Patent Publication Number: US-11648598-B2

Title: Corrugated pipe forming apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This non-provisional application claims the benefit under 35 U.S.C. § 119(a) to Patent Application No. 10-2020-0167510, filed in the Republic of Korea on Dec. 3, 2020, which is hereby expressly incorporated by reference into the present application. 
     BACKGROUND OF THE DISCLOSURE 
     Field of the Disclosure 
     The present disclosure relates to a corrugated pipe forming apparatus, and more particularly, to a corrugated pipe forming apparatus in which a surface of a smooth pipe made of metal is pressed inward by a screw protrusion formed on a dies to form a valley on the surface of the smooth pipe. 
     Related Art 
     As a device for continuously forming the valleys spaced apart from each other on the surface of a metal smooth pipe, a screw protrusion rotates the ring-shaped dies formed on an inner peripheral surface thereof along the surface of the smooth pipe while linearly moving the smooth pipe at a predetermined speed, and the screw protrusion presses the surface of the smooth pipe inward to continuously form a valley on the surface of the smooth pipe. 
     The dies is rotatably disposed in a circular opening of a support block installed in a forming barrel rotated by a motor, and the support block is installed movably in a straight line so that the center of the dies can be changed in the molding barrel. 
     Korean Patent No. 89-002878 discloses an apparatus for continuously forming valleys at regular intervals on the surface of a corrugated metal pipe. 
       FIG.  10    schematically illustrates a typical metal corrugated pipe forming apparatus in a state in which the center O 2  of a ring-shaped dies D formed with a screw protrusion T on an inner peripheral surface is located eccentrically from the center O 1  of a smooth pipe  5   a  so that a valley is formed in a smooth pipe  5   a  while the screw protrusion T rotates along the surface of the smooth pipe  5   a.    
     When the radius of the inner peripheral surface of the dies D on which the screw protrusion T is formed is set to be twice the radius of the smooth pipe  5   a , the dies D is rotated by ½ from a predetermined portion of the surface of the smooth pipe, for example, starting at point C and contacting point C again. The forming barrel in which the support block on which the dies is disposed is rotatably built is rotated once around O 1  along the trajectory of B. 
     Accordingly, the bearing interposed between the support block rotated integrally with the forming barrel and the dies rotated along the surface of the smooth pipe is accompanied by a relative rotational movement of an inner ring and an outer ring. 
     In a typical corrugated pipe forming apparatus, the rotational speed of the forming barrel and the support block is approximately 2000 rpm. When the radius of the inner peripheral surface of the dies is twice the radius of the smooth pipe as described above, the relative rotational speed of the inner ring and the outer ring of the bearing becomes 1000 rpm, and thus high heat is generated between the outer ring and the inner ring due to sliding or rolling friction. 
     The high heat shortens the life of the bearing and surrounding components. 
     In addition, the appropriate temperature at which a valley can be efficiently formed while not changing the structure of the corrugated pipe during forming the corrugated pipe is 150° C. to 200° C. Due to the high-speed rotation of the bearing and the high heat generated during work hardening according to the forming of the corrugated pipe, the inside of the forming barrel rises above the above temperature and in severe cases it rises to 300 degrees Celsius or more. Thus, because the structure of the corrugated pipe changes, the strength of the corrugated pipe becomes weak. 
     Accordingly, in order to reduce the heat generated in the bearing and to allow the inner and outer rings to rotate relatively smoothly, it is necessary to always fill the space between the inner and outer rings with lubricating oil. 
     However, due to the high-speed rotation of the support block and the relatively high-speed rotation of the inner and outer rings, the lubricating oil leaks through the gap between the inner and outer rings (see the gap  43  shown in  FIGS.  5 A to  5 C ) for a short time. Accordingly, it is necessary to stop the operation of the forming apparatus from time to time and re-inject the lubricating oil. Moreover, the leaked lubricating oil is scattered around and the corrugated pipe is contaminated. 
