FENCE POST

Abstract

A fence system, post, and method of manufacture are herein disclosed. The post includes a shaft, and an overmold layer extending at least a portion of a length of the shaft. The overmold layer includes a plurality of external attachment locating features for selectively securing wire locating attachments at predetemlined locations along the length of the shaft. The fence system includes a plurality of the posts and a plurality of wire locating attachments configured to be attached to the external attachment locating features of the posts.

Claims

1. A fence post, comprising: a shaft; an overmold layer surrounding the shaft and extending along at least 50% of a length of the shaft; wherein the overmold layer comprises one or more stress relief features, wherein each stress relief feature comprises a plurality of link portions provided on alternating sides of the shaft along a longitudinal axis of the shaft, and a plurality of traversing portions extending across the longitudinal axis between the link portions, wherein neighboring link portions of the plurality of link portions on each side of the shaft are spaced apart along the longitudinal axis to provide an air gap between the neighboring link portions, wherein at least two of the plurality of link portions on each side of the shaft have a first air gap above the link portion and a second air gap below the link portion along the longitudinal axis.

2. The fence post of claim 1, wherein each of the plurality of traversing portions surrounds the shaft.

3. The fence post of claim 1, wherein the plurality of link portions and the plurality of traversing portions form a series of cantilever beams extending in alternating directions across the longitudinal axis of the shaft.

4. The fence post of claim 1, wherein the plurality of link portions and the plurality of traversing portions form a helix.

5. The fence post of claim 1, wherein the plurality of link portions are evenly spaced apart along the longitudinal axis of the shaft.

6. The fence post of claim 1, wherein the one or more stress relief features are positioned between portions of the overmold layer continuously surrounding the shaft.

7. The fence post of claim 1, wherein a cross-sectional area of the stress relief feature at any one point is at least 30 mm.sup.2.

8. The fence post of claim 1, wherein a cross-sectional area of the stress relief feature at any one point is less than 40 mm.sup.2.

9. The fence post of claim 1, wherein the shaft is made of a fibre-reinforced plastics material, and the overmold layer is made of a different plastics material to the shaft.

10. The fence post of claim 1, wherein the overmold layer extends along at least 90% of the length of the shaft.

11. The fence post of claim 1, wherein the fence post includes a first end configured to be inserted into the ground in use, and a second end distal from the first end, and wherein the fence post further includes at least one cap configured to be attached to the overmold layer and fit over an end of the shaft extending beyond the overmold layer at the second end of the fence post.

12. The fence post of claim 11, wherein the at least one cap includes one or more of: an end cap including one or more slots extending along the longitudinal axis of the fence post and configured to receive one or more lateral catches extending from the overmold layer, and a tip cap made of a tougher material than the overmold layer.

13. The fence post of claim 1, including a foot at one end of the shaft, configured to be inserted into the ground to locate the fence post in place, and having an elongate shaft portion coaxial with the longitudinal axis of the shaft, wherein the foot includes at least one of: at least one fin extending along at least a portion of the elongate shaft portion, and a flange extending from the elongate shaft portion at a position distal from the tip of the fence post.

14. The fence post of claim 1, further comprising a plurality of attachment locating features formed in a radially outward facing surface of the overmold layer, each of the attachment locating features configured to enable selective connection of a wire locating attachment in use.

15. The fence post of claim 14, wherein each attachment locating feature comprises one or more projections extending radially outward from a surrounding portion of the overmold layer.

16. The fence post of claim 14, wherein each of the attachment locating features comprise at least two bearing surfaces facing in different directions, the at least two bearing surfaces configured to bear against the wire locating attachment in use to restrict movement relative to the post in at least two directions.

17. The fence post of claim 1, wherein the shaft comprises a radially outward facing shaft surface, and further comprises a deviation in the radially outward facing shaft surface engaging with the overmold layer.

