WO2005102531A1

WO2005102531A1 - Roller mill

Info

Publication number: WO2005102531A1
Application number: PCT/EP2005/004112
Authority: WO
Inventors: Reinhard Rüter
Original assignee: Reinhard Rüter Maschinenbau
Priority date: 2004-04-22
Filing date: 2005-04-18
Publication date: 2005-11-03
Also published as: EP1740309B1; DE502005005621D1; ATE410231T1; EP1740309A1

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

ROLLING CHAIR

The invention relates to a roller mill with two grinding rollers which can be adjusted relative to one another to form a roller gap and which are coupled to one another in terms of drive in such a way that they rotate at different peripheral speeds.

Roller mills are used in grinding plants to grind grain and comparable products. By means of suitable coupling gears, which are mostly formed today by toothed belts, the two grinding rollers are coupled to one another in such a way that their mostly corrugated circumferential 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 cereal grains, but also shear and friction forces due to the different circumferential speeds of the rollers, so that the product is not only crushed but also ground.

If no product is fed into the nip, the grinding rollers should be set apart so that they do not rub against each other and therefore wear out prematurely. In known roller mills, an engagement and disengagement mechanism is provided for turning the rollers on and off, with which one of the two rollers is moved radially with respect to the other roller by hand or with the aid of a pneumatic or hydraulic drive. It is also known to couple the engaging and disengaging mechanism with a drive for a feed roller, via which the product is fed into the nip. This ensures that the rollers are automatically disengaged when the feed roller is switched off and therefore no product is fed. However, if the product supply is already interrupted upstream of the feed roller, the rollers must be disengaged by hand, unless a suitable sensor is available to detect the lack of product.

The object of the invention is to provide a roller mill with a simplified engagement and disengagement mechanism.

This object is achieved according to the invention in that at least one of the grinding rollers is movable in a direction tangential to the roller gap. stored and is elastically biased in this direction in a position in which the nip is enlarged to a predetermined size.

The predetermined Maj3 of the nip in the disengaged position is chosen 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. When product is fed into the nip, frictional forces are thus transmitted from one roller to the other by the product grains due to the different peripheral speeds, so that a tangential force acting against the pretension acts on the movably mounted roller. This roller is adjusted by the frictional forces so that the roller gap shrinks further by itself. Since this also increases the frictional forces, there is a self-reinforcing effect, with the result that the roller engages itself due to the product. If the product does not appear, the roller springs back into the disengaged position due to the elastic pretension.

Since the waltz chair is also self-releasing in the event of a product shortage, a high level of functional reliability is achieved. Another advantage is that no pneumatic or hydraulic drive source is required for the automatic engagement and disengagement of the rollers. This also avoids the risk that the ground food will be contaminated by a leak in the hydraulic system.

Advantageous refinements and developments of the invention are specified in the subclaims.

It would be conceivable to pretension the roller with the greater peripheral 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. However, the movably mounted roller is preferably that which has the lower peripheral speed, and is biased against the transport direction and is indented by the product in the transport direction.

The engaged position of the movably mounted roller is preferably limited by a stop which has a predetermined breaking point. If If foreign bodies get jammed in the roller gap, the predetermined breaking point breaks, so that the movably mounted roller can swing through in the direction of transport and thus major damage can be avoided.

The coupling mechanism 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 the mechanical stress on the bearings of the grinding rollers is reduced in the grinding operation, since the belt drive counteracts the moving apart 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.

Circular belt drives are particularly preferred, the belts of which loop around the associated pulleys several times and mesh with one another at the intersection points. This makes it possible to transmit high torques and to minimize the skewing of the drive belts.

Coupling gears are preferably provided on both axial ends of the two grinding rollers. In this way, a uniform roller pressure can be achieved over the length of the nip.

While in conventional roller mills each grinding roller and the associated axis or the associated axle stub form an inseparable unit so that the roller can withstand the high mechanical complaints, in a preferred embodiment of the invention the grinding roller has a cylindrical roller body which is detachable on both ends by centering disks is completed, each carry a stub axle. If the grinding rollers have to be re-grooved or re-sharpened, this design enables the two centering disks to be pulled apart axially so that the cylindrical roller body can be removed without having to dismantle the bearings and the coupling drives. This considerably reduces the work and time required to change the roll.

The invention also relates to a roller mill with two grinding rollers which can be adjusted relative to one another to form a roller gap and which drive are coupled so that they with different

Rotate circumferential speeds, in which at least one of the grinding rollers has a cylindrical roller body which is closed at both ends by releasable centering disks, each bearing an axle stub.

