WO1999024724A1

WO1999024724A1 - Self-tightening nut for use with wooden members

Info

Publication number: WO1999024724A1
Application number: PCT/AU1998/000935
Authority: WO
Inventors: Hamid Hakakzadeh Zanjani
Original assignee: Hamid Hakakzadeh Zanjani
Priority date: 1997-11-11
Filing date: 1998-11-09
Publication date: 1999-05-20
Also published as: AU1014199A

Abstract

Self-tightening nut (1) is positioned by rotating housing (10) relative to shaft (2) so as to engage nut (18) with thread (26). The shaft receiving aperture in upper housing (25) has an internal thread, so that continued rotation of housing (10) after lower housing (23) has abutted against member (6) stresses torsion spring (12). Lock nut (22) is screwed onto shaft (2) and is brought into tight frictional engagement with upper housing (25) so as to lock end (14) of spring (12) into a stationary position with respect to shaft (2). Spring (12) in its stressed state provides a torsional bias between lock nut (22) and nut (18). Should members (4 or 6) shrink, the force exerted by spring (12) will cause nut (18) to rotate down shaft (2) to prevent any loosening of the joint and so prevent any gap between fastened members (4, 6) and concrete (7).

Description

SELF-ΗGHTENING NUT FOR USE WITH WOODEN MEMBERS DESCRIPTION

This invention relates to fastening apparatus and methods.

Nut and bolt fastening arrangements are well known. A problem with these arrangements occurs when there is some movement, particularly shrinkage, of the members which the apparatus fastens. Shrinkage of members such as timber members is particularly common as timber dries with age, and there are many timber joints, particularly in the construction industry, which are fastened using nuts and bolts or similar fastening arrangements. It is often important in a structural sense for the members to be fastened together without any significant movement or play being present between the members that are connected.

One solution to the problem of preventing the fastened members from parting is to provide a spring between one of the members and the head of the bolt or the nut. The disadvantage with this approach is that movement of the fastened members will still occur if the forces attempting to part the members can overcome the force exerted by the spring.

It is an object of the present invention to provide fastening apparatus which will at least go some way toward overcoming the foregoing disadvantages, or which will at least provide the public with a useful choice.

In one aspect the invention may broadly be said to consist in fastening apparatus including a confinement means, and a biasing means, the construction and arrangement being such that when the apparatus mounted on a shaft to fasten a plurality of members together, the confinement means is able to move relative to the shaft in a direction toward the fastened members under influence of the biasing means but is prevented from moving in a direction away from the fastened members so that in use the apparatus prevents any substantial separation of the fastened members.

Preferably the confinement comprise a unidirectional gripping means. Alternatively the confinement means comprise an engagement member having an internal thread and the biasing means comprises a torsional biasing means.

Preferably the apparatus includes a housing which surrounds the biasing means.

Preferably the apparatus includes an anchor means, the biasing means being provided between the anchoring means and the confinement means.

Preferably the anchor means comprises a fastening nut.

Preferably the biasing means comprises a spring, preferably a coil spring.

Preferably the unidirectional gripping means comprises a segmented gripping nut.

Alternatively the unidirectional gripping means comprises a star grip.

Preferably the housing has walls which telescope to accommodate movement of the confinement means away from the anchor means.

Preferably the apparatus includes a holding means to prevent the torsional biasing means from applying force to the engagement member if required.

Preferably a release means is provided to allow the holding means to be selectively released.

In a further aspect the invention may broadly be said to consist in shaft gripping apparatus including a plurality of shaft engaging segments generally defining a central aperture to receive a shaft a biasing means to apply a force to the segments in substantially one direction along the shaft, and segment movement means to allow the segments to move relative to each other to alter the size or shape of the central aperture and thereby allow the segments to release the shaft to allow the apparatus to move along the shaft in response to the biasing means or allow the segments to grip the shaft to prevent movement of the apparatus along the shaft in opposition to the biasing means.

In a further aspect the invention may broadly be said to consist in fastening apparatus including a fastening member having a shaft in use disposed through a fastened member being fastened by the apparatus, unidirectional gripping means mounted on the shaft and being able to move in a direction toward

the fastened member, biasing means to maintain a force on tne unidirectional gripping means so that in use the unidirectional gripping means is maintained substantially adjacent to the fastened member.

In a further aspect the invention may broadly be said to consist in fastening apparatus including a fastening member having a shaft in use disposed through a fastened member being fastened by the apparatus, the shaft having an external thread thereon, an engagement member mounted on the shaft and having a corresponding internal thread, a torsional biasing means that applies a force to the engagement member in a direction to rotate the engagement member to move the engagement member toward the fastened member so that in use the engagement member is maintained substantially adjacent to the fastened member.

