SE542163C2 - 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.

Description

Chair and Method for Fixing Chair to a Supporting Surface The Technical Field of the Invention The present invention relates to a chair for supporting a reinforcement element for concrete on a supporting surface, for example arranged on a tunnel wall or roof surface, said chair being made of a plastic material and 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 member and a reinforcement bar locking device fixed to an opposite end of the intermediate part, the locking device being provided with a member for receiving the reinforcement element. Furthermore, the present invention relates to a method for fixing a reinforcement element for concrete on a supporting surface in a predetermined distance from said supporting surface, where a chair for supporting the reinforcement element is connected to the supporting surface, the chair being made of plastic and comprising a base member configured to be attached to the supporting surface and a reinforcement bar locking device for receiving and locking the reinforcement element.

Background for the Invention In many cases, there is a need for a waterproof and/or fire proof lining of a wall or a roof, such as for example the walls and/or roof of a tunnel, and at the same time 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, the lining being arranged as a continuous lining across the tunnel in successive lengthwise sections, forming a water tight barrier. In addition reinforcement is fixed to the same rock anchors whereupon a layer of concrete is shot on to the concrete, the lining serving as formwork for such shotcrete.

In order to reinforce the concrete reinforcement is required, either as reinforcement rebars extending both in a longitudinal direction of the tunnel and also in 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 of the flexible lining from being displaced during concreting and in order to secure the required minimum distance from the lining to the reinforcement and to secure the require coverage of the reinforcement. Hence, it has previously been proposed to use a number of chairs, either fixed to rock behind the lining, or to the lining itself, if possible. Such fixing operation is both tedious and time consuming. At the same time the lining may be excessively punctured, establishing points or areas prone to leakage of water through the lining or membrane.

There exist several prior art solutions for fixing reinforcement to a lining or an insulating liner for walls or tunnels. Typical methods may be to screw the chair into the supporting wall; or to glue the chair to the supporting surface or to allow the chair to rest due to its own weight and the reinforcement on a more or less horizontally oriented supporting surface.

In order to be able to attach the chair by a screwing method, the supporting wall must be of a character allowing a screw end of a chair to be screwed into the supporting wall.

The most pertinent method for attachment closest to the method according to the present invention, and the method with most similar features with the method and chair according to the present invention, is to use glue for attaching and fixing the chair to the supporting surface. Use of glue incorporates a number of inherent drawbacks. Firstly, the glue itself must be of a two-component type, preferably mixed in the outlet of a glue pistol or melt glue pistol. Such glue is expensive, requiring a clean surface in order to secure sufficient and adequate gluing effect. Moreover, such method also requires a period of time for enable the glue to cure. Hence, the method is both expensive due to time taken and the cost of the glue. Moreover, 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 the entire contact area of the chair. As a consequence, it is experienced that some of the chairs drops off during placing of the reinforcement and/or during concreting, the shotcrete being applied at a high impact on the supporting surface, reinforcement and chair. In areas where one or more chairs have dropped off, the supporting surface will yield during the shotcreting operation, forcing the supporting surface outwards towards the tunnel wall behind. In such regions the layer of shotcrete will as a consequence be thicker, thus consuming more concrete than necessary due to the yielding outwards, thus increasing the time taken for the concreting process and the added volume of concrete necessary.

From NO 333588 it is known a chair for fixing reinforcement nets or bar at a predetermined distance from an insulated tunnel wall. The chair comprises a threaded section intended to be screwed into the insulating material until a stop surface enters into engagement with the surface of the insulation. A part of the chair is configured to project outwards from the insulation with two parallel discs arranged at a predefined distance from the insulation, securing adequate position for the reinforcement 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 concrete coverage is obtained in the shotcreting process or not.

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

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

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

WO2010049691 discloses a spacer for reinforcement to be hold in a defined distance from a support/shutter during pouring of concrete. The spacer comprises a rigid base member which can be welded to said support. By welding the reinforcement to the spacer a prefabricated reinforcement cage for later installation on site is provided. The spacer is typically made of several materials. For reinforcement elements of steel, the reinforcement is welded to a spacer contact element of steel.

There is a need for a robust chair that may be affixed to a water tight membrane or lining without puncturing the lining and which in a quick and efficient manner may be fixed to the lining. Moreover there is a need for a chair that allows quick and efficient mounting on-site of the reinforcement and where the reinforcement is maintained in the intended position subsequent to fixing and during the shotcreting process where both, the chair, the lining, and the fixation of the chair to the lining are subjected to large forces and rough impact. Furthermore, there is a need for a chair and a method which allows a secure supporting of the reinforcement independently of the position and orientation of the chair to which the reinforcement is attached to, also including chairs fixed to the lining which are vertically arranged or being attached to the roof of a tunnel.

