Grinding device

Abstract

A grinding device, in particular a vertical mill for grinding a grinding material, the grinding device including at least two grinding elements that are movable relative to one another, wherein the two grinding elements together form at least one grinding portion in which the grinding material is grindable by the two grinding elements; and at least one contact pressure device including at least one hydraulic cylinder including a cylinder operating chamber and at least one gas spring including a spring operating chamber, wherein the cylinder operating chamber and the spring operating chamber are flow connected with one another, wherein a contact force is impartible upon at least one of the grinding elements by the at least one contact pressure device and the grinding elements are pressable onto one another by the contact force.

Claims

1. A grinding device for grinding a grinding material, the grinding device comprising: at least two grinding elements that are movable relative to one another, wherein the at least two grinding elements together form at least one grinding portion in which the grinding material is grindable by the at least two grinding elements; and at least one contact pressure device including at least one hydraulic cylinder including a cylinder operating chamber, and at least one gas spring including a spring operating chamber, wherein the cylinder operating chamber and the spring operating chamber are flow connected with one another, wherein a contact force is impartible upon at least one of the at least two grinding elements by the at least one contact pressure device and the at least two grinding elements are pressable onto one another by the contact force, wherein a smallest flowable cross-sectional surface between the cylinder operating chamber and the spring operating chamber amounts to at least 40% of a cross-sectional surface of the cylinder operating chamber.

2. The grinding device according to the claim 1, wherein a smallest flowable cross sectional surface between the cylinder operating chamber and the spring operating chamber amounts to at least 60% of a cross sectional surface of the cylinder operating chamber.

3. The grinding device according to claim 1, wherein the at least one gas spring is formed by a bladder accumulator.

4. The grinding device according to claim 1, wherein the at least one hydraulic cylinder and the at least one gas spring are configured as an integrated contact pressure device, wherein the cylinder operating chamber and the spring operating chamber transition into one another with a constant cross section, and wherein the hydraulic fluid is arranged between a piston of the contact pressure device and a gas cushion of the contact pressure device.

5. The grinding device according to claim 1, wherein the contact force that is applicable by the contact pressure device is variable.

6. The grinding device according to claim 1, wherein a drive power of the grinding device is at least 0.2 MW or a volume pass through of the grinding material of the grinding device is at least 5 tons per hour.

7. The grinding device according to claim 1, wherein the at least one hydraulic cylinder and the at least one gas spring form a closed hydraulic system.

8. The grinding device according to claim 1, wherein the at least one hydraulic cylinder includes exactly one cylinder operating chamber.

9. The grinding device according to claim 1, wherein a drive power of the grinding device is at least 0.2 MW and a volume pass through of the grinding material of the grinding device is at least 5 tons per hour.

10. A grinding device for grinding a grinding material, the grinding device comprising: at least two grinding elements that are movable relative to one another, wherein the at least two grinding elements together form at least one grinding portion in which the grinding material is grindable by the at least two grinding elements; and at least one contact pressure device including at least one hydraulic cylinder including a cylinder operating chamber, and at least one gas spring including a spring operating chamber, wherein the cylinder operating chamber and the spring operating chamber are flow connected with one another, wherein a contact force is impartible upon at least one of the at least two grinding elements by the at least one contact pressure device and the at least two grinding elements are pressable onto one another by the contact force, wherein a smallest flowable cross-sectional surface between the cylinder operating chamber and the spring operating chamber amounts to at least 10% of a cross-sectional surface of the cylinder operating chamber, or wherein a connecting section extending between a first transitional cross-section of a connecting component communicating with the cylinder operating chamber and a second transitional cross-section of the connecting component communicating with the spring operating chamber has a maximum length of 100 cm; the grinding device further comprising a damping device through which a flow velocity of a hydraulic fluid flowing between the cylinder operating chamber and the spring operating chamber is reducible, wherein a degree of damping of the damping device differs advantageously for different flow directions of the hydraulic fluid, and wherein the degree of damping for a flow of the hydraulic fluid into a direction oriented away from a piston of the hydraulic cylinder is advantageously greater than for a flow of the hydraulic fluid in a direction oriented towards the piston of the hydraulic cylinder.

11. The grinding device according to the claim 10, wherein the degree of damping of the damping device is variable as a function of the direction of the flow of the hydraulic fluid.

12. The grinding device according to claim 10, wherein the damping device is formed by a throttle plate including pass through openings, and wherein the damping device includes at least one blocking device which is moveable relative to the throttle plate and through which blocking device the pass through openings of the throttle plate are at least partially closeable.

