WO2017017053A1

WO2017017053A1 - Improved movement control joint

Info

Publication number: WO2017017053A1
Application number: PCT/EP2016/067635
Authority: WO
Inventors: Seamus Devlin
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-07-24
Filing date: 2016-07-25
Publication date: 2017-02-02
Anticipated expiration: 2018-01-24
Also published as: GB2540629A; GB201513123D0

Abstract

An improved control joint for sealing movement gaps in the floors walls and roofs of buildings has an elongate, compressible body with an elongate central mushroom‐shaped cap above a stem rising from the body, and lateral arms extending outwards and upwards from the body. The lateral arms and the O‐shape section compress when installed within a gap and allow the device to open and close in response to movement while sealing the gap against the ingress of water, dirt and other contaminants. Said O‐shaped section having a central mushroom‐shaped cap the base of which along with the sloping tops of the lateral arms serve to resist loading from traffic passing over the seal while at the same time providing support for the edges of the gap which may be brittle and in many instances subject to damage under traffic loads if unsupported.

Description

Improved Movement Control Joint

FIELD OF THE INVENTION The present invention relates to a movement joint. BACKGROUND OF THE INVENTION

Buildings generally employ wet components such as concrete and mortar in their construction and, over time these dry, the components shrink and this can cause surface cracking of both the component and any finishes applied to it. Similarly buildings are subjected to expansion and contraction forces arising from thermal gain and loss of construction components. Thermal gains and losses can arise from external factors such as winter/summer and day/night cycling or from imposed heating and/or cooling from underfloor heating and cooling systems. Other factors such as wind loading, settlement and service loads all conspire to expose the structure to a rather complex, stochastic, often three-dimensional movement pattern of overlapping shear and extension/compression movements.

To cater for these complex movements it is common practice to either leave a gap between adjoining building components or to cut into building substrates to accommodate and induce movement to occur in predictable locations. Gaps are generally left in walls and floors are often sawn to induce cracking and thereafter accommodate expansion and contraction due to thermal gain and loss, wind loading and settlement of the building element. These gaps and saw cuts are commonly referred to as movement joints or control joints.

Gaps and saw cuts have to be sealed afterwards to prevent the ingress of water and other contaminants and the materials used to seal them must be flexible enough to stretch and compress in response to the contraction and expansion of buildings components. Sealants and caulk as well as factory-formed jointing systems are normally used to fill these gaps.

Walls and floors are often covered with decorative finishes and movement joints in the underlying substrates must be carried through these finishes in order to prevent them becoming damaged as the underlying substrate deflects in response to the forces applied. Sealants, caulks and factory-formed joint systems are also inserted between decorative finishes to accommodate movement.

The sealant, caulk and factory-formed jointing systems currently used to accommodate movement between building components have limitations.

Sealants & Caulk

Sealants and caulk may be of varying viscosities and they are applied between two substrates to seal the gap and to accommodate differential movement between the substrates.

The problems start with curing; sealants and caulk comprise liquid polymers which cure to form an elastomer and the curing process is based upon sealant chemistry with specific formulations requiring different environmental influences to make the cure transition. External factors such as temperature and relative humidity can have a dramatic effect upon the curing process and the many differing types of components such as base polymers, plasticisers, dehydrating agents, mineral fillers/extenders/reinforcers, cross-linkers, UV and anti-oxidant additives, wetting agents, levelling agents, thixotropes, thickeners, adhesion additives and catalysts mean that it is almost impossible to make accurate performance comparisons between differing product offerings. A common complaint is that it is often difficult to select the correct caulk or sealant for an intended application and environment.

As noted above variables in chemical composition are affected by the environment experienced by the sealant during the curing process such that the failure risk due to low temperature and either high or low humidity (depending upon the sealant formulation) is increased substantially. Building components exhibit cyclical movement due to thermal gain and loss and movement in the structure during sealant's cure phase can cause surface cracking of the sealant, cohesion and/or loss of adhesion to the su bstrates. Research and testing by Jones & Lacasse (see Jones, T.G.B., Hutchinson, A.R. & Lacasse, M.A. 1999, 'Effect of movement waveforms on the experimental performance of newly sealed joints', in Durability of Building and Construction Sealants, RILEM Proceedings PRO 10, ed AT. Wolf, RILEM Publications, Paris, pp. 211-227) and Wolf (see Wolf, AT. 1999, 'Progress towards the development of a durability test method for sealants', in Durability of Building Sealants, RILEM Report 21, ed AT. Wolf, RILEM Publications, Paris, pp. 365-380) clearly demonstrated the negative impact of mechanical cycling during a sealant's cure period on the properties of sealed joints. Sealants are vulnerable to failure during their cure cycle.

