PALE

BACKGROUND OF THE INVENTION
Field Of Invention

This invention relates to a pale. More specifically, although not exclusively, this invention relates to a pale for use in a palisade fence and to a fence (e.g. a palisade fence) comprising at least one such pale.

Description of Related Art

It is known to build palisade fences in order to prevent access to an area by unauthorised persons. Palisade fences 1 tend to include spaced apart posts 2 joined by horizontal rails 3 to which pales 4 are attached (as shown in FIG. 1). The posts 2 tend to be supported in concrete 2C, while the pales 4 often have security heads 40 at their free, uppermost end. One important consideration of palisade fence design and manufacture is to ensure that the gaps T between individual adjacent pales 4 are small enough to ensure the security of the fence. The size of each gap T is a function of the so called “face to view” d of the pales 4 and the centre-to-centre spacing S between adjacent pales 4 (i.e. the pitch of the pales 4). Providing palisade fencing 1 with gap T dimensions not exceeding specific values has been found to be of particular commercial importance. Clearly, minimising the number of pales used whilst ensuring the security of the fence would be beneficial. However, it is not usually practical to do so.

British Standard 1722-12: 2006 (Fences—Part 12: Specification for steel palisade fences) specifies standards which palisade fences must meet or exceed before they can be classified as either general purpose (GP) or security purpose (SP) fencing. It is advantageous for manufacturers to be able to designate their fencing and component parts thereof as conforming to the standards required for GP and/or SP fencing.

One requirement of the standard relates to deflection upon loading of the pales 4 of a fence and is tested via a three-point bending test, whereby pales 4 for a GP fence should not deflect by more than 8 mm under a load of 2.5 kN and pales 4 for a SP fence should not deflect by more than 10 mm under a load of 3.5 kN. BS 1722-12: 2006 further specifies that corrugated pales 4 for GP fencing should have a minimum face to view d of 65 mm while corrugated pales 4 for SP fencing should have a minimum face to view d of 70 mm and that the maximum centre-to-centre spacing S between pales 4 should be 155 mm. The standard recommends that components should be formed from a steel having a minimum yield strength of 235 N/mm (material grade S235JR is recommended). The standard further discloses typical pale 4 profile thicknesses (which have been found satisfactory) for corrugated ‘W-shape’ profiles of 2.5 mm for GP fencing and 3.0 mm for SP fencing. Pales 4 may be formed by either hot or cold forming processes and still satisfy the standard.

Examples of prior art pales are discussed in the applicant's British patents GB2249327 and GB2372758 and WO95/33113.

Palisade fences 1 are material intensive structures and are generally manufactured from metals, particularly steel. It will be appreciated that reduction of the centre-to-centre spacing S between pales 4 will result in the use of an increased number of pales 4 for any given length of palisade fencing 1 with a consequential increase in material usage. The use of large quantities of metal in palisade fences 1 results in fencing which can be financially expensive as well as negatively impacting the environment.

BRIEF SUMMARY OF THE INVENTION

It is a first non-exclusive object of the invention to provide an improved palisade fence which satisfies and/or mitigates one or more of the above-mentioned issues and/or requirements.

Accordingly, an aspect of the invention provides a pale for a palisade fence, the pale comprising a longitudinal web and two longitudinal side portions, respective first and second longitudinal side portions extending from each side of the longitudinal web at an angle greater than 70 degrees and less than or equal to 90 degrees.

Another aspect of the invention provides a pale for a palisade fence, the pale comprising a longitudinal web and two longitudinal side portions, respective first and second longitudinal side portions extending from each side of the longitudinal web at an angle greater than 64 degrees and less than or equal to 90 degrees, wherein the pale has a thickness of less than 1.8 mm.

It has been surprisingly found that a pale with longitudinal side portions extending from either side of a longitudinal web by an angle within the above range provides improved resistance to deflection under load relative to prior art pales. Furthermore, it has been surprisingly found that pales according to the invention may be manufactured from less material than prior art pales whilst maintaining or increasing their resistance to deflection under load over said prior art pales. Yet further, it has been found that pales according to the invention may be manufactured with a similar face to view as prior art pales such that the same or a similar number of pales according to the invention are required for any given length of palisade fencing. As such, pales according to the invention can lead to significant material savings (and hence reduced weight, cost and processing requirements) as compared to pales of the prior art.