13. The grinding device according to claim 10, wherein the damping device includes a throttle cross section which is sized differently as a function of a direction of the flow of the hydraulic fluid, and wherein the throttle cross section is advantageously larger when the hydraulic flows in a direction oriented away from the piston of the hydraulic cylinder, than when the hydraulic flows in an opposite direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is now described in more detail based on embodiments with reference to drawing figures, wherein:

(2) FIG. 1 illustrates a known grinding device;

(3) FIG. 2 illustrates a first grinding device according to the invention with a plurality of individual gas springs;

(4) FIG. 3 illustrates a detail of a contact pressure device of the grinding device according to FIG. 2;

(5) FIG. 4 illustrates another grinding device according to the invention with a plurality of individual gas springs configured as bladder reservoirs;

(6) FIG. 5 illustrates a detail of a contact pressure device of the grinding device according to FIG. 4;

(7) FIG. 6 illustrates another grinding device according to the invention with an integral embodiment of a cylinder operating chamber and a spring operating chamber; and

(8) FIG. 7 illustrates a sectional view through a contact pressure dev e of the grinding device according to FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

(9) A first embodiment which is illustrated in FIG. 1 illustrates a known grinding device 100 wherein the illustration according to FIG. 1 is reduced to essential components of the grinding device 100. The grinding device 100 illustrated herein is a so called vertical mill. The vertical mill includes a total of 5 grinding elements 2, 3 wherein four grinding elements 2 interact as rollers 4 with the grinding elements 3 configured as a grinding plate 5. Grinding material which is not illustrated herein is arranged on the grinding plate 5.

(10) The grinding plate 5 is driven by a drive device that is not illustrated so that it rotates about a vertical axis. The movement of the grinding plate 5 moves the grinding material arranged thereon, wherein the grinding material is moved along under the rollers 4 wherein the rollers are being dragged, this means they rotate about a horizontal rotation axis 6 solely due to the rotation of the grinding plate 5. There is no active drive for the rollers 4, but it can be easily implemented.

(11) The rollers 4 are preloaded in a vertical direction by a contact pressure device 101, this means they are pressed by the contact pressure device 101 in a direction towards the grinding plate 5 or towards a grinding bed formed from the grinding material. Under a pressure of the contact pressure device 101 and under a weight of the rollers 4 the grinding material is ground on the grinding plate 5, wherein the rollers and the grinding plate, thus the grinding elements 2, 3 move relative to one another.

(12) The contact pressure device 101 includes a hydraulic cylinder 8 which is not visible in FIG. 1 and a gas spring 9. Both components are flow connected by a flow connector 102 which is provided as a tubular conduit. A spring operating chamber of the gas spring 9 includes a gas cushion which is formed from nitrogen. A cylinder operating chamber of the hydraulic cylinder 8, the connector 102 and a portion of the spring operating chamber of the gas spring 9 arranged outside of the gas cushion are filled with a hydraulic fluid.

(13) When a vertical displacement of one of the roller 4 occurs during operation of the grinding device 100 a piston of the hydraulic cylinder 8 of the contact pressure device 101 which piston is connected with a bearing axle 11 of the roller 4 is moved in a vertical direction. Thus, the piston displaces the hydraulic fluid provided in the cylinder operating chamber wherein the hydraulic fluid subsequently flows at least partially through the connector 102 into the spring operating chamber of the gas spring 9. Thus, the gas cushion in the gas spring 9 is compressed and an additional reset force is generated on top of the preload recited supra wherein the reset force is stored as potential energy in the gas when the gas cushion is compressed. As soon as the roller 4 can move back again towards the grinding bed or the grinding plate 5, the hydraulic fluid is pressed from the spring operating chamber of the gas spring back into the cylinder operating chamber of the hydraulic cylinder 8 and the piston of the hydraulic cylinder 8 is accordingly moved back into its prior position.

(14) A smallest flowable cross sectional surface of the connection component 102 of the grinding device 100 is particularly small relative to a cross sectional surface of the cylinder operating chamber and only amounts to a few percent of the cylinder operating chamber, thus approximately 2%. This typical embodiment that is known in the art causes the problems recited supra in detail.

(15) Furthermore a connection distance which extends between the cylinder operating chamber of the hydraulic cylinder 8 and the spring operating chamber of the gas spring 9 within the connection component 102 is approximately 200 cm long in the illustrated embodiment. Thus, a total amount of hydraulic fluid is accumulated in the connecting component 102 so that a substantial force would be required for an instantaneous acceleration of this hydraulic fluid which force cannot be applied due to the very small available cross sectional surface of the connecting component 102. Consequently the connecting component 102 that is known in the art acts as a “plug” which almost prevents a flow of the hydraulic fluid from the hydraulic cylinder 8 to the gas spring 9 in a range of high load frequencies.