Following curing, joint sealants are exposed to cyclic mechanical strain and environmental degradation factors. Cyclic joint movement, sunlight, temperature variations (heat, cold) and moisture (water) are considered to be the primary environmental and service degradation factors leading to sealed joint failure. Weathering and service factors such as dirt accumulation, acid rain, cleaning solvents, microbial growth and an inherent incompatibility with other building materials also lead to the deterioration of sealants and caulk in the fabric of buildings.

Work towards an accelerated durability test method was started in 1989 within the International Standardisation Organisation and over the past decade the ISO TC59/SC8 and ILEM TC139-DBS committees have been trying to develop a series a durability test standards for sealants. This discussion is ongoing and no common standard for sealant testing has been issued thus far. In the main this is due to the complexities of the chemistry of sealants combined with differing cure reaction mechanisms and times and all the environmental factors. Currently there is no single measure for the durability performance of a sealant.

Over time sealants and caulks progressively age and harden and durability testing by both RILEM (see RILEM 2001, 'RILEM TC 139-DBS: Durability test method - Determination of changes in adhesion, cohesion and appearance of elastic weatherproofing sealants for high movement fagade joints after exposure to artificial weathering', Materials & Structures, Vol. 34, December 2001, pp 579-588) and Miyauchi et al (see Miyauchi, H., Enomoto, N., Sugiyama, S. & Tanaka, K. 2004, 'Artificial Weathering and Cyclic Movement Test Results Based on the RILEM TC139-DBS Durability Test Method for Construction Sealants', Durability of Building and Construction Sealants and Adhesives, ASTM STP 1453, A. T. Wolf, Ed., ASTM International, West

Conshohocken, PA, 2004) have shown that fatigue cycling substantially accelerates sealant degradation including cracking, crazing, chalking and lack of adhesion and cohesion. These failures serve to compromise the longevity of sealants and thereby undermine the sealant's principal function; to seal the gap throughout the movement cycling service life of the structure.

To be effective and to meet their stated movement performance sealants and caulk have to be installed within gaps and saw cuts at a given width-to-depth ratio and the surfaces of substrates to which these materials have to be bonded often need considerable preparation and priming. Sealants and caulks are installed and formed on site and site conditions often do not lend themselves to textbook installation. If the installed sealant is too shallow for a given width of gap and movement then the sealant will tend to split down the middle when it comes under the strain imposed by shrinkage due to drying and thermal loss. If the installed sealant is too deep for a given width and movement then the sealant will tend to delaminate from the substrate when it comes under the strain imposed by shrinkage due to drying and thermal loss. The quality of site workmanship and site conditions often become the factors determining the longevity or otherwise of the seal installed. These failures of the sealant or caulk mean that the seal material is failing in its principal objectives of preventing the ingress of water and other contaminants whilst at the same time accommodating movement in the fabric of the building over its service life.

The width of sealants used as movement joints rarely exceeds 25mm as when installed in floors the sealant has to endure impact and abrasion from pedestrians and wheeled vehicles and the wider the seam of sealant or caulking, proportionately the higher the rate of attrition. When sealant or caulking is installed in walls in wide seams of greater than 25mm width the sealant often sags out of the gap or saw cut under the force of its own weight. This is termed 'slump' in the construction industry.

The flexible nature of sealants means that they are rarely appropriate for use in floors. Gaps and sawn joints formed in underlying substrates have to be carried up through hard and relatively brittle concrete finishes and floor coverings such as ceramic tiles and natural stone. The edges of such materials are easily chipped by the passage of traffic. This is particularly the case where a movement joint filled with sealant or caulk traverses a floor. The sealant provides little or no lateral support to the arris of the brittle finish with the result that attrition from pedestrian and wheeled traffic cause cracking and failure at the unsupported edge.

The term 'spalling' is used in the construction industry for such chipping, and spalled finish materials are regarded as compromised and generally lead to progressive failure of the floor as contaminants, water and other debris can leak into the gap or saw cut through the spalled areas.

Sealants, caulks and factory-formed joints used in floors also share the common problem of the direct relationship between gap width and seal flexibility on the one hand and resistance to wear and penetration on the other. A soft flexible wide seal will move more but will tend to sustain greater damage from pedestrian and vehicular traffic than a narrow gap filled with harder, relatively more inflexible fillers. Flexibility and hardness are conflicting factors and often a compromise has to be reached where two sealants are used at separate points in the

construction timetable. This compromise is epitomised by the advice from The UK's Concrete Society Report TR34 'Concrete Industrial Ground Floors - A guide to design and construction' which advises "Initially a soft sealant, typically with Shore A hardness below 30 and a Movement Accommodation Factor of 25% should be used. This should be replaced later with a harder sealant that will provide support for traffic and the joint arris. These may debond in due course and should be replaced as required". This approach causes extra work, cost and disruption to both the contractors erecting the structure and the client who is using the building.