In use, the pale may be attached to rails at one or more (e.g. two) locations along the substantially flat, longitudinal central web via fastening devices, for example, rivets and/or bolts. The pale may comprise one or more apertures for locating the one or more fastening devices.

The pale may have a thickness of between about 1 mm and about 2 mm, say between about 1 mm and about 1.9 mm. The pale may have a thickness of less than 1.8 mm. It will be appreciated that such thicknesses are below the suggested values in the aforementioned British Standard. The pale may satisfy the requirements of British Standard 1722-12: 2006 regarding general purpose (GP) palisade fences and/or security (SP) palisade fences.

A further aspect of the invention provides a pale for a palisade fence, the pale having a thickness of less than 1.8 mm and satisfying the requirements of British Standard 1722-12: 2006 regarding general purpose (GP) palisade fences and/or security (SP) palisade fences.

The pale according to the second aspect may, but need not, comprise any one or more features of the first aspect. For example, the pale may comprise any one or more of: a longitudinal web, one or two longitudinal side portions.

One, e.g. a first, of the two longitudinal side portions may extend from one, e.g. a first, side of the longitudinal web, for example at an angle greater than 64 degrees, preferably greater than 70 degrees, and less than or equal to 90 degrees. Another, e.g. a second, of the two longitudinal side portions may extend from another, e.g. a second, side of the longitudinal web, for example at an angle greater than 64 degrees, preferably greater than 70 degrees, and less than or equal to 90 degrees.

In embodiments the angle may be greater than 65 degrees and less than 85 degrees, for example greater than 66 degrees and less than 80 degrees, e.g. greater than 67 degrees and less than 75 degrees. The angle may be greater than 64, 65 or 70 degrees and less than 90 degrees.

In embodiments, the angle may be greater than any one of 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, or 89 degrees and less than any one of 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, 66, or 65 degrees. Preferably, the angle is greater than any one of 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, or 89 degrees and less than any one of 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, or 71 degrees

During a three-point bending test the pale may have a maximum deflection at its middle of less than or equal to 8 mm (e.g. less than 7 mm, 6 mm or 5 mm) when subjected to a load of 2.5 Kn. During a three-point bending test (600 mm span) the pale may have a maximum deflection at its middle of less than or equal to 10 mm (e.g. less than 9 mm, 8 mm, or 7 mm) when subjected to a load of 3.5 kN.

The pale may have a thickness of between 1 mm and 2 mm, for example, between any one of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 mm to any one of 2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1 mm. The pale may have a thickness of between about 1 mm and about 1.8 mm, e.g. between about 1.1 mm and about 1.8 mm, for example from 1 mm or 1.1 mm to 1.7, 1.6, 1.5, 1.4, 1.3 or 1.2 mm. The pale may have a thickness of between any one of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 mm to any one of 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1 mm.

The pale may be formed from metal, for example from steel. The steel may have a yield stress greater than 235 N/mm², for example greater than 250 N/mm², say greater than 270 N/mm², e.g. greater than 290 N/mm², 300 N/mm², 310 N/mm², 320 N/mm², 330 N/mm², 340 N/mm², 350 N/mm², 360 N/mm², 370 N/mm², 380 N/mm², 390 N/mm², 400N/mm², 410 N/mm², 420 N/mm², 430 N/mm², 440 N/mm², 450 N/mm², 460 N/mm², 470 N/mm², 480 N/mm²or 490 N/mm².

The pale may be cold formed, e.g. by rolling and/or by press braking. The pale may be hot formed, e.g. by rolling and/or by pressing.

Preferably, the pale may have a cross-sectional area of less than 205 mm², e.g. less than 200 mm², 195 mm², 190 mm², 185 mm², 180 mm²or 175 mm², extending along a major proportion of its length.

One or both of the longitudinal side portions (where provided) may comprise strengthening means or a strengthener. The strengthening means or strengthener may comprise a longitudinal formation. The strengthening means or strengthener may comprise a further longitudinal formation. The longitudinal formation and/or the further longitudinal formation may comprise a longitudinally extending corrugation or rib. The strengthening means or strengthener may comprise one or more projections and/or depressions. Where the strengthening means or strengthener comprises plural projections and/or depressions they may be provided in a random or repeating pattern, e.g. extending longitudinally along the pale.

