DK2504117T3

DK2504117T3 - Process for manufacturing a device for connecting reinforcements

Info

Publication number: DK2504117T3
Application number: DK10790458.3T
Authority: DK
Inventors: Edgar Henri Gérard Albert Thirion
Original assignee: Thirion Edgar Henri Gerard Albert
Priority date: 2009-11-26
Filing date: 2010-11-15
Publication date: 2018-11-12
Also published as: WO2011064466A1; EP3495068A1; EP3495068B1; EP2504117B1; FR2952840B1; FR2952840A1; EP2504117A1; DK3495068T3

Description

TECHNICAL FIELD

The present invention relates to a device for connecting reinforcing bars, to a method of manufacturing such devices for connecting reinforcing bars, and to the reinforcing sets of bars made with these devices.

The technical field of the invention is that of manufacturing steel reinforcing bars for reinforced concrete.

STATE OF THE ART

The invention applies in particular to devices for connecting end to end two steel reinforcing bars having ends that are threaded, which devices comprise a tapped sleeve that is screw-fastened onto the threaded ends of the reinforcing bars to be connected together end to end.

The invention makes it possible to obtain such a sleeve having an outside surface that includes irregularities increasing adherence between the sleeve and concrete (in which the sleeve is designed to be embedded).

When making structures out of reinforced concrete such as buildings or engineering works, it is generally important to obtain good bonding between the concrete and the sets of reinforcing bars embedded in the concrete, so as to ensure the strength of those structures.

This bonding results in particular from the concrete adhering on the reinforcing bars. This is particularly important for structures that need to withstand high dynamic loads, such as shocks or vibrations, over the entire lifetime of the structure.

In patent EP 728 880, which is considered as the closest prior art, it is proposed to manufacture such connection sleeves from so-called "high adherence" reinforcing bars.

Such reinforcing bars are subject to a variety of requirements and standards such that the standards NF-A-36-016-1 and EN10080, which define in particular alloys, or grades, of steel used for manufacturing such reinforcing bars, mechanical characteristics of such steels, and geometrical characteristics of the reinforcing bars.

Reinforcing bars or rods of this type present irregularities on their outside surfaces, which may be projecting and referred to as "ribs", or on the contrary may be recessed and then referred to as "indentations".

There are drawbacks to using that type of reinforcing bar to manufacture sleeves for connecting reinforcing bars together end to end by sectioning and drilling a solid bar, as proposed in patent EP 728 880.

Using bars that comply with those standards for manufacturing connection sleeves means that it is not possible to select the grade of steel, the diameter of the bar, and the shapes of the irregularities needed for obtaining connection sleeves that are optimized as a function of stresses specific to using such sleeves in a structure to be constructed.

Another drawback results from the fact that those reinforcing bars generally do not present uniform mechanical characteristics across their section, in particular due to their method of manufacture by rolling.

As a result, the mechanical characteristics of a sleeve made from such a reinforcing bar may not be adapted to the characteristics of the two reinforcing bars that it is used to connect, which does not allow for an optimized connection.

Proposals are also made, in patent US 7 032 286, to manufacture such sleeves using a method involving successively first heat treatment of a blank, forging the blank to form a first blind cavity, second heat treatment, and then making a second blind cavity by forging.

The resulting sleeve, which includes a partition separating the two cavities, is then shrunk onto the ends of two reinforcing bars to be assembled, the shrinking causing ribs to form on the outside face of the sleeve. A drawback of this method is that the partition makes it difficult to obtain uniform shrinkage along the length of the sleeve, and that the rigidity of the connection formed by shrinking between the sleeve and the reinforcing bars is difficult to control, especially when shrinking is performed with a portable tool. Furthermore, removal of that partition would require an additional operation.

Moreover, the shrinking of the sleeve wall does not enable proper control of the position and depth of the external ribs that are designed to lock the sleeve to the concrete surrounding it.

SUMMARY OF THE INVENTION

The invention provides a method of fabricating a sleeve or a nut, for connecting steel reinforcing bars together end to end for a reinforced concrete structure, which method comprises the following operations: - forming irregularities on the outside surface of a steel blank, which is generally solid, by forging; - forming a cylindrical cavity passing through the forged blank; and - tapping the cylindrical cavity.

