EP1740309B1 - Roller mill - Google Patents

Abstract

Disclosed is a roller mill comprising two grinding rollers (10, 12) which can be placed against each other in such a way that a roller gap (14) is formed while being drivingly coupled to each other so as to rotate at different peripheral speeds. At least one (12) of the grinding rollers is mounted so as to be movable in a tangential direction at the roller gap (14) while being elastically preloaded in said direction in a position in which the roller gap is enlarged to a predetermined size.

Description

The invention relates to a roller mill with two mutually engageable to form a nip roller grinding rollers, which are drivingly coupled together so that they rotate at different peripheral speeds.

Roller mills are used in mill operations for grinding cereals and similar products. By suitable coupling gears, which are today usually formed by toothed belts, the two grinding rollers are coupled together so that their mostly fluted peripheral surfaces move in the same direction at the nip, so that the product is transported through the nip. Not only compressive forces act on the grain grains, but also shearing and frictional forces due to the different circumferential speeds of the rolls, so that the product is not only squeezed but also crushed.

If no product is fed into the nip, the grinding rollers should be placed away from each other so that they do not rub against each other and thereby wear prematurely. To turn on and off the rollers is in one off CH664506B Known roll mills an engagement and disengagement mechanism provided by means of which one of the two rolls by hand or me by means of a pneumatic or hydraulic drive is moved radially with respect to the other roller. It is also known to couple the input and output mechanism with a drive for a feed roller, through which the product is fed into the nip. This ensures that the rollers are automatically disengaged when the feed roller is turned off and thus no product is supplied. However, if the product feed is already interrupted upstream of the feed roll, the rolls must be disengaged by hand, unless a suitable sensor for detecting product shortage is present.

The object of the invention is to provide a roller mill with a simplified input and Ausrückmechanismus.

This object is achieved on the basis of a Wahenstuhl described above according to the invention that at least one of the grinding rollers movably mounted in a direction tangential to the nip and elastically biased in that direction to a position in which the nip is increased to a predetermined extent.

The predetermined amount of the nip in the disengaged position is selected depending on the product to be ground so that the width of the nip is still slightly smaller than the average diameter of the product particles. Thus, when product is fed into the nip, due to the different peripheral speeds, frictional forces are transmitted through the product granules from one roll to another so that a tangential, counter-biasing, force acts on the movably mounted roll. This roller is adjusted by the frictional forces so that the nip further reduces itself. Since the frictional forces continue to increase as well, a self-reinforcing effect occurs, with the result that the roller engages by itself. If the product fails, the roller springs back into the disengaged position due to the elastic bias.

Thus, since the roller mill is also self-releasing in the case of product shortage, high functional reliability is achieved. Another advantage is that the automatic engagement and disengagement of the rollers no pneumatic or hydraulic power source is needed. This also avoids the risk of contamination of the ground food due to a leak in the hydraulic system.

Advantageous embodiments and further developments of the invention are specified in the subclaims.

It would be conceivable to bias the roller with the larger circumferential speed in the transport direction of the product, so that it is braked by the friction of the product particles and springs back against the transport direction. Preferably, however, the movably mounted roller is that which has the smaller peripheral speed, and is biased against the transporting direction and is engaged by the product in the transporting direction.

The indented position of the movably mounted roller is preferably limited by a stop having a predetermined breaking point. If Foreign bodies in the nip should jam, it comes to a breakage of the predetermined breaking point, so that the movably mounted roller can swing through in the transport direction and thus greater damage can be avoided.

The coupling gear for the two grinding rollers is preferably formed by a crossed, ie 8-shaped belt drive, which has the necessary flexibility for the engagement and disengagement of the rollers. This design of the coupling gear also has the advantage that in the grinding operation, the mechanical stress on the bearings of the grinding rollers is reduced, since the belt drive counteracts a separation of the two rollers. At the same time, the arrangement can be chosen so that a certain self-regulation of the roller pressure is achieved.

Particularly preferred are round belt drives whose belts each wrap around the associated pulleys several times and intermesh with one another at the intersection points. This makes it possible to transmit high torques and minimize the skew of the drive belt.

Preferably, coupling gears are provided at both axial ends of the two grinding rollers. As a result, can be achieved over the length of the nip uniform roller pressure.