In embodiments the first longitudinal side portion may comprise first and second longitudinal side walls, e.g. connected to one another at one of their longitudinal edges by a further longitudinal web. The second longitudinal side portion may comprise first and second longitudinal side walls, e.g. connected to one another at one of their longitudinal edges by a further longitudinal web. One or both first longitudinal side walls may comprise the longitudinal formation (where provided). The longitudinal formation may be provided at about the midpoint of the first longitudinal side wall or walls. One or both of the second longitudinal side walls may comprise the further longitudinal formation (where provided). The further longitudinal formation may be provided at about the midpoint of the second longitudinal side wall or walls.

The longitudinal web (where provided) may be substantially flat. One or both of the further longitudinal webs (where provided) may be substantially flat. One or both of the further longitudinal webs may be substantially parallel to the longitudinal web. One or both of the further longitudinal webs may be arched or pointed.

The second longitudinal side wall (where provided) may comprise a free longitudinal edge portion. The second longitudinal side wall may comprise a lip, e.g. the free longitudinal edge portion may comprise a lip. The lip may be in-turned. The lip may comprise a free longitudinal edge of the second longitudinal side wall.

The free longitudinal edge may be adjacent a major surface of the second longitudinal side wall. The free longitudinal edge may be spaced from a major surface of the second longitudinal side wall.

The free longitudinal edge portion may substantially define a plane with the longitudinal web.

The pale comprises a face to view which may be greater than 65 mm and less than 155 mm, for example greater than 65 mm and less than 120 mm, e.g. greater than 65 mm and less than 95 mm, e.g. less than 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82 or 81 mm, say 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 or 80 mm. For example, the pale may comprise a face to view which is greater than any one of 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 138, 139, 140, 141, 142, 143, 144, 145, 146, 147, 148, 149, 150, 151, 152, 153, 154 mm and less than any one of 155, 154, 153, 152, 151, 150, 149, 148, 147, 146, 145, 144, 143, 142, 141, 140, 139, 138, 137, 136, 135, 134, 133, 132, 131, 130, 129, 128, 127, 126, 125, 124, 123, 122, 121, 120, 119, 118, 117, 116, 115, 114, 113, 112, 111, 110, 109, 108, 107, 106, 105, 104, 103, 102, 101, 100, 99, 98, 97, 96, 95, 94, 93, 92, 91, 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, 75, 74, 73, 72, 71, 70, 69, 68, 67, or 66 mm.

In an embodiment, the pale may have a face to view of from greater than 65 mm to less than 85 mm, or less than 80 mm, or less than 75 mm.

The pale may comprise a longitudinal web and two longitudinal side portions, respective first and second longitudinal side portions extending from each side of the longitudinal web at an angle greater than 65 degrees and less than or equal to 85 degrees, wherein the pale has a thickness of between 1.2 mm to 1.8 mm, and the pale comprises a face to view of greater than 65 mm and less than 95 mm.

The pale may comprise a longitudinal web and two longitudinal side portions, respective first and second longitudinal side portions extending from each side of the longitudinal web at an angle greater than 65 degrees and less than or equal to 80 degrees (e.g. greater than 65 degrees and less than or equal to 78 degrees), wherein the pale has a thickness of between 1.2 mm to 1.8 mm (e.g. between 1.2 mm to 1.5 mm), and the pale comprises a face to view of greater than or equal to 70 mm and less than 80 mm.

The pale may comprise a security head, e.g. at a free end thereof. The security head may be configured to inhibit or prohibit or prevent an intruder from climbing thereover. The security head may comprise a rounded, a rounded and notched, a square, a pointed, a triple pointed and splayed or a triple pointed, splayed and returned head.

A further aspect of the invention provides a palisade fence comprising one or more pales as described above. A plurality of pales may be provided. The centre-to-centre spacing of at least two adjacent pales may be from 120 mm to 175 mm, for example between 125 mm and 160 mm. The centre to centre spacing may be 155 mm.

A yet further aspect of the invention provides a palisade fence comprising two posts and at least one rail extending between the posts and at least one pale as described above.

A still further aspect of the invention provides a kit of parts for a palisade fence, the kit comprising two posts, at least one rail and at least one pale as described above.

For the avoidance of doubt, any of the features described herein apply equally to any aspect of the invention.

