Patent ID: 12252895

DETAILED DESCRIPTION

FIG.1Aillustrates a fence post100. The post100has a core shaft102(not clearly seen inFIG.1A, but seeFIG.1B) onto which an overmold layer104(herein referred to as “the overmold”) is applied. The post100has a head106at one end, and a foot108at the other end distal from the head106.

The overmold104includes a first stress relief feature110aat a mid-point between the head106and the foot108, and a second stress relief feature110badjacent to the foot108. The stress relief features110aand110bwill be described in greater detail below.

The overmold104also includes a plurality of external attachment locating features for selectively securing wire locating attachments (not illustrated inFIG.1A) at predetermined locations112a-112malong the length of the post100between the head106and the second stress relief feature110b. Details of the attachment locating features will be described further below.

Referring toFIG.1B, in this exemplary embodiment the shaft102is a rod having a solid cross-section with a diameter of approximately 16.0 mm and made of fiberglass—and may herein be referred to as “the rod”.

The rod102includes a number of external locating features spaced apart at several locations114a-calong its length. Referring toFIG.1C, the external locating features are annular grooves116, which guide the formation of internal rings118on the overmold104during molding (as seen inFIG.1D). The interlocking grooves116and rings118restrict longitudinal movement of the rod102relative to the overmold layer104.

Referring toFIG.2A, at the head106of the post100, the rod102projects beyond a first end120of the overmold104by approximately 13 mm. In this exemplary embodiment the rod102initially extends above the overmold104by 8 mm, but the overmold104may shrink down the rod102by approximately 5 mm following molding.

Two barbs122aand122bare located on opposite sides of the first end120. As seen inFIG.2B, the post includes a cap124made of glass fibre reinforced nylon, configured to fit over the exposed end of the rod102and including fastener apertures126a(and126b—as seen inFIG.2C) into which the barbs122a(and112b—as seen inFIG.2C) may project to locate the cap124relative to the overmold104. The slot shaped nature of the fastener apertures126aand126baccommodates shrinkage of the overmold104.

Referring toFIG.2C, the cap124includes an end portion128having an inner surface130which may bear against a first end surface132of the rod102. Further, the interior surface of the sides of the cap124may include a plurality of radially extending ribs to grip onto the rod102, centralize the cap124relative to the longitudinal axis of the rod102, and limit longitudinal movement along the rod102during ramming.

FIG.3Ashows the foot108of the post100in greater detail. The foot108includes a shaft portion300, with a flange302between the shaft portion300and the second strain relief feature110bof the post100. Four fins304a-d(fin304bnot shown inFIG.3A, seeFIG.3C) are evenly spaced around the shaft portion300, extending radially from its longitudinal axis.

Each of the fins304a-dincludes a series of transverse ridges306and grooves308forming a corrugated pattern through a central portion of each of the fins304a-d. By way of example, the corrugations may have an amplitude of approximately 2 mm (plus the wall thickness of the fin304a-d) and a pitch of approximately 8.8 mm. In the exemplary embodiment illustrated, each fin304a-dincludes at least one slot310.

Similar to the head106of the post, the foot108is capped by a separate part: tip312. Referring toFIG.3B, the rod102extends through the entirety of the shaft portion300of the foot, and projects beyond its end. The tip312fits over the exposed end of the rod102. As seen inFIG.3C, the interior314of the foot108at its end includes planar key surfaces316aand316b. The tip312(as seen inFIG.3D) has a body318with a conical nose320at one end. At its other end the tip312, a cavity322provides for receiving the exposed end of the rod102(as seen inFIG.3B), with a key flange324having opposing keying surfaces326aand326bon its exterior against which the planar key surfaces316aand316bof the foot108(as seen inFIG.3C) are formed during molding.

FIG.3E, illustrates an alternative embodiment toFIG.3C, in which the interior314of the foot108at its end includes a plurality of indents328a-d. The tip312(as seen inFIG.3F) has a number of protrusions330a-dspaced around its exterior about which the indents328a-dof the foot108(as seen inFIG.3E) are formed during molding.

FIG.4A-Cillustrate the structure of the stress relief feature110, extending continuously between solid portions of the overmold104. The stress relief feature110includes a plurality of transverse stress relief members in the form of disks400a-e, having a central bore402(in which the rod102is located—seeFIG.4BandFIG.4C).

The disks400a-eare produced by forming transverse slots404a-fon alternating sides of the overmold104along the length of the stress relief feature110, leaving neighboring disks400a-econnected by vertical link members406a-f. Each disk400a-eand vertical link member606a-fessentially acts as a cantilever beam—allowing flexure in each cantilever beam, and therefore the stress relief feature as a whole.

