| JP3936701 | WIRE ROPE TENSIONER |
| JP3219139 | CURING WIRE NETTING FRAME FOR TEMPORARY CONSTRUCTION WORK |
| JP11311029 | CLAMP FOR SHEET |
| Claims 1. A safety device for covering ends of concrete reinforcement bars, the safety device comprising: a tube, the tube: having an elongate central portion, having at each end a hollow for receiving an end of a concrete reinforcement bar, and being at least partly elastic, wherein the device is configured so as to be able to be formed by a user into an in use state in which the open ends of the tube are generally parallel to one another and located between 100 mm and 400 mm apart. 2. A safety device as claimed in claim 1, n which the length of the tube is in the range of 450 mm to 900 mm. 3. A safety device as claimed in claim 1, in which the length of the tube is in the range of 600 mm to 750 mm. 4. A safety device as claimed in any preceding claim, wherein the dimensions and material of the safety device are selected such that the safety device requires a bending force of between 10 N and 500 N to bend the tube from a resting state to the in use state. 5. A safety device as claimed in any of claims 1 to 3, wherein the dimensions and material of the safety device are selected such that the safety device requires a bending force of between 80 N and 150 N to bend the tube from a resting state to the in use state. 6. A safety device as claimed in any preceding claim, wherein the central portion of the tube is substantially solid or filled with material. 7. A safety device as claimed in any preceding claim, wherein the safety device comprises a strengthening or reinforcing material, such as a strengthening or reinforcing foam, filling a central portion of the tube. 8. A safety device as claimed in claim 7, wherein the tube is formed generally of a first material and is reinforced or strengthened with a second material. 9. A safety device as claimed in any preceding claim, wherein the tube is generally straight when not in use. 10. A safety device as claimed in any preceding claim, wherein the safety device comprises a cap, the cap being closed at one end and open at the other end, the cap having an external dimension comparable to an internal dimension of the interior of the end of the tube, the cap having an outwardly extending flange at its open end that is larger that the internal dimension of the tube, the cap being located in an end of the tube so as to limit the maximum extent of movement of an end of a concrete reinforcing rod into the safety device. 11. A safety device as claimed in claim 10, wherein the cap is secured in the end of the tube. 12. An arrangement comprising: two concrete reinforcement bars, each having an end directed generally upwardly, the concrete reinforcement bars being located between 100 mm and 400 mm apart; and a safety device as claimed in any preceding claim, wherein each open end of the safety device is engaged with an end of a respective one of the concrete reinforcement bars. 13. An arrangement as claimed in claim 13, wherein the arrangement comprises three or more concrete reinforcement bars arranged in a row and wherein the safety device is engaged with two concrete reinforcement bars that are not adjacent in the row. 14. An arrangement comprising: two concrete reinforcement bars, each having an end directed generally upwardly, the concrete reinforcement bars being located between 100 mm and 400 mm apart; and a safety device comprising a tube, the tube: having an elongate central portion, having at each end a hollow for receiving an end of a concrete reinforcement bar, and being at least partly elastic, wherein the safety device is configured so as to be able to be formed by a user into an in use state in which each open end of the tube is engaged with an end of a respective one of the concrete reinforcement bars. 15. An arrangement as claimed in claim 14, in which the length of the tube is in the range of 450 mm to 900 mm. 16. An arrangement as claimed in claim 14, in which the length of the tube is in the range of 600 mm to 750 mm. 17. An arrangement as claimed in any of claims 14 to 16, wherein the dimensions and material of the safety device are selected such that the safety device requires a bending force of between 10 N and 500 N to bend the tube from a resting state to the in use state. 18. An arrangement as claimed in any of claims 14 to 16, wherein the dimensions and material of the safety device are selected such that the safety device requires a bending force of between 80 N and 150 N to bend the tube from a resting state to the in use state. 19. An arrangement as claimed in any of claims 14 to 18, wherein the central portion of the tube is substantially solid or filled with material. 20. An arrangement as claimed in any of claims 14 to 19, wherein the safety device comprises a strengthening or reinforcing material, such as a strengthening or reinforcing foam, filling a central portion of the tube. 21. An arrangement as claimed in claim 20, wherein the tube is formed generally of a first material and is reinforced or strengthened with a second material. 22. An arrangement as claimed in any of claims 14 to 21 , wherein the tube is generally straight when not in use. 23. An arrangement as claimed in any of claims 14 to 22, wherein the safety device comprises a cap, the cap being closed at one end and open at the other end, the cap having an external dimension comparable to an internal dimension of the interior of the end of the tube, the cap having an outwardly extending flange at its open end that is larger that the internal dimension of the tube, the cap being located in an end of the tube so as to limit the maximum extent of movement of an end of a concrete reinforcing rod into the safety device. 24. An arrangement as claimed in claim 23, wherein the cap is secured in the end of the tube. 25. An arrangement as claimed in any of claims 14 to 24, wherein the arrangement comprises three or more concrete reinforcement bars arranged in a row and wherein the safety device is engaged with two concrete reinforcement bars that are not adjacent in the row. |
This invention relates to a safety device for covering ends of concrete reinforcement bars. The invention relates also to an arrangement comprising concrete reinforcement bars and a safety device.