While in conventional roll mills each grinding roller and the associated axle or the associated stub axle form an inseparable unit, so that the roller can withstand the high mechanical complaints, in a preferred embodiment of the invention, the grinding roller on a cylindrical roller body, which at both ends by releasable centering is completed, each carrying a stub axle. If the grinding rollers must be nachgeriffelt or resharpened, this design makes it possible to pull the two centering axially apart, so that the cylindrical roller body can be removed without the need for this, the bearings and the coupling drives must be removed. As a result, the labor and time required for a roll change is significantly reduced.

The invention also relates to a roller mill with two with the formation of a nip against each other engagable grinding rollers, the driving are coupled together so that they rotate at different peripheral speeds, wherein at least one of the grinding rollers has a cylindrical roller body, which is completed at both ends by releasable, each having a stub axle bearing centering.

The invention also relates to a roller mill with two mutually engageable to form a nip grinding rollers, which are coupled by a coupling gear together so that they rotate at different peripheral speeds, wherein the coupling gear is a crossed round belt drive, the round belt wraps around such pulleys multiple such, that the intersecting Trumms of the round belt mesh comb-shaped.

In the following an embodiment of the invention will be explained in more detail with reference to the drawing.

Fig. 1

eine schematische Stirnansicht eines erfindungsgemäßen Walzenstuhls in ausgerückter Position;

Fig. 2

den Walzenstuhl nach Figur 1 in eingerückter Position;

Fig. 3

den Walzenstuhl nach Figur 2 in einer vereinfachten Draufsicht;

Fig. 4

eine schematische Stirnansicht eines Kopplungsgetriebes;

Fig. 5

eine vergrößerte Darstellung des Kopplungsgetriebes in der Draufsicht;

Fig. 6

einen axialen Teilschnitt durch eine Mahlwalze im betriebsbereiten Zustand; und

Fig. 7

einen Teilschnitt durch die Mahlwalze im ausbaufähigen Zustand.

Show it:

Fig. 1

a schematic end view of a roll mill according to the invention in the disengaged position;

Fig. 2

after the roller chair FIG. 1 in the engaged position;

Fig. 3

after the roller chair FIG. 2 in a simplified plan view;

Fig. 4

a schematic end view of a coupling gear;

Fig. 5

an enlarged view of the coupling gear in plan view;

Fig. 6

an axial section through a grinding roller in the ready state; and

Fig. 7

a partial section through the grinding roller in expandable state.

FIG. 1 shows a roller mill with two grinding rollers, hereinafter referred to as rollers 10, 12, which together form a nip 14. The associated machine frame and drive means and the like are in FIG. 1 omitted for the sake of clarity. The roller 10 is fixedly mounted with stub axles 16 in the machine frame and is driven in a clockwise direction. The roller 12, however, is mounted with its stub axles 18 in a rocker 20, which in turn is pivotable about an axis parallel to the nip 14 and with this approximately at the same level axis 22.

By a in FIG. 1 not shown coupling mechanism, which will be described in more detail below, the roller 12 is coupled to the roller 10 so that it rotates at a slightly lower peripheral speed than the roller 10 in the counterclockwise direction. At the nip 14, therefore, the peripheral surfaces of the two grinding rollers move at slightly different speeds in the same direction so that the product fed into the nip is transported down through the nip 14.

Since the roller 12 is mounted in the rocker 20, it can move together with their stub axles 18 in an approximately vertical direction, ie in a direction parallel to an imaginary tangent, which rests in the nip on the circumference of the roller 10. FIG. 1 shows the rollers 10, 12 in the disengaged position in which the nip 14 has a predetermined width and the rollers do not touch each other. In this state, the rocker 20 is biased by a spring 24 up against a stop 26. The stop 26 is arranged so that the width of the nip 14 is slightly smaller than the average particle diameter of the product fed to the nip.

