WO1998010158A1

WO1998010158A1 - Threaded fastener having insertion depth indicator

Info

Publication number: WO1998010158A1
Application number: PCT/AU1997/000585
Authority: WO
Inventors: Rodney Mackay Sim
Original assignee: Reid Construction Systems Pty. Ltd.
Priority date: 1996-09-06
Filing date: 1997-09-08
Publication date: 1998-03-12
Also published as: AUPO219296A0

Abstract

Disclosed are threaded fasteners having insertion depth indicators (14) positioned periodically along the thread (12). Also disclosed are devices (100) having internal thread adapted to engage with and secure to an externally threaded bar wherein the device has an aperture or apertures (124) extending from an outside surface to the internal thread to allow the ingress of concrete laitance or other flowable material thereto.

Description

Invention 1 Threaded Fastener Having Insertion Depth Indicator

Field of the Invention

The following invention relates to a threaded fastener having an insertion depth indicator thereon.

The strength development of a nut and bolt or threaded bar combination is dependent upon the number of threads engaged between the nut and the bolt or threaded bar. For each thread profile there is a minimum number of threads which must be engaged such that the design strength of the union between the nut and the bar is equivalent to the design load required. This is especially relevant in the design of coupling devices for joining or terminating steel bars or other reinforcement tendons such as fibre reinforced plastics bars and wires used for the reinforcement of concrete.

Construction standards normally require that the devices used for reinforcement bars or tendons be designed to ensure that the strength of the joint and of the devices themselves exceed a certain multiple of the yield strength of the bar or in some cases (such as in seismic design) exceed the ultimate tensile strength of the bar itself.

When threaded components are used as such devices on threaded reinforcement bars and tendons, the design requirement for such devices is that a defined length of threaded engagement be achieved between the device and the tendon according to the design of the thread in order to achieve the design requirements imposed by the construction codes.

Continuously threaded bars have the disadvantage that there is no way of determining the depth of embedment once the bar is inserted into the coupling other than by time consuming measuring, and marking the required embedment depth before insertion. Marking of the bar needs to be indelible to avoid the possibility of deterioration when exposed to the weather. Object of the Invention

It is the object of the present invention to overcome or substantially ameliorate the above disadvantages and/or more generally to provide a simple and indelible method of determining the insertion depth of the bar in the device to enable inspection

5 of the made-up coupling to provide assurance to the construction engineer that the device has been properly connected and will achieve the design load requirement.

Disclosure of the Invention

There is disclosed herein a bar comprising external threads and periodic visually, physically distinguishable markers. ιo There is further disclosed herein a bar comprising external threads, periodic ones of which are visually, physically distinguishable from others.

There is further disclosed herein an externally threaded bar having at least one visually, physically distinguishable thread spaced from an end of the bar.

Typically, the means of visually, physically distinguishing the threads can i s comprise a tooth or slot in the thread.

Alternatively, the distinguishable feature could be a thread of different overall shape to the remaining threads of the bar.

Alternatively, the visually distinguishing feature could be a marker cut in the thread. 20 Alternatively, the distinguishing feature could be a missing thread.

Typically, the visually distinguishing thread or feature could be spaced at a period equivalent to a plurality of teeth, typically four or more.

Brief Description of the Drawings

A preferred form of the present invention will now be described by way of 25 example with reference to the accompanying drawings, wherein: Fig. 1 is a schematic elevational view of a threaded bar, Fig. 2 is a schematic end elevational view of the bar of Fig. 1 , Fig. 3 is a schematic cross sectional elevational view of an end portion of the bar of Fig. 1 inserted into a device body,

Fig. 4 is a schematic elevational view of an elongate bar showing the periodicity of markers, and Figs. 5 to 9 and 9A are schematic cross sectional end elevational views of alternative means of marking the threads of a bar.

Description of the Preferred Embodiments

In Fig. 1 there is schematically depicted a bar 10 having external thread 12 thereon. At a predetermined period P, the threads 13 at those locations have a marker 14 thereon. As shown in Fig. 1 , marker 14 can be a cut, tooth or slot as illustrated.