In a further aspect the invention may broadly be said to consist in a method of fastening a plurality of members using fastening apparatus disposed on a shaft to attach the members together, the fastening apparatus comprising a confinement means and a biasing means, the method comprising the steps of:

biasing the confinement means in a direction toward the members, allowing the confinement means to move relative to the shaft toward the members to maintain the members and the confinement means substantially in contact with each other, and preventing the confinement means from moving in direction away from the members.

1 The invention may also broadly be said to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of the said parts, elements or features, and where elements or features are mentioned herein and which have known equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

The invention consists of the forgoing and also envisages constructions of which the following gives examples.

One preferred form of the present invention will now be described with reference to the accompanying drawings in which;

Figure 1A is a diagrammatic elevation in partial cross-section of a first embodiment of the invention shown disposed in a first position,

Figure 1B is a diagrammatic elevation in partial cross-section of the embodiment of figure 1 A, shown disposed in a second position,

Figure 2 is a diagrammatic elevation in partial cross-section of a second embodiment of the invention,

Figure 2A is a diagrammatic plan view of a gripping apparatus used in the apparatus of figure 2,

Figure 2B is an expanded diagrammatic partial elevation of part of the gripping apparatus of figures 2 and 2A,

Figure 2C is a further view of the embodiment of figure 2 shown disposed in a first position,

Figure 2D is a further view of the embodiment of figures 2 and 2C shown disposed in a second position,

Figure 3 is a diagrammatic elevation in partial cross-section of a third embodiment of the invention, and Figure 3A is a diagrammatic plan view of gripping apparatus used in the apparatus of figure 3,

Figure 4 is a diagrammatic elevation of a further development of the apparatus of figure 2,

Figure 4A is a plan view of the moving bits used in the apparatus of figure 4,

Figure 4B depicts the spring force 12 and the gripping angle of the moving bits of figure 4 and 4A,

Figure 4C is a diagrammatic plan view of the bits guide of figure 4, and

Figure 4D is a diagrammatic elevation of the bits guide of figure 4.

Referring to figure 1A, a first embodiment of fastening apparatus is shown generally referenced 1. The fastening apparatus is shown mounted on the shaft 2 of a fastening member such as a bolt which is disposed between or through members 4 which are to be fastened between a further member 6 and to a concrete member 7 by use of the shaft 2 and the fastening apparatus 1A. The shaft has a curved securing portion 8 which is embedded in concrete 7. In the figure, members 4 are preferably timber members, such as those used in building construction, and may shrink over time as the timber dries, it will be seen that the apparatus may be used to effect a number of different fastening arrangements.

The end 8 could comprise a bolt head, for example, and may also be located adjacent to or in contact with members 4, that is, one end of the shaft 2 does not necessarily have to be embedded in concrete.

The apparatus 1A generally comprises a housing 10 within which a biasing means comprising a spring 12 is located which is connected to a tightening or anchoring nut 22 at end 14 for example and is connected to an internal confinement or engagement nut 18 at the other end 20. The tightening or anchoring nut 22 is provided externally of the housing 10.

The housing 10 has two separate members, a lower housing 23 and an upper housing 25. Protruding engaging edges 27 and 29 provided on the lower and the upper housing respectively allow the housing to telescope to a collapsed stated, but prevent it from separating once it reaches an expanded state.

In figure 1 A, the apparatus is shown in a first position immediately after installation. In use, the apparatus of figure 1A is positioned as shown in figure 1A by rotating the housing relative to the shaft 2 so as to engage the engagement nut 18 with the thread 26 of the shaft. The shaft receiving aperture provided in upper part 25 of the housing preferably has an internal thread, so that continued rotation of the housing torsionally stresses the spring 12 after the nut 18 has caused the lower housing 23 to come into abutment with member 6. Nut 22 is then screwed onto the shaft and is brought into a tight frictional engagement with the upper housing 25 so as to lock end 14 of the spring 12 in a stationary angular position with respect to the shaft 2. The arrangement also prevents end 14 moving up the shaft 2.

If the shaft receiving aperture in the upper housing part 25 is not threaded, then two anchoring or locking nuts 22 may be used to secure the end 14 of the spring.

The spring, in its torsionally stressed state, provides a torsional biasing effect between the anchor nut 22 and the engagement nut 18. A low friction washer 19, such as a TEFLON washer, is provided between the lower end of the housing and the nut 18 to allow nut 18 to rotate freely while still maintaining force on the connected members. The result of the arrangement is that if there is any shrinkage of fastened members 4 or 6, the force exerted by spring 12 will force the engagement nut 18 to rotate down the threaded shaft 2 to prevent any gap between the fastened members 4 and 6 and concrete 7.

In figure 1B the member 4 has shrunk and it will be seen that the nut 18 has followed the upper surface of member 6 to maintain the members in a fastened relationship with each other.

