description thereto is directed to a simplified example of such an 
arrangement, and the number of roller mills, sifters and purifiers which 
are provided in an actual installation is chosen in dependence upon the 
type of material to be handled by a given plant, and the quantities of 
that material and the product to be produced. Thus FIG. 3 is a schematic 
representation of a large plant having up to twenty roller mills indicated 
at 200, with up to twenty sifters indicated at 201 and up to ten purifiers 
indicated at 202. 
FIG. 9 shows in schematic outline the arrangement for blending the flour 
from the various outlets 159, 167, 176, 180, 185 and 191 of FIG. 5 into 
finished product. The outlets are connected to respective flow diverter 
valves 210 which are three-way control valves so that the flow of flour on 
the outlets can be directed selectively to one of three mixing conveyors 
211. Thus it can be seen that in each of the conveyors 211, by selective 
operation of the valves 210 the various grades of flour produced can be 
blended together along the three channels provided by the conveyors 211. 
The conveyors 211 are preferably of a vibratory horizontal type which 
promotes mixing of the flour therein as it passes along to one end 212 
where the finished flour product leaves the conveyor 211 to pass to a 
respective colour intensity meter 213 which is an electronic/electrical 
device arranged to give a print-out at 214 of a measure of the colour 
intensity of the finished product, and an electrical signal at 215 which 
is related to that colour intensity. The finished flour product passes 
from the meter 213 to a finished product weighing machine 216 which gives 
on the line 217 an electrical signal indicative of the weight of finished 
product passing through the weighing machine and thence to an outlet 
conduit 218 to pass to finished product storage and management. 
FIG. 4 shows the arrangement for storing and bagging the flour produced in 
the milling/separating arrangement of FIGS. 3 and 5. The finished flour of 
the three blends leaving the milling arrangement in the conduits 218 is 
elevated by a group of pneumatic elevators to be stored in selected ones 
of a group of three mixing silos 220. The various grades of flours from 
the three conduits 218, may be individually mixed by re-circulation 
through the silos 220 or those grades may be mixed together by 
re-circulation through one of the silos. Vibratory feeder devices 223 are 
provided one at the bottom of each of the silos 220 to feed flour therein 
onto a conveyor system indicated generally at 224 by which it may be 
re-circulated for mixing or carried to an elevator 225 onto a conveyor 
system 226. The conveyor system 226 is arranged so that it can carry the 
flour to the top of a series of storage silos 227 where the finished flour 
can be stored in various types and grades. 
The silos 227 are each provided with vibratory feeder devices 228 by which 
flour therein may be fed by way of a weigher 229, to a mixer 330, where 
different types of flour may be further mixed and returned to a selected 
storage silo; or passed either to temporary storage in silos 231 prior to 
passing to bagging machinery 232, or passed to temporary storage in silos 
233 for loading on bulk transport vehicles such as lorry 235. The control 
of the vibratory feeds and other conveyor elements may be directed by a 
computer device indicated schematically at 30. Additives for the flour 
such as vitamins may be stored in bins 236, and added to the mixer 230 by 
way of a weigher 234 again and on the control of the computer 30. 
Also shown in FIG. 4 is a storage silo 229 with associated equipment, 
collecting devices and elevators and feeding devices in which bran and 
other waste material from the various stages of operation of the plant, 
such as the outlets 173 and 189 in FIG. 5, are collected and stored for 
subsequent use, for instance in animal feed stuffs. 
FIGS. 10, 11, 12 and 13 show in schematic block outline an 
electrical/electronic control system for the control of the plant 
described above. The various machine elements in the plant described above 
may be arranged in conventional manner to operate under the control of 
electrical, electromagnetic and electromechanical control devices, with 
various electric motors and other actuators being used to drive the 
various machine elements and to operate various control functions on those 
machine elements. Such a control arrangement involves electrical 
interlocking to ensure safety of operation of the plant and proper 
sequence of operation of the plant in known manner per se. The 
conventional electrical control equipment and interlocking arrangements 
are indicated in FIGS. 10, 11, 12 and 13 by the reference block 14 and the 
various associated control actuators and like devices are indicated by the 
reference block 16. 
