CN212703676U - Three-roller reducing and sizing mill - Google Patents

Abstract

The utility model provides a three-roller reducing and sizing rolling mill, which ensures that each roller has rigid support to ensure the radial positioning precision of the roller core and meets the eccentric adjustment of the roller core, and comprises a case, wherein the inner ends of a first long shaft, a second long shaft and a third long shaft which are positioned in the same plane and arranged at an included angle of 120 degrees are respectively fixedly connected with the first roller, the second roller and the third roller, a first roller left bearing and a first roller right bearing are arranged between the first long shaft and the first roller left bearing seat and the first roller right bearing seat, and the U-shaped frame simultaneously completes the axial positioning between the first roller left bearing and the first roller right bearing and the first roller left bearing seat and the first roller right bearing seat; the shaft cores of the outer cylindrical surfaces of the left and right bearing blocks of the first roller and the hole cores of the bearing holes of the left and right bearings of the first roller inside the shaft cores are eccentrically arranged, so that products with various specifications can be rolled; the U-shaped frame also ensures the synchronous rotation adjustment of the left bearing seat and the right bearing seat of the first roller.

Description

Three-roller reducing and sizing mill

Technical Field

The utility model relates to a three-high mill for roll line rod sizing finish rolling equipment.

Background

For bar rolling, a reducing and sizing mill is additionally arranged behind a bar finishing mill group, so that the dimensional precision of a product can be obviously improved, excellent product performance can be obtained, and the method is suitable for rolling production of high-quality special steel. In terms of rolling principle, the most significant advantage of the reducing and sizing rolling mill is that hard alloy wheel disc-shaped rollers are selected, the three rollers are arranged in a Y shape or delta shape, the included angles of the roller cores of the rollers are 120 degrees, for example, for round steel finish rolling, each roller provides a restraint range of one third of the arc length of the circular section, and uniform reducing and sizing restraint applied along the radial direction within the trisection circumference range of the circular section of the wire rod is obtained.

In view of the efforts of the skilled person, various embodiments of the three-roll reducing mill have been disclosed, such as "three-roll mill stand with lateral change with respect to the mill pass line" (document No. CN105764621B) (hereinafter referred to as document 1), "a two-stage lateral drive three-roll mill" (document No. CN105363792B) (hereinafter referred to as document 2), and "a three-roll mill with oil-water separation" (document No. CN109926450A) (hereinafter referred to as document 3).

For a three-roller reducing diameter rolling mill, the precision of the rolled hole shape directly influences the rolling precision of a product.

Some of the functions and technical indexes are important, such as whether the specification of the roller can be changed, the axial positioning of the roller core of the roller, the supporting scheme of the roller and the like.

In document 1, the chock supporting the roll is positioned after being translated in a direction parallel to the roll core, and the three rolls are driven by respective independent power shafts.

The solution adopted by document 1, as described in its specification paragraphs 0060, 0061, "roll-holding cartridge 3", is also provided with radial guides 20, 20', 21', 22', which allow the sliding movement of the yoke-type abutments 6, 6', 6 "and the sliding movement of the respective rolls 2, 2', 2" along the axes of said abutments, and allow the possible extraction from the roll-holding cartridge 3 by sliding in a radial direction with respect to a point X ' (point X ' is along the rolling axis X when the roll-holding cartridge 3 is mounted in the operating position in the rolling stand 100). These yoke seats 6, 6', 6 ″ are also provided with respective pairs of axial resting surfaces 27, 27', 26', 28', advantageously obtained on the seats themselves or on elements complementary to the radial guides 20, 20', 21', 22 '. "(paragraph 0060 of document 1), and" in fact, the roll-holding cartridge 3 is open at said radial guides 20, 20', 21', 22 'to allow the radial sliding of the yoke-type seats 6, 6', 6 "of the work rolls without having to remove the cartridge. ", it can be seen that the work rolls 2, 2', 2" are respectively and independently mounted on the yoke type supports 6, 6', 6", the radial guides 20, 20', 21', 22 'of the yoke type supports 6, 6', 6" are radially displaced under the condition of circumferential limit, the surfaces of the roll cores of the work rolls 2, 2', 2 "are kept on the same plane during the displacement, the formed rolling pass depends on the machining and assembling precision between the rolls 2, 2', 2" and the yoke type supports 6, 6', 6", the machining and assembling precision between the yoke type supports 6, 6', 6" and the radial guides 20, 20', 21', 22 'and the hydraulic bladder 4, 4', 4 "device for locking the radial outward movement, the accumulated error is large due to too many machining and assembling dimension chains of the components, and the control extension part 5, 5 'and 5' are coaxially connected, so that the assembly precision is difficult to ensure, and the natural hole shape precision cannot be ensured.

