Improved safety fence construction

Abstract

The present invention provides an improved safety fence 200, 300 and method of construction of the safety fence. The fence and method comprise a bow top safety fence 200, 300 comprising tubular pales

Description

A safety fence, otherwise termed a bow top fence, is a form of metal fencing usable in situations such as playgrounds where a form of partition is required which is robust but will not present and significant risk injury. This is achieved by a metal io construction made from elongate bars of metal bent in half and welded into apertures in horizontal rails to form fence pales. The effectiveness of this form of fence with its simple construction is established, however, it is still susceptible to improvement. An example of a currently used system can be found in EP1538283A1, which discloses a self-raking bow top fence panel comprises two horizontal rails supporting 15 a plurality of composite pales, each pale comprising two separate vertical legs, each leg being independently pivotably mounted to at least one of the rails. The bows or curved elements forming the top of the fence are preferably provided by the top section of one of the tubular legs of each pale which is bent over to form a downwardly facing socket which receives the upper end of the second leg. The legs 20 may be retained in apertures in the rails by means of fixed transverse pins which enable each leg to pivot independently in the rail, the relative movement between the two legs of each pale being accommodated by movement of the reduced diameter upper end of the second leg in the socket. The bent leg is preferably pinned to both rails while the straight leg may be pinned to both rails or to the lower rail only. 25 The present invention The present invention provides a bow top safety fence comprising, tubular pales and tubular fence tops upon the pales. The use of tubular construction has the advantage that for a given weight of steel the surface area is larger and therefore a person impacting the fence is presented with a higher surface and hence less direct injury. In addition, the use of tubes provides a greater degree of resilient deformation and hence the resistance to distortion upon a similar effect of a person impacting the fence is reduced. Put simply, if a child runs into a fence with hollow bars of diameter 2 cm rather than solid bars of diameter 1 5 cm then bruising will be less because the force is spread and less because of greater fence deflection as the fence will flex, albeit to a small extent, more than a fence made of solid rods. The pales are preferably constructed from tubular steel between 1.5 and 3.5 cm in diameter and with a wall thickness between 1 and 3 mm. This has been found to 21 03 25 optimally provide the above characteristics, more specifically between 1.75 and 2.5 cm in diameter and with a wall thickness between 1.5 and 2.5 mm. In the present invention the tubular fence tops are preferably separate units placed upon the pales and secured in place. This provides a much more efficient method of construction as it is no longer necessary to bend long elongate bars in half to create the bow top but this has created by placing separate individual loops upon the pales. In addition, this also provides a first construction with pale is secured in rails which can be topped as a separate fence unit in its own right and adapted by means of adding the loops to create a bow top fence when that is required. This provides more efficient stock management. In the present invention the tubular fence tops are preferably telescoped into or onto the tubular pales, more preferably onto the pales. By providing a differential diameter between the tops and the pales, one tube may be inserted into the other to provide rapid location suitable for a further joining step. This improves production and reduces waste. This differential diameter may be obtained by swaging, preferably by swaging the pale, particularly the tope end of the pale. In the present invention the tubular fence tops are preferably secured to the tubular pales by crimping a first tube, be it the top loop / bow or the pale, onto the corresponding pale or top loop / bow. Preferably the pale, optionally swaged, telescopes into the top loop and is secured by crimping. This provides an overhang to reduce moisture ingress. This is more efficient than a construction which requires welding, as fences of this type are typically constructed. It also avoids the toxic welding / flux residues which otherwise need to be cleaned off such safety fencing before use. In the present invention the top loops are preferably secured to the pales by the pales being seated within the inside diameter of the top loops. This provides an overhanging edge at the joint which is less susceptible to catching on an object, such as a hand moving over the tubing. In addition, it reduces the potential for the ingress of moisture, such as rain. In a preferred method of construction the present invention welding may be completely avoided, whilst providing a robust and strong fence construction. In an additional method of securing, such as where an low force (such as less than 10N per join) interference fit is used to initially secure top loop to pale and optionally pale to rail, subsequent galvanising or powder coating is preferably used to provide strong joins. This occurs from capillary action of the galvanising liquid or paint (powder coat when being fused) sealing the joins. Sherardising is unsuitable to achieve this effect. Detailed description The present invention will now be illustrated by means of the following diagrams which provide: figure 1 a representative prior art bow top fence construction using metal rods; figure 2 a first construction step of a fence according to the present invention using metal tubes; figure 3 a second construction step over a fence according to the present invention by adding bow tops to a tubular fence construction; figure 4 shows a third construction step applicable to the present invention by adding a telescoped bow top to tubular pales and optional securing by means of crimping; and figure 5 shows an alternative third construction step applicable to the present