A device for unwinding a coil of post-tensioning strand

Abstract

The present invention provides a device for unwinding a coil of post-tensioning strand comprising a cage (1) intended for receiving the coil of post-tensioning strand (3), rollers (9) arranged inside the cage on which the coil of post-tensioning strand is placed. The interior of the cage (1) has a cylindrical shape that is defined by a body (4), a side wall (5), a swing door (6), and a cover (7). In the central part of the interior of the cage (1) there is a support structure (8) attached to the side wall (5) comprising at least one roller (9). Inside the cage (1) there are at least three rollers (9) arranged circumferentially, spaced at equal distances from each other. The cover (7) comprises an aperture (71). Moreover the side wall (5) and door (6) comprise an inspection aperture (53), (63).

Description

[0001] A device for unwinding a coil of post-tensioning strand

[0002] Field of the invention

[0003] The invention concerns a device for unwinding a coil of post-tensioning strand intended for post-tensioned concrete elements, in particular post-tensioned slabs.

[0004] State of the art

[0005] Tensioning strands used in construction for tensioning concrete structures are delivered by the manufacturers of these strands to customers, e.g. plants producing prefabricated concrete elements or construction firms making concrete structures, in the form of coils. Such a coil is usually in the form of a coiled strand or tendon tied at several points with bundles to prevent it from unwinding on its own. This way, the tensioning strand takes up less volume, making it easier and cheaper to store and transport.

[0006] A coil of post-tensioning strand accumulates potential energy, which is transformed into kinetic energy when it is uncoiled. This phenomenon finds a useful application in kinetic accumulators, devices that convert potential energy, such as that of a spring element, into kinetic energy. However, in many cases, the change in the form of energy, taking place in an uncontrolled and violent manner, can lead to undesirable effects in the surrounding surroundings.

[0007] The unwinding of the coil of post-tensioning strand and the conversion of potential energy into kinetic energy poses a risk of people within the strand's range of movement being struck by the strand. A major risk is posed by the ends of the strand, particularly the one containing the anchorage. The ends of a strand that has had a high potential energy when uncoiled can move at high speed, which, with the significant weight of the strand itself, can pose a very high risk of serious injury if it strikes a human being.

[0008] From the state of the art, solutions are known to facilitate the unwinding of sheet metal coils or cables. The French patent application FR2726207A1 discloses the cage, especially for thin steel strip used for reinforcing concrete, consists of rigid members joined together with a gap between them large enough for the reel. It also has an articulated top member, and two pivoted balance arms in the bottom of the cage with flanges rollers on their ends to support the reel. The centre of the cage's lower section and the top member have vertical rollers which retain the side of the reel. As the reel is being unwound its sides are supported by the vertical rollers, while the balance arm rollers adjust to the reducing diameter of the reel.

[0009] From another French patent application FR2258230A1 is known an unrolling mechanism for material coiled on a bobbin. The mechanism consists of a vertical cylinder which forms the frame. The central base is cut away to allow a ball race to be located under the base. The ball race supports a turntable. The top end cover of the cylinder is detachable and serves as a lid. There are 4 rollers (11) which are located vertically on the outside of the coiled material and are used to support and material. The material leaves the mechanism by a vertical slot in the container. Alternative bearing arrangements are possible and the roll may be turned onto a horizontal axis.

[0010] The aim of the present invention is to provide a device that will make it possible to unwind a coil of post-tensioning strand in a safe manner without risk of injury to workers.

[0011] Summary of the invention

[0012] The object of the invention is a device for unwinding a coil of post-tensioning strand, comprising a cage intended for receiving a coil of post-tensioning strand, rollers arranged inside the cage on which the post-tensioning strand coil is placed. An axis of rotation of the rollers is parallel to an axis of the coil. According to the invention the interior of the cage has a cylindrical shape that is defined by a body, a side wall, a swing door arranged across from the side wall, and a cover mounted to the body arranged between the side wall and the swing door. In the central part of the interior of the cage there is a support structure attached to the side wall comprising at least one roller, the axis of rotation of which is parallel to the axis of the post-tensioning strand coil placed inside the cage. Inside the cage there are at least three rollers arranged circumferentially, spaced at equal distances from each other. The cover comprises an aperture. Moreover the side wall and the swing door comprise an inspection aperture. A support structure with at least one roller, located in the central part of the interior of the body, is intended to support the coil of post-tensioning strand inserted into the device, before cutting the ties. When the ties are cut, the coils of the strand are loosened and it starts to rest on the rollers arranged circumferentially in the cage.