Document 2 has three serious defects, one is that the roll core of three rolls is initially a theoretical design position which can be regarded as being in the same plane, the bevel gear i 6.1 is driven to rotate by the motor 6.0 of the roll gap adjusting mechanism 6, the bevel gear i 6.1 is driven to rotate the bevel gear ii 6.2, the roll gap adjusting gear 6.3 and the bevel gear ii 6.2 rotate coaxially and drive the gear ring 6.4 to rotate, the gear ring 6.4 drives the pinion 6.6 to rotate, the worm 6.7 and the pinion 6.6 rotate coaxially and drive the turbine 6.8 and the lead screw 6.9 to rotate, the lead screw 6.9 drives the square nut 6.10 to pull the wedge block 6.5 outwards, the compression spring 7.1 of the balance roll bearing seat 7 jacks up the roll bearing seat 7, and at the time, the roll core keeps translating parallel to the plane of the initial position, and the complexity of the eccentric adjusting mechanism is hard to imagine; secondly, the roller body of the roller is arranged on the roller 5 in a suspension manner, the displacement is obvious when the roller is subjected to a bending force, and the rolling precision is difficult to ensure; and thirdly, the three transmission shafts 4 are positioned in a plane and are parallel to the surface of the three rollers 5 and are sequentially arranged along the advancing direction of the rolled piece, the three transmission shafts 4 are positioned at the downstream part of the rolled piece which passes through the roller for rolling, bevel gears on the transmission shafts 4 are directly adjacent to and exposed in an area with serious atomization of the cooling liquid, and the service life of the bevel gears is difficult to guarantee.

In the document 3, aiming at the defects in the prior art indicated by the conventional small memorial archways, the hole pattern adjustment is realized by using the principle of eccentric adjustment, and the specific scheme is that an upper eccentric sleeve 13 and a lower eccentric sleeve 16 with teeth at local parts are further arranged between a bearing seat sleeve 9 at two ends of one short shaft 3 and a rolling mill box 2, an upper worm 15 and a lower worm 17 which are perpendicular to the different surfaces of the short shaft 3 are further arranged on the rolling mill box 2, the upper worm 15 and the upper eccentric sleeve 13 as well as the lower worm 17 and the lower eccentric sleeve 16 form a worm and gear structure respectively, and the upper worm 15 and the lower worm 17 realize synchronous rotation through a synchronous gear 19. In the pass adjusting scheme provided by the document 3, only one of the short shafts 3 (namely, the short shaft 3 at the lower right part in the drawing) is provided with a support, and since the bearing seats and the shaft cores of the long shaft 1 and the short shaft 3 at the lower left part are fixed, whether the adjusting scheme provided by the document 3 can achieve the desired target is tentatively not the case, but as for the adjusting scheme, firstly, the bearings 5 are arranged on the shaft bodies of the short shafts 3 at the two ends of the roller 12 and the bearing sleeve 9, and an upper eccentric sleeve 13 and a lower eccentric sleeve 16 with teeth are also arranged between the bearing sleeve 9 and the rolling mill box 2, turbines matched with the upper worm 15 and the lower worm 17 need to be arranged on the outer walls of the upper eccentric sleeve 13 and the lower eccentric sleeve 16, and since the turbine teeth are just arranged on the supporting surfaces of the outer walls of the upper eccentric sleeve 13 and the lower eccentric sleeve 16, the processing difficulty of the turbine teeth is increased and the supporting stress surface area is reduced, particularly, the hidden danger of pressure concentration of the outer walls of the upper eccentric sleeve 13 and the lower eccentric sleeve 16 is increased; secondly, the outer walls of the upper eccentric sleeve 13 and the lower eccentric sleeve 16 are respectively matched with the upper worm 15 and the lower worm 17 for transmission, two worm and gear transmission mechanisms need to be arranged, the arrangement difficulty of the transmission mechanisms is increased while equipment is increased, in order to realize synchronous equidirectional rotation of the two transmission mechanisms, the two transmission mechanisms are additionally provided with synchronous mechanisms, the simplest scheme of the synchronous gear 19 also needs to be realized by arranging three gears, and the structure is too complex.