invention by adding a telescoped bow top to swaged pales. The present invention is illustrated by the figures which provide the following features, like features having like numerals: 10 prior art bow top fence; 20 steel bar of upper rail 30 steel bar of lower rail 40 pale formed from U-shaped steel bar 50 pale portion of U-shaped steel bar 60 bow top portion of U-shaped steel bar 100 first construction of a steel fence according to the present invention; 120 tubular upper rail offence; 122 upper aperture in rail 120 124 lower aperture in rail 120 130 tubular lower rail of fence; 150 separate tubular pales; 200 second construction step of a steel fence according to the present invention; 250 U-shaped, preferably tubular, section attachable to the upper ends of the pales; 252 linear ends of the upper section 250; 330 construction step of a steel fence according to the present invention; 360 arrow showing crimping action applied to telescoped tubes for securing the construction; 370 swaged portion of tubular pale 372 shoulder between swaged and unswaged portions 374 unswaged portion of tubular pale The terms bow top and curved or loop top are, unless the context clearly indicates otherwise used as synonyms. Referring now to the figures. Figure 1 shows a prior art bow top fence made from metal bars 40, construction comprises three steps, taking elongate metal bars bending each in half to provide pales 40 comprising vertical bars 50 and top loops 60. These are then placed through apertures in top rail 20 and bottom rail 30, which are steel bars with apertures therein. The construction is then welded to provide a finished fence section. Figure 2 shows a first edge of construction of a bow top fence. A plurality of tubes 150 are prepared as pales for the fence, these are then inserted through pre-prepared apertures in rails 120, 130 of the fence. Very preferably these apertures are configured to be of slightly smaller size than the tubes and the tubes are compression inserted through the apertures so as to bond the pales into the rails by an interference fit. This avoids a welding step. To facilitate this, ends of the rails 150, either one or both ends, may be swaged to a smaller diameter such as to permit that portion of the tube to pass through the tubular rail unhindered and only to bind when the shoulder of the pale impinges upon the smaller sized aperture in the rail. This form of construction is particularly advantageous as by swaging the ends of the rails the diameter of the pales can be reduced such that it will fit, i.e., telescope, inside itself (by this is meant that the same raw material stock for the bow top, described below, and the pale may be used and the ends of the pale reduced so as to fit within that of the b ow top. This has the double advantage that in one processing step the pales may be formed so that they are effectively compression fitted within the rails and also within the bow tops. Figure 3 illustrates a second stage of construction of the bow top fence of the present invention in which bow top to 50 is inserted upon pales 150, such as above, but also optionally below rails 120 and 130 respectively. This has the particular advantage that a fencing unit such as shown in figure 2 can be first produced which is itself a valid stock item and this can be done rapidly adapted to provide a further stock item, the bow top fence, by adding the bow tops. Figure 4 shows in more detail, a cross section 300, of a bow top 250 being located upon pales 150 such that a joining step may then take place. The preferred joining step is a crimping step by compressing the larger diameter tube as indicated by arrows 360. Figure 5 is equivalent to figure 4 but in which the swaged rail is utilised during that by means of two, optionally combined into one compression step the fence is formed. In viewing this figure, it is important to realise that the figure is purely schematic and that the walls of the tubes are provided with nominal cross sectional thickness (except for the rail 120). The pales 150 are swaged 370 at their upper end thus providing a junction 372 between the swaged and the un-reduced sections of the tube. Swaging is not a process which is realistically applied to a solid bar without very specialist machinery. In inserting the pales 150 through the rail 120 the swaged portion passes readily through large aperture 124, an aperture configured so that it binds with the unswaged portion 374 of the pale. He swaged portion passing closely through or in an interference fit through smaller upper aperture 122 of the rail. By this means a single compressive action forms the lower part of the fence. This advantageous combination is extended by the addition of the bow top 250 worthy reduction due to the swaging 370 enables the end of the pale to be inserted into material of the same provenance (i.e., the same raw material feedstock of tube) as that of the pale, this greatly simplifies stock keeping and improves production efficiency, such as lengths of tube left over from putting the pales can be used, after suitably forming into a semicircle for use as the bow tops. The bow tops are then similarly press fit onto the pales in a strong and robust construction is made without the requirement for any welding. In a preferred embodiment pale 150 may be further swaged, or only swaged at the very upper and so as to accommodate bow top to 50. This avoids a ridge at the bottom of the bow top where it joins the pale. Apertures 122, 124, may preferably be formed with a series of teeth, either internally castellated or a star shape so that the pale when inserted engages with the teeth to provide the interference fit, this allows greater tolerance in the hole size which can be important when temperature in the workshop changes. To give context, this form of construction using four vertical pales (2 cm diameter, 2 mm wall thickness) along with the relevant to rails (too many to wall thickness for centimetres width 2 cm depth) and to bow tops was found to be capable of withstanding a tensile force between the bow tops on the lower rail of 1,000kg. As noted above the present invention provides a fast and efficient manner of producing an improved bow top fence construction.

