Patent Description:
A chemical anchor is an anchor that is mechanically fixed to a support material with the aid of a resin and a hardener or activator for polymerizing the resin.

At present there exist chemical anchors for solid materials and chemical anchors for hollow materials.

In the case of a solid material, a hole may be drilled a capsule of resin slid into it containing a capillary tube filled with hardener, before crushing the combination and mixing the two components. It is also possible to drill a hole and to inject into it resin and a polymerization hardener or activator that mix inside it. A stud or a screw may serve as fastening element.

In the case of a hollow material, after drilling a hole in the wall of the material, a tubular screen may be inserted into it, after which resin and a hardener are injected, the resin expelled from the screen, once polymerized, fastening the screen to the rear of the wall. Stud and screw may also be used as fastening elements.

For a hollow material, there is also known an element including a bearing flange to which is attached a split skirt, the skirt being adapted i) to be pulled against the rear face of the wall by the link connecting it to the flange bearing against the front face of the wall and ii) to receive by injection a mixture of resin and hardener to fasten the element to the rear of the wall.

The prior art notably includes the document <CIT>.

With many chemical anchors, it is necessary to inject resin while in <CIT> the applicant has sought to circumvent this relatively laborious injection. Thus, a chemical anchor is proposed that can not only adapt equally well to a hollow material and to a solid material but whose fastening is no longer purely chemical but also mechanical.

A chemical anchor from publication <CIT> is shown here in <FIG>. The anchor <NUM> includes a tubular sheath <NUM> with a longitudinal axis <NUM>, wherein the sheath <NUM> extends between a first end including bearing means <NUM>, which are formed by an annular bearing flange, and a second end <NUM> opposite the flange <NUM>.

A piston member <NUM> is housed in the sheath <NUM> at the level of its second end <NUM>. A screw <NUM> is intended to be engaged in the anchor <NUM> and to be screwed into the member <NUM> in order to cause it to move longitudinally inside the sheath <NUM>. The latter may comprise means for longitudinally guiding the member <NUM>.

In the example represented, the sheath <NUM> comprises two adjacent longitudinal portions: a first portion 12a including the second end <NUM> and a second portion 12b including the bearing means <NUM>. Here the first portion 12a is formed by a cylindrical envelope that is solid or not perforated, unlike the second portion 12b which is perforated and has slots <NUM> passing through it in the radial direction relative to the longitudinal axis <NUM> of the anchor and the sheath. The second portion 12b may be covered by an external envelope made of a relatively flexible and deformable material, preferably one that can be torn by traction and/or compression.

The openings <NUM> have a two-fold function. On the one hand they allow polymerizable resin to pass from the interior of the sheath <NUM> to the exterior. They may further allow longitudinal compression or deformation of the second portion 12b of the sheath.

The second portion 12b defines a cylindrical internal cavity <NUM> that is empty. The first portion 12a defines a cylindrical internal cavity <NUM> containing the polymerizable resin.

In known manner, the resin may be a single-component resin or a two-component resin. It may therefore comprise either a single resin component <NUM> intended to polymerize in contact with air or moisture, for example, or a resin component 30a and a hardener component 30b intended to be mixed.

When the resin comprises a single component, that component may be housed in a capsule <NUM> located in the aforementioned first portion 12a of the sheath <NUM>. This capsule <NUM> is preferably made from a material that can be torn or broken, for example glass. It is preferably substantially cylindrical and centred on the longitudinal axis <NUM> of the anchor.

The anchor <NUM> further comprises a sleeve <NUM> mounted on the sheath <NUM> at a distance from its longitudinal ends. In the example represented, the sleeve <NUM> has an annular shape and the sheath passes through it. In longitudinal section it has a substantially frustoconical shape the larger base of which is located on the same side as the bearing means <NUM> of the anchor. The sleeve <NUM> may be made of foam. It may comprise cells and have a spongy structure.

The anchor <NUM> further comprises stop means <NUM> intended to cooperate with the member <NUM> to limit its longitudinal travel inside the sheath <NUM>. In the example represented, these stop means <NUM> are formed at the level of or by the sleeve <NUM> and in particular at the level of or by the smaller diameter end of the sleeve. Here one of the functions of the sleeve is therefore to limit the travel of the member <NUM> in the sheath <NUM> when screwing in the screw <NUM>. Alternatively, the stop means could be carried by the sheath <NUM>.