Since the required insertion depth is a function of the number of teeth required for engagement, the bar 1 1 incorporates the distinguishing marks 14 which repeat along the length of the bar. The interval or period P is equal to a multiple or fraction of the required insertion depth of the bar. The bar can be cut at the point of a distinguishing tooth before insertion into the device. As shown in Fig. 3, the end of a bar 1 1 is shown inserted into a device body 15 having internal thread 16 therein. Full engagement of the thread is evident because a distinguishing tooth 14 appears at the entry to the device body. Alternatively, the tooth 14 could be just hidden from view within the device body when the bar was fully screwed home. If the bar were not fully engaged, then the fact would be evident by the position of the distinguishing tooth 14 being displaced from the entry to the device body 15 by some distance.

For bars produced by rolling of the thread profile onto the bar (eg hot or cold rolled steel reinforcement bars), the distinguishing mark could take the form of a change in the geometry or form of a tooth with the required periodicity to mark the length of the insertion depth of the device. The mark could include part of the tooth removed, absence of a tooth or changed form of the tooth to indicate to the user that this was the marker tooth. Fig. 4 shows a typical periodicity of marker 14 which, as mentioned earlier, could take the form of a missing tooth at the position 17 shown in the figure 4A.

It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, the invention is not limited to bars used for the reinforcement of concrete. Such a combination of marked bars and devices could find application in a wide range of engineering applications where certainty of the strength of the union between the device and the threaded bar was required after make-up of the union.

Further modifications are illustrated in Figs. 5 to 9 and 9A. For example Fig. 5 depicts what might be the normal thread 12 of a bar whereas Fig. 6 shows a marker tooth. This arrangement could be reversed such that the ordinary threads are those of Fig. 6, whereas the marker tooth is that of Fig. 5. Similar comments apply also for Figs. 7 to 9 and 9A wherein Fig. 7 might represent the normal tooth and Fig. 8, 9 or 9A the marker tooth. For example, in Fig. 8, a marker tooth can have a notch 18 cut therefrom. In Fig. 9 a tooth is removed, whereas in Fig. 9A a portion of a tooth is removed.

Also, it should be appreciated that the concept of the present invention can equally be applicable to threaded fasteners such as bolts.

Invention 2 Threaded Fasteners having Means to allow Ingress thereto of

Concrete/Grout

Field of the Invention When concrete reinforcement bars are joined by threaded systems, there is the potential for clearance to exist between the joining threads which results in slip of the bar within the joint which alters the elastic behaviour of the joint compared to a non- joined bar. Some construction standards place limits on the degree of slip allowed.

The traditional method of overcoming slip has been the use of torque nuts in addition to the coupling device which induces a pre-load in the coupling and transfers the applied load through the coupling body rather than through the threads of the coupling device and the threaded bar. Unfortunately, this method is both expensive and difficult to implement because it requires the use of additional components and the nuts must be tightened with torque wrenches in confined spaces.

Object of the Invention

It is the object of the present invention to overcome or substantially ameliorate the above disadvantages and/or more generally to provide a means to lock threaded components together to take up clearances and reduce slip therebetween.

Disclosure of the Invention There is disclosed herein a device having internal thread adapted to engage with and secure to an externally threaded bar, the device comprising an aperture or apertures extending from an outside surface thereof to the internal thread to allow the ingress of concrete laitance or other flowable material thereto.

There is further disclosed herein an externally threaded bar, an end of which is adapted to be received within the bore of an internally threaded device, the threaded bar comprising a leak path and/or a missing tooth or teeth adapted to allow the ingress of concrete laitance or other flowable material between the threads of the coupled components.

The leak path can be provided internally and/or externally of the core of the bar itself. There is further disclosed herein a combination of an internally threaded device and an externally threaded bar threadingly engaged therewith, the combination comprising means to allow the ingress of laitance or other flowable material to the interconnected threads thereof.