This makes it possible to obtain an internally-threaded sleeve or nut, having mechanical strength and adherence to concrete that are improved.

In particular, the forged couplers/sleeves present increased resistance to fatigue and to breaking, with the fiber of the steel being retained during the forming process.

Forging can also eliminate certain points of weakness such as cracks or flaws in the steel used to manufacture couplers.

In implementations of the invention: - a cylindrical cavity in the blank of a sleeve may be formed by longitudinal drilling of the forged blank; - the cylindrical cavity in the blank of a nut may be formed, at least in part, by forging, simultaneously or consecutively with forging to form a flared portion of the nut and/or recessed indentations on the flared portion; - the blank may be heated to reach a temperature that is not less than 400°C, in particular a temperature situated in the range 400°C to 1000°C; - alternatively, the forging operation may be performed when cold; - the operation of forging the sleeve and/or nut may be performed in a plurality of steps, using a set of dies specific to each step, i.e. by using several separate sets of dies; - the outside surface of the sleeve or nut may be marked by removing material or by forging so as to form recessed or raised signs enabling characteristics of the sleeve or nut to be identified, such as characteristics of the steel constituting it and/or characteristics identifying the manufacturer of the sleeve or nut; this marking operation may be performed substantially simultaneously with the forging and irregularity forming operations; - the marking of the outside surface of the sleeve or of the nut may also include an operation of depositing material on the surface; - the sleeves may be fabricated from a steel presenting an elastic limit situated in the range 200 megapascals (200 MPa) to 1000 MPa, in particular a steel presenting an elastic limit situated in the range 400 MPa to 600 MPa; - the sleeves may be fabricated from a steel presenting elongation under maximum load situated in the range about 1% to 10%, in particular a steel presenting elongation under maximum load situated in the range 3% to 7%.

The invention makes it possible, simply and with good repeatability, to produce sleeves and nuts having mechanical and geometrical characteristics, in particular the shapes of the recessed and raised irregularities, that are optimized relative to the operating constraints of the reinforcing bar connection devices of which they form part.

On the surface of a sleeve at both ends there may be formed a network of elongate and tapering irregularities, of identical dimensions, which are regularly disposed/spaced apart on the (substantially cylindrical) outside surface of the sleeve.

The irregularities may extend along portions of circles situated in planes that are perpendicular to the longitudinal axis of the sleeve.

The irregularities may also extend along portions of helices having the longitudinal axis of the sleeve as their axis.

The irregularities may present a smooth surface extending over a cylindrical cap; the cap may be defined by a losange-shaped outline, or may also be defined by a curvilinear outline, at least in part.

The greatest dimension of these irregularities is preferably greater than one millimeter, e.g. of the order of one or several centimeters, whereas the depth (of recessed irregularities) or thickness (of raised irregularities) is of the order of one or several millimeters.

Furthermore, (micro)irregularities of size close to one millimeter or less can also be formed by removing material, by deforming the outside surface of the blank, or else by depositing material on the outside surface of the sleeve and/or nut.

Depending on the characteristics required for the sleeve and/or nut, the blanks of these parts could also be subjected to annealing, deburring, and/or shot peening operations.

Other aspects, characteristics and advantages of the invention appear from the following description, which refers to the accompanying figures and illustrates, in non-limiting manner, the preferred methods of performing the invention.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a perspective view of the sleeve in one embodiment.

Figure 2 shows the Figure 1 sleeve in longitudinal section view.

Figure 3 is a perspective view of the sleeve in another embodiment.

Figure 4 shows the Figure 3 sleeve in longitudinal section view.

Figure 5 is a perspective view showing a nut suitable for co-operating with a sleeve such as those shown in Figures 1 to 4, in order to form a connection device such as those shown in Figures 7 to 10, in an embodiment.

Figure 6 shows the Figure 5 nut in longitudinal section view.

Figures 7 and 8 show a portion of a set of bars in an embodiment, in two configurations: in the configuration corresponding to Figure 7, two lock nuts have been screw-fastened onto the respective threaded ends of two bars, and a sleeve has been screw-fastened onto the threaded end of a first one of the two bars; in the configuration corresponding to Figure 8, the sleeve has been screw-fastened onto the threaded end of the second bar.

Figures 9 and 10 show a portion of a set of bars in another embodiment, in two respective configurations similar to those in Figures 7 and 8.