The other functions of the sleeve <NUM> depend on the use that is made of the chemical anchor <NUM>. In the situation represented in which the anchor is used in a hollow support material, the sleeve <NUM> is intended to be impregnated with resin. After hardening of the resin, the sleeve bears axially on an internal face of a wall of the support material to improve the anchoring of the anchor in the support material.

In the situation represented in which the anchor is used in a solid material, the sleeve is intended to be compressed radially so as not to impede the introduction of the anchor into the support material.

In both cases, the user who is screwing in the screw <NUM> can then feel that the screwing torque increases because of the resistance associated with the piston member <NUM> bearing on the sleeve. In this position, the resin has filled a sufficient volume in the sheath (the aforementioned empty cavity) and is in contact with the cylindrical internal surface of the hole, which anchors the anchor in the support material. In this case it is therefore not necessary or even possible to screw the screw in further to compress the anchor longitudinally.

However, while the anchor <NUM> of <FIG> provides improvements over other designs, it is nevertheless problematic because the user cannot observe the multiple stages of the fixing operation. In particular, it is not intuitive for users to complete the screwing because they have to continue rotating the screw without being able to see any of the fixing operation in action. Furthermore, the end point for the user to stop screwing is indefinite and approximate as any change in the screwing torque, which may be due to varying resistance caused by the different stages of the fixing operation, can make the user assume fixing is complete. Accordingly, there is no guarantee of setting the anchor correctly first time, leading to a lack of reliability of the anchor.

Furthermore, document <CIT> describes an expansion anchor assembly including, for example, a spacer sleeve and a serially arranged distance sleeve with a washer positioned on the spacer sleeve end between the distance sleeve end and an annular collar of the spacer sleeve. Here, when tightening the bolt, the head pushes the spacer sleeve through the washer so that the projection collar is either deformed or sheared off and the spacer sleeve is driven into the interior of the distance sleeve.

Therefore, it is an object of the present invention to provide an indicator assembly for an anchor that is simple, effective and economical.

According to a first aspect of the invention, there is provided an indicator assembly for an anchor, comprising:.

In this way, the indicator assembly locates snugly with an anchor and is operably coupled such that when a screw is received into the anchor the shoulder portion can bear evenly against the assembly. Furthermore, once the fixing operation of the anchor is complete, the shoulder portion will fit flush within the anchor.

Advantageously, any one of said at least two frangible connector elements may be adapted to break at a predetermined shear force provided between said shoulder portion of the screw and said matching circular aperture of said plate member.

In this way, indicator member will only detach from the indicator assembly when the contraction force from the shoulder portion acts provides sufficient bearing pressure. Any bearing pressure provided while the screw is enabling the fixing operation will leave the indictor intact until the fixing operation is complete. The separation of the indicator member from the indicator assembly will then readily provide the user with feedback that fixing operation is complete, and the anchor is safely installed.

Advantageously, said at least two frangible connector elements may protrude radially inward from said circular aperture towards said proximal end portion of said guide member. In this way, the indicator assembly has frangible connectors arranged in a space efficient way so that they sit within the indicator assembly. Furthermore, the frangible connectors are ideally positioned to engage directly with the shoulder portion of the screw, and thereby bear the shear force, so that they are broken in a reliable, predictable manner.

Advantageously, said at least two connector elements may be made from polymer.

Advantageously, said plate member may be an annular disc arranged concentric with and substantially congruent with a flange portion provided at the opening of the sheath, during use.

Advantageously, said plate member may comprise a handle portion. Thus, the indicator member can be easily removed from the anchor once it has detached from the guide member.

Advantageously, said guide member may be adapted to couplingly slide in and irreversibly attach to the sheath at the opening.

Advantageously, said guide member may comprise protrusions adapted to couplingly engage with an interior structure of the sheath.

