Grinding gap adjusting device for milling roller mills

A grinding clearance adjustment device for milling roller frames is disclosed, in which a casing contains two grinding rollers, one of which is constructed as a pivotable loose roller. Adjustment members, for the rollers are provided, as well as a device for the automatic setting of the grinding clearance by means of a remotely controllable drive motor, the latter being coupled to the adjustment members via transmission means. The motor operates through a clutch. In the preferred embodiment, the adjustment members are constructed as a first closed standard component, which has a lever-transmitted setting part with a longer and a shorter lever arm and which is laterally positioned in the vicinity of the grinding rollers. The drive motor and clutch are constructed as a second closed standard component, which is spaced from the first standard component, and the adjustment forces derived from the drive motor are coupled to the longer lever arm of setting part. In addition, the adjustment members are provided with a manual setting means which can be utilized simultaneously with the automatic, motor adjustment.

TECHNICAL FIELD 
The invention relates to a grinding gap adjusting device for milling roller 
mills, in which a casing contains two grinding rollers, whereof one is 
constructed as a pivotable loose roller, together with adjusting members 
and a device for the automatic setting of the grinding gap by means of a 
remotely controllable drive motor, the latter being coupled to the 
adjusting members by transmission means, while a clutch is interposed. 
PRIOR ART 
Special account must be taken of three operating states in grinding gap 
adjusting devices for milling roller mills. If a large foreign body, such 
as a screw, enters the grinding gap then the shock pressure which occurs 
must be immediately absorbed, this generally being carried out with a 
mechanical overload protection device for the pair of rollers. 
The grinding rollers, particularly in the case of grooved rollers, must 
automatically pass into a disengaged position when there is no material to 
be ground, because otherwise the two grinding rollers would rub against 
one another as a result of their different speeds and would damage one 
another. 
Finally, for normal milling or grinding operation, the spacing of the 
grinding rollers (grinding gap) must be very accurately setable. 
Experience has shown that for the setting of the grinding gap, a mechanical 
grinding gap setting device is superior to other, e.g. corresponding 
hydraulic setting devices. The grinding gap adjustment milling roller mill 
is a very complex overall process, although the actual adjustment process 
per se is simple and this is apparent from the statements made in European 
Patent 13 023. Thus, it has hitherto not been possible e.g. to 
satisfactorally determine definite parameters (such as the grinding 
pressure or motor power consumption), which would be suitable as starting 
parameters for the automatic setting of the grinding gap (roller gap) in 
accordance with the particular requirements. For economic reasons, it was 
necessary to numerically limit the influencing parameters detectable and 
required for a regulation. The control and regulating processes perform 
automatic regulation operations without any direct view from the outside 
and normally exclude manual actions. If a milling plant is to be 
controlled in an optimum manner, for all unforeseeable disturbance 
variables, which can have widely differing causes, the human being 
ultimately remains an important part of the plant control. Thus, if there 
is a need for both an automatic regulation and a manual action, it is 
necessary to accept very complicated equipment. 
DISCLOSURE OF THE INVENTION 
On the basis of this, the problem of the present invention is to provide a 
particularly favourable solution for an appropriate automation of the 
grinding gap while maintaining the possibility of manual action in 
connection with milling roller mills. 
According to the invention this is achieved in the case of a device of the 
aforementioned type in that the adjusting members form a first closed 
standard component having a lever-transmitted part with a longer and a 
shorter lever arm and laterally arranged in the vicinity of the grinding 
rollers, that the drive motor and clutch are constructed as a second 
standard component, installed in spaced manner from the first standard 
component, the adjusting forces derived from the drive motor acting on the 
drive motor acting on the longer lever arm of the setting part and that 
the adjusting members are additionally provided with a manual setting 
means. 
Whereas the hitherto known solutions for automatically operable milling 
roller mills it has been assumed that, also from the constructional 
standpoint, the automatic means must be given priority over the means for 
a manual action, in such known solutions generally a geared motor has been 
directly connected to tension members for setting the grinding rollers (cf 
e.g. FIG. 6 of European Patent 13 023). However, in the solution of the 
present invention the traditional setting means have been combined as an 
independent, closed subassembly and it was very soon found that the path 
taken by the invention was extremely advantageous and led to a surprising 
number of advantages. The inventive solution has revealed that the 
replacement of the hitherto known manual setting by an automatic setting 
means need not lead to a new type of grinding, e.g. by a "harder" or 
"softer" control of the rollers and the like. In fact the invention 
retains the stability of the setting of the grinding rollers. 