18. A fence system, including: a plurality of fence posts, each fence post comprising: a shaft; an overmold layer surrounding the shaft and extending along at least 50% of a length of the shaft; wherein the overmold layer comprises one or more stress relief features, wherein each stress relief feature comprises a plurality of link portions provided on alternating sides of the shaft along a longitudinal axis of the shaft, and a plurality of traversing portions extending across the longitudinal axis between the link portions, wherein neighboring link portions of the plurality of link portions on each side of the shaft are spaced apart along the longitudinal axis to provide an air gap between the neighboring link portions, wherein at least two of the plurality of link portions on each side of the shaft has a first air gap above the link portion and a second air gap below the link portion along the longitudinal axis, and wherein a plurality of attachment locating features are formed in a radially outward facing surface of the overmold layer; and a plurality of wire locating attachments configured to be attached to the attachment locating features of the fence posts.

19. The fence system of claim 18, wherein each wire locating attachment includes at least one pair of arms configured to extend about at least a portion of the overmold layer of the fence post, each arm having a catching surface configured to bear against the overmold layer to restrict radial movement of the wire locating attachment away from the fence post, as well as axial movement around the fence post, until released by a user.

20. The fence system of claim 18, wherein each wire locating attachment includes at least one locating feature configured to interact with at least one of the attachment locating features of the overmold layer to restrict movement of the wire locating attachment along the longitudinal axis of the fence post until released by a user.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0090] Further aspects of the present invention will become apparent from the following description which is given by way of example only and with reference to the accompanying drawings in which:

[0091] FIG. 1A is a front view of an exemplary post according to an aspect of the present disclosure;

[0092] FIG. 1B is a perspective view of an exemplary rod for use in the post;

[0093] FIG. 1C is a side enlarged view of the exemplary rod;

[0094] FIG. 1D is a side cross-sectional view of the exemplary post;

[0095] FIG. 2A is a perspective view of an end of the exemplary post with an exemplary end cap removed;

[0096] FIG. 2B is a perspective view of the end of the exemplary post with the exemplary end cap attached;

[0097] FIG. 2C is a side cross-sectional view of the end of the exemplary post;

[0098] FIG. 3A is a perspective view of an exemplary foot of the exemplary post;

[0099] FIG. 3B is a side cross-sectional view of the foot of the exemplary post;

[0100] FIG. 3C is an end cross-sectional view of the foot of the exemplary post;

[0101] FIG. 3D is a perspective view of an exemplary cap tip for the exemplary foot;

[0102] FIG. 3E is an end cross-sectional view of another exemplary embodiment of a foot of the exemplary post;

[0103] FIG. 3F is a perspective view of another exemplary cap tip for the exemplary foot;

[0104] FIG. 4A is a perspective view of an exemplary stress relief feature for the exemplary post;

[0105] FIG. 4B is a side view of the exemplary stress relief feature;

[0106] FIG. 4C is a front view of the exemplary stress relief feature;

[0107] FIG. 5A is a perspective view of an exemplary wire attachment feature for the exemplary post;

[0108] FIG. 5B is a side view of the exemplary wire attachment feature;

[0109] FIG. 5C is a front view of the exemplary wire attachment feature;

[0110] FIG. 6A is a perspective view of an exemplary wire locating attachment for use with the exemplary post;

[0111] FIG. 6B is a top view of the exemplary wire locating attachment;

[0112] FIG. 6C is a side view of the exemplary wire locating attachment;

[0113] FIG. 6D is a front view of the exemplary wire locating attachment;

[0114] FIG. 7A is a perspective view of the exemplary wire locating attachment secured to the exemplary post;

[0115] FIG. 7B is a side view of the exemplary wire locating attachment secured to the post;

[0116] FIG. 8 is a perspective view of the exemplary post with a plurality of the exemplary wire locating attachments secured thereto, and

[0117] FIG. 9 is a perspective view of a fence including a plurality of the exemplary posts.

DETAILED DESCRIPTION

[0118] FIG. 1A illustrates a fence post 100. The post 100 has a core shaft 102 (not clearly seen in FIG. 1A, but see FIG. 1B) onto which an overmold layer 104 (herein referred to as the overmold) is applied. The post 100 has a head 106 at one end, and a foot 108 at the other end distal from the head 106.

