SE1650768A1 - Chair and Method for Fixing Chair to a Supporting Surface - Google Patents

Abstract

This publication relates to a chair for supporting a reinforcement member for concrete on a supporting surface, for example arranged on a tunnel wall or roof surface, comprising a base member configured to be attached to the supporting surface; preferably an intermediate part fixed to and extending out from one side of the base and a reinforcement bar locking device fixed to an opposite end of the intermediate part, the locking device being provided with member for receiving the reinforcement member.The chair is made of a plastic material that may be fixed by welding to the supporting surface and that both the supporting surface and at least the base part of the chair are made of compatible plastic materials that allow welding by hot air.The publication relates also to a method for affixing such chair to a supporting surface.To be published together with Fig. 3

Description

Chair and Method for Fixing Chair to a Supporting Surface The Technical Field of the inventionThe present invention relates to a chair for supporting a reinforcement element for concrete on a supporting surface, for example arranged on a tunnel wallor roof surface, said chair being made of a plastic material and comprising a basemember configured to be attached to the supporting surface; preferably anintermediate part fixed to and extending out from one side of the base member and areinforcement bar locking device fixed to an opposite end of the intermediate part,the locking device being provided with a member for receiving the reinforcementelement. Furthermore, the present invention relates to a method for fixing areinforcement element for concrete on a supporting surface in a predetermineddistance from said supporting surface, where a chair for supporting thereinforcement element is connected to the supporting surface, the chair being madeof plastic and comprising a base member configured to be attached to thesupporting surface and a reinforcement bar locking device for receiving and lockingthe reinforcement element.

Background for the inventionln many cases, there is a need for a Waterproof and/or fire proof lining of awall or a roof, such as for example the walls and/or roof of a tunnel, and at the sametime there is a requirement that such linings or membranes are covered by concrete.The lining is affixed to the wall /roof by means of rock anchors fixed to the rock, thelining being arranged as a continuous lining across the tunnel in successivelengthwise sections, forming a water tight barrier. ln addition reinforcement is fixed tothe same rock anchors whereupon a layer of concrete is shot on to the concrete, thelining serving as formwork for such shotcrete.ln order to reinforce the concrete reinforcement is required, either as reinforcement rebars extending both in a longitudinal direction of the tunnel and alsoin transverse direction, following the contour of the lining, or as reinforcement nets.Such reinforcement is affixed to rock, prior to shotcreting in order to prevent parts ofthe flexible lining from being displaced during concreting and in order to secure therequired minimum distance from the lining to the reinforcement and to secure therequire coverage of the reinforcement. Hence, it has previously been proposed touse a number of chairs, either fixed to rock behind the lining, or to the lining itself, ifpossible. Such fixing operation is both tedious and time consuming. At the same time the lining may be excessively punctured, establishing points or areas prone toleakage of water through the lining or membrane.

There exist several prior art solutions for fixing reinforcement to a lining or aninsulating liner for walls or tunnels. Typical methods may be to screw the chair intothe supporting wall; or to glue the chair to the supporting surface or to allow the chairto rest due to its own weight and the reinforcement on a more or less horizontallyoriented supporting surface. ln order to be able to attach the chair by a screwing method, the supportingwall must be of a character allowing a screw end of a chair to be screwed into thesupporting wall.

The most pertinent method for attachment closest to the method according tothe present invention, and the method with most similar features with the methodand chair according to the present invention, is to use glue for attaching and fixingthe chair to the supporting surface. Use of glue incorporates a number of inherentdrawbacks. Firstly, the glue itself must be of a two-component type, preferably mixedin the outlet of a glue pistol or melt glue pistol. Such glue is expensive, requiring aclean surface in order to secure sufficient and adequate gluing effect. l\/loreover,such method also requires a period of time for enable the glue to cure. Hence, themethod is both expensive due to time taken and the cost of the glue. l\/loreover,experience has shown that the quality of the gluing effect may vary substantially,both due to lack of or varying proper distribution of a uniform layer of glue over theentire contact area of the chair. As a consequence, it is experienced that some of thechairs drops off during placing of the reinforcement and/or during concreting, theshotcrete being applied at a high impact on the supporting surface, reinforcementand chair. ln areas where one or more chairs have dropped off, the supportingsurface will yield during the shotcreting operation, forcing the supporting surfaceoutwards towards the tunnel wall behind. ln such regions the layer of shotcrete willas a consequence be thicker, thus consuming more concrete than necessary due tothe yielding outwards, thus increasing the time taken for the concreting process andthe added volume of concrete necessary.

