ROLL CRUSHER AND METHOD OF CRUSHING USING THE SAME

Abstract: An object to be crushed is fed into a crushing chamber defined between a pair of rollers facing each other and is compressed and crushed between these rollers. A flange (12) is formed at both ends of either one of the rollers (3) to cover the lower parts of both end openings of the crushing chamber. The remaining portions of the both end openings of the crushing chamber are covered with a holding member (11) disposed fixedly. This structure can prevent the object from overflowing from the crushing chamber. If one of the pair of rollers is used as a driving roller with the other being permitted to rotate freely and the two are rotated at low speed at an initial stage, even coarse particles can be forcibly entrapped and crushed. The crushing capacity of the roll crusher can be improved by setting the crushing gap between the rollers to 0.6 to 2.4 times a particle size that permits 80% of an object to pass and by controlling feed quantity so that the quantity of the passing object is within the range of 0.5 to 0.8 times the theoretical capacity of the crusher.

Description: The invention relates to a roll crusher for crushing rocks and ores, etc. US-A-3 497 321 discloses a machine for densifying and aggregating fine-granular mineral salt material in a rolling mill. The material is passed through the gap between two rollers, which are rotating in opposite direction. In a hopper chute for supplying the material to be aggregated to the rollers a number of downwardly extending rods or tubes is supported, the lower ends of which terminate above the narrowest spot of the roller gap. Due to this construction and the dimension of the gap by the rolling operation highly densified material in the form of longitudinal strips with intermediate strips of non-densified fine-granular material are produced. JP-Y1-35-22688 discloses a flour mill having a rotating roll and an interlocking roll, interlocking with said rotating roll through a pair of reduction gears. Said reduction gear is rotatably supported by a shaft of said interlocking roll and comprises a clutch disposed between said reduction gear and said shaft of said interlocking roll. Whether or not the clutch is on or off the interlocking roll and the rotating roll are rotating with the same or different speeds, having different effects on the flour to be ground. There has been known another type of roll crusher, as shown in Figs. 5 and 6, in which a pair of rolls 2 and 3 respectively facing each other and rotating in adverse direction to each other is provided, feed material such as rocks and ores to be crushed is supplied through the supply port 5 into the crushing chamber 6, that is, a space formed in between the pair of rolls, and the feed material supplied is crushed by compression while being rolled with said pair of rolls 2 and 3. The type of roll crusher has a crushing chamber 6 (a region indicated by chain line) as shown in Figs. 7a and 7b, whose longitudinal side faces 6a and 6b are formed respectively by the outer surfaces of the pair of rolls 2 and 3, and whose end faces 6c and 6d coincide with the openings formed in between the end faces 2a and 2b as well as 3a and 3b of said pair of respective rolls 2 and 3. But the crushing chamber shown is an example for explanation, therefore not necessarily limited to the shape, but varying to a convenient space region depending on crushing condition. On the other hand, some roll crusher according to the prior art is provided with side plates called cheek plates to prevent crushed stock from flowing out from the end openings 6c and 6d of the crushing chamber 6. During the process of crushing by the rolls 2 and 3, this type of roll crusher has no capability sufficient to prevent material being crushed from being pushed out of the crushing chamber 6 through the lower end portions of the end openings 6c and 6d (higher pressure applied on material to be crushed here), thus resulting in higher pressure applied on the rolls 2 and 3 at the roll center, and in lower pressure at both ends. Concerning such roll crushers with cheek plates, a comparable construction is disclosed in JP-Y1-29 76 94. This document refers to a guide made of bamboo for kneading vinyl. This guide is used in a kneading machine and comprises plates made of bamboo having a large number of bamboo strips. The plates are overlapped and adhered with each other so that the string of each bamboo strip crosses at an angle of 10° to 15° to the side edge of the guide. Repeated crushing with aforementioned different pressures distributed on the rollers may cause partial wear of the rolls 2 and 3, as shown in Fig. 8, thus resulting in an ununiform shape with the smaller middle section and the larger end sections. Such partial wear cannot maintain a constant axial crushing clearance between rolls. Therefore, in crushing material with a relatively