Factory-formed Joints

Factory-formed joints seek to serve a useful function in that as they are made in a factory they tend to reduce the impact of workmanship and site conditions upon the correct installation of a jointing system. Similarly these systems are fully cured before they leave the factory and are not affected by environmental conditions during the cure period.

They do however present a number of severe limitations in that, unlike sealants and caulking they require mechanical connection to the substrate to function. This connection is normally formed through the attachment of a central flexible material to preferentially rigid side members which are then keyed into an adhesive or a bedding mortar. These generally rigid members are designed to stretch and compress the central flexible material of the joint system, said flexible material generally being manufactured from thermoplastic plastics such as Polyvinylchloride and

Polyurethane or synthetic rubbers such as Polychloroprene, Ethylene Propylene Diene Monomer, Santoprene and Silicone.

The integrity of the bond between the rigid members and the adhesive or mortar bed has a direct influence on the performance of the factory-formed joint in that the adhesive or mortar bed must be strong enough grip the rigid members such that they stretch the flexible portion of the joint and open the joint when building elements begin to contract through drying shrinkage and thermal loss. The tensile strength of most cementitious adhesives and mortars varies between 0.5N/mm² and 1.0N/mm² and rarely exceeds 2.5N/mm². As a consequence the tensile strength of the flexible section of factory-formed joints must be significantly less than this value otherwise the mechanical bond between cementitious adhesive/mortar and the factory-formed joint will fail. Table 1 below shows a list of the most common materials used to form the flexible portion of a factory-formed movement joint.

Table 1: Common Materials used as the Flexible Component of a Movement Joint

.Mi mum Tens ile

Material

Strength N/mm7

Polyvi nylchl ori de ( PVC) Flexible extruded 6.9

Polyuretha ne Flexible extruded 5.8

Polychloroprene (Neoprene) Flexible extruded 10.2

Ethyl ene Propyl ene Diene Monomer ( EPD ) Flexible extruded 9,4

Sa nto rene Flexible extruded 8.8

Si l icone Flexible extruded 6.2

As can be seen the minimum tensile strength of these materials is significantly greater than the maximum tensile strength of the adhesive and mortar used to mechanically fix these movement joints in place. The result is that, when building elements begin to contract th rough drying shrinkage and thermal loss the bond between the adhesive, mortar and facto ry-formed joint will fail before the joint can open to accommodate the movement. The factory-fo rmed joint will fail to open under tensile strain resulting in be delamination of the rigid side members from the adhesive or mortar thus compromising the seal and allowing the passage of water and other contaminants into the gap or saw cut.

There is a design of factory-formed control joint which will open up in response to movement and which is not mechanically fixed by bonding, shown in US Patent Number 6,574,933 'Movement Joint'. This joint comprises compressible filler held within a rigid envelope wh ich is compressed and installed into a preformed gap or saw cut of predetermined width. As the joint is pre- compressed it will open up when the substrates either side of it shrink due to drying and thermal contraction. One limitation of this type of joint is that it is only suitable for na rrow gaps less than 5mm wide. When used in gaps wider than 5mm the flexible core material protrudes beyond the joint surface when the joint comes under compression as the surrounding substrates expand due to thermal gain. This is a limitation in the use of this type of factory-formed joint as the ejection of the flexible material under compression can cause a trip hazard if joints wider than 5mm are used in floors.

One further limitation of the type of factory-formed joint shown in US Patent Number 6,574,933 derives directly from gap and saw cut width limitations. Like sealants the opening and closing capacity of the flexible core of a given material and hardness of this type of joint is determined by the width of the gap. The wider the gap; the greater the movement capacity of the joint. The width of the gaps for this type of joint is limited to 5mm maximum and as a consequence the magnitude of movement that these joint systems can accommodate is limited.

Yet another drawback of factory-formed joints is that they normally have rigid side plates with a web which allows the joint to be mechanically fixed by engagement in the adhesive or mortar bed either side of the gap. The exigencies of transporting these products means that they are generally supplied in 2.0 to 3.0 metre lengths resulting in butt joints between sections. These butt joints can allow water, debris and other contaminants enter the gap.