From NO 333588 it is known a chair for fixing reinforcement nets or bar at apredetermined distance from an insulated tunnel wall. The chair comprises athreaded section intended to be screwed into the insulating material until a stopsurface enters into engagement with the surface of the insulation. A part of the chairis configured to project outwards from the insulation with two parallel discs arrangedat a predefined distance from the insulation, securing adequate position for thereinforcement with respect to the insulation. The chair is also provided with a spy, i.e. a devise to enable the concreting operator to identify whether an adequate concretecoverage is obtained in the shotcreting process or not.

US 3,673,753 describes a concrete reinforcing bar support device whichincludes a base supporting an upright pedestal, configured to rest more or less firmlyon a more or less horizontal surface. A lower clamping portion is supported by thepedestal which has a first rod-receiving open passageway therethrough. Resilientdetents extend from the lower clamping portion to retain detents extend from thelower clamping portion to retain a reinforcing rod disposed through the firstpassageway. An upper clamping portion is provided which includes a pair of hookmembers extending from the lower clamping portion. Each of the hook members hasa mouth opening in the same direction to define a second rod-receiving passagewaywhich is normally disposed to the first passageway. The chair disclosed is of a typeintended to rest on a more or less horizontal surface without any fixing means to thesupporting surface.

US 2008/0178554 discloses a chair for supporting one or more reinforcementbars in a concrete structure. The chair includes a base member having a centeredopening, a pair of opposing first leg members extending upwards from the basemember at a first angle, a pair of opposing second leg member extending upwardsfrom the base element at a second angle, and a strap-shaped locking cradle. Thestrap-shaped locking cradle includes an arc-shaped receiving portion attached to thefirst and second leg members, a flexible portion suitable for wrapping over the barsand a fastener to affix the flexible portion to the arc-shaped receiving portion or oneof the first leg members such that transverse and vertical movement of the bars islimited and longitudinal movement of bars is allowed. The chair is also provided witha centrally arranged spike extending downwards from the cradle and downwardspast the base, intended to be forced into the ground.

AU564990 discloses a bar chair adapted to support reinforcement re-bars inconcrete. The re-bar chair has an upstanding portion connected with its lower endwith a main base portion and includes at its upper end a support head having acavity formed therein which can receive and retain a reinforcement bar. The cavityhas a base portion which is fixed at a predetermined fixed distance from said baseportion.

WO2010049691 discloses a spacer for reinforcement to be hold in a defineddistance from a support/shutter during pouring of concrete. The spacer comprises arigid base member which can be welded to said support. By welding thereinforcement to the spacer a prefabricated reinforcement cage for later installationon site is provided. The spacer is typically made of several materials. For reinforcement elements of steel, the reinforcement is welded to a spacer contactelement of steel.

There is a need for a robust chair that may be affixed to a water tightmembrane or lining without puncturing the lining and which in a quick and efficientmanner may be fixed to the lining. l\/loreover there is a need for a chair that allowsquick and efficient mounting on-site of the reinforcement and where thereinforcement is maintained in the intended position subsequent to fixing and duringthe shotcreting process where both, the chair, the lining, and the fixation of the chairto the lining are subjected to large forces and rough impact. Furthermore, there is aneed for a chair and a method which allows a secure supporting of the reinforcementindependently of the position and orientation of the chair to which the reinforcementis attached to, also including chairs fixed to the lining which are vertically arranged orbeing attached to the roof of a tunnel. lt should be appreciated that the lining on the one hand, although fixed to thetunnel wall by means of the rock anchors, is flexible and pliable, so that the distancebetween the lining and the established or mounted reinforcement may vary due tosaid flexibility. On the other hand the reinforcement fixed to the rock anchors forms aquite rigid frame structure. Because of the varying distance between the fixed rein-forcement and the flexible lining, and in order to secure an even distance betweenthese two elements, chairs are used. Said chairs are fixed subsequent to mountingof the lining and reinforcement on the surface to be concreted, the chairs being usedto obtain the correct distance between the lining and the fixed reinforcement. As aconsequence sometimes the lining must be pushed away from the reinforcementand in other instances the chairs are used to pull the lining towards the fixedreinforcement. lt is therefor a need for a chair and a fixing method that secureadequate fixing very quickly, enabling pulling or pushing the lining into requiredposition rapidly after fixing of the chair.

