GB2518463A

GB2518463A - Improvements in or relating to anchor bolts

Info

Publication number: GB2518463A
Application number: GB1402957.3A
Authority: GB
Inventors: James Clement
Original assignee: EXCALIBUR SCREWBOLTS Ltd
Current assignee: EXCALIBUR SCREWBOLTS Ltd
Priority date: 2013-09-24
Filing date: 2014-02-19
Publication date: 2015-03-25
Also published as: WO2015044627A1; GB201316968D0; GB201402957D0

Abstract

A removable anchorbolt 30 comprises a shank 39 having a helical or threaded substrate engagement portion 35 and a drive head portion 37. The distal end of the anchorbolt is inserted into a concrete mix and the concrete allowed to set, but the concrete does not bond to the threaded portion and as a result removed by rotating the drive portion. A flange element may be provided to rest on the wet concrete.

Description

Improvements in or relating to Anchor Bolts

Field of the Invention

The present invention relates to fasteners such as scewbolts in general and to s anchor bolts in particular. Anchor bolts are used in a number of industries, particularly the construction industry, where a fastening is required to fix another structure by the use of props or otherwise, for example in the construction of formwork and other temporary or permanent constructions.

Background to the Invention

Formwork is the term given to either temporary or permanent moulds into which concrete or similar materials are poured. Whilst concrete has some considerable strength in resisting compressive loads, it has relatively poor tensile or torsional strength and to provide further integrity to erections, reinforcement is provided, typically by the use of steel reinforcement rods. To mould these structures, temporary formwork, scaffolding and/or false work is built about the reinforcement rods, to define the external shape of the structure once completed.

Figure 1 shows an example of formwork 10 as typically employed in the construction of a concrete column. Vertical pieces of wood or metal 12, referred to as soldiers, abut against formwork 13 to define a rectangular enclosure into which concrete can be poured, the pieces of wood being retained in position in the horizontal plane by horizontally oriented support beams 14, of wood or metal, and are restrained by wedges (not shown). A threaded tie bar (not shown) extends horizontally through the formwork, from a first side to another, the tie bar being fastened by way of a wing nut (not shown) acting against a waler plate (not shown). One end of such a tie bar could be retained by use of a wing nut (not shown), the wing nut abutting against a waler plate.

One issue with formwork is that, once erected, the formwork needs to remain in position, not only by maintenance of an effectively sealed mould enclosure per se, but the temporary structure is also required to resist lateral movement both prior to any concrete being poured and whilst the concrete is setting. In a tall structure, wind forces may be an issue; in a busy building site, one will also need to prevent movement from accidental collision, for example with a barrow, etc. Concrete normally sets hard within 24 hours; it is believed full strength will not be provided for some days, depending on the thickness of the concrete s element. Additives to the concrete may accelerate curing, indeed, may increase the time taken for cure. During such periods, the structure will typically need to be supported by the provision of props 11 depending from an upper portion of the formwork to the ground, where they are bolted to or otherwise attached to ground anchors 19, laterally spaced from a base of the formwork 10.

io Equally, especially in the case of concrete buildings and the like where structures are added one storey at a time, the formwork for upstanding members is propped up or otherwise supported in relation to one or more ground anchors.

Similarly a tunnel system will need to be braced to prevent lateral movement by the use of ground anchors. There are other uses for ground anchors.

IC) is Some ground anchors have design lives of over 100 years. Referring now to Figure 2, there is shown a permanent ground anchor 20, comprising a first length of rod 20i and a distal length of rod 20ii, the lengths of rod being fastened together by means of a coupler 22. The distal end of the distal length of rod further comprises a drill bit 21; this type of ground anchor is rotated as it is inserted into the ground so as to create a hole in the ground 23, so that through the use of a grout I concrete mix, the anchor can fixedly engage with the ground, which can comprise a variety of types: concrete, deposited stones /clay etc.. In the event that the ground comprises rock or concrete, then the anchor bolt need only comprise a first length of screwbolt, which is fitted with the drill bit, fastened to the end of the single length of screwbolt. The material drilled out is removed, grout inserted and then the rods replaced, the rods being provided with a textured radial surface to engage with the grout, a vibratory poker typically being employed to remove voids due to an accumulation of air and other gases arising from the setting of the grout. A hexagonal bolt is fitted to a threaded proximal section of the bolt, which abuts a washer or bearing plate 25, which in turn, abuts a waler plate 26, the waler plate being in contact with a protective sheet pile 27 positioned about the opening of the grouted section, to protect the bar and qrout assembly from fluid ingress and thus from corrosion, a special formulation of grout may be provided, enclosed by a sleeve, typically applied on manufacture of the anchor system, to ensure that a water based grout does not adversely affect the rod, where it is to remain for many years.

In the alternative, the proximal length of rod may be enclosed within a sheath or s tube, whereby the fixing grout does not engage with the proximal section of rod, which rod may be disengaged with the distal section of rod, which distal section of rod, complete with drill bit 21 and coupler 22 remains within the ground, thus still remaining an expensive system, with the loss of components despite any subsequent reuse of the proximal section of rod. Notwithstanding this, it has io often proved difficult to remove the rod, with the rod being cut off by power tools and the anchor bolt hole is filled in.

In a still further alternative, some companies provide anchor bolts comprising a number of wire-rope strands -strand anchors, which are heat treated such that at distal points of the strands, the strands can be forced to rupture upon IC) is application of a specified torsional force. The strands are contained within sleeves above the rupture points, the remainder of the distal end being secured within grout. Strand movement is contained by a steel cap at the top of the jack. Following strand rupture all the strands can be withdrawn, with only short sections of the distal ends of the strands remaining at the base of the borehole.