     In order to address an issue above, a gasket can be disposed to shield the gap between the inner and outer rings, but the gasket is separated from a predetermined position due to the bearing rotating at high speed, and the gasket loses its function due to heat loss. 
     RELATED ART DOCUMENT 
     Patent Document 
     (Patent document 1) Korean Patent No. 89-002878, Aug. 8, 1989 
     SUMMARY OF THE DISCLOSURE 
     An aspect of the present disclosure is directed to providing an apparatus capable of continuously forming a high-quality corrugated pipe by preventing leakage of the lubricant oil injected into a bearing. 
     Another aspect of the present disclosure is directed to providing a corrugated pipe forming apparatus capable of preventing damage and heat loss of the bearing and surrounding elements by reducing the generation of heat accompanied by rolling friction of the bearing and extending the lifespan. 
     Another aspect of the present disclosure is directed to providing an apparatus capable of forming a corrugated pipe of always constant quality by improving the formability of organically coupled rotating components. 
     The aspects of the present disclosure are not limited to those mentioned above, and other aspects not mentioned herein will be clearly understood by those skilled in the art from the following description. 
     A corrugated pipe forming apparatus according to an embodiment of the present disclosure includes: a support block rotated by power of a motor, in which a circular opening is formed therein; a bearing including an outer ring fixedly connected to an inner peripheral surface of the support block and an inner ring disposed to rotate relative to the outer ring; a dies disposed in the circular opening of the support block, in which a circular hole is formed through which a smooth pipe enters, a screw protrusion forming a valley on a surface of the smooth pipe is formed on the inner peripheral surface, and at least a portion thereof is inserted into an inner ring and connected to the inner ring; and a fastening ring disposed to face the dies in the circular opening of the support block and connected to the dies, wherein the support block has a shielding wall formed to protrude toward the fastening ring on a first lateral side, and the shielding wall is formed to cover a first gap formed between a first sidewall of the outer ring and a first sidewall of the inner ring. 
     The fastening ring may be disposed to face the dies based on the bearing to be fastened to the dies. 
     In addition, the corrugated pipe forming apparatus further includes a forming barrel connected to a power transmission device for transmitting power of a motor and having a space formed therein, wherein the support block may be disposed in the space of the forming barrel, a screw rod may be connected movably to the forming barrel, and the support block may be disposed to be movable in a straight line within the space by the screw rod. 
     In addition, the shielding wall may protrude radially inward toward the center of the circular opening to cover the entire first sidewall of the outer ring and a portion of the first sidewall of the inner ring. 
     In addition, the shielding wall includes a first shielding portion covering the first sidewall of the outer ring and the first gap, and a second shielding portion covering a portion of the first sidewall of the inner ring, wherein the second shielding portion may be formed to have a smaller front and rear width than the first shielding portion, and may be disposed to be spaced apart from the first sidewall of the inner ring. 
     In addition, the second shielding portion may cover ½ of a radial width of the first sidewall of the inner ring from an outer peripheral surface of the inner ring toward a radially inner side. 
     In addition, the fastening ring includes a boss portion inserted into an inner side of the first sidewall of the inner ring, and an outwardly protrusion rim extending in a radially outward direction from the boss portion, wherein the outwardly protrusion rim may be in close contact with a portion of the first sidewall of the inner ring. 
     In addition, the corrugated pipe forming apparatus may further include a side cover fastened to a second lateral side opposite to the first lateral side of the support block and having an opening hole formed therein so that a front surface of the dies is exposed. 
     In addition, the inner and outer rings may be disposed such that a second sidewall opposite the first sidewall enters from a surface of the second lateral side of the support block toward a first lateral side of the support block, and the side cover may be formed to cover a second gap formed on the second sidewall of the inner and outer rings to shield them. 
     In addition, the side cover may include a plate body covering a surface of the second lateral side of the support block, and an inner protrusion rim extending radially inwardly from the plate body toward the opening hole and protruding toward the inner and outer rings to shield a second gap formed between second sidewalls of the inner and outer rings. 