Thus, by either irreversible attachment, or by coupling engagement, as the guide member is located into the opening of a sheath, it slides smoothly into place through guiding contact with the sheath. Once into position, the guide member fits substantially within the first end of the sheath so that it is operably engaged with a surface, recess or aperture on the inner wall of second portion of the sheath to lock the indicator assembly to the anchor. Thus, when a screw is received into the anchor, the indicator assembly cannot be accidentally drawn out of the anchor.

Advantageously, said guide member and said indicator member may be made from polymer.

Advantageously, the indicator assembly may further include at least one resilient contact portion protruding radially inwards from said distal end portion of said guide member, configured to guidingly engage with the screw, during use. Preferably, said at least one contact portion may comprise two diametrically opposed lugs configured to operably mesh with the thread of the screw, during use.

In this way, and in contrast to known systems, as the screw is received and rotated within an anchor, its tip is directed precisely towards the piston member. This occurs even as the screw travels through the resin capsule such that, when it reaches the piston member it instantly engages with its corresponding screw thread. Thus, misalignment of the screw with the piston member is prevented. With the screw correctly aligned, it is able to engage with the piston member and urge it towards the sheath in a smooth action, without interference or mis-engagement, in order to move the resin mixture.

Advantageously, said indicator member may be adapted to provide a visual contrast over the anchor. Preferably, said visual contrast may be provided by a predetermined shape and/or colour.

Advantageously, an anchor may be provided including an indicator assembly in accordance with the invention.

Example embodiment(s) of the invention are now described, by way of example only, hereinafter with reference to the accompanying drawings, in which:.

In the drawings, like reference numerals refer to like parts.

The described example embodiment relates to a chemical anchor systems as shown in <FIG>. However, the invention is not necessarily restricted to chemical anchors and may also be used with any other anchor system, chemical and mechanical.

Certain terminology is used in the following description for convenience only and is not limiting. The words 'right', 'left', 'lower', 'upper', 'front', 'rear', 'upward', 'down' and 'downward' designate directions in the drawings to which reference is made and are with respect to the described component when assembled and mounted. The words 'inner', 'inwardly' and 'outer', 'outwardly' refer to directions toward and away from, respectively, a designated centreline or a geometric centre of an element being described (e.g. central axis), the particular meaning being readily apparent from the context of the description.

Like reference numerals are used to depict like features throughout.

Referring now to <FIG> and <FIG>, the indicator assembly <NUM> has a longitudinal axis <NUM> and is provided with a guide member <NUM> and an indicator member <NUM>.

The indicator member <NUM> includes an annular portion <NUM> with a central aperture <NUM> formed by an inner edge <NUM>. The inner edge <NUM> is circular with a radius <NUM> and its axis located on the longitudinal axis <NUM>.

An outer perimeter is formed by an outer edge <NUM> which includes a tab or handle portion <NUM> extending radially outward from it. The indicator member <NUM> is substantially flat with a front face <NUM> and back face <NUM>.

The guide member <NUM> is provided with a collar portion <NUM> with a first end <NUM> arranged proximal the inner edge <NUM> of the indicator member <NUM>. Thus, the collar portion <NUM> extends in a direction away from the back face <NUM>. At a second end <NUM>, distal to the inner edge <NUM>, a pair of guide arms <NUM> is provided which continue to extend away from the back face <NUM>.

The collar portion <NUM> has a substantially cylindrical wall with a wall axis and an inner surface diameter indicated as by D1 of <FIG>. In this particular example, D1 is <NUM>. The wall axis is with the longitudinal axis <NUM>. The cylindrical wall is provided with a pair of expanded portions <NUM> in which arcuate sections of the wall have a larger diameter, such that the corresponding outer surfaces of the collar <NUM> are <NUM>.

The cylindrical wall is further provided with a pair of diametrically opposed projections <NUM> on its outer surface. Together with the expanded portions <NUM>, the projections <NUM> act to maintain the guide member <NUM> concentrically when the indicator assembly <NUM> is coupled to the opening of a sheath <NUM> of an anchor <NUM>.

Furthermore, one or more of the expanded portions <NUM> and projections <NUM> operably engages with a surface on the inner wall of the internal cavity <NUM> of the anchor <NUM>. In this way relative rotation of the guide member <NUM> with respect to the anchor may be prevented.