[0119] The overmold 104 includes a first stress relief feature 110a at a mid-point between the head 106 and the foot 108, and a second stress relief feature 110b adjacent to the foot 108. The stress relief features 110a and 110b will be described in greater detail below.

[0120] The overmold 104 also includes a plurality of external attachment locating features for selectively securing wire locating attachments (not illustrated in FIG. 1A) at predetermined locations 112a-112m along the length of the post 100 between the head 106 and the second stress relief feature 110b. Details of the attachment locating features will be described further below.

[0121] Referring to FIG. 1B, in this exemplary embodiment the shaft 102 is a rod having a solid cross-section with a diameter of approximately 16.0 mm and made of fiberglassand may herein be referred to as the rod.

[0122] The rod 102 includes a number of external locating features spaced apart at several locations 114a-c along its length. Referring to FIG. 1C, the external locating features are annular grooves 116, which guide the formation of internal rings 118 on the overmold 104 during molding (as seen in FIG. 1D). The interlocking grooves 116 and rings 118 restrict longitudinal movement of the rod 102 relative to the overmold layer 104.

[0123] Referring to FIG. 2A, at the head 106 of the post 100, the rod 102 projects beyond a first end 120 of the overmold 104 by approximately 13 mm. In this exemplary embodiment the rod 102 initially extends above the overmold 104 by 8 mm, but the overmold 104 may shrink down the rod 102 by approximately 5 mm following molding.

[0124] Two barbs 122a and 122b are located on opposite sides of the first end 120. As seen in FIG. 2B, the post includes a cap 124 made of glass fibre reinforced nylon, configured to fit over the exposed end of the rod 102 and including fastener apertures 126a (and 126bas seen in FIG. 2C) into which the barbs 122a (and 112bas seen in FIG. 2C) may project to locate the cap 124 relative to the overmold 104. The slot shaped nature of the fastener apertures 126a and 126b accommodates shrinkage of the overmold 104.

[0125] Referring to FIG. 2C, the cap 124 includes an end portion 128 having an inner surface 130 which may bear against a first end surface 132 of the rod 102. Further, the interior surface of the sides of the cap 124 may include a plurality of radially extending ribs to grip onto the rod 102, centralize the cap 124 relative to the longitudinal axis of the rod 102, and limit longitudinal movement along the rod 102 during ramming.

[0126] FIG. 3A shows the foot 108 of the post 100 in greater detail. The foot 108 includes a shaft portion 300, with a flange 302 between the shaft portion 300 and the second strain relief feature 110b of the post 100. Four fins 304a-d (fin 304b not shown in FIG. 3A, see FIG. 3C) are evenly spaced around the shaft portion 300, extending radially from its longitudinal axis.

[0127] Each of the fins 304a-d includes a series of transverse ridges 306 and grooves 308 forming a corrugated pattern through a central portion of each of the fins 304a-d. By way of example, the corrugations may have an amplitude of approximately 2 mm (plus the wall thickness of the fin 304a-d) and a pitch of approximately 8.8 mm. In the exemplary embodiment illustrated, each fin 304a-d includes at least one slot 310.

[0128] Similar to the head 106 of the post, the foot 108 is capped by a separate part: tip 312. Referring to FIG. 3B, the rod 102 extends through the entirety of the shaft portion 300 of the foot, and projects beyond its end. The tip 312 fits over the exposed end of the rod 102. As seen in FIG. 3C, the interior 314 of the foot 108 at its end includes planar key surfaces 316a and 316b. The tip 312 (as seen in FIG. 3D) has a body 318 with a conical nose 320 at one end. At its other end the tip 312, a cavity 322 provides for receiving the exposed end of the rod 102 (as seen in FIG. 3B), with a key flange 324 having opposing keying surfaces 326a and 326b on its exterior against which the planar key surfaces 316a and 316b of the foot 108 (as seen in FIG. 3C) are formed during molding.

[0129] FIG. 3E, illustrates an alternative embodiment to FIG. 3C, in which the interior 314 of the foot 108 at its end includes a plurality of indents 328a-d. The tip 312 (as seen in FIG. 3F) has a number of protrusions 330a-d spaced around its exterior about which the indents 328a-d of the foot 108 (as seen in FIG. 3E) are formed during molding.