Within the scope of this application it is expressly envisaged that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. Features described in connection with one aspect or embodiment of the invention are applicable to all aspects or embodiments, unless such features are incompatible.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

FIG. 1 is a front elevation of a prior art palisade fence;

FIG. 2 is a sectional view of a prior art pale;

FIG. 3 is a sectional view of a pale according to a first embodiment of the invention;

FIG. 4 is a perspective view of a prior art test rig used to test pales;

FIGS. 5a is a sectional view of a pale not according to the invention FIGS. 5b and 5c are sectional views of pales according to alternative embodiments of the invention;

FIG. 6 is a plot of the results of testing the pales of FIGS. 5a to 5c;

FIG. 7 is a sectional view of a pale according to an alternative embodiment of the invention;

FIG. 8 is a plot of the results of testing the pales of FIG. 2 and FIG. 7;

FIG. 9a is a sectional view of a prior art pale and FIGS. 9b and 9c are sectional views of pales according to alternative embodiments of the invention;

FIGS. 10 and 11 are plots of the results of testing the pales of FIG. 7 formed from steels with different yield strengths; and

FIG. 12 depicts front elevation views of six different security heads of pales according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 2, there is shown a prior art W-shaped pale 4′ which was cold roll formed from a steel strip of width 112.77 mm and thickness t of 1.85 mm. The pale 4′ includes a substantially flat, longitudinal central web 5′ with first and second longitudinal side portions 6′, 7′ projecting from either side of the central web 5′ at an angle θ′ of 62°. The formed pale 4′ has a face to view d of 65.00 mm and is commercially available from Hadley Industries PLC as UltraPALE®200.

The first longitudinal side portion 6′ includes first and second longitudinal side walls 60′, 61′ connected to one another by an arched, further longitudinal web 62′ extending between respective proximate longitudinal edges. Longitudinally extending corrugations 63′ are included at the midpoint of the first and second longitudinal side walls 60′, 61′. A free, longitudinal edge portion 64′ of the second, longitudinal side wall 61′ extends beyond a plane P defined by the substantially flat, longitudinal central web 5′. The free, longitudinal edge portion 64′ includes an inturned lip 65′ with a free longitudinal edge 66′ which is adjacent a first, inner surface of the second, longitudinal side wall 61′.

The second longitudinal side portion 7′ includes first and second longitudinal side walls 70′, 71′ connected to one another by an arched, further longitudinal web 72′ extending between respective proximate longitudinal edges. Longitudinally extending corrugations 73′ are included at the midpoint of the first and second longitudinal side walls 70′, 71′. A free, longitudinal edge portion 74′ of the second, longitudinal side wall 71′ extends beyond the plane P defined by the substantially flat, longitudinal central web 5′. The free, longitudinal edge portion 74′ includes an in-turned lip 75′ with a free longitudinal edge 76′ which is adjacent a first, inner surface of the second, longitudinal side wall 71′.

In use, the pale 4′ is attached to rails 3 (as shown in FIG. 1) at two locations along the substantially flat, longitudinal central web 5′ via fastening devices (not shown), commonly rivets or bolts.

Referring now to FIG. 3, there is shown, according to one embodiment of the invention, an improved W-shape pale 4, where like references (absent the prime (′)) refer to like features which will not be described further herein. The first and second longitudinal side portions 6, 7 extend from the substantially flat, longitudinal central web 5 (e.g. from a plane

P parallel therewith) at an angle θ which is greater than 64 degrees and less than or equal to 90 degrees, say greater than 65 degrees and less than 85 degrees, for example greater than 66 degrees and less than 80 degrees, e.g. greater than 67 degrees and less than 75 degrees. Preferably, the angle is greater than 70 degrees and less than 90 degrees.

The further longitudinal web 62 of the first longitudinal side portion 6 is substantially flat in this embodiment. The free, longitudinal edge portion 64 of the second longitudinal side wall 61 extends to lie in line with a plane P defined by the substantially flat, longitudinal central web 5. The free, longitudinal edge 66 of the second, longitudinal side wall 61, is turned in to contact the first, inner surface thereof.

The further longitudinal web 72 of the second longitudinal side portion 7 is substantially flat in this embodiment. The free, longitudinal edge portion 74 of the second longitudinal side wall 71 extends to lie in line with a plane P defined by the substantially flat, longitudinal central web 5. The free, longitudinal edge 76 of the second, longitudinal side wall 71, is turned in to contact the first, inner surface thereof.

The pale 4 has a face to view d of between 65 and 155 mm, for example between 65 and 120 mm, e.g. between 65 and 95 mm, say 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 or 80 mm.