Stress produced by shrinkage of the overmold104is accommodated by this flexure, reducing the likelihood of material failure and the formation of cracks. Similarly, the flexure may accommodate stress on the overmold104while the post is in use—for example if a load is applied by an animal brushing against the fence.

As seen inFIG.1A, the stress relief features110aand110bhave been positioned at approximately equal spacing from the head106. Referring toFIG.1B, the sets of groves114aand114bon the fiberglass rod102are positioned be located approximate the middle of each section of overmold104between the stress relief features110a-c. This allows each section of overmold104to shrink away from each stress relief features110a-c. For the foot108section, in which it is envisioned that most of the shrinkage will pull the stress relief feature110cdownwards.

It is envisaged that in the middle section of the overmold104—i.e on either side of the stress relief feature110b—may experience a shrinkage of approximately 5 mm in each direction. As such, the stress relief feature110bmay need to accommodate in the order of 10 to 12 mm of movement.

In an exemplary embodiment the material used for the overmold104may 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.

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 feature110suggests the stress in the disks400a-eand vertical link members406a-fis 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.

In an exemplary embodiment the thickness of the disks400a-emay be different. It is envisaged that this may assist in balancing the amount of deflection each of the disks400a-ewill move. As the stress relief feature110may be produced by molding onto the fiberglass rod102, the inside surface of the stress relief feature110is in contact with the rod102when the post100is 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 feature110is configured such that the disks400a-ehave the same thickness, the two disks400aand400eat each end of the stress relief feature110(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. disks400aand400e, may be increased to be a little more rigid and therefore pull the next disc along the axis of the fiberglass rod102to provide a more uniform appearance.

The tool features of the mold used to form the slots404a-fmay also be used to hold the rod102in place within the cavity of the mold defining the overmold104. The connected structure of the stress relief feature also allows for a continuous flow path within the cavity through which material forming the overmold104may pass.

FIG.5A-Cillustrates front and rear attachment locating features500a(and500bpositioned at each of the predetermined locations112a-112m(as shown inFIG.1A). The attachment locating features500aand500bmay herein be referred to as “index features”.

Between the index features500aand500b, on the sides of the overmold104, left and right vertical ridges502aand502bextend the length of the overmold104(interrupted by the strain relief features110aand110billustrated inFIG.1A).

With reference to the front index feature500a, each index feature includes a transverse groove504a, with a first locating recess506apositioned above the groove504a, and a second locating recess508apositioned below the groove504a. Each of the locating recesses506aand508aincludes a first transverse locating surface510afacing the groove504a, and a second transverse locating surface512afacing away from the groove504a.

Referring toFIG.5B, each of the vertical ridges (for example, ridge502billustrated inFIG.5B) includes a front catch surface516band a rear catch surface518b.

FIG.6A-Dillustrates a wire locating attachment600(herein referred to as “the clip”) to be secured to the post100using the index features. The clip600includes a body602, with a first pair of arms604and a second pair of arms606extending from the body602, with a gap608therebetween.

Referring toFIGS.6B and6D, each pair of arms includes a left arm609and a right arm610, the arms609and610ending in an outwardly flaring barb612and614respectively. The barbs612and614include barb catch surfaces616and618respectively, facing towards the body602. A first locating protrusion620aand a second protrusion620bextend from the body602in the same direction as the arms. The first locating protrusion620aand second protrusion620bare complementary in shape with the locating recesses506and508of the index features500.

Referring toFIG.7A, the clip600may be pushed onto a desired indexing feature (for example front indexing feature500aas shown inFIG.5A), with the flared barbs612and614guiding the arms610and614outwardly over the vertical ridges502. Once the barbs612and614are passed the ridges502, the resilient nature of the arms610and614closes them such that the barb catch surfaces616and618are positioned against the rear catch surface518b—resisting removal of the clip600from the post100.

Simultaneously the first locating protrusion620aand the second protrusion620bare nested within the locating recesses506aand508arespectively, to resist movement of the clip600along the post600.

InFIG.7B, it may be seen that the body602of the clip600, together with the transverse groove504a, defines an aperture700through which a length of wire may pass—thereby locating the wire at a desired height.

FIG.8illustrates a post100to which a plurality of the clips600a-hhave been secured. It should be appreciated that the clips600a-hmay be secured in any number of combinations to achieve a variety of fence configurations.

FIG.9illustrates a fence900, in which a number of posts100have been spaced apart. Wires902a-gspan between the posts100, secured by clips600a,600b, and600d-h(not clearly seen inFIG.9, but refer toFIG.8). In this exemplary embodiment, a strain post904is provided at one end of the fence900, to which the wires902a-gmay be secured using any suitable means known in the art.

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

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.

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.

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.

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.

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.

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.