Protrusions <NUM> are also provided at the second end <NUM> of the collar portion <NUM>, spaced apart on the outer surface of the cylindrical wall. The protrusions <NUM> operably engage with a surface, recess or aperture on the inner wall of second portion 12b of the sheath <NUM> to lock the indicator assembly <NUM> to the anchor <NUM> (see <FIG>). Thus, when a screw <NUM> is received into the anchor <NUM> the indicator assembly <NUM> cannot be accidentally drawn out of the anchor <NUM>.

In this way, as the guide member <NUM> is located into the opening of a sheath <NUM> (see <FIG>), it slides smoothly into place through guiding contact initially between the sheath <NUM> and first the protrusions <NUM>, followed by the projections <NUM> and expanded portions <NUM>. Once into position, the guide member <NUM> fits substantially within the first end of the sheath with its longitudinal axis <NUM> lying along the longitudinal axis <NUM> of the anchor.

Also provided on the collar portion <NUM> are a pair of inwardly projecting ribs <NUM> (see <FIG>) which extend axially along the inner surface of the cylinder. The ribs <NUM> extend away from its first end <NUM> and continue onto the inner surface of the guide arms <NUM>.

The guide arms <NUM> are arranged to be diametrically opposed around the longitudinal axis <NUM>. The inner and outer surfaces of the guide arms <NUM> are continuous with the inner and outer surfaces of the cylindrical wall so that the wall thickness and curvature of the guide arms <NUM> generally correspond with the cylindrical wall. The guide arms <NUM> each terminate with an inwardly directed arcuate rib <NUM> that follows the general curvature of the guide arm's inner surface.

The inner surfaces of the ribs <NUM> are configured to form portions of a screw thread. Further, additional portions <NUM> of the screw thread are provided on the inner surface of the collar portion <NUM>. <FIG> illustrates a screw <NUM> engaged with the indicator assembly <NUM> in the absence of other features of the anchor. Together the ribs <NUM> and additional portions <NUM> are adapted to engage with the thread of the screw <NUM> of an anchor <NUM> as it is received into the guide member <NUM>.

Both the guide arms <NUM> and the additional portions <NUM> are resilient enough that they can expand apart to accommodate screws with slightly different diameters, or to easily accommodate both the threaded portion <NUM> and unthreaded portions <NUM> of the same screw which may have different diameters.

The guide member <NUM> and indicator member <NUM> are moulded to form a single part. The inner edge <NUM> of the indicator member <NUM> includes a series of connector elements <NUM> (see <FIG>) extending radially inwards so that they bridge from the inner edge <NUM> to the outer surfaces of the expanded portions <NUM> and the projections <NUM>.

When used with a chemical anchor <NUM>, as shown in <FIG>, the indicator assembly <NUM> is operably coupled to the opening of the sheath <NUM> as described above and also shown in <FIG>. The guide member <NUM> is substantially surrounded by the second portion of the sheath 12b so that the guide arms <NUM> extend away from the flange <NUM>. In contrast, the back face <NUM> of the indicator member <NUM> engages with the flange <NUM> and remains outside the sheath <NUM>. Further, once the indicator assembly <NUM> is operably coupled into the sheath <NUM> of the anchor <NUM>, the protrusions <NUM> of the indicator assembly <NUM> operably engage with a surface, a recess or an aperture on the inner wall of the internal cavity <NUM> of the sheath <NUM> so as to fixingly lock the indicator assembly <NUM> to the anchor <NUM>.

The screw <NUM> includes a shoulder portion <NUM>, also known as a cylindrical bearing shoulder, that is configured to cooperate with the indicator member <NUM>. The shoulder portion <NUM> is sized so as to fit snugly within the aperture <NUM> defined by the inner edge <NUM>. In other words, the diameter of the inner edge <NUM> is sufficiently larger than the outer diameter D2 of the shoulder portion <NUM>.

However, when the screw <NUM> first contacts the indicator assembly <NUM>, the shoulder portion <NUM> is prevented from being received into the inner edge <NUM> by the connector elements <NUM> (see <FIG>).