The pale 4 has a thickness t greater than 1.0 mm and less than 2.5 mm, say greater than 1.0 mm and less than 2.0 mm, for example greater than 1.0 mm and less than 1.9 mm, e.g. from 1.1 to 1.75 mm thick.

The pale 4 is formed from a steel having a yield stress greater than 235N/mm².

Testing:

Pales according to the invention (as well as prior art pales) were tested as per the following test:

- Test—Three point bending test
- A rig 100 according to BS 1722-12:2006 was set up as shown in FIG. 4, comprising a pair of parallel support rollers SR spaced by 600 mm with a loading pad LP equidistant therebetween and parallel thereto. Pales to be tested were placed upon the support rollers SR with the loading pad LP acting against the uppermost surface of the pale under test. A force of 2.5 kN was applied to each test sample and the deflection thereof measured. A force of 3.5 kN was then applied to each test sample and the deflection thereof measured. Six test specimens of each type of pale were tested in this rig 100, with each sample tested individually. Three samples were tested with the central web uppermost and three samples were tested with the central web downmost. The results were averaged for each type of pale under test.

Referring now to FIGS. 5a to 5c (integers similar or identical to the first embodiment are identified by a preceding ‘1’ for the embodiment of FIG. 5a, a ‘2’ for the embodiment of FIG. 5b and a ‘3’ for the embodiment of FIG. 5c), there are shown three simplified pales 14, 24, 34. The first and second longitudinal side portions 16, 26, 36, 17, 27, 37 of each of the simplified pales 14, 24, 34 include only first side walls 160, 260, 360, 170, 270, 370. Furthermore, the first side walls 160, 260, 369, 170, 270, 370 are free from the longitudinally extending corrugations 63, 73 as shown in the pale 4 of FIG. 3.

The first and second longitudinal side portions 16, 17 of the pale 14 shown in FIG. 5a extend at an angle θ of 62° from the longitudinal central web 15. The pale 14 is a simplified approximation of the prior art pale 4′ shown in FIG. 2. The first and second longitudinal side portions 26, 27 of the pale 24 shown in FIG. 5b extend at an angle θ of 72° from the longitudinal central web 25. The first and second longitudinal side portions 36, 37 of the pale 34 shown in FIG. 5c extend at an angle θ of 82° from the longitudinal central web 35.

Batches of pales 14, 24, 34 as shown in FIGS. 5a, 5b and 5c were manufactured by brake pressing according to the following characteristics:

TABLE 1

Batches of simplified pales

Steel

Pale
yield

Batch
angle
stress

name
(⊖)
(N/mm²)

A
62°
290

B
72°
290

C
82°
290

D
62°
550

E
72°
550

F
82°
550

Each batch of pales 14, 24, 34 was tested using the test rig 100 as described above, with the results shown in FIG. 6 and Table 3 below.

TABLE 3

Average maximum force

resisted by pales 14, 24, 34

Average

maximum

force (N)

Batch
resisted

A
722.00

B
813.33

C
884.67

D
1216.67

E
1350.00

F
1420.00

As can be seen from the results shown in FIG. 6, batch C (having an angle of 82°) resisted a greater load before deflecting to a similar extension as batch B (having an angle of 72°) which in turn resisted a greater load before deflecting to a similar extension as batch A (having an angle of 62°). Similarly, batch F (having an angle of 82°) resisted a greater load before deflecting to a similar extension as batch E (having an angle of 72°) which in turn resisted a greater load before deflecting to a similar extension as batch D (having an angle of 62°). Therefore, increasing the angle θat which the longitudinal side portions 16, 26, 36, 17, 27, 37 extend from the longitudinal central web 15, 25, 35 resulted in increased resistance to deflection under load. However, the improvement to resistance under load was greater between batches A and D (θ=62°) and batches B and E (θ=72°) than between batches B and E (θ=72°) and batches C and F (θ=82°) (i.e. ΔForce_BA>ΔForce_CBand ΔForce_ED>ΔForce_FE. Therefore, it appears as though the benefit of increasing the angle θ may decline as the angle θ approaches 90°.