It should be appreciated that the lining on the one hand, although fixed to the tunnel wall by means of the rock anchors, is flexible and pliable, so that the distance between the lining and the established or mounted reinforcement may vary due to said flexibility. On the other hand the reinforcement fixed to the rock anchors forms a quite rigid frame structure. Because of the varying distance between the fixed reinforcement and the flexible lining, and in order to secure an even distance between these two elements, chairs are used. Said chairs are fixed subsequent to mounting of the lining and reinforcement on the surface to be concreted, the chairs being used to obtain the correct distance between the lining and the fixed reinforcement. As a consequence sometimes the lining must be pushed away from the reinforcement and in other instances the chairs are used to pull the lining towards the fixed reinforcement. It is therefor a need for a chair and a fixing method that secure adequate fixing very quickly, enabling pulling or pushing the lining into required position rapidly after fixing of the chair.

Summary of the Invention An object of the present invention is to provide a method and a chair suitable for affixing reinforcement bars or nets to a membrane covering the roof and walls for example in tunnels, forming reinforcement for shotcrete shot onto the wall/roof. In particular it is an object of the present invention to provide a method which is suitable for 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 can be 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 being configured 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 method for affixing the chair and also the reinforcement to be supported in an attractive manner for the operator to establish the reinforcement for subsequent concreting or shotcreting.

A further object of the present invention is to provide a chair and a method for fixing the chair to a membrane or a lining that may resist the forces and impact imposed by concrete shot onto the lining and reinforcement during the shotcreting process.

A further object of the present invention is to provide a chair and a method that allows an effective locking and fixing mechanism of the reinforcement bar to a chair attached on a lining or membrane which is either vertical; curved or downwards hanging 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 method for fixing the chair to the membrane that provide a robust and rigid connection between the chair and the membrane or lining, also including flexible types of membranes, without puncturing the lining during the fixing stage or during shotcreting.

The objects are achieved by a chair and a method for affixing such chair to a supporting 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 a reinforcement element for concrete on a supporting surface, for example arranged on a tunnel wall or roof surface. Said chair is made of a plastic material and comprises 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 member and a reinforcement bar locking device arranged at an opposite end of the intermediate part the locking device being provided with a member for receiving the reinforcement element. The chair is fixed by welding to the supporting surface and both the supporting surface and at least the base member of the chair are made of plastic materials suitable for welding by a hot medium, such as air.

The base can be bendable or flexible. The advantage of a pliable/deflectable base member is a simplified and improved fixation of the base member to the support surface during thermal welding, in particular being also suitable for application 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 or portion 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. Such outwards projections may enhance the welding process and the end result.

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

The bar locking device can be in a form of at least one outwardly deflectable surface, enabling the reinforcement member to be snapped into an aperture of the locking device. Preferably, the at least one outwards deflecting surface is upon completed receipt of a reinforcement element bent or pressed together, enabling welding to an adjacent surface, thereby closing the snapping part of the locking device.

In another aspect the present invention relates to a method for fixing a reinforcement element for concrete on a supporting surface in a predetermined distance from said supporting surface, where a chair for supporting the reinforcement element is connected to the supporting surface, the chair being made of plastic and comprising a base member configured to be attached to the supporting surface and a reinforcement bar locking device for receiving and locking the reinforcement element. The supporting surface and at least the base member of the chair are made of plastic materials suitable for welding by hot air. Said method comprises 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 supporting surface, (iii) affixing the reinforcement bar to the locking device.

In a preferred method according to the present invention, the base of the chair is bendable and both the supporting surface and adjoining surface of the base is heated and then pressed together. Preferably, the reinforcement element is inserted and snapped into an aperture in the reinforcement bar locking device.

It is further preferred that hot air is blown in along the supporting surface under the bottom surface of the chair, and that a slot is provided during the initial stage of the heating into which hot air is blown, enabling at least the bottom surface of the base and possibly also the supporting surface to be exposed to the heat, whereupon the heated base is pressed down into contact with the preferably heated supporting surface.

The chair can be tilted slightly, forming for example an initial angle in the order of 45 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 the opposite side of the heating source, the base surface portion being pressed down onto the supporting surface. During at least this initial stage, the surface of the base surface receives a curved surface, the base being pressed down towards the supporting surface.