(16) This problem is solved by a first embodiment of a grinding device 1 according to the invention which is illustrated in FIG. 2. The grinding device 1 illustrated herein includes a contact pressure device 7 which is mounted at a so called force frame 12 through which the forces caused by the contact pressure device 7 are reacted in a foundation 22. Like in the grinding device 100 the piston of the hydraulic cylinder 8 is mounted on the bearing axle 11 of the roller 4 in order to push down the roller 4 by the bearing axle 11, thus to press it onto the grinding bed.

(17) In the illustrated embodiment the hydraulic cylinder 8 extends with a constant cross section above the force frame 12. At each hydraulic cylinder 8 a total of six gas springs 8 are connected which are respectively flow connected with a proper connector 10 with the cylinder operating chamber of the hydraulic cylinder 8. The connectors 10 are easily recognizable in a detailed representation according to FIG. 3. The individual connectors 10 are substantially similar to the connector 102 of the grinding device 100 with respect to their smallest cross sectional surface. However, contrary to the grinding device 100 known in the art plural connectors 10 are connected in parallel so that the hydraulic fluid which is displaced from the hydraulic cylinder 8 during a piston movement is overall provided with a cross sectional surface through which it can exit from the cylinder operating chamber, wherein the cross sectional surface corresponds to six times an individual cross sectional surface of each connecting component 10. This way a surface ratio of the smallest cross section surface (equals six times the smallest cross section surface of the six individual connection components 10) between the cylinder operating chamber and the spring operating chamber relative to the cross sectional surface of the cylinder operating chamber of approximately 40% is provided in the illustrated embodiment.

(18) This significant enlargement of the flowable cross section according to the invention resolves the previously described “plugging effect” or the stiffening effect of the connector.

(19) In a detail of the contact pressure device 7 which is illustrated in FIG. 3 an individual hydraulic cylinder 8, six connection components 10 connected therewith and a respectively associated gas spring 9 are visible particularly well. A cylinder operating chamber of the hydraulic cylinder 8 is completely filled with the hydraulic fluid so that the connection components 10 can be easily connected at an outer jacket 23 of the hydraulic cylinder 8 with an elevation offset. An illustrated “vertical” arrangement of the gas springs 9 in which the respective connection component is connected at the gas spring 9 at a bottom side of the respective gas spring 9 and the gas cushion is arranged in an upper section of the gas spring 9, is particularly advantageous in order to prevent that the gas cushion is flow enveloped or enclosed by the hydraulic fluid as can be the case for a reverse arrangement of the connection component 10 and the gas cushion.

(20) In another embodiment which is illustrated in FIG. 4 the gas springs 8 of a contact pressure device 7′ of a grinding device 1′ are formed by bladder accumulators 13 which are respectively individually connected analogously to the grinding device 1 illustrated in FIGS. 2 and 3 by a proper connecting component 10′ at the hydraulic cylinder 8. In the illustrated embodiment a total of seven gas springs 9 or bladder accumulators 13 are provided. Bladder accumulators 13 are easily available in many shapes so that the grinding device 1′ is an embodiment that can be installed quickly and economically when modernizing existing grinding devices.

(21) For illustration purposes FIG. 5 depicts a detail of the bladder accumulator 13 that is arranged at the cylinder operating chamber of the hydraulic cylinder 8. The connection elements 10′ thus include a cross sectional surface which approximately corresponds to 60% of the cross sectional surface of the hydraulic cylinder 8. Furthermore the connection components respectively include a throttle element.

(22) Another embodiment which is illustrated in FIG. 6 includes an additional grinding device 1′ according to the invention whose contact pressure device 7′ differs from the contact pressure device of the remaining embodiments. The hydraulic cylinder 8 and the gas spring 9 of the contact pressure device 7″ are configured as an integral component, this means the cylinder operating chamber and the spring operating chamber transition into one another seamlessly while maintaining a constant cross section and are no longer discernably separated from one another. This means for the illustrated contact pressure device 7″ that the piston protrudes into the hydraulic cylinder 8 from the bearing axle 11, thus from below, and that the piston is supported axially moveable in the hydraulic cylinder 8. The hydraulic fluid typically a hydraulic oil is arranged on a side of the piston which is oriented away from the bearing axle 11. In so far the configuration of the contact pressure device 7′ corresponds to the configuration of the contact pressure devices 7 and 101.

(23) However in the contact pressure device 7″ the gas spring 9 is not configured separately any longer but integrated directly at a “top side” of the hydraulic cylinder 8 which renders a discernable differentiation of the cylinder operating chamber and the contact pressure device 7″ impossible. Thus, the gas cushion associated with the gas spring 9 is arranged at a top side 14 of the contact pressure device 7″, wherein the gas cushion is preloaded. The hydraulic fluid directly contacts the gas cushion so that the cylinder operating chamber and the spring operating chamber are jointly arranged in a continuous space.