Each of batches D, E and F (manufactured from steel with a yield stress of 550 N/mm²) demonstrated increased resistance to deflection under load over their corresponding (according to the same angle θ) batches A, B and C (manufactured from steel with a yield stress of 290 N/mm²). Therefore, increasing the yield stress of the steel from which the pales 14, 24, 34 were manufactured resulted in increased resistance to deflection under load. Furthermore, the ratio of increase between corresponding batches (having the same angle θ) is similar, suggesting that the increase in resistance to deflection obtained by increasing the yield stress of the steel is independent (or only marginally dependent) of the effect of altering the angle θ.

Moreover, batches B (θ=72°) and C (θ=82°) demonstrate increased resistance to load at smaller distances of deflection than does batch D (θ=62°) even though batches B and C were manufactured from steel with a yield stress of 290 N/mm²while batch D was manufactured from steel with a yield stress of 550 N/mm². Without wishing to be bound by any theory it may therefore be the case that at smaller distances of deflection the angle θof the pale 14, 24, 34 has a more significant effect on resistance to deflection than does the yield stress of the steel from which the pale 14, 24, 34 is manufactured. This is a surprising result given that the yield strength of the steel for batches B and C is about half of that of batch D. Furthermore, it is possible to compare the average maximum forces resisted by the pales 14, 24, 34 (as shown in Table 3) for pales 14, 24, 34 having the same angle θ. This comparison reveals that increasing the yield stress from 290 N/mm²to 550 N/mm²as from batch A to D (θ=62°) increased the maximum force resisted by 1.685 times, as from batch B to E (θ=72°) increased the maximum force resisted by 1.660 times, and as from batch C to F (θ=82°) increased the maximum force resisted by 1.605 times. Clearly, as the angle e increases the effect of increasing the yield stress becomes less significant. Therefore, as the angle θ increases, the effect of increasing the angle θ has a decreasing relative effect (with respect to increasing the yield stress of the steel) on the maximum force resisted by the pales 14, 24, 34.

Referring now to FIG. 7 (integers similar or identical to the first embodiment shown in FIG. 3 are identified by a preceding ‘4’), there is shown a pale 44 which differs from the pale 4 shown in FIG. 3 in that the first and second longitudinal side walls 460, 470, 461, 471 of the first and second longitudinal side portions 46, 47 are free from longitudinally extending corrugations. Furthermore, the free, longitudinal edge portions 464, 474 of the second longitudinal side walls 461, 471 do not include an in-turned lip.

Tests were conducted of pales 44 as shown in FIG. 7 and prior art UltraPALE 200 pales 4′ as shown in FIG. 2, with characteristics as follows:

TABLE 3

Tested pale characteristics

UltraPALE 200
1.2 mm
1.7 mm

Characteristic
pale 4′
pale 44
pale 44

Thickness t (mm)
1.85
1.19
1.72

Cross-sectional
208.62
153.33
212.51

area (mm²)

Angle ⊖
62.0
71.0
71.0

Results of Testing:

Referring now to FIG. 8, there are shown the results of testing of pales 4′, 44 with characteristics shown in Table 1 using the test rig 100 shown in FIG. 4. The 1.2 mm pale 44 test results are denoted in line form for face up testing (labelled as G1) and in dashed line form for face down testing (labelled as G2). The 1.7 mm pale 44 test results are denoted in line form for face up testing (labelled as H1) and in dashed line form for face down testing (labelled as H2). The UltraPALE 200 pale 4′ test results are denoted in line form for face up testing (labelled as J).

As can be seen from the results, both the 1.2 mm pale 44 (both face up and face down) and the 1.7 mm pale 44 (both face up and face down) provide greater resistance to deflection than does the prior art pale 4′ for deflections less than or equal to 8 mm.

The 1.2 mm pale 44 withstood an average load of 2.803 kN before deflecting by 8 mm, while the prior art pale 4′ withstood an average load of only 2.563 kN before deflecting by 8 mm. Therefore, although both pales 4′ 44 may be classified as suitable for use in general purpose palisade fencing the 1.2 mm pale 44 achieved a greater resistance to deflection.

The 1.2 mm pale 44 (face up) provides greater resistance to deflection than does the prior art pale 4′ (face up) for deflections less than or equal to 10 mm. Moreover, the 1.2 mm pale 44 (face down) provides very similar resistance to deflection to the prior art pale 4′ (face up) for deflections up to 10 mm.

