GB2495305A - Fence incorporating bracket for connecting upright post to horizontal cross rail - Google Patents

Abstract

The fence includes a post and rail connected together using a bracket wherein the bracket is a U or C shape member with a base and front and rear uprights. The base comprises a number of aperture diameter extrusions used as fixing holes to the post. The front and rear uprights include similar holes which are opposite each other in each upright. The base may be formed from two sloped parts defining an angle for accommodating the curvature of a circular or round post. The holes may protrude outwardly such that they are cut, dig or are forced into the post from tightening of screws into the fixing holes into the post. The rear upright may slide into a sawn retaining slot or slit in the cross rails.

Description

FENCE INCORPORATING A UNIVERSAL BRACKET

DESCRIPTION

The present invention relates to a fence incorporating a bracket that is used to secure all common fence rails, examples being half round, arris and cant rails, to all common fence posts, examples being square, rectangular, half round and round, the bracket being capable of fixing the rails both horizontally and angular to the posts.

The most common methods used at present are either the mortice slot method, which usually secures rectangular or arris type rails to square or rectangular posts, or by nailing rail to post, used predominantly when securing half round rails to either round or half round posts.

The mortice slot method is expensive and it is difficult to replace damaged rails.

The nailing process presents problems with the wood splitting outwardly from the position of the nail, is unsightly and again not easy to replace rails which is essential on rural fencing due to damage caused by animals.

The aim of the present invention is to produce a multipurpose bracket at low cost therefore the material content kept to a minimum, but with added strength at the critical screw positions to enable the secure fixing of a half round rail to a round post and being visually acceptable, this being the most difficult example to achieve.

In accordance with the present invention there is provided a fence comprising of an upright fence post, a cross rail and a substantially U shaped member having a concave or flat base with staggered diameter extrusions as fixing holes extending outwardly from the said base.

The front upright of the bracket can have similar diameter extrusions as fixing holes extending inwards from the said upright.

The rear upright will have clearance holes directly opposite the extrusions on the front upright to accept the body of a screw.

Firstly the extrusions on the base of the bracket will be staggered to prevent splitting along the grain of the wood whilst fixing to a post.

Secondly as the screw will pass through the centre hole of the extrusion it will stay parallel to the inside wall of the extrusion and thus the screw will drive squarely into the post at this position.

Thirdly as the screw is tightened the extrusion extending from the base or upright of the bracket will be forced into the wood of the post or rail. This acts as a dowelling process to prevent movement from front to back, up or down or any twisting motion of the bracket between post and rail.

A fourth point being, the extrusion when forced into the wood will displace a diameter section of wood around the core diameter of the screw, directly below the head of the screw, thus increasing the pullout force of the screw and locking its position.

A fifth point being, that the extrusion will give maximum strength below the screw head thus preventing the bracket pulling over the head of the screw when using a thin gauge material for the said bracket.

A sixth point being that when using a concave base or similar, with staggered extrusion fixing holes, this will achieve a greater clamping surface area when fixed to a round post.

A final point being, the bracket enables the cross rail or arris rail to be slid into position between existing posts positioning them correctly and securely whereby the bracket is screwed through its base into the post, with the two uprights extending at 90 degrees from the inner face of the post and parallel to it. The cross rail or arris rail is cut to fit between the posts but having a retaining saw cut at each end so as the rail can slide onto the extending uprights into the correct position and thus hiding the rear upright which enters into the said retaining saw cut. (similar to patent no GB2447662).

The invention will be further described by way of example with reference to the accompanying drawings in which: Fig. 1 shows the formed bracket whereas: (A) Location for countersunk screw heads are extruded to give maximum localised strength and mechanical advantage to the bracket in the stressed areas most likely to suffer plastic deformation under load. The Form also acts as a key (Fig. 3, 4), increasing the surface area of contact between bracket & wood securing it in position as well as compressing the wood (Fig.3, 4) around the screw shank as it is tightened, increasing the friction and therefore clamping force between the wood and the screw.

(B) Clearance holes allow the screws to pass through the retaining slot in the rail and behind the bracket, acting as a restraining pin to control movement. The clearance gap between screw and hole diameter allows the bracket assembly to flex a pre-determined amount when put under load, spreading the forces throughout the assembly for evenly distributed stresses due to the load on the wood being taken up by the flex of the bracket.

(C) The formed edges of the bracket dig into the wood when the screws are tightened (Fig. 4) giving the bracket a positive location on its outer edges increasing its resistance to twisting & tipping movements from externally applied forces.

The edges also act as a fulcrum when the base of the bracket is screwed to a piece of wood, this moves the sides in towards the centre acting as a spring clamp (Fig. 2) to conveniently hold the rail in place before the assembly is finally fastened into its finished position with more screws enabling one person to perform a two person job.

(D) Shows a formed section to provide clearance at the base of the bracket, allowing the screws to operate the lever effect of the bracket (Fig. 2) when tightened & providing the positive location at the extremities of the bracket which increases its resistance to movement when clamped in position compared with a flat bottom bracket. (Fig. 4) The shape also allows the bracket to fit securely to both round & flat surfaces. (Fig. 4) Fig.2 Represents the lever/adjustmenticlamping action of the bracket where clamping screw pressure is applied to the base, the fulcrum points at the extremities pivot the front and rear uprights at angles ranging up to and through 90 degrees giving a total movement of up to 20 degrees per upright. Fig3

Shows the universal bracket disassembled from a fence rail where: (A) Depicts a saw slot which functions to hide part of the bracket from view and retains the rear upright. Using a shallow saw cut allows the rear leg of the bracket to slide freely into this cut slot thus allowing a restricted movement when a screw is inserted through the rai (B) Provides a visual representation of the indent compressed into a piece of wood when the screws of the assembly are tightened, showing the increased surface area which keys the bracket to the wood and the displacement of volume which increases the compression locally around the shank of the screw, increasing the clamping force.

