Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21H—MAKING PARTICULAR METAL OBJECTS BY ROLLING, e.g. SCREWS, WHEELS, RINGS, BARRELS, BALLS
  • B21H3/00—Making helical bodies or bodies having parts of helical shape
  • B21H3/02—Making helical bodies or bodies having parts of helical shape external screw-threads ; Making dies for thread rolling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
  • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
  • B21J5/06—Methods for forging, hammering, or pressing; Special equipment or accessories therefor for performing particular operations
  • B21J5/12—Forming profiles on internal or external surfaces
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21H—MAKING PARTICULAR METAL OBJECTS BY ROLLING, e.g. SCREWS, WHEELS, RINGS, BARRELS, BALLS
  • B21H1/00—Making articles shaped as bodies of revolution
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
  • B21K1/00—Making machine elements
  • B21K1/56—Making machine elements screw-threaded elements
• • E—FIXED CONSTRUCTIONS
  • E04—BUILDING
  • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
  • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
  • E04C5/16—Auxiliary parts for reinforcements, e.g. connectors, spacers, stirrups

Definitions

• the present invention relates to a method for working a thread onto a deformed bar of the type used for reinforcing concrete.
• a reinforcing bar is typically a steel bar manufactured with surface deformations to provide a locking anchorage with the surrounding concrete, and is also known as a "deformed bar”.
• the deformed bars are supplied in pre-cut lengths and accordingly it may be necessary to connect several bars end to end for use depending upon the size of the construction work.
• One known method of connecting the bars is by using a latching process wherein end portions of the two bars are overlapped and bound by steel wires.
• this connection method results in significant loss of material since the end portions are required to overlap. Additionally, this method requires considerable labour to connect the bars, and furthermore, the connections become weak with age which correspondingly weakens the overall structure.
• connection end portions Another method of connecting the bars has been proposed which includes heating the connection end portions and upsetting the connection end portions by exertion of force in the axial direction.
• loss of material is caused by shrinking the length of the deformed bar.
• the elongation rate may decrease by a change in the material structure between the heated portion and the non-heated portion. This will result in the connection end portion becoming weak on impact, and an irregular structure distribution may result.
• a cold process for connecting the bar ends has been developed involving using a thread portion at the connection end portion of each connecting bar, and a connecting piece or coupler is threaded between the two bars around the corresponding threaded portions.
• a cut thread portion is formed at the connection ends.
• a rolled thread portion is formed at the connection ends after finishing the cutting operation.
• the tensile strength and the hardness of the deformed bar becomes very high by work hardening and a value of impact absorption energy is rapidly decreased. This results in the structure of the upset portion becoming non-uniformly formed.
• CA 2,268,878 Another method of working a thread of a connection end portion has been disclosed in CA 2,268,878.
• This method includes swaging the deformed bar at normal temperature such that a maximum diameter of the connection end portion is equal to or slightly larger than a diameter of a cylindrical body of the deformed bar or slightly smaller than a diameter of the deformed bar depending on a degree of working, and rolling a thread portion onto the outer peripheral face of the connection end portion.
• the present invention uses a pressing step to press thread marks onto a deformed bar before a rolling step to form the final thread on the bar.
• the present invention provides a method for working a thread onto a deformed bar of the type used for reinforcing concrete, the method comprising the steps of: pressing the deformed bar to a predetermined diameter using a die having thread formations thereon to correspondingly form thread marks on the deformed bar; and rolling the pressed deformed bar to form the final thread.
• the step of pressing the deformed bar to a predetermined diameter using a die having thread formations thereon comprises cold-pressing the deformed bar.
• the step of rolling the pressed deformed bar to form the final thread comprises cold-rolling the pressed deformed bar.
• a deformed bar for reinforcing concrete having at least one thread thereon, wherein the thread is worked by the method above is also provided.
• the present invention and/or forms thereof increases the quality and consistency of the final thread on the deformed bar, as the thread marks are formed on the bar preferably at the same angle and pitch of the roller thread, which causes less resistance during the rolling step. This also enhances the life expectancy of the rollers, which reduces construction cost and accordingly achieves the object.
• Figure 1a through Figure 10 are stage views showing a method for working a thread onto a deformed bar for reinforcing concrete in accordance with one embodiment of the present invention, in particular:
• Figure 1 a shows a front elevational view of a pressing die for use with the embodiment of the present invention
• Figure 1b shows a side elevational view of the pressing die of Figure 1a
• Figure 1 c shows a perspective view of the pressing die of Figure 1 a
• Figure 2a shows a front elevational view of the pressing die of Figure 1a with a deformed bar located between the parts of the die;
• Figure 2b shows a side elevational view of Figure 2a
• Figure 3a shows a front elevational view of the pressing die and bar of Figure 2a with arrows indicating the pressing step
• Figure 3b shows a side elevational view of Figure 3a
• Figure 4a shows a front elevational view of the pressing die and bar of Figure 3a with the die in the pressed position
• Figure 4b shows a side elevational view of Figure 4a
• Figure 5a shows a front elevational view of the pressing die and bar of Figure 3a after the pressing step with the die in the open position
• Figure 5b shows a side elevational view of Figure 5a, showing the thread marks formed on the bar
• Figure 6a shows a front elevational view of the pressing die and bar of Figure 5a, showing the bar being rotated;
• Figure 6b shows a side elevational view of Figure 6a
• Figure 7a shows a front elevational view of the pressing die and rotated bar of Figure 6a with the die again in the pressed position;
