Patent Application
20080245128
The present invention relates to reinforcement for concrete or other cemetitious construction and more specifically to a method and apparatus for forming such reinforcing.
In the construction industry, structures (such as walls, floors, slabs, columns and the like) of concrete are produced by positioning reinforcing such as steel reinforcing bars in a region where concrete is then poured to produce the structure. The bars are supported in desired positions and often there is a need to join lengths of bars to each other to ensure that the reinforcing not only is correctly positioned, but is able to transmit load across the coupling so that the bars can accommodate a large part or even their full axial capacity in either tension or compression.
Co-pending International application filed by the Applicant entitled “A Reinforcing Bar” discloses reinforcing incorporating a termination that extends along an end portion of the bar and that is arranged to form part of an interlock to connect the bar to another member. Whilst a reinforcing bar of this design has substantial practical benefit, it is necessary to be able to manufacture the bar inexpensively and reliably to enable it to be commercially acceptable to the market.
According to a first aspect, there is provided a method of forming a metal reinforcing bar comprising the step of forming a termination on an enlarged end portion of the bar, the termination being shaped to form part of an interlock to connect the bar to another member.
In a particular form, the end portion is heated before forming the termination and in one form, the termination is at least partially formed by a forging process, which is typically either a hot or warm forging process. Further, in one form, the cooling of the end portion is controlled so that the heating or the end portion does not substantially alter the material properties of the bar. In one form, the reinforcing bar is formed from steel and the end portion is heated to a temperature to allow forging (for example above 1000° C. for a hot forge or above 700° C. for a warm forge) and, after forging, the end portion is allowed to cool to a temperature of less than 460° C. under substantially ambient conditions. In another form, where the bar is tempered, the heated end may undergo an initial quenching process to reduce the steel temperature rapidly (say to 600° C.) and then allow the end portion to cool under ambient temperature conditions to less than 460° C.
An advantage of at least one embodiment of the method of forming the bar described above is that the termination is made as an integral part of bar. As such the strength of the termination can be properly matched to the strength of the bar. A major problem with prior art couplers that use separate components is the fact that the reinforcing bar may vary in strength (for example nominal 500 MPa may vary from 500 MPa to an allowed top strength of 650 MPa). This means that couplers may be mismatched with extremely strong bars so the couplers need to be made to accommodate this possible mismatch. This can have attendant problems as it may reduce the ductile properties of the coupler itself by providing a coupler of higher strength than required. The integral nature of the termination to the shaft obviates this mismatch and allows for ductility and strength of the coupling to be correctly matched to the bar shaft.
Further, by forming the termination from an enlarged end, the strength at the resultant coupling using the termination may be greater than the bar being joined. In one form, the coupling has a strength of approximately 110% of the strength of the bar although as will be appreciated this could be varied by varying the dimensions of the various components in the termination.
In a particular embodiment, a preform of the termination is formed by the forging operation; and the finished termination is formed in a subsequent milling operation of the preform. This arrangement has the advantage of allowing a more angular profile on the termination than may otherwise be reliably provided solely by a forging operation. However, it is to be appreciated that depending on the profile of the termination, it may be shaped without requiring a milling process.
In one form, the method uses reinforcing bar having a substantially constant cross section as feed stock. In that arrangement, the method further comprises the steps of enlarging an end portion of the bar and forming the termination on the enlarged end portion. In one form this step of enlarging the end portion is part of the forging operation and is undertaken whilst the end portion is heated.
In one form, the termination is shaped to incorporate an engagement face incorporating locking formations thereon. A engagement face which is profiled in this shape is disclosed in the Applicant's corresponding International application entitled “A Reinforcing Bar”, the contents of which are herein incorporated by cross reference.
In yet a further aspect, the invention provides a forming apparatus for reinforcing bars, the apparatus comprising a multi stage forming line arranged to receive the reinforcing bars and to form a termination on an enlarged end of the reinforcing bars, the termination being shaped to form part of an interlock to connect the bar to another member.
In one form, the forming line incorporates a heating stage having at least one heating station arranged to heat the end portion of the reinforcing bar; and a forging stage having at least one forging station arranged to at least partially shape the termination on the heated end portion by a forging process. In a particular arrangement, the forging station incorporates a plurality of cooperating dies that are operative to shape the heated end portion.
In one form, the forging stage further comprises a trimming station arranged to trim the at least partially shaped termination following processing of the end portion by the forging station.