An embodiment of the control system of the invention will now be described, 
with particular reference to the control of only some parts of the plant 
discussed above, in particular the control of the assembly of roller mills 
for milling the wheat to flour (FIGS. 3 and 5). 
In this consideration the discussion will concentrate initially on one 
process parameter in the operation of the mill rolls, that is to say the 
roll gap parameter value. 
Such an assembly of mill rolls is indicated generally at block 10 in FIG. 
10 and this assembly comprises the actual machinery indicated at 12 and 
the interlocking and actuating elements discussed above associated with 
those mill rolls are indicated at 14 and 16. 
FIG. 6 shows in schematic outline a typical roller mill machine in which a 
pair of mill rolls 230 and 231 are rotatably mounted in respective 
housings 232 and 233 which are in turn mounted on a base or frame 234. The 
housing 232 is fixed on the base 234 whereas the housing 233 is pivotable 
about an axis 235 so that the roll 231 may be swung in the housing 233 
relative to the roll 232 thus to control the milling gap between them. A 
lead screw actuating device shown schematically at 236 is arranged to be 
operative between the housings 232 and 233 so that rotation of the lead 
screw 237 adjusts the separation of the housings and thus the roll gap. An 
electric servo-motor 238 with suitable reduction gearing is provided to 
drive the lead screw 237 under the control of a servo amplifier. A handle 
device 239 which may include suitable reduction gearing is also provided 
on the lead screw so that the roll gap adjustment may be made manually by 
the miller. 
A probe 240 is provided on the housing 232 to cooperate with a transducer 
241 which is mounted on the housing 233 and arranged to give an electrical 
signal which is dependent on the distance between the probe 240 and the 
transducer 241 and which is thus dependent on the gap between the rolls 
230 and 231. A servo control system including a comparator device and a 
servo amplifier indicated generally at 242 is provided to control the 
servo motor 238 in response to a comparison of the output signal from the 
transducer 241 and an electrical signal indicative of a desired roll gap 
value provided on an input line 53, to produce an error signal which is 
amplified to control the servo motor 238 in known manner per se. Thus the 
roll gap may be set by the servo motor to a value in accordance with any 
desired value signal on the line 53 and maintained at that value. A switch 
26 is provided between the servo motor 238 and the control amplifier 242 
so that the servo motor may be disconnected and the lead screw operated 
manually by the handle device 239. 
Thus in this typical machine element there is provided a first level of 
control that is to say manual control by the handle 239, and a second 
level of control that is to say automatic control by the servo motor 238 
to maintain the roll gap to a value demanded by the signal on the line 53. 
In the event of failure of the servo control system for any cause, or if 
otherwise desired, the switch 26 may be opened and control can revert from 
the second level of automatic control to the first level of manual 
control. 
Each of the roller mills of FIGS. 3 and 5 may be equipped in the fashion 
discussed with reference to FIG. 6 although in some instances it may be 
that only selected ones of the roll pairs are so arranged particularly the 
earlier roll pairs such as 200A, B, C, K, P and S, the remainder being 
only manually controlled and adjusted by the miller. 
The mill rolls of FIGS. 3 and 5 which may be servo controlled are examples 
of process elements in the mill which may be considered as being situated 
in process zones indicated at 51 through to 51N in FIG. 11. The associated 
servo control amplifiers 242 are examples of control units indicated at 50 
through to 50N. A line 53 to each control unit 50 is connected to an 
associated switch 27 by which it may be selectively connected to a device 
52 by which an electrical value such as voltage may be manually set to 
give a set value representative of the desired roll gap parameter value, 
or to a line leading to a control computer device 30 which is arranged to 
provide an electrical signal corresponding to the desired roll gap 
parameter value. 
Thus by means of the switch 27, the control of each process zone, of which 
the roller mill is an example, can be switched from the second level of 
control discussed above in which the desired roll gap value is determined 
by the manual setting of the device 52, to a third level of automatic 
control in which the roll gap value is determined by the computer device 
30 in accordance with a programme operative in that computer device. In 
the event of failure of the computer device the switch 27 can be operated 
so that the setting control of the roll gap reverts from the third level 
of automatic control, back to the second level of manual setting of the 
automatic control given by the servo system. 