The invention also relates to a roller mill with two grinding rollers which can be adjusted relative to one another to form a roller gap and which are coupled to one another by a coupling gear in such a way that they rotate at different circumferential speeds, in which the coupling gear is a crossed circular belt drive, the round belt of which loops around associated pulleys several times, that the intersecting strands of the round belt intermesh in a comb-like manner.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing.

Show it:

1 shows a schematic end view of a roller mill according to the invention in the disengaged position;

Figure 2 shows the roller mill of Figure 1 in the engaged position.

3 shows the roller mill according to FIG. 2 in a simplified top view;

Fig. 4 is a schematic end view of a coupling gear;

5 shows an enlarged illustration of the coupling transmission in a top view;

6 shows an axial partial section through a grinding roller in the operational state; and FIG. 7 shows a partial section through the grinding roller in the expandable state. FIG. 1 shows a roller mill with two grinding rollers, hereinafter referred to as rollers 10, 12, which together form a roller gap 14. The associated machine frame and drive devices and the like have been omitted in FIG. 1 for reasons of clarity. The roller 10 is mounted with stub axles 16 stationary in the machine frame and is driven clockwise. The roller 12, on the other hand, is mounted with its stub axles 18 in a rocker arm 20 which in turn can be pivoted about an axis 22 which is parallel to the roller gap 14 and is approximately at the same height therewith.

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

Since the roller 12 is mounted in the rocker 20, it can move together with its stub axles 18 in an approximately vertical direction, that is to say in a direction parallel to an imaginary tangent which bears against the circumference of the roller 10 in the roller gap. Figure 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 upwards against a stop 26 by a spring 24. The stop 26 is arranged so that the width of the nip 14 is slightly smaller than the average particle diameter of the product that is fed to the nip.

If, as shown in FIG. 2, the product 28 is now fed into the roller gap 14 from above, the individual product particles, for example grain kernels, are lightly squeezed in the roller gap. The roller 10, which rotates at a greater peripheral speed, tends to accelerate the product downwards. 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 cannot be accelerated, a downward force F arises which acts on the rocker arm 20 via the stub axle 18 and tends to move it downward around the To pivot axis 22. This pivoting movement of the rocker 20 out of the position shown in FIG. 1, however, leads to a further narrowing of the roller gap 14 and thus to a further increase in the frictional forces and thus also the force F. In this way, the rocker 20 and the roller 12 driven by a self-reinforcing effect against the force of the spring 24 into the position shown in Figure 2. 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 can be finely adjusted, for example, with the aid of an eccentric integrated in the axis 22.

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

In Figure 2, the rocker 20 rests against a stop 30 which is designed as a predetermined breaking point and normally prevents the rocker 20 from striking downward. Only in exceptional cases, such as when a foreign body jams in the nip 14, does the predetermined breaking point break, so that the stop 30 releases the rocker 20 and can spring it downward by enlarging the nip. An additional safety measure can optionally be that the axle stub 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 in their operating position by strong springs.

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

In Figure 3, the roller mill is shown in simplified top view. A machine frame can be seen with side parts 32, 34 and bearing housings 36, in which the roller 10 with its stub axles 16 is mounted. The roller 10 is driven by a motor 38 and a belt drive 40. In the side parts 32, 34 there is also an eccentric shaft 42 on which the axis 22 of the rocker 20 is arranged eccentrically. The eccentric shaft 42 can be rotated with an adjusting lever 44, so that the working width of the nip 14 can be precisely adjusted by appropriately displacing the axis 22. can be put. The stub axles 18 of the roller 12 extend freely through openings 46 in the side parts 32, 34 and are mounted in the rocker arm 20 with bearing housings 48.

⁽ . The stub axles 16, 18 of the rollers 10 and 12 are coupled to one another on both sides by coupling gears 50. These coupling gears 50 are designed as round belt drives and each have a round belt 52 which wraps the associated pulleys 54, 56 multiple 8-shaped and through the dead weight of a dancer 58 is kept under tension 10. The intersecting runs of the round belt 52 intermesh in a comb-like manner between the belt pulleys 54, 56.

Due to this construction, the coupling gears 50 are able to follow the pivoting movements of the rocker 20 when the roller 12 15 is engaged and disengaged. The round belts 52 preferably have a certain intrinsic elasticity, so that the slight changes in distance between the pulleys 54 and 56 can be buffered until a compensation has taken place via the dancer 58. The surface of the round belt 52 preferably has a relatively high coefficient of friction, so that in combination with the

20 multiple wrapping of the pulleys results in good power transmission. The tension of the round belts 52 set by the weight of the dancers 58 can therefore be relatively low.