Summary of the lnvention An object of the present invention is to provide a method and a chair suitablefor affixing reinforcement bars or nets to a membrane covering the roof and walls forexample in tunnels, forming reinforcement for shotcrete shot onto the wall/roof. lnparticular it is an object of the present invention to provide a method which is suitablefor effective affixing of a chair to membranes which are flexible and not rigid.

Another object of the present invention is to provide a chair which quickly canbe fixed on-site to a supporting surface by thermal hot gas such as hot air welding,either vertical; curved or downwards hanging from a roof surface and at the same time being easy to manufacture, leaving the casting mould easily; and also beingconfigured to easily receiving the reinforcement bars or nets to be supported.

Yet another object of the present invention is to provide a chair and a methodfor affixing the chair and also the reinforcement to be supported in an attractivemanner for the operator to establish the reinforcement for subsequent concreting orshotcreting.

A further object of the present invention is to provide a chair and a method forfixing the chair to a membrane or a lining that may resist the forces and impactimposed by concrete shot onto the lining and reinforcement during the shotcretingprocess.

A further object of the present invention is to provide a chair and a methodthat allows an effective locking and fixing mechanism of the reinforcement bar to achair attached on a lining or membrane which is either vertical; curved or downwardshanging from a roof surface, such as on walls and roofs of a tunnel.

A still further object of the present invention is to provide a chair and a methodfor fixing the chair to the membrane that provide a robust and rigid connectionbetween the chair and the membrane or lining, also including flexible types ofmembranes, without puncturing the lining during the fixing stage or duringshotcreting.

The objects are achieved by a chair and a method for affixing such chair to asupporting surface as further defined by the independent claims, while embodiments,alternatives, modifications and variants are defined by the dependent claims.

The present invention relates in one aspect to a suitable chair for supporting areinforcement element for concrete on a supporting surface, for example arrangedon a tunnel wall or roof surface. Said chair is made of a plastic material andcomprises a base member configured to be attached to the supporting surface;preferably an intermediate part fixed to and extending out from one side of the basemember and a reinforcement bar locking device arranged at an opposite end of theintermediate part the locking device being provided with a member for receiving thereinforcement element. The chair is fixed by welding to the supporting surface andboth the supporting surface and at least the base member of the chair are made ofplastic materials suitable for welding by a hot medium, such as air.

The base can be bendable or flexible. The advantage of a pliable/deflectablebase member is a simplified and improved fixation of the base member to thesupport surface during thermal welding, in particular being also suitable forapplication in combination with a flexible support surface. Preferably, the chair has a thickness and/or material flexibility that enables the base to be bent at a rim point orportion during an initial stage of installation.

The bottom surface of the base, configured to face towards the supporting surface,can be provided with fins, ridges, points or protrusions or unevenness. Suchoutwards projections may enhance the welding process and the end result.

The intermediate part can be in the form of a single stem projecting outwardsfrom the base and forming an integrated part with the base.