It will be seen that each roller mill or other process zone may be 
similarly provided with such second and third level control and that in 
the event of failure of the computer device 30 they can all be reverted on 
operation of the switches 27 to the second level of control, whereas in 
the event of failure the servo system in any one of the process zones, 
that process zone can revert on operation of the associated switch 26 to 
the first level of manual control, without affecting the third level 
control of the remaining process zones by the computer device 30. 
The computer device 30 comprises two basic parts. The first is a programmed 
processor 40 with associated control and access key-board and display 
devices for use by the miller, and the second is a storage or memory 
device 42 in which the various desired values of operating parameters at 
different process zones of the plant, in the specific example discussed 
above the roll gap, are stored. Thus from previous experience, a 
tabulation of parameter values for all the process zones under the control 
of the computer device 30, which are applicable to a given milling 
operation for a given wheat or other material to be milled, may be 
pre-stored in the memory 42. The miller may by entry on the key-board of 
the processor 40 select a pattern of parameter values, such as the roll 
gap values discussed above, applicable to the circumstances which he is 
faced with in operation of the plant and the very nature of the plant, so 
that the computer device 30 may automatically under the third level of 
control set the various process elements in the process zones to operate 
at various pre-stored parameter values and these values will be maintained 
at the desired values by the associated servo systems. 
The pre-stored parameter values may be up-dated at any time by the miller. 
To achieve this the signals corresponding to the actual values of 
parameter values, such as the measured roll gap appearing on the lines 52 
are connected by lines S1 to the computer device 30. Thus if the miller 
manually adjusts any particular parameter value such as a roll gap while 
the process element is switched to the first level of control by means of 
its associated switch 26, to improve the performance of the plant at any 
given time, that new value can be substituted or stored separately in the 
memory 42 by appropriate access and entry through the processor 40. 
Similarly, if the miller switches any process zone to second level control 
by the associated switch 27, he can adjust the parameter value by means of 
the associated set value device 52 and again the new value can be stored. 
The processor 40 may be provided by sensing means indicated at 45, with 
signals conveying information as to various ambient conditions such as 
ambient temperature and humidity, the measured moisture content of wheat 
to be milled and flow properties of wheat to be milled, and the processor 
can be programmed to modify the desired parameter values set up in the 
various process zones either by computing to modify the values taken from 
the memory 42 in the initial setting up of the machine for the particular 
material to be milled, or by modifying the addresses from which the 
processor 40 selects the particular values and thus to select different 
pre-stored values derived from experience. 
Similarly the processor 40 may be provided with information as to the 
conditions at each particular roller mill such as roll temperature as 
sensed by sensor 243 (FIG. 6), temperature of product and mill roll 
pressure as sensed by sensor 244 (FIG. 6), power consumption, roll speeds 
both relative and absolute, or conditions at other process zones and it 
can be programmed to modify the roll gap value demanded for each 
particular mill roll pair to compensate for any distortions which these 
factors may have. 
While the above discussion has been with regard to controlling the mill 
roll gap, it would be appreciated that mill roll pressure could equally be 
measured by a transducer similarly arranged to that indicated at 408, and 
the control system arranged to operate to control the mill roll pressure. 
Again if desired, the operating parameter of which the actual value is 
measured and compared with a desired value signal need not be the 
parameter which is directly varied by the servo motor or system. Thus roll 
pressure might be the parameter measured and compared while the servo 
controls the roll gap resulting in a related and simultaneous variation in 
roll pressure. 
The miller in control of the milling plant is indicated in FIGS. 10, 11, 12 
and 13 at M and dotted lines are indicated at M1, M2, M3 and M4 to 
indicate channels of manual control for the miller. Lines AS, AR and AV 
indicate schematically the interaction of the conventional electrical and 
interlocking systems 14 and actuators 16 with both the computer device 30 
and the control devices or amplifiers 50 and the process elements in the 
process zones 51. 
While discussion of the control system shown in FIGS. 10 and 11 has been 
directed to the roller mills of FIGS. 3 and 5, it will be appreciated that 
the other process elements in other process zones or stages such as those 
shown in FIGS. 1, 2 and 4 may each, as applicable, be controlled by a 
similar control system under an associated computer device 30. 