     In addition, the inner protrusion rim may protrude radially inwardly so as to cover the entire second sidewall of the outer ring and a portion of the second sidewall of the inner ring. 
     In addition, the inner protrusion rim may protrude to cover ½ of a radial width from an outer peripheral surface of the second sidewall of the inner ring. 
     In addition, the inner protrusion rim is in contact with the second sidewall of the outer ring, and the inner protrusion rim is formed so that a rear surface of an inner edge enters more forward than other parts of the inner protrusion rim, so that the inner edge is spaced apart from the inner ring. 
     In addition, the dies includes a core portion inserted into an inner ring and a flange portion extending radially outward from the core portion, and a part of the second sidewall of the inner ring not covered by the inner protrusion rim is in close contact with the flange portion of the dies. 
     In addition, the forming barrel is formed with a through hole connecting the space of the forming barrel and an external space, so that heat generated during forming of the corrugated pipe may be radiated to an outside through the through hole. 
     According to various embodiments of the present disclosure, the present disclosure has the following advantages. 
     First, the shielding wall formed on the first lateral side of the support block shields the first gap formed on the first sidewall of the bearing, and the side cover fastened to the second lateral side of the support block shields the second gap formed on the second sidewall of the bearing. Hence, the lubricating oil injected into the bearing does not leak even when the bearing rotates at high speed, so the corrugated pipe can be continuously manufactured without the need to frequently inject high-concentration lubricating oil such as grease into the bearing. 
     Second, since leakage of the lubricating oil injected into the bearing is prevented, the frictional heat between the inner and outer rings is reduced, and the frictional heat between the screw protrusion of the dies forming a corrugation and the surface of the smooth pipe is reduced, and thus age hardening is also reduced. Hence, it is possible to manufacture a high-quality corrugated pipe without changing the metal structure as well as extending the life of each component. 
     Third, the formability of the rotating dies, the fastening ring, and the support block is improved, so that it is possible to always provide a corrugated pipe of uniform quality. 
     Fourth, heat is radiated through the through hole formed in the forming pipe, so that the corrugated pipe can always be formed under an appropriate temperature condition. 
     The advantages of the present disclosure are not limited to those mentioned above, and other advantages not mentioned herein will be clearly understood by those skilled in the art from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view showing a corrugated pipe forming machine including a corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIG.  2    is an exploded perspective view of a corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIG.  3    is a cross-sectional view of a corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIG.  4    is a perspective view in which a forming barrel cover is omitted from the corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIGS.  5 A- 5 C  are views showing a support block included in the corrugated pipe forming apparatus according to an embodiment of the present disclosure.  FIG.  5 A  is a front view of the support block.  FIG.  5 B  is a rear view of the support block.  FIG.  5 C  is a cross-sectional view taken along line A-A of  FIG.  5 B . 
         FIG.  6    is a perspective view of a dies included in the corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIG.  7    is a perspective view of a fastening ring included in the corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIG.  8    is a rear view of a side cover included in the corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
         FIG.  9    is a cross-sectional view in which a support block, a dies, a fastening ring and a side cover of the corrugated pipe forming apparatus according to an embodiment of the present disclosure are assembled. 
         FIG.  10    is an explanatory diagram in which a valley is formed on the surface of a smooth pipe by a rotating die. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Advantages, features, and methods of accomplishing the same of the present disclosure will become apparent with reference to embodiments described in detail below together with the accompanying drawings. However, the present disclosure is not limited by embodiments disclosed hereinafter, and may be implemented in various forms. Rather, these embodiments are provided to so that this disclosure will be through and complete and will fully convey the scope of the present disclosure to those skilled in the technical field to which the present disclosure pertains, and the present disclosure will only be defined by the appended claims. Like reference numerals refer to like elements throughout the specification. 
