GB2244777A

GB2244777A - A nut for use with self-tapping screws

Info

Publication number: GB2244777A
Application number: GB9026973A
Authority: GB
Inventors: Graham Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-04-26
Filing date: 1990-12-12
Publication date: 1991-12-11
Anticipated expiration: 2010-12-12
Also published as: GB9009453D0; GB9026973D0; GB2244777B

Abstract

The nut is in the form of a cuboidal plastics body 1, each side face 2 - 7 of the body 1 having an unthreaded aperture 15 - 20 of different circular cross-section, to accommodate self-tapping screws of differing diameters. The axes of the apertures 15 - 20 intersect at the centre of the body in a mutually perpendicular configuration. The axis of each aperture 15 - 20 is substantially perpendicular to the respective side face of the body 1. The two smallest apertures 15 and 16 are mutually aligned and lead into each other. The next two apertures 17 and 18 are mutually aligned, as are the two largest apertures 19 and 20. The four larger apertures 17 - 20 are blind ending and terminate just short of the communicating apertures 15 and 16, being separated therefrom by end walls 21 - 24 respectively. A self-tapping screw inserted into an aperture can penetrate into the opposed aperture. <IMAGE>

Description

NUT FOR USE WITH SELF-TAPPIN6 SCREWS TECHNICAL FIELD OF THE INVENTION This invention relates to a nut for use with selftapping screws. The term "self-tapping screw" is intended to cover any form of threaded screw which is capable of forming its own complimentary screw thread upon insertion into a plain-walled hole in a suitable material, e.g. chipboard screws, wood screws and socalled self-tapping screws of the kind which are intended for metal.

BACKGROUND There are numerous circumstances in which it is necessary to insert a self-tapping screw into a panel formed of soft or thin material. In such a case there is a considerable risk of overti ghteni ng the screw so that the thread is stripped from the hole and/or the panel is deformed.

Plastics nuts for self-tapping screws already exist (see GB 1 423 202 for example), but in general they can only be used effectively with one size of screw.

An object of the present invention is to provide a simple and low-cost nut which is not limited to one particular size of self-tapping screw.

SUMMARY OF THE INVENTION According to a first aspect, the present invention proposes a nut for use with a self-tapping screw in the form of a substantially cuboidal body having at least two screw-receiving apertures, each of the said apertures being disposed substantially perpendicular to a respective side face of the body and opening substantially in the centre of the respective side face, and the apertures being of mutually different cross sectional area.

According to a second aspect, the invention further proposes a nut for use with a self-tapping screw in the form of a substantially cuboidal body having at least two screw-receiving apertures which each open at a respective side face of the body, the axes of the said apertures being arranged to intersect, or at least pass in very close mutual proximity, substantially at the centre of the body ("the intersection point") the said axes being disposed substantially perpendicular to the respective side face of the body, and the apertures being of mutually different cross sectional area.

Being of differing cross sectional areas the apertures can receive screws of different diameters, (but not normally at the same time).

The nut can be provided with any number of such apertures between two and six, thus allowing for use with up to six different screw sizes.

All of the apertures may be in mutual communication at the intersection point. It is preferred however for at least one of the apertures to include, adjacent to the intersection point, a formation which is engageable by a screw inserted therein. Such a formation can thus strengthen the engagement between the nut and the respective screw. The formation may be provided by an end wall of the aperture, which may be completely closed or partially open to the other aperture/s.

It is preferred for each aperture to be paired with an aperture on the opposite side of the nut, so that any screw can pass right through the nut. Such a pair of apertures may be of the same size, although they are preferably of different sizes to increase the number of sizes with which the nut can be used.

Where the nut contains three or more apertures of differing cross sectional areas it is preferred that apertures which are closest to each other in terms of size are arranged to open on opposite sides of the nut.

