Patent Description:
Devices for pre-stressing a structure are well known. In these devices, a sheet, a rod or a rope is connected to a structure by bolting or bonding. Also, pre-stressing devices having wedge-shaped plates are known. These devices are cumbersome to use and difficult to tension. Such solutions usually involve complex anchorage configurations with many components. Furthermore, it is technically complex to apply stress with such devices. Furthermore, the known devices are large and therefore, they need much space. Known pre-stressing devices are for example known from <CIT>, <CIT>, <CIT> or <CIT>.

It is therefore an object of the present invention to improve the solutions of the prior art and to provide a tensioning device which is simple, reliable, with less components and easy attachable to a structure as well as the corresponding methods and uses.

The object is achieved by a tensioning device for pre-stressing, post-tensioning or providing a confining pressure to a structure according to claim <NUM>, a method for pre-stressing a structure according to claim <NUM>, the use of a tensioning device for pre-stressing a structure according to claim <NUM> and the use of a tensioning device for for restressing, detensioning or releasing a confining pressure from a structure according to claim <NUM>.

The object is achieved by a tensioning device for pre-stressing, post-tensioning or providing a confining pressure to a concrete structure according to claim <NUM>.

The tensioning device comprises a steel sheet and at least one roller for tensioning the sheet. The sheet is wrapped around the roller. The roller is designed such that the sheet is gripped and/or tensioned by a rotation of the roller. Such a device is easy to use and reliable. Since the steel sheet is gripped and/or tensioned by a rotation of the roller, the connection between the steel sheet and the roller is very simple and error resistant. Moreover, the device comprises less parts and there are a few parts necessary for tensioning the steel sheet. The roller can be easily adapted for steel sheets with different geometries, thicknesses and length. Therefore, different prestressing forces can be adapted as needed.

The tensioning device can comprise two rollers, one at each end of the sheet.

The roller can be designed such that it grips one or two sheet ends, wherein the sheet ends can be ends of the same or two sheets.

The roller can comprise metal and/or another material like plastic. Preferably, the roller is made of steel or a metal alloy. The tensioning device can comprise a connecting element to connect the tensioning device to a structure. The connecting element can be a structural connecting element.

The connecting element enables a fixation of the tensioning device to a structure. This way stress can be created relative to the structure. Additionally, the tensioning device can be used to detension in case this is needed. The connecting element can be at least one bolt or screw. It can comprise an adhesive. The connecting device can also be a removable connecting device. In this case the tensioning device is used for stressing, pre-stressing or detensioning and removed after fixing the sheet to the structure, for example by bolting the sheet to the structure.

The connection device can also be non-removable to create a permanent possibility for prestressing, restressing, detensioning or creating or releasing a confining pressure.

The connection element can comprise metal or plastic or another material or combination of materials such as fibre-reinforced material. Preferably, the connecting element is made out of steel or an alloy. The connecting element can comprise different materials. The connecting element can comprise holes, where screws, bolts or nails can be inserted. This way the connecting element can be connected to a structure. For connecting the connecting element to a concrete structure common tools and machines, which are usually available on-site, like a hammer drill or dowels, can be used. The connecting element can be connected to a metal structure by welding or by rivets. The connecting element can comprise a holding element for the roller, for example a clevis frame.

The roller of the tensioning device can have a longitudinal axis which is essentially orthogonal to a longitudinal axis of the sheet.

Therefore, the steel sheet can be wrapped around the roller easily.

The longitudinal axis of the sheet is the direction of the longest extension of the sheet. The longitudinal axis of the roller is the rotational axis of the roller.

The connecting element can comprise a connecting surface. The connecting surface and the longitudinal axis of the roller can have a distance of less than <NUM>. The connecting surface and the longitudinal axis of the roller can also have a distance of less than <NUM>.

The connecting surface enables a defined connection to a structure surface. Additionally, the steel sheet can be mounted close to the surface of the structure which reduced the occurrence of moments or torques on parts of the tensioning device and the connection to the structure. It is also possible that the steel sheet touches the surface of the structure. This allows high forces to be transmitted. Since there are no or only few lever arms, no large torques are generated relative to the structure. Therefore, the structure which has to be tensioned as well as the tensioning device can be dimensioned advantageously. This creates a device in combination with the structure which is very effective and efficient.