The screw <NUM> is introduced into the sheath <NUM> in the known manner in order to engage the capsule <NUM> and piston member <NUM>. However, in contrast to the known fixing operation, the method proceeds differently with the indicator assembly <NUM> of the invention coupled to the anchor <NUM>. Two examples of the fixing operation are described below with reference to the sequences shown in <FIG> and <FIG>.

In both modes of operation, the anchor <NUM> is introduced into a hole in a support material (see <FIG> and <FIG>). The indicator assembly <NUM> and anchor <NUM> may already be coupled at this point, or the indicator assembly <NUM> may be introduced into and coupled to the anchor only after the anchor has been introduced into the hole.

As the screw <NUM> is introduced (i.e. screwed in), the ribs <NUM> and additional portions <NUM> of the indicator assembly <NUM> guide and axially centre the screw <NUM> so that it is received along the anchor axis <NUM> (see <FIG> and <FIG>). The threaded surface of the screw <NUM> engages and cooperates with the guide member <NUM> through the thread provided by the additional portions <NUM> and ribs <NUM>.

Thereafter, rotation of the screw <NUM> enables it to move longitudinally along axis <NUM>. In this way, and in contrast to known systems, as the screw <NUM> is rotated its tip 22a is directed precisely towards the piston member <NUM>. This occurs even as the screw <NUM> travels through the resin capsule <NUM> (see <FIG> and <FIG>) such that, when it reaches the piston member <NUM> it instantly engages with its corresponding screw thread (see <FIG> and <FIG>). Thus, misalignment of the screw <NUM> with the piston member <NUM> is prevented.

With the screw <NUM> correctly aligned, screw <NUM> is able to engage with the piston member <NUM> and urge it towards the sheath <NUM> in a smooth action, without interference or mis-engagement, in order to move the resin mixture.

Thus, as shown in <FIG>, when the anchor <NUM> is fastened to a hollow support material, the screw <NUM> rotates and urges the piston member <NUM> into the sheath, thereby mixing and expelling the resin into the sleeve <NUM> as described above. In this configuration, the contracting force provided by the screw <NUM>, i.e. the force acting to urge the piston member <NUM>, causes the shoulder portion <NUM> to bear against the connector elements <NUM>, while at the same time moving the piston member <NUM> as shown by arrow F1.

Continued rotation of the screw <NUM> maintains the contracting force, expelling resin into the sleeve (see <FIG>) until the piston member <NUM> reaches the stop means <NUM>. Thereafter, the contracting force acts to deform the sheath <NUM>, so that the sleeve <NUM> and expelled resin travel along the axis <NUM> towards the indicator assembly <NUM> until the sleeve <NUM> abuts the inside surface of the hollow wall (see <FIG>).

With the longitudinal compression and travel of the piston member <NUM> thus meeting its limit at the inside surface of the hollow wall, the contraction force provided by the screw <NUM> now acts in the direction F2. Thus, the bearing pressure of the shoulder portion <NUM> against the connector elements <NUM> increases until, at a predetermined force, the connector elements <NUM> are sheared through by the shoulder portion <NUM>.

The shearing action detaches the indicator member <NUM> from the guide member <NUM> (see <FIG>). The detachment may be visually detectable by the user rotating the screw as the connector members <NUM> are suddenly broken allowing the indicator member to become loose and move away from the guide member <NUM>, thereby providing visual indication that the fixing operation is complete. Additionally or alternatively, the detachment may provide an audible noise or even provide a tactile feedback to the user.

The same benefits are observed when fixing an anchor <NUM> to a solid support material (see <FIG>). Once the screw <NUM> engages the piston member <NUM>, the shoulder portion <NUM> bears against the connector member <NUM> (see <FIG>). Thus, the contracting force generated by rotation of the screw <NUM> acts in direction of arrow F1 and moves the piston member <NUM> into the sheath <NUM>. In this way, the piston member expels resin from the sheath <NUM> (see <FIG>).

With the anchor <NUM> located in a solid wall, the sleeve <NUM> is not free to take up a large volume of resin. However, the resin is still able to flow into the residual space between the hole in the support material and the sheath <NUM> (see <FIG>). The piston member <NUM> is also still able to travel some distance towards along axis <NUM> towards the indicator assembly <NUM>.