The invention disclosed offers an improved device which solves the problems of both sealants and factory-formed jointing systems as disclosed above. SUMMARY OF THE INVENTION

The invention provides a control joint device for sealing a movement gap defined between adjacent edges of two components of a building's structure, the device comprising:

an elongate, compressible body adapted to be compressibly inserted into said gap,; a first arm extending upwardly from a first side of said body such that when said device is compressibly inserted in said gap, said first arm lies within the gap against one of the component edges;

a second arm extending upwardly from a second side of said body such that when said device is compressibly inserted in said gap, said second arm lies within the gap against the other of the component edges;

a central member extending upwardly from said body between said first and second arms, the central member having a cap, the cap having an underside facing the body and a top side facing away from the body; the arms and central member being dimensioned such that in use the first arm bears against the underside of the cap on the first side and the second arm bears against the underside of the cap on the second side. The present invention thus allows a factory-formed movement joint to be provided which is designed to fill gaps and saw cuts left or formed between elements of construction to allow for differential movement of these components. The device, being compressibly inserted in the gap, will open to compensate for the drying shrinkage and thermal contraction of building elements. Similarly the device will close in response to expansion of buildings elements due to thermal gain, wind loading and other similar factors.

Unlike sealants or existing preformed joint systems the present invention simplifies joint selection. Selection is based upon the required movement capacity of any gap formed between elements of a structure. The movement defines which product within the range of the present invention is most appropriate and this in turn informs gap width.

The device of the invention has been designed to be produced in a controlled environment in a factory so as to limit the negative impact of workmanship and site conditions which regularly affect the installation and performance of sealants and caulking. Similarly the invention is fully cured before it is installed and doesn't suffer from the cure or width-to-depth ratio problems associated with sealants.

Unlike sealants, the device can be substantially manufactured from plastic polymers the aging characteristics of which are well understood. More than 2,000 accelerated aging testing protocols have been accepted by the American Society for Testing and Materials (ASTM) and, depending on product application, the polymer employed will be matched to the environment to maximise service life.

As the device is not subject to 'slump' the width of the gap is not a limiting factor in the design of the proposed device as there are few limitations beyond the extrusion width limits of existing thermoplastic and synthetic rubber extrusion technology. Similarly the movement capacity of the invention is only limited by existing extrusion technology. The device is trafficable by pedestrians and vehicles and resists penetration and damage by such traffic. Similarly, throughout the movement cycle accommodated by the device, it has been designed to support and prevent damage to the arris of brittle finishes such as concrete, ceramic tiles and natural stone by the aforementioned pedestrians and vehicles.

The device of the invention provides smooth transit for pedestrian and vehicles and in preferred embodiments as described below it typically only exhibits slight vertical displacement when the movement joint is fully closed, the displacement being significantly less than the 6.35mm advised as the maximum permissible by Americans with Disabilities Act (ADA) legislation.

The device is compressed and inserted into the movement gap and, unlike preformed control joints it does not require mechanical connection to the substrates either side of the gap. As the gap opens and closes so the present invention responds by expanding and compressing to fill the gap.

Preferably, each of the first and second arms has an angled surface at a free end thereof, the angled surface sloping downwardly and inwardly away from the respective edge against which the arm is situated in use, and wherein the cap has an underside with a pair of angled surfaces, , one at each side of the central member, each angled surface sloping upwardly and outwardly away towards the first or second side, respectively; the arms and cap being dimensioned such that in use the angled surface of the first arm bears against the respective angled surface of the underside of the cap on the first side and the angled surface of the second arm bears against the respective angled surface of the underside of the cap on the second side. The device is designed to prevent the ingress of debris, water and other contaminants throughout both opening and closing movement cycles, with the angled surfaces of the arms bearing against the underside of the cap, and the arms also bearing against the side walls of the cut or gap.

Preferably, the central member is carried on the compressible body such that the central member moves vertically upwards with increased compression of the body and downwards with relaxation of the body, said movement tending to maintain the contact between said angled surfaces under different compressive states. In a preferred form, said compressible body is tubular, with the central member being mounted on the upper part of said tubular body.

Preferably, the central member is formed integrally with and emerges from the upper part of said tubular body.

Preferably, the arms are resilient, plate-like structures extending parallel to the elongate axis of the compressible body. Preferably, the central member further comprises a stem connected at one end to said body and at said other end to said cap. While preferred devices show such a stem-and-cap structure, having a mushroom-like shape, the cap can also be mounted directly on the resilient structure, transitioning outward from that structure to define the underside against which the plate-like members bear.

Preferably, the cap is an elongate member extending parallel to the elongate axis of the compressible body.

Preferably, the stem is a resilient planar member extending parallel to the elongate axis of the compressible body.

