AU2009202701A1 - A protective cap - Google Patents

Description

P/00/011 Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: UNDERWOOD COMPANIES HOLDINGS PTY LTD Actual Inventor(s): Daniel Charles Underwood Bruce Ian Ireland Alistair Ash Ryan Rogers Address for Service: INTELLEPRO Patent & Trade Mark Attorneys Level 7 102 Adelaide Street BRISBANE, QLD, 4000 (GPO Box 1339, BRISBANE, 4001) Invention Title: A PROTECTIVE CAP Details of Associated Provisional Australian Patent Application No Application(s) No(s): 2008903435 filed 4 July 2008 The following statement is a full description of this invention, including the best method of performing it known to me: 2 A PROTECTIVE CAP FIELD OF THE INVENTION THIS INVENTION relates to a protective cap and in particular but not limited to a protective cap to be placed over the exposed ends of starter bars 5 on construction sites. Starter bars are usually lengths of rebar protruding from concrete and are used to tie concrete sections together by tying the starter bars into the reinforcing of an adjacent slab to be poured later. BACKGROUND TO THE INVENTION Protective caps have been used to protect workers from injury from the 10 exposed ends of starter bars and generally involve a mushroom shaped cap moulded from plastics the cap usually has a tubular section having internal vanes which are deformed as the cap is pushed over the end of the starter bar. The cap is retained by reason of the deformation of the vanes in the interior of the cap. This also serves to properly align the end of the starter bar 15 with the centre of the cap since the vanes are usually set tangential to the bar. It is usual that the caps satisfy drop tests. The applicant's caps have been tested using a 114 kilogram bag of sand dropped from 3.05m onto the cap located in operative position on a vertical reinforcement bar. There are two primary factors that are taken into account in the 20 design of present starter bar caps. These include achieving proper alignment of the bar with the centre of the cap and secondly, ensuring that the cap will not be punctured or fracture or break away in which case the bar may pass through the cap and cause impalement. In some cases caps employ the use of a metal plate in the cap. This 25 can be made as part of the cap or one part of an assembly of cap parts. The 3 metal plate is used to enhance the strength of the cap thus rather than placing a wholly plastic cap over the end of the bars, a metal barrier is included and this is positioned directly above the bar. There are various examples where a plastic cap is used to locate a 5 metal insert of some form over the end of the bar. One example involves a two part cap involving a smaller plastic portion having a metal disc which is located over the end of the bar and then a larger cap fits telescopically over the smaller cap leaving an air gap. This cap is designed to have two operative functions, firstly, the impact of a person falling 10 on the bar is cushioned by the damping effect of the telescopic action on the internal air pressure in the gap and secondly, the metal insert is designed to provide a barrier to the bar puncturing through the top of the cap. While this cap works in principle, the two part construction means that on site there has to be an inventory of both parts and these have to be brought together and 15 located over the bar. It is often not easy to know that the metal insert is in place. This is not as simple a procedure as a single all in one cap and the parts can be lost and the multiple parts can be incorrectly installed reducing their effectiveness. It would therefore be desirable to produce caps that are in a single piece not requiring the necessity for alignment of parts or an inventory 20 of multiple matching parts. The inclusion of some form of metal insert formed into the cap also creates problems arising from the metal being included as part of a cap assembly in so far as the distribution of load through the cap upon impact can cause damage to the cap at the plastics metal interface. This can result in 25 failure of the cap. Plastics is easily damaged and while it is undesirable that 4 damaged caps be used at all, it would be desirable to ensure that if a damaged cap were reused that it would still be effective. US patents 5,381,636; 5,729,941; 5,824,253; and 5,946,871 all to Kassardjian; describe a cap where an insert in the form of a flat metal plate is 5 molded into the cap using an injection molding technique by first locating the flat metal plate in predetermined position in the mold so that it is in the correct position for molding. The metal plate is of complex shape having circumferentially spaced slots so that braces are molded in the plastic and extend through the slots. The plate also includes spaced holes which are 10 used to align the plate within the mold. One problem with this arrangement is that due to the slots, the plate is weakened so the plate is quite thick. Furthermore, in the preferred forms the bar end impinges directly on the plate providing a slippery metal to metal contact. A sideways knock can damage or misalign a cap. This can easily happen on a construction site, say from a 15 loaded hopper strung from a crane striking a group of caps. This may lead to a potentially tragic accident since the sight of bars across a construction site can give a false sense of security when in fact there is a defective cap on a bar. Since they all look the same it is not easy to detect which are in proper position when there are a large number across a site. Another problem arises from the 20 metal plate. being partially exposed and this can promote separation of the metal from the plastics. US patent 5,943,836 also to Kassardjian compares the flat metal plate to a collar and implies deficiencies in his earlier patents to use of a flat metal plate since he changes to an inverted metal collar so that the end of the bar 25 fits into the collar in order to protect against the sideways or off-centre impacts.