In a particular embodiment, the forging stage further comprises an upset station arranged to enlarge the heated end portion of the reinforcing bars prior to processing of those end portions by the forging station. In one form, the upset station incorporates at least one forging punch operative to enlarge the heated end portion.
In a particular embodiment, the forming line further comprises a cooling stage subsequent to the forging stage, the cooling stage being arranged to control the cooling of the heated end portion so that the heating of the end portions of the bars do not substantially alter the material properties of the bars. In one form, where the bar is tempered steel, the heating stage is operative to heat the end portions of the reinforcing bars to a temperature suitable for hot or warm forging and wherein the cooling stage is operative to allow quench cooling of the end portions to a first temperature and than to a second lesser temperature under substantially ambient conditions.
In a particular embodiment, a preform of the termination is formed in the forging stage and the forming line further comprises a milling stage including at least one milling station operative to finish the termination by milling of the preform. Typically, the milling stage is subsequent to the cooling stage.
In a particular arrangement, at least one of the stations is moveable into and out of register with the end portions of the reinforcing bars. In this way the feeding of the reinforcing bars through the forming line may be simplified as they need only progress in one direction along those stages of the forming line.
In a particular arrangement, the apparatus further comprises a feed assembly operative to feed individual reinforcing bars through the forming line. In a particular arrangement, the apparatus is operative to receive reinforcing bars of different diameters and the rate of feed of the feed assembly changes along at least some of the stages depending on the diameter of the bar.
In a particular form, the forming line is arranged to form terminations on opposite ends of the reinforcing bars. In one form, at least one of the stages incorporates first and second spaced apart stations that are operative to engage with the opposite ends of the reinforcing bars simultaneously. In one form, the spacing between the first and second stations of the at least one stage is able to be varied to allow for forming of reinforcing bars of different lengths. In another form, the feed assembly is operative to rotate the reinforcing bars to enable a station of at least one of the stages to process the respective opposite ends of the reinforcing bars sequentially.
Typically a controller is provided that is operative to control operation of the feed assembly and the various stages of the forming line. Further a quality assurance process may be provided as part of a finishing stage to check the dimensions and the integrity of the reinforcing bar terminations. This stage may utilise imaging equipment to enable an image of the bar to be assessed against a pre-stored criteria.
In further aspects, the invention relates to a reinforcing bar production facility and to a method of producing reinforcing bar. These aspects incorporate the methods and/or apparatus described above to enable a fully integrated system of manufacture of the bar with the terminations.
It is convenient to hereinafter describe embodiments of the present invention with reference to the accompanying drawings. It is to be appreciated however that the particularity of the drawings and the related description is to be understood as not limiting the preceding broad description of the invention.
In the drawings:
Turning firstly to
The reinforcing bar 10 further includes a termination 12 which extends along an end portion of the bar to the terminal end 13 of the reinforcing bar 10. Whilst not shown, typically the bar would also include a similar termination at its other end 25. In the illustrated form, the termination 12 is integrally formed with the shaft 11 and is enlarged as compared to that shaft (i.e. it extends radially outwardly from a central axis CL of the reinforcing bar a greater distance than the shaft). A transition zone 14 is present between the shaft 11 and the enlarged termination 12.
The termination 12 includes an engagement face 15 which extends along a length of the bar 10 and projects outwardly therefrom. This engagement face 15 is profiled to include locking formations which enables the bar 10 to be coupled to another bar or other object to form an interlock as will be discussed in more detail below. The locking formations in the illustrated form comprise a plurality of spaced apart upstands 16, 17, 18 and 19 and a plurality of recesses 20, 21, 22 and 23. The majority of these recesses 21, 22 and 23 extend between adjacent ones of the upstands (16, 17, 18 and 19). A proximal one of the recesses 20 extends between a hub portion 24 of the termination and the most proximal upstand 16.
The termination is configured as a part cylinder having a diameter which is greater than the axis of the shaft 11. Furthermore, the engagement face 15 is formed effectively as a “cut out” from that cylindrical termination. However, it is to be appreciated that whist the engagement face 15 may be considered as a cut out portion, it is not limited to such a method of manufacturing as the termination may be formed by a forging operation of the like into its final shape without the need for any substantial removal of material. Such a process is described in detail below.