It is common on construction sites to find partially completed reinforced concrete structures. Reinforced concrete pillars and walls typically are grown upwards. As part of the process, concrete reinforcement bars typically are left protruding upwards vertically from one level of concrete. Further concrete reinforcement bars are then secured to the exposed ends of the protruding concrete reinforcement bars, and the extended bars then are encased in concrete, for instance using a mould. If the pillar or wall is to be grown further upwards, the ends of the newly added concrete reinforcement bars will protrude from the top of the new level of concrete.
Exposed concrete reinforcement bars constitute a hazard on construction sites. A person falling onto the exposed ends of concrete reinforcement bars can suffer serious harm or even death. The likelihood of harm is increased by the fact that the ends of such concrete reinforcement bars tend to be found generally between 0.5 metres and 1 metre above ground level. As such, a person falling onto the ends of the concrete reinforcement bars typically will be travelling at a significant velocity at the time of impact on the ends of the bars. In forming a concrete wall, concrete reinforcement bars will typically be provided in plural rows, with adjacent bars being separated by a distance of approximately 100 or 200 millimetres. The spacing is such that a person may land on the ends of two or three concrete reinforcement bars if falling onto the incomplete concrete wall.
It is known to protect the ends of concrete reinforcement bars with so-called mushroom caps. These are formed of a plastics material and have a recess for receiving an end of a concrete reinforcement bar opposite a dome. The dome faces upwards in use and constitutes a larger surface area, thereby reducing the risk of serious harm to a user falling on the concrete reinforcement bars. The mushroom caps are so-called because their shape resembles that of a mushroom.
The invention was made in this context. In accordance with the present invention there is provided a safety device for covering ends of concrete reinforcement bars, the safety device comprising:
a tube, the tube:
having an elongate central portion,
having at each end a hollow for receiving an end of a concrete reinforcement bar, and
being at least partly elastic,
wherein the device is configured so as to be able to be formed by a user into an in use state in which the open ends of the tube are generally parallel to one another and located between 100 mm and 400 mm apart.
This safety device can provide a number of advantages over the prior art mushroom cap. One advantage is a decreased likelihood of the safety device being inadvertently or accidentally removed from the ends of the concrete reinforcement bars. This results at least in part from the elasticity of the safety device, which results in a reactive force between a concrete reinforcement bar and the safety device providing some friction resistance against removal of the safety device. Additionally, the safety device can provide a more comfortable impact for a user accidentally falling onto the ends of the concrete reinforcement bars. This results in part from the relatively large surface area of the loop that is formed by the safety device as it extends between the ends of two concrete reinforcement bars, and is caused in part by the ability of the safety device to deform elastically, thereby providing some cushioning.
Another advantage is the decreased likelihood of the safety device being lost. This results from the fact that if the safety device becomes detached at one end the other end can remain attached. A user can then easily replace the detached end on the reinforcing rod. With a prior art mushroom cap, the cap would be knocked to the floor where it could become a trip hazard and/ or be lost.
The amount of cushioning provided depends on the forces that are required to deform the tube in its in use state. In turn, this depends on the length of the tube, the separation between the concrete reinforcement rods on which the safety device is installed and the relevant physical properties of the tube. This depends also on the relevant physical properties of a material that is used to fill a central portion of the tube. Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a perspective view of a safety device according to the present invention;
Figure 2 is a diagram illustrating the safety device of Figure 1 installed on some concrete reinforcement rods;
Figure 3 is a schematic perspective diagram illustrating a safety device according to some embodiments of the present invention; and
Figure 4 is a schematic diagram illustrating a safety device in accordance with other embodiments of the present invention. In the drawings, like reference numerals are used to denote like elements.