The sheet can be connected to the roller using connection means. The connection means can be screws, rivets, one or more slots or grooves and/or a weld seam.

This makes the connection between the sheet and the roller very stable and reliable. Screws, rivets, one or more slots or grooves or a weld seam can be attached using tools or machines, which are usually available on-site. Therefore, the sheet can be connected to the roller on-site very easily.

In case of the connection means being a groove. The groove can be placed on the outer surface of the roller. The groove can have a longitudinal axis. The longitudinal axis of the groove can be parallel to the longitudinal axis of the roller. For tensioning the steel sheet, the steel sheet can be arranged partly in the groove of the roller. Then the roller can be rotated. In this case, the steel sheet is held by a combination of form fit and friction. When the steel sheet is wrapped around the roller several times, there is friction between the layers of the several windings of the sheet.

The sheet has a length, a height and a width, wherein the width is at least four times as large as the height. The height is less than <NUM>. The height can be less than <NUM>.

Through these measurements, the sheet can be wrapped around the roller easily and nevertheless create the tension needed.

The sheet can comprise steel or be made from steel. The steel sheet has a yield strength of <NUM> to <NUM> MPa, tensile strength of <NUM> to <NUM> MPa and can have a thickness of <NUM> to <NUM>.

Those strengths values lead to an optimal possibility of tensioning or stressing a structure. Using these values it is not necessary to use a shape memory alloy which is expensive and complicated to use.

The sheet can have a length of more than <NUM> meter or more than <NUM> meters. The sheet can have a length of more than <NUM> meters or more than <NUM> meters.

The steel sheet can be at least partially pre-rolled, and/or pre-mounted on the roller or be connected to the roller on site.

The roller of the tensioning device can be rotatably mounted.

Therefore, it is easy for tensioning the steel sheet by turning the roller.

The roller can be mounted using bearings. The roller can be mounted using ball bearings, needle bearings or taper roller bearings or with other types of bearings.

The roller of the tensioning device can comprise a first end and a second end. The first end and/or the second end can comprise a connection element, to which a tensioning tool is connectable in a torque transmitting way.

The connection element makes it possible to connect a tensioning tool to the roller. Therefore, it is easy to tension the sheet using a tensioning tool. Tensioning tools such as a wrench or a hydraulic wrench, in particular a torque wrench, are usually available on-site. The applied force can be correlated to the hydraulic pressure and calibrated. Therefore, no extra equipment besides tools, which are usually available on-site, is needed for operating the tensioning device. Since the tensioning tool is connectable and removable to the connection element, a plurality of tensioning devices can be operated with only one tensioning tool. This makes it very effective to tension several structures with several tensioning devices. Therefore, only one tensioning tool is necessary for this.

The connection element can have a torque transmitting shape, for example be a hexagon head or a hexagon socket. The connection element can also be a slot. The tensioning tool can be a wrench, which can be hydraulically powered. Essential is that the tensioning tool can be connected to the roller in a torque transmitting way.

The tensioning device can comprise at least one locking device. The locking device can be mounted to the roller. The locking device can be mounted to the first end and/or the second end of the roller. The locking device can prevent the rotational movement of the roller in at least one direction of rotation.

With the locking device, the movement of the roller can be blocked effectively. Therefore, after tensioning the tensioning device and blocking the movement of the roller with the locking device, the tensioning tool can be removed and can be used for a tensioning another tensioning device. Therefore, the locking device makes it efficient to operate a plurality of tensioning devices with only one tensioning tool.

The locking device can for example be a steel plate with a recess which is formed like a hexagon socket. Such a plate can be attached to a roller with a connection element which is formed like a hexagon head. The locking device can be plugged to the connection element of the roller. It is also possible, that the locking device is fixed to the connecting element. The locking device can be fixed to the connecting element with screws and/or rivets and/or a weld seam. Essentially is, that the moving of the roller is blocked in at least one direction of rotation by the locking device.