Turning now to
The coupling 50 is formed by interconnecting the terminations 12I and 12II to form an interlock 51 with the upstands of one termination interfitting within a corresponding recesses of the other termination. The interlock extends along an axis (designated A-A) which, in the illustrated form, is coaxial with the central axis of the respective reinforcing bars 10I and 10II. Furthermore, once the terminations 12I and 12II are interconnected along their engagement faces 15I and 15II the exterior surface of the termination forms a complete cylinder (which in the illustrated form is a circular cylinder) having a diameter which is greater than the diameter of the respective shafts 11I and 11II.
The coupling 50 also includes a retaining device 52 which is arranged to prevent separation of the terminations. In the illustrated form, the retaining device 51 is in the form of a sleeve, typically a metal sleeve having an internal bore which is just slightly larger than the exterior diameter of the cylinder formed by the interconnected terminations. In this way the sleeve can slide over the lapping terminations and is typically retained in place by a wire tie or the like.
Turning to
The apparatus 100 includes five principal stages; being a heating stage 101; a forging stage 102; a cooling stage 103; a machining stage 104 and a finishing stage 105. The apparatus further comprises a feed assembly 106 which is arranged to control the movement of the reinforcing bars through the apparatus 100.
The feed assembly 106 takes the reinforcing bars from an in-feed mechanism 107 through to a discharge mechanism 108. During this movement the feed assembly 106 presents the ends (13,25) of the reinforcing bars 10 in a position where each station of each of the five stages may undertake the required processing of the respective bars 10.
At the in-feed mechanism 107 the reinforcing bars, which are of a pre-specified length of substantially constant diameter, are disposed on to a table and are fed into a magazine. A feeder system then indexes one bar at a time to be received onto a heating conveyor 109, which forms part of the feed assembly 106.
The heating conveyor 109 includes continuous chains 110 on which locating and carrying brackets (not shown) are mounted to receive the bars 10 so as to keep them at a discrete distances apart and in a parallel relationship. The conveyor 109 is able to accommodate bar lengths typically ranging from 1.5 metres to 8 metres.
The heating stage 101 is in the form of a pair of three stage induction coil heating stations 111 and 112. These heating stations are disposed opposing one another so as to be able to engage with and heat opposite ends of respective bars simultaneously. To cater for reinforcing bars of different length, one induction heating station 111 is fixed whilst the other 112 is mounted to allow movement of the stations to vary the gap therebetween so as to accommodate bars of different length.
The heating conveyor 109 presents the respective ends 13,25 of the bars 10 at the heating stations 111 and 112. The stations are movable inwards and outwards so as to be able to move in and out of register with the respective bar ends. As the heating stations are 3-stage coil inductors, the stations are caused to register three times with each bar, with the bar moving into each of the three coils. The heating conveyor 109 is arranged to index the bar in line with each of these three coils with this indexing occurring when the stations are moved out of register with the respective bar ends 13, 25.
In one form, where the reinforcing bars are made from steel, the heating stage is arranged to heat the end portions of the bar to in excess of 1000° C. In one application this temperature is set at 1150° C. However it will be appreciated that the temperature may vary depending on the metallurgy of the bar or the type of forging process that is used.
On exiting the heating stage 101 the reinforcing bars are then conveyed to the forming stage 102 which includes three discrete stations, being upset station 113, forging station 114, and trim station 115.
As best illustrated in
In the upset station 113, the respective ends of the reinforcing bar are enlarged. The upset station includes a first and second forging punch (118, 119) as best illustrated in
Once the end portion of the reinforcing bar is enlarged, it is then moved into register with the forging station 114. The forging station 114 includes first and second dies 120, 121 which cooperate to shape the enlarged end portion to form a preform 30 of the termination 12. That preform 30 is close to the final shape of the termination 12 and includes the general shape of the engagement face 15 and the upstands 16,17,18 and 19 and recesses 20, 21, 22 and 23. However, the transitions between the upstands and the recesses are not fully defined and as material needs to be removed to make these transitions more angular. This processing step is done in the milling stage 104 as will be discussed below.
After the end portion has been shaped by the forging station 114 it is then passed to the trim station 115 where excess flashing is removed which extends about the perimeter of the preform 30. This is achieved again by a set of cooperating dies 122, 123 as best illustrated in the
It is to be appreciated that the forging station could be configured in a similar manner to the heating stage where two sets of stations are located at opposite ends of the bars so that the forging of the ends is conducted simultaneously rather than sequentially. The main advantage of using only one set of stations for the forging stage 102 as illustrated is that it reduces the overall cost of the forming line 100 without any significant loss in processing time of the bars 10.