Next, since document 3 aims to adjust the position of the core of one roll, it is not necessary to provide a device for adjusting the cores of three rolls simultaneously, and it is not sufficient to adjust the cores synchronously when the rolls are worn or when rolls of different specifications are installed. In addition, in the document 3, since only one power shaft, i.e., the major axis 1 and both minor axes 3 have no active rotation moment, the friction force applied to the minor axes 3 by the rolled material drives the minor axes 3 to rotate, and therefore, the synchronous rotation of the three rolls 12 cannot be realized.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a three-roller subtracts sizing rolling mill ensures that each roll possesses the rigidity and supports in order to ensure its roller core radial positioning accuracy, and satisfies the eccentric regulation of roller core.

In order to realize the above-mentioned purpose, the utility model discloses a following technical scheme three-roller subtracts sizing mill, including quick-witted case, quick-witted incasement is arranged in to the back section of first, two, three major axis, and the inner end that is located the coplanar and be first each other that 120 contained angles were arranged, two, three major axis has linked firmly first, two, three rolls respectively, and first, two, three major axis link to each other with the power drive shaft to the tip that quick-witted case outside extended, and first, two, three rolls close on the side roll edge on the curve profile encloses into rolling pass A, its characterized in that: the left and right bearing seats of the first roller are respectively arranged at two ends of the first roller, a left and right bearing of the first roller is arranged between the first long shaft and the left and right bearing seats of the first roller, a U-shaped frame is connected between the left and right bearing seats of the first roller, the roller body part of the first roller far away from the rolling pass area is positioned at the cavity part of the U-shaped frame, a left and right mounting holes for mounting the left and right bearing seats of the first roller are arranged on the case, the U-shaped frame is accommodated in the vacant part between the left and right mounting holes, and the left and right bearing seats of the first roller are axially limited and are matched with the case in a circumferential rotating way; the shaft cores of the outer cylindrical surfaces of the left and right bearing blocks of the first roller and the hole cores of the bearing holes of the left and right bearings of the first roller inside the shaft cores are eccentrically arranged; bearing seats, bearings and U-shaped frame assembly structures at two ends of the first roller, the second roller and the third roller are the same as an eccentric arrangement scheme; and a gear is arranged on the first roll left bearing block and/or the first roll right bearing block, and the gear is meshed with the power gear to drive the first roll left bearing block and the first roll right bearing block to deflect in the same direction.

In the scheme, the left and right bearing seats of the first roller are respectively arranged at the two ends of the first roller, so that the position stability of the roller core of the first roller is ensured, and the first roller is supported by the left and right bearing seats of the first roller and the left and right bearings of the first roller arranged in the left and right bearing seats of the first roller, so that the first roller obtains rigid support and avoids the deflection phenomenon of the roller core of the first roller caused by the action of bending moment, and the stability of the rolling pass A is ensured; the U-shaped frame is arranged to ensure that the axial position of one of the left bearing seat and the right bearing seat of the first roller can be positioned at the same time, namely the left bearing seat and the right bearing seat of the first roller can be positioned at the same time in the axial direction, so that the axial positioning structure is simplified, and meanwhile, the U-shaped frame simultaneously completes the axial positioning between the left bearing seat and the right bearing seat of the first roller and the left bearing seat and the right bearing seat of the first; the shaft cores of the outer cylindrical surfaces of the left and right bearing blocks of the first roller and the hole cores of the bearing holes of the left and right bearings of the first roller inside the bearing blocks are eccentrically arranged, and the position of the shaft core of the bearing can be adjusted by rotating the bearing blocks, so that rollers with different roller diameter specifications can be installed, and the requirement of rolling products with various specifications is met; the arrangement of the U-shaped frame also ensures the synchronous rotation adjustment of the left bearing seat and the right bearing seat of the first roller, and when power is supplied to one of the bearing seats, the bearing seats and the power are synchronously deflected to directly drive the roller core of the roller to be in parallel offset, namely to perform eccentric motion.