If now, as in FIG. 2 shown, the product 28 is fed from above into the nip 14, the individual product particles, such as cereal grains, are slightly squeezed in the nip. The roller 10, which rotates at a higher peripheral speed, tends to accelerate the product downwardly. The product therefore exerts a downward frictional force on the circumference of the roller 12, which rotates at a lower circumferential speed. Since the rotation of the roller 12 can not be accelerated, creates a downward force F, which acts on the swingarm 20 via the stub axles 18 and has a tendency to down to the To pivot axis 22. This pivotal movement of the rocker 20 from the in FIG. 1 However, the position shown leads to a further narrowing of the nip 14 and thus to a further increase in the frictional forces and thus the force F. In this way, the rocker 20 and the roller 12 by a self-reinforcing effect against the force of the spring 24 in the in FIG. 2 shown position driven. In this position, the nip 14 is narrowed to its working width, so that the product 28 is finely ground. The working width of the nip 14 is finely adjustable, for example by means of an integrated eccentric in the axis 22.

If the product 28 fails, the rocker 20 springs under the action of the spring 24 back into the in FIG. 1 shown position back.

In FIG. 2 is the rocker 20 to a stop 30, which is designed as a predetermined breaking point and normally prevents penetration of the rocker 20 down. Only in exceptional cases, such as when a foreign body jammed in the nip 14, there is a breakage of the predetermined breaking point, so that the stopper 30 releases the rocker 20 and this can feather down by enlarging the nip. An additional safety measure may optionally be that the stub axle 16 of the roller 10 and / or the axis 22 of the rocker 20 are resiliently mounted in horizontally movable bearing blocks, which are held by strong springs in their operating position.

The spring 24, which is shown here schematically as a helical spring, can optionally be replaced by a torsion spring, which is integrated in the axle 22.

In FIG. 3 the roller mill is shown simplified in plan view. One recognizes a machine frame with side parts 32, 34 and bearing housings 36, in which the roller 10 is mounted with its stub axles 16. The drive of the roller 10 via a motor 38 and a belt drive 40. In the side parts 32, 34 also has an eccentric shaft 42 is mounted on which the axis 22 of the rocker 20 is arranged eccentrically. With a lever 44, the eccentric shaft 42 can rotate so that adjusted by appropriate displacement of the axis 22, the working width of the nip 14 precisely can be. The axle stubs 18 of the roller 12 extend freely through openings 46 of the side parts 32, 34 and are mounted with bearing housings 48 in the rocker 20.

The stub axles 16, 18 of the rollers 10 and 12 are coupled on both sides by coupling gear 50 with each other. These coupling gear 50 are designed as a round belt drives and each have a round belt 52, the associated pulleys 54, 56 wraps around multiple 8-shaped and is held by the weight of a dancer 58 under tension. The intersecting trims of the round belt 52 engage between the pulleys 54, 56 in a comb-like manner.

Due to this structure, the coupling gears 50 are able to follow the pivotal movements of the rocker 20 during engagement and disengagement of the roller 12. The round belts 52 preferably have a certain inherent elasticity, so that the slight spacing changes between the pulleys 54 and 56 can be buffered until over the dancer 58 has been compensated. The surface of the round belt 52 preferably has a relatively high coefficient of friction, so that in combination with the multiple wrap of the pulleys results in a good power transmission. The adjusted by the weight of the dancer 58 tension of the round belt 52 may therefore be relatively low.

In FIG. 4 one of the coupling gear 50 is shown in an end view. In idling mode, ie, in the position according to FIG. 1 , the power flow from the directly driven by the motor 38 pulley 56 to the pulley 54, so that the Trumms that in FIG. 4 60, which are pulling trumms. These exert on the rocker 20 a small downward force component, which, however, does not overcome the force of the spring 24.

In the grinding operation ( FIG. 2 ), however, the roller 12 is driven by the product in the nip 14 directly through the roller 10, so that the coupling gear 50 acts as a brake. In this case, the Trumms 62 are the pulling Trumms.

When the rocker 20 upon arrival of product from the in FIG. 1 shown position in the position FIG. 2 goes over, the pulley 54 moves down so that the tension in the strand 62 increases. These trims 62 are therefore immediately able to exert a braking action on the roller 12 when the product tends to accelerate this roller. This contributes to a rapid buildup of the force F, which pivots the rocker 20 further down.