In Figure 1, a safety device 10 is shown comprising generally a first end portion 11, a second end portion 12 and a central portion 13. The central portion 13 is elongate, and only the ends of the central portion 13 are shown in Figure 1. The safety device 10 comprises a tube 14. The tube 14 is annular, having a generally cylindrical outer surface and a generally cylindrical inner surface. The thickness of the material constituting the tube wall is denoted at dimension X in Figure 1. The external diameter of the tube 14 is denoted V in the Figure, and the internal diameter is denoted W.
The first end portion 11 includes at its end an opening 15. The opening 15 has a generally circular cross section of diameter W. A corresponding opening 16 is present at the second end portion 12.
Optionally, the central portion 13 of the tube 14 is filled with a reinforcing material 17. The reinforcing material 17 extends from a first end 18, located at the boundary between the first end portion 11 and the central portion 13, to a second end 19, located at the boundary between the second end portion 12 and the central portion 13. The distance between the end 18 of the reinforcing material 17 and the opening 15 at the first end portion 11 is indicated at Y in the drawing. Similarly, the distance between the second end 19 of the reinforcing material 17 and the opening 16 at the second end portion 12 is indicated at Y. These two dimensions may have different values. The overall length of the tube 14 is indicated at Z in the Figure.
Example dimensions of the safety device 10 are as follows. The length Z of the tube 14 may be in the range of 450 millimetres to 900 millimetres, and more preferably is in the range of 600 millimetres to 750 millimetres. The thickness X of the wall of the tube 14 may be in the range of 1 millimetre to 4 millimetres, and more preferably is in the range of 2 millimetres to 3 millimetres. The length Y of the distance between an end 18, 19 of the reinforcing material 17 and the opening 15, 16 at the corresponding end portion 11, 12 may be in the range of 50 millimetres to 200 millimetres, and more preferably is in the range of 70 millimetres to 150 millimetres. The internal diameter W of the tube 14 may be in the range of 8 millimetres to 35 millimetres. More preferably, the internal dimension W is in the range of 16 millimetres to 32 millimetres. The external diameter V of the tube 14 is equal to the internal dimension W plus twice the thickness X of the tube 14, so may be in the range of 10 millimetres to 43 millimetres, and more preferably is in the range of 18 millimetres to 40 millimetres. These dimensions are non-limiting on the scope of protection unless otherwise stated.
Figure 2 shows the safety device 10 of Figure 1 installed on some concrete reinforcement bars. Here, a row of four concrete reinforcement bars 20, 21, 22, 23 is provided. The row is generally linear, with adjacent bars being approximately equally spaced. The separation between adjacent bars may for instance be in the range of 80 mm to 250 mm, and more preferably is in the range of 100 mm to 200 mm. The exact arrangement of the concrete reinforcement bars depends on the techniques selected for use in the particular
construction. It would be appreciated that the concrete reinforcement bars 20 to 23 protrude from a concrete base (not shown).
A first safety device 10 is connected between the ends of the first and third concrete reinforcement bars 20, 22. A second safety device 10 is connected between the ends of the second and fourth concrete reinforcement bars 21, 23. The second of these safety devices 10 will now be discussed in detail.
The first end portion 11 of the safety device 10 is engaged with the end of the concrete reinforcement bar 21. Engagement in this case means that the end of the concrete bar 21 is inserted into the opening 15 up to the end 18 of the reinforcing material 17. As such, the concrete reinforcing bar 21 is within the tube 14 of the safety device 10 for approximately dimension Y. Similarly, the second end portion 12 is engaged with the end of the fourth concrete reinforcement rod 23, which is contained within the tube 14. The central portion
13 forms an arch between the first and second end portions 11, 12. Since the concrete reinforcement rods 21, 23 are generally parallel to one another, the safety device 10 is forced to adopt a "C" shape, with the first and second end portions 11, 12 pointed in the same direction but spaced parallel from one another. The distance between the first and second end portions 11, 12 is equal to the distance between the second and fourth concrete reinforcement rods 21, 23, which in this example is between 160 millimetres and 500 millimetres, and more preferably between 200 millimetres and 400 millimetres. The elasticity of the safety device 10, which results from the material constituting the tube
14 and also the material constituting the reinforcing material 17, as well as the safety device 10, means that in the "C" shape shown in Figure 2 the tendency of the safety device to return to a straight configuration is prevented by the concreted reinforcement rods 21, 23. It will be appreciated that this results in a reactive force between the first and second end portions 11, 12 and their respective reinforcement rods 21, 23. In particular, a reactive force is provided between the end of the first end portion 11 that is rightmost in the Figure and the part of the concrete reinforcement rod that it contacts. A corresponding reactive force is provided between the corresponding part of the second end portion 12 and the concrete reinforcement rod 23. These reactive forces and the coefficient of friction at the contact points requires a substantial force in an upwards direction in order to remove the safety device 10 from the ends of the concrete reinforcement rods 21, 23.