The bar locking device can be in a form of at least one outwardly deflectablesurface, enabling the reinforcement member to be snapped into an aperture of thelocking device. Preferably, the at least one outwards deflecting surface is uponcompleted receipt of a reinforcement element bent or pressed together, enablingwelding to an adjacent surface, thereby closing the snapping part of the lockingdevice. ln another aspect the present invention relates to a method for fixing areinforcement element for concrete on a supporting surface in a predetermineddistance from said supporting surface, where a chair for supporting thereinforcement element is connected to the supporting surface, the chair being madeof plastic and comprising a base member configured to be attached to thesupporting surface and a reinforcement bar locking device for receiving and lockingthe reinforcement element. The supporting surface and at least the base member ofthe chair are made of plastic materials suitable for welding by hot air. Said methodcomprises the following steps: (i) heating of the bottom surface of the chairs base and/or of the supporting surface by hot air,(ii) pressing the heated surface of the base of the chair onto the supportingsurface, (iii) affixing the reinforcement bar to the locking device. ln a preferred method according to the present invention, the base of the chair isbendable and both the supporting surface and adjoining surface of the base isheated and then pressed together. Preferably, the reinforcement element is insertedand snapped into an aperture in the reinforcement bar locking device. lt is further preferred that hot air is blown in along the supporting surface underthe bottom surface of the chair, and that a slot is provided during the initial stage ofthe heating into which hot air is blown, enabling at least the bottom surface of thebase and possibly also the supporting surface to be exposed to the heat, whereuponthe heated base is pressed down into contact with the preferably heated supportingsurface.

The chair can be tilted slightly, forming for example an initial angle in the order of45 degree between the supporting surface and the bottom surface of the chair.

During this stage the portion of the base is in contact, the contact being on theopposite side of the heating source, the base surface portion being pressed downonto the supporting surface. During at least this initial stage, the surface of the basesurface receives a curved surface, the base being pressed down towards thesupporting surface.

Preferably, the hot air supplied is in the region of 500 °C; the surfaces beingheated for 2 to 6 seconds; and then the surface of the chair to be attached ispressed onto the heated supporting surface. l\/loreover, the opening in the locking device for inserting of the reinforcementelement into the aperture is closed upon completed insert of the reinforcementelement into the aperture. Preferably, the opening is closed by means of welding bywelding using hot air from a heat generating device.

For additional measure securing that the assembled reinforcement bars do notunintentionally dropping out of the locking element, the chair is oriented in such wayon a more or less vertical surface that the opening is oriented upwards.

The material used for fabricating the chair may be any suitable plastic materialwhich is stable enough for the purpose of the invention and can be welded to thelining by heat. Preferably, not necessarily the chair is made of polyolefin. lt should beappreciated that tests has shown that the welded chair in fixed, welded position maywithstand loads exceeding 500 Newton, in fact up to 1000 Newton.

Preferably, all parts of the chair are made of the same material and are producedas an integrated structure. This facilitates the manufacturing process and is thuseconomically more preferred. However, the skilled person will understand that theinvention is not restricted to a chair which is only produced from one material.Although, less preferred, the chair may comprise a combination of different materialssuch as metal and plastic components with the precondition that those parts to bewelded are made of a material suitable for thermo-welding such as by hot air/gas i.e.the base member to be welded on the supporting surface and/or the surfaces of thelips belonging to the reinforcement locking device.

According to the present invention the time taken for fixing the chair to thesupporting surface or wall is in the order of up to five to six seconds and sufficientfixing force is instantaneously achieved. This means that the time taken forestablishing a completely reinforced wall or surface may be substantially reduced,resulting in considerate construction time and cost saving and a more efficientconstruction process. lt should also be appreciated that the fixation force, i.e. the binding forcebetween the base of the chair and the supporting lining or membrane is enhanced.The chair according to the present invention may also be welded to insulation liningswith the same degree of success.

According to the present invention a method and a chair that is endurablyfixed to the lining, being immediately or at least within a timeframe of maximum 10seconds, able to resist the pushing or pulling forces on the joint between the base ofthe chair and the lining without breaking, are obtained.