Figures 11 and 12 are diagrams showing two steps in a method of manufacturing a sleeve by forging, in an implementation of the invention .

Figures 13 and 14 are diagrams showing two steps of a method of manufacturing a nut by forging, in an implementation of the invention .

DETAILED DESCRIPTION OF THE INVENTION

Unless explicitly or implicitly stated to the contrary, structurally or functionally identical or similar elements or members are given identical references in the various figures.

Making a reinforcing bar structure, such as a reinforcing cage, for a reinforced concrete structure may require end-to-end connection of two steel reinforcing bars.

To this end, the respective threaded ends 51, 52 of two bars 25, 26, that are placed facing each other, can be connected solely by a threaded sleeve, or else by a connection device 50 incorporating, as well as a threaded sleeve 20, 23, one or two nuts 71 as shown in Figures 7 to 10.

In the configurations shown in Figures 7 and 8 the length of each threaded portion 51, 52 of the bars 25, 26 is at least equal to the sum of the thickness of a nut 71 plus half the length of the threaded sleeve 20, these dimensions being measured along the longitudinal axis 49 shared by the bars, the nuts, and the sleeve .

The bars 25, 26 are connected together by screw-fastening a nut 71 followed by a sleeve 20 onto the end of the bar 25, by screwfastening a nut 71 onto the end of the second bar 26 (cf. Figure 7), and then by screw-fastening the bar 26 into that part of the threaded portion of the sleeve 20 that remains free so as to give the configuration shown in Figure 8.

The bars, the nuts, and the sleeve 20 are rigidly connected together by tightening the two nuts 71 respectively against the two longitudinal ends of the sleeve 20.

In comparison with Figures 7 and 8, the threaded portion 51 of the bar 25 shown in Figures 9 and 10 is longer so that, as shown in Figure 9, a nut 71 and almost all of the sleeve 23 can be engaged (screw-fastened) on this portion 51.

After a nut 71 has been screw-fastened on the end 52 of the bar 26, the ends 51 and 52 being placed in mutual alignment and substantially in mutual contact, the sleeve 23 can be screw-fastened onto the end 52, without requiring relative rotation of the bars 25, 26, by unscrewing the sleeve in part from the bar 25.

The configuration shown in Figure 10 is reached by tightening the two nuts 71 against the sleeve 23.

With reference to Figures 1 to 4 in particular, the sleeves 20, 23 are generally of tubular shape, extending about a longitudinal axis 21, and they have a longitudinal passage passing therethrough provided with a cylindrical thread 22 that results from tapping.

The nature of the steel alloy and the diameter of the blanks used to manufacture sleeves and nuts are selected as a function of the mechanical and geometrical characteristics of the connection device to be manufactured. The steel constituting the sleeve may present at least one mechanical characteristic that is distinct from that of the steel constituting the reinforcing bars; in particular, the ductility of the steel constituting the sleeve may be greater than the ductility of the steel constituting the reinforcing bars. A tubular sleeve blank may be obtained by cutting up a tube or else by forging and drilling, the length of the blank being determined as a function of the length 24 (Figure 2) that is desired for the sleeve.

The length 24 of the sleeve may be close to twice the diameter of the bars that are to be connected by the sleeve.

Each of the sleeves 20, 23 and of the nuts 71 includes irregularities 27 to 34, 39 to 41, 63 formed respectively on their outside faces.

In the embodiment shown in Figures 3, 4, 9, and 10, the body of the sleeve 23 is provided with a central rib 39 that extends along a circumference of the body, on either side of a transverse midplane having its trace in the plane of Figure 4 given reference 48.

The central rib 39 is uninterrupted, and bordered on either side by indentations 30, 31 that extend along portions of helices having the longitudinal axis 21 of the sleeve as their axis, in such a manner that the central rib 39 presents a width, measured parallel to the axis 21, that varies depending on the point of the circumference of the body that is under consideration.

The body of the sleeve 23 is also provided with two uninterrupted end ribs 40, 41 each of which extends along a circumference of the body from one of the two longitudinal ends 75, 76 of the body, and each of which also presents a width that varies (cf. Figures 3 and 4).