With the safety devices 10 supported in a "C" shape, a user cannot fall directly onto an end of one of the concrete reinforcement bars 20 to 23. Any such fall would be cushioned by one or both of the safety devices 10. In the event of a person falling onto one of the safety devices 10, part of the force would be communicated into a force pushing the
corresponding concrete reinforcing bars away from one another and part of the force would be commuted into bending the safety device 10. Depending on the location and direction of impact, bending of the safety device 10 could occur in the plane of Figure 2 and/ or in a plane perpendicular to Figure 2. Bending could occur primarily in the central portion 13, or might occur primarily at the junction between the central portion 13 and one of the end portions 11, 12. The location and extent of bending depends primarily on the location and direction of impact and also on the resistance of the safety device to bending. The resistance to bending of the safety device 10 is dependent to a large extent on the modulus of elasticity, or bending stiffness, of the safety device 10.
The configuration, including the various dimensions and choice of materials, of the safety device 10 is selected to provide a suitable resistance to bending. A suitable resistance to bending is one that allows the safety device 10 to be bent into the in use shape by a user without the use of tools or other special equipment yet provides sufficient cushioning in the event of a person falling onto the safety device.
Installation of the safety device 10 by a user typically involves the user grasping the an end portion 11, 12 with each hand, with their wrists facing downwards. The user then rotates their arms and push their hands towards one another until the safety device is formed into a "C" shape with the ends facing downwards. The user then manoeuvres the ends of the safety device 10 such as to locate the ends of the rods 21, 32 into the openings 15, 16. This may be performed one at a time, or simultaneously. On release by the user, the safety device 10 is installed and is secured in place by the reactive forces between the safety device and the rods 21, 23.
Alternatively the use may place the first end 11 of the safety device 10 onto one rod 21 whilst the safety device is straight, with one opening 15 receiving the rod and the other opening 16 facing upwards. The user can then grasp the second end 12 with one of two hands and bend it across and then downwards, against the reactive force provided by the action of the rod 21 against the first end 11, and guide the other rod 23 into the second opening 16. Releasing the safety device 10 once the second 12 has been pushed downwards to the maximum extend then results in the safety device 10 being secured in place by the reactive forces between the safety device and the rods 21, 23.
In either case the force required to move the ends 11, 12 of the safety device further increases with increased displacement. The mechanics involved can be likened to those of bending beams (although the displacement here is much greater than is found in beam bending) and elastic extension (although it is not elastic extension in the normal sense).
The maximum resistance to bending is selected so as to be achievable by a user at the displacement of the safety device when in the in use state. The maximum thus depends on the particular user, since a physically strong user is able to exert more force than a physically weak user. So as to allow operation by a sufficient proportion of the relevant population, the dimensions and material of the safety device 10 are selected such that the safety device requires a bending force of up to 500 N (or 50 kg) to bend the tube from its resting state to the in use state. In the in use state the safety device 10 is bent into a "C" shape with the ends parallel to one another and approximately 300mm apart. In other embodiments, the dimensions and material of the safety device 10 are selected such that the safety device requires a bending force of up to 300 N (or 30 kg) and in others up to 150 N (or 15 kg) to bend the tube from its resting state to the in use state. These latter embodiments allow operation by less physically strong users, and thus are usable by a greater proportion of the population. The lower the required force, the easier it is to operate the safety device.
The minimum force required to bend the safety device into the in use position determines the effectiveness of the safety device to protect a user who has fallen onto it.. To a limit, the greater the minimum force required, the more effective is the safety device. The dimensions and material of the safety device 10 are selected such that the safety device requires a bending force of more than up to 10 N (or 1 kg) to bend the tube from its resting state to the in use state. Again, in the in use state the safety device 10 is bent into a "C" shape with the ends parallel to one another and approximately 300mm apart. In other embodiments, the dimensions and material of the safety device 10 are selected such that the safety device requires a bending force of more than 30 N (or 3 kg) and in others more than 80 N (or 8 kg) to bend the tube from its resting state to the in use state.
In preferred embodiments, the bending force required to bend the tube from its resting state to the in use state is in the range of 80 N (or 8 kg) to 150 N (15kg).