5 In one two part embodiment the collar is molded into a cap top, the top clips onto a smaller cap. This has the disadvantage of being two parts although the collar is fully encompassed by the plastic. Kassardjian uses a 1 /8th inch or 3 mm thick hot rolled A36 steel in his collar. 5 US patent application 2002/0116887 to Niday et al. describes a double curved barrier plate which can be metal with the concave surface presented downward toward the rebar. The plate is substantially the same area as the underlying -plastic cap apart from a small plastic outer margin. The plate is fastened in situ to the top of the cap so that it is the exposed upper surface of 10 the cap. The underlying plastic has a central hole so the centre of the metal plate is exposed underneath to the end of the bar so there is direct metal to metal contact. It may be further strengthened by using a small central plate below the barrier plate. Kassardjian also prefers direct metal to metal contact although as 15 mentioned above in one embodiment, effectively an adapter for standard non reinforced caps it is molded in. The plate of Niday et al. is exposed so is not fully surrounded by plastics but it has holes in the plate and it relies on enlarged ends of plastics projections molded through these holes and a surrounding margin of plastic to keep the plate in place. The projections can 20 be knocked off. However, like Kassardjian, Niday et al. teaches that the end of the bar should be located hard up against the metal plate. The above prior art are examples of the use of a metal reinforcement in the form of a plate positioned atop the bar with a plastics carrier to aid positioning the plate directly over the bar. Kassardjian in 5,943,836 uses a 25 deep collar just marginally wider than the bar while Niday et al by contrast 6 adopts a very wide slightly curved dish. The small deep collar has the advantage of housing the end of the bar so there is certainty in the geometrical relationship between bar and cap but in one sense the collar is just an enlargement of the bar and could together with the bar punch through the cap. 5 Thus, the metal to plastic interface is an area of significant stress in Kassardjian's cap. Niday et al. overcomes this disadvantage by making the metal insert of much larger area than the cross sectional area of the bar and if he needs greater strength he just thickens the centre. Niday et al. uses a square plate with a double curve and the bar engaging the plate so 10 presumably the double curve minimises the prospect of the bar sliding on the metal as appears to be the problem with the earlier Kassardjian flat plate versions. The metal to plastic interface in one direction is good in the sense that the large surface area of the plate is molded against the plastic cap but the retaining projections are relatively week and are exposed at the surface so 15 the caps can be easily damaged. Both Kassardjian and Niday et al. teach different molding processes resulting in quite different caps. OUTLINE OF THE INVENTION Accordingly, it is an object of the present invention to provide a cap including a metal barrier where the structure of the cap minimises the risk of 20 damage to the cap at the metal to plastic interface. In one embodiment this is achieved first by the design of the metal barrier and then this is further enhanced by the relative disposition of the metal barrier in the plastic to provide effective distribution of stress. According to one aspect of the present invention there is provided a thin 25 metal barrier disc for a domed top cap, the disc having a relatively wide 7 concave/convex annular flange surrounding a central depression, the concave side of the annular flange of the disc being on the same side as the central depression, the surface area of the flange being substantially greater than the surface are of the depression. Preferably, the disc is adapted for the purpose 5 of being moulded within the dome of the cap. By way of analogy, the disc is analogous in shape to a saucer having a central raised section on one side and a depression opposite on the other side while the annular periphery is dished. For the purpose of the disc being adapted to be moulded into the dome 10 of a protective cap, the disc preferably includes locating means adapted to locate the disc in pre-determined operative position within a mould to ensure that in the final product the disc is in operative alignment with the central axis of a reinforcement bar so as to be disposed generally within an imaginary curved surface with the central axis of the starter bar coincident with the centre 15 of the disc and a tangent to the disc at its centre is at right angles to the central axis of the bar. In the preferred form the depression has a flat bottom and the disc is dished around the depression. In this sense the plastic is used as a carrier and alignment device for the metal disc relative to the end of the reinforcement bar. However, it is 20 preferred that the curve of the disc generally match the underlying curve of the cap. In a further aspect the is provided a domed bar cap having a metal insert comprising a curved metal disc having an outer peripheral edge and opposite sides all surrounded by plastics, the dome cap having a curved upper 25 surface and the metal insert having a curved peripheral annular flange 8 surrounding a central depression, the cap having a central bar alignment collar, the collar having a blind bore aligned with the centre of the depression and terminating adjacent the depression at a position slightly higher than the peripheral edge of the disc. 5 Preferably, the central depression is opposite a central projection and there being a circular juncture defined by a circular bend in the disc between the depression and the peripheral annular flange, the cap having a tubular stem, domed upper surface, a curved under-surface and circumferentially spaced oblique braces extending between the stem and the under-surface of 10 the cap, the curved under-surface in the region of the flange