(24) The variant of the grinding device 1″ illustrated in FIG. 6 is particularly advantageous. In particular according to the definition the ratio of the smallest cross sectional surface between the hydraulic cylinder 8 and the gas spring 9 relative to the cross sectional surface of the cylinder operating chamber is equal to one, whereas the connection distance between the cylinder operating chamber and the spring operating chamber according is equal to zero per definition. Thus, this embodiment includes the best possible combination of hydraulic cylinder 8 and gas spring 9 which is furthermore producible in a particularly simple and cost effective manner.

(25) FIG. 7 eventually illustrates a detail of the contact pressure device 7″, wherein the contact pressure device 7″ is illustrated in a longitudinal sectional view. The hydraulic cylinder 8 is configured herein as so called “plunger cylinder”, wherein a plunger piston 24 is arranged in a lower portion of the contact pressure device 7″. A center portion 25 of the contact pressure device 7″ is filled with the hydraulic fluid wherein the center portion 25 is arranged in front of a portion 21 of the contact pressure device 7 that includes the gas cushion formed by nitrogen. The gas cushion is separated in a sealing manner by a separation piston 20 from the hydraulic fluid, wherein the separating piston 20 is supported in a “floating manner” in the contact pressure device 7″ so that it can move freely in an axial direction of the contact pressure device 7″.

(26) A damping device 15 configured as a throttle plate 16 is particularly significant in this respect. The throttle plate 16 includes a plurality of pass through openings 17 which form a constriction of the flow cross section of the hydraulic fluid in the contact pressure device 7″. The damping device 15 is interpreted herein as a component that is arranged strictly for damping purposes and not a connecting component in the sense of the connecting components 10 and 10′ of the embodiments described supra.

(27) An interpretation of this type of the illustrated damping device 15, however, is still possible. Thus, in the sense of claim 1 the throttle plate 16 represents the connecting component between the cylinder operating chamber and the spring operating chamber, wherein the cylinder operating chamber is arranged on the side of the throttle plate 16 oriented towards the plunger piston 24 and the spring operating chamber is arranged accordingly on a top side of the throttle plate. The transition cross sections would be formed according to claim 1 by the transitions from the respective operating chambers (cylinder and spring operating chambers) to the pass through openings 17, wherein the connection distance would correspond to a length, this means to an extension of the throttle plate 16 in an axial direction of the contact pressure device 7″ (thickness of the throttle plate 16). The throttle plate 16 has a thickness of 1 cm so that a risk of stiffening the contact pressure device 7′ as provided in the prior art is not provided due to the small masses that need to be accelerated.

(28) The damping device 15 provides a flow resistance when the hydraulic fluid flows through the pass through openings 17 with the hydraulic fluid wherein the flow resistance is opposite to the flow direction and leads to a braking of the hydraulic fluid or to a reduction of its flow velocity. A resistance of the damping device 15 is thus proportional to the flow velocity of the hydraulic fluid.

(29) The damping device 15 furthermore includes a blocking device 18. The blocking device 18 is rotatable about a vertical longitudinal axis of the contact pressure device 7″ relative to the throttle plate 16, wherein solid, herein triangular blocking elements 19 of the blocking device 18 are configured to move over the pass through openings 17 of the throttle plate 16 and thus close the throttle plate 16. Simultaneously a free portion below the blocking elements 19 which is not visible in FIG. 7 is released in that a flow cross section between a top side and a bottom side of the damping device 15 is configured without installations. Consequently the damping device 15 is illustrated in the position shown in FIG. 7 in its maximum damping position since all free portions are closed and only portions are released in which the hydraulic fluid has to be “pressed” through the pass through openings 17 of the throttle plate 16 which creates the desired friction. Rotating the blocking device 18 can be used to flexibly adapt a level of damping of the damping device 15.

REFERENCE NUMERALS AND DESIGNATIONS

(30) 1, 1, 1′ grinding device 2 grinding element 3 grinding element 4 roller 5 grinding plate 6, rotation axis 7, 7′ contact pressure device 8 hydraulic cylinder 9 gas spring 10, 10 connecting component 11 bearing axle 12 load frame 13 bladder accumulator 14 top side 15 damping device 16 throttle plate 17 pass through opening 18 blocking device 19 blocking element 20 separating piston 21 portion 22 foundation 23 jacket 24 plunger piston 25 jacket 100 grinding device 101 contact pressure device 102 connecting component