Strand Anchors are typically employed in built-up areas where there exists easement restrictions for example, due to the proximity of sewers, basements etc. Where the ground anchor is to be placed in concrete, it is fairly common, in the opening up of a hole for passage of the drill bit to be impeded by a rod comprising part of the reinforcing steel rods of the concrete structure, requiring the drilling process to be re-started in an adjacent area. Once the hole has been created, the anchor bolt is inserted and grouted in. It will be appreciated that the drilling operation is a "hit and miss" operation which takes up time, damages drill bits and can lead to construction delay. It is worth noting that a drill bit for rotary percussion drilling of concrete will not cut through steel. Additionally, once a masonry drill bit has hit steel, it is likely to considerably shorten the life of the drill bit attached to the end of the anchor bolt, which it may not seem to be an issue for a single use drill bit, it will increase the time taken to drill a subsequent hole and may even need to be replaced, again taking time and increasing cost.

Employment laws and construction of building regulations also require barrier systems on constructions site -typically adjacent the perimeter of multi-storey s buildings, noting that many such buildings will have full enclosure of floors as a first or second fit. Such safety fences can be retained in place by anchor bolts.

Object to the Invention The present invention seeks to provide an improved ground anchor system for construction use. The present invention also seeks to provide a screwbolt for use io as a ground work anchor, especially for use with formwork and the support of ancillary structures, where simple insertion and simple removal can be enabled.

The present invention also seeks to provide a method of installing ground anchors and removal of such anchors.

IC) is Statement of Invention

In accordance with a first aspect of the present invention, there is provided a method of providing a removable anchorbolt in a concrete base, wherein the anchorbolt has a shank portion having a helical substrate engagement thread at a distal end, a coupler engagement/drive head portion, the coupler and drive head being positioned at or near a proximal portion of the bolt, wherein the helical substrate engagement thread is provided with a lubricious coating, the method comprising the following steps; Providing a volume of a fluid concrete mix where it is desired to provide an anchor bolt; Inserting said distal end of the anchorbolt into the fluid concrete mix such that the external screwthread is completely or substantially immersed; Allowing a period of time for the concrete to set prior to use of the anchorbolt, the arrangement being such that the concrete will have releasably bonded to the external screwthread such that subsequent rotation of the drive head can enable removal of the anchorbolt and enable re-use thereof. Conveniently, vibratory pokers are employed to enable removal of voids within the concrete as it sets. Conveniently, as the screwthreaded portion of the anchorbolt is inserted into the cement, the screwthreaded portion is vibrated, rotated or otherwise moved in a reciprocating fashion, whereby to prevent the formation of voids about the screwthread, such that the concrete surrounds the screwbolt intimately.

In accordance with another aspect of the invention, there is provided a fluid s concrete anchorbolt, wherein the anchorbolt comprises a generally cylindrical shank with an axis, said shank having a substrate engagement portion at a distal end, and a coupler engagement/drive head portion at a distal end portion, wherein the substrate engagement portion comprises a helical thread and the coupler/head portion comprises a drive means whereby to enable rotation of the anchorbolt about its axis; wherein the helical substrate engagement thread is provided with a lubricious coating, whereby, in use, removal of the anchorbolt can be facilitated.

The lubricious coating of the substrate engagement thread can comprise a dry is film lubricant, such as a fluoropolymer coating; a fluoropolymer coating within a If) polymer matrix and a molybdenum disulphide coating. The dry film coating can be applied directly to the anchor bolt. The dry film coating can be applied upon a base adhesion coating applied to the anchorbolt to create a chemical bond 0 between the base coat and the top coat. The lubricious coating can have a (Q c thickness in the range of 1 -25 microns. Conveniently, the fluid concrete O anchorbolt, is coated with a dry film lubricant with a friction coefficient from 0.2 -0.01.

The anchorbolt is selected such that it is sized and dimensioned to provide appropriate resistance to directional tensile loads, in use. By appropriate choice of dry lubricant, the concrete will not permanently bond to the external screwthread. The concrete is provided as a wet pour. The term concrete is to be understood as to include all types of concrete mixes, including grouts and the like. Only the section of the anchorbolt comprising a screwthread is immersed in the concrete so that the dry film lubricant screwthread enables the anchorbolt to be removed upon rotation in the anti-clockwise direction (in the case of a normal screwthread). The screwbolt can be removed by the use of a suitable tool with respect to the drive head portion, which is conveniently of a hexagonal or square cross-section.

Conveniently, the anchorbolt is provided as an assembly with a flange element positioned about the shank, wherein the method, prior to or during insertion of the anchorbolt in the fluid concrete mix, includes the step of positioning the s flange about the shank, such that flow of the fluid concrete mix is prevented from contacting with the shank where there is no helical thread, the flange extending about the shank in a plane, preventing the bolt from sinking within the concrete, whereby to enable the anchorbolt to be subsequently removed without damage to the concrete. The flange element conveniently comprises a io planar member having one of an aperture or a slot from an outer circumference of the planar member surrounding the anchorbolt and is operably positioned about the shank, and assists in a positioning of the anchorbolt with respect to a fluid concrete mix. The flange also helps in preventing fluid concrete mix from contacting with the shank where there is no helical thread.