This arrangement ensures that each screw has the maximum engagement with the nut upon insertion into the appropriate aperture. In some instances where a long screw is inserted into an aperture of the correct size the screw may, for part of its length, be tapping into an undersize or oversize aperture, but in practice there will still be a degree of engagement with an oversize aperture, and the plastics material will be sufficiently resilient to yield in the case of an undersize aperture. It is further preferred that the two apertures of smallest cross sectional area open at opposed faces of the nut and are in mutual communication at the intersection point, the larger aperture/s being blind ending short of the intersection point.This arrangement allows for easy penetration of the intersection point by the larger screw/s without reducing the tapping surface area available to the two smaller screws.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is exemplified in the accompanying drawings, in which: Figure 1 is a perspective view of a nut of the invention, Figure 2 is a section through the nut of Fig.

?, Figure 3 is a section through a further nut of the invention, and Figure 4 is section IV-IV through the nut of Fig. 3.

DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Fig.s 1 and 2, the nut is formed from a substantially cuboidal body I of UPVC, although it may also be of Nylon or other tough but yieldable and non-brittle plastics material. The body 1 thus has six square side faces 2 to 7, and contains three smooth walled through-bores 8, 9 and 10 of circular crosssection, the axes of which intersect at the centre of the body in a mutually perpendicular configuration.

Each of the bores is disposed substantially perpendicular to a respective pair of opposed side faces of the body and opens substantially in the centre of the respective side face. The three bores are of mutually different cross sectional area, and the smallest diameter bore 10 extends completely through the body l. Each bore 8 - 10 has two halves which form apertures of equal diameter opening on opposite sides of the body 1. The apertures 8a and 8b of the largest bore are separated by mutually spaced dividing walls 11 and 12 (Fig. 2) which define part of the mid region of the smallest bore 10. These walls 11 and 12 also form a restriction in the mid region of intermediate sized bore 9.The terminal outer ends of each of the six apertures are of frusto-conical shape forming countersunk portions 13 adjacent to the junction of the aperture with each of the side faces 2 to 7.

The diameters of the apertures formed by the bores 8 to 10 may be chosen to receive standard sizes of screw, e.g. No. 4, No. 6 and No. 8 screws. It would also be possible however for the opposed apertures to be of different cross sectional areas, so that a single nut can be adapted to receive up to six different sizes of screw. In many cases provision for three sizes of screw will be sufficient.

Although not shown, the corners and edges of the body l may be chamfered or rounded.

In use, the nut may be placed behind a panel to receive a self-tapping screw which is inserted through the panel. The screw will be inserted into the most appropriately sized aperture so that as it is driven into the nut the screw forms a thread in the side wall of the aperture. The nut may be held by hand or by a spanner. The countersunk portions 13 receive any material from the nut which is forced out by the tapping action of the screw, and any material of the panel which may be forced rearwardly by the screw or during drilling of the panel. Thus, the adjacent side face of the nut is able to abut the panel and provide a firm hold during the final tightening of the screw. In most instances there will thus be a firm frictional engagement between the nut and the screw so that the nut is virtually self-locking.To assist in holding the nut firmly against rotation when the screw is first- inserted, a further screw, a metal rod or similar article may be inserted for a short distance into one of the other unused apertures.

When an appropriately sized screw is inserted into one of the larger apertures 8a, 8b, its tip will rupture the walls 11 and 12, the material from which will be forced out into the intermediate sized bore 9. Thus, the mid-region of the larger bore will still engage the thread of the screw. When a screw is inserted into the intermediate sized bore 9 it will urge the walls 11 and 12 apart which will again engage the screw thread.

Finally, if a screw is inserted into the smaller bore 10 this will again thread itself into the walls 11 and 12. The tapping length of each aperture is thus maximised. The particular configuration of the dividing walls 11 and 12 may vary, the important thing being that at least one of the larger diameter apertures includes a formation in its mid region which is engageable by a screw inserted into a smaller aperture, yet which yields or ruptures when a screw is inserted into the larger apertures.