On the other hand, the trims 62 also tend to pivot the rocker 20 back up. In general, however, the torque exerted by the runners 62 on the rocker 20 is smaller than the torque resulting from the force F at the nip because the force application point of the runners 62 on the pulley 54 is closer to the axis 22 of the rocker than the nip, so that the force F acts through a larger lever arm. Only when the nip force in the nip becomes so large due to the above-described self-reinforcing effect that the roll 12 tends to rotate at the same peripheral speed as the roll 10, the tensile stress of the tufts 62 is outweighed, so that the rolling pressure in the nip is relaxed again. By this effect, the increase of the rolling pressure is limited and an overload of the stopper 30 is avoided.

If the product is ground in the nip, it tends to push the two rolls 10, 12 apart, so that correspondingly high radial forces act on the bearings of the stub axles 16, 18. However, part of these forces are absorbed by the round belts 52 of the coupling gears 50 in the construction described here, so that the stress on the bearings is reduced.

Since the coupling gears 50 are provided at both ends of the rollers 10, 12, the forces transmitted by the coupling gears to the opposite ends of the roller 12 and the rocker 20 are substantially equal to each other, so that a uniform rolling pressure over the entire length of the nip 14th is reached.

In FIG. 5 the profile of the pulleys 54, 56 is shown in more detail. The pulley 54, which is associated with the roller 12 and has the larger diameter, has grooves 64 with an approximately semi-cylindrical Profile adapted to the cross section of the round belt 52 and this gives good guidance. The pulley 56, however, has grooves 66 which are approximately offset to the grooves 64 in gap and have a greater width than this. The bottom of the grooves 66 is also conically tapered outwardly (away from the roller 10). The Trumms 60 can therefore run with relatively little skew on the inside of the respective groove 66 (above in FIG. 5 ), while the runners 62, which are the dragging runners in the grinding operation, ensure that the round belt when circulating around the pulley 56 to the outside (down in FIG. 5 ) is displaced on the conical bottom of the groove 66 and then expires on the outside of the groove 66 and enters into the groove 64 of the pulley 54 without a large change in direction. In this way it is achieved that the round belt 52 in the multiple wrapping of the pulleys 54, 56 each have only a slight skew and only a little mechanical stress.

In addition, it is ensured that the comb-shaped intermeshing Trumms 60, 62 pass without contact and without rubbing each other, although they have only a small distance from each other.

Another advantageous effect of this arrangement is that the round belt 52 is also rotated about its longitudinal axis during rotation about the pulley 56, so that it is uniformly worn over its entire circumference.

The grinding rolls 10, 12 have, as usual, on their grinding surface, i.e., their outer peripheral surface, a longitudinal, mostly slightly twisted corrugation, by which the grinding effect is improved. These grinding surfaces must be reworked from time to time and resharpened, which requires the removal of the grinding rollers from the roll mill. With reference to Figures 6 and 7, a construction of the grinding rollers will now be described, which allows a particularly simple and time-saving removal of the rollers. As an example, the roller 10 is shown as representative of both grinding rollers.

A cylindrical roller body 68, whose outer peripheral surface forms the grinding surface 70, has a planar end face 72 at both ends and an inner cone 74 at the inner peripheral edge. The roller body 68 is at both Ends completed by a centering 76. The centering disk 76 rests with its outer peripheral region on a flat annular surface 78 on the end face 72 of the roller body and has within this annular surface two annular, concentric cutouts 80, 82. These undercuts define an annular, to some extent intrinsic elastic web 84, which forms an outer cone 86 complementary to the inner cone 74.

The stub axle 16 is tubular and firmly welded to the centering disc 76. The stub axle 16 carries the pulley 56 shown here only schematically and a rolling bearing 88 which is received axially displaceable in the bearing housing 36.

The roller body 68 receives a clamping piece 90, which is held by spokes 92 coaxially in the roller body and has at each end a threaded hole 94. In each of the hollow stub axle 16, a threaded bolt 96 is inserted from the open end, which is screwed into the threaded bore 94 of the clamping piece 90. In this way, the two centering discs 76 are firmly clamped to the roller body 68. By abutment of the annular surfaces 78 on the end faces 72, an axis-parallel alignment of the stub axle 16 with respect to the roller body 68 is achieved, and the webs 84 with their outer cone 86 ensure precise centering. Since the webs 84 can yield somewhat elastically, the outer cone 86 can optionally also be made slightly spherical.

Since the stub axle 16 and the roller body 68 are clamped together axially via the clamping piece 90, the flexural rigidity of the stub axle is increased for a given cross-section.