As with the fixing operation for a hollow wall, the fixing operation in a solid support material reaches a point at which the longitudinal travel of the piston member <NUM> is stopped (see <FIG>). At this point, a significant volume of resin will surround at least the distal end of the anchor <NUM>. With this limit reached, the contraction force again acts in the direction F2 thereby increasing the bearing pressure of the shoulder portion <NUM> against the connector members <NUM> until, at a predetermined force, they are sheared by the shoulder portion <NUM>. The shearing action thus visually and/or audibly, and/or even tactibly, indicates that fixing operation is complete and that the indicator member <NUM> has detached from the guide member <NUM> in the same manner as described above (see <FIG>).

In this way, as the screw <NUM> is rotated, although the user may feel varying levels of resistance at different points of the fixing operation, the prospect of stopping prematurely is reduced. Even if the screwing becomes momentarily more difficult, the user will understand that the piston member still needs to move and so the user will keep rotating the screw <NUM> until the indicator member <NUM> detaches.

Thus, the indicator assembly <NUM> guarantees that all steps in the fixing operation occur smoothly and consequently, that the anchor is safely installed. Any risk that the resin is inadequately expelled from the sheath or that it remains stored in the sheath and separated from the hollow or solid is avoided.

Further, the same fixing operation and indicator function is provided regardless of whether the anchor <NUM> is fixed to a solid or hollow wall.

Both the guide member <NUM> and indicator member <NUM> may be injection moulded from thermoplastic polymer. Suitable polymers include polyoxymethylene (POM) or polybutylene terephthalate (PBT).

In this example, both components, guide member <NUM> and indicator member <NUM>, are made from the same polymer, the colour of this indicator member <NUM> and guide member <NUM> has to provide a visual contrast over the anchor. In this way, the indicator member <NUM>, which is removed once the anchor <NUM> is secured in place, can be easily seen and it thereby provides a clear visual indication that it has detached from the guide member <NUM>.

In a further example, the guide member <NUM> and indicator member <NUM> may be fabricated from different materials.

The number, dimensions and materials of the connector members <NUM> of the indicator assembly <NUM> may be adapted in many ways depending on the chemical anchor it is to be used with. Accordingly, the shear force required to detach the indicator member <NUM> from the guide member <NUM> may be changed by either providing a different number or different dimensions of the connector members <NUM>. Alternatively or additionally, the material(s) used for the connector members <NUM> may be chosen so as to provide the desired breaking characteristics when subjected to the bearing pressure of the shoulder portion <NUM>. In this way, the indicator assembly <NUM> can be optimised for use with different types of chemical anchors, for example, an indicator assembly <NUM> that is suitable for a larger anchor <NUM>, which requires increased effort to expel resin, may need to detach at a higher breaking force. On the other hand, an indicator assembly <NUM> suitable for a smaller anchor <NUM> may need to detach at a lower breaking force.

Furthermore, the material(s) of the indicator assembly <NUM> may be selected so as to reduce elongation under tensile force, such as provided by the shoulder portion <NUM> during use. Accordingly, the connector members <NUM> may bear a higher bearing pressure without deforming, meaning that the indicator member <NUM> detaches from the guide member <NUM> with a 'cleaner' or more noticeable break, or with a louder noise.

Claim 1:
An indicator assembly (<NUM>) for an anchor (<NUM>), comprising:
a guide member (<NUM>), having a distal end portion (<NUM>), operably coupleable to an opening of a sheath (<NUM>) of the anchor, and a proximal end portion (<NUM>), configured to guidingly receive a screw (<NUM>) entering the opening of the sheath, said guide member being adapted to centralise the screw with a central axis (<NUM>) of the sheath during use;
an indicator member (<NUM>), operably frangibly coupled to said proximal end portion of said guide member, characterized in that, said indicator member (<NUM>) is configured to operably engage with a shoulder portion (<NUM>) of the screw, so as to physically detach from said guide member at a predetermined force provided by the shoulder portion of the screw onto said indicator member during use, wherein said indicator member comprises a plate member (<NUM>) having a concentrically arranged circular aperture (<NUM>) that is configured to matchingly receive the shoulder portion of the screw, during use, and wherein said plate member is operably coupled to said proximal end portion of said guide member via at least two frangible connector elements (<NUM>).