INTO A FORMWORK

TECHNICAL FIELD

The present invention relates to a nail plate adapted to hold a tubular anchor sleeve or threaded socket when a concrete member is produced. The nail

5 plate is attached to the formwork and the socket is treaded to the nail plate before the concrete is poured into the form. The nail plate is easily attached to the formwork, and may be removed in an easy way after the concrete has set.

BACKGROUND ART

10 Concrete constructions are normally provided with some kind of reinforcement to increase the strength and to prevent cracking. The reinforcement may be single reinforcement bars (rebars), reinforcement grids/meshes, different kinds of fibres or other. The concrete construction may be a preformed part, e.g. a wall or a floor section, which is produced at a production site distant from the building site. The concrete section must in this case be moved from the production site to the building site. For this purpose, it is common to insert one or more anchor points into the concrete section that can be used to lift the concrete section. Such an anchor point often comprises a threaded socket that is moulded into the concrete section,

20 to which a lifting member can be screwed.

Threaded inserts may also be positioned in the concrete section for attaching and holding different objects to the concrete section. It is e.g. possible to insert a number of threaded sockets into a roof section, to which

25 a cable channel and/or armatures can be attached in an easy way. This will save a lot of additional and time consuming work when the installations of a building are completed. Threaded inserts may also be inserted into wall sections or floor sections, adapted to hold other components. Inserts may also be used when securing two adjacent concrete sections to each other. The threaded socket is commonly held by a nail plate during the pouring and setting of the concrete. The nail plate is attached to the formwork prior to pouring, and the socket is threaded to the nail plate. The most common types of nail plates are nailing plates attached by nails or glue nail plates attached to the formwork by glue. Glue nail plates work well in some situations, but rely on a clean and dry formwork to attach properly. They are well suited for vertical sockets but may not hold larger sockets securely in a horizontal direction.

A further purpose of a nail plate is to create a countersink at the threaded socket, such that the top part of the threaded socket is positioned below the concrete surface. A glue nail plate is provided with a flat bottom surface where glue can be applied to the complete bottom surface. Since a glue nail plate is relatively thin, it will create a shallow countersink. A nailing plate has a higher disc section and a hollow body, and the lower bearing surface is not large enough to apply glue on.

Nailing plates are normally attached to the formwork with several nails, in order to secure the nail plate from dislocation due to rotation around a nail. The nail plate may for this reason be provided with several indentations on the disc part of the nail plate, which indicates where a nail is to be inserted. Since the nail plate is hollow, the indentations show the position of a tubular nail guide, which is used to guide and support a nail in a sideway manner. A nail guide is important when relatively thin nails are used to attach a nail plate to a formwork, and may prevent a thin nail from bending.

When the nail plate is attached to the formwork, a socket is threaded to the threaded part of the nail plate, and the concrete is poured. When the concrete has set, the formwork is removed from the concrete section. The nail plate with the nails will release from the formwork and will remain in the concrete. Sometimes, like for glue nail plates, it is possible to unscrew the nail plate directly from the concrete with a rotating movement, but normally, the nail plate adheres too strongly to the concrete to allow for an easy removal. This may be due to the unused indentations of the nail plate but is primarily due to the nail heads that extends above the surface of the nail plate and are moulded to the concrete, which will prohibit the nail plate from being unscrewed. This will require some additional manual work, e.g. by loosening or removing the nails with a plier before the nail plate is unscrewed, which may damage the nail plate such that it can not be unscrewed at all. It may also be necessary to remove the nail plate by a chisel.

EP3569795A1 describes a wedge-shaped nail plate that will allow a threaded socket to be moulded to a concrete section in an angled direction.

DE29820924U1 shows a nail plate that is adapted to be attached to a formwork by a single, central nail. The stud is not threaded and is adapted for holding circular or rectangular sockets by press fit. Since the socket will not be threaded to the stud, there will not be any rotational forces acting on the nail plate that may dislocate the nail plate.

EP3037606B1 , DE8508772U1 , DE19711537A1 and DE2355799 A1 show other examples of nail plates that are adapted to position a socket in a concrete section.

These known nail plates may all be difficult to remove from the set concrete. There is thus room for an improved nail plate.