Brief Description of the Drawings ln the following embodiments of the invention shall be described in closerdetails, referring to the accompanying drawings, wherein: Figure 1 shows schematically a cross section through a tunnel, prior toshotcreting, indicating a lining, a plurality of chairs and affixed reinforcement; Figure 2 shows schematically a section of a wall surface, indication horizontaland vertical reinforcement, supported by chairs; Figure 3 shows schematically a side view of one embodiment of a chairaccording to the present invention; Figure 4 shows schematically a view of the chair disclosed in Figure 3, rotated90 degrees; Figure 5 shows in enlarged scale a section of the entrance for reinforcementbars in the reinforcement bar locking device, marked by A in Figure 3; Figure 6 shows in enlarged scale a section of the base of the chair, markedwith B in Figure 3; Figure 7 shows schematically a view of the chair disclosed in figures 3 and 4,seen from above; Figure 8 shows schematically a bottom view of the chair, indicating the bottomsurface of the base member intended to be faced towards the lining.

Figure 9 shows schematically a first stage in the process of affixing a chair toa supporting surface, where only a rear part of the base is in contact with thesupporting surface, the rear part being pressed downwards towards the supportingsurface; Figure 10 shows schematically a second step in the affixing process, where athermal heat source adds heat to the contact surface of the base and thecorresponding supporting surface; Figure 11 shows schematically a third stage where the heat source is in theprocess of being retracted from the slot between supporting surface and the corresponding bottom surface of the base, while increasing areas of the heated basesurface is in the process of coming into contact with the corresponding heatedsurface of the supporting surface; Figure 12 shows schematically the stage where the chair is fixed to thesupporting surface, ready to receive the reinforcement e|ement(s); Figure 13 shows schematically a possible next stage in the process of affixingreinforcement to the supporting surface, where a reinforcement bar is in the processof being inserted in the bar Iocking device; Figure 14 shows schematically a stage where the reinforcement bar has beeninserted into a centrally arranged aperture of the chair; Figure 15 shows schematically a stage where guiding lips forming theentrance to the aperture of the bar Iocking device is in the process of being heatedas a preparation for c|osing the entrance; and Figure 16 shows schematically the stage where the thermal heat source is inthe process of being retracted and the guiding lips are welded together.

Detailed Description of Embodiments disc/osed in the Drawings The following description of the exemplary embodiments refers to theaccompanying drawings. The same reference numbers in different drawings identifythe same or similar elements. The following detailed description does not limit theinvention. lnstead, the scope of the invention is defined by the appended claims. Thefollowing embodiments are discussed, for simplicity, with regard to a method forwelding a chair to a lining or to insulation, creating a proper and adequate fixing of thechair to the supporting surface.

Reference throughout the specification to “one embodiment” or “anembodiment” means that a particular feature, structure, or characteristic described inconnection with an embodiment is included in at least one embodiment of the subjectmatter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in anembodiment” in various places throughout the specification is not necessarily referringto the same embodiment. Further, the particular features, structures, or characteristicsmay be combined in any suitable manner in one or more embodiments.

Figure 1 shows schematically a cross section through a tunnel 10, prior toshotcreting, indicating a lining/ supporting surface11, a plurality of chairs 12 andaffixed reinforcement bars 20. As indicated the lining 11 is fixed to the rock by meansof bolts 14 drilled into the surrounding rock and penetrating the lining 11. ln order tosecure water tightness the penetration is sealed and conventional sealing materialwith load distributing discs (not shown) are used. The lining 11 may be of flexible and bendable sheets extending for example as a unit following the entire profile shape ofthe tunnel 10. ln the longitudinal direction of the tunnel 10, sections of transverselyextending lining sheets 11 are arranged in an overlapping pattern.

Typically, the lining/supporting surface 11 used in accordance with the presentinvention is flexible and not rigid, although the skilled person will understand that themethod for fixation and the use of the chair according to the present invention arenot necessarily restricted to such flexible linings.

As indicated on the right side of Figure 1 with a shaded area (also indicatedby an arrow in the right lower corner of the drawing) concrete has been castedshowing both the filling between the supporting lining 11, the reinforcement 20 and inaddition the required outer layer of concrete for coverage of the reinforcement 20,covering the spies 18.

Figure 2 shows schematically a section of a wall surface, indication ofhorizontal and vertical reinforcement bars 20,20”, supported by chairs 12 configuredin a pre-determined pattern.

