AU2018205080B2

AU2018205080B2 - Coupler for threaded reinforcing bar

Info

Publication number: AU2018205080B2
Application number: AU2018205080A
Authority: AU
Inventors: Thomas James Murdoch
Original assignee: Illinois Tool Works Inc
Current assignee: Illinois Tool Works Inc
Priority date: 2017-07-20
Filing date: 2018-07-10
Publication date: 2024-08-08
Anticipated expiration: 2038-07-10
Also published as: AU2018205080A1

Abstract

C:\Interwovn\NRPortbl\DCC\PLW\17320449 I.dox-l0072018 -7 ABSTRACT A coupler for mounting to externally threaded reinforcing bar for use in concrete construction, the fitting comprising a body having a portion with an internal thread for engagement with the thread of the reinforcing bar, wherein the thread form at the inner end portion of the internal thread includes on one of its flanks an enlargement of progressively increasing extension, the enlargement extending towards the opposing flank of the thread to provide an increasing friction fit with the thread of the bar, the enlargement being only on a part of the face of the flank whereby the remainder of the face of the flank forms, in conjunction with the adjacent flank of the bar thread during tightening, a void for receiving material displaced during tightening. 1/4 10 12 11b FIGURE 1 11a 12 AA 13 13 FIGURE 2

Description

1/4

12

11b

FIGURE 1

11a

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AA

13 13

FIGURE 2

COUPLER FOR THREADED REINFORCING BAR

The present invention relates to a coupler for threaded reinforcing bar for use in concrete construction.

One form of reinforcing bar used in concrete construction incorporates a continuous coarse external thread. The thread not only acts to form a key between the bar and concrete, it also enables a range of supplementary fittings easily to be applied to the bar by engagement of a mating thread with that of the bar. One such threaded reinforcing bar is marketed under the trade mark "ReidBar" by the ramsetreid division of ITW Australia Pty Ltd, a related entity of the present applicants. As previously mentioned, the thread on the reinforcing bar is quite coarse and its pitch ranges from 8mm for a bar of 12mm diameter to around 16.5mm for a bar diameter of 32mm.

Internally threaded fittings for mounting over the end of threaded reinforcing bar for example for coupling lengths of bar in series tend, principally for cost considerations, to be of cast construction, cast iron predominantly, with the internal thread being formed during casting by a sand core. The internal thread formed in this way is not formed to the degree of accuracy which would be expected from a conventionally tapped thread and, moreover, the external thread on the bar itself is not formed to a particularly high degree of accuracy. A consequence of this is that there may not be a particularly tight engagement between the fitting and the bar and some slippage can occur between the bar and the fitting.

Slippage of a coupler on a threaded reinforcing bar can have serious consequences and relevant construction standards require that slip be limited to 0.1mm under a loading of 450 mPa using a 500 grade bar, which can be difficult to achieve as the coarse thread of the reinforcing bar is typically formed to a tolerance of 0.5mm. While slippage can be avoided by filling the interior of the coupler with an epoxy cement or by mounting a lock nut on the bar to tighten against the end of the coupler, these measures add to the time and cost of installing the coupler to the bar.

It is desirable to provide a coupler that can accommodate the loose tolerances of the 25947036.1:DCC reinforcing bar and minimise slip of the coupler along the reinforcing bar to within the required standard.

Alternatively or additionally, it is desirable to at least provide the public with a useful choice.

According to the present invention, there is provided a coupler for mounting to externally threaded reinforcing bar for use in concrete construction, the coupler comprising a body having a portion with an internal thread for engagement with a thread of a reinforcing bar, wherein a thread form at an inner end portion of the internal thread includes opposing flanks and an enlargement of progressively increasing extension on one of the flanks, the enlargement extending towards the other of the opposing flanks of the internal thread to provide an increasing friction fit with the thread of the reinforcing bar, the enlargement being only on a part of a face of the flank whereby during tightening of the coupler onto the reinforcing bar, the remainder of the face of the flank forms, in conjunction with an adjacent flank of the thread of the reinforcing bar, a void for receiving material displaced during the tightening.