The flow control devices 114, 122 and 126 in FIG. 2 are a further example 
of process elements in other process zones which may be controlled by the 
computer device 30. 
FIG. 7 shows such flow devices in a little more detail, and illustrate the 
flow devices 114 although the others operate in an exactly similar manner. 
Each flow device comprises a pivotally mounted plate 250 which is 
resiliently biased against angular deflection by the momentum of grain or 
other material falling on the plate as it flows through the device. The 
angle of deflection is converted to an electrical signal on the line 251 
by means of a suitable transducer not shown, and this electrical signal is 
compared with a desired value electrical signal on the line 53a in a 
comparator and servo amplifier indicated at 252 to provide a control 
signal on a line 253 which is operative to adjust the position of a flow 
control valve embodied in the device. Thus it can be seen that the flow is 
controlled by a servo loop to a value set by the signal on the line 53. A 
signal indicative of the actual flow value is available on the line 52a. 
Line 53a is connected to a switch 27a so that line 53a can be connected to 
a manually adjustable set value device 52a if desired. 
Thus is can be seen that the flow control device 14 can operate under the 
third level of control as the roller mill discussed above, being 
controlled by the computer device 30 in an exactly similar manner, or in 
the alternative through operation of the switch 27a, it can be reverted to 
a second level of control in which the servo loop is under the control of 
the set value device 52a. 
Again if the line 253 is provided with a switch similar to the switch 26 in 
the roller mill arrangement, and the flow control valve is provided with 
manual adjustment, it could revert to first level control. 
Another example of a process element and process zone which can be 
controlled by the computer device 30 is the arrangement at the stations 
120 and 125 in FIG. 2 for adding moisture to the wheat to be milled, this 
arrangement being illustrated in slightly more detail in FIG. 8. The grain 
to be moistened passes first through a moisture measuring device 260 which 
gives an electrical signal on the line 261 indicative of the moisture 
content of the grain. Based on the value indicated by the signal on the 
line 21, the amount of water needed to be added to the grain in the 
watering device which is indicated at 262, may be determined either 
locally in a device 263 or by the computer device 30. As a result of this 
determination, a flow rate for water flowing into the watering device 262 
can be determined having regard to the flow rate of grain through the 
device, and this flow rate is controlled by a servo controlled valve 264 
which is under the control of a servo amplifier control device 265. The 
device 265 is provided with an actual flow rate signal on the line 266 
from a transducer within the valve 264 and this is available to the 
computer device 30 on the line 52b. A desired flow rate for the water is 
fed to the device 265 on the line 53b which can derive a value either from 
the computer device 30, or by operation of the switch 27b from the 
manually adjustable set value device 52b. Again the valve 264 may be 
manually adjustable, and a switch may be provided in the servo control 
line 267 between it and the control device 265. Thus it can be seen that 
the flow of water to the watering device can be operated under the so 
called first level of control or manual adjustment, or under second level 
of control by means of the set value device 52b , or under the third level 
of control by the computer device 30. Further the computer device 30 can 
be programmed to calculate appropriate amounts of water to be added having 
regard to the type of grain, the circumstances of the process and other 
ambient conditions such as temperature and humidity, etc., and on the 
basis of information provided to it by the device 260 and other sensors, 
it can provide a calculation of the time that the grain should rest in the 
silos 121 for the water added at this stage to be absorbed into the grain. 
The blending arrangement of FIG. 9 is another example of a process zone 
which can be under the control of the computer device 30. If the miller 
enters requirements of the final product into the computer device 30, and 
it is suitably programmed, having regard to the other process parameters 
throughout the milling plant, the computer device 30 can control the 
operation of the flow valves 210 in FIG. 9 to create a blend of flour in 
the selected one of the conveyors 211. A signal on the line 215 from the 
colour intensity measuring device can be fed to the computer device 30, 
and by suitable programming, the computer device 30 can modify the 
operation of the valves 210 from a pre-stored or pre-set pattern to 
achieve a desired colour intensity value having regard to the product 
required and information entered to the computer by the miller. In a 
further arrangement the signals on the lines 215 may be fed to a servo 
amplifier device 219, where they are compared with a respective desired 
value signal derived from the computer device 30 (or by means of a switch 
device not shown with a manually set desired value) and the amplifier 
device 219 is arranged to control the valves 210 to achieve the desired 
colour intensity value. 