Figure 3 shows schematically a side view of one embodiment of a chair 12according to the present invention. As indicated the disclosed embodiment of thechair 12 comprises a base member 15 having a circular foot print; an intermediatepart 16 in form of a stem projecting upwards from the base 15; a reinforcement barlocking device 17; and a spy 18. The purpose of the spy 18 is to serve as anindicator for required concrete thickness during the shotcreting process. Concrete isshot on to the supporting element and the concrete so as to achieve an eventhickness of concrete over the entire surface of the supporting surface. The length ofthe spy 18 is chosen so as to secure sufficient concrete coverage for thereinforcement. The spy is a preferred, optional feature and may be omitted. l\/loreover, it should be appreciated that the distance from the base 15 to thereinforcement bar locking device 17 is configured such that sufficient concrete mayalso be placed between the supporting surface 11 and the reinforcement 20.

The reinforcement bar locking device 17 comprises a ventrally arrangedaperture 19 with an area somewhat larger than the cross sectional area of thereinforcement bar 20 to be inserted into the aperture (locking or entrance space) 19.ln order to enable reinforcement bars 20 to be inserted into the aperture 19, thereinforcement bar locking device 17 is provided with a opening/throat 21 through thesidewall to enable the reinforcement bar 20 to be inserted sideways into the aperture19. ln order to ease such insertion, the throat 21 is associated with centering devicesin the form of two outwardly deflectable surfaces /lips 22 extending sideways outfrom the throat 21. As shown in Figure 3, the cross sectional area between the lips 11 22 is typically increasing outwards and at the outer end, the cross sectional area ofsaid opening is equal to or larger than the cross sectional area of the reinforcementbar to be sideways inserted between the lips 22, through the throat 21 into theaperture 19.

Figure 4 shows schematically a view of the chair 12 disclosed in Figure 3,rotated 90 degrees.

Figure 5 shows in enlarged scale a section of the entrance for reinforcementbar 20 in the reinforcement bar locking device 17, marked by A in Figure 3. Asshown, the entrance is formed of two lips 22 establishing an opening or a slotextending inwards to the central aperture 19 through a throat 21. The dimensionsand the material used in the lips 22 are configured such that the throat 21 may beforced more open when introducing a reinforcement bar 20 sideways into theaperture 19. l\/loreover, the lips 22 are also configured such that the lips 22 may bepressed or forced together when closing the throat subsequent to insertion of thereinforcement bar 20. Preferably, the lips are deflectable for this purpose allowingthat the inner surfaces of the lips contact each other when pressed towards eachother. The surfaces of the lips 22 can be permanently fixed and closed by means ofthermal welding. The inner surfaces of the lips 22 are for the welding purposepreferably provided with a slightly uneven surface, for example formed by beans orbulbs or fins 23. The uneven surfaces contribute to an improved welding process.

Figure 6 shows in enlarged scale a section of the base 15 of the chair 12,marked with B in Figure 3. As indicated, the bottom surface 24 of the base 15intended to face the supporting surface or lining 11 is preferably provided with aslightly uneven surface, for example formed by beans or bulbs or fins 23.

Figure 7 shows schematically a view of the chair 12 disclosed in figures 3 and4, seen from above. The Figure indicates the base 15, the reinforcement bar lockingdevice 17 and the spy 18. As indicated the lips 22 projects more or less sideways outfrom the reinforcement bar locking device 17, while the spy 18 projects more or lessperpendicular up from the reinforcement bar locking device 17.

Figure 8 shows schematically a bottom view of the chair 12, indicating thebottom surface 24 intended to be faced towards the lining 11. ln order to secureadequate welded contact fixing the chair securely to the lining, the bottom surface ispreferably provided with a slightly uneven surface, for example formed by beans orbulbs or fins 23. l\/loreover, parallel beads 23 are disclosed.

Figure 9 shows schematically a first stage in the process of affixing a chair 12to a supporting surface 11, where only a rear part of the base 15 is in contact withthe supporting surface 11, the rear part being pressed downwards towards the 12 supporting surface 11. As a consequence, a gap 26 is formed and the half of thebase in the region of its contact point with the supporting surface 11 will be bentwhile the remaining part, i.e. the fore part of the base 15 will remain more or lessplane.