small clearance in such case as making crushed sand, crushing clearance at the middle section is too large, although the rolls come into a close contact with each other with zero clearance at both ends. This partial wear of rolls has been long well known as the worst defect of the roll crusher, which causes a failure of effective crushing, thus necessitating laborious repair work to abrade the roll surface for a uniform axial crushing clearance between rolls. Heretofore, in crushing rocks or ores by the roll crusher, to have a large crushing ratio, roll clearance is adjusted to be equal to or smaller than the particle size of desired products. Particularly for fine particle products, to have a large fraction of fine particles in crushed products, it was common for roll clearance to be adjusted to about 1/2 particle size of desired products. Crushing mechanism according to the prior art may be described as follows. A clearance between a pair of opposing rolls 2 and 3, that is, crushing clearance S is smaller than particle diameter F of feed material to be crushed, and equal to or smaller than the particle diameter P of desirable products. Particles of material to be crushed are subjected to a continuously increasing compressive load and are eventually broken from the time when they come into contact with the surfaces of the pair of the opposing rolls to the time when they pass between the closest positions of the two opposing rolls. As stated above, the roll crusher according to the prior art has a small crushing clearance S, thus limiting the throughput capacity of feed material through the crushing chamber, resulting in a low productivity of products. Especially, the smaller the particle size of desirable products, the smaller the crushing clearance, thus further restricting the productivity. And, because feed material to be crushed is pressed by the roll 2 and 3 from the left and right sides, the size and shape of broken particles are regulated as regards the horizontal direction, but no regulation cannot be expected as regards other two directions such as vertical and parallel to the longitudinal direction of the rolls. Therefore, products according to the prior art include a large fraction of particles having sizes larger than the crushing clearance S, and it is well known that they contain a lot of flat or slender particles. The object of the invention is to provide a uniform longitudinal (axial direction of rolls) pressure distribution in the crushing chamber for a high compression crushing effect and for prevention of partial wear of rolls in the axial direction thereof. To achieve the object of the invention, the invention provides a roll crusher according the preamble of claim 1, being characterized by flanges fixed to the end surfaces of either roll for rotation with the roll, having a radius at least a crushing clearance between the rolls larger than that of the roll, and disposed to block end openings of aforesaid crushing chamber, as well as by stationary block members disposed to block an area of the end openings of aforesaid crushing chamber other than the area blocked by aforesaid flanges, and to prevent material to be crushed from flowing out of the end openings of the crushing chamber. To achieve a simplified mechanism for driving the rolls at reduced cost, a preferred embodiment of the invention provides a roll crusher, in which a pair of rolls facing each other is provided, feed material is supplied into a space formed in between these two rolls or a crushing chamber, and the feed material to be crushed is compressed for crushing while being rolled up with aforesaid pair of rolls, being characterized by one roll of aforesaid pair of rolls or a driver roll being power driven for rotation, and the other roll or a follower roll being rotated freely or at least together with the driver roll through the material rolled up in between the rolls while the material being crushed. Brief Description of Drawings Fig. 1 is a sectional side view of an embodiment according to the invention; Fig. 2 is a sectional plan view of Fig. 1 taken along line II-II; Fig. 3 is a top view of the roll crusher as shown in Fig. 1; Fig. 4 is a sectional view of Fig. 1 taken along line IV-IV; Figs. 5 and 6 are sectional views of the roll crusher according to the prior art; Figs. 7a and 7b are perspective views showing the crushing chamber; Fig. 8 is a view showing partial wear of rolls in the roll axial direction; Fig. 9 is a sectional view showing an example of the roll driving device; Fig. 10 is a sectional view showing another example of the roll driving device; Fig. 11 is a view showing the gear train for use in the device in Fig. 10; and Fig. 12 is a sectional view showing other example of the roll driving device. Best Mode for carrying out the Invention Figs. 1 and 2 show an example of a roll crusher according to the invention. In these drawings, the