     Hereinafter, a corrugated pipe forming apparatus according to embodiments of the present disclosure will be described with reference to the accompanying drawings. 
       FIG.  1    is a schematic representation of a corrugated pipe forming machine including a corrugated pipe forming apparatus according to an embodiment of the present disclosure. 
     Referring to  FIG.  1   , the corrugated pipe forming machine  1  includes a motor  2  for generating a rotational force, a power transmission devices  3   a  to  3   d  for transmitting power generated from the motor  2 , and a corrugated pipe forming apparatus  10  which is rotated by receiving power from the power transmission devices  3   a  to  3   d.    
     The power transmission devices  3   a  to  3   d  include a first pulley  3   a  connected to a rotation shaft of the motor  2 , a second pulley  3   b  spaced apart from the first pulley  3   a , a belt  3   c  connecting the first pulley  3   a  and the second pulley  3   b , and a power transmission shaft  3   d  connected to a forming barrel  20  of the corrugated pipe forming apparatus and the second pulley  3   b.    
     In this embodiment, a pulley mechanism has been described as an example as the power transmission device, but a known power transmission device such as a gear train may be used. 
     The smooth pipe  5   a  is transferred in a straight line at a constant speed by a known transfer mechanism (not shown) toward the space formed inside the forming barrel  20 , the smooth pipe  5   a  is continuously formed with a valley on its surface in the forming barrel, and the corrugated pipe  5   b  in which the valley is formed continues to advance at a constant speed. 
     A known corrugated pipe support device (not shown) or a guide device (not shown) may be disposed after the forming barrel so that the corrugated pipe  5   b  may be continuously transferred without being bent after being formed. 
       FIG.  2    is an exploded perspective view of a corrugated pipe forming apparatus  10  according to an embodiment of the present disclosure, and  FIG.  3    is a partially assembled cross-sectional view of  FIG.  2   . 
     Referring to  FIGS.  2  and  3   , the corrugated pipe forming apparatus  10  according to an embodiment of the present disclosure includes the forming barrel  20  which is connected to the aforementioned power transmission shaft  3   d  and rotates when a motor is operated, the support block  30  disposed so as to be movable in a vertical direction in a space  21  formed in the forming barrel  20 , the bearing  40  disposed on the inner side of the inner peripheral surface of the support block  30 , and a dies  50  having at least a portion thereof inserted into the bearing  40  to form a valley on a surface of the smooth pipe  5   a.    
     The dies  50  has a circular hole  51  into which the smooth pipe  5   a  enters, and a screw protrusion  52  is formed to protrude inward on the inner peripheral surface forming the circular hole  51 , thus forming a valley on a surface of the smooth pipe  5   a  entered into the circular hole  51 . 
     Based on the bearing  40  disposed on the inner side of the inner peripheral surface of the support block  30 , the fastening ring  60  is disposed to face the dies  50 . 
     The fastening ring  60  is fastened with a known fastening portion, for example, a bolt  91  so that at least a portion thereof is inserted into the bearing  40  and fixed to the dies  50 . 
     In the forming barrel  20 , the upper and lower screw rods  23  and  25  are disposed to penetrate toward the support block  30 . In the initial state, by adjusting the upper and lower screw rods  23  and  25  to adjust the upper and lower positions of the support block  30 , the position of the dies  50  may be set so that the screw protrusion  52  formed on the dies  50  presses the surface of the smooth pipe  5   a  inward to form a valley in the smooth pipe  5   a.    
     The forming barrel cover  80  is fastened to the front surface of the forming barrel  20  with bolts  93 . 
     Referring to  FIG.  3   , the forming barrel  20  is disposed to rotate about the central axis O 1  of the smooth pipe  5   a  or the corrugated pipe  5   b , and the support block  30  and the dies  50  are disposed so that the eccentric axis O 2  spaced a predetermined distance from the central axis O 1  becomes the center so that the support block  30  and the dies  50  may be rotated so that the eccentric axis O 2  of the dies  50  and the support block  30  rotate around the central axis O 1  as the center. 