[0013] The roller on the supporting structure aims to reduce the friction between the strand and this structure during the unwinding of the strand, particularly when the coils are loosened after the ties have been cut. Preferably, the support structure is cube-shaped with rollers at its four opposite edges. Preferably, there are two rollers at each of the opposite edges. The placement of rollers at each corner of the support structure significantly eliminates the number of points where the strand could rub against this structure as it uncoils.

[0014] Preferably, inside the cage there are sixteen rollers arranged circumferentially, spaced at equal distances from each other. Thanks to this multiple rollers and their appropriate positioning, proper support is provided for the strand being uncoiled around the circumference of the cage. The strand, no matter how it is positioned during unwinding, is always in contact with the rollers, which reduce the friction between the pulled strand and the cage.

[0015] Preferably, the body of the cage is made up of two rings arranged coaxially and connected by transverse profiles.

[0016] Preferably, the side wall is made up of a frame, and a cover in which there is the inspection aperture. The cover protects the operator from the rapidly moving strand when cutting the ties holding it as coil. The inspection aperture provides the operator with access to the interior of the cage to cut the ties.

[0017] Preferably, the door is made up of a frame and a cover in which there is the inspection aperture. The door is fixed to the body pivotably by means of at least one hinge. The cover and the inspection aperture in the door have the same functions as in the side wall.

[0018] Preferably, the aperture in the cover extends over its entire width between the side wall and the door. This aperture is used to take the end of the strand out of the interior of the cage, in order for it to be pulled by the operator.

[0019] Preferably, the rollers are attached to the body and to the support structure by means of mounts, the mount of each roller being inseparably connected to the body or to the support structure and the mount of each roller being detachably connected to these elements.

[0020] This way of attaching the rollers to the body and the supporting structure allows them to be easily removed for replacement or repair, in the event of damage.

[0021] Preferably, the cage is set on a stand. The stand includes legs with mounting brackets. Placing the cage on a stand, at some distance from the surface, eliminates the need for the operator to bend down to insert the coil of post-tensioning strand inside the cage. This reduces the risk of back injury when carrying the weight of the strand. Mounting brackets allow the device to be anchored to the surface, preventing it from moving while the strand is being uncoiled.

[0022] Preferably, the cage is oriented vertically. The vertical position should be understood as the position in which the axis of the post-tensioning strand coil placed in the cage is horizontal - parallel to the surface of the ground on which the device is placed. This position of the cage makes it easier for the operator to insert the strand coil into the cage.

[0023] The advantage of the solution according to the invention is that it makes it possible to unwinding coils of post-tensioning strands in a safe manner, eliminating the risk of accidentally hitting people by the unwinding strand. A cover attached to the body of the cage, and covers in the side wall and door prevent the end of the strand from falling out of the cage. The large number of rollers around the circumference of the cage provides a large number of points along which the strand being rolled. As a result, friction between the strand and the interior of the cage is minimised, so that unwinding the coil requires little physical effort.

[0024] Brief description of drawings

[0025] The invention is shown by means of exemplary embodiment on a drawing, in which: fig. 1 shows a device for unwinding the coil of post-tensioning strand in the first embodiment in a perspective view; fig. 2 shows the device according to the invention in the first embodiment in a side view, with the coil of post-tensioning strand placed inside; fig. 3 shows the device in the first embodiment in a side view, with the door opened; fig. 4 shows the device in the second embodiment in a side view; fig. 5 shows the device in a front view; fig. 6 shows the roll in a perspective view.

[0026] Detailed description

[0027] The device for unwinding a coil of post-tensioning strand, illustrated in figs. 1-5, consists of a cage 1 mounted on a stand 2. The cage 1 is designed for placing a post-tensioning strand coil 3 inside it. Depending on the size of the coil, its weight, and the size of the cage 1, one or more coils can be placed inside it.

[0028] The interior of cage 1 has cylindrical shape - it is circular in side view, as shown in fig. 2. This shape of the interior of the cage is the most optimal, due to the shape of the strand coils. The external shape of the cage 1 is irrelevant to the operation of the device. In the embodiment of the invention, the external shape of the cage is also circular in side view. This shape results from the design of the cage 1.