Figure 10 shows schematically a second step in the affixing process, where athermal heat source 25, such as a heat pistol or gun, adds heat to the contactsurface 24 of the base 15 and the corresponding supporting surface 11. Preferably,the thermal fluid used may be air, and the temperature may for example be around500 °C. As the surfaces are heated, for example for 2 to 6 seconds the outer layer,the boundary layer, on both surfaces 24,11 is softened or partly melted along thesurface, whereupon the heat source 25 is retracted and the a tilting force (ref. thearrow), is applied to the chair, thereby increasing gradually the contact area betweenthe bottom surface 24 of the base 15 and the upper surface of the supportingsurface 11. Such retracting movement of the heat source 25 is indicated by thearrow in Figure 10.

The skilled person in the field is well known with different types of heatpistols/guns and these are therefore not described in more detail. Furthermore, theskilled person would understand that other types of thermal heat sources 25 may beused in the welding process apart from hot air emitting sources, although the laterones are preferred.

Figure 11 shows schematically a third stage where the heat generating source25 is completely retracted and the front end of the base 15 is pressed downwardstowards the supporting surface 11.

Figure 12 shows schematically the stage where the thermal heat source 25is completely retracted, the entire base15 area of the chair 12 is in complete contactwith the supporting surface 11 and the chair 12 is fixed to the supporting surface 11,ready to receive the reinforcement element(s) 20.

The base member 15 can be bendable due to the type and structure of thechosen material and/or the thickness and shape of the base member. Theadvantage of this feature is an improved contact of the bottom surface of the base 15and the supporting surface 11 during the welding process. Furthermore, a non-rigidbase member allows a more effective application of the above described method ofheating whereby the supporting surface 11 and the bottom surface 24 can be heatedby hot air/gas simultaneously and on-site using the same heat generating device 17,only leaving a narrow slot between them without any danger to puncture or damagethe lining 11 by a rigid base. This is particularly preferred if the lining 11 is flexibleallowing a better and more robust connection. 13 Figure 13 shows schematically a possible next stage in the process of affixingthe reinforcement 20 to the supporting surface 11, where a reinforcement bar 20 is inthe process of being inserted through the lips 22 and the throat 21, into the centrallyarranged aperture 19 of the bar Iocking device 17. Figure 14 shows schematicallythe stage where the reinforcement bar 20 has been inserted into the centrallyarranged aperture 19 of the reinforcement bar Iocking device 17.

Figure 15 shows schematically the stage where the guiding lips 22 are heatedby a thermal heating device 25 as a preparation for closing the lips 22 and the throat21 by thermal welding, ref. the arrows in Figure 15, indicating the closing forceapplied to the lips 22, and Figure 16 shows schematically the completed stage wherethe lips are closed and the thermal heating device 25 is in the process of beingremoved, the reinforcement bar 20 being in locked position. lt should be appreciated that even though all Figures show the supportingsurface 11 to be in a horizontal position, the supporting surface 11 may be vertical orforming part of an arced ceiling, for example in a tunnel, without deviating from theinventive concept. l\/loreover, the chair may have any suitable shape as long as it may bepossible to weld the chair in an appropriate, predetermined manner to the supportingsurface and keeping the reinforcement in a stable, fixed position with respect to thesupporting surface, and as long as the installed reinforcement and the chairs forfixing the reinforcements to the supporting surface also function as a stiffening orreinforcing element also for the supporting surface during shotcreting, where thesupporting surface is subjected to large and heavy impact from the concrete shot onto the surface.

Claims (16)

Claims

1. Chair (12) for supporting a reinforcement element (20) for concrete on asupporting surface (11), for example arranged on a tunnel wall or roof surface, saidchair (12) being made of a plastic material and comprising a base member (15)configured to be attached to the supporting surface (11); preferably an intermediatepart (16) fixed to and extending out from one side of the base member (15) and areinforcement bar locking device (17) fixed to an opposite end of the intermediatepart (16), the locking device (17) being provided with a member for receiving thereinforcement element (20), c h a r a c t e r i z e d i n that the chair (12) is fixed bywelding to the supporting surface (11) and that both the supporting surface (11) andat least the base member (15) of the chair (12) are made of plastic materials suitablefor welding by a hot medium, such as air.