In Figure 4, one of the coupling gear 50 is ones shown, in an end view ^'25 represents. In idle mode, that is, in the position shown in Figure 1, the power flow goes from the pulley 56 directly driven by the motor 38 to the pulley 54, so that the trumms, designated 60 in Figure 4, are the pulling trims. These exert a small downward force component on the rocker 20, which, however, does not overcome the force of the spring 24 30.

In the grinding operation (FIG. 2), on the other hand, the roller 12 is driven directly by the roller 10 via the product in the roller gap 14, so that the coupling gear 50 acts as a brake. In this case, the trumms 62 are the pulling 35 trumms. When the rocker 20 moves from the position shown in FIG. 1 to the position according to FIG. 2 when product arrives, the pulley 54 moves downward, so that the tensile stress in the runs 62 increases. These trumps 62 are therefore immediately able to apply a braking effect to the roller 12 if the product tends to accelerate this roller. This contributes to a rapid build-up of the force F, which pivots the rocker 20 further down.

On the other hand, the trumms 62 also have the tendency to pivot the rocker 20 upwards again. In general, however, the torque exerted on the rocker arm 20 by the trumps 62 is less than the torque which results from the force F at the roller gap, because the force application point of the trumms 62 on the pulley 54 is closer to the axis 22 of the rocker arm than the roller gap, so that the force F acts over a larger lever arm. Only when the clamping force in the nip becomes so great due to the self-reinforcing effect described above that the roller 12 has the tendency to rotate at the same peripheral speed as the roller 10, does the tension of the trumps 62 predominate, so that the roller pressure in the roller nip is relaxed again. This effect limits the increase in the rolling pressure and prevents the stop 30 from being overloaded.

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

Since the coupling gears 50 are provided on both ends of the rollers 10, 12, the forces transmitted through the coupling gears to the opposite ends of the roller 12 and the rocker 20 are essentially the same, so that a uniform rolling pressure over the entire length of the nip 14 is achieved.

5 shows the profile of the pulleys 54, 56 in more detail. The pulley 54, which is assigned to the roller 12 and has the larger diameter, has grooves 64 with an approximately semi-cylindrical Profile on which is adapted to the cross section of the round belt 52 and this gives good guidance. The pulley 56, on the other hand, has grooves 66 which are approximately offset from the grooves 64 and have a greater width than this. The bottom of the grooves 66 is also tapered outwards (away from the roller 10). The trumms 60 can therefore run in with a relatively slight skew on the inside of the respective groove 66 (top in FIG. 5), while the trumms 62, which are the pulling trumms in the grinding operation, ensure that the round belt rotates around the pulley 56 as it rotates shifted outwards (downwards in FIG. 5) on the conical bottom of the groove 66 and then runs out on the outside of the groove 66 and runs into the groove 64 of the pulley 54 without a major change in direction. In this way it is achieved that the round belt 52 has only a slight skew when the belt pulleys 54, 56 are wrapped several times and is only subjected to little mechanical stress.

This also ensures that the interdigitated strands 60, 62 run past one another without contact and without rubbing, although they are only a short distance apart.

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

The grinding rollers 10, 12 have, as usual, on their grinding surface, i.e. , their outer circumferential surface, a longitudinal, mostly slightly wired corrugation by which the grinding effect is improved. These grinding surfaces must be reworked and re-sharpened from time to time, for which it is necessary to remove the grinding rollers from the roller mill. A structure of the grinding rollers is now described with reference to FIGS. 6 and 7, which enables a particularly simple and time-saving removal of the rollers. The roller 10 is shown as an example for both grinding rollers.

A cylindrical roller body 68, the outer circumferential surface of which forms the grinding surface 70, has a flat end surface 72 on both ends and an inner cone 74 on the inner circumferential edge. The roller body 68 is attached to the ends closed by a centering disk 76. The centering disk 76 lies with its outer circumferential area on a flat annular surface 78 on the end face 72 of the roller body and has two annular, concentric undercuts 80, 82 within this annular surface. These undercuts delimit an annular, to a certain extent inherently elastic web 84 which forms an outer cone 86 which is complementary to the inner cone 74.

The stub shaft 16 is tubular and welded firmly to the centering disk 76. The stub axle 16 carries the pulley 56, which is only shown schematically here, and a roller bearing 88, which is received in the bearing housing 36 in an axially displaceable manner.