In the embodiment shown in Figures 1, 2, 7, and 8, the body of the sleeve 20 is provided on its substantially cylindrical outside face with raised irregularities, or ribs, 27 to 29 that extend along portions of circles situated in planes that are perpendicular to the longitudinal axis 21 of the sleeve.

These ribs are spaced apart in pairs by recessed irregularities that extend along portions of helices having the longitudinal axis 21 of the sleeve as their axis, and of depth 45 that is of the order of one or several millimeters.

As a result, the ribs have the shape of quadrilateral facets, in particular a losange shape that is curved with the radius of the cylindrical envelope of the body.

With reference to Figures 5 and 6 in particular, the nut 71 is essentially constituted by an annular portion 61 and by a flared portion 62 that extends from the annular portion.

The portion 61 of the nut has a plane face 81 arranged to bear against a plane end face of a sleeve.

The flared portion 62, which extends the annular portion 61 along the longitudinal axis 82 of the nut, is provided in its periphery with four indentations 63 that are spaced apart regularly (by 90 degrees). The portion 62 is defined by a frustoconical surface 73, or chamfer, forming an angle 74 with the axis 82 (cf. Figure 6).

The indentations 63 are of substantially cylindrical shape, of identical dimensions, extending substantially parallel to the axis 82 of the nut, and they open out in the second end face 85 of the nut that is parallel to the first end face 81.

The indentations 63 facilitate adherence of the concrete on the outside face of the nut and they can be used to tighten or loosen the nut by means of a tool comprising a plurality of pins of shape that is complementary to the shape of the indentations 63.

In order to manufacture a sleeve, the irregularities can be formed on the outside surface of a solid blank, by forging in two steps .

With reference to Figure 11, a pair of dies 65 of substantially identical shape are used. Each die includes a cavity defined by a surface 79 in the general shape of a half cylinder, and in which grooves 67 are recessed, the shape of the grooves corresponding to a portion of the shape of a raised irregularity to be formed on the sleeve blank.

Alternatively, the inside surfaces 79 of the dies may include ribs of shape corresponding to a portion of the shape of a recessed irregularity to be formed on the sleeve blank.

Since the surfaces 79 of the dies 65 extend parallel to the longitudinal axis 59 of the pre-heated blank 55, the dies are placed in contact with the blank 55 by being moved along arrows 53, and they are caused to bear against the outside surface 56 of the blank so that the irregularities 67 of the dies cause irregularities to be formed on the blank 55, such as those given reference 28 in Figure 12.

With reference to Figure 12, in a second forging step, a second pair of dies 66 is used, which dies are similar to the first dies 65 but are of shape that is substantially different, which dies are pressed along arrows 54 against the pre-formed blank, so as to obtain at the surface of the blank irregularities having the sought-after final shape.

The blank as obtained in this way can then be drilled and tapped in order to obtain the sleeve.

In order to manufacture a nut, the irregularities on the outside surface of a solid blank, and also on at least a portion of the central cavity of the nut, can be formed by forging in a single step.

With reference to Figures 13 and 14, a pair of dies 68, 69 is used. The die 69 includes a central cavity 77 defined by a surface in the general shape of a half cylinder of axis 89.

The second die 68 is substantially in the form of a body of revolution about the axis 89, and comprises a raised central portion 70a of shape that corresponds to at least a portion of the shape of the central cavity to be formed on the blank 57 of the nut.

The die 68 also comprises a recessed portion extending around the portion 70a, that comprises a sloping surface 70b for forming the sloping surface 73 of the nut, and projections 70c on the surface 70b for forming irregularities 63 on the surface 73 of the nut.

The pre-heated blank 57 is placed between the dies 68, 69 or in the cavity 77, and the dies are brought closer (arrow 100 Figure 13). The die 68 pressing on the top face 58 of the blank 57 makes it possible to form simultaneously the flared portion of the nut and at least a portion of the central cavity of the nut.