having a curve substantially parallel to the curve of the under-surface. BRIEF DESCRIPTION OF THE DRAWINGS In order that the present invention may be more readily understood and be put into practical effect, reference will now be made to the accompanying 15 drawings which illustrate preferred embodiments of the invention and wherein: Figure 1 is a drawing illustrating the general principle by which a protective cap is utilised on a construction site; Figures 2A to 2E are respective underside plan, side, radial section, transparent and perspective views of a typical cap according to the invention; 20 Figure 3 is a schematic drawing illustrating part of the interior of a mould showing the relationship between the barrier plate and the operation of the mould; Figure 4 is a perspective view similar to Figure 2E; Figure 5 is a perspective view of a cap for a larger size bar; 25 Figure 6 is a section showing the interior of another form of cap; 9 Figures 7 and 8 illustrate typical bars upon which caps according to the present invention may be used; and Figure 9 illustrates a further embodiment. METHOD OF PERFORMANCE 5 Referring to the drawings and initially to Figure 1 there is illustrated three starter bars 10, 11 and 12 protruding from a concrete slab 13 and a worker illustrated at 14 has tripped and is in the process of falling upon the bars 10, 11 and 12. The bars have protective caps 13 disposed over the bars. It will be appreciated that these caps are operating as safety caps and injury to 10 the worker 14 will be reduced as compared to the situation where the bars 10, 11 and 12 were not capped. In such situation the worker 14 would most likely be impaled upon the bars resulting in serious injury or death. The caps have a domed upper surface 14 and a tubular base portion 15 so that the domed upper surface 14 serves to deflect and provide a smoother impact surface. 15 The tubular section 15 serves to centrally locate the dome relative to the ends of the bars and align the cap to the central axis of the bars 10, 11 and 12. It will however be appreciated that subject to the direction at which the person 14 strikes the cap the applied force to the cap and the bar could result in the cap breaking or fracturing depending upon its design and there is still some 20 chance, albeit a small one, that the end of the bar could penetrate the cap and the-cap slide down over the bar exposing the point of the bar or tip of the bar which then would impale the person 14. Referring now to Figures 2A through to 2E, the cap 16 according to the present invention is illustrated, the cap having a domed upper surface 17, a 25 tubular stem section 18 and braces 19 extending from an underside 20 of the 10 dome on to the tubular section 18. The tubular section has longitudinally extending ribs 21 and a central bar passage 22 so that a reinforcing bar, not shown, may be inserted into the tubular section 18 to locate the cap centrally on the end of the bar. The braces 19 are circumferentially spaced and extend 5 radially across the dome. Moulded into the dome is a barrier plate 23 which in this case is a thin metal circular disc about 2mm thick. The plate 23 has an annular flange 24 and a central depression 25. In use the disc is centrally located relative to the central axis of the tube section 18 so that in use it is disposed symmetrically across the end of a reinforcement bar so as to be 10 evenly positioned across that bar. The annular flange 24 is concave downwardly toward the bar and this concavity is illustrated by the line shown in phantom at 26 effectively providing an internal metal barrier which is curved around its marginal edge forming the flange 24. This means that the metal plastic interface with the dome of the 15 plastic making up the cap and the metal barrier plate are both curved in the same direction thus reducing the likelihood of cap failure in the region of the plastics to metal interface. In order to ensure that the metal barrier is correctly located in the final product, the metal barrier includes in this case three locating notches 26, 27 and 28, and the operation of this aspect of the 20 invention is illustrated in the schematic of Figure 3 whereby retractable supporting pins 29 of the mould apparatus protrude through the notches 26, 27 and 28 to support the plate in its position in the mould. These leave the holes 30, 31 and 32 in the finished product. The internal passage 22 in the tubular section 18 may include internal 25 ribs 33 or internal vanes 34 or a combination of the two so that the cap may be 11 pushed down and effectively screwed on to the end of a bar. In the case of reinforcing bars two cap sizes are envisaged to cover the usual bar sizes and these are illustrated in Figures 4 and 5. Figure 6 illustrates a cap with a slightly different dome size and a 5 slightly different tube size. In Figure 7 there is illustrated a reinforcement bar and in Figure 8 a star picket whereby illustrating two possible applications of the invention. Of course the caps may be employed wherever it is desirable to cap a bar, post or rod or the like. 10 Figure 9 is similar to Figures 6, 7 and 8 in so far as it illustrates a cap applicable to a smaller bar size. Referring to Figures 6 and 9 which are similar to Figure 2C the caps 35 and 36 show that application of the invention to different sized caps where in cap 35 the depression 37 is suited to a larger bar cross-section than in the 15 depression 38. In each case the depression is located nearer the top of the dome at 39 and the flanges 40 and 41 are located nearer the under-surface 42 such that there is a relatively thick section of plastic above the juncture 43. between the flange and the depression and at 44. Also the stem 45 and the stem 46 each include a blind bores 47 and 48 terminating just above the 20 juncture 43. Whilst the above has been given by way of illustrative example of the present invention many variations and modifications will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set out in the appended claims. 25

