GB2362936A

GB2362936A - Device for holding together broken fasteners

Info

Publication number: GB2362936A
Application number: GB0116754A
Authority: GB
Inventors: Barry Littlewood
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-07-10
Filing date: 2001-07-10
Publication date: 2001-12-05
Anticipated expiration: 2021-07-10
Also published as: GB0116754D0; GB2362936B

Abstract

A male fastener such as a bolt, screw or rivet includes a tie (4) in an axial bore (9). The tie (4) is held by restraining means (7) so that should the fastener rupture, such as due to fatigue, the broken fastener is held together by the tie (4).

Description

1 M CRANICAL FASTENING DEVICE This invention relates to mechanical

fastening devices.

2362936 When sections of engineering assemblies are clamped together using threaded and non threaded fasteners such as nuts, bolts, screws, rivets and other types of fixings, there is applied a mathematically calculated pre-load to the fasteners, which ensures the sections remain clamped together under normal operating conditions. However, under adverse conditions, variable dynamic loading occurs and there is a vast range of combinations and permutations of shear and tensile loads on the fasteners. As a consequence, there is movement of the fasteners relative to the clamped sections producing a loss of effective tension in the fastener which can result in fatigue and eventual fracture or the complete rotational loosening and separation in the case of threaded fasteners. Although such incidents are relatively few the direct and consequential effects can be catastrophic. If any of the components of the fractured or rotationally loosened fastener system are caused to become detached from the clamped assembly sections, for example, on an overhead crane or a vehicle wheel or become trapped in a pump, electric motor, chain or any other piece of equipment, commercial operations can be hafted resulting in costly down time and expensive maintenance repairs as well as the compromising of safety.

Objects of the invention, therefore, are to prevent fractured or rotationally loosened components of fasteners from becoming detached from the engineering assembly during operation thus preventing damage to the assembly and to nearby equipment, ensuring a safer working environment.

According to the present invention there is provided a mechanical fastening device that resists the detachment of component parts of mechanical fasteners and fixings from clamped sections of engineering assemblies should fracture or rotational loosening of the fasteners or fixings occur.

A male fastener or fixing is selected, an axial bore introduced along its full length and the fastener or fixing passed into the openings of assembly sections to be clamped together until, in cases where the fastener or fixing has a head, the head bears against the chosen outer surface of the assembly and the opposite end is secured by appropriate means depending upon the form of the fastener or fixing. A tie is inserted along the bore and restraining devices attached to both ends of the tie to prevent it from moving out of the axial bore, the distance between the restraining devices of the tie, their strength and the strength of the tie being such that should separation of the fastener or fixings occur the tie and restrainers will prevent the separated components from becoming detached from the assembly.

2- BRILEE DESCMECTION OF DRAWINGS Figures 1, 2. 3 and 4 Shows the mechanical fastening device in assembly sections before and after separation, caused by fracture and rotation, when clamped together using a male threaded fastener and an open female threaded fastener.

figures 5, 6 and 7 Shows the mechanical fastening device in assembly sections before and after separation, caused by fracture, when clamped together using a male threaded fastener in a tapped blind hole.

Figure 8 Shows a section of the axial bore and tie in a male threaded fastener used in a blind hole situation or where there is no access to one end of the system, utilising a hinged clip as a restraining device.

Figures 9,10 and 11 Shows the mechanical fastening device in assembly sections before and after separation, caused by fracture when clamped together using a solid rivet as a nonthreaded fastener.

FIGURE 1 1:

DESCRIPTION OF EMBODIMENTS

Shows the assembly sections (5) clamped together by a male threaded fastener having a head (1) and an open female threaded fastener (2). Between the head and one of the outer surfaces of the assembly sections (5) and between the open female threaded fastener (2) and the other outer surface of the assembly sections (5) are washers (6) which could be flat or spring. If the underside of the head of the male threaded fastener (1) was washer faced and if the open female threaded fastener (2) was also washer faced there would be no need for any washers. To those skilled in the art the selection or otherwise of washers would be based on the fastener components available.

Along the full length of the axis of the male threaded fastener (1) is an axial bore (9) through which is inserted a flexible tie (4) in the form of an extension spring. Attached to both ends of the spring are clips that act as restraining devices (3 and 7) In order to prevent the open threaded fastener (2) from becoming rotatably detached, the restraining device (3) at this end of the male threaded fastener (1) must have a maximum dimension larger than the diameter of the male threaded fastener.

There are many alternative methods of assembling the component parts of the system which those skilled in the art can determine depending on site and installation conditions. For example, the axial bore (9) could be introduced in the male threaded fastener (1) before it is secured to the sections or afterwards. The tie (4) could be one of a variety of flexible forms or could even be rigid provided it and the restraining devices (7) met the requirements of resisting the detachment of the component parts should separation take place. The selection of restraining clips (3) & (7) is almost endless and the positioning of them could be carried out when the tie (4) is installed or indeed one of them could be attached to the trailing end of the tie (4) before it is inserted in the bore (9). The hinged clip (16) as shown in figure 8 could also be utilised.

