GB2564450A

GB2564450A - A fastener

Info

Publication number: GB2564450A
Application number: GB1711124.6A
Authority: GB
Inventors: Wilkinson Michael
Original assignee: TITE RANGE DEVELOPMENTS Ltd; Tite Range Dev Ltd
Current assignee: TITE RANGE DEVELOPMENTS Ltd; Tite Range Dev Ltd
Priority date: 2017-07-11
Filing date: 2017-07-11
Publication date: 2019-01-16
Anticipated expiration: 2037-07-11
Also published as: GB2564450B; GB201711124D0

Abstract

A fastener (200) comprises an elongate shank portion (204) terminating at a tip region (206) and has a substantially non-circular cross section defining a major axis and a minor axis. At least one thread (208) extends at least partially along the shank portion (204). The thread (208) starts nearer the minor axis than the major axis and may start at the minor axis.

Description

A FASTENER

The present invention relates to a fastener and in particular, but not exclusively, to a screw for use primarily with soft and hardwoods, low-, medium-, and high-density fibreboard, but also with plastics, masonry, and metals, or the like.

Typically, a screw includes a head portion, a shank portion, a tip, and at least one spiral screw thread extending from the tip at least partially along the shank towards the head portion. Conventional screws typically have either a single thread or a twin thread disposed on a round shank with either a single or double gimlet thread start. Single and twin thread screws provide different advantages depending on the intended application for the screw, along with different disadvantages. For example, a single threaded screw having a single gimlet thread start at its tip tends to kick over on insertion and is undesirably driven into timber at an angle. A twin threaded screw that has two (double) gimlet thread starts at its tip tends to start balanced when driven into timber so does not tend to kick over on insertion. However, a double threaded screw tends to ream the timber as it is driven therein, whereas a single threaded screw tends to ream the timber less and thus provides a higher pull-out retention. Attempts have been made to provide an improved screw, such as the screw described in GB2454464, but the above-mentioned problem/s still exist.

It is an aim of certain embodiments of the present invention to provide a screw that does not kick over on insertion and is substantially balanced as it is being driven into a substrate, whilst also causing little or no reaming to the surface of the substrate on insertion and whilst being driven into the substrate.

According to a first aspect of the present invention there is provided a fastener comprising: an elongate shank portion terminating at a tip region and having a substantially non-circular cross section defining a major axis and a minor axis; and at least one thread extending at least partially along the shank portion, wherein the thread starts at least proximal to the minor axis.

Optionally, the major axis is oriented substantially perpendicular to the minor axis.

Optionally, the thread starts at the minor axis.

Optionally, the thread starts at or at least proximal to the tip region.

Optionally, the thread start comprises a pronounced thread portion having an angle of around 25 to 45 degrees with respect to a longitudinal axis of the fastener.

Optionally, a depth of the pronounced thread portion between a crest of the thread and the longitudinal axis is between around 0.9 to around 5.4mm.

Optionally, a maximum dimension of the shank portion along the major axis is between around 1,2mm to around 7.2mm and a minimum dimension of the shank portion along the minor axis is between around 1,05mm to around 3.32mm.

Optionally, a maximum outer diameter of the thread along the major axis is between around 2mm and 12mm and a minimum outer diameter of the thread along the minor axis is between around 1.75mm and 10.5mm.

Optionally, the thread extends along the shank portion by at least around 25% from at least proximal the tip region.

Optionally, the fastener further comprises at least one further thread disposed proximal the head portion and spaced apart from the at least one thread.

Optionally, the at least one further thread is a single or twin thread.

Optionally, a length of the fastener is between around 6 mm and around 1000mm.

Optionally, the shank portion comprises the non-circular cross section along its entire length.

Optionally, the non-circular cross section is substantially oval, polygonal or trilobular.

Optionally, the fastener further comprises a non-threaded shank portion proximal a head portion located at a distal end of the fastener relative to the tip region.

Optionally, the head portion comprises a substantially circular cross section.

Optionally, the fastener further comprises a tapered collar portion located between the head portion and the shank portion.

According to a second aspect of the present invention there is provided a method of manufacturing a fastener, comprising: providing an elongate shank portion terminating at a tip region, wherein the shank portion has a substantially non-circular cross section defining a major axis and a minor axis; and providing at least one thread on the shank portion such that the thread extends at least partially along the shank portion and starts at least proximal to the minor axis.

Optionally, providing the at least one thread comprises machining the thread on to the shank portion.