The nut of Fig.s 3 and 4 is of similar external shape and material to that of Fig.s 1 and 2, but the configuration of the apertures is different. Each square side face 2 - 7 of the body 1 contains a smooth walled aperture 15 - 20 of circular cross-section, the axes of which intersect at the centre of the body in a mutually perpendicular configuration. Each aperture is substantially perpendicular to the respective side face of the body 1 and all six bores are of different cross sectional area. The two smallest apertures 15 and 16, which are intended to accept No. 2 and No. 4 screws, are mutually aligned and lead into each other (Fig. 3).

The next two apertures 17 and 18 are intended for No. 6 and No. 8 screws and are mutually aligned, as are the two largest apertures 19 and 20, which are intended for No. 10 and No. 12 screws. The larger apertures 17 - 20 are blind ending and terminate just short of the communicating apertures 15 and 16, being separated therefrom by end walls 21 - 24 respectively.

The nut of Fig.s 3 and 4 is used in the same way as that of Fig.s 1 and 2. When an appropriately sized screw is inserted into one of the four larger apertures 17 - 20 it will break through the respective end walls 21 - 24 and may, if inserted far enough, extend into the opposed aperture. In each case, the portion of the screw which enters the opposed aperture will still have some engagement with that aperture due to the resilience of the plastics material.

In each case the nut may be formed by injection moulding.

The nut of the present invention is inexpensive, completely non-corrosive, and is suitable for a range of screw sizes. Generally, the cross-sectional area of the nut face adjacent to a panel or other object being fixed is large in proportion to the cross-sectional area of the screw being used, obviating the need for a washer to support the panel. This contrasts with a similar sized pre-threaded nut and bolt where the surface area of the nut adjacent to the panel is relatively small.

The majority of households, and some work environments, carry a small stock of wood screws or self tapping screws but rarely do they hold any similar sized prethreaded nuts and bolts. The use of the present nut in conjunction with a range of sizes of wood screws or self-tapping screws provides a ready source of screw and nut combinations for general fixing applications.

The physical size (volume) of the present nut would normally be much greater than a metal prethreaded nut would be for a given screw size. As a result, the nut can usually be held against rotation by hand during tightening of the screw.

Claims

1. A nut for use with a self-tapping screw in the form of a substantially cuboidal body having at least two screw-receiving apertures, each of the said apertures being disposed substantially perpendicular to a respective side face of the body and opening substantially in the centre of the respective side face, and the apertures being of mutually different cross sectional area.

2. A nut for use with a self-tapping screw in the form of a substantially cuboidal body having at least two screw-receiving apertures which each open at a respective side face of the body, the axes of the said apertures being arranged to intersect, or at least pass in very close mutual proximity, substantially at the centre of the body ("the intersection point"), the said axes being disposed substantially perpendicular to the respective side face of the body, and the apertures being of mutually different cross sectional area.

3. A nut according to Claim 2, in which at least one of the apertures includes, adjacent to the intersection point, a formation which is engageable by a screw when inserted into the said aperture.

4. A nut according to Claim 3, in which the formation comprises an end wall of the respective aperture.

5. A nut according to any preceding claim, in which each aperture is paired with an aperture on the opposite side of the nut, such that when a screw is inserted into one of the apertures it can pass into the paired aperture.

6. A nut according to any preceding claim which contains three or more apertures of differing cross sectional areas, and in which the apertures which are closest to each other in terms of cross sectional area open on opposite sides of the nut.

7. A nut according to Claim 2, or any preceding claim which is appended to Claim 2, which contains three or more apertures of differing cross sectional areas, and in which the two apertures of smallest cross sectional area open at opposite faces of the nut and are in mutual communication at the intersection point, the larger aperture/s being blind ending short of the intersection point.

8. A nut for use with a self-tapping screw which is substantially as described with reference to Figures 1 and 2 of the drawings.

9. A nut for use with a self-tapping screw which is substantially as described with reference to Figures 3 and 4 of the drawings.