Claims (6)

1. A thin metal barrier disc when used in a domed top cap, the disc having a relatively wide concave/convex annular flange surrounding a central 5 depression, the concave side of the annular flange of the disc being on the same side as the central depression, the surface area of the flange being substantially greater than the surface are of the depression.

2. A thin metal barrier disc according to claim 1 wherein the disc is adapted for the purpose of being moulded within the dome of the cap. 10

3. A thin metal barrier disc according to claim 2 wherein for the purpose of the disc being adapted to be moulded into the dome of a protective cap, the disc includes a centre and locating means adapted to locate the disc in pre-determined operative position within a mould to ensure that in the final product the disc depression is in operative alignment with the 15 central axis of a reinforcement bar so as to be disposed generally within an imaginary curved surface with the central axis of the starter bar coincident with the centre of the disc and a tangent to the disc at its centre is at right angles to the central axis of the bar.

4. In a domed bar cap a thin metal barrier disc comprising a curved metal 20 disc having an outer peripheral edge and opposite side faces all surrounded by plastics, the domed cap having a curved upper surface and the metal insert having a curved peripheral annular flange surrounding a central depression, the cap having a central bar alignment collar, the collar having a blind bore aligned with the centre of 25 the depression and terminating adjacent the depression at a position slightly higher than the peripheral edge of the disc. 13

5. In a domed bar cap according to claim 4 having a central vertical axis wherein through a longitudinal cross-section a thin metal barrier disc appears as a curved wire surrounded by plastics, the wire being non straight having opposite outer ends and an outer margin on each side of 5 the central axis curving up to a central raised section the domed cap having a curved upper surface and the metal insert having a curved peripheral annular flange surrounding a central depression, the cap having a central bar alignment collar, the collar having a blind bore aligned with the centre of the depression and terminating adjacent the 10 depression at a position slightly higher than the peripheral edge of the disc.

6- In a domed bar cap according to claim 4, the central depression being opposite a central projection and there being a circular juncture defined by a circular bend in the disc between the depression and the 15 peripheral annular flange, the cap having a tubular stem, domed upper surface, a curved under-surface and circumferentially spaced oblique braces extending between the stem and the under-surface of the cap, the curved under-surface in the region of the flange having a curve substantially parallel to the under-surface. 20