In a simple embodiment, the flange can comprise a circular element about a hole through which the anchorbolt can be passed. The flange can extend some 2 -10 cm about the anchorbolt and can be manufactured from a number of 0 different materials, conveniently being a polymeric plastics -so that is can (Q20 resiliently grip the shank of the anchorbolt or being made from a rigid plastics, 0 conveniently with a collar, such that positioning can be made to a coupler element, for example a nut having an internal thread which can rotate about a corresponding machine threaded portion of the shank to enable correct position of the anchorbolt to be attained. Equally, materials such as cardboard could also be used; the flange and collar could comprise separate elements. The axis of the collar need not be perpendicular with respect to the disc, whereby the anchorbolt, once positioned does not lie perpendicularly to the surface of the concrete. This can be of advantage where the anchor bolt extends tens of centimetres above the ground and the forces to be applied in relation to the anchor bolt could bend or otherwise damage the anchorbolt and cause difficulty in subsequent removal of the anchorbolt.

The concrete into which the anchorbolt is set can comprise part of a concrete base or can comprise a small volume within a stable ground surface such as a rock bed or prior concrete structure. That is to say, there may be a pre-existing hole of sufficient size to enable concrete to be placed and the anchorbolt to be subsequently inserted.

It is believed that the flange, such as a disc flange, provides a surface area to prevent the weight of the bolt allowing the bolt to sink into the viscous and aggregate laden concrete as it sets, the aggregate nature of the cement, together with surface tension, affecting the normal rules for floating bodies. The flange can comprise other shapes: for example, the flange could be io manufactured as a comb-like element, as a rectangular strip with rectangular indentations as opposed to apertures, which could be broken off in units or pairs of units; Together with a shank element, of a general "U" cross-section, the flange and shank could be removed simply, after turning the nut to loosen the flange and shank so that, a temporary construction member could be installed in is addition or as opposed to the anchor bolt providing a fixing for cabling etc.. For example, the temporary construction member could comprise a post. By the use of a temporary post, temporary fencing could be provided. A temporary 1-enclosure could be provided; a substantial bracing element could be provided, 0 possibly with the use of two or more anchor bolts, for example to enable a crane (Q 20 to be secured on a temporary basis. Numerous other advantageous construction 0 features can be enabled.

In accordance with a further aspect of the invention, there is provided a method of manufacturing an anchor bolt, comprising the following steps; providing a circularly cylindrical anchorbolt blank to a thread rolling mechanism to define a helical bore wall engagement configuration about a first, distal end of the blank, by a thread rolling apparatus, as is known; thread-rolling the anchorbolt blank between a fixed die and a displaceable die, the two dies being spaced apart by a gap therebetween, said gap being equal to the core diameter of the blank, moving the displaceable die in a reciprocating fashion such that the blank is plastically deformed whereby to provide an external screwthread; cleaning the anchorbolt so that the surface of the bolt is clean prior to coating; and coating the anchorbolt with dry lubricant.

Conveniently, the coupler engagement head portion of the screwbolt is a machined thread and the coupler has a corresponding internal thread. Other forms of connection are possible, using, for example eyes, whereby cables, bolts and other assemblies can be affixed to the anchorbolt. Such other assemblies s can include: posts, temporary railing, secure mounts for equipment and constructional bracing in general.

The dry lubricant is conveniently a fluoropolymer and is coated directly to the steel, the fluoropolymer being coated by way of standard spray-guns, preferably io upon a base coat, ideally with an adhesion assist layer. The fluoropolymer can also be coated by way of powder coating and dipping.

As will be realised, the screw bolt can be re-used several times, as well as the coupler, tie bar, post, flange or comb or other pre-fabricated member. All items is are separately replaceable, nonetheless, in the event that any item is damaged or is otherwise of no further use. Since many building structures, such as formwork, will use several hundreds of anchor systems, cost savings can be 1-substantial; no anchorbolts remain nor need removal by destructive grinding 0 etc., simplifying construction procedures. Further, no anchor bolts will remain in (Q 20 the substrate, which can be of benefit in minimising further corrosion risks, 0 avoiding rust stains arising therefrom and similar issues.

By the use of a M20 screwbolt axial forces (tensile loads) of up to 25 tonnes can be supported in concrete. Such sizes of Screwbolt are most commonly used in the building industry for ground-works, although it will be appreciated that other sizes may be preferably employed in different situations. Conveniently, the screwbolt comprises a twin helix threaded shank, which is known to provide a good grip on the inside surface walls of holes in masonry. The present invention has applications across a range of construction sectors including repair work, especially in communication networks such as vehicular highways, railways and tunnelling. The secure substrate anchoring together with re-usability can provide an increased efficiency and improved costs on many major engineering and construction products around the world.

Conveniently, the anchorbolt further comprises a cap which locates with the distal end of the anchorbolt, whereby to provide a visible indicator to the presence of the anchorbolt once the anchorbolt has been placed in concrete.

The cap, conveniently of a general mushroom shape, if made from a suitable s polymer/rubber-like material can also provide a shock protection to traffic about the anchorbolt, when in use.

Brief Description of the Ficiures

For a better understanding of the present invention, reference will now be made, io by way of example only, to the Figures as shown in the accompanying drawing sheets, wherein:-Figure 1 illustrates a known formwork arrangement; Figure 2 shows a known two-part ground anchor; Figure 3 shows a complete a rock anchor arrangement in accordance with a first is aspect of the present invention; Figure 3a shows the screwbolt of the ground anchor of Figure 3, without the fittings of the ground anchor; Figure 4a shows a first anchor bolt assembly in accordance with the present 0 invention in perspective view; (Q 20 Figures 4b & 4c show side views of two variant anchor bolt assemblies in 0 accordance with the present invention; Figure 5a shows formwork for the base of a structure, with reinforcing rods; Figure Sa shows concrete being poured into the formwork structure of Figure 5a; Figure Sc shows the formwork after the concert has been poured, together with a ground anchor in accordance with the invention; Figures 5d and 5e show two formers for use with a reinforcing steel lattice; Figures 5f -5h show stages in the positioning of an anchor bolt prior to pouring of concrete; Figure 6 shows how the flange of the anchor assembly enables the assembly to float on the concrete; Figure Ga shows a mushroom cover in accordance with a further aspect of the invention; Figure Gb shows a side view of a further mushroom cover in accordance with a further aspect of the invention; Figure 7 shows an anchor of the present invention being employed to assist in the support of a stanchion; Figures Sa and Sb show sections of first and second flange magazines in accordance with another aspect of the invention; s Figure Sc shows a three-section flange unit from above, with a tubular stanchion attached to a middle flange element; Figure 8d shows a three-section flange stanchion erected after use of device per Figure 8c; and, Figures 8e -8h show various shank designs.