Preferably, the cap has an upper surface which presents a rounded or flat surface across the gap, bridging the components of the building structure. Preferably, the cap is resiliently deformable.

Preferably, the central member further comprises a stem connected at one end to said body and at said other end to said cap, and the cap is wider than the stem when viewed in a plane transverse to the elongate axis of the body, such that on either side of the stem, below the cap, a respective space is defined.

Further, preferably, upon compression of a gap in which the device is fitted, said spaces accommodate said arms being compressed inwardly. Preferably, when the device is in a relaxed state prior to insertion into a compressive gap, the arms are biased outwardly at an angle to the vertical.

Preferably, the respective angled surfaces of the arms and cap are designed to match one another when the device is inserted into said gap. The device may be designed with an insertion width or range of insertion widths in mind, so that when compressed into such a width the angled surfaces match.

Preferably, the angled surfaces assume an angle from the horizontal of between 10 and 80 degrees in normal use, preferably between 20 and 60 degrees, more preferably between 25 and 45 degrees.

Suitably, the body, arms and central member are integrally extruded from an extrudable thermoplastic material such as PVC, Polyethylene, Polyurethane, or Polypropylene or a synthetic rubber such as Silicone, Neoprene, or EPDM.

Preferably, said device has a relaxed state, and a range of operating compressed states ranging from a minimally compressed operating state in which the device will just remain in position in a gap during normal use, to a maximally compressed state in which the arms and cap remain in contact without damage to the device, the device being dimensioned such that said minimally and maximally compressed states lie outside the expected maximum and minimum ranges of width achieved under a normal expected range of environmental conditions, for a movement gap to which the device is to be fitted. There is also provided a method of filling a movement gap, comprising the steps of: determining maximum and minimum ranges of width for said movement gap under a normal expected range of environmental conditions; selecting a control joint device as described and claimed herein such that said minimally and maximally compressed states of said device lie outside the determined maximum and minimum ranges of width for said movement gap; and fitting said control joint device into said gap under compression.

Preferably, the device is provided as a continuous length, optionally in a coiled form. This means that unlike factory-formed joints, joins every two to three metres are avoided and thus a continuous seal is formed. In one form the compressible body is substantially O-shaped and is designed to be compressed and friction fitted into gaps and saw cuts formed between building elements. The compression of the joint causes the outer arms and faces of the O-section to press against the walls of the gap or saw cut and hold the movement joint in place and under compression.

Preferably, the magnitude of compression is calculated such that the compression set characteristics of the thermoplastic or synthetic rubber material are accounted for whilst permitting the O-shape to open up and close by predetermined magnitudes in response to movement between the elements of construction. The device is thus superior to other factory- formed joints which cannot open in response to structural deflection.

One further advantage of the device according to the invention is its ability to support the vulnerable edges of building elements where brittle finishes are exposed to loading. Caulk and sealant provide little or no lateral support to the arris of the brittle finish with the result that attrition from pedestrian and wheeled traffic cause cracking and failure at the unsupported edge.

This support is given by a combination of the device being held under compression throughout the movement cycle of the structure allied with a design comprising a central cap component which has an angled base that substantially transfers load applied vertically to the joint outwards to support the substrate on either side of the arms.

The central part of the compressible body is preferably topped by a mushroom-shaped cap which arises from the top of preferably hollow body and flares outwards from this point to form the angled bases of the cap's mushroom shape. At its outer limit these surfaces return inwardly to form the substantially convex curve of the top of the mushroom shape herein described.

The device also has external arms either side which preferably extend outwards from the body. These external arms are designed to close as the invention is compressed into a gap such that the upward sloping bases of the mushroom shaped cap lie parallel, directly above and in contact with the tops of the arms which have substantially inward sloping angled returns. When installed in a movement gap the bases of the mushroom shaped cap touch the inward sloping angled returns of the arms. The inward sloping angled returns of the arms serve to offer support to the upward sloping bases of the mushroom cap when said cap comes under loading from pedestrian and vehicular traffic or other such forces. The result of the angled slope design is that a load applied to the mushroom cap translates into an outward force transferred through the arms and to the walls of the gap or saw cut such that the friction between the body's arms and these walls increases, with the result that under loading the joint becomes increasingly resistant to being pressed into the gap or saw cut.

The arms will tend to close and the cap will rise slightly when the gap or saw cut closes and the joint comes under increased compression from the expansion of abutting building elements. The arms will tend to open and the cap will drop slightly when the partially compressed joint is relaxed as the gap or saw cut opens due to contraction of abutting building elements.