Once both ends of the bars have been shaped by the forging stage 102 the bars then enter the cooling stage 103. A cooling conveyor 124 forms part of the feed assembly 106 and is of similar construction as the heater conveyor 109 including two sets of endless chains 110.
The cooling stage 103 is set up to control the cooling of the end portions of the reinforcing bars 10 so that the properties of the end portions are not substantially affected by the heating of those bars. In this way, the end portions of the bars retain the same material properties as the bar shafts 11.
The cooling stage 103 includes three parts. A first part comprises quenching stations 125, 126. In a similar design as in the heating stage 101 one of the quenching stations is fixed whilst the other 126 is movable so as to cater for reinforcing bars of separate length. In use, many reinforcing bars are formed from tempered steel and the purpose of the quenching station is to return the temper to the end portions. This is achieved by quickly cooling the surface of the bars by forcing water over the heated bar surface. During this quenching process typically the surface temperature of the bar reduces to approximately 600° C. although again it is to be appreciated that the specific temperatures could vary depending on the construction of the bar. Further in some instances where non-tempered steel is used for the feed stock, this quenching part may be bypassed.
After leaving the quenching stage the reinforcing bars are then moved along the cooling conveyor 124 for sufficient time to allow the temperature of the bar to reduce to a lower threshold (typically in the order of 460° C.) under ambient temperature conditions. The length of the cooling time to achieve this lower threshold will vary depending on the thickness of the bar. In tests conducted by the applicant it is found that for steel reinforcing bars ranging between 16 mm to 35 mm, the cooling time is between 300 and 500 seconds. This is represented in the graph in
Once the bar has reached this lower threshold temperature it can then be cooled rapidly without affecting the properties of the steel. In the illustrated form, the cooling stage 103 includes a pair of water coolers 127,128 which pass a stream of water over the bar ends to more quickly reduce the temperature of the end portions then would otherwise occur if left to cool under ambient temperature conditions.
Following the cooling stage 103, the bars 10 are then passed to the milling stage 104 where a pair of milling stations 129,130 machine the preform 30 of the terminations into their finished stage. Again one station 130 is movable relative to the other to cater for differing bar lengths. The milling stations 129,130 include a set of gang milling cutters which traverse over the preform 30 whilst they are hydraulically clamped in a stationary position. The milling operation is done in several roughing and finishing operations with the bars being indexed several times through the milling stations and are clamped on different parts of the finished profile to facilitate complete machining of the whole termination.
Following the milling stage 104, the bars are then moved to a finishing stage 105 which includes finish stations 131,132 to clean the surface of the terminations and then to final QA and inspection stations 133,134. These QA stations 133,134 consist of an electronic comparative system using digital cameras. The stations check the finished profile against reference data held in memory and give off a signal to the operating system if a termination is outside the scope of the specification. These stations may also include a self-diagnostic mode allowing the operator to take corrective action.
Once the bars have passed through the QA system, they are then discharged on to the discharge mechanism 108 so that they can be bundled and then strapped for transport.
An advantage of the apparatus as disclosed is that it may be fully automated. In this regard the various stations are typically operated under hydraulic power which in turn is operated under a central controller. In particular in certain stages of the operation, most notably during the heating and cooling stages, the times that the bar may need to remain in those stages may vary depending on the diameter of the bar. This can be achieved by controlling the feed assembly 106 and in particular the speed of the respective conveyors 109,124.
The apparatus 100 can be fully integrated into a production facility for reinforcing bars. As will be appreciated by those skilled in the art, reinforcing bars are typically made in continuous lengths which are then cut into stock lengths where they are stockpiled. For any particular job, an order is placed which typically specifies both the length and the diameter of the bar. This order is fulfilled by cutting lengths of bar from the stockpile. The apparatus 100 can be integrated into this process. Whilst previously the bars would be cut to their exact size, when using the apparatus 100 they are made slightly larger to take into account the termination formation process undertaken by the apparatus 100. These lengths are then fed into the apparatus 100 which is set based on both the length of the bars as well as their diameter (under operation of the controller) and are then fed through the forming line. Accordingly, the reinforcing bars with these terminations can be manufactured in the same facility as standard reinforcing bar and in that way can be offered as an optional stock item which is fulfilled in a manner consistent with standard reinforcing bar.
In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.
Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005900557 | Feb 2005 | AU | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/AU06/00164 | 2/8/2006 | WO | 00 | 4/2/2008 |