Detailed description of the Preferred Embodiments

There will now be described, by way of example only, the best mode contemplated by the inventor for carrying out the present invention. In the following description, numerous specific details are set out in order to provide a U) is complete understanding to the present invention. It will be apparent to those skilled in the art, that the present invention may be put into practice with variations of the specific. r

Referring now to Figure 3, there is shown a ground anchor in accordance with the invention, prior to placement in concrete. The ground anchor 30 comprises a screwbolt 31, a flange 32, a washer 33 and threaded nut (M20) 34. Referring to Figure 3b, the screwbolt 31 comprises, from a first, proximal end: a hexagonal drive shank 37 -which extends for approximately 40mm; an M20 threaded shank member 38 is then provided for 40mm; a non-threaded shank 39, which extends to some 40mm, and which then continues as a twin-threaded 35 masonry screw-thread towards the distal end 36, which extends to some 8mm. This length of shank has been found suitable under test for supporting a prop bar which is attached to an eye-bolt member (not shown). The eye-bolt member has an internal screwthread such that it can engage with the M20 thread of the threaded shank portion of the screwbolt. A prop which is associated with formwork or other structure can be bolted via the eye-bolt member, conveniently with the use of a further bolt, arranged through the eye.

A bottle screw arrangement may be provided with the prop, to increase or decrease the length of the prop to suit; other common attachment methods may be employed.

As shall be discussed below, the hole in which the anchor bolt shall lie (when in use) shall comprise a concrete encasement, substantially level with the start of s the thread (i.e. the part of the thread closest to the machined thread section of the anchorbolt. By having the level of the cement at the same level of the start of the thread, the thread does not need to cut as such when a torque is applied to the bolt, upon removal, reducing the torque needed to turn the device, thereby reducing the amount of strain exerted on the material of the anchorbolt io (usually steel), so that its integrity is maximised. By use of the collar and disc element, the chance of binding of the anchorbolt to the concrete is minimised.

Figure 4a shows the anchorbolt assembly of the invention in perspective view, the nut 34 and washer 33 abut the collar 42 associated with the flange 32.

Figure 4b shows a variant, where bolt axis is not perpendicular to the axis of the LI') is collar and flange 32. This enables the anchor bolt to be positioned at angles other than perpendicular to the surface of the cement. This can enable the safe support of props acting towards taller, laterally displaced points, without fear of the forces seeking to cause failure of the anchor. Figure 4c shows a still further variant, where the collar and flange are manufactured from a polymeric plastics, whereby the collar grips the anchorbolt, whereby to dispense with the nut 34 and washer 33.

To enable the screwbolt to be firmly attached to the concrete, a number of special measures need to be taken; the choice of material must be selected such that it has sufficient tensile strength. Such steels are well known in the art and the exact composition of steel need not be discussed. The lubricious coating must be compatible with concrete. As discussed above, the use of greases and oils are incompatible with concrete structures as is appreciated in the art, since the oils and greases seep into cracks and causing the concrete structure to crumble. Additionally, it is known that the use of low friction coatings on screwthreads can result in the underloading of fasteners. Nonetheless, inventors have determined that a range of dry film lubricants can be selected; preferred dry film lubricants can have considerable abrasion resistance whereby to reduce scoring of screwthreads. Whilst in a temporary anchor system, corrosion is not normally a problem, such coatings can indeed provide significant degrees of corrosion resistance and so can be stored on construction sites where they can be available for use at appropriate times, without becoming unduly rusty or have s reacted with respect to other metals in a galvanic corrosion attack.

Friction results from two surfaces sliding across each other and friction is quantified as a dimensionless number that describes the reduction of drag (force) between the sliding parts, whereas release is the property of a surface io which results in an inability of substances to adhere to it and is a function of surface energy. Dry film lubricants have been used since the 1960's as an alternative to fluid lubricants for minimizing friction and preventing seizing and galling, in high or low temperature environments where fluids may freeze or vaporize. Specifically, the inventors of the present invention have determined is that certain abrasion resistant fluoropolymer composite coatings based upon PTFE and similar compounds can provide appropriate dry-film lubrication. There are a number of highly fluorinated polymers which were originally developed for 1-non-stick properties and although non-stick properties are distinguished from 0 low friction properties -these have been developed for other applications. (Q20