[0130] FIG. 4A-C illustrate the structure of the stress relief feature 110, extending continuously between solid portions of the overmold 104. The stress relief feature 110 includes a plurality of transverse stress relief members in the form of disks 400a-e, having a central bore 402 (in which the rod 102 is locatedsee FIG. 4B and FIG. 4C).

[0131] The disks 400a-e are produced by forming transverse slots 404a-f on alternating sides of the overmold 104 along the length of the stress relief feature 110, leaving neighboring disks 400a-e connected by vertical link members 406a-f. Each disk 400a-e and vertical link member 606a-f essentially acts as a cantilever beamallowing flexure in each cantilever beam, and therefore the stress relief feature as a whole.

[0132] Stress produced by shrinkage of the overmold 104 is accommodated by this flexure, reducing the likelihood of material failure and the formation of cracks. Similarly, the flexure may accommodate stress on the overmold 104 while the post is in usefor example if a load is applied by an animal brushing against the fence.

[0133] As seen in FIG. 1A, the stress relief features 110a and 110b have been positioned at approximately equal spacing from the head 106. Referring to FIG. 1B, the sets of groves 114a and 114b on the fiberglass rod 102 are positioned be located approximate the middle of each section of overmold 104 between the stress relief features 110a-c. This allows each section of overmold 104 to shrink away from each stress relief features 110a-c. For the foot 108 section, in which it is envisioned that most of the shrinkage will pull the stress relief feature 110c downwards.

[0134] It is envisaged that in the middle section of the overmold 104i.e. on either side of the stress relief feature 110bmay experience a shrinkage of approximately 5 mm in each direction. As such, the stress relief feature 110b may need to accommodate in the order of 10 to 12 mm of movement.

[0135] In an exemplary embodiment the material used for the overmold 104 may be a fractional melt HDPE. Fractional melt is defined by a melt flow index (MFI) test performed to ASTM D1238 (a standard test method for finding the MFI value). So a fractional melt plastic is one that has an MFI less than 1 g/10 min at 190 C. In this exemplary embodiment the material also has a maximum tensile strength of 27 MPa and a flexural modulas of 1370 MPa.

[0136] A person skilled in the art will appreciate that there is no specific guide or level of stress a part must be below to prevent stress cracking. The applicant has identified that reducing the likelihood of cracking is influenced by the type of material, keeping the high stress areas free of sharp corners (or stress raisers) and keeping the overall stress as low as possible. FEA analysis of the stress relief feature 110 suggests the stress in the disks 400a-e and vertical link members 406a-f is around the 13 to 14 MPa range with a couple of higher areas around the 26 MPa level. The higher levels appear to be located on smooth surfaces and do not appear to be close to stress raiser points, and as such present a relatively low risk of cracking.

[0137] In an exemplary embodiment the thickness of the disks 400a-e may be different. It is envisaged that this may assist in balancing the amount of deflection each of the disks 400a-e will move. As the stress relief feature 110 may be produced by molding onto the fibreglass rod 102, the inside surface of the stress relief feature 110 is in contact with the rod 102 when the post 100 is removed from the molding tool. The shrinkage movement does have some force behind it, but it has to overcome the frictional force between the fiberglass and the HDPE. Testing has shown that when the stress relief feature 110 is configured such that the disks 400a-e have the same thickness, the two disks 400a and 400e at each end of the stress relief feature 110 (closest to the overmolded sections) tend to move more than the next discs in. The thickness of the first arms from each end, i.e. disks 400a and 400e, may be increased to be a little more rigid and therefore pull the next disc along the axis of the fiberglass rod 102 to provide a more uniform appearance.

[0138] The tool features of the mold used to form the slots 404a-f may also be used to hold the rod 102 in place within the cavity of the mold defining the overmold 104. The connected structure of the stress relief feature also allows for a continuous flow path within the cavity through which material forming the overmold 104 may pass.