The outer faces of the compressible body and/or of the arms are preferably formed with serrations. Alternatively or additionally, some or all of these outer surfaces have an adhesive layer applied. These serrations and/or adhesive layers assist in maintaining the joint in position between the sides of the gap or saw cut and help to prevent it being pressed further into the gap or saw cut.

When the device is partially closed and inserted into a gap or saw cut the gap dimension is termed 'the installation width'. Those experienced in the field will be able to select an appropriate width of device for a given installation width such that, when installed, the device has only been partially and not fully closed. This will allow the gap or saw cut into which the device has been inserted to open and close from this installation width in response to the expansion and contraction of building elements.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a gap or saw cut formed between differing building elements to facilitate expansion and contraction within the structure arising from the drying shrinkage and thermal gain and loss of building elements.

Figure 2 shows a sectional view of a form of the device that has been designed to be compressed into a gap or saw cut formed between two building elements. Figure 3 shows a sectional view of a further embodiment of device where the outer thermoplastic arms of the O-shaped section have been replaced by metal arms which a co-extruded with the thermoplastic material.

Figure 4 shows a sectional view of the device of Fig. 2 extruded from thermoplastic or synthetic rubber as detailed in Figure 2 installed within a gap or saw cut formed between building elements. Figure 5 shows a sectional view of the device of Fig. 2, shown in a closed position wherein the device has been further compressed from the state of Fig. 4 following, for example thermal expansion of the abutting building elements.

Figure 6 illustrates a sectional view of the device of Fig. 2, shown in an open position wherein the device has expanded from the state of Fig. 4 following, for example thermal contraction of the abutting building elements.

Figure 7 is a force diagram showing how a vertical force applied to the central mushroom top of the device is partially transferred outwards into the abutting substrates.

Figure 8 shown how the slope of the base of the mushroom cap and the arms of the device serve to translate the vertical force into a lateral force acting outwards into the substrate 9.

DETAILED DESCRIPTION OF THE DRAWINGS

Figure 1 shows a rebate which has been formed by leaving a gap 10 between two elements 9 of a building. Alternatively the gap may comprise a saw cut which divides and element into smaller components. Such gaps are left or formed at regular intervals as part of the normal process of construction to accommodate deflections arising from a number of factors including the drying shrinkage of wet components as well as expansion and contraction of said components as their temperature increases and decreases. Figure 2 displays one form of the device in cross-section comprising an extrusion made from either thermoplastic or synthetic rubber. The thermoplastic or synthetic rubber used can be extruded as a single hardness or as a composite product where materials of differing durometer hardnesses are extruded together to form a single unit. Similarly composite materials comprising differing polymers may be used to form the material.

In this form the present invention is substantially O-shaped and has been designed to be compressed and friction fitted into gaps and saw cuts formed between building elements. The device comprises a central member having a mushroom-shaped cap 1 which is attached by a stem to an inverted U-shape the arms of which are connected to the outer arms 2 of the O-shaped joint. The top faces of the outer arms 2 are angled inwards 3 towards the centre of the joint while the base 4 of the mushroom-shaped cap 1 slope outwards such that when closed the top faces 3 are parallel and in contact with the faces of the base 4. The O-shaped outer arms 2 of the joint are connected to the mushroom cap 1 by means of an inverted U-shape the arms of which 8 are attached to the lower extremities of the outer arms 2 of the O-shaped section. The invention has gaps 5 between the outer arms 2 of the O-shaped section and on either side of the stem of the mushroom shaped cap 1. These gaps 5 are designed to simplify the tooling required to extrude the device and accommodate the compression of the device when it is either being emplaced or in operation. Optionally the outer faces of the arms 2 may be serrated 6 have an adhesive layer 7 applied to improve the grip between the device and the walls of the gap or saw cut 10 shown in Figure 1.

Some applications may require that the outer edges of the seal are reinforced with metal hence in Figure 3 the invention is shown with the outer thermoplastic arms of the O-shaped section replaced by metal arms 12 which a co-extruded with the thermoplastic material 13. These metal arms may comprise extruded or folded sections made from typically aluminium, brass, stainless steel, zinc or other formable metals.

Figure 4 shows a cross -sectional view of the device when it has been compressed and located within a gap 10 formed between two elements 9. This figure shows the device at its nominal installed width position from which point it can open and close in response to movement of the structure. Preferentially the joint has been designed to be installed in a mid-movement position such that, after taking account of the potential compression set of the material employed, from this midpoint the joint can open and close by an equal distance. Those experienced in the field will be able to select an appropriate width of joint for a given installation width wherein, when installed, the joint has only been partially and not fully closed. This will allow the gap or saw cut into which the joint has been inserted to open and close from this installation width in response to the expansion and contraction of building elements.