Referring now to Figure 3, a safety device 10 is shown including a tube 14 constituted generally of a first material and reinforced with a second material. For instance, the first material may be a flexible plastics material. The second material comprises an elongate member that is formed integrally with the first material. The second material may be a less flexible and stronger material. For instance, the first material may be polythene or polyethylene. The second material may be a malleable metal. Alternatively, the second material may be a relatively inflexible plastic, such as nylon. The second material may be plural fibres that are twisted or braided together.
The second material is formed in one or more lengths that extend along the tube 14. In the example shown in Figure 3, there are two lines 30, 31 that extend helically along the tube in an anticlockwise direction and third and fourth lines 32, 33 that extend along the tube 14 in a clockwise direction.
An effect of the second material is to increase the resistance to bending of the safety device 10. As such, the safety device 10 shown in Figure 3 has a significantly higher resistance to bending than does a corresponding arrangement that is absent of reinforcing material. The safety device 10 of Figure 3 may not be provided with any reinforcing material within the bore of the tube 14. Alternatively, reinforcing material 17, such as is described in relation to Figure 1 above, may be provided in the bore of the tube 14.
In other embodiments a spring that is resistant to bending is provided within the tube. Here the spring, for instance a coil spring, can be inserted into the tube and then fixed in place. Alternatively, the tube may be formed around the spring, for instance by heat shrinking. Alternatively the tube may be a solid rod, for instance made of a rubberised plastics material.
Referring now to Figure 4, another embodiment of a safety device 10 is shown. Here, a tube 14 is provided. The tube 14 has the same construction as that described above in relation to Figure 1. The tube 14 is absent of reinforcing material formed integrally with the tube. However, reinforcing foam or other reinforcing material 17 is provided within the central portion 13 of the safety device 10.
At each of the first and second ends 11, 12 is provided a cap. A cap 40 provided at the first end 11 of the safety device 10 is illustrated at 40 in the Figure. The cap 40 comprises a generally tubular portion 41, a flange portion 42 and a blocking portion 43. The outer diameter of the tubular portion 41 is approximately equal to the inner diameter of the tube 14. At one end of the tubular portion 41, the flange 42 extends outwardly by an amount approximately equal to the thickness of the tube 14. As such, the outermost extent of the flange 42 is approximately flush with the tube 14 when the cap 40 is inserted into the first end 11 of the safety device 10. The blocking portion 43 is provided at the end of the tube portion opposite to the flange 42. The cap 40 is moulded as a one-piece component. The cap 40 may be made of high density polyethylene (HDPE), or other such suitable material. The tubular part 41 may be tapered slightly so as to ease moulding. In use, the safety device 10 of Figure 4 is provided over the end of a concrete
reinforcement rod until the end of the rod contacts the blocking member 43. This has two effects. The first is that the extent of penetration of the rod into the safety device 10 is set by the length of the cap 40. The second is that the end of the concrete reinforcement rod is prevented from contacting the reinforcing material 17. This helps to preserve the integrity of the safety device 10 and increases its useful life.
The inner surface of the tubular part 41 of the cap 40 may be roughened or otherwise provided with surface features in order to provide for improving engagement between the cap 40 and the external surface of a concrete reinforcement rod. This can make it more difficult to remove the safety device 10 from a concrete reinforcement rod once installed. The maximum diameter of a concrete reinforcement rod that can be accommodated by the safety device 10 of Figure 4 is determined by the inside diameter of the cap 40, rather than the inside diameter of the tube 14.
The presence of reinforcing material 17, such as reinforcing foam, in any of the above described embodiments increases the resistance to bending, compared to the safety device 10 incorporating a tube 14 alone. This is achieved by the reinforcing material 17 being resistant to compression, since compression of parts of the material occurs as the tube 14 is bent into the in use position. The presence of reinforcing material 17, such as reinforcing foam, also helps to prevent kinks being formed in the tube 14 as it is bent. A kink can allow easier bending of the tube, so it is desired to prevent the formation of kinks. In embodiments where the reinforcing material 17 and/ or the tube 14 is not fully elastic, the safety device 10 will remain slightly bent after it has been removed from installation on concrete reinforcement rods. In these embodiments, it is advantageous for the safety device 10 to be bent in the same way when subsequently reinstalled on other concrete reinforcement rods. However, the direction in which the safety device 10 was bent on a previous installation is apparent from visual inspection because the safety device 10 will clearly be seen as bent towards that position.