Drawings

Fig. 1 and 2 are schematic perspective views of the present invention;

fig. 3 is a schematic structural diagram of the present invention;

FIG. 4 is a schematic plan view of the roll assembly of the present invention;

FIG. 5 is a schematic perspective view of a housing;

FIG. 6 is a schematic view of an assembly structure of a bearing seat and a shaft sleeve;

FIG. 7 is a schematic view of the assembled structure of the long shaft, roll and chock assembly;

FIG. 8 is a schematic structural view of a shaft sleeve and left bearing seat assembly;

FIG. 9 is a sectional view A-A of FIG. 8;

FIG. 10 is a schematic structural view of a U-shaped frame;

fig. 11 is a left side view of fig. 10.

Detailed Description

With reference to fig. 1, 2, 3 and 4, a three-roll reducing diameter rolling mill comprises a machine box 10, wherein the inner sections of a first long shaft 20, a second long shaft 30 and a third long shaft 40 are arranged in the machine box 10, the inner ends of the first long shaft 20, the second long shaft 30 and the third long shaft 40 which are positioned in the same plane and arranged at an included angle of 120 degrees are fixedly connected with a first roll 21, a second roll 31 and a third roll 41 respectively, the end parts of the first long shaft 20, the second long shaft 30 and the third long shaft 40 extending towards the outside of the machine box 10 are connected with a power driving shaft, and the curve outlines on the roll edges of the first roll 21, the second roll 31 and the third roll 41 close to each other enclose a rolling pass a, and is characterized in that: the two ends of the first roller 21 are respectively provided with a first roller left bearing block 22 and a first roller right bearing block 23, a first roller left bearing block 221 and a first roller right bearing block 231 are arranged between the first long shaft 20 and the first roller left bearing block 22 and the first roller right bearing block 23, a U-shaped frame 24 is connected between the first roller left bearing block 22 and the first roller right bearing block 23, the roller body part of the first roller 21 far away from the rolling pass A is positioned at the cavity part of the U-shaped frame 24, the case 10 is provided with a left mounting hole 11 and a right mounting hole 12 for mounting the first roller left bearing block 22 and the first roller right bearing block 23, the U-shaped frame 24 is accommodated in the vacant part between the left mounting hole 11 and the right mounting hole 12, and the first roller left bearing block 22 and the first roller right bearing block 23 are axially limited and; the shaft cores of the outer cylindrical surfaces of the left and right bearing blocks 22 and 23 of the first roller and the hole cores of the bearing holes of the left and right bearings 221 and 231 of the first roller inside the shaft cores are eccentrically arranged; the bearing seats, the bearings and the U-shaped frame 24 at the two ends of the first, second and third rollers 21, 31 and 41 have the same assembly structure and eccentric arrangement scheme; the first roll left chock 22 and/or the first roll right chock 23 are/is provided with a gear which is meshed with a power gear to drive the first roll left chock 22 and the first roll right chock 23 to deflect in the same direction.

For convenience of description and understanding, the technical features of the present invention are defined by using the terms of inside and outside directions, and it should be understood that the term is closer to the center of the rolling pass, that is, the term is the inside end, and vice versa, the term is the outside end, the outside or the outside section, etc.; the left and right positions of the first roll left and right chocks 22 and 23 are defined in a posture in which the first long axis 20 is horizontally arranged with the inner end thereof on the right as shown in the drawing. The expression left and right chocks for the other rolls should be understood when they are arranged in the same attitude as the first long axis 20.

The scheme provides the first roll 21 with the first roll left and right bearing blocks 22 and 23 and the corresponding first roll left and right bearings 221 and 231 which are symmetrically arranged, and the roll core of the first roll 21 is basically kept stable in the rolling process, so that the rolling precision is basically guaranteed.

In the scheme, the first, second and third long shafts 20, 30 and 40 have the same shape and size, and the corresponding bearing seats, bearings and U-shaped frames matched with the shafts are the same, so that the design workload of parts is undoubtedly reduced, the reserve quantity of spare parts is also reduced, and the universal interchangeability of the parts is increased; during rolling, the first, second and third long shafts 20, 30 and 40 are driven by respective power shafts, so that synchronous rotation of the rollers is ensured, and rolling precision is ensured.

The first roll left chock 22 and/or the first roll right chock 23 are provided with gears, and the gears are meshed with power gears to drive the former to communicate with the first roll left and right chocks 22, 23 to deflect in the same direction, and it should be noted here that the power gears may be gears independent of the three long shafts, or gears provided on the second and third long shafts 30, 40, and related preferred schemes will be described below.