Disclosed herein is a coupler for mounting to externally threaded reinforcing bar for use in concrete construction, the fitting comprising a body having a portion with an internal thread for engagement with the thread of the reinforcing bar, wherein the thread form at the inner end portion of the internal thread includes on one of its flanks an enlargement of progressively increasing extension, the enlargement extending towards the opposing flank of the thread to provide a progressively increasing friction fit with the thread of the bar, the enlargement being only on a part of the face of the flank whereby the remainder of the face of the flank forms, in conjunction with the adjacent flank of the bar thread during tightening, a void for receiving material displaced during tightening.

Preferred embodiments of the invention will be described, by way of non-limiting example only, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a coupler of one embodiment of the invention, the coupler joining ends of adjacent threaded reinforcing bars; 25947036.1:DCC

Figure 2 is a side view of the coupler; Figure 3 is a sectional view side view of the coupler, taken along line A-A of Figure 2; Figure 4 is a sectional view side view of the coupler, taken along line C-C of Figure 6; Figure 5 is an end view of the coupler; Figure 6 is an enlarged view of detail B as indicated in Figure 3; Figure 7 is an enlarged view of detail D as indicated in Figure 3; Figure 8 is an enlarged view of detail E as indicated in Figure 4; and Figure 9 is an enlarged partial view of section F-F as indicated in Figure 5.

With reference to Figure 1, there is shown a coupler 10 according to a preferred embodiment of the present invention. The coupler 10 is configured forjoining ends of sections of threaded reinforcing bar 1la, 1lb in end to end relation.

The coupler 10 has a body 12 in which ends of adjacent sections of reinforcing bars lla, 1lb can be received. As can be seen in Figure 3, the body 12 has an internal thread 14 formed therein and an internal stop or stand 16 against which ends of the adjacent sections 1la, 1lb can abut. The internal stand 16 may be circumferential and extend the entire circumference of the body 12, though in other embodiments, it may only extend partially within the body 12 and be in the form of a localised boss or extension extending inwardly from the body 12. Externally, the coupler 10 is formed with hexagonal or other formations to permit gripping by a spanner or wrench. The coupler is formed by casting, for example from cast iron, with the internal threads being formed by casting using a disposable sand core. To this extent the coupler is substantially conventional.

Turns of the internal thread 14 adjacent the stand 16 are formed on their inner flank, i.e. the flank closer to the stand 16, with a protuberance or enlargement 18 in the part of that flank adjacent the crest of the thread so as to reduce the thread width in the part adjacent the crest. In practice the protuberance 18 will only be present within the final 1 to 2 thread turns adjacent the stand and will progressively increase in thickness from zero to a maximum adjacent the stand whereby the width of the internal thread will progressively 25947036.1:DCC reduce in the zone of the crest, in the final turn(s) adjacent the stand. Due to the progressively reducing thread width in that zone as the reinforcing bar is advanced toward the stand 16, frictional engagement between the coupler 10 and the bar is increased to lock the coupler 10 onto the reinforcing bar.

As can be seen in greater detail in Figures 7 and 8, the protuberance 18 is of curved or bulbous form but could be of other shape. It should be noted that the portion of the thread flank inwardly of the protuberance, i.e. the portion of the flank adjacent the thread root, is inwardly displaced relative to the protuberance as considered in its thickness direction whereby when the bar is engaged in that portion of the internal thread a void will exist between the portion of the thread flank inwardly of the protuberance and the facing portion of the thread of the bar. As a consequence in the final stages of engagement between the bar and coupler some flow of material can occur from the protuberance into the void. Accordingly, while the frictional engagement engendered between the inner flank of the thread of the bar and the protuberance of the facing inner flank on the thread of the coupler will prevent slippage or at least minimise slippage to within the required standard, the frictional engagement will not necessitate the need for a high tightening torque. More specifically, the contact between the inner flank of the bar thread and the adjacent part of the coupler thread as defined by the protuberance will be more like a line contact rather than a face contact which would arise if the frictional engagement were to occur over the entire height of the two thread flanks and which would likely require a powered wrench to achieve the required tightness.