Preferably the device can comprise a series of holes or apertures extending from an outside surface thereof to the internal threads.

Alternatively and/or additionally, the device can comprise an array of missing thread segments to allow the ingress of laitance or other flowable material thereto.

Thus means are provided to enable the access of concrete laitance into the device so that it can fill or partially fill the voids between the teeth of the coupling and the threaded bar. Once set, this then prevents the bar from moving relative to the device even under extreme loads when the surrounding concrete has failed. This ensures that the components will continue to transfer the full applied load during post- elastic stresses. This is especially important under seismic loading conditions.

Brief Description of the Drawings A preferred form of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:

Figs. 10 and 10A are schematic end elevational views of devices having a means to allow the ingress of laitance thereto,

Figs. 1 1 and 11A are schematic cross sectional side elevational views of the device of Figs. 10 and 10A, and

Figs 12A to 12F show additional embodiments. Description of the Preferred Embodiments

In Figs. 10 and 11 of the accompanying drawings there is schematically depicted a device 100 having an internal bore 101 into which an externally threaded rod can be threadingly received. The bore 101 has internal thread 102 therein. As illustrated, a slot 103 is provided which in effect removes a portion of teeth 104. The passage defined by slot 103 allows the ingress of concrete laitance to the spaces between the internal threads 102 and the external mating threads of a reinforcement bar. Figs. 10A to 11A depict an embodiment wherein the slot 103 extends only partially way through the bore 101. In Figs. 12A and 12B there is depicted an ordinary attachment device 120.

This device is internally threaded for engagement with the external thread of a bar 121 but allows no means for the ingress of concrete laitance thereto. Figs. 12C and 12D show a device 123 having an internal bore therein. The device 123 further comprises a series of transverse apertures or holes 124 which extend from an outside surface thereof to the internal bore. That is, the holes 124 directly communicate concrete laitance outside the device 123 to the threaded interengagement between the internal threads of the device and external threads of the bar 122.

This theme is also applied in the embodiment of Figs. 12E and 12F. In this case, rather than providing a plurality of holes 124, a plurality of lengthwise slots 125 are provided.

Thus, means for access are achieved by designing the devices with holes or other apertures to promote ingress of concrete laitance. Such apertures can be defined by holes penetrating the wall of the device through to the bore either with or by providing "leak channels" along the threaded section by partial removal of the teeth or alteration of the geometry or form of the teeth to permit the passage of laitance from the entry of the device between the threaded bar and the device. Both of these methods can be used singularly or in combination. Provision may also be made on the bar itself to facilitate the leak path by modification of the form of the teeth, partial removal of one or successive teeth in such a way as to channel the laitance into the coupling.

It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, two or more slots 103 can be provided each spaced radially about the internal thread 102.

Invention 3 A Combination of Inventions 1 and 2

Disclosure of the Invention

There is disclosed herein in combination a bar comprising external threads and 5 periodic visually, physically distinguishable markers, or a bar comprising external threads, periodic ones of which are visually, physically distinguishable from others, or an externally threaded bar having at least one visually, physically distinguishable thread spaced from an end of the bar. and ι o a device having internal thread by which the bar is threadingly secured thereto, the device comprising an aperture or apertures extending from an outside surface thereof to the internal thread to allow the ingress of concrete laitance or other flowable material thereto.

Additionally and/or alternatively to the provision of said aperture or apertures, 15 the bar can comprise a leak path and/or a missing tooth or teeth adapted to allow the ingress of concrete laitance or other flowable material between the threads of the coupled components.

Brief Description of the Drawings

A preferred form of the present invention will now be described by way of 0 example with reference to the accompanying drawings, wherein:

Fig. 13 is a schematic cross sectional elevational view of a marked threaded bar threadingly engaged with a device body,

Fig. 14 illustrates in cross sectional end elevation an alternatively distinguished bar, 5 Fig. 15 is schematic elevational view of the alternative bar of Fig. 14,

Figs. 16A to 16D are schematic elevational views of bars having alternative thread configurations, and Figs. 17A to 17E are schematic end elevational views of alternative threaded bars.