     A through hole  26  is formed in the forming barrel  20  to communicate the external space and the space  21  inside the forming barrel  20 , so that high heat generated during corrugated pipe forming may be discharged to the outside through the through hole  26 . Accordingly, heat generated during corrugated pipe forming is radiated to an outside to prevent the structure of the corrugated pipe from being deteriorated. 
       FIG.  4    is a perspective view in which the support block  30  and the dies  50  are assembled to the forming barrel  20 . Referring to  FIGS.  3  and  4   , the support block  30  is disposed in the space  21  of the forming barrel  20  so as to be movable up and down while being guided by a pair of guiders  27  formed to be spaced apart from each other inside the forming barrel  20 , and the header  39  may be fixed to the upper side of the support block  30  with a fastening screw  381 . 
     The header  39  may be formed integrally with the support block  30 . 
     The upper screw rod  23  may be screwed to the upper side of the forming barrel  20 , the lower screw rod  25  may be screwed to the lower side, and a groove  391  with one side cut out is formed in the header  39 , and the end  231  of the upper screw rod  23  may be inserted into the groove  391 . 
     Accordingly, when the upper and lower screw rods  23  and  25  are rotated, the support block  30  is moved in the up and down directions, the support block  30  is moved to a predetermined position, and then the nut  24  is fastened. Then, the support block  30  is fixed at a predetermined position within the space  21  of the forming barrel  20 . 
       5 A is a front view of the support block  30  in which the header is omitted and the bearing  40  is coupled,  FIG.  5 B  is a rear view of the support block  30 , and  FIG.  5 C  is a cross-sectional view taken along line A-A of  FIG.  5 B . 
     The support block  30  has a circular opening  31  formed therein, and a ring-shaped bearing  40  is disposed inside the inner peripheral surface  32  of the support block  30  forming the circular opening  31 . The bearing  40  may include an outer ring  42  and an inner ring  41 , and a ball  46  (see  FIG.  5 C ) or a roller may be disposed between the inner and outer rings. The bearing  40  may include a retainer for disposing the ball  46  at a predetermined position, but the illustration thereof is omitted here. 
     Referring to  FIGS.  5 A and  5 C , the support block  30  has a fixing ring  44  and a bridge  44   a  for fixing the bearing  40  in the inner side of the inner peripheral surface  32  fixedly disposed, and the outer ring  42  is fixed to the inside of the bridge  44   a.    
     Hereinafter, the bridge  44   a  will be described as a component included in the fixing ring  44 . The bridge  44   a  may be omitted from the above. 
     An inner ring  41  is disposed inside the outer ring  42  to be rotatable relative to the outer ring  42 , and an annular gap  43  is formed between the inner and outer rings  41  and  42 . 
     The gap  43  includes a first annular gap  43   a  formed in a first sidewall of the inner and outer rings  41  and  42  and a second annular gap  43   b  formed in a second sidewall opposite to the first sidewall. 
     Accordingly, when the inner and outer rings  41  and  42  are rotated relative to each other, the lubricating oil injected into an inner space of the inner and outer rings may leak to the outside of the bearing through the gap  43 . 
     Referring to  FIGS.  5 B and  5 C , the support block  30  is formed with a shielding wall  330  protruding radially inward toward the center O 2  of the circular opening  31  on a first lateral side  33  so that the first gap  43   a  is covered so as to be shielded. 
     The shielding wall  330  may include a first shielding portion  331  covering a first lateral side of the fixing ring  44 , the entire first sidewall of the outer ring  42 , and the first gap  43   a , and a second shielding portion  332  covering a portion of the first sidewall of the inner ring  41 . 
     It is preferable that the second shielding portion  332  protrudes toward the inner side of the inner ring  41  to cover up to a part corresponding to ½ of the width W 1  in the radial direction of the first sidewall. 