DISCLOSURE OF INVENTION

An object of the invention is therefore to provide an improved nail plate adapted to hold a threaded socket. The solution to the problem according to the invention is described in the characterizing part of claim 1 regarding the nail plate. The other claims contain advantageous embodiments and further developments of the nail plate.

In a nail plate adapted to hold a threaded socket when pouring concrete, where the nail plate comprises a hollow body, where the nail plate comprises a circular disc section and a stud section, where the disc section is provided with an upper surface, a side surface and a bearing surface, adapted to bear on a formwork for the concrete, where the bearing surface is arranged opposite of the upper surface of the disc section, where the stud section is provided with an outer thread and an upper stud surface having an edge portion and a central section, where the stud section is arranged on the upper surface of the disc section, the object of the invention is achieved in that the nail plate is provided with a central tube that extends downwards from the central section, and that the central section comprises a weakening section that attaches the central tube to the edge portion of the central section.

By this first embodiment of the nail plate according to the invention, a nail plate that can be attached to a formwork in an easy and reliable manner with a screw or a nail is provided. The nail plate will further simplify the removal of the formwork from the set concrete by allowing the screw or nail to detach from the nail plate and to remain attached to the formwork. With the screw or nail detached from the nail plate, the nail plate can be removed from the concrete and the socket by a rotating movement and a tool. The threaded stud may be adapted for threaded sockets having a thread from M8 up to M50 or more. Other types of threads are of course also possible to use.

Since the screw or nail attaches the nail plate to the formwork through the weakening section of the nail plate, the weakening section will break when the formwork is removed. The screw or nail will thus detach from the nail plate and the removal opening of the nail plate can be accessed with a removal tool, without the nail or screw blocking the access to the removal opening.

The weakening section that connects the central tube to the edge portion may consist of several ribs arranged between the edge portion of the nail plate and the central tube. In the shown example, four ribs are used, and a suitable number may be between three to six ribs. The area of the ribs may e.g. constitute half of the area of the weakening section. The thickness of the ribs may be the same as the wall thickness of the edge portion. The wall thickness of the ribs may also be reduced when compared to the wall thickness of the edge portion, or the wall thickness may even be thicker, depending on the width of the ribs. It is however important that the strength of the weakening section is reduced when compared to the edge section, such that the weakening section will break when the formwork is removed from the concrete block.

The weakening section may also consist of a closed circular wall section arranged between the edge portion and the central tube. The wall thickness of the weakening section is in this example reduced when compared to the wall thickness of the edge section, and may e.g. be half or a third of the wall thickness of the edge section.

The central tube preferably comprises an entrance hole in which a screw or nail can be inserted. The central tube may also comprise a closed dimple indicating the position of the central tube, such that an operator easily can position a screw or a nail in the proper orientation. The screw or nail must in this case be forced through the dimple to enter the central tube. The central tube may also be provided with a bevel that corresponds to the conical shape of a screw head.

The bearing surface of the central tube preferably extends to a plane positioned somewhat above the bearing surface of the nail plate. A suitable distance between the bearing surface of the central tube and the bearing surface of the nail plate is 0,2-3 mm, depending on the size of the nail plate and/or the size and thickness of the weakening section. This will allow the circumference of the disc section to be pressed against the formwork when a screw or nail holds the nail plate to the formwork with the tube bearing surface bearing on the formwork. The weakening section will allow the central section to flex somewhat without breaking, such that the screw or nail will pull the nail plate towards the formwork.

In an advantageous development of the invention, the central section is recessed with respect to the edge portion of the stud section. This will allow the edge portion to take the load of a hammer when a nail is used to attach the nail plate to a formwork. This will prevent the central tube to be damaged or deformed by a nail that is inserted too deep, and will prevent the weakening section to break by a nail that is inserted too deep. The recessed central section will also help to prevent a screw to be inserted too deep, when a screw bit holder with an adjustable screw depth or a drywall screwdriver is used. When the outer wall of the screwdriver hits the edge portion, the screw is prevented from being inserted further into the formwork. The entrance hole of the central tube may be bevelled with an angle that corresponds to the countersunk screw head.