[0029] According to the invention the cage 1 comprises a cylinder-shaped body 4, a side wall 5 fixed on one side of the body, and a swing door 6 fixed on the other side of the body, opposite the side wall. In addition, on the outer side of the body 4, there is a cover 7 extending between the side wall 5 and the door 6, substantially around its circumference. The body 4 is made of two rings arranged coaxially and connected by transverse profiles. These elements are made of metal. They are connected by welded joints. A cover 7 arranged on the outer side of the body 4 prevents the strand 3, in particular its ends, from escaping from the cage during its unwinding from the coil. For this purpose, it has been made of sheet metal of sufficient thickness to withstand the impact of metal cables. The cover 7 can be connected to the body 4 by means of welded, riveted or other similar connections.

[0030] The side wall 5, like the cover 7, prevents the strand 3, in particular its ends, from escaping outside the cage during its unwinding from the coil. For this purpose, it comprises a cover 51 which is attached to a frame 52. The cover 51 is made of sheet metal. The frame 52 serves as a supporting structure for the cover 51. It is fixed to the body 4 inseparably. There is an inspection aperture 53 in the cover 51, which is designed to provide an operator of the device with access to the interior of the cage, for example to cut the ties by which the coil of posttensioning strand is bound. The size of the inspection aperture 53 is arranged the so that the operator has access to the ties holding the coil in its rolled-up form, while at the same time the cover 51 maintains its function. In the example embodiment, the inspection aperture 53 has a circular shape. It is centrally positioned on the side wall 5.

[0031] The door 6 is intended to provide access to the interior of the cage 1 in order to insert the strand coil 3 therein. In addition, they serve the same function of the sidewall 5, namely to prevent the strand, in particular its ends, from escaping from the cage during its unwinding from the coil. They contain a cover 61, which is fixed to the frame 62. They also have an inspection aperture 63, which serves the same purpose as the inspection aperture 53 in the side wall 5. The door 6 is fixed to the body 4 by means of two hinges, and has a lock to keep it closed during the unwinding of the coil 3.

[0032] According to the invention, there is an aperture 71 in the cover 7. This serves to guide the end of the strand out of the interior of the cage 1. After cutting the ties of the coil, the operator of the device pulls on the end of the strand protruding from the aperture, unwinding the coil.

[0033] In the central part of the interior of the cage 1 there is a support structure 8, which is attached to the side wall 5. In the first embodiment of the invention shown in fig. 1 -3 the support structure 8 is cube-shaped, built of metal profiles. The support structure 8 extends over the entire width of the interior of the cage 1, from the side wall 5 to the door 6. Its size is selected to fit within the hole of the coil of post-tensioning strand. The function of the support structure 8 is to provide support to the coil of post-tensioning strand 3 placed in the device, before the ties are cut. Of course, not in every instance does a tied coil have to rest on the support structure 8. Where the diameter of the coil is slightly smaller than the diameter of the body 4, the tied coil will not rest on the support structure 8, but directly on the elements at the circumference of the body. The support structure 8 contains, in an first embodiment of the invention, at each of the four free edges 81 of the cube two rollers 9. By the term free edges is meant those edges of the cube which do not form the side walls of the figure located at the side wall 5 and the door 6, but are the edges connecting these two side walls. The axis of rotation of the rollers 9 is parallel to the axis of the coil of the prestressing strand 3 placed inside the cage 1. The strand that rests on the rollers rotates them as it is pulled by the operator. This keeps the friction between the strand to a minimum, resulting in less effort required to pull the strand and unwind it.

[0034] In other possible embodiments of the invention, the support structure may have the shape of a circle or other prism, e.g. a triangular prism. In the second embodiment of the invention shown in fig. 4 the support structure 8 has the shape of a triangular prism with rollers fixed on the tips of the triangle.

[0035] According to the invention, inside the cage, on the circumference of the cage 1, there are sixteen rollers 9 spaced apart from each other at equal distances. These are designed to support the strand as it is uncoiled. When the ties are cut, the coil loosens and the strand rests on the rollers 9. As the strand is pulled by the operator, the friction between the strand and the rollers 9 causes them to rotate, reducing the force required to pull the strand from inside the cage 1 and unroll it. The arrangement of the rollers 9 around the circumference of the cage provides points to reduce the friction in pulling the strand, regardless of where the strand contacts the interior of the cage 1.