During installation the compression of the joint causes the outer arms 2 of the O-shaped section to press against the walls of the gap or saw cut and the optional serrations 6 and/or adhesive 7 serve to hold the movement joint in place while it remains under compression. During compression of the device the gaps 5 have closed due to the two outer arms 2 of the O-shaped device being pressed inwards. As they are pressed inwards they slide progressively beneath the central mushroom cap 1 which lifts in response to both the closure of the arms 2 and the compression of the arms 8 of the inverted U-shape which forms part of the stem of the mushroom shaped cap 1. The action of the legs 8 being closed together raises the mushroom cap

1 so that the arms 2 of the O-shaped section fit beneath and in contact with the sloping bases 11 of the mushroom cap 1 such that contact between the central mushroom cap 1 and the side arms

2 is maintained and they still offer support when mushroom shaped cap 1 comes under loading through the movement cycle of the gap.

Figure 5 shows a cross -sectional view of the device when it has been further compressed than shown in Figure 4. Such compression can arise from the expansion of the abutting materials 9 due to expansion arising from thermal gain in which case the gap 10 will close putting the device under further compression. Under this increased compression of the device the gaps 5 have been further reduced due to the two outer arms 2 of the O-shaped device being pressed increasingly inwards. As they are pressed inwards they slide progressively beneath the central mushroom cap 1 which lifts in response to both the closure of the arms 2 and the compression of the arms 8 of the inverted U-shape which forms part of the stem of the mushroom shaped cap 1. The action of the legs 8 being closed together raises the mushroom cap 1 by a distance shown as that between points 12 and 13 where 12 denotes the location of the junction between the arms 8 of the inverted U-shape when the joint is initially installed as shown in Figure 3. The device has been designed such that the uplift of the mushroom cap 1 is matched by the outer arms of the O- shaped section moving inwards and offering continuous contact and support via the sloping bases 11 of the mushroom cap 1. This ensures that these arms still offer support and transfer loading to the substrate when mushroom shaped cap 1 comes under load.

Figure 6 shows a cross -sectional view of the device when the compression shown in Figures 3 and 4 has been partially released due to the gap or saw cut 10 opening in response to deflections within the fa bric of the building. Such deflections can arise from drying shrinkage or contraction due to thermal loss wherein the substrates 9 contract. Under the release of compression the gaps 5 open up as the two outer arms 2 of the O-shaped device extend outwards. As they extend outwards they slide progressively from beneath the central mushroom cap 1 which drops in response to the opening of both the arms 2 and the arms 8 of the inverted U-shape which forms part of the stem of the mushroom shaped cap 1. The action of the legs 8 being opened draws the mushroom cap 1 downwards such that contact is continuously maintained between the bases 11 of the mushroom cap 1 and the top sloping edges of the arms 2 of the O-shaped section. By maintaining contact between the central mushroom cap 1 and the side arms 2 support is offered when mushroom shaped cap 1 comes under loading. Thus the central mushroom-shaped cap is supported through the entire range of movement which is within the capacity of the device to accommodate.

Thus the device when installed under compression can accommodate movement cycling wherein the gap 10 opens or closes.

Figure 7 demonstrates how a load applied to the mushroom-shaped cap at point 14 shown in this Figure would become separate forces 15 at 90° to the plane of the slope of the interface between the slope of the arms 2, and 11 the base of the mushroom cap 1 and 16 in the direction of the plane of the slope. This force 14 is also transferred through the legs 8 of the inverted U-shape wherein the directional components of the load are applied partially in the direction of the legs 17 and also at right angles to this thrust 18. The component forces 15 and 17 serve to transfer part of the applied load 14 outwards towards the walls of the gap 10. In doing so, these forces serve to increase the support the device provides to the arrises of the gap thus helping to prevent damage to brittle finishes. Similarly the load transferred outwards serves to increase the friction coefficient at the interface between the device and the walls of the gap 10 and thereby increase resistance of the invention against pressed downwards into the gap 10. Figure 8 shows the impact of a load F_g applied at point A on the sloping top of one of the outer arms of the O-shaped device. The angle of the slope is Θ and depending upon the gradient of this slope the total load is translated into two forces F_x and F_y. Where F_x is applied along the plane of the slope and where the value of F_x = F_gSin9 and F_y = F_gCos9.