[0139] FIG. 5A-C illustrates front and rear attachment locating features 500a (and 500b positioned at each of the predetermined locations 112a-112m (as shown in FIG. 1A). The attachment locating features 500a and 500b may herein be referred to as index features.

[0140] Between the index features 500a and 500b, on the sides of the overmold 104, left and right vertical ridges 502a and 502b extend the length of the overmold 104 (interrupted by the strain relief features 110a and 110b illustrated in FIG. 1A).

[0141] With reference to the front index feature 500a, each index feature includes a transverse groove 504a, with a first locating recess 506a positioned above the groove 504a, and a second locating recess 508a positioned below the groove 504a. Each of the locating recesses 506a and 508a includes a first transverse locating surface 510a facing the groove 504a, and a second transverse locating surface 512a facing away from the groove 504a.

[0142] Referring to FIG. 5B, each of the vertical ridges (for example, ridge 502b illustrated in FIG. 5B) includes a front catch surface 516b and a rear catch surface 518b.

[0143] FIG. 6A-D illustrates a wire locating attachment 600 (herein referred to as the clip) to be secured to the post 100 using the index features. The clip 600 includes a body 602, with a first pair of arms 604 and a second pair of arms 606 extending from the body 602, with a gap 608 therebetween.

[0144] Referring to FIG. 6B and 6D, each pair of arms includes a left arm 609 and a right arm 610, the arms 609 and 610 ending in an outwardly flaring barb 612 and 614 respectively. The barbs 612 and 614 include barb catch surfaces 616 and 618 respectively, facing towards the body 602. A first locating protrusion 620a and a second protrusion 620b extend from the body 602 in the same direction as the arms. The first locating protrusion 620a and second protrusion 620b are complementary in shape with the locating recesses 506 and 508 of the index features 500.

[0145] Referring to FIG. 7A, the clip 600 may be pushed onto a desired indexing feature (for example front indexing feature 500a as shown in FIG. 5A), with the flared barbs 612 and 614 guiding the arms 610 and 614 outwardly over the vertical ridges 502. Once the barbs 612 and 614 are passed the ridges 502, the resilient nature of the arms 610 and 614 closes them such that the barb catch surfaces 616 and 618 are positioned against the rear catch surface 518bresisting removal of the clip 600 from the post 100.

[0146] Simultaneously the first locating protrusion 620a and the second protrusion 620b are nested within the locating recesses 506a and 508a respectively, to resist movement of the clip 600 along the post 600.

[0147] In FIG. 7B, it may be seen that the body 602 of the clip 600, together with the transverse groove 504a, defines an aperture 700 through which a length of wire may passthereby locating the wire at a desired height.

[0148] FIG. 8 illustrates a post 100 to which a plurality of the clips 600a-h have been secured. It should be appreciated that the clips 600a-h may be secured in any number of combinations to achieve a variety of fence configurations.

[0149] FIG. 9 illustrates a fence 900, in which a number of posts 100 have been spaced apart. Wires 902a-gspan between the posts 100, secured by clips 600a, 600b, and 600d-h (not clearly seen in FIG. 9, but refer to FIG. 8). In this exemplary embodiment, a strain post 904 is provided at one end of the fence 900, to which the wires 902a-g may be secured using any suitable means known in the art.

[0150] The entire disclosures of all applications, patents and publications cited above and below, if any, are herein incorporated by reference.

[0151] Reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in the field of endeavor in any country in the world.

[0152] The disclosure may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, in any or all combinations of two or more of said parts, elements or features.

[0153] Wherein the foregoing description reference has been made to integers or components having known equivalents thereof, those integers are herein incorporated as if individually set forth.

[0154] It should be noted that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. Such changes and modifications may be made without departing from the spirit and scope of the disclosure and without diminishing its attendant advantages. It is therefore intended that such changes and modifications be comprised within the present disclosure.

[0155] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0156] Explicitly referenced embodiments herein were chosen and described in order to best explain the principles of the disclosure and their practical application, and to enable others of ordinary skill in the art to understand the disclosure and recognize many alternatives, modifications, and variations on the described example(s). Accordingly, various implementations other than those explicitly described are within the scope of the disclosure, and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.