[0036] The rollers 9 are attached to the body 4 and the support structure 8 by means of mounts 91, 92. The mount 91 of each roller is inseparably connected to the body 4 and the support structure 8, while the mount 92 is detachably connected to these elements. The use of a detachable connection of one of the mounts facilitates the removal of the roller from the device for replacement or repair. The detachable connection, as shown in fig. 5, is implemented by means of a screw connection consisting of two screws.

[0037] The stand 2 is made of metal profiles. It is equipped with four legs 21, which ends with mounting brackets 22. These brackets enable the device to be anchored to the surface, preventing it from moving or tipping over during the unwinding of the coils of posttensioning strand. The cage 1 is oriented vertically on the base 2. The vertical positioning of the cage 2 means a position where the axis of the coil of post-tensioning strand inserted into the cage is parallel to the surface of the ground on which the device is placed.

[0038] The device according to the invention may interact with a strand moving device, which pulls the strand by the end protruding from the aperture 71. Thus, unwinding a coil of posttensioning strand by means of the device does not require much physical effort from the person operating the device. The strand moving device may take the form of at least one drive roller and at least one hold-down roller, between which the end of the post-tensioning strand is inserted. The drive roller may be driven by an electric motor. The strand moving device may be free-standing, i.e. not connected to the device for unwinding the posttensioning strand coil, or it may be attached to the stand or directly to the cage. The strand moving device is not an object of the invention and is not a necessary element for the implementation of the present invention.

Claims

Claims1. A device for uncoiling a coil of post-tensioning strand, comprising a cage intended for receiving a coil of post-tensioning strand, rollers arranged inside the cage on which the post-tensioning strand coil is placed, wherein an axis of rotation of the rollers is parallel to an axis of the coil, characterized in that a interior of the cage (1) has a cylindrical shape that is defined by a body (4), a side wall (5), a swing door (6) arranged across from the side wall, and a cover (7) mounted to the body (4) arranged between the side wall (5) and the swing door (6), in the central part of the interior of the cage (1) there is a support structure (8) attached to the side wall (5) comprising at least one roller (9), the axis of rotation of which is parallel to the axis of the coil of post-tensioning strand (3) placed inside the cage (1), inside the cage (1) there are at least three rollers (9) arranged circumferentially, spaced at equal distances from each other, the cover (7) comprises an aperture (71), moreover the side wall (5) and the swing door (6) comprise an inspection aperture (53), (63).

2. The device according to claim 1, wherein the support structure (8) is cube-shaped with rollers (9) at its four opposite edges (81).

3. The device according to claim 2, wherein there are two rollers (9) at each of the opposite edges (81).

4. The device according to claim 1 or 2 or 3, wherein inside the cage (1) there are sixteen rollers (9) arranged circumferentially, spaced at equal distances from each other.

5. The device according to any preceding claims from 1 to 4, wherein the body (4) of the cage is made up of two rings arranged coaxially and connected by transverse profiles.

6. The device according to any preceding claims from 1 to 5, wherein the side wall (5) is made up of a frame (51), and a cover (52) in which there is the inspection aperture (53).

7. The device according to any preceding claims from 1 to 6, wherein the door (6) is made up of a frame (61) and a cover (62) in which there is the inspection aperture (63), and is fixed to the body (4) pivotably by means of at least one hinge.

8. The device according to any preceding claims from 1 to 7, wherein the aperture (71) in the cover (7) extends over its entire width between the side wall (5) and the door(6).

9. The device according to any preceding claims from 1 to 8, wherein the rollers (9) are attached to the body (4) and to the support structure (8) by means of mounts (91) (92), the mount (91) of each roller being inseparably connected to the body (4) or to the support structure (8) and the mount (92) of each roller being detachably connected to these elements.

10. The device according to any preceding claims from 1 to 9, wherein the cage (1) is set on a stand (2).

11. The device according to claim 10, wherein the stand (2) includes legs (21) with mounting brackets (22).

12. The device according to any preceding claims from 1 to 11, wherein the cage (1) is oriented vertically.

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