In a further embodiment (not shown) of the invention, the spring 12 is initially provided in an expanded diameter condition, being held open beyond its diameter in its natural state by an actuation pin (not shown). Once the shaft 2 has been positioned as shown in figure 1 A, the housing 10 comprising the spring 12 and engagement member comprising nut 18 is positioned as shown in figure 1A by rotating the housing relative to shaft 2 so as to engage the engagement nut 18 with the thread 26 of the shaft and continue rotating the housing until the engagement nut 18 and the housing 10 have reached the position shown in figure 1A.

The anchoring means comprising nut 22 is then engaged with thread 26, again by rotating the nut 22 relative to shaft 2 to engage the anchoring nut 22 firmly with the housing 10 so that the position shown in figure 1 A is attained.

Once in position, the actuation pin is released. This will allow the spring to freely contract, but to contract to any significant extent, the ends of the spring will need to rotate relative to each other. Thus the spring provides a torsional biasing effect between the anchor nut 22 and the engagement nut 18. The result of the arrangement is that if there is any shrinkage of fastened members 4 or 6 the force exerted by spring 12 will force the engagement nut 18 to rotate down the threaded shaft 2 to prevent separation of the fastened members 4 and 6.

Referring now to figure 2, a second embodiment of the invention is shown generally referenced 30. The shaft 2, thread 26, members 4 and 6, and bolt end 8 have the same references as the apparatus of figure 1A. The apparatus 30 generally comprises a housing having two separate members, a lower housing 32 and an upper housing 34. Protruding engaging edges 36 and 38 provided on the lower and the upper housing respectively allow the housing to telescope to a collapsed stated, but prevent it from separating once it reaches an expanded state.

A biasing means comprising a spring 12 is located within the housing, being provided between the upper end of the housing 34 and a segmented gripping nut 44 which is preferably of a mandrel type. The segmented gripping nut 44, when being forced toward member 4 by spring 12 is essentially unidirectional, in that its design allows it to move downwardly about the thread 26 of the bolt shaft 2, but not back up the shaft toward the spring. Figure 2A shows the segments of the gripping nut 44 in plan view. It can be seen that there are three segments 45, although there could be only two, or more if required.

The operation of the gripping nut can be described with reference to figure 2B in which a part of the gripping nut and shaft 2 are shown in more detail. The segment 45 has teeth 47 corresponding to thread 26 of shaft 2. The inclined surface 49 of the segment has a corresponding inclined surface 51 provided on an internal surface of the lower housing 32. It will be seen that as the lower housing 32 moves down the shaft, 2, the segment 45 will be forced outwardly and downwardly as the teeth 47 follow the angle of the thread 26. Once the teeth 47 pass the outer diameter of the thread 26, the segment is forced into contact again with the inclined surface 51 which forces the teeth 47 back into contact with the thread 26. To ensure that the segment is forced back into the interstices in the thread 26, it is preferred that the angle of surface 51 with respect to the centre line 53 of the shaft 2 is less than the angle between the inclined surface of each ridge of the thread and centre line 53.

In use, the apparatus 30 of figure 2 is located about the shaft 2 by rotating the housing so that the segmented gripping nut 44 rotates relative to the shaft 2 so that the housing including the nut 44 is located about the shaft 2 as shown in figure 2C, then the anchoring nut 22 is engaged with the bolt shaft 2, again by rotating relative to the shaft so as to engage the internal thread provided on the anchoring nut 22 with the thread 26 of the bolt shaft 2. Once the position shown in figure 2 has been realised, the user continues to rotate the anchoring nut 22 relative to the shaft 2 and relative to the housing 34 so as to compress the spring 12. The spring 12 is preferably compressed to a desired extent when the upper part of the upper housing 34 contacts or approaches edge 36 of the lower housing. In this compressed position, the spring applies force toward the shaft end 8 against the gripping nut 44. Thus, as members 4 and 6 shrink or move during use over time, the nut 44 is forced by the spring 12 downwardly toward shaft end 8 so as to confine the fastened members 4 and 6 to prevent them from moving apart. Figure 2D shows the disposition of the apparatus after members 4 have shrunk over time.

Turning now to figure 3, the fastening apparatus of the third embodiment is generally referenced 50 and the arrangement of the housing, spring and anchor nut 46 (referenced

22 in the preceding figures) is substantially the same as those shown in figure 2.