Optionally, machining comprises thread rolling.

Optionally, the method further comprises providing a head portion of the fastener distal to the tip region.

Optionally, the method further comprises coating the fastener.

Description of the Drawings

Certain embodiments of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1a illustrates a side view of conventional screw with a circular shank;

Figure 1 b illustrates an end view of the screw of Figure 1 a;

Figure 1 c illustrates a side view of the screw of Figures 1 a and 1 b when driven into a substrate;

Figure 1d illustrates an end view of the screw of Figure 1c;

Figure 2a illustrates a side view of a screw with a substantially non-circular shank according to certain embodiments of the present invention;

Figure 2b illustrates an end view of the screw of Figure 2a;

Figure 2c illustrates a side view of the screw of Figures 2a and 2b when driven into a substrate;

Figure 2d illustrates an end view of the screw of Figure 2c;

Figure 3 illustrates an end view of the gimlet tip region of the screw of Figures 2a to 2d; and

Figure 4 illustrates a side view of the gimlet tip region of Figure 3.

Detailed Description

As illustrated in Figures 1a and 1b, a conventional screw 100 is circular in cross section along its entire length. It includes a tapered head portion 102, a shank portion 104 and a gimlet tip 106. A single spiral thread 108 extends from the tip to provide a single gimlet thread start and extends, in this instance, around 65-75% along the length of the shank portion towards the head portion to provide a non-threaded shank portion 110. A tapered collar portion 112 is disposed between the head portion 102 and the shank portion 104 to provide sufficient material for a drive recess 114 in the head portion for receiving a suitable driver, e.g. a screwdriver or powered driver bit, and to avoid ‘cam-out’ when the screw is driven, whilst maintaining the torsional strength of the screw particularly between the head and shank portions. As illustrated in Figures 1c and 1d, the conventional screw 100 is unbalanced and tends to kick over immediately, and at least within 90 degrees of clockwise rotation about its longitudinal axis 116, when driven into a substrate, such as timber, plastic, or the like. Once the screw is askew, a higher insertion torque is required to drive the screw fully into the substrate relative to the torque required if the screw was driven in true, i.e. substantially perpendicularly with respect to the substrate surface. Furthermore, an unbalanced screw being driven into the substrate at an angle thereto may not hit a target, e.g. an underlying substrate, will not sit flush in a hinge, door handle, or the like, causes undesirable friction and heat when being driven into the substrate/s, causes undesirable damage to the substrate surface itself, and looks untidy.

As illustrated in Figures 2a and 2b, a screw 200 in accordance with certain embodiments of the present invention includes a tapered head portion 202 having a substantially circular cross section, and a shank portion 204 extending from the head portion to a gimlet tip 206 wherein the shank portion has a substantially non-circular cross section along at least a portion of its length from the tip. In the illustrated embodiment, the shank portion 204 has a substantially oval or elliptical cross section along its entire length from the tip 206 to a tapered collar portion 212 located between the head portion and the shank portion. Alternatively, the non-circular shank portion 204 may have a different cross-sectional shape such as trilobular, regular or irregular polygonal, or the like. In a similar manner to the conventional screw 100 described above, the tapered collar portion 212 provides sufficient material for a drive recess 214, e.g. cross or hex recess, in the head portion for receiving a suitable driver, e.g. a screwdriver or powered driver bit, and to avoid ‘cam-out’ when the screw is driven about its longitudinal axis 216, whilst maintaining the torsional strength of the screw particularly between the head and shank portions. The head portion 202 may include a plurality of spaced apart ribs which are oriented to ream out a tapered recess in the substrate to eliminate the need to separately countersink the material prior to inserting the screw. Whilst a tapered head portion 202 and collar portion 212 are illustrated, these features are in no way limiting to the present invention and are optional features. For example, the screw 200 may not include a head portion as such and instead include a drive recess in the drive end of the screw distal from the tip for a suitable tool to engage with to drive the screw into a substrate. Alternatively, the drive end of the screw may have a substantially square, hexagonal or the like cross section for a suitable drive socket to engage with to drive the screw into a substrate. A single spiral thread 208 extends from the gimlet tip 206 to provide a pronounced single gimlet thread start and, in this instance, extends around 65-75% along the length of the shank portion 204 towards the head portion 202 to provide a non-threaded shank portion 210. The pronounced gimlet tip allows the screw to start immediately into most building materials without requiring a pre-drilled pilot hole.