     The front and rear widths of the first and second shielding portions  331  and  332  may be formed identically, and the front and rear widths t 1  of the first shielding portion  331  are formed to be larger than front and rear widths t 2  of the second shielding portion  332 , so that the first sidewall of the outer ring  42  is in close contact with the first shielding portion  331 , and the first sidewall of the inner ring  41  is spaced apart from the second shielding portion  332 , and thus the inner ring  41  may be rotated without interference of the shielding wall  330 . 
     In the annular space S 1  formed between the inner peripheral surface of the inner ring  41  from the inner peripheral surface of the shielding wall  330 , the outwardly protrusion rim  64  of the fastening ring to be described later is positioned. 
     The second lateral side of the fixing ring  44  and the second sidewall of each of the inner and outer rings  41  and  42  are disposed to enter a predetermined distance dl from the surface of the second lateral side  34  of the support block  30  toward the rear where the first lateral side  33  is positioned, so that a second annular space S 2  is formed between the inner peripheral surface  32  of the support block  30  and the inner peripheral surface of the inner ring  41 . 
     In the second annular space S 2 , a 2-1 annular space S 3  located between the inner peripheral surface  32  of the support block  30  and a portion of the second sidewall of the inner ring  41  is covered by a side cover  70  to be described later, and the second gap  43   b  formed in the second sidewall of the inner rings  41  and  42  is shielded. 
     The flange portion  54  of the dies, which will be described later, is located in the remaining annular space S 4  located inside the radius of the second annular space S 2 . 
       FIG.  6    is a perspective view of the dies  50 ,  FIG.  7    is a perspective view of the fastening ring  60 ,  FIG.  8    is a perspective view of the side cover  70 , and  FIG.  9    is a perspective view in which the dies  50 , the fastening ring  60 , and the side cover  70  are assembled to the support block  30 . 
     Referring to  FIGS.  6 ,  7  and  9   , the dies  50  and the fastening ring  60  are disposed to face each other based on the bearing  40  and are fixedly fastened to each other with the fastening bolts  91 . 
     Referring to  FIGS.  7  and  9   , the fastening ring  60  is disposed on the first lateral side  33  of the support block  30 , and is formed in a ring shape having a hollow  61  through which the aforementioned smooth pipe passes, and includes a boss portion  63  inserted into an inner ring  41  and having a fastening hole  65  formed therein, and an outwardly protrusion rim  64  extending radially outward from one side of the boss portion  63 . 
     When the boss portion  63  of the fastening ring  60  is inserted into an inner space of the inner ring  41 , the outer peripheral surface of the boss portion  63  is in close contact with the inner peripheral surface of the inner ring  41 , and the outwardly protrusion rim  64  is inserted into the first annular space S 1  so that the front surface of the outwardly protrusion rim  64  is in close contact with a portion of the first sidewall of the inner ring  41  and is separated from the inner peripheral surface of the second shielding portion  332  of the shielding wall  330 . 
     Accordingly, the fastening ring  60  may be rotated together with the inner ring  41  without being interfered with the shielding wall  300 . 
     The surface of the first lateral side  33  of the support block  30  and the rear surface  60   a  of the fastening ring  60  may form a continuous same plane. 
     Referring to  FIGS.  6  and  9   , the dies  50  includes a circular hole  51  through which the aforementioned smooth pipe enters, a core portion  53  in which a screw protrusion  52  is formed on an inner peripheral surface and the inner ring  41  is inserted, and a flange portion  54  extending radially outward from the core portion  53 . 
     In the dies  50 , when the core portion  53  is inserted into the inner ring  41 , the outer peripheral surface of the core portion  53  is in close contact with the inner peripheral surface of the inner ring  41 , and the flange portion  54  is located in the aforementioned 2-2 annular space S 4 , and the rear surface of the flange portion  14  is in close contact with a portion of the second sidewall of the inner ring  41 . 