0 Fluoropolymer ceramic composite coatings are blends of high performance resins and fluoropolymer lubricants. These coatings can provide a dry film lubricant that produces a smooth, hard, slick coating and provides excellent resistance to corrosion, to chemicals and abrasion. These coatings are typically applied using a one coat system that fuses the coating to the substrate for remarkable adhesion. In addition to very low coefficients of friction, fluoropolymers offer exceptional resistance to heat, cold, corrosion and chemical infiltration. Certain fluoropolymers are marketed under the Xylan brand name, where the fluoropolymer compounds are retained in a matrix of organic polymers. The specific properties of Xylan formulations depend on the materials used to form the total coating and their ratio to one another. It has been found that an anchorbolt having its screwthread coated with Xylan 1010 provides a particularly useful high tensile strength coating in view of its abrasion-resistant lubriciousness. A matrix coating is one in which some soft ingredients, such as the lubricant (PTFE), are enveloped in others (the matrix) such as harder, more wear-resistant binders. If PTFE, for example, is used by itself (without the matrix), and is exposed to a wear surface, it quickly wears away. Combined with the matrix, however, the new structure solves the engineering problems as it s protects itself. Matrix coatings are adjustable. A still further dry film lubricant is molybdenum disulphide, which can adhere directly to the base metal of a coated part. Typical friction coefficients vary from about 0.06 -0.02 for PTFE and PTFE derivative coatings to about 0.15 for molybdenum coatings, the coatings being of a thickness of about 25 microns.

io The overall anchor bolt is formed by thread rolling with a helical bore wall engagement configuration by a thread rolling apparatus, as is known. A thread-rolling station comprises a fixed die and a displaceable die; the two dies are spaced apart by a gap therebetween being equal to the core diameter of the product being rolled. The displaceable die is displaceable in reciprocating is fashion. In use, a blank is inserted between the fixed and moving dies by manual or mechanical means as is known in the thread-rolling art. The reciprocating action of the moving die then carries the blank between them. r

o During this process, the blank is plastically deformed as the blank rolls along the faces of the dies. This gives rise to formation of the helical bore engagement configuration: die grooves give rise to ridges in the anchorbolt and die ridges give rise to grooves in the anchorbolt. In the case of the example shown in Figure 3, both helical ridges are formed on the shank with identical helix angles with the result that the ridges are, of course, parallel one to another and separated by the same pitch throughout the extent of the helix. Both ridges serve as a screw thread for enabling removal of the anchorbolt device. Both ridges are of generally frusto-conical form in cross-section. Each ridge has an upstand from the surrounding basal surface of the shank which is uniform throughout the helix, with both upstands being the same as one another. The first and second ridges define a helical groove forming part of helical engagement configuration. Once the anchor bolt has been formed, the anchorbolt is cleaned prior to coating; surface preparation of the fastener prior to coating being a very important step.

Whilst the fluoropolymer can be coated directly to the steel, it is preferred to provide a series of base and adhesion coats, to improve anti-abrasion qualities and to improve corrosion resistance. The adhesion coat creates a chemical bond between the base coat and the top coat.

Wet coating of the fluorpolymer is simply performed using standard spray-guns; liquid to be sprayed is loaded into a spray gun and, under pressure, atomized as it is sprayed onto the surface of the item. This can be performed either by handheld or automated spray guns that coat parts as they pass by on a io production line. The spraying process can be performed within a large temperature range and the curing schedule can take from hours to days, dependent upon the ambient temperature. The top coat, a heat cured fluoropolymer coating containing PTFE, is used to seal the two under coatings and give easy on/easy off characteristics. The coating can be machine finished.

is Other methods of application include powder coating followed by subsequent IC') melting of the coating.

The invention will be better understood with reference to Figures 5a-c; Figure 5a r o shows a portion of formwork 50 having side panel 51 supported by beams 52.

Inside the formwork are reinforcing bars or steel rods 53, to be employed to reinforce the concrete, once poured and set or cured and are commonly referred to as rebars. Figure Sb shows a chute 54, which provides concrete 55 into the formwork. Once the concrete 56 has been poured to the desired level, then the anchorbolt assembly 30, per Figure 5c is placed in the concrete, the placement process taking place in a gentle reciprocating oscillatory or vibratory fashion, whereby the portion of screwthread below the flange 32 is immersed in the concrete, the flange providing a convenient indicator that the screwthreaded portion has been inserted to a sufficient extent. It will be realised that the length of the screwth read assembly is dictated by the calculated loads that need to be supported; this 80mm length can be much greater in length. The hardening of concrete occurs asymptotically, meaning that most of the final strength will be achieved after a short time, though some further hardening can occur depending on the cement type and admixtures.

When an anchorbolt is required to be placed within a concrete base for a particular purpose, such as the support of formwork, the base will sometimes need to be placed with a reasonable degree of accuracy. It has been found that additional shaped wire elements are placed at specified anchorbolt points to s locate an anchorbolt in a specific location. To enable this to be accomplished, wire formers having a notch defined along a length thereof, with the wire formers being attached to the rebars which are placed within an area to be filled with concrete, conveniently by binding wire, which is generally used to tie overlapping rebars at the corner ends and junctions and therefore readily io available. Figures Sd and Se show two examples of formers 57, 58 suitable for use with the invention, each former having at least one notch or apex section 59, former 58 having a multiple of notches, being arranged in a general sine wave shape. Figure Sf shows some reinforcing bars arranged at right-angles, the bars being fastened together with binding wire at some of the bar crossings.

is In Figure Sg, a former 57 is tied by binding wire 60 to the rebars. In Figure Sh, an anchorbolt is shown resting against the notch 59 of the former 57, prior to the pouring of liquid concrete to the arrangement. Whilst the formers need not be of wire as such, it will be appreciated that a former attachable to the rebar 0 prior to the pouring of concrete can assist in ensuring the position of an (Q 20 anchorbolt can be determined with a sufficient degree of accuracy.