The eccentric scheme is that the shaft cores of the outer cylindrical surfaces of the left and right bearing blocks 22 and 23 of the first roller and the hole cores of the bearing holes of the left and right bearings 221 and 231 of the first roller are eccentrically arranged, see fig. 8 and 9, and aims to solve the problem that the assembly and eccentric adjustment of the rollers with different specifications can still be realized to meet the rolling hole pattern A with the precision requirement when the sizes of the roller diameters are different and the rolling hole pattern A is out of tolerance due to abrasion, and the synchronous equidirectional eccentric arrangement of the left and right bearing blocks 22 and 23 of the first roller ensures that the roller cores are displaced in a parallel offset manner. In fig. 9, there are two centers, wherein the left side is the center of the outer cylindrical surface of the shaft sleeve 25, the first roll left chock 22 and the first roll right chock 23, and the right side is the center of the inner hole of the shaft sleeve 25, the first roll left chock 22 and the first roll right chock 23, and the two centers are arranged at intervals to form an eccentricity.

Referring to fig. 3, 4, 6 and 7, the outer end of the left bearing seat 22 of the first roller is axially connected with the small-diameter pipe end of the stepped tubular shaft sleeve 25 in a limiting manner, the large-diameter pipe section of the shaft sleeve 25 is installed in the shaft sleeve installation hole 13 on the chassis 10, the external flange of the large-diameter pipe end of the shaft sleeve 25 is in a resisting limiting fit with the orifice end face of the shaft sleeve installation hole 13, and the U-shaped frame 24 is in a resisting limiting fit with the orifice end face of the left installation hole 11. The outer end of the first roller left bearing block 22 is connected with the small-diameter pipe end of the stepped tubular shaft sleeve 25, the outer part of the obtained assembly is in a dumbbell shape with a small middle section and large radial sizes at two ends, so that the right bearing blocks of the rollers are arranged close to the roller bodies of the corresponding rollers as much as possible, the roller diameter of the rollers can be made as small as possible, and the rollers with small roller diameters can be matched with one another to form a rolling pass. The scheme also provides simple and effective axial positioning, namely, the bearing support positions at three positions are axially positioned through the axial limiting in the opposite directions at the two positions, namely, the external flanging at the large-diameter pipe end of the shaft sleeve 25 and the orifice end face of the shaft sleeve mounting hole 13 form a resisting limiting fit, and the U-shaped frame 24 and the orifice end face of the left mounting hole 11 form a resisting limiting fit.

By adopting the scheme, the accumulated processing and assembling errors can be compensated by matching the positioning ring pad 251 and the positioning ring pad 255 with proper thicknesses, so that the high-precision requirement processing of characteristic parts attached to complex parts, such as bearing seats, mounting holes and the like, is avoided, and the processing difficulty and cost are obviously reduced.

In order to further reduce the volume and the weight of the equipment, the ends of the left and right bearing blocks 22 and 23 of the first roller, which are far away from the roller, are tapered, and the sections of the tapered surfaces are reduced from the near to the far roller.

More preferably, the large diameter portion 25a of the sleeve 25 has a tapered portion 25c that transitions from the large diameter portion to the small diameter portion 25 b.

The scheme is to ensure that the three rollers can be mutually matched to form the rolling pass A under the condition of ensuring that the roller diameter is small. The front sections of the three rollers are close to each other as much as possible and enclose a regular triangle area, the center of the regular triangle is the center of the rolling pass A, the distance from the center to each side of the triangle is correspondingly small, and the roller diameter of the roller can be selected to be smaller.

Referring to fig. 10 and 11, the U-shaped frame 24 includes left and right frame plates 241 and 242, the left and right frame plates 241 and 242 have holes for the first long shaft 20 to pass through, a cross beam 243 is connected between the left and right frame plates 241 and 242, the cross beam 243 and the left and right frame plates 241 and 242 are connected by bolts, a key 244 is arranged on the joint surface to form a key connection, the length direction of the key 244 is consistent with the radial direction of the first long shaft 20, and the left and right frame plates 241 and 242 are connected by bolts 245 with the end surfaces of the left and right bearing seats 22 and 23 of the first roll on the side where the left and right frame plates 241 and 242 are located.