The nail plate is also provided with a removal opening at the rear side of the nail plate, arranged inside the disc section. The removal opening is used to unscrew the nail plate from the concrete section and the threaded socket. The removal opening may be straight or may be cross-shaped and is adapted to cooperate with a removal tool that e.g. can be driven by an electric screwdriver.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which

Fig. 1 shows a first embodiment of a nail plate according to the invention,

Fig. 2 shows a cut view of the nail plate of Fig. 1 ,

Fig. 3 shows a nail plate according to the invention from below, and

Fig. 4 shows a nail plate according to the invention supporting a threaded socket.

MODES FOR CARRYING OUT THE INVENTION

The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims.

Figs. 1 to 3 show a first embodiment of a nail plate according to the invention adapted to hold a sleeve anchor or threaded socket during pouring and casting concrete, and Fig. 4 shows a nail plate holding a threaded socket. The nail plate 1 comprises a body 2 which forms the body of the nail plate and which comprises a disc section 3 and a stud section 4. The body 2 of the nail plate is hollow. The disc section 3 is circular and is provided with an upper surface 5 and a side surface 6. The side surface is preferably angled by e.g. 20 - 30 degrees when compared to a centre axis 17 of the nail plate. The angled side surface will facilitate the removal of the nail plate from a concrete block.

The nail plate may be attached to a formwork with a central screw or nail, but may also be arranged to be attached to a formwork in a conventional manner, with several nails through the disc section. The upper surface may in this case be provided with several shallow indentations or markings 21 . A marking show the position where a nail is to be applied if the nail plate is to be attached to a formwork with nails in a conventional manner. Below each marking, a tubular nail guide 22 may be arranged that will guide and support a nail such that it will not bend and that the insertion angle will be perpendicular to the formwork surface. The height of the disc section 3 may vary depending on the required indentation in the concrete block.

The stud section 4 is arranged on the upper surface 5 of the disc section 3 and comprises an outer thread 7 arranged on the side of the stud section. The stud section also comprises an upper stud surface 8 having an edge portion 9 and a central section 10. The central section 10 comprises a weakening section 12 and the upper part of a central tube 11 that is attached to the edge portion 9 through the weakening section 12. The weakening section 12 constitutes an intended breaking point that will allow the central tube 11 to break away from the edge portion 9. In the example shown in Fig. 1 , the weakening section consists of a plurality of ribs 13 extending between the edge portion and the central section. The weakening section may also consist of a closed surface having a reduced thickness when compared to the edge section. The central tube 11 is provided with an entrance hole 15. The hole 15 may be open or may be closed with a thin wall through which a screw or nail can be forced when the nail plate is to be attached to a formwork. The hole of the central tube may be provided with a bevel 14 that corresponds to the conical shape of a screw head.

The length of the central tube will decide the force with which the nail plate is attached to the formwork and will further prevent a nail or screw to be inserted too far into the formwork. The wall thickness of the central tube is selected such that the central tube will not deform or break when a screw or nail attaches the nail plate to the formwork. Depending on the size of the nail plate, the wall thickness and the diameter of the central tube will vary. For a smaller nail plate, a thinner screw or nail will be used to attach the nail plate to the formwork, and the dimensions of the central tube may be relatively small. For a larger nail plate, a thicker screw or nail will be used, and the dimensions of the central tube are adapted to this.

When a nail or screw attaches a nail plate to a formwork, the lower bearing surface 20 of the central tube 11 will bear on the formwork. In order to provide a secure attachment of the nail plate to the formwork, the central tube 11 preferably extend downwards to a plane 18 positioned somewhat above the bearing surface 16 of the nail plate, such that the bearing surface 20 of the central tube is aligned with the plane 18. A suitable distance between the plane 18, i.e. the bearing surface 20 of the central tube, and the bearing surface 16 of the disc section 3 is 0,2-3 mm, depending on the size of the nail plate and/or the size and thickness of the weakening section. This will allow the circumference of the disc section to be pressed against the formwork when a screw or nail holds the nail plate to the formwork with the bearing surface of the central tube pressed to the formwork. The weakening section 12 will allow the central section 10 to flex somewhat without breaking, such that the screw or nail will pull the nail plate towards the formwork. The dimensions of the weakening section together with the length of the central tube sets the force that will press the nail plate towards the formwork. This will ensure that the nail plate is securely attached to the formwork such that it will not rotate, and that concrete will not be able to enter between the bearing surface of the nail plate and the formwork.