CLAIMS 1. A method of fabricating a sleeve (20, 23) or a nut (71) for connecting steel reinforcing bars together end to end, the method comprising the following operations: • forming irregularities (27 to 31, 39 to 41, 63) on the outside surface (56, 58) of a steel blank (55, 57) by forging; • forming a cylindrical cavity (46, 47) passing through the forged blank; and • tapping the cylindrical cavity. 2. A method according to claim 1, wherein the cylindrical cavity is formed in the blank (55) of a sleeve by drilling. 3. A method according to claim 1, wherein the cylindrical cavity is formed in the blank (57) of a nut, at least in part, by forging. 4. A method according to any one of claims 1 to 3, wherein the blank is heated to reach a temperature that is not less than 400°C, in particular a temperature situated in the range 400°C to 1000°C. 5. A method according to any one of claims 1 to 4, wherein the forging operation is performed in a plurality of steps, using a set of dies (65, 66) specific to each step. 6. A method according to any one of claims 1 to 5, wherein the outside surface of the sleeve or nut is marked by forging so as to form signs enabling characteristics of the sleeve or nut to be identified. 7. A method according to any one of claims 1 to 6, wherein the sleeve or nut is fabricated from a steel blank presenting an elastic limit situated in the range 200 MPa to 1000 MPa, and presenting elongation under maximum load situated in the range 1% to 10%. 8. A method according to any one of claims 1 to 7, wherein irregularities (27 to 31) are formed at the surface of a sleeve, which irregularities extend along portions of circles situated in planes perpendicular to the longitudinal axis (21) of the sleeve, or along portions of helices having the longitudinal axis (21) of the sleeve as their axis. 9. A method according to any one of claims 1 to 8, wherein the greatest dimension of the irregularities is greater than one millimeter, the depth (45) of recessed irregularities being of the order of one or several millimeters. 10. A method according to any one of claims 1 to 9, wherein an uninterrupted central rib (39) is formed at the surface of the sleeve extending along a circumference of the body of the sleeve. 11. A method according to claim 10, wherein the central rib (39) is bordered on either side by indentations (30, 31) and presents varying width. 12. A method according to claim 11, wherein the indentations bordering the central rib extend along portions of helices having the longitudinal axis of the sleeve as their axis. 13. A method according to any one of claims 1 to 12, wherein an uninterrupted rib (40, 41) is formed at each end of a sleeve, which ribs extend along a circumference of the body of the sleeve and present varying width.

Claims

A method of manufacturing a sleeve (20, 23) or a nut (71) for connecting steel reinforcements, comprising the following steps: - forming unevenness (27 to 31, 39 to 41, 63) on the outside (56, 58) ) of a steel blank (55, 57) by forging, forming a cylindrical cavity (46, 47) extending through the forged blank, and threading into the cylindrical cavity.

The method of claim 1, wherein the shaping of the cylindrical cavity in the blank (55) of a sleeve occurs by drilling.

The method of claim 1, wherein the forming of the cylindrical cavity in the blank (57) of a nut, at least in part, is by forging.

A method according to any one of claims 1 to 3, wherein the blank is heated to a temperature of at least 400 ° C, in particular to a temperature in a range ranging from 400 ° C to 1000 ° C. .

A method according to any one of claims 1 to 4, wherein the forging operation is performed in several steps, using a set of matrices (65, 66) specific to each step in each step.

A method according to any one of claims 1 to 5, wherein the outside of the sleeve or nut is marked by forging so as to produce signs which enable identification of the sleeve or nut.

A method according to any one of claims 1 to 6, wherein the sleeve or nut is made of a steel blank comprising a limit of elasticity ranging from 200 Megapascal (200 MPa) to 1000 MPa and which at maximum load exhibits an expansion that ranges from 1% to 10%.

A method according to any one of claims 1 to 7, wherein on the surface of a sleeve an irregularity (27 to 31) is formed which extends along parts of circles lying in planes perpendicular to the longitudinal axis of the sleeve (21). , or along pieces of spirals whose axis is the longitudinal axis of the sleeve (21).

Method according to any one of claims 1 to 8, wherein the largest dimension of the unevenness is greater than one millimeter, the depth (45) of the unevenness recesses being of the order of one or more millimeters.

A method according to any one of claims 1 to 9, wherein an uninterrupted central rib (39) is formed on the surface of a sleeve which extends along a circumference of the sleeve body.

The method of claim 10, wherein the central rib (39) is defined on both sides by recesses (30, 31) and has varying widths.

The method of claim 11, wherein the recesses defining on both sides the central rib extend along pieces of spirals whose axis is the longitudinal axis of the sleeve.

A method according to any one of claims 1 to 12, wherein on each end of a sleeve is formed a continuous rib (40, 41) extending along a circumference of the sleeve body and of varying widths.