Accordingly, these features have the same reference numerals as those of figure 2. The main difference between the embodiment shown in figure 3 and that of figure 2 is that the apparatus of figure 3 has a star grip mechanism 52 rather than the segmented gripping nut 44. For purposes of clarity, the star grip mechanism 52 is shown separately from the remainder of the apparatus 50 and plan view referred to as figure 3A. The star grip mechanism 52 essentially operates as a confinement or unidirectional gripping means. As can be seen from figures 3 and 3A, the mechanism 52 has a plurality of inwardly facing teeth 54 which are generally angled upwardly pointing in a direction opposite the unidirectional path of travel of the mechanism. Thus the teeth allow the mechanism to be forced downwardly toward shaft end 8 by the spring 40, but engage with the thread 26 of

8

SUBSTTTUTE SHEET (Rule 26) (RO/AU) the bolt to prevent any movement away from the shaft end 8. Accordingly, over time, as members 4 and 6 move or shrink, the apparatus 50 ensures that the members are not able to substantially move apart.

It will be seen that in all the embodiments shown in figures 1 A to 3 the apparatus could be held in place by a bolt head rather than a tightening nut 22 (figure 1 A) or tightening nut 46 (figures 2 and 3). In other words, the shaft could be reversed in its overall position so that the apparatus 1A, 30 and 50 is in each case tightened into its initial position by rotating a bolt head, the tightening nut at the other end of the bolt being in direct contact with one of the members to be fastened.

Turning now to figure 4, the stopper 60 inside the housing ensures that the moving bits do not travel too far toward the inside of the housing while the self-tightening nut is initially pushed onto the shaft, which may produce risk of misplacement of the bits. In addition, the stopper makes it easier to push the nut onto the shaft without turning it. This makes a quicker installation of the fastener possible.

The washer 62 on top of the moving bits determines the accurate stopping location of the bits and transfers the forces of the spring to the central part of the bits to ensure their smooth gliding along the shaft. The bits are designed with an elevated edge 64 (figure 4B) to receive the spring force which is transferred through the washer at the closest point to the shaft (threaded rod).

The rotation stoppers 66 (figure 4D) ensure that the self-tightening nut can be undone and re-used. Without these rotation stoppers it may happen that, while undoing the fasteners, the rotation of the housing is not transferred to the bits.

The modified edges of the bits 68 (figure 4A) shorten their horizontal travel in order to allow an easier movement on the shaft and ensure the smooth functioning of the fastener.

The shaft will experience a stronger tearing force in cases where the tightened members expand. This force is transferred to the bits which are placed in a funnel-like bed 32 (figure 2D). The stronger the tearing force becomes, the stronger the tightening force will be. In contrast, in cases where the members shrink, the spring 12 (figure 2D) will move the bits towards the shrunken members. The movement is caused as a result of the spring force which varies according to the thread angel α of the bits (figure 4B). The measurement of the thread angle α is inversely proportional to the spring force; the bigger the angle α (figure 4B), the smaller is the required force on spring 12 to move the moving bits 44 along the shaft 2.

It will be seen that the present invention has considerable advantages over the prior art. The unidirectional movement provided by the invention ensures that as there is movement or reduction in size of the members being fastened (whether through shrinkage or through wear and tear for example) a secure fastening engagement is maintained between the fastened members. Clearly, the invention has many applications, which include structural timber members, or any other members which are prone to shrinkage, separation or wear. For example, the invention may be used to secure machine parts that in use are prone to separation through wear or vibration.

Claims

CLAIMSThe claims defining the invention are as follows:

1. A self-tightening nut sitting about a shaft (threaded rod) between a conventional nut and a member (or consecutive members), which are tightened by the apparatus moving unidirectional toward the members to be tightened.

2. A self-tightening nut made of a number of bits (jaws) (fig. 2B, 45) with teeth corresponding to a thread (fig. 2B, 26), and an inclined surface (fig. 2B, 49) corresponding with the inclined surface of the lower housing (fig. 2B, 51 ).

3. A self-tightening nut comprising an inner and outer telescopic housing (fig. 5) which limits the longitudinal expansion of the apparatus and the longitudinal movement of the bits (fig. 2B, 45) and transfers torsion force to the end-piece (bits guide fig. 5).

4. A self-tightening nut of claim 3 wherein the telescopic housing contains a spring which moves the bits along the shaft toward the members to be tightened.

5. A self-tightening nut of claims 1 to 4 wherein the apparatus has a function that can be repeated or extended when the nut on top of the apparatus is tightened again after the initial installation.

6. A self-tightening nut of claim 1 wherein the shaft can be made of any diameter.

7. A self-tightening nut of claim 1 wherein the conventional nut may be a star grip or a similar tightening device.

8. A self-tightening nut of claim 1 wherein its material should be appropriate to its expected life-time.

9. A self-tightening nut of claims 1 and 2 wherein the thread of the shaft may be made of any form.

10. A self-tightening nut of claim 2 wherein the material and the length of the bits is appropriate to the tie-down force required.

11. A self-tightening nut of claims 1 to 4 wherein the apparatus can be unscrewed in order to be used elsewhere.

12. A self-tightening nut substantially as herein described with reference to the accompanying drawings.