The sheet can be wrapped around the at least a quarter of the circumference of at least one roller. The sheet can also be wrapped around at least half the circumference of at least one roller.

This ensures that the sheet is attached to the roller in a particularly secure and stable manner.

The sheet can be wrapped around the entire circumference of the roller. The steel sheet can also be wrapped several times around the circumference of the roller.

The object of the invention is further achieved by a method for pre-stressing, post-tensioning or providing a confining pressure to a structure , according to claim <NUM>, using a tensioning device according to the invention as described before.

The sheet comprises a first sheet end and a second sheet end.

Such a method is reliable and effective.

The first sheet end can be connected to the structure using rivets, nails or screws or by stapling. Furthermore, the first sheet end can be connected to the structure by a second roller.

The fixation point can be a connection to the first roller such that it is possible to wrap the sheet around a structure, e.g. a container, and imply a confining pressure using just one roller being connected to both ends of the sheet at least indirectly via the tensioning device. The fixation point in this case is a fixation point for both sheet ends and does not necessarily imply the fixation point to remain at a fixed position. The fixation point further is not necessarily a separate device but a point of connection of two or more devices.

When the sheet is wrapped around the roller, no further connection parts such as screws are needed. Therefore, the method is cheap, simple and reliable.

The roller can comprise a connection element to which a tension tool is connectable. Therefore, the method can comprise the following steps:.

Tension the tensioning device by tensioning tool makes it very easy to operate the tension device.

The tensioning tool can be a wrench. The tensioning tool can also be a hydraulic wrench.

The tensioning device can comprise a locking device for locking the roller. The method can comprise the following steps:.

The locking device can also fix the roller by preventing the roller in both rotational directions. Therefore, after fixing the locking device to the roller, the tensioning tool can be removed and be used for tensioning another tension device.

The locking device can be plugged to one end of the roller. It is also possible that the locking device is fixed so the connecting element, for example with screws, rivets or a weld seam.

The method can also comprise the following steps:.

With this method, it is possible to tension the steel sheet with the tensioning device and then remove the tensioning device.

Therefore, it is possible to tension many steel sheets with just one tension device. In this way, it is very efficient to use a tensioning device.

The roller can be turned into the opposite direction to de-tension the sheet.

The object of the invention is also achieved by the use of a tensioning device according to the invention for pre-stressing, post-tensioning or providing a confining pressure to a structure by tensioning a sheet using a rotational movement of the roller and in particular fixing the sheet after tensioning, according to claim <NUM>.

The object of the invention is also achieved by the use of a tensioning device according to the invention for pre-stressing, detensioning or releasing a confining pressure from a structure by using a rotational movement of the roller, according to claim <NUM>.

The invention is further described in embodiments by means of figures in the following:.

<FIG> shows a bottom view of a tensioning device <NUM> comprising a steel sheet <NUM> and two rollers <NUM>. The steel sheet <NUM> connects the two rollers <NUM>. The longitudinal axes <NUM> of the rollers <NUM> are parallel. The longitudinal axis <NUM> of the sheet <NUM> is orthogonal to the longitudinal axes <NUM>, in particular the axis of rotation, of the rollers <NUM>. A first sheet end <NUM> is wrapped around the first roller <NUM> and a second sheet end <NUM> is wrapped around the second roller <NUM>. Each roller comprises a first end <NUM> and a second end <NUM>. The first end <NUM> and the second end <NUM> of each roller have connection elements <NUM>. The connection elements <NUM> are hexagon heads. The rollers <NUM> each comprise a connection means <NUM>. The connections means <NUM> of each roller is a groove <NUM>. The longitudinal axis, i.e. the longest extension, of the groove <NUM> is parallel to the longitudinal axis <NUM> of the rollers <NUM>. The grooves <NUM> are arranged over the whole height of the rollers <NUM>. The first sheet end <NUM> is arranged in the groove <NUM> of the first roller <NUM> and the second sheet end <NUM> is arranged in the groove <NUM> of the second roller <NUM>. The rollers <NUM> or one of the rollers <NUM> can be rotated to stress the sheet. By connecting the rollers <NUM> to a structure the structure can be pre-stressed, post-tensioned or even de-tensioned if needed. The rollers <NUM> can remain on the structure or removed after connecting the sheet directly to the structure.