Furthermore, this similarity of performance was achieved even though the UltraPALE 200 pale 4′ has an average cross-sectional area of 208.62 mm²while the 1.2 mm pale 44 has an average cross-sectional area of only 153.33 mm², representing a 26.5% reduction in area and therefore in material usage. Without wishing to be bound by any theory it is believed that the increase in the angle θ from 62.0° to 71.0° results in increased resistance to localised deformation around the first and second longitudinal side portions 46, 47 leading to a subsequent reduction in overall deflection.

The 1.7 mm pale 44 demonstrates even greater resistance to deflection than does the 1.2 mm pale 44. Indeed, the 1.7 mm pale 44 exceeded both a 2.5 kN load before deflecting by 8 mm and a 3.5 kN load before deflecting by 10 mm. The 1.7 mm pale 44 therefore successfully passed both the GP and SP palisade fencing deflection tests, in contrast to the prior art pale 4′ which deflected by 10 mm at a load less than 3.5 kN. Accordingly, the 1.7 mm pale 44 could have been made even thinner (and thereby further reduce cross sectional area) and still surpass the results of the prior art pale 4′ and meet both the SP and GP standards.

Furthermore, neither the 1.2 mm nor the 1.7 mm pales 44 included longitudinally extending corrugations or longitudinal edge portions 464, 474 with in-turned lips, in contrast to the prior art pales 4′. Without wishing to be bound by any theory, it is believed that the in-turned lips 65′, 75′ further strengthen the prior art pale 4′, whilst the longitudinally extending corrugations 63′, 73′ provide increased resistance to deflection under loading. Therefore, were the 1.2 mm and 1.7 mm pales 44 to include either or both of these features they would have produced further improved results over the prior art pales 4′. Moreover, the 1.2 mm and 1.7 mm pales 44 were manufactured by break pressing whilst the prior art pales 4′ were manufactured by cold roll forming.

Referring now to FIGS. 9a to 9c (integers similar or identical to the first embodiment are identified by a preceding ‘5’ for the prior art pale of FIG. 9a, a ‘6’ for the embodiment of FIG. 9b and a ‘7’ for the embodiment of FIG. 9c), there are shown three pales 54, 64, 74 with the same face to view d of 70.0 mm and width w of longitudinal central web 55, 65, 75. However, the prior art pale 54 shown in FIG. 9a has first and second longitudinal side portions 56, 57 which extend from either side of the longitudinal central web 55 at an angle θ of 62°, whilst the pale 64 according to the invention shown in FIG. 9b includes an angle θ of 72° and the pale 74 according to the invention shown in FIG. 9c includes an angle θ of 82°.

By substantially maintaining the face to view d of the pales 64, 74 shown in FIGS. 9b and 9c relative to the prior art pale 54 shown in FIG. 9a the same number of pales 54, 64, 74 are required for a given length of fencing whilst substantially maintaining the gap T between adjacent pales 54, 64, 74 (see FIG. 1). Clearly, increasing the number of pales 54, 64, 74 in any given length of fencing would result in an increase in the volume of steel required (all other factors remaining the same) and hence an increase in the expense of a palisade fence 1 thus formed. Therefore, by maintaining the number of pales 64, 74 required in any given length of fencing relative to the prior art pales 54 this increase in expense is avoided.

In order that the pale 64 shown in FIG. 9b maintains the same face to view d as the prior art pale 54 shown in FIG. 9a the further longitudinal webs 662, 672 have a relatively increased width. The pale 74 of FIG. 9c demonstrates this increase even more markedly. Therefore, it will be understood that increasing the angle θ requires an increased width of strip in order to maintain the same face to view d. Consequently, for pales 54, 64, 74 having the same thickness t increasing the angle θ whilst maintaining the face to view d dimension results in an increase in the cross-sectional area and consequently in the volume of steel used.

Balancing the angle θ, thickness t, strength and face to view d of the pale allows a fence to be produced which satisfies the applicable standards and substantially reduces the amount of pale material used as compared to the prior art. Accordingly, it has been surprisingly found that a slight but significant change in geometry can lead to pales which demonstrate increased resistance to deflection during loading and/or require reduced quantities of pale material for their construction in comparison with prior art pales.

Referring now to FIGS. 10 and 11, there are shown the results of testing 1.2 mm thick and 1.7 mm thick pales 44 as shown in FIG. 7 formed from steels with different yield stresses. It can be seen from FIGS. 10 and 11 that increasing the yield stress of the steel used results in pales 44 having increased resistance to deflection under loading.