Accordingly, the present invention also provides a method of use. In accordance with another aspect of the present invention, there is provided a method of providing a removable anchorbolt in a concrete base. A fluid concrete mix is poured into a three-dimensional space where it is desired to provide an anchor bolt, the space typically being provided with reinforcement bars -which cannot be seen upon pouring. Once the concrete has been poured -and settled with a vibratory poker or otherwise -the anchorbolt is placed in an appropriate position in wet concrete, the distal end of the screwthread being placed in the concrete such that the thread is immersed, but no further. In the event that the anchorbolt cannot be positioned in sufficient depth by reason of the presence of a reinforcement bar, then a further attempt to place the anchorbolt is made in an adjacent area. The anchorbolt is moved in a reciprocating and/or cyclical and/or vibratory fashion to reduce the chance of voids forming about the screwthread, as the concrete sets, whereby to increase the integrity of the concrete grip once set. The anchor may be suspended in the concrete as it sets by means of a jig -it would be too long for an operator to suspend by hand.

However, by use of the collar and disc -if of a rigid plastics then it is positioned s about the shank by adjustment of a threaded nut positioned about the machined screwthread of the anchorbolt, whereby to ensure the disk lies level with the end of the helical screwthread about the distal section of the anchorbolt; in the alternative, of the disc and collar assembly is manufactured form an elastic plastics material, then the collar may well elastomerically grip the shank of the anchorbolt. By the use of the disk then the anchorbolt will not sink within the concrete before the concrete has fully set. The diameter of the disk has been found to be in the region of 2 -5 times the diameter of the anchorbolt, the collar is conveniently 1 -5 times the diameter in axial length (height) is Following an appropriate length of time for the concrete to set, the anchorbolt can be utilised, the anchorbolt having been selected such that it is sized and dimensioned such that, in use, it can provide appropriate resistance to 1-directional tensile loads, the arrangement being such that the concrete will not 0 have bonded to the external screwthread such that subsequent rotation of the (Q 20 drive head can enable removal of the anchorbolt and enable re-use thereof.

Figure 6 shows how the anchorbolt assembly 30 is arranged, after setting of the concrete, ready to be connected with a fastener, to enable the anchor to locate with a prop, support or other system, with an eyebolt or otherwise. Whilst the anchorbolt assembly is awaiting use, a dome shaped cover 61 can be fastened.

Conveniently, the dome shape element -akin to a mushroom shape -has an internal recess corresponding in shape to accept the hexagonal drive (or other terminating portion of the anchorbolt) at the proximal end of the bolt, whereby the cover may be simply placed upon the exposed anchorbolt. The fit may be a simple slide fit, but other means of connection, for example the use of a recessed hexagonal drive grub screw. The cover can be used to indicate that the anchor bolt is there and to reduce the likelihood of the anchor bolt causing damage. The cover can be colour coded to indicate different types of anchor bolt or different functions associated with a particular anchorbolt. The cover may have an aperture for a prop upon connection with a prop, as indicated in Figure 6b. The cover may be provided with markings, to enable bespoke covers, with appropriate apertures to be made at the time of installation.

s As will be appreciated the use of ground anchors is not restricted to use in relation to formwork. With reference to Figure 7, other applications can include the support of stanchions 70 for safety fences around building site -which are required by national regulations, as well as by common sense, for buildings which are more than one storey high and which are not provided with continuous io walling about the constructions site. Figure 7a shows a similar scenario where the base of a stanchion is fastened by two anchor bolts in accordance with the invention.

With reference to Figures 8a -8d, to assist in the use of two or more bolts is associated with a fastening, in accordance with a further aspect of the invention IC') flange elements can be produced in a number of materials for different purposes. Figure 8a, in particular, shows five elements of a flange as part of a 1-continuous plastics moulding 80, conveniently referred to as a magazine of 0 flange elements 81 each equipped with a "U" aperture, whereby to be positioned (,,Q 20 about the anchor bolt one in a position to be placed as the concrete is due to be O poured. The flange element can be folded about fold lines, where by to be separated from a magazine or length of flanges. In figure Sb, the magazine of flanges have apertures 82 on alternate sides, which may be more appropriate for certain situations. Figure Sc shows a length of three flange units wherein a three-unit flange base 85 has a tubular stub 86 present. In this case the flanges are made from 5mm steel and are produced in fixed length units. Upon installation a three-length plastics flange arrangement is employed with two anchor bolts, in apertures 82' and 82". After the concrete has set, the stub 86 can be fitted to a three-length steel flange -in this case stub 86 is fastened by way of a bolt 87, secured by a nut 88. The metal flange complete with stub is then positioned in place of the three-flange plastics unit, the metal flange being similarly dimensioned and therefore providing a secure base. It will be appreciated that other types of stub or the like can be fabricated using bolts or being welded together. The stub can enable the insertion of a longer stanchion or enable mating with the foot of a further barricade, foot of a support leg for a tool and the like, per Figure Sd, wherein a stanchion 90 is is placed within the stub, the stanchion being attached by the use of bolt 89. In accordance with this further aspect of the invention, the shank of the flange is shown as being s separable, it being noted that whilst the concrete sets, no substantial forces act upon the flanges or shanks. Accordingly, to assist in placement the shanks can be of various sizes and may also extend for 280° about the bolt as opposed to completely encircling the bolt, whereby removal of the threaded nut need not be performed whilst installing a permanent flange. Figures Se, Sf, Sg and 8h show io some examples of shank; Figure Sh showing the shank placed about a threaded bolt 92, to provide a better understanding, the shank being removable laterally from the bolt, as well as axially of the bolt.

Once the requirement for the anchorbolt has been satisfied, the hexagonal drive is at the proximal end of the anchorbolt can be driven so as to remove the If) anchorbolt, by virtue of its lubricious coating. The anchorbolt can then be re-used in another environment, the lubricious coating providing multiple uses.