The scheme is a specific example of the U-shaped frame 24, and the left frame plate 241, the right frame plate 242 and the middle lintel 243 are connected by the key 244, so that the three plates are connected into a whole and have synchronous rotation rigidity, and the synchronous rotation performance is difficult to guarantee by simply using bolt connection. During assembly, the first roll left and right bearing blocks 22 and 23 and the bearings therein are installed in the corresponding installation holes 11 and 12, the left and right frame plates 241 and 242 are connected with the first roll left and right bearing blocks 22 and 23, respectively, and the lintel 243 is placed between the left and right frame plates 241 and 242 and connected. The advantageous assembly of the above-described construction is evident.

Referring to fig. 6, labyrinth seals are arranged between the left and right frame plates 241 and 242 and the left and right chock 22 and 23 of the first roll on the side where the left and right frame plates are located, and form axial positioning fit with the outer ring of the bearing. It can be seen that the left and right frame plates 241, 242 also function as bearing end caps.

In order to realize the power transmission of eccentric adjustment, the first roll left bearing block 22 and/or the first roll right bearing block 23 are/is provided with bevel gears which are meshed with the bevel gears arranged on the bearing blocks correspondingly arranged on the second long shaft 30 and the third long shaft 40 to form a transmission mechanism of eccentric adjustment. Thus, a torque input end can be selected, then the conical teeth meshed with each other transmit torque to realize eccentric adjustment, and the left and right bearing blocks 22 and 23 of the first roller are used for the work of the bearing block of the fixed bearing, have the functions of a core component of the eccentric adjustment and are also used as carriers of the eccentric adjustment.

More preferably, a power input bevel gear 451 is arranged at the inner end surface of the third shaft sleeve 45 of the third long shaft 40, and first, second and 431 power output bevel gears are arranged on the third roll left and right bearing blocks 42 and 43 and are respectively meshed with the second roll bevel gear 321 on the second roll left bearing block 32 and the first roll bevel gear 232 on the first roll right bearing block 23.

In the scheme, a power input bevel gear 451 is arranged at the inner end face of a third shaft sleeve 45 of a third long shaft 40 and used for receiving external driving torque, and the third shaft sleeve 45 is integrally connected with left and right bearing blocks 42 and 43 of a third roller in the axial direction and the circumferential direction, so that the third shaft sleeve 45 and the left and right bearing blocks 42 and 43 of the third roller are synchronously and eccentrically rotated, and the torque is respectively meshed with a first roller bevel gear 232 on a right bearing block 23 of the first roller and a third roller bevel gear 332 on a left bearing block 32 of the second roller through power output bevel gears I, II 421 and 431 to be transmitted, so that the synchronous and eccentric rotation of the three rollers is realized.

The outer end face of each bearing seat close to the matching position of the three rollers is in a conical surface shape, and the corresponding bevel gears are arranged on the corresponding conical surfaces. Therefore, the rolling pass which is matched with each other and is required for enclosure can be formed when the roll diameter of the roll is smaller.

In order to meet the above requirements, the front tapered surfaces of the first roll left chock 22 and the second roll right chock 33 have concave tapered surfaces 221 and 331 respectively arranged adjacent to each other. Therefore, under the condition that the size of the gear is reduced as much as possible, the meshing of all gear pairs can be realized, and the remarkable compact and simplified structure is realized.

Claims (9)

1. A three-roll reducing and sizing mill comprises a machine box (10), wherein the inner sections of a first long shaft (20), a second long shaft (30) and a third long shaft (40) are arranged in the machine box (10), the inner ends of the first long shaft (20), the second long shaft (30) and the third long shaft (40) which are positioned in the same plane and arranged at an included angle of 120 degrees are fixedly connected with a first roller (21), a second roller (31) and a third roller (41) respectively, the end parts of the first long shaft (20), the second long shaft (30) and the third long shaft (40) extending towards the outside of the machine box (10) are connected with a power driving shaft, and the curve outlines on the adjacent side roll edges of the first roller (21), the second roller (31) and the third roller (41): the two ends of a first roller (21) are respectively provided with a first roller left bearing block and a first roller right bearing block (22 and 23), a first roller left bearing block and a first roller right bearing block (221 and 231) are arranged between a first long shaft (20) and the first roller left bearing block and the first roller right bearing block (22 and 23), a U-shaped frame (24) is connected between the first roller left bearing block and the first roller right bearing block (22 and 23), a roller body part of the first roller (21) far away from a rolling pass A is positioned in a cavity part of the U-shaped frame (24), a left mounting hole and a right mounting hole (11 and 12) for mounting the first roller left bearing block and the first roller right bearing block (22 and 23) are arranged on a case (10), the U-shaped frame (24) is accommodated in a vacant part between the left mounting hole and the right mounting hole (11 and 12), and axial limiting and circumferential rotation matching are formed between the first roller left bearing block and the first; the shaft cores of the outer cylindrical surfaces of the left and right bearing blocks (22, 23) of the first roller and the hole cores of the bearing holes of the left and right bearings (221, 231) of the first roller inside the shaft cores are eccentrically arranged; the bearing seats, the bearings and the U-shaped frames (24) at the two ends of the first, second and third rollers (21, 31, 41) have the same assembly structure and eccentric arrangement scheme; the first roll left bearing block (22) and/or the first roll right bearing block (23) are/is provided with a gear, and the gear is meshed with the power gear to drive the first roll left bearing block and the first roll right bearing block (22 and 23) to deflect in the same direction.