Now, if the roller body 68 is to be replaced, so need only a few simple steps, the two threaded bolt 96 is released and unscrewed out of the threaded holes 94. Subsequently, the stub axles 16 with their respective centering disks 76 can be pulled off axially from the roller body 68, so that the webs 84 are released from the inner cone 74, as in FIG FIG. 7 is shown. The axially fixed seated on the stub axle 16 bearings 88 can thereby move axially in the bearing housings 36.

In the in FIG. 7 shown state, the roller body 68 can now be removed in the radial direction from the space between the centering discs 76 and replaced by a freshly processed roller body. The latter can then just as easily be reinstalled by reversing the processes described above and clamped with the aid of the threaded bolts 96, whereby it is precisely aligned and centered.

Claims (18)

1. A roll mill having two grinding rolls (10, 12) which are adjustable in relation to one another in order to form a roll gap (14) and which are drivably coupled together so that they rotate with different circumferential speeds, characterised in that at least one (12) of the grinding rolls is mounted so as to be movable in a tangential direction at the roll gap (14) and in this direction is resiliently biased into a position in which the roll gap is enlarged to a predetermined size.
2. A roll mill according to claim 1, characterised in that the movably mounted grinding roll (12) is the grinding roll having the lower circumferential speed and in that it is biased in the direction counter to the direction of rotation of this roll at the roll gap (14).
3. A roll mill according to claim 1 or 2, characterised in that the movably mounted grinding roll (12) is rotatably mounted in a rocker (20) which is pivotable about an axis (22) lying approximately in one plane with the rotation axes of the two grinding rolls (10, 12).
4. A roll mill according to any one of the preceding claims, characterised in that the movement of the movably mounted grinding roll (12) in the direction counter to the direction of the bias is limited by a stop (30).
5. A roll mill according to claim 4, characterised in that the stop (30) is removable by means of a predetermined breaking point.
6. A roll mill according to any one of the preceding claims, characterised in that a coupling transmission (50) for drivably coupling the two grinding rolls (10, 12) is formed as a crossed belt drive.
7. A roll mill according to claim 6, characterised in that the coupling transmission (50) is a round belt drive, the round belt (52) of which is repeatedly looped around associated belt pulleys (54, 56) so that the crossing sides (60, 62) of the round belt intermesh.
8. A roll mill according to claim 7, characterised in that the round belt (52) is held under tension by a dancer (58).
9. A roll mill according to claim 7 or 8, characterised in that at least one (56) of the belt pulleys has grooves (66), the width of which is greater than the cross-section of the round belt (52) and the base of which is conically tapered towards one side.
10. A roll mill according to any one of the preceding claims, characterised in that the grinding rolls (10, 12) are coupled at both ends by a respective coupling transmission (50).
11. A roll mill according to any one of the preceding claims, characterised in that at least one of the grinding rolls (10, 12) has a cylindrical roll body (68) which is closed at both ends by detachable centring discs (76) each carrying an axle stub (16).
12. A roll mill according to claim 11, characterised in that the axle stubs (16) are axially displaceably held in associated bearing housings (36).
13. A roll mill according to claims 6 and 12, characterised in that the belt pulleys (54, 56) of the coupling transmissions (50) are each arranged directly on the axle stubs (16).
14. A roll mill according to any one of claims 11 to 13, characterised in that the centring discs (76) each have an annular surface (78) resting against a flat end face (72) of the roll body (68), and inside the annular surface (78) have an outer cone (86) which engages in a complementary inner cone (74) of the roll body (68).
15. A roll mill according to claim 14, characterised in that the outer cone (86) is formed on an intrinsically resilient intermediate piece (84).
16. A roll mill according to any one of claims 11 to 15, characterised in that the centring discs (76) and the roll body (68) can be axially secured together.
17. A roll mill according to claim 16, characterised in that threaded members (96) for securing the centring discs (76) and the roll body (68) are coaxially inserted into the tubular axle stubs (16) from opposite ends and are secured together inside the roll body (68) by thread engagement.
18. A roll mill according to claim 17, characterised in that the threaded members are threaded bolts (96) and in that a clamping piece (90) is held coaxially in the roll body (68) and at both ends has threaded bores (94) into which the threaded bolts (96) are screwed.

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