     The dies  50  and the fastening ring  60  disposed to face each other based on the inner ring  41  are fastened to each other by fastening portion such as bolts  91 , and the flange portion  54  of the dies  50  and the outwardly protrusion rim  64  of the fastening ring  60  are assembled to be pressed against the first and second sidewalls of the inner ring, respectively, so that the dies  50 , the fastening ring  60 , and the inner ring  41  are integrally and firmly coupled. 
     Referring to  FIGS.  8  and  9   , the side cover  70  covered on the second lateral side  34  of the support block  30  includes a plate body  74  in which an opening hole  71  is formed and is in contact with the surface of the second lateral side  34 , and an inner protrusion rim  73  extending radially inward from the plate body  74  and protruding backward through the fixing ring  44  and the bearing  40 . 
     The inner protrusion rim  73  of the side cover  70  is disposed in the 2-1 annular space S 3  described above, and the plate body  74  is covered on the surface of the second lateral side  34  of the support block  30  and is fixed to the support block  30  by fastening portion such as nuts and screws inserted into the fastening hole  75 . 
     Accordingly, the rear surface of the inner protrusion rim  73  of the side cover  70  is in contact with the entire second sidewall of the second lateral side of the fixing ring  44  and the second sidewall of the outer ring  42 , and is located in front of a portion of the second sidewall of the inner ring  41 . Since the second annular gap  43   b  formed between second sidewalls of the inner and outer rings  41  and  42  is shielded, the lubricating oil injected into the bearing  40  is prevented from leaking through the second gap  43   b.    
     It is preferable that the inner protruding rim  73  of the side cover  70  is covered from an outer peripheral surface of the second sidewall of the inner ring  41  to ½ of a radial width W 1  of the inner ring  41 . 
     In addition, the inner protrusion rim  73  is formed so that the inner edge  731  enters slightly forward than the other parts of the inner protrusion rim  73 , so that the inner edge  731  is disposed to be spaced apart from the second sidewall of the inner ring  41  so that the inner ring  41  may be rotated without interference from the side cover  70 . 
     ½ of the width in the radial direction of the second lateral wall of the inner ring  41  not covered by the side cover  70  is disposed in front of the flange portion  54  of the dies  50 , and the outer peripheral surface of the flange portion is spaced apart from the inner peripheral surface of the inner edge  731  of the inner protrusion rim  73 . 
     Accordingly, the dies  50 , the fastening ring  60 , and the inner ring  41  may be rotated without interference from the support block  30  and the side cover  70 . 
     The front surface  50   a  of the dies  50  and the front surface  70   a  of the side cover  70  may form a continuous plane. 
     As described above, in the present disclosure, the gap  43  formed between the inner and outer rings of the bearing  40  is shielded by the shielding wall  330  formed on the first lateral side of the support block and the inner protrusion rim  73  of the side cover  70  fastened to the second lateral side of the support block  30 . Hence, leakage of the lubricating oil injected into the bearing is completely prevented even when the bearing  40  rotates at a high speed, and a high-quality corrugated pipe may be continuously manufactured. 
     Hereinbefore, although preferred embodiments of the present disclosure have been illustrated and described, the present disclosure is not limited to the specific embodiments described above, and it goes without saying that persons having ordinary skills in the technical field to which the present disclosure pertains may implement the present disclosure by various modifications thereof without departing from gist of the present disclosure defined by the claims, and such modifications are not to be construed individually from the technical spirit and scope of the present disclosure. 
     DETAILED DESCRIPTION OF MAIN ELEMENTS 
     
         
           5   a : smooth pipe 
           5   b : corrugated pipe 
           20 : forming barrel 
           30 : support block 
           300 : shielding wall 
           40 : bearing 
           41 : inner ring 
           42 : outer ring 
           43 : gap 
           44 : fixing ring 
           50 : dies 
           52 : screw protrusion 
           60 : fastening ring 
           70 : side cover 
           80 : forming barrel cover