Thus, the device according to the invention represents an addition to a 
rolling mill, which can be fitted at any subsequent time, e.g. if only 
part of the frame of a roller mill is to be provided with an automatic 
means. As a milling roller mill already constitutes a very compact machine 
for the type of operation (processing of flour-type products), 
accessibility to the remaining components is not made more difficult by 
the inventive arrangement of a second subassembly at a distance from the 
grinding roller pair. If necessary, the rolling mill can be operated 
without the automatic means via the manual setting of the adjusting 
members. 
In a very advantageous embodiment of the invention, the clutch is 
constructed as an adjustable slip clutch, which permits an automatic 
grinding roller adjustment means on the basis of given setpoints or 
desired values, e.g. the clearance between the grinding rollers. The 
setting can take place on the basis of a predetermined program or setpoint 
diagram. As faults and disturbances are unavoidable under practical 
conditions, the slip clutch limits incorrect action. It also makes it 
possible to prevent the setting of e.g. the grinding gap, or pressure to 
undesirably high values, so that the rolling mill or roller bearings could 
be destroyed. 
It has proved very advantageous if a first standard component is provided 
at both bearing ends of the grinding rollers, together with a second 
standard component common to both bearing ends and further means for the 
automatic parallel adjustment of the loose roller, the first standard 
component being controllable by the second standard component via a 
slipless transmission. This permits a particularly simple, subsequent 
attachment to existing roller mills which are already in operation, so 
that it is possible to achieve the greater economics inherent therein on 
all existing milling roller mills and the latter can also be subsequently 
equipped for further automation, without it being necessary to provide new 
roller mills. 
A further advantageous development of the invention with respect to ease of 
operation comprises the drive motor driving an adjusting spindle by the 
transmission means, such as a chain, said spindle engaging on the longer 
lever arm of the setting part which, in particularly preferred manner, is 
more than three times as long as the shorter lever arm and to which is 
fitted a hand adjustment wheel, which is preferably provided with an 
indicating device in the form of an indicator clock. Preferably the hand 
adjustment wheel is provided with an indicating device or a position 
indicator which is once again preferably constructed in the form of an 
indicator clock, which as a dial gauge can be directly constructionally 
integrated into the hand wheel. Thus, for each automatic correction, the 
hand wheel is correspondingly moved along and the particular position is 
indicated thereon. It is particularly advantageous if the second standard 
component is positioned in the vicinity of the roller mill base. 
A further advantageous development of the grinding clearance adjustment 
device according to the invention comprises providing a position 
indicator, which is controllable by the transmission means or by the 
adjustment members. Preferably such a position indicator is constituted by 
a potentiometer. Particularly advantageously the transmission means 
transmit the adjusting force by a slipless transmission, the position 
indicator being coupled directly via a chain either to the slipless 
transmission or to the driven side of the clutch. The slipless 
transmission is preferably constituted by a toothed belt, a chain or 
similar means, which simultaneously move the position indicator. 
The position indicator, which is preferably connected to a suitable 
position indication means, at all times permits an indication and a back 
indication of the precise position of both grinding rollers, particularly 
if the position indicator is fitted to the driven side of the clutch, i.e. 
in a direct forced connection with the adjustment members. In practice, it 
has proved particularly appropriate for the purpose of controlling the 
drive motor by the operator, for the position indicator to have a digital 
display and manual input keys on the roller mill casing. This can lead to 
an appropriate control of the drive motor by the operator, e.g. the senior 
miller, if corresponding desired roller position values have been reached. 
A further advantageous development of the grinding gap adjustment device 
according to the invention comprise providing a digital display and manual 
input keys on the roller mill casing for the control of the drive motor. 
For the remote control of the drive motor a program-controlled computer is 
preferably provided and on this preferably superimposed a common computer 
connected upstream of the computers of several roller mills. However, in 
certain cases it can be very advantageous not to have an upstream 
connection or arrangement and instead to associate a common computer with 
one or more setpoint stores with a plurality of roller mills. These 
measures permit a direct control of all the roller mills in accordance 
with predetermined setpoint diagrams, i.e. there is a true control 
process. 