• Figure 7b shows a side elevational view of Figure 7a
• Figure 8a shows a front elevational view of the pressing die and bar of Figure 7a after the pressing step with the die in the open position;
• Figure 8b shows a side elevational view of Figure 8a, showing the further thread marks formed on the bar;
• Figure 9 shows a cold-rolling step for forming the final thread, with the pressed bar located between two rollers;
• FIG. 10 shows the deformed bar with final thread formed thereon.
• the die 10 is formed of two parts 10a and 10b, although other shapes and configurations of dies may be used, for example the die may only include one part.
• the die 10 is formed of DF-2 material, which exhibits a hardness of between 52 to 58 on the Rockwell scale.
• the die 10 comprises a substantially semi-circular channel 12 in each part 10a and 10b thereof.
• a first portion of the channel 12 comprises thread formations 14 including a plurality of ribs and nodes for pressing into the deformed bar.
• the second portion of the channel 12 comprises a depth greater than the first portion, with a third portion of varying depth connecting the first and second portions.
• the length of the thread formations portion of the channel 12 may vary depending upon the length of thread required on the deformed bar and the length of the die 10.
• the thread formations 14 may extend along the entire length of the channel 12.
• a deformed bar 16 for reinforcing concrete is inserted into the die 10, as indicated by the arrow 17, with the location where the thread to be formed is positioned at the portion of the die 10 having the thread formations 14.
• the deformed bar 16 comprises a cylindrical body with ribs 20 and nodes 22 formed on an outer peripheral face.
• the deformed bar 16 is in the range of 380 yield strength to 600 yield strength.
• the preferred diameter of the deformed bar 16 is 10 mm to 50 mm, although other sizes could be used as desired.
• the two die portions 10a and 10b are pressed together, as indicated by the arrows 23 in Figures 3a and 3b, and Figures 4a and 4b.
• the pressing together causes the diameter of the deformed bar 16 within the first portion of the die 10 to be reduced to the predetermined diameter while also causing thread marks to form on the bar 16 corresponding to the thread formations 14 on the die 10.
• the pressing step may also straighten the bar 16 should the connection end portion be slightly bent relative to an intermediary portion of the deformed bar.
• the pressing is performed while the deformed bar 16 is at a normal room or cold temperature.
• the pressure is applied using a hydraulic machine, typically applying pressure in the range of 800 PSI to 3,000 PSI depending upon the deformed bar size and the yield strength.
• the time for which the pressure is applied is dependent upon the materials and the diameter of the bar 16.
• the die portions 10a and 10b are separated, as indicated by the arrows 25 in Figures 5a and 5b, and the deformed bar 16 is released.
• the deformed bar 16 will have thread marks 24 worked on part of the circumference of the bar.
• the pitch and depth of the thread marks 24 formed will be dependent on the diameter of the deformed bar 16.
• Various kinds and shapes of thread marks may be worked, such as a circular thread or a triangular thread, however preferably the thread is a circular thread.
• the bar 16 is then rotated by approximately 90 degrees to position the part of the bar without the thread marks within the die.
• the die 10 is then pressed together as shown in Figures 7a and 7b, to forms thread marks around the remaining (unthreaded) portion of the bar.
• the die is released as shown in Figures 8a and 8b, the entire circumference of the bar has thread marks formed thereon. In other forms and configurations of the die, it may not be necessary to rotate the deformed bar as one press may enable the thread marks to be formed around the entire circumference.
• the bar 16 with the thread marks 24 then undergoes a rolling step as indicated in Figure 9.
• the bar 16 is placed between two rollers 26 which cold-roll into the thread marks 24 on the bar 16, forming the deeper, final, thread.
• the thread pitch of the rollers 26 will vary depending upon the size of the deformed bar 16. Typically, a deformed bar with a diameter of 10 mm will result in having a pitch of about 1.5 mm and a depth of about 0.8 mm, whereas a deformed bar with a diameter of 50 mm will typically have a pitch of about 4.0 mm and a depth of about 2.0 mm.
• the rolling step is performed while the bar 16 is at a normal room or cold temperature to ensure there is no alteration of the inherent properties of the bar 16 to cause weakness.
• the rolling step comprises using a conventional rolling machine that is known to a person skilled in the art.
• the working pressure during the rolling of the final thread ranges from 800 PSI to 2,000 PSI.
• the revolutions of the roller machine are standard with the particular machine, and do not impact on the quality of the final thread on the deformed bar.
• the final thread is formed within 2 to 25 seconds depending upon the size of the bar 16 and the length of the thread.
• each threaded end of the bar 16 may be connected to another bar 16 by use of a coupler.
• the coupler comprises corresponding thread formations on an inner surface thereof, which accordingly mate with the thread formed on the outer surface of the ends of the bar 16.
• the present embodiment increases the quality and consistency of the final thread on the deformed bar, as the thread marks, are formed on the bar preferably at the same angle and pitch of the roller thread, which causes less resistance during the rolling step. This also enhances the life expectancy of the rollers, which reduces construction cost. It will be appreciated that persons skilled in the art could implement the present invention in different ways to the one described above, and variations may be produced without departing from its spirit and scope.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Architecture (AREA)
• Civil Engineering (AREA)
• Structural Engineering (AREA)
• Reinforcement Elements For Buildings (AREA)
• Forging (AREA)
• Reduction Rolling/Reduction Stand/Operation Of Reduction Machine (AREA)

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Citations (4)

• 2008
  • 2008-03-24 SG SG200802314-5A patent/SG155801A1/en unknown
  • 2008-11-06 WO PCT/SG2008/000424 patent/WO2009120153A1/en active Application Filing
  • 2008-11-06 KR KR1020107002114A patent/KR20100027242A/ko active Search and Examination
  • 2008-11-06 CN CN2008801091602A patent/CN101965236A/zh active Pending

Patent Citations (4)

Non-Patent Citations (1)

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