same members as the roll crusher according to the prior art shown in Fig. 5 are given by the same numerals. The differences of a roll crusher according to the invention from the roll crusher according to the prior art are: block members or cheek plates 11 which prevent feed material to be crushed from flowing out of a crushing chamber 6 by blocking end surface openings 6c and 6d in the crushing chamber 6 (Fig. 7b), and flanges 12 which prevent the feed material to be crushed from being pushed out of the crushing chamber 6 through lower end portions under high pressure applied to the feed material to be crushed in the end surface openings 6c and 6d. The flanges 12 are fixed to end faces of one roll 3 for rotating together with the roll 3. The radius of the flange 12 is at least a crushing clearance in between the rolls larger than that of the roll 3. Because the flange 12 rotates integrally with the roll 3, there is little relative dislocation thereof to feed material to be compressed and crushed in between the rolls 2 and 3 under high pressure. As a result, there is little wear on the flange 12, permitting preservation of the function of the flange 12 to maintain the axially uniform pressure applied to the rolls 2 and 3 even under the progress of the wear of the rolls 2 and 3 after long service, thus preventing partial wear of the rolls 2 and 3, and maintaining a desirable interparticle crushing effect. A fixed plate 7 and a slide gate 8 are provided in a supply port 5 of feed material. A rod 9 is connected to the slide gate 8 as shown in Fig. 3. The movement of the rod 9 as shown in Arrow AA' can adjust the spacing between the fixed plate 7 and the slide gate 8, which in turn adjusts the amount of material to be fed into the crushing chamber from the supply port 5. The leading edge of the slide gate 8 is curved so that the section of the supply port 5 is wider in the end portions than the middle portion, which is to compensate short supply of material to the side wall portions of the supply port 5 (that is, both end portions of the crushing chamber 6) due to friction and to supply feed material uniformly over the length of the crushing chamber 6. The longitudinal length L of the supply port 5, as shown in Figs. 3 and 4, is designed essentially equal to the spacing between both flanges 12 of the roll 3 and slightly longer than the axial length L' of the roll 2. This, together with the curvature of the leading edge of the slide gate 8 as described above, is to supply feed material uniformly over the length of the rolls 2 and 3. Sign BE in Fig. 2 is bearings for supporting the rolls 2 and 3. A roll crusher shown in Fig. 1 uses the less worn flanges 12 to prevent feed material from being pushed out of the crushing chamber 6 in the axial direction of the rolls 2 and 3 by the compression force of the rolls 2 and 3, thus resulting in a uniform distribution of the pressure applied to the rolls 2 and 3 as well as of the compression force of particles of material to be crushed acting on each other, over the whole area of the longitudinal direction (roll axial direction) for a long period of service. As a result, partial wear of the rolls can be prevented for long, thus maintaining a desirable interparticle crushing effect. Fig. 9 shows a driving device to drive for rotation of particularly a pair of rolls 2 and 3. The roll 3 on the right side of the drawing is supported on a frame 1 with bearings BE1 and connected to a drive power such as the output shaft of a motor 10 through a coupling 19. The motor 10 drives the roll 3 for counterclockwise rotation in Fig. 1. The roll 2 on the left side of the drawing is supported with bearings BE2 rotatably (can be rotated freely). In crushing, first one roll 3 is rotated by the motor 10 counterclockwise in the Fig. 1. Then the other roll 2 is rotated clockwise in the drawing through the material being crushed in the crushing chamber 6. As a result, the stock is broken while being rolled up in between the rolls 2 and 3 rotating adversely to each other. Because the follower roll 2 follows the driving roll 3 and rotates at a nearly same speed as the driving roll 3, crushing is positively performed without any trouble. Here, only one driving power is used for the rolls 2 and 3, thus resulting in a simple configuration of the whole roll crusher, leading to cost reduction. Incidentally, it is desirable that with a roll crusher the relative positions of the rolls can be varied, that is, the rolls is brought closer or removed away, in order to adjust particle size of crushed products or to compensate wear of the rolls 2 and 3 to maintain a constant clearance of the rolls. For this purpose, the bearing BE2 supporting the follower roll 2 according to the invention is so fixed to the frame 1 that the bearing BE2 can be moved as shown by Arrow AA'. In this case, because the roll 2 is rotating freely without any motor or other