Preferably, the hot air supplied is in the region of 500 °C; the surfaces being heated for 2 to 6 seconds; and then the surface of the chair to be attached is pressed onto the heated supporting surface.

Moreover, the opening in the locking device for inserting of the reinforcement element into the aperture is closed upon completed insert of the reinforcement element into the aperture. Preferably, the opening is closed by means of welding by welding using hot air from a heat generating device.

For additional measure securing that the assembled reinforcement bars do not unintentionally dropping out of the locking element, the chair is oriented in such way on a more or less vertical surface that the opening is oriented upwards.

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

Preferably, all parts of the chair are made of the same material and are produced as an integrated structure. This facilitates the manufacturing process and is thus economically more preferred. However, the skilled person will understand that the invention is not restricted to a chair which is only produced from one material.

Although, less preferred, the chair may comprise a combination of different materials such as metal and plastic components with the precondition that those parts to be welded 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 the lips belonging to the reinforcement locking device.

According to the present invention the time taken for fixing the chair to the supporting surface or wall is in the order of up to five to six seconds and sufficient fixing force is instantaneously achieved. This means that the time taken for establishing a completely reinforced wall or surface may be substantially reduced, resulting in considerate construction time and cost saving and a more efficient construction process.

It should also be appreciated that the fixation force, i.e. the binding force between 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 linings with the same degree of success.

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

Brief Description of the Drawings In the following embodiments of the invention shall be described in closer details, referring to the accompanying drawings, wherein: Figure 1 shows schematically a cross section through a tunnel, prior to shotcreting, indicating a lining, a plurality of chairs and affixed reinforcement; Figure 2 shows schematically a section of a wall surface, indication horizontal and vertical reinforcement, supported by chairs; Figure 3 shows schematically a side view of one embodiment of a chair according to the present invention; Figure 4 shows schematically a view of the chair disclosed in Figure 3, rotated 90 degrees; Figure 5 shows in enlarged scale a section of the entrance for reinforcement bars 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, marked with 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 bottom surface 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 to a supporting surface, where only a rear part of the base is in contact with the supporting surface, the rear part being pressed downwards towards the supporting surface; Figure 10 shows schematically a second step in the affixing process, where a thermal heat source adds heat to the contact surface of the base and the corresponding supporting surface; Figure 11 shows schematically a third stage where the heat source is in the process of being retracted from the slot between supporting surface and the corresponding bottom surface of the base, while increasing areas of the heated base surface is in the process of coming into contact with the corresponding heated surface of the supporting surface; Figure 12 shows schematically the stage where the chair is fixed to the supporting surface, ready to receive the reinforcement element(s); Figure 13 shows schematically a possible next stage in the process of affixing reinforcement to the supporting surface, where a reinforcement bar is in the process of being inserted in the bar locking device; Figure 14 shows schematically a stage where the reinforcement bar has been inserted into a centrally arranged aperture of the chair; Figure 15 shows schematically a stage where guiding lips forming the entrance to the aperture of the bar locking device is in the process of being heated as a preparation for closing the entrance; and Figure 16 shows schematically the stage where the thermal heat source is in the process of being retracted and the guiding lips are welded together.

Detailed Description of Embodiments disclosed in the Drawings The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a method for welding a chair to a lining or to insulation, creating a proper and adequate fixing of the chair to the supporting surface.

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

Figure 1 shows schematically a cross section through a tunnel 10, prior to shotcreting, indicating a lining/ supporting surfacel 1, a plurality of chairs 12 and affixed reinforcement bars 20. As indicated the lining 11 is fixed to the rock by means of bolts 14 drilled into the surrounding rock and penetrating the lining 11. In order to secure water tightness the penetration is sealed and conventional sealing material with 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 of the tunnel 10. In the longitudinal direction of the tunnel 10, sections of transversely extending lining sheets 11 are arranged in an overlapping pattern.

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

As indicated on the right side of Figure 1 with a shaded area (also indicated by an arrow in the right lower corner of the drawing) concrete has been casted showing both the filling between the supporting lining 11, the reinforcement 20 and in addition 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 of horizontal and vertical reinforcement bars 20,20’, supported by chairs 12 configured in a pre-determined pattern.