Claims

21 03 251. A bow top safety fence (200, 300) comprising tubular rails (120, 130), tubular pales (150) and tubular fence tops (250) positioned upon the pales (150), wherein the fence tops are compression fitted (360) to the pales.

2. The fence of claim 1 were in the tubular fence tops (250) telescope with the tubular rails.

3. The fence of claim 1 or claim 2 or in the tubular fence tops (250) are semi-circular.

4. The fence of claim 1, claim 2 or claim 3 wherein the tubular fence tops are semicircular with linear elongate ends configured to accommodate the upper ends of the pales.

5. The fence of any preceding claim wherein the upper ends of the pales are swaged (370).

6. The fence of any preceding claim wherein the rails (120, 130) are tubular.

7. The fence of claim 6 wherein the rails have pre-formed apertures for receiving the pales.

8. The fence of claim 7 were in the pales are retained in the rails by a compression or interference fit.

9. The fence of any preceding claim wherein the pales are constructed from tubular steel between 1.5 and 3.5 cm in diameter and with a wall thickness between 1 and 3 mm.

10. A method of constructing a bow top safety fence (200, 300) comprising providing tubular pales (150), tubular fence tops (250), and rails, wherein the pales are securable within apertures of the rails and the tubular fence tops are secured to the pales, the assembly being secured to form a section offence.

11. The method of claim 10 wherein the tubular fence tops telescope with the rails.

12. The method of claim 11 wherein the tubular fence tops (250) telescope into the pales and are secured between elongate extensions (252) of the fence tops inserted into the rails.

13. The method of any of claims 10, 11 and 12 wherein the fence tops (250) are compression secured (360) to the pales.

14. The method any of claims 10 to 13 wherein one or more ends of the pales are swaged in a swage forming step.

15. The method of any of claims 10 to 14 wherein the pales (150) are inserted into tubular rails (120, 130).

16. The method of claim 15 wherein the pales (150) are inserted into the rails (120, 130) under force to provide a compression / interference fit.

17. The method of claim 15 or claim 16 when the tubular rails have pre-formed apertures therein to receive the pales.

18. A kit of parts suitable to create the bow top safety fence of any of claims 1 to 9 or to perform the method of construction of any of claims 10 to 17.21 03 25

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