The non-threaded shank portion 210 is aptly no less than around 15% of the length of the screw and acts as a dowel to allow jointed material, e.g. two timber components, to be efficiently clamped together without ‘jacking’ apart which can otherwise occur with a fully threaded screw. However, the present invention is not limited to partially threaded screws and the single thread may extend fully along the shank portion if desired. Further alternatively, the single thread 208 may extend partially along the shank portion 204 from the gimlet tip 206 and be a primary thread wherein a secondary thread is provided between the head portion and the primary thread and spaced apart therefrom. Such a secondary thread may be a single or a double, e.g. high-low, thread which helps to secure an upper jointed component of a pair of clamped components and eliminate screw protrusion in the event of component movement and/or material shrinkage over time. Such a secondary thread may be substantially circular or non-circular in cross section. Furthermore, whilst for the purposes of the illustrated example the single thread aptly starts at or at least proximal to the gimlet tip, the thread may alternatively start at any location along the shank, albeit at or at least proximal to the minor diameter of the oval/elliptical shank portion, if desired.

The single thread 208 has a thread angle of between around 30-60 degrees and aptly around 40 degrees for efficient thread cutting and pull-out retention. The pitch of the thread is between around 1 mm to 6mm and aptly around 2.6mm when applied to a 4mm diameter screw. Aptly the ratio of the pitch and the oval major thread diameter is around 2:3 +/- around 10%, being up to around 50% coarser than conventional woodscrews, reducing insertion torque and allowing relatively high insertion speed which is up to around twice that of a conventional screw. Aptly, the major diameter of the oval thread, i.e. the maximum cross-sectional outer dimension of the thread along the semi-major axis (see Figure 3), is between around 2mm to 12mm and aptly around 4mm when applied to a 4mm screw. Aptly, the minor diameter of the oval thread, i.e. the minimum cross-sectional outer dimension of the thread along the semi-minor axis, is between around 1,75mm to 10.5mm and aptly around 3.6mm when applied to a 4mm fastener. Aptly, the maximum diameter of the shank portion (i.e. the inner diameter of the thread along the semi-major axis) is between around 1.2 to 7.2mm and aptly around 2.4mm when applied to a 4mm fastener. Aptly, the minimum diameter of the shank portion (i.e. the inner diameter of the thread along the semi-minor axis) is between around 1.05 to 3.32 mm and aptly around 2.16 mm when applied to a 4mm fastener.

In accordance with certain embodiments of the present invention, and as shown best in Figures 3 and 4, the single thread 208 starts substantially pronounced at or at least proximal to the gimlet tip 206 and, more specifically, at least proximal to the semi-minor axis of the substantially oval/elliptical cross-sectional shank tip 206.

Aptly, the thread 208 extends substantially from the semi-minor axis. The pronounced gimlet thread start is located on, or at least proximal to, the minor diameter of, or at least proximal to, the oval tip region to engage immediately into the substrate when the screw is driven therein, albeit to a lesser penetration than the portion of thread on the major diameter further along the helix at around 90 degrees of rotation. The pronounced gimlet thread at around 90 degrees rotation is disposed on the major diameter of the oval shank and cuts into the substrate to a penetration depth of around 1,8mm on a 4mm diameter screw which creates higher friction than the thread start located on the minor diameter and in turn counters the kick-over forces exhibited by the start on the minor diameter. At around 90 degrees of rotation, the screw has driven into the substrate to a depth of around 2.9mm. At this depth, the relatively steep side of the pronounced gimlet start further resists kick-over and the forces are countered as the screw drives into the substrate. With reference to Figure 4, the pronounced gimlet thread start defines an angle ‘a’ of between around 48-58 degrees, and aptly around 53 degrees, relative to a lateral axis perpendicular to the longitudinal axis of the screw, and an angle ‘d’ of between around 32-42 degrees, and aptly around 37 degrees, relative to the longitudinal axis of the screw. Angle ‘b’ is between around 55-65 degrees, and aptly around 60 degrees, relative to the lateral axis, and angle ‘c’ is between around 55-65 degrees, and aptly around 60 degrees, to the longitudinal axis of the screw. Aptly, a depth of the pronounced thread portion between a crest of the thread and the longitudinal axis is between around 0.9 to 5.4, and preferably around 1.8mm, for a 4mm fastener. Any in-balance is minimal and not enough to overcome the force of the driver, so the fastener drives true without kick-over, eliminating any possible reaming of the substrate. Timber damage and blistering throughout insertion is also significantly reduced.