The central section 10 may be recessed with respect to the edge portion 9 of the stud section. The recess is around 1 mm deep and corresponds to the thickness of a nail head. When a nail is inserted, the edge portion will take the load of a hammer when the nail is sufficiently inserted into the formwork. This will prevent the weakening section to be damaged or broken by a nail that is inserted too deep. The recessed central section will also help to prevent a screw to be inserted too deep, when a screw bit holder with an adjustable screw depth or a drywall screwdriver is used. When the outer wall of the screwdriver hits the edge portion, the screw is prevented from being inserted further into the formwork. The entrance hole of the central tube may be bevelled with an angle that corresponds to the countersunk screw head.

By the weakening section, the screw or nail together with the central tube will detach from the rest of the nail plate when a formwork is removed from a set concrete block. With the nail or screw removed from the nail plate, the removal of the nail plate from the concrete block and the threaded socket is facilitated. When a screw is used to attach the nail plate to a formwork, the screw can easily be removed from the formwork without damaging the formwork. In this way, both the screw and the formwork may be used again. A nail can also easily be removed form the formwork, such that the formwork is undamaged.

The nail plate 1 is also provided with a removal opening 19 at the rear side of the nail plate, arranged inside the disc section 3. The removal opening is used to unscrew the nail plate from the concrete block and the threaded socket. The removal opening may be straight or may be cross-shaped and is adapted to cooperate with a removal tool that e.g. can be driven by an electric screwdriver.

The advantage of the inventive nail plate is that it allows a nail plate to be removed from a set concrete block and an embedded threaded socket in an easy and quick manner in a one step operation. When the formwork is removed from the set concrete block, the nail or screw that has attached the nail plate to the formwork will detach from the body of the nail plate, and will remain attached to the formwork together with the central tube. When the formwork is removed, the nail plate can easily be removed from the threaded socket with a rotating movement.

A further advantage is that the nail plate can be attached to the formwork in an easy manner, by using a single screw or nail. The nail plate is preferably intended to be attached with a screw, but nails are also possible to use. The advantage of using a screw is that the screw will give a more secure attachment of the nail plate to the formwork due to the thread of the screw. Often, the formwork is relatively thin, and may be e.g. 12 mm thick. A screw that is 10 mm longer than the height of the nail plate will thus give a secure attachment without the screw extending through the formwork and sticking out on the other side of the formwork. Screws or nails that extend through the formwork may be dangerous and may hurt a user. A screw holding the central tube is easy to unscrew from the formwork, and since the screw is not damaged, it may be reused. The formwork may also be used again.

The inventive nail plate may also be used for automatic attachment of nail plates to a formwork by a robot due to the one step operation possibility. Since the nail plate is attached to the formwork with a single screw, it is well adapted to be used by an industrial robot. The robot will position the nail plate at a predefined position, and will attach the nail plate to the formwork with a screw through the central hole. When the formwork is removed, the robot will also be able to remove the nail plate from the concrete block and the threaded socket by using a removal tool that fits in the removal opening of the nail plate. By the weakening section, it is ensured that the screw is detached from the body of the nail plate, such that the screw does not prevent the removal tool to enter the removal opening. The robot can thus unscrew the nail plate from the threaded socket in a predictable manner. The robot may also clean the formwork by unscrewing all remaining screws with central tubes.

The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims. The nail plate may be made from any suitable material. REFERENCE SIGNS

1 : Nail plate

2: Body

3: Disc section

4: Stud section

5: Upper surface

6: Side surface

7: Thread

8: Upper stud surface

9: Edge portion

10: Central section

11 : Central tube

12: Weakening section

13: Rib

14: Bevel

15: Hole

16: Bearing surface

17: Centre axis

18: Plane

19: Removal opening

20: Tube bearing surface

21 : Marking

22: Nail guide

30: Threaded socket