Over and beyond the control process, the grinding clearance adjustment 
device can also form part of a regulating mechanism and the grinding 
result or the, particle fineness resulting from the grinding gap width can 
be chosen as the quantity to be regulated and controlled in accordance 
with the grinding gap. 
Preferably the output signals of a grinding pressure measuring device 
and/or a pressure threshold switch associated with the grinding rollers 
can be applied to the input of said computer. As desired, either a 
pressure threshold switch and/or a position threshold switch can be used 
for overload protection purposes in those fault cases caused by incorrect 
control instructions for the setting of the grinding clearance. Preferably 
the output signals of a power requirement measuring device and/or a power 
consumption threshold switch associated with the grinding rollers are 
applied to the computer input. However, the output signals of a roller 
clearance measuring device and/or a clearance threshold switch associated 
with the grinding rollers can also be applied to the computer input. It is 
also advantageous if a safety element setable to selectable limit values 
for the grinding pressure or power requirement or roller gap is 
simultaneously effectively provided both for the motor and the manual 
setting mechanism.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 shows a milling roller mill with adjustment members as a subassembly 
1 and with a controllable adjustment drive as a second subassembly 2. Two 
grinding rollers 41, 42 are supported on a common support 3. Loose roller 
42 is pivotably fixed to a fixed eccentric stud 4, the engagement and 
disengagement being controlled by a lever 5 and a disengaging cylinder 6. 
As a result of the pivoting movement of lever 5, the eccentric stud 4 is 
rotated and leads to a horizontal displacement of the lower part of the 
pivotable bearing box 7, so that a rough setting of the clearance of the 
two grinding rollers is possible. However, this device would be too 
inaccurate for a precise setting and it is consequently only used for 
bringing the grinding rollers 41, 42 into an engaged or disengaged 
position or into two fixed positions. The actual fine setting is brought 
about by means of an adjusting spindle 8, which by rotation directly moves 
a setting arm 9 about a fixed pivot bearing 10. The upper, shorter lever 
arm of setting arm 9 is non-positively connected with the pivotable 
bearing box 7 via a tie rod 11. Force transmission takes place by means of 
cutting edges, which on one side form part of a spring overload protection 
device 12. On the other side an adjustable retaining button 13 and a 
pressure meter 14 with pressure indicator 15 are provided on tie rod 11. 
To permit a parallel setting of the grinding rollers when carrying out 
servicing, it is possible to carry out a correction on the necessary side 
by means of setscrews 43, 44. The adjusting spindle 8 is held fixed by 
bearing 10' and can now be operated by a hand wheel 16, which has a 
directly installed indicator clock 17 (FIG. 2), or by motor means, namely 
a transmission chain 18, as well as a geared or drive motor 19. Drive 
motor 19 is fixed to the roller mill 26 and is directly connected with the 
transmission chain 18 or adjustment spindle 8 by means of a slip clutch 20 
and a sprocket 21. 
However, the adjustment motor 19 and slip clutch 20 could also be fixed to 
any other appropriate point, e.g. to the outside of the rolling mill. The 
free inner space of the column base is, however, the most suitable point 
for the location of the adjustment drive with a view to optimising the 
overall conditions. Slip clutch 20 can be constituted by any suitable slip 
clutch, which transmits minimum torques and which at a given preselectable 
torque can release by slipping the forced connection or no longer 
transmits the adjustment force of the motor means extending beyond a given 
torque. However, the minimum torque must only be sufficiently large that 
it can be overcome with the hand wheel 16 and consequently a grinding gap 
setting can be brought about without any manual rotation of geared motor 
19. 
A position indicator 22 is directly connected with transmission chain 18 
via a chain 23 and a sprocket 24, so that any movement of transmission 
chain 19 is recorded in position indicator 23 and is passed on to the 
desired points. As can be gathered from FIGS. 1 and 2, very few individual 
components are required for the motor adjustment means. The major 
component, the drive motor 19 and clutch 20 are preferably arranged in the 
vicinity of a lower, free recess in the roller mill stand 26, so that it 
is possible at any time to attach the second subassembly to all the 
automatic grinding clearance setting means to correspondingly constructed, 
older milling roller mills. If suitably designed, the subassembly can be 
constructed in the form of a closed standard component, so that the 
subsequent installation is further facilitated and accelerated. As milling 
roller mills are generally constructed in duplicated form, this is 
indicated in FIG. 1 by a dot-dash axis 27. Each roller pair of the two 
mill halves may or may not be equipped with such automatic adjustment 
means. 