In the illustrated embodiment, the protuberance 18 extends for two revolutions of the internal thread 14 and terminates at the stand 16. It will be appreciated that the protuberance 18 may not necessarily extend all of the way to the stand 16 and that it may extend for slightly more than or less than two revolutions.

Although in one form the protuberance is continuous over its angular extent, it may alternatively be interrupted over its angular extent so as to reduce the tightening torque somewhat.

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Figure 6 illustrates the normal internal thread 14 formed in the body 12. In the illustrated embodiment, the coupler 10 is configured for 20mm diameter bars lla, 1lb and has a major diameter of 22.84mm and minor diameter of 20mm. The external diameter of the coupler is 35mm and has hexagon portions 13 (see Figure 2) that are 37mm across the flats (A/F). Returning to the internal thread 14, in the illustrated embodiment the height of each crest Y is 1.42mm, the width W is 4.96mm, the thread pitch P is 10.9mm and the thread has a thread angle of 90 degrees.

Figures 7 to 9 illustrate the progressively thickening protuberance 18 in more detail, with reference to locations indicated in Figure 5, the protuberance 18 being indicated by material added to the normal thread.

In this regard, from section F-F of Figure 9, it can be seen that at the -3 degree location, the increased thickness of the flank Xl is zero. Figure 7 illustrates the thickness X2 at the zero degree location, which is 0.05mm. The zero degree location indicates commencement of the protuberance 18.

The thickness X3 of the protuberance 18 at the 90 degree position (Figure 8) from the commencement increases to 0.37mm.

The height X4 of the protuberance 18 at the 180 degree location (Figure 7) from the commencement increases to 0.44mm.

The height X5 of the protuberance 18 at the 270 degree location (Figure 8) from the commencement, then increases to 0.55mm.

Although the invention has been described with reference to a coupler for coupling two lengths of threaded reinforcing bar in end-to-end relation, it will be understood that the invention is applicable to a wide variety of internally threaded couplers for mounting on the end of the bar. By way of non-limiting example, the coupler may alternatively be in the form of a tubular insert internally threaded at one end portion as described above for engagement over the threaded reinforcing bar, and internally threaded at its other end 25947036.1:DCC portion with a standard thread for receiving a standard bolt or standard threaded bar, or it may be in the form of a grouter in which the other end portion of the fitting is of hollow construction which permits anchoring therein of bar by means of a cement composition.

The embodiments have been described by way of example only and modifications are possible within the scope of the invention disclosed.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

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Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A coupler for mounting to externally threaded reinforcing bar for use in concrete construction, the coupler comprising a body having a portion with an internal thread for engagement with a thread of a reinforcing bar, wherein a thread form at an inner end portion of the internal thread includes opposing flanks and an enlargement of progressively increasing extension on one of the flanks, the enlargement extending towards the other of the opposing flanks of the internal thread to provide an increasing friction fit with the thread of the reinforcing bar, the enlargement being only on a part of a face of the flank whereby during tightening of the coupler onto the reinforcing bar, the remainder of the face of the flank forms, in conjunction with an adjacent flank of the thread of the reinforcing bar, a void for receiving material displaced during the tightening.

2. A coupler according to claim 1, wherein the enlargement is of rounded form.

3. A coupler according to claim 1 or claim 2, wherein the enlargement is formed adjacent a crest of the internal thread.

4. A coupler according to any one of claims 1 to 3, wherein the enlargement is formed on no more than about two turns of the internal thread.

5. A coupler according to any one of claims 1 to 4 for coupling two threaded reinforcing bars in end to end relation, the coupler having respective internal threads extending inwardly from opposite ends and separated at their inner ends by an internal stop, the thread form of each internal thread including an enlargement of progressively increasing extension as defined in claim 1.

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