<FIG> shows a bottom view of a tensioning device <NUM> comprising a steel sheet <NUM>, two rollers <NUM> and two connecting elements <NUM>. The connecting elements <NUM> are clevis frames. Each clevis frame 7a comprises two shanks, which are arranged parallel to each other. The two rollers <NUM> are arranged rotatably in the clevis frames 7a. Each clevis frame 7a comprises two shanks. Each shank comprises an essentially circular cut-out. A first end <NUM> of each roller <NUM> is arranged rotatably in the cut-out of the first shank of each clevis frame 7a. A second end <NUM> of each roller <NUM> is arranged rotatably in the cut-out of the second shank of each clevis frame 7a. The clevis frames 7a have a plurality of connection holes <NUM>. By means of the connection holes, the clevis frames 7a can be fixed to a structure with nails or screws. Same references designate same components.

<FIG> shows a bottom view of a tensioning device <NUM> comprising a steel sheet <NUM> and two rollers <NUM> with connection elements <NUM>. The connection elements <NUM> are hexagon heads <NUM>. The hexagon heads <NUM> are arranged on the first end <NUM> and the second end <NUM> of each roller <NUM>. The hexagon heads <NUM> protrude from the shank of each clevis frame <NUM>. Same references designate same components.

<FIG> shows a bottom view of a tensioning device <NUM> comprising a steel sheet <NUM> and two rollers <NUM> with connection elements <NUM> and a locking device <NUM>. The locking device <NUM> has a cut-out which is formed like a hexagon socket. The locking device <NUM> is arranged on the hexagon head <NUM> of one roller <NUM> preventing the rotational movement of the roller <NUM> in both directions of rotation. The locking device <NUM> is connected to the shank of the clevis frame <NUM> with four screws. Same references designate same components.

<FIG> shows a bottom view of a tensioning device <NUM> comprising a steel sheet <NUM> and one roller <NUM> with connection elements <NUM>. The steel sheet <NUM> is connected to the tensioning element <NUM> with its first sheet end <NUM>. With the second sheet end <NUM>, the steel sheet <NUM> can be fixed to a structure by screws, nails or other connection means. Same references designate same components.

<FIG> shows a bottom view of a tensioning device <NUM> comprising a steel sheet <NUM> and one roller <NUM> with connection elements <NUM> and a locking device <NUM>. The locking device <NUM> is arranged on the hexagon head <NUM> of the roller <NUM> preventing the rotational movement of the roller <NUM> in both directions of rotation. The locking device <NUM> is connected to the shank of the clevis frame 7a with four screws. Same references designate same components.

Claim 1:
Tensioning device (<NUM>) for pre-stressing, post-tensioning or providing a confining pressure to a structure (<NUM>), in particular a concrete structure (<NUM>), comprising a sheet (<NUM>), wherein the sheet comprises a first sheet end (<NUM>) and a second sheet end (<NUM>), and at least one roller (<NUM>) for tensioning the sheet (<NUM>), wherein the first sheet end (<NUM>) is connectable to the structure (<NUM>) and the sheet (<NUM>) is wrapped around the roller (<NUM>) and wherein the roller (<NUM>) comprises a structural connecting element (<NUM>) to connect the tensioning device to the structure (<NUM>) and the roller (<NUM>) is designed such that the second sheet end (<NUM>) is connected to the roller (<NUM>) and the sheet (<NUM>) is tensioned by a rotation of the roller (<NUM>) wherein the sheet (<NUM>) has a length, a height and a width, wherein the width is at least four times as large as the height characterized in that the height is less than <NUM>, in particular less than <NUM> and the sheet (<NUM>) is a steel sheet having a yield strength of <NUM> to <NUM> MPa and a tensile strength of <NUM> to <NUM> MPa.