1-Notwithstanding this, in view of safety consideration, especially emanating from 0 national building regulations, and in view of unknown prior loadings, it is prudent (Q20 to limit the number of multiple uses.

It will be appreciated that in the provision of temporary anchorbolts in accordance with the invention, there will be no specific need for the drilling of holes as such. This is of considerable benefit to the construction industry -operators of drilling machines cannot operate such tools for long periods of time with the employment laws of many countries prohibiting sustained drilling operation by workers. Again, this adds time to the process and increases the cost. Once the formwork has been removed or other body requiring lateral support, then the ground anchor is removed -presently, in the use of known systems, this cannot be guaranteed and frequently the anchor bolt remains within the ground and any protruding features are removed by a grinding operation. In contrast, in accordance with the invention, after removal of the anchorbolt by unscrewing the screwthreaded portion from the ground, the hole will be filled in or otherwise plugged.

Claims

Claims 1. A method of providing a removable anchorbolt in a concrete base, wherein the anchorbolt has a shank portion having a helical substrate engagement thread at a distal end, a coupler engagement/drive head portion, the coupler s and drive head being positioned at or near a proximal portion of the bolt, wherein the helical substrate engagement thread is provided with a lubricious coating, the method comprising the following steps; providing a volume of a fluid concrete mix where it is desired to provide an anchor bolt; io inserting said distal end of the anchorbolt into the fluid concrete mix such that the external screwthread is completely or substantially immersed; and, allowing a period of time for the concrete to set prior to use of the anchorbolt, the arrangement being such that the concrete will not have bonded to the external screwthread such that subsequent rotation of the drive head can enable is removal of the anchorbolt and enable re-use thereof.
2. A method according to claim 1 wherein the anchorbolt is provided as an r 0 assembly with a plastics flange element positioned about the shank, wherein the method further comprises the following step, prior to or during insertion of the anchorbolt in the fluid concrete mix: positioning the plastics flange element about the shank, whereby to position the anchorbolt within the fluid concrete mix, whereby the flange sits upon the surface of the concrete as it sets.
3. A method according to claim 2 wherein the anchorbolt flange element comprises an elastic plastics moulding which can resiliently grip with the shank.
4. A method according to claim 2 wherein the anchorbolt flange element comprises an rigid plastics moulding which can slide along the shank, the anchor bolt further comprising an adjustment means about the proximal portion of the anchorbolt, complementary to the coupler engagement/drive head to engage with the coupler engagement/drive head, to prevent movement of the flange with toward the proximal end, the method further comprising the step of operating the adjustment means to position the flange and thereby the extent of the anchorbolt within the fluid concrete mix.
5. A method according to claim 2 wherein the anchorbolt flange element s comprises a plastics element having a substantially planar surface and one of an aperture or a cut-out through which the anchorbolt can pass through, the anchorbolt further comprising an adjustment means about the proximal portion of the anchorbolt, complementary to the coupler engagement/drive head to engage with the coupler engagement/drive head, to abut against the flange or a io determine a position of the flange with respect to the movement of the flange with toward the proximal end, the method further comprising the step of operating the adjustment means to position the flange and thereby the extent of the anchorbolt within the fluid concrete mix.is
6. A method according to claim 2 -5, wherein the flange element is IC) manufactured as a plastics member, the method comprising the step of removing the plastics member after the concrete has set and placing a weight bearing flange in its place prior to fastening one or more elements to the metal O flange element, employing a threaded nut having a thread complementary to the (Q 20 coupler engagement/drive head.
7. A method according to claim 2 -5, wherein the flange element is manufactured as a continuous product comprising a plurality of flange elements; the method step further including the step of separating one or more flange elements from the continuous product of flange element.
8. A method according to any one of claims 1 -6, wherein the lubricious coating of the substrate engagement thread can comprise a dry film lubricant.
9. A method according to claim 8, wherein the dry film lubricant is selected from one of; a fluoropolymer coating; a fluoropolymer coating within a polymer matrix and molybdenum disulphide.
10. A method according to claim 9, wherein the dry film coating is applied directly to the anchor bolt.
11. A method according to claim 9, wherein the dry film coating is applied s upon a base adhesion coating, which base coat is applied to the anchorbolt.
12. An anchorbolt, wherein the anchorbolt comprises a generally cylindrical shank with an axis, said shank having a substrate engagement portion at a distal end, and a coupler engagement/drive head portion at a distal end portion, io wherein the substrate engagement portion comprises a helical thread and the coupler/head portion comprises a drive means whereby to enable rotation of the anchorbolt about its axis; wherein the helical substrate engagement thread is provided with a lubricious coating, whereby, in use, removal of the anchorbolt can be facilitated.IC')
13. An anchorbolt according to claim 12, wherein the lubricious coating of the substrate engagement thread comprises a dry film lubricant. r0
14. An anchorbolt according to claim 13, wherein the dry film lubricant is (,,Q 20 selected from one of; a fluoropolymer coating; a fluoropolymer coating within a O polymer matrix and molybdenum disulphide.
15. An anchorbolt according to claim 13, wherein the dry film coating is applied directly to the anchor bolt.
16. An anchorbolt according to claim 13, wherein the dry film coating is applied upon one or more base coats, which base coat(s) are applied to the anchorbolt.
17. An anchorbolt according any one of claims 12 -16, wherein the lubricious coating has a thickness in the range of 1 -25 microns.
18. An anchorbolt according any one of claims 12 -17, wherein the lubricious coating has a friction coefficient from 0.2 -0.01.