While the above discussion has been directed more or less to the use of one 
computer device 30, it will be appreciated that various of the process 
zones may be controlled by separate computer devices such as that 
indicated at 30, for instance the zones arising in FIGS. 1, 2, 3 and 4 may 
be controlled by respective computer devices 30. 
FIGS. 12 and 13 show in schematic outline two versions of a fourth level of 
control in which such a series of control computer devices 30 may be 
connected to be under the direction of a main computer device 60. The main 
computer device 60 may be provided with key-board entry display means and 
storage means whereby the miller may select in accordance with the 
programming of the main computer 60 various pre-stored overall operating 
schemes for the plant in accordance with the particular product which he 
has to handle at any time. The main computer 60 may be programmed to take 
care of the overall timing of the operation of the plant bearing in mind 
the various sequencing and delays for the product through various stages 
of the plant, and may take over the overall management of the plant on a 
week to week or month to month basis according to the predicted output 
requirements for the plant and expected intakes of various types of wheat 
and other material to be milled. 
The main computer 60 may also derive information for book-keeping purposes 
from the various weighing devices through the plant and from flow 
measuring devices so that product stock control and financial and other 
management may be carried out for the whole plant by the computer device 
60. 
Again by means of switches 63 (FIG. 12) in the event of failure of the main 
computer 60, control may revert from the fourth to the third level of 
control under the individual computer devices 30. Again there can be 
interaction between the interlocking and actuating devices 14 and 16 with 
the main computer 60 and the miller. 
With suitable programming the computer devices 30 discussed above, together 
with the computer 60 if such is used, may be programmed to take care of 
the management and operation of the whole milling plant. The head miller 
will be aware of the various types of cereal such as wheat or rye in a 
flour and semolina milling plant, or maize in a maize milling plant, which 
he has in stock in the intake storage silos 108. He will be aware of the 
needs into the future of the various types of flour that the plant is 
required to produce, and past experience will enable the various operating 
parameters for the various process zones in the machine to be stored in 
the memory of the computer. Thus the miller will be in a position to enter 
data relating to the types of cereal available from storage together with 
such details for the various types of wheat which may be hard wheats, soft 
wheats or durum wheats, the data being for example in terms of ash 
content, protein content and gluten content of the wheat. He may also 
enter into the computer details of the required finished product in terms 
of the cereal blend or wheat blend in terms of the percentage quantities 
of the various types of raw cereal which should be processed and blended 
into the finished product. 
The miller can also enter into the computer data relating to the ambient 
conditions such as the moisture content of the wheat in storage, the time 
of year when the wheat was harvested in conjunction with the area from 
which the wheat has come, the time for which the wheat has been stored, 
the specific weight or density of the wheat and such other factors. 
The computer can be initially provided with data of the various process 
elements in the plant such as the type and number of roller mills to be 
used, data of the characteristics of the various other process items such 
as wetting equipment, filtering equipment, purifiers and the various 
throughput capacities of such machines. 
The computer can also be provided with target values which the miller 
wishes to achieve in the milling process, for instance the yield of white 
flour, the flour blend and quality, the brightness, the ash content, and 
baking properties. 
By suitable programming the computer devices can be arranged to work on 
such input data and select from data stored within the computer memory on 
the basis of past experience in milling the cereals in question to 
whatever final product is desired, to provide output signals to the 
various process elements in various process zones to control those process 
elements in accordance with that past experience to produce the required 
product. Such output signals, as discussed above with respect to the 
described embodiment, immediately influence the parameter which they seek 
to control since the output signals are compared at each site with signals 
representing actual values of that parameter or with signals which vary 
simultaneously with that parameter in a servo loop system. Such an 
arrangement is to be distinguished from a situation where process 
parameters are varied to produce a change in result further down the 
process stream where a measurement or assessment of that result is used as 
an input signal to the control system. 
Again as discussed above the miller can manually intervene in the second or 
first level of control in the various process zones to modify the 
operation of the plant against the operation determined by the computer so 
as to improve the operation against past experience, or against the mode 
proposed by the computer. These modified values can again as discussed be 
stored in the computer memory either as a separate group of values, or as 
a modification to the existing group of values which is being used at the 
time. 