In the case of the embodiment shown in FIG. 2, there is a subassembly 1 and 
2 on either bearing end. It is also possible to place on either end a hand 
wheel 16 with an integrated indicator clock 17. Both bearing ends or sides 
are in each case provided with a drive motor 19, a position indicator 22 
and a transmission chain 18. Thus, on both bearing sides the roller 
clearance can be controlled by means of motor 19 and chain 18 or can be 
set by the operator using hand wheel 16. Indicator clock 17 could be 
replaced by a digital display 45 and manual input keys 46. It would also 
be conceivable that for a certain starting period hand wheel 16 and manual 
input keys 45 could simultaneously be provided for acquainting the 
operating personnel. It is also possible to provide the digital display 45 
or indicator clock 17 either alone or simultaneously, which may be 
advantageous in certain cases. 
FIG. 3 is an alternative to the embodiment of FIG. 2 and in it only hand 
wheel 16 and indicator clock 17 are provided in duplicated form to the 
left and right for an individual correction. In a further simplification, 
there need only be a single hand wheel 16 in place of the left and 
right-hand hand wheels. A necessary correction on one side can take place 
by means of nuts 43, 44 (FIG. 1), so that only one hand wheel 16 with 
indicator clock 17 is required e.g. in the case of large mills where there 
is rarely a change to the product mixture or which always have the same 
end products. The setting of the grinding clearance also takes place by 
means of a drive motor 19 in the case of FIG. 3, the adjustment path 
transferred via a chain 39 or 40 to the other bearing side. Using the 
corresponding automatic means, this permits a parallel adjustment of the 
grinding rollers. 
FIG. 1 shows a drive 28 for grinding rollers 41 and 42 (shown in dot-dash 
line manner). An electrical power requirement measuring and indicating 
device 29 can also be provided in the drive system. Thus, e.g. the 
electrical power consumption can be limited to upper and lower values and 
on exceeding the preselected range, e.g. the grinding rollers are 
disengaged. 
Another possibility consists of the effective spacing of the bearing box 
parts being determined by means of a roller clearance measuring and 
indicating device 30 (cf FIG. 1). Particularly when using grooved rollers, 
the roller clearance monitoring means very simply prevents incorrect 
instructions or commands which would lead to the mechanical destruction of 
at least certain parts of the rolling mill. 
FIG. 4 once again shows such a device diagrammatically, supplemented by 
further control linkages. All the signals of a roller mill are coordinated 
and controlled by means of a computer 31 in FIG. 4, whereby said computer 
can poll the necessary desired or set values from a central computer 32 
with store 33. In FIG. 4, position indicator 22 is also equipped with a 
position threshold switch 34, which can be set to desired thresholds, so 
as to prevent an incorrect setting by the automatic means. In the 
represented position, the position threshold switch 34 has the advantage 
that it is also possible to prevent an incorrect manual setting because 
the hand wheel and also the automatic adjustment means lead to a 
corresponding path displacement of transmission chain 18 and chain 23. In 
the same way as adjustment motor 19, position indicator 22 can be 
connected to an input--output device 35, which receives or supplies 
corresponding signals with respect to computer 31, corresponding to the 
digital display 45 and manual input keys 46 in FIG. 2. In the same sense, 
the pressure measuring and indicating device 14, 15 can be connected to 
computer 31. As a function of the degree of development of a rolling mill, 
it is possible to provide one more protection means on the same mill. If 
e.g. grooved rollers are fitted, grinding pressure monitoring is less 
appropriate, but monitoring the clearance of the grinding rollers via 
position indicator 22 or spacing measuring means 36 is advantageous. The 
opposite conditions prevail in the case of smooth rollers, where pressure 
monitoring leads to great advantages. The computer 37 and signal lines 38 
in FIG. 4 indicate that the computer 32 with its memory or store 33 can 
control a plurality and possibly even all the roller mills in a mill and 
can, if necessary, coordinate regulating functions. 
It has proved particularly advantageous if the digital display 45 provides 
readings in the same manner of value representation as the hand wheel 
indication, e.g. values according to a time representation on a clock 
(e.g. hand wheel is at position 15.30 hours and the digital display also 
shows 15.30 hours). 
A further important advantage is that the impiricle values of non-automated 
or non-remotely controllable roller mills are useable in compared form for 
producing or improving corresponding control programs.