It is further shown from FIG. 10 that the 1.2 mm thick pale 44 (with test results labelled K1) needs to be formed from a steel with a yield stress of 306 N/mm²in order to deflect by less than 8 mm when subjected to a load of 2.5 kN (and hence satisfy the GP fencing requirement of the aforementioned British Standard). The 1.7 mm thick pale 44 (with test results labelled L1) needs to be formed from a steel with a yield stress of less than 280 N/mm²(which has been extrapolated from the results shown in FIG. 10 to be 199 N/mm²) in order to satisfy the same GP fencing requirement.

From FIG. 11 it is shown that the 1.2 mm thick pale 44 (with test results labelled K2) needs to be formed from a steel with a yield stress of 436 N/mm²in order to deflect by less than 10 mm when subjected to a load of 3.5 kN (and hence satisfy the SP fencing requirement of the British Standard). The 1.7 mm thick pale 44 (with test results labelled L2) needs to be formed from a steel having a yield stress of only 292 N/mm²in order to satisfy the same SP fencing requirement.

As shown in Table 2 above, a 1.2 mm thick pale has a smaller cross-sectional area than does a 1.7 mm thick pale, and hence a smaller volume. Therefore, a 1.2 mm thick pale requires less steel than does a 1.7 mm thick pale, with a consequently reduced expense of steel and a reduced weight of the pale (and hence reduced expense of transportation). However, and in order that the pale satisfies the requirements of the British Standard for GP and/or SP fencing, the yield stress of steel used for a 1.2 mm thick pale should be higher than the yield stress of steel used for a 1.7 mm thick pale. It will be appreciated that increasing the yield stress of steel results in a more expensive metal. Therefore, although a 1.7 mm thick pale requires more steel than does a 1.2 mm thick pale the steel required by the 1.7 mm thick pale to satisfy the requirement of the British Standard of GP and/or SP fencing is less expensive per volume than is the steel required by a 1.2 mm thick pale. Furthermore, formation of pales using steel with higher yield stresses requires more force and consequently (without wishing to be bound by any theory) may result in greater tool wear, leading to shorter tool life and consequent increased expense (e.g. according to calculations, 1.2 mm thick mild steel (S275) requires a force of 1.86 kN to form a 90° bend in a 20 mm length, whereas a different steel (S235) requires a force of 1.57 kN, the corresponding forces being 3.24 kN and 2.65 kN for a 1.7 mm thick steel.

As is explained above, increasing the angle θ results in increased resistance to deflection under loading (as shown in FIG. 6). Therefore, with an increased angle θ the thickness t of a pale can be reduced whilst maintaining the same or generating an enhanced resistance to deflection under loading. By reducing the thickness t of the pale the cross-sectional area and consequently the volume of steel used is also reduced. However (and as explained above), in order to maintain the same face to view d at an increased angle θ the strip width must be increased, consequently increasing the cross-sectional area and hence the volume of steel used. However, by using a steel having a higher yield stress it is possible to reduce the thickness t of the pale and hence reduce the quantity of steel used. It has been surprisingly found that all of the above factors are interrelated and that it is most beneficial to provide pales having an angle θ greater than 64° or 65°, preferably greater than 70°, but less than 90°, say less than 85°.

Referring now to FIG. 12, there are shown six different security heads suitable for the pales 4 shown in FIG. 1. Head (a) shows a rounded and notched head, head b shows a rounded head, head c shows a plain, square head, head d shows a pointed head, head e shows a triple pointed and splayed head and head f shows a triple pointed, splayed and returned head.

It will be appreciated by those skilled in the art that several variations to the aforementioned embodiments are envisaged without departing from the scope of the invention. For example, although only a single longitudinal extending corrugation 63, 73 is shown in each longitudinal side wall 60, 70, 61, 71 of the pale 4 shown in FIG. 3 this need not be the case and instead there may be any suitable number of longitudinally extending corrugations 63, 73, for example 0, 1, 2, 3, 4, 5, 6, etc. Additionally or alternatively, although the longitudinally extending corrugations 63, 73 are shown in the pale 4 at the midpoint of the longitudinal side walls 60, 70, 61, 71 this need not be the case and instead the longitudinally extending corrugations 63, 73 may be included at any suitable location of said longitudinal side walls 60, 70, 61, 71.

It will also be appreciated by those skilled in the art that any number of combinations of the aforementioned features and/or those shown in the appended drawings provide clear advantages over the prior art and are therefore within the scope of the invention described herein.

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