The roller body 68 receives a clamping piece 90, which is held coaxially in the roller body by spokes 92 and has a threaded bore 94 at both ends. In each of the hollow stub axles 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 disks 76 are firmly clamped to the roller body 68. By placing the annular surfaces 78 on the end faces 72, an axially parallel alignment of the stub axles 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 designed to be slightly spherical.

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

If the roller body 68 is now to be replaced, the two threaded bolts 96 need only be loosened in a few steps and unscrewed from the threaded bores 94. The stub axles 16 with their respective centering disks 76 can then be axially pulled off the roller body 68, so that the webs 84 come free from the inner cone 74, as shown in FIG. The roller bearings 88, which are axially fixed on the stub shaft 16, can move axially in the bearing housings 36. In the state shown in FIG. 7, the roller body 68 can now be removed in the radial direction from the space between the centering disks 76 and replaced by a freshly refurbished roller body. The latter can then be just as easily reassembled by reversing the processes described above and braced using the threaded bolts 96, whereby it is precisely aligned and centered.

Claims

1. Roll mill with two mutually adjustable grinding rollers (12, 12) to form a roller gap (14), which are coupled in terms of drive so that they rotate at different peripheral speeds, characterized in that at least one (12) of the grinding rollers in one on the roller gap (14) movably supported in the tangential direction and is elastically pretensioned in this direction into a position in which the roll gap is enlarged to a predetermined dimension.

2. Roller mill according to claim 1, characterized in that the movably mounted grinding roller (12) is that grinding roller with the smaller peripheral speed and that it is biased in the direction opposite to the direction of rotation of this roller at the roller gap (14).

3. Roller mill according to claim 1 or 2, characterized in that the movably mounted grinding roller (12) is rotatably mounted in a rocker arm (20) which is pivotable about an axis (22) which is connected to the axes of rotation of the two grinding rollers (10, 12) lies approximately in one plane.

4. Roller mill according to one of the preceding claims, characterized in that the movement of the movably mounted grinding roller (12) in the direction opposite to the direction of the bias is limited by a stop (30).

5. Roller mill according to claim 4, characterized in that the stop (30) can be canceled by a predetermined breaking point.

6. Roller mill according to one of the preceding claims, characterized in that a coupling gear (50) for driving coupling of the two grinding rollers (10, 12) is designed as a crossed belt drive.

7. Roller mill according to claim 6, characterized in that the coupling gear (50) is a round belt drive, the round belt (52) associated pulleys (54, 56) wraps several times so that the intersecting strands (60, 62) of the round belt intermesh.

8. Roller mill according to claim 7, characterized in that the round belt (52) is held under tension by a dancer (58).

9. Roller mill according to claim 7 or 8, characterized in that at least one (56) of the pulley grooves (66), the width of which is greater than the cross section of the round belt (52) and the bottom is tapered to one side.

10. Roller mill according to one of the preceding claims, characterized - characterized in that the grinding rollers (10, 12) are coupled at both ends by a coupling gear (50).

11. Roller mill according to one of the preceding claims, characterized in that at least one of the grinding rollers (10, 12) has a cylindrical roller body (68) which is closed at both ends by releasable, each having an axle stub (16) carrying centering discs (76) ,

12. Roller mill according to claim 1 1, characterized in that the stub axles (16) are held axially displaceably in associated bearing housings (36).

13. Roller mill according to claims 6 and 12, characterized in that the pulleys (54, 56) of the coupling gear (50) are each arranged directly on the stub axles (16).

14. Roller mill according to one of claims 1 1 to 13, characterized in that the centering discs (76) each have an annular surface (78) on a flat end face (72) of the roller body (68) and within the annular surface (78) an outer cone (86), which engages in a complementary inner cone (74) of the roller body (68).

15. Roller mill according to claim 14, characterized in that the outer cone (86) is formed on an inherently elastic web (84).

16. Roller mill according to one of claims 1 1 to 15, characterized in that the centering discs (76) and the roller body (68) are axially clamped together.

17. Roller mill according to claim 6, characterized in that threaded elements (96) for bracing the centering disks (76) and the roller body (68) from opposite ends are inserted coaxially into the tubular axle stub (16) and inside the roller body (68) Thread engagement are clamped together.

18. Roller mill according to claim 17, characterized in that the threaded elements are threaded bolts (96) and that in the roller body (68) a clamping piece (90) is held coaxially, which has threaded holes (94) at both ends into which the threaded bolts ( 96) are screwed in.