FIGURE 2 Shows fractured surfaces (10) of the male threaded fastener (1) being present due to its tensile fracture. Under normal working conditions the separated components (11) of the fastening and the washers (6) could have become detached from the assembly sections (5) with possible consequential damage but the flexible tie (4), and the restraining clips (3) & (7) have prevented this from happening by virtue of the increase in length of the fractured fastening system being contained by the tie (4) and the restraining clips (3) & (7).

FIGURE 3 Shows separated components (1) (2) and (6) of the fastening system being present because the fractured surfaces (12) are the result of a shear fracture of the male threaded fastener (I). Again, because of the presence of the flexible tie (4) and the restraining clips (3) & (7) the extension in length of the fractured components has been L-- contained and the detachment of the separated components from the assembly sections has been prevented.

FIGURE 4 Shows a situation where the rotational separation of the fastener components (1) (2) and (6) has occurred but again detachment from the assembly sections (5) has been prevented by the presence of the flexible tie (4) and the restraining clips (3) and (7). The importance of the maximum dimension of the restraining clip (3) is shown here.

FIGITRE 5 Shows one of the assembly sections (13) being clamped having a tapped blind hole into which is screwed a male threaded fastener having a head (14). The tie (4) shown is an extension spring but the restraining clip (15) at the threaded end of the male threaded fastener (14) has a maximum dimension which is less than the diameter of the tapped hole. If this efip is the type that is not hinged then it must be attached to the tie (4) in the axial bore (9) before the male threaded fastener (14) is tightened against the chosen outer surface of the clamped sections. The restraining device (7) can be attached to the tie (4) before or after the final tightening.

As described in figure 1 there are many methods of assembling the components of the system which those sleffled in the art can determine depending on site and installation conditions.

FIGURE 6 Shows the male threaded fastener (14) of the fastening system having suffered a tensile C) ftacture but the separated components of the head of the male threaded fastener (14) and the washers (6) have been prevented from becorning detached from the assembly sections by the action of the tie (4) and the restraining devices (7) & (15).

FIGURE 7 Shows the male threaded fastener (14) with a shear fracture but again the separated components (6) & (14) of the fastening system have been prevented from becoming detached from the assembly sections by the action of the tie (4) and restraining devices (7) & (15) FIGURE 8 Shows a type of hinged clip (16) that could be used in a tapped blind hole situation or in a situation involving an open threaded fastener and a stud having a head, where the head is difficult to access, Such an example would be a vefficle wheel stud where only the nut end is accessible. The tie (4) and clip (16) could be inserted into the axial bore (9) of the stud ftom the nut end and the sides of the clip (16) by virtue of the hinge at the tie end are caused to move towards the tie (4) as it is passed through the axial bore (9) of the male threaded fastener (14). As it exits the opposite end the sides of the chp (16) spring outwards from the tie (4) and act as the restraining device.

EIGURE 9 Shows a solid rivet (19) as an example of a non-threaded fastener. Although the method of clamping the sections (21) is obviously different to that of a threaded fastener the method of preventing any separated components of the fastening system from becoming detached from the assembly sections (21) is as already described whereby the tie (17) is inserted in the axial bore (18) and restraining devices (20) attached.

FIGURES 10 AND 11 Show how the component parts (19) & (21) of the fastener system have becoirfe separated due to tensile and shear fracture respectively but have been prevented from becoming detached from the assembly sections (2 1) by the actions of the tie (17) in the axial bore (18) and the restraining devices (20) The axial bore (18) in this system may be best introduced after the clamping operation, but the site conditions, the size of the non-threaded fastener (19) the size of the bore (18) and the size of the tie (17) would all determine how best those skilled in the art would undertake the operation.

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Claims

I/ A mechanical device used with fasteners and fixings for clamping together sections of engineering assemblies that are subject to variable dynamic loading, that resists the detachment from the assembly of component parts of the fasteners and fixings should separation occur, whereby a male fastener or fixing is selected, an axial bore introduced along its full length and the fastener or fixing passed into the openings of the assembly sections to be clamped together until, in cases where the fastener or fixing has a head, the head bears against the chosen outer surface of the assembly and the opposite end is secured by appropriate means depending on the form of the fastener or fixing, a tie being inserted along the bore and restraining devices attached to both ends of the tie to prevent it from moving out of the axial bore, the distance between the restraining devices of the tie, their strength, and the strength and flexibility of the tie being such that should separation of the fasteners or fixings occur the tie and the restrainers will prevent the separated components from becoming detached from the assembly.

2/ A mechanical fastening device according to claimI characterised by the male fastener having threads on at least one end for engagement With a female counterpart.

3/ A mechanical fastening device according to claim 2 characterised by the male fastener having a hexagon head, a socket head, a square head or any other form of head.

4/ A mechanical fastening device according to claim 2 characterised by the threads on the male threaded fastener extending to the head.