driving means provided, the movement of the bearing BE2 or the roll 2 is easily made, thus permitting a simple adjustment of crushing clearance of rolls. Fig. 10 shows another exampel of the driving device for the rolls 2 and 3. In this drawing the same members as those shown in Fig. 9 are given by the same numerals. The follower roll 2 is connected to the driver roll 3 through a gear train 20, which transmits the rotational force of the driver roll 3 to the follower roll 2. The gear train 20 consists of, for instance, four gears 21, 22, 23 and 24 meshing with each other as shown in Fig. 11, and further a one-way clutch 25 is provided between the last gear 24 and the shaft 2a of the follower roll 2. The gear train 20 is so designed that the follower roll 2 rotates at a speed at least 5% slower than the driver roll 3. The one-way clutch 25 is installed to transmit the clockwise rotation of the last gear 24 (Fig. 11) to the roll shaft 2a, but not to transmit the adverse rotation. In crushing, first, the motor 10 rotates the driver roll 3 counterclockwise in Fig. 11, at this time the follower roll 2 rotates clockwise at a speed at least 5% slower because of the gear train 20. Supplied in between the rolls 2 and 3 under this condition, the material to be crushed are rolled up in between the rolls 2 and 3 which have started rotation. Once the material is rolled up in between rolls, the interference of the material adds up the rotation speed of the follower roll 2 nearly to that of the driver roll 3, then the one-way clutch 25 functions to allow the free rotation of the follower roll 2 without restricted by the rotation of the last gear 24 or the driver roll 3. At that time, each gear in the gear train 20 makes so-called racing. With the embodiment in Fig. 9, because the follower roll 2 does not rotate together with the driver roll 3 at first, it may happen that, when entering feed material includes coarser particles, the coarser particles cannot be nipped, in other words, effective "nip angle" (the maximum nipping angle which allows crushing in between rolls) becomes smaller. On the contrary, with the embodiment in Fig. 10, in which the follower roll 2 rotates at a lower speed from the beginning, there is no such chance as stated above. Besides, the gear train 20 intends only to transmit rotation during no load or light load, and only races during crushing. Therefore, it does not be required to transmit large torque and to have much strength, thus reducing additional cost. As described above, it is desirable that at least one of the rolls 2 and 3 can be moved for adjustment of the crushing clearance of rolls. In the case of Fig. 11, the position of the roll 2 can be shifted by rocking the idle gears 22 and 23 about the roll shaft 3a as shown by Arrow EE'. Fig. 12 shows a further different embodiment for the driving device, in which the follower roll 2 of the embodiment in Fig. 9 is provided with an auxiliary motor 30 to drive. The auxiliary motor 30 can be turned ON or OFF as required by a controller (not shown). Switching the auxiliary motor 30 OFF allows the follower roll 2 to be rotated freely. Alternatively, a clutch can be introduced between the auxiliary motor 30 and the follower roll 2. ON or OFF of the clutch can switch the follower roll 2 to be rotated by the auxiliary motor 30 or freely. The rotational speed of the follower roll 2 by the auxiliary motor 30 may be the same as that of the driver roll 3 by the motor 10. Both speeds are not necessary the same, but, as in the case of Fig. 10, the follower roll 2 may be driven by the auxiliary motor 30 through a one-way clutch so that the rotation speed of the follower roll 2 is at least 5% slower than that of the driver roll 3. When the rolls 2 and 3 are rotating under no load or light load, the auxiliary motor 30 is switched ON to rotate the follower roll 2, at this time, the driver roll 3 has already been driven by the motor 10. Under this condition, feed material is supplied in between the rolls 2 and 3, and crushing starts. Once crushing starts, the auxiliary motor 30 is turned OFF, and since then the follower roll 2 is brought into free rotation or rotating while following the driver roll 3 through material being crushed. Further crushing operation is performed under this conditions. As stated above, under no load or light load, the auxiliary motor 30 is energized to rotate the follower roll 2, but since this rotation does not require large torque, a very inexpensive motor can be used for the auxiliary motor 30, thus contributing no noticeable increase in cost. Therefore, as compared with the case when the rolls are independently driven, cost is lowered. At the same time, since the follower roll 2 is rotated beforehand under no load, as with the case in the device shown in Fig. 10, coarse particles of feed material can be crushed, in other words, a large effective nip angle can be maintained.