The above dimensions may vary proportionally for different screw diameters, e.g. greater than a 4mm diameter screw, and a length of the screw may be between around 6-1000mm depending on its technical application.

The screw is aptly made from hardened carbon steel but may be made from other suitable materials such as brass, stainless steel, hardened plastic, or the like, depending on its intended application. Likewise, the thread dimensions may be tailored to suit a particular application and the head portion may be countersunk, round, raised, cheesehead, hexagonal, or the like. The drive recess in the head portion may be a cross recess, a slotted recess, a hex recess, or the like, to receive a correspondingly shaped drive tool. The screw may be electroplated, galvanised, or coated with organic treatments to prevent corrosion. The screw may be manufactured by cutting a wire to a predetermined length, providing the head portion to the blank, optionally polishing the blank, machining the thread on the blank by rolling or cutting, and optionally cleaning, e.g. by tumble finishing, and coating the screw.

Certain embodiments of the present invention therefore provide a screw that does not kick over on insertion, is substantially balanced as it is being driven into a substrate, and requires relatively low insertion torque, whilst also causing little or no reaming to the surface of the substrate at the start of and during insertion.

Claims

1. A fastener comprising: an elongate shank portion terminating at a tip region and having a substantially non-circular cross section defining a major axis and a minor axis; and at least one thread extending at least partially along the shank portion, wherein the thread starts at least proximal to the minor axis.

2. The fastener as claimed in claim 1, wherein the major axis is oriented substantially perpendicular to the minor axis.

3. The fastener as claimed in claim 1 or 2, wherein the thread starts at the minor axis.

4. The fastener as claimed in any preceding claim, wherein the thread starts at or at least proximal to the tip region.

5. The fastener as claimed in claim 4, wherein the thread start comprises a pronounced thread portion having an angle of around 25 to 45 degrees with respect to a longitudinal axis of the fastener.

6. The fastener as claimed in claim 5, wherein a depth of the pronounced thread portion between a crest of the thread and the longitudinal axis is between around 0.9 to around 5.4mm.

7. The fastener as claimed in any preceding claim, wherein a maximum dimension of the shank portion along the major axis is between around 1,2mm to around 7.2mm and a minimum dimension of the shank portion along the minor axis is between around 1.05mm to around 3.32mm.

8. The fastener as claimed in any preceding claim, wherein a maximum outer diameter of the thread along the major axis is between around 2mm and 12mm and a minimum outer diameter of the thread along the minor axis is between around 1.75mm and 10.5mm.

9. The fastener as claimed in any preceding claim, wherein the thread extends along the shank portion by at least around 25% from at least proximal the tip region.

10. The fastener as claimed in any preceding claim, further comprising at least one further thread disposed proximal the head portion and spaced apart from the at least one thread.

11. The fastener as claimed in claim 10, wherein the at least one further thread is a single or twin thread.

12. The fastener as claimed in any preceding claim, wherein a length of the fastener is between around 6 mm and around 1000mm.

13. The fastener as claimed in any preceding claim, wherein the shank portion comprises the non-circular cross section along its entire length.

14. The fastener as claimed in any preceding, wherein the non-circular cross section is substantially oval, polygonal or trilobular.

15. The fastener as claimed in any preceding claim, further comprising a non-threaded shank portion proximal a head portion located at a distal end of the fastener relative to the tip region.

16. The fastener as claimed in claim 15, wherein the head portion comprises a substantially circular cross section.

17. The fastener as claimed in claim 15 or 16, further comprising a tapered collar portion located between the head portion and the shank portion.

18. A method of manufacturing a fastener, comprising: providing an elongate shank portion terminating at a tip region, wherein the shank portion has a substantially non-circular cross section defining a major axis and a minor axis; and providing at least one thread on the shank portion such that the thread extends at least partially along the shank portion and starts at least proximal to the minor axis.

19. The method as claimed in claim 18, wherein the major axis is oriented substantially perpendicular to the minor axis.

20. The method as claimed in claim 18 or 19, wherein providing the at least one thread comprises machining the thread on to the shank portion.

21. The method as claimed in claim 20, wherein machining comprises thread rolling.

22. The method as claimed in any of claims 18 to 21, further comprising providing a head portion of the fastener distal to the tip region.

23. The method as claimed in any of claims 18 to 22, further comprising coating the fastener.