In this way it will be seen that the experience of the head miller can be 
stored away in the computer memory in such a fashion that the computer can 
make use of that experience in setting the various process elements in the 
various process zones of the plant to mimic the miller's own manner of 
operating the plant in the light of his experience. 
It will be appreciated that the various servo systems, and indeed the 
computer devices can be provided with circuitry and where appropriate 
programming to monitor all the actual values of process parameters so that 
in the event that any of these exceed certain limits, for safety purposes 
the relevant process element can be shut down or other suitable alarm can 
be given. Again it will be appreciated that by suitable programming the 
computer or computers can be so arranged that the signal values supplied 
to the various process zones during start-up or shut down of the plant can 
be modified both as to magnitude and sequence of application to control 
safely the start-up and shut-down procedures, as well as operating in a 
steady state in a milling operation. 
FIGS. 14 and 15 illustrate schematically one possible arrangement in which 
the data relating to various process parameters may be stored in a memory 
matrix in one of the computer devices 30. 
The memory 42 is preferably organised in a matrix fashion as shown 
schematically in FIG. 15 where data is shown stored in a three-dimensional 
matrix with the various process parameter values or output values stored 
in vertical columns, with tabulations of various mixtures of cereals 
disposed in rows to the left and right as seen in various qualities of 
finished product stored into and out of the plane of the paper in FIG. 15. 
Thus the computer on being given data as to the particular mixture of 
cereals and quality of finished product, can select the appropriate 
vertical column of process parameters which will give the required result. 
In Table I below is set out a typical tabulation for mixtures, three being 
shown with various operating parameter values. The mixtures shown may be 
for instance made up with various percentages of Canadian wheat, two 
varieties of local wheat, some rye, and for instance some French wheat. 
It can be seen from the above description, that the invention, and the 
various embodiments of it, provide a computer control arrangement which 
can considerably assist the miller in setting up a milling plant to deal 
with various raw cereal materials and finished products, and control it in 
its processing of the cereal to the finished product on an automatic 
basis. 
TABLE I 
__________________________________________________________________________ 
Relationship between predetermined characteristics and 
operative parameters (control signals or storage date) 
Example: 1. 2. 3. 
__________________________________________________________________________ 
Cleaning 
Mill throughput Tonne/h 
7.0 6.5 8.0 
Mill throughput Tonne/h 
(8.5) (8.0) (12) 
Mill throughput Tonne/h 
(9.0) (9.5) (10) 
Grain mixture properties Predetermined 
Canada western % 
10 30 25 characteristics 
Inland I % 50 20 25 
Inland II % 10 10 20 
Rye % 5 5 10 
French % 25 35 20 
Grain moisture content 
Moisture content % 
16.5 16 17.2 
Moisture content % 
(16.2) 
(15.8) (17.0) 
Moisture content % 
(16.8) 
(16.5) (17.3) 
Grain mixture M 
M1 M2 M3 Tangent values 
Milling Predetermined 
Grain mixture M 
M1 M2 M3 characteristics 
Grain moisture content 
16.5 16.0 17.2 
Mill throughput 
7.0 6.5 8.0 
Roll gap B1 relative 
0.62 0.71 0.60 operative 
Roll gap B2 value 
0.44 0.47 0.48 process 
Roll gap B3 0.31 0.25 0.37 parameters 
Roll gap C1 0.151 0.172 0.142 
(control 
Roll gap C2 0.132 0.151 0.135 
signals) 
Roll gap C3 0.116 0.122 0.110 
Milled material mixture Predetermined 
Grain mixture 
M1 M2 M3 characteristics 
Mill throughput 
7 6.5 8.0 operative 
Mix valve 1 I I I process 
Mix valve 2 I II parameters 
Mix valve 3 III II II (control signals) 
Flour Quality Q 
Q1, Q2, Q3 
Q1, Q3, Q5 
Q1, Q2, Q4 
Tangent 
Flour Lightness % 
I 100 100 100 values 
II (90) 
(95) (90) 
III (70) 
(75) (70) 
Yield % 80.5 79.3 78.5 
__________________________________________________________________________