Figure 3 shows schematically a side view of one embodiment of a chair 12 according to the present invention. As indicated the disclosed embodiment of the chair 12 comprises a base member 15 having a circular foot print; an intermediate part 16 in form of a stem projecting upwards from the base 15; a reinforcement bar locking device 17; and a spy 18. The purpose of the spy 18 is to serve as an indicator for required concrete thickness during the shotcreting process. Concrete is shot on to the supporting element and the concrete so as to achieve an even thickness of concrete over the entire surface of the supporting surface. The length of the spy 18 is chosen so as to secure sufficient concrete coverage for the reinforcement. The spy is a preferred, optional feature and may be omitted.

Moreover, it should be appreciated that the distance from the base 15 to the reinforcement bar locking device 17 is configured such that sufficient concrete may also be placed between the supporting surface 11 and the reinforcement 20.

The reinforcement bar locking device 17 comprises a ventrally arranged aperture 19 with an area somewhat larger than the cross sectional area of the reinforcement bar 20 to be inserted into the aperture (locking or entrance space) 19. In order to enable reinforcement bars 20 to be inserted into the aperture 19, the reinforcement bar locking device 17 is provided with a opening/throat 21 through the sidewall to enable the reinforcement bar 20 to be inserted sideways into the aperture 19. In order to ease such insertion, the throat 21 is associated with centering devices in the form of two outwardly deflectable surfaces /lips 22 extending sideways out from the throat 21. As shown in Figure 3, the cross sectional area between the lips 22 is typically increasing outwards and at the outer end, the cross sectional area of said opening is equal to or larger than the cross sectional area of the reinforcement bar to be sideways inserted between the lips 22, through the throat 21 into the aperture 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 reinforcement bar 20 in the reinforcement bar locking device 17, marked by A in Figure 3. As shown, the entrance is formed of two lips 22 establishing an opening or a slot extending inwards to the central aperture 19 through a throat 21. The dimensions and the material used in the lips 22 are configured such that the throat 21 may be forced more open when introducing a reinforcement bar 20 sideways into the aperture 19. Moreover, the lips 22 are also configured such that the lips 22 may be pressed or forced together when closing the throat subsequent to insertion of the reinforcement bar 20. Preferably, the lips are deflectable for this purpose allowing that the inner surfaces of the lips contact each other when pressed towards each other. The surfaces of the lips 22 can be permanently fixed and closed by means of thermal welding. The inner surfaces of the lips 22 are for the welding purpose preferably provided with a slightly uneven surface, for example formed by beans or bulbs 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 15 intended to face the supporting surface or lining 11 is preferably provided with a slightly 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 and 4, seen from above. The Figure indicates the base 15, the reinforcement bar locking device 17 and the spy 18. As indicated the lips 22 projects more or less sideways out from the reinforcement bar locking device 17, while the spy 18 projects more or less perpendicular up from the reinforcement bar locking device 17.

Figure 8 shows schematically a bottom view of the chair 12, indicating the bottom surface 24 intended to be faced towards the lining 11. In order to secure adequate welded contact fixing the chair securely to the lining, the bottom surface is preferably provided with a slightly uneven surface, for example formed by beans or bulbs or fins 23. Moreover, parallel beads 23 are disclosed.

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

Figure 10 shows schematically a second step in the affixing process, where a thermal heat source 25, such as a heat pistol or gun, adds heat to the contact surface 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 around 500 °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 the surface, whereupon the heat source 25 is retracted and the a tilting force (ref. the arrow), is applied to the chair, thereby increasing gradually the contact area between the bottom surface 24 of the base 15 and the upper surface of the supporting surface 11. Such retracting movement of the heat source 25 is indicated by the arrow in Figure 10.

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

Figure 11 shows schematically a third stage where the heat generating source 25 is completely retracted and the front end of the base 15 is pressed downwards towards the supporting surface 11.

Figure 12 shows schematically the stage where the thermal heat source 25 is completely retracted, the entire basel 5 area of the chair 12 is in complete contact with 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 the chosen material and/or the thickness and shape of the base member. The advantage of this feature is an improved contact of the bottom surface of the base 15 and the supporting surface 11 during the welding process. Furthermore, a non-rigid base member allows a more effective application of the above described method of heating whereby the supporting surface 11 and the bottom surface 24 can be heated by 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 damage the lining 11 by a rigid base. This is particularly preferred if the lining 11 is flexible allowing a better and more robust connection.

Figure 13 shows schematically a possible next stage in the process of affixing the reinforcement 20 to the supporting surface 11, where a reinforcement bar 20 is in the process of being inserted through the lips 22 and the throat 21, into the centrally arranged aperture 19 of the bar locking device 17. Figure 14 shows schematically the stage where the reinforcement bar 20 has been inserted into the centrally arranged aperture 19 of the reinforcement bar locking device 17.