5/ A mechanical fixing according to claim 2 characterised by the male threaded fastener being a piece of studding.

6/ A mechanical fastening device according to claim 2 characterised by the male threaded fastener being a length of studding or an engineers stud whereby the head could be a female threaded fastener screwed to the studding or engineers stud until it bears against the chosen outer surface of the clamped assembly sections.

7/ A mechanical fastening device according to claim 2 characterised by the female threaded counterpart being a hexagon, square, or any other shape of nut or open female threaded fastener used to facilitate the clamping of the assembly sections S/ A mechanical fixing device according to claim 2 characterised by the male threaded fastener having two threaded ends and both ends being engaged with open female threaded counterparts, that bear against the outer surfaces of the assembly sections.

9/ A mechanical fixing device according to claim 2 characterised by the female counterpart being a tapped blind hole.

10/ A mechanical fixing device according to claim 9 characterised by male threaded fasteners having a head.

A mechanical fixing device according to claim 9 characterised by the male threaded fastener having threads at one end engaged in the tapped blind hole and threads at the other end engaged by an open female threaded fastener bearing against the chosen outer surface of the assembly section.

12/ A mechanical fixing device according to claim 1 characterised by washers used between the head of the male threaded fastener and the outer surface of the assembly section to be clamped and between the female threaded fastener and the other outer surface of the assembly section.

13/ A mechanical fixing device according to claim 1 characterised by the fasteners being nonthreaded.

14/ A mechanical fixing device according to claim 13 characterised by the fastener being a solid rivet.

15/ A mechanical fixing device according to claim 13 characterised by the fastener being a hollow rivet.

16/ A mechanical fixing device according to claim 13 characterised by the fastener being pins having external circlips at the outer surfaces of the assembly sections.

17/ A mechanical fixing device according to claim 13 characterised by the non-threaded fastener being any other solid or hollow mechanical component used for clamping assembly sections.

181 A mechanical fixing device according to claim 1 characterised by axial bores being introduced along the fuU length of all the male threaded fasteners.

19/ A mechanical fixing device according to claim 18 characterised by the axial bore being introduced along the full length of the male threaded fastener prior to its passing into the openings of the assembly sections to be clamped.

20/ A mechanical fixing device according to claim 18 characterised by the axial bore being introduced along the full length of the male threaded fastener after clamping has been undertaken.

21/ A mechanical fixing device according to claim 1 characterised by a tie being inserted along the axial bore of the male fastener used to clamp the assembly sections.

22/ A mechanical fixing device according to claim 21 characterised by the tie being inserted along the axial bore of a male threaded fastener before the clamping operation takes place.

23/ A mechanical fixing device according to claim 21 characterised by the tie being inserted along the axial bore of a male threaded fastener after the clamping operation takes place.

91 24/ A mechanical fixing device according to claim 21 characterised by the tie being flexible such as an extension or compression spring, a cable or any form of flexible material.

25/ A mechanical fixing device according to claim 21 characterised by the tie being C rigid.

26/ A mechanical fixing device according to claim 21 characterised by the length of the tie being greater than the length of the fastening system in order to contain the increase in length of the separated components.

27/ A mechanical fixing device according to claim 1 characterised by the tie in the axial bore of the male fastener having restraining devices attached to it, the distance between them being in excess of the length of the fastening system.

28/ A mechanical fixing device according to claim 27 characterised by the restraining devices being attached after the insertion of the tie in the axial bore of the male fastener where both ends of the fastening system are accessible.

29/ A mechanical fixing device according to claim 27 characterised by the restraining device being initially attached to the trailing end of the tie before the tie is passed through the axial bore of the male fastener after which the other restraining device is attached to the leading end.

30/ A mechanical fixing device according to claim 27 characterised by the leading end of the tie having attached to it a hinged type of clip that is capable of being passed along the axial bore of the male fastener such that when it exits the forward end of the axial bore the hinged parts of the clip spring outwards and form a restraining device that is useful in fastening systems utilising a tapped blind hole where the male threaded fastener has already been inserted, or where one end of the fastening system, such as the head end of a wheel stud, is difficult to access.

31/ A mechanical fixing device according to claim 30 characterised by the restraining device attached to the trailing end of the tie.

32/ A mechanical fixing device according to claim 27 characterised by the restraining devices being any of several types of clips that can be utilised to best effect by those skilled in the art.

33/ A mechanical fixing device according to claim 27 characterised by the restraining device in a fastening system using one or more threaded fasteners as a maximum dimension greater than the diameters of the male counterparts, 34/ A mechanical fixing device according to claim 27 charactensed by the restraining device used on the threaded end of a male threaded fastener engaged in a tapped hole 35/ A mechanical fixing device according to claim 1 characterised by those skilled in the art being able to use a range of combinations of all the aforementioned fastening components to ensure that no detachment of separation of fastener parts occurs, 36/ A mechanical fixing device according to all previous claims characterised by all the fastener components being manufactured from any material used to produce fasteners.