Claims: A roll crusher having a pair of rolls (2,3) facing each other, in which feed material to be crushed is fed into a space or a crushing chamber (6) formed in between these rolls (2,3), the pair of said rolls (2,3) rolls up the material to compress and crush, and blocking members (11) are fixedly disposed above and along the axial direction of said rolls (2,3) to block regions in the end openings (6c,6d) of said crushing chamber (6) characterized by flanges (12) fixed to the end surfaces of one or the other of said rolls (2,3) for rotation together with said roll (2,3), and having a radius at least a crushing clearance larger than that of said roll (2,3) to block end openings of said crushing chamber (6), and the blocking members (11) disposed to block regions in the end openings (6c,6d) of said crushing chamber (6) other than those covered by said flanges (12), and fixedly disposed to prevent feed material from flowing out of the end openings (6c,6d) of said crushing chamber (6). A roll crusher as claimed in claim 1, wherein a feed opening (5) is provided to supply said feed material, and the length (L) in the roll axis direction of said feed opening (5) is essentially equal to the inside spacing of said blocking members (11). A roll crusher as claimed in claim 1 or claim 2, wherein an opening area for at least a part of the feed passage to feed said material can be adjusted. A roll crusher as claimed in one of claims 1 to 3, wherein at least some fractions of the passage to feed said material are wide in regions corresponding to the end portions of said crushing chamber (6) and narrow in the region corresponding to the center. A roll crusher as claimed in one of claims 1 to 4, in which the pair of said rolls (2,3) rolls up feed material to crush, comprising: a driver roll (3), one of the pair of said rolls, being driven for rotation, and a follower roll (2), the other roll, rotating freely put together with said driver roll (3) through the material rolled up in between said rolls at least while crushing is effected. A roll crusher as claimed in claim 5, wherein said follower roll (2) is driven for rotation during no load or light load before crushing. A roll crusher as claimed in claim 6, wherein power transmission means (20) is provided in between said driver and follower rolls (3,2), and said follower roll (2) is rotated beforehand by transmitting the rotation of the said driver roll to said follower roll through said power transmission means (20). A roll crusher as claimed in claim 7, wherein said power transmission means (20) has a gear train (20) transmitting reduced rotation of said driver roll (3) to said follower roll (2), and a one-way clutch (25) disposed in between said gear train (20) and said follower roll (2) to transmit only a rotation toward a direction as involving feed material to said follower roll (2). A roll crusher as claimed in claim 6, wherein a small capacity of auxiliary motor (30) is provided to rotate said follower roll (2) beforehand. A roll crusher as claimed in claim 9, wherein a rotation speed of said follower roll (2) driven by said auxiliary motor (30) is slower than that of said driver roll (3), and a one-way clutch (25) is provided to transmit only a rotation toward a direction as involving feed material to said follower roll (2).

Inventors: TAKAGI FUMIO NITTETSU MINING C, TAKAHASHI NOBUHIRO NITTETSU MI, TAKAGI, FUMIO NITTETSU MINING CO. LTD., TAKAHASHI, NOBUHIRO NITTETSU MINING CO. LTD.
Applicants: NITTETSU MINING CO LTD, NITTETSU MINING CO., LTD.
Application year: 1988
Main classification: B02C4
IPC codes: B02C4