Fig. 4 Displays a typical example of a disengaged bracket from a round post.

(A) Is showing the compression of wood or other suitable material between the two outer edges of the base of the bracket (Fig. 1, C) providing a good fit for many shapes and sizes of surface and resistance to movement as a result of a positive location.

(B) Displays the offset location of the fixing holes which helps to prevent splitting along the grain by screwing into different sections of grain line, also shows similar indents as explained for fig 3 (B).

Fig. 5 Shows a full bracket assembly with close up section views of: (A) Compression of the wood around the shank of the screw formed by the internal diameter of the extrusion, whilst the outside diameter acts to key the bracket position, to the wood. When the assembly is put under load the form of the extrusion takes the fixing screw out of shear and into tension, increasing the potential load of failure by approximately two thirds.( shear strength is one third of tensile strength).

(B) Clearance between screw diameter and hole in bracket to allow the assembly to flex within the sawn slot when under load.

The arrangement will now be explained in more detail The bracket will have a preferred minimum of two extrusions in the base and two in the front upright. However it is envisaged that the extrusions will always be required in the base of the bracket to achieve the extra fixing strength required between bracket and post but may not be required in the front upright if the rail used is for lightweight type fencing. The base of the bracket may be flat, concave or angular slopes intersecting inwardly at the centre of the base width as fig 1D, to suit flat or round surfaces.

The extrusions will protrude from the base or upright at a depth of a preferred minimum of twice the material thickness of the bracket.

The inside diameter of the extrusion will be a clearance fit on the diameter of the screw used. The outside of the extrusion will be this inside size plus two material thicknesses. This material thickness will depend on the size of bracket used for the corresponding size of fence required. A preferred thickness would be 0.8mm, The material would be stainless steel or steel with a corrosive preventive coating.

The arris rail or cross rail will have a single retaining saw cut at its ends that run parallel with the front face of the rail and equal or greater in depth to that of the height of the uprights of the bracket. The centre line of the saw cut will be the size between the inner faces of the two formed uprights of the bracket, plus half the thickness of the material used for the bracket. The width of the saw slot will be greater than the thickness of the bracket to enable the rear upright to slide into the said slot and also hiding this part of the bracket.(similar to patent no.GB2447662).

The front upright when containing the extrusions will be sprung open to accept the front face of the rail. When screwed into position the extrusions will be forced into the rail giving strong anchorage at the fixing positions. The screw will extend through the clearance holes in the rear upright of the bracket through the retaining saw slot and back into the cross rail, resulting in a pre -determined, restricted movement of the rear upright in the said retaining saw slot, thus allowing controlled flexing of the assembly.

This movement can take place within 360 degrees about the centre axis of the fixing screws. The amount of movement is determined by the clearance given between the inside diameter of the hole and the outside diameter of the fixing screw. As an example if the screw had a diameter of 5mm passing through an 8mm hole, this would allow the upright to move 1.5mm before being restrained by the screw. The controlled flexing of the bracket reduces the stress at the contact area between the screw and the wood of the rail by up to 9G, therefore increased load can be applied to the assembly before failure occurs.

When a screw is fully tightened within the extrusion, the force required to pull the said extrusion over the head of the screw is increased by 29% as against a plain screw hole.

These percentage advantages are calculated using finite element analysis.

Various modifications may be made to the described embodiment and it is desired to include all such modifications as fall within the scope of the invention.

Claims (1)

1. <claim-text>CLAIMS1 A fence comprising of an upright fence post, a cross rail and a bracket in the form of a substantially U shaped member having a base with diameter extrusions used as fixing holes to the post, whilst the front upright also having similar diameter extrusions used as fixing holes to the cross rail, with screw clearance hole positions in the rear upright directly opposite the extrusions in the said front upright.</claim-text> <claim-text>2 A fence as claimed in claim 1 wherein the bracket is formed of stainless steel or steel with a corrosive preventive coating.</claim-text> <claim-text>3 A fence as claimed in claims 1 or 2 whereas the base of the U shaped member has two inward angular slopes intersecting at the centre of its width.</claim-text> <claim-text>4 A fence as claimed in claim 3 whereas a preferred minimum of two diameter extrusions protrude outwardly from the base and used as fixing holes to the post.</claim-text> <claim-text>S A fence as claimed in claims 3 or 4 whereas the extrusions protruding from the base will be forced into the post on fully tightening the flxing screws.</claim-text> <claim-text>6 A fence as claimed in claims 1 or 2 whereas the front upright of the substantially U shaped member contains a preferred minimum of two diameter extrusions protruding inwardly and are used as fixing holes to the cross rail.</claim-text> <claim-text>7 A fence as claimed in any of the preceding claims whereas the rear upright slides into a sawn retaining slot in the cross rail and has screw clearance holes directly opposite the extrusions in the front upright.S A fence as claimed in claims 6 or? whereas fixing screws will pass through the extrusions located in the front upright, then into the rail and extend through the clearance holes in the rear upright,then back into the rail.S A fence as claimed in claims 6-8 in which when the said fixing screws are fully tightened the extruded protrusions will be forced into the cross rail.</claim-text>