Description of the Preferred Embodiments

In Fig. 13 of the accompanying drawings there is depicted a device body 100 5 having threadingly engage therein an externally threaded bar 10.

As with Invention 1 , the bar 10 comprises at periodic spacings a number of slots 14. The slots 14 can serve to allow the ingress of concrete laitance to the space between the inserted portion of the bar 10 and the device body 100.

As shown in Figs. 14 and 15, slots 14 can form a spiral formation about the ι o rod 10. Thus the ingress of laitance material can follow the spiral path into the thread space. As an alternative, the slot could be continuous and in-line.

As shown in Fig. 16, the slots 14 can be positioned in a number of various configurations to allow the ingress of laitance material. Further to this theme, and as shown in Fig. 17, differing shaped notches can be provided either in-line, staggered or 15 in a spiral formation. In Fig. 17A, the inside bore 210 of device 100 is shown. The inside reference diameter of the teeth within the bore of device 100 is shown by reference numeral 200. Reference 230 indicates the bar tooth outside shape, whereas the reference diameter for the core of the bar 10 is shown by reference numeral 220.

Variations on this theme are shown in Figs. 17B to 17E. 20 It should be appreciated that modifications and alterations obvious to those skilled in the art are not to be considered as beyond the scope of the present invention. For example, the device body 100 can comprise apertures as described with reference to Fig. 12.

Claims

The claims defining the invention are as follows :-

1. A bar comprising external threads and periodic visually, physically distinguishable markers.

2. A bar comprising external threads, periodic ones of which are 5 visually, physically distinguishable from others.

3. An externally threaded bar having at least one visually, physically distinguishable thread spaced from an end of the bar.

4. The bar of claim 1 , wherein the means of visually, physically distinguishing the threads can comprise a tooth or slot in the thread. ι o

5. The bar of claim 1. wherein the distinguishable marker comprises a thread of different overall shape to the remaining threads of a bar.

6. The bar of claim 1 , wherein the visually distinguishable marker is cut in the thread.

7. The bar of claim 1 , wherein the distinguishing marker is a missing 15 thread.

8. A device having internal thread adapted to engage with and secure to an externally threaded bar, the device comprising an aperture or apertures extending from an outside surface thereof to the internal thread to allow the ingress of concrete laitance or other flowable material thereto. 0

9. An externally threaded bar, an end of which is adapted to be received within the bore of an internally threaded device, the threaded bar comprising a leak path and/or a missing tooth or teeth adapted to allow the ingress of concrete laitance or other flowable material between the threads of the coupled components.

10. The bar of claim 9, wherein the leak path is provided internally and/or 5 externally of the core of the bar itself.

11. A combination of an internally threaded device and an externally threaded bar threadingly engaged therewith, the combination comprising means to allow the ingress of laitance or other flowable material to the interconnected threads thereof.

12. The combination of claim 11, wherein the device comprises a series of holes or apertures extending from an outside surface thereof to the internal threads.

13. The combination of claim 11 , wherein the device can comprise an array of missing thread segments to allow the ingress of laitance or other flowable material thereto.

14. In combination a bar comprising external threads and periodic visually, physically distinguishable markers, or a bar comprising external threads, periodic ones of which are visually, physically distinguishable from others, or an externally threaded bar having at least one visually, physically distinguishable thread spaced from an end of the bar, and a device having internal thread by which the bar is threadingly secured thereto, the device comprising an aperture or apertures extending from an outside surface thereof to the internal thread to allow the ingress of concrete laitance or other flowable material thereto.

15. The combination of claim 14 wherein additionally and/or alternatively to the provision of said aperture or apertures, the bar comprises a leak path and/or a missing tooth or teeth adapted to allow the ingress of concrete laitance or other flowable material between the threads of the coupled components.