Vertical imposed loading applied to the mushroom shaped cap is transferred from the upward sloping bases of the cap through the inward sloping angled returns of the outer arms of the O- section and out to the walls of the gap or saw cut. It can be shown that as the load applied on the mushroom cap is transferred through angled planes in such a way that the force applied acts in two directions; at an angle along the Y-axis at 90° to the plane of the slope and along the corresponding X axis down the plane of the slope. Using an example of a force (F_g) of 100N applied through a 30° slope angle, the resultant components of this force comprising (F_x) applied down the plane of the slope and (F_y) applied at 90° to the plane of the slope: F_x = F_gSin30° = 100 x 0.5 = 50N down the plane of the slope

F_y = F_gCos30° = 100 x 0.866 = 86.6N applied at an angle of 30° to the plane of the slope

Claims

1. A control joint device for sealing a movement gap defined between adjacent edges of two components of a building's structure, the device comprising:

a central member extending upwardly from said body between said first and second arms, the central member having a cap, the cap having an underside facing the body and a top side facing away from the body;

the arms and central member being dimensioned such that in use the first arm bears against the underside of the cap on the first side and the second arm bears against the underside of the cap on the second side.

2. The control joint device of claim 1, wherein each of the first and second arms has an angled surface at a free end thereof, the angled surface sloping downwardly and inwardly away from the respective edge against which the arm is situated in use, and wherein the cap has an underside with a pair of angled surfaces, one at each side of the central member, each angled surface sloping upwardly and outwardly away towards the first or second side, respectively; the arms and cap being dimensioned such that in use the angled surface of the first arm bears against the respective angled surface of the underside of the cap on the first side and the angled surface of the second arm bears against the respective angled surface of the underside of the cap on the second side.

3. The control joint device of claim 1 or 2, wherein the central member is carried on the compressible body such that the central member moves vertically upwards with increased compression of the body and downwards with relaxation of the body, said movement tending to maintain the contact between said angled surfaces under different compressive states.

4. The control joint device of any preceding claim, wherein said compressible body is tubular, with the central member being mounted on the upper part of said tubular body.

5. The control joint device of claim 4, wherein the central member is formed integrally with and emerges from the upper part of said tubular body.

6. The control joint device of any preceding claim, wherein the arms are resilient, plate-like structures extending parallel to the elongate axis of the compressible body.

7. The control joint device of any preceding claim, wherein the cap is an elongate member extending parallel to the elongate axis of the compressible body.

8. The control joint device of any preceding claim, wherein the central member further comprises a stem connected at one end to said body and at said other end to said cap.

9. The control joint device of claim 8, wherein the stem is a resilient planar member extending parallel to the elongate axis of the compressible body.

10. The control joint device of any preceding claim, wherein the cap has an upper surface which presents a rounded or flat surface across the gap, bridging the components of the building structure.

11. The control joint device of any preceding claim, wherein the cap is resiliently deformable.

12. The control joint device of any preceding claim, wherein the central member further comprises a stem connected at one end to said body and at said other end to said cap, and wherein the cap is wider than the stem when viewed in a plane transverse to the elongate axis of the body, such that on either side of the stem, below the cap, a respective space is defined.

13. The control joint device of claim 12, wherein upon compression of a gap in which the device is fitted, said spaces accommodate said arms being compressed inwardly.

14. The control joint device of any preceding claim, wherein when the device is in a relaxed state prior to insertion into a compressive gap, the arms are biased outwardly at an angle to the vertical.

15. The control joint device of claim 2 or any claim dependent thereon, wherein the respective angled surfaces of the arms and cap are designed to match one another when the device is inserted into said gap.

16. The control joint device of claim 15, wherein said angled surfaces assume an angle from the horizontal of between 10 and 80 degrees in normal use, preferably between 20 and 60 degrees, more preferably between 25 and 45 degrees.

17. The control joint device of any preceding claim, wherein the body, arms and central member are integrally extruded from an extrudable thermoplastic material such as PVC,

Polyethylene, Polyurethane, or Polypropylene or a synthetic rubber such as Silicone, Neoprene, or EPDM.

18. The control joint device of any preceding claim, wherein said device has a relaxed state, and a range of operating compressed states ranging from a minimally compressed operating state in which the device will just remain in position in a gap during normal use, to a maximally compressed state in which the arms and cap remain in contact without damage to the device, the device being dimensioned such that said minimally and maximally compressed states lie outside the expected maximum and minimum ranges of width achieved under a normal expected range of environmental conditions, for a movement gap to which the device is to be fitted.

19. A method of filling a movement gap, comprising the steps of: determining maximum and minimum ranges of width for said movement gap under a normal expected range of

environmental conditions; selecting a control joint device according to claim 18 such that said minimally and maximally compressed states of said device lie outside the determined maximum and minimum ranges of width for said movement gap; and fitting said control joint device into said gap under compression.