19. A fluid concrete anchorbolt according any one of claims 12 -16, wherein the anchorbolt is further provided with a flange element operably positioned about the shank, wherein the flange element comprises a disc like member s surrounding the anchorbolt, whereby to prevent fluid concrete mix from contacting with the shank where there is no helical thread.
20. A fluid concrete anchorbolt according any one of claims 12 -16, wherein the anchorbolt is further provided with a flange element operably positioned io about the shank, wherein the flange element comprises a planar member having one of an aperture or a slot from an outer circumference of the planar member surrounding the anchorbolt, whereby to assist in positioning of the anchorbolt with respect to a fluid concrete mix and to prevent fluid concrete mix from contacting with the shank where there is no helical thread.IC')
21. A fluid concrete anchorbolt according to claim 19 or 20, wherein the anchorbolt flange element comprises an elastic plastics moulding which can resiliently grip with the shank.(,,Q 20
22. A fluid concrete anchorbolt according to claim 19 or 20, wherein the O anchorbolt flange element comprises a rigid plastics moulding which can slide along the shank, the anchor bolt further comprising an adjustment means about the proximal portion of the anchorbolt, complementary to the coupler engagement/drive head to engage with the coupler engagement/drive head, to prevent movement of the flange with toward the proximal end.
23. A fluid concrete anchorbolt according to claim 19 or 20, wherein the anchorbolt coupler engagement/drive head comprises a machined helical thread and the adjustment means comprises an internally threaded nut, complementary to the machined helical thread of the anchorbolt.
24. A fluid concrete anchorbolt according to any one of claims 19 -23, wherein the anchorbolt flange element lies in a plane, which plane is not perpendicular to the axis of the anchorbolt.
25. A fluid concrete anchorbolt according to any one of claims 12 -24, wherein the anchorbolt further comprises a cap which locates with the distal end of the anchorbolt, whereby to provide a visible indicator to the presence of the S anchorbolt.
26. A kit of parts comprising: an anchorbolt, and a flange element wherein the anchorbolt comprises a generally cylindrical shank with an axis, said shank having a substrate engagement portion at a distal end, and a coupler io engagement/drive head portion at a distal end portion, wherein the substrate engagement portion comprises a helical thread and the coupler/head portion comprises a drive means whereby to enable rotation of the anchorbolt about its axis; wherein the helical substrate engagement thread is provided with a lubricious coating, whereby, in use, removal of the anchorbolt can be facilitated; is wherein the first flange element is operably positioned about the shank as the concrete sets, the flange element defining a weight-bearing surface such that in combination with a threaded nut having a thread complementary to the coupler engagement/drive head, the flange element can be employed to secure one or 0 more temporary structures. (Q20O
27. A kit of parts comprising: an anchorbolt, first and second flange elements wherein the anchorbolt comprises a generally cylindrical shank with an axis, said shank having a substrate engagement portion at a distal end, and a coupler engagement/drive head portion at a distal end portion, wherein the substrate engagement portion comprises a helical thread and the coupler/head portion comprises a drive means whereby to enable rotation of the anchorbolt about its axis; wherein the helical substrate engagement thread is provided with a lubricious coating, whereby, in use, removal of the anchorbolt can be facilitated; wherein the first flange element is a plastics member and is operably positioned about the shank as the concrete sets, the flange element defining a surface features in the concrete; wherein the second flange element comprises a weight-bearing flange element such that in combination with a threaded nut having a thread complementary to the coupler engagement/drive head, the second flange element can be employed to secure one or more temporary structures.
28. A kit of parts according to claim 26 or 27, wherein the kit further includes s wire binding and a former, the former having one or more curved portions, wherein the former can be attached to reinforcing bars associated with a structure by the wore binding, the former with the curved portions enabling a correct placement of an anchorbolt either prior to pouring, during the pouring or after the pouring of fluid concrete.
29. A method of manufacturing an anchor bolt, comprising the following steps; Providing a circularly cylindrical anchorbolt blank to a thread rolling mechanism to define a helical bore wall engagement configuration about a first, distal end of is the blank, by a thread rolling apparatus, as is known; thread-rolling the anchorbolt blank between a fixed die and a displaceable die, i--the two dies being spaced apart by a gap therebetween, said gap being equal to the core diameter of the blank, 0 moving the displaceable die in a reciprocating fashion such that the blank is (Q 20 plastically deformed whereby to provide an external screwthread; O cleaning the anchorbolt so that the surface of the bolt is clean prior to coating; coating the anchorbolt with dry lubricant.
30. A method of manufacturing an anchor bolt according to claim 29, wherein the dry lubricant is a fluoropolymer and is coated directly to the steel, the fluoropolymer being coated by way of standard spray-guns
31. A method of manufacturing an anchor bolt according to claim 29, wherein the dry lubricant is a fluoropolymer and is coated upon a base coat and, optionally, an adhesion assist layer, the fluoropolymer being coated by way of standard spray-guns
32. A method of manufacturing an anchor bolt according to claim 30 or 31 wherein the fluoropolymer is coated by way of a dipping process, wherein the fluoropoymer with solvent is present within a dipping tank.s
33. A method of manufacturing an anchor bolt according to claim 30 or 31 wherein the fluoropolymer is coated by way of powder coating followed by subsequent melting of the coating.
34. A method of providing a removable anchorbolt in a concrete base, io substantially as herein described, with reference to any one or more of the figures as shown in the accompanying drawing sheets.
35. An anchorbolt, substantially as herein described, with reference to any one or more of the figures as shown in the accompanying drawing sheets.If)
36. A method of manufacturing an anchorbolt substantially as herein described, with reference to any one or more of the figures as shown in the 1-accompanying drawing sheets. (0