2. Chair (12) according to claim 1, wherein the base (15) is bendable or flexible.

3. Chair (12) according to one of the claims 1 or 2, wherein the bottom surface(24) of the base (15), configured to face towards the supporting surface (11), isprovided with fins, ridges, points or protrusions or unevenness (23).

4. Chair (12) according to one of the claims 1 to 3, wherein the chair (15) has athickness and/or material flexibility that enables the base (15) to be bent at a rimpoint or portion (B) during an initial stage of installation.

5. Chair (12) according to one of the claims 1 to 4 , wherein the intermediate part(16) is in the form of a single stem projecting outwards from the base (15) andforming an integrated part with the base (15).

6. Chair (12) according to one of the claims 1 to 5, wherein the bar lockingdevice (17) is in a form of at least one outwardly deflectable surface (22), enablingthe reinforcement member (20) to be snapped into an aperture (19) of the lockingdevice (17).

7. Chair (12) according to claim 6, wherein the at least one outwards deflectingsurface may upon completed receipt of a reinforcement element be bent or pressedtogether, enabling welding to an adjacent surface, thereby closing the snapping partof the locking device.

8. Method for fixing a reinforcement element (20) for concrete on a supportingsurface (11) in a predetermined distance from said supporting surface (11), where achair (12) for supporting the reinforcement element (20) is connected to thesupporting surface (11), the chair being made of p|astic and comprising a basemember (15) configured to be attached to the supporting surface and areinforcement bar Iocking device (17) for receiving and Iocking the reinforcementelement (20) ,c h a r a c t e r i z e d i n that the supporting surface (11) and at least the basemember (15) of the chair (12) are made of p|astic materials suitable for welding byhot air, the method comprising the following steps: (iv)heating of the bottom surface (24) of the chairs (12) base (15) and/or of the supporting surface (11) by hot air,(v) pressing the heated surface of the base (15) of the chair (12) onto thesupporting surface (11),(vi) affixing the reinforcement bar to the Iocking device (17).

9. l\/lethod according to claim 8, wherein the base (15) of the chair (12) isbendable and that both the supporting surface (11) and adjoining surface of the baseis heated and then pressed together.

10. l\/lethod according to claim 8 or 9, wherein the reinforcement element (20) isinserted and snapped into an aperture (19) in the reinforcement bar Iocking device(17).

11. l\/lethod according to one of the claims 8 to 10, wherein hot air is blown inalong the supporting surface (11) under the bottom surface (24) of the chair (12),and that a slot is provided during the initial stage of the heating into which hot air isblown, enabling at least the bottom surface (24) of the base (15) and possibly alsothe supporting surface (11) to be exposed to the heat, whereupon the heated base(15) is pressed down into contact with the preferably heated supporting surface (11).

12. l\/lethod according to claim one of the claims 8 to 11, wherein the chair (12)preferably is tilted slightly, forming for example an initial angle in the order of 45degree between the supporting surface (11) and the bottom surface (24) of the chair(12), the portion of the base (15) in contact with the supporting surface (11) being onopposite side of the heating source (25), and the initial bottom surface forming a 16 curved surface, where after the base (15) being pressed down towards thesupporting surface (11).

13. Method according to one of the claims 8-12, wherein the air temperature ofthe hot air supplied is in the region of 500 °C; the surfaces (11, 24) being heated for2 to 6 seconds; and then the surface (24) of the chair (12) to be attached is pressedonto the heated supporting surface (11).

14. l\/lethod according to one of the claims 10-13, wherein the opening (21) in theIocking device (17) for inserting of the reinforcement element into the aperture (19)is closed upon completed insert of the reinforcement element (20) into the aperture(19).

15. l\/lethod according to claim 14, wherein the opening (21) is closed by meansof welding by welding using hot air from a heat generating device (25).

16. l\/lethod according to one of the claims 8 to 15, wherein the chair (12) isoriented in such way on a more or less vertical surface that the opening (21) isoriented upwards.