2. The three roll reducing diameter mill of claim 1, wherein: the outer end of a first roller left bearing seat (22) is axially limited and connected with the small-diameter pipe end of a step tubular shaft sleeve (25), the large-diameter pipe section of the shaft sleeve (25) is installed in a shaft sleeve installation hole (13) in a case (10), a resisting limit fit is formed between an external flanging of the large-diameter pipe end of the shaft sleeve (25) and the orifice end face of the shaft sleeve installation hole (13), and a resisting limit fit is formed between a U-shaped frame (24) and the orifice end face of a left installation hole (11).

3. The three roll reducing diameter mill of claim 1, wherein: an outer positioning ring pad (251) is arranged between an external flanging of a large-diameter pipe end of the shaft sleeve (25) and an orifice end face of the shaft sleeve mounting hole (13) to form a resisting limit fit, and an inner positioning ring pad (255) is arranged between the U-shaped frame (24) and the orifice end face of the left mounting hole (11) to form a resisting limit fit.

4. The three roll reducing mill according to claim 1, 2 or 3, characterized in that: the U-shaped frame (24) comprises a left frame plate (241) and a right frame plate (242), holes for the first long shaft (20) to pass through are formed in the left frame plate (241) and the right frame plate (242), a lintel (243) is connected between the left frame plate (241) and the right frame plate (242), the lintel (243) is connected with the left frame plate (241) and the right frame plate (242) through bolts, a key joint is formed by arranging the key (244) on a binding face, the length direction of the key (244) is consistent with the radial direction of the first long shaft (20), and the left frame plate (241) and the right frame plate (242) are connected with the end faces of the left bearing seat (22) and the right bearing seat (23) of the first roller on.

5. The three roll reducing diameter mill of claim 4, wherein: labyrinth seals are arranged between the left frame plate (241) and the right frame plate (242) and the left bearing seat (22) and the right bearing seat (23) of the first roller on the side where the left frame plate and the right frame plate are located, and the labyrinth seals and the bearing outer rings form axial positioning fit.

6. The three roll reducing diameter mill of claim 1, wherein: the first roll left bearing block (22) and/or the first roll right bearing block (23) are/is provided with bevel gears which are meshed with bevel gears arranged on bearing blocks correspondingly arranged on the second long shaft (30) and the third long shaft (40) to form a transmission mechanism for eccentric adjustment.

7. The three roll reducing diameter mill of claim 6, wherein: the end face of the inner end of a third shaft sleeve (45) of a third long shaft (40) is provided with a power input bevel gear (451), and power output bevel gears I and II (421 and 431) are arranged on left and right bearing blocks (42 and 43) of a third roller and are respectively meshed with a second roller bevel gear (321) on a left bearing block (32) of the second roller and a first roller bevel gear (232) on a right bearing block (23) of the first roller.

8. The three roll reducing mill according to claim 1, 6 or 7, characterized in that: the outer end face of each bearing seat close to the matching position of the three rollers is in a conical surface shape, and the corresponding bevel gears are arranged on the corresponding conical surfaces.

9. The three roll reducing diameter mill of claim 7, wherein: concave conical surfaces (221, 331) are respectively arranged on the conical surfaces of the front ends of the first roll left bearing block (22) and the second roll right bearing block (33) and are adjacent to each other.

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