Figure 15 shows schematically the stage where the guiding lips 22 are heated by a thermal heating device 25 as a preparation for closing the lips 22 and the throat 21 by thermal welding, ref. the arrows in Figure 15, indicating the closing force applied to the lips 22, and Figure 16 shows schematically the completed stage where the lips are closed and the thermal heating device 25 is in the process of being removed, the reinforcement bar 20 being in locked position.

It should be appreciated that even though all Figures show the supporting surface 11 to be in a horizontal position, the supporting surface 11 may be vertical or forming part of an arced ceiling, for example in a tunnel, without deviating from the inventive concept.

Moreover, the chair may have any suitable shape as long as it may be possible to weld the chair in an appropriate, predetermined manner to the supporting surface and keeping the reinforcement in a stable, fixed position with respect to the supporting surface, and as long as the installed reinforcement and the chairs for fixing the reinforcements to the supporting surface also function as a stiffening or reinforcing element also for the supporting surface during shotcreting, where the supporting surface is subjected to large and heavy impact from the concrete shot on to the surface.

Claims (11)

Patent Claims

1. Chair (12) for supporting a reinforcement element (20) for concrete on a supporting surface (11), for example arranged on a tunnel wall or roof surface, said chair (12) being made of a plastic material and comprising a base member (15) configured to be attached to the supporting surface (11); a reinforcement bar locking device (17) being provided with a member for receiving the reinforcement element (20), wherein the locking device (17) is in a form of at least one outwardly deflectable surface (22), enabling the reinforcement element (20) to be snapped into an aperture (19) of the locking device (17), characterzedn that the chair (12) is fixed by welding to the supporting surface (11) and that both the supporting surface (11) and at least the base member (15) of the chair (12) are made of plastic materials suitable for welding by a hot medium, such as air, and wherein the at least one outwards deflecting surface may upon completed receipt of a reinforcement element be bent or pressed together, enabling welding to an adjacent surface, thereby closing the snapping part of the locking device.

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), is provided 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 a thickness and/or material flexibility that enables the base (15) to be bent at a rim point or portion (B) during an initial stage of installation.

5. Chair (12) according to one of the claims 1 to 4, wherein an intermediate part (16), is fixed to and extending out from one side of the base member (15) and the reinforcement bar locking device (17) is fixed to an opposite end of the intermediate part (16), wherein the intermediate part (16) is in the form of a single stem projecting outwards from the base (15) and forming an integrated part with the base (15).

6. Method for fixing a reinforcement element (20) for concrete on a supporting surface (11) in a predetermined distance from said supporting surface (11), where a chair (12) for supporting the reinforcement element (20) is connected to the supporting surface (11), the chair being made of plastic and comprising a base member (15) configured to be attached to the supporting surface and a reinforcement bar locking device (17) with an aperture (19) with an opening (21) for receiving and locking the reinforcement element (20), characterzedn that the supporting surface (11) and at least the base member (15) of the chair (12) are made of plastic materials suitable for welding by hot air, the method further comprising the steps: (i) heating of the bottom surface (24) of the chairs (12) base (15) and/or of the supporting surface (11) by hot air, (ii) welding the base (15) of the chair (12) onto the supporting surface (11), (iii) affixing the reinforcement bar to the locking device (17) by snapping the reinforcement element (20) into the aperture (19) and (iv) closing the opening (21) in the locking device (17) by means of welding using hot air from a heat generating device (25).

7. Method according to claim 6, wherein the base (15) of the chair (12) is bendable and that both the supporting surface (11) and adjoining surface of the base is heated and then pressed together.

8. Method according to claim 6 or 7, wherein hot air is blown in along 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 is blown, enabling at least the bottom surface (24) of the base (15) and possibly also the 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).

9. Method according to claim one of the claims 6 to 8, wherein the chair (12) preferably is tilted slightly, forming for example an initial angle in the order of 45 degree 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 on opposite side of the heating source (25), and the initial bottom surface forming a curved surface, where after the base (15) being pressed down towards the supporting surface (11).

10. Method according to one of the claims 6-9, wherein the air temperature of the hot air supplied is in the region of 500 °C; the surfaces (11, 24) being heated for 2 to 6 seconds; and then the surface (24) of the chair (12) to be attached is pressed onto the heated supporting surface (11).

11. Method according to one of the claims 6 to 10, wherein the chair (12